Effects of XIST/miR-137 axis on neuropathic pain by targeting TNFAIP1 in a rat model

The role of non-coding RNAs in neuropathic pain

Neuropathic pain (NPP) is a refractory pain syndrome, caused by damage or disease of the somatosensory nervous system and characterized by spontaneous pain, hyperalgesia, abnormal pain and sensory abnormality. Non-coding RNAs (ncRNAs), including microRNA (miRNA), long non-coding RNA (lncRNA), circular RNA (circRNA) and Piwi interacting RNA (piRNA), play a notable role in initiation and maintenance of NPP. In this review, we summarize the role of ncRNAs in NPP and their underlaying mechanism. Generally, ncRNAs are interacted with mRNA, protein or DNA to regulate the molecules and signals assciated with neuroinflammation, ion channels, neurotrophic factors and others, and then involved in the occurrence and development of NPP. Therefore, this review not only contributes to deepen our understanding of the pathophysiological mechanism of NPP, but also provides theoretical basis for the development of new therapy strategies for this disorder.

Non-coding RNAs in diabetic foot ulcer- a focus on infected wounds

Diabetes mellitus is associated with a wide range of neuropathies, vasculopathies, and immunopathies, resulting in many complications. More than 30% of diabetic patients risk developing diabetic foot ulcers (DFUs). Non-coding RNAs (ncRNAs), including microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs), play essential roles in various biological functions in the hyperglycaemic environment that determines the development of DFU. Ulceration results in tissue breakdown and skin barrier scavenging, thereby facilitating bacterial infection and biofilm formation. Many bacteria contribute to diabetic foot infection (DFI), including Staphylococcus aureus (S. aureus) et al. A heterogeneous group of "ncRNAs," termed small RNAs (sRNAs), powerfully regulates biofilm formation and DFI healing. Multidisciplinary foot care interventions have been identified for nonhealing ulcers. With an appreciation of the link between disease processes and ncRNAs, a novel therapeutic model of bioactive materials loaded with ncRNAs has been developed to prevent and manage diabetic foot complications.

Knocking down TNFAIP1 alleviates inflammation and oxidative stress in pediatric pneumonia through PI3K/Akt/Nrf2 pathway

BACKGROUND

Pneumonia is an acute respiratory infection with increasing global incidences. Children are more susceptible to pneumonia than adults, and its incidences grow extremely high during peak seasons. Thus, it is necessary to investigate the pathogenesis and molecular mechanism of childhood pneumonia.

METHODS

This study examined the role of tumor necrosis factor alpha-inducible protein 1 (TNFAIP1) in lipopolysaccharide (LPS)-induced pneumonia mice. After LPS exposure, lung function, TNFAIP1 activation, infarction volume, oxidative stress, lung tissue apoptosis ratio, and inflammatory response were assessed by immunohistochemistry staining, hematoxylin and eosin staning, Western blot analysis, terminal deoxynucleotidyl transferase dUTP nick end labelling assay, and enzyme-linked-immunosorbent serologic assay, respectively. The mechanism of TNFAIP1 regulating phosphoinositide 3-kinases (PI3K)-protein kinase B (Akt)-nuclear factor erythroid 2-related factor 2 (Nrf2) pathway was analyzed by Western blot analysis.

RESULTS

TNFAIP1 expression was enhanced in the LPS-induced pneumonia mice but was negatively correlated with the LPS-induced lung injury. Silencing TNFAIP1 alleviated inflammatory response, production of reactive oxygen species (ROS), and cellular apoptosis in LPS-induced pneumonia. Moreover, PI3K/Akt/Nrf2 signaling pathways were predominantly involved in the TNFAIP1-mediated lung injury, which also played a role in the process of LPS-induced pneumonia.

CONCLUSION

This study suggested that TNFAIP1 acted as a negative regulator of acute pneumonia by attenuating inflammatory response, production of ROS, and cellular apoptosis via PI3K/Akt/Nrf2 pathway. The findings suggested that TNFAIP1 is a potential candidate for pneumonia therapy.

CRISPR/Cas9-Mediated Knockout of tnfaip1 in Zebrafish Plays a Role in Early Development

TNF α-induced protein 1 (TNFAIP1) was first identified in human umbilical vein endothelial cells and can be induced by tumor necrosis factor α (TNFα). Early studies have found that TNFAIP1 is involved in the development of many tumors and is closely associated with the neurological disorder Alzheimer's disease. However, little is known about the expression pattern of TNFAIP1 under physiological conditions and its function during embryonic development. In this study, we used zebrafish as a model to illustrate the early developmental expression pattern of tnfaip1 and its role in early development. First, we examined the expression pattern of tnfaip1 during early zebrafish development using quantitative real-time PCR and whole mount in situ hybridization and found that tnfaip1 was highly expressed in early embryonic development and, subsequently, expression became localized to anterior embryonic structures. To investigate the function of tnfaip1 during early development, we constructed a model of a stably inherited tnfaip1 mutant using the CRISPR/Cas9 system. Tnfaip1 mutant embryos showed significant developmental delays as well as microcephaly and microphthalmia. At the same time, we found decreased expression of the neuronal marker genes tuba1b, neurod1, and ccnd1 in tnfaip1 mutants. Analysis of transcriptome sequencing data revealed altered expression of the embryonic development related genes dhx40, hspa13, tnfrsf19, nppa, lrp2b, hspb9, clul1, zbtb47a, cryba1a, and adgrg4a in the tnfaip1 mutants. These findings suggest an important role for tnfaip1 in the early development of zebrafish.

Upregulation of LncRNA71132 in the spinal cord regulates hypersensitivity in a rat model of bone cancer pain

ABSTRACT

Bone cancer pain (BCP) is a pervasive clinical symptom which impairs the quality life. Long noncoding RNAs (lncRNAs) are enriched in the central nervous system and play indispensable roles in numerous biological processes, while its regulatory function in nociceptive information processing remains elusive. Here, we reported that functional modulatory role of ENSRNOT00000071132 (lncRNA71132) in the BCP process and sponging with miR-143 and its downstream GPR85-dependent signaling cascade. Spinal lncRNA71132 was remarkably increased in the rat model of bone cancer pain. The knockdown of spinal lncRNA71132 reverted BCP behaviors and spinal c-Fos neuronal sensitization. Overexpression of spinal lncRNA71132 in naive rat generated pain behaviors, which were accompanied by increased spinal c-Fos neuronal sensitization. Furthermore, it was found that lncRNA71132 participates in the modulation of BCP by inversely regulating the processing of miR-143-5p. In addition, an increase in expression of spinal lncRNA71132 resulted in the decrease in expression of miR-143 under the BCP state. Finally, it was found that miR-143-5p regulates pain behaviors by targeting GPR85. Overexpression of miR-143-5p in the spinal cord reverted the nociceptive behaviors triggered by BCP, accompanied by a decrease in expression of spinal GPR85 protein, but no influence on expression of gpr85 mRNA. The findings of this study indicate that lncRNA71132 works as a miRNA sponge in miR-143-5p-mediated posttranscriptional modulation of GPR85 expression in BCP. Therefore, epigenetic interventions against lncRNA71132 may potentially work as novel treatment avenues in treating nociceptive hypersensitivity triggered by bone cancer.

