Microglial function in human APOE3 and APOE4 transgenic mice: altered arginine transport

Biomarkers of Migraine: An Integrated Evaluation of Preclinical and Clinical Findings

In recent years, numerous efforts have been made to identify reliable biomarkers useful in migraine diagnosis and progression or associated with the response to a specific treatment. The purpose of this review is to summarize the alleged diagnostic and therapeutic migraine biomarkers found in biofluids and to discuss their role in the pathogenesis of the disease. We included the most informative data from clinical or preclinical studies, with a particular emphasis on calcitonin gene-related peptide (CGRP), cytokines, endocannabinoids, and other biomolecules, the majority of which are related to the inflammatory aspects and mechanisms of migraine, as well as other actors that play a role in the disease. The potential issues affecting biomarker analysis are also discussed, such as how to deal with bias and confounding data. CGRP and other biological factors associated with the trigeminovascular system may offer intriguing and novel precision medicine opportunities, although the biological stability of the samples used, as well as the effects of the confounding role of age, gender, diet, and metabolic factors should be considered.

Migraine and thyroid dysfunction: Co-occurrence, shared genes and biological mechanisms

BACKGROUND AND PURPOSE

Migraine and thyroid dysfunction, particularly hypothyroidism, are common medical conditions and are known to have high heritability. Thyroid function measures, thyroid stimulating hormone (TSH) and free thyroxine (fT4), are also known to be genetically influenced. Although observational epidemiological studies report an increased co-occurrence of migraine and thyroid dysfunction, a clear and combined interpretation of the findings is currently lacking. A narrative review is provided of the epidemiological and genetic association evidence linking migraine, hypothyroidism, hyperthyroidism and thyroid hormones TSH and fT4.

METHODS

An extensive literature search was conducted in the PubMed database for epidemiological, candidate gene and genome-wide association studies using the terms migraine, headache, thyroid hormones, TSH, fT4, thyroid function, hypothyroidism and hyperthyroidism.

RESULTS

Epidemiological studies suggest a bidirectional relationship between migraine and thyroid dysfunction. However, the nature of the relationship remains unclear, with some studies suggesting migraine increases the risk for thyroid dysfunction whilst other studies suggest the reverse. Early candidate gene studies have provided nominal evidence for MTHFR and APOE, whilst more recently genome-wide association studies have provided robust evidence for THADA and ITPK1 being associated with both migraine and thyroid dysfunction.

CONCLUSIONS

These genetic associations improve our understanding of the genetic relationship between migraine and thyroid dysfunction, provide an opportunity to develop biomarkers to identify migraine patients most likely to benefit from thyroid hormone therapy, and indicate that further cross-trait genetic studies have excellent potential to provide biological insight into their relationship and inform clinical interventions.

Protein Expression of Amino Acid Transporters Is Altered in Isolated Cerebral Microvessels of 5xFAD Mouse Model of Alzheimer's Disease

Membrane transporters such as ATP-binding cassette (ABC) and solute carrier (SLC) transporters expressed at the neurovascular unit (NVU) play an important role in drug delivery to the brain and have been demonstrated to be involved in Alzheimer's disease (AD) pathogenesis. However, our knowledge of quantitative changes in transporter absolute protein expression and functionality in vivo in NVU in AD patients and animal models is limited. The study aim was to investigate alterations in protein expression of ABC and SLC transporters in the isolated brain microvessels and brain prefrontal cortices of a widely used model of familial AD, 5xFAD mice (8 months old), using a sensitive liquid chromatography tandem mass spectrometry-based quantitative targeted absolute proteomic approach. Moreover, we examined alterations in brain prefrontal cortical and plasmatic levels of transporter substrates in 5xFAD mice compared to age-matched wild-type (WT) controls. ASCT1 (encoded by Slc1a4) protein expression in the isolated brain microvessels and brain prefrontal cortices of 5xFAD mice was twice higher compared to WT controls (p = 0.01). Brain cortical levels of ASCT1 substrate, serine, were increased in 5xFAD mice compared to WT animals. LAT1 (encoded by Slc7a5) and 4F2hc (encoded by Slc3a2) protein expressions were significantly altered in the isolated brain microvessels of 5xFAD mice compared to WT controls (p = 0.008 and p = 0.05, respectively). Overall, the study provides important information, which is crucial for the optimal use of the 5xFAD mouse model in AD drug development and for investigating novel drug delivery approaches. In addition, the findings of the study shed light on the novel potential mechanisms underlying AD pathogenesis.

