Effect of taurine on vascular dysfunction in an in vitro ischemia-reperfusion model of rat thoracic aorta.

OBJECTIVE: The primary objective of this study was to evaluate the protective effect of taurine on endothelial dysfunction in a vascular ischemia-reperfusion (IR) model. METHODS: Thoracic aortas of 9 male Sprague-Dawley rats (350-500 g) were cut into rings and randomized into control (n = 7), IR (n = 8), IR + taurine 1 mM (n = 7), IR + taurine 10 mM (n = 8), IR + taurine 30 mM (n = 8), and IR + taurine 100 mM (n = 5) groups. Aortic rings in the IR group were stored in 0.9% saline at 4 °C for 24 h, placed in Krebs-Henseleit solution gassed with 95%O2 + 5%CO2 at 37 °C, and exposed to sodium hypochlorite (200 µM) for 30 min. Responses to KCl (80 mM), phenylephrine (10-10-10-4 M), acetylcholine (10-10-10-4 M), and sodium nitroprusside (SNP, 10-11-10-5 M) were recorded. Emax (maximum response) and pD2 (negative logarithm of concentration producing half-maximum response) were calculated. RESULTS: IR decreased KCl contraction (control 1047 ± 176 mg, IR 682 ± 128 mg, p = 0.0007), which was reversed by 30 and 100 mM taurine (960 ± 313 mg, p = 0.02 and 1066 ± 488 mg, p = 0.02, respectively). IR impaired phenylephrine, acetylcholine, and SNP responses (p < 0.0001). Taurine did not affect IR-impaired phenylephrine contractions. IR decreased both pD2 (control, 7.1 ± 0.1; IR, 6.0 ± 0.2; p < 0.01) and Emax (control, 83.5 ± 2.7%; IR, 26.8 ± 2.5%; p < 0.0001) of acetylcholine relaxation, both of which were reversed by 100 mM taurine (pD2, 7.2 ± 0.1; p < 0.001; Emax, 45.4 ± 2.6%; p < 0.0001). For SNP relaxation, IR decreased pD2 (control 8.2 ± 0.1, IR 7.7 ± 0.1, p < 0.01), which was reversed by 100 mM taurine (8.5 ± 0.1, p < 0.0001). CONCLUSION: Taurine protects endothelial function after IR injury. Further studies should explore the mechanism of this effect and the potential of adding taurine to vascular graft storage solutions.

A meta-analysis of animal studies evaluating the effect of hydrogen sulfide on ischemic stroke: is the preclinical evidence sufficient to move forward?

Hydrogen sulfide (H2S) is a gasotransmitter that has been studied for its potential therapeutic effects, including its role in the pathophysiology and treatment of stroke. This systematic review and meta-analysis aimed to determine the sufficiency of overall preclinical evidence to guide the initiation of clinical stroke trials with H2S and provide tailored recommendations for their design. PubMed, Web of Science, Scopus, EMBASE, and MEDLINE were searched for studies evaluating the effect of any H2S donor on in vivo animal models of regional ischemic stroke, and 34 publications were identified. Pooling of the effect sizes using the random-effect model revealed that H2S decreased the infarct area by 34.5% (95% confidence interval (CI) 28.2-40.8%, p < 0.0001), with substantial variability among the studies (I2 = 89.8%). H2S also caused a 37.9% reduction in the neurological deficit score (95% CI 29.0-46.8%, p < 0.0001, I2 = 63.8%) and in the brain water content (3.2%, 95% CI 1.4-4.9%, p = 0.0014, I2 = 94.6%). Overall, the studies had a high risk of bias and low quality of evidence (median quality score 5/15, interquartile range 4-9). The majority of the included studies had a "high" or "unclear" risk of bias, and none of the studies overall had a "low" risk. In conclusion, H2S significantly improves structural and functional outcomes in in vivo animal models of ischemic stroke. However, the level of evidence from preclinical studies is not sufficient to proceed to clinical trials due to the low external validity, high risk of bias, and variable design of existing animal studies.

Effects of hypoxia versus ischaemia on vascular functions of isolated rat thoracic aorta: revisiting the in vitro vascular ischaemia/reperfusion model.

