Saudi Cultural Missions Theses & Dissertations
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Item Restricted In Vitro Cytotoxic and Genotoxic Assessment of Nano Polyethylene Terephthalate Exposure on A549 Cells(University of Copenhagen, 2023-05-30) Alzaben, Mohammad; Roursgaard, MartinGlobal plastic production in 2019 amounted to 359 million tons, with the European Union contributing 17%. Plastic has caused environmental and health concerns. Nanoplastics, tiny fragments of plastic measuring less than 1μm in size, have become ubiquitous in the environment. As a result of plastic pollution and poor waste management, nanoplastics have infiltrated several ecosystems, including oceans, freshwater bodies, and even the air we breathe. Studies have linked exposure to MP/NP to adverse health effects such as Pneumoconiosis, chronic bronchitis, allergic and asthmatic reactions, and lung and digestive system cancer, raising concerns about their potential health effects. This study aims to assess two main biological adverse effects of nanoplastics, cytotoxicity and genotoxicity, on human lung carcinoma epithelial cells (A549). We chose polyethylene terephthalate (PET) because it is one of the top-produced plastic polymers. We found that NPET significantly induces ROS production and DNA strand breaks = 0.10 lesions/106 bp at the highest concentration (125 μg/ml).7 0Item Restricted Modulation of Aryl Hydrocarbon Receptor-Regulated Genes by Methylmercury(University of Alberta, 2024) Alqahtani, Mohammed Ali; Ayman, ElKadiEnvironmental pollution poses a significant threat to public health, with various contaminants contributing to a wide range of adverse health effects. Among these contaminants, ؤ (MeHg) and the aryl hydrocarbon receptor (AHR) ligand 2,3,7,8-tetrachlorodibenzodioxin (TCDD) are particularly concerning due to their persistence in the environment and potent biological activities. Both compounds have been extensively studied for their individual effects, but the potential health risks associated with their combined exposure are less understood. The primary objective of this work was to investigate the individual and combined effects of MeHg and TCDD on AHR-regulated enzymes. This investigation was conducted using the murine hepatoma Hepa-1c1c7 cell line and extended to mouse hepatic and extrahepatic tissues. The effects of MeHg on Ahr-regulated gene expression were examined in the absence and presence of TCDD, along with evaluations of protein expression and enzymatic catalytic activity. In hepatic tissue, both MeHg and Hg2+ inhibited the TCDD-mediated induction of Cyp1a1/1a2 mRNA levels. However, only Hg2+ inhibited the TCDD-mediated induction of CYP1A1/1A2 protein and catalytic activity at posttranscriptional levels, indicating differential modulation by Hg2+ and MeHg. Additionally, the inhibitory role of HO-1 (heme oxygenase-1) on CYP1A activity induced by TCDD was investigated in vitro using the HO-1 competitive inhibitor tin-mesoporphyrin, which partially restored the MeHg-mediated decrease in CYP1A1 activity. In extrahepatic tissues, MeHg exhibited mainly inhibitory effects, particularly decreasing the basal level of Cyp1a1 and Cyp1a2 mRNA and protein, which was more evident at the 24-hour time point in kidneys, followed by hearts. Similarly, when mice were co-exposed, MeHg reduced the TCDD-induced Cyp1a1 and Cyp1a2 expression. However, MeHg potentiated kidney Cyp1b1 mRNA expression, opposing the observed change in its protein level. Exposure to MeHg induces several antioxidant enzymes, including NAD(P)H:quinone oxidoreductase (NQO1), whose expression is regulated by both AHR and nuclear factor erythroid 2-related factor-2 (NRF2). This co-regulation prompted an investigation into which transcription factor primarily orchestrates NQO1 expression upon MeHg exposure. Our findings demonstrate that NQO1 induction by MeHg is, at least in part, mediated by NRF2. In conclusion, the findings of this work reveal an intricate interplay between MeHg and TCDD on AHR-regulated CYP1 enzymes, with notable inhibitory effects that might be significant for procarcinogen metabolism. Varied responses across tissues highlight the potential implications for environmental health.7 0Item Restricted Investigating the Role of Zinc in Manganese-induced Hepatotoxicity(Florida International University, 2024) Alandanoosi, Afnan; Liuzzi, Juan; Palacios, Cristina; Narayanan Vijaya; George, FlorenceThe objective of this study was to investigate the role of zinc (Zn) status in manganese (Mn) -induced hepatotoxicity using epidemiological data and vitro experiments. First, we conducting epidemiological study using the National Health and Nutrition Examination Survey (NHANES) to determine the relationship between Zn status and blood Mn levels on enzymatic markers of liver damage. The findings indicated that without the regression interaction of Zn intake or serum Zn, blood Mn exhibits a direct (positive) association with Alkaline Phosphatase (ALP) and Aspartate Amino transferase (AST). The results however showed that with the interaction of blood Mn and Zn intake at the second quartile (Q2) (marginal low Zn intake), a negative association was found with ALP in model 1,model 2 (corrected by age and gender), and model 3 (corrected by age, gender, race, education, BMI, alcohol, smoking and diabetes ). A similar association was found between Q4 (adequate/high Zn intake) and Lactate Dehydrogenase (LDH) activity in all three models of the study. Second, the effect of Zn deficiency and adequacy on Mn toxicity and the expression level of the cellular Mn efflux transporter SCL30A10 in human hepatocytes was evaluated. Mitochondria oxidative stress, apoptosis, and cell death and proliferation studies showed that exposure to elevated levels of Mn increased oxidative stress, apoptosis, and cell death. Mn exposure also