Evidence and opportunities of hypothermia in acute ischemic stroke: Clinical trials of systemic versus selective hypothermia

RBM3 Promotes Anti-inflammatory Responses in Microglia and Serves as a Neuroprotective Target of Ischemic Stroke

Ischemic stroke is a major cause of death and disability in adults. Hypothermic treatment is successful in treating neonatal cerebral ischemia, but its application is restricted in adult patients due to complex management strategies and severe adverse effects. Two homologous RNA-binding proteins, RBM3 and CIRP, are the only known cold-inducible proteins in vertebrates, and their expression levels are robustly elevated by mild to moderate hypothermia. In previous studies, we and others have demonstrated that both RBM3 and CIRP mediate the neuroprotective and neurogenic effects of hypothermia in cell and animal models. However, CIRP can also be detrimental to neurons by triggering neuroinflammatory responses, complicating its post-stroke functions. In this study, we compared the properties of the two cold-inducible RNA-binding proteins after ischemic stroke. Our results indicated that RBM3 expression was stimulated in the ischemic brain of stroke patients, while CIRP expression was not. In an experimental model, RBM3 can ameliorate ischemic-like insult by promoting neuronal survival and eliciting anti-inflammatory responses in activated microglia, while the impact of CIRP was intriguing. Collectively, our data supported the notion that RBM3 may be a more promising therapeutic target than CIRP for treating ischemic stroke. We further demonstrated that zr17-2, a small molecule initially identified to target CIRP, can specifically target RBM3 but not CIRP in microglia. zr17-2 demonstrated anti-inflammatory and neuroprotective effects after ischemic stroke both in vitro and in vivo, suggesting its potential therapeutic value.

Longer Periods of Hypothermia Provide Greater Protection Against Focal Ischemia: A Systematic Review of Animal Studies Manipulating Treatment Duration

Decades of animal research show therapeutic hypothermia (TH) to be potently neuroprotective after cerebral ischemic injuries. While there have been some translational successes, clinical efficacy after ischemic stroke is unclear. One potential reason for translational failures could be insufficient optimization of dosing parameters. In this study, we conducted a systematic review of the PubMed database to identify all preclinical controlled studies that compared multiple TH durations following focal ischemia, with treatment beginning at least 1 hour after ischemic onset. Six studies met our inclusion criteria. In these six studies, six of seven experiments demonstrated an increase in cerebroprotection at the longest duration tested. The average effect size (mean Cohen's d ± 95% confidence interval) at the shortest and longest durations was 0.4 ± 0.3 and 1.9 ± 1.1, respectively. At the longest durations, this corresponded to percent infarct volume reductions between 31.2% and 83.9%. Our analysis counters previous meta-analytic findings that there is no relationship, or an inverse relationship between TH duration and effect size. However, underreporting often led to high or unclear risks of bias for each study as gauged by the SYRCLE Risk of Bias tool. We also found a lack of investigations of the interactions between duration and other treatment considerations (e.g., method, delay, and ischemic severity). With consideration of methodological limitations, an understanding of the relationships between treatment parameters is necessary to determine proper "dosage" of TH, and should be further studied, considering clinical failures that contrast with strong cerebroprotective results in most animal studies.

The effect of inadvertent systemic hypothermia after mechanical thrombectomy in patients with large-vessel occlusion stroke

Background and aims

Postinterventional hypothermia is a frequent complication in patients with large-vessel occlusion strokes (LVOS) after mechanical thrombectomy (MT). This inadvertent hypothermia might potentially have neuroprotective but also adverse effects on patients' outcomes. The aim of the study was to determine the rate of hypothermia in patients with LVOS receiving MT and its influence on functional outcome.

Methods

We performed a monocentric, retrospective study using a prospectively derived databank, including all LVOS patients receiving MT between 2015 and 2021. Predictive values of postinterventional body temperature and body temperature categories (hyperthermia (≥38°C), normothermia (35°C-37.9°C), and hypothermia (<35°C)) on functional outcome were analyzed using multivariable Bayesian logistic regression models. Favorable outcome was defined as modified Rankin Scale (mRS) ≤3.

