Limb Ischemic Conditioning Improved Cognitive Deficits via eNOS-Dependent Augmentation of Angiogenesis after Chronic Cerebral Hypoperfusion in Rats

The emerging role of nitric oxide in the synaptic dysfunction of vascular dementia

With an increase in global aging, the number of people affected by cerebrovascular diseases is also increasing, and the incidence of vascular dementia-closely related to cerebrovascular risk-is increasing at an epidemic rate. However, few therapeutic options exist that can markedly improve the cognitive impairment and prognosis of vascular dementia patients. Similarly in Alzheimer's disease and other neurological disorders, synaptic dysfunction is recognized as the main reason for cognitive decline. Nitric oxide is one of the ubiquitous gaseous cellular messengers involved in multiple physiological and pathological processes of the central nervous system. Recently, nitric oxide has been implicated in regulating synaptic plasticity and plays an important role in the pathogenesis of vascular dementia. This review introduces in detail the emerging role of nitric oxide in physiological and pathological states of vascular dementia and summarizes the diverse effects of nitric oxide on different aspects of synaptic dysfunction, neuroinflammation, oxidative stress, and blood-brain barrier dysfunction that underlie the progress of vascular dementia. Additionally, we propose that targeting the nitric oxide-sGC-cGMP pathway using certain specific approaches may provide a novel therapeutic strategy for vascular dementia.

Remote ischemic conditioning prevents ischemic cerebrovascular events in children with moyamoya disease: a randomized controlled trial

BACKGROUND

Moyamoya disease (MMD) is a significant cause of childhood stroke and transient ischemic attacks (TIAs). This study aimed to assess the safety and efficacy of remote ischemic conditioning (RIC) in children with MMD.

METHODS

In a single-center pilot study, 46 MMD patients aged 4 to 14 years, with no history of reconstructive surgery, were randomly assigned to receive either RIC or sham RIC treatment twice daily for a year. The primary outcome measured was the cumulative incidence of major adverse cerebrovascular events (MACEs). Secondary outcomes included ischemic stroke, recurrent TIA, hemorrhagic stroke, revascularization rates, and clinical improvement assessed using the patient global impression of change (PGIC) scale during follow-up. RIC-related adverse events were also recorded, and cerebral hemodynamics were evaluated using transcranial Doppler.

RESULTS

All 46 patients completed the final follow-up (23 each in the RIC and sham RIC groups). No severe adverse events associated with RIC were observed. Kaplan-Meier analysis indicated a significant reduction in MACEs frequency after RIC treatment [log-rank test (Mantel-Cox), P = 0.021]. At 3-year follow-up, two (4.35%) patients had an ischemic stroke, four (8.70%) experienced TIAs, and two (4.35%) underwent revascularization as the qualifying MACEs. The clinical improvement rate in the RIC group was higher than the sham RIC group on the PGIC scale (65.2% vs. 26.1%, P < 0.01). No statistical difference in cerebral hemodynamics post-treatment was observed.

CONCLUSIONS

RIC is a safe and effective adjunct therapy for asymptomatic children with MMD. This was largely due to the reduced incidence of ischemic cerebrovascular events.

A novel stroke rehabilitation strategy and underlying stress granule regulations through inhibition of NLRP3 inflammasome activation

OBJECTIVE

Dynamic changes in ischemic pathology after stroke suggested a "critical window" of enhanced neuroplasticity immediately after stroke onset. Although physical exercise has long been considered a promising strategy of stroke rehabilitation, very early physical exercise may exacerbate brain injury. Since remote ischemic conditioning (RIC) promotes neuroprotection and neuroplasticity, the present study combined RIC with sequential exercise to establish a new rehabilitation strategy for a better rehabilitative outcome.

METHODS

A total of 120 adult male Sprague-Dawley rats were used and divided into five groups: (1) sham, (2) stroke, (3) stroke with exercise, (4) stroke with RIC, and (5) stroke with RIC followed by exercise. Brain damage was evaluated by infarct volume, neurological deficit, cell death, and lactate dehydrogenase (LDH) activity. Long-term functional outcomes were determined by grid walk tests, rotarod tests, beam balance tests, forelimb placing tests, and the Morris water maze. Neuroplasticity was evaluated through measurements of both mRNA and protein levels of synaptogenesis (synaptophysin [SYN], post-synaptic density protein-95 [PSD-95], and brain-derived neurotrophic factor [BDNF]) and angiogenesis (vascular endothelial growth factor [VEGF], angiopoietin-1 [Ang-1], and angiopoietin-2 [Ang-2]). Inflammasome activation was measured by concentrations of interleukin-18 (IL-18) and IL-1β detected by enzyme-linked immunosorbent assay (ELISA) kits, mRNA expressions of NLR pyrin domain containing 3 (NLRP3), apoptosis-associated speck-like protein containing a C-terminal caspase recruitment domain (ASC), IL-18 and IL-1β, and protein quantities of NLRP3, ASC, cleaved-caspase-1, gasdermin D-N (GSDMD-N), and IL-18 and IL-1β. Stress granules (SGs), including GTPase-activating protein-binding protein 1 (G3BP1), T cell-restricted intracellular antigen-1 (TIA1), and DEAD-box RNA helicase 3X (DDX3X) were evaluated at mRNA and protein levels. The interactions between DDX3X with NLRP3 or G3BP1 were determined by immunofluorescence and co-immunoprecipitation.

RESULTS

Early RIC decreased infarct volumes, neurological deficits, cell death, and LDH activity at post-stroke Day 3 (p < 0.05). All treatment groups showed significant improvement in functional outcomes, including sensory, motor, and cognitive functions. RIC and exercise, as compared to RIC or physical exercise alone, had improved functional outcomes after stroke (p < 0.05), as well as synaptogenesis and angiogenesis (p < 0.05). RIC significantly reduced mRNA and protein expressions of NLRP3 (p < 0.05). SGs formation peaked at 0 h after ischemia, then progressively decreased until 24 h postreperfusion, which was reversed by RIC (p < 0.05). The assembly of SGs consumed DDX3X and then inhibited NLRP3 inflammasome activation.

CONCLUSIONS

RIC followed by exercise induced a better rehabilitation in ischemic rats, while early RIC alleviated ischemia-reperfusion injury via stress-granule-mediated inhibition of NLRP3 inflammasome.

