Progesterone and low-dose vitamin D hormone treatment enhances sparing of memory following traumatic brain injury

Gain-of-function of progesterone receptor membrane component 2 ameliorates ischemic brain injury

OBJECTIVE

Progesterone receptor membrane component 2 (PGRMC2) belongs to the membrane-associated progesterone receptor family, which regulates multiple pathophysiological processes. However, the role of PGRMC2 in ischemic stroke remains unexplored. The present study sought to determine the regulatory role of PGRMC2 in ischemic stroke.

METHODS

Male C57BL/6J mice were subjected to middle cerebral artery occlusion (MCAO). The protein expression level and localization of PGRMC2 were examined by western blotting and immunofluorescence staining. The gain-of-function ligand of PGRMC2 (CPAG-1, 45 mg/kg) was intraperitoneally injected into sham/MCAO mice, and brain infarction, blood-brain barrier (BBB) leakage, and sensorimotor functions were evaluated by magnetic resonance imaging, brain water content, Evans blue extravasation, immunofluorescence staining, and neurobehavioral tests. The astrocyte and microglial activation, neuronal functions, and gene expression profiles were revealed by RNA sequencing, qPCR, western blotting, and immunofluorescence staining after surgery and CPAG-1 treatment.

RESULTS

Progesterone receptor membrane component 2 was elevated in different brain cells after ischemic stroke. Intraperitoneal delivery of CPAG-1 reduced infarct size, brain edema, BBB leakage, astrocyte and microglial activation, and neuronal death, and improved sensorimotor deficits after ischemic stroke.

CONCLUSION

CPAG-1 acts as a novel neuroprotective compound that could reduce neuropathologic damage and improve functional recovery after ischemic stroke.

Brain Trauma and the Secondary Cascade in Humans: Review of the Potential Role of Vitamins in Reparative Processes and Functional Outcome

An estimated sixty-nine million people sustain a traumatic brain injury each year. Trauma to the brain causes the primary insult and initiates a secondary biochemical cascade as part of the immune and reparative response to injury. The secondary cascade, although a normal physiological response, may also contribute to ongoing neuroinflammation, oxidative stress and axonal injury, continuing in some cases years after the initial insult. In this review, we explain some of the biochemical mechanisms of the secondary cascade and their potential deleterious effects on healthy neurons including secondary cell death. The second part of the review focuses on the role of micronutrients to neural mechanisms and their potential reparative effects with regards to the secondary cascade after brain injury. The biochemical response to injury, hypermetabolism and excessive renal clearance of nutrients after injury increases the demand for most vitamins. Currently, most research in the area has shown positive outcomes of vitamin supplementation after brain injury, although predominantly in animal (murine) models. There is a pressing need for more research in this area with human participants because vitamin supplementation post-trauma is a potential cost-effective adjunct to other clinical and therapeutic treatments. Importantly, traumatic brain injury should be considered a lifelong process and better evaluated across the lifespan of individuals who experience brain injury.

Multi-Mechanistic Approaches to the Treatment of Traumatic Brain Injury: A Review

Traumatic brain injury (TBI) is a leading cause of death and disability worldwide. Despite extensive research efforts, the majority of trialed monotherapies to date have failed to demonstrate significant benefit. It has been suggested that this is due to the complex pathophysiology of TBI, which may possibly be addressed by a combination of therapeutic interventions. In this article, we have reviewed combinations of different pharmacologic treatments, combinations of non-pharmacologic interventions, and combined pharmacologic and non-pharmacologic interventions for TBI. Both preclinical and clinical studies have been included. While promising results have been found in animal models, clinical trials of combination therapies have not yet shown clear benefit. This may possibly be due to their application without consideration of the evolving pathophysiology of TBI. Improvements of this paradigm may come from novel interventions guided by multimodal neuromonitoring and multimodal imaging techniques, as well as the application of multi-targeted non-pharmacologic and endogenous therapies. There also needs to be a greater representation of female subjects in preclinical and clinical studies.

Nutritional interventions to support acute mTBI recovery

When mild traumatic brain injury (mTBI) occurs following an impact on the head or body, the brain is disrupted leading to a series of metabolic events that may alter the brain's ability to function and repair itself. These changes may place increased nutritional demands on the body. Little is known on whether nutritional interventions are safe for patients to implement post mTBI and whether they may improve recovery outcomes. To address this knowledge gap, we conducted a systematic review to determine what nutritional interventions have been prescribed to humans diagnosed with mTBI during its acute period (<14 days) to support, facilitate, and result in measured recovery outcomes.

Effects of Progesterone on Preclinical Animal Models of Traumatic Brain Injury: Systematic Review and Meta-analysis

Since the publication of two phase III clinical trials not supporting the use of progesterone in patients with traumatic brain injury (TBI), several possible explanations have been postulated, including limitations in the analysis of results from preclinical evidence. Therefore, to address this question, a systematic review and meta-analysis was performed to evaluate the effects of progesterone as a neuroprotective agent in preclinical animal models of TBI. A total of 48 studies were included for review: 29 evaluated brain edema, 21 evaluated lesion size, and 0 studies reported the survival rate. In the meta-analysis, it was found that progesterone reduced brain edema (effect size - 1.73 [- 2.02, - 1.44], p < 0.0001) and lesion volume (effect size - 0.40 [- 0.65, - 0.14], p = 0.002). Lack of details in the studies hindered the assessment of risk of bias (through the SYRCLE tool). A funnel plot asymmetry was detected, suggesting a possible publication bias. In conclusion, preclinical studies show that progesterone has an anti-edema effect in animal models of TBI, decreasing lesion volume or increasing remaining tissue. However, more studies are needed using assessing methods with lower risk of histological artifacts.

