Archives des Biologie cellulaire, développement et évolution

A promising new therapeutic approach for patients with arteriovenous malformations

Posted on July 18, 2024July 25, 2024 by Graziella Cara

Phospho-ERK (red), Green Fluorescent Protein (cyan) and DAPI coimmunofluorescence on spleen sections from mice carrying a KRAS G12C endothelial mutation © Guillaume Canaud

The teams of the translational medicine and targeted therapies unit of the Necker-Enfants Malades AP-HP hospital, Inserm, Paris Cité University within the Necker–Enfants Malades Institute, coordinated by professors Guillaume Canaud (Université Paris Cité, AP-HP) and Laurent Guibaud (Hospices Civils de Lyon, Reference Center for Superficial Vascular Anomalies), conducted a study showing a promising effect of the anticancer drug sotorasib for arteriovenous malformations secondary to a mutation in the G12C type KRAS gene. The results were the subject of a publication published on July 17, 2024 in the New England Journal of Medicine.

An arteriovenous malformation (AVM) results from abnormal connections between arteries and veins. AVMs are frequently associated with symptoms such as pain, bleeding, heart failure, cosmetic deformity or organ compression. These malformations generally progress over time. AVMs are in most cases of genetic origin, either “germinal” and therefore familial, or sporadic due to a localized genetic mutation. In many of the latter cases, the gene responsible is the KRAS gene, a gene involved in cell growth, proliferation and survival. There are different types of KRAS mutation. At the moment, no drug treatment is approved for these pathologies.

Sotorasib, developed by Amgen, is an anticancer drug used to treat a type of lung cancer, advanced non-small cell lung cancer (NSCLC), with a mutation in the KRAS gene, the KRAS G12C mutation. The drug thus selectively targets the KRAS p.G12C protein.

The teams of Professors Guibaud and Canaud identified the presence of a KRAS G12C mutation in two adult patients with severe AVMs and without therapeutic resources. They then decided to create two mouse models developing vascular malformations secondary to a KRAS G12C mutation in order to better understand the pathophysiology of these malformations. Preclinical models have largely recapitulated the malformations observed in humans. Using these two models, they then tested and demonstrated the effectiveness of sotorasib in preventing the development of vascular malformations and significantly improving the survival of mice.

Based on these results, Professors Guibaud and Canaud obtained authorization for the use of sotorasib from the Amgen laboratory to administer it to these two patients as part of their therapeutic care.

In the weeks following the start of treatment, both patients noted a clear improvement in their symptoms (stopping of bleeding, healing of chronic skin ulcerations, disappearance of pain and recovery of deafness), a clinically visible reduction in malformation. This last result was then confirmed by MRI. After 2 years of follow-up, patients did not develop resistance to treatment.

This work demonstrates the interest in obtaining a molecular diagnosis for this type of rare disease and the possibility of repositioning highly targeted drugs developed for other indications, as the researchers had previously done for alpelisib in the syndrome of CLOVES and related syndromes.

These results will need to be confirmed by future studies on a larger number of patients. These drug repositionings open up new therapeutic fields, in particular for AVMs, for which these drugs could be combined with surgical treatment or in interventional radiology.

Cell contraction drive the initial shaping of human embryos

Posted on May 1, 2024May 2, 2024 by Graziella Cara

Human embryo at the blastocyst stage ready to implant. The nuclear envelope of the cells appears in blue and the actin cytoskeleton in orange. © Julie Firmin et Jean-Léon Maître (Institut Curie, Université PSL, CNRS UMR3215, INSERM U934)

Human embryo compaction, an essential step in the first days of an embryo’s development, is driven by the contractility of its cells. This is the finding of a team of scientists from CNRS, Institut Curie, Inserm, AP-HP and the Collège de France. Published in the 1^st May edition of Nature, these results contradict the presupposed driving role of cell adhesion in this phenomenon and pave the way for improved assisted reproductive technology (ART).

In humans, embryonic cell compaction is a crucial step in the normal development of an embryo. Four days after fertilisation, cells move closer together to give the embryo its initial shape. Defective compaction prevents the formation of the structure that ensures the embryo can implant in the uterus. In assisted reproductive technology (ART), this stage is carefully monitored before an embryo is implanted.

An interdisciplinary research team¹ led by scientists at the Genetics and Developmental Biology Unit at the Institut Curie (CNRS/Inserm/Institut Curie) studying the mechanisms at play in this still little-known phenomenon has made a surprising discovery: human embryo compaction is driven by the contraction of embryonic cells. Compaction problems are therefore due to faulty contractility in these cells, and not a lack of adhesion between them, as was previously assumed. This mechanism had already been identified in flies, zebrafish and mice, but is a first in humans.

By improving our understanding of the early stages of human embryonic development, the research team hopes to contribute to the refinement of ART as nearly one third of inseminations are unsuccessful today.²

The results were obtained by mapping cell surface tensions in human embryonic cells. The scientists also tested the effects of inhibiting contractility and cell adhesion and analysed the mechanical signature of embryonic cells with defective contractility.

