The Role of the Activation of the TRPV1 Receptor and of Nitric Oxide in Changes in Endothelial and Cardiac Function and Biomarker Levels in Hypertensive Rats

Lipopolysaccharide pretreatment increases the sensitivity of the TRPV1 channel and promotes an anti-inflammatory phenotype of capsaicin-activated macrophages

BACKGROUND

The transient receptor potential vanilloid 1 (TRPV1) is well-established in neuronal function, yet its role in immune reactions remains enigmatic. The conflicting data on its inflammatory role, suggesting both pro-inflammatory and anti-inflammatory effects upon TRPV1 stimulation in immune cells, adds complexity. To unravel TRPV1 immunomodulatory mechanisms, we investigated how the TRPV1 agonist capsaicin influences lipopolysaccharide (LPS)-induced pro-inflammatory macrophage phenotypes.

RESULTS

Changes in the surface molecules, cytokine production, and signaling cascades linked to the phenotype of M1 or M2 macrophages of the J774 macrophage cell line and bone marrow-derived macrophages, treated with capsaicin before or after the LPS-induced inflammatory reaction were determined. The functional capacity of macrophages was also assessed by infecting the stimulated macrophages with the intracellular parasite Leishmania mexicana.

CONCLUSION

Our findings reveal that TRPV1 activation yields distinct macrophage responses influenced by the inflammatory context. LPS pre-treatment followed by capsaicin activation prompted increased calcium influx, accompanied by a shift toward an anti-inflammatory M2b-like polarization state.

Affinin, Isolated from Heliopsis longipes, Induces an Antihypertensive Effect That Involves CB1 Cannabinoid Receptors and TRPA1 and TRPV1 Channel Activation

In previous studies, we demonstrated that the ethanolic extract of Heliopsis longipes roots and its main alkamide, affinin, elicit a vasorelaxant effect through a mechanism involving activation of the gasotransmitter pathways and stimulation of cannabinoid type 1 receptors and transient receptor potential ankyrin 1 and transient receptor potential vanilloid 1 channels. However, it has not yet been demonstrated whether the EEH and affinin are capable of lowering high blood pressure. Therefore, the aim of the present study was to determine the effect of the oral administration of the EEH and affinin on the systolic blood pressure of NG-nitro-L-arginine methyl ester-induced hypertensive rats and to explore the participation of cannabinoid receptors and transient receptor potential channels in the mechanism of action of this alkamide. Our results showed that the ethanolic extract of H. longipes and affinin significantly lowered systolic blood pressure and induced an improvement in endothelial function, which is associated with increased serum nitric oxide levels. Inhibition of cannabinoid type 1 receptors by rimonabant (3 mg/kg), transient receptor potential ankyrin 1 channels by HC-030031 (8 mg/kg), and transient receptor potential vanilloid 1 channels by capsazepine (5 mg/kg) significantly decreased the antihypertensive effect induced by affinin, suggesting that the blood pressure-lowering effect of this alkamide involves activation of cannabinoid type 1 receptors and transient receptor potential ankyrin 1 and transient receptor potential vanilloid 1 channels.

Kaempferol protects against cardiovascular abnormalities induced by nitric oxide deficiency in rats by suppressing the TNF-α pathway

Kaempferol is a natural flavonoid compound that exhibits various pharmacological actions. However, there are few reports regarding the role of kaempferol in cardiovascular abnormalities. This study aimed to assess whether kaempferol could prevent cardiovascular malfunction and hypertrophy provoked by chronic inhibition of nitric oxide (NO) formation in rats. Rats (180-200 g) were treated daily with Nω-nitro-L-arginine methyl ester hydrochloride (L-NAME) (40 mg/kg, in drinking water) for five weeks concomitant with kaempferol (oral administration) at a dose of 20 mg/kg or 40 mg/kg or lisinopril (5 mg/kg). Kaempferol partially prevented the progression of hypertension provoked by NO inhibition (p < 0.05). Left ventricular malfunction and hypertrophy present in hypertensive rats were alleviated by concurrent administration of kaempferol (p < 0.05). Furthermore, L-NAME rats had increased sympathetic nerve-mediated vasoconstriction and decreased acetylcholine-induced vasorelaxation and aortic wall thickening, which were resolved by kaempferol treatment (p < 0.05). Kaempferol restored tissue superoxide formation, malondialdehyde, catalase activity, plasma nitric oxide metabolites, tumor necrosis factor-alpha (TNF-α) and interleukin-6 in L-NAME rats (p < 0.05). Overexpression of tumor necrosis factor receptor 2 (TNFR2), phosphatidylinositol 3-kinases (PI3K), AKT serine/threonine kinase 1 (Akt1) and smad2/3 in heart tissue and upregulation of tumor necrosis factor receptor 1 (TNFR1), phosphorylated nuclear factor-kappaB (p-NF-κB) and transforming growth factor beta 1 (TGF-β1) in vascular tissue were suppressed by kaempferol (p < 0.05). In conclusion, kaempferol exerts antihypertensive, cardioprotective, antioxidant, and anti-inflammatory effects in NO-dependent hypertensive rats. The underlying mechanisms of kaempferol in preventing cardiovascular changes induced by L-NAME were due to the suppression of the TNF-α pathway.

