MiR-1906 Attenuates Neuropathic Pain in Rats by Regulating the TLR4/mTOR/ Akt Signaling Pathway

The role of N6-methyladenosine modification in rodent models of neuropathic pain: from the mechanism to therapeutic potential

Neuropathic pain (NP) is a common chronic pain condition resulted from lesions or diseases of somatosensory nervous system, but the pathogenesis remains unclear. A growing body of evidence supports the relationship between pathogenesis and N6-methyladenosine (m6A) modifications of RNA. However, studies on the role of m6A modifications in NP are still at an early stage. Elucidating different etiologies is important for understanding the specific pathogenesis of NP. This article provides a comprehensive review on the role of m6A methylation modifications including methyltransferases ("writers"), demethylases ("erasers"), and m6A binding proteins ("readers") in NP models. Further analysis of the pathogenic mechanism relationship between m6A and NP provided novel theoretical and practical significance for clinical treatment of NP.

Taselisib moderates neuropathic pain through PI3K/AKT signaling pathway in a rat model of chronic constriction injury

BACKGROUND

Neuropathic pain is a chronic condition commonly caused by inflammation-induced disturbances or lesions of somatosensory functions in the nervous system. The aim of this study was to investigate the effects and mechanisms of Taselisib on chronic constriction injury (CCI)-induced neuropathic pain in rats.

METHODS

The rats were divided into four groups: sham group, sham + Taselisib (10mg/kg orally once a day) group, CCI group, and CCI + Taselisib (10mg/kg orally once a day) group. Pain behavioral tests, recorded by measuring paw withdrawal threshold (PWT) and thermal withdrawal latency (TWL), were conducted on days 0, 3, 7, 14, and 21 after surgery. After testing, the animals were euthanized and spinal dorsal horns were collected. Pro-inflammatory cytokines were quantified using ELISA and qRT-PCR. PI3K/pAKT signaling was assessed using Western blot and immunofluorescence.

RESULTS

PWT and TWL were significantly reduced after CCI surgery, but were successfully increased by Taselisib treatment. Taselisib treatment notably suppressed the upregulation of pro-inflammatory cytokines, including IL-6, IL-1β, and TNF-⍺. Taselisib treatment significantly reduced the elevated phosphorylation of AKT and PI3K induced by CCI.

CONCLUSION

Taselisib can alleviate neuropathic pain by inhibiting the pro-inflammatory response, potentially through the PI3K/AKT signaling pathway.

The miR-1906 mimic attenuates bone loss in osteoporosis by down-regulating the TLR4/MyD88/NF-κB pathway

In this study, the ability of microRNA-1906 (miR-1906) to attenuate bone loss in osteoporosis was evaluated by measuring the effects of a miR-1906 mimic and inhibitor on the cellular toxicity and cell viability of MC3T3-E1 cells. Bone marrow-derived macrophage (BMM) cells were isolated from female mice, and tartrate-resistant acid phosphatase signalling was performed in miR-1906 mimic-treated, receptor-activated nuclear factor kappa-B (NF-κB) ligand (RANKL)-induced osteoclasts. In-vivo, osteoporosis was induced by ovariectomy (OVX). Rats were treated with 500 nmol/kg of the miR-1906 mimic via intrathecal administration for 10 consecutive days following surgery. The effect of the miR-1906 mimic on bone mineral density (BMD) in OVX rats was observed in the whole body, lumbar vertebrae and femur. Levels of biochemical parameters and cytokines in the serum of miR-1906 mimic-treated OVX rats were analysed. The mRNA expression of toll-like receptor 4 (TLR4), myeloid differentiation primary response 88 (MyD88), p-38 and NF-κB in tibias of osteoporotic rats (induced by ovariectomy) was observed using quantitative reverse-transcription polymerase chain reaction. Treatment with the miR-1906 mimic reduced cellular toxicity and enhanced the cell viability of MC3T3-E1 cells. Furthermore, osteoclastogenesis in miR-1906 mimic-treated, RANKL-induced osteoclast cells was reduced, whereas the BMD in the miR-1906 mimic-treated group was higher than in the OVX group of rats. Treatment with the miR-1906 mimic also increased levels of biochemical parameters and cytokines in the serum of ovariectomised rats. Finally, mRNA expression levels of TLR4, MyD88, p-38 and NF-κB were lower in the tibias of miR-1906 mimic-treated rats than in those of OVX rats. In conclusion, the miR-1906 mimic reduces bone loss in rats with ovariectomy-induced osteoporosis by regulating the TLR4/MyD88/NF-κB pathway.

Interaction between non-coding RNAs and Toll-like receptors

Toll-like receptors (TLRs) are a large group of pattern recognition receptors which are involved in the regulation of innate immune responses. Based on the interplay between TLRs and adapter molecules, two distinctive signaling cascades, namely the MyD88-dependent and TRIF-dependent pathways have been recognized. TLRs are involved in the development of a wide variety of diseases including cancer and autoimmune disorders. A large body of evidence has shown interaction between two classes of non-coding RNAs, namely microRNAs (miRNAs) and long noncoding RNAs (lncRNAs). These interactions have prominent roles in the pathogenesis of several disorders including infectious disorders, autoimmune conditions and neoplastic disorders. This review aims at description of the interaction between these non-coding RNAs and TLRs.

