Aryl Hydrocarbon Receptor Activation in Pulmonary Alveolar Epithelial Cells Limits Inflammation and Preserves Lung Epithelial Cell Integrity.

The aryl hydrocarbon receptor (AHR) is a receptor/transcription factor widely expressed in the lung. The physiological roles of AHR expressed in the alveolar epithelium remain unclear. In this study, we tested the hypothesis that alveolar epithelial AHR activity plays an important role in modulating inflammatory responses and maintaining alveolar integrity during lung injury and repair. AHR is expressed in alveolar epithelial cells (AECs) and is active. AHR activation with the endogenous AHR ligand, FICZ (5,11-dihydroindolo[3,2-b] carbazole-6-carboxaldehyde), significantly suppressed inflammatory cytokine expression in response to inflammatory stimuli in primary murine AECs and in the MLE-15 epithelial cell line. In an LPS model of acute lung injury in mice, coadministration of FICZ with LPS suppressed protein leak, reduced neutrophil accumulation in BAL fluid, and suppressed inflammatory cytokine expression in lung tissue and BAL fluid. Relevant to healing following inflammatory injury, AHR activation suppressed TGF-ß-induced expression of genes associated with epithelial-mesenchymal transition. Knockdown of AHR in primary AECs with shRNA or in CRISPR-Cas-9-induced MLE-15 cells resulted in upregulation of α-smooth muscle actin (αSma), Col1a1, and Fn1 and reduced expression of epithelial genes Col4a1 and Sdc1. MLE-15 clones lacking AHR demonstrated accelerated wound closure in a scratch model. AHR activation with FICZ enhanced barrier function (transepithelial electrical resistance) in primary murine AECs and limited decline of transepithelial electrical resistance following inflammatory injury. AHR activation in AECs preserves alveolar integrity by modulating inflammatory cytokine expression while enhancing barrier function and limiting stress-induced expression of mesenchymal genes.

The Cytochrome P450 2C8*3 Variant (rs11572080) Is Associated with Improved Asthma Symptom Control in Children and Altered Lipid Mediator Production and Inflammatory Response in Human Bronchial Epithelial Cells.

This study investigated an association between the cytochrome P450 (CYP) 2C8*3 polymorphism with asthma symptom control in children and changes in lipid metabolism and pro-inflammatory signaling by human bronchial epithelial cells (HBECs) treated with cigarette smoke condensate (CSC). CYP genes are inherently variable in sequence, and while such variations are known to produce clinically relevant effects on drug pharmacokinetics and pharmacodynamics, the effects on endogenous substrate metabolism and associated physiologic processes are less understood. In this study, CYP2C8*3 was associated with improved asthma symptom control among children: Mean asthma control scores were 3.68 (n = 207) for patients with one or more copies of the CYP2C8*3 allele versus 4.42 (n = 965) for CYP2C8*1/*1 (P = 0.0133). In vitro, CYP2C8*3 was associated with an increase in montelukast 36-hydroxylation and a decrease in linoleic acid metabolism despite lower mRNA and protein expression. Additionally, CYP2C8*3 was associated with reduced mRNA expression of interleukin-6 (IL-6) and C-X-C motif chemokine ligand 8 (CXCL-8) by HBECs in response to CSC, which was replicated using the soluble epoxide hydrolase inhibitor, 12-[[(tricyclo[3.3.1.13,7]dec-1-ylamino)carbonyl]amino]-dodecanoic acid. Interestingly, 9(10)- and 12(13)- dihydroxyoctadecenoic acid, the hydrolyzed metabolites of 9(10)- and 12(13)- epoxyoctadecenoic acid, increased the expression of IL-6 and CXCL-8 mRNA by HBECs. This study reveals previously undocumented effects of the CYP2C8*3 variant on the response of HBECs to exogenous stimuli. SIGNIFICANCE STATEMENT: These findings suggest a role for CYP2C8 in regulating the epoxyoctadecenoic acid:dihydroxyoctadecenoic acid ratio leading to a change in cellular inflammatory responses elicited by environmental stimuli that exacerbate asthma.

