Retigabine and gabapentin restore channel function and neuronal firing in a cellular model of an epilepsy-associated dominant-negative KCNQ5 variant.

KCNQ5 encodes the voltage-gated potassium channel KV7.5, a member of the KV7 channel family, which conducts the M-current. This current is a potent regulator of neuronal excitability by regulating membrane potential in the subthreshold range of action potentials and mediating the medium and slow afterhyperpolarization. Recently, we have identified five loss-of-function variants in KCNQ5 in patients with genetic generalized epilepsy. Using the most severe dominant-negative variant (R359C), we set out to investigate pharmacological therapeutic intervention by KV7 channel openers on channel function and neuronal firing. Retigabine and gabapentin increased R359C-derived M-current amplitudes in HEK cells expressing homomeric or heteromeric mutant KV7.5 channels. Retigabine was most effective in restoring K+ currents. Ten µM retigabine was sufficient to reach the level of WT currents without retigabine, whereas 100 µM of gabapentin showed less than half of this effect and application of 50 µM ZnCl2 only significantly increased M-current amplitude in heteromeric channels. Overexpression of KV7.5-WT potently inhibited neuronal firing by increasing the M-current, whereas R359C overexpression had the opposite effect and additionally decreased the medium afterhyperpolarization current. Both aforementioned drugs and Zn2+ reversed the effect of R359C expression by reducing firing to nearly normal levels at high current injections. Our study shows that a dominant-negative variant with a complete loss-of-function in KV7.5 leads to largely increased neuronal firing which may explain a neuronal hyperexcitability in patients. KV7 channel openers, such as retigabine or gabapentin, could be treatment options for patients currently displaying pharmacoresistant epilepsy and carrying loss-of-function variants in KCNQ5.

Gabapentin attenuates cardiac remodeling after myocardial infarction by inhibiting M1 macrophage polarization through the peroxisome proliferator-activated receptor-γ pathway.

OBJECTIVES: Inflammation regulates ventricular remodeling after myocardial infarction (MI), and gabapentin exerts anti-inflammatory effects. We investigated the anti-inflammatory role and mechanism of gabapentin after MI. METHODS: Rats were divided into the sham group (n = 12), MI group (n = 20), and MI + gabapentin group (n = 16). MI was induced by left coronary artery ligation. The effects of gabapentin on THP-1-derived macrophages were examined in vitro. RESULTS: In vivo, 1 week after MI, gabapentin significantly reduced inducible nitric oxide synthase (iNOS; M1 macrophage marker) expression and decreased pro-inflammatory factors (tumor necrosis factor [TNF]-α and interleukin [IL]-1ß). Gabapentin upregulated the M2 macrophage marker arginase-1, as well as CD163 expression, and increased the expression of anti-inflammatory factors, including chitinase-like 3, IL-10, and transforming growth factor-ß. Four weeks after MI, cardiac function, infarct size, and cardiac fibrosis improved after gabapentin treatment. Gabapentin inhibited sympathetic nerve activity and decreased ventricular electrical instability in rats after MI. Tyrosine hydroxylase and growth-associated protein 43 were suppressed after gabapentin treatment. Gabapentin downregulated nerve growth factor (NGF) and reduced pro-inflammatory factors (iNOS, TNF-α, and IL-1ß). In vitro, gabapentin reduced NGF, iNOS, TNF-α, and IL-1ß expression in lipopolysaccharide-stimulated macrophages. Mechanistic studies revealed that the peroxisome proliferator-activated receptor-γ antagonist GW9662 attenuated the effects of gabapentin. Moreover, gabapentin reduced α2δ1 expression in the macrophage plasma membrane and reduced the calcium content of macrophages. CONCLUSION: Gabapentin attenuates cardiac remodeling by inhibiting inflammation via peroxisome proliferator-activated receptor-γ activation and preventing calcium overload.

Characterizing Opioid Prescribing Trends of Medical Oncologists From 2013 to 2019: Analysis From the Centers for Medicare & Medicaid Services Medicare Part D Prescribers Database.

