Dialysis membrane-induced neutrophil apoptosis is mediated through free radicals

Patients on hemodialysis are prone to infection. Neutrophils are the host's first line of defense against certain invading pathogenic microorganisms. Since apoptotic neutrophils are functionally compromised we examined the ef fect of dialysis membranes on neutrophil apoptosis. Dialysis patients showe d greater (p < 0.001) neutrophil apoptosis when compared with control subje cts. Cellulose acetate membranes directly promoted (p < 0.001) neutrophil a poptosis. Cellulose acetate membrane-treated neutrophils exhibited greater apoptosis (p < 0.01) when compared with polysulfone membrane-treated neutro phils. Superoxide dismutase (SOD) partly inhibited the cellulose acetate me mbrane-induced neutrophil apoptosis, whereas both catalase and dimethylthio urea (DMTU) inhibited the polysulfone membrane-induced neutrophil apoptosis . Similarly, L-NAME, a nitric oxide synthase inhibitor, attenuated both the cellulose acetate and the polysulfone membrane-induced neutrophil apoptosi s. In addition, cellulose acetate and monocyte interaction products promote d (p < 0.001) neutrophil apoptosis. These results suggest that dialysis mem branes can promote neutrophil apoptosis directly as well as through their i nteraction with monocytes. The direct effect of dialysis membranes seems to be mediated partly through the generation of reactive oxygen species.