PGC-1α activation ameliorates cancer-induced bone pain via inhibiting apoptosis of GABAergic interneurons

Cancer-induced bone pain (CIBP) stands out as one of the most challenging issues in clinical practice due to its intricate and not fully elucidated pathophysiological mechanisms. Existing evidence has pointed toward the significance of peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) down-regulation in contributing to pain behaviors in various rodent models of neuropathic pain. In our current study, we aimed to investigate the role of PGC-1α in CIBP. Our results unveiled a reduction in PGC-1α expression within the spinal cord of CIBP rats, particularly in GABAergic interneurons. Notably, intrathecal administration of the PGC-1α activator ZLN005 suppressed the loss of spinal GABAergic interneurons. This suppression was achieved by inhibiting caspase-3-mediated apoptosis, ultimately leading to the alleviation of mechanical allodynia in CIBP rats. Further exploration into the mechanism revealed that PGC-1α activation played a pivotal role in mitigating ATP depletion and reactive oxygen species accumulation linked to mitochondrial dysfunction. This was achieved through the restoration of mitochondrial biogenesis and the activation of the SIRT3-SOD2 pathway. Impressively, the observed effects were prominently reversed upon the application of SR18292, a specific PGC-1α inhibitor. In conclusion, our findings strongly suggest that PGC-1α activation acts as a potent inhibitor of apoptosis in spinal GABAergic interneurons. This inhibition is mediated by the improvement of mitochondrial function, facilitated in part through the enhancement of mitochondrial biogenesis and the activation of the SIRT3-SOD2 pathway. The results of our study shed light on potential therapeutic avenues for addressing CIBP.

The Emerging Role of Quercetin in the Treatment of Chronic Pain

Despite much research efforts being devoted to designing alternative pharmacological interventions, chronic pain remains to be an unresolved clinical problem. Quercetin, a compound that belongs to the flavonoids family, is abundantly found in fruits and vegetables. Emerging evidence indicates that quercetin possesses anti-nociceptive effects in different rodent models of chronic pain, including inflammatory pain, neuropathic pain and cancer pain. In this review, we summarize the mechanisms underlying the analgesic effect of quercetin in preclinical studies. These studies showed that quercetin exerts potent analgesic effects against chronic pain via suppressing neuroinflammation and oxidative stress as well as modulation of synaptic plasticity, GABAergic system, and opioidergic system. Considering that the safety of quercetin is well established, it has great potential for clinical use in pain treatment.

Galectin-3 in Microglia-Mediated Neuroinflammation: Implications for Central Nervous System Diseases

Microglial activation is one of the common hallmarks shared by various central nervous system (CNS) diseases. Based on surrounding circumstances, activated microglia play either detrimental or neuroprotective effects. Galectin-3 (Gal-3), a group of β-galactoside-binding proteins, has been cumulatively revealed to be a crucial biomarker for microglial activation after injuries or diseases. In consideration of the important role of Gal-3 in the regulation of microglial activation, it might be a potential target for the treatment of CNS diseases. Recently, Gal-3 expression has been extensively investigated in numerous pathological processes as a mediator of neuroinflammation, as well as in cell proliferation. However, the underlying mechanisms of Gal-3 involved in microgliamediated neuroinflammation in various CNS diseases remain to be further investigated. Moreover, several clinical studies support that the levels of Gal-3 are increased in the serum or cerebrospinal fluid of patients with CNS diseases. Thus, we summarized the roles and underlying mechanisms of Gal-3 in activated microglia, thus providing a better insight into its complexity expression pattern, and contrasting functions in CNS diseases.

Targeting α7 nicotinic acetylcholine receptors for chronic pain

Despite rapid advances in the field of chronic pain, it remains extremely challenging in the clinic. Pain treatment strategies have not improved for decades as opioids remain the main prescribed drugs for chronic pain management. However, long-term use of opioids often leads to detrimental side effects. Therefore, uncovering the mechanisms underlying the development and maintenance of chronic pain may aid the discovery of novel therapeutics to benefit patients with chronic pain. Substantial evidence indicates downregulation of α7 nicotinic acetylcholine receptors (α7 nAChR) in the sciatic nerve, dorsal root ganglia, and spinal cord dorsal horn in rodent models of chronic pain. Moreover, our recent study and results from other laboratories demonstrate that potentiation of α7 nAChR attenuates pain behaviors in various murine models of chronic pain. This review summarized and discussed the preclinical evidence demonstrating the therapeutic potential of α7 nAChR agonists and allosteric modulators in chronic pain. This evidence indicates that potentiation of α7 nAChR is beneficial in chronic pain, mostly by alleviating neuroinflammation. Overall, α7 nAChR-based therapy for chronic pain is an area with great promise, but more research regarding its detailed mechanisms is warranted.

