Hydrogen Sulfide Attenuates Hypertensive Inflammation via Regulating Connexin Expression in Spontaneously Hypertensive Rats.

BACKGROUND Hydrogen sulfide (H2S) has anti-inflammatory and anti-hypertensive effects, and connexins (Cxs) are involved in regulation of immune homeostasis. In this study, we explored whether exogenous H2S prevents hypertensive inflammation by regulating Cxs expression of T lymphocytes in spontaneously hypertensive rats (SHR). MATERIAL AND METHODS We treated SHR with sodium hydrosulfide (NaHS) for 9 weeks. Vehicle-treated Wistar-Kyoto rats (WKYs) were used as a control. The arterial pressure was monitored by the tail-cuff method, and vascular function in basilar arteries was examined by pressure myography. Hematoxylin and eosin staining was used to show vascular remodeling and renal injury. The percentage of T cell subtypes in peripheral blood, surface expressions of Cx40/Cx43 on T cell subtypes, and serum cytokines level were determined by flow cytometry or ELISA. Expression of Cx40/Cx43 proteins in peripheral blood lymphocytes was analyzed by Western blot. RESULTS Chronic NaHS treatment significantly attenuated blood pressure elevation, and inhibited inflammation of target organs, vascular remodeling, and renal injury in SHR. Exogenous NaHS also improved vascular function by attenuating KCl-stimulated vasoconstrictor response in basilar arteries of SHR. In addition, chronic NaHS administration significantly suppressed inflammation of peripheral blood in SHR, as evidenced by the decreased serum levels of IL-2, IL-6, and CD4/CD8 ratio and the increased IL-10 level and percentage of regulatory T cells. NaHS treatment decreased hypertension-induced Cx40/Cx43 expressions in T lymphocytes from SHR. CONCLUSIONS Our data demonstrate that H2S reduces hypertensive inflammation, at least partly due to regulation of T cell subsets balance by Cx40/Cx43 expressions inhibition.

TLR4 mediates MAPK-STAT3 axis activation in bladder epithelial cells.

The role of Toll-like receptor 4 (TLR4) in immune cells is well characterized, but its biological properties in bladder epithelial cells (BECs), especially reciprocal crosstalk between mitogen-activated protein (MAP) kinase pathway and signal transducer and activator of transcription (STAT)3-mediated signal transduction elicited by TLR4 have not been demonstrated so far. The present studies were to demonstrate the signal transduction and inflammatory cytokine response elicited through activation of TLR4 in BECs with a special focus on the crosstalk between the MAPK-pathway and STAT3-mediated signals and its regulatory relevance for the inflammatory response towards lipopolysaccharide (LPS). We selected human bladder cancer T24 cell line in the present study and examined its expression of TLR4 by reverse transcriptase polymerase chain reaction (RT-PCR) and immunohistochemistry. The expression of p38, extracellular signal regulated kinase (ERK), c-Jun NH2-terminal kinase (JNK), and STAT3 were performed by RT-PCR, quantitative PCR, and Western blotting. Signal transduction was analyzed by Western blotting. Interleukin-6 (IL-6) and interleukin-10 (IL-10) secretion in culture supernatants were tested by human enzyme-linked immunosorbent assay (ELISA) kit. BECs of rat infection in vivo model and patients with cystitis glandularis (CG) were analyzed as described above. Our study demonstrated that TLR4 was significantly upregulated following LPS treatment, with the maximum mRNA expression occurring at 4 h after stimulation. Activation of TLR4 signaling by LPS resulted in phosphorylation of MAPK and STAT pathways and upregulation of IL-10 in dose- and time-dependent manners in T24 cells. Pretreatment of cells with SB203580 (inhibitor of p38) and SP600125 (inhibitor of JNK) attenuated LPS-induced IL-10 expression, whereas it markedly inhibited the STAT3 expression. IL-10 mRNA expression was increased in inflamed lesions compared to noninflamed tissue in rats and patients with CG disease. Our results demonstrate that activation of TLR4 signaling in BECs induces IL-10 expression via activation of p38 and JNK, and the activation of STAT-3 was upregulated. Our data indicated that the reciprocal crosstalk between the MAPK pathway and STAT3-mediated signal transduction forms a critical axis successively activated by LPS in BECs.