Effects of cyclooxygenase inhibition on canine coronary artery blood flow and thrombosis

ACE2 in the renin-angiotensin system

In 2020 we are celebrating the 20th anniversary of the angiotensin-converting enzyme 2 (ACE2) discovery. This event was a landmark that shaped the way that we see the renin-angiotensin system (RAS) today. ACE2 is an important molecular hub that connects the RAS classical arm, formed mainly by the octapeptide angiotensin II (Ang II) and its receptor AT1, with the RAS alternative or protective arm, formed mainly by the heptapeptides Ang-(1-7) and alamandine, and their receptors, Mas and MrgD, respectively. In this work we reviewed classical and modern literature to describe how ACE2 is a critical component of the protective arm, particularly in the context of the cardiac function, coagulation homeostasis and immune system. We also review recent literature to present a critical view of the role of ACE2 and RAS in the SARS-CoV-2 pandemic.

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.

Transmission pathways and mediators as the basis for clinical pharmacology of pain

INTRODUCTION

Mediators in pain transmission are the targets of a multitude of different analgesic pharmaceuticals. This review explores the most significant mediators of pain transmission as well as the pharmaceuticals that act on them. Areas covered: The review explores many of the key mediators of pain transmission. In doing so, this review uncovers important areas for further research. It also highlights agents with potential for producing novel analgesics, probes important interactions between pain transmission pathways that could contribute to synergistic analgesia, and emphasizes transmission factors that participate in transforming acute injury into chronic pain. Expert commentary: This review examines current pain research, particularly in the context of identifying novel analgesics, highlighting interactions between analgesic transmission pathways, and discussing factors that may contribute to the development of chronic pain after an acute injury.

A primary role for kinin B1 receptor in inflammation, organ damage, and lethal thrombosis in a rat model of septic shock in diabetes

Diabetes mellitus and septic shock increase the incidence of mortality by thrombosis. Although kinin B1 receptor (B1R) is involved in both pathologies, its role in platelet function and thrombosis remains unknown. This study investigates the expression, the inflammatory, and pro-thrombotic effects of B1R in a model of septic shock in diabetic rats. Sprague-Dawley rats were made diabetic with streptozotocin (STZ) (65 mg/kg, i.p.). Four days later, control and STZ-diabetic rats were injected with lipopolysaccharide (LPS) (2 mg/kg, i.p.) or the vehicle. B1R antagonist (SSR240612, 10 mg/kg by gavage) was given either acutely (12 and 24 h prior to endpoint analysis) or daily for up to 7 days. Moreover, a 7-day treatment was given either with cyclooxygenase (COX)-2 inhibitor (niflumic acid, 5 mg/kg, i.p.), non-selective COX-1 and COX-2 inhibitor (indomethacin, 10 mg/kg, i.p.), non-selective nitric oxide synthase (NOS) inhibitor (L-NAME, 50 mg/kg by gavage), iNOS inhibitor (1400W, 5 mg/kg, i.p.), or heparin (100 IU/kg, s.c.). The following endpoints were measured: edema and vascular permeability (Evans blue dye), B1R expression (qRT-PCR, western blot, flow cytometry), aggregation in platelet-rich plasma (optical aggregometry), and organ damage (histology). Rats treated with STZ, LPS, and STZ plus LPS showed significant increases in edema and vascular permeability (heart, kidney, lung, and liver) and increased expression of B1R in heart and kidney (mRNA) and platelets (protein). Lethal septic shock induced by LPS was enhanced in STZ-diabetic rats and was associated with lung and kidney damage, including platelet micro-aggregate formation. SSR240612 prevented all these abnormalities as well as STZ-induced hyperglycemia and LPS-induced hyperthermia. Similarly to SSR240612, blockade of iNOS and COX-2 improved survival. Data provide the first evidence that kinin B1R plays a primary role in lethal thrombosis in a rat model of septic shock in diabetes. Pharmacological rescue was made possible with B1R antagonism or by inhibition of iNOS and COX-2, which may act as downstream mechanisms.

