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Le stress oxydatif est impliqué dans l’expression du récepteur B1 des kinines (RB1) dans différents modèles de diabète et d'hypertension. Puisque l'angiotensine II (Ang II) et l'endothéline-1 (ET-1) sont des peptides prooxydants impliqués dans les maladies cardiovasculaires, leur contribution dans l'augmentation de l'expression du RB1 a été étudiée dans des cellules musculaires lisses vasculaires (CMLV). Le QRT-PCR et l’immunobuvardage de type Western ont été utilisés pour mesurer l’expression du RB1 dans des CMLV dérivées de la lignée A10 et de l’aorte de rats Sprague-Dawley. Cette étude montre que l’Ang II augmente l’expression du RB1 (ARNm et protéine) en fonction de la concentration et du temps (maximum 1 μM entre 3-6 h). Cette augmentation implique le récepteur AT1, la PI3K et le NF-κB, mais non le récepteur AT2 et ERK1/2. Aussi, le récepteur ETA de l’ET-1 est impliqué dans la réponse à l’Ang II à 6-8 h et non à 1-4 h. Par contre, l’ET-1 augmente l’expression du RB1 (maximum 2-4 h) via la stimulation des récepteurs ETA et ETB. L’augmentation du RB1 causée par l’Ang II et l’ET-1 est bloquée par les antioxydants (N-acétyl-cystéine et diphénylèneiodonium). Ces résultats suggèrent que l’Ang II induit le RB1 dans les CMLV par le récepteur AT1 dans la première phase, et par la libération d’ET-1 (majoritairement par ETA) dans la phase tardive, via le stress oxydatif et l’activation de la PI3K et du NF-κB. Ces résultats précisent le mécanisme impliqué dans la surexpression du RB1 ayant des effets néfastes dans le diabète et l'hypertension. / Oxidative stress is involved in the overexpression of kinin B1 receptor (B1R) in various models of diabetes and hypertension. Since angiotensin II (Ang II) and endothelin-1 (ET-1) are pro-oxidative peptides involved in cardiovascular diseases, their contribution in increasing the expression of B1R was examined in vascular smooth muscle cells (VSMC). QRT-PCR and Western blot analysis were used to measure the expression of B1R in VSMC derived from A10 cell line and the aorta of Sprague-Dawley rats. This study shows that Ang II increases the expression of B1R (mRNA and protein) in a concentration- and time-dependent manner (maximum 1 μM between 3-6 h). This increase involves AT1 receptor, PI3K and NF-κB, but not AT2 receptor and ERK1/2. Moreover, ETA receptor is involved in the effect of Ang II at 6-8 h but not at 1-4 h. However, ET-1 increases expression of B1R (maximum 2-4 h) via stimulation of ETA and ETB receptors. Ang II and ET-1-induced increase expression of B1R is blocked by antioxidants (N-acetyl-L-cysteine and diphenyleneiodonium). These results suggest that Ang II induces B1R in VSMC by AT1 receptor in the first phase and by releasing ET-1 (predominantly by ETA receptor) in the late phase, via oxidative stress and activation of PI3K and NF-κB. These results clarify the mechanism involved in the overexpression of B1R which has adverse effects in diabetes and hypertension.

