This diploma thesis is part of a project aiming for the development of low molecular compounds which would be capable to inhibit the interaction between human transcription factor FOXO3 and DNA. Main goal of this thesis is the characterization of the interaction between the low molecular inhibitor S9 and the DNA-binding domain of FOXO3 protein (FOXO3-DBD) by using variety of biophysical methods such as NMR, microscale thermophoresis and native electrophoresis. FOXO transcription factors are important and evolutionary conserved regulatory proteins, which are involved in many crucial cellular processes. The activity of FOXO proteins is regulated by posttranslational modifications, out of which the most important are phosphorylation, acetylation and ubiquitination. Forkhead transcription factors participate in a variety of different cellular functions and are part of several signaling pathways. Its expression might be tissue specific. They contain approximately 100 amino acids long DNA- binding domain composed of several parts. Among its main functions belong the regulation of cell cycle and apoptosis, proliferation and cell differentiation, metabolism control and stress- response regulation. Tumor cells of lymfoblastome have developed resistance against chemotherapy by increasing activity of FOXO3...

archives@tulane.edu / 1 / Margaret Brooks

Le facteur de transcription Foxo3 régule la progression du cycle cellulaire, la survie cellulaire ou encore la réparation de l'ADN. En plus de ses fonctions de gène suppresseur de tumeur, de nombreuses études ont montré le rôle crucial de Foxo3 dans les cellules du système immunitaire en particulier les cellules dendritiques ou encore les LT CD8+ dans un contexte d'infection virale. Cependant, le rôle de Foxo3 dans les LT CD4+ n'est pas encore bien connu. Ainsi, mon projet de thèse s'est intéressé à analyser le rôle de Foxo3 dans le compartiment T CD4+ dans un modèle animal d'auto-immunité. Mes résultats de Thèse montrent que le niveau d'expression de Foxo3 dans les LT CD4+ est dépendant de la force du signal reçu par le récepteur T. De plus, suite à l'activation des LT CD4+ in vitro, nous avons montré que les LT CD4+ déficients pour Foxo3 présentent un défaut de production d'IFN-? et de GM-CSF. La dissection des mécanismes moléculaires impliqués nous a permis d'identifier une nouvelle cible transcriptionnelle directe de Foxo3, le facteur de transcription Eomes, connu comme étant impliqué dans la production d'IFN-? par les LT CD8+ et identifié comme un gène de susceptibilité à la sclérose en plaques. Afin d'étudier le rôle de Foxo3 dans l'auto-immunité nous avons utilisé le modèle murin de sclérose en plaque, l'encéphalomyélite auto-immune expérimentale ou EAE. Nous avons observé que les souris déficientes pour Foxo3 développent une EAE significativement moins sévère que les souris contrôles et que cette diminution de sévérité est associée à un défaut de production d'IFN-? et de GM-CSF par les LT CD4+. Ainsi ces résultats montrent pour la première fois que Foxo3 joue un rôle crucial dans le compartiment T CD4+ et révèlent le rôle essentiel de l'axe Foxo3-Eomes dans la différentiation des LT CD4+ effecteurs et dans la susceptibilité à l'inflammation du système nerveux central. / Foxo3 transcription factor regulates cell cycle progression, survival and DNA repair pathways. In addition to its role as a tumor suppressor gene, studies have established the crucial role of Foxo3 in immune cells, notably in dendritic cells and CD8+ T cells in the context of a viral infection. However, the role of Foxo3 in CD4+ T cell function is still unknown. My PhD project was therefore to address the role of Foxo3 in CD4+ T cell biology and its role in the pathophysiology of autoimmunity. Results obtained during my PhD showed that Foxo3 expression level in CD4+ T cells is dynamically controlled by T-cell receptor signaling strength and that, after in vitro stimulation, Foxo3-deficient CD4+ T cells exhibited decreased secretion of IFN-? and GM-CSF. By dissecting the underlying molecular mechanisms, we have identified a new direct target gene of Foxo3, the transcription factor Eomes, known to be involved in IFN-? production by CD8+ T cells and as a susceptibility gene for multiple sclerosis. This led us to hypothesize that Foxo3 could be involved in the susceptibility to central nervous system inflammation. To test this hypothesis, we used the well-established animal model of multiple sclerosis, the experimental autoimmune encephalomyelitis (EAE). We showed that Foxo3 deficiency is associated with decreased susceptibility to EAE and that Foxo3-deficient CD4+ T cells fail to differentiate into pathogenic IFN-?? and GM-CSF+ producing cells. Collectively, this study is the first to demonstrate the highly specialize function of Foxo3 in effector CD4+ T cells and reveals the essential role of the Foxo3-Eomes axis in CD4+ T cell commitment and susceptibility to central nervous system inflammation.

