The interference of chlorogenic acid on Toll-like receptor 9 signal pathway in herpes simplex virus-1 infected microglia

Objective To investigate the interference of chlorogenic acid (CGA) on Toll-like receptor 9 (TLR9) signal pathway in herpes simplex virus (HSV)-1-induced responses in BV2 microglia. Methods The cellular model was established with BV2 cells stimulated by herpes simplex virus-1 (HSV-1) and then treated with CGA at different concentrations (25, 50, 100 ng/ml). Cell viability was measured by the methyl thiazol tetrazolium (MTT) assay. The mRNA and protein expression of TLR9 and bone marrow differentiation factor 88 (Myd88) was detected by reverse transcriptase-polymerase chain reaction (RT-PCR), and Western blotting respectively. The serum tumor necrosis factor-α (TNF-α) levels were determined by enzyme linked immunosorbent assay (ELISA) and RT-PCR. Results The cell survival rate was significantly improved after CGA treatment [model group: (43.0±8.7)%; CGA group: (57.0±8.4)%, (64.0±7.6)%, (84.0±4.2)%], and CGA inhibited the increases in TLR9, Myd88, TNF-α (comparison of protein expression: 0.84±0.05 vs. 0.18±0.13, P=0.000; 0.89±0.03 vs. 0.76±0.11, P=0.002; 292.34±8.16 vs. 20.76±5.72, P=0.000; relative expression of mRNA: 3.01±0.87, 5.79±0.72, 20.12±10.17, P=0.000) following HSV-1 challenge in BV2 cells. Conclusion In HSV-1 infected microglia cellular model, CGA inhibits the inflammatory reaction in herpes simplex virus encephalitis (HSE) via the suppression of TLR9, Myd88, TNF-α in TLR9 signal pathway. Key words: Chlorogenic acid; Inflammation; Toll-like receptor 9; Bone marrow differentiation factor 88; Herpes simplex virus-1