Inhibition of c-Jun NH2-terminal kinase stimulates mu opioid receptor expression via p38 MAPK-mediated nuclear NF-κB activation in neuronal and non-neuronal cells

pNaktide mitigates inflammation-induced neuronal damage and behavioral deficits through the oxidative stress pathway

Neuroinflammation is closely related to the etiology and progression of neurodegenerative diseases such as Parkinson disease and Alzheimer disease. pNaktide, an Src inhibitor, exerts antioxidant effects by mimicking Na/K-ATPase. It has been verified that its anti-inflammation and anti-oxidation ability could be embodied in obesity, steatohepatitis, uremic cardiomyopathy, aging, and prostate cancer. This study aimed to investigate the effects and mechanisms of pNaktide in lipopolysaccharide (LPS)-induced behavioral damage, neuroinflammation, and neuronal damage. We found that pNaktide improved anxiety, memory, and motor deficits. pNaktide inhibited MAPK and NF-κB pathways induced by TLR4 activation, inhibited the NLRP3 inflammasome complex, and reduced the expression of inflammatory factors, complement factors, and chemokines. pNaktide inhibited the activation of Nrf2 and HO-1 antioxidant stress pathways by LPS and reduced the level of oxidative stress. Inhibition of autophagy and enhancement of apoptosis induced by LPS were also alleviated by pNaktide, which restored LPS-induced injury to newborn neurons in the hippocampus region. In summary, pNaktide attenuates neuroinflammation, reduces the level of oxidative stress, has neuroprotective effects, and may be used for the treatment of neuroinflammation-related diseases.

Crosstalk between Mu-Opioid receptors and neuroinflammation: Consequences for drug addiction and pain

Mu-Opioid Receptors (MORs) are well-known for participating in analgesia, sedation, drug addiction, and other physiological functions. Although MORs have been related to neuroinflammation their biological mechanism remains unclear. It is suggested that MORs work alongside Toll-Like Receptors to enhance the release of pro-inflammatory mediators and cytokines during pathological conditions. Some cytokines, including TNF-α, IL-1β and IL-6, have been postulated to regulate MORs levels by both avoiding MOR recycling and enhancing its production. In addition, Neurokinin-1 Receptor, also affected during neuroinflammation, could be regulating MOR trafficking. Therefore, inflammation in the central nervous system seems to be associated with altered/increased MORs expression, which might regulate harmful processes, such as drug addiction and pain. Here, we provide a critical evaluation on MORs' role during neuroinflammation and its implication for these conditions. Understanding MORs' functioning, their regulation and implications on drug addiction and pain may help elucidate their potential therapeutic use against these pathological conditions and associated disorders.

JNK signaling provides a novel therapeutic target for Rett syndrome

Background

Rett syndrome (RTT) is a monogenic X-linked neurodevelopmental disorder characterized by loss-of-function mutations in the MECP2 gene, which lead to structural and functional changes in synapse communication, and impairments of neural activity at the basis of cognitive deficits that progress from an early age. While the restoration of MECP2 in animal models has been shown to rescue some RTT symptoms, gene therapy intervention presents potential side effects, and with gene- and RNA-editing approaches still far from clinical application, strategies focusing on signaling pathways downstream of MeCP2 may provide alternatives for the development of more effective therapies in vivo. Here, we investigate the role of the c-Jun N-terminal kinase (JNK) stress pathway in the pathogenesis of RTT using different animal and cell models and evaluate JNK inhibition as a potential therapeutic approach.

Results

We discovered that the c-Jun N-terminal kinase (JNK) stress pathway is activated in Mecp2-knockout, Mecp2-heterozygous mice, and in human MECP2-mutated iPSC neurons. The specific JNK inhibitor, D-JNKI1, promotes recovery of body weight and locomotor impairments in two mouse models of RTT and rescues their dendritic spine alterations. Mecp2-knockout presents intermittent crises of apnea/hypopnea, one of the most invalidating RTT pathological symptoms, and D-JNKI1 powerfully reduces this breathing dysfunction. Importantly, we discovered that also neurons derived from hiPSC-MECP2 mut show JNK activation, high-phosphorylated c-Jun levels, and cell death, which is not observed in the isogenic control wt allele hiPSCs. Treatment with D-JNKI1 inhibits neuronal death induced by MECP2 mutation in hiPSCs mut neurons.

