Purinergic P2X7 Receptors Participate in Disturbed Intracellular Calcium Homeostasis in Peripheral Blood Mononuclear Cells of Patients with Chronic Kidney Disease

Abstract

Background: P2X₇ receptors intervene with lymphocyte activation and are responsible for multiple processes, including calcium influx. Here, we studied the participation of P2X₇ receptors in disturbed intracellular calcium homeostasis regulation in early-stage chronic kidney disease (CKD). Methods: The study involved 20 healthy volunteers and 20 CKD stage 2–3 patients. The free cytosolic calcium concentration ([Ca²⁺]_i) was measured using fluorimetry. The P2X₇ pore function was evaluated by the fluorescent dye ethidium bromide. Results: In peripheral blood mononuclear cells (PBMCs) of patients, [Ca²⁺]_i, intracellular calcium stores and the capacitative calcium entry were increased when compared with healthy subjects. The agonist of P2X₇ receptor BzATP caused a sustained increase in [Ca²⁺]_i in both groups, but the effect was smaller in patients. The antagonist at the P2X₇ receptor KN-62 reduced [Ca²⁺]_i in patients, but had no effect in healthy subjects. In patients, the permeability of ethidium bromide through P2X₇ pores, as well as through BzATP-activated and KN-62-inhibited pores, was distinct from permeability in healthy volunteers. Conclusions: These results demonstrate that the calcium signaling pathway in PBMCs of CKD patients is defective already in CKD stage 2–3, and the pore-forming P2X₇ receptors are involved in these pathophysiological processes.