Biomedical subjects

Donna H Wang

Publications and source records attributed to Donna H Wang.

At least 19 recordsLinked to original sources

PubMed2006

Enhanced oxidative stress in kidneys of salt-sensitive hypertension: role of sensory nerves.

To determine the mechanism(s) underlying enhanced oxidative stress in kidneys of salt-sensitive hypertension, neonatal Wistar rats were given vehicle or capsaicin (CAP, 50 mg/kg sc) on the first and second days of life. After being weaned, male rats were assigned into four groups and treated for 2 wk with the following: vehicle + a normal sodium diet (NS, 0.4%, CON-NS), vehicle + a high-sodium diet (HS, 4%, CON-HS), CAP + NS (CAP-NS), and CAP + HS (CAP-HS). Systolic blood pressure was significantly increased in CAP-HS but not CAP-NS or CON-HS rats. Plasma and urinary 8-iso-prostaglandin F(2alpha) levels increased by approximately 40% in CON-HS and CAP-HS rats compared with their respective controls fed a NS diet (P < 0.05), and these parameters were higher in CAP-HS compared with CON-HS rats. Superoxide (O(2)(-)*) levels in the renal cortex and medulla increased by approximately 45% in CAP-HS compared with CON-HS, CON-NS, and CAP-NS rats (P < 0.05). Enhanced O(2)(-)* levels in the cortex and medulla in CAP-HS rats were prevented by preincubation of renal tissues with apocynin, a selective NAD(P)H oxidase inhibitor. Protein expression of NAD(P)H oxidase subunits, including p47(phox) and gp91(phox) in the renal cortex and medulla, was significantly increased in CAP-HS compared with CON-HS, CON-NS, and CAP-NS rats. In contrast, protein expression and activities of Cu/Zn SOD and Mn SOD were significantly increased in the renal medulla in both CAP-HS and CON-HS but in the cortex in CAP-HS rats only. Creatinine clearance decreased by approximately 45% in CAP-HS rats compared with CON-HS, CON-NS, and CAP-NS rats (P < 0.05). O(2)(-)* levels in the renal cortex of CAP-HS rats negatively correlated with creatinine clearance (r = -0.76; P < 0.001). Therefore, regardless of enhanced SOD activity to suppress oxidative stress, increased oxidative stress in the kidney of CAP-treated rats fed a HS diet is likely the result of increased expression and activities of NAD(P)H oxidase, which may contribute to decreased renal function and increased blood pressure in these rats. Our results suggest that sensory nerves may play a compensatory role in attenuating renal oxidative stress during HS intake.

Analgesics, Non-Narcotic↗

PubMed2006

Development of hypertension and kidney hypertrophy in transgenic mice overexpressing ARAP1 gene in the kidney.

Angiotensin II regulates blood pressure via activation of the type 1 receptor. We previously identified a novel angiotensin II type 1 receptor-associated protein and demonstrated that it promotes receptor recycling to the plasma membrane. To delineate the pathophysiological function of the ARAP1 in the kidneys, we generated transgenic mice that overexpress rat ARAP1 cDNA specifically in proximal tubules and tested the hypothesis that proximal tubule-specific overexpression of ARAP1 causes hypertension. Two lines of male transgenic mice, 650 and 670, displayed kidney-specific transgene expression. Systolic blood pressure was significantly elevated by &20 to 25 mm Hg in these lines of mice at 20 weeks of age compared with their nontransgenic litter mates. Urine volume, but not water intake, was significantly decreased in both lines compared with nontransgenic controls. The kidney/body weight ratio was significantly increased in both lines compared with their nontransgenic litter mates at 12 and 20 weeks of age. In contrast, no difference was observed in the ratio of brain, spleen, heart, and testis to body weight between male transgenic and nontransgenic animals. Inhibitions of the renin-angiotensin system completely normalized the systolic blood pressure of transgenic mice. Moreover, low salt intake prevented the development of hypertension, whereas high salt intake exacerbated the increase in blood pressure in transgenic mice. Therefore, our data show that proximal tubule-specific overexpression of ARAP1 leads to hypertension, suggesting that renal ARAP1 plays an important role in the regulation of blood pressure and renal function via activation of the intrarenal renin-angiotensin system.

Adaptor Proteins, Signal Transducing↗

PubMed2006

Probing membrane proteins using atomic force microscopy.