Conclusions

As a summary, we found altered JNK signaling in models of RTT and suggest that D-JNKI1 treatment prevents clinical symptoms, with coherent results at the cellular, molecular, and functional levels. This is the first proof of concept that JNK plays a key role in RTT and its specific inhibition offers a new and potential therapeutic tool to tackle RTT.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-021-01190-2.

Recent advances in studies of molecular hydrogen in the treatment of pancreatitis

Pancreatitis is an inflammatory disease of the pancreas characterized by acinar cell injury and is associated with the abnormal release of trypsin, which results in high mortality due to systemic inflammatory response syndrome (SIRS) and multiple organ dysfunction syndrome (MODS). The inflammatory response, impaired autophagic flux, endoplasmic reticulum stress (ERS) and their interactions are involved in the development of pancreatitis. Molecular hydrogen (H₂) is a novel antioxidant that possesses the features of selective scavenging of oxygen free radicals and nontoxic metabolites and has been shown to be efficacious for treating infection, injury, tumors, ischemia-reperfusion organ injury, metabolic disease and several other diseases. Recent studies have found that H₂ is also useful in the treatment of pancreatitis, which may be related to the mechanism of antioxidative stress, anti-inflammation, anti-apoptosis, regulation of immunity and regulation of molecular pathways. This review focuses on the pathogenesis of pancreatitis and the research progress and potential mechanisms of H₂ against pancreatitis to provide theoretical bases for future research and clinical application of H₂ therapy for pancreatitis.

Canonical Notch signaling is required for bone morphogenetic protein-mediated human osteoblast differentiation

Osteoblast differentiation of bone marrow-derived human mesenchymal stem cells (hMSC) can be induced by stimulation with canonical Notch ligand, Jagged1, or bone morphogenetic proteins (BMPs). However, it remains elusive how these two pathways lead to the same phenotypic outcome. Since Runx2 is regarded as a master regulator of osteoblastic differentiation, we targeted Runx2 with siRNA in hMSC. This abrogated both Jagged1 and BMP2 mediated osteoblastic differentiation, confirming the fundamental role for Runx2. However, while BMP stimulation increased Runx2 and downstream Osterix protein expression, Jagged1 treatment failed to upregulate either, suggesting that canonical Notch signals require basal Runx2 expression. To fully understand the transcriptomic profile of differentiating osteoblasts, RNA sequencing was performed in cells stimulated with BMP2 or Jagged1. There was common upregulation of ALPL and extracellular matrix genes, such as ACAN, HAS3, MCAM, and OLFML2B. Intriguingly, genes encoding components of Notch signaling (JAG1, HEY2, and HES4) were among the top 10 genes upregulated by both stimuli. Indeed, ALPL expression occurred concurrently with Notch activation and inhibiting Notch activity for up to 24 hours after BMP administration with DAPT (a gamma secretase inhibitor) completely abrogated hMSC osteoblastogenesis. Concordantly, RBPJ (recombination signal binding protein for immunoglobulin kappa J region, a critical downstream modulator of Notch signals) binding could be demonstrated within the ALPL and SP7 promoters. As such, siRNA-mediated ablation of RBPJ decreased BMP-mediated osteoblastogenesis. Finally, systemic Notch inhibition using diabenzazepine (DBZ) reduced BMP2-induced calvarial bone healing in mice supporting the critical regulatory role of Notch signaling in BMP-induced osteoblastogenesis.

Citral-induced analgesia is associated with increased spinal serotonin, reduced spinal nociceptive signaling, and reduced systemic oxidative stress in arthritis

ETHNOPHARMACOLOGICAL RELEVANCE

Citral (3,7-dimethyl-2,6-octadienal) is the main component of Cymbopogon citratus (DC) Stapf, an herb with analgesic properties. Arthritic pain is the main unpleasant component of rheumatoid arthritis. The pharmacological approaches used to treat arthritic pain are often accompanied by adjuvant drugs or non-pharmacological treatments, showing a constant need in identifying new efficient analgesic drugs.

AIM OF THE STUDY

To test the hypothesis that citral, which is a monoterpenoid compound with therapeutic properties, reduces nociception, spinal pro-nociceptive and pro-inflammatory signaling, and systemic oxidative stress in arthritic rats.

