Vitamin D receptor activation influences the ERK pathway and protects against neurological deficits and neuronal death

Effects of the Interaction between Dietary Vitamin D3 and Vitamin K3 on Growth, Skeletal Anomalies, and Expression of Bone and Calcium Metabolism-Related Genes in Juvenile Gilthead Seabream (Sparus aurata)

The interaction between vitamin D and vitamin K is crucial for regulating bone metabolism and maintaining calcium homeostasis across diverse animal species due to their complementary roles in calcium metabolism and bone health. However, research on this interaction of vitamin D and K in fish, particularly Mediterranean species like gilthead seabream, is limited or not studied. This study aimed to understand the effects of different dietary combinations of vitamin D3 and K3 on juvenile gilthead seabream. Accordingly, seabream juveniles were fed with varying combinations of vitamin D3/vitamin K3 (mg/kg diet) for 3 months: (0.07/0.01), (0.20/0.58), (0.19/1.65), (0.51/0.74), (0.56/1.00). At the end of the trial, survival, growth, body morphology, serum calcitriol, and vertebral mineral composition remained unaffected by varying vitamin levels, while gene expression patterns related to bone formation, resorption, and calcium regulation in various tissues were significantly influenced by both vitamins and their interaction. Gilthead seabream juveniles fed the 0.07/0.01 mg/kg diet upregulated calcium-regulating genes in the gills, indicating an effort to enhance calcium absorption to compensate for dietary deficiencies. Conversely, an increase in vitamin D3 and K3 up to 0.19 and 1.65 mg/kg, respectively, upregulated bone formation, bone remodeling, and calcium homeostasis-related gene expression in vertebra and other tissues. On the contrary, a dietary increase in these vitamins up to 0.56 mg/kg vitamin D3 and 1.00 mg/kg vitamin K3 downregulated calcium metabolism-related genes in tissues, suggesting an adverse interaction resulting from elevated levels of these vitamins in the diet. Hence, sustaining an equilibrium in the dietary intake of vitamin D3 and vitamin K3, in an appropriately combined form, may potentially induce interactions between the vitamins, contributing to favorable effects on bone development and calcium regulation in gilthead seabream juveniles.

Tremendous Fidelity of Vitamin D3 in Age-related Neurological Disorders

Vitamin D3 (VD) is a secosteroid hormone and shows a pleiotropic effect in brain-related disorders where it regulates redox imbalance, inflammation, apoptosis, energy production, and growth factor synthesis. Vitamin D3's active metabolic form, 1,25-dihydroxy Vitamin D3 (1,25(OH)2D3 or calcitriol), is a known regulator of several genes involved in neuroplasticity, neuroprotection, neurotropism, and neuroinflammation. Multiple studies suggest that VD deficiency can be proposed as a risk factor for the development of several age-related neurological disorders. The evidence for low serum levels of 25-hydroxy Vitamin D3 (25(OH)D3 or calcidiol), the major circulating form of VD, is associated with an increased risk of Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), dementia, and cognitive impairment. Despite decades of evidence on low VD association with neurological disorders, the precise molecular mechanism behind its beneficial effect remains controversial. Here, we will be delving into the neurobiological importance of VD and discuss its benefits in different neuropsychiatric disorders. The focus will be on AD, PD, and HD as they share some common clinical, pathological, and epidemiological features. The central focus will be on the different attributes of VD in the aspect of its anti-oxidative, anti-inflammatory, anti-apoptotic, anti-cholinesterase activity, and psychotropic effect in different neurodegenerative diseases.

Curcumin inhibits cerebral ischaemia-reperfusion injury and cell apoptosis in rats through the ERK-CHOP-caspase-11 pathway

CONTEXT

Curcumin has a significant effect on cerebral ischaemia-reperfusion injury (CIRI). However, the underlying mechanism is less studied.

OBJECTIVE

This study investigates the role and mechanism of curcumin in CIRI.

