Long term exposure to deltamethrin causes a dual effect on plasma membrane Ca²⁺-ATPase activity and reduces its mRNA levels in human lymphocytes

271-278Deltamethrin (Delt), a type II pyrethroid used worldwide, is chemically and biologically stable and displays mild toxicity in mammals, but chronic exposure causes toxic effects on the immune system. In order to clarify the damage of deltamethrin to lymphocytes, we studied the effect of deltamethrin on the catalytic activity and expression levels of the plasma membrane Ca2+-ATPase (PMCA) using human lymphocytes as a model. Lymphocytes were incubated with Delt at concentrations ranging from 2 to 133 µM for 36 h, followed by plasma membrane purification and analysis of PMCA activity. A significant increase of 122% in PMCA activity was observed with 2 µM Delt, while concentrations of 40 and 60 µM inhibited activity of PMCA to 58.3% below the control. The viability of lymphocytes was most affected at concentrations higher than 133 µM, the concentration that inhibited PMCA activity to 30.5%. Expression of PMCA was assessed by qPCR and the data showed a decrease in the amount of PMCA transcripts as a result of treatment with deltamethrin. Our results have shown that deltamethrin treatment of human lymphocytes in culture influences PMCA activity as measured in isolated plasma membranes as well as the PMCA mRNA levels sampled at different time points. It indicates disruption of the enzyme activity which would compromise cellular signaling and eventually may lead to cell death