Impact of CYP3A5 Polymorphisms on Pediatric Asthma Outcomes.

Genetic variation among inhaled corticosteroid (ICS)-metabolizing enzymes may affect asthma control, but evidence is limited. This study tested the hypothesis that single-nucleotide polymorphisms (SNPs) in Cytochrome P450 3A5 (CYP3A5) would affect asthma outcomes. Patients aged 2-18 years with persistent asthma were recruited to use the electronic AsthmaTracker (e-AT), a self-monitoring tool that records weekly asthma control, medication use, and asthma outcomes. A subset of patients provided saliva samples for SNP analysis and participated in a pharmacokinetic study. Multivariable regression analysis adjusted for age, sex, race, and ethnicity was used to evaluate the impact of CYP3A5 SNPs on asthma outcomes, including asthma control (measured using the asthma symptom tracker, a modified version of the asthma control test or ACT), exacerbations, and hospital admissions. Plasma corticosteroid and cortisol concentrations post-ICS dosing were also assayed using liquid chromatography-tandem mass spectrometry. Of the 751 patients using the e-AT, 166 (22.1%) provided saliva samples and 16 completed the PK study. The e-AT cohort was 65.1% male, and 89.6% White, 6.0% Native Hawaiian, 1.2% Black, 1.2% Native American, 1.8% of unknown race, and 15.7% Hispanic/Latino; the median age was 8.35 (IQR: 5.51-11.3) years. CYP3A5*3/*3 frequency was 75.8% in White subjects, 50% in Native Hawaiians and 76.9% in Hispanic/Latino subjects. Compared with CYP3A5*3/*3, the CYP3A5*1/*x genotype was associated with reduced weekly asthma control (OR: 0.98; 95% CI: 0.97-0.98; p < 0.001), increased exacerbations (OR: 6.43; 95% CI: 4.56-9.07; p < 0.001), and increased asthma hospitalizations (OR: 1.66; 95% CI: 1.43-1.93; p < 0.001); analysis of 3/*3, *1/*1 and *1/*3 separately showed an allelic copy effect. Finally, PK analysis post-ICS dosing suggested muted changes in cortisol concentrations for patients with the CYP3A5*3/*3 genotype, as opposed to an effect on ICS PK. Detection of CYP3A5*3/3, CYPA35*1/*3, and CYP3A5*1/*1 could impact inhaled steroid treatment strategies for asthma in the future.

Zhx2 Is a Candidate Gene Underlying Oxymorphone Metabolite Brain Concentration Associated with State-Dependent Oxycodone Reward.

Understanding the pharmacogenomics of opioid metabolism and behavior is vital to therapeutic success, as mutations can dramatically alter therapeutic efficacy and addiction liability. We found robust, sex-dependent BALB/c substrain differences in oxycodone behaviors and whole brain concentration of oxycodone metabolites. BALB/cJ females showed robust state-dependent oxycodone reward learning as measured via conditioned place preference when compared with the closely related BALB/cByJ substrain. Accordingly, BALB/cJ females also showed a robust increase in brain concentration of the inactive metabolite noroxycodone and the active metabolite oxymorphone compared with BALB/cByJ mice. Oxymorphone is a highly potent, full agonist at the mu opioid receptor that could enhance drug-induced interoception and state-dependent oxycodone reward learning. Quantitative trait locus (QTL) mapping in a BALB/c F2 reduced complexity cross revealed one major QTL on chromosome 15 underlying brain oxymorphone concentration that explained 32% of the female variance. BALB/cJ and BALB/cByJ differ by fewer than 10,000 variants, which can greatly facilitate candidate gene/variant identification. Hippocampal and striatal cis-expression QTL (eQTL) and exon-level eQTL analysis identified Zhx2, a candidate gene coding for a transcriptional repressor with a private BALB/cJ retroviral insertion that reduces Zhx2 expression and sex-dependent dysregulation of cytochrome P450 enzymes. Whole brain proteomics corroborated the Zhx2 eQTL and identified upregulated CYP2D11 that could increase brain oxymorphone in BALB/cJ females. To summarize, Zhx2 is a highly promising candidate gene underlying brain oxycodone metabolite levels. Future studies will validate Zhx2 and its site of action using reciprocal gene editing and tissue-specific viral manipulations in BALB/c substrains. SIGNIFICANCE STATEMENT: Our findings show that genetic variation can result in sex-specific alterations in whole brain concentration of a bioactive opioid metabolite after oxycodone administration, reinforcing the need for sex as a biological factor in pharmacogenomic studies. The cooccurrence of female-specific increased oxymorphone and state-dependent reward learning suggests that this minor yet potent and efficacious metabolite of oxycodone could increase opioid interoception and drug-cue associative learning of opioid reward, which has implications for cue-induced relapse of drug-seeking behavior and for precision pharmacogenetics.

