Mitochondria are involved in the development of organ failure in critical care diseases. However, the mechanisms underlying mitochondrial dysfunction are not clear yet. Inducible hemoxygenase (HO-1), a member of the heat shock protein family, is upregulated in critical care diseases and considered to confer cytoprotection against oxidative stress. However, one of the products of HO-1 is Fe 2 þ which multiplies the damaging potential of reactive oxygen species catalyzing Fenton reaction. The aim of this study was to clarify the relevance of free iron metabolism to the oxidative damage of the liver in endotoxic shock and its impact on mitochondrial function. Endotoxic shock in rats was induced by injection of lipopolysaccharide (LPS) at a dose of 8 mg/kg (i.v.). We observed that the pro-inflammatory cytokine TNF-a and the liver necrosis marker aspartate aminotransferase were increased in blood, confirming inflammatory response to LPS and damage to liver tissue, respectively. The levels of free iron in the liver were significantly increased at 4 and 8 h after onset of endotoxic shock, which did not coincide with the decrease of transferrin iron levels in the blood, but rather with expression of the inducible form of heme oxygenase (HO-1). The proteins important for sequestering free iron (ferritin) and the export of iron out of the cells (ferroportin) were downregulated facilitating the accumulation of free iron in cells. The temporarily increased concentration of free iron in the liver correlated with the temporary impairment of both mitochondrial function and tissue ATP levels. Addition of exogenous iron ions to mitochondria isolated from control animals resulted in an impairment of mitochondrial respiration similar to that observed in endotoxic shock in vivo. Our data suggest that free iron released by HO-1 causes mitochondrial dysfunction in pathological situations accompanied by endotoxic shock.

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Sulfur bath therapy represents the oldest form of treatment for patients with different types of rheumatic disorders. However, scientific reports about the beneficial effects of this form of therapy are controversial, rare and of poor scientific quality. Also, little is known about the role and underlying molecular mechanisms of H2S. Therefore, this topic encouraged us to investigate the influence of H2S on fibroblasts isolated from the synovial membrane of RA (rheumatoid arthritis) patients. FLSs (fibroblast-like synoviocytes) were treated with different concentrations of an exogenous H2S donor (NaHS). At defined time points, secretion of IL-6 was quantified by ELISA. Activation/deactivation of MAPKs (mitogen-activated protein kinases), p38 and p44/42 MAPK (ERK1/2) were confirmed by Western blot experiments. FLSs constitutively express and secrete large quantities of IL-6 and IL-8. Data provided prove that, in FLSs, constitutive as well as IL-1beta-induced expression of IL-6 is transiently and partially down-regulated by the short treatment of cells with low concentrations of NaHS. Another key finding is that H2S deactivates p44/42 MAPK (ERK1/2). Long-term exposure of FLSs to H2S provides stimulatory effects, leading to reinforced activation of p38 MAPK and ERK1/2 accompanied by upregulation of IL-6 expression. Presented data seem of importance for studying (patho-) physiological functions of H2S and also for re-evaluating sulfur spa therapy as one of the oldest forms of therapy for rheumatic disorders.

Mitogen-activated protein kinases (MAPKs) play a central role in inflammatory processes, and their blockage represents pharmacological approaches in the treatment of autoimmune diseases like rheumatoid arthritis (RA). Alternatively, H(2)S has long been used in sulphur bath therapy for patients suffering from different types of rheumatic disorders, but reports about the beneficial effects of this form of therapy are controversial, rare and of poor scientific quality. The human chondrocyte cell line C-28/I2 was treated with two different MAPK inhibitors (SB203580 and U0126) or with various concentrations of the H(2)S donor Natrium hydrogen sulphide (NaHS). Thereafter, the secretion of IL-6 and IL-8 was quantified by enzyme-linked immunosorbent assays (ELISAs). The impact of NaHS on the regulation of p38 and ERK1/2 MAPK was confirmed by Western blot experiments. Furthermore, IL-6 and IL-8 expression was quantified by real-time polymerase chain reaction (RT-PCR) and ELISAs from cells which were exposed to SB203580, U0126 and NaHS and stimulated by IL-1β. The C-28/I2 cells constitutively expressed large quantities of IL-6 and IL-8. The data provided prove that in these cells, constitutive as well as IL-1β-induced IL-6 and IL-8 expression was partially and transiently blocked by the treatment of cells with both MAPK inhibitors and NaHS. Presented data seem to be important in evaluating the beneficial functions of MAPK inhibitors and H(2)S in immune-pathophysiological processes.

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