Increased cyclooxygenase-2-derived prostanoids contributes to the hyperreactivity to noradrenaline in mesenteric resistance arteries from offspring of diabetic rats

Finerenone protects against progression of kidney and cardiovascular damage in a model of type 1 diabetes through modulation of proinflammatory and osteogenic factors

The non-steroidal mineralocorticoid receptor antagonist (MRA) finerenone (FIN) improves kidney and cardiovascular outcomes in patients with chronic kidney disease (CKD) in type 2 diabetes (T2D). We explored the effect of FIN in a novel model of type 1 diabetic Munich Wistar Frömter (MWF) rat (D) induced by injection of streptozotocin (15 mg/kg) and additional exposure to a high-fat/high-sucrose diet. Oral treatment with FIN (10 mg/kg/day in rat chow) in diabetic animals (D-FIN) was compared to a group of D rats receiving no treatment and a group of non-diabetic untreated MWF rats (C) (n = 7-10 animals per group). After 6 weeks, D and D-FIN exhibited significantly elevated blood glucose levels (271.7 ± 67.1 mg/dl and 266.3 ± 46.8 mg/dl) as compared to C (110.3 ± 4.4 mg/dl; p < 0.05). D showed a 10-fold increase of kidney damage markers Kim-1 and Ngal which was significantly suppressed in D-FIN. Blood pressure, pulse wave velocity (PWV) and arterial collagen deposition were lower in D-FIN, associated to an improvement in endothelial function due to a reduction in pro-contractile prostaglandins, as well as reactive oxygen species (ROS) and inflammatory cytokines (IL-1, IL-6, TNFα and TGFβ) in perivascular and perirenal adipose tissue (PVAT and PRAT, respectively). In addition, FIN restored the imbalance observed in CKD between the procalcifying BMP-2 and the nephroprotective BMP-7 in plasma, kidney, PVAT, and PRAT. Our data show that treatment with FIN improves kidney and vascular damage in a new rat model of DKD with T1D associated with a reduction in inflammation, fibrosis and osteogenic factors independently from changes in glucose homeostasis.

Maternal Hyperglycemia Induces Autonomic Dysfunction and Heart Failure in Older Adult Offspring

AIMS

Offspring exposed to an adverse fetal environment, such as gestational diabetes, may manifest increased susceptibility to several chronic diseases later in life. In the present study, the cardiovascular function of three different ages of offspring from diabetic rats was evaluated.

METHODS AND RESULTS

Diabetes mellitus was induced in pregnant rats by a single dose of streptozotocin (50 mg/kg). The offspring from diabetic (OD) and control rats (OC) were evaluated at three different ages: 6, 12 or 18 months. In the corresponding OC groups, fasting glycemia, baseline mean arterial pressure, and sympathetic tonus increased in the OD rats at 12 (OD12) and 18 (OD18) months of age, while cardiac hypertrophy was observed in all OD groups. Cardiac function evaluation in vivo showed low left ventricular systolic pressure and+dP/dt in the OD18 rats, suggesting a systolic dysfunction. OD12 and OD18 groups showed high left ventricle end-diastolic pressure, suggesting a diastolic dysfunction. OD groups showed an age-related impairment of both baroreflex-mediated tachycardia and baroreflex-mediated bradycardia in OD12 and OD18 rats. In isolated hearts from OD18 rats, both inotropic and tachycardiac responses to increasing isoproterenol were significantly reduced compared to the corresponding OC group.

CONCLUSION

These results suggest that gestational diabetes triggers the onset of hyperglycemia hypertension with impaired baroreflex sensitivity and heart failure in older age of offspring, representing important risk factors for death. Therefore, ensuring optimal glycemic control in diabetic pregnancy is important and serves as a key to preventing cardiovascular disease in the offspring in their older age.

