Upregulation of miR-375 level ameliorates morphine analgesic tolerance in mouse dorsal root ganglia by inhibiting the JAK2/STAT3 pathway

Bioinformatic Analysis from a Descriptive Profile of miRNAs in Chronic Migraine

Chronic migraines have been described chiefly only from a clinical perspective. However, searching for reliable molecular markers has allowed for the discovery of the expression of different genes mainly associated with inflammation, neuro-vascularization, and pain-related pathways. The interest in microRNAs (miRs) that can regulate the expression of these genes has gained significant relevance since multiple miRs could play a key role in regulating these events. In this study, miRs were searched in samples from patients with chronic migraine, and the inclusion criteria were carefully reviewed. Different bioinformatic tools, such as miRbase, targetscan, miRPath, tissue atlas, and miR2Disease, were used to analyze the samples. Our findings revealed that some of the miRs were expressed more (miR-197, miR-101, miR-92a, miR-375, and miR-146b) and less (miR-133a/b, miR-134, miR-195, and miR-340) than others. We concluded that, during chronic migraine, common pathways, such as inflammation, vascularization, neurodevelopment, nociceptive pain, and pharmacological resistance, were associated with this disease.

Effect of spirocyclopiperazinium salt compound LXM-15 on spinal nerve injury in rats

BACKGROUND

Currently available therapies for neuropathic pain show limited efficacy. This study aimed to investigate the anti-nociceptive effect of the spirocyclopiperazinium salt compound LXM-15 in spinal nerve ligation (SNL) rats and to explore the potential mechanisms.

METHODS

Mechanical allodynia and thermal hyperalgesia tests were used to evaluate the effects of LXM-15 in SNL rats. The expression of CaMKIIα, CREB, JAK2, STAT3, c-fos and TNF-α was detected by western blotting, ELISA or qRT-PCR analysis. Receptor blocking test was performed to explore possible target.

RESULTS

Administration of LXM-15 (1, 0.5, 0.25 mg/kg, i.g.) dose-dependently attenuated mechanical allodynia and thermal hyperalgesia in rats subjected to SNL (p < 0.01, p < 0.05), and the effects were completely blocked by peripheral α7 nicotinic or M4 muscarinic receptor antagonist (p > 0.05). LXM-15 significantly decreased the overexpression of phosphorylated CaMKIIα, CREB, JAK2 and STAT3 proteins and the mRNA levels of TNF-α and c-fos (p < 0.01, p < 05). All of the effects could be blocked by α7 or M4 receptor antagonist. Furthermore, LXM-15 reduced the protein expression of TNF-α and c-fos (p < 0.01, p < 0.05). No significant acute toxicity or abnormal hepatorenal function was observed.

CONCLUSIONS

This is the first study to report that LXM-15 exerts significant anti-nociceptive effect on SNL rats. This effect may occur by activating peripheral α7 nicotinic and M4 muscarinic receptors, further inhibiting the CaMKIIα/CREB and JAK2/STAT3 signalling pathways, and finally inhibiting the expression of TNF-α and c-fos.

SIGNIFICANCE

Existing treatments for neuropathic pain show limited efficacy with severe adverse reactions. This paper is the first to report that LXM-15, a new spirocyclopiperazinium salt compound, exerts a significant anti-nociception in SNL rats without obvious toxicity. The underlying mechanisms include activating peripheral α7 nicotinic and M4 muscarinic receptors, then inhibiting the signalling pathways of CaMKIIα/CREB and JAK2/STAT3 and the expressions of TNF-α and c-fos. This study sheds new light on the development of novel analgesic drugs with fewer side effects.

Targeting the JAK2/STAT3 signaling pathway for chronic pain

Chronic pain is a notable health concern because of its prevalence, persistence, and associated mental stress. Drugs targeting chronic pain with potent abirritation, and minimal side effects remain unidentified. Substantial evidence indicates that the Janus Kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) signaling pathway plays a distinct and critical role in different stages of chronic pain. Aberrant activation of the JAK2/STAT3 signaling pathway is evident in multiple chronic pain models. Moreover, an increasing number of studies have demonstrated that the downregulation of JAK2/STAT3 can attenuate chronic pain in different animal models. In this review, we investigated the mechanism and role of the JAK2/STAT3 signaling pathway in modulating chronic pain. The aberrant activation of JAK2/STAT3 can trigger chronic pain by interacting with microglia and astrocytes, releasing proinflammatory cytokines, inhibiting anti-inflammatory cytokines, and regulating synaptic plasticity. We also retrospectively reviewed current reports on JAK2/STAT3 pharmacological inhibitors that demonstrated their significant therapeutic potential in different types of chronic pain. In summary, our results provide strong evidence that the JAK2/STAT3 signaling pathway is a promising therapeutic target for chronic pain.

