Inhibition of the JAK2/STAT3 pathway and cell cycle re-entry contribute to the protective effect of remote ischemic pre-conditioning of rat hindlimbs on cerebral ischemia/reperfusion injury

AIMS

Remote ischemic pre-conditioning (RIPC) protects against ischemia/reperfusion (I/R) injury. However, the mechanisms underlying this protection remain unclear. In the present study, we investigated the role of Janus-activated kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) pathway and cell cycle arrest, and their relationship with neuronal apoptosis following RIPC.

METHODS

A rat cerebral I/R injury model was induced by middle cerebral artery occlusion (MCAO), and AG490 was used to investigate the mechanisms of RIPC. p-JAK2-, p-STAT3-, cyclin D1-, and cyclin-dependent kinase 6 (CDK6) expression was assessed by Western blotting and immunofluorescence staining.

RESULTS

RIPC reduced the infarct volume, improved neurological function, and increased neuronal survival. Furthermore, p-JAK2 and p-STAT3 were detected during the initial phase of reperfusion; the expression levels were significantly increased at 3 and 24 h after reperfusion and were suppressed by RIPC. Additionally, the MCAO-induced upregulation of the cell cycle regulators cyclin D1 and CDK6 was ameliorated by RIPC. Meanwhile, cyclin D1 and CDK6 were colocalized with p-STAT3 in the ischemic brain.

CONCLUSION

RIPC ameliorates the induction of the JAK2/STAT3 pathway and cell cycle regulators cyclin D1 and CDK6 by MCAO, and this net inhibition of cell cycle re-entry by RIPC is associated with downregulation of STAT3 phosphorylation.

Plasma Exosomes at the Late Phase of Remote Ischemic Pre-conditioning Attenuate Myocardial Ischemia-Reperfusion Injury Through Transferring miR-126a-3p

Background: Remote ischemic pre-conditioning (RIPC) alleviated the myocardial ischemia-reperfusion injury, yet the underlying mechanisms remain to be fully elucidated, especially at the late phase. Searching a key component as a transfer carrier may provide a novel insight into RIPC-mediated cardioprotection in the condition of myocardial ischemia-reperfusion.

Objective: To investigate the cardioprotective effect of plasma exosomes at the late phase of RIPC and its potential signaling pathways involved.

Methods and Results: Exosomes were isolated from the plasma of rats 48 h after the RIPC or control protocol. Although the total plasma exosomes level had no significant change at the late phase of RIPC (RIPC-exosome) compared with the control exosomes (Control-exosome), the RIPC-exosome afforded remarkable protection against myocardial ischemia-reperfusion (MI/R) injury in rats and hypoxia-reoxygenation (H/R) injury in cells. The miRNA array revealed significant enrichment of miR-126a-3p in RIPC-exosome. Importantly, both miR-126a-3p inhibitor and antagonist significantly blunted the cardioprotection of RIPC-exosome in H/R cells and MI/R rats, respectively, while miR-126a-3p mimic and agomir showed significant cardioprotection against H/R injury in cells and MI/R injury in rats. Mechanistically, RIPC-exosome, especially exosomal miR-126a-3p, activated the reperfusion injury salvage kinase (RISK) pathway by enhancing the phosphorylation of Akt and Erk1/2, and simultaneously inhibited Caspase-3 mediated apoptotic signaling.

Conclusions: Our findings reveal a novel myocardial protective mechanism that plasma exosomes at the late phase of RIPC attenuate myocardial ischemia-reperfusion injury via exosomal miR-126a-3p.

Remote Ischemic Conditioning Reduced Acute Lung Injury After Traumatic Brain Injury in the Mouse

ABSTRACT

Traumatic brain injury (TBI) can induce acute lung injury (ALI). The exact pathomechanism of TBI-induced ALI is poorly understood, limiting treatment options. Remote ischemic conditioning (RIC) can mitigate detrimental outcomes following transplants, cardiac arrests, and neurological injuries. In this study, we hypothesized that RIC would reduce TBI-induced ALI by regulating the sphingosine-1-phosphate (S1P)-dependent pathway, a central regulator of endothelial barrier integrity, lymphocyte, and myokine trafficking. Male mice were subjected to either diffuse TBI by midline fluid percussion or control sham injury and randomly assigned among four groups: sham, TBI, sham RIC, or TBI RIC; RIC was performed 1 h prior to TBI. Mice were euthanized at 1-h postinjury or 7 days post-injury (DPI) and lung tissue, bronchoalveolar lavage (BAL) fluid, and blood were collected. Lung tissue was analyzed for histopathology, irisin myokine levels, and S1P receptor levels. BAL fluid and blood were analyzed for cellularity and myokine/S1P levels, respectively. One-hour postinjury, TBI damaged lung alveoli and increased neutrophil infiltration; RIC preserved alveoli. BAL from TBI mice had more neutrophils and higher neutrophil/monocyte ratios compared with sham, where TBI RIC mice showed no injury-induced change. Further, S1P receptor 3 and irisin-associated protein levels were significantly increased in the lungs of TBI mice compared with sham, which was prevented by RIC. However, there was no RIC-associated change in plasma irisin or S1P. At 7 DPI, ALI in TBI mice was largely resolved, with evidence for residual lung pathology. Thus, RIC may be a viable intervention for TBI-induced ALI to preserve lung function and facilitate clinical management.