Effects of SC-560 in combination with cisplatin or taxol on angiogenesis in human ovarian cancer xenografts

This study was designed to evaluate the effect of cyclooxygenase-1 (COX-1) inhibitor, SC-560, combined with cisplatin or taxol, on angiogenesis in human ovarian cancer xenografts. Mice were treated with intraperitoneal (i.p.) injections of SC-560 6 mg/kg/day, i.p. injections of cisplatin 3 mg/kg every other day and i.p. injections of taxol 20 mg/kg once a week for 21 days. Vascular endothelial growth factor (VEGF) mRNA levels were detected by reverse transcription-polymerase chain reaction (RT-PCR); microvessel density (MVD) was determined by immunohistochemistry; and prostaglandin E₂ (PGE₂) levels were determined using ELISA. Expression levels of VEGF mRNA and MVD in treatment groups were inhibited significantly when compared with the control group (p < 0.05 for all), and SC-560 combined with cisplatin displayed a greater reduction in the expression of VEGF and MVD than SC-560 or cisplatin alone (p < 0.05). SC-560 combined with taxol showed a greater inhibition on VEGF mRNA expression than SC-560 or taxol alone (p < 0.05). The level of PGE₂ in treatment groups was significantly reduced when compared with the control group (p < 0.01 for all). These findings may indicate that cisplatin or taxol supplemented by SC-560 in human ovarian cancer xenografts enhances the inhibition effect of cisplatin or taxol alone on angiogenesis.

The COX-2/PGI2 receptor axis plays an obligatory role in mediating the cardioprotection conferred by the late phase of ischemic preconditioning

Background

Pharmacologic studies with cyclooxygenase-2 (COX-2) inhibitors suggest that the late phase of ischemic preconditioning (PC) is mediated by COX-2. However, nonspecific effects of COX-2 inhibitors cannot be ruled out, and the selectivity of these inhibitors for COX-2 vs. COX-1 is only relative. Furthermore, the specific prostaglandin (PG) receptors responsible for the salubrious actions of COX-2-derived prostanoids remain unclear.

Objective

To determine the role of COX-2 and prostacyclin receptor (IP) in late PC by gene deletion.

Methods

COX-2 knockout (KO) mice (COX-2^−/−), prostacyclin receptor KO (IP^−/−) mice, and respective wildtype (WT, COX-2^+/+ and IP^+/+) mice underwent sham surgery or PC with six 4-min coronary occlusion (O)/4-min R cycles 24 h before a 30-min O/24 h R.

Results

There were no significant differences in infarct size (IS) between non-preconditioned (non-PC) COX-2^+/+, COX-2^−/−, IP^+/+, and IP^−/− mice, indicating that neither COX-2 nor IP modulates IS in the absence of PC. When COX-2^−/− or IP^−/− mice were preconditioned, IS was not reduced, indicating that the protection of late PC was completely abrogated by deletion of either the COX-2 or the IP gene. Administration of the IP selective antagonist, RO3244794 to C57BL6/J (B6) mice 30 min prior to the 30-min O had no effect on IS. When B6 mice were preconditioned 24 h prior to the 30-min O, IS was markedly reduced; however, the protection of late PC was completely abrogated by pretreatment of RO3244794.

Conclusions

This is the first study to demonstrate that targeted disruption of the COX-2 gene completely abrogates the infarct-sparing effect of late PC, and that the IP, downstream of the COX-2/prostanoid pathway, is a key mediator of the late PC. These results provide unequivocal molecular genetic evidence for an essential role of the COX-2/PGI2 receptor axis in the cardioprotection afforded by the late PC.

Oxygen Sensing, Cardiac Ischemia, HIF-1α and Some Emerging Concepts

Oxygen plays a critical role in the perpetuation and propagation of almost all forms of life. The primary site of cellular oxygen consumption is the mitochondrial electron transport chain and in addition, oxygen is also used as a substrate for various enzymes involved in cellular homeostasis. Although our knowledge of the biochemistry and physiology of oxygen transport is century old, recent development of sophisticated tools of biophysical chemistry revealed that tissue oxygenation and oxygen sensing is a highly evolved process, especially in mammals. Perturbation of normal oxygen supply is associated with diseases like tumorigenesis, myocardial infarction and stroke. Available information suggests that when tissue oxygen supply is limited, mitochondria emanate signals involving reactive oxygen species generation which in turn stabilizes oxygen sensing transcription factor HIF-1. Upon stabilization, HIF-1 elicits necessary genetic response to cope with the diminished oxygen level. In view of such critical role of HIF-1 in cellular oxygen sensing, recently there has been a heightened interest in understanding the biology of HIF-1 in the context of cardiovascular system. The following review describes some of the recent advances in this regard.

Leukocyte count affects expression of reference genes in canine whole blood samples

Background

The dog is frequently used as a model for hematologic human diseases. In this study the suitability of nine potential reference genes for quantitative RT-PCR studies in canine whole blood was investigated.

