Investigation On The Effect Of Losartan On Occurrence And Development Of Aortic Dissection And Its Mechanisms

Part I: Retrospective analysis of the prognostic effect of ARB on non-Marfan aortic dissectionObjective: To assess the prognostic effect of ARB use on patients with non-Marfan's aortic dissection.Methods: Patients with Debakey type ?,Standford A aortic dissection were consecutively recruited to Guangdong Provincial People's Hospital and Jieyang People's Hospital between January 2010 and January 2015.The inclusion criteria were: patients with proximal laceration hematoma on the proximal breach of the first dissection,patients who underwent elective arotic surgery or unsurgery within 1 year for various reasons.Exclusion criteria: patients with Marfan's syndrome,patients with ACEI use during the onset of AD.According to ARB use or not during the onset of AD,eligible subjects were divided into two groups,the ARB group and the non-ARB group(control group).The follow-up was performed based on database,as well as by telephone.The follow-up data includes patient's symptoms and chief complaints,blood pressure,heart rate,and aortic CTA data.Endpoints and in-hospital events were recorded.Results: There was no significant differences in baseline data,including age,gender,heart rate,smoking status,and the incidence of diabetes.There were no deaths and urgent surgical cases in both groups during the follow-up period.The aortic-CTA follow-up demonstrated the absorption of the dissection of the proximal inverse avulsed hematoma,wheras the reduction was significantly larger in the ARB group as compared with the non-ARB group [(9.34 ± 3.69)mm vs(4.60±1.98)mm,increased by P<0.001],suggesting that hematoma absorption was more remarkable in the ARB group.The maximum vascular diameter at the dissection in both groups expanded during the follow-up,wheras the aortic expansion in the ARB group decreased by approximately 57% relative to the non-ARB group [(1.02 ± 1.18)mm vs(2.36 ± 1.19)mm,P<0.001],indicating a delayed aortic dilation in the ARB group by comparison to the non-ARB group.Conclusions: Independently of BP reduction,ARB use in patients with non-Marfan's aortic dissection may facilitate the absorption of reverse-tear hematoma at the proximal end of the dissection,as well as delay the aortic dilation.Part II: Prospective analysis of the prognostic effect of Losartan on aortic dissection in non-Marfan's syndromeObjectives: Prospective analysis of the prognostic effect of Losartan on patients with non-Marfan's aortic dissection.Methods: Patients with Debakey type III aortic dissection and reverse tear hematoma,wheras without insufficient rivet area for TEVAR were consecutively recruited from Guangdong Provincial People's Hospital and Jieyang People's Hospital from January 2015 to December 2017.Eligible subjects were randomly assigned into Losartan group(could not use neither ACEI and nor ARB antihypertensive drugs except losartan)and control group(neither ACEI nor ARB antihypertensive drugs could not be used).Follow-up included clinical events and a comparison of aortic CTA and surgical methods at 3 months.Results: There were no significant discrepancies between the two groups in age,gender,smoking rate,history of diabetes,systolic blood pressure at admission and at the last follow-up;there was no significant difference between the distance from the proximal end of the hematoma to the breach and the maximum vessel diameter at the dissection;There were no deaths or emergency surgery cases in the group.At the last follow-up,compared with the control group,the distance from the proximal end to the breach was reduced by approximately 33% [(14.71 + 4.47)mm vs(21.7 + 4.90)mm,P < 0.001];the maximum vessel diameter at the dissection was reduced by approximately 8% [(38.48 + 4.27)mm vs(41.94 + 4.83)mm,P= 0.004].Futhermore,90.3% of the patients in the Losartan group who could be downgraded to undergo TEVAR surgery after conservative treatment were significantly higher than the control group(66.7%).Conclusions: For patients with aortic dissection caused by nonMarfan's syndrome.Losartan can promote the absorption of the reversetear hematoma and slow the expansion independently of BP reduction.Part III: The investigation into the effect of losartan on the development of aortic dissection in SD ratsObjectives:To investigate the effects of