PURPOSE: Opioid prescribing trends in medical oncology are poorly defined past 2017, the year after the CDC updated opioid prescription guidelines in noncancer settings. We aim to characterize pain management by medical oncologists by analyzing opioid and gabapentin prescribing trends from 2013 to 2019, identify physician-related factors associated with prescribing patterns, and assess whether CDC guidelines for nononcologic settings changed prescribing patterns. METHODS: The Centers for Medicare & Medicaid Services (CMS) Medicare Part D Prescribers-by Provider, CMS Medicare Part D Prescribers-by Provider and Drug, and CMS Medicare Physician National Downloadable files from 2013 to 2019 were merged by National Provider Identification. The database included physicians' sex, years of practice, regions, and practice settings. Multivariable binary logistic regression identified significant predictors of total opioid, long-acting opioid, and gabapentin prescriptions. RESULTS: Binary logistic regression modeling revealed no significant difference in mean daily total opioid prescriptions from 2013 to 2017. Daily opioid prescriptions by medical oncologists decreased significantly after 2017 (P < .001). Increased opioid prescribing was associated with physician male sex (P < .001), practicing over 10 years (P < .001), and practice in nonurban areas (P < .001). Opioid prescribing was greatest in the South and Midwest United States (P < .001). The same patterns were observed with total long-acting opioid prescriptions, whereas gabapentin prescribing increased from 2013 to 2019 (P < .001). CONCLUSION: Opioid prescriptions by medical oncologists decreased significantly from 2013 to 2019, but this decrease was most substantial from 2017 to 2019. These results may imply that the 2016 CDC guidelines influenced medical oncologists, particularly more junior physicians in urban settings, to manage chronic cancer pain with alternative therapies.

Non-oestrogen-based and complementary therapies for menopause.

Women are living a significant portion of their adult lives in the post-reproductive phase, and many seek help for debilitating menopausal symptoms. Every individual's experience of menopausal transition is unique. Adopting a holistic approach to managing the menopause using a combination of lifestyle, hormonal, and non-hormonal interventions is key to maximise the quality of life of affected women. However, many opt to use non hormonal options or have contraindications to using hormonal therapy. Studies have shown that several pharmacological non-hormonal medications such as SSRIs, SSRI/SNRIs, Gabapentin, and Pregabalin are effective for managing vasomotor symptoms as well as other menopausal symptoms. Their main side effects are dry mouth, nausea, constipation, reduced libido, and loss of appetite. Clonidine is the only non-hormonal drug which is licenced for control of vasomotor symptoms in the UK, but has several side effects including dizziness and sleep disturbance. Cognitive Behavioural Therapy is recommended as a treatment for anxiety, sleep problems and vasomotor symptoms related to menopausal transition. Evidence for clinical efficacy and safety of herbal remedies and alternative therapies remains weak. Studies with neurokinin receptor 3 antagonists on women with hot flushes have shown improvement in vasomotor symptoms and results of large-scale studies are awaited.

Modulating Nrf-2/HO-1, apoptosis and oxidative stress signaling pathways by gabapentin ameliorates sepsis-induced acute kidney injury.

PURPOSE: Globally, sepsis, which is a major health issue resulting from severe infection-induced inflammation, is the fifth biggest cause of death. This research aimed to evaluate, for the first time, the molecular effects of gabapentin's possible nephroprotective potential on septic rats by cecal ligation and puncture (CLP). METHODS: Sepsis was produced by CLP in male Wistar rats. Evaluations of histopathology and renal function were conducted. MDA, SOD, GSH, TNF-α, IL-1ß, and IL-6 levels were measured. qRT-PCR was utilized to determine the expression of Bax, Bcl-2, and NF-kB genes. The expression of Nrf-2 and HO-1 proteins was examined by western blotting. RESULTS: CLP caused acute renal damage, elevated the blood levels of creatinine, BUN, TNF-α, IL-1ß, and IL-6, reduced the expression of Nrf-2 and HO-1 proteins and the Bcl-2 gene expression, and upregulated NF-kB and Bax genes. Nevertheless, gabapentin dramatically diminished the degree of the biochemical, molecular, and histopathological alterations generated by CLP. Gabapentin reduced the levels of proinflammatory mediators and MDA, improved renal content of GSH and SOD, raised the expression of Nrf-2 and HO-1 proteins and Bcl-2 gene, and reduced the renal expression of NF-kB and Bax genes. CONCLUSION: Gabapentin mitigated the CLP-induced sepsis-related acute kidney injury through up-regulating Nrf-2/HO-1 pathway, repressing apoptosis, and attenuating the oxidative stress status by reducing the levels of the proinflammatory mediators and enhancing the antioxidant status.

