Search

Control of chronic pain is frequently inadequate and/or associated with intolerable adverse effects, prompting a frantic search for new therapeutics and new therapeutic targets. Nearly two decades of preclinical and clinical research supports the involvement of http://www.guidetopharmacology.org/GRAC/FamilyDisplayForward?familyId=78 in temperature perception, nociception and sensitization. Although there has been considerable excitement around the therapeutic potential of this channel family since the cloning and identification of http://www.guidetopharmacology.org/GRAC/ObjectDisplayForward?objectId=507 cation channels as the http://www.guidetopharmacology.org/GRAC/LigandDisplayForward?ligandId=2486 receptor more than 20 years ago, only modulators of a few channels have been tested clinically. TRPV1 channel antagonists have suffered from side effects related to the channel's role in temperature sensation; however, high dose formulations of capsaicin have reached the market and shown therapeutic utility. A number of potent, small molecule antagonists of http://www.guidetopharmacology.org/GRAC/ObjectDisplayForward?objectId=485 channels have recently advanced into clinical trials for the treatment of inflammatory and neuropathic pain, and http://www.guidetopharmacology.org/GRAC/ObjectDisplayForward?objectId=500 antagonists are following closely behind for cold allodynia. http://www.guidetopharmacology.org/GRAC/ObjectDisplayForward?objectId=509, http://www.guidetopharmacology.org/GRAC/ObjectDisplayForward?objectId=510, http://www.guidetopharmacology.org/GRAC/ObjectDisplayForward?objectId=494 and http://www.guidetopharmacology.org/GRAC/ObjectDisplayForward?objectId=495 channels have also been of significant interest. This review discusses the preclinical promise and status of novel analgesic agents that target TRP channels and the challenges that these compounds may face in development and clinical practice.

Background Breast cancer 2 (BRCA2)-associated breast and ovarian cancers are sensitive to platinum-based chemotherapy. It is unknown whether BRCA2-associated prostate cancer responds favorably to such treatment. Methods A retrospective analysis of a single-institution cohort of men with castration-resistant, metastatic prostate cancer was performed to determine the association between carrier status of pathogenic BRCA2 germline variants and prostate-specific antigen response to carboplatin-based chemotherapy. From 2001 through 2015, 8081 adult men with prostate cancer who had a consultation and/or underwent treatment at Dana-Farber Cancer Institute provided blood samples and consented to analyses of biologic material and clinical records. A subgroup of 141 men received at least 2 doses of carboplatin and docetaxel for castration-resistant disease (94% were also taxane refractory). These patients were categorized according to the absence or presence of pathogenic germline mutations in BRCA2 based on DNA sequencing from whole blood. The primary outcome was the response rate to carboplatin/docetaxel chemotherapy, defined according to a decline in prostate-specific antigen that exceeded 50% within 12 weeks of initiating this regimen. Associations between BRCA2 mutation status and response to carboplatin-based chemotherapy were tested using the Fisher exact test, with a 2-sided P value Results Pathogenic germline BRCA2 variants were observed in 8 of 141 men (5.7%; 95% confidence interval, 2.5%-10.9%). Six of 8 BRCA2 carriers (75%) experienced prostate-specific antigen declines >50% within 12 weeks, compared with 23 of 133 noncarriers (17%; absolute difference, 58%; 95% confidence interval, 27%-88%; P Conclusions BRCA2-associated, castration-resistant prostate cancer is associated with a higher likelihood of response to carboplatin-based chemotherapy than non-BRCA2-associated prostate cancer. Cancer 2017;123:3532-9. © 2017 American Cancer Society.

Transient receptor potential (TRP) channels are important mediators of sensory signals with marked effects on cellular functions and signalling pathways. Indeed, mutations in genes encoding TRP channels are the cause of several inherited diseases in humans (the so-called 'TRP channelopathies') that affect the cardiovascular, renal, skeletal and nervous systems. TRP channels are also promising targets for drug discovery. The initial focus of research was on TRP channels that are expressed on nociceptive neurons. Indeed, a number of potent, small-molecule TRPV1, TRPV3 and TRPA1 antagonists have already entered clinical trials as novel analgesic agents. There has been a recent upsurge in the amount of work that expands TRP channel drug discovery efforts into new disease areas such as asthma, cancer, anxiety, cardiac hypertrophy, as well as obesity and metabolic disorders. A better understanding of TRP channel functions in health and disease should lead to the discovery of first-in-class drugs for these intractable diseases. With this review, we hope to capture the current state of this rapidly expanding and changing field.

