Dimethyl Itaconate Attenuates CFA-Induced Inflammatory Pain via the NLRP3/ IL-1ß Signaling Pathway.

Itaconate plays a prominent role in anti-inflammatory effects and has gradually been ushered as a promising drug candidate for treating inflammatory diseases. However, its significance and underlying mechanism for inflammatory pain remain unexplored. In the current study, we investigated the effects and mechanisms of Dimethyl Itaconate (DI, a derivative of itaconate) on Complete Freund's adjuvant (CFA)-induced inflammatory pain in a rodent model. Here, we demonstrated that DI significantly reduced mechanical allodynia and thermal hyperalgesia. The DI-attenuated neuroinflammation was evident with the amelioration of infiltrative macrophages in peripheral sites of the hind paw and the dorsal root ganglion. Concurrently, DI hindered the central microglia activation in the spinal cord. Mechanistically, DI inhibited the expression of pro-inflammatory factors interleukin (IL)-1ß and tumor necrosis factor alpha (TNF-α) and upregulated anti-inflammatory factor IL-10. The analgesic mechanism of DI was related to the downregulation of the nod-like receptor protein 3 (NLRP3) inflammasome complex and IL-1ß secretion. This study suggested possible novel evidence for prospective itaconate utilization in the management of inflammatory pain.

Imaging the Deep Spinal Cord Microvascular Structure and Function with High-Speed NIR-II Fluorescence Microscopy.

The spinal cord (SC) is crucial for a myriad of somatosensory, autonomic signal processing, and transductions. Understanding the SC vascular structure and function thus plays an integral part in neuroscience and clinical research. However, the dense layers of myelinated ascending axons on the dorsal side inconveniently grant the SC tissue with high optical scattering property, which significantly hinders the imaging depth of the SC vasculature in vivo. Commonly used antiscattering techniques such as multiphoton fluorescence microscopy have low imaging speed and cannot capture the rapid vascular particle flow without significant motion blur. Here, advantage of the high penetration of near-infrared (NIR)-II fluorescence is taken to demonstrate a deep SC vascular structural image stack up to 350 µm, comparable to two-photon microscopy. Furthermore, the red blood cells are labelled with the clinically approved NIR dye indocyanine. The combination of a fast NIR camera and indocyanine green-red blood cells (RBCs) makes it possible to attain high-speed 100 frame-per-second NIR-II imaging to identify the corresponding changes in RBC velocity during the external hind leg stimulus. For the first time, it is established that the NIR-II region would be a promising spectral window for SC imaging. NIR-II fluorescence microscopy has excellent potential for clinical and basic science research on SC.

Long-term development of dynamic changes in neurovascular coupling after acute temporal lobe epilepsy.

Epilepsy is an abnormal brain state that may be induced by synchronous neuronal activation and also abnormalities in energy metabolism or the oxygen supply vascular system. Neurovascular coupling (NVC), the relationship between neuron, capillary, and penetrating artery, remains unexplored on a fine-scale with respect to the pathology process after acute temporal lobe epilepsy (TLE). Here we use two-photon microscopy (TPM) to provide high temporal-spatial resolution imaging to identify changes in NVC during spontaneous and electro-stimulated (ES) states in awake mice. Implantation of a long-term craniotomy window allowed TPM recording of the pathological development after the acute Kainic Acid temporal lobe epilepsy model. Our results provide direct evidence that the capillary and penetrating artery are not correlated to rhythmic neuronal activity during acute epilepsy. During the CSD period, NVC shows a strong correlation. We demonstrate that NVC exhibits nonlinear dynamics after status epilepticus. Furthermore, the vascular correlation to neuronal signals in spontaneous and ES states shows dynamic changes which correlate to the evolution after acute TLE. Understanding NVC in all TLE stages, from the acute through the TLE pathological development, may provide new therapeutic pathways.

Dimethyl itaconate inhibits neuroinflammation to alleviate chronic pain in mice.

The metabolite itaconate has both anti-inflammatory and immunomodulatory effects. However, its influence on chronic pain is unclear. Here, we demonstrated that intraperitoneal injection of the itaconate derivative dimethyl itaconate (DI) alleviated chronic pain symptoms, such as allodynia and hyperalgesia, in spinal nerve ligation (SNL) and inflammatory pain models. Moreover, intraperitoneal DI reduced the secretion of inflammatory cytokines (i.e., interleukin-1ß, tumour necrosis factor-alpha) in dorsal root ganglion (DRG), spinal cord and hind paw tissues, suppressed the activation of macrophages in the DRG and glial cells in the spinal dorsal horn and decreased the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) in the DRG and spinal cord. DI boosted nuclear factor-erythroid 2 p45-related factor 2 (Nrf2) levels in the DRG and spinal cord of SNL mice. Intraperitoneal administration of the Nrf2 inhibitor ML385 abolished the analgesic effect of DI and decreased the expression of Nrf2 in the DRG and spinal cord. Similarly, administration of DI potently reversed the lipopolysaccharide (LPS)-induced inflammatory effect in microglia. Reduction of endogenous itaconate levels by pretreatment with immune-responsive gene 1 (IRG1) siRNA blocked Nrf2 expression, which impaired the analgesic and anti-inflammatory effects of DI in vitro. Therefore, our findings revealed for the first time that intraperitoneal DI elicited anti-inflammatory effect and sustained chronic pain relief, which may be regarded as a promising therapeutic agent for chronic pain treatment.

