Study On The Anti-Atherosclerotic Effect And Blood Lipid-Lowering Mechanism Of Levofloxacin

Background and objective:Atherosclerosis（AS）is a chronic inflammatory disease and the main cause of many cardiovascular diseases.Levofloxacin is a synthetic broad-spectrum antibacterial agent that is widely used in clinical treatment of many diseases.In previous research,we discovered by chance that levofloxacin could reduce blood lipid levels in Apo E knockout(Apo E^-/-)mice fed with high-fat diet,and delay the initiation and progression of atherosclerosis.We speculated that levofloxacin could have anti-atherosclerotic effect by reducing the level of blood lipids.Therefore,the purpose of this study is to reveal the anti-atherosclerotic effect of levofloxacin and the underlying mechanism of reducing blood lipids.There is currently no research report on the anti-atherosclerotic effect of levofloxacin.Methods:The anti-atherosclerotic effect,toxicity and side effects of levofloxacin,and the mechanism of reducing blood lipids were explored mainly through animal experiments.（1）Animal grouping,feeding and administration:Apo E^-/-C57BL/6 mice were selected and randomly divided into five groups:control group（Control）,model group（Model）,low-dose levofloxacin group（Low）,middle-dose levofloxacin group（Middle）,and high-dose levofloxacin group（High）.The mice in the control group were fed with a normal diet while the mice in other four groups were fed with a high-fat diet;The mice in low-dose,middle-dose,and high-dose levofloxacin groups were intravenously injected with 20 mg/kg/2d,60 mg/kg/2d,and 120 mg/kg/2d of levofloxacin,respectively during modeling.（2）Detection of anti-atherosclerotic effect:After 14 weeks of modeling,we analyzed the level of blood lipids and the accumulation of lipid plaque in aortic arch,whole length of the aorta,and aortic root,respectively.Moreover,an in vitro cell experiment of intracellular lipid deposition was conducted.（3）Detection of toxicity and side effects:The kits were used to detect three liver function indicators,namely,aspartate aminotransferase（AST）,alanine aminotransferase（ALT）,and lactate dehydrogenase（LDH）,histochemistry and H&E staining were performed on varuous tissues including the liver,spleen,kidney,lung and others.（4）Investigation on the mechanism of lowering blood lipids:The content of pro-protein converting enzyme subtilisin/kexin type 9（PCSK9）in blood,total cholesterol（TC）and triglyceride（TG）in the liver were measured,the m RNA/protein expression levels of multiple key molecules related to lipid metabolism in the liver were also detected by RT-q PCR and Western Blot.Results:（1）Compared with the control group,the levels of blood lipids and atherosclerotic plaque in the model group were significantly increased,proving that the mose model of atherosclerosis was established successfully.（2）Compared with the model group,low,middle and high doses of levofloxacin significantly reduced the levels of TC,TG,and low-density lipoprotein-cholesterol（LDL-C）in blood of mice,as well as atherosclerotic plaques in aortic arch,total length of aorta,and aortic root of mice.In addition,the data from in vitro cell experiments confirmed that levofloxacin could inhibit lipid accumulation in Raw264.7 cells activated by oxidized low density lipoprotein and in Hep G2 cells induced by oleic acid.These data together proved that levofloxacin is able to inhibit the process of atherosclerosis and has a potential anti-atherosclerotic effect.（3）Low,middle,and high doses of levofloxacin significantly increased the contents of AST,ALT,and LDH in blood of mice,and a high dose of levofloxacin caused morphological changes in the liver and spleen,suggesting that levofloxacin has potential toxicity and side effects to a certain degree.（4）Compared with model group,low-,middle-,and high-dose levofloxacin treatments decreased the levels of PCSK9 in blood and TG in liver,and significantly increased the m RNA expressions of LDL receptor（LDLR）,LDLR-related protein 1（LRP1）,and Scavenger receptor class B type I（SR-BI）,indicating that levofloxacin can promote the uptake and clearance of plasma lipoproteins by the liver.（5）Levofloxacin significantly up-regulated the m RNA expression of ATP binding cassette transporter A1（ABCA1）,ATP binding cassette transporter G5（ABCG5）,ATP binding cassette transporter G8（ABCG8）,and cholesterol 7α-hydroxylase（CYP7A1）,as well as the protein expression of ABCG5.The results show that levofloxacin can increase the excretion and catabolism of cholesterol in the liver.Conclusion and significance:Levofloxacin can reduce blood lipids by inhibiting the accumulation of TG in the liver,promoting the uptake of plasma lipoproteins,and increasing the excretion and catabolism of cholesterol in the liver,finally delaying the initiation and progression of atherosclerosis although the side effects of levofloxacin need to be overcome.This study provides a new therapeutic strategy for the treatment of atherosclerosis,and further expands the application of levofloxacin and even other quinolones in biomedicine.