Effects of local hypothermia on neuronal cell apoptosis after intracerebral hemorrhage in rats

Targeting focal ischemic and hemorrhagic stroke neuroprotection: Current prospects for local hypothermia

Therapeutic hypothermia (TH) has applications dating back millennia. In modern history, however, TH saw its importation into medical practice where investigations have demonstrated that TH is efficacious in ischemic insults, notably cardiac arrest and hypoxic-ischemic encephalopathy. As well, studies have been undertaken to investigate whether TH can provide benefit in focal stroke (i.e., focal ischemia and intracerebral hemorrhage). However, clinical studies have encountered various challenges with induction and maintenance of post-stroke TH. Most clinical studies have attempted to use body-wide cooling protocols, commonly hindered by side effects that can worsen post-stroke outcomes. Some of the complications and difficulties with systemic TH can be circumvented by using local hypothermia (LH) methods. Additional advantages include the potential for lower target temperatures to be achieved and faster TH induction rates with LH. This systematic review summarizes the body of clinical and preclinical LH focal stroke studies and raises key points to consider for future LH research. We conclude with an overview of LH neuroprotective mechanisms and a comparison of LH mechanisms with those observed with systemic TH. Overall, whereas many LH studies have been conducted preclinically in the context of focal ischemia, insufficient work has been done in intracerebral hemorrhage. Furthermore, key translational studies have yet to be done in either stroke subtype (e.g., varied models and time-to-treat, studies considering aged animals or animals with co-morbidities). Few clinical LH investigations have been performed and the optimal LH parameters to achieve neuroprotection are unknown.

Melatonin Protects Against Ischemic Brain Injury by Modulating PI3K/AKT Signaling Pathway via Suppression of PTEN Activity

Stroke is one of the leading causes of death and disability worldwide with limited therapeutic options. Melatonin can attenuate ischemic brain damage with improved functional outcomes. However, the cellular mechanisms of melatonin-driven neuroprotection against post-stroke neuronal death remain unknown. Here, distal middle cerebral artery occlusion (dMCAO) was performed in C57BL/6j mice to develop an ischemic stroke in vivo model. Melatonin was injected intraperitoneally immediately after ischemia, and 24 and 48 hours later. Melatonin treatment, with 5 to 20 mg/kg, elicited a dose-dependent decrease in infarct volume and concomitant increase in sensorimotor function. At the molecular level, phosphorylation of PTEN and Akt were increased, whereas PTEN activity was decreased in melatonin treated animals 72 hours after dMCAO. At the cellular level, oxygenglucose deprivation (OGD) challenge of neuronal cell line Neuro-2a (N2a) and primary neurons supported melatonin’s direct protection against neuronal cell death. Melatonin treatment reduced LDH release and neuronal apoptosis at various time points, markedly increased Akt phosphorylation in neuronal membrane, but significantly suppressed it in the cytoplasm of post-OGD neurons. Mechanistically, melatonin-induced Akt phosphorylation and neuronal survival was blocked by Wortmannin, a potent PIP3 inhibitor, exposing increased PI3K/Akt activation as a central player in melatonin-driven neuroprotection. Finally, PTEN knock-down through siRNA significantly inhibited PI3K/Akt activation and cell survival following melatonin treatment, suggesting that melatonin protection against ischemic brain damage, is at least partially, dependent on modulation of the PTEN/PI3K/Akt signaling axis.

The relationship between estrogen-induced phenotypic transformation and proliferation of vascular smooth muscle and hypertensive intracerebral hemorrhage

Background

To explore the effect of estrogen on human cerebral vascular smooth muscle cells (VSMCs) and to clarify the molecular mechanism of estrogen inhibition of VSMC proliferation, which could provide an important reference basis for the clinical treatment of hypertensive intracerebral hemorrhage.

Method

Firstly, the effects of different concentrations of estradiol and estrogen receptor (ESR) blocker (tamoxifen) on the proliferation of human VSMCs and the expression of estrogen-related receptor gene (ESR: ESR1, ESR2, GPER), myocardin (MYOCD), serum reaction factor (SRF), and apoptosis gene caspase-3 were measured to discover the effect and mechanism of tamoxifen on the proliferation and apoptosis of VSMCs. Secondly, the effects of estradiol on human VSMCs treated with angiotensin II (Ang II) were observed by measuring the expression of vascular smooth muscle markers, α-smooth muscle actin (α-SMA), SM22α, FLN, MCP-1, and TLR4.

Results

Estradiol inhibited the proliferation of VSMCs by upregulating the expression of ESR1, ESR2, and GPER and downregulating the expression of caspase-3, MYOCD, and SRF, thereby inhibiting the apoptosis of vascular smooth muscle. At the same time, tamoxifen had opposite effects. Angiotensin II decreased the expression of α-SMA and SM22α and promoted the expression of FLN, MCP-1, and TLR4 protein, while estrogen had the opposite effects.