Evaluating the efficacy of prototype antiseizure drugs using a preclinical pharmacokinetic approach.

OBJECTIVE: Pharmacokinetics (PK) of a drug drive its exposure, efficacy, and tolerability. A thorough preclinical PK assessment of antiseizure medications (ASMs) is therefore essential to evaluate the clinical potential. We tested protection against evoked seizures of prototype ASMs in conjunction with analysis of plasma and brain PK as a proof-of-principle study to enhance our understanding of drug efficacy and duration of action using rodent seizure models. METHODS: In vivo seizure protection assays were performed in adult male CF-1 mice and Sprague Dawley rats. Clobazam (CLB), N-desmethyl CLB (NCLB), carbamazepine (CBZ), CBZ-10,11-epoxide (CBZE), sodium valproate (VPA), and levetiracetam (LEV) concentrations were quantified in plasma and brain using liquid chromatography-tandem mass spectrometry. Mean concentrations of each analyte were calculated and used to determine PK parameters via noncompartmental analysis in Phoenix WinNonLin. RESULTS: NCLB concentrations were approximately 10-fold greater than CLB in mice. The antiseizure profile of CLB was partially sustained by NCLB in mice. CLB concentrations were lower in rats than in mice. CBZE plasma exposures were approximately 70% of CBZ in both mice and rats, likely contributing to the antiseizure effect of CBZ. VPA showed a relatively short half-life in both mice and rats, which correlated with a sharp decline in efficacy. LEV had a prolonged brain and plasma half-life, associated with a prolonged duration of action in mice. SIGNIFICANCE: The study demonstrates the utility of PK analyses for understanding the seizure protection time course in mice and rats. The data indicate that distinct PK profiles of ASMs between mice and rats likely drive differences in drug efficacy between rodent models.

Effect of combustion particle morphology on biological responses in a Co-culture of human lung and macrophage cells.

Atmospheric aging of combustion particles alters their chemical composition and morphology. Previous studies have reported differences in toxicological responses after exposure to fresh versus aged particles, with chemical composition being the prime suspect behind the differences. However, less is known about the contribution of morphological differences in atmospherically aged particles to toxicological responses, possibly due to the difficulty in resolving the two properties (composition and morphology) that change simultaneously. This study altered the shape of lab-generated combustion particles, without affecting the chemical composition, from fractal-like to a more compact spherical shape, using a water condensation-evaporation method. The two shapes were exposed to a co-culture of human airway epithelial (A549) and differentiated human monocyte (THP-1) cells at air-liquid interface (ALI) conditions. The particles with different shapes were deposited using an electrostatic field-based ALI chamber. For the same mass dose, both shapes were internalized by cells, induced a pro-inflammatory response (IL-8 and TNFα), and enhanced CYP1A1 gene expression compared to air controls. The more compact spherical particles (representative of atmospherically aged particles) induced more early apoptosis and release of TNFα compared to the more fractal-like particles. These results suggest a contribution of morphology to the increased toxicity of aged combustion-derived particles.

Dynamic Expression of Transient Receptor Potential Vanilloid-3 and Integrated Signaling with Growth Factor Pathways during Lung Epithelial Wound Repair following Wood Smoke Particle and Other Forms of Lung Cell Injury.