Long-term outcomes and potential mechanisms of offspring exposed to intrauterine hyperglycemia

Diabetes mellitus during pregnancy, which can be classified into pregestational diabetes and gestational diabetes, has become much more prevalent worldwide. Maternal diabetes fosters an intrauterine abnormal environment for fetus, which not only influences pregnancy outcomes, but also leads to fetal anomaly and development of diseases in later life, such as metabolic and cardiovascular diseases, neuropsychiatric outcomes, reproduction malformation, and immune dysfunction. The underlying mechanisms are comprehensive and ambiguous, which mainly focus on microbiota, inflammation, reactive oxygen species, cell viability, and epigenetics. This review concluded with the influence of intrauterine hyperglycemia on fetal structure development and organ function on later life and outlined potential mechanisms that underpin the development of diseases in adulthood. Maternal diabetes leaves an effect that continues generations after generations through gametes, thus more attention should be paid to the prevention and treatment of diabetes to rescue the pathological attacks of maternal diabetes from the offspring.

Blood vessel assessment using computed tomography : Effects of ephedrine on uterine artery

Background: Ephedrine increased blood pressure due to the contractile properties of resistance vessels. Excessive contraction of the uterine arteries might cause fetal distress. This study was to determine the diameter of the uterine artery of female New Zealand rabbits after the administration of different doses of ephedrine using CT.

Methods: Thirty-two rabbits were randomly divided into a control group (Group C), low dosage group (Group L), medium dosage group (Group M) and high dosage group (Group H). Normal saline and doses corresponding to the human dose of 7.5, 15 and 30 mg of ephedrine were injected respectively. The marginal ear and uterine artery diameters were measured 5, 10, 15, 30, and 45 min after injection using CT, and the hemodynamic changes were recorded.

Results: The increase in mean arterial pressure in group M (p = 0.009), and H (p = 0.013) was higher than that in group C. Compared with group C, substantial contraction of the marginal ear artery was observed at the three doses of ephedrine. There were no differences in the uterine artery diameter among groups L, M and C, However, in Group H, a significant contraction of the uterine artery compared with the other groups (p < 0.001) was observed.

Discussion: CT can be used to evaluate the effects of drugs on organs and blood vessels. Ephedrine can not only constrict the peripheral blood vessels but also do not affect the uterine artery at a dose of 15 mg or less. However, the dose should not exceed 30 mg, which may cause severe uterine artery depression.

Endothelium-dependent contraction: The non-classical action of endothelial prostacyclin, its underlying mechanisms, and implications

Although commonly thought to produce prostacyclin (prostaglandin I₂ ; PGI₂ ) that evokes vasodilatation and protects vessels from the development of diseases, the endothelial cyclooxygenase (COX)-mediated metabolism has also been found to release substance(s) called endothelium-derived contracting factor(s) (EDCF) that causes endothelium-dependent contraction and implicates in endothelial dysfunction of disease conditions. Various mechanisms have been proposed for the process; however, the major endothelial COX metabolite PGI₂ , which has been classically considered to activate the I prostanoid receptor (IP) that mediates vasodilatation and opposes the effects of thromboxane (Tx) A₂ produced by COX in platelets, emerges as a major EDCF in health and disease conditions. Our recent studies from genetically altered mice further suggest that vasomotor reactions to PGI₂ are collectively modulated by IP, the vasoconstrictor Tx-prostanoid receptor (TP; the prototype receptor of TxA₂ ) and E prostanoid receptor-3 (EP3; a vasoconstrictor receptor of PGE₂ ) although with differences in potency and efficacy; a contraction to PGI₂ reflects activities of TP and/or EP3 outweighing that of the concurrently activated IP. Here, we discuss the history of endothelium-dependent contraction, evidences that support the above hypothesis, proposed mechanisms for the varied reactions to endothelial PGI₂ synthesis as well as the relation of its dilator activity to the effect of another NO-independent vasodilator mechanism, the endothelium-derived hyperpolarizing factor. Also, we address the possible pathological and therapeutic implications as well as questions remaining to be resolved or limitations of our above findings obtained from genetically altered mouse models.

Down-regulation of AMPK/PPARδ signalling promotes endoplasmic reticulum stress-induced endothelial dysfunction in adult rat offspring exposed to maternal diabetes

AIMS

Exposure to maternal diabetes is associated with increased prevalence of hypertension in the offspring. The mechanisms underlying the prenatal programming of hypertension remain unclear. Because endoplasmic reticulum (ER) stress plays a key role in vascular endothelial dysfunction in hypertension, we investigated whether aberrant ER stress causes endothelial dysfunction and high blood pressure in the offspring of dams with diabetes.

