[Tacrolimus Induces Pain by Upregulating the Synaptic Expression of AMPA Receptors in the Spinal Cord Dorsal Horn].

Objective: To investigate the effects of long-term administration of tacrolimus (also known as FK506) on the pain-related behaviors in mice and to study the underlying mechanism of pain induced by FK506 via measuring the effect of FK506 on the synaptic expression and phosphorylation of alpha-amino-3-hyroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor in the spinal cord dorsal horn of mice.

Methods: 1) A total of 24 mice were evenly and randomly assigned to two groups, a FK506 group and a Saline group. The FK506 group was given daily intraperitoneal injection of FK506 and the Saline group received normal saline.

GPR39 regulated spinal glycinergic inhibition and mechanical inflammatory pain.

G protein-coupled receptor 39 (GPR39) senses the change of extracellular divalent zinc ion and signals through multiple G proteins to a broad spectrum of downstream effectors. Here, we found that GPR39 was prevalent at inhibitory synapses of spinal cord somatostatin-positive (SOM) interneurons, a mechanosensitive subpopulation that is critical for the conveyance of mechanical pain. GPR39 complexed specifically with inhibitory glycine receptors (GlyRs) and helped maintain glycinergic transmission in a manner independent of G protein signalings.

Upregulation of RCAN1.4 in spinal dorsal horn is involved in inflammatory pain hypersensitivity.

The calcium/calmodulin-dependent protein phosphase calcineurin (CaN) regulates synaptic plasticity by controlling the phosphorylation of synaptic proteins including AMPA type glutamate receptors. The regulator of calcineurin 1 (RCAN1) is characterized as an endogenous inhibitor of CaN and its dysregulation is implicated in multiple neurological disorders. However, whether RCAN1 is engaged in nociceptive processing in the spinal dorsal horn remains unrevealed.

BDNF modulated KCC2 ubiquitylation in spinal cord dorsal horn of mice.

The K-Cl co-transporter 2 (KCC2) is a neuron-specific Cl extruder in the dorsal horn of spinal cord. The low intracellular Cl concentration established by KCC2 is critical for GABAergic and glycinergic systems to generate synaptic inhibition. Peripheral nerve lesions have been shown to cause KCC2 dysfunction in adult spinal cord through brain-derived neurotrophic factor (BDNF) signaling, which switches the hyperpolarizing inhibitory transmission to be depolarizing and excitatory.

Functional expression of glycine receptors in DRG neurons of mice.

Glycine receptor is one of the chloride-permeable ion channels composed of combinations of four α subunits and one β subunit. In adult spinal cord, the glycine receptor α1 subunit is crucial for the generation of inhibitory neurotransmission. The reduced glycinergic inhibition is regarded as one of the key spinal mechanisms underlying pathological pain symptoms.

Ubiquitination and functional modification of GluN2B subunit-containing NMDA receptors by Cbl-b in the spinal cord dorsal horn.

-methyl-d-aspartate (NMDA) glutamate receptors (NMDARs) containing GluN2B subunits are prevalent early after birth in most brain regions in rodents. Upon synapse maturation, GluN2B is progressively removed from synapses, which affects NMDAR function and synaptic plasticity. Aberrant recruitment of GluN2B into mature synapses has been implicated in several neuropathologies that afflict adults.

Analgesic action of adenosine A1 receptor involves the dephosphorylation of glycine receptor α1 subunit in spinal dorsal horn of mice.

Glycine receptor α1 subunit is located at inhibitory synapses in the superficial dorsal horn of adult spinal cord and is engaged in the glycinergic inhibition of nociceptive neuronal excitability and transmission. The α1 phosphorylation at Ser380 by extracellular signal-regulated kinase (ERK) has been shown to decrease glycinergic synaptic currents and contribute to spinal disinhibition. Here we found that peripheral inflammation induced by Complete Freund's Adjuvant increased Ser380 phosphorylation in spinal cord dorsal horn of mice, which was repressed by specific activation of adenosine A1 receptor (A1R).

SNAP25/syntaxin4/VAMP2/Munc18-1 Complexes in Spinal Dorsal Horn Contributed to Inflammatory Pain.

Soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) have been implicated in the trafficking of postsynaptic glutamate receptors, including N-methyl-d-aspartate (NMDA)-subtype glutamate receptors (NMDARs) that are critical for nociceptive plasticity and behavioral sensitization. However, the components of SNAREs complex involved in spinal nociceptive processing remain largely unknown. Here we found that SNAP25, syntaxin4, VAMP2 and Munc18-1 were localized at postsynaptic sites and formed the complex in the superficial lamina of spinal cord dorsal horn of rats.

Spinophilin negatively controlled the function of transient receptor potential vanilloid 1 in dorsal root ganglia neurons of mice.

