Association of obstructive sleep apnea with cardiometabolic diseases and cardiovascular mortality.

BACKGROUND: Obstructive sleep apnea (OSA) is one of the leading respiratory disorders, increasing the risk of cardiometabolic diseases. In the study, we investigated the association between OSA and the risk of cardiometabolic diseases and all-cause and cardiovascular mortality in adults. METHODS: Participants were enrolled in the National Health and Nutrition Examination Survey. The baseline covariates were compared between participants with and without OSA status. Multivariable logistic regression was performed to explore the association between OSA and cardiometabolic diseases, while Cox proportional regression was performed for all-cause and cardiovascular mortality. RESULTS: OSA status was positively associated with higher risks of cardiometabolic diseases, including hypertension (odds ratio [OR] 1.28, 95% confidence interval [CI] 1.14-1.45; p < 0.001), diabetes (OR 1.46, 95% CI 1.22-1.76; p < 0.001), and cardiovascular diseases (OR 1.29, 95% CI 1.08-1.54; p = 0.006) after adjusting for numerous covariates. However, no associations of OSA with all-cause or cardiovascular mortality were observed. CONCLUSION: OSA was associated with a higher risk of hypertension, diabetes, and cardiovascular diseases, but had no significant association with all-cause or cardiovascular mortality in adults.

Improving middle school students' geometry problem solving ability through hands-on experience: An fNIRS study.

Hands-on learning is proposed as a prerequisite for mathematics learning in kindergarten and primary school. However, it remains unclear that whether hands-on experience aids understanding of geometry knowledge for middle school students. We also know little about the neural basis underlying the value of hands-on experience in math education. In this study, 40 right-handed Chinese students (20 boys and 20 girls) with different academic levels were selected from 126 seventh-grade students in the same school, who learnt "Axisymmetric of an Isosceles Triangle" in different learning style (hands-on operation vs. video observation). Half of them operated the concrete manipulatives while the other half watched the instructional videos. The learning-test paradigm and functional near-infrared spectroscopy (fNIRS) technique were used to compare the differences in geometry reasoning involved in solving well-structured problems and ill-structured problems. Behavioral results showed that hands-on experience promoted students' performances of geometry problem-solving. Students with lower academic level were more dependent on hands-on experience than those with higher academic level. The fNIRS results showed that meaningful hands-on experience with concrete manipulatives related to learning contents increased reactivation of the somatosensory association cortex during subsequent reasoning, which helped to improve the problem-solving performance. Hands-on experience also reduced students' cognitive load during the well-structured problem-solving process. These findings contribute to better understand the value of hands-on experience in geometry learning and the implications for future mathematics classroom practices.

Triglyceride Glucose Index Was a Predictor of 6-Month Readmission Caused by Pulmonary Infection of Heart Failure Patients.

Objectives: Insulin resistance is associated with the prognosis of heart failure (HF) patients. The triglyceride glucose (TyG) index is a simple marker of insulin resistance. However, it remains unclear whether the TyG index is associated with the incidence of readmission in patients with HF. Methods: We enrolled 901 patients with completed records on serum triglyceride and glucose in our study. The TyG index was calculated as log (fasting triglycerides (mg/dL) x fasting glucose (mg/dL)/2). There were 310 cases of readmission and the average TyG index was 7.8 ± 0.7. Restricted cubic spline was fitted to explore the linearity of TyG index associating with 6-month readmission of HF patients. Logistic regression analysis was performed to explore the association between TyG index quartile and the incidence of 6-month readmission. Results: Only the 6-month readmission was significantly different among TyG quartiles, and it was the highest (41.9%) in the lowest quartile (ranging 6.17∼7.36). the TyG index was nonlinearly associated with 6-month readmission (p for nonlinearity = 0.009), with the lower level of TyG index increasing the risk of 6-month readmission. Besides, multivariable logistic analysis showed that the lowest TyG quartile was associated with a higher incidence of 6-month readmission in the unadjusted model (odds ratio [OR] 1.74, 95% confidence interval [CI] 1.18-2.57; p=0.005), partially adjusted model (OR 1.82, 95%CI 1.22-2.72; p=0.004), and fully-adjusted model (OR 1.65, 95%CI 1.09-2.45; p=0.024). The association was consistent across gender and diabetes group. Conclusion: A lower TyG index independently increased the risk of 6-month readmission in HF patients, which could be a prognostic factor in heart failure.

