RORγt-Expressing Pathogenic CD4+ T Cells Cause Brain Inflammation during Chronic Colitis.

Neurobehavioral disorders and brain abnormalities have been extensively reported in both Crohn's disease and ulcerative colitis patients. However, the mechanism causing neuropathological disorders in inflammatory bowel disease patients remains unknown. Studies have linked the Th17 subset of CD4+ T cells to brain diseases associated with neuroinflammation and cognitive impairment, including multiple sclerosis, ischemic brain injury, and Alzheimer's disease. To better understand how CD4+ T lymphocytes contribute to brain pathology in chronic intestinal inflammation, we investigated the development of brain inflammation in the T cell transfer model of chronic colitis. Our findings demonstrate that CD4+ T cells infiltrate the brain of colitic Rag1 -/- mice in proportional levels to colitis severity. Colitic mice developed hypothalamic astrogliosis that correlated with neurobehavioral disorders. Moreover, the brain-infiltrating CD4+ T cells expressed Th17 cell transcription factor retinoic acid-related orphan receptor γt (RORγt) and displayed a pathogenic Th17 cellular phenotype similar to colonic Th17 cells. Adoptive transfer of RORγt-deficient naive CD4+ T cells failed to cause brain inflammation and neurobehavioral disorders in Rag1 -/- recipients, with significantly less brain infiltration of CD4+ T cells. The finding is mirrored in chronic dextran sulfate sodium-induced colitis in Rorcfl/fl Cd4-Cre mice that showed lower frequency of brain-infiltrating CD4+ T cells and astrogliosis despite onset of significantly more severe colitis compared with wild-type mice. These findings suggest that pathogenic RORγt+CD4+ T cells that aggravate colitis migrate preferentially into the brain, contributing to brain inflammation and neurobehavioral disorders, thereby linking colitis severity to neuroinflammation.

Integrated regulation of PKA by fast and slow neurotransmission in the nucleus accumbens controls plasticity and stress responses.

Cortical glutamate and midbrain dopamine neurotransmission converge to mediate striatum-dependent behaviors, while maladaptations in striatal circuitry contribute to mental disorders. However, the crosstalk between glutamate and dopamine signaling has not been entirely elucidated. Here we uncover a molecular mechanism by which glutamatergic and dopaminergic signaling integrate to regulate cAMP-dependent protein kinase (PKA) via phosphorylation of the PKA regulatory subunit, RIIß. Using a combination of biochemical, pharmacological, neurophysiological, and behavioral approaches, we find that glutamate-dependent reduction in cyclin-dependent kinase 5 (Cdk5)-dependent RIIß phosphorylation alters the PKA holoenzyme autoinhibitory state to increase PKA signaling in response to dopamine. Furthermore, we show that disruption of RIIß phosphorylation by Cdk5 enhances cortico-ventral striatal synaptic plasticity. In addition, we demonstrate that acute and chronic stress in rats inversely modulate RIIß phosphorylation and ventral striatal infusion of a small interfering peptide that selectively targets RIIß regulation by Cdk5 improves behavioral response to stress. We propose this new signaling mechanism integrating ventral striatal glutamate and dopamine neurotransmission is important to brain function, may contribute to neuropsychiatric conditions, and serves as a possible target for the development of novel therapeutics for stress-related disorders.

Inhibition of STAT-mediated cytokine responses to chemically-induced colitis prevents inflammation-associated neurobehavioral impairments.

