Biological significance of miR-126 expression in atrial fibrillation and heart failure

We investigated the biological significance of microRNA-126 (miR-126) expression in patients with atrial fibrillation (AF) and/or heart failure (HF) to examine the possible mechanism of miR-126-dependent AF and development of HF. A total of 103 patients were divided into three groups: AF group (18 men and 17 women, mean age: 65.62±12.72 years), HF group (17 men and 15 women, mean age: 63.95±19.71 years), and HF-AF group (20 men and 16 women, mean age: 66.56±14.37 years). Quantitative real-time PCR was used to measure relative miR-126 expression as calculated by the 2−ΔΔCt method. miR-126 was frequently downregulated in the 3 patient groups compared with controls. This reduction was significantly lower in permanent and persistent AF patients than in those with paroxysmal AF (P<0.05, t-test). Moreover, miR-126 expression was markedly lower in the HF-AF group compared with the AF and HF groups. The 3 patient groups had higher N-terminal prohormone brain natriuretic peptide (NT-proBNP) levels, lower left ventricular ejection fraction (LVEF), larger left atrial diameter, and higher cardiothoracic ratio compared with controls. There were significant differences in NT-proBNP levels and LVEF among the AF, HF, and HF-AF groups. Pearson correlation analysis showed that relative miR-126 expression was positively associated with LVEF, logarithm of NT-proBNP, left atrial diameter, cardiothoracic ratio, and age in HF-AF patients. Multiple linear regression analysis showed that miR-126 expression was positively correlated with LVEF, but negatively correlated with the logarithm of NT-pro BNP and the cardiothoracic ratio (all P<0.05). Serum miR-126 levels could serve as a potential candidate biomarker for evaluating the severity of AF and HF. However, to confirm these results, future studies with a larger and diverse patient population are necessary.

Biological significance of miR-126 expression in atrial fibrillation and heart failure.

We investigated the biological significance of microRNA-126 (miR-126) expression in patients with atrial fibrillation (AF) and/or heart failure (HF) to examine the possible mechanism of miR-126-dependent AF and development of HF. A total of 103 patients were divided into three groups: AF group (18 men and 17 women, mean age: 65.62±12.72 years), HF group (17 men and 15 women, mean age: 63.95±19.71 years), and HF-AF group (20 men and 16 women, mean age: 66.56±14.37 years). Quantitative real-time PCR was used to measure relative miR-126 expression as calculated by the 2-ΔΔCt method. miR-126 was frequently downregulated in the 3 patient groups compared with controls. This reduction was significantly lower in permanent and persistent AF patients than in those with paroxysmal AF (P<0.05, t-test). Moreover, miR-126 expression was markedly lower in the HF-AF group compared with the AF and HF groups. The 3 patient groups had higher N-terminal prohormone brain natriuretic peptide (NT-proBNP) levels, lower left ventricular ejection fraction (LVEF), larger left atrial diameter, and higher cardiothoracic ratio compared with controls. There were significant differences in NT-proBNP levels and LVEF among the AF, HF, and HF-AF groups. Pearson correlation analysis showed that relative miR-126 expression was positively associated with LVEF, logarithm of NT-proBNP, left atrial diameter, cardiothoracic ratio, and age in HF-AF patients. Multiple linear regression analysis showed that miR-126 expression was positively correlated with LVEF, but negatively correlated with the logarithm of NT-pro BNP and the cardiothoracic ratio (all P<0.05). Serum miR-126 levels could serve as a potential candidate biomarker for evaluating the severity of AF and HF. However, to confirm these results, future studies with a larger and diverse patient population are necessary.

P2 purinergic receptor activation of neuronal nitric oxide synthase and guanylyl cyclase in the dorsal facial area of the medulla increases blood flow in the common carotid arteries of cats.

In the dorsal facial area (DFA) of the medulla, an activation of either P2 purinergic receptor or nitric oxide synthase (NOS) results in the release of glutamate, leading to an increase in blood flow of the common carotid artery (CCA). It is not known whether activation of the P2 receptor by ATP may mediate activation of NOS/guanylyl cyclase to cause glutamate release and/or whether L-Arg (nitric oxide (NO) precursor) may also cause ATP release from any other neuron, to cause an increase in CCA flow. We demonstrated that microinjections of P2 receptor agonists (ATP, α,ß-methylene ATP) or NO precursor (L-arginine) into the DFA increased CCA blood flow. The P2-induced CCA blood flow increase was dose-dependently reduced by pretreatment with NG-nitro-arginine methyl ester (L-NAME, a non-specific NOS inhibitor), 7-nitroindazole (7-NI, a relatively selective neuronal NOS inhibitor) or methylene blue (MB, a guanylyl cyclase inhibitor) but not by that with D-NAME (an isomer of L-NAME) or N5-(1-iminoethyl)-L-ornithine (L-NIO, a potent endothelial NOS inhibitor). Involvement of glutamate release in these responses were substantiated by microdialysis studies, in which perfusions of ATP into the DFA increased the glutamate concentration in dialysates, but co-perfusion of ATP with L-NAME or 7-NI did not. Nevertheless, the arginine-induced CCA blood flow increase was abolished by combined pretreatment of L-NAME and MB, but not affected by pretreatment with a selective P2 receptor antagonist, pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS). In conclusion, ATP activation of the P2 receptor in the DFA induced activation of neuronal NOS/guanylyl cyclase, which causes glutamate release leading to an increase in CCA blood flow. However, arginine activation of neuronal NOS/guanylyl cyclase, which also caused glutamate release and CCA blood flow increase, did not induce activation of P2 receptors. These findings provide important information for drug design and/or developing therapeutic strategies for the diseases associated with CCA blood flow that supplies intra- and extra-cranial tissues.