To gain insights into how biological molecules function, advanced technologies enabling imaging, sensing, and actuating single molecules are required. The atomic force microscope (AFM) would be one of novel potential tools for these tasks. In this study, techniques and efforts using AFM to probe biomolecules are introduced and reviewed. The state-of-art techniques for characterizing specific single receptor using the functionalized AFM tip are discussed. An example of studying the angiotensin II type 1 (AT1) receptors expressed in sensory neuronal cells by AFM with a functionalized tip is given. Perspectives for identifying and characterizing specific individual membrane proteins using AFM in living cells are provided. Given that many diseases have their roots at the molecular scale and are best understood as a malfunctioning biological nanomachines, the prospects of these unique techniques in basic biomedical research or in clinical practice are beyond our imagination.

Animals↗

PubMed2006

Differential mechanisms mediating depressor and diuretic effects of anandamide.

BACKGROUND: Anandamide (AEA), one of the endocannabinoid compounds, has an important regulatory function by serving as an autocrine/paracrine or endocrine factor throughout the body via activation of the cannabinoid receptor 1 (CB1) and/or the transient receptor potential vanilloid type 1 (TRPV1) channels. However, the role of AEA in the regulation of renal excretory function is largely unknown. The present study was designed to test the hypothesis that intrarenal administration of AEA enhances renal excretory function leading to a decrease in blood pressure. METHODS: A metabolically stable analog of AEA, methanandamide (MethA, 300 nmol/kg per min), was infused into the left renal medulla of anesthetized Wistar rats with or without a selective TRPV1 antagonist, capsazepine (Capz, 150 nmol/kg per min) or a selective cannabinoid receptor 1 (CB1) antagonist, AM251 (Am, 150 nmol/kg per min). Ureters were cannulated for collection of urine. A laser-Doppler flowmeter was used to determine the changes of blood flow in the cortex and medulla of the infused kidney. RESULTS: In the absence of the changes in cortical and medullary blood flow, unilateral intramedullary infusion of MethA significantly increased urine flow rate by 64% ipsilaterally and 62% contralaterally without changing sodium excretion when compared to vehicle controls (P < 0.01). Neither Capz nor Am blocked the MethA-induced increases in urine flow rate bilaterally. Intramedullary infusion of MethA significantly decreased mean arterial pressure (MAP) (P < 0.01), which was blocked by Am but not Capz. Denervation of the infused kidney blocked the MethA-induced increases in urine flow rate bilaterally without altering MethA-induced decreases in MAP. CONCLUSIONS: Therefore, our data show that intramedullary infusion of AEA increases urine volume excretion and decreases blood pressure via distinct operational mechanisms. While activation of the CB1 receptor may underlie AEA-induced depressor effects, the diuretic effect of AEA appears to be mediated by neuronal reflex of the kidney, which is not sensitive to blockade of the TRPV1 or CB1 receptor.

Animals↗

PubMed2006

Impaired vasodilation in response to perivascular nerve stimulation in mesenteric arteries of TRPV1-null mutant mice.

BACKGROUND: The role of the transient receptor potential vanilloid type 1 (TRPV1) channels expressed in perivascular sensory nerves in the regulation of vascular reactivity is largely unknown. This study was designed to test the hypothesis that vasodilation induced by electrical field stimulation (EFS) of perivascular sensory nerves is mediated by the TRPV1 via release of sensory neurotransmitters in wild-type (WT) mice, and this effect is abolished in gene-targeted TRPV1-null mutant (TRPV1(-/-)) mice. METHODS: Isolated mesenteric resistance arteries from WT and TRPV1(-/-)) mice were perfused and pretreated with guanethedine and atropine to block sympathetic and parasympathetic nerve activity, respectively. After precontracting with phenylephrine, changes of vascular diameters induced by EFS were monitored in the absence or presence of the TRPV1 receptor antagonist capsazepine; the calcitonin gene-related peptide (CGRP) receptor antagonist, CGRP8-37; or the substance P (SP) receptor antagonist, RP67580. RESULTS: EFS-induced vasodilation was significantly reduced in arteries in TRPV1(-/-)) mice when compared to that of WT mice. Capsazepine and CGRP8-37 attenuated vasodilation induced by EFS in WT but not TRPV1(-/-)) mice. In contrast, RP67580 had no effect on the EFS-induced vasodilation in WT or TRPV1(-/-)) mice. The release of CGRP in the face of EFS challenge was significantly increased in both WT and TRPV1(-/-)) arteries, which was attenuated by capsazepine in WT but not TRPV1(-/-)) arteries. Exogenous CGRP caused dose-dependent vasodilation to a similar degree in WT and TRPV1(-/-)) arteries. CONCLUSIONS: Our data show that in WT mice transmural stimulation of perivascular sensory nerves activates the TRPV1, leading to CGRP release from sensory nerve endings; and blockade of CGRP, but not SP, receptors abolishes TRPV1-mediated vasodilation during EFS. All these effects are impaired in TRPV1(-/-)) mice, indicating that TRPV1 plays a key role in modulating perivascular sensory nerve-mediated vasodilation.