Pregabalin produces similar effects as gabapentin for preanesthetic sedation in cats.

OBJECTIVE: To compare the effects of oral pregabalin versus gabapentin on sedation quality and anesthesia recovery times in cats in a typical perioperative setting. ANIMALS: 50 healthy cats with > 1 kg body weight presenting for elective surgery. METHODS: In this randomized, prospective clinical trial, cats presenting to the University of California-Davis Veterinary Medical Teaching Hospital were assigned to receive buprenorphine 0.02 mg/kg IM followed by 1 of 2 oral sedation treatments: pregabalin 4 mg/kg or gabapentin 10 mg/kg. Cats were then anesthetized using a standardized protocol. Physical examination parameters and behavioral scores were measured by 2 treatment-blinded veterinarians to compare sedation levels before and after drug administration. Inadequate sedation for handling or IV catheter placement was addressed by dexmedetomidine administration. After surgery was completed, anesthesia recovery times and quality were assessed by the same veterinarians. The effects of pregabalin versus gabapentin on body temperature, respiratory rate, and heart rate were analyzed using Student t tests; behavioral assessments were analyzed using Wilcoxon signed-rank tests; and drug treatment effects on dexmedetomidine sedation rescue and frequency of delirium during anesthetic recovery were analyzed using Fisher exact tests. A P < .05 indicated statistical significance. RESULTS: There was no significant difference in change of physiologic parameters or sedation scores before and after sedation between groups. The need for rescue sedation for IV catheter placement and the incidence of emergence delirium were infrequent and similar for both treatments. CLINICAL RELEVANCE: At the doses studied, oral pregabalin and gabapentin produced indistinguishable effects as adjunctive perioperative sedation agents in cats.

Effects of Acute and Chronic Gabapentin Treatment on Cardiovascular Function of Rats.

Gabapentin (GBP), a GABA analogue, is primarily used as an anticonvulsant for the treatment of partial seizures and neuropathic pain. Whereas a majority of the side effects are associated with the nervous system, emerging evidence suggests there is a high risk of heart diseases in patients taking GBP. In the present study, we first used a preclinical model of rats to investigate, firstly, the acute cardiovascular responses to GBP (bolus i.v. injection, 50 mg/kg) and secondly the effects of chronic GBP treatment (i.p. 100 mg/kg/day × 7 days) on cardiovascular function and the myocardial proteome. Under isoflurane anesthesia, rat blood pressure (BP), heart rate (HR), and left ventricular (LV) hemodynamics were measured using Millar pressure transducers. The LV myocardium and brain cortex were analyzed by proteomics, bioinformatics, and western blot to explore the molecular mechanisms underlying GBP-induced cardiac dysfunction. In the first experiment, we found that i.v. GBP significantly decreased BP, HR, maximal LV pressure, and maximal and minimal dP/dt, whereas it increased IRP-AdP/dt, Tau, systolic, diastolic, and cycle durations (* p < 0.05 and ** p < 0.01 vs. baseline; n = 4). In the second experiment, we found that chronic GBP treatment resulted in hypotension, bradycardia, and LV systolic dysfunction, with no change in plasma norepinephrine. In the myocardium, we identified 109 differentially expressed proteins involved in calcium pathways, cholesterol metabolism, and galactose metabolism. Notably, we found that calmodulin, a key protein of intracellular calcium signaling, was significantly upregulated by GBP in the heart but not in the brain. In summary, we found that acute and chronic GBP treatments suppressed cardiovascular function in rats, which is attributed to abnormal calcium signaling in cardiomyocytes. These data reveal a novel side effect of GBP independent of the nervous system, providing important translational evidence to suggest that GBP can evoke adverse cardiovascular events by depression of myocardial function.

Evaluation of trans- and cis-4-[18F]Fluorogabapentin for Brain PET Imaging.