Downregulation of TNFAIP1 alleviates OGD/R‑induced neuronal damage by suppressing Nrf2/GPX4‑mediated ferroptosis

TNFα-induced protein 1 (TNFAIP1) serve a role in neurovascular disease. However, the potential role and molecular mechanism of TNFAIP1 in cerebral ischemia-reperfusion (I/R) remains elusive. In the present study, reverse transcription-quantitative PCR and western blotting were used to assess TNFAIP1 mRNA and protein expression levels in PC12 cells. Furthermore, using Cell Counting Kit-8, flow cytometry and western blotting, cell viability and apoptosis were evaluated. Oxidative stress was evaluated using DCFH-DA staining and ELISA was used for assessment of inflammatory factors. Expression of components in the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway and ferroptosis were assessed using western blotting analysis and an iron assay kit. TNFAIP1 expression was significantly upregulated in oxygen glucose deprivation and reperfusion (OGD/R)-injured PC12 cells. However, knocking down TNFAIP1 expression restored PC12 cell viability and decreased apoptosis following OGD/R-challenge. Furthermore, TNFAIP1 silencing significantly suppressed OGD/R-induced oxidative stress and inflammatory damage in PC12 cells. TNFAIP1 knockdown inhibited ferroptosis via activation of the Nrf2 signaling pathway in OGD/R-injured PC12 cells. Erastin treatment reversed the beneficial effects of TNFAIP1 knockdown on PC12 cell viability, apoptosis alleviation, oxidative stress and inflammation following OGD/R treatment. These results suggested that TNFAIP1 knockdown could alleviate OGD/R-induced neuronal cell damage by suppressing Nrf2-mediated ferroptosis, which might lay the foundation for the investigation of targeted-therapy for cerebral I/R injury in clinic.

Non-coding RNA and n6-methyladenosine modification play crucial roles in neuropathic pain

After peripheral nerve injury, pain signals are transmitted from primary sensory neurons in the dorsal root ganglion (DRG) to the central nervous system. Epigenetic modification affects neuropathic pain through alterations in the gene expression in pain-related areas and glial cell activation. Recent studies have shown that non-coding RNA and n6-methyladenosine (m6A) methylation modification play pivotal regulatory roles in the occurrence and maintenance of neuropathic pain. Dysregulation of the RNA m6A level via dynamic changes in methyltransferase and demethylase after central or peripheral nerve injury commonly regulates pain-associated genes, contributing to the induction and maintenance of neuropathic pain. The dynamic process has significant implications for the development and maintenance of neuropathic pain. However, the underlying mechanisms by which non-coding RNA and m6A RNA modification regulate neuropathic pain are not well-characterized. This article elucidates the multiple mechanisms of non-coding RNA and m6A methylation in the context of neuropathic pain, and summarizes its potential functions as well as recent advances.

The etiological roles of miRNAs, lncRNAs, and circRNAs in neuropathic pain: A narrative review

Background

Non‐coding RNAs (ncRNAs) are involved in neuropathic pain development. Herein, we systematically searched for neuropathic pain‐related ncRNAs expression changes, including microRNAs (miRNAs), long non‐coding RNAs (lncRNAs), and circular non‐coding RNAs (circRNAs).

Methods

We searched two databases, PubMed and GeenMedical, for relevant studies.

Results

Peripheral nerve injury or noxious stimuli can induce extensive changes in the expression of ncRNAs. For example, higher serum miR‐132‐3p, ‐146b‐5p, and ‐384 was observed in neuropathic pain patients. Either sciatic nerve ligation, dorsal root ganglion (DRG) transaction, or ventral root transection (VRT) could upregulate miR‐21 and miR‐31 while downregulating miR‐668 and miR‐672 in the injured DRG. lncRNAs, such as early growth response 2‐antisense‐RNA (Egr2‐AS‐RNA) and Kcna2‐AS‐RNA, were upregulated in Schwann cells and inflicted DRG after nerve injury, respectively. Dysregulated circRNA homeodomain‐interacting protein kinase 3 (circHIPK3) in serum and the DRG, abnormally expressed lncRNAs X‐inactive specific transcript (XIST), nuclear enriched abundant transcript 1 (NEAT1), small nucleolar RNA host gene 1 (SNHG1), as well as ciRS‐7, zinc finger protein 609 (cirZNF609), circ_0005075, and circAnks1a in the spinal cord were suggested to participate in neuropathic pain development. Dysregulated miRNAs contribute to neuropathic pain via neuroinflammation, autophagy, abnormal ion channel expression, regulating pain‐related mediators, protein kinases, structural proteins, neurotransmission excitatory–inhibitory imbalances, or exosome miRNA‐mediated neuron–glia communication. In addition, lncRNAs and circRNAs are essential in neuropathic pain by acting as antisense RNA and miRNA sponges, epigenetically regulating pain‐related molecules expression, or modulating miRNA processing.

Conclusions

Numerous dysregulated ncRNAs have been suggested to participate in neuropathic pain development. However, there is much work to be done before ncRNA‐based analgesics can be clinically used for various reasons such as conservation among species, proper delivery, stability, and off‐target effects.

Emerging roles of lncRNAs in the pathogenesis, diagnosis, and treatment of trigeminal neuralgia

Trigeminal neuralgia (TN) is one of the most common neuropathic pain disorders and is often combined with other comorbidities if managed inadequately. However, the present understanding of its pathogenesis at the molecular level remains lacking. Long noncoding RNAs (lncRNAs) play crucial roles in neuropathic pain, and many studies have reported that specific lncRNAs are related to TN. This review summarizes the current understanding of lncRNAs in the pathogenesis, diagnosis, and treatment of TN. Recent studies have shown that the lncRNAs uc.48+, Gm14461, MRAK009713 and NONRATT021972 are potential candidate loci for the diagnosis and treatment of TN. The current diagnostic system could be enhanced and improved by a workflow for selecting transcriptomic biomarkers and the development of lncRNA-based molecular diagnostic systems for TN. The discovery of lncRNAs potentially impacts drug selection for TN; however, the current supporting evidence is limited to preclinical studies. Additional studies are needed to further test the diagnostic and therapeutic value of lncRNAs in TN.

MicroRNA-137 inhibits the inflammatory response and extracellular matrix degradation in lipopolysaccharide-stimulated human nucleus pulposus cells by targeting activin a receptor type I

This study aimed to investigate the role played by microRNA (miR)-137 in intervertebral disc degeneration via targeting activin A receptor type I (ACVR1) and the underlying mechanism. Human nucleus pulposus cells were exposed to 10 ng/mL lipopolysaccharide (LPS) to establish an in vitro intervertebral disc degeneration model. ACVR1, extracellular matrix degradation-associated genes (aggrecan and collagen type II) and miR-137 levels were assessed using reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and Western blotting assays. The MTT (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide) assay and flow cytometry were used to evaluate nucleus pulposus cell viability and apoptosis. Additionally, the association between miR-137 and ACVR1 was predicted and verified using bioinformatic software and dual-luciferase reporter assays. Furthermore, the secretion of inflammatory factors was analyzed via enzyme linked immunosorbent assay (ELISA). Our results confirmed that ACVR1 was upregulated in lipopolysaccharide-treated nucleus pulposus cells. Lipopolysaccharide suppressed cell viability, promoted apoptosis, enhanced the secretion of inflammatory factors, and reduced aggrecan and collagen type II expression. However, these results were reversed upon ACVR1 silencing. Our data revealed that ACVR1 directly targets miR-137 and is negatively regulated by miR-137 in nucleus pulposus cells. Additionally, the miR-137 mimic promoted cell growth, reduced cell apoptosis, reduced the secretion of inflammatory cytokines, and accelerated extracellular matrix accumulation in lipopolysaccharide-exposed nucleus pulposus cells. However, ACVR1 plasmid abolished the functions of the miR-137 mimic in lipopolysaccharide-exposed nucleus pulposus cells. Together, these findings indicate that miR-137 suppresses the inflammatory response and extracellular matrix degradation in lipopolysaccharide-treated nucleus pulposus cells by targeting ACVR1.

