Combined Vagal Stimulation and Limb Remote Ischemic Perconditioning Enhances Cardioprotection via an Anti-inflammatory Pathway

Role of remote ischaemic conditioning in fracture healing and orthopaedic surgery-a systematic review and narrative synthesis

INTRODUCTION

Remote ischaemic conditioning (RIC) involves the use of controlled and transient ischemia and reperfusion cycles, commonly of the upper or lower limb, to mitigate cellular damage from ischaemic events. Studies have demonstrated that RIC may have anti-inflammatory and cardiovascular protective effects and thus could represent a novel therapeutic strategy to improve outcomes following orthopaedic surgery. This review aimed to comprehensively describe the current pre-clinical and clinical evidence for RIC in orthopaedics.

METHODS

MEDLINE and EMBASE via OVID (1966-March 2024) were searched using a systematic search strategy for randomised controlled trials (RCTs) investigating the effects of RIC on fracture, bone healing, and orthopaedics. Both pre-clinical and clinical RCTs were included.

RESULTS

Three pre-clinical RCTs (comprising of 198 rats in models of experimental fracture) met the inclusion criteria. These showed that RIC was associated with enhanced callus formation (volume and biomechanical strength) post-fracture, reduced oxidative stress and upregulated osteoblastic activity. Sixteen clinical RCTs, involving 628 patients, investigated RIC in 6 different elective orthopaedic procedures (knee, lower limb, cervical, shoulder, general, hip fracture). RIC protocols varied in cycle frequency, duration, and pressure, but all were given as a single dose at induction of anaesthesia. Significant results included reductions in oxidative stress, improved cerebral and peripheral oxygenation, and reduced pain scores and analgesia use. Only 1 study (n = 648) evaluated RIC in acute hip fracture and demonstrated an early cardioprotective effect.

CONCLUSION

The potential therapeutic effects of RIC in orthopaedic surgery is supported by preliminary evidence from pre-clinical and clinical studies. Trials to date are largely small but warrant investigation in well-powered multicentre RCTs. There are still many unanswered questions about the optimal RIC parameters (cuff pressure, frequency and duration) in orthopaedic surgery and determining which patients may benefit most from this therapy.

Vagal nerve stimulation in myocardial ischemia/reperfusion injury: from bench to bedside

The identification of acute cardioprotective strategies against myocardial ischemia/reperfusion (I/R) injury that can be applied in the catheterization room is currently an unmet clinical need and several interventions evaluated in the past at the pre-clinical level have failed in translation. Autonomic imbalance, sustained by an abnormal afferent signalling, is a key component of I/R injury. Accordingly, there is a strong rationale for neuromodulation strategies, aimed at reducing sympathetic activity and/or increasing vagal tone, in this setting. In this review we focus on cervical vagal nerve stimulation (cVNS) and on transcutaneous auricular vagus nerve stimulation (taVNS); the latest has the potential to overcome several of the issues of invasive cVNS, including the possibility of being used in an acute setting, while retaining its beneficial effects. First, we discuss the pathophysiology of I/R injury, that is mostly a consequence of the overproduction of reactive oxygen species. Second, we describe the functional anatomy of the parasympathetic branch of the autonomic nervous system and the most relevant principles of bioelectronic medicine applied to electrical vagal modulation, with a particular focus on taVNS. Then, we provide a detailed and comprehensive summary of the most relevant pre-clinical studies of invasive and non-invasive VNS that support its strong cardioprotective effect whenever there is an acute or chronic cardiac injury and specifically in the setting of myocardial I/R injury. The potential benefit in the emerging field of post cardiac arrest syndrome (PCAS) is also mentioned. Indeed, electrical cVNS has a strong anti-adrenergic, anti-inflammatory, antioxidants, anti-apoptotic and pro-angiogenic effect; most of the involved molecular pathways were already directly confirmed to take place at the cardiac level for taVNS. Pre-clinical data clearly show that the sooner VNS is applied, the better the outcome, with the possibility of a marked infarct size reduction and almost complete left ventricular reverse remodelling when VNS is applied immediately before and during reperfusion. Finally, we describe in detail the limited but very promising clinical experience of taVNS in I/R injury available so far.