Results

Of the 480 included LVOS patients with MT (46.0% men; mean ± SD age 73 ± 12.9 years), 5 (1.0%) were hyperthermic, 382 (79.6%) normothermic, and 93 (19.4%) hypothermic. Postinterventional hypothermia was significantly associated with unfavorable functional outcome (mRS > 3) after 90 days (OR 2.06, 95% CI 1.01-4.18, p = 0.045). For short-term functional outcome, patients with hypothermia had a higher discharge NIHSS (OR 1.38, 95% CI 1.06 to 1.79, p = 0.015) and a higher change of NIHSS from admission to discharge (OR 1.35, 95% CI 1.03 to 1.76, p = 0.029).

Conclusion

Approximately a fifth of LVOS patients in this cohort were hypothermic after MT. Hypothermia was an independent predictor of unfavorable functional outcomes. Our findings warrant a prospective trial investigating active warming during MT.

Impact of immediate postrecanalization cooling on outcome in acute ischemic stroke patients with a large ischemic core: prospective cohort study

BACKGROUND

Patients with large acute ischemic strokes (AIS) often have a poor prognosis despite successful recanalization due to multiple factors including reperfusion injury. The authors aim to describe our preliminary experience of endovascular cooling in patients with a large AIS after recanalization.

METHODS

From January 2021 to July 2022, AIS patients presenting with large infarcts (defined as ASPECTS ≤5 on noncontrast CT or ischemic core ≥50 ml on CT perfusion) who achieved successful recanalization after endovascular treatment were analyzed in a prospective registry. Patients were divided into targeted temperature management (TTM) and non-TTM group. Patients in the TTM group received systemic cooling with a targeted core temperature of 33° for at least 48 h. The primary outcome is 90-day favorable outcome [modified Rankin Scale (mRS) 0-2]. The secondary outcomes are 90-day good outcome (mRS 0-3), mortality, intracranial hemorrhage and malignant cerebral edema within 7 days or at discharge.

RESULTS

Forty-four AIS patients were recruited (15 cases in the TTM group and 29 cases in the non-TTM group). The median Alberta Stroke Program Early CT Score (ASPECTS) was 3 (2-5). The median time for hypothermia duration was 84 (71.5-147.6) h. The TTM group had a numerically higher proportion of 90-day favorable outcomes than the non-TTM group (46.7 vs. 27.6%, P=0.210), and no significant difference were found regarding secondary outcomes (all P>0.05). The TTM group had a numerically higher rates of pneumonia (66.7 vs. 58.6%, P=0.604) and deep vein thrombosis (33.3 vs. 13.8%, P=0.138). Shivering occurred in 4/15 (26.7%) of the TTM patients and in none of the non-TTM patients (P=0.009).

CONCLUSIONS

Postrecanalization cooling is feasible in patients with a large ischemic core. Future randomized clinical trials are warranted to validate its efficacy.

Targeted Temperature Management for Patients with Acute Ischemic Stroke: A Literature Review

Despite significant advances in medical imaging, thrombolytic therapy, and mechanical thrombectomy, acute ischemic strokes (AIS) remain a major cause of mortality and morbidity globally. Targeted temperature management (TTM) has emerged as a potential therapeutic intervention, aiming to mitigate neuronal damage and improve outcomes. This literature review examines the efficacy and challenges of TTM in the context of an AIS. A comprehensive literature search was conducted using databases such as PubMed, Cochrane, Web of Science, and Google Scholar. Studies were selected based on relevance and quality. We identified key factors influencing the effectiveness of TTM such as its timing, depth and duration, and method of application. The review also highlighted challenges associated with TTM, including increased pneumonia rates. The target temperature range was typically between 32 and 36 °C, with the duration of cooling from 24 to 72 h. Early initiation of TTM was associated with better outcomes, with optimal results observed when TTM was started within the first 6 h post-stroke. Emerging evidence indicates that TTM shows considerable potential as an adjunctive treatment for AIS when implemented promptly and with precision, thereby potentially mitigating neuronal damage and enhancing overall patient outcomes. However, its application is complex and requires the careful consideration of various factors.