decreased cell proliferation. Noteworthy, Zn depletion was found to enhance Mn induced apoptosis and cell death. Lastly, the mRNA expression of SLC30A10 was significantly decreased by Mn exposure (p < 0.05). However, no significant difference in the protein expression level of SCL30A10 was found. This suggests that there was no compensatory regulatory response of this transporter expression to either Zn deficiency or Mn exposure for the time point analyzed. Overall, the results from the epidemiological data and in vitro studies indicate that Zn deficiency could enhance the toxic effects of Mn. The results underscore the importance of having an adequate Zn intake in mitigating Mn induced cytotoxicity.63 0Item Restricted Zinc as a potential therapy for Burkitt’s lymphoma(Saudi Digital Library, 2022-06-30) Alhazmi, Bader Ahmed H; Khanim, Farhat; Bunce, ChrisBurkitts lymphoma (BL) is a form of non-Hodgkin lymphoma (NHL) that arises from germinal center B cells. BL is characterized by translocations of the C-MYC oncogene to immunoglobulin light and heavy chain loci resulting in its constitutive deregulated expression. BL shows a rapid and aggressive growth pattern. There are three different forms of BL; sporadic BL (sBL), immunodeficiency-associated BL and endemic BL (eBL) which accounts for ~50% of all paediatric cancers in Sub-Saharan Africa. Due to financial restrictions, treatment and supportive care options are limited resulting in poorer outcomes in low - middle income countries (LMICs). Thus, there is a need to develop new affordable effective low toxicity treatments for eBL. Prior to this study, a panel of BL cell lines were tested against an in-house custom drug repurposing library developed in our lab (FMC Library) that contains ~100 approved and commonly used drug. This screen identified the nutritional supplement zinc acetate as an effective anti-BL candidate. Dose response studies showed that all BL cell lines tested had little/no response to zinc at 50 μM whereas 100 μM zinc killed all BL cell lines. In contrast, 100 μM zinc acetate induced no killing against a panel of non-BL cell lines including acute myeloid leukaemia (AML) which is a non BL cell tumour, diffuse large B cell lymphoma (DLBCL) which represent a B cell lymphoma that arise from germinal centre B cells and EBV infected lymphoblastoid cell lines (LCL) as a control cells. The latter were used as karyotypically normal B cell controls. Cell death in BL cells was associated with positive flow cytometry staining for propidium iodide and annexin V and activation of caspase 3 and 9 (western blotting) indicating cell death by apoptosis. The proto-oncogene C-MYC is mutated or deregulated in >50% of cancers. In BL, deregulated expression occurs as a consequence of translocation of C-MYC on chromosome 8q24 to either the immunoglobulin heavy chain enhancer region on 14q32 (85% of cases) or the immunoglobulin kappa light chain or lambda loci on 2p12 or 22q11, respectively (15% of cases). Thus, the effect of zinc on C-MYC protein levels were studied. Western blot analysis showed that 100 μM zinc was able to reduce C MYC protein levels rapidly and sustainably in BL cell lines whereas no change in C MYC protein levels was observed in non-BL cell lines. Zinc-induced reduction of C-MYC protein levels was time-dependent, reducing by approximately 20% after 6 hours with little/no protein detectable after 24 hours. C-MYC protein levels were not reduced following treatment with 50 μM zinc. Quantitative real time PCR (qRT-PCR) also showed a rapid reduction in C-MYC mRNA levels in BL cell lines after 6 hours exposure to 100 μM but not upon exposure to 50 μM. Again, no reduction in C-MYC mRNA levels was seen in non-BL cell lines. Translocations of other genes to the immunoglobulin loci occur in other forms of NHL. The DLBCL cell line SU-DHL-4 has a t(14;18) translocation resulting in deregulated expression of the protooncogene BCL2. Western blotting showed no decrease in BCL 2 protein levels in SU-DHL-4 in response to either 100 μM or 50 μM zinc acetate after 6 or 24 hours indicating a selectivity of zinc action against C-MYC protein in BL cells. To further investigate the role of altered C-MYC expression in zinc-mediated killing of BL cells, the eBL cell lines Raji and Namalwa were stably transfected with C-MYC using a piggyBac transposon system that allows gene expression under a constitutively active promoter. However, overexpression of C-MYC from an alternative promoter did not rescue BL cells from killing by 100µM zinc. Although western blotting showed that C MYC protein levels were protected after 6 hours, protein reduction and loss of viability was again observed after 24 hours indicating that loss of C-MYC is important in zinc mediated killing of BL cells. In a second approach to rescue C-MYC expression, the proteasome inhibitor Bortezomib was used to inhibit C-MYC protein degradation via the ubiquitin-proteasome system (UPS). Whilst increases were observed in overall ubiquitinated proteins indicating bortezomib was working, western blotting and flow cytometry showed no rescue of C-MYC protein levels. Furthermore, bortezomib did not rescue cells from zinc-mediated killing after 24 hours. In conclusion, findings from this study have identified that 100 mM zinc is effective at killing BL cell lines selectively, and that this killing is associated with activation of apoptotic markers. Treatment with zinc resulted in a rapid and sustained reduction in C-MYC mRNA and protein levels that could not be rescued through constitutive overexpression or the use of proteasome inhibitors. Given that zinc deficiency is common in sub-Saharan Africa and that zinc supplementation is safely used to treat diarrhoeal episodes in children, the studies proposed here indicate that zinc may safely be used as an adjunctive therapy to target C-MYC in BL.38 0