Changes Of Protein Kinase Cα,δ And ε Isoforms And Mechanism In The Cardioprotective Effect Of The Late Exercise Preconditioning

Objective: Myocardial ischemia/reperfusion （I/R） injury is an frequentevent in the setting of cardiopathy, and ischemia preconditioning （IP） is oneof the most powerful experimental measurements against I/R so far. Thetreatment of repeated and transient I/R allows myocardium to increase intolerance against the subsequent prolonged I/R injury, which is defined as IP.IP-like effect of cardioprotection induced by exercise is defined as Exercisepreconditioning （EP）. Protein kinase C （PKC） α, δ and ε isoforms are thekey mediators in the signaling pathway of the cardioprotection of EP.However, the exact mechanism by which PKC α, δ and ε mediate thecardioprotection effect is unclear. Given that the early and late biphasicpattern of the cardioprotective effect, the late exercise preconditioning（LEP）is more prospective in the clinical relevance, because its protective windowduration lasts2³days and its protective function is more abundant than theearly exercise preconditioning. This present study investigated theprotective effect of LEP on the myocardium undergoing the exhaustiveexercise and the change in the expression and distribution of PKC α, δ and εduring the cardioprotective effect, and explored the mechanism by whichtheir cross-talk implicates the cardioprotective effect, mostly in the contextof IP.Methods: One hundred and fifty SD rats were randomly assigned to Cgroup, EE group, LEP group, CHE+LEP group, LEP+EE group and CHE+LEP+EE group. The rat model of EP was set up by means of the single boutof intermittent high-intensity treadmill exercise, the rat model of acutemyocardial injury in the manner of exhaustive treadmill exercise, andchelerythrine（CHE） was used to inhibit PKC α, δ and ε. ELISA, CLIA,HBFP staining,Western Blot and IHC were utilized to measure the serumconcentration of NT-proBNP and cTnI, the ischemic and anoxic change ofmyocardium and the expression and distribution of the total andphosphorylated PKC α, δ and ε, respectively. Results:（1） Compared with Group C, the serum concentration ofNT-proBNP and cTnI was significantly increased, and ischemia and anoxiawas serious in Group EE; The serum concentration of NT-proBNP wasmarkedly decreased in group LEP. Compared with Group EE, the serumconcentration of cTnI, myocardial ischemia and anoxia was notablyworsened, and the run-to-exhaustion distance of rats was remarkablyenhanced in Group LEP+EE. Compared with Group LEP+EE, the serumconcentration of NT-proBNP was apparently lowered, myocardial ischemiaand anoxia was dramatically alleviated.（2） Paralleled with Group C, theexpression level of PKCα and p-PKCα^Ser-657significantly rose and p-PKCαSer-657translocated to sarcolemma and nucleus in Group EE; the expressionlevel of PKCα notably increased. Paralleled with Group LEP, the expressionlevel of PKCα and p-PKCα^Ser-657significantly decreased, PKCα didn’tappear on the intercalated discs, and p-PKCα^Ser-657didn’t converge on thesarcolemma in the Group CHE+LEP. Paralleled with Group EE, theexpression level of PKCα and p-PKCα^Ser-657markedly fell, PKCα wasn’tdistributed to the cell contact, and p-PKCα^Ser-657didn’t emerge on thesarcolemma and nucleus in Group LEP+EE. Paralleled with Group LEP+EE,PKCα wasn’t presented on the intercalated disc and p-PKCαSer-65wasshowed on the sarcolemma in Group CHE+LEP+EE.（3） Relative to GroupC, the expression level of PKCδ and p-PKCδ^Thr-507apparently enhanced andp-PKCδ^Thr-507localized in the peri-nucleus in Group EE; the expressionlevel of PKCδ remarkably increased in Group LEP. Relative to Group LEP,the expression level of PKCδ markedly rose in Group CHE+LEP. Relative toGroup EE, the expression level of PKCδ and p-PKCδ^Thr-507dramaticallydecreased and p-PKCδ^Thr-507didn’t emerge on the intercalated disc,sarcolemma and nucleus in Group LEP+EE. Relative to Group LEP+EE, theexpression level of PKCδ and p-PKCδ^Thr-507notably enhanced, and p-PKCδThr-507localized on the intercalated disc and cell contact in GroupCHE+LEP+EE.（4） By contrast with Group C, the expression level of PKCεwas significantly added in Group EE; the expression level of PKCε notablyrose and p-PKCε^Ser-729was distributed on the sarcolemma and cell contactin Group LEP. By contrast with Group LEP, the expression level of PKCεand p-PKCε^Ser-729were markedly reduced in Group CHE+LEP. By contrastwith Group EE, p-PKCε^Ser-729apparently localized on the sarcolemma andcell contact in Group LEP+EE. By contrast with Group LEP+EE, theexpression level of p-PKCε^Ser-729remarkably decreased. Conclusions:（1） EP is of non-injury method of preconditioning, and thetreatment of LEP possesses the cardioprotective effect on the myocardiumundergoing the exhaustive exercise. CHE doesn’t abolish thecardioprotective effect of LEP on the myocardium undergoing theexhaustive exercise, on the contrary, it promotes the cardioprotection tosome extent.（2） It is well comprehensive that Serum concentration ofNT-proBNP and cTnI, myocardium staining and exercise performance areassociatedly utilized in the assessment of protection effect of EP.（3） Thecardioprotective effect of LEP on the myocardium undergoing theexhaustive exercise is linked with the down-regulation of the expressionand activation level and the inhibition of translocation of sarcolemma andnucleus of activated PKCα to some purpose.（4） The cardioprotective effectof LEP on the myocardium undergoing the exhaustive exercise is connectedwith the activation level of PKCδ and the inhibition of translocation ofsarcolemma, nucleus and cell contact of activated PKCδ to a certain degree.（5） The cardioprotective effect of LEP on the myocardium undergoing theexhaustive exercise is implicated in the translocation of sarcolemma andcell contact of activated PKCε to a certain extent.（6） The cardioprotectiveeffect of LEP on the myocardium undergoing the exhaustive exercise is, inpart, involved in the ratio enhancement of activation level of PKCε andPKCδ （7） The mechanism by which LEP protects the myocardiumundergoing the exhaustive exercise is likely to be that the cross-talk ofchange of expression and distribution of PKC α， δ and ε gives birth to thecomprehensively biological effect.（8） CHE affects the expression anddistribution of PKC α， δ and ε, but it may be independent of PKC that CHEis implicated in the protective effect of LEP on the myocardium undergoingthe exhaustive exercise.