METHODS AND RESULTS

Pregnant Sprague-Dawley rats were intraperitoneally injected with streptozotocin (35 mg/kg) or citrate buffer at Day 0 of gestation. Compared with control mother offspring (CMO), the diabetic mother offspring (DMO) had higher blood pressure and impaired endothelium-dependent relaxation in mesenteric arteries, accompanied by decreased AMPK phosphorylation and PPARδ expression, increased ER stress markers, and reactive oxygen species (ROS) levels. The inhibition of ER stress reversed these aberrant changes in DMO. Ex vivo treatment of mesenteric arteries with an AMPK agonist (A769662) or a PPARδ agonist (GW1516) improved the impaired EDR in DMO and reversed the tunicamycin-induced ER stress, ROS production, and EDR impairment in mesenteric arteries from CMO. The effects of A769662 were abolished by co-treatment with GSK0660 (PPARδ antagonist), whereas the effects of GW1516 were unaffected by Compound C (AMPK inhibitor).

CONCLUSION

These results suggest an abnormal foetal programming of vascular endothelial function in offspring of rats with maternal diabetes that is associated with increased ER stress, which can be ascribed to down-regulation of AMPK/PPARδ signalling cascade.

Sex differences in the role of phospholipase A2 -dependent arachidonic acid pathway in the perivascular adipose tissue function in pigs

KEY POINTS

The fat surrounding blood vessels (perivascular adipose tissue or PVAT) releases vasoactive compounds that regulate vascular smooth muscle tone. There are sex differences in the regulation of vascular tone, but, to date, no study has investigated whether there are sex differences in the regulation of blood vessel tone by PVAT. This study has identified that the cyclooxygenase products thromboxane and PGF_2α are released from coronary artery PVAT from pigs. Thromboxane appears to mediate the PVAT-induced contraction in arteries from females, whereas PGF_2α appears to mediate the contraction in arteries from males. These sex differences in the role of these prostanoids in the PVAT-induced contraction can be explained by a greater release of thromboxane from PVAT from female animals and greater sensitivity to PGF_2α in the porcine coronary artery from males.

ABSTRACT

Previous studies have demonstrated that perivascular adipose tissue (PVAT) causes vasoconstriction. In this present study, we determined the role of cyclooxygenase-derived prostanoids in this contractile response and determined whether there were any sex differences in the regulation of vascular tone by PVAT. Contractions in isolated segments of coronary arteries were determined using isolated tissue baths and isometric tension recording. Segments were initially cleaned of PVAT, which was then re-added to the tissue bath and changes in tone measured over 1 h. Levels of PGF_2α and thromboxane B₂ (TXB₂ ) were quantified by ELISA, and PGF_2α (FP) and thromboxane A₂ (TP) receptor expression determined by Western blotting. In arteries from both male and female pigs, re-addition of PVAT caused a contraction, which was partially inhibited by the cyclooxygenase inhibitors indomethacin and flurbiprofen. The FP receptor antagonist AL8810 attenuated the PVAT-induced contraction in arteries from males, whereas the TP receptor antagonist GR32191B inhibited the PVAT-induced contraction in arteries from females. Although there was no difference in PGF_2α levels in PVAT between females and males, PGF_2α produced a larger contraction in arteries from males, correlating with a higher FP receptor expression. In contrast, release of TXB₂ from PVAT from females was greater than from males, but there was no difference in the contraction by the TXA₂ agonist U46619, or TP receptor expression in arteries from different sexes. These findings demonstrate clear sex differences in PVAT function in which PGF_2α and TXA₂ antagonists can inhibit the PVAT-induced vasoconstriction in male and female PCAs, respectively.

Losartan reverses COX-2-dependent vascular dysfunction in offspring of hyperglycaemic rats

AIMS

This study examined whether chronic treatment with losartan, an angiotensin II type 1 receptor (AT₁R) antagonist, might reverse COX-2-mediated vascular dysfunction in mesenteric resistance arteries (MRA) from offspring of hyperglycaemic rats.

