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One of the first signs of viral infection is body-wide aches and pain. Although this type of pain usually subsides, at the extreme, viral infections can induce painful neuropathies that can last for decades. Neither of these types of pain sensitization is well understood. A key part of the response to viral infection is production of interferons (IFNs), which then activate their specific receptors (IFNRs) resulting in downstream activation of cellular signaling and a variety of physiological responses. We sought to understand how type I IFNs (IFN-α and IFN-β) might act directly on nociceptors in the dorsal root ganglion (DRG) to cause pain sensitization. We demonstrate that type I IFNRs are expressed in small/medium DRG neurons and that their activation produces neuronal hyper-excitability and mechanical pain in mice. Type I IFNs stimulate JAK/STAT signaling in DRG neurons but this does not apparently result in PKR-eIF2α activation that normally induces an anti-viral response by limiting mRNA translation. Rather, type I IFNs stimulate MNK-mediated eIF4E phosphorylation in DRG neurons to promote pain hypersensitivity. Endogenous release of type I IFNs with the double-stranded RNA mimetic poly(I:C) likewise produces pain hypersensitivity that is blunted in mice lacking MNK-eIF4E signaling. Our findings reveal mechanisms through which type I IFNs cause nociceptor sensitization with implications for understanding how viral infections promote pain and can lead to neuropathies.It is increasingly understood that pathogens interact with nociceptors to alert organisms to infection as well as to mount early host defenses. Although specific mechanisms have been discovered for diverse bacterial and fungal pathogens, mechanisms engaged by viruses have remained elusive. Here we show that type I interferons, one of the first mediators produced by viral infection, act directly on nociceptors to produce pain sensitization. Type I interferons act via a specific signaling pathway (MNK-eIF4E signaling), which is known to produce nociceptor sensitization in inflammatory and neuropathic pain conditions. Our work reveals a mechanism through which viral infections cause heightened pain sensitivity.
Learn More >Cluster headache (CH) shows a more severe clinical picture than migraine (Mig). We tested whether brain changes can explain such difference. Multimodal MRI was acquired in attack-free patients with CH (n = 12), Mig (n = 13) and in normal controls (NC, n = 13). We used FSL for MRI data analysis and nonparametric permutation testing for voxelwise analyses (p < 0.01, corrected). CH showed lower grey matter (GM) volume, compared to Mig and NC, in frontal cortex regions (inferior frontal gyrus and frontal pole [FP], respectively) and, only compared to Mig, in lateral occipital cortex (LOC). Functional connectivity (FC) of CH was higher than Mig and NC within working memory and executive control networks and, only compared to Mig, between cerebellar and auditory language comprehension networks. In the attack-free state, the CH brain seems to be characterized by: (i) GM volume decrease, compared to both Mig and NC, in pain modulation regions (FP) and, only with respect to Mig, in a region of visual processing modulation during pain and working memory (LOC); (ii) increased FC at short range compared to both Mig and NC and at long range only with respect to Mig, in key cognitive networks, likely due to maladaptation towards more severe pain experience.
Learn More >Although new persistent opioid use and high-risk prescribing have been recognized as important postoperative complications among younger patients (18-64 years of age), little is known about the incidence for postoperative opioid use among older patients (>65 years of age).
Learn More >Migraine is characterized by sensory hypersensitivity and habituation deficits. Slow brushing over the skin activates C-tactile nerve fibers, which mediate pleasant touch and analgesic effects in healthy subjects. As this function is altered in painful conditions, we aimed to examine whether the C-tactile processing is disrupted in migraines.