Attenuation of esophageal anastomotic stricture through remote ischemic conditioning in a rat model

Anastomotic stricture is a typical complication of esophageal atresia surgery. Remote ischemic conditioning (RIC) has demonstrated multiorgan benefits, however, its efficacy in the esophagus remains unclear. This study aimed to investigate whether applying RIC after esophageal resection and anastomosis in rats could attenuate esophageal stricture and improve inflammation. Sixty-five male Sprague-Dawley rats were categorized into the following groups: controls with no surgery, resection and anastomosis only, resection and anastomosis with RIC once, and resection and anastomosis with RIC twice. RIC included three cycles of hind-limb ischemia followed by reperfusion. Inflammatory markers associated with the interleukin 6/Janus kinase/ signal transducer and activator of transcription 3 (IL-6/JAK/STAT3) and tumor necrosis factor-alpha/nuclear factor-κB (TNF-α/NF-kB) signaling pathways were evaluated with RNA and protein works. The RIC groups showed significantly lower stricture rates, lower inflammatory markers levels than the resection and anastomosis-only group. The RIC groups had significantly lower IL-6 and TNFa levels than the resection and anastomosis-only group, confirming the inhibitory role of remote ischemic conditioning in the IL-6/JAK/STAT3 and TNF-α/NF-kB signaling pathways. RIC after esophageal resection and anastomosis can reduce the inflammatory response, improving strictures at the esophageal anastomosis site, to be a novel noninvasive intervention for reducing esophageal anastomotic strictures.

Inflammation in Myocardial Ischemia/Reperfusion Injury: Underlying Mechanisms and Therapeutic Potential

Acute myocardial infarction (MI) occurs when blood flow to the myocardium is restricted, leading to cardiac damage and massive loss of viable cardiomyocytes. Timely restoration of coronary flow is considered the gold standard treatment for MI patients and limits infarct size; however, this intervention, known as reperfusion, initiates a complex pathological process that somewhat paradoxically also contributes to cardiac injury. Despite being a sterile environment, ischemia/reperfusion (I/R) injury triggers inflammation, which contributes to infarct expansion and subsequent cardiac remodeling and wound healing. The immune response is comprised of subsets of both myeloid and lymphoid-derived cells that act in concert to modulate the pathogenesis and resolution of I/R injury. Multiple mechanisms, including altered metabolic status, regulate immune cell activation and function in the setting of acute MI, yet our understanding remains incomplete. While numerous studies demonstrated cardiac benefit following strategies that target inflammation in preclinical models, therapeutic attempts to mitigate I/R injury in patients were less successful. Therefore, further investigation leveraging emerging technologies is needed to better characterize this intricate inflammatory response and elucidate its influence on cardiac injury and the progression to heart failure.

Manipulation of the inflammatory reflex as a therapeutic strategy

The cholinergic anti-inflammatory pathway is the efferent arm of the inflammatory reflex, a neural circuit through which the CNS can modulate peripheral immune responses. Signals communicated via the vagus and splenic nerves use acetylcholine, produced by Choline acetyltransferase (ChAT)+ T cells, to downregulate the inflammatory actions of macrophages expressing α7 nicotinic receptors. Pre-clinical studies using transgenic animals, cholinergic agonists, vagotomy, and vagus nerve stimulation have demonstrated this pathway's role and therapeutic potential in numerous inflammatory diseases. In this review, we summarize what is understood about the inflammatory reflex. We also demonstrate how pre-clinical findings are being translated into promising clinical trials, and we draw particular attention to innovative bioelectronic methods of harnessing the cholinergic anti-inflammatory pathway for clinical use.