Conclusions

Estrogen suppresses apoptosis by inhibiting the proliferation of human VSMCs and preventing it from changing from contractile to synthetic. Estrogen can further prevents vascular damage and regulate peripheral inflammatory reaction, thereby producing a protective effect on cardiovascular and cerebrovascular.

Matrix Metalloproteinases in Acute Intracerebral Hemorrhage

Spontaneous intracerebral hemorrhage (ICH) accounts for 10-30% of all strokes and affects more than one million people every year worldwide, and it is the stroke subtype associated with the highest rates of mortality and residual disability. So far, clinical trials have mainly targeted primary cerebral injury and have substantially failed to improve clinical outcomes. The understanding of the pathophysiology of early and delayed injury after ICH is, hence, of paramount importance to identify potential targets of intervention and develop effective therapeutic strategies. Matrix metalloproteinases (MMPs) represent a ubiquitous superfamily of structurally related zinc-dependent endopeptidases able to degrade any component of the extracellular matrix. They are upregulated after ICH, in which different cell types, including leukocytes, activated microglia, neurons, and endothelial cells, are involved in their synthesis and secretion. The aim of this review is to summarize the available experimental and clinical evidence about the role of MMPs in brain injury following spontaneous ICH and provide critical insights into the underlying mechanisms.

Time-effect relationship of acupuncture on histopathology, ultrastructure, and neuroethology in the acute phase of cerebral hemorrhage

Many clinical studies have addressed the treatment of acute cerebral hemorrhage using acupuncture. However, few studies have examined the relationship between time of acupuncture and curative effect on cerebral hemorrhage. By observing the effect of acupuncture on changes in histopathology, ultrastructure, and neuroethology in a cerebral hemorrhage model of rats, we have directly examined the time-effect relationship of acupuncture. The rat model of cerebral hemorrhage was produced by slowly injecting autologous blood to the right caudate nucleus. The experimental groups were: 3-, 9-, 24-, and 48-hour model groups; and 3-, 9-, 24-, and 48-hour acupuncture groups. The sham-operation group was used for comparison. Acupuncture was performed at the Neiguan (PC6) and Renzhong (DU26) acupoints, twice a day, 6 hours apart, for 5 consecutive days. Brain tissue changes were observed by light microscopy and transmission electron microscopy. Neuroethology was assessed using Bederson and Longa scores. Our results show that compared with the sham-operation and model groups, Bederson and Longa scores were lower in each acupuncture group, with visibly improved histopathology and brain tissue ultrastructure. Further, the results were better in the 3- and 9-hour acupuncture groups than the 24- and 48-hour acupuncture groups. Our findings show that acupuncture treatment can relieve pathological and ultrastructural deterioration and neurological impairment caused by the acute phase of cerebral hemorrhage, and may protect brain tissue during this period. In addition, earlier acupuncture intervention following cerebral hemorrhage (by 3 or 9 hours) is associated with a better treatment outcome.

Neuroprotective and neuroregenerative potential of pharmacologically-induced hypothermia with D-alanine D-leucine enkephalin in brain injury

Neurovascular disorders, such as traumatic brain injury and stroke, persist as leading causes of death and disability - thus, the search for novel therapeutic approaches for these disorders continues. Many hurdles have hindered the translation of effective therapies for traumatic brain injury and stroke primarily because of the inherent complexity of neuropathologies and an inability of current treatment approaches to adapt to the unique cell death pathways that accompany the disorder symptoms. Indeed, developing potent treatments for brain injury that incorporate dynamic and multiple disorder-engaging therapeutic targets are likely to produce more effective outcomes than traditional drugs. The therapeutic use of hypothermia presents a promising option which may fit these criteria. While regulated temperature reduction has displayed great promise in preclinical studies of brain injury, clinical trials have been far less consistent and associated with adverse effects, especially when hypothermia is pursued via systemic cooling. Accordingly, devising better methods of inducing hypothermia may facilitate the entry of this treatment modality into the clinic. The use of the delta opioid peptide D-alanine D-leucine enkephalin (DADLE) to pharmacologically induce temperature reduction may offer a potent alternative, as DADLE displays both the ability to cause temperature reduction and to confer a broad profile of other neuroprotective and neuroregenerative processes. This review explores the prospect of DADLE-mediated hypothermia to treat neurovascular brain injuries, emphasizing the translational steps necessary for its clinical translation.