The role of hexokinases from grape berries (Vitis vinifera L.) in regulating the expression of cell wall invertase and sucrose synthase genes.

In plants, hexokinase (HXK, EC 2.7.1.1) involved in hexose phosphorylation, plays an important role in sugar sensing and signaling. In this study, we found that at Phase I of grape berry development, lower hexose (glucose or fructose) levels were concomitant with higher HXK activities and protein levels. After the onset of ripening, we demonstrated a drastic reduction in HXK activity and protein levels accompanied by a rising hexose level. Therefore, our results revealed that HXK activity and protein levels had an inverse relationship with the endogenous glucose or fructose levels during grape berry development. A 51 kDa HXK protein band was detected throughout grape berry development. In addition, HXK located in the vacuoles, cytoplasm, nucleus, proplastid, chloroplast, and mitochondrion of the berry flesh cells. During grape berry development, HXK transcriptional level changed slightly, while cell wall invertase (CWINV) and sucrose synthase (SuSy) expression was enhanced after véraison stage. Intriguingly, when sliced grape berries were incubated in different glucose solutions, CWINV and SuSy expression was repressed by glucose, and the intensity of repression depended on glucose concentration and incubation time. After sliced, grape berries were treated with different glucose analogs, CWINV and SuSy expression analyses revealed that phosphorylation of hexoses by hexokinase was an essential component in the glucose-dependent CWINV and SuSy expression. In the meantime, mannoheptulose, a specific inhibitor of hexokinase, blocked the repression induced by glucose on CWINV and SuSy expression. It suggested that HXK played a major role in regulating CWINV and SuSy expression during grape berry development.

Glutamate release upon purinergic action in the dorsal facial area of the medulla increases blood flow in the common carotid artery in cats.

Interactions of glutamatergic and purinergic actions in the medulla regulate important cardiovascular functions. The glutamatergic action in dorsal facial area (DFA) of the medulla increases blood flow of common carotid artery (CCA) in cats. We hypothesized that interactions of glutamatergic and purinergic actions in the DFA may regulate the CCA blood flow. Purinergic and glutamatergic agonists and antagonists were microinjected into the DFA through a four-barrel tubing in anesthetized cats. Drug effects were evaluated by changes in the CCA blood flow. Microinjection with 20 nmol ATP or alpha,beta-methyleneATP (alpha,beta-MeATP, a P2 purinergic receptor agonist) induced an increase of the CCA blood flow. This increase was dose-dependently reduced by prior administration with 1,3-dipropyl-8-p-sulfophenylxanthine (DPSPX, a specific P1 purinergic receptor antagonist), or pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS, a selective P2 purinergic receptor antagonist) as well as with MK-801 (a non-competitive NMDA receptor antagonist) or glutamate diethyl ester (GDEE, a competitive AMPA/kainate receptor antagonist). It was almost completely blocked by administrations with combined maximal doses of P1 and P2 receptor antagonists as well as NMDA and AMPA receptor antagonists. Nevertheless, P1 receptor agonist induced only mild and poorly reproducible increase in the CCA blood flow. In conclusion, prominent P2 and minor P1 purinergic receptors appear to be present in the DFA; the purinergic activation can mediate a release of glutamate that stimulates NMDA and AMPA to induce the increase of the CCA blood flows. These findings may provide important information for developing therapeutic strategy for diseases involving the CCA blood flow, such as hypertensive disease and cerebral ischemia.

Regulation of the common carotid arterial blood flow by nicotinic receptors in the medulla of cats.

