Curcumin ameliorates high glucose‐induced acute vascular endothelial dysfunction in rat thoracic aorta

• 1 The aims of the present study were to explore the protective effect of curcumin against the acute vascular endothelial dysfunction induced by high glucose and to investigate the possible role of heme oxygenase (HO)‐1 in this protective action.
• 2 Thoracic aortic rings, with or without endothelium, obtained from male Sprague‐Dawley rats were mounted in an organ bath. Isometric contraction of the rings was recorded. After completion of the organ bath studies, rings were homogenized and centrifuged (30 000 g, 4°C, 15 min) and HO activity was determined in the supernatant.
• 3 After 2 h incubation of aortic rings in the presence of high glucose (44 mmol/L), the relaxation evoked by acetylcholine (3 × 10^?8 to 3 × 10^?5 mol/L) was significantly decreased only in rings with an intact endothelium. When rings were coincubated in the presence of curcumin (10^?13 to 10^?11 mol/L) and high glucose, curcumin reversed the vasodilator dysfunction induced by high glucose dose dependently.
• 4 Curcumin (10^?11 mol/L) increased HO activity in the aortic rings compared with activity in control rings (63.1 ± 3.6 vs control 43.2 ± 2.9 pmol/mg per h, respectively; P < 0.01). Protoporphyrin IX zinc (10^?6 mol/L), an inhibitor of HO‐1, offset the protective effects of curcumin. In addition, the non‐selective guanylate cyclase (GC) inhibitor methylene blue (10^?6 mol/L) completely abolished the protective effects of curcumin.
• 5 In conclusion, the results of the present study show that curcumin alleviates the acute endothelium‐dependent vasodilator dysfunction induced by high glucose in rat aortic rings. Increased HO‐1 activity and stimulation of GC may be involved in the protective effects of curcumin.

     

The depressor and vasodilator effects of rutaecarpine are mediated by calcitonin gene-related peptide

Previous studies have shown that rutaecarpine has depressor and vasodilator effects, and activates vanilloid receptors to evoke calcitonin gene-related peptide (CGRP) release. In the present study, we examined whether the depressor and vasodilator effects of rutaecarpine are related to the stimulation of endogenous CGRP release via activation of vanilloid receptors in rats. Rutaecarpine (30, 100, or 300 microg/kg, i. v.) caused a depressor effect concomitantly with an increase in the plasma concentrations of CGRP in a dose-dependent manner, and the effects of rutaecarpine were abolished by pretreatment with capsaicin (50 mg/kg, s. c.) which depletes neurotransmitters in sensory nerves. In aortic and superior mesenteric arterial rings, rutaecarpine (10 (-7)-10(-5) M) or capsaicin (3 x 10(-9)-3 x 10(-6) M) caused a concentration-dependent vasodilator response, which was significantly attenuated by capsazepine (10(-5) M), a competitive vanilloid receptor antagonist, or by CGRP-(8-37) (10(-6) M), a selective CGRP receptor antagonist. After pretreatment with capsaicin (10(-5) M) for 20 min, vasodilator responses to rutaecarpine were also markedly attenuated. Similarly, pretreatment with rutaecarpine (10(-5) M) for 20 min also attenuated vasodilator responses to capsaicin. These results suggest that the depressor and vasodilator effects of rutaecarpine are related to stimulation of endogenous CGRP release via activation of vanilloid receptors in rats.     

HYPOXIA-INDUCIBLE FACTOR-1 IMPROVES THE ACTIONS OF POSITIVE INOTROPIC AGENTS IN STUNNED CARDIAC MYOCYTES

• 1 In the present study, we tested hypothesis that upregulation of hypoxia‐inducible factor‐1 (HIF‐1) would improve the actions of positive inotropic agents in cardiac myocytes after simulated ischaemia–reperfusion (I/R).
• 2 Hypoxia‐inducible factor‐1α was upregulated with deferoxamine (150 mg/kg per day for 2 days). Rabbit cardiac myocytes were subjected to simulated ischaemia (15 min, 95% N₂–5% CO₂) and reperfusion (re‐oxygenation) and compared with control myocytes. Cell contraction and calcium transients were measured at baseline and after forskolin (10^?7 and 10^?6 mol/L) or ouabain (10^?5 and 10^?4 mol/L).
• 3 Under control conditions, high‐dose forskolin and ouabain increased percentage shortening by 20 and 18%, respectively. Deferoxamine‐treated control myocytes responded similarly. In stunned myocytes, forskolin and ouabain did not significantly increase shortening (increases of 8% and 9%, respectively). Deferoxamine restored the effects of forskolin (+26%) and ouabain (+28%) in stunning. The results for maximum shortening and relaxation rates were similar. The increased calcium transients caused by forskolin and ouabain were also depressed in stunned myocytes, but were maintained by HIF‐1 upregulation.
• 4 These results suggest that simulated I/R impaired the functional and calcium transient effects of positive inotropic agents. Upregulation of HIF‐1 protects cardiac myocyte function after I/R by maintaining calcium release.