The MT1 receptor as the target of ramelteon neuroprotection in ischemic stroke

Stroke is the leading cause of death and disability worldwide. Novel and effective therapies for ischemic stroke are urgently needed. Here, we report that melatonin receptor 1A (MT1) agonist ramelteon is a neuroprotective drug candidate as demonstrated by comprehensive experimental models of ischemic stroke, including a middle cerebral artery occlusion (MCAO) mouse model of cerebral ischemia in vivo, organotypic hippocampal slice cultures ex vivo, and cultured neurons in vitro; the neuroprotective effects of ramelteon are diminished in MT1-knockout (KO) mice and MT1-KO cultured neurons. For the first time, we report that the MT1 receptor is significantly depleted in the brain of MCAO mice, and ramelteon treatment significantly recovers the brain MT1 losses in MCAO mice, which is further explained by the Connectivity Map L1000 bioinformatic analysis that shows gene-expression signatures of MCAO mice are negatively connected to melatonin receptor agonist like Ramelteon. We demonstrate that ramelteon improves the cerebral blood flow signals in ischemic stroke that is potentially mediated, at least, partly by mechanisms of activating endothelial nitric oxide synthase. Our results also show that the neuroprotection of ramelteon counteracts reactive oxygen species-induced oxidative stress and activates the nuclear factor erythroid 2-related factor 2/heme oxygenase-1 pathway. Ramelteon inhibits the mitochondrial and autophagic death pathways in MCAO mice and cultured neurons, consistent with gene set enrichment analysis from a bioinformatics perspective angle. Our data suggest that Ramelteon is a potential neuroprotective drug candidate, and MT1 is the neuroprotective target for ischemic stroke, which provides new insights into stroke therapy. MT1-KO mice and cultured neurons may provide animal and cellular models of accelerated ischemic damage and neuronal cell death.

Remote Ischemic Conditioning for Motor Recovery after Acute Ischemic Stroke

BACKGROUND

Remote ischemic conditioning (RIC) has shown an impressive neuroprotective effect on acute ischemic stroke (AIS) in animal experiments. But whether chronic RIC improves long-term functional outcomes remains unclear.

MATERIALS AND METHODS

We performed a non-randomized controlled trial. Eligible patients (aged 18 -80 y) with hemiplegia caused by AIS were allocated to the RIC group and the control group. All participants received normal protocol rehabilitation therapy. Patients in the RIC group underwent RIC twice daily for 90 days. The outcome included the 90-day Fugl-Meyer Assessment (FMA) scores and modified Rankin's scale (mRS) scores, as well as changes in angiogenesis-related factors in serum from baseline to 90 days.

RESULTS

Twenty-seven patients were included in the analysis (13 in the RIC group and 14 in the control group). There was no significant difference in 90-day total FMA scores between the two groups. Lower limb FMA scores at day 90 were significantly higher in the RIC group (32.8±8.7 vs. 24.8±5.4, adjusted P =0.042). The proportion of favorable outcome (mRS<2) was higher in the RIC group than that in the control group, but no significant difference was detected (8 [61.5%] vs. 7 [50%], P =0.705). A significant increase has been found in the level of epidermal growth factor (EGF) in serum (9.4 [1.1 to 25.7] vs. -8.7 [-15.1 to 4.7], P =0.036) after chronic RIC procedure.

CONCLUSION

This study investigated the role that RIC plays in AIS recovery, especially in motor function. RIC may have beneficial effects on lower limbs recovery by enhancing the EGF level. The effect of RIC on motor recovery should be further validated in future studies.

Remote ischemic conditioning alleviates chronic cerebral hypoperfusion-induced cognitive decline and synaptic dysfunction via the miR-218a-5p/SHANK2 pathway

Vascular cognitive impairment (VCI) due to chronic cerebral hypoperfusion (CCH), is the second leading cause of dementia. Although synaptic impairment plays a critical role in VCI, its exact mechanism remains unknown. Our previous research revealed that remote ischemic conditioning (RIC) could alleviate cognitive decline resulting from CCH, however, its effects on synaptic impairment remain unclear. In this study, we confirmed that RIC alleviated both cognitive decline and its associated synaptic dysfunction caused by CCH. RNA sequencing revealed that CCH increased in miR-218a-5p expression, which was decreased by RIC. Elevated miR-218a-5p levels limited the benefits of RIC, however, inhibiting miR-218a-5p in hippocampal CA1 neurons rescued synaptic dysfunction. Additionally, we found that SHANK2 is a downstream target of miR-218a-5p, and inhibiting SHANK2 expression reduced the alleviation caused by hypoxic conditioning in synaptic impairment in vitro. In conclusion, our results suggested that RIC alleviated synaptic impairment via the miR-218a-5p/SHANK2 pathway, which could be a potential biomarker or therapeutic target for cognitive impairment caused by CCH.

Relationship between insulin-like growth factor-1 and cerebral small vessel disease and its mechanisms: advances in the field

Insulin-like growth factor-1 (IGF-1) is an active polypeptide protein that closely resembles the structural sequence of insulin and is involved in a variety of metabolic processes in the body. Decreased IGF-1 circulation levels are associated with an increased risk of stroke and a poorer prognosis, but the relationship with cerebral small vessel disease (cSVD) is unclear. Some studies found that the level of IGF-1 in patients with cSVD was significantly reduced, but the clinical significance and underlying mechanisms are unknown. This article reviews the correlation between IGF-1 and cerebrovascular disease and explores the potential relationship and mechanism between IGF-1 and cSVD.

Remote ischemic conditioning in necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a devastating intestinal inflammatory disorder, most prevalent in premature infants, and associated with a high mortality rate that has remained unchanged in the past two decades. NEC is characterized by inflammation, ischemia, and impaired microcirculation in the intestine. Preclinical studies by our group have led to the discovery of remote ischemic conditioning (RIC) as a promising non-invasive intervention in protecting the intestine against ischemia-induced damage during early-stage NEC. RIC involves the administration of brief reversible cycles of ischemia and reperfusion in a limb (similar to taking standard blood pressure measurement) which activate endogenous protective signaling pathways that are conveyed to distant organs such as the intestine. RIC targets the intestinal microcirculation and by improving blood flow to the intestine, reduces the intestinal damage of experimental NEC and prolongs survival. A recent Phase I safety study by our group demonstrated that RIC was safe in preterm infants with NEC. A phase II feasibility randomized controlled trial involving 12 centers in 6 countries is currently underway, to investigate the feasibility of RIC as a treatment for early-stage NEC in preterm neonates. This review provides a brief background on RIC as a therapeutic strategy and summarizes the progression of RIC as a treatment for NEC from preclinical investigation to clinical evaluation.

Necrotizing enterocolitis: recent advances in treatment with translational potential

Necrotizing enterocolitis (NEC) is one of the most prevalent and devastating gastrointestinal disorders in neonates. Despite advances in neonatal care, the incidence and mortality due to NEC remain high, highlighting the need to devise novel treatments for this disease. There have been a number of recent advancements in therapeutic approaches for the treatment of NEC; these involve remote ischemic conditioning (RIC), stem cell therapy, breast milk components (human milk oligosaccharides, exosomes, lactoferrin), fecal microbiota transplantation, and immunotherapy. This review summarizes the most recent advances in NEC treatment currently underway as well as their applicability and associated challenges and limitations, with the aim to provide new insight into the paradigm of care for NEC worldwide.