BACKGROUND AND PURPOSE: Actions of glutamate and serotonin on their respective receptors in the dorsal facial area (DFA) of the medulla are known to regulate common carotid arterial (CCA) blood flow in cats. Less is known about acetylcholine action on its nicotinic receptor (nAChR) subtypes in the DFA for regulation of CCA blood flow and this aspect was investigated. EXPERIMENTAL APPROACH: Nicotinic and muscarinic agonists and antagonists were microinjected into the DFA through a three-barrel tubing in anesthetized cats. RESULTS: CCA blood flow was dose-dependently increased by nicotine (a non-selective nAChR agonist) and choline (a selective alpha7-nAChR agonist). These effects of nicotine were attenuated by alpha-bungarotoxin (an alpha7-nAChR antagonist), methyllycaconitine (an alpha7-nAChR antagonist), mecamylamine (a relatively selective alpha3beta4-nAChR antagonist) and dihydro-beta-erythroidine (a relatively selective alpha4beta2-nAChR antagonist). The choline-induced flow increase was attenuated by alpha-bungarotoxin and mecamylamine, but not by dihydro-beta-erythroidine. Muscarinic agonists (muscarine and methacholine) and antagonist (atropine) affected neither the basal nor the nicotine-induced increase in the CCA blood flow. CONCLUSIONS AND IMPLICATIONS: Functional alpha7, alpha4beta2, and alpha3beta4 subunits of the nAChR appear to be present on the DFA neurons. Activations of these receptors increase the CCA blood flow. The present findings do not preclude the presence of other nAChRs subunits. Muscarinic receptors, if any, on the DFA are not involved in regulation of the CCA blood flow. Various subtypes of nAChRs in the DFA may mediate regulation of the CCA and cerebral blood flows.

Comparison of heart failure in children with enterovirus 71 rhombencephalitis and cats with norepinephrine cardiotoxicity.

The mechanism of heart failure in patients with enterovirus 71 rhombencephalitis (brain stem encephalitis) remains unknown. Our previous reports hypothesized that a catecholamine storm induced by rhombencephalitis may account for the heart failure. The aim of this study was to develop a novel feline model of norepinephrine cardiotoxicity and compare the resulting heart failure to that in children with enterovirus 71 rhombencephalitis. Nine of 75 children (12%) with enterovirus 71 rhombencephalitis (5 boys and 4 girls; age, 4-28 months; median age, 16 months) were complicated with left ventricular hypokinesia (ejection fraction, 31 +/- 9%). Six cats (weight, 3.03 +/- 0.64 kg) were administered intravenous norepinephrine 30 microg/kg/min for 3 hours. Echocardiography assessed the left ventricular diameter and function before and after the administration of norepinephrine. Pathology studies included hematoxylin and eosin stain and in situ terminal deoxyribonucleotidyl transferase-mediated dUTP nick end-labeling assay. In the feline model, norepinephrine induced significant left ventricular dilatation (end diastolic diameter from 1.18 +/- 0.19 to 1.62 +/- 0.22 cm, p = 0.001; endsystolic diameter from 0.54 +/- 0.09 to 1.36 +/- 0.32 cm, p = < 0.001) and hypokinesia (ejection fraction from 87.5 +/- 4.1 to 35.2 +/- 16.3%, p = 0.001). Heart specimens from 4 patients and six cats showed similar pathology findings, including myocardial hemorrhage, cardiomyocyte apoptosis, and coagulative myocytolysis, which is characterized by sarcoplasmic coagulation, granulation, vacuolization, myofibrillar waving, and disruption. Both groups showed no significant inflammatory reaction. In conclusion, heart failure in patients with enterovirus 71 rhombencephalitis is similar to that in cats with norepinephrine cardiotoxicity. Norepinephrine cardiotoxicity may play a role in the pathogenesis of heart failure in enterovirus 71 rhombencephalitis.

Accumulation of phosphocreatine and creatine in the cells and fluid of mouse seminal vesicles is regulated by testosterone.

We have recently established that phosphocreatine (PCr), a high-energy phosphate compound known to serve as an intracellular energy reserve, accumulates in the seminal vesicular fluid (SVF) of the mouse and the rat. To investigate whether the accumulation of PCr in the extracellular fluid of the seminal vesicles of mice is androgen-dependent, young adult mice (Swiss Webster, 6-7 wk old) were orchidectomized. Involution of the seminal vesicles following orchidectomy resulted in the total absence of SVF. Administration of testosterone propionate (TP) 2 wk later at a daily dose of 5 micrograms/g b.w. caused a rapid increase in the weights of seminal vesicle tissue (SVT) and SVF and also increased the concentration of PCr in SVF. The concentration of PCr in SVF increased rapidly from 3.0 mumol/g on Day 2 to a peak value of 11.1 +/- 0.5 mumol/g on Day 6. The increase in PCr concentration in SVF coincided with the enhanced rate of secretion of specific proteins by androgen-responsive epithelial cells. The creatine (Cr) concentration in SVF also increased from 12.6 mumol/g on Day 2 to 41.1 +/- 4.6 mumol/g on Day 8. The concentrations of PCr in SVF of TP-treated mice were about twice those in the age-matched intact controls. The concentrations of PCr and of Cr in SVT also increased from 1.1 +/- 0.5 mumol/g and 1.7 +/- 0.8 mumol/g, respectively, on Day 0 to the steady-state levels of 5.3 +/- 0.7 mumol/g and 14.8 +/- 2.7 mumol/g by Day 8. These results demonstrate that the accumulation of PCr in the fluid of mouse seminal vesicle is regulated by androgen.