Pain
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The dominant view in the field of pain is that peripheral neuropathic pain is driven by microglia in the somatosensory processing region of the spinal dorsal horn. Here, to the contrary, we discovered a form of neuropathic pain that is independent of microglia. Mice in which the nucleus pulposus (NP) of the intervertebral disc was apposed to the sciatic nerve developed a constellation of neuropathic pain behaviours: hypersensitivity to mechanical, cold, and heat stimuli. ⋯ Pain hypersensitivity was also prevented by genetically disrupting the neurotrophin brain-derived neurotrophic factor selectively in macrophages. Moreover, the behavioural phenotypes as well as the molecular mechanisms of NP-induced pain hypersensitivity were not different between males and females. Our findings reveal a previously unappreciated mechanism for by which a discrete peripheral nerve lesion may produce pain hypersensitivity, which may help to explain the limited success of microglial inhibitors on neuropathic pain in human clinical trials.
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Galcanezumab, a monoclonal antibody against calcitonin gene-related peptide, is an emerging migraine preventative. We hypothesized that the preventive effects are conveyed via the modulation of somatosensory processing and that certain sensory profiles may hence be associated with different clinical responses. We recruited migraine patients (n = 26), who underwent quantitative sensory tests over the right V1 dermatome and forearm at baseline (T0), 2 to 3 weeks (T1) and 1 year (T12) after monthly galcanezumab treatment. ⋯ However, baseline heat pain threshold (OR: 2.13, 95% CI: 1.08-4.19, P = 0.029) on the forearm was a robust predictor for a clinical response 3 months later. In summary, our data demonstrated that galcanezumab modulates pain thresholds specifically in the V1 dermatome, but this modulation is short-lasting and irrelevant to clinical response. Instead, the clinical response may be determined by individual sensibility even before the administration of medication.
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The transient receptor potential ion channel TRPM3 is highly prevalent on nociceptive dorsal root ganglion (DRG) neurons, but its functions in neuronal plasticity of chronic pain remain obscure. In an animal model of nonspecific low back pain (LBP), latent spinal sensitization known as nociceptive priming is induced by nerve growth factor (NGF) injection. Here, we address the TRPM3-associated molecular basis of NGF-induced latent spinal sensitization at presynaptic level by studying TRPM3-mediated calcium transients in DRG neurons. ⋯ TRPM3 activation provokes an outbreak of pulsatile superoxide production (mitoflash) that comes in the form of a surge in frequency being tunable. We suggest that mitoflash pulsations downstream of TRPM3 activation might be an early signaling event initiating pain sensitization. Tuning of mitoflash activity would be a novel bottom-up therapeutic strategy for chronic pain conditions such as LBP and beyond.
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People with an evening (E)-type preference (ie, chronotype) experience musculoskeletal (MSK) pain and reduced health-related quality of life (HRQoL) more often than morning (M) types. Musculoskeletal pain is a well-established contributor to reduced HRQoL. This study aimed to evaluate whether eveningness amplifies the association between MSK pain and HRQoL in contrast to morningness. ⋯ After adjustments, this was particularly seen in terms of NPS and pain frequency. Our findings suggest that eveningness intensifies the association between MSK pain and HRQoL, and, thus, they are indicative of E-types being more sensitive than M-types to the consequences of MSK pain. As such, MSK pain treatment and rehabilitation actions to improve HRQoL should be especially targeted at E-types.
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Pain and related consequences could contribute to comorbid illness and premature mortality in homeless and precariously housed persons. We analyzed longitudinal data from an ongoing naturalistic prospective study of a community-based sample (n = 370) to characterize risk factors and consequences of bodily pain. The aims were to describe bodily pain and associations with symptoms and psychosocial function, investigate factors that may increase or ameliorate pain, and examine the consequences of pain for symptoms, functioning, and all-cause mortality. ⋯ The frequency of prescribed and nonprescribed opioid use had nonlinear relationships with pain: intermittent use was associated with severe pain, without reverse association or change with the overdose epidemic. Greater longitudinal mean pain severity was associated with premature mortality, poorer functioning, and suicidal ideation. Considering the relationships between pain, intermittent opioid use, and depressive symptoms could improve health care for precariously housed patients.