The Monocytic Cell Line THP-1 as a Validated and Robust Surrogate Model for Human Dendritic Cells

We have implemented an improved, cost-effective, and highly reproducible protocol for a simple and rapid differentiation of the human leukemia monocytic cell line THP-1 into surrogates for immature dendritic cells (iDCs) or mature dendritic cells (mDCs). The successful differentiation of THP-1 cells into iDCs was determined by high numbers of cells expressing the DC activation markers CD54 (88%) and CD86 (61%), and the absence of the maturation marker CD83. The THP-1-derived mDCs are characterized by high numbers of cells expressing CD54 (99%), CD86 (73%), and the phagocytosis marker CD11b (49%) and, in contrast to THP-1-derived iDCs, CD83 (35%) and the migration marker CXCR4 (70%). Treatment of iDCs with sensitizers, such as NiSO4 and DNCB, led to high expression of CD54 (97%/98%; GMFI, 3.0/3.2-fold induction) and CD86 (64%/96%; GMFI, 4.3/3.2-fold induction) compared to undifferentiated sensitizer-treated THP-1 (CD54, 98%/98%; CD86, 55%/96%). Thus, our iDCs are highly suitable for toxicological studies identifying potential sensitizing or inflammatory compounds. Furthermore, the expression of CD11b, CD83, and CXCR4 on our iDC and mDC surrogates could allow studies investigating the molecular mechanisms of dendritic cell maturation, phagocytosis, migration, and their use as therapeutic targets in various disorders, such as sensitization, inflammation, and cancer.

Ligandability Assessment of Human Glutathione Transferase M1-1 Using Pesticides as Chemical Probes

Glutathione transferases (GSTs; EC 2.5.1.18) form a group of multifunctional enzymes that are involved in phase II of the cellular detoxification mechanism and are associated with increased susceptibility to cancer development and resistance to anticancer drugs. The present study aims to evaluate the ligandability of the human GSTM1-1 isoenzyme (hGSTM1-1) using a broad range of structurally diverse pesticides as probes. The results revealed that hGSTM1-1, compared to other classes of GSTs, displays limited ligandability and ligand-binding promiscuity, as revealed by kinetic inhibition studies. Among all tested pesticides, the carbamate insecticide pirimicarb was identified as the strongest inhibitor towards hGSTM1-1. Kinetic inhibition analysis showed that pirimicarb behaved as a mixed-type inhibitor toward glutathione (GSH) and 1-chloro-2,4-dinitrobenzene (CDNB). To shine a light on the restricted hGSTM1-1 ligand-binding promiscuity, the ligand-free crystal structure of hGSTM1-1 was determined by X-ray crystallography at 1.59 Å-resolution. Comparative analysis of ligand-free structure with the available ligand-bound structures allowed for the study of the enzyme's plasticity and the induced-fit mechanism operated by hGSTM1-1. The results revealed important structural features of the H-site that contribute to xenobiotic-ligand binding and specificity. It was concluded that hGSTM1-1 interacts preferentially with one-ring aromatic compounds that bind at a discrete site which partially overlaps with the xenobiotic substrate binding site (H-site). The results of the study form a basis for the rational design of new drugs targeting hGSTM1-1.

Cholinesterases and neurotoxicity as highly sensitive biomarkers for an organophosphate insecticide in a freshwater gastropod (Chilina gibbosa) with low sensitivity carboxylesterases

In the Upper Valley of Río Negro and Río Neuquén in Argentina, agriculture represents the second most important economic activity. Azinphos-methyl has been found in water from this region throughout the year at a maximum concentration of 22.48 μg L(-1) during the application period. Toxicological studies on local non-target species have been performed mostly on vertebrates, while mollusks, which could be more sensitive, have not been studied so far. This work aims to characterize cholinesterase (ChE) and carboxilesterase (CE) activities of Chilina gibbosa, a freshwater gastropod native to southern Argentina and Chile. These enzymes, together with neurotoxicity signals, are evaluated herein after as sensitive biomarkers of exposure to azinphos-methyl at environmentally relevant concentrations. Effects of azinphos-methyl on antioxidant defenses: glutathione (GSH), catalase (CAT), superoxide dismutase (SOD) and glutathione S-transferase (GST) are also studied in order to complete a set of biomarkers with different sensitivity and specificity, to propose C. gibbosa as a sentinel species. The highest specific activity was obtained with acetylthiocholine as substrate, followed by propionylthiocholine (83% in comparison to acetylthiocholine) and butyrylthiocholine (19%).The lowest Km and the highest efficiency for ChE were obtained with acetylthiocholine. Regarding CEs activities, a higher efficiency was obtained with p-nitrophenyl butyrate than with p-nitrophenyl acetate. Eserine produced significant inhibition of ChE activity (81% with 0.001 mM and 98% with 1mM) while iso-OMPA did not produce any significant effect on ChE. Our results show that C. gibbosa ChE is very sensitive to azinphos-methyl (CI50 0.02 μg L(-1)) while CEs are inhibited at higher concentrations (CI50 1,000 μg L(-1)). CEs have been reported to be more sensitive to OPs than ChEs in most of the aquatic invertebrates protecting the organisms from neurotoxic effects. In contrast, C. gibbosa, has ChE which are much more sensitive to azinphos-methyl than CEs and shows marked signs of neurotoxicity. Regarding antioxidant defenses, GSH levels were significantly increased by 0.02 and 20 μg L(-1) azinphos-methyl (80 and 103%, respectively), CAT activity was increased 85% only at 0.02 μg L(-1) and SOD and GST did not show any significant response. Since ChE activity, neurotoxicity signs, GSH and CAT are sensitive biomarkers of acute exposure to azinphos-methyl at environmental concentrations C. gibbosa could be included as sentinel species in monitoring programs of pesticide hazard in regions of Argentina and Chile.

