The journal of pain : official journal of the American Pain Society
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Both autonomic nervous system dysfunction and immune system activation are characteristic of chronic pain after limb injuries. Cholinergic agonists reduce immune system activation in many settings. We hypothesized, therefore, that alpha-7 nicotinic acetylcholine receptor (α7nAChR) agonist administration would reduce nociceptive and immune changes after tibia fracture and cast immobilization in mice. ⋯ PERSPECTIVE: These studies evaluate the effects of a selective α7nAChR agonist in a tibial fracture/cast immobilization model of limb pain. Administration of the drug reduced nociceptive and functional changes 4 weeks after injury. These novel findings suggest that well-tolerated α7nAChR agonists may be viable analgesics for chronic pain after limb injuries.
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Chronic pain is driven by factors across the biopsychosocial spectrum. Previously, we demonstrated that magnetic resonance images (MRI)-based brain-predicted age differences (brain-PAD: brain-predicted age minus chronological age) were significantly associated with pain severity in individuals with chronic knee pain. We also previously identified four distinct, replicable, multidimensional psychological profiles significantly associated with clinical pain. ⋯ Repeated measures ANOVA revealed no significant change in profile-related brain-PAD differences over time, but there was a significant decrease in brain-PAD for profile 4 (high optimism/high positive affect), with P = .045. Moreover, profile-related differences in pain severity at baseline were partly explained by brain-PAD differences between profile 3 and 1, or 2; but brain-PAD did not significantly mediate the influence of variations in profiles on changes in pain severity over time. PERSPECTIVE: Accelerated brain aging could underlie the psychological-pain relationship, and psychological characteristics may predispose individuals with chronic knee pain to worse health outcomes via neuropsychological processes.
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The molecular processes driving the transition from acute to chronic low back pain (LBP) remain poorly understood and are likely to be sexually dimorphic. This study aimed to explore sex differences in the serum proteomic profile of people experiencing an acute LBP episode and determine if serum protein concentrations were associated with three-month outcome. Serum samples were collected through venepuncture from 30 female and 29 male participants experiencing an acute LBP episode. ⋯ This data provides preliminary evidence that biological processes during an acute LBP episode may contribute to the resolution, or persistence, of LBP symptoms at 3 months, however, these processes differ between males and females. PERSPECTIVE: Differential expression of serum proteins was observed between male and female participants during an acute LBP episode. This preliminary work provides a foundation for future research targeting distinct immune system processes in males and females that may interfere with the transition from acute to chronic LBP.
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Spinal cord injury (SCI) affects ∼500,000 people worldwide annually, with the majority developing chronic neuropathic pain. Following SCI, approximately 60% of these individuals are diagnosed with comorbid mood disorders, while only ∼21% of the general population will experience a mood disorder in their lifetime. We hypothesize that nociceptive and depressive-like dysregulation occurs after SCI and is associated with aberrant macrophage infiltration in segmental pain centers. ⋯ In conclusion, moderate unilateral cervical SCI caused the development of pain-related and depressive-like behaviors in a subset of mice and these behavioral changes are consistent with immune system activation in the segmental pain pathway. PERSPECTIVE: These experiments characterized pain-related and depressive-like behaviors and correlated these changes with the immune response post-SCI. While humanizing the rodent is impossible, the results from this study inform clinical literature to closely examine sex differences reported in humans to better understand the underlying shared etiologies of pain and depressive-like behaviors following central nervous system trauma.
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In early 2020, countries across the world imposed lockdown restrictions to curb the spread of the Covid-19 coronavirus. Lockdown conditions, including social and physical distancing measures and recommended self-isolation for clinically vulnerable groups, were proposed to disproportionately affect those living with chronic pain, who already report reduced access to social support and increased isolation. Yet, empirical evidence from longitudinal studies tracking the effects of prolonged and fluctuating lockdown conditions, and potential psychological factors mediating the effects of such restrictions on outcomes in chronic pain populations, is lacking. ⋯ Offering remote management options for low mood could be particularly beneficial for this vulnerable population in the event of future implementation of lockdown restrictions. PERSPECTIVE: This longitudinal study demonstrates the impact of Covid-19 lockdown restrictions on people with chronic pain. Findings suggest a complex interaction of psychosocial factors that impacted various aspects of pain experience in patients, which offer the potential to inform clinical strategies for remote medicine and future crises.