Involvement of cysteinyl leukotrienes in angiotensin II-induced contraction in isolated aortas from transgenic (mRen-2)27 rats

Evaluation of urinary cysteinyl leukotrienes as biomarkers of severity and putative therapeutic targets in COVID-19 patients

BACKGROUND

Cysteinyl leukotrienes (CysLT) are potent inflammation-promoting mediators, but remain scarcely explored in COVID-19. We evaluated urinary CysLT (U-CysLT) relationship with disease severity and their usefulness for prognostication in hospitalized COVID-19 patients. The impact on U-CysLT of veno-venous extracorporeal membrane oxygenation (VV-ECMO) and of comorbidities such as hypertension and obesity was also assessed.

METHODS

Blood and spot urine were collected in "severe" (n = 26), "critically ill" (n = 17) and "critically ill on VV-ECMO" (n = 17) patients with COVID-19 at days 1-2 (admission), 3-4, 5-8 and weekly thereafter, and in controls (n = 23) at a single time point. U-CysLT were measured by ELISA. Routine markers, prognostic scores and outcomes were also evaluated.

RESULTS

U-CysLT did not differ between groups at admission, but significantly increased along hospitalization only in critical groups, being markedly higher in VV-ECMO patients, especially in hypertensives. U-CysLT values during the first week were positively associated with ICU and total hospital length of stay in critical groups and showed acceptable area under curve (AUC) for prediction of 30-day mortality (AUC: 0.734, p = 0.001) among all patients.

CONCLUSIONS

U-CysLT increase during hospitalization in critical COVID-19 patients, especially in hypertensives on VV-ECMO. U-CysLT association with severe outcomes suggests their usefulness for prognostication and as therapeutic targets.

The Role of Genetic Polymorphism in the Formation of Arterial Hypertension, Type 2 Diabetes and their Comorbidity

BACKGROUND

Hereditary component plays a significant role in the formation of insulin resistance (IR) - one of the pathogenetic links of arterial hypertension (AH) and type 2 diabetes mellitus (DM2). However, the genetic predisposition to IR can not be realized and does not manifest itself clinically in the absence of appropriate factors of the environment (excessive nutrition, low physical activity, etc.).

OBJECTIVE

The review summarizes the results of studies which describe the contribution of genetic polymorphism to the formation and progression of AH, DM2 and their comorbidity in various populations.

RESULTS

In many studies, it has been established that genetic polymorphism of candidate genes is influenced by the formation, course and complication of AH and DM2. According to research data, the modulating effect of polymorphism of some genetic markers of AH and DM2 on metabolism and hemodynamics has been established. The results of numerous studies have shown a higher frequency of occurrence of AH and DM2, as well as their more severe course with adverse genetic polymorphisms. At the same time, the role of genetic polymorphism in the formation of AH and DM2 differs in different populations.

CONCLUSION

Contradictory data on the influence of gene polymorphisms on the formation of AH and DM2 in different populations, as well as a small number of studies on the combined effects of several polymorphisms on the formation of comorbidity, determine the continuation of research in this direction.

Angiotensin II triggers release of leukotriene C4 in vascular smooth muscle cells via the multidrug resistance-related protein 1

The multidrug resistance-related protein-1 (MRP1) is important for the management of oxidative stress in vascular cells in vivo. Substrates of MRP1 are, among others, glutathione and the leukotriene C(4) (LTC(4)), an eicosanoid and mediator of inflammation. Angiotensin (Ang) II infusion results in MRP1(-/-) mice compared to wild-type mice in improved endothelial function and reduced reactive oxygen species (ROS) formation. However, the interaction between Ang II, LTC(4) and MRP1 is not completely understood and has never been investigated in vitro. Ang II induced in vascular smooth muscle cells (VSMC) the release of LTC(4) and the generation of ROS. Pharmacologic inhibition of MRP1 via MK 571 significantly reduced Ang II-induced ROS release (L012-luminescence) in VSMC. The release of ROS after Ang II stimulation is inhibited, to a comparable degree, by blockade of the Cys-LT1 receptor with montelukast. Incubation of VSMC with recombined LTC(4) and Ang II caused enhanced rates of proliferation in VSMC. This effect can be rescued by either MRP1 or Cys-LT1 receptor inhibition. Accordingly, stimulation of VSMC with LTC(4) reduces intracellular levels of glutathione, but does not affect apoptosis. LTC(4) stimulation results in a significant activation of MRP1, but does not alter MRP1 expression. These findings indicate a connection between Ang II, MRP1 and LTC(4). Both, MRP1 and LTC(4), are potentially promising targets for atheroprotective therapy.