Altered endocannabinoid metabolism compromises the brain-CSF barrier and exacerbates chronic deficits after traumatic brain injury in mice

Endocannabinoids [2-arachidonoylglycerol (2-AG) and N-arachidonoylethanolamine (AEA)], endogenously produced arachidonate-based lipids, are anti-inflammatory physiological ligands for two known cannabinoid receptors, CB1 and CB2, yet the molecular and cellular mechanisms underlying their effects after brain injury are poorly defined. In the present study, we hypothesize that traumatic brain injury (TBI)-induced loss of endocannabinoids exaggerates neurovascular injury, compromises brain-cerebrospinal fluid (CSF) barriers (BCB) and causes behavioral dysfunction. Preliminary analysis in human CSF and plasma indicates changes in endocannabinoid levels. This encouraged us to investigate the levels of endocannabinoid-metabolizing enzymes in a mouse model of controlled cortical impact (CCI). Reductions in endocannabinoid (2-AG and AEA) levels in plasma were supported by higher expression of their respective metabolizing enzymes, monoacylglycerol lipase (MAGL), fatty acid amide hydrolase (FAAH), and cyclooxygenase 2 (Cox-2) in the post-TBI mouse brain. Following increased metabolism of endocannabinoids post-TBI, we observed increased expression of CB2, non-cannabinoid receptor Transient receptor potential vanilloid-1 (TRPV1), aquaporin 4 (AQP4), ionized calcium binding adaptor molecule 1 (IBA1), glial fibrillary acidic protein (GFAP), and acute reduction in cerebral blood flow (CBF). The BCB and pericontusional cortex showed altered endocannabinoid expressions and reduction in ventricular volume. Finally, loss of motor functions and induced anxiety behaviors were observed in these TBI mice. Taken together, our findings suggest endocannabinoids and their metabolizing enzymes play an important role in the brain and BCB integrity and highlight the need for more extensive studies on these mechanisms.

Mitochondrial oxidative stress in brain microvascular endothelial cells: Triggering blood-brain barrier disruption

Blood-brain barrier disruption plays an important role in central nervous system diseases. This review provides information on the role of mitochondrial oxidative stress in brain microvascular endothelial cells in cellular dysfunction, the disruption of intercellular junctions, transporter dysfunction, abnormal angiogenesis, neurovascular decoupling, and the involvement and aggravation of vascular inflammation and illustrates related molecular mechanisms. In addition, recent drug and nondrug therapies targeting cerebral vascular endothelial cell mitochondria to repair the blood-brain barrier are discussed. This review shows that mitochondrial oxidative stress disorder in brain microvascular endothelial cells plays a key role in the occurrence and development of blood-brain barrier damage and may be critical in various pathological mechanisms of blood-brain barrier damage. These new findings suggest a potential new strategy for the treatment of central nervous system diseases through mitochondrial modulation of cerebral vascular endothelial cells.

A review of remote ischemic conditioning as a potential strategy for neural repair poststroke

Ischemic stroke is one of the major disabling health-care problem and multiple different approaches are needed to enhance rehabilitation, in which neural repair is the structural basement. Remote ischemic conditioning (RIC) is a strategy to trigger endogenous protect. RIC has been reported to play neuroprotective role in acute stage of stroke, but the effect of RIC on repair process remaining unclear. Several studies have discovered some overlapped mechanisms RIC and neural repair performs. This review provides a hypothesis that RIC is a potential therapeutic strategy on stroke rehabilitation by evaluating the existing evidence and puts forward some remaining questions to clarify and future researches to be performed in the field.

Nanomedicine in Neuroscience: An Application Towards the Treatment of Various Neurological Diseases

Absatract:

The effectiveness, cell viability, and selective delivery of medications and diagnostic substances to target organs, tissues, and organs are typical concerns in the care and prognosis of many illnesses. Neurological diseases pose complex challenges, as cerebral targeting represents a yet unresolved challenge in pharmacotherapy, owing to the blood-brain boundary, a densely com-pacted membrane of endothelial cells that prohibits undesired chemicals from reaching the brain. Engineered nanoparticles, with dimensions ranging from 1 to 100 nm, provide intriguing biomedi-cal techniques that may allow for resolving these issues, including the ability to cross the blood-brain barrier. It has substantially explored nanoparticles in the previous century, contributing to sub-stantial progress in biomedical studies and medical procedures. Using many synthesized nanoparti-cles on the molecular level has given many potential gains in various domains of regenerative medi-cine, such as illness detection, cascaded cell treatment, tissue regeneration, medication, and gene editing. This review will encapsulate the novel developments of nanostructured components used in neurological diseases with an emphasis on the most recent discoveries and forecasts for the future of varied biological nanoparticles for tissue repair, drug inventions, and the synthesizing of the deliv-ery mechanism.

The Role of Plasma Extracellular Vesicles in Remote Ischemic Conditioning and Exercise-Induced Ischemic Tolerance

Ischemic conditioning and exercise have been suggested for protecting against brain ischemia-reperfusion injury. However, the endogenous protective mechanisms stimulated by these interventions remain unclear. Here, in a comprehensive translational study, we investigated the protective role of extracellular vesicles (EVs) released after remote ischemic conditioning (RIC), blood flow restricted resistance exercise (BFRRE), or high-load resistance exercise (HLRE). Blood samples were collected from human participants before and at serial time points after intervention. RIC and BFRRE plasma EVs released early after stimulation improved viability of endothelial cells subjected to oxygen-glucose deprivation. Furthermore, post-RIC EVs accumulated in the ischemic area of a stroke mouse model, and a mean decrease in infarct volume was observed for post-RIC EVs, although not reaching statistical significance. Thus, circulating EVs induced by RIC and BFRRE can mediate protection, but the in vivo and translational effects of conditioned EVs require further experimental verification.

Daily Remote Ischemic Conditioning Can Improve Cerebral Perfusion and Slow Arterial Progression of Adult Moyamoya Disease—A Randomized Controlled Study

Background and Purpose

Moyamoya disease (MMD) is a complicated cerebrovascular disease with recurrent ischemic or hemorrhagic events. This study aimed to prove the safety and efficacy of remote ischemic conditioning (RIC) on MMD.

Methods

In total, 34 patients with MMD participated in this pilot, prospective randomized controlled study for 1 year. 18 patients were allocated into the RIC group, and 16 patients accepted routine medical treatment only. RIC-related adverse events were recorded. The primary outcome was the improvement ratio of mean cerebral blood flow (mCBF) in middle cerebral artery territory measured by multidelay pseudocontinuous arterial spin labeling, and the secondary outcomes were the cumulative incidence of major adverse cerebrovascular events (MACEs), the prevalence of stenotic-occlusive progression, and periventricular anastomosis at 1-year follow-up.

