The Study Of KLF4 Protects Against Liver By Inhibiting Apelin In Acute Liver Injury

BackgroundAcute liver injury refers to some disorders of liver function,which can be caused by some factors,including viral infection,hepatotoxic drugs,toxic chemicals and hepatic ischemia-reperfusion.Its pathogenesis is complex,including oxidative stress,hepatocyte apoptosis and necrosis,which is seen as the starting factor and common path to many liver diseases.If there is no timely medical treatment,acute liver injury can develop liver fibrosis,liver cirrhosis and even liver cancer.These diseases may have an adverse impact on the humans’health.There are many factors which can cause damage to liver include in hepatitis virus,abused drugs and chemical toxins.For mild and moderate liver injury,liver cells can occur regeneration,necrosis and apoptisis.These processes are linked to liver inflammation.Krüppel-like factor 4（KLF4）is a transcription factor with a zinc finger structure and this zinc finger which located in carboxyl-terminal characteristic zinc finger structure can bind to the CACCC element which rich in GC of the DNA,so as to regulate transcription activation or inhibition.Another the amino terminal of KLF4 is highly dispersed,which can bind to different activation factors.This characteristic may lead to functional of KLF4.The basically biological function of KLF4 which plays an important role in cell cycle regulation,cell proliferation,differentiation,apoptosis,inflammation and other physiological or pathological processes.Studies have shown that the overexpression of KLF4 could be regarded as an inhibitory factor.Overexpression of KLF4 can inhibit the developing of liver fibrosis/cirrhosis.KLF4 can also inhibit the activation of fibroblasts through varieties of ways,thereby inhibiting the development of fibrosis and tumors.Apelin is an importantly bioactive peptide,which is an endogenous ligand of G protein-coupled receptor APJ.It can activate the APJ receptor through autocrine and paracrine,and the combination of apelin and APJ plays the pathological and physiological function.Apelin plays an important role in the physiology,pathophysiology,inflammation and angiogenesis of many organs,but its role in acute liver disease is unclear.Studies have found that the expression of apelin in the liver mainly occured in activated hepatic stellate cells.Apelin can stimulate inflammation and fibrosis,indicating that the activation of apelin can be associated with liver injury.The study of KLF4 and apelin in acute liver injury has not been reported so far.Our experimental datas showed that the expression of KLF4 reduced in acute liver injury,while the expression of apelin increased dramantically,so we thought that KLF4 and apelin may have an association in acute liver injury.ObjectivesThe aim was to investigate the interaction and effect of KLF4 and apelin in acute liver injury,and to verify KLF4 can protect against liver by inhibiting apelin.MethodsThe animal model was constructed with the strain of C57BL/6,the age of 6-8 weeks and the weight of about 25g wild male mice.Model I:The male wild mice were randomly divided into two groups:the control group and the CCl₄-treated group.The CCl₄-treated group received an intraperitoneal injection of a mixture of 0.2%carbon tetrachloride（CCl₄,0.2%）and oil（99.8%）at a dose of 10ml/kg body weight.The control group received an intraperitoneal injection of the same volume of oil.The mice were scarified at 24h after the CCl₄ injection.Blood was collected to detect the activity of ALT/AST in mice serum.The mice were perfused with 4℃pre-cooled PBS by left ventricle,and then the liver was taken out.Part of the liver tissue was carried out HE staining after a series of treatments to observe the degree of liver injury in mice from the morphological aspects.Immunohistochemistry was used to detect the expression of KLF4 and apelin in the mice liver.Another part of the liver tissue was used to extract total mRNA and total protein by ultrasonic crushing to detect the changes of KLF4 and apelin from the aspects of mRNA and protein in acute liver injury.Model II:The male wild mice were randomly divided into four groups:GFP group,KLF4 group,GFP+CCl₄ group,KLF4+CCl₄ group.The first day,the GFP plasmids（0.5mg/kg+1.2ml NaCl）and KLF4plasmids（0.5mg/kg+1.2ml Nacl）were injected into the tail vein,according to the groups requirements.The same time on the third day injected the corresponding plasmids（0.5mg/kg+1.2ml Nacl）once according to the first day of the method and dose;the fourth day,the last two groups received an intraperitoneal injection of a mixture of 0.2%carbon tetrachloride（CCl₄,0.2%）and oil（99.8%）at a dose of10ml/kg body weight.The first two groups received an intraperitoneal injection of the same volume of oil.The mice were scarified at 24 h after the CCl₄ injection.The following steps were the same as Model I.Results1 After treatment with CCl₄,the results of HE staining and serum ALT/AST show that the livers of mice have undergone acute injury.2 Comparing with the control groups,the expression of KLF4 in CCl₄-induced group declines while the expression of apelin increases.3 The results of HE staining and ALT/AST show that the liver damaging situation in KLF4+CCl₄group was significantly worse than those of in GFP+CCl₄ group.4.The expression of KLF4 in KLF4+CCl₄ group is significantly higher than those of in GFP+CCl₄ group,while the expression apelin is opposite.Conclusions1 In acute liver injury,the expression of apelin is significantly up-regulated,the expression of KLF4 is significantly decreased,apelin and KLF4 are closely related to liver injury.2 In acute liver injury,KLF4 can protect the liver by inhibiting the expression of apelin and prevent the developing of acute liver injury,suggesting that KLF4 has a potential role in the treatment of acute liver injury.