Vitamin D deficiency increases blood-brain barrier dysfunction after ischemic stroke in male rats

Higher dietary vitamin D intake influences brain and mental function in elderly Americans: a cross-sectional analysis

Background

Vitamin D is known to have a potential impact on cognitive function and mental health. This study aims to assess the association between dietary vitamin D intake and cognitive performance, as well as depression, in an elderly U.S. population.

Methods

Data from the National Health and Nutrition Examination Survey (NHANES) 2013-2014 were analyzed. A total of 1,344 elderly participants were categorized into three tertiles based on their dietary vitamin D intake (D2 + D3). Cognitive function was measured using the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) test, Digit Symbol Substitution Test (DSST), and Animal Fluency Test, while depression was assessed through the Patient Health Questionnaire-9 (PHQ-9). Adjustments were made for confounding variables, including age, sex, race, education, physical activity level, and other dietary factors.

Results

After adjustment for confounders, individuals in the 3rd tertile of vitamin D intake (≥4.9 mcg/day) had significantly reduced odds of low performance on the CERAD test (OR: 0.77, 95% CI: 0.57-0.98; p = 0.031) and Animal Fluency test (OR: 0.63, 95% CI: 0.49-0.85; p = 0.013) compared to the 1st tertile of intake (≤2.4 mcg/day). Similarly, participants in the 3rd tertile of vitamin D intake had lower odds of depression (PHQ-9 score > 4) after adjustment (OR: 0.68, 95% CI: 0.48-0.99; p = 0.046).

Conclusion

Our findings suggest that dietary vitamin D intake is associated with improved cognitive function and depressive symptoms in elderly individuals. However, further longitudinal studies are needed to establish causality and explore the underlying mechanisms.

Vitamin D: The crucial neuroprotective factor for nerve cells

Vitamin D is well known for its role in regulating the absorption and utilization of calcium and phosphorus as well as bone formation, and a growing number of studies have shown that vitamin D also has important roles in the nervous system, such as maintaining neurological homeostasis and protecting normal brain function, and that neurons and glial cells may be the targets of these effects. Most reviews of vitamin D's effects on the nervous system have focused on its overall effects, without distinguishing the contributors to these effects. In this review, we mainly focus on the cells of the central nervous system, summarizing the effects of vitamin D on them and the related pathways. With this review, we hope to elucidate the role of vitamin D in the nervous system at the cellular level and provide new insights into the prevention and treatment of neurodegenerative diseases in the direction of neuroprotection, myelin regeneration, and so on.

Supplementation and Mitigating Cognitive Decline in Older Adults With or Without Mild Cognitive Impairment or Dementia: A Systematic Review

This systematic literature review aims to answer the question of how micronutrients might influence the development and progression of dementia. In the present work, we focused on an overview of an updated review of relevant literature published in the last two decades. This review aims to delineate the relationship between micronutrient supplementation and cognitive decline in older subjects. In carrying out this review, we followed PRISMA, and our literature search was performed on PubMed. This systematic review includes only primary studies that have investigated the efficacy of nutritional interventions for the prevention of dementia and improvement of cognitive function in subjects aged 65 years or older with normal cognition, mild cognitive impairment (MCI), or Alzheimer's disease (AD). A gross heterogeneity of studies forbids the possibility of a direct comparison of the results. A review of the inclusion criteria and restrictions has been conducted to check the validity and reliability of the results. In this review, thirty-three primary studies were included. Results have shown that supplementation with vitamin D, probiotics, and PUFAs would most likely reduce cognitive decline, dementia, or AD compared with vitamins A, B, C, and E, which were seen to be relatively ineffective. Of note, when considering vitamin B supplementation, positive effects were only observed in non-aspirin users having high ω-3 fatty acid (ω-3 FA) plasma levels. In some cases, however, there were genotypic differences in subjects in response to vitamin B supplementation.

Exploring the Missing link between vitamin D and autism spectrum disorder: Scientific evidence and new perspectives

Aim

This study aims to address the key question of the causal relationship between serum levels of 25-hydroxyvitamin D (vitamin D) and autism spectrum disorders (ASD).

Methods

Publicly available Genome-Wide Association Study (GWAS) datasets were used to conduct the bidirectional Two-sample MR analyses using methods including inverse-variance weighted (IVW), weighted median, MR-Egger regression, simple mode, MR-PRESSO test, Steiger filtering, and weighted mode, followed by BWMR for validation.

Results

The MR analysis indicated that there was no causal relationship between Vitamin D as the exposure and ASD as the outcome in the positive direction of the MR analysis (IVW: OR = 0.984, 95 % CI: 0.821-1.18, P = 0.866). The subsequent BWMR validation stage yielded consistent results (OR = 0.984, 95 % CI 0.829-1.20, P = 0.994). Notably, in the reverse MR analysis with ASD as the exposure and Vitamin D as the outcome, the results suggested that the occurrence of ASD could lead to decreased Vitamin D levels (IVW: OR = 0.976, 95 % CI: 0.961-0.990, P = 0.000855), with BWMR findings in the validation stage confirming the discovery phase (OR = 0.975, 95 % CI: 0.958-0.991, P = 0.00297). For the positive MR analysis, no pleiotropy was detected in the instrumental variables. Similarly, no pleiotropy or heterogeneity was detected in the instrumental variables for the reverse MR analysis. Sensitivity analysis using the leave-one-out approach for both positive and reverse instrumental variables suggested that the MR analysis results were robust.

Conclusion

Through the discovery and validation analysis process, we can confidently assert that there is no causative link between Vitamin D and ASD, and that supplementing Vitamin D is not expected to provide effective improvement for patients with ASD. Our study significantly advances a new perspective in ASD research and has a positive impact on medication guidance for patients with ASD.

Acute calcitriol treatment mitigates vitamin D deficiency-associated mortality after intracerebral haemorrhage

OBJECTIVE

Vitamin D deficiency (VDD) is emerging as a predictor of poor prognosis in various neurological conditions, where clinical outcomes are often worse in stroke patients with VDD. This study aimed to provide experimental evidence on whether and how pre-existing VDD would affect survival and neurofunctional outcomes in intracerebral haemorrhage (ICH), and to evaluate whether acute vitamin D (VD) supplementation would improve post-stroke outcomes.

