PGE2 plays an important role in liver inflammation and carcinogenesis. Its metabolism is regulated by a cascade of reactions catalyzed by enzymes including COX-1/2, mPGES-1/2, 15-PGDH. Among these regulators, mPGES-1 is a cytokine-inducible enzyme mainly responsible for catalyzing terminal synthesis of PGE2, 15-PGDH catalyzes the oxidation of PGE2 to 15-keto-PGE2. In this context, we exogenously expressed mPGES-1 or 15-PGDH genes in mice hepatocytes to constitute a physiological condition ideal for evaluating PGE2 and its metabolites function in liver pathogenesis. In the first part, we developed transgenic mice with targeted expression of mPGES-1 in the liver and assessed the response of the transgenic mice to Fas-induced hepatocyte apoptosis and acute liver injury. Compared to wild type mice, the mPGES-1 Tg mice showed less liver hemorrhage, lower serum alanine transaminase and aspartate transaminase levels, less hepatic necrosis/apoptosis, and lower levels of caspase activation after intraperitoneal injection of the anti-Fas antibody Jo2. Western blotting analyses revealed increased expression and activation of the serine/threonine kinase Akt and associated anti-apoptotic molecules in the liver tissues of Jo2-treated mPGES-1 Tg mice. Pretreatment with the mPGES-1 inhibitor (MF63) or the Akt inhibitor (Akt inhibitor V) restored the susceptibility of the mPGES-1 Tg mice to Fas-induced liver injury. Our findings provide novel evidence that mPGES-1 prevents Fas-induced liver injury through activation of Akt and related signaling. This finding is consistent with previous reports of the anti-apoptotic and pro-proliferative role of PGE2. Our results suggest that induction of mPGES-1 or treatment with PGE2 may represent a potential therapeutic strategy for the prevention and treatment of Fas-associated liver injuries. In the second part, we generated transgenic mice with targeted expression of 15-PGDH in the liver and the animals were subjected to LPS/GalN-induced acute liver inflammation and injury. Compared to the wild type mice, the 15-PGDH Tg mice showed lower levels of alanine aminotransferase and aspartate aminotransferase, less liver tissue damage, less hepatic apoptosis/necrosis, less macrophage activation, and lower inflammatory cytokine production. In Kupffer cell cultures, treatment with 15-keto-PGE2 or the conditioned medium (CM) from 15-PGDH Tg hepatocyes inhibited LPS-induced cytokine production. Both 15-keto-PGE2 and the CM from15-PGDH Tg hepatocyes also up-regulated the expression of PPAR-γ downstream genes in Kupffer cells. In cultured hepatocytes, 15-keto-PGE2 treatment or 15-PGDH overexpression did not influence TNF-α-induced hepatocyte apoptosis. These findings suggest that 15-PGDH protects against LPS/GalN-induced liver injury and the effect is mediated via 15-keto-PGE2, which activates PPAR-γ in Kupffer cells and thus inhibits their ability to produce inflammatory cytokines. Accordingly, we observed that the PPAR-γ antagonist, GW9662, reversed the effect of 15-keto-PGE2 in Kupffer cell in vitro and restored the susceptibility of 15-PGDH Tg mice to LPS/GalN-induced acute liver injury in vivo. Our findings not only support the pro-inflammatory role of PGE2, but also reveal a novel anti-inflammatory role of 15-keto-PGE2. The data suggest that induction of 15-PGDH expression or utilization of a 15-keto-PGE2 analog may be therapeutic for treatment of endotoxin-associated liver inflammation/injury. Consistent with a pro-carcinogenic role for PGE2, overexpression mPGES-1 enhances growth of either HCC or cholangiocarcinoma cells, while overexpression 15-PGDH inhibits tumor cell growth in vitro. In the third part, we use a pharmacological method to induce 15-PGDH in cholangiocarcinoma tumor cells to inhibit PGE2 production. Our results indicated that treatment of human cholangiocarcinoma cells (CCLP1 and