Factors impacting the formation of 3-MCPD esters and glycidyl esters during deep fat frying of chicken breast meat

The effect of the frying temperature, frying duration and the addition of NaCl on the formation of 3-monochloropropane-1,2-diol (3-MCPD) esters and glycidyl esters (GE) in palm olein after deep frying was examined in this study. The eight frying systems were deep-fat frying (at 160 and 180 °C) of chicken breast meat (CBM) (with 0, 1, 3 and 5% sodium chloride, NaCl) for 100 min/day for five consecutive days. All oil samples collected after each day were analyzed for 3-MCPD ester, GE, and free fatty acid (FFA) contents, specific extinctions at 232 and 268 nm (K 232 and K 268), p-anisidine value (pA), and fatty acid composition. There was a significant (p < 0.05) decrease in the 3-MCPD esters and a significant (p < 0.05) decrease in the GE with the increasing of the frying duration. There were significant (p < 0.05) increases in the 3-MCPD esters formed when the concentration of NaCl increased from 0 to 5%. The addition of NaCl to the CBM during deep frying had no significant effect on the GE generation. The FFA contents, K 232 and K 268 and pA showed that all the frying oils were within the safety limit

The immunochemical cross-reactivity between cytoplasmic and mitochondrial mammalian lysyl-tRNA synthetases

Animal and fungal cells (in contrast to prokaryotes) contain two distinct sets of related aminoacyl-tRNA synthetases (aaRSs) encoded by nuclear genes and functioning in cytosol and mitochondria. The structural differences between mitochondrial and cytoplasmic enzymes may reflect the functional adaptation to fulfil mitochondrial processes in addition to protein synthesis. Mitochondrial import of nuclearencoded tRNAs has been described in yeast, plants and protozoans but it has not been observed in mammalian cells. Ifs established that mitochondrial lysyl-tRNA synthetase (MSK) plays a prominent role in the transport of tRNA into yeast mitochondria for complementation o f mitochondrial tRNAs genes mutations. We tried to identify MSK homologues in mammalian cells with the help of monospecific antibodies against pre-MSK by ELISA and Western-blot analysis. We have identified cross-reactive proteins in mitochondrial and cytoplasmic fractions of mammalian cell lysates. These data, together with the results of cross-aminoacylation on mitochondrial and cytoplasmic tRNAs, suggest the presence of common antigenic determinants in the mitochondrial and cytoplasmic lysyl-tRNA synthetases from higher animals.Клітини еукаріот на відміну від прокаріот містять дві різні групи аміноацил-тРНК синтетаз, які кодуються ядерним геномом та функціонують в цитозолі і мітохондріях. Струк­турні відмінності між ферментами мітохондрій і цитоплаз­ми можуть бути відображенням функціональної адаптації до процесів, які відбуваються в мітохондріях, крім участі в біосинтезі білка. Імпорт цитозольних тРНК у мітохондрії описано для дріжджів, рослин і найпростіиіих, однак він не спостерігався в клітинах ссавців. Виявлено, що мітохондріальна лізил-тРНК синтетаза (MSK) відіграє провідну роль у транспорті тРНК у мітохондрії дріжджів для комплемен­тації мутацій мітохондріальних генів тРНК За допомогою моноспецифічних антитіл проти npe-MSK ми зробили спробу ідентифікувати гомологи MSK у клітинах ссавців методами ELISA і Вестерн-блотинга. В цитоплазматичних і міто­хондріальних фракціях лізатів клітин ссавців нам вдалося виявити білки, які мають імунологічний перехрест з MSK Разом з результатами перехресного аміноацилювання ці дані дають підставу для припущення щодо наявності спільних антигенних детермінант у мітохондріальних і цитоплазма­тичних лізил-тРНК синтетаз ссавців.Клетки эукариот (в отличие от клеток прокариот) содержат две различные группы аминоацил-тРНК синтетаз, кодируе­мых ядерным геномом и функционирующих в ц и то золе и митохондриях. Структурные отличия между ферментами митохондрий и цитоплазмы могут быть отражением функци­ональной адаптации к процессам, происходящим в митохонд­риях помимо участия в биосинтезе белка Импорт цитозольных тРНК в митохондрии описан у дрожжей, растений и простейших, однако не наблюдался в клетках млекопитаю­щих. Установлено, что митохондриальная лизил-тРНК син­тетаза (MSK) играет ведущую роль в транспорте тРНК в митохондрии дрожжей для комплементации мутаций митохондриальных генов тРНК. С помощью моноспецифических антител против npe-MSK мы попытались идентифицировать гомологи MSK в клетках млекопитающих методами ELISA и Вестерн-блотинга. В цитоплазматических и митохондриальных фракциях лизатов клеток млекопитающих нам удалось обнаружить белки, имеющие иммунологический перекрест с MSK В совокупности с результатами перекрестного аминоацилирования эти данные дают основание предположить нали­чие общих антигенных детерминант у митохондриальных и цитоплазматических лизил-тРНК синтетаз высших живо­тных

