Effect of Angiotensin 1-7 Peptide Agonist AVE 0991 on Diabetic Endothelial Dysfunction in an Experimental Animal Model: A Possible Tool to Treat Diabetic Erectile Dysfunction.

Background The renin-angiotensin system and its metabolites are crucial in the pathogenesis and progression of complications of diabetes. Aim In this study, we aimed to evaluate the effect of angiotensin 1-7 non-peptide agonist AVE 0991 (576 ug/kg/day i.p.) on diabetic endothelial dysfunction. Materials and methods In this experimental animal study, we investigated the effects of angiotensin 1-7 non-peptide agonist AVE 0991 (576 ug/kg/day i.p.) treatment in male Wistar rats. Diabetes was created via injecting streptozotocin (55 mg/kg/i.p., single dose). Following the cavernous tissue submaximal phenylephrine contraction, relaxation responses were obtained by applying electrical field stimulation (0.5 ms, 40 V) for 15 seconds at 2, 4, 8, 16, 32, and 64 Hz, with two-minute intervals, respectively. To evaluate the effect of nitric oxide, the responses were compared by incubating with 100 mM N(gamma)-nitro-L-arginine methyl ester (L-NAME) for 20 minutes. Additionally, Y-27632 and sodium nitroprusside responses were evaluated in tissues contracted with submaximal doses of phenylephrine. Results Following a submaximal contraction of phenylephrine in the aorta rings, relaxation responses obtained with acetylcholine, sodium nitroprusside, and Y-27632 were impaired in diabetic rats; however, significant results were obtained with treatment. Although there was no significance between the groups in the electrical field stimulation responses, there was a significant dose-dependent difference in the treatment group in this parameter after L-NAME, sodium nitroprusside, and Y-27632 relaxation. Conclusions We determined that treatment with a non-peptide receptor antagonist of angiotensin 1-7, an enzyme detected in the aortic and cavernosum endothelium, may be a promising alternative for treating the complications of diabetes.

Evaluation of the effect of intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc radiotherapy (VMAT) techniques on survival response in cell lines with a new radiobiological modeling.

BACKGROUND: The optimal radiobiological model, which assesses the biological effects of novel radiotherapy techniques that concurrently modify multiple physical factors, has not yet been defined. This study aimed to investigate the impact of intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) on cellular response in head and neck cancer and melanoma models. METHODS: Clonogenic analysis, DNA double-strand break analysis, apoptosis, and cell cycle analysis were performed on cancer stem cell models, cancer models, and normal tissue cell models to assess radiation sensitivity. RESULTS: The segmented radiation approach used in IMRT applications enhanced radiosensitivity and cytotoxicity in the cancer models, while changes in dose rate had varying effects on cytotoxicity depending on the tumor cell type. VMAT increased cellular resistance, favoring treatment outcomes. CONCLUSIONS: The biological processes were influenced differently by dose rate, IMRT, and VMAT depending on the tumor cell type. The selection of the most appropriate technique is crucial in representing new radiotherapy approaches. The obtained data can serve as a model to address clinical questions in daily practice. The integration of non-standard outcomes with standard applications should be considered in clinical settings.

Urotensin receptor antagonist palosuran attenuates cyclosporine-a-induced nephrotoxicity in rats.

BACKGROUND: Cyclosporine-A (CsA) is widely used for immunosuppressive therapy in renal transplantation. Nephrotoxicity is the main dose-limiting undesirable consequence of CsA. Urotensin II (U-II), a novel peptide with a powerful influence on vascular biology, has been added to the list of potential renal vascular regulators. Upregulation of the urotensin receptors and elevation of plasma U-II levels are thought to possibly play a role in the etiology of renal failure. OBJECTIVES: The present study examines this hypothesis by evaluating renal function and histology with regard to the potential role of U-II and its antagonist, palosuran, in the pathogenesis of CsA-induced nephrotoxicity in rats. MATERIAL AND METHODS: Male Sprague-Dawley rats were treated with CsA (15 mg/kg, for 21 days, intraperitoneally) or CsA + palosuran (300 mg/kg, for 21 days). Renal function was measured and histopathology, U-II immunostaining and protein detection with western blotting of the kidneys were performed. RESULTS: Cyclosporine-A administration caused a marked decline in creatinine clearance (Ccr). Fractional sodium excretion (FENa) tended to increase in the CsA-treated rats. Plasma U-II levels decreased in the CsA-treated rats. Cyclosporine-A treatment resulted in a marked deterioration in renal histology and an increase in the expression of U-II protein in the kidneys. Palosuran's improvement of renal function manifested as a significant decrease in serum creatinine levels and a significant increase in urine creatinine levels, resulting in a marked increase in Ccr. Palosuran produced a significant normalization of kidney histology and prevented an increase in U-II expression. CONCLUSIONS: Cyclosporine-A-induced renal impairment was accompanied by an increase in U-II expression in kidneys and a contrary decrease in systemic U-II levels. Palosuran improved the condition of rats suffering from renal dysfunction by preventing the decrease in renal U-II expression without affecting the systemic levels of U-II. The protective effect of palosuran in CsA nephrotoxicity is possibly independent of its U-II receptor antagonism.

