Neuropathic pain: principles of diagnosis and treatment

Comparison of the use of opioids only and pregabalin add-on for the treatment of neuropathic pain in cervical myelopathy patients: a pilot trial

Among patients with cervical myelopathy who were diagnosed with neuropathic pain (NP) by the LANSS test, the study participants were randomly assigned to one of the two study groups. The participants in one study group received opioids only, while those in the other group received opioids and pregabalin. Thirty-nine patients were analyzed in the study (20 patients in the opioid-only group and 19 in the pregabalin add-on group). The LANSS, neck pain, and arm pain scores in the pregabalin add-on group improved significantly compared with those in the opioid-only group after the first 4 weeks (p = 0.005, 0.001 and 0.035, respectively), but there was no significant difference between the two groups during the next 4 weeks (p = 0.615, 0.377 and 0.716, respectively). There was no significant difference in the neck disability index and EuroQol-5Dimension scores after four weeks and eight weeks of follow-up. Adverse events were reported by four patients (20.0%) in the opioid-only group and five patients (26.3%) in the pregabalin add-on group (p = 0.716). However, over time, the occurrence of side effects and dropouts increased in the pregabalin add-on group. This exploratory pilot study suggests that pregabalin add-on treatment is more efficient than the use of opioids alone at the beginning of NP treatment in cervical myelopathy patients. However, prescribing pregabalin add-on treatment for more than four weeks should be done cautiously.

The role of P2X4 receptor in neuropathic pain and its pharmacological properties

Neuropathic pain (NPP) is a common symptom of most diseases in clinic, which seriously affects the mental health of patients and brings certain pain to patients. Due to its pathological mechanism is very complicated, and thus, its treatment has been one of the challenges in the field of medicine. Therefore, exploring the pathogenesis and treatment approach of NPP has aroused the interest of many researchers. ATP is an important energy information substance, which participates in the signal transmission in the body. The P2 × 4 receptor (P2 × 4R) is dependent on ATP ligand-gated cationic channel receptor, which can be activated by ATP and plays an important role in the transmission of information in the nervous system and the formation of pain. In this paper, we provide a comprehensive review of the structure and function of the P2 × 4R gene. We also discuss the pathogenesis of NPP and the intrinsic relationship between P2 × 4R and NPP. Moreover, we explore the pharmacological properties of P2 × 4R antagonists or inhibitors used as targeted therapies for NPP.

Opioids in Older Adults: Indications, Prescribing, Complications, and Alternative Therapies for Primary Care

The fact that opioids are valuable tools for the management of pain has been known and used for thousands of years. Currently, millions of Americans are treated annually with opioids, and many of these patients are elderly. Opioids present risks to geriatric patients, some of which are unique to the population, and providers should have a good grasp of those risks. An understanding of how to select appropriate medications for the management of pain and of the myriad of alternatives available for pain management is vital to the care of older patients. This article presents a review, for primary care providers, of issues unique to opioid management in older adults.

Evaluation of Treatment Patterns and Direct Costs Associated with the Management of Neuropathic Pain

Background

Neuropathic pain has a prevalence of 2-17% in the general population. Diagnosis and treatment of neuropathic pain are not fully described in different populations. The aim was to determine the treatment patterns and direct costs of care associated with the management of neuropathic pain from the onset of the first symptom to up to two years after diagnosis.

Methods

From a drug-claim database, a cohort of randomly selected outpatients diagnosed with neuropathic pain was obtained from an insurer in Colombia and followed up for two years after diagnosis. The clinical records were reviewed individually to identify the study variables, including the time needed to make the diagnosis, the medical and paraclinical resources used, the pharmacological therapy for pain management, and the direct costs associated with care.

Results

We identified 624 patients in 49 cities, with a mean age of 50.3 ± 14.1 years, of which 324 were men (51.9%). An average of 90 days passed from the initial consultation until the diagnosis of neuropathic pain, the most frequent being lumbosacral radiculopathy (57.9%). 34.5% of the cohort had at least one diagnostic imaging procedure, and 16% had an electromyography. On average, they were treated by a general practitioner twice. 91.7% received initial treatment with tramadol, carbamazepine, amitriptyline, imipramine, or pregabalin, and 60.4% received combined therapy. The mean cost of care for two years for each patient was US$246.3.

Conclusions

Patients with neuropathic pain in Colombia are being diagnosed late, are using therapeutic agents not recommended as first-line treatment by clinical practice guidelines, and are being treated for short periods of time.

Bone-Marrow-Derived Mononuclear Cells Relieve Neuropathic Pain after Spinal Nerve Injury in Mice

Treating neuropathic pain is a critical clinical issue. Although numerous therapies have been proposed, effective treatments have not been established. Therefore, safe and feasible treatment methods are urgently needed. In this study, we investigated the therapeutic effects of autologous intrathecal administration of bone-marrow-derived mononuclear cells (MNCs) on neuropathic pain. We generated a mouse model of neuropathic pain by transecting the spinal nerve and evaluated neuropathic pain by measuring the mechanical threshold in the following 14 days. Mice in the MNC injection group had a higher mechanical threshold than those in the buffer group. We assessed the effect of MNC treatment on the dorsal root ganglia and spinal cord by immunohistochemistry, mRNA expression, and cytokine assay. The migration and accumulation of microglia were significantly suppressed in the MNC group, and the mRNA expression of inflammatory cytokines such as interleukin (IL)-6, IL-1β, and tumor necrosis factor alpha (TNF-α) was markedly downregulated. Furthermore, MNC administration tended to suppress various cytokines in the cerebrospinal fluid of the model mice. In conclusion, our results suggest that intrathecal injection of MNCs relieves neuropathic pain and might be a promising cell therapy for the treatment of this condition.

Chronic pain is common in mitochondrial disease

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Chronic pain is common in patients with mitochondrial disease.

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Pain due to mitochondrial disease is primarily of neuropathic nature.

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Distribution, intensity and type of pain are genetically determined.

In the absence of cure, the main objectives in the management of patients with mitochondrial disease are symptom control and prevention of complications. While pain is a complicating symptom in many chronic diseases and is known to have a clear impact on quality of life, its prevalence and severity in people with mitochondrial disease is unknown. We conducted a survey of pain symptoms in patients with genetically confirmed mitochondrial disease from two UK mitochondrial disease specialist centres. The majority (66.7%) of patients had chronic pain which was primarily of neuropathic nature. Presence of pain did not significantly impact overall quality of life. The m.3243A>G MTTL1 mutation was associated with higher pain severity and increased the likelihood of neuropathic pain compared to other causative nuclear and mitochondrial gene mutations. Although previously not considered a core symptom in people with mitochondrial disease, pain is a common clinical manifestation, frequently of neuropathic nature, and influenced by genotype. Therefore, pain-related symptoms should be carefully characterised and actively managed in this patient population.

Comparison of neuropathic pain characteristics associated with total brachial plexus injury before and after surgical repair: A retrospective study

OBJECTIVES

The goal of this study was to compare clinical characteristics of neuropathic pain associated with total brachial plexus injury before and after surgeries and to correlate possible contributing factors concerning to the pain prognosis.

