Ankyrin-rich membrane spanning protein as a novel modulator of transient receptor potential vanilloid 1-function in nociceptive neurons

BACKGROUND

The ion channel TRPV1 is mainly expressed in small diameter dorsal root ganglion (DRG) neurons, which are involved in the sensation of acute noxious thermal and chemical stimuli. Direct modifications of the channel by diverse signalling events have been intensively investigated, but little is known about the composition of modulating macromolecular TRPV1 signalling complexes. Here, we hypothesize that the novel adaptor protein ankyrin-rich membrane spanning protein/kinase D interacting substrate (ARMS) interacts with TRPV1 and modulates its function in rodent DRG neurons.

METHODS

We used immunohistochemistry, electrophysiology, microfluorimetry and immunoprecipitation experiments to investigate TRPV1 and ARMS interactions in DRG neurons and transfected cells.

RESULTS

We found that TRPV1 and ARMS are co-expressed in a subpopulation of DRG neurons. ARMS sensitizes TRPV1 towards capsaicin in transfected HEK 293 cells and in mouse DRG neurons in a PKA-dependent manner. Using a combination of functional imaging and immunocytochemistry, we show that the magnitude of the capsaicin response in DRG neurons depends not only on TRPV1 expression, but on the co-expression of ARMS alongside TRPV1.

CONCLUSION

These data indicate that ARMS is an important component of the signalling complex regulating the sensitivity of TRPV1.

SIGNIFICANCE

The study identifies ARMS as an important component of the signalling complex regulating the sensitivity of excitatory ion channels (TRPV1) in peripheral sensory neurons (DRG neurons) and transfected cells.

Electric Stimulation for Pain Relief in Patients with Fibromyalgia: A Systematic Review and Meta-analysis of Randomized Controlled Trials

BACKGROUND

Fibromyalgia (FM) is a syndrome whose primary symptoms include chronic widespread muscle pain and fatigue. The treatment of patients with FM aims to provide symptomatic relief and improvement in physical capacities to perform daily tasks and quality of life. Invasive or non-invasive electric stimulation (ES) is used for pain relief in patients with FM.

OBJECTIVE

This systematic review aimed to assess the effects of treatment with ES, combined or not combined with other types of therapy, for pain relief in patients with FM.

STUDY DESIGN

Systematic review and meta-analysis.

SETTING

Electronic search was conducted on databases (from the inception to April 2016): MEDLINE (accessed by PubMed), EMBASE, Cochrane Central Register of Controlled Trials (Cochrane CENTRAL), and Physiotherapy Evidence Database (PEDro).

METHODS

Two independent reviewers assessed the eligibility of studies based on the inclusion criteria: randomized controlled trials (RCTs) examining the effects of ES combined or not with other types of treatment for pain relief in patients with FM (according to the American College of Rheumatology), regardless of the ES dosages. The primary outcome was pain, assessed by the visual analogue scale (VAS). The secondary outcomes extracted were quality of life, assessed by short form-36 health survey (SF- 36), and fatigue, assessed by VAS.

RESULTS

Nine studies were included, with 301 patients. The meta-analysis for pain showed positive effect of ES treatment versus control [-1.24 (95% CI: -2.39 to -0.08; I²: 87%, P = 0.04) n = 8 RCTs]. The sensitivity analysis for pain showed significant results for invasive ES, combined or not with other types of therapy [-0.94 (95% CI, -1.50 to -0.38; I² 0%, P = 0.001) n = 3 RCTs]. No significant improvement was found regarding quality of life [-3.48 (95% CI: -12.58 to 5.62; I²: 0%, P = 0.45), n = 2 RCTs] or fatigue [-0.57 (95% CI, -1.25 to 0.11; I² 34%, P = 0.100; n = 4 RCTs].

LIMITATIONS

This systematic review included a small number of studies and reduced number of participants in each study. Furthermore, most of the studies showed some biases and lack of methodological quality.

