Calbindin-D28K expression induced by glial cell line-derived neurotrophic factor in substantia nigra neurons dependent on PI3K/Akt/NF-kappaB signaling pathway

Glial cell line-derived neurotrophic factor contributes to alcoholic-induced liver injury by regulating the NF-κB pathway

BACKGROUND

Alcoholic liver disease (ALD) is associated with high morbidity and mortality worldwide. The pathogenesis of ALD is not completely understood. Although accumulating evidence suggests an important role of glial cell line-derived neurotrophic factor (GDNF) in several diseases, there are no data concerning its role in ALD. This study compared patients with ALD with control subjects and used a mouse model and a cell culture model to investigate the function of GDNF in ALD and its mechanism of action in hepatocyte injury.

METHODS

Serum levels of GDNF were measured in 25 patients with ALD and 25 healthy control subjects. A 4-week Lieber-DeCarli ethanol (EtOH) liquid diet combined with the Gao-Binge model was used in the mouse study. Mouse primary hepatocytes and Huh-7 cells were used for cell experiments. The parameters of liver injury, inflammatory cytokines, and lipid metabolism were measured.

RESULTS

Patients with alcoholic hepatitis had higher serum GDNF than control subjects. Expression of GDNF mRNA and protein was markedly increased in mice in the chronic-plus-binge ALD mouse model. The level of GDNF mRNA was upregulated in primary hepatic stellate cells isolated from ethanol-fed mouse liver. Ethanol induced GDNF expression in LX2 cells. The levels of inflammatory cytokines (tumor necrosis factor α, interleukin 1β, and monocyte chemotactic protein 1) were significantly increased after GDNF stimulation in primary hepatocytes and Huh-7 cells. After GDNF stimulation, levels of both p-AKT and p-NF-κB were significantly increased in primary hepatocytes and Huh-7 cells. The NF-κB activity induced by GDNF was significantly decreased by an NF-κB inhibitor, which limited hepatocyte injury and inflammation.

CONCLUSIONS

The concentration of GDNF is increased in the circulation of ALD patients. GDNF promotes alcohol-induced liver injury and inflammation via the activation of NF-κB, which mediates hepatocyte injury and inflammatory cytokine expression. Based on these findings, GDNF is a potential therapeutic target for preventing or ameliorating liver injury in ALD.

Possible role of glial cell line-derived neurotrophic factor for predicting cognitive impairment in Parkinson's disease: a case-control study

Glial cell line-derived neurotrophic factor (GDNF) plays an important role in the protection of dopaminergic neurons, but there are few reports of the relationship between GDNF and its precursors (α-pro-GDNF and β-pro-GDNF) and cognitive impairment in Parkinson’s disease. This study aimed to investigate the relationship between the serum levels of GDNF and its precursors and cognitive impairment in Parkinson’s disease, and to assess their potential as a diagnostic marker. Fifty-three primary outpatients and hospitalized patients with Parkinson’s disease (23 men and 30 women) with an average age of 66.58 years were enrolled from the Affiliated Hospital of Xuzhou Medical University of China in this case-control study. The patients were divided into the Parkinson’s disease with cognitive impairment group (n = 27) and the Parkinson’s disease with normal cognitive function group (n = 26) based on their Mini-Mental State Examination, Montreal Cognitive Assessment, and Clinical Dementia Rating scores. In addition, 26 age- and sex-matched healthy subjects were included as the healthy control group. Results demonstrated that serum GDNF levels were significantly higher in the Parkinson’s disease with normal cognitive function group than in the other two groups. There were no significant differences in GDNF precursor levels among the three groups. Correlation analysis revealed that serum GDNF levels, GDNF/α-pro-GDNF ratios, and GDNF/β-pro-GDNF ratios were moderately or highly correlated with the Mini-Mental State Examination, Montreal Cognitive Assessment, and Clinical Dementia Rating scores. To explore the risk factors for cognitive impairment in patients with Parkinson’s disease, logistic regression analysis and stepwise linear regression analysis were performed. Both GDNF levels and Hoehn-Yahr stage were risk factors for cognitive impairment in Parkinson’s disease, and were the common influencing factors for cognitive scale scores. Neither α-pro-GDNF nor β-pro-GDNF was risk factors for cognitive impairment in Parkinson’s disease. A receiver operating characteristic curve of GDNF was generated to predict cognitive function in Parkinson’s disease (area under the curve = 0.859). This result indicates that the possibility that serum GDNF can correctly distinguish whether patients with Parkinson’s disease have cognitive impairment is 0.859. Together, these results suggest that serum GDNF may be an effective diagnostic marker for cognitive impairment in Parkinson’s disease. However, α-pro-GDNF and β-pro-GDNF are not useful for predicting cognitive impairment in this disease. This study was approved by Ethics Committee of the Affiliated Hospital of Xuzhou Medical University, China (approval No. XYFY2017-KL047-01) on November 30, 2017.