Human embryo at the 4-cell stage. Cell DNA appears in red and their actin cytoskeleton in blue. The cell on the right has just split its genome into two and is about to divide. © Julie Firmin et Jean-Léon Maître (Institut Curie, Université PSL, CNRS UMR3215, INSERM U934)

1 – Scientists from the following entities also took part in the study: the Centre interdisciplinaire de recherche en biologie (CNRS/Collège de France/Inserm), the Reproductive Biology Department – CECOS (AP-HP) and the Institut Cochin (CNRS/Inserm/Université Paris Cité).

2 – Source: Agence de la biomédecine

Obesity: opt for omega 3 fatty acids to prevent the associated risks

Posted on February 20, 2024March 8, 2024 by Graziella Cara

In yellow, microglia (immune cells of the brain) activated by the pro-inflammatory nature of a sunflower oil-enriched diet (fluorescence microscopy). © Clara Sanchez/Inserm

Obesity is a major public health problem, affecting around 650 million adults worldwide[1], and is often associated with systemic and cerebral inflammation as well as anxiety and cognitive disorders, such as memory deficits. In a new study, researchers from Inserm, CNRS and Université Côte d’Azur at the Institute of Molecular and Cellular Pharmacology tried to understand more precisely how diet can cause obesity, and its associated comorbidities. They focused more specifically on omega 6 (ω6) and omega 3 (ω3) fatty acids, exploring the health effects of various diets with different ratios of fatty acids (see box below). Their findings indicate that a diet enriched with ω6 (in this case, sunflower oil) is strongly associated with changes in metabolism, inflammation and cognitive functions, whereas one enriched with ω3 (in this case, rapeseed oil) has certain preventive effects. This research makes it possible to envisage dietary interventions based on a low ω6/ω3 ratio (thus with a preference for rapeseed oil over sunflower oil) to combat obesity and its associated neurological disorders. These findings have been published in Brain Behavior and Immunity.

According to the WHO, cases of obesity have almost tripled in number worldwide since 1975. Obesity is associated with numerous comorbidities (type 2 diabetes, cardiovascular diseases, osteoarthritis, cancer and cognitive disorders) and high mortality. While its causes are complex and involve the interaction of several factors, dietary imbalance is recognised as being the major contributing factor.

What is more, previous studies[1] have shown that obesity is associated not only with metabolic dysfunction, but also chronic inflammation in the peripheral organs (adipose tissues, liver, skeletal muscles and pancreas), as well as in the central nervous system (neuroinflammation). This neuroinflammation in obesity is characterised by an increase in pro-inflammatory markers in the region of the hypothalamus, an area of the brain known to control dietary behaviour[2]. However, the nature of the nutritional lipids that could be responsible for this neuroinflammation has not yet been elucidated.

In a new study, researchers from Inserm, CNRS and Université Côte d’Azur specifically focused on certain fatty acids that are essential for our bodies to function properly, and are known for having anti- and pro-inflammatory properties: omega 3 and 6 (see box below). Their objective was to better understand whether omega 3 and 6 are involved in the phenomenon of neuroinflammation in the context of a high-fat diet (so-called ‘obesogenic diet’), and whether they can be associated with the development of obesity.

Their research is also based on the observation of an increasingly strong trend in developed countries towards an excessive consumption of omega 6, whose inflammatory properties are abundantly documented in the scientific literature[4].

Omega 3 and omega 6: the importance of getting the right balance

Omega 3 and omega 6 fatty acids are essential for the correct functioning of the body, which is unable to produce or synthesise them on its own. They therefore need to come from the diet and respect a certain balance (referred to as the omega 6/omega 3 ratio), in order to combine the pro-inflammatory properties of omega 6 with the anti-inflammatory properties of omega 3.

Omega 6 fatty acids: e.g. linoleic and gamma-linolenic acids, are found in many oils, such as sunflower and corn oils
Omega 3 fatty acids: e.g. eicosapentaenoic and docosahexaenoic acids, are found in oily fish, and alpha-linolenic acid in oils such as flax, hemp, rapeseed, walnut or soya

In animal models, the scientists evaluated the health effects of three obesogenic diets – high in lipids – each with a different fatty acids ratio.

In these diets, the researchers used vegetable oils that can be found in the shops, namely rapeseed (rich in omega 3) and sunflower (rich in omega 6). The first diet contained a high omega 6/omega 3 ratio, meaning that it was highly enriched in omega 6 and therefore in sunflower oil. The second had an intermediate ratio, with balanced levels of omega 3 and omega 6. And the third was highly enriched in omega 3 and therefore in rapeseed oil.

Through different examinations, the scientists measured the various effects of these diets on weight gain and fat storage, glucose homeostasis[5] response, development of anxiety and cognitive disorders, and brain inflammation.

At the end of the experiment, which lasted up to 5 months, the scientists observed (results summarised in the diagram below):

altered metabolism, neuroinflammation and cognitive functions, including increased anxiety and spatial memory disorders in the obese mice fed a diet enriched with omega 6, and therefore sunflower oil,
a protective effect of the omega 3-enriched, high-rapeseed oil diet, on weight gain, regulation of glucose homeostasis and the development of cognitive disorders.