METHODS

Experimental ICH models were induced in mice with and without VDD. Haematoma size was measured using T2*-weighted MRI and haemoglobin concentration. Post-ICH mortality, neurofunctional outcomes and the extent of blood-brain barrier (BBB) leakage were assessed to identify their correlations with VD status. Therapeutic benefits of acute VD administration were also evaluated.

RESULTS

Mice with VDD exhibited significantly higher acute mortality rates and more severe motor deficits than mice without VDD post-ICH. Marked haematoma expansion and increased Evans blue extravasation were observed in VDD mice, suggesting that VDD was associated outcomes with increased BBB disruption. Acute treatment with a loading dose of VD (calcitriol) significantly improved outcomes in VDD mice.

CONCLUSION

This study provides novel insights into the pathophysiological mechanisms at play in ICH concomitant with VDD and a scientific rationale for acute treatment with VD.

Vitamin D and ischemic stroke - Association, mechanisms, and therapeutics

Confronting the rising tide of ischemic stroke and its associated mortality and morbidity with ageing, prevention and acute management of ischemic stroke is of paramount importance. Mounting observational studies have established a non-linear association of vitamin D status with cardiovascular diseases, including ischemic stroke. Paradoxically, current clinical trials fail to demonstrate the cardiovascular benefits of vitamin D supplementation. We aim to update recent clinical and experimental findings on the role of vitamin D in the disease course of ischemic stroke, from its onset, progression, recovery, to recurrence, and the established and alternative possible pathophysiological mechanisms. This review justifies the necessities to address stroke etiological subtypes and focus on vitamin D-deficient subjects for investigating the potential of vitamin D supplementation as a preventive and therapeutic approach for ischemic stroke. Well-powered clinical trials are warranted to determine the efficacy, safety, timing, target individuals, optimal dosages, and target 25OHD concentrations of vitamin D supplementation in the prevention and treatment of ischemic stroke.

Vitamin D as a Modulator of Neuroinflammation: Implications for Brain Health

Neuroinflammation represents a critical immune response within the brain, playing a pivotal role in defense against injury and infection. However, when this response becomes chronic, it can contribute to the development of various neurodegenerative and psychiatric disorders. This bibliographic review delves into the role of vitamin D in modulating neuroinflammation and its implications for brain health, particularly in the context of neurological and psychiatric disorders. While vitamin D is traditionally associated with calcium homeostasis and bone health, it also exerts immunomodulatory and neuroprotective effects within the central nervous system. Through comprehensive analysis of preclinical and clinical studies, we uncover how vitamin D, acting through its receptors in glial cells, may influence the production of proinflammatory cytokines and antioxidants, potentially mitigating the cascade of events leading to neuronal damage. Clinical research has identified vitamin D deficiency as a common thread in the increased risks of multiple sclerosis, Parkinson's disease, Alzheimer's, and depression, among others. Furthermore, preclinical models suggest vitamin D's regulatory capacity over inflammatory mediators, its protective role against neuronal apoptosis, and its contribution to neurogenesis and synaptic plasticity. These insights underscore the potential of vitamin D supplementation not only in slowing the progression of neurodegenerative diseases but also in improving the quality of life for patients suffering from psychiatric conditions. Future clinical studies are essential to validate these findings and further our understanding of vitamin D's capacity to prevent or alleviate symptoms, opening new avenues for therapeutic strategies against neuroinflammation-related pathologies. Neuroinflammation is a crucial immune response in the brain against injuries or infections, but its persistence can lead to diseases such as Alzheimer's, Parkinson's, multiple sclerosis, and depression. Cholecalciferol (Vitamin D3) emerges as a regulator of neuroinflammation, present in brain cells such as astrocytes and microglia, modulating immune function. Vitamin D's mechanisms of action include cytokine modulation and regulation of nuclear and mitochondrial genes. It adjusts inflammatory mediators and antioxidants, resulting in neuroprotective effects. Additionally, vitamin D impacts neurotransmitter synthesis and brain plasticity. This positions vitamin D as a potential adjunct in treating diseases like Alzheimer's and Parkinson's. Lastly, its role in intestinal microbiota and serotonin synthesis contributes to psychiatric disorders like schizophrenia and depression. Thus, vitamin D presents a novel therapeutic approach for neuroinflammatory, neurodegenerative, and neuropsychiatric diseases.

Association between Vitamin D and Short-Term Functional Outcomes in Acute Ischemic Stroke

Vitamin D (Vit D) affects musculoskeletal performance and central nervous system neuroprotection. We aimed to investigate the association between serum Vit D levels and short-term functional outcomes in patients with acute ischemic stroke. This study involved patients with acute ischemic stroke confirmed on brain MRI. The National Institutes of Health Stroke Scale (NIHSS) was used to assess initial stroke severity upon admission. We evaluated the functional outcomes using the Berg Balance Scale (BBS), Manual Function Test (MFT), Korean Mini-Mental State Examination (K-MMSE), Korean version of the modified Barthel Index (K-MBI) within three weeks from the onset of stroke, and modified Rankin Scale (mRS) score at discharge. Overall, 192 patients were finally included and divided into three groups: Vit D sufficient (n = 28), insufficient (n = 49), and deficient (n = 115). Multivariate analysis showed that the Vit D deficient group presented with a higher risk of initially severe stroke (p = 0.025) and poor functional outcomes on the BBS (p = 0.048), MFT (p = 0.017), K-MMSE (p = 0.001), K-MBI (p = 0.003), and mRS (p = 0.032) compared to the Vit D sufficient group. Vit D deficiency may be associated with severe initial stroke and poor short-term post-stroke functional outcomes.

Vascular multiple sclerosis: addressing the pathogenesis, genetics, pro-angiogenic factors, and vascular abnormalities, along with the role of vascular intervention

Dysfunction in the epithelium, breakdown of the blood-brain barrier, and consequent leukocyte and T-cell infiltration into the central nervous system define Vascular Multiple Sclerosis. Multiple sclerosis (MS) affects around 2.5 million individuals worldwide, is the leading cause of neurological impairment in young adults, and can have a variety of progressions and consequences. Despite significant discoveries in immunology and molecular biology, the root cause of MS is still not fully understood, as do the immunological triggers and causative pathways. Recent research into vascular anomalies associated with MS suggests that a vascular component may be pivotal to the etiology of MS, and there can be actually a completely new entity in the already available classification of MS, which can be called 'vascular multiple sclerosis'. Unlike the usual other causes of MS, vascular MS is not dependent on autoimmune pathophysiologic mechanisms, instead, it is caused due to the blood vessels pathology. This review aims to thoroughly analyze existing information and updates about the scattered available findings of genetics, pro-angiogenetic factors, and vascular abnormalities in this important spectrum, the vascular facets of MS.