Methadone administered to rat dams during pregnancy and lactation affects the circadian rhythms of their pups

The circadian clock is one of the most important homeostatic systems regulating the majority of physiological functions. Its proper development contributes significantly to the maintenance of health in adulthood. Methadone is recommended for the treatment of opioid use disorders during pregnancy, increasing the number of children prenatally exposed to long-acting opioids. Although early-life opioid exposure has been studied for a number of behavioral and physiological changes observed later in life, information on the relationship between the effects of methadone exposure and circadian system development is lacking. Using a rat model, we investigated the effects of prenatal and early postnatal methadone administration on the maturation of the circadian clockwork in the suprachiasmatic nucleus (SCN) and liver, the rhythm of aralkylamine N-acetyltransferase (AA-NAT) activity in the pineal gland, and gene expression in the livers of 20-day-old rats. Our data show that repeated administration of methadone to pregnant and lactating mothers has significant effect on rhythmic gene expression in the SCN and livers and on the rhythm of AA-NAT in the offspring. Similar to previous studies with morphine, the rhythm amplitudes of the clock genes in the SCN and liver were unchanged or enhanced. However, six of seven specific genes in the liver showed significant downregulation of their expression, compared to the controls in at least one experimental group. Importantly, the amplitude of the AA-NAT rhythm was significantly reduced in all methadone-treated groups. As there is a strong correlation with melatonin levels, this result could be of importance for clinical practice.

Research progress of p38 as a new therapeutic target against morphine tolerance and the current status of therapy of morphine tolerance

With the development of the medical industry, new painkillers continue to appear in people's field of vision, but so far no painkiller can replace morphine. While morphine has a strong analgesic effect, it is also easy to produce pain sensitivity and tolerance. Due to the great inter-individual differences in patient responses, there are few clear instructions on how to optimise morphine administration regimens, which complicates clinicians' treatment strategies and limits the effectiveness of morphine in long-term pain therapy. P38MAPK is a key member of the MAPK family. Across recent years, it has been discovered that p38MAPK rises dramatically in a wide range of morphine tolerance animal models. Morphine tolerance can be reduced or reversed by inhibiting p38MAPK. However, the role and specific mechanism of p38MAPK are not clear. In this review, we synthesise the relevant findings, highlight the function and potential mechanism of p38MAPK in morphine tolerance, as well as the present status and efficacy of morphine tolerance therapy, and underline the future promise of p38MAPK targeted morphine tolerance treatment.

Noncoding RNAs: Novel Targets for Opioid Tolerance

As a global health problem, chronic pain is one of the leading causes of disability, and it imposes a huge economic and public health burden on families and society. Opioids represent the cornerstone of analgesic drugs. However, opioid tolerance caused by long-term application of opioids is a major factor leading to drug withdrawal, serious side effects caused by dose increases, and even the death of patients, placing an increasing burden on individuals, medicine, and society. Despite efforts to develop methods to prevent and treat opioid tolerance, no effective treatment has yet been found. Therefore, understanding the mechanism underlying opioid tolerance is crucial for finding new prevention and treatment strategies. Noncoding RNAs (ncRNAs) are important parts of mammalian gene transcriptomes, and there are thousands of unique noncoding RNA sequences in cells. With the rapid development of high-throughput genome technology, research on ncRNAs has become a hot topic in biomedical research. In recent years, studies have shown that ncRNAs mediate physiological and pathological processes, including chromatin remodeling, transcription, posttranscriptional modification and signal transduction, which are key regulators of physiological processes in developmental and disease environments and have become biomarkers and potential therapeutic targets for various diseases. An increasing number of studies have found that ncRNAs are closely related to the development of opioid tolerance. In this review, we have summarized the evidence that ncRNAs play an important role in opioid tolerance and that ncRNAs may be novel targets for opioid tolerance.

DNA Methylation and Non-Coding RNAs during Tissue-Injury Associated Pain

While about half of the population experience persistent pain associated with tissue damages during their lifetime, current symptom-based approaches often fail to reduce such pain to a satisfactory level. To provide better patient care, mechanism-based analgesic approaches must be developed, which necessitates a comprehensive understanding of the nociceptive mechanism leading to tissue injury-associated persistent pain. Epigenetic events leading the altered transcription in the nervous system are pivotal in the maintenance of pain in tissue injury. However, the mechanisms through which those events contribute to the persistence of pain are not fully understood. This review provides a summary and critical evaluation of two epigenetic mechanisms, DNA methylation and non-coding RNA expression, on transcriptional modulation in nociceptive pathways during the development of tissue injury-associated pain. We assess the pre-clinical data and their translational implication and evaluate the potential of controlling DNA methylation and non-coding RNA expression as novel analgesic approaches and/or biomarkers of persistent pain.

