Evidence of sex differences in ozone-induced oxysterol and cytokine levels in differentiated human nasal epithelial cells.

Acute exposure to ozone (O) causes upper and lower airway inflammation. We and others have previously demonstrated that O oxidizes lipids, particularly cholesterol, into electrophilic oxysterols, such as secosterol B (SecoB), which can adduct proteins, thus altering cellular signaling pathways. To investigate how O-derived oxysterols influence cytokine and chemokine release, nasal epithelial cells (HNECs) from healthy donors (N = 18 donors) were exposed to 0.

Melatonin Vapes Contain Potential Contaminants and Alter the Human Bronchial Epithelial Transcriptome.

Melatonin vaping products, touted for their faster absorption than oral melatonin supplements, have been gaining popularity among adolescents as sleep aid. Here, we elucidated the response of human bronchial epithelial cells (hBECs) to high levels of melatonin from vaped aerosols, investigated the uptake of melatonin by hBECs , and characterized the chemical composition of three commercially available melatonin vapes. Melatonin vape exposure decreased the secretion of chemokines and produced an immunosuppressive gene expression signature.

Spatially heterogeneous lipid dysregulation in tuberculous meningitis.

Tuberculous (TB) meningitis is the deadliest form of extrapulmonary TB which disproportionately affects children and immunocompromised individuals. Studies in pulmonary TB have shown that Mycobacterium tuberculosis can alter host lipid metabolism to evade the immune system. Cholesterol lowering drugs (i.

Inhibition of post-lanosterol biosynthesis by fentanyl: potential implications for Fetal Fentanyl Syndrome (FFS).

A recent study discovered a novel, complex developmental disability syndrome, most likely caused by maternal fentanyl use disorder. This Fetal Fentanyl Syndrome (FFS) is biochemically characterized by elevated 7-dehydrocholesterol (7-DHC) levels in neonates, raising the question if fentanyl inhibition of the dehydrocholesterol reductase 7 (DHCR7) enzyme is causal for the emergence of the pathophysiology and phenotypic features of FFS. To test this hypothesis, we undertook a series of experiments on Neuro2a cells, primary mouse neuronal and astrocytic cultures, and human dermal fibroblasts (HDFs) with DHCR7 and DHCR7 genotype.

GAPDH inhibition mediated by thiol oxidation in human airway epithelial cells exposed to an environmental peroxide.

Intracellular redox homeostasis in the airway epithelium is closely regulated through adaptive signaling and metabolic pathways. However, inhalational exposure to xenobiotic stressors such as secondary organic aerosols (SOA) can alter intracellular redox homeostasis. Isoprene hydroxy hydroperoxide (ISOPOOH), a ubiquitous volatile organic compound derived from the atmospheric photooxidation of biogenic isoprene, is a major contributor to SOA.

Intramolecular H-Atom Transfers in Alkoxyl Radical Intermediates Underlie the Apparent Oxidation of Lipid Hydroperoxides by Fe(II).

The one-electron reduction of lipid hydroperoxides by low-valent iron species is believed to be a driver of cellular lipid peroxidation and associated ferroptotic cell death. We investigated reactions of cholesterol 7α-OOH, the primary cholesterol autoxidation product, with Fe to find that 7-ketocholesterol (7-KC, an oxidation product) is the major product under these (reducing) conditions. Mechanistic studies reveal the intervention of a 1,2-H-atom shift upon formation of the 7-alkoxyl radical to yield a ketyl radical that can be oxidized by either Fe or O to give 7-KC, the most abundant oxysterol .

Plasma sterols and vitamin D are correlates and predictors of ozone-induced inflammation in the lung: A pilot study.

Background: Ozone (O3) exposure causes respiratory effects including lung function decrements, increased lung permeability, and airway inflammation. Additionally, baseline metabolic state can predispose individuals to adverse health effects from O3. For this reason, we conducted an exploratory study to examine the effect of O3 exposure on derivatives of cholesterol biosynthesis: sterols, oxysterols, and secosteroid (25-hydroxyvitamin D) not only in the lung, but also in circulation.

Dose-Response Effects of 7-Dehydrocholesterol Reductase Inhibitors on Sterol Profiles and Vesicular Stomatitis Virus Replication.

