Repeated Non-Invasive Limb Ischemic Preconditioning Confers Cardioprotection Through PKC-Ԑ/STAT3 Signaling in Diabetic Rats

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.

Effects of Cardiovascular Risk Factors on Cardiac STAT3

“…After five weeks of diabetes induction, they found that myocardial STAT3 activation (at the Ser727 site) was lower in the diabetic group. Later the same research group confirmed these results in STZ-induced type I diabetes models [ 29 , 30 ] and demonstrated that phosphorylation and activation of STAT3 at Tyr705 was also decreased in diabetes [ 29 , 30 , 31 ]. Besides type I diabetes models, reduction of cardiac STAT3 expression was also described in a type II diabetes model, i.e., STAT3 mRNA was downregulated in non-obese Goto-Kakizaki rats [ 25 ].…”

“…Moreover, similar trends were observed in in vitro models of diabetes. In H9c2 cells subjected to high glucose conditions (25 mM glucose added to the medium), the non-ischaemic baseline STAT3 phosphorylation (Tyr705 and/or Ser727) and activation was significantly decreased [ 29 , 32 ]. Similarly, exposure of isolated adult rat ventricular cardiomyocytes to high glucose conditions also resulted in reduced non-ischaemic baseline phosphorylation and activation of STAT3 (Tyr705) [ 33 ].…”

Heat shock protein 70: A promising therapeutic target for myocardial ischemia–reperfusion injury

“…For the mechanisms involved, RIPC‐induced cardioprotective effects are, at least in part, dependent on exosomes which significantly accumulate in the plasma during RIPC and subsequently alleviate myocardial I/R injury via their antiapoptotic properties (Minghua et al, ; Vicencio et al, ). In addition, other related mechanisms have been revealed, such as protein kinase C‐ε (PKC‐ε) overexpression (C. Wang et al, ), STAT5‐dependent antiapoptotic signaling pathway induction (H. Chen et al, ) and glucagon‐like peptide‐1 activation (Basalay et al, ).…”

Deletion of Rap1 protects against myocardial ischemia/reperfusion injury through suppressing cell apoptosis via activation of STAT3 signaling

“…As an essential component of the survivor activating factor enhancement pathway, activation of STAT3 signaling has been implicated in protecting the heart from myocardial I/R injury under both ischemic pre-or post-conditioning protocols and basal conditions. [32][33][34][35] Mice with cardiac-specific knockout of STAT3 develop significantly greater myocardial IS within the left ventricle, which is associated with increased cardiac apoptosis, reduced cardiac function, and reduced survival. 36 In contrast, cardiac-specific transgenic mice expressing STAT3 exhibit reduced myocardial IS and cardiomyocyte apoptosis when compared with non-transgenic littermates.…”