     

DIRECT EFFECT OF DEXMEDETOMIDINE ON RAT ISOLATED AORTA INVOLVES ENDOTHELIAL NITRIC OXIDE SYNTHESIS AND ACTIVATION OF THE LIPOXYGENASE PATHWAY

• 1 The aims of the present in vitro study were to examine the roles of pathways associated with arachidonic acid metabolism in dexmedetomidine‐induced contraction and to determine which endothelium‐derived vasodilators are involved in the endothelium‐dependent attenuation of vasoconstriction elicited by dexmedetomidine.
• 2 Dexmedetomidine (10^?9–10^?6 mol/L) concentration–response curves were constructed in: (i) aortic rings with no drug pretreatment; (ii) endothelium‐denuded aortic rings pretreated with either 2 × 10^?5 mol/L quinacrine dihydrochloride, 10^?5 mol/L nordihydroguaiaretic acid (NDGA), 3 × 10^?5 mol/L indomethacin or 10^?5 mol/L fluconazole; and (iii) endothelium‐intact aortic rings pretreated with either 5 × 10^?5 mol/L N^G‐nitro‐l‐ arginine methyl ester (l ‐NAME), 10^?5 mol/L fluconazole, 10^?5 mol/L indomethacin, 10^?5 mol/L glibenclamide, 5 × 10^?3 mol/L tetraethylammonium or 5 × 10^?5 mol/L l ‐NAME plus rauwolscine (10^?5, 10^?6 mol/L). The production of nitric oxide (NO) metabolites was determined in human umbilical vein endothelial cells treated with dexmedetomidine.
• 3 Quinacrine dihydrochloride, NDGA and indomethacin attenuated the dexmedetomidine‐induced contraction of endothelium‐denuded rings. Dexmedetomidine (10^?7–10^?6 mol/L)‐induced contractions of endothelium‐denuded rings were enhanced compared with those of endothelium‐intact rings, as were dexmedetomidine‐induced contractions of endothelium‐intact rings pretreated with l ‐NAME or tetraethylammonium. Rauwolscine attenuated dexmedetomidine‐induced contractions in endothelium‐intact rings pretreated with l ‐NAME. Dexmedetomidine (10^?6 mol/L) was found to activate NO production.
• 4 Taken together, the results indicate that dexmedetomidine‐induced contraction of aortic rings involves activation of the lipoxygenase and cyclo‐oxygenase pathways and is attenuated by increased NO production following stimulation of endothelial α₂‐adrenoceptors by dexmedetomidine.

     

The cardioprotection of rutaecarpine is mediated by endogenous calcitonin related-gene peptide through activation of vanilloid receptors in guinea-pig hearts

Previous investigations have shown that calcitonin gene-related peptide (CGRP) protects against myocardial ischemia-reperfusion injury and that rutaecarpine activates vanilloid receptors to evoke CGRP release. In the present study, we examined whether rutaecarpine enhances preservation with cardioplegia in guinea-pig hearts, and whether the protective effects of rutaecarpine are related to stimulation of endogenous CGRP release via activating vanilloid receptors. The isolated guinea-pig heart was arrested using St. Thomas Hospital solution, and then reperfused with normothermic Krebs-Henseleit solution for 30 min after a 4-h hypothermic ischemic period. Hypothermic ischemia caused a decline in cardiac function (left ventricular pressure, +/-dp/dt(max), heart rate and coronary flow) and an increased release of creatine kinase during reperfusion. Rutaecarpine at the concentration of 1.0 microM significantly improved the recovery of cardiac function and reduced the release of creatine kinase during reperfusion after hypothermic ischemia. Rutaecarpine at the concentration of 3.0 microM significantly reduced the release of creatine kinase and increased the coronary flow, but only caused a slight improvement of left ventricular pressure, +/-dp/dt(max), heart rate during reperfusion. The cardioprotective effects of rutaecarpine were abolished by capsazepine, a competitive vanilloid receptor antagonist, or by CGRP (8-37), a selective CGRP receptor antagonist. Rutaecarpine at the concentration of 1.0 or 3.0 microM significantly increased the release of CGRP, which was also abolished by capsazepine. These results suggest that rutaecarpine enhances preservation with cardioplegia in guinea-pig hearts and that the protective effects of rutaecarpine are due to stimulation of endogenous CGRP release via activating vanilloid receptors.     

