Circulatory shock最新文献

This work studies the role that nitric oxide (NO) plays in ischemia/reperfusion (I/R) of the rat kidney. Sprague-Dawley rats, weighing 250-300 g, were subjected to 75 min of warm ischemia and contralateral nephrectomy. The animals were divided into six groups (n = 12 per group): ischemic control (IC) with normal saline, L-NG-mono-methyl-arginine (L-NMMA) 50 mg/kg, L-arginine (L-Arg) 300 mg/kg, Na-nitroprusside (Na-NP) 2.5 mg/kg, the combination of L-NMMA+Na-NP at the doses used before, and the sham group. All animals received the drug intravenously 60 min prior to ischemia. Survival was evaluated at seven days. Renal damage was assessed by kidney function tests (serum creatinine and blood urea nitrogen) and light histology. Lipid peroxidation was measured in renal tissue using the thiobarbituric acid assay. Significantly better survival was seen in the Na-NP group, as compared to the rest of the study. Serum creatinine at 24 and 48 hr showed a significant difference between the Na-NP group and the other groups. Histological damage was minimal in the Na-NP group. Clearly, the Na-NP had the most beneficial effect in survival and histological structure. Lipid peroxidation was significantly different, with the lower levels seen in the L-NMMA group and the higher levels in the Na-NP group. In base to these results, we conclude that exogenous NO has a beneficial and protective effect of the ischemically damaged rat kidney. This protection is independent of lipid peroxidation. Endogenous NO production does not play a role in I/R injury in our model.

CD40 functional responses can be triggered by binding of mAb G28-5. Here we show that G28-5 induces partial CD40 responses and functions as a partial antagonist of natural CD40 ligand, gp39, by preventing gp39 binding. Fab fragments of G28-5 retain inhibitory activity but lose crosslinking-dependent stimulatory activity. The synergistic interaction of CD40 signals with PMA or CD20 show differential requirements for CD40 crosslinking and different sensitivity to cyclosporine A, suggesting that CD40 receptor may use different effector mechanisms for synergy with calcium-dependent CD20 signals or with calcium-independent signals from PMA. Activation of NF-kappa B occurred in RAJI cells by G28-5 or by gp39 treatment, and was CD40 crosslinking-dependent. These results suggest that activation of NF-kappa B is involved in some CD40 receptor signals and may be related to CD40 effects on stimulation or inhibition of apotosis.

Addition of purified GM1 gangliosides inhibited lipopolysaccharide (LPS)-stimulated proliferation of purified B cells by greater than 90%. Addition of gangliosides to B cells as late as 120 min after the addition of LPS still inhibited B-cell proliferation, suggesting that inhibition did not simply reflect direct binding of LPS to gangliosides. Gangliosides also inhibited proliferation of B cells stimulated by anti-Ig antibodies, albeit to a lesser degree than inhibition of the LPS-stimulated response. The finding that B-cell proliferation stimulated by the combination of PMA+ionomycin was also inhibited by gangliosides suggests that its inhibitory activity did not reflect interference with binding of the B-cell stimuli to membrane receptors. The inhibitory effect of gangliosides was not restricted to B cells, since LPS-induced TNF production by macrophages was also inhibited in vitro. The inhibitory activity of gangliosides was also seen in vivo, and mice injected with soluble gangliosides or implanted with slow-release pellets impregnated with gangliosides showed reduced TNF production in vivo in response to LPS. Mice that were implanted with these slow-release pellets were also protected from LPS-induced lethality. Thus, while only 10% of control mice survived injection with LPS+galactosamine, the experimental group showed a 64% survival. It is likely that this protective effect reflects the ability of gangliosides to suppress LPS-mediated TNF production. This model provides a basis for studying a regulatory role for gangliosides in B-cell activation in vitro and macrophage activation in vitro and in vivo. Furthermore, it suggests new approaches to suppress the toxic effects induced by LPS in vivo.

We have here provided evidence that TNF mediated cytotoxicity is genetically, pharmacologically, and temporally distinct from the cytotoxicity mediated by TNF/CHX. Most studies on TNF cytotoxicity have been done by the combined use of TNF/CHX. The relevance of this approach to the physiological mechanisms underlying cytotoxicity by TNF alone is at present unclear. We have described a system in which overexpression of the p75-TNFR causes TNF-resistant cells to become TNF-sensitive. These cells are killed by TNF alone in a very short period of time and they are a useful system to study the mechanism of TNF-cytotoxicity.

Tumor necrosis factor-alpha (TNF-alpha) was reported to be important in the induction of septic shock. After i.v. injection of recombinant TNF-alpha (rTNF-alpha), BALB/c mice bearing Meth A fibrosarcoma (Meth A), but not normal mice, died of shock. Tumor cells are known to release many biological components. In this study, we examined the role of the tumor in the toxicity of rTNF-alpha in mice. Meth A cells maintained i.p. in mice were cultured for 24 hr in vitro. Conditioned medium (CM) obtained from the Meth A cells was given i.v. to mice, and 2 to 7 days later, i.v. injection of rTNF-alpha induced death in the animals. rTNF-alpha treatment 4 days after Meth A CM gave the maximum effect. rTNF-alpha did not induce death in mice treated with CM from spleen cells. However, after the Meth A cells were passaged 2 or 3 times in in vitro culture, the CM did not potentiate the toxicity of rTNF-alpha in mice. rTNF-alpha induced symptoms of disseminated intravascular coagulation (DIC) on coagulation parameters in the blood, and high plasma tissue factor (TF) activity in Meth A CM-treated mice and Meth A tumor-bearing mice. These results suggest that factor(s) are released from tumor cells activated by interaction with host cells, and injection of rTNF-alpha and the factor(s) results in the induction of DIC syndrome leading to host death.

In order to analyse the physiological relevance of the 55 kDa tumor necrosis factor receptor 1 (TNFR1) and its role in various TNF related pathological conditions, such as septic shock, we have generated mice by gene targeting deficient for TNFR1 expression. The TNFR1-deficient mice are unable to cope with Listeria monocytogenes infections but mount an apparently normal immune response when challenged with Vaccinia or LCMV viruses. They are resistant to the lethal effects of lipopolysaccharide (LPS) after sensitization with D-galactosamine (D-GalN) but remain sensitive to very high doses of LPS given alone. We have analyzed functions relevant to inflammatory processes, such as adhesion, secondary factor release, and proliferation in fibroblasts derived from these mice. We show that the TNFR1 virtually monopolises TNF-mediated signaling in all these situations and that the 75 kDa TNFR2 seems to be largely restricted to an accessory role, which is compatible with the previously established "ligand passing" hypothesis.

Activated T cells express a number of cell surface proteins that play an important role in cell contact-dependent interactions with cells in the immune system, including B cells, macrophages and other T cells. Among these T cell-expressed proteins are members of the TNF ligand family, which includes TNF, lymphotoxin (LT)-alpha and -beta, and the ligands for CD27, CD30, CD40, 4-1BB, OX-40, and Fas. The recent cloning of a number of these ligands has paved the way for a detailed analysis of the role of these molecules in immune responses. Initial studies have suggested that most, if not all, of these ligands co-stimulate T-cell proliferation. It is becoming increasingly apparent, however, that members of the TNF ligand family play unique and critical roles in both the development of the immune system and in immune responses to specific pathogens.