Findings

The expression of these genes was measured in whole blood samples of 263 individual dogs, representing 73 different breeds and a group of 40 mixed breed dogs, categorized into healthy dogs and dogs with internal and hematological diseases, and dogs that underwent a surgical procedure. GeNorm analysis revealed that a combination of 5 to 6 of the most stably expressed genes constituted a stable normalizing factor. Evaluation of the expression revealed different ranking of reference genes in Normfinder and GeNorm. The disease category and the white blood cell count significantly affected reference gene expression.

Conclusions

The discrepancy between the ranking of reference genes in this study by Normfinder and Genorm can be explained by differences between the experimental groups such as "disease category" and "WBC count". This stresses the importance of assessing the expression stability of potential reference genes for gene experiments in canine whole blood anew for each specific experimental condition.

Pathophysiology of cyclooxygenases in cardiovascular homeostasis

Cyclooxygenase (COX) catalyzes the conversion of arachidonic acid into prostaglandin H(2) (PGH(2)), which is subsequently converted to the prostanoids PGE(2), PGI(2), PGF(2alpha), and thromboxane A(2). COX has 2 distinct membrane-anchored isoenzymes: COX-1 and COX-2. COX-1 is constitutively expressed in most normal tissues; COX-2 is highly induced by proinflammatory mediators in the setting of inflammation, injury, and pain. Inhibitors of COX activity include conventional nonselective nonsteroidal anti-inflammatory drugs and selective nonsteroidal anti-inflammatory drugs, such as COX-2 inhibitors. The adverse effects of COX inhibitors on the cardiovascular system have been addressed in the last few years. In general, COX inhibitors have many effects, but those most important to the cardiovascular system can be direct (through the effects of prostanoids) and indirect (through alterations in fluid dynamics). Despite reports of detrimental human cardiovascular events associated with COX inhibitors, short, long, and lifetime preclinical toxicology studies in rodents and nonrodents have failed to identify these risks. This article focuses on the expression and function of COX enzymes in normal and pathologic conditions of the cardiovascular system and discusses the cardiovascular pathophysiologic complications associated with COX inhibition.

Effects of a cyclooxygenase-2 preferential inhibitor in young healthy dogs exposed to air pollution: a pilot study

Residency in cities with high air pollution is associated with neuroinflammation and neurodegeneration in healthy children, young adults, and dogs. Nonsteroidal anti-inflammatory drugs may offer neuroprotection. The authors measured the plasma concentrations of 3-nitrotyrosine and the cerebro-spinal-fluid concentrations of prostaglandin E2 metabolite and the oligomeric form of amyloid derived diffusible ligand; measured the mRNA expression of cyclooxygenase-2, interleukin 1beta, CD14, and Aquaporin-4 in target brain areas; and evaluated brain MRI, cognition, and neuropathology in 8 dogs treated with a preferential cyclooxygenase-2 inhibitor (Nimesulide) versus 7 untreated litter-matched Mexico City dogs. Nimesulide significantly decreased nitrotyrosine in plasma (p < .0001), frontal gray IL1beta (p = .03), and heart IL1beta (p = .02). No effect was seen in mRNA COX2, amyloid, and PGE2 in CSF or the MRI white matter lesions. All exposed dogs exhibited olfactory bulb and frontal accumulation of Abeta(42) in neurons and blood vessels and frontal vascular subcortical pathology. White matter hyperintense MRI frontal lesions were seen in 4/6 non-treated and 6/8 treated dogs. Nonsteroidal anti-inflammatory drugs may offer limited neuroprotection in the setting of severe air pollution exposures. The search for potentially beneficial drugs useful to ameliorate the brain effects of pollution represents an enormous clinical challenge.