TFK-1) with ω-3 PUFA (DHA) or transfection of these cells with the Fat-1 gene (encoding Caenorhabditis elegans desaturase which converts ω-6 PUFA to ω-3 PUFA) significantly increased 15-PGDH protein level in cholangiocarcinoma cell lines. Human cholangiocarcinoma cells treated with DHA or transfected with a Fat-1 expression vector showed reduction of miRNA26a and miRNA26b (both miRNAs target 15-PGDH mRNA thus inhibiting 15-PGDH translation). Consistent with these findings, we observed that overexpression of miR26a or miR26b decreased 15-PGDH protein, reversed ω-3 PUFA-induced accumulation of 15-PGDH protein, and prevented ω-3 PUFA-induced inhibition of cholangiocarcinoma cell growth. Knockdown of 15-PGDH also attenuated ω-3 PUFA-induced inhibition of tumor cell growth. We observed that ω-3 PUFA suppressed miRNA26a and miRNA26b by inhibiting c-myc, a transcription factor that co-regulates a gene cluster comprised of miR-26a/b and carboxy-terminal domain RNA polymerase II polypeptide A small phosphatases (CTDSPs). Accordingly, overexpression of c-myc enhanced the expression of miRNA26a/b and prevented ω-3 PUFA-induced inhibition of tumor cell growth. Taken together, our results support a pro-tumorigenic role for PGE2, and suggest induction of 15-PGDH as potential way for the prevention and treatment of human cholangiocarcinoma. / 1 / LU YAO

Ever since the advent of computer-aided drug design (CADD), in silico simulation methods have greatly accelerated the drug discovery process and lead to the discovery of numerous drug candidates. With the exponential growth of computational power, we nowadays simulate biologic systems at a scale unimaginable a decade ago and thus provides perspectives for drug design. In this dissertation research, combining in silico simulation methods like molecular docking and molecular dynamics (MD) simulation with organic synthesis, in vitro/in vivo experiments and clinical data mining, we developed new drug discovery strategies. These strategies were applied in our drug discovery projects and led to the discovery of inhibitors of microsomal prostaglandin E2 synthase 1 (mPGES-1) and butyrylcholinesterase (BChE) as potential drug candidates. Protein mPGES-1 is known as an ideal target for next generation of anti-inflammatory drugs without the side-effects of currently available anti-inflammatory drugs. Unfortunately, almost all the previously reported human mPGES-1 inhibitors are inactive (or possess very low activity) against mouse or rat mPGES-1 that prevents using well-established mouse/rat models of inflammation, pain, and other diseases for preclinical studies. It would be extremely challenging for the mPGES-1-based drug development to follow traditional drug discovery and development route. In order to solve this problem, we developed and applied Drug Repurposing Effort Applying Integrated Modeling-in vitro/vivo-Clinical Data Mining (DREAM-in-CDM) strategy in this project. With molecular dynamics simulation, we observed the process of how mPGES-1 adopts an alternative conformation to control the access of co-factor GSH (glutathione) and its impact on the function of the protein. Based on the simulation results, we not only found an explanation for the difference between the X-ray and CryoEM (cryogenic electron microscopy) structure of mPGES-1 but also used molecular docking method to identify FDA approved drug, lapatinib, as an mPGES-1 inhibitor by virtual screening and the subsequent in vitro experiments. By mining the available clinical trial data, we found solid evidence that lapatinib can be used to relieve various types of pain in cancer patients. Since lapatinib is very well tolerated, we expect lapatinib to be repurposed as a new treatment for cancer-related pain. BChE has been identified as an ideal drug target for the treatment of Alzheimer’s disease (AD) and heroin overdose. The