New Vistas in microRNA Regulatory Interactome in Neuropathic Pain

Neuropathic pain is a chronic pain condition seen in patients with diabetic neuropathy, cancer chemotherapy-induced neuropathy, idiopathic neuropathy as well as other diseases affecting the nervous system. Only a small percentage of people with neuropathic pain benefit from current medications. The complexity of the disease, poor identification/lack of diagnostic and prognostic markers limit current strategies for the management of neuropathic pain. Multiple genes and pathways involved in human diseases can be regulated by microRNA (miRNA) which are small non-coding RNA. Several miRNAs are found to be dysregulated in neuropathic pain. These miRNAs regulate expression of various genes associated with neuroinflammation and pain, thus, regulating neuropathic pain. Some of these key players include adenylate cyclase (Ac9), toll-like receptor 8 (Tlr8), suppressor of cytokine signaling 3 (Socs3), signal transducer and activator of transcription 3 (Stat3) and RAS p21 protein activator 1 (Rasa1). With advancements in high-throughput technology and better computational power available for research in present-day pharmacology, biomarker discovery has entered a very exciting phase. We dissect the architecture of miRNA biological networks encompassing both human and rodent microRNAs involved in the development of neuropathic pain. We delineate various microRNAs, and their targets, that may likely serve as potential biomarkers for diagnosis, prognosis, and therapeutic intervention in neuropathic pain. miRNAs mediate their effects in neuropathic pain by signal transduction through IRAK/TRAF6, TLR4/NF-κB, TXIP/NLRP3 inflammasome, MAP Kinase, TGFβ and TLR5 signaling pathways. Taken together, the elucidation of the landscape of signature miRNA regulatory networks in neuropathic pain will facilitate the discovery of novel miRNA/target biomarkers for more effective management of neuropathic pain.

Differential Expression of Long Non-Coding RNAs and Their Role in Rodent Neuropathic Pain Models

Neuropathic pain, which is accompanied by an unpleasant sensation, affects the patient’s quality of life severely. Considering the complexity of the neuropathic pain, there are huge unmet medical needs for it while current effective therapeutics remain far from satisfactory. Accordingly, exploration of mechanisms of neuropathic pain could provide new therapeutic insights. While numerous researches have pointed out the contribution of sensory neuron-immune cell interactions, other mechanisms of action, such as long non-coding RNAs (lncRNAs), also could contribute to the neuropathic pain observed in vivo. LncRNAs have more than 200 nucleotides and were originally considered as transcriptional byproducts. However, recent studies have suggested that lncRNAs played a significant role in gene regulation and disease pathogenesis. A substantial number of long non-coding RNAs were expressed differentially in neuropathic pain models. Besides, therapies targeting specific lncRNAs can significantly ameliorate the development of neuropathic pain, which reveals the contribution of lncRNAs in the generation and maintenance of neuropathic pain and provides a new therapeutic strategy. The primary purpose of this review is to introduce recent studies of lncRNAs on different neuropathic pain models.

Advances With Non-coding RNAs in Neuropathic Pain

Neuropathic pain (NP) is one of the most common types of clinical pain. The common causes of this syndrome include injury to the central or peripheral nervous systems and pathological changes. NP is characterized by spontaneous pain, hyperalgesia, abnormal pain, and paresthesia. Because of its diverse etiology, the pathogenesis of NP has not been fully elucidated and has become one of the most challenging problems in clinical medicine. This kind of pain is extremely resistant to conventional treatment and is accompanied by serious complications. Non-coding RNAs (ncRNAs), such as microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs), contribute to diverse biological processes by regulating the expression of various mRNAs involved in pain-related pathways, at the posttranscriptional level. Abnormal regulation of ncRNAs is closely related to the occurrence and development of NP. In this review, we summarize the current state of understanding of the roles of different ncRNAs in the development of NP. Understanding these mechanisms can help develop novel therapeutic strategies to prevent or treat chronic pain.

Roles of Long Non-coding RNAs in the Development of Chronic Pain

Chronic pain, a severe public health issue, affects the quality of life of patients and results in a major socioeconomic burden. Only limited drug treatments for chronic pain are available, and they have insufficient efficacy. Recent studies have found that the expression of long non-coding RNAs (lncRNAs) is dysregulated in various chronic pain models, including chronic neuropathic pain, chronic inflammatory pain, and chronic cancer-related pain. Studies have also explored the effect of these dysregulated lncRNAs on the activation of microRNAs, inflammatory cytokines, and so on. These mechanisms have been widely demonstrated to play a critical role in the development of chronic pain. The findings of these studies indicate the significant roles of dysregulated lncRNAs in chronic pain in the dorsal root ganglion and spinal cord, following peripheral or central nerve lesions. This review summarizes the mechanism underlying the abnormal expression of lncRNAs in the development of chronic pain induced by peripheral nerve injury, diabetic neuropathy, inflammatory response, trigeminal neuralgia, spinal cord injury, cancer metastasis, and other conditions. Understanding the effect of lncRNAs may provide a novel insight that targeting lncRNAs could be a potential candidate for therapeutic intervention in chronic pain.

[Regulatory role of long non-coding RNA in peripheral nerve injury and neural regeneration]

Objective

To summarize the regulatory role of long non-coding RNA (lncRNA) in peripheral nerve injury (PNI) and neural regeneration.

Methods

The characteristics and mechanisms of lncRNA were summarized and its regulatory role in PNI and neural regeneration were elaborated by referring to relevant domestic and foreign literature in recent years.

Results

Neuropathic pain and denervated muscle atrophy are common complications of PNI, affecting patients' quality of life. Numerous lncRNAs are upregulated after PNI, which promote the progress of neuropathic pain by regulating nerve excitability and neuroinflammation. Several lncRNAs are found to promote the progress of denervated muscle atrophy. Importantly, peripheral nerve regeneration occurs after PNI. LncRNAs promote peripheral nerve regeneration through promoting neuronal axonal outgrowth and the proliferation and migration of Schwann cells.

Conclusion

At present, the research on lncRNA regulating PNI and neural regeneration is still in its infancy. The specific mechanism remains to be further explored. How to achieve clinical translation of experimental results is also a major challenge for future research.