Protein phosphatase-1 (PP1) is ubiquitously distributed in the nervous system and catalyzes the dephosphorylation of numerous substrates. The specificity and efficacy of PP1-mediated dephosphorylation depend on scaffolding proteins that anchor PP1 to the close vicinity of substrates. Spinophilin is one of the scaffolding proteins which are able to direct PP1 into postsynaptic density and regulate the synaptic transmission and plasticity.

mGluR5/ERK signaling regulated the phosphorylation and function of glycine receptor α1ins subunit in spinal dorsal horn of mice.

Inhibitory glycinergic transmission in adult spinal cord is primarily mediated by glycine receptors (GlyRs) containing the α1 subunit. Here, we found that α1ins, a longer α1 variant with 8 amino acids inserted into the intracellular large loop (IL) between transmembrane (TM)3 and TM4 domains, was expressed in the dorsal horn of the spinal cord, distributed at inhibitory synapses, and engaged in negative control over nociceptive signal transduction. Activation of metabotropic glutamate receptor 5 (mGluR5) specifically suppressed α1ins-mediated glycinergic transmission and evoked pain sensitization.

A synthetic peptide disturbing GluN2A/SHP1 interaction in dorsal root ganglion attenuated pathological pain.

Src Homology 2 domain-containing protein tyrosine phosphatase 1 (SHP1) interacts specifically with GluN2A subunit of N-methyl-D-aspartate (NMDA) subtype of glutamate receptors in spinal cord dorsal horn. This molecular interaction is involved in the development of GluN2A-dependent spinal sensitization of nociceptive behaviors. Intrathecal application of a GluN2A-derived polypeptide (short for pep-GluN2A) has been shown to disturb spinal GluN2A/SHP1 interaction and inhibit inflammatory pain.

Ubiquitination and inhibition of glycine receptor by HUWE1 in spinal cord dorsal horn.

Glycine receptors (GlyRs) are pentameric proteins that consist of α (α1-α4) subunits and/or β subunit. In the spinal cord of adult animals, the majority of inhibitory glycinergic neurotransmission is mediated by α1 subunit-containing GlyRs. The reduced glycinergic inhibition (disinhibition) is proposed to increase the excitabilities and spontaneous activities of spinal nociceptive neurons during pathological pain.

Activity-dependent Synaptic Recruitment of Neuroligin 1 in Spinal Dorsal Horn Contributed to Inflammatory Pain.

Neuroligin 1 (NLGN1), a cell adhesion molecule present at excitatory glutamatergic synapses, has been shown to be critical for synaptic specialization and N-methyl-d-aspartate (NMDA)-subtype glutamate receptor-dependent synaptic plasticity. Whether and how NLGN1 is engaged in nociceptive behavioral sensitization remains largely unknown. In this study, we found an activity-dependent regulation of NLGN1 synaptic expression in pain-related spinal cord dorsal horns of mice.

Disruption of SHP1/NMDA receptor signaling in spinal cord dorsal horn alleviated inflammatory pain.

Src-homology 2 domain-containing protein tyrosine phosphatase-1 (SHP1) is one of the non-receptor-like phosphatases that are highly enriched in hematopoietic cells. Although accumulating evidence has implicated the protein tyrosine phosphatases in the regulation of nociceptive transmission and plasticity, it is largely unknown whether SHP1 was expressed in pain-related spinal cord dorsal horn and engaged in the synaptic modification of nociceptive signals. Here we found that SHP1 was present in spinal neurons of rats and functionally coupled to GluN2A subunit-containing N-methyl-d-aspartate subtype of glutamate receptors, one of the key players in central sensitization of nociceptive behaviors.

Inhibition of protein tyrosine phosphatase 1B in spinal cord dorsal horn of rats attenuated diabetic neuropathic pain.

Protein tyrosine phosphatase 1B (PTP1B) has been shown to dephosphorylate and inactivate insulin receptors, which contributes to the pathogenesis of diabetes. Neuropathic pain is one of the severe complications that results from diabetic neuropathy. However, whether PTP1B was involved in the development of diabetic neuropathic pain is largely unknown.

Enhanced Activities of δ Subunit-containing GABA Receptors Blocked Spinal Long-term Potentiation and Attenuated Formalin-induced Spontaneous Pain.

The δ subunit-containing γ-Aminobutyric acid type A receptors (δ-GABARs) are located at extrasynaptic sites and persistently active in the control of neuronal excitability. Here we recorded primary afferent C fiber-evoked field potentials in the superficial dorsal horn of rat spinal cords in vivo and investigated the possible influence of δ-GABARs activities on nociceptive synaptic transmission. We found that δ-GABARs-preferring agonist 4,5,6,7-tetrahydroisoxazolol [4,5-c] pyridine-3-ol (THIP), when topically applied onto spinal cord dorsum, inhibited the basal synaptic responses in a dose-dependent manner.