Gabapentin, a selective ligand for the α2δ subunit of voltage-dependent calcium channels, is an anticonvulsant medication used in the treatment of neuropathic pain, epilepsy, and other neurological conditions. We recently described two radiofluorinated derivatives of gabapentin (trans-4-[18F]fluorogabapentin, [18F]tGBP4F, and cis-4-[18F]fluorogabapentin, [18F]cGBP4F) and showed that these compounds accumulate in the injured nerves in a rodent model of neuropathic pain. Given the use of gabapentin in brain diseases, here we investigate whether these radiofluorinated derivatives of gabapentin can be used for imaging α2δ receptors in the brain. Specifically, we developed automated radiosynthesis methods for [18F]tGBP4F and [18F]cGBP4F and conducted dynamic PET imaging in adult rhesus macaques with and without preadministration of pharmacological doses of gabapentin. Both radiotracers showed very high metabolic stability, negligible plasma protein binding, and slow accumulation in the brain. [18F]tGBP4F, the isomer with higher binding affinity, showed low brain uptake and could not be displaced, whereas [18F]cGBP4F showed moderate brain uptake and could be partially displaced. Kinetic modeling of brain regional time-activity curves using a metabolite-corrected arterial input function shows that a one-tissue compartment model accurately fits the data. Graphical analysis using Logan or multilinear analysis 1 produced similar results as compartmental modeling, indicating robust quantification. This study advances our understanding of how gabapentinoids work and provides an important advancement toward imaging α2δ receptors in the brain.

Gabapentin alleviated the cough hypersensitivity and neurogenic inflammation in a guinea pig model with repeated intra-esophageal acid perfusion.

OBJECTIVE: The anti-tussive effect of gabapentin and its underlying neuromodulatory mechanism were investigated via a modified guinea pig model of gastroesophageal reflux-related cough (GERC). METHODS: Intra-esophageal perfusion with hydrochloric acid (HCl) was performed every other day 12 times to establish the GERC model. High-dose gabapentin (48 mg/kg), low-dose gabapentin (8 mg/kg), or saline was orally administered for 2 weeks after modeling. Cough sensitivity, airway inflammation, lung and esophagus histology, levels of substance P (SP), and neurokinin-1 (NK1)-receptors were monitored. RESULTS: Repeated intra-esophageal acid perfusion aggravated the cough sensitivity in guinea pigs in a time-dependent manner. The number of cough events was significantly increased after 12 times HCl perfusion, and the hypersensitivity period was maintained for 2 weeks. The SP levels in BALF, trachea, lung, distal esophagus, and vagal ganglia were increased in guinea pigs receiving HCl perfusion. The intensity of cough hypersensitivity in the GERC model was significantly correlated with increased SP expression in the airways. Both high and low doses of gabapentin administration could reduce cough hypersensitivity exposed to HCl perfusion, attenuate airway inflammatory damage, and inhibit neurogenic inflammation by reducing SP expression from the airway and vagal ganglia. CONCLUSIONS: Gabapentin can desensitize the cough sensitivity in the GERC model of guinea pig. The anti-tussive effect is associated with the alleviated peripheral neurogenic inflammation as reflected in the decreased level of SP.

Effects of gabapentin on intraocular pressure, tear production and horizontal pupil diameter in New Zealand White rabbits.

BACKGROUND: This study aimed to investigate the effects of gabapentin on various ocular parameters in New Zealand White rabbits. METHODS: A randomised, placebo-controlled crossover study design was employed. Eight New Zealand White rabbits were randomly assigned to receive either oral gabapentin at a dosage of 15 mg/kg or an oral placebo, with a 1-week washout period between treatments. Intraocular pressure, tear production and horizontal pupil diameter were measured at baseline (T0) and at 30, 60, 90, 120, 180, 240 and 360 minutes after drug administration. Physiological and behavioural changes were also recorded for both treatments following drug administration. RESULTS: The administration of gabapentin did not have any significant effects on the ocular parameters measured in this study. However, the rabbits exhibited some muscle relaxation with partially closed eyes during handling, and they were slightly easier to remove from the cage when treated with gabapentin compared to the placebo treatment. LIMITATIONS: In this study, the ocular effects of gabapentin were assessed in only a small number of healthy rabbits. These effects may differ in rabbits with pre-existing eye conditions or in those receiving other medications. CONCLUSIONS: Our findings suggest that gabapentin treatment does not have a significant impact on intraocular pressure, tear production or horizontal pupil diameter in rabbits.

Effect of Gabapentin-Fluoxetine Derivative GBP1F in a Murine Model of Depression, Anxiety and Cognition.

