Structural and Functional Studies of S-(2-Carboxyethyl)-L-Cysteine and S-(2-Carboxyethyl)-l-Cysteine Sulfoxide

Insecticidal non-proteinogenic amino acid S-(2-carboxyethyl)-L-cysteine (β-CEC) and its assumed metabolite, S-(2-carboxyethyl)-l-cysteine sulfoxide (β-CECO), are present abundantly in a number of plants of the legume family. In humans, these amino acids may occur as a result of exposure to environmental acrylonitrile or acrylamide, and due to consumption of the legumes. The β-CEC molecule is a homolog of S-carboxymethyl-l-cysteine (carbocisteine, CMC), a clinically employed antioxidant and mucolytic drug. We report here detailed structural data for β-CEC and β-CECO, as well as results of in vitro studies evaluating cytotoxicity and the protective potential of the amino acids in renal tubular epithelial cells (RTECs) equipped with reporters for activity of seven stress-responsive transcription factors. In RTECs, β-CEC and the sulfoxide were not acutely cytotoxic, but activated the antioxidant Nrf2 pathway. β-CEC, but not the sulfoxide, induced the amino acid stress signaling, which could be moderated by cysteine, methionine, histidine, and tryptophan. β-CEC enhanced the cytotoxic effects of arsenic, cadmium, lead, and mercury, but inhibited the cytotoxic stress induced by cisplatin, oxaliplatin, and CuO nanoparticles and acted as an antioxidant in a copper-dependent oxidative DNA degradation assay. In these experiments, the structure and activities of β-CEC closely resembled those of CMC. Our data suggest that β-CEC may act as a mild activator of the cytoprotective pathways and as a protector from platinum drugs and environmental copper cytotoxicity.

The Effects of Sodium Fluoride (NaF) Treatment on the PI3K/Akt Signal Pathway in NRK-52E Cells

The effects of the element fluorine on the phosphoinositide-3-kinase-protein kinase B/Akt (PI3K/Akt) pathway has a significant role in regulation of intracellular molecular mechanisms. NRK-52E rat kidney epithelial cell line was selected as the material of the study. NaF was used as the fluorine source in the study. The NaF dose was determined with the MTT assay. The NaF concentrations were determined as the proliferation concentration of 10 μM and IC₂₅ (2250 μM) and IC₅₀ (4250 μM) for 24 h. In the study, the erb-b2 receptor tyrosine kinase 2 (ERBB2), phosphoinositide-3-kinase (PI3K), Protein kinase B (PKB,Akt), Mammalian target of rapamycin (mTOR), and the Tumor protein 53 (TP53) genes were considered as the target genes. NaF concentration was administered on the cells. Total mRNA was isolated. mRNAs were turned into cDNA. The expression levels of the target genes were determined by RT-qPCR method. According to the results obtained in the study, the low NaF concentration increased the expression levels of the ERBB2, PI3K, and Akt genes, while the higher concentrations did not significantly affect these levels. The expression of mTOR decreased at all given concentrations. The expression of the TP53 gene did not change at the low concentration, while it increased at the high concentrations. Based on the results, it may be stated that fluorine may inhibit the kinase enzymes in the PI3K/Akt pathway. In summary, in the pathogenesis of the cell damage caused by fluorine in the NRK-52E cell line, the PI3K/Akt/mTOR pathway is an important signal pathway.

In Vitro Evaluation of the Apoptotic, Autophagic, and Necrotic Molecular Pathways of Fluoride

Prolonged exposure to high doses of fluoride causes chronic poisoning called fluorosis, which affects many tissues and causes serious health problems. This study was planned to investigate the apoptotic, autophagic, and necrotic molecular pathways of fluoride. Sodium fluoride (NaF) was administered to normal rat kidney epithelial (NRK-52E) cells. The NaF IC₅₀ value was determined using the MTT assay. The expression of the genes in the autophagic, apoptotic, and necrotic pathways was determined by real-time PCR. It was determined that there were significant changes in NaF-induced molecular pathways depending on the time. There were no increases in apoptotic and necrotic pathway markers except for Atg3, an autophagy gene, at the 3rd and the 12th hours. However, there was an induction in all cell death signaling pathways at 24 h. The molecular mechanisms demonstrated NaF-induced cellular death in the NRK-52E cell line. It was concluded that these molecular mechanisms were activated with NaF, and different mechanisms accelerated the cellular death at the 24th hour.