ABSTRACT
Objective:To investigate the role and mechanism of microRNA-499 (miR-499) regulating α-myosin heavy chain (α-MHC) and β-myosin heavy chain (β-MHC) gene axis in septic myocardial dysfunction (SMD) and its significance.Methods:Sixty healthy adult male Sprague-Dawley (SD) rats were divided into phosphate buffered saline (PBS) control group (PBS group), lipopolysaccharide (LPS) induced SMD model group (LPS group), miR-499 agonist pretreatment group (agomir+LPS group), and miR-499 inhibitor pretreatment group (antagomir+LPS group) by random number table, with 15 rats in each group. SMD rat model was reproduced by intraperitoneal injection of LPS 10 mg/kg. The PBS group was intraperitoneally injected with the same amount of PBS. The two pretreatment groups were injected with agomir 30 mg/kg or antagomir 80 mg/kg through the caudal vein for 3 days, once a day. PBS group and LPS group were not pretreated. Echocardiography was detected 5 hours after LPS injection, and relevant indexes were recorded. The expression of miR-499 in plasma and myocardial tissue was detected by real-time quantitative polymerase chain reaction (qPCR). Western blotting was used to detect the protein expressions of α-MHC and β-MHC in myocardial tissue. Plasma N-terminal pro-brain natriuretic peptide (NT-proBNP), a marker of heart failure, was measured by electrochemiluminescence.Results:Compared with the PBS group, the rats in LPS group were depressed. Additionally, LPS down-regulated the level of miR-499 in plasma and myocardial tissue, decreased α-MHC expression in myocardial tissue and up-regulated the expression of β-MHC. Echocardiography showed that left ventricular ejection fraction (LVEF), left ventricle fractional shortening (LVFS), cardiac output (CO), stroke volume (SV) and heart rate (HR) decreased by 49.1%, 59.2%, 48.8%, 39.4% and 15.9%, respectively, and the level of plasma NT-proBNP increased significantly in LPS group, indicating that LPS could induce cardiac dysfunction in rats. Compared with the LPS group, after pretreatment with agomir to overexpress the miR-499, LVEF and LVFS were significantly increased [LVEF: 0.662±0.020 vs. 0.323±0.024, LVFS: (36.16±1.43)% vs. (20.20±1.32)%, both P < 0.01], which suggested that the cardiac function of rats was improved in agomir+LPS group. At the same time, pretreatment with agomir significantly down-regulated the β-MHC protein expression (β-MHC/GAPDH: 0.74±0.04 vs. 2.97±0.34, P < 0.01), significantly up-regulated α-MHC protein expression (α-MHC/GAPDH: 1.59±0.05 vs. 0.74±0.14, P < 0.01), and significantly decreased the plasma NT-proBNP level (ng/L: 114.49±6.85 vs. 334.13±4.36, P < 0.01). After pretreatment with antagomir to inhibit the expression of miR-499, echocardiography showed that LVEF and LVFS were significantly lower than those in the LPS group [LVEF: 0.297±0.021 vs. 0.323±0.024, LVFS: (19.38±1.52)% vs. (21.20±1.32)%, both P < 0.01], which suggested that the cardiac function of rats was significantly inhibited. At the same time, pretreatment with antagomir significantly down-regulated α-MHC protein expression in myocardial tissue (α-MHC/GAPDH: 0.63±0.03 vs. 0.74±0.14, P < 0.01), significantly up-regulated β-MHC protein expression (β-MHC/GAPDH: 3.03±0.47 vs. 2.97±0.34, P < 0.01), and significantly increased the level of plasma NT-proBNP (ng/L: 373.91±4.23 vs. 334.13±4.36, P < 0.05). Conclusions:miR-499 could regulate the expression of α-MHC and β-MHC which improved cardiac dysfunction caused by sepsis. Targeted regulation of miR-499 expression may be an effective way to treat SMD.
ABSTRACT
By means of retrograde HRP tracing method, the innervation of the left half of cervical portion of oesophagus in cats was investigated in this study. The HRP-labelled cells were found bilaterally in the retrofacial nuclei, nuclei supraspinalis, nuclei dorsomedialis and ipsilaterally in the dorsal motor nucleus of the vagus nerve, solitary nucleus, nucleus ambiguus, intermediate zone, nucleus retroambiguus and spinal nucleus of the accessory nerve. The distribution of the labelled cells in the dorsal motor nucleus of vagus nerve showed certain localization characteristics. They were more numerous at the levels above and below the obex. The labelled sympathetic preganglionic neurons with long axons appeared in T_1-T_3 spinal segments at the injected side (88.96%) and mainly in T_2(66.45%). The majority of labelled cells were located in the intermediolateral nucleus(95.02%); and the rest were in the lateral funiculus, intercalated nucleus and dorsolateral nucleus of the ventral horn, there were two of preganglionic neurons (i.e. parasympathetic and sympathetic) innervating the oesophagus. The postganglionic neurons were mainly located in the stellate ganglion(61.99%), anterior and middle cervical ganglia, and T_2-T_5 ganglia of the sympathetic trunk, bilaterally. There were some labelled cells in the nodose ganglion and the C_1 to T_5 spinal ganglia(mainly in C_6 and T_2). The ratio between the labelled cells in the nodose ganglion and the spinal ganglia is 2.6:1, which means that the afferent fibres ran predominantly via vagus nerve.