Cyclooxygenase-2 Inhibition Limits Angiotensin II-Induced DNA Oxidation and Protein Nitration in Humans

Contribution of cyclooxygenase-2 overexpression to enhancement in tonically active glutamatergic inputs to the rostral ventrolateral medulla in hypertension

OBJECTIVE

Cyclooxygenase (COX) is critical in regulating cardiovascular function, but its role involved in the central control of blood pressure (BP) is uncovered. The tonic glutamatergic inputs to the rostral ventrolateral medulla (RVLM) are enhanced in hypertension. Here, the present study was designed to investigate the effect and mechanism of central COX on tonic glutamatergic inputs to the RVLM and BP regulation.

METHODS

Wistar-Kyoto (WKY) rats and spontaneous hypertensive rats (SHRs) received RVLM microinjection of adeno-associated viral vectors to promote or inhibit the COX2 expression were subjected to subsequent experiments. Glutamate level and glutaminase expression were detected by ELISA and western blot, respectively. The function of tonic glutamatergic inputs was assessed by BP response to microinjection of the glutamate receptor antagonist into the RVLM. PC12 cells were used to detect the underlying signal pathway.

RESULTS

The RVLM COX2 expression and prostaglandin E2 level were significant higher in SHRs than in WKY rats. Overexpression of COX2 in the RVLM produced an increase in basal BP, RVLM glutamate level, and glutaminase expression in WKY rats, while they were significantly reduced by interfering with COX2 expression in SHRs. Microinjections of the glutamate receptor antagonist into the RVLM produced a significant BP decrease in WKY rats with COX2 overexpression pretreatment. Furthermore, the increased levels of BP, glutamate content, and glutaminase activity in the RVLM evoked by central infusion of angiotensin II were attenuated in COX2 knockout mice. It was also found that prostaglandin E2 increased supernatant glutamate level and phosphorylation of signal transducer and activator of transcription 3 in PC12 cells.

CONCLUSION

Our findings suggest that upregulated COX2 expression enhances the tonically active glutamatergic inputs to the RVLM, which is associated with cardiovascular regulation in hypertension.

Nitrotyrosine, Nitrated Lipoproteins, and Cardiovascular Dysfunction in Patients with Type 2 Diabetes: What Do We Know and What Remains to Be Explained?

Diabetes mellitus (DM) is a strong risk factor for the development of cardiovascular diseases (CVDs), which are the most important cause of morbidity and mortality in the population of patients living with DM. DM is associated with lipid metabolism disorders characterized by a decrease in the high-density lipoprotein blood concentration, an increase in the triglyceride blood concentration, and the presence of modified lipoproteins not routinely measured in clinical practice. Nitrated lipoproteins are produced by the nitration of the tyrosyl residues of apolipoproteins by myeloperoxidase. There is some evidence from the research conducted showing that nitrated lipoproteins may play a role in the development of cardiovascular dysfunction, but this issue requires further investigation. It was found that the nitration of HDL particles was associated with a decrease in caspase-3 and paraoxonase-1 activity, as well as a decrease in the activity of cholesterol transport via ABCA1, which reduces the protective effect of HDL particles on the cardiovascular system. Less information has been collected about the role of nitrated LDL particles. Thus far, much more information has been obtained on the relationship of nitrotyrosine expression with the presence of cardiovascular risk factors and the development of cardiovascular dysfunction. The purpose of this paper is to provide an extensive review of the literature and to present the most important information on the current state of knowledge on the association between nitrotyrosine and nitrated lipoproteins with dysfunction of the cardiovascular system, especially in patients living with DM. Moreover, directions for future research in this area were discussed.

Activation of Nrf2 in Mice Causes Early Microvascular Cyclooxygenase-Dependent Oxidative Stress and Enhanced Contractility

