| BackgroundChronic heart failure has become one of the most important cardiovascular diseases around the world. One of its characteristics is the overenhanced sympathetic nerve activity, which play an important role in the progress of CHF. Paraventricular nucleus is one of the important cardiovascular integrative centers. Our previous studies showed that in acute experiments the reactive oxygen species in PVN generated from NAD(P)H oxidase mediated the effects of Ang II on sympathetic nerve activity, especially the superoxide anions and hydrogen peroxide.Cooper-zinc superoxide dismutase is a kind of antioxide isoenzyme in cytoplasm, which catalyzes the conversion of superoxide radicals into hydrogen peroxides. Long term administration of tempol, a SOD mimic, normalizes the enhanced baseline sympathetic outflow of CHF rats. However, it is unknown whether scavenging the superoxide anions in the PVN in long term has beneficial effects on the sympathetic nerve activity and dysfunction of CHF rats. And CuZnSOD has short half life and high metabolic rate, which prevent the research from long term scanvenging the superoxide anions in PVN. With the development of molecular biology, gene therapy, as new treatment methods, show large prospects, in addition to traditional medication. Protein overexpression technology with the recombinational adenovirus vector carrying the target gene has become more sophisticated. CuZnSOD gene transfer into PVN can facilitate the research on the effects of the central superoxide anions on sympathetic nerve activity, which lay the theoretical and experimental foundation for further exploration of the CHF gene therapy.Objective1. To determine whether recombinant adenoviral vectors harboring human CuZnSOD can be transferred in PVN and continue to express in long term.2. To determine whether the enhanced sympathetic nerve activity after myocardial infarction can be normalized by CuZnSOD overexpression in PVN of CHF rats.3. To determine whether the CuZnSOD overexpression in PVN can improve the myocardial remodeling and cardiac dysfunction in CHF rats. Methods and ResultsThe rats were randomly divided into MI and Sham groups which were respectively subjected to the coronary ligation or sham operation. The Ad-SOD or Ad-null (1×1012 particles·ml-1) was respectively microinjected into the PVN immediately after the coronary ligation or sham operation. The final experiment was carried out at the end of the eighth week of the surgery. CuZnSOD expression in the PVN was determined with Western blotting. The activity of CuZnSOD in the PVN was measured according to its scavenging ability of the homogenates to superoxide anions using Ultraviolet Spectrophotometry. Determine baseline RSNA. Plasma norepinephrine level was determined by high-performance liquid chromatography. The cardiac sympathetic afferent reflex was evaluated by application of capsaicin to the epicardial surface of anterior wall of the left ventricle. Heart slices were stained with hematoxylin-eosin staining for morphologic examination or Masson's trichrome staining for assessment of interstitial fibrosis or TUNEL assay for apoptosis. Echocardiography and hemodynamic measurement were performed to envaluate the ventricular function.Results:1. CuZnSOD expression and activity, superoxide anionsCompared with sham rats, MI rats show lower CuZnSOD expression and activity, but higher superoxide anions level. Compared with null rats, Ad-CuZnSOD treated rats showed higher expression and activity of CuZnSOD and lower superoxide anions level.2. Baseline sympathetic nerve activity and plasma norepinephrine concentrationMI rats show higher baseline sympathetic nerve activity and plasma norepinephrine concentration than sham rats. Overexpression of CuZnSOD in PVN attenuated the increased baseline sympathetic nerve activity and plasma norepinephrine concentration in MI rats.3. CSARMI could induce enhanced CSAR. CuZnSOD gene transfer improved the enhanced CSAR after maycardial infarction.4. Weight and ScarMI rats showed significant increase in heart to body weight ratio and wet lung to body weight ratio compared with Sham rats. A dense scar was found in the anterior ventricular wall in each MI rat, but not in any Sham rat. Overexpression of CuZnSOD in PVN decreased the heart weight, but there was no significant difference in the infarct area between MI-SOD rats and MI-null rats.5. Heart slices for HE staining, Masson's trichrome staining and TUNEL assayCardiomyocyte size was considerably increased in MI rats in both border and remote zones of the infarction, which was attenuated by Ad-SOD. Ad-SOD inhibited the collagen deposition caused by MI. The collagen volume fraction significantly increased in MI rats, which was attenuated by Ad-SOD. In the border zone, the percentage of TUNEL-positive cardiomyocytes was markedly reduced in the MI-SOD group relative to MI-null group. In the remote zone, PVN CuZnSOD overexpression did not show significant effect on the increased percentage of TUNEL-positive cardiomyocytes in MI rats.6. EchocardiographyCompared with Sham-null rats, the LVEDD, LVESD, LVEDV and LVESV increased, while the IVSd, IVSs, SI, FS and EF decreased in MI-null rats. These changes caused by the MI were significantly attenuated by Ad-SOD.7. HemodynamicsThe LVEDP increased and LVdP/dtmax decreased in MI-null rats. The left ventricular dysfunction was significantly improved by treatment with Ad-SOD.Conclusions1. CuZnSOD can be successfully transferred into the PVN, and keep persistent expression and stable activity.2. Overexpression of CuZnSOD in the PVN normalized the enhanced baseline sympathetic nerve activity, and attenuated the enhanced CSAR in MI rats.3. Overexpression of CuZnSOD in the PVN attenuated the cardiac hypertrophy, collagen deposition and apoptosis in the border zone after myocardial infarction, and improved the ventricular dysfunction in MI rats. |
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