ZNF382 controls mouse neuropathic pain via silencer-based epigenetic inhibition of Cxcl13 in DRG neurons.

Nerve injury-induced changes of gene expression in dorsal root ganglion (DRG) are critical for neuropathic pain genesis. However, how these changes occur remains elusive. Here we report the down-regulation of zinc finger protein 382 (ZNF382) in injured DRG neurons after nerve injury. Rescuing this down-regulation attenuates nociceptive hypersensitivity. Conversely, mimicking this down-regulation produces neuropathic pain symptoms, which are alleviated by C-X-C motif chemokine 13 (CXCL13) knockdown or its receptor CXCR5 knockout. Mechanistically, an identified cis-acting silencer at distal upstream of the Cxcl13 promoter suppresses Cxcl13 transcription via binding to ZNF382. Blocking this binding or genetically deleting this silencer abolishes the ZNF382 suppression on Cxcl13 transcription and impairs ZNF382-induced antinociception. Moreover, ZNF382 down-regulation disrupts the repressive epigenetic complex containing histone deacetylase 1 and SET domain bifurcated 1 at the silencer-promoter loop, resulting in Cxcl13 transcriptional activation. Thus, ZNF382 down-regulation is required for neuropathic pain likely through silencer-based epigenetic disinhibition of CXCL13, a key neuropathic pain player, in DRG neurons.

MeCP2 Epigenetic Silencing of Oprm1 Gene in Primary Sensory Neurons Under Neuropathic Pain Conditions.

Opioids are the last option for the pharmacological treatment of neuropathic pain, but their antinociceptive effects are limited. Decreased mu opioid receptor (MOR) expression in the peripheral nervous system may contribute to this. Here, we showed that nerve injury induced hypermethylation of the Oprm1 gene promoter and an increased expression of methyl-CpG binding protein 2 (MeCP2) in injured dorsal root ganglion (DRG). The downregulation of MOR in the DRG is closely related to the augmentation of MeCP2, an epigenetic repressor, which could recruit HDAC1 and bind to the methylated regions of the Oprm1 gene promoter. MeCP2 knockdown restored the expression of MOR in injured DRG and enhanced the analgesic effect of morphine, while the mimicking of this increase via the intrathecal infusion of viral vector-mediated MeCP2 was sufficient to reduce MOR in the DRG. Moreover, HDAC1 inhibition with suberoylanilide hydroxamic acid, an HDAC inhibitor, also prevented MOR reduction in the DRG of neuropathic pain mice, contributing to the augmentation of morphine analgesia effects. Mechanistically, upregulated MeCP2 promotes the binding of a high level of HDCA1 to hypermethylated regions of the Oprm1 gene promoter, reduces the acetylation of histone H3 (acH3) levels of the Oprm1 gene promoter, and attenuates Oprm1 transcription in injured DRG. Thus, upregulated MeCP2 and HDAC1 in Oprm1 gene promoter sites, negatively regulates MOR expression in injured DRG, mitigating the analgesic effect of the opioids. Targeting MeCP2/HDAC1 may thus provide a new solution for improving the therapeutic effect of opioids in a clinical setting.

MMP24 Contributes to Neuropathic Pain in an FTO-Dependent Manner in the Spinal Cord Neurons.

Nerve injury-induced gene expression change in the spinal cord is critical for neuropathic pain genesis. RNA N6-methyladenosine (m6A) modification represents an additional layer of gene regulation. We showed that spinal nerve ligation (SNL) upregulated the expression of matrix metallopeptidase 24 (MMP24) protein, but not Mmp24 mRNA, in the spinal cord neurons. Blocking the SNL-induced upregulation of spinal MMP24 attenuated local neuron sensitization, neuropathic pain development and maintenance. Conversely, mimicking MMP24 increase promoted the spinal ERK activation and produced evoked nociceptive hypersensitivity. Methylated RNA Immunoprecipitation Sequencing (MeRIP-seq) and RNA Immunoprecipitation (RIP) assay indicated the decreased m6A enrichment in the Mmp24 mRNA under neuropathic pain condition. Moreover, fat-mass and obesity-associated protein (FTO) was colocalized with MMP24 in spinal neurons and shown increased binding to the Mmp24 mRNA in the spinal cord after SNL. Overexpression or suppression of FTO correlates with promotion or inhibition of MMP24 expression in cultured spinal cord neurons. In conclusion, SNL promoted the m6A eraser FTO binding to the Mmp24 mRNA, which subsequently facilitated the translation of MMP24 in the spinal cord, and ultimately contributed to neuropathic pain genesis.

