Chunyan Wang1,2, Haobo Li1,3, Sheng Wang4, Xiaowen Mao1, Dan Yan1, Stanley S Wong1, Zhengyuan Xia1,3, Michael G Irwin1. 1. Department of Anesthesiology, The University of Hong Kong, Hong Kong, China. 2. Department of Anesthesiology, Shenzhen People's Hospital and Shenzhen Anesthesiology Engineering Center, the Second Clinical Medical College of Jinan University, Shenzhen, China. 3. State Key Laboratory of Pharmaceutical Biotechnology, The University of Hong Kong, Hong Kong, China. 4. Department of Anesthesiology, Guangdong Cardiovascular Institute, Guangdong General Hospital, Guangdong Academy of Medical Sciences, Guangdong, China.
Abstract
BACKGROUND/AIMS: Protein kinase C(PKC)-ε activation is a mechanism of preconditioning cardioprotection but its role in repeated non-invasive limb ischemic preconditioning (rNLIP) mediated cardioprotection against myocardial ischemia/reperfusion (I/R) injury in diabetes is unknown. METHODS: Eight-week streptozotocin-induced diabetic and non-diabetic Sprague-Dawley rats were subjected to I/R without or with rNLIP. In vitro, H9C2 cells were cultured with high glucose (HG) and subjected to hypoxia/re-oxygenation (H/R) without or with PKC-ε or STAT3 gene knock-down in the absence or presence of remote time hypoxia preconditioning (HPC). RESULTS: Diabetic rats displayed larger post-ischemic myocardial infarct size and higher troponin-I release with concomitant cardiac PKC-ԑ overexpression and activation manifested as increased membrane translocation, while phosphorylated STAT3 (p-STAT3) and Akt (p-Akt) were lower compared to non-diabetic rats (all P<0.05). rNLIP reduced infarct size in both non-diabetic and diabetic rats. rNLIP reduced post-ischemic cardiac PKC-ԑ activation in diabetic while increased PKC-ԑ activation in non-diabetic rats, resulting in increased cardiac p-STAT3 and p-Akt. In H9C2 cells, HG increased PKC-ԑ expression and exacerbated post-H/R injury, accompanied with reduced p-STAT3 and p-Akt, which were all reverted by HPC. These HPC protective effects were abolished by either PKC-ԑ or STAT3 gene knock-down, except that PKC-ԑ gene knock-down reverted HG and H/R-induced reduction of p-STAT3. CONCLUSION: rNLIP attenuates diabetic heart I/R injury by mitigating HG-induced PKC-ԑ overexpression and, subsequently, activating STAT3.
BACKGROUND/AIMS: Protein kinase C(PKC)-ε activation is a mechanism of preconditioning cardioprotection but its role in repeated non-invasive limb ischemic preconditioning (rNLIP) mediated cardioprotection against myocardial ischemia/reperfusion (I/R) injury in diabetes is unknown. METHODS: Eight-week streptozotocin-induced diabetic and non-diabeticSprague-Dawley rats were subjected to I/R without or with rNLIP. In vitro, H9C2 cells were cultured with high glucose (HG) and subjected to hypoxia/re-oxygenation (H/R) without or with PKC-ε or STAT3 gene knock-down in the absence or presence of remote time hypoxia preconditioning (HPC). RESULTS:Diabeticrats displayed larger post-ischemic myocardial infarct size and higher troponin-I release with concomitant cardiac PKC-ԑ overexpression and activation manifested as increased membrane translocation, while phosphorylated STAT3 (p-STAT3) and Akt (p-Akt) were lower compared to non-diabeticrats (all P<0.05). rNLIP reduced infarct size in both non-diabetic and diabeticrats. rNLIP reduced post-ischemic cardiac PKC-ԑ activation in diabetic while increased PKC-ԑ activation in non-diabeticrats, resulting in increased cardiac p-STAT3 and p-Akt. In H9C2 cells, HG increased PKC-ԑ expression and exacerbated post-H/R injury, accompanied with reduced p-STAT3 and p-Akt, which were all reverted by HPC. These HPC protective effects were abolished by either PKC-ԑ or STAT3 gene knock-down, except that PKC-ԑ gene knock-down reverted HG and H/R-induced reduction of p-STAT3. CONCLUSION:rNLIP attenuates diabetic heart I/R injury by mitigating HG-induced PKC-ԑ overexpression and, subsequently, activating STAT3.
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