Treatment with NADPH oxidase inhibitor apocynin alleviates diabetic neuropathic pain in rats.

Increased reactive oxygen species by the activation of NADPH oxidase (NOX) contributes to the development of diabetic complications. Apocynin, a NOX inhibitor, increases sciatic nerve conductance and blood flow in diabetic rats. We investigated potential protective effect of apocynin in rat diabetic neuropathy and its precise mechanism of action at molecular level. Rat models of streptozotocin-induced diabetes were treated with apocynin (30 and 100 mg/kg per day, intragastrically) for 4 weeks. Mechanical hyperalgesia and allodynia were determined weekly using analgesimeter and dynamic plantar aesthesiometer. Western blot analysis and histochemistry/immunohistochemistry were performed in the lumbar spinal cord and sciatic nerve respectively. Streptozotocin injection reduced pain threshold in analgesimeter, but not in aesthesiometer. Apocynin treatment increased pain threshold dose-dependently. Western blot analysis showed an increase in catalase and NOX-p47phox protein expression in the spinal cord. However, protein expressions of neuronal and inducible nitric oxide synthase (nNOS, iNOS), superoxide dismutase, glutathion peroxidase, nitrotyrosine, tumor necrosis factor-α, interleukin-6, interleukin-1ß, aldose reductase, cyclooxygenase-2 or MAC-1 (marker for increased microgliosis) in the spinal cord remained unchanged. Western blot analysis results also demonstrated that apocynin decreased NOX-p47phox expression at both doses and catalase expression at 100 mg/kg per day. Histochemistry of diabetic sciatic nerve revealed marked degeneration. nNOS and iNOS immunoreactivities were increased, while S-100 immunoreactivity (Schwann cell marker) was decreased in sciatic nerve. Apocynin treatment reversed these changes dose-dependently. In conclusion, decreased pain threshold of diabetic rats was accompanied by increased NOX and catalase expression in the spinal cord and increased degeneration in the sciatic nerve characterized by increased NOS expression and Schwann cell loss. Apocynin treatment attenuates neuropathic pain by decelerating the increased oxidative stress-mediated pathogenesis in diabetic rats.

The effect of platelet-rich plasma on motility changes in experimental caustic esophageal burn.

BACKGROUND: Besides stricture formation, diminished esophageal motility after caustic esophageal burns also plays a role in the deterioration of the clinical course. In this study, we aimed to investigate the effect of caustic burn on the esophageal contractions and the effect of platelet-rich plasma (PRP) on these changes. METHODS: Twenty-one Wistar albino rats were divided into three groups [Sham operation (n = 8), caustic esophageal burn with NaOH (n = 6), PRP treatment after caustic burn (n = 7)]. After 3 weeks, esophagectomy was performed and contractions and EFS responses were evaluated in the organ bath. RESULTS: KCl- and acetylcholine-induced responses were reduced in the Burn group, but increased in Sham and PRP groups (p < 0.05). EFS responses were higher in Burn group compared to the other groups. Response with L-arginine was increased in Burn group, but decreased in PRP group. There was more decrease in the contraction in Sham and PRP groups compared to the Burn group after SNP (sodium nitroprusside) incubation (p < 0.05). L-NAME (Nω-Nitro-L-arginine methyl ester) did not change the EFS responses in the Burn group, but EFS responses were decreased significantly in Sham and PRP groups (p < 0.05). EFS responses were decreased in all groups, but more in the Sham and PRP groups after Y-27632 (Rho-kinase inhibitor) incubation (p < 0.05). CONCLUSIONS: For the first time, we demonstrated that both cholinergic and non-adrenergic non-cholinergic mechanisms are responsible for the altered motility in corrosive esophageal injury. Our results suggest that PRP treatment may be helpful in regulating the esophageal motility and decreasing altered contractions in corrosive burns. This effect may also contribute to the reduction of stricture formation, especially by reducing inappropriate contractions of the esophageal wall during the post-burn healing phase.

