Exercise Training Attenuates Acute ß-Adrenergic Receptor Activation-Induced Cardiac Inflammation via the Activation of AMP-Activated Protein Kinase.

Exercise has proven cardiac benefits, but the underlying mechanisms of exercise that protect the heart from acute sympathetic stress injuries remain unknown. In this study, adult C57BL/6J mice and their AMP-activated protein kinase α2 knockout (AMPKα2-/-) littermates were either subjected to 6 weeks of exercise training or housed under sedentary conditions and then treated with or without a single subcutaneous injection of the ß-adrenergic receptor (ß-AR) agonist isoprenaline (ISO). We investigated the differences in the protective effects of exercise training on ISO-induced cardiac inflammation in wild-type (WT) and AMPKα2-/- mice using histology, enzyme-linked immunosorbent assay (ELISA) and Western blotting analyses. The results indicated that exercise training alleviated ISO-induced cardiac macrophage infiltration, chemokines and the expression of proinflammatory cytokines in wild-type mice. A mechanism study showed that exercise training attenuated the ISO-induced production of reactive oxygen species (ROS) and the activation of NLR Family, pyrin domain-containing 3 (NLRP3) inflammasomes. In cardiomyocytes, the ISO-induced effects on these processes were inhibited by AMP-activated protein kinase (AMPK) activator (metformin) pretreatment and reversed by the AMPK inhibitor (compound C). AMPKα2-/- mice showed more extensive cardiac inflammation following ISO exposure than their wild-type littermates. These results indicated that exercise training could attenuate ISO-induced cardiac inflammation by inhibiting the ROS-NLRP3 inflammasome pathway in an AMPK-dependent manner. Our findings suggested the identification of a novel mechanism for the cardioprotective effects of exercise.

Aloin alleviates pathological cardiac hypertrophy via modulation of the oxidative and fibrotic response.

AIMS: Pathological cardiac hypertrophy is a characteristic feature in many cardiovascular diseases (CVDs). Aloin is an anthraquinone glycoside from Aloe species, and the effect of aloin on cardiac hypertrophy and associated fibrotic changes have not been elucidated. This study investigated the effect of aloin against the isoproterenol (ISO)-induced cardiac hypertrophy in rats. MAIN METHODS: Cardiac hypertrophy experimental model was induced in rats by subcutaneous injection of ISO for 14 days. Meanwhile, the animals were administered orally with aloin at doses of 25 and 50 mg/kg/day. On the 15th day, cardiac echocardiography was performed, the heart was collected and subjected for histopathological, gene expression, and immunoblot studies. Additionally, the effect of aloin on ISO-induced hypertrophic changes in H9c2 cells was investigated. KEY FINDINGS: Aloin markedly alleviated ISO-induced heart injury, reduced cardiac hypertrophy, improved cardiac function, and histological alterations in the heart. Mechanistically, aloin attenuated ISO-induced fibrosis via inhibition of the levels of collagen I, α-smooth muscle actin (α-SMA), fibronectin, transforming growth factor-ß (TGF-ß) and pSmad2/3 proteins in the heart. Aloin alleviated ISO-induced myocardial oxidative damage and up-regulated the levels of antioxidant transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) proteins. Moreover, aloin treatment attenuated ISO-induced hypertrophic changes and the generation of reactive oxygen species (ROS) in H9c2 cells in vitro. SIGNIFICANCE: Our findings demonstrated that aloin alleviated ISO-induced cardiac hypertrophy and fibrosis via inhibiting TGF-ß/pSmad2/3 signaling and restoring myocardial antioxidants, and therefore has promising therapeutic potential against cardiac hypertrophy and fibrosis.

[8]-Gingerol exerts anti-myocardial ischemic effects in rats via modulation of the MAPK signaling pathway and L-type Ca2+ channels.

