Effects of endothelial and inducible nitric oxide synthases inhibition on circulatory function in rats after myocardial infarction

Stable Gastric Pentadecapeptide BPC 157 May Counteract Myocardial Infarction Induced by Isoprenaline in Rats

We revealed that the stable gastric pentadecapeptide BPC 157, a useful peptide therapy against isoprenaline myocardial infarction, as well as against isoprenaline myocardial reinfarction, may follow the counteraction of the recently described occlusion-like syndrome, induced peripherally and centrally, which was described for the first time in isoprenaline-treated rats. BPC 157 (10 ng/kg, 10 µg/kg i.p.), L-NAME (5 mg/kg i.p.), and L-arginine (200 mg/kg i.p.) were given alone or together at (i) 30 min before or, alternatively, (ii) at 5 min after isoprenaline (75 or 150 mg/kg s.c.). At 30 min after isoprenaline 75 mg/kg s.c., we noted an early multiorgan failure (brain, heart, lung, liver, kidney and gastrointestinal lesions), thrombosis, intracranial (superior sagittal sinus) hypertension, portal and caval hypertension, and aortal hypotension, in its full presentation (or attenuated by BPC 157 therapy (given at 5 min after isoprenaline) via activation of the azygos vein). Further, we studied isoprenaline (75 or 150 mg/kg s.c.) myocardial infarction (1 challenge) and reinfarction (isoprenaline at 0 h and 24 h, 2 challenges) in rats (assessed at the end of the subsequent 24 h period). BPC 157 reduced levels of all necrosis markers, CK, CK-MB, LDH, and cTnT, and attenuated gross (no visible infarcted area) and histological damage, ECG (no ST-T ischemic changes), and echocardiography (preservation of systolic left ventricular function) damage induced by isoprenaline. Its effect was associated with a significant decrease in oxidative stress parameters and likely maintained NO system function, providing that BPC 157 interacted with eNOS and COX2 gene expression in a particular way and counteracted the noxious effect of the NOS-blocker, L-NAME.

The prognostic value of estimating stroke volume before and after exercise during treadmill stress echocardiography

BACKGROUND

Stress echocardiography (SE) is an established technique for assessment of coronary artery disease (CAD) which is difficult to perform and interpret. Left ventricular stroke volume (SV) is readily estimated with Doppler echocardiography. It can be affected by myocardial ischemia, with possible adjunctive value during SE.

METHODS

Patients underwent Bruce protocol SE with SV estimated before and after maximal treadmill exertion post routine regional wall analysis. Incremental change in SV (ΔSV) with exercise was measured.

RESULTS

A derivation cohort (n = 273) was established to test the hypothesis. An optimal cutoff for detection on inducible ischemia was ΔSV ≤ +10 mL. The validation cohort of consecutive patients (n = 1093, 376 [34%] female; age 59 ± 12 years) were followed clinically after SE for 20 460 patient-months. There were 1000 patients with nonischemic SE, and 93 patients with studies suggestive of myocardial ischemia. Secondary analysis yielded 831 patients with a normal exercise response (ΔSV > +10 mL) and 192 with an abnormal ΔSV ≤ +10 mL. Time to first combined adverse cardiac event (composite of angina, acute coronary syndrome, cardiac revascularization, worsening New York Heart Association (NYHA) class, a reduction in EF, and cardiovascular death) was analyzed and adjusted using Cox proportional hazards regression. The hazard ratio for an adverse event with an abnormal ΔSV response (≤10 mL) was 10.3 (95% confidence intervals 5.6-19.1, P < .0001).

CONCLUSIONS

Stroke volume assessment during SE is feasible and readily performed. It is simple, practical, and has incremental diagnostic and prognostic value when added to exercise regional wall-motion analysis.

The impact of electric fields on testis physiopathology, sperm parameters and DNA integrity-The role of resveratrol

This study investigated the long-term effects of electric fields (EF) which might cause physiopathological or morphological changes in the testis tissues of rats. We assumed that using resveratrol (RES) might reduce harmful effects of the EF. Thirty-two male Wistar Albino rats were randomly divided into four groups with eight animals in each; control, EF, EF + RES and RES. Malondialdehyde (MDA), superoxide dismutase, catalase, glutathione peroxidase and histopathological parameters were evaluated in testis tissue. Epididymal sperm count, motility and DNA damage were studied. Total testosterone, follicle-stimulating hormone, luteinising hormone, estradiol and growth hormone levels were evaluated in the plasma samples. EF caused statistically significant increase in MDA levels, body weight and DNA damage. A significant decrease was detected in sperm count and motility. The histopathological examination of the testes showed the germ cell decrease in the seminiferous epithelium with oedema and vascular congestion in the interstitial tissue. In immunohistochemical examination, the increase in the apoptotic cells number was detected. RES partially ameliorated biochemical, histopathological and immunohistochemical findings in the EF + RES group. These findings clearly demonstrated that EF can cause damage in rat testis. RES can ameliorate the damage caused by EF.

Aminoguanidine Prevents Fructose-Induced Arterial Stiffening in Wistar Rats: Aortic Impedance Analysis

Fructose has been reported as a potent agent in forming advanced glycation end products (AGEs) and, thus, may play a significant role in the pathogenesis of diabetic complications. Herein, we determined the effects of aminoguanidine (AG), an inhibitor of AGEs, on the mechanical properties of the arterial system in fructose-fed (FF) rats, using aortic impedance analysis. Rats at 2 months were given 10% fructose in drinking water for 2 weeks and compared with untreated age-matched controls. Meanwhile, FF rats were treated for 2 weeks with AG (daily peritoneal injections of 50 mg kg−1) and compared with the untreated FF group. Neither fructose nor AG affects body weight, blood glucose level, and basal heart rate. In comparison with controls, FF rats showed a decrease in cardiac output in the absence of any significant changes in mean aortic pressure, having increased total peripheral resistance (Rp), at 51.1 ± 2.9 versus 66.2 ± 1.9 mm Hg sec ml−1 (P < 0.05). Fructose also contributed to an increase in aortic characteristic impedance (Zc), from 1.528 ± 0.094 to 1.933 ± 0.084 mm Hg sec ml−1 (P < 0.05) and a decrease in wave transit time (τ), from 22.6 ± 0.6 to 19.2 ± 0.7 msec (P < 0.05). The elevated Zc and the reduced τ suggest that fructose may cause a detriment to the aortic distensibility in animals. After exposure to AG, FF rats exhibited a significant improvement in physical properties of the resistance vessels, as evidenced by the reduction of 21.3% in Rp. Meanwhile, AG retarded the fructose-induced decline in aortic distensibility, as reflected in the decrease of 16.0% in Zc (P < 0.05) and the increase of 18.1% in τ (P < 0.05). By contrast, AG exerted no effects on the mechanical properties of Windkessel vessels, as well as resistance vessels, in normal diet controls. We conclude that AG may prevent the fructose-derived changes in arterial stiffening, possibly through inhibition of the fructose-derived advanced glycation end product formation in Wistar rats.