selectivity of a therapeutically useful inhibitor for BChE over AChE is very important. Unfortunately, there is no good selective BChE inhibitor. With a robust and virtual screening strategy combining with in vitro experiments, we identified a series of compounds from the NCI compound depository as BChE inhibitors with novel scaffolds, high activity and selectivity at the same time. The most potent compound was re-synthesized and the enantiomers of the compound were separated for the first time. The binding mode of the most potent compound was also analyzed and the origin of its high activity and selectivity was revealed that will guide the development of BChE selective inhibitors in the future. In addition, a new tacrine-based BChE affinity chromatography resin was developed. The developed new resin has enabled us to more conveniently and efficiently purify the BChE proteins with improved high purity. In general, we have successfully developed new drug discovery strategies to identify novel inhibitors of different enzymes. With these newly developed strategies, we expect additional drug discoveries to be made in the foreseeable future.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) are currently widely used as fever and pain relief in patients with arthritis and other inflammatory symptoms. NSAIDs effect by inhibiting cyclooxygenase-1 (COX-1) and/or cyclooxygenase-2 (COX-2). COX isozymes (COXs) are key enzymes in the biosynthesis of prostaglandin H2 (PGH2) from arachidonic acid (AA). It is now clear that prostaglandin E2 (PGE2), one of the downstream products of PGH2, is the main mediator in both chronic and acute inflammation. Microsomal prostaglandin E synthase (mPGES-1) is the terminal enzyme of COX-2 in the PGE2 biosynthesis pathway. Different from other two constitutively expressed PGE2 synthase (PGES), mPGES-2 and cPGES, mPGES-1 is induced by pro-inflammatory stimuli and responsible for the production of PGE2 related to inflammation, fever and pain. For these reasons, selective inhibition of mPGES-1 is expected to suppress inflammation induced PGE2 production and, therefore, will exert anti-inflammatory activity while avoid the side effects of COXs inhibitors, such as gastrointestinal (GI) toxicity, and cardiovascular events. A combination of computational and experimental approaches was used to discovery mPGES-1 inhibitors with new scaffolds. The methods used include molecular docking, molecular dynamic simulation, molecular mechanics-Poisson-Boltzmann surface area (MM-PBSA) binding free energy calculation, and in vitro activity assays. Our large-scale structure-based virtual screening was performed on compounds in the NCI libraries, containing a total of ~260,000 compounds. 7 compounds have been determined for their IC50 values (about 300 nM to 8000 nM). What’s more, these new inhibitors of mPGES-1 identified from virtual screening did not shown significant inhibition against COX isozymes even at substantially high concentrations (e.g. 100 µM). Rational methodology for drug design and organic synthesis were applied to generate three series of mPGES-1 inhibitors with different scaffolds. In total, about 200 compounds were synthesized and tested for their in vitro inhibition against human mPGES-1. Compounds with high potency against human mPGES-1 were further screened for their inhibition against mouse mPGES-1 and selectivity of human mPGES-1 over COXs. Several compounds were identified as submicromolar inhibitors against human mPGES-1 with high selectivity over COXs. In general, we have successfully identified a library of compounds as potent mPGES-1 inhibitors without significant inhibition against COXs. Structure information and in vitro activity evaluation data generated from the virtual screening and the library of compounds will be used to guide future design and synthesis of the mPGES-1 inhibitors.