Neuro-Inflammation Modulation and Post-Traumatic Brain Injury Lesions: From Bench to Bed-Side

Head trauma is the most common cause of disability in young adults. Known as a silent epidemic, it can cause a mosaic of symptoms, whether neurological (sensory-motor deficits), psychiatric (depressive and anxiety symptoms), or somatic (vertigo, tinnitus, phosphenes). Furthermore, cranial trauma (CT) in children presents several particularities in terms of epidemiology, mechanism, and physiopathology-notably linked to the attack of an immature organ. As in adults, head trauma in children can have lifelong repercussions and can cause social and family isolation, difficulties at school, and, later, socio-professional adversity. Improving management of the pre-hospital and rehabilitation course of these patients reduces secondary morbidity and mortality, but often not without long-term disability. One hypothesized contributor to this process is chronic neuroinflammation, which could accompany primary lesions and facilitate their development into tertiary lesions. Neuroinflammation is a complex process involving different actors such as glial cells (astrocytes, microglia, oligodendrocytes), the permeability of the blood-brain barrier, excitotoxicity, production of oxygen derivatives, cytokine release, tissue damage, and neuronal death. Several studies have investigated the effect of various treatments on the neuroinflammatory response in traumatic brain injury in vitro and in animal and human models. The aim of this review is to examine the various anti-inflammatory therapies that have been implemented.

Vitamin D Deficiency and Prognosis after Traumatic Brain Injury with Intracranial Injury: A Multi-Center Observational Study

Vitamin D may be important for neuroprotection after traumatic brain injury (TBI) by modifying the inflammatory response. The objective of this study was to evaluate the association between vitamin D deficiency and functional and survival outcomes in patients with TBI and intracranial injury. This study was a prospective multi-center cohort study conducted on adult TBI patients, with intracranial hemorrhage or diffuse axonal injury confirmed by radiological examination, admitted to five participating emergency departments (EDs) from December 2018 to June 2020. The study outcomes were good functional recovery at hospital discharge and survival at 6-months after injury. The primary exposure was serum vitamin D deficiency (0-10 ng/mL). Multi-level logistic regression analysis was performed to estimate the association between vitamin D deficiency and the study outcomes. Among 606 patients, 101 (16.7%) patients had vitamin D deficiency at the time of ED arrival. Good functional recovery was observed in 65.2% (395/606) of total population, and this proportion was significantly lower in the vitamin D deficiency group than the non-deficiency group (56.4 vs. 66.9%, p = 0.04, adjusted odds ratio (OR; 95% confidence interval [CI]): 0.56 (0.36-0.88)). Overall survival rate at 6 months after injury was 79.5% (434/546), and patients with vitamin D deficiency had significantly lower likelihood of survival at 6 months than patients without deficiency [75.0 vs. 80.3%, adjusted OR (95% CI): 0.59 (0.39-0.89)]. Vitamin D deficiency is associated with poor functional outcomes at hospital discharge and mortality at 6-months after injury in TBI patients with intracranial hemorrhage or diffuse axonal injury.

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.

Omega-3 Fatty Acids and Vitamin D Decrease Plasma T-Tau, GFAP, and UCH-L1 in Experimental Traumatic Brain Injury

Traumatic brain injury (TBI) results in neuronal, axonal and glial damage. Interventions targeting neuroinflammation to enhance recovery from TBI are needed. Exercise is known to improve cognitive function in TBI patients. Omega-3 fatty acids and vitamin D reportedly reduce inflammation, and in combination, might improve TBI outcomes. This study examined how an anti-inflammatory diet affected plasma TBI biomarkers, voluntary exercise and behaviors following exposure to mild TBI (mTBI). Adult, male rats were individually housed in cages fitted with running wheels and daily running distance was recorded throughout the study. A modified weight drop method induced mTBI, and during 30 days post-injury, rats were fed diets supplemented with omega-3 fatty acids and vitamin D₃ (AIDM diet), or non-supplemented AIN-76A diets (CON diet). Behavioral tests were periodically conducted to assess functional deficits. Plasma levels of Total tau (T-tau), glial fibrillary acidic protein (GFAP), ubiquitin c-terminal hydrolase L1 (UCH-L1) and neurofilament light chain (NF-L) were measured at 48 h, 14 days, and 30 days post-injury. Fatty acid composition of food, plasma, and brain tissues was determined. In rats exposed to mTBI, NF-L levels were significantly elevated at 48 h post-injury (P < 0.005), and decreased to levels seen in uninjured rats by 14 days post-injury. T-tau, GFAP, and UCH-L1 plasma levels did not change at 48 h or 14 days post-injury. However, at 30 days post-injury, T-tau, GFAP and UCH-L1 all significantly increased in rats exposed to mTBI and fed CON diets (P < 0.005), but not in rats fed AIDM diets. Behavioral tests conducted post-injury showed that exercise counteracted cognitive deficits associated with mTBI. The AIDM diets significantly increased docosahexaenoic acid levels in plasma and brain tissue (P < 0.05), and in serum levels of vitamin D (P < 0.05). The temporal response of the four injury biomarkers examined is consistent with studies by others demonstrating acute and chronic neural tissue damage following exposure to TBI. The anti-inflammatory diet significantly altered the temporal profiles of plasma T-tau, GFAP, and UCH-L1 following mTBI. Voluntary exercise protected against mTBI-induced cognitive deficits, but had no impact on plasma levels of neurotrauma biomarkers. Thus, the prophylactic effect of exercise, when combined with an anti-inflammatory diet, may facilitate recovery in patients with mTBI.

Stroke-Induced Peripheral Immune Dysfunction in Vitamin D-Deficient Conditions: Modulation by Progesterone and Vitamin D

Vitamin D deficiency (Ddef) alters morphology and outcomes after a stroke. We investigated the interaction of Ddef following post-stroke systemic inflammation and evaluated whether administration of progesterone (P) or vitamin D (D) will improve outcomes. Ddef rats underwent stroke with lipopolysaccharide (LPS)-induced systemic inflammation. Rats were randomly divided into 9 groups and treated with P, D, or vehicle for 4 days. At day 4, rats were tested on different behavioral parameters. Markers of neuronal inflammation, endoplasmic reticulum stress, oxidative stress, white matter integrity, and apoptosis were measured along with immune cell populations from the spleen, thymus, and blood. Severely altered outcomes were observed in the Ddef group compared to the D-sufficient (Dsuf) group. Stroke caused peripheral immune dysfunction in the Dsuf group which was worse in the Ddef group. Systemic inflammation exacerbated injury outcomes in the Dsuf group and these were worse in the Ddef group. Monotherapy with P/D showed beneficial functional effects but the combined treatment showed better outcomes than either alone. Ddef as a comorbid condition with stroke worsens stroke outcomes and can delay functional recovery. Combination treatment with P and D might be promising for future stroke therapeutics in Ddef.