MATERIALS AND METHODS

Male 12-month-old offspring of hyperglycaemic (O-DR) and normoglycaemic (O-CR) rats were treated with losartan (15mg·kg·day^-1) during 2months. Third order MRA of untreated and losartan-treated O-DR and O-CR were mounted in wire myograph for isometric tension measurements. COX-2 expression was analyzed by Western blot; TxA₂, PGE₂ and PGF_2α release was measured using commercial kits.

KEY FINDINGS

O-DR showed increased blood pressure, impaired acetylcholine-induced vasodilation and increased noradrenaline-induced vasoconstriction than O-CR. All these parameters were normalized by losartan in O-DR. Pre-incubation of MRA with indomethacin (COX-1/2 inhibitor), NS-398 (COX-2 inhibitor) or tempol (superoxide dismutase mimetic) increased relaxation to acetylcholine and reduced contraction to noradrenaline only in O-DR. COX-2 expression, TxA₂, PGE₂ and PGF_2α release were increased in O-DR. In losartan-treated O-DR, NS-398, indomethacin or tempol failed to produce any effect on acetylcholine or noradrenaline responses. Losartan treatment reduced COX-2 expression, TxA₂, PGE₂ and PGF_2α release in O-DR.

SIGNIFICANCE

The present results reveal that chronic losartan administration in O-DR normalizes endothelial function in MRA by correcting the existing COX-2 overexpression and the imbalance between endothelium-derived relaxing and contracting factors. These findings not only support the beneficial effects of AT₁ receptor antagonist in O-DR, but also suggest the implication of angiotensin II as a putative mediator of hyperglycemia-programmed vascular dysfunction in rats.

Hyperglycaemia in pregnant rats causes sex-related vascular dysfunction in adult offspring: role of cyclooxygenase-2

NEW FINDINGS

What is the central question of this study? Hyperglycaemia during pregnancy induces vascular dysfunction and hypertension in male offspring. Given that female offspring from other fetal programming models are protected from the effects of fetal insult, the present study investigated whether there are sex differences in blood pressure and vascular function in hyperglycaemia-programmed offspring. What is the main finding and its importance? We demonstrated that hyperglycaemia in pregnant rats induced vascular dysfunction and hypertension only in male offspring. We found sex differences in oxidative stress and cyclooxygenase-2-derived prostanoid production that might underlie the vascular dysfunction. These differences, particularly in resistance arteries, may in part explain the absence of hypertension in female offspring born to hyperglycaemic dams. Exposure to maternal hyperglycaemia induces hypertension and vascular dysfunction in adult male offspring. Given that female offspring from several fetal programming models are protected from the effects of fetal insult, in this study we analysed possible differences relative to sex in blood pressure and vascular function in hyperglycaemia-programmed offspring. Hyperglycaemia was induced on day 7 of gestation (streptozotocin, 50 mg kg^-1 ). Blood pressure, acetylcholine and phenylephrine or noradrenaline responses were analysed in the aorta and mesenteric resistance arteries of 3-, 6- and 12-month-old male and female offspring. Thromboxane A₂ release was analysed with commercial kits and superoxide anion (O₂^- ) production by dihydroethidium-emitted fluorescence. Male but not female offspring of hyperglycaemic dams (O-DR) had higher blood pressure than control animals (O-CR). Contraction in response to phenylephrine increased and relaxation in response to acetylcholine decreased only in the aorta from 12-month-old male O-DR and not in age-matched O-CR. Contractile and vasodilator responses were preserved in both the aorta and mesenteric resistance arteries from female O-DR of all ages. Pre-incubation with tempol, superoxide dismutase, indomethacin, NS-398, furegrelate or SQ29548 decreased contraction in response to phenylephrine and potentiated relaxation in response to acetylcholine in 12-month-old male O-DR aorta. In this artery, thromboxane A₂ release and O₂^- generation were greater in O-DR than O-CR groups. In conclusion, exposure to hyperglycaemia in utero results in sex-specific and age-dependent hypertension. The fact that vascular function is preserved in female O-DR may in part explain the absence of hypertension in this group. In contrast, the peripheral artery dysfunction associated with increased cyclooxygenase-2-derived production of vasoconstrictor prostanoids could underlie the increased blood pressure in male O-DR.