Nitric oxide attenuates microglia proliferation by sequentially facilitating calcium influx through TRPV2 channels, activating NFATC2, and increasing p21 transcription

Microglia proliferation is critical for proper development and function of the central nervous system (CNS), while dysregulation of proliferation contributes to pathology. We recently reported that male inducible nitric oxide synthase knockout (iNOS^-/-) mice displayed significantly more proliferating microglia in their postnatal cortex than age-matched wildtype (WT) male mice. Moreover, nitric oxide (NO) signaling in mouse microglia greatly upregulates calcium entry through transient receptor potential vanilloid type 2 (TRPV2) channels. Considering that TRPV2 activity restricts astrocytic proliferation within glioma tissues, we investigated the roles of iNOS/NO signaling and TRPV2 expression in the regulation of microglial proliferation in vitro using assays of calcium imaging, immunocytochemistry, western blot, and polymerase chain reaction. Results showed that non-dividing microglia exhibited substantially higher expression of TRPV2 on the plasma membrane and significantly larger calcium influx through TRPV2 channels in comparison to dividing microglia. Additionally, non-dividing WT microglia exhibited significantly more NO production than dividing WT microglia. Furthermore, the NO-donor NOC18 increased the nuclear translocation of nuclear factor of activated T-cells cytoplasmic 2 (NFATC2) and the mRNA of the cyclin-dependent kinase inhibitor p21 and decreased the percentage of dividing WT and iNOS^-/- microglia in culture. Importantly, the presence of the TRPV2 inhibitor tranilast abolished these effects of NOC18. Together, results from this study indicated that iNOS/NO signaling inhibits microglial proliferation through TRPV2-mediated calcium influx, nuclear translocation of the transcription factor NFATC2, and p21 expression. [Figure: see text].

Role of Apolipoprotein E in the tangled mystery of pain

Pain is one of the common and debilitating health manifestations associated with the majority of diseased conditions, thus making it a serious health concern worldwide. While trying to decipher the cryptic mechanism of pain in hope to provide better gene-based therapeutics, researchers have concluded pain to be of multigenic origin making it hard to cure. Apolipoprotein E is a protein coded by APOE gene containing 4 exons, located on chromosome 19q13.2. It is among the key regulators of various crucial body functions such as lipid transport, apoptosis, vitamin k pathway, and cognition, hence, it is highly suspected to play a pivotal role in the nociception process. However, very few studies have tried and succeeded to find a direct involvement of APOE in pain processing. The current article attempts to throw light on some of the major clinical research findings which strengthen the hypothesis stating that apolipoprotein E has a concealed yet deeply embedded association with the pain regulating pathways, through several underlying physiological, biochemical and neurological processes, that in turn, decide the fate of pain sensation in a complex manner.

Neurodevelopment, Nutrition, and Inflammation: The Evolving Global Child Health Landscape

The last decade has witnessed major reductions in child mortality and a focus on saving lives with key interventions targeting major causes of child deaths, such as neonatal deaths and those due to childhood diarrhea and pneumonia. With the transition to Sustainable Development Goals, the global health community is expanding child health initiatives to address not only the ongoing need for reduced mortality, but also to decrease morbidity and adverse exposures toward improving health and developmental outcomes. The relationship between adverse environmental exposures frequently associated with factors operating in the prepregnancy period and during fetal development is well established. Also well appreciated are the developmental impacts (both short- and long-term) associated with postnatal factors, such as immunostimulation and environmental enteropathy, and the additional risks posed by the confluence of factors related to malnutrition, poor living conditions, and the high burden of infections. This article provides our current thinking on the pathogenesis and risk factors for adverse developmental outcomes among young children, setting the scene for potential interventions that can ameliorate these adversities among families and children at risk.