Nuclear factor erythroid factor E2-related factor 2 (Nrf2) transcribes antioxidant genes that reduce the blood pressure (BP), yet its activation with tert-butylhydroquinone (tBHQ) in mice infused with angiotensin II (Ang II) increased mean arterial pressure (MAP) over the first 4 days of the infusion. Since tBHQ enhanced cyclooxygenase (COX) 2 expression in vascular smooth muscle cells (VSMCs), we tested the hypothesis that tBHQ administration during an ongoing Ang II infusion causes an early increase in microvascular COX-dependent reactive oxygen species (ROS) and contractility. Mesenteric microarteriolar contractility was assessed on a myograph, and ROS by RatioMaster™. Three days of oral tBHQ administration during the infusion of Ang II increased the mesenteric microarteriolar mRNA for p47^phox, the endothelin type A receptor and thromboxane A₂ synthase, and increased the excretion of 8-isoprostane F_2α and the microarteriolar ROS and contractions to a thromboxane A₂ (TxA₂) agonist (U-46,619) and endothelin 1 (ET1). These were all prevented in Nrf2 knockout mice. Moreover, the increases in ROS and contractility were prevented in COX1 knockout mice with blockade of COX2 and by blockade of thromboxane prostanoid receptors (TPRs). In conclusion, the activation of Nrf2 over 3 days of Ang II infusion enhances microarteriolar ROS and contractility, which are dependent on COX1, COX2 and TPRs. Therefore, the blockade of these pathways may diminish the early adverse cardiovascular disease events that have been recorded during the initiation of Nrf2 therapy.

Treatment of glioblastoma with re-purposed renin-angiotensin system modulators: Results of a phase I clinical trial

Glioblastoma is the most common and most aggressive primary brain cancer in adults. Standard treatment of glioblastoma consisting of maximal safe resection, adjuvant radiotherapy and chemotherapy with temozolomide, results in an overall median survival of 14.6 months. The aggressive nature of glioblastoma has been attributed to the presence of glioblastoma stem cells which express components of the renin-angiotensin system (RAS). This phase I clinical trial investigated the tolerability and efficacy of a treatment targeting the RAS and its converging pathways in patients with glioblastoma. Patients who had relapsed following standard treatment of glioblastoma who met the trial criteria were commenced on dose-escalated oral RAS modulators (propranolol, aliskiren, cilazapril, celecoxib, curcumin with piperine, aspirin, and metformin). Of the 17 patients who were enrolled, ten completed full dose-escalation of the treatment. The overall median survival was 19.9 (95% CI:14.1-25.7) months. Serial FET-PET/CTs showed a reduction in both tumor volume and uptake in one patient, an increase in tumor uptake in nine patients with decreased (n = 1), unchanged (n = 1) and increased (n = 7) tumor volume, in the ten patients who had completed full dose-escalation of the treatment. Two patients experienced mild side effects and all patients had preservation of quality of life and performance status during the treatment. There is a trend towards increased survival by 5.3 months although it was not statistically significant. These encouraging results warrant further clinical trials on this potential novel, well-tolerated and cost-effective therapeutic option for patients with glioblastoma.

Melatonin, Its Metabolites and Their Interference with Reactive Nitrogen Compounds

Melatonin and several of its metabolites are interfering with reactive nitrogen. With the notion of prevailing melatonin formation in tissues that exceeds by far the quantities in blood, metabolites come into focus that are poorly found in the circulation. Apart from their antioxidant actions, both melatonin and N¹-acetyl-5-methoxykynuramine (AMK) downregulate inducible and inhibit neuronal NO synthases, and additionally scavenge NO. However, the NO adduct of melatonin redonates NO, whereas AMK forms with NO a stable product. Many other melatonin metabolites formed in oxidative processes also contain nitrosylatable sites. Moreover, AMK readily scavenges products of the CO₂-adduct of peroxynitrite such as carbonate radicals and NO₂. Protein AMKylation seems to be involved in protective actions.

Vascular Inflammation in Hypertension: Targeting Lipid Mediators Unbalance and Nitrosative Stress

Arterial hypertension is a worldwide public health threat. High Blood Pressure (BP) is commonly associated with endothelial dysfunction, nitric oxide synthases (NOS) unbalance and high peripheral vascular resistance. In addition to those, inflammation has also been designated as one of the major components of BP increase and organ damage in hypertension. This minireview discusses vascular inflammatory triggers of high BP and aims to fill the existing gaps of antiinflammatory therapy of hypertension. Among the reasons discussed, enhanced prostaglandins rather than resolvins lipid mediators, immune cell infiltration and oxidative/nitrosative stress are pivotal players of BP increase within the inflammatory hypothesis. To address these inflammatory targets, this review also proposes new concepts in hypertension treatment with non-steroidal antiinflammatory drugs (NSAIDs), nitric oxide-releasing NSAIDs (NO-NSAIDs) and specialized proresolving mediators (SPM). In this context, the failure of NSAIDs in hypertension treatment seems to be associated with the reduction of endogenous NO bioavailability, which is not necessarily an effect of all drug members of this pharmacological class. For this reason, NO-releasing NSAIDs seem to be safer and more specific therapy to treat vascular inflammation in hypertension than regular NSAIDs.