Le laboratoire a identifié récemment la protéine DDB2 comme ayant une activité dans la régulation de l’expression de gènes cibles tels que SOD2, BCL2 et NFKBIA, conférant ainsi à cette protéine un rôle dans le contrôle de la progression métastatique et dans la réponse thérapeutique des cellules tumorales mammaires. Cependant, l’activité réelle de DDB2 dans la transcription génique reste à définir, car sa structure ne permet pas d’expliquer son influence sur l’expression de ses gènes cibles. Cette activité peut être soit inhibitrice comme pour SOD2 et BCL2, soit activatrice comme NFKBIA qui code la protéine IκBα, suggérant que DDB2 doit s’associer avec des inhibiteurs ou des activateurs de la transcription génique, ou en favoriser le recrutement. Afin d’identifier ces partenaires potentiels, susceptibles de participer à son activité transcriptionnelle, nous avons développé une approche de « DNA pull-down », couplée à une analyse protéomique globale par spectrométrie de masse à partir des cellules tumorales mammaires MCF-7 surexprimant naturellement DDB2. Nous avons révélé la présence du complexe UV-DDB (DDB2, DDB1 et Cul4A) sur le promoteur des gènes SOD2 et NFKBIA. Nous avons également mis en évidence que ce complexe, connu pour participer aux premières étapes de la réparation de l’ADN lésé par des rayonnements UV, favorise le recrutement de l’histone acétyl transférase p300 sur le promoteur du gène NFKBIA, expliquant en partie le rôle activateur de DDB2 sur ce gène cible. Notre analyse protéomique à révéler, avec un score élevé, la présence des protéines hnRNP K et J sur le promoteur du gène NFKBIA et d’une manière indépendante de toute interaction physique avec DDB2. La forme J, très peu décrite, présente une affinité plus grande pour le promoteur du gène NFKBIA que la forme K. De plus, nous l’avons observée strictement nucléaire et liée à la chromatine. De manière intéressante, nous montrons que la forme J est surexprimée dans le noyau des cellules tumorales MDA-MB231 métastatiques, comparativement aux cellules T47D non métastatiques. Par la suite, nous avons évalué l’importance des hnRNP K et J dans la transcription du gène NFKBIA par rapport à DDB2 et un régulateur bien décrit tel que le facteur de transcription Sp1. Nos résultats indiquent que les protéines hnRNP K et J, lorsqu’elles sont surexprimées, jouent un rôle de répresseur du gène NFKBIA et ce même en présence des activateurs DDB2 et Sp1. L’ensemble de ce travail a contribué à montrer la présence de protéines, pouvant participer à l’activité transcriptionnelle de DDB2, telles que le complexe UV-DDB et p300. En dehors de tout partenariat avec DDB2, il a été mis en évidence une relation entre les hnRNP K et J et l’activité constitutive de NF-κB, en particulier avec la forme J, qui, par son expression corrélée à l’agressivité des cellules tumorales mammaires, présente un intérêt clinique potentiel en tant que marqueur prédictif de la progression métastatique, tout comme DDB2 / The laboratory has recently identified the DDB2 (Damaged-DNA Binding 2) protein as a regulator of target gene expression like SOD2, BCL2 and NFKBIA, thus conferring to this protein a role in control of metastatic progression and therapeutic response of breast cancer cells. However, the real activity of DDB2 in gene transcription remains to be defined because its structure cannot entirely explain its influence on target gene expression. This protein can act either as an inhibitor like for the SOD2 and BCL2 genes or as an enhancer like for the NFKBIA gene, encoding IκBα protein. This suggests that DDB2 must associate with, or promote recruitment, of inhibitors or activators of gene transcription. In order to search and identify potential partners that could participate in its transcriptional activity, we developed a “DNA pull-down” approach associated with a global proteomic analysis by mass spectrometry from MCF-7 breast cancer cells overexpressing naturally DDB2. With this approach, we reveal the presence of the UV-DDB complex composed by DDB2, DDB1 and Cullin 4A proteins on the SOD2 and NFKBIA gene promoters. We also highlighted that this complex, known for its role in first steps of UV-induced DNA lesion repair, promotes the recruitment of the p300 histone acetyl transferase on the NFKBIA gene promoter, which may explain, in part, the enhancer activity of DDB2 on this target gene. The proteomic analysis from the “DNA pull-down” also reveals, with