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JAK/STAT pathway regulation of GABAA receptor expression after differing severities of experimental TBI.

ABSTRACT: Synaptic inhibition in the adult brain is primarily mediated by the ?-aminobutyric acid (GABA) type A receptor (GABA(A)R). The distribution, properties, and dynamics of these receptors are largely determined by their subunit composition. Alteration of subunit composition after a traumatic brain injury (TBI) may result in abnormal increased synaptic firing and possibly contribute to injury-related pathology. Several studies have shown that the Janus Kinase/Signal Transducer and Activator of Transcription (JAK/STAT) signaling pathway can alter GABA(A)R subunit expression. The present study investigated changes in JAK/STAT pathway activation after two different severities of experimental TBI in the mouse using the controlled cortical impact (CCI) model. It also investigated whether modulating the activation of the JAK/STAT pathway after severe controlled cortical impact (CCI-S) with a JAK/STAT inhibitor (WP1066) alters post-traumatic epilepsy development and/or neurological recovery after injury. Our results demonstrated differential changes in both the activation of STAT3 and the expression of the GABA(A)R ?1 and ?2 subunit levels that were dependent on the severity of the injury. The change in the GABA(A)R ?1 subunit levels appeared to be at least partly transcriptionally mediated. We were able to selectively reverse the decrease in GABA(A)R ?1 protein levels with WP1066 treatment after CCI injury. WP1066 treatment also improved the degree of recovery of vestibular motor function after injury. These findings suggest that the magnitude of JAK/STAT pathway activation and GABA(A)R ?1 subunit level decrease is dependent on injury severity in this mouse model of TBI. In addition, reducing JAK/STAT pathway activation after severe experimental TBI reverses the decrease in the GABA(A)R ?1 protein levels and improves vestibular motor recovery.

SUBMITTER: Raible DJ

PROVIDER: S-EPMC5969808 | biostudies-literature | 2015 Sep

REPOSITORIES: biostudies-literature

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JAK/STAT pathway regulation of GABAA receptor expression after differing severities of experimental TBI.

Raible Daniel J DJ Frey Lauren C LC Del Angel Yasmin Cruz YC Carlsen Jessica J Hund Dana D Russek Shelley J SJ Smith Bret B Brooks-Kayal Amy R AR

Experimental neurology 20150711

Synaptic inhibition in the adult brain is primarily mediated by the γ-aminobutyric acid (GABA) type A receptor (GABA(A)R). The distribution, properties, and dynamics of these receptors are largely determined by their subunit composition. Alteration of subunit composition after a traumatic brain injury (TBI) may result in abnormal increased synaptic firing and possibly contribute to injury-related pathology. Several studies have shown that the Janus Kinase/Signal Transducer and Activator of Trans ...[more]

PMID: 26172316

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Project description:BackgroundThe JAK/STAT pathway transduces signals from multiple cytokines and controls haematopoiesis, immunity and inflammation. In addition, pathological activation is seen in multiple malignancies including the myeloproliferative neoplasms (MPNs). Given this, drug development efforts have targeted the pathway with JAK inhibitors such as ruxolitinib. Although effective, high costs and side effects have limited its adoption. Thus, a need for effective low cost treatments remains.Methods & findingsWe used the low-complexity Drosophila melanogaster pathway to screen for small molecules that modulate JAK/STAT signalling. This screen identified methotrexate and the closely related aminopterin as potent suppressors of STAT activation. We show that methotrexate suppresses human JAK/STAT signalling without affecting other phosphorylation-dependent pathways. Furthermore, methotrexate significantly reduces STAT5 phosphorylation in cells expressing JAK2 V617F, a mutation associated with most human MPNs. Methotrexate acts independently of dihydrofolate reductase (DHFR) and is comparable to the JAK1/2 inhibitor ruxolitinib. However, cells treated with methotrexate still retain their ability to respond to physiological levels of the ligand erythropoietin.ConclusionsAminopterin and methotrexate represent the first chemotherapy agents developed and act as competitive inhibitors of DHFR. Methotrexate is also widely used at low doses to treat inflammatory and immune-mediated conditions including rheumatoid arthritis. In this low-dose regime, folate supplements are given to mitigate side effects by bypassing the biochemical requirement for DHFR. Although independent of DHFR, the mechanism-of-action underlying the low-dose effects of methotrexate is unknown. Given that multiple pro-inflammatory cytokines signal through the pathway, we suggest that suppression of the JAK/STAT pathway is likely to be the principal anti-inflammatory and immunosuppressive mechanism-of-action of low-dose methotrexate. In addition, we suggest that patients with JAK/STAT-associated haematological malignancies may benefit from low-dose methotrexate treatments. While the JAK1/2 inhibitor ruxolitinib is effective, a £43,200 annual cost precludes widespread adoption. With an annual methotrexate cost of around £32, our findings represent an important development with significant future potential.

Project description:ObjectiveTo explore the molecular mechanisms of fatty liver hemorrhagic syndrome (FLHS) in laying hens, an experiment was conducted to reveal the differences in histopathological observation and gene expression between FLHS group and normal group.MethodsWe compared the histopathological difference using hematoxylin and eosin staining and proceeded with RNA sequencing of adipose tissue to search differentially expressed genes and enriched biological processes and pathways. Then we validated the mRNA expression levels by real-time polymerase chain reaction and quantified protein levels in the circulation by enzyme-linked immunosorbent assay.ResultsWe identified 100 differentially expressed transcripts corresponding to 66 genes (DEGs) were identified between FLHS-affected group and normal group. Seven DEGs were significantly enriched in the immune response process and lipid metabolic process, including phospholipase A2 group V, WAP kunitz and netrin domain containing 2, delta 4-desaturase sphingolipid 2, perilipin 3, interleukin-6 (IL-6), ciliary neurotrophic factor (CNTF), and suppressor of cytokine signaling 3 (SOCS3). And these genes could be the targets of immune response and be involved in metabolic homeostasis during the process of FLHS in laying hens. Based on functional categories of the DEGs, we further proposed a model to explain the etiology and pathogenesis of FLHS. IL-6 and SOCS3 mediate inflammatory responses and the satiety hormone of leptin, induce dysfunction of Jak-STAT signaling pathway, leading to insulin resistance and lipid metabolic disorders. Conversely, CNTF may reduce tissue destruction during inflammatory attacks and confer protection from inflammation-induced insulin resistance in FLHS chickens.ConclusionThese findings highlight the therapeutic implications of targeting the JAK-STAT pathway. Inhibition of IL6 and SOCS3 and facilitation of CNTF could serve as a favorable strategy to enhance insulin action and improve glucose homoeostasis, which are of importance for treating obesity-related disorders for chickens.

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JAK/STAT pathway regulation of GABAA receptor expression after differing severities of experimental TBI.

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JAK/STAT pathway regulation of GABAA receptor expression after differing severities of experimental TBI.

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