Association of the Apolipoprotein E polymorphism with migraine: a meta-analysis

Background

Apolipoprotein E (ApoE) gene has been reported to be associated with migraine and tension-type headache (TTH), but the results are conflicting. This study aimed to evaluate the association of ApoE with migraine by a meta-analysis.

Methods

MEDLINE, ISI Web of Knowledge, The Cochrane Central Register of Controlled Trials, and EMBASE databases were searched to identify eligible studies published in English from 2000 to 2014. Data were extracted using standardized forms. The association was assessed by relative risk (RR) with 95 % confidence intervals (CIs) using a fixed or random effects model.

Results

Four studies, comprising 649 migraineurs, 229 TTH subjects and 975 controls, met all the criteria and were included in the meta-analysis. No significant difference was found comparing genotypic and allelic frequencies in the case of migraineurs versus controls and TTH subjects versus controls. Only when migraineurs and TTH subjects were considered as a whole group, ApoE4 was found to increase the relative risk of headache by 1.48 (95 % CI 1.16, 1.90; P = 0.002), compared to controls.

Conclusions

ApoE ε4 allele is not associated with migraine susceptibility, but is positively related to headache (including migraine and TTH).

Apolipoprotein E Mimetic Promotes Functional and Histological Recovery in Lysolecithin-Induced Spinal Cord Demyelination in Mice

Objective

Considering demyelination is the pathological hallmark of multiple sclerosis (MS), reducing demyelination and/or promoting remyelination is a practical therapeutic strategy to improve functional recovery for MS. An apolipoprotein E (apoE)-mimetic peptide COG112 has previously demonstrated therapeutic efficacy on functional and histological recovery in a mouse experimental autoimmune encephalomyelitis (EAE) model of human MS. In the current study, we further investigated whether COG112 promotes remyelination and improves functional recovery in lysolecithin induced focal demyelination in the white matter of spinal cord in mice.

Methods

A focal demyelination model was created by stereotaxically injecting lysolecithin into the bilateral ventrolateral funiculus (VLF) of T8 and T9 mouse spinal cords. Immediately after lysolecithin injection mice were treated with COG112, prefix peptide control or vehicle control for 21 days. The locomotor function of the mice was measured by the beam walking test and Basso Mouse Scale (BMS) assessment. The nerve transmission of the VLF of mice was assessed in vivo by transcranial magnetic motor evoked potentials (tcMMEPs). The histological changes were also examined by by eriochrome cyanine staining, immunohistochemistry staining and electron microscopy (EM) method.

Results

The area of demyelination in the spinal cord was significantly reduced in the COG112 group. EM examination showed that treatment with COG112 increased the thickness of myelin sheaths and the numbers of surviving axons in the lesion epicenter. Locomotor function was improved in COG112 treated animals when measured by the beam walking test and BMS assessment compared to controls. TcMMEPs also demonstrated the COG112-mediated enhancement of amplitude of evoked responses.

Conclusion

The apoE-mimetic COG112 demonstrates a favorable combination of activities in suppressing inflammatory response, mitigating demyelination and in promoting remyelination and associated functional recovery in animal model of CNS demyelination. These data support that apoE-mimetic strategy may represent a promising therapy for MS and other demyelination disorders.

Thioredoxin-80 is a product of alpha-secretase cleavage that inhibits amyloid-beta aggregation and is decreased in Alzheimer's disease brain

