Duration of streptozotocin-induced diabetes differentially affects p38-mitogen-activated protein kinase (MAPK) phosphorylation in renal and vascular dysfunction

Background: In the present study we tested the hypothesis that progression of streptozotocin (STZ)-induced diabetes (14-days to 28-days) would produce renal and vascular dysfunction that correlate with altered p38- mitogen-activated protein kinase (p38-MAPK) phosphorylation in kidneys and thoracic aorta. Methods: Male Sprague Dawley rats (350-400 g) were randomized into three groups: sham (N = 6), 14-days diabetic (N = 6) and 28-days diabetic rats (N = 6). Diabetes was induced using a single tail vein injection of STZ (60 mg/kg, I.V.) on the first day. Rats were monitored for 28 days and food, water intake and plasma glucose levels were noted. At both 14-days and 28-days post diabetes blood samples were collected and kidney cortex, medulla and aorta were harvested from each rat. Results: The diabetic rats lost body weight at both 14-days (-10%) and 28-days (-13%) more significantly as compared to sham (+10%) group. Glucose levels were significantly elevated in the diabetic rats at both 14-days and 28-days post-STZ administration. Renal dysfunction as evidenced by renal hypertrophy, increased plasma creatinine concentration and reduced renal blood flow was observed in 14-days and 28-days diabetes. Vascular dysfunction as evidenced by decreased carotid blood flow was observed in 14-days and 28-days diabetes. We observed an up-regulation of inducible nitric oxide synthase (iNOS), prepro endothelin-1 (preproET-1) and phosphorylated p38-MAPK in thoracic aorta and kidney cortex but not in kidney medulla in 28-days diabetes group. Conclusion: The study provides evidence that diabetes produces vascular and renal dysfunction with a profound effect on signaling mechanisms at later stage of diabetes. © 2005 Chen et al; licensee BioMed Central Ltd

Modulation of Myocardial Mitochondrial Mechanisms during severe Polymicrobial Sepsis in the Rat

Background: We tested the hypothesis that 5-Hydroxydecanoic acid (5HD), a putative mitoKATP channel blocker, will reverse sepsis-induced cardiodynamic and adult rat ventricular myocyte (ARVM) contractile dysfunction, restore mitochondrial membrane permeability alterations and improve survival. Methodology/Principal Findings: Male Sprague-Dawley rats (350-400 g) were made septic using 400 mg/kg cecal inoculum, ip. Sham animals received 5% dextrose water, ip. The Voltage Dependent Anion Channels (VDAC1), Bax and cytochrome C levels were determined in isolated single ARVMs obtained from sham and septic rat heart. Mitochondria and cytosolic fractions were isolated from ARVMs treated with norepinephrine (NE, 10 µmoles) in the presence/absence of 5HD (100 µmoles). A continuous infusion of 5HD using an Alzet pump reversed sepsis-induced mortality when administered at the time of induction of sepsis (-40%) and at 6 hr post-sepsis (-20%). Electrocardiography revealed that 5HD reversed sepsis-induced decrease in the average ejection fraction, Simpsons+m Mode (53.5±2.5 in sepsis and 69.2±1.2 at 24 hr in sepsis+5HD vs. 79.9±1.5 basal group) and cardiac output (63.3±1.2 mL/min sepsis and 79.3±3.9 mL/min at 24 hr in sepsis+5HD vs. 85.8±1.5 mL/min basal group). The treatment of ARVMs with 5HD also reversed sepsis-induced depressed contractility in both the vehicle and NE-treated groups. Sepsis produced a significant downregulation of VDAC1, and upregulation of Bax levels, along with mitochondrial membrane potential collapse in ARVMs. Pretreatment of septic ARVMs with 5HD blocked a NE-induced decrease in the VDAC1 and release of cytochrome C. Conclusion: The data suggest that Bax activation is an upstream event that may precede the opening of the mitoKATP channels in sepsis. We concluded that mitoKATP channel inhibition via decreased mitochondrial membrane potential and reduced release of cytochrome C provided protection against sepsis-induced ARVM and myocardial contractile dysfunction. © 2011 Chopra et al

Operation of Circuit Breaker with the help of Password

A circuit breaker is an electrical switch use to protect an electrical circuit from damage caused by faults. Its basic function is to detect a fault condition and protect from it. Fuse operates once after that it must be replaced but a circuit breaker can be reset to resume normal condition. During the manual operation, we see inoperable electrical accidents to the line man are rises during maintenance due to improper communication between the maintenance staff and the substation staff. In order to prevent such accidents, password based circuit breaker is design so that only authentic person can operate it with a password. There is also a facility of changing the password. The system is fully controlled by the microcontroller. The password is saved in an EEPROM, interfaced to the microcontroller and the password can be changed any time. A keypad is used to submit the password and a relay to operate circuit breaker, which is indicated by a bulb. Any wrong attempt to open the circuit breaker by entering the wrong password an alert will be shown in the LCD