NFAT5 Deficiency Alleviates Formalin-Induced Inflammatory Pain Through mTOR

Nuclear factor of activated T cells (NFAT5) is a well-known transcription factor that regulates the expression of genes involved in osmotic stress. However, the role of NFAT5 in inflammatory pain remains unknown. Here, we studied the function of NFAT5 in inflammatory pain using NFAT5-heterozygous (Het) mice. To study inflammatory pain, we injected 10 µL of 2% formalin into the right hind paws of mice and monitored pain behaviors, such as licking, lifting, and flinching, for 60 min. After the first 15 min (phase I), there were no significant differences in pain behaviors between wild-type (WT) and NFAT5-Het mice. However, from 15–60 min (phase II), NFAT5-Het mice displayed significantly fewer pain behaviors compared to WT mice. Further, the expression levels of inflammatory-pain-related factors, including c-Fos, phosphorylated extracellular signal-regulated kinase (p-ERK), and phosphorylated n-methyl-D-aspartate receptor subunit 2B (p-NR2B), were significantly elevated in the spinal dorsal neurons of formalin-treated WT mice but was not elevated in NFAT5-Het mice. Similarly, c-Fos, p-ERK, and p-NR2B levels were significantly higher in glutamate-treated PC12 neuronal cells but were not affected by Nfat5 silencing in glutamate-treated PC12 cells. Altogether, our findings suggest that NFAT5 deficiency may mitigate formalin-induced inflammatory pain by upregulating mammalian target of rapamycin (mTOR) expression and downregulating its downstream factors in spinal dorsal neurons. Therefore, NFAT5 is a potential therapeutic target for the treatment of inflammatory pain.

An Investigation of the Molecular Mechanisms Underlying the Analgesic Effect of Jakyak-Gamcho Decoction: A Network Pharmacology Study

Herbal drugs have drawn substantial interest as effective analgesic agents; however, their therapeutic mechanisms remain to be fully understood. To address this question, we performed a network pharmacology study to explore the system-level mechanisms that underlie the analgesic activity of Jakyak-Gamcho decoction (JGd; Shaoyao-Gancao-Tang in Chinese and Shakuyaku-Kanzo-To in Japanese), an herbal prescription consisting of Paeonia lactiflora Pallas and Glycyrrhiza uralensis Fischer. Based on comprehensive information regarding the pharmacological and chemical properties of the herbal constituents of JGd, we identified 57 active chemical compounds and their 70 pain-associated targets. The JGd targets were determined to be involved in the regulation of diverse biological activities as follows: calcium- and cytokine-mediated signalings, calcium ion concentration and homeostasis, cellular behaviors of muscle and neuronal cells, inflammatory response, and response to chemical, cytokine, drug, and oxidative stress. The targets were further enriched in various pain-associated signalings, including the PI3K-Akt, estrogen, ErbB, neurotrophin, neuroactive ligand-receptor interaction, HIF-1, serotonergic synapse, JAK-STAT, and cAMP pathways. Thus, these data provide a systematic basis to understand the molecular mechanisms underlying the analgesic activity of herbal drugs.

Baicalin attenuates inflammatory pain associated depressive symptoms via Akt-mediated adult hippocampal neurogenesis

Depression is one of main symptoms accompanying thermal hyperalgesia and mechanical allodynia induced by inflammatory pain. On physiological level, depressive symptoms could be attenuated by sufficient level of hippocampal neural plasticity. Adult hippocampal neurogenesis (AHN) plays critical roles in clearing panic memory, increasing psychiatric adaptability and preventing depressive emotion. Thus, targeting AHN is the applicable strategy to improve neural functions impaired and attenuate inflammatory pain. Previous reports indicate natural compound baicalin (BA) is one of the effective agents to promote AHN. In present study, we tested the effects of BA in mouse model of inflammatory pain as well as its biological underpinning. Behavioral tests indicate that BA treatment attenuated thermal hyperalgesia, mechanical allodynia and depressive symptoms. Meanwhile, treatment of BA promoted growth and differentiation of neural stem cells in hippocampus. AHN blocker temozolomide (TMZ) resulted in significant suppressed effects of BA to promote AHN, suggesting the critical role of AHN in regulating behavioral effects of BA to inflammatory pain. Akt plays the critical roles in the effects of BA to attenuate inflammatory pain induced symptoms. Prohibiting of Akt with GSK960693 dramatically prevented the effects of BA in attenuating inflammatory pain induced behavioral symptoms. Taken together, BA is the potential pain killer to alleviating inflammatory pain via Akt-mediated adult hippocampal neurogenesis.

Effect of lycopene on pain facilitation and the SIRT1/mTOR pathway in the dorsal horn of burn injury rats

To explore the effect of intrathecal injection of lycopene on pain facilitation, glial activation, and the SIRT1/mTOR pathway in the dorsal horn of rats with burn injury pain (BIP). Here we found that the mechanical pain threshold increased in the lycopene group compared with that of the control group, (P < 0.05). Compared with expression in the sham group, mTOR, pS6, p4EBP, GFAP, and Iba-1 decreased and SIRT1 increased in the lycopene group (P < 0.01). Glial activation in the spinal dorsal horn of BIP rats was alleviated by lycopene (P < 0.01). The SIRT1 and mTOR were mainly distributed in neurons in the spinal dorsal horn in the BIP model. Intrathecal injection of 3-MA (a mTOR agonist) or EX-527 (an inhibitor of Sirt1) partially antagonized lycopene-induced analgesia. Intrathecal injection of rapamycin (an mTOR inhibitor) or SRT1720 (an agonist of Sirt1) induced analgesia in BIP rats. 3-MA abrogated the SRT1720-induced analgesic effects. The present data indicated that the SIRT1/mTOR pathway changed in the spinal dorsal horn of BIP rats; Lycopene alleviated the pain sensitization of BIP rats by regulating the SIRT1/mTOR pathway and glial activation in the spinal dorsal horn.