Preventive Effect of Local Lidocaine Administration on the Formation of Traumatic Neuroma.

BACKGROUND: Traumatic neuroma is a common sequela of peripheral nerve injury or amputation, which often leads to severe neuropathic pain. The present study investigated the effect of local lidocaine administration on preventing the formation of traumatic neuroma. METHODS: Forty-eight male Sprague-Dawley rats were randomly assigned to two groups. The lidocaine group underwent sciatic nerve transection, followed by an injection of lidocaine (0.5%) around the proximal of a severed sciatic nerve under ultrasound-guidance 2-7 days after neurectomy. In the control group, rats received an injection of saline following neurectomy. The autotomy score, mechanical allodynia, thermal hyperalgesia, histological assessment, expression of neuroma, and pain-related markers were detected. RESULTS: Lidocaine treatment reduced the autotomy score and attenuated mechanical allodynia and thermal hyperalgesia. The mRNA expression of α-SMA, NGF, TNF-α, and IL-1ß all significantly decreased in the lidocaine group in comparison to those in the saline control group. The histological results showed nerve fibers, demyelination, and collagen hyperplasia in the proximal nerve stump in the saline control group, which were significantly inhibited in the lidocaine group. CONCLUSIONS: The present study demonstrated that local lidocaine administration could inhibit the formation of painful neuroma due to traumatic nerve injury.

Skin Cancer Risk Prediction in Heart Transplant Recipients.

OBJECTIVES: This study was undertaken to derive a risk prediction model for skin cancer utilizing the United Network for Organ Sharing database population. MATERIALS AND METHODS: Of the 24734 adults (>18 years old) heart transplant recipients (2000-2015) in the United Network for Organ Sharing database, 2625 recipients developed skin cancer. Univariate and multivariate Cox regression analyses were performed; P values, hazard ratios, and confidence intervals were derived. The model was tested using receiver operating characteristics curves and area under the curves. MATLAB software (MathWorks) was used for analyses. RESULTS: Multivariate analysis showed that White patients had a hazard ratio of 31.7 compared with Black patients (P < .001). Male patients had a hazard ratio of 2.52 (P < .001) compared with female patients. Malignancy at listing showed a hazard ratio of 1.77 (P < .001). Thymoglobulin had a hazard ratio of 1.19 (P = .005) compared with other induction agents. The receiver operating characteristic curves generated for 5 years, 8 years, and 10 years after transplant showed area under the curve values of 0.78, 0.77, and 0.76, respectively, in the training set and 0.75, 0.75, and 0.74, respectively, in the validation set. CONCLUSIONS: Male sex, White ethnicity, older age, malignancy at the time of listing or at time of transplant, and thymoglobulin induction are major risk factors for skin cancers after transplant. This risk prediction model has a C statistic of 0.75. To our knowledge,this is the firsttime such a model has been generated for skin cancers in this population.

Mechanosensitive Ion Channel TMEM63A Gangs Up with Local Macrophages to Modulate Chronic Post-amputation Pain.

Post-amputation pain causes great suffering to amputees, but still no effective drugs are available due to its elusive mechanisms. Our previous clinical studies found that surgical removal or radiofrequency treatment of the neuroma at the axotomized nerve stump effectively relieves the phantom pain afflicting patients after amputation. This indicated an essential role of the residual nerve stump in the formation of chronic post-amputation pain (CPAP). However, the molecular mechanism by which the residual nerve stump or neuroma is involved and regulates CPAP is still a mystery. In this study, we found that nociceptors expressed the mechanosensitive ion channel TMEM63A and macrophages infiltrated into the dorsal root ganglion (DRG) neurons worked synergistically to promote CPAP. Histology and qRT-PCR showed that TMEM63A was mainly expressed in mechanical pain-producing non-peptidergic nociceptors in the DRG, and the expression of TMEM63A increased significantly both in the neuroma from amputated patients and the DRG in a mouse model of tibial nerve transfer (TNT). Behavioral tests showed that the mechanical, heat, and cold sensitivity were not affected in the Tmem63a-/- mice in the naïve state, suggesting the basal pain was not affected. In the inflammatory and post-amputation state, the mechanical allodynia but not the heat hyperalgesia or cold allodynia was significantly decreased in Tmem63a-/- mice. Further study showed that there was severe neuronal injury and macrophage infiltration in the DRG, tibial nerve, residual stump, and the neuroma-like structure of the TNT mouse model, Consistent with this, expression of the pro-inflammatory cytokines TNF-α, IL-6, and IL-1ß all increased dramatically in the DRG. Interestingly, the deletion of Tmem63a significantly reduced the macrophage infiltration in the DRG but not in the tibial nerve stump. Furthermore, the ablation of macrophages significantly reduced both the expression of Tmem63a and the mechanical allodynia in the TNT mouse model, indicating an interaction between nociceptors and macrophages, and that these two factors gang up together to regulate the formation of CPAP. This provides a new insight into the mechanisms underlying CPAP and potential drug targets its treatment.

