NF‑κB/IκBα signaling pathways are essential for resistance to heat stress‑induced ROS production in pulmonary microvascular endothelial cells.

The results of a previous study demonstrated that heat stress (HS) triggered oxidative stress, which in turn induced the apoptosis of epithelial cells. These results uncovered a novel mechanism underlying the activation of NF‑κB in primary human umbilical vein endothelial cells. The present study aimed to further investigate the role of NF‑κB/IκBα signaling pathways in the inhibition of HS‑induced reactive oxygen species (ROS) generation and cytotoxicity in endothelial cells. The results of the present study demonstrated that HS triggered a significant amount of NF‑κB and IκBα nuclear translocation without IκBα degradation in a time‑dependent manner. Mutant constructs of IκBα phosphorylation sites (Ser32, Ser36) were employed in rat pulmonary microvascular endothelial cells (PMVECs). Cell Counting Kit‑8 assays demonstrated that both the small interfering (si)RNA‑mediated knockdown of p65 and IκBα mutant constructs significantly decreased cell viability and aggravated ROS accumulation in HS‑induced rat PMVECs compared with the control. Additionally, western blot analysis revealed that p65 siRNA attenuated the protein expression of IκBα. However, IκBα mutant constructs failed to attenuate NF‑κB activation and nuclear translocation, indicating that IκBα‑independent pathways contributed to NF‑κB activity and nucleus translocation in a time‑dependent manner following HS. Collectively, the results of the present study suggested that the NF‑κB/IκBα pathway was essential for resistance to HS‑induced ROS production and cytotoxicity in rat PMVECs, and that it could be a potential therapeutic target to reduce the mortality and morbidity of heat stroke.