Esophageal Epithelial Resistance and Lower Esophageal Sphincter Muscle Contraction Increase in a Chronic Diabetic Rabbit Model.

BACKGROUND: Esophageal motility disorders and possibly gastroesophageal reflux disease are common in patients with diabetes mellitus. AIMS: We aimed to investigate both the electrophysiological characteristics of the esophageal epithelium and the contractility of the lower esophageal sphincter (LES) muscle in alloxane-induced diabetic rabbits. METHODS: Electrophysiological properties were measured using an Ussing chamber method. An acid-pepsin model was employed with pH 1.7 or weakly acidic (pH 4) Ringer and/or pepsin. Smooth muscle strips of the LES were mounted in an isolated organ bath. Contractile responses to an electrical field stimulation and cumulative concentrations of acetylcholine were recorded. Contractility of the muscle strips were tested in the presence of Rho-kinase inhibitor (Y-27632) and nonspecific nitric oxide inhibitor (L-NAME). RESULTS: The resistance of diabetic tissue perfused in the pH 1.7 Ringer decreased 17 %; pepsin addition decreased it by 49 %. The same concentrations caused a more distinct loss of resistance in the control tissues (22 and 76 %, p < 0.05). The perfusion of tissues in increased concentrations of luminal and serosal glucose did not change the tissue resistance and voltage. Diabetes significantly increased both the electrical field stimulation and acetylcholine-induced contractions in the LES muscle strips (p < 0.01). Incubation with Y-27632 significantly decreased the acetylcholine-induced contractions in a concentration-dependent manner (p < 0.01). CONCLUSIONS: The acid-pepsin model in the diabetic rabbit esophageal tissue had less injury compared with the control. The diabetic rabbit LES muscle had higher contractility, possibly because of the activation of the Rho-Rhokinase pathway. Our results show that in a chronic diabetic rabbit model the esophagus resists reflux by activating mechanisms of mucosal defense and increasing the contractility of the LES.

Role of digoxin-like immunoreactive substance in the pathogenesis of transient tachypnea of newborn.

BACKGROUND: Transient tachypnea of newborn (TTN) is usually observed in term or near-term infants. It constitutes an important part of the respiratory distress cases observed in the neonatal intensive care unit (NICU). AIM: This paper examines the effects of digoxin-like immunoreactive substance (DLIS) on fluid and ion balance, hemodynamic and echocardiographic parameters of neonates with TTN. METHODS: Plasma DLIS, Na(+), K(+), urea, creatinine, serum and urine osmolarity, urine FeNa(+), 24-hour urine output, echocardiographic investigation and mean blood pressure, and clinical parameters of disease severity were recorded in TTN group and compared with control on the 1st and 7th days of their lives. RESULTS: Plasma DLIS levels were statistically higher in TTN group (0.66 ± 0.37 ng/mL) compared to control group (0.24 ± 0.20 ng/mL) both on the 1st day (P < 0.01) and the 7th day (P < 0.05). For TTN group, significant correlation was found between plasma DLIS levels and maximum respiratory rate, duration of tachypnea, and length of hospitalization on the 1st day. Plasma DLIS levels were correlated negatively with serum osmolarity levels. Plasma DLIS levels were positively correlated with urine output, urinary FeNa(+) levels, cardiac output, left ventricles end diastolic diameters, and right ventricles end diastolic diameters. CONCLUSIONS: Increased DLIS levels were correlated with disease severity in cases with TTN. This increase may be a primary or secondary event in the disease progress. It may help reduce the fluid overload due to already disturbed cardiac functions in patients by increasing urine output and natriuresis; however it may also contribute to disease pathogenesis, by inhibiting alveolar Na(+)-K(+)-ATPase which further decreases fetal alveolar fluid resorption.

The effects of vitamin d on gentamicin-induced acute kidney injury in experimental rat model.

