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Crotalphine (CRP) is a structural analogue to a peptide that was first identified in the crude venom from the South American rattlesnake . This peptide induces a potent and long-lasting antinociceptive effect that is mediated by the activation of peripheral opioid receptors. The opioid receptor activation regulates a variety of intracellular signaling, including the mitogen-activated protein kinase (MAPK) pathway. Using primary cultures of sensory neurons, it was demonstrated that crotalphine increases the level of activated ERK1/2 and JNK-MAPKs and this increase is dependent on the activation of protein kinase Cζ (PKCζ). However, whether PKCζ-MAPK signaling is critical for crotalphine-induced antinociception is unknown. Here, we biochemically demonstrated that the systemic crotalphine activates ERK1/2 and JNK and decreases the phosphorylation of p38 in the lumbar spinal cord. The in vivo pharmacological inhibition of spinal ERK1/2 and JNK, but not of p38, blocks the antinociceptive effect of crotalphine. Of interest, the administration of a PKCζ pseudosubstrate (PKCζ inhibitor) prevents crotalphine-induced ERK activation in the spinal cord, followed by the abolishment of crotalphine-induced analgesia. Together, our results demonstrate that the PKCζ-ERK signaling pathway is involved in crotalphine-induced analgesia. Our study opens a perspective for the PKCζ-MAPK axis as a target for pain control.
Learn More >Migraine with aura may respond differently to therapies than migraine without aura. Individuals with migraine with aura have an elevated vascular risk, necessitating a safety assessment of migraine preventive treatments in this patient subgroup.
Learn More >Aquaporins (AQPs) play critical physiological roles in water balance in the central nervous system (CNS). Aquaporin-4 (AQP4), the principal aquaporin expressed in the CNS, has been implicated in the processing of sensory and pain transmission. Akt signaling is also involved in pain mediation, such as neuroinflammatory pain and bone cancer pain. Previously, we found that expression of AQP4 and p-Akt was altered in the rat spinal cord after spinal nerve ligation (SNL). Here, we further investigated the effects of the AQP4 and Akt pathways in the spinal dorsal horn (SDH) on the pathogenesis of neuropathic pain (NP). Spinal AQP4 was significantly upregulated after SNL and was primarily expressed in astrocytes in the SDH. Inhibition of AQP4 with TGN-020 attenuated the development and maintenance of NP by inhibiting glial activation and anti-neuroinflammatory mechanisms. Moreover, inhibition of AQP4 suppressed astrocyte activation both in the SDH and in primary cultures.Similar to AQP4, we found that p-Akt was also significantly elevated after SNL. Inhibition of Akt with MK2206 suppressed AQP4 upregulation and astrocyte activation both in vivo and in vitro. Furthermore, Akt blockade with MK2206 alleviated neuropathic pain in the early and late phases after SNL. These results elucidate the mechanisms involved in the roles of Akt/Aquaporin-4 signaling in the development and maintenance of NP. AQP4 is likely to be a novel therapeutic target for neuropathic pain management.
Learn More >Chronic pelvic pain (CPP) is a common gynaecological condition accounting for 20% of all gynaecological referrals. There are wide ranges of causes with overlapping symptomatology, therefore the management of the condition is a formidable challenge for clinicians. The aetiology of CPP is heterogeneous and in many cases, no clear diagnosis can be reached. It is in this scenario that the label of chronic pelvic pain syndrome (CPPS) can be applied. We defined women with CPPS as having a minimum duration of pain of at least 6 months, including with a diagnosis of pelvic congestion syndrome, but excluding pain caused by a condition such as endometriosis. Many surgical interventions have been tried in isolation or in conjunction with non-surgical interventions in the management with variable results. Surgical interventions are invasive and carry operative risks. Surgical interventions must be evaluated for their effectiveness prior to their prevalent use in the management of women with CPPS.
Learn More >Non-steroidal anti-inflammatory drugs (NSAIDs) are the commonly used therapeutic interventions of inflammation and pain that competitively inhibit the cyclooxygenase (COX) enzymes. Several side effects like gastrointestinal and renal toxicities are associated with the use of these drugs. The therapeutic anti-inflammatory benefits of NSAIDs are produced by the inhibition of COX-2 enzymes, while undesirable side effects arise from the inhibition of COX-1 enzymes.
