Caspase inhibition restored collagen I and fibronectin release in human lung fibroblasts exposed to cigarette smoke

Caspases and gasdermins have been extensively studied in immune cells, but their involvement in human lung fibroblasts (HLFs), the main extracellular matrix (ECM) source, in chronic obstructive pulmonary disease (COPD), is poorly understood. Recent evidence suggests a link between caspases and ECM remodeling in dermal fibroblasts, scar tissue, and mice glomerulonephritis models. It is known that caspases can be activated by oxidative stress, and active caspase-3 is the executor of gasderminE (GSDME). Caspases and gasdermins involvement in cigarette smoke (CS)-induced responses of HLFs is unknown. We tested whether caspases and GSDME are activated in HLFs exposed to CS extract (CSE) and their role in ECM remodeling. MRC5 lung fibroblasts were treated with CSE with/ without the antioxidant N-acetyl cysteine (NAC), and caspase-8 (z-IETD) inhibitor. The effect on caspase-1/-8/-3 activation, GSDME cleavage, ECM remodeling (collagen I, COL1, and fibronectin, FN), and mitochondrial ROS (mROS) generation was measured. Key findings were validated in patient-derived HLFs (phLFs). In MRC5, CSE induced activation of caspase-1/-8/-3/7, mROS generation, and COL1 and FN decrease. NAC inhibited mROS and all caspases activation. CSE caused caspase-8-dependent activation of caspase-3, leading to the activation of GSDME. Inhibition of caspase 8 and mROS restored FN and COL1 levels. In phLFs, activation of caspase-1/-8, decreased COL1/FN, and effect of NAC were confirmed. This study showed that CSE can activate mROS and the inflammatory axis caspase-8/-3/GSDME in HLFs. Caspases inhibition restored FN and COL1 levels, providing a possible mechanism underlying ECM remodeling in COPD.