Therapeutic Effects of Vitamin D on Vaginal, Sexual, and Urological Functions in Postmenopausal Women

Recent years have witnessed the emergence of growing evidence concerning vitamin D's potential role in women's health, specifically in postmenopausal women. This evidence also includes its connection to various genitourinary disorders and symptoms. Numerous clinical studies have observed improvements in vulvovaginal symptoms linked to the genitourinary syndrome of menopause (GSM) with vitamin D supplementation. These studies have reported positive effects on various aspects, such as vaginal pH, dryness, sexual functioning, reduced libido, and decreased urinary tract infections. Many mechanisms underlying these pharmacological effects have since been proposed. Vitamin D receptors (VDRs) have been identified as a major contributor to its effects. It is now well known that VDRs are expressed in the superficial layers of the urogenital organs. Additionally, vitamin D plays a crucial role in supporting immune function and modulating the body's defense mechanisms. However, the characterization of these effects requires more investigation. Reviewing existing evidence regarding vitamin D's impact on postmenopausal women's vaginal, sexual, and urological health is the purpose of this article. As research in this area continues, there is a potential for vitamin D to support women's urogenital and sexual health during the menopausal transition and postmenopausal periods.

The Role of Vitamin D in Neuroprotection in Multiple Sclerosis: An Update

Multiple sclerosis (MS) is a complex neurological condition that involves both inflammatory demyelinating and neurodegenerative components. MS research and treatments have traditionally focused on immunomodulation, with less investigation of neuroprotection, and this holds true for the role of vitamin D in MS. Researchers have already established that vitamin D plays an anti-inflammatory role in modulating the immune system in MS. More recently, researchers have begun investigating the potential neuroprotective role of vitamin D in MS. The active form of vitamin D, 1,25(OH)₂D₃, has a range of neuroprotective properties, which may be important in remyelination and/or the prevention of demyelination. The most notable finding relevant to MS is that 1,25(OH)₂D₃ promotes stem cell proliferation and drives the differentiation of neural stem cells into oligodendrocytes, which carry out remyelination. In addition, 1,25(OH)₂D₃ counteracts neurodegeneration and oxidative stress by suppressing the activation of reactive astrocytes and M1 microglia. 1,25(OH)₂D₃ also promotes the expression of various neuroprotective factors, including neurotrophins and antioxidant enzymes. 1,25(OH)₂D₃ decreases blood-brain barrier permeability, reducing leukocyte recruitment into the central nervous system. These neuroprotective effects, stimulated by 1,25(OH)₂D₃, all enhance neuronal survival. This review summarizes and connects the current evidence supporting the vitamin D-mediated mechanisms of action for neuroprotection in MS.

Vitamin D in atherosclerosis and cardiovascular events

Both experimental and clinical findings linking vitamin D to cardiovascular (CV) risk have prompted consideration of its supplementation to improve overall health. Yet several meta-analyses do not provide support for the clinical effectiveness of this strategy. Meanwhile, the understanding of the roles of vitamin D in the pathophysiology of CV diseases has evolved. Specifically, recent work has revealed some non-classical pleiotropic effects of vitamin D, increasing the complexity of vitamin D signalling. Within particular microenvironments (e.g. dysfunctional adipose tissue and atherosclerotic plaque), vitamin D can act locally at cellular level through intracrine/autocrine/paracrine feedforward and feedback circuits. Within atherosclerotic tissues, 'local' vitamin D levels may influence relevant systemic consequences independently of its circulating pool. Moreover, vitamin D links closely to other signalling pathways of CV relevance including those driving cellular senescence, ageing, and age-related diseases-among them CV conditions. This review updates knowledge on vitamin D biology aiming to clarify the widening gap between experimental and clinical evidence. It highlights the potential reverse causation confounding correlation between vitamin D status and CV health, and the need to consider novel pathophysiological concepts in the design of future clinical trials that explore the effects of vitamin D on atherosclerosis and risk of CV events.

Microglia/macrophages require vitamin D signaling to restrain neuroinflammation and brain injury in a murine ischemic stroke model

Vitamin D deficiency is associated with worse clinical outcomes after ischemic stroke; nevertheless, the pathophysiological mechanisms remain largely unexplored. In this study, we characterized the molecular mechanisms of how vitamin D signaling modulated stroke progression in male mouse ischemia-reperfusion stroke models. We found that vitamin D receptor (VDR) exhibited a predominant upregulation in peri-infarct microglia/macrophages following cerebral ischemia. Conditional Vdr inactivation in microglia/macrophages markedly augmented infarct volumes and neurological deficits. VDR-deficient microglia/macrophages exhibited a more primed proinflammatory phenotype with substantial secretion of TNF-α and IFN-γ. These inflammatory cytokines further enhanced CXCL10 release from endothelial cells and blood-brain barrier disruption, and ultimately infiltration of peripheral T lymphocytes. Notably, blocking TNF-α and IFN-γ significantly ameliorated stroke phenotypes in Vdr conditional knockout mice. Collectively, VDR signaling in microglia/macrophages plays a crucial role in restraining ischemia-elicited neuroinflammation and stroke progression. Our findings delineate a novel mechanism underlying the association between vitamin D deficiency and poor stroke outcomes, and underline the significance of maintaining a functional vitamin D signaling in the management of acute ischemic stroke.

Role of Vitamin D Deficiency in the Pathogenesis of Cardiovascular and Cerebrovascular Diseases

Deficiency in vitamin D (VitD), a lipid-soluble vitamin and steroid hormone, affects approximately 24% to 40% of the population of the Western world. In addition to its well-documented effects on the musculoskeletal system, VitD also contributes importantly to the promotion and preservation of cardiovascular health via modulating the immune and inflammatory functions and regulating cell proliferation and migration, endothelial function, renin expression, and extracellular matrix homeostasis. This brief overview focuses on the cardiovascular and cerebrovascular effects of VitD and the cellular, molecular, and functional changes that occur in the circulatory system in VitD deficiency (VDD). It explores the links among VDD and adverse vascular remodeling, endothelial dysfunction, vascular inflammation, and increased risk for cardiovascular and cerebrovascular diseases. Improved understanding of the complex role of VDD in the pathogenesis of atherosclerotic cardiovascular diseases, stroke, and vascular cognitive impairment is crucial for all cardiologists, dietitians, and geriatricians, as VDD presents an easy target for intervention.

