Aerobic exercise training increases nitrergic innervation function and decreases sympathetic innervation function in mesenteric artery from rats fed a high-fat diet

Supplementation with the Symbiotic Formulation Prodefen® Increases Neuronal Nitric Oxide Synthase and Decreases Oxidative Stress in Superior Mesenteric Artery from Spontaneously Hypertensive Rats

In recent years, gut dysbiosis has been related to some peripheral vascular alterations linked to hypertension. In this work, we explore whether gut dysbiosis is related to vascular innervation dysfunction and altered nitric oxide (NO) production in the superior mesenteric artery, one of the main vascular beds involved in peripheral vascular resistance. For this purpose, we used spontaneously hypertensive rats, either treated or not with the commercial synbiotic formulation Prodefen^® (10⁸ colony forming units/day, 4 weeks). Prodefen^® diminished systolic blood pressure and serum endotoxin, as well as the vasoconstriction elicited by electrical field stimulation (EFS), and enhanced acetic and butyric acid in fecal samples, and the vasodilation induced by the exogenous NO donor DEA-NO. Unspecific nitric oxide synthase (NOS) inhibitor L-NAME increased EFS-induced vasoconstriction more markedly in rats supplemented with Prodefen^®. Both neuronal NO release and neuronal NOS activity were enhanced by Prodefen^®, through a hyperactivation of protein kinase (PK)A, PKC and phosphatidylinositol 3 kinase-AKT signaling pathways. The superoxide anion scavenger tempol increased both NO release and DEA-NO vasodilation only in control animals. Prodefen^® caused an increase in both nuclear erythroid related factor 2 and superoxide dismutase activities, consequently reducing both superoxide anion and peroxynitrite releases. In summary, Prodefen^® could be an interesting non-pharmacological approach to ameliorate hypertension.

Monoaminergic Receptors as Modulators of the Perivascular Sympathetic and Sensory CGRPergic Outflows

Blood pressure is a highly controlled cardiovascular parameter that normally guarantees an adequate blood supply to all body tissues. This parameter is mainly regulated by peripheral vascular resistance and is maintained by local mediators (i.e., autacoids), and by the nervous and endocrine systems. Regarding the nervous system, blood pressure can be modulated at the central level by regulating the autonomic output. However, at peripheral level, there exists a modulation by activation of prejunctional monoaminergic receptors in autonomic- or sensory-perivascular fibers. These modulatory mechanisms on resistance blood vessels exert an effect on the release of neuroactive substances from the autonomic or sensory fibers that modify blood pressure. Certainly, resistance blood vessels are innervated by perivascular: (i) autonomic sympathetic fibers (producing vasoconstriction mainly by noradrenaline release); and (ii) peptidergic sensory fibers [producing vasodilatation mainly by calcitonin gene-related peptide (CGRP) release]. In the last years, by using pithed rats, several monoaminergic mechanisms for controlling both the sympathetic and sensory perivascular outflows have been elucidated. Additionally, several studies have shown the functions of many monoaminergic auto-receptors and hetero-receptors expressed on perivascular fibers that modulate neurotransmitter release. On this basis, the present review: (i) summarizes the modulation of the peripheral vascular tone by adrenergic, serotoninergic, dopaminergic, and histaminergic receptors on perivascular autonomic (sympathetic) and sensory fibers, and (ii) highlights that these monoaminergic receptors are potential therapeutic targets for the development of novel medications to treat cardiovascular diseases (with some of them explored in clinical trials or already in clinical use).

Enhanced sympathetic neurotransduction in the superior mesenteric artery in a rat model of heart failure: role of noradrenaline and ATP