Animals↗

PubMed2005

A novel mechanism contributing to development of Dahl salt-sensitive hypertension: role of the transient receptor potential vanilloid type 1.

To determine the role of the transient receptor potential vanilloid type 1 (TRPV1) channels in development of hypertension in Dahl salt-sensitive (DS) rats fed a high-salt diet (HS), male DS and Dahl salt-resistant (DR) rats were maintained on a low-salt diet (LS) or HS for 3 weeks. HS significantly increased systolic blood pressure in DS+HS rats compared with DS+LS, DR+HS, and DR+LS rats. Intravenous bolus injection of capsazepine (3 mg/kg), a selective TRPV1 antagonist, significantly increased mean arterial pressure in conscious DR+HS rats compared with DR+LS, DS+/-HS, and DS+/-LS rats. In contrast, capsaicin (10 or 30 microg/kg), a selective TRPV1 agonist, dose-dependently decreased mean arterial pressure in all of the groups with the most profound magnitude in DR+HS rats compared with the other 3 groups. TRPV1 expression in mesenteric resistance arteries and the renal cortex and medulla, calcitonin gene-related peptide levels in dorsal root ganglia, and calcitonin gene-related peptide-positive sensory nerve density in mesenteric resistance arteries were significantly decreased in DS+HS rats compared with DS+LS, DR+HS, and DR+LS rats. Taken together, our data indicate that the TRPV1 receptor is activated and its expression upregulated during HS intake in DR rats, which acts to prevent salt-induced increases in blood pressure. In contrast, TRPV1 expression and function are impaired in DS rats, which renders DS rats sensitive to salt load in terms of blood pressure regulation.

Animals↗

PubMed2005

TRPV1 gene knockout impairs postischemic recovery in isolated perfused heart in mice.

BACKGROUND: Although pharmacological studies suggest that the transient receptor potential vanilloid type 1 (TRPV1) channels expressed in sensory nerve fibers innervating the heart may exert a cardioprotective effect, definitive evidence supporting such a notion is lacking. In addition, function and regulation of sensory neuropeptides, namely, calcitonin gene-related peptide (CGRP) and substance P (SP), in the face of challenges induced by cardiac injury in the presence or absence of the TRPV1 are largely unknown. METHODS AND RESULTS: The hearts of gene-targeted TRPV1-null mutant (TRPV1(-/-)) mice or wild-type (WT) mice were perfused in a Langendorff apparatus in the presence or absence of capsazepine (a TRPV1 receptor antagonist), CGRP, CGRP(8-37) (a CGRP receptor antagonist), SP, or RP67580 (a neurokinin-1 [NK1] receptor antagonist) when hearts were subjected to 40 minutes of ischemia and 30 minutes of reperfusion. Hemodynamic alterations and SP release measured by radioimmunoassay were assessed before and after ischemia/reperfusion injury of the heart. Expression of the NK1 receptor in the hearts of TRPV1(-/-) and WT mice were determined with the use of Western blot analyses. Impairment of postischemic recovery, defined by increased left ventricular end-diastolic pressure (LVEDP) and decreased left ventricular developed pressure (LVDP) and coronary flow (CF), was more severe in TRPV1(-/-) hearts than in WT hearts. Although it had no effect on postischemic recovery of TRPV1(-/-) hearts, blockade of the TRPV1 with capsazepine caused a most severe impairment of postischemic recovery in WT hearts compared with untreated WT and TRPV1(-/-) hearts. Exogenous CGRP and SP produced a significant improvement in postischemic recovery in both TRPV1(-/-) and WT hearts, and the maximal functional improvement in TRPV1(-/-) hearts was not different from that of WT hearts except that SP-induced increases in LVDP were larger in the former than in the latter. Blockade of the NK1 receptor with RP67580, but not blockade of the CGRP receptor with CGRP(8-37), caused more severe impairment in postischemic recovery in both TRPV1(-/-) and WT hearts than in untreated hearts in both genotypes. The release of SP after ischemia/reperfusion injury was increased in both WT and TRPV1(-/-) hearts, albeit with a smaller magnitude of the increase in the latter. Capsazepine attenuated injury-induced SP release in WT but not TRPV1(-/-) hearts. There was no difference in the expression of the NK1 receptor between the 2 genotype hearts. CONCLUSIONS: Thus, our data show that (1) TRPV1 gene deletion decreases injury-induced SP release and impairs cardiac recovery function after ischemia/reperfusion injury; (2) TRPV1 gene deletion leads to reconditioning of the heart with improved postischemic recovery compared with that induced by acute TRPV1 blockade and in terms of cardiac response to exogenous SP; and (3) blockade of the NK1 but not CGRP receptors worsens postischemic recovery of hearts in both genotypes. Taken together, these data indicate that TRPV1 plays a role in protecting the heart from injury possibly via increasing SP release and that deletion of this receptor reconditions the heart for escaping, at least in part, from injury possibly via enhancing NK1 receptor function.