Vitamin D3 Supplement Attenuates Blood-Brain Barrier Disruption and Cognitive Impairments in a Rat Model of Traumatic Brain Injury

This study was designed to study the effects of vitamin D3 supplementation on the cognitive dysfunction and neurological function of traumatic brain injury (TBI) and the possible underlying mechanisms. To this purpose, different doses of vitamin D3 were intraperitoneally injection to TBI rats for one week before TBI surgery and three consecutive weeks after TBI. Brain edema evaluation was conducted on the third day and Evans blue staining for blood-brain barrier (BBB) permeability on the seventh day after TBI. Rat behavior was assessed by evaluation of neurological scores and morris water maze. It was revealed that vitamin D levels increased in serum after the administration of vitamin D3 for one week. TBI led to neurological deficit, together with brain edema, BBB disruption and inflammation. Vitamin D3 supplement ameliorated neurological deficit and cognitive impairments induced by TBI. Vitamin D3 administration reduced brain edema and impairments of blood-brain barrier induced by TBI, as well as decreased inflammatory response in TBI rat brain. Our results showed that vitamin D3 administration alleviated neurobehavioral deficits and improved brain edema after TBI. Vitamin D3 inhibited inflammatory cytokines and decreased BBB disruption in TBI rats. Vitamin D3 may be used for the treatment of TBI as a protective intervention.

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.

Cholecalciferol abolishes depressive-like behavior and hippocampal glucocorticoid receptor impairment induced by chronic corticosterone administration in mice

Several attempts have been made to understand the role of cholecalciferol (vitamin D₃) in the modulation of neuropsychiatric disorders. Notably, the deficiency of vitamin D₃ is considered a pandemic and has been postulated to enhance the risk of major depressive disorder (MDD). Therefore, this study aims to investigate the antidepressant-like effect of cholecalciferol in a mouse model of depression induced by corticosterone, and the possible role of glucocorticoid receptors (GR), NLRP3 and autophagic pathways in this effect. Corticosterone administration (20 mg/kg, p.o., for 21 days) significantly increased the immobility time and grooming latency, as well as reduced the total time spent grooming in mice subjected to the tail suspension test (TST) and splash test (ST), respectively. Importantly, these behavioral alterations were associated with reduced GR immunocontent in the hippocampus of mice. Conversely, the repeated administration of cholecalciferol (2.5 μg/kg, p.o.) in the last 7 days of corticosterone administration was effective to prevent the increased immobility time in the TST and the reduced time spent grooming in the ST, and partially abolished the increase in the grooming latency induced by corticosterone, suggesting its antidepressant-like effect. These behavioral effects were similar to those exerted by fluoxetine (10 mg/kg, p.o.). Moreover, the corticosterone-induced reduction on hippocampal GR immunocontent was not observed in mice treated with cholecalciferol. Additionally, cholecalciferol treatment per se reduced the immunocontent of NLRP3 inflammasome-related proteins ASC, caspase-1, and TXNIP in the hippocampus of mice. No alterations on hippocampal immunocontent of the autophagic-related proteins phospho-mTORC1, beclin-1, and LC3A/B were observed following cholecalciferol treatment and/or corticosterone administration. Collectively, our results provide insights into the effects of cholecalciferol in depression-related behaviors that seem to be related, at least in part, to GR modulation.

Neuroprotective effect of paricalcitol in a rat model of transient global cerebral ischemia

Background

Paricalcitol is known to attenuate ischemic-reperfusion injury of various organs. However, it is not known whether paricalcitol prevents neuronal injury after global cerebral ischemia. The purpose of this study is to investigate the neuroprotective effect of paricalcitol in a rat model of transient global cerebral ischemia.

Methods

This is a prospective, randomized experimental study. Male Sprague-Dawley rats that survived 10 min of four-vessel occlusion were randomly assigned to two treatment groups: one group was treated with paricalcitol 1 μg/kg IP, and the other was given an equivalent volume of normal saline IP. Drugs were administered at 5 min, 1 day, 2 days, and 3 days after ischemia. Neurologic function was assessed at 2 h, 1 day, 2 days, 3 days, and 4 days after ischemia. We tested motor function 3 days after ischemia using the rotarod test. Also, we tested memory function 4 days after ischemia using the passive avoidance test. We assessed neuronal degeneration in the hippocampus of surviving rats 4 days after ischemia.

Results

Eight rats were allocated to each group. No significant differences were found between the groups in terms of survival rate, motor coordination, or memory function. The neurological function score 2-h post-ischemia was significantly higher in the paricalcitol group (p = 0.04). Neuronal degeneration was significantly less in the paricalcitol group compared with the control group (p = 0.01).

Conclusions

Paricalcitol significantly attenuated neuronal injury in the hippocampus. Although motor coordination, memory function, and survival rate were not significantly improved by paricalcitol treatment in this study, paricalcitol remains a potential neuroprotective drug after global cerebral ischemia.

Neuroprotective Role of Oral Vitamin D Supplementation on Consciousness and Inflammatory Biomarkers in Determining Severity Outcome in Acute Traumatic Brain Injury Patients: A Double-Blind Randomized Clinical Trial

BACKGROUND AND OBJECTIVE

Early management of traumatic brain injury (TBI) is essential. We aimed to evaluate the efficacy of vitamin D over early clinical outcome and serum cytokine levels in patients with moderate to severe brain injury.

METHODS

Thirty-five patients with moderate to severe traumatic brain injury who were admitted to the ICU unit were recruited into the study. Subjects were randomly allocated to a treatment regimen comprising either a one-time oral dose of 120,000 IU (two tablets of 60,000 IU each) of vitamin D (n = 20) or 8 mg of saccharide (two tablets of 4 g each) as placebo (n = 15). The main parameters evaluated included duration of mechanical ventilation and ICU stay, Glasgow Coma Scale (GCS) and cytokine levels (interleukin (IL)-6, tumour necrosis factor (TNF)-α, interferon (IFN)-γ, IL-2).