La sclérodermie (sclérose systémique, ScS) est une maladie auto-immune du tissu conjonctif caractérisée  par  l’épaississement  de  la  peau,  l’apparition  spontanée de lésions cicatricielles, des maladies   des   vaisseaux   sanguins,   divers   degrés   d’inflammation,   en   association   avec   un   système   immunitaire hyperactif. La pathogénèse exacte de cette maladie est inconnue et aucun traitement approprié   n’est   disponible.   La fibrose est un élément distinctif de la maladie de ScS et est considérée   résulter   d’une   incapacité   à   mettre   fin   de   façon   appropriée   à   la   réponse   normale   de   réparation   des   plaies.   L’analyse   histologique   du   stade   initial   de   la   ScS   révèle   une   infiltration   périvasculaire de cellules mononucléaires dans le derme, associée à une synthèse accrue de collagène dans les fibroblastes environnants. Ainsi, la compréhension des moyens de contrôler le stade inflammatoire de la ScS pourrait être bénéfique pour contrôler la progression de la maladie peu après son apparition. La mPGES-1 est une enzyme inductible qui agit en aval de la cyclo- oxygénase (COX) pour catalyser spécifiquement la conversion de la prostaglandine (PG) H2 en PGE2. La mPGES-1  joue  un  rôle  clé  dans  l’inflammation,  la  douleur  et  l’arthrite;;  toutefois,  le   rôle de la mPGES-1 dans les mécanismes de fibrose, spécifiquement en rapport avec la ScS humaine, est inconnu. Mon laboratoire a précédemment montré que les souris à mPGES-1 nulle sont résistantes à la fibrose   cutanée   induite   par   la   bléomycine,   à   l’inflammation,   à   l’épaississement  cutané,  à  la  production  de  collagène  et  à  la  formation  de  myofibroblastes.  Sur  la   base  de  ces  résultats,  j’ai  formulé  l’hypothèse  que  l’inhibition pharmacologique de la mPGES-1 régulera à la baisse la production de médiateurs pro-inflammatoires et pro-fibreux au cours de la maladie   de   ScS.   Afin   d’explorer   le   rôle   de   la   mPGES-1   dans   l’inflammation   et   la   fibrose   associées  à  la  maladie  de  ScS,  j’ai  d’abord  examiné  l’expression  de  la  mPGES-1 dans la peau normale comparativement à des biopsies de peau extraites de patients atteints de ScS. Mes résultats ont montré que la mPGES-1 est nettement élevée dans la peau de patients atteints de ScS en comparaison avec la peau humaine normale. De plus, les niveaux de PGE2 dérivés de la mPGES-1 étaient également significativement plus élevés dans les fibroblastes cutanés isolés de patients  atteints  de  ScS  comparativement  aux  fibroblastes  isolés  de  témoins  sains.  J’ai  également   étudié  l’effet  de  l’inhibition pharmacologique de la mPGES-1  sur  l’expression  de  marqueurs  pro- fibreux.   Mes   études   ont   montré   que   l’expression   de   médiateurs   pro-fibreux clés (α-SMA, endothéline-1, collagène de type 1 et facteur de croissance du tissu conjonctif (FCTC)) est élevée dans les fibroblastes cutanés ScS en comparaison avec les fibroblastes cutanés normaux. Un traitement avec un inhibiteur de la mPGES-1 a eu pour effet de réduire significativement l’expression  de  l’α-SMA,  de  l’endothéline-1, du collagène de type 1 mais pas du FCTC dans les fibroblastes  ScS,  sans  effet  significatif  sur  les  fibroblastes  normaux.  J’ai  en  outre  examiné  l’effet   de  l’inhibition  de  la  mPGES-1 sur des cytokines pro-inflammatoires clés impliquées dans la pathologie de la ScS, incluant IL-6, IL-8 et MCP-1.  L’inhibition  pharmacologique  de  la  mPGES- 1 a eu pour effet de réduire significativement les niveaux de production de cytokines pro- inflammatoires IL6, IL8 et MCP-1 dans les fibroblastes avec lésion ScS comparativement à des fibroblastes non traités. De plus, les patients atteints de ScS ont présenté des niveaux plus élevés de p-AKT, de p-FAK et de p-SMAD3 en comparaison avec les fibroblastes cutanés normaux. L’inhibiteur  de  la  mPGES-1 a pu réguler à la baisse cette expression accrue de p-AKT et de p- FAK, mais pas de p-SMAD3,  dans  les  fibroblastes  ScS.  