Ischaemic post‐conditioning in rats: Responder and non‐responder differ in transcriptome of mitochondrial proteins

Abstract

Ischaemic post‐conditioning (IPoC) is a clinical applicable procedure to reduce reperfusion injury. Non‐responsiveness to IPoC possibly caused by co‐morbidities limits its clinical attractiveness. We analysed differences in the expression of mitochondrial proteins between IPoC responder (IPoC‐R) and non‐responder (IPoC‐NR). Eighty rats were randomly grouped to sham, ischaemia/reperfusion (I/R), IPoC or ischaemic pre‐conditioning (IPC, as positive cardioprotective intervention) in vivo. Infarct sizes were quantified by plasma troponin I levels 60 minutes after reperfusion. After 7 days, rats were sacrificed and left ventricular tissue was taken for post hoc analysis. The transcriptome was analysed by qRT‐PCR and small RNA sequencing. Key findings were verified by immunoblots. I/R increased plasma troponin I levels compared to Sham. IPC reduced troponin I compared to I/R, whereas IPoC produced either excellent protection (IPoC‐R) or no protection (IPoC‐NR). Twenty‐one miRs were up‐regulated by I/R and modified by IPoC. qRT‐PCR analysis revealed that IPoC‐R differed from other groups by reduced expression of arginase‐2 and bax, whereas the mitochondrial uncoupling protein (UCP)‐2 was induced in IPC and IPoC‐R. IPoC‐R and IPoC‐NR synergistically increased the expression of non‐mitochondrial proteins like VEGF and SERCA2a independent of the infarct size. Cardiac function was more closely linked to differences in mitochondrial proteins than on regulation of calcium‐handling proteins. In conclusion, healthy rats could not always be protected by IPoC. IPoC‐NR displayed an incomplete responsiveness which is reflected by different changes in the mitochondrial transcriptome compared to IPoC‐R. This study underlines the importance of mitochondrial proteins for successful long‐term outcome.

Swiprosin-1/EFhD-2 Expression in Cardiac Remodeling and Post-Infarct Repair: Effect of Ischemic Conditioning

“…In order to address the question of whether induction of cardiac expression of swiprosin-1 in post ischemic hearts is related to the extent of cardiac repair, swiprosin-1 mRNA expression was analyzed next in rat hearts 7 days after ischemia/reperfusion (I/R). These hearts have previously been used to establish the effect of ischemic pre-and postconditioning on cardiac remodeling [17]. Here, we show that swiprosin-1 mRNA expression is induced by I/R.…”

“…However, either ischemic preconditioning (IPC) or IPoC abrogate this induction (Figure 2A). IPC and IPoC have proven effects on infarct sizes as quantified by troponin I plasma levels 1 h after reperfusion [17]. The mRNA expression of swiprosin-1 showed a linear relationship to the infarct size, suggesting that the amount of expression is related to cardiac repair processes ( Figure 2B).…”

“…In the cardiac tissue used for this analysis, mRNA expression of 72 different genes related to cardiac biology was analyzed (see ref. 17). A detailed analysis of further coregulated mRNAs with both miRs was performed by investigating a potential linear correlation between mRNAs and miRs.…”

Cardioprotective Effect of Novel Matrix Metalloproteinase Inhibitors

“…In a recent study, we highlighted the presence of a phenomenon that accompanies ischemic postconditioning and leads to diverse effects, distinguishing responders and non-responders to postconditioning stimuli in terms of the infarct size reduction. This phenomenon is supposed to be, at least partially, based on the individual polymorphisms of the downstream signaling pathways of postconditioning stimuli, including Jun dimerization protein type 2 (JDP2) and activator protein-1 (AP-1) [ 2 ]. Therefore, in the present study, we may suppose that the ratio of animals not responding to the cardioprotective signals evoked by ilomastat was higher than previously published, which might lead to the loss of significant infarct size reductions.…”

“…However, even after promising preclinical attempts aiming to trigger these cardioprotective mechanisms, the translation of the results into clinical practice has remained untried. The development of new cardioprotective compounds is challenging due to translation difficulties, including difficulties in reproducibility, at least in part due to the significant number of non-responder animals [ 2 , 3 ] and, moreover, due to the presence of several additional factors including cardiovascular co-morbidities, e.g., hyperlipidemia or diabetes mellitus [ 4 ]. Many cardioprotective strategies act through common end-effectors and may be suboptimal in patients with comorbidities [ 5 ].…”