Adenosine A1 receptor potentiated glycinergic transmission in spinal cord dorsal horn of rats after peripheral inflammation.

Adenosine is present at the extracellular space within spinal cord dorsal horn and engaged in the processing of nociceptive sensory signals. Systemic or spinal administration of exogenous adenosine produces a potent analgesia against pathological pain. Here we found that inhibitory glycinergic neurotransmission was an important target for adenosine regulation.

Striatal-enriched phosphatase 61 inhibited the nociceptive plasticity in spinal cord dorsal horn of rats.

Striatal-enriched phosphatase 61 (STEP61) is a member of intracellular protein tyrosine phosphatases, which is involved in the regulation of synaptic plasticity and a line of neuropsychiatric disorders. This protein tyrosine phosphatase is also abundant in pain-related spinal cord dorsal horn neurons. However, whether and how this tyrosine phosphatase modulates the nociceptive plasticity and behavioral hypersensitivity remain largely unknown.

Activity-dependent dephosphorylation of paxillin contributed to nociceptive plasticity in spinal cord dorsal horn.

The enzymatic activity of protein tyrosine kinase Src is subjected to the regulation by C-terminal Src kinase (CSK) and protein tyrosine phosphatases (PTPs). Aberrant Src activation in the spinal cord dorsal horn is pivotal for the induction and development of nociceptive behavioral sensitization. In this study, we found that paxillin, one of the well-characterized cell adhesion components involved in cell migration and survival, integrated CSK and PTPs' signaling to regulate Src-dependent nociceptive plasticity.

Spinophilin-Targeted Protein Phosphatase-1 Alleviated Inflammatory Pain by Negative Control of MEK/ERK Signaling in Spinal Cord Dorsal Horn of Rats.

Unlabelled: Protein phosphatase-1 (PP1), anchored by regulatory or targeting proteins at excitatory glutamatergic synapses, controls the phosphorylation of postsynaptic substrates and regulates the neurotransmission and plasticity. Here, we found that spinophilin, an actin-binding protein that targets PP1 at postsynaptic density, served as a scaffold for extracellular signal-regulated kinase (ERK) signaling components. Through the C-terminal PDZ domain, spinophilin directly interacted with ERK and its upstream mitogen-activated protein kinase kinase (MEK).

Berberine Regulated Lipid Metabolism in the Presence of C75, Compound C, and TOFA in Breast Cancer Cell Line MCF-7.

Berberine interfering with cancer reprogramming metabolism was confirmed in our previous study. Lipid metabolism and mitochondrial function were also the core parts in reprogramming metabolism. In the presence of some energy-related inhibitors, including C75, compound C, and TOFA, the discrete roles of berberine in lipid metabolism and mitochondrial function were elucidated.

Peripheral inflammation activated focal adhesion kinase signaling in spinal dorsal horn of mice.

Focal adhesion kinase (FAK) is one of the nonreceptor protein tyrosine kinases critical for the dynamic regulation of cell adhesion structures. Recent studies have demonstrated that FAK is also localized at excitatory glutamatergic synapses and is involved in long-term modification of synaptic strength. However, whether FAK is engaged in nociceptive processing in the spinal dorsal horn remains unresolved.

GABAergic inhibition regulated pain sensitization through STEP61 signaling in spinal dorsal horn of mice.

Background: The reduction of γ-aminobutyric acid (GABA) type A receptor-mediated inhibition has long been implicated in spinal sensitization of nociceptive responses. However, it is largely unknown which signaling cascades in spinal dorsal horn neurons are initiated by the reduced inhibition to trigger pain hypersensitivity.

Methods: GABAergic inhibition was manipulated by intrathecal application of GABA type A receptor antagonist bicuculline in intact mice or by GABA type A receptor agonist muscimol in complete Freund's adjuvant-injected mice.

Ht31 peptide inhibited inflammatory pain by blocking NMDA receptor-mediated nociceptive transmission in spinal dorsal horn of mice.

A kinase anchoring proteins (AKAPs) assemble cAMP-dependent protein kinase (PKA) into signaling complexes with a wide range of ion channels, including N-methyl-d-aspartate (NMDA)-subtype glutamate receptor (NMDAR) that is critical for the central sensitization of nociceptive behaviors. Although PKA has been widely described in the regulation of NMDAR-dependent nociceptive transmission and plasticity, the roles of AKAPs in these processes are largely unknown as yet. The present study interfered with AKAPs/PKA interaction by introducing stearated Ht31 peptide (St-Ht31) into spinal dorsal horn neurons, and investigated the possible changes of primary afferent-evoked, NMDAR-mediated excitatory postsynaptic currents (NMDAR-EPSCs).