title: Isoeugenol destabilizes IL-8 mRNA expression in THP-1 cells through induction of the negative regulator of mRNA stability tristetraprolin.
abstract: We previously demonstrated in the human promyelocytic cell line THP-1 that all allergens tested, with the exception of the prohapten isoeugenol, induced a dose-related release of interleukin-8 (IL-8). In the present study, we investigated whether this abnormal behavior was regulated by the AU-rich element-binding proteins HuR and tristetraprolin (TTP) or by the downstream molecule suppressor of cytokine signaling (SOCS)-3. The contact allergens isoeugenol, diethylmaleate (DEM), and 2,4-dinitrochlorobenzene (DNCB), and the irritant salicylic acid were used as reference compounds. Chemicals were used at concentrations that induced a 20% decrease in cell viability as assessed by propidium iodide staining, namely 100 μg/ml (0.61 mM) for isoeugenol, 100 μg/ml (0.58 mM) for DEM, 3 μg/ml (14.8 μM) for DNCB, and 250 μg/ml (1.81 mM) for salicylic acid. Time course experiments of IL-8 mRNA expression and assessment of IL-8 mRNA half-life, indicated a decreased IL-8 mRNA stability in isoeugenol-treated cells. We could demonstrate that a combination and regulation of HuR and TTP following exposure to contact allergens resulted in a different modulation of IL-8 mRNA half-life and release. The increased expression of TTP in THP-1 cells treated with isoeugenol results in destabilization of the IL-8 mRNA, which can account for the lack of IL-8 release. In contrast, the strong allergen DNCB failing to up-regulate TTP, while inducing HuR, resulted in longer IL-8 mRNA half-life and protein release. SOCS-3 was induced only in isoeugenol-treated cells; however, its modulation did not rescue the lack of IL-8 release, indicating that it is unlikely to be involved in the lack of IL-8 production. Finally, the destabilization effect of isoeugenol on IL-8 mRNA expression together with SOCS-3 expression resulted in an anti-inflammatory effect, as demonstrated by the ability of isoeugenol to modulate LPS or ionomycin-induced cytokine release.
authors.affiliation: Department of Pharmacological Sciences, Faculty of Pharmacy, Laboratory of Toxicology, Università degli Studi di Milano, Via Balzaretti 9, 20133, Milan, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Galbiati
authors.forename: Alice
authors.initials: A
authors.lastname: Carne
authors.forename: Montserrat
authors.initials: M
authors.lastname: Mitjans
authors.forename: Corrado Lodovico
authors.initials: CL
authors.lastname: Galli
authors.forename: Marina
authors.initials: M
authors.lastname: Marinovich
authors.forename: Emanuela
authors.initials: E
authors.lastname: Corsini
mesh_terms: D000485:Allergens / Q000494:pharmacology*; D002460:Cell Line; D016207:Cytokines / Q000378:metabolism; D004137:Dinitrochlorobenzene / Q000494:pharmacology; D005054:Eugenol / Q000031:analogs & derivatives* / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D016209:Interleukin-8 / Q000096:biosynthesis* / Q000235:genetics; D009000:Monocytes / Q000187:drug effects* / Q000378:metabolism; D020871:RNA Stability / Q000187:drug effects*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins / Q000378:metabolism; D051816:Tristetraprolin / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism
chemical_list: D000485:Allergens; D016207:Cytokines; D004137:Dinitrochlorobenzene; D016209:Interleukin-8; D012333:RNA, Messenger; C106644:SOCS3 protein, human; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D051816:Tristetraprolin; D005054:Eugenol; C036643:isoeugenol