Cannabinoids shift the basal ganglia miRNA m6A methylation profile towards an anti-inflammatory phenotype in SIV-infected Rhesus macaques

Epitranscriptomic modifications modulate diverse biological processes, such as regulation of gene expression, abundance, location and function. In particular, N6-methyladenosine (m6A) methylation has been shown to regulate various disease processes, including cancer and inflammation. While there is evidence that m6A modification is functionally relevant in neural development and differentiation, the role of m6A modification in HIV neuropathogenesis is unknown. Here, we identified direct m6A modifications in miRNAs from BG tissues of Rhesus Monkeys (RMs) that were either vehicle-treated uninfected (VEH), SIV-infected combination anti-retroviral therapy (cART) treated (VEH/SIV/cART), or THC:CBD treated VEH/SIV/cART (THC:CBD/SIV/cART) RMs. We detected m6A modifications across all BG tissues. SIV infection promoted an overall hypomethylated m6A profile. While the overall hypomethylated m6A profile was not significantly impacted by THC:CBD treatment, specific miRNAs, particularly those predicted to target proinflammatory genes showed markedly reduced m6A methylation levels compared to the VEH treated RMs. Additionally, we found that specific BG tissue miRNAs bearing m6A epi-transcriptomic marks were also transferred to BG-derived extracellular vesicles (EVs). Mechanistically, we identified the DRACH motif of the seed region of miR-194-5p to be significantly m6A hypomethylated, which was predicted to directly target STAT1, an important interferon-activated transcription factor known to drive neuroinflammation, in diseases ranging from Alzheimer to Parkinson and Huntington disease. Notably, THC:CBD treatments significantly reduced m6A methylation of 43 miRNA species directly involved in regulating CNS network genes, thus providing a possible mechanist explanation on the beneficial effects of THC:CBD treatments noted in several disease involving neuroinflammation. Our findings also underscore the need for investigating the qualitative, posttranscriptional modification changes in the RNA profiles along with the more traditional, qualitative alterations in pathological conditions or after various treatment regimens.