Prolonged hypothermia exposure diminishes neuroprotection for severe ischemic-hypoxic primary neurons

Synergetic effect of mild hypothermia and antioxidant treatment on ROS-mediated neuron injury under oxygen-glucose deprivation investigated by scanning electrochemical microscopy

Ischemic stroke and reperfusion injury result in neuronal damage and dysfunction associated with oxidative stress, leading to overproduction of cellular reactive oxygen species (ROS) and reactive nitrogen species (RNS). In situ monitoring of the transient ROS and RNS effluxes during rapid pathologic processes is crucial for understanding the relationship between progression of cell damage and role of oxidative stress, and developing the corresponding neuroprotective strategies. Herein, we built oxygen glucose deprivation (OGD) and mild hypothermic (MH) models to mimic the in vitro conditions of ischemic stroke and MH treatment. We used scanning electrochemical microscopy (SECM) to in situ monitor H2O2 and nitric oxide (NO) effluxes from HT22 cells under the OGD and MH treatment conditions. Through quantitative analysis of the H2O2 and NO efflux results, we found that the cellular oxidative stress was primarily manifested through ROS release under OGD conditions, and the MH treatment partially suppressed the excessive H2O2 and NO production induced by reoxygenation. Moreover, the synergistic therapeutic effect of MH with antioxidant treatment significantly reduced the oxidative stress and enhanced the cell survival. Our work reveals the crucial role of oxidative stress in OGD and reperfusion processes, and the effective improvement of cell viability via combination of MH with antioxidants, proposing promising therapeutic interventions for ischemic stroke and reperfusion injury.

Differential Mitochondrial Bioenergetics in Neurons and Astrocytes Following Ischemia-Reperfusion Injury and Hypothermia

The close interaction between neurons and astrocytes has been extensively studied. However, the specific behavior of these cells after ischemia-reperfusion injury and hypothermia remains poorly characterized. A growing body of evidence suggests that mitochondria function and putative transference between neurons and astrocytes may play a fundamental role in adaptive and homeostatic responses after systemic insults such as cardiac arrest, which highlights the importance of a better understanding of how neurons and astrocytes behave individually in these settings. Brain injury is one of the most important challenges in post-cardiac arrest syndrome, and therapeutic hypothermia remains the single, gold standard treatment for neuroprotection after cardiac arrest. In our study, we modeled ischemia-reperfusion injury by using in vitro enhanced oxygen-glucose deprivation and reperfusion (eOGD-R) and subsequent hypothermia (HPT) (31.5 °C) to cell lines of neurons (HT-22) and astrocytes (C8-D1A) with/without hypothermia. Using cell lysis (LDH; lactate dehydrogenase) as a measure of membrane integrity and cell viability, we found that neurons were more susceptible to eOGD-R when compared with astrocytes. However, they benefited significantly from HPT, while the HPT effect after eOGD-R on astrocytes was negligible. Similarly, eOGD-R caused a more significant reduction in adenosine triphosphate (ATP) in neurons than astrocytes, and the ATP-enhancing effects from HPT were more prominent in neurons than astrocytes. In both neurons and astrocytes, measurement of reactive oxygen species (ROS) revealed higher ROS output following eOGD-R, with a non-significant trend of differential reduction observed in neurons. HPT after eOGD-R effectively downregulated ROS in both cells; however, the effect was significantly more effective in neurons. Lipid peroxidation was higher after eOGD-R in neurons, while in astrocytes, the increase was not statistically significant. Interestingly, HPT had similar effects on the reduction in lipoperoxidation after eOGD-R with both types of cells. While glutathione (GSH) levels were downregulated after eOGD-R in both cells, HPT enhanced GSH in astrocytes, but worsened GSH in neurons. In conclusion, neuron and astrocyte cultures respond differently to eOGD-R and eOGD-R + HTP treatments. Neurons showed higher sensitivity to ischemia-reperfusion insults than astrocytes; however, they benefited more from HPT therapy. These data suggest that given the differential effects from HPT in neurons and astrocytes, future therapeutic developments could potentially enhance HPT outcomes by means of neuronal and astrocytic targeted therapies.

