Hyperbaric oxygen for experimental intracerebral hemorrhage

Neuroprotective Therapies for Spontaneous Intracerebral Hemorrhage

Patients who survive the initial ictus of spontaneous intracerebral hemorrhage (ICH) remain vulnerable to subsequent injury of the perilesional parenchyma by molecular and cellular responses to the hematoma. Secondary brain injury after ICH, which contributes to long-term functional impairment and mortality, has emerged as an attractive therapeutic target. This review summarizes preclinical and clinical evidence for neuroprotective therapies targeting secondary injury pathways following ICH. A focus on therapies with pleiotropic antiinflammatory effects that target thrombin-mediated chemotaxis and inflammatory cell migration has led to studies investigating statins, anticholinergics, sphingosine-1-phosphate receptor modulators, peroxisome proliferator activated receptor gamma agonists, and magnesium. Attempts to modulate ICH-induced blood-brain barrier breakdown and perihematomal edema formation has prompted studies of nonsteroidal antiinflammatory agents, matrix metalloproteinase inhibitors, and complement inhibitors. Iron chelators, such as deferoxamine and albumin, have been used to reduce the free radical injury that ensues from erythrocyte lysis. Stem cell transplantation has been assessed for its potential to enhance subacute neurogenesis and functional recovery. Despite promising preclinical results of numerous agents, their outcomes have not yet translated into positive clinical trials in patients with ICH. Further studies are necessary to improve our understanding of the molecular events that promote damage and inflammation of the perihematomal parenchyma after ICH. Elucidating the temporal and pathophysiologic features of this secondary brain injury could enhance the clinical efficacy of neuroprotective therapies for ICH.

The efficacy of hyperbaric oxygen in hemorrhagic stroke: experimental and clinical implications

Hemorrhagic stroke, accounting for 10-30% of stroke cases, carries high rates of morbidity and mortality. This review presents the current knowledge on the efficacy of hyperbaric oxygen (HBO)-based modalities in the preclinical research on hemorrhagic stroke. Both preconditioning and post-treatment with HBO are considered as prospective therapeutic options. High efficacy of HBO therapy (HBOT) for brain hemorrhage has been noted. We found that moderate hyperbaric pressures appear optimal for therapeutic effect, while the therapeutic window of opportunity is short. HBO preconditioning offers more modest neuroprotective benefit as compared to HBO post-treatment for experimental intracerebral hemorrhage. We advocate for mandatory calculations of percent changes in the experimentally investigated indexes of HBO effectiveness and stress the need to design new clinical trials on HBO for hemorrhagic stroke.

Hyperbaric oxygen therapy and preconditioning for ischemic and hemorrhagic stroke

To date, the therapeutic methods for ischemic and hemorrhagic stroke are still limited. The lack of oxygen supply is critical for brain injury following stroke. Hyperbaric oxygen (HBO), an approach through a process in which patients breathe in 100% pure oxygen at over 101 kPa, has been shown to facilitate oxygen delivery and increase oxygen supply. Hence, HBO possesses the potentials to produce beneficial effects on stroke. Actually, accumulated basic and clinical evidences have demonstrated that HBO therapy and preconditioning could induce neuroprotective functions via different mechanisms. Nevertheless, the lack of clinical translational study limits the application of HBO. More translational studies and clinical trials are needed in the future to develop effective HBO protocols.

Normobaric oxygen therapy inhibits HIF-1α and VEGF expression in perihematoma and reduces neurological function defects

It is unknown whether normobaric oxygen (NBO) therapy exerts neuroprotective effects against human intracerebral hemorrhage (ICH). In this study, the potential of NBO therapy for salvaging brain damage following ICH was investigated in a rodent model with oxygen delivered at different concentrations. A total of 164 male Sprague-Dawley rats were induced with ICH using a collagenase injection and divided randomly into one ICH control group (no treatment, n=86) and three NBO treatment groups (35, 50, or 90% oxygen, n=26/group). Twenty-six rats were used as sham controls. The Neurological Severity Score (NSS) was evaluated. Contents of brain water, hypoxia-inducible factor 1α (HIF-1α), and vascular endothelial growth factor (VEGF) were measured in the perihematoma. A cellular apoptosis assay was performed. Compared with the sham control group, the ICH control group had higher NSS following ICH, which peaked at 24 h and began to decrease after 72 h. ICH rats also showed higher contents of brain water, HIF-1α, and VEGF (peaked at 72 h) in the ipsilateral perihematoma tissue than in the contralateral brain tissue. Compared with the ICH control group, all NBO groups showed improved NSSs, decreased contents of brain water, HIF-1α and VEGF, and fewer apoptotic cells in the perihematoma at 72 h after ICH, but statistical significance of these changes was achieved only with oxygen delivered at 90% (P<0.05, two-way analysis of variance). These results suggest that NBO therapy with oxygen delivered at 90% conferred best neuroprotection to ICH rats, potentially through amelioration of brain edema by suppressing HIF-1α and VEGF expression in the perihematoma.