Ozone preconditioning protects rabbit heart against global ischemia-reperfusion injury in vitro by up-regulating HIF-1α

Myocardial ischemia-reperfusion injury (MIRI) is a major factor that leads to cardiac dysfunction in cardiovascular surgery during extracorporeal circulation. Recent studies have found that ozone (O₃) has protective effect on MIRI caused by the anterior descending branch of the ligated left coronary artery. However, whether O₃ preconditioning has the same protective effect on global MIRI and the mechanism underlying this clinical treatment remains elusive. Here, we hypothesized that O₃ preconditioning (O₃P) could protect rabbit heart against global MIRI in vitro by up-regulating HIF-1α. Rabbits were treated intraperitoneally with O₂/O₃ mixture with different concentrations and then injected with YC-1 (inhibitor of HIF-1α) before the establishment of the global MIRI model using the Langendorff isolated heart perfusion apparatus. We investigated the effects of O₃ preconditioning on cardiac systolic function, myocardial infarction, inflammatory response, mitochondrial function, myocardial pathological changes and arrhythmias. We found that the heart with O₃ preconditioning significantly increased HR, LVDP and IL-10 expression, and decreased IL-6 expression, CK-MB, cTnT and cTnI concentration, myocardial infarction area, myocardial pathological injury and the occurrence of ventricular tachycardia and ventricular fibrillation. Meanwhile, the level of HIF-1α was significantly increased. However, after treatment of specific inhibitor of HIF-1α, the protective effect of O₃ preconditioning was reversed completely. Our data indicates that O₃ preconditioning has protective effect on MIRI and this protective effect is positively associated with dosage of O₃. Energy metabolism disorder is the initial stage of MIRI and up-regulation of HIF-1α plays an important role in reducing mitochondrial dysfunction.

Challenges facing the clinical translation of cardioprotection: 35 years after the discovery of ischemic preconditioning

Since coronary reperfusion was introduced into clinical practice in the late 1970s, the further translation of several successful animal experiments on cardioprotection into clinical practice has been disappointing to date. Animal experiments are often performed on young, healthy animals lacking the risk factors, co-morbidities and co-medications characteristic of acute myocardial infarction patients. Many hopes were kindled in 1986 when ischemic preconditioning was discovered. However, it is not yet known how long ischemia can last and what is the best modality for additional cardioprotection through conditioning to obtain benefits. There is a lack of experimental studies on the long-term effects of additional cardioprotection, in addition to the reduction in infarct size; in particular, there is a lack of studies on vessel protection, repair, inflammation, remodeling, and mortality. The reproducibility and robustness of experimental studies are often limited by species differences, the role of co-morbidities, vascular damage, inflammatory processes, and co-medications, which are not adequately considered. In particular, inflammatory processes, including NLRP3 inflammasome, play an important role in the long-term effects. Future studies should focus on interventions/agents with robust preclinical data and should recruit patients who truly have the potential to benefit from further cardioprotection. Here we focus on the main mechanisms and targets of cardioprotection during remote conditioning and their alteration by one of the most common co-morbidities, namely diabetes, in which microvascular lesions and inflammatory processes play extremely important roles.

Does remote ischaemic conditioning reduce inflammation? A focus on innate immunity and cytokine response

The benefits of remote ischaemic conditioning (RIC) have been difficult to translate to humans, when considering traditional outcome measures, such as mortality and heart failure. This paper reviews the recent literature of the anti-inflammatory effects of RIC, with a particular focus on the innate immune response and cytokine inhibition. Given the current COVID-19 pandemic, the inflammatory hypothesis of cardiac protection is an attractive target on which to re-purpose such novel therapies. A PubMed/MEDLINE™ search was performed on July 13th 2020, for the key terms RIC, cytokines, the innate immune system and inflammation. Data suggest that RIC attenuates inflammation in animals by immune conditioning, cytokine inhibition, cell survival and the release of anti-inflammatory exosomes. It is proposed that RIC inhibits cytokine release via a reduction in nuclear factor kappa beta (NF-κB)-mediated NLRP3 inflammasome production. In vivo, RIC attenuates pro-inflammatory cytokine release in myocardial/cerebral infarction and LPS models of endotoxaemia. In the latter group, cytokine inhibition is associated with a profound survival benefit. Further clinical trials should establish whether the benefits of RIC in inflammation can be observed in humans. Moreover, we must consider whether uncomplicated MI and elective surgery are the most suitable clinical conditions in which to test this hypothesis.

Papaverine Perfusion via the Aortic Root before Heart Re-beating Alleviates Myocardial Injury after Heart Valve Replacement

AIM

Myocardial injury is inevitable during cardiac surgical procedures and reducing myocardial injury in patients with CPB surgery is the focus of current research. Papaverine is accepted as an ideal coronary vasodilator. This study was to estimate the effect of papaverine perfusion via the aortic root before heart re-beating on patients undergoing heart valve replacement.