Introduction: The in vitro rat vascular ischaemia and reperfusion model is used to evaluate the molecular and functional effects of potential agents against ischaemia and reperfusion injury of autologous graft veins. However, there is no consensus on whether hypoxia, rather than ischaemia, is sufficient to induce vascular dysfunction. Aim: To compare the effects of hypoxia and ischaemia, with or without reperfusion, on the vascular functions of isolated thoracic aortic rings of rats. Material and methods: Thoracic aortas of 12 male Sprague-Dawley rats (350-500 g, 18-24 months old) were isolated and divided into rings that were randomly allocated to control, ischaemia, hypoxia, ischaemia-reperfusion, and hypoxia-reperfusion groups. Aortic rings other than those of the control group were stored at 4°C for 24 h in saline. For ischaemia, saline was gassed with nitrogen. After 24 h, aortic rings in the ischaemia-reperfusion and hypoxia-reperfusion groups were incubated with 200 µM sodium hypochlorite for 30 min. Vascular and endothelial functions were tested in an organ bath set-up. Results: Vascular response to potassium chloride (80 mM) decreased in all experimental groups compared to the control group (p = 0.007), but phenylephrine-induced contraction (10-5 M) increased only in the ischaemia-reperfusion group (p < 0.0001). Acetylcholine (10-11-10-5 M)-induced endothelium-dependent vasorelaxations were impaired in all groups - particularly in the ischaemia-reperfusion group (p = 0.0011). Sodium nitroprusside (10-12-10-7 M)-induced endothelium-independent vasorelaxations were similar across all groups (p = 0.1258). Conclusions: Ischaemia followed by reperfusion should be implanted to achieve maximum endothelial and contractile dysfunction in vitro, and to replicate ischaemia and reperfusion injury of autologous graft veins.

Effect of hydrogen sulfide on ischemia-reperfusion injury of kidney: A systematic review and meta-analysis of in vivo animal studies.

Hydrogen sulfide (H2S) has been shown to be effective against kidney ischemia-reperfusion injury (IRI) in animal studies. We aimed to evaluate the current evidence from in vivo animal studies for the protective effects of H2S against kidney IRI by systematically reviewing the literature and performing a meta-analysis. Based on the preregistered protocol (PROSPERO: CRD42021295469); PubMed, Medline, Embase, Web of Science, and Scopus were searched to identify in vivo animal studies evaluating the effect of H2S against kidney IRI. Standardized mean difference (SMD) with 95% confidence interval (CI) was calculated and pooled using random-effects meta-analysis. Twenty-two articles complied with eligibility criteria, from which the creatinine levels of 152 control animals and 182 animals treated with H2S from 27 individual experiments were pooled. H2S treatment significantly decreased serum creatinine (SMD = -1.82 [95% CI -1.12, -2.51], p < 0.0001), blood urea nitrogen (-2.50 [-1.46, -3.54], p < 0.0001), tissue malondialdehyde (-2.59 [-3.30, -1.88], p < 0.0001), tunel positive cells (-3.16 [-4.38, -1.94], p < 0.0001), and tubular damage score (-2.01 [-3.03, -0.99], p < 0.0001). There was a high heterogeneity across studies (I2 = 83.5% for serum creatinine level). In meta-regression analysis, the type of H2S donor and its application time accounted for 11.3% (p = 0.025) and 16.6% (p = 0.039) of heterogeneity, respectively. Accordingly, H2S protects the kidney against IRI only if it is given as GYY4137 before or during ischemia. Although H2S is a potential candidate against kidney IRI, further well-designed preclinical studies focusing on GYY4137 are warranted before clinical implication.

Effect of rosuvastatin on spatial learning, memory, and anxiety-like behaviour in ovariectomized rats.

The effect of rosuvastatin (Ros) on cognitive function and anxiety-like behaviour in ovariectomized rats were evaluated. Eighteen female Wistar rats (218-310 g, 6-8 months old) were allocated into sham (n = 6), ovariectomy (Ovx, n = 6) or Ovx + Ros (up to eighth week n = 6, then n = 4) groups. Ros was administered at 20 mg/kg/day by oral gavage for 12 weeks. Behavioural tests were performed at 4, 8 and 12 weeks following Ovx. At 12 weeks, Ovx group had significantly longer escape latency than the sham group at the first day of the four-day training period of the Morris Water Maze test (p < .01). In the Elevated Plus Maze test, Ovx group spent significantly more time in the closed arms than the sham group (p < .01), and this anxiety-like behavioural effect of Ovx was prevented by 12-weeks Ros treatment (p < .05). In conclusion, Ros prevents memory deficit and anxiety-like behaviour in the ovariectomized rats, a model for human surgical menopause. Impact StatementWhat is already known on this subject? Reduced levels of oestrogen in surgical postmenopausal period has been linked to an increased risk of cognitive dysfunction. Although statins have been shown to improve cognitive function in experimental and clinical studies, there are limited studies evaluating the effect of statins on the cognitive decline and anxiety-like behaviour associated with surgical menopause.What do the results of this study add? Rosuvastatin, a long-acting statin, prevents learning and memory deficit and anxiety-like behaviour in the ovariectomized rat model.What are the implications of these findings for future clinical practice and/or future clinical research? These findings will form the basis for further experimental and clinical research on the effects of statins on cognitive functions and anxiety-like behaviour in the surgical menopause.