Ces  résultats  ont  suggéré  que  l’inhibition   de la mPGES-1 pourrait être une méthode viable pour réduire le développement de sclérose cutanée et constituent une cible thérapeutique potentielle pour contrôler les mécanismes fibreux et inflammatoires associés à la pathophysiologie de la maladie de ScS. L’un   des   autres   processus   critiques   reliés   à   l’évolution de la réponse fibreuse associée à la maladie de ScS est la différenciation des fibroblastes en des cellules activées spécialisées iii iv appelées myofibroblastes, responsables de déclencher une signalisation adhésive excessive et le dépôt excessif de matrice extracellulaire,   conduisant   à   la   destruction   de   l’architecture   de   l’organe.   Ainsi,   l’identification   des   facteurs   endogènes   qui   initient/   favorisent   la   différenciation   fibroblaste-myofibroblaste peut mener à des stratégies thérapeutiques prometteuses pour contrôler  l’excès  de  signalisation  adhésive  et  de  fibrose  associé  à  la  maladie  de  ScS.  Des  études   antérieures  dans  le  domaine  de  la  biologie  du  cancer  ont  suggéré  que  l’éphrine  B2,  une  protéine   transmembranaire appartenant à la famille des éphrines, est impliquée dans la signalisation adhésive   et   le   remodelage   extracellulaire.   Cependant,   son   rôle   dans   la   fibrose   n’a   jamais   été   exploré.   Dans   la   deuxième   partie   de   mon   étude,   j’ai   donc   étudié   le   rôle   de   l’éphrine   B2   dans   la   fibrose.   Mes   études   montrent   que   l’expression   de   l’éphrine   B2   est   significativement   augmentée   dans la peau humaine ScS comparativement à la peau normale. Plus important encore, le traitement in vitro de   fibroblastes   de   la   peau   humaine   normale   avec   de   l’éphrine   B2   recombinante est capable de transformer des fibroblastes en cellules myofibroblastiques manifestant toutes les caractéristiques myofibroblastiques typiques, incluant la formation accrue de  fibres  de  tension,  des  adhérences  focales,  l’activation  accrue  de  la  FAK,  un  accroissement  de   l’expression  et  de  la  migration  de  fibroblastes  et  de  leur  adhérence  à  la  fibronectine  à  la  fois  chez   les   fibroblastes   cutanés   normaux   et   ScS.   En   outre,   j’ai   traité   des   souris   avec   de   l’éphrine   B2   recombinante et montré que ces souris ont développé une fibrose cutanée significative associée à une épaisseur dermique et à une synthèse de collagène augmentées, une teneur en hydroxyproline (teneur en collagène) accrue et un nombre accru de myofibroblastes exprimant de   l’α-SMA, une activation augmentée de la FAK et de marqueurs pro-fibreux incluant le collagène de type 1 et le FCTC. Dans  l’ensemble,  mes  études  ont  identifié  deux  médiateurs  endogènes  cruciaux  impliqués  dans  la   propagation  de  l’inflammation  et  de  la  fibrose  associées  à  la  maladie  de  ScS.  L’inhibition  de  la   mPGES-1   pourrait   représenter   une   bonne   stratégie   alternative   pour   contrer   l’inflammation   et   la   fibrose au moins durant les stades précoces de la maladie de ScS. De plus, une signalisation excessive   de   l’éphrine B2 favorise la signalisation adhésive et fibreuse en déclenchant la différenciation   de   fibroblastes   en   myofibroblastes   par   l’activation   de   la   voie   de   signalisation   de   la  FAK.  