Made available in DSpace on 2018-08-01T21:35:18Z (GMT). No. of bitstreams: 1 tese_10162_Tese_Geralda Gillian Silva Sena.pdf: 2587415 bytes, checksum: 3fdd7aac2f0d6ee10dfb11e20153b98f (MD5) Previous issue date: 2016-07-15 / Nas últimas décadas, observou-se crescimento mundial da população idosa, associado ao aumento da longevidade. Múltiplos fatores, entre eles, ambientais, comportamentais e genéticos, podem influenciar na longevidade humana. Existe grande interesse no desenvolvimento de produtos naturais com propriedades funcionais e/ou de saúde. Exopolissacarídeos (EPS) fúngicos, como a (1&#8594;3;1&#8594;6)-&#946;-D-glucana botriosferana, sintetizado por Botryosphaeria rhodina MAMB-05, são candidatos promissores por serem considerados modificadores da resposta biológica. O presente estudo visou: a) investigar em seres humanos possíveis biomarcadores da longevidade, por meio da avaliação da frequência de polimorfismos nos genes FOXO3 (rs2802292), SOD2 (rs4880), APOE (rs429358 e rs7412) e SIRT1 (rs2273773) em amostra de idosos da Grande Vitória, ES, bem como seu estado de estresse oxidativo e o nível de integridade do DNA; b) avaliar antimutagenicidade, mutagenicidade e citotoxicidade da botriosferana, em camundongos Swiss, jovens e idosos, de ambos os sexos, bem como seus potenciais hipolipidêmico, hipoglicêmico e antiaterogênico em camundongos idosos knockout para receptor de LDL (LDLr-/-), e seu background (C57BL/6). Para alcançar os objetivos: a) na amostra de idosos, foram caracterizados dados demográficos, sócioeconômicos, antropométricos, bioquímicos, clínicos e estilo de vida. Polimorfismos genéticos foram analisados pela reação em cadeia da polimerase em tempo real; malondialdeído, por cromatografia líquida de alta eficiência e danos genômicos, pelo Ensaio do Cometa em grupos de longevos e controles (&#8805; 85 anos e 70-75 anos); b) com animais - botriosferana, foi administrada, via gavage (doses 7,5, 15 e 30 mg/kg p.c./dia), em protocolo de pré-tratamento de 30 dias (camundongos jovens) e 15 dias (camundongos idosos) para investigar seus potenciais mutagênico e anticitogenotóxico contra danos induzidos pela ciclofosfamida. O teste do Micronúcleo foi realizado em eritrócitos de sangue periférico e medula óssea dos camundongos. Efeitos glicolipidêmico e ateroprotetor do EPS (30 mg/kg p.c./dia, por gavage) entre animais LDLr-/-, que receberam dieta aterogênica, foram verificados por meio das medidas de glicose plasmática e perfil lipídico, após tratamento de 15 dias, com kits colorimétricos comerciais. A lesão aterosclerótica foi quantificada por meio da análise da deposição lipídica aórtica (en face), com Oil-Red-O. A análise estatística foi realizada por meio dos testes &#967;², exato de Fisher, Tukey, t Student, Mann-Whitney, Kruskal-Wallis e Equilíbrio de Hardy-Weinberg (HW) (p<0,05). Entre os idosos longevos e controles, os níveis plasmáticos de malondialdeído e dano ao DNA apresentaram valores semelhantes. Observou-se associação positiva entre o rs2802292 FOXO3 e longevidade. Características 12 bioquímicas e antropométricas, relacionadas ao envelhecimento saudável, mostraram resultados significativos. Nos ensaios in vivo, botriosferana, nas três doses, não foi mutagênica, nem citotóxica, exerceu efeito antimutagênico e ainda reduziu o percentual de danos entre animais jovens e idosos (Swiss, C57BL/6 e LDLr-/-). Houve redução nos níveis plasmáticos de glicose (36%), melhora no perfil lipídico (reduções de 53,8-84,3%) e diminuição da deposição lipídica aórtica (32,8%) de LDLr-/- ateroscleróticos tratados com esse EPS. Nossos resultados constituem informações inéditas acerca da longevidade humana, na população brasileira, e contribuem para o futuro promissor da geriatria genômica e da medicina personalizada. Além disso, indicam que botriosferana possui efeitos biológicos relevantes, sendo candidato promissor no desenvolvimento de novos produtos terapêuticos.

