The Effects of Lipopolysaccharide Derivatives in Rodent Models of Cardiac Arrhythmia.

BACKGROUND: Several previous studies have suggested that sublethal doses of Escherichia coli lipopolysaccharide (endotoxin) and monophosphoryl lipid A Re595, a nonpyrogenic derivative of Salmonella minnesota lipopolysaccharide, exhibit antiarrhythmic effects in the rat model of ischemia-reperfusion arrhythmias. METHODS: In this study, the protective effect of lipopolysaccharide derivatives was also further investigated in drug (aconitine or ouabain)-induced arrhythmia models, and conclusions were drawn with particular emphasis on the molecular characteristics of different types of lipopolysaccharide. RESULTS: The importance of the molecular structure for the antiarrhythmic effect of monophosphoryl lipid A and E. coli lipopolysaccharide was tested in the ischemia-reperfusion arrhythmia model. In contrast to monophosphoryl lipid A from Salmonella typhimurium SL 684 which has only monophosphoryl residue in its structure, monophosphoryl lipid A Re595, obtained from S. minnesota, and E. coli lipopolysaccharide which have both mono and diphosphoryl residue reduced the duration of ventricular tachycardia (e.g., during reperfusion: vehicle: 176 ± 22.8; monophosphoryl lipid A Re595: 132.83 ± 12.1, as second, n=8-10, P < .05) and the incidence of ventricular fibrillation. The antiarrhythmic effects of E. coli lipopolysaccharide and monophosphoryl lipid A Re595 in ischemia-reperfusion arrhythmia model were absent in either aconitine- (e.g., onset time for ventricular ectopic beats: saline 25.3 5.0, E. coli lipopolysaccharide 24.3 ± 7.1; vehicle: 24.0 ± 4.5, monophosphoryl lipid A SL684 23.8 ± 4.3, as second, n=6, P > .05) or ouabain-induced arrhythmia models in mice. CONCLUSION: Therefore, we conclude that lipopolysaccharide derivatives exhibit antiarrhythmic effect only in ischemia-reperfusion arrhythmias, and lipopolysaccharide should possess diphosphoryl groups in its subcomponent composition for this antiarrhythmic effect.

Key concepts in biosimilar medicines: What physicians must know.

Biologics' are a class of medications produced by living cells using recombinant DNA technology. Biologics have had an important impact in many areas of medicine, and in particular in rheumatology and oncology. However, the high cost of these agents is a growing concern, particularly as more products become available and their use for the treatment of immune-mediated inflammatory diseases continues to expand. Biosimilars, also called follow-on biologics, have been viewed as a potential cost-saving alternative to traditional therapies. Currently, a product can be considered biosimilar to a reference product if there are no clinically meaningful differences in terms of safety, purity, and potency. In this review, the most important key concepts about biosimilars were summarized for physicians emphasizing the status in Turkey.

Effects of Genetic Polymorphisms of Drug Transporter ABCB1 (MDR1) and Cytochrome P450 Enzymes CYP2A6, CYP2B6 on Nicotine Addiction and Smoking Cessation.

OBJECTIVES: To determine the effects of genetic polymorphisms of ABCB1 (MDR1), CYP2A6, CYP2B6 on smoking status, and clinical outcomes of smoking cessation therapies in a Turkish population. METHODS: 130 smokers and 130 non-smokers were recruited. Individuals who never smoked were described as non-smokers. 130 smokers were treated with nicotine replacement therapy (NRT) (n = 40), bupropion (n = 47), bupropion + NRT (n = 15), and varenicline (n = 28). Smokers were checked by phone after 12 weeks of treatment whether they were able to quit smoking or not. Genotyping and phenotyping were performed. RESULTS: Cessation rates were as follows; 20.0% for NRT, 29.8% for bupropion, 40.0% for bupropion + NRT, 57.1% for varenicline (p = 0.013). The frequency of ABCB1 1236TT-2677TT-3435TT haplotype was significantly higher in non-smokers as compared to smokers (21.5% vs. 10.8, respectively; p = 0.018). Neither smoking status nor smoking cessation rates were associated with genetic variants of CYP2A6 (p = 0.652, p = 0.328, respectively), or variants of CYP2B6 (p = 0.514, p = 0.779, respectively). CONCLUSION: Genetic variants of the drug transporter ABCB1 and the 1236TT-2677TT-3435TT haplotype was significantly associated with non-smoking status. Neither ABCB1 nor CYP2A6, CYP2B6 genetic variants were associated with smoking cessation rates at the 12th week of drug treatment.

