Effects of Commercial Glucose-Based Peritoneal Dialysates on Peripheral Blood Phagocytes Apoptosis

Abstract

Background Variable glucose-lactate-based peritoneal dialysates have negative effects on peritoneal macrophages and peripheral blood leukocytes, reducing the capacity of leukocytes for chemotaxis, bacterial killing. But few reports exist on cell apoptosis. To investigate the effects of glucose-lactate-based peritoneal dialysates on cultured phagocytes (monocytes and neutrophils), we focused on studying phagocyte apoptosis after brief exposure to commercial peritoneal dialysates. Methods Cell apoptosis is measured by flow cytometry (FCM) to detect phosphatidylserine (PS) exposure on early apoptotic cells using fluorescein-labeled annexin V. To mimic the composition of dialysate in vivo, where the freshly instilled solution mixes with the residual dialysate from the previous cycle, we performed the experiments using a mixture of fresh and spent dialysate (9:1). In our transient exposure experiments, monocytes and neutrophils were separately incubated in each of the test solutions (1.5% glucose an d 4.25% glucose dialysates) for 10 minutes or 30 minutes and afterward separated and resuspended in RPMI 1640 medium and cultured over the indicated time. Results After exposure to 1.5% glucose dialysates for 10 minutes, monocytes and neutrophils exhibited normally spontaneous apoptosis. After exposure to 4.25% glucose dialysate, monocytes underwent apoptosis increasingly, 21% % 5.0% versus 9.8% % 3.6% (p < 0.05) at 24 hours and 47% % 6.2% versus 16% % 4.0% (p < 0.01) at 72 hours compared with controls. For neutrophils, the results were discouraging: hypertonic dialysate not only increased apoptosis [65.36% % 2.6% versus 34.17% % 8.52% (p < 0.01) at 72 hours], but also induced cell necrosis. When incubation time was prolonged for 30 minutes, 1.5% dialysate acted like 4.25% dialysate, with the rate of apoptosis increasing rapidly [40% % 4.0% versus 16% % 4.0% (p < 0.01) at 72 hours for monocytes, and 66.90% % 5.6% versus 34.17% % 8.52% (p < 0.01) at 72 hours for neutrophils]. Conclusion Glucose-lactate-based peritoneal dialysates can induce peripheral blood phagocyte apoptosis in vitro, which indicates that glucose plays an important role in triggering cell apoptosis. Therefore, looking for new, physiologic peritoneal dialysis fluids to replace conventional fluids is reasonable.