The cardioprotective effect of microRNA-103 inhibitor against isoprenaline-induced myocardial infarction in mice through targeting FADD/RIPK pathway.

OBJECTIVE: The current study investigates the effect of the innovative phosphorothioate modified backbone locked nucleic acid (LNA) of microRNA-103 (miR-103) specifically designed for systemic delivery in the silencing of miR-103 in experimentally induced myocardial infarction (MI). MicroRNA-103 is a small non-coding RNA which regulates Fas-associated protein with death domain (FADD) gene expression, which is a negative regulator for necroptosis occurs during the progression of MI. MATERIALS AND METHODS: Experimental male mice were allocated into three groups; the first group received normal saline, the second group was injected with isoprenaline and served as the infarcted control, while the third group was treated with LNA miR-103 power inhibitor before isoprenaline injection. Blood and heart samples were used for biochemical analysis of miR-103, FADD, receptor-interacting protein kinase (RIPK), nuclear factor-κß, tumor necrosis factor-α, interleukin-6, troponin-I and creatine kinase-MB (CK-MB) as well as the histological examination of heart tissue. RESULTS: The treated mice showed marked improvement in the troponin-I and CK-MB levels with almost normal histological structure of heart tissue. Significant inhibition of miR-103 accompanied by increased FADD expression and markedly decreased expression of the other biomarkers were observed in the hearts of the treated mice. CONCLUSIONS: LNA miR-103 inhibitor is a potent cardioprotective agent and can be a promising treatment against MI through targeting FADD/RIPK pathway.

Fecal metabolomics based on mass spectrometry to investigate the mechanism of qishen granules against isoproterenol-induced chronic heart failure in rats.

Qishen granules, derived from clinical experience formula, has been widely used to improve and treat myocardial ischemic chronic heart failure in China. However, the mechanism of action of Qishen granules in the treatment of chronic heart failure is unclear. This study aimed to discover potential biomarkers of isoproterenol-induced chronic heart failure rats and investigate the potential mechanism of Qishen granules treatment of chronic heart failure. The fecal metabolomics method based on ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry was used to analyze the therapeutic effect and metabolic changes of Qishen granules on chronic heart failure rats. Totally, 17 potential biomarkers were identified, involving bile acid metabolism, fatty acid metabolism, inflammatory response, and amino acid metabolism. For bile acid metabolism, we selected 12 bile acids (two of which were potential biomarkers in nontargeted metabolomics) for quantitative analysis. The quantitative results of bile acids showed that after Qishen granules treatment, the contents of bile acids such as ursodeoxycholic acid and glycodeoxycholic acid were similar to those of health group. This study helps to understand the pathogenesis of isoproterenol-induced chronic heart failure and the therapeutic mechanism of Qishen granules from the perspective of metabolic pathways.

The protective effect of piperine against isoproterenol-induced inflammation in experimental models of myocardial toxicity.

Myocardial infarction (MI) eventually exacerbates inflammatory response due to the release of inflammatory and pro-inflammatory factors. The aim of this study is to explore the protective efficacy of piperine supplementation against the inflammatory response in isoproterenol (ISO)-induced MI. Masson Trichome staining was executed to determine myocardial tissue architecture. Immunohistochemistry was performed for IL-6, TNF-α. RT-PCR studies were performed to ascertain the gene expression of IL-6, TNF-α, iNOS, eNOS, MMP-2, MMP-9, and collagen-III. Western blotting was performed to determine expression of HIF-1α, VEGF, Nrf-2, NF-ƙB, Cox-2, p-38, phospho-p38, ERK-1/2, phospho-ERK-1/2, and collagen-I. HIF-1α, VEGF, and iNOS expression were significantly upregulated with concomitant decline in eNOS expression in the heart myocardial tissue of rats received ISO alone whereas piperine pretreatment prevented these changes in ISO administered rats. Current results revealed ROS-mediated activation of MAPKs, namely, p-p38, p-ERK1/2 in the heart tissue of ISO administered group. Piperine pretreatment significantly prevented these changes in ISO treated group. NF-κB is involved in the modulation of gene expressions responsible for tissue repair. ISO-induced NF-κB-p65 expression was significantly reduced in the group pretreated with piperine and mitigated extent of myocardial inflammation. A significant increase in cardiac fibrosis upon ISO treatment was reported due to the increased hydroxyproline content, MMP-2 & 9 and upregulation of collagen-I protein compared to control group. All these cardiac hypertrophy markers were decreased in 'piperine pretreated ISO administered group' compared to group received ISO injection. Current findings concluded that piperine as a nutritional intervention could prevent inflammation of myocardium in ISO-induced MI.