Animals↗

PubMed2005

VR1-mediated depressor effects during high-salt intake: role of anandamide.

This study was designed to test the hypothesis that increased sensitivity of blood pressure to anandamide (AEA), an endocannabinoid compound, occurs during high-salt intake, which can be blocked by a selective vanilloid receptor 1(VR1) antagonist, capsazepine (CAPZ). Intravenous administration of a metabolically stable analog, methanandamide (MethA), dose-dependently decreased mean arterial pressure (MAP) in conscious rats fed a high-sodium diet (HS) for 3 weeks but it had a minimal effect in normal sodium (NS)-treated rats. The MethA-induced decrease in MAP was significantly attenuated but not abolished by CAPZ, or a selective cannabinoid receptor 1 (CB1) antagonist, SR141716A, administered separately in HS-treated rats. The MethA-induced depressor effect was prevented by the combined administration of CAPZ and SR141716A in HS-treated rats. Likewise, administration of capsaicin, a selective VR1 receptor agonist, dose-dependently decreased MAP in both HS- and NS-treated rats. The depressor effect of capsaicin was more profound in HS-treated rats, which was prevented by CAPZ. Western blot showed that expression of VR1 but not CB1 in mesenteric arteries was increased in HS-treated compared with NS-treated rats. Therefore, these data show that: (1) HS upregulates mesenteric VR1 expression; (2) HS increases sensitivity of blood pressure to AEA; and (3) HS-induced enhancement of the depressor effect of AEA can be prevented only when both VR1 and CB1 receptors are blocked. These results indicate that AEA contributes to the prevention of salt induced increases in blood pressure via, at least in part, activating the VR1 receptor.

Animals↗

PubMed2005

Regulation of TRPV1 by a novel renally expressed rat TRPV1 splice variant.

The capsaicin receptor and transient receptor potential channel TRPV1 senses heat, protons, and vanilloid agonists in peripheral sensory ganglia. Abundant data have suggested the presence of potentially novel splice variants in the kidney. We report a novel rat TRPV1 splice variant, TRPV1(VAR), cloned from kidney papilla. TRPV1(VAR) cDNA was identified in multiple kidney tissues. Its sequence was fully compatible with potential splice donor and acceptor sites in the rat TRPV1 gene. TRPV1(VAR) is predicted to encode a truncated form of TRPV1 consisting of the NH2-terminal 248 residues of TRPV1 (all within the NH2-terminal intracellular domain) followed by five nonconsensus amino acids (Arg-Glu-Ala-Met-Trp) and a stop codon. The variant utilizes the same consensus Kozak sequence as canonical TRPV1. A band of the appropriate molecular mass was identified in rat kidney papillary (but not medullary) lysates immunoblotted with an antibody directed against the NH2 terminus of TRPV1, whereas an antibody recognizing the TRPV1 COOH terminus failed to detect it. Upon heterologous expression in HEK 293 cells, TRPV1(VAR) potentiated the ability of cotransfected TRPV1 to confer calcium influx in response to resiniferatoxin. TRPV1(VAR) did not influence expression or cell surface localization of cotransfected TRPV1. TRPV1(VAR) protein product associated with the NH2 terminus of canonical TRPV1. Interestingly, when expressed in the COS-7 epithelial cell line, TRPV1(VAR) functioned in a dominant-negative acting capacity, partially blocking TRPV1-dependent resiniferatoxin responsiveness. We conclude that TRPV1(VAR) is one of perhaps several TRPV1 splice variants expressed in rat kidney and that it may serve to modulate TRPV1 responsiveness in some tissues.

Alternative Splicing↗

PubMed2005

Diuresis and natriuresis caused by activation of VR1-positive sensory nerves in renal pelvis of rats.