RESULTS

The results indicated an improvement in the level of consciousness after 7 days in the vitamin D-treated group compared with placebo. An elevation in GCS score by 3.86 units in the vitamin D-treated group with a 0.19-unit descent in the control group was recorded. Duration of mechanical ventilation was reduced in the vitamin D-treated group compared with the control group (4.7 days vs. 8.2 days, p value 0.0001). A noticeable reduction was recorded in inflammatory biomarkers (cytokines) in the vitamin D-treated group (IL-6 p = 0.08, TNF-α p = 0.02, IL-2 p = 0.36) with notable elevation in IFN-γ (p = 0.65) compared to the control group.

CONCLUSION

In the acute phase of moderate to severe traumatic brain injury, vitamin D supplementation plays a vital role and has a favourable effect on the consciousness level of patients. Clinical trial Registry (CTRI) No. CTRI/2019/05/019259.

Effects of vitamin D on drugs: Response and disposal

Vitamin D supplementation and vitamin D deficiency are common in clinical experience and in daily life. Vitamin D not only promotes calcium absorption and immune regulation, but also changes drug effects (pharmacodynamics and adverse reactions) and drug disposal in vivo when combined with various commonly used clinical drugs. The extensive physiological effects of vitamin D may cause synergism effects or alleviation of adverse reactions, and vitamin D's affect on drugs in vivo disposal through drug transporters or metabolic enzymes may also lead to changes in drug effects. Herein, the effects of vitamin D combined with commonly used drugs were reviewed from the perspective of drug efficacy and adverse reactions. The effects of vitamin D on drug transport and metabolism were summarized and analyzed. Hopefully, more attention will be paid to vitamin D supplementation and deficiency in clinical treatment and drug research and development.

Calcitriol alleviates global cerebral ischemia-induced cognitive impairment by reducing apoptosis regulated by VDR/ERK signaling pathway in rat hippocampus

BACKGROUND

Vitamin D (VD) has important neuroprotective functions in the central nervous system. However, further exploration is still needed in the neuroprotective effects of VD monomer therapy on global cerebral ischemia (GCI) and its potential molecular mechanism.

OBJECTIVE

To investigate whether calcitriol, a biologically active metabolite of VD, could alleviate cognitive impairment induced by GCI via reducing cell apoptosis and activating the extracellular signal-regulated kinase (ERK) signaling pathway.

METHODS

A total of 145 adult male Sprague Dawley rats were randomly divided into five groups: Sham group (n = 45), GCI group (n = 45), calcitriol treatment group (GCI + calcitriol, n = 45), PD98059 treatment group (n = 5) and vehicle group (n = 5). Morris water maze test was used for evaluating spatial learning and memory functions. Neurological Severity Score and wet-dry weight method were applied to detect neurological deficits and brain water content, respectively. Hematoxylin and eosin staining, transmission electron microscopy, and terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick end-labeling staining were performed for evaluating the changes of hippocampal CA1 neurons. Immunocytochemistry, immunofluorescence chemistry, and western blot analysis were performed for evaluating the changes of related proteins.

RESULTS

Calcitriol significantly ameliorated the spatial learning and memory impairments, improved neurological function, attenuated brain edema, and improved the morphological defects in the CA1 area of the hippocampus. Besides, calcitriol reduced GCI-induced cell apoptosis and reversed the up-regulation of pro-apoptotic proteins (Caspase-3 and Bax) and the down-regulation of anti-apoptotic protein (Bcl-2). Furthermore, calcitriol also increased the expression of VD receptors (VDR) and activated the ERK signaling pathway. Moreover, the p-ERK1/2 inhibitor PD98059 reversed the effect of calcitriol on the expression of apoptosis-related proteins.

CONCLUSIONS

Calcitriol may have a protective effect against GCI-induced cognitive impairments via inhibition of apoptotic cascade by activating the VDR/ERK signaling pathway.

Immunomodulatory effects of Calcitriol in acute spinal cord injury in rats

Pharmacological therapy options for spinal cord injury (SCI) in acute phase have so far been limited, thus we focused on Calcitriol, FDA-approved biologically active form of vitamin D whose neuroprotective effects are increasingly recognized, to ameliorating damage following acute SCI in rats. Calcitriol (1 μg/kg) treatment for 7 consecutive days after SCI was compared SCI control and Sham control rat groups. Calcitriol-treated group had significantly improved outcome in standard functional recovery evaluation test (BBB) 12 weeks after SCI compared to SCI control, which was confirmed by increased ventral horn motor neurons in Calcitriol-treated group. In addition, proliferation test performed on lymphocytes from spleen and lymph nodes one week after SCI showed that calcitriol injection has a significant regulatory effect on Division Index (DI) in response to MBP stimulation compared to control SCI groups, which was associated with significant reduction in IFN-γ and IL-17A secretion and leukocyte infiltration into injury site. Along with confirmation of immunoregulatory aspects of Calcitriol treatment against myelin antigens in SCI, this study has shown that reducing the extent of progressive tissue loss by Calcitriol therapy in acute phase, could result in better recovery after SCI.

Levels of 25-hydroxyvitamin D3, biochemical parameters and symptoms of depression and anxiety in healthy individuals

Growing evidence support the role of vitamin D in brain function and behavior. This study investigated the relationship between 25-hydroxyvitamin D₃ [25(OH)D₃] levels, biochemical profile and symptoms of depression and anxiety in healthy individuals. Symptoms of depression were assessed by the Beck Depression Inventory (BDI) and anxiety was evaluated with the State-Trait Anxiety Inventory (STAI). Our sample included 36 individuals, mostly women 27(75%), 36.39 ± 9.72 years old, non-smokers 31(86.1%), body mass index of 26.57 ± 3.92 kg/m², 27.95 ± 7.50% body fat. Participants were divided into those with 25(OH)D₃ levels lower than 40 ng/mL (mean 28.16 ± 7.07) and equal or higher than 40 ng/mL (mean 53.19 ± 6.32). Those with lower 25(OH)D₃ had higher levels of triacylglycerol, triacylglycerol/high density lipoprotein (HDL) ratio, high glucose and homeostatic model assessment of insulin resistance (HOMA-IR) index. No changes were observed in sociodemographic variables, body composition, inflammatory parameters and cortisol. Additionally, in the groups with low and high 25(OH)D₃ levels, STAI state, STAI trait and BDI scores were not statistically different. Levels of 25(OH)D₃ were inversely and independently associated with glucose and HOMA-IR, but not associated with triacylglycerol, depression and anxiety scores. Lower levels of 25(OH)D₃ were associated with dysfunction in glucose metabolism but not with depression and anxiety in healthy individuals.