Preparation and characterization of cyclodextrin nanosponges for organic toxic molecule removal.

Cyclodextrin-based nanosponges (CD-NS) are considered as safe and biocompatible systems for removing toxic molecules from the body. Rapid removal of toxic molecules that are formed in the body from certain food constituents, is relevant especially for patients affected by chronic kidney disease. Within the scope of this study, innovative cyclodextrin polymers were synthesized to form nanosponges able to remove indole, before it could form the toxic indoxyl sulfate in the body. Furthermore, in vivo studies were carried out using the two optimal CD-NS formulations by assessing physicochemical properties, stability, indole adsorption capacity and in vitro cytotoxicity. NS prepared from ß-cyclodextrin cross-linked with toluene diisocyanate was found to be the most effective NS with an in vitro indole adsorption capacity of over 90%. In addition, this derivative was more stable in gastrointestinal media. Animal studies further revealed that oral CD-NSs did not tend to accumulate and damage gastrointestinal tissues and are excreted from the GI tract with minimal absorption. In conclusion, this study suggests that CD-NS formulations are effective and safe in removing toxic molecules from the body. Their potential use in veterinary or human medicine could reduce dialysis frequency and avoid hepatic and cardiac toxicity avoiding the indole formation.

In vivo evaluation of chitosan based local delivery systems for atorvastatin in treatment of periodontitis.

Periodontitis is a local inflammatory disease initiated by bacteria accumulation and results in cytokine mediated alveolar bone resorption and tissue destruction. In this study, the effect of locally delivered atorvastatin (2% w/v) containing chitosan formulations in the treatment of periodontitis was evaluated in rats with ligature induced periodontitis. The levels of interleukin-1beta (IL-1ß), IL-6, IL-8, IL-10, transforming growth factor-ß1 (TGF-ß1), TGF-ß2 and TGF-ß3 were measured after treatment with formulations. Histomorphometric analysis included the measurements of the area of alveolar bone and the distance between cemento-enamel junction (CEJ) and connective tissue attachment to tooth. Inflammatory and osteoclastic activity scores were given semiquantitatively. Following the administration of atorvastatin, release of pro-inflammatory (IL-1ß, IL-6 and IL-8) and anti-inflammatory (TGF-ß1 and TGF-ß2) cytokines was found to decrease, with a significant alveolar bone healing, when compared to that of control. The anti-inflammatory effect was observed to enhance in presence of chitosan. These findings suggest that chitosan based delivery system for a statin group drug, atorvastatin is a promising for the treatment of periodontal disease.

Cardioprotective effects of Viscum album L. subsp. album (European misletoe) leaf extracts in myocardial ischemia and reperfusion.

ETHNOPHARMACOLOGICAL RELEVANCE: Viscum album L. (European mistletoe) is a hemiparasitic plant belonging to Loranthaceae family and has been used in Turkish traditional medicine for the treatment of cardiovascular disorders and heart diseases such as hypertension, tachycardia and angina pectoris. AIM OF THE STUDY: The present study investigated the cardioprotective effects of V. album leaf extracts in myocardial ischemia and reperfusion injury in rats. MATERIAL AND METHODS: Lyophilized aqueous (AVa) and methanolic (MVa) extracts of V. album were prepared from dried leaf. The isolated hearts were perfused with V. album extracts prior to and during 35min of ischemia induced by coronary artery occlusion. After 120min of coronary reperfusion, infarct size was determined by triphenyltetrazolium staining. RESULTS: Both AVa and MVa extracts reduced the extent of infarction compared with untreated control hearts, but protective effect of MVa had more potential in low concentration; infarct size as proportion of ischemic risk zone: AVa 17.5±1.5%; Mva 20.3±2.5%, both P<0.01 versus control 38.1±1.4%. This protective effect was comparable to infarct limitation induced by ischemic preconditioning (21.5±2.4%). Inhibition of nitric oxide synthesis with L-NG-nitroarginine methyl ester completely abrogated the protection afforded by both extracts. ATP-sensitive K+ channel blockade by glibenclamide abrogated the protection afforded by MVa while attenuating, but not abolishing, the protective action of Ava. CONCLUSIONS: This study provided the first experimental evidence that V. album leaf extracts can mediate nitric oxide-dependent cardioprotection against myocardial injury produced by ischemia/reperfusion insult. With this study, popular usage of V. album extracts in Turkish folk medicine as a remedy for cardiac diseases was justified.