Hypothermia is Associated with Improved Neurological Outcomes After Mechanical Thrombectomy

BACKGROUND

Acute ischemic stroke (AIS) is the second leading cause of death globally. Mechanical thrombectomy (MT) has improved patient prognosis but expedient treatment is still necessary to minimize anoxic injury. Lower intraoperative body temperature decreases cerebral oxygen demand, but the role of hypothermia in treatment of AIS with MT is unclear.

METHODS

We retrospectively reviewed patients undergoing MT for AIS from 2014 to 2020 at our institution. Patient demographics, comorbidities, intraoperative parameters, and outcomes were collected. Maximum body temperature was extracted from minute-by-minute anesthesia readings, and patients with maximal temperature below 36°C were considered hypothermic. Risk factors were assessed by χ2 and multivariate ordinal regression.

RESULTS

Of 68 patients, 27 (40%) were hypothermic. There was no significant association of hypothermia with patient age, comorbidities, time since last known well, number of passes intraoperatively, favorable revascularization, tissue plasminogen activator use, and immediate postoperative complications. Hypothermic patients exhibited better neurologic outcome at 3-month follow-up (P = 0.02). On multivariate ordinal regression, lower maximum intraoperative body temperature was associated with improved 3-month outcomes (P < 0.001), when adjusting for other factors influencing neurological outcomes. Other significant protective factors included younger age (P = 0.03), better revascularization (P = 0.03), and conscious sedation (P = 0.02).

CONCLUSIONS

Lower intraoperative body temperature during MT was independently associated with improved neurological outcome in this single center retrospective series. These results may help guide clinicians in employing therapeutic hypothermia during MT to improve long-term neurologic outcomes from AIS, although larger studies are needed.

INTRACOLON COOLING INCREASES SURVIVAL RATE IN THE RAT MODEL OF LETHAL HEMORRHAGE

ABSTRACT

Background: The objective of this study was to investigate whether transrectal intracolon (TRIC) cooling can prolong the survival duration in a rat hemorrhagic shock (HS) model. Methods: A lethal HS was induced by bleeding 47% of the total blood volume. A TRIC device was placed into the colon to maintain the intracolon temperature either at 37°C (TRIC37) or at 10°C (TRIC10) post-HS. In the surface cooling (SC) rats, the body temperatures were maintained at the same level as the esophageal temperature of the TRIC10 rats. A separated group of TRIC10 rats were resuscitated (Res) at 90 min post-HS. A total of six groups were as follows: (i) Sham TRIC37 (n = 5), (ii) Sham TRIC10 (n = 5), (iii) HS TRIC37 (n = 5), (iv) HS TRIC10 (n = 6), (v) HS SC (n = 6), and (vi) HS TRIC10 + Res (n = 6). Results: An average post-HS survival time was 18.4 ± 9.4 min in HS TRIC37 and 82 ± 27.82 min in the HS SC group. In striking contrast, the HS TRIC10 group exhibited an average survival time of 150.2 ± 66.43 min. The post-HS blood potassium level rose significantly in the HS TRIC37 and HS SC, whereas it remained unchanged in the TRIC10 groups. Post-HS intestinal damage occurred in HS TRIC37 and HS SC groups but virtually absent in HS TRIC10 groups. After resuscitation at 90 min post-HS, all HS TRIC10 rats were fully recovered from the lethal HS. Conclusions: TRIC10 reversed the high blood potassium level, prevented the intestinal damage, and prolonged the survival duration by sixfold relative to normothermia and by twofold compared with SC post-HS. All TRIC10 rats were successfully resuscitated at 90 min post-HS.