The reversible effects of glial cell line-derived neurotrophic factor (GDNF) in the human brain

Glial cell line-derived neurotrophic factor (GDNF) is a potent survival factor, and a member of the transforming growth factor β (TGF-β) superfamily acting on different neuronal activities. GDNF was originally identified as a neurotrophic factor crucially involved in the survival of dopaminergic neurons of the nigrostriatal pathway and is currently an established therapeutic target in Parkinson's disease. However, GDNF was later reported to be highly expressed in gliomas, especially in glioblastomas, and was demonstrated as a potent proliferation factor involved in the development and migration of gliomas. Here, we review our current understanding and progress made so far by researchers in our laboratories with references to relevant articles to support our discoveries. We present past and recent discoveries on the mechanisms involved in the protection of neurons by GDNF and examine its emerging roles in gliomas, as well as reasons for the abnormal expression in Glioblastoma Multiforme (GBM). Collectively, our work establishes a paradigm by which the ability of GDNF to protect dopaminergic neurons from degradation and its corresponding effects on glioma cells points to an underlying biological vulnerability in the effects of GDNF in the normal brain which can be subverted for use by cancer cells. Hence, presenting novel opportunities for intervention in glioma therapies.

Quantitative proteomic analysis of Parkin substrates in Drosophila neurons

BACKGROUND

Parkin (PARK2) is an E3 ubiquitin ligase that is commonly mutated in Familial Parkinson's Disease (PD). In cell culture models, Parkin is recruited to acutely depolarised mitochondria by PINK1. PINK1 activates Parkin activity leading to ubiquitination of multiple proteins, which in turn promotes clearance of mitochondria by mitophagy. Many substrates have been identified using cell culture models in combination with depolarising drugs or proteasome inhibitors, but not in more physiological settings.

METHODS

Here we utilized the recently introduced BioUb strategy to isolate ubiquitinated proteins in flies. Following Parkin Wild-Type (WT) and Parkin Ligase dead (LD) expression we analysed by mass spectrometry and stringent bioinformatics analysis those proteins differentially ubiquitinated to provide the first survey of steady state Parkin substrates using an in vivo model. We further used an in vivo ubiquitination assay to validate one of those substrates in SH-SY5Y cells.

RESULTS

We identified 35 proteins that are more prominently ubiquitinated following Parkin over-expression. These include several mitochondrial proteins and a number of endosomal trafficking regulators such as v-ATPase sub-units, Syx5/STX5, ALiX/PDCD6IP and Vps4. We also identified the retromer component, Vps35, another PD-associated gene that has recently been shown to interact genetically with parkin. Importantly, we validated Parkin-dependent ubiquitination of VPS35 in human neuroblastoma cells.

CONCLUSIONS

Collectively our results provide new leads to the possible physiological functions of Parkin activity that are not overtly biased by acute mitochondrial depolarisation.

Integrated mass spectrometry imaging and omics workflows on the same tissue section using grid-aided, parafilm-assisted microdissection

BACKGROUND

In spite of the number of applications describing the use of MALDI MSI, one of its major drawbacks is the limited capability of identifying multiple compound classes directly on the same tissue section.