Vitamin D serum level predicts stroke clinical severity, functional independence, and disability—A retrospective cohort study

Background

Stroke is a leading cause of mortality and disability and one of the most common neurological conditions globally. Many studies focused on vitamin D as a stroke risk factor, but only a few focused on its serum level as a predictor of stroke initial clinical severity and recovery with inconsistent results. The purpose of this study was to assess the relationship between serum vitamin D levels and stroke clinical severity at admission and functional independence and disability at discharge in Saudi Arabia.

Methodology

A retrospective cohort study of adult ischemic stroke patients who had their vitamin D tested and admitted within 7 days of exhibiting stroke symptoms at King Abdulaziz Medical City (KAMC) Jeddah, Saudi Arabia. Based on vitamin D level, the patients were categorized into normal [25(OH)D serum level ≥ 75 nmol/L], insufficient [25(OH)D serum level is 50–75 nmol/L], and deficient [25(OH)D serum level ≤ 50 nmol/L]. The primary outcome was to assess the vitamin D serum level of ischemic stroke patients’ clinical severity at admission and functional independence at discharge. The National Institute of Health Stroke Scale (NIHSS) was used to assess the clinical severity, whereas the modified Rankin scale (mRS) was used to assess functional independence and disability.

Results

The study included 294 stroke patients, out of 774, who were selected based on the inclusion and exclusion criteria. The mean age of the participants was 68.2 ± 13.4 years, and 49.3% were male. The patients’ distribution among the three groups based on their vitamin D levels is: normal (n = 35, 11.9%), insufficient (n = 66, 22.5%), and deficient (n = 196, 65.6%). After adjusting for potential covariates, regression analysis found a significant inverse relationship of NIHSS based on 25(OH)D serum level (beta coefficient: −0.04, SE: 0.01, p = 0.003). Patients with deficient serum vitamin D level also had significantly higher odds of worse functional independence in mRS score [OR: 2.41, 95%CI: (1.13–5.16), p = 0.023] when compared to participants with normal vitamin D level.

Conclusion

Low vitamin D levels were associated with higher severity of stroke at admission and poor functional independence and disability at discharge in patients with acute ischemic stroke. Further randomized clinical and interventional studies are required to confirm our findings.

Targeting organic cation transporters at the blood-brain barrier to treat ischemic stroke in rats

Drug discovery and development for stroke is challenging as evidenced by few drugs that have advanced beyond a Phase III clinical trial. Memantine is a N-methyl-d-aspartate (NMDA) receptor antagonist that has been shown to be neuroprotective in various preclinical studies. We have identified an endogenous BBB uptake transport system for memantine: organic cation transporters 1 and 2 (Oct1/Oct2). Our goal was to evaluate Oct1/Oct2 as a required BBB mechanism for memantine neuroprotective effects. Male Sprague-Dawley rats (200-250 g) were subjected to middle cerebral artery occlusion (MCAO) for 90 min followed by reperfusion. Memantine (5 mg/kg, i.v.) was administered 2 h following intraluminal suture removal. Specificity of Oct-mediated transport was evaluated using cimetidine (15 mg/kg, i.v.), a competitive Oct1/Oct2 inhibitor. At 2 h post-MCAO, [³H]memantine uptake was increased in ischemic brain tissue. Cimetidine inhibited blood-to-brain uptake of [³H]memantine, which confirmed involvement of an Oct-mediated transport mechanism. Memantine reduced post-MCAO infarction and brain edema progression as well as improved neurological outcomes during post-stroke recovery. All positive effects of memantine were attenuated by co-administration of cimetidine, which demonstrates that Oct1/Oct2 transport is required for memantine to exert neuroprotective effects in ischemic stroke. Furthermore, Oct1/Oct2-mediated transport was shown to be the dominant mechanism for memantine brain uptake in the MCAO model despite a concurrent increase in paracellular "leak." These novel and translational findings provide mechanistic evidence for the critical role of BBB transporters in CNS delivery of stroke therapeutics, information that can help such drugs advance in clinical trials.

Full spectrum of vitamin D immunomodulation in multiple sclerosis: mechanisms and therapeutic implications

Vitamin D deficiency has been associated with the risk of multiple sclerosis, disease activity and progression. Results from in vitro experiments, animal models and analysis of human samples from randomized controlled trials provide comprehensive data illustrating the pleiotropic actions of Vitamin D on the immune system. They globally result in immunomodulation by decreasing differentiation of effector T and B cells while promoting regulatory subsets. Vitamin D also modulates innate immune cells such as macrophages, monocytes and dendritic cells, and acts at the level of the blood–brain barrier reducing immune cell trafficking. Vitamin D exerts additional activity within the central nervous system reducing microglial and astrocytic activation. The immunomodulatory role of Vitamin D detected in animal models of multiple sclerosis has suggested its potential therapeutic use for treating multiple sclerosis. In this review, we focus on recent published data describing the biological effects of Vitamin D in animal models of multiple sclerosis on immune cells, blood–brain barrier function, activation of glial cells and its potential neuroprotective effects. Based on the current knowledge, we also discuss optimization of therapeutic interventions with Vitamin D in patients with multiple sclerosis, as well as new technologies allowing in-depth analysis of immune cell regulations by vitamin D.

The comprehensive mechanistic insight into the effects of vitamin D on dementia – a review

Purpose

This paper aims to depict the mechanistic role of vitamin D on dementia prevention, relief of the severity and the complication of the disease. All papers indexed in scientific databases, including Scopus, Elsevier, PubMed, Embase and Google Scholar between 2000 and 2021 were extracted and discussed. To present the mechanistic role of vitamin D in declining the severity of dementia, keywords including dementia, vitamin D, oxidative stress, inflammation, amyloid beta-Peptides were used.

Design/methodology/approach

Dementia is a prevalent cognitive disorder worldwide, especially in elderly people, which is accompanied by serious disabilities. Besides genetic, biological and lifestyle factors are involved in the incidence of dementia. An unhealthy diet along with micronutrient deficiencies are among modifiable factors. Vitamin D is one of the important micronutrients in brain health. Besides the involvement in gene expression, bone mineralization, apoptosis, inflammation, skeletal maturation, neurotropic action and hemostasis of phosphate and calcium, vitamin D also exerts neuroprotective effects via genomic and non-genomic pathways.

