Crif1 deficiency in dopamine neurons triggers early-onset parkinsonism.

Mitochondrial dysfunction has been implicated in Parkinson's Disease (PD) progression; however, the mitochondrial factors underlying the development of PD symptoms remain unclear. One candidate is CR6-interacting factor1 (CRIF1), which controls translation and membrane insertion of 13 mitochondrial proteins involved in oxidative phosphorylation. Here, we found that CRIF1 mRNA and protein expression were significantly reduced in postmortem brains of elderly PD patients compared to normal controls. To evaluate the effect of Crif1 deficiency, we produced mice lacking the Crif1 gene in dopaminergic neurons (DAT-CRIF1-KO mice). From 5 weeks of age, DAT-CRIF1-KO mice began to show decreased dopamine production with progressive neuronal degeneration in the nigral area. At ~10 weeks of age, they developed PD-like behavioral deficits, including gait abnormalities, rigidity, and resting tremor. L-DOPA, a medication used to treat PD, ameliorated these defects at an early stage, although it was ineffective in older mice. Taken together, the observation that CRIF1 expression is reduced in human PD brains and deletion of CRIF1 in dopaminergic neurons leads to early-onset PD with stepwise PD progression support the conclusion that CRIF1-mediated mitochondrial function is important for the survival of dopaminergic neurons.

Characterization of acute pain-induced behavioral passivity in mice: Insights from statistical modeling.

Affective-motivational disturbances are highly inconsistent in animal pain models. The reproducibility of the open-field test in assessing anxiety, malaise or disability remains controversial despite its popularity. While traumatic, persistent or multiregional pain models are commonly considered more effective in inducing negative affect or functional impairment, the early psychobehavioral changes before pain chronification are often underexplored. Here, we aimed to clarify the fundamental relationship between hypernociception and passive distress-like behavior using a model of transient inflammatory pain. To minimize latent confounders and increase data consistency, male C57BL/6N mice were habituated to the open-field arena 6 times before receiving the unilateral intraplantar injection of prostaglandin E2 (PGE2) or vehicle. Open-field (40-min exploration) and nociceptive behavior were evaluated repeatedly along the course of hypernociception in both wild-type and transgenic mice with a known pronociceptive phenotype. To reduce subjectivity, multivariate open-field behavioral outcomes were analyzed by statistical modeling based on exploratory factor analyses, which yielded a 2-factor solution. Within 3 hr after PGE2 injection, mice developed significantly reduced center exploration (factor 1) and a marginally significant increase in their habituation tendency (factor 2), which were not apparent in vehicle-injected mice. The behavioral passivity generally improved as hypernociception subsided. Therefore, transient inflammatory irritation is sufficient to suppress mouse open-field exploratory activity. The apparent absence of late affective-motivational changes in some rodents with prolonged hypernociception may not imply a lack of preceding or underlying neuropsychological alterations. Procedural pain after invasive animal experiments, however small, should be assessed and adequately controlled as a potential research confounder.

Aldose Reductase and the Polyol Pathway in Schwann Cells: Old and New Problems.

Aldose reductase (AR) is a member of the reduced nicotinamide adenosine dinucleotide phosphate (NADPH)-dependent aldo-keto reductase superfamily. It is also the rate-limiting enzyme of the polyol pathway, catalyzing the conversion of glucose to sorbitol, which is subsequently converted to fructose by sorbitol dehydrogenase. AR is highly expressed by Schwann cells in the peripheral nervous system (PNS). The excess glucose flux through AR of the polyol pathway under hyperglycemic conditions has been suggested to play a critical role in the development and progression of diabetic peripheral neuropathy (DPN). Despite the intensive basic and clinical studies over the past four decades, the significance of AR over-activation as the pathogenic mechanism of DPN remains to be elucidated. Moreover, the expected efficacy of some AR inhibitors in patients with DPN has been unsatisfactory, which prompted us to further investigate and review the understanding of the physiological and pathological roles of AR in the PNS. Particularly, the investigation of AR and the polyol pathway using immortalized Schwann cells established from normal and AR-deficient mice could shed light on the causal relationship between the metabolic abnormalities of Schwann cells and discordance of axon-Schwann cell interplay in DPN, and led to the development of better therapeutic strategies against DPN.