Multidrug resistance protein-1 affects oxidative stress, endothelial dysfunction, and atherogenesis via leukotriene C4 export

BACKGROUND

We recently showed that the multidrug resistance related protein-1 (MRP1) is important for the management of oxidative stress in vascular cells. However, the underlying mechanism and the in vivo relevance of these findings remain elusive. We hypothesize that inside-outside transport of leukotriene C(4) (LTC(4)) via MRP1 is a substantial proatherogenic mechanism in the vasculature. To test this hypothesis, we investigated the effects of MRP1 inhibition and LTC(4) receptor blockade (Cys-LT1 receptor) in vitro and in vivo.

METHODS AND RESULTS

MRP1 is expressed abundantly in vascular smooth muscle cells (VSMCs). Pharmacological inhibition of MRP1 via MK571 reduces angiotensin II-induced reactive oxygen species release by 59% (L012 fluorescence) in VSMCs. The release of reactive oxygen species after angiotensin II stimulation also is inhibited by blockade of the Cys-LT1 receptor with montelukast. Incubation of VSMCs with recombined LTC(4) causes enhanced rates of reactive oxygen species and proliferation in wild-type and MRP1(-/-) VSMCs. Accordingly, the LTC(4) release in the cell culture supernatant of MRP1(-/-) VSMCs is significantly decreased compared with wild-type cells. To extend our observations to the in vivo situation, atherosclerosis-prone apolipoprotein E-deficient mice on a high-cholesterol diet were treated with placebo, the MRP1 inhibitor MK571, or the Cys-LT1 receptor inhibitor montelukast for 6 weeks. Treatment with MK571 or montelukast reduced vascular reactive oxygen species production, significantly improved endothelial function, and ameliorated atherosclerotic plaque generation by 52% and 61%, respectively.

CONCLUSIONS

These findings indicate that MRP1 and LTC(4) exert proatherosclerotic effects and that both MRP1 and LTC(4) are potentially promising targets for atheroprotective therapy.

The 5 lipoxygenase system in the vasculature: emerging role in health and disease

Activation of the 5 lipoygenase (5LO) system within the vascular bed requires the presence of several cell types with distinct transcellular cross-talk mechanisms, resulting in the generation of 5LO produced metabolites and increased expression of receptors for these metabolites in vascular cells. The key products in this system, the leukotriens LTB4, LTC4 and LTD4, are potent mediators of vascular inflammation initiated by white blood cells and sustained or propagated thereafter through amplified metabolite generation and direct effects in endothelial and vascular smooth muscle cells. Leukotrienes act to enhance cell permeability and increase oxidative stress, vascular smooth muscle cell migration and arterial tone. 5LO activation is highly regulated, and is apparently both model/species-specific and region-specific. 5LO activation is also linked to plaque progression, plaque stability, activation of matrix metalloproteinases, propensity to coronary and cerebrovascular events and the evolution of aortic aneurysms. Genetic variants in the 5LO activating protein are strongly linked to increased cardiovascular risk and may serve as useful markers for future therapy targeting down regulation of 5LO expression and activity as a means to combat cardiovascular disease.

Effect of 5-lipoxygenase blockade on blood pressure and acetylcholine-evoked endothelium-dependent contraction in aorta from spontaneously hypertensive rats

OBJECTIVE

Cysteinyl leukotrienes (cysLT) are pro-inflammatory and vasoactive products suspected to be involved in the regulation of vascular tone and blood pressure in hypertension.