Comparison of endothelin and nitric oxide synthase blockers on hemorheological parameters in endotoxemic rats.

BACKGROUND/AIM: Septic shock is an important health problem that vastly alters cardiovascular and hemodynamic status. Increased production of nitric oxide (NO) and endothelin is a counterpart of this endotoxemic state. This study was conducted to test the hypothesis that nonselective NO synthesis blocker (L-NAME), inducible NO synthesis blocker (L-canavanine), or endothelin receptor antagonist (bosentan) will reverse the effects of sepsis on hemorheological parameters. MATERIALS AND METHODS: Forty-eight male Sprague-Dawley rats were used in 8 groups: saline (control), endotoxin, bosentan, L-NAME, L-canavanine, endotoxin + bosentan, endotoxin + L-NAME, and endotoxin + L-canavanine. Blood was withdrawn at the 4th hour of endotoxemic state. Erythrocyte deformability and erythrocyte aggregation were determined by laser-assisted optical rotational cell analyzer at 37 °C. Plasma viscosity (mPa.s) was measured by a cone-plate viscometer with 0.5 mL of plasma. RESULTS: Endotoxin administration significantly increased aggregation half-time and lowered erythrocyte aggregation amplitude and aggregation index compared to the control, indicating a slower and weaker aggregation pattern. L-NAME and L-canavanine alleviated the effects of endotoxin on erythrocyte aggregation without altering the values in the control animals. However, bosentan did not perform such a restoration. CONCLUSION: This finding suggests that these restoration effects of the blockers occur via their modulation of nitric oxide synthesis rather than through the endothelin pathway.

Effects of ATP-sensitive potassium channel blockers on vascular hyporeactivity, mesenteric blood flow, and survival in lipopolysaccharide-induced septic shock model.

In this study, the possible therapeutic effects of various ATP-sensitive potassium channel (KATP) blockers (glibenclamide, repaglinide, 5-HD, HMR-1098) have been tested in experimental septic shock model. Rats were given lipopolysaccharide (1 mg·kg(-1)) to create experimental shock model and 4 h later, under 400 mg·kg(-1) chloral hydrate anesthesia, parameters such as blood pressure, mesenteric blood flow, the response of mesenteric circulation to phenylephrine (vasoconstrictor stimulation), and organ and oxidative damage were analyzed. Also 75 mg·kg(-1) lethal dose of lipopolysaccharide was given to mice and effects of KATP blockers on survival have been tested. Non-selective blocker glibenclamide with sulphonylurea structure and sarcolemmal KATP channel blocker HMR-1098, which have the similar chemical structure, have improved the pathological parameters such as decrease in mesenteric blood flow, vascular hyporeactivity, but could not prevent the decrease in blood pressure, and oxidative and organ damage that were observed in the shock model. Also, both blockers have decreased the mortality rate from 80% to 40%-50%. Similar (preventive) therapeutic effects were not observed with non-selective blocker repaglinide and mitochondrial KATP channel blocker 5-HD, which were non-sulphonylurea structure. As a result, only KATP channel blockers that have sulphonylurea structure can be a new therapeutic approach in septic shock.

The effect of coniine on presynaptic nicotinic receptors.

Toxicity of coniine, an alkaloid of Conium maculatum (poison hemlock), is manifested by characteristic nicotinic clinical signs including excitement, depression, hypermetria, seizures, opisthotonos via postsynaptic nicotinic receptors. There is limited knowledge about the role of presynaptic nicotinic receptors on the pharmacological and toxicological effects of coniine in the literature. The present study was undertaken to evaluate the possible role of presynaptic nicotinic receptors on the pharmacological and toxicological effects of coniine. For this purpose, the rat anococcygeus muscle and guinea-pig atria were used in vitro. Nicotine (100 µM) elicited a biphasic response composed of a relaxation followed by contraction through the activation of nitrergic and noradrenergic nerve terminals in the phenylephrine-contracted rat anococcygeus muscle. Coniine inhibited both the nitrergic and noradrenergic response in the muscle (-logIC(50) = 3.79 ± 0.11 and -logIC(50) = 4.57 ± 0.12 M, respectively). The effect of coniine on nicotinic receptor-mediated noradrenergic transmission was also evaluated in the guinea-pig atrium (-logIC(50) = 4.47 ± 0.12 M) and did not differ from the -logIC(50) value obtained in the rat anococcygeus muscle. This study demonstrated that coniine exerts inhibitory effects on nicotinic receptor-mediated nitrergic and noradrenergic transmitter response.