Depression can be associated with chronic systemic inflammation, and production of peripheral proinflammatory cytokines and upregulation of the kynurenine pathway have been implicated in pathogenesis of depression. However, the mechanistic bases for these comorbidities are not yet well understood. As tryptophan 2,3-dioxygenase (TDO) and indoleamine 2,3-dioxygenase (IDO), which convert tryptophan to kynurenine, are rate-limiting enzymes of the kynurenine pathway, we screened TDO or IDO inhibitors for effects on the production of proinflammatory cytokines in a mouse macrophage cell line. The TDO inhibitor 680C91 attenuated LPS-induced pro-inflammatory cytokines including IL-1ß and IL-6. Surprisingly, this effect was TDO-independent, as it occurred even in peritoneal macrophages from TDO knockout mice. Instead, the anti-inflammatory effects of 680C91 were mediated through the suppression of signal transducer and activator of transcription(STAT) signaling. Furthermore, 680C91 suppressed production of proinflammatory cytokines and STAT signaling in an animal model of inflammatory bowel disease. Specifically, 680C91 effectively attenuated acute phase colon cytokine responses in male mice subjected to dextran sulfate sodium (DSS)-induced colitis. Interestingly, this treatment also prevented the development of anxiodepressive-like neurobehaviors in DSS-treated mice during the recovery phase. The ability of 680C91 to prevent anxiodepressive-like behavior in response to chemically-induced colitis appeared to be due to rescue of attenuated dopamine responses in the nucleus accumbens. Thus, inhibition of STAT-mediated, but TDO-independent proinflammatory cytokines in macrophages can prevent inflammation-associated anxiety and depression. Identification of molecular mechanisms involved may facilitate the development of new treatments for gastrointestinal-neuropsychiatric comorbidity.

Extracellular superoxide dismutase is important for hippocampal neurogenesis and preservation of cognitive functions after irradiation.

Cranial irradiation is widely used in cancer therapy, but it often causes cognitive defects in cancer survivors. Oxidative stress is considered a major cause of tissue injury from irradiation. However, in an earlier study mice deficient in the antioxidant enzyme extracellular superoxide dismutase (EC-SOD KO) showed reduced sensitivity to radiation-induced defects in hippocampal functions. To further dissect the role of EC-SOD in neurogenesis and in response to irradiation, we generated a bigenic EC-SOD mouse model (OE mice) that expressed high levels of EC-SOD in mature neurons in an otherwise EC-SOD-deficient environment. EC-SOD deficiency was associated with reduced progenitor cell proliferation in the subgranular zone of dentate gyrus in KO and OE mice. However, high levels of EC-SOD in the granule cell layer supported normal maturation of newborn neurons in OE mice. Following irradiation, wild-type mice showed reduced hippocampal neurogenesis, reduced dendritic spine densities, and defects in cognitive functions. OE and KO mice, on the other hand, were largely unaffected, and the mice performed normally in neurocognitive tests. Although the resulting hippocampal-related functions were similar in OE and KO mice following cranial irradiation, molecular analyses suggested that they may be governed by different mechanisms: whereas neurotrophic factors may influence radiation responses in OE mice, dendritic maintenance may be important in the KO environment. Taken together, our data suggest that EC-SOD plays an important role in all stages of hippocampal neurogenesis and its associated cognitive functions, and that high-level EC-SOD may provide protection against irradiation-related defects in hippocampal functions.

Possible role of nitric oxide (NO) in the regulation of gender related differences in stress induced anxiogenesis in rats.

Gender related differences in stress induced neurobehavioral disorders have been reported although the mechanisms involved are not yet clear. The present study investigated the role of nitric oxide, an important biomodulator in the sex related differences in stress induced anxiety like behavior in rats. Restraint stress (RS for 1 h) was used as the experimental stressor and the effects of NO modulators were assessed in the elevated plus maze (EPM) test in both male and female rats. No metabolites (NOx) and asymmetric dimethyl arginine (ADMA) were measured in brain homogenates of these rats for corroborative purposes. RS induced anxiogenesis in both male and female rats and such changes were greater in males as compared to females. The behavioral alterations were associated with enhanced levels of ADMA and reductions in levels of NOx in brain homogenates - the effects being greater in intensity in males as compared to females. Pretreatment with NO precursor L-arginine (500 mg/kg) reversed the RS induced behavioral and biochemical changes, while NO synthase inhibitor L-NAME (50 mg/kg) had opposite effects. Additionally, Formestane (50 mg/kg), an estrogen synthesis blocker, aggravated stress induced anxiogenesis with a corresponding increase in ADMA and decrease in NOx levels in the females. To our knowledge, this is the first report indicating the involvement of ADMA, an endogenous nitric oxide synthase inhibitor in stress induced neurobehavioral changes. Furthermore, it is also evident that nitric oxide and its interactions with estrogens play a crucial modulatory role in the differential anxiogenic response to stress among males and females.

Cdk5 mediates rotational force-induced brain injury.