METHODS

We demonstrate the use of grid-aided, parafilm-assisted microdissection to perform MALDI MS imaging and shotgun proteomics and metabolomics in a combined workflow and using only a single tissue section. The grid is generated by microspotting acid dye 25 using a piezoelectric microspotter, and this grid was used as a guide to locate regions of interest and as an aid during manual microdissection. Subjecting the dissected pieces to the modified Folch method allows to separate the metabolites from proteins. The proteins can then be subjected to digestion under controlled conditions to improve protein identification yields.

RESULTS

The proof of concept experiment on rat brain generated 162 and 140 metabolite assignments from three ROIs (cerebellum, hippocampus and midbrain/hypothalamus) in positive and negative modes, respectively, and 890, 1303 and 1059 unique proteins. Integrated metabolite and protein overrepresentation analysis identified pathways associated with the biological functions of each ROI, most of which were not identified when looking at the protein and metabolite lists individually.

CONCLUSIONS

This combined MALDI MS imaging and multi-omics approach further extends the amount of information that can be generated from single tissue sections.

GENERAL SIGNIFICANCE

To the best of our knowledge, this is the first report combining both imaging and multi-omics analyses in the same workflow and on the same tissue section.

Gelatin Nanostructured Lipid Carriers Incorporating Nerve Growth Factor Inhibit Endoplasmic Reticulum Stress-Induced Apoptosis and Improve Recovery in Spinal Cord Injury

Clinical translation of growth factor therapies faces multiple challenges; the most significant one is the short half-life of the naked protein. Gelatin nanostructured lipid carriers (GNLs) had previously been used to encapsulate the basic fibroblast growth factor to enhance the functional recovery in hemiparkinsonian rats. In this research, we comparatively study the enhanced therapy between nerve growth factor (NGF) loaded GNLs (NGF-GNLs) and NGF only in spinal cord injury (SCI). The effects of NGF-GNLs and NGF only were tested by the Basso-Beattie-Bresnahan (BBB) locomotion scale, inclined plane test, and footprint analysis. Western blot analysis and immunofluorescent staining were further performed to identify the expression of ER stress-related proteins, neuron-specific marker neuronal nuclei (NeuN), and growth-associated protein 43 (GAP43). Correlated downstream signals Akt/GSK-3β and ERK1/2 were also analyzed with or without inhibitors. Results showed that NGF-GNLs, compared to NGF only, enhanced the neuroprotection effect in SCI rats. The ER stress-induced apoptosis response proteins CHOP, GRP78 and caspase-12 inhibited by NGF-GNL treatment were more obvious. Meanwhile, NGF-GNLs in the recovery of SCI are related to the inhibition of ER stress-induced cell death via the activation of downstream signals PI3K/Akt/GSK-3β and ERK1/2.

New alterations at potentially regulated regions of the Glial Derived Neurotrophic Factor gene in bipolar disorder

INTRODUCTION

Glial Derived Neurotrophic Factor (GDNF) plays an important role in the survival and differentiation of neurons. We examined 5'upstream and 3' untranslated region of the GDNF gene by PCR amplification and direct sequencing to explore the effect of alteration in the potentially regulated part of GDNF in bipolar disorder.

MATERIALS AND METHODS

Sixty-six patients with bipolar disorder, 27 first degree relatives of these patients and 56 healthy volunteers were screened for mutations and polymorphisms in GDNF gene.

RESULTS

Seven previously reported polymorphisms and additional three novel allele variants of GDNF were detected. Association test of rs2075680 C>A SNP showed significant difference between patients and healthy subjects with higher allele frequency in healthy subjects performing Chi-square test. However, there was no significant difference after multiple test corrections between groups. There were no significant differences in association test of rs2075680 C>A SNP between first degree relatives and healthy volunteers/patients. rs142426358 T>C SNP was seen only in one patient with an early age of illness onset. New T>A alterations were found in chromosome locations 5:37812784 and 5:37812782 in two male bipolar disorder patients with age of illness onset 12 and 24 years.

LIMITATIONS

The sample size was relatively small.

DISCUSSION

Our study proposes the suggestive association between polymorphisms in the potential regulatory sites of GDNF and bipolar disorder.