Antitumor Efficacy of Bacillus Calmette-Guerin Loaded Cationic Nanoparticles for Intravesical Immunotherapy of Bladder Tumor Induced Rat Model.

For bladder cancer, intravesical chemo/immunotherapy is widely used as adjuvant therapy after surgical transurethral resection. Bacillus Calmette-Guerin (BCG) is a live attenuated Mycobacterium of the same family as tuberculosis, that is capable of inducing a local inflammatory response upon instillation into the bladder. Intravesical therapy with BCG has proved to be more effective in the prophylaxis and treatment of superficial bladder tumors than most chemotherapeutic agents used for the same indication. However, compared to intravesical chemotherapy, BCG immunotherapy provokes more pronounced local and systemic reactions. In addition to the commonly induced granulomatous inflammatory changes in the bladder, which produce irritative symptoms, this therapy may cause systemic side effects varying from mild malaise and fever to, in rare instances, life-threatening or fatal sepsis. Nanoparticles with positive surface charge and mucoadhesive properties were developed to overcome these side effects. Hence, the aim of this study was to optimize and evaluate cationic chitosan (CS) nanoparticles encapsulating BCG in terms of antitumor efficacy after intravesical administration in bladder tumor, induced in rat model. It was found that nanoparticle formulations of 269-375 nm in size can be produced with 42% encapsulation efficiency. The zeta potential was positive and was suitable for intravesical administration. Antitumor efficacy was determined over the parameters of histopathological evaluation, survival rate and mean bladder weight in comparison to treatment with commercial BCG solution. Concerning survival rates, BCG-loaded chitosan nanoparticles resulted in significantly longer survival than BCG commercial product (up to 86 days of survival with no systemic side effects). When compared to healthy bladder weight averages, all groups (especially BCG commercial solution) showed higher bladder weights confirming tumor formation. Histopathological findings confirmed antitumor activity in all treatment groups and optimum findings were observed in groups treated with CS nanoparticles encapsulating BCG. At the same time, significant nanoparticle accumulation in bladder tissues was observed especially for BCG-loaded CS group. In this study, it was clearly observed that cationic CS nanoparticles provide a significantly improved perspective in intravesical immunotherapy of bladder tumors.

Cationic core-shell nanoparticles for intravesical chemotherapy in tumor-induced rat model: safety and efficacy.

Mitomycin C (MMC) has shown potent efficacy against a wide spectrum of cancers and is clinical first choice in superficial bladder tumors. However, intravesical chemotherapy with MMC has been ineffective due to periodical discharge of the bladder and instability of this drug in acidic pH, both resulting in high rate of tumor recurrence and insufficiency to prevent progression. Nanocarriers may be a promising alternative for prolonged, effective and safe intravesical drug delivery due to their favorable size, surface properties and optimum interaction with mucosal layer of the bladder wall. Hence, the aim of this study was to evaluate and optimize cationic core-shell nanoparticles formulations (based on chitosan (CS) and poly-ϵ-caprolactone (PCL)) in terms of antitumor efficacy after intravesical administration in bladder tumor induced rat model. Antitumor efficacy was determined through the parameters of survival rate and nanoparticle penetration into the bladder tissue. Safety of the formulations were evaluated by histopathological evaluation of bladder tissue as well as observation of animals treated with MMC bound to nanoparticles. Results indicated that chitosan coated poly-ϵ-caprolactone (CS-PCL) nanoparticles presented the longest survival rate among all treatment groups as evaluated by Kaplan-Meier plotting. Histopathological evaluation revealed that cationic nanoparticles were localized and accumulated in the bladder tissue. As intravesical chemotherapy is a local therapy, no MMC was quantified in blood after intravesical instillation indicating no systemic uptake for the drug which could have subsequently led to side effects. In conclusion, core-shell type cationic nanoparticles may be effective tools for the intravesical chemotherapy of recurrent bladder tumors.