β2-adrenoreceptor agonist ameliorates mechanical allodynia in paclitaxel-induced neuropathic pain via induction of mitochondrial biogenesis

Chemotherapy-induced neuropathic pain is a debilitating and common side effect of cancer treatment and so far no effective drug is available for treatment of the serious side effect. Previous studies have demonstrated β2-adrenoreceptor (ADRB2) agonists can attenuate neuropathic pain. However, the role of ADRB2 in paclitaxel -induced neuropathic pain (PINP) remains unclear. In this study, we investigated the effect of formoterol, a long-acting ADRB2 agonist, and related mechanisms in PINP. A rat model of PINP was established by intraperitoneal injection of paclitaxel (2 mg/kg) every other day with a final cumulative dose of 8 mg/kg. Hind paw withdrawal thresholds (PWTs) in response to von Frey filament stimuli were used to evaluate mechanical allodynia. Western blot was used to examine the expression of ADRB2, peroxisome proliferator-activated receptor coactivator-1α (PGC-1α), nuclear respiratory factors 1 (NRF1) and mitochondrial transcription factor A (TFAM) and the immunofluorescence was to detect the cellular localization of ADRB2 and PGC-1α in the spinal cord. Moreover, we measured mitochondrial DNA (mtDNA) copy number by qPCR. In our study, formoterol attenuated established PINP and delayed the onset of PINP. Formoterol restored ADRB2 expression as well as mtDNA copy number and PGC-1α, NRF1, and TFAM protein expression, which are major genes involved in mitochondrial biogenesis, in the spinal cord of PINP rats. Moreover, we found the analgesic effect of formoterol against PINP was partially abolished by PGC-1α inhibitor SR-18292. Collectively, these results demonstrated the activation of ADRB2 with formoterol ameliorates PINP at least partially through induction of mitochondrial biogenesis.

The Role of the GABAergic System in Diseases of the Central Nervous System

It is well known that the central nervous system (CNS) is a complex neuronal network and its function depends on the balance between excitatory and inhibitory neurons. Disruption of the excitatory/inhibitory (E/I) balance is the main cause for the majority of the CNS diseases. In this review, we will discuss roles of the inhibitory system in the CNS diseases. The GABAergic system as the main inhibitory system, is essential for the appropriate functioning of the CNS, especially as it is engaged in the formation of learning and memory. Many researchers have reported that the GABAergic system is involved in regulating synaptic plasticity, cognition and long-term potentiation. Some clinical manifestations (such as cognitive dysfunctions, attention deficits, etc.) have also been shown to emerge after abnormalities in the GABAergic system accompanied with concomitant diseases, that include Alzheimer's disease (AD), Parkinson's disease (PD), Autism spectrum disorder (ASD), Schizophrenia, etc. The GABAergic system consists of GABA, GABA transporters, GABAergic receptors and GABAergic neurons. Changes in any of these components may contribute to the dysfunctions of the CNS. In this review, we will synthesize studies which demonstrate how the GABAergic system participates in the pathogenesis of the CNS disorders, which may provide a new idea that might be used to treat the CNS diseases.

GLP-1R activation ameliorated novel-object recognition memory dysfunction via regulating hippocampal AMPK/NF-κB pathway in neuropathic pain mice

Growing evidences indicate that neuropathic pain is frequently accompanied with cognitive impairments, which aggravate the decrease in the quality of life of chronic pain patients. Furthermore, it has been shown that the activation of Glucagon-like-peptide-1receptor (GLP-1R) improved memory deficit in multiple diseases, including Alzheimer's disease (AD), stroke. However, whether GLP-1R activation could improve memory impairment induced by neuropathic pain and the mechanisms underlying the effect of the activation of GLP-1R on memory protection have not yet been established. The spared nerve injury (SNI) model was established as a kind of neuropathic pain. And novel-object recognition memory (hippocampus-dependent memory) was tested by the novel object recognition test (NORT). The expression levels of GLP-1, GLP-1R, adenosine monophosphate-activated protein kinase (AMPK), p-AMPKThr172, nuclear factor κ B p65 (NF-κB p65), interleukin-1beta (IL-1β), IL-1β p17 (mature IL-1β), tumor necrosis factor-alpha (TNF-α) and the synaptic proteins were tested in the murine hippocampus with memory deficits caused by neuropathic pain. Then, exenatide acetate (Ex-4, a GLP-1R agonist), exendin (9-39) (Ex(9-39), a GLP-1R antagonist) and Compound C dihydrochloride (CC, an AMPK inhibitor) were used to test the effects of the activation of GLP-1R in the mice with neuropathic pain. First, we uncovered that neuropathic pain could inhibit GLP-1/GLP-R axis, disturb inflammatory signaling pathway, increase the expression of IL-1β, IL-1β p17 and TNF-α, downregulate the synaptic proteins (postsynaptic density protein 95 (PSD95) and Arc). Subsequently, we reported that Ex-4 treatment could improve recognition memory impairment, increase the ratio of p-AMPKThr172/AMPK, inhibit the phosphorylation NF-κB p65 and decrease the expression of IL-1β, IL-1β p17 and TNF-α, upregulate the levels of PSD95 and Arc. Moreover, we found that Ex(9-39) and CC treatment could abrogate the memory protection of activation of GLP-1R in mice with neuropathic pain. The results indicated that the activation of GLP-1R could improve recognition memory impairment via regulating AMPK/NF-κB pathway, improving neuroinflammation, reversing the decreased level of synaptic proteins in neuropathic pain mice.