originality, the presence of heterogeneous ribonucleoproteins K and J (hnRNP K and J) on the NFKBIA gene promoter with a high recovery score among many other proteins and independently of any physical interaction with DDB2. The J form, very poorly described, shows a higher affinity for NFKBIA gene promoter than the K form. Furthermore, we observed that the J form is strictly nuclear and mostly bound to chromatin, while the K form is also found in cytoplasm. Interestingly, we show that the J form is overexpressed in nucleus of metastatic breast cancer MDA-MB231 cells by comparison with non-metastatic breast cancer T47D cells. Then, we evaluated the importance of hnRNP K and J proteins in NFKBIA gene transcription compared with DDB2 and with a well-known regulator, the Sp1 transcription factor. Our results show that hnRNP K and J proteins, when they are overexpressed, play a repressor role on NFKBIA gene expression by binding on its promoter even in presence of DDB2 and Sp1 activators. Taken together, these data show that some proteins could participate in DDB2 transcriptional activity, like the UV-DDB complex and the p300 protein. Outside of any interaction with DDB2, this work highlights a relationship between the hnRNP K and J proteins, and NF-κB constitutive activity, especially with the J form. This latter has an expression correlated with aggressiveness of breast cancer cells and a potential clinical interest as a predictive marker of metastatic progression, like DDB2

Le stress oxydatif est impliqué dans l’expression du récepteur B1 des kinines (RB1) dans différents modèles de diabète et d'hypertension. Puisque l'angiotensine II (Ang II) et l'endothéline-1 (ET-1) sont des peptides prooxydants impliqués dans les maladies cardiovasculaires, leur contribution dans l'augmentation de l'expression du RB1 a été étudiée dans des cellules musculaires lisses vasculaires (CMLV). Le QRT-PCR et l’immunobuvardage de type Western ont été utilisés pour mesurer l’expression du RB1 dans des CMLV dérivées de la lignée A10 et de l’aorte de rats Sprague-Dawley. Cette étude montre que l’Ang II augmente l’expression du RB1 (ARNm et protéine) en fonction de la concentration et du temps (maximum 1 μM entre 3-6 h). Cette augmentation implique le récepteur AT1, la PI3K et le NF-κB, mais non le récepteur AT2 et ERK1/2. Aussi, le récepteur ETA de l’ET-1 est impliqué dans la réponse à l’Ang II à 6-8 h et non à 1-4 h. Par contre, l’ET-1 augmente l’expression du RB1 (maximum 2-4 h) via la stimulation des récepteurs ETA et ETB. L’augmentation du RB1 causée par l’Ang II et l’ET-1 est bloquée par les antioxydants (N-acétyl-cystéine et diphénylèneiodonium). Ces résultats suggèrent que l’Ang II induit le RB1 dans les CMLV par le récepteur AT1 dans la première phase, et par la libération d’ET-1 (majoritairement par ETA) dans la phase tardive, via le stress oxydatif et l’activation de la PI3K et du NF-κB. Ces résultats précisent le mécanisme impliqué dans la surexpression du RB1 ayant des effets néfastes dans le diabète et l'hypertension. / Oxidative stress is involved in the overexpression of kinin B1 receptor (B1R) in various models of diabetes and hypertension. Since angiotensin II (Ang II) and endothelin-1 (ET-1) are pro-oxidative peptides involved in cardiovascular diseases, their contribution in increasing the expression of B1R was examined in vascular smooth muscle cells (VSMC). QRT-PCR and Western blot analysis were used to measure the expression of B1R in VSMC derived from A10 cell line and the aorta of Sprague-Dawley rats. This study shows that Ang II increases the expression of B1R (mRNA and protein) in a concentration- and time-dependent manner (maximum 1 μM between 3-6 h). This increase involves AT1 receptor, PI3K and NF-κB, but not AT2 receptor and ERK1/2. Moreover, ETA receptor is involved in the effect of Ang II at 6-8 h but not at 1-4 h. However, ET-1 increases expression of B1R (maximum 2-4 h) via stimulation of ETA and ETB receptors. Ang II and ET-1-induced increase expression of B1R is blocked by antioxidants (N-acetyl-L-cysteine and diphenyleneiodonium). These results suggest that Ang II induces B1R in VSMC by AT1 receptor in the first phase and by releasing ET-1 (predominantly by ETA receptor) in the late phase, via oxidative stress and activation of PI3K and NF-κB. These results clarify the mechanism involved in the overexpression of B1R which has adverse effects in diabetes and hypertension.