Anti-inflammatory effects of limb ischaemic preconditioning are mediated by sensory nerve activation in rats

We have shown that ischaemic preconditioning ameliorates both the local periosteal and the systemic leukocyte activation evoked by limb ischaemia–reperfusion. We hypothesized that the activation of chemosensitive afferent nerves by transient ischaemia contributes to the protective mechanisms of ischaemic preconditioning via a calcitonin gene-related peptide (CGRP)-dependent mechanism. In Sprague–Dawley rats, 60-min complete limb ischaemia was followed by 180 min of reperfusion. In further experiments, the CGRP analogue hCGRP (0.3 μg kg^?1) or ischaemic preconditioning (2?×?10-min ischaemia/10-min reperfusion) was applied prior to the ischaemia–reperfusion insult. Ischaemic preconditioning was performed in three subgroups in which animals received the CGRP receptor antagonist CGRP_8–37 (30 μg kg^?1 h^?1), the chemosensitive afferent nerve inactivator resiniferatoxin (3?×?15 μg kg^?1, sc), or vehicle. The effects of CGRP_8-37 and resiniferatoxin on ischaemia–reperfusion without ischaemic preconditioning were also evaluated. In the tibial periosteum of rats, intravital fluorescence microscopy and immunohistochemistry revealed significant attenuations of ischaemia-reperfusion-induced post-ischaemic leukocyte–endothelial interactions (rolling and adherence in the postcapillary venules) and tissue intracellular adhesion molecule expression following ischaemic preconditioning or hCGRP administration. Administration of CGRP_8-37 or pretreatment of animals with resiniferatoxin reversed the anti-inflammatory effects of limb ischaemic preconditioning, but failed to affect the microcirculatory consequences of ischaemia–reperfusion without ischaemic preconditioning. The results suggest that activation of the chemo- (capsaicin-) sensitive afferent nerves is involved in the mechanisms of microcirculatory anti-inflammatory protection provided by limb ischaemic preconditioning. Controlled activation of chemosensitive C-fibres or the CGRP receptors by the induction of ischaemic preconditioning or other means may furnish therapeutic benefit by ameliorating the periosteal microcirculatory consequences of tourniquet ischaemia.     

Protective effects of rutaecarpine in cardiac anaphylactic injury is mediated by CGRP

Previous investigations have indicated that rutaecarpine activates the vanilloid receptor to evoke calcitonin gene-related peptide (CGRP) release. CGRP has been shown to alleviate cardiac anaphylactic injury. In the present study, the effect of rutaecarpine on cardiac anaphylaxis was examined. Challenge of presensitized guinea-pig hearts with a specific antigen caused marked decreases in coronary flow (CF), left ventricular pressure (LVP) and its derivatives (+/- dp/dt(max)), an increase in heart rate, and prolongation of the P-R interval. Rutaecarpine (0.3 or 1 microM) markedly increased the content of calcitonin gene-related peptide (CGRP) in the coronary effluent and decreased the content of tumor necrosis factor-alpha (TNF-alpha) in myocardial tissues concomitantly with a significant improvement of cardiac function and alleviation of the extension of the P-R interval. Rutaecarpine at the concentration of 1 microM also inhibited the sinus tachycardia. The protective effects of rutaecarpine on cardiac anaphylaxis were abolished by CGRP (8-37), a selective CGRP receptor antagonist. These results suggest that the protective effects of rutaecarpine on cardiac anaphylactic injury are related to inhibition of TNF-alpha production by stimulation of CGRP release.     

Effect of YC-1, an NO-independent,superoxide-sensitive stimulator of soluble guanylyl cyclase,on smooth muscle responsiveness to nitrovasodilators