Mechanism of acitretin-induced relaxations in isolated rat thoracic aorta preparations.

Acitretin is a member of vitamin A-derived retinoids, and its effect on vascular smooth muscle had not yet been studied. The aim of this study is to investigate the effect of acitretin, a retinoid, on vascular smooth muscle contractility. Thoracic aorta preparations obtained from 34 male Sprague-Dawley rats (355 ± 15 g) were studied in isolated organ baths containing Krebs-Henseleit solution. The relaxation responses were obtained with acitretin (10-12-10-4 M) in endothelium-preserved and endothelium-denuded aorta preparations precontracted with submaximal concentration of phenylephrine (10-6 M). The role of retinoic acid receptors (RARs), nitric oxide, adenylyl, and guanylyl cyclase enzymes, and potassium channels in these relaxation responses were investigated. Acitretin produced concentration-dependent relaxations, which were independent of its solvent dimethylsulfoxide (DMSO), in endothelium-denuded phenylephrine-precontracted thoracic aorta preparations. While incubation with the RAR antagonist (AGN193109, 10-5 M) had no effect on these relaxations; nitric oxide synthase inhibitor (L-NG-Nitro arginine methyl ester (L-NAME), 10-4 M), adenylyl cyclase inhibitor (SQ2253, 10-5 M), guanylyl cyclase inhibitor (oxadiazolo [4,3-a] quinoxalin-1-one (ODQ), 10-6 M), and potassium channel blocker (tetraethylammonium (TEA), 10-2 M) significantly eliminated the relaxation responses induced by acitretin. Acitretin induces relaxation in rat isolated thoracic aorta preparations without endothelium, which may be mediated by nitric oxide, cyclic adenosine monophosphate, and cyclic guanosine monophosphate-dependent kinases and potassium channels.

Relaxant effect of diallyl sulfide on nonpregnant rat uterus: Involvement of voltage-dependent calcium channels.

AIM: We aimed to determine the effect and mechanism of action of diallyl sulfide (DAS), an active component of sulfur-containing foods such as garlic on rat uterine activity. METHODS: Isometric tension changes in longitudinal uterine strips obtained from 20 female Sprague-Dawley rats (250-300 g) in estrus stage of estrous cycle were studied in isolated organ baths containing Krebs-Henseleit solution. RESULTS: Diallyl sulfide (10-8 -10-6 M) caused a concentration-dependent relaxation on KCl (60 mM)-induced contractions and inhibited spontaneous peristaltic activity of uterine strips (P < 0.05). None of the following antagonists significantly changed the inhibitory effect of DAS on both KCl-precontracted uterine strips and spontaneous peristaltic activity of the uterus (P > 0.05): nitric oxide synthase inhibitor L-NAME (10-4 M), hydrogen sulfide-producing enzymes cystation ß synthase and cystation γ-lyase inhibitors, aminooxyacetic acid (10-4 M) and propargylglycine (10-3 M) and nonselective cyclooxygenase inhibitor indomethacin (10-4 M). However, in calcium-free Krebs solution containing high KCl (30 mM), DAS significantly inhibited CaCl2 (10-5 -10-2 M)-induced uterine contractions in a concentration-dependent manner (P < 0.05). CONCLUSION: Diallyl sulfide has a relaxing effect on KCl-contracted rat uterus strips and an inhibitory effect on spontaneous uterine activity, possibly by decreasing the calcium influx into the cytoplasm of uterine smooth muscle cells.

Effects of Algan Hemostatic Agent on bleeding time in a rat tail hemorrhage model.