Cholesterol is ubiquitous in cells; it plays a critical role in membrane structure and transport as well as in intracellular trafficking processes. There are suggestions that cholesterol metabolism is linked to innate immunity with inhibitors of DHCR7, the last enzyme in the cholesterol pathway, suggested to have potential as viral therapeutics nearly a decade ago. In fact, there are a number of highly prescribed pharmaceuticals that are off-target inhibitors of DHCR7, causing increased cellular levels of 7-dehydrodesmosterol (7-DHD) and 7-dehydrocholesterol (7-DHC).

Glucocorticoids are induced while dihydrotestosterone levels are suppressed in 5-alpha reductase inhibitor treated human benign prostate hyperplasia patients.

Background: The development of benign prostatic hyperplasia (BPH) and medication-refractory lower urinary tract symptoms (LUTS) remain poorly understood. This study attempted to characterize the pathways associated with failure of medical therapy for BPH/LUTS.

Methods: Transitional zone tissue levels of cholesterol and steroids were measured in patients who failed medical therapy for BPH/LUTS and controls.

Expressing the Human Cholesteryl Ester Transfer Protein Minigene Improves Diet-Induced Fatty Liver and Insulin Resistance in Female Mice.

Mounting evidence has shown that CETP has important physiological roles in adapting to chronic nutrient excess, specifically, to protect against diet-induced insulin resistance. However, the underlying mechanisms for the protective roles of CETP in metabolism are not yet clear. Mice naturally lack CETP expression.

Oxysterols Modify NLRP2 in Epithelial Cells, Identifying a Mediator of Ozone-induced Inflammation.

Ozone (O) is a prevalent air pollutant causing lung inflammation. Previous studies demonstrate that O oxidizes lipids, such as cholesterol, in the airway to produce oxysterols, such as secosterol A (SecoA), which are electrophiles that are capable of forming covalent linkages preferentially with lysine residues and that consequently modify protein function. The breadth of proteins modified by this oxysterol as well as the biological consequences in the lung are unknown.

Screening ToxCast™ for Chemicals That Affect Cholesterol Biosynthesis: Studies in Cell Culture and Human Induced Pluripotent Stem Cell-Derived Neuroprogenitors.

Background: Changes in cholesterol metabolism are common hallmarks of neurodevelopmental pathologies. A diverse array of genetic disorders of cholesterol metabolism support this claim as do multiple lines of research that demonstrate chemical inhibition of cholesterol biosynthesis compromises neurodevelopment. Recent work has revealed that a number of commonly used pharmaceuticals induce changes in cholesterol metabolism that are similar to changes induced by genetic disorders with devastating neurodevelopmental deficiencies.

Small Molecule Antipsychotic Aripiprazole Potentiates Ozone-Induced Inflammation in Airway Epithelium.

Inhaled ground level ozone (O) has well described adverse health effects, which may be augmented in susceptible populations. While conditions, such as pre-existing respiratory disease, have been identified as factors enhancing susceptibility to O-induced health effects, the potential for chemical interactions in the lung to sensitize populations to pollutant-induced responses has not yet been studied. In the airways, inhaled O reacts with lipids, such as cholesterol, to generate reactive and electrophilic oxysterol species, capable of causing cellular dysfunction and inflammation.

Identification and characterization of prescription drugs that change levels of 7-dehydrocholesterol and desmosterol.

Regulating blood cholesterol (Chol) levels by pharmacotherapy has successfully improved cardiovascular health. There is growing interest in the role of Chol precursors in the treatment of diseases. One sterol precursor, desmosterol (Des), is a potential pharmacological target for inflammatory and neurodegenerative disorders.

Probes for protein adduction in cholesterol biosynthesis disorders: Alkynyl lanosterol as a viable sterol precursor.

The formation of lipid electrophile-protein adducts is associated with many disorders that involve perturbations of cellular redox status. The identities of adducted proteins and the effects of adduction on protein function are mostly unknown and an increased understanding of these factors may help to define the pathogenesis of various human disorders involving oxidative stress. 7-Dehydrocholesterol (7-DHC), the immediate biosynthetic precursor to cholesterol, is highly oxidizable and gives electrophilic oxysterols that adduct proteins readily, a sequence of events proposed to occur in Smith-Lemli-Opitz syndrome (SLOS), a human disorder resulting from an error in cholesterol biosynthesis.

Ozone-derived Oxysterols Affect Liver X Receptor (LXR) Signaling: A POTENTIAL ROLE FOR LIPID-PROTEIN ADDUCTS.