DESIGN

We investigated, in spontaneously hypertensive rats (SHR), the involvement of cysLT in the in-vivo regulation of blood pressure and the in-vitro endothelium-dependent contraction to acetylcholine in isolated aorta.

METHODS

SHR and Wistar-Kyoto rats (WKY) were orally treated for 3 weeks with either the cysLT biosynthesis inhibitor MK-886 (0.1 mg/ml) or vehicle. After mean arterial blood pressure (MABP) measurement, aortic ring preparations were removed from all groups of animals, and contractions and relaxations were monitored subsequent to stimulation with acetylcholine.

RESULTS

MABP was higher in SHR. Chronic treatment with MK-886 did not alter MABP in either SHR or WKY. In the presence of the N-nitro-L-arginine (L-NA, 100 micromol/l), and on prostaglandin F2alpha (PGF2alpha)-induced tone, acetylcholine evoked concentration-dependent contractions in intact aortic rings from SHR only. Pretreatment with either MK-886 (10 micromol/l), the 5-lipoxygenase (5-LO) inhibitor AA861 (10 micromol/l), or the cysLT1 receptor antagonist MK571 (1 micromol/l) reduced (P < 0.05) acetylcholine-induced contractions in intact aortic rings from SHR only. Acetylcholine-induced contractions were weaker (P < 0.01) in SHR chronically treated with MK-886 than in SHR. In the presence of L-NA, leukotriene (LT) D4 induced greater (P < 0.05) concentration-dependent contractions in aortic rings from SHR than from WKY. MK571 abolished LTD4-evoked contractions.

CONCLUSION

These data suggested that 5-LO-derived products, through the activation of cysLT1 receptors, could be involved in the endothelium-dependent contraction to acetylcholine in aorta from SHR but not in the regulation of MABP in SHR.

Urinary leukotriene E4 excretion is increased in type 1 diabetic patients: a quantification by liquid chromatography-tandem mass spectrometry

OBJECTIVE

Diabetes mellitus is associated with inflammatory state and increased cardiovascular mortality. Leukotrienes are arachidonic acid metabolites derived from the 5-lipoxygenase pathway that possess vasoactive, chemotactic and proinflammatory properties. The aim of this study was to evaluate (1) the urinary excretion of leukotriene E4 (LTE4) in type 1 diabetic subjects and healthy volunteers and (2) the influence of glycemic control attested by HbA(1C) on LTE4 excretion.

METHODS AND RESULTS

Urinary excretion of LTE(4), measured by liquid chromatography-tandem mass spectrometry, was significantly (P=0.033) increased in diabetic patients (median [10th-90th percentiles]: 42.1 pg/mg creatinine [16.7-71.4], n=34), compared to healthy subjects (25.5 pg/mg creatinine [13.9-54.1], n=28). Subgroup analysis indicated a trend towards increased LTE4 excretion in patients with poor glycemic control [(HbA(1C)> or =9% or plasma glucose >18 mmol/L): 43.3 pg/mg creatinine [21.6-70.5], n=14], whereas no difference was observed between patients with good metabolic control [(HbA(1C)< or =7.5%): 36.4 pg/mg creatinine [15.8-83.4], n=20] and healthy subjects.

CONCLUSIONS

This study suggested that increased LTE4 excretion in type 1 diabetic state might reflect systemic activation of the 5-lipoxygenase pathway. It could be a determinant of underlying inflammatory state and vascular disease.

5-lipoxygenase expression and activity in aorta from streptozotocin-induced diabetic rats