Myocardial ischemia (MI) remains the leading cause of mortality worldwide. Therefore, it is urgent to seek the treatment to protect the heart. [8]-Gingerol (8-Gin), one of the most active ingredients in ginger, has antioxidant, cardiotonic, and cardiovascular protective properties. The present study elucidated the cardioprotection effects and underlying mechanisms of 8-Gin in isoproterenol (ISO)-induced MI. ISO (85 mg/kg/d) was subcutaneously injected for 2 consecutive days to induce acute MI model in rats. Electrocardiography, oxidative stress levels, calcium concentrations, and apoptosis degree were observed. The effects of 8-Gin on L-type Ca2+ current (ICa-L ), contraction, and Ca2+ transients were monitored in rat myocytes via patch-clamp and IonOptix detection systems. 8-Gin decreased J-point elevation and heart rate and improved pathological heart damage. Moreover, 8-Gin reduced the levels of CK, LDH, and MDA, ROS production, and calcium concentrations in myocardial tissue, while increased the activities of SOD, CAT, and GSH. In addition, 8-Gin down-regulated Caspase-3 and Bax expressions, while up-regulated Bcl-2 expression. 8-Gin produced a marked decrease in the expression of p38, JNK, and ERK1/2 proteins. 8-Gin inhibited ICa-L , cell contraction, and Ca2+ transients in isolated rat myocytes. The results indicate that 8-Gin could exert anti-myocardial ischemic effects, which may be associated with oxidative stress reduction, cardiomyocytes apoptosis inhibition through MAPK signaling pathway, and Ca2+ homeostasis regulation via ICa-L modulation.

Exploring cardioprotective potential of esculetin against isoproterenol induced myocardial toxicity in rats: in vivo and in vitro evidence.

BACKGROUND: Esculetin is a natural coumarin derivative from various plants with multiple pharmacological effects. Hence, the present study was undertaken to explore the cardio protective potential of esculetin against isoproterenol induced myocardial toxicity in rats. METHODS: The treatment schedule was fixed for 28 days and the rats were divided into five groups of six each. Rats of group I received the normal saline and served as normal control, group II was received ISO (100 mg/kg body weight) for last two consecutive days of the study and served as disease control. Groups III and IV received esculetin 10 and 20 mg/kg body weight respectively once a day per oral for 28 days along with ISO for last two consecutive days of the study. Cardiac biomarkers such as CK-MB and LDH, membrane bound Na+ /K+ ATPases activity, myocardial lysosomal enzymes activity and tissue antioxidants status were estimated in the heart tissue samples. The histopathological changes in the myocardium were also assessed. Further, DPPH assay was done to evaluate the free radicals scavenging potential of esculetin. Cytoxicity assay, intracellular ROS levels by DCFDA assay and m-RNA expression of TNF-α, IL-6 and NF-κB by quantitative RT-PCR in H9c2 cell lines. RESULTS: The increased levels of CK-MB, LDH, LPO, myocardial lysosomal enzymes and membrane bound Na+ /K+ ATPase levels by ISO administration was significantly increased with concomitant decrease in tissue antioxidant enzymes such as GSH, Catalase, and SOD. Pre-treatment with esculetin for 28 days has significantly decreased the levels of cardiac bio-markers, lysosomal enzymes, membrane bound Na+ /K+ ATPase levels as well as Lipid peroxides which is in contrary to the ISO group. Amelioration of the antioxidant levels were also found in esculetin treated groups. Histopathological examination of heart reveals that myocardial degeneration, mononuclear cell infiltration was noticed in ISO treated rats, whereas the same was restored with esculetin treatment. In H9C2 cell lines esculetin could effectively reduced intracellular ROS inhibition and m-RNA expression of pro-inflammatory cytokines including TNF-α, IL-6 and NF-κB to prevent apoptosis or cell necrosis. CONCLUSION: The study provides the evidence of cardioprotective potentials of esculetin against isoproterenol induced myocardial infarction by antioxidant and myocardial membrane stabilization along with in vitro protection from arsenic induced ROS cell necrosis or apoptosis in H9C2 cells.

Pancreatic Islets Exhibit Dysregulated Adaptation of Insulin Secretion after Chronic Epinephrine Exposure.