Sex-related responses after traumatic brain injury: Considerations for preclinical modeling

Traumatic brain injury (TBI) has historically been viewed as a primarily male problem, since men are more likely to experience a TBI because of more frequent participation in activities that increase risk of head injuries. This male bias is also reflected in preclinical research where mostly male animals have been used in basic and translational science. However, with an aging population in which TBI incidence is increasingly sex-independent due to falls, and increasing female participation in high-risk activities, the attention to potential sex differences in TBI responses and outcomes will become more important. These considerations are especially relevant in designing preclinical animal models of TBI that are more predictive of human responses and outcomes. This review characterizes sex differences following TBI with a special emphasis on the contribution of the female sex hormones, progesterone and estrogen, to these differences. This information is potentially important in developing and customizing TBI treatments.

Repurposing and repositioning neurosteroids in the treatment of traumatic brain injury: A report from the trenches

The field of neuroprotection after brain injuries has been littered with failed clinical trials. Finding a safe and effective treatment for acute traumatic brain injury remains a serious unmet medical need. Repurposing drugs that have been in use for other disorders is receiving increasing attention as a strategy to move candidate drugs more quickly to trial while reducing the very high cost of new drug development. This paper describes our own serendipitous discovery of progesterone's neuroprotective potential, and the strategies we are using in repurposing and developing this hormone for use in brain injuries-applications very different from its classical uses in treating disorders of the reproductive system. We have been screening and testing a novel analog that maintains progesterone's therapeutic properties while overcoming its physiochemical challenges, and testing progesterone in combination treatment with another pleiotropic hormone, vitamin D. Finally, our paper, in the context of the problems and pitfalls we have encountered, surveys some of the factors we found to be critical in the clinical translation of repurposed drugs. This article is part of the Special Issue entitled 'Drug Repurposing: old molecules, new ways to fast track drug discovery and development for CNS disorders'.

Vitamin D Receptor Activation Influences NADPH Oxidase (NOX2) Activity and Protects against Neurological Deficits and Apoptosis in a Rat Model of Traumatic Brain Injury

Traumatic brain injury (TBI) is a worldwide phenomenon which results in significant neurological and cognitive deficits in humans. Vitamin D (VD) is implicated as a therapeutic strategy for various neurological diseases now. Recently, inhibition of the NADPH oxidase (NOX₂) was reported to protect against oxidative stress (ROS) production. However, whether alterations in NOX₂ expression and NOX activity are associated with calcitriol (active metabolite of VD) treatment following TBI remains unclear. In the present study, rats were randomly assigned to the sham, TBI, and calcitriol-treated groups. Calcitriol was administered intraperitoneally (2 μg/kg) at 30 min, 24 h, and 48 h after TBI insult. We observed that calcitriol treatment alleviated neurobehavioral deficits and brain edema following TBI. At the molecular levels, administration of calcitriol activated the expression of VDR and downregulated NOX₂ as well as suppressed apoptosis cell rate in the hippocampus CA1 region of TBI rats. In conclusion, our findings indicate that the protective effects of calcitriol may be related to the modulation of NADPH oxidase and thereby ultimately inhibited the progression of apoptosis. Calcitriol may be promising as a protective intervention following TBI, and more study is warranted for its clinical testing in the future.

Effects of Female Sex Steroids Administration on Pathophysiologic Mechanisms in Traumatic Brain Injury

Secondary brain damage following initial brain damage in traumatic brain injury (TBI) is a major cause of adverse outcomes. There are many gaps in TBI research and a lack of therapy to limit debilitating outcomes in TBI or enhance the neurogenesis, despite pre-clinical and clinical research performed in TBI. Females show harmful outcomes against brain damage including TBI less than males, independent of different TBI occurrence. A significant reduction in secondary brain damage and improvement in neurologic outcome post-TBI has been reported following the use of progesterone and estrogen in many experimental studies. Although useful features of sex steroids including progesterone have been identified in TBI clinical trials I and II, clinical trials III have been unsuccessful. This review article focuses on evidence of secondary injury mechanisms and neuroprotective effects of estrogen and progesterone in TBI. Understanding these mechanisms may enable researchers to achieve greater success in TBI clinical studies. It seems that the design of clinical studies should be revised due to translation loss of animal studies to clinical studies. The heterogeneous and complex nature of TBI, the endogenous levels of sex hormones at the time of taking these hormones, the therapeutic window of the drug, the dosage of the drug, the selection of appropriate targets in evaluation, the determination of responsive population, gender and age based on animal studies should be considered in the design of TBI human studies in future.

Prevalence and correlates of vitamin D deficiency in adults after traumatic brain injury

OBJECTIVES

Traumatic brain injury (TBI) is a major cause of long-term disability with variable recovery. Preclinical studies suggest that vitamin D status influences the recovery after TBI. However, there is no published clinical data on links between vitamin D status and TBI outcomes. The aim was to determine the (i) prevalence of vitamin D deficiency/insufficiency, and associations of vitamin D status with (ii) demographic factors and TBI severity, and with (iii) cognitive function, symptoms and quality of life, in adults after TBI.

DESIGN

Retrospective audit of patients seen between July 2009 and March 2015. Serum vitamin D (25-hydroxy-cholecalciferol) was categorized as deficient (<40 nmol/l), insufficient (40-70 nmol/l) or replete (>70 nmol/l).