First identified over a decade ago, Astrocyte Elevated Gene-1 (AEG-1) has been studied extensively due to early reports of its overexpression in various cancer cell lines. Research groups all over the globe including our own have since identified AEG-1 overexpression in cancers of diverse lineages including cancers of the liver, colon, skin, prostate, breast, lung, esophagus, neurons and neuronal glia as compared to matched normal tissue. A comprehensive and convincing body of data currently points to AEG-1 as an essential component, critical to the progression and perhaps onset of cancer. AEG-1 is a potent activator of multiple pro-tumorigenic signal transduction pathways such as mitogen-activated protein extracellular kinase (MEK)/ extracellular signal-regulated kinase (ERK), phosphotidyl-inositol-3-kinase (PI3K)/Akt/mTOR, NF-κB and Wnt/β-catenin pathway. In addition, studies show that AEG-1 not only alters global gene and protein expression profiles, it also modulates fundamental intracellular processes, such as transcription, translation and RNA interference in cancer cells most likely by functioning as a scaffold protein. The mechanisms by which AEG-1 is overexpressed in cancer have been studied extensively and it is clear that multiple layers of regulation including genomic amplification, transcriptional, posttranscriptional, and posttranslational controls are involved however; the mechanism by which AEG 1 itself induces its oncogenic effects is still poorly understood. Just as questions remain about the exact role of AEG-1 in carcinogenesis, very little is known about the role of AEG-1 in regulating normal physiological functions in the liver. With the help of the Massey Cancer Center Transgenic/Knockout Mouse Core, our lab has successfully created a germline-AEG-1 knockout mouse (AEG-1-/-) as a model to interrogate AEG-1 function in vivo. Here I present the insights gained from efforts to analyze this novel AEG-1-/- mouse model. Aspects of the physiological functions of AEG-1 will be covered in chapter two wherein details of the characterization of the AEG-1-/- mouse are described including the role of AEG-1 in lipid metabolism. Chapter three discusses novel discoveries about the specific role of AEG-1 in mediating hepatocarcinogenesis by modulating NF-κB, a critical inflammatory pathway. First identified over a decade ago, Astrocyte Elevated Gene-1 (AEG-1) has been studied extensively due to early reports of its overexpression in various cancer cell lines. Research groups all over the globe including our own have since identified AEG-1 overexpression in cancers of diverse lineages including cancers of the liver, colon, skin, prostate, breast, lung, esophagus, neurons and neuronal glia as compared to matched normal tissue. A comprehensive and convincing body of data currently points to AEG-1 as an essential component, critical to the progression and perhaps onset of cancer. AEG-1 is a potent activator of multiple pro-tumorigenic signal transduction pathways such as mitogen-activated protein extracellular kinase (MEK)/ extracellular signal-regulated kinase (ERK), phosphotidyl-inositol-3-kinase (PI3K)/Akt/mTOR, NF-κB and Wnt/β-catenin pathway. In addition, studies show that AEG-1 not only alters global gene and protein expression profiles, it also modulates fundamental intracellular processes, such as transcription, translation and RNA interference in cancer cells most likely by functioning as a scaffold protein. The mechanisms by which AEG-1 is overexpressed in cancer have been studied extensively and it is clear that multiple layers of regulation including genomic amplification, transcriptional, posttranscriptional, and posttranslational controls are involved however; the mechanism by which AEG 1 itself induces its oncogenic effects is still poorly understood. Just as questions remain about the exact role of AEG-1 in carcinogenesis, very little is known about the role of AEG-1 in regulating normal physiological functions in the liver. With the help of the Massey Cancer Center Transgenic/Knockout Mouse Core, our lab has successfully created a germline-AEG-1 knockout mouse (AEG-1-/-) as a model to interrogate AEG-1 function in vivo. Here I present the insights gained from efforts to analyze this novel AEG-1-/- mouse model. Aspects of the physiological functions of AEG-1 will be covered in chapter two wherein details of the characterization of the AEG-1-/- mouse are described including the role of AEG-1 in lipid metabolism. Chapter three discusses novel discoveries about the specific role of AEG-1 in mediating hepatocarcinogenesis by modulating NF-κB, a critical inflammatory pathway.

