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Browsing Medical Science by Author "Chuturgoon, Anil Amichund."

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    An investigation into kojic acid-associated mitochondrial toxicity and inflammation in melanoma cells (SK-MEL-1).
    (2023) Suritham, Tamzin Kimera.; Chuturgoon, Anil Amichund.; Ghazi, Terisha.
    ojic acid (KA), 5-hydroxy-2-(hydroxymethyl)-4H-pyran-4-one, is used in agriculture, food, and cosmetics. KA is known to have antimicrobial, antifungal, antioxidant, and anti-inflammatory properties. The cosmetic industry's increasing interest in KA is due to its ability to inhibit tyrosinase activity resulting in skin lightening. The mitochondria play a key role in maintaining homeostasis and ensuring efficient melanin production. Therefore, mitochondrial dysfunction has severe effects on the skin. This study investigates mitochondrial stress, antioxidant responses, protein kinase signalling and inflammation in human melanoma (SK-MEL-1) cells. The mitochondria are important in processing metabolites and supplying the cell with energy in the form of ATP. KA interacts with key mitochondrial homeostasis proteins. Our results found an increase in macromolecule damage specifically lipid peroxidation and protein oxidation. Due to oxidative conditions, increased Nrf2 expression was observed. LON protease is ATP-dependent and regulated by Sirtuin 3 expression. Mitochondrial function was affected illustrated by decreased ATP production leading to decreased LON protease and Sirtuin 3 protein expression. Following increased oxidative stress, KA suppressed the expression of protein kinases but increased inflammatory mediators. There was decreased expression of phospho-Akt, Akt, phospho-GSK3β, p38 and ERK1/2. The mediation of the NLRP3 inflammasome involves priming and activation. At concentrations with high proliferation, NFκB gene and protein expression was activated. The protein kinase signalling pathways are known as mediators of inflammation; however, protein and gene expression of inflammatory mediators was increased following KA treatment. The inflammasome was subsequently activated as shown by an increase in intracellular caspase 1 levels as well as NLRP3, ILβ and IL-6 expression. KA induced mitochondrial stress and suppressed mitochondrial homeostasis proteins. The increased Nrf2 expression could have further downregulated LON protease expression and increased macromolecule damage. Oxidative conditions could have activated the inflammasome pathway independent of protein kinase signalling. In conclusion, KA displayed mitochondrial toxicity following acute exposure by suppressing mitochondrial homeostasis, protein kinase pathways and initiating inflammation. 1
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    Deoxynivalenol downregulates NRF2-induced cytoprotective response in human hepatocellular carcinoma (HepG2) cells.
    (2017) Ndlovu, Siqiniseko Sinikiwe.; Chuturgoon, Anil Amichund.; Nagiah, Savania.
    Deoxynivalenol (DON) is a mycotoxin produced by Fusarium species that commonly infect agricultural foods. DON exhibits multiple toxic effects in both animals and humans, binding to the A site of the 28S ribosome and inhibits peptidyl transferase and protein elongation. It induces cytotoxicity through oxidative stress and inhibition of protein synthesis. Liver cells possess the antioxidant signalling mediator - Nuclear erythroid-2-Related factor (NRF2) that is activated in response to oxidative stress. There is no sufficient work done to show if the HepG2cells have an ability to withstand the molecular modifications induced by DON. The aim of the study was to investigate the cytotoxicity of DON and its effect on the NRF2 antioxidant response in HepG2 cells. The MTT assay was used to determine a dose response of DON (72 hr) on cell viability and to generate an IC50 value to use in subsequent assays. The intracellular concentration of GSH and ATP was determined using Luminometry. Lipid peroxidation and membrane damage were assessed by TBARS and LDH cytotoxicity assays respectively. Protein expression of NRF2, phosphorylated (p-)NRF2, catalase (CAT), superoxide dismutase (SOD)2, and Sirtuin (Sirt)3 was quantified by Western Blotting. The mRNA expressions of GPx, CAT and SOD2 were quantified using qPCR. DON decreased cell viability in a dose-dependent manner with an IC50 value of 26.17 μM. DON caused a significant decrease in the intracellular GSH concentration (1.77-fold, p= 0.0005). There was a significant decrease in the intracellular ATP content (1.92-fold, p= 0.0002).The study shows an induced lipid peroxidation and membrane damage in HepG2 cells by DON, as there was a significant increase in extracellular levels of both MDA (1.89-fold, p=0.0020) and LDH (1.35-fold, p=0.0207). DON reduced total NRF2 expression (0.30-fold, p= 0.0017), however activated p-NRF2 was significantly up-regulated (3.54-fold, p= 0.0085). There was a downregulation in the NRF2 target antioxidant proteins: CAT (0.33-fold, p= 0.005) with a concomitant decrease in CAT mRNA levels (0.02-fold, p= 0.0003), SOD2 (0.02-fold, p= 0.0137), with a parallel trend in the levels of SOD2 mRNA (0.06-fold, p= 0.0020) by DON. This toxin also significantly decreased the mRNA expression of GPx levels (0.03-fold, p= 0.0006). The expression of a mitochondrial stress response Sirt3 was significantly decreased (0.14-fold, p= 0.0058). Taken together, the data shows that DON causes oxidative stress and downregulates the NRF2-induced cytoprotection in HepG2 cells. Keywords: Deoxynivalenol Antioxidant response NRF-2