PATIENTS AND METHODS

Thirty patients with both total brachial plexus injury and neuropathic pain were included. Neuropathic pain was evaluated in terms of pain intensities, symptoms and regions. Pain intensities were evaluated by a visual analogue scale. The Neuropathic Pain Symptoms Inventory questionnaire and body maps were used to compare the pain symptoms and regions. Demographic data, injury and repair information were evaluated to analyze the possible factors influencing the prognosis.

RESULTS

The average pain score of all participants was 7.13 ± 2.46 preoperatively and 5.40 ± 2.08 postoperatively. All patients were divided into Pain Relief Group and Pain Aggravation Group. Older age (p = 0.042), machine traction injury (p = 0.019)and nerve transplantation(p = 0.015) seemed to be related with pain aggravation. Paroxysmal pain was aggravated after surgical repairs (p = 0.041), while paresthesia/dysesthesia improved after surgery (p = 0.003). The permanent component of the pain (spontaneous pain) did not show any significant change (p = 0.584). Pain in C5 (p < 0.001) and C6 (p = 0.031) dermatomes got relieved after surgery.

CONCLUSION

This study revealed the neuropathic pain of most patients with total brachial plexus injury was alleviated after neurosurgery, and the pain prognosis of different symptoms and regions varied after the nerve repair.

Evidence for Dietary Agmatine Sulfate Effectiveness in Neuropathies Associated with Painful Small Fiber Neuropathy. A Pilot Open-Label Consecutive Case Series Study

Peripheral neuropathies associated with painful small fiber neuropathy (SFN) are complex conditions, resistant to treatment with conventional medications. Previous clinical studies strongly support the use of dietary agmatine as a safe and effective treatment for neuropathic pain. Based on this evidence, we conducted an open-label consecutive case series study to evaluate the effectiveness of agmatine in neuropathies associated with painful SFN (Study Registry: ClinicalTrials.gov, System Identifier: NCT01524666). Participants diagnosed with painful SFN and autonomic dysfunctions were treated with 2.67 g/day agmatine sulfate (AgmaSet^® capsules containing G-Agmatine^® brand of agmatine sulfate) for a period of 2 months. Before the beginning (baseline) and at the end of the treatment period, participants answered the established 12-item neuropathic pain questionnaire specifically developed to distinguish symptoms associated with neuropathy and to quantify their severity. Secondary outcomes included other treatment options and a safety assessment. Twelve patients were recruited, and 11 patients—8 diagnosed with diabetic neuropathy, two with idiopathic neuropathy and one with inflammatory neuropathy—completed the study. All patients showed improvement in neuropathic pain to a varied extent. The average decrease in pain intensity was 26.0 rating points, corresponding to a 46.4% reduction in overall pain (p < 0.00001). The results suggest that dietary agmatine sulfate has a significant effect in reducing neuropathic pain intensity associated with painful SFN resistant to treatment with conventional neuropathic pain medications. Larger randomized placebo-controlled studies are expected to establish agmatine sulfate as a preferred treatment.

Use of psychiatric drugs in Dermatology

Patients with psychocutaneous disorders often refuse psychiatric intervention in their first consultations, leaving initial management to the dermatologist. The use of psychotropic agents in dermatological practice, represented by antidepressants, antipsychotics, anxiolytics, and mood stabilizers, should be indicated so that patients receive the most suitable treatment rapidly. It is important for dermatologists to be familiar with the most commonly used drugs for the best management of psychiatric symptoms associated with dermatoses, as well as to manage dermatologic symptoms triggered by psychiatric disorders.

Plasma disposition of gabapentin after the intragastric administration of escalating doses to adult horses

Background

In humans, gabapentin an analgesic, undergoes non‐proportional pharmacokinetics which can alter efficacy. No information exists on the pharmacokinetics of dosages >20 mg/kg, escalating dosages or dose proportionality of gabapentin in horses.

Hypothesis and Objectives

Gabapentin exposure in plasma would not increase proportionally relative to the dose in horses receiving dosages ≥20 mg/kg. To assess the plasma pharmacokinetics of gabapentin after nasogastric administration of gabapentin at dosages of 10 to 160 mg/kg in adult horses.

Animals

Nine clinically healthy adult Arabian and Quarter Horses.

Methods

In a randomized blinded trial, gabapentin was administered by nasogastric intubation to horses at 10, 20 mg/kg (n = 3) and 60, 80, 120, 160 mg/kg (n = 6). Plasma was collected before and at regular times over 64 hours after administration of gabapentin. Gabapentin was quantified using a validated chromatographic method. Dose proportionality was estimated using a power model. Pharmacokinetic parameters were estimated using compartmental pharmacokinetic analysis.

Results

Plasma pharmacokinetics parameters of gabapentin were estimated after nasogastric administration at dosages of 10 to 160 mg/kg. Gabapentin plasma concentration increased with dose increments. However, the area under the concentration curve from zero to infinity and maximal plasma concentration did not increase proportionally relative to the dose in horses.

Conclusions and Clinical Importance

Gabapentin exposure in plasma is not proportional relative to the dose in horses receiving nasogastric dosages of 10 to 160 mg/kg.

Neuropathic Pain Dysregulates Gene Expression of the Forebrain Opioid and Dopamine Systems

Disturbances in the function of the mesostriatal dopamine system may contribute to the development and maintenance of chronic pain, including its sensory and emotional/cognitive aspects. In the present study, we assessed the influence of chronic constriction injury (CCI) of the sciatic nerve on the expression of genes coding for dopamine and opioid receptors as well as opioid propeptides in the mouse mesostriatal system, particularly in the nucleus accumbens. We demonstrated bilateral increases in mRNA levels of the dopamine D1 and D2 receptors (the latter accompanied by elevated protein level), opioid propeptides proenkephalin and prodynorphin, as well as delta and kappa (but not mu) opioid receptors in the nucleus accumbens at 7 to 14 days after CCI. These results show that CCI-induced neuropathic pain is accompanied by a major transcriptional dysregulation of molecules involved in dopaminergic and opioidergic signaling in the striatum/nucleus accumbens. Possible functional consequences of these changes include opposite effects of upregulated enkephalin/delta opioid receptor signaling vs. dynorphin/kappa opioid receptor signaling, with the former most likely having an analgesic effect and the latter exacerbating pain and contributing to pain-related negative emotional states.

The role and pharmacological properties of the P2X7 receptor in neuropathic pain

Neuropathic Pain (NPP) is caused by direct or indirect damage to the nervous system and is a common symptom of many diseases. Clinically, drugs are usually used to suppress pain, such as (lidocaine, morphine, etc.), but the effect is short-lived, poor analgesia, and there are certain dependence and side effects. Therefore, the investigation of the treatment of NPP has become an urgent problem in medical, attracting a lot of research attention. P2X7 is dependent on Adenosine triphosphate (ATP) ion channel receptors and has dual functions for the development of nerve damage and pain. In this review, we explored the link between the P2X7 receptor (P2X7R) and NPP, providing insight into the P2X7R and NPP, discussing the pathological mechanism of P2 X7R in NPP and the biological characteristics of P2X7R antagonist inhibiting its over-expression for the targeted therapy of NPP.