Aristolochic Acid I Induced Autophagy Extenuates Cell Apoptosis via ERK 1/2 Pathway in Renal Tubular Epithelial Cells

Autophagy is a lysosomal degradation pathway that is essential for cell survival and tissue homeostasis. However, limited information is available about autophagy in aristolochic acid (AA) nephropathy. In this study, we investigated the role of autophagy and related signaling pathway during progression of AAI-induced injury to renal tubular epithelial cells (NRK52E cells). The results showed that autophagy in NRK52E cells was detected as early as 3–6 hrs after low dose of AAI (10 µM) exposure as indicated by an up-regulated expression of LC3-II and Beclin 1 proteins. The appearance of AAI-induced punctated staining of autophagosome-associated LC3-II upon GFP-LC3 transfection in NRK52E cells provided further evidence for autophagy. However, cell apoptosis was not detected until 12 hrs after AAI treatment. Blockade of autophagy with Wortmannin or 3-Methyladenine (two inhibitors of phosphoinositede 3-kinases) or small-interfering RNA knockdown of Beclin 1 or Atg7 sensitized the tubular cells to apoptosis. Treatment of NRK52E cells with AAI caused a time-dependent increase in extracellular signal-regulated kinase 1 and 2 (ERK1/2) activity, but not c-Jun N-terminal kinase (JNK) and p38. Pharmacological inhibition of ERK1/2 phosphorylation with U0126 resulted in a decreased AAI-induced autophagy that was accompanied by an increased apoptosis. Taken together, our study demonstrated for the first time that autophagy occurred earlier than apoptosis during AAI-induced tubular epithelial cell injury. Autophagy induced by AAI via ERK1/2 pathway might attenuate apoptosis, which may provide a protective mechanism for cell survival under AAI-induced pathological condition

Absorption and Metabolism of cis-9,trans-11-CLA and of Its Oxidation Product 9,11-Furan Fatty Acid by Caco-2 Cells

Furan fatty acids (furan-FA) can be formed by auto-oxidation of conjugated linoleic acids (CLA) and may therefore be ingested when CLA-containing foodstuff is consumed. Due to the presence of a furan ring structure, furan-FA may have toxic properties, however, these substances are toxicologically not well characterized so far. Here we show that 9,11-furan-FA, the oxidation product of the major CLA isomer cis-9,trans-11-CLA (c9,t11-CLA), is not toxic to human intestinal Caco-2 cells up to a level of 100 μM. Oil-Red-O staining indicated that 9,11-furan-FA as well as c9,t11-CLA and linoleic acid are taken up by the cells and stored in the form of triglycerides in lipid droplets. Chemical analysis of total cellular lipids revealed that 9,11-furan-FA is partially elongated probably by the enzymatic activity of cellular fatty acid elongases whereas c9,t11-CLA is partially converted to other isomers such as c9,c11-CLA or t9,t11-CLA. In the case of 9,11-furan-FA, there is no indication for any modification or activation of the furan ring system. From these results, we conclude that 9,11-furan-FA has no properties of toxicological relevance at least for Caco-2 cells which serve as a model for enterocytes of the human small intestine

Assessment of the Role of Renal Organic Anion Transporters in Drug-Induced Nephrotoxicity

