The effect of long term nicotine exposure on endothelial function in rats.

Nicotine is one of the main chemicals in the cigarettes responsible for addiction formation. Many researches investigating the effects of nicotine on coronary heart disease and atherosclerosis have been published. The robustness of endothelial cells is very important in the development of atherosclerosis. The aim of this study is to evaluate the effect of nicotine exposure on the indicators of endothelial function either by examining the vascular reactivity of aorta taken from rats exposed to nicotine during prenatal (starting by the mating period) and postnatal periods (6 weeks after delivery), or by determining the protein expression of nitric oxide synthase (NOS) enzymes, NADPH oxidase (Nox) and nitrotyrosine. Chronic nicotine exposure at 6 mg/L in drinking water produced a significant decrease in phenylephrine contractility of thoracic aortic rings compared to control and low dose exposure group (0.4 mg/L, p < 0.001). Endothelium-dependent relaxations to acetylcholine increased dose-dependently while no changes were observed in endothelium-independent relaxations to sodium nitroprusside and protein expressions in rat thoracic aorta. It has been concluded that long term nicotine exposure does not have serious effects on endothelial vasodilator response directly and does not change protein expression of NOS or Nox enzymes. However, more studies should be done for the exact mechanisms responsible for the effect of nicotine on endothelial function.

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.

Effects of cyanocobalamin and its combination with morphine on neuropathic rats and the relationship between these effects and thrombospondin-4 expression.

BACKGROUND: Thrombospondin-4 (TSP4) upregulates in the spinal cord following peripheral nerve injury and contributes to the development of neuropathic pain (NP). We investigated the effects of cyanocobalamin alone or in combination with morphine on pain and the relationship between these effects and spinal TSP4 expression in neuropathic rats. METHODS: NP was induced by chronic constriction injury (CCI) of the sciatic nerve. Cyanocobalamin (5 and 10 mg/kg/day) was administered 15 days before CCI and then for 4 and 14 postoperative days. Morphine (2.5 and 5 mg/kg/day) was administered only post-CCI. Combination treatment included cyanocobalamin and morphine, 10 and 5 mg/kg/day, respectively. All drugs were administered intraperitoneally. Nociceptive thresholds were detected by esthesiometer, analgesia meter, and plantar test, and TSP4 expression was assessed by western blotting and fluorescence immunohistochemistry. RESULTS: CCI decreased nociceptive thresholds in all tests and induced TSP4 expression on the 4th postoperative day. The decrease in nociceptive thresholds persisted except for the plantar test, and the increased TSP4 expression reversed on the 14th postoperative day. Cyanocobalamin and low-dose morphine alone did not produce any antinociceptive effects. High-dose morphine improved the decreased nociceptive thresholds in the esthesiometer when administered alone but combined with cyanocobalamin in all tests. Cyanocobalamin and morphine significantly induced TSP4 expression when administered alone in both doses for 4 or 14 days. However, this increase was less when the two drugs are combined. CONCLUSIONS: The combination of cyanocobalamin and morphine is more effective in antinociception and partially decreased the induced TSP4 expression compared to the use of either drug alone.

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.

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.

Neuroprotective effects of melatonin upon the offspring cerebellar cortex in the rat model of BCNU-induced cortical dysplasia.

Cortical dysplasia is a malformation characterized by defects in proliferation, migration and maturation. This study was designed to evaluate the alterations in offspring rat cerebellum induced by maternal exposure to carmustine-[1,3-bis (2-chloroethyl)-1-nitrosoure] (BCNU) and to investigate the effects of exogenous melatonin upon cerebellar BCNU-induced cortical dysplasia, using histological and biochemical analyses. Pregnant Wistar rats were assigned to five groups: intact-control, saline-control, melatonin-treated, BCNU-exposed and BCNU-exposed plus melatonin. Rats were exposed to BCNU on embryonic day 15 and melatonin was given until delivery. Immuno/histochemistry and electron microscopy were carried out on the offspring cerebellum, and levels of malondialdehyde and superoxide dismutase were determined. Histopathologically, typical findings were observed in the cerebella from the control groups, but the findings consistent with early embryonic development were noted in BCNU-exposed cortical dysplasia group. There was a marked increase in the number of TUNEL positive cells and nestin positive cells in BCNU-exposed group, but a decreased immunoreactivity to glial fibrillary acidic protein, synaptophysin and transforming growth factor beta1 was observed, indicating a delayed maturation, and melatonin significantly reversed these changes. Malondialdehyde level in BCNU-exposed group was higher than those in control groups and melatonin decreased malondialdehyde levels in BCNU group (P<0.01), while there were no significant differences in the superoxide dismutase levels between these groups. These data suggest that exposure of animals to BCNU during pregnancy leads to delayed maturation of offspring cerebellum and melatonin protects the cerebellum against the effects of BCNU.