Verbascoside protects from LPS-induced septic cardiomyopathy via alleviating cardiac inflammation, oxidative stress and regulating mitochondrial dynamics.

BACKGROUND: Verbascoside (VB), as an active component of multiple medicinal plants, has been proved to exert anti-oxidative, anti-aging and neuroprotective effects. This study was designed to investigate whether VB could play a cardioprotective role in septic heart injury. METHODS: Mice were injected with lipopolysaccharide (LPS; 10 mg/kg) to induce sepsis. The treatment group received an intraperitoneally injection of VB (20 mg/kg) before LPS challenge. Transthoracic echocardiography, ELISA, immunofluorescence, and qPCR were performed to assess the effect of VB on heart function, oxidative stress, inflammation and apoptosis. Transmission electronic microscopy and immunoblotting were used to evaluate the mitochondrial morphology and biogenesis of the septic heart. In vitro experiments were also performed to repeat above-mentioned assays. RESULTS: Compared with LPS group, the VB treatment group showed improved cardiac function in sepsis. VB alleviated oxidative stress and inflammatory cell infiltration, as well as cardiomyocyte apoptosis. Specifically, VB could restore sepsis-induced mitochondrial alterations via regulating mitochondrial biogenesis. These results were also confirmed in in vitro experiments. CONCLUSION: Verbascoside could protected from sepsis-induced cardiomyopathy by inhibiting oxidative stress, inflammation, and apoptosis, as well as promoting mitochondrial biogenesis.

Difference of immune cell infiltration between stable and unstable carotid artery atherosclerosis.

Atherosclerotic plaque instability contributes to ischaemic stroke and myocardial infarction. This study is to compare the abundance and difference of immune cell subtypes within unstable atherosclerotic tissues. CIBERSORT was used to speculate the proportions of 22 immune cell types based on a microarray of atherosclerotic carotid artery samples. R software was utilized to illustrate the bar plot, heat map and vioplot. The immune cell landscape in atherosclerosis was diverse, dominated by M2 macrophages, M0 macrophages, resting CD4 memory T cells and CD8 T cells. There was a significant difference in resting CD4 memory T cells (p = 0.032), T cells follicular helper (p = 0.033), M0 (p = 0.047) and M2 macrophages (p = 0.012) between stable and unstable atherosclerotic plaques. Compared with stable atherosclerotic plaques, unstable atherosclerotic plaques had a higher percentage of M2 macrophages. Moreover, correlation analysis indicated that the percentage of naïve CD4 T cells was strongly correlated with that of gamma delta T cells (r = 0.93, p < 0.001), while memory B cells were correlated with plasma cells (r = 0.85, p < 0.001). In summary, our study explored the abundance and difference of specific immune cell subgroups at unstable plaques, which would aid new immunotherapies for atherosclerosis.

Discovery of Selective Pituitary Adenylate Cyclase 1 Receptor (PAC1R) Antagonist Peptides Potent in a Maxadilan/PACAP38-Induced Increase in Blood Flow Pharmacodynamic Model.

Inhibition of the pituitary adenylate cyclase 1 receptor (PAC1R) is a novel mechanism that could be used for abortive treatment of acute migraine. Our research began with comparative analysis of known PAC1R ligand scaffolds, PACAP38 and Maxadilan, which resulted in the selection of des(24-42) Maxadilan, 6, as a starting point. C-terminal modifications of 6 improved the peptide metabolic stability in vitro and in vivo. SAR investigations identified synergistic combinations of amino acid replacements that significantly increased the in vitro PAC1R inhibitory activity of the analogs to the pM IC90 range. Our modifications further enabled deletion of up to six residues without impacting potency, thus improving peptide ligand binding efficiency. Analogs 17 and 18 exhibited robust in vivo efficacy in the rat Maxadilan-induced increase in blood flow (MIIBF) pharmacodynamic model at 0.3 mg/kg subcutaneous dosing. The first cocrystal structure of a PAC1R antagonist peptide (18) with PAC1R extracellular domain is reported.