Targeting temperature-sensitive transient receptor potential channels in hypertension: far beyond the perception of hot and cold

Transient receptor potential (TRP) channels are nonselective cation channels and participate in various physiological roles. Thus, changes in TRP channel function or expression have been linked to several disorders. Among the many TRP channel subtypes, the TRP ankyrin type 1 (TRPA1), TRP melastatin type 8 (TRPM8), and TRP vanilloid type 1 (TRPV1) channels are temperature-sensitive and recognized as thermo-TRPs, which are expressed in the primary afferent nerve. Thermal stimuli are converted into neuronal activity. Several studies have described the expression of TRPA1, TRPM8, and TRPV1 in the cardiovascular system, where these channels can modulate physiological and pathological conditions, including hypertension. This review provides a complete understanding of the functional role of the opposing thermo-receptors TRPA1/TRPM8/TRPV1 in hypertension and a more comprehensive appreciation of TRPA1/TRPM8/TRPV1-dependent mechanisms involved in hypertension. These channels varied activation and inactivation have revealed a signaling pathway that may lead to innovative future treatment options for hypertension and correlated vascular diseases.

Effect of hypoandrogenism on expression of transient receptor potential vanilloid channels in rat penile corpus cavernosum and erectile function

BACKGROUND

Hypoandrogenism is a cause of erectile dysfunction (ED). Vascular smooth muscle cell contraction and relaxation are regulated by TRPV1-4 channels. However, the influence of hypoandrogenism on TRPV1-4 and its relationship with erectile function remain unclear.

AIM

To reveal whether hypoandrogenism affects erectile function by influencing TRPV1-4 expression in the corpus cavernosum of rats.

METHODS

Male Sprague-Dawley rats (N = 36) aged 8 weeks were assigned to 6 groups at random (n = 6): sham operation, castrated, castrated + testosterone replacement, sham operation + transfection, castrated + transfection, and castrated + empty transfection. Four weeks after castration, 20 μL of lentiviral vector (1 × 108 TU/mL) carrying the TRPV4 gene was injected into the penile cavernous tissue of the transfection groups. One week after transfection, the maximum intracavernous pressure (ICPmax)/mean arterial pressure (MAP) and the content of TRPV1-4, phosphorylated eNOS (p-eNOS)/eNOS, and nitric oxide (NO) in penile cavernous tissue of each group were measured.

OUTCOMES

Under low androgen conditions, TRPV4 expression in endothelial cells in the rat penile cavernosum was sharply reduced, resulting in a decrease in p-eNOS/eNOS and NO content, which could inhibit erectile function.

RESULTS

In rat penile cavernous tissue, TRPV1-4 was expressed in the cell membranes of endothelial cells and smooth muscle cells. The ICPmax/MAP and the content of TRPV4, p-eNOS/eNOS, and NO end product nitrite level in rat penile cavernous tissue was markedly reduced in the castrated group as compared with the sham group (P < .05). The ICPmax/MAP and the content of TRPV4, p-eNOS/eNOS, and NO end product nitrite level in rat penile cavernous tissue were markedly improved in the castrated + transfection group vs the castrated group (P < .01).

CLINICAL IMPLICATIONS

Upregulation of TRPV4 expression in penile cavernosum tissue might be a viable therapeutic for ED caused by hypoandrogenism.