Maternal morphine intake during pregnancy and lactation affects the circadian clock of rat pups

Early-life morphine exposure causes a variety of behavioural and physiological alterations observed later in life. In the present study, we investigated the effects of prenatal and early postnatal morphine on the maturation of the circadian clockwork in the suprachiasmatic nucleus and the liver, and the rhythm in aralkylamine N-acetyltransferase activity in the pineal gland. Our data suggest that the most affected animals were those born to control, untreated mothers and cross-fostered by morphine-exposed dams. These animals showed the highest mesor and amplitude in the rhythm of Per2, Nr1d1 but not Per1 gene expression in the suprachiasmatic nuclei (SCN) and arrhythmicity in AA-NAT activity in the pineal gland. In a similar pattern to the rhythm of Per2 expression in the SCN, they also expressed Per2 in a higher amplitude rhythm in the liver. Five of seven specific genes in the liver showed significant differences between groups in their expression. A comparison of mean relative mRNA levels suggests that this variability was caused mostly by cross-fostering, animals born to morphine-exposed dams that were cross-fostered by control mothers and vice versa differed from both groups of natural mothers raising offspring. Our data reveal that the circadian system responds to early-life morphine administration with significant changes in clock gene expression profiles both in the SCN and in the liver. The observed differences between the groups suggest that the dose, timing and accompanying stress events such as cross-fostering may play a role in the final magnitude of the physiological challenge that opioids bring to the developing circadian clock.

Epigenetic Alterations in Prescription Opioid Misuse: New Strategies for Precision Pain Management

Prescription opioids are used for some chronic pain conditions. However, generally, long-term therapy has unwanted side effects which may trigger addiction, overdose, and eventually cause deaths. Opioid addiction and chronic pain conditions have both been associated with evidence of genetic and epigenetic alterations. Despite intense research interest, many questions about the contribution of epigenetic changes to this typology of addiction vulnerability and development remain unanswered. The aim of this review was to summarize the epigenetic modifications detected in specific tissues or brain areas and associated with opioid prescription and misuse in patients who have initiated prescribed opioid management for chronic non-cancer pain. The review considers the effects of opioid exposure on the epigenome in central and peripheral tissues in animal models and human subjects and highlights the mechanisms in which opioid epigenetics may be involved. This will improve our current understanding, provide the basis for targeted, personalized pain management, and thus balance opioid risks and benefits in managing chronic pain.

The prolactin receptor long isoform regulates nociceptor sensitization and opioid-induced hyperalgesia selectively in females

Pain is more prevalent in women for reasons that remain unclear. We have identified a mechanism of injury-free nociceptor sensitization and opioid-induced hyperalgesia (OIH) promoted by prolactin (PRL) in females. PRL signals through mutually inhibitory long (PRLR-L) and short (PRLR-S) receptor isoforms, and PRLR-S activation induces neuronal excitability. PRL and PRLR expression were higher in females. CRISPR-mediated editing of PRLR-L promoted nociceptor sensitization and allodynia in naïve, uninjured female mice that depended on circulating PRL. Opioids, but not trauma-induced nerve injury, decreased PRLR-L promoting OIH through activation of PRLR-S in female mice. Deletion of both PRLR-L and PRLR-S (total PRLR) prevented, whereas PRLR-L overexpression rescued established OIH selectively in females. Inhibition of circulating PRL with cabergoline, a dopamine D2 agonist, up-regulated PRLR-L and prevented OIH only in females. The PRLR-L isoform therefore confers protection against PRL-promoted pain in females. Limiting PRL/PRLR-S signaling pharmacologically or with gene therapies targeting the PRLR may be effective for reducing pain in a female-selective manner.

MiR-124-3p alleviates the dezocine tolerance against pain by regulating TRAF6 in a rat model

MicroRNAs (miRNAs) play important roles in drug tolerance and regulating pain. The purpose of the present study is to explore the regulatory mechanism of miR-124-3p on dezocine tolerance against pain in a rat model. The expression of miR-124-3p and TRAF6 in spinal cord of rats was detected by quantitative reverse-transcription PCR. The paw withdrawal latency (PWL) and maximal potential efficiency % of rats were detected by PWL assay. The levels of IL-1β and TNF-α in spinal cord tissues of rats were measured by ELISA assay. The interaction between TRAF6 and miR-124-3p was predicted by TargetScan software (http://www.targetscan.org) and confirmed by the dual-luciferase reporter assay. The protein level of TRAF6 was determined by western blot. MiR-124-3p expression was highly downregulated in a dezocine-resistant model. MiR-124-3p overexpression could alleviate dezocine tolerance in rats. TRAF6 expression was significantly upregulated in a dezocine-resistant model. MiR-124-3p targeted TRAF6 and TRAF6 was negatively modulated by miR-124-3p. In addition, overexpression of TRAF6 could reverse the inhibitory effects of miR-124-3p on dezocine tolerance. Overexpression of miR-124-3p alleviates dezocine tolerance against pain via regulating TRAF6 in a rat model, providing a possible solution to address dezocine tolerance in clinical.

MicroRNA-375-mediated regulation of ILC2 cells through TSLP in allergic rhinitis

Background

Studies have shown that the number and function of type II innate lymphoid cells (ILC2) in peripheral blood of allergic rhinitis (AR) children increased significantly. This study aims to evaluate the role of miR-375 in the regulation of the differentiation and function of ILC2 through both in vivo and in vitro studies.

