The Effects of Pharmacological Hypothermia Induced by Neurotensin Receptor Agonist ABS 201 on Outcomes of CPR

Selective Brain Cooling: A New Horizon of Neuroprotection

Therapeutic hypothermia (TH), which prevents irreversible neuronal necrosis and ischemic brain damage, has been proven effective for preventing ischemia-reperfusion injury in post-cardiac arrest syndrome and neonatal encephalopathy in both animal studies and clinical trials. However, lowering the whole-body temperature below 34°C can lead to severe systemic complications such as cardiac, hematologic, immunologic, and metabolic side effects. Although the brain accounts for only 2% of the total body weight, it consumes 20% of the body's total energy at rest and requires a continuous supply of glucose and oxygen to maintain function and structural integrity. As such, theoretically, temperature-controlled selective brain cooling (SBC) may be more beneficial for brain ischemia than systemic pan-ischemia. Various SBC methods have been introduced to selectively cool the brain while minimizing systemic TH-related complications. However, technical setbacks of conventional SBCs, such as insufficient cooling power and relatively expensive coolant and/or irritating effects on skin or mucosal interfaces, limit its application to various clinical settings. This review aimed to integrate current literature on SBC modalities with promising therapeutic potential. Further, future directions were discussed by exploring studies on interesting coping skills in response to environmental or stress-induced hyperthermia among wild animals, including mammals and birds.

Cerebral and myocardial mitochondrial injury differ in a rat model of cardiac arrest and cardiopulmonary resuscitation

Brain mitochondria are more sensitive to global ischemia compared to heart mitochondria. Complex I in the electron transport chain (ETC) is sensitive to ischemic injury and is a major control point of the rate of ADP stimulated oxygen consumption. The purpose of this study was to explore whether changes in cerebral and myocardial mitochondria differ after cardiac arrest. Animals were randomized into 4 groups (n = 6): 1) Sham 2) VF 3) VF+CPR 4) ROSC 1hr. Ventricular Fibrillation (VF) was induced through a guide wire advanced from the right jugular vein into the ventricle and untreated for 8 min. Resuscitation was attempted with a 4J defibrillation after 8 min of cardiopulmonary resuscitation (CPR). Brain mitochondria and cardiac mitochondrial subpopulations were isolated. Calcium retention capacity was measured to assess susceptibility to mitochondrial permeability transition pore opening. ADP stimulated oxygen consumption and ETC activity assays were performed. Brain mitochondria are far more sensitive to injury during cardiac arrest and resuscitation compared to cardiac mitochondria. Complex I is highly sensitive to injury in brain mitochondria. With markedly decreased calcium retention capacity, mitochondria contribute to cerebral reperfusion injury. Therapeutic preservation of cerebral mitochondrial activity and mitochondrial function during cardiac arrest may improve post-resuscitation neurologic function.

Targeted temperature management and early neuro-prognostication after cardiac arrest

Targeted temperature management (TTM) is a recommended neuroprotective intervention for coma after out-of-hospital cardiac arrest (OHCA). However, controversies exist concerning the proper implementation and overall efficacy of post-CA TTM, particularly related to optimal timing and depth of TTM and cooling methods. A review of the literature finds that optimizing and individualizing TTM remains an open question requiring further clinical investigation. This paper will summarize the preclinical and clinical trial data to-date, current recommendations, and future directions of this therapy, including new cooling methods under investigation. For now, early induction, maintenance for at least 24 hours, and slow rewarming utilizing endovascular methods may be preferred. Moreover, timely and accurate neuro-prognostication is valuable for guiding ethical and cost-effective management of post-CA coma. Current evidence for early neuro-prognostication after TTM suggests that a combination of initial prediction models, biomarkers, neuroimaging, and electrophysiological methods is the optimal strategy in predicting neurological functional outcomes.