Chronic adrenergic stimulation is the dominant factor in impairment of the ß-cell function. Sustained adrenergic exposure generates dysregulated insulin secretion in fetal sheep. Similar results have been shown in Min6 under the elevated epinephrine condition, but impairments after adrenergic removal are still unknown and a high rate of proliferation in Min6 has been ignored. Therefore, we incubated primary rats' islets with half maximal inhibitory concentrations of epinephrine for three days, then determined their insulin secretion responsiveness and related signals two days after removal of adrenaline via radioimmunoassay and qPCR. Insulin secretion was not different between the exposure group (1.07 ± 0.04 ng/islet/h) and control (1.23 ± 0.17 ng/islet/h), but total islet insulin content after treatment (5.46 ± 0.87 ng/islet/h) was higher than control (3.17 ± 0.22 ng/islet/h, p < 0.05), and the fractional insulin release was 36% (p < 0.05) lower after the treatment. Meanwhile, the mRNA expression of Gαs, Gαz and Gß1-2 decreased by 42.8% 19.4% and 24.8%, respectively (p < 0.05). Uncoupling protein 2 (Ucp2), sulphonylurea receptor 1 (Sur1) and superoxide dismutase 2 (Sod2) were significantly reduced (38.5%, 23.8% and 53.8%, p < 0.05). Chronic adrenergic exposure could impair insulin responsiveness in primary pancreatic islets. Decreased G proteins and Sur1 expression affect the regulation of insulin secretion. In conclusion, the sustained under-expression of Ucp2 and Sod2 may further change the function of ß-cell, which helps to understand the long-term adrenergic adaptation of pancreatic ß-cell.

Rosuvastatin and low-dose carvedilol combination protects against isoprenaline-induced myocardial infarction in rats: Role of PI3K/Akt/Nrf2/HO-1 signalling.

Rosuvastatin has been shown to activate PI3K/Akt/Nrf2/HO-1 pathway, which promotes cell survival in the myocardium. This study investigated the therapeutic benefit of adding rosuvastatin to low-dose carvedilol in protection against myocardial infarction (MI). Rosuvastatin (RSV) and carvedilol (CAR) were given for 7 consecutive days with concurrent administration of two doses of isoprenaline (ISP) on 6th and 7th days to induce MI. Isoprenaline injections caused detrimental alterations in the myocardial architecture and electrocardiogram (ECG) pattern and significantly increased the infarct size, heart index and serum levels of cardiotoxicity markers compared to the control group. ISP induced oxidative damage, inflammatory and apoptotic events and downregulated PI3K/Akt/Nrf2/HO-1 signalling pathway compared to the control values. Treatment with low-dose CAR and/or RSV prevented the ECG and histopathological alterations induced by ISP, and also reduced the infarct size, heart index, serum creatine kinase-MB, cardiac troponin-I and C-reactive protein levels compared to ISP group. CAR and/or RSV treatment restored the activity of superoxide dismutase and total antioxidant capacity with a consequent reduction in lipid peroxides level. Further, they decreased the expression of nuclear factor (NF)-κB (p65) and increased the phosphorylated PI3K and Akt, which may activate the anti-apoptotic signalling as evidenced by the decreased active caspase 3 level. The combination therapy has a more significant effect in the most studied parameters than their monotherapy, which may be because of the activation of PI3K/Akt Nrf2/HO-1 pro-survival signalling pathway. This study highlights the potential benefits of combining RSV with low-dose CAR in case of MI.

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.

Sinapic acid safeguards cardiac mitochondria from damage in isoproterenol-induced myocardial infarcted rats.

Myocardial infarction (MI) is a life-threatening disease. In this study, we examined the anti-mitochondrial damaging effects of sinapic acid (SA) in isoproterenol (ISO)-induced myocardial infarcted rats. Myocardial infarcted rats were prepared by injecting ISO (100 mg/kg body weight) on the 9th and 10th day. Rats were pretreated and cotreated with SA (12 mg/kg body weight) orally, daily for 10 days. A considerable increase in serum lactate dehydrogenase, creatine kinase, myoglobin, and cardiac troponin-T was noticed in the ISO-induced rats. ISO also significantly amplified lipid peroxidation and calcium ions, and depleted the antioxidant system and mitochondrial enzymes in rat's heart mitochondria. SA treatment improved the distorted above- mentioned biochemical parameters in ISO-treated rats with its anti-mitochondrial damaging effects. This ultrastructural study on heart mitochondria and in vitro studies also confirmed the effects of SA. The current findings are suggestive of SA's cardioprotective effects.

The conventional isoproterenol-induced heart failure model does not consistently mimic the diaphragmatic dysfunction observed in patients.

