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.

Chronic pain is a common condition that seriously affects the quality of human life with variable etiology and complicated symptoms; people who suffer from chronic pain may experience anxiety, depression, insomnia, and other harmful emotions. Currently, chronic pain treatments are nonsteroidal anti-inflammatory drugs and opioids; these drugs are demonstrated to be insufficient and cause severe side effects. Therefore, research into new therapeutic strategies for chronic pain is a top priority. In recent years, stem cell transplantation has been demonstrated to be a potent alternative for the treatment of chronic pain. Mesenchymal stem cells (MSCs), a type of pluripotent stem cell, exhibit multi-directional differentiation, promotion of stem cell implantation, and immune regulation; they have also been shown to exert analgesic effects in several chronic pain models. Exosomes produced by MSCs have been demonstrated to relieve painful symptoms with fewer side effects. In this review, we summarize the therapeutic use of MSCs in various chronic pain studies. We also discuss ways to enhance the treatment effect of MSCs. We predict in the future, cell-free therapies for chronic pain will develop from exosomes secreted by MSCs.

Neuropathic pain (NP) is a type of chronic pain that is different from the common type of pain. The mechanisms of NP are still poorly understood. Exploring the key genes and neurobiological changes in NP could provide important diagnostic and treatment tools for clinicians. GSE24982 is an mRNA-seq dataset that we downloaded from the Gene Expression Omnibus database to identify key genes in NP. Differentially expressed genes (DEGs) were identified using the BRB-ArrayTools software and R. Functional and pathway enrichment analyses of the DEGs were performed using Metascape. A protein–protein interaction network was created and visualized using Cytoscape. A total of 123 upregulated DEGs were obtained. Among these genes, p53 was the node with the highest degree; hence, we validated it experimentally using a chronic constriction injury mouse model. Our results showed that overexpression of the p53 gene, and the subsequent increase in caspase-3 expression, in dorsal root ganglion neurons led to increased apoptotic changes in these neurons. p53 may therefore be partly responsible for the development of chronic constriction injury-induced NP.

General anesthesia is a drug-induced reversible state comprised of altered states of consciousness, amnesia, analgesia, and immobility. The medial frontal cortex (mPFC) has been discovered to modulate the level of consciousness through cholinergic and glutamatergic pathways. The optogenetic tools combined with in vivo electrophysiological recording were used to study the neural oscillatory modulation mechanisms in mPFC underlying the loss of consciousness (LOC) and emergence. We found that optogenetic activation of both cholinergic and glutamatergic neurons in the basal forebrain (BF) reversed the hypnotic effect of propofol and accelerated the emergence from propofol-induced unconsciousness. The cholinergic light-activation during propofol anesthesia increased the power in the β (12–20 Hz) and low γ (20–30 Hz) bands. Conversely, glutamatergic activation increased the power at less specific broad (1–150 Hz) bands. The cholinergic-induced alteration to specific power bands after LOC had opposite effects to that of propofol. These results suggested that the cholinergic system might act on more specific cortical neural circuits related to propofol anesthesia.

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.