Thioredoxin-1 (Trx1) is an endogenous dithiol reductant and antioxidant that was shown to be decreased in Alzheimer's disease (AD) neurons. A truncated form of Trx1, thioredoxin 80 (Trx80), was reported to be secreted from monocytes having cytokine activity. Here, we show that Trx80 is present in human brain in an aggregated form. Trx80 localizes mainly to neurons and is dramatically decreased in AD brains. Trx80 levels in cerebrospinal fluid (CSF) correlate with those of the classical AD biomarkers amyloid-β (Aβ) 1-42 and total tau. Moreover, Trx80 measurements in CSF discriminate between patients with stable mild cognitive impairment, prodomal AD and mild AD. We report that ADAM10 and 17, two α-secretases processing the Aβ precursor protein, are responsible for Trx80 generation. In contrast to the periphery, Trx80 has no pro-inflammatory effects in glia, either by itself or in combination with Aβ or apolipoprotein E. Instead, Trx80 inhibits Aβ(1-42) aggregation and protects against its toxicity. Thus, a reduction in Trx80 production would result in increased Aβ polymerization and enhanced neuronal vulnerability. Our data suggest that a deficit in Trx80 could participate in AD pathogenesis.

Vascular gene polymorphisms (EDNRA -231 G>A and APOE HhaI) and risk for migraine

Migraine is a neurovascular disorder, and hence, any alteration in vascular endothelial function by either the endothelin system or the apolipoproteins may contribute to its pathophysiology. Thus, we investigated the role of EDNRA -231 G>A and APOE HhaI polymorphism for a possible association with migraine. Genotyping of 613 subjects consisting of 217 migraine subjects, 217 healthy controls (HC), and 179 subjects with tension-type headache was performed using the standard PCR-RFLP method. Data were analyzed by taking the Bonferroni-corrected p-values into account. We found significant difference in the frequency of EDNRA AA genotype between migraine subjects when compared with HC (p-value = 0.005; OR = 2.542; confidence interval [CI] = 1.329-4.863). A similar trend was shown by female migraine subjects at genotype and allele levels. The association of EDNRA -231 G>A polymorphism with migraine fit a recessive model (migraine vs. HC, p-value = 0.002; OR = 1.917; CI = 2.268-2.898). Female migraineurs without aura (MO) followed a similar trend. In the case of APOE HhaI polymorphism, E3E4 and E2E3 genotypes conferred risk when taken together in case of migraine versus HC (p-value = 0.005; OR = 2.715; CI = 1.342-5.490) and migraine with aura (MA) versus HC (p-value = 0.004; OR = 3.422; CI = 7.992). The risk was also seen after stratification on the basis of gender in female migraineurs (total migraine and MA). The interaction of EDNRA and APOE genotypes did not show further significance. The AA genotype and A allele of EDNRA -231 G>A polymorphism conferred risk for total migraine and MO. In APOE HhaI polymorphism, E3E4 and E2E3 conferred risk when taken together in total migraine and MA.

The immune-modulatory role of apolipoprotein E with emphasis on multiple sclerosis and experimental autoimmune encephalomyelitis

Apolipoprotein E (apoE) is a 34.2 kDa glycoprotein characterized by its wide tissue distribution and multiple functions. The nonlipid-related properties of apoE include modulating inflammation and oxidation, suppressing T cell proliferation, regulating macrophage functions, and facilitating lipid antigen presentation by CD1 molecules to natural killer T (NKT) cells, and so forth. Increasing studies have revealed that APOE ε allele might be associated with multiple sclerosis (MS), although evidence is still not sufficient enough. In this review, we summarized the current progress of the immunomodulatory functions of apoE, with special focus on the association of APOE ε allele with the clinical features of MS and of its animal model experimental autoimmune encephalomyelitis (EAE).

ApoE polymorphisms and diarrheal outcomes in Brazilian shanty town children

A series of studies have shown that the heavy burdens of diarrheal diseases in the first 2 formative years of life in children living in urban shanty towns have negative effects on physical and cognitive development lasting into later childhood. We have shown that APOE4 is relatively common in shanty town children living in Brazil (13.4%) and suggest that APOE4 has a protective role in cognitive development as well as weight-for-height in children with heavy burdens of diarrhea in early childhood (64/123; 52%), despite being a marker for cognitive decline with Alzheimer's and cardiovascular diseases later in life. APOE2 frequency was higher among children with heaviest diarrhea burdens during the first 2 years of life, as detected by PCR using the restriction fragment length polymorphism method, raising the possibility that ApoE-cholesterol balance might be critical for growth and cognitive development under the stress of heavy diarrhea burdens and when an enriched fat diet is insufficient. These findings provide a potential explanation for the survival advantage in evolution of genes, which might raise cholesterol levels during heavy stress of diarrhea burdens and malnutrition early in life.

