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Access Type
WSU Access
Date of Award
January 2023
Degree Type
Dissertation
Degree Name
Ph.D.
Department
Pharmacology
First Advisor
SAMSON JAMESDANIEL
Abstract
Abstract
The anti-cancer drug cisplatin is used in 10-20% of all cancer treatment and cisplatin-induced hearing loss (CIHL) and synaptopathy is manifested in 60-80% of patients undergoing chemotherapy with cisplatin. Combined with the intricate structure of the cochlea, it becomes exceedingly difficult to eliminate cisplatin and thus it is retained in the cochlea indefinitely, thereby, exacerbating the damage to the inner ear. Although many possible molecular mechanisms can cause ototoxicity with cisplatin, yet the complete process remains elusive and therefore the survivors are left with social impediments and isolations, particularly the pediatric survivors who face difficulty with social integration and development. Nitration of cochlear proteins are known to occur with cisplatin in rodents and targeting nitrative stress has proven successful in vitro.Based on previous studies, cochlear proteins were found to be nitrated with cisplatin, among which LMO4 was most abundantly nitrated. Therefore, my first aim was to investigate if cisplatin induced nitrative stress in the neuromast of zebrafish. It is well known that cisplatin causes loss of hair cells in the neuromast of zebrafish however, changes in the levels of LMO4 protein with cisplatin treatment has not been explored. I hypothesized that cisplatin causes loss of hair cells in the neuromast of zebrafish which is accompanied by decrease in the levels of LMO4 proteins and increase in nitrative stress. My result suggested that loss of hair cells correlated with decrease in LMO4 and increase in the levels of 3-nitrotyrosine which is a marker of nitrative stress. Moreover, cisplatin increased activated Caspase-3 levels in hair cells suggesting apoptosis. This study is significant because it is the first study to validate that cisplatin induced both a decrease in LMO4 levels and increase in nitrative stress production in non-mammalian models as well which correlated with hair cell loss. Moreover, zebrafish can be used as a useful model to screen for oto-protectants if cisplatin induced hair cells loss occur by a similar mechanism in both mammalian and non-mammalian models. My next aim was to investigate the efficacy of peroxynitrite decomposition catalyst (PNDC) in preventing cisplatin induced cytotoxicity in vitro. PNDCs can scavenge peroxynitrites which are by-products of nitric oxide and superoxide, produced during increased oxidative/nitrative stress and have the potential to nitrate critical proteins. I hypothesized that PNDC intervention prevents the cytotoxic effect of cisplatin on UB/OC1 cells (derived from embryonic mouse organ of corti) by inhibiting the production of nitrative stress and apoptotic pathway. My result indicated that PNDC downregulated the expression of pro-apoptotic genes, upregulated anti-apoptotic genes and inhibited generation of nitrative stress, suggesting it’s efficacy in combating cisplatin-induced cytotoxicity in vitro. My last aim was to determine changes in the abundance of cochlear synaptosomal protein fraction with cisplatin treatment and investigate the efficacy of PNDC. I hypothesized that cisplatin induced synaptopathy by modulating the abundance of cochlear synaptosomal proteins and intervention with PNDC mitigates cisplatin induced changes in protein abundance and synaptopathy. My result demonstrated that cisplatin induced synaptopathy by modulating amplitude, latency of wave I and interpeak latency between waves III-I, V-I in auditory brainstem response. Cisplatin further caused dysregulation in the abundance of several synaptosomal proteins involved in calcium binding, synapses, endocytosis pathway and calcium signaling. Moreover, intervention with PNDC inhibited the changes due to cisplatin on the abundance of protein fraction as well as on amplitude, latency and interpeak latency, suggesting it’s possible efficacy against cisplatin mediated cochlear synaptopathy. Overall, my study provides evidence of increasing nitrative stress as well as changes in protein levels with cisplatin treatment which include LMO4 protein in zebrafish and UB/OC1 cells and synaptosomal proteins in the mice model. Furthermore, it is suggested that inhibiting nitrative stress can prove useful in terms of synaptic dysfunction with cisplatin and therefore can be explored further.
Recommended Citation
Shahab, Monazza, "Role Of Nitrative Stress In Cisplatin Induced Ototoxicity And Synaptic Dysfunction" (2023). Wayne State University Dissertations. 3846.
https://digitalcommons.wayne.edu/oa_dissertations/3846