Pain
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The mechanisms responsible for the persistence of chemotherapy-induced peripheral neuropathy (CIPN) in a significant proportion of cancer survivors are still unknown. Our previous findings show that CD8 T cells are necessary for the resolution of paclitaxel-induced mechanical allodynia in male mice. In this study, we demonstrate that CD8 T cells are not only essential for resolving cisplatin-induced mechanical allodynia, but also to normalize spontaneous pain, numbness, and the reduction in intraepidermal nerve fiber density in male and female mice. ⋯ Moreover, adoptive transfer of cisplatin-educated CD8 T cells to Rag2 mice prevented CIPN development induced by either cisplatin or paclitaxel, indicating that the activity of the educated CD8 T is not cisplatin specific. In conclusion, resolution of CIPN requires in vivo education of CD8 T cells by exposure to cisplatin. Future studies should examine whether ex vivo CD8 T cell education could be applied as a therapeutic strategy for treating or preventing CIPN in patients.
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Nociception reliably elicits an autonomic nervous system (ANS) response. Because pain and ANS circuitry interact on multiple spinal, subcortical, and cortical levels, it remains unclear whether autonomic responses are simply a reflexive product of noxious stimulation regardless of how stimulation is consciously perceived or whether the experience of pain mediates ANS responses to noxious stimulation. To test these alternative predictions, we examined the relative contribution of noxious stimulation and individual pain experience to ANS responses in healthy volunteers who underwent 1 or 2 pain assessment tasks. ⋯ Although both pain and noxious heat stimulation predicted skin conductance response and pupil dilation response in separate analyses, the individual pain experience statistically mediated effects of noxious heat on both outcomes. Furthermore, moderated mediation revealed that evidence for this process was stronger when stimulation was perceived as painful compared with when stimulation was perceived as nonpainful, although this difference emerged late, in the 4-second period after thermal stimulation. These findings suggest that pain appraisal regulates the heat-evoked autonomic response to noxious stimulation, documenting the flexibility of the autonomic pain response to adjust to perceived or actual changes in environmental affordances above and beyond nociceptive input.
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Complex regional pain syndrome (CRPS) develops after fracture. The acute CRPS phenotype resembles exaggerated inflammation, which is explained by local and systemic activation of a proinflammatory network including peptides and cytokines. Epidemiologic data suggest that inactivation of the peptidase angiotensin-converting enzyme in patients treated for hypertension increases the odds to develop CRPS. ⋯ For this purpose, we developed a dabsyl-bradykinin (DBK)-based assay and used it to investigate patients with CRPS, as well as healthy and pain (painful diabetic neuropathy [dPNP]) controls. The major result is that the degradation of DBK to fragments 1-8 and 1-5 in healthy control and dPNP is shifted to higher values for DBK1-8 and lower values for DBK1-5 at 1 hour of incubation in patients with CRPS. Using this novel reporter peptide assay, we have been able to show that the resolving protease network for mediators such as BK might be different in patients with CRPS; having a look at the clinical signs, which resemble inflammation, this resolving protease network is probably less effective in CRPS.
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Few investigations examine patterns of opioid and nonopioid analgesic prescribing and concurrent pain intensity ratings before and after institution of safer prescribing programs such as the October 2013 Veterans Health Administration system-wide Opioid Safety Initiative (OSI) implementation. We conducted a quasi-experimental pre-post observational study of all older U. S. veterans (≥50 years old) with osteoarthritis of the knee or hip. ⋯ No changes in nonsteroidal anti-inflammatory drug prescribing were seen. A small rise in the percentage of those reporting pain but not mean pain intensity ratings continued over the study period with no changes associated with OSI. Changes in analgesic prescribing trends were not paralleled by changes in reported pain intensity for older veterans with osteoarthritis.
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Accumulating evidence has shown that complicated brain systems are involved in the development and maintenance of chronic low back pain (cLBP), but the association between brain functional changes and clinical outcomes remains unclear. Here, we used resting-state functional magnetic resonance imaging (fMRI) and multivariate pattern analysis to identify abnormal functional connectivity (FC) between the default mode, sensorimotor, salience, and central executive brain networks in cLBP and tested whether abnormal FCs are related to pain and comorbid symptoms. Fifty cLBP patients and 44 matched healthy controls (HCs) underwent an fMRI scan, from which brain networks were identified by independent component analysis. ⋯ Finally, we found that resting-state FC could discriminate cLBP patients from HCs with 91% accuracy in the first cohort and 78% accuracy in the validation cohort. Our findings suggest that the medial prefrontal cortex/rostral anterior cingulate cortex may be an important hub for linking the default mode network with the other 3 networks in cLBP patients. Elucidating the altered FCs and their association with clinical outcomes will enhance our understanding of the pathophysiology of cLBP and may facilitate the development of pain management approaches.