Genotoxic Effect of Arsenate and Arsenite in Human HaCat Cells in Culture Using Comet Assay

Arsenic is an environmental chemical of toxicological concern today since it is a human genotoxin and chronic exposure is associated with development of cancers, including skin. Inorganic arsenate is metabolically reduced to arsenite by glutathione (GSH) prior to methylation. The aim of this study was to determine the relative toxic effects of arsenate and arsenite in HaCat cells (immortalized human keratinocytes) in vitro by measuring cytotoxicity, DNA damage, depletion of glutathione and apoptotic and necrotic events. HaCat cells were treated with arsenate and arsenite (10 μM) for DNA damage detection using Comet assay and cytotoxicity (10, 60 and 100 μM) all measured at 24 hr. In some experiment arsenate or arsenite (10 μM) was added at the same time as BSO 10 μM for 24 hr, and GSH levels were measured by HPLC with fluorescence detection. Flow cytometry was used to investigate apoptotic and necrotic events following arsenate and arsenite (10 μM) treatment for 24 hr. Arsenate and arsenite at 60 and 100 μM, but not 10 μM, reduced the number of adherent viable cells with time. Therefore, DNA damage could only be measured at 10 μM as at higher concentrations the cells did not produce classical Comets but showed fragmentation. DNA damage was significantly (p < 0.001) increased in cells treated for 24 hr with 10 μM arsenate and arsenite compared to control. GSH levels were significantly increased in HaCat cells treated with10 μM arsenate and arsenite (p < 0.05, p < 0.001, respectively) compared to control. Cells treated with buthionine sulphoximine (BSO) at the same time as arsenate had increased GSH levels (p < 0.001), but arsenite and BSO did not increase cellular GSH. Arsenate and arsenite increased apoptosis, and arsenate increased necrosis, although none of the values reached statistical significance. Arsenite was more cytotoxic than arsenate. Arsenate and arsenite are known to produce oxidative stress involving ROS formation and depletion of glutathione. The increase in GSH levels at low doses of arsenate and arsenite, and by arsenate even in the presence of BSO.

The SLC7A11: sperm mitochondrial function and non-canonical glutamate metabolism

Spermatozoa are redox-regulated cells, and stallion spermatozoa, in particular, present an intense mitochondrial activity in which large amounts of reactive oxygen species (ROS) are produced. To maintain the redox potential under physiological conditions, sophisticated mechanisms ought to be present, particularly in the mitochondria. In the present study, we investigated the role of the SLC7A11 antiporter. This antiporter exchanges intracellular glutamate for extracellular cystine. In the spermatozoa, cystine is reduced to cysteine and used for GSH synthesis. The importance of the antiporter for mitochondrial functionality was studied using flow cytometry and UHPLC/MS/MS approaches. Intracellular GSH increased in the presence of cystine, but was reduced in the presence of Buthionine sulphoximine (BSO), a γ-glutamylcysteine synthetase inhibitor (P < 0.001). Inhibition of the SLC7A11 antiporter with sulfasalazine caused a dramatic drop in intracellular GSH (P < 0.001) and in the percentage of spermatozoa showing active mitochondria (P < 0.001). These findings suggest that proper functionality of this antiporter is required for the mitochondrial function of spermatozoa. We also describe that under some conditions, glutamate may be metabolized following non-conventional pathways, also contributing to sperm functionality. We provide evidences, that the stallion spermatozoa have important metabolic plasticity, and also of the relation between redox regulation and metabolic regulation. These findings may have important implications for the understanding of sperm biology and the development of new strategies for sperm conservation and treatment of male factor infertility.

