The Role Of Prenatal Cold Exposure In Blood Pressure Elevation Of Adult Offspring

1?Effect of sympathetic nervous system on blood pressure in offspring prenatal cold exposure induced.1.1 Background:Hypertension is an important cause of death and other cardiovascular diseases.There is increasing evidence that ambient temperature is closely related to blood pressure.The environmental factors not only affect individuals,but also relate to the growth in offspring.Previous studies have shown that adverse environment such as infection and inflammation in pregnancy can lead to the increase of blood pressure in offspring.As cold stress can cause physiological changes in the maternal generation,We believe that cold stress can also affect offspring growth.Whether or not cold stress during pregnancy could result in blood pressure elevation in offspring reminds unclear.In addition,the overactivation of central and peripheral sympathetic nervous system exists in individuals with pregnancy hypertension and preeclampsia induced by cold stress.Howerer,long-term activation of sympathetic nervous system and RASS system may damage the development of intrauterine fetus.Therefore,we infer that cold stress during pregnancy may cause blood pressure elevation in offspring,which may be due to Central and peripheral sympathetic nerve hyperexcitability1.2 Objective:The experiment is to establish a model of offspring during cold stress in pregnancy and confirm whether prenatal cold stress lead to the elevation of blood pressure would be analyzed.Moreover the mechanisms in paraventricular nucleus that prenatal cold stress of the blood pressure elevation in cold-induced offspring can be found.This study might identify the development origins of hypertension and provide therapeutic targets and preventive measures for hypertension.1.3 Methods:In this experiment,the 8-10 weeks SD rats were placed in cold environment of about2-6?for 8 hours every day during pregnancy.The changes of blood pressure in offspring were observed continuously from 4 weeks after birth.The blood pressure of offspr ings was measured by non-invasive tail-cuff method.Heart rate variability?HRV?was recorded In vivo.The sympathetic receptor antagonist?peripheral alpha 1,beta receptor antagonist,central alpha 2 receptor agonist?were feed by gavage to observe the changes systolic blood pressure,urine volume,urine sodiun in offspring.Western blot was used to detect AT ₁receptor expression in PVN.Metabolic changes in PVN were observed by magnetic resonance imaging?MRS?.After microinjection of AT₁R antagonist losartan into PVN,we used stereotaxis to monitor systolic blood pressure,heart rate?HR?and enzymes in rats.The ELISA was used to messure the expression of inflammatory factors IL-1,IL-6,TNF-alpha in PVN and the expression of excitatory glutamatergic neuron receptor GRIN2B and inhibitory gamma-aminobutyric neuron receptor GAD65 in the paraventricular nucleus were observed by immunohistochemical assay?IHC?.1.4 Results:1.Compared with the normal offspring group,systolic blood pressure,diastolic blood pressure and mean arterial blood pressure of the cold-induced offspring group increased significantly from 8 weeks to 24 weeks of age?P<0.05?.2.Compared with the normal offspring group,urine and sodium excretions in the cold-induced offspring group were significantly lower?P<0.05?.3.Compared with the normal offspring group,HR and HRV in the cold-induced offspring group was significantly higher than that in the normal offspring group?P<0.05?.4.The normal offspring group and the cold-induced offspring group were feed on with alpha 1 receptor antagonist prazosin?1mg/kg*d?,beta receptor antagonist propranolol?30mg/kg*d?,and alpha 2 agonist clonidine?0.2mg/kg*d?by gavage.The SBP of both group decreased,but the cold-induced offspring group decreased more significantly?P<0.05?and compared with the normal offspring,the The urine and sodium excretions of the cold-induced offspring group increased more significantly?P<0.05?.5.After renal denervation,the SBP in cold-induced offspring group decreased more?P<0.05?,and the urine sodium and urine volume increased more?P<0.05?.The change of the SBP,urine and sodium in normal offspring group were not obvious.6.The ratios of N-acetylaspartate?NAA?/creatine?Cr?and Choline?Cho?