The therapeutic potential of Nrf2 inducers in chronic pain: Evidence from preclinical studies

Chronic pain remains an enormous health problem affecting approximatively 30% of the world's population. Opioids as the first line analgesics often leads to undesirable side effects when used long term. Therefore, novel therapeutic targets are urgently needed to the development of more efficacious analgesics. Substantial evidence indicates that excessive reactive oxygen species (ROS) are extremely important to the development of chronic pain. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a master transcription factor regulating endogenous antioxidant defense. Emerging evidence suggests that Nrf2 and its downstream effectors are implicated in chronic inflammatory and neuropathic pain. Notably, controversial results have been reported regarding the expression of Nrf2 and its downstream targets in peripheral and central regions involved in pain transmission. However, our recent studies and results from other laboratories demonstrate that Nrf2 inducers exert potent analgesic effects in various murine models of chronic pain. In this review, we summarized and discussed the preclinical evidence demonstrating the therapeutic potential of Nrf2 inducers in chronic pain. These evidence indicates that Nrf2 activation are beneficial in chronic pain mostly by alleviating ROS-associated pathological processes. Overall, Nrf2-based therapy for chronic pain is an area with great promise, but more research regarding its detailed mechanisms is warranted.

Nox2 contributes to reactive oxygen species-induced redox imbalance in cancer-induced bone pain

We have recently demonstrated that reactive oxygen species (ROS) scavengers ameliorate mechanical allodynia in a rat model of cancer-induced bone pain (CIBP). In the present study, we investigated anti-nociceptive effect of Nox inhibitor apocynin in CIBP in rats. Mechanical allodynia was assessed by Von Frey tests in sham and CIBP group of rats. Western blotting and immunofluorescence technique were conducted to assess the expression levels and cellular localization of Nox2. Results illustrated that after intra-tibial implantation with tumor cells, Nox2 and ROS were both up-regulated in the spinal cord of rats. Injection of apocynin could dose-dependently decrease the abundance of Nox2 and inhibit the development of CIBP. Furthermore, pretreatment with the apocynin could delay the development of CIBP. This study for the first time proved that Nox2 inhibitors could downregulate the production of ROS in CIBP rats, which highlights the fact that Nox inhibitor is an important therapeutic option for CIBP and that, precise targeting inhibitor of different subtypes of Nox enzymes is needed to developed in future.

Development and Validation of a Nomogram for Assessing Survival in Patients With COVID-19 Pneumonia

Background

The outbreak of coronavirus disease (COVID-19) in 2019 has spread worldwide and continues to cause great threat to peoples’ health as well as put pressure on the accessibility of medical systems. Early prediction of survival of hospitalized patients will help the clinical management of COVID-19, but such a prediction model which is reliable and valid is still lacking.

Methods

We retrospectively enrolled 628 confirmed cases of COVID-19 using positive RT-PCR tests for SARS-CoV-2 in Tongji Hospital in Wuhan, China. These patients were randomly grouped into a training cohort (60%) and a validation cohort (40%). In the training cohort, least absolute shrinkage and selection operator (LASSO) regression analysis and multivariate Cox regression analysis were utilized to identify prognostic factors for in-hospital survival of patients with COVID-19. A nomogram based on the three variables was built for clinical use. Areas under the ROC curves (AUC), concordance index (C-index) and calibration curve were used to evaluate the efficiency of the nomogram in both the training and validation cohorts.

Results

Hypertension, higher neutrophil-to-lymphocyte ratio and increased NT-proBNP value were found to be significantly associated with poorer prognosis in hospitalized patients with COVID-19. The three predictors were further used to build a prediction nomogram. The C-index of the nomogram in the training and validation cohorts was 0.901 and 0.892, respectively. The AUC in the training cohort was 0.922 for 14- day and 0.919 for 21-day probability of in-hospital survival, while in the validation cohort was 0.922 and 0.881, respectively. Moreover, the calibration curve for 14- day and 21-day survival also showed high coherence between the predicted and actual probability of survival.

Conclusion

We managed to build a predictive model and constructed a nomogram for predicting in-hospital survival of patients with COVID-19. This model represents good performance and might be utilized clinically in the management of COVID-19.

Nrf2 activation ameliorates mechanical allodynia in paclitaxel-induced neuropathic pain

Paclitaxel-induced neuropathic pain (PINP) is refractory to currently used analgesics. Previous studies show a pivotal role of oxidative stress in PINP. Because the nuclear factor erythroid-2-related factor 2 (Nrf2) has been considered as the critical regulator of endogenous antioxidant defense, we here explored whether activation of Nrf2 could attenuate PINP. A rat model of PINP was established by intraperitoneal injection of paclitaxel (2 mg/kg) every other day with a final cumulative dose of 8 mg/kg. Hind paw withdrawal thresholds (PWTs) in response to von Frey filament stimuli were used to assess mechanical allodynia. We showed that a single dose of Nrf2 activator, oltipraz (10, 50, and 100 mg/kg), dose-dependently attenuated established mechanical allodynia, whereas repeated injection of oltipraz (100 mg· kg-1· d-1, i.p. from d 14 to d 18) almost abolished the mechanical allodynia in PINP rats. The antinociceptive effect of oltipraz was blocked by pre-injection of Nrf2 inhibitor trigonelline (20 mg/kg, i.p.). Early treatment with oltipraz (100 mg· kg-1· d-1, i.p. from d 0 to d 6) failed to prevent the development of the PINP, but delayed its onset. Western blot and immunofluorescence analysis revealed that the expression levels of Nrf2 and HO-1 were significantly upregulated in the spinal cord of PINP rats. Repeated injection of oltipraz caused further elevation of the expression levels of Nrf2 and HO-1 in the spinal cord of PINP rats, which was reversed by pre-injection of trigonelline. These results demonstrate that oltipraz ameliorates PINP via activating Nrf2/HO-1-signaling pathway in the spinal cord.

