Time course of sympathetic neural hyperactivity after uncomplicated acute myocardial infarction

Renal Sympathetic Denervation Improves Outcomes in a Canine Myocardial Infarction Model

BACKGROUND Myocardial infarction (MI) is the main cause of heart failure (HF), and sympathetic nerve activity is associated with prognosis chronic heart failure. Renal sympathetic denervation (RDN) is noted for its powerful effect on the inhibition of sympathetic nerve activity. This study investigated the effect of RDN on heart failure in dogs after myocardial infarction. MATERIAL AND METHODS The experimental animals were randomized into 2 groups: the MI group (n=12) and the sham operation group (n=6). In the MI group we established an MI model by permanently ligating the left anterior descending branch. After 4 weeks, the MI dogs were randomly divided into 2 groups: the MI+RDN group (MI+renal sympathetic denervation, n=6) and the simple MI group (n=6). Animals in the MI+RDN group underwent both surgical and chemical renal denervation. RESULTS Compared with sham operation group, left ventricular fraction shortening (LVFS) and left ventricular ejection fraction (LVEF) were significantly reduced in the simple MI group, while the reduction was partly reversed in the MI+RDN group. RDN reduced sympathetic nerve activity and release of B-type natriuretic peptide (BNP) and Angiotensin II (AngII) in the MI+ RDN group but not in the simple MI group. CONCLUSIONS Canine renal sympathetic denervation prevents myocardial malignant remodeling by lowering the activity of the systemic sympathetic nerve and inhibiting renin-angiotensin-aldosterone system (RASS) activation, providing a new target and method for the treatment of heart failure.

Changes in Sympathetic Innervation of Rat Caudal Artery in Experimental Myocardial Infarction. Effect of Semax Peptide

Activation of the sympathetic nervous system aggravates the course of myocardial infarction. Semax peptide moderated the degree of this activation and prevented the increase in the density of sympathetic endings in rat caudal artery in 28 days after ischemia or ischemia/reperfusion. The peptide reduced the density of α-adrenoreceptors in the caudal artery of rats with myocardial infarction. Semax produced no effect on β-adrenoreceptors in both experimental models. The experiments on isolated segments of the caudal artery revealed reduced vascular responsiveness to electrical stimulation and norepinephrine infusion in rats treated with Semax after ischemia/reperfusion injury.

Exploration of P2X3 in the rat stellate ganglia after myocardial ischemia

ATP is implicated in peripheral pain signaling by actions on P2X receptors, especially P2X(3) receptor. Cardiac primary afferents running in the sympathetic nerves are considered to be essential pathways for transmission of cardiac nociception to the central nervous system. Because little is known about P2X(3) involvement in cardiac nociception, this study observed the difference in P2X(3) localization and expression in stellate ganglia (SG) from naive rats and in a pathological model of myocardial ischemic injury induced by repeated subcutaneous isoprenaline injections. Distribution of P2X(3) and morphometry of neurons in SG were investigated by immunohistochemistry, Western blotting, in situ hybridization (ISH) and by sterological study. Diffuse cytoplasmic P2X(3) immunolabelling was observed by light microsocopy. No nuclear labeling was detected. The intensity of P2X(3) labeling in the experimental myocardial ischemic injury group was increased in relation to that of the control group. Numerical densities of stellate ganglion neurons in the experimental group were higher than those of the control group. By Western blotting and ISH, the signals of P2X(3) protein and its mRNA in the myocardial ischemic group were higher than those of the control group. The P2X(3) labeling intensity and the numerical density in SG of the experimental myocardial ischemic injury group were enhanced, suggesting the involvement of P2X(3) receptor for the transmission of pain after myocardial ischemic injury.

C-reactive protein-induced expression of CD40-CD40L and the effect of lovastatin and fenofibrate on it in human vascular endothelial cells

Inflammation plays a pivotal role in the formation of atherosclerosis. In addition to being a risk marker for cardiovascular diseases, the role of C-reactive protein (CRP) in atherogenesis has been supported by more recent data. CD40-CD40L system is proven to be an important mediator of several auto-immune and chronic inflammation diseases. Interruption of CD40-CD40L signaling pathway not only reduces the initiation and progression of atherosclerotic lesions, but also modulates plaque architecture. By using a flow cytometry and western blotting, we found that incubation of human umbilical vein endothelial cells (HUVECs) with CRP resulted in a time- and dose-dependent increase in the cell-surface expression of CD40 and CD40L. In addition, CRP (25 microg/ml) increased gelatinolytic activities of MMP-2 and MMP-9. Anti-CD40 antibody significantly reversed the upregulated activities of MMP-2 and MMP-9 induced by CRP with gelatin zymography. Furthermore, lovastatin (10(-7), 10(-6), 10(-5) mol/l) and fenofibrate (5 x 10(-5), 10(-4), 2 x 10(-4) mol/l) significantly diminished the expression of CD40, CD40L and gelatinase activities (MMP-2, MMP-9) induced by CRP in HUVECs. In conclusion, our data provide evidence to support the direct pro-inflammatory effects of CRP via CD40-CD40L signaling pathway involved in the pathogenesis of atherosclerosis, and lovastatin and fenofibrate possess anti-inflammatory effects independent of their lipid-lowering action.

Increased cardiac sympathetic nerve activity following acute myocardial infarction in a sheep model

The time course of cardiac sympathetic nerve activity (CSNA) following acute myocardial infarction (MI) is unknown. We therefore undertook serial direct recordings of CSNA, arterial blood pressure (MAP) and heart rate (HR) in 11 conscious sheep before and after MI, and compared them with 10 controls. Conscious CSNA recordings were taken daily from electrodes glued into the thoracic cardiac nerves. Infarction was induced under pethidine and diazepam analgesia by applying tension to a coronary suture. MI size was assessed by left ventricular planimetry (%) at postmortem, peak troponin T and brain natriuretic peptide levels (BNP). Baroreflex slopes were assessed daily using phenylephrine-nitroprusside ramps. The mean infarcted area was 14.4 +/- 2.9%, troponin T 1.88 +/- 0.39 microg l(-1) and BNP 8.4 +/- 1.3 pmol l(-1). There were no differences in haemodynamic parameters or CSNA between groups at baseline. MAP and HR remained constant following MI. CSNA burst frequency increased from baseline levels of 55.8 +/- 7.1 bursts min(-1) to levels of 77.5 +/- 8.7 bursts min(-1) at 2 h post-MI, and remained elevated for 2 days (P < 0.001). CSNA burst area also increased and was sustained for 7 days following MI (P= 0.016). Baroreflex slopes for pulse interval and CSNA did not change. CSNA increases within 1 h of the onset of MI and is sustained for at least 7 days. The duration of this response may be longer because the recording fields decrease with time. This result is consistent with a sustained cardiac excitatory sympathetic reflex.