‘While obesity was previously attributed to an increase in the inflammatory state, our study shows that such a state depends on the type of diet to which the animal is exposed. In other words, it is a diet high in omega 6 that is responsible for the inflammatory phenomena observed and not the obesity itself,’ explains Clara Sanchez, Inserm post-doctoral researcher and first author of the article.
‘This study also shows, for the first time, the protective effect against obesity and the associated inflammatory phenomena that a lipid-enriched diet can present, provided it promotes the consumption of omega 3. This research makes it possible to envisage dietary interventions based on a low ω6/ω3 ratio to combat obesity and its associated neurological disorders,’ explains Carole Rovère, Inserm researcher and last author of the article.

In their discovery, the scientists also observed in these mice a change in the shape of certain brain cells located in the hypothalamus – known as microglia – which appear to activate in response to a high-omega 6 diet. Their research will now focus on better understanding the specific role of these cells in obesity.

[1]WHO, 2016

[2]Gregor and Hotamisligil, 2011; Thaler et al., 2012

[3] Baufeld et al., 2016; Cansell et al., 2021; De Souza et al., 2005; Le Thuc et Rovère, 2016; Salvi et al., 2022

[4] The WHO recommends consuming a ratio of omega 6 to omega 3 of 5:1. However, in Western societies our actual consumption is more like 15:1!

[5]Glucose homeostasis is a state of balance between the intake of glucose (intestinal absorption following a meal or production of glucose by the liver) and its use (glucose entry and use in the organs).

New cell senescence discoveries open up therapeutic avenues in fighting age-related diseases

Posted on February 19, 2024March 7, 2024 by Graziella Cara

An increase in glycerol kinase (GK) enzyme activity on its own is capable of halting cell proliferation and initiating a programme of senescence. The blue staining of the cells is a biomarker of senescence. This image shows cells overexpressing the GK enzyme. © Khaled Tighanimine/team Mario Pende.

Cell senescence is a physiological process that has been associated in many studies with age-related diseases. Yet the biological mechanisms of senescence and how it could constitute a relevant therapeutic target in fighting these diseases remain poorly understood. In a new study published in Nature Metabolism, scientists from Inserm, Université Paris Cité and CNRS at the Necker Enfants Malades Institute have identified metabolic modifications, i.e. changes in how energy is used by the cells, associated with senescence. This study also suggests that these metabolic changes, which lead to the accumulation of fat in the cells, could be a promising therapeutic target in age-related diseases.

Cell senescence is a physiological process in which a cell’s functions change and it irreversibly ceases to divide. It is induced by acute or chronic exposure of the body to physiological stress signals (such as damage caused to DNA, ageing, oncogenesis[1], etc.). While it is now well established that the accumulation of senescent cells in the body contributes to age-related diseases, its role in the initiation of these diseases and the various underlying mechanisms involved is not yet fully understood.

To increase knowledge on the subject, Inserm researcher Mario Pende and his colleagues have for several years, and particularly as part of the AgeMed scientific programme (see box), studied the metabolic changes that occur in cells during the process of senescence.

Senescence is characterised by inflammation and metabolic reprogramming – i.e. by a change in how the cells use energy.

‘Understanding the metabolic changes that occur in the cells during ageing is therefore key, as this could open up new avenues for targeting senescence and reaping health benefits,’ explains Pende.

In their new study, the scientists started by using approaches from the fields of transcriptomics (analysis of all RNA molecules resulting from genome transcription) and metabolomics (analysis of metabolites – small organic compounds derived from the body) to study these changes in vitro, in senescent cells subjected to various stresses.

Combining these different methods enabled them to identify a distinct metabolic ‘signature’ associated with senescence. In the senescent cells, they observed an accumulation of several metabolites: lactate, alpha-ketoglutarate, glycerol-3-phosphate (G3P) and phosphoethanolamine (pEtN). These accumulations result from changes in the activity of certain enzymes (including one called glycerol kinase). These findings were then confirmed in other cell types and in animal models.

‘Combined with other measurements, this metabolic signature can be used as a biomarker of cell ageing, enabling it to be monitored over an individual’s lifetime,’ emphasises Pende.

In the second part of the study, the scientists also sought to modulate the metabolic changes they had observed, to see if they could reduce the harmful effects of senescence on health. Using molecules that inhibit glycerol kinase activity, they saw a reduction in senescence-related inflammation along with decreased fat accumulation in the cells (triglycerides).

‘While we were unable to restart the cell cycle and encourage the senescent cells to multiply again, we clearly observed a reduction in the inflammatory markers associated with the senescence process. All in all, our findings therefore indicate that regulating the metabolic change observed in senescent cells could be a promising strategy for targeting cell senescence in age-related diseases,’ concludes Pende.

[1] The conversion of a normal cell into a cancer cell

Inserm Transfert has filed a patent for this research.