To test the hypothesis that activation of the vanilloid receptor 1 (VR1) expressed in sensory nerves innervating the renal pelvis leads to diuresis and natriuresis, a selective VR1 receptor agonist, capsaicin (2.4 nmol), or vehicle was perfused intravenously or into the left renal pelvis of anesthetized rats at a rate without changing renal perfusion pressure. Mean arterial pressure was not altered by capsaicin administered intravenously or into the renal pelvis. Capsaicin perfusion into the left renal pelvis but not intravenously caused significant increases in urine flow rate and urinary sodium excretion bilaterally in a dose-dependent manner, which were abolished by capsazepine, a selective VR1 receptor antagonist, given ipsilaterally to the renal pelvis or by ipsilateral renal denervation. Capsaicin given intravenously or into the left renal pelvis increased plasma calcitonin gene-related peptide levels to the same extent. Increased plasma calcitonin gene-related peptide levels induced by capsaicin (68.9+/-2.8 pg/mL) perfusion into the renal pelvis was prevented either by capsazepine (22.5+/-10.1 pg/mL) given ipsilaterally into the renal pelvis or by ipsilateral renal denervation (25.9+/-2.3 pg/mL). Taken together, our data show that unilateral activation of VR1-positive sensory nerves innervating the renal pelvis leads to bilateral diuresis and natriuresis via a mechanism that is independent of plasma calcitonin gene-related peptide levels. These data suggest that VR1-positive sensory nerves in the kidney enhance renal excretory function, a mechanism that may be critically involved in sodium and fluid homeostasis.

Animals↗

PubMed2005

ET(A) receptor blockade prevents renal dysfunction in salt-sensitive hypertension induced by sensory denervation.

To test the hypothesis that activation of the endothelin type A (ET(A)) receptor contributes to decreased renal excretory function and increased blood pressure in sensory nerve-degenerated rats fed a high-salt diet, neonatal Wistar rats were given vehicle or capsaicin (CAP, 50 mg/kg s.c.) on the first and second day of life. After being weaned, vehicle or CAP-treated rats were fed a normal (NS, 0.5%) or a high- (HS, 4%) sodium diet for 2 wk with or without ABT-627 (5 mg x kg(-1) x day(-1), a selective ET(A) receptor antagonist). Systolic blood pressure increased in CAP-treated rats fed a HS diet (CAP-HS) compared with vehicle-treated rats fed a HS diet (CON-HS, 145 +/- 7 vs. 89 +/- 5 mmHg, P < 0.05). Creatinine clearance and fractional sodium excretion (FE(Na)) decreased in CAP-HS rats compared with CON-HS rats (creatinine clearance, 0.54 +/- 0.05 vs. 0.81 +/- 0.09 ml x min(-1) x 100 g body wt(-1); FE(Na), 8.68 +/- 0.99 vs. 12.53 +/- 1.47%, respectively; P < 0.05). Water and sodium balance increased in CAP-HS rats compared with CON-HS (water balance, 20.2 +/- 1.5 vs. 15.5 +/- 1.9 ml/day; sodium balance, 11.9 +/- 3.1 vs. 2.4 +/- 0.3 meq/day, respectively; P < 0.05). The endothelin (ET)-1 levels in plasma and isolated glomeruli increased by about twofold in CAP-HS rats compared with CON-HS rats (P < 0.05). ABT-627 prevented the decrease in creatinine clearance and FE(Na), the increase in water and sodium balance, and the increase in blood pressure in CAP-HS rats (P < 0.05). Therefore, the blockade of the ET(A) receptor ameliorates the impairment of renal excretory function and prevents the elevation in blood pressure in salt-sensitive hypertension induced by degeneration of sensory nerves, indicating that the activation of the ET(A) receptor impairs renal function and contributes to the development of a salt-induced increase in blood pressure in this model.

Animals↗

PubMed2005

Statins reduce connexin40 and connexin43 expression in atherosclerotic aorta of rabbits.

BACKGROUND: Gap junction protein connexin43 (Cx43) expression was enhanced in proliferating smooth muscle cells (SMCs) in the neointima of atherosclerotic lesions. HMG-CoA Reductase Inhibitors (statins) can reduce Cx43 expression in vivo and in vitro. Connexin40 (Cx40) is also a very important connexin in SMCs of arterial wall. METHODS: We observed the expression of Cx40 and Cx43 in a rabbit model of a high-cholesterol diet and investigated the effect of lovastatin (10 mg.kg-1.d-1, 2 weeks) or fluvastatin (10 mg.kg-1.d-1, 2 weeks) on these changes by the methods of western blotting, RT-PCR, immunohistochemistry, and transmission electron microscope. RESULTS: There was abundant expression of Cx40 mRNA and protein in SMCs of rabbit aorta. Besides Cx43, Cx40 expression was also obviously upregulated in atherosclerotic plaques. Treatment with statins reduced the over-expression of Cx43 and Cx40 in atherosclerotic lesion. Cx40 and Cx43 gap junction quantity from each of the arteries obtained at the different drug treatment levels revealed no significant difference. Neointimal SMCs had abundant, large gap junctions, whereas normal SMCs had smaller, less frequent junctions. Statins also normalized the enlarged gap junctions. CONCLUSIONS: These results provide novel in vivo evidence for the key role of gap junctions in atherogenesis and the possible mechanism in antiatherogenic effect of statins.

