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AMP activated protein kinase (AMPK) is a multifunctional kinase that negatively regulates mechanistic target of rapamycin (mTOR) and mitogen activated protein kinase (MAPK) signaling, two signaling pathways that are linked to pain promotion after injury, such as surgical incision. AMPK can be activated directly using positive allosteric modulators as well as indirectly through the upregulation of upstream kinases such as liver kinase B1 (LKB1) which is a mechanism of action of metformin. Metformin's anti-hyperalgesic effects have been shown to occur only in male mice, raising questions about how metformin regulates pain sensitivity. We used metformin as well as other structurally distinct AMPK activators narciclasine, ZLN-024 and MK8722 to treat incision-induced mechanical hypersensitivity and hyperalgesic priming in male and female mice. We found that metformin was the only AMPK activator to have sex specific effects. We also found that indirect AMPK activators metformin and NCLS were able to reduce mechanical hypersensitivity and block hyperalgesic priming while direct AMPK activators, ZLN-024 and MK8722 only blocked priming. Direct and indirect AMPK activators stimulated AMPK in dorsal root ganglion (DRG) neuron cultures to a similar degree. However, incision decreased phosphorylated AMPK (p-AMPK) in DRG. Because AMPK phosphorylation is required for kinase activity, we interpret our findings as evidence that indirect AMPK activators are more effective for treating pain hypersensitivity after incision because they are able to drive increased p-AMPK through upstream kinases like LKB1. These findings have important implications for the development of AMPK-targeting therapeutics for pain treatment. SIGNIFICANCE STATEMENT: Non-opioid treatments for post-surgical pain are needed. Our work focused on whether direct or indirect AMPK activators would show greater efficacy for inhibiting incisional pain and also tested for potential sex differences. We conclude that indirect AMPK activators are likely to be more effective as potential therapeutics for post-surgical pain because they inhibit acute pain caused by incision and also prevent long-term neuronal plasticity that is involved in persistent post-surgical pain. Our work points to the natural product, indirect AMPK activator, narciclasine, as an excellent starting point for development of therapeutics.
Learn More >Addiction neuroscience models posit that recurrent drug use increases reactivity to drug-related cues and blunts responsiveness to natural rewards, propelling a cycle of hedonic dysregulation that drives addictive behavior. Here, we assessed whether a cognitive intervention for addiction, Mindfulness-Oriented Recovery Enhancement (MORE), could restructure reward responsiveness from valuation of drug-related reward back to valuation of natural reward. Before and after 8 weeks of MORE or a support group control, prescription opioid users ( = 135) viewed opioid and natural reward cues while an electroencephalogram biomarker of target engagement was assessed. MORE was associated with decreased opioid cue-reactivity and enhanced capacity to regulate responses to opioid and natural reward cues. Increased positive affective responses to natural reward cues were associated with decreased craving and mediated MORE's therapeutic effects on opioid misuse. This series of randomized experiments provide the first neurophysiological evidence that an integrative behavioral treatment can remediate hedonic dysregulation among chronic opioid users.
Learn More >Medication-overuse headache is defined as headache occurring on more than 15 days in a month in people with pre-existing primary headache, and developing as a consequence of regular overuse of acute headache treatments. Medication-overuse headache is common in general neurology clinics and can be difficult to manage. Most patients have a background of migraine, which has slowly transformed over months and years from the episodic to chronic form; with this comes an increased use of acute migraine treatment. This paper identifies who is at risk of developing medication-overuse headache, and reviews preventive measures and current treatment strategies.
Learn More >Changes in brain morphology are hypothesized to be an underlying process that drive the widespread pain and motor impairment in patients with chronic neck pain. However, no earlier research assessed whole-brain cortical morphology in these patients. This case-control study assesses group-differences in whole-brain morphology between female healthy controls (HC; n = 34), and female patients with chronic idiopathic neck pain (CINP; n = 37) and whiplash-associated disorders (CWAD; n = 39). Additionally, the associations between whole-brain morphology and motor performance including balance, strength, and neuromuscular control were assessed. Cortical volume, thickness, and surface area were derived from high resolution T1-weighted images. T2*-weighted images were obtained to exclude traumatic brain injury. Vertex-wise general-linear-model-analysis revealed cortical thickening in the left precuneus and increased volume in the left superior parietal gyrus of patients with CINP compared to HC, and cortical thickening of the left superior parietal gyrus compared to HC and CWAD. Patients with CWAD showed a smaller cortical volume in the right precentral and superior temporal gyrus compared to HC. ANCOVA-analysis revealed worse neuromuscular control in CWAD compared to HC and CINP, and in CINP compared to HC. Patients with CWAD showed decreased levels of strength and sway area compared to CINP and HC. Partial correlation analysis revealed significant associations between the volume of the precentral gyrus, and neuromuscular control and strength together with an association between the volume of the superior temporal gyrus and strength. Our results emphasize the role of altered gray matter alterations in women with chronic neck pain, and its association with pain and motor impairment.