The role of apolipoprotein E in Guillain-Barré syndrome and experimental autoimmune neuritis

Apolipoprotein E (apoE) is a 34.2 kDa glycosylated protein characterized by its wide tissue distribution and multiple functions. ApoE has been widely studied in lipid metabolism, cardiocerebrovascular diseases, and neurodegenerative diseases like Alzheimer's disease and mild cognitive impairment, and so forth. Recently, a growing body of evidence has pointed to nonlipid related properties of apoE, including suppression of T cell proliferation, regulation of macrophage function, facilitation of lipid antigen presentation by CD1 molecules to natural killer T (NKT) cells, and modulation of inflammation and oxidation. By these properties, apoE impacts physiology and pathophysiology at multiple levels. The present paper summarizes updated studies on the immunoregulatory function of apoE, with special focus on isoform-specific effects of apoE on Guillain-Barré syndrome (GBS) and its animal model experimental autoimmune neuritis (EAN).

Heterogeneity of microglial activation in the innate immune response in the brain

The immune response in the brain has been widely investigated and while many studies have focused on the proinflammatory cytotoxic response, the brain's innate immune system demonstrates significant heterogeneity. Microglia, like other tissue macrophages, participate in repair and resolution processes after infection or injury to restore normal tissue homeostasis. This review examines the mechanisms that lead to reduction of self-toxicity and to repair and restructuring of the damaged extracellular matrix in the brain. Part of the resolution process involves switching macrophage functional activation to include reduction of proinflammatory mediators, increased production and release of anti-inflammatory cytokines, and production of cytoactive factors involved in repair and reconstruction of the damaged brain. Two partially overlapping and complimentary functional macrophage states have been identified and are called alternative activation and acquired deactivation. The immunosuppressive and repair processes of each of these states and how alternative activation and acquired deactivation participate in chronic neuroinflammation in the brain are discussed.

APOE genotype-specific differences in the innate immune response

Apolipoprotein-E protein is an endogenous immunomodulatory agent that affects both the innate and the adaptive immune responses. Since individuals with the APOE4 gene demonstrate worsened pathology and poorer outcomes in many neurological disorders, we examined isoform-specific differences in the response of microglia, the primary cellular component of the brain's innate immune response, in detail. Our data demonstrate that microglia derived from APOE4/4 targeted replacement mice demonstrate a pro-inflammatory phenotype that includes altered cell morphology, increased NO production associated with increased NOS2 mRNA levels, and higher pro-inflammatory cytokine production (TNFalpha, IL-6, IL12p40) compared to microglia derived from APOE3/3 targeted replacement mice. The effect is gene dose-dependent and increases with the number of APOE4 gene alleles. The APOE genotype-specific immune profile observed in the microglial immune response is also observed in the cortex of aged APOE3/3 and APOE4/4 mice treated with lipopolysacchride (LPS) and in peripheral (peritoneal) macrophages. To determine if APOE4's action resulted from an isoform-specific difference in effective levels of the apolipoproteins, we generated mice expressing only a single allele of APOE3. Immune-stimulated macrophages from APOE3/0 mice demonstrated an increased inflammatory response compared to APOE3/3 mice, but less than in APOE4/4 mice. These data suggest that inhibition of inflammation depends upon the dose of apoE3 protein available and that apoE4 protein may alter inflammation partly by dose effects and partly by being qualitatively different than apoE3. Overall, these data emphasize the important role of apolipoprotein E and of the APOE genotype on the immune responses that are evident in most, if not all, neurological disease.