Animals↗

PubMed2005

Regulation of connexin expression after balloon injury: possible mechanisms for antiproliferative effect of statins.

Statins, the 3-hydroxy-3-methylglutaryl-cooenzyme A (HMG-CoA) reductase inhibitors, have been shown to inhibit the migration of macrophages and smooth muscle cell proliferation leading to an antiproliferative effect. Although this beneficial effect of statins has been suggested to be independent of lipid lowering properties, the possible mechanisms responsible for this action is largely unknown. Gap junctions, which serve as channels for direct intercellular exchange of ions, secondary messengers, and small signaling molecules, play an important role in tissue homeostasis and regulation of growth, differentiation, and development. This study was designed to test the hypothesis that expression of the component proteins of gap junctions, connexins 40 and 43 (Cx40 and Cx43), is upregulated in arteries subjected to balloon injury and that this upregulation can be suppressed by statin therapy. Male New Zealand white rabbits were subjected to injury in which an angioplasty catheter was introduced into the right iliac artery from the femoral artery under fluoroscopic guidance. Five groups of rabbits (n = 6 to 7) were treated for 2 weeks with one of the following: balloon injury (BL); BL+lovastatin (BL+L, 10 mg/kg/day); BL+fluvastatin (BL+F, 10 mg/kg/day); sham operation (Sham); and control (Con). Immunohistochemistry studies showed that Cx40 and Cx43 were expressed in normal smooth muscle cells (SMC) throughout the media. Reverse transcription-polymerase chain reaction and Western blot analysis showed that Cx40 and Cx43 mRNA and protein expression was elevated after injury (P < .001 for both proteins and both assays), and these elevations were suppressed by lovastatin and fluvastatin to a similar degree (P < .05 for both drugs and both assays). Immunostaining of Cx40 and Cx43 was consistently enhanced in the neointimal area after injury and lovastatin and fluvastatin reduced staining of these proteins in the lessened neointimal layer. Transmission electron microscopy revealed that there were abundant gap junctions between neointimal SMC as well as fewer and smaller gap junctions after statin treatment. Therefore, balloon injury causes upregulation of Cx40 and Cx43 in neointimal SMC. Lovastatin and fluvastatin suppress upregulated Cx40 and Cx43 expression and reduce neointimal proliferation, suggesting that Cx40 and Cx43 may play a role in statin-induced antiproliferative effect.

Animals↗

PubMed2005

Development of angiotensin II-induced hypertension: role of CGRP and its receptor.

OBJECTIVE: To determine the role of endogenous calcitonin gene-related peptide (CGRP) and its receptor in development of angiotensin II (Ang II)-induced hypertension. DESIGN AND METHODS: Seven-week-old male Wistar rats were given either Ang II (100 ng/kg per min) or saline via mini osmotic pumps with or without minoxidil (9 mg/kg per day) in their drinking water for 10 days. Mean arterial pressure (MAP) and its response to alpha-CGRP (1 microg/kg, iv) and its receptor antagonist, CGRP(8-37) (1 mg/kg, iv), were determined in conscious and unrestrained rats. Radioimmunoassay and Western blotting were employed, respectively, to determine CGRP levels in plasma and dorsal root ganglia (DRG) and CGRP receptor protein content in mesenteric arteries. RESULTS: After the 10-day treatment, MAP was higher in the Ang II group compared to control (Con), control plus minoxidil (Con-Min), and Ang II plus minoxidil (Ang II-Min) (P < 0.01). CGRP decreased MAP in the Ang II group compared to Con, Con-Min and Ang II-Min rats (P < 0.01). In contrast, CGRP8-37 increased MAP in Con-Min and Ang II-Min groups compared with Con and Ang II groups (P < 0.01). Radioimmunoassay showed that CGRP levels in plasma and DRG were not different among the four groups. Western blots showed that calcitonin receptor-like receptor (CRLR) and receptor activity-modifying protein 1 (RAMP1), which constitute a CGRP receptor, were significantly upregulated in mesenteric arteries in the Ang II group compared to the other three groups (P < 0.05). CONCLUSION: These data indicate that long-term Ang II infusion is accompanied by an increase in CGRP receptor expression in mesenteric arteries but not in CGRP levels in plasma and DRG. The increase in mesenteric CGRP receptor expression appears to be pressure dependent and to enhance the blood pressure response to CGRP. Minoxidil enhances the hypertensive effect of CGRP8-37 to the same degree in control and Ang II-treated rats, indicating that this KATP channel activator sensitizes the blood pressure response regardless of the baseline pressure while CGRP receptors are blocked.