The healthy development of a living cell requires precise spatial-temporal gene expression. The code that dictates when and where genes are expressed is stored in a pattern of specific sequence motifs, which can be recognised by transcription factors. Understanding the interaction between these DNA sequence motifs and transcription factors will help to elucidate how genomic sequences build transcriptional control networks. However, the DNA-binding specificities of ~1400 human transcription factors are largely unknown. The in vivo DNA-binding events of transcription factors involve great subtlety, because most transcription factors recognise degenerate sequence motifs and related transcription factors often prefer similar or even identical sequences. Forkhead transcription factors exemplify these challenges. To understand how members within the Forkhead transcription factor family gain their binding and functional specificities, we used chromatin immunoprecipitation coupled with high-throughput sequencing (ChIP-seq) to interrogate the genome-wide chromatin binding events of three Forkhead transcription factors: FOXM1, FOXO3 and FOXK2. We find that FOXM1 specifically binds to the promoters of a large array of genes whose activities peak at the G2 and M phases of the cell cycle. The canonical Forkhead consensus GTAAACA is not enriched within the FOXM1 cistrome. It gains its own specific binding events and biological functions by interacting and cooperating with the MMB complex. FOXO3 and FOXK2 are recruited to chromatin by the canonical Forkhead consensus GTAAACA, and they bind both shared and specific regions in the genome. FOXO3 mostly binds to the regions which are also bound by FOXK2, but no competitive or assisted binding between FOXO3 and FOXK2 is detected within those regions. Overall, these results help explain how individual members of the Forkhead transcription factor family gain binding specificity within the genome yet raises new questions of how functional specificity is achieved by other family members.

Les cancers du sein de sous-type luminal B sont associés à un mauvais pronostic. Afin de mieux comprendre la biologie de ce sous-type, nous avons étudié au sein de 188 tumeurs mammaires de différents sous-types, les anomalies du nombre de copies, les méthylations de l'ADN, les profils d'expression génique et les mutations somatiques dans 9 gènes sélectionnés. Un total respectif de 237 et 101 oncogènes et gènes suppresseurs de tumeurs (TSG) candidats présentaient une dérégulation de l'expression en relation avec leur CNA. 88% des TSG potentiels étaient localisés sur le bras chromosomique 6q. 101 oncogènes candidats ont été validés sur une série publique de 5765 cancers du sein, et l'expression de 67 gènes était associée à un mauvais pronostic au sein des tumeurs luminales. 24 gènes présentaient une dérégulation de l'expression en relation avec un haut niveau de méthylation de l'ADN. FOXO3, PIK3CA et TP53 étaient les gènes les plus fréquemment mutés parmi les 9 testés. Dans une méta-analyse de séquençage de nouvelle génération regroupant 875 cancers du sein, les gènes les plus fréquemment mutés dans le sous-type luminal B étaient PIK3CA, TP53 et GATA3. Les nombreuses altérations moléculaires ciblaient des voies de signalisation communes, incluant 3 axes pouvant jouer un rôle majeur dans le sous-type luminal B : la voie TP53 et l'instabilité chromosomique, les voies de signalisation PI3K/AKT/MTOR/FOXO et MAPK/JNK, et les altérations des facteurs de transcription et épigénomiques. En conclusion, nous avons établi un répertoire de gènes candidats dans le sous-type luminal B qui pourraient être impliqués dans le développement et/ou l'hormonorésistance de ce sous-type. / Breast cancers (BCs) of the luminal B subtype have a poor prognosis. To better understand this subtype we studied in 188 BCs of various molecular subtypes, DNA copy number aberrations, DNA promoter methylation, gene expression profiles, and somatic mutations in nine selected genes. A total of 237 and 101 luminal B-specific candidate oncogenes and tumor suppressor genes (TSGs) presented a deregulated expression in relation with their CNAs. Interestingly, 88% of the potential TSGs are located within chromosome arm 6q. 101 candidate oncogenes were validated in a public series of 5,765 BCs and the overexpression of 67 was associated with poor survival in luminal tumors. 24 genes presented a deregulated expression in relation with a high DNA methylation level. FOXO3, PIK3CA and TP53 were the most frequent mutated genes among the nine tested. In a meta-analysis of next-generation sequencing data in 875 BCs, PIK3CA, TP53 and GATA3 were the most frequent mutated genes. Numerous molecular alterations targeted common signalling pathway, included 3 ways wich may play a major in the luminal B subtype: TP53 pathway and chromosomal instability, PI3K/AKT/MTOR/FOXO and MAPK/JNK pathway, and epigenomic and transcription factors alterations. In conclusion, we have reported a repertoire of luminal B candidate genes that may be involved in the development and/or hormone resistance of this subtype.

