MicroRNA-96 is required to prevent allodynia by repressing voltage-gated sodium channels in spinal cord

A novel isoquinoline alkaloid HJ-69 isolated from Zanthoxylum bungeanum attenuates inflammatory pain by inhibiting voltage-gated sodium and potassium channels

ETHNOPHARMACOLOGY RELEVANCE

Zanthoxylum bungeanum Maxim. (Z. bungeanum), a member of the Rutaceae family, has a rich history of traditional use in Asia for treating arthritis and toothache conditions. As characteristic chemical components, numerous kinds of alkaloids have been extracted from plants and their diverse biological activities have been reported. However, research on the isoquinoline alkaloid, a specific type of alkaloids, in Z. bungeanum was scarce.

AIM OF THE STUDY

The study aimed to isolate a novel isoquinoline alkaloid from Z. bungeanum and explore its pharmacological activity in vitro and analgesic activity in vivo.

MATERIALS AND METHODS

Isoquinoline alkaloid isolation and identification from Z. bungeanum were conducted using chromatographic and spectroscopic methods. The whole-cell patch-clamp technique was applied to assess its impact on neuronal excitability, and endogenous voltage-gated potassium (Kv) and sodium (Nav) currents in acutely isolated mouse small-diameter dorsal root ganglion (DRG) neurons. Its inhibitory impacts on channels were further validated with HEK293 cells stably expressing Nav1.7 and Nav1.8, and Chinese hamster ovary (CHO) cells transiently expressing Kv2.1. The formalin inflammatory pain model was utilized to evaluate the potential analgesic activity in vivo.

RESULTS

A novel isoquinoline alkaloid named HJ-69 (N-13-(3-methoxyprop-1-yl)rutaecarpine) was isolated and identified from Z. bungeanum for the first time. HJ-69 significantly suppressed the firing frequency and amplitudes of action potentials in DRG neurons. Consistently, it state-dependently inhibited endogenous Nav currents of DRG neurons, with half maximal inhibitory concentration (IC50) values of 13.06 ± 2.06 μM and 30.19 ± 2.07 μM for the inactivated and resting states, respectively. HJ-69 significantly suppressed potassium currents in DRG neurons, which notably inhibited the delayed rectifier potassium (IK) currents (IC50 = 6.95 ± 1.29 μM) and slightly affected the transient outward potassium (IA) currents (IC50 = 523.50 ± 39.16 μM). Furtherly, HJ-69 exhibited similar potencies on heterologously expressed Nav1.7, Nav1.8, and Kv2.1 channels, which correspondingly represent the main components in neurons. Notably, intraperitoneal administration of 30 mg/kg and 100 mg/kg HJ-69 significantly alleviated pain behaviors in the mouse inflammatory pain model induced by formalin.

CONCLUSION

The study concluded that HJ-69 is a novel and active isoquinoline alkaloid, and the inhibition of Nav and Kv channels contributes to its analgesic activity. HJ-69 may be a promising prototype for future analgesic drug discovery based on the isoquinoline alkaloid.

Overexpression of miR-96 leads to retinal degeneration in mice

Double knockout of miR-183 and miR-96 results in retinal degeneration in mice; however, single knockout of miR-96 leads to developmental delay but not substantial retinal degeneration. To further explore the role of miR-96, we overexpressed this miRNA in mouse retinas. Interestingly, we found that overexpression of miR-96 at a safe dose results in retinal degeneration in the mouse retina. The retinal photoreceptors dramatically degenerated in the miR-96-overexpressing group, as shown by OCT, ERG and cryosectioning at one month after subretinal injection. Degenerative features such as TUNEL signals and reactive gliosis were observed in the miR-96-overexpressing retina. RNA-seq data revealed that immune responses and microglial activation occurred in the degenerating retina. Further qRT‒PCR and immunostaining experiments verified the microglial activation. Moreover, the number of microglia in the miR-96-overexpressing retinas was significantly increased. Our findings demonstrate that appropriate miR-96 expression is required for mouse retinal homeostasis.

MiR-146a alleviates inflammatory bowel disease in mice through systematic regulation of multiple genetic networks

Introduction

Inflammatory bowel disease (IBD) is a chronic disease involving multiple genes, and the current available targeted drugs for IBD only deliver moderate efficacy. Whether there is a single gene that systematically regulates IBD is not yet known. MiR-146a plays a pivotal role in repression of innate immunity, but its function in the intestinal inflammation is sort of controversy, and the genetic regulatory networks regulated by miR-146a in IBD has not been revealed.