Results

In total, 30 of the 34 patients with MMD completed the final follow-up (17 in the RIC group and 13 in the control group). No adverse events of RIC were observed. The mCBF improvement ratio of the RIC group was distinctively higher compared with the control group (mCBF−whole-brain: 0.16 ± 0.15 vs. −0.03 ± 0.13, p = 0.001). Stenotic-occlusive progression occurred in 11.8% hemispheres in the RIC group and 38.5% in the control group (p = 0.021). The incidence of MACE was 5.9% in the RIC group and 30.8% in the control group (hazard ratio with RIC, 0.174; 95% CI, 0.019–1.557; p = 0.118). No statistical difference was documented in the periventricular anastomosis between the two groups after treatment.

Conclusions

Remote ischemic conditioning has the potential to be a safe and effective adjunctive therapy for patients with MMD largely due to improving cerebral blood flow and slowing the arterial progression of the stenotic-occlusive lesions. These findings warrant future studies in larger trials.

Immune Modulation as a Key Mechanism for the Protective Effects of Remote Ischemic Conditioning After Stroke

Remote ischemic conditioning (RIC), which involves a series of short cycles of ischemia in an organ remote to the brain (typically the limbs), has been shown to protect the ischemic penumbra after stroke and reduce ischemia/reperfusion (IR) injury. Although the exact mechanism by which this protective signal is transferred from the remote site to the brain remains unclear, preclinical studies suggest that the mechanisms of RIC involve a combination of circulating humoral factors and neuronal signals. An improved understanding of these mechanisms will facilitate translation to more effective treatment strategies in clinical settings. In this review, we will discuss potential protective mechanisms in the brain and cerebral vasculature associated with RIC. We will discuss a putative role of the immune system and circulating mediators of inflammation in these protective processes, including the expression of pro-and anti-inflammatory genes in peripheral immune cells that may influence the outcome. We will also review the potential role of extracellular vesicles (EVs), biological vectors capable of delivering cell-specific cargo such as proteins and miRNAs to cells, in modulating the protective effects of RIC in the brain and vasculature.

Preclinical evidence of remote ischemic conditioning in ischemic stroke, a metanalysis update

Remote ischemic conditioning (RIC) is a promising therapeutic approach for ischemic stroke patients. It has been proven that RIC reduces infarct size and improves functional outcomes. RIC can be applied either before ischemia (pre-conditioning; RIPreC), during ischemia (per-conditioning; RIPerC) or after ischemia (post-conditioning; RIPostC). Our aim was to systematically determine the efficacy of RIC in reducing infarct volumes and define the cellular pathways involved in preclinical animal models of ischemic stroke. A systematic search in three databases yielded 50 peer-review articles. Data were analyzed using random effects models and results expressed as percentage of reduction in infarct size (95% CI). A meta-regression was also performed to evaluate the effects of covariates on the pooled effect-size. 95.3% of analyzed experiments were carried out in rodents. Thirty-nine out of the 64 experiments studied RIPostC (61%), sixteen examined RIPreC (25%) and nine tested RIPerC (14%). In all studies, RIC was shown to reduce infarct volume (- 38.36%; CI - 42.09 to - 34.62%) when compared to controls. There was a significant interaction caused by species. Short cycles in mice significantly reduces infarct volume while in rats the opposite occurs. RIPreC was shown to be the most effective strategy in mice. The present meta-analysis suggests that RIC is more efficient in transient ischemia, using a smaller number of RIC cycles, applying larger length of limb occlusion, and employing barbiturates anesthetics. There is a preclinical evidence for RIC, it is safe and effective. However, the exact cellular pathways and underlying mechanisms are still not fully determined, and its definition will be crucial for the understanding of RIC mechanism of action.

Interactions between remote ischemic conditioning and post-stroke sleep regulation

Sleep disturbances are common in patients with stroke, and sleep quality has a critical role in the onset and outcome of stroke. Poor sleep exacerbates neurological injury, impedes nerve regeneration, and elicits serious complications. Thus, exploring a therapy suitable for patients with stroke and sleep disturbances is imperative. As a multi-targeted nonpharmacological intervention, remote ischemic conditioning can reduce the ischemic size of the brain, improve the functional outcome of stroke, and increase sleep duration. Preclinical/clinical evidence showed that this method can inhibit the inflammatory response, mediate the signal transductions of adenosine, activate the efferents of the vagal nerve, and reset the circadian clocks, all of which are involved in sleep regulation. In particular, cytokines tumor necrosis factor α (TNFα) and adenosine are sleep factors, and electrical vagal nerve stimulation can improve insomnia. On the basis of the common mechanisms of remote ischemic conditioning and sleep regulation, a causal relationship was proposed between remote ischemic conditioning and post-stroke sleep quality.

Remote but not Distant: a Review on Experimental Models and Clinical Trials in Remote Ischemic Conditioning as Potential Therapy in Ischemic Stroke

Stroke is one of the main causes of neurological disability worldwide and the second cause of death in people over 65 years old, resulting in great economic and social burden. Ischemic stroke accounts for 85% of total cases, and the approved therapies are based on re-establishment of blood flow, and do not directly target brain parenchyma. Thus, novel therapies are urgently needed. In this review, limb remote ischemic conditioning (RIC) is revised and discussed as a potential therapy against ischemic stroke. The review targets both (i) fundamental research based on experimental models and (ii) clinical research based on clinical trials and human interventional studies with healthy volunteers. Moreover, it also presents two approaches concerning RIC mechanisms in stroke: (i) description of the underlying cerebral cellular and molecular mechanisms triggered by limb RIC that promote neuroprotection against stroke induced damage and (ii) the identification of signaling factors involved in inter-organ communication following RIC procedure. Limb to brain remote signaling can occur via circulating biochemical factors, immune cells, and/or stimulation of autonomic nervous system. In this review, these three hypotheses are explored in both humans and experimental models. Finally, the challenges involved in translating experimentally generated scientific knowledge to a clinical setting are also discussed.

Cyclic Hypoxia Conditioning Alters the Content of Myoblast-Derived Extracellular Vesicles and Enhances Their Cell-Protective Functions

Remote ischemic conditioning (RIC) is a procedure that can attenuate ischemic-reperfusion injury by conducting brief cycles of ischemia and reperfusion in the arm or leg. Extracellular vesicles (EVs) circulating in the bloodstream can release their content into recipient cells to confer protective function on ischemia-reperfusion injured (IRI) organs. Skeletal muscle cells are potential candidates to release EVs as a protective signal during RIC. In this study, we used C2C12 cells as a model system and performed cyclic hypoxia-reoxygenation (HR) to mimic RIC. EVs were collected and subjected to small RNA profiling and proteomics. HR induced a distinct shift in the miRNA profile and protein content in EVs. HR EV treatment restored cell viability, dampened inflammation, and enhanced tube formation in in vitro assays. In vivo, HR EVs showed increased accumulation in the ischemic brain compared to EVs secreted from normoxic culture (N EVs) in a mouse undergoing transient middle cerebral artery occlusion (tMCAO). We conclude that HR conditioning changes the miRNA and protein profile in EVs released by C2C12 cells and enhances the protective signal in the EVs to recipient cells in vitro.