Ultrastructural Characteristics of Neuronal Death and White Matter Injury in Mouse Brain Tissues After Intracerebral Hemorrhage: Coexistence of Ferroptosis, Autophagy, and Necrosis

Although intracerebral hemorrhage (ICH) is a devastating disease worldwide, the pathologic changes in ultrastructure during the acute and chronic phases of ICH are poorly described. In this study, transmission electron microscopy was used to examine the ultrastructure of ICH-induced pathology. ICH was induced in mice by an intrastriatal injection of collagenase. Pathologic changes were observed in the acute (3 days), subacute (6 days), and chronic (28 days) phases. Compared with sham animals, we observed various types of cell death in the injured striatum during the acute phase of ICH, including necrosis, ferroptosis, and autophagy. Different degrees of axon degeneration in the striatum were seen in the acute phase, and axonal demyelination was observed in the ipsilateral striatum and corpus callosum at late time points. In addition, phagocytes, resident microglia, and infiltrating monocyte-macrophages were present around red blood cells and degenerating neurons and were observed to engulf red blood cells and other debris. Many synapses appeared abnormal or were lost. This systematic analysis of the pathologic changes in ultrastructure after ICH in mice provides information that will be valuable for future ICH pathology studies.

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.

Antipsychotic inductors of brain hypothermia and torpor-like states: perspectives of application

Hypothermia and hypometabolism (hypometabothermia) normally observed during natural hibernation and torpor, allow animals to protect their body and brain against the damaging effects of adverse environment. A similar state of hypothermia can be achieved under artificial conditions through physical cooling or pharmacological effects directed at suppression of metabolism and the processes of thermoregulation. In these conditions called torpor-like states, the mammalian ability to recover from stroke, heart attack, and traumatic injuries greatly increases. Therefore, the development of therapeutic methods for different pathologies is a matter of great concern. With the discovery of the antipsychotic drug chlorpromazine in the 1950s of the last century, the first attempts to create a pharmacologically induced state of hibernation for therapeutic purposes were made. That was the beginning of numerous studies in animals and the broad use of therapeutic hypothermia in medicine. Over the last years, many new agents have been discovered which were capable of lowering the body temperature and inhibiting the metabolism. The psychotropic agents occupy a significant place among them, which, in our opinion, is not sufficiently recognized in the contemporary literature. In this review, we summarized the latest achievements related to the ability of modern antipsychotics to target specific receptors in the brain, responsible for the initiation of hypometabothermia.

Meta-Analysis of Pre-Clinical Trials of Therapeutic Hypothermia for Intracerebral Hemorrhage

Therapeutic hypothermia (TH) is a potent neuroprotectant for experimental ischemic stroke, but studies of TH for intracerebral hemorrhage (ICH) are emerging. We systematically reviewed the experimental literature to assess TH efficacy for ICH. We found 18 suitable papers; quality scores were moderately good. Compared with normothermia, TH reduced measures of edema (mean effect size (95% CI) -1.6873 (-2.3640, -1.0106), p < 0.0001) or blood-brain barrier leakage (p < 0.0001) and improved behavioral outcomes (p < 0.0001). There was no evidence of publication bias. In this meta-analysis of available preclinical studies of ICH, TH is potently effective for reducing perihematomal edema and for improving behavioral outcomes.

Intracerebral Hemorrhage: Perihemorrhagic Edema and Secondary Hematoma Expansion: From Bench Work to Ongoing Controversies

Intracerebral hemorrhage (ICH) is a medical emergency, which often leads to severe disability and death. ICH-related poor outcomes are due to primary injury causing structural damage and mass effect and secondary injury in the perihemorrhagic region over several days to weeks. Secondary injury after ICH can be due to hematoma expansion (HE) or a consequence of repair pathway along the continuum of neuroinflammation, neuronal death, and perihemorrhagic edema (PHE). This review article is focused on PHE and HE and will cover the animal studies, related human studies, and clinical trials relating to these mechanisms of secondary brain injury in ICH patients.

Hypothermia and Rewarming Activate a Macroglial Unfolded Protein Response Independent of Hypoxic-Ischemic Brain Injury in Neonatal Piglets

Therapeutic hypothermia provides incomplete neuroprotection after hypoxia-ischemia (HI)-induced brain injury in neonates. We previously showed that cortical neuron and white matter apoptosis are promoted by hypothermia and early rewarming in a piglet model of HI. The unfolded protein response (UPR) may be one of the potential mediators of this cell death. Here, neonatal piglets underwent HI or sham surgery followed by 29 h of normothermia, 2 h of normothermia + 27 h of hypothermia or 18 h of hypothermia + rewarming. Piglets recovered for 29 h. Immunohistochemistry for endoplasmic reticulum to nucleus signaling-1 protein (ERN1), a marker of UPR activation, was used to determine the ratios of ERN1+ macroglia and neurons in the motor subcortical white matter and cerebral cortex. The ERN1+ macroglia were immunophenotyped as oligodendrocytes and astrocytes by immunofluorescent colabeling. Temperature (p = 0.046) and HI (p < 0.001) independently affected the ratio of ERN1+ macroglia. In sham piglets, sustained hypothermia (p = 0.011) and rewarming (p = 0.004) increased the ERN1+ macroglia ratio above that in normothermia. HI prior to hypothermia diminished the UPR. Ratios of ERN1+ macroglia correlated with white matter apoptotic profile counts in shams (r = 0.472; p = 0.026), thereby associating UPR activation with white matter apoptosis during hypothermia and rewarming. Accordingly, macroglial cell counts decreased in shams that received sustained hypothermia (p = 0.009) or rewarming (p = 0.007) compared to those in normothermic shams. HI prior to hypothermia neutralized the macroglial cell loss. Neither HI nor temperature affected ERN1+ neuron ratios. In summary, delayed hypothermia and rewarming activate the macroglial UPR, which is associated with white matter apoptosis. HI may decrease the macroglial endoplasmic reticulum stress response after hypothermia and rewarming.