Identification of neuropathic pain-associated genes and pathways via random walk with restart algorithm

BACKGROUND

Neuropathic pain (NP) develops from neuropathic lesions or diseases affecting the nervous system, and has become a serious public health issue due to its complex symptoms, high incidence and long duration. At present, the exact pathogenesis of NP is still unclear. In this study, we sought to identify the genes as well as the related molecular mechanisms associated with NP occurrence and development.

METHODS

We firstly identified the differentially expressed genes between NP spinal nerve ligation (SNL) rats and control sham rats and then projected them onto a STRING network for functional association analysis. Then, Random Walk with Restart (RWR) was conducted to find some new NP-related genes, with their potential functions sequentially analyzed by GO annotation and KEGG pathway analysis.

RESULTS

Some new NP-related genes, like Gng13, C3 and Cxcl2, were identified by RWR analysis. Meanwhile, some biological functions like inflammatory responses, chemotaxis and immune responses, as well as some signaling pathways, such as those involved in neuroactive ligand-receptor interactions, complement and blood coagulation cascade reactions, and cytokine-receptor interactions that the new NP- related genes were most activated were found to be associated with NP occurrence and development.

CONCLUSIONS

This study extends our knowledge of NP occurrence and development and provides new therapeutic targets for future NP treatment.

Levo-corydalmine attenuates microglia activation and neuropathic pain by suppressing ASK1-p38 MAPK/NF-κB signaling pathways in rat spinal cord

BACKGROUND AND OBJECTIVES

Neuropathic pain is partially refractory to currently available treatments. Although some studies have reported that apoptosis signal-regulating kinase 1 (ASK1) may inhibit chronic pain, the mechanisms underlying this process have not been fully elucidated.

METHODS

Chronic constriction injury (CCI) of the rat sciatic nerve was used to establish a neuropathic pain model. Nociception was assessed using von Frey hair and Hargreaves' methods. Western blot and immunofluorescence were used to detect the cell signaling pathway. BV2 cell line was cultured for in vitro evaluation.

RESULTS

Our results indicated that spinal ASK1 was co-expressed with the microglia marker ionized calcium binding adaptor 1. Additionally, intrathecal administration of ASK1 inhibitor suppressed the activation of spinal microglia and attenuated CCI-induced neuropathic pain. The ASK1 inhibitor also decreased the levels of phosphorylated ASK1 (p-ASK1), p65, p38 mitogen-activated protein kinase (MAPK) and tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) messenger RNA in lipopolysaccharide-stimulated BV2 microglia cells. Intragastric administration of levo-corydalmine (l-CDL) significantly attenuated CCI-induced neuropathic pain and inhibited the expression of p-ASK1 in the spinal cord. l-CDL conspicuously suppressed the activation of spinal microglia in vitro and in vivo. Translocation of nuclearfactor-kappa B (NF-κB) and upregulation of p-p65, TNF-α, IL-1β were inhibited by l-CDL. Further, the analgesic effects of l-CDL were associated with reduced levels of phosphorylated protein kinase C (PKC γ), c-JunNH2-terminal kinase, and extracellular signal-regulated kinase.

CONCLUSIONS

This study showed that the expression of ASK1 in spinal microglia and ASK1 inhibitor suppressed microglia activation via suppression of p38 MAPK/NF-κB, which ultimately attenuated CCI-induced neuropathic pain. l-CDL also inhibited the ASK1-P38 MAPK/NF-κB axis to attenuate CCI-induced neuropathic pain.

Prevalence and associated predictors for patients developing chronic neuropathic pain following burns

BACKGROUND

Chronic pain, unrelated to the burn itself, can manifest as a long-term complication in patients sustaining burn injuries. The purpose of this study was to determine the prevalence of chronic neuropathic pain (CNP) and compare burn characteristics between patients who developed CNP and patients without CNP who were treated at a burn center.

METHODS

A single-center, retrospective analysis of 1880 patients admitted to the adult burn center was performed from 1 January 2014 to 1 January 2019. Patients included were over the age of 15 years, sustained a burn injury and were admitted to the burn center. CNP was diagnosed clinically following burn injury. Patients were excluded from the definition of CNP if their pain was due to an underlying illness or medication. Comparisons between patients admitted to the burn center with no pain and patients admitted to the burn center who developed CNP were performed.

RESULTS

One hundred and thirteen of the 1880 burn patients developed CNP as a direct result of burn injury over 5 years with a prevalence of 6.01%. Patients who developed CNP were a significantly older median age (54 years vs. 46 years, p = 0.002), abused alcohol (29% vs. 8%, p < 0.001),abused substances (31% vs. 9%, p < 0.001), were current daily smokers (73% vs. 33%, p < 0.001), suffered more full-thickness burns (58% vs. 43%, p < 0.001), greater median percent of total body surface area (%TBSA) burns (6 vs. 3.5, p < 0.001), were more often intubated on mechanical ventilation (33% vs. 14%, p < 0.001), greater median number of surgeries (2 vs. 0, p < 0.001) and longer median hospital length of stay (LOS) (10 days vs. 3 days, p < 0.001), compared to those who did not develop CNP, respectively. Median patient follow-up was 27 months.

CONCLUSIONS

The prevalence of CNP over 5 years was 6.01% in the burn center. Older ages, alcohol abuse, substance abuse, current daily smoking, greater percent of total body surface area (%TBSA) burns, third degree burns, being intubated on mechanical ventilation, having more surgeries and longer hospital LOS were associated with developing CNP following burn injury, compared to patients who did not develop CNP following burn injury.

Regeneration enhancers: Starting a journey to unravel regulatory events in tissue regeneration

Regeneration, an ability to replace lost body parts, is widespread across animal species. While mammals poorly regenerate most tissues, teleost fish and urodele amphibians possess remarkable regenerative capacity. Earlier work demonstrated that genes driving regeneration are evolutionarily conserved, indicating that a key factor in diverse tissue regeneration is not the presence or absence of regeneration-driving genes but the mechanisms controlling activation of these genes after injury. Thus, understanding the regulatory events of tissue regeneration could provide the means for unlocking latent capacities for tissue regeneration. After injury, cells undergo extensive epigenetic changes to establish new transcriptional programs for tissue regeneration. Gene transcription in eukaryotes is a complicated process that requires specific interactions between trans-acting regulators and cis-regulatory DNA elements. Among cis-regulatory elements, enhancers are essential to control precise gene expression. Recently, multiple regeneration/injury-associated enhancers have been identified in several model organisms. In this review, we highlight recently discovered regeneration/injury enhancers and their specific characteristics. We also discuss how abnormal regulation of regeneration enhancers influences animal development and physiology. Investigation of regeneration enhancers potentially allows us to begin understanding the fundamental biology of tissue regeneration and inspires new solutions for manipulating regenerative ability.