Heart failure (HF) impairs diaphragm function. Animal models realistically mimicking HF should feature both the cardiac alterations and the diaphragmatic dysfunction characterizing this disease. The isoproterenol-induced HF model is widely used, but whether it presents diaphragmatic dysfunction is unknown. However, indirect data from research in other fields suggest that isoproterenol could increase diaphragm function. The aim of this study was to test the hypothesis that the widespread rodent model of isoproterenol-induced HF results in increased diaphragmatic contractility. Forty C57BL/6J male mice were randomized into 2 groups: HF and healthy controls. After 30 days of isoproterenol infusion to establish HF, in vivo diaphragmatic excursion and ex vivo isolated diaphragm contractibility were measured. As compared with healthy controls, mice with isoproterenol-induced HF showed the expected changes in structural and functional echocardiographic parameters and lung edema. isoproterenol-induced HF increased in vivo diaphragm excursion (by ≈30%, p<0.01) and increased by ≈50% both ex vivo peak specific force (p<0.05) and tetanic force (p<0.05) at almost all 10-100 Hz frequencies (p<0.05), with reduced fatigue resistance (p<0.01) when compared with healthy controls. Expression of myosin genes encoding the main muscle fiber types revealed that Myh4 was higher in isoproterenol-induced HF than in healthy controls (p<0.05), suggesting greater distribution of type IIb fibers. These results show that the conventional isoproterenol-induced HF model increases diaphragm contraction, a finding contrary to what is observed in patients with HF. Therefore, this specific model seems limited for translational an integrative HF research, especially when cardio-respiratory interactions are investigated.

Clenbuterol: a new toxic substance in paediatrics.

A 13-year-old girl presented to the emergency department with acute onset of chest pain, nausea and tremor. The patient denied drug ingestion, and urine toxicology was negative. ECG demonstrated sinus tachycardia, prolonged QTc (541 ms) and ST depression. Laboratory testing demonstrated metabolic acidosis, hypokalaemia, hypophosphataemia and hyperglycaemia. She was commenced on continuous cardiac monitoring and treated with intravenous fluids and electrolyte replacement. Presenting features and laboratory abnormalities resolved within 48 hours. The National Poisons Information Service and Clinical Biochemistry were integral to her management, advising the clinical team on the likeliest aetiology. Five weeks after discharge, urine toxicology, using mass spectrometry, identified clenbuterol. Clenbuterol is an oral ß2-agonist with anabolic and lipolytic effects that is misused as a performance and image enhancing drug. Clinicians must be aware of the increasing availability of these drugs and their potential for causing harm in children and adolescents.

Rosuvastatin and retinoic acid may act as 'pleiotropic agents' against ß-adrenergic agonist-induced acute myocardial injury through modulation of multiple signalling pathways.

Cardiovascular disorders constitute the principal cause of deaths worldwide and will continue as the major disease-burden by the year 2060. A significant proportion of heart failures occur because of use and misuse of drugs and most of the investigational agents fail to achieve any clinical relevance. Here, we investigated rosuvastatin and retinoic acid for their "pharmacological pleiotropy" against high dose ß-adrenergic agonist (isoproterenol)-induced acute myocardial insult. Rats were pretreated with rosuvastatin and/or retinoic acid for seven days and the myocardial injury was induced by administering isoproterenol on the seventh and eighth day. After induction, rats were anaesthetized for electrocardiography, then sacrificed and different samples were collected/stored for various downstream assays. Myocardial injury with isoproterenol resulted in increased cardiac mass, decreased R-wave amplitude, increased QRS and QT durations; elevated levels of cardiac markers like cTnI, CK-MB, ALT and AST; increased lipid peroxidation, protein carbonylation and tissue nitric oxide levels; decreased endogenous antioxidants like SOD, CAT, GR, GST, GPx and total antioxidant activity; increased inflammatory markers like TNF-α and IL-6; decreased the mRNA expression of Nrf2 and Bcl-2; increased the mRNA expression of Bax, eNOS and iNOS genes. Pretreatment with rosuvastatin and/or retinoic acid mitigated many of the above biochemical and pathological alterations. Our results demonstrate that rosuvastatin and retinoic acid exert cardioprotective effects and may act as potential agents in the prevention of ß-adrenergic agonist-induced acute myocardial injury in rats. Cardioprotective potential of rosuvastatin and retinoic acid could be attributed to their influence on the redox pathways, immunomodulation, membrane stability, Nrf2 preservation, iNOS and Bax expression levels. Thus, they may act directly or indirectly at various steps, the breakpoints, in the pathophysiological cascade responsible for cardiac injury. Our study gives insights about the pharmacological pleiotropism of rosuvastatin and retinoic acid.

Fuziline alleviates isoproterenol-induced myocardial injury by inhibiting ROS-triggered endoplasmic reticulum stress via PERK/eIF2α/ATF4/Chop pathway.

