NF­κB/IκBα signaling pathways are essential for resistance to heat stress­induced ROS production in pulmonary microvascular endothelial cells.

ABSTRACT

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 NF­κB in primary human umbilical vein endothelial cells. The present study aimed to further investigate the role of NF­κB/IκBα signaling pathways in the inhibition of HS­induced reactive oxygen species (ROS) generation and cytotoxicity in endothelial cells. The results of the present study demonstrated that HS triggered a significant amount of NF­κB and IκBα nuclear translocation without IκBα degradation in a time­dependent manner. Mutant constructs of IκBα phosphorylation sites (Ser32, Ser36) were employed in rat pulmonary microvascular endothelial cells (PMVECs). Cell Counting Kit­8 assays demonstrated that both the small interfering (si)RNA­mediated knockdown of p65 and IκBα mutant constructs significantly decreased cell viability and aggravated ROS accumulation in HS­induced 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 NF­κB activation and nuclear translocation, indicating that IκBα­independent pathways contributed to NF­κB activity and nucleus translocation in a time­dependent manner following HS. Collectively, the results of the present study suggested that the NF­κB/IκBα pathway was essential for resistance to HS­induced 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.