Phospholipid N-methylation as a Signal Transduction Mechanism in Normal and Failing Hearts

The phospholipid N-methylation pathway comprises of three successive N-terminal methylations of phosphatidylethanolamine where S-adenosyl-L-methionine acts as the physiological donor. Under optimal conditions in cardiac membranes, the catalytic sites I, II, and III of methyltransferase have been identified which are responsible for the synthesis of the major product, phosphatidyl-N-monomethylethanolamine, phosphatidyl-N,N-dimethylethanolamine, and phosphatidylcholine, respectively. The characterization of the phosphatidylethanolamineN-methyltransferase system has shown that each of the catalytic sites exhibits different biochemical properties. The phospholipid N-methylation pathway has also been observed to regulate heart function by inducing localized structural, compositional, and functional changes in cardiac membranes under different pathological conditions of chronic nature. This review deals with the phosphatidylethanolamine N-methylation–mediated signal transduction mechanism involving modification of the Ca2+-transporting activities of the sarcolemmal and sarcoplasmic reticular membranes of the cardiomyocyte. In this regard, special attention is given to the status of this pathway and its relevance for the functioning of membrane-related Ca2+-transport systems in heart dysfunction due to different cardiac pathologies, such as diabetes-induced cardiomyopathy, catecholamine-induced cardiomyopathy, genetically linked cardiomyopathy, and adriamycin-induced cardiomyopathy. In addition, changes in phosphatidylethanolamine N-methylation in heart dysfunction due to cardiac hypertrophy, Ca2+-paradox hearts, and ischemic-reperfused hearts have been described. It is suggested that an increase in phosphatidylethanolamine N-methylation activity may play an adaptive role, whereas a depression may contribute towards contractile dysfunction. This revised version was published online in July 2006 with corrections to the Cover Date.     

HIV vaccine preparedness studies in the organization for economic co-operation and development (OECD) countries

HIV vaccine development remains an urgent priority. This article is a systematic review of HIV vaccine preparedness studies in the high-income 30 Organization for Economic Co-operation and Development countries, to identify factors important for HIV vaccine trial development in injection drug users (IDU), men who have sex with men (MSM), and women at heterosexual risk (WAHR) across these countries. Of 27 articles we identified, willingness to participate (WTP) was assessed in eight studies involving IDU, 11 involving MSM, and one involving WAHR. WTP ranged in IDU at 41-86%, MSM at 23-94%, and in WAHR, it was at 81%. Studies reported recruitment of high-risk individuals. Retention was assessed in eight studies involving IDU, five involving MSM, and three involving WAHR. IDU were retained at a range of 3-98%, MSM at 70-95% and WAHR at 67-92%. This review provides an in-depth summary of HIV vaccine preparedness studies that were conducted in the Organization for Economic Co-operation and Development countries.     

Depressed responsiveness of phospholipase C isoenzymes to phosphatidic acid in congestive heart failure

The cardiac sarcolemmal membrane cis -unsaturated fatty acid-sensitive phospholipase D hydrolyzes phosphatidylcholine to form phosphatidic acid. The functional significance of phosphatidic acid is indicated by its ability to increase [Ca(2+)](i)and augment cardiac contractile performance via the activation of phospholipase C. Accordingly, we tested the hypothesis that a defect occurs in the membrane level of phosphatidic acid and/or the responsiveness of cardiomyocytes to phosphatidic acid in congestive heart failure due to myocardial infarction. Myocardial infarction was produced in rats by ligation of the left coronary artery while sham-operated animals served as control. At 8 weeks after surgery, the experimental animals were at a stage of moderate congestive heart failure. Compared to sham controls, phosphatidic acid-mediated increase in [Ca(2+)](i), as determined by the fura 2-AM technique, was significantly reduced in failing cardiomyocytes. Immunoprecipitation of sarcolemmal phospholipase C isoenzymes using specific monoclonal antibodies revealed that the stimulation of phospholipase C gamma(1)and delta(1)phosphatidylinositol 4,5-bisphosphate hydrolyzing activities by phosphatidic acid was decreased in the failing heart. Although the activity of phospholipase C beta(1)in the failing heart was higher than the control, phosphatidic acid did not stimulate this isoform in control sarcolemma, and produced an inhibitory action in the failing heart preparation. Furthermore, the specific binding of phosphatidic acid to phospholipase C gamma(1)and delta(1)isoenzymes was decreased, whereas binding to phospholipase beta(1)was absent in the failing heart. A reduction in the intramembranal level of phosphatidic acid derived via cis -unsaturated fatty acid-sensitive phospholipase D was also seen in the failing heart. These findings suggest that a defect in phosphatidic acid-mediated signal pathway in sarcolemma may represent a novel mechanism of heart dysfunction in congestive heart failure.     