Inhibition of TNFAIP1 ameliorates the oxidative stress and inflammatory injury in myocardial ischemia/reperfusion injury through modulation of Akt/GSK-3β/Nrf2 pathway

Tumor necrosis factor α-induced protein 1 (TNFAIP1) has been documented as a vital regulator of apoptosis and oxidative stress under various pathological conditions. However, whether TNFAIP1 plays a role in myocardial ischemia/reperfusion (I/R) injury has not been well investigated. This work aimed to evaluate the possible role of TNFAIP1 in mediating myocardial I/R injury. Firstly, we demonstrated that TNFAIP1 expression was dramatically increased in rat cardiomyocytes following hypoxia/reoxygenation (H/R) in vitro, and in rat myocardial tissues following I/R treatment in vivo. Silencing of TNFAIP1 alleviated H/R-induced apoptosis, oxidative stress and inflammatory response in rat cardiomyocytes in vitro. Moreover, knockdown of TNFAIP1 ameliorated I/R-induced myocardial injury, infarction size, cardiac apoptosis, oxidative stress and inflammatory response in vivo. Further investigation elucidated that knockdown of TNFAIP1 enhanced the activation of nuclear factor erythroid 2-related factor 2 (Nrf2) signaling associated with modulation of the Akt/glycogen synthase kinase-3β (GSK-3β) pathway in vitro and in vivo. Inhibition of Akt markedly abrogated TNFAIP1-knockdown-mediated Nrf2 activation in cardiomyocytes following H/R injury. In addition, suppression of Nrf2 significantly diminished TNFAIP1-knockdown-induced cardioprotective effects in H/R-exposed cardiomyocytes. In summary, this work elucidates that inhibition of TNFAIP1 ameliorates myocardial I/R injury by potentiating Nrf2 signaling via the modulation of the Akt/GSK-3β pathway. Our study highlights a vital role of the TNFAIP1/Akt/GSK-3β/Nrf2 pathway in mediating myocardial I/R injury and suggests TNFAIP1 as an attractive target for treatment of this disease.

XIST promotes apoptosis and the inflammatory response in CSE-stimulated cells via the miR-200c-3p/EGR3 axis

Background

Chronic obstructive pulmonary disease (COPD) is a disease that causes obstructed airways and abnormal inflammatory responses in the lungs. Early growth response 3 (EGR3) has been revealed to play a vital role in the regulation of the inflammatory response in certain diseases. We aimed to explore the role of EGR3 and its upstream mechanism in COPD.

Methods and result

In the present study, 16HBE cells were treated with cigarette smoke extract (CSE) to mimic the inflammatory response in vitro. RT-qPCR revealed that the expression of EGR3 was upregulated in lungs from COPD patients. EGR3 expression in 16HBE cells was increased by CSE treatment. Moreover, flow cytometry analysis and western blot analysis showed that EGR3 downregulation inhibited 16HBE cell apoptosis. EGR3 silencing decreased the protein levels of IL-6, TNF-α, IL-1β and COX2 in CSE-stimulated 16HBE cells. In addition, EGR3 was targeted by microRNA-200c-3p (miR-200c-3p) in 16HBE cells. MiR-200c-3p expression was significantly decreased in lung tissues from COPD patients compared to that in healthy controls. Furthermore, miR-200c-3p bound to lncRNA X-inactive specific transcript (XIST) in 16HBE cells. Additionally, XIST expression was elevated in lung tissues from COPD patients. Rescue assays indicated that EGR3 overexpression counteracted the effects of XIST downregulation on apoptosis and inflammation in CSE-stimulated 16HBE cells.

Conclusion

The XIST/miR-200c-3p/EGR3 axis facilitated apoptosis and inflammation in CSE-stimulated 16HBE cells. These findings may provide novel insight for treating COPD by alleviating lung inflammation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-021-01582-8.

LncRNA X inactive-specific transcript promotes osteoclast differentiation through Tgif2 by acting as a ceRNA of miR-590-3p in a murine model

Aim: This study aims to investigate whether long noncoding RNA (lncRNA)  X-inactive specific transcript (Xist) can regulate osteoclast differentiation in osteoporosis and the mechanism. Materials & methods: The mouse model of osteoporosis was established by ovariectomy surgery. Osteoclast differentiation from RAW264.7 cells was induced in vitro. The relationships between associated genes were assessed. Results: Xist and Tgif2 were upregulated, but miR-590-3p was downregulated in ovariectomy mouse femurs and cell models. Xist knockdown or miR-590-3p overexpression inhibited Tgif2 expression and osteoclast differentiation. Tgif2 and Xist were the targets of miR-590-3p. Increased miR-590-3p expression inhibited Tgif2 level and osteoclast differentiation, while Xist overexpression reversed these effects. Conclusion: Xist serves as a ceRNA of miR-590-3p to promote Tgif2 level; thereby, contributing to osteoclast differentiation.

Biological Function of Long Non-coding RNA (LncRNA) Xist

Long non-coding RNAs (lncRNAs) regulate gene expression in a variety of ways at epigenetic, chromatin remodeling, transcriptional, and translational levels. Accumulating evidence suggests that lncRNA X-inactive specific transcript (lncRNA Xist) serves as an important regulator of cell growth and development. Despites its original roles in X-chromosome dosage compensation, lncRNA Xist also participates in the development of tumor and other human diseases by functioning as a competing endogenous RNA (ceRNA). In this review, we comprehensively summarized recent progress in understanding the cellular functions of lncRNA Xist in mammalian cells and discussed current knowledge regarding the ceRNA network of lncRNA Xist in various diseases. Long non-coding RNAs (lncRNAs) are transcripts that are more than 200 nt in length and without an apparent protein-coding capacity (Furlan and Rougeulle, 2016; Maduro et al., 2016). These RNAs are believed to be transcribed by the approximately 98-99% non-coding regions of the human genome (Derrien et al., 2012; Fu, 2014; Montalbano et al., 2017; Slack and Chinnaiyan, 2019), as well as a large variety of genomic regions, such as exonic, tronic, and intergenic regions. Hence, lncRNAs are also divided into eight categories: Intergenic lncRNAs, Intronic lncRNAs, Enhancer lncRNAs, Promoter lncRNAs, Natural antisense/sense lncRNAs, Small nucleolar RNA-ended lncRNAs (sno-lncRNAs), Bidirectional lncRNAs, and non-poly(A) lncRNAs (Ma et al., 2013; Devaux et al., 2015; St Laurent et al., 2015; Chen, 2016; Quinn and Chang, 2016; Richard and Eichhorn, 2018; Connerty et al., 2020). A range of evidence has suggested that lncRNAs function as key regulators in crucial cellular functions, including proliferation, differentiation, apoptosis, migration, and invasion, by regulating the expression level of target genes via epigenomic, transcriptional, or post-transcriptional approaches (Cao et al., 2018). Moreover, lncRNAs detected in body fluids were also believed to serve as potential biomarkers for the diagnosis, prognosis, and monitoring of disease progression, and act as novel and potential drug targets for therapeutic exploitation in human disease (Jiang W. et al., 2018; Zhou et al., 2019a). Long non-coding RNA X-inactive specific transcript (lncRNA Xist) are a set of 15,000-20,000 nt sequences localized in the X chromosome inactivation center (XIC) of chromosome Xq13.2 (Brown et al., 1992; Debrand et al., 1998; Kay, 1998; Lee et al., 2013; da Rocha and Heard, 2017; Yang Z. et al., 2018; Brockdorff, 2019). Previous studies have indicated that lncRNA Xist regulate X chromosome inactivation (XCI), resulting in the inheritable silencing of one of the X-chromosomes during female cell development. Also, it serves a vital regulatory function in the whole spectrum of human disease (notably cancer) and can be used as a novel diagnostic and prognostic biomarker and as a potential therapeutic target for human disease in the clinic (Liu et al., 2018b; Deng et al., 2019; Dinescu et al., 2019; Mutzel and Schulz, 2020; Patrat et al., 2020; Wang et al., 2020a). In particular, lncRNA Xist have been demonstrated to be involved in the development of multiple types of tumors including brain tumor, Leukemia, lung cancer, breast cancer, and liver cancer, with the prominent examples outlined in Table 1. It was also believed that lncRNA Xist (Chaligne and Heard, 2014; Yang Z. et al., 2018) contributed to other diseases, such as pulmonary fibrosis, inflammation, neuropathic pain, cardiomyocyte hypertrophy, and osteoarthritis chondrocytes, and more specific details can be found in Table 2. This review summarizes the current knowledge on the regulatory mechanisms of lncRNA Xist on both chromosome dosage compensation and pathogenesis (especially cancer) processes, with a focus on the regulatory network of lncRNA Xist in human disease.

