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Heat stress and gut‑derived endotoxinemia are common causes of multiple organ dysfunction syndrome in heat stroke patients. Evidence has demonstrated that cell apoptosis in the small intestine serves an important role in the pathogenesis of heatstroke, which leads to increased intestinal permeability to endotoxin or lipopolysaccharides (LPS) from the gut entering the circulation. However, little is known about the potential underlying mechanisms mediating heat stress combined with LPS‑induced intestinal epithelial cell apoptosis. In the present study, LPS combined with heat stress induced production of reactive oxygen species (ROS), mitochondrial membrane potential disruption and cell apoptosis, which eventually led to increased intestinal permeability and reduced epithelial resistance in the IEC‑6 cell line. Inductions in ROS, mitochondrial membrane potential disruption and cell apoptosis were detected by using an ROS assay kit, 5,5',6,6'‑tetrachloro‑1,1',3,3'tetraethylbenzimidazo carbocyanine iodide dye kit and annexin V‑fluorescein isothiocyanate apoptosis kit, respectively. The effect of ROS on mitogen activated protein kinases (MAPKs) and c‑Jun activation was investigated using the antioxidant drug, butylated hydroxyanisole (BHA) by western blotting. The results of the present study demonstrated that ROS is essential to activate p38, extracellular signal‑regulated kinase (ERK) and c‑Jun, but not c‑Jun N‑terminal kinase (JNK), in LPS combined with heat stress treated cells. Furthermore, ROS, and activation of p38, JNK and c‑Jun, were revealed to serve pro‑apoptosis roles which aggravated damage to epithelial barrier integrity, as assessed by flow cytometry using Annexin V‑fluorescein isothiocyanate staining and pretreatment of cells with specific inhibitors of ROS, JNK, p38 and c‑Jun (BHA, SP600125, SB203580 and c‑Jun peptide, respectively). Transepithelial electrical resistance and horseradish peroxidase permeability were detected in cells treated with LPS combined with heat stress, which revealed that ERK serves an anti‑apoptosis role, as determined by pretreatment of cells with PD98059, a specific inhibitor of ERK. In conclusion, these findings suggested a novel role of the ROS signaling pathway which involved activation of MAPKs and c‑Jun, following LPS combined with heat stress‑induced IEC‑6 cell apoptosis and impairment of the epithelial barrier. These results may facilitate understanding of pathological conditions involving ROS, such as heat stroke. [ABSTRACT FROM AUTHOR]

Our previous study indicated that when human umbilical vein endothelial cells (HUVECs), which are involved in endothelial barrier function, are heat stressed, levels of protease-activated receptor 1 (PAR1) are increased significantly. In the present study, it was demonstrated that PAR1 serves a vital role in heat stress-induced HUVEC apoptosis. When the PAR1 inhibitor, SCH79797 (SCH), or a small interfering RNA (siRNA) targeting PAR1 were used to inhibit PAR1 signaling, a marked decrease in cell apoptosis, caspase-3 activity and the expression of the pro-apoptotic protein B-cell lymphoma 2 (Bcl-2) associated X (Bax), as well as increased expression of the anti-apoptotic Bcl-2 family member, myeloid cell leukemia 1 (Mcl-1), were observed. In addition, heat stress-induced apoptosis, caspase-3 activity and the expression of Bax were significantly increased following administration of the PAR1 agonist, TFLLR-NH2 or adenovirus overexpression of PAR1. This was accompanied by decreased protein expression levels of Mcl-1. Furthermore, it was identified that the DNA binding activity of the nuclear factor (NF)-κB p65 subunit increased and c-Jun activation was reduced as a result of inhibition of PAR1 signaling by SCH or siRNA-mediated PAR1 knockdown in heat stress-induced HUVECs. Additionally, our previous study reported that NF-κB p65 activation may have an anti-apoptosis effect on heat stressed HUVECs, whereas in the present study c-Jun activation had a pro-apoptosis effect on heat stressed HUVECs. Taken together, these results indicated that PAR1 signaling-mediated c-Jun activation promotes early apoptosis of HUVEC cells induced by heat stress. [ABSTRACT FROM AUTHOR]