Fuziline, an aminoalcohol-diterpenoid alkaloid derived from Aconiti lateralis radix preparata, has been reported to have a cardioprotective activity in vitro. However, the potential mechanism of fuziline on myocardial protection remains unknown. In this study, we aimed to explore the efficacy and mechanism of fuziline on isoproterenol (ISO)-induced myocardial injury in vitro and in vivo. As a result, fuziline effectively increased cell viability and alleviated ISO-induced apoptosis. Meanwhile, fuziline significantly decreased the production of ROS, maintained mitochondrial membrane potential (MMP) and blocked the release of cytochrome C, suggesting that fuziline could play the cardioprotective role through restoring the mitochondrial function. Fuziline also could suppress ISO-induced endoplasmic reticulum (ER) stress via the PERK/eIF2α/ATF4/Chop pathway. In addition, using ROS scavenger NAC could decrease ISO-induced apoptosis and block ISO-induced ER stress, while PERK inhibitor GSK2606414 did not reduce the production of ROS, indicating that excess production of ROS induced by ISO triggered ER stress. And fuziline protected against ISO-induced myocardial injury by inhibiting ROS-triggered ER stress. Furthermore, fuziline effectively improved cardiac function on ISO-induced myocardial injury in rats. Western blot analysis also showed that fuziline reduced ER stress-induced apoptosis in vivo. Above these results demonstrated that fuziline could reduce ISO-induced myocardial injury in vitro and in vivo by inhibiting ROS-triggered ER stress via the PERK/eIF2α/ATF4/Chop pathway.

Cardioprotective effects of a Fructus Aurantii polysaccharide in isoproterenol-induced myocardial ischemic rats.

CALB-3, a purified acidic hetero-polysaccharide isolated from Fructus aurantii, has been shown to exert cardioprotective effects in vitro. Recently, we investigated the protective effects of CALB-3 on myocardial injury and its possible mechanisms of action using a rat model of myocardial ischemia. In this study, a myocardial ischemia model was established via intragastric administration of 2 mg/kg isoproterenol (ISO) to male Sprague-Dawley rats (200-220 g) daily for 3 days. We found that pretreatment with CALB-3 (50, 100, and 200 mg/kg, i.g.) daily for 21 days prevented ISO-induced myocardial damage, including improvement in electrocardiographic parameters, and decrease in serum cardiac enzymes, heart vacuolation, and TUNEL-positive cells. We used western blotting to identify the underlying mechanisms and determine the possible signal pathways involved. We found that CALB-3 pretreatment prevented apoptosis, increased the expression of antioxidant enzymes, and enhanced the binding of Nrf2 to the antioxidant response element. In addition, CALB-3 activated the phosphorylation of PI3K/Akt and ERK to increase the cytoprotective effect. Overall, our results show that CALB-3 is a promising polysaccharide for protecting against myocardial injury induced by ISO.

Effects of ANP on pulmonary vein electrophysiology, Ca2+ homeostasis and adrenergic arrhythmogenesis via PKA.

Atrial fibrillation (AF) is the most common form of arrhythmia and increases the risk of stroke and heart failure (HF). Pulmonary veins (PVs) are important sources of triggers that generate AF, and calcium (Ca2+ ) overload participates in PV arrhythmogenesis. Neurohormonal activation is an important cause of AF. Higher atrial natriuretic peptide (ANP) level predicts paroxysmal AF occurrence in HF patients. However, it is not clear if ANP directly modulates electrophysiological characteristics and Ca2+ homeostasis in the PVs. Conventional microelectrodes, whole-cell patch-clamp, and the Fluo-3 fluorimetric ratio technique were performed using isolated rabbit PV preparations or single isolated PV cardiomyocytes before and after ANP administration. We found that ANP (1, 10, and 100 nmol/L) concentration-dependently decreased spontaneous activity in PV preparations. ANP (100 nmol/L) decreased isoproterenol (1 µmol/L)-induced PV spontaneous activity and burst firing. AP811 (100 nmol/L, NPR-C agonist), H89 (1µmol/L, PKA inhibitor) decreased isoproterenol-induced PV spontaneous activity or burst firing, but successive administration of ANP had no further effect on PV activity. KT5823 (1 µmol/L, PKG inhibitor) decreased isoproterenol-induced PV spontaneous activity but did not change isoproterenol-induced PV burst firing, whereas successive administration of ANP did not change isoproterenol-induced PV burst firing. ANP decreased intracellular Ca2+ transient and sarcoplasmic reticulum Ca2+ content in single PV cardiomyocytes. ANP decreased the late sodium current, L-type Ca2+ current, but did not change nickel-sensitive Na+ -Ca2+ exchanger current in single PV cardiomyocytes. In conclusion, ANP directly regulates PV electrophysiological characteristics and Ca2+ homeostasis and attenuates isoproterenol-induced arrhythmogenesis through NPR-C/cAMP/PKA signal pathway.