Glutathione S-transferase (GST) family in barley: identification of members, enzyme activity, and gene expression pattern

Barley (Hordeum vulgare) is one of the most important cereals in many developing countries where drought stress considerably diminishes agricultural production. Glutathione S-transferases (GSTs EC 2.5.1.18) are multifunctional enzymes which play a crucial role in cellular detoxification and oxidative stress tolerance. In this study, 84 GST genes were identified in barley by a comprehensive in silico approach. Sequence alignment and phylogenetic analysis grouped these HvGST proteins in eight classes. The largest numbers of the HvGST genes (50) were included in the Tau class followed by 21 genes in Phi, five in Zeta, two in DHAR, two in EF1G, two in Lambda, and one each in TCHQD and Theta classes. Phylogenetic analysis of the putative GSTs from Arabidopsis, rice, and barley indicated that major functional diversification within the GST family predated the monocot/dicot divergence. However, intra-specious duplication seems to be common. Expression patterns of five GST genes from Phi and Tau classes were investigated in three barley genotypes (Yusof [drought-tolerant], Moroc9-75 [drought-sensitive], and HS1 [wild ecotype]) under control and drought-stressed conditions, during the vegetative stage. All investigated genes were up-regulated significantly under drought stress and/or showed a higher level of transcripts in the tolerant cultivar. Additionally, GST enzyme activity was superior in Yusof and induced in the extreme-drought-treated leaves, while it was not changed in Moroc9-75 under drought conditions. Moreover, the lowest and highest levels of lipid peroxidation were observed in the Yusof and Moroc9-75 cultivars, respectively. Based on the achieved results, detoxification and antioxidant activity of GSTs might be considered an important factor in the drought tolerance of barley genotypes for further investigations.

De novo galectin-3 expression influences the response of melanoma cells to isatin-Schiff base copper (II) complex-induced oxidative stimulus

Galectin-3, a ubiquitous member of the galectin family, has been shown to control cellular proliferation, adhesion, migration and apoptosis; thus, it has a role in tumor development and progression. Galectin-3 expression is both up- and down-regulated during melanoma progression. However, conflicting data regarding its roles in tumor biology prompted us to investigate if the presence of galectin-3 influences the response of melanoma cells to a novel metallodrug because metastatic melanoma acquires chemo resistance and is reported to be redox-sensitive. Previously, it was demonstrated that the complex [bis-(2-oxindol-3-yl-imino)-2-(2-aminoethyl) pyridine-N,N'] copper (II) perchlorate, herein referred to as [Cu(isaepy)], induces ROS formation and apoptosis in neuroblastoma cells through mitochondrial uncoupling and the activation of AMPK/p38/p53 signaling. Here, we used a model of vertical growth melanoma (TM1), in which GAL3 expression is lost during tumor progression. When de novo expressed, galectin-3 was found to be ubiquitously present in all subcellular compartments. Our results demonstrate that de novo galectin-3 expression impairs the cellular antioxidant system and renders TM1G3 cells more susceptible than GAL3-null TM1MNG3 cells to [Cu(isaepy)] treatment. This compound, in contrast with the redox inactive [dichloro (2-oxindol-3-yl-imino)-2-(2-aminoethyl) pyridine-N,N'] zinc (II), herein referred to as [Zn(isaepy)], leads to increased intracellular ROS accumulation, increased carbonyl stress, increased mitochondrial depolarization, decreased cell adhesion, increased p38 activation and apoptosis in TM1G3, compared with TM1MNG3. Cell death was shown to be dependent on a hydrogen peroxide-derived species and on the activation of p38. Because mitochondria are a target of both [Cu(isaepy)] and galectin-3, we propose that the presence of galectin-3 in this organelle favors increased ROS production, thereby inducing oxidative cellular damage and apoptotic death. Therefore, [Cu(isaepy)] may be envisaged as a possible anti-melanoma strategy, particularly for melanomas that express galectin-3.