Learn More >Multimorbidity and pain are both common among older adults, yet pain treatment strategies for older patients with multimorbidity have not been well characterized. To assess the prevalence and relationship between multimorbidity and opioid prescribing in hospitalized older medical patients with pain. We collected demographic, morbidity, pain, and analgesic treatment data through structured review of the electronic medical records of a consecutive sample of 238 medical patients, aged ≥65 years admitted between November 2014 and May 2015 with moderate-to-severe pain by numerical pain rating scale (range 4-10). We used the Cumulative Illness Rating Scale for Geriatrics (CIRS-G) to assess multimorbidity and cumulative illness burden. We examined the relationship between morbidity measures and opioid prescribing at hospital discharge using multivariate regression analysis. The mean age was 75 ± 8 years, 57% were female and 50% were non-White. Mean CIRS-G total score was 17 ± 6, indicating high cumulative illness burden. Ninety-nine percent of patients had multimorbidity, defined as moderate-to-extremely severe morbidity in ≥2 organ systems. Sixty percent of patients received an opioid prescription at discharge. In multivariate analyses adjusted for age, race, and gender, patients with a discharge opioid prescription were significantly more likely to have higher cumulative illness burden and chronic pain. Among older medical inpatients, multimorbidity was nearly universal, and patients with higher cumulative illness burden were more likely to receive a discharge opioid prescription. More studies of benefits and harms of analgesic treatments in older adults with multimorbidity are needed to guide clinical practice.
Learn More >Persistent and in particular neuropathic pain is a major health care problem with still insufficient pharmacological treatment options. This triggered research activities aimed at finding analgesics with a novel mechanism of action. Results of these efforts will need to pass through the phases of drug development, in which experimental human pain models are established components often implemented as chemical hyperalgesia induced by capsaicin. We aimed at ranking the various readouts of the human capsaicin-based pain model with respect to the most relevant information about the effects of a potential reference analgesic. In a placebo-controlled, randomised cross-over study, seven different pain-related readouts were acquired in 16 healthy subjects before and after oral administration of 300 mg pregabalin. The sizes of the effect on pain induced by intradermal injection of capsaicin were quantified by calculating Cohen's d. While in four of the seven pain-related parameters, pregabalin provided a small effect judged by values of Cohen's d exceeding 0.2, an item-categorization technique implemented as computed ABC analysis identified the pain intensities in the area of secondary hyperalgesia and of allodynia as the most suitable parameters to quantify the analgesic effects of pregabalin. Results of this study provide further support for the ability of the intradermal capsaicin pain model to show analgesic effects of pregabalin. Results can serve as a basis for the designs of studies where the inclusion of this particular pain model and pregabalin is planned.
Learn More >Cannabis or cannabinoids produce characteristic tetrad effects – analgesia, hypothermia, catalepsy, and suppressed locomotion, which are generally believed to be mediated by the activation of cannabinoid CB1 receptors (CB1Rs). Given recent findings of CB2 and GPR55 receptors in the brain, we examined whether CB2 and GPR55 receptors are also involved in cannabinoid action.
Learn More >This study aimed to develop a method that objectively measures the clinical benefits of ketamine infusions to treat complex regional pain syndrome (CRPS), thus making it possible, for the first time, to determine the optimal dosing of ketamine and duration of treatment to treat CRPS.
Learn More >There is unmet need to design an analgesic with fewer side effects for severe pain management. Although traditional opioids are the most effective painkillers, they are accompanied by severe adverse responses, such as respiratory depression, constipation symptoms, tolerance, withdrawal, and addiction. We indicated BPR1M97 as a dual mu opioid receptor (MOP)/nociceptin-orphanin FQ peptide (NOP) receptor full agonist and investigated the pharmacology of BPR1M97 in multiple animal models. In vitro studies on BPR1M97 were assessed using cyclic-adenosine monophosphate production, β-arrestin, internalization, and membrane potential assays. In vivo studies were characterized using the tail-flick, tail-clip, lung functional, heart functional, acetone drop, von Frey hair, charcoal meal, glass bead, locomotor activity, conditioned place preference (CPP) and naloxone precipitation tests. BPR1M97 elicited full agonist properties for all cell-based assays tested in MOP-expressing cells. However, it acted as a G protein-biased agonist for NOP. BPR1M97 initiated faster antinociceptive effects at 10 min after subcutaneous injection and elicited better analgesia in cancer-induced pain than morphine. Unlike morphine, BPR1M97 caused less respiratory, cardiovascular, and gastrointestinal dysfunction. In addition, BPR1M97 decreased global activity and induced less withdrawal jumping precipitated by naloxone. Thus, BPR1M97 could serve as a novel small molecule dual receptor agonist for antinociception with fewer side effects than morphine.
Learn More >We examined the proportion of patients initiating extended-release (ER) opioids who become long-term users and describe how pain-related diagnoses before initiation of opioid therapy vary between drugs and over time.
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