Progress in AQP Research and New Developments in Therapeutic Approaches to Ischemic and Hemorrhagic Stroke

Cerebral edema often manifests after the development of cerebrovascular disease, particularly in the case of stroke, both ischemic and hemorrhagic. Without clinical intervention, the influx of water into brain tissues leads to increased intracranial pressure, cerebral herniation, and ultimately death. Strategies to manage the development of edema constitute a major unmet therapeutic need. However, despite its major clinical significance, the mechanisms underlying cerebral water transport and edema formation remain elusive. Aquaporins (AQPs) are a class of water channel proteins which have been implicated in the regulation of water homeostasis and cerebral edema formation, and thus represent a promising target for alleviating stroke-induced cerebral edema. This review examines the significance of relevant AQPs in stroke injury and subsequently explores neuroprotective strategies aimed at modulating AQP expression, with a particular focus on AQP4, the most abundant AQP in the central nervous system.

Therapeutic Hypothermia Does Not Mitigate Iron-Induced Injury in Rat

Intracerebral hemorrhage (ICH) is often a devastating stroke, and there are no clinically proven neuroprotective treatments. Considerable research points to iron toxicity as a leading contributor to secondary damage after ICH. Iron, released from degraded erythrocytes, catalyzes free radical production, thereby causing cell death in the ensuing days and weeks. Therapeutic hypothermia (TH) is a potential neuroprotective strategy for ICH, but results from animal studies are inconsistent and generally weaker than that found in ischemia models. Thus, we examined whether TH (∼33°C for 24-72 hours) would specifically mitigate iron toxicity, which we modeled by infusing 3.8 μg of FeCl2 in 30 μL of sterile saline into the striatum of rats. Rats were subjected to whole-body cooling beginning 1 hour after FeCl2 infusion. Use of TH reduced (p = 0.025) the small bleed caused by FeCl2 infusion (∼6 μL). However, TH did not lessen FeCl2-induced edema at 24 and 72 hours postinfusion, nor were behavioral impairments (e.g., walking) or brain injury (at 7 and 28 days) attenuated by TH. These results suggest that TH does not directly protect against iron toxicity, which indicates that this is not a means by which TH improves the outlook after ICH.

Prolonged Localized Mild Hypothermia Does Not Affect Seizure Activity After Intracerebral Hemorrhage in Rats

Intracerebral hemorrhage (ICH) is a devastating stroke with high morbidity and mortality. Post-ICH seizures are a common complication, potentially increasing brain injury and the risk of delayed epilepsy. Mild therapeutic hypothermia (HYPO, ∼33°C) is neuroprotective against several brain insults, such as ischemia, while also mitigating seizure incidence and severity in some instances. Therefore, we tested whether brain-selective HYPO reduced electrographic seizure activity after a collagenase-induced striatal ICH in rats. Animals were injected unilaterally with 0.14 U of bacterial collagenase, implanted with a unilateral brain cooling device, and a probe to bilaterally record electroencephalographic (EEG) activity. Cooling began 6 hours after collagenase infusion and was maintained for 48 hours, followed by rewarming over 6 hours. Our protocol did not affect EEG activity in naïve rats, nor did it increase bleeding after ICH (∼50 μL). Epileptiform activity commonly occurred in untreated ICH rats (∼60% of animals), but HYPO did not affect the incidence, timing, total duration of seizures, or the peaks occurring during epileptiform activity. However, longer average duration was detected on the ipsilateral side to stroke in the HYPO group (p < 0.05). Cooling did not affect neurological deficits (e.g., circling), measured 7 and 14 days after ICH, or lesion volume (∼35 mm(3)). In addition, there was no relationship among endpoints (e.g., seizures and lesion size). In summary, HYPO failed to reduce seizure activity after ICH, which fits with our separate findings that cooling does not mitigate thrombin and iron-mediated secondary injury mechanisms thought to cause seizures after ICH. Additional research is needed to identify better HYPO protocols and the use of cotreatments to maximize the benefit of HYPO to ICH patients.