losartan on the progression of AD in SD rats.Methods: SD mice were induced by either AEEA(hydroxyethyldiamine,150mg/kg/d)or isovolumic saline.The AEEA-induced SD mice were divided,according to the antihypertensive drug intervention,into losartan intervention group(AEEA induction +Losartan 20 mg / kg / d gavage),Amlodipine intervention group(AEEA induction + amlodipine group 6.5mg / kg / d gavage)and saline control group(AEEA induction + isovolumic saline gavage)group.All SD mice,were therefore divided into 4 groups with 12 mice in each group.After 4 weeks,the tail blood pressure,aortic diameter,and number of dissection findings were measured in the above 4 groups.Western-blot was used to detect the expression of TGF-?1,Smad2,Smad3,Smad4.Results: The tail blood pressure data suggests that there was no significant difference in blood pressure between Losartan intervention group and Amlodipine intervention group [(118 ± 7.4)mmHg vs(120.10 ± 16.2)mmHg,P = 0.81].Ultrasound data indicates a significant reduction in aortic dilation,including the ascending aorta,aortic arch,and descending aorta,of the losartan intervention group relative to the Amlodipine intervention group [(2.83 ± 0.20)mm vs(3.28 ± 0.23)mm,reduction by approximately 14%;(2.52 ± 0.30)mm vs(3.27 ± 0.25)mm,reduction by approximately 23%;(2.94 ± 0.28)mm vs(3.46 ± 0.29)mm,reduction by approximately 15%,respectively;all P<0.001].HE staining for aortic tissue demonstrated that under the setting of AEEA induction,the incidence of dissection in the Losartan intervention group was significantly reduced by 28% and 19%,respectively,as compared with the saline group and the amlodipine group,(all P<0.01).In addition,compared with the normal saline induced group,AEEA induction significantly increased the expression of miR-145 in aortic tissues by 2.5 fold(P<0.05),and losartan intervention decreased the expression of miR-145 in aortic tissues of AEEA induced SD rats by approximately(P<0.05).Losartan intervention significantly reduced the expression of TGF-?1,Smad2,Smad3,Smad4 protein by 25%,25%,15%,respectively;while upregulated p-Akt expression on protein level in aortic tissues of AEEA-induced mice by approximately 50%(all P< 0.05).Conclusions: Independently of lowering BP,losartan,as an ARB,can prevent AD progression by inhibiting TGF-? signaling pathway and by promoting PI3K/Akt kinase pathway,as well as via downregulating miR-145 expression.Part IV: The ectopic expression and involvement of miR145 in the pathogenesis of aortic dissection through modulating apoptosis ?proliferation and migration of VSMCs.Background: To investigate whether miR-145 was involved in the pathogenesis of thoracic aortic dissection(AD)via regulating the apoptosis,proliferation and migration of the VSMCs(vascular smooth muscle cells).Methods: qPCR detected miR-145 levels in dissection patients and healthy controls respectively.Dissection aortic tissue was obtained from 6 patients undergoing ascending aortic replacement with Stanford Type A aortic dissection,and normal control aortic specimens were obtained from 4 normal organ donors.The distribution and expression of miR-145 in aortic tissue were detected by FISH and qPCR.The SMAD3 expression were detected at the mRNA and protein levels by qPCR and Western-blot,respectively.Subsequently,VSMCs were transfected with miR-145 mimics or inhibitors in vitro.MTT assay was used to detect proliferation,Transwell assay was used to detect migration,and flow cytometry was used to detect apoptosis.At the mRNA and the protein levels,the exprepression of SMAD3 in VSMCs were tested by qPCR and Western-blot,respectively.Results: Plasma level and aorta specimen level of miR-145 were both markedly increased in AD group as compared with control group(P< 0.05).miR-145 mainly located in VSMCs.Under the stimulation of angiotensin II,miR-145 mimics significantly induced VSMC proliferation,migration,wheras miR-145 inhibitors remarkably suppressed VSMC proliferation,migration as well as apoptosis in vitro.The luciferase reporter assay confirmed that SMAD3,is a potential target gene of miR-145 and further.The expression of SMAD3 was modulated by miR-145.Conclusions: miR-145 is definitely upregulated in the settings of AD.miR-145 induced VSMC proliferation,migration and apoptosis through targeting SMAD3,and hence might be potentially implicated in the development of AD.