Fasudil protects against isoproterenol-induced myocardial infarction in mice via inhibiting Rho/ROCK signaling pathway.

OBJECTIVE: Myocardial infarction (MI) is one of the most common diseases in cardiovascular medicine, and the risk of MI is very serious. Therefore, the purpose of this study was to explore the effect of fasudil on isoproterenol (ISO)-induced MI in mice. MATERIALS AND METHODS: Forty C57BL/6 mice were divided into four groups, namely, control group, MI group, low dose fasudil and MI treatment group (low fasudil group), high dose fasudil, and MI treatment Group (high fasudil group). MI group and the fasudil group were injected subcutaneously with ISO (85 mg/kg) twice, and every 24 h MI was induced. Low-dose and high-dose fasudil groups were treated with 3 mg/kg/day and 10 mg/kg/day for 4 weeks before the injection of ISO. Cardiac function measured in the fourth week after ISO injection, and body weight and whole heart weight were weighed. Infarct area and thickness were analyzed by HE staining. Besides, the degree of myocardial damage was measured by detecting serum CK and LDH, and excised heart tissue was detected by Real Time-Polymerase Chain Reaction (PCR) and Western blot. RESULTS: In MI group, the cardiac function was significantly decreased: the left ventricular short axis shortening rate (FS) and left ventricular ejection fraction (EF) were significantly decreased, the left ventricular volume was significantly increased, and the myocardial injury markers CK and LDH were significantly increased. In addition, fasudil treatment significantly relieved heart function after MI in a dose-dependent manner, reducing cardiomyocytes oxidative damage, inhibiting apoptosis. CONCLUSIONS: Fasudil can reduce ISO-induced MI, reducing cardiomyocytes oxidative damage, inhibiting apoptosis by inhibiting the Rho/ROCK signaling pathway.

Anti-Ischemic Activity of Fabomotizole Hydrochloride under Conditions of Endothelial Dysfunction.

Anti-ischemic activity of fabomotizole hydrochloride was studied on the model of subendocardial ischemia in rats with endothelial dysfunction. Endothelial dysfunction was modeled by intragastric administration of methionine (3 g/kg, once a day for 7 days). Acute subendocardial ischemia was induced in narcotized rats by intraperitoneal injection of isoproterenol (20 µg/kg/min over 5 min). Fabomotizole hydrochloride (intraperitoneally, 15 mg/kg) significantly reduced isoproterenol-induced ST segment depression in animals with endothelial dysfunction and with intact vasculature.

Role of TRPP2 in mouse airway smooth muscle tension and respiration.