Methods

The expression of miR-375, thymic stromal lymphopoietin (TSLP) and the frequency of ILC2 were detected and compared between AR children and controls by real-time polymerase chain reaction (PCR), enzyme-linked immunosorbnent assay (ELISA) and flow cytometry, respectively. The miR-375 mimics or inhibitors were transfected into human nasal epithelial cells (HNECs), and the production of TSLP was detected by ELISA. HNECs and ILC2s were co-cultured to explore the role of miR-375 on ILC2s. AR mice models were established to prove the effect of miR-375 on ILC2s in vivo.

Results

The expression of TSLP, miR-375, and the frequency of ILC2 were significantly higher in AR compared with controls. We found that the TSLP expression by HNECs were significantly higher when transfected with miR-375 mimics than in those transfected with miR-control and miR-375 inhibitor. In the coculture system, HNECs transfected with miR-375 mimics promote the type II cytokines production by ILC2, and this effect was blocked by anti-TSLP. Our results also showed that the miR-375 inhibitors attenuate allergic symptoms and production of type II cytokines in AR mice.

Conclusions

Our findings suggest that miR-375-mediated regulation of ILC2 cells through TSLP, providing new potential treatment target for AR.

Integrating Pathophysiology in Migraine: Role of the Gut Microbiome and Melatonin

BACKGROUND

The pathoetiology and pathophysiology of migraine are widely accepted as unknown.

METHODS

The current article reviews the wide array of data associated with the biological underpinnings of migraine and provides a framework that integrates previously disparate bodies of data.

RESULTS

The importance of alterations in stress- and pro-inflammatory cytokine- induced gut dysbiosis, especially butyrate production, are highlighted. This is linked to a decrease in the availability of melatonin, and a relative increase in the N-acetylserotonin/melatonin ratio, which has consequences for the heightened glutamatergic excitatory transmission in migraine. It is proposed that suboptimal mitochondria functioning and metabolic regulation drive alterations in astrocytes and satellite glial cells that underpin the vasoregulatory and nociceptive changes in migraine.

CONCLUSION

This provides a framework not only for classical migraine associated factors, such as calcitonin-gene related peptide and serotonin, but also for wider factors in the developmental pathoetiology of migraine. A number of future research and treatment implications arise, including the clinical utilization of sodium butyrate and melatonin in the management of migraine.

Endogenous opiates and behavior: 2017

This paper is the fortieth consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2017 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonists and antagonists. The review is subdivided into the following specific topics: molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (1), the roles of these opioid peptides and receptors in pain and analgesia in animals (2) and humans (3), opioid-sensitive and opioid-insensitive effects of nonopioid analgesics (4), opioid peptide and receptor involvement in tolerance and dependence (5), stress and social status (6), learning and memory (7), eating and drinking (8), drug abuse and alcohol (9), sexual activity and hormones, pregnancy, development and endocrinology (10), mental illness and mood (11), seizures and neurologic disorders (12), electrical-related activity and neurophysiology (13), general activity and locomotion (14), gastrointestinal, renal and hepatic functions (15), cardiovascular responses (16), respiration and thermoregulation (17), and immunological responses (18).

Up-regulation of microRNA-375 ameliorates the damage of dopaminergic neurons, reduces oxidative stress and inflammation in Parkinson's disease by inhibiting SP1

Background: This study is conducted to investigate the protective role of elevated microRNA-375 (miR-375) in dopaminergic neurons in Parkinson’s disease through down-regulating transcription factor specificity protein 1 (SP1).

Results: The successfully modeled rats with Parkinson’s disease showed aggregated neurobehavioral change, increased neuroinflammatory response and oxidative stress, and lowered dopamine content. Parkinson’s disease rats treated with overexpressed miR-375 displayed improved neurobehavioral change, ameliorated neuroinflammatory response and oxidative stress, heightened dopamine content and abated neuronal apoptosis by down-regulating SP1. Up-regulation of SP1 reversed the protective effect of upregulated miR-375 on Parkinson’s disease.

Conclusion: Up-regulation of miR-375 ameliorated the damage of dopaminergic neurons, reduced oxidative stress and inflammation in Parkinson’s disease by inhibiting SP1.

Methods: Parkinson’s disease rat model was established by targeted injection of 6-hydroxydopamine to damage the substantia nigra striatum. The successfully modeled Parkinson’s disease rats were intracerebroventricularly injected with miR-375 mimics or pcDNA3.1-SP1. The functions of miR-375 and SP1 in neurobehavioral change, neuroinflammatory response, oxidative stress, dopamine content and expression of apoptosis-related proteins in the substantia nigra of Parkinson’s disease rats were evaluated. The target relation of miR-375 and SP1 was confirmed by bioinformatics analysis and dual luciferase reporter gene assay.

