Fgr contributes to hemorrhage-induced thalamic pain by activating NF-κB/ERK1/2 pathways

The Role of the Thalamus in Nociception: Important but Forgotten

Pain is a complex response to noxious stimuli. Upon detection of the nociceptive stimulus by first-order neurons or nociceptors, an action potential ascends to the spinal dorsal horn, a crucial site for synapsing with second-order neurons. These second-order neurons carry the nociceptive stimulus to supraspinal regions, notably the thalamus. Although extensive research has focused on spinal-level nociceptive mechanisms (e.g., neurotransmitters, receptors, and glial cells), the thalamus is still poorly elucidated. The role of the thalamus in relaying sensory and motor responses to the cortex is well known. However, a comprehensive understanding of the mechanisms in the synapse between the second-order and third-order neurons that transmit this impulse to the somatosensory cortex, where the response is processed and interpreted as pain, is still lacking. Thus, this review investigated the thalamus's role in transmitting nociceptive impulses. Current evidence indicates the involvement of the neurotransmitters glutamate and serotonin, along with NMDA, P2X4, TLR4, FGR, and NLRP3 receptors, as well as signaling pathways including ERK, P38, NF-κB, cytokines, and glial cells at nociceptive synapses within the thalamus.

PDCD4-induced oxidative stress through FGR/NF-κB axis in rectal cancer radiotherapy-induced AKI

This study aimed to investigate the molecular mechanism of the effect of PDCD4 on radiotherapy-induced acute kidney injury (AKI) in rectal cancer through the regulation of FGR/NF-κB signaling. Differentially expressed genes were identified using Gene Expression Omnibus (GEO) datasets (GSE90627 for rectal cancer and GSE145085 for AKI) and R software. The human renal tubular epithelial cell line, HK-2, was used to establish an in vitro model of radiotherapy-induced AKI. RT-qPCR and western blotting were used to detect gene and protein expression levels, respectively. Cell proliferation and apoptosis were assessed using the CCK-8 assay and flow cytometry, respectively. The malondialdehyde and superoxide dismutase levels in the cell culture supernatants were determined. Additionally, an in vivo AKI model was established using BALB/c mice, and kidney tissue morphology, expression of the renal injury molecule KIM-1, apoptosis of renal tubular cells, and TAS and TOS in serum were evaluated. Bioinformatics analysis revealed the upregulated expression of PDCD4 in AKI. In vitro experiments demonstrated that PDCD4 induced apoptosis in renal tubular cells by promoting FGR expression, which activated the NF-κB signaling pathway and triggered an oxidative stress response. In vivo animal experiments confirmed that PDCD4 promoted oxidative stress response and radiotherapy-induced AKI through the activation of the FGR/NF-κB signaling pathway. Silencing PDCD4 attenuated radiotherapy-induced AKI. Our findings suggest that PDCD4 may induce radiotherapy-induced AKI in rectal cancer by promoting FGR expression, activating the NF-κB signaling pathway, and triggering an oxidative stress response.

The role of orphan G protein-coupled receptors in pain

G protein-coupled receptors (GPCRs), which form the largest family of membrane protein receptors in humans, are highly complex signaling systems with intricate structures and dynamic conformations and locations. Among these receptors, a specific subset is referred to as orphan GPCRs (oGPCRs) and has garnered significant interest in pain research due to their role in both central and peripheral nervous system function. The diversity of GPCR functions is attributed to multiple factors, including allosteric modulators, signaling bias, oligomerization, constitutive signaling, and compartmentalized signaling. This review primarily focuses on the recent advances in oGPCR research on pain mechanisms, discussing the role of specific oGPCRs including GPR34, GPR37, GPR65, GPR83, GPR84, GPR85, GPR132, GPR151, GPR160, GPR171, GPR177, and GPR183. The orphan receptors among these receptors associated with central nervous system diseases are also briefly described. Understanding the functions of these oGPCRs can contribute not only to a deeper understanding of pain mechanisms but also offer a reference for discovering new targets for pain treatment.