Adipocyte fatty acid-binding protein exacerbates cerebral ischaemia injury by disrupting the blood-brain barrier.

AIMS: Adipocyte fatty acid-binding protein (A-FABP) is an adipokine implicating in various metabolic diseases. Elevated circulating levels of A-FABP correlate positively with poor prognosis in ischaemic stroke (IS) patients. No information is available concerning the role of A-FABP in the pathogenesis of IS. Experiments were designed to determine whether or not A-FABP mediates blood-brain barrier (BBB) disruption, and if so, to explore the molecular mechanisms underlying this deleterious effects. METHODS AND RESULTS: Circulating A-FABP and its cerebral expression were increased in mice after middle cerebral artery occlusion. Genetic deletion and pharmacological inhibition of A-FABP alleviated cerebral ischaemia injury with reduced infarction volume, cerebral oedema, neurological deficits, and neuronal apoptosis; BBB disruption was attenuated and accompanied by reduced degradation of tight junction proteins and induction of matrix metalloproteinases-9 (MMP-9). In patients with acute IS, elevated circulating A-FABP levels positively correlated with those of MMP-9 and cerebral infarct volume. Mechanistically, ischaemia-induced elevation of A-FABP selectively in peripheral blood monocyte-derived macrophages and cerebral resident microglia promoted MMP-9 transactivation by potentiating JNK/c-Jun signalling, enhancing degradation of tight junction proteins and BBB leakage. The detrimental effects of A-FABP were prevented by pharmacological inhibition of MMP-9. CONCLUSION: A-FABP is a key mediator of cerebral ischaemia injury promoting MMP-9-mediated BBB disruption. Inhibition of A-FABP is a potential strategy to improve IS outcome.

Endothelial-specific Crif1 deletion induces BBB maturation and disruption via the alteration of actin dynamics by impaired mitochondrial respiration.

Cerebral endothelial cells (ECs) require junctional proteins to maintain blood-brain barrier (BBB) integrity, restricting toxic substances and controlling peripheral immune cells with a higher concentration of mitochondria than ECs of peripheral capillaries. The mechanism underlying BBB disruption by defective mitochondrial oxidative phosphorylation (OxPhos) is unclear in a mitochondria-related gene-targeted animal model. To assess the role of EC mitochondrial OxPhos function in the maintenance of the BBB, we developed an EC-specific CR6-interactin factor1 (Crif1) deletion mouse. We clearly observed defects in motor behavior, uncompacted myelin and leukocyte infiltration caused by BBB maturation and disruption in this mice. Furthermore, we investigated the alteration in the actin cytoskeleton, which interacts with junctional proteins to support BBB integrity. Loss of Crif1 led to reorganization of the actin cytoskeleton and a decrease in tight junction-associated protein expression through an ATP production defect in vitro and in vivo. Based on these results, we suggest that mitochondrial OxPhos is important for the maturation and maintenance of BBB integrity by supplying ATP to cerebral ECs.

Exchange protein directly activated by cAMP (Epac) 1 plays an essential role in stress-induced exercise capacity by regulating PGC-1α and fatty acid metabolism in skeletal muscle.

Exchange protein directly activated by cAMP (Epac) mediates cAMP-mediated cell signal independent of protein kinase A (PKA). Mice lacking Epac1 displayed metabolic defect suggesting possible functional involvement of skeletal muscle and exercise capacity. Epac1 was highly expressed, but not Epac 2, in the extensor digitorum longus (EDL) and soleus muscles. The exercise significantly increased protein expression of Epac 1 in EDL and soleus muscle of wild-type (WT) mice. A global proteomics and pathway analyses revealed that Epac 1 deficiency mainly affected "the energy production and utilization" process in the skeletal muscle. We have tested their forced treadmill exercise tolerance. Epac1-/- mice exhibited significantly reduced exercise capacity in the forced treadmill exercise and lower number of type 1 fibers than WT mice. The basal protein level of proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) was reduced in the Epac1-/- mice. Furthermore, increasing expression of PGC-1α by exercise was also significantly attenuated in the skeletal muscle of Epac1-/- mice. The expressions of downstream target genes of PGC-1α, which involved in uptake and oxidation of fatty acids, ERRα and PPARδ, and fatty acid content were lower in muscles of Epac1-/-, suggesting a role of Epac1 in forced treadmill exercise capacity by regulating PGC-1α pathway and lipid metabolism in skeletal muscle. Taken together, Epac1 plays an important role in exercise capacity by regulating PGC-1α and fatty acid metabolism in the skeletal muscle.

