Recreational and medical use of cannabis among HIV-infected individuals has increased in recent years. In SIV-infected macaques, chronic administration of Δ9-tetrahydrocannabinol (Δ9-THC), inhibited viral replication, intestinal inflammation and slowed disease progression. Persistent gastrointestinal disease/inflammation has been proposed to facilitate microbial translocation, systemic immune activation and promote disease progression. Cannabinoids including Δ9-THC attenuated intestinal inflammation in mouse colitis models and SIV-infected rhesus macaques. To determine if the anti-inflammatory effects of Δ9-THC involved differential microRNA (miRNA) modulation, we profiled miRNA expression at 14, 30 and 60 days post-infection (DPI) in the intestine of uninfected macaques receiving Δ9-THC (n=3) and SIV-infected macaques administered either vehicle (VEH/SIV; n=4) or THC (THC/SIV; n=4). Chronic Δ9-THC administration to uninfected macaques significantly and positively modulated intestinal miRNA expression by increasing the total number of differentially expressed miRNAs from 14 to 60DPI. At 60DPI, ∼28% of miRNAs showed decreased expression in VEH/SIV compared to none in the THC/SIV group. Furthermore, compared to the VEH/SIV group, THC selectively upregulated the expression of miR-10a, miR-24, miR-99b, miR-145, miR-149 and miR-187 previously been shown to target proinflammatory molecules. NOX4, a potent reactive oxygen species generator was confirmed as a direct miR-99b target. A significant increase in NOX4+ crypt epithelial cells was detected in VEH/SIV compared to the THC/SIV group. We speculate that miR-99b-mediated NOX4 downregulation may protect the intestinal epithelium from oxidative stress-induced damage. These results support a role for differential miRNA induction in THC-mediated suppression of intestinal inflammation. Whether similar miRNA modulation occurs in other tissues requires further investigation.

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Gastrointestinal tract (GI) disease/inflammation is a hallmark of HIV/SIV infection. Previously, we showed that chronic treatment of SIV-infected macaques with Δ9 tetrahydrocannabinol (Δ9-THC) increased survival and decreased viral replication and infection induced gastrointestinal inflammation. Here, we show that chronic THC administration to SIV-infected macaques induced an anti-inflammatory microRNA expression profile in the intestine at 60DPI. These included several miRNAs bioinformatically predicted to directly target CXCL12, a chemokine known to regulate lymphocyte and macrophage trafficking into the intestine. Specifically, miR-99b was significantly upregulated in THC-treated SIV-infected macaques and confirmed to directly target NADPH oxidase 4 (NOX4), a reactive oxygen species generator known to damage intestinal epithelial cells. Elevated miR-99b expression was associated with a significantly decreased number of NOX4+ epithelial cells in the intestines of THC-treated SIV-infected macaques. Overall, our results show that selective upregulation of anti-inflammatory miRNA expression, contributes to THC-mediated suppression of gastrointestinal inflammation and maintenance of intestinal homeostasis.
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