| Objective: Hypertension(HTN)is an independent risk factor of atrial fibrillation(AF).Hydrostatic pressure refers to the lateral pressure of blood flow on a unit area of blood vessels.When hypertension occurs,the mechanical stress in the atrium including hydrostatic pressure increases,and atrial diastolic and systolic dysfunction,which further leads to atrial remodeling and AF.Our previous studies had found that high hydrostatic pressure could participate in myocardial fibrosis by activating the Smad signaling pathway.Previous studies had shown that transcriptional co-activator p300 was involved in TGF-β1-induced fibrosis,while p300 could participate in the regulation of p53.While,some studies had found that the p53/Smad3 pathway was involved in the increased expression of plasminogen activator type-1(PAI-1)induced by TGF-β1 to promote fibrosis.This study intends to investigate whether high hydrostatic pressure is involved in atrial fibrosis through the p300/p53/Smad3 pathway.Methods:(1)Collecting left atrial appendage tissues of 3 groups of patients with sinus rhythm(SR),simple AF,hypertension combined AF and collecting the heart color Doppler ultrasound data of the 3 groups of patients.The paraffin sections of 3 groups of patients were processed by HE and Masson staining to observe the structure and fibrosis degree of left atrial appendage tissue of each group.(2)Use Western blot to detect p300,p53,Smad3/p-Smad3 and fibrosis-related factors collage typeⅠα1 chain(Col-1A1),collage type Ⅲ α1 chain(Col-3A1),matrix metalloproteinase 2(MMP-2),matrix metalloproteinase 9(MMP-9)and TGF-βexpression in the tissues of patients and primary cultured atrial appendage fibroblasts with different treatments.(3)Alpha-smooth muscle actin(α-SMA),a marker of cardiac fibroblasts,was detected by immunofluorescence to identify the fibroblasts.(4)The CCK-8 method was used to detect the changes in the proliferation ability of atrial appendage fibroblasts with different treatments.Results:(1)In the human left atrial appendage tissue,HE and Masson staining showed that the AF group and HTN combined with AF group had more fibrous connective tissue and disordered tissue arrangement.(2)In the human left atrial appendage tissue,the expression of p300,p53 and Smad3 in the HTN combined with AF group was significantly higher than that in patients with AF alone and SR(P < 0.01),and the expression of p300,p53 and Smad3 in AF patients was significantly higher than that in patients with SR(P < 0.01);At the same time,the expression of fibrosis-related protein in the HTN combined with AF group was higher than that in patients with AF alone and SR(P < 0.05),and the expression of fibrosis-related protein in AF patients was significantly higher than that in SR patients(P < 0.05).(3)40mm Hg high hydrostatic pressure could promote the expression of p300,p53 and Smad3/ pSmad3 in mouse atrial appendage fibroblasts.(P < 0.05).At the same time,40 mm Hg high hydrostatic pressure stimulation could also promote the expression of Col-1A1,MMP-2/9 and TGF-β in atrial fibroblasts(P < 0.05).(4)High concentration(10 μmol/L)curcumin could significantly reverse the increase in the expression of p300,p53,Smad3 and fibrosis-related indicators in mouse atrial appendage fibroblasts induced by high hydrostatic pressure(P < 0.05).(5)After adding p300 siRNA to mouse atrial appendage fibroblasts,the increase in the expression of p300,p53,Smad3 and fibrosis indicators caused by high hydrostatic pressure was reversed(P < 0.05).(6)After p53 siRNA was added to mouse atrial appendage fibroblasts,the increase in Smad3 and fibrosis index expression caused by high hydrostatic pressure was reversed(P < 0.05).(7)Compared with 0 mm Hg,culture under hydrostatic pressure of 20 mm Hg and 40 mm Hg can promote the proliferation of fibroblasts(P < 0.01).After adding p300 inhibitor curcumin,the proliferation ability of fibroblasts is inhibited(P < 0.01).Conclusion: This study preliminarily verified that high hydrostatic pressure can participate in atrial fibrosis through the p300/p53/Smad3 pathway.In human left atrial tissue,the expression of fibrosis-related proteins such as p300/p53 and Smad3 in patients with HTN combined with AF is up-regulated.In mouse atrial appendage fibroblasts,high hydrostatic pressure can increase the expression of transcriptional co-activator p300 and up-regulate the expression of p53,thereby further promoting the expression of downstream Smad3 and related fibrotic factors,and further causing atrial fibrosis and AF.At the same time,it has been verified that curcumin and other p300 HAT inhibitors can reverse atrial fibrosis caused by high hydrostatic pressure through the p300/p53/Smad3 pathway,which may reduce the incidence of AF and improve the prognosis of AF,providing new therapeutic targets for the prevention and treatment of AF. |
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