Heart failure (HF) is associated with neurohumoral activation, which in turn leads to an increased peripheral resistance. In mesenteric vasculature, perivascular innervation plays relevant role maintaining vascular tonus and resistance. Therefore, we aimed to determine the possible alterations in superior mesenteric artery (SMA) perivascular innervation function in HF rats. HF was induced by coronary artery occlusion in male Wistar rats, and sham-operated (SO) rats were used as controls. After 12 wk, a greater vasoconstrictor response to electrical field stimulation (EFS) was observed in endothelium-intact and endothelium-denuded SMA of HF rats. Alpha-adrenoceptor antagonist phentolamine diminished this response in a higher magnitude in HF than in SO animals. However, the noradrenaline (NA) reuptake inhibitor desipramine increased EFS-induced vasoconstriction more in segments from HF rats. Besides, EFS-induced NA release was greater in HF animals, due to a higher tyrosine hydroxylase expression and activity. P2 purinoceptor antagonist suramin reduced EFS-induced vasoconstriction only in segments from SO rats, and adenosine 5'-triphosphate (ATP) release was lower in HF than in SO. Moreover, nitric oxide (NO) synthase inhibitor N^ω-nitro-L-arginine methyl ester (L-NAME) enhanced EFS-induced vasoconstriction in a similar extent in both groups. HF was not associated with changes in EFS-induced NO release or the vasodilator response to NO donor sodium nitroprusside. In conclusion, HF postmyocardial infarction enhanced noradrenergic function and diminished purinergic cotransmission in SMA and did not change nitrergic innervation. The net effect was an increased sympathetic participation on the EFS-induced vasoconstriction that could help to understand the neurotransduction involved on the control of vascular tonus in HF.NEW & NOTEWORTHY This study reinforces the pivotal role of noradrenergic innervation in the regulation of mesenteric vascular tone in a rat model of heart failure. Moreover, our results highlight the counteracting role of ATP and NA reuptake, and help to understand the signaling pathways involved on the control of vascular tonus and resistance in heart failure postmyocardial infarction.

Nitrergic perivascular innervation in health and diseases: Focus on vascular tone regulation

For a long time, the vascular tone was considered to be regulated exclusively by tonic innervation of vasoconstrictor adrenergic nerves. However, accumulating experimental evidence has revealed the existence of nerves mediating vasodilatation, including perivascular nitrergic nerves (PNN), in a wide variety of mammalian species. Functioning of nitrergic vasodilator nerves is evidenced in several territories, including cerebral, mesenteric, pulmonary, renal, penile, uterine and cutaneous arteries. Nitric oxide (NO) is the main neurogenic vasodilator in cerebral arteries and acts as a counter-regulatory mechanism for adrenergic vasoconstriction in other vascular territories. In the penis, NO relaxes the vascular and cavernous smooth muscles leading to penile erection. Furthermore, when interacting with other perivascular nerves, NO can act as a neuromodulator. PNN dysfunction is involved in the genesis and maintenance of vascular disorders associated with arterial and portal hypertension, diabetes, ageing, obesity, cirrhosis and hormonal changes. For example defective nitrergic function contributes to enhanced sympathetic neurotransmission, vasoconstriction and blood pressure in some animal models of hypertension. In diabetic animals and humans, dysfunctional nitrergic neurotransmission in the corpus cavernosum is associated with erectile dysfunction. However, in some vascular beds of hypertensive and diabetic animals, an increased PNN function has been described as a compensatory mechanism to the increased vascular resistance. The present review summarizes current understanding on the role of PNN in control of vascular tone, its alterations under different conditions and the associated mechanisms. The knowledge of these changes can serve to better understand the mechanisms involved in these disorders and help in planning new treatments.

Beneficial Effect of a Multistrain Synbiotic Prodefen® Plus on the Systemic and Vascular Alterations Associated with Metabolic Syndrome in Rats: The Role of the Neuronal Nitric Oxide Synthase and Protein Kinase A

A high fat diet (HFD) intake is crucial for the development and progression of metabolic syndrome (MtS). Increasing evidence links gut dysbiosis with the metabolic and vascular alterations associated with MtS. Here we studied the use of a combination of various probiotic strains together with a prebiotic (synbiotic) in a commercially available Prodefen® Plus. MtS was induced by HFD (45%) in male Wistar rats. Half of the MtS animals received Prodefen® Plus for 4 weeks. At 12 weeks, we observed an increase in body weight, together with the presence of insulin resistance, liver steatosis, hypertriglyceridemia and hypertension in MtS rats. Prodefen® Plus supplementation did not affect the body weight gain but ameliorated all the MtS-related symptoms. Moreover, the hypertension induced by HFD is caused by a diminished both nitric oxide (NO) functional role and release probably due to a diminished neuronal nitric oxide synthase (nNOS) activation by protein kinase A (PKA) pathway. Prodefen® Plus supplementation for 4 weeks recovered the NO function and release and the systolic blood pressure was returned to normotensive values as a result. Overall, supplementation with Prodefen® Plus could be considered an interesting non-pharmacological approach in MtS.