MATERIALS AND METHODS

Complete Freund's adjuvant (CFA) was administrated in the left knee joint of rats. Oral treatment with citral was performed during eight days and mechanical allodynia was monitored during the period of treatment to evaluate the analgesic effect of citral. We assessed the levels of serotonin (5-hydroxytryptamine, 5-HT) in the lumbar dorsal horn of the spinal cord (DHSC) and the profiles of expression of the glycogen synthase kinase-3β (GSK3β), which is a 5-HT-regulated intracellular protein, and of the stress-activated protein kinase (SAPK)/jun N-terminal kinase (JNK) in the DHSC. Plasma levels of superoxide dismutase (SOD) were assessed as an indicator of oxidative stress.

RESULTS

Administration of CFA induced mechanical allodynia associated with reduced spinal GSK3β phosphorylation, increased spinal SAPK/JNK phosphorylation, and increased plasma SOD levels. Oral administration of citral reversed mechanical allodynia, increased endogenous spinal 5-HT levels, reduced spinal SAPK/JNK phosphorylation, and reduced plasma SOD levels.

CONCLUSION

Citral shows anti-nociceptive effects in an animal model of arthritic pain by modulating spinal nociceptive signaling.

Schisandrin B ameliorates high-glucose-induced vascular endothelial cells injury by regulating the Noxa/Hsp27/NF-κB signaling pathway

Background: To address the molecular mechanism of the anti-inflammation effects of schisandrin B (Sch B) in atherosclerosis, we examined injured HMEC-1, HBMEC, and HUVEC-12 cells induced by high glucose (HG). Methods: Western blot was performed to detect the levels of the proteins Hsp27, Noxa, TLR5, p-IκBα, and p-p65 in HG-induced cells, while ELISA was used to analyze the inflammatory cytokines TNF-α, IL-6, MCP-1, and IL-1β in cells with Hsp27 or Noxa stable expression. Results: Overexpression of Hsp27 upregulated the inflammatory cytokines and the release of IκBα, promoted transportation of p65 into the nucleus, and lastly, affected the inflammation process, while Sch B counteracted the upregulation. In addition, the effect of Noxa overexpression, which is different from Hsp27 overexpression, was consistent with that of Sch B treatment. Conclusions: Sch B may inhibit the inflammatory cascade and alleviate the injury to HMEC-1, HBMEC, and HUEVC-12 cells caused by HG by regulating the Noxa/Hsp27/NF-κB signaling pathway.

Innate Immune Signaling and Alcohol Use Disorders

Innate immune signaling is an important feature in the pathology of alcohol use disorders. Alcohol abuse causes persistent innate immune activation in the brain. This is seen in postmortem human alcoholic brain specimens, as well as in primate and rodent models of alcohol consumption. Further, in vitro models of alcohol exposure in neurons and glia also demonstrate innate immune activation. The activation of the innate immune system seems to be important in the development of alcohol use pathology, as anti-immune therapies reduce pathology and ethanol self-administration in rodent models. Further, innate immune activation has been identified in each of the stages of addiction: binge/intoxication, withdrawal/negative affect, and preoccupation/craving. This suggests that innate immune activation may play a role both in the development and maintenance of alcoholic pathology. In this chapter, we discuss the known contributions of innate immune signaling in the pathology of alcohol use disorders, and present potential therapeutic interventions that may be beneficial for alcohol use disorders.

Inhibition of TPPP3 attenuates β-catenin/NF-κB/COX-2 signaling in endometrial stromal cells and impairs decidualization

Embryo implantation and decidualization are critical events that occur during early pregnancy. Decidualization is synchronized by the crosstalk of progesterone and the cAMP signaling pathway. Previously, we confirmed the role of TPPP3 during embryo implantation in mice, but the underlying role and mechanism of TPPP3 in decidualization has not yet been understood. The current study was aimed to investigate the role of TPPP3 in decidualization in vivo and in vitro. For in vivo experiments, decidual reaction was artificially induced in the uteri of BALB/c mice. TPPP3 was found to be highly expressed during decidualization, whereas in the uteri receiving TPPP3 siRNA, decidualization was suppressed and the expression of β-catenin and decidual marker prolactin was reduced. In human endometrium, TPPP3 protein was found to be predominantly expressed in the mid-secretory phase (LH+7). In the primary culture of human endometrial stromal cells (hESCs), TPPP3 siRNA knockdown inhibited stromal-to-decidual cell transition and decreased the expression of the decidualization markers prolactin and IGFBP-1. Immunofluorescence and immunoblotting experiments revealed that TPPP3 siRNA knockdown suppressed the expression of β-catenin, NF-κB and COX-2 in hESCs during decidualization. TPPP3 inhibition also decreased NF-kB nuclear accumulation in hESCs and suppressed NF-κB transcriptional promoter activity. COX-2 expression was significantly decreased in the presence of a selective NF-kB inhibitor (QNZ) implicating that NF-kB is involved in COX-2 expression in hESCs undergoing decidualization. TUNEL assay and FACS analysis revealed that TPPP3 knockdown induced apoptosis and caused loss of mitochondrial membrane potential in hESCs. The study suggested that TPPP3 plays a significant role in decidualization and its inhibition leads to the suppression of β-catenin/NF-κB/COX-2 signaling along with the induction of mitochondria-dependent apoptosis.