Temporal Changes of Spinal Transcriptomic Profiles in Mice With Spinal Nerve Ligation

Neuropathic pain (NP) is an intractable disease accompanying with allodynia, hyperalgesia and spontaneous pain. Accumulating evidence suggested that large volume of neurotransmitters, genes, and signaling pathways were implicated with the initiation and development of NP, while the underlying mechanism still remained poorly understood. Therefore, it was extremely important to further elucidate the potential regulatory networks for developing appropriate treatment options. Here, the RNA-Seq high-throughput sequencing was employed to determine the genes expression change in mice undergoing spinal nerve ligation (SNL). Meanwhile, the differentially expressed genes (DEGs) were analyzed by using integrated Differential Expression and Pathway analysis (iDEP) tools and String database. Then, quantitative real-time PCR (qRT-PCR) was employed to detect the expression of hub gens. The results showed that the DEGs mainly comprised 1712 upregulated and 1515 downregulated genes at 7 days, and consisted of 243 upregulated and 357 downregulated genes at 28 days after surgery, respectively. Additionally, 133 genes and two pathways including retrograde endocannabinoid signaling and cardiac muscle contraction collectively participated in biological reactions of 7th and 28th day after operation. Moreover, the results showed that the mRNA and protein expression of Ccl5, Cacna2d1, Cacna2d2, Cacnb2, Gabrb3, GluA1, and GluA2 were significantly upregulated in SNL-7/28d group than that of in Sham-7/28d group (SNL-7d vs. Sham-7d; SNL-28d vs. Sham-28d; P < 0.05). And the level of Glra2, Glra4, Glra3, Grik1, Grik2, NR1, NR2A, and NR2B was obviously increased in SNL-7d group compared to Sham-7d group (P < 0.05), but which was no statistical difference between SNL-28d group and Sham-28d group. Therefore, these results provided new perspectives and strategies for deeply illuminating the underlying mechanism, and identifying the key elements for treating NP.

Emerging Roles of Long Non-coding RNAs in Chronic Neuropathic Pain

Chronic neuropathic pain, a type of chronic and potentially disabling pain caused by a disease or injury of the somatosensory nervous system, spinal cord injury, or various chronic conditions, such as viral infections (e.g., post-herpetic neuralgia), autoimmune diseases, cancers, and metabolic disorders (e.g., diabetes mellitus), is one of the most intense types of chronic pain, which incurs a major socio-economic burden and is a serious public health issue, with an estimated prevalence of 7–10% in adults throughout the world. Presently, the available drug treatments (e.g., anticonvulsants acting at calcium channels, serotonin-noradrenaline reuptake inhibitors, tricyclic antidepressants, opioids, topical lidocaine, etc.) for chronic neuropathic pain patients are still rare and have disappointing efficacy, which makes it difficult to relieve the patients’ painful symptoms, and, at best, they only try to reduce the patients’ ability to tolerate pain. Long non-coding RNAs (lncRNAs), a type of transcript of more than 200 nucleotides with no protein-coding or limited capacity, were identified to be abnormally expressed in the spinal cord, dorsal root ganglion, hippocampus, and prefrontal cortex under chronic neuropathic pain conditions. Moreover, a rapidly growing body of data has clearly pointed out that nearly 40% of lncRNAs exist specifically in the nervous system. Hence, it was speculated that these dysregulated lncRNAs might participate in the occurrence, development, and progression of chronic neuropathic pain. In other words, if we deeply delve into the potential roles of lncRNAs in the pathogenesis of chronic neuropathic pain, this may open up new strategies and directions for the development of novel targeted drugs to cure this refractory disorder. In this article, we primarily review the status of chronic neuropathic pain and provide a general overview of lncRNAs, the detailed roles of lncRNAs in the nervous system and its related diseases, and the abnormal expression of lncRNAs and their potential clinical applications in chronic neuropathic pain. We hope that through the above description, readers can gain a better understanding of the emerging roles of lncRNAs in chronic neuropathic pain.

From Pathogenesis to Novel Therapeutics for Spinocerebellar Ataxia Type 3: Evading Potholes on the Way to Translation

Spinocerebellar ataxia type 3 (SCA3), also known as Machado-Joseph disease (MJD), is a neurodegenerative disorder caused by a polyglutamine expansion in the ATXN3 gene. In spite of the identification of a clear monogenic cause 25 years ago, the pathological process still puzzles researchers, impairing prospects for an effective therapy. Here, we propose the disruption of protein homeostasis as the hub of SCA3 pathogenesis, being the molecular mechanisms and cellular pathways that are deregulated in SCA3 downstream consequences of the misfolding and aggregation of ATXN3. Moreover, we attempt to provide a realistic perspective on how the translational/clinical research in SCA3 should evolve. This was based on molecular findings, clinical and epidemiological characteristics, studies of proposed treatments in other conditions, and how that information is essential for their (re-)application in SCA3. This review thus aims i) to critically evaluate the current state of research on SCA3, from fundamental to translational and clinical perspectives; ii) to bring up the current key questions that remain unanswered in this disorder; and iii) to provide a frame on how those answers should be pursued.

Crosstalk between Cdk5/p35 and ERK1/2 signalling mediates spinal astrocyte activity via the PPARγ pathway in a rat model of chronic constriction injury

The specific mechanisms underlying cyclin-dependent kinase 5 (Cdk5)-mediated neuropathic pain at the spinal cord level remain elusive. The aim of the present study was to explore the role of crosstalk between Cdk5/p35 and extracellular signal-regulated kinase 1/2 (ERK1/2) signalling in mediating spinal astrocyte activity via the PPARγ pathway in a rat model of chronic constriction injury (CCI). Here, we quantified pain behaviour after CCI; detected the localization of p35, Cdk5, phosphorylated ERK1/2 (pERK1/2), phosphorylated peroxisome proliferator-activated receptor γ (pPPARγ), neuronal nuclei (a neuronal marker), glial fibrillary acidic protein (GFAP, an activated astrocyte marker) and ionized calcium binding adaptor molecule 1 (a microglial marker) in the dorsal horn using immunofluorescence; measured the protein levels of Cdk5, p35, pERK1/2, pPPARγ and GFAP using western blot analysis; and gauged the enzyme activity of Cdk5/p35 kinase using a Cdk5/p35 kinase activity assay kit. Tumour necrosis factor-α, interleukin (IL)-1β and IL-6 levels were measured using enzyme-linked immunosorbent assay (ELISA). Ligation of the right sciatic nerve induced mechanical allodynia; thermal hyperalgesia; and the time-dependent upregulation of p35, pERK1/2 and GFAP and downregulation of pPPARγ. p35 colocalized with Cdk5, pERK1/2, pPPARγ, neurons and astrocytes but not microglia. Meanwhile, intrathecal injection of the Cdk5 inhibitor roscovitine, the mitogen-activated ERK kinase (MEK) inhibitor U0126 and the PPARγ agonist pioglitazone prevented or reversed behavioural allodynia, increased pPPARγ expression, inhibited astrocyte activation and alleviated proinflammatory cytokine (tumour necrosis factor-α, IL-1β, and IL-6) release from activated astrocytes. Furthermore, crosstalk between the Cdk5/p35 and ERK1/2 pathways was observed with CCI. Blockade of either Cdk5/p35 or ERK1/2 inhibited Cdk5 activity. These findings indicate that spinal crosstalk between the Cdk5/p35 and ERK1/2 pathways mediates astrocyte activity via the PPARγ pathway in CCI rats and that targeting this crosstalk could be an effective strategy to attenuate CCI and astrocyte-derived neuroinflammation.