Introduction. Acute kidney injury (AKI) pathogenesis is complex. Findings of gentamicin nephrotoxicity are seen in 30% of the AKI patients. Vitamin D has proven to be effective on renin expression, inflammatory response, oxidative stress, apoptosis, and atherosclerosis. We aimed to investigate the effect of vitamin D in an experimental rat model of gentamicin-induced AKI. Methods. Thirty nonuremic Wistar albino rats were divided into 3 groups: Control group, 1 mL saline intramuscular (im) daily; Genta group, gentamicin 100 mg/kg/day (im); Genta + vitamin D, gentamicin 100 mg/kg/day (im) in addition to 1 α , 25 (OH)2D3 0.4 mcg/kg/day subcutaneously for 8 days. Blood pressures and 24-hour urine were measured. Blood urea and creatinine levels and urine tubular injury markers were measured. Renal histology was semiquantitatively assessed. Results. Urea, creatinine and urine neutrophil gelatinase-associated lipocalin, and kidney injury molecule-1 were all increased in Genta group indicating AKI model. Systolic blood pressure decreased, but urine volume and glutathione increased in Genta + Vit D group compared to Control group. Histological scores indicating tubular injury increased in Genta and Genta + Vit D groups. Conclusions. Vitamin D does not seem to be effective on histological findings although it has some beneficial effects via RAS system and a promising effect on antioxidant system.

Resveratrol attenuates doxorubicin-induced cellular damage by modulating nitric oxide and apoptosis.

Although doxorubicin (DOX) is a commonly used chemotherapeutic agent its clinical use is restricted due to its organ toxicities. The present investigation relates to reducing DOX induced side effects to the liver, kidney and ileum by usage of the antioxidant, anti-inflammatory agent, resveratrol (RES) and to investigate the role of nitric oxide synthase (NOS) in the process. Wistar rats were divided into four groups: control (saline i.p); DOX (20 mg/kg i.p), RES (20 mg/kg i.p) and DOX (20mg/kg i.p)+RES (20 mg/kg i.p). Immunohistochemical activity of both iNOS and eNOS were evaluated after DOX treatment and ultrastructural changes such as cellular damage and mitochondrial degeneration were evaluated. Degenerative ultrastructural changes were demonstrated especially in the DOX treated group. Variations in biochemical marker levels of oxidative stress on ischemia in tissues were not observed. Our data indicate that RES may prevent cellular damage in the early phase of DOX induced toxicity. RES could be used with its beneficial effects during early cellular damage in organ toxicity after DOX treatment in cancer patients.

Effect Of G2706A and G1051A polymorphisms of the ABCA1 gene on the lipid, oxidative stress and homocystein levels in Turkish patients with polycystic ovary syndrome.

BACKGROUND: Obesity, insulin resistance and hyperandrogenism, crucial parameters of Polycystic ovary syndrome (PCOS) play significant pathophysiological roles in lipidemic aberrations associated within the syndrome. Parts of the metabolic syndrome (low HDL and insulin resistance) appeared to facilitate the association between PCOS and coronary artery disease, independently of obesity. ABCA1 gene polymorphism may be altered this components in PCOS patients.In this study, we studied 98 PCOS patients and 93 healthy controls. All subjects underwent venous blood drawing for complete hormonal assays, lipid profile, glucose, insulin, malondialdehyde, nitric oxide, disulfide levels and ABCA genetic study. RESULTS: In PCOS group fasting glucose, DHEAS, 17-OHP, free testosterone, total-cholesterol, triglyceride, LDL-cholesterol and fibrinogen were significantly different compare to controls. The genotype ABCA G2706A distribution differed between the control group (GG 60.7%, GA 32.1%, AA 7.1%) and the PCOS patients (GG 8.7%, GA 8.7%, AA 76.8%). The frequency of the A allele (ABCAG2706A) was higher in PCOS patients than control group with 13,0% and 23,2%, respectively. In this study, the homocystein and insulin levels were significantly higher in PCOS patients with ABCA G1051A mutant genotype than those with heterozygote and wild genotypes. CONCLUSIONS: We found higher percentage of AA genotype and A allele of ABCA G2706A in PCOS patients compare to controls. The fasting insulin and homocystein levels were significantly higher in PCOS patients with ABCA G1051A mutant genotype than those with heterozygote and wild genotypes.

Methylenetetrahydrofolate reductase C677T gene polymorphism in Turkish patients with polycystic ovary syndrome.