Piezo2 Contributes to Traumatic Brain Injury by Activating the RhoA/ROCK1 Pathways

Traumatic brain injury (TBI) can lead to short-term and long-term physical and cognitive impairments, which have significant impacts on patients, families, and society. Currently, treatment outcomes for this disease are often unsatisfactory, due at least in part to the fact that the molecular mechanisms underlying the development of TBI are largely unknown. Here, we observed significant upregulation of Piezo2, a key mechanosensitive ion channel protein, in the injured brain tissue of a mouse model of TBI induced by controlled cortical impact. Pharmacological inhibition and genetic knockdown of Piezo2 after TBI attenuated neuronal death, brain edema, brain tissue necrosis, and deficits in neural function and cognitive function. Mechanistically, the increase in Piezo2 expression contributed to TBI-induced neuronal death and subsequent production of TNF-α and IL-1β, likely through activation of the RhoA/ROCK1 pathways in the central nervous system. Our findings suggest that Piezo2 is a key player in and a potential therapeutic target for TBI.

DExH-box helicase 9 modulates hippocampal synapses and regulates neuropathic pain

Experimental studies have shown that neuropathic pain impairs hippocampal synaptic plasticity. Here, we sought to determine the underlying mechanisms responsible for synaptic changes in neuropathic painful mouse hippocampal neurons. Beyond demonstrating proof-of-concept for the location of DExH-box helicase 9 (DHX9) in the nucleus, we found that it did exist in the cytoplasm and DHX9 depletion resulted in structural and functional changes at synapses in the hippocampus. A decrease of DHX9 was observed in the hippocampus after peripheral nerve injury; overexpression of DHX9 in the hippocampus significantly alleviated the nociceptive responses and improved anxiety behaviors. Mimicking DHX9 decrease evoked spontaneous pain behavioral symptoms and anxiety emotion in naïve mice. Mechanistically, we found that DHX9 bound to dendrin (Ddn) mRNA, which may have altered the level of synaptic- and dendritic-associated proteins. The data suggest that DHX9 contributes to synapses in hippocampal neurons and may modulate neuropathic pain and its comorbidity aversive emotion.

Peroxisome proliferator-activated receptor gamma agonist pioglitazone alleviates hemorrhage-induced thalamic pain and neuroinflammation

BACKGROUND

Thalamic pain frequently occurs after stroke and is a challenging clinical issue. However, the mechanisms underlying thalamic pain remain unclear. Neuroinflammation is a key determining factor in the occurrence and maintenance of hemorrhage-induced thalamic pain. Pioglitazone is an agonist of peroxisome proliferator-activated receptor gamma (PPARγ) and shows anti-inflammatory effects in multiple diseases. The present work focused on exploring whether PPARγ is related to hemorrhage-induced thalamic pain.

METHODS

Immunostaining was conducted to analyze the cellular localization of PPARγ and co-localization was evaluated with NeuN, ionized calcium-binding adapter molecular 1 (IBA1), and glia fibrillary acidic protein (GFAP). Western blot analyses were used to evaluate MyD88, pNF-κB/NF-κB, pSTAT6/STAT6, IL-1β, TNF-α, iNOS, Arg-1, IL-4, IL-6, and IL-10 expression. Behavioral tests in mice were conducted to evaluate continuous pain hypersensitivity.

RESULTS

We found that pioglitazone appeared to mitigate the contralateral hemorrhage-induced thalamic pain while inhibiting inflammatory responses. Additionally, Pioglitazone induced phosphorylation of STAT6 and suppressed the phosphorylation NF-κB in our model of thalamic pain. These effects could be partially reversed with the PPARγ antagonist GW9662.

CONCLUSION

The PPARγ agonist pioglitazone can mitigate mechanical allodynia by suppressing the NF-κB inflammasome while activating the STAT6 signal pathway, which are well-known to be associated with inflammation.

Stroke-Induced Central Pain: Overview of the Mechanisms, Management, and Emerging Targets of Central Post-Stroke Pain

The incidence of stroke plays the foremost role in the genesis of central neuropathic pain. Central post-stroke pain (CPSP) is a central pain arising from a vascular lesion in the central nervous system that elicits somatosensory deficits, often contralateral to stroke lesions. It is expressed as continuous or intermittent pain accompanied by sensory abnormalities like dysesthesia and allodynia. CPSP remains de-emphasized due to the variation in onset and diversity in symptoms, besides the difficulty of distinguishing it from other post-stroke pains, often referred to as a diagnosis of exclusion. Spinothalamic dysfunction, disinhibition of the medial thalamus, and neuronal hyperexcitability combined with deafferentation in thalamocortical regions are the mechanisms underlying central pain, which play a significant role in the pathogenesis of CPSP. The treatment regimen for CPSP seems to be perplexed in nature; however, based on available studies, amitriptyline and lamotrigine are denoted as first-line medications and non-pharmacological choices may be accounted for cases intractable to pharmacotherapy. This review attempts to provide an overview of the mechanisms, existing management approaches, and emerging targets of CPSP. A profound understanding of CPSP aids in optimizing the quality of life among stroke sufferers and facilitates further research to develop newer therapeutic agents for managing CPSP.