PATIENTS

A total of 353 adults seen in tertiary hospital clinic (75·4% lighter skinned, 74·8% male, age median 35·1 year, range 26·6-48·3 year), 0·3-56·5 months after TBI (74·5% moderate-severe).

MEASUREMENTS

Serum vitamin D concentrations; Addenbrooke's Cognitive Examination (ACE-R), Beck Depression Inventory-II (BDI-II), SF-36 Quality of Life, Pittsburgh Sleep Quality Index.

RESULTS

In total, 46·5% of patients after TBI had vitamin D deficiency and 80·2% insufficiency/deficiency. Patients with vitamin D deficiency had lower ACE-R scores than those of vitamin D replete (mean effect size ± SEM 4·5 ± 2·1, P = 0·034), and higher BDI-II scores than those of vitamin D insufficient (4·5 ± 1·6, P = 0·003), correcting for age, gender, time since TBI and TBI severity. There was no association between vitamin D status and markers of TBI severity, sleep or quality of life.

CONCLUSION

Vitamin D deficiency is common in patients after TBI and associated with impaired cognitive function and more severe depressive symptoms.

Progesterone neuroprotection: The background of clinical trial failure

Since the first pioneering studies in the 1990s, a large number of experimental animal studies have demonstrated the neuroprotective efficacy of progesterone for brain disorders, including traumatic brain injury (TBI). In addition, this steroid has major assets: it easily crosses the blood-brain-barrier, rapidly diffuses throughout the brain and exerts multiple beneficial effects by acting on many molecular and cellular targets. Moreover, progesterone therapies are well tolerated. Notably, increased brain levels of progesterone are part of endogenous neuroprotective responses to injury. The hormone thus emerged as a particularly promising protective candidate for TBI and stroke patients. The positive outcomes of small Phase 2 trials aimed at testing the safety and potential protective efficacy of progesterone in TBI patients then provided support and guidance for two large, multicenter, randomized and placebo-controlled Phase 3 trials, with more than 2000 TBI patients enrolled. The negative outcomes of both trials, named ProTECT III and SyNAPSE, came as a big disappointment. If these trials were successful, progesterone would have become the first efficient neuroprotective drug for brain-injured patients. Thus, progesterone has joined the numerous neuroprotective candidates that have failed in clinical trials. The aim of this review is a reappraisal of the preclinical animal studies, which provided the proof of concept for the clinical trials, and we critically examine the design of the clinical studies. We made efforts to present a balanced view of the strengths and limitations of the translational studies and of some serious issues with the clinical trials. We place particular emphasis on the translational value of animal studies and the relevance of TBI biomarkers. The probability of failure of ProTECT III and SyNAPSE was very high, and we present them within the broader context of other unsuccessful trials.

Vitamins and nutrients as primary treatments in experimental brain injury: Clinical implications for nutraceutical therapies

With the numerous failures of pharmaceuticals to treat traumatic brain injury in humans, more researchers have become interested in combination therapies. This is largely due to the multimodal nature of damage from injury, which causes excitotoxicity, oxidative stress, edema, neuroinflammation and cell death. Polydrug treatments have the potential to target multiple aspects of the secondary injury cascade, while many previous therapies focused on one particular aspect. Of specific note are vitamins, minerals and nutrients that can be utilized to supplement other therapies. Many of these have low toxicity, are already FDA approved and have minimal interactions with other drugs, making them attractive targets for therapeutics. Over the past 20 years, interest in supplementation and supraphysiologic dosing of nutrients for brain injury has increased and indeed many vitamins and nutrients now have a considerable body of the literature backing their use. Here, we review several of the prominent therapies in the category of nutraceutical treatment for brain injury in experimental models, including vitamins (B2, B3, B6, B9, C, D, E), herbs and traditional medicines (ginseng, Gingko biloba), flavonoids, and other nutrients (magnesium, zinc, carnitine, omega-3 fatty acids). While there is still much work to be done, several of these have strong potential for clinical therapies, particularly with regard to polydrug regimens. This article is part of a Special Issue entitled SI:Brain injury and recovery.

Cholecalciferol (vitamin D₃) improves functional recovery when delivered during the acute phase after a spinal cord trauma

In a previous study, based on a rat model of thoracic spinal cord compression, we demonstrated that cholecalciferol (Vitamin D3), delivered at the dose of 200 IU/kg/day, significantly improved ventilatory frequency and spasticity. In order to confirm the restorative potential of vitamin D, we performed a new study, using a rat model of left cervical hemisection (C2). From Day 1 or Day 7, animals received, during three months, a weekly oral bolus of either cholecalciferol, at the dose of 500 IU/kg/day, or vehicle, namely triglycerides. Rats were assessed every month, using a ladder test for sensori-locomotor ability and neuromuscular capacity. Three months after injury, H-reflex was recorded from left extensor digitorum muscle in order to measure the reflexivity of the sub-lesional region. Ventilatory frequency was also monitored during an electrically induced muscle fatigue of the hindlimb known to enhance muscle metaboreflex and increase respiratory rate. After recording the phrenic nerve activity, ipsilateral to the lesion, during spontaneous breathing, animals were artificially ventilated while paralyzed with a neuromuscular blocking agent and then the brainstem respiratory centres were provoked to maximal output by temporarily stopping the ventilator. Spinal cords were immunostained with an anti-neurofilament antibody to evaluate axon numbers. We show here that vitamin D-treated animals display i) an enhanced locomotor activity, ii) an improved breathing when hindlimb muscle was electrically stimulated to induce fatigue, iii) an H-reflex depression similar to control animals, iv) a phrenic nerve activity response to a temporary asphyxial stress and v) a non significant decreased number of axons in the proximal stump when compared with the Sham group. This new set of data confirms that vitamin D is a potent molecule that could be tested in clinical trials assessing functional recovery in para-/tetra-plegic patients, shortly after a trauma.

