SERCA overexpression reduces hydroxyl radical injury in murine myocardium.
Hydroxyl radicals (*OH) are involved in the pathogenesis of ischemia-reperfusion injury and are observed in clinical situations, including acute heart failure, stroke, and myocardial infarction. Acute transient exposure to *OH causes an intracellular Ca(2+) overload and leads to impaired contractility. We investigated whether upregulation of sarcoplasmic reticulum Ca(2+)-ATPase function (SERCA) can attenuate *OH-induced dysfunction. Small, contracting right ventricular papillary muscles from wild-type (WT) SERCA1a-overexpressing (transgenic, TG) and SERCA2a heterogeneous knockout (HET) mice were directly exposed to *OH. This brief 2-min exposure led to a transient elevation of diastolic force (F(dia)) and depression of developed force (F(dev)). In WT mice, F(dia) increased to 485 +/- 49% and F(dev) decreased to 11 +/- 3%. In sharp contrast, in TG mice F(dia) increased only to 241 +/- 17%, whereas F(dev) decreased only to 51 +/- 5% (P < 0.05 vs. WT). In HET mice, F(dia) rose more than WT (to 597 +/- 20%, P < 0.05), whereas F(dev) was reduced in a similar amount. After approximately 45 min after *OH exposure, a new steady state was reached: F(dev) returned to 37 +/- 6% and 32 +/- 6%, whereas F(dia) came back to 238 +/- 28% and 292 +/- 17% in WT and HET mice, respectively. In contrast, the sustained dysfunction was significantly less in TG mice: F(dia) and F(dev) returned to 144 +/- 20% and 67 +/- 6%, respectively. Before exposure to *OH, there is decrease in phospholamban (PLB) phosphorylation at Ser16 (pPLBSer16) and PLB phosphorylation at Thr17 (pPLBThr17) in TG mice and an increase in pPLBSer16 and pPLBThr17 in HET mice versus WT. After exposure to *OH there is decrease in pPLBSer16 in WT, TG, and HET mice but no significant change in the level of pPLBThr17 in any group. The results indicate that SERCA overexpression can reduce the *OH-induced contractile dysfunction in murine myocardium, whereas a reduced SR Ca(2+)-ATPase activity aggravates this injury. Loss of pPLB levels at Ser16 likely amplifies the differences observed in injury response.
Hiranandani
Nitisha
N
Dept. of Physiology and Cell Biology, The Ohio State University, Columbus, OH 43210-1218, USA.
Bupha-Intr
Tepmanas
T
Janssen
Paul M L
PM
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D017665:Hydroxyl Radical / Q000009:adverse effects / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D009200:Myocardial Contraction / Q000502:physiology; D015428:Myocardial Reperfusion Injury / Q000209:etiology / Q000378:metabolism* / Q000517:prevention & control; D009206:Myocardium / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D018384:Oxidative Stress / Q000502:physiology; D010766:Phosphorylation; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation; D000099211:Phospholamban
D002118:Calcium; D002135:Calcium-Binding Proteins; D017665:Hydroxyl Radical; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000099211:Phospholamban; C506944:Atp2a1 protein, mouse