The transient receptor potential polycystin-2 (TRPP2) is encoded by the Pkd2 gene, and mutation of this gene can cause autosomal dominant polycystic kidney disease (ADPKD). Some patients with ADPKD experience extrarenal manifestations, including radiologic and clinical bronchiectasis. We hypothesized that TRPP2 may regulate airway smooth muscle (ASM) tension. Thus, we used smooth muscle-Pkd2 conditional knockout (Pkd2SM-CKO) mice to investigate whether TRPP2 regulated ASM tension and whether TRPP2 deficiency contributed to bronchiectasis associated with ADPKD. Compared with wild-type mice, Pkd2SM-CKO mice breathed more shallowly and faster, and their cross-sectional area ratio of bronchi to accompanying pulmonary arteries was higher, suggesting that TRPP2 may regulate ASM tension and contribute to the occurrence of bronchiectasis in ADPKD. In a bioassay examining isolated tracheal ring tension, no significant difference was found for high-potassium-induced depolarization of the ASM between the two groups, indicating that TRPP2 does not regulate depolarization-induced ASM contraction. By contrast, carbachol-induced contraction of the ASM derived from Pkd2SM-CKO mice was significantly reduced compared with that in wild-type mice. In addition, relaxation of the carbachol-precontracted ASM by isoprenaline, a ß-adrenergic receptor agonist that acts through the cAMP/adenylyl cyclase pathway, was also significantly attenuated in Pkd2SM-CKO mice compared with that in wild-type mice. Thus, TRPP2 deficiency suppressed both contraction and relaxation of the ASM. These results provide a potential target for regulating ASM tension and for developing therapeutic alternatives for some ADPKD complications of the respiratory system or for independent respiratory disease, especially bronchiectasis.

Duration of ß-adrenoceptor blockade associated with once-daily oral administration of atenolol in healthy dogs.

OBJECTIVE To test the hypothesis that once-daily oral administration of atenolol would attenuate the heart rate response to isoproterenol for 24 hours. ANIMALS 20 healthy dogs. PROCEDURES A double-blind randomized placebo-controlled crossover study was conducted. Dogs were assigned to receive atenolol (1 mg/kg, PO, q 24 h) or a placebo for 5 to 7 days. After a washout period of 7 days, dogs then received the other treatment. Heart rate at rest (HRr) and heart rate induced by administration of isoproterenol (HRi) as a constant rate infusion (0.2 µg/kg/min for 5 to 7 minutes) were obtained by use of ECG 0, 0.25, 3, 6, 12, 18, and 24 hours after administration of the final dose of atenolol or the placebo. A mixed-model ANOVA was used to evaluate effects of treatment, time after drug or placebo administration, treatment-by-time interaction, period, and sequence on HRr and HRi. RESULTS Effects of sequence or period were not detected. There was a significant effect of treatment and the treatment-by-time interaction on HRi. Atenolol significantly attenuated HRi for 24 hours but did so maximally at 3 hours (least squares mean ± SE, 146 ± 5 beats/min and 208 ± 5 beats/min for atenolol and placebo, respectively). The effect at 24 hours was small (193 ± 5 beats/min and 206 ± 5 beats/min for atenolol and placebo, respectively). Atenolol had a small but significant effect on HRr. CONCLUSIONS AND CLINICAL RELEVANCE This study of healthy dogs receiving atenolol supported a recommendation for a dosing interval < 24 hours.

Suppression of isoproterenol-induced cardiotoxicity in rats by raspberry ketone via activation of peroxisome proliferator activated receptor-α.

The peroxisome proliferator-activated receptor-α (PPAR-α) controls the lipid and glucose metabolism and also affects inflammation, cell proliferation and apoptosis during cardiovascular disease. Raspberry ketone (RK) is a red raspberry (Rubusidaeus, Family-Rosaceae) plant constituent, which activates PPAR-α. This study was conducted to assess the cardioprotective action of RK against isoproterenol (ISO)-induced cardiotoxicity. Wistar rats were randomly divided into six groups (six rats/group). Rats were orally administered with RK (50, 100 and 200 mg/kg, respectively) and fenofibrate (standard, 80 mg/kg) for 28 days and ISO was administered (85 mg/kg, subcutaneously) on 27th and 28th day. Administration of ISO in rats significantly altered hemodynamic and electrocardiogram patterns, total antioxidant capacity, PPAR-α, and apolipoprotein C-III levels. These myocardial aberrations were further confirmed during infarct size, heart weight to body weight ratio and immunohistochemical assessments (caspase-3 and nuclear factor-κB). RK pretreatment (100 and 200 mg/kg) significantly protected rats against oxidative stress, inflammation, and dyslipidemia caused by ISO as demonstrated by change in hemodynamic, biochemical and histological parameters. The results so obtained were quite comparable with fenofibrate. Moreover, RK was found to have binding affinity with PPAR-α, as confirmed by docking analysis. PPAR-α expression and concentration was also found increased in presence of RK which gave impression that RK probably showed cardioprotection via PPAR-α activation, however direct binding study of RK with PPAR-α is needed to confirm this assumption.