Astrocytic endothelin-1 overexpression promotes neural progenitor cells proliferation and differentiation into astrocytes via the Jak2/Stat3 pathway after stroke.

BACKGROUND: Endothelin-1 (ET-1) is synthesized and upregulated in astrocytes under stroke. We previously demonstrated that transgenic mice over-expressing astrocytic ET-1 (GET-1) displayed more severe neurological deficits characterized by a larger infarct after transient middle cerebral artery occlusion (tMCAO). ET-1 is a known vasoconstrictor, mitogenic, and a survival factor. However, it is unclear whether the observed severe brain damage in GET-1 mice post stroke is due to ET-1 dysregulation of neurogenesis by altering the stem cell niche. METHODS: Non-transgenic (Ntg) and GET-1 mice were subjected to tMCAO with 1 h occlusion followed by long-term reperfusion (from day 1 to day 28). Neurological function was assessed using a four-point scale method. Infarct area and volume were determined by 2,3,5-triphenyltetra-zolium chloride staining. Neural stem cell (NSC) proliferation and migration in subventricular zone (SVZ) were evaluated by immunofluorescence double labeling of bromodeoxyuridine (BrdU), Ki67 and Sox2, Nestin, and Doublecortin (DCX). NSC differentiation in SVZ was evaluated using the following immunofluorescence double immunostaining: BrdU and neuron-specific nuclear protein (NeuN), BrdU and glial fibrillary acidic protein (GFAP). Phospho-Stat3 (p-Stat3) expression detected by Western-blot and immunofluorescence staining. RESULTS: GET-1 mice displayed a more severe neurological deficit and larger infarct area after tMCAO injury. There was a significant increase of BrdU-labeled progenitor cell proliferation, which co-expressed with GFAP, at SVZ in the ipsilateral side of the GET-1 brain at 28 days after tMCAO. p-Stat3 expression was increased in both Ntg and GET-1 mice in the ischemia brain at 7 days after tMCAO. p-Stat3 expression was significantly upregulated in the ipsilateral side in the GET-1 brain than that in the Ntg brain at 7 days after tMCAO. Furthermore, GET-1 mice treated with AG490 (a JAK2/Stat3 inhibitor) sh owed a significant reduction in neurological deficit along with reduced infarct area and dwarfed astrocytic differentiation in the ipsilateral brain after tMCAO. CONCLUSIONS: The data indicate that astrocytic endothelin-1 overexpression promotes progenitor stem cell proliferation and astr ocytic differentiation via the Jak2/Stat3 pathway.

Sphingosine 1-phosphate stimulates eyelid closure in the developing rat by stimulating EGFR signaling.

In many mammals, the eyelids migrate over the eye and fuse during embryogenesis to protect the cornea from damage during birth and early life. Loss-of-function mutations affecting the epidermal growth factor receptor (EGFR) signaling pathway cause an eyes-open-at-birth (EOB) phenotype in rodents. We identified an insertional mutation in Spinster homolog 2 (Spns2) in a strain of transgenic rats exhibiting the EOB phenotype. Spns2, a sphingosine 1-phosphate (S1P) transporter that releases S1P from cells, was enriched at the tip of developing eyelids in wild-type rat embryos. Spns2 expression or treatment with S1P or any one of several EGFR ligands rescued the EOB Spns2 mutant phenotype in vivo and in tissue explants in vitro and rescued the formation of stress fibers in primary keratinocytes from mutants. S1P signaled through the receptors S1PR1, S1PR2, and S1PR3 to activate extracellular signal-regulated kinase (ERK) and EGFR-dependent mitogen-activated protein kinase kinase kinase 1 (MEKK1)-c-Jun signaling. S1P also induced the nuclear translocation of the transcription factor MAL in a manner dependent on EGFR signaling. MAL and c-Jun stimulated the expression of the microRNAs miR-21 and miR-222, both of which target the metalloprotease inhibitor TIMP3, thus promoting metalloprotease activity. The metalloproteases ADAM10 and ADAM17 stimulated EGFR signaling by cleaving a membrane-anchored form of EGF to release the ligand. Our results outline a network by which S1P transactivates EGFR signaling through a complex mechanism involving feedback between several intra- and extracellular molecules to promote eyelid fusion in the developing rat.