Willingness to engage in and current status of social participation among Chinese merchant sailors.

China has the largest population of sailors in the world, but little is known of their social participation. This study examined Chinese merchant sailors' social participation using a nationwide survey. Across 12 Chinese provinces, 7,296 merchant sailors completed the questionnaire on sailor' willingness to engage in and status of social participation. The results showed that most Chinese merchant sailors were willing to participate in social affairs, but few of them reported having joined relevant social organizations, over half of sailors reported never having participated in public affairs, and half of them chose to ignore when they faced with an obvious mistake in shipping-related information in the media. Most of sailors reported unknowing the role of the labor union related to Chinese seafarers and NGO related to navigation well, and their evaluation of these organizations were mostly negative. Chinese merchant sailors reported higher expectations of services in terms of protection of rights, providing information and technology, and providing employment opportunity. We conclude that Chinese merchant sailors have willingness to social participation although the reality is not positive and discuss implications for improving the social participation of Chinese merchant sailors.

PAC1 receptor blockade reduces central nociceptive activity: new approach for primary headache?

Pituitary adenylate cyclase activating polypeptide-38 (PACAP38) may play an important role in primary headaches. Preclinical evidence suggests that PACAP38 modulates trigeminal nociceptive activity mainly through PAC1 receptors while clinical studies report that plasma concentrations of PACAP38 are elevated in spontaneous attacks of cluster headache and migraine and normalize after treatment with sumatriptan. Intravenous infusion of PACAP38 induces migraine-like attacks in migraineurs and cluster-like attacks in cluster headache patients. A rodent-specific PAC1 receptor antibody Ab181 was developed, and its effect on nociceptive neuronal activity in the trigeminocervical complex was investigated in vivo in an electrophysiological model relevant to primary headaches. Ab181 is potent and selective at the rat PAC1 receptor and provides near-maximum target coverage at 10 mg/kg for more than 48 hours. Without affecting spontaneous neuronal activity, Ab181 effectively inhibits stimulus-evoked activity in the trigeminocervical complex. Immunohistochemical analysis revealed its binding in the trigeminal ganglion and sphenopalatine ganglion but not within the central nervous system suggesting a peripheral site of action. The pharmacological approach using a specific PAC1 receptor antibody could provide a novel mechanism with a potential clinical efficacy in the treatment of primary headaches.

Discovery of the Migraine Prevention Therapeutic Aimovig (Erenumab), the First FDA-Approved Antibody against a G-Protein-Coupled Receptor.

In 2018, the United States Food and Drug Administration (FDA) approved Aimovig (erenumab) for the prevention of migraine. Erenumab is the first FDA approved antibody therapeutic against a G-protein-coupled receptor, the canonical receptor of calcitonin gene related peptide (CGRP-R). A novel, epitope-focused antigen was created to reconstruct the extracellular domains of the CGRP-R in a stable conformation. Successful inoculation of XenoMouse animals and careful screening yielded multiple candidate molecules for high potency and exquisite selectivity toward the CGRP-R over related receptors. These efforts led to the discovery of erenumab which has demonstrated the desired efficacy and safety profiles in multiple clinical studies for the prevention of migraine. The innovation developed in the discovery of erenumab furthers the ability to target G-coupled protein receptors using antibody approaches.

Gender differences in children's pedestrian behaviors: Developmental effects.