Practical approach to a patient with chronic pain of uncertain etiology in primary care

Chronic pain of uncertain etiology often presents a challenge to both patients and their health care providers. It is a complex condition influenced by structural and physiological changes in the peripheral and central nervous systems, and it directly influences, and is modulated by, psychological well-being and personality style, mood, sleep, activity level and social circumstances. Consequently, in order to effectively treat the pain, all of these need to be evaluated and addressed. An effective management strategy takes a multidisciplinary biopsychosocial approach, with review of all current medications and identification and careful withdrawal of those that may actually be contributing to ongoing pain. The management approach is primarily nonpharmacological, with carefully considered addition of medication, beginning with pain-modulating treatments, if necessary. In this article, we present a primary care approach to the assessment and management of a patient with chronic pain where the cause cannot be identified.

Efficacy of a topical gabapentin gel in a cisplatin paradigm of chemotherapy-induced peripheral neuropathy

BACKGROUND

Chemotherapy induced peripheral neuropathy (CIPN) has been attributed to chemotherapeutic agents such as cisplatin which adversely affect disease outcome leading to increased cancer related morbidity. The clinical efficacy of systemic gabapentin in neuropathic pain management is limited by central side-effects in addition to a scarceness of conclusive evidence of its efficacy in CIPN management. The topical route therefore may provide a relatively safe alternative for neuropathic pain treatment in general and CIPN in particular.

METHODS

Cisplatin induced neuropathic nociception was established in rats after a single weekly cisplatin injection (3.0 mg/kg, intraperitoneally) for 4 weeks. The evoked neuropathic sensation of allodynia was assessed by plantar application of von Frey monofilaments as the paw withdrawal threshold (PWT), whereas the expression of heat-hypoalgesia was determined on a hot-plate as paw withdrawal latency (PWL). Gabapentin gel (10% w/w) was applied three-times daily on the hind paws while in a concurrent systemic study, gabapentin was administered daily (75 mg/kg, intraperitoneally) for 4 weeks. To assess any evidence of neurological adverse symptoms of cisplatin and the central side-effect propensity of systemic or topical gabapentin, evaluation of motor coordination (rotarod test) and gait (footprint analysis) were performed.

RESULTS

Cisplatin invoked a progressive development of neuropathic hind paw allodynia (decreased PWT, days 7-28) and heat hypoalgesia (increased PWL, days 21-28). Topical gabapentin significantly delayed the expression of both allodynia on protocol days 21 and 28 and heat-hypoalgesia (day 28). Systemic gabapentin displayed a comparative anti-neuropathic predisposition through a sustained suppression of tactile allodynia on days 14 and 21-28 as well as thermal hypoalgesia (days 21 and 28). Systemic gabapentin also impaired motor coordination and gait thus affirming its clinically documented central side effects, but these outcomes were not evident after topical treatment.

CONCLUSIONS

Both topical and systemic gabapentin exhibit a propensity to attenuate CIPN in a cisplatin paradigm. Gabapentin applied topically may therefore provide an adjunctive or alternative route for CIPN management upon cessation of systemic medications due to intolerable side-effects.

Introduction of pulsed radiofrequency cautery in infraorbital nerve block method for postoperative pain management of trauma-induced zygomaticomaxillary complex fracture reduction

Although various cases of neuralgia and its treatments have been reported, not enough evidence is present to recommend a single type of treatment as the most effective. The patient we have dealt with experienced significant interferences in his daily life due to chronic allodynia, but the symptom could not be resolved via previously reported treatments. We report a case of which a patient who presented infraorbital neuralgia after trauma was successfully treated by a novel treatment strategy. The patient was treated by applying infraorbital nerve block and pulsed radiofrequency cautery side by side. Through this report, we evaluate proper prevention and treatment strategies for patients who develop infraorbital neuralgia through similar etiologies.

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Real-Time In Vivo Control of Neural Membrane Potential by Electro-Ionic Modulation

Theoretically, by controlling neural membrane potential (V_m) in vivo, motion, sensation, and behavior can be controlled. Until now, there was no available technique that can increase or decrease ion concentration in vivo in real time to change neural membrane potential. We introduce a method that we coin electro-ionic modulation (EIM), wherein ionic concentration around a nerve can be controlled in real time and in vivo. We used an interface to regulate the Ca²⁺ ion concentration around the sciatic nerve of a frog and thus achieved stimulation and blocking with higher resolution and lower current compared with electrical stimulation. As EIM achieves higher controllability of V_m, it has potential to replace conventional methods used for the treatment of neurological disorders and may bring a new perspective to neuromodulation techniques.

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EIM regulates extracellular ion concentration in vivo in real time

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EIM stimulates or blocks the nerve via Ca²⁺ ion depletion or enhancement

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EIM achieves selective stimulation or blocking of large or small axons

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EIM is the most superior neuromodulation method for real-life applications

Emerging role of nanomedicine in the treatment of neuropathic pain

Neuropathic pain (NeP) is a complex chronic pain condition associated with nerve injury. Approximately, 7-10% of the general population across the globe is suffering from this traumatic condition, but the existing treatment strategies are inadequate to deliver pain relief and are associated with severe adverse effects. To overcome these limitations, lot of research is focussed on developing new molecules with high potency and fewer side effects, novel cell and gene-based therapies and modification of the previously approved drugs by different formulation aspects. Nanomedicine has attracted a lot of attention in the treatment of many diverse pathological conditions because of their unique physiochemical and biological properties. In this manuscript, we highlighted the emerging role of nanomedicine in different therapies (drug, cell and gene), also we emphasised on the challenges associated with nanomedicine such as development of well-characterised nanoformulation, scaling of batches with reproducible results and toxicity along with this we discussed about the future of nanomedicine in the treatment of neuropathic pain.

Metformin reduces c-Fos and ATF3 expression in the dorsal root ganglia and protects against oxaliplatin-induced peripheral sensory neuropathy in mice

Oxaliplatin is a third-generation platinum drug commonly used as the first line treatment of metastatic colorectal cancer. Oxaliplatin-based anticancer regimens course with dose-limiting neurotoxicity. The pharmacological strategies used to manage such side effect are not totally effective. Metformin is an anti-diabetic drug that is described to negatively modulate painful diabetic neuropathy. Then, this study aimed to assess the effect of metformin in the oxaliplatin-induced peripheral sensory neuropathy in mice. For that purpose, Swiss male mice were injected with oxaliplatin (1, 2 or 4 mg/kg, i.v., twice a week with a total of nine injections) alone or in combination with daily administration of metformin (250 mg/kg, p.o.). Thermal and mechanical nociceptive tests were performed once a week for five weeks. Then, the animals were euthanized on day 35 post-first injection of oxaliplatin and the dorsal root ganglia were harvested for the assessment of c-Fos and ATF3 expressions. Oxaliplatin caused a nociceptive response accompanied by the increased expression of c-Fos and ATF3 in the dorsal root ganglia and spinal cord. In addition, the oxaliplatin-associated nociception was significantly attenuated by metformin (P < 0.05), which also reduced the expression of c-Fos and ATF3 (P < 0.05). Therefore, metformin protected from the peripheral sensory neuropathy induced by oxaliplatin, which was confirmed by the reduction of c-Fos and ATF3 expression, two known neuronal activation and damage markers, respectively.

Pain perception in patients with hidradenitis suppurativa

BACKGROUND

Pain is a prominent symptom of hidradenitis suppurativa (HS) and has been defined as a domain in the Core Outcome Set for the disease. Quality and intensity of pain is influenced by depression and anxiety, both of which are associated with HS.