Resveratrol protects against isoproterenol induced myocardial infarction in rats through VEGF-B/AMPK/eNOS/NO signalling pathway.

According to our previous results, resveratrol (RSV, 3, 5, 4-trihydroxystilbene), a naturally polyphenolic phytoalexin, could attenuate myocardial ischemia/reperfusion injury through up-regulation of vascular endothelial growth factor B (VEGF-B) in isolated rat heart or H9c2 cells. However, the molecular mechanism remains unclear. In this study, we investigated the protective effect of RSV on myocardial infarction (MI) in rats and further explored the underlying signal pathway after VEGF-B. Rats received RSV or normal saline by intragastric administration for 7 consecutive days and followed by subcutaneously isoproterenol (ISO) or normal saline injections for another 2 days. We found that RSV pretreatment prevented the unfavourable changes in HW/BW, HW/TL, infarct size, and cell apoptosis in ISO-treated rats. Moreover, superoxide and malondialdehyde (MDA) production were significantly reduced and superoxide dismutase (SOD) was increased by RSV in ISO-treated rats. Furthermore, it showed that RSV pretreatment increased VEGF-B, p-eNOS and p-AMPK expression, and NO production in ISO-treated rats. Using Neonatal Rat Ventricular Myocytes (NRVM), we found that VEGF-B siRNA could abolish the cardio-protective effect of RSV. The enhanced ratios of eNOS phosphorylation to eNOS expression induced by RSV were markedly reversed by VEGF-B siRNA in NRVM also. Meantime, we found that the effect of VEGF-B knock-down on eNOS activation was rescued by AMPK activator AICAR. L-NAME, a NOS inhibitor, could inhibit RSV enhanced eNOS phosphorylation but had no effect on VEGF-B expression in NRVM or in rats. Collectively, our results indicate that RSV exerts cardio-protection from ISO-induced myocardial infarction through VEGF-B/AMPK/eNOS/NO signalling pathway.

Preventive effect of apigenin against isoproterenol-induced apoptosis in cardiomyoblasts.

We investigated the effect of apigenin, a dietary flavonoid, on isoproterenol hydrochloride (ISO)-induced apoptotic signaling in cardiomyoblast H9C2 cells. The results showed that apigenin treatment (10 µM) prevented ISO (31.25 µM)-induced lipid peroxidative levels and antioxidants status in H9C2 cells. Furthermore, apigenin inhibited expression of inflammatory markers in ISO-treated cells. In addition, apigenin prevented ISO-induced DNA damage and apoptotic signaling through modulating the expression of Bax, caspase-3, -8 and -9, cytochrome c, and Fas proteins in H9C2 cells. It is concluded that apigenin prevents ISO-induced antioxidants depletion, oxidative DNA damage, inflammatory, and apoptotic signaling in H9C2 cells. Thus, the present results demonstrated that apigenin has a cardioprotective effect on cardiomyoblasts cells.

Trace Element Determination and Cardioprotection of Terminalia pallida Fruit Ethanolic Extract in Isoproterenol Induced Myocardial Infarcted Rats by ICP-MS.