/Cr of the PVN were acquired by the MRS.The results showed that the NAA/Cr ratios in cold-induced offspring group were significantly lower than that of the normal offspring group?P<0.05?,whereas the Cho/Cr ratios in the cold-induced offspring group were higher than that of the control group?P<0.05?.7.Western Blot and IHC showed that the AT₁R expression in PVN of the cold-induced offspring group was significantly higher than that of the normal offspring group?P<0.05?..After microinjection of AT₁R antagonist losartan into PVN,The SBP both decreased.But the cold-induced offspring decreased more significantly than the normal offspring?P<0.05?.8.IHC showed the excitatory glutamate receptor GRIN2B in the cold-induced offspring group was higher than that in the normal group?P<0.05?,and the inhibitory glutamate receptor GAD65 in the the cold-induced offspring group was significantly lower than that in the normal group?P<0.05?.9.The expression of IL-1,IL-6 and TNF-?in PVN was measured by ELISA.The cold-induced offspring was significantly higher than that in the normal group?P<0.05?.1.5 Conclusion:Prenatal cold exposure can improve neuronal activity,renin-angiotensin-aldosterone system?RAAS?overactivation and inflammatory in offspring paraventricular nucleus which leads to renal sympathetic nerve overactivation.It cause renal dysfuncyon and the increase of blood pressure in offspring.2?Effect of mesenteric vascular function on blood pressure in offspring prenatal cold exposure induced.2.1 Background:Previous studies have shown that adverse environment stress such as infection and air pollution are associated with the vasorelaxation dysfunction in offspring,which are mainly due to high expression of G protein-coupled receptor kinase 4 and low expression of dopamine receptor.The increase of blood pressure is related to peripheral vascular resistance,and mesenteric artery is an important component of peripheral vascul ar resistance.Therefore,we infer that Prenatal cold exposure may cause the increase of blood pressure in offspring,which may be related to the change of vasorelaxation function.2.2 Objective:The experiment is to analyze the changes of vasorelaxation function in the offspring induced by prenatal cold exposure and to explore the mechanism of vasorelaxation function change.This study may provide theoretical basis for explaining the pathogenesis of hypertension in offspring.2.3 Methods:The vascular function was measured in offspring at 16 weeks.The Ach-induced relaxtion and the fenoldapamin-induced relaxtion were tested in endothelium-intact mesenteric arteries and endothelium-denuded mesenteric arteries.Western blot was used to detect D₁R/GRK4 expression in superior mesenteric artery.The expression of D₁R in cell membrane and cytoplasm was measured by Western blot.Co-Immunoprecipitation?Co-IP?experiment was used to find the expression of D₁R phosphorylation.2.4 Results:1.Compared with the normal offspring group,the cold-induced offspring showed more decreased acetylcholine?Ach?-induced relaxation and fenoldapamin-induced rel-axation in endothelium-intact mesenteric ateries.The cold-induced offspring also show-ed decreased fenoldapamin-induced relaxation in endothelium-denuded?E-?mesenteric ateries.But there was no difference of acetylcholine?Ach?-induced relaxation in endothelium-denuded ateries between the normal offspring group and the cold-induced offspring.2.Western Blot showed the D₁R expression of the mesenteric arteries in the cold-induced offspring group was lower than that in the normal offspring group?P<0.05?,in which the D₁R receptors on the cell membrane decreased significantly?P<0.05?,the D₁R receptors in the cytoplasm increased?P<0.05?,and the GRK4 was higher than that in the normal offspring.3.Co-IP showed the phosphorylation D₁R level of the mesenteric arteries in the cold-induced offspring group was higher than that in the normal offspring group?P<0.05?.4?Western Blot showed GRK4 expression of the mesenteric arteries in the cold-induced offspring group was higher than that in the normal offspring?P<0.05?2.5 Conclusion:Prenatal cold exposure can increase the expression of GRK4 in offspring mesenteric artery which induces D₁R internalization and expression reduction.It decreases mesenteric artery relaxation function,which causes the increase of blood pressure in offspring.3 Total Conclusion:Prenatal cold exposure can induce neurons excitability improving,renin-angiotensin-aldosterone system?RAAS?overactivation and inflammation in offspring PVN region which contributes to an increase in renal sympathetic activity.On the one hand the sympathetic activity overactivation might enhance blood vessels constraction and decrease arteries relaxation function.On the other hand it might cause renal dysfuncyon.Both of them result in the increase of blood pressure in offspring.