Angiotensin II↗

PubMed2005

The vanilloid receptor and hypertension.

Mammalian transient receptor potential (TRP) channels consist of six related protein sub-families that are involved in a variety of pathophysiological function, and disease development. The TRPV1 channel, a member of the TRPV sub-family, is identified by expression cloning using the "hot" pepper-derived vanilloid compound capsaicin as a ligand. Therefore, TRPV1 is also referred as the vanilloid receptor (VR1) or the capsaicin receptor. VR1 is mainly expressed in a subpopulation of primary afferent neurons that project to cardiovascular and renal tissues. These capsaicin-sensitive primary afferent neurons are not only involved in the perception of somatic and visceral pain, but also have a "sensory-effector" function. Regarding the latter, these neurons release stored neuropeptides through a calcium-dependent mechanism via the binding of capsaicin to VR1. The most studied sensory neuropeptides are calcitonin gene-related peptide (CGRP) and substance P (SP), which are potent vasodilators and natriuretic/diuretic factors. Recent evidence using the model of neonatal degeneration of capsaicin-sensitive sensory nerves revealed novel mechanisms that underlie increased salt sensitivity and several experimental models of hypertension. These mechanisms include insufficient suppression of plasma renin activity and plasma aldosterone levels subsequent to salt loading, enhancement of sympathoexcitatory response in the face of a salt challenge, activation of the endothelin-1 receptor, and impaired natriuretic response to salt loading in capsaicin-pretreated rats. These data indicate that sensory nerves counterbalance the prohypertensive effects of several neurohormonal systems to maintain normal blood pressure when challenged with salt loading. The therapeutic utilities of vanilloid compounds, endogenous agonists, and sensory neuropeptides are also discussed.

Animals↗

PubMed2004

Prevention of endothelin-1-induced increases in blood pressure: role of endogenous CGRP.

To determine the role of endothelin-1 (ET-1) and its receptors in the regulation of calcitonin gene-related peptide (CGRP) release, male Wistar rats were divided into six groups and subjected to the following treatments for 1 wk with or without ABT-627 (an ET(A) receptor antagonist, 5 mg.kg(-1).day(-1) in drinking water) or A-192621 (an ET(B)-receptor antagonist, 30 mg.kg(-1).day(-1) by oral gavage): control (Con), ET-1 (5 ng.kg(-1).min(-1) iv), Con + ABT-627, Con + A-192621, ET-1 + ABT-627, and ET-1 + A-192621. Baseline mean arterial pressure (MAP, mmHg) was higher (P < 0.05) in Con + A-192621 (122 +/- 4) and ET-1 + A-192621 (119 +/- 4) groups compared with Con (104 +/- 6), ET1 (106 +/- 3), Con + ABT-627 (104 +/- 3), and ET1 + ABT-627 (100 +/- 3) groups. Intravenous administration of CGRP(8-37) (a CGRP receptor antagonist, 1 mg/kg) increased MAP (P < 0.05) in ET-1 (13 +/- 1), Con + A-192621 (12 +/- 1), and ET-1 + A-192621 (15 +/- 3) groups compared with Con (4 +/- 1), Con-ABT-627 (4 +/- 1), and ET-1 + ABT-627 (5 +/- 1) groups. Plasma CGRP levels (in pg/ml) were increased (P < 0.05) in ET-1 (57.5 +/- 6.1), Con + A-192621 (53.9 +/- 3.4), and ET-1 + A-192621 (60.4 +/- 3.0) groups compared with Con (40.4 +/- 1.6), Con + ABT-627 (40.0 +/- 2.9), and ET-1 + ABT-627 (42.6 +/- 1.9) groups. Plasma ET-1 levels (in pg/ml) were higher (P < 0.05) in ET-1 (2.8 +/- 0.2), ET-1 + ABT-627 (3.2 +/- 0.4), Con + A-192621 (3.3 +/- 0.4), and ET-1 + A-192621 (4.6 +/- 0.3) groups compared with Con (1.1 +/- 0.2) and Con-ABT-627 (1.3 +/- 0.2) groups. Therefore, our data show that ET-1 infusion leads to increased CGRP release via activation of the ET(A) receptor, which plays a compensatory role in preventing ET-1-induced elevation in blood pressure.