MATERIALS AND METHODS

CIRI model Sprague-Dawley rats were divided into model, positive control and curcumin low/middle/high dose (50, 100 and 200 mg/kg/d) groups (n = 10 each). Drug intervention was administered by gavage once a day for 4 weeks. We calculated the neurobehavioural score and observed the cerebral infarct volume. Glial cytopathological changes were observed after haematoxylin-eosin staining. Apoptosis was detected by TUNEL (TdT mediated dUTP nick end labelling). Extracellular signal-regulated protein kinase (ERK), C/EBP-homologous protein (CHOP) and caspase-11 mRNA were detected by real-time PCR. Phosphorylated ERK (p-ERK), phosphorylated CHOP (p-CHOP) and caspase-11 were detected by Western blot. Superoxide dismutase (SOD) activity was detected by xanthine oxidation method; malondialdehyde (MDA) content by thiobarbituric acid colorimetry; and, glutathione (GSH) by spectrophotometry.

RESULTS

Compared with control, the neurobehavioural scores, neuronal apoptosis, MDA, IL-1β, IL-18, mRNAs and protein levels of ERK/p-ERK, CHOP/p-CHOP and caspase-11 in model group were significantly higher (p < 0.01). Compared with model, the positive control and medium/high dose curcumin groups were significantly lower (p < 0.01). However, SOD and GSH decreased significantly in model group but increased significantly in positive control and medium/high dose curcumin groups (p < 0.01). Moreover, curcumin significantly alleviated ischaemic state and neuroinflammation (p < 0.01).

DISCUSSION AND CONCLUSIONS

Curcumin may alleviate CIRI through ERK-CHOP-caspase-11 pathway. Our results may provide new insights into the pathogenesis of CIRI, and contribute to the development of treatment strategies for CIRI.

Double-Edged Sword of Vitamin D3 Effects on Primary Neuronal Cultures in Hypoxic States

The use of vitamin D3 along with traditional therapy opens up new prospects for increasing the adaptive capacity of nerve cells to the effects of a wide range of stress factors, including hypoxia-ischemic processes. However, questions about prophylactic and therapeutic doses of vitamin D3 remain controversial. The purpose of our study was to analyze the effects of vitamin D3 at different concentrations on morpho-functional characteristics of neuron-glial networks in hypoxia modeling in vitro. We showed that a single administration of vitamin D3 at a high concentration (1 µM) in a normal state has no significant effect on the cell viability of primary neuronal cultures; however, it has a pronounced modulatory effect on the functional calcium activity of neuron-glial networks and causes destruction of the network response. Under hypoxia, the use of vitamin D3 (1 µM) leads to total cell death of primary neuronal cultures and complete negation of functional neural network activity. In contrast, application of lower concentrations of vitamin D3 (0.01 µM and 0.1 µM) caused a pronounced dose-dependent neuroprotective effect during the studied post-hypoxic period. While the use of vitamin D3 at a concentration of 0.1 µM maintained cell viability, preventive administration of 0.01 µM not only partially preserved the morphological integrity of primary neuronal cells but also maintained the functional structure and activity of neuron-glial networks in cultures. Possible molecular mechanisms of neuroprotective action of vitamin D3 can be associated with the increased expression level of transcription factor HIF-1α and maintaining the relationship between the levels of BDNF and TrkB expression in cells of primary neuronal cultures.

Benefits of vitamin D supplementation to attenuate TBI secondary injury?

Vitamin D supplementation has been shown to improve outcomes for patients suffering from a variety of illnesses such as stroke and cancer. Vitamin D deficiencies have been associated with longer hospital stays, greater severity of symptoms, and death in some complex cases. Due to vitamin D’s burgeoning role in improving patient outcomes, a new sector of research is focusing on the lesser-known implications of vitamin D on health. Traumatic brain injury (TBI) affects approximately 69 million people worldwide per year. Here, we summarize the current scientific understanding of vitamin D dynamics with TBI to elucidate a potential way to lessen the cascade of secondary damage after an initial insult, with the goal of improving overall patient outcomes. Because vitamin D supplementation has been correlated with better outcomes in other pathologies involving immune and inflammatory molecules, it is important to study the potential effect of vitamin D deficiency (VDD) and supplementation on TBI outcomes. Research on vitamin D supplementation in TBI remains in the preliminary stages. There is still much to learn about vitamin D deficiency, dosage, variants of supplementary forms, mechanisms, and its role in TBI.