Effects of Different Hypothermia on the Results of Cardiopulmonary Resuscitation in a Cardiac Arrest Rat Model

Objective

To investigate the optimal temperature of hypothermia treatment in rats with cardiac arrest caused by ventricular fibrillation (VF) after the return of spontaneous circulation (ROSC).

Methods

A total of forty-eight male Sprague-Dawley rats were induced by VF through the guidewire with a maximum of 5 mA current and untreated for 8 min. Cardiopulmonary resuscitation (CPR) was performed for 8 min followed by defibrillation (DF). Resuscitated rats were then randomized into the normothermia (37°C) group, milder (35°C) group, mild (33°C) group, or moderate (28°C) group. Hypothermia was immediately induced with surface cooling. The target temperature was maintained for 4 h before rewarming to 37 ± 0.5°C. Moreover, at the end of the 4 h, a rat in each group was randomly selected to be sacrificed for the cerebral cortex electron microscopy observation (n = 1). The other resuscitated animals were observed for up to 72 h after ROSC (n = 7). Left ventricular ejection fraction (LVEF) and left ventricular end diastolic volume (LVEDV) were measured. Survival time, survival rate, and neurological deficit score (NDS) were recorded for 72 h.

Results

During hypothermia, higher LVEF was observed in the hypothermia groups when compared with normothermia group (35°C vs. 37°C, p < 0.05, 33°C and 28°C vs. 37°C, p < 0.01). Among the hypothermia groups, LVEF was higher in the 28°C group than that of 35°C (p < 0.05). However, both the heart rate (HR) (p < 0.01) and LVEDV (28°C vs. 35°C, p < 0.01, 28°C vs. 37°C and 33°C, p < 0.05) were lowest in the 28°C group when compared with the other groups. There were no significant differences of LVEF and LVEDV between the group 35°C and 33°C (p > 0.05). After rewarming, the LVEF of 35°C group was higher than that of group 37°C, 33°C, and 28°C (35°C vs. 37°C and 28°C, p < 0.01, 35°C vs. 33°C, p < 0.05). Group 35°C and 33°C resulted in longer survival (p < 0.01), higher survival rate (p < 0.01), and lower NDS (35°C vs. 37°C and 28°C, p < 0.01, 33°C vs. 37°C and 28°C, p < 0.05) compared with the group 37°C and 28°C. The extent of damage to cerebral cortex cells in group of 35°C and 33°C was lighter than that in group of 37°C and 28°C. The 35°C group spent less time in the process of cooling and rewarming than the group 33°C and 28°C (p < 0.01).

Conclusions

An almost equal protective effect of milder hypothermia (35°C) and mild hypothermia (33°C) in cardiac arrest (CA) rats was achieved with more predominant effect than moderate hypothermia (28°C) and normothermia (37°C). More importantly, shorter time spent in cooling and rewarming was required in the 35°C group, indicating its potential clinical application. These findings support the possible use of milder hypothermia (35°C) as a therapeutic agent for postresuscitation.