OBJECTIVES

To describe HS-related pain quantitatively and qualitatively; and to investigate how disease severity, depression and anxiety correlate with self-reported pain quality.

METHODS

Pain perception was investigated using the McGill Pain Questionnaire. Symptoms of depression and anxiety were examined using the Hospital Anxiety and Depression Scale. Statistical analyses investigated differences in number of words chosen (NWC) and pain-rating index rank [PRI(R)] in patients with severe disease and in patients with depression/anxiety.

RESULTS

A total of 138 patients with HS were recruited in an outpatient clinic (October 2017-March 2018). Patients presented a median NWC of 11·5 and a PRI(R) of 59·0%. Most common descriptors were 'shooting' (83%), 'itchy' (79%) and 'blinding' (75%). Patients with depression or anxiety presented significantly higher PRI(R)s [depressed 65% vs. non-depressed 57% (P = 0·015); anxious 65% vs. nonanxious 57% (P = 0·004)]. Patients with involvement of three or more HS regions vs. those with fewer than three involved regions exhibited a significantly higher NWC (13 vs. 8; P = 0·048).

CONCLUSIONS

HS-related pain includes nociceptive and neuropathic pain, and perception appears to be influenced by disease severity, anxiety and depression. A multimodal pain management strategy may be the most appropriate; however, more detailed studies are necessary to define recommendations on pain management. What's already known about this topic? Pain is a core outcome domain hidradenitis suppurativa. Few studies have addressed this significant clinical problem. What does this study add? This study suggests that HS pain comprises both nociceptive and neuropathic pain. Pain appears associated to depression, anxiety and severity of the disease.

Characterizing Abdominal Pain in Patients With Gastroparesis Into Neuropathic and Nociceptive Components

INTRODUCTION

The cause of abdominal pain (AP) in gastroparesis (Gp) is often not known; hence, its treatment can be challenging. Preoccupation with or increased attention (hypervigilance) to pain is associated with perceived pain severity and psychosocial disability. The aims of this study were to (1) characterize AP in Gp patients into neuropathic and nociceptive pain components; (2) assess these patients for hypervigilance to pain.

MATERIALS AND METHODS

Gp patients with AP as an important symptom, seen from June 2017 to November 2017 were given validated questionnaires to characterize their AP. Carnett's sign (worsened AP/tenderness on head/shoulder lift and/or leg lift) was assessed on examination.

RESULTS

Of 32 patients (87% females), 20 had idiopathic Gp, and 9 had diabetic Gp. AP severity using Patient Assessment of Gastrointestinal Symptoms averaged 4.3±0.2 (standard error of mean) for upper AP and 2.3±0.3 for lower AP. AP was typically located in epigastrium (53.1%), and described as sharp (75%). Eleven patients (35.5%) met criteria for neuropathic pain on Neuropathic Pain Questionnaire. Twenty patients (62.5%) had positive Carnett's sign suggesting somatic pain. Fifteen patients (48.4%) were hypervigilant to pain on Pain Vigilance and Awareness Questionnaire.

CONCLUSIONS

Of Gp patients with AP, over one third have a neuropathic component to their pain whereas nearly two thirds have characteristics of somatic pain. Almost half of the Gp patients with AP are hypervigilant to pain. Determining the underlying cause of AP and hypervigilance to pain in Gp patients may assist in devising appropriate treatment strategies.

Chronic pain in cats: Recent advances in clinical assessment

PRACTICAL RELEVANCE

Chronic pain is a feline health and welfare issue. It has a negative impact on quality of life and impairs the owner-cat bond. Chronic pain can exist by itself or may be associated with disease and/or injury, including osteoarthritis (OA), cancer, and oral and periodontal disease, among others.

CLINICAL CHALLENGES

Chronic pain assessment is a fundamental part of feline practice, but can be challenging due to differences in pain mechanisms underlying different conditions, and the cat's natural behavior. It relies mostly on owner-assessed behavioral changes and time-consuming veterinary consultations. Beyond OA - for which disease-specific clinical signs have been described - little is known regarding other feline conditions that produce chronic pain.

RECENT ADVANCES

Knowledge of the subject has, however, greatly improved in the past few years, informed by study of the mechanisms of pain in cats with OA and the development of pain scales that can be used by owners or veterinarians. Pain scales may facilitate the diagnosis and follow-up evaluation of chronic painful conditions, providing a basis for therapeutic decision-making. Assessment of quality of life is also recommended in cats with chronic pain, and its improvement can be used as a positive outcome in response to therapy.

AIMS

This article reviews recent advances and presents the challenges and some future perspectives on clinical chronic pain assessment. The most common feline chronic conditions associated with pain are also described.

Effect of HDAC2/Inpp5f on neuropathic pain and cognitive function through regulating PI3K/Akt/GSK-3β signal pathway in rats with neuropathic pain

The effect of histone deacetylase (HDAC)2/Inositol polyphosphate-5-phosphatase F (Inpp5f) on neuropathic pain and cognitive dysfunction through regulating PI3K/Akt/GSK-3β signal pathway in rats with neuropathic pain was investigated. A total of 80 SPF mature male SD rats were averagely randomized into the sham operation group, the model group, the HDAC2 intervention group (group A) and the Inpp5f intervention group (group B). The rat models of neuropathic pain were established in the model group, and groups A and B. At the 15th day after modeling, rats in group A were transfected with the interference vector of HDAC2, and rats in group B were transfected with the overexpression vector of Inpp5f. Rats in the four groups were observed before modeling, after modeling/before intervention and 3 days after intervention in terms of paw thermal withdrawal latency (PWL), paw withdrawal mechanical threshold (PWT) and changes in cognitive function (Morris water maze and passive avoidance task). Then the rats were sacrificed. RT-qPCR and western blot analysis were used to detect the levels of HDAC2 mRNA, Inpp5f mRNA, phosphorylated PI3K (p-PI3K), phosphorylated AKT (p-AKT), phosphorylated GSK-3β (p-GSK-3β) in rat brain tissue. Correlation of HDAC2 mRNA with Inpp5f mRNA expression levels was detected by Pearsons correlation analysis. Compared with the sham operation group, PWL was significantly lower while PWT was higher in the other 3 groups (P<0.05). Three days after intervention, PWL was significantly higher while PWT was significantly lower (P<0.05). Inhibiting the expression of HDAC2 or promoting the expression of Inpp5f can effectively improve cognitive function in rats (P<0.05). After intervention, compared with the sham operation group, rats in the other 3 groups had higher HDAC2 mRNA level and lower Inpp5f mRNA level (P<0.05). In conclusion, neuropathic pain can cause an increase in HDAC2 expression level and a decrease in Inpp5f expression level, and activate the PI3K/Akt/GSK-3β signal pathway. Inhibition of HDAC2 expression can inhibit the activation of PI3K/Akt/GSK-3β signal pathway through increasing Inpp5f expression, thus improving the condition and cognitive disorder of rats with neuropathic pain.

Mechanisms, Predictors, and Challenges in Assessing and Managing Painful Chemotherapy-Induced Peripheral Neuropathy

OBJECTIVE

To describe the known predictors and pathophysiological mechanisms of chronic painful chemotherapy-induced peripheral neuropathy (CIPN) in cancer survivors and the challenges in assessing and managing it.