PICK1 inhibits the E3 ubiquitin ligase activity of Parkin and reduces its neuronal protective effect.

Parkin functions as a multipurpose E3 ubiquitin ligase, and Parkin loss of function is associated with both sporadic and familial Parkinson's disease (PD). We report that the Bin/Amphiphysin/Rvs (BAR) domain of protein interacting with PRKCA1 (PICK1) bound to the really interesting new gene 1 (RING1) domain of Parkin and potently inhibited the E3 ligase activity of Parkin by disrupting its interaction with UbcH7. Parkin translocated to damaged mitochondria and led to their degradation in neurons, whereas PICK1 robustly inhibited this process. PICK1 also impaired the protective function of Parkin against stresses in SH-SY5Y cells and neurons. The protein levels of several Parkin substrates were reduced in young PICK1-knockout mice, and these mice were resistant to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-mediated toxicity. Taken together, the results indicate that PICK1 is a potent inhibitor of Parkin, and the reduction of PICK1 enhances the protective effect of Parkin.

Suppression of Pax2 Attenuates Allodynia and Hyperalgesia through ET-1-ETAR-NFAT5 Signaling in a Rat Model of Neuropathic Pain.

Endothelin-1 (ET-1) and its receptors (ETAR/ETBR) emerge to be a key signaling axis in neuropathic pain processing and are recognized as new therapeutic targets. Yet, little is known on the functional regulation of ET-1 axis during neuropathic pain. Bioinformatics analysis indicated that paired box gene 2 (Pax2) or nuclear factor of activated T-cells 5 (NFAT5), two transcription factors involved in the modulation of neurotransmission, may regulate ET-1. Therefore, we hypothesized that ET-1 axis may be regulated by Pax2 or NFAT5 in the development of neuropathic pain. After partial sciatic nerve ligation (pSNL), rats displayed allodynia and hyperalgesia, which was associated with increased mRNA and protein expressions of spinal Pax2, NFAT5, and mRNA levels of ET-1 and ETAR, but not ETBR. Knockdown of Pax2 or NFAT5 with siRNA, or inhibition of ETAR with BQ-123 attenuated pSNL-induced pain-like behaviors. At molecular level, Pax2 siRNA, but not NFAT5 siRNA, downregulated ET-1 and ETAR, while ETAR inhibitor reduced NFAT5, indicating Pax2 in the upstream of ET-1 axis with NFAT5 in the downstream. Further, suppression of Pax2 (inhibiting ET-1) or impairment of ET-1 signaling (inhibition of ETAR and/or decrease of NFAT5) deactivated mitogen-activated protein kinases (MAPK) and nuclear factor-kappa B (NF-κB) signaling pathways, supporting the significance of functional regulation of ET-1 axis in neuropathic pain signaling. These findings demonstrate that Pax2 targeting ET-1-ETAR-NFAT5 is a novel regulatory mechanism underlying neuropathic pain.

A spontaneously immortalized Schwann cell line from aldose reductase-deficient mice as a useful tool for studying polyol pathway and aldehyde metabolism.

The increased glucose flux into the polyol pathway via aldose reductase (AR) is recognized as a major contributing factor for the pathogenesis of diabetic neuropathy, whereas little is known about the functional significance of AR in the peripheral nervous system. Spontaneously immortalized Schwann cell lines established from long-term cultures of AR-deficient and normal C57BL/6 mouse dorsal root ganglia and peripheral nerves can be useful tools for studying the physiological and pathological roles of AR. These cell lines, designated as immortalized knockout AR Schwann cells 1 (IKARS1) and 1970C3, respectively, demonstrated distinctive Schwann cell phenotypes, such as spindle-shaped morphology and immunoreactivity to S100, p75 neurotrophin receptor, and vimentin, and extracellular release of neurotrophic factors. Conditioned media obtained from these cells promoted neuronal survival and neurite outgrowth of cultured adult mouse dorsal root ganglia neurons. Microarray and real-time RT-PCR analyses revealed significantly down-regulated mRNA expression of polyol pathway-related enzymes, sorbitol dehydrogenase and ketohexokinase, in IKARS1 cells compared with those in 1970C3 cells. In contrast, significantly up-regulated mRNA expression of aldo-keto reductases (AKR1B7 and AKR1B8) and aldehyde dehydrogenases (ALDH1L2, ALDH5A1, and ALDH7A1) was detected in IKARS1 cells compared with 1970C3 cells. Exposure to reactive aldehydes (3-deoxyglucosone, methylglyoxal, and 4-hydroxynonenal) significantly up-regulated the mRNA expression of AKR1B7 and AKR1B8 in IKARS1 cells, but not in 1970C3 cells. Because no significant differences in viability between these two cell lines after exposure to these aldehydes were observed, it can be assumed that the aldehyde detoxification is taken over by AKR1B7 and AKR1B8 in the absence of AR.