Ainsi,  l’inhibition  d’éphrine  B2  bloquera  la  formation  de  fibroblastes-myofibroblastes et régulera à la baisse la fibrose associée à la maladie de ScS. En somme, la mPGES-1  et  l’éphrine   B2 semblent toutes deux des cibles attrayantes pour le traitement de la ScS et des troubles fibreux qui y sont reliés. / Scleroderma (Systemic sclerosis, SSc) is an autoimmune disease of the connective tissue featuring skin thickening, spontaneous scarring, and blood vessel disease, varying degrees of inflammation, associated with an overactive immune system. The exact pathogenesis of this disease is unknown and there is no appropriate treatment available. Fibrosis is a hallmark of SSc disease and is considered to arise due to an inability to appropriately terminate the normal wound repair response. Histological analysis of the initial stage of SSc reveals perivascular infiltrates of mononuclear cells in the dermis, which is associated with increased collagen synthesis in the surrounding fibroblasts. Thus understanding how to control the inflammatory stage of SSc may be of benefit in controlling the progression of early onset disease. mPGES-1 is an inducible enzyme that acts downstream of cyclooxygenase (COX) to specifically catalyze the conversion of prostaglandin (PG) H2 to PGE2. mPGES-1 plays a key role in inflammation, pain and arthritis; however, the role of mPGES-1 in fibrotic mechanisms especially with respect to human SSc is unknown. My laboratory has previously shown that mPGES-1-null mice are resistant to bleomycin-induced skin fibrosis, inflammation, cutaneous thickening, collagen production and myofibroblast formation. Based on these results I hypothesized that pharmacological inhibition of mPGES-1 will downregulate the production of pro-inflammatory and pro-fibrotic mediators during SSc disease. To explore the role of mPGES-1 in inflammation and fibrosis associated with SSc disease, I first investigated the expression of mPGES-1 in normal skin compared to skin biopsies extracted from SSc patients. My results showed that mPGES-1 is markedly elevated in SSc skin compared to normal human skin. In addition, the levels of mPGES-1- derived PGE2 were also significantly higher in skin fibroblasts isolated from SSc patients compared to fibroblasts isolated from healthy controls. I further investigated the effect of pharmacological inhibition of mPGES-1 on the expression of pro-fibrotic markers. My studies showed the expression of key pro-fibrotic mediators (α-SMA, endothelin-1, collagen type 1 and connective tissue growth factor) are elevated in SSc skin fibroblasts compared to normal skin fibroblasts. Treatment with mPGES-1 inhibitor resulted in significant reduction in the expression of α-SMA, endothelin-1, collagen type 1 but not CTGF in SSc and normal fibroblasts. Further, I investigated the effect of mPGES-1 inhibition on key pro-inflammatory cytokines implicated in SSc pathology including IL-6, IL-8 and MCP-1. Pharmacological inhibition of mPGES-1 resulted in significant reduction in the production levels of pro-inflammatory cytokines, IL6, IL8 and MCP-1 in SSc-lesioned fibroblasts compared to untreated fibroblasts. In addition, SSc patients exhibited higher levels of p-AKT, p-FAK and p-SMAD3 compared to normal skin fibroblasts. mPGES-1 inhibitor was able to down regulate this increased expression of p-AKT, p-FAK but not p-SMAD3 in SSc fibroblasts. These results suggested that inhibition of mPGES-1 may be a viable method to alleviate the development of cutaneous sclerosis and is a potential therapeutic target to control fibrotic and inflammatory mechanisms associated with the pathophysiology of SSc disease. One of the other critical processes associated with the evolution of fibrotic response associated with SSc disease is the differentiation of fibroblasts into specialized activated cells called myofibroblasts