Hypothermic neuroprotection by targeted cold autologous blood transfusion in a non-human primate stroke model

Over decades, nearly all attempts to translate the benefits of therapeutic hypothermia in stroke models of lower-order species to stroke patients have failed. Potentially overlooked reasons may be biological gaps between different species and the mismatched initiation of therapeutic hypothermia in translational studies. Here, we introduce a novel strategy of selective therapeutic hypothermia in a non-human primate ischemia-reperfusion model, in which autologous blood was cooled ex vivo and the cool blood transfusion was administered at the middle cerebral artery just after the onset of reperfusion. Cold autologous blood cooled the targeted brain rapidly to below 34 °C while the rectal temperature remained around 36 °C with the assistance of a heat blanket during a 2-h hypothermic process. Therapeutic hypothermia or extracorporeal-circulation related complications were not observed. Cold autologous blood treatment reduced infarct sizes, preserved white matter integrity, and improved functional outcomes. Together, our results suggest that therapeutic hypothermia, induced by cold autologous blood transfusion, was achieved in a feasible, swift, and safe way in a non-human primate model of stroke. More importantly, this novel hypothermic approach conferred neuroprotection in a clinically relevant model of ischemic stroke due to reduced brain damage and improved neurofunction. This study reveals an underappreciated potential for this novel hypothermic modality for acute ischemic stroke in the era of effective reperfusion.

Hemolysis performance analysis and a novel estimation model of roller pump system

OBJECTIVE

Hemolysis performance is a crucial criterion for roller pumps utilized in life supporting system. In this study, the factor of hemolysis for roller pumps was selected as the target, and an estimation formulation was built to evaluate its hemolysis.

METHODS

Several models were proposed and then simulated with the assistant of Computational fluid dynamics (CFD) framework. The hemolysis performance was calculated using the power law model based on CFD and the estimation model in accordance with geometry parameters proposed in this study. The results of the in vitro experiments were compared with the simulation results. Power law model with the lowest error was utilized in following analysis.

RESULTS

As indicated by the simulation result, the rotary speed most significantly affected the hemolysis performance of roller blood pumps, followed by roller number and diameter of tube. The index of hemolysis (IH) for roller blood pumps at a rotary speed of 20-100 rpm ranged from 8.73E-7 to 8.07E-5. The relative error of the estimation model (4.93%) was lower than of the power law model (6.78%).

CONCLUSION

The IH led by pumps shows a significant, nonlinear relationship with the rotary speed. The design of multiple rollers design is harmful for hemolysis performance and larger diameter of tube exhibits decreased hemolysis at constant flow rate. An estimation formula was proposed with lower relative error for roller pump with the same shell set, which exhibited reduced computation and elevated convenience. And it can be utilized in hemolysis estimation of roller pumps potentially.

Temperature-dependent structural plasticity of hippocampal synapses

The function of the central nervous system (CNS) is strongly affected by temperature. However, the underlying processes remain poorly understood. Here, we show that hypothermia and hyperthermia trigger bidirectional re-organization of presynaptic architecture in hippocampal neurons, resulting in synaptic strengthening, and weakening, respectively. Furthermore, hypothermia remodels inhibitory postsynaptic scaffold into enlarged, sparse synapses enriched in GABAA receptors. This process does not require protein translation, and instead is regulated by actin dynamics. Induction of hypothermia in vivo enhances inhibitory synapses in the hippocampus, but not in the cortex. This is confirmed by the proteomic analysis of cortical synapses, which reveals few temperature-dependent changes in synaptic content. Our results reveal a region-specific form of environmental synaptic plasticity with a mechanism distinct from the classic temperature shock response, which may underlie functional response of CNS to temperature.

Therapeutic hypothermia for stroke: Unique challenges at the bedside

Therapeutic hypothermia has shown promise as a means to improving neurological outcomes at several neurological conditions. At the clinical level, it has been shown to improve outcomes in comatose survivors of cardiac arrest and in neonatal hypoxic ischemic encephalopathy, but has yet to be convincingly demonstrated in stroke. While numerous preclinical studies have shown benefit in stroke models, translating this to the clinical level has proven challenging. Major obstacles include cooling patients with typical stroke who are awake and breathing spontaneously but often have significant comorbidities. Solutions around these problems include selective brain cooling and cooling to lesser depths or avoiding hyperthermia. This review will cover the mechanisms of protection by therapeutic hypothermia, as well as recent progress made in selective brain cooling and the neuroprotective effects of only slightly lowering brain temperature. Therapeutic hypothermia for stroke has been shown to be feasible, but has yet to be definitively proven effective. There is clearly much work to be undertaken in this area.

