Pain
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Although opioids continue to be used internationally for noncancer pain, evidence to date on the comparative safety of different opioids is sparse and conflicting. The aim of this study was to examine the comparative risk of all-cause mortality in patients newly initiated on opioids for noncancer pain, across 3 jurisdictions in the United Kingdom (UK), United States, and Canada. A multicentre retrospective, population-based cohort study was conducted. ⋯ In addition, other factors associated with higher mortality were being on combination opioids, fentanyl, buprenorphine, and oxycodone. Compared with those on <50 morphine milligram equivalents/day, patients on higher-doses experience an incremental increase in risk. In new users of opioids, compared with codeine, strong opioids, including morphine, fentanyl, buprenorphine, oxycodone, and combination opioids, and those on ≥50 morphine milligram equivalent/day were associated with a higher subsequent risk of all-cause mortality.
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The peripheral inflammatory response is an attractive therapeutic target for pain treatment. Neutrophils are the first circulating inflammatory cells recruited to sites of injury, but their contribution to pain outcomes is unclear. We performed a systematic review and meta-analysis of original preclinical studies, which evaluated the effect of preemptive neutrophil depletion on pain outcomes (PROSPERO registration number: CRD42022364004). ⋯ Analyses regarding intervention unveiled a lower pain reduction for some commonly used methods for neutrophil depletion, such as injection of antineutrophil serum or an anti-Gr-1 antibody, than for other agents such as administration of an anti-Ly6G antibody, fucoidan, vinblastine, CXCR1/2 inhibitors, and etanercept. In conclusion, the contribution of neutrophils to pain depends on pain etiology (experimental model), pain outcome, and the neutrophil depletion strategy. Further research is needed to improve our understanding on the mechanisms of these differences.
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Neuropathic pain is a pervasive medical challenge currently lacking effective treatment options. Molecular changes at the site of peripheral nerve injury contribute to both peripheral and central sensitization, critical components of neuropathic pain. This study explores the role of the G-protein-coupled bile acid receptor (GPBAR1 or TGR5) in the peripheral mechanisms underlying neuropathic pain induced by partial sciatic nerve ligation in male mice. ⋯ Besides, myeloid-cell-specific TGR5 knockdown in the injured nerve site exacerbated both neuropathic pain and neuroinflammation, which was substantiated by bulk RNA-sequencing and upregulated expression levels of inflammatory mediators (including CCL3, CCL2, IL-6, TNF α, and IL-1β) and the increased number of monocytes/macrophages at POD7. Furthermore, the activation of microglia in the spinal cord on POD7 and POD14 was altered when TGR5 in the sciatic nerve was manipulated. Collectively, TGR5 activation in the injured nerve site mitigates neuropathic pain by reducing neuroinflammation, while TGR5 knockdown in myeloid cells worsens pain by enhancing neuroinflammation.
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Chronic musculoskeletal pain (CMP) and coexisting mental health conditions impact young people; however, little is known about their lived and care experiences. In a prospectively registered systematic review with qualitative evidence synthesis (PROSPERO: CRD42022369914), we explored the following: (1) lived physical, psychological, and social experiences; and (2) care experiences/preferences of young people living with CMP and mental health conditions. Inclusion criteria: studies using qualitative methods; participants aged 16 to 24 years with CMP and coexisting mental health condition(s); phenomenon explored included lived and/or care experiences. ⋯ Care experiences/preferences yielded 3 themes (8 findings): navigating healthcare systems (2 findings, moderate confidence); receiving appropriate care (3 findings, very low-moderate confidence); point-of-care experiences and care preferences (3 findings, very low-moderate confidence). Chronic musculoskeletal pain and mental health conditions are interconnected, significantly impacting young people's lives, identities, and socialisation, yet services for CMP and mental health are often inadequate and poorly integrated. The mechanisms and interplay of CMP and mental health require deeper exploration, including how young people may be better supported with personalised, holistic, developmentally and/or life-stage-appropriate integrated care.
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Nociceptors with somata in dorsal root ganglia (DRGs) readily switch from an electrically silent state to a hyperactive state of tonic, nonaccommodating, low-frequency, irregular discharge of action potentials (APs). Spontaneous activity (SA) during this state is present in vivo in rats months after spinal cord injury (SCI) and has been causally linked to SCI pain. Intrinsically generated SA and, more generally, ongoing activity (OA) are induced by various neuropathic conditions in rats, mice, and humans and are retained in nociceptor somata after dissociation and culturing, providing a powerful tool for investigating its mechanisms and functions. ⋯ The most consistent electrophysiological alteration associated with OA was enhancement of DSFs. An unexpected discovery after plantar incisions was hyperexcitability in neurons from thoracic DRGs that innervate dermatomes distant from the injured tissue. Potential in vivo functions of widespread, low-frequency nociceptor OA consistent with these and other findings are to contribute to hyperalgesic priming and to drive anxiety-related hypervigilance.