Findings

Vitamin D up-regulates the expression of various genes involved in dementia incidence via various mechanisms. Decreasing oxidative stress and the neuro-inflammatory cytokines levels, regulation of the expression of alternated Proteins including Tau and Amyloid-ß, calcium homeostasis in the central nervous system and also vascular are considered main mechanisms.

Originality/value

Considering the importance of diet in preventing dementia, adherence to a healthy diet that provides essential nutrients to brain function seems to be urgent. Controlling serum levels of vitamin D periodically and providing vitamin D by related sources or supplements, if there is a deficiency, is recommended. Future studies are needed to clarify other related mechanisms.

Micronutrient Improvement of Epithelial Barrier Function in Various Disease States: A Case for Adjuvant Therapy

The published literature makes a very strong case that a wide range of disease morbidity associates with and may in part be due to epithelial barrier leak. An equally large body of published literature substantiates that a diverse group of micronutrients can reduce barrier leak across a wide array of epithelial tissue types, stemming from both cell culture as well as animal and human tissue models. Conversely, micronutrient deficiencies can exacerbate both barrier leak and morbidity. Focusing on zinc, Vitamin A and Vitamin D, this review shows that at concentrations above RDA levels but well below toxicity limits, these micronutrients can induce cell- and tissue-specific molecular-level changes in tight junctional complexes (and by other mechanisms) that reduce barrier leak. An opportunity now exists in critical care—but also medical prophylactic and therapeutic care in general—to consider implementation of select micronutrients at elevated dosages as adjuvant therapeutics in a variety of disease management. This consideration is particularly pointed amidst the COVID-19 pandemic.

Nutritional Supplementation of Naturally Occurring Vitamin D to Improve Hemorrhagic Stroke Outcomes

Vitamin D deficiency, if left untreated, is associated with bone disorders, cardiovascular damage, and an increased risk of ischemic stroke. While there are various nutritional options for the natural intake of vitamin D, we hope to elucidate the potential mechanisms dietary vitamin D may play in hemorrhagic stroke pathology. This scoping review outlines findings from studies relevant to the biochemical activity of vitamin D, the impact of vitamin D deficiency on hemorrhagic stroke outcomes, and the potential benefit of nutritional vitamin D on hemorrhagic stroke outcomes. Here, we analyze the relevant factors that can lead to vitamin D deficiency, and subsequently, a higher risk of hemorrhagic stroke incidence with worsened subsequent outcomes. The neuroprotective mechanisms through which vitamin D works to attenuate hemorrhagic stroke onset and post-stroke outcomes have not yet been thoroughly examined. However, researchers have proposed several potential protective mechanisms, including reduction of blood brain barrier disturbance by inhibiting the production of reactive oxygen species, mitigation of inflammation through a reduction of levels of proinflammatory cytokines, and prevention of cerebral vasospasm and delayed cerebral ischemia following subarachnoid hemorrhage and intracerebral hemorrhage. While more research is needed and there are limitations to vitamin D supplementation, vitamin D as a whole may play a significant role in the dynamics of hemorrhagic stroke. Further research should focus on expanding our understanding of the neuroprotective capacity and mechanisms of vitamin D, as well as how vitamin D supplementation could serve as an effective course of treatment of hemorrhagic strokes.

The Role of Supplementation with Natural Compounds in Post-Stroke Patients

Malnutrition is a serious problem in post-stroke patients. Importantly, it intensifies with hospitalization, and is related to both somatic and psychological reasons, as well as is associated with the insufficient knowledge of people who accompany the patient. Malnutrition is a negative prognostic factor, leading to a reduction in the quality of life. Moreover, this condition significantly extends hospitalization time, increases the frequency of treatment in intensive care units, and negatively affects the effectiveness of rehabilitation. Obtaining growing data on the therapeutic effectiveness of new compounds of natural origin is possible through the use of pharmacodynamic and analytical methods to assess their therapeutic properties. The proper supply of nutrients, as well as compounds of natural origin, is an important element of post-stroke therapy, due to their strong antioxidant, anti-inflammatory, neuroprotective and neuroplasticity enhancing properties. Taking the above into account, in this review we present the current state of knowledge on the benefits of using selected substances of natural origin in patients after cerebral stroke.

Effects of exogenous vitamin D on endoplasmic reticulum stress-related factors in the vitamin D deficiency rats with cerebral ischemia

We observed the potential neuroprotective effect of exogenous vitamin D on cerebral ischemia in vitamin D deficiency rats and explored its mechanism. Sixty Sprague Dawley rats were randomly divided into three groups including control (CON) group, vitamin D deficiency (VDD) group and vitamin D deficiency combined with exogenous vitamin D (VDD + VD) group, with 20 rats in each group. The rats in the CON group were fed with normal diet, while the rats in the VDD and VDD + VD groups with vitamin D-deficient diet for 8 weeks, and then underwent middle cerebral artery occlusion (MCAO). Six hours later, exogenous 25-hydroxyvitaminD (25-VD₃) was intravenously injected into the rats of the VDD + VD group every 24 h for 4 times. Motor behaviors were significantly better and 25-VD₃ level in the left brain tissue was significantly higher in the CON group than in the VDD and VDD + VD groups 102 h after MCAO (all P < 0.05). Although the motor behaviors, infarct volume and 25-VD₃ level in brain tissue showed a good tendency in the VDD + VD group as compared with VDD group, the two groups were not significantly different (all P > 0.05). GPR78 was significantly higher, but apoptosis and CHOP significantly lower in the VDD + VD group than in the VDD group (all P < 0.05). The aggravation of cerebral ischemia caused by vitamin D deficiency is possibly due to up-regulating GRP78 and down-regulating CHOP in brain tissue.

Single high-dose vitamin D3 injection and clinical outcomes in brain tumor resection: A randomized, controlled clinical trial

BACKGROUND & AIMS

Vitamin D is known as a neuroprotective hormone with anti-inflammatory and immune-modulatory properties. We evaluated the effect of vitamin D3 injection on vitamin D status and clinical outcomes in patients with low serum levels of 25-hydroxyvitamin D [25(OH)D] undergoing craniotomy for brain tumor resection.