Inserm’s cross-cutting AgeMed programme

Mario Pende’s team is an active member of AgeMed, a research programme that aims to decipher the cell mechanisms involved in the ageing process. The teams of Eric Gilson, Oliver Bischof and Bertrand Friguet have also participated in this study.

The objective is to identify cell pathways and molecular targets that will ultimately enable the development of innovative medical practices to prevent and cure age-related diseases.

For more information, visit inserm.fr (article only available in French): https://www.inserm.fr/nous-connaitre/programme-transversal-agemed/

Type 2 diabetes: discovery of a new biological cardiovascular risk marker

Posted on January 31, 2024March 5, 2024 by Graziella Cara

Image taken from the January-February 2013 issue of Science & Santé magazine, Special Feature, page 30. Human pancreatic beta cells. In blue, the cell nuclei; in red, the insulin contained in the cells.

Scientists from Inserm, Université Paris Cité and CNRS at the Necker Enfants Malades Institute in Paris have identified a new prognostic marker for cardiovascular risk in people with type 2 diabetes (T2D). Led by Inserm researcher Nicolas Venteclef, the team has shown that the number of white blood cells circulating in the blood, as well as certain subtypes, is associated with stroke or myocardial infarction risk over the next ten years. Published in Circulation Research, this finding could make it possible to screen for T2D patients with the highest risk in order to improve prevention. The team filed a patent at the end of 2023 to protect their discovery.

During their lives, people with type 2 diabetes (T2D) have an approximate two-fold higher risk of an atherosclerosis-related cardiovascular event, such as myocardial infarction or stroke, in relation to those without T2D. Atherosclerosis is a disease characterised by the presence of plaques along the wall of the arteries that can rupture and obstruct blood flow.

Identifying those who are most at risk of developing this disease out of the T2D population remains very difficult. The ten-year predictive scores that integrate various cardiovascular risk factors, such as age, smoking and cholesterol levels, are unreliable when applied to this population, including when T2D-specific factors (duration of diabetes, HbA1c glycated haemoglobin, etc.) are taken into account. So it is important to identify new predictive factors for this specific population.

In a new study, the team of Inserm researcher Nicolas Venteclef at the Necker Enfants Malades Institute (Inserm/Université Paris Cité/CNRS) looked at monocytes – a category of white blood cells circulating in the blood, which are directly involved in the onset and progression of atherosclerosis. By evaluating the number of monocytes in the blood and the subtypes present in T2D patients, the researchers wanted to see if these parameters could constitute markers associated with cardiovascular risk.

In atherosclerosis, the blood monocytes are ‘recruited’ in the internal walls of the arteries. There, they differentiate into macrophages, which are cells able to capture ‘bad cholesterol’ and produce inflammatory molecules. The more the macrophages accumulate, the more lipids they capture, increasing the inflammation and the growth of the atherosclerotic plaque. Eventually, these plaques can damage the arterial wall, obstruct the vessel, or rupture.

Three cohorts of patients

The team based their research on three cohorts of T2D patients. Firstly, in AngioSafe-2[1], a cohort including 672 T2D patients, the researchers saw that the circulating monocyte count was positively correlated with the extent of atherosclerotic plaque and thus with the risk of atherosclerosis-related cardiovascular events, regardless of patient age and duration of T2D. In other words, the higher the circulating monocyte count, the greater the risk of a cardiovascular event.

This initial finding was confirmed in a second cohort, GLUTADIAB, comprising 279 people with T2D. This research also included the molecular analysis of circulating monocytes in both cohorts, making it possible to identify certain subtypes of monocytes predominant in T2D subjects with high cardiovascular risk.

What remained to be understood was how the scientists could use this finding to predict cardiovascular risk. A third cohort, SURDIAGENE, which follows people with T2D[2], enabled the authors to obtain the total circulating monocyte counts for 757 patients receiving follow-up in the cardiovascular prevention setting. When correlating these counts with the cases of myocardial infarction or stroke occurring in the cohort, they found that T2D patients with monocyte counts above a certain threshold (0.5 × 10⁹/L) had a five to seven times higher risk of cardiovascular events within ten years compared to those with counts below this threshold.

Armed with these findings, the scientists filed a patent to protect their discovery. They are now working on developing an electronic sensor to measure circulating monocytes from the collection of a drop of blood[3] by classifying them according to subtype. Ultimately, their objective is to include this analysis in the existing prognostic cardiovascular risk scores, in order to identify T2D patients most at risk and improve prevention.

Inserm Transfert has filed a patent for this research.

