Mass spectrometry-based metabolomics study of nicotine exposure in THP-1 monocytes.

The tobacco alkaloid nicotine is known for its activation of neuronal nicotinic acetylcholine receptors. Nicotine is consumed in different ways such as through conventional smoking, e-cigarettes, snuff or nicotine pouches. The use of snuff has been associated with several adverse health effects, such as inflammatory reactions of the oral mucosa and oral cavity cancer. We performed a metabolomic analysis of nicotine-exposed THP-1 human monocytes. Cells were exposed to 5 mM of the alkaloid for up to 4 h, and cell extracts and medium subjected to untargeted liquid chromatography high-resolution mass spectrometry. Raw data processing revealed 17 nicotine biotransformation products. Among these, cotinine and nornicotine were identified as the two major cellular biotransformation products. The application of multi- and univariate statistical analyses resulted in the annotation, up to a certain level of identification, of 12 compounds in the cell extracts and 13 compounds in the medium that were altered by nicotine exposure. Of these, four were verified as methylthioadenosine, cytosine, uric acid, and L-glutamate. Methylthioadenosine levels were affected in both cells and the medium, while cytosine, uric acid, and L-glutamate levels were affected in the medium only. The effects of smoking on the pathways involving these metabolites have been previously demonstrated in humans. Most of the other discriminating compounds, which were merely tentatively or not fully identified, were amino acids or amino acid derivatives. In conclusion, our preliminary data suggest that some of the potentially adverse effects related to smoking may also be expected when nicotine is consumed via snuff or nicotine pouches.

The dental monomer 2-hydroxyethyl methacrylate (HEMA) causes transcriptionally regulated adaptation partially initiated by electrophilic stress.

OBJECTIVES: Cellular responses including cell death are induced by in vitro exposure to the un-polymerized dental monomer 2-hydroxyethyl methacrylate (HEMA). Activation of the Nrf2/ARE signaling pathway has been suggested to mediate the cellular responses. Activation of this pathway may occur either indirectly through generation of increased oxidative stress or through direct binding to cysteine thiols due to the electrophilic properties of HEMA. The objective of this study was to elucidate the potential mechanism of Nrf2/ARE pathway activation after HEMA exposure. METHODS: Global gene expression was investigated after exposure of the human bronchial epithelial cell line BEAS-2B to 2mM HEMA for 4h. After exposure to 0.5, 1 or 2mM HEMA for up to 24h, western analysis was performed for selected proteins. Finally, the levels of the same proteins were determined after treatment with either the antioxidants Vitamin C, Trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid) or BSO (L-buthioninesulfoximine), an inhibitor of GSH formation. RESULTS: Several of the 25 genes with the highest increase in gene transcription are related to oxidative stress responses. Increased levels of 5 corresponding proteins (HO-1, GCLC, GCLM, NQO1 and SQSTM1) were observed. Antioxidant treatment as well as inhibition of GSH did not affect upregulation of these proteins. Thus, increased ROS or reduced GSH levels appear to be of limited importance in the observed HEMA-induced changes. SIGNIFICANCE: Knowledge of the cellular responses to HEMA is important to evaluate the safety of HEMA-containing biomaterials. The results support that HEMA activates the Nrf2-ARE transcriptional pathway directly through its electrophilic properties.

Di-n-butyl phthalate modifies PMA-induced macrophage differentiation of THP-1 monocytes via PPARγ.

The present study examined the effects of di-n-butyl phthalate (DBP) on phorbol myristate acetate (PMA)-induced macrophage differentiation of THP-1 monocytes, determined by morphological classification and flow cytometry. Focusing on the expression of the surface marker CD36, the potential role of peroxisome proliferator-activated receptor gamma (PPARγ) was examined using various PPARγ agonists and antagonists. As the PPARγ ligand-binding domain contains multiple ligand-binding sites (LBS), agonist and antagonists targeting the different sites were used. DBP accelerated PMA-induced morphological changes and increased expression of CD36, although to a lesser degree than the PPARγ agonists rosiglitazone and 15-deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2). A proteomics screening revealed that DBP enhanced the expression of PPARγ-regulated proteins. During combined exposures, DBP partly attenuated the effect of rosiglitazone, an agonist binding reversibly to PPARγ's canonical LBS. In contrast, DBP increased expression of CD36 in combination with 15d-PGJ2 which binds irreversibly to the canonical LBS. Thus, DBP appears to interact with both the canonical and alternative LBS. Accordingly, the antagonist GW9662, which binds to the canonical LBS, only partly reduced the DBP-induced CD36 expression, while the dual-site antagonist SR16832 completely blocked the effects of DBP. Overall, the results show that DBP modifies PMA-induced differentiation of THP-1 cells through interaction with PPARγ.