Higher Levels of Hcy are associated with several clinical conditions, among them non-insulin-dependent diabetes mellitus, endometrial dysplasia and hypertension with insulin resistance, and polycystic ovary syndrome. The purpose of this study was to investigate the serum homocystein levels and other metabolic parameters in relationship with the MTHFR C677T gene polymorphism in patients with PCOS. Our study included 86 young women with PCOS constituting the study group and 70 healthy women constituting the control group. Homocystein levels, metabolic, and hormonal parameters were measured, and genetic analysis of the MTHFR C677T gene polymorphism was performed in all the subjects. A statistically significant difference was observed in mean homocystein levels between patients with PCOS when compared to the control group. The MTHFR 677 CC genotypes had significantly higher proportions in the control group compared to the PCOS patients (χ(2) = 21.381, P < 0.001). Our data show that homocystein levels were higher than normal subjects in patients with PCOS and that the MTHFR C677T gene polymorphism does not influence homocystein levels of patients with PCOS.

Apocynin restores endothelial dysfunction in streptozotocin diabetic rats through regulation of nitric oxide synthase and NADPH oxidase expressions.

AIM: Increased production of reactive oxygen species (ROS) in the diabetic vasculature results in the impairment of nitric oxide (NO)-mediated relaxations leading to impaired endothelium-dependent vasodilation. An important source of ROS is nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, and the inhibition of this enzyme is an active area of interest. This study aimed to investigate the effects of apocynin, an NADPH oxidase inhibitor, on endothelial dysfunction and on the expression of NO synthase (NOS) and NADPH oxidase in thoracic aorta of diabetic rats. METHOD: Streptozotocin (STZ)-diabetic rats received apocynin (16 mg/kg per day) for 4 weeks. Endothelium-dependent and -independent relaxations were determined in thoracic aortic rings. Western blotting and RT-PCR analysis were performed for NOSs and NADPH oxidase in the aortic tissue. RESULTS: Acetylcholine-induced relaxations and l-NAME-induced contractions were decreased in diabetic aorta. The decrease in acetylcholine and l-NAME responses were prevented by apocynin treatment without a significant change in plasma glucose levels. Endothelial NOS (eNOS) protein and mRNA expression exhibited significant decrease in diabetes, while protein and/or mRNA expressions of inducible NOS (iNOS) as well as p22(phox) and gp91(phox) subunits of NADPH oxidase were increased, and these alterations were markedly prevented by apocynin treatment. CONCLUSION: NADPH oxidase expression is increased in diabetic rat aorta. NADPH oxidase-mediated oxidative stress is accompanied by the decreased eNOS and increased iNOS expressions, contributing to endothelial dysfunction. Apocynin effectively prevents the increased NADPH oxidase expression in diabetic aorta and restores the alterations in NOS expression, blocking the vicious cycle leading to diabetes-associated endothelial dysfunction.

Fenofibrate treatment enhances antioxidant status and attenuates endothelial dysfunction in streptozotocin-induced diabetic rats.

Diabetic endothelial dysfunction is accompanied by increased oxidative stress and upregulated proinflammatory and inflammatory mediators in the vasculature. Activation of peroxisome proliferator-activated receptor-alpha (PPAR-α) results in antioxidant and anti-inflammatory effects. This study was designed to investigate the effect of fenofibrate, a PPAR-α activator, on the endothelial dysfunction, oxidative stress, and inflammation in streptozotocin diabetic rats. Diabetic rats received fenofibrate (150 mg kg(-1) day(-1)) for 4 weeks. Fenofibrate treatment restored the impaired endothelium-dependent relaxation and increased basal nitric oxide availability in diabetic aorta, enhanced erythrocyte/liver superoxide dismutase and catalase levels, ameliorated the abnormal serum/aortic thiobarbituric acid reactive substances, and prevented the increased aortic myeloperoxidase without a significant change in serum total cholesterol and triglyceride levels. It did not affect the decreased total homocysteine level and the increased tumor necrosis factor-α level in the serum of diabetic rats. Fenofibrate-induced prevention of the endothelial function seems to be related to its potential antioxidant and antiinflammatory activity.

Effect of ascorbic Acid on incisional wound healing in streptozotocin-induced diabetic rats.