CONCLUSIONS

This meta-analysis indicates that there is low-quality evidence for the effectiveness of ES for pain relief in patients with FM. However, moderate-quality evidence for the effectiveness of electroacupuncture (EA), combined or not combined with other types of treatment, was found for pain relief.

CLINICAL TRIAL REGISTRATION INFORMATION

PROSPERO under the identification CRD42015025323Key words: Electric stimulation, electroacupuncture, transcutaneous electric nerve stimulation, pain, fibromyalgia, review, physical therapy, rehabilitation.

Effects of Electrical Stimulation in Spastic Muscles After Stroke

Background and Purpose—

Neuromuscular electric stimulation (NMES) has been used to reduce spasticity and improve range of motion in patients with stroke. However, contradictory results have been reported by clinical trials. A systematic review of randomized clinical trials was conducted to assess the effect of treatment with NMES with or without association to another therapy on spastic muscles after stroke compared with placebo or another intervention.

Methods—

We searched the following electronic databases (from inception to February 2015): Medline (PubMed), EMBASE, Cochrane Central Register of Controlled Trials and Physiotherapy Evidence Database (PEDro). Two independent reviewers assessed the eligibility of studies based on predefined inclusion criteria (application of electric stimulation on the lower or upper extremities, regardless of NMES dosage, and comparison with a control group which was not exposed to electric stimulation), excluding studies with <3 days of intervention. The primary outcome extracted was spasticity, assessed by the Modified Ashworth Scale, and the secondary outcome extracted was range of motion, assessed by Goniometer.

Results—

Of the total of 5066 titles, 29 randomized clinical trials were included with 940 subjects. NMES provided reductions in spasticity (−0.30 [95% confidence interval, −0.58 to −0.03], n=14 randomized clinical trials) and increase in range of motion when compared with control group (2.87 [95% confidence interval, 1.18–4.56], n=13 randomized clinical trials) after stroke.

Conclusions—

NMES combined with other intervention modalities can be considered as a treatment option that provides improvements in spasticity and range of motion in patients after stroke.

Clinical Trial Registration Information—

URL: http://www.crd.york.ac.uk/PROSPERO . Unique identifier: CRD42014008946.

Pharmacokinetic properties of MH84, a γ-secretase modulator with PPARγ agonistic activity

Alzheimer's disease (AD) is the most common cause of dementia. Since no causative treatment is available, new therapeutic options are utmost needed. Several pirinixic acid derivatives, including MH84 (2-((4,6-bis(4-(trifluoromethyl)phenethoxy)pyrimidin-2-yl)thio)hexanoic acid), have shown promising in vitro results as γ-secretase modulators as well as PPARγ activators as potential pharmacological compounds against AD. Using a newly developed and validated sensitive LC-MS (APCI-qTOF mass analyzer) method, the pharmacokinetic and long-term accumulating properties as well as the blood-brain-barrier permeability of MH84 were evaluated in a preclinical animal study. MH84 was administered to mice by oral gavage with a dose of 12 mg/kg. Nine time points from 0.5 to 48 h with 6 animals per point were investigated. Additionally 6 animals were fed daily, for 21 days with an identical dose to determine possible long-term accumulation in plasma and brain tissue. The sample preparation was performed by a liquid-liquid extraction on Extrelut(®) columns whereas the LC separation was operated on a MulthoHigh 100 RP 18-5 μ column (125 × 4 mm) using an isocratic mobile phase of formic acid (0.1% (v/v))-methanol mixture (11:89 (v/v)) at a flow rate of 1 ml/min. The validation confirmed the new LC-MS method to be precise, accurate and reliable. After oral application, Cmax and Tmax of unmetabolized MH84 was determined to be 10.90 μg/ml and 3h in plasma. In brain tissue a constant level of 300 to maximum 320.64 ng/g was found after 1.5-6h. Daily gavage for 21 days did not lead to a long-term drug accumulation in the brain. The efficacy of the obtained MH84 levels needs to be investigated in further preclinical pharmacodynamic animal studies.