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.

Hyperbaric oxygen preconditioning attenuates neuroinflammation after intracerebral hemorrhage in rats by regulating microglia characteristics

Intracerebral Hemorrhage (ICH) results in a detrimental neurologic disorder with complicated secondary brain injury. Hyperbaric oxygen preconditioning (HBOP) may be a safe and effective therapeutic method for ICH victims. Our previous studies have demonstrated that HBOP induces neuroprotection in cerebral ischemia and traumatic brain injury. This study aimed to investigate whether HBOP could alleviate neuroinflammation by regulating changes in microglia characteristics in a rat model of ICH. ICH was induced by autologous arterial blood injection, and animals were sacrificed at 12, 24, and 72 h post injury. We measured motor function and brain water content to evaluate the extent of inflammation. Fluoro-Jade C and TNF-α staining was used to characterize neuronal degeneration and neuroinflammatory cytokines, and immunofluorescence staining was performed for CD11b to show activated microglia and Iba-1 to show microglia. Our results indicate that motor dysfunction and brain water content are alleviated by HBOP, and Fluoro-Jade C staining demonstrates that neuron degeneration decreased in the HBOP group. The growth of Iba-1-positive microglia decreased in the HBOP group. Moreover, TNF-α was dynamically reduced in the HBOP group compared with the ICH group. CD11b-Iba-1 double staining demonstrated that the ratio of CD11b and Iba-1 was significantly decreased in the HBOP group. Overall, the data demonstrated that HBOP could significantly alleviate the ICH-induced neuroinflammation by regulating microglia characteristics changing. The phenomenon may propel the progress of the relation between microglia and HBOP and represent a novel target for ICH treatment.

Effect of hyperbaric oxygen preconditioning on peri-hemorrhagic focal edema and aquaporin-4 expression

The aim of the present study was to investigate the effect of hyperbaric oxygen preconditioning (HBO-PC) on peri-hemorrhagic focal edema and aquaporin-4 (AQP-4) expression in an experimental intracerebral hemorrhage (ICH) rat model. Sixty-six Sprague Dawley® rats were divided into three groups: The sham-surgery group (SHG; n=6); the control group (A-ICH; n=30), in which the rats were injected with autologous blood; and the experimental HBO-PC group (P-HBO; n=30). The rats underwent brain edema and AQP-4 detection at 5 postoperative time-points (24, 48 and 72 h and 5 and 7 days). The water content in the brain tissues of the A-ICH animals was higher than that in the brain tissues of the SHG rats at each time-point (P<0.05), and the edema in the P-HBO was significantly more severe 24 and 48 h postoperatively than that at 7 days postoperatively (P<0.05). The difference between the P-HBO and A-ICH was significant at 48 and 72 h postoperatively (P<0.05). AQP-4 was expressed in the post-hemorrhagic rat brains of all groups; the SHG animals exhibited low expression, while the A-ICH animals exhibited an increased expression 24 h postoperatively. In the A-ICH, expression peaked at 48 h postoperatively and began to decrease gradually after 72 h. At the 7-day time-point, the expression level in the A-ICH was closer to but still higher than that of the SHG animals (P<0.05). The differences between the P-HBO and A-ICH animals at the postoperative 24-h, 48-h and 7-day time-points were statistically significant (P<0.05). In conclusion, HBO-PC may downregulate AQP-4 expression to reduce the intracerebral edema, thus strengthening tolerance to ICH and protecting the nerves.