Tempol-nebivolol therapy potentiates hypotensive effect increasing NO bioavailability and signaling pathway

Nebivolol is a third generation beta blocker with endothelial nitric oxide synthase (eNOS) agonist properties. Considering the role of reactive oxygen species (ROS) in the uncoupling of eNOS, we hypothesized that the preadministration of an antioxidant as tempol, could improve the hypotensive response of nebivolol in normotensive animals increasing the nitric oxide (NO) bioavailability by a reduction of superoxide (O2(•-)) basal level production in the vascular tissue. Male Sprague Dawley rats were given tap water to drink (control group) or tempol (an antioxidant scavenger of superoxide) for 1 week. After 1 week, Nebivolol, at a dose of 3 mg/kg, was injected intravenously to the control group or to the tempol-treated group. Mean arterial pressure, heart rate, and blood pressure variability were evaluated in the control, tempol, nebivolol, and tempol nebivolol groups, as well as, the effect of different inhibitor as Nβ-nitro-l-arginine methyl ester (L-NAME, a Nitric oxide synthase blocker) or glybenclamide, a KATP channel inhibitor. Also, the expression of α,β soluble guanylate cyclase (sGC), phospho-eNOS, and phospho-vasodilator-stimulated phosphoprotein (P-VASP) were evaluated by Western Blot and cyclic guanosine monophosphate (cGMP) levels by an enzyme-linked immunosorbent assay (ELISA) commercial kit assay. We showed that pretreatment with tempol in normotensive rats produces a hypotensive response after nebivolol administration through an increase in the NO bioavailability and sGC, improving the NO/cGMP/protein kinase G (PKG) pathway compared to that of the nebivolol group. We demonstrated that tempol preadministration beneficiates the response of a third-generation beta blocker with eNOS stimulation properties, decreasing the basal uncoupling of eNOS, and improving NO bioavailability. Our results clearly open a possible new strategy therapeutic for treating hypertension.

Pentadecapeptide BPC 157 and the esophagocutaneous fistula healing therapy

Esophagocutaneous fistulas are a failure of the NO-system, due to NO-synthase blockage by the NOS-blocker L-NAME consequently counteracted by l-arginine and gastric pentadecapeptide BPC 157 (l-arginine <BPC 157), precipitating a therapeutic benefit. Previously, there was an established BPC 157-NO-system interaction. BPC 157 GEPPPGKPADDAGLV, MW 1419 (LD1 not achieved), is a safe and stable anti-ulcer peptide, successful in inflammatory bowel disease trials, counteracting esophagitis, sphincter failure, gastrointestinal and skin ulcers, gastrocutaneous or colocutaneous fistulas. We treated rats with established cervical esophagocutaneous fistulas throughout four days (both open skin and esophageal defects, with significant leakage) with BPC 157 (parenterally and perorally) and L-NAME (blocking NO genesis) and l-arginine (NO-substrate) alone or in combination. RT-PCR investigated eNOS, iNOS, COX-2 mRNA levels in the fistulas. We evidenced a closely inter-related process of unhealed skin, esophageal defects, unhealed fistulas (up regulated eNOS, iNOS and COX2 mRNA levels), usually lethal, particularly NO-system related and therapy dependent. Generally, the course of fistula healing was accelerated either to a greater extent (with BPC 157 (in particular, less eNOS gene expression) completely counteracting L-NAME effects, in L-NAME+BPC 157 and L-NAME+l-arginine+BPC 157 groups), or to a lesser extent (with l-arginine). Conversely, the process was aggravated, rapidly and prominently (with L-NAME). In particular, BPC 157 was effective either given per-orally/intraperitoneally, in μg- and ng-regimens. Shortly, defects started to heal, with less fistula leakage and no mortality at day 4. Failure of pyloric and lower esophageal sphincter pressure was restored, with practically no esophagitis.

BACE1 levels are elevated in congestive heart failure

Cardiovascular (CV) diseases are known to have a negative impact on the brain and neurocognition, and contribute to the development of vascular dementia and neurodegenerative diseases such as Alzheimer's disease (AD). Among CV diseases, congestive heart failure (CHF) after myocardial infarction (MI) is a condition where the ability of the left ventricle to eject blood to the circulation is impaired. As a consequence, CHF triggers inflammation and results in reduced cerebral blood flow which are considered among the risk factors for development of AD. However, biochemical alterations in the brain following MI and CHF remain unknown. To address this issue, we investigated microglia activation; levels of BACE1, the key rate-limiting enzyme involved in the pathogenesis of AD; and VEGF levels in the hippocampus and cortex following MI. We created MI by the ligation of the left anterior descending coronary artery in Sprague-Dawley male rats and collected brains either 3 days after MI (AMI) or 21 days after MI (CHF). We investigated microglia activation in AMI and CHF brains by immunohistochemistry and immunoblotting using macrophage/microglia marker Ionized calcium binding adaptor molecule 1 (Iba-1), and observed activated morphology of microglia in the cortex of rats in both AMI and CHF. We also showed the levels of BACE1 were increased in the cortex and hippocampus of CHF rats. To determine whether hypoxia occurs in the CHF brain, we assessed levels of VEGF in the hippocampus and cortex. Western blotting analysis showed up-regulation of VEGF in the hippocampus of CHF brains. These results suggest that neuroinflammation takes place secondary to myocardial infarction. In addition, CHF-induced hypoxia might play a role in the elevation of BACE1 and VEGF levels.

Effects of olmesartan on arterial stiffness in rats with chronic renal failure

Background

It has been suggested that the antioxidant properties of olmesartan (OLM), an angiotensin II type 1 receptor (AT₁R) blocker, contribute to renal protection rather than blood pressure lowering effects despite the fact that causal relationships between hypertension and renal artery disease exist. This study aimed to examine the hypothesis whether the antioxidative activities of OLM were correlated to arterial stiffness, reactive oxygen species and advanced glycation end products (AGEs) formation in rats with chronic renal failure (CRF).

Methods

CRF rats were induced by 5/6 nephrectomy and randomly assigned to an OLM (10 mg/day) group or a control group. Hemodynamic states, oxidative stress, renal function and AGEs were measured after 8 weeks of OLM treatment.

Results

All the hemodynamic derangements associated with renal and cardiovascular dysfunctions were abrogated in CRF rats receiving OLM. Decreased cardiac output was normalized compared to control (p <0.05). Mean aortic pressure, total peripheral resistance and left ventricular weight/body weight ratio were reduced by 21.6% (p <0.05), 28.2% (p <0.05) and 27.2% ((p <0.05). OLM also showed beneficial effects on the oscillatory components of the ventricular after-load, including 39% reduction in aortic characteristic impedance (p < 0.05), 75.3% increase in aortic compliance (p <0.05) and 50.3% increase in wave transit time (p < 0.05). These results implied that OLM attenuated the increased systolic load of the left ventricle and prevented cardiac hypertrophy in CRF rats. Improved renal function was also reflected by increases in the clearances of BUN (28.7%) and serum creatinine (SCr, 38.8%). In addition to these functional improvements, OLM specifically reduced the levels of malondialdehyde (MDA) equivalents in aorta and serum by 14.3% and 25.1%, as well as the amount of AGEs in the aortic wall by 32% (p < 0.05) of CRF rats.

