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

Abstract

Context: Toll-like receptor 4 (TLR4)-independent inflammatory and apoptosis responses contribute to β-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 β 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 α (TNF-α) 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-κB in NIT-1 cells, and p65 NF-κB in INS-1 cells.

Results: BBR (1.25, 2.5 and 5 μM) or TLR4 inhibitor (TAK-242, 1 μM) 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 μM. 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 μM) could significantly reduce the levels of MCP-1, IL-6 and TNF-α, insulin and JNK and NF-κB phosphorylation in NIT-1 cells, as well as the p65 NF-κB in INS-1 cells.

Discussion and conclusion: BBR could ameliorate LPS-induced β-cell injury through the TLR4-independent JNK/NF-κB pathway. Thus, this pathway may be a potential target for the prevention and treatment of DM.

• β-cell injury
• diabetes mellitus
• inflammatory cytokines
• INS-1 cells
• insulin level
• NIT-1 cells