Methods

RT-qPCR was employed to detect the expression of miR-146a in IBD patients and in a mouse IBD model induced by dextran sulfate sodium (DSS), and then we generated a miR-146a knock-out mouse line with C57/Bl6N background. The disease activity index was scored in DSS-treated miR-146a deficiency mice and their wild type (WT) littermates. Bulk RNA-sequencing, RT-qPCR and immunostaining were done to illustrate the downstream genetic regulatory networks of miR-146a in flamed colon. Finally, the modified miR-146a mimics were used to treat DSS-induced IBD in miR-146a knock-out and WT IBD mice.

Results

We showed that the expression of miR-146a in the colon was elevated in dextran sulfate sodium (DSS)-induced IBD mice and patients with IBD. DSS induced dramatic body weight loss and more significant rectal bleeding, shorter colon length, and colitis in miR-146a knock-out mice than WT mice. The miR-146a mimics alleviated DSS-induced symptoms in both miR-146a-/- and WT mice. Further RNA sequencing illustrated that the deficiency of miR-146a de-repressed majority of DSS-induced IBD-related genes that cover multiple genetic regulatory networks in IBD, and supplementation with miR-146a mimics inhibited the expression of many IBD-related genes. Quantitative RT-PCR or immunostaining confirmed that Ccl3, Saa3, Csf3, Lcn2, Serpine1, Serpine2, MMP3, MMP8, MMP10, IL1A, IL1B, IL6, CXCL2, CXCL3, S100A8, S100A9, TRAF6, P65, p-P65, and IRAK1 were regulated by miR-146a in DSS induced IBD. Among them, MMP3, MMP10, IL6, IL1B, S100A8, S100A9, SERPINE1, CSF3, and IL1A were involved in the active stage of IBD in humans.

Discussion

Our date demonstrated that miR-146a acts as a top regulator in C57/BL6N mice to systematically repress multiple genetic regulatory networks involved in immune response of intestine to environment factors, and combinatory treatment with miR-146a-5p and miR-146a-3p mimics attenuates DSS-induced IBD in mice through down-regulating multiple genetic regulatory networks which were increased in colon tissue from IBD patients. Our findings suggests that miR-146a is a top inhibitor of IBD, and that miR-146a-5p and miR-146a-3p mimics might be potential drug for IBD.

miR-9a-5p expression is decreased in the hippocampus of rats resistant to lamotrigine: A behavioural, molecular and bioinformatics assessment

The major obstacle in developing new treatment strategies for refractory epilepsy is the complexity and poor understanding of its mechanisms. Utilizing the model of lamotrigine-resistant seizures, we evaluated whether changes in the expression of sodium channel subunits are responsible for the diminished responsiveness to lamotrigine (LTG) and if miRNAs, may also be associated. Male rats were administered LTG (5 mg/kg) before each stimulation during kindling acquisition. Challenge stimulation following LTG exposure (30 mg/kg) was performed to confirm resistance in fully kindled rats. RT-PCR was used to measure the mRNA levels of sodium channel subunits (SCN1A, SCN2A, and SCN3A) and miRNAs (miR-155-5p, miR-30b-5p, miR-137-3p, miR-342-5p, miR-301a-3p, miR-212-3p, miR-9a-5p, and miR-133a-3p). Western blot analysis was utilized to measure Nav1.2 protein, and bioinformatics tools were used to perform target prediction and enrichment analysis for miR-9a-5p, the only affected miRNA according to the responsiveness to LTG. Amygdala kindling seizures downregulated Nav1.2, miR-137-3p, miR-342-5p, miR-155-5p, and miR-9a-5p as well as upregulated miR-212-3p. miR-9a-5p was the only molecule decreased in rats resistant to LTG. The bioinformatic assessment and disease enrichment analysis revealed that miR-9a-5p targets expressed with high confidence in the hippocampus are the most significantly associated with epilepsy. Due to the miR-9a-5p dysregulation, major pathways affected are neurotrophic processes, neurotransmission, inflammatory response, cell proliferation and apoptosis. Interaction network analysis identified LTG target SCN2A as interacting with highest number of genes regulated by miR-9-5p. Further studies are needed to propose specific genes and miRNAs responsible for diminished responsiveness to LTG. miR-9a-5p targets, like KCNA4, KCNA2, CACNB2, SCN4B, KCNC1, should receive special attention in them.