Conclusion

OLM treatment could ameliorate arterial stiffness in CRF rats with concomitant inhibition of MDA and AGEs levels through the reduction of oxidative stress in aortic wall.

Regulation of endothelial nitric oxide synthase and asymmetric dimethylarginine by matrine attenuates isoproterenol-induced acute myocardial injury in rats

OBJECTIVES

This study was designed to investigate the cardioprotective effects of matrine on regulation of endothelial nitric oxide synthase (eNOS) and asymmetric dimethylarginine (ADMA) in isoproterenol-induced acute myocardial ischaemic rats.

METHODS

Male Sprague-Dawley rats were pretreated with matrine (200, 100 and 50 mg/kg) orally for 10 days. Acute myocardial injury was induced in rats by subcutaneous injection of isoproterenol. Serum and haemodynamic parameters, histopathological variables and expression of protein levels were analysed.

KEY FINDINGS

Oral administration of matrine (200, 100 and 50 mg/kg) significantly attenuated isoproterenol-induced cardiac necrosis and left ventricular dysfunction. Matrine treatment restored impaired ventricular Akt and eNOS protein expression with concomitant increased phosphorylation of Akt (Ser473) and eNOS (Ser1177), and also restored glycogen synthase kinase 3β activity, as indicated by increased phosphorylation at Ser 9. Moreover, treatment with matrine had no effect on the isoproterenol-induced elevated protein arginine methyltransferase 1 protein expression, but could significantly normalize the reduced dimethylarginine dimethylaminohydrolase 2 expression and attenuate the increased serum level of ADMA. The expression of catechol-o-methyltransferase and monoamine oxidase did not differ among all groups (all P > 0.05).

CONCLUSIONS

Our results suggested that matrine protects against isoproterenol-induced myocardial ischaemia via eNOS and ADMA pathway.

Heme oxygenase-1 overexpression fails to attenuate hypertension when the nitric oxide synthase system is not fully operative

Heme oxygenase (HO) is an enzyme that is involved in numerous secondary actions. One of its products, CO, seems to have an important but unclear role in blood pressure regulation. CO exhibits a vasodilator action through the activation of soluble guanylate cyclase and the subsequent production of cyclic guanosine monophosphate (cGMP). The aim of the present study was to determine whether pathological and pharmacological HO-1 overexpression has any regulatory role on blood pressure in a renovascular model of hypertension. We examined the effect of zinc protoporyphyrin IX (ZnPP-IX) administration, an inhibitor of HO activity, on mean arterial pressure (MAP) and heart rate in sham-operated and aorta-coarcted (AC) rats and its interaction with the nitric oxide synthase (NOS) pathway. Inhibition of HO increased MAP in normotensive rats with and without hemin pretreatment but not in hypertensive rats. Pretreatment with NG-nitro-L-arginine methyl ester blocked the pressor response to ZnPP-IX, suggesting a key role of NOS in the cardiovascular action of HO inhibition. In the same way, AC rats, an experimental model of hypertension with impaired function and low expression of endothelial NOS (eNOS), did not show any cardiovascular response to inhibition or induction of HO. This finding suggests that eNOS was necessary for modulating the CO response in the hypertensive group. In conclusion, the present study suggests that HO regulates blood pressure through CO only when the NOS pathway is fully operative. In addition, chronic HO induction fails to attenuate the hypertensive stage induced by coarctation as a consequence of the impairment of the NOS pathway.

Prevention of arterial stiffening by pyridoxamine in diabetes is associated with inhibition of the pathogenic glycation on aortic collagen

BACKGROUND AND PURPOSE

Our team previously demonstrated that diabetes induces a deterioration in vascular dynamics, in parallel with the enhanced formation of advanced glycation end products. The aim of this study was to determine whether prevention of the arterial stiffening by pyridoxamine in diabetes is associated with inhibition of the pathogenic glycation on aortic collagen.

EXPERIMENTAL APPROACH

Diabetes was induced in rats by a single tail vein injection with 55 mg.kg(-1) steptozotocin (STZ). After induction of hyperglycaemia, animals were treated for 8 weeks with pyridoxamine (1 g.L(-1) in drinking water) and compared with the age-matched untreated diabetic controls. Pulse wave reflection along the vasculature was derived using the impulse response function of the filtered aortic input impedance spectra.

KEY RESULTS

Treatment of this experimental diabetes with pyridoxamine resulted in a significant increase in wave transit time and a decrease in wave reflection factor, indicating that pyridoxamine attenuates the diabetes-induced augmentation in systolic load of the left ventricle coupled to its arterial system. Meanwhile, pyridoxamine therapy ameliorated the diabetes-related cardiac hypertrophy, as evidenced by the reduction in ratio of the left ventricular weight to body weight. Glycation-derived modification of aortic collagen was also found to be attenuated by administration of pyridoxamine to the STZ-induced diabetic rats.

CONCLUSIONS AND IMPLICATIONS

Pyridoxamine imparts significant protection against the diabetes-induced deterioration in pulsatile arterial load imposed on the heart, at least partly through inhibition of the formation of advanced glycation end products and their accumulation on aortic collagen of the STZ-treated rats.

Resveratrol: a promising agent in promoting cardioprotection against coronary heart diseaseThis article is one of a selection of papers from the NATO Advanced Research Workshop on Translational Knowledge for Heart Health (published in part 2 of a 2-part Special Issue)

The inverse association between alcohol intake and coronary heart disease has been consistently reported in cross-culture, case–control, and cohort studies. Over the past couple of decades, however, many studies have explained promising health benefits associated with wine consumption. Some studies suggest that red wine is more cardioprotective than white wine, possibly due to the increased content of flavanoid antioxidants found in red wine. Several experimental studies, including ours, support the evidence that these beneficial effects are due to resveratrol, the polyphenolic compound present in red wine. Many studies have provided evidence that resveratrol possesses antioxidant and antiapoptotic effects apart from activation of longevity proteins (such as SIRT-1). We have recently reported the angiogenic, antihypercholesterolemic, and antidiabetic effects of resveratrol and the mechanisms involved in reduced ventricular remodeling and increased cardiac functions. We have also shown different strategic target molecules involved in resveratrol-mediated cardioprotection. Therefore, this review discusses the potential effect of resveratrol and the mechanisms involved in resveratrol-mediated cardioprotection during myocardial infarction, hypercholesterolemia, and diabetes rendering its beneficial effects during health and disease.