Made available in DSpace on 2014-06-11T19:26:05Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-17Bitstream added on 2014-06-13T20:54:04Z : No. of bitstreams: 1 freitas_pc_me_sjrp.pdf: 528091 bytes, checksum: d630cd8e1a7a4fdc34c7e9200a36b8b5 (MD5) / Síndromes Mielodisplásicas (SMD) compreendem um conjunto heterogêneo de doenças hematopoéticas caracterizadas por hematopoese ineficaz, que geralmente apresentam citopenias no sangue periférico, medula óssea hipercelular, diferenciação celular displásica e propensão ao desenvolvimento de leucemia mielóide aguda. São classificadas em oito tipos e a incidência anual é estimada entre dois e 12 casos por 100.000 pessoas da população em geral e em até 50 casos por 100.000 indivíduos com idades superiores a 60 anos. A análise cromossômica das células da medula óssea dos doentes ao diagnóstico detecta alterações diretamente relacionadas com o prognóstico em aproximadamente 50% dos casos. Alguns genes também foram relacionados à etiologia e prognóstico das mielodisplasias. O gene FOXO3, um supressor de tumor, embora não estudado anteriormente em SMD, é um dos genes que mais se expressam no tecido hematopoético normal. Alterações neste gene poderiam resultar em hematopoese anormal, pois já foram relacionadas a outros tipos de câncer, com mutações descritas no éxon 1. O objetivo deste trabalho foi estudar células da medula óssea de doentes com SMD de qualquer tipo, ao diagnóstico, para investigar a presença de alterações cromossômicas e de mutações no éxon 1 do FOXO3. A análise citogenética foi realizada em metáfases submetidas ao bandamento GTG, obtidas de culturas de curta duração de células da medula, sem estimulação mitogênica. Para a análise molecular foi extraído o DNA, realizada a amplificação gênica pela Reação em Cadeia da Polimerase e realizado o sequenciamento direto do éxon 1. Entre os 25 casos analisados, três (12%) apresentaram alterações cromossômicas clonais isoladas: deleção intersticial do braço longo do cromossomo 5; monossomia do cromossomo 21 e monossomia do cromossomo 22. Todas puderam ser relacionadas... / Myelodysplastic syndrome (MDS) constitute a heterogeneous group of hematopoietic diseases characterized by ineffective hematopoiesis usually with peripheral blood cytopenia, hypercellular bone marrow, dysplastic differentiation and a tendency to evolve to acute myeloid leukemia. They are classified in eight categories by the World Health Organization. The annual incidence is estimated at between two and 12 cases per 100,000 individuals in the general population and up to 50 cases per 100,000 of over 60-year olds. A chromosomal analysis of bone marrow cells at diagnosis identifies changes directly related to prognosis in approximately 50% of cases. Additionally, some genes are also associated to the etiology and prognosis of myelodysplasia. Although not previously studied in respect to MDS, a tumor suppressor, FOXO3, is one of the most commonly expressed genes in normal hematopoietic tissue. Changes in this gene could therefore result in abnormal hematopoiesis, as mutations described in exon 1 have already been associated with other types of cancer. The aim of this study was to investigate chromosomal alterations and mutations in exon 1 of FOXO3 in bone marrow cells from patients diagnosed with any type of MDS. Cytogenetic analysis was performed on metaphases submitted to GTG banding, obtained from short-term cultures of bone marrow cells without mitogenic stimulation. To evaluate mutations in the FOXO3 gene, DNA was extracted from the bone marrow, gene amplification was achieved by polymerase chain reaction and direct sequencing was performed. Of the 25 cases analyzed, three (12%) showed clonal chromosomal abnormalities in isolation characterized as the interstitial deletion of the long arm of chromosome 5, monosomy 21 and monosomy 22. All were correlated to the diagnosis and/or prognosis of patients. No mutations were detected in exon 1, but the 159C>T polymorphism was detected... (Complete abstract click electronic access below)