METHODS

All the patients enrolled in this study were admitted during 2013-2015. The basic clinical characteristics of the patients preoperative, intraoperative, and postoperative were compared. The immunochemistry assays and enzyme-linked immunosorbent assay (ELISA) were performed to assess the serum biomarkers. Western blot and immunohistochemistry (IHC) were undertaken to detect the expression of associated proteins.

RESULTS

Patients receiving papaverine perfusion via the aortic root before heart re-beating during heart valve replacement surgery under CPB showed less extracorporeal circulation time and CPB time, higher automatic heartbeat recovery rate, less mechanical ventilation time, shorter ICU and in-hospital stay, less leak of cTnI and CK-MB, and weaker inflammatory response than the patients in control group. In addition, the protein expression of IL-6/8/10 and TNF-α was reduced by the perfusion of papaverine. The IHC staining for NFκB was depressed in papaverine group.

CONCLUSION

Papaverine perfusion presented positive effect during valve replacement; this cardioprotective effect may be associated with inhibition of inflammatory response and NF-κB. These findings provided new clues for reduction of myocardial injury during cardiac surgery.

Remote ischemic preconditioning reduces myocardial ischemia-reperfusion injury through unacylated ghrelin-induced activation of the JAK/STAT pathway

Remote ischemic preconditioning (RIPC) offers cardioprotection against myocardial ischemia-reperfusion injury. The humoral factors involved in RIPC that are released from parasympathetically innervated organs have not been identified. Previous studies showed that ghrelin, a hormone released from the stomach, is associated with cardioprotection. However, it is unknown whether or not ghrelin is involved in the mechanism of RIPC. This study aimed to determine whether ghrelin serves as one of the humoral factors in RIPC. RIPC group rats were subjected to three cycles of ischemia and reperfusion for 5 min in two limbs before left anterior descending (LAD) coronary artery ligation. Unacylated ghrelin (UAG) group rats were given 0.5 mcg/kg UAG intravenously 30 min before LAD ligation. Plasma levels of UAG in all groups were measured before and after RIPC procedures and UAG administration. Additionally, JAK2/STAT3 pathway inhibitor (AG490) was injected in RIPC and UAG groups to investigate abolishment of the cardioprotection of RIPC and UAG. Plasma levels of UAG, infarct size and phosphorylation of STAT3 were compared in all groups. Infarct size was significantly reduced in RIPC and UAG groups, compared to the other groups. Plasma levels of UAG in RIPC and UAG groups were significantly increased after RIPC and UAG administration, respectively. The cardioprotective effects of RIPC and UAG were accompanied by an increase in phosphorylation of STAT3 and abolished by AG490. This study indicated that RIPC reduces myocardial ischemia and reperfusion injury through UAG-induced activation of JAK/STAT pathway. UAG may be one of the humoral factors involved in the cardioprotective effects of RIPC.

Protective effect of renal ischemic postconditioning in renal ischemic-reperfusion injury

Background

Renal ischemic postconditioning (RIPo) can protect the kidney from renal ischemia/reperfusion injury (RIRI). However, the underlying molecular mechanisms for RIPo in renal protection remained elusive. This study aimed to investigate the renoprotective effects of RIPo in an RIR rat model.

Method

The Sprague Dawley (SD) rats were randomly divided into three groups respectively: sham group, the RIRI group and the RIPo group. The levels of proteinuria, blood urea nitrogen (BUN), creatinine (Cr), malondialdehyde (MDA), superoxide dismutase (SOD), lactate dehydrogenase (LDH), reactive oxidative species (ROS), interleukins (IL)-6, IL-1β, and IL-18 were measured by ELISA. Apoptotic cells and caspase-3 positive cells were detected by TUNEL assay and immunohistochemistry, respectively. The protein expressive levels of caspase-3, caspase-9, ATG8, Beclin1, p62, LC3-II, P-P13K, P-AKT and P-mTOR were detected by western blot.