Valsartan therapy in heart failure after myocardial infarction: the role of endothelial dependent vasorelaxation

Angiotensin II receptor blockade (ARB) increases vasorelaxation in heart failure by enhancing endothelial nitric oxide (NO). To determine the effects of valsartan on NO-mediated peripheral vascular function after myocardial infarction (MI), we treated adult male Sprague-Dawley rats immediately after MI with valsartan for 3 weeks (sham, n = 10; MI, n = 11) and 6 weeks (sham, n = 6; MI, n = 8). At both time points, valsartan lowered (P < 0.05) left ventricular (LV) systolic pressure (103 +/- 4 and 107 +/- 4 vs. 93 +/- 3 and 85 +/- 4 mm Hg, respectively) and LV end-diastolic pressure (25 +/- 1 and 25 +/- 2 to 13 +/- 2 and 18 +/- 3 mm Hg, respectively). Valsartan lowered (P < 0.05) LV dP/dt only at 6 weeks (4676 +/- 168 and 4503 +/- 232 vs. 4539 +/- 281 and 3372 +/- 417 mm Hg/sec); valsartan shortened (P < 0.05) the time constant of LV relaxation or tau only at 3 weeks (24.2 +/- 1.8 and 26.5 +/- 2.3 vs. 20.1 +/- 0.7 and 23.8 +/- 1.4 msec). At 6 weeks, the vasorelaxation response to acetycholine in aortic rings was decreased (P < 0.05) with MI and improved at acetycholine doses (10, 10, and 10; P < 0.06) with valsartan. Endothelial nitric oxide synthase (eNOS) protein was undetectable in aortic tissue from valsartan treated rats or from aortic tissue incubated with valsartan (2.5, 25, and 50 mg/mL). These data suggest that valsartan improves cardiac function after MI by modulating LV remodeling, decreasing LV end-diastolic pressure, and enhancing both LV diastolic and endothelial function. These effects are mediated, in part, by NO but upregulation of eNOS may not be required for improved systemic endothelial function in heart failure.

Aminoguanidine prevents arterial stiffening and cardiac hypertrophy in streptozotocin-induced diabetes in rats

The formation of advanced glycation endproducts (AGEs) on collagen within the arterial wall may be responsible for the development of diabetic vascular injury. This study was to examine the role of aminoguanidine (AG), an inhibitor of AGEs formation, in the prevention of arterial stiffening and cardiac hypertrophy in streptozotocin (STZ) induced diabetes in rats. Diabetes was induced in animals by a single tail vein injection with 65 mg kg(-1) STZ. After confirmation of the development of hyperglycemia (2 days later), rats were treated for 8 weeks with AG (daily peritoneal injections of 50 mg kg(-1)) and compared with the age-matched untreated diabetic controls. After exposure to AG, the STZ-diabetic rats showed no alterations in cardiac output, aortic pressure profiles, total peripheral resistance, and aortic characteristic impedance. By contrast, treatment of this experimental diabetes with AG resulted in a significant increase in wave transit time (tau), from 20.4+/-0.6 to 24.7+/-0.5 ms (P<0.05) and a decrease in wave reflection factor (R(f)), from 0.78+/-0.04 to 0.53+/-0.02 (P<0.05). The decreased R(f) associated with the increased tau suggest that AG may retard the diabetes-induced augmentation in systolic load of the left ventricle coupled to its arterial system. Meanwhile, the diminished ratio of left ventricular weight to body weight suggests that prevention of the diabetes-related cardiac hypertrophy by AG may correspond to the drug-induced decline in aortic stiffening. Glycation-derived modification on aortic collagen was also found to be enhanced in rats with diabetes (+65.3%, P<0.05) and the advanced glycation process was retarded by AG treatment. We conclude that long-term administration of AG to the STZ-treated rats imparts significant protection against the diabetes-derived deterioration in vascular dynamics, at least partly through inhibition of the AGEs accumulation on collagen in the arterial wall.

Pretreatment With Angiotensin Receptor Blockade Prevents Left Ventricular Dysfunction and Blunts Left Ventricular Remodeling Associated With Acute Myocardial Infarction

Background— This study was designed to determine the effects of pretreatment with an angiotensin receptor blocker on left ventricular (LV) function and remodeling during acute myocardial infarction (MI).

Methods and Results— Sprague-Dawley rats were pretreated with candesartan (10 mg · kg −1 · d −1 ) for 2 weeks and studied at 1, 3, and 6 minutes after MI. Compared with untreated rats, pretreatment with candesartan lowered ( P <0.05) LV systolic pressure and the first derivative of LV pressure with respect to time but did not change LV end-diastolic pressure or improve LV regional function. With candesartan pretreatment, LV fractional shortening and ejection fraction increased ( P <0.05) by 37% and 28%, and LV chamber dilation was attenuated ( P <0.05). At 6 minutes after MI, LV endothelial nitric oxide synthase decreased in the infarcted and noninfarcted wall 47% ( P =0.04) and 70% ( P =0.002), and constitutive microtubulin increased 260% ( P =0.0005) and 111% ( P =0.003). Candesartan had no effect on LV tissue endothelial nitric oxide synthase levels but attenuated the increase in constitutive microtubulin by 77% ( P =0.004) and 37% ( P <0.05).

Conclusions— Pretreatment with candesartan before an acute MI improves global LV function, prevents LV dilation, and blunts the increase in constitutive microtubulin, with minimal effects on LV hemodynamics, regional function, or tissue endothelial nitric oxide synthase. Thus, candesartan given before an MI attenuates LV remodeling and alters the cytoskeleton matrix of the left ventricle.

Aminoguanidine prevents arterial stiffening in a new rat model of type 2 diabetes

BACKGROUND

Formation of advanced glycation end-products (AGEs) on collagen within the arterial wall may be responsible for the development of diabetic vascular injury. This study focused on investigating the role of aminoguanidine (AG), an inhibitor of AGE formation, in the prevention of noninsulin-dependent diabetes mellitus (NIDDM)-derived arterial stiffening and cardiac hypertrophy in rats.

MATERIALS AND METHODS

The NIDDM was induced in male Wistar rats, which were administered intraperitoneally with 180 mg kg(-1) nicotinamide (NA) 30 min before an intravenous injection of 50 mg kg(-1) streptozotocin (STZ). After induction of diabetes mellitus type 2, animals receiving daily peritoneal injections with 50 mg kg(-1) AG for 8 weeks were compared with the age-matched, untreated, diabetic controls.

RESULTS

After exposure to AG, the STZ-NA diabetic rats had improved aortic distensibility, as evidenced by 18.8% reduction of aortic characteristic impedance (P < 0.05). Treatment of the experimental syndrome with AG also resulted in a significant increase in wave transit time (+23.7%, P < 0.05) and a decrease in wave reflection factor (-26.6%, P < 0.05), suggesting that AG may prevent the NIDDM-induced augmentation in systolic load of the left ventricle. Also, the glycation-derived modification on aortic collagen was found to be retarded by AG. The diminished ratio of left ventricular weight to body weight suggested that prevention of the diabetes-related cardiac hypertrophy by AG may correspond to the drug-induced decline in aortic stiffening.