PPARγ activation mitigates mechanical allodynia in paclitaxel-induced neuropathic pain via induction of Nrf2/HO-1 signaling pathway

Paclitaxel-induced neuropathic pain (PINP) is a dose-limiting side effect and is refractory to widely used analgesic drugs. Previous studies have demonstrated a protective role of peroxisome proliferator-activated receptor gama (PPARγ) in neuropathic pain. However, whether PPARγ activation could alleviate PINP remains to be elucidated. Our previous study has validated the analgesic effect of oltipraz, an nuclear factor erythroid-2 related factor 2 (Nrf2) activator, in a rat model of PINP. In this study, we tested the hypothesis that rosiglitazone, a selective agonist of PPARγ, could attenuate PINP through induction of Nrf2/heme oxygenase-1 (HO-1) signaling pathway. Paclitaxel was injected intraperitoneally on four alternate days to induce neuropathic pain. Paw withdrawal threshold was used to evaluate mechanical allodynia. Western blot and immunofluorescence were used to examine the expression and distribution of PPARγ, Nrf2 and HO-1 in the spinal cord. Our results showed that rosiglitazone attenuated established PINP and delayed the onset of PINP via activation of PPARγ, which were reversed by PPARγ antagonist GW9662. Moreover, rosiglitazone inhibited downregulation of PPARγ in the spinal cord of PINP rats. Furthermore, the analgesic effect of rosiglitazone against PINP was abolished by trigonelline, an Nrf2 inhibitor. Finally, rosiglitazone significantly increased expression of Nrf2 and HO-1 in the spinal cord of PINP rats. Collectively, these results indicated that PPARγ activation might mitigate PINP through activating spinal Nrf2/HO-1 signaling pathway. Our results may provide an alternative option for PINP patients.

Disruption of the GABAergic system contributes to the development of perioperative neurocognitive disorders after anesthesia and surgery in aged mice

Aims

Perioperative neurocognitive disorders (PND) are associated with cognitive impairment in the preoperative or postoperative period, and neuroinflammation is thought to be the most important mechanisms especially during the postoperative period. The GABAergic system is easily disrupted by neuroinflammation. This study investigated the impact of the GABAergic system on PND after anesthesia and surgery.

Methods

An animal model of laparotomy with inhalation anesthesia in 16‐month‐old mice was addressed. Effects of the GABAergic system were assessed using biochemical analysis. Pharmacological blocking of α5GABA_ARs or P38 mitogen‐activated protein kinase (MAPK) were applied to investigate the effects of the GABAergic system.

Results

After laparotomy, the hippocampus‐dependent memory and long‐term potentiation were impaired, the levels of IL‐6, IL‐1β and TNF‐α up‐regulated in the hippocampus, the concentration of GABA decreased, and the protein levels of the surface α5GABA_ARs up‐regulated. Pharmacological blocking of α5GABA_ARs with L655,708 alleviated laparotomy induced cognitive deficits. Further studies found that the P38 MAPK signaling pathway was involved and pharmacological blocking with SB203,580 alleviated memory dysfunctions.

Conclusions

Anesthesia and surgery caused neuroinflammation in the hippocampus, which consequently disrupted the GABAergic system, increased the expressions of surface α5GABA_ARs especially through the P38 MAPK signaling pathway, and eventually led to hippocampus‐dependent memory dysfunctions.

Berberine protects against ischemia-reperfusion injury: A review of evidence from animal models and clinical studies

Ischemia-reperfusion (I/R) injury is accompanied with high morbidity and mortality and has seriously negative social and economic influences. Unfortunately, few effective therapeutic strategies are available to improve its outcome. Berberine is a natural medicine possessing multiple beneficial biological activities. Emerging evidence indicates that berberine has potential protective effects against I/R injury in brain, heart, kidney, liver, intestine and testis. However, up-to-date review focusing on the beneficial role of berberine against I/R injury is not yet available. In this paper, results from animal models and clinical studies are concisely presented and its mechanisms are discussed. We found that berberine ameliorates I/R injury in animal models via its anti-oxidant, anti-apoptotic and anti-inflammatory effects. Moreover, berberine also attenuates I/R injury by suppressing endoplasmic reticulum stress and promoting autophagy. Additionally, regulation of periphery immune system may also contributes to the beneficial effect of berberine against I/R injury. Although clinical evidence is limited, the current studies indicate that berberine may attenuate I/R injury via inhibiting excessive inflammatory response in patients. Collectively, berberine might be used as an alternative therapeutic strategy for the management of I/R injury.

