The potential roles of stress-induced phosphoprotein 1 and connexin 43 in rats with reperfusion arrhythmia

Objective: Connexin 43 (Cx43) is a critical gene for maintaining myocardial homeostasis. Interestingly, Cx43 and stress-induced phosphoprotein 1 (STIP1) were recorded to be lowly expressed in ischemia/reperfusion (I/R). However, their impacts on reperfusion arrhythmia (RA) remain to be explored. Our study aimed to find out the related underlying mechanisms.

Methods: After the establishment of an isolated heart model through Langendorff perfusion, the heart rate, conduction activation time, conduction velocity, and conduction direction of the left ventricle were evaluated, along with the apoptotic rate detection in the collected myocardial tissues. After the construction of a hypoxia/reoxygenation (H/R)-induced cellular model, cell apoptosis, intercellular communication, cell viability, and the content of reactive oxygen species, superoxide dismutase, malondialdehyde, and lactic dehydrogenase were measured. The expression of Cx43 and STIP1 was determined in both rat heart and cell models. The bindings of STIP3 and Cx43 to heat shock protein 90 (HSP90) and heat shock protein 70 (HSP70) were verified.

Results: Relative to the corresponding controls, Cx43 and STIP1 were decreased in myocardial tissues of RA rats and H/R-stimulated H9C2 cells, where Cx43-binding HSP70 and HSP90 were respectively increased and decreased, and ubiquitination level of Cx43 was enhanced. STIP1 overexpression promoted protein expression of Cx43, intercellular communication, and cell viability, and reduced cell apoptosis and oxidative stress in H/R-stimulated H9C2 cells.

Conclusion: STIP1 promoted Cx43 expression to improve intercellular communication and reduce oxidative stress in H/R-stimulated H9C2 cells.