Chromosomal instability (CIN) has been implicated in multidrug resistance and the silencing of the ceramide transporter, CERT, promotes sensitization to diverse cytotoxics. An improved understanding of mechanisms governing multidrug sensitization might provide insight into pathways contributing to the death of CIN cancer cells. Using an integrative functional genomics approach, we find that CERT‐specific multidrug sensitization is associated with enhanced autophagosome–lysosome flux, resulting from the expression of LAMP2 following CERT silencing in colorectal and HER2+ breast cancer cell lines. Live cell microscopy analysis revealed that CERT depletion induces LAMP2‐dependent death of polyploid cells following exit from mitosis in the presence of paclitaxel. We find that CERT is relatively over‐expressed in HER2+ breast cancer and CERT protein expression acts as an independent prognostic variable and predictor of outcome in adjuvant chemotherapy‐treated patients with primary breast cancer. These data suggest that the induction of LAMP2‐dependent autophagic flux through CERT targeting may provide a rational approach to enhance multidrug sensitization and potentiate the death of polyploid cells following paclitaxel exposure to limit the acquisition of CIN and intra‐tumour heterogeneity. Copyright © 2011 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Background and objectives This study was performed to determine the incidence of 'wrong blood in tube' (WBIT)-type errors at our institution during the past 5 years, to analyse their root cause and to evaluate the efficacy of preventive measures that have been implemented since 2006. Methods All reports of mislabelled and miscollected specimens detected between January 2005 and December 2009 were reviewed. Of these, WBIT-type errors were further analysed as they represent a major risk for mistransfusion. Results Between 2005 and 2009, 59,373 type and screens were performed at our institution and a total of 26 major errors (WBIT) were identified. Of the errors, eight were detected by discrepant typing results (in comparison with historic blood type), six were discovered by the clinical service and 12 were identified in the blood bank by other means. Our estimated 'raw' WBIT rate (1 in 2283 samples) is comparable to that (1:2262) in the published literature. Since 2006, our nursing policy mandates that 'all type, screen and cross will have two witnesses to the correct ID of the patient and labeling is done at the bedside at the time of the draw.' This has reduced (from 11 in 2006 to 5 in 2007), but did not eliminate, our WBIT problem that persisted into 2008 and 2009 (three and seven incidents, respectively). Since 2009, we also require a second, independently drawn sample in previously un-typed patients who are likely to be transfused. Conclusion We conclude that WBITs continue to represent a leading cause of potential mistransfusions at our institution. Changes in nursing (two witnesses to correct ID) and/or blood bank policy (check-type with a second specimen) may reduce, but not eliminate, this persistent problem. Clearly, additional safety measures are required to prevent WBIT-type errors.

Chromosomal instability (CIN) is a common cause of tumour heterogeneity and poor prognosis in solid tumours and describes cell-cell variation in chromosome structure or number across a tumour population. In this article we consider evidence suggesting that CIN may be targeted and may influence response to distinct chemotherapy regimens, using HER2-positive breast cancer as an example. Pre-clinical models have indicated a role for HER2 signalling in initiating CIN and defective cell-cycle control, and evidence suggests that HER2-targeting may attenuate this process. Anthracyclines and platinum agents may target tumours with distinct patterns of karyotypic complexity, whereas taxanes may have preferential activity in tumours with relative chromosomal stability. A greater understanding of karyotypic complexity and identification of methods to directly examine and target CIN may support novel strategies to improve outcome in cancer.