Inhibition of macrophage migration inhibitory factor attenuates inflammation and fetal kidney injury in a rat model of acute pancreatitis in pregnancy

Acute pancreatitis in pregnancy (APIP) is a severe disease during pregnancy that mostly occurs during the third trimester. It can lead to additional complications including preterm delivery and high fetal mortality. In this study, we investigated the protective effects of (S, R)-3-(4-hydroxyphenyl)-4, 5dihydro-5-isoxazole acetic methyl ester (ISO-1), an inhibitor of macrophage migration inhibitory factor (MIF), on fetal kidney injury associated with the maternal acute necrotizing pancreatitis (ANP) and its potential mechanisms in a rat model. The APIP rat model was induced by retrograde infusion of sodium taurocholate saline solution into biliopancreatic duct. ISO-1 was given by intraperitoneally injection 30 min before the model was induced. The levels of maternal serum amylase, lipase, tumor necrosis factor-α (TNF-α) and interleukins (IL)-1β were measured. Maternal pancreas and fetal kidney injury were evaluated, and the expressions of MIF, phospho-p38MAPK (p-p38), nuclear factor-κB (NF-κB), TNF-α, IL-1β in fetal kidneys were detected. The results showed that fetal rats exhibited obvious acute kidney injury during APIP, and pregnant rats pretreated with ISO-1 notably attenuated the lesions. ISO-1 also significantly reduced the expression of MIF and the activations of p38MAPK, NF-κB, as well as the levels of TNF-α and IL-1β. These results indicated that ISO-1 could attenuate fetal kidney injury in pregnant rats with ANP by inhibiting MIF mediated p38MAPK/NF-κB signal pathways to reduce inflammatory response.

NF-KappaB Pathway Is Involved in Bone Marrow Stromal Cell-Produced Pain Relief

Bone marrow stromal cells (BMSCs) produce long-lasting attenuation of pain hypersensitivity. This effect involves BMSC's ability to interact with the immune system and activation of the endogenous opioid receptors in the pain modulatory circuitry. The nuclear factor kappa B (NF-κB) protein complex is a key transcription factor that regulates gene expression involved in immunity. We tested the hypothesis that the NF-κB signaling plays a role in BMSC-induced pain relief. We focused on the rostral ventromedial medulla (RVM), a key structure in the descending pain modulatory pathway, that has been shown to play an important role in BMSC-produced antihyperalgesia. In Sprague-Dawley rats with a ligation injury of the masseter muscle tendon (TL), BMSCs (1.5 M/rat) from donor rats were infused i.v. at 1 week post-TL. P65 exhibited predominant neuronal localization in the RVM with scattered distribution in glial cells. At 1 week, but not 8 weeks after BMSC infusion, western blot and immunostaining showed that p65 of NF-κB was significantly increased in the RVM. Given that chemokine signaling is critical to BMSCs' pain-relieving effect, we further evaluated a role of chemokine signaling in p65 upregulation. Prior to infusion of BMSCs, we transduced BMSCs with Ccl4 shRNA, incubated BMSCs with RS 102895, a CCR2b antagonist, or maraviroc, a CCR5 antagonist. The antagonism of chemokines significantly reduced BMSC-induced upregulation of p65, suggesting that upregulation of p65 was related to BMSCs' pain-relieving effect. We then tested the effect of a selective NF-κB activation inhibitor, BAY 11-7082. The mechanical hyperalgesia of the rat was assessed with the von Frey method. In the pre-treatment experiment, BAY 11-7082 (2.5 and 25 pmol) was injected into the RVM at 2 h prior to BMSC infusion. Pretreatment with BAY 11-7082 attenuated BMSCs' antihyperalgesia, but post-treatment at 5 weeks post-BMSC was not effective. On the contrary, in TL rats receiving BAY 11-7082 without BMSCs, TL-induced hyperalgesia was attenuated, consistent with dual roles of NF-κB in pain hypersensitivity and BMSC-produced pain relief. These results indicate that the NF-κB signaling pathway in the descending circuitry is involved in initiation of BMSC-produced behavioral antihyperalgesia.