Musical therapy attenuates neuroma pain by modifying leptin expression.

BACKGROUND: Accumulating evidence reveals that music therapy appears to help patients with pain. However, there is a limited understanding of the underlying mechanisms. Several studies indicate that leptin level has a crucial relationship with acute and chronic pain. Herein, we evaluated the effects of music stimulation and the potential roles of adipokines (leptin) in pain behaviors. METHODS: We used a tibial neuroma transposition (TNT) rat model to mimic neuroma pain. Adult male Sprague-Dawley rats were randomly assigned to one of the three groups (n = 6):group 1 (GC), TNT with white noise; group 2(GM), TNT with music; and group 3(GH), TNT. White noise and music stimulation was given once a day following surgery until the end of the study (42nd day). Pain behavioral tests were carried out before surgery and on the 3rd, 10th, 14th, 21st, 28th, 35th, and 42nd days after surgery. At the end of the observation period, we analyzed the histological samples of blood, spinal cord, and prefrontal cortex to investigate the role of leptin in pain behaviors modulated by white noise and sound stimulation. RESULT: Music therapy might improve the pain of TNT rats. Music stimulation ameliorated paw withdrawal thermal latency (PWTL) from the 3rd day after the surgery while the mechanical pain was improved 21 days after the operation.Music stimulation also increased leptin expression in the spinal cord, prefrontal cortex.White noise had no obvious effect. CONCLUSION: Music therapy might improve the pain of TNT rats. Besides, music stimulation ameliorated TNT-induced pain behaviors and affected leptin expression.

Deep Neural Network-Based Survival Analysis for Skin Cancer Prediction in Heart Transplant Recipients.

Heart-transplant recipients are at high risk of developing skin cancer, while Squamous Cell Carcinoma (SCC) and Basal Cell Carcinoma (BCC) are commonly detected. This paper utilized the database from the United Network for Organ Sharing (UNOS) to study the incidence rate of SCC and BCC among heart transplant recipients. Cox proportional hazards model and two deep neural network-based models were studied, and their performance were compared. In addition, Lasso regression, Chi-square test, and Wilcoxon signed-rank test were applied to identify key risk factors. The neural network-based survival models showed better accuracy compared to the standard Cox regression model, which indicates the advantage of deep learning approaches in survival analysis and risk prediction for post-transplant skin cancer.This study investigates the performance of deep learning (DL) models in clinical applications for predicting the risk of skin cancer in heart transplant recipients. The DL models outperform the standard models in assessing the incidence rate of skin cancer across different time spans.

Risk Prediction Model for Basal Cell Carcinoma in Cardiac Allograft Recipients.

BACKGROUND: Basal cell carcinoma (BCC) is the second most common skin cancers in posttransplant patients. Long-term immunosuppression predisposes the patients to higher risk. This study was undertaken to develop a risk prediction model using the United Network for Organ Sharing (UNOS) database. MATERIALS AND METHODS: Heart transplant recipients (2000~2015) from the UNOS database were analyzed. The Cox proportional hazards model was applied to screen the predictors associated with the development of BCC. Stepwise forward selection with Akaike information criterion was done to obtain the multivariate model. Area under the curve was derived from the receiver operating characteristics curve to assess the quality of the prediction model. A risk scoring system was developed to stratify patients into different risk groups, and the occurrence rates of posttransplant BCC among different groups were compared. RESULTS: There were 24,374 patients who received heart transplantation within this study period, and 1211 recipients have been reported with BCC. The multivariate model provides area under the curves at 5, 8, and 10 years posttransplant of 0.77, 0.76, and 0.76, respectively, in the derivation set and 0.75, 0.74, and 0.74, respectively, in the validation set. The predicted and observed probabilities of developing BCC in 5 years agree well across different risk groups. Kaplan-Meier survival curves were generated, which demonstrate significant differences between subjects in different risk groups. CONCLUSION: A risk prediction model has been generated for the first time for BCC with a c-statistic of ≥0.74 in both derivation and validation sets, making it a good tool for risk stratification.

