Differential signatures of protein glycosylation and phosphorylation in human Chang liver cells induced by TCDD treatment.

Dioxins are a class of polyhalogenated aromatic hydrocarbons that induces a wide spectrum of toxic responses in animals. Health effects have been studied intensively, but the detailed molecular mechanisms are quite complex and not yet fully understood. In this study, the effects of model dioxin, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on protein modifications such as glycosylation and phosphorylation were extensively studied. Using 2-D electrophoresis, various protein visualizations techniques, protein modification-dependent enrichments techniques and mass spectrometry, we performed comparative proteomic investigations on Chang human liver cells before and after the treatment with TCDD. Many glycoproteins and phosphoproteins were found to be affected by the TCDD treatment. The glycosylations on Cathepsin B, HSP60, the subunit 5 of chaperonin containing TCP1 complex, and Prolyl 4-hydroxylase beta-subunit were increased. Heat shock 70 kDa protein 5 and ATP synthase beta subunit showed enhanced or reduced phosphorylation, respectively. Two microtubule associated proteins, Microtubule-associated protein 1S and ARP1 actin-related protein 1 homolog A showed enhanced tyrosine phosphorylation. The data in this study provide interesting insights on the molecular and biochemical events of TCDD-mediated toxicities.

Glycoproteomic analysis of plasma from patients with atopic dermatitis: CD5L and ApoE as potential biomarkers.

Atopic dermatitis (AD) is an inflammatory skin disorder that is both uncomfortable and distressing to patients, and its prevalence has been steadily increasing. It is obvious that the identification of efficient markers of AD in plasma would offer the possibility of effective diagnosis, prevention, and treatment strategies. In this study, a proteomic approach was used to analyze plasma glycoproteins from both children with AD and healthy child donors. Several protein spots showing significant quantitative changes in the AD patients were identified. Through sequential studies, it was confirmed that CD5L and ApoE were significantly up-regulated or down-regulated, respectively, in the plasma from AD patients compared with that from healthy donors. In addition, we suggest that the up-regulated CD5L in AD patients causes eosinophilia by inhibiting apoptosis or promoting the proliferation of eosinophils either in combination with or without IL-5. The glycoproteomic data in this study provides clues to understanding the mechanism of atopic alterations in plasma and suggests AD-related proteins can be used as candidate markers for AD.

Quantitative relationship of dioxin-responsive gene expression to dioxin response element in Hep3B and HepG2 human hepatocarcinoma cell lines.

Dioxin response element (DRE) is a cis-acting DNA sequence mediating the 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced gene expression. The present study was undertaken to elucidate TCDD-responsive gene expression profiles and their relationships to the number of DREs in liver cancer cells. Hep3B and HepG2 human hepatocarcinoma cells were exposed to 50-nM TCDD for 0, 1, 2 and 4h in culture, after which gene expression profiles were analyzed by the microarray hybridization using a chip containing 24,000 cDNAs prepared from the human liver. The TCDD-responsive expression levels in each gene were calculated by dividing the densitometric values of the hybridization signal for h1, h2 and h4 by that of h0, followed by transformation of the resulting data into a log scale with the base of 2. Up- and down-regulated gene expressions were defined as >0.585 and <-0.585 by the log scale (>1.5 and <1/1.5 arithmetically), respectively, exhibited at any time after h0. Hep3B and HepG2 cells had 27 and 58 TCDD-responsive, up-regulated genes, respectively, of which 78% (21/27) and 62% (36/58) had one or more DREs. Of these 85, 80 genes were up-regulated exclusively in one of the two lines, with CYP1A1 and PPP1R15A being so regulated in both lines. Expression levels of the up-regulated genes at h1, h2 and h4 were correlated with each other (P<0.01) and the mean of these regressed to the number of DRE(s) in both lines (P<0.01). However, expression of a total of 93 TCDD-responsive, down-regulated genes, of which 46% contained DRE(s), had no relation to the number of DRE(s). In conclusion, results suggest that DREs may cooperatively mediate the expression of TCDD-responsive genes in liver cancer cells.