Renal and cardiovascular characterization of COX-2 knockdown mice

Selective cyclooxygenase-2 (COX-2) inhibitors (coxibs) increase the incidence of cardiovascular and cerebrovascular events. Complete disruption of the murine gene encoding COX-2 ( Ptgs2) leads to renal developmental problems, as well as female reproductive anomalies and patent ductus arteriosus of variable penetrance in newborns, thus rendering this genetic approach difficult to compare with coxib administration. Here, we created hypomorphic Ptgs2 (COX-2Neo/Neo) mice in which COX-2 expression is suppressed to an extent similar to that achieved with coxibs, but not eliminated, in an attempt to circumvent these difficulties. In LPS-challenged macrophages and cytokine-stimulated endothelial cells obtained from COX-2Neo/Neo mice, COX-2 expression was reduced 70–90%, and these mice developed a mild renal phenotype compared with COX-2 mice possessing an active site mutation (COX-2Y385F/Y385F), with minimal signs of renal dysfunction as measured by FITC-inulin clearance and blood urea nitrogen. These COX-2 knockdown mice displayed an increased propensity for thrombogenesis compared with their wild-type (COX-2+/+) littermates observed by intravital microscopy in cremaster muscle arterioles upon ferric chloride challenge. Measurement of urinary prostanoid metabolites indicated that COX-2Neo/Neo mice produced 50% less prostacyclin but similar levels of PGE2 and thromboxane compared with COX-2+/+ mice in the absence of any blood pressure and ex vivo platelet aggregation abnormalities. COX-2Neo/Neo mice, therefore, provide a genetic surrogate of coxib therapy with disrupted prostacyclin biosynthesis that predisposes to induced arterial thrombosis.

Differential involvement of COX1 and COX2 in the vasculopathy associated with the alpha-galactosidase A-knockout mouse

The lysosomal storage disorder Fabry disease is characterized by excessive globotriaosylceramide (Gb3) accumulation in major organs such as the heart and kidney. Defective lysosomal alpha-galactosidase A (Gla) is responsible for excessive Gb3 accumulation, and one cell sensitive to the effects of Gb3 accumulation is vascular endothelium. Endothelial dysfunction is associated with Fabry disease and excessive cellular Gb3. We previously demonstrated that excessive vascular Gb3 in a mouse model of Fabry disease, the Gla-knockout (Gla(-/0)) mouse, results in abnormal vascular function, which includes abnormal endothelium-dependent contractions, a vascular phenomenon known to involve cyclooxygenase (COX). Therefore, we hypothesized that the vasculopathy in the Gla knockout mouse may be due to a vasoactive COX-derived product. To test this hypothesis, vascular reactivity experiments were performed in aortic rings from wild-type (Gla(+/0)) and Gla(-/0) mice in the presence and absence of specific and nonspecific COX inhibitors. Specific inhibition of COX1 or COX2 in endothelium-intact rings from Gla(-/0) mice decreased overall phenylephrine contractility compared with untreated Gla(-/0) rings, whereas COX inhibitors had no effect on contractility in endothelium-denuded rings. Nonspecific inhibition of COX with indomethacin (10 micromol/l) or COX1 inhibition with valeryl salicylate (3 mmol/l) improved endothelial function in rings from Gla(-/0) mice, but COX2 inhibition with NS-398 (1 micromol/l) further increased endothelial dysfunction in rings from Gla(-/0) mice. These results suggest that, in the Gla(-/0) mice, COX1 and COX2 activity are increased and localized in the endothelium, producing vasopressor and vasorelaxant products, which contribute to the Fabry-related vasculopathy.

Estrogen protects the heart from ischemia-reperfusion injury via COX-2-derived PGI2

There is an accumulating body of data to suggest that estrogen mediates its cardioprotective effects via cyclooxygenase activation and synthesis of prostaglandins (PG), specifically PGI2. We hypothesized that inhibition of COX-2 would prevent estrogen's cardioprotective effects after myocardial ischemia-reperfusion. Acute treatment with 17beta-estradiol (E2; 20 microg/rabbit) increased COX-2 protein expression and activity in the myocardium. To determine the effects of COX-2 inhibition on infarct size after E2 treatment, New Zealand white rabbits were anesthetized and administered the COX-2 inhibitor nimesulide (5 mg/kg) or vehicle intravenously 30 minutes before an intravenous injection of E2. Thirty minutes after estrogen treatment, the coronary artery was occluded for 30 minutes followed by 4 hours of reperfusion. E2 significantly decreased infarct size as a percent of area at risk when compared to vehicle (18.9 +/- 3.1 versus 47.0 +/- 4.1; P < 0.001). Pretreatment with nimesulide nullified the infarct size sparing effect of E2 (55.8 +/- 5.6). Treatment with the PGI2 receptor antagonist RO3244794 also abolished the protective effects of E2 (45.3 +/- 4.5). The results indicate that estrogen protects the myocardium from ischemia-reperfusion injury through increased production of COX-2-derived PGI2. The data indicate that selective COX-2 inhibitors might counteract the potential cytoprotective effects of estrogen in premenopausal or postmenopausal women.