Date of Award

2011

Embargo Period

8-1-2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Pathology and Laboratory Medicine

College

College of Graduate Studies

First Advisor

Lisa L. Cunningham

Second Advisor

Craig C. Beeson

Third Advisor

Debra J. Hazen-Martin

Fourth Advisor

Hainan Lang

Fifth Advisor

Rick G. Schnellmann

Sixth Advisor

Christina Voelkel-Johnson

Abstract

Cisplatin is a highly successful and widely used chemotherapy for the treatment of various solid malignancies in both adult and pediatric patients. Side effects of cisplatin include nephrotoxicity and ototoxicity. Cisplatin's ototoxic effect results in part from damage to and death of cochlear hair cells. Mechanisms underlying cisplatin-induced hair cell death are poorly understood and have been attributed to DNA damage, oxidative stress, and inflammation. This study was designed to determine the role of p53 in cisplatin-induced hair cell death and to investigate heat shock proteins (HSPs) as potential protectants against cisplatin-induced hair cell death using adult mouse utricle as an in vitro model of mature mammalian hair cells. p53 is a well-known transcription factor involved in the DNA damage response. Using p53-/- mice and wild-type litter mates, results indicate that p53 is not necessary for cisplatin-induced death of hair cells and hearing loss. Heat shock has been previously shown to inhibit cisplatin-induced hair cell death. Since HSP70 is upregulated following sublethal heat shock, the role ofHSP70 in heat shock-conferred protection against cisplatin was investigated. HSP70 is necessary for the protective effect conferred by heat shock against cisplatin-induced hair cell death. Constitutive expression of inducible HSP70 offered modest protection against cisplatin-induced hair cell death, indicating that HSP70 is sufficient to protect against cisplatin. HSP32, a stress-inducible protein responsible for the catabolism of free heme, has been shown to protect against oxidative and inflammatory stress in multiple systems. Cobalt protoporphyrin IX (CoPPIX) -induced HSP32 was previously shown to inhibit cisplatin-induced death of hair cells from neonatal rat cochlear explants. Results indicate that HSP32 offers significant protection against cisplatin-induced hair cell death in cultured adult mouse utricle at multiple cisplatin concentrations, that CoPPIX induces expression ofHSP32 primarily in resident macrophages of mouse utricle, and that macrophages are necessary for the protection conferred by CoPPIX-induced HSP32 against cisplatin. Due to the robust protection conferred by HSP32, it may prove promising in the design of a co-therapy for the prevention of cisplatin-induced hearing loss.

Rights

All rights reserved. Copyright is held by the author.

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