An Fgr kinase inhibitor attenuates sepsis-associated encephalopathy by ameliorating mitochondrial dysfunction, oxidative stress, and neuroinflammation via the SIRT1/PGC-1α signaling pathway

BACKGROUND

Sepsis-associated encephalopathy (SAE) is characterized by diffuse brain dysfunction, long-term cognitive impairment, and increased morbidity and mortality. The current treatment for SAE is mainly symptomatic; the lack of specific treatment options and a poor understanding of the underlying mechanism of disease are responsible for poor patient outcomes. Fgr is a member of the Src family of tyrosine kinases and is involved in the innate immune response, hematologic cancer, diet-induced obesity, and hemorrhage-induced thalamic pain. This study investigated the protection provided by an Fgr kinase inhibitor in SAE and the underlying mechanism(s) of action.

METHODS

A cecal ligation and puncture (CLP)-induced mouse sepsis model was established. Mice were treated with or without an Fgr inhibitor and a PGC-1α inhibitor/activator. An open field test, a novel object recognition test, and an elevated plus maze were used to assess neurobehavioral changes in the mice. Western blotting and immunofluorescence were used to measure protein expression, and mRNA levels were measured using quantitative PCR (qPCR). An enzyme-linked immunosorbent assay was performed to quantify inflammatory cytokines. Mitochondrial membrane potential and morphology were measured by JC-1, electron microscopy, and the MitoTracker Deep Red probe. Oxidative stress and mitochondrial dysfunction were analyzed. In addition, the regulatory effect of Fgr on sirtuin 1 (SIRT1) was assessed.

RESULTS

CLP-induced sepsis increased the expression of Fgr in the hippocampal neurons. Pharmacological inhibition of Fgr attenuated CLP-induced neuroinflammation, the survival rate, cognitive and emotional dysfunction, oxidative stress, and mitochondrial dysfunction. Moreover, Fgr interacted with SIRT1 and reduced its activity and expression. In addition, activation of SIRT1/PGC-1α promoted the protective effects of the Fgr inhibitor on CLP-induced brain dysfunction, while inactivation of SIRT1/PGC-1α counteracted the benefits of the Fgr inhibitor.

CONCLUSIONS

To our knowledge, this is the first report of Fgr kinase inhibition markedly ameliorating SAE through activation of the SIRT1/PGC-1α pathway, and this may be a promising therapeutic target for SAE.

Blocking Pannexin-1 Channels Alleviates Thalamic Hemorrhage-Induced Pain and Inflammatory Depolarization of Microglia in Mice

Central post-stroke pain (CPSP) is a neuropathic pain syndrome that frequently occurs following cerebral stroke. The pathogenesis of CPSP is mainly due to thalamic injury caused by ischemia and hemorrhage. However, its underlying mechanism is far from clear. In the present study, a thalamic hemorrhage (TH) model was established in young male mice by microinjection of 0.075 U of type IV collagenase into the unilateral ventral posterior lateral nucleus and ventral posterior medial nucleus of the thalamus. We found that TH led to microglial pannexin (Panx)-1, a large-pore ion channel, opening within the thalamus accompanied with thalamic tissue injury, pain sensitivities, and neurological deficit, which were significantly prevented by either intraperitoneal injection of the Panx1 blocker carbenoxolone or intracerebroventricular perfusion of the inhibitory mimetic peptide 10Panx. However, inhibition of Panx1 has no additive effect on pain sensitivities upon pharmacological depletion of microglia. Mechanistically, we found that carbenoxolone alleviated TH-induced proinflammatory factors transcription, neuronal apoptosis, and neurite disassembly within the thalamus. In summary, we conclude that blocking of microglial Panx1 channels alleviates CPSP and neurological deficit through, at least in part, reducing neural damage mediated by the inflammatory response of thalamic microglia after TH. Targeting Panx1 might be a potential strategy in the treatment of CPSP.