New Applications of HBOC-201: A 25-Year Review of the Literature

If not cured promptly, tissue ischemia and hypoxia can cause serious consequences or even threaten the life of the patient. Hemoglobin-based oxygen carrier-201 (HBOC-201), bovine hemoglobin polymerized by glutaraldehyde and stored in a modified Ringer's lactic acid solution, has been investigated as a blood substitute for clinical use. HBOC-201 was approved in South Africa in 2001 to treat patients with low hemoglobin (Hb) levels when red blood cells (RBCs) are contraindicated, rejected, or unavailable. By promoting oxygen diffusion and convective oxygen delivery, HBOC-201 may act as a direct oxygen donor and increase oxygen transfer between RBCs and between RBCs and tissues. Therefore, HBOC-201 is gradually finding applications in treating various ischemic and hypoxic diseases including traumatic hemorrhagic shock, hemolysis, myocardial infarction, cardiopulmonary bypass, perioperative period, organ transplantation, etc. However, side effects such as vasoconstriction and elevated methemoglobin caused by HBOC-201 are major concerns in clinical applications because Hbs are not encapsulated by cell membranes. This study summarizes preclinical and clinical studies of HBOC-201 applied in various clinical scenarios, outlines the relevant mechanisms, highlights potential side effects and solutions, and discusses the application prospects. Randomized trials with large samples need to be further studied to better validate the efficacy, safety, and tolerability of HBOC-201 to the extent where patient-specific treatment strategies would be developed for various clinical scenarios to improve clinical outcomes.

The effect of mild hypothermia plus rutin on the treatment of spinal cord injury and inflammatory factors by repressing TGF-β/smad pathway

Purpose

To probe the mechanism of mild hypothermia combined with rutin in the treatment of spinal cord injury (SCI).

Methods

Thirty rats were randomized into the following groups: control, sham, model, mild hypothermia (MH), and mild hypothermia plus rutin (MH+Rutin). We used modified Allen’s method to injure the spinal cord (T10) in rats, and then treated it with MH or/and rutin immediately. BBB scores were performed on all rats. We used HE staining for observing the injured spinal cord tissue; ELISA for assaying TNF-α, IL-1β, IL-8, Myeloperoxidase (MPO), and Malondialdehyde (MDA) contents; Dihydroethidium (DHE) for measuring the reactive oxygen species (ROS) content; flow cytometry for detecting apoptosis; and both RT-qPCR and Western blot for determining the expression levels of TGF-β/Smad pathway related proteins (TGF-β, Smad2, and Smad3).

Results

In comparison with model group, the BBB score of MH increased to a certain extent and MH+Rutin group increased more than MH group (p < 0.05). After treatment with MH and MH+Rutin, the inflammatory infiltration diminished. MH and MH+Rutin tellingly dwindled TNF-β, MDA and ROS contents (p < 0.01), and minified spinal cord cell apoptosis. MH and MH+Rutin could patently diminished TGF-β1, Smad2, and Smad3 expression (p < 0.01).

Conclusions

MH+Rutin can suppress the activation of TGF-β/Smad pathway, hence repressing the cellular inflammatory response after SCI.

Intravenous thrombolysis in combination with mild hypothermia therapy in the treatment of acute cerebral infarction

Objective

To investigate the efficacy of recombinant tissue plasminogen activator (rt-PA) intravenous thrombolysis in combination with mild hypothermia therapy in the treatment of acute cerebral infarction.

Methods

One hundred and thirty-two patients with acute cerebral infarction who were admitted to our hospital were selected and grouped into a control group and an observation group, 66 each group. Patients in the control group were given conventional treatment in combination with local mild hypothermia therapy, and patients in the observation group were given rt-PA intravenous thrombolysis on the basis of conventional treatment and local mild hypothermia therapy. National institute of health stroke scale (NIHSS) score and intracranial pressure (ICP) of the two groups before and after treatment was recorded. The efficacy of the two groups was evaluated. The modified Rankin scale (MRS) score was followed up for three months. The blood samples of the patients were collected before and after thrombolysis. Superoxide dismutase (SOD) and malondialdehyde (MDA) levels in the plasma were detected.

Results

The NIHSS score of the two groups decreased in the 1^st, 3^rd and 7^th day after treatment compared to before treatment (p<0.05), but the NIHSS score of the two groups had no significant difference at different time points after treatment (p>0.05). The ICP of the two groups decreased in the 1^st, 3^rd and 7^th day after treatment compared to before treatment (p<0.05), and the decrease of ICP of the observation group was more significant than that of the control group at the same time point (1^st, 3^rd and 7^th day after treatment) (p<0.05). The clinical efficacy of the observation group was higher than that of the control group after treatment, and the difference was statistically significant (p<0.05). The MDA concentration of both groups decreased at different time points after treatment (p<0.05), but the SOD concentration increased (p<0.05). The MDA concentration of the observation group was lower than that of the control group at different time points after treatment (p<0.05), and the SOD concentration of the observation group was higher than that of the control group (p<0.05).