The Role of CXCR3 in Neurological Diseases

BACKGROUND

Neurological diseases have become an obvious challenge due to insufficient therapeutic intervention. Therefore, novel drugs for various neurological disorders are in desperate need. Recently, compelling evidence has demonstrated that chemokine receptor CXCR3, which is a G protein-coupled receptor in the CXC chemokine receptor family, may play a pivotal role in the development of neurological diseases. The aim of this review is to provide evidence for the potential of CXCR3 as a therapeutic target for neurological diseases.

METHODS

English journal articles that focused on the invovlement of CXCR3 in neurological diseases were searched via PubMed up to May 2017. Moreover, reference lists from identified articles were included for overviews.

RESULTS

The expression level of CXCR3 in T cells was significantly elevated in several neurological diseases, including multiple sclerosis (MS), glioma, Alzheimer's disease (AD), chronic pain, human T-lymphotropic virus type 1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and bipolar disorder. CXCR3 antagonists showed therapeutic effects in these neurological diseases.

CONCLUSION

These studies provided hard evidence that CXCR3 plays a vital role in the pathogenesis of MS, glioma, AD, chronic pain, HAM/TSP and bipolar disorder. CXCR3 is a crucial molecule in neuroinflammatory and neurodegenerative diseases. It regulates the activation of infiltrating cells and resident immune cells. However, the exact functions of CXCR3 in neurological diseases are inconclusive. Thus, it is important to understand the topic of chemokines and the scope of their activity in neurological diseases.

Role of curcumin in the management of pathological pain

BACKGROUND

Pathological pain conditions can be triggered after peripheral nerve injury and/or inflammation. It is a major clinical problem that is poorly treated with available therapeutics. Curcumin is a phenolic compound derived from Curcuma longa, being widely used for its antioxidant, anti-inflammatory and immunomodulatory effects.

PURPOSE

This review systematically summarized updated information on the traditional uses of curcumin in order to explore antinociceptive effects in pathological pain and evaluate future therapeutic opportunities clinically. Moreover, some structure-activity relationships would greatly enrich the opportunity of finding new and promising lead compounds and promote the reasonable development of curcumin.

METHODS

PubMed were searched and the literature from the year 1976 to January 2018 was retrieved using keywords pain and curcumin.

RESULTS

This review systematically summarized updated information on the traditional uses, chemical constituents and bioactivities of curcumin, and highlights the recent development of the mechanisms of curcumin in the pathological pain by sciatic nerve injury, spinal cord injury, diabetic neuropathy, alcoholic neuropathy, chemotherapy induced peripheral neuroinflammtion, complete Freund's adjuvant (CFA) injection or carrageenan injection. Importantly, the clinical studies provide a compelling justification for its use as a dietary adjunct for pain relief. And we also present multiple approaches to improve bioavailability of curcumin for the treatment of pathological pain.

CONCLUSION

This review focuses on pre-clinical and clinical studies in the treatment of pathological pain. Although the mechanisms of pain mitigating effects are not very clear, there is compelling evidence proved that curcumin plays an essential role. However, further high-quality clinical studies should be undertaken to establish the clinical effectiveness of curcumin in patients suffering from pathological pain. Potential methods of increase the water solubility and bioavailability of curcumin still need to be studied. These approaches will help in establishing it as remedy for pathological pain.

Minocycline as a promising therapeutic strategy for chronic pain

Chronic pain remains to be a clinical challenge due to insufficient therapeutic strategies. Minocycline is a member of the tetracycline class of antibiotics, which has been used in clinic for decades. It is frequently reported that minocycline may has many non-antibiotic properties, among which is its anti-nociceptive effect. The results from our lab and others suggest that minocycline exerts strong analgesic effect in animal models of chronic pain including visceral pain, chemotherapy-induced periphery neuropathy, periphery injury induced neuropathic pain, diabetic neuropathic pain, spinal cord injury, inflammatory pain and bone cancer pain. In this review, we summarize the mechanisms underlying the analgesic effect of minocycline in preclinical studies. Due to a good safety record when used chronically, minocycline may become a promising therapeutic strategy for chronic pain in clinic.

PGE2-EP3 signaling exacerbates hippocampus-dependent cognitive impairment after laparotomy by reducing expression levels of hippocampal synaptic plasticity-related proteins in aged mice

AIM

Multifactors contribute to the development of postoperative cognitive dysfunction (POCD), of which the most important mechanism is neuroinflammation. Prostaglandin E2 (PGE2) is a key neuroinflammatory molecule and could modulate hippocampal synaptic transmission and plasticity. This study was designed to investigate whether PGE2 and its receptors signaling pathway were involved in the pathophysiology of POCD.

METHODS

Sixteen-month old male C57BL/6J mice were exposed to laparotomy. Cognitive function was evaluated by fear conditioning test. The levels of PGE2 and its 4 distinct receptors (EP1-4) were assessed by biochemical analysis. Pharmacological or genetic methods were further applied to investigate the role of the specific PGE2 receptors.

RESULTS

Here, we found that the transcription and translation level of the EP3 receptor in hippocampus increased remarkably, but not EP1, EP2, or EP4. Immunofluorescence results showed EP3 positive cells in the hippocampal CA1 region were mainly neurons. Furthermore, pharmacological blocking or genetic suppression of EP3 could alleviate surgery-induced hippocampus-dependent memory deficits and rescued the expression of plasticity-related proteins, including cAMP response element-binding protein (CREB), activity-regulated cytoskeletal-associated protein (Arc), and brain-derived neurotrophic factor (BDNF) in hippocampus.

