CALML3 mediates oxidative stress-induced apoptosis in human lens epithelial cells through PI3K/Akt pathway

The pathogenic factors of cataract are multivariate, among which oxidative stress is of great importance in the development of various types of cataract through causing damage to the lens epithelial cells, especially apoptosis. The cellular calcium (Ca2+) homeostasis is a necessary condition to maintain lens transparency in the lens epithelial cells. The purpose of our investigation was to identify the function of Calmodulin-like protein 3 (CALML3) in H2O2-induced apoptosis of human lens epithelial (HLE) cells and the underlying molecular mechanisms involved. Human lens epithelial cell line, HLEB-3, was treated with a series of concentrations of H2O2 (100, 300 and 500 mu M) and following focused on assessment of cell viability, apoptosis, accumulation of intracellular ROS and intracellular Ca2+ concentration by the MTT assay and flow cytometry analysis, respectively. The protein expression levels of CALML3, Caspase-3, Caspase-9, Cytochrome c (Cyt-c), p-Akt and Akt was measured by western blotting. In the present study, CALML3 overexpression inhibited cell apoptosis, generation of ROS, increased intracellular Ca2+, and the release of Cyt-c from the mitochondria into the cytosol caused by H2O2 in HLEB-3 cells. CALML3 overexpression also attenuated the increased expression of Caspase-3 and Caspase-9 in HLEB-3 cells induced by H2O2. Moreover, CALML3 overexpression attenuated the reduced activation of Akt induced by H2O2. To investigate the underlying mechanism by which CALML3 overexpression may inhibit H2O2-induced HLEB-3 cell injury through activating Akt signaling, PI3K inhibitor LY294002 was introduced in H2O2-induced HLEB-3 cells after CALML3 overexpression. We found that LY294002 reversed the protective effect of CALML3 overexpression against H2O2-induced injury in HLEB-3 cells. In conclusion, our data showed that CALML3 overexpression leads to a significant reduction of apoptosis after H2O2 treated, suggested that CALML3 upregulation may protect against H2O2-induced cataractogenesis. The underlying mechanism by which CALML3 overexpression protects against HLEB-3 cell apoptosis could be related to activation of PI3K/Akt pathway.