[1] recruited in the diabetes departments of the Lariboisière and Bichat Claude Bernard AP-HP hospitals

[2] Followed up in the endocrinology department of Nantes University Hospital

[3] in partnership with the PRINT’UP public institute

Discovery of the role of a brain regulator involved in psychiatric illnesses

Posted on December 11, 2023December 18, 2023 by Graziella Cara

It was widely accepted that families of synaptic receptors transmitted excitatory, and others inhibitory, messages to neurons. © Adobe Stock

Contrary to all expectations, GluD1 – a receptor considered to be excitatory – has been shown in the brain to play a major role in controlling neuron inhibition. Given that alterations in the GluD1 gene are encountered in a certain number of neurodevelopmental and psychiatric disorders, such as autism (ASD) and schizophrenia, this discovery opens up new therapeutic avenues to combat the imbalances between excitatory and inhibitory neurotransmissions associated with these disorders. Published in Science, this research is the result of collaborations between researchers from Inserm, CNRS and ENS at the ENS Institute of Biology (IBENS, Paris, France) with their colleagues at the MRC Laboratory of Molecular Biology in Cambridge, UK.

The complexity of the brain’s function reveals many surprises. While it was widely accepted in brain activity that families of synaptic receptors (situated at the extremity of a neuron) transmitted excitatory, and others inhibitory, messages to neurons, a study co-led by Inserm researchers Pierre Paoletti and Laetitia Mony at the ENS Institute of Biology has shed new light on this.

To understand what it is all about, we need to go back to the basics. An ‘excitatory’ synapse triggers the creation of a nerve message in the form of an electrical current if a receptor on its surface is able to bind to an excitatory neurotransmitter present in the interneuronal space, most often glutamate. This is called ‘neuronal excitation’. However, an ‘inhibitory’ synapse prevents this neuronal excitation by releasing an inhibitory neurotransmitter, often GABA. This is called ‘neuronal inhibition’. Thus, the families of glutamate receptors (iGluR) and GABA receptors (GABAAR) are considered to have opposite roles.

Toutefois, un sous-type de récepteur au glutamate appelé GluD1 intriguait les scientifiques. En effet, alors qu’il est censé avoir un rôle excitateur, celui-ci est préférentiellement retrouvé au niveau de synapses inhibitrices. Cette observation, effectuée par l’équipe de la chercheuse Inserm Cécile Charrier à l’Institut de Biologie de l’ENS en 2019, avait interpellé la communauté scientifique car le gène GluD1 est souvent associé à des troubles du neurodéveloppement comme l’autisme ou à des maladies psychiatriques de type troubles bipolaires ou schizophrénie, dans les études génétiques de population humaine. Comprendre le rôle de ce récepteur représente donc un enjeu de taille. Pour y voir plus clair, l’équipe de Pierre Paoletti a étudié ses propriétés moléculaires et sa fonction, à partir de cerveaux de souris, au niveau de l’hippocampe où il est fortement exprimé.

However, a glutamate receptor subtype called GluD1 intrigued the scientists. Although it is meant to have an excitatory role, it is preferentially found at the inhibitory synapses. This observation, made by the team of Inserm researcher Cécile Charrier at the ENS Institute of Biology in 2019, attracted the interest of the scientific community because the GluD1 gene is often associated with neurodevelopmental disorders (e.g. autism) or psychiatric conditions (e.g. bipolar disorders or schizophrenia) in human population genetic studies. Understanding the role of this receptor is therefore a major challenge. To find out more, Paoletti’s team used mouse brains to study its molecular properties and function in the hippocampus where it is strongly expressed.

An atypical role

Contrary to its name, the researchers already knew that the GluD1 receptor is unable to bind to glutamate. But in this study they were surprised to find that it bound GABA. Radu Aricescu’s team in Cambridge even described in the publication the fine atomic structure of the site where GluD1 interacts with GABA, using a technique called X-ray crystallography[1].

In principle, its role in the brain is therefore not excitatory of neuronal activity but inhibitory. Taking this finding into account, can we still say that this receptor belongs to the glutamate receptor family?

‘While the question remains, the analyses of phylogeny (relationships between genes and proteins) and the structural data do all show that it belongs to it. However, it is possible that certain mutations acquired during the course of evolution have profoundly modified its functional properties’, explains Paoletti.

Another source of curiosity is that this receptor does not function as a ‘conventional’ glutamate receptor or as a GABA receptor. Both cause the opening of channels in the cell membrane enabling the passage of ions responsible for the excitation or inhibition of the neuron. The GluD1 receptor however does not allow any channels to be opened. Its activity results from other internal mechanisms within the cell, which remain to be clarified.

Finally, this research suggests a major regulatory role for GluD1 in relation to the inhibitory synapses. Indeed, when activated by the presence of GABA, the inhibitory synapse is more effective. This manifests as a greater inhibitory response that lasts for a few dozen minutes.

‘In other words, GluD1 reinforces the inhibition signal. Perhaps by promoting the recruitment of new GABA receptors at the synapse? In any case, we are talking about a key regulator’, explains Mony.

For the scientists who contributed to this research, this discovery marks a real step forward.

‘These findings pave the way for a better understanding of the imbalances between excitatory and inhibitory messages in the brain in neurodevelopmental and psychiatric disorders, such as ASD and schizophrenia, or in conditions characterised by neuronal hyperexcitability, such as epilepsy. Following that, it will be important to study the potential of GluD1 as a therapeutic target for restoring better balance and reducing symptoms in these disorders’, they conclude.