UNLABELLED: Abstract: Background. Abdominal wall repair after celiotomy is important because insufficient incisional wound strength results in wound failures such as fascial dehiscence and herniation. Ascorbic acid has been shown to play an important role in wound healing. The purpose of this study was to investigate whether ascorbic acid improves incisional wound healing in a diabetic rat. METHODS: Male Wistar-Albino streptozosin-induced diabetic rats (n = 20) were divided into two groups: control group (CG; n = 10), and daily 200 mg/kg ascorbic acid (study group, [SG], n = 10) given orally. Ten animals from each group were euthanized on postoperative day (POD) 14 after wounding; breaking strength, histologic examination, and tissue hydroxyproline levels were analyzed. RESULTS: The hydroxyproline tissue content of the abdominal fascia in the ascorbic acid treatment group was superior to the control group, and the difference was statistically significant (P < 0.05). The tensiometric analyses revealed that tensile strength for the midline incision was significantly higher in the study group compared to the control group (P < 0.05). Significant differences were found in the results of histologic examination of tissue specimens between the two groups regarding acute inflammation, chronic inflammation, granulation tissue fibroblast maturation, collagen deposition, and neovascularization on POD 14 (P < 0.05). CONCLUSION: The present study demonstrates that administration of ascorbic acid prior to laparotomy expedites wound healing in a rat. On the contrary, we suggest that it could confer benefits to tissue healing by significantly enhancing tissue hydroxyproline levels, neovascularization, fibroblast maturation, and collagen deposition.

Reversal of doxorubicin-induced vascular dysfunction by resveratrol in rat thoracic aorta: Is there a possible role of nitric oxide synthase inhibition?

OBJECTIVE: The natural antioxidant, resveratrol has been suggested to protect against doxorubicin-induced cardiotoxicity. Although derangements in nitric oxide (NO) synthesis contribute to vascular endothelial dysfunction caused by doxorubicin, the effects of resveratrol on these parameters have not been evaluated yet. We investigated the impact of resveratrol on doxorubicin-induced vascular dysfunction in rat thoracic aorta with regard to NO synthesis in an experimental, prospective, controlled study. METHODS: Wistar rats were assigned to 5 groups; doxorubicin (n=9), vehicle (dimethylsulphoxide) (n=8), resveratrol (n=8), doxorubicin+resveratrol (n=10), controls (n=9). Contractile and relaxant responses were evaluated on the isolated thoracic aortas. The expressions of endothelial (eNOS) and inducible (iNOS) isoforms of NO-synthase were also examined histopathologically on the aortas. Statistical analysis was performed by ANOVA for repeated measures for the response curves and one-way ANOVA for the pD2 (-log EC50) and Emax (maximum phenylephrine contraction) values with subsequent Bonferroni test. RESULTS: Doxorubicin (20 mg/kg, i.p), not only decreased the contractile responses to phenylephrine (p<0.001), but also attenuated the relaxant responses to acetylcholine (ACh) (p=0.002), calcium ionophore (A23187) (p=0.002) and sodium nitroprusside (SNP) (p=0.007). Immunohistochemistry revealed increased (p<0.05) eNOS and iNOS protein expressions after doxorubicin treatment. Coadministration of resveratrol (10 mg/kg/i.p.) reversed the increased expression of both NOS isoforms (p<0.05). Similarly, it prevented the doxorubicin-induced attenuation in ACh- (p=0.013) and A23187- (p=0.038) induced responses. In healthy rats the antioxidant did not cause significant changes. CONCLUSION: Prevention of excessive NO formation through eNOS and iNOS overexpression by resveratrol might contribute to the reversal of vascular endothelial dysfunction associated with doxorubicin treatment.

Therapeutic concentrations of tacrolimus do not interfere with endothelial nitric oxide synthesis in rat thoracic aortas and coronary arteries.

This study aimed to investigate the potential effect of in vivo administration of immunosuppressive agent FK-506 (tacrolimus) on the endothelial function of rat thoracic aortas with respect to nitric oxide (NO) synthesis. In vitro effect of the drug on NO synthesis in cultured rat coronary microvascular endothelial cells (CMEC) was also studied.In vivo administration of tacrolimus (1 mg/kg/d, intramuscular) to rats for 14 days resulted in decreased relaxant responses to the higher concentrations (1 to 30 muM) of acetylcholine in the aortas; however, responses to calcium ionophore A23187, sodium nitroprusside, L-arginine, and L-NAME did not change significantly. No changes were observed in phenylephrine-induced contractions in endothelium-denuded or -intact preparations. Administration of the vehicle for 14 days did not affect these parameters. In order to evaluate the in vitro effect of tacrolimus on NO release, CMEC isolated from rat hearts were incubated with either tacrolimus (0.01, 0.1 microM) or the vehicle. Basal, calcium ionophore-stimulated, or interleukin-1 beta-induced NO synthesis was determined by measuring total nitrite in the media. Neither tacrolimus nor the vehicle changed nitrite accumulation. It has been concluded that therapeutic concentrations of tacrolimus do not alter NO production in rat thoracic aorta or cultured CMEC; however, it impairs relaxant responses of rat aorta induced by higher concentrations of acetylcholine, possibly through changes in the downstream of receptor activation or through an imbalance between endothelium-dependent relaxant and contracting factors within the endothelium in favor of the contracting factor(s).

