Per- and post-remote ischemic conditioning attenuates ischemic brain injury via inhibition of the TLR4/MyD88 signaling pathway in aged rats

The potential mechanism and clinical application value of remote ischemic conditioning in stroke

Some studies have confirmed the neuroprotective effect of remote ischemic conditioning against stroke. Although numerous animal researches have shown that the neuroprotective effect of remote ischemic conditioning may be related to neuroinflammation, cellular immunity, apoptosis, and autophagy, the exact underlying molecular mechanisms are unclear. This review summarizes the current status of different types of remote ischemic conditioning methods in animal and clinical studies and analyzes their commonalities and differences in neuroprotective mechanisms and signaling pathways. Remote ischemic conditioning has emerged as a potential therapeutic approach for improving stroke-induced brain injury owing to its simplicity, non-invasiveness, safety, and patient tolerability. Different forms of remote ischemic conditioning exhibit distinct intervention patterns, timing, and application range. Mechanistically, remote ischemic conditioning can exert neuroprotective effects by activating the Notch1/phosphatidylinositol 3-kinase/Akt signaling pathway, improving cerebral perfusion, suppressing neuroinflammation, inhibiting cell apoptosis, activating autophagy, and promoting neural regeneration. While remote ischemic conditioning has shown potential in improving stroke outcomes, its full clinical translation has not yet been achieved.

Remote limb ischemic preconditioning alleviated spinal cord injury through inhibiting proinflammatory immune response and promoting the survival of spinal neurons

STUDY DESIGN

Experimental animal study.

OBJECTIVES

To investigate the protective effect of remote limb ischemia preconditioning (RLPreC) on traumatic spinal cord injury (SCI) and explore the underlying biological mechanisms using RNA sequencing.

SETTING

China Rehabilitation Science Institute; Beijing; China.

METHODS

spinal cord injury was induced in mice using a force of 0.7 N. RLPreC treatment was administered. Motor function, pain behavior, and gene expression were assessed.

RESULTS

RLPreC treatment significantly improved motor function and reduced pain-like behavior in SCI mice. RNA-Seq analysis identified 5247 differentially expressed genes (DEGs). GO analysis revealed enrichment of immune response, inflammatory signaling, and synaptic transmission pathways among these DEGs. KEGG analysis indicated suppression of inflammation and promotion of synapse-related pathways.

CONCLUSIONS

RLPreC is a promising therapeutic strategy for improving motor function and alleviating pain after traumatic SCI. RNA-Seq analysis provides insights into potential therapeutic targets and warrants further investigation.

Remote ischemic conditioning slows blood-retinal barrier damage in type 1 diabetic rats

Diabetic retinopathy (DR) is one of the major complications of diabetes and can cause severe visual impairment. Blood-retina barrier (BRB) destruction resulted from chronic hyperglycemia underlines its major pathological process. However, current treatments have limited efficacy and may even cause serious complications. Remote ischemic conditioning (RIC), through repeated transient mechanical occlusion of limb blood vessels, has been confirmed to promote blood-brain barrier integrity after stroke, but its role in BRB disruption has not been elucidated. This study aimed to investigate the protective effects of RIC on the BRB in diabetic rats and its potential mechanisms. 48 Sprague-Dawley rats were randomly assigned to the Sham group, Sham + RIC group, diabetes mellitus (DM) group and DM+RIC group. The diabetic model was successfully induced by intraperitoneal injection of streptozotocin. RIC treatment was administered daily and lasted for 9 weeks. In functional analysis, RIC improved the retinal function based on electroretinogram data and reduced the leakage of BRB in diabetic rats. In proteomic analysis, tight junction pathway was enriched after RIC treatment, in which Patj gene was significantly increased. We also found that RIC increased mRNA levels of Patj, claudin-1 and zonula occludens (ZO)-1, protein expression of claudin-1 when compared with diabetic models. In conclusion, RIC slowed BRB damage in diabetic rats, which may be related to the preservation of tight junction proteins. RIC may be a promising protective strategy for the treatment of DR.

Age and efficacy of remote ischemic conditioning in acute ischemic stroke

AIMS

A post hoc analysis of RICAMIS trial to evaluate functional outcomes in relation to patient age.