Ectopic expression of Nav1.7 in spinal dorsal horn neurons induced by NGF contributes to neuropathic pain in a mouse spinal cord injury model

Neuropathic pain (NP) induced by spinal cord injury (SCI) often causes long-term disturbance for patients, but the mechanisms behind remains unclear. Here, our study showed SCI-induced ectopic expression of Nav1.7 in abundant neurons located in deep and superficial laminae layers of the spinal dorsal horn (SDH) and upregulation of Nav1.7 expression in dorsal root ganglion (DRG) neurons in mice. Pharmacologic studies demonstrated that the efficacy of the blood-brain-barrier (BBB) permeable Nav1.7 inhibitor GNE-0439 for attenuation of NP in SCI mice was significantly better than that of the BBB non-permeable Nav1.7 inhibitor PF-05089771. Moreover, more than 20% of Nav1.7-expressing SDH neurons in SCI mice were activated to express FOS when there were no external stimuli, suggesting that the ectopic expression of Nav1.7 made SDH neurons hypersensitive and Nav1.7-expressing SDH neurons participated in central sensitization and in spontaneous pain and/or walking-evoked mechanical pain. Further investigation showed that NGF, a strong activator of Nav1.7 expression, and its downstream JUN were upregulated after SCI in SDH neurons with similar distribution patterns and in DRG neurons too. In conclusion, our findings showed that the upregulation of Nav1.7 was induced by SCI in both SDH and DRG neurons through increased expression of NGF/JUN, and the inhibition of Nav1.7 in both peripheral and spinal neurons alleviated mechanical pain in SCI mice. These data suggest that BBB permeable Nav1.7 blockers might relieve NP in patients with SCI and that blocking the upregulation of Nav1.7 in the early stage of SCI via selective inhibition of the downstream signaling pathways of NGF or Nav1.7-targeted RNA drugs could be a strategy for therapy of SCI-induced NP.

Research progress on the mechanism of chronic neuropathic pain

Chronic neuropathic pain (CNP) refers to pain that lasts for more than three months due to a disease or an injury to the somatosensory nervous system. The incidence of CNP has been increasing in the world, causing it to become a global concern and patients often experience spontaneous pain, hyperalgesia, abnormal pain or even abnormal sensation as some of its main symptoms. In addition to serious pain and poor physical health, CNP also negatively affects patients' mental health, thus impacting the overall quality of their lives. The pathogenesis of CNP is not clear, but some studies have proved that central sensitization, peripheral sensitization, neuroinflammation, dysfunction in descending nociceptive modulatory systems, oxidative stress reaction, activation of glial cells and psychological factors play an important role in the occurrence and development of CNP. In this context, this article summarizes the current research progress on the mechanism of CNP to provide a basis for further research in preventing and treating the disease.

Long Noncoding RNA, MicroRNA, Zn Transporter Zip14 (Slc39a14) and Inflammation in Mice

Integration of non-coding RNAs and miRNAs with physiological processes in animals, including nutrient metabolism, is an important new focus. Twenty-three transporter proteins control cellular zinc homeostasis. The transporter Zip14 (Slc39a14) responds to proinflammatory stimuli. Using enterocyte-specific Zip14 knockout mice and RNA-sequencing and quantitative polymerase chain reaction (qPCR), we conducted transcriptome profiling of proximal small intestine, where Zip14 is highly expressed, using RNA from whole intestine tissue, isolated intestinal epithelial cells (IECs) and intestinal organoids. H19, U90926, Meg3, Bvht, Pvt1, Neat1 and miR-7027 were among the most highly expressed genes. Enterocyte-specific deletion of Zip14 demonstrated tissue specific expression, as such these changes were not observed with skeletal muscle. Chromatin immunoprecipitation (ChIP) assays of chromatin from isolated intestinal epithelial cells showed that enterocyte-specific Zip14 deletion enhanced binding of proinflammatory transcription factors (TFs) signal transducer and activator of transcription 3 (STAT3) and nuclear factor kappa beta (NF-ĸβ) to promoters of H19, Meg3 and U90926. We conclude enterocyte-specific ablation of Zip14 restricts changes in those RNAs to the intestine. Binding of proinflammatory TFs, NF-ĸβ and STAT3 to the H19, Meg3 and U90926 promoters is consistent with a model where Zip14 ablation, leads to increased TF occupancy, allowing epigenetic regulation of specific lncRNA genes.