Therapeutic Potential of Remote Ischemic Conditioning in Vascular Cognitive Impairment

Vascular cognitive impairment (VCI) is a heterogeneous disease caused by a variety of cerebrovascular diseases. Patients with VCI often present with slower cognitive processing speed and poor executive function, which affects their independence in daily life, thus increasing social burden. Remote ischemic conditioning (RIC) is a non-invasive and efficient intervention that triggers endogenous protective mechanisms to generate neuroprotection. Over the past decades, evidence from basic and clinical research has shown that RIC is promising for the treatment of VCI. To further our understanding of RIC and improve the management of VCI, we summarize the evidence on the therapeutic potential of RIC in relation to the risk factors and pathobiologies of VCI, including reducing the risk of recurrent stroke, decreasing high blood pressure, improving cerebral blood flow, restoring white matter integrity, protecting the neurovascular unit, attenuating oxidative stress, and inhibiting the inflammatory response.

Limb Remote Ischemic Conditioning Ameliorates Cognitive Impairment in Rats with Chronic Cerebral Hypoperfusion by Regulating Glucose Transport

Cognitive impairment is closely associated with the slowing of glucose metabolism in the brain. Glucose transport, a rate-limiting step of glucose metabolism, plays a key role in this phenomenon. Previous studies have reported that limb remote ischemic conditioning (LRIC) improves cognitive performance in rats with chronic cerebral hypoperfusion (CCH). Here, we determined whether LRIC could ameliorate cognitive impairment in rats with CCH by regulating glucose transport. A total of 170 male Sprague-Dawley rats were used. Animals subjected to permanent double carotid artery occlusion (2VO) were assigned to the control or LRIC treatment group. LRIC was applied beginning 3 days after the 2VO surgery. We found that LRIC can improve learning and memory; decrease the ratio of ADP/ATP; increase glucose content; upregulate the expression of pAMPKα, GLUT1 and GLUT3; and increase the number of GLUT1 and GLUT3 transporters in cerebral cortical neurons. The expression of GLUT1 and GLUT3 in the cortex displayed a strong correlation with learning and memory. Pearson correlation analysis showed that the levels of GLUT1 and GLUT3 are correlated with neurological function scores. All of these beneficial effects of LRIC were ablated by application of the AMPK inhibitor, dorsomorphin. In summary, LRIC ameliorated cognitive impairment in rats with CCH by regulating glucose transport via the AMPK/GLUT signaling pathway. We conclude that AMPK-mediated glucose transport plays a key role in LRIC. These data also suggest that supplemental activation of glucose transport after CCH may provide a clinically applicable intervention for improving cognitive impairment.

Remote Ischemic Postconditioning vs. Physical Exercise After Stroke: an Alternative Rehabilitation Strategy?

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.

Dimethyl fumarate improves cognitive deficits in chronic cerebral hypoperfusion rats by alleviating inflammation, oxidative stress, and ferroptosis via NRF2/ARE/NF-κB signal pathway

Cerebrovascular disease and its risk factors cause persistent decrease of cerebral blood flow, chronic cerebral hypoperfusion (CCH) is the major foundation of vascular cognitive impairment (VCI). The hippocampus is extremely vulnerable to cerebral ischemia and hypoxia. Oxidative stress and neuroinflammation injury are important pathophysiological mechanisms of this process, which is closely related to hippocampal neurons damage and loss. Dimethyl fumarate (DMF), an FDA-approved therapeutic for multiple sclerosis (MS), plays a protective role in multiple neurological disorders. Studies have shown that DMF exerts anti-inflammatory and antioxidant effects via the NRF2/ARE/NF-κB signaling pathway. Thus, this study aimed to evaluate the neuroprotective effect of DMF in the CCH rat model. Ferroptosis, a novel defined iron-dependent cell death form, were found to be strongly associated with the pathophysiology of CCH. Emerging evidences have shown that inhibition of ferroptosis by targeting NRF2 exerted neuroprotective effect in neurodegeneration diseases. We also investigated whether DMF can alleviate cognitive deficits through inhibition of ferroptosis by the NRF2 signaling pathway in this study. DMF was intragastric for consecutive five weeks (100 mg/kg/day). Then behavior test and histological, molecular, and biochemical analysis were performed. We found that DMF treatment significantly improved cognitive deficits and partially reversed hippocampus neuronal damage and loss caused by CCH. And DMF treatment decreased hippocampus IL-1β, TNF-α, and IL-6 pro-inflammatory cytokines concentration, and mediated the NF-κB signaling pathway. And DMF also alleviated hippocampus oxidative stress through reducing MDA, and increasing GSH and SOD levels, which are also closely associated with ferroptosis. Besides, DMF treatment reduced the expression of PTGS2, and increased the expression of FTH1 and xCT, and the iron content is also reduced, which were the important features related to ferroptosis. Furthermore, DMF activated the NRF2/ARE signaling pathway and upregulated the expression of HO-1, NQO1 and GPX4. These outcomes indicated that DMF can improve cognitive impairment in rats with CCH, possibly through alleviating neuroinflammation, oxidative stress damage and inhibiting ferroptosis of hippocampal neurons. Overall, our results provide new evidence for the neuroprotective role of DMF.

The Roles of Nitric Oxide Synthase/Nitric Oxide Pathway in the Pathology of Vascular Dementia and Related Therapeutic Approaches

Vascular dementia (VaD) is the second most common form of dementia worldwide. It is caused by cerebrovascular disease, and patients often show severe impairments of advanced cognitive abilities. Nitric oxide synthase (NOS) and nitric oxide (NO) play vital roles in the pathogenesis of VaD. The functions of NO are determined by its concentration and bioavailability, which are regulated by NOS activity. The activities of different NOS subtypes in the brain are partitioned. Pathologically, endothelial NOS is inactivated, which causes insufficient NO production and aggravates oxidative stress before inducing cerebrovascular endothelial dysfunction, while neuronal NOS is overactive and can produce excessive NO to cause neurotoxicity. Meanwhile, inflammation stimulates the massive expression of inducible NOS, which also produces excessive NO and then induces neuroinflammation. The vicious circle of these kinds of damage having impacts on each other finally leads to VaD. This review summarizes the roles of the NOS/NO pathway in the pathology of VaD and also proposes some potential therapeutic methods that target this pathway in the hope of inspiring novel ideas for VaD therapeutic approaches.