Remote Ischemic Pre-Conditioning Attenuates Adverse Cardiac Remodeling and Mortality Following Doxorubicin Administration in Mice

Objectives

Because of its multifaceted cardioprotective effects, remote ischemic pre-conditioning (RIPC) was examined as a strategy to attenuate doxorubicin (DOX) cardiotoxicity.

Background

The use of DOX is limited by dose-dependent cardiotoxicity and heart failure. Oxidative stress, mitochondrial dysfunction, inflammation, and autophagy modulation have been proposed as mediators of DOX cardiotoxicity.

Methods

After baseline echocardiography, adult male CD1 mice were randomized to either sham or RIPC protocol (3 cycles of 5 min femoral artery occlusion followed by 5 min reperfusion) 1 h before receiving DOX (20 mg/kg, intraperitoneal). The mice were observed primarily for survival over 85 days (86 mice). An additional cohort of 50 mice was randomized to either sham or RIPC 1 h before DOX treatment and was followed for 25 days, at which time cardiac fibrosis, apoptosis, and mitochondrial oxidative phosphorylation were assessed, as well as the expression profiles of apoptosis and autophagy markers.

Results

Survival was significantly improved in the RIPC cohort compared with the sham cohort (p = 0.007). DOX-induced cardiac fibrosis and apoptosis were significantly attenuated with RIPC compared with sham (p < 0.05 and p < 0.001, respectively). Although no mitochondrial dysfunction was detected at 25 days, there was a significant increase in autophagy markers with DOX that was attenuated with RIPC. Moreover, DOX caused a 49% decline in cardiac BCL2/BAX expression, which was restored with RIPC (p < 0.05 vs. DOX). DOX also resulted in a 17% reduction in left ventricular mass at 25 days, which was prevented with RIPC (p < 0.01), despite the lack of significant changes in left ventricular ejection fraction.

Conclusions

Our preclinical results suggested that RIPC before DOX administration might be a promising approach for attenuating DOX cardiotoxicity.

Protective effect of remote ischemic pre-conditioning on patients undergoing cardiac bypass valve replacement surgery: A randomized controlled trial

Remote ischemic pre-conditioning (RIPC) may have a protective effect on myocardial injury associated with cardiac bypass surgery (CPB). The objective of the present study was to investigate the effect of RIPC on ischemia/reperfusion (I/R) injury and to assess the underlying mechanisms. A total of 241 patients who underwent valve replacement were randomly assigned to receive either RIPC (n=121) or control group (n=120). The primary endpoint was peri-operative myocardial injury (PMI), which was determined by serum Highly sensitive cardiac troponin T (hsTnT). The secondary endpoint was the blood gas indexes, acute lung injury and length of intensive care unit stay, length of hospital stay and major adverse cardiovascular events. The results indicated that in comparison with control group, RIPC treatment reduced the levels of hsTnT at 6 and 24 h post-CPB (P<0.001), as well as the alveolar-arterial oxygen pressure difference and respiratory index after CPB. Furthermore, RIPC reduced the incidence of acute lung injury by 15.3% (54.1% in the control group vs. 41.3% in the RIPC group, P=0.053). It was indicated that RIPC provided myocardial and pulmonary protection during CPB. In addition, the length of the intensive care unit and hospital stay was reduced by RIPC. Mechanistic investigation revealed a reduced content of soluble intercellular adhesion molecule-1, endothelin-1 and malondialdehyde, as well as elevated levels of nitric oxide in the RIPC group compared with those in the control group. This indicated that RIPC protected against I/R injury associated with CPB through reducing the inflammatory response and oxidative damage, as well as improving pulmonary vascular tension. In conclusion, RIPC reduced myocardial and pulmonary injury associated with CPB. This protective effect may be associated with the inhibition of the inflammatory response and oxidative injury. The present study proved the efficiency of this approach in reducing ischemia/reperfusion injury associated with cardiac surgery. Clinical trial registry no. ChiCTR1800015393.