Oval Cells Contribute to Fibrogenesis of Marginal Liver Grafts under Stepwise Regulation of Aldose Reductase and Notch Signaling.

Background and Aims: Expanded donor criteria poses increased risk for late phase complications such as fibrosis that lead to graft dysfunction in liver transplantation. There remains a need to elucidate the precise mechanisms of post-transplant liver damage in order to improve the long-term outcomes of marginal liver grafts. In this study, we aimed to examine the role of oval cells in fibrogenic development of marginal liver grafts and explore the underlying mechanisms. Methods: Using an orthotopic rat liver transplantation model and human post-transplant liver biopsy tissues, the dynamics of oval cells in marginal liver grafts was evaluated by the platform integrating immuno-labeling techniques and ultrastructure examination. Underlying mechanisms were further explored in oval cells and an Aldose reductase (AR) knockout mouse model simulating marginal graft injury. Results: We demonstrated that activation of aldose reductase initiated oval cell proliferation in small-for-size fatty grafts during ductular reaction at the early phase after transplantation. These proliferative oval cells subsequently showed prevailing biliary differentiation and exhibited features of mesenchymal transition including dynamically co-expressing epithelial and mesenchymal markers, developing microstructures for extra-cellular matrix degradation (podosomes) or cell migration (filopodia and blebs), and acquiring the capacity in collagen production. Mechanistic studies further indicated that transition of oval cell-derived biliary cells toward mesenchymal phenotype ensued fibrogenesis in marginal grafts under the regulation of notch signaling pathway. Conclusions: Oval cell activation and their subsequent lineage commitment contribute to post-transplant fibrogenesis of small-for-size fatty liver grafts. Interventions targeting oval cell dynamics may serve as potential strategies to refine current clinical management.

Endothelial overexpression of endothelin-1 modulates aortic, carotid, iliac and renal arterial responses in obese mice.

Endothelin-1 (ET-1) is essential for mammalian development and life, but it has also been implicated in increased cardiovascular risk under pathophysiological conditions. The aim of this study was to determine the impact of endothelial overexpression of the prepro-endothelin-1 gene on endothelium-dependent and endothelium-independent responses in the conduit and renal arteries of lean and obese mice. Obesity was induced by high-fat-diet (HFD) consumption in mice with Tie-1 promoter-driven, endothelium-specific overexpression of the prepro-endothelin-1 gene (TEThet) and in wild-type (WT) littermates on a C57BL/6N background. Isometric tension was measured in rings (with endothelium) of the aorta (A), carotid (CA) and iliac (IA) arteries as well as the main (MRA) and segmental renal (SRA) arteries; all experiments were conducted in the absence or presence of L-NAME and/or the COX inhibitor meclofenamate. The release of prostacyclin and thromboxane A2 was measured by ELISA. In the MRA, TEThet per se increased contractions to endothelin-1, but the response was decreased in SRA in response to serotonin; there were also improved relaxations to acetylcholine but not insulin in the SRA in the presence of L-NAME. HFD per se augmented the contractions to endothelin-1 (MRA) and to the thromboxane prostanoid (TP) receptor agonist U46619 (CA, MRA) as well as facilitated relaxations to isoproterenol (A). The combination of HFD and TEThet overexpression increased the contractions of MRA and SRA to vasoconstrictors but not in the presence of meclofenamate; this combination also augmented further relaxations to isoproterenol in the A. Contractions to endothelin-1 in the IA were prevented by endothelin-A receptor antagonist BQ-123 but only attenuated in obese mice by BQ-788. The COX-1 inhibitor FR122047 abolished the contractions of CA to acetylcholine. The release of prostacyclin during the latter condition was augmented in samples from obese TEThet mice and abolished by FR122047. These findings suggest that endothelial TEThet overexpression in lean animals has minimal effects on vascular responsiveness. However, if comorbid with obesity, endothelin-1-modulated, prostanoid-mediated renal arterial dysfunction becomes apparent.