CONCLUSION

This study showed that PGE2-EP3 signaling pathway was involved in the progression of POCD and identified EP3 receptor as a promising treatment target.

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.

The Role of Spinal GABAB Receptors in Cancer-Induced Bone Pain in Rats

Cancer-induced bone pain (CIBP) remains a major challenge in advanced cancer patients because of our lack of understanding of its mechanisms. Previous studies have shown the vital role of γ-aminobutyric acid B receptors (GABABRs) in regulating nociception and various neuropathic pain models have shown diminished activity of GABABRs. However, the role of spinal GABABRs in CIBP remains largely unknown. In this study, we investigated the specific cellular mechanisms of GABABRs in the development and maintenance of CIBP in rats. Our behavioral results show that acute as well as chronic intrathecal treatment with baclofen, a GABABR agonist, significantly attenuated CIBP-induced mechanical allodynia and ambulatory pain. The expression levels of GABABRs were significantly decreased in a time-dependent manner and colocalized mostly with neurons and a minority with astrocytes and microglia. Chronic treatment with baclofen restored the expression of GABABRs and markedly inhibited the activation of cyclic adenosine monophosphate (cAMP)-dependent protein kinase and the cAMP-response element-binding protein signaling pathway.

PERSPECTIVE

Our findings provide, to our knowledge, the first evidence that downregulation of GABABRs contribute to the development and maintenance of CIBP and restored diminished GABABRs attenuate CIBP-induced pain behaviors at least partially by inhibiting the protein kinase/cAMP-response element-binding protein signaling pathway. Therefore, spinal GABABR may become a potential therapeutic target for the management of CIBP.

Sevoflurane-induced isoelectric EEG and burst suppression: differential and antagonistic effect of added nitrous oxide

The objective of this study was to investigate whether nitrous oxide influenced the ED50 of sevoflurane for induction of isoelectric electroencephalogram (ED50_isoelectric ) differently from its influence on the ED50 of sevoflurane for electroencephalogram burst suppression (ED50_burst ). In a prospective, randomised, double-blind, parallel group, up-down sequential allocation study, 77 ASA physical status 1 and 2 patients received sevoflurane induction and, after tracheal intubation, were randomly allocated to receive sevoflurane with either 40% oxygen in air (control group) or 60% nitrous oxide in oxygen mixture (nitrous group). The ED50_isoelectric in the two groups was determined using Dixon's up and down method, starting at 2.5% with 0.2% step size of end-tidal sevoflurane. The electroencephalogram was considered as isoelectric when a burst suppression ratio of 100% lasted > 1 min. The subsequent concentrations of sevoflurane administered were determined by the presence or absence of isoelectric electroencephalogram in the previous patient in the same group. The ED50_isoelectric in the nitrous group 4.08 (95%CI, 3.95-4.38)% was significantly higher than that in the control group 3.68 (95%CI, 3.50-3.78)% (p < 0.0001). The values for ED50_burst were 3.05 (95%CI, 2.66-3.90)% and 3.02 (95%CI, 3.00-3.05)% in nitrous group and control group, respectively (p = 0.52). The addition of 60% nitrous oxide increases ED50_isoelectric , but not the ED50_burst of sevoflurane. Neither result indicates an additive effect of anaesthetic agents, as might be expected, and possible reasons for this are discussed.

PI3K/Akt Pathway: A Potential Therapeutic Target for Chronic Pain

Chronic pain is among the most disabling and costly disorders, with prevalence ranging from 10% to 55%. However, current therapeutic strategies for chronic pain are unsatisfactory due to our poor understanding of its mechanisms. Thus, novel therapeutic targets need to be found in order to improve these patients' quality of life. PI3K and its downstream Akt are widely expressed in the spinal cord, particularly in the laminae I-IV of the dorsal horn, where nociceptive C and Aδ fibers of primary afferents principally terminate. Recent studies have demonstrated their critical roles in the development and maintenance of chronic pain. In this review, we summarized the roles and mechanisms of PI3K/Akt pathway in the progression of chronic pain through sciatic nerve injury, diabetic neuropathy, spinal cord injury, bone cancer, opioid tolerance, or opioid-induced hyperalgesia.

Targeting glia for bone cancer pain

INTRODUCTION

Bone cancer pain (BCP) remains to be a clinical challenge with limited pharmaceutical interventions. Therefore, novel therapeutic targets for the management of BCP are in desperate need. Recently, a growing body of evidence has suggested that glial cells may play a pivotal role in the pathogenesis of BCP. Areas covered: This review summarizes the recent progress in the understanding of glia in BCP and reveals the potential therapeutic targets in glia for BCP treatment. Expert opinion: Pharmacological interventions inhibiting the activation of glial cells, suppressing glia-derived proinflammatory cytokines, cell surface receptors, and the intracellular signaling pathways may be beneficial for the pain management of advanced cancer patients. However, these pharmacological interventions should not disrupt the normal function of glia cells since they play a vital supportive and protective role in the central nervous system.

