Emulsified isoflurane postconditioning improves survival and neurological outcomes in a rat model of cardiac arrest

Targeting Neuronal GPR65 With Delayed BTB09089 Treatment Improves Neurorehabilitation Following Ischemic Stroke

BACKGROUND

GPR65 (G protein-coupled receptor 65) can sense extracellular acidic environment to regulate pathophysiological processes. Pretreatment with the GPR65 agonist BTB09089 has been proven to produce neuroprotection in acute ischemic stroke. However, whether delayed BTB09089 treatment and neuronal GPR65 activation promote neurorestoration remains unknown.

METHODS

Ischemic stroke was induced in wild-type (WT) or GPR65 knockout (GPR65-/-) mice by photothrombotic ischemia. Male mice were injected intraperitoneally with BTB09089 every other day at days 3, 7, or 14 poststroke. AAV-Syn-GPR65 (adenoassociated virus-synapsin-GPR65) was utilized to overexpress GPR65 in the peri-infarct cortical neurons of GPR65-/- and WT mice. Motor function was monitored by grid-walk and cylinder tests. The neurorestorative effects of BTB09089 were observed by immunohistochemistry, Golgi-Cox staining, and Western blotting.

RESULTS

BTB09089 significantly promoted motor outcomes in WT but not in GPR65-/- mice, even when BTB09089 was delayed for 3 to 7 days. BTB09089 inhibited the activation of microglia and glial scar progression in WT but not in GPR65-/- mice. Meanwhile, BTB09089 reduced the decrease in neuronal density in WT mice, but this benefit was abolished in GPR65-/- mice and reemerged by overexpressing GPR65 in peri-infarct cortical neurons. Furthermore, BTB09089 increased the GAP43 (growth-associated protein-43) and synaptophysin puncta density, dendritic spine density, dendritic branch length, and dendritic complexity by overexpressing GPR65 in the peri-infarct cortical neurons of GPR65-/- mice, which was accompanied by increased levels of p-CREB (phosphorylated cAMP-responsive element-binding protein). In addition, the therapeutic window of BTB09089 was extended to day 14 by overexpressing GPR65 in the peri-infarct cortical neurons of WT mice.

CONCLUSIONS

Our findings indicated that delayed BTB09089 treatment improved neurological functional recovery and brain tissue repair poststroke through activating neuronal GRP65. GPR65 overexpression may be a potential strategy to expand the therapeutic time window of GPR65 agonists for neurorehabilitation after ischemic stroke.

Isoflurane Preconditioning Alleviates Hypoxia/Reoxygenation-Induced Cardiomyocyte Injury by Inhibiting miR-195-3p Expression

To investigate the role of microRNA-195-3p (miR-195-3p) in hypoxia/reoxygenation (H/R)-induced cardiomyocyte injury. AC16 human cardiomyocyte cells were cultured and pretreated with different concentrations of isoflurane (ISO) (1%, 2%, and 3%), followed by 6 h each of hypoxia and reoxygenation to construct H/R cell models. The optimum ISO concentration was assessed based on the cell viability. miR-195-3p expression was regulated by in vitro cell transfection. Cell viability was determined by MTT assay, and apoptosis was evaluated by flow cytometry. The levels of myocardial injury and inflammation were determined by enzyme-linked immunosorbent assay. Compared with the control group, the cell viability of the H/R group had significantly decreased and that of ISO pretreatment had increased in a dose-dependent manner. Therefore, we selected a 2% ISO concentration for pretreatment. MiR-195-3p expression had significantly increased in the H/R group and decreased after 2% ISO pretreatment. Additionally, the number of apoptotic cells and the levels of lactate dehydrogenase, creatine kinase-myoglobin binding, cardiac troponin I, interleukin (IL)-1β, IL-6, and tumor necrosis factor-α had increased significantly. ISO preconditioning inhibited H/R-induced AC16 cell damage, whereas miR-195-3p overexpression reversed the protective effects of ISO on cardiomyocytes. The expression of phosphatase and tensin homolog deleted on chromosome 10 (PTEN) was reduced in the H/R-induced AC16 cells, and PTEN is a downstream target gene of miR-195-3p. Preconditioning with 2% ISO plays a protective role in H/R-induced AC16 cell damage by inhibiting miR-195-3p expression.

