Microvascular display of xanthine oxidase and NADPH oxidase in the spontaneously hypertensive rat

OBJECTIVE: Oxygen free radical production in hypertension may be associated with elevated arteriolar tone and organ injury. Previous results suggest an enhanced level of oxygen free radical formation in microvascular endothelium and in circulating neutrophils associated with xanthine oxidase activity in the spontaneously hypertensive rats (SHR) compared with their normotensive controls, the Wistar Kyoto rats (WKY). The aim of this study was to gain more detailed understanding of where oxidative enzymes are located in the microcirculation. METHODS: An approach was developed to delineate the cellular distribution of two selected oxidative enzymes, xanthine oxidase and nicotinamide adenine dinucleotide phosphate (NADPH) dependent oxidase (protein 67-kDa fraction). Immunolabeling with peroxidase substrate was utilized, which permits full delineation of the primary antibody in all microvascular structures of the mesentery. RESULTS: Xanthine oxidase is present in the endothelium of all segments of the microcirculation, in mast cells, and in parenchymal cells of the mesentery. NADPH oxidase can be detected in the endothelium, leukocytes, and mast cells and with lower levels in parenchymal cells. The mesentery of WKY and SHR has similar enzyme distributions with enhancements on the arteriolar and venular side of the microcirculation that coincide with the sites of enhanced free radical production recently reported. Immune label measurements under standardized conditions indicate that both enzymes are significantly enhanced in the SHR. Adrenalectomy, which serves to reduce the blood pressure and free radical production of the SHR to normotensive levels, leads to a reduction of NADPH and xanthine oxidase to normotensive levels, while supplementation of adrenalectomized SHR with dexamethasone significantly increases the oxidase expression in several parts of the microcirculation to levels above the WKY rats. CONCLUSION: The results indicate that enhanced expression of NADPH and xanthine oxidase in the SHR depends on an adrenal pathway that is detectable in the arteriolar and venular network at high and low pressure regions of the circulation.     

Integrins and regulation of the microcirculation: from arterioles to molecular studies using atomic force microscopy

Integrins are an important class of receptors for extracellular matrix proteins that can mediate both force transmission, by virtue of their connections with the cell matrix and cytoskeleton; and signal transduction, resulting from the assemblages of signaling proteins that associate with focal contacts. Consequently, integrins have been proposed to be the mechanosensor in vascular smooth muscle and endothelial cells and to play a central role in mechanotransduction. In this regard, mechanical force is an important stimulus for many vascular functions, including contractile and relaxation processes,proliferation, migration, attachment, and cell phenotype determination. Collectively, these functions define physiological properties of the vasculature such as control of blood flow, capillary pressure,permeability, and peripheral vascular resistance, and play a role in pathophysiological processes like hypertension, diabetes, and arteriosclerosis. Our knowledge concerning how integrins sense and transduce physical forces into cellular signals and which integrins are involved is incomplete. Compared to other cell surface receptors, integrins have a relatively low affinity for their binding sites on the extracellular matrix and their affinity can be regulated. These characteristics of integrin-ligand interaction may facilitate dynamic processes such as cell migration, cell remodeling, and contractile activation in response to external forces. Important questions remain concerning the nature and origin of integrin-mediated signaling in the vascular wall.     

In vivo properties of potassium channels in cerebral blood vessels during diabetes mellitus

OBJECTIVE: While potassium (K+) channels are important in basal tone and dilatation of large and small cerebral vessels, the effect of diabetes mellitus on K+ channels remains unclear. The goal of this study was to identify the influence of diabetes on responses of cerebral vessels to inhibition/activation of K+ channels. METHODS: The authors measured in vivo responses of pial arterioles and the basilar artery to inhibition/activation of K+ channels in nondiabetic and diabetic rats using intravital microscopy. RESULTS: Pial arterioles from nondiabetic and diabetic rats constricted to barium chloride (BaCl2) and 4-aminopyridine (4-AP). However, the magnitude of vasoconstriction to BaCl2 was greater in nondiabetic than in diabetic rats. Tetraethylammonium (TEA) did not alter diameter of pial arterioles in nondiabetic or diabetic rats. In addition, dilatation of pial arterioles to KCl and NS-1619 was less in diabetic compared to nondiabetic rats. The basilar artery from nondiabetic and diabetic rats constricted in a similar manner to BaCl2 and 4-AP. In contrast, vasoconstriction to TEA was greater in diabetic than nondiabetic rats. Similar to that reported for pial arterioles, dilatation of the basilar artery to KCl and NS-1619 was less in diabetic than nondiabetic rats. CONCLUSIONS: Inward-rectifier (Kir) and voltage-dependent (Kv), but not calcium-activated (Kca), K+ channels are active under basal conditions in pial arterioles, while Kir, Kv, and Kca are active under basal conditions in the basilar artery of nondiabetic and diabetic rats. In addition, activation of Kir and Kca channels produces less cerebral vasodilatation in diabetic compared to nondiabetic rats. These findings provide new and important information regarding the influence of diabetes on the role of K+ channels in the regulation of cerebral vascular diameter.     