BACKGROUND: Algan Hemostatic Agent (AHA) is a multi-herbal extract containing a standardized amount of Achillea millefolium, Juglans regia, Lycopodium clavatum, Rubus caesius or Rubis fruciosus, Viscum album, and Vitis vinifera, each of which is effective in hemostasis. In this study, we aimed to investigate the effects of AHA on bleeding time in a rat tail hemorrhage model. METHODS: Forty-eight Sprague Dawley rats (5-7 weeks old, 180-210 g) were randomly and equally allocated to six groups as follows: heparin plus saline (heparinized control), heparin plus AHA-soaked sponge, heparin plus liquid form of AHA, saline (non-heparinized control), AHA-soaked sponge and liquid form of AHA. Heparin (640 IU/kg) was administered intraperitoneally three times a day for three days in heparinized groups. For the bleeding model, the tail of rats was transected. According to the study group, either saline- or AHA-soaked sponge or liquid form of AHA was applied over the hemorrhage area. In AHA- or saline-soaked sponge groups, once the bleeding time had started, it was checked every 10 seconds. If the bleeding did not stop after 40 seconds, it was accepted as a failure. In liquid AHA group, the duration of bleeding was measured using a chronometer and defined as the time (seconds) from wounding until the bleeding stopped. RESULTS: Bleeding time in the heparinized and non-heparinized control groups was over 40 seconds. After applying the sponge form of AHA on the wound area, bleeding time was significantly shortened to less than 20 seconds in both heparinized and non-heparinized rats (p<0.001 for both). The liquid form of AHA stopped bleeding in 5.0±1.2 seconds and 8.0±1.3 seconds in heparinized and non-heparinized groups, respectively. CONCLUSION: AHA is a highly effective topical hemostatic agent in a rat tail hemorrhage model, thus may provide for a unique clinically effective option for control of bleeding during surgical operations or other emergencies.

Cyclosporine A-induced acute hepatotoxicity in guinea pigs is associated with endothelin-mediated decrease in local hepatic blood flow.

AIMS: To bring further insight into the mechanism of cyclosporine A (CsA)-induced hepatotoxicity, the acute effect of CsA on local hepatic blood flow (LHBF) and its association with systemic hemodynamics, histopathological and biochemical indicators of liver toxicity were studied in guinea pigs in vivo. The association of endothelin (ET) and/or Cremophor-EL (C-EL, vehicle in parenteral CsA preparation) with CsA effects was also investigated. MAIN METHODS: Animals were assigned into five groups; control, CsA, C-EL, Bosentan (non-selective ET receptor antagonist)+CsA, and BQ-123 (ET(A) receptor antagonist)+CsA. CsA was infused intravenously (i.v.) at 20 and 10mg/kg doses by 15 min interval. Antagonists were administered 15 min before CsA infusion. LHBF and mean arterial blood pressure (MAP) changes were simultaneously recorded. Blood and liver samples were collected for biochemical and histopathological examinations. KEY FINDINGS: CsA, but not C-EL, decreased LHBF by 53.3% at the end of 30 min. Although being non-significant, CsA slightly increased MAP suggesting that, CsA-induced acute decrease in LHBF was likely independent of MAP changes. Bosentan (5mg/kg, i.v.) and BQ-123 (1mg/kg, i.v.) pre-treatments prevented the CsA-induced decrease in LHBF suggesting that CsA decreases LHBF through an ET-related mechanism. Additionally, CsA, but not its vehicle C-EL, caused marked acute pathological changes in the liver morphology. SIGNIFICANCE: CsA-induced findings of acute hepatotoxicity were prevented by bosentan and BQ-123 pre-treatments. Thus, CsA seems to exert acute hepatotoxic effect through ET-related mechanisms.

The role of nitric oxide in the electrical field stimulation-induced contractions of sphincter of oddi and gallbladder strips in Guinea pigs.