LncRNAs linc00311 and AK141205 are identified as new regulators in STAT3-mediated neuropathic pain in bCCI rats

Neuropathic pain is a severe disease caused by lesions or diseases in the somatosensory system. Long non-coding RNAs (lncRNAs) are important in the development and maintenance of neuropathic pain. However, the precise role of lncRNAs in regulating neuropathic pain remains largely unknown. In this study, a rat model of bilateral chronic constriction injury (bCCI) was established, and microarray was applied to analyze differentially expressed lncRNAs among sham group, bCCI group and the experimental group (bCCI rats administrated with a specific STAT3 inhibitor WP1066). Linc00311 and lncRNA-AK141205 were uncharacterized lncRNAs both upregulated by > 2 folds in bCCI model compared with Sham group, and they were downregulated by > 2 folds following WP1066 administration compared with bCCI group. Downregulation of linc00311 and lncRNA-AK141205 by specific siRNAs significantly attenuated mechanical allodynia, thermal and cold hyperalgesia in bCCI rats. In addition, inhibition of linc00311 and lncRNA-AK141205 inactivated the signal transducer and activator of transcription 3 (STAT3) signaling in spinal microglia in vivo and in vitro. Inhibition of linc00311 and lncRNA-AK141205 could reduce activation of STAT3 and production of proinflammatory cytokines. Moreover, activating STAT3 with SD19 could antagonize the effect of the suppressive effect of siRNAs on production of proinflammatory cytokines. Hence, it is likely that silencing linc00311 and lncRNA-AK141205 may be a promising and novel treatment for neuropathic pain.

Retracted Article: Upregulation of miR-26b alleviates morphine tolerance by inhibiting BDNF via Wnt/β-catenin pathway in rats

Background: Morphine is a commonly used analgesic drug. However, long-term use of morphine will cause tolerance which limits its clinical application in pain treatment. MicroRNAs (miRNAs) have been reported to be involved in the morphine tolerance, but the underlying mechanism is still poorly understood. Methods: Tail flick test was used to measure the maximum possible effect (MPE). Quantitative real-time PCR was employed to detect miR-26b, BDNF, and Wnt5a expression in rat dorsal root ganglia (DRG). Luciferase report assay was introduced to verify the binding relationship between miR-26b and Wnt5a. BDNF, Wnt5a and β-catenin protein level were tested by western blotting. Results: MiR-26b was down-regulated during the development of morphine tolerance while BDNF was upregulated. Overexpression of miR-26b or BDNF inhibition alleviated morphine tolerance. Wnt5a was directly targeted and inhibited by miR-26b via binding to the 3'-UTR of Wnt5a. The Wnt/β-catenin pathway was active in morphine tolerant rats. Moreover, overexpression of Wnt5a could partially enhance miR-26 mimic-mediated morphine tolerance, while a Wnt5a inhibitor could attenuate the tolerance. Conclusion: The present study demonstrated that miR-26b overexpression alleviated morphine tolerance by inhibiting BDNF via the Wnt/β-catenin pathway in rats, highlighting a promising target for the treatment of morphine tolerance.

Electroacupuncture treatment upregulates α7nAChR and inhibits JAK2/STAT3 in dorsal root ganglion of rat with spared nerve injury

Background

Neuropathic pain with complicated mechanism severely disrupts patient quality of life. The novel approaches and more effective management should be further investigated. It was reported that alpha-7 nicotinic acetylcholine receptor (α7nAChR) and janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) signaling in dorsal root ganglion (DRG) contributed to the pathogenesis of neuropathic pain. Our previous study has shown that electroacupuncture (EA) alleviated neuropathic pain via activating α7nAChR in the spinal cord. However, whether the effect of 2 Hz EA on spared nerve injury (SNI)-induced neuropathic pain is mediated through modulation of α7nAChR and JAK2/STAT3 pathway in the DRG remains unclear.

Materials and methods

The SNI-induced neuropathic pain rat model was used in this study. After application of 2 Hz EA treatment to SNI rats on day 3, 7, 14 and 21 post-surgery, the expression levels of α7nAChR, JAK2/STAT3 and some cytokines in DRG were determined by qRT-PCR and Western blot analysis.

Results

We found that SNI induced significant down-regulation of α7nAChR mRNA and protein expression. SNI also obviously elicited the decrease in anti-inflammatory cytokine IL-10 protein expression. The enhancement of p-JAK2, p-STAT3, pro-inflammatory cytokines IL-1β and IL-6 protein levels induced by SNI were also observed. However, 2 Hz EA treatment to SNI rats distinctly improved α7nAChR and IL-10 levels and reduced p-JAK2, p-STAT3, IL-1β and IL-6 expression in the DRG.

Conclusion

Our present study suggested that 2 Hz EA treatment indeed activated α7nAChR, suppressed JAK2/STAT3 signaling and re-balanced the relationship between pro-inflammatory and anti-inflammatory cytokines in DRG of SNI rat, which provided insight into our understanding of the mechanism for 2 Hz EA to attenuate neuropathic pain.