Kinetics and Signal Activation Properties of Circulating Factor(s) From Healthy Volunteers Undergoing Remote Ischemic Pre-Conditioning

Although remote ischemic pre-conditioning (RIPC) reduced infarct size in animal experiments and proof-of-concept clinical trials, recent phase III trials failed to confirm cardioprotection during cardiac surgery. Here, we characterized the kinetic properties of humoral factors that are released after RIPC, as well as the signal transduction pathways that were responsible for cardioprotection in an ex vivo model of global ischemia reperfusion injury. Venous blood from 20 healthy volunteers was collected at baseline and 5 min, 30 min, 1 h, 6 h, and daily from 1 to 7 days after RIPC (3 × 5/5 min upper-limb ischemia/reperfusion). Plasma-dialysates (cut-off: 12 to 14 kDa; dilution: 1:20) were infused into Langendorff-perfused mouse hearts subjected to 20/120 min global ischemia/reperfusion. Infarct size and phosphorylation of signal transducer and activator of transcription (STAT)3, STAT5, extracellular-regulated kinase 1/2 and protein kinase B were determined. In a subgroup of plasma-dialysates, an inhibitor of STAT3 (Stattic) was used in mouse hearts. Perfusion with baseline-dialysate resulted in an infarct size of 39% of ventricular mass (interquartile range: 36% to 42%). Perfusion with dialysates obtained 5 min to 6 days after RIPC significantly reduced infarct size by ∼50% and increased STAT3 phosphorylation beyond that with baseline-dialysate. Inhibition of STAT3 abrogated these effects. These results suggest that RIPC induces the release of cardioprotective, dialyzable factor(s) within 5 min, and that circulate for up to 6 days. STAT3 is activated in murine myocardium by RIPC-induced human humoral factors and is causally involved in cardioprotection.

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Pre-clinical and early phase clinical studies with remote ischemic preconditioning (RIPC) appeared promising; however, RIPC was not effective in phase III clinical trials.

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To improve the translation of RIPC into clinical practice, the kinetic properties and functional effects of humoral factors released after RIPC in humans were characterized ex vivo.

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Venous blood from 20 healthy volunteers was collected at baseline and 5 min, 30 min, 1 h, 6 h and daily from 1 to 7 days after RIPC. Plasma dialysates were infused into Langendorff-perfused mouse hearts subjected to 20/120 min global ischemia/reperfusion.

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Perfusion with dialysates obtained 5 min to 6 days after RIPC significantly reduced infarct size by ∼50% when compared to perfusion with dialysates obtained at baseline prior to RIPC, and increased STAT3 phosphorylation beyond values obtained with baseline-dialysate.

The Impact of Remote Ischemic Pre-Conditioning on Contrast-Induced Nephropathy in Patients Undergoing Coronary Angiography and Angioplasty: A Double-Blind Randomized Clinical Trial

Background and objective

Contrast-induced nephropathy (CIN) is an acute major complication following intravascular administration of iodinated contrast agents; however, the best approach for preventing CIN is not clear. Remote ischemic pre-conditioning (RIPC) is a new, non-pharmacological method that has been considered for the prevention of CIN following coronary angiography. This study assessed the effects of RIPC with four brief episodes of upper limb ischemia and reperfusion in the prevention of contrast-induced nephropathy (CIN) after coronary angiography and/or angioplasty.

Methods

In this double-blind randomized clinical trial, we enrolled 51 patients with chronic stable angina and non-ST elevation acute coronary syndrome (NSTE.ACS), and they underwent coronary angiography and/or angioplasty. Standard fluid therapy with normal saline was prescribed for all patients before and after the procedure. The patients were divided into two groups, i.e., a study group of patients who had undergone RIPC intervention and a control group of patients who had not undergone RIPC. One hour before the procedure, a sphygmomanometer cuff was placed around one arm and inflated up to 50 mmHg above the systolic pressure for five minutes; then, the cuff was deflated for another five minutes, and this cycle was repeated four times. The patients’ serum creatinine levels were measured at baseline and 48 hours after the procedure, and the incidence of CIN was calculated.

Results

Twenty-one males and 30 females were studied in two groups, i.e., an RIPC intervention group (n = 25) and a control group (n = 26) that were homogenous considering baseline characteristics. No significant difference was observed in the mean level of serum creatinine between the two groups at a post-intervention time of 48 hours (RICP: 1.74 ± 0.70 mg/dL vs. Control: 1.75 ± 0.87 mg/dL; P = 0.64). However, a lower incidence rate of CIN was observed 48 hours after the administration of the contrast medium in the RIPC group, but it was not statistically significant (RIPC: 23.1% vs. Control: 12.0%; P = 0.30).

Conclusion

It seems that adequate fluid therapy is still the most effective strategy for preventing CIN and that RIPC might have additional protective effects in very high risk patients, such as those with severe renal insufficiency and heart failure.