Fibrinolysis and Remote Ischemic Conditioning: Mechanisms and Treatment Perspectives in Stroke

Stroke is a leading cause of death and disability. Intravenous thrombolysis and mechanical thrombectomy have greatly improved outcomes in acute ischemic stroke (AIS). However, only a minority of patients receive reperfusion therapies, highlighting the need for novel neuroprotective therapies. Remote ischemic conditioning (RIC), consisting of brief, intermittent extremity occlusion and reperfusion induced with an inflatable cuff, is a potential neuroprotective therapy in acute stroke. The objective of this narrative review is to describe the effect of RIC on endogenous fibrinolysis and, from this perspective, investigate the potential of RIC in the prevention and treatment of stroke. A systematic literature search was performed in PubMed, and human studies in English were included. Seven studies had investigated the effect of RIC on fibrinolysis in humans. Long-term daily administration of RIC increased endogenous fibrinolysis, whereas a single RIC treatment did not acutely influence endogenous fibrinolysis. Fifteen studies had investigated the effect of RIC as a neuroprotective therapy in the prevention and treatment of stroke. Long-term RIC administration proved effective in reducing new cerebral vascular lesions in patients with established cerebrovascular disease. In patients with acute stroke, RIC was safe and feasible, though its clinical efficacy as a neuroprotectant is yet unproven. In conclusion, a single RIC treatment does not affect fibrinolysis in the acute phase, whereas long-term RIC administration may increase endogenous fibrinolysis. Increased endogenous fibrinolysis is unlikely to be the mediator of the acute neuroprotective effect of RIC in stroke patients, whereas it may partly explain the reduced stroke recurrence associated with long-term RIC treatment.

Ischemic Conditioning Ameliorated Hypertension and Vascular Remodeling of Spontaneously Hypertensive Rat via Inflammatory Regulation

Vascular remodeling is an initial step in the development of hypertension. Limb remote ischemic conditioning (LRIC) is a physiological treatment that induces endogenous protective effect during acute ischemic injury. However, the impact of long-term LRIC on hypertension, a chronic disease, is unknown. In this study, we aimed to investigate the LRIC effect on blood pressure and vascular remodeling in spontaneously hypertensive rat (SHR) model and patients with prehypertension and early-stage hypertension. LRIC of rats was performed once a day for 6-weeks. Blood pressure, vascular remodeling (cross-sectional area, extracellular deposition, and smooth muscle cell area), inflammation (inflammatory factors, and inflammatory cells) were compared among normotensive Wistar-Kyoto rats (WKY), WKY RIC group, SHR control group, and SHR RIC. Long-term LRCI treatment (twice a day for 4-weeks) was performed on patients with prehypertension or early-stage hypertension. Blood pressure and pulse wave velocity (PWV) were analyzed before and after LRIC treatment. LRIC treatment decreased blood pressure in SHR (n = 9-10). LRIC ameliorated vascular remodeling by decreasing cross-sectional area, suppressing deposition of the extracellular matrix, and hypertrophy of smooth muscle cell in conduit artery and small resistance artery (n = 7). LRIC decreased proinflammatory factors while increasing the anti-inflammatory factors in the circulation (n = 5). LRIC decreased circulating monocyte and natural killer T-cell levels (n = 5). Furthermore, LRIC treatment decreased blood pressure and improved vascular stiffness in patients (n = 20). In conclusion, long term LRIC could decrease blood pressure and ameliorate vascular remodeling via inflammation regulation. LRIC could be a preventive treatment for people with blood pressure elevation or prehypertension.

Mini Review (Part I): An Experimental Concept on Exercise and Ischemic Conditioning in Stroke Rehabilitation

Stroke remains a leading cause of adult death and disability. Poststroke rehabilitation is vital for reducing the long-term sequelae of brain ischemia. Recently, physical exercise training has been well established as an effective rehabilitation tool, but its efficacy depends on exercise parameters and the patient's capacities, which are often altered following a major cerebrovascular event. Thus, ischemic conditioning as a rehabilitation intervention was considered an “exercise equivalent,” but the investigation is still in its relative infancy. In this mini-review, we discuss the potential for physical exercise or ischemic conditioning and its relation to angiogenesis, neurogenesis, and plasticity in stroke rehabilitation. This allows the readers to understand the context of the research and the application of ischemic conditioning in poststroke rehabilitation.

Pathological changes in neurovascular units: Lessons from cases of vascular dementia

Vascular dementia (VD) is the second leading cause of dementia after Alzheimer's disease (AD). The decrease of cerebral blood flow (CBF) to different degrees is one of the main causes of VD. Neurovascular unit (NVU) is a vessel‐centered concept, emphasizing all the cellular components play an integrated role in maintaining the normal physiological functions of the brain. More and more evidence shows that reduced CBF causes a series of changes in NVU, such as impaired neuronal function, abnormal activation of glial cells, and changes in vascular permeability, all of which collectively play a role in the pathogenesis of VD. In this paper, we review NVU changes as CBF decreases, focusing on each cellular component of NVU. We also highlight remote ischemic preconditioning as a promising approach for VD prevention and treatment from the NVU perspective of view.

Remote ischemic conditioning counteracts the intestinal damage of necrotizing enterocolitis by improving intestinal microcirculation

Necrotizing enterocolitis (NEC) is a devastating disease of premature infants with high mortality rate, indicating the need for precision treatment. NEC is characterized by intestinal inflammation and ischemia, as well derangements in intestinal microcirculation. Remote ischemic conditioning (RIC) has emerged as a promising tool in protecting distant organs against ischemia-induced damage. However, the effectiveness of RIC against NEC is unknown. To address this gap, we aimed to determine the efficacy and mechanism of action of RIC in experimental NEC. NEC was induced in mouse pups between postnatal day (P) 5 and 9. RIC was applied through intermittent occlusion of hind limb blood flow. RIC, when administered in the early stages of disease progression, decreases intestinal injury and prolongs survival. The mechanism of action of RIC involves increasing intestinal perfusion through vasodilation mediated by nitric oxide and hydrogen sulfide. RIC is a viable and non-invasive treatment strategy for NEC.

Necrotizing enterocolitis (NEC) is one of the most lethal gastrointestinal emergencies in neonates needing precision treatment. Here the authors show that remote ischemic conditioning is a non-invasive therapeutic method that enhances blood flow in the intestine, reduces damage, and improves NEC outcome.

Increasing the expression of microRNA-126-5p in the temporal muscle can promote angiogenesis in the chronically ischemic brains of rats subjected to two-vessel occlusion plus encephalo-myo-synangiosis

BACKGROUND

miR-126-5p plays an important role in promoting endothelial cell (EC) proliferation. We thus explored whether miR-126-5p can promote EC proliferation and angiogenesis in chronically ischemic brains (CIBs).

RESULTS

Improved revascularization in moyamoya patients was correlated with upregulated miR-126-5p expression in the TM and DM. In vitro experiments showed that miR-126-5p promoted EC proliferation through the PI3K/Akt pathway. CIBs from the agomir group exhibited significantly higher p-Akt, VEGF, CD31 and eNOS expression compared with the control CIBs. The ICBP and the RCF were significantly better in the agomir compared with the control group.

