Effects of organophosphorus insecticides on G protein-coupled receptor kinase-2 mediated phosphorylation of M2 muscarinic receptors / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To explore the effect of organophosphorus insecticides (OPs) on G protein-coupled receptor kinase 2 mediated phosphorylation of M2 muscarinic receptors in vitro and to understand an alternative target of the OPs for human and other animals.</p><p><b>METHODS</b>The acetylcholine M2 muscarinic receptors (mAChR2) were purified from rat brain by single step affinity chromatography. In vitro experiments, the purified mAChR2, G-protein coupled receptor kinase 2 (GRK2) and the (gamma-p32) labeled ATP were incubated with paraoxon (PO), chlorpyrifos oxon (CPO) or chlorpyrifos (CPF) of varying concentrations. The proteins were separated by the polyacrylamide gel electrophoresis. The gels were dried and the phosphorylation of mAChR2 was detected with autoradiograms. Bands containing M2 receptor were excised and counted by liquid scintillation.</p><p><b>RESULTS</b>CPO inhibited phosphorylation of M2 muscarinic receptors by GRK2 with a median inhibition concentration (IC(50)) at 70 micromol/L. CPF also inhibited M2 receptors phosphorylation, but was less potent and less efficacious than that of CPO. PO and parathion (PT) had little effect on the receptor phosphorylation under the same conditions. CPO and CPF didn't inhibit the beta2 Adrenalin (beta2-AR) receptor phosphorylation also mediated by GRK2.</p><p><b>CONCLUSION</b>CPO and CPF can selectively inhibit the GRK2 mediated mAChR2 phosphorylation while PO and PT have no this effect.</p>

Alterations of beta-Adrenergic Receptor Signaling in Cardiac Hypertrophy and Heart Failure: beta-Adrenergic Receptor Desensitization in Cardiac Disease

beta-adrenergic receptors (betaAR) belong to the large family of G protein-coupled receptors that form the interface between the sympathetic nervous and cardiovascular systems. G protein-coupled receptors undergo adaptation to repeated or prolonged agonist stimulation, which is termed desensitization. Significant betaAR desensitization occurs with the development of cardiac hypertrophy and heart failure, and uncoupling of betaARs and defects in this pathway might be primary elements underlying the transition from compensated to uncompensated cardiac failure. Decreasing the level of myocardial betaARK1 in established heart failure is a novel approach to improving impaired betaAR receptor function, and potentially alter the pathogenesis of this disease.

Association between betaARK1 Level of Circulating Mononuclear Leukocytes and Left Ventrcular mass in Non-treated Hypertensive Patients

BACKGROUND: Beta-adrenergic receptor Kinase 1(betaARK1) is a serine/threonine kinase attached, which inhibits the coupling of beta-adrenergic receptor with G-protein. Myocardial betaARK1 level is usually elevated in heart failure and hypertrophy, but it is not known whether the circulating betaARK1 level is related with the degree of cardiac hypertrophy. This study was performed to evaluate the association of the betaARK1 level in circulating mononuclear leukocytes(MNL) in untreated hypertension with left ventricular mass in hypertensive patients. Method: Nineteen non-treated hypertensive patients were included for this study. High blood pressure was confirmed when systolic BP is over 150 mmHg or diastoli BP is over 95 mmHg. Echocardiography was performed to evaluate the degree of hypertrophy by measuring the left ventricular mass index(LVMI) and relative wall thickness(RWT), and test the LV function by measuring the ejection fraction(EF) according to ASE guideline. At the same time, blood was collected from each patient and MNL were isolated by gradient centrifuge with Ficoll-400. Total RNA was purified from MNL and semi-quantitative RT-PCR was performed. After reverse transcription, PCR was done with primers for human betaARK1 and GAPDH as external control. betaARK1 levels were expressed by ratio to GAPDH level and estimated the relations with clinical and Echocardiographic parameters. Result: We studied confirmed 19 hypertensive patients(10 men and 9 women, mean age of 50.6 years). Echocardiographically measured indices(mean+/-SD) were as follows; LVMI(137.3+/-30.6g/m2), PWT(0.53+/-0.09) and EF(54.6+/-8.5%). Ratio of betaARK1 levels to GAPDH was from 0.10 to 0.96 (0.62+/-0.25). betaARK1 levels were correlated with LVMI(correlation coefficient: r=.502, p=.029) and RWT(r=.627, p=.004). But Systolic BP(r=0.009, p=.93), diastolic BP(r=.07, p=.85) or EF(r=.045, p=.84) were not related to level of betaARK1. CONCLUSIONS: The betaARK1 level of circulating MNL was correlated well with the degree of the cardiac hypertrophy estimated by LVMI and RWT. This data suggests that activation of sympatho-adrenal system would exert a major role in developing cardiac hypertrophy and we can expect the decreased responsiveness to catecholamine in the heart of hypertensive patients. betaARK1 in circulating MNL might be used as a predictor or marker for LV hypertrophy in hypertensive patients.