METHODS

Patients in RICAMIS were divided into six age groups. The primary outcome was excellent functional outcome at 90 days, defined as modified Rankin Scale (mRS) score of 0-1. Compared with patients receiving usual care alone, we investigated the association of remote ischemic conditioning (RIC) effect with functional outcomes in each group and the interaction between RIC effect and age.

RESULTS

Of 1776 patients, 498 were assigned to <60 years, 326 to 60 to <65 years, 325 to 65 to <70 years, 278 to 70 to <75 years, 206 to 75 to <80 years, and 143 to ≥80 years. Higher proportions of primary outcome were found associated with RIC in <60 years group (72.6% vs. 64.8%; adjusted risk difference [RD], 6.8%; 95% CI, -1.6% to 15.1%; p = 0.11), 60 to <65 years group (70.7% vs. 67.1%; adjusted RD, 3.1%; 95% CI, -7.2% to 13.3%; p = 0.56), 65 to <70 years group (70.5% vs. 63.6%; adjusted RD, 3.5%; 95% CI, -6.8% to 13.8%; p = 0.51), 70 to <75 years group (59.7% vs. 54.9%; adjusted RD, 4.7%; 95% CI, -7.1% to 16.4%; p = 0.61), 75 to <80 years group (61.5% vs. 55.9%; adjusted RD, 5.7%; 95% CI, -7.8% to 19.1%; p = 0.41), and ≥ 80 years group (59.2% vs. 59.7%; adjusted RD, -2.6%; 95% CI, -18.8% to 13.5%; p = 0.75). No significant interaction between RIC effect and age was found among groups.

CONCLUSIONS

This is the first report that RIC effect may be attenuated with increasing age in patients with acute moderate ischemic stroke with respect to functional outcome.

Neuroadaptive Biochemical Mechanisms of Remote Ischemic Conditioning

This review summarizes the currently known biochemical neuroadaptive mechanisms of remote ischemic conditioning. In particular, it focuses on the significance of the pro-adaptive effects of remote ischemic conditioning which allow for the prevention of the neurological and cognitive impairments associated with hippocampal dysregulation after brain damage. The neuroimmunohumoral pathway transmitting a conditioning stimulus, as well as the molecular basis of the early and delayed phases of neuroprotection, including anti-apoptotic, anti-oxidant, and anti-inflammatory components, are also outlined. Based on the close interplay between the effects of ischemia, especially those mediated by interaction of hypoxia-inducible factors (HIFs) and steroid hormones, the involvement of the hypothalamic-pituitary-adrenocortical system in remote ischemic conditioning is also discussed.

Effect of remote ischemic conditioning on the immune-inflammatory profile in patients with traumatic hemorrhagic shock in a randomized controlled trial

Resuscitation induced ischemia/reperfusion predisposes trauma patients to systemic inflammation and organ dysfunction. We investigated the effect of remote ischemic conditioning (RIC), a treatment shown to prevent ischemia/reperfusion injury in experimental models of hemorrhagic shock/resuscitation, on the systemic immune-inflammatory profile in trauma patients in a randomized trial. We conducted a prospective, single-centre, double-blind, randomized, controlled trial involving trauma patients sustaining blunt or penetrating trauma in hemorrhagic shock admitted to a Level 1 trauma centre. Patients were randomized to receive RIC (four cycles of 5-min pressure cuff inflation at 250 mmHg and deflation on the thigh) or a Sham intervention. The primary outcomes were neutrophil oxidative burst activity, cellular adhesion molecule expression, and plasma levels of myeloperoxidase, cytokines and chemokines in peripheral blood samples, drawn at admission (pre-intervention), 1 h, 3 h, and 24 h post-admission. Secondary outcomes included ventilator, ICU and hospital free days, incidence of nosocomial infections, 24 h and 28 day mortality. 50 eligible patients were randomized; of which 21 in the Sham group and 18 in the RIC group were included in the full analysis. No treatment effect was observed between Sham and RIC groups for neutrophil oxidative burst activity, adhesion molecule expression, and plasma levels of myeloperoxidase and cytokines. RIC prevented significant increases in Th2 chemokines TARC/CCL17 (P < 0.01) and MDC/CCL22 (P < 0.05) at 24 h post-intervention in comparison to the Sham group. Secondary clinical outcomes were not different between groups. No adverse events in relation to the RIC intervention were observed. Administration of RIC was safe and did not adversely affect clinical outcomes. While trauma itself modified several immunoregulatory markers, RIC failed to alter expression of the majority of markers. However, RIC may influence Th2 chemokine expression in the post resuscitation period. Further investigation into the immunomodulatory effects of RIC in traumatic injuries and their impact on clinical outcomes is warranted.ClinicalTrials.gov number: NCT02071290.