The Emerging Application of Itaconate: Promising Molecular Targets and Therapeutic Opportunities.

Metabolites have recently been found to be involved in significant biological regulation and changes. Itaconate, an important intermediate metabolite isolated from the tricarboxylic acid cycle, is derived from cis-aconitate decarboxylation mediated by immune response gene 1 in mitochondrial matrix. Itaconate has emerged as a key autocrine regulatory component involved in the development and progression of inflammation and immunity. It could directly modify cysteine sites on functional substrate proteins which related to inflammasome, signal transduction, transcription, and cell death. Itaconate can be a connector among immunity, metabolism, and inflammation, which is of great significance for further understanding the mechanism of cellular immune metabolism. And it could be the potential choice for the treatment of inflammation and immune-related diseases. This study is a systematic review of the potential mechanisms of metabolite associated with different pathology conditions. We briefly summarize the structural characteristics and classical pathways of itaconate and its derivatives, with special emphasis on its promising role in future clinical application, in order to provide theoretical basis for future research and treatment intervention.

Intraoperative Neuromonitoring in Thyroid and Parathyroid Surgery.

Background: It has been reported that the incidence of recurrent laryngeal nerve (RLN) injury is higher in an operational procedure in the thyroid and parathyroid region. Elevating voice pitch is achieved by the cricothyroid contraction, which in turn is innervated by the external branch of the superior laryngeal nerve (EBSLN). Due to the subtle nature and clinical variability of EBSLN damage, diagnosis may be difficult. The use of intraoperative neuromonitoring (IONM) as a supplement to enhance surgical identification in thyroid and parathyroid operation appeared to have collected momentum with operators. Methods: IONM clinical usage rationale, efficiency, and safety profile are discussed in this overview in thyroid and parathyroid surgery. Results: IONM usage incurred numerous skepticisms in decreasing the frequency of EBSLN or RLN injury. However, a recent article has shown the efficacy and benefits of using IONM in thyroid and parathyroid procedures. IONM facilitates the recognition of RLN and EBSLN, verifies its functional integrity, localizes the site of a nerve injury, and gives postsurgical function feedback. This technique has been successful in reducing rates of bilateral laryngeal paralysis, with the elevated safety profile for surgical patients. Conclusions: It is recommended using IONM in all thyroidectomies and in high-risk parathyroidectomies.

Acquired Fanconi syndrome secondary to light chain deposition disease associated with monoclonal gammopathy of renal significance: A case report.

RATIONALE: Renal Fanconi syndrome (FS) is a rare complication of monoclonal gammopathy. It is characterized by the impairment of renal proximal tubular function leading to normoglycemic glycosuria, aminoaciduria, hypophosphatemia, hypouricemia and proximal renal tubular acidosis. Renal impairment in monoclonal gammopathy, without fulfilling the criteria of multiple myeloma, is categorized as monoclonal gammopathy of renal significance (MGRS). PATIENT CONCERNS: A 54-year-old male presented with progressively aggravated bone pain and limitation of activity was admitted to our department. A proximal renal tubular damage was suggested by hypophosphatemia, compensated metabolic acidosis, renal glycosuria, aminoaciduria, and hypouricemia. M-protein of IgA kappa was detected by immunofixation electrophoresis. Mildly increased plasma cells were found in bone marrow cytomorphologic examination. Renal biopsy revealed diffuse linear monoclonal IgA-kappa light chain deposits along tubular basement membranes (TBMs), while lambda was negative. Electron microscopy showed granular electron-dense deposits along the outer aspect of TBMs. DIAGNOSES: The patient was diagnosed as FS induced osteomalacia secondary to monoclonal gammopathy of renal significance (MGRS) (IgA-κ type) and LCDD. INTERVENTIONS: He was treated with bortezomib, supplementation by phosphate, alkali agents, and active vitamin D. He responded well to the treatment symptomatically. OUTCOMES: We reported a rare case of adult acquired FS with hypophosphatemic osteomalacia secondary to LCDD associated with MGRS and the patient was successfully treated with bortezomib. LESSONS: Although few cases of LCDD with isolated symptoms of tubulointerstitial nephropathy, rather than glomerular symptoms have been reported. It still needs to be recognized as a differential diagnosis in monoclonal gammopathy.