Polymorphism in apolipoprotein E among migraineurs and tension-type headache subjects

Nitric oxide plays an important role in the pathogenesis of migraine as well as tension-type headache. Studies suggest that the expression of molecules involved in the pathogenesis of headache, i.e., nitric oxide and interleukin, is influenced by apolipoprotein E (APOE) and is gene specific. Hence, we hypothesized that APOE polymorphism may be associated with migraine as well as tension-type headache.The study sample comprised of three groups: migraineurs, tension-type headache subjects as well as a healthy control group. A total of 50 subjects in each group were included after screening for the inclusion and exclusion criteria. None of the subjects was a blood relative of any other subject included in the present study. Their venous blood was drawn and stored at −20°C. Genomic DNA extraction was performed with a commercial kit and simple sequence-specific primer PCR was performed to assess the APOE polymorphism. Data were analyzed with the help of SPSS V11.0 for Windows. χ² test and logistic regression analysis were run. The results of the study showed that APOE ε2 gene increases the risk of migraine as compared to the control group and the tension-type headache group (OR = 4.85; 95% CI = 1.92–12.72; P < 0.001 and OR = 2.31; 95% CI = 1.08–4.94; P = 0.01, respectively). Interestingly, APOE ε4 gene was protective against migraine as well as tension-type headache. This study shows that APOE ε2 gene increases the risk of migraine, while APOE ε4 gene is protective against migraine and tension-type headache. Further research is required to confirm the findings of the present study in a larger sample and to elucidate the role of APOE polymorphism in headache.

The APOE4 genotype alters the response of microglia and macrophages to 17beta-estradiol

The apolipoprotein E4 (APOE4) gene is a well-known risk factor for Alzheimer's disease (AD) and other neurological disorders. Post-menopausal women with AD who express at least one APOE4 gene have more severe neuropathology and worsened cognitive scores than their non-expressing counterparts. Since 17beta-estradiol down-regulates inflammation as part of its neuroprotective role, we examined the effect of 17beta-estradiol on the response of microglia to immune activation as a function of APOE genotype. Our data show that the anti-inflammatory activity of 17beta-estradiol is significantly reduced in APOE4 targeted replacement mice compared to APOE3 mice. A significant interaction between APOE genotype and the response to 17beta-estradiol was observed for NO and cytokine production by immune activated microglia. The genotype specific effect was not restricted to brain macrophages since peritoneal macrophages from APOE4 ovariectomized mice also demonstrated a significant difference in 17beta-estradiol responsiveness. ERbeta protein levels in APOE4 microglia were higher than APOE3 microglia, suggesting a difference in post-translational protein regulation in the presence of the APOE4 gene. Overall, our data indicate that the APOE genotype may be a critical component in assessing the effectiveness of 17beta-estradiol's action and may impact the neuroprotective role of 17beta-estradiol and of hormone replacement therapy on brain function when the APOE4 gene is expressed.

Malnutrition as an enteric infectious disease with long-term effects on child development

Malnutrition is a major contributor to mortality and is increasingly recognized as a cause of potentially lifelong functional disability. Yet, a rate-limiting step in achieving normal nutrition may be impaired absorptive function due to multiple repeated enteric infections. This is especially problematic in children whose diets are marginal. In malnourished individuals, the infections are even more devastating. This review documents the evidence that intestinal infections lead to malnutrition and that malnutrition worsens intestinal infections. The clinical data presented here derive largely from long-term cohort studies that are supported by controlled animal studies. Also reviewed are the mechanisms by which enteric infections lead to undernutrition and by which malnutrition worsens enteric infections, with implications for potential novel interventions. Further intervention studies are needed to document the relevance of these mechanisms and, most importantly, to interrupt the vicious diarrhea-malnutrition cycle so children may develop their full potential.

Role of apolipoprotein E4 in protecting children against early childhood diarrhea outcomes and implications for later development

Our group and others have reported a series of studies showing that heavy burdens of diarrheal diseases in the formative first two years of life in children in urban shantytowns have profound consequences of impaired physical and cognitive development lasting into later childhood and schooling. Based on these previous studies showing that apolipoprotein E4 (APOE4) is relatively common in favela children, we review recent data suggesting a protective role for the APOE4 allele in the cognitive and physical development of children with heavy burdens of diarrhea in early childhood. Despite being a marker for cognitive decline with Alzheimer's and cardiovascular diseases later in life, APOE4 appears to be important for cognitive development under the stress of heavy diarrhea. The reviewed findings provide a potential explanation for the survival advantage in evolution of the thrifty APOE4 allele and raise questions about its implications for human development under life-style changes and environmental challenges.