Prior studies revealed increased expression of the transient receptor potential vanilloid-3 (TRPV3) ion channel after wood smoke particulate matter (WSPM) treatment of human bronchial epithelial cells (HBECs). TRPV3 attenuated pathologic endoplasmic reticulum stress and cytotoxicity mediated by transient receptor potential ankyrin-1. Here, the basis for how TRPV3 expression is regulated by cell injury and the effects this has on HBEC physiology and WSPM-induced airway remodeling in mice was investigated. TRPV3 mRNA was rapidly increased in HBECs treated with WSPM and after monolayer damage caused by tryptic disruption, scratch wounding, and cell passaging. TRPV3 mRNA abundance varied with time, and stimulated expression occurred independent of new protein synthesis. Overexpression of TRPV3 in HBECs reduced cell migration and wound repair while enhancing cell adhesion. This phenotype correlated with disrupted mRNA expression of ligands of the epidermal growth factor, tumor growth factor-ß, and frizzled receptors. Accordingly, delayed wound repair by TRPV3 overexpressing cells was reversed by growth factor supplementation. In normal HBECs, TRPV3 upregulation was triggered by exogenous growth factor supplementation and was attenuated by inhibitors of growth factor receptor signaling. In mice, subacute oropharyngeal instillation with WSPM also promoted TRPV3 mRNA expression and epithelial remodeling, which was attenuated by TRPV3 antagonist pre- and cotreatment. This latter effect may be the consequence of antagonist-induced TRPV3 expression. These findings provide insights into the roles of TRPV3 in lung epithelial cells under basal and dynamic states, as well as highlight potential roles for TRPV3 ligands in modulating epithelial damage/repair. SIGNIFICANCE STATEMENT: Coordinated epithelial repair is essential for the maintenance of the airways, with deficiencies and exaggerated repair associated with adverse consequences to respiratory health. This study shows that TRPV3, an ion channel, is involved in coordinating repair through integrated repair signaling pathways, wherein TRPV3 expression is upregulated immediately after injury and returns to basal levels as cells complete the repair process. TRPV3 may be a novel target for understanding and/or treating conditions in which airway/lung epithelial repair is not properly orchestrated.

Transient Receptor Potential Ankyrin-1 and Vanilloid-3 Differentially Regulate Endoplasmic Reticulum Stress and Cytotoxicity in Human Lung Epithelial Cells After Pneumotoxic Wood Smoke Particle Exposure.

This study investigated the roles of transient receptor potential (TRP) ankyrin-1 (TRPA1) and TRP vanilloid-3 (TRPV3) in regulating endoplasmic reticulum stress (ERS) and cytotoxicity in human bronchial epithelial cells (HBECs) treated with pneumotoxic wood smoke particulate matter (WSPM) and chemical agonists of each channel. Functions of TRPA1 and TRPV3 in pulmonary epithelial cells remain largely undefined. This study shows that TRPA1 activity localizes to the plasma membrane and endoplasmic reticulum (ER) of cells, whereas TRPV3 resides primarily in the ER. Additionally, treatment of cells using moderately cytotoxic concentrations of pine WSPM, carvacrol, and other TRPA1 agonists caused ERS as a function of both TRPA1 and TRPV3 activities. Specifically, ERS and cytotoxicity were attenuated by TRPA1 inhibition, whereas inhibiting TRPV3 exacerbated ERS and cytotoxicity. Interestingly, after treatment with pine WSPM, TRPA1 transcription was suppressed, whereas TRPV3 was increased. TRPV3 overexpression in HBECs conferred resistance to ERS and an attenuation of ERS-associated cell cycle arrest caused by WSPM and multiple prototypical ERS-inducing agents. Alternatively, short hairpin RNA-mediated knockdown of TRPV3, like the TRPV3 antagonist, exacerbated ERS. This study reveals previously undocumented roles for TRPA1 in promoting pathologic ERS and cytotoxicity elicited by pneumotoxic WSPM and TRPA1 agonists, and a unique role for TRPV3 in fettering pathologic facets of the integrated ERS response. SIGNIFICANCE STATEMENT: These findings provide new insights into how wood smoke particulate matter and other transient receptor potential ankyrin-1 (TRPA1) and transient receptor potential vanilloid-3 (TRPV3) agonists can affect human bronchial epithelial cells and highlight novel physiological and pathophysiological roles for TRPA1 and TRPV3 in these cells.

