ABSTRACT
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 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 α1 and γ2 subunit levels that were dependent on the severity of the injury. The change in the GABA(A)R α1 subunit levels appeared to be at least partly transcriptionally mediated. We were able to selectively reverse the decrease in GABA(A)R α1 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 α1 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 α1 protein levels and improves vestibular motor recovery.
Subject(s)
Brain Injuries/metabolism , Brain Injuries/physiopathology , Janus Kinases/metabolism , Receptors, GABA-A/metabolism , STAT Transcription Factors/metabolism , Signal Transduction/physiology , Analysis of Variance , Animals , Disease Models, Animal , Electroencephalography , Exploratory Behavior , Gene Expression Regulation/physiology , Janus Kinases/genetics , Male , Mice , Motor Activity/physiology , RNA, Messenger/metabolism , Receptors, GABA-A/genetics , Recognition, Psychology , STAT Transcription Factors/genetics , Time FactorsABSTRACT
The JAK2-STAT3 signaling pathway has been shown to regulate the expression of genes involved in cell survival, cell proliferation, cell-cycle progression, and angiogenesis in development and after cerebral insults. Until recently, little has been known about the effects of this pathway activation after cerebral insults and if blocking this pathway leads to better recovery. This review exams the role of this pathway after 3 cerebral insults (traumatic brain injury, stroke, and status epilepticus).
ABSTRACT
Oligonucleotides modified with conformationally restricted nucleotides such as locked nucleic acid (LNA) monomers are used extensively in molecular biology and medicinal chemistry to modulate gene expression at the RNA level. Major efforts have been devoted to the design of LNA derivatives that induce even higher binding affinity and specificity, greater enzymatic stability, and more desirable pharmacokinetic profiles. Most of this work has focused on modifications of LNA's oxymethylene bridge. Here, we describe an alternative approach for modulation of the properties of LNA: i.e., through functionalization of LNA nucleobases. Twelve structurally diverse C5-functionalized LNA uridine (U) phosphoramidites were synthesized and incorporated into oligodeoxyribonucleotides (ONs), which were then characterized with respect to thermal denaturation, enzymatic stability, and fluorescence properties. ONs modified with monomers that are conjugated to small alkynes display significantly improved target affinity, binding specificity, and protection against 3'-exonucleases relative to regular LNA. In contrast, ONs modified with monomers that are conjugated to bulky hydrophobic alkynes display lower target affinity yet much greater 3'-exonuclease resistance. ONs modified with C5-fluorophore-functionalized LNA-U monomers enable fluorescent discrimination of targets with single nucleotide polymorphisms (SNPs). In concert, these properties render C5-functionalized LNA as a promising class of building blocks for RNA-targeting applications and nucleic acid diagnostics.
Subject(s)
Nucleic Acids/chemistry , Oligodeoxyribonucleotides/chemistry , Oligonucleotides/chemistry , Organophosphorus Compounds/chemistry , Organophosphorus Compounds/chemical synthesis , RNA/chemistry , Uridine/analogs & derivatives , Molecular Conformation , Nucleic Acid Conformation , Uridine/chemical synthesis , Uridine/chemistryABSTRACT
The gamma-aminobutyric acid (GABA) type A receptor (GABA(A)R) is responsible for most fast synaptic inhibition in the adult brain. The GABA(A)R protein is composed of multiple subunits that determine the distribution, properties, and dynamics of the receptor. Several studies have shown that the Janus kinase/signal transducer and activator of transcription (JaK/STAT) and early growth response 3 (Egr3) signaling pathways can alter GABA(A)R subunit expression after status epilepticus (SE). In this study we investigated changes in these pathways after experimental TBI in the rat using a lateral fluid percussion injury (FPI) model. Our results demonstrated changes in the expression of several GABA(A)R subunit levels after injury, including GABA(A)R α1 and α4 subunits. This change appears to be transcriptional, and there is an associated increase in the phosphorylation of STAT3, and an increase in the expression of Egr3 and inducible cAMP element repressor (ICER) after FPI. These findings suggest that the activation of the JaK/STAT and Egr3 pathways after TBI may regulate injury-related changes in GABA(A)R subunit expression.