Uremic concentrations of guanidino compounds inhibit neutrophil superoxide production

Abstract

Background. In uremia, diminished reactive oxygen intermediate (ROI) production is an important consequence of impaired neutrophil function. We have studied the effect of guanidino compounds, known uremic toxins, on neutrophil ROI production in vitro. Methods. Neutrophils from healthy volunteers were exposed for three hours to individual or mixed guanidino compounds (GCmix) at concentrations encountered in uremic plasma. After removal of guanidino compounds, neutrophils were activated by adhesion, N-formyl-methionyl-leucyl-phenyalanine (fMLP), phorbol 12-myristate 13-acetate (PMA), or opsonized zymosan, and superoxide production was measured by lucigenin chemiluminescence (CL). The direct effect of guanidino compounds on superoxide production in activated neutrophils was also measured. The energy status (ATP and creatine phosphate), antioxidant status (total glutathione), and glycolytic flux (lactate production) were measured. Results. The GCmix pretreatment decreased the superoxide production in activated neutrophils (fMLP or zymosan) by 50% (P < 0.01) and the ATP concentration by 60% (P < 0.05), and it inhibited glycolytic flux (lactate production) by 45% (P < 0.01), but did not alter glutathione concentration. Simultaneous exposure to GCmix and activation did not inhibit nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity in cell lysates, but inhibited superoxide formation in zymosan-activated intact neutrophils, and this inhibition was reversed following removal of the guanidino compounds. Conclusion. Guanidino-succinate, -propionate, and -butyrate were individually as potent as the GCmix. Inhibition of neutrophil superoxide generation by guanidino compounds results from a depressed energy status. Uremic concentrations of guanidino compounds significantly inhibit neutrophil metabolism, and this has serious implications for their function in host defense.