Analgesic efficacy of opioids in chronic pain: recent meta-analyses

Opioids are regularly administered in acute and cancer pain. In chronic non-cancer pain (CNCP), however, their use is controversial. Previous meta-analyses and randomized controlled trials (RCTs) lack methodological homogeneity and comparable data. Here we analysed the maximum analgesic efficacies of opioids and non-opioids compared with placebo, and of physiotherapy and psychotherapy compared with active or waiting-list controls. We screened 3647 citations and included RCTs if treatment duration was at least 3 weeks, data were sufficient for meta-analysis, and criteria for high quality were met. Only 46 studies (10 742 patients) met the criteria. Weighted and standardized mean differences (WMD, SMD) between pain intensities were pooled to conduct separate meta-analyses for each treatment category. At the end of treatment the WMD for pain reduction (100-point scale) was 12.0 for 'strong' opioids, 10.6 for 'weak' opioids, 8.4 for non-opioids (each vs. placebo), 5.5 for psychotherapy and 4.5 for physiotherapy (each vs. active controls). Dropout rates were high in pharmacological studies. The 95% confidence intervals using the outcomes of control groups did not indicate statistical differences between efficacies of the five interventions. Because not enough eligible head-to-head trials were available, our analysis is limited to adjusted indirect comparisons. The heterogeneity of pre-post pain differences in control groups did not allow the definition of a common comparator. In conclusion, although there were statistically significant differences between maximum treatment efficacies, no intervention per se produced clinically important improvements in average pain intensity. Thus, opioids alone are inappropriate and multimodal treatment programmes may be required for CNCP.

LINKED ARTICLES

This article is part of a themed section on Opioids: New Pathways to Functional Selectivity. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-2.

Electrical stimulation and electromagnetic field use in patients with diabetic neuropathy: systematic review and meta-analysis

BACKGROUND

Painful diabetic neuropathy (PDN) is a common complication of diabetes mellitus, and pharmacological therapies are ineffective in many patients. Therefore, other treatment modalities should be considered, including electrical stimulation and electromagnetic fields.

OBJECTIVES

The research objective was to evaluate the effect of treatment with electrical stimulation and electromagnetic fields on pain and sensitivity in patients with painful diabetic neuropathy compared with placebo or another intervention.

METHOD

We searched the following electronic databases (from inception to April 2012): MEDLINE (accessed by PubMed), LILACS, Physiotherapy Evidence Database (PEDro), EMBASE and Cochrane CENTRAL. We included randomized trials that compared electrical stimulation or electromagnetic fields with control groups in which the objective was to assess pain and sensitivity in patients with PDN. Two reviewers independently extracted the data. A random-effects model was used for the main analysis.

RESULTS

The search retrieved 1336 articles, of which 12 studies were included. Reductions in the mean pain score were significantly greater in the TENS (transcutaneous electrical nerve stimulation) group than in the placebo group [-0.44 (95% CI: -0.79 to -0.09; I2: 0%)]. There was no improvement in pain relief when electromagnetic fields were compared with the control group [-0.69 (95% CI: -1.86 to 0.48; I2: 63%)].

CONCLUSIONS

We found that TENS improved pain relief in patients with diabetic neuropathy, while no such improvement was observed with the use of electromagnetic field treatment. Due to the methodological differences between the studies, a meta-analysis for the outcome of sensitivity could not be performed.

Involvement of cytokines, chemokines and adhesion molecules in opioid analgesia

Tissue destruction is accompanied by an inflammatory reaction. The inflammatory reaction leads to activation of nociceptors and the sensation of pain. Several mediators are responsible for pain and hyperalgesia in inflammation including cytokines, chemokines, nerve growth factor as well as bradykinin, prostaglandins and ATP. Simulatenously however, analgesic mediators are secreted: opioid peptides, somatostatin, endocannabinoids and certain cytokines. Opioid peptides secreted from immune cells are so far the best studied peptides in peripheral inflammatory pain control. This system is hampered for example by anti-adhesion molecule treatment. Novel immunosuppressive drugs for treatment of autoimmune disease targetting cytokines, chemokines or adhesion molecules should therefore be evaluated for potential harmful effects on pain.