Cellular and Molecular Targets for Non-Invasive, Non-Pharmacological Therapeutic/Rehabilitative Interventions in Acute Ischemic Stroke

BACKGROUND

Cerebral circulation delivers the blood flow to the brain through a dedicated network of sanguine vessels. A healthy human brain can regulate cerebral blood flow (CBF) according to any physiological or pathological challenges. The brain is protected by its self-regulatory mechanisms, which are dependent on neuronal and support cellular populations, including endothelial ones, as well as metabolic, and even myogenic factors.

OBJECTIVES

Accumulating data suggest that "non-pharmacological" approaches might provide new opportunities for stroke therapy, such as electro-/acupuncture, hyperbaric oxygen therapy, hypothermia/cooling, photobiomodulation, therapeutic gases, transcranial direct current stimulations, or transcranial magnetic stimulations. We reviewed the recent data on the mechanisms and clinical implications of these non-pharmaceutical treatments.

METHODS

To present the state-of-the-art for currently available non-invasive, non-pharmacological-related interventions in acute ischemic stroke, we accomplished this synthetic and systematic literature review based on the Preferred Reporting Items for Systematic Principles Reviews and Meta-Analyses (PRISMA).

RESULTS

The initial number of obtained articles was 313. After fulfilling the five steps in the filtering/selection methodology, 54 fully eligible papers were selected for synthetic review. We enhanced our documentation with other bibliographic resources connected to our subject, identified in the literature within a non-standardized search, to fill the knowledge gaps. Fifteen clinical trials were also identified.

DISCUSSION

Non-invasive, non-pharmacological therapeutic/rehabilitative interventions for acute ischemic stroke are mainly holistic therapies. Therefore, most of them are not yet routinely used in clinical practice, despite some possible beneficial effects, which have yet to be supplementarily proven in more related studies. Moreover, few of the identified clinical trials are already completed and most do not have final results.

CONCLUSIONS

This review synthesizes the current findings on acute ischemic stroke therapeutic/rehabilitative interventions, described as non-invasive and non-pharmacological.

Directly Cooling Gut Prevents Mortality in the Rat Model of Reboa Management of Lethal Hemorrhage

BACKGROUND

Resuscitative endovascular balloon occlusion of the aorta (REBOA) is a lifesaving technique for the management of lethal torso hemorrhage. Its benefit, however, must be weighed against the lethal distal organ ischemia-reperfusion injury (IRI). This study uses a novel direct gut cooling technique to manage the distal organ IRI.

METHODS

A rat lethal hemorrhage model was established by bleeding of 50% of the estimated total blood volume via inferior vena cava. A novel TransRectal Intra-Colon (TRIC) temperature management device was positioned in the descending colon either to maintain intra-colon temperature at 37°C or 12°C. The upper body temperature was maintained at as close to 37°C as possible in both groups. A 2F Fogarty balloon catheter was inserted via the femoral artery into the descending thoracic aorta for the implementation of REBOA. After REBOA, the balloon was deflated, and the shed blood was returned. The temperature managements were continued for additional 180 to 270 min during the post-REBOA period.

RESULTS

All rats subjected to REBOA management of lethal hemorrhage at 37°C had severe histopathological gut and abdominal organ IRI, severe functional deficits, and died within 24 h with 100% mortality. By contrast, directly cooling the colon to 10°C to 12°C with the novel TRIC device abolished mortality, and dramatically improved ABG parameters, prevented the abdominal organ injury, and reduced the functional deficits during the 7-day post-REBOA period.

CONCLUSIONS

Direct trans-rectal colon cooling during REBOA management of lethal hemorrhage offers extraordinary functional improvement and amazing tissue protection, and abolishes mortality.