LncRNA p21, downregulating miR-181b, aggravates neuropathic pain by upregulating Tnfaip1 and inhibit the AKT/CREB axis

Recently, there is evidence that long non-coding RNA p21 may play a regulatory role in the development of neuropathic pain (NPP), but it remains to be studied. In this study, we found that lncRNA p21 and tumor necrosis factor alpha-induced protein 1 (Tnfaip1) expression were up-regulated and miR-181b expression was down-regulated in lipopolysaccharide (LPS)-induced and activated BV-2 microglia. The results of flow cytometry and ELISA suggested that overexpression of lncRNA p21 or Tnfaip1 promoted apoptosis and inflammatory factors secretion, and miR-181b overexpression inhibited apoptosis and secretion of inflammatory factors. Luciferase reporter gene analysis validated the adsorption of miR-181b by lncRNA p21. In addition, the targeting relationship between miR-181b and Tnfaip1 was determined. Next, the up-regulation of lncRNA p21 and miR-181b was used as a reversal experiment, and the results suggested that the up-regulation of miR-181b attenuated the promoting effect of lncRNA p21 and Tnfaip1 on apoptosis and inflammatory response, which may be related to the activation of AKT/cAMP response element binding protein (CREB) axis. Finally, the rat model of SNL with lncRNA p21 knockdown was constructed, and the results of paw retraction mechanical threshold (PWMT) and paw retraction thermal latency (PWTL) measurements showed that knockdown of lncRNA p21 alleviated neuropathic pain in rats. In conclusion, our study found that the lncRNA p21/miR-181b/Tnfaip1 axis probably plays an important role in the progression of neuropathic pain, among which lncRNA p21 may become a new insight in the treatment of neuropathic pain.

LncRNA XIST promotes inflammation by downregulating GRα expression in the adenoids of children with OSAHS

Whether glucocorticoid receptor α (GRα) serves a role in obstructive sleep apnea/hypopnea syndrome (OSAHS) remains unclear. However, it has been reported that GRα expression is decreased in the adenoids of patients with OSAHS. The present study aimed to evaluate the role of GRα in OSAHS and the underlying mechanism. Bioinformatics assays revealed that long noncoding RNA (lncRNA) X inactivate-specific transcript (XIST) was closely associated with GRα. Furthermore, reverse transcription-quantitative PCR showed that the expression of lncRNA XIST was significantly increased in the adenoids of patients with OSAHS compared with healthy controls. Further in vitro studies by Pearson correlation analysis, RNA pull-down assay, western blot analysis and ELISA demonstrated that XIST significantly decreased the expression of GRα and that significantly increased the production of inflammatory cytokines, including interleukin (IL)-8, tumor necrosis factor α, IL-6 and IL-1β, while the overexpression of GRα significantly decreased the production of these inflammatory cytokines in NP69 cells, a human nasopharyngeal epithelial cell line. Furthermore, XIST significantly increased the protein levels of nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) subunits, including Rel-B, c-Rel, P52, P50 and P65, which are associated with the transcription of cytokines. The stimulatory effect of XIST was significantly inhibited by the NF-κB inhibitor EVP4593. These results indicated that the stimulatory effect of XIST was dependent on NF-κB. In summary, the present study demonstrated that the XIST-GRα-NF-κB signaling pathway contributed to inflammation in the adenoids of patients with OSAHS.

The Expanding Regulatory Mechanisms and Cellular Functions of Long Non-coding RNAs (lncRNAs) in Neuroinflammation

LncRNAs have emerged as important regulatory molecules in biological processes. They serve as regulators of gene expression pathways through interactions with proteins, RNA, and DNA. LncRNA expression is altered in several diseases of the central nervous system (CNS), such as neurodegenerative disorders, stroke, trauma, and infection. More recently, it has become clear that lncRNAs contribute to regulating both pro-inflammatory and anti-inflammatory pathways in the CNS. In this review, we discuss the molecular pathways involved in the expression of lncRNAs, their role and mechanism of action during gene regulation, cellular functions, and use of lncRNAs as therapeutic targets during neuroinflammation in CNS disorders.

Cullin3-TNFAIP1 E3 Ligase Controls Inflammatory Response in Hepatocellular Carcinoma Cells via Ubiquitination of RhoB

Rho family GTPase RhoB is the critical signaling component controlling the inflammatory response elicited by pro-inflammatory cytokines. However, the underlying mechanisms of RhoB degradation in inflammatory response remain unclear. In this study, for the first time, we identified that TNFAIP1, an adaptor protein of Cullin3 E3 ubiquitin ligases, coordinated with Cullin3 to mediate RhoB degradation through ubiquitin proteasome system. In addition, we demonstrated that downregulation of TNFAIP1 induced the expression of pro-inflammatory cytokines IL-6 and IL-8 in TNFα-stimulated hepatocellular carcinoma cells through the activation of p38/JNK MAPK pathway via blocking RhoB degradation. Our findings revealed a novel mechanism of RhoB degradation and provided a potential strategy for anti-inflammatory intervention of tumors by targeting TNFAIP1-RhoB axis.

TNFAIP1 Is Upregulated in APP/PS1 Mice and Promotes Apoptosis in SH-SY5Y Cells by Binding to RhoB

Alzheimer's disease (AD) poses a significant threat to human life and health. The intraneuronal accumulation of β-amyloid (Aβ) plaques in the brains of AD patients results in neuronal cell death, which is a key factor that triggers multiple changes in the pathogenesis of AD. The inhibition of Aβ-induced neuronal cell death may potentially help in the intervention and treatment of AD. Our previous study reported that tumor necrosis factor α-induced protein 1 (TNFAIP1) is induced by and promotes Aβ_25-35-induced neurotoxicity in mouse neuronal cells, but the roles and regulatory mechanisms of TNFAIP1 are still largely unknown. In this study, our experimental results show that TNFAIP1 and p-TNFAIP1 (phosphorylation of TNFAIP1 at Ser280) are overexpressed in the neurons of the cortex and hippocampus in the brains of APP/PS1 mice, and the transcription factor NF-κB is involved in the Aβ-induced upregulation of TNFAIP1. Moreover, our results suggest that TNFAIP1 contributes to the Aβ-induced reactive oxygen species (ROS) production, decreased mitochondrial membrane potential (∆Ψm), and neuronal cell death in human SH-SY5Y cells. We further revealed that Aβ increases the binding of TNFAIP1 to RhoB, and knockdown of RhoB attenuates the TNFAIP1-induced apoptosis of human SH-SY5Y cells. These data suggest that TNFAIP1 is closely associated with AD pathogenesis, and overexpression of TNFAIP1 in the neurons of the brains of AD patients plays a role in apoptosis, at least in part, via RhoB signaling.

miR-29c-3p Increases Cell Viability and Suppresses Apoptosis by Regulating the TNFAIP1/NF-κB Signaling Pathway via TNFAIP1 in Aβ-Treated Neuroblastoma Cells

Alzheimer's disease (AD) is the most common cause of dementia among older people in worldwide. miR-29c-3p was reported to play a role in AD development. However, the detail function of miR-29c-3p in AD remains unclear. The aim of this research is to analyze the functional mechanism of miR-29c-3p in AD. The RNA levels of miR-29c-3p and Tumor necrosis factor-α-inducible protein-1 (TNFAIP1) were detected by Quantitative real time polymerase chain (qRT-PCR) reaction. Western blot assay was carried out to examine the protein levels of TNFAIP1, Bax, B-cell lymphoma-2 (Bcl-2), Cleaved caspase 3, and Nuclear factor-k-gene binding (NF-κB). The interaction between miR-29c-3p and TNFAIP1 was predicted by online tool TargrtScan and verified using the dual luciferase reporter assay and RNA immunoprecipitation RIP (RIP) assay. Besides, cell proliferation and apoptosis rate were determined by 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2-H-tetrazolium bromide (MTT) assay and flow cytometry analysis, respectively. Aβ treatment decreased miR-29c-3p expression and increased TNFAIP1 expression. Overexpression of miR-29c-3p mitigated the effects of Aβ on proliferation and apoptosis. Similarly, knockdown of TNFAIP1 also reversed the effects of Aβ on cell progression. Interestingly, miR-29c-3p suppressed the expression of TNFAIP1 via binding to 3'UTR of TNFAIP1 mRNA. As expected, overexpression of TNFAIP1 reversed the effects of miR-29c-3p on Aβ-mediated cell progression. Besides, we also confirmed that miR-29c-3p affected Aβ-mediated cell progression by regulating TNFAIP1/NF-κB signaling pathway. In conclusion, our findings confirmed that miR-29c-3p attenuated Aβ-induced neurotoxicity through regulation of NF-κB signaling pathway by directly targeting TNFAIP1, providing the potential value for the treatment of AD patients.

Interactions Among lncRNAs/circRNAs, miRNAs, and mRNAs in Neuropathic Pain

Neuropathic pain (NP) is directly caused by an injury or disease of the somatosensory nervous system. It is a serious type of chronic pain that is a burden to the economy and public health. Although recent studies have improved our understanding of NP, its pathogenesis has not been fully elucidated. Noncoding RNAs, including lncRNAs, circRNAs, and miRNAs, are involved in the pathological development of NP through many mechanisms. In addition, extensive evidence suggests that novel regulatory mechanisms among lncRNAs/circRNAs, miRNAs, and mRNAs play a crucial role in the pathophysiological process of NP. In this review, we comprehensively summarize the regulatory relationship among lncRNAs/circRNAs, miRNAs, and mRNAs and emphasize the important role of the lncRNA/circRNA-miRNA-mRNA axis in NP.

Advances with Long Non-Coding RNAs in Diabetic Peripheral Neuropathy

Long non-coding RNAs (lncRNAs) are a group of non-coding RNAs longer than 200 nucleotides, which are defined as transcripts. The lncRNAs are involved in regulating gene expression at epigenetic, transcriptional, and post-transcriptional levels. Recent studies have found that lncRNA is closely related to many diseases like neurological diseases, endocrine and metabolic disorders. Diabetic peripheral neuropathy (DPN) is one of the most common chronic complications of diabetes mellitus. In this review, we highlight the latest research related to lncRNAs in DPN.

TNFAIP1 Mediates Formaldehyde-Induced Neurotoxicity by Inhibiting the Akt/CREB Pathway in N2a Cells

Formaldehyde (FA) is a common air pollutant. Exposure to exogenous FA can cause damage to the nervous system, such as learning and memory impairment, balance dysfunction, and sleep disorders. Excessive production of endogenous FA also causes memory impairment and is thought to be associated with Alzheimer's disease (AD). Tumor necrosis factor alpha-induced protein 1 (TNFAIP1) plays a crucial role in neurodevelopment and neurological diseases. However, the role of TNFAIP1 in FA-induced neurotoxicity is unclear. Herein, using a mouse neuroblastoma cell line (N2a cells), we explored the mechanism of TNFAIP1 in FA-induced neurotoxicity, the involvement of the Akt/CREB signaling pathway, and how the expression of TNFAIP1 is regulated by FA. We found that exposure to 100 μM or 200 μM FA for 24 h led to decreased cell viability, increased cell apoptosis and neurite retraction, increased reactive oxygen species (ROS) levels, upregulated protein expression of TNFAIP1 and decreased the levels of phosphorylated Akt and CREB in the Akt/CREB pathway. Knockdown of TNFAIP1 using a TNFAIP1 small interfering RNA (siRNA) expression vector prevented FA from inhibiting the Akt/CREB pathway, thus reducing cell apoptosis and restoring cell viability and neurite outgrowth. Clearance of ROS by vitamin E (Vit E) repressed the FA-mediated upregulation of TNFAIP1 expression. These results suggest that FA increases the expression of TNFAIP1 by inducing oxidative stress and that upregulated TNFAIP1 then inhibits the Akt/CREB pathway, consequently leading to cell apoptosis and neurite retraction. Therefore, TNFAIP1 is a potential target for alleviating FA-induced neurotoxicity and related neurological disorders.

Xist attenuates acute inflammatory response by female cells

Biological sex influences inflammatory response, as there is a greater incidence of acute inflammation in men and chronic inflammation in women. Here, we report that acute inflammation is attenuated by X-inactive specific transcript (Xist), a female cell-specific nuclear long noncoding RNA crucial for X-chromosome inactivation. Lipopolysaccharide-mediated acute inflammation increased Xist levels in the cytoplasm of female mouse J774A.1 macrophages and human AML193 monocytes. In both cell types, cytoplasmic Xist colocalizes with the p65 subunit of NF-κB. This interaction was associated with reduced NF-κB nuclear migration, suggesting a novel mechanism to suppress acute inflammation. Further supporting this hypothesis, expression of 5' XIST in male cells significantly reduced IL-6 and NF-κB activity. Adoptive transfer of male splenocytes expressing Xist reduced acute paw swelling in male mice indicating that Xist can have a protective anti-inflammatory effect. These findings show that XIST has functions beyond X chromosome inactivation and suggest that XIST can contribute to sex-specific differences underlying inflammatory response by attenuating acute inflammation in women.

Long non-coding RNA X-inactive specific transcript silencing ameliorates primary graft dysfunction following lung transplantation through microRNA-21-dependent mechanism

Background

Primary graft dysfunction (PGD) is a known acute lung injury (ALI) and a major cause of fatality post-lung transplantation. Though some long non-coding RNAs (lncRNAs) have been studied in ALI through regulation of microRNAs (miRNAs), their effects on PGD remain undefined. The present study aims to explore the underlying mechanism of lncRNA X-inactive specific transcript (XIST) in PGD after lung transplantation.

Methods

Initially, the expression of miR-21, IL-12A and XIST was determined by RT-qPCR and western blot analysis. The dual luciferase reporter assay, RNA pull-down and RIP assay were performed to identify the targeting relationship between miR-21 and IL-12A and the binding relationship between miR-21 and XIST. Loss- and gain-of-function investigations were conducted in rats treated with prolonged cold ischemia and polymorphonuclear neutrophils (PMNs).

Findings

miR-21 was decreased, whilst XIST and IL-12A were increased in the bronchoalveolar lavage fluid of PGD patients after lung transplantation. Enhanced miR-21 expression in rats and PMNs resulted in downregulated expression of pro-inflammatory factors and chemokines, and enhanced the apoptosis of PMNs. XIST was found to upregulate IL-12A expression in a miR-21-dependent manner. Additionally, XIST silencing enhanced the apoptosis of PMNs and inhibited the neutrophil extracellular trap (NET) formation through upregulation of miR-21 but downregulation of IL-12A in vivo.

Interpretation

In summary, lncRNA XIST upregulates IL-12A by binding to miR-21, thereby inducing NET formation and accelerating PGD after lung transplantation. This suggests that inhibition of XIST and NET may be beneficial for the treatment of PGD.

Identification of neuropathic pain-associated genes and pathways via random walk with restart algorithm

BACKGROUND

Neuropathic pain (NP) develops from neuropathic lesions or diseases affecting the nervous system, and has become a serious public health issue due to its complex symptoms, high incidence and long duration. At present, the exact pathogenesis of NP is still unclear. In this study, we sought to identify the genes as well as the related molecular mechanisms associated with NP occurrence and development.

METHODS

We firstly identified the differentially expressed genes between NP spinal nerve ligation (SNL) rats and control sham rats and then projected them onto a STRING network for functional association analysis. Then, Random Walk with Restart (RWR) was conducted to find some new NP-related genes, with their potential functions sequentially analyzed by GO annotation and KEGG pathway analysis.

RESULTS

Some new NP-related genes, like Gng13, C3 and Cxcl2, were identified by RWR analysis. Meanwhile, some biological functions like inflammatory responses, chemotaxis and immune responses, as well as some signaling pathways, such as those involved in neuroactive ligand-receptor interactions, complement and blood coagulation cascade reactions, and cytokine-receptor interactions that the new NP- related genes were most activated were found to be associated with NP occurrence and development.

CONCLUSIONS

This study extends our knowledge of NP occurrence and development and provides new therapeutic targets for future NP treatment.

Targeting XIST induced apoptosis of human osteosarcoma cells by activation of NF-kB/PUMA signal

The long noncoding RNA X-inactive specific transcript (XIST) plays vital roles in tumor progression. However, the underlying mechanisms remain unclear. This study investigated the effects and mechanisms of targeting XIST on osteosarcoma (OS) cells in vitro and in vivo. We used shRNA to knockdown XIST to evaluate cell growth and apoptosis in U2OS cells in vitro and xenograft formation in vivo. An observed relationship between XIST and the p53 upregulated modulator of apoptosis (PUMA) and nuclear factor-kappa B (NF-kB) pathway was further explored by using small interfering RNA (siRNA). Our results showed that suppression of XIST by short hairpin RNA (shRNA) impeded U2OS cell growth, induced apoptosis and lessened OS xenograft tumor growth. Targeting XIST increased NF-kB-dependent PUMA upregulation in U2OS cells. Upregulation of PUMA is correlated with suppression of XIST-induced apoptosis in U2OS cells. Therefore, inhibition of XIST could promote U2OS cell death via activation of NF-kB/PUMA pathways.

Knockdown of long noncoding RNA XIST mitigates the apoptosis and inflammatory injury of microglia cells after spinal cord injury through miR-27a/Smurf1 axis

Spinal cord injury (SCI) is a devastating neuropathological condition. Long noncoding RNA X-inactive specific transcript (XIST) is an acknowledged cancer-related gene and participates in the development of SCI. However, role of XIST in SCI remains to be well revealed. Expression of XIST, miRNA-27a-3p (miR-27a) and smad ubiquitination regulatory factor 1 (Smurf1) was detected using RT-qPCR and western blotting. Cell apoptosis and inflammatory injury were assessed by sulforhodamine B (SRB) assay, flow cytometry, western blotting and enzyme-linked immunosorbent assay. The relationship among miR-27a, XIST and Smurf1 was confirmed by dual-luciferase reporter assay, RNA immunoprecipitation and RNA pull-down assay. As a result, we observed higher level of XIST and Smurf1, but lower level of miR-27a in SCI rats and lipopolysaccharide (LPS)-induced primary microglial cells. in vitro, LPS induced SCI microglia cells as described by decreased cell viability and B cell lymphoma 2 (Bcl-2) expression, and increased cell apoptosis rate, Bax and cleaved caspase 3 levels, and tumor necrosis factor α (TNF-α) and interleukin 6 (IL-6) secretions. in vivo, a T10 laminectomy caused SCI rats as evidenced by decreased Basso-Beattie-Bresnahan Locomotor Rating Scale (BBB) score and induced expression of Bax, cleaved caspase 3, TNF-α and IL-6. However, silencing of XIST could mitigate the apoptosis and inflammatory injury in LPS-induced microglia and SCI rats. Mechanically, miR-27a interacted with XIST and Smurf1 via target binding. Either miR-27a downregulation or Smurf1 overexpression partially reversed the role of XIST deletion in LPS-treated microglial cells. Collectively, knockdown of XIST could alleviate the apoptosis and inflammatory injury of SCI models in vitro and in vivo through directly modulating miR-27a/Smurf1 axis.

Emerging Roles of Long Non-coding RNAs in Chronic Neuropathic Pain

Chronic neuropathic pain, a type of chronic and potentially disabling pain caused by a disease or injury of the somatosensory nervous system, spinal cord injury, or various chronic conditions, such as viral infections (e.g., post-herpetic neuralgia), autoimmune diseases, cancers, and metabolic disorders (e.g., diabetes mellitus), is one of the most intense types of chronic pain, which incurs a major socio-economic burden and is a serious public health issue, with an estimated prevalence of 7–10% in adults throughout the world. Presently, the available drug treatments (e.g., anticonvulsants acting at calcium channels, serotonin-noradrenaline reuptake inhibitors, tricyclic antidepressants, opioids, topical lidocaine, etc.) for chronic neuropathic pain patients are still rare and have disappointing efficacy, which makes it difficult to relieve the patients’ painful symptoms, and, at best, they only try to reduce the patients’ ability to tolerate pain. Long non-coding RNAs (lncRNAs), a type of transcript of more than 200 nucleotides with no protein-coding or limited capacity, were identified to be abnormally expressed in the spinal cord, dorsal root ganglion, hippocampus, and prefrontal cortex under chronic neuropathic pain conditions. Moreover, a rapidly growing body of data has clearly pointed out that nearly 40% of lncRNAs exist specifically in the nervous system. Hence, it was speculated that these dysregulated lncRNAs might participate in the occurrence, development, and progression of chronic neuropathic pain. In other words, if we deeply delve into the potential roles of lncRNAs in the pathogenesis of chronic neuropathic pain, this may open up new strategies and directions for the development of novel targeted drugs to cure this refractory disorder. In this article, we primarily review the status of chronic neuropathic pain and provide a general overview of lncRNAs, the detailed roles of lncRNAs in the nervous system and its related diseases, and the abnormal expression of lncRNAs and their potential clinical applications in chronic neuropathic pain. We hope that through the above description, readers can gain a better understanding of the emerging roles of lncRNAs in chronic neuropathic pain.

Functional roles of lncRNAs and its potential mechanisms in neuropathic pain

Neuropathic pain (NP) is ranked as one of the major forms of chronic pain and emerges as a direct consequence of a lesion or disease affecting the somatosensory nervous system. Despite great advances into the mechanisms of NP, clinical practice is still not satisfactory. Fortunately, progress in elucidating unique features and multiple molecular mechanisms of long non-coding RNAs (lncRNAs) in NP has emerged in the past 10 years, suggesting that novel therapeutic strategies for pain treatment may be proposed. In this review, we will concentrate on recent studies associated with lncRNAs in NP. First, we will describe the alterations of lncRNA expression after spinal cord injury (SCI) and peripheral nerve injury (PNI), and then we illustrate the role of some specific lncRNAs in detail, which may offer new insights into our understanding of the etiology and pathophysiology of NP. Finally, we put special emphasis on the altered expression of lncRNAs in the diverse biological process of NP. Recent advances we summarized above in the development of NP may facilitate translation of these findings from bench to bedside in the future.

Network and pathway-based analysis of microRNA role in neuropathic pain in rat models

The molecular mechanisms underlying neuropathic pain (NP) remain poorly understood. Emerging evidence has suggested the role of microRNAs (miRNAs) in the initiation and development of NP, but the specific effects of miRNAs in NP are largely unknown. Here, we use network- and pathway-based methods to investigate NP-induced miRNA changes and their biological functions by conducting a systematic search through multiple electronic databases. Thirty-seven articles meet the inclusion criteria. Venn analysis and target gene forecasting are performed and the results indicate that 167 overlapping target genes are co-regulated by five down-regulated miRNAs (rno-miR-183, rno-miR-96, rno-miR-30b, rno-miR-150 and rno-miR-206). Protein-protein interaction network analysis shows that 77 genes exhibit interactions, with cyclic adenosine monophosphate (cAMP)-dependent protein kinase catalytic subunit beta (degree = 11) and cAMP-response element binding protein 1 (degree = 10) having the highest connectivity degree. Gene ontology analysis shows that these target genes are enriched in neuron part, neuron projection, somatodendritic compartment and nervous system development. Moreover, analysis of Kyoto Encyclopedia of Genes and Genomes reveals that three pathways, namely, axon guidance, circadian entrainment and insulin secretion, are significantly enriched. In addition, rno-miR-183, rno-miR-96, rno-miR-30b, rno-miR-150 and rno-miR-206 are consistently down-regulated in the NP models, thus constituting the potential biomarkers of this disease. Characterizing these miRNAs and their target genes paves way for their future use in clinical practice.

Identification of changed expression of mRNAs and lncRNAs in osteoarthritic synovium by RNA-sequencing

Long non-coding RNAs (lncRNAs) are recently reported to regulate the homeostasis of cartilage in osteoarthritis (OA), but their regulatory roles in OA synovium remain elusive. This study aimed to identify the differentially expressed mRNAs and lncRNAs in OA synovium and further explore the function of differentially expressed lncRNAs in OA progression through bioinformatics analysis. We started with RNA-sequencing in 5 OA synovium samples and 5 healthy controls to compare the expression of mRNAs and lncRNAs. GO analysis and KEGG pathway analysis were performed to annotate the function of differentially expressed mRNAs. Then real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was admitted in 17 osteoarthritic synovium and 18 healthy controls to confirm the changes of the expression of the selected lncRNAs. LncRNA-mRNA co-expression network was constructed to predict the potential molecular regulatory mechanisms of specifically expressed lncRNAs in OA synovium. 384 mRNAs and 17 lncRNAs were detected to be differentially expressed in OA synovium. The expressions of 4 lncRNAs were confirmed by qRT-PCR. We found the differentially expression lncRNAs could potentially regulate OA progression through pathways regarding to immune response through the lncRNA-mRNA network and further annotation for co-expression mRNAs. Our results indicated that lncRNAs may play key roles in OA synovitis and may have potential value in OA diagnosis.

Emerging roles of long non-coding RNAs in neuropathic pain

Neuropathic pain, a type of chronic and potentially disabling pain resulting from primary injury/dysfunction of the somatosensory nervous system and spinal cord injury, is one of the most intense types of chronic pain, which incurs a significant economic and public health burden. However, our understanding of its cellular and molecular pathogenesis is still far from complete. Long non‐coding RNAs (lncRNAs) are important regulators of gene expression and have recently been characterized as key modulators of neuronal functions. Emerging evidence suggested that lncRNAs are deregulated and play pivotal roles in the development of neuropathic pain. This review summarizes the current knowledge about the roles of deregulated lncRNAs (eg, KCNA2‐AS, uc.48+, NONRATT021972, MRAK009713, XIST, CCAT1) in the development of neuropathic pain. These studies suggested that specific regulation of lncRNAs or their downstream targets might provide novel therapeutic avenues for this refractory disease.

The rs1625579 T>G polymorphism in the miRNA-13 gene confers a risk of early- onset Kawasaki disease in a southern Chinese population

Background

Kawasaki disease (KD) mainly manifests as excessive inflammation and vascular endothelial cell injury. This disease generally occurs in children younger than 5 years of age and is more severe in children younger than 12 months. KD affects males and females at a ratio of 1.5:1. Polymorphisms of the rs1625579 locus in the miR-13 gene are associated with schizophrenia susceptibility, and high glucose-induced upregulation of miR-137 in vascular endothelial cells promotes monocyte chemotaxis and inflammatory cytokine secretion in gestational diabetes mellitus. However, researchers have not reported whether rs1625579 is associated with KD susceptibility or onset. Therefore, we investigated the relationship between the miRNA-13 rs1625579 T>G polymorphism and KD susceptibility.

Methods

TaqMan real-time polymerase chain reaction was applied to determine the genotypes of 532 patients with KD (365 males and 167 females) and 623 control subjects (402 males and 221 females).

Results

Comparison of all cases with all controls revealed that the rs1625579 T>G polymorphism was not associated with KD susceptibility. However, a subgroup analysis revealed that subjects with the rs1625579 TG/GG genotypes exhibited a significantly higher onset risk for KD before 12 months of age than carriers of the TT genotype (adjusted age and gender odds ratio=1.99, 95% CI=1.04-3.83; P=0.039).

Conclusion

Our results indicate that the rs1625579 T>G polymorphism confers a risk of early-onset KD in southern Chinese children.

miR-34a-mediated regulation of XIST in female cells under inflammation

Background

Evidence is overwhelming for sex differences in pain, with women representing the majority of the chronic pain patient population. There is a need to explore novel avenues to elucidate this sex bias in the development of chronic inflammatory pain conditions. Complex regional pain syndrome (CRPS) is a chronic neuropathic pain disorder, and the incidence of CRPS is greater in women than in men by ~4:1. Since neurogenic inflammation is a key feature of CRPS, dysregulation of inflammatory responses can be a factor in predisposing women to chronic pain.

Methods

Our studies investigating alterations in circulating microRNAs (miRNAs) in whole blood from female CRPS patients showed significant differential expression of miRNAs between responders and poor responders to ketamine treatment. Several of these miRNAs are predicted to target the long noncoding RNA, X-inactive-specific transcript (XIST). XIST mediates X-chromosome inactivation and is essential for equalizing the expression of X-linked genes between females and males. Based on the well-established role in inflammatory process, we focused on miR-34a, one of the miRNAs predicted to target XIST, and downregulated in CRPS patients responding poorly to ketamine.

Results

Our in vitro and in vivo models of acute inflammation and data from patients with CRPS showed that miR-34a can regulate XIST under inflammation directly, and through pro-inflammatory transcription factor Yin-Yang 1 (YY1). XIST was significantly upregulated in a subset of CRPS patients responding poorly to ketamine.

Conclusion

Since dysregulation of XIST can result in genes escaping inactivation or reactivation in female cells, further investigations on the role of XIST in the predominance of chronic inflammatory and pain disorders in women is warranted.