L’évolution d’une cellule tumorale initiée à une tumeur solide nécessite, à chaque étape, un microenvironnement favorable à sa survie et à sa croissance. Le microenvironnement tumoral est comparé à un foyer d’inflammation chronique dont la composition cellulaire et moléculaire est complexe. Les cellules souches mésenchymateuses (CSM) représentent l’un des principaux acteurs cellulaires présents. Elles migrent vers les sites tumoraux où elles soutiennent l’inflammation, l’angiogenèse et le développement tumoral en activant plusieurs voies de signalisation. Une des voies majeures qui contribuent à l’inflammation est la voie de signalisation NF-B. L’initiation de cette voie provient de la membrane cellulaire entre autres des cavéoles. Nous soumettons l’hypothèse que l’une des cavines, protéines associées aux cavéoles, modulerait le phénotype inflammatoire etou migratoire dans les CSM traitées à la cytokine TNF- (facteur de nécrose tumorale ) en modulant la voie de signalisation NF-B. En effet, nous avons observé une régulation à la hausse de l’expression de la COX-2 (cyclooxygénase-2) et une diminution de l’expression d’IκB qui sont synonymes de l’activation de la voie NF-B dans les CSM que nous avons traitées au TNF-. Nous avons trouvé que le TNF- induit la migration des CSM, et que la répression génique de la Cavine-2 augmente significativement la migration des CSM traitées par le TNF-. La répression génique de la Cavine-2 vient aussi amplifier la tubulogenèse dans les CSM en réponse au TNF-. D’un point de vue moléculaire, la répression génique de la Cavine-2 a montré une très forte amplification de l'expression protéique de la COX-2 dans les CSM en réponse au TNF-. Dans ces mêmes cellules où la Cavine-2 a été réprimée, et suite à un traitement au TNF-, le pic de phosphorylation est plus intense et la courbe de phosphorylation est plus prolongée dans le temps. Ces observations nous permettent d’affirmer que la Cavine-2 a un rôle répresseur sur l’expression de COX-2. Collectivement, nos résultats montrent que la Cavine-2 peut être proposée comme un gène suppresseur de tumeur et est de ce fait, une bonne cible thérapeutique dans les CSM qui permettraient d’agir à des stades précoces du développement tumoral. / The evolution of an initiated tumor cell into a solid tumor requires at each stage a favorable microenvironment for its survival and growth. The tumor microenvironment is compared to a chronic inflammation site with a cellular and molecular complex composition. Mesenchymal stem cells (MSC) have important roles in tumor microenvironment. They migrate to tumor sites where they maintain the inflammation, angiogenesis and tumor development by activating multiple signaling pathways. One of the major pathways that contribute to inflammation is the NF-B signaling pathway. The initiation of this pathway comes from the cell membrane and caveolae. Our hypothesis is that one of cavins, proteins associated to caveolae, modulates the inflammatory phenotype and migration in MSC treated with TNF-. We suggest that this process is modulated by a NF-B signaling pathway. Indeed, we observed an up-regulation of the expression of the cyclooxygenase-2 (COX-2) and a decrease in the expression of IκB which suggest that activation of the NF-B pathway is involved in the MSC treated with TNF. We found that the TNF- induced migration in the MSC, and the knockout of Cavin-2 significantly increased migration of MSC treated with TNF-. The silencing of Cavin-2 considerably increased tubulogenesis of MSC treated with TNF-. At the molecular level, knockout of Cavin-2 showed a very strong amplification of protein expression of COX-2 in the MSC in response to TNF-. In these same cells where Cavin-2 was repressed and treated with TNF-, the peak of phosphorylation of pIB is more intense and the phosphorylation curve is sustained in time. These observations allow us to assert that Cavin-2 has a repressing role on the expression of COX-2. Collectively, our results show that the gene encoding Cavin-2 can be proposed as tumor suppressor gene. This study allowed us to identify new therapeutic targets: Cavins proteins.