STRENGTHS AND LIMITATIONS

The specific mechanism of TRPV4 in ED needs to be further verified by androgen receptor or TRPV4 gene knockout experiments.

CONCLUSION

Hypoandrogenism may cause ED by reducing the expression of TRPV4 in rat penile cavernous tissue. Upregulation of TRPV4 expression in penile cavernous tissue can increase the ratio of p-eNOS/eNOS and NO levels and ameliorate the erectile function of castrated rats.

Potential mechanism of transient receptor potential cation channel subfamily V member 1 combined with an ATP‑sensitive potassium channel in severe preeclampsia

Severe preeclampsia is one of the most serious obstetric diseases. However, the pathogenesis of the disease is not fully understood. In the present study, placental artery and blood serum was collected from patients with severe preeclampsia, as well as from normal pregnant women. The results of reverse transcription-quantitative (q)PCR, western blotting, and immunohistochemical staining revealed markedly decreased transient receptor potential cation channel subfamily V member 1 (TRPV1), ATP-sensitive potassium channel (KATP) subtype Kir6.1/SUR2B and endothelial nitric oxide synthase (eNOS) expression in severe preeclampsia tissue specimens compared with those in samples from normal pregnant women. The nitrate reduction method indicated lower NO levels in the tissue specimens and serum of patients with severe preeclampsia. Moreover, hematoxylin-eosin staining showed that the endothelial cell layer in the placental artery of patients with severe preeclampsia was notably damaged. To investigate the potential role of TRPV1-KATP channels in severe preeclampsia, HUVECs were used for in vitro experiments. The samples were divided into a control group, a TRPV1 agonist group (capsaicin) and a TRPV1 inhibitor group (capsazepine). qPCR and western blotting revealed that the relative gene and protein expression levels of TRPV1, Kir6.1, SUR2B and eNOS in the control group were significantly lower than those in the capsaicin group and considerably higher than those in the capsazepine group. Based on previous studies and the results of the present study, we hypothesized that impairment of the endothelial TRPV1-KATP channels results in decreased eNOS/NO pathway activity, which may be one of the mechanisms involved in severe preeclampsia. The increase in NO generation mediated by TRPV1-KATP may be a suitable target for the management of severe preeclampsia.

Co-administration of metformin and/or glibenclamide with losartan reverse NG-nitro-l-arginine-methyl ester-streptozotocin-induced hypertensive diabetes and haemodynamic sequelae in rats

Over the years, there have been opinions on whether to reduced blood pressure (BP) to a different levels in patients with diabetes mellitus. Hence, this study investigated the efficacy of the co-administration of losartan (angiotensin receptor blocking antihypertensive agent) with metformin and/or glibenclamide (antidiabetic agents) on hypertensive-diabetic experimental rats induced by N^G-nitro-l-arginine-methyl-ester hydrochloride (l-NAME), and streptozotocin (STZ). STZ (45 mg/kg, i.p.)-induced diabetic rats combined with l-NAME (40 mg/kg, p.o.)-induced hypertension were allotted into different groups. Group 1 received distilled water (10 mL/kg) and served as normal control, group 2 comprised hypertensive diabetic rats with distilled water, groups 3-5 were hypertensive-diabetic rats but received combination treatments of losartan + metformin, losartan + glibenclamide, and losartan + metformin + glibenclamide daily for 8 weeks, respectively. Our finding revealed no changes in the body weights, but there was a significant increase in fasting blood sugar levels in l-NAME - STZ-induced hypertensive-diabetes, which were lowered by losartan + metformin, losartan + glibenclamide, and losartan + metformin + glibenclamide treatments. Moreover, the increased systolic-BP, mean arterial pressure but not diastolic-BP and heart rate by l-NAME + STZ were attenuated more significantly by losartan + metformin + glibenclamide between weeks 2-8 relative to hypertensive-diabetic control. l-NAME + STZ-induced elevated levels of lactate dehydrogenase and creatinine kinase, were differentially reversed by losartan + metformin, losartan + glibenclamide, and losartan + metformin + glibenclamide. However, l-NAME + STZ-induced decreased nitrite level was significantly restored by all treatments, suggesting increased nitrergic transmission. Additionally, l-NAME + STZ-induced degeneration of pancreatic islet and myocardial cells were dramatically alleviated by losartan + metformin + glibenclamide treatments. Our findings suggest hyperglycemia with raised systolic-BP should be managed with losartan combined with both metformin and glibenclamide than single combination of losartan with antidiabetics.