Capsaicinoid metabolism by the generalist Helicoverpa armigera and specialist H. assulta: Species and tissue differences.

Helicoverpa armigera and H. assulta are two of the few insects that can feed on hot pepper fruits. Capsaicin and dihydrocapsaicin (i.e., capsaicinoids) are the principal pungent compounds in hot peppers. To explore possible molecular mechanisms of adaptation that allow these two species to consume capsaicinoids, the capacity of the three detoxification tissues (fat body, midgut, and Malpighian tubule) of the two pests, to metabolically degrade capsaicin and dihydrocapsaicin, was compared. The results showed that capsaicin and dihydrocapsaicin were metabolized by crude enzyme preparations from all three tissues of the two pests. Five metabolites of capsaicin, and five metabolites of dihydrocapsaicin were identified. Tissue and species differences in the degree of capsaicin and dihydrocapsaicin metabolism were observed. The specialist H. assulta had an overall greater capacity to degrade the capsaicinoids compared to the generalist H. armigera. Further, the midgut was the most significant contributor to capsaicinoid metabolism. The notably high specific activity in Malpighian tubules of H. armigera also further highlights the significance of this organ in xenobiotic detoxification. Alkyl hydroxylation and dehydrogenation were the main pathways for the oxidative biotransformation of both capsaicin and dihydrocapsaicin by cytochrome P450s. This study provides evidence that enhanced metabolic decomposition of capsaicinoids may be an adaptation explaining dietary preferences for Capsicum fruits by these two pests.

trans-Anethole of Fennel Oil is a Selective and Nonelectrophilic Agonist of the TRPA1 Ion Channel.

Transient receptor potential (TRP) cation channels are molecular targets of various natural products. TRPA1, a member of TRP channel family, is specifically activated by natural products such as allyl isothiocyanate (mustard oil), cinnamaldehyde (cinnamon), and allicin (garlic). In this study, we demonstrated that TRPA1 is also a target of trans-anethole in fennel oil (FO) and fennel seed extract. Similar to FO, trans-anethole selectively elicited calcium influx in TRPA1-expressing mouse sensory neurons of the dorsal root and trigeminal ganglia. These FO- and anethole-induced calcium responses were blocked by a selective TRPA1 channel antagonist, HC-030031. Moreover, both FO and trans-anethole induced calcium influx and transmembrane currents in HEK293 cells stably overexpressing human TRPA1 channels, but not in regular HEK293 cells. Mutation of the amino acids S873 and T874 binding site of human TRPA1 significantly attenuated channel activation by trans-anethole, whereas pretreating with glutathione, a nucleophile, did not. Conversely, activation of TRPA1 by the electrophile allyl isothiocyanate was abolished by glutathione, but was ostensibly unaffected by mutation of the ST binding site. Finally, it was found that trans-anethole was capable of desensitizing TRPA1, and unlike allyl isothiocyanate, it failed to induce nocifensive behaviors in mice. We conclude that trans-anethole is a selective, nonelectrophilic, and seemingly less-irritating agonist of TRPA1.

Transient Receptor Potential Ion Channel-Dependent Toxicity of Silica Nanoparticles and Poly(amido amine) Dendrimers.

