Delta-8-tetrahydrocannabinol ameliorates murine autoimmune hepatitis and is associated with epigenetic modulation of immune responses.

AIM OF THE STUDY: Cannabinoids have gained attention for their ability to modulate immune responses and suppress inflammation. However, the effect of Δ8-THC, a minor cannabinoid found in Cannabis, has not been explored in autoimmune hepatitis. To address knowledge gap, the present study aimed to investigate the hepatoprotective and immunoregulatory properties of Δ8-THC in experimental autoimmune hepatitis and to identify molecular and epigenetic mechanisms underlying its immunoregulatory effects. METHODS: miRNA sequencing and flow cytometric analysis were performed using hepatic immune cells from female C57BL/6 mice treated with ConA (12.5 mg/kg, i.v.) and Δ8-THC (20 mg/kg, i.p.). Differential miRNA expressions were analyzed using the edgeR, and miRNA targets were predicted using Ingenuity Pathway Analysis. Target gene expression was validated by qRT-PCR and Western blot. Functional assays including miRNA mimic/inhibitor transfection and CD4+ T-cell differentiation were performed to validate target gene regulation by miRNAs and its role in CD4+ T-cell differentiation. RESULTS: Δ8-THC markedly suppressed ConA-induced autoimmune hepatitis by restoring immune homeostasis within the liver through suppression of inflammatory monocytes, neutrophils, and natural killer cells, and preservation of tolerogenic Kupffer cells. In addition, Δ8-THC reshaped the hepatic lymphoid compartment, diminishing inflammatory CD4+ T-cell responses while favoring regulatory T-cell expansion. These effects were associated with the preservation of miR-100-5p and miR-199a-3p expression in the liver, whereas both miRNAs were markedly downregulated following ConA treatment. mTOR, a central regulator of T-cell differentiation, was identified as a target of these miRNAs. Consistent with these findings, Δ8-THC reduced mTOR expression and upregulated hepatoprotective miRNAs in both in vivo and in vitro models. Functional analyses with miRNA overexpression and inhibition approaches verified the direct regulation of mTOR by these miRNAs in T cells and RAW 264.7 cells. In naïve CD4+ T cells, miRNA gain- and loss-of-function experiments demonstrated that miR-100-5p/miR-199a-3p-mediated suppression of mTOR promotes regulatory T-cell differentiation while limiting Th1 and Th17 polarization. CONCLUSION: Our results identify Δ8-THC as a promising hepatoprotective and anti-inflammatory compound that ameliorates ConA-induced autoimmune hepatitis by influencing CD4+ T-cell differentiation potentially through the miR-100-5p/miR-199a-3p-mTOR axis, highlighting its potential therapeutic value in autoimmune and inflammatory disorders.