Risk prediction model for cutaneous squamous cell carcinoma in adult cardiac allograft recipients.

BACKGROUND: Heart transplant recipients are at higher risk of developing skin cancer than the general population due to the long-term immunosuppression treatment. Cancer has been reported as one of the major causes of morbidity and mortality for patients after heart transplantation. Among different types of skin cancers, cutaneous squamous cell carcinoma (cSCC) is the most common one, which requires timely screening and better management. AIM: To identify risk factors and predict the incidence of cSCC for heart transplant recipients. METHODS: We retrospectively analyzed adult heart transplant recipients between 2000 and 2015 extracted from the United Network for Organ Sharing registry. The whole dataset was randomly divided into a derivation set (80%) and a validation set (20%). Uni- and multivariate Cox regression were done to identify significant risk factors associated with the development of cSCC. Receiver operating charac-teristics curves were generated and area under the curve (AUC) was calculated to assess the accuracy of the prediction model. Based on the selected risk factors, a risk scoring system was developed to stratify patients into different risk groups. A cumulative cSCC-free survival curve was generated using the Kaplan-Meier method for each group, and the log-rank test was done to compare the inter-group cSCC rates. RESULTS: There were 23736 heart-transplant recipients during the study period, and 1827 of them have been reported with cSCC. Significant predictors of post-transplant cSCC were older age, male sex, white race, recipient and donor human leukocyte antigen (HLA) mismatch level, malignancy at listing, diagnosis with restrictive myopathy or hypertrophic myopathy, heart re-transplant, and induction therapy with OKT3 or daclizumab. The multivariate model was used to predict the 5-, 8- and 10-year incidence of cSCC and respectively provided AUC of 0.79, 0.78 and 0.77 in the derivation set and 0.80, 0.78 and 0.77 in the validation set. The risk scoring system assigned each patient with a risk score within the range of 0-11, based on which they were stratified into 4 different risk groups. The predicted and observed 5-year probability of developing cSCC match well among different risk groups. In addition, the log-rank test indicated significantly different cSCC-free survival across different groups. CONCLUSION: A risk prediction model for cSCC among heart-transplant recipients has been generated for the first time. It offers a c-statistic of ≥ 0.77 in both derivation and validation sets.

Machine Learning Algorithm Guiding Local Treatment Decisions to Reduce Pain for Lung Cancer Patients with Bone Metastases, a Prospective Cohort Study.

INTRODUCTION: As life expectancy increases for lung cancer patients with bone metastases, the need for personalized local treatment to reduce pain is expanding. METHODS: Patients were treated by a multidisciplinary team (MDT), and local treatment including surgery, percutaneous osteoplasty, or radiation. Visual analog scale (VAS) and quality of life (QoL) scores were analyzed. VAS at 12 weeks after treatment was the main outcome. We developed and tested machine learning models to predict which patients should receive local treatment. Model discrimination was evaluated by the area under curve (AUC), and the best model was used for prospective decision-making accuracy validation. RESULTS: Under the direction of MDT, 161 patients in the training set, 32 patients in the test set, and 36 patients in the validation set underwent local treatment. VAS in surgery, percutaneous osteoplasty, and radiation groups decreased significantly to 4.78 ± 1.28, 4.37 ± 1.36, and 5.39 ± 1.31 at 12 weeks, respectively (p < 0.05), with no significant differences among the three datasets, and improved QoL was also observed (p < 0.05). A decision tree (DT) model that included VAS, bone metastases character, Frankel classification, Mirels score, age, driver gene, aldehyde dehydrogenase 2, and enolase 1 expression had a best AUC in predicting whether patients would receive local treatment of 0.92 (95% CI 0.89-0.94) in the training set, 0.85 (95% CI 0.77-0.94) in the test set, and 0.88 (95% CI 0.81-0.96) in the validation set. CONCLUSION: Local treatment provided significant pain relief and improved QoL. There were no significant differences in reducing pain and improving QoL among training, test, and validation sets. The DT model was best at determining whether patients should receive local treatment. Our machine learning model can help guide clinicians to make local treatment decisions to reduce pain. TRIAL REGISTRATION: Trial registration number ChiCRT-ROC-16009501.

