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Bio

Honors & Awards

  • Pitch Competition Winner, The Bridge Program in collaboration with Queensland University of Technology (2019)
  • Visualise Your Thesis 3rd Place, University of Technology Sydney (2019)
  • AMP Amplify National Finalist, AMP Limited (2018)
  • FameLab NSW State Finalist, British Council of Australia (2018)
  • Dr Lorraine Holley Essay Prize, University of Technology Sydney (2017)
  • Dean?s Merit List of Academic Excellence, University of Technology Sydney (2016)
  • Doctoral Scholarship, University of Technology Sydney (2016)
  • Best Rapid Fire Presentation, Algae Research Symposium (2015)
  • Dr Chau Chak Wing Scholar, University of Technology Sydney (2014)

Professional Education

  • Doctor of Philosophy, University Of Technology, Sydney (2020)
  • Bachelor (Undeclared), University Of Technology, Sydney (2015)
  • Doctor of Philosophy, University of Technology Sydney (2020)
  • B. Medical Science (Honours), University of Technology Sydney (2016)

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Publications

All Publications

  • Toxicity and bioaccumulation of two non-protein amino acids synthesised by cyanobacteria, beta-N-Methylamino-L-alanine (BMAA) and 2,4-diaminobutyric acid (DAB), on a crop plant. Ecotoxicology and environmental safety Samardzic, K., Steele, J. R., Violi, J. P., Colville, A., Mitrovic, S. M., Rodgers, K. J. 2020; 208: 111515

    Abstract

    In order to study the toxicity of the cyanobacterial non-protein amino acids (NPAAs) L-beta-N-methylamino-L-alanine (BMAA) and its structural isomer L-2,4-diaminobutyric acid (DAB) in the forage crop plant alfalfa (Medicago sativa), seedlings were exposed to NPAA-containing media for four days. Root growth was significantly inhibited by both treatments. The content of derivatised free and protein-bound BMAA and DAB in seedlings was then analysed by LC-MS/MS. Both NPAAs were detected in free and protein-bound fractions with higher levels detected in free fractions. Compared to shoots, there was approximately tenfold more BMAA and DAB in alfalfa roots. These results suggest that NPAAs might be taken up into crop plants from contaminated irrigation water and enter the food chain. This may present an exposure pathway for NPAAs in humans.

    View details for DOI 10.1016/j.ecoenv.2020.111515

    View details for PubMedID 33099142

  • L-DOPA causes mitochondrial dysfunction in vitro: A novel mechanism of L-DOPA toxicity uncovered INTERNATIONAL JOURNAL OF BIOCHEMISTRY & CELL BIOLOGY Giannopoulos, S., Samardzic, K., Raymond, B. A., Djordjevic, S. P., Rodgers, K. J. 2019; 117: 105624

    Abstract

    In Parkinson's disease (PD), as in many other neurodegenerative disorders, mitochondrial dysfunction, protein misfolding, and proteotoxic stress underly the disease process. For decades, the primary symptomatic treatment for PD has been the dopamine precursor L-DOPA (Levodopa). L-DOPA however can initiate protein misfolding through its ability to mimic the protein amino acid L-tyrosine, resulting in random errors in aminoacylation and L-DOPA becoming mistakenly inserted into the polypeptide chain of proteins in place of L-tyrosine. In the present study we examined the impact that the generation of DOPA-containing proteins had on human neuroblastoma cell (SH-SY5Y) function in vitro. We showed that even in the presence of antioxidants there was a significant accumulation of cytosolic ubiquitin in DOPA-treated cells, an upregulation in the endosomal-lysosomal degradation system, deleterious changes to mitochondrial morphology and a marked decline in mitochondrial function.The effects of L-DOPA on mitochondrial function were not observed with D-DOPA, the stereoisomer of L-DOPA that cannot be inserted into proteins so did not result from oxidative stress. We could fully protect against these effects by co-treatment with L-tyrosine, supporting the view that misincorporation of L-DOPA into proteins contributed to these cytotoxic effects, leading us to suggest that co-treatment with L-tyrosine could be beneficial therapeutically.

    View details for DOI 10.1016/j.biocel.2019.105624

    View details for Web of Science ID 000501660700008

    View details for PubMedID 31654750

  • Cell death and mitochondrial dysfunction induced by the dietary non-proteinogenic amino acid l-azetidine-2-carboxylic acid (Aze) AMINO ACIDS Samardzic, K., Rodgers, K. J. 2019; 51 (8): 1221?32

    Abstract

    In addition to the 20 protein amino acids that are vital to human health, hundreds of naturally occurring amino acids, known as non-proteinogenic amino acids (NPAAs), exist and can enter the human food chain. Some NPAAs are toxic through their ability to mimic protein amino acids and this property is utilised by NPAA-containing plants to inhibit the growth of other plants or kill herbivores. The NPAA L-azetidine-2-carboxylic acid (Aze) enters the food chain through the use of sugar beet (Beta vulgaris) by-products as feed in the livestock industry and may also be found in sugar beet by-product fibre supplements. Aze mimics the protein amino acid L-proline and readily misincorporates into proteins. In light of this, we examined the toxicity of Aze to mammalian cells in vitro. We showed decreased viability in Aze-exposed cells with both apoptotic and necrotic cell death. This was accompanied by alterations in endosomal-lysosomal activity, changes to mitochondrial morphology and a significant decline in mitochondrial function. In summary, the results show that Aze exposure can lead to deleterious effects on human neuron-like cells and highlight the importance of monitoring human Aze consumption via the food chain.