Millions of traumatic brain injuries (TBIs) occur annually. TBIs commonly result from falls, traffic accidents, and sports-related injuries, all of which involve rotational acceleration/deceleration of the brain. During these injuries, the brain endures a multitude of primary insults including compression of brain tissue, damaged vasculature, and diffuse axonal injury. All of these deleterious effects can contribute to secondary brain ischemia, cellular death, and neuroinflammation that progress for weeks, months, and lifetime after injury. While the linear effects of head trauma have been extensively modeled, less is known about how rotational injuries mediate neuronal damage following injury. Here, we developed a new model of repetitive rotational head trauma in rodents and demonstrated acute and prolonged pathological, behavioral, and electrophysiological effects of rotational TBI (rTBI). We identify aberrant Cyclin-dependent kinase 5 (Cdk5) activity as a principal mediator of rTBI. We utilized Cdk5-enriched phosphoproteomics to uncover potential downstream mediators of rTBI and show pharmacological inhibition of Cdk5 reduces the cognitive and pathological consequences of injury. These studies contribute meaningfully to our understanding of the mechanisms of rTBI and how they may be effectively treated.

Systemic Administration of a Brain Permeable Cdk5 Inhibitor Alters Neurobehavior.

Cyclin-dependent kinase 5 (Cdk5) is a crucial regulator of neuronal signal transduction. Cdk5 activity is implicated in various neuropsychiatric and neurodegenerative conditions such as stress, anxiety, depression, addiction, Alzheimer's disease, and Parkinson's disease. While constitutive Cdk5 knockout is perinatally lethal, conditional knockout mice display resilience to stress-induction, enhanced cognition, neuroprotection from stroke and head trauma, and ameliorated neurodegeneration. Thus, Cdk5 represents a prime target for treatment in a spectrum of neurological and neuropsychiatric conditions. While intracranial infusions or treatment of acutely dissected brain tissue with compounds that inhibit Cdk5 have allowed the study of kinase function and corroborated conditional knockout findings, potent brain-penetrant systemically deliverable Cdk5 inhibitors are extremely limited, and no Cdk5 inhibitor has been approved to treat any neuropsychiatric or degenerative diseases to date. Here, we screened aminopyrazole-based analogs as potential Cdk5 inhibitors and identified a novel analog, 25-106, as a uniquely brain-penetrant anti-Cdk5 drug. We characterize the pharmacokinetic and dynamic responses of 25-106 in mice and functionally validate the effects of Cdk5 inhibition on open field and tail-suspension behaviors. Altogether, 25-106 represents a promising preclinical Cdk5 inhibitor that can be systemically administered with significant potential as a neurological/neuropsychiatric therapeutic.

A modified standard American diet induces physiological parameters associated with metabolic syndrome in C57BL/6J mice.

Investigations into the causative role that western dietary patterns have on obesity and disease pathogenesis have speculated that quality and quantity of dietary fats and/or carbohydrates have a predictive role in the development of these disorders. Standard reference diets such as the AIN-93 rodent diet have historically been used to promote animal health and reduce variation of results across experiments, rather than model modern human dietary habits or nutrition-related pathologies. In rodents high-fat diets (HFDs) became a classic tool to investigate diet-induced obesity (DIO). These murine diets often relied on a single fat source with the most DIO consistent HFDs containing levels of fat up to 45-60% (kcal), higher than the reported human intake of 33-35% (kcal). More recently, researchers are formulating experimental animal (pre-clinical) diets that reflect mean human macro- and micronutrient consumption levels described by the National Health and Nutrition Examination Survey (NHANES). These diets attempt to integrate relevant ingredient sources and levels of nutrients; however, they most often fail to include high-fructose corn syrup (HFCS) as a source of dietary carbohydrate. We have formulated a modified Standard American Diet (mSAD) that incorporates relevant levels and sources of nutrient classes, including dietary HFCS, to assess the basal physiologies associated with mSAD consumption. Mice proffered the mSAD for 15 weeks displayed a phenotype consistent with metabolic syndrome, exhibiting increased adiposity, fasting hyperglycemia with impaired glucose and insulin tolerance. Metabolic alterations were evidenced at the tissue level as crown-like structures (CLS) in adipose tissue and fatty acid deposition in the liver, and targeted 16S rRNA metagenomics revealed microbial compositional shifts between dietary groups. This study suggests diet quality significantly affects metabolic homeostasis, emphasizing the importance of developing relevant pre-clinical diets to investigate chronic diseases highly impacted by western dietary consumption patterns.

