Dynamic remodeling of TRPC5 channel-caveolin-1-eNOS protein assembly potentiates the positive feedback interaction between Ca2+ and NO signals

The cell signaling molecules nitric oxide (NO) and Ca2+ regulate diverse biological processes through their closely coordinated activities directed by signaling protein complexes. However, it remains unclear how dynamically the multi-component protein assemblies behave within the signaling complexes upon the interplay between NO and Ca2+ signals. Here we demonstrate that TRPC5 channels activated by stimulation of G-protein-coupled ATP receptors mediate Ca2+ influx, that triggers NO production from endothelial NO synthase (eNOS), inducing secondary activation of TRPC5 via cysteine S-nitrosylation and eNOS in vascular endothelial cells. Mutations in the caveolin-1-binding domains of TRPC5 disrupt its association with caveolin-1 and impair Ca2+ influx and NO production, suggesting that caveolin-1 serves primarily as the scaffold for TRPC5 and eNOS to assemble into the signal complex. Interestingly, during ATP receptor activation, eNOS is dissociated from caveolin-1 and in turn directly associates with TRPC5, which accumulates at the plasma membrane dependently on Ca2+ influx and calmodulin (CaM). This protein reassembly likely results in a relief of eNOS from the inhibitory action of caveolin-1 and an enhanced TRPC5 S-nitrosylation by eNOS localized in the proximity, thereby facilitating the secondary activation of Ca2+ influx and NO production. In isolated rat aorta, vasodilation induced by acetylcholine was significantly suppressed by the TRPC5 inhibitor AC1903. Thus, our study provides evidence that dynamic remodeling of the protein assemblies among TRPC5, eNOS, caveolin-1, and CaM determines the ensemble of Ca2+ mobilization and NO production in vascular endothelial cells.

Transient receptor potential ankyrin 1 (TRPA1) modulators: Recent update and future perspective

The transient receptor potential ankyrin 1 (TRPA1) channel is a non-selective cation channel that senses irritant chemicals. Its activation is closely associated with pain, inflammation, and pruritus. TRPA1 antagonists are promising treatments for these diseases, and there has been a recent upsurge in their application to new areas such as cancer, asthma, and Alzheimer's disease. However, due to the generally disappointing performance of TRPA1 antagonists in clinical studies, scientists must pursue the development of antagonists with higher selectivity, metabolic stability, and solubility. Moreover, TRPA1 agonists provide a deeper understanding of activation mechanisms and aid in antagonist screening. Therefore, we summarize the TRPA1 antagonists and agonists developed in recent years, with a particular focus on structure-activity relationships (SARs) and pharmacological activity. In this perspective, we endeavor to keep abreast of cutting-edge ideas and provide inspiration for the development of more effective TRPA1-modulating drugs.

窒素原子を含む結合活性化学種の発見

In this review, the authors review and explain their research on "Discovery of Bonding Active Species Containing Nitrogen Atoms" from the past to the present. The authors are interested in new chemical phenomena, especially in the activation of chemical bonds containing nitrogen atoms, and have conducted research to discover chemical bonds with new properties. The activated chemical bonds containing nitrogen atoms are the following (Fig. 1). (1) Rotationally activated C-N bonds by pyramidalization of amide nitrogen atoms (2) N-N bond cleavage ability with reduced bond strength by pyramidalization of nitrosamine nitrogen atoms (3) Transient hetero atom-N bond formation by neighboring group participation of a halogen electron to the nitrogen cation. (4) A unique carbon cation reaction involving nitrogen atoms, especially nitro groups (C-NO₂ bond) and ammonium ions (C-NH₃⁺ bond). These purely basic chemistry discoveries unexpectedly led to the creation of functional materials, especially biologically active molecules. We will explain how new chemical bonds led to the creation of new functions.