Tamoxifen attenuates reactive astrocyte-induced brain metastasis and drug resistance through the IL-6/STAT3 signaling pathway.

Brain metastasis affects approximately 20%-30% of patients with triple-negative breast cancers (TNBCs). Even small metastatic lesions in the brain can trigger severe neurological impairments and result in extremely short survival time. Recently, active astrocytes were reported to be associated with brain metastases. However, how activated astrocytes regulate the behaviors of disseminated breast cancer cells in the brain remains unknown. In this study, human primary astrocytes were stimulated with IL-1ß to form active astrocytes to study the cross-talk between stromal cells (astrocytes) and TNBC cells in brain metastases. Our results showed that active astrocytes significantly increase the malignancy of TNBC cells and prevent them from undergoing apoptosis caused by doxorubicin. We also found that the high level of IL-6 secreted by activated astrocytes was responsible for the drug resistance of breast cancer, which could be abolished by treatment of astrocytes with tamoxifen (TAM). The blockage of active astrocyte-derived IL-6 by a neutralizing antibody resulted in the attenuation of drug resistance, consequently enhancing the sensitivity of breast cancer cells to doxorubicin. Furthermore, the possible involved TAM-modulated drug resistance mechanism may be associated with a decrease in IL-6 expression in astrocytes and the downregulation of MAPK and JAK2/STAT3 signaling in cancer cells. Our data suggested that TAMs might reduce drug resistance through the IL-6/JAK2/STAT3 signaling pathway, providing a possible therapy to treat brain metastasis in TNBCs, as estrogen receptor inhibitors (TAMs, etc.) can cross the blood-brain barrier.

Ultrasonography-Guided Radiofrequency Ablation for Painful Stump Neuromas to Relieve Postamputation Pain: A Pilot Study.

OBJECTIVE: Postamputation pain (PAP) is a serious problem, and thus far, there is no perfect treatment strategy. Clinically, minimally invasive treatments for peripheral neuromas are simple and feasible. This study aimed to investigate the immediate and long-term effects of ultrasonography-guided radiofrequency ablation (RFA) on PAP. METHODS: Eighteen PAP subjects with painful peripheral neuromas were treated with ultrasonography-guided RFA. RESULTS: A total of 18 PAP subjects were included in the final analyses. Fourteen of the 17 subjects with residual limb pain (RLP) (82.4%) had successful outcomes. A successful outcome was noted in 9 of the 13 subjects with phantom limb pain (PLP) (69.2%). There were no significant associations between symptom relief and sex, age, or the duration of symptoms. There were no severe complications. CONCLUSIONS: Ultrasonography-guided RFA for painful stump neuromas can effectively relieve stump pain and PLP in amputees with PAP (follow-up time was 12 months). Ultrasonography-guided RFA is easy and safe and does not involve radiation exposure, making it very suitable for clinical applications.

Regular Swimming Exercise Attenuated Neuroma Pain in Rats: Involvement of Leptin and Adiponectin.

Accumulating evidence demonstrates the beneficial effects of physical exercise on pain conditions; however, the underlying mechanisms are not understood thoroughly. The purpose of the present study was to investigate the effects of regular swimming exercise on neuroma pain and the possible roles of adipokines (leptin and adiponectin) in the pain behaviors modulated by exercise. The results showed that 5 weeks of regular swimming exercise relieved pain behaviors in a rat model of neuroma pain and normalized the dysregulation of circulating leptin and adiponectin in plasma induced by nerve injury. Moreover, regular swimming exercise reversed the altered expressions of leptin receptor and adiponectin receptor 1 in neuroma. In addition, the administration of exogenous leptin to the neuroma site dampened the effects of regular swimming exercise on neuroma pain and adiponectin administration alleviated the neuroma pain in the non-exercised neuroma rats. These findings indicate that leptin and adiponectin might be involved in mediating the beneficial effects of exercise on neuroma pain. PERSPECTIVE: Perspective: Identifying which endogenous processes are activated by specific exercise regimes would likely reveal novel therapeutic targets for the treatment of neuropathic pain. The current study suggests that adipokines might be involved in pain behaviors modulated by exercise and thus presents them as potential targets for pain management.