High Fructose Corn Syrup-Moderate Fat Diet Potentiates Anxio-Depressive Behavior and Alters Ventral Striatal Neuronal Signaling.

The neurobiological mechanisms that mediate psychiatric comorbidities associated with metabolic disorders such as obesity, metabolic syndrome and diabetes remain obscure. High fructose corn syrup (HFCS) is widely used in beverages and is often included in food products with moderate or high fat content that have been linked to many serious health issues including diabetes and obesity. However, the impact of such foods on the brain has not been fully characterized. Here, we evaluated the effects of long-term consumption of a HFCS-Moderate Fat diet (HFCS-MFD) on behavior, neuronal signal transduction, gut microbiota, and serum metabolomic profile in mice to better understand how its consumption and resulting obesity and metabolic alterations relate to behavioral dysfunction. Mice fed HFCS-MFD for 16 weeks displayed enhanced anxiogenesis, increased behavioral despair, and impaired social interactions. Furthermore, the HFCS-MFD induced gut microbiota dysbiosis and lowered serum levels of serotonin and its tryptophan-based precursors. Importantly, the HFCS-MFD altered neuronal signaling in the ventral striatum including reduced inhibitory phosphorylation of glycogen synthase kinase 3ß (GSK3ß), increased expression of ΔFosB, increased Cdk5-dependent phosphorylation of DARPP-32, and reduced PKA-dependent phosphorylation of the GluR1 subunit of the AMPA receptor. These findings suggest that HFCS-MFD-induced changes in the gut microbiota and neuroactive metabolites may contribute to maladaptive alterations in ventral striatal function that underlie neurobehavioral impairment. While future studies are essential to further evaluate the interplay between these factors in obesity and metabolic syndrome-associated behavioral comorbidities, these data underscore the important role of peripheral-CNS interactions in diet-induced behavioral and brain function. This study also highlights the clinical need to address neurobehavioral comorbidities associated with obesity and metabolic syndrome.

Differential role of nitric oxide (NO) in acute and chronic stress induced neurobehavioral modulation and oxidative injury in rats.

The present study evaluated the effects of acute and chronic restraint stress (RS 1 h or 6 h), and their modulation by nitrergic agents on neurobehavioral and oxidative stress markers in rats. Acute RS (1 h or 6 h) reduced open arm entries (OAE) and open arm time (OAT) in the elevated plus maze test - which were attenuated by the NO precursor, L-arginine but not influenced appreciably by the NO synthase inhibitor, L-NAME. These behavioral changes were associated with differential changes in brain NO metabolites (NOx) but consistently reduced GSH and raised MDA levels in comparison to the control group. Following RS 1 h x 10 the neurobehavioral suppression and changes in brain oxidative stress markers were less pronounced as compared to the acute RS (1 h) group indicating adaptation. L-arginine pretreatment facilitated this adaptation to chronic RS (1 h). Interestingly RS 6 h x 10, induced severe behavioral suppression and aggravation of MDA and NOx levels and L-NAME pretreatment tended to protect against these chronic RS induced aggravations. These results suggest that acute and chronic RS induces duration/intensity dependent neurobehavioral and oxidative injury which are under the differential regulatory control of NO.

Age related differences in stress-induced neurobehavioral responses in rats: modulation by antioxidants and nitrergic agents.

The effect of restraint stress (RS) on neurobehavioral and brain oxidative/nitrosative stress markers and their modulation by antioxidants and nitrergic agents were evaluated in young (2 months) and old (16 months) male Wistar rats. Exposure to RS, induced anxiogenesis when tested in the elevated plus maze (EPM) and open field (OF) tests and such changes were greater in the old as compared to the young rats. These behavioral alterations were associated with enhanced levels of malondialdehyde (MDA) and reductions in glutathione (GSH), catalase (CAT) and nitric oxide metabolites (NOx) levels in brain homogenates-the effects being greater in intensity in the old as compared to the young animals. Pretreatment with antioxidants, alpha-tocopherol (25 and 50mg/kg) and N-acetylcysteine (100 and 200mg/kg) consistently reversed the RS-induced behavioral and biochemical alterations in both young and old rats. Similar attenuations of RS-induced changes were seen after pretreatment with NO precursor L-arginine (500 and 1000mg/kg) while the NO synthase inhibitor N-nitro L-arginine methyl ester (L-NAME) (50 and 100mg/kg) tended to aggravate the effects of RS in both age groups of rats. The results suggest that susceptibility to stress-induced neurobehavioral alterations may increase with age and interactions of reactive oxygen species (ROS) and nitric oxide in the central nervous system may exert a regulatory influence in such age dependent responses to stress.