The endothelial cyclooxygenase pathway: Insights from mouse arteries

To date, cyclooxygenase-2 (COX-2) is commonly believed to be the major mediator of endothelial prostacyclin (prostaglandin I2; PGI2) synthesis that balances the effect of thromboxane (Tx) A2 synthesis mediated by the other COX isoform, COX-1 in platelets. Accordingly, selective inhibition of COX-2 is considered to cause vasoconstriction, platelet aggregation, and hence increase the incidence of cardiovascular events. This idea has been claimed to be substantiated by experiments on mouse models, some of which are deficient in one of the two COX isoforms. However, results from our studies and those of others using similar mouse models suggest that COX-1 is the major functional isoform in vascular endothelium. Also, although PGI2 is recognized as a potent vasodilator, in some arteries endothelial COX activation causes vasoconstrictor response. This has again been recognized by studies, especially those performed on mouse arteries, to result largely from endothelial PGI2 synthesis. Therefore, evidence that supports a role for COX-1 as the major mediator of PGI2 synthesis in mouse vascular endothelium, reasons for the inconsistency, and results that elucidate underlying mechanisms for divergent vasomotor reactions to endothelial COX activation will be discussed in this review. In addition, we address the possible pathological implications and limitations of findings obtained from studies performed on mouse arteries.

Maternal Hyperleptinemia Is Associated with Male Offspring's Altered Vascular Function and Structure in Mice

Children of mothers with gestational diabetes have greater risk of developing hypertension but little is known about the mechanisms by which this occurs. The objective of this study was to test the hypothesis that high maternal concentrations of leptin during pregnancy, which are present in mothers with gestational diabetes and/or obesity, alter blood pressure, vascular structure and vascular function in offspring. Wildtype (WT) offspring of hyperleptinemic, normoglycemic, Leprdb/+ dams were compared to genotype matched offspring of WT-control dams. Vascular function was assessed in male offspring at 6, and at 31 weeks of age after half the offspring had been fed a high fat, high sucrose diet (HFD) for 6 weeks. Blood pressure was increased by HFD but not affected by maternal hyperleptinemia. On a standard diet, offspring of hyperleptinemic dams had outwardly remodeled mesenteric arteries and an enhanced vasodilatory response to insulin. In offspring of WT but not Leprdb/+ dams, HFD induced vessel hypertrophy and enhanced vasodilatory responses to acetylcholine, while HFD reduced insulin responsiveness in offspring of hyperleptinemic dams. Offspring of hyperleptinemic dams had stiffer arteries regardless of diet. Therefore, while maternal hyperleptinemia was largely beneficial to offspring vascular health under a standard diet, it had detrimental effects in offspring fed HFD. These results suggest that circulating maternal leptin concentrations may interact with other factors in the pre- and post -natal environments to contribute to altered vascular function in offspring of diabetic pregnancies.

Role of cyclooxygenase-1 and -2 in endothelium-dependent contraction of atherosclerotic mouse abdominal aortas

The objective of this study was to determine the role of cyclooxygenase (COX)-1 or -2 in endothelium-dependent contraction under atherosclerotic conditions. Atherosclerosis was induced in apoE knockout (apoE(-/-)) mice and those with COX-1(-/-) (apoE(-/-)-COX-1(-/-)) by feeding with high fat and cholesterol food. Aortas (abdominal or the whole section) were isolated for functional and/or biochemical analyses. As in non-atherosclerotic conditions, the muscarinic receptor agonist acetylcholine (ACh) evoked an endothelium-dependent, COX-mediated contraction following NO synthase (NOS) inhibition in abdominal aortic rings from atherosclerotic apoE(-/-) mice. Interestingly, COX-1 inhibition not only abolished such a contraction in rings showing normal appearance, but also diminished that in rings with plaques. Accordingly, only a minor contraction (<30% that of apoE(-/-) counterparts) was evoked by ACh (following NOS inhibition) in abdominal aortic rings of atherosclerotic apoE(-/-)-COX-1(-/-) mice with plaques, and none was evoked in those showing normal appearance. Also, the contraction evoked by ACh in apoE(-/-)-COX-1(-/-) abdominal aortic rings with plaques was abolished by non-selective COX inhibition, thromboxane-prostanoid (TP) receptor antagonism, or endothelial denudation. Moreover, it was noted that ACh evoked a predominant production of the prostacyclin (PGI2, which mediates abdominal aortic contraction via TP receptors in mice) metabolite 6-keto-PGF1α, which was again sensitive to COX-1 inhibition or COX-1(-/-). Therefore, in atherosclerotic mouse abdominal aortas, COX-1 can still be the major isoform mediating endothelium-dependent contraction, which probably results largely from PGI2 synthesis as in non-atherosclerotic conditions. In contrast, COX-2 may have only a minor role in such response limited to areas of plaques under the same pathological condition.