METHODS

Patients with benign brain tumors and serum 25(OH)D levels ≤20 ng/mL were randomized to two groups with an equal number of subjects. The study group (n = 30) received intramuscular injection of 300,000 IU vitamin D3 prior to surgery. The control group (n = 30) was left without intervention, and both groups underwent routine therapies.

RESULTS

On day 5 after craniotomy, the serum 25(OH)D levels increased significantly in the study group (P= <0.001). The length of ICU and hospital stay was significantly lower in the study group compared to the control group (P = 0.01 and P = 0.008, respectively). It was true when the age, tumor size, tumor type, Karnofsky Performance Scale (KPS) score, and calcium and albumin levels at baseline entered the logistic regression model (OR = 0.17 (95%CI = 0.04-0.72, P = 0.01), and OR = 0.19 (95%CI = 0.04-0.82, P = 0.02), respectively). With and without the application of logistic regression analysis, there was no significant difference in perioperative complications.

CONCLUSIONS

Intramuscular injection of 300,000 IU of vitamin D3 in patients with low serum levels of 25(OH)D undergoing craniotomy, could rise safely the serum 25(OH)D level. This intervention, significantly reduced the length of ICU stay and hospitalization.

REGISTERED UNDER

Clinicaltrials.gov.identifier no: NCT03248544. Date: 8/14/2017.

Preoperative Serum Level of Vitamin D is a Possible Protective Factor for Peritumoral Brain Edema of Meningioma: A Cross Sectional Study

Meningioma is associated with the development of vasogenic edema defined as disrupted blood brain barrier. Vitamin D3 through its own nuclear receptor can regulate the expression of many effective agents on the integrity of the blood brain barrier. This study aimed to investigate the association between preoperative serum levels of 25(OH)D and peritumoral brain edema in patients with meningioma. One hundred and twelve patients with meningioma completed the study. Serum 25(OH)D levels assessment and magnetic resonance imaging (MRI) were done for all patients at the beginning of the study. The percentage of edema index (EI) was used to estimate the extent of peritumoral brain edema through preoperative MRI. The median serum level of 25(OH)D in the patients with the percentage of EI < 100% was significantly higher than those with > 100% (65.58 vs. 37.33, P < 0.001). The median percentage of EI was 24.9. Preoperative serum levels of 25(OH)D had an inverse and significant correlation with the percentage of EI as by increasing each 1 ng/mL of serum 25(OH)D, EI was decreased approximately 4% (95% CI; -5.984 to -1.952, P < 0.001). Vitamin D may be a protective factor for peritumoral brain edema of meningioma.

Post-ischemic stroke systemic inflammation: Immunomodulation by progesterone and vitamin D hormone

Post-stroke systemic inflammation, due to the injury itself and exacerbated by in-hospital infections, can increase morbidity and mortality in stroke patients. In this study, we examined the immunomodulatory effects of progesterone (P4) alone and in combination with vitamin D hormone (VDH) on acute phase post-stroke peripheral immune dysfunction and functional/behavioral deficits. Adult rats underwent transient middle cerebral artery occlusion/reperfusion (tMCAO) and delayed systemic inflammation was induced by injections of lipopolysaccharide (LPS) beginning 24 h post-stroke. Animals were tested for behavioral outcomes and immune function at day 4 post-stroke. We also measured infarction volume and markers of neuronal inflammation (GFAP, IL-6) and apoptosis (cleaved caspase-3) in brain post-stroke. We observed the worst stroke outcomes in the stroke + systemic inflammation group compared to the stroke-alone group. Flow cytometric analysis of different subsets of immune cells in blood, spleen and thymus revealed peripheral immune dysfunction which was restored by both P4 and VDH monotherapy. P4 monotherapy reduced infarction volume, behavioral/functional deficits, peripheral immune dysfunction, neuronal inflammation, and apoptosis induced by post-stroke systemic inflammation. Combination treatment with P4+VDH improved outcomes better than monotherapy. Our findings can be taken to suggest that the current standard of care for stroke and post-stroke infection can be substantially improved by P4 and VDH combination therapy.

YiQiFuMai Lyophilized Injection ameliorates tPA-induced hemorrhagic transformation by inhibiting cytoskeletal rearrangement associated with ROCK1 and NF-κB signaling pathways

ETHNOPHARMACOLOGICAL RELEVANCE

Thrombolytic therapy with tissue plasminogen activator (tPA) after ischemic stroke exacerbates blood-brain barrier (BBB) breakdown and leads to hemorrhagic transformation (HT). YiQiFuMai Lyophilized Injection (YQFM) is a modern preparation derived from Sheng-mai San (a traditional Chinese medicine). YQFM attenuates the BBB dysfunction induced by cerebral ischemia-reperfusion injury. However, whether YQFM can suppress tPA-induced HT remains unknown.

AIM OF THE STUDY

We investigated the therapeutic effect of YQFM on tPA-induced HT and explored the underlying mechanisms in vivo and in vitro to improve the safety of tPA use against stroke.

METHODS

Male C57BL/6J mice were subjected to 45 min of ischemia and 24 h of reperfusion. tPA (10 mg/kg) were infused 2 h after occlusion and YQFM (0.671 g/kg) was injected 2.5 h after occlusion. The in vitro effect of YQFM (100, 200, 400 μg/mL) on tPA (60 μg/mL)-induced dysfunction of the microvascular endothelial barrier in the brain following oxygen-glucose deprivation/reoxygenation (OGD/R) was observed in bEnd.3 cells.

RESULTS

YQFM suppressed tPA-induced high hemoglobin level in the brain, mortality, neurologic severity score, BBB permeability, expression and activation of matrix metalloproteinase (MMP)-9 and MMP-2, and degradation of tight-junction proteins. Furthermore, YQFM significantly blocked tPA-induced brain microvascular endothelial permeability and phosphorylation of Rho-associated kinase (ROCK)1, myosin light chain (MLC), cofilin and p65 in vivo and in vitro.

CONCLUSION

YQFM suppressed tPA-induced HT by inhibiting cytoskeletal rearrangement linked with ROCK-cofilin/MLC pathways and inhibiting the nuclear factor-kappa B pathway to ameliorate BBB damage caused by tPA.