DATA SOURCES

PubMed/Medline, CINAHL, Scopus, and PsycINFO.

CONCLUSION

The research on chronic painful CIPN is limited. Additional research is needed to identify the predictors and pathophysiological mechanisms of chronic painful CIPN to inform the development of assessment tools and management options for this painful and possibly debilitating condition.

IMPLICATIONS FOR NURSING PRACTICE

Recognition of the predictors of chronic painful CIPN and proactive CIPN assessment and palliative management are important steps in reducing its impact on physical function and quality of life.

Lack of analgesic effects of transcranial pulsed electromagnetic field stimulation in neuropathic pain patients: A randomized double-blind crossover trial

BACKGROUND

Neuromodulation is nowadays investigated as a promising method for pain relief. Research indicates that a single 30-minute stimulation with transcranial pulsed electromagnetic fields (tPEMF) can induce analgesic effects. However, it is unknown whether tPEMF can induce analgesia in neuropathic pain patients.

OBJECTIVE

To evaluate the effect of tPEMF on spontaneous pain and heat pain in neuropathic pain patients.

METHODS

This study had a randomized double-blind crossover design. Twenty neuropathic pain patients received 30-minutes of tPEMF and 30-minutes sham stimulation. Primary outcomes were pain intensity, pain aversion and heat pain. Secondary outcomes included affect, cognition, and motor function, to investigate safety, tolerability and putative working mechanisms of tPEMF. Outcomes were assessed before, during and after stimulation.

RESULTS

No differences in analgesic effects between tPEMF and sham stimulation were found for pain intensity, pain aversion or heat pain. No differences between tPEMF and sham stimulation were observed for affect, motor, and cognitive outcomes.

CONCLUSION

A single 30-minute tPEMF stimulation did not induce analgesic effects in neuropathic pain patients, compared to sham. Further study is needed to determine whether prolonged stimulation is necessary for analgesic effects.

Adipose-Derived Mesenchymal Stem Cells Applied in Fibrin Glue Stimulate Peripheral Nerve Regeneration

Mesenchymal stem cells (MSCs) hold a great promise for cell therapy. To date, they represent one of the best choices for the treatment of post-traumatic injuries of the peripheral nervous system. Although autologous can be easily transplanted in the injured area, clinical advances in this filed have been impaired by lack of preservation of graft cells into the injury area after transplantation. Indeed, cell viability is not retained after injection into the blood stream, and cells injected directly into the area of injury either are washed off or inhibit regeneration through scar formation and neuroma development. This study proposes a new way of MSCs delivery to the area of traumatic injury by using fibrin glue, which not only fixes cells at the site of application but also provides extracellular matrix support. Using a sciatic nerve injury model, MSC derived from adipose tissue embedded in fibrin glue were able to enter the nerve and migrate mainly retrogradely after transplantation. They also demonstrated a neuroprotective effect on DRG L5 sensory neurons and stimulated axon growth and myelination. Post-traumatic changes of the sensory neuron phenotype were also improved. Importantly, MSCs stimulated nerve angiogenesis and motor function recovery. Therefore, our data suggest that MSC therapy using fibrin glue is a safe and efficient method of cell transplantation in cases of sciatic nerve injury, and that this method of delivery of regeneration stimulants could be beneficial for the successful treatment of other central and peripheral nervous system conditions.

The efficacy of pregabalin for the treatment of neuropathic pain in Japanese subjects with moderate or severe baseline pain

Purpose

Although analyses of pooled clinical trial data have reported how international populations respond to pregabalin by baseline neuropathic pain (NeP) severity, no studies have evaluated this specifically in patients from Japan. Thus, this post hoc pooled analysis evaluated the efficacy of pregabalin in Japanese subjects for treating moderate or severe baseline NeP.

Patients and methods

Data were pooled from three placebo-controlled trials enrolling Japanese subjects with postherpetic neuralgia (PHN), diabetic peripheral neuropathy (DPN), and spinal cord injury (SCI). The efficacy of pregabalin was evaluated by baseline pain severity (moderate or severe NeP). The trials on PHN and DPN included a 1-week titration of pregabalin from 150 mg/day to 300 or 600 mg/day; the SCI trial included a 4-week dose optimization phase (150 mg/day, titrated up to 600 mg/day). Treatment durations were 13–16 weeks (excluding 1-week taper periods), and pregabalin was administered in two divided doses per day.

Results

Mean baseline pain scores and demographic characteristics were comparable between treatment cohorts. Pregabalin treatment significantly reduced pain scores from baseline to endpoint compared with placebo in subjects with both moderate (P<0.001) and severe (P<0.05) baseline pain. Significant improvements in mean sleep scores from baseline to endpoint were associated with pregabalin compared with placebo in subjects with both moderate and severe baseline pain (both P<0.0001). A greater proportion of subjects in both pain cohorts achieved a ≥30% reduction in pain from baseline with pregabalin vs placebo (P<0.05). Higher proportions of pregabalin-treated vs placebo-treated subjects shifted to a less severe pain category at endpoint. Consistent with the known safety profile of pregabalin, common adverse events included dizziness, somnolence, weight gain, and peripheral edema.

Conclusion

Pregabalin demonstrated efficacy for pain relief and sleep improvement with a consistent safety profile in Japanese subjects with either moderate or severe baseline pain severity.

ClinicalTrials.gov identifiers

NCT0039490130, NCT0055347522, NCT0040774524

Microencapsulated olfactory ensheathing-cell transplantation reduces pain in rats by inhibiting P2X4 receptor overexpression in the dorsal root ganglion

The aim of this study was to determine the role of microencapsulated olfactory ensheathing-cell transplantation (MC-OEC) in rats in which pain was induced by sciatic nerve injury, and its relationship with the expression level of the P2X4 receptor in the dorsal root ganglion. Olfactory bulb tissues of healthy Sprague-Dawley rats were collected to culture olfactory ensheathing cells using differential attachment methods. Ninety-six healthy Sprague-Dawley rats were randomly assigned to the sham, chronic constriction injury (CCI), olfactory ensheathing cell (OEC), and MC-OEC groups. Mechanical paw withdrawal thresholds were measured 7 and 14 days after surgery. The expression of P2X4 receptor genes in the L4-5 dorsal root ganglion was detected by reverse transcriptase polymerase chain reaction, fluorescence in-situ hybridization, and western blotting. Seven and 14 days after the surgery, the mechanical paw withdrawal thresholds of rats in the MC-OEC, OEC, and CCI groups were decreased compared with the sham group. The expression level of the P2X4 receptor in the L4-5 dorsal root ganglion in CCI, OEC, and MC-OEC groups was increased compared with the sham group. All differences between groups were statistically significant. Transplantation of OEC and MC-OEC can reduce neuropathic pain and inhibit the overexpression of the P2X4 receptor in the L4-5 dorsal root ganglion. The transplantation of MC-OEC was more effective in the MC-OEC group than in the OEC group.