Decompensated liver cirrhosis and neural regulation of mesenteric vascular tone in rats: role of sympathetic, nitrergic and sensory innervations

We evaluated the possible alterations produced by liver cholestasis (LC), a model of decompensated liver cirrhosis in sympathetic, sensory and nitrergic nerve function in rat superior mesenteric arteries (SMA). The vasoconstrictor response to electrical field stimulation (EFS) was greater in LC animals. Alpha-adrenoceptor antagonist phentolamine and P2 purinoceptor antagonist suramin decreased this response in LC animals more than in control animals. Both non-specific nitric oxide synthase (NOS) L-NAME and calcitonin gene related peptide (CGRP) (8-37) increased the vasoconstrictor response to EFS more strongly in LC than in control segments. Vasomotor responses to noradrenaline (NA) or CGRP were greater in LC segments, while NO analogue DEA-NO induced a similar vasodilation in both experimental groups. The release of NA was not modified, while those of ATP, nitrite and CGRP were increased in segments from LC. Alpha 1 adrenoceptor, Rho kinase (ROCK) 1 and 2 and total myosin phosphatase (MYPT) expressions were not modified, while alpha 2B adrenoceptor, nNOS expression and nNOS and MYPT phosphorylation were increased by LC. Together, these alterations might counteract the increased splanchnic vasodilation observed in the last phases of decompensated liver cirrhosis.

Aerobic exercise training protects against endothelial dysfunction by increasing nitric oxide and hydrogen peroxide production in LDL receptor-deficient mice

BACKGROUND

Endothelial dysfunction associated with hypercholesterolemia is an early event in atherosclerosis characterized by redox imbalance associated with high superoxide production and reduced nitric oxide (NO) and hydrogen peroxide (H2O2) production. Aerobic exercise training (AET) has been demonstrated to ameliorate atherosclerotic lesions and oxidative stress in advanced atherosclerosis. However, whether AET protects against the early mechanisms of endothelial dysfunction in familial hypercholesterolemia remains unclear. This study investigated the effects of AET on endothelial dysfunction and vascular redox status in the aortas of LDL receptor knockout mice (LDLr(-/-)), a genetic model of familial hypercholesterolemia.

METHODS

Twelve-week-old C57BL/6J (WT) and LDLr(-/-) mice were divided into sedentary and exercised (AET on a treadmill 1 h/5 × per week) groups for 4 weeks. Changes in lipid profiles, endothelial function, and aortic NO, H2O2 and superoxide production were examined.

RESULTS

Total cholesterol and triglycerides were increased in sedentary and exercised LDLr(-/-) mice. Endothelium-dependent relaxation induced by acetylcholine was impaired in aortas of sedentary LDLr(-/-) mice but not in the exercised group. Inhibition of NO synthase (NOS) activity or H2O2 decomposition by catalase abolished the differences in the acetylcholine response between the animals. No changes were noted in the relaxation response induced by NO donor sodium nitroprusside or H2O2. Neuronal NOS expression and endothelial NOS phosphorylation (Ser1177), as well as NO and H2O2 production, were reduced in aortas of sedentary LDLr(-/-) mice and restored by AET. Incubation with apocynin increased acetylcholine-induced relaxation in sedentary, but not exercised LDLr(-/-) mice, suggesting a minor participation of NADPH oxidase in the endothelium-dependent relaxation after AET. Consistent with these findings, Nox2 expression and superoxide production were reduced in the aortas of exercised compared to sedentary LDLr(-/-) mice. Furthermore, the aortas of sedentary LDLr(-/-) mice showed reduced expression of superoxide dismutase (SOD) isoforms and minor participation of Cu/Zn-dependent SODs in acetylcholine-induced, endothelium-dependent relaxation, abnormalities that were partially attenuated in exercised LDLr(-/-) mice.

CONCLUSION

The data gathered by this study suggest AET as a potential non-pharmacological therapy in the prevention of very early endothelial dysfunction and redox imbalance in familial hypercholesterolemia via increases in NO bioavailability and H2O2 production.

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.