Conclusion

rt-PA intravenous thrombolysis in combination with mild hypothermia therapy has significant efficacy in the treatment of acute cerebral infarction. It can effectively relieve neurological function. Its action mechanism may be realized by relieving oxidative stress response.

Glibenclamide Enhances the Therapeutic Benefits of Early Hypothermia after Severe Stroke in Rats

Glibenclamide (GBC) is an antidiabetic drug that is in a class of medications known as sulfonylureas, which play critical roles in attenuating brain edema and reducing mortality in ischemic stroke patients. Therapeutic hypothermia (TH) is another robust neuroprotectant that prevents brain swelling and improves the neurological outcomes of stroke patients. However, whether the combination of GBC and TH can be used as a reliable neuroprotectant in ischemic stroke remains largely unknown. We used the middle cerebral artery occlusion (MCAO) rat model as well as oxygen and glucose deprivation-reoxygenation (OGD/R) endothelial cells as ischemic stroke models to investigate the efficacy and mechanisms of treating ischemic stroke with the combination of GBC and TH. The serum glucose, mortality rate, neurobehavioral functions, tight junctions, endothelial cells and inflammatory cytokines were evaluated in the stroke models after treatment with GBC, TH or the combination of them. After 5-hour occlusion and subsequent reperfusion, rats exhibited a large volume of hemispheric swelling and a high mortality rate. Stroke rats treated with the combined therapy did not exhibit hypoglycemia. The combination of GBC and TH exhibited synergistic neuroprotective effects in stroke rats that were associated with greater reductions in edema volume, better improvement in neurobehavioral functions, prevention of tight junction loss, and reduction of expression of the inflammatory cytokines COX-2 and iNOS. In OGD/R endothelia cells, the combination reduced endothelial cell death. This study demonstrated that both GBC and TH are neuroprotective after the severe stroke; however, combined therapy with GBC and TH enhanced the efficiency and efficacy of the effects of TH and GBC in the treatment of ischemia. This combined therapy may facilitate the clinical translation of TH management for severe stroke. The combination of GBC and TH seems to be a feasible and promising clinical strategy to alleviate cerebral injury following severe stroke.

The Combination of Human Urinary Kallidinogenase and Mild Hypothermia Protects Adult Rats Against Hypoxic-Ischemic Encephalopathy-Induced Injury by Promoting Angiogenesis and Regeneration