Actinobacillus actinomycetemcomitans is present in elevated proportions and numbers in dental bacterial biofilms of patients with localized aggressive periodontitis. This variant of periodontal disease, occurring in adolescents and young adults, is characterized by rapid and severe destruction of the connective tissues and bone supporting the teeth, eventually culminating in tooth loss. The cytolethal distending toxin (Cdt) is a newly discovered bacterial protein toxin, uniquely present in A. actinomycetemcomitans among all known to-date oral bacterial species. The Cdt has the capacity to inhibit mammalian cell growth, but its putative role in the pathogenesis of the disease is unclear. The aim of this in vitro work has been to study the effects of A. actinomycetemcomitans on periodontal connective tissue cell cultures, and to evaluate the possible involvement of its Cdt. A. actinomycetemcomitans inhibited the proliferation of gingival and periodontal ligament fibroblasts, as a result of a combined arrest at the G1 and G2/M phases of the cell cycle. This growth inhibition was non-lethal and the cells remained metabolically active, although their DNA synthesis was reduced. The intoxicated cells exhibited increased size and irregular structure, characterized by distension and elongation. This cellular enlargement occurred in both G1 and G2/M phase arrested cells. The Cdt of A. actinomycetemcomitans was responsible for the observed growth inhibition, as well as the concomitant morphological alterations. The possible induction of inflammatory cytokines related to bone resorption was investigated in response to A. actinomycetemcomitans, and the involvement of Cdt was evaluated. Extensive focus was given to the study of receptor activator of NF-κB ligand (RANKL) expression, a membrane-bound ligand that signals osteoclast progenitors to differentiate and fuse into mature osteoclasts, activating bone resorption. It was demonstrated that A. actinomycetemcomitans induced RANKL mRNA and protein expression in the cells studied, but did not affect the expression of its decoy receptor, osteoprotegerin. This induction was solely attributed to its Cdt, as demonstrated by the use of a cdt-knockout A. actinomycetemcomitans strain, purified recombinant Cdt, and antibodies blocking the Cdt. In addition, this event was not mediated by pro-inflammatory cytokines known to stimulate RANKL. Interleukin-6 mRNA and protein expression were also enhanced by A. actinomycetemcomitans, but Cdt had limited involvement in this enhancement. In conclusion, two distinct mechanisms by which A. actinomycetemcomitans Cdt may be involved in the pathogenesis of localized aggressive periodontitis are proposed. Firstly, the growth arrest of the resident fibroblasts may impair the physiological connective tissue remodelling equilibrium and lead to connective tissue attachment loss. Secondly, the induction of RANKL by these cells, residing in the proximity of the alveolar bone, may locally stimulate osteoclastogenesis and promote alveolar bone resorption. This work also provides further insights to the understanding of Cdt mechanisms of action, contributing to the global characterization of the toxin’s virulence.

