Neuroscience
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Lipophilic neurotransmitters (NTs) such as dopamine are chemical messengers enabling neurotransmission by adhering onto the extracellular surface of the post-synaptic membrane in a synapse, followed by binding to their receptors. Previous studies have shown that the strength of the NT-membrane association is dependent on the lipid composition of the membrane. Negatively charged lipids such as phosphatidylserine, phosphatidylglycerol, and phosphatidic acid have been indicated to promote NT-membrane binding, however these anionic lipids reside almost exclusively in the intracellular leaflet of the post-synaptic membrane instead of the extracellular leaflet facing the synaptic cleft. ⋯ The in silico results suggest that gangliosides form a charge-based vestibule in front of the post-synaptic membrane, attracting amphipathic NTs to the vicinity of the membrane. The results also stress the importance to understand the significance of the structural details of NTs, as exemplified by the GM1-acetylcholine interaction. In a larger context, the NT-membrane adherence, coupled to lateral diffusion in the membrane plane, is proposed to improve neurotransmission efficiency by advancing NT entry into the membrane-embedded ligand-binding sites.
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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. ⋯ 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.
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Besides physical insult, spinal cord injury (SCI) can also result from transient ischemia, such as ischemia-reperfusion SCI (I/R SCI) as a postoperative complication. Increasing evidence has suggested that oxidative stress and related reactive aldehyde species are key contributors to cellular injury after SCI. Previous work in spinal cord contusion injury has demonstrated that acrolein, both a key product and an instigator of oxidative stress, contributes to post-traumatic hyperalgesia. ⋯ Taken together, these results support the causal role of acrolein in inducing hyperalgesia after I/R SCI via activation and upregulation of TRPA1 channels. Furthermore, endogenously produced acrolein resulting from metabolic abnormality in the absence of mechanical insults appears to be capable of heightening pain sensitivity after SCI. Our data also further supports the notion of acrolein scavenging as an effective analgesic as well neuroprotective strategy in conditions where oxidative stress and aldehyde toxicity is implicated.
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A disintegrin and metalloprotease protein 23 (ADAM23) is a transmembrane type I glycoprotein involved with the development and maintenance of the nervous system, including neurite outgrowth, neuronal adhesion and differentiation and regulation of synaptic transmission. In addition, ADAM23 seems to participate in immune response and tumor establishment through interaction with different members of integrin receptors. Here, we describe a novel monoclonal antibody (DL11C8) that specifically recognizes the cysteine-rich domain of both pre-protein (100 kDa) and mature (70 kDa) forms of ADAM23 from different species, including human, rodents and avian orthologs. ⋯ Indeed, the mature ADAM2370 kDa partitions between raft and non-raft membrane domains, while the pro-protein ADAM23100 kDa is mainly expressed in non-raft domains. These membranous distributions were observed in both different brain regions homogenates and primary cultured neurons lysates from mouse cortex and cerebellum. Taken together, these findings point out ADAM23 as a lipid raft molecular component.
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Previous studies have shown that chronic stress and chronic stress hormone treatment induce oxidative damage in rodents. Thioredoxin (Trx) is a small redox protein that plays an important role in regulation of oxidative protein cysteine modification. A Trx reduced state is maintained by thioredoxin reductase (TrxR), and the thioredoxin-interacting protein (Txnip) is an endogenous inhibitor of Trx. ⋯ Using immunocytochemistry we also found that chronic corticosterone treatment increased Txnip in both nucleus and cytosol, while glucocorticoid receptor inhibitor RU486 can block corticosterone-increased Txnip protein levels. Using biotin switch, dimedone conjugation and CRISPR/Cas9 methods we found that chronic corticosterone treatment increased protein nitrosylation and sulfenylation, while knocking out Txnip blocked corticosterone-induced protein nitrosylation and sulfenylation. Since Trx can reduce cysteine oxidative protein modification such as nitrosylation and sulfenylation, our findings suggest that chronic corticosterone treatment may upregulate Txnip by targeting glucocorticoid receptor, subsequently inhibiting Trx activity and enhancing oxidative protein cysteine modification, which contributes to corticosterone-caused oxidative damage.