The Cardioprotective Effects of Late-Phase Remote Preconditioning of Trauma Depends on Neurogenic Pathways and the Activation of PKC and NF-κB (But Not iNOS) in Mice

Hydrogen sulfide restores cardioprotective effects of remote ischemic preconditioning in aged rats via HIF-1α/Nrf2 signaling pathway

The present study explored the therapeutic potential of hydrogen sulfide (H₂S) in restoring aging-induced loss of cardioprotective effect of remote ischemic preconditioning (RIPC) along with the involvement of signaling pathways. The left hind limb was subjected to four short cycles of ischemia and reperfusion (IR) in young and aged male rats to induce RIPC. The hearts were subjected to IR injury on the Langendorff apparatus after 24 h of RIPC. The measurement of lactate dehydrogenase, creatine kinase and cardiac troponin served to assess the myocardial injury. The levels of H₂S, cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE), nuclear factor erythroid 2-related factor 2 (Nrf2), and hypoxia-inducible factor (HIF-1α) were also measured. There was a decrease in cardioprotection in RIPC-subjected old rats in comparison to young rats along with a reduction in the myocardial levels of H₂S, CBS, CSE, HIF-1α, and nuclear: cytoplasmic Nrf2 ratio. Supplementation with sodium hydrogen sulfide (NaHS, an H₂S donor) and l-cysteine (H₂S precursor) restored the cardioprotective actions of RIPC in old hearts. It increased the levels of H₂S, HIF-1α, and Nrf2 ratio without affecting CBS and CSE. YC-1 (HIF-1α antagonist) abolished the effects of NaHS and l-cysteine in RIPC-subjected old rats by decreasing the Nrf2 ratio and HIF-1α levels, without altering H₂S.The late phase of cardioprotection of RIPC involves an increase in the activity of H₂S biosynthetic enzymes, which increases the levels of H₂S to upregulate HIF-1α and Nrf2. H₂S has the potential to restore aging-induced loss of cardioprotective effects of RIPC by upregulating HIF-1α/Nrf2 signaling.

Late Phases of Cardioprotection During Remote Ischemic Preconditioning and Adenosine Preconditioning Involve Activation of Neurogenic Pathway

BACKGROUND

The role of the neurogenic pathway in early phases of cardioprotection during remote ischemic preconditioning (RIPC) and adenosine preconditioning is reported.

AIM

This study was designed to explore the involvement of the neurogenic pathway in late phases of cardioprotection during RIPC and adenosine preconditioning.

MATERIAL AND METHODS

Fifty-four Wistar rats were used and divided into 9 experimental groups. RIPC was induced by tying the blood pressure cuff around the hind limb and subjecting to 4 cycles of inflation and deflation of 5 minutes each. In early RIPC, the heart was isolated immediately after the last episode of RIPC, whereas in late RIPC, the heart was isolated 24 hours after the last cycle of RIPC. In a similar way, adenosine preconditioning was instituted in early and late phases by either isolating the heart 40 minutes or 24 hours after adenosine (4 mg/kg, intraperitoneally [i.p.]) administration. Isolated hearts were subjected to ischemia-reperfusion (I/R) injury on the Langendorff's system.

RESULTS

Both early and late phases of RIPC and adenosine preconditioning significantly abrogated I/R-induced myocardial injury in terms of decrease in the release of lactate dehydrogenase, creatine kinase, and decrease in infarct size. Pretreatment with hexamethonium, a ganglion blocker (20 mg/kg, i.p.), significantly abolished the cardioprotective effects of both early and late phases of RIPC and adenosine preconditioning.

CONCLUSION

Apart from the involvement of the neurogenic pathway in the early phases, there is a critical role of the neurogenic pathway in the late phase of cardioprotection during RIPC and adenosine preconditioning.

Neural mechanisms in remote ischaemic conditioning in the heart and brain: mechanistic and translational aspects

Remote ischaemic conditioning (RIC) is a promising method of cardioprotection, with numerous clinical studies having demonstrated its ability to reduce myocardial infarct size and improve prognosis. On the other hand, there are several clinical trials, in particular those conducted in the setting of elective cardiac surgery, that have failed to show any benefit of RIC. These contradictory data indicate that there is insufficient understanding of the mechanisms underlying RIC. RIC is now known to signal indiscriminately, protecting not only the heart, but also other organs. In particular, experimental studies have demonstrated that it is able to reduce infarct size in an acute ischaemic stroke model. However, the mechanisms underlying RIC-induced neuroprotection are even less well understood than for cardioprotection. The existence of bidirectional feedback interactions between the heart and the brain suggests that the mechanisms of RIC-induced neuroprotection and cardioprotection should be studied as a whole. This review, therefore, addresses the topic of the neural component of the RIC mechanism.

Remote Postconditioning Induced by Trauma Protects the Mouse Heart against Ischemia Reperfusion Injury. Involvement of the Neural Pathway and Molecular Mechanisms

PURPOSE

Abdominal superficial surgical incision elicits cardioprotection against myocardial ischemia reperfusion (I/R) injury in mice. This cardioprotective phenomenon, termed remote preconditioning of trauma (RPCT), results in an 80 to 85 % reduction in cardiac infarct size. We evaluated cardioprotection and the molecular mechanisms of remote postconditioning of trauma (RPostCT) in a murine I/R injury model.

METHODS

Mice were analyzed using a previously established I/R injury model. An abdominal superficial surgical incision was made 45 min after myocardial ischemia at the end of coronary occlusion, and infarct size was determined 24 h after reperfusion.

RESULTS

The results indicated that a strong cardioprotective effect occurred during RPostCT (56.94 ± 2.71 % sham vs. 15.58 ± 2.16 % RPostCT; the mean area of the infarct divided by the mean area of the region at risk; p ≤ 0.05; n = 10). Furthermore, pharmacological intervention revealed neurogenic signaling involvement in the beneficial effects of RPostCT via sensory and sympathetic thoracic nerves. Pharmacological experiments in transgenic mice demonstrated that bradykinin receptors, β-adrenergic receptors (AR), and protein kinase C were implicated in the cardioprotective effects of RPostCT.

CONCLUSIONS

RPostCT significantly decreased myocardial infarction size via neurogenic transmission and various signaling pathways. This study describes a new cardiac I/R injury prevention method that might lead to the development of therapies that are more clinically relevant for myocardial I/R injury.

Neurogenic pathways in remote ischemic preconditioning induced cardioprotection: Evidences and possible mechanisms

Remote ischemic preconditioning (RIPC) is an intrinsic phenomenon whereby 3~4 consecutive ischemia-reperfusion cycles to a remote tissue (noncardiac) increases the tolerance of the myocardium to sustained ischemiareperfusion induced injury. Remote ischemic preconditioning induces the local release of chemical mediators which activate the sensory nerve endings to convey signals to the brain. The latter consequently stimulates the efferent nerve endings innervating the myocardium to induce cardioprotection. Indeed, RIPC-induced cardioprotective effects are reliant on the presence of intact neuronal pathways, which has been confirmed using nerve resection of nerves including femoral nerve, vagus nerve, and sciatic nerve. The involvement of neurogenic signaling has been further substantiated using various pharmacological modulators including hexamethonium and trimetaphan. The present review focuses on the potential involvement of neurogenic pathways in mediating remote ischemic preconditioning-induced cardioprotection.