Dexamethasone effects on vascular flow and organ injury in septic mice.

BACKGROUND: To demonstrate the effects of low-dose dexamethasone treatment on mesenteric artery blood flow, oxidative injury, vascular reactivity, and survival in Swiss albino mice with intra-abdominal polymicrobial sepsis accomplished by cecal ligation and puncture (CLP). METHODS: Mice were allocated to CLP + saline, CLP + dexamethasone, sham + saline, and sham + dexamethasone subgroups to evaluate blood flow, organ injury, and vascular response to consecutive phenylephrine administrations at 24, 48, and 72 h. Survival rates were also evaluated in a different group of mice. Dexamethasone (1 mg/kg/d) and saline (4 mL/kg/d) were administered intraperitoneally to mice 2 h after CLP or sham procedure, whichever appropriate, and repeated once a day until evaluation time at 48 and 72 h. Relaparotomy was performed at the concerned time and mesenteric blood flow was measured, and liver, lung, and peritoneum samples were obtained. Alteration in mesenteric blood flow response to intravenous phenylephrine injections was recorded at the related time intervals in different mice groups. Survival group was followed up by 7-d administration of dexamethasone or saline for 18 d. RESULTS: The significant fall in mesenteric blood flow after CLP ameliorated with dexamethasone treatment at 48 and 72 h. Dexamethasone also diminished the malonyl dialdehyde level, which is an indicator of organ injury raised after CLP, at 24 h in liver, lung, and peritoneum samples. Dexamethasone therapy has significantly enhanced the vascular response to phenylephrine injections at all doses; however, no change was observed in survival rates. CONCLUSIONS: Low-dose dexamethasone has beneficial effects on mesenteric blood flow and organ injury in experimental sepsis models.

Prolonged retention and in vivo evaluation of cationic nanoparticles loaded with Mitomycin C designed for intravesical chemotherapy of bladder tumours.

To overcome the recurrence problem in bladder tumours; nanoparticles with positive surface charge may improve interaction with biological membranes for intravesical administration. The aim of this study was to design, develop and evaluate (in vitro-in vivo) cationic nanoparticles based on chitosan, poly-L-lysine or polycaprolactone for the effective intravesical delivery of chemotherapeutic agent MMC in a rat model. Poly-L-lysine-coated polycaprolactone nanoparticles and chitosan-coated polycaprolactone nanoparticles were prepared by the double emulsion technique. Chitosan nanoparticles were prepared by ionic gelation. It was found that nanoparticle formulations of 160-320 nm in size can be produced in 14-35% encapsulation efficiency. Variability in the particle size of nanoparticles depended on the preparation method. Encapsulation was increased by two-fold for CS-PCL as a result of the double emulsion technique. Commercial MMC product in solution form and cationic nanoparticle formulations were compared for in vivo bladder retention properties and effect of formulations on urine volume.

Antinociceptive, free radical-scavenging, and cytotoxic activities of Acanthus hirsutus Boiss.

In vivo antinociceptive and in vitro radical scavenging and cytotoxic activities of Acanthus hirsutus Boiss. aqueous extract were investigated to give a new insight into plant usage in traditional medicine. The extract showed significant antinociceptive activity in acetic acid-induced writhing test in mice after oral application and did not change the hind-leg retraction period in the hot-plate test for any dose applied. In addition, the extract showed radical-scavenging activity against 2,2-diphenyl-1-picryl-hydrazyl, nitric oxide, and superoxide radicals similar to those of standard compounds 3-t-butyl-4-hydroxyanisole, ascorbic acid (vitamin C), and quercetin. The gallic acid equivalent total phenolic content of the plant was found to be 65.4 mg/g dry extract. Cytotoxic activity of the aqueous extract was tested against 3 different cancer cell lines-Hep-2 (human larynx epidermoid carcinoma), RD (human rhabdomyosarcoma), and L20B (transgenic murine L cells)-and 1 noncancerous cell line (VERO) using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide method. Through the phytochemical studies, the following compounds were isolated: 3 lignan glucosides [(-)-syringaresinol-di-O-ß-glucopyranoside, (-)-medioresinol-di-O-ß-D-glucopyranoside, (-)-pinoresinol-4'-O-ß-glucopyranoside], 2 benzoxazinoids [2-hydroxy-1,4-benzoxazin-3(4H)-one, (2R)-2-O-ß-glucopyranosyl-1,4-benzoxazin-3(4H)-one], 4 phenylethanoid glycosides (acteoside, leucosceptoside A, martynoside, hattushoside), and 2 phenylpropanoid glucosides (sinapyl aldehyde-4-O-ß-glucopyranoside, sinapyl alcohol-4-O-ß-glucopyranoside). Cytotoxic and radical-scavenging activities of the isolated compounds were also determined. 2-hydroxy-1,4-benzoxazin-3(4H)-one and acteoside were the most active compounds in both experiments.

