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Hyperalgesia and allodynia are frequent symptoms of inflammatory pain. Neuronal excitability induced by brain-derived neurotrophic factor (BDNF)-tyrosine receptor kinase B (TrkB) cascade has a role in the modulation of inflammatory pain. The effects of 3a,4,5,9b-tetrahydro-4-(1-naphthalenyl)-3H-cyclopentan[c]quinoline8-sulfonamide (TQS), an α7 nicotinic acetylcholine receptor positive allosteric modulator (nAChR PAM), on hippocampal BDNF, cation-chloride cotransporters, NKCC1 and KCC2, expression in inflammatory pain are not known. The objective of the study was to determine the effects of TQS on BDNF, NKCC1, and KCC2 expression in the hippocampus following lipopolysaccharide (LPS)-induced allodynia and hyperalgesia in a mouse model of inflammatory pain.
Learn More >Calcium (Ca) is the primary stimulus for transmembrane protein 16 (TMEM16) Ca-activated chloride channels and phospholipid scramblases, which regulate important physiological processes ranging from smooth muscle contraction to blood coagulation and tumor progression. Binding of intracellular Ca to two highly conserved orthosteric binding sites in transmembrane helices (TMs) 6-8 efficiently opens the permeation pathway formed by TMs 3-7. Recent structures of TMEM16K and TMEM16F scramblases revealed an additional Ca binding site between TM2 and TM10, whose functional relevance remains unknown. Here, we report that Ca binds with high affinity to the equivalent third Ca site in TMEM16A to enhance channel activation. Our cadmium (Cd) metal bridging experiments reveal that the third Ca site's conformational states can profoundly influence TMEM16A's opening. Our study thus confirms the existence of a third Ca site in TMEM16A, defines its functional importance in channel gating, and provides insight into a long-range allosteric gating mechanism of TMEM16 channels and scramblases.
Learn More >Psychological stress is a risk factor for irritable bowel syndrome, a functional gastrointestinal pain disorder featuring abnormal brain-gut connectivity. The guanylate cyclase-C (GC-C) agonist linaclotide has been shown to relieve abdominal pain in IBS-C and exhibits antinociceptive effects in rodent models of post-inflammatory visceral hypersensitivity. However, the role GC-C signaling plays in psychological stress-induced visceral hypersensitivity is unknown. Here, we test the hypothesis that GC-C agonism reverses stress-induced colonic hypersensitivity via inhibition of nociceptive afferent signaling resulting in normalization of stress-altered corticotropin-releasing factor (CRF) expression in brain regions involved in pain perception and modulation.
Learn More >The sigma 1 receptor (S1R) is a molecular chaperone protein located in the endoplasmic reticulum and plasma membranes and has been shown to play important roles in various pathological disorders including pain and, as recently discovered, COVID-19. Employing structure- and QSAR-based drug design strategies, we rationally designed, synthesized, and biologically evaluated a series of novel triazole-based S1R antagonists. Compound exhibited potent binding affinity for S1R, high selectivity over S2R and 87 other human targets, acceptable metabolic stability, slow clearance in liver microsomes, and excellent blood-brain barrier permeability in rats. Further studies in rats showed that exhibited negligible acute toxicity in the rotarod test and statistically significant analgesic effects in the formalin test for acute inflammatory pain and paclitaxel-induced neuropathic pain models during cancer chemotherapy. These encouraging results promote further development of our triazole-based S1R antagonists as novel treatments for pain of different etiologies.
Learn More >Pain management following spine surgery remains a challenge. The significant use of opioids may lead to opioid-related adverse events. These complications can increase perioperative morbidity and rapidly expend health care resources by developing chronic pain. Although intraoperative pain control for surgery has been studied in the literature, a thorough assessment of the effect in spine surgery is rarely reported. The objective of the present study was to examine the outcomes of intraoperative intravenous lidocaine and intrawound or epidural bupivacaine use in spine surgery.