Effect of intrathecal NIS-lncRNA antisense oligonucleotides on neuropathic pain caused by nerve trauma, chemotherapy, or diabetes mellitus

BACKGROUND

Blocking increased expression of nerve injury-specific long non-coding RNA (NIS-lncRNA) in injured dorsal root ganglia (DRG) through DRG microinjection of NIS-lncRNA small hairpin interfering RNA or generation of NIS-lncRNA knockdown mice mitigates neuropathic pain. However, these strategies are impractical in the clinic. This study employed a Food and Drug Administration (FDA)-approved antisense oligonucleotides strategy to examine the effect of NIS-lncRNA ASOs on neuropathic pain.

METHODS

Effects of intrathecal injection of NIS-lncRNA antisense oligonucleotides on day 7 or 14 after chronic constriction injury (CCI) of the sciatic nerve, fourth lumbar (L4) spinal nerve ligation, or intraperitoneal injection of paclitaxel or streptozotocin on the expression of DRG NIS-lncRNA and C-C chemokine ligand 2 (CCL2, an NIS-lncRNA downstream target) and nociceptive hypersensitivity were examined. We also assessed whether NIS-lncRNA antisense oligonucleotides produced cellular toxicity.

RESULTS

Intrathecal NIS-lncRNA antisense oligonucleotides attenuated CCI-induced mechanical allodynia, heat hyperalgesia, cold hyperalgesia, and ongoing nociceptive responses, without changing basal or acute nociceptive responses and locomotor function. Intrathecal NIS-lncRNA antisense oligonucleotides also blocked CCI-induced increases in NIS-lncRNA and CCL2 in the ipsilateral L3 and L4 DRG and hyperactivities of neurones and astrocytes in the ipsilateral L3 and L4 spinal cord dorsal horn. Similar results were found in antisense oligonucleotides-treated mice after spinal nerve ligation or intraperitoneal injection of paclitaxel or streptozotocin. Normal morphologic structure and no cell loss were observed in the DRG and spinal cord of antisense oligonucleotides-treated mice.

CONCLUSION

These findings further validate the role of NIS-lncRNA in trauma-, chemotherapy-, or diabetes-induced neuropathic pain and demonstrate potential clinical application of NIS-lncRNA antisense oligonucleotides for neuropathic pain management.

Combination of single-nucleus and bulk RNA-seq reveals the molecular mechanism of thalamus haemorrhage-induced central poststroke pain

Central poststroke pain (CPSP) induced by thalamic haemorrhage (TH) can be continuous or intermittent and is accompanied by paresthesia, which seriously affects patient quality of life. Advanced insights into CPSP mechanisms and therapeutic strategies require a deeper understanding of the molecular processes of the thalamus. Here, using single-nucleus RNA sequencing (snRNA-seq), we sequenced the transcriptomes of 32332 brain cells, which revealed a total of four major cell types within the four thalamic samples from mice. Compared with the control group, the experimental group possessed the higher sensitivity to mechanical, thermal, and cold stimuli, and increased microglia numbers and decreased neuron numbers. We analysed a collection of differentially expressed genes and neuronal marker genes obtained from bulk RNA sequencing (bulk RNA-seq) data and found that Apoe, Abca1, and Hexb were key genes verified by immunofluorescence (IF). Immune infiltration analysis found that these key genes were closely related to macrophages, T cells, related chemokines, immune stimulators and receptors. Gene Ontology (GO) enrichment analysis also showed that the key genes were enriched in biological processes such as protein export from nucleus and protein sumoylation. In summary, using large-scale snRNA-seq, we have defined the transcriptional and cellular diversity in the brain after TH. Our identification of discrete cell types and differentially expressed genes within the thalamus can facilitate the development of new CPSP therapeutics.