Milnacipran attenuates hyperalgesia and potentiates antihyperalgesic effect of tramadol in rats with mononeuropathic pain.

Milnacipran is a non-tricyclic antidepressant drug which selectively inhibits serotonin and noradrenaline re-uptake and is recommended in the treatment of various chronic pain syndromes. Many studies have shown that compounds known to block monoamine uptake potentiate the antinociceptive effects of opioids. This study investigates the effect of milnacipran alone or in combination with an opiodergic drug, i.e. tramadol, on hyperalgesia in a rat model of neuropathic pain. The contribution of serotonergic, noradrenergic and opioidergic systems in the potential antihyperalgesic effect of milnacipran has also been examined. Chronic constriction injury was induced in rats by loose ligation of the sciatic nerve and neuropathic pain was evaluated 14 days after surgery. Intraperitoneal acute injection of milnacipran 60 mg/kg produced an antihyperalgesic effect which was prevented by pretreating systemically with alpha-methyl-p-tyrosine, an inhibitor of noradrenaline synthesis; parachlorophenylalanine, an inhibitor of serotonin synthesis; and naloxone, an antagonist of opioidergic receptors. Co-administration of milnacipran 40 mg/kg with tramadol (20 and 40 mg/kg) potentiated the antihyperalgesic effect of tramadol. Milnacipran has an antihyperalgesic effect mediated by serotonergic, noradrenergic and opioidergic systems and the combined use of tramadol with milnacipran potentiates the effect of tramadol in the management of neuropathic pain.

Aprotinin impairs coronary endothelial function and down-regulates endothelial NOS in rat coronary microvascular endothelial cells.

OBJECTIVE: The non-specific serine protease inhibitor aprotinin is currently used to reduce blood loss and the need for blood transfusion after cardiopulmonary bypass. We have recently reported that aprotinin impairs endothelium-dependent but not endothelium-independent relaxations in rat thoracic aortic rings due to its inhibitory effect on endothelial nitric oxide (NO) production. In light of these findings, the current study was designed to investigate the effects of aprotinin on coronary endothelial function in isolated rat hearts and on the expression of endothelial NO synthase (eNOS) in cultured rat coronary microvascular endothelial cells (CMEC). METHODS: Hearts obtained from Sprague-Dawley rats were perfused on a constant flow Langendorff isolated heart system and coronary perfusion pressure and cardiac parameters were recorded. The coronary relaxant responses to bolus infusions of bradykinin (BK) and sodium nitroprusside (SNP) were recorded in the absence and presence of aprotinin. Total RNA and protein samples were extracted from CMEC incubated with aprotinin or the vehicle, 0.9% NaCl. RT-PCR-Southern blotting and Western analyses were carried out to assess eNOS mRNA and protein levels, respectively. RESULTS: Aprotinin (125 and 250 kIU/ml) increased coronary perfusion pressure without changing the heart rate and cardiac contractility. Aprotinin inhibited BK-induced coronary vasodilatation at 250 kIU/ml, but not at 125 kIU/ml concentrations. The relaxant response to SNP did not change in response to either concentration of the drug. Incubation of CMEC with aprotinin down-regulated eNOS mRNA and protein at 250 kIU/ml, but not at 125 kIU/ml concentration. CONCLUSION: These data suggest that aprotinin selectively inhibits NO synthesis at higher doses (> or = 250 kIU/ml) and therefore impairs endothelium-dependent coronary vascular tone. This effect of the drug may contribute to its 'blood-sparing' action, but may also account for the increase in the incidence of postoperative graft thrombosis observed in clinical practice during aprotinin therapy.

Impaired activities of antioxidant enzymes elicit endothelial dysfunction in spontaneous hypertensive rats despite enhanced vascular nitric oxide generation.