Objectives: Human Urinary Kallidinogenase (HUK) is a tissue kallikrein that plays neuroprotective role in ischemic conditions via different mechanisms. Mild hypothermia (MH) is another robust neuroprotectant that reduces mortality but does not profoundly ameliorate the neurological outcome in hypoxic-ischemic encephalopathy (HIE) patients. However, whether the combination of HUK and MH can be used as a promising neuroprotective treatment in HIE is unknown. Methods: One-hundred and forty-four adult Wistar rats were randomly divided into five groups: Sham, HIE, HUK, MH and a combination of HUK and MH treatment. The HIE rat model was established by right carotid dissection followed by hypoxia aspiration. The survival curve was created within 7 days, and the neurological severity scores (NSS) were assessed at days 0, 1, 3, and 7. Nissl staining, Terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL), immunofluorescent staining and western blotting were used to evaluate neuronal survival, apoptosis and necrosis, tight-junction proteins Claudin-1 and Zonula occludens-1 (ZO-1), vascular endothelial growth factor (VEGF), doublecortex (DCX), bradykinin receptor B1 (BDKRB1), BDKRB2 and Ki67 staining. Results: The combined treatment rescued all HIE rats from death and had a best survival curve compared to HIE. The Combination also reduced the NSS scores after HIE at days 7, better than HUK or MH alone. The combination of HUK and MH reserved more cells in Nissl staining and inhibited neuronal apoptosis and necrosis as well as significantly attenuated HIE-induced decreases in claudin-1, ZO-1, cyclin D1 and BDKRB1/B2 in comparison to HUK or MH treatment alone. Moreover, the combined treatment increased the expression of VEGF and DCX as well as the number of Ki67-labeled cells. Conclusions: This study demonstrates that both HUK and MH are neuroprotective after HIE insult; however, the combined therapy with HUK and MH enhanced the efficiency and efficacy of either therapy alone in the treatment of HIE, at least partially by promoting angiogenesis and regeneration and rescuing tight-junction loss. The combination of HUK and MH seems to be a feasible and promising clinical strategy to alleviate cerebral injury following HIE insult. Highlights: -The combination of HUK and MH distinctly reduces neurological dysfunction in HIE rats.-HUK enhances the neuroprotective effects of MH in HIE.-MH attenuates tight-junction disruption, upregulates the BDKR B1/2, DCX and cyclin D1.-The combination of MH and HUK enhances the expressions of MH/HUK mediated-BDKR B1/2, DCX, cyclin D1 and Ki67 positive cells.

Mild hypothermia protects neurons against oxygen glucose deprivation via poly (ADP-ribose) signaling

OBJECTIVE

Hypothermia is a neuroprotective mechanism that has been validated for use in alleviating neonatal hypoxic-ischemic (HI) brain injury. Nevertheless, it is unclear whether poly (ADP-ribose) (PAR) signaling is involved in hypothermia-induced neuroprotection. In this study, we investigated whether mild hypothermia rescues oxygen glucose deprivation (OGD)-induced cell death by modifying PAR-relative protein expression, such as AIF, PARP-1, and PAR polymer, in primary-cultured hippocampal neurons.

METHODS

We analyzed neuronal morphology and related protein expression of PAR signaling after OGD followed by mild hypothermia in primary-cultured newborn hippocampal neurons.

RESULTS

Hypothermic treatment resulted in improved neuronal viability and alleviated DNA damage. Results from the protein assay showed that hypothermia attenuated nuclear translocation of apoptosis-inducing factor (AIF), inhibited overactivation of poly(ADP-ribose) polymerase-1 (PARP-1), and decreased production of PAR polymer induced by PARP-1 activation after OGD.

CONCLUSIONS

These results showed that mild hypothermia partially protects immature hippocampal neurons against OGD injury in part by interfering with the PAR signaling pathway.

Mild hypothermia protects hippocampal neurons from oxygen-glucose deprivation injury through inhibiting caspase-3 activation

Mild hypothermia (MH) is thought to be one of the most effective therapeutic methods to treat hypoxic-ischemic encephalopathy (HIE) after cardiac arrest (CA). However, its precise mechanisms remain unclear. In this research, hippocampal neurons were cultured and treated with mild hypothermia and Ac-DEVD-CHO after oxygen-glucose deprivation (OGD). The activity of caspase-3 was detected, in order to find the precise concentration of Ac-DEVD-CHO with the same protective role in OGD injury as MH treatment. Western blot and immunofluorescence staining were conducted to analyze the effects of MH and Ac-DEVD-CHO on the expressions of caspase-3, caspase-8, and PARP. The neuronal morphology was observed with an optical microscope. The lactic acid dehydrogenase (LDH) release rate, neuronal viability, and apoptotic rate were also detected. We found that MH (32 °C) and Ac-DEVD-CHO (5.96 μMol/L) had equal effects on blocking the activation of caspase-3 and the OGD-induced cleavage of PARP, but neither had any effect on the activation of caspase-8, which goes on to activate caspase-3 in the apoptotic pathway. Meanwhile, both MH and Ac-DEVD-CHO had similar effects in protecting cell morphology, reducing LDH release, and inhibiting OGD-induced apoptosis in neurons. They also similarly improved neuronal viability after OGD. In conclusion, caspase-3 serves as a key intervention point of the key modulation site or regulatory region in MH treatment that protects neuronal apoptosis against OGD injury. Inhibiting the expression of caspase-3 had a protective effect against OGD injury in MH treatment, and caspase-3 activation could be applied to evaluate the neuroprotective effectiveness of MH on HIE.