Three-Dimensional Anorectal Manometry Enhances Diagnostic Gain by Detecting Sphincter Defects and Puborectalis Pressure

Digestive Diseases and Sciences - Constipation and fecal incontinence (FI) are common and are often evaluated with anorectal manometry. Three-dimensional high-resolution anorectal manometry (HRAM)...     

Cardiovascular effects of acebutolol following coronary artery occlusion and reperfusion in anaesthetized dog.

1 The effects of 5 mg/kg acebutolol given intravenously were investigated in anaesthetized dogs after (a) ligation of the left anterior descending coronary artery and (b) coronary reperfusion following 60 min of ligation of the anterior descending coronary artery. 2 Coronary artery ligation produced, after 4 to 6 h, persistent multiple ventricular ectopic beats and abnormalities of R and T waves and of the S-T segment. Administration of acebutolol, after the development of persistent ventricular arrhythmias, restored normal sinus rhythm within 5 min of injection. Electrocardiographic abnormalities were also reduced. 3 Coronary artery reperfusion (following 60 min of ligation) resulted in multiple ventricular ectopic beats, ventricular tachycardia and/or ventricular fibrillation. Pretreatment with acebutolol, 15 min before starting reperfusion, markedly reduced the arrhythmias. 4 Acebutolol did not affect peak inspiratory airway pressure. 5 Acebutolol produced significant bradycardia and slight, transient, hypotension. It was without effect on left ventricular systolic pressure, left ventricular end-diastolic pressure, cardiac output or pulmonary arterial pressure. 6 These results suggest beneficial effects of acebutolol in myocardial ischaemia and coronary reperfusion, without any significant risk of cardiodepression or bronchospasm.     

Cataract formation is prevented by administration of verapamil to diabetic rats

The purpose of the present study was to examine the effects on cataractogenesis of daily sc administration of the Ca2+ antagonist drug verapamil to diabetic rats. Streptozotocin-induced diabetic rats were given verapamil half-way through the 8-week experimental period or during the full 8 weeks of diabetes. Verapamil administration had no effect on the high blood glucose values, low circulating insulin levels, or elevated triglyceride and cholesterol concentrations in the diabetic rats. Untreated diabetic rats had a 90% incidence of cataracts. Four weeks of verapamil administration reduced this incidence to 41%, and a full 8 weeks of drug treatment further lowered the incidence to 20%. Diltiazem, another Ca2+ antagonist, lowered the incidence of cataracts in the diabetic rats to a similar extent. Verapamil administration to the diabetic animals also partially protected against the presence of retinal microangiopathy in the diabetic animals. Lenticular hydration and lipid accumulation were only indirectly related to cataractogenesis in the diabetic rats and its protection by verapamil treatment. Lenticular electrolyte imbalance, particularly Ca2+, in the diabetic animals was closely correlated with cataract formation, and verapamil significantly reduced the alterations in these ion concentrations. The present results demonstrate the efficacy of verapamil as a protective agent against cataractogenesis and some retinal damage in diabetic animals. Most importantly, this occurs in the absence of any change in the glycemic status of the diabetic animals. The findings strongly support a role for lenticular Ca2+ imbalance in cataract development in diabetes and provide initial evidence to suggest its clinical use in the diabetic population at risk for blindness.     

Inhibition of serotonin-induced vascular smooth muscle cell proliferation by sarpogrelate.

Antiproliferative behavior of sarpogrelate (Anplag, MCI-9042, (+/-)-1-[2-[2-(3-methoxyphenyl)ethyl]phenoxy]-3-(dimethylamino)-2-pro pyl hydrogen succinate hydrochloride), a serotonin 2A (5-HT2A) receptor antagonist, was established using radioactive incorporation of [(3)H]thymidine, [(3)H]uridine, and [(3)H]phenylalanine in cultured rat aortic smooth muscle cells in response to a 5-HT-induced cytokine trigger. Fluorescence-activated cell sorting was used to confirm these observations. 5-HT-induced DNA, RNA, and protein synthesis were inhibited maximally at a concentration of 1 microM sarpogrelate. Although other cytokines such as platelet-derived growth factor and endothelin also induced DNA, RNA, and protein synthesis in rat aortic smooth muscle cells, cell proliferation was not influenced by sarpogrelate, even at large pharmacological concentrations (10 microM). Sarpogrelate's antiproliferative actions were found to be more potent than ketanserin. These data indicate that sarpogrelate operates as a specific inhibitor of 5-HT-mediated cell proliferation and is a good candidate for preventing serotonin-induced neointimal hyperplasia.     