1. We studied the effects of 3-(5′-hydroxymethyl-2′furyl)-1-benzyl indazole (YC-1) on the activity of purified soluble guanylyl cyclase (sGC), the formation of guanosine-3′ : 5′ cyclic monophosphate (cyclic GMP) in vascular smooth muscle cells (VSMC), and on the tone of rabbit isolated aortic rings preconstricted by phenylephrine (PE). In addition, we assessed the combined effect of YC-1, and either NO donors, or superoxide anions on these parameters.
2. YC-1 elicited a direct concentration-dependent activation of sGC (EC₅₀ 18.6±2.0 μM), which was rapid in onset and quickly reversible upon dilution. YC-1 altered the enzyme kinetics with respect to GTP by decreasing K_M and increasing V_max. Activation of sGC by a combination of sodium nitroprusside (SNP) and YC-1 was superadditive at low and less than additive at high concentrations, indicating a synergistic activation of the enzyme by both agents. A specific inhibitor of sGC, 1H-(1,2,4)-oxdiazolo-(4,3-a)-6-bromo-quinoxazin-1-one (NS 2028), abolished activation of the enzyme by either compound.
3. YC-1 induced a concentration-dependent increase in intracellular cyclic GMP levels in rat cultured aortic VSMC, which was completely inhibited by NS 2028. YC-1 applied at the same concentration as SNP elicited 2.5 fold higher cyclic GMP formation. Cyclic GMP-increases in response to SNP and YC-1 were additive.
4. YC-1 relaxed preconstricted endothelium-denuded rabbit aortic rings in a concentration-dependent manner (50% at 20 μM) and markedly increased cyclic GMP levels. Relaxations were inhibited by NS 2028. A concentration of YC-1 (3 μM), which elicited only minor effects on relaxation and cyclic GMP, increased the vasodilator potency of SNP and nitroglycerin (NTG) by 10 fold and markedly enhanced SNP- and NTG-induced cyclic GMP formation.
5. Basal and YC-1-stimulated sGC activity was sensitive to inhibition by superoxide (O₂⁻) generated by xanthine/xanthine oxidase, and was protected from this inhibition by superoxide dismutase (SOD). YC-1-stimulated sGC was also sensitive to inhibition by endogenously generated (O₂⁻ in rat preconstricted endothelium-denuded aortic rings. Relaxation to YC-1 was significantly attenuated in aortae from spontaneously hypertensive rats (SHR), which generated O₂⁻ at a higher rate than aortae from normotensive Wistar Kyoto rats (WKY). SOD restored the vasodilator responsiveness of SHR rings to YC-1.
6. In conclusion, these results indicate that YC-1 is an NO-independent, O₂⁻-sensitive, direct activator of sGC in VSMC and exerts vasorelaxation by increasing intracellular cyclic GMP levels. The additive or even synergistic responses to NO-donors and YC-1 in cultured VSMC and isolated aortic rings apparently reflect the direct synergistic action of YC-1 and NO on the sGC. The synergism revealed in this in vitro study suggests that low doses of YC-1 may be of therapeutic value by permitting the reduction of nitrovasodilator dosage.

     

ENDOTHELIUM-DERIVED RELAXING FACTOR, HYPERTENSION AND CHRONIC PARATHYROIDECTOMY IN SPONTANEOUSLY HYPERTENSIVE AND WISTAR-KYOTO RATS

• 1 Parathyroidectomy (PTX) lessens the development of hypertension in young spontaneously hypertensive rats (SHR) and the involved mechanisms remain to be elucidated. We have studied here the aortic vascular reactivity to both norepinephrine (NE) and acetylcholine in 10 week old male PTX SHR and Wistar-Kyoto (WKY) rats.
• 2 Depolarized (KCl 100 mmol/L) and NE (1 μmol/L or cumulative 10^-9-10^--⁵ mol/L) precontracted intact aortic rings from PTX rats show a significant and unexpected increase of maximal contractile responses in normotensive and hypertensive animals. These results are also obtained with low extracellular ionized calcium levels (0.625 and 0.9 mmol/L) similar to PTX ionized plasma calcium. N^ω-Nitro-L-arginine methyl ester (l-NAME, 20 μmol/L) potentiates the NE response in SHR and WKY rats, more significantly in control than in PTX animals.
• 3 In the presence of indomethacin (10 μmol/L) in SHR the potentiating effect of PTX on NE contraction is still observed, ruling out a specific production of vasoconstrictors from the arachidonic cascade by the PTX rat aortic endothelium.
• 4 After PTX a moderate impairment of acetylcholine relaxant responses is observed in SHR and WKY rat aortas and basal aortic cyclic guanosine 3′-4′ monophosphate (cGMP) content is also decreased; nevertheless sodium nitroprusside causes a similar relaxation. Furthermore in l-NAME-treated aortas and in the presence of l-arginine (100 μmol/L), acetylcholine (1 μmol/L) produces a significantly less pronounced relaxation in PTX rats.
• 5 In conclusion, the enhancement of NE contractile response in PTX rat aortas is not linked to the strain but probably related to a decrease in endothelial nitric oxide (NO) release or activity. Enhancement of force generation that we describe does not directly participate in the attenuated hypertension observed in SHR after parathyroidectomy.