INTRODUCTION: All child pedestrians are vulnerable to road traffic injuries, but there is evidence that boys may be at greater risk than girls, at least among some age groups. METHOD: To create effective intervention programs, research on how boys and girls of particular ages behave as pedestrians, and whether there are gender differences that increase risk for particular genders at particular ages, is needed. In this study, 255 boys and 235 girls in grade 1 through 6 from two primary schools in Nantong city, China, were unobtrusively videotaped when walking to school in the morning. Videotapes were reviewed and coded for seven pedestrian safety behaviors, including activities related to crossing streets (walking instead of running/hopping, observing traffic, using the crosswalk instead of walking outside the crosswalk, and keeping close to an accompanying adult) and those related to walking alongside busy streets (walking instead of running/hopping on the sidewalk, not playing on the sidewalk, walking alone instead of walking side-by-side with a partner). RESULTS: Results revealed that as a whole, boys played on the sidewalk more often than girls (p < 0.01) and crossed with an accompanying adult more than girls (p < 0.05), while girls walked side-by-side with partners more often than boys (p < 0.05). With a few exceptions, boys and girls in the younger grades (1-2) as well as those in the older grades (5-6) behaved fairly similarly as pedestrians, but boys and girls in the middle grades (3-4) presented with several significant gender-based differences. In the middle grades, boys watched traffic more than girls while crossing (p < 0.01); ran, hopped and played on the sidewalk more often than girls (p < 0.05); and walked side-by-side less often with partners than girls (p < 0.05). We also detected different gender-based trends in the development of pedestrian skills. With increasing age, girls performed more safely in pedestrian tasks, but boys did not show a similar developmental trend. CONCLUSIONS: We conclude that boys and girls exhibit different characteristics in their pedestrian behaviors and discuss implications for prevention.

Neural Respiratory Drive Measured Using Surface Electromyography of Diaphragm as a Physiological Biomarker to Predict Hospitalization of Acute Exacerbation of Chronic Obstructive Pulmonary Disease Patients.

BACKGROUND: Neural respiratory drive (NRD) using diaphragm electromyography through an invasive transesophageal multi-electrode catheter can be used as a feasible clinical physiological parameter in patients with chronic obstructive pulmonary disease (COPD) to provide useful information on the treatment response. However, it remains unknown whether the surface diaphragm electromyogram (EMGdi) could be used to identify the deterioration of clinical symptoms and to predict the necessity of hospitalization in acute exacerbation of COPD (AECOPD) patients. METHODS: COPD patients visiting the outpatient department due to acute exacerbation were enrolled in this study. All patients who were subjected to EMGdi and classical parameters such as spirometry parameters, arterial blood gas analysis, COPD assessment test (CAT) score, and the modified early warning score (MEWS) in outpatient department, would be treated effectively in the outpatient or inpatient settings according to the Global Initiative for Chronic Obstructive Lung Disease guideline. When the acute exacerbation of the patients was managed, all the examination above would be repeated. RESULTS: We compared the relationships of admission-to-discharge changes (Δ) in the normalized value of the EMGdi, including the change of the percentage of maximal EMGdi (ΔEMGdi%max) and the change of the ratio of minute ventilation to the percentage of maximal EMGdi (ΔVE/EMGdi%max) with the changes of classical parameters. There was a significant positive association between ΔEMGdi%max and ΔCAT, ΔPaCO2, and ΔpH. The change (Δ) of EMGdi%max was negatively correlated with ΔPaO2/FiO2in the course of the treatment of AECOPD. Compared with the classical parameters including forced expiratory volume in 1 s, MEWS, PaO2/FiO2, the EMGdi%max (odds ratio 1.143, 95% confidence interval 1.004-1.300) has a higher sensitivity when detecting the early exacerbation and enables to predict the admission of hospital in the whole cohort. CONCLUSIONS: The changes of surface EMGdi parameters had a direct correlation with classical measures in the whole cohort of AECOPD. The measurement of NRD by surface EMGdi represents a practical physiological biomarker, which may be helpful in detecting patients who should be hospitalized timely.

Fast and accurate separation of the paclitaxel from yew extracum by a pseudo simulated moving bed with solvent gradient.