We previously reported an activation of the 5-lipoxygenase pathway in aorta from streptozotocin-induced diabetic rats. The aim of this study was to investigate whether this activation was associated with an increased expression of 5-lipoxygenase, an increased cysteinyl leukotriene (CysLT) production in response to arachidonic acid or calcium ionophore A23187 and/or a hypersensitivity of the aorta to CysLTs in streptozotocin-induced diabetic rats. In aorta from diabetic and control rats, reverse transcriptase-PCR and western blot analysis with a specific 5-lipoxygenase antibody provided evidence for the presence of 5-lipoxygenase in aorta. However, the expression of 5-lipoxygenase was not significantly different between diabetic and control rats. Challenge by A23187 (10 microM) and arachidonic acid (10 microM and 0.1 mM) with or without A23187 (10 micromol/l) induced a significant increase of CysLT release (measured by enzyme immunoassay) that was in the same range in aorta from control and diabetic rats. In contrast, aortas from diabetic rats showed a greater sensitivity to LTC4 and LTD4 contractile effects. These data suggested that the activation of the 5-lipoxygenase pathway previously reported in streptozotocin-induced diabetic rats could be explained by an augmented sensitivity to CysLTs of the diabetic aorta.

Chronic intermittent hypoxia increases infarction in the isolated rat heart

Coronary heart disease is frequently associated with obstructive sleep apnea syndrome and treating obstructive sleep apnea appears to significantly improve the outcome in coronary heart disease. Thus we have developed a rat model of chronic intermittent hypoxia (IH) to study the influence of this condition on myocardial ischemia-reperfusion tolerance and on functional vascular reactivity. Wistar male rats were divided in three experimental groups ( n = 12 each) subjected to chronic IH (IH group), normoxia (N group), or control conditions (control group). IH consisted of repetitive cycles of 1 min (40 s with inspired O2fraction 5% followed by 20 s normoxia) and was applied for 8 h during daytime, for 35 days. Normoxic cycles were applied in the same conditions, inspired O2fraction remaining constant at 21%. On day 36, mean arterial blood pressure (MABP) was measured before isolated hearts were submitted to an ischemia-reperfusion protocol. The thoracic aorta and left carotid artery were also excised for functional reactivity studies. MABP was not significantly different between the three experimental groups. Infarct sizes (in percent of ventricles) were significantly higher in IH group (46.9 ± 3.6%) compared with N (26.1 ± 2.8%) and control (21.7 ± 2.1%) groups. Vascular smooth muscle function was similar in aorta and carotid arteries from all groups. The endothelium-dependent relaxation in response to acetylcholine was also similar in aorta and carotid arteries from all groups. Chronic IH increased heart sensitivity to infarction, independently of a significant increase in MABP, and did not affect vascular reactivity of aorta and carotid arteries.

N-Domain angiotensin I-Converting enzyme expression in renal artery of Wistar, Wistar kyoto, and spontaneously hypertensive rats

One of the most intriguing features in kidney transplantation is the finding that kidneys from hypertensive rats can transfer arterial hypertension on transplantation into normotensive rats. Some evidence also suggest that, in humans undergoing renal transplantation, the genotype of the donor kidney determines the blood pressure in the recipient. The renin-angiotensin-aldosterone system is the major etiological candidate in hypertension because it plays an important role in the control of cardiovascular homeostasis. Angiotensin-converting enzyme (ACE) cleaves the C-terminal from angiotensin I as well as from bradykinin. Thus, by generating the potent vasoconstrictor angiotensin II and by degrading the vasodepressor bradykinin, ACE is considered to play a role in blood pressure regulation. We have previously described the presence of N-domain ACE in urine of Wistar (W), Wistar Kyoto (WKY), and spontaneously hypertensive rats (SHR), all of which can hydrolyze the vasodilator peptide Angiotensin 1-7 and also the N-Acetyl-Ser-Asp-Lys-Pro, two peptides described as specific for N-domain ACE. These findings suggest that the 90 kd ACE isoform found in urine and in tissues of SHR is a possible genetic marker of hypertension. Based on the fact that the renal artery has an important role in the control of renal blood flow, we evaluated the presence of N-domain ACE in the renal artery of hypertensive and normotensive rats. Using Western blotting techniques on the renal arteries of W and WKY rats, we detected the 190-kd ACE (similar to somatic ACE) and also the 65-kd ACE previously described in urine and renal tissue as N-domain ACE. The 65-kd and 90-kd isoforms of ACE were also detected in renal arteries in SHR rats. Further studies are required to understand the role of 90-kd enzyme described as a possible local marker of hypertension, its contribution in angiotensin catabolism, and whether this abnormal form of the enzyme has any link with the development and transfer of hypertension after transplantation.

