Research On The Role Of The HIF-1α And Its Target Genes In The Pathogenesis Of Neonatal Hypoxic Pulmonary Hypertension

Background:Hypoxic pulmonary hypertension(HPH) for the newborn is characterised by increasing pulmonary artery pressure(PAH) because of various diseases caused by hypoxia which can lead to neonatal pulmonary vascular spasm,pulmonary vascular resistance increased,the end of PAH.If the children with pulmonary arterial pressure over systemic arterial pressure,arising right to left shunt from the atrium and(or) the blood levels of artery catheter,the persistent pulmonary hypertension for the newborn (PPHN) is developed.HPH for the newborn is common in neonate,which has different characteristics from adults and older children,because its onset is acute,progress qulckly,but prompt treatment can reversed the results.Because its clinical manifestations are not typical,early diagnosis is difficulty.Echocardiography diagnosis of pulmonary hypertension is the most important non-invasive method.At present the mechanism of the HPH is unclear.There are some reports about HPH said that,hypoxia lead to damage of vascular endothelial dysfunction,causing imbalance of vascular shrinkage factor(endothelial-1,ET-1) and diastolic factor(nitric oxide,NO),which rolling in vascular smooth muscle,leading to the occurrence of pulmonary high pressure.However,in the pathogenesis of newborns HPH,the role of ET-1 and NO through the hypoxia inducible factor-1 alpha(HIF-1α) activating of ET-1 and inducible nitric oxide synthase(iNOS) gene is still not clear,no report related to HIF-1α,iNOS,ET-1,NO,and neonatal pulmonary artery pressure.HPH can make right ventricular function involvemem in newborns.Right ventricular dysfunction in the early clinical features is non-performance,which is difficulty in treatment.Echocardiography in the evaluation of cardiac function has been widely used,new detection method can be applied to the right ventricular function studies,which Tei index is considered the overall valuable indicators of evaluation of ventricular function,Tissue Doppler imaging(TDI) technology can be used to determine right ventricular systolic and diastolic function,But there are few relevant reports about right ventricular function in newborns with HPH.Purpose:1.To monitor the changes of pulmonary artery systolic pressure(PASP) in hypoxic neonates by using echocardiography methods,in order to getting early diagnosis of neonatal HPH and PPHN,so giving timely treatment to improve the prognosis.2.To monitor the changes of PASP in newborns with HPH and changes of indicators of blood gas analysis,changes of the serum HIF-1α,ET-1,iNOS,to understand the relationship between the HIF-1α,ET-1,iNOS and HPH neonatal PASP; To detect expression of HIF-1α,ET-1,iNOS's mRNA and protein in lung tissue of HPH neonatal,infer the role of HIF-1αand its target genes in the pathogenesis of neonatal HPH.It provided for reference to further explore new therapies.3.To compare the role in right ventricular ejection fraction(RVEF),tricuspid E / A value,the right ventricle Tei index and tissue Doppler imaging(TDI) related indicators in evaluating early functional changes of the right ventricle of HPH neonatal,this study could found early sensitive indicator of the right ventricular dysfunction of newborn, which provide the basis for guiding the treatment and implementation of early intervention.Methods:Ninety-seven cases of newborns were included in the present study,they were chosen completely at random from June,2006 to July 2008 in the first affiliated hospital of Xinjiang Medical university.75 cases of newborns were hypoxic pulmonary hypertension(HPH) group,while 22 cases of newborns which has other heart and lung disease without symptoms of hypoxia were control group.Group of newborns with HPH will be divided into three subgroups,including mild HPH group of 29 cases (40mmHg≤PASP＜50mmHg),moderate HPH group of 25 cases(50mmHg≤PASP＜70mmHg),severe HPH group of 21 cases(PASP≥70mmHg).1.97 cases of newborns after birth in the first 1,3,7 d which were divided into the HPH three groups and the control group were conducted echocardiography of PASP respectively.While they were determined concentration of HIF-1α,ET-1,iNOS with ELASA and the left-around arterial blood for blood gas analysis.Comparing level of each group of neonatal serum HIF-1α,iNOS,ET-1difference in the three time points, and PASP,blood gas analysis indicators of changes in serum HIF-1α,ET-1,iNOS changes,understand the relevance of HIF-1α,ET-1,iNOS and HPH