Learn More >Within physical therapy, manual therapy is known to be effective for managing temporomandibular disorders (TMDs). However, manual therapy is a broad term including different approaches applied to different body regions. This is the first systematic review that aims to evaluate the effectiveness of manual therapy applied specifically to the craniomandibular structures (Cranio-Mandibular Manual Therapy (CMMT)) on pain and maximum mouth opening in people with TMD. This systematic review was developed based on a pre-determined published protocol which was prospectively registered with PROSPERO (CRD42019160213). A search of MEDLINE, Embase, CINAHL, ZETOC, Web of Science, SCOPUS, PEDro, PubMed, Cochrane Library and Best Evidence, EBM reviews-Cochrane Central Register of Controlled Trials, Index to Chiropractic Literature ChiroAccess and Google Scholar databases was conducted from inception until October 2020. Randomised controlled trials comparing the effect of CMMT on pain and maximum mouth opening versus other types of treatment in TMDs were included. Two reviewers independently screened articles for inclusion, extracted data, assessed risk of bias with the revised Cochrane risk of bias tool for randomised trials and evaluated the overall quality of evidence with the Grading of Recommendations, Assessment, Development and Evaluations. A total of 2720 records were screened, of which only 6 (293 participants) satisfied the inclusion criteria. All studies showed some concerns in risk of bias, except for one, which was high risk of bias. The overall quality of evidence was very low for all outcomes because of high heterogeneity and small sample sizes. All studies showed a significant improvement in pain and maximum mouth opening for CMMT from baseline in the mid-term, but only two showed superiority compared to other interventions. Given the high heterogeneity and small sample sizes of the included studies, a quantitative synthesis was not performed. There is the need for future high methodology research investigating different manual therapy techniques applied to different regions and different populations (e.g., chronic versus acute TMD) to determine what is most effective for pain and maximum mouth opening in patients with TMDs.
Learn More >Bacterial products can act on neurons to alter signaling and function. In the present study, we found that dorsal root ganglion (DRG) sensory neurons are enriched for ANTXR2, the high-affinity receptor for anthrax toxins. Anthrax toxins are composed of protective antigen (PA), which binds to ANTXR2, and the protein cargoes edema factor (EF) and lethal factor (LF). Intrathecal administration of edema toxin (ET (PA + EF)) targeted DRG neurons and induced analgesia in mice. ET inhibited mechanical and thermal sensation, and pain caused by formalin, carrageenan or nerve injury. Analgesia depended on ANTXR2 expressed by Na1.8 or Advillin neurons. ET modulated protein kinase A signaling in mouse sensory and human induced pluripotent stem cell-derived sensory neurons, and attenuated spinal cord neurotransmission. We further engineered anthrax toxins to introduce exogenous protein cargoes, including botulinum toxin, into DRG neurons to silence pain. Our study highlights interactions between a bacterial toxin and nociceptors, which may lead to the development of new pain therapeutics.
Learn More >Chronic exertional compartment syndrome (CECS) is a condition occurring most frequently in the lower limbs and often requires corrective surgery to alleviate symptoms. Amongst military personnel, the success rates of this surgery can be as low as 20%, presenting a challenge in determining whether surgery is worthwhile. In this study, the data of 132 fasciotomies for CECS was analysed and using combinatorial feature selection methods, coupled with input from clinicians, identified a set of key clinical features contributing to the occupational outcomes of surgery. Features were utilised to develop a machine learning model for predicting return-to-work outcomes 12-months post-surgery. An AUC of 0.85 ± 0.08 was achieved using a linear-SVM, trained using 6 features (height, mean arterial pressure, pre-surgical score on the exercise-induced leg pain questionnaire, time from initial presentation to surgery, and whether a patient had received a prior surgery for CECS). To facilitate trust and transparency, interrogation strategies were used to identify reasons why certain patients were misclassified, using instance hardness measures. Model interrogation revealed that patient difficulty was associated with an overlap in the clinical characteristics of surgical outcomes, which was best handled by XGBoost and SVM-based models. The methodology was compiled into a machine learning framework, termed AITIA, which can be applied to other clinical problems. AITIA extends the typical machine learning pipeline, integrating the proposed interrogation strategy, allowing to user to reason and decide whether to trust the developed model based on the sensibility of its decision-making.
Learn More >Neuropathic pain induces changes in neuronal excitability and synaptic connectivity in deep layers of the anterior cingulate cortex (ACC) that play a central role in the sensory, emotional and affective consequences of the disease. However, how this impacts ACC in vivo activity is not completely understood. Using a mouse model, we found that neuropathic pain caused an increase in ACC in vivo activity, as measured by the indirect activity marker c-Fos and juxtacellular electrophysiological recordings. The enhanced firing rate of ACC neurons in lesioned animals was based on a change in the firing pattern towards bursting activity. Despite the proportion of ACC neurons recruited by noxious stimuli was unchanged during neuropathic pain, responses to noxious stimuli were characterized by increased bursting. Thus, this change in coding pattern may have important implications for the processing of nociceptive information in the ACC and could be of great interest to guide the search for new treatment strategies for chronic pain.
Learn More >Chronic lower back pain is a common report in the general population. A dysfunctional sacroiliac joint (SIJ) is estimated to be responsible for one in five patients with lower back pain. Minimally invasive sacroiliac joint fusion (MISJF) is a surgical procedure to treat SIJ dysfunction. During the procedure, the SIJ is stabilised by implants inserted percutaneously under fluoroscopy guidance. Postoperatively, patients often report a lot of pain, which contributes to patients taking high doses of painkillers (opioids for example,) and preventing early mobilisation. In several orthopaedic procedures, intraoperative infiltration of the wound bed results in decreased consumption of analgesics, earlier mobilisation and shorter hospitalisation time. The aim of this study is to investigate the effectiveness of intraoperative SIJ infiltration with analgesia in reducing postoperative pain after MISJF.
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