Effects of chitosan oligosaccharide (COS) on the glycerol-induced acute renal failure in vitro and in vivo.

The purpose of this study was to investigate the effects of chitosanoligosaccharide (COS) on the change of inflammatory response, renal function factor, and renal oxidative stress in glycerol-induced ARF in vitro and in vivo. The molecular weight of COS was approximately below 10 kDa with 90% degree of deacetylation. Renal proximal tubular cells were treated with only COS (0, 0.01, 0.025, 0.05, 0.075 and 0.1%) or COS in the presence of glycerol (4mM). And rats were administered with glycerol (50%, 8 ml/kg) by intramuscular injection for the induction of ARF. For identification the protection effect of COS in the glycerol-induced ARF, rats were administered by COS (0.05 and 0.1%) using P.O. injection. The enzymatic activity of the released RDPase was assayed by the fluorometric method. The level of TNF-alpha in kidney or the culture medium was quantified using ELISA kit (R&D Systems, Minneapolis, USA) and, nitrite concentration was determined by the Griess reaction. We showed that COS stimulated the production of TNF-alpha, NO and the released RDPase. Glycerol increased the concentration of RDPase in kidney and decreased the released RDPase in proximal tubular cells. And, glycerol increased the production of NO, TNF-alpha, creatinine, and MDA, and decreased SOD. However, COS recovered the glycerol-induced inflammatory response, renal function factor, and antioxidant effect in kidney. COS had the antioxidant activity and the anti-inflammatory effect. And maybe that characteristics could help recover the glycerol-induced ARF.

Release of renal dipeptidase from glycosylphosphatidylinositol anchor by insulin-triggered phospholipase C/intracellular Ca2+.

Glycosylphosphatidylinositol (GPI) anchored proteins appear to be released from the plasma membrane due to various extracellular stimuli. To determine the signaling pathway from insulin to GPI-protein, the release of GPI-renal dipeptidase (RDPase, EC 3.4.13.19) from porcine proximal tubules, stimulated by insulin, was explored. Insulin stimulated the release of RDPase in a concentration-dependent manner (half maximal release at 0.58 nM), which peaked at 10-20 min. Western blot analysis, with antibody against the cross-reacting determinant (CRD), revealed that RDPase was released by a GPI-specific phospholipase C (GPI-PLC), and was shown to be Ca2+-dependent. A PI-PLC inhibitor, U73122, effectively blocked the effect of insulin on the release of RDPase, suggesting insulin is associated with an intracellular PI-PLC. Insulin treatment increased the production of intracellular Ca2+ from porcine proximal tubules. Intracellular Ca2+, coupled with insulin, facilitated the releases of RDPase, an inhibitor of inositol trisphosphate-dependent Ca2+ from the endoplasmic reticulum, and a Ca2+ channel blocker that blocked the effect of insulin. Taken together, these results suggest that insulin, in part, may activate a GPI-PLC, via PI-PLC/intracellular Ca2+, which may consequently stimulate the release of RDPase.

Mast cells play a key role in the development of late airway hyperresponsiveness through TNF-alpha in a murine model of asthma.

We have investigated the role of TNF-alpha in mast cell-mediated late airway hyperresponsiveness (AHR) using mast cell-deficient WBB6F1-W/W(v) (W/W(v)) mice in a murine model of asthma, which exhibits a biphasic increase in AHR. TNF-alpha levels in the airway and magnitude of late AHR in response to airway allergen challenge were severely impaired in W/W(v) mice compared to their littermates. In addition to TNF-alpha, cytosolic phospholipase A(2) (cPLA(2)) phosphorylation and enzymatic activity in the lungs were also impaired in W/W(v) mice. Either anti-TNF-alpha antibody or an inhibitor of cPLA(2) abolished late AHR in congeneic +/+ mice. Intratracheal administration of TNF-alpha resulted in increases in late AHR, cPLA(2 )phosphorylation, cPLA(2 )activity, and phosphorylation of mitogen-activated protein kinases. Mast cell replacement restored airway TNF-alpha level, cPLA(2 )phosphorylation and enzymatic activity in the lungs as well as late AHR in W/W(v) mice. These data indicate that mast cells play a key role in the development of late AHR through liberation of TNF-alpha.

Platelet-activating factor-mediated NF-kappaB dependency of a late anaphylactic reaction.

Anaphylaxis is a life-threatening systemic allergic reaction with the potential for a recurrent or biphasic pattern. Despite an incidence of biphasic reaction between 5 and 20%, the molecular mechanism for the reaction is unknown. Using a murine model of penicillin V-induced systemic anaphylaxis, we show an autoregulatory cascade of biphasic anaphylactic reactions. Induction of anaphylaxis caused a rapid increase in circulating platelet-activating factor (PAF) levels. In turn, the elevated PAF contributes to the early phase of anaphylaxis as well as the subsequent activation of the nuclear factor (NF)-kappaB, a crucial transcription factor regulating the expression of many proinflammatory cytokines and immunoregulatory molecules. The induction of NF-kappaB activity is accompanied by TNF-alpha production, which, in turn, promotes late phase PAF synthesis. This secondary wave of PAF production leads eventually to the late phase of anaphylactic reactions. Mast cells do not appear to be required for development of the late phase anaphylaxis. Together, this work reveals the first mechanistic basis for biphasic anaphylactic reactions and provides possible therapeutic strategies for human anaphylaxis.