INDUCTION OF HEMOLYSIS AND ERYPTOSIS BY OCCUPATIONAL POLLUTANT NICKEL CHLORIDE IS MEDIATED THROUGH CALCIUM INFLUX AND P38 MAP KINASE SIGNALING

Abstract

Objectives: Nickel (Ni) is an abundant environmental hazard and an occupational pollutant. Exposure to Ni compounds is prevalent in electroplating workers and in the printing industry, among others. The toxicity of Ni manifests as dermatological, gastrointestinal, respiratory, allergic, and cardiovascular symptoms. In particular, hyperbilirubinemia and reticulocytosis have been detected in intoxicated subjects; an observation possibly implicating selective red blood cell (RBC) toxicity. Herein, the interaction of nickel chloride (NiCl2) with human RBCs and associated molecular mechanisms are described. Material and Methods: Cells from healthy donors were incubated for 24 h at 37°C in the presence or absence of 0.5-10 mM of NiCl2, and cytotoxicity was determined through hemoglobin leakage by colorimetry under different experimental conditions. Eryptotic markers were also identified by flow cytofluorometry using Annexin-V-FITC tagging for phosphatidylserine (PS) exposure, light scatter properties for cellular dimensions, Fluo4/AM labeling for intracellular calcium, and H2DCFDA staining for reactive oxygen species (ROS). Additionally, small molecule inhibitors were used to probe the signaling pathways involved. Results: It was found that NiCl2at 10 mM caused profound intracellular calcium overload and significant calcium-dependent hemolysis. Also, NiCl2reduced forward scatter and increased side scatter, Annexin- positive cells, and ROS levels. Importantly, NiCl2-induced hemolysis was significantly attenuated by the exclusion of extracellular calcium, and in the presence of p38 MAP kinase (MAPK) inhibitor SB203580. Conclusions: It is concluded that NiCl2induces p38 MAPK-dependent hemolysis, and stimulates the canonical features of premature eryptosis. This report presents the first description of the molecular mechanisms underlying the hemolytic and eryptotic potential of NiCl2and, thus, may explain changes in hematological parameters observed in poisoning victims.