Application of Zebrafish Model in the Suppression of Drug-Induced Cardiac Hypertrophy by Traditional Indian Medicine Yogendra Ras

Zebrafish is an elegant vertebrate employed to model the pathological etiologies of human maladies such as cardiac diseases. Persistent physiological stresses can induce abnormalities in heart functions such as cardiac hypertrophy (CH), which can lead to morbidity and mortality. In the present study, using zebrafish as a study model, efficacy of the traditional Indian Ayurveda medicine “Yogendra Ras” (YDR) was validated in ameliorating drug-induced cardiac hypertrophy. YDR was prepared using traditionally described methods and composed of nano- and micron-sized metal particles. Elemental composition analysis of YDR showed the presence of mainly Au, Sn, and Hg. Cardiac hypertrophy was induced in the zebrafish following a pretreatment with erythromycin (ERY), and the onset and reconciliation of disease by YDR were determined using a treadmill electrocardiogram, heart anatomy analysis, C-reactive protein release, and platelet aggregation time-analysis. YDR treatment of CH-induced zebrafish showed comparable results with the Standard-of-care drug, verapamil, tested in parallel. Under in-vitro conditions, treatment of isoproterenol (ISP)-stimulated murine cardiomyocytes (H9C2) with YDR resulted in the suppression of drug-stimulated biomarkers of oxidative stress: COX-2, NOX-2, NOX-4, ANF, troponin-I, -T, and cardiolipin. Taken together, zebrafish showed a strong disposition as a model for studying the efficacy of Ayurvedic medicines towards drug-induced cardiopathies. YDR provided strong evidence for its capability in modulating drug-induced CH through the restoration of redox homeostasis and exhibited potential as a viable complementary therapy.

Cardio-renal safety of non-steroidal anti-inflammatory drugs

Non-steroidal anti-inflammatory drugs (NSAIDs) are among the most widely used therapeutic class in clinical medicine. These are sub-divided based on their selectivity for inhibition of cyclooxygenase (COX) isoforms (COX-1 and COX-2) into: (1) non-selective (ns-NSAIDs), and (2) selective NSAIDs (s-NSAIDs) with preferential inhibition of COX-2 isozyme. The safety and pathophysiology of NSAIDs on the renal and cardiovascular systems have continued to evolve over the years following short- and long-term treatment in both preclinical models and humans. This review summarizes major learnings on cardiac and renal complications associated with pharmaceutical inhibition of COX-1 and COX-2 with focus on preclinical to clinical translatability of cardio-renal data.

Human cerebral blood flow control during hypoxia: focus on chronic pulmonary obstructive disease and obstructive sleep apnea

The brain is a vital organ that relies on a constant and adequate blood flow to match oxygen and glucose delivery with the local metabolic demands of active neurons. Thus exquisite regulation of cerebral blood flow (CBF) is particularly important under hypoxic conditions to prevent a detrimental decrease in the partial pressure of oxygen within the brain tissues. Cerebrovascular sensitivity to hypoxia, assessed as the change in CBF during a hypoxic challenge, represents the capacity of cerebral vessels to respond to, and compensate for, a reduced oxygen supply, and has been shown to be impaired or blunted in a number of conditions. For instance, this is observed with aging, and in clinical conditions such as untreated obstructive sleep apnea (OSA) and in healthy humans exposed to intermittent hypoxia. This review will 1) provide a brief overview of cerebral blood flow regulation and results of pharmacological intervention studies which we have performed to better elucidate the basic mechanisms of cerebrovascular regulation in humans; and 2) present data from studies in clinical and healthy populations, using a translational physiology approach, to investigate human CBF control during hypoxia. Results from studies in patients with chronic obstructive pulmonary disease and OSA will be presented to identify the effects of the disease processes on cerebrovascular sensitivity to hypoxia. Data emerging from experimental human models of intermittent hypoxia during wakefulness will also be reviewed to highlight the effects of intermittent hypoxia on the brain.