Mild hypothermia protects against oxygen glucose deprivation/reoxygenation-induced apoptosis via the Wnt/β-catenin signaling pathway in hippocampal neurons

Mild hypothermia is thought to be one of the most effective therapies for cerebral ischemia/reperfusion injuries. Our previous research revealed that mild hypothermia inhibits the activation of caspase-3 and protects against oxygen glucose deprivation/reoxygenation (OGD/R)-induced injury in hippocampal neurons. However, the mechanisms behind the activation of caspase-3 remain unclear. The aims of this study were to determine whether the protective effects of mild hypothermia were exerted through the Wnt/β-catenin signaling pathway. We found that, under OGD/R conditions, the pathway was down regulated, but mild hypothermia induced the reactivation of the Wnt/β-catenin signaling pathway, which had been suppressed by OGD/R injury. Mild hypothermia also caused the down regulation of the expression of apoptosis promoting proteins (Bax cleaved caspase-3), up-regulated the expression of apoptosis inhibiting proteins (Bcl-2), and ameliorated OGD/R injury-induced apoptosis. The protective effects of mild hypothermia were blocked by DKK1 (an antagonist of the canonical Wnt signaling pathway). Taken together, these results indicate that the Wnt/β-catenin signaling pathway mediates the protective effects of mild hypothermia against OGD/R-induced apoptosis. Our study provides evidence that mild hypothermia reactivates the Wnt/β-catenin signaling pathway, which is suppressed by OGD/R injury, in hippocampal neurons and protects neurons from OGD/R-induced apoptosis via the reactivation of the Wnt/β-catenin signaling pathway, ultimately suggesting that mild hypothermia could have therapeutic effects on OGD/R-induced apoptosis.

Effects of Topical Icing on Inflammation, Angiogenesis, Revascularization, and Myofiber Regeneration in Skeletal Muscle Following Contusion Injury

Contusion injuries in skeletal muscle commonly occur in contact sport and vehicular and industrial workplace accidents. Icing has traditionally been used to treat such injuries under the premise that it alleviates pain, reduces tissue metabolism, and modifies vascular responses to decrease swelling. Previous research has examined the effects of icing on inflammation and microcirculatory dynamics following muscle injury. However, whether icing influences angiogenesis, collateral vessel growth, or myofiber regeneration remains unknown. We compared the effects of icing vs. a sham treatment on the presence of neutrophils and macrophages; expression of CD34, von Willebrands factor (vWF), vascular endothelial growth factor (VEGF), and nestin; vessel volume; capillary density; and myofiber regeneration in skeletal after muscle contusion injury in rats. Muscle tissue was collected 1, 3, 7, and 28 d after injury. Compared with uninjured rats, muscles in rats that sustained the contusion injury exhibited major necrosis, inflammation, and increased expression of CD34, vWF, VEGF, and nestin. Compared with the sham treatment, icing attenuated and/or delayed neutrophil and macrophage infiltration; the expression of vWF, VEGF, and nestin; and the change in vessel volume within muscle in the first 7 d after injury (P < 0.05). By contrast, icing did not influence capillary density in muscle 28 d after injury (P = 0.59). The percentage of immature myofibers relative to the total number of fibers was greater in the icing group than in the sham group 28 d after injury (P = 0.026), but myofiber cross-sectional area did not differ between groups after 7 d (P = 0.35) and 28 d (P = 0.30). In conclusion, although icing disrupted inflammation and some aspects of angiogenesis/revascularization, these effects did not result in substantial differences in capillary density or muscle growth.