Enhanced neuropeptide Y immunoreactivity and vasoconstriction in mesenteric small arteries from the early non-obese diabetic mouse

Neuropeptide Y: Direct vasoconstrictor and facilitatory effects on P2X1 receptor-dependent vasoconstriction in human small abdominal arteries

Neuropeptide Y (NPY) is co-released with norepinephrine and ATP by sympathetic nerves innervating arteries. Circulating NPY is elevated during exercise and cardiovascular disease, though information regarding the vasomotor function of NPY in human blood vessels is limited. Wire myography revealed NPY directly stimulated vasoconstriction (EC50 10.3 ± 0.4 nM; N = 5) in human small abdominal arteries. Maximum vasoconstriction was antagonised by both BIBO03304 (60.7 ± 6%; N = 6) and BIIE0246 (54.6 ± 5%; N = 6), suggesting contributions of both Y1 and Y2 receptor activation, respectively. Y1 and Y2 receptor expression in arterial smooth muscle cells was confirmed by immunocytochemistry, and western blotting of artery lysates. α,β-meATP evoked vasoconstrictions (EC50 282 ± 32 nM; N = 6) were abolished by suramin (IC50 825 ± 45 nM; N = 5) and NF449 (IC50 24 ± 5 nM; N = 5), suggesting P2X1 mediates vasoconstriction in these arteries. P2X1, P2X4 and P2X7 were detectable by RT-PCR. Significant facilitation (1.6-fold) of α,β-meATP-evoked vasoconstrictions was observed when submaximal NPY (10 nM) was applied between α,β-meATP applications. Facilitation was antagonised by either BIBO03304 or BIIE0246. These data reveal NPY causes direct vasoconstriction in human arteries which is dependent upon both Y1 and Y2 receptor activation. NPY also acts as a modulator, facilitating P2X1-dependent vasoconstriction. Though in contrast to the direct vasoconstrictor effects of NPY, there is redundancy between Y1 and Y2 receptor activation to achieve the facilitatory effect.

Neuropeptide Y facilitates P2X1 receptor-dependent vasoconstriction via Y1 receptor activation in small mesenteric arteries during sympathetic neurogenic responses

ATP, norepinephrine and NPY are co-released by sympathetic nerves innervating arteries. ATP elicits vasoconstriction via activation of smooth muscle P2X receptors. The functional interaction between neuropeptide Y (NPY) and P2X receptors in arteries is not known. In this study we investigate the effect of NPY on P2X1-dependent vasoconstriction in mouse mesenteric arteries. Suramin or P2X1 antagonist NF449 abolished α,β-meATP evoked vasoconstrictions. NPY lacked any direct vasoconstrictor effect but facilitated the vasoconstrictive response to α,β-meATP. Mesenteric arteries expressed Y1 and Y4 receptors, but not Y2 or Y5. Y1 receptor inhibition (BIBO3304) reversed NPY facilitation of the α,β-meATP-evoked vasoconstriction. L-type Ca2+ channel antagonism (nifedipine) had no effect on α,β-meATP-evoked vasoconstrictions, but completely reversed NPY facilitation. Electrical field stimulation evoked sympathetic neurogenic vasoconstriction. Neurogenic responses were dependent upon dual α1-adrenergic (prazosin) and P2X1 (NF449) receptor activation. Y1 receptor antagonism partially reduced neurogenic vasoconstriction. Isolation of the P2X1 component by α1-adrenergic blockade allowed faciliatory effects of Y1 receptor activation to be explored. Y1 receptor antagonism reduced the P2X1 receptor component during neurogenic vasoconstriction. α1-adrenergic and P2X1 receptors are post-junctional receptors during sympathetic neurogenic vasoconstriction in mesenteric arteries. In conclusion, we have identified that NPY lacks a direct vasoconstrictor effect in mesenteric arteries but can facilitate vasoconstriction by enhancing the activity of P2X1, following activation by exogenous agonists or during sympathetic nerve stimulation. The mechanism of P2X1 facilitation by NPY involved activation of the NPY Y1 receptor and the L-type Ca2+ channel.