Translational Block in Stroke: A Constructive and "Out-of-the-Box" Reappraisal

Why can we still not translate preclinical research to clinical treatments for acute strokes? Despite > 1000 successful preclinical studies, drugs, and concepts for acute stroke, only two have reached clinical translation. This is the translational block. Yet, we continue to routinely model strokes using almost the same concepts we have used for over 30 years. Methodological improvements and criteria from the last decade have shed some light but have not solved the problem. In this conceptual analysis, we review the current status and reappraise it by thinking "out-of-the-box" and over the edges. As such, we query why other scientific fields have also faced the same translational failures, to find common denominators. In parallel, we query how migraine, multiple sclerosis, and hypothermia in hypoxic encephalopathy have achieved significant translation successes. Should we view ischemic stroke as a "chronic, relapsing, vascular" disease, then secondary prevention strategies are also a successful translation. Finally, based on the lessons learned, we propose how stroke should be modeled, and how preclinical and clinical scientists, editors, grant reviewers, and industry should reconsider their routine way of conducting research. Translational success for stroke treatments may eventually require a bold change with solutions that are outside of the box.

Staying Cool in Space: A Review of Therapeutic Hypothermia and Potential Application for Space Medicine

Despite rigorous health screenings, medical incidents during spaceflight missions cannot be avoided. With long-duration exploration flights on the rise, the likelihood of critical medical conditions with no suitable treatment on board will increase. Therapeutic hypothermia (TH) could serve as a bridge treatment in space prolonging survival and reducing neurological damage in ischemic conditions such as stroke and cardiac arrest. We conducted a review of published studies to determine the potential and challenges of TH in space based on its physiological effects, the cooling methods available, and clinical evidence on Earth. Currently, investigators have found that application of low normothermia leads to better outcomes than mild hypothermia. Data on the impact of hypothermia on a favorable neurological outcome are inconclusive due to lack of standardized protocols across hospitals and the heterogeneity of medical conditions. Adverse effects with systemic cooling are widely reported, and could be reduced through selective brain cooling and pharmacological cooling, promising techniques that currently lack clinical evidence. We hypothesize that TH has the potential for application as supportive treatment for multiple medical conditions in space and recommend further investigation of the concept in feasibility studies.

Selective-cerebral-hypothermia-induced neuroprotection against-focal cerebral ischemia/reperfusion injury is associated with an increase in SUMO2/3 conjugation

Selective cerebral hypothermia is considered an effective treatment for neuronal injury after stroke and avoids the complications of general hypothermia. Several recent studies hanve suggested that SUMO2/3 conjugation occurs following cerebral ischemia/reperfusion (I/R) injury. However, the relationship between the cerebral protective effect of selective cerebral hypothermia and SUMO2/3 conjugation remains unclear. In this study, we investigated the effect of selective cerebral hypothermia on SUMO2/3 conjugation during focal cerebral I/R injury. A total of 140 Sprague-Dawley rats were divided into four groups. In the sham group, only the carotid artery was exposed. The endoluminal filament technique was used to induce middle cerebral artery occlusion in the other three groups. After 2 h of occlusion, the filaments were slowly removed to allow blood reperfusion in the I/R group. In the hypothermia (HT) group and normothermia (NT) group, normal saline at 4 °C and 37 °C, respectively , was perfused through the carotid artery, followed by the restoration of blood flow. The results of the modified neurological severity score (mNSS), 2,3,5-triphenyltetrazolium chloride (TTC) staining, hematoxylin-eosin (HE) staining, and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining demonstrated that selective cerebral hypothermia significantly decreased I/R-induced neuronal injury (mNSS, n = 8, 24 h, HT (5.88 ± 2.36) vs. I/R (8.63 ± 3.38), P < 0.05. 48 h, HT (5.75 ± 2.25) vs. I/R (8.5 ± 2.88), P < 0.05. Cerebral infarct volume percentages, n = 5, HT (18.71 ± 2.13) vs. I/R (41.52 ± 2.90), P < 0.01. Cell apoptosis rate, n = 5, 24 h, HT (21.28 ± 2.61) vs. I/R (43.72 ± 4.30), P < 0.05. 48 h, HT (20.50 ± 2.53) vs. I/R (38.94 ± 2.93), P < 0.05). The expression of Ubc9 and conjugated SUMO2/3 proteins was increased at 24 and 48 h after reperfusion in the 3 non-sham groups, and hypothermia further upregulated the expression of Ubc9 and conjugated SUMO2/3 proteins in the HT group. The expression of SENP3 was increased in the NT group and I/R group, while it was decreased in the HT group at 24 and 48 h after reperfusion (Relative quantities, n = 5, Ubc9, 24 h, HT (2.44 ± 0.22) vs. I/R (1.55 ± 0.39), P < 0.05. 48 h, HT (2.69 ± 0.16) vs. I/R (2.25 ± 0.33), P < 0.05. SENP3, 24 h, HT (0.47 ± 0.15) vs. I/R (2.18 ± 0.43), P < 0.05. 48 h, HT (0.72 ± 0.06) vs. I/R (1.51 ± 0.19), P < 0.05. conjugated SUMO2/3 proteins, 24 h, HT (2.84 ± 0.24) vs. I/R (2.51 ± 0.20), P < 0.05. 48 h, HT (2.73 ± 0.13) vs. I/R (2.44 ± 0.13), P < 0.05). Further analysis showed that the variation in SENP3 expression was more obvious than that in Ubc9 under hypothermia intervention in the HT group. These findings suggest that selective cerebral hypothermia could increase SUMO2/3 modification mainly via down-regulating the expression of SENP3, and then exert neuroprotective effects in rats with cerebral I/R injury.