Background and Objective: Gabapentin is a commonly prescribed antiepileptic agent for seizures, which is also used for pain and addiction management. Due to growing evidence of its abuse liability, there has been an incentive to synthesise potentially useful gabapentin derivatives devoid of adverse effects. A gabapentin adduct with a fluoxetine moiety, GBP1F, was assessed for any sedative, cognitive, anxiolytic, or antidepressant-like actions in murine behavioral models. Materials and Methods: Selected groups of mice were used for each behavioral paradigm, and the effect of GBP1F (5, 10, and 15 mg/kg) was assessed using spontaneous locomotor activity, the tail suspension test, elevated plus maze test, and the Y maze test models. Immediately following behavioral experiments, postmortem striatal and hippocampal tissues were evaluated for the effect of GBP1F on concentrations of dopamine, DOPAC, HVA, serotonin, 5-HIAA, vitamin C, and noradrenaline using high performance liquid chromatography with electrochemical detection. Results: GBP1F induced a mild suppression of locomotor activity, ameliorated anxiety and depression-like behavior, did not alter cognitive behavior, and raised serotonin and 5-HIAA concentrations in the hippocampus and striatum. GBP1F also positively enhanced dopamine and vitamin C tissue levels in the striatum. Thus, GBP1F represents a compound with anxiolytic- and antidepressant-like effects though further studies are warranted at the molecular level to focus on the precise mechanism(s) of action.

Inhibition of T-Type Calcium Channels With TTA-P2 Reduces Chronic Neuropathic Pain Following Spinal Cord Injury in Rats.

Spinal cord injury (SCI)-induced neuropathic pain (SCI-NP) develops in up to 60 to 70% of people affected by traumatic SCI, leading to a major decline in quality of life and increased risk for depression, anxiety, and addiction. Gabapentin and pregabalin, together with antidepressant drugs, are commonly prescribed to treat SCI-NP, but their efficacy is unsatisfactory. The limited efficacy of current pharmacological treatments for SCI-NP likely reflects our limited knowledge of the underlying mechanism(s) responsible for driving the maintenance of SCI-NP. The leading hypothesis in the field supports a major role for spontaneously active injured nociceptors in driving the maintenance of SCI-NP. Recent data from our laboratory provided additional support for this hypothesis and identified the T-type calcium channels as key players in driving the spontaneous activity of SCI-nociceptors, thus providing a rational pharmacological target to treat SCI-NP. To test whether T-type calcium channels contribute to the maintenance of SCI-NP, male and female SCI and sham rats were treated with TTA-P2 (a blocker of T-type calcium channels) to determine its effects on mechanical hypersensitivity (as measured with the von Frey filaments) and spontaneous ongoing pain (as measured with the conditioned place preference paradigm), and compared them to the effects of gabapentin, a blocker of high voltage-activated calcium channels. We found that both TTA-P2 and gabapentin reduced mechanical hypersensitivity in male and females SCI rats, but surprisingly only TTA-P2 reduced spontaneous ongoing pain in male SCI rats. PERSPECTIVES: SCI-induced neuropathic pain, and in particular the spontaneous ongoing pain component, is notoriously very difficult to treat. Our data provide evidence that inhibition of T-type calcium channels reduces spontaneous ongoing pain in SCI rats, supporting a clinically relevant role for T-type channels in the maintenance of SCI-induced neuropathic pain.

Glioblastoma remodelling of human neural circuits decreases survival.

Gliomas synaptically integrate into neural circuits1,2. Previous research has demonstrated bidirectional interactions between neurons and glioma cells, with neuronal activity driving glioma growth1-4 and gliomas increasing neuronal excitability2,5-8. Here we sought to determine how glioma-induced neuronal changes influence neural circuits underlying cognition and whether these interactions influence patient survival. Using intracranial brain recordings during lexical retrieval language tasks in awake humans together with site-specific tumour tissue biopsies and cell biology experiments, we find that gliomas remodel functional neural circuitry such that task-relevant neural responses activate tumour-infiltrated cortex well beyond the cortical regions that are normally recruited in the healthy brain. Site-directed biopsies from regions within the tumour that exhibit high functional connectivity between the tumour and the rest of the brain are enriched for a glioblastoma subpopulation that exhibits a distinct synaptogenic and neuronotrophic phenotype. Tumour cells from functionally connected regions secrete the synaptogenic factor thrombospondin-1, which contributes to the differential neuron-glioma interactions observed in functionally connected tumour regions compared with tumour regions with less functional connectivity. Pharmacological inhibition of thrombospondin-1 using the FDA-approved drug gabapentin decreases glioblastoma proliferation. The degree of functional connectivity between glioblastoma and the normal brain negatively affects both patient survival and performance in language tasks. These data demonstrate that high-grade gliomas functionally remodel neural circuits in the human brain, which both promotes tumour progression and impairs cognition.