Involvement of the VGF-derived peptide TLQP-62 in nerve injury-induced hypersensitivity and spinal neuroplasticity

Neuroplasticity in the dorsal horn after peripheral nerve damage contributes critically to the establishment of chronic pain. The neurosecretory protein VGF (nonacronymic) is rapidly and robustly upregulated after nerve injury, and therefore, peptides generated from it are positioned to serve as signals for peripheral damage. The goal of this project was to understand the spinal modulatory effects of the C-terminal VGF-derived peptide TLQP-62 at the cellular level and gain insight into the function of the peptide in the development of neuropathic pain. In a rodent model of neuropathic pain, we demonstrate that endogenous levels of TLQP-62 increased in the spinal cord, and its immunoneutralization led to prolonged attenuation of the development of nerve injury-induced hypersensitivity. Using multiphoton imaging of submaximal glutamate-induced Ca responses in spinal cord slices, we demonstrate the ability of TLQP-62 to potentiate glutamatergic responses in the dorsal horn. We further demonstrate that the peptide selectively potentiates responses of high-threshold spinal neurons to mechanical stimuli in singe-unit in vivo recordings. These findings are consistent with a function of TLQP-62 in spinal plasticity that may contribute to central sensitization after nerve damage.

LRP1 deficiency in microglia blocks neuro-inflammation in the spinal dorsal horn and neuropathic pain processing

Following injury to the peripheral nervous system (PNS), microglia in the spinal dorsal horn (SDH) become activated and contribute to the development of local neuro-inflammation, which may regulate neuropathic pain processing. The molecular mechanisms that control microglial activation and its effects on neuropathic pain remain incompletely understood. We deleted the gene encoding the plasma membrane receptor, LDL Receptor-related Protein-1 (LRP1), conditionally in microglia using two distinct promoter-Cre recombinase systems in mice. LRP1 deletion in microglia blocked development of tactile allodynia, a neuropathic pain-related behavior, after partial sciatic nerve ligation (PNL). LRP1 deletion also substantially attenuated microglial activation and pro-inflammatory cytokine expression in the SDH following PNL. Because LRP1 shedding from microglial plasma membranes generates a highly pro-inflammatory soluble product, we demonstrated that factors which activate spinal cord microglia, including lipopolysaccharide (LPS) and colony-stimulating factor-1, promote LRP1 shedding. Proteinases known to mediate LRP1 shedding, including ADAM10 and ADAM17, were expressed at increased levels in the SDH after PNL. Furthermore, LRP1-deficient microglia in cell culture expressed significantly decreased levels of interleukin-1β and interleukin-6 when treated with LPS. We conclude that in the SDH, microglial LRP1 plays an important role in establishing and/or amplifying local neuro-inflammation and neuropathic pain following PNS injury. The responsible mechanism most likely involves proteolytic release of LRP1 from the plasma membrane to generate a soluble product that functions similarly to pro-inflammatory cytokines in mediating crosstalk between cells in the SDH and in regulating neuropathic pain.

Is health related quality of life influenced by diabetic neuropathic pain among type II diabetes mellitus patients in Ethiopia?

BACKGROUND

Polyneuropathy is one of the commonest complications of long-standing diabetes. Progressive sensory loss can predispose patients to foot ulcer and the neuropathy oftentimes causes pain. The pain can significantly affect the quality of life of patients.

OBJECTIVES

To describes the health-related quality of life of patients with type II diabetes mellitus suffering from painful diabetic peripheral neuropathy at two referral hospitals in Addis Ababa, Ethiopia, 2017.

METHODS

An institution based cross sectional study with internal comparison was conducted among a sample of 220 type II diabetes mellitus patients in a 1:1 matched ratio of those with and without diabetes associated peripheral neuropathic pain. All were having regular follow up at two hospitals in Addis Ababa, Ethiopia. The Short Form (SF-36) health-related quality of life instrument was used to collect data on quality of life while basic socio-demographic and other disease specific features were collected using a structured questionnaire. Descriptive statistics was used to examine the mean scores of health related quality of life. Cronbach's alpha coefficient and Pearson's correlation coefficient were applied to estimate the internal consistency, and the level of agreement between the different domains of SF-36, respectively. To measure association between health related quality of life domains and explanatory variables, independent T-test and ANOVA were performed followed by multiple linear regression analyses.

RESULTS

The health related quality of life of type II diabetes mellitus patients with peripheral neuropathic pain was poorer than those without pain in all the eight domains and the two summary scores by SF-36 (p < 0.001). Higher mean score difference was observed in Mental Component Summary Score (MCS) (14.6) compared to Physical Component Score (PCS) (9.3). Among the eight domains, the largest mean difference was found with the physical one (39.1) followed by mental health (38.2) and physical functioning (30). Pain intensity had a statistically significant negative correlation with all domains as well as the two summary scores. Younger age, a higher level of education, being single, a higher monthly income, normal body mass index, HbA1c less than seven mmo/L, absence of other diabetic complications and taking only oral hypoglycemic agents were found to predict better health related quality of life.

CONCLUSION

The presence of diabetic peripheral neuropathic pain was found to negatively influence the health-related quality of life of type II diabetic patients; the greatest impact being on the 'role physical' and 'mental health' domains. Older age, presence of diabetes related complications, longer duration of illness negatively influenced the health-related quality of life.

Gabapentin versus Transdermal Fentanyl Matrix for the Alleviation of Chronic Neuropathic Pain of Radicular Origin: A Randomized Blind Multicentered Parallel-Group Noninferiority Trial

A number of studies have been published proposing various approaches to the treatment of neuropathic pain; however, to our knowledge, no attempts have been made to compare gabapentin and fentanyl in patients with lumbar radiculopathy. We evaluated the relative efficacy and safety of fentanyl matrix and gabapentin for the treatment of chronic neuropathic pain of radicular origin. The study was designed as a randomized blind multicentered parallel-group noninferiority trial. A total of 108 patients with moderate-to-severe pain (≥4 intensity on an 11-point numeric rating scale) were randomly prescribed either fentanyl matrix or gabapentin over a period of 56 days. In the primary analysis, the noninferiority of fentanyl matrix treatment was evaluated in relation to the efficacy of gabapentin based on the pain intensity difference (PID) at 56 days after the first dose of the drugs. Secondary endpoints included pain relief, improvement in functional status (the Korean-Oswestry Disability Index (K-ODI)), improvement in depressive symptoms (Korean-Beck Depression Index (K-BDI)) between the 28th and 56th day, and adverse events (AEs). Analysis of the primary efficacy endpoint established the noninferiority of fentanyl matrix compared with gabapentin, with no statistically significant difference observed in the PID after 56 days for the two treatment groups. Similarly, analysis of pain relief revealed no significant differences between the groups on days 28 and 56. There was no difference in the K-ODI and K-BDI between the groups during the study period. The overall incidence of at least one AE was similar for fentanyl matrix (67.3%) and gabapentin (69.6%). The most commonly reported AEs for patients treated with fentanyl matrix and gabapentin included dizziness (30.8% vs. 44.6%, respectively), somnolence (26.9% vs. 35.7%), and constipation (15.4% vs. 17.9%). This study demonstrated that the analgesic effect of fentanyl matrix is noninferior in comparison with gabapentin and supports the use of fentanyl matrix as an effective and safe treatment for moderate-to-severe chronic neuropathic pain. This trial is registered with NCT01127100.