Nicotinamide adenine dinucleotide phosphate (NAPDH) oxidase (NOX) is an enzyme complex with the sole function of producing superoxide anion and reactive oxygen species (ROS) at the expense of NADPH. ...Vital to the immune system as well as cellular signaling, NOX is also involved in the pathologies of a wide variety of disease states. Particularly, it is an integral player in many neurological diseases, including stroke, TBI, and neurodegenerative diseases. Pathologically, NOX produces an excessive amount of ROS that exceed the body's antioxidant ability to neutralize them, leading to oxidative stress and aberrant signaling. This prevalence makes it an attractive therapeutic target and as such, NOX inhibitors have been studied and developed to counter NOX's deleterious effects. However, recent studies of NOX have created a better understanding of the NOX complex. Comprised of independent cytosolic subunits, p47-
, p67-
, p40-
and
, and membrane subunits, gp91-
and p22-
, the NOX complex requires a unique activation process through subunit interaction. Of these subunits, p47-
plays the most important role in activation, binding and translocating the cytosolic subunits to the membrane and anchoring to p22-
to organize the complex for NOX activation and function. Moreover, these interactions, particularly that between p47-
and p22-
, are dependent on phosphorylation initiated by upstream processes involving protein kinase C (PKC). This review will look at these interactions between subunits and with PKC. It will focus on the interaction involving p47-
with p22-
, key in bringing the cytosolic subunits to the membrane. Furthermore, the implication of these interactions as a target for NOX inhibitors such as apocynin will be discussed as a potential avenue for further investigation, in order to develop more specific NOX inhibitors based on the inhibition of NOX assembly and activation.
Sublethal hypoxic or ischemic events can improve the tolerance of tissues, organs, and even organisms from subsequent lethal injury caused by hypoxia or ischemia. This phenomenon has been termed ...hypoxic or ischemic preconditioning (HPC or IPC) and is well established in the heart and the brain. This review aims to discuss HPC and IPC with respect to their historical development and advancements in our understanding of the neurochemical basis for their neuroprotective role. Through decades of collaborative research and studies of HPC and IPC in other organ systems, our understanding of HPC and IPC-induced neuroprotection has expanded to include: early- (phosphorylation targets, transporter regulation, interfering RNA) and late- (regulation of genes like EPO, VEGF, and iNOS) phase changes, regulators of programmed cell death, members of metabolic pathways, receptor modulators, and many other novel targets. The rapid acceleration in our understanding of HPC and IPC will help facilitate transition into the clinical setting.
A depressive or hibernation-like effect of chlorpromazine and promethazine (C + P) on brain activity was reported to induce neuroprotection, with or without induced-hypothermia. However, the ...underlying mechanisms remain unclear. The current study evaluated the pharmacological function of C + P on the inhibition of neuroinflammatory response and inflammasome activation after ischemia/reperfusion. A total of 72 adult male Sprague–Dawley rats were subjected to 2 h middle cerebral artery occlusion (MCAO) followed by 6 or 24 h reperfusion. At the onset of reperfusion, rats received C + P (8 mg/kg) with temperature control. Brain cell death was detected by measuring CD68 and myeloperoxidase (MPO) levels. Inflammasome activation was measured by mRNA levels of NLRP3, IL-1β, and TXNIP, and protein quantities of NLRP3, IL-1β, TXNIP, cleaved-Caspase-1, and IL-18. Activation of JAK2/STAT3 pathway was detected by the phosphorylation of STAT3 (p-STAT3) and JAK2 (p-JAK2), and the co-localization of p-STAT3 and NLRP3. Activation of the p38 pathway was assessed with the protein levels of p-p38/p38. The mRNA and protein levels of HIF-1α, FoxO1, and p-FoxO1, and the co-localization of p-STAT3 with HIF-1α or FoxO1 were quantitated. As expected, C + P significantly reduced cell death and attenuated the neuroinflammatory response as determined by reduced CD68 and MPO. C + P decreased ischemia-induced inflammasome activation, shown by reduced mRNA and protein expressions of NLRP3, IL-1β, TXNIP, cleaved-Caspase-1, and IL-18. Phosphorylation of JAK2/STAT3 and p38 pathways and the co-localization of p-STAT3 with NLRP3 were also inhibited by C + P. Furthermore, mRNA levels of HIF-1α and FoxO1 were decreased in the C + P group. While C + P inhibited HIF-1α protein expression, it increased FoxO1 phosphorylation, which promoted the exclusion of FoxO1 from the nucleus and inhibited FoxO1 activity. At the same time, C + P reduced the co-localization of p-STAT3 with HIF-1α or FoxO1. In conclusion, C + P treatment conferred neuroprotection in stroke by suppressing neuroinflammation and NLRP3 inflammasome activation. The present study suggests that JAK2/STAT3/p38/HIF-1α/FoxO1 are vital regulators and potential targets for efficacious therapy following ischemic stroke.