Fundamental to the design and development of nanoparticles for applications in nanomedicine is a detailed understanding of their biologic fate and potential toxic effects. Transient receptor potential (TRP) ion channels are a large superfamily of cation channels with varied physiologic functions. This superfamily is classified into six related subfamilies: TRP canonical, TRP vanilloid (TRPV), TRP melastatin (TRPM), TRP ankyrin (TRPA), TRP polycystin, and TRP mucolipin. TRPA1, TRPM2, and TRPM8 are nonselective Ca2+-permeable cation channels which regulate calcium pathways under oxidative stress, whereas TRPV4 can be activated by oxidative, osmotic, and thermal stress as well as different fatty acid metabolites. Using a series of well characterized silica nanoparticles with variations in size (approximately 50-350 nm in diameter) and porosity, as well as cationic and anionic poly(amido amine) (PAMAM) dendrimers of similar size, we examined the toxicity of these nanoparticles to human embryonic kidney-293 cells overexpressing different TRP channels. The data show that the toxicity of mesoporous silica nanoparticles was influenced by expression of the TRPA1 and TRPM2 channels, whereas the toxicity of smaller nonporous silica nanoparticles was only affected by TRPM8. Additionally, TRPA1 and TRPM2 played a role in the cytotoxicity of cationic dendrimers, but not anionic dendrimers. TRPV4 did not seem to play a significant role in silica nanoparticle or PAMAM toxicity.

Wood and Biomass Smoke: Addressing Human Health Risks and Exposures.

Air pollutants from burning wood and biomass pose serious human health risks. Recent discoveries link the chemistry of smoke emissions with biochemical sensors and biological effect mediators. Strategic thinking of complex underlying factors is needed to protect people from harm.

Differential Activation of TRPA1 by Diesel Exhaust Particles: Relationships between Chemical Composition, Potency, and Lung Toxicity.

Diesel exhaust particulate (DEP) causes pulmonary irritation and inflammation, which can exacerbate asthma and other diseases. These effects may arise from the activation of transient receptor potential ankyrin-1 (TRPA1). This study shows that a representative DEP can activate TRPA1-expressing pulmonary C-fibers in the mouse lung. Furthermore, DEP collected from idling vehicles at an emissions inspection station, the tailpipe of an on-road "black smoker" diesel truck, waste DEP from a diesel exhaust filter regeneration machine, and NIST SRM 2975 can activate human TRPA1 in lung epithelial cells to elicit different biological responses. The potency of the DEP, particle extracts, and selected chemical components was compared in TRPA1 over-expressing HEK-293 and human lung cells using calcium flux and other toxicologically relevant end-point assays. Emission station DEP was the most potent and filter DEP the least. Potency was related to the percentage of ethanol extractable TRPA1 agonists and was equivalent when equal amounts of extract mass was used for treatment. The DEP samples were further compared using scanning electron microscopy, energy-dispersive X-ray spectroscopy, gas chromatography-mass spectrometry, and principal component analysis as well as targeted analysis of known TRPA1 agonists. Activation of TRPA1 was attributable to both particle-associated electrophiles and non-electrophilic agonists, which affected the induction of interleukin-8 mRNA via TRPA1 in A549 and IMR-90 lung cells as well as TRPA1-mediated mucin gene induction in human lung cells and mucous cell metaplasia in mice. This work illustrates that not all DEP samples are equivalent, and studies aimed at assessing mechanisms of DEP toxicity should account for multiple variables, including the expression of receptor targets such as TRPA1 and particle chemistry.

Secondary Metabolites of Onygenales Fungi Exemplified by Aioliomyces pyridodomos.

Fungi from the order Onygenales include human pathogens. Although secondary metabolites are critical for pathogenic interactions, relatively little is known about Onygenales compounds. Here, we use chemical and genetic methods on Aioliomyces pyridodomos, the first representative of a candidate new family within Onygenales. We isolated 14 new bioactive metabolites, nine of which are first disclosed here. Thirty-two specialized metabolite biosynthetic gene clusters (BGCs) were identified. BGCs were correlated to some of the new compounds by heterologous expression of biosynthetic genes. Some of the compounds were found after one year of fermentation. By comparing BGCs from A. pyridodomos with those from 68 previously sequenced Onygenales fungi, we delineate a large biosynthetic potential. Most of these biosynthetic pathways are specific to Onygenales fungi and have not been found elsewhere. Family level specificity and conservation of biosynthetic gene content are evident within Onygenales. Identification of these compounds may be important to understanding pathogenic interactions.