Learn More >To describe treatment patterns of migraine patients in the Japan Medical Data Center (JMDC) database.
Learn More >There is an ethical obligation to notify individuals about potential pain associated with diagnoses, treatments, and procedures; however, supplying this information risks inducing nocebo hyperalgesia. Currently there are few empirically-derived strategies for reducing nocebo hyperalgesia. Since nocebo effects are linked to negative affectivity, we tested the hypothesis that a positive affect induction can disrupt nocebo hyperalgesia from verbal suggestion. Healthy volunteers (N =147) were randomly assigned to conditions in a 2 (Affect Induction: Positive vs. Neutral) by 2 (Verbal Suggestion: No Suggestion vs. Suggestion of Pain Increase) between-subjects design. Participants were induced to experience positive or neutral affect by watching movie clips for 15 mins. Next, participants had an inert cream applied to their non-dominant hand and suggestion was manipulated by telling only half the participants the cream could increase the pain of the upcoming cold pressor test. Subsequently, all participants underwent the cold pressor test (8C ±.04C), wherein they submerged the non-dominant hand and rated pain intensity on numerical rating scales every 20 sec up to two mins. In the neutral affect conditions, there was evidence for the nocebo hyperalgesia effect: participants given the suggestion of pain displayed greater pain than participants not receiving this suggestion, ps<.05. Demonstrating a blockage effect, nocebo hyperalgesia did not occur in the positive affect conditions, ps>.5. This is the first study to show that positive affect may disrupt nocebo hyperalgesia thereby pointing to a novel strategy for decreasing nocebo effects without compromising the communication of medical information to patients in clinical settings.
Learn More >Although migraine and persistent post-traumatic headache often share phenotypic characteristics, few studies have interrogated the pathophysiological differences underlying these headache types. While there is now some indication of differences in brain structure between migraine and persistent post-traumatic headache, differences in brain function have not been adequately investigated. The objective of this study was to compare static and dynamic functional connectivity patterns in migraine versus persistent post-traumatic headache using resting-state magnetic resonance imaging.
Learn More >Opioids are very potent and efficacious drugs, traditionally used for both acute and chronic pain conditions. However, the use of opioids is frequently associated with the occurrence of adverse effects or clinical problems. Other than adverse effects and dependence, the development of tolerance is a significant problem, as it requires increased opioid drug doses to achieve the same effect. Mechanisms of opioid tolerance include drug-induced adaptations or allostatic changes at the cellular, circuitry, and system levels. Dose escalation in long-term opioid therapy might cause opioid-induced hyperalgesia (OIH), which is a state of hypersensitivity to painful stimuli associated with opioid therapy, resulting in exacerbation of pain sensation rather than relief of pain. Various strategies may provide extra-opioid analgesia. There are drugs that may produce independent analgesic effects. A tailored treatment provided by skilled personnel, in accordance with the individual condition, is mandatory. Any treatment aimed at reducing opioid consumption may be indicated in these circumstances. Interventional techniques able to decrease the pain input may allow a decrease in the opioid dose, thus reverting the mechanisms producing tolerance of OIH. Intrathecal therapy with local anesthetics and a sympathetic block are the most common techniques utilized in these circumstances.
Learn More >Interstitial cystitis is a chronic inflammatory condition of the urinary bladder with an unclear etiology. Currently, there are no widely accepted long-term treatment options available for patients with IC, with the European Association of Urology (EAU, 2017 guidelines), American Urology Association (AUA, 2014 guidelines), and the Royal College of Obstetricians and Gynaecologists (RCOG, 2016 guidelines) all suggesting various different conservative, pharmacological, intravesical, and surgical interventions. The endocannabinoid system represents a potential target for IC treatment and management. Activation of cannabinoid receptor 2 (CBR2) with various agonists has previously been shown to reduce leukocyte differentiation and migration, in addition to inhibiting the release of pro-inflammatory cytokines at the site of inflammation. These receptors have been identified in the detrusor and sensory nerves of the urothelium in various mammalian species, including humans. We hypothesize that by inhibiting the enzymes responsible for the catabolism of endogenous cannabinoids locally, bladder concentrations of CBR2 agonists will increase, particularly 2-arachidonyl glycerol, resulting in a diminished inflammatory response.
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