S-nitrosylation of connexin43 hemichannels elicits cardiac stress-induced arrhythmias in Duchenne muscular dystrophy mice.

Patients with Duchenne muscular dystrophy (DMD) commonly present with severe ventricular arrhythmias that contribute to heart failure. Arrhythmias and lethality are also consistently observed in adult Dmdmdx mice, a mouse model of DMD, after acute ß-adrenergic stimulation. These pathological features were previously linked to aberrant expression and remodeling of the cardiac gap junction protein connexin43 (Cx43). Here, we report that remodeled Cx43 protein forms Cx43 hemichannels in the lateral membrane of Dmdmdx cardiomyocytes and that the ß-adrenergic agonist isoproterenol (Iso) aberrantly activates these hemichannels. Block of Cx43 hemichannels or a reduction in Cx43 levels (using Dmdmdx Cx43+/- mice) prevents the abnormal increase in membrane permeability, plasma membrane depolarization, and Iso-evoked electrical activity in these cells. Additionally, Iso treatment promotes nitric oxide (NO) production and S-nitrosylation of Cx43 hemichannels in Dmdmdx heart. Importantly, inhibition of NO production prevents arrhythmias evoked by Iso. We found that NO directly activates Cx43 hemichannels by S-nitrosylation of cysteine at position 271. Our results demonstrate that opening of remodeled and S-nitrosylated Cx43 hemichannels plays a key role in the development of arrhythmias in DMD mice and that these channels may serve as therapeutic targets to prevent fatal arrhythmias in patients with DMD .

Effects of clenbuterol administration on mitochondrial morphology and its regulatory proteins in rat skeletal muscle.

Clenbuterol induces a slow-to-fast fiber type transition in skeletal muscle. This muscle fiber transition decreased mitochondrial oxidative capacity and respiratory function. We hypothesized that the clenbuterol-mediated reduction in oxidative capacity is associated with the alteration in mitochondrial morphology. To verify this hypothesis, we examined whether clenbuterol alters mitochondrial morphology and mitochondrial regulatory proteins in rat skeletal muscle. Clenbuterol was administered to rats via drinking water (30 mg/L) for 3 weeks. Myosin heavy chain (MHC) isoform composition, mitochondrial morphology, and fusion and fission regulatory protein levels in deep region and superficial region in tibialis anterior (TA) muscles were assessed. Clenbuterol induced the fiber type transition from slow to fast in both the regions of TA. The levels of optic atrophy protein 1, mitofusin 2, and mitochondrial fission 1, but not of dynamin-related protein 1, significantly decreased in deep and superficial muscles after clenbuterol administration (P < 0.01). Also, observation using the transmission electron microscopy showed a decrease in mitochondrial volume (P < 0.05) and an increase in proportion of continuous or interacting mitochondria across Z-lines (P < 0.05). We showed that clenbuterol administration induces a transition in the muscle fiber type composition toward fast phenotype and causes alterations in mitochondrial morphology with a concomitant decrease in mitochondrial fusion and fission regulatory protein levels. These mitochondrial morphological alterations may influence deleterious effects on skeletal muscle metabolism.

Toxicity From Unintentional Pediatric Ingestion of a Performance-Enhancing Drug: A Case Report With Review of Clenbuterol Toxicity and Treatment.

BACKGROUND: Clenbuterol is a long-acting ß-adrenergic agonist that is not Food and Drug Administration-approved for use in the United States, but may be obtained without a prescription from various unregulated sellers. It has seen increasing use as a performance-enhancing drug for sports. Literature on pediatric toxicity and treatment is limited. CASE REPORT: We report a case of a 2-year-old female presenting after an exploratory ingestion of clenbuterol. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Use of performance-enhancing agents is increasing and physicians should be aware of the potential toxicity of intentional and unintentional ingestions of ß-adrenergic agonists. Patients may exhibit nausea, vomiting, tremor, tachycardia, and hypotension, along with laboratory abnormalities, including hyperglycemia, hypophosphatemia, hypokalemia, and hyperglycemia. Hypotension might not respond to adrenergic agents and may require administration of ß-adrenergic antagonists to maintain adequate perfusion.