Results

Our results showed that pretreatment with RIPo significantly reduced ischemic pathological and morphological changes. The levels of proteinuria, BUN, and Cr were also significantly reduced by RIPo pretreatment. Besides, ATG8, LC3-II and Beclin-1 were upregulated in the RIPo group, but p62 was downregulated. Moreover, RIPo pretreatment resulted in higher levels of phosphorylated PI3K, Akt, and mTOR. These results showed that RIPo protects the kidneys of rats from IRI with suppressed apoptosis and activated autophagy. Mechanically, the activated PI3K/AKT/mTOR signaling pathway were activated.

Conclusions

Collectively, our data demonstrated that RIPo could suppress Inflammatory response, oxidative stress, apoptosis and induce autophagy as well as activate the PI3K/AKT/mTOR pathway, which may play an important role in renal protection against RIRI.

Galanthamine improves myocardial ischemia-reperfusion-induced cardiac dysfunction, endoplasmic reticulum stress-related apoptosis, and myocardial fibrosis by suppressing AMPK/Nrf2 pathway in rats

Background

Myocardial ischemia/reperfusion (I/R) injury is an important cause of myocardial infarction and heart failure after cardiovascular surgery. Galanthamine (Gal) is an important Amaryllidaceae alkaloid with anti-acetylcholinesterase and anti-inflammatory activity. The purpose of this study was to investigate the role of Gal in myocardial I/R injury.

Methods

In this study, an animal model of myocardial I/R injury was constructed, and the rats were divided into five groups (n=10): the sham, I/R model, I/R + Gal (1 mg/kg), I/R + Gal (3 mg/kg), and I/R + Aspirin (20 mg/kg) groups. The expression of related proteins was detected by Western blotting and Immunohistochemistry, and Histological lesion was detected by HE staining.

Results

Results showed that Gal improves I/R-induced cardiac dysfunction in rats. Moreover, Gal inhibits I/R-induced endoplasmic reticulum stress (ERS)-related apoptosis by suppressing the expression of CHOP, Cleaved caspase 12, and caspase 3, and promoting the expression of CADD34 and BiP in rats. Furthermore, Gal mitigates I/R-induced myocardial fibrosis through restraining the expression of α-SMA and Collagen I in rats. Mechanically, Gal promoted the expression of AMPKα1, Nrf2 and HO-1. However, AMPK inhibitor Compound C exhibited the opposite effects. Collectively, this finding suggests that Gal improves I/R-induced cardiac dysfunction, ERS-related apoptosis, and myocardial fibrosis by activating AMPK/Nrf2 pathway in myocardial I/R rats.

Conclusions

Given this evidence, Gal may be a potential therapeutic drug for the treatment of I/R injury.

Acute and chronic remote ischemic conditioning attenuate septic cardiomyopathy, improve cardiac output, protect systemic organs, and improve mortality in a lipopolysaccharide-induced sepsis model

Remote ischemic conditioning (RIC) is acutely cardioprotective in ischemia-reperfusion injury. We aimed to evaluate the effect of RIC on septic cardiomyopathy and associated multi-organ failure in a lipopolysaccharide (LPS)-induced sepsis mouse model. Balb/c mice were divided into sham, LPS, and LPS + RIC groups. LPS 10 mg/kg or saline control was injected intraperitoneally. RIC was performed by four cycles of 5 min ischemia and 5 min reperfusion of the left lower limb just before the LPS injection. Cardiac function on echocardiography, circulating mediators, blood biochemistry, and MAPK signalling was assessed. Survival 7 days after LPS injection was evaluated in sham-treated, RIC, and daily repeated RIC groups. An LPS-induced decrease in cardiac output was ameliorated by RIC with preserved left ventricular systolic function. LPS-induced increases in TNF-α, IL-1β, IL-6, and high-mobility group box 1 protein (HMGB1) were significantly suppressed by RIC. RIC also suppressed increases in plasma cardiac troponin I, aspartate transaminase, alanine transaminase, blood urea nitrogen, and creatinine with suppressed ERK and JNK phosphorylation in heart, liver, and kidney tissue. RIC significantly improved survival rate (p = 0.0037). Survival rate in the daily repeated RIC group was 100%, and it was higher than that in the RIC group (p = 0.0088). In summary, RIC reduced circulating and myocardial inflammatory mediators associated with septic cardiomyopathy, and led to improved ventricular function, cardiac output, and survival. Our data also revealed that chronic RIC has additional benefit in terms of mortality in sepsis. While further studies are required, RIC may be a clinically useful tool to ameliorate sepsis-induced cardiomyopathy.