The role of PPARγ in chemotherapy-evoked pain

Although millions of people are diagnosed with cancer each year, survival has never been greater thanks to early diagnosis and treatments. Powerful chemotherapeutic agents are highly toxic to cancer cells, but because they typically do not target cancer cells selectively, they are often toxic to other cells and produce a variety of side effects. In particular, many common chemotherapies damage the peripheral nervous system and produce neuropathy that includes a progressive degeneration of peripheral nerve fibers. Chemotherapy-induced peripheral neuropathy (CIPN) can affect all nerve fibers, but sensory neuropathies are the most common, initially affecting the distal extremities. Symptoms include impaired tactile sensitivity, tingling, numbness, paraesthesia, dysesthesia, and pain. Since neuropathic pain is difficult to manage, and because degenerated nerve fibers may not grow back and regain normal function, considerable research has focused on understanding how chemotherapy causes painful CIPN so it can be prevented. Due to the fact that both therapeutic and side effects of chemotherapy are primarily associated with the accumulation of reactive oxygen species (ROS) and oxidative stress, this review focuses on the activation of endogenous antioxidant pathways, especially PPARγ, in order to prevent the development of CIPN and associated pain. The use of synthetic and natural PPARγ agonists to prevent CIPN is discussed.

Elaboration of Non-naturally Occurring Helical Tripeptides as p53-MDM2/MDMX Interaction Inhibitors

Protein-protein interactions (PPIs) are often mediated by helical, strand and/or coil secondary structures at the interface regions. We previously showed that non-naturally occurring, stable helical trimers of bicyclic β-amino acids (Abh) with all-trans amide bonds can block the p53-MDM2/MDMX α-helix-helix interaction, which plays a role in regulating p53 function. Here, we conducted docking and molecular dynamics calculations to guide the structural optimization of our reported compounds, focusing on modifications of the C-terminal/N-terminal residues. We confirmed that the modified peptides directly bind to MDM2 by means of thermal shift assay, isothermal titration calorimetry, and enzyme-linked immunosorbent assay (ELISA) experiments. Biological activity assay in human osteosarcoma cell line SJSA-1, which has wild-type p53 and amplification of the Mdm2 gene, indicated that these peptides are membrane-permeable p53-MDM2/MDMX interaction antagonists that can rescue p53 function in the cells.

Cross-talk between the calcium channel TRPV4 and reactive oxygen species interlocks adhesive and degradative functions of invadosomes

Invadosomes support cell invasion by coupling both acto-adhesive and extracellular matrix degradative functions, which are apparently antagonistic. β1-integrin dynamics regulate this coupling, but the actual sensing mechanism and effectors involved have not yet been elucidated. Using genetic and reverse genetic approaches combined with biochemical and imaging techniques, we now show that the calcium channel TRPV4 colocalizes with β1-integrins at the invadosome periphery and regulates its activation and the coupling of acto-adhesive and degradative functions. TRPV4-mediated regulation of podosome function depends on its ability to sense reactive oxygen species (ROS) in invadosomes' microenvironment and involves activation of the ROS/calcium-sensitive kinase Ask1 and binding of the motor MYO1C. Furthermore, disease-associated TRPV4 gain-of-function mutations that modulate ECM degradation are also implicated in the ROS response, which provides new perspectives in our understanding of the pathophysiology of TRPV4 channelopathies.

TRPA1 and TRPV1 channels participate in atmospheric-pressure plasma-induced [Ca2+]i response

Despite successful clinical application of non-equilibrium atmospheric pressure plasma (APP), the details of the molecular mechanisms underlying APP-inducible biological responses remain ill-defined. We previously reported that exposure of 3T3L1 cells to APP-irradiated buffer raised the cytoplasmic free Ca²⁺ ([Ca²⁺]_i) concentration by eliciting Ca²⁺ influx in a manner sensitive to transient receptor potential (TRP) channel inhibitors. However, the precise identity of the APP-responsive channel molecule(s) remains unclear. In the present study, we aimed to clarify channel molecule(s) responsible for indirect APP-responsive [Ca²⁺]_i rises. siRNA-mediated silencing experiments revealed that TRPA1 and TRPV1 serve as the major APP-responsive Ca²⁺ channels in 3T3L1 cells. Conversely, ectopic expression of either TRPA1 or TRPV1 in APP-unresponsive C2C12 cells actually triggered [Ca²⁺]_i elevation in response to indirect APP exposure. Desensitization experiments using 3T3L1 cells revealed APP responsiveness to be markedly suppressed after pretreatment with allyl isothiocyanate or capsaicin, TRPA1 and TRPV1 agonists, respectively. APP exposure also desensitized the cells to these chemical agonists, indicating the existence of a bi-directional heterologous desensitization property of APP-responsive [Ca²⁺]_i transients mediated through these TRP channels. Mutational analyses of key cysteine residues in TRPA1 (Cys421, Cys621, Cys641, and Cys665) and in TRPV1 (Cys258, Cys363, and Cys742) have suggested that multiple reactive oxygen and nitrogen species are intricately involved in activation of the channels via a broad range of modifications involving these cysteine residues. Taken together, these observations allow us to conclude that both TRPA1 and TRPV1 channels play a pivotal role in evoking indirect APP-dependent [Ca²⁺]_i responses.