E74-like factor 1 contributes to nerve trauma-induced nociceptive hypersensitivity through transcriptionally activating matrix metalloprotein-9 in dorsal root ganglion neurons

ABSTRACT

Nerve trauma-induced alternations of gene expression in the neurons of dorsal root ganglion (DRG) participate in nerve trauma-caused nociceptive hypersensitivity. Transcription factors regulate gene expression. Whether the transcription factor E74-like factor 1 (ELF1) in the DRG contributes to neuropathic pain is unknown. We report here that peripheral nerve trauma caused by chronic constriction injury (CCI) of unilateral sciatic nerve or unilateral fourth lumbar spinal nerve ligation led to the time-dependent increases in the levels of Elf1 mRNA and ELF1 protein in injured DRG, but not in the spinal cord. Preventing this increase through DRG microinjection of adeno-associated virus 5 expressing Elf1 shRNA attenuated the CCI-induced upregulation of matrix metallopeptidase 9 (MMP9) in injured DRG and induction and maintenance of nociceptive hypersensitivities, without changing locomotor functions and basal responses to acute mechanical, heat, and cold stimuli. Mimicking this increase through DRG microinjection of AAV5 expressing full-length Elf1 upregulated DRG MMP9 and produced enhanced responses to mechanical, heat, and cold stimuli in naive mice. Mechanistically, more ELF1 directly bond to and activated Mmp9 promoter in injured DRG neurons after CCI. Our data indicate that ELF1 participates in nerve trauma-caused nociceptive hypersensitivity likely through upregulating MMP9 in injured DRG. E74-like factor 1 may be a new target for management of neuropathic pain.

Role of Sensory Pathway Injury in Central Post-Stroke Pain: A Narrative Review of Its Pathogenetic Mechanism

Central post-stroke pain (CPSP) is a severe chronic neuropathic pain syndrome that is a direct result of cerebrovascular lesions affecting the central somatosensory system. The pathogenesis of this condition remains unclear owing to its extensive clinical manifestations. Nevertheless, clinical and animal experiments have allowed a comprehensive understanding of the mechanisms underlying CPSP occurrence, based on which different theoretical hypotheses have been proposed. We reviewed and collected the literature and on the mechanisms of CPSP by searching the English literature in PubMed and EMBASE databases for the period 2002-2022. Recent studies have reported that CPSP occurrence is mainly due to post-stroke nerve injury and microglial activation, with an inflammatory response leading to central sensitization and de-inhibition. In addition to the primary injury at the stroke site, peripheral nerves, spinal cord, and brain regions outside the stroke site are involved in the occurrence and development of CPSP. In the present study, we reviewed the mechanism of action of CPSP from both clinical studies and basic research based on its sensory pathway. Through this review, we hope to increase the understanding of the mechanism of CPSP.

Src family kinases (SFKs): critical regulators of microglial homeostatic functions and neurodegeneration in Parkinson's and Alzheimer's diseases

c-Src was the first protein kinase to be described as capable of phosphorylating tyrosine residues. Subsequent identification of other tyrosine-phosphorylating protein kinases with a similar structure to c-Src gave rise to the concept of Src family kinases (SFKs). Microglia are the resident innate immune cell population of the CNS. Under physiological conditions, microglia actively participate in brain tissue homeostasis, continuously patrolling the neuronal parenchyma and exerting neuroprotective actions. Activation of pathogen-associated molecular pattern (PAMP) and damage-associated molecular pattern (DAMP) receptors induces microglial proliferation, migration toward pathological foci, phagocytosis, and changes in gene expression, concurrent with the secretion of cytokines, chemokines, and growth factors. A significant body of literature shows that SFK stimulation positively associates with microglial activation and neuropathological conditions, including Alzheimer's and Parkinson's diseases. Here, we review essential microglial homeostatic functions regulated by SFKs, including phagocytosis, environmental sensing, and secretion of inflammatory mediators. In addition, we discuss the potential of SFK modulation for microglial homeostasis in Parkinson's and Alzheimer's diseases.