Alterations in perivascular innervation function in mesenteric arteries from offspring of diabetic rats

BACKGROUND AND PURPOSE

We have reported that exposure to a diabetic intrauterine environment during pregnancy increases blood pressure in adult offspring, but the mechanisms involved are not completely understood. This study was designed to analyse a possible role of perivascular sympathetic and nitrergic innervation in the superior mesenteric artery (SMA) in this effect.

EXPERIMENTAL APPROACH

Diabetes was induced in pregnant Wistar rats by a single injection of streptozotocin. Endothelium-denuded vascular rings from the offspring of control (O-CR) and diabetic rats (O-DR) were used. Vasomotor responses to electrical field stimulation (EFS), NA and the NO donor DEA-NO were studied. The expressions of neuronal NOS (nNOS) and phospho-nNOS (P-nNOS) and release of NA, ATP and NO were determined. Sympathetic and nitrergic nerve densities were analysed by immunofluorescence.

KEY RESULTS

Blood pressure was higher in O-DR animals. EFS-induced vasoconstriction was greater in O-DR animals. This response was decreased by phentolamine more in O-DR animals than their controls. L-NAME increased EFS-induced vasoconstriction more strongly in O-DR than in O-CR segments. Vasomotor responses to NA or DEA-NO were not modified. NA, ATP and NO release was increased in segments from O-DR. nNOS expression was not modified, whereas P-nNOS expression was increased in O-DR. Sympathetic and nitrergic nerve densities were similar in both experimental groups.

CONCLUSIONS AND IMPLICATIONS

The activity of sympathetic and nitrergic innervation is increased in SMA from O-DR animals. The net effect is an increase in EFS-induced contractions in these animals. These effects may contribute to the increased blood pressure observed in the offspring of diabetic rats.

Constrictor prostanoids and uridine adenosine tetraphosphate: vascular mediators and therapeutic targets in hypertension and diabetes

Vascular dysfunction plays a pivotal role in the development of systemic complications associated with arterial hypertension and diabetes. The endothelium, or more specifically, various factors derived from endothelial cells tightly regulate vascular function, including vascular tone. In physiological conditions, there is a balance between endothelium-derived factors, that is, relaxing factors (endothelium-derived relaxing factors; EDRFs) and contracting factors (endothelium-derived contracting factors; EDCFs), which mediate vascular homeostasis. However, in disease states, such as diabetes and arterial hypertension, there is an imbalance between EDRF and EDCF, with a reduction of EDRF signalling and an increase of EDCF signalling. Among EDCFs, COX-derived vasoconstrictor prostanoids play an important role in the development of vascular dysfunction associated with hypertension and diabetes. Moreover, uridine adenosine tetraphosphate (Up4 A), identified as an EDCF in 2005, also modulates vascular function. However, the role of Up4 A in hypertension- and diabetes-associated vascular dysfunction is unclear. In the present review, we focused on experimental and clinical evidence that implicate these two EDCFs (vasoconstrictor prostanoids and Up4 A) in vascular dysfunction associated with hypertension and diabetes.