Increased expression of endothelial cell nitric oxide synthase (ecNOS) in afferent and glomerular endothelial cells is involved in glomerular hyperfiltration of diabetic nephropathy

Summary The overproduction of nitric oxide (NO) is reported in the diabetic kidney and considered to be involved in glomerular hyperfiltration. The precise mechanism of NO production in the diabetic kidney is, however, not known. In this report, we compare the localization of endothelial cell nitric oxide synthase (ecNOS) isoform expression in the kidney tissue of streptozotocin (STZ)-induced diabetic rats and 5/6 nephrectomized rats and clarify the pivotal role of ecNOS for the glomerular hyperfiltration in the early stages of diabetic nephropathy. In diabetic rats, the diameters of afferent arterioles, the glomerular volume, creatinine clearance, and urinary NO₂/NO₃ were increased after the induction of diabetes. Efferent arterioles were, however, not altered. Insulin or L-NAME treatment returned the diameters of afferent arterioles, glomerular volume, creatinine clearance, and urinary NO₂/NO₃ to normal. The expression of ecNOS in afferent arterioles and glomeruli of diabetic rats increased during the early stages of the disease, but was not altered in efferent arterioles. Treatment with either insulin or L-NAME decreased ecNOS expression in afferent arterioles and in glomeruli. In contrast, the ecNOS expression was upregulated in both afferent and efferent arterioles and in the glomeruli of 5/6 nephrectomized rats, where the dilatation of afferent and efferent arterioles and glomerular enlargement were observed. Treatment with L-NAME ameliorated the ecNOS expression and dilatation of arterioles. We conclude that enhanced NO synthesis by ecNOS in afferent arterioles and glomerular endothelial cells in response to the hyperglycaemic state could cause preferential dilatation of afferent arterioles, which ultimately induces glomerular enlargement and glomerular hyperfiltration. [Diabetologia (1998) 41: 1426–1434] Received: 5 January 1998 and in revised form: 27 April 1998     

Low intravascular pressure activates endothelial cell TRPV4 channels,local Ca2+ events,and IKCa channels,reducing arteriolar tone

Endothelial cell (EC) Ca²⁺-activated K channels (SK_Ca and IK_Ca channels) generate hyperpolarization that passes to the adjacent smooth muscle cells causing vasodilation. IK_Ca channels focused within EC projections toward the smooth muscle cells are activated by spontaneous Ca²⁺ events (Ca²⁺ puffs/pulsars). We now show that transient receptor potential, vanilloid 4 channels (TRPV4 channels) also cluster within this microdomain and are selectively activated at low intravascular pressure. In arterioles pressurized to 80 mmHg, ECs generated low-frequency (∼2 min⁻¹) inositol 1,4,5-trisphosphate receptor-based Ca²⁺ events. Decreasing intraluminal pressure below 50 mmHg increased the frequency of EC Ca²⁺ events twofold to threefold, an effect blocked with the TRPV4 antagonist RN1734. These discrete events represent both TRPV4-sparklet- and nonsparklet-evoked Ca²⁺ increases, which on occasion led to intracellular Ca²⁺ waves. The concurrent vasodilation associated with increases in Ca²⁺ event frequency was inhibited, and basal myogenic tone was increased, by either RN1734 or TRAM-34 (IK_Ca channel blocker), but not by apamin (SK_Ca channel blocker). These data show that intraluminal pressure influences an endothelial microdomain inversely to alter Ca²⁺ event frequency; at low pressures the consequence is activation of EC IK_Ca channels and vasodilation, reducing the myogenic tone that underpins tissue blood-flow autoregulation.     

Vascular protective effects of ACE inhibitors and calcium antagonists: Theoretical basis for a combination therapy in hypertension and other cardiovasular diseases