Activation of TRPV3 by Wood Smoke Particles and Roles in Pneumotoxicity.

Wood/biomass smoke particulate materials (WBSPM) are pneumotoxic, but the mechanisms by which these materials affect lung cells are not fully understood. We previously identified transient receptor potential (TRP) ankyrin-1 as a sensor for electrophiles in WBSPM and hypothesized that other TRP channels expressed by lung cells might also be activated by WBSPM, contributing to pneumotoxicity. Screening TRP channel activation by WBSPM using calcium flux assays revealed TRPV3 activation by materials obtained from burning multiple types of wood under fixed conditions. TRPV3 activation by WBSPM was dependent on the chemical composition, and the pattern of activation and chemical components of PM agonists was different from that of TRPA1. Chemical analysis of particle constituents by gas chromatography-mass spectrometry and principal component analysis indicated enrichment of cresol, ethylphenol, and xylenol analogues, plus several other chemicals among the most potent samples. 2,3-, 2,4-, 2,5-, 2,6-, 3,4-, and 3,5-xylenol, 2-, 3-, and 4-ethylphenol, 2-methoxy-4-methylphenol, and 5,8-dihydronaphthol were TRPV3 agonists exhibiting preferential activation versus TRPA1, M8, V1, and V4. The concentration of 2,3- and 3,4-xylenol in the most potent samples of pine and mesquite smoke PM (<3 µm) was 0.1-0.3% by weight, while that of 5,8-dihydronaphthol was 0.03%. TRPV3 was expressed by several human lung epithelial cell lines, and both pine PM and pure chemical TRPV3 agonists found in WBSPM were more toxic to TRPV3-over-expressing cells via TRPV3 activation. Finally, mice treated sub-acutely with pine particles exhibited an increase in sensitivity to inhaled methacholine involving TRPV3. In summary, TRPV3 is activated by specific chemicals in WBSPM, potentially contributing to the pneumotoxic properties of certain WBSPM.

Activation of Human Transient Receptor Potential Melastatin-8 (TRPM8) by Calcium-Rich Particulate Materials and Effects on Human Lung Cells.

To better understand how adverse health effects are caused by exposure to particulate materials, and to develop preventative measures, it is important to identify the properties of particles and molecular targets that link exposure with specific biologic outcomes. Coal fly ash (CFA) is a by-product of coal combustion that can affect human health. We report that human transient receptor potential melastatin-8 (TRPM8) and an N-terminally truncated TRPM8 variant (TRPM8-Δ801) are activated by CFA and calcium-rich nanoparticles and/or soluble salts within CFA. TRPM8 activation by CFA was potentiated by cold temperature involving the phosphatidylinositol 4,5-bisphosphate binding residue (L1008), but was independent of the icilin and menthol binding site residue Y745 and, essentially, the N-terminal amino acids 1-800. CFA, calcium nanoparticles, and calcium salts also activated transient receptor potential vanilloid-1 (TRPV1) and transient receptor potential ankyrin-1 (TRPA1), but not TRPV4. CFA treatment induced CXCL1 and interleukin-8 mRNA in BEAS-2B and primary human bronchial epithelial cells through activation of both TRPM8 and TRPV1. However, neither mouse nor rat TRPM8 was activated by these materials, and Trpm8 knockout had no effect on cytokine induction in the lungs of CFA-instilled mice. Amino acids S921 and S927 in mouse Trpm8 were identified as important for the lack of response to CFA. These results imply that TRPM8, in conjunction with TRPV1 and TRPA1, might sense selected forms of inhaled particulate materials in human airways, shaping cellular responses to these materials, and improving our understanding of how and why certain particulate materials elicit different responses in biologic systems, affecting human health.

Characterization of Transient Receptor Potential Vanilloid-1 (TRPV1) Variant Activation by Coal Fly Ash Particles and Associations with Altered Transient Receptor Potential Ankyrin-1 (TRPA1) Expression and Asthma.