Suppression of HDAC2 in Spinal Cord Alleviates Mechanical Hyperalgesia and Restores KCC2 Expression in a Rat Model of Bone Cancer Pain

Epigenetic modulation participates in the mechanism of multiple types of pathological pain, so targeting the involved regulators may be a promising strategy for pain treatment. Our previous research identified the analgesic effect of the histone deacetylase (HDAC) inhibitor trichostatin A (TSA) on mechanical hyperalgesia in a rat model of bone cancer pain (BCP) via restoration of μ-opioid receptor (MOR) expression. However, the specific types of HDACs contributing to BCP have not been explored. The present study investigated the expression pattern of some common HDACs and found that HDAC2 was up-regulated in a time-dependent manner in the lumbar spinal cord of BCP rats. TSA application suppressed HDAC2 expression in cultured PC12 cells and reversed the augmented HDAC2 in BCP rats. An RNA-interfering strategy confirmed the essential role of HDAC2 in the modulation of mechanical hyperalgesia following tumor cell inoculation, and we further examined its possible downstream targets. Notably, HDAC2 knock-down did not restore MOR expression, but it robustly reversed the down-regulation of potassium-chloride cotransporter 2 (KCC2). The impaired KCC2 expression is a vital mechanism of many types of pathological pain. Therefore, our results demonstrated that HDAC2 in spinal cord contributed to the mechanical hyperalgesia in BCP rats, and this effect may be associated with KCC2 modulation.

Histone deacetylase 2 is involved in µ‑opioid receptor suppression in the spinal dorsal horn in a rat model of chronic pancreatitis pain

Chronic pain occurs in ~85–90% of chronic pancreatitis (CP) patients. However, as the pathogenesis of CP pain remains to be fully understood, the current therapies for CP pain remain inadequate. Emerging evidence has suggested that the epigenetic modulations of genes are involved in chronic pain. In the present study, intrapancreatic trinitrobenzene sulfonic acid infusions were used to establish a CP model in rats. Mechanical allodynia was measured with von Frey filaments. Immunofluorescent staining analysis was used to observe the expression changes of histone deacetylase 2 (HDAC2) and µ-opioid receptor (MOR), and intrathecal administration of the selective HDAC2 inhibitor AR-42 was used to assess the underlying mechanisms. The expression levels of c-Jun N-terminal kinase (JNK) in the thoracic spinal cord were detected by western blotting, and the mRNA expression levels of interleukin (IL)1-β, IL-6 and tumor necrosis factor (TNF)-α were detected by reverse transcription-quantitative polymerase chain reaction. The results demonstrated that HDAC2 expression was upregulated during the course of CP induction, while MOR activity in the thoracic spinal dorsal horn was significantly suppressed. Intrathecal infusion of AR-42 significantly attenuated CP-induced mechanical allodynia, with rescued MOR activity. Additionally, HDAC2 facilitated the release of inflammatory cytokines, including IL-1β, IL-6 and TNF-α. These results suggested that the underlying mechanisms of HDAC2 regulating MOR activity under CP induction may occur via promoting the release of inflammatory cytokines, thus activating the JNK signaling pathway. The present study suggested that the epigenetic-regulated disturbance of MOR is dependent on the endogenous analgesia system in CP, which may a provide novel therapeutic strategy for treating pain in CP.

Epigenetic Activation of μ-Opioid Receptor Gene via Increased Expression and Function of Mitogen- and Stress-Activated Protein Kinase 1

Since the discovery of μ-opioid receptor (MOR) gene two decades ago, various regulatory factors have been shown to interact with the MOR promoter and modulate transcript levels. However, the majority of early transcriptional studies on MOR gene have not addressed how intracellular signaling pathways mediate extracellular modulators. In this study, we demonstrate that MOR epigenetic regulation requires multiple coordinated signals converging at the MOR promoter, involving mitogen-activated protein kinase (MAPK) activation and mitogen- and stress-activated protein kinase 1 (MSK1)-ranges of intracellular signaling pathways similar to those activated by opioid agonists. Inhibiting p38 MAPK or extracellular signal-regulated kinase (ERK) 1/2 MAPK (upstream activators of MSK1) reduced MOR expression levels; accordingly, the functional role of MSK1, but not MSK2, was demonstrated using genetic approaches. However, for maximal MSK1 effect, an open chromatin configuration was required, because in vitro CpG methylation of the MOR promoter abolished MSK1 activity. Finally, endogenous MSK1 levels concomitantly increased to regulate MOR gene expression during neuronal differentiation of P19 cells, suggesting a conserved role of this kinase in the epigenic activation of MOR in neurons. Taken together, our findings indicate that the expression of MOR gene requires the activity of intracellular signaling pathways that have been implicated in the behavioral outcomes of opioid drugs, which suggests that an autoregulatory mechanism may function in opioid systems.