The aim of this study was to investigate the modulatory role of nitric oxide (NO) in the electrical field stimulation (EFS)-induced contractions of isolated sphincter of Oddi (SO) and gallbladder strips from guinea pigs. EFS was used to activate the intrinsic nerves in SO and gallbladder strips. EFS produced frequency-dependent biphasic contractile responses in the SO strips. A smaller contraction, "on response", occurred during EFS, which was followed by a bigger contraction, "off response". Both responses were completely and irreversibly abolished by tetrodotoxin (TTX) (10(-6) M). Atropine (10(-6) M) inhibited the "on response", but not the "off response". EFS produced frequency-dependent monophasic contractile responses in gallbladder strips, which were completely and irreversibly abolished by TTX (10(-6) M) and atropine (10(-6) M). A nitric oxide synthase (NOS) inhibitor, NG-nitro-L-arginine (10(-4) M and 3 x 10(-4) M, in SO and gallbladder strips, respectively), significantly increased all EFS-induced contractions of SO and gallbladder strips. L-Arginine, but not D-arginine reversed the effect induced by the NOS inhibitor, at all frequencies, in both strips. These results suggested that NO released from nitrergic nerve endings might play a regulatory role in the cholinergic neurotransmission of guinea pig SO and gallbladder strips. The "off response" in he SO preparations might be a rebound increase that was modulated by the nonadrenergic, noncholinergic inhibitory mediator NO.

Mechanism of action of the cisapride-induced vasodilatation in renal vasculature of rat.

BACKGROUND & OBJECTIVES: Cisapride is a prokinetic agent with cholinomimetic and 5-HT4 receptor agonistic properties. It has been proposed that cisapride-induced hypotension is partly mediated by cholinergic system. The aim of this study was to investigate the mechanism of cisapride-induced dilatation in the rat isolated perfused kidney. METHODS: Left kidneys of Wistar rats were isolated and perfused via renal artery and the perfusion pressure was recorded. Cisapride given as bolus injections (10(-10)-3x10(-5) mol/l) produced dose-dependent dilatations. Perfusion of antagonists or inhibitors was started 30min before the onset of phenylephrine perfusion. RESULTS: 4-Diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP; blocker of M1, and M3 muscarinic receptors; 10(-7) mol/l) inhibited the responses to the lower doses of cisapride while, dextran (10(-7) mol/l), glibenclamide (inhibitor of ATP-sensitive potassium channels; 10(-5) mol/l) and capsaicin (for neuromediator depletion; 10(-6) mol/l) inhibited those to the higher doses. Dilatations induced by most of the doses of cisapride were inhibited by atropine (non-selective muscarinic receptor antagonist; 10(-7) mol/l), methylene blue (inhibitor of soluble guanylate cyclase; 10(-5) mol/l), 1H-[1,2,4] oxadiazolo-[4,3-a] Quinoxalin-1-One (ODQ; inhibitor of soluble guanylate cyclase; 10(-5) mol/l), and NG-nitro-L-arginine (L-NOARG; NO synthase inhibitor; 10(-4) mol/l). Inhibition induced by L-NOARG was reversed by L-arginine (10(-3) mol/l). The dilatation induced by cisapride was not affected by GR113808 (5-HT4 receptor antagonist; 10(-7) mol/l) and indomethacin (cyclooxygenase inhibitor; 10(-5) mol/l). INTERPRETATION & CONCLUSION: The findings indicated that cisapride caused vasodilatation through the release of nitric oxide (NO) as a result of the release of a substance acting on muscarinic receptors, in the renal vascular bed of the rat. The role of 5-HT4 receptors and prostanoids seemed unlikely.

Calcium-antagonistic activity of sumatriptan in the rat anococcygeus muscle.

The relaxant effect of sumatriptan, a 5-HT(1B/1D) receptor agonist, on the rat anococcygeus muscle was investigated. Sumatriptan induced concentration-dependent relaxations of the phenylephrine-precontracted rat anococcygeus muscle. N(G)-nitro-L-arginine, methylene blue, glibenclamide, tetrodotoxin, indomethacin, GR 113808, GR 55562, methysergide, ketanserin, ICS 205930, clozapine, methiothepin, metergoline, mesulergine, and ritanserin did not inhibit the relaxations induced by sumatriptan. Sumatriptan converted calcium-induced contractions into relaxations in the preparations depolarized by a calcium-free, high-potassium solution. In membrane preparations obtained from the rat anococcygeus muscle, the basal rate of cAMP production by adenylate cyclase was 4.77 +/- 0.02 pmol/mg protein/min (n = 15). The enzyme activity was increased to 104 +/- 51.7 pmol/mg protein/min by forskolin (10(-4) mol/l), but did not change in the presence of sumatriptan. The mRNA expression of 5-HT(1B), 5-HT(1D), and 5-HT(7) receptors was not observed in the rat anococcygeus muscle. The results indicate that sumatriptan causes relaxation of the precontracted rat anococcygeus muscle by a calcium-antagonistic activity.