Natural Indoles, Indole-3-Carbinol (I3C) and 3,3’-Diindolylmethane (DIM), Attenuate Staphylococcal Enterotoxin B-Mediated Liver Injury by Downregulating miR-31 Expression and Promoting Caspase-2-Mediated Apoptosis

Abstract

Staphylococcal enterotoxin B (SEB) is a potent superantigen capable of inducing inflammation characterized by robust immune cell activation and proinflammatory cytokine release. Exposure to SEB can result in food poisoning as well as fatal conditions such as toxic shock syndrome. In the current study, we investigated the effect of natural indoles including indole-3-carbinol (I3C) and 3,3’-diindolylmethane (DIM) on SEB-mediated liver injury. Injection of SEB into D-galactosamine-sensitized female C57BL/6 mice resulted in liver injury as indicated by an increase in enzyme aspartate transaminase (AST) levels, induction of inflammatory cytokines, and massive infiltration of immune cells into the liver. Administration of I3C and DIM (40mg/kg), by intraperitonal injection, attenuated SEB-induced acute liver injury, as evidenced by decrease in AST levels, inflammatory cytokines and cellular infiltration in the liver. I3C and DIM triggered apoptosis in SEB-activated T cells primarily through activation of the intrinsic mitochondrial pathway. In addition, inhibitor studies involving caspases revealed that I3C and DIM-mediated apoptosis in these activated cells was dependent on caspase-2 but independent of caspase-8, 9 and 3. In addition, I3C and DIM caused a decrease in Bcl-2 expression. Both compounds also down-regulated miR-31, which directly targets caspase-2 and influences apoptosis in SEB-activated cells. Our data demonstrate for the first time that indoles can effectively suppress acute hepatic inflammation caused by SEB and that this may be mediated by decreased expression of miR-31 and consequent caspase-2-dependent apoptosis in T cells.

Marijuana-derived Δ-9-tetrahydrocannabinol suppresses Th1/Th17 cell-mediated delayed-type hypersensitivity through microRNA regulation

“…Draining lymph node cells from DTH mice were transfected (HiPerFect- Qiagen) with either miRNA mimics or inhibitors (Qiagen) for 6 h with target gene expression assessed 24 h after transfection. The transfection was performed as detailed in our previous publications [11, 40]. We found that miR-29b inhibitor significantly increased IFN-γ levels compared to miR-29b overexpression (Fig.…”

3,3'-Diindolylmethane Ameliorates Staphylococcal Enterotoxin B-Induced Acute Lung Injury through Alterations in the Expression of MicroRNA that Target Apoptosis and Cell-Cycle Arrest in Activated T Cells

“…Transfection was performed as described (Busbee et al, 2015). Splenocytes were cultured in complete (10% FBS, 10 mM L-glutamine, 10 mM Hepes, 50 mM b-mercaptoethanol, and 100 mg/ml penicillin) RPMI 1640 medium (11875-093; Life Technologies Corp., Waltham, MA).…”

Function and regulation of microRNA‐31 in development and disease

“…Lastly, a number of non‐protein molecules (hormones and indoles) were demonstrated to regulate miR‐31 expression (Kuokkanen et al, ; Busbee et al, ). A number of studies reported that miR‐31 expression is activated by RELA (p65 subunit of NF‐κB) and SP1 (a zinc‐finger transcription factor) in esophageal cells under conditions that lack zinc (Alder et al, ; Fong et al, ; Taccioli et al, ).…”