COX-2 mediated induction of endothelium-independent contraction to bradykinin in endotoxin-treated porcine coronary artery

This study examined the vascular effects of bradykinin in health and vascular inflammation comparing responses of isolated pig coronary arteries in the absence and presence of endotoxins. Bradykinin induced contractions in lipopolysaccharide-treated, but not untreated, arterial rings without endothelium. The B2-receptor antagonist HOE140, but not the B1-receptor inhibitor SSR240612, blocked these endothelium-independent contractions in response to bradykinin. The bradykinin-induced contractions were blocked by indomethacin, celecoxib, and terbogrel but not valeryl salicylate, AH6809, AL 8810, or RO1138452. They were attenuated by N-(p-amylcinnamoyl) anthranilic acid, and by diethyldithiocarbamate plus tiron but not by L-NAME. Quantitative reverse-transcription polymerase chain reaction revealed significant upregulations of messenger RNA expressions of B1 receptors, COX-2, and thromboxane A synthase 1 (TBXAS1) following lipopolysaccharide incubation but not of B2 receptors or COX-1. The present data demonstrate that bradykinin induces contractions mediated by the COX-2 pathway in endotoxin-treated pig coronary arteries. These results support differential roles of bradykinin in health and disease.

Vascular endothelial function is improved by oral glycine treatment in aged rats

Glycine has been used to reduce oxidative stress and proinflammatory mediators in some metabolic disorders; however, its effect on the vasculature has been poorly studied. The aim of this work was to explore the effect of glycine on endothelial dysfunction in aged rats. Aortic rings with intact or denuded endothelium were obtained from untreated or glycine-treated male Sprague-Dawley rats at 5 and 15 months of age. Concentration-response curves to phenylephrine (PHE) were obtained from aortic rings incubated with N(G)-nitro-l-arginine methyl ester (l-NAME), superoxide dismutase (SOD), indomethacin, SC-560, and NS-398. Aortic mRNA expression of endothelial nitric oxide synthase (eNOS), NADPH oxidase 4 (NOX-4), cyclooxygenase 1 (COX-1), cyclooxygenase 2 (COX-2), tumour necrosis factor (TNF)-α, and interleukin-1 β was measured by real time RT-PCR. The endothelial modulation of the contraction by PHE was decreased in aortic rings from aged rats. Glycine treatment improved this modulator effect and increased relaxation to acetylcholine. Glycine augmented the sensitivity for PHE in the presence of l-NAME and SOD. It also reduced the contraction by incubation with indomethacin, SC-560, and NS-398. Glycine increased the mRNA expression of eNOS and decreased the expression of COX-2 and TNF-α. Glycine improved the endothelium function in aged rats possibly by enhancing eNOS expression and reducing the role of superoxide anion and contractile prostanoids that increase the nitric oxide bioavailability.

Vasomotor Reaction to Cyclooxygenase-1-Mediated Prostacyclin Synthesis in Carotid Arteries from Two-Kidney-One-Clip Hypertensive Mice

This study tested the hypothesis that in hypertensive arteries cyclooxygenase-1 (COX-1) remains as a major form, mediating prostacyclin (prostaglandin I2; PGI2) synthesis that may evoke a vasoconstrictor response in the presence of functional vasodilator PGI2 (IP) receptors. Two-kidney-one-clip (2K1C) hypertension was induced in wild-type (WT) mice and/or those with COX-1 deficiency (COX-1-/-). Carotid arteries were isolated for analyses 4 weeks after. Results showed that as in normotensive mice, the muscarinic receptor agonist ACh evoked a production of the PGI2 metabolite 6-keto-PGF1α and an endothelium-dependent vasoconstrictor response; both of them were abolished by COX-1 inhibition. At the same time, PGI2, which evokes contraction of hypertensive vessels, caused relaxation after thromboxane-prostanoid (TP) receptor antagonism that abolished the contraction evoked by ACh. Antagonizing IP receptors enhanced the contraction to the COX substrate arachidonic acid (AA). Also, COX-1-/- mice was noted to develop hypertension; however, their increase of blood pressure and/or heart mass was not to a level achieved with WT mice. In addition, we found that either the contraction in response to ACh or that evoked by AA was abolished in COX-1-/- hypertensive mice. These results demonstrate that as in normotensive conditions, COX-1 is a major contributor of PGI2 synthesis in 2K1C hypertensive carotid arteries, which leads to a vasoconstrictor response resulting from opposing dilator and vasoconstrictor activities of IP and TP receptors, respectively. Also, our data suggest that COX-1-/- attenuates the development of 2K1C hypertension in mice, reflecting a net adverse role yielded from all COX-1-mediated activities under the pathological condition.