Hypertension is an important cardiovascular risk factor. High blood pressure per se is not a disease but a hemodynamic alteration associated with vascular disease. Two classes of drugs are especially effective in lowering blood pressure and preventing cardiovascular complications, angiotensin converting enzyme (ACE) inhibitors and calcium antagonists. The hemdynamic effects of ACE inhibitors and calcium antagonists are complementary. While ACE inhibitors inhibit the renin-angiotensin system and reduce sympathetic outflow, calcium antagonists dilate large conduit and resistance arteries. Certain calcium antagonists, such as verapamil, lower heart rate. In the blood vessel wall, the local vascular effects of ACE inhibitors and calcium antagonists are also complementary. While ACE inhibitors inhibit activation of angiotensin I into angiotensin II and prevent the breakdown of bradykinin (which stimulates nitric oxide and prostacyclin formation), calcium antagonists inhibit the effects of vasoconstrictor hormones such as angiotensin II at the level of vascular smooth muscle by reducing calcium inflow and facilitating the vasodilator effects of nitric oxide. Calcium antagonists reduce smooth muscle cell proliferation and atherosclerosis. In hypertensive animals, verapamil and trandolapril normalize endothelial dysfunction. In large angiographic trials, nifedipine and nicardipine reduced the development of new atherosclerotic plaques. After myocardial infarction, verapamil reduces mortality and cardiac events in patients without heart failure. In contrast, ACE inhibitors are effective after myocardial infarction in patients with impaired left ventricular function. Urinary albumin excretion rate decreases during ACE inhibitor therapy or with a calcium antagonist such as verapamil; combination of the two drugs has an additive effect. In resistance arteries, hypertension is associated with an increased media/lumen ratio. ACE inhibitors, but not beta-blockers, markedly improve these structural changes. In summary, ACE inhibitors and calcium antagonists have a complementary profile, both in their hemodynamic and local vascular action. Hence, combination therapy with these two classes of drugs appears particularly useful in patients with hypertension, not only to lower blood pressure, but hopefully to achieve improved cardiovascular protection.     

IgA肾病患者肾小动脉病变与临床及病理特点的相关性

目的探讨IgA肾病患者肾小动脉病变与临床、病理的相关性。方法 60例IgA肾病患者,根据肾小动脉病变程度分为未见明显病理改变组(A组,25例)、肾小动脉增厚组(B组,31例)和肾小动脉增厚伴透明样变组(C组,4例),分析三组肾小动脉病变程度与其临床指标及病理学参数的相关性。结果三组肾小动脉病变程度与血肌酐水平(P<0.01)、血尿酸(P<0.05)、收缩压(P<0.05)、舒张压(P<0.05)呈明显正相关。三组肾小动脉病变程度与内皮细胞增生指数(P<0.01)、系膜细胞增生指数(P<0.05)、肾小球慢性化指数(P<0.01)、间质炎症指数(P<0.01)、肾小管萎缩纤维化指数(P<0.05)呈明显正相关。结论肾小动脉病变在IgA肾病中病情评估中有重要作用,可作为预测肾脏预后的指标之一。     

苏木乙酸乙酯提取物对野百合碱诱导肺动脉高压大鼠肺动脉压、血浆BNP及肺小动脉的影响

目旳 研究苏木乙酸乙酯提取物对野百合碱诱导肺动脉高压大鼠肺动脉压、血浆脑钠肽(BNP)及肺小动脉的影响.方法 采用完全随机化的分组方法将50只健康雄性SD大鼠随机分为空白组、模型组、苏木乙酸乙酯高剂量组、苏木乙酸乙酯低剂量组、阿魏酸钠组,每组10只.除空白组外,其余组大鼠采用腹腔注射野百合碱方法制备肺动脉高压模型.实验...     

活血化痰通络方早期治疗风痰瘀阻证急性小动脉闭塞型脑梗死的临床研究

目的 观察活血化痰通络方早期治疗风痰瘀阻证急性小动脉闭塞型脑梗死的临床疗效.方法 将2018年8月1日—2019年9月30日在湖北省中西医结合医院神经内科住院的240例风痰瘀阻证急性小动脉闭塞型脑梗死患者随机分成治疗组和对照组,每组120例.对照组给予常规西药治疗,治疗组在西药治疗基础上给予活血化痰通络方治疗2周.观察...     

A Role for Dietary Copper in Nitric Oxide-Mediated Vasodilation

Objective : This study was designed to investigate the role of dietary copper in nitric oxide-mediated arteriolar dilation. Methods : Male weanling Sprague—Dawley rats were fed a purified diet that was either copper-adequate (6.0 μg Cu per g diet) or copper-deficient (0.3 μg Cu per g diet) for a period of 4 weeks. Each rat was anesthetized with pentobarbital and its cremaster muscle was positioned in a Krebs'-fdled bath to which graded concentrations of vasoactive agents were added. In the first series, responses to norepineph-rine (NE 10^?9-10^?6 M) and acetylcholine (ACH 10^?7-10^?4 M) were compared in third-order arterioles. Second, the dilator response to 10^?5 M ACH in the absence and presence of 240 U/ml Cu, Zn-superoxide dismutase (SOD) was determined. Third, arteriolar dilation was determined in response to NO-independent stimulation of soluble guanylate cyclase with hydrogen peroxide (10^?7-10^?5 M) and to dibutyryl cGMP (10^?6-10^?4 M), dibutyryl cAMP (10^?6-10^?4 M), and papaverine (10^?4M). Results : The arteriole constrictor response to NE and the dilator response to hydrogen peroxide, dibutyryl cGMP and cAMP, and papaverine were not different between the dietary groups. Copper deficiency attenuated the ACH-induced dilation, but the response was restored in the presence of SOD. Conclusions : The inactivation of cytosolic Cu, Zn-SOD by restriction of dietary copper results in the depression of NO-mediated vascular smooth-muscle relaxation probably by interaction of NO with superoxide.