responsible for triggering excessive adhesive signaling and deposition of excessive extracellular matrix (ECM) leading to the destruction of organ architecture. Thus identifying endogenous factors which initiate/promote fibroblast-myofibroblast differentiation can lead to promising therapeutic strategies to control excessive adhesive signaling and fibrosis associated with SSc disease. Previous studies in cancer biology have suggested that ephrin B2, a transmembrane protein belonging to the family of ephrins, is involved in adhesive signaling and extracellular remodeling. However its role in fibrosis has never been explored. Therefore, in second part of my study, I investigated the role of ephrin B2 in fibrosis. My studies show ephrin v vi B2 expression is significantly enhanced in human SSc skin versus normal skin. Most importantly, in vitro treatment of normal human skin fibroblasts with recombinant ephrin B2 is able to transform fibroblasts into myofibroblastic cells exhibiting all typical myofibroblastic- characteristics including increased stress fibre formation, focal adhesions, increased activation of FAK, increased expression of and enhanced fibroblast migration and adhesion to fibronectin in both normal and SSc skin fibroblasts. Further, I treated mice with recombinant ephrin B2 and showed that these mice developed significant skin fibrosis associated with enhanced dermal thickness and collagen synthesis, increased hydroxyproline content (collagen content) and increased number of α-SMA-expressing myofibroblasts, enhanced activation of FAK and pro- fibrotic markers including type-I collagen and CTGF. Overall, my studies have identified two crucial endogenous mediators involved in propagating inflammation and fibrosis associated with SSc disease. mPGES-1 inhibition may present a good alternative strategy to counteract inflammation and fibrosis at least during early stages of SSc disease. Further, excessive ephrin B2 signaling promotes adhesive and fibrotic signaling by triggering fibroblast to myofibroblast differentiation via activation of the FAK signaling pathway. Thus, inhibition of ephrin B2 will block fibroblast-myofibroblast formation and downregulate fibrosis associated with SSc disease. Overall, both mPGES-1 and ephrin B2 seems to be attractive targets for treatment of SSc and related fibrotic disorders.

No description available.

As the principal pro-inflammatory prostanoid, prostaglandin E2 (PGE2) serves as mediator of pain and fever in inflammatory reactions. The biosynthesis of PGE2 starts from arachidonic acid (AA). Cyclooxygenase (COX)-1 and/or COX-2 converts AA to prostaglandin H2 (PGH2), and PGE2 synthases transform PGH2 to PGE2. Current mainstream approach for treating inflammation-related symptoms remains the application of traditional non-steroidal anti-inflammatory drugs (tNSAIDs) and selective COX-2 inhibitors (coxibs). As both categories shut down the biosynthesis of all downstream prostanoids, their application renders several deleterious effects including gastrointestinalulceration and cardiovascular risk. Microsomal prostaglandin E2 synthase-1 (mPGES-1) inhibitors, specifically blocking the production of inflammation-related PGE2, are expected to reduce the adverse effects while retain the anti-inflammation activity. Although several compounds have been reported, only a few have entered clinical trials and none was on the market. Particularly, most of the reported human mPGES-1 inhibitors were not active for wild-type mouse/rat mPGES-1 enzymes, which prevents using the well-established mouse/rat models of inflammation in preclinical studies. Therefore, we expect our designed inhibitors to also be potent against mouse mPGES-1 and thus is suitable for preclinical testing in wild-type mice.

