Prenatal Exposure To Immuno-Inflammatory Stimulants Result In Left Ventricle And Vasuclar Remodeling In Rats And Its Mechanisms

BACKGROUD: Cardiovascular disease ranks among the leading causes of morbidity and mortality in adult populations in most countries in the world. Hypertension is a major risk factor of cardiovascular diseases and its underlying pathogenetic mechanisms are still not well elucidated. Significant progress in understanding the etiology of cardiovascular disease has come from recent recognition that inflammation plays a key role in its development. Accumulating clinical evidences have implied that inflammation was also related to hypertension to some extent. Sesso and his colleagues reported a positive relationship between increased serum levels of C-reactive protein and the risk for development of incident hypertension in participants of the Women's Health Study. Bautista et al discovered the serum level of IL-6 elevated in hypertensive patients.Moreover, Events in utero appear to have a significant role in the development of cardiovascular dysfunction in adulthood. Emerging evidence indicates that there are multiple causes of hypertension and that adverse conditions experienced in utero can increase the incidence of hypertension in adulthood. Systemic inflammatory response during pregnancy represents one form of stressful event for the fetus. In a previous study, we showed that prenatal exposure to lipopolysaccharide (LPS), commonly used to mimic prenatal infection, resulted in hypertension in rat offspring. We mentioned the hypothesis that maternal inflammation could induce hypertension in offspring. However, does the stressful event of maternal inflammation only result in hypertension in offspring? Are there anyother cardiovascular events come out accompanied with hyepertension? Therefore, in the present study, we investigated the prolonged hypothesis that, as a common pathophysiological phenomenon, maternal inflammatory stress can not only cause hypertension but also can cause hypermyotrophy in adult offspring.AIM: The study is designed to study the effects of prenatal exposure to LPS on the function and construction of cardiac and vascular in offspring in rats. In addition, the effects of an inhibitor of the nuclear transcription factor NF-κB (pyrrolidine dithiocarbamate, PDTC) on this process were assessed.METHODS:1. Twenty-four time-mated Sprague-Dawley (SD) rats'dams were randomly divided into three groups: a control group, an LPS group, and an LPS+PDTC group. The rats in these groups were intraperitoneally administered vehicle, 0.79mg /kg LPS, or LPS plus 100mg/kg PDTC, respectively. LPS was given on the 8th, 10th and 12th days, whereas PDTC was given from the 8th to the 14th day during gestation. The pups were randomly chosen to be included in this study (males: controls, n=18; LPS-treated, n = 18; LPS+PDTC-treated, n=18; females: controls, n =18; LPS-treated, n = 18; LPS+PDTC-treated, n=18).2. The pups'systolic blood pressure (SBP) was measured once every tow months from the 2th month to 8th month with tail-cuff method. At the end of 4th and 8th month of the experiment, the heart mass index (HMI) and the LV mass index (LVMI) was evaluated. In addition, LV and RV structure and function, vascular structure and their microstructure and ultrastructure were examined using echocardiography, routine light microscopy and transmission electron microscopy, respectively.3. The blood plasma level of endothelin-1 (ET-1) was measured by RIA, and the serum level of nitric oxide (NO) was measured by nitrate reductase method.4. The expression of NF-κBp65, Bcl-2 and Bax antigen in left ventricles and the NF-κBp65, PCNA on VSMCs were done through immunohistochemical technique. The TdT mediated nick dUTP end labeling (TUNEL) technique was used to observe the apoptosis of cardiomyocytes in left ventricles.RESULTS1. There were no significant differences in the number of progeny per dam (P>0.05). Meanwhile, no significant differences were discovered about the ratio of male births to female births in each litter (P>0.05). The body weights of newborn pups did not differ much between the LPS, LPS+PDTC and control groups (P>0.05).2. All offspring to LPS exposed dams showed increased systolic blood pressure (P<0.05). They reached the standard of hypertension at the end of 6th month.3. As compared with the control group, prenatal exposure to LPS increased LV posterior wall thickness(PWT) on 4th month in offspring, and the thickness of the interventricular septum(IVST), LVMI, E/A index and Tei index(P<0.05) on 8th month in offspring were singnificantly increased in LPS group.There were no change in LPS+PDTC group(P>0.05).4. In prenatal LPS-treated offspring, the microstructure of left ventricles was as follows: the cardiomyocytes hypertrophy, interstitium fibrosis and myofibrilla lined up in disorder. However, prenatal treated with PDTC improved these morphological changes to some extent.5. The MT, LD and the media/lumen ratios (MT/LD) were increased significantly in offspring with LPS-exposed dam by comparison of control (P<0.05) on 4th month. However, there were no change in LPS+PDTC group (P>0.05).6. In prenatal LPS-treated rats, the ultrastructure of left ventricular cadiocytes was observed as the mitochondria swell and medullary sheath-like degeneration, the sarcoplasmic reticulum enlarged and the myofilaments dissolved and the Z lines broken. However, prenatal treated with PDTC improved these morphological changes.7. At the end of the 2th, 4th, 6th, 8th month, the blood plasma level of ET-1 of LPS-exposed dam was higher than the control (P<0.05). Until the 8th month, the level of ET-1 was (151.07±19.03)μmol/L, which was nearly doubled comparing with the control (78.56±12.39)μmol/L and LPS+PDTC group (84.78±5.71)μmol/L (P<0.01).8. The NF-κBp65 was activited in left ventricular cadiocytes and VSMCs in LPS group(P<0.01). However, there was almost no expression in control and LPS+PDTC group.9. As compared with the control group, prenatal exposure to LPS induced the apoptosis of cardiomyocytes and the over-expression of the Bax antigen and the low-expression of Bcl-2 antigen in the left ventricle tissues, respectively (P<0.01). However, prenatal treated with PDTC markedly attenuated the above changes.10. Compared with the control, the VSMCs proliferation activity was obviously increased in LPS group (P<0.01). While there were no change in the LPS+PDTC group.11. There were no significant differences in the serum level of NO in offspring among LPS , LPS+PDTC group and control group at the end of the 2th, 4th, 6th, 8th month (P>0.05).CONCLUSION1. Prenatal exposure to LPS results in left ventricle and vasuclar remodeling on the 4th month in offspring in rats.2. The blood plasma level of ET-1 and the expression of NF-κBp65 of LPS-exposed group is higher than the control. These changes might be the potential underlying mechanism of development of hypermyotrophy and vascular remodeling.3. Prenatal LPS exposure induced left ventricle remodeling. The mechanism is associated with the apoptosis in left ventricular cardiomyocytes to some extent. The mechanism may be relative to the overexpression of Bax antigen, low expression of Bcl-2 antigen.4. Prenatal LPS exposure induced vascular remodeling, which is relative to the impressing effect on the proliferation of VSMCs and the disequilibrium between the serum level of ET-1 and NO.5. There were no hypertension, hypermyotrophy and vascular remodeling in LPS+PDTC group. It showed that prenatal treated with inhibitor of the nuclear transcription factor NF-κB (pyrrolidine dithiocarbamate, PDTC) could reversed the effection of maternal inflammation on cardiovascular diseases in offapring in rats.