Hyperbaric oxygen for cerebral vasospasm and brain injury following subarachnoid hemorrhage

The impact of acute brain injury and delayed neurological deficits due to cerebral vasospasm (CVS) are major determinants of outcomes after subarachnoid hemorrhage (SAH). Although hyperbaric oxygen (HBO) had been used to treat patients with SAH, the supporting evidence and underlying mechanisms have not been systematically reviewed. In the present paper, the overview of studies of HBO for cerebral vasospasm is followed by a discussion of HBO molecular mechanisms involved in the protection against SAH-induced brain injury and even, as hypothesized, in attenuating vascular spasm alone. Faced with the paucity of information as to what degree HBO is capable of antagonizing vasospasm after SAH, the authors postulate that the major beneficial effects of HBO in SAH include a reduction of acute brain injury and combating brain damage caused by CVS. Consequently, authors reviewed the effects of HBO on SAH-induced hypoxic signaling and other mechanisms of neurovascular injury. Moreover, authors hypothesize that HBO administered after SAH may "precondition" the brain against the detrimental sequelae of vasospasm. In conclusion, the existing evidence speaks in favor of administering HBO in both acute and delayed phase after SAH; however, further studies are needed to understand the underlying mechanisms and to establish the optimal regimen of treatment.

Efficacy of hyperbaric oxygen treatment for depression in the convalescent stage following cerebral hemorrhage

The present study aimed to evaluate the clinical efficacy of hyperbaric oxygen (HBO) treatment for depression in the convalescent stage following cerebral hemorrhage. A total of 60 cases of patients with depression in the convalescent stage following cerebral hemorrhage (2–6 months) were randomly divided into the treatment group (treated with HBO, 30 cases) and the control group (treated with Deanxit, 30 cases). Prior to treatment and at 4 weeks post-treatment, efficacy was evaluated by the Hamilton Depression Scale (HAMD) and nerve function defect scores. There was a significant difference in the total efficacy between the two groups (P<0.05), and a significant difference in the HAMD scores (P<0.05). There were also significant differences between the pre- and post-treatment HAMD scores within the two groups (both P<0.05). HBO is able to significantly improve the degree of depression in the convalescent stage following cerebral hemorrhage and also promote nerve function recovery.

Neuroprotective effects of hyperbaric oxygen treatment on traumatic brain injury in the rat

This study was designed to evaluate the potential benefits of hyperbaric oxygen (HBO) in the treatment of traumatic brain injury (TBI). The right cerebral cortex of rats was injured by the impact of a 20-g object dropped from a predetermined height. The rats received HBO treatment at 3 ATA for 60 min after TBI. Neurological behavior score, brain water content, neuronal loss in the hippocampus, and cell apoptosis in brain tissue surrounding the primary injury site were examined to determine brain damage severity. Three and six hours after TBI, HBO-treated rats displayed a significant reduction in brain damage. However, by 12 h after TBI, the efficacy of HBO treatment was considerably attenuated. Furthermore, at 24, 48, and 72 h after TBI, the HBO treatment did not show any notable effects. In contrast, multiple HBO treatments (three or five times in all), even when started 48 h after TBI, remarkably reduced neurology deficit scores and the loss of neuronal numbers in the hippocampus. Although multiple treatments started at 48 h significantly improved neurological behaviors and reduced brain injury, the overall beneficial effects were substantially weaker than those seen after a single treatment at 6 h. These results suggest that: (1) HBO treatment could alleviate brain damage after TBI; (2) a single treatment with HBO has a time limitation of 12 h post-TBI; and (3) multiple HBO treatments have the possibility to extend the post-TBI delivery time window. Therefore, our results clearly suggest the validity of HBO therapy for the treatment of TBI.

Vascular Dysfunction in Brain Hemorrhage: Translational Pathways to Developing New Treatments from Old Targets

Hemorrhagic stroke which is a form of stroke that affects 20% of all stroke patients is a devastating condition for which new treatments must be developed. Current treatment methods are quite insufficient to reduce long term morbidity and high mortality rate, up to 50%, associated with bleeding into critical brain structures, into ventricular spaces and within the subarachnoid space. During the last 10-15 years, significant advances in the understanding of important mechanisms that contribute to cell death and clinical deficits have been made. The most important observations revolve around a key set of basic mechanisms that are altered in brain bleeding models, including activation of membrane metalloproteinases, oxidative stress and both inflammatory and coagulation pathways. Moreover, it is now becoming apparent that brain hemorrhage can activate the ischemic stroke cascade in neurons, glial cells and the vascular compartment. The activation of multiple pathways allows comes the opportunity to intervene pharmacologically using monotherapy or combination therapy. Ultimately, combination therapy or pleiotropic compounds with multi-target activities should prove to be more efficacious than any single therapy alone. This article provides a comprehensive look at possible targets for small molecule intervention as well as some new approaches that result in metabolic down-regulation or inhibition of multiple pathways simultaneously.