Morphine tolerance is attenuated in germfree mice and reversed by probiotics, implicating the role of gut microbiome

Prolonged exposure to opioids results in analgesic tolerance, drug overdose, and death. The mechanism underlying morphine analgesic tolerance still remains unresolved. We show that morphine analgesic tolerance was significantly attenuated in germfree (GF) and in pan-antibiotic-treated mice. Reconstitution of GF mice with naïve fecal microbiota reinstated morphine analgesic tolerance. We further demonstrated that tolerance was associated with microbial dysbiosis with selective depletion in Bifidobacteria and Lactobacillaeae. Probiotics, enriched with these bacterial communities, attenuated analgesic tolerance in morphine-treated mice. These results suggest that probiotic therapy during morphine administration may be a promising, safe, and inexpensive treatment to prolong morphine's efficacy and attenuate analgesic tolerance. We hypothesize a vicious cycle of chronic morphine tolerance: morphine-induced gut dysbiosis leads to gut barrier disruption and bacterial translocation, initiating local gut inflammation through TLR2/4 activation, resulting in the activation of proinflammatory cytokines, which drives morphine tolerance.

Novel biomarkers to assess in utero effects of maternal opioid use: First steps toward understanding short- and long-term neurodevelopmental sequelae

Maternal opioid use disorder is common, resulting in significant neonatal morbidity and cost. Currently, it is not possible to predict which opioid-exposed newborns will require pharmacotherapy for neonatal abstinence syndrome. Further, little is known regarding the effects of maternal opioid use disorder on the developing human brain. We hypothesized that novel methodologies utilizing fetal central nervous system-derived extracellular vesicles isolated from maternal blood can address these gaps in knowledge. Plasma from opioid users and controls between 9 and 21 weeks was precipitated and extracellular vesicles were isolated. Mu opioid and cannabinoid receptor levels were quantified. Label-free proteomics studies and unbiased small RNA next generation sequencing was performed in paired fetal brain tissue. Maternal opioid use disorder increased mu opioid receptor protein levels in extracellular vesicles independent of opioid equivalent dose. Moreover, cannabinoid receptor levels in extracellular vesicles were upregulated with opioid exposure indicating cross talk with endocannabinoids. Maternal opioid use disorder was associated with significant changes in extracellular vesicle protein cargo and fetal brain micro RNA expression, especially in male fetuses. Many of the altered cargo molecules and micro RNAs identified are associated with adverse clinical neurodevelopmental outcomes. Our data suggest that assays relying on extracellular vesicles isolated from maternal blood extracellular vesicles may provide information regarding fetal response to opioids in the setting of maternal opioid use disorder. Prospective clinical studies are needed to evaluate the association between extracellular vesicle biomarkers, risk of neonatal abstinence syndrome and neurodevelopmental outcomes.

High throughput metabolomics-proteomics investigation on metabolic phenotype changes in rats caused by Radix Scrophulariae using ultra-performance liquid chromatography with mass spectrometry

Radix Scrophulariae, a traditional Chinese herb, is used to treat various diseases, including H₂O₂-induced apoptosis in cardiomyocytes, HaCaT cells, hyperuricaemia, and depression. This study screened metabolites, proteins and common pathways to better understand both the therapeutic effects and side effects of this herb. Methods: Untargeted metabolomics based on UPLC-TOF-MS, coupled with proteomics based on nano-UPLC-Q-Exactive-MS/MS, were used to investigate the effects of R. Scrophulariae in rats. Fifty-one identified metabolites in urine samples and 76 modulated proteins in liver tissue were potential biomarkers for R. Scrophulariae treatment. The biomarkers and common pathways involved were steroid hormone biosynthesis, drug metabolism-cytochrome p450, drug metabolism-other enzymes, pentose and glucuronate interconversions, and starch and sucrose metabolism. Some biomarkers were beneficial for treating diseases such as cancer, tuberculosis and isovaleric acidaemia, while other biomarkers caused side effects. Metabolomic and proteomic analyses of R. Scrophulariae-treated rats provided valuable information on the biological safety and efficacy of using R. Scrophulariae clinically.

Radix Scrophulariae, a traditional Chinese herb, is used to treat various diseases, including H₂O₂-induced apoptosis in cardiomyocytes, HaCaT cells, hyperuricaemia, and depression.

The Emerging Perspective of Morphine Tolerance: MicroRNAs

Morphine has unfavorable side effects including analgesic tolerance. Morphine tolerance counteracts analgesic efficacy and drives dose escalation. The mechanisms underlying morphine tolerance remain disputed, which has prevented the development of therapies to maximize and sustain analgesic efficacy. Morphine tolerance is an adaptive process induced by chronic morphine that has been shown to result from complex alterations at the molecular level with μ opioid receptors (MORs), as well as at the synaptic, cellular, and circuit levels. MicroRNAs are noncoding RNAs that have been proposed to regulate gene expression and degradation at the posttranscriptional level, including the MOR, as well as synaptic plasticity and neuroplasticity, in both the peripheral and central nervous systems. This review covers some of the most striking microRNA functions involved in morphine tolerance and presents limitations on our knowledge of their physiological roles.

