Abstract
BackgroundInduction 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-β-D-glucoside (TSG) on LPS-mediated induction of pro-inflammatory factors in microglia.MethodsWestern blot, ELISA, and Hoechst 33258 were used to measure the protein expression, TNF-α/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-κB binding activity were assayed by commercial kits.ResultsTSG reduced iNOS protein expression as well as TNF-α, 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-α, and IL-6. TSG failed to suppress IκB-α degradation, NF-κB phosphorylation and nuclear translocation, and ERK1/2, JNK, and p38 phosphorylation. TSG, however, markedly reduced the binding of NF-κB to its DNA element. Chromatin immunoprecipitation (ChIP) assays confirmed that TSG reduced NF-κB 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-κB binding to its DNA element were diminished by TSG.ConclusionsThese studies demonstrate that TSG attenuates LPS-mediated induction of pro-inflammatory factors in microglia through reducing the binding activity of NF-κB. This might help us to further understand the pharmacological role of TSG in inflammatory response in the central nervous system.
Highlights
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
We found that tetrahydroxystilbene 2-O-β-D-glucoside (TSG) reduces inducible NO synthase (NOS) (iNOS) expression and nitric oxide (NO), Tumor necrosis factor-α (TNF-α), and IL-6 release in microglia in a way that is independent of mitogen-activated protein kinase (MAPK)-inhibitor of κB α (IκB-α)-nuclear factor κB (NF-κB) activation but likely represses NFκB binding activity
TSG suppresses the induction of pro-inflammatory factors in LPS-stimulated BV-2 cells To determine the working concentration and effective period of TSG for induction of pro-inflammatory factors, we first investigated the dose- and time-dependent effects of TSG on iNOS expression in BV-2 cells
Summary
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. Microglia are the resident immune cells in the central nervous system (CNS). They serve as the neuron-pathological sensor under various conditions such as inflammation [1,2]. IL-6 treatment ameliorates trimethyltin-induced injury in neurons [15]. Both TNF-α and IL-6 were confirmed to enhance neurotoxicity [5,6]. Control of induction of cellular cytokines in microglia might be important for regulation of numerous physiological or pathological processes
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