Learn More >Fibromyalgia (FM) is a chronic widespread pain condition that overlaps with multiple comorbid health conditions and contributes to considerable patient distress. The aim of this review was to provide a systematic overview of psychiatric and chronic pain comorbidities among patients diagnosed with FM and to inform the development of recommendations for the design of clinical trials. Thirty-one, cross-sectional, clinical epidemiology studies that evaluated patients diagnosed with FM were included for review. None of the reviewed studies reported on the incidence of these comorbidities. Sample size-weighted prevalence estimates were calculated when prevalence data were reported in 2 or more studies for the same comorbid condition. The most prevalent comorbidity across all studies reviewed was depression/major depressive disorder (MDD) with over half of the patients included having this diagnosis in their lifetime (weighted prevalence up to 63%). In addition, nearly one-third of FM patients examined had current or lifetime bipolar disorder, panic disorder, or post-traumatic stress disorder. Less common psychiatric disorders reported included generalized anxiety disorder, obsessive compulsive disorder, and specific phobias (agoraphobia, social phobia). There were fewer studies that examined chronic pain comorbidities among FM patients, but when evaluated, prevalence was also high ranging from 39% to 76% (i.e., chronic tension-type or migraine headache, irritable bowel syndrome, myofascial pain syndrome, and temporomandibular disorders). The results of the review suggest that depression and chronic pain conditions involving head/jaw pain and IBS were elevated among FM patients compared to other conditions in the clinic-based studies. In contrast, anxiety-related disorders were much less common. Addressing the presence of these comorbid health conditions in clinical trials of treatments for FM would increase the generalizability and real-world applicability of FM research.
Learn More >Effective treatments for chronic pain without abuse liability are urgently needed. One in 5 adults suffer chronic pain and half of these patients report inefficient treatment. Mu opioid receptor agonists (MOP), including oxycodone, tramadol and morphine, are often prescribed to treat chronic pain, however, use of drugs targeting MOP can lead to drug dependency, tolerance and overdose deaths. Kappa opioid receptor (KOP) agonists have antinociceptive effects without abuse potential; however, they have not been utilised clinically due to dysphoria and sedation. We hypothesise that mixed opioid receptor agonists targeting the KOP and delta opioid receptor (DOP) would have a wider therapeutic index, with the rewarding effects of DOP negating the negative effects of KOP. MP1104, an analogue of 3-Iodobenzoyl naltrexamine, is a novel mixed opioid receptor agonist with potent antinociceptive effects mediated via KOP and DOP in mice without rewarding or aversive effects. In this study, we show MP1104 has potent, long-acting antinociceptive effects in the warm-water tail-withdrawal assay in male and female mice and rats; and is longer acting than morphine. In the paclitaxel-induced neuropathic pain model in mice, MP1104 reduced both mechanical and cold allodynia and unlike morphine, did not produce tolerance when administered daily for 23 days. Moreover, MP1104 did not induce sedative effects in the open-field locomotor activity test, respiratory depression in mice using whole-body plethysmography, or have cross-tolerance with morphine. This data supports the therapeutic development of mixed opioid receptor agonists, particularly mixed KOP/DOP agonists, as non-addictive pain medications with reduced tolerance.
Learn More >Secondary to the complex care, involved specialty providers, and various etiologies, chronic pelvic pain patients do not receive holistic care.
Learn More >The authors provide a comprehensive summary of all randomized, controlled trials (n = 76) involving the clinical administration of liposomal bupivacaine (Exparel; Pacira Pharmaceuticals, USA) to control postoperative pain that are currently published. When infiltrated surgically and compared with unencapsulated bupivacaine or ropivacaine, only 11% of trials (4 of 36) reported a clinically relevant and statistically significant improvement in the primary outcome favoring liposomal bupivacaine. Ninety-two percent of trials (11 of 12) suggested a peripheral nerve block with unencapsulated bupivacaine provides superior analgesia to infiltrated liposomal bupivacaine. Results were mixed for the 16 trials comparing liposomal and unencapsulated bupivacaine, both within peripheral nerve blocks. Overall, of the trials deemed at high risk for bias, 84% (16 of 19) reported statistically significant differences for their primary outcome measure(s) compared with only 14% (4 of 28) of those with a low risk of bias. The preponderance of evidence fails to support the routine use of liposomal bupivacaine over standard local anesthetics.
Learn More >Although survivors of childhood cancer are at risk of chronic pain, the impact of pain on daily functioning is not well understood.
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