Vasoconstrictor role of cyclooxygenase-1-mediated prostacyclin synthesis in non-insulin-dependent diabetic mice induced by high-fat diet and streptozotocin

This study tested the hypothesis that in diabetic arteries, cyclooxygenase (COX)-1 mediates endothelial prostacyclin (PGI2) synthesis, which evokes vasoconstrictor activity under the pathological condition. Non-insulin-dependent diabetes was induced to C57BL/6 mice and those with COX-1 deficiency (COX-1−/− mice) using a high-fat diet in combination with streptozotocin injection. In vitro analyses were performed 3 mo after. Results showed that in diabetic aortas, the endothelial muscarinic receptor agonist ACh evoked an endothelium-dependent production of the PGI2 metabolite 6-keto-PGF1α, which was abolished in COX-1−/− mice. Meanwhile, COX-1 deficiency or COX-1 inhibition prevented vasoconstrictor activity in diabetic abdominal aortas, resulting in enhanced relaxation evoked by ACh. In a similar manner, COX-1 deficiency increased the relaxation evoked by ACh in nitric oxide synthase-inhibited diabetic renal arteries. Also, in diabetic abdominal aortas and/or renal arteries, both PGI2 and the COX substrate arachidonic acid evoked contractions similar to those of nondiabetic mice. However, the contraction to arachidonic acid, but not that to PGI2, was abolished in vessels from COX-1−/− mice. Moreover, we found that 3 mo after streptozotocin injection, systemic blood pressure increased in diabetic C57BL/6 mice but not in diabetic COX-1−/− mice. These results explicitly demonstrate that in the given arteries from non-insulin-dependent diabetic mice, COX-1 remains a major contributor to the endothelial PGI2 synthesis that evokes vasoconstrictor activity under the pathological condition. Also, our data suggest that COX-1 deficiency prevents or attenuates diabetic hypertension in mice, although this could be related to the loss of COX-1-mediated activities derived from both vascular and nonvascular tissues.

Regulation of rat intrapulmonary arterial tone by arachidonic acid and prostaglandin E2 during hypoxia

AIMS

Arachidonic acid (AA) and its metabolites, prostaglandins (PG) are known to be involved in regulation of vascular homeostasis including vascular tone and vessel wall tension, but their potential role in Hypoxic pulmonary vasoconstriction (HPV) remains unclear. In this study, we examined the effects of AA and PGE2 on the hypoxic response in isolated rat intrapulmonary arteries (IPAs).

METHODS AND RESULTS

We carried out the investigation on IPAs by vessel tension measurement. Isotetrandrine (20 µM) significantly inhibited phase I, phase IIb and phase IIc of hypoxic vasoconstriction. Both indomethacin (100 µM) and NS398 attenuated KPSS-induced vessel contraction and phase I, phase IIb and phase IIc of HPV, implying that COX-2 plays a primary role in the hypoxic response of rat IPAs. PGE2 alone caused a significant vasoconstriction in isolated rat IPAs. This constriction is mediated by EP4. Blockage of EP4 by L-161982 (1 µM) significantly inhibited phase I, phase IIb and phase IIc of hypoxic vasoconstriction. However, AH6809 (3 µM), an antagonist of EP1, EP2, EP3 and DP1 receptors, exerted no effect on KPSS or hypoxia induced vessel contraction. Increase of cellular cAMP by forskolin could significantly reduce KPSS-induced vessel contraction and abolish phase I, phase II b and phase II c of HPV.

CONCLUSION

Our results demonstrated a vasoconstrictive effect of PGE2 on rat IPAs and this effect is via activation of EP4. Furthermore, our results suggest that intracellular cAMP plays dual roles in regulation of vascular tone, depending on the spatial distribution of cAMP and its coupling with EP receptor and Ca(2+) channels.