CONCLUSION

Increasing miR-126-5p expression in the TM can promote EC proliferation and angiogenesis in CIBs of 2VO+EMS rats through the PI3K/Akt pathway.

METHODS

We assessed the correlation between revascularization and miR-126-5p expression in the temporal muscle (TM) and dura mater (DM) of moyamoya patients. The effect of miR-126-5p on EC proliferation and downstream signaling pathways was explored in vitro. We established an animal model of two-vessel occlusion plus encephalo-myo-synangiosis (2VO+EMS), transfected the TM with miR-126-5p agomir/antagomir, compared the expression of miR-126-5p and relevant downstream cytokines in brain tissue among different groups, and investigated the improvement in cerebral blood perfusion (ICBP) and the recovery of cognitive function (RCF).

Effects of Remote Ischemic Conditioning on Cerebral Hemodynamics in Ischemic Stroke

Ischemic stroke is one of the most common cerebrovascular diseases and is the leading cause of disability all over the world. It is well known that cerebral blood flow (CBF) is disturbed or even disrupted when ischemic stroke happens. The imbalance between demand and shortage of blood supply makes ischemic stroke take place or worsen. The search for treatments that can preserve CBF, especially during the acute phase of ischemic stroke, has become a research hotspot. Animal and clinical experiments have proven that remote ischemic conditioning (RIC) is a beneficial therapeutic strategy for the treatment of ischemic stroke. However, the mechanism by which RIC affects CBF has not been fully understood. This review aims to discuss several possible mechanisms of RIC on the cerebral hemodynamics in ischemic stroke, such as the improvement of cardiac function and collateral circulation of cerebral vessels, the protection of neurovascular units, the formation of gas molecules, the effect on the function of vascular endothelial cells and the nervous system. RIC has the potential to become a therapeutic treatment to improve CBF in ischemic stroke. Future studies are needed to highlight our understanding of RIC as well as accelerate its clinical translation.

Shixiang Plaster, a Traditional Chinese Medicine, Promotes Healing in a Rat Model of Diabetic Ulcer Through the receptor for Advanced Glycation End Products (RAGE)/Nuclear Factor kappa B (NF-κB) and Vascular Endothelial Growth Factor (VEGF)/Vascular Cell Adhesion Molecule-1 (VCAM-1)/Endothelial Nitric Oxide Synthase (eNOS) Signaling Pathways

Background

Shixiang plaster is a traditional Chinese medicine has been used to treat chronic ulcers, including diabetic ulcers. Aminoguanidine is a hydrazine derivative that inhibits the formation of advanced glycosylation end products (AGEs). This study aimed to investigate the effects of shixiang plaster and aminoguanidine on wound healing in the streptozotocin-induced rat model of diabetes and the molecular mechanisms involved.

Material/Methods

Sprague-Dawley rats treated with intraperitoneal streptozotocin and given surgical wounds were divided into the untreated chronic ulcer group (n=10), the aminoguanidine group (n=10), the shixiang plaster group (n=10), and the control group with sham surgery (n=10). Granulation tissue samples underwent light microscopy to evaluate angiogenesis and immunohistochemistry to identify AGE, vascular endothelial growth factor (VEGF), and CD34 expression. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and Western blot measured mRNA and protein expression of receptor for advanced glycation end products (RAGE), vascular cell adhesion molecule-1 (VCAM-1), nuclear factor kappa B (NF-κB) and endothelial nitric oxide synthase (eNOS).

Results

The shixiang plaster group showed a significant increase in angiogenesis in ulcer granulation tissue, significantly reduced expression of AGEs and increased expression of VEGF and CD34 expression in granulation tissue compared with the untreated chronic ulcer group (p<0.05). The shixiang plaster group showed significantly down-regulated expression of RAGE and VCAM-1 compared with the untreated chronic ulcer group (p<0.05). Shixiang plaster promoted angiogenesis by activating the NF-κB p65 associated pathway and eNOS activation.

Conclusions

Shixiang plaster promoted healing in a rat model of diabetic ulcer through the RAGE/NF-κB and VEGF/VCAM-1/eNOS signaling pathways.

Animal Models of Chronic Cerebral Hypoperfusion: From Mouse to Primate

Vascular cognitive impairment (VCI) or vascular dementia occurs as a result of brain ischemia and represents the second most common type of dementia after Alzheimer’s disease. To explore the underlying mechanisms of VCI, several animal models of chronic cerebral hypoperfusion have been developed in rats, mice, and primates. We established a mouse model of chronic cerebral hypoperfusion by narrowing the bilateral common carotid arteries with microcoils, eventually resulting in hippocampal atrophy. In addition, a mouse model of white matter infarct-related damage with cognitive and motor dysfunction has also been established by asymmetric common carotid artery surgery. Although most experiments studying chronic cerebral hypoperfusion have been performed in rodents because of the ease of handling and greater ethical acceptability, non-human primates appear to represent the best model for the study of VCI, due to their similarities in much larger white matter volume and amyloid β depositions like humans. Therefore, we also recently developed a baboon model of VCI through three-vessel occlusion (both the internal carotid arteries and the left vertebral artery). In this review, several animal models of chronic cerebral hypoperfusion, from mouse to primate, are extensively discussed to aid in better understanding of pathophysiology of VCI.

NT3P75-2 gene-modified bone mesenchymal stem cells improve neurological function recovery in mouse TBI model

BACKGROUND

The attainment of extensive neurological function recovery remains the key challenge for the treatment of traumatic brain injury (TBI). Transplantation of bone marrow-derived mesenchymal stem cells (BMSCs) has been shown to improve neurological function recovery after TBI. However, the survival of BMSCs after transplantation in early-stage TBI is limited, and much is unknown about the mechanisms mediating this neurological function recovery. Secretion of neurotrophic factors, including neurotrophin 3 (NT3), is one of the critical factors mediating BMSC neurological function recovery. Gene mutation of NT3 (NT3^P75-2) has been shown to enhance the biological function of NT3 via the reduction of the activation of the P75 signal pathway. Thus, we investigated whether NT3^P75-2 gene-modified BMSCs could enhance the survival of BMSCs and further improve neurological function recovery after TBI.

METHODS

The ability of NT3^P75-2 induction to improve cell growth rate of NSC-34 and PC12 cells in vitro was first determined. BMSCs were then infected with three different lentiviruses (green fluorescent protein (GFP), GFP-NT3, or GFP-NT3^P75-2), which stably express GFP, GFP-NT3, or GFP-NT3^P75-2. At 24 h post-TBI induction in mice, GFP-labeled BMSCs were locally transplanted into the lesion site. Immunofluorescence and histopathology were performed at 1, 3, and/or 7 days after transplantation to evaluate the survival of BMSCs as well as the lesion volume. A modified neurological severity scoring system and the rotarod test were chosen to evaluate the functional recovery of the mice. Cell growth rate, glial activation, and signaling pathway analyses were performed to determine the potential mechanisms of NT3^P75-2 in functional recovery after TBI.