Secondary damage and neuroinflammation in the spinal dorsal horn mediate post-thalamic hemorrhagic stroke pain hypersensitivity: SDF1-CXCR4 signaling mediation

Central post-stroke pain (CPSP) is an intractable neuropathic pain, which can be caused by primary lesion of central somatosensory system. It is also a common sequelae of the thalamic hemorrhagic stroke (THS). So far, the underlying mechanisms of CPSP remain largely unknown. Our previous studies have demonstrated that SDF1-CXCR4 signaling in the hemorrhagic region contributes to the maintenance of the THS pain hypersensitivity via mediation of the thalamic neuroinflammation. But whether the spinal dorsal horn, an initial point of spinothalamic tract (STT), suffers from retrograde axonal degeneration from the THS region is still unknown. In this study, neuronal degeneration and loss in the spinal dorsal horn were detected 7 days after the THS caused by intra-thalamic collagenase (ITC) injection by immunohistochemistry, TUNEL staining, electron microscopy, and extracellular multi-electrode array (MEA) recordings, suggesting the occurrence of secondary apoptosis and death of the STT projecting neuronal cell bodies following primary THS via retrograde axonal degeneration. This retrograde degeneration was accompanied by secondary neuroinflammation characterized by an activation of microglial and astrocytic cells and upregulation of SDF1-CXCR4 signaling in the spinal dorsal horn. As a consequence, central sensitization was detected by extracellular MEA recordings of the spinal dorsal horn neurons, characterized by hyperexcitability of both wide dynamic range and nociceptive specific neurons to suprathreshold mechanical stimuli. Finally, it was shown that suppression of spinal neuroinflammation by intrathecal administration of inhibitors of microglia (minocycline) and astrocytes (fluorocitrate) and antagonist of CXCR4 (AMD3100) could block the increase in expression levels of Iba-1, GFAP, SDF1, and CXCR4 proteins in the dorsal spinal cord and ameliorate the THS-induced bilateral mechanical pain hypersensitivity, implicating that, besides the primary damage at the thalamus, spinal secondary damage and neuroinflammation also play the important roles in maintaining the central post-THS pain hypersensitivity. In conclusion, secondary neuronal death and neuroinflammation in the spinal dorsal horn can be induced by primary thalamic neural damage via retrograde axonal degeneration process. SDF1-CXCR4 signaling is involved in the mediation of secondary spinal neuroinflammation and THS pain hypersensitivity. This finding would provide a new therapeutic target for treatment of CPSP at the spinal level.

Prediction of Fetal Growth Restriction for Fetal Umbilical Arterial/Venous Blood Flow Index Evaluated by Ultrasonic Doppler under Intelligent Algorithm

The empirical wavelet transform (EWT) algorithm was applied in ultrasound to explore the predictive value for fetal growth restriction (FGR) in fetal arteriovenous indexes. 142 pregnant women who received prenatal ultrasonic examination and delivered were selected. They were classified into control group and FGR group. There were 102 patients with normal pregnancy in the control group, and 40 patients with delayed fetal growth in the FGR group. The extended triple collocation (ETC) algorithm was employed to divide the Fourier spectrum of signals adaptively, and the constructed small filter banks were classified into corresponding intervals. The instantaneous frequency was analyzed, and the arterial blood flow indexes of the two groups were compared. The results showed that the time-frequency analysis method under EWT had lower normalization error and higher accuracy. The inner diameter and cross-sectional area of FGR were remarkably smaller than those of the control group, and the differences were statistically significant (P < 0.05). There were no significant differences in mean blood flow and mean blood velocity between the control group and FGR group (P > 0.05). The arterial blood flow parameters of the systolic flow velocity (VS) and the diastolic flow velocity (VD) in the FGR group were notably lower than those in the control group, and the differences were significant (P < 0.05). In conclusion, the frequency principal component extracted by EWT algorithm was less disturbed by noise, which could accurately and effectively evaluate fetal arteriovenous blood flow indexes and predict FGR.

miR‑223 ameliorates thalamus hemorrhage‑induced central poststroke pain via targeting NLRP3 in a mouse model