[1] A physicochemical analysis technique based on the diffraction of X-rays by the matter to determine its molecular composition and 3D structure.

First Digital Mapping of the Immune Cells Responsible for Allergies

Posted on August 31, 2023September 4, 2023 by Graziella Cara

Marking of the different mast cell populations (in green and red), which are major players in allergic responses, on contact with neurons (white) in mouse skin. © Dr. Marie Tauber and Dr. Lilian Basso.

Allergic diseases affect up to one third of the world’s population, and their prevalence is on the increase. In order to develop more targeted and effective therapies, research is mobilizing to better understand the biological and cell mechanisms involved in the onset of allergies. Mast cells – a type of immune cell – is of particular interest to scientists and doctors, but there is little data about them at present. In a new study published in Journal of Experimental Medicine in July 2023, researchers from Inserm, CNRS and Université Toulouse III – Paul-Sabatier, at the Toulouse Institute for Infectious and Inflammatory Diseases (Infinity), broadened our understanding of these cells and created the first digital mapping of mast cells in humans. These findings open up avenues for the adaptation of therapeutic strategies.

Allergic diseases are a major public health problem, to the extent that the World Health Organization (WHO) has classified allergy as being the world’s fourth leading chronic disease. It is currently estimated that 25 to 30% of the population suffers from an allergy, be it food, skin or respiratory allergy, and this proportion could increase to 50% by 2050. A better understanding of the underlying biological mechanisms is a key step if we are to develop more targeted and effective therapies.

This is the goal of Inserm researcher Nicolas Gaudenzio and his team at the Toulouse Institute for Infectious and Inflammatory Diseases. In 2019, the scientists had published a first article in Nature Immunology, showing the crucial role played by immune cells known as “mast cells” in the initiation of eczema. This research has given rise to new therapies that are currently in development.

Mast cells remain poorly understood by scientists. We know that their functions go far beyond problems of allergies and that they can have roles that are either beneficial (such as in fighting bacteria) or not, depending on the pathology. Research has also led to their classification into two large families of mast cells: the CTMCs found mainly in the skin and the MMCs located mainly in the gut mucosa.

However, much remains to be learned about these cells that are complex to study, especially because it is difficult to extract them from tissue.

“If we are to understand how we can act on mast cells and block their harmful action in terms of allergic diseases, we need to improve our knowledge of these cells. This involves determining their location, if there are several types beyond the dichotomy which has traditionally been described, and whether their functions differ according to the tissues in which they are located,” points out Gaudenzio.

In this new study, the research team used more recent technologies to study mast cells more precisely in mice and humans. The scientists used the single-cell sequencing technique: they sequenced the RNA of individual cells from several organs in order to extract their individual “identity card”.

Analyzing human cells with this method reveals a much more complex image than has hitherto been described. Indeed, the cells of over thirty human organs were analyzed thanks to advanced techniques for exploring data banks and bioinformatics. The researchers thus identified not two but seven different subtypes of mast cells, with various characteristics and functions.

From this data, the team was able to create and enable open access to the first “digital mapping” of human mast cells, which allows any scientist to see at a glance which mast cell subtype is associated with which organ and learn more about its function.

This diagram shows, in a simplified way, the distribution of the different mast cell subtypes through different organs of the body.

This approach represents a major paradigm shift since the new mapping makes it possible, just by querying a database, to better understand the natural diversity of mast cells in allergic diseases, and thus open up a process of reflection on the need to adapt therapies to more precisely target the cell subtypes involved.

“This study is the first foundation stone of a vast building that is expected to transform the anti-allergy therapies and move towards a greater personalization of treatments, with more efficacy and fewer side effects. We will continue to supplement this mapping by studying mast cells in different disease settings, in treated and untreated patients alike, so that it is as precise as possible for the scientific and medical community that is working on allergies,” concludes Gaudenzio.

Inflammation and cancer: identifying the role of copper paves the way for new therapeutic applications

Posted on April 26, 2023April 28, 2023 by Graziella Cara

The research team developed a “drug prototype” capable of mitigating both the mechanisms of inflammation and the processes potentially involved in metastatic spread. © Institut Curie / BELONCLE Frank

For the first time, researchers from Institut Curie, the CNRS and Inserm have uncovered a previously unknown chain of biochemical reactions. This chain involves copper and leads to metabolic and epigenetic alterations[1] that activate inflammation and tumorigenesis. But there is more; the research team developed a “drug prototype” capable of mitigating both the mechanisms of inflammation and the processes potentially involved in metastatic spread. Published in the journal Nature on April 26, 2023, these results provide hope for new therapeutic opportunities to control inflammation and cancer.

Inflammation is a complex biological process that can eradicate pathogens and promotes repair of damaged tissues. However, deregulation of the immune system can lead to uncontrolled inflammation and produce lesions instead. Inflammation is also involved in cancer. The molecular mechanisms underlying inflammation are not fully understood, and so developing new drugs represents a significant challenge.