Cancer cell-secreted IGF2 instigates fibroblasts and bone marrow-derived vascular progenitor cells to promote cancer progression.

Local interactions between cancer cells and stroma can produce systemic effects on distant organs to govern cancer progression. Here we show that IGF2 secreted by inhibitor of differentiation (Id1)-overexpressing oesophageal cancer cells instigates VEGFR1-positive bone marrow cells in the tumour macroenvironment to form pre-metastatic niches at distant sites by increasing VEGF secretion from cancer-associated fibroblasts. Cancer cells are then attracted to the metastatic site via the CXCL5/CXCR2 axis. Bone marrow cells transplanted from nude mice bearing Id1-overexpressing oesophageal tumours enhance tumour growth and metastasis in recipient mice, whereas systemic administration of VEGFR1 antibody abrogates these effects. Mechanistically, IGF2 regulates VEGF in fibroblasts via miR-29c in a p53-dependent manner. Analysis of patient serum samples showed that concurrent elevation of IGF2 and VEGF levels may serve as a prognostic biomarker for oesophageal cancer. These findings suggest that the Id1/IGF2/VEGF/VEGFR1 cascade plays a critical role in tumour-driven pathophysiological processes underlying cancer progression.

Crosstalk of metabolic factors and neurogenic signaling in adult neurogenesis: Implication of metabolic regulation for mental and neurological diseases.

Metabolic disorders like diabetes and obesity are commonly companied with neurological diseases and psychiatric disorders. Accumulating evidences indicated that cellular metabolic factors affect adult neurogenesis and have modulating effects on neurodegenerative disorders and psychiatric diseases. Adult neurogenesis contains multiple steps including proliferation of neural stem cells, lineage commitments of neural progenitor cells, maturation into functional neurons, and integration into neuronal network. Many intrinsic and extrinsic factors produced from neural stem/progenitor cells and their microenvironment or neurogenic niche take roles in modulating neurogenesis and contribute to the brain repair and functional recoveries in many neurological diseases and psychiatric disorders. In this article, we review current progress about how different growth factors, neurotrophin, neurotransmitters and transcriptional factors work on regulating neurogenic process. In particular, we emphasize the roles of the cellular metabolic factors, such as insulin/IGF signaling, incretins, and lipid metabolic signaling molecules in modulating adult neurogenesis, and discuss their impacts on neurological behaviors. We propose that the metabolic factors could be the new therapeutic targets for adult neurogenesis. Plus, the metabolism-regulating drugs have the potentials for treatment of neurodegenerative diseases and mental disorders.

Longitudinal Assessments of Normal and Perilesional Tissues in Focal Brain Ischemia and Partial Optic Nerve Injury with Manganese-enhanced MRI.

Although manganese (Mn) can enhance brain tissues for improving magnetic resonance imaging (MRI) assessments, the underlying neural mechanisms of Mn detection remain unclear. In this study, we used Mn-enhanced MRI to test the hypothesis that different Mn entry routes and spatiotemporal Mn distributions can reflect different mechanisms of neural circuitry and neurodegeneration in normal and injured brains. Upon systemic administration, exogenous Mn exhibited varying transport rates and continuous redistribution across healthy rodent brain nuclei over a 2-week timeframe, whereas in rodents following photothrombotic cortical injury, transient middle cerebral artery occlusion, or neonatal hypoxic-ischemic brain injury, Mn preferentially accumulated in perilesional tissues expressing gliosis or oxidative stress within days. Intravitreal Mn administration to healthy rodents not only allowed tracing of primary visual pathways, but also enhanced the hippocampus and medial amygdala within a day, whereas partial transection of the optic nerve led to MRI detection of degrading anterograde Mn transport at the primary injury site and the perilesional tissues secondarily over 6 weeks. Taken together, our results indicate the different Mn transport dynamics across widespread projections in normal and diseased brains. Particularly, perilesional brain tissues may attract abnormal Mn accumulation and gradually reduce anterograde Mn transport via specific Mn entry routes.