     

Beneficial effects of 3-aminobenzamide,an inhibitor of poly (ADP-ribose) synthetase in a rat model of splanchnic artery occlusion and reperfusion

1. Peroxynitrite, a potent cytotoxic oxidant formed by the reaction of nitric oxide with superoxide anion, and hydroxyl radical, formed in the iron-catalysed Fenton reaction, are important mediators of reperfusion injury. In in vitro studies, DNA single strand breakage, triggered by peroxynitrite or by hydroxyl radical, activates the nuclear enzyme poly (ADP-ribose) synthetase (PARS), with consequent cytotoxic effects. Using 3-aminobenzamide, an inhibitor of PARS, we investigated the role of PARS in the pathogenesis of splanchnic artery occlusion shock.
2. Splanchnic artery occlusion and reperfusion shock (SAO/R) was induced in rats by clamping both the superior mesenteric artery and the coeliac trunk for 45 min, followed by release of the clamp (reperfusion). At 60 min after reperfusion, animals were killed for histological examination and biochemical studies.
3. SAO/R rats developed a significant fall in mean arterial blood pressure, significant increase of tissue myeloperoxidase activity and marked histological injury to the distal ileum. SAO/R was also associated with a significant mortality (0% survival at 2 h after reperfusion).
4. There was a marked increase in the oxidation of dihydrorhodamine 123 to rhodamine (a marker of peroxynitrite-induced oxidative processes) in the plasma of the SAO/R rats, starting early after reperfusion, but not during ischaemia alone. Immunohistochemical examination demonstrated a marked increase in the immunoreactivity to nitrotyrosine, a specific ‘footprint'' of peroxynitrite, in the necrotic ileum in shocked rats, as measured at 60 min after the start of reperfusion.
5. In addition, in ex vivo studies in aortic rings from shocked rats, we found reduced contractions to noradrenaline and reduced responsiveness to a relaxant effect to acetylcholine (vascular hyporeactivity and endothelial dysfunction, respectively).
6. In a separate set of studies, using a 4000 Dalton fluorescent dextran tracer, we investigated the changes in epithelial permeability associated with SAO/R. Ten minutes of reperfusion, after 30 min of splanchnic artery ischaemia, resulted in a marked increase in epithelial permeability.
7. There was a significant increase in PARS activity in the intestinal epithelial cells, as measured 10 min after reperfusion ex vivo. 3-Aminobenzamide, a pharmacological inhibitor of PARS (applied at 10 mg kg⁻¹, i.v., 5 min before reperfusion, followed by an infusion of 10 mg kg⁻¹ h⁻¹), significantly reduced ischaemia/reperfusion injury in the bowel, as evaluated by histological examination. Also it significantly improved mean arterial blood pressure, improved contractile responsiveness to noradrenaline, enhanced the endothelium-dependent relaxations and reduced the reperfusion-induced increase in epithelial permeability.
8. 3-Aminobenzamide also prevented the infiltration of neutrophils into the reperfused intestine, as evidenced by reduced myeloperoxidase activity. It improved the histological status of the reperfused tissues, reduced the production of peroxynitrite in the late phase of reperfusion and improved survival.
9. In conclusion, our study demonstrates that the PARS inhibitor 3-aminobenzamide exerts multiple protective effects in splanchnic artery occlusion/reperfusion shock. We suggest that peroxynitrite and/or hydroxyl radical, produced during the reperfusion phase, trigger DNA strand breakage, PARS activation and subsequent cellular dysfunction. The vascular endothelium is likely to represent an important cellular site of protection by 3-aminobenzamide in SAO shock.

     

Early and delayed cardioprotection by heat stress is mediated by calcitonin gene-related peptide

Brief ischaemia or heat stress protects the myocardium against ischaemia-reperfusion injury. Heat stimulus evokes release of sensory nerve transmitters, including calcitonin gene-related peptide (CGRP). Since CGRP has been shown to play an important role in the mediation of ischaemic preconditioning, the present study examined whether early or delayed preconditioning induced by retrograde hyperthermic perfusion in vitro or by whole-body hyperthemia in vivo also involves endogenous CGRP. Isolated rat hearts were perfused in the Langendorff mode and subjected to 30 min global ischaemia and 30 min reperfusion. Heart rate, coronary flow, left ventricular pressure and its first derivatives (±dp/dt) were recorded and the CGRP-like immunoreactivity (CGRP-LI) content and the release of creatine kinase (CK) during reperfusion were measured. Retrograde hyperthermic perfusion (42 °C) for 5 min improved the recovery of cardiac function, decreased the release of CK and elevated the content of CGRP-LI in the coronary effluent. CGRP_8–37 (10^–7 mol/l), a selective CGRP receptor antagonist, abolished the cardioprotection by heat stress. Pretreatment with capsaicin (50 mg/kg s.c.), which specifically depletes sensory nerve transmitter content, abolished both the cardioprotection and the increased release of CGRP-LI. Whole-body hyperthermia (42 °C for 15 min) caused an increase in the plasma concentration of CGRP-LI. Early or delayed protection was shown in the hearts obtained from the animals subjected to whole-body hyperthermia 10 min or 48 h before the experiments. The early or delayed protection by heat stress was also abolished by pretreatment with capsaicin. The present study suggests that, in the rat, the early and delayed cardioprotection induced by heat stress involves endogenous CGRP. Received: 31 December 1998 / Accepted: 6 April 1999     