In the present review we have attempted to assess the involvement of the organic anion transporters OAT1, OAT2, OAT3, and OAT4, belonging to the SLC22 family of polyspecific carriers, in drug-induced renal damage in humans. We have focused on drugs with widely recognized nephrotoxic potential, which have previously been reported to interact with OAT family members, and whose underlying pathogenic mechanism suggests the participation of tubular transport. Thus, only compounds generally believed to cause kidney injury either by means of direct tubular toxicity or crystal nephropathy have been considered. For each drug, or class of agents, the evidence for actual transport mediated by individual OATs under in vivo conditions is discussed. We have then examined their role in the context of other carriers present in the renal proximal tubule sharing certain substrates with OATs, as these are critical determinants of the overall contribution of OAT-dependent transport to intracellular accumulation and transepithelial drug secretion, and thus the impact it may have in drug-induced nephrotoxicity

Extra-Renal Elimination of Uric Acid via Intestinal Efflux Transporter BCRP/ABCG2

Urinary excretion accounts for two-thirds of total elimination of uric acid and the remainder is excreted in feces. However, the mechanism of extra-renal elimination is poorly understood. In the present study, we aimed to clarify the mechanism and the extent of elimination of uric acid through liver and intestine using oxonate-treated rats and Caco-2 cells as a model of human intestinal epithelium. In oxonate-treated rats, significant amounts of externally administered and endogenous uric acid were recovered in the intestinal lumen, while biliary excretion was minimal. Accordingly, direct intestinal secretion was thought to be a substantial contributor to extra-renal elimination of uric acid. Since human efflux transporter BCRP/ABCG2 accepts uric acid as a substrate and genetic polymorphism causing a decrease of BCRP activity is known to be associated with hyperuricemia and gout, the contribution of rBcrp to intestinal secretion was examined. rBcrp was confirmed to transport uric acid in a membrane vesicle study, and intestinal regional differences of expression of rBcrp mRNA were well correlated with uric acid secretory activity into the intestinal lumen. Bcrp1 knockout mice exhibited significantly decreased intestinal secretion and an increased plasma concentration of uric acid. Furthermore, a Bcrp inhibitor, elacridar, caused a decrease of intestinal secretion of uric acid. In Caco-2 cells, uric acid showed a polarized flux from the basolateral to apical side, and this flux was almost abolished in the presence of elacridar. These results demonstrate that BCRP contributes at least in part to the intestinal excretion of uric acid as extra-renal elimination pathway in humans and rats

Exposure assessment of process-related contaminants in food by biomarker monitoring

Exposure assessment is a fundamental part of the risk assessment paradigm, but can often present a number of challenges and uncertainties. This is especially the case for process contaminants formed during the processing, e.g. heating of food, since they are in part highly reactive and/or volatile, thus making exposure assessment by analysing contents in food unreliable. New approaches are therefore required to accurately assess consumer exposure and thus better inform the risk assessment. Such novel approaches may include the use of biomarkers, physiologically based kinetic (PBK) modelling-facilitated reverse dosimetry, and/or duplicate diet studies. This review focuses on the state of the art with respect to the use of biomarkers of exposure for the process contaminants acrylamide, 3-MCPD esters, glycidyl esters, furan and acrolein. From the overview presented, it becomes clear that the field of assessing human exposure to process-related contaminants in food by biomarker monitoring is promising and strongly developing. The current state of the art as well as the existing data gaps and challenges for the future were defined. They include (1) using PBK modelling and duplicate diet studies to establish, preferably in humans, correlations between external exposure and biomarkers; (2) elucidation of the possible endogenous formation of the process-related contaminants and the resulting biomarker levels; (3) the influence of inter-individual variations and how to include that in the biomarker-based exposure predictions; (4) the correction for confounding factors; (5) the value of the different biomarkers in relation to exposure scenario’s and risk assessment, and (6) the possibilities of novel methodologies. In spite of these challenges it can be concluded that biomarker-based exposure assessment provides a unique opportunity to more accurately assess consumer exposure to process-related contaminants in food and thus to better inform risk assessment