The trace elements and minerals in Terminalia pallida fruit ethanolic extract (TpFE) were determined by the instrument inductively coupled plasma-mass spectrometry (ICP-MS), and the cardioprotection of TpFE against isoproterenol (ISO)-administered rats was studied. Rats were pretreated with TpFE (100, 300, and 500 mg/kg bw) for 30 days, with concurrent administration of ISO (85 mg/kg bw) for two consecutive days. The levels of trace elements and minerals in TpFE were below the permitted limits of World Health Organization standards. ISO administration significantly increased the heart weight and cardiac marker enzymes in serum, xanthine oxidase, sodium, and calcium in the heart, whereas significantly decreased body weight, reduced glutathione, glutathione-S-transferase, superoxide dismutase, and potassium in the heart. Oral pretreatment of TpFE significantly prevented the ISO-induced alterations. This is the first report that revealed the determination of trace elements and mineral nutrients of TpFE by ICP-MS which plays a principal role in the herbal drug discovery for the treatment of cardiovascular diseases.

Autophagy suppresses isoprenaline-induced M2 macrophage polarization via the ROS/ERK and mTOR signaling pathway.

The objective of this study was to examine the effect of autophagy on stress-induced M2 macrophage polarization in the tumor microenvironment of breast cancer and to determine whether the underlying mechanism was related to the reactive oxygen species (ROS)/ERK and mTOR pathway. In vitro, we found that the basal autophagy level in mouse RAW 264.7 macrophages decreased with the incubation of tumor cell culture supernatant. Similarly, the polarization of RAW 264.7 to M2 macrophages was inhibited by the autophagy inducer rapamycin and increased by the autophagy inhibitor 3-MA or by siBeclin1. In addition, we found that not only was M2 molecule expression down-regulated but intracellular ROS generation was also blocked by autophagy induction. In vivo, we observed that mice that received an isoprenaline injection as a stress agent exhibited augmented implanted breast tumor growth, lung metastasis, intratumoral mRNA expression of M2 molecules and serum ROS generation. In contrast, the intratumoral expression of LC3-II and Beclin1 was decreased. In addition, we observed that isoprenaline induced the up-regulation of the intratumoral expression of phosphorylated mTOR, phosphorylated ERK1/2, phosphorylated Tyr705-STAT3 and HIF-1α, whereas rapamycin induced an opposite effect on the same molecules and could abolish the effects of isoprenaline. These results suggest that autophagy might suppress M2 macrophage polarization induced by isoprenaline via the ROS/ERK and mTOR signaling pathway. Our findings provide a theoretical basis for why high levels of stress hormones accelerate the progression of breast cancer, and autophagy may play a role in determining the outcomes of cancer therapy.

Cardioprotective effects of iron chelator HAPI and ROS-activated boronate prochelator BHAPI against catecholamine-induced oxidative cellular injury.

Catecholamines may undergo iron-promoted oxidation resulting in formation of reactive intermediates (aminochromes) capable of redox cycling and reactive oxygen species (ROS) formation. Both of them induce oxidative stress resulting in cellular damage and death. Iron chelation has been recently shown as a suitable tool of cardioprotection with considerable potential to protect cardiac cells against catecholamine-induced cardiotoxicity. However, prolonged exposure of cells to classical chelators may interfere with physiological iron homeostasis. Prochelators represent a more advanced approach to decrease oxidative injury by forming a chelating agent only under the disease-specific conditions associated with oxidative stress. Novel prochelator (lacking any iron chelating properties) BHAPI [(E)-N-(1-(2-((4-(4,4,5,5-tetramethyl-1,2,3-dioxoborolan-2-yl)benzyl)oxy)phenyl)ethylidene) isonicotinohydrazide] is converted by ROS to active chelator HAPI with strong iron binding capacity that efficiently inhibits iron-catalyzed hydroxyl radical generation. Our results confirmed redox activity of oxidation products of catecholamines isoprenaline and epinephrine, that were able to activate BHAPI to HAPI that chelates iron ions inside H9c2 cardiomyoblasts. Both HAPI and BHAPI were able to efficiently protect the cells against intracellular ROS formation, depletion of reduced glutathione and toxicity induced by catecholamines and their oxidation products. Hence, both HAPI and BHAPI have shown considerable potential to protect cardiac cells by both inhibition of deleterious catecholamine oxidation to reactive intermediates and prevention of ROS-mediated cardiotoxicity.