Central poststroke pain (CPSP) is a central neuropathic pain syndrome that occurs following a stroke and mainly manifests as pain and paresthesia in the body region corresponding to the brain injury area. At present, due to the lack of clinical attention given to CPSP, patients suffer from long-term pain that seriously affects their quality of life. Current literature indicates that microRNA (miR)-223 can impede inflammation and prevent collateral damage. The NLR family pyrin domain containing 3 (NLRP3) inflammasome induces IL-18 and IL-1β secretion and maturation and participates in the inflammatory response. Previous evidence has confirmed that miR-223 can negatively regulate NLRP3 in the development of inflammatory responses. However, whether the miR-223 targeting of NLRP3 is involved in CPSP remains unclear. In the present study, the expression of miR-223 was detected by reverse transcription-quantitative PCR analysis. The expression levels of NLRP3, caspase-1, ASC, IL-18, IL-1β, ERK1/2, p-ERK1/2 and GFAP were detected by western blot analysis. The results demonstrated that thalamic hemorrhagic stroke triggered by microinjection of collagenase Ⅳ (Coll IV) into the ventral posterior lateral (VPL) nucleus results in pain hypersensitivity. miR-223 expression level were significantly reduced in the CPSP model. The expression levels of NLRP3, caspase-1, ASC, IL-18 and IL-1β were significantly increased in the CPSP model. The expression level of GFAP was detected to determine astrocyte activation. The results demonstrated that astrocyte activation induced by Coll IV produced a CPSP model. The p-ERK1/2 expression level was demonstrated to be significantly increased in the CPSP model. The introduction of an miR-223 agomir significantly attenuated thalamic pain and significantly decreased the levels of NLRP3, caspase-1, ASC and proinflammatory cytokines (IL-18 and IL-1β). Furthermore, introducing a miR-223 antagomir into the VPL nucleus of naïve mice mimicked thalamic pain and significantly increased the levels of NLRP3, caspase-1, ASC and proinflammatory cytokine levels (IL-18 and IL-1β). These results indicated that miR-223 inhibited NLRP3 inflammasome activity (caspase-1, NLRP3 and ASC), which ameliorated thalamus hemorrhage-induced CPSP in mice via NLRP3 downregulation. In conclusion, these results may determine the mechanisms underlying CPSP and facilitate development of targeted therapy for CPSP.

C/EBPβ Participates in Nerve Trauma-Induced TLR7 Upregulation in Primary Sensory Neurons

Nerve trauma-induced toll-like receptor 7 (TLR7) expression level increases in primary sensory neurons in injured dorsal root ganglion (DRG) avails to neuropathic pain, but the reason is still unknown. In the current study, we showed that unilateral lumbar 4 (L4) spinal nerve ligation (SNL) upregulated CCAAT/enhancer-binding protein-β (C/EBPβ) expression in ipsilateral L4 DRG. Preventing this elevation attenuated the SNL-induced upregulation of TLR7 in the ipsilateral L4 DRG and inhibited cold/thermal hyperalgesia and mechanical allodynia. In injected DRG, mimicking nerve trauma-induced C/EBPβ upregulation increased TLR7 levels, augmented responses to cold/thermal/mechanical stimuli, and caused ipsilateral spontaneous pain with no SNL. Mechanistically, SNL upregulated binding of increased C/EBPβ to Tlr7 promoter in ipsilateral L4 DRG. Accorded that C/EBPβ could trigger the activation of Tlr7 promoter and co-expressed with Tlr7 mRNA in individual DRG neurons, our findings strongly suggest the role of C/EBPβ in nerve trauma-mediated TLR7 upregulation in injured primary sensory neurons.

A Model for the Signal Initiation Complex Between Arrestin-3 and the Src Family Kinase Fgr

Arrestins regulate a wide range of signaling events, most notably when bound to active G protein-coupled receptors (GPCRs). Among the known effectors recruited by GPCR-bound arrestins are Src family kinases, which regulate cellular growth and proliferation. Here, we focus on arrestin-3 interactions with Fgr kinase, a member of the Src family. Previous reports demonstrated that Fgr exhibits high constitutive activity, but can be further activated by both arrestin-dependent and arrestin-independent pathways. We report that arrestin-3 modulates Fgr activity with a hallmark bell-shaped concentration-dependence, consistent with a role as a signaling scaffold. We further demonstrate using NMR spectroscopy that a polyproline motif within arrestin-3 interacts directly with the SH3 domain of Fgr. To provide a framework for this interaction, we determined the crystal structure of the Fgr SH3 domain at 1.9 Å resolution and developed a model for the GPCR-arrestin-3-Fgr complex that is supported by mutagenesis. This model suggests that Fgr interacts with arrestin-3 at multiple sites and is consistent with the locations of disease-associated Fgr mutations. Collectively, these studies provide a structural framework for arrestin-dependent activation of Fgr.

FTO (Fat-Mass and Obesity-Associated Protein) Participates in Hemorrhage-Induced Thalamic Pain by Stabilizing Toll-Like Receptor 4 Expression in Thalamic Neurons

[Figure: see text].