Aldose reductase deficiency leads to oxidative stress-induced dopaminergic neuronal loss and autophagic abnormality in an animal model of Parkinson's disease.

Fungicide exposure causes degeneration of dopaminergic neurons and contributes to Parkinson's disease (PD). Benomyl inhibits enzymes responsible for detoxifying the reactive dopamine metabolite 3,4-dihydroxyphenylacetaldehyde. Aldose reductase (AR) is known as tetrahydrobiopterin (BH4) reductase that generates BH4, a cofactor for tyrosine hydroxylase (TH) involved in dopamine synthesis. AR also acts as an aldehyde reductase involved in detoxifying 3,4-dihydroxyphenylacetaldehyde. In PD patients, the level of AR is significantly lower in the cerebellum. To determine if AR deficiency contributes to PD, AR wild-type (AR+/+) and knockout (AR-/-) mice were administrated with 1-methyl-4-phenyl -1,2,3,6- tetrahydropyridine (MPTP). The MPTP-treated AR-/- mice showed more severe behavioral deficits and brain damage than that of AR+/+ mice. Contrary to expectation, under normal or MPTP-treated condition, AR-/- mice showed a significant elevation of BH4 and dopamine in the midbrain, suggesting that either AR does not contribute to BH4 production, or other BH4 synthetic pathways are induced. The AR-/- brain showed upregulation of peroxynitrite, inducible nitric oxide synthase and downregulation of antioxidant enzymes, Cu/Zn superoxide dismutase (SOD) and peroxiredoxin 2 (Prx2), which indicate an increase in oxidative stress. In line with the animal data, pretreating the SH-SY5Y cells with AR inhibitors (Fidarestat or Epalrestat) before MPP+ treatment, increased severe cell death and mitochondrial fragmentation with downregulation of SOD were observed when compared to the MPP+ treatment alone. Cycloxygenase 2 (COX2), which can lead to the oxidation of dopamine, was upregulated in AR-/- brains. Autophagic proteins, beclin-1 and LC3B were also downregulated. The loss of dopaminergic neurons was associated with activation of p-ERK1/2. These findings suggest that AR plays an important role in protecting dopaminergic neuron against neurotoxic metabolites in PD.

Crosstalk between astrocytic CXCL12 and microglial CXCR4 contributes to the development of neuropathic pain.

BACKGROUND: Chemokine axis chemokine C-X-C motif ligand 12/C-X-C chemokine receptor type 4 (CXCL12/CXCR4) is an emerging pain modulator, but mechanisms for its involvement in neuropathic pain remain unclear. Here, we aimed to study whether CXCL12/CXCR4 axis modulated the development of neuropathic pain via glial mechanisms. In this study, two mouse models of neuropathic pain, namely partial sciatic nerve ligation (pSNL) model and chronic post-ischemia pain (CPIP) model, were used. RESULTS: In the dorsal horn of L3-L5 segment of spinal cord, CXCL12 and CXCR4 were expressed in both astrocyte and microglia in normal mice. In the pSNL or CPIP model, the expression level of CXCL12 in the ipsilateral L3-L5 segment of mice spinal cord was increased in an astrocyte-dependent manner on post-operative day (POD) 3. Intrathecal administration of CXCL12 with AMD3100 (CXCR4 antagonist) or minocycline (microglia activation inhibitor), but not fluorocitrate (astrocyte activation inhibitor), reversed CXCL12-indued mechanical allodynia in naïve mice. In these models, AMD3100 and AMD3465 (CXCR4 antagonist), administered daily from 1 h before surgery and up to POD 3, attenuated the development of mechanical allodynia. Moreover, AMD3100 administered daily from 1 h before surgery and up to POD 3 downregulated mRNA levels of tumor necrosis factor alpha, interleukin 1ß, and interleukin 6 in the ipsilateral L3-L5 segment of spinal cord in the pSNL and CPIP models on POD 3. CONCLUSION: This study demonstrates the crosstalk between astrocytic CXCL12 and microglial CXCR4 in the pathogenesis of neuropathic pain using pSNL and CPIP models. Our results offer insights for the future research on CXCL12/CXCR4 axis and neuropathic pain therapy.