A pseudo simulated moving bed (SMB) with solvent gradient was used to trap and separate paclitaxel from yew extracum. This SMB process consisted of three steps: feeding, purification and recovery. In comparison with methanol/water as an eluent, acetonitrile/water could give a better separation but had a poor dissolubility of the yew extracum, and therefore methanol/water was used in the feeding followed by acetonitrile/water in the purification. In the first two steps, water was deliberately added into zone III to modulate the eluotropic strength of the liquid entering zone III, so as to make paclitaxel separation from impurities be more efficient. Once most of impurities discarded, the columns were in turn eluted to recover the trapped paclitaxel of 98% yield with a purity of 78% from the yew extracum containing 1.5% paclitaxel. Afterward, an additional operation of crystallization improved the purity further to 97.8% with the yield of 95%.

Pharmacological characterization of potent and selective NaV1.7 inhibitors engineered from Chilobrachys jingzhao tarantula venom peptide JzTx-V.

Identification of voltage-gated sodium channel NaV1.7 inhibitors for chronic pain therapeutic development is an area of vigorous pursuit. In an effort to identify more potent leads compared to our previously reported GpTx-1 peptide series, electrophysiology screening of fractionated tarantula venom discovered the NaV1.7 inhibitory peptide JzTx-V from the Chinese earth tiger tarantula Chilobrachys jingzhao. The parent peptide displayed nominal selectivity over the skeletal muscle NaV1.4 channel. Attribute-based positional scan analoging identified a key Ile28Glu mutation that improved NaV1.4 selectivity over 100-fold, and further optimization yielded the potent and selective peptide leads AM-8145 and AM-0422. NMR analyses revealed that the Ile28Glu substitution changed peptide conformation, pointing to a structural rationale for the selectivity gains. AM-8145 and AM-0422 as well as GpTx-1 and HwTx-IV competed for ProTx-II binding in HEK293 cells expressing human NaV1.7, suggesting that these NaV1.7 inhibitory peptides interact with a similar binding site. AM-8145 potently blocked native tetrodotoxin-sensitive (TTX-S) channels in mouse dorsal root ganglia (DRG) neurons, exhibited 30- to 120-fold selectivity over other human TTX-S channels and exhibited over 1,000-fold selectivity over other human tetrodotoxin-resistant (TTX-R) channels. Leveraging NaV1.7-NaV1.5 chimeras containing various voltage-sensor and pore regions, AM-8145 mapped to the second voltage-sensor domain of NaV1.7. AM-0422, but not the inactive peptide analog AM-8374, dose-dependently blocked capsaicin-induced DRG neuron action potential firing using a multi-electrode array readout and mechanically-induced C-fiber spiking in a saphenous skin-nerve preparation. Collectively, AM-8145 and AM-0422 represent potent, new engineered NaV1.7 inhibitory peptides derived from the JzTx-V scaffold with improved NaV selectivity and biological activity in blocking action potential firing in both DRG neurons and C-fibers.

Immunohistochemical localization of the calcitonin gene-related peptide binding site in the primate trigeminovascular system using functional antagonist antibodies.

Calcitonin gene-related peptide (CGRP) is a potent vasodilator and a neuromodulator implicated in the pathophysiology of migraine. It binds to the extracellular domains of calcitonin receptor-like receptor (CLR) and receptor activity-modifying protein (RAMP) 1 that together form the CGRP receptor. Antagonist antibodies against CGRP and its binding site at the receptor are clinically effective in preventing migraine attacks. The blood-brain barrier penetration of these antagonist antibodies is limited, suggesting that a potential peripheral site of action is sufficient to prevent migraine attacks. To further understand the sites of CGRP-mediated signaling in migraine, we used immunohistochemical staining with recently developed antagonist antibodies specifically recognizing a fusion protein of the extracellular domains of RAMP1 and CLR that comprise the CGRP binding pocket at the CGRP receptor in monkey and man. We confirmed binding of the antagonist antibodies to human vascular smooth muscle cells (VSMCs) of dural meningeal arteries and neurons in the trigeminal ganglion, both of which are likely sites of action for therapeutic antibodies in migraine patients. We further used one of these antibodies for detailed mapping on cynomolgus monkey tissue and found antagonist antibody binding sites at multiple levels in the trigeminovascular system: in the dura mater VSMCs, in neurons and satellite glial cells in the trigeminal ganglion, and in neurons in the spinal trigeminal nucleus caudalis. These data reinforce and clarify our understanding of CGRP receptor localization in a pattern consistent with a role for CGRP receptors in trigeminal sensitization and migraine pathology.