Effects of Curcumin Nanoparticles in Isoproterenol-Induced Myocardial Infarction.

Curcumin has anti-inflammatory, antioxidative, anticarcinogenic, and cardiovascular protective effects. Our study is aimed at evaluating the effects of pretreatment with curcumin nanoparticles (CCNP) compared to conventional curcumin (CC) on isoproterenol (ISO) induced myocardial infarction (MI) in rats. Fifty-six Wistar-Bratislava white rats were randomly divided into eight groups of seven rats each. Curcumin and curcumin nanoparticles were given by gavage in three different doses (100 mg/kg body weight (bw), 150 mg/kg bw, and 200 mg/kg bw) for 15 days. The MI was induced on day 13 using 100 mg/kg bw ISO administered twice, with the second dose 24 h after the initial dose. The blood samples were taken 24 h after the last dose of ISO. The antioxidant, anti-inflammatory, and cardioprotective effects were evaluated in all groups. All doses of CC and CCNP offered a cardioprotective effect by preventing creatine kinase-MB leakage from cardiomyocytes, with the best result for CCNP. All the oxidative stress parameters were significantly improved after CCNP compared to CC pretreatment. CCNP was more efficient than CC in limiting the increase in inflammatory cytokine levels (such as TNF-α, IL-6, IL-1α, IL-1ß, MCP-1, and RANTES) after MI. MMP-2 and MMP-9 levels decreased more after pretreatment with CCNP than with CC. CCNP better prevented myocardial necrosis and reduced interstitial edema and neutrophil infiltration than CC, on histopathological examination. Therefore, improving the bioactivity of curcumin by nanotechnology may help limit cardiac injury after myocardial infarction.

Dipeptidyl peptidase-4 inhibition prevents vascular dysfunction induced by ß-adrenergic hyperactivity.

Chronic stimulation of the ß-adrenergic sympathetic system induces vascular dysfunction which is associated with increased inflammatory cytokines production. A recently proposed therapy to control vascular injury through inflammatory processes involves inhibition of the enzyme dipeptidyl peptidase-IV (DPP4). The present study investigates whether the inhibition of DPP4 prevents the increase in inflammatory markers induced by isoproterenol and restores endothelial function in vivo and in vitro. Male Wistar rats were divided into four groups: vehicle (VHC), an isoproterenol-treated group (ISO), a sitagliptin-treated group (SITA), and an isoproterenol and sitagliptin-treated group (ISO + SITA). The ISO group exhibited significantly increased contractile responses to phenylephrine associated with reduced endothelial participation, which was totally prevented by DPP4 inhibition. In vitro incubation with isoproterenol had no effect on vascular smooth muscle cells, however isoproterenol increased the activity of DPP4 and the expression of inflammatory cytokines in endothelial cells, while sitagliptin reduced the level of cytokines to basal level. In conclusion, we have shown that beta-adrenergic receptor activation can increase DPP4 activity, which was associated with vascular dysfunction and cytokine expression in endothelial cells. The important role of DPP4 was further supported by sitagliptin, which reversed vascular changes induced by isoproterenol in vivo and in vitro.

Genistein reverses isoproterenol-induced cardiac hypertrophy by regulating miR-451/TIMP2.

Cardiomyocyte hypertrophy, a prevalent clinical condition is deeply associated with many physiological factors. The underlying mechanisms of cardiomyocyte hypertrophy are not yet fully understood. In this study, H9C2 cells were treated with genistein, miR-451 mimic, miR-451 inhibitor and isoproterenol for 24 h, to study the effect of genistein on isoproterenol-induced myocardial hypertrophy in vitro. Simultaneously, ICR mice were treated with genistein for 21 days to evaluate the effects of the phytochemical on isoproterenol-induced myocardial hypertrophy in vivo. Results showed that isoproterenol induced cardiac hypertrophy and down-regulated the expression of miR-451 and up-regulated miR-451's target gene TIMP2. Genistein increased the expression of miR-451 and inhibited the isoproterenol-induced cardiac hypertrophy. This study explored the function of genistein from the epigenetic level, suggesting that miR-451 may play a significant role in the genistein-assisted amelioration of isoproterenol-induced cardiac hypertrophy both in vitro and in vivo.