Antinociceptive activity of coniine in mice.

ETHNOPHARMACOLOGICAL RELEVANCE: Hemlock was used as an analgesic in certain ethnopharmacological traditions and there has been no record about the antinociceptive effect of coniine which is the major alkaloid compound of Hemlock. AIM OF THIS STUDY: The present study was undertaken to evaluate the possible antinociceptive activity of coniine. MATERIAL AND METHODS: Antinociceptive activity of coniine was tested dose in Hotplate test (thermal pain model) and in Writhing test (chemical pain model) in different nociception models. RESULTS: Coniine caused a prolongation in reaction time in Hotplate test at 20mg/kg dose. In addition, it was observed that coniine decreased the number of writhes in Writhing test. Both data indicated an antinociceptive effect of coniine. A rotarod test was also conducted in order to clarify, whether this activity was related with a loss of locomotion or with an analgesic activity. None of the chemical agents at those doses used in experiments caused a loss of locomotor activity. It was also shown that antinociceptive effect of morphine was potentialized by coniine which was inhibited by nicotinic receptor blocker mecamylamine (1mg/kg). CONCLUSION: Coniine has antinociceptive effect via the nicotinic receptors. A pharmacological assessment about the painless death of Socrates due to Hemlock (coniine) toxicity has also been presented by using this data.

Effect of intraarticular injection of lornoxicam on the articular cartilage & synovium in rat.

BACKGROUND & OBJECTIVE: Intraarticular (i.a) drug application is consider to be a new therapeutic approach for the treatment of postoperative pain after arthroscopic knee surgery without any systemic adverse effects. Lornoxicam, a nonsteroid anti-inflammatory drug is a short acting agent, and its anti-inflammatory and analgesic activity may be effective in the postoperative pain management in minor surgery. In this study, the effects of intraarticular administration of lornoxicam on the synovium and articular cartilage in the rat knee joint were investigated. METHODS: Lornoxicam (0.25 ml) was given as an injection into the right knee joint and 0.25 ml of 0.9 per cent saline solution by injection into the left knee joint as a control in 25 rats. Groups of five rats were sacrificed by a lethal injection of ketamine 1st, 2nd, 7th, 14th and 21st days after lornoxicam administration. Knee joints were detached, fixed in 10 per cent buffered formalin and decalcified. Serial sections of 5 microm were stained with haematoxylin-eosin and evaluated for the presence of inflammation in the articular, periarticular regions and synovium. Inflammatory changes in the joints were graded according to a five-point scale, histologically. RESULTS: There were no significant differences in inflammation and cartilage degeneration, between control and lornoxicam applied knees. Grade 3 inflammatory changes occurred only in one knee in lornoxicam group, at 24 h after injection. No pathological changes were observed in both groups at any time point. INTERPRETATION & CONCLUSION: Lornoxicam did not show significant effect on inflammation on rat synovia in knee joint. Further studies including in human need to be done before any recommendations are made for i.a. administration of lornoxicam.

Chemical preconditioning effect of 3-nitropropionic acid in anesthetized rat heart.