TRPV1 Contributes to Modulate the Nitric Oxide Pathway and Oxidative Stress in the Isolated and Perfused Rat Heart during Ischemia and Reperfusion

The transient vanilloid receptor potential type 1 (TRPV1) regulates neuronal and vascular functions mediated by nitric oxide (NO) and by the calcitonin gene-related peptide (CGRP). Here, we study the participation of TRPV1 in the regulation of myocardial injury caused by ischemia-reperfusion and in the control of NO, tetrahydrobiopterin (BH4), the cGMP pathway, CGRP, total antioxidant capacity (TAC), malondialdehyde (MDA) and phosphodiesterase-3 (PDE-3). Isolated hearts of Wistar rats perfused according to the Langendorff technique were used to study the effects of an agonist of TRPV1, capsaicin (CS), an antagonist, capsazepine (CZ), and their combination CZ+CS. The hearts were subjected to three conditions: (1) control, (2) ischemia and (3) ischemia-reperfusion. We determined cardiac mechanical activity and the levels of NO, cGMP, BH4, CGRP, TAC, MDA and PDE-3 in ventricular tissue after administration of CS, CZ and CZ+CS. Western blots were used to study the expressions of eNOS, iNOS and phosphorylated NOS (pNOS). Structural changes were determined by histological evaluation. CS prevented damage caused by ischemia-reperfusion by improving cardiac mechanical activity and elevating the levels of NO, cGMP, BH4, TAC and CGRP. TRPV1 and iNOS expression were increased under ischemic conditions, while eNOS and pNOS were not modified. We conclude that the activation of TRPV1 constitutes a therapeutic possibility to counteract the damage caused by ischemia and reperfusion by regulating the NO pathway through CGRP.

Arterial stiffness is associated with oxidative stress and endothelial activation among persons with treated HIV in Zambia

BACKGROUND

Cardiovascular disease (CVD) prevalence is rising among persons with HIV (PLWH) in sub-Saharan Africa. Oxidative stress and endothelial activation, resulting in reduced vascular compliance, are contributors to CVD risk. However, there is a paucity of vascular health data in this population.

OBJECTIVES

To assess the relationships of oxidative stress and endothelial activation with vascular stiffness among PLWH.

METHOD

Fifty-four PLWH on antiretroviral therapy > 5 years and 57 HIV-negative controls, all aged 18-45 years, were enrolled from the University Teaching Hospital, Lusaka, Zambia. Oxidative stress was measured by nitrotyrosine, a peroxynitrite biomarker, and endothelial activation by soluble intercellular adhesion molecule-1 (sICAM-1) plasma levels. Vascular compliance was measured using carotid-radial pulse wave velocity (crPWV) and arterial stiffness index (crASI).

RESULTS

PLWH had higher sICAM-1 levels (median 345 ng/mL) compared to controls (275 ng/mL, p < 0.01), as well as higher nitrotyrosine levels (297 versus 182 nM; p = 0.02). Median crPWV was similar between the groups, but PLWH had higher crASI (2.4 versus 2.2 cm/ms; p < 0.05). After adjusting for age, fat mass, and blood pressure, the estimated effect of a one unit increase in nitrotyrosine on crPWV were twofold higher in the PLWH, but neither reached significance. In a model pooling all participants, there were significant differences in the relationship of nitrotyrosine with crPWV and crASI by HIV status.

CONCLUSION

PLWH in sub-Saharan Africa had significantly greater oxidative stress and endothelial activation compared to HIV-negative individuals. These factors may contribute to increased arterial stiffness and higher CVD prevalence in this population.

