Angiopoietin-like 4 knockdown attenuates cigarette smoke extract–induced oxidative stress and apoptosis in lung bronchial epithelial cells by inhibiting NADPH oxidase

It has been found that angiopoietin-like 4 (ANGPTL4) expression is increased in the serum of patients with chronic obstructive pulmonary disease (COPD). Herein, cigarette smoke extract (CSE) was used to stimulate oxidative stress in bronchial epithelial cells BEAS-2B, and the role and potential mechanism of ANGPTL4 in smoking-induced lung dysfunction were explored. The roles of different concentrations of CSE (0, 1, 2.5, 5, or 10%) in cell viability and ANGPTL4 levels were evaluated. Following ANGPTL4 being knocked down, the effects of ANGPTL4 knockdown on oxidative stress and apoptosis were determined. Moreover, the level of NADPH oxidase 2 (NOX2) was upregulated to assess the mediated role of NOX in the regulation of ANGPTL4, along with JNK/p38 MAPK signaling. CSE treatment elevated the level of ANGPTL4, and ANGPTL4 knockdown reduced CSE-induced oxidative stress, apoptosis, and NOX level in BEAS-2B cells. The greatest degree of alteration was found in NOX2, and additional NOX2 overexpression broke the inhibitory influences of ANGPTL4 knockdown on oxidative stress and apoptosis. Otherwise, ANGPTL4 knockdown hindered the activation of JNK/p38 MAPK signaling, whereas NOX2 overexpression activated this signaling pathway. Together, ANGPTL4 knockdown attenuated CSE-induced oxidative stress, apoptosis, and activation of JNK/MAPK signaling by inhibiting NOX.