    View details for DOI 10.1007/s00726-019-02763-w

    View details for Web of Science ID 000480488100010

    View details for PubMedID 31302779

  • Cytotoxicity and mitochondrial dysfunction caused by the dietary supplement l-norvaline TOXICOLOGY IN VITRO Samardzic, K., Rodgers, K. J. 2019; 56: 163?71

    Abstract

    In addition to the 20 protein amino acids that are encoded for protein synthesis, hundreds of other naturally occurring amino acids, known as non-proteinogenic amino acids (NPAAs) exist. It is well known that some NPAAs are toxic through their ability to mimic protein amino acids, either in protein synthesis or in other metabolic pathways, and this property is utilised by some plants to inhibit the growth of other plants or kill herbivores. L-norvaline is an NPAA readily available for purchase as a dietary supplement. In light of previous evidence of l-norvaline's antifungal, antimicrobial and herbicidal activity, we examined the toxicity of l-norvaline to mammalian cells in vitro and showed that l-norvaline decreased cell viability at concentrations as low as 125??M, caused necrotic cell death and significant changes to mitochondrial morphology and function. Furthermore, toxicity was reduced in the presence of structurally similar 'protein' amino acids, suggesting l-norvaline's cytotoxicity could be attributed to protein amino acid mimicry.

    View details for DOI 10.1016/j.tiv.2019.01.020

    View details for Web of Science ID 000460823000019

    View details for PubMedID 30703532

  • Cyanobacterial Neurotoxins: Their Occurrence and Mechanisms of Toxicity NEUROTOXICITY RESEARCH Rodgers, K. J., Main, B. J., Samardzic, K. 2018; 33 (1): 168?77

    Abstract

    Cyanobacteria are some of the oldest organisms on earth, and have evolved to produce a battery of toxic metabolites, including hepatotoxins, dermatoxins, and neurotoxins. In this review, we focus on the occurrence and mechanisms of toxicity of a number of neurotoxins synthesised by these ancient photosynthetic prokaryotes. We discuss the evidence linking ?-methylamino-L-alanine (BMAA), a non-protein amino acid, to an unusual neurological disease complex reported on the island of Guam in the 1950s, and how 60 years later, the role that BMAA plays in human disease is still unclear. There is now evidence that BMAA is also produced by some eukaryotes, and can bioaccumulate in food chains; this combined with higher frequency of cyanobacterial blooms globally, increases the potential for human exposure. Three BMAA isomers that often co-occur with BMAA have been identified, and the current knowledge on the toxicity of these molecules is presented. The acute alkaloid toxins; anatoxin-a, homoanatoxin-a and the saxitoxins, and the organophosphate neurotoxin anatoxin-a(S) are also discussed. In many cases, human exposure to a cocktail of cyanobacterial neurotoxins is likely; however, the implications of combined exposure to these toxins have not been fully explored. Increased understanding of the combined effects of cyanobacterial neurotoxins is required to fully understand how these molecules impact on human health.

    View details for DOI 10.1007/s12640-017-9757-2

    View details for Web of Science ID 000417881600016

    View details for PubMedID 28585115

  • Oxidised protein metabolism: recent insights BIOLOGICAL CHEMISTRY Samardzic, K., Rodgers, K. J. 2017; 398 (11): 1165?75

    Abstract

    The 'oxygen paradox' arises from the fact that oxygen, the molecule that aerobic life depends on, threatens its very existence. An oxygen-rich environment provided life on Earth with more efficient bioenergetics and, with it, the challenge of having to deal with a host of oxygen-derived reactive species capable of damaging proteins and other crucial cellular components. In this minireview, we explore recent insights into the metabolism of proteins that have been reversibly or irreversibly damaged by oxygen-derived species. We discuss recent data on the important roles played by the proteasomal and lysosomal systems in the proteolytic degradation of oxidatively damaged proteins and the effects of oxidative damage on the function of the proteolytic pathways themselves. Mitochondria are central to oxygen utilisation in the cell, and their ability to handle oxygen-derived radicals is an important and still emerging area of research. Current knowledge of the proteolytic machinery in the mitochondria, including the ATP-dependent AAA+ proteases and mitochondrial-derived vesicles, is also highlighted in the review. Significant progress is still being made in regard to understanding the mechanisms underlying the detection and degradation of oxidised proteins and how proteolytic pathways interact with each other. Finally, we highlight a few unanswered questions such as the possibility of oxidised amino acids released from oxidised proteins by proteolysis being re-utilised in protein synthesis thus establishing a vicious cycle of oxidation in cells.

    View details for DOI 10.1515/hsz-2017-0124

    View details for Web of Science ID 000412726500001

    View details for PubMedID 28600903

  • Toxic Nonprotein Amino Acids PLANT TOXINS Rodgers, K. J., Samardzic, K., Main, B. J., Carlini, C. R., LigabueBraun, R., Gopalakrishnakone, P. 2017: 263?85

    View details for DOI 10.1007/978-94-007-6464-4_9

    View details for Web of Science ID 000460669400014

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