Efficacy and Safety of Gabapentin in Improving Sleep Quality of Patients with Sensory Nervous System Diseases: A Meta-Analysis.

Context: Sensory nervous-system diseases are chronic diseases that injury or disease of the somatosensory nervous system causes. Sleep disorders usually accompany these diseases, and in turn, worsen their conditions and form a vicious circle that brings great difficulties in clinical treatment. Objective: The study intended to systematically evaluate the clinical efficacy and safety of gabapentin in improving the sleep quality of patients with sensory nervous-system diseases using a meta-analysis, so as to provide evidence-based medical evidence for clinical treatment. Design: The research team performed a comprehensive narrative review by searching the China National Knowledge Infrastructure (CNKI), Chinese Scientific Journal (VIP), WANFANG, Chinese Biomedical Database (CBM), PubMed, Embase, Cochrane Library, and ClinicalTrials.gov databases. The search terms included gabapentin, 1-(aminomethyl)-cyclohexaneacetic acid, gabapentin hexal, gabapentin-ratiopharm, sleep, and insomnia. Setting: The review took place in the Department of Neurology at the First People's Hospital of Linping District in Hangzhou, China. Outcome Measures: The research team extracted the data from the studies meeting the inclusion criteria and then transferred them into the Review Manager 5.3 software for meta-analysis. The outcome measures included scores: (1) for the improvement in the degree of sleep interference score; (2) for the improvement in sleep quality; (3) for the rate of poor sleep quality; (4) for the rate awakenings of >5 per night; and (5) for the incidence of adverse reactions. Results: The research team found eight RCTs with 1269 participants, including 637 participants in a gabapentin test group and 632 participants in the placebo control group. The meta-analysis showed that the decrease in the degree of sleep interference [mean deviation (MD) = -0.86, 95% CI: (-0.91, -0.82), P < .00001] and the improvement in sleep quality [odds ratio (OR) = 2.64, 95% CI: (1.90, 3.67), P < .00001] in gabapentin group were significantly higher than those in placebo group (P < .05), while the rate of poor sleep quality [OR = 0.43, 95% CI: (0.23, 0.79), P = .007] and the rate of > 5 night awakenings [OR = 0.01, 95% CI: (0.05, 0.70), P = .01] in gabapentin group were significantly lower than those in placebo group (P < .05). No statistically significant differences existed in the incidence of adverse reactions between the two groups. Conclusions: Gabapentin is safe and effective in improving the sleep quality of patients with sensory nervous-system diseases. Due to the limitations of sample size and types of diseases in the current study, the field needs multicenter, large-sample, and high-quality RCTs for further validation in the future.

EMC chaperone-CaV structure reveals an ion channel assembly intermediate.

Voltage-gated ion channels (VGICs) comprise multiple structural units, the assembly of which is required for function1,2. Structural understanding of how VGIC subunits assemble and whether chaperone proteins are required is lacking. High-voltage-activated calcium channels (CaVs)3,4 are paradigmatic multisubunit VGICs whose function and trafficking are powerfully shaped by interactions between pore-forming CaV1 or CaV2 CaVα1 (ref. 3), and the auxiliary CaVß5 and CaVα2δ subunits6,7. Here we present cryo-electron microscopy structures of human brain and cardiac CaV1.2 bound with CaVß3 to a chaperone-the endoplasmic reticulum membrane protein complex (EMC)8,9-and of the assembled CaV1.2-CaVß3-CaVα2δ-1 channel. These structures provide a view of an EMC-client complex and define EMC sites-the transmembrane (TM) and cytoplasmic (Cyto) docks; interaction between these sites and the client channel causes partial extraction of a pore subunit and splays open the CaVα2δ-interaction site. The structures identify the CaVα2δ-binding site for gabapentinoid anti-pain and anti-anxiety drugs6, show that EMC and CaVα2δ interactions with the channel are mutually exclusive, and indicate that EMC-to-CaVα2δ hand-off involves a divalent ion-dependent step and CaV1.2 element ordering. Disruption of the EMC-CaV complex compromises CaV function, suggesting that the EMC functions as a channel holdase that facilitates channel assembly. Together, the structures reveal a CaV assembly intermediate and EMC client-binding sites that could have wide-ranging implications for the biogenesis of VGICs and other membrane proteins.