CONCLUSIONS

Long-term administration of AG to the STZ-NA diabetic rats imparts significant protection against the NIDDM-derived impairment in vascular dynamics, at least partly through inhibition of the AGE accumulation on collagen in the arterial wall.

Arterial stiffening and cardiac hypertrophy in a new rat model of type 2 diabetes

BACKGROUND

We determined the effects of NIDDM on haemodynamic parameters describing arterial wall elasticity and cardiac hypertrophy in rats administered streptozotocin (STZ) and nicotinamide (NA), using the aortic impedance analysis.

METHODS

Male Wistar rats at 2 months were administered intraperitoneally 180 mg kg(-1) of NA, 30 min before an intravenous injection of 50 mg kg(-1) STZ, to induce type 2 diabetes. The STZ-NA rats were divided into two groups, 4 weeks and 8 weeks after induction of diabetes, and compared with untreated age-matched controls. Pulsatile aortic pressure and flow signals were measured by a high-fidelity pressure sensor and electromagnetic flow probe, respectively, and were then subjected to Fourier transformation for the analysis of aortic input impedance.

RESULTS

In each diabetic group, the experimental syndrome was characterized by a moderate and stable hyperglycaemia and a relative deficiency of insulin secretion. However, the 8-week but not the 4-week STZ-NA diabetic rats showed a decrease in cardiac output in the absence of any significant changes in mean aortic pressure, having increased total peripheral resistance. The diabetic syndrome at 8 weeks also contributed to an increase in aortic characteristic impedance, from 1.49 +/- 0.33 (mean +/- SD) to 1.95 +/- 0.28 mmHg s mL(-1) (P < 0.05), suggesting a detriment to the aortic distensibility in NIDDM. Meanwhile, the STZ-NA diabetic animals after 8 weeks had an increased wave reflection factor (0.46 +/- 0.09 vs. 0.61 +/- 0.13, P < 0.05) and decreased wave transit time (25.8 +/- 3.8 vs. 20.6 +/- 2.8 ms, P < 0.05). Ratio of the left ventricular weight to body weight was also enhanced in the 8-week STZ-NA diabetic rats.

CONCLUSION

The heavy intensity with early return of the pulse wave reflection may augment systolic load of the left ventricle coupled to the arterial system, leading to cardiac hypertrophy in the rats at 8 weeks after following STZ and NA administration.

Upregulation of lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) in endothelial cells by nitric oxide deficiency

Endothelial cell dysfunction (ECD) is emerging as a common denominator for diverse cardiovascular abnormalities associated with inhibition of endothelial nitric oxide (NO) synthase (eNOS). Elevated levels of asymmetric dimethylarginine (ADMA), a potent eNOS inhibitor, are common in renal failure and may contribute to ECD. Through DNA microarray screening of genes modulated in human umbilical vein endothelial cells (HUVEC) by NG-nitro-l-arginine methyl ester (l-NAME), we found a 1.8-fold increase in low-density lipoprotein receptor-1 (LOX-1) expression. LOX-1 is a major endothelial receptor for oxidized low-density lipoproteins (OxLDL) and is assumed to play a role in the initiation and progression of atherosclerosis. Here, we confirmed the upregulation of LOX-1 mRNA and protein level by quantitative RT-PCR and Western blot analysis. Increased expression of LOX-1 was associated with the accumulation of DiI-labeled OxLDL (DiI-OxLDL) in ADMA- and l-NAME-pretreated HUVEC. To evaluate the contribution of LOX-1 in ADMA-induced accumulation of OxLDL by HUVEC, we used the competitive receptor inhibitor, soluble LOX-1. Treatment of HUVEC with soluble LOX-1 was associated with an approximately two- to threefold inhibition of DiI-OxLDL uptake in l-NAME- or ADMA-treated HUVEC. In conclusion, ADMA- or l-NAME-induced NO deficiency leads to the increased expression of LOX-1 mRNA and protein in HUVEC, which in turn results in the accumulation of OxLDL. Competition with LOX-1-soluble extracellular domain reduces OxLDL accumulation. In summary, elevated ADMA levels, i.e., in patients with renal failure, may be responsible for endothelial accumulation of OxLDL via upregulated LOX-1 receptor, thus contributing to endothelial lipidosis and dysfunction.

Nitric Oxide Mediates Benefits of Angiotensin II Type 2 Receptor Overexpression During Post-Infarct Remodeling

We hypothesized that nitric oxide (NO) mediates the benefits of cardiac angiotensin II type 2 (AT(2)-R) overexpression during postmyocardial infarction (post-MI) remodeling. Eleven wild-type (WT) C57BL/6 mice and 28 transgenic (TG) mice with AT(2)-R overexpression were studied by cardiac magnetic resonance imaging (CMR) at baseline and days 1 and 28 post-MI induced by left anterior descending artery occlusion and reperfusion. Sixteen TG mice were treated from day 1 through 28 post-MI with the NO synthase inhibitor N(G)-nitro-l-arginine methyl ester in drinking water at 1 mg/mL (TG-Rx). Left ventricular mass index (LVMI), end-diastolic volume index (EDVI) and end-systolic volume index (ESVI), wall thickness, percent thickening, and ejection fraction (EF) were measured. Infarct size on day 1 was assessed by post-contrast CMR. Interstitial collagen was quantified in noninfarcted regions. At baseline, heart rate (HR), blood pressure (BP), LVMI, EDVI, and ESVI were similar between groups, as were infarct size and weekly post-MI HR and systolic BP. By day 28 post-MI, EDVI and ESVI were similar in WT and TG-Rx, but significantly lower in TG (ESVI: 1.41+/-0.18 microL/g versus 2.53+/-0.14 microL/g in WT; 2.17+/-0.14 microL/g in TG-Rx; P<0.008 for both). At day 28, EF was higher in TG (46.3%+/-2.9%) compared with WT and TG-Rx (32.7+/-2.3% and 33.7+/-2.3, respectively; P<0.003 for both). Wall thickening at day 28 post-MI was greater in the base and mid-LV in TG than WT and TG-Rx. Noninfarcted region interstitial collagen was similar between groups. Thus, the NO pathway may mediate much of the benefits of cardiac AT(2)-R overexpression during post-MI remodeling.