Interleukin-6: an emerging regulator of pathological pain

Interleukin-6 is an inflammatory cytokine with wide-ranging biological effects. It has been widely demonstrated that neuroinflammation plays a critical role in the development of pathological pain. Recently, various pathological pain models have shown elevated expression levels of interleukin-6 and its receptor in the spinal cord and dorsal root ganglia. Additionally, the administration of interleukin-6 could cause mechanical allodynia and thermal hyperalgesia, and an intrathecal injection of anti-interleukin-6 neutralizing antibody alleviated these pain-related behaviors. These studies indicated a pivotal role of interleukin-6 in pathological pain. In this review, we summarize the recent progress in understanding the roles and mechanisms of interleukin-6 in mediating pathological pain associated with bone cancer, peripheral nerve injury, spinal cord injury, chemotherapy-induced peripheral neuropathy, complete Freund’s adjuvant injection, and carrageenan injection. Understanding and regulating interleukin-6 could be an interesting lead to novel therapeutic strategies for pathological pain.

Activation of spinal phosphatidylinositol 3-kinase/protein kinase B mediates pain behavior induced by plantar incision in mice

The etiology of postoperative pain may be different from antigen-induced inflammatory pain and neuropathic pain. However, central neural plasticity plays a key role in incision pain. It is also known that phosphatidylinositol 3-kinase (PI3K) and protein kinase B/Akt (PKB/Akt) are widely expressed in laminae I-IV of the spinal horn and play a critical role in spinal central sensitization. In the present study, we explored the role of PI3K and Akt in incision pain behaviors. Plantar incision induced a time-dependent activation of spinal PI3K-p110γ and Akt, while activated Akt and PI3K-p110γ were localized in spinal neurons or microglias, but not in astrocytes. Pre-treatment with PI3K inhibitors, wortmannin or LY294002 prevented the activation of Akt brought on by plantar incision in a dose-dependent manner. In addition, inhibition of spinal PI3K signaling pathway prevented pain behaviors (dose-dependent) and spinal Fos protein expression caused by plantar incision. These data demonstrated that PI3K signaling mediated pain behaviors caused by plantar incision in mice.

Minimal alveolar concentration of sevoflurane for induction of isoelectric electroencephalogram in middle-aged adults

BACKGROUND

We determined the minimal alveolar concentration (MAC) of sevoflurane inducing an isoelectric EEG in 50% of adult subjects (MACie).

METHODS

We included 31 middle-aged subjects; 30 subjects finished the study protocol and received sevoflurane at preselected concentrations according to a modified Dixon 'up-and-down' design starting at 1.7 vol% with 0.2 vol% steps size. General anaesthesia was induced and maintained with sevoflurane; tracheal intubation was facilitated with cisatracurium. After a period of 30 min before skin incision, the state of isoelectric EEG was considered as significant when a burst suppression ratio of 100% lasted for >1 min. The haemodynamic responses to skin incision and the vasopressor requirement to maintain stable haemodynamic status were also analysed according to the EEG state.

RESULTS

MACie was 3.5% (95% confidence interval, 3.4-3.7%) in middle-aged subjects. When compared with subjects not in isoelectric EEG state, subjects in isoelectric EEG state received more phenylephrine to maintain stable haemodynamics (10 of 10 compared with 7 of 20 subjects, P=0.001) and experienced less sympathetic responses to skin incision (1 of 10 compared with 11 of 20 subjects, P=0.024).

CONCLUSIONS

MACie for sevoflurane was ∼2.1 times MAC for immobilization in phenobarbital premedicated middle-aged adults. Sevoflurane-induced isoelectric EEG state is associated with significant cardiovascular depression but reduced haemodynamic responses to skin incision.

Subarachnoid transplantation of immortalized galanin-overexpressing astrocytes attenuates chronic neuropathic pain

Treatment of chronic neuropathic pain resulted from peripheral nerve injury is one of the most difficult problems in modern clinical practice. The use of cell lines as biologic "minipumps" to chronically deliver anti-nociceptive molecules into the pain-processing centers of spinal cord is a newly developing technique for the treatment of pain. Moreover, spinal administration of exogenous galanin (GAL) is a useful target for the treatment of chronic pain after nerve injury. Because of better histocompatibility, lower immunogenicity and reproducibility, immortalized astrocytes (IAST) have been served as a promising cellular vehicle to deliver therapeutic molecules into CNS. In this study, the rat IAST was transfected with rat preprogalanin cDNA and the galanin-synthesizing and secreting cell line, IAST/GAL, was isolated. After cells were transplanted into the subarachnoid space of rats with chronic neuropathic pain induced by spared nerve injury (SNI) of sciatic nerve, their analgesic potential was evaluated by behavioral tests. The results showed that IAST/GAL transfected with preprogalanin gene could express and secrete significantly higher level of GAL protein in vitro and in vivo as compared with control cells. In addition, the pain-related behaviors, thermal hyperalgesia and mechanical allodynia were significantly alleviated during the 1-7 weeks after grafts of IAST/GAL cells, which could be reversed by galanin receptor antagonist M35 temporarily. Taken together, these data suggest that subarachnoid transplant of immortalized galanin-overexpressing astrocytes near the pain-processing centers was able to reverse the development of chronic neuropathic pain, which offers an adjunct approach to currently used therapies for the pain management.