Chronic L-Name-Treatment Produces Hypertension by Different Mechanisms in Peripheral Tissues and Brain: Role of Central eNOS

The goal of our study was to analyze the time course of the effect of N^G-nitro-L-arginine methyl ester (L-NAME) on nitric oxide synthase (NOS) isoforms and nuclear factor–κB (NF-κB) protein expression, total NOS activity, and blood pressure (BP) in rats. Adult 12-week-old male Wistar rats were subjected to treatment with L-NAME (40 mg/kg/day) for four and seven weeks. BP was increased after 4- and 7-week L-NAME treatments. NOS activity decreased after 4-week-L-NAME treatment; however, the 7-week treatment increased NOS activity in the aorta, heart, and kidney, while it markedly decreased NOS activity in the brainstem, cerebellum, and brain cortex. The 4-week-L-NAME treatment increased eNOS expression in the aorta, heart, and kidney and this increase was amplified after 7 weeks of treatment. In the brain regions, eNOS expression remained unchanged after 4-week L-NAME treatment and prolonged treatment led to a significant decrease of eNOS expression in these tissues. NF-κB expression increased in both peripheral and brain tissues after 4 weeks of treatment and prolongation of treatment decreased the expression in the aorta, heart, and kidney. In conclusion, decreased expression of eNOS in the brain regions after 7-week L-NAME treatment may be responsible for a remarkable decrease of NOS activity in these regions. Since the BP increase persisted after 7 weeks of L-NAME treatment, we hypothesize that central regulation of BP may contribute significantly to L-NAME-induced hypertension.

Nebivolol combined with tetrahydrobiopterin affects diastolic function in spontaneously hypertensive rats via the nitric oxide/cyclic guanosine monophosphate signalling pathway

BACKGROUND

Hypertension is the the primary cause of diastolic heart failure. Oxidative stress plays an important role in cardiac diastolic dysfunction caused by hypertension. The occurrence of oxidative stress is related to the level of nitric oxide (NO) in the body. Tetrahydrobiopterin (BH4) is an essential cofactor for NO synthesis. Nebivolol can reduce myocardial oxidative stress and increase NO activity. Therefore, we investigated the effects of monotherapy or combination therapy of different doses of BH4 and nebivolol on cardiac diastolic function in spontaneously hypertensive rats, and preliminarily expounded the related mechanisms.

METHODS

Left ventricular function was evaluated by non-invasive echocardiographic assessment and invasive right carotid artery catheterization methods. ELISA was used to measure myocardial 3-nitrotyrosine content, NO production, and cyclic guanosine monophosphate (cGMP) concentration in the myocardium; quantitative real-time PCR (qRT-PCR) was used to determine endothelial nitric oxide synthase (eNOS), phospholamban and sarcoplasmic reticulum Ca2+-ATPase 2a (SERCA2a) mRNA expression levels; Western blot was used to detect the protein expression levels of eNOS and eNOS dimers in myocardial tissue, and immunohistochemical detection of cGMP expression in the myocardium was performed.

RESULTS

Studies have shown that compared with those in the control group, NO generation and the expression level of myocardial eNOS mRNA, eNOS expression of dimers, phospholamban, SERCA2a and cGMP increased significantly after the combined intervention of BH4 and nebivolol, while the expression of 3-nitrotyrosine was significantly decreased.

CONCLUSIONS

The combined treatment group had a synergistic effect on reducing myocardial oxidative stress, increasing eNOS content, and increasing NO production, and had a more obvious protective effect on diastolic dysfunction through the nitric oxide/cyclic guanosine monophosphate (NO/cGMP) pathway.

TRPC and TRPV Channels' Role in Vascular Remodeling and Disease

Transient receptor potentials (TRPs) are non-selective cation channels that are widely expressed in vascular beds. They contribute to the Ca²⁺ influx evoked by a wide spectrum of chemical and physical stimuli, both in endothelial and vascular smooth muscle cells. Within the superfamily of TRP channels, different isoforms of TRPC (canonical) and TRPV (vanilloid) have emerged as important regulators of vascular tone and blood flow pressure. Additionally, several lines of evidence derived from animal models, and even from human subjects, highlighted the role of TRPC and TRPV in vascular remodeling and disease. Dysregulation in the function and/or expression of TRPC and TRPV isoforms likely regulates vascular smooth muscle cells switching from a contractile to a synthetic phenotype. This process contributes to the development and progression of vascular disorders, such as systemic and pulmonary arterial hypertension, atherosclerosis and restenosis. In this review, we provide an overview of the current knowledge on the implication of TRPC and TRPV in the physiological and pathological processes of some frequent vascular diseases.