Vitamin D and atherosclerosis

PURPOSE OF REVIEW

To provide an overview of the association between vitamin D deficiency and atherosclerosis.

RECENT FINDINGS

Vitamin D exerts protective effects on atherosclerosis through multiple mechanisms. It has been shown to protect against endothelial dysfunction, vascular smooth muscle cell proliferation and migration, and modulation of the immune system, as well as the inflammatory response. In addition, vitamin D has been shown to have systemic effects on insulin resistance, dyslipidemia, and hypertension.

SUMMARY

Vitamin D deficiency is widely prevalent in the United States and worldwide. Although deficiency of this fat-soluble vitamin is usually associated with musculoskeletal disorder, it is associated with a wide range of disease processes that include multiple organ systems. Recently, there has been mounting evidence linking vitamin D deficiency to cardiovascular disease and atherosclerosis.

GDNF is a novel ethanol-responsive gene in the VTA: implications for the development and persistence of excessive drinking

Glial cell line-derived neurotrophic factor (GDNF) is a potent inhibitor of ethanol consumption and relapse, and GDNF heterozygous knockout mice display increased reward sensitivity to ethanol and consume more ethanol after a period of abstinence than their wild-type littermates. Here, we tested whether ethanol alters GDNF expression in the ventral tegmental area (VTA; GDNF's site of action) and/or the nucleus accumbens (NAc; the main source of GDNF), and if so, determine the role of the endogenous growth factor in the regulation of ethanol consumption. Systemic administration of ethanol increased GDNF expression and protein levels in the VTA, but not the NAc. Additionally, GDNF levels were elevated after an ethanol-drinking session in rats that consumed ethanol in the intermittent-access two-bottle choice procedure for 1 week, but not 7 weeks. Deprivation following 7 weeks of excessive ethanol intake reduced GDNF levels, while a short ethanol binge drinking period following deprivation upregulated GDNF expression. Importantly, knockdown of GDNF within the VTA using adenovirus expressing short hairpin RNA facilitated the escalation of ethanol drinking by ethanol-naïve rats, but not by rats with a history of excessive ethanol consumption. These results suggest that during initial ethanol-drinking experiences, GDNF in the VTA is increased and protects against the development of excessive ethanol intake. However, the growth factor's protective response to ethanol breaks down after protracted excessive ethanol intake and withdrawal, resulting in persistent, excessive ethanol consumption.

Physiological Function and Characterization of TRPCs in Neurons

Ca²⁺ entry is essential for regulating vital physiological functions in all neuronal cells. Although neurons are engaged in multiple modes of Ca²⁺ entry that regulates variety of neuronal functions, we will only discuss a subset of specialized Ca²⁺-permeable non-selective Transient Receptor Potential Canonical (TRPC) channels and summarize their physiological and pathological role in these excitable cells. Depletion of endoplasmic reticulum (ER) Ca²⁺ stores, due to G-protein coupled receptor activation, has been shown to activate TRPC channels in both excitable and non-excitable cells. While all seven members of TRPC channels are predominately expressed in neuronal cells, the ion channel properties, mode of activation, and their physiological responses are quite distinct. Moreover, many of these TRPC channels have also been suggested to be associated with neuronal development, proliferation and differentiation. In addition, TRPCs also regulate neurosecretion, long-term potentiation and synaptic plasticity. Similarly, perturbations in Ca²⁺ entry via the TRPC channels have been also suggested in a spectrum of neuropathological conditions. Hence, understanding the precise involvement of TRPCs in neuronal function and in neurodegenerative conditions would presumably unveil avenues for plausible therapeutic interventions for these devastating neuronal diseases.

The effect of acute administration of vitamin D on micro vascular endothelial function in Caucasians and South Asian Indians

BACKGROUND

Vitamin D is a modulator of the immune system. There is some limited evidence that it also increases local blood flow in response to stress.

MATERIAL AND METHODS

In the present study, we examined 20 age matched subjects; 10 whom were from India and 10 Caucasians from the United States. Subjects were administered 4000 IU of Vitamin D3 for 3 weeks at breakfast. The function of the endothelial cells was evaluated in 2 ways; first, the response to 4 minutes of vascular occlusion was measured with a laser Doppler flow meter and second, the blood flow response to local heat at 42°C for 6 minutes.