neonatal PASP and indicators of blood gas analysis.2.By semi-quantitative reverse transcriptase-polymerase chain reaction(RT-PCR) method and western blotting to detect HIF-1α,ET-1,iNOS mRNA and protein expression in the lung tissue,from HPH five cases of neonatal deaths and other reasons (Non-heart and lung diseases) four cases of neonatal deaths(nine cases have been family members agreed),which compared HIF-1α,ET-1,iNOS mRNA and protein expression of the similarities and differences between HPH and non-HPH neonatal lung tissue.3.The same way on these 97 cases of newborns were conducted by echocardiography to detect indicators of right ventricular function in traditional ultrasound,the right ventricle Tei index and TDI relevant indicators,in order to evaluate various value of responding right ventricuiar function.Results:1.PASP of three case groups after 1 day are higher than in the control group,and PaO₂,PaO₂/FiO₂ was negatively correlated.With the improvement of symptoms of hypoxia,PASP decreased.To mild to moderate group with the first 3 day after birth, hypoxia pointer return to normal,PASP resume in No.7 day after birth.To severe group, hypoxia pointer restore to normal in No.7 day after birth,PASP is still higher than normal.2.HIF-1α,ET-1 levels of three case group increased significantly first day after birth,(in addition to levels of iNOS in the mild group),and aggravated with the increased level of PASP.It was a negative correlation with PaO₂,PaO₂/FiO₂,and was positively related PASP.With the improvement of hypoxia and decline of PASP,HIF-1αwas lower in serum levels,which its recovery was synchronization with recovery of hypoxia indicators,quicker than the recovery of PASP.In addition to the mild group,the recovery of PASP and ET-1 level was sync,slower than the serum levels of HIF-1αand the resumption of hypoxia indication.Correlation coefficient of three indicators in the HIF-1α,PASP and hypoxia indication was biggest,relative to HIF-1αand ET-1,change of iNOS level was weaker.3.The mRNAs and protein of HIF-1α,ET-1,iNOS from Lung died of severe HPH patients were clearly expressed.4.With conventional ultrasound method measured,right ventricuiar function of HPH newborn showed that systolic and diastolic function of right ventricuiar reduced after one day,three days,and seven days at severe HPH group.5.Tei index of the right ventricle showed that Tei index in case groups of were higher than the control group,overall function of the right ventricle decreased,PASP and Tei index of right ventricular was positively related,changes was sync,hypoxia symptoms resumed faster,while PASP and function of right ventricular recovered slow.6.TDI technology found that diastolic function of the right ventricle was more involved,and the resumption of slow,even after the restoration of the pulmonary artery pressure;Function changes of systolic and diastolic,lack of oxygen and changes of pulmonary artery pressure is not completely parallel.Conclusion:1.Neonatal HPH is hypoxia-induced pulmonary vascular spasm in the early time, which can resume by treatment timely,but if the pulmonary artery pressure is still high in 7 days after birth(especially in the stage PPHN),is difficulty in treatment. Echocardiography can be used convenient,timely and accurate to diagnosis of neonatal HPH and PPHN.2.HPH was correlated to HIF-1α,ET-1,iNOS level in serum.We can speculate that hypoxia can improve a expression of HIF-1a,causing increase of ET-1 and iNOS, leading to balance disorders in ET-1 and NO,HPH occurred,so it is involved in the pathogenesis of neonatal HPH3.The mRNAs and protein of HIF-1α,ET-1,iNOS from Lung died of severe HPH patients were clearly expressed.So inferred that hypoxia activate HIF-1αexpression in the activation of the transcription level ET and iNOS of gene expression,which participates in pathogenesis of pulmonary hypertension.4.Conventional echocardiography can be found severe HPH newborn with right ventricular dysfunction.Tei index of right ventricle can be sensitive to discovery right ventricular dysfunction in HPH newborn,.The superiority of TDI technology were able to determine right ventricular systolic and diastolic function change than Tei index in its many targets,and the changes of Systolic and diastolic function is not completely parallel with hypoxia and PASP.So illness can not be judged only on the basis of hypoxia symptoms,it is need to use ultrasound to monitor changes about pulmonary artery pressure and function of right ventricular,timely diagnosis and treatment.