Withaferin A Inhibits Helicobacter pylori-induced Production of IL-1beta in Dendritic Cells by Regulating NF-kappaB and NLRP3 Inflammasome Activation

Helicobacter pylori infection is associated with chronic gastritis, peptic ulcer, and gastric cancer. There is evidence that IL-1beta is associated with the development of gastric cancer. Therefore, downregulation of H. pylori-mediated IL-1beta production may be a way to prevent gastric cancer. Withaferin A (WA), a withanolide purified from Withania somnifera, is known to exert anti-inflammatory and anti-tumor effects. In the present study, we explored the inhibitory activity of WA on H. pylori-induced production of IL-1beta in murine bone marrow-derived dendritic cells (BMDCs) and the underlying cellular mechanism. Co-treatment with WA decreased IL-1beta production by H. pylori in BMDCs in a dose-dependent manner. H. pylori-induced gene expression of IL-1beta and NLRP3 (NOD-like receptor family, pyrin domain containing 3) were also suppressed by WA treatment. Moreover, IkappaB-alpha phosphorylation by H. pylori infection was suppressed by WA in BMDCs. Western blot analysis revealed that H. pylori induced cleavage of caspase-1 and IL-1beta, as well as increased procaspase-1 and pro IL-1beta protein levels, and that both were suppressed by co-treatment with WA. Finally, we determined whether WA can directly inhibit ac tivation of the NLRP3 inflammasome. NLRP3 activators induced IL-1beta secretion in LPS-primed macrophages, which was inhibited by WA in a dose-dependent manner, whereas IL-6 production was not affected by WA. Moreover, cleavage of IL-1beta and caspase-1 by NLRP3 activators was also dose-dependently inhibited by WA. These findings suggest that WA can inhibit IL-1beta production by H. pylori in dendritic cells and can be used as a new preventive and therapeutic agent for gastric cancer.

SUMO Proteins are not Involved in TGF-beta1-induced, Smad3/4-mediated Germline alpha Transcription, but PIASy Suppresses it in CH12F3-2A B Cells

TGF-beta induces IgA class switching by B cells. We previously reported that Smad3 and Smad4, pivotal TGF-beta signal-transducing transcription factors, mediate germline (GL) alpha transcription induced by TGF-beta1, resulting in IgA switching by mouse B cells. Post-translational sumoylation of Smad3 and Smad4 regulates TGF-beta-induced transcriptional activation in certain cell types. In the present study, we investigated the effect of sumoylation on TGF-beta1-induced, Smad3/4-mediated GLalpha transcription and IgA switching by mouse B cell line, CH12F3-2A. Overexpression of small ubiquitin-like modifier (SUMO)-1, SUMO-2 or SUMO-3 did not affect TGF-beta1-induced, Smad3/4-mediated GLalpha promoter activity, expression of endogenous GLalpha transcripts, surface IgA expression, and IgA production. Next, we tested the effect of the E3 ligase PIASy on TGF-beta1-induced, Smad3/4-mediated GLalpha promoter activity. We found that PIASy overexpression suppresses the GLalpha promoter activity in cooperation with histone deacetylase 1. Taken together, these results suggest that SUMO itself does not affect regulation of GLalpha transcription and IgA switching induced by TGF-beta1/Smad3/4, while PIASy acts as a repressor.