L’arthrose ou ostéoarthrose (OA) est l’affection rhumatologique la plus fréquente au monde. Elle est caractérisée principalement par une perte du cartilage articulaire et l’inflammation de la membrane synoviale. L’interleukine (IL)-1ß, une cytokine pro-inflammatoire, joue un rôle très important dans la pathogenèse de l’OA. Elle exerce son action en induisant l’expression des enzymes cyclo-oxygénase 2 (COX-2), prostaglandine E synthétase microsomale 1 (mPGES-1) et l’oxyde nitrique synthétase inductible (iNOS) ainsi que la production de la prostaglandine E2 (PGE2) et de l’oxyde nitrique (NO). Ces derniers (PGE2 et NO) contribuent à la synovite et la destruction du cartilage articulaire par leurs effets pro-inflammatoires, pro-cataboliques, anti-anaboliques, pro-angiogéniques et pro-apoptotiques. Les modifications épigénétiques, telles que la méthylation de l’ADN, et l’acétylation et la méthylation des histones, jouent un rôle crucial dans la régulation de l’expression des gènes. Parmi ces modifications, l’acétylation des histones est la plus documentée. Ce processus est contrôlé par deux types d’enzymes : les histones acétyltransférases (HAT) qui favorisent la transcription et les histones déacétylases (HDAC) qui l’inhibent. L’objectif de ce travail est d’examiner le rôle des enzymes HDAC dans la régulation de l’expression de la COX-2, mPGES-1 et iNOS. Nous avons montré qu’au niveau des chondrocytes, les inhibiteurs des HDAC (iHDAC), trichostatine A (TSA) et butyrate de sodium (NaBu), suppriment l’expression de la COX-2 et iNOS au niveau de l’ARNm et protéique, ainsi que la production de la PGE2 et du NO, induites par l’IL-1ß. L’effet inhibiteur à lieu sans affecter l’activité de liaison à l’ADN du facteur de transcription NF-κB (nuclear factor κ B). La TSA et le NaBu inhibent également la dégradation induite par l’IL-1ß des protéoglycanes au niveau du cartilage. Nous avons également montré, qu’au niveau des fibroblastes synoviaux, les iHDAC, TSA, NaBu et acide valproïque (VA), suppriment l’expression de la mPGES-1 ainsi que la production de la PGE2 induites par l’IL-1ß. En utilisant diverses approches expérimentales, nous avons montré que HDAC4 est impliquée dans l’induction de l’expression de la mPGES-1 par l’IL-1ß. HDAC4 exerce son action, via son activité déacétylase, en augmentant l’activité transcriptionnelle de Egr-1 (early growth factor 1), facteur de transcription principal de l’expression de la mPGES-1. L’ensemble de ces résultats suggère que les inhibiteurs des HDAC pourraient être utilisés dans le traitement de l’OA. / Osteoarthritis (OA) is the most common form of arthritic diseases in the world. It is primarily characterized by the loss of articular cartilage and inflammation of the synovial membrane. Interleukin (IL)-1ß is a pro-inflammatory cytokine that plays a major role in the pathogenesis of OA. It induces the expression of cyclo-oxygenase 2 (COX-2), microsomal prostaglandin E synthase-1 (mPGES-1), inducible nitric oxide synthase (iNOS), as well as the production of prostaglandin E2 (PGE2) and nitric oxide (NO). The later (PGE2 and NO) contribute to articular cartilage destruction and synovitis through their pro-inflammatory, pro-catabolic, anti-anabolic, pro-angiogenic and pro-apoptotic effects. Epigenetic modifications such as DNA methylation, histone acetylation and methylation play a crucial role in gene expression. Among these modifications, histone acetylation is the most studied. Histone acetylation is determined by two types of enzymes: histone acetyltransferases (HAT) and histone deacetylases (HDAC) which activate and repress transcription, respectively. The purpose of these studies is to examine the role of HDAC enzymes in the regulation of COX-2, mPGES-1, and iNOS expression. We demonstrated that HDAC inhibitors (HDACi), trichostatin A (TSA) and sodium butyrate (NaBu), suppressed the Il-1ß-induced transcription and translation of COX-2 and iNOS, as well as the production of PGE2 and NO in chondrocytes. The inhibitory effect of HDACi on transcription does not affect the binding activity of NF-κB (nuclear factor κ B) to DNA. Treatment with TSA and NaBu also inhibited the Il-1ß-induced degradation of proteoglycan in cartilage explants. We also showed that HDACi, TSA, NaBu and valproic acid (VA), suppressed IL-1-induced-mPGES-1 expression and the production of PGE2 in synovial fibroblasts. Our data indicated that HDAC4 is involved in Il-1ß-induced expression of mPGES-1. HDAC4, through its deacetylase activity, up-regulated the transcriptional activity of Egr-1 (early growth factor-1), a principal transcription factor for the expression of mPGES-1. From our studies we propose that HDAC inhibitors can be used in the treatment of OA.

No description available.

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