The effects of amiodarone in ovarian injury due to oxidative stress and inflammation caused by ischemia-reperfusion

OBJECTIVE

Ovarian ischemia constitutes 2-3% of all gynecological emergencies. New-generation therapeutic agents need to be discovered, in addition to invasive interventions capable of reducing the risk of potential ovarian ischemia to a minimum and protecting against potential adverse outcomes.

AIMS

To investigate the effects of amiodarone (AMD) on ischemia-reperfusion-induced oxidative stress and inflammation-induced ovarian damage.

METHODS

The control group, received intraperitoneal (i.p.) injection of saline solution. The ischemia group (I-Group), was subjected to ischemia-induced injury without drug administration. The ischemia + AMD (50 mg/kg) group was subjected to ischemia injury and also received i.p. 50 mg/kg AMD prior to induction of ovarian ischemia. The ischemia-reperfusion (I/R group) was exposed to ischemia and reperfusion-induced injury without drug administration. The I/R + AMD (50 mg/kg) group underwent I/R injury together with i.p. administration of 50 mg/kg AMD prior to induction of ovarian I/R. The Sham + AMD group received intraperitoneal (i.p.) injection of 50 mg/kg AMD alone. In this study performed thiobarbituric acid reactive substances (TBARS), thiol (-SH), interleukin 1 Beta (IL-1β), interleukin 6 (IL-6), toll-like receptor 4 (TLR4) and nuclear factor-kappa B(NF-κβ).

RESULTS

Increased oxidative stress and inflammation as a result of ovarian I and I/R application activated the cascade. AMD was not sufficient to reduce the oxidative stress and inflammation. TLR4 and NF-kβ, which were up-regulated by triggering oxidative stress and inflammation, were not regressed by the effects of AMD.

CONCLUSIONS

AMD, used as an antiarrhythmic agent, was found to be insufficient, despite its antioxidant and anti-inflammatory properties, to reduce the experimentally induced ovarian tissue damage.

Remote Ischemic Conditioning in Ischemic Stroke and Myocardial Infarction: Similarities and Differences

Acute myocardial infarction and ischemic stroke are leading causes of morbidity and mortality worldwide. Although reperfusion therapies have greatly improved the outcomes of patients with these conditions, many patients die or are severely disabled despite complete reperfusion. It is therefore important to identify interventions that can prevent progression to ischemic necrosis and limit ischemia-reperfusion injury. A possible strategy is ischemic conditioning, which consists of inducing ischemia – either in the ischemic organ or in another body site [i.e., remote ischemic conditioning (RIC), e.g., by inflating a cuff around the patient's arm or leg]. The effects of ischemic conditioning have been studied, alone or in combination with revascularization techniques. Based on the timing (before, during, or after ischemia), RIC is classified as pre-, per-/peri-, or post-conditioning, respectively. In this review, we first highlight some pathophysiological and clinical similarities and differences between cardiac and cerebral ischemia. We report evidence that RIC reduces circulating biomarkers of myocardial necrosis, infarct size, and edema, although this effect appears not to translate into a better prognosis. We then review cutting-edge applications of RIC for the treatment of ischemic stroke. We also highlight that, although RIC is a safe procedure that can easily be implemented in hospital and pre-hospital settings, its efficacy in patients with ischemic stroke remains to be proven. We then discuss possible methodological issues of previous studies. We finish by highlighting some perspectives for future research, aimed at increasing the efficacy of ischemic conditioning for improving tissue protection and clinical outcomes, and stratifying myocardial infarction and brain ischemia patients to enhance treatment feasibility.