Pharmacologic Characterization of AMG 334, a Potent and Selective Human Monoclonal Antibody against the Calcitonin Gene-Related Peptide Receptor.

Therapeutic agents that block the calcitonin gene-related peptide (CGRP) signaling pathway are a highly anticipated and promising new drug class for migraine therapy, especially after reports that small-molecule CGRP-receptor antagonists are efficacious for both acute migraine treatment and migraine prevention. Using XenoMouse technology, we successfully generated AMG 334, a fully human monoclonal antibody against the CGRP receptor. Here we show that AMG 334 competes with [(125)I]-CGRP binding to the human CGRP receptor, with a Ki of 0.02 nM. AMG 334 fully inhibited CGRP-stimulated cAMP production with an IC50 of 2.3 nM in cell-based functional assays (human CGRP receptor) and was 5000-fold more selective for the CGRP receptor than other human calcitonin family receptors, including adrenomedullin, calcitonin, and amylin receptors. The potency of AMG 334 at the cynomolgus monkey (cyno) CGRP receptor was similar to that at the human receptor, with an IC50 of 5.7 nM, but its potency at dog, rabbit, and rat receptors was significantly reduced (>5000-fold). Therefore, in vivo target coverage of AMG 334 was assessed in cynos using the capsaicin-induced increase in dermal blood flow model. AMG 334 dose-dependently prevented capsaicin-induced increases in dermal blood flow on days 2 and 4 postdosing. These results indicate AMG 334 is a potent, selective, full antagonist of the CGRP receptor and show in vivo dose-dependent target coverage in cynos. AMG 334 is currently in clinical development for the prevention of migraine.

Peptide antagonists of the calcitonin gene-related peptide (CGRP) receptor with improved pharmacokinetics and pharmacodynamics.

Antagonism of the calcitonin gene-related peptide (CGRP) receptor may be a useful approach for migraine treatment. Selective PEGylated peptide antagonists to the CGRP receptor are described, derived from CGRP(8-37) with polymer derivatization at an engineered lysine-25 residue. Potent PEGylated peptides with improved pharmacokinetics were identified through peptide side-chain modification to mitigate metabolic liabilities. PEGylated Ac-Trp-[Cit(11,18),hArg(24),Lys(25),Asp(31),Pro(34),1-Nal(35)]CGRP(8-37)-NH2, 9, elicits a dose-dependent reduction of intradermal CGRP-induced local blood flow in rodents with an ED50 of 0.52 mg kg(-1) without any overt adverse effects.

Identification of potent, selective, and metabolically stable peptide antagonists to the calcitonin gene-related peptide (CGRP) receptor.

Calcitonin gene-related peptide (CGRP) is a 37-residue neuropeptide that can be converted to a CGRP(1) receptor antagonist by the truncation of its first seven residues. CGRP(8-37), 1, has a CGRP(1) receptor K(i) = 3.2 nM but is rapidly degraded in human plasma (t(1/2) = 20 min). As part of an effort to identify a prolonged in vivo circulating CGRP peptide antagonist, we found that the substitution of multiple residues in the CGRP peptide increased CGRP(1) receptor affinity >50-fold. Ac-Trp-[Arg(24),Lys(25),Asp(31),Pro(34),Phe(35)]CGRP(8-37)-NH(2), 5 (K(i) = 0.06 nM) had the highest CGRP(1) receptor affinity. Using complimentary in vitro and in vivo metabolic studies, we iteratively identified degradation sites and prepared high affinity analogues with significantly improved plasma stability. Ac-Trp-[Cit(11,18),hArg(24),Lys(25),2-Nal(27,37),Asp(31),Oic(29,34),Phe(35)]CGRP(8-37)-NH(2), 32 (K(i) = 3.3 nM), had significantly increased (>100-fold) stability over 1 or 5, with a cynomolgus monkey and human in vitro plasma half-life of 38 and 68 h, respectively.