Orientador: Agnes Cristina Fett Conte / Banca: Cleide Largman Borovik / Banca: Cláudia Regina Bonini Domingos / Resumo: Síndromes Mielodisplásicas (SMD) compreendem um conjunto heterogêneo de doenças hematopoéticas caracterizadas por hematopoese ineficaz, que geralmente apresentam citopenias no sangue periférico, medula óssea hipercelular, diferenciação celular displásica e propensão ao desenvolvimento de leucemia mielóide aguda. São classificadas em oito tipos e a incidência anual é estimada entre dois e 12 casos por 100.000 pessoas da população em geral e em até 50 casos por 100.000 indivíduos com idades superiores a 60 anos. A análise cromossômica das células da medula óssea dos doentes ao diagnóstico detecta alterações diretamente relacionadas com o prognóstico em aproximadamente 50% dos casos. Alguns genes também foram relacionados à etiologia e prognóstico das mielodisplasias. O gene FOXO3, um supressor de tumor, embora não estudado anteriormente em SMD, é um dos genes que mais se expressam no tecido hematopoético normal. Alterações neste gene poderiam resultar em hematopoese anormal, pois já foram relacionadas a outros tipos de câncer, com mutações descritas no éxon 1. O objetivo deste trabalho foi estudar células da medula óssea de doentes com SMD de qualquer tipo, ao diagnóstico, para investigar a presença de alterações cromossômicas e de mutações no éxon 1 do FOXO3. A análise citogenética foi realizada em metáfases submetidas ao bandamento GTG, obtidas de culturas de curta duração de células da medula, sem estimulação mitogênica. Para a análise molecular foi extraído o DNA, realizada a amplificação gênica pela Reação em Cadeia da Polimerase e realizado o sequenciamento direto do éxon 1. Entre os 25 casos analisados, três (12%) apresentaram alterações cromossômicas clonais isoladas: deleção intersticial do braço longo do cromossomo 5; monossomia do cromossomo 21 e monossomia do cromossomo 22. Todas puderam ser relacionadas... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Myelodysplastic syndrome (MDS) constitute a heterogeneous group of hematopoietic diseases characterized by ineffective hematopoiesis usually with peripheral blood cytopenia, hypercellular bone marrow, dysplastic differentiation and a tendency to evolve to acute myeloid leukemia. They are classified in eight categories by the World Health Organization. The annual incidence is estimated at between two and 12 cases per 100,000 individuals in the general population and up to 50 cases per 100,000 of over 60-year olds. A chromosomal analysis of bone marrow cells at diagnosis identifies changes directly related to prognosis in approximately 50% of cases. Additionally, some genes are also associated to the etiology and prognosis of myelodysplasia. Although not previously studied in respect to MDS, a tumor suppressor, FOXO3, is one of the most commonly expressed genes in normal hematopoietic tissue. Changes in this gene could therefore result in abnormal hematopoiesis, as mutations described in exon 1 have already been associated with other types of cancer. The aim of this study was to investigate chromosomal alterations and mutations in exon 1 of FOXO3 in bone marrow cells from patients diagnosed with any type of MDS. Cytogenetic analysis was performed on metaphases submitted to GTG banding, obtained from short-term cultures of bone marrow cells without mitogenic stimulation. To evaluate mutations in the FOXO3 gene, DNA was extracted from the bone marrow, gene amplification was achieved by polymerase chain reaction and direct sequencing was performed. Of the 25 cases analyzed, three (12%) showed clonal chromosomal abnormalities in isolation characterized as the interstitial deletion of the long arm of chromosome 5, monosomy 21 and monosomy 22. All were correlated to the diagnosis and/or prognosis of patients. No mutations were detected in exon 1, but the 159C>T polymorphism was detected... (Complete abstract click electronic access below) / Mestre