Recognition Mechanism of a Novel Gabapentinoid Drug, Mirogabalin, for Recombinant Human α2δ1, a Voltage-Gated Calcium Channel Subunit.

Mirogabalin is a novel gabapentinoid drug with a hydrophobic bicyclo substituent on the γ-aminobutyric acid moiety that targets the voltage-gated calcium channel subunit α2δ1. Here, to reveal the mirogabalin recognition mechanisms of α2δ1, we present structures of recombinant human α2δ1 with and without mirogabalin analyzed by cryo-electron microscopy. These structures show the binding of mirogabalin to the previously reported gabapentinoid binding site, which is the extracellular dCache_1 domain containing a conserved amino acid binding motif. A slight conformational change occurs around the residues positioned close to the hydrophobic group of mirogabalin. Mutagenesis binding assays identified that residues in the hydrophobic interaction region, in addition to several amino acid binding motif residues around the amino and carboxyl groups of mirogabalin, are critical for mirogabalin binding. The A215L mutation introduced to decrease the hydrophobic pocket volume predictably suppressed mirogabalin binding and promoted the binding of another ligand, L-Leu, with a smaller hydrophobic substituent than mirogabalin. Alterations of residues in the hydrophobic interaction region of α2δ1 to those of the α2δ2, α2δ3, and α2δ4 isoforms, of which α2δ3 and α2δ4 are gabapentin-insensitive, suppressed the binding of mirogabalin. These results support the importance of hydrophobic interactions in α2δ1 ligand recognition.

N-palmitoylethanolamide synergizes the antinociception of morphine and gabapentin in the formalin test in mice.

OBJECTIVE: The antinociceptive pharmacological interaction between N-palmitoylethanolamide (PEA) and morphine (MOR), as well as gabapentin (GBP), was investigated to obtain synergistic antinociception at doses where side effects were minimal. In addition, the possible antinociceptive mechanism of PEA + MOR or PEA + GBP combinations was explored. METHODS: Individual dose-response curves (DRCs) of PEA, MOR and GBP were evaluated in female mice in which intraplantar nociception was induced with 2% formalin. Isobolographic method was used to detect the pharmacological interaction in the combination of PEA + MOR or PEA + GBP. KEY FINDINGS: The ED50 was calculated from the DRC; the order of potency was MOR > PEA > GBP. The isobolographic analysis was obtained at a 1:1 ratio to determine the pharmacological interaction. The experimental values of flinching (PEA + MOR, Zexp = 2.72 ± 0.2 µg/paw and PEA + GBP Zexp = 2.77 ± 0.19 µg/paw) were significantly lower than those calculated theoretically (PEA + MOR Zadd = 7.78 ± 1.07 and PEA + GBP Zadd = 24.05 ± 1.91 µg/paw), resulting in synergistic antinociception. Pretreatment with GW6471 and naloxone demonstrated that peroxisome proliferator-activated receptor alpha (PPARα) and opioid receptors are involved in both interactions. CONCLUSIONS: These results suggest that MOR and GBP synergistically enhance PEA-induced antinociception through PPARα and opioid receptor mechanisms. Furthermore, the results suggest that combinations containing PEA with MOR or GBP could be of interest in aiding the treatment of inflammatory pain.

A preliminary study to identify existing drugs for potential repurposing in breast cancer based on side effect profile.