Defective lysosomal arginine transport in juvenile Batten disease

Mutations in the CLN3 gene, which encodes a lysosomal membrane protein, are responsible for the neurodegenerative disorder juvenile Batten disease. A previous study on the yeast homolog to CLN3, designated Btn1p, revealed a potential role for CLN3 in the transport of arginine into the yeast vacuole, the equivalent organelle to the mammalian lysosome. Lysosomes isolated from lymphoblast cell lines, established from individuals with juvenile Batten disease-bearing mutations in CLN3, but not age-matched controls, demonstrate defective transport of arginine. Furthermore, we show that there is a depletion of arginine in cells derived from individuals with juvenile Batten disease. We have, therefore, characterized lysosomal arginine transport in normal lysosomes and show that it is ATP-, v-ATPase- and cationic-dependent. This and previous studies have shown that both arginine and lysine are transported by the same transport system, designated system c. However, we report that lysosomes isolated from juvenile Batten disease lymphoblasts are only defective for arginine transport. These results suggest that the CLN3 defect in juvenile Batten disease may affect how intracellular levels of arginine are regulated or distributed throughout the cell. This assertion is supported by two other experimental approaches. First, an antibody to CLN3 can block lysosomal arginine transport and second, expression of CLN3 in JNCL cells using a lentiviral vector can restore lysosomal arginine transport. CLN3 may have a role in regulating intracellular levels of arginine possibly through control of the transport of this amino acid into lysosomes.

Oxidative and antioxidative potential of brain microglial cells

Microglial cells are the resident immune cells of the central nervous system. These cells defend the central nervous system against invading microorganisms and clear the debris from damaged cells. Upon activation, microglial cells produce a large number of neuroactive substances that include cytokines, proteases, and prostanoids. In addition, activated microglial cells release radicals, such as superoxide and nitric oxide, that are products of the enzymes NADPH oxidase and inducible nitric oxide synthase, respectively. Microglia-derived radicals, as well as their reactive reaction products hydrogen peroxide and peroxynitrite, have the potential to harm cells and have been implicated in contributing to oxidative damage and neuronal cell death in neurological diseases. For self-protection against oxidative damage, microglial cells are equipped with efficient antioxidative defense mechanisms. These cells contain glutathione in high concentrations, substantial activities of the antioxidative enzymes superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase, as well as NADPH-regenerating enzymes. Their good antioxidative potential protects microglial cells against oxidative damage that could impair important functions of these cells in defense and repair of the brain.

Y+ and y+ L arginine transporters in neuronal cells expressing tyrosine hydroxylase

Arginine is a semi-essential amino acid that serves as sole substrate for enzymes involved in diverse cell processes including redox balance via nitric oxide synthase (NOS) and cell proliferation via arginase. Neurons that express nNOS require intracellular arginine to generate nitric oxide (NO). Using a TH+ neuronal cell line (CAD cells), we show that neuronal NO production is largely dependent on extracellular arginine. Although a small intracellular pool exists in CAD cells, the lack of mRNA for argininosuccinate synthase (AS), a rate limiting enzyme for arginine recycling, suggests that intracellular pools are not re-supplied by this mechanism in this sub-class of neurons. Rather, arginine is taken up from the extracellular media by two primary transport systems, the y+ and the y+ L systems. The expression of CAT1, CAT3, y+ LAT1 and y+ LAT2 mRNAs supports the presence of each system. CAD cell arginine transport is depressed by increased extracellular K+ levels and demonstrates that variations in membrane potential control neuronal arginine uptake. Short term exposure to the oxidizing agents, rotenone and Angeli's salt, but not FeSO4, increases arginine transport. The regulation of arginine uptake by physiological factors suggests that arginine supply adapts in a moment-to-moment fashion to the changing needs of the neuron.