Effect Of Heme Oxygenase-1(HO-1) On Regulation Of Mitochondrial Fusion And Fission In LPS-induced Acute Lung Injury In Rats

Objective Acute lung injury(ALI) is a common disease induced by many factors including infection,trauma,shock et.ag.ALI is a typical appearance in lung for acute respiratory distress syndrome(ARDS) and multiple organ dysfunction syndrome(MODS).ALI can lead to acute hypoxemic respiratory failure. Among these,neutrophil infiltration is an important manifestation of acute lung injury, which can generate a large number of oxygen free radicals, and oxidative stress induced by oxygen free radicals is the important cause for acute lung injury.Studies have shown that HO-1 catalyzes the heme to bilirubin,CO and iron,which is the first and rate-limiting step in the process.Meanwhile,HO-1 has a protective effect of tissues and organs,and it is an important component of endogenous antioxidant stress system in the body. Mitochondria are highly dynamic organelles in mammals, which are the main place to produce oxygen free radicals, and play an important role in the biological activity of cells,this process is based on the ability of mitochondria to undergo frequent fusion and fission. Mitochondria fusion are regulated by Mfn1,Mfn2 and OPA1.The fission of mitochondria is mainly regulated by Drp1 and another molecule Fis1,which relies on Drp1 during fission. However, whether HO-1’s endogenous protection on endotoxin acute lung injury through the regulation of mitochondrial dynamics,there are no reports at home and abroad.We established the model of ALI in rats induced by intravenous lipopolysaccharide(LPS) via the tail vein,then carotid artery bled to death animals after 6h,collecting lung tissues to observe the changes of malondialdehyde(MDA) content,superoxide dismutase(SOD) activity and pathological results in lung tissues.Real-time fluorescent quantitative reverse transcription PCR(RT-PCR) and Western blot were used to determine m RNAs and proteins expression changes of HO-1,mitochondrial fission related proteins Drp1,Fis1 as well as mitochondrial fusion related proteins Mfn1,Mfn2 and OPA1.Methods One hundred healthy male Sprague-Dawley rats weighing 160-180 g were randomly divided into ten groups(n=10): control group,LPS group, LPS+Hemin group,LPS+Zn PP-IX group,LPS+Hemin+Zn PP-IX group,Hemin group,Zn PP-IX group,Hemin+ Zn PP-IX group,LPS+ Na HCO3 group and LPS+Na OH group.Drugs were injected via tail vein, group C received 0.9% saline vehicle 1ml.Group L,group LH,group LZ,group LHZ,group LNa HCO3 and group LNa OH received LPS 5mg/kg dissolved in 1ml saline to copy acute lung injury models in rats. Group LH,group LZ and group LHZ received 100 mg/kg Hemin dissolved by Na OH in 1ml or(and) Zn PP-IX dissolved by Na HCO3 in 1ml after establishing the model successfully.The animals were sacrificed 6h by carotid artery bleeding after intravenous LPS or 0.9% saline vehicle.The lungs were immediately removed for measuring the changes of malondialdehyde(MDA) content,superoxide dismutase(SOD) activity and pathological results,then detected m RNAs and proteins expression of HO-1,mitochondrial fission related proteins Drp1、Fis1 and mitochondrial fusion related proteins Mfn1,Mfn2,OPA1 in lung tissue used RT-PCR and Western blot analysis..Results Compared with group C, group L,group LHZ,group LNa HCO3 and group LNa OH showed MDA content increased(P < 0.05), SOD activity decreased significantly(P < 0.05), the pathological results showed obviously lung tissues damage, RT-PCR and western blot results showed that m RNAs and proteins expression of Drp1,Fis1 increased in rats lungs(P < 0.05), Mfn1,Mfn2 and OPA1 reduced(P < 0.05). Compared with group L, MDA content in lung tissues reduced(P < 0.05) while SOD activity increased(P < 0.05) in group LH, the pathological results showed a relieved lung tissue damage, RT-PCR and western blot results showed that m RNAs and proteins expression of mitochondrial fission related proteins Drp1,Fis1 decreased(P < 0.05), mitochondria fusion related proteins Mfn1,Mfn2 and OPA1 increased(P < 0.05).In addition,compared with the group L,lung tissues of group LZ indicated an increased MDA content(P < 0.05) and a decreased SOD activity(P < 0.05), the pathological results showed an aggravated lung tissues damage,RT-PCR and western blot results showed that m RNAs and proteins expression of mitochondrial fission related proteins Drp1,Fis1 increased(P < 0.05), mitochondria fusion related proteins Mfn1,Mfn2 and OPA1 reduced(P < 0.05)Conclusion Expression of mitochondrial fusion related proteins reduced while mitochondrial fission related proteins increased in acute lung injury in rats; Increased expression of HO-1 contributed to a up-regulated mitochondrial fusion proteins expression and a down-regulated mitochondrial fission proteins expression,HO-1’s endogenous organ protection might be associated with mediated change of mitochondria fusion – fission expression.