OBJECTIVE: Enhanced oxidative stress is involved in mediating the endothelial dysfunction associated with hypertension. The aim of this study was to investigate the relative contributions of pro-oxidant and anti-oxidant enzymes to the pathogenesis of endothelial dysfunction in genetic hypertension. METHODS: Dilator responses to endothelium-dependent and endothelium-independent agents such as acetylcholine (ACh) and sodium nitroprusside were measured in the thoracic aortas of 28-week-old spontaneously hypertensive rats (SHR) and their matched normotensive counterparts, Wistar Kyoto rats (WKY). The activity and expression (mRNA and protein levels) of endothelial nitric oxide synthase (eNOS), p22-phox, a membrane-bound component of NAD(P)H oxidase, and antioxidant enzymes, namely, superoxide dismutases (CuZn- and Mn-SOD), catalase and glutathione peroxidase (GPx), were also investigated in aortic rings. RESULTS: Relaxant responses to ACh were attenuated in phenylephrine-precontracted SHR aortic rings, despite a 2-fold increase in eNOS expression and activity. Although the activity and/or expression of SODs, NAD(P)H oxidase (p22-phox) and GPx were elevated in SHR aorta, catalase activity and expression remained unchanged compared to WKY. Pretreatment of SHR aortic rings with the inhibitor of xanthine oxidase, allopurinol, and the inhibitor of cyclooxygenase, indomethacin, significantly potentiated ACh-induced relaxation. Pretreatment of SHR rings with catalase and Tiron, a superoxide anion (O(2)(-)) scavenger, increased the relaxant responses to the levels observed in WKY rings whereas pyrogallol, a O(2)(-)-generator, abolished relaxant responses to ACh. CONCLUSION: These data demonstrate that dysregulation of several enzymes, resulting in oxidative stress, contributes to the pathogenesis of endothelial dysfunction in SHR and indicate that the antioxidant enzyme catalase is of particular importance in the reversal of this defect.

Effects of angiotensin II on nitric oxide generation in proliferating and quiescent rat coronary microvascular endothelial cells.

Nitric oxide (NO) and the mitogenic peptide angiotensin II (Ang II) have been implicated in endothelial cell growth. However, the putative relationship between these two opposing agents with respect to endothelial cell growth remains unknown. In this study, proliferating and confluent rat coronary microvascular endothelial cells (CMEC) were treated with different doses of Ang II, Ca2+ ionophore A23187, or valsartan (an Ang II type 1 (AT1) receptor inhibitor) alone or in combination for 24 h before measuring the nitrite levels as an index of NO generation. NO production and endothelial NO synthase (eNOS) mRNA/protein expression were found to be 3-fold greater in proliferating vs. quiescent CMEC. Treatments of CMEC with Ang II or Ca2+ ionophore A23187 equally increased NO production without altering the fold-difference in the basal release of NO from proliferating vs. confluent CMEC. Valsartan abolished NO production in CMEC treated with Ang II but not Ca2+ ionophore A23187. Treatments of endothelium-intact vascular rings with Ang II (1 nmol/l to 10 micromol/l) plus valsartan or PD-123319, an Ang II type 2 (AT2) receptor inhibitor, attenuated vascular responses to acetylcholine in an Ang II dose-dependent manner. In these rings, phenylephrine produced significant increases in contractile responses only at nmol/l concentrations of Ang II. In contrast, pharmacological and mechanical inactivation of endothelium enhanced contractile responses to phenylephrine at micromol/I concentrations of Ang II. These data demonstrate that Ang II stimulates NO production in CMEC in both an AT1- and an AT2 receptor-regulated manner, and that this stimulation of NO may be beneficial in counterbalancing the direct vasoconstrictor effect of Ang II on underlying smooth muscle cells.

Agmatine attenuates neuropathic pain in rats: possible mediation of nitric oxide and noradrenergic activity in the brainstem and cerebellum.

Effect of agmatine (10-400 mg/kg) on neuropathic pain in a rat model produced by loose ligatures around the common sciatic nerve was studied. The involvement of possible alterations in nitric oxide (NO) levels [measured as its stable metabolites nitrate + nitrite] and in noradrenergic activity [measured as norepinephrine and 3-methoxy-4-hydroxyphenylethylene glycol (MHPG) levels] in this effect was also investigated biochemically in the brainstem and cerebellum. Agmatine increased the neuropathic pain threshold at 300 and 400 mg/kg. There was almost a twofold increase in nitrate + nitrite levels in the brainstem and cerebellum of the rats with neuropathic pain and agmatine decreased the high nitrate + nitrite levels only in the brainstem at 300 mg/kg and both in the brainstem and cerebellum at 400 mg/kg. Ligation of sciatic nerve resulted in almost twofold increase in norepinephrine and MHPG levels only in the brainstem of the rats. Agmatine decreased MHPG levels at 300 and 400 mg/kg, however it decreased norepinephrine levels only at the higher dose. These findings indicate that agmatine decreases neuropathic pain, an effect which may involve the reduction of NO levels and noradrenergic activity in the brain.