Short ischemic episodes increase tolerance against subsequent severe ischemia in the heart. Nitropropionate (3-NP), an irreversible inhibitor of succinic dehydrogenase of the mitochondrial complex II, was shown to induce protective effect against ischemic brain injury. The aim of this study was to investigate the possible protective effect of 3-NP on regional ischemia in preconditioned rat heart in vivo. Hearts were assigned into three groups: first, in order to induce ischemic preconditioning (IP) 5 min ischemia separated by 10 min reperfusion protocol was used; second, non-preconditioned group was used as control; and third, 3-NP (20 mg/kg, i.p.) was injected 3 h before the surgical procedure in order to induce chemical preconditioning. In all these groups, 30 min regional ischemia was followed by 60 min reperfusion. Infarct size, bax expression, number of ventricular ectopic beats (VEB), duration of ventricular tachycardia (VT) and ventricular fibrillation (VF) were significantly decreased in ischemic preconditioning and 3-NP pretreatment groups, whereas bcl-2 values were not markedly changed in these groups during occlusion period. These results showed that in the anesthetized rat heart 3-NP induced chemical preconditioning by decreasing infarct size, number of VEB, duration of VT and VF. Protective effect is associated with via decreased production of bax protein expression.

Tezosentan attenuates organ injury and mesenteric blood flow decrease in endotoxemia and cecal ligation and puncture.

BACKGROUND: Decreased mesenteric blood flow and multiple organ injury due to free radicals are the consequences of septic shock. Since the blockade of endothelin receptors was reported to exert beneficial effects, we investigated the effects of tezosentan, a novel dual endothelin receptor antagonist, in two different experimental models of septic shock induced either by the injection of Escherichia coli endotoxin (ETX, 20 mg/kg, i.p.) or by cecal ligation and puncture (CLP). STUDY DESIGN: Swiss albino mice received tezosentan (10 mg/kg, i.p.) or its solvent saline (0.9% NaCl, w/v) twice at 2 and 22 h after ETX or CLP. At 24 h, the animals were anesthetized and the mesenteric blood flow was monitored for 15 min by using perivascular ultrasonic Doppler flowmeter. Then the animals were exsanguinated, and spleen, liver, and kidneys were isolated accordingly for histopathological examination. Thiobarbituric acid reacting substances and glutathione and myeloperoxides activities were also determined in the liver. RESULTS: In both ETX and CLP models, there was a decrease in mesenteric blood flow which was blocked by tezosentan. Similarly, tezosentan significantly attenuated the histopathological injury inflicted by both models. Although the glutathione levels were decreased and thiobarbituric acid reacting substances and myeloperoxidase activity were increased by ETX and CLP, tezosentan has failed to block these alterations in a consistent manner. However, a significant interaction between CLP and tezosentan with regard to myeloperoxidase activity and glutathione should be taken as partial evidence to explain the underlying mechanism of protection offered by tezosentan against liver injury. CONCLUSIONS: Therefore, we concluded that tezosentan, by working via mechanisms mostly other than the blockade of free radical induced damage, is a useful treatment option for combating the deleterious effects of septic shock such as mesenteric ischemia as well as liver, spleen, and kidney injury.

Glibenclamide attenuates the antiarrhythmic effect of endotoxin with a mechanism not involving K(ATP) channels.

The role of K(ATP) channels in the antiarrhythmic effect of Escherichia coli endotoxin-induced nitric oxide synthase (iNOS) was examined in an anesthetised rat model of myocardial ischemia and reperfusion arrhythmia by using glibenclamide (1 mg kg(-1)), nateglinide (10 mg kg(-1)) and repaglinide (0.5 mg kg(-1)). Endotoxin (1 mg kg(-1)) was administered intraperitoneally 4 h before the occlusion of the left coronary artery and glibenclamide, nateglinide or repaglinide was administered 30 min before coronary artery occlusion. We also evaluated the effects of K(ATP) channel blockers and nonselective K(+) channel blocker tetraethylammonium (TEA) on cardiac action potential configuration in the atria obtained from endotoxemic rats. The mean arterial blood pressure of rats receiving endotoxin was lower during both the occlusion and reperfusion periods. Endotoxin significantly reduced the total number of ectopic beats and the duration of ventricular tachycardia. Glibenclamide, but not nateglinide and repaglinide, prevented the hypotension and antiarrhythmic effects of endotoxin. Atria obtained from endotoxin-treated rats had prolonged action potential duration. This effect was abolished with pretreatment of iNOS inhibitors, l-canavanine and dexamethasone and perfusion of glibenclamide, but not with TEA and non-sulfonylurea drug, nateglinide. We demonstrated that glibenclamide inhibits the antiarrhythmic effect of endotoxin and this effect does not appear to involve K(ATP) channels.