Emerging roles of microRNAs in morphine tolerance

Morphine is commonly used in clinical management to alleviate moderate-to-severe pain. However, prolonged and repeated use of morphine leads to tolerance. Morphine tolerance is a challenging clinical problem that limits its clinical application in pain treatment. The mechanisms underlying morphine tolerance are still not completely understood. MicroRNAs (miRNAs) are small noncoding RNAs containing 18~22 nucleotides that modulate gene expression in a post-transcriptional manner, and their dysregulation causes various diseases. miRNAs bind to the 3ʹ-UTR (untranslated region) of target gene mRNA, inhibiting or destabilizing translation of the transcripts. Morphine causes differential miRNA upregulation or downregulation. This review will present evidence for the contribution of miRNAs to tolerance of the antinociception effect of opioids.

CircScd1 Promotes Fatty Liver Disease via the Janus Kinase 2/Signal Transducer and Activator of Transcription 5 Pathway

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is one of the most common liver diseases in affluent countries. Recent studies have reported that circular RNAs (circRNAs) are important regulators of hepatic steatosis. However, the role and mechanism of circRNA in NAFLD are poorly understood.

AIMS

This study is to reveal the role and mechanism of circRNA in NAFLD.

METHODS

Through NAFLD-related circRNA microarrays, we used real-time quantitative reverse transcription-polymerase chain reaction to screen circScd1 levels in control and test groups of mice fed a high-fat diet. RNA interference and over-expression plasmid vectors were used to manipulate the expression of circScd1, and the biological effects were evaluated by oil red staining, triglyceride detection, and western blot analysis.

RESULTS

CircScd1 expression was significantly lower in NAFLD tissues than in control tissues. Moreover, over-expression of circScd1 significantly inhibited the formation of lipid droplets. Western blot analyses showed that the protein levels of Janus kinase 2 (JAK2) and signal transducer and activator of transcription 5 (STAT5) were significantly increased. However, knockdown of circScd1 significantly promoted the degree of hepatocellular lipidosis and reduced the expression levels of JAK2 and STAT5.

CONCLUSIONS

Aberrant expression of circScd1 affects the extent of hepatocellular lipidosis in NAFLD and promotes fatty liver disease via the JAK2/STAT5 pathway.

Differential effects of chronic stress in young-adult and old female mice: cognitive-behavioral manifestations and neurobiological correlates

Stress-related psychopathology is highly prevalent among elderly individuals and is associated with detrimental effects on mood, appetite and cognition. Conversely, under certain circumstances repeated mild-to-moderate stressors have been shown to enhance cognitive performance in rodents and exert stress-inoculating effects in humans. As most stress-related favorable outcomes have been reported in adolescence and young-adulthood, this apparent disparity could result from fundamental differences in how aging organisms respond to stress. Furthermore, given prominent age-related alterations in sex hormones, the effect of chronic stress in aging females remains a highly relevant yet little studied issue. In the present study, female C57BL/6 mice aged 3 (young-adult) and 20-23 (old) months were subjected to 8 weeks of chronic unpredictable stress (CUS). Behavioral outcomes were measured during the last 3 weeks of the CUS protocol, followed by brain dissection for histological and molecular end points. We found that in young-adult female mice, CUS resulted in decreased anxiety-like behavior and enhanced cognitive performance, whereas in old female mice it led to weight loss, dysregulated locomotion and memory impairment. These phenotypes were paralleled by differential changes in the expression of hypothalamic insulin and melanocortin-4 receptors and were consistent with an age-dependent reduction in the dynamic range of stress-related changes in the hippocampal transcriptome. Supported by an integrated microRNA (miRNA)-mRNA expression analysis, the present study proposes that, when confronted with ongoing stress, neuroprotective mechanisms involving the upregulation of neurogenesis, Wnt signaling and miR-375 can be harnessed more effectively during young-adulthood. Conversely, we suggest that aging alters the pattern of immune activation elicited by stress. Ultimately, interventions that modulate these processes could reduce the burden of stress-related psychopathology in late life.

miR-375 prevents nasal mucosa cells from apoptosis and ameliorates allergic rhinitis via inhibiting JAK2/STAT3 pathway

This study aims to explore the roles, and related mechanisms of miR-375 in nasal mucosa cells apoptosis and allergic rhinitis. Here, miR-375 was found to be decreased in the epithelia of nasal mucosa of allergic rhinitis mice and TNF-α-stimulated nasal mucosa cells, while JAK2 expression exhibited an opposite effect. Mechanistically, miR-375/JAK2 regulatory axis was identified in nasal mucosa cells via luciferase reporter, qRT-PCR, western blot and RNA immune co-precipitation (RIP) assays. Pre- or post-injection of miR-375 agomir following ovalbumin (OVA) treatment attenuated OVA-induced allergic rhinitis, characterized as the downregulation of IL-6 and TNF-α secretion, and upregulation of IL-10 secretion, these effects were attenuated by infection with JAK2 adenovirus through nasal cavity inhalation. Additionally, overexpression of miR-375 reversed TNF-α-mediated nasal mucosa cells apoptosis, which was attenuated by JAK2 overexpression. Therefore, our results indicate that miR-375 prevents nasal mucosa cells from apoptosis and ameliorates allergic rhinitis via inhibiting JAK2/STAT3 pathway.