Sepsis-induced myocardial dysfunction

Despite the fact that septic patients exhibit altered cardiac function, it is not considered a major pathology during sepsis. Thus, the molecular mechanisms underlying sepsis-induced myocardial dysfunction have not been studied extensively. In a polymicrobial septic rat model, +dP/dt and -dP/dt on day 1 were not altered but found depressed later, i.e., at 3 and 7 days postsepsis. Diastolic dysfunction characterized by an elevation of the time constant of left ventricular relaxation, tau, was evident at 1, 3, and 7 days postsepsis. Recent data from our laboratory demonstrated that sepsis-induced cardiodynamic alterations correlated with upregulation of TNF receptor-associated death domain, Bax, Smac (both mitochondrial and cytosolic fractions), total nuclear factor κB expression, p38-mitogen-activated protein kinase and c-Jun N-terminal kinase phosphorylation, and cytochrome c levels in the rat heart at 3 and 7 days postsepsis. Data from various laboratories emphasized that molecular myocardial alteration, which occurs during early and late stages of sepsis, needs to be elucidated thoroughly. A poor understanding of myocardial signaling during early sepsis could be one of the main reasons for limited success of pharmacotherapeutic options for sepsis. We anticipate that an increased understanding of pathophysiological mechanisms leading to sepsis-induced myocardial dysfunction would generate new enthusiasm among various research groups in this area of research. ©2007The Shock Society

Despite minimal hemodynamic alterations endotoxemia modulates NOS and p38-MAPK phosphorylation via metalloendopeptidases

In the present study, we hypothesized that endotoxemia produces metalloendopeptidase (MEPD)-dependent generation of endothelin-1 (ET-1) and alters NOS expression correlating with p38-mitogen-activated protein kinase (MAPK) phosphorylation in thoracic aorta. Male Sprague-Dawley rats (350-400 g) were subjected to two groups randomly; sham-treated (N = 10) and lipopolysaccharide (LPS)-treated (N = 10) (E. coli LPS 2 mg/kg bolus + 2 mg/kg infusion for 30 min). The animals in each group were further subdivided into vehicle and MEPD inhibitor phosphoramidon (1 mg/kg bolus, PHOS)-treated groups. LPS produces a significant decrease in mean arterial pressure (MAP) at 2 h post endotoxemia that was blocked by PHOS. PHOS attenuated LPS-induced increase in tumor necrosis factor-alpha (TNF-α) concentration at 2- and 24 h post-LPS administration. LPS significantly elevated plasma concentrations of ET-1 at 2- and 24 h post endotoxemia. An upregulated preproET-1 expression following both LPS and MEPD inhibition was observed in thoracic aorta at 2 h post treatment. PHOS effectively blocked conversion of preproET-1 to ET-1 in thoracic aorta locally at 24 h post treatment in endotoxic rats. PHOS inhibited LPS-induced upregulation of inducible NOS (iNOS), downregulation of endothelial NOS (eNOS) and elevation of NO byproducts (NO x) in thoracic aorta. PHOS also blocked LPS-induced upregulated p38-MAPK phosphorylation in thoracic aorta at 24 h post endotoxemia. The data revealed that LPS induces MEPD-sensitive inflammatory response syndrome (SIRS) at 2- and 24 h post endotoxemia. We concluded that inhibition of MEPD not only decreases the levels of ET-1 but also simultaneously downregulates protein expression of iNOS and phosphorylated p38-MAPK while increasing eNOS in thoracic aorta during SIRS in endotoxemia. We suggest that MEPD-dependent ET-1 and NO mechanisms may be involved in endotoxemia-induced altered p38-MAPK phosphorylation. © 2004 Kluwer Academic Publishers

Apoptotic cardiomyocyte hypertrophy during sepsis and septic shock results from prolonged exposure to endothelin precursor

Septic shock is a complex cardiovascular dysfunction which leads to regional circulatory alterations and multi-organ dysfunction in humans and animal models. To elucidate the role of stress-activated signaling molecules in the regulation of myocardial dysfunction, we have developed and standardized isolated ventricular myocyte techniques. These techniques allow the assessment of cardiodynamics at cellular (ventricular myocyte) level. These studies are carried out in a well defined model of systemic inflammatory response syndrome following polymicrobial sepsis in the rat. Evidence is provided that sepsis-induced myocardial dysfunction produces indications (signs) of early stages of heart failure. This evidence correlates with upregulation of stress-activated protein kinase cascade. These findings suggest that prolonged exposure to endothelin precursor causes decompensatory hypertrophy in adult rat ventricular myocytes (ARVMs) during sepsis. The decompensatory hypertrophy could, in turn, results in increased cytosolic caspases-3 activity in ARVMs

Mechanisms involved in apoptosis events contributing to sepsis-induced myocardial dysfunction

