Platelet activating factor receptors drive CXC chemokine production, neutrophil influx and edema formation in the lungs of mice injected with Tityus serrulatus venom.

Lung injury is a common finding and a frequent cause of death in cases of severe human envenoming by scorpion sting. The present work investigated the effects of pretreatment with a platelet activation factor receptor (PAFR) antagonist and a CXCR2 inhibitor on the lung injury induced by subcutaneous injection of Tityus serrulatus venom (TsV) in mice. Lung injury was assessed by evaluating the extravasation of Evans blue dye, as an index of increased vascular permeability, the neutrophil accumulation (mieloperoxidase activity), the concentration of tumor necrosis factor-alpha (TNF-alpha) and the chemokine KC in the lung after TsV administration. Neutrophil influx was preceded by the production of KC and dependent on CXCR2, as shown by the ability of repertaxin, a CXCR2 inhibitor, to prevent an increase of MPO activity in the lung. Repertaxin had no effect on TsV-induced lethality. The PAFR antagonist (UK-74,505) significantly reduced TsV-induced vascular permeability changes and neutrophil influx in the lungs. The inhibition of neutrophil influx was associated with inhibition of the production of the CXCR2-active chemokine KC. UK-74,505 had no effect on the lethality induced by TsV. In conclusion, these results show that the influx of neutrophils in the lungs of mice injected with TsV is dependent on the activation of PAFR and on PAFR-dependent production of the chemokine KC as well as activation of CXCR2 on neutrophils. Although lung injury may contribute to late lethality after TsV envenoming, acute lethality is not modified by inhibitors of neutrophil influx.

Repertaxin, a novel inhibitor of rat CXCR2 function, inhibits inflammatory responses that follow intestinal ischaemia and reperfusion injury.

1. Neutrophils are thought to play a major role in the mediation of reperfusion injury. CXC chemokines are known inducers of neutrophil recruitment. Here, we assessed the effects of Repertaxin, a novel low molecular weight inhibitor of human CXCL8 receptor activation, on the local, remote and systemic injuries following intestinal ischaemia and reperfusion (I/R) in the rat. 2. Pre-incubation of rat neutrophils with Repertaxin (10(-11)-10(-6) m) inhibited the chemotaxis of neutrophils induced by human CXCL8 or rat CINC-1, but not that induced by fMLP, PAF or LTB(4), in a concentration-dependent manner. Repertaxin also prevented CXCL8-induced calcium influx but not CXCL8 binding to purified rat neutrophils. 2. In a model of mild I/R injury (30 min of ischaemia and 30 min of reperfusion), Repertaxin dose-dependently (3-30 mg kg(-1)) inhibited the increase in vascular permeability and neutrophil influx. Maximal inhibition occurred at 30 mg kg(-1). 4. Following severe I/R injury (120 min of ischaemia and 120 min of reperfusion), Repertaxin (30 mg kg(-1)) markedly prevented neutrophil influx, the increase in vascular permeability both in the intestine and the lungs. Moreover, there was prevention of haemorrhage in the intestine of reperfused animals. 5. Repertaxin effectively suppressed the increase in tissue (intestine and lungs) and serum concentrations of TNF-alpha and the reperfusion-associated lethality. 6. For comparison, we also evaluated the effects of an anti-CINC-1 antibody in the model of severe I/R injury. Overall, the antibody effectively prevented tissue injury, systemic inflammation and lethality. However, the effects of the antibody were in general of lower magnitude than those of Repertaxin. 7. In conclusion, CINC-1 and possibly other CXC chemokines, acting on CXCR2, have an important role during I/R injury. Thus, drugs, such as Repertaxin, developed to block the function of the CXCR2 receptor may be effective at preventing reperfusion injury in relevant clinical situations.