The role of food intake regulating peptides in cardiovascular regulation

Obesity is a risk factor that worsens cardiovascular events leading to higher morbidity and mortality. However, the exact mechanisms of relation between obesity and cardiovascular events are unclear. Nevertheless, it has been demonstrated that pharmacological therapy for obesity has great potential to improve some cardiovascular problems. Therefore, it is important to determine the common mechanisms regulating both food intake and blood pressure. Several hormones produced by peripheral tissues work together with neuropeptides involved in the regulation of both food intake and blood pressure. Anorexigenic (food intake lowering) hormones such as leptin, glucagon-like peptide-1 and cholecystokinin cooperate with α-melanocyte-stimulating hormone, cocaine- and amphetamine-regulated peptide as well as prolactin-releasing peptide. Curiously their collective actions result in increased sympathetic activity, especially in the kidney, which could be one of the factors responsible for the blood pressure increases seen in obesity. On the other hand, orexigenic (food intake enhancing) peptides, especially ghrelin released from the stomach and acting in the brain, cooperates with orexins, neuropeptide Y, melanin-concentrating hormone and galanin, which leads to decreased sympathetic activity and blood pressure. This paradox should be intensively studied in the future. Moreover, it is important to know that the hypothalamus together with the brainstem seem to be major structures in the regulation of food intake and blood pressure. Thus, the above mentioned regions might be essential brain components in the transmission of peripheral signals to the central effects. In this short review, we summarize the current information on cardiovascular effects of food intake regulating peptides.

Neuropeptide Y in the noradrenergic neurons induces the development of cardiometabolic diseases in a transgenic mouse model

Neuropeptide Y (NPY) is a neuropeptide widely expressed in the brain and a peptide transmitter of sympathetic nervous system (SNS) co-released with noradrenaline (NA) in prolonged stress. Association of a gain-of-function polymorphism in the human NPY gene with dyslipideamia, diabetes and vascular diseases suggests that increased NPY plays a role in the pathogenesis of the metabolic syndrome in humans. In the hypothalamus, NPY plays an established role in the regulation of body energy homeostasis. However, the effects of NPY elsewhere in the brain and in the SNS are less explored. In order to understand the role of NPY co-expressed with NA in the sympathetic nerves and brain noradrenergic neurons, a novel mouse model overexpressing NPY in noradrenergic neurons was generated. The mouse displays metabolic defects such as increased adiposity, hepatosteatosis, and impaired glucose tolerance as well as stress-related hypertension and increased susceptibility to vascular wall hypertrophy. The mouse phenotype closely reflects the findings of the several association studies with human NPY gene polymorphisms, and fits with the previous work on the effects of stress-induced NPY release on metabolism and vasculature. Thus, in addition of promoting feeding and obesity in the hypothalamus, NPY expressed in the noradrenergic neurons in the brain and in the SNS induces the development of cardiometabolic diseases.

Adenosine actions are preserved in corpus cavernosum from obese and type II diabetic db/db mouse

INTRODUCTION

Erectile dysfunction (ED) in diabetes is associated with autonomic neuropathy and endothelial dysfunction. Whereas the nonadrenergic-noncholinergic (NANC)/neurogenic nitric oxide pathway has received great attention in diabetes-associated ED, few studies have addressed sympathetic overactivity.

AIM

To test the hypothesis that adenosine-induced inhibition of adrenergic-mediated contractile responses in mouse corpus cavernosum is impaired in the presence of diabetes.

METHODS

The db/db (obesity and type II diabetes caused by a leptin receptor mutation) mouse strain was used as a model of obesity and type II diabetes, and standard procedures were performed to evaluate functional cavernosal responses.

MAIN OUTCOME MEASURES

Increased cavernosal responses to sympathetic stimulation in db/db mice are not associated with impaired prejunctional actions of adenosine.

RESULTS

Electrical field stimulation (EFS)-, but not phenylephrine (PE)-, induced contractions are enhanced in cavernosal strips from db/db mice in comparison with those from lean littermates. Direct effects of adenosine, 2-chloro-adenosine, A(1) receptor agonist C-8031 (N6 cyclopentyladenosine), and sodium nitroprusside are similar between the strips from lean and db/db mice, whereas relaxant responses to acetylcholine and NANC stimulation are significantly impaired in the cavernosal strips from db/db mice. 5'-Iodotubercidin (adenosine kinase inhibitor) and dipyridamole (inhibitor of adenosine transport), as well as the A(1) agonist C-8031, significantly and similarly inhibit contractions induced by stimulation of adrenergic nerves in the cavernosal strips from lean and db/db mice.

CONCLUSIONS

Results from this study suggest that corpora cavernosa from obese and diabetic db/db mice display altered neural-mediated responses that would favor penile detumescence, i.e., increased contractile response to adrenergic nerve stimulation and decreased relaxant responses upon activation of NANC nerves. However, increased cavernosal responses to adrenergic nerve stimulation are not due to impaired negative modulation of sympathetic neurotransmission by adenosine in this diabetic model.