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.

Calcitriol Suppresses HIF-1 and HIF-2 Transcriptional Activity by Reducing HIF-1/2α Protein Levels via a VDR-Independent Mechanism

Hypoxia-inducible transcription factors 1 and 2 (HIFs) are major mediators of cancer development and progression and validated targets for cancer therapy. Although calcitriol, the biologically active metabolite of vitamin D, was attributed with anticancer properties, there is little information on the effect of calcitriol on HIFs and the mechanism underling this activity. Here, we demonstrate the negative effect of calcitriol on HIF-1/2α protein levels and HIF-1/2 transcriptional activity and elucidate the molecular mechanism of calcitriol action. We also reveal that the suppression of vitamin D receptor (VDR) expression by siRNA does not abrogate the negative regulation of HIF-1α and HIF-2α protein levels and HIF-1/2 transcriptional activity by calcitriol, thus testifying that the mechanism of these actions is VDR independent. At the same time, calcitriol significantly reduces the phosphorylation of Akt protein kinase and its downstream targets and suppresses HIF-1/2α protein synthesis by inhibiting HIF1A and EPAS1 (Endothelial PAS domain-containing protein 1) mRNA translation, without affecting their mRNA levels. On the basis of the acquired data, it can be proposed that calcitriol reduces HIF-1α and HIF-2α protein levels and inhibits HIF-1 and HIF-2 transcriptional activity by a VDR-independent, nongenomic mechanism that involves inhibition of PI3K/Akt signaling pathway and suppression of HIF1A and EPAS1 mRNA translation.

Parecoxib exhibits anti-inflammatory and neuroprotective effects in a rat model of transient global cerebral ischemia

Transient global cerebral ischemia (tGCI) induces inflammation leading to secondary brain injury. Data suggested that cyclooxygenase-2 (COX-2) is involved in the occurrence and development of inflammatory reaction after reperfusion; however, the effectiveness of a highly selective COX-2 inhibitor, parecoxib, to counteract tGCI remains to be determined. Thus, the aim of this study was to investigate the potential protective actions of parecoxib in a rat model of tGCI and the role inflammation plays in this disorder. Adult male Sprague-Dawley rats were administered parecoxib 10 or 20 mg/kg intraperitoneally (ip) at 5 min, 24 or 48 hr after tGCI. Control rats received an equal volume of 0.9% saline. The rat model of tGCI was established using the method of bilateral common carotid artery occlusion combined with arterial hypotension. The following parameters were measured: Neurological Severity Score, morphological changes in the hippocampal CA1 region, Evans blue (EB) extravasation, brain water content, levels of matrix metalloproteinase-9 (MMP-9), zonula occludens-1 (ZO-1), neuronal apoptosis, the protein expression of Bcl-2, Bax, COX-2, prostaglandin E2 (PGE₂), interleukin-1β (IL-1β), and tumor necrosis factor-α (TNF-α). Parecoxib treatment significantly improved neurological function and morphological defects in the hippocampal CA1 region, reduced levels of COX-2, PGE₂, IL-1β, and TNF-α. In addition, parecoxib attenuated brain edema and BBB destruction as evidenced by increased ZO-1 expression and decreased MMP-9 expression. Further, parecoxib reduced neuronal apoptosis via diminished protein expression of Bax and enhanced expression of Bcl-2.

RNAi-mediated knockdown of VDR surprisingly suppresses cell growth in Jurkat T and U87-MG cells

Vitamin D receptor (VDR) is a nuclear receptor for 1,25-Dihydroxyvitamin D3. VDR is expressed in many types of cells and involved in different biological processes such as immunity and inflammation. In addition, the role for VDR has been indicated in different diseases including multiple sclerosis (MS). In this study, we investigated the effects of VDR knockdown on growth, apoptosis, cell cycle, and some inflammatory gene expressions in Jurkat and U87-MG cell lines.