The Regulatory Mechanisms and Therapeutic Potential of MicroRNAs: From Chronic Pain to Morphine Tolerance

Chronic pain, including cancer-related pain, is a pain condition often caused by inflammation or dysfunctional nerves. Chronic pain treatment poses a significant health care challenge, where opioids especially morphine are widely used and patients often develop tolerance over time with aggravated pain. microRNA (miRNA) is known to play important roles in regulating gene expressions in the nervous system to affect neuronal network plasticity related to algogenesis and the developing of morphine tolerance. In this article, we reviewed studies conducted in rodent animal models investigating the mechanisms of miRNAs regulation in chronic pain with different phenotypes and morphine tolerance. In addition, the potential of targeting miRNAs for chronic pain and morphine tolerance treatment is also reviewed. Finally, we point out the directions of the future research in chronic pain and morphine tolerance.

Sinomenine attenuates cancer-induced bone pain via suppressing microglial JAK2/STAT3 and neuronal CAMKII/CREB cascades in rat models

Cancer-induced bone pain is one of the most severe types of pathological pain, which often occurs in patients with advanced prostate, breast, and lung cancer. It is of great significance to improve the therapies of cancer-induced bone pain due to the opioids' side effects including addiction, sedation, pruritus, and vomiting. Sinomenine, a traditional Chinese medicine, showed obvious analgesic effects on a rat model of chronic inflammatory pain, but has never been proven to treat cancer-induced bone pain. In the present study, we investigated the analgesic effect of sinomenine after tumor cell implantation and specific cellular mechanisms in cancer-induced bone pain. Our results indicated that single administration of sinomenine significantly and dose-dependently alleviated mechanical allodynia in rats with cancer-induced bone pain and the effect lasted for 4 h. After tumor cell implantation, the protein levels of phosphorylated-Janus family tyrosine kinase 2 (p-JAK2), phosphorylated-signal transducers and activators of transcription 3 (p-STAT3), phosphorylated-Ca2+/calmodulin-dependent protein kinase II (p-CAMKII), and phosphorylated-cyclic adenosine monophosphate response element-binding protein (p-CREB) were persistently up-regulated in the spinal cord horn. Chronic intraperitoneal treatment with sinomenine markedly suppressed the activation of microglia and effectively inhibited the expression of JAK2/STAT3 and CAMKII/CREB signaling pathways. We are the first to reveal that up-regulation of microglial JAK2/STAT3 pathway are involved in the development and maintenance of cancer-induced bone pain. Moreover, our investigation provides the first evidence that sinomenine alleviates cancer-induced bone pain by inhibiting microglial JAK2/STAT3 and neuronal CAMKII/CREB cascades.

Overexpression of microRNA-375 impedes platelet-derived growth factor-induced proliferation and migration of human fetal airway smooth muscle cells by targeting Janus kinase 2

The abnormal proliferation and migration of airway smooth muscle (ASM) cells play a critical role in airway remodeling during the development of asthma. MicroRNAs (miRNAs) have emerged as critical regulators of ASM cell proliferation and migration in airway remodeling. In this study, we aimed to investigate the potential role of miR-375 in the regulation of platelet-derived growth factor (PDGF)-induced fetal ASM cell proliferation and migration. Our results showed that miR-375 expression was significantly decreased in fetal ASM cells that were treated with PDGF. Functional data showed that overexpression of miR-375 inhibited the proliferation and migration of fetal ASM cells, whereas inhibition of miR-375 enhanced the proliferation and migration of fetal ASM cells. The results of bioinformatics analysis and a dual-luciferase reporter assay showed that miR-375 binds directly to the 3'-untranslated region of Janus kinase 2 (JAK2). Further data confirmed that miR-375 negatively regulates the expression of JAK2 in fetal ASM cells. Moreover, miR-375 also impeded the PDGF-induced activation of signal transducer and activator of transcription 3 (STAT3) in fetal ASM cells. However, restoration of JAK2 expression partially reversed the inhibitory effect of miR-375 on fetal ASM cell proliferation and migration. Overall, our results demonstrate that miR-375 inhibits fetal ASM cell proliferation and migration by targeting JAK2/STAT3 signaling. Our study provides a potential therapeutic target for the development of novel treatment strategies for pediatric asthma.