Browsing by Author "Mohan, Jivanka."

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Current Antiretroviral Drugs- An investigation of metabolic syndrome promotion in HepG2 cells.
(2022) Mohan, Jivanka.; Chuturgoon, Anil Amichund.; Ghazi, Terisha.
Metabolic Syndrome (MetS) affects more than 20% of adults globally. Furthermore, the prevalence of MetS in HIV-infected patients on chronic antiretroviral (ARV) therapy continues to rise rapidly. This is alarming as a significant portion of people are HIV-infected worldwide, with the highest incidence experienced in Sub-Saharan Africa. An estimated 21% of people receiving ARV treatment display insulin resistance associated with mitochondrial dysfunction and inflammation. The current study aimed to determine the disruptions of metabolic processes associated with ARV use (Tenofovir disoproxil fumarate (TDF), Lamivudine (3TC) and Dolutegravir (DTG)) following a 120-h exposure period in HepG2 liver cells. Thereafter mitochondrial stress, inflammasome activation and insulin resistance promotion were assessed. Following HepG2 cellular ARV exposure, it was found that mitochondrial stress proteins SIRT3 and UCP2 expressions were significantly suppressed. Due to these aberrations, endogenous cellular attempts to activate the antioxidant responses (pNrf2, SOD2, CAT) and mitochondrial maintenance systems (PINK1 and p62) in selected singular and combinational ARV treatments seemed insufficient. This resulted in lipid oxidative damage and reduced ATP production. These results indicate that ARVs induce mitochondrial dysfunction in liver cells. Furthermore, it was deduced that combinational ARV exposure promoted inflammasome activation at a genomic level. This was seen in increased expression of NLRP3 mRNA expression and caspase-1 activity with coinciding elevation in IL-1β in mRNA expression. Additionally, JNK expression was upregulated, with correlating increases in p-IRS1 protein expression and decreased IRS1 mRNA expression being observed. Consequently, both PI3K and AKT mRNA expression was suppressed, whilst miR-128a expression was significantly upregulated. It can be deduced that the combinational use of ARVs induced mitochondrial dysfunction and subsequently prompted inflammasome activation. This led to dysregulation of the IRS1/PI3K/AKT insulin signalling pathway and the initiation/promotion of insulin resistance. This is further supported through miRNA activation, suggesting possibilities for future studies on in vivo ARV use and related epigenetic changes.
Fumonisin B2 induces mitochondrial stress and mitophagy in Hek293 cells.
(2019) Mohan, Jivanka.; Chuturgoon, Anil Amichund.; Sheik-Abdul, Naeem.
Food insecurity poses a significant socio-economic problem in third world economies, particularly in countries that rely heavily on maize and maize products. Ubiquitous soil fungi parasitize agricultural commodities and produce mycotoxins. Fumonisin B2 (FB2), a neglected mycotoxin, is produced by several Fusarium species. The aim of this study was to investigate mitochondrial stress responses in human embryonic kidney (Hek293) cells exposed to FB2 for 24 hours (hr). Cell viability was assessed via the methylthiazol tetrazolium (MTT) assay and the half maximal inhibitory concentration (IC50) value (317.4 μM) was generated. Additional concentrations of 100 μM and 500 μM were selected to achieve a broader toxic profile of FB2. Reactive oxygen species (ROS) was quantified (fluorescence), mitochondrial membrane depolarisation (fluorescence) was assessed and adenosine triphosphate (ATP) concentration was evaluated (luminometry) to assess mitochondrial integrity. The relative expression of mitochondrial stress response proteins, Sirtuin 3 (SIRT3), Nuclear factor (erythroid-derived 2)-like 2 (Nrf2), LON protease (LONP1), PTEN-induced putative kinase 1 (PINK1), ubiquitin-binding adaptor p62 (p62) and heat shock protein 60 (HSP60) was determined by western blots. Transcript levels of SIRT3, PINK1 and microRNA-27b (miR-27b) was assessed using quantitative PCR (qPCR). Results indicated that both low and high concentrations of FB2 that were within the naturally occurring concentration range of the compound were able to induce mitochondrial dysfunction. FB2 (IC50) downregulated mitochondrial stress proteins and upregulated mitophagy markers. Despite upregulation of mitochondrial stress maintenance proteins at the highest concentration (500 μM) of FB2, mitophagic markers increased with subsequent cell death; whilst at a lower concentration (100 μM) of FB2, mitochondrial stress protein expressions were upregulated resulting in decreased expression of mitophagic markers and cell proliferation. In conclusion, FB2 was cytotoxic to the kidney derived Hek293 cells via induction of mitochondrial stress and mitophagy. Keywords: Fumonisin B2, mitophagy, mitochondrial stress, PINK1, Nrf2, SIRT3, human kidney cells, microRNA