Berberine modulates ASK1 signaling mediated through TLR4/TRAF2 via upregulation of miR-23a

The current study was designed to explore the underlying therapeutic effect of berberine (BBR), an alkaloid compound against LPS (1 μg/ml)/TNFα (10 ng/ml) mediated apoptosis signal-regulating kinase 1 (ASK1) signaling in RAW 264.7 macrophages and adjuvant-induced arthritic synovial macrophages (AA-SM) with relation to miR-23a levels. LPS and TNFα stimulation abrogated the expression of miR-23a resulting in TLR4/TRAF2 mediated ASK1 activation and downstream phosphorylation of p38 mitogen-activated protein kinase (p38 MAPK). BBR (25-75 μM) treatment ameliorated the gene expression levels of TLR4, TRAF2, TNFα, IL-6, and IL-23 through the upregulation of miR-23a. Subsequently, BBR suppressed the levels of TLR4/TRAF2 mediated phosphorylation of ASK1/p38 and attenuated the expression of various pro-inflammatory cytokines (TNFα, IL-6 & IL-23) in RAW 264.7 macrophages and AA-SM cells. BBR was able to counteract these factors through activation of miR-23a levels in LPS/TNFα stimulated RAW 264.7 macrophages and AA-SM cells. NQDI1 (30 μM) treatment inhibited ASK1 activation resulting in basal levels of miR-23a, owing to the conclusion that ASK1 activation downregulates miR-23a levels inside the cells. Overall, our current findings predict that BBR is a potential candidate for therapeutic targeting of TLR4/TRAF2 mediated ASK1 activation in inflammatory and in RA pathogenesis possibly through post-transcriptional gene silencing via upregulation of miR-23a.