Alterations of brain tissue in fetal rats exposed to nicotine in utero: possible involvement of nitric oxide and catecholamines.

Histopathological changes in the brains of embryos from female rats treated with nicotine during pregnancy and possible involvement of nitric oxide (NO) and catecholamines in the nicotine-induced abnormalities of developing brain were investigated. Sexually mature female Wistar rats were given 1, 2, and 3 mg/kg nicotine hydrogen tartrate (NHT) subcutaneously for 20 days after mating. Levels of cotinine, a nicotine metabolite, in the maternal plasma increased dose-dependently. Fetus and fetal brain weights were significantly lower in all nicotine-treated groups. Light microscopy of hippocampal CA1 area showed a decrease in the number of cells per unit area. Electron microscopy of the same region revealed a dose-dependent increase in intracytoplasmic edema, mitochondrial swelling, dilation of rough endoplasmic reticulum, nuclear configurative abnormalities, and condensation of the nuclear chromatin. Nitrate + nitrite levels in fetal brain homogenates were significantly lower in the groups treated with 2 and 3 mg/kg NHT. Norepinephrine and normetanephrine (NMN) levels were significantly higher in 2 and 3 mg/kg NHT groups, as well as dopamine, 3-methoxy-4-hydroxyphenylethyleneglycole (MHPG), and dihydroxyphenylacetic acid levels in the 3-mg/kg NHT group. In conclusion, maternal nicotine exposure may lead to structural abnormalities of the fetal brain tissue and may result in decreased levels of NO and increased levels of catecholamines and their metabolites.

Antihyperalgesic and antiallodynic effect of sirolimus in rat model of adjuvant arthritis.

Sirolimus is an immunosupressive drug that specifically inhibit the activation of T-lymphocytes. This study was undertaken to investigate whether treatment with sirolimus exert analgesic effect in rat adjuvant-induced arthritis, an animal model of rheumatoid arthritis. Arthritis was induced by a single subcutaneous injection of Freund's complete adjuvant to male Wistar rats that were divided into four groups; control (saline), vehicle (ethanol), sirolimus 0.75 and sirolimus 1.5. Sirolimus (0.75 and 1.5mg/kg/day) was administered intraperitoneally using Monday-Wednesday-Friday dosing schedule for 29 days, this dosing regimen revealed acceptable trough blood concentrations in arthritic rats. Adjuvant inoculation resulted in paw inflammation, hyperalgesia and allodynia as assessed by pletismometer, analgesymeter and dynamic plantar aesthesiometer respectively. Light microscopic evaluation of the arthritic metacarpophalangeal joints revealed synovial hypertrophy with inflammatory cellular infiltration, cartilage destruction and partial subchondral bone resorption. ELISA tests of serum TNF-α, IL-1ß or IL-6 did not show any change in arthritic rats, while Western blotting analysis revealed a significant increase in TNF-α (P<0.001), but not IL-1ß or IL-6, protein expression in the lumbar spinal cord of arthritic rats. Treatment with sirolimus significantly decreased the arthritic lesions (P<0.001) and paw swelling (P<0.05), alleviated the histological features in the metacarpophalangeal joint, resulted in antihyperalgesic and antiallodynic effects without affecting the locomotor activity and prevented the increased spinal cord TNF-α level (P<0.05). It seems that prevention of the increased TNF-α expression in the spinal cord may partially contribute to the antihyperalgesic effect of sirolimus in adjuvant arthritic rats and sirolimus could be a promising immunosupressive agent in the treatment of arthritic pain.

Antihyperalgesic and antiallodynic effect of sirolimus in neuropathic pain and the role of cytokines in this effect.