Mammalian Transient Receptor Potential TRPA1 Channels: From Structure to Disease

The transient receptor potential ankyrin (TRPA) channels are Ca²⁺-permeable nonselective cation channels remarkably conserved through the animal kingdom. Mammals have only one member, TRPA1, which is widely expressed in sensory neurons and in non-neuronal cells (such as epithelial cells and hair cells). TRPA1 owes its name to the presence of 14 ankyrin repeats located in the NH₂ terminus of the channel, an unusual structural feature that may be relevant to its interactions with intracellular components. TRPA1 is primarily involved in the detection of an extremely wide variety of exogenous stimuli that may produce cellular damage. This includes a plethora of electrophilic compounds that interact with nucleophilic amino acid residues in the channel and many other chemically unrelated compounds whose only common feature seems to be their ability to partition in the plasma membrane. TRPA1 has been reported to be activated by cold, heat, and mechanical stimuli, and its function is modulated by multiple factors, including Ca²⁺, trace metals, pH, and reactive oxygen, nitrogen, and carbonyl species. TRPA1 is involved in acute and chronic pain as well as inflammation, plays key roles in the pathophysiology of nearly all organ systems, and is an attractive target for the treatment of related diseases. Here we review the current knowledge about the mammalian TRPA1 channel, linking its unique structure, widely tuned sensory properties, and complex regulation to its roles in multiple pathophysiological conditions.

TRPA1/NOX in the soma of trigeminal ganglion neurons mediates migraine-related pain of glyceryl trinitrate in mice

Glyceryl trinitrate is administered as a provocative test for migraine pain. Glyceryl trinitrate causes prolonged mechanical allodynia in rodents, which temporally correlates with delayed glyceryl trinitrate-evoked migraine attacks in patients. However, the underlying mechanism of the allodynia evoked by glyceryl trinitrate is unknown. The proalgesic transient receptor potential ankyrin 1 (TRPA1) channel, expressed by trigeminal nociceptors, is sensitive to oxidative stress and is targeted by nitric oxide or its by-products. Herein, we explored the role of TRPA1 in glyceryl trinitrate-evoked allodynia. Systemic administration of glyceryl trinitrate elicited in the mouse periorbital area an early and transient vasodilatation and a delayed and prolonged mechanical allodynia. The systemic, intrathecal or local administration of selective enzyme inhibitors revealed that nitric oxide, liberated from the parent drug by aldehyde dehydrogenase 2 (ALDH2), initiates but does not maintain allodynia. The central and the final phases of allodynia were respectively associated with generation of reactive oxygen and carbonyl species within the trigeminal ganglion. Allodynia was absent in TRPA1-deficient mice and was reversed by TRPA1 antagonists. Knockdown of neuronal TRPA1 by intrathecally administered antisense oligonucleotide and selective deletion of TRPA1 from sensory neurons in Advillin-Cre; Trpa1^fl/fl mice revealed that nitric oxide-dependent oxidative and carbonylic stress generation is due to TRPA1 stimulation, and resultant NADPH oxidase 1 (NOX1) and NOX2 activation in the soma of trigeminal ganglion neurons. Early periorbital vasodilatation evoked by glyceryl trinitrate was attenuated by ALDH2 inhibition but was unaffected by TRPA1 blockade. Antagonists of the calcitonin gene-related peptide receptor did not affect the vasodilatation but partially inhibited allodynia. Thus, although both periorbital allodynia and vasodilatation evoked by glyceryl trinitrate are initiated by nitric oxide, they are temporally and mechanistically distinct. While vasodilatation is due to a direct nitric oxide action in the vascular smooth muscle, allodynia is a neuronal phenomenon mediated by TRPA1 activation and ensuing oxidative stress. The autocrine pathway, sustained by TRPA1 and NOX1/2 within neuronal cell bodies of trigeminal ganglia, may sensitize meningeal nociceptors and second order trigeminal neurons to elicit periorbital allodynia, and could be of relevance for migraine-like headaches evoked by glyceryl trinitrate in humans.