The future of neuroprotection in stroke

Investigators acknowledge the limitations of rodent or non-human primate stroke models, hundreds of putative neuroprotectants have been evaluated in preclinical models, but not one has entered the clinical realm. Initial studies focused on the neuron, but in recent years the focus has widened to also include other neural cells including astrocytes, pericytes and endothelial cells, which together form the neurovascular unit. Some new developments raise renewed hope for neuroprotection: the appearance of new compounds with multiple mechanisms of action, or the promulgation of new standards for a rigorous preclinical testing. At the bedside in the last 5 years, uric acid and nerinetide are the only compounds tested for clinical efficacy in randomised controlled trials (RCTs), where all patients had to receive reperfusion therapies, either intravenous thrombolysis and/or mechanical thrombectomy. In addition, otaplimastat, 3K3A-activated protein C (APC), intra-arterial verapamil and intra-arterial hypothermia were also assessed in combination with reperfusion therapy, but in RCTs that only included feasibility or safety outcomes. Some of these compounds yielded promising results which are discussed in this review. Altogether, a deeper knowledge of the mechanisms involved in the ischaemic death process at the neurovascular unit, an improved preselection and evaluation of drugs at the preclinical stage and the testing of putative neuroprotectants in enriched clinical studies of patients receiving reperfusion therapies, might prove more effective than in the past to reverse a dismal situation that has lasted already too long.

RNA Binding Protein Motif 3 Inhibits Oxygen-Glucose Deprivation/Reoxygenation-Induced Apoptosis Through Promoting Stress Granules Formation in PC12 Cells and Rat Primary Cortical Neurons

As a sensitive cold-shock protein, RNA binding protein motif 3 (RBM3) exhibits a neuroprotective function in the condition of brain injury. However, how RBM3 is involved in acute ischemic stroke by affecting stress granules (SGs) remains unclear. Here, we established an oxygen-glucose deprivation/reperfusion (OGD/R) model in rat primary cortical neurons and PC12 cells to explore the potential mechanism between RBM3 and SG formation in acute ischemic/reperfusion (I/R) condition. The immunofluorescence results showed that the SG formation significantly decreased in rat primary cortical neurons and PC12 cells during the reperfusion period after 6 h of OGD stimulation. The western blot results, flow cytometry analysis, and cell viability assessment showed that the RBM3 expression and ratio of cell viability significantly decreased, while the rate of apoptosis increased in PC12 cells during the reperfusion period after 6 h of OGD stimulation. Co-immunoprecipitation (Co-IP) and immunofluorescence indicated that RBM3 and GTPase-activating protein-binding protein 1 (G3BP1) colocalized cytoplasm of PC12 cells after 6 h of OGD stimulation when the SGs formation reached the highest level. Besides, overexpression and knockdown of the RBM3 were achieved via plasmid transfection and CRISPR-Cas9 technology, respectively. The results of overexpression and knockdown of RBM3 gene illustrated the pivotal role of RBM3 in affecting SG formation and apoptosis level in OGD-treated PC12 cells. In conclusion, RBM3 could combine with G3BP1 resulted in increasing stress granules generation in rat primary cortical neurons and PC12 cells after 6 h of oxygen-glucose deprivation (OGD) injury, which ultimately reduced the apoptosis in OGD-induced cells. Our study may enable a new promising target for alleviating ischemia-reperfusion injury in cells.