As far back as 2020, Dr. Raphaël Rodriguez, CNRS research director and head of the Chemical Biology team at Institut Curie (Equipe Labellisé Ligue Contre le Cancer) at the Cellular and Chemical Biology laboratory (Institut Curie/CNRS/Inserm), had shed new light on a membrane receptor called CD44, which marks immune responses, inflammation and cancer progression. Dr. Rodriquez and his team showed that CD44 helped import iron into cell[2], triggering a series of reactions leading to activation of genes involved in the metastatic process.

“This is a cell plasticity phenomenon we continued to study, investigating other metals potentially internalized by CD44, notably copper,” he explains.

Copper causing epigenetic alterations

Along with his colleagues[3], Dr. Rodriguez has now reached a new milestone.

The research team managed to identify a signaling pathway involving copper and leading to the expression of pro-inflammatory genes in macrophages, the cells present in all tissues and playing an important role in innate immunity.

Once internalized in macrophages, copper enters into the mitochondria (the organelle responsible for cell respiration and energy production), where it catalyzes the oxidation of NADH into NAD⁺ (nicotinamide adenine dinucleotide, a molecule needed for the activity of certain enzymes). The increase of NAD⁺ in cells enables the activity of certain enzymes involved in the production of metabolites essential for epigenetic regulation. These metabolites thus, contribute to the activation of genes involved in inflammation.

Inflammation and cancer: shared molecular mechanisms

The scientists did not stop there, they also designed molecules able to bind to copper, inspired from the structure of metformin.[4] By testing these new molecules on models of acute inflammation, they found that a synthetic dimer of metformin, LCC-12 (also termed Supformin), reduced activation of macrophages and attenuated inflammation.

“Our work has enabled us to develop a drug prototype that inactivates copper chemistry in the cell’s metabolic machinery, thus blocking expression of the genes involved in inflammation”, explains Dr. Rodriguez.

To finish, they applied this therapeutic strategy to cancer cell models engaged in an epithelial-mesenchymal transition[5]. Here again, Supformin blocked the cellular mechanism and thus the cell transformation.

“The genes activated in cancer cells are not the same as those expressed in immune cells, but the chain reaction leading to epigenetic alterations is identical”, explains Dr. Rodriguez.

These results thus reveal the role of copper in cancer cells and their ability to adopt a metastatic nature.

Dr. Raphaël Rodriguez concludes: “Our study reveals that the inflammatory and cancer processes depend on similar molecular mechanisms and could therefore in the future benefit from similar innovative therapies, such as those tested with Supformin.”

The explanations of Dr. Raphaël Rodriguez in video :

[1]Epigenetics is the study of the mechanisms at play in gene regulation, which is essential to the action of cells and to maintaining their identity. Unlike genetic mutations, which are permanent, epigenetic modifications on DNA or histones are reversible.

[2] Read the press release “Cancer: a new mechanism that regulates cell activity involving iron”: https://curie.fr/sites/default/files/medias/documents/2020-08/CPCNRS-CD44ferCancer-FR-emb.pdf

[3] This study was conducted at Institut Curie, in the Cellular and Chemical Biology unit (Institut Curie, CNRS, Inserm), in collaboration with UVSQ, Raymond Poincaré hospital (AP-HP), Gustave Roussy hospital, the Institut de chimie moléculaire et des matériaux d’Orsay (CNRS/University Paris-Saclay), the Multimodal Imaging Center (CNRS/Institut Curie/Inserm/University Paris-Saclay), the Center for Infection and Immunity of Lille (CNRS/Inserm/Institut Pasteur de Lille/CHU of Lille/University of Lille), Institute of Pharmacology and Structural Biology (CNRS/University of Toulouse III) along with British and Australian researchers.

[4]Metformin is a treatment used for Type-2 diabetes, and is able to form a bimolecular complex with copper.

[5] Epithelial-mesenchymal transition is the first step in enabling cancer cells to metastasize.

A blood factor involved in depression

Posted on February 21, 2023March 3, 2023 by Graziella Cara

A small group of neural stem cells isolated from mice and cultured in vitro observed under a confocal microscope. (LaminB1 in green, Sox2 in red) © Perception and Memory Unit – Institut Pasteur

The process of aging is often related to the onset of cognitive decline, depression and memory loss. Scientists from the Institut Pasteur, CNRS and Inserm have discovered that administration of the GDF11 protein, which is known to regenerate murine neural stem cells, improves cognitive abilities and reduces the depressive state in aged mice. They also demonstrated the mechanism of action of this protein in different mouse models. The scientists then investigated these results further in relation to depression, and showed that in humans, the levels of GDF11 are inversely related to depressive episodes. The results of this study were published in the journal Nature Aging on February 2, 2023.

The process of aging is often related to the onset of neurological symptoms such as cognitive decline, memory loss or mood disorders such as depression. Previous studies have shown that the growth factor GDF11, a protein found in blood, has a beneficial effect on olfactory perception and on the generation of new cells in the brains of aged mice. The mechanism of action of GDF11 in the brain remained unknown.