Diels–Alder reactions between hexafluoro-2-butyne and bis-furyl dienes: kinetic versus thermodynamic control

The tandem [4+2] cycloaddition between hexafluoro-2-butyne and bis-furyl diens can lead to “pincer” or “domino”-adducts.

Distinct Mechanism of Cysteine Oxidation-Dependent Activation and Cold Sensitization of Human Transient Receptor Potential Ankyrin 1 Channel by High and Low Oxaliplatin

Oxaliplatin, a third-generation platinum-based chemotherapeutic agent, displays unique acute peripheral neuropathy triggered or enhanced by cold, and accumulating evidence suggests that transient receptor potential ankyrin 1 (TRPA1) is responsible. TRPA1 is activated by oxaliplatin via a glutathione-sensitive mechanism. However, oxaliplatin interrupts hydroxylation of a proline residue located in the N-terminal region of TRPA1 via inhibition of prolyl hydroxylase (PHD), which causes sensitization of TRPA1 to reactive oxygen species (ROS). Furthermore, PHD inhibition endows cold-insensitive human TRPA1 (hTRPA1) with ROS-dependent cold sensitivity. Since cysteine oxidation and proline hydroxylation regulate its activity, their association with oxaliplatin-induced TRPA1 activation and acquirement of cold sensitivity were investigated in the present study. A high concentration of oxaliplatin (1 mM) induced outward-rectifier whole-cell currents and increased the intracellular Ca²⁺ concentration in hTRPA1-expressing HEK293 cells, but did not increase the probability of hTRPA1 channel opening in the inside-out configuration. Oxaliplatin also induced the rapid generation of hydrogen peroxide, and the resultant Ca²⁺ influx was prevented in the presence of glutathione and in cysteine-mutated hTRPA1 (Cys641Ser)-expressing cells, whereas proline-mutated hTRPA1 (Pro394Ala)-expressing cells showed similar whole-cell currents and Ca²⁺ influx. By contrast, a lower concentration of oxaliplatin (100 μM) did not increase the intracellular Ca²⁺ concentration but did confer cold sensitivity on hTRPA1-expressing cells, and this was inhibited by PHD2 co-overexpression. Cold sensitivity was abolished by the mitochondria-targeting ROS scavenger mitoTEMPO and was minimal in cysteine-mutated hTRPA1 (Cys641Ser or Cys665Ser)-expressing cells. Thus, high oxaliplatin evokes ROS-mediated cysteine oxidation-dependent hTRPA1 activation independent of PHD activity, while a lower concentration induces cold-induced cysteine oxidation-dependent opening of hTRPA1 via PHD inhibition.

Nitric oxide-induced oxidative stress impairs pacemaker function of murine interstitial cells of Cajal during inflammation

The pacemaker function of interstitial cells of Cajal (ICC) is impaired during intestinal inflammation. The aim of this study is to clarify the pathophysiological mechanisms of ICC dysfunction during inflammatory condition by using intestinal cell clusters. Cell clusters were prepared from smooth muscle layer of murine jejunum and treated with interferon-gamma and lipopolysaccharide (IFN-γ+LPS) for 24h to induce inflammation. Pacemaker function of ICC was monitored by measuring cytosolic Ca(2+) oscillation in the presence of nifedipine. Treatment with IFN-γ+LPS impaired the pacemaker activity of ICC with increasing mRNA level of interleukin-1 beta, tumor necrosis factor-alpha and interleukin-6 in cell clusters; however, treatment with these cytokines individually had little effect on pacemaker activity of ICC. Treatment with IFN-γ+LPS also induced the expression of inducible nitric oxide synthase (iNOS) in smooth muscle cells and resident macrophages, but not in ICC. Pretreatment with NOS inhibitor, L-NAME or iNOS inhibitor, 1400W ameliorated IFN-γ+LPS-induced pacemaker dysfunction of ICC. Pretreatment with guanylate cyclase inhibitor, ODQ did not, but antioxidant, apocynin, to suppress NO-induced oxidative stress, significantly suppressed the impairment of ICC function induced by IFN-γ+LPS. Treatment with IFN-γ+LPS also decreased c-Kit-positive ICC, which was prevented by pretreatment with L-NAME. However, apoptotic ICC were not detected in IFN-γ+LPS-treated clusters, suggesting IFN-γ+LPS stimulation just changed the phenotype of ICC but not induced cell death. Moreover, ultrastructure of ICC was not disturbed by IFN-γ+LPS. In conclusion, ICC dysfunction during inflammation is induced by NO-induced oxidative stress rather than NO/cGMP signaling. NO-induced oxidative stress might be the main factor to induce phenotypic changes of ICC.

