Heat shock transcription factor 1 acts as an endogenous protective mechanism in mechanically stretched alveolar epithelial cells.

Mechanical ventilation is a key respiratory support measure for critically ill patients. During improper ventilation, continuous exposure of alveolar epithelial cells (AECs) to abnormal mechanical environment can lead to ventilator-induced lung injury (VILI). Heat shock transcription factor 1 (HSF1) is a stress-responsive transcriptional regulator that orchestrates cytoprotective heat shock protein (HSP) expression in response to diverse stresses, including thermal and oxidative stress, but its role in stretch-induced AEC injury remains unclear. In this study, A549 cells were subjected to biaxial cyclic stretch to model mechanical stress associated with VILI in vitro. Consistent with the established role of YAP as a mechanotransduction regulator activated by cyclic stretch, we observed YAP signaling activation in our biaxial stretch system. Transcriptomic analysis revealed that mechanical stretch markedly induced the expression of HSP genes, and subsequent validation confirmed that stretch activated HSF1 and increased HSF1-dependent HSP expression. Pharmacological inhibition of HSF1 with DTHIB or CRISPR-Cas9-mediated HSF1 knockout attenuated stretch-induced HSP expression, while exacerbating ROS accumulation, cell death, and IL-6 production. Moreover, oxidative-stress-associated HSF1 targets were significantly enriched among stretch-induced genes, antioxidant treatment partially suppressed stretch-induced HSF1 activation, and HSF1 knockout increased oxidative stress after stretch. These findings indicate that HSF1 functions as an endogenous cytoprotective feedback mechanism in mechanically stretched AECs by inducing HSP expression and limiting stretch-induced oxidative damage and inflammatory injury. Activation of the HSF1-HSP axis may therefore represent a potential strategy for mitigating epithelial injury during VILI.