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Prenatal Exposure to Lipopolysaccharide Results in Vascular Reactivity Dysfunction in Offspring Rats

Author: HeXiaoYan
Tutor: LiXiaoHui
School: Third Military Medical University
Course: Pharmacology
Keywords: prenatal stress inflammation vascular reactivity Ang Ⅱ eNOS NF-κB
CLC: R714.7
Type: Master's thesis
Year: 2012
Downloads: 45
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Abstract

Hypertension is a leading cause of death and disability. One-quarter of the world’sadult population has hypertension, and this is likely to increase to29%by2025. Ourinstitution has choosed Lipopolysaccharide (LPS) as inflammatory stimulant exposure tomaternal gestation period and measured systolic blood pressure of offspring rats. The resultshowed that prenatal exposure to LPS resulted in hypertension in rat offspring rats.Furthermore, we choosed the intervention of nuclear factor kappaB (NF-κB) is as a keytarget and the result show that the offspring rats’ high blood pressure can be reversed. Onthe basis of these trials, we mentioned the hypothesis that prenatal exposure toinflammation could induce hypertension in offspring rats.The vascular system is not only the regulation system of blood pressure, but also thetarget organ of hypertension. The contractive reactivity of isolated aorta, femoral artery,renal artery, caudal artery, mesenteric arteries were increase in spontaneously hypertensiverats and renal hypertension, which is related with the development mechanism ofspontaneously hypertensive rats and renal hypertension. Vascular reactivity to endothelin-1(ET-1) in mesenteric vessels is increase in DOCA-salt hypertensive rats. These results showvascular reactivity is closely associated with hypertension.We will focus on vascular reactivity and study this mechanism. We use norepinephrine(NE) and sodium Nitroprusside (SNP) as the stimulating agent to measure prenatalexposure to LPS resulting in vascular reactivity dysfunction. To clarify this mechanism, wewill exam the protein expression level of angiotensin Ⅱ, angiotensin Ⅱ type1receptor(AT1R) and type2receptor(AT2R), the activity of nitric oxide synthase (NOS), theprotein expression level of nuclear factor kappaB (NF-κB) and inflammatory factor invascular. In addition, we will exam the result of the intervention of nuclear factor kappaBreverse to the abnormal change. The aim of the whole experiment is that prenatal exposureto inflammation results in vascular reactivity dysfunction and its mechanism, which may be one reason of high blood pressure.Methods1. The pregnant rats were randomly divided into four groups, i.e. control group, LPSgroup, PDTC group and LPS plus PDTC group. Rats in these groups were administeredintraperitoneally with vehicle,0.79mg/kg LPS,100mg/kg PDTC, LPS plus PDTC,respectively. LPS was given on8th,10th and12th day while PDTC from8th to14th dayduring gestation. The rats in LPS group were given a vehicle injection on days9,11,13,14and rats in control group were given every day during8~14day.2. The measurement of systolic blood pressure in offspring ratsThe systolic blood pressure in offspring rats was measured once every four weeks at8：00~12：00a.m. every day using the standard tail-cuff method.3. The vascular reactivity of thoracic aortaThe thoracic aorta was removed and cut into rings with the width of3~5mm. Thebathing solution was maintained at37℃and continuously gassed with oxyen. The vascularreactivity was measured using norepinephrine (NE) and sodium nitroprusside (SNP).4. Angiotensin Ⅱ of vascular tissue was determined in offspring rats at5th and16th week of age by immunohistochemical staining (IHC). AT1and AT2protein expressionlevel of vascular tissue in offspring rats at5th and16th week was assessed by Westernblotting.5. Endothelial nitric oxide synthase (eNOS) and phosphorylation of endothelial nitricoxide synthase (p-eNOS) of vascular tissue were determined in offspring rats at5th and16th week of age by immunohistochemical staining (IHC).6. NF-κB of vascular tissue was determined in offspring rats at5th and16th week ofage by immunohistochemical staining (IHC).7. Interleukin-6(IL-6) and Tumor necrosis factor-α (TNF-α) of vascular tissue wereassessed at5th and16th week of age by enzyme-linked immunoassay (ELISA).Results1. As compared with control group, prenatal exposure to LPS significantly increasesthe systolic blood pressure in offspring rats at8th week age（p<0.05),12th week age(p<0.01) and16th week age(p<0.01).But prenatal exposure to LPS plus PDTC cansignificantly decrease the systolic blood pressure in offspring rats compared with LPS group(p<0.05).2. Compared with control group, prenatal exposure to LPS significantly elevates thecontractive reactivity of thoracic aorta to NE（p<0.01）but decreases the diastolic reactivityof thoracic aorta to SNP（p>0.05）; prenatal exposure to LPS plus PDTC can significantlyreduce the contractive reactivity compared with LPS group（p<0.01）, but increase thediastolic reactivity（p>0.05）.3. At the age of5week, the protein level of AngⅡ in LPS group is not different fromcontrol group, meanwhile, the protein level of AT1and AT2is too little to do statistics.At16th week, prenatal exposure to LPS significantly elevates the protein expressionlevel of AngⅡ（p<0.05）,elevates the protein expression level of AT1（p<0.01）andincreases in the ratio of AT1/AT2compared with control group（p<0.01）; compared withLPS group, prenatal exposure to LPS plus PDTC can significantly decrease the proteinexpression level AngⅡ（p<0.01）and significantly decrease in the ratio of AT1/AT2in thevascular tissue（p<0.05）4. Compared with control group, prenatal exposure to LPS significantly elevates theprotein expression level of eNOS （p<0.01）, but decreases p-eNOS protein level（p<0.05）, resulting in a significant decrease in the ratio of p-eNOS/eNOS in the vasculartissue（p<0.01）; prenatal exposure to LPS plus PDTC can decrease eNOS protein level,increased significantly p-eNOS protein level（p<0.01）, and result in at increase in the ratioof p-eNOS/eNOS at the age of5weeks.As compared with control group, prenatal exposure to LPS significantly decreasesp-eNOS protein level（p<0.05）, resulting in a significant decrease in the ratio of p-eNOS/eNOS in the vascular tissue at16th week age.（p<0.01）.5. Compared with control group, prenatal exposure to LPS significantly elevates theprotein expression level of NF-κB of vascular tissue （p <0.01）, but prenatal exposure toLPS plus PDTC can significantly decrease the protein expression level compared with LPSgroup（p<0.01）at the age of5th week and16th week.6. At5th week, prenatal exposure to LPS plus PDTC can decrease significantly IL-6level compared with LPS group（p<0.05）At the age of16weeks, prenatal exposure to LPS elevates significantly TNF-α level（p<0.01）compared with control group, and prenatal exposure to LPS plus PDTC can decrease significantly TNF-α level compared with LPS group（p <0.01）.Conclusion1. Prenatal inflammation exposure results in vascular reactivity dysfunction inoffspring rats，especially increases vascular contractive reactivity.2. The mechanism of prenatal inflammation exposure resulting in vascular reactivitydysfunction in offspring rats may be associated with the change of Ang Ⅱ and its receptorsprotein level, levels of eNOS activity and the activation of NF-κBp65.3. NF-κB activation is implicated in vascular reactivity dysfunction. The interventionof NF-κB can improve vascular reactivity dysfunction.4. Prenatal inflammation exposure results in vascular reactivity dysfunction and highblood pressure. The intervention of inflammation can improve vascular reactivitydysfunction and high blood pressure. It suggests that prenatal inflammation exposureresulting in vascular reactivity dysfunction is one mechanism of high blood pressure.

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