RESULTS

The results of the experiments showed that, as reported previously, the endothelial function in people from India was less than their Caucasian counterparts. The blood flow response to heat was reduced after 3 weeks administration of vitamin D in both groups and the response to vascular occlusion in the Caucasian group. But there was only a 20% reduction in the blood flow response to heat in the Caucasian group and a 50% reduction in the group from India.

CONCLUSIONS

Thus acute doses of vitamin D may increase vascular tone and reduce blood flow to tissue during stressors. Dosages administered for a longer duration may have beneficial effects on endothelial function but this was not examined here.

Role of calbindin-D28K in estrogen treatment for Parkinson's disease

Studies have shown that estrogen has neuroprotective effects on the nigrostriatal system. The present study established a Parkinson's disease model in C57BL/6 mice by intraperitoneal injection of 1-methyl-4-phenyl-1,2,3,6-tetrapyridine. The mice were subjected to 17β estradiol injection into the lateral ventricle. Immunofluorescence double staining showed that estrogen increased tyrosine hydroxylase and calbindin-D28K expression and co-expression in dopaminergic neurons of midbrain substantia nigra pars compacta of model mice. Behavior experiments showed that estrogen improved swimming and hanging behaviors in this mouse model of Parkinson's disease.

Parkinson's disease: don't mess with calcium

The hallmark of the movement disorder Parkinson's disease (PD) is progressive degeneration of dopaminergic neurons. Mitochondrial dysfunction, impaired ubiquitin-mediated proteolysis of α-synuclein, and ER stress are each implicated in the complex and poorly understood sequence of events leading to dopaminergic neuron demise. In this issue of the JCI, Selvaraj et al. report that in a mouse neurotoxin-based model of PD, reduced Ca2+ influx through transient receptor potential C1 (TRPC1) channels in the plasma membrane of dopaminergic neurons triggers a cell death-inducing ER stress response. These new findings suggest that TRPC1 channels normally function in Ca2+-mediated signaling pathways that couple adaptive/neurotrophic responses to metabolic and oxidative stress and suggest that disruption of these pathways may contribute to PD.

Pitx3 is a critical mediator of GDNF-induced BDNF expression in nigrostriatal dopaminergic neurons

Pitx3 is a critical homeodomain transcription factor for the proper development and survival of mesodiencephalic dopaminergic (mdDA) neurons in mammals. Several variants of this gene have been associated with human Parkinson's disease (PD), and lack of Pitx3 in mice causes the preferential loss of substantia nigra pars compacta (SNc) mdDA neurons that are most affected in PD. It is currently unclear how Pitx3 activity promotes the survival of SNc mdDA neurons and which factors act upstream and downstream of Pitx3 in this context. Here we show that a transient expression of glial cell line-derived neurotrophic factor (GDNF) in the murine ventral midbrain (VM) induces transcription of Pitx3 via NF-κB-mediated signaling, and that Pitx3 is in turn required for activating the expression of brain-derived neurotrophic factor (BDNF) in a rostrolateral (SNc) mdDA neuron subpopulation during embryogenesis. The loss of BDNF expression correlates with the increased apoptotic cell death of this mdDA neuronal subpopulation in Pitx3(-/-) mice, whereas treatment of VM cell cultures with BDNF augments the survival of the Pitx3(-/-) mdDA neurons. Most importantly, only BDNF but not GDNF protects mdDA neurons against 6-hydroxydopamine-induced cell death in the absence of Pitx3. As the feedforward regulation of GDNF, Pitx3, and BDNF expression also persists in the adult rodent brain, our data suggest that the disruption of the regulatory interaction between these three factors contributes to the loss of mdDA neurons in Pitx3(-/-) mutant mice and perhaps also in human PD.