Ischemic stroke destroys blood–brain barrier (BBB) integrity. There are currently no effective treatments available in the clinical setting. Post-ischemia treatment with phenothiazine drugs combined ...chlorpromazine and promethazine (C+P) has been shown to be neuroprotective in stroke. The present study determined the effect of C+P in BBB integrity. Sprague-Dawley rats were divided into the following groups (n=8 each): (1) stroke, (2) stroke treated by C+P with temperature control, and (3) stroke treated by C+P without temperature control. Infarct volume and neurological deficits were measured to assess the neuroprotective effect of C+P. BBB permeability was determined by brain edema and Evans blue leakage. Expression of BBB integral molecules, including proteins of aquaporin-4 and -9 (AQP-4, AQP-9), matrix metalloproteinase-2 and -9 (MMP-2, MMP-9), zonula occludens-1 (ZO-1), claudin-1/5, occludin, and laminin were determined by Western blot. Stroke caused brain infarction and neurological deficits, as well as BBB damage, which were all attenuated by C+P through drug-induced hypothermia. When the reduced temperature was controlled to physiological levels, C+P still conferred neuroprotection, suggesting a therapeutic effect independent of hypothermia. Furthermore, C+P significantly attenuated the increase in AQP-4, AQP-9, MMP-2, and MMP-9 levels after stroke, and reversed the decrease in tight junction protein (ZO-1, claudin-1/5, occludin) and basal laminar protein (laminin) levels. This study clearly indicates a beneficial effect of C+P on BBB integrity after stroke, which may be independent of drug-induced hypothermia. These findings further prove the clinical target and cell-signal communication of C+P treatment, which may direct us closer toward the development of an efficacious neuroprotective therapy.
There remain debates on neuroprotection and rehabilitation techniques for acute ischemic stroke patients. Therapeutic physical exercise following stroke has shown promise but is challenging to apply ...clinically. Ischemic conditioning, which has several clinical advantages, is a potential neuroprotective method for stroke rehabilitation that is less understood. In the present study, the rehabilitative properties and mechanisms of physical exercise and remote ischemic postconditioning (RIPostC) after stroke were compared and determined. A total of 248 adult male Sprague-Dawley rats were divided into five groups: (1) sham, (2) stroke, (3) stroke with intense treadmill exercise, (4) stroke with mild treadmill exercise, and (5) stroke with RIPostC. Focal ischemia was evaluated by infarct volume and neurological deficit. Long-term functional outcomes were represented through neurobehavioral function tests: adhesive removal, beam balance, forelimb placing, grid walk, rota-rod, and Morris water maze. To further understand the mechanisms underlying neurorehabilitation and verify the presence thereof, we measured mRNA and protein levels of neuroplasticity factors, synaptic proteins, angiogenesis factors, and regulation molecules, including HIF-1α, BDNF, TrkB, and CREB. The key role of HIF-1α was elucidated by using the inhibitor, YC-1. Both exercise intensities and RIPostC significantly decreased infarct volumes and neurological deficits and outperformed the stroke group in the neurobehavioral function tests. All treatment groups showed significant increases in mRNA and protein expression levels of the target molecules for neurogenesis, synaptogenesis, and angiogenesis, with intermittent further increases in the RIPostC group. HIF-1α inhibition nullified most beneficial effects and indicative molecule expressions, including HIF-1α, BDNF, TrkB, and CREB, in both procedures. RIPostC is equally, or superiorly, effective in inducing neuroprotection and rehabilitation compared to exercise in ischemic rats. HIF-1α likely plays an important role in the efficacy of neuroplasticity conditioning, possibly through HIF-1α/BDNF/TrkB/CREB regulation.
Oligodendrocytes (OLs), the myelin-forming cells of the central nervous system, are integral to axonal integrity and function. Hypoxia-ischemia episodes can cause severe damage to these vulnerable ...cells through excitotoxicity, oxidative stress, inflammation, and mitochondrial dysfunction, leading to axonal dystrophy, neuronal dysfunction, and neurological impairments. OLs damage can result in demyelination and myelination disorders, severely impacting axonal function, structure, metabolism, and survival. Adult-onset stroke, periventricular leukomalacia, and post-stroke cognitive impairment primarily target OLs, making them a critical therapeutic target. Therapeutic strategies targeting OLs, myelin, and their receptors should be given more emphasis to attenuate ischemia injury and establish functional recovery after stroke. This review summarizes recent advances on the function of OLs in ischemic injury, as well as the present and emerging principles that serve as the foundation for protective strategies against OLs deaths.
•Recent advances on the function of OLs in ischemic stroke.•More attention should be paid to treatment strategies for OLs, myelin sheath, and their receptors.•The present and emerging principles that serve as the foundation for protective strategies against OLs deaths.