Temporal limits of therapeutic hypothermia onset in clinical trials for acute ischemic stroke: How early is early enough?

Stroke is one of the leading causes of mortality and morbidity worldwide, and yet, current treatment is limited to thrombolysis through either t-PA or mechanical thrombectomy. While therapeutic hypothermia has been adopted in clinical contexts such as neuroprotection after cardiac resuscitation and neonatal hypoxic-ischemic encephalitis, it is yet to be used in the context of ischemic stroke. The lack of ameliorative effect in ischemic stroke patients may be tied to the delayed cooling induction onset. In the trials where the cooling was initiated with significant delay (mostly systemic cooling methods), minimal benefit was observed; on the other hand, when cooling was initiated very early (mostly selective cooling methods), there was significant efficacy. Another timing factor that may play a role in amelioration may be the onset of cooling relative to thrombolysis therapy. Current understanding of the pathophysiology of acute ischemic injury and ischemia-reperfusion injury suggests that hypothermia before thrombolysis may be the most beneficial compared to cooling initiation during or after reperfusion. As many of the systemic cooling methods tend to require longer induction periods and extensive, separate procedures from thrombolysis therapy, they are generally delayed to hours after recanalization. On the other hand, selective cooling was generally performed simultaneously to thrombolysis therapy. As we conduct and design therapeutic hypothermia trials for stroke patients, the key to their efficacy may lie in quick and early cooling induction, both respective to the symptom onset and thrombolysis therapy.

Insightful Backbone Modifications Preventing Proteolytic Degradation of Neurotensin Analogs Improve NTS1-Induced Protective Hypothermia

Therapeutic hypothermia represents a brain-protective strategy for multiple emergency situations, such as stroke or traumatic injury. Neurotensin (NT), which exerts its effects through activation of two G protein-coupled receptors, namely NTS1 and NTS2, induces a strong and long-lasting decrease in core body temperature after its central administration. Growing evidence demonstrates that NTS1 is the receptor subtype mediating the hypothermic action of NT. As such, potent NTS1 agonists designed on the basis of the minimal C-terminal NT(8-13) bioactive fragment have been shown to produce mild hypothermia and exert neuroprotective effects under various clinically relevant conditions. The high susceptibility of NT(8-13) to protease degradation (half-life <2 min) represents, however, a serious limitation for its use in pharmacological therapy. In light of this, we report here a structure-activity relationship study in which pairs of NT(8-13) analogs have been developed, based on the incorporation of a reduced Lys⁸-Lys⁹ bond. To further stabilize the peptide bonds, a panel of backbone modifications was also inserted along the peptide sequence, including Sip¹⁰, D-Trp¹¹, Dmt¹¹, Tle¹², and TMSAla¹³. Our results revealed that the combination of appropriate chemical modifications leads to compounds exhibiting improved resistance to proteolytic cleavages (>24 h; 16). Among them, the NT(8-13) analogs harboring the reduced amine bond combined with the unnatural amino acids TMSAla¹³ (4) and Sip¹⁰ (6) or the di-substitution Lys¹¹ - TMSAla¹³ (12), D-Trp¹¹-TMSAla¹³ (14), and Dmt¹¹-Tle¹² (16) produced sustained hypothermic effects (−3°C for at least 1 h). Importantly, we observed that hypothermia was mainly driven by the increased stability of the NT(8-13) derivatives, instead of the high binding-affinity at NTS1. Altogether, these results reveal the importance of the reduced amine bond in optimizing the metabolic properties of the NT(8-13) peptide and support the development of stable NTS1 agonists as first drug candidate in neuroprotective hypothermia.