Transient receptor potential (TRP) channels are activated by environmental particulate materials. We hypothesized that polymorphic variants of transient receptor potential vanilloid-1 (TRPV1) would be uniquely responsive to insoluble coal fly ash compared with the prototypical soluble agonist capsaicin. Furthermore, these changes would manifest as differences in lung cell responses to these agonists and perhaps correlate with changes in asthma symptom control. The TRPV1-I315M and -T469I variants were more responsive to capsaicin and coal fly ash. The I585V variant was less responsive to coal fly ash particles due to reduced translation of protein and an apparent role for Ile-585 in activation by particles. In HEK-293 cells, I585V had an inhibitory effect on wild-type TRPV1 expression, activation, and internalization/agonist-induced desensitization. In normal human bronchial epithelial cells, IL-8 secretion in response to coal fly ash treatment was reduced for cells heterozygous for TRPV1-I585V. Finally, both the I315M and I585V variants were associated with worse asthma symptom control with the effects of I315M manifesting in mild asthma and those of the I585V variant manifesting in severe, steroid-insensitive individuals. This effect may be due in part to increased transient receptor potential ankyrin-1 (TRPA1) expression by lung epithelial cells expressing the TRPV1-I585V variant. These findings suggest that specific molecular interactions control TRPV1 activation by particles, differential activation, and desensitization of TRPV1 by particles and/or other agonists, and cellular changes in the expression of TRPA1 as a result of I585V expression could contribute to variations in asthma symptom control.

Identification of Cyclic Depsipeptides and Their Dedicated Synthetase from Hapsidospora irregularis.

Seven cyclic depsipeptides were isolated from Hapsidospora irregularis and structurally characterized as the calcium channel blocker leualacin and six new analogues based on the NMR and HRESIMS data. These new compounds were named leualacins B-G. The absolute configurations of the amino acids and 2-hydroxyisocaproic acids were determined by recording the optical rotation values. Biological studies showed that calcium influx elicited by leualacin F in primary human lobar bronchial epithelial cells involves the TRPA1 channel. Through genome sequencing and targeted gene disruption, a noniterative nonribosomal peptide synthetase was found to be involved in the biosynthesis of leualacin. A comparison of the structures of leualacin and its analogues indicated that the A2 and A4 domains of the leualacin synthetase are substrate specific, while A1, A3, and A5 can accept alternative precursors to yield new molecules.

Activation of Transient Receptor Potential Ankyrin-1 by Insoluble Particulate Material and Association with Asthma.

Inhaled irritants activate transient receptor potential ankyrin-1 (TRPA1), resulting in cough, bronchoconstriction, and inflammation/edema. TRPA1 is also implicated in the pathogenesis of asthma. Our hypothesis was that particulate materials activate TRPA1 via a mechanism distinct from chemical agonists and that, in a cohort of children with asthma living in a location prone to high levels of air pollution, expression of uniquely sensitive forms of TRPA1 may correlate with reduced asthma control. Variant forms of TRPA1 were constructed by mutating residues in known functional elements and corresponding to single-nucleotide polymorphisms in functional domains. TRPA1 activity was studied in transfected HEK-293 cells using allyl-isothiocynate, a model soluble electrophilic agonist; 3,5-ditert butylphenol, a soluble nonelectrophilic agonist and a component of diesel exhaust particles; and insoluble coal fly ash (CFA) particles. The N-terminal variants R3C and R58T exhibited greater, but not additive, activity with all three agonists. The ankyrin repeat domain-4 single nucleotide polymorphisms E179K and K186N exhibited decreased response to CFA. The predicted N-linked glycosylation site residues N747A and N753A exhibited decreased responses to CFA, which were not attributable to differences in cellular localization. The pore-loop residue R919Q was comparable to wild-type, whereas N954T was inactive to soluble agonists but not CFA. These data identify roles for ankyrin domain-4, cell surface N-linked glycans, and selected pore-loop domain residues in the activation of TRPA1 by insoluble particles. Furthermore, the R3C and R58T polymorphisms correlated with reduced asthma control for some children, which suggest that TRPA1 activity may modulate asthma, particularly among individuals living in locations prone to high levels of air pollution.