Deciphering Subtype-Selective Modulations in TRPA1 Biosensor Channels

The transient receptor potential (TRP) proteins are a family of ion channels that act as cellular sensors. Several members of the TRP family are sensitive to oxidative stress mediators. Among them, TRPA1 is remarkably susceptible to various oxidants, and is known to mediate neuropathic pain and respiratory, vascular and gastrointestinal functions, making TRPA1 an attractive therapeutic target. Recent studies have revealed a number of modulators (both activators and inhibitors) that act on TRPA1. Endogenous mediators of oxidative stress and exogenous electrophiles activate TRPA1 through oxidative modification of cysteine residues. Non-electrophilic compounds also activate TRPA1. Certain non-electrophilic modulators may act on critical non-cysteine sites in TRPA1. However, a method to achieve selective modulation of TRPA1 by small molecules has not yet been established. More recently, we found that a novel N-nitrosamine compound activates TRPA1 by S-nitrosylation (the addition of a nitric oxide (NO) group to cysteine thiol), and does so with significant selectivity over other NO-sensitive TRP channels. It is proposed that this subtype selectivity is conferred through synergistic effects of electrophilic cysteine transnitrosylation and molecular recognition of the non-electrophilic moiety on the N-nitrosamine. In this review, we describe the molecular pharmacology of these TRPA1 modulators and discuss their modulatory mechanisms.

Different Contribution of Redox-Sensitive Transient Receptor Potential Channels to Acetaminophen-Induced Death of Human Hepatoma Cell Line

Acetaminophen (APAP) is a safe analgesic antipyretic drug at prescribed doses. Its overdose, however, can cause life-threatening liver damage. Though, involvement of oxidative stress is widely acknowledged in APAP-induced hepatocellular death, the mechanism of this increased oxidative stress and the associated alterations in Ca²⁺ homeostasis are still unclear. Among members of transient receptor potential (TRP) channels activated in response to oxidative stress, we here identify that redox-sensitive TRPV1, TRPC1, TRPM2, and TRPM7 channels underlie Ca²⁺ entry and downstream cellular damages induced by APAP in human hepatoma (HepG2) cells. Our data indicate that APAP treatment of HepG2 cells resulted in increased reactive oxygen species (ROS) production, glutathione (GSH) depletion, and Ca²⁺ entry leading to increased apoptotic cell death. These responses were significantly suppressed by pretreatment with the ROS scavengers N-acetyl-L-cysteine (NAC) and 4,5-dihydroxy-1,3-benzene disulfonic acid disodium salt monohydrate (Tiron), and also by preincubation of cells with the glutathione inducer Dimethylfumarate (DMF). TRP subtype-targeted pharmacological blockers and siRNAs strategy revealed that suppression of either TRPV1, TRPC1, TRPM2, or TRPM7 reduced APAP-induced ROS formation, Ca²⁺ influx, and cell death; the effects of suppression of TRPV1 or TRPC1, known to be activated by oxidative cysteine modifications, were stronger than those of TRPM2 or TRPM7. Interestingly, TRPV1 and TRPC1 were labeled by the cysteine-selective modification reagent, 5,5′-dithiobis (2-nitrobenzoic acid)-2biotin (DTNB-2Bio), and this was attenuated by pretreatment with APAP, suggesting that APAP and/or its oxidized metabolites act directly on the modification target cysteine residues of TRPV1 and TRPC1 proteins. In human liver tissue, TRPV1, TRPC1, TRPM2, and TRPM7 channels transcripts were localized mainly to hepatocytes and Kupffer cells. Our findings strongly suggest that APAP-induced Ca²⁺ entry and subsequent hepatocellular death are regulated by multiple redox-activated cation channels, among which TRPV1 and TRPC1 play a prominent role.