Repeated administration of vanilloid receptor TRPV1 antagonists attenuates hyperthermia elicited by TRPV1 blockade.

Capsaicin, the active ingredient in some pain-relieving creams, is an agonist of a nonselective cation channel known as the transient receptor potential vanilloid type 1 (TRPV1). The pain-relieving mechanism of capsaicin includes desensitization of the channel, suggesting that TRPV1 antagonism may be a viable pain therapy approach. In agreement with the above notion, several TRPV1 antagonists have been reported to act as antihyperalgesics. Here, we report the in vitro and in vivo characterization of a novel and selective TRPV1 antagonist, N-(4-[6-(4-trifluoromethyl-phenyl)-pyrimidin-4-yloxy]-benzothiazol-2-yl)-acetamide I (AMG 517), and compare its pharmacology with that of a closely related analog, tert-butyl-2-(6-([2-(acetylamino)-1,3-benzothiazol-4-yl]oxy)pyrimidin-4-yl)-5-(trifluoromethyl)phenylcarbamate (AMG8163). Both AMG 517 and AMG8163 potently and completely antagonized capsaicin, proton, and heat activation of TRPV1 in vitro and blocked capsaicin-induced flinch in rats in vivo. To support initial clinical investigations, AMG 517 was evaluated in a comprehensive panel of toxicology studies that included in vivo assessments in rodents, dogs, and monkeys. The toxicology studies indicated that AMG 517 was generally well tolerated; however, transient increases in body temperature (hyperthermia) were observed in all species after AMG 517 dosing. To further investigate this effect, we tested and showed that the antipyretic, acetaminophen, suppressed the hyperthermia caused by TRPV1 blockade. We also showed that repeated administration of TRPV1 antagonists attenuated the hyperthermia response, whereas the efficacy in capsaicin-induced flinch model was maintained. In conclusion, these studies suggest that the transient hyperthermia elicited by TRPV1 blockade may be manageable in the development of TRPV1 antagonists as therapeutic agents. However, the impact of TRPV1 antagonist-induced hyperthermia on their clinical utility is still unknown.

Molecular determinants of vanilloid sensitivity in TRPV1.

Vanilloid receptor 1 (TRPV1), a membrane-associated cation channel, is activated by the pungent vanilloid from chili peppers, capsaicin, and the ultra potent vanilloid from Euphorbia resinifera, resiniferatoxin (RTX), as well as by physical stimuli (heat and protons) and proposed endogenous ligands (anandamide, N-arachidonyldopamine, N-oleoyldopamine, and products of lipoxygenase). Only limited information is available in TRPV1 on the residues that contribute to vanilloid activation. Interestingly, rabbits have been suggested to be insensitive to capsaicin and have been shown to lack detectable [(3)H]RTX binding in membranes prepared from their dorsal root ganglia. We have cloned rabbit TRPV1 (oTRPV1) and report that it exhibits high homology to rat and human TRPV1. Like its mammalian orthologs, oTRPV1 is selectively expressed in sensory neurons and is sensitive to protons and heat activation but is 100-fold less sensitive to vanilloid activation than either rat or human. Here we identify key residues (Met(547) and Thr(550)) in transmembrane regions 3 and 4 (TM3/4) of rat and human TRPV1 that confer vanilloid sensitivity, [(3)H]RTX binding and competitive antagonist binding to rabbit TRPV1. We also show that these residues differentially affect ligand recognition as well as the assays of functional response versus ligand binding. Furthermore, these residues account for the reported pharmacological differences of RTX, PPAHV (phorbol 12-phenyl-acetate 13-acetate 20-homovanillate) and capsazepine between human and rat TRPV1. Based on our data we propose a model of the TM3/4 region of TRPV1 bound to capsaicin or RTX that may aid in the development of potent TRPV1 antagonists with utility in the treatment of sensory disorders.