Blood-Brain Barrier: More Contributor to Disruption of Central Nervous System Homeostasis Than Victim in Neurological Disorders

The blood-brain barrier (BBB) is a dynamic but solid shield in the cerebral microvascular system. It plays a pivotal role in maintaining central nervous system (CNS) homeostasis by regulating the exchange of materials between the circulation and the brain and protects the neural tissue from neurotoxic components as well as pathogens. Here, we discuss the development of the BBB in physiological conditions and then focus on the role of the BBB in cerebrovascular disease, including acute ischemic stroke and intracerebral hemorrhage, and neurodegenerative disorders, such as Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis (MS). Finally, we summarize recent advancements in the development of therapies targeting the BBB and outline future directions and outstanding questions in the field. We propose that BBB dysfunction not only results from, but is causal in the pathogenesis of neurological disorders; the BBB is more a contributor to the disruption of CNS homeostasis than a victim in neurological disorders.

Ablation of Vitamin D Signaling Compromises Cerebrovascular Adaptation to Carotid Artery Occlusion in Mice

Vitamin D insufficiency has been associated with increased incidence and severity of cerebrovascular disorders. We analyzed the impact of impaired vitamin D signaling on the anatomical and functional aspects of cerebrovascular adaptation to unilateral carotid artery occlusion (CAO), a common consequence of atherosclerosis and cause of ischemic stroke. Cerebrocortical blood flow (CoBF) showed a significantly increased drop and delayed recovery after CAO in mice carrying a functionally inactive vitamin D receptor (VDR) with the most sustained perfusion deficit in the temporal cortex. To identify the cause(s) for this altered adaptation, the extent of compensatory blood flow increase in the contralateral carotid artery and the morphology of pial collaterals between the anterior and middle cerebral arteries were determined. Whereas VDR deficiency had no significant influence on the contralateral carotid arterial blood flow increase, it was associated with decreased number and increased tortuosity of pial anastomoses resulting in unfavorable changes of the intracranial collateral circulation. These results indicate that VDR deficiency compromises the cerebrovascular adaptation to CAO with the most sustained consequences in the temporal cortex. The dysregulation can be attributed to the altered development and function of pial collateral circulation whereas extracranial vessels may not be impaired.

Vitamin D and Stroke: Effects on Incidence, Severity, and Outcome and the Potential Benefits of Supplementation

Vitamin D serum level has been positively associated with improved cardiovascular health, especially with reduction of stroke risk. This systemic review summarizes and synthesizes findings from studies relevant to the relationship between vitamin D and stroke risk, severity, and outcome; potential mechanisms explaining such a relationship; and outcomes from vitamin D supplementation. The literature shows that vitamin D deficiency is a significant risk factor for ischemic stroke, with sun exposure, sex, age, race, diabetes, and genetics playing a role as well. Stroke severity and short- and long-term outcomes also worsen with vitamin D deficiency. The neuroprotective mechanisms by which vitamin D operates to mitigate stroke onset and outcomes have yet to be fully studied, but researchers have proposed several pathways, including promotion of certain neuroprotective growth factors, reduction of arterial pressure through vasodilation, and inhibition of reactive oxygen species. There is some evidence that vitamin D supplementation could lower stroke risk and improve recovery, though outcomes can also be negligible or negative. Although results are mixed and the limitations of vitamin D supplementation merit some caution, vitamin D overall plays a significant role in stroke health. Future research should further develop understanding of the neuroprotective mechanisms of vitamin D and study how supplementation could be administered effectively in stroke treatment.

Vitamin D strengthens the bladder epithelial barrier by inducing tight junction proteins during E. coli urinary tract infection

Tight junction proteins are pivotal to prevent bacterial invasion of the epithelial barrier. We here report that supplementation with vitamin D can strengthen the urinary bladder lining. Vitamin D deficient and sufficient mice were infected with Escherichia coli (E. coli) transurethrally to cause urinary tract infection. In addition, bladder biopsies were obtained from postmenopausal women before and after a 3-month period of supplementation with 25-hydroxyvitamin D₃ (25D₃) and ex vivo infected with E. coli. In biopsies, obtained before E. coli infection, vitamin D had no impact on tight junction proteins. However, during E. coli infection, vitamin D induced occludin and claudin-14 in mature superficial umbrella cells of the urinary bladder, as demonstrated by immunohistochemistry. Increased cell-cell adhesion consolidating the epithelial integrity is thereby promoted. We here describe a novel role of vitamin D in the urinary tract supporting vitamin D supplementation to restore the bladder epithelial integrity.

Microphysiological systems for recapitulating physiology and function of blood-brain barrier

Central nervous system (CNS) diseases are emerging as a major issue in an aging society. Although extensive research has focused on the development of CNS drugs, the limited transport of therapeutic agents across the blood-brain barrier (BBB) remains a major challenge. Conventional two-dimensional culture dishes do not recapitulate in vivo physiology and real-time observations of molecular transport are not possible in animal models. Recent advances in engineering techniques have enabled the generation of more physiologically relevant in vitro BBB models, and their applications have expanded from fundamental biological research to practical applications in the pharmaceutical industry. In this article, we provide an overview of recent advances in the development of in vitro BBB models, with a particular focus on the recapitulation of BBB function. The development of biomimetic BBB models is postulated to revolutionize not only fundamental biological studies but also drug screening.

Protective effects of vitamin D against injury in intestinal epithelium

BACKGROUND

Vitamin D deficiency is associated with intestinal barrier dysfunction, which contributes to pathogenesis of acute intestinal injury in children. We aim to investigate the effects of vitamin D on intestinal injury in intestinal epithelial cells and organoids.

METHODS

Lipopolysaccharide (LPS) was used to induce injury in intestinal epithelial cells (IEC-18) and organoids, and the effect of vitamin D was assessed. Cell viability was measured and inflammation cytokines TNFα and IL-8 were quantified. FITC-dextran 4 kDa (FD4) permeability was measured using Transwell while tight junction markers were assessed by immunofluorescence staining in IEC-18 and intestinal organoids. Data were compared using one-way ANOVA with Bonferroni post-test.

RESULTS

IEC-18 viability was decreased by LPS treatment, but was prevented by vitamin D. The upregulation of inflammation was inhibited by vitamin D, which also decreased epithelium permeability. Vitamin D restored tight junction ZO-1 and claudin 2. In addition, vitamin D decreased TNFα expression and prevented the disruption of ZO-1 in injured organoids.

CONCLUSIONS

Vitamin D rescued epithelial barrier function by improving permeability and restoring tight junctions, leading to decrease inflammation. This study confirms the protective effects of vitamin D, which could be used as a treatment strategy for infants at risk of developing intestinal injury.