Researchers from the Institut Pasteur, CNRS and Inserm have discovered that long-term administration of the GDF11 protein to aged mice improves their memory and significantly reduces behavioral disturbances related to depression, allowing them to return to a behavior similar to that seen in younger mice.

The scientists conducted further studies in different aged mouse models or mouse models with depression-like behavioral disorders and in vitro neuronal cultures, which enabled them to identify the molecular mechanism of action of GDF11. They discovered that administration of GDF11 activates the natural process of intracellular cleaning, called “autophagy”, in the brain and the elimination of senescent cells. The GDF11 protein thus indirectly increases cell turnover in the hippocampus and restores neuronal activity.

To better understand the link between depressive disorders and the GDF11 protein in humans, scientists from the Institut Pasteur, CNRS and Inserm, in collaboration with scientists from McMaster University, quantified the protein in the blood serum of an international cohort of young patients with major depressive disorder. They observed that GDF11 levels are significantly lower in these patients. Moreover, by measuring the levels of this protein at different stages, the scientists observed a fluctuation in the level depending on the depressive state.

“This work provides clinical evidence linking low blood levels of GDF11 to mood disorders in patients with depression,” said Lida Katsimpardi, a researcher in the Institut Pasteur’s Perception and Memory Unit, affiliated with Inserm at the Institut Necker-Enfants Malades, and co-last author of the study. “In the future, this molecule could be used as a biomarker to diagnose depressive episodes. It could also serve as a therapeutic molecule for the treatment of cognitive and affective disorders,” she concludes.

A Bacterium to Protect the Microbiota from the Harmful Effect of Food Additives

Posted on January 16, 2023January 27, 2023 by Graziella Cara

Section showing the interaction of the microbiota and the intestinal epithelium in the colon. In blue, the mucus secreted by the intestinal epithelium in protection against the microbiota. In pink, the epithelial cell nuclei. © Noëmie Daniel/Inserm

Emulsifiers are food additives that are used to improve texture and extend shelf life. They are found in many processed products (ice cream, packaged cakes, sauces, etc.) despite having demonstrated harmful effects on intestinal balance. In a new study, scientists from Inserm, CNRS and Université Paris Cité at Institut Cochin in Paris sought to counteract these effects by using Akkermansia muciniphila, a bacterium naturally present in the intestine, to repopulate and thus strengthen the intestinal epithelium. The addition of this bacterium to the gut microbiota is thought to prevent the damage caused by the consumption of emulsifiers. These data, published in Gut, confirm the growing potential of Akkermansia muciniphila as a probiotic.

Emulsifiers are consumed by millions of people every day and are among the most widely used additives in the food industry. Something that is not surprising given that they improve the texture of foods and extend their shelf life. For example, emulsifiers such as lecithin and polysorbates ensure the smooth texture of mass-produced ice cream and prevent it from melting too quickly once served.

Previous studies by the team of Benoît Chassaing, Inserm researcher at Institut Cochin (Inserm/CNRS/Université Paris Cité), have shown the consumption of certain emulsifiers to lead to alterations of the gut microbiota [1] and how it interacts with the digestive system. Such alterations lead to chronic gut inflammation and metabolic dysregulation. More specifically, this research has shown the consumption of food emulsifiers to induce the ability of certain elements of the microbiota to come into close contact with the epithelium, which is the first line of defense of the digestive tract and usually sterile.

In this new study, the researchers wanted to counteract the harmful effects caused by the consumption of emulsifiers by reinforcing the intestinal epithelium. To do this, they focused more specifically on the bacterium Akkermansia muciniphila, which, being naturally present in the intestine has already been shown to have an impact on the interactions of the microbiota with the rest of the body.

It is also known that the quantity of this bacterium is reduced when emulsifiers are consumed.

In the study, groups of mice were fed emulsifying agents as part of their diet, which for some of them was supplemented with a daily dose of Akkermansia muciniphila. The scientists saw that while the consumption of food emulsifiers was sufficient to induce the chronic inflammation associated with metabolic alterations and high blood glucose, the mice receiving Akkermansia muciniphila were totally protected against such effects. The administration of Akkermansia muciniphila was also sufficient in preventing all molecular alterations normally induced by the consumption of emulsifying agents, including the encroachment of bacteria into the wall of the epithelium.

“This research supports the notion that using Akkermansia muciniphila as a probiotic could be an approach to maintaining metabolic and intestinal health in the face of modern stressors such as emulsifiers that promote chronic gut inflammation, and the resulting harmful consequences. Furthermore, this suggests that colonization of the intestine with Akkermansia muciniphila could be predictive of individual propensity to develop intestinal and metabolic disorders following the consumption of emulsifiers: the greater the presence of the bacterium, the more likely the individual is protected from the harmful effects of food additives on the microbiota,” explains Chassaing, the last author of the study.

[1] All of the microorganisms – non-pathogenic (commensal) bacteria, viruses, parasites, and fungi – that live in the intestine.

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Category: Biologie cellulaire, développement et évolution