When inhaled, ozone (O) interacts with cholesterols of airway epithelial cell membranes or the lung-lining fluid, generating chemically reactive oxysterols. The mechanism by which O-derived oxysterols affect molecular function is unknown. Our data show that in vitro exposure of human bronchial epithelial cells to O results in the formation of oxysterols, epoxycholesterol-α and -β and secosterol A and B (Seco A and Seco B), in cell lysates and apical washes.

Inhibitors of 7-Dehydrocholesterol Reductase: Screening of a Collection of Pharmacologically Active Compounds in Neuro2a Cells.

A small library of pharmacologically active compounds (the NIH Clinical Collection) was assayed in Neuro2a cells to determine their effect on the last step in the biosynthesis of cholesterol, the transformation of 7-dehydrocholesterol (7-DHC) to cholesterol promoted by 7-dehydrocholesterol reductase, DHCR7. Of some 727 compounds in the NIH Clinical Collection, over 30 compounds significantly increased 7-DHC in Neuro2a cells when assayed at 1 μM. Active compounds that increased 7-DHC with a Z-score of +3 or greater generally gave rise to modest decreases in desmosterol and increases in lanosterol levels.

The Effect of Small Molecules on Sterol Homeostasis: Measuring 7-Dehydrocholesterol in Dhcr7-Deficient Neuro2a Cells and Human Fibroblasts.

Well-established cell culture models were combined with new analytical methods to assess the effects of small molecules on the cholesterol biosynthesis pathway. The analytical protocol, which is based on sterol derivation with the dienolphile PTAD, was found to be reliable for the analysis of 7-DHC and desmosterol. The PTAD method was applied to the screening of a small library of pharmacologically active substances, and the effect of compounds on the cholesterol pathway was determined.

Assay of protein and peptide adducts of cholesterol ozonolysis products by hydrophobic and click enrichment methods.

Cholesterol undergoes ozonolysis to afford a variety of oxysterol products, including cholesterol-5,6-epoxide (CholEp) and the isomeric aldehydes secosterol A (seco A) and secosterol B (seco B). These oxysterols display numerous important biological activities, including protein adduction; however, much remains to be learned about the identity of the reactive species and the range of proteins modified by these oxysterols. Here, we synthesized alkynyl derivatives of cholesterol-derived oxysterols and employed a straightforward detection method to establish secosterols A and B as the most protein-reactive of the oxysterols tested.

Probing lipid-protein adduction with alkynyl surrogates: application to Smith-Lemli-Opitz syndrome.

Lipid modifications aid in regulating (and misregulating) protein function and localization. However, efficient methods to screen for a lipid's ability to modify proteins are not readily available. We present a strategy to identify protein-reactive lipids and apply it to a neurodevelopmental disorder, Smith-Lemli-Opitz syndrome (SLOS).

Superoxide reaction with tyrosyl radicals generates para-hydroperoxy and para-hydroxy derivatives of tyrosine.

Tyrosine-derived hydroperoxides are formed in peptides and proteins exposed to enzymatic or cellular sources of superoxide and oxidizing species as a result of the nearly diffusion-limited reaction between tyrosyl radical and superoxide. However, the structure of these products, which informs their reactivity in biology, has not been unequivocally established. We report here the complete characterization of the products formed in the addition of superoxide, generated from xanthine oxidase, to several peptide-derived tyrosyl radicals, formed from horseradish peroxidase.

Biotinylated probes for the analysis of protein modification by electrophiles.

Formation of covalent protein adducts by lipid electrophiles contributes to diseases and toxicities linked to oxidative stress, but analysis of the adducts presents a challenging analytical problem. We describe selective adduct capture using biotin affinity probes to enrich protein and peptide adducts for analysis by liquid chromatography-tandem mass spectrometry (LC-MS/MS). One approach employs biotinamidohexanoic acid hydrazide to covalently label residual carbonyl groups on adducts.

Tyrosine-lipid peroxide adducts from radical termination: para coupling and intramolecular Diels-Alder cyclization.

Free radical co-oxidation of polyunsaturated lipids with tyrosine or phenolic analogues of tyrosine gave rise to lipid peroxide-tyrosine (phenol) adducts in both aqueous micellar and organic solutions. The novel adducts were isolated and characterized by 1D and 2D NMR spectroscopy as well as by mass spectrometry (MS). The spectral data suggest that the polyunsaturated lipid peroxyl radicals give stable peroxide coupling products exclusively at the para position of the tyrosyl (phenoxy) radicals.