Combination Therapies for Traumatic Brain Injury: Retrospective Considerations

Patients enrolled in clinical trials for traumatic brain injury (TBI) may present with heterogeneous features over a range of injury severity, such as diffuse axonal injury, ischemia, edema, hemorrhage, oxidative damage, mitochondrial and metabolic dysfunction, excitotoxicity, inflammation, and other pathophysiological processes. To determine whether combination therapies might be more effective than monotherapy at attenuating moderate TBI or promoting recovery, the National Institutes of Health funded six preclinical studies in adult and immature male rats to evaluate promising acute treatments alone and in combination. Each of the studies had a solid rationale for its approach based on previous research, but only one reported significant improvements in long-term outcomes across a battery of behavioral tests. Four studies had equivocal results because of a lack of sensitivity of the outcome assessments. One study demonstrated worse results with the combination in comparison with monotherapies. While specific research findings are reported elsewhere, this article provides an overview of the study designs, insights, and recommendations for future research aimed at therapy development for TBI.

Progesterone and vitamin D combination therapy modulates inflammatory response after traumatic brain injury

OBJECTIVE

Inflammation is an important component of the response to traumatic brain injury (TBI). Progesterone has been shown to inhibit neuroinflammation following (TBI) and may do so through Toll-like receptor (TLR)-mediated pathways. In vitro studies indicate that 1,25-dihydroxyvitamin D(3) (VDH) may also modulate the inflammatory response through the TLR4 pathway. This study tested the hypothesis that PROG and VDH would exert additive and synergistic neuroprotective effects compared with individual treatment by modulating TLR4/NF-κB-mediated inflammation pathways after TBI in rats.

RESEARCH DESIGN AND METHODS

Bilateral medial frontal cortical impact injury was induced in young adult Sprague-Dawley rats. Progesterone (i.p., 16 mg kg^-1 body weight) and VDH (1 µg kg^-1 body weight) were injected separately or combined at 1 and 6 hours after surgery. Rats were killed 24 hours post-surgery and peri-contusional brain tissue harvested for immunostaining and protein measurement.

RESULTS

TLR4, phosphorylation of NF-κB, neuronal loss and astrocyte activation were significantly reduced with combination treatment after TBI compared to each agent given individually.

CONCLUSIONS

At 24 hours after TBI, combination therapy shows greater efficacy in reducing neuroinflammation compared to progesterone and VDH given separately, and does so by modulating the TLR4/NF-κB signalling pathway.

Vitamin D as a neurosteroid affecting the developing and adult brain

Vitamin D deficiency is prevalent throughout the world, and growing evidence supports a requirement for optimal vitamin D levels for the healthy developing and adult brain. Vitamin D has important roles in proliferation and differentiation, calcium signaling within the brain, and neurotrophic and neuroprotective actions; it may also alter neurotransmission and synaptic plasticity. Recent experimental studies highlight the impact that vitamin D deficiency has on brain function in health and disease. In addition, results from recent animal studies suggest that vitamin D deficiency during adulthood may exacerbate underlying brain disorders and/or worsen recovery from brain stressors. An increasing number of epidemiological studies indicate that vitamin D deficiency is associated with a wide range of neuropsychiatric disorders and neurodegenerative diseases. Vitamin D supplementation is readily available and affordable, and this review highlights the need for further research.

Progesterone for neuroprotection in pediatric traumatic brain injury

OBJECTIVE

To provide an overview of the preclinical literature on progesterone for neuroprotection after traumatic brain injury and to describe unique features of developmental brain injury that should be considered when evaluating the therapeutic potential for progesterone treatment after pediatric traumatic brain injury.

DATA SOURCES

National Library of Medicine PubMed literature review.

STUDY SELECTION

The mechanisms of neuroprotection by progesterone are reviewed, and the preclinical literature using progesterone treatment in adult animal models of traumatic brain injury is summarized. Unique features of the developing brain that could either enhance or limit the efficacy of neuroprotection by progesterone are discussed, and the limited preclinical literature using progesterone after acute injury to the developing brain is described. Finally, the current status of clinical trials of progesterone for adult traumatic brain injury is reviewed.

DATA EXTRACTION AND DATA SYNTHESIS

Progesterone is a pleiotropic agent with beneficial effects on secondary injury cascades that occur after traumatic brain injury, including cerebral edema, neuroinflammation, oxidative stress, and excitotoxicity. More than 40 studies have used progesterone for treatment after traumatic brain injury in adult animal models, with results summarized in tabular form. However, very few studies have evaluated progesterone in pediatric animal models of brain injury. To date, two human phase II trials of progesterone for adult traumatic brain injury have been published, and two multicenter phase III trials are underway.

CONCLUSIONS

The unique features of the developing brain from that of a mature adult brain make it necessary to independently study progesterone in clinically relevant, immature animal models of traumatic brain injury. Additional preclinical studies could lead to the development of a novel neuroprotective therapy that could reduce the long-term disability in head-injured children and could potentially provide benefit in other forms of pediatric brain injury (global ischemia, stroke, and statue epilepticus).

Pharmacotherapy of traumatic brain injury: state of the science and the road forward: report of the Department of Defense Neurotrauma Pharmacology Workgroup

Despite substantial investments by government, philanthropic, and commercial sources over the past several decades, traumatic brain injury (TBI) remains an unmet medical need and a major source of disability and mortality in both developed and developing societies. The U.S. Department of Defense neurotrauma research portfolio contains more than 500 research projects funded at more than $700 million and is aimed at developing interventions that mitigate the effects of trauma to the nervous system and lead to improved quality of life outcomes. A key area of this portfolio focuses on the need for effective pharmacological approaches for treating patients with TBI and its associated symptoms. The Neurotrauma Pharmacology Workgroup was established by the U.S. Army Medical Research and Materiel Command (USAMRMC) with the overarching goal of providing a strategic research plan for developing pharmacological treatments that improve clinical outcomes after TBI. To inform this plan, the Workgroup (a) assessed the current state of the science and ongoing research and (b) identified research gaps to inform future development of research priorities for the neurotrauma research portfolio. The Workgroup identified the six most critical research priority areas in the field of pharmacological treatment for persons with TBI. The priority areas represent parallel efforts needed to advance clinical care; each requires independent effort and sufficient investment. These priority areas will help the USAMRMC and other funding agencies strategically guide their research portfolios to ensure the development of effective pharmacological approaches for treating patients with TBI.