ISCHAEMIC POST-CONDITIONING PROTECTS BOTH ADULT AND AGED SPRAGUE-DAWLEY RAT HEART FROM ISCHAEMIA–REPERFUSION INJURY THROUGH THE PHOSPHATIDYLINOSITOL 3-KINASE–AKT AND GLYCOGEN SYNTHASE KINASE-3β PATHWAYS

• 1 Numerous studies have demonstrated that ischaemic post‐conditioning (IPoC) protects adult rats from myocardial ischaemia‐reperfusion (I/R) injury. Recent evidence suggests compromised cardioprotection by IPoC in aged mice. The present study was designed to test the hypothesis that IPoC protects against I/R injury in aged hearts, potentially through a phosphatidylinositol 3‐kinase (PI3‐K)–Akt‐ and glycogen synthase kinase (GSK)‐3β‐dependent mechanism.
• 2 Hearts from adult (3–4 months) or aged (16–18 months) Sprague‐Dawley rats were subjected in vivo to 30 min ischaemia followed by 3 h reperfusion. Ischaemic post‐conditioning (four cycles of 10 s reperfusion–10 s ischaemia) was applied at the beginning of reperfusion, either alone or in combination with the PI3‐K inhibitor LY294002 (0.3 mg/kg). Infarct size and the phosphorylation of Akt and GSK‐3β were determined.
• 3 Ischaemic post‐conditioning reduced infarct size in both adult and aged rat hearts. This protection was accompanied by a significant increase in phosphorylation of Akt and GSK‐3β. LY294002 abolished the IPoC‐induced phosphorylation of Akt and GSK‐3β, as well as the infarct‐limiting effect of IPoC in adult and aged rats. In addition, IPoC significantly attenuated plasma concentrations of creatine kinase and lactate dehydrogenase after reperfusion in both adult and aged rats.
• 4 In conclusion, IPoC, at the onset of reperfusion, reduces myocardial infarct size in both adult and aged rat hearts, potentially through a PI3‐K‐, Akt‐ and GSK‐3β‐dependent mechanism.

     

Role of calcitonin gene-related peptide in ischaemic preconditioning in diabetic rat hearts

1. It has been suggested that calcitonin gene-related peptide (CGRP) is involved in the protection provided by ischaemic preconditioning in rat hearts and that ischaemic preconditioning is absent in diabetic rat hearts. 2. In the present study, we tested the relationship between sensory nerve function and ischaemic preconditioning in diabetic rats. 3. In 4- and 8-week diabetic rats and age-matched non- diabetic controls, 30 min global ischaemia and 40 min reperfusion caused a significant decrease in cardiac function and a marked increase in creatine kinase (CK) release. Ischaemic preconditioning, by three cycles of 5 min ischaemia and 5 min reperfusion, improved the recovery of cardiac function and decreased CK release during reperfusion in 4-week diabetic rat hearts. However, the cardioprotection afforded by ischaemic preconditioning was lost in 8-week diabetic rat hearts. Pretreatment with CGRP for 5 min also significantly improved the recovery of cardiac function and decreased CK release in rats subjected to 4 or 8 weeks of diabetes. 4. The content of CGRP in the coronary effluent during ischaemic preconditioning was significantly increased in 4-week diabetic rat hearts (P < 0.05). However, only a slight increase in the release of CGRP was shown in 8-week diabetic rat hearts (P > 0.05). 5. In summary, the present results suggest that the protection afforded by ischaemic preconditioning is attenuated in diabetic rats and that the change may be related to the reduction in CGRP release in diabetic rat hearts.     