Protective effects of dietary ginger (Zingiber officinales Rosc.) on lindane-induced oxidative stress in rats.

The protective effect of dietary feeding of Zingiber officinales Rosc. (ginger) against lindane-induced oxidative stress was investigated in male albino rats. Oxidative stress was monitored by estimating the extent of lipid peroxidation, activities of the oxygen free radical (OFR) scavenging enzymes superoxide dismutase (SOD) and catalase (CAT) and the status of the glutathione redox cycle antioxidants. Lindane administration (30 mg/kg bw orally for 4 weeks) was associated with enhanced lipid peroxidation and compromised antioxidant defenses in rats fed a normal diet. Concomitant dietary feeding of ginger (1%w/w) significantly attenuated lindane-induced lipid peroxidation, accompanied by modulation of OFR scavenging enzymes as well as reduced glutathione (GSH) and the GSH dependent enzymes glutathione peroxidase (Gpx), glutathione reductase (GR) and glutathione-S-transferase (GST) in these rats. These findings suggest that a diet containing naturally occurring compounds is effective in exerting protective effects by modulating oxidative stress.

HMGB1: A Common Biomarker and Potential Target for TBI, Neuroinflammation, Epilepsy, and Cognitive Dysfunction.

High mobility group box protein 1 (HMGB1) is a ubiquitous nuclear protein released by glia and neurons upon inflammasome activation and activates receptor for advanced glycation end products (RAGE) and toll-like receptor (TLR) 4 on the target cells. HMGB1/TLR4 axis is a key initiator of neuroinflammation. In recent days, more attention has been paid to HMGB1 due to its contribution in traumatic brain injury (TBI), neuroinflammatory conditions, epileptogenesis, and cognitive impairments and has emerged as a novel target for those conditions. Nevertheless, HMGB1 has not been portrayed as a common prognostic biomarker for these HMGB1 mediated pathologies. The current review discusses the contribution of HMGB1/TLR4/RAGE signaling in several brain injury, neuroinflammation mediated disorders, epileptogenesis and cognitive dysfunctions and in the light of available evidence, argued the possibilities of HMGB1 as a common viable biomarker of the above mentioned neurological dysfunctions. Furthermore, the review also addresses the result of preclinical studies focused on HMGB1 targeted therapy by the HMGB1 antagonist in several ranges of HMGB1 mediated conditions and noted an encouraging result. These findings suggest HMGB1 as a potential candidate to be a common biomarker of TBI, neuroinflammation, epileptogenesis, and cognitive dysfunctions which can be used for early prediction and progression of those neurological diseases. Future study should explore toward the translational implication of HMGB1 which can open the windows of opportunities for the development of innovative therapeutics that could prevent several associated HMGB1 mediated pathologies discussed herein.

Estrogen actions on brain and behavior: recent insights and future challenges.

Recent advances in our knowledge of estrogen action in the brain suggest that this steroid is not solely an endocrine factor but plays important but hitherto largely unrecognized physiological and pathophysiological roles that are not directly involved in reproductive processes. Estrogens are now known to influence a wide variety of functions in the mammalian brain ranging from regulation of various aspects of neurotransmitter function and modulation of behaviour to the stimulation of differentiation and plasticity of distinct neuronal populations and circuits. Acting via both genomic and nongenomic mechanisms estrogens can influence higher cognitive functions, pain mechanisms, fine motor skills, mood, susceptibility to. seizures, and also appear to have important neuroprotective function in relation to stroke damage and neurodegenerative disorders. This review focuses on new advancements from clinical and basic studies on estrogen action in the central nervous system especially illustrating the brain regions and cell types in which estrogens produce their effects, emphasizing new knowledge regarding estrogen actions outside the hypothalamus and pituitary gland. Current therapeutic strategies to develop suitable estrogen receptor modulators with a selective spectrum of action in the brain and priorities for future research are also briefly discussed.