Differential Contributions of Alcohol and the Nicotine-Derived Nitrosamine Ketone (NNK) to Insulin and Insulin-Like Growth Factor Resistance in the Adolescent Rat Brain

AIMS

Since epidemiologic studies suggest that tobacco smoke toxins, e.g. the nicotine-derived nitrosamine ketone (NNK) tobacco-specific nitrosamine, can be a co-factor in alcohol-related brain disease (ARBD), we examined the independent and additive effects of alcohol and NNK exposures on spatial learning/memory, and brain insulin/IGF signaling, neuronal function and oxidative stress.

METHODS

Adolescent Long Evans rats were fed liquid diets containing 0 or 26% caloric ethanol for 8 weeks. During weeks 3-8, rats were treated with i.p. NNK (2 mg/kg, 3×/week) or saline. In weeks 7-8, ethanol groups were binge-administered ethanol (2 g/kg; 3×/week). In week 8, at 12 weeks of age, rats were subjected to Morris Water Maze tests. Temporal lobes were used to assess molecular indices of insulin/IGF resistance, oxidative stress and neuronal function.

RESULTS

Ethanol and NNK impaired spatial learning, and NNK ± ethanol impaired memory. Linear trend analysis demonstrated worsening performance from control to ethanol, to NNK, and then ethanol + NNK. Ethanol ± NNK, caused brain atrophy, inhibited insulin signaling through the insulin receptor and Akt, activated GSK-3β, increased protein carbonyl and 3-nitrotyrosine, and reduced acetylcholinesterase. NNK increased NTyr. Ethanol + NNK had synergistic stimulatory effects on 8-iso-PGF-2α, inhibitory effects on p-p70S6K, tau and p-tau and trend effects on insulin-like growth factor type 1 (IGF-1) receptor expression and phosphorylation.

CONCLUSIONS

Ethanol, NNK and combined ethanol + NNK exposures that begin in adolescence impair spatial learning and memory in young adults. The ethanol and/or NNK exposures differentially impair insulin/IGF signaling through neuronal growth, survival and plasticity pathways, increase cellular injury and oxidative stress and reduce expression of critical proteins needed for neuronal function.

Interactive effects of dietary fat/carbohydrate ratio and body mass index on iron deficiency anemia among Taiwanese women

Whether being overweight or obese is associated with increased risk of iron deficiency anemia (IDA) remains controversial. We evaluated the dietary intakes and risk for IDA in relation to body mass index (BMI). One thousand two hundred and seventy-four females aged ≥19 years, enrolled in the third Nutrition and Health Survey in Taiwan (NAHSIT) 2005–2008, were selected. Half of the women were either overweight (24.0%) or obese (25.3%). The overall prevalence of anemia, iron deficiency and IDA among adult women was 19.5%, 8.6% and 6.2%. BMI showed a protective effect on IDA: overweight (odds ratio, OR: 0.365 (0.181–0.736)) and obese (OR: 0.480 (0.259–0.891)) when compared with normal weight. Univariate analysis identified increased IDA risk for overweight/obese women who consumed higher dietary fat but lower carbohydrate (CHO) (OR: 10.119 (1.267–80.79)). No such relationship was found in IDA women with normal weight (OR: 0.375 (0.036–4.022)). Analysis of interaction(s) showed individuals within the highest BMI tertile (T3) had the lowest risk for IDA and the risk increased with increasing tertile groups of fat/CHO ratio; OR 0.381 (0.144–1.008; p = 0.051), 0.370 (0.133–1.026; p = 0.056) and 0.748 (0.314–1.783; p = 0.513); for T1, T2 and T3, respectively. In conclusion, a protective effect of BMI on IDA may be attenuated in women who had increased fat/CHO ratio.