Multitarget Strategies to Reduce Myocardial Ischemia/Reperfusion Injury: JACC Review Topic of the Week

Many treatments have been identified that confer robust cardioprotection in experimental animal models of acute ischemia and reperfusion injury. However, translation of these cardioprotective therapies into the clinical setting of acute myocardial infarction (AMI) for patient benefit has been disappointing. One important reason might be that AMI is multifactorial, causing cardiomyocyte death via multiple mechanisms, as well as affecting other cell types, including platelets, fibroblasts, endothelial and smooth muscle cells, and immune cells. Many cardioprotective strategies act through common end-effectors and may be suboptimal in patients with comorbidities. In this regard, emerging data suggest that optimal cardioprotection may require the combination of additive or synergistic multitarget therapies. This review will present an overview of the state of cardioprotection today and provide a roadmap for how we might progress towards successful clinical use of cardioprotective therapies following AMI, focusing on the rational combination of judiciously selected, multitarget therapies. This paper emerged as part of the discussions of the European Union (EU)-CARDIOPROTECTION Cooperation in Science and Technology (COST) Action, CA16225.

Effect of Autophagy Inhibition on the Protection of Ischemia Preconditioning against Myocardial Ischemia/Reperfusion Injury in Diabetic Rats

BACKGROUND

Ischemia preconditioning (IPC) remains the most powerful intervention of protection against myocardial ischemia/reperfusion injury (IRI), but diabetes can weaken or eliminate its cardioprotective effect and detailed mechanisms remain unclear. In this study, we aimed to explore whether changes of autophagy in the diabetic condition are attributable to the decreased cardioprotective effect of IPC.

METHODS

Sixty diabetic male Sprague-Dawley rats were randomly divided into the control (C), IRI, rapamycin (R), wortmannin (W), rapamycin + IPC (R + IPC), and wortmannin + IPC (W + IPC) groups. The in vivo rat model of myocardial IRI was established by ligaturing and opening the left anterior descending coronary artery via the left thoracotomy. Durations of ischemia and reperfusion are 30 min and 120 min, respectively. Blood samples were taken at 120 min of reperfusion for measuring serum concentrations of troponin I (TnI) and creatine kinase isoenzyme MB (CK-MB) using the enzyme-linked immunosorbent assay. The infarct size was assessed by Evans blue and triphenyltetrazolium chloride staining. The expressions of LC3-II, beclin-1, phosphoinositide 3-kinase (PI3K), mammalian target of rapamycin (mTOR), and P-Akt/Akt ratio in the ischemic myocardium were assessed by Western blotting.

RESULTS

Compared to the IRI group, infarct size (56.1% ± 6.1% vs. 75.4 ± 7.1%, P < 0.05), serum cTnI (0.61 ± 0.21 vs. 0.95 ± 0.26 ng/ml, P < 0.05), and CK-MB levels (6.70 ± 1.25 vs. 11.51 ± 2.35 ng/ml, P < 0.05) obviously decreased in the W + IPC group. Compared with the C group, myocardial expressions of LC3-II (0.46 ± 0.04 and 0.56 ± 0.04 vs. 0.36 ± 0.04, P < 0.05) and beclin-1 (0.34 ± 0.08 and 0.38 ± 0.07 vs. 0.24 ± 0.03, P < 0.05) evidently increased, and myocardial expressions of mTOR (0.26 ± 0.08 and 0.25 ± 0.07 vs. 0.38 ± 0.06, P < 0.05), PI3K (0.29 ± 0.04 and 0.30 ± 0.03 vs. 0.38 ± 0.02, P < 0.05), and P-Akt/Akt ratio (0.49 ± 0.10 and 0.48 ± 0.06 vs. 0.72 ± 0.07, P < 0.05) markedly decreased in the IRI and R groups, indicating an increased autophagy. Compared with the IRI group, myocardial expression of beclin-1 (0.26 ± 0.03 vs. 0.34 ± 0.08, P < 0.05) significantly decreased, and myocardial expressions of mTOR (0.36 ± 0.04 vs. 0.26 ± 0.08, P < 0.05), PI3K (0.37 ± 0.03 vs. 0.29 ± 0.04, P < 0.05), and P-Akt/Akt ratio (0.68 ± 0.05 vs. 0.49 ± 0.10, P < 0.05) increased obviously in the W + IPC group, indicating a decreased autophagy.

