Dissertations, Theses, and Capstone Projects

Date of Degree

9-2024

Document Type

Dissertation

Degree Name

Ph.D.

Program

Biology

Advisor

Julio Gallego-Delgado

Committee Members

Jayne Raper

Stephen Redenti

Sandra Pinho

Kirk Deitsch

Subject Categories

Biology

Keywords

malaria, acute kidney injury, apoptosis

Abstract

Malaria-associated acute kidney injury (MAKI) is a form of severe malaria (SM), which is usually caused by Plasmodium falciparum infection. Until recently, the impact of this particular complication of SM was severely underestimated and research in this area has been neglected. There is in fact a high prevalence (40-60%) of MAKI in SM patients and the associated risk of mortality and development of comorbidities is high. Furthermore, pediatric patients that recover often develop long-term complications such as chronic kidney disease or neurocognitive defects. The need for adjunctive therapies and early diagnostic biomarkers specific to this SM complication is critical but there is little basic research and the infrastructure with which to study this pathology is lacking. The objectives of this study were to develop an in vivo model of MAKI using mice and to use this model, in conjunction with in vitro assays utilizing human renal cells and Plasmodium falciparum-infected red blood cells (PfiRBCs), to identify molecular pathways of tubular epithelial cell death in the context of MAKI. Lateral nephrectomies were performed on wild-type mice prior to infection with Plasmodium berghei NK65/NY, a species/strain that infects rodents, and mice developed tubular damage characteristic of MAKI. Development of acute kidney injury (AKI) was assessed by histopathological evaluation and detection of AKI- specific markers, Cystatin C (CysC), blood urea nitrogen (BUN), and neutrophil gelatinase-associated lipocalin (NGAL) in serum or urine. These mice exhibited signs of early-stage AKI and sustained tubular damage, which is consistent with what has been reported in MAKI patients. The activation of multiple cell death pathways was evaluated to determine the mode of tubular epithelial cell death contributing to renal damage in these animals. Activation of Fas- dependent extrinsic apoptosis was detected in the proximal tubules of these mice through immunostaining, immunoblotting, and immunohistochemistry. This finding was corroborated in vitro when inhibition of extrinsic apoptosis rescued human proximal tubular epithelial cells (HPTEC) from PfiRBC-induced cytotoxicity. Furthermore, it was demonstrated that lysed uninfected erythrocytes alone do not induce similar cytotoxic effects in these cells, suggesting that PfiRBC-induced HPTEC death is not triggered by cell-free heme or hemoglobin but rather by factors unique to PfiRBC rupture. The outcomes of this study provide the field with standardized systems to study MAKI in vivo and in vitro that can be used to investigate signaling mechanisms underlying this pathology, identify reliable biomarkers for early diagnosis/prognosis, and preclinically test potential adjuvant treatments for this specific complication of SM. Furthermore, through this work, a molecular pathway involved in tubular damage in MAKI has been described for the very first time. These results contribute to the limited body of knowledge regarding MAKI pathogenesis and provide a basis for further research into potential molecular targets for disease intervention.

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