Role of receptor-interacting protein 1/receptor-interacting protein 3 in inflammation and necrosis following chronic constriction injury of the sciatic nerve.

Nerve damage often leads to nervous system dysfunction and neuropathic pain. The serine-threonine kinases receptor-interacting protein 1 (RIP1) and 3 (RIP3) are associated with inflammation and cell necrosis. This study aimed to explore the role of RIP1 and RIP3 in sciatic nerve chronic constriction injury (CCI) in mice. On a total of thirty mice, sciatic nerve CCI was performed. The paw withdrawal threshold was measured using Von Frey filaments. The mRNA expression and protein levels of inflammatory factors RIP1 and RIP3 in the dorsal root ganglion (DRG), spinal cord (SC) and hippocampus (HIP) were also determined. We found that paw withdrawal threshold was significantly reduced from the second day after the operation, and the levels of tumour necrosis factor-α and interferon-γ in DRG, SC and HIP were significantly increased on the eighth and 14th days in CCI mice. Furthermore, the downstream signalling molecules of RIP1 and RIP3, GTPase dynamin-related protein-1, NLR family pyrin domain containing-3 (NLRP3) and nuclear factor κB-p65 were upregulated. Increased protein levels of programmed cell death protein 1, which indicate cell death of peripheral and central nervous tissue, were induced by CCI of the sciatic nerve. Overall, this study showed that RIP1 and RIP3 were highly expressed in DRG, SC and HIP of the sciatic nerve in CCI mice and may be involved in chronic neuroinflammation and neuronecrosis.

Effects of ultrasound-guided stellate ganglion block on cervical vascular blood flow: study protocol for a randomized controlled trial.

BACKGROUND: The stellate ganglion block (SGB) can lead to vasodilation of the head and neck. However, controversy remains concerning the changes in extracerebral blood flow. The objective of this study is to assess the effects of SGB on the blood flow to the neck. METHODS: A randomized controlled crossover trial with 38 participants will be conducted. Participants who have primary headaches will be assigned to either group A or B. Patients in group A will receive SGB with 6 ml 1% lidocaine, and after a one-week washout period, they will undergo the second SGB with 6 ml normal saline. In contrast, patients in group B will receive the opposite protocol. Data will be collected at baseline (T0) and at 15 min after the first intervention (T1), 15 min before the second intervention (T2), 15 min after the second intervention (T3) and at a 3-week follow up (T4). T1 is the primary time point for the primary outcome analysis. The primary outcomes include the peak systolic velocity (PSV), the end diastolic velocity (EDV), resistance index (RI) and vessel diameter of the common carotid artery (CCA) and vertebral artery (VA). The secondary outcomes include the rate of ptosis, the rate of conjunctival flushing, and the numerical rating scale (NRS) pain score. Additionally, adverse events (AEs) or serious adverse events (SAEs) will be collected at each assessment point. DISCUSSION: This study will comprehensively investigate the efficacy of SGB in extracerebral blood flow. Our research may also suggest that SGB will be effective in reducing pain in patients with primary headaches. TRIAL REGISTRATION: Chinese Clinical Trial Registry, identifier ChiCTR-IOR-17011536 . Registered on 1 June 2017.

Swimming Training Reduces Neuroma Pain by Regulating Neurotrophins.

