Tert-butyl hydroperoxide-mediated vascular responses in DOCA-salt hypertensive rats

Pathobiological Mechanisms of Endothelial Dysfunction Induced by tert-Butyl Hydroperoxide via Apoptosis, Necrosis and Senescence in a Rat Model

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.

ERK/Nrf2 pathway activation by caffeic acid in HepG2 cells alleviates its hepatocellular damage caused by t-butylhydroperoxide-induced oxidative stress

Background

Several studies have found that caffeic acid (CA), a well-known phytochemical, displays important antioxidant and anti-cancer activities. However, no evidence exists on the protective effect and its mechanisms that CA treatment alone has against oxidative stress induced by tert-butyl hydroperoxide (t-BHP) in HepG2 cells.

Methods

Hepatoprotective activities such as cell viability, mRNA expression, and report gene assay were measured using HepG2 cell. Three types of genes and proteins related with detoxification in liver were used for measuring the hepatoprotective effects. Statistical analysis was performed using one-way ANOVA test and differences among groups were evaluated by Tukey’s studentized range tests.

Results

The present study indicate that treatment with CA up-regulates heme oxygenase-1 (HO-1) and glutamate-cysteine ligase (GCL) mRNA and protein expressions in a CA-dose-dependent manner. In addition, translocation of nuclear factor-E2 p45-related factor (Nrf2) from the cytoplasm to the nucleus and phosphorylation of extracellular signal-regulated kinase, ERK and c-Jun N-terminal kinase, JNK which have been shown to be involved in mitogen-activated protein kinases, MAPKs are significantly enhanced by CA treatment. Furthermore, in cell nuclei, CA enhances the 5′-flanking regulatory region of human antioxidant response element (ARE) and activates the ARE binding site.

Conclusion

Therefore, CA proved to be a stimulant of the expression of detoxification enzymes such as HO-1, GCLC, and GCLM through the ERK/Nrf2 pathway, and it may be an effective chemoprotective agent for protecting liver damage against oxidative damage.

Graphical abstract

Electronic supplementary material

The online version of this article (10.1186/s12906-019-2551-3) contains supplementary material, which is available to authorized users.

Molecular characterization of reactive oxygen species in systemic and pulmonary hypertension

Hypertension, commonly recognized as high blood pressure, is a serious disease that affects millions of people worldwide. Similar to many physiological disorders, hypertension consists of several different cellular signaling pathways that involve various molecular messengers. Recent studies have shown that reactive oxygen species (ROS) play a substantial role in the development of both systemic and pulmonary hypertension, contributing to the pathology of this disease. However, the exact molecular mechanism of ROS in hypertension is not completely understood. In this review, we extensively examine and discuss the most recent experimental findings regarding the role of ROS in both pulmonary and systemic hypertension. Current studies show that excessive ROS not only promote JAK/STAT (janus kinase/signal transducers and activators of transcription)-mediated vascular remodeling in an angiotensin (ANG) II-induced hypertension model but also decrease the nitric oxide bioavailability. Furthermore, it has been shown that ROS generation can be mitigated through the inhibition of upstream ANG II or by blocking key ROS generators, such as nicotinamide adenine dinucleotide phosphate oxidase. Thus, various treatment options have been explored. Yet, as discussed in the current review, the regulation of ROS via novel antioxidant therapies may provide an alternative treatment for hypertension in the future.

Proteomics in investigation of protein nitration in kidney disease: technical challenges and perspectives from the spontaneously hypertensive rat

Kidneys are the mammalian organs with widest range of oxidative status ranging from the well-perfused cortex to the relatively anoxic medulla. This organ is of key interest from the perspective of hypertension, an important contributor to human mortality, and there has been growing use of the spontaneously hypertensive rat (SHR) as a model to explore oxidative stress in hypertensive kidney. Nitrosative stress is often associated with oxidative stress and, like oxidative stress, can lead to covalent modification of protein side-chains. It is especially relevant to kidney because of high levels of both nitrite/nitrate and nitric oxide synthase in medulla. Because of their relatively low abundance and their well-known role in signal transduction, nitration of tyrosines to 3-nitrotyrosines (3NT) is of particular interest in this regard. This modification has the potential to contribute to changes in regulation, in protein activity and may provide a means of specific targeting of key proteins. Mass spectrometry (MS) offers a promising route to detecting this modification. This review surveys protein nitration in kidney disease and highlights opportunities for MS detection of nitrated residues in the SHR.

Chemistry and antihypertensive effects of tempol and other nitroxides

Nitroxides can undergo one- or two-electron reduction reactions to hydroxylamines or oxammonium cations, respectively, which themselves are interconvertible, thereby providing redox metabolic actions. 4-Hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (tempol) is the most extensively studied nitroxide. It is a cell membrane-permeable amphilite that dismutates superoxide catalytically, facilitates hydrogen peroxide metabolism by catalase-like actions, and limits formation of toxic hydroxyl radicals produced by Fenton reactions. It is broadly effective in detoxifying these reactive oxygen species in cell and animal studies. When administered intravenously to hypertensive rodent models, tempol caused rapid and reversible dose-dependent reductions in blood pressure in 22 of 26 studies. This was accompanied by vasodilation, increased nitric oxide activity, reduced sympathetic nervous system activity at central and peripheral sites, and enhanced potassium channel conductance in blood vessels and neurons. When administered orally or by infusion over days or weeks to hypertensive rodent models, it reduced blood pressure in 59 of 68 studies. This was accompanied by correction of salt sensitivity and endothelial dysfunction and reduced agonist-evoked oxidative stress and contractility of blood vessels, reduced renal vascular resistance, and increased renal tissue oxygen tension. Thus, tempol is broadly effective in reducing blood pressure, whether given by acute intravenous injection or by prolonged administration, in a wide range of rodent models of hypertension.