Effect of homocysteine on nitric oxide production in coronary microvascular endothelial cells.

Hyperhomocysteinemia is widely recognized as an independent risk factor for coronary artery vascular disease, although the underlying mechanisms are not well understood. This study aims to investigate the effect of homocysteine on nitric oxide (NO) production in coronary microvascular endothelial cells (CMECs) and putative mechanisms mediating this effect. CMECs were isolated on Langendorff system by collagenase perfusion of hearts from male rats and cultured. The effect of homocysteine (0.01 to 1 mM) on basal and stimulated NO production was evaluated by measuring nitrite in the culture media after incubation with or without N(G)-nitro-L-arginine methyl ester (L-NAME) (1 mM), superoxide dismutase (100 U/mL), or catalase (1000 U/mL) for 24 h. Total nitrite was measured using Griess reaction after reduction of nitrate to nitrite with nitrate reductase. Homocysteine did not affect basal nitrite accumulation; however, it significantly increased the nitrite accumulation induced by the calcium ionophore A23187 or interleukin-1beta only at 1 mM. This effect of homocysteine was significantly inhibited by L-NAME, superoxide dismutase, and catalase. In conclusion, homocysteine increases NO release from stimulated CMECs without affecting basal NO production, which is probably accompanied by increased production of reactive oxygen species. It can be postulated that endothelial cells generate NO in order to minimize the damage caused by homocysteine.

Acute myocardial infarction following an arthropod bite: is hereditary thrombophilia a contributing factor?

Acute myocardial infarction (AMI) due to arthropod envenomation has rarely been reported in the literature. In the present report, we describe two cases who developed AMI following an arthropod bite. Coronary angiograms revealed normal coronary arteries in both patients. Both events were probably secondary to coronary artery thrombosis and/or coronary artery vasospasm. Both patients were subsequently found to be heterozygous for prothrombin mutation (G20210A). As a result, we recommend ruling out the possibility of hereditary thrombophilias in young patients with AMI developing after an arthropod bite.

Effect of vitamin E and C supplementation combined with oral antidiabetic therapy on the endothelial dysfunction in the neonatally streptozotocin injected diabetic rat.

BACKGROUND: This study investigates the contribution of vitamin supplementation to the efficacy of oral antidiabetic therapy on the reversal of endothelial dysfunction in a model of type-2 diabetes in rat. METHODS: Diabetes was induced by streptozotocin injection to neonatal rats which were breastfed for 4 weeks, then fed 6 weeks with normal food or food supplemented with 2% vitamin E and 4% vitamin C. Some diabetic rats were treated with gliclazide for 6 weeks. Endothelium-dependent and -independent relaxations to acetylcholine and sodium nitroprusside (SNP) were recorded in thoracic aortic rings. Plasma insulin, HbA(1c) and antioxidant vitamins (A, C and E); plasma and aortic malondialdehyde (MDA) levels were determined. RESULTS: Induction of diabetes resulted in decreased body weight and increased blood glucose, plasma insulin and HbA(1c) levels compared to controls. Acetylcholine relaxation was impaired in diabetic aorta, while SNP relaxation remained unchanged. Aortic MDA level was significantly higher, while plasma vitamin levels were lower in diabetic rats. Diminished acetylcholine response, enhanced aortic MDA level and decreased plasma vitamin levels were all restored after gliclazide and/or vitamin therapy. However, vitamin supplementation in control rats significantly impaired acetylcholine relaxations and increased aortic MDA levels. CONCLUSIONS: Apparently, a selective endothelial dysfunction accompanies the imbalance in oxidant/antioxidant status in the type-2 diabetes model of rat and gliclazide and/or vitamin supplementation improves the impairment in diabetic vasculature. However, vitamin supplementation triggers oxidative stress in normal aortic tissue, thereby, leads to endothelial dysfunction; indicating that nutritional extra-supplementation of antioxidant vitamins isn't advisable for normal subjects, although it's beneficial in disease status.