The role of neuroimmune signaling in alcoholism

Alcohol consumption and stress increase brain levels of known innate immune signaling molecules. Microglia, the innate immune cells of the brain, and neurons respond to alcohol, signaling through Toll-like receptors (TLRs), high-mobility group box 1 (HMGB1), miRNAs, pro-inflammatory cytokines and their associated receptors involved in signaling between microglia, other glia and neurons. Repeated cycles of alcohol and stress cause a progressive, persistent induction of HMGB1, miRNA and TLR receptors in brain that appear to underlie the progressive and persistent loss of behavioral control, increased impulsivity and anxiety, as well as craving, coupled with increasing ventral striatal responses that promote reward seeking behavior and increase risk of developing alcohol use disorders. Studies employing anti-oxidant, anti-inflammatory, anti-depressant, and innate immune antagonists further link innate immune gene expression to addiction-like behaviors. Innate immune molecules are novel targets for addiction and affective disorders therapies. This article is part of the Special Issue entitled "Alcoholism".

Hydrogen-Rich Saline Attenuates Acute Hepatic Injury in Acute Necrotizing Pancreatitis by Inhibiting Inflammation and Apoptosis, Involving JNK and p38 Mitogen-Activated Protein Kinase-dependent Reactive Oxygen Species

OBJECTIVES

The objective of this study was to study the role of hydrogen-rich saline (HRS) on acute hepatic injury (AHI) in acute necrotizing pancreatitis (ANP).

METHODS

Rats were used for this study and an ANP model was induced by injecting 5% sodium taurocholate into the biliary-pancreatic duct. Experiments were performed in 3 groups: sham, ANP, and ANP + HRS (HRS). Animals were killed at 3, 12, and 24 hours after operation, and then blood and tissue samples were harvested. Various physiological, histological, and cellular and molecular parameters were analyzed.

RESULTS

Analyses of serum, lipase, alanine transaminase, and aspartate aminotransferase indicated that ANP-induced AHI model was established successfully and HRS attenuated hepatic dysfunction. Hepatic superoxide dismutase and malondialdehyde levels showed HRS against oxidative stress. Cellular and molecular analyses including p-p38, p-JNK, p-ERK, and caspase-3, caspase-9, NF-κB, and TNF-α in hepatic tissues revealed that HRS attenuated ANP-induced AHI by inhibiting apoptosis and phosphorylation of JNK and p38, as well as NF-κB activation.

CONCLUSIONS

Hydrogen-rich saline plays a protective role in ANP-induced AHI through inhibiting inflammation and apoptosis, involving JNK and p38 MAPK-dependent reactive oxygen species.

Post-Transcriptional Regulation of the Human Mu-Opioid Receptor (MOR) by Morphine-Induced RNA Binding Proteins hnRNP K and PCBP1

Expression of the mu-opioid receptor (MOR) protein is controlled by extensive transcriptional and post-transcriptional processing. MOR gene expression has previously been shown to be altered by a post-transcriptional mechanism involving the MOR mRNA untranslated region (UTR). Here, we demonstrate for the first time the role of heterogeneous nuclear ribonucleic acids (hnRNA)-binding protein (hnRNP) K and poly(C)-binding protein 1 (PCBP1) as post-transcriptional inducers in MOR gene regulation. In the absence of morphine, a significant level of MOR mRNA is sustained in its resting state and partitions in the translationally inactive polysomal fraction. Morphine stimulation activates the downstream targets hnRNP K and PCPB1 and induces partitioning of the MOR mRNA to the translationally active fraction. Using reporter and ligand binding assays, as well as RNA EMSA, we reveal potential RNP binding sites located in the 5'-untranslated region of human MOR mRNA. In addition, we also found that morphine-induced RNPs could regulate MOR expression. Our results establish the role of hnRNP K and PCPB1 in the translational control of morphine-induced MOR expression in human neuroblastoma (NMB) cells as well as cells stably expressing MOR (NMB1). J. Cell. Physiol. 232: 576-584, 2017. © 2016 Wiley Periodicals, Inc.