Histamine H3 Receptor Agonist Imetit Attenuated Isoproterenol Induced Renin Angiotensin System and Sympathetic Nervous System Overactivity in Myocardial Infarction of Rats.

BACKGROUND: Myocardial infarction is an alarming health issue, needs great attention. The present study investigated the role of histamine-H3 receptor (H3R) agonist imetit in relationship to sympathetic and renin angiotensin system in Wistar rats. MATERIALS AND METHODS: Subcutaneous injection of isoproterenol (85 mg/kg) on last 2 consecutive days in per se group and 7 days treatment of different groups at 24 h interval induced myocardial infarction in Wistar rats. H3R agonist imetit (10 mg/kg), H3R antagonist thioperamide (5 mg/kg), losartan (10 mg/kg) were administered orally to evaluate imetit's cardioprotective potential effect by measuring plasma cardiac antioxidant markers, angiotensin II, norepinephrine levels and histopathological analysis. RESULTS: Isoproterenol significantly elevated the angiotensin II and norepinephrine levels in rat plasma. This study revealed that pre-treatment with imetit similar to losartan attenuated norepinephrine and angiotensin II levels whereas thioperamide showed its antagonistic effect by diminishing imetit's effects. Furthermore, its protective effect was confirmed by restoration of cardiac antioxidant markers and histopathological improvement of myocardium integrity. CONCLUSION: This study confirm imetit's cardioprotective potential and also reveals renin angiotensin system, sympathetic system and H3R correlation in isoproterenol induced toxicity in rats. However, molecular studies must be warranted to prove the role of H3R in myocardial infarction.

OMEGA-3 POLYUNSATURATED FATTY ACIDS NORMALIZE THE FUNCTION OF MITOCHONDRIA, ACTIVITY OF ENZYMES OF PROOXIDANT-ANTIOXIDANT SYSTEM AND THE EXPRESSION OF CYTOCHROME Р450 2Е1 AFTER ISOPROTERENOLINDUCED MYOCARDIAL INJURY.

We have studied the influence of dietary ω-3 polyunsaturated fatty acids (ω-3 PUFA) on the functioning of subsarcolemmal and interfibrillar mitochondrial fractions of rat myocardium, changes in expression of cytochrome P450 (CYP2E1) and the activity of enzymes of prooxidant-antioxidant system after isoproterenol-induced myocardial injury. It has been found that in vivo administration of ω-3 PUFA (Epadol 0.1 ml/100 gr of weight for 4 weeks) significantly reduced the swelling of subsarcolemmal and interfibrillar mitochondrial fractions by 65.52% 54.84% respectively, pointing for a decrease of damage of the mitochondrial function evoked by in vivo administration of isoproterenol. In vivo administration of ω-3 PUFAs prevents a decrease in the activity of antioxidant enzymes catalase and superoxide dismutase (2.65 and 7.1- fold, respectively) after isoproterenol-induced myocardial injury. We suggest that the development of oxidative stress after isoproterenol-induced myocardial injury can be caused by a significant increase in the expression of cytochrome P450 2E1 (73.3%), and administration of ω-3 PUFAs prevents such changes.

Triptolide alleviates isoprenaline-induced cardiac remodeling in rats via TGF-ß1/Smad3 and p38 MAPK signaling pathway.

