TSG (2,3,4′, 5-tetrahydroxystilbene 2-Oβ-D- glucoside) suppresses induction of pro-inflammatory factors by attenuating the binding activity of nuclear factor-.B in microglia

Background: Induction of pro-inflammatory factors is one of the characteristics of microglia activation and can be regulated by numerous active components of Chinese traditional herbs. Suppression of pro-inflammatory factors is beneficial to alleviate microglia-mediated cell injury. The present study aims to investigate the effect and possible mechanism of 2,3,4', 5-tetrahydroxystilbene 2-O-beta-D-glucoside (TSG) on LPS-mediated induction of pro-inflammatory factors in microglia. Methods: Western blot, ELISA, and Hoechst 33258 were used to measure the protein expression, TNF-a/ IL-6 content, and apoptotic nuclei, respectively. The mRNA level was measured by real time-PCR. Nitric oxide (NO) content, lactate dehydrogenase (LDH) content, and NF-kappa B binding activity were assayed by commercial kits. Results: TSG reduced iNOS protein expression as well as TNF-a, IL-6, and NO content in LPS-stimulated BV-2 cells. TSG attenuated the increase in apoptotic nuclei, caspase-3 cleavage, and LDH content induced by BV-2 cell-derived conditioned medium in primary hippocampal neurons. Mechanistic studies showed that TSG reduced the mRNA level of iNOS, TNF-a, and IL-6. TSG failed to suppress I.B-a degradation, NF-.B phosphorylation and nuclear translocation, and ERK1/ 2, JNK, and p38 phosphorylation. TSG, however, markedly reduced the binding of NF-kappa B to its DNA element. Chromatin immunoprecipitation (ChIP) assays confirmed that TSG reduced NF-kappa B binding to the iNOS promoter. These findings were ascertained in primary microglia where the LPS-induced increase in iNOS expression, NO content, apoptotic nuclei, and NF-.B binding to its DNA element were diminished by TSG. Conclusions: These studies demonstrate that TSG attenuates LPS-mediated induction of pro-inflammatory factors in microglia through reducing the binding activity of NF-kappa B. This might help us to further understand the pharmacological role of TSG in inflammatory response in the central nervous system.