Regulation of cyclooxygenase-2 expression in rat oviductal epithelial cells: Evidence for involvement of GPR30/Src kinase-mediated EGFR signaling

The oviduct plays a crucial role in female reproduction by regulating gamete transport, providing a specific microenvironment for fertilization and early embryonic development. Cyclooxygenase (COX)-derived prostaglandins play essential role in carrying out these oviduct-specific functions. Estrogen upregulates COX-2 expression in rat oviduct; however, the mechanisms responsible for regulation of COX-2 expression in rat oviductal epithelial cells (OECs) remain unclear. In the present study, we proposed that estrogen induces COX-2 expression via G-protein coupled receptor i.e., GPR30 in OECs. To investigate this hypothesis, we examined the effects of E2-BSA, ICI 182,780, GPR30 agonist and GPR30 antagonist on COX-2 expression and explored potential signaling pathway leading to COX-2 expression. Co-localization experiments revealed GPR30 to be primarily located in the peri-nuclear space, which was also the site of E2-BSA-fluorescein isothiocyanate (E2-BSA-FITC) binding. The E2-BSA induced-COX-2 and prostaglandin release were subjected to regulation by both EGFR and PI3K signaling as inhibitors of c-Src kinase (PP2), EGFR (EGFR inhibitor) and PI-3 kinase (LY294002) attenuated E2-BSA mediated effect. These results suggest that EGFR transactivation leading to activation of PI-3K/Akt pathway participates in COX-2 expression in rat OECs. Interestingly, E2-BSA induced COX-2 expression and subsequent prostaglandin release were abolished by NF-κB inhibitor. In addition, E2-BSA induced the nuclear translocation of p65-NF-κB and up-regulated the NF-κB promoter activity in rat OECs. Taken together, results demonstrated that E2-BSA induced the COX-2 expression and consequent PGE2 and PGF2α release in rat OECs. These effects are mediated through GPR30-derived EGFR transactivation and PI-3K/Akt cascade leading to NF-κB activation.

The opioid antagonist, β-funaltrexamine, inhibits NF-κB signaling and chemokine expression in human astrocytes and in mice

Opioid-immune crosstalk occurs when opioid drugs alter the activity of the immune system. In this study, the opioid antagonist β-funaltrexamine (β-FNA) decreases the expression and release of an inflammatory chemokine, interferon-γ inducible protein-10 (CXCL10) from normal human astrocytes stimulated by interleukin 1β (IL-1β). β-FNA decreased CXCL10 by an unknown action that did not involve the mu opioid receptor (MOR). As IL-1β acts through its receptor to activate NF-κB/MAPK signaling pathways which leads to CXCL10 expression and release, key steps in the IL-1β signaling pathways were examined following β-FNA treatment. IL-1β-induced activation of p38 mitogen-activated protein kinases (p38 MAPK) was inhibited by β-FNA as shown by decreased p38 MAPK phosphorylation in treated cells. β-FNA also decreased the levels of activated subunits of NF-κB (p50 and p65) in treated astrocytes. The impact of β-FNA was also observed in proteins that act to negatively regulate NF-κB signaling. IL-1β upregulated the expression of A20, a ubiquitin (Ub)-editing enzyme that dampens NF-κB signaling by altering ubiquination patterns on IL-1 receptor second messengers, and the increase in A20 was significantly inhibited by β-FNA treatment. Inhibition of the Ub-activating enzyme E1 by the inhibitor PYR41 also decreased CXCL10 release, like β-FNA, and concurrent treatment with both PYR41 and β-FNA inhibited CXCL10 more than did either agent alone. In mice, lipopolysaccharide-induced CXCL10 expression in the brain was inhibited by treatment with β-FNA. These findings suggest that β-FNA exerts an anti-inflammatory action in vitro and in vivo that is MOR-independent and possibly due to the alkylating ability of β-FNA.

Impact of nuclear factor-κB on restoration of neuron growth and differentiation in hippocampus of degenerative brain

The mode of action of nuclear factor-κB (NF-κB) has been extensively observed in different aspects of cell growth and proliferation. The transcription factor regulates various genes controlling inflammation and anti-inflammatory responses in different tissues. Thus, NF-κB signal gains a therapeutic prospect. The activation of NF-κB requires nuclear localization of its p65 subunit. Research also indicates an impact of phosphorylated p65 on the transcription of genes during cell growth and the immune response. Following the trends in investigations over decades, different observations suggest that NF-κB activation and phosphorylation of p65 regulate neuronal plasticity. Also, inhibition of NF-κB activation is a well-demonstrated way to attenuate inflammation. In addition to anti-inflammatory drugs, recent researches unwind a way to regulate regeneration and repair tissue damage. Thus, keeping a critical view on NF-κB signals, we propose the importance of natural or synthetic NF-κB activators for neurogenesis.