Depletion of miR-96 Delays, But Does Not Arrest, Photoreceptor Development in Mice

Purpose

Abundant retinal microRNA-183 cluster (miR-183C) has been reported to be a key player in photoreceptor development and functionality in mice. However, whether there is a protagonist in this cluster remains unclear. Here, we used a mutant mouse model to study the role of miR-96, a member of miR-183C, in photoreceptor development and functionality.

Methods

The mature miR-96 sequence was removed using the CRISPR/Cas9 genome-editing system. Electroretinogram (ERG) and optical coherence tomography (OCT) investigated the changes in structure and function in mouse retinas. Immunostaining determined the localization and morphology of the retinal cells. RNA sequencing was conducted to observe retinal transcription alterations.

Results

The miR-96 mutant mice exhibited cone developmental delay, as occurs in miR-183/96 double knockout mice. Immunostaining of cone-specific marker genes revealed cone nucleus mislocalization and exiguous Opn1mw/Opn1sw in the mutant (MT) mouse outer segments at postnatal day 10. Interestingly, this phenomenon could be relieved in the adult stages. Transcriptome analysis revealed activation of microtubule-, actin filament–, and cilia-related pathways, further supporting the findings. Based on ERG and OCT results at different ages, the MT mice displayed developmental delay not only in cones but also in rods. In addition, a group of miR-96 potential direct and indirect target genes was summarized for interpretation and further studies of miR-96–related retinal developmental defects.

Conclusions

Depletion of miR-96 delayed but did not arrest photoreceptor development in mice. This miRNA is indispensable for mouse photoreceptor maturation, especially for cones.

microRNA-Based Network and Pathway Analysis for Neuropathic Pain in Rodent Models

Neuropathic pain (NP) is poorly managed, and in-depth mechanisms of gene transcriptome alterations in NP pathogenesis are not yet fully understood. To determine microRNA-related molecular mechanisms of NP and their transcriptional regulation in NP, PubMed, Embase, Web of Science and CINAHL Complete (EBSCO) were searched from inception to April 2021. Commonly dysregulated miRNAs in NP were assessed. The putative targets of these miRNAs were determined using TargetScan, Funrich, Cytoscape and String database. A total of 133 literatures containing miRNA profiles studies and experimentally verify studies were included. Venn analysis, target gene prediction analysis and functional enrichment analysis indicated several miRNAs (miR-200b-3p, miR-96, miR-182, miR-183, miR-30b, miR-155 and miR-145) and their target genes involved in known relevant pathways for NP. Targets on transient receptor potential channels, voltage-gated sodium channels and voltage-gated calcium channels may be harnessed for pain relief. A further delineation of signal processing and modulation in neuronal ensembles is key to achieving therapeutic success in future studies.

Spinal Cord Stimulation and Treatment of Peripheral or Central Neuropathic Pain: Mechanisms and Clinical Application

Spinal cord stimulation (SCS) as an evidence-based interventional treatment has been used and approved for clinical use in a variety of pathological states including peripheral neuropathic pain; however, until now, it has not been used for the treatment of spinal cord injury- (SCI-) induced central neuropathic pain. This paper reviews the underlying mechanisms of SCS-induced analgesia and its clinical application in the management of peripheral and central neuropathic pain. Evidence from recent research publications indicates that nociceptive processing at peripheral and central sensory systems is thought to be modulated by SCS through (i) inhibition of the ascending nociceptive transmission by the release of analgesic neurotransmitters such as GABA and endocannabinoids at the spinal dorsal horn; (ii) facilitation of the descending inhibition by release of noradrenalin, dopamine, and serotonin acting on their receptors in the spinal cord; and (iii) activation of a variety of supraspinal brain areas related to pain perception and emotion. These insights into the mechanisms have resulted in the clinically approved use of SCS in peripheral neuropathic pain states like Complex Regional Pain Syndrome (CRPS) and Failed Back Surgery Syndrome (FBSS). However, the mechanisms underlying SCS-induced pain relief in central neuropathic pain are only partly understood, and more research is needed before this therapy can be implemented in SCI patients with central neuropathic pain.