Calcitriol protects the Blood-Brain Barrier integrity against ischemic stroke and reduces vasogenic brain edema via antioxidant and antiapoptotic actions in rats

BACKGROUND

Vasogenic brain edema is the most important complication of ischemic stroke that aggravates primary brain injury. Ischemia-Reperfusion (IR)-induced Blood-Brain Barrier (BBB) impairment limits the use of recombinant tissue plasminogen activator (r-tPA) by increasing the possibility of hemorrhagic transformation and contributing to vasogenic edema and neuroinflammation. This study examined the effects of post-ischemic treatment with calcitriol on cerebral infarction, vasogenic edema formation and BBB disruption in a rat model of ischemic stroke.

METHODS

Male Sprague-Dawley rats were divided into three main groups, including the sham, IR + vehicle and IR + calcitriol groups. Transient focal cerebral ischemia was induced by a 60-min-long occlusion of the left middle cerebral artery. The infarct volume, brain edema, BBB permeability and antioxidant enzyme activities were evaluated 24 h after ischemia. Immunohistochemical analysis was conducted to investigate cell apoptosis and Brain-Derived Neurotrophic Factor (BDNF) protein expression five days after ischemia.

RESULTS

Compared to the IR + vehicle group, the IR + calcitriol group showed a reduced brain infarction volume, attenuated brain edema formation and improved BBB function. These protective effects were followed by the upregulation of antioxidant enzyme activities in the brain tissue. Additionally, a diminished cell apoptosis and an increased BDNF immunoreactivity were obtained in the IR + calcitriol group.

CONCLUSION

Calcitriol may reduce brain injury and attenuate vasogenic edema by upregulating antioxidant enzymes activities, reducing cell apoptosis and increasing BDNF protein in the brain tissue in a rat model of ischemic stroke.

Gender, hyperandrogenism and vitamin D deficiency related functional and morphological alterations of rat cerebral arteries

Hyperandrogenism is a risk factor of cerebrovascular diseases as androgens can alter markedly the regulation of cerebrovascular tone. We examined the combined impact of androgen excess and vitamin D deficiency (VDD), a common co-morbidity in hyperandrogenic disorders, on remodeling and testosterone-induced vascular responses of anterior cerebral arteries (ACA) in order to evaluate the interplay between androgens and VDD in the cerebral vasculature. Male and female Wistar rats were either fed with vitamin D deficient or vitamin D supplemented diet. Half of the female animals from both groups received transdermal testosterone treatment. After 8 weeks, vessel lumen, wall thickness and testosterone-induced vascular tone of isolated ACA were determined using pressure microangiometry and histological examination. Androgen receptor protein expression in the wall of cerebral arteries was examined using immunohistochemistry. In female rats only combined VDD and testosterone treatment decreased the lumen and increased the wall thickness of ACA. In males, however VDD by itself was able to decrease the lumen and increase the wall thickness. Vascular reactivity showed similar alterations: in females, testosterone constricted the ACA only after combined VDD and hyperandrogenism, whereas in males VDD resulted in increased testosterone-induced contractions in spite of decreased androgen receptor expression. In conclusion, a marked interplay between hyperandrogenism and VDD results in inward remodeling and enhanced testosterone-induced constrictions of cerebral arteries, which might compromise the cerebral circulation and thus, increase the risk of stroke in the long term. In addition, the early cerebrovascular manifestation of VDD appears to require androgen excess and thus, depends on gender.

What is the Current Role for Vitamin D and the Risk of Stroke?

INTRODUCTION

Increasing evidence supports the relationship between vitamin D and stroke. Vitamin D has now been proposed as a prognostic biomarker also for functional outcome in stroke patients.

METHODS

A revision of the data suggests that low vitamin D is associated more with ischemic than with haemorrhagic stroke, even if the role of optimal vitamin D levels for vascular wall is still unclear. Vitamin D deficiency induces with different mechanisms an alteration of vascular wall.

RESULTS

However, to date, the research supporting the effectiveness of vitamin D supplementation in stroke and in post-stroke recovery is still inadequate and conclusive evidences have not been published.

CONCLUSION

In this review, we provide a better understanding of the role of vitamin D in stroke.

Semaphorin 3A Contributes to Secondary Blood-Brain Barrier Damage After Traumatic Brain Injury

Semaphorin 3A (SEMA3A) is a member of the Semaphorins family, a class of membrane-associated protein that participates in the construction of nerve networks. SEMA3A has been reported to affect vascular permeability previously, but its influence in traumatic brain injury (TBI) is still unknown. To investigate the effects of SEMA3A, we used a mouse TBI model with a controlled cortical impact (CCI) device and a blood–brain barrier (BBB) injury model in vitro with oxygen-glucose deprivation (OGD). We tested post-TBI changes in SEMA3A, and its related receptors (Nrp-1 and plexin-A1) expression and distribution through western blotting and double-immunofluorescence staining, respectively. Neurological outcomes were evaluated by modified neurological severity scores (mNSSs) and beam-walking test. We examined BBB damage through Evans Blue dye extravasation, brain water content, and western blotting for VE-cadherin and p-VE-cadherin in vivo, and we examined the endothelial cell barrier through hopping probe ion conductance microscopy (HPICM), transwell leakage, and western blotting for VE-cadherin and p-VE-cadherin in vitro. Changes in miR-30b-5p were assessed by RT-PCR. Finally, the neuroprotective function of miR-30b-5p is measured by brain water content, mNSSs and beam-walking test. SEMA3A expression varied following TBI and peaked on the third day which expressed approximate fourfold increase compared with sham group, with the protein concentrated at the lesion boundary. SEMA3A contributed to neurological function deficits and secondary BBB damage in vivo. Our results demonstrated that SEMA3A level following OGD injury almost doubled than control group, and the negative effects of OGD injury can be improved by blocking SEMA3A expression. Furthermore, the expression of miR-30b-5p decreased approximate 40% at the third day and 60% at the seventh day post-CCI. OGD injury also exhibited an effect to approximately decrease 50% of miR-30b-5p expression. Additionally, the expression of SEMA3A post-TBI is regulated by miR-30b-5p, and miR-30b-5p could improve neurological outcomes post-TBI efficiently. Our results demonstrate that SEMA3A is a significant factor in secondary BBB damage after TBI and can be abolished by miR-30b-5p, which represents a potential therapeutic target.