Functionally selective signaling for morphine and fentanyl antinociception and tolerance mediated by the rat periaqueductal gray

Functionally selective signaling appears to contribute to the variability in mechanisms that underlie tolerance to the antinociceptive effects of opioids. The present study tested this hypothesis by examining the contribution of G protein-coupled receptor kinase (GRK)/Protein kinase C (PKC) and C-Jun N-terminal kinase (JNK) activation on both the expression and development of tolerance to morphine and fentanyl microinjected into the ventrolateral periaqueductal gray of the rat. Microinjection of morphine or fentanyl into the periaqueductal gray produced a dose-dependent increase in hot plate latency. Microinjection of the non-specific GRK/PKC inhibitor Ro 32-0432 into the periaqueductal gray to block mu-opioid receptor phosphorylation enhanced the antinociceptive effect of morphine but had no effect on fentanyl antinociception. Microinjection of the JNK inhibitor SP600125 had no effect on morphine or fentanyl antinociception, but blocked the expression of tolerance to repeated morphine microinjections. In contrast, a microinjection of Ro 32-0432 blocked the expression of fentanyl, but not morphine tolerance. Repeated microinjections of Ro 32-0432 blocked the development of morphine tolerance and inhibited fentanyl antinociception whether rats were tolerant or not. Repeated microinjections of SP600125 into the periaqueductal gray blocked the development of tolerance to both morphine and fentanyl microinjections. These data demonstrate that the signaling molecules that contribute to tolerance vary depending on the opioid and methodology used to assess tolerance (expression vs. development of tolerance). This signaling difference is especially clear for the expression of tolerance in which JNK contributes to morphine tolerance and GRK/PKC contributes to fentanyl tolerance.

Endogenous opiates and behavior: 2013

This paper is the thirty-sixth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2013 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia; stress and social status; tolerance and dependence; learning and memory; eating and drinking; alcohol and drugs of abuse; sexual activity and hormones, pregnancy, development and endocrinology; mental illness and mood; seizures and neurologic disorders; electrical-related activity and neurophysiology; general activity and locomotion; gastrointestinal, renal and hepatic functions; cardiovascular responses; respiration and thermoregulation; and immunological responses.

Ketamine reduces the induced spinal p38 MAPK and pro-inflammatory cytokines in a neuropathic rats

BACKGROUND

Neuropathic rats created by spinal nerve ligation are known to show higher levels of p38, c-Jun NH2-terminal kinase, and extracellular signal-regulated kinase p44/42 (ERK 1/2) of the mitogen-activated protein kinases (MAPKs). The authors of this study aimed to understand the effect of ketamine on p38 MAPK and inflammatory responses, as well as its effect on the development of neuropathic pain.

METHODS

The neuropathic rats were prepared by Chung's method with Sprague-Dawley rats. The research was carried out on three groups, a sham-operated group, a neuropathic pain and normal saline (NP + NS) group, and a neuropathic pain and ketamine (NP + Keta) group. The normal saline or ketamine was infused into the neuropathic rats through a mini-osmotic pump implanted in the subcutaneous space. After a week, the quantities of phospho-p38, p38 MAPK and pro-inflammatory cytokines were measured and compared through western blots and reverse transcriptase-polymerase chain reaction.

RESULTS

In comparison to the control group, the NP + NS group showed a significant increase of phospho-p38 and p38 MAPK, as well as of the proinflammatory cytokines, tumor necrosis factor α (TNFα), and intercellular adhesion molecule 1 (ICAM1). However, in the NP + Keta group, phospho-p38, p38 MAPK and TNFα and, ICAM1 were reduced in comparison to the NP + NS group. The paw withdrawal threshold test also showed the trend of recovery from the mechanical allodynia in the NP + Keta group.

CONCLUSIONS

In the development of neuropathic pain, p38 MAPK and inflammatory responses are significantly related, and the use of ketamine reduces p38 MAPK and proinflammatory cytokines. Thus, the adequate use of ketamine could be effective for the prevention and treatment of neuropathic pain following peripheral injury.