1. Department of Natural Biotechnology, Nanhua University, Chiayi, Taiwan
2. Cardiovascular Center, Department of Anesthesiology and Department of Internal Medicine, Taichung Veterans General Hospital, Taichung, Taiwan
3. Department of Medicine, National Yang-Ming University, School of Medicine, Taipei, Taiwan
Background: Endothelial dysfunction is one of the underlying causes for vascular diseases. tert-Butyl hydroperoxide (t-BHP), a short-chain lipid hydroperoxide analog, has been reported to cause adverse effects in different systems. However, the adverse actions of t-BHP on inducing endothelial dysfunction are unclear and remain under investigation. Aim of the present study was to identify the pathobiological mechanisms of t-BHP in rat aortic endothelial cells and thoracic aorta.
Methods: Primary cultured cells were treated with vehicle or t-BHP (50, 100, 250, 500, and 1,000 μM). Cells were harvested and specific analyses regarding cellular apoptosis, necrosis, and senescence were conducted. Additionally, t-BHP (0.1, 0.2, and 0.4 mmol/kg body weight) or vehicle were administered to male rats (the young group at 6 weeks of age and the mature adult group at 24 weeks of age) daily through intraperitoneal injections. At 10 days after the first drug treatment apoptotic endothelial toxicity was evaluated by biochemical, histological, and immunofluorescent staining analyses.
Results: Dose-dependent effects of t-BHP were observed for the reduction of cell viability, deterioration of cell toxicity, initiation of cell cycle arrest, and triggering of apoptosis and necrosis. Moreover, increase of cells stained positive for senescence-associated beta-galactosidase (SA-β-Gal), amelioration of telomerase activity, and precipitations of necrotic, cell cycle, and apoptotic signaling regulatory proteins were also found in the in vitro model. In the in vivo study, results indicated that t-BHP at higher doses enlarged the intima-medial thickness of descending aorta in the mature adult group, but led to aortic narrowing in the young group. Increased injuries were observed by upregulating endothelial apoptosis- and senescence-positive staining, along with caspase-3 activity and down-regulating telomerase activity.
Conclusion: These results confirmed that t-BHP impaired aortic endothelial cell survival at least partially by the activation of p53-mediated signaling pathways, inhibition of cell cycle regulatory proteins, and initiation of cellular senescence-related signaling pathways. In conclusion, t-BHP was found to be a major trigger for impairing aortic endothelial cell survival and deteriorating vascular dysfunction in experimental practice.
Keywords: apoptosis, cell cycle, p53, rat aortic endothelial cells, telomerase activity, tert-butyl peroxide (t-BHP)