In peripheral sensory neurons, the vanilloid receptor TRPV1 (transient receptor potential vanilloid subfamily, member 1) functions as a molecular integrator of painful stimuli, including those mediated by capsaicin, acid, and heat. Antagonist blockade of TRPV1 activation is under investigation by several pharmaceutical companies in an effort to identify novel agents for pain management. TRPV1 is also expressed, albeit at lower levels, in the brain and in non-neuronal tissues, where its function(s) remains elusive. The contribution of TRPV1 receptor activity to physiological reflexes and disease states is complex and is only beginning to be understood. Consequently, the resultant effects of TRPV1 antagonists on the body may be unforeseen. Indeed, clinical trials with a number of TRPV1 antagonists were recently terminated due to their marked hyperthermic activity. In this review article, the medicinal chemistry of TRPV1 antagonists is discussed inasmuch as it relates to the efficacy, safety, tolerability and potential side effects of these compounds. In addition, the available information on the current status of the clinical trials with TRPV1 antagonists is summarized. Drug Dev Res 68:477–497, 2007. © 2008 Wiley-Liss, Inc.

Phorboid 20-homovanillates modified on ring C to mimic the constitution and conformation of the ultrapotent vanilloid resiniferatoxin (RTX) and on the AB ring system to suppress the tumour-promoting potential of the terpenoid core were prepared. Several unexpected reactions were discovered, and the structure-activity relationships for this class of vanilloid ligands were expanded. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

There is mounting evidence that the vanilloid (capsaicin) receptor; transient receptor potential channel, vanilloid subfamily member 1 (TRPV1), is subjected to multiple interacting levels of control. The first level is by reversible phosphorylation catalyzed by intrinsic kinases (e.g. protein kinase A and C) and phosphatases (e.g. calcineurin), which plays a pivotal role in receptor sensitization vs. tachyphylaxis. In addition, this mechanism links TRPV1 to intracellular signaling by various important endogenous as well as exogenous substances such as bradykinin, ethanol, nicotin and insulin. It is not clear, however, whether phosphorylation per se is sufficient to liberate TRPV1 under the inhibitory control of phosphatydylinositol-4,5-bisphosphate. The second level of control is by forming TRPV1 heteromers and their association with putative regulatory proteins. The next level of regulation is by subcellular compartmentalization. The membrane form of TRPV1 functions as a nonselective cation channel. On the endoplasmic reticulum, TRPV1 is present in two differentially regulated forms, one of which is inositol triphosphate-dependent whereas the other is not. These three TRPV1 compartments provide a versatile regulation of intracellular Ca(2+) levels. Last, there is a complex and poorly understood regulation of TRPV1 activity via control of gene expression. Factors that downregulate TRPV1 expression include vanilloid treatment and growth factor (notably, nerve growth factor) deprivation. By contrast, TRPV1 appears to be upregulated during inflammatory conditions. Interestingly, following experimental nerve injury and in animal models of diabetic neuropathy TRPV1 is present on neurons that do not normally express TRPV1. Combined, these findings imply an important role for aberrant TRPV1 expression in the development of neuropathic pain and hyperalgesia. In humans, disease-related changes in TRPV1 expression have already been described (e.g. inflammatory bowel disease and irritable bowel syndrome). The mechanisms that regulate TRPV1 gene expression under pathological conditions are unknown but a better understanding of these pathways has obvious implications for rational drug development.

In the present study, the effects of the novel vanilloid agonist, 12-phenylacetate 13-acetate 20-homovanillate (PPAHV), on oxygen consumption (VO2) and vascular resistance (perfusion pressure, PP) were investigated in the constant flow, perfused rat hindlimb. The acute desensitizing properties of this novel synthetic agent were also examined. Maximum stimulation of VO2 was produced by 0.2 μM PPAHV (ΔVO2, 0.83±0.06 μmol g−1 h−1) and was accompanied by mild vasoconstriction (increase in PP; 8.0±1.1 mmHg). The highest concentration of PPAHV tested (2 μM) caused inhibition of VO2 (ΔVO2, −2.73±0.51 μmol g−1 h−1) and strong vasoconstriction (ΔPP, 42.0±1.2 mmHg). Capsazepine (10 μM) caused a parallel shift to the right of both VO2 and PP concentration-response curves for PPAHV (pKb=5.00), indicative of competitive binding to vanilloid receptors. The stimulation of VO2 produced by 0.2 μM PPAHV decreased, but was not completely abolished, after repeated infusion of PPAHV (change in VO2, first infusion, 0.66±0.18 μmol g−1 h−1; sixth infusion, 0.29±0.08 μmol g−1 h−1, P