Solid dispersion of rutaecarpine improved its antihypertensive effect in spontaneously hypertensive rats

It was reported previously that rutaecarpine produced a hypotensive effect in phenol‐induced and 2‐kidney, 1‐clip hypertensive rats. However, the same dose of crude rutaecarpine did not produce significant hypotensive effects when applied to spontaneously hypertensive rats (SHR). In the present study, a different dose of rutaecarpine solid dispersion was administered intragastrically to SHR. The systolic blood pressure was monitored by the tail‐cuff method with an electro‐sphygmomanometer. The plasma concentration of rutaecarpine, calcitonin gene‐related peptide (CGRP) and the mRNA levels of CGRP in dorsal root ganglion were determined. The results showed that administration of the solid dispersion significantly increased the blood concentration of rutaecarpine, accompanied by significant hypotensive effects in SHR in a dose‐dependent manner. The levels of plasma CGRP were also elevated significantly, concomitantly with the increased mRNA levels in the dorsal root ganglion in a dose‐dependent manner. It was concluded that a change of the dosage from the crude drug to solid dispersion could improve significantly the efficiency of rutaecarpine absorption and increase its plasma concentration. The anti‐hypertensive effect exerted by rutaecarpine solid dispersion in SHR is mediated by CGRP. Copyright © 2008 John Wiley & Sons, Ltd.     

Effects of inhibitors of the activity of poly (ADP-ribose) synthetase on the liver injury caused by ischaemia-reperfusion: a comparison with radical scavengers

1. Poly (ADP-ribose) synthetase (PARS) is a nuclear enzyme activated by strand breaks in DNA which are caused by reactive oxygen species (ROS) and peroxynitrite. Excessive activation of PARS may contribute to the hepatocyte injury caused by ROS in vitro and inhibitors of PARS activity reduce the degree of reperfusion injury of the heart, skeletal muscle and brain in vivo. Here we compared the effects of various inhibitors of the activity of PARS with those of deferoxamine (an iron chelator which prevents the generation of hydroxyl radicals) and tiron (an intracellular scavenger of superoxide anion) on the degree of hepatic injury caused by ischaemia and reperfusion of the liver in the anaesthetized rat or rabbit.
2. In the rat, ischaemia (30 or 60 min) and reperfusion (120 min) of the liver resulted in significant increases in the serum levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) indicating the development of liver injury. Intravenous administration of the PARS inhibitors 3-aminobenzamide (3-AB, 10 mg kg⁻¹ or 30 mg kg⁻¹), 1,5-dihydroxyisoquinoline (ISO, 1 mg kg⁻¹) or 4-amino-1,8-naphthalimide (4-AN, 3 mg kg⁻¹) before reperfusion did not reduce the degree of liver injury caused by ischaemia-reperfusion.
3. In contrast to the PARS inhibitors, deferoxamine (40 mg kg⁻¹) or tiron (300 mg kg⁻¹) significantly attenuated the rise in the serum levels of AST and ALT caused by ischaemia-reperfusion of the liver of the rat.
4. In the rabbit, the degree of liver injury caused by ischaemia (60 min) and reperfusion (120 min) was also not affected by 3-AB (10 mg kg⁻¹) or ISO (1 mg kg⁻¹).
5. These results support the view that the generation of oxygen-derived free radicals mediates the liver injury associated with reperfusion of the ischaemic liver by mechanism(s) which are independent of the activation of PARS.

     

Exogenous L‐arginine attenuates the effects of angiotensin II on renal hemodynamics and the pressure natriuresis–diuresis relationship

相似文献   

Study of in vivo and in vitro resting vasodilator nitric oxide tone in normotensive and genetically hypertensive rats

The effects of N^G-nitro- -arginine ( -NNA) on mean arterial pressure and the effects of both -NNA and methylene blue on isolated aorta tone, were studied in order to elucidate potential alterations in vasodilator resting nitric oxide (NO) tone in genetic hypertension. -NNA produced a significantly greater increase of mean arterial pressure in spontaneously hypertensive rats (SHR) than in Wistar Kyoto (WKY) rats; in both cases, -arginine completely inhibited the -NNA hypertensive effect. Neither ganglion blockade with hexamethonium nor cyclooxygenase inhibition with indomethacin significantly modified the effect of -NNA in both rat strains. In intact aorta rings, after submaximally contraction with KCl (25 mM), both -NNA and methylene blue induced strong dose-dependent contractions. The maximum contractions were, however, significantly greater in WKY rats than in SHR. The mechanical elimination of endothelium markedly inhibited both -NNA and methylene blue maximum contractions. In intact rings, -arginine completely inhibited the -NNA effects in both rat strains; in rubbed rings, the -arginine inhibitory effects were strong in WKY rats but not important and erratic in SHR. -Arginine had no effect on the contractions induced only by KCl in any of the preparations. In WKY rat-rubbed rings, sodium nitroprusside was significantly more effective in relaxing the contractions in response to 25 mM KCl than the contractions in response to methylene blue. These results indicate that contractions induced by -NNA and methylene blue in isolated aorta are principally due to the inhibition of an important endothelial resting vasodilator NO tone. They also show that hypertension reduces the resting vasodilator NO tone in isolated rat aorta, in spite of enhancing the total vasodilator NO tone in anaesthetized rat.     