Angiotensin subtype 1 rReceptor (AT1) blockade improves vasorelaxation in heart failure by up-regulation of endothelial nitric-oxide synthase via activation of the AT2 receptor

To determine whether angiotensin receptor blockade decreases vascular tone in heart failure by improving endothelial-dependent vasorelaxation and increasing nitric oxide (NO) bioavailability, we treated infarcted adult male Sprague-Dawley rats with candesartan for 7 days or 8 weeks (10 mg/kg/day in drinking water). Candesartan, at both time points, lowered left ventricular (LV) systolic pressure (P < 0.05) (122 +/- 22 versus 74 +/- 16 and 73 +/- 10 mm Hg) and LV dP/dt (5914 +/- 1294 versus 2857 +/- 1672 versus 3175 +/- 769 mm Hg/s), but lowered LV end-diastolic pressure only at 8 weeks (16.9 +/- 9.7 versus 11.2 +/- 5.7 versus 6.9 +/- 5.3 mm Hg). The vasorelaxation response to acetylcholine (ACh) in thoracic aortic segments was decreased with infarction (P < 0.05), remained unchanged with 1 week of candesartan, but increased 84 and 86% at 10-4 and 10-5 M ACh (P < 0.05) at 8 weeks. The enhanced candesartan-induced vasorelaxation at 8 weeks was abolished with NG-nitro-l-arginine methyl ester (200 microM). In bovine pulmonary endothelial cells, 20 microM candesartan increased endothelial nitric-oxide synthase (eNOS) protein levels (P < 0.05) (28.9 +/- 2.6 versus 16.1 +/- 3.7 intensity units/microg of protein); the increased eNOS was abolished by a specific angiotensin subtype 2 (AT2) receptor antagonist, PD 123319. These data suggest that AT1 receptor blockade enhances vasorelaxation in heart failure by increasing NO bioavailability, in part via an AT2 receptor-mediated up-regulation of eNOS protein.

Nitric oxide and cardiac function: ten years after, and continuing

Nitric oxide (NO) is produced from virtually all cell types composing the myocardium and regulates cardiac function through both vascular-dependent and -independent effects. The former include regulation of coronary vessel tone, thrombogenicity, and proliferative and inflammatory properties as well as cellular cross-talk supporting angiogenesis. The latter comprise the direct effects of NO on several aspects of cardiomyocyte contractility, from the fine regulation of excitation-contraction coupling to modulation of (presynaptic and postsynaptic) autonomic signaling and mitochondrial respiration. This multifaceted involvement of NO in cardiac physiology is supported by a tight molecular regulation of the three NO synthases, from cellular spatial confinement to posttranslational allosteric modulation by specific interacting proteins, acting in concert to restrict the influence of NO to a particular intracellular target in a stimulus-specific manner. Loss of this specificity, such as produced on excessive NO delivery from inflammatory cells (or cytokine-stimulated cardiomyocytes themselves), may result in profound cellular disturbances leading to heart failure. Future therapeutic manipulations of cardiac NO synthesis will necessarily draw on additional characterization of the cellular and molecular determinants for the net effect of this versatile radical on the cardiomyocyte biology.

Aminoguanidine prevents age-related aortic stiffening in Fisher 344 rats: aortic impedance analysis

(1) We determined the effects of long-term treatment with aminoguanidine (AG), an inhibitor of advanced glycation end products, on the mechanical properties of the arterial system in aged Fisher 344 rats, using the aortic impedance analysis. (2) Normotensive rats were treated from 18 to 24 months with AG (1 g/l-1 in drinking water) and compared with a control group. Pulsatile aortic pressure and flow signals were measured and then subjected to Fourier transformation for the analysis of aortic input impedance. Wave transit time was determined using the impulse response function of the filtered aortic input impedance spectra. (3) With no alteration in body weight, rats treated with AG had decreased heart weight compared with the aged untreated controls. (4) AG did not affect arterial blood pressure; however, the age-related increase in total peripheral resistance was prevented by AG. (5) AG retarded the age-related decline in aortic distensibility, as evidenced by a reduction of 25.2% in aortic characteristic impedance and an increase of 28.1% in wave transit time. (6) Meanwhile, the increase in wave reflection factor in aging rats was reduced by 32.3% by AG. Both the increased wave transit time and the decreased wave reflection factor suggest that AG may prevent the age-related augmentation in systolic loading condition for the left ventricle coupled to the arterial system. (7) We conclude that long-term treatment with AG may impart significant protection against aortic stiffening and cardiac hypertrophy in aged Fisher 344 rats.

Protective role of endothelial nitric oxide synthase

Nitric oxide is a versatile molecule, with its actions ranging from haemodynamic regulation to anti-proliferative effects on vascular smooth muscle cells. Nitric oxide is produced by the nitric oxide synthases, endothelial NOS (eNOS), neural NOS (nNOS), and inducible NOS (iNOS). Constitutively expressed eNOS produces low concentrations of NO, which is necessary for a good endothelial function and integrity. Endothelial derived NO is often seen as a protective agent in a variety of diseases. This review will focus on the potential protective role of eNOS. We will discuss recent data derived from studies in eNOS knockout mice and other experimental models. Furthermore, the role of eNOS in human diseases is described and possible therapeutic intervention strategies will be discussed.

Effects of diabetes and gender on mechanical properties of the arterial system in rats: aortic impedance analysis

We determined the effects of diabetes and gender on the physical properties of the vasculature in streptozotocin (STZ)-treated rats based on the aortic input impedance analysis. Rats given STZ 65 mg/kg i.v. were compared with untreated age-matched controls. Pulsatile aortic pressure and flow signals were measured and were then subjected to Fourier transformation for the analysis of aortic input impedance. Wave transit time was determined using the impulse response function of the filtered aortic input impedance spectra. Male but not female diabetic rats exhibited an increase in cardiac output in the absence of any significant changes in arterial blood pressure, resulting in a decline in total peripheral resistance. However, in each gender group, diabetes contributed to an increase in wave reflection factor, from 0.47 +/- 0.04 to 0.84 +/- 0.03 in males and from 0.46 +/- 0.03 to 0.81 +/- 0.03 in females. Diabetic rats had reduced wave transit time, at 18.82 +/- 0.60 vs 21.34 +/- 0.51 msec in males and at 19.63 +/- 0.37 vs 22.74 +/- 0.57 msec in females. Changes in wave transit time and reflection factor indicate that diabetes can modify the timing and magnitude of the wave reflection in the rat arterial system. Meanwhile, diabetes produced a fall in aortic characteristic impedance from 0.023 +/- 0.002 to 0.009 +/- 0.001 mmHg/min/kg/ml in males and from 0.028 +/- 0.002 to 0.014 +/- 0.001 mmHg/min/kg/ml in females. With unaltered aortic pressure, both the diminished aortic characteristic impedance and wave transit time suggest that the muscle inactivation in diabetes may occur in aortas and large arteries and may cause a detriment to the aortic distensibility in rats with either sex. We conclude that only rats with male gender diabetes produce a detriment to the physical properties of the resistance arterioles. In spite of male or female gender, diabetes decreases the aortic distensibility and impairs the wave reflection phenomenon in the rat arterial system.

