McSweeney, Kristen (2023) Identification and use of novel vasodilators in the prevention of cisplatin-induced acute kidney injury. PhD thesis, Victoria University.

Abstract

Background: Cisplatin (CDDP) is a potent chemotherapy; however, its use is limited by its dose-limiting side effect, nephrotoxicity, which primarily manifests as acute kidney injury (AKI) and occurs in 20-30% of patients. Cisplatin-induced acute kidney injury (CIAKI) is characterised by afferent arteriole vasoconstriction stimulated by CDDP-induced endothelial dysfunction. Endothelial dysfunction is characterised by impaired endothelial nitric oxide synthase (eNOS) phosphorylation, reduced nitric oxide (NO) bioavailability, and increased renal microvasculature vasoconstriction. This subsequently reduces renal blood flow, increases vascular resistance, and decreases glomerular capillary blood pressure and net filtration pressure, resulting in a reduced glomerular filtration rate (GFR). When untreated reduced GFR can quickly worsen and manifest in the clinical presentation of CIAKI. This decreases patient quality of life and increases the risk of mortality, thus, novel vasodilators are required. The direction of this thesis was split into three studies: Chapters 3 and 4, identification of novel pharmaceutical vasodilators (LKB1 and BX); Chapter 5, establishing a dose of CDDP without causing irreversible kidney pathologies in an animal model and Chapter 6, assessment of the identified novel vasodilator with the most significant potential determined in Chapters 3 and 4. Method: In chapters 3 and 4, New Zealand White (male) rabbit blood vessels (thoracic aorta, interlobar arteries, and mesenteric arteries) were assessed for vascular function using isometric tension analysis to determine a novel vasodilator to be used in a CIAKI model. Chapter 5, A clinical and physiologically relevant model of CIAKI, was used to determine the efficacy of two clinically relevant doses of CDDP (6.25 and 12.5 mg/kg) to induce reversible pathological kidney damage. Mice were euthanised 72 hours after CDDP administration. Chapter 6, This regimen (12.5 mg/kg) was chosen to assess BX in the prevention of CIAKI. Mice received a daily dose of BX (5, 0.5 or 0.05 mg/kg) on days 0-3 and a single dose of 12.5mg/kg of CDDP on day one via IP injection. Mice were euthanised for ex vivo experiments, including isometric tension for vascular function analysis, histology to determine kidney damage via periodic acid Schiff’s (PAS) stain and immunohistochemistry (IHC) to investigate protein expression of kidney injury, ER stress and pro-inflammatory biomarkers associated with CIAKI. RT2 profiler PCR was used analyse gene up/down-regulation of genes associated with nephrotoxicity, and SEM was used to investigate the effects of platinum accumulation. Significant Results and Conclusions: Chapters 3 and 4, LKB1 and BX were direct vasodilators. Both drugs partly mediated their effects through K+ channels; however, LKB1-induced relaxation was also partly endothelial-dependent. BX was chosen to progress within the model of CIAKI. This was justified due to the ability of BX to induce vasodilation mainly through non-endothelial-dependent mechanisms. Chapter 5, the results of the CIAKI dose-finding study showed that CDDP 12.5 mg/kg induced a more clinically relevant degree of damage to both the kidney and the vasculature compared to 6.25 mg/kg, suggesting it is a more suitable dose for use in this CIAKI model. Chapter 6, BX improved acetylcholine (ACH)-induced relaxation suggesting it may influence endothelial function. Surprisingly, BX reduced angiotensin II (ANGII)-induced vasoconstriction, suggesting it may display ARB properties. BX significantly reduced protein expression of key biomarkers associated with CIAKI, including kidney injury molecular 1 (KIM-1), glucose-regulated protein 78 (GRP78), intracellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1) and E-Selectin. This pilot study provides evidence that BX could inhibit CIAKI. A more extensive animal study is warranted to confirm these results.

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