The investigation of the pyrethroid insecticide lambda-cyhalothrin (LCT)-affected Ca ²⁺ homeostasis and -activated Ca ²⁺ -associated mitochondrial apoptotic pathway in normal human astrocytes: The evaluation of protective effects of BAPTA-AM (a selective Ca ²⁺ chelator)

Exposure to insecticides has been found to have deleterious effects on human health. Lambda-cyhalothrin (LCT), a mixture of isomers of cyhalothrin, is a pyrethroid insecticide routinely used in pest control programs. LCT was reported to cause neurotoxic effects in various models. However, the mechanism of underlying effect of LCT on cytotoxicity in normal human brain cells is still elusive. This study examined whether LCT affected Ca ²⁺ homeostasis and Ca ²⁺ -related physiology in Gibco® Human Astrocytes (GHA cells), and explored whether BAPTA-AM (1,2-bis(2-aminophenoxy)ethane-N,N,N'N'-tetraacetic acid), a selective Ca ²⁺ chelator, has protective effects on LCT-treated GHA cells. The data show that LCT (10–15 μM) concentration-dependently induced cytotoxicity in both GHA cells and DI TNC1 normal rat astrocytes but only induced intracellular Ca ²⁺ concentration ([Ca ²⁺ ] _i ) rises in GHA cells. In terms of Ca ²⁺ signaling in GHA cells, LCT-induced [Ca ²⁺ ] _i rises were reduced by removing extracellular Ca ²⁺ and were inhibited by store-operated Ca ²⁺ channel modulators (2-APB, econazole or SKF96365). In Ca ²⁺ -free medium, pretreatment with the endoplasmic reticulum Ca ²⁺ pump inhibitor thapsigargin abolished LCT-induced [Ca ²⁺ ] _i rises. Conversely, incubation with LCT abolished thapsigargin-induced [Ca ²⁺ ] _i rises. Regarding cytotoxicity, LCT evoked apoptosis by regulating apoptotic protein expressions (Bax, BCl-2, cleaved caspase-9/-3). This apoptotic response was significantly inhibited by prechelating cytosolic Ca ²⁺ with BAPTA-AM. Together, in GHA cells, LCT induced [Ca ²⁺ ] _i rises by inducing Ca ²⁺ entry via store-operated Ca ²⁺ channels and Ca ²⁺ release from the endoplasmic reticulum. Moreover, BAPTA-AM has a protective effect on inhibiting LCT-activated mitochondrial apoptotic pathway. This study provided new insights into the molecular protective mechanism of LCT-induced cytotoxicity in normal human astrocytes.