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Perivascular Adipose Tissue's Impact on Norepinephrine-Induced Contraction of Mesenteric Resistance Arteries.

ABSTRACT: Background: Perivascular adipose tissue (PVAT) can decrease vascular contraction to NE. We tested the hypothesis that metabolism and/or uptake of vasoactive amines by mesenteric PVAT (MPVAT) could affect NE-induced contraction of the mesenteric resistance arteries. Methods: Mesenteric resistance vessels (MRV) and MPVAT from male Sprague-Dawley rats were used. RT-PCR and Western blots were performed to detect amine metabolizing enzymes. The Amplex® Red Assay was used to quantify oxidase activity by detecting the oxidase reaction product H₂O₂ and the contribution of PVAT on the mesenteric arteries' contraction to NE was measured by myography. Results: Semicarbazide sensitive amine oxidase (SSAO) and monoamine oxidase A (MAO-A) were detected in MRV and MPVAT by Western blot. Addition of the amine oxidase substrates tyramine or benzylamine (1 mM) resulted in higher amine oxidase activity in the MRV, MPVAT, MPVAT's adipocyte fraction (AF), and the stromal vascular fraction (SVF). Inhibiting SSAO with semicarbazide (1 mM) decreased amine oxidase activity in the MPVAT and AF. Benzylamine-driven, but not tyramine-driven, oxidase activity in the MRV was reduced by semicarbazide. By contrast, no reduction in oxidase activity in all sample types was observed with use of the monoamine oxidase inhibitors clorgyline (1 ?M) or pargyline (1 ?M). Inhibition of MAO-A/B or SSAO individually did not alter contraction to NE. However, inhibition of both MAO and SSAO increased the potency of NE at mesenteric arteries with PVAT. Addition of MAO and SSAO inhibitors along with the H₂O₂ scavenger catalase reduced PVAT's anti-contractile effect to NE. Inhibition of the norepinephrine transporter (NET) with nisoxetine also reduced PVAT's anti-contractile effect to NE. Conclusions: PVAT's uptake and metabolism of NE may contribute to the anti-contractile effect of PVAT. MPVAT and adipocytes within MPVAT are a source of SSAO.

SUBMITTER: Ayala-Lopez N

PROVIDER: S-EPMC5296360 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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Perivascular Adipose Tissue's Impact on Norepinephrine-Induced Contraction of Mesenteric Resistance Arteries.

Ayala-Lopez Nadia N Thompson Janice M JM Watts Stephanie W SW

Frontiers in physiology 20170208

<b>Background:</b> Perivascular adipose tissue (PVAT) can decrease vascular contraction to NE. We tested the hypothesis that metabolism and/or uptake of vasoactive amines by mesenteric PVAT (MPVAT) could affect NE-induced contraction of the mesenteric resistance arteries. <b>Methods:</b> Mesenteric resistance vessels (MRV) and MPVAT from male Sprague-Dawley rats were used. RT-PCR and Western blots were performed to detect amine metabolizing enzymes. The Amplex® Red Assay was used to quantify oxi ...[more]

PMID: 28228728

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Project description:Evidence suggests that ethanol-induced hypertension is associated with increased cardiovascular responsiveness to vasopressors in vivo and enhanced reactivity of isolated arteries to vasopressors ex vivo. The underlying mechanisms are not well understood and the contribution of ethanol metabolites to vascular effects induced by ethanol consumption are unclear. Mesenteric resistance arteries were harvested from Sprague-Dawley rats. Pressure myography was utilized to test effects of ethanol, acetaldehyde and phosphatidylethanol on myogenic tone and on vasoconstriction induced by phenylephrine, arginine vasopressin (aVP), endothelin-1 and KCl. Ethanol, acetaldehyde and phosphatidylethanol concentrations were monitored during the experiments. Ethanol concentrations in the vessel bath decreased with a half-life of 25min; acetaldehyde and phosphatidylethanol concentrations remained constant. Pretreatment with ethanol dose-dependently increased the potency of phenylephrine to induce vasoconstriction 4-fold (p<0.01). These effects were comparable when arteries were pre-treated with a single dose of ethanol for 30min and when ethanol concentrations were kept constant during 30min and 60min of pretreatment. While ethanol also dose-dependently increased the potency of aVP to induce vasoconstriction 1.7-fold (p<0.05), it did not affect vasoconstriction induced by endothelin-1 or KCl. Acetaldehyde pre-treatment (30 min) dose-dependently increased the potency of phenylephrine to induce vasoconstriction 2.7-fold (p<0.01) but did not affect other vasoconstrictor responses. Phosphatidylethanol did not affect any vasoconstrictor responses. Ethanol and its metabolites did not affect myogenic tone. These data suggest that ethanol and acetaldehyde selectively sensitize intrinsic constrictor responses upon activation of vascular α1-adrenergic and/or vasopressin receptors at clinically relevant concentrations. Our findings support the concept that enhanced vasoreactivity to vasoactive hormones contributes to the development of hypertension induced by ethanol consumption. Ex vivo exposure of resistance arteries to ethanol and acetaldehyde resembles effects of chronic ethanol consumption on intrinsic vascular function, and thus could serve as test platform to evaluate interventions aimed to mitigate vascular effects associated with ethanol consumption.

Project description:Objective- Perivascular adipose tissue (PVAT) contains an independent adrenergic system that can take up, metabolize, release, and potentially synthesize the vasoactive catecholamine norepinephrine. Norepinephrine has been detected in PVAT, but the mechanism of its protection within this tissue is unknown. Here, we investigate whether PVAT adipocytes can store norepinephrine using VMAT (vesicular monoamine transporter). Approach and Results- High-performance liquid chromatography identified norepinephrine in normal male Sprague Dawley rat aortic, superior mesenteric artery, and mesenteric resistance vessel PVATs, and retroperitoneal fat. Real-time polymerase chain reaction revealed VMAT1 and VMAT2 mRNA expression in the adipocytes and stromal vascular fraction of mesenteric resistance vessel PVAT. Immunofluorescence demonstrated the presence of VMAT1 and VMAT2, and the colocalization of VMAT2 with norepinephrine, in the cytoplasm of adipocytes in mesenteric resistance vessel PVAT. A protocol was developed to capture real-time uptake of Mini 202-a functional and fluorescent VMAT probe-in live rat PVAT adipocytes. Mini 202 was taken up by freshly isolated and differentiated adipocytes from mesenteric resistance vessel PVAT and adipocytes from thoracic aortic and superior mesenteric artery PVATs. In adipocytes freshly isolated from mesenteric resistance vessel PVAT, addition of rose bengal (VMAT inhibitor), nisoxetine (norepinephrine transporter inhibitor), or corticosterone (organic cation 3 transporter inhibitor) significantly reduced Mini 202 signal. Immunofluorescence supports that neither VMAT1 nor VMAT2 is present in retroperitoneal adipocytes, suggesting that PVAT adipocytes may be unique in storing norepinephrine. Conclusions- This study supports a novel function of PVAT adipocytes in storing amines in a VMAT-dependent manner. It provides a foundation for future studies exploring the purpose and mechanisms of norepinephrine storage by PVAT in normal physiology and obesity-related hypertension.

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Perivascular Adipose Tissue's Impact on Norepinephrine-Induced Contraction of Mesenteric Resistance Arteries.

Publications

Perivascular Adipose Tissue's Impact on Norepinephrine-Induced Contraction of Mesenteric Resistance Arteries.

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