INTRODUCTION: Neuroma formation after peripheral nerve transection leads to severe neuropathic pain in amputees. Previous studies suggested that physical exercise could bring beneficial effect on alleviating neuropathic pain. However, the effect of exercise on neuroma pain still remained unclear. In addition, long-term exercise can affect the expression of neurotrophins (NT), such as nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), which play key roles in nociceptor sensitization and nerve sprouting after nerve injury. Here, we investigated whether long-term swimming exercise could relieve neuroma pain by modulating NT expression. METHODS: We used a tibial neuroma transposition (TNT) rat model to mimic neuroma pain. After TNT surgery, rats performed swimming exercise for 5 wk. Neuroma pain and tactile sensitivities were detected using von Frey filaments. Immunofluorescence was applied to analyze neuroma formation. NGF and BDNF expressions in peripheral neuroma, dorsal root ganglion, and the spinal cord were measured using enzyme-linked immunosorbent assay and Western blotting. RESULTS: TNT led to neuroma formation, induced neuroma pain, and mechanical allodynia in hind paw. Five-week swimming exercise inhibited neuroma formation and relieved mechanical allodynia in the hind paw and neuroma pain in the lateral ankle. The analgesic effect lasted for at least 1 wk, even when the exercise ceased. TNT elevated the expressions of BDNF and NGF in peripheral neuroma, dorsal root ganglion, and the spinal cord to different extents. Swimming also decreased the elevation of NT expression. CONCLUSIONS: Swimming exercise not only inhibits neuroma formation induced by nerve transection but also relieves pain behavior. These effects might be associated with the modulation of NT.

Ultrasound-guided alcohol neurolysis and radiofrequency ablation of painful stump neuroma: effective treatments for post-amputation pain.

BACKGROUND: Post-amputation pain (PAP) is highly prevalent after limb amputation, and stump neuromas play a key role in the generation of the pain. Presently, PAP refractory to medical management is frequently treated with minimally invasive procedures guided by ultrasound, such as alcohol neurolysis and radiofrequency ablation (RFA). OBJECTIVE: To record the immediate and long-term efficacy of alcohol neurolysis and RFA. We first used alcohol neurolysis and then, when necessary, we performed RFA on PAP patients. STUDY DESIGN: Prospective case series. SETTING: Pain management center. METHODS: Thirteen subjects were treated with ultrasound-guided procedures. RESULTS: All patients were treated with neurolysis using alcohol solutions guided by ultrasound. Seven (54%) of 13 subjects achieved pain relief after 1-3 alcohol injection treatments. The remaining 6 subjects obtained pain relief after receiving 2 administrations of ultrasound-guided RFA. After a 6-month follow-up evaluation period, pain quantities were also assessed. Both stump pain (including intermittent sharp pain and continuous burning pain) and phantom pain were relieved. The frequency of intermittent sharp pain was decreased, and no complications were noted during the observation. CONCLUSION: The use of ultrasound guidance for alcohol injection and RFA of painful stump neuromas is a simple, radiation-free, safe, and effective procedure that provides sustained pain relief in PAP patients. In this case series, RFA was found to be an effective alternative to alcohol injection.

Anti-nociceptive roles of the glia-specific metabolic inhibitor fluorocitrate in paclitaxel-evoked neuropathic pain.

Paclitaxel (Taxol) is a powerful chemotherapy drug used in breast cancers, but it often causes neuropathic pain, leading to the early cessation of therapy and poor treatment outcomes. Approaches for the management of paclitaxel-induced neuropathic pain are urgently needed. The involvement of spinal astrocytes in the pathogenesis of paclitaxel-induced neuropathy has been reported, but little is known about the role of fluorocitrate (FC), a selective inhibitor of astrocyte activation, during neuropathic pain related to paclitaxel treatment. In this study, we investigated the effects of FC on paclitaxel-induced neuropathic pain. Glial fibrillary acidic protein (GFAP) expression was determined to assess astrocyte activation. To explore the mechanisms involved, the expression of glial glutamate transporter 1 (GLT-1) and the activation of mitogen-activated protein kinases in the spinal dorsal horn were analyzed. The results showed that paclitaxel decreased the mechanical nociceptive thresholds and increased GFAP expression, leading to spinal astrocyte activation. After paclitaxel treatment, GLT-1 was significantly down-regulated, and the phosphorylation of ERK1/2 and JNK were obviously up-regulated. However, paclitaxel treatment did not increase p38 phosphorylation. Additional studies showed that paclitaxel-evoked mechanical hypersensitivity was reduced by FC treatment. Moreover, FC treatment inhibited the activation of astrocytes and reversed the changes in GLT-1 expression and MAPK phosphorylation. Further study indicated that FC did not influence the antitumor effect of paclitaxel, suggesting that FC blocked paclitaxel-induced neuropathic pain without antagonizing its antitumor effect. Together, these results suggested that paclitaxel induced astrocyte-specific activation, which may contribute to mechanical allodynia and hyperalgesia, and that FC could be a potential therapeutic agent for paclitaxel-induced neuropathic pain.