Comparison of the Protective Effect of Different Mild Therapeutic Hypothermia Temperatures on Intestinal Injury After Cardiopulmonary Resuscitation in Rats

BACKGROUND

Therapeutic temperature management (TTM) is the standard treatment protocol for unconscious post-resuscitation patients. However, there is still controversy about the ideal targeted temperature of mild hypothermia therapy. Additionally, studies about protective therapy for post-resuscitation intestinal injury are very limited. Therefore, this study was performed to explore: whether mild hypothermia therapy can exert a protective effect on post-resuscitation intestinal injury; the protective effect of different targeted temperatures on post-resuscitation intestinal injury and the ideal targeted temperature; the potential protective mechanism of mild hypothermia therapy for post-resuscitation intestinal injury.

METHODS

Ventricular fibrillation was electrically induced and untreated for 6 min while defibrillation was attempted after 8 min of cardiopulmonary resuscitation in 15 rats. After successful resuscitation, animals were randomized into three groups: control; TTM-35; TTM-33. In animals of the control group, temperature was maintained at 37 ± 0.2°C for 6 h. In animals of the two TTM groups, temperature was maintained at 33 ± 0.2°C or 35 ± 0.2°C for 6 h, respectively. During mild hypothermia therapy, intestinal microcirculation was measured at 60, 240, and 360 min after resuscitation. Animals were euthanized 6.5 h after resuscitation. The morphological changes in the intestinal tissue, systemic and local inflammatory factors, and intestinal injury markers were measured and analyzed. The tight junction proteins in the intestinal epithelium, cell-cell contact protein E-cadherin expression, myosin light chain (MLC) and myosin light chain kinase levels, and the NF-κB p65 signaling pathway were analyzed by western blotting.

RESULTS

Compared with results in the control group, mild hypothermia therapy (TTM-33 and TTM-35 groups) significantly improved post-resuscitation intestinal microcirculation and pathological scores, decreased systemic and local intestinal tissue inflammatory factor levels, inhibited the NF-κB signaling pathway and downstream MLC phosphorylation, and significantly decreased MLC phosphorylation-associated loss of intestinal tight junction proteins and E-cadherin (P < 0.05). A 33°C target temperature could exert more protective effects than 35°C on post-resuscitation intestinal injury, such as improving intestinal microcirculation, decreasing intestinal ischemia factor iFABP, and plasma endotoxin levels, inhibiting the NF-κB signaling pathway and downstream MLC phosphorylation, and suppressing the loss of intestinal tight junctions and E-cadherin (P < 0.05).

CONCLUSIONS

Mild hypothermia therapy can improve post-resuscitation intestinal injury, and a targeted temperature of 33°C may confer more benefit for mitigation of intestinal injury as compared with a targeted temperature of 35°C.

Therapeutic approaches targeting the neurotensin receptors

Introduction: Neurotensin is a gut-brain peptide hormone, a 13 amino acid neuropeptide found in the central nervous system and in the GI tract. The neurotensinergic system is implicated in various physiological and pathological processes related to neuropsychiatric and metabolic machineries, cancer growth, food, and drug intake. NT mediates its functions through its two G protein-coupled receptors: neurotensin receptor 1 (NTS1/NTSR1) and neurotensin receptor 2 (NTS2/NTSR2). Over the past decade, the role of NTS3/NTSR3/sortilin has also gained importance in human pathologies. Several approaches have appeared dealing with the discovery of compounds able to modulate the functions of this neuropeptide through its receptors for therapeutic gain.Areas covered: The article provides an overview of over four decades of research and details the drug discovery approaches and patented strategies targeting NTSR in the past decade.Expert opinion: Neurotensin is an important neurotransmitter that enables crosstalk with various neurotransmitter and neuroendocrine systems. While significant efforts have been made that have led to selective agonists and antagonists with promising in vitro and in vivo activities, the therapeutic potential of compounds targeting the neurotensinergic system is still to be fully harnessed for successful clinical translation of compounds for the treatment of several pathologies.