Simvastatin restores endothelial NO-mediated vasorelaxation in large arteries after myocardial infarction

Congestive heart failure (CHF) after myocardial infarction is associated with diminished endothelial nitric oxide (NO)-mediated vasorelaxation. The 3-hydroxy-3-methylglutaryl-CoA reductase inhibitors have been shown to modulate vascular tone independent of the effects on lipid lowering. We hypothesized that simvastatin restores NO-dependent vasorelaxation with CHF. We found that incubation of the normal rat aorta with 0.1 mM simvastatin for 24 h enhanced ACh-mediated vasorelaxation (P < 0.05). Moreover, simvastatin increased (P < 0.05) endothelial NO synthase (eNOS) protein content by >200% (82.0 +/- 14.0 vs. 21.6 +/- 7.9% II/microg). In cultured endothelial cells, simvastatin (10 and 20 microM) increased eNOS levels by 114.7 +/- 39.9 and 212.0 +/- 75.0% II/microg protein, respectively (both P < 0.05; n = 8). In the rat coronary artery ligation model, oral gavage with 20 mg. kg(-1). day(-1) simvastatin for 3 wk decreased (P < 0.05) mean arterial pressure (121 +/- 20 vs. 96.5 +/- 10.8 mmHg) and left ventricular change in pressure with time (4,500 +/- 700 vs. 4,091 +/- 1,064 mmHg/s, n = 6). Simvastatin reduced (P < 0.05) basal vasoconstriction and improved ACh-mediated vasorelaxation in CHF arterial rings. Inhibition of NO generation by N(G)-nitro-L-arginine methyl ester (100 microM) abolished the ACh-induced vasorelaxation in all rats. In conclusion, chronic treatment of CHF with simvastatin restores endothelial NO-dependent dysfunction and upregulates eNOS protein content in arterial tissue.

Inhibition of NOS II prevents cardiac dysfunction in myocardial infarction and congestive heart failure

Strong expression of the inducible form of nitric oxide synthase (NOS II) has been shown in the myocardium of patients with myocardial infarction (MI). We hypothesized that NOS II plays an important role in the development of MI and subsequent heart failure and that inhibition of NOS II may beneficially alter the course of the disease. Long-term administration (2 mo) of the selective NOS II inhibitor S-methylisothiourea (SMT) to rats with MI significantly improved cardiac function. A significant drop in mortality, lung water content, infarct size, and cardiomyocyte hypertrophy was also associated with the use of SMT. Plasma concentration of nitrite and nitrate was also reduced by SMT. Short-term administration of SMT (first 2 wk only) significantly reduced infarct size; however, it did not improve cardiac dysfunction measured 2 mo after MI. These findings demonstrate that induction of NOS II during MI exerts negative effects on cardiac function and structure. Long-term administration of a selective NOS II inhibitor may prove to be beneficial in the treatment of MI and congestive heart failure.

Protective effects of M40403, a selective superoxide dismutase mimetic, in myocardial ischaemia and reperfusion injury in vivo

1. Myocardial injury caused by ischaemia and reperfusion comes from multiple pathogenic events, including endothelial damage, neutrophil extravasation into tissue, mast cell activation, and peroxidation of cell membrane lipids. These events are followed by myocardial cell alterations resulting eventually in cell necrosis. An enhanced formation of reactive oxygen species is widely accepted as a stimulus for tissue destruction and cardiac failure. 2. In this study, we have investigated the cardioprotective effects of M40403 in myocardial ischaemia-reperfusion injury. M40403 is a low molecular weight, synthetic manganese containing superoxide dismutase mimetic (SODm) that selectively removes superoxide anion. Ischaemia was induced in rat hearts in vivo by ligating the left anterior descending coronary artery. Thirty minutes after the induction of ischaemia, the ligature was removed and reperfusion allowed to occur for at least 60 min. M40403 (0.1-1 mg kg(-1)) was given intravenously 15 min before ischaemia. 3. The results obtained in this study showed that M40403 significantly reduced the extent of myocardial damage, mast cell degranulation and the incidence of ventricular arrhythmias. Furthermore, M40403 significantly attenuated, in a dose-dependent manner, neutrophil infiltration in the myocardium as well as the associated induction of lipid peroxidation. Calcium overload seen post-reperfusion of the ischaemic myocardium was also reduced by M40403. 4. Immunohistochemical analysis for nitrotyrosine revealed a positive staining in cardiac tissue taken after reperfusion: this was attenuated by M40403. Moreover reperfused cardiac tissue sections showed positive staining for P-selectin and for anti-intercellular adhesion molecule (ICAM-1) in the vascular endothelial cells. M40403 treatment markedly reduced the intensity and degree of P-selectin and ICAM-1 in these tissues. No staining for nitrotyrosine, P-selectin or ICAM-1 was found in cardiac tissue taken at the end of the ischaemic period. 5. Overall, M40403 treatment reduced the morphological signs of myocardial cell injury and significantly improved survival. 6. Taken together, these results clearly indicate that M40403 treatment exerts a protective effect against ischaemia-reperfusion-induced myocardial injury, supporting a key role for superoxide anion in reperfusion injuries. This suggests that synthetic enzymes of SOD such as M40403, offer a novel therapeutic approach for the treatment of ischaemic heart disease where superoxide anion plays a dominant role.

Nitric oxide production is maintained in exercising swine with chronic left ventricular dysfunction

Left ventricular (LV) dysfunction caused by myocardial infarction (MI) is accompanied by endothelial dysfunction, most notably a loss of nitric oxide (NO) availability. We tested the hypothesis that endothelial dysfunction contributes to impaired tissue perfusion during increased metabolic demands as produced by exercise, and we determined the contribution of NO to regulation of regional systemic, pulmonary, and coronary vasomotor tone in exercising swine with LV dysfunction produced by a 2- to 3-wk-old MI. LV dysfunction resulted in blunted systemic and coronary vasodilator responses to ATP, whereas the responses to nitroprusside were maintained. Exercise resulted in blunted systemic and pulmonary vasodilator responses in MI that resembled the vasodilator responses in normal (N) swine following blockade of NO synthase with N(omega)-nitro-L-arginine (L-NNA, 20 mg/kg iv). However, L-NNA resulted in similar decreases in systemic (43 +/- 3% in N swine and 49 +/- 4% in MI swine), pulmonary (45 +/- 5% in N swine and 49 +/- 4% in MI swine), and coronary (28 +/- 4% in N and 35 +/- 3% in MI) vascular conductances in N and MI swine under resting conditions; similar effects were observed during treadmill exercise. Selective inhibition of inducible NO synthase with aminoguanidine (20 mg/kg iv) had no effect on vascular tone in MI. These findings indicate that while agonist-induced vasodilation is already blunted early after myocardial infarction, the contribution of endothelial NO synthase-derived NO to regulation of vascular tone under basal conditions and during exercise is maintained.

