Inhibition Of PI3K-γ Attenuates LPS Induced Sepsis Related Cardiac Dysfunction In Mice

ObjectiveTo explore the effect of phosphatidylinositol3-kinase-γ(PI3K-γ) uponLPS induced myocardial damage and cardiac dysfunction.Methods100male C57bl/6mice were randomly divided into five groups:control group,LPS group,selective inhibitor for PI3K-γ(AS605240group),selective inhibitor for PI3K(LY294002group),diethylsulfoxide(DMSO group)(n=20/group).To induceendotoxemia,mice were injected intraperitoneally with10mg/kgLipopolysaccharides(LPS) or PBS alone for control group. Mice werepretreated with a selective PI3Kγ inhibitor AS605240(10mg/kg,intraperitoneally) or selective PI3K inhibitor LY294002(10mg/kg,intraperitoneally) in0.05%DMSO diluted with phosphate bufferedsaline (DMSO/PBS) or an equal volume of DMSO/PBS1h prior to LPSadministration. All mice were evaluated at6,12,24hour after LPSadministration, Cardiac function was examined by echocardiography, theserum for TNF-α,IL-6,cTnI,H-FABP was detected by ELISA,histopathological examination was observed by HE stain, RT-PCR wasused to detect the expression of akt,PI3Kγ,NF-Κb,IL-6,TNF-α mRNA andWestern Blot to detect the expression of akt,p-akt,PI3Kγ protein.Results(1) The general situation Con group was the same as the normal mice. LPS group began toexhibit a series of character at6h after LPS administration,includingreduced activity, depressed, anorexia, increased eye purulent secretions,erected and dull hair and so on,while at24h were more severe. Thesymptoms of LPS+AS605240group was better than LPS group. Thesymptoms of LPS+LY294002group was worse than LPS group,and therewas no significant difference between LPS+DMSO group and LPS group.(2) Pathological changesOptical microscope: There were no significant pathological changes inmyocardial tissue in Con group. It was clear that the LPS group showedmyocardial congestion and edema, inflammatory cell infiltration, focalmyocardial fiber breakage; LPS+AS605240group showed that the abovechanges were obviously lighter. There were no significant differenceamong LPS+LY294002group，LPS+DMSO group and LPS group.Transmission electron microscope: The myocardial tissue of Congroup showed a large number of rows of mitochondria, and themitochondrial cristae was smooth and complete. The myocardial tissue ofLPS group showed mitochondrial disorder and increased,part ofmitochondria cristae broken, dissolved, myocardial nucleus swelling and,the gap widened,myocardial interstitial mononuclear cell infiltration. Thesechanges can be seen locally in LPS+AS605240group, but lighter. Therewere no significant difference among LPS+LY294002group，LPS+DMSOgroup and LPS group.(3)Cardiac echocardiographyCardiac function was examined at24h after LPS challenge,there wasno obvious abnormalities in Con group. LPS group showed decreasedcardiac function compared with Con group,and LPS+AS605240group showed improved cardiac function compared with LPS group. There wereno significant difference among LPS+LY294002group，LPS+DMSO groupand LPS group.(4) Protein expression changePhosphorylation of Akt in the heart tissues of LPS-treated mice was greatlydecreased as compared to that in control mice（P<0.05）, LPS+AS605240group showed increased p-akt compared to LPS group （P<0.05）,therewere no significant difference between LPS+DMSO group and LPS group（P>0.05）.However,the level of Akt protein was not changed in any of thegroups tested. The expression of PI3Kγin LPS group was significantlyincreased （P<0.05）,pretreated with AS605240could release the change（P<0.05）, There were no significant difference among LPS+LY294002group,LPS+DMSO group and LPS group（P>0.05）.(5) Changes of cardiac biomarkers cTnI、HFABPThe level of cTnI,H-FABP increased after the administration of LPS ascompared to those levels in control mice, and at12h to reach the peak(P<0.05).The LPS induced increase in cTnI,H-FABP levels wassignificantly reduced by administration of AS605240(P<0.05).There wereno significant difference among LPS+LY294002group,LPS+DMSO groupand LPS group（P>0.05）.(6) Changes of inflammatory CytokinesThe level of TNF-α, IL-6increased after the administration of LPS ascompared to those levels in control mice, and at12h to reach the peak(P<0.05).The LPS induced increase in cTnI,H-FABP levels wassignificantly reduced by administration of AS605240(P<0.05).There were no significant difference among LPS+LY294002group,LPS+DMSO groupand LPS group（P>0.05）.ConclusionInhibition the expression of PI3Kγ could effectively reducemyocardial damage and improve cardiac function in SIMD, PI3Kγ could beseen as a new marker of myocardial injury as well as potential targets fortherapy, with extensive research prospects.