RESULTS

Overall, NT3^P75-2 improved cell growth rate of NSC-34 and PC12 cells in vitro. In addition, NT3^P75-2 significantly improved the survival of transplanted BMSCs and neurological function recovery after TBI. Overexpression of NT3^P75-2 led to a significant reduction in the activation of glial cells, brain water content, and brain lesion volume after TBI. This was associated with a reduced activation of the p75 neurotrophin receptor (P75NTR) and the c-Jun N-terminal kinase (JNK) signal pathway due to the low affinity of NT3^P75-2 for the receptor.

CONCLUSIONS

Taken together, our results demonstrate that administration of NT3^P75-2 gene-modified BMSCs dramatically improves neurological function recovery after TBI by increasing the survival of BMSCs and ameliorating the inflammatory environment, providing a new promising treatment strategy for TBI.

Vascular Cognitive Impairment: Information from Animal Models on the Pathogenic Mechanisms of Cognitive Deficits

Vascular cognitive impairment (VCI) is the second most common cause of cognitive deficit after Alzheimer's disease. Since VCI patients represent an important target population for prevention, an ongoing effort has been made to elucidate the pathogenesis of this disorder. In this review, we summarize the information from animal models on the molecular changes that occur in the brain during a cerebral vascular insult and ultimately lead to cognitive deficits in VCI. Animal models cannot effectively represent the complex clinical picture of VCI in humans. Nonetheless, they allow some understanding of the important molecular mechanisms leading to cognitive deficits. VCI may be caused by various mechanisms and metabolic pathways. The pathological mechanisms, in terms of cognitive deficits, may span from oxidative stress to vascular clearance of toxic waste products (such as amyloid beta) and from neuroinflammation to impaired function of microglia, astrocytes, pericytes, and endothelial cells. Impaired production of elements of the immune response, such as cytokines, and vascular factors, such as insulin-like growth factor 1 (IGF-1), may also affect cognitive functions. No single event could be seen as being the unique cause of cognitive deficits in VCI. These events are interconnected, and may produce cascade effects resulting in cognitive impairment.

Potential Applications of Remote Limb Ischemic Conditioning for Chronic Cerebral Circulation Insufficiency

Chronic cerebral circulation insufficiency (CCCI) refers to a chronic decrease in cerebral blood perfusion, which may lead to cognitive impairment, psychiatric disorders such as depression, and acute ischemic stroke. Remote limb ischemic conditioning (RLIC), in which the limbs are subjected to a series of transient ischemic attacks, can activate multiple endogenous protective mechanisms to attenuate fatal ischemic injury to distant organs due to acute ischemia, such as ischemic stroke. Recent studies have also reported that RLIC can alleviate dysfunction in distant organs caused by chronic, non-fatal reductions in blood supply (e.g., CCCI). Indeed, research has indicated that RLIC may exert neuroprotective effects against CCCI through a variety of potential mechanisms, including attenuated glutamate excitotoxicity, improved endothelial function, increased cerebral blood flow, regulation of autophagy and immune responses, suppression of apoptosis, the production of protective humoral factors, and attenuated accumulation of amyloid-β. Verification of these findings is necessary to improve prognosis and reduce the incidence of acute ischemic stroke/cognitive impairment in patients with CCCI.

Calpain inhibitor MDL28170 improves the transplantation-mediated therapeutic effect of bone marrow-derived mesenchymal stem cells following traumatic brain injury

Background

Studies have shown that transplantation of bone marrow-derived mesenchymal stem cells (BMSCs) protects against brain damage. However, the low survival number of transplanted BMSCs remains a pertinent challenge and can be attributed to the unfavorable microenvironment of the injured brain. It is well known that calpain activation plays a critical role in traumatic brain injury (TBI)-mediated inflammation and cell death; previous studies showed that inhibiting calpain activation is neuroprotective after TBI. Thus, we investigated whether preconditioning with the calpain inhibitor, MDL28170, could enhance the survival of BMSCs transplanted at 24 h post TBI to improve neurological function.

Methods

TBI rat model was induced by the weight-drop method, using the gravitational forces of a free falling weight to produce a focal brain injury. MDL28170 was injected intracranially at the lesion site at 30 min post TBI, and the secretion levels of neuroinflammatory factors were assessed 24 h later. BMSCs labeled with green fluorescent protein (GFP) were locally administrated into the lesion site of TBI rat brains at 24 h post TBI. Immunofluorescence and histopathology were performed to evaluate the BMSC survival and the TBI lesion volume. Modified neurological severity scores were chosen to evaluate the functional recovery. The potential mechanisms by which MDL28170 is involved in the regulation of inflammation signaling pathway and cell apoptosis were determined by western blot and immunofluorescence staining.

Results

Overall, we found that a single dose of MDL28170 at acute phase of TBI improved the microenvironment by inhibiting the inflammation, facilitated the survival of grafted GFP-BMSCs, and reduced the grafted cell apoptosis, leading to the reduction of lesion cavity. Furthermore, a significant neurological function improvement was observed when BMSCs were transplanted into a MDL28170-preconditioned TBI brains compared with the one without MDL28170-precondition group.

Conclusions

Taken together, our data suggest that MDL28170 improves BMSC transplantation microenvironment and enhances the neurological function restoration after TBI via increased survival rate of BMSCs. We suggest that the calpain inhibitor, MDL28170, could be pursued as a new combination therapeutic strategy to advance the effects of transplanted BMSCs in cell-based regenerative medicine.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1210-4) contains supplementary material, which is available to authorized users.

Normobaric oxygen: a novel approach for treating chronic cerebral circulation insufficiency

Chronic cerebral circulation insufficiency (CCCI) is viewed as an alarming state induced by long-term reduction in cerebral perfusion, which is associated with neurological deficits and high risk of stroke occurrence or recurrence. CCCI accounts for a large proportion of both outpatients and inpatients with cerebrovascular diseases, while management of CCCI remains a formidable challenge to clinicians. Normobaric oxygen (NBO) is an adjuvant hyperoxygenation intervention supplied with one atmosphere pressure (1 ATA =101.325 kPa). A plethora of studies have demonstrated the efficacy of NBO on the penumbra in acute stroke. NBO has been shown to increase the oxygen pressure, raise the intracranial blood flow, protect blood–brain barrier and enhance neuroprotective effects. As similar underlying mechanisms are shared by the penumbra in stroke and the ischemic–hypoxic brain tissues in CCCI, we speculate that NBO may serve as a promising therapeutic strategy for attenuating short-term symptoms or improving long-term clinical outcomes among patients with CCCI. Due to the scant research exploring the efficacy and safety of NBO for treating CCCI so far, both experimental and clinical studies are warranted to verify our hypothesis in the future.