L'arthrose (OA) est une maladie articulaire dégénérative, classée comme la forme la plus fréquente au monde. Elle est caractérisée par la dégénérescence du cartilage articulaire, l’inflammation de la membrane synoviale, et le remodelage de l’os sous-chondral. Ces changements structurels et fonctionnels sont dues à de nombreux facteurs. Les cytokines, les prostaglandines (PG), et les espèces réactives de l'oxygène sont les principaux médiateurs impliqués dans la pathophysiologie de l'OA. L'interleukine-1β (IL-1β) est une cytokine pro-inflammatoire majeure qui joue un rôle crucial dans l'OA. L'IL-1β induit l'expression de la cyclooxygénase-2 (COX-2), la microsomale prostaglandine E synthase-1 (mPGES-1), la synthase inductible de l'oxyde nitrique (iNOS), ainsi que leurs produits la prostaglandine E2 (PGE2) et l'oxyde nitrique (NO). Ce sont des médiateurs essentiels de la réponse inflammatoire au cours de l'OA qui contribuent aux mécanismes des douleurs, de gonflement, et de destruction des tissus articulaires. Les modifications épigénétiques jouent un rôle très important dans la régulation de l’expression de ces gènes pro-inflammatoires. Parmi ces modifications, la méthylation/ déméthylation des histones joue un rôle critique dans la régulation des gènes. La méthylation/ déméthylation des histones est médiée par deux types d'enzymes: les histones méthyltransférases (HMT) et les histones déméthylases (HDM) qui favorisent l’activation et/ou la répression de la transcription. Il est donc nécessaire de comprendre les mécanismes moléculaires qui contrôlent l’expression des gènes de la COX-2, la mPGES-1, et l’iNOS. L'objectif de cette étude est de déterminer si la méthylation/déméthylation des histones contribute à la régulation de l’expression des gènes COX-2, mPGES-1, et iNOS dans des chondrocytes OA humains induits par l'IL-1β. Nous avons montré que la méthylation de la lysine K4 de l'histone H3 (H3K4) par SET-1A contribue à l’activation des gènes COX-2 et iNOS dans les chondrocytes humains OA induite par l'IL-1β. Nous avons également montré que la lysine K9 de l’histone H3 (H3K9) est déméthylée par LSD1, et que cette déméthylation contribue à l’expression de la mPGES-1 induite par IL-1β dans les chondrocytes humains OA. Nous avons aussi trouvé que les niveaux d'expression des enzymes SET-1A et LSD1 sont élevés au niveau du cartilage OA. Nos résultats montrent, pour la première fois, l'implication de la méthylation/ déméthylation des histones dans la régulation de l’expression des gènes COX-2, mPGES-1, et iNOS. Ces données suggèrent que ces mécanismes pourraient être une cible potentielle pour une intervention pharmacologique dans le traitement de la physiopathologie de l'OA. / Osteoarthritis (OA) is a disabling disease classified as the most common form of arthritis worldwide. It is characterized by cartilage degeneration, synovium inflammation, and subchondral bone remodeling resulting in a loss of joint function. These structural and functional changes are due to numerous factors. Cytokines, prostaglandins (PG), and reactive oxygen species are the major mediators implicated in the pathophysiology of OA. Interleukin-1 (IL-1) is a major pro-inflammatory cytokine that plays a crucial role in OA. IL-1 induces the expression of Cyclo-oxygenase-2 (COX-2), microsomal prostaglandin E synthase-1 (mPGES-1), inducible nitric oxide synthase (iNOS), as well as their products prostaglandin E2 (PGE2) and nitric oxide (NO). These are critical mediators of the inflammatory response during OA causing pain, swelling, and joint tissue destruction. The activation of these pro-inflammatory genes results from different changes at the level of chromatin known as epigenetic modifications. Epigenetic modifications such as DNA methylation and histone modifications play a crucial role in gene expression. Among these modifications, histone methylation/demethylation is the most critical one. Histone methylation/demethylation is mediated by two types of enzymes: histone methyltransferases (HMT) and histone demethylases (HDM) which can either activate or repress transcription. It is therefore necessary to understand the molecular mechanisms which underlie the regulation of COX-2, mPGES-1, and iNOS expression. The objective of this study is to investigate whether histone methylation/demethylation can modulate COX-2, mPGES-1, and iNOS expression in IL-1 induced OA human chondrocytes. We demonstrated that histone H3 lysine K4 (H3K4) methylation by SET-1A contributes to IL-1-induced COX-2 and iNOS expression in human OA Chondrocytes. We showed also that LSD1-mediated demethylation of histone H3 lysine 9 (H3K9) contributes to IL-1β-induced mPGES-1 expression in human OA chondrocytes. We found that levels of SET-1A and LSD1 expression are elevated in OA cartilage as compared with normal cartilage. Our data demonstrates, for the first time, the implication of histone methylation/demethylation in COX-2, mPGES-1, and iNOS regulation suggesting that these mechanisms could be a potential target for pharmacological intervention in the treatment of the pathophysiology of OA.

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