Circulating microRNA expression profile: a novel potential predictor for chronic nervous lesions.

The mechanisms of chronic neuropathic pain are not clear. Serum microRNAs (miRNAs) might show a special feature for chronic nervous lesions. However, little is known about the changes in circulating miRNAs for the neuropathic pain. Therefore, changes in the circulating miRNAs expression profile for the neuropathic pain were investigated. Serum was collected from rats before and after spinal nerve ligation (SNL) surgery, and a microarray analysis was performed to determine the changes in miRNA expression profile. The expression of inflammatory cytokines in serum from the same individuals, including interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and monocyte chemotactic protein-1 (MCP-1), was also measured. The results showed that the expression levels of IL-6, TNF-α, and MCP-1 were significantly elevated in SNL rats which were significantly correlated with pain levels. Nine miRNAs with significantly different expression levels before and after SNL surgery were identified by microarray analysis, which were further validated by quantitative real-time polymerase chain reaction analyses. Compared with naive rats without SNL surgery, the expression of five miRNAs (hsa-miR-221, hsa-miR-34c, hsa-miR-21, hsa-miR-30a-5p, and hsa-miR-206) in the serum of rats after SNL surgery was decreased and four miRNAs (hsa-miR-31-5p, hsa-miR-133b, hsa-miR-22, and hsa-miRPlus-A1087) were increased, suggesting that miRNA changes may involve in the regulation of neuropathic pain. TargetScan was used to predict mRNA targets for these miRNAs, and the results showed that the transcripts with multiple predicted target sites belonged to neurologically important pathways. Bioinformatics analysis revealed that several target genes are related to the activation of cell signaling associated with nervous lesions. In this study, the changes to miRNA profiles in serum under neuropathic pain conditions were shown for the first time, suggesting that circulating miRNAs profile in serum is a potential predictor for neuropathic pain.

Positive feedback loop of autocrine BDNF from microglia causes prolonged microglia activation.

BACKGROUND/AIMS: Microglia, which represent the immune cells of the central nervous system (CNS), have long been a subject of study in CNS disease research. Substantial evidence indicates that microglial activation functions as a strong neuro-inflammatory response in neuropathic pain, promoting the release of pro-inflammatory cytokines, such as tumor necrosis factor (TNF)-α. In addition, activated microglia release brain-derived neurotrophic factor (BDNF), which acts as a powerful cytokine. In this study, we performed a series of in vitro experiments to examine whether a positive autocrine feedback loop existed between microglia-derived BDNF and subsequent microglial activation as well as the mechanisms underlying this positive feedback loop. METHODS: Because ATP is a classic inducer of microglial activation, firstly, we examined ATP-activated microglia in the present study. Secondly, we used TrkB/Fc, the BDNF sequester, to eliminate the effects of endogenous BDNF. ATP-stimulated microglia without BDNF was examined. Finally, we used exogenous BDNF to further determine whether BDNF could directly activate BV2 microglia. In all experiments, to quantify BV2 microglia activation, the protein levels of CD11b, a microglial activation marker, were measured by western blot. A Transwell migration assay was used to examine microglial migration. To assess the synthesis and release of proinflammatory cytokines, western blot was used to measure BDNF synthesis, and ELISA was used to quantify TNF-α release. RESULTS: In our present research, we have observed that ATP dramatically activates microglia, enhancing microglial migration, increasing the synthesis of BDNF and up-regulating the release of TNF-α. Microglial activation is inhibited following the sequestration of endogenous BDNF, resulting in impaired microglial migration and decreased TNF-α release. Furthermore, exogenous BDNF can also activate microglia to subsequently enhance migration and increase TNF-α release. CONCLUSION: Therefore, we suggest that microglial activation increases the synthesis of BDNF and that the release of BDNF can, in turn, activate microglia. A positive autocrine BDNF feedback loop from microglia may contribute to prolonged microglial activation.