The cell lines were transfected with plasmids encoding short hairpin RNA specific to VDR mRNA. Next, growth, apoptosis, and cell cycle were evaluated using MTT assay and annexin VDR along with flowcytometry. Then the mRNA expression of some genes was determined by real-time PCR at 24 h and 48 h after transfection.

The cell growth and apoptosis of VDR-shRNA transfected Jurkat T cells and U87-MG cells were surprisingly changed compared with those in control cells. The expression of IL-10, NF-KB, TGF-β1, TGF-β R I, and TGF-β R II in two cell lines transfected with VDR-shRNA was significantly changed compared to control cells.

VDR showed a new unexpected function to control cell growth in vitro. In addition, while VDR knocking down in two different cell lines of U87-MG and Jurkat cells had different effects on NF-kB and TGF-beta expression levels, its effects on cell growth and apoptosis were similar. This may suggest that these two different cell lines can show similar anti-proliferative effects by different downstream signalling pathways. Therefore, these data may be useful to design novel diagnostic and therapeutic methods for diseases such as MS.

Vitamin D receptor activation regulates microglia polarization and oxidative stress in spontaneously hypertensive rats and angiotensin II-exposed microglial cells: Role of renin-angiotensin system

Hypertension is one of the major predisposing factors for neurodegenerative disease characterized with activated renin-angiotensin system (RAS) in both periphery and brain. Vitamin D (VitD) is recently recognized as a pleiotropic hormone with strong neuroprotective properties. While multiple lines of evidence suggest that VitD can act on RAS, the evidence concerning the crosstalk between VitD and RAS in the brain is limited. Therefore, this study aims to evaluate whether VitD can modulate brain RAS to trigger neuroprotective actions in the brain of spontaneously hypertensive rats (SHR). Our data showed that calcitriol treatment induced VDR expression and inhibited neural death in the prefrontal cortex of SHR. Sustained calcitriol administration also inhibited microglia M1 polarization, but enhanced M2 polarization, accompanied with decreased expression of proinflammatory cytokines. We then further explored the potential mechanisms and showed that SHR exhibited overactivated classical RAS with increased expression of angiotensin II (Ang II) receptor type 1 (AT1), angiotensin converting enzyme (ACE) and Ang II production, whereas the counteracting arm of traditional RAS, ACE2/Ang(1-7)/MasR, was impaired in the SHR brain. Calcitriol nonsignificantly suppressed AT1 and ACE but markedly reduced Ang II formation. Intriguingly, calcitriol exerted pronouncedly impact on ACE2/Ang(1-7)/MasR axis with enhanced expression of ACE2, MasR and Ang(1-7) generation. Meanwhile, calcitriol ameliorated the overactivation of NADPH-oxidase (Nox), the downstream of RAS, in SHR, and also mitigated oxidative stress. In microglial (BV2) cells, we further found that calcitriol induced ACE2 and MasR with no significant impact on ACE and AT1. In accordance, calcitriol also attenuated Ang II-induced Nox activation and ROS production, and shifted the microglia polarization from M1 to M2 phenotype. However, co-treatment with A779, a specific MasR antagonist, abrogated the antioxidant and neuroimmune modulating actions of VitD. These findings strongly indicate the involvement of ACE2/Ang(1-7)/MasR pathway in the neuroprotective mechanisms of VitD in the hypertensive brain.

The combined presence of hypertension and vitamin D deficiency increased the probability of the occurrence of small vessel disease in China

BACKGROUND

The exact relationship between 25-hydroxyvitamin D [25(OH) D] levels and small vessel disease (SVD) are not clear in China. The aim of this study was to determine such the association between 25(OH) D and SVD in China.

METHODS

We retrospectively enrolled 106 patients with SVD and 115 controls between Jan 2017 and Dec 2017. All the subjects were categorized into three subgroups according to the level of 25 (OH) D: vitamin D deficiency (< 12 ng/ml), insufficiency (12-20 ng/ml) and sufficiency (> 20 ng/ml).