Rat model of asphyxia-induced cardiac arrest and resuscitation

Neurologic injury after cardiopulmonary resuscitation is the main cause of the low survival rate and poor quality of life among patients who have experienced cardiac arrest. In the United States, as the American Heart Association reported, emergency medical services respond to more than 347,000 adults and more than 7,000 children with out-of-hospital cardiac arrest each year. In-hospital cardiac arrest is estimated to occur in 9.7 per 1,000 adult cardiac arrests and 2.7 pediatric events per 1,000 hospitalizations. Yet the pathophysiological mechanisms of this injury remain unclear. Experimental animal models are valuable for exploring the etiologies and mechanisms of diseases and their interventions. In this review, we summarize how to establish a standardized rat model of asphyxia-induced cardiac arrest. There are four key focal areas: (1) selection of animal species; (2) factors to consider during modeling; (3) intervention management after return of spontaneous circulation; and (4) evaluation of neurologic function. The aim was to simplify a complex animal model, toward clarifying cardiac arrest pathophysiological processes. It also aimed to help standardize model establishment, toward facilitating experiment homogenization, convenient interexperimental comparisons, and translation of experimental results to clinical application.

The Effects of Volatile Anesthetics on Lung Ischemia-Reperfusion Injury: Basic to Clinical Studies

Case reports from as early as the 1970s have shown that intravenous injection of even a small dose of volatile anesthetics result in fatal lung injury. Direct contact between volatile anesthetics and pulmonary vasculature triggers chemical damage in the vessel walls. A wide variety of factors are involved in lung ischemia-reperfusion injury (LIRI), such as pulmonary endothelial cells, alveolar epithelial cells, alveolar macrophages, neutrophils, mast cells, platelets, proinflammatory cytokines, and surfactant. With a constellation of factors involved, the assessment of the protective effect of volatile anesthetics in LIRI is difficult. Multiple animal studies have reported that with regards to LIRI, sevoflurane demonstrates an anti-inflammatory effect in immunocompetent cells and an anti-apoptotic effect on lung tissue. Scattered studies have dismissed a protective effect of desflurane against LIRI. While a single-center randomized controlled trial (RCT) found that volatile anesthetics including desflurane demonstrated a lung-protective effect in thoracic surgery, a multicenter RCT did not demonstrate a lung-protective effect of desflurane. LIRI is common in lung transplantation. One study, although limited due to its small sample size, found that the use of volatile anesthetics in organ procurement surgery involving "death by neurologic criteria" donors did not improve lung graft survival. Future studies on the protective effect of volatile anesthetics against LIRI must examine not only the mechanism of the protective effect but also differences in the effects of different types of volatile anesthetics, their optimal dosage, and the appropriateness of their use in the event of marked alveolar capillary barrier damage.

Ischemic Conditioning and neonatal hypoxic ischemic encephalopathy: a literature review

Hypoxic Ischemic Encephalopathy (HIE) is the result of severe anoxic brain injury during the neonatal period and causes life-long morbidity and premature mortality. Currently, therapeutic hypothermia immediately after birth is the standard of care for clinically relevant HIE. However, therapeutic hypothermia alone does not provide complete neuroprotection and there is an urgent need for adjunctive therapies. Ischemic conditioning is an adaptive process of endogenous protection in which small doses of sub-lethal ischemia can provide a protection against a lethal ischemic event. Remote Ischemic Post-conditioning (RIPC), a form of ischemic conditioning, is highly translatable for HIE diagnosed immediately after birth as the conditioned ischemic stimulus is applied at the limb after the lethal ischemic episode. A number of studies in neonatal rats have demonstrated that RIPC is effective at reducing injury in focal cerebral ischemia models and improves neurological outcomes. In this review, we focus on the available data on HIE and its current treatment, models in HIE studies, ischemic conditioning/RIPC and its mechanism. We discuss in particular the effect of RIPC on neonatal brain with HIE. We postulate that combining RIPC with standard therapeutic hypothermia can be an attractive therapeutic approach for HIE.