Sepsis, a progressive immunological, metabolic and cardiovascular disorder, is a major cause of morbidity and mortality in Intensive care units (ICU) worldwide. Models simulating sepsis, such as endotoxemia, peritonitis, cecal ligation and puncture, provide substantial molecular and cellular evidence for structural and functional damage to cardiac myocytes during sepsis. Clinical evidence suggests abnormal left ventricular impairment and cardiac contractile dysfunction during sepsis. Norepinephrine (NE), a clinically approved positive inotrope traditionally used in ICUs for hemodynamic support, can also cause increased lactate levels and cardiomyocyte toxicity during early stages of sepsis. Our recent results demonstrated that sepsis-induced myocyte dysfunction (SIMD) is associated with decreased time of deformation and loss of contractile activity in the myocytes. The data further support the involvement of the apoptotic pathway, particularly mitochondrial-mediated intrinsic apoptosis cascade in sepsis-induced myocardial dysfunction. The recent data from our laboratory demonstrated that SIMD is a potentially life threatening event which can be exacerbated by the use of positive inotropes such as NE, which are ideally used in the management of sepsis. © 2011 Bentham Science Publishers

Metalloendopeptidase inhibition regulates phosphorylation of p38-mitogen-activated protein kinase and nitric oxide synthase in heart after endotoxemia.

We tested the hypothesis that metalloendopeptidase inhibition using phosphoramidon during induction of endotoxemia 24 h later would down-regulate the protein expression of myocardial inducible nitric oxide synthase (iNOS) and phosphorylation of p38-mitogen-activated protein kinase (p38-MAPK). Male Sprague-Dawley rats (350-400 g) were randomly divided into sham-treated and LPS-treated groups (Escherichia. coli lipopolysaccharide [LPS] 2 mg/kg bolus + 2 mg/kg infusion for 30 min). The animals in each group were further subdivided into vehicle- and phosphoramidon (1 mg/kg bolus)-treated subgroups. Blood and heart samples were collected at 2- and 24-h postendotoxemia/phosphoramidon treatment. LPS at 2 h after its administration produced a significant decrease in mean arterial pressure that was blocked by phosphoramidon treatment. LPS at 2 and 24 h produced a significant elevation in the concentration of left ventricular endothelin-1 (ET-1) both in heart and plasma as compared with control group. This LPS-induced left ventricular ET-1 elevation at 24 h was significantly reduced by phosphoramidon. No significant alterations were observed in the myocardial protein expression of preproET-1, iNOS, and eNOS at 2 h post LPS. In 24-h post treatment groups phosphoramidon upregulated the expression of myocardial preproET-1 protein both in control and endotoxemic rat groups. Also, LPS-induced upregulated protein expression of myocardial-inducible nitric oxide synthase and increased levels of nitric oxide byproducts at 24 h were blocked by phosphoramidon. Phosphoramidon inhibited LPS-induced down-regulated expression of myocardial endothelial nitric oxide synthase and upregulated p38-MAPK phosphorylation. These results indicated that inhibition of metalloendopeptidase during induction of endotoxemia could regulate the phosphorylation of myocardial p38-MAPK and iNOS protein expression at 24-h post endotoxemia. We concluded that inhibition of metalloendopeptidases during early endotoxemia not only decreased the biosynthesis of ET-1 in heart locally but also simultaneously down-regulated myocardial protein expression of iNOS and p38-MAPK phosphorylation in the later stage of endotoxemia

Contractile response of norepinephrine is modulated by caspase-3 in adult rat ventricular myocytes isolated from septic rat heart

Sepsis accounts for 50% of intensive care unit deaths due to cardiac dysfunction. The cellular mechanisms following norepinephrine (NE) during sepsis are undefined. Using a septic adult rat ventricular myocyte (ARVM) paradigm, we examined the molecular mechanism responsible for the blunted contractile response of NE. We tested the hypothesis that NE-induced increases in active caspase-3 contribute to sepsis-induced ARVM contractile dysfunction. Single ARVMs were isolated from hearts harvested from sham and septic male rats. The contractile properties and expression of caspase-3 cascade proteins were determined in ARVMs treated with NE with and without QVD-OPH, prazosin and atenolol to characterize the effect of NE on their mechanical properties. Septic ARVMs exhibited a significant decrease in peak shortening (PS) compared to sham ARVMs. The effect of NE on the PS of the sham ARVMs was more pronounced compared to the septic ARVMs, suggesting a blunted contractile response of NE. NE in the presence of QVD-OPH ameliorated the sepsis-induced decrease in PS at 18 h but not at 1 h, while the effect of NE on sepsis-induced contractile response remained unaffected at 18 h by prazosin and atenolol. An up-regulated expression of caspase-3 in NE-treated septic ARVMs was reversed by QVD-OPH, as seen by the increased number of septic ARVMs exhibiting caspase-3 fluorescence. Transfection of ARVMs using caspase-3 siRNA blocked sepsis-induced up-regulation of caspase-3 and increased PS following NE treatment. These data suggest that caspase-3 inhibition ameliorated sepsis-induced decreased ARVM contractility and blocked the blunted contractile response of NE. © 2009 Elsevier Ltd. All rights reserved