Necroptotic cell death in failing heart: relevance and proposed mechanisms

As cardiomyocytes have a limited capability for proliferation, renewal, and repair, the loss of heart cells followed by replacement with fibrous tissue is considered to result in the development of ventricular dysfunction and progression to heart failure (HF). The loss of cardiac myocytes in HF has been traditionally believed to occur mainly due to programmed apoptosis or unregulated necrosis. While extensive research work is being carried out to define the exact significance and contribution of both these cell death modalities in the development of HF, recent knowledge has indicated the existence and importance of a different form of cell death called necroptosis in the failing heart. This new cell damaging process, resembling some of the morphological features of passive necrosis as well as maladaptive autophagy, is a programmed process and is orchestrated by a complex set of proteins involving receptor-interacting protein kinase 1 and 3 (RIP1, RIP3) and mixed lineage kinase domain-like protein (MLKL). Activation of the RIP1–RIP3–MLKL signaling pathway leads to disruption of cation homeostasis, plasma membrane rupture, and finally cell death. It seems likely that inhibition of any site in this pathway may prove as an effective pharmacological intervention for preventing the necroptotic cell death in the failing heart. This review is intended to describe general aspects of the signaling pathway associated with necroptosis, to describe its relationship with cardiac dysfunction in some models of cardiac injury and discuss its potential relevance in various types of HF with respect to the underlying pathologic mechanisms.     

Sarcoplasmic reticulum Ca(2+)/Calmodulin-dependent protein kinase is altered in heart failure

Although Ca(2+)/calmodulin-dependent protein kinase-II (CaMK) is known to phosphorylate different Ca(2+) cycling proteins in the cardiac sarcoplasmic reticulum (SR) and regulate its function, the status of CaMK in heart failure has not been investigated previously. In this study, we examined the hypothesis that changes in the CaMK-mediated phosphorylation of the SR Ca(2+) cycling proteins are associated with heart failure. For this purpose, heart failure in rats was induced by occluding the coronary artery for 8 weeks, and animals with >30% infarct of the left ventricle wall plus septum mass were used. Noninfarcted left ventricle was used for biochemical assessment; sham-operated animals served as control. A significant depression in SR Ca(2+) uptake and release activities was associated with a decrease in SR CaMK phosphorylation of the SR proteins, ryanodine receptor (RyR), Ca(2+) pump ATPase (SR/endoplasmic reticulum Ca(2+) ATPase [SERCA2a]), and phospholamban (PLB) in the failing heart. The SR protein contents for RyR, SERCA2a, and PLB were decreased in the failing hearts. Although the SR Ca(2+)/calmodulin-dependent CaMK activity, CaMK content, and CaMK autophosphorylation were depressed, the SR phosphatase activity was enhanced in the failing heart. On the other hand, the cAMP-dependent protein kinase-mediated phosphorylation of RyR and PLB was not affected in the failing heart. On the basis of these results, we conclude that alterations in SR CaMK-mediated phosphorylation may be partly responsible for impaired SR function in heart failure.     

Status of myocardial antioxidants in ischemia-reperfusion injury

BACKGROUND: Myocardial ischemia-reperfusion represents a clinically relevant problem associated with thrombolysis, angioplasty and coronary bypass surgery. Injury of myocardium due to ischemia-reperfusion includes cardiac contractile dysfunction, arrhythmias as well as irreversible myocyte damage. These changes are considered to be the consequence of imbalance between the formation of oxidants and the availability of endogenous antioxidants in the heart. OBSERVATIONS: An increase in the formation of reactive oxygen species during ischemia-reperfusion and the adverse effects of oxyradicals on myocardium have now been well established by both direct and indirect measurements. Although several experimental studies as well as clinical trials have demonstrated the cardioprotective effects of antioxidants, some studies have failed to substantiate the results. Nonetheless, it is becoming evident that some of the endogenous antioxidants such as glutathione peroxidase, superoxide dismutase, and catalase act as a primary defense mechanism whereas the others including vitamin E may play a secondary role for attenuating the ischemia-reperfusion injury. The importance of various endogenous antioxidants in suppressing oxidative stress is evident from the depression in their activities and the inhibition of cardiac alterations which they produce during ischemia-reperfusion injury. The effects of an antioxidant thiol containing compound, N-acetylcysteine, and ischemic preconditioning were shown to be similar in preventing changes in the ischemic-reperfused hearts. CONCLUSIONS: The available evidence support the role of oxidative stress in ischemia-reperfusion injury and emphasize the importance of antioxidant mechanisms in cardioprotection.