RESULTS

Among 106 SVD patients, 80 (75.5%) were men and the mean age was 61.6 ± 13.2 years. The deficiency of 25(OH) D was observed in 76 (71.7%) of SVD patients and 47 (40.9%) of controls (P = 0.001). Compared with controls, patients with SVD were more likely to be male, a stroke history, smokers, with hyperlipidemia, higher systolic and diastolic blood pressure and low-density lipoprotein, and lower of 25(OH)D level (P < 0.05). Logistic regression analysis revealed the level of 25 (OH) D as an independent predictor of SVD (OR 0.772, 95% CI 0.691-0.862, P = 0.001). Compared with the sufficient 25 (OH) D group, the ORs of SVD in deficient and insufficient 25(OH)D group were 5.609 (95% CI 2.006-15.683) and 1.077 (95% CI: 0.338-3.428) after adjusting for potential confounders, respectively. In hypertensives with vitamin D deficient and insufficient group compared with sufficient group, the ORs of SVD increased to 9.738 (95% CI 2.398-39.540) and 1.108 (95% CI 0.232-5.280), respectively (Pinteraction = 0.001).

CONCLUSION

We found significant associations between SVD and 25(OH)D deficiency. The combined presence of hypertension and vitamin D deficiency increased the probability of developing SVD. Our findings will warrant further prospective studies in the future.

Effect of β-patchoulene on cerebral ischemia-reperfusion injury and the TLR4/NF-κB signaling pathway

β-patchoulene (β-PAE), an active constituent of the Pogostemon cablin, is well known for its anti-inflammatory and antioxidative functions in various diseases. However, little is known about the impact of β-PAE on the cerebral ischemia-reperfusion (I/R) injury. The current study aimed to determine the neuroprotective effect of β-PAE and the underlying mechanisms on cerebral I/R injury. Following pretreatment with β-PAE (10 mg/kg body weight) by tail intravenous injection for 1 h, Sprague-Dawley rats were subjected to middle cerebral artery occlusion for 2 h and reperfusion for 24 h. The results indicated that pretreatment with β-PAE could diminish the infarct volume, decrease the brain water content, reduce the neurological deficit score and restore the mitochondrial membrane potential, compared with the untreated I/R injury group. Furthermore, cell apoptosis was markedly suppressed by β-PAE, and this effect was associated with the decreased apoptosis regulator BAX/apoptosis regulator Bcl-2 expression ratio and caspase-3 activity. In addition, β-PAE significantly inhibited the release of proinflammatory factors, including tumor necrosis factor-α, interleukin (IL)-1β and IL-6. Superoxide generation and malondialdehyde levels were reduced while the levels of glutathione peroxidase and superoxide dismutase were elevated following treatment with β-PAE, indicating the antioxidative role of β-PAE in cerebral I/R injury. Furthermore, the Toll-like receptor 4 (TLR4)/nuclear factor-κB (NF-κB) signaling pathway was inhibited by β-PAE, as demonstrated by the decreased TLR4 expression and nuclear translocation of p65, and increased IκBα level. Taken together, the results suggested that β-PAE may exhibit a neuroprotective effect on cerebral I/R injury in rats through inactivating the TLR4/NF-κB signaling pathway.

The regulatory role of Toll-like receptors after ischemic stroke: neurosteroids as TLR modulators with the focus on TLR2/4

Ischemic stroke is the most common cerebrovascular disease and considered as a worldwide leading cause of death. After cerebral ischemia, different pathophysiological processes including neuroinflammation, invasion and aggregation of inflammatory cells and up-regulation of cytokines occur simultaneously. In this respect, Toll-like receptors (TLRs) are the first identified important mediators for the activation of the innate immune system and are widely expressed in glial cells and neurons following brain trauma. TLRs are also able to interact with endogenous and exogenous molecules released during ischemia and can increase tissue damage. Particularly, TLR2 and TLR4 activate different downstream inflammatory signaling pathways. In addition, TLR signaling can alternatively play a role for endogenous neuroprotection. In this review, the gene and protein structures, common genetic polymorphisms of TLR2 and TLR4, TLR-related molecular pathways and their putative role after ischemic stroke are delineated. Furthermore, the relationship between neurosteroids and TLRs as neuroprotective mechanism is highlighted in the context of brain ischemia.