Oxidative stress contributes to vascular endothelial dysfunction in heart failure

Congestive heart failure (HF) is characterized by inadequate nitric oxide (NO) production in the vasculature. Because NO is degraded by oxygen radicals, we hypothesized that NO is degraded faster in HF from inadequate peripheral arterial antioxidant reserves. HF was induced in male Sprague-Dawley rats by left coronary artery ligation. Vascular endothelial function was evaluated by measuring the NO-mediated vasorelaxation response to acetylcholine (ACh; 10(-9)-10(-4) M) in excised aortas. This was repeated with the free radical generator pyrogallol (20 microM) and again with pyrogallol and superoxide dismutase (SOD; 60 U/ml). Aortic and myocardial SOD activity was also determined. ACh-induced vasorelaxation was reduced in HF (n = 9) compared with normal control rats (n = 11; P < 0.001). Pyrogallol further reduced vasorelaxation in HF: 74 +/- 11% at 10(-4) M ACh versus 58 +/- 10% in normal control rats (P < 0.004). There was a trend (P = 0.06) toward reduced SOD activity in HF aortas. In conclusion, altered NO-dependent vasorelaxation in HF is in part due to excessive degradation of NO and is likely related to reduced vascular SOD activity.

Comparison of cardiac and regional hemodynamic responses to N-methyl-L-arginine and aminoguanidine infusions in conscious pigs

The aim of this study was to elucidate cardiac and regional hemodynamics using a nonspecific inhibitor of the constitutive and inducible nitric oxide synthase (NOS), N-methyl-L-arginine (L-NMA), and a specific inhibitor of the inducible NOS, aminoguanidine, in conscious pigs. Animals were divided into two groups. After hemodynamics were stabilized, animals in group 1 (n = 5) received an infusion of L-NMA at 300 microg/kg per min, i.v., over 60 min, and group 2 (n = 5) received an infusion of aminoguanidine, infused at 1 mg/kg per min over 60 min. Hemodynamic parameters including arterial blood pressure, heart rate, cardiac output, dP/dt, and carotid, coronary, hepatic, portal, mesenteric, and renal blood flows were continuously recorded before and 5, 15, 30, 45, 60, and 120 min after L-NMA infusion or aminoguanidine infusion, or both. The L-NMA vasopressor response (20%) was associated with a significant increase in systemic vascular resistance (45%). Carotid, hepatic, and renal vascular resistance increased significantly by 95%, 110%, and 20%, respectively, at 60 min after L-NMA infusion. Finally, heart rate, cardiac output, dP/dt, and portal and mesenteric blood flows remained unchanged after L-NMA infusion. In contrast, aminoguanidine infused at 1 mg/kg per min over 60 min did not change systemic arterial blood pressure or regional blood flow in conscious pigs. Furthermore, aminoguanidine had no effect on acetylcholine vasodilator effects. In conclusion, the lack of pressor effects and of agonist-stimulated NO production induced by aminoguanidine suggests that aminoguanidine is a weak inhibitor of the constitutive NOS. Compared with L-NMA, the selectivity of aminoguanidine may decrease possible side effects that could occur as a result of inhibition of constitutive NOS.

Vascular beta-adrenergic receptor system is dysfunctional after myocardial infarction

We identified abnormalities in the vascular beta-adrenergic receptor (beta-AR) signaling pathway in heart failure after myocardial infarction (MI). To examine these abnormalities, we measured beta-AR-mediated hemodynamics, vascular reactivity, and the vascular beta-AR molecular signaling components in rats with heart failure after MI. Six weeks after MI, these rats had an increased left ventricular (LV) end-diastolic pressure, decreased LV systolic pressure, and decreased rate of LV pressure change (dP/dt). LV dP/dt responses to isoproterenol were shifted downward, although the responses for systemic vascular resistance were shifted upward in heart failure rats (P < 0.05). Isoproterenol- and IBMX-induced vasorelaxations were blunted in heart failure rats (P < 0.05) with no change in the forskolin-mediated vasorelaxation. These changes were associated with the following alterations in beta-AR signaling (P < 0.05): decreases in beta-AR density (aorta: 58.7 +/- 6.0 vs. 35.7 +/- 1.9 fmol/mg membrane protein; carotid: 29.6 +/- 5.6 vs. 18.0 +/- 3.9 fmol/mg membrane protein, n = 5), increases in G protein-coupled receptor kinase activity levels (relative phosphorimage counts of 191 +/- 39 vs. 259 +/- 26 in the aorta and 115 +/- 30 vs. 202 +/- 7 in the carotid artery, n = 5), and decreases in cGMP and cAMP in the carotid artery (0.85 +/- 0.10 vs. 0.31 +/- 0.06 pmol/mg protein and 2.3 +/- 0.3 vs. 1.2 +/- 0.1 pmol/mg protein, n = 5) with no change in Galpha(s) or Galpha(i )in the aorta. Thus in heart failure there are abnormalities in the vascular beta-AR system that are similar to those seen in the myocardium. This suggests a common neurohormonal mechanism and raises the possibility that treatment in heart failure focused on the myocardium may also affect the vasculature.

Gene transfer of endothelial nitric oxide isoform decreases rat hindlimb vascular resistance in vivo

The objective of this study was to design a methodology of gene transfer into a resistance vascular bed and to show if such a method can be used to examine the physiological function of a given gene product in vivo. We developed such a method and validated it by defining the role in vivo of endothelial nitric oxide synthase (eNOS). In a constant flow perfused rat hindlimb, gene transfer to the vascular endothelium was accomplished by incubating a "first-generation" serotype 5, replication-deficient, adenoviral vector (1.2 X 10(9) plaque-forming units/ml) containing cDNA encoding either the eNOS or the beta-galactosidase (beta-Gal) gene in the hindlimb vasculature for 30 min. Five days after infection, immunohistochemical staining for eNOS localized recombinant gene expression to vascular endothelial cells and eNOS protein levels were increased fourfold (11.9 +/- 6.6 vs. 2.9 +/- 1.3 intensity units/microg protein, n = 4, p < 0.05). Perfusion pressures were measured at different flow rates (10-50 ml/min). In addition, basal and acetylcholine (ACh)-stimulated vascular resistance (VR) in phenylephrine (PE)-precontracted (100 microM) hindlimb was measured at constant flow. There were flow-dependent increases (p < 0.05) in perfusion pressure. Overexpression of eNOS shifted the pressure-flow curve downward and administration of N(G)-nitro-L-arginine methyl ester (L-NAME) shifted the curve upward. Compared with beta-Gal-transfected rats, PE-induced VR decreased (p < 0.05) in eNOS-transfected rats (100 +/- 27 vs. 164 +/- 49 mmHg, n = 5). Addition of 100 microM L-NAME increased (p < 0.05) PE-induced VR in both eNOS-transfected and control rats (145 +/- 50 and 232 +/- 38 mmHg, n = 5, p < 0.05), respectively, which was partially abolished by L-arginine pretreatment. ACh-induced vasorelaxation was increased 45% (p < 0.05) in eNOS-transfected hindlimbs. L-NAME decreased (p < 0.05) ACh-induced vasorelaxation by 58% in eNOS-transfected hindlimbs versus 25% in beta-Gal-transfected hindlimbs (p < 0.05). We used this gene transfer method to examine the physiological function of a gene product in vivo and showed that (1) the flow-pressure relationship in the hindlimb vascular bed is NO dependent and (2) the eNOS enzyme modulates NO-mediated vasorelaxation in the rat hindlimb resistance arteries in vivo.