Attenuation of berberine on lipopolysaccharide-induced inflammatory and apoptosis responses in β-cells via TLR4-independent JNK/NF-κB pathway

Context: Toll-like receptor 4 (TLR4)-independent inflammatory and apoptosis responses contribute to beta-cell failure in diabetes mellitus (DM). Berberine (BBR), a bioactive isoquinoline derivative alkaloid, ameliorates the inflammatory response in DM. Objective: This study explored the protective mechanisms of BBR on TLR4-independent inflammation response in beta cells. Materials and methods: Lipopolysaccharide (LPS; 100 ng/ml) was used to induce the inflammatory response in NIT-1 and rat insulinoma (INS-1) cells for 24 h. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and colony formation assays were used for the determination of cell viability. The levels of monocyte chemoattractant protein (MCP-1), interleukin 6 (IL-6), tumor necrosis factor alpha (TNF-alpha) and insulin in cultured supernatant were detected by enzyme-linked immunosorbent assay kits. Western blot analysis was performed for the expression of p-c-Jun N-terminal kinase (JNK) and p65 NF-kappa B in NIT-1 cells, and p65 NF-kappa B in INS-1 cells. Results: BBR (1.25, 2.5 and 5 mu M) or TLR4 inhibitor (TAK-242, 1 mu M) increased remarkably NIT-1 cell viability by 72.6 + 5.0, 85.9 + 9.3, 94.7 + 7.1 and 92.6 + 8.4%. The EC50 of BBR was 1.14 mu M. Colony formation assay showed that BBR increased the number of colonies of NIT-1 and INS-1 cells. BBR, TAK-242 or SP-600125 (1 mu M) could significantly reduce the levels of MCP-1, IL-6 and TNF-alpha, insulin and JNK and NF-kappa B phosphorylation in NIT-1 cells, as well as the p65 NF-kappa B in INS-1 cells. Discussion and conclusion: BBR could ameliorate LPS-induced beta-cell injury through the TLR4-independent JNK/NF-kappa B pathway. Thus, this pathway may be a potential target for the prevention and treatment of DM.