Triptolide (TPL) is a diterpene triepoxide with potent immunosuppressive and anti-inflammatory properties. It is the main effective component of the traditional Chinese herb Tripterygium wilfordii Hook F and has been used in China for centuries to treat immune-related disorders. The present study was conducted to investigate the effects of TPL on cardiac remodeling in rats. Age matched male Wistar rats were used in this study. Cardiac remodeling rat model was established by hypodermic injection of isoprenaline for ten days. The rats were treated with TPL (20 or 100 µg/kg/d) for six consecutive weeks. At the end of the study, the cardiac function, collagen volume fraction, perivascular collagen area and hydroxyproline concentration were studied. Echocardiography, Masson staining, immunohistochemistry, western blot and real-time polymerase chain reaction were performed. The protein and mRNA expression of transforming growth factor-ß1 (TGF-ß1), drosophila mothers against decapentaplegic protein 3 (Smad3) and p38 mitogen activated protein kinase (p38 MAPK) were analyzed. The results indicated that TPL treatment significantly reduced the collagen volume fraction, perivascular collagen area, ventricular weight/body weight ratio and hydroxyproline concentration in myocardial tissue compared with the model group. In addition, it also improved the cardiac function. TPL attenuated cardiac remodeling in rats by down-regulating the p38 MAPK and TGF-ß1/Smad3 signaling pathways. TPL treatment significantly attenuated cardiac fibrosis and improved cardiac function through suppressing the p38 MAPK and TGF-ß1/Smad3 signaling pathway in isoprenaline-induced cardiac remodeling rats. Our findings suggested that TPL might be a novel complementary medicine in the treatment of chronic heart failure.

Involvement of ß3-adrenoceptors in the inhibitory control of cholinergic activity in human bladder: Direct evidence by [(3)H]-acetylcholine release experiments in the isolated detrusor.

Bladder overactivity (OAB) is a multifactorial bladder disorder that requires therapeutics superior to the current pharmacological treatment with muscarinic antagonists. ß3-adrenoceptor (ß3-ADR) agonists represent a novel promising approach that differently addresses the parasympathetic pathway, but the clinical efficacy of these drugs has not been fully elucidated to date. Therefore, we aimed to study the pharmacological mechanisms activated by ß3-ADR agonists at muscular and neural sites in the isolated human bladder. Detrusor smooth muscle strips obtained from male patients undergoing total cystectomy were labelled with tritiated choline and stimulated with electrical field stimulation (EFS). EFS produced smooth muscle contraction and simultaneous acetylcholine ([(3)H]-ACh) release, which mostly reflects the neural origin of acetylcholine. Isoprenaline (INA), BRL37344 and mirabegron inhibited the EFS-evoked contraction and [(3)H]-ACh release in a concentration-dependent manner, yielding concentration-response curves (CRCs) that were shifted to the right by the selective ß3-ADR antagonists L-748,337 and SR59230A. Based on the agonist potency estimates (pEC50) and apparent affinities (pKb) of antagonists evaluated from the CRCs of agonists, our data confirm the occurrence of ß3-ADRs at muscle sites. Moreover, our data are consistent with the presence of inhibitory ß3-ADRs that are functionally expressed at the neural site. Taken together, these findings elucidate the mechanisms activated by ß3-ADR agonists because neural ß3-ADRs participate in the inhibition of detrusor motor drive by reducing the amount of acetylcholine involved in the cholinergic pathway.

Cardioprotective role of H3R agonist imetit on isoproterenol-induced hemodynamic changes and oxidative stress in rats.

The cardioprotective role of histamine H3 receptor (H3R) agonist imetit (IMT) in isoproterenol (ISO)-induced alterations of hemodynamic and oxidative stress was investigated in Wistar rats. In this study, rats were treated with IMT (5 and 10 mg/kg, per orally [p.o.]), carvedilol (10 mg/kg, p.o.) and ISO control group (normal saline) for 7 d, with concurrent subcutaneous administration of ISO (85 mg/kg) at 24 h interval on last two consecutive days whereas control group was administered with vehicle only. ISO significantly attenuated cardiac antioxidant enzymes superoxide dismutase, catalase and increased plasma cardiac injury biomarkers creatine kinase-MB, alanine transaminase and aspartate transaminase. ISO also altered cardiac activity as evidenced by decrease in blood pressure (34.60%) and increase in heart rate (11.40%). The damage due to oxidative stress was revealed by histopathology alterations such as myocyte necrosis, myofibrillar degeneration and pyknotic nucleus. However, pre-treatment with IMT demonstrated restoration of hemodynamic alterations along with significant preservation of antioxidants and myocyte injury-specific marker enzymes. Furthermore, protective effect of IMT was reconfirmed by the histopathological salvage of myocardium. Results of the present study demonstrated the cardioprotective potential of IMT, as evidenced by favorable improvement in ISO-induced hemodynamic, plasma cardiac biomarkers and tissue antioxidant status along with maintenance of integrity of myocardium.

