DNA methylation profiling of colonic epithelium from chronically SIV infected rhesus macaques
HIV and pathogenic SIV infection are characterized by gastrointestinal mucosal damage and immune dysfunction that is not reversed by combination anti-retroviral therapy (cART). Increasing evidence points to the contribution of aberrant epigenetic changes to the pathogenesis of gastrointestinal diseases. Nevertheless, the role of epigenetic mechanisms in HIV/SIV-induced gastrointestinal mucosal dysfunction remains understudied. Using reduced-representation bisulfite sequencing, we identified HIV/SIV infection in combination anti-retroviral therapy (cART)-naive rhesus macaques (RMs) to induce marked hypomethylation throughout promoter-associated CpG islands (paCGIs) in genes related to inflammatory response (NLRP6, cGAS), cellular adhesion and proliferation in colonic epithelial cells (CEs). Moreover, low-dose delta-9-tetrahydrocannabinol (THC) administration reduced NLRP6 protein expression in CE by hypermethylating the NLRP6 paCGI and blocked polyI:C induced NLRP6 upregulation in vitro. In cART suppressed SIV-infected RMs, NLRP6 protein upregulation associated with significantly increased expression of necroptosis-driving proteins; phosphorylated-RIPK3(Ser199), phosphorylated-MLKL(Thr357/Ser358), and HMGB1. Most strikingly, supplementing cART with THC effectively reduced NLRP6 and necroptosis-driving protein expression to pre-infection levels. These findings for the first time demonstrate that NLRP6 upregulation and ensuing activation of necroptosis promote HIV/SIV-induced gastrointestinal mucosal dysfunction and that epigenetic modulation using phytocannabinoids represents a feasible therapeutic modality for alleviating HIV/SIV-induced gastrointestinal inflammation and associated comorbidities. Overall design: Colonic epithelium DNA methylation profiles of uninfected control (n=5) and chronically SIV-infected rhesus macaques that were treated with vehicle (n=7) or delta-9-tetrahydrocannabinol (THC) (n=6) were generated by reduced representation bisulfite sequencing