Modulation of stress-induced neurobehavioral changes and brain oxidative injury by nitric oxide (NO) mimetics in rats.

The present study evaluated the effects of NO mimetics on stress-induced neurobehavioral changes and the possible involvement of ROS-RNS interactions in rats. Restraint stress (RS) suppressed both percent open arm entries and time spent in the open arms in the elevated plus maze (EPM) test. These RS-induced changes in EPM activity were attenuated by the NO mimetics, l-arginine, isosorbide dinitrate and molsidomine, in a differential manner. RS-exposed rats showed (a) increased lipid peroxidation (MDA) and (b) lowered reduced glutathione (GSH) and NO metabolites (NOx), in brain homogenates of these animals. Pretreatment with the NO mimetics also differentially influenced RS-induced changes in brain oxidative stress markers. The results suggest that NO may protect against stress-induced anxiogenic behavior and oxidative injury in the brain and highlight the significance of ROS-RNS interactions.

Possible involvement of free radicals in the differential neurobehavioral responses to stress in male and female rats.

The effect of restraint stress (RS) on neurobehavioral and brain oxidative stress parameters, and their modulation by antioxidants were evaluated in male and cycling female rats. Exposure to RS suppressed both open arm entries and open arm time in the elevated plus maze and these changes were more marked in males than in females. Assay of brain homogenates revealed that the behavioral suppression was associated with similar differential increases in malondialdehye (MDA) and decreases in glutathione (GSH), superoxide dismutase (SOD) and catalase (CAT) levels in males and females. Pretreatment with alpha-tocopherol (25 and 50 mg/kg) and N-acetylcysteine (100 and 200 mg/kg), attenuated the stress induced alteration of behavioral and oxidative stress markers in a consistent manner in both male and female rats. These findings suggest that males may be more susceptible than females to stress induced neurobehavioral changes and free radicals may exert a regulatory influence in such gender dependent responses to stress.

Comparative effect of topical application of lindane and permethrin on oxidative stress parameters in adult scabies patients.

OBJECTIVES: The insecticides lindane and permethrin are commonly used for treatment of scabies. Animal studies have shown the presence of insecticide induced oxidative stress. Hence, this study was undertaken to assess and compare the effects of topical application of lindane and permethrin on oxidative stress parameters in scabies patients. DESIGN AND METHODS: Patients were alternatively assigned to treatment by either 1% lindane lotion or 5% permethrin cream. Blood samples were collected before and 12-14 h after the application of the drugs and evaluated for oxidative stress parameters and compared with healthy controls. RESULTS: Serum malondialdehyde (MDA) levels, erythrocyte superoxide dismutase (SOD) and catalase (CAT) activity were significantly increased while blood glutathione (GSH) levels were significantly decreased in the lindane group as compared to controls and the permethrin group. The permethrin treated group showed a non significant alteration in the oxidative stress parameters. CONCLUSION: Topical application of lindane induced significant oxidative stress as compared to permethrin which appears to be a safer option for the treatment of scabies.

Role of free radicals in stress-induced neurobehavioural changes in rats.

Effect of restraint stress (RS) and its modulation by antioxidants were evaluated on elevated plus maze (EPM) and open field (OF) tests in rats. Restraint stress (RS for 1 hr) reduced the number of open arm entries, as also the time spent on open arms indicating enhanced anxiogenic response in the EPM test as compared to normal non RS group of rats. Pretreatment with ascorbic acid (100 and 200 mg/kg) and alpha-tocopherol (30 and 60 mg/kg) attenuated these RS-induced effects. In the OF test, RS-reduced (a) ambulations; and (b) rearings, whereas an increase was seen in (a) latency of entry and (b) number of fecal boluses. The RS-induced changes in OF parameters were reversed after pretreatment with the antioxidants, (ascorbic acid and alpha tocopherol). Biochemical data showed that RS enhanced MDA levels in both serum and brain, and these were attenuated after pretreatment with the antioxidants. The pharmacological and biochemical results indicate that free radicals might be involved in such stress-induced neurobehavioural effects.