CONCLUSIONS

Increased autophagy in the diabetic myocardium is attributable to decreased cardioprotection of IPC, and autophagy inhibited by activating the PI3K-Akt-mTOR signaling pathway can result in an improved protection of IPC against diabetic myocardial IRI.

Vagus nerve stimulation exerts cardioprotection against myocardial ischemia/reperfusion injury predominantly through its efferent vagal fibers

Vagus nerve stimulation (VNS) has been shown to exert cardioprotection against myocardial ischemia/reperfusion (I/R) injury. However, whether the cardioprotection of VNS is mainly due to direct activation through its ipsilateral efferent fibers (motor) rather than indirect effects mediated by the afferent fibers (sensory) have not been clearly understood. We hypothesized that VNS exerts cardioprotection predominantly through its efferent vagal fibers. Thirty swine (30-35 kg) were randomized into five groups: I/R no VNS (I/R), and left mid-cervical VNS with both vagal trunks intact (LC-VNS), with left vagus nerve transection (LtVNX), with right vagus nerve transection (RtVNX) and with atropine pretreatment (Atropine), respectively. VNS was applied at the onset of ischemia (60 min) and continued until the end of reperfusion (120 min). Cardiac function, infarct size, arrhythmia score, myocardial connexin43 expression, apoptotic markers, oxidative stress markers, inflammatory markers (TNF-α and IL-10) and cardiac mitochondrial function, dynamics and fatty acid oxidation (MFN2, OPA1, DRP1, PGC1α and CPT1) were determined. LC-VNS exerted cardioprotection against myocardial I/R injury via improvement of mitochondrial function and dynamics and shifted cardiac fatty acid metabolism toward beta oxidation. However, LC-VNS and LtVNX, both efferent vagal fibers are intact, produced more profound cardioprotection, particularly infarct size reduction, decreased arrhythmia score, oxidative stress and apoptosis and attenuated mitochondrial dysfunction compared to RtVNX. These beneficial effects of VNS were abolished by atropine. Our findings suggest that selective efferent VNS may potentially be effective in attenuating myocardial I/R injury. Moreover, VNS required the contralateral efferent vagal activities to fully provide its cardioprotection.

Synthetic CpG oligonucleotides induce a genetic profile ameliorating murine myocardial I/R injury

We previously demonstrated that pre‐conditioning with CpG oligonucleotide (ODN) 1668 induces quick up‐regulation of gene expression 3 hours post‐murine myocardial ischaemia/reperfusion (I/R) injury, terminating inflammatory processes that sustain I/R injury. Now, performing comprehensive microarray and biocomputational analyses, we sought to further enlighten the “black box” beyond these first 3 hours. C57BL/6 mice were pretreated with either CpG 1668 or with control ODN 1612, respectively. Sixteen hours later, myocardial ischaemia was induced for 1 hour in a closed‐chest model, followed by reperfusion for 24 hours. RNA was extracted from hearts, and labelled cDNA was hybridized to gene microarrays. Data analysis was performed with BRB ArrayTools and Ingenuity Pathway Analysis. Functional groups mediating restoration of cellular integrity were among the top up‐regulated categories. Genes known to influence cardiomyocyte survival were strongly induced 24 hours post‐I/R. In contrast, proinflammatory pathways were down‐regulated. Interleukin‐10, an upstream regulator, suppressed specifically selected proinflammatory target genes at 24 hours compared to 3 hours post‐I/R. The IL1 complex is supposed to be one regulator of a network increasing cardiovascular angiogenesis. The up‐regulation of numerous protective pathways and the suppression of proinflammatory activity are supposed to be the genetic correlate of the cardioprotective effects of CpG 1668 pre‐conditioning.