Inhibition of leukotriene synthesis with MK-886 prevents a rise in blood pressure and reduces noradrenaline-evoked contraction in L-NAME-treated rats

(1) Long-term treatment of rats with Nomega-nitro-l-arginine methyl ester (l-NAME) induces hypertension associated with inflammatory and vascular changes. Leukotrienes are proinflammatory vasoactive products that are suspected to be involved in the pathogenesis of hypertension. We investigated, in rats chronically treated with l-NAME, the involvement of leukotrienes in the in vivo regulation of blood pressure and the in vitro contraction elicited by noradrenaline in isolated aorta. (2) Rats were randomly assigned to four groups and orally treated for 3 weeks with l-NAME (1 mg ml-1), l-NAME (1 mg ml-1) plus the leukotriene biosynthesis inhibitor MK-886 (0.1 mg ml-1), MK-886 (0.1 mg ml-1) alone or vehicle (Methocel, 0.1%). All the drugs were added to the drinking fluid. (3) The mean arterial blood pressure (MABP) increased significantly in l-NAME-treated rats (173.3+/-9.4 mmHg (n=25)) vs Methocel-treated rats (110.7+/-4.8 mmHg (n=11), P<0.001). Chronic treatment with MK-886 prevented this rise in MABP. (4) Aortic rings with or without endothelium were suspended in organ baths for recording isometric changes in response to noradrenaline. Pretreatment with either MK-886 (10 microm), the CysLT1 receptor antagonist MK571 (1 microm) or the dual CysLT1/CysLT2 receptor antagonist BAY-u9773 (0.1 microm) reduced (P<0.05) noradrenaline-induced contractions in intact aortic rings from l-NAME-treated rats only. (5) Noradrenaline (0.3 microm) induced a two-fold increase in cysteinyl leukotriene (CysLT) release (measured by enzyme immunoassay) in intact aortic rings from l-NAME-treated rats only. (6) These data suggested (1) a role for the 5-lipoxygenase pathway in the regulation of blood pressure in l-NAME-treated rats and (2) the involvement of endothelial CysLTs in noradrenaline-induced contraction in aorta from l-NAME-treated rats.

Brain nitric oxide synthase activity in spontaneously hypertensive rats during the development of hypertension

OBJECTIVES

Blockade of neuronal nitric oxide synthase (nNOS) in the brain induced an increase in mean arterial pressure of spontaneously hypertensive rats (SHR). We hypothesize that increased nitric oxide (NO) synthesis in the brain compensates for hypertension. Therefore, we measured NOS activity in different brain regions in SHR at prehypertensive, onset and established hypertension, and compared with age-matched Wistar-Kyoto (WKY) rats.

METHOD

NOS activity was measured by the ability of tissue homogenate to convert [3H]l-arginine to [3H]l-citrulline in a Ca2+- and NADPH-dependent manner.

RESULTS

NOS activity was impaired in the cerebral cortex and brainstem of prehypertensive SHR. At established hypertension, SHR showed an augmentation in NOS activity in hypothalamus and brainstem. Chronic treatment of SHR with the angiotensin-1 converting enzyme (ACE)-inhibitor, enalapril, and the AT(1) receptor antagonist, losartan, normalized NOS activity in the hypothalamus but not in the brainstem. Treatment with a peripheral vasodilator, hydralazine, did not affect NOS activity.

CONCLUSION

Attenuated NOS activity in the cortex and brainstem of prehypertensive SHR may play a role in the pathogenesis of hypertension. The upregulated NOS activity in the hypothalamus and brainstem of SHR possibly serves to compensate for hypertension. Hypothalamic, but not brainstem, NO is involved in antihypertensive effects of ACE inhibition and AT(1) receptor blockade. Since a blood pressure decrease per se had no effect on NOS activity, it appears that central sympathetic activity influenced by endogenous angiotensin II, rather than blood pressure, represents the stimulus for the increased NOS activity in the hypothalamus of SHR.