Remote ischaemic conditioning (RIC) triggers endogenous protective pathways in distant organs such as the kidney, heart and brain, and represents an exciting new paradigm in neuroprotection. RIC ...involves repetitive inflation and deflation of a blood pressure cuff on the limb, and is safe and feasible. The exact mechanism of signal transmission from the periphery to the brain is not known, but both humoral factors and an intact nervous system seem to have critical roles. Early-phase clinical trials have already been conducted to test RIC in the prehospital setting in acute ischaemic stroke, and in subarachnoid haemorrhage for the prevention of delayed cerebral ischaemia. Furthermore, two small randomized clinical trials in patients with symptomatic intracranial atherosclerosis have shown that RIC can reduce recurrence of stroke and have neuroprotective activity. RIC represents a highly practical and translatable therapy for acute, subacute, and chronic neurological diseases with an ischaemic or inflammatory basis. In this Review, we consider the principles and mechanisms of RIC, evidence from preclinical models and clinical trials that RIC is beneficial in neurological disease, and how the procedure might be used in the future in disorders such as vascular cognitive impairment and traumatic brain injury.
Exercise therapy is commonly recommended and is often considered to be the gold standard of rehabilitation in patients with ischemic stroke. However, implementation and standardization of exercise ...therapy are challenging as patients vary in their abilities, disabilities, and willingness to participate in exercise rehabilitation after a cerebrovascular event. Remote ischemic conditioning (RIC) is a more passive and accessible therapy that, although remains in its infancy, has the potential to confer similar neuroprotective effects as exercise. In the previously published Part I of this Mini Review, we examined the biochemical evidence for exercise and RIC and noted that the in vitro results may be misleading outside of the context of clinical application. In the present review, we investigate the various clinical parameters by which exercise and RIC therapy may be most beneficial to ischemic stroke victims. We also extend our discussion to consider the therapeutic combination of RIC and exercise therapy to maximize functional outcomes after stroke.
Although physical exercise has been demonstrated to augment recovery of the post-stroke brain, the question of what level of exercise intensity optimizes neurological outcomes of post-stroke ...rehabilitation remains unsettled. In this study, we aim to clarify the mechanisms underlying the intensity-dependent effect of exercise on neurologic function, and thereby to help direct the clinical application of exercise-based neurorehabilitation. To do this, we used a well-established rat model of ischemic stroke consisting of cerebral ischemia induction through middle cerebral artery occlusion. Ischemic rats were subsequently assigned either to a control group entailing post-stroke rest, or to one of two exercise groups distinguished by the intensity of their accompanying treadmill regimens. After 24 h of reperfusion, exercise was initiated. Infarct volume, apoptotic cell death, and neurological defects were quantified in all groups at 3 days, and motor and cognitive function were tracked up to day 28. Additionally, Western blotting was used to assess the influence of our interventions on several proteins related to synaptogenesis and neuroplasticity (growth-associated protein 43, microtubule-associated protein, postsynaptic density-95, synapsin I, hypoxia inducible factor-1α, brain-derived neurotrophic factor, nerve growth factor, tyrosine kinase B, and cAMP response element binding protein). Our results were in equal parts encouraging and surprising. Both mild and intense exercise significantly decreased infarct volume, cell death, and neurological deficits. Motor and cognitive function, as determined using an array of tests such as beam balance, forelimb placing, and the Morris water maze, were also significantly improved by both exercise protocols. Interestingly, while an obvious enhancement of neuroplasticity proteins was shown in both exercise groups, mild exercise rats demonstrated a stronger effect on the expressions of Tau (p<0.01), brain-derived neurotrophic factor (p<0.01), and tyrosine kinase B (p<0.05). These findings contribute to the growing body of literature regarding the positive effects of both mild and intense long-term treadmill exercise on brain injury, functional outcome, and neuroplasticity. Additionally, the results may provide a base for our future study regarding the regulation of HIF-1α on the BDNF/TrkB/CREB pathway in the biochemical processes underlying post-stroke synaptic plasticity.
Adjuvant neuroprotective therapies for acute ischemic stroke (AIS) have demonstrated benefit in animal studies, albeit without human translation. We investigated the safety and efficacy of high-flow ...normobaric oxygen (NBO) after endovascular recanalization in anterior circulation stroke. This is a prospective randomized controlled study. Eligible patients were randomized to receive high-flow NBO by a Venturi mask (FiO
2
50%, flow 15 L/min) or routine low-flow oxygen supplementation by nasal cannula (flow 3 L/min) after vessel recanalization for 6 h. Patient demographics, procedural metrics, complications, functional outcomes, symptomatic intracranial hemorrhage (sICH), and infarct volume were assessed. A total of 91 patients were treated with high-flow NBO. NBO treatment revealed a common odds ratio of 2.2 (95% CI, 1.26 to 3.87) favoring the distribution of global disability scores on the mRS at 90 days. The mortality at 90 days was significantly lower in the NBO group than in the control group, with an absolute difference of 13.86% (rate ratio, 0.35; 95% CI, 0.13–0.93). A significant reduction of infarct volume as determined by MRI was noted in the NBO group. The median infarct volume was 9.4 ml
versus
20.5 ml in the control group (beta coefficient, − 20.24; 95% CI, − 35.93 to − 4.55). No significant differences were seen in the rate of sICH, pneumonia, urinary infection, and seizures between the 2 groups. This study suggests that high-flow NBO therapy after endovascular recanalization is safe and effective in improving functional outcomes, decreasing mortality, and reducing infarct volumes in anterior circulation stroke patients within 6 h from stroke onset.
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