Long-term treatment with angiotensin converting enzyme inhibitor restores reduced calcitonin gene-related peptide-containing vasodilator nerve function in mesenteric artery of spontaneously hypertensive rats

Effects of long-term treatment with angiotensin converting enzyme (ACE) inhibitor on decreased function of calcitonin gene-related peptide (CGRP)-containing vasodilator nerves (CGRP nerves) in mesenteric resistance artery were investigated in spontaneously hypertensive rats (SHR). Eight-week-old SHR were treated for 7 weeks with 0.1% captopril, 0.01% temocapril, 0.05% pindolol or 0.005% hydralazine in drinking water. Long-term treatment with each drug significantly lowered mean blood pressure of SHR. In isolated and perfused mesenteric vascular beds with active tone, periarterial nerve stimulation (PNS) (0.5 to 8 Hz) produced frequency-dependent vasodilations, which were abolished by CGRP(8-37) (CGRP-receptor antagonist) and significantly smaller in SHR than in normotensive Wistar Kyoto rats. Treatment of SHR with captopril and temocapril but not with pindolol and hydralazine resulted in significantly greater PNS-induced vasodilation than in non-treated SHR, but ACE-inhibitor treatment did not affect vasodilation induced by exogenous CGRP. In captopril-treated SHR preparations, PNS evoked significantly larger CGRP-like immunoreactive release than in non-treated SHR. In non-treated 15-week-old SHR preparations, direct perfusion of captopril or temocapril (0.1 microM and 1 microM) did not modify frequency-dependent vasodilation in response to PNS. These results suggest that long-term ACE inhibitor treatment prevents or restores CGRP nerve function reduction in SHR.     

Serial changes in adipocytokines and cardiac function in a rat model of the metabolic syndrome

相似文献   

CARDIOPROTECTIVE EFFECT OF l-GLUTAMATE IN OBESE TYPE 2 DIABETIC ZUCKER FATTY RATS

• 1 Because diabetic hearts have an increased threshold for cardioprotection by ischaemic preconditioning (IPC), we hypothesized that protection by l ‐glutamate during reperfusion is restricted in Type 2 diabetic hearts. Previously, we found that l ‐glutamate‐mediated postischaemic cardioprotection mimics IPC.
• 2 Rat hearts were studied in a Langendorff preparation perfused with Krebs’–Henseleit solution and subjected to 40 min global no‐flow ischaemia, followed by 120 min reperfusion. l ‐Glutamate (0, 15 and 30 mmol/L) was added to the perfusate during reperfusion of hearts from non‐diabetic (Wistar‐Kyoto) and diabetic (Zucker diabetic fatty (ZDF)) rats, studied at 16 weeks of age. The infarct size (IS)/area‐at‐risk (AAR) ratio was the primary end‐point. Expression of l ‐glutamate excitatory amino acid transporter (EAAT) 1 (mitochondrial) and EAAT3 (sarcolemmal) was determined by quantitative polymerase chain reaction and immunoblotting.
• 3 The ISS/AAR ratio did not differ between control hearts from Wistar‐Kyoto and ZDF rats (0.52 ± 0.03 and 0.51 ± 0.04, respectively; P = 0.90). l ‐Glutamate (15 mmol/L) significantly reduced the IS/AAR ratio in non‐diabetic hearts, but not in diabetic hearts, compared with their respective controls. The higher concentration of l ‐glutamate (30 mmol/L) reduced infarct size in diabetic hearts to the same degree as in non‐diabetic hearts (IS/AAR 0.35 ± 0.03 (P = 0.002) and 0.34 ± 0.03 (P = 0.004), respectively). The mitochondrial l ‐glutamate transporter EAAT1 was downregulated in hearts from ZDF rats at both the mRNA and protein levels (P < 0.0005 and P < 0.0001, respectively). However, there was no change in EAAT3 expression at the protein level. Myocardial l ‐glutamate content was increased by 43% in diabetic hearts (P < 0.0001).
• 4 Hearts from obese diabetic rats have an elevated threshold for metabolic postischaemic cardioprotection by l ‐glutamate. These findings may reflect underlying mechanisms of inherent resistance against additional cardioprotection in the diabetic heart.