Nuclear sirtuins and inflammatory signaling pathways.

The regulation of chronic inflammation has received considerable research attention in recent years because of its contribution to the pathogenesis of chronic diseases such as arthritis, diabetes, metabolic syndrome and obesity. Thus, strategies that inhibit the inflammatory state may be beneficial in improving the pathophysiology of several inflammation-related disorders. Sirtuins are a family of histone deacetylases that contain seven enzymatic activities in mammals (SIRT1-SIRT7) and function to suppress gene transcription by epigenetic mechanisms. Nuclear sirtuins (SIRT 1, 2, 6 and 7) in particular may play an important role in the regulation of inflammatory responses. In the present review, we assessed the roles of nuclear sirtuins in inflammatory reactions: SIRT1 has been shown to suppress NF-κb activity, the master regulator of cellular inflammatory response, decrease COX-2 and iNOS production, and increase antioxidant gene expression that suppressed inflammation. SIRT2 activity included the deacetylation of p65 subunit of NF-κß and RIP-1, while SIRT6 has been shown to interact with p65/RelA bound to the NF-κß promoter region and repress transcriptional activity. Furthermore, recent studies have shown that the absence of SIRT7 produced an increase in inflammation, illustrating that SIRT7 also functioned to decrease inflammation. Given their significant roles in the regulation of chronic inflammation, nuclear sirtuins represent potential therapeutic targets in the control of chronic inflammatory diseases.

IKKß regulates endothelial thrombomodulin in a Klf2-dependent manner.

BACKGROUND: Endothelial thrombomodulin (TM) is critically involved in anticoagulation, anti-inflammation, cytoprotection and normal fetal development. Tumor necrosis factor alpha (TNFα) suppresses TM expression. OBJECTIVE: TNFα has been shown to down-regulate TM partly via activation of nuclear factor kappa B (NF-κB). However, because the TM promoter lacks an NF-κB binding site, the direct involvement of NF-κB has been controversial. We investigated the role of the upstream regulatory serine kinase, inhibitory kappa-B kinase-ß (IKKß), in TM expression and function with or without TNFα treatment. METHODS: Inhibition of IKKß was achieved by specific chemical inhibitors, siRNA or shRNA. TM expression was assessed by qRT-PCR, Western blot, flow cytometry, luciferase reporter assay and chromatin immune-precipitation (ChIP) assay. TM function was estimated by generation of activated protein C (APC). NF-κB activation was determined by immunocytochemistry. RESULTS AND CONCLUSIONS: IKKß inhibition increased TM expression and function, and attenuated TNFα-mediated TM down-regulation. In contrast, inhibition of downstream canonical NF-κB protein family members p50 and p65 (RelA) failed to up-regulate TM expression and did not affect IKKß inhibition-mediated TM over-expression. However, knockdown of cRel and RelB, family members of the canonical and non-canonical NF-κB pathway, respectively, resulted in TM over-expression. IKKß inhibition caused over-expression, increased promoter activity and enhanced binding of Krüppel-like factor 2 (Klf2) to the TM promoter, which positively regulates TM expression. Finally, knockdown of Klf2 completely attenuated IKKß inhibition-mediated TM up-regulation. We conclude that IKKß regulates TM in a Klf2-dependent manner.