Animals↗

PubMed2004

Activation of the renin-angiotensin system in alpha-calcitonin gene-related peptide/calcitonin gene knockout mice.

OBJECTIVE: To test the hypotheses that circulating or tissue renin-angiotensin system (RAS) activity is increased in alpha-calcitonin gene-related peptide (alpha CGRP) knockout mice, and that this contributes to the increased blood pressure in these mice. DESIGN AND METHODS: Three- to six-month-old male alpha CGRP/calcitonin knockout mice and wild-type controls were studied. Mean arterial pressure (MAP) and its response to an angiotensin II type 1 (AT1) receptor blocker, losartan (3 mg/kg intravenously), were determined in conscious, unrestrained knockout mice and wild-type mice. Radioimmunoassay and western blot were used, respectively, to determine plasma renin activity (PRA) and AT1 receptor protein content in tissues. RESULTS: Basal MAP and PRA were significantly greater in the knockout mice than in the wild-type mice. In contrast, AT1 receptor content in the renal medulla was significantly decreased in the knockout mice compared with that in wild-type mice. AT1 receptor content in the renal cortex and mesenteric resistance arteries was not different in the knockout and wild-type mice. Losartan produced a significant decrease in MAP in the knockout mice compared with that in wild-type mice. CONCLUSION: Activity of the circulating RAS, but not tissue AT1 receptor expression, is increased in alpha CGRP/calcitonin knockout mice, which may contribute to the increase in blood pressure in this mouse model. The mechanism(s) responsible for the increased activity of the circulating RAS in the absence of alpha CGRP throughout the developmental stages of these animals remains to be determined.

Animals↗

PubMed2004

Increased salt sensitivity induced by sensory denervation: role of superoxide.

AIM: To test the hypothesis that production of superoxide in mesenteric resistance arteries is increased and contributes to the development of hypertension induced by sensory denervation plus high salt intake. METHODS: Newborn Wistar rats were given capsaicin 50 mg/kg sc on the 1st and 2nd d of life. After weaning, male rats were grouped as follows and treated for 3 weeks with: capsaicin pretreatment plus normal sodium diet (0.5 %, CAP-NS), CAP plus high sodium diet (4 %, CAP-HS), control plus NS (CON-NS), or CON-HS. Both tail-cuff systolic blood pressure and mean arterial pressure (MAP) were measured in each of the groups. Western blot analysis was used for measurement of manganese superoxide dismutase (MnSOD) and endothelial nitric oxide synthase (eNOS) in the mesenteric resistance arteries. Lucigenin chemiluminescence assay was used for superoxide production in the mesenteric resistance arteries. The Griess method was used for measurement of nitrite/nitrate levels in plasma. RESULTS: Both tail-cuff pressure and MAP were higher in CAP-HS compared with CAP-NS, CON-HS, and CON-NS rats (P<0.05). Both MnSOD and eNOS in the mesenteric resistance arteries were increased in CAP-HS compared with CAP-NS, CON-HS, and CON-NS (P<0.05). However, nitrite/nitrate levels in plasma were not different among 4 groups. Acute iv administration of tempol, a membrane-permeable superoxide scavenger, decreased MAP in both CAP-HS and CON-HS when compared with their respective controls. However, the decreases of MAP between these two groups were not different. Chronic treatment with tempol failed to prevent the development of hypertension in CAP-HS rats. Superoxide production in the mesenteric resistance arteries was increased in CAP-HS compared with CAP-NS, CON-HS, and CON-NS (P<0.05). However, chronic treatment with tempol did not prevent the increase of mesenteric superoxide production in CAP-HS rats. CONCLUSIONS: Regardless of increased vascular MnSOD levels, salt sensitive hypertension induced by sensory degeneration is associated with increased vascular superoxide production. Although tempol is incapable of preventing the development of hypertension in sensory denervated rats fed a high salt diet, increased superoxide levels may contribute to exacerbated vascular impairment which may take longer time to develop. Given that superoxide may be produced by sources other than mitochondrion, future studies using other inhibitors (eg, inhibitors of NADPH oxidase and xanthine oxidase) may unveil the effectiveness of reducing superoxide on lowering blood pressure in this model.

Animals↗