Recent studies have revealed that T lymphocytes play a role in neuropathic pain following nerve injury in rats through releasing several cytokines. Sirolimus is an immunosuppressive antibiotic inhibiting T cell activation. This study aimed to determine the effect of sirolimus on hyperalgesia and allodynia and on serum and spinal cord TNF-alpha, IL-1beta and IL-6 levels in rat neuropathic pain. Neuropathic pain was induced by loose ligation of the sciatic nerve and evaluated by tests measuring the mechanical hyperalgesia and allodynia. Sirolimus (0.75 and 1.5 mg/kg) was administered intraperitoneally once every 3 days for 2 weeks (7 doses totally). This dosing regimen revealed acceptable blood concentrations in neuropathic rats. Chronic constriction injury of the sciatic nerve resulted in hyperalgesia and allodynia. Serum levels of cytokines remained unchanged in neuropathic rats. However, TNF-alpha, but not IL-1beta or IL-6, protein level was increased in the spinal cord tissue as evaluated by Western blotting analysis. Treatment with sirolimus resulted in antihyperalgesic and antiallodynic effects and prevented the increased spinal cord TNF-alpha level. It seems that sirolimus could be a promising immunosuppressive agent in the treatment of neuropathic pain.

Effect of prolonged administration of bovine lactoferrin in neuropathic pain: involvement of opioid receptors, nitric oxide and TNF-alpha.

AIMS: This study aimed to investigate the effect of prolonged administration of bovine milk lactoferrin (bLF) on hyperalgesia and allodynia in a rat model of neuropathic pain and to determine the involvement of c-Fos, TNF-alpha, nitric oxide and opioidergic systems in this effect. MAIN METHODS: Neuropathic pain was induced in rats by loose ligation of the right sciatic nerve and evaluated by tests measuring the mechanical and thermal hyperalgesia and allodynia. bLF (50, 100, and 200mg/kg) alone or in combination with opioidergic antagonists were administered intraperitoneally to the rats with neuropathic pain. c-Fos and NADPH-d immunocytochemistry and Western blotting for TNF-alpha, iNOS and nNOS were performed in the lumbar spinal cord of rats. Plasma TNF-alpha levels were determined with ELISA. KEY FINDINGS: Prolonged, but not single, administration of bLF produced antihyperalgesic and antiallodynic effects in neuropathic rats. Pretreatment with opioidergic antagonists significantly decreased this effect. Prolonged administration of bLF decreased c-Fos and NADPH-d immunoreactivity and TNF-alpha and iNOS expressions at 50 and 100mg/kg and nNOS expression at 100mg/kg in the lumbar spinal cord of neuropathic rats. Plasma TNF-alpha levels remained unchanged after bLF treatment. SIGNIFICANCE: Prolonged administration of bLF exerts antihyperalgesic and antiallodynic effect in neuropathic rats; down-regulation of both TNF-alpha and iNOS expressions and potentiation of opioidergic system in the lumbar spinal cord can contribute to this effect.

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.

Nitric oxide does not downregulate Rho-kinase (ROCK-2) expression in rat coronary endothelial cells.

Rho kinase (ROCK) and nitric oxide (NO) are important targets in cardiovascular diseases. Therefore, we investigated the possible influence of NO on Rho kinase (ROCK-2 isoform) expressions in cultured rat coronary microvascular endothelial cells. The cells were isolated from Wistar rats on a Langendorff system, and were incubated overnight (approximately 16 h) with an NO generator, A-23187 (10 to 10 M), NO donors, such as sodium nitroprusside (10 to 10 M), glyceryl trinitrate (10 to 10 M), 2,2'-(hydroxynitrosohydrazono)bis-ethanimine (10 to 10 M), and NaNO2 (10 to 10 M) or a nitric oxide synthase (NOS) inhibitor, N-nitro-L-arginine methylester (2 x 10 M), or two ROCK inhibitors, (+)-(R)-trans-4-(1-aminoethyl)- N-(4-pyridyl) cyclohexanecarboxamide dihydrochloride monohydrate (Y-27632, 10 M) and fasudil (10 M) in the absence or presence of thrombin (4 U/mL). ROCK-2 and endothelial NOS (eNOS) expressions were detected by Western blotting. Moreover, nitrite/nitrate levels were detected by Griess method in the presence of the ROCK inhibitors. The NO donors and the NO generator had no significant effects on ROCK-2 expression. Y-27632 and fasudil did not alter eNOS expression and NO production. Nitrite/nitrate levels were 4.4 +/- 0.32 microM in control and 4.0 +/- 0.93 microM and in Y-27632 group. These results demonstrate that prolong NO donation could not suppress the expression of ROCK-2 protein, and the ROCK inhibitor did not change e-NOS expression and NO production in the cultured rat coronary microvascular endothelial cells.

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).