Long-term effects of ageing and ovariectomy on aversive and recognition memory and DNA damage in the hippocampus of female rats

OBJECTIVE

This study investigated the influence of ageing - in particular the decrease of gonadal hormone levels during the ageing process - on the memory and the levels of DNA damage in the hippocampus of female rats.

METHODS

Three groups of female Wistar rats were investigated: Group I consisted of non-ovariectomised, adult animals (6 months old); Group II consisted of non-ovariectomised, aged animals (18 months old); and Group III consisted of ovariectomised, aged animals (18 months old). The memory of the animals in these groups was examined via novel object recognition and inhibitory avoidance tests. The hippocampus tissue samples of all animals were obtained via biopsy and used to quantify the DNA damage using a Comet Assay.

RESULTS

According to our findings, the process of ageing results in a change during the behavioural tests. To prevent genotoxic damage to the hippocampus caused by the ageing process, lowered hormone levels seem to be part of a protective biochemical mechanism in the body of rats. Animals that were previously submitted to an ovariectomy adapted better to these lower levels of hormones.

CONCLUSION

Our results indicate that ovariectomy can provide beneficial long-term effects on the memory. However, this could be specific to the kind of memory examined, as the aversive memory deficits caused by ageing were not affected by ovariectomy.

Progesterone in experimental permanent stroke: a dose-response and therapeutic time-window study

Currently, the only approved treatment for ischaemic stroke is tissue plasminogen activator, a clot-buster. This treatment can have dangerous consequences if not given within the first 4 h after stroke. Our group and others have shown progesterone to be beneficial in preclinical studies of stroke, but a progesterone dose-response and time-window study is lacking. We tested male Sprague-Dawley rats (12 months old) with permanent middle cerebral artery occlusion or sham operations on multiple measures of sensory, motor and cognitive performance. For the dose-response study, animals received intraperitoneal injections of progesterone (8, 16 or 32 mg/kg) at 1 h post-occlusion, and subcutaneous injections at 6 h and then once every 24 h for 7 days. For the time-window study, the optimal dose of progesterone was given starting at 3, 6 or 24 h post-stroke. Behavioural recovery was evaluated at repeated intervals. Rats were killed at 22 days post-stroke and brains extracted for evaluation of infarct volume. Both 8 and 16 mg/kg doses of progesterone produced attenuation of infarct volume compared with the placebo, and improved functional outcomes up to 3 weeks after stroke on locomotor activity, grip strength, sensory neglect, gait impairment, motor coordination and spatial navigation tests. In the time-window study, the progesterone group exhibited substantial neuroprotection as late as 6 h after stroke onset. Compared with placebo, progesterone showed a significant reduction in infarct size with 3- and 6-h delays. Moderate doses (8 and 16 mg/kg) of progesterone reduced infarct size and improved functional deficits in our clinically relevant model of stroke. The 8 mg/kg dose was optimal in improving motor, sensory and memory function, and this effect was observed over a large therapeutic time window. Progesterone shows promise as a potential therapeutic agent and should be examined for safety and efficacy in a clinical trial for ischaemic stroke.

Progesterone and vitamin D: Improvement after traumatic brain injury in middle-aged rats

Progesterone (PROG) and vitamin D hormone (VDH) have both shown promise in treating traumatic brain injury (TBI). Both modulate apoptosis, inflammation, oxidative stress, and excitotoxicity. We investigated whether 21 days of VDH deficiency would alter cognitive behavior after TBI and whether combined PROG and VDH would improve behavioral and morphological outcomes more than either hormone alone in VDH-deficient middle-aged rats given bilateral contusions of the medial frontal cortex. PROG (16 mg/kg) and VDH (5 μg/kg) were injected intraperitoneally 1 h post-injury. Eight additional doses of PROG were injected subcutaneously over 7 days post-injury. VDH deficiency itself did not significantly reduce baseline behavioral functions or aggravate impaired cognitive outcomes. Combination therapy showed moderate improvement in preserving spatial and reference memory but was not significantly better than PROG monotherapy. However, combination therapy significantly reduced neuronal loss and the proliferation of reactive astrocytes, and showed better efficacy compared to VDH or PROG alone in preventing MAP-2 degradation. VDH+PROG combination therapy may attenuate some of the potential long-term, subtle, pathophysiological consequences of brain injury in older subjects.

Progesterone's role in neuroprotection, a review of the evidence

The sex hormone progesterone has been shown to improve outcomes in animal models of a number of neurologic diseases, including traumatic brain injury, ischemia, spinal cord injury, peripheral nerve injury, demyelinating disease, neuromuscular disorders, and seizures. Evidence suggests it exerts its neuroprotective effects through several pathways, including reducing edema, improving neuronal survival, and modulating inflammation and apoptosis. In this review, we summarize the functional outcomes and pathophysiologic mechanisms attributed to progesterone treatment in neurologic disease. We then comment on the breadth of evidence for the use of progesterone in each neurologic disease family. Finally, we provide support for further human studies using progesterone to treat several neurologic diseases.

The transcriptomic response of mixed neuron-glial cell cultures to 1,25-dihydroxyvitamin d3 includes genes limiting the progression of neurodegenerative diseases

Seasonal or chronic vitamin D deficiency and/or insufficiency is highly prevalent in the human population. Receptors for 1,25-dihydroxyvitamin D3, the hormonal metabolite of vitamin D, are found throughout the brain. To provide further information on the role of this hormone on brain function, we analyzed the transcriptomic profiles of mixed neuron-glial cell cultures in response to 1,25-dihydroxyvitamin D3. 1,25-dihydroxyvitamin D3 treatment increases the mRNA levels of 27 genes by at least 1.9 fold. Among them, 17 genes were related to neurodegenerative and psychiatric diseases, or brain morphogenesis. Notably, 10 of these genes encode proteins potentially limiting the progression of Alzheimer's disease. These data provide support for a role of 1,25-dihydroxyvitamin D3 in brain disease prevention. The possible consequences of circannual or chronic vitamin D insufficiencies on a tissue with a low regenerative potential such as the brain should be considered.