Breast cancer is the most commonly diagnosed cancer and the second leading cause of cancer-related death in women after lung cancer. The present study aims to identify potential drug candidates using the PROMISCUOUS database for breast cancer based on side effect profile and then proceed with in silico and in vitro studies. PROMISCUOUS database was used to construct a group of drugs that share maximum side effects with letrozole. Based on the existing literature, ropinirole, risperidone, pregabalin, and gabapentin were selected for in silico and in vitro studies. The molecular docking was carried out using AUTODOCK 4.2.6. MCF-7 cell line was used to evaluate the anti-cancer activity of the selected drugs. PROMISCUOUS database revealed that as many as 23 existing drugs shared between 62 and 79 side-effects with letrozole. From docking result, we found that, ropinirole showed a good binding affinity (-7.7 kcal/mol) against aromatase compared to letrozole (-7.1 kcal/mol) which was followed by gabapentin (-6.4 kcal/mol), pregabalin (-5.7 kcal/mol) and risperidone (-5.1 kcal/mol). From the in vitro results, ropinirole and risperidone showed good anti-cancer activity of IC50 with 40.85±11.02 µg/ml and 43.10±9.58 µg/ml cell viability. Based on this study results and existing literature we conclude that risperidone, pregabalin, and gabapentin are not ideal candidates for repurposing in breast cancer but ropinirole could be an excellent choice for repurposing in breast cancer after further studies.

Gabapentin alleviates myocardial ischemia-reperfusion injury by increasing the protein expression of GABAARδ.

Gabapentin is a commonly used analgesic in the clinic to reduce opioid consumption. It is well known that gabapentin can reduce cerebral ischemia-reperfusion injury (IRI). However, it remains unclear whether gabapentin can reduce myocardial IRI. Before the performance of myocardial ischemia and reperfusion (I/R), rats received gabapentin without or with an intravenous injection of PI3K inhibitor (LY294002), or an intraspinal injection of lentivirus-mediated GABAARδ-shRNA. The myocardial IRI were evaluated by calculating the infarction area, arrhythmia score and myocardial apoptosis. The activity of PI3K/Akt and the expression of GABAARδ were quantified by western blotting. The effect of gabapentin on myocardial I/R was further demonstrated in vitro by establishing oxygen-glucose deprivation and reoxygenation in cardiomyocytes. After I/R in vivo, there were significant increases in infarction area, arrhythmia and Bax protein expression in the myocardium, as well as a decrease of GABAARδ in the spinal cord. Meanwhile, I/R also decreased the protein expression of PI3K/Akt and Bcl-2. Gabapentin pretreatment successfully attenuated IRI including reducing the myocardial infarction area and apoptosis. This effect was abolished by both the systemic inhibition of PI3K/Akt and the intraspinal suppression of GABAARδ. However, gabapentin pretreatment failed to prevent cellular injury induced by OGD/R in cardiomyocytes. Therefore, the myocardial protective effect of gabapentin may be attributed to activating PI3K/Akt in the myocardium and upregulating GABAARδ in the spinal cord. Gabapentin achieved a potent protective effect on the myocardium during the course of routine clinical treatment.

Synergistic effect of ellagic acid and gabapentin in a rat model of neuropathic pain.

BACKGROUND: Neuropathic pain is a subtype of chronic pain characterized by a primary lesion or dysfunction of the peripheral or central nervous system. The current pain management of neuropathic pain is inadequate and needs new medications. AIM: We studied the effects of 14 days of intraperitoneal ellagic acid (EA) and gabapentin administration in a rat model of neuropathic pain induced by chronic constriction injury (CCI) of the right sciatic nerve. METHODS: Rats were divided into six groups: (1) control, (2) CCI, (3) CCI + EA (50 mg/kg), 4) CCI + EA (100 mg/kg), 5) CCI + gabapentin (100 mg/kg), and 6) CCI + EA (100 mg/kg) + gabapentin (100 mg/kg). Behavioral tests, including mechanical allodynia, cold allodynia, and thermal hyperalgesia, were conducted on days - 1(pre-operation), 7, and 14 post-CCI. In addition, at day 14 post-CCI, spinal cord segments were collected to measure the expression of inflammatory markers, including tumor necrosis factor-alpha (TNF-α), nitric oxide (NO), and oxidative stress markers, including malondialdehyde (MDA) and thiol. RESULTS: CCI increased mechanical allodynia, cold allodynia, and thermal hyperalgesia in rats which were reduced by treatment with EA (50 or 100 mg/kg), gabapentin, or their combination. CCI increased TNF-α, NO, and MDA levels and decreased thiol content in the spinal cord, which all were reverted by administration of EA (50 or 100 mg/kg), gabapentin, or their combination. CONCLUSION: This is the first report on ellagic acid's ameliorative effect in rats' CCI-induced neuropathic pain. This effect can be attributed to its anti-oxidative and anti-inflammatory, thus making it potentially useful as an adjuvant to conventional treatment.