Essential Hypertension and Human Skin Blood Flow

描述（由申请人提供）：人体皮肤循环是一个可接近的，具有代表性的血管床，用于体内检查导致原发性高血压（HT）血管功能障碍的机制。这一建议是我们之前研究年龄和高血压相关变化在控制反射介导的皮肤血流量增加中的血管机制的合理延伸。我们提出的研究扩展了我们之前的研究，将最先进的一氧化氮（NO）特异性体内方法（局部加热和皮内微透析）与人类皮肤样本的体外分析相结合，以检查HT患者皮肤血管舒张（VD）信号受损的精确信号机制。与高温疗法相关的血管功能障碍是多方面的，但包括由一氧化氮合成酶（内皮和神经元一氧化氮合成酶）表达和活性受损以及氧化应激增加引起的一氧化氮生物利用度的整体降低。尽管高血压患者皮肤NO依赖性VD明显减弱，但产生NO的NOS异构体合成NO的改变尚不清楚。增强的诱导型NOS和减弱的构成型NOS同工酶与HT相关的炎症和肾上腺素能神经血管状态有关。假设ht诱导的减少血管中nos合成NO的机制包括(1)炎症诱导的iNOS合成NO的增加，通过s -亚硝基化改变精氨酸酶动力学（降低Km）；(2)血液动力学诱导的精氨酸酶的上调——如果精氨酸酶的底物l -精氨酸（L-arg）被精氨酸酶优先代谢，这两种情况都有助于限制通过组成性NOS合成NO——(3)由于L-arg和/或必需的辅助因子（四氢生物蝶呤（BH4））可用性不足，通过不偶联的NOS增加氧化剂的产生。精氨酸酶的上调也通过l -鸟氨酸介导的多胺和脯氨酸合成的增加与高血压诱导的血管壁重塑的发病机制有关。因此，炎症、精氨酸酶上调、NOS解偶联和有害的血管壁重塑与HT有一定的联系。这项拟议的研究将结合体内和体外方法来检验HT患者皮肤血管中炎症、氧化应激和NO产生之间的假定联系。特异性目标1将研究NOS亚型介导皮肤NO依赖性减弱，特异性目标2将研究精氨酸酶在通过组成性NOS调节l -精氨酸合成NO的可用性中的作用，特异性目标3将研究氧化应激和辅酶BH4可用性的作用，因为它们与NOS解耦有关。我们还将通过测量实时相对氧化剂的产生来研究精氨酸酶上调与BH4缺乏在NOS解偶联中的机制联系。公众相关性：美国四分之一的人口未确诊或正在接受原发性高血压治疗。这种健康问题普遍存在，并造成情感、身体和经济上的损失。这些研究的结果将为高血压对皮肤血管的影响提供新的重要信息。此外，这些结果将为高血压血管病理的皮肤血流调节和潜在的治疗干预策略提供见解。

DESCRIPTION (provided by applicant): The human cutaneous circulation is an accessible, representative vascular bed for in vivo examination of mechanisms that contribute to vascular dysfunction with essential hypertension (HT). This proposal is a logical extension of our previous work investigating the vascular mechanisms underlying age and hypertensive-related changes in the control of reflex-mediated increases in skin blood flow. The proposed studies expand our previous research by pairing state-of-the-art nitric oxide (NO) specific in vivo methodologies (local heating and intradermal microdialysis) with in vitro analysis of human skin samples to examine the precise signaling mechanisms underlying impaired cutaneous vasodilatory (VD) signaling in humans with HT. Vascular dysfunction associated with HT is multifaceted but involves global decreases in NO bioavailability induced by impairments in constitutive NO-synthases (endothelial and neuronal NOS) expression and activity as well as increased oxidant stress. Although, cutaneous NO-dependent VD is clearly attenuated in hypertensive humans alterations in NO synthesis from the NOS isoforms producing NO are unresolved. Augmented inducible NOS and attenuated constitutive NOS isozymes are implicated in the inflammatory and hyperadrenergic neurovascular state associated with HT. Putative HT-induced mechanisms decreasing NO synthesis from the constitutive NOSs in the vasculature include (1) an inflammatory-induced increase in iNOS- synthesized NO which changes arginase enzyme kinetics (decreased Km) through S-nitrosylation, (2) a hemodynamic-induced upregulation of arginase-- both of which serve to limit NO synthesis through constitutive NOSs due to preferential metabolism if the NOS substrate L-arginine (L-arg) by arginase-- and (3) an increase in oxidant production through uncoupled NOS due to inadequate L-arg and/or essential cofactor (tetrahydriobiopterin (BH4)) availability. Upregulated arginase is also linked to the pathogenesis of hypertension-induced vessel wall remodeling through increased L-ornithine-mediated polyamine and proline synthesis. Thus, there is a mechanism linking inflammation, upregulated arginase, NOS uncoupling and deleterious vessel wall remodeling with HT. The proposed investigation will pair in vivo and in vitro methodologies to examine the putative link between inflammation, oxidant stress, and NO production in the cutaneous vasculature of humans with HT. Specific Aim 1 will examine the NOS isoforms mediating attenuated cutaneous NO-dependent, Specific Aim 2 will examine the role of arginase in regulating L-arginine availability for NO synthesis through the constitutive NOSs, and Specific Aim 3 will examine roles of oxidative stress and cofactor BH4 availability as they relate to NOS uncoupling. We will also examine the mechanistic link between upregulated arginase and BH4 deficiency on NOS uncoupling by measuring real time relative oxidant production. PUBLIC RELEVANCE: One quarter of the population in the United States has undiagnosed or is being treated for essential hypertension. This health issue is pervasive and exacts emotional, physical, and financial costs. The results from these proposed studies will provide new and important information on the vascular effects of hypertension in the skin. Further, these results will provide insight into the regulation of skin blood flow and potential therapeutic intervention strategies for hypertensive vascular pathology.