1 Although the cloned rat vanilloid receptor VR1 appears to account for both receptor binding and calcium uptake, the identification of vanilloids selective for one or the other response is of importance because these ligands may induce distinct patterns of biological activities. 2 Phorbol 12,13-didecanoate 20-homovanillate (PDDHV) evoked 45Ca(2+)-uptake by rat dorsal root ganglion neurons (expressing native vanilloid receptors) in culture with an EC50 of 70 nM but inhibited [3H]-resiniferatoxin (RTX) binding to rat dorsal root ganglion membranes with a much lower potency (Ki>10,000 nM). This difference in potencies represents a more than 100 fold selectivity for capsaicin-type pharmacology. 3 45Ca2+ influx by PDDHV was fully inhibited by the competitive vanilloid receptor antagonist capsazepine, consistent with the calcium uptake occurring via vanilloid receptors. 4 PDDHV induced calcium mobilization in CHO cells transfected with the cloned rat vanilloid receptor VR1 with an EC50 of 125 nM and inhibited [3H]-RTX binding to these cells with an estimated Ki of 10,000 nM. By contrast, PDDHV failed to evoke a measurable calcium response in non-transfected CHO cells, confirming its action through VR1. 5 We conclude that PDDHV is two orders of magnitude more potent for inducing calcium uptake than for inhibiting RTX binding at vanilloid receptors, making this novel vanilloid a ligand selective for capsaicin-type pharmacology. These results emphasize the importance of monitoring multiple endpoints for evaluation of vanilloid receptor structure-activity relations. Furthermore, PDDHV now provides a tool to explore the biological correlates of capsaicin-type vanilloid pharmacology.

A [3H]-resiniferatoxin (RTX) binding assay utilizing rat spinal cord membranes was employed to identify novel vanilloids in a collection of natural products of fungal origin. Of the five active compounds found (scutigeral, acetyl-scutigeral, ovinal, neogrifolin, and methyl-neogrifolin), scutigeral (Ki=19 μM), isolated from the edible mushroom Albatrellus ovinus, was selected for further characterization. Scutigeral induced a dose-dependent 45Ca uptake by rat dorsal root ganglion neurons with an EC50 of 1.6 μM, which was fully inhibited by the competitive vanilloid receptor antagonist capsazepine (IC50=5.2 μM). [3H]-RTX binding isotherms were shifted by scutigeral (10–80 μM) in a competitive manner. The Schild plot of the data had a slope of 0.8 and gave an apparent Kd estimate for scutigeral of 32 μM. Although in the above assays scutigeral mimicked capsaicin, it was not pungent on the human tongue up to a dose of 100 nmol per tongue, nor did it provoke protective wiping movements in the rat (up to 100 μM) upon intraocular instillation. In accord with being non-pungent, scutigeral (5 μM) did not elicit a measurable inward current in isolated rat dorsal root ganglion neurons under voltage-clamp conditions. It did, however, reduce the proportion of neurons (from 61 to 15%) that responded to a subsequent capsaicin (1 μM) challenge. In these neurons, scutigeral both delayed (from 27 to 72 s) and diminished (from 5.0 to 1.9 nA) the maximal current evoked by capsaicin. In conclusion, scutigeral and its congeners form a new chemical class of vanilloids, the triprenyl phenols. Scutigeral promises to be a novel chemical lead for the development of orally active, non-pungent vanilloids. British Journal of Pharmacology (1999) 126, 1351–1358; doi:10.1038/sj.bjp.0702440