An enantiomerically pure formulation of esmolol attenuates hypotension and preserves heart rate control in dogs.

BACKGROUND: Esmolol is marketed as a racemate (RS-esmolol) with hypotension being the most frequently reported adverse event. Previously, it has been shown that the S-enantiomer (S-esmolol) possesses all of the heart rate (HR) control. The authors studied whether S-esmolol alone mitigates hypotension at similar degrees of HR control compared with RS-esmolol. METHODS: The effects of RS- and S-esmolol on blood pressure (BP) were compared at multiple infusion rates producing similar HR control in dogs (N=21). Differences in BP were further interrogated by monitoring global cardiovascular function and included the R-enantiomer (R-esmolol) (N=3). RESULTS: S-esmolol at half the rate (µg kg min) of RS-esmolol provided the same degree of HR control over all infusion rates. RS-esmolol lowered BP by 3, 6, 11, 20, and 38 mmHg at 90, 300, 600, 1,000, and 2,000 µg kg min, compared with 2, 4, 5, 10, and 16 mmHg at 45, 150, 300, 500, and 1,000 µg kg min for S-esmolol. Decreased BP with RS-esmolol was attributed to decreases in left ventricular developed pressure (LVDP) (-34 mmHg), LVdP/dt+max (-702 mmHg/s), and cardiac output (-1 l/min). R-esmolol also decreased BP (-10 mmHg), LVDP (-10 mmHg), LVdP/dt+max (-241 mmHg/s), and cardiac output (to -0.2 l/min). S-esmolol reversed these trends toward pre-esmolol values by increasing BP (+13 mmHg), LVDP (+12 mmHg), LVdP/dt+max (+76 mmHg/s), and cardiac output (+0.4 l/min). CONCLUSIONS: R-enantiomer provided no HR control, but contributed to the hypotension with RS-esmolol, which appears to be due to negative inotropy. Thus, an S-enantiomer formulation of esmolol may provide similar HR control with less hypotension.

Metformin protects the myocardium against isoproterenol-induced injury in rats through alleviating endoplasmic reticulum stress.

Clinical studies have suggested that metformin, a widely used antidiabetic agent, exerts a direct cardioprotective effect on cardiovascular disease in addition to its blood glucose-lowering activity. This study was designed to identify the role of metformin in rats with isoproterenol (ISO)-induced myocardial injury and to investigate its underlying mechanism. A rat model of myocardial ischemic injury was established by the subcutaneous injection of a high dose of ISO, a beta-adrenergic agonist. The results showed that pretreatment of metformin significantly reduced rat mortality induced by ISO, attenuated the increased plasma lactate dehydrogenase activity and myocardium malondialdehyde level, alleviated the hemodynamic disturbance, inhibited the upregulated gene expression of myocardial probrain natriuretic peptide and alleviated the myocardial morphological injury and apoptosis induced by ISO. Furthermore, western blot analysis showed that metformin suppressed the overexpression of the endoplasmic reticulum stress (ERS) markers cleaved caspase-12 and CEBP-homologous protein induced by ISO and increased the phosphorylation of AMP-activated protein kinase (AMPK). In conclusion, these data suggest that metformin might protect the myocardium against acute ischemic injury in rats at least partially by activating AMPK and alleviating aberrant ERS. These findings might provide further experimental evidence for treating patients at risk of ischemic heart disease with metformin.