Evaluation of NR2B peptide as subunit vaccines against experimental neuropathic pain

BACKGROUND

NR2B containing N-methyl-D-aspartate (NMDA) receptor plays an important role in the facilitation and maintenance of neuropathic pain. The discrete distribution of NR2B subunit in the central nervous system (CNS) may support reduced side effects of agents that act selectively at this site. Therefore, we investigated the hypothesis that a humoral autoimmune response targeting the NR2B subunit of NMDA receptor relieves pain like behaviours produced by peripheral injury.

METHODS

Rats were immunized subcutaneously with NR2B-Keyhole Limpet Hemocyanin (NR2B-KLH) three times at two-week intervals. NR2B specific IgG titres in sera and cerebrospinal fluid were determined by indirect ELISA. Seven days after the third immunization, 2 of the 3 terminal branches of the sciatic nerve (tibial and common peroneal nerves) were tightly ligated. Behavioural testing was carried out on every other day after surgery, until 7 days after surgery. The lumbar spinal cord (L4-6) was removed on day 7 after ligation. The expression of NR2B protein in the lumbar spinal cord was determined using Western blotting.

RESULTS

After the second vaccination, NR2B specific IgG in sera was detected to be > 0.5 microg/ml in six of nine rats. After the third vaccination, all the immunized rats had > 2.2 microg/ml. Titres of NR2B specific IgG in sera peaked 42 days post initial immunization and persisted for over 70 days. No NR2B specific IgG was detected in sera from PBS or KLH group. The behavioural thresholds in NR2B group were significantly higher than those in PBS and KLH groups on day 7 after ligation. NR2B specific IgG in CSF in NR2B group could not be detected on day 1 before spinal dissection; but could be detected on day 7 after surgery. The expression of NR2B protein in group NR2B was significantly lower than in PBS and KLH groups on day 7 after surgery.

CONCLUSION

The NR2B peptide could be used as a vaccine against neuropathic pain, which could be associated with reduction of NR2B protein in the lumbar spinal cord.

[The cellular location and significance of p38alpha/beta isoforms in the lumbar spinal cord of the bone cancer pain rats]

OBJECTIVE

To examine the cellular distribution and location of p38alpha/beta isoforms in the lumbar spinal cord of the bone cancer pain rats.

METHODS

Twenty SD female rats weighing 180 - 220 g were randomly divided into 2 groups (n = 10 each): group A (control group): intra-tibial injection of 3 microl Hank's solution; group B (model group): intra-tibial injection of 3 microl MADB-106 mammary gland carcinoma cells of rats (4.8 x 10(3)/microl). Mechanical withdrawal threshold and radiant heat threshold of rats' hind paws were measured every other day from one day before operation until 14 days later. The lumbar 4 ~ 5 spinal cord was removed on the 14th day. The cellular distribution and location of the spinal p38alpha/beta immunoreactivity were detected by immunohistochemistry SABC and double immunofluorescence methods.

RESULTS

No significant differences in mechanical withdrawal threshold and radiant heat threshold were found at all time points in group A. During the first 6 days of post-operation there was obvious difference in radiant heat stimulus between group A and B (P < 0.05); on the 14th day after operation, mechanical pain threshold and radiant heat threshold in group B were significantly different from that of group A (P < 0.05). The p38alpha/beta immunoreactivity of group B in laminae I approximately IV of dorsal horn showed stronger staining than group A (P < 0.05). Double immunofluorescence confocal micrographs showed that spinal p38alpha and the neuronal marker neuronal N (NeuN) were colocalized in the dorsal horn, indicating that p38alpha was expressed in neurons. Double immunofluorescence micrographs demonstrated that antibodies against p38beta and the microglia marker OX42 labeled the same cell, indicating that p38beta was expressed in microglia.

CONCLUSION

Our studies indicate that p38alpha and p38beta are involved in the generation and maintenance of bone cancer pain states. p38alpha is predominantly expressed in neurons, while p38beta is expressed in microglia.

Effects of music on target-controlled infusion of propofol requirements during combined spinal-epidural anaesthesia

The sedative effects of music were evaluated using the bispectral index (BIS) during target-controlled infusion (TCI) propofol. A total of 110 women undergoing hysterectomy were randomly allocated to receive either music or no music. Propofol was administered using target-controlled infusion and the concentration adjusted gradually to achieve an observer's assessment of alertness/sedation (OAA/S) score of 3 intra-operatively. The haemodynamic and bispectral index values during the sedation phase were recorded. Interleukin-6 was evaluated before, immediately after and 1 h following intervention. The music group had a significant reduction in mean (SD) induction time of sedation: 12 (12) min vs. 18 (12) min, p < 0.01; propofol target concentration: 1.6 (0.3) microg.ml(-1) vs. 2.4 (0.4) microg.ml(-1), p < 0.0001; intra-operative amount of propofol: 171 (98) mg vs. 251 (92) mg, p < 0.0001; and significantly higher levels of satisfaction with their peri-operative care: 9.6 (0.6) compared to the control group: 8.1 (1.0), p < 0.0001. No other differences were found. The results show the influence of music on the induction time of sedation, concentration and level of propofol during surgery, and suggest sedative benefits of music.