Calbindin-D28K inhibits apoptosis in dopaminergic neurons by activation of the PI3-kinase-Akt signaling pathway

Calbindin-D28k (CaBP) has a neuroprotective effect on dopaminergic (DA) neurons in several models of Parkinson's disease. We used the DA cell line MN9D to explore the mechanisms underlying CaBP-mediated protection against the neurotoxin 6-hydroxydopamine (6-OHDA) of DA neurons. In MN9D cells that were transfected with the expression vector pcDNA3-CB containing CaBP cDNA, the expression level of CaBP was significantly increased. After treating with 6-OHDA, a significant decrease in the apoptosis rate of the transfected MN9D cells was noted, as well as an obvious increase in the expression of phosphorylation of Akt (p-Akt); however, no significant change in the expression of total Akt or phospho-p100 (p-p100) occurred after this treatment. After treatment with wortmannin, an inhibitor of the PI3-kinase-Akt (PI-3K/Akt) signal pathway, an increase in the expression level of CaBP was observed, but there were no other obvious changes of the experimental index mentioned previously in the groups transfected with pcDNA3-CB. These studies suggest that CaBP has a significant role in protecting DA cells against the apoptosis induced by 6-OHDA--through PI-3K/Akt signaling pathway--where the non-canonical nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling pathway might have no relevance.

c-Ret-mediated hearing loss in mice with Hirschsprung disease

A significantly increased risk for dominant sensorineural deafness in patients who have Hirschsprung disease (HSCR) caused by endothelin receptor type B and SOX10 has been reported. Despite the fact that c-RET is the most frequent causal gene of HSCR, it has not been determined whether impairments of c-Ret and c-RET cause congenital deafness in mice and humans. Here, we show that impaired phosphorylation of c-Ret at tyrosine 1062 causes HSCR-linked syndromic congenital deafness in c-Ret knockin (KI) mice. The deafness involves neurodegeneration of spiral ganglion neurons (SGNs) with not only impaired phosphorylation of Akt and NF-kappaB but decreased expression of calbindin D28k in inner ears. The congenital deafness involving neurodegeneration of SGNs in c-Ret KI mice was rescued by introducing constitutively activated RET. Taken together with our results for three patients with congenital deafness with c-RET-mediated severe HSCR, our results indicate that c-Ret and c-RET are a deafness-related molecule in mice and humans.

Expanding the substantial interactome of NEMO using protein microarrays

Signal transduction by the NF-kappaB pathway is a key regulator of a host of cellular responses to extracellular and intracellular messages. The NEMO adaptor protein lies at the top of this pathway and serves as a molecular conduit, connecting signals transmitted from upstream sensors to the downstream NF-kappaB transcription factor and subsequent gene activation. The position of NEMO within this pathway makes it an attractive target from which to search for new proteins that link NF-kappaB signaling to additional pathways and upstream effectors. In this work, we have used protein microarrays to identify novel NEMO interactors. A total of 112 protein interactors were identified, with the most statistically significant hit being the canonical NEMO interactor IKKbeta, with IKKalpha also being identified. Of the novel interactors, more than 30% were kinases, while at least 25% were involved in signal transduction. Binding of NEMO to several interactors, including CALB1, CDK2, SAG, SENP2 and SYT1, was confirmed using GST pulldown assays and coimmunoprecipitation, validating the initial screening approach. Overexpression of CALB1, CDK2 and SAG was found to stimulate transcriptional activation by NF-kappaB, while SYT1 overexpression repressed TNFalpha-dependent NF-kappaB transcriptional activation in human embryonic kidney cells. Corresponding with this finding, RNA silencing of CDK2, SAG and SENP2 reduced NF-kappaB transcriptional activation, supporting a positive role for these proteins in the NF-kappaB pathway. The identification of a host of new NEMO interactors opens up new research opportunities to improve understanding of this essential cell signaling pathway.

GDNF--a potential target to treat addiction

The glial cell line-derived neurotrophic factor (GDNF) is a secreted protein, best known for its role in the development of the central and peripheral nervous systems and the survival of adult dopaminergic neurons. More recently, accumulating evidence suggests that GDNF plays a unique role in negatively regulating the actions of drugs of abuse. In this article, we review these data and highlight the possibility that the GDNF pathway may be a promising target for the treatment of addiction.