Patulin suppresses α1-adrenergic receptor expression in HEK293 cells

Patulin (PAT) is a common mycotoxin contaminant of apple products linked to impaired metabolic and kidney function. Adenosine monophosphate activated protein kinase (AMPK), abundantly expressed in the kidney, intercedes metabolic changes and renal injury. The alpha-1-adrenergic receptors (α1-AR) facilitate Epinephrine (Epi)-mediated AMPK activation, linking metabolism and kidney function. Preliminary molecular docking experiments examined potential interactions and AMPK-gamma subunit 3 (PRKAG3). The effect of PAT exposure (0.2–2.5 µM; 24 h) on the AMPK pathway and α1-AR was then investigated in HEK293 human kidney cells. AMPK agonist Epi determined direct effects on the α1-AR, metformin was used as an activator for AMPK, while buthionine sulphoximine (BSO) and N-acetyl cysteine (NAC) assessed GSH inhibition and supplementation respectively. ADRA1A and ADRA1D expression was determined by qPCR. α1-AR, ERK1/2/MAPK and PI3K/Akt protein expression was assessed using western blotting. PAT (1 µM) decreased α1-AR protein and mRNA and altered downstream signalling. This was consistent in cells stimulated with Epi and metformin. BSO potentiated the observed effect on α1-AR while NAC ameliorated these effects. Molecular docking studies performed on Human ADRA1A and PRKAG3 indicated direct interactions with PAT. This study is the first to show PAT modulates the AMPK pathway and α1-AR, supporting a mechanism of kidney injury.

Amentoflavone prevents sepsis-associated acute lung injury through Nrf2-GCLc-mediated upregulation of glutathione

Sepsis is a serious medical problem that is one of the main causes of high mortality in intensive care units. Fifty percent of patients with severe sepsis will develop acute lung injury (ALI). Amentoflavone (AMF) is a polyphenolic compound possessing potent anti-inflammatory activities. The present study was designed to explore the protective effects of AMF against ALI in CLP-induced septic rats. The results showed that AMF administration protected against septic ALI, as reflected by marked amelioration of histological injury of lung tissues and decrease of pulmonary edema in CLP-treated rats. AMF ameliorated CLP-induced increase of systemic and lung TNF-α and IL-1β and the binding activity of p65 NF-κB, indicating the inhibition of inflammation induced by CLP. Moreover, AMF prevented CLP-induced oxidative stress, as evidenced by increase of oxygen consumption rate, decrease of TBARS content, increase of SOD activity and GSH level in lung tissue of CLP-treated rats. CLP resulted in significant decrease of mRNA expression of Nrf2 and GCLc, which was inhibited by AMF. AMF-induced protective effects on ALI, inflammation, and oxidative stress were inhibited by lentivirus-mediated shRNA of Nrf2 and buthionine sulphoximine (BSO), an inhibitor of GSH synthesis. AMF increased Nrf2-binding activity with GCLc promoters in lung tissue of CLP-treated rats. The results suggested that AMF protected against ALI in septic rats through upregulation of Nrf2-GCLc signaling, enhancement of GSH antioxidant defense, reduction of oxidative stress and final amelioration of inflammation and histological injury of lung. The data provide new therapeutic options for the treatment of sepsis-associated ALI.

Role of GSH in the modulation of NOS-2 expression in the weaned mammary gland

GSH delivery to the lactating mammary gland is essential for the maintenance of lactation as its decrease leads to apoptosis and involution of the mammary gland. In fact, it has already been demonstrated that some of the changes in gene expression found in the lactating mammary gland after forced weaning are reproduced in rats treated with buthionine sulphoximine to deplete GSH levels. An oligonucleotide microarray experiment would give us a better knowledge of the mRNA expression patterns during lactation and after weaning and the possible functions of GSH in the modulation of these events.

Inhibition of liver trans-sulphuration pathway by propargylglycine mimics gene expression changes found in the mammary gland of weaned lactating rats: role of glutathione

In the lactating mammary gland, weaning produces mitochondrial cytochrome c release and nuclear DNA fragmentation, as determined by gel electrophoresis. This is followed by a significant decrease in lactation. Weaning for 2 h produces an early induction of the tumour suppressor/transcription factor p53, whereas the oncoprotein c-Jun and c-Jun N-terminal kinase are elevated after 24 h of weaning when compared with controls. The expression of p21cip1 and p27kip1, cyclin-dependent kinase inhibitors, was significantly higher in weaned rats when compared with control lactating rats. All the changes mentioned above also happen in the lactating mammary gland when propargylglycine, an inhibitor of the liver trans-sulphuration pathway, is administered. This effect is partially reversed by N-acetylcysteine administration. The administration of buthionine sulphoximine, an irreversible inhibitor of γ-glutamylcysteine synthetase, to lactating rats produces a decrease in GSH levels and changes in protein concentrations and gene transcripts similar to those in rats with impaired trans-sulphuration pathway. These data suggest that the inter-tissue flux of GSH is an important mechanism of l-cysteine delivery to the lactating mammary gland and emphasize the importance of this physiological event in maintaining the gene expression required to sustain lactation.