The synthetic cannabinoid CB1 receptor antagonist rimonabant (sold in the United Kingdom under the brand name Acomplia) was reported to improve the profile of cardiovascular risk factors in obese patients with the metabolic syndrome, a cluster of metabolic disorders that often precedes the onset of type II diabetes. Rimonabant is shown in the current issue of British Journal of Pharmacology to attenuate weight gain in Zucker rats, an experimental model of insulin resistance. Neutrophil and monocyte counts were lowered by rimonabant administration. Both platelet activation (by ADP) and aggregation (in response to thrombin) were inhibited. Circulating pro-inflammatory cytokine levels (monocyte chemotactic protein 1, MCP1 and Regulated upon Activation, Normal T-cell Expressed and Secreted, RANTES) were also reduced. Furthermore, fibrinogen levels returned to normal. These favourable anti-inflammatory and anti-thrombotic actions imply for rimonabant a peripheral, direct action on some cardiovascular risk factors.

1. The irritant fungal terpenoid isovelleral caused protective eye-wiping movements in the rat upon intraocular instillation and showed cross-tachyphylaxis with capsaicin, the pungent principle in hot pepper. 2. Isovelleral induced a dose-dependent calcium uptake by rat dorsal root ganglion neurones cultured in vitro with an EC50 of 95 nM, which was fully inhibited by the competitive vanilloid receptor antagonist capsazepine. 3. Isovelleral inhibited specific binding of [3H]-resiniferatoxin (RTX), an ultrapotent capsaicin analogue, to rat trigeminal ganglion or spinal cord preparations with an IC50 of 5.2 microM; in experiments in which the concentration of [3H]-RTX was varied, isovelleral changed both the apparent affinity (from 16 pM to 37 pM) and the co-operativity index (from 2.1 to 1.5), but not the Bmax. 4. The affinity of isovelleral for inducing calcium uptake or inhibiting RTX binding was in very good agreement with the threshold dose (2.2. nmol) at which it provoked pungency on the human tongue. 5. For a series of 14 terpenoids with an unsaturated 1,4-dialdehyde, a good correlation was found between pungency on the human tongue and affinity for vanilloid receptors on the rat spinal cord. 6. The results suggest that isovelleral-like compounds produce their irritant effect by interacting with vanilloid receptors on capsaicin-sensitive sensory neurones. Since these pungent diterpenes are structurally distinct from the known classes of vanilloids, these data provide new insights into structure-activity relations and may afford new opportunities for the development of drugs targeting capsaicin-sensitive pathways.

1. The potential role of capsaicin-sensitive nerves in the relaxation of the rat external urethral sphincter (REUS) was evaluated by demonstrating the existence of specific vanilloid (capsaicin) receptors and by investigating the sensory neurotransmitter(s) putatively involved in this relaxation. 2. Capsaicin (1 microM) relaxed REUS strips precontracted with noradrenaline (NA) (0.1 mM). This effect underwent desensitization and it was absent in preparations taken from adult capsaicin-pretreated rats. 3. Capsaicin-induced relaxation of NA-precontracted REUS was mimicked by calcitonin gene-related peptide (CGRP, 0.3-10 microM), but not by substance P (1 microM), vasoactive intestinal polypeptide (VIP, 1 microM), alpha-beta methylene ATP (10 microM), gamma-aminobutyric acid (GABA, 3 mM) or galanin (1 microM). A cross-tachyphylaxis between capsaicin (1 microM) and CGRP (1 microM) was observed. Both capsaicin and CGRP-induced relaxation were partially antagonized by the proposed CGRP antagonist, CGRP (8-37) (10 microM). 4. Electrical field stimulation (EFS, 2.5 Hz, 60 V, 1 ms, trains of 5 s every 5 min) of REUS evoked a contraction characterized by a largely adrenergic slowly developing tonic contraction with superimposed fast twitches due to the striated component of the strips. Both capsaicin (1 microM) and CGRP (0.01-1 microM) produced an almost complete inhibition of EFS-induced tonic contraction. A cross-tachyphylaxis between capsaicin and CGRP was observed. Furthermore, these inhibitory actions were unaffected by CGRP (8-37) (10 microM). 5. [3H]-resiniferatoxin displayed specific, saturable binding to rat urethral membranes. Data were consistent with a single site with a Kd of 105 pM and a Bmax of 40 fmol mg-1 protein. This binding was inhibited by capsaicin with a Ki of 0.6 microM and it was reduced by approximately 80% in preparations taken from rats that had undergone surgical ablation of the major pelvic ganglion 4 days earlier.6. In conclusion we have demonstrated the existence of vanilloid receptors on capsaicin-sensitive nerves innervating the rat urethra mainly through the major pelvic ganglion. The activation of this set of nerves could lead to a local release of CGRP that in turn elicits a remarkable urethral relaxation. Such a mechanism could be of relevance in physiological conditions to facilitate urine expulsion during micturition and in pathological conditions to help removal of noxious stimuli following mechanical/chemical irritation of the lower urinary tract.

The cover picture showsEuphorbia resinifera Berg and its constituent resiniferatoxin (RTX), a phorboid that acts as an ultrapotent biological analogue of capsaicin, the hot principle of chili pepper and the archetypal vanilloid. Ever since its isolation, interest within the organic community for phorbol has been high on account of its challenging structure, puzzling reactivity, and remarkable bioactivity. Diacyl derivatives of phorbol can act as ultrapotent analogues of the endolipid sn-1,2-diacylglycerol (DAG) and show powerful tumour-promoting properties. The more recent discovery that certain non-tumour-promoting phorbol derivatives and phorbol-related compounds can activate vanilloid receptors of the TRPV1 and TRPV4 type has made phorbol very interesting also for neurosciences. The article by G. Appendino et al. on p. 3413 ff. describes the synthesis of hybrid phorbol-resiniferatoxin of interest for the study of vanilloid receptors, which discloses some new and unpredictable aspects of the chemistry of phorbol. (Photo courtesy by Prof. Mauro Ballero, University of Cagliari)

Resiniferatoxin (RTX), unlike the structurally related phorbol esters, acts as an ultrapotent analog of capsaicin, the pungent principle of the red pepper. A homovanillyl group is an essential structural feature of capsaicin and the most prominent feature distinguishing resiniferatoxin from typical phorbol-related compounds. In this report, we examine the RTX-like activity of two 20-homovanillyl esters of diterpene derivatives with particular similarities to RTX. The potency of 12-deoxyphorbol 13-phenylacetate 20-homovanillate (dPP-HV) was comparable to RTX for local induction and desensitization of chemical pain but was 2–4 orders of magnitude less potent for the other RTX responses tested (stimulation and desensitization of neurogenic inflammation and hypothermia). Mezerein 20-homovanillate (Mez-HV) displayed very weak activity in pain induction and was inactive in the other assays. The parent derivatives - resiniferonol orthophenylacetate, 12-deoxyphorbol 13-phenylacetate and mezerein - were inactive in inducing RTX-like effects. Reciprocally, the presence of the 20-homovanillate ester reduced binding affinities to protein kinase C by 11-, 130- and 690-fold for RTX, dPP-HV and Mez-HV, respectively. Our findings provide further evidence for heterogeneity among capsaicin-sensitive pathways. Most significantly, our results demonstrate that esterincation of phorbol-related diterpenes with homovanillic acid can yield capsaicin analogs with unique activities.

The effects of methotrexate (MTX) and N-phosphonacetyl L-aspartate (PALA) with and without 12-O-tetradecanoyl-phorbol-13-acetate (TPA) have been tested on the cell-cycle traverse of mouse 3T6 and Chinese hamster V79 cell lines. MTX, whether administered with or without TPA, had very little effect on the cell cycle of the V79 Chinese hamster cell line. However, low MTX concentrations produced a significant G1 accumulation in the mouse 3T6 cell line after 24 hr, and this was accentuated by TPA treatment. These findings parallel previous observations that TPA enhances the recovery of MTX- and PALA-resistant mouse 3T6 cell clones but has little or no effect on drug-resistant colony recovery in the V79 Chinese hamster cell line. The possibility that the increase in accumulation of cells in G1 might permit the rescue of an increased proportion of cells due to the release of purines and pyrimidines from dying cells is discussed. Such rescue should occur irrespective of whether or not the cell line has the ability to amplify its target genes.