Long Noncoding RNA H19 Induces Neuropathic Pain by Upregulating Cyclin-Dependent Kinase 5-Mediated Phosphorylation of cAMP Response Element Binding Protein

The role of Cdk5 in neurological disorders

Neurological disorders are a group of disorders with motor, sensory or cognitive damage, caused by dysfunction of the central or peripheral nervous system. Cyclin-dependent kinases 5 (Cdk5) is of vital significance for the development of the nervous system, including the migration and differentiation of neurons, the formation of synapses, and axon regeneration. However, when the nervous system is subject to pathological stimulation, aberrant activation of Cdk5 will induce abnormal phosphorylation of a variety of substrates, resulting in a cascade signaling pathway, and thus lead to pathological changes. Cdk5 is intimately related to the pathological mechanism of a variety of neurological disorders, such as A-β protein formation in Alzheimer’s disease, mitochondrial fragmentation in cerebral ischemia, and apoptosis of dopaminergic neurons in Parkinson’s disease. It is worth noting that Cdk5 inhibitors have been reported to have neuroprotective effects by inhibiting related pathological processes. Therefore, in this review, we will briefly introduce the physiological and pathological mechanisms of Cdk5 in the nervous system, focusing on the recent advances of Cdk5 in neurological disorders and the prospect of targeted Cdk5 for the treatment of neurological disorders.

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.

LncRNA H19 modulates neuropathic pain through miR-141/GLI2 axis in chronic constriction injury (CCI) rats

BACKGROUND

The participation of long non-coding RNAs (lncRNAs) in progressions of chronic pain has been evaluated. We explored mechanisms of lncRNA H19 in chronic constriction injury (CCI)-induced neuropathic pain model in vivo.

METHODS

The expressions of lncRNA H19, microRNA-141, and GLI Family Zinc Finger 2 (GLI2) in CCI rats were determined by using RT-qPCR. Paw withdrawal threshold (PWT) and paw withdrawal latency (PWL) were used as neuropathic pain index implying mechanical allodynia and thermal hyperalgesia. The protein concentrations of IL-1β, IL-6 and TNF-α in rats were examined by ELISA assay. RT-qPCR analyzed gene expression changes of lncRNA H19, miR-141 and GLI2. Online bioinformatics predictions supported that the bindings between miR-141 and GLI2 and dual luciferase reporter method, and RNA pull-down assays determined connections within lncRNA H19, miR-141 and GLI2 in HEK 293 cells.

RESULTS

LncRNA H19 was upregulated in the tissues of rats. Also, thermal hyperalgesia and mechanical allodynia were inhibited by lncRNA H19 suppression in rats. Moreover, IL-1β, IL-6 and TNF-α protein concentrations were suppressed by the downregulation of lncRNA H19 in rats. Furthermore, miR-141 was reduced in CCI rats and restored by the lncRNA H19 knockdown, suggesting the potential negative associations of miR-141 with lncRNA H19. GLI2 targeted miR-141 and GLI2 was increased in CCI rats. Additionally, the neuropathic pain was inhibited by the inhibition of GLI2 in rats, which was reversed by the miR-141 inhibitors.

CONCLUSION

LncRNA H19 aggravated the neuropathic pain of CCI rats through miR-141/GLI2 axis, implying that lncRNA H19 might be a biomarker for the inflammation-related neuropathic 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.

Long non-coding RNA H19: Physiological functions and involvements in central nervous system disorders

Central nervous system (CNS) disorders are some of the most complex and challenging diseases because of the intricate structure and functions of the CNS. Long non-coding RNA (LncRNA) H19, which had been mistaken for "transcription noise" previously, has now been found to be closely related to the development and homeostasis of the CNS. Several recent studies indicate that it plays an important role in the pathogenesis, treatment, and even prognosis of CNS disorders. LncRNA H19 is correlated with susceptibility to various CNS disorders such as intracranial aneurysms, ischemic stroke, glioma, and neuroblastoma. Moreover, it participates in the pathogenesis of CNS disorders by regulating transcription, translation, and signaling pathways, suggesting that it is a promising biomarker and therapeutic target for these disorders. This article reviews the functions and mechanisms of lncRNA H19 in various CNS disorders, including cerebral ischemia, cerebral hemorrhage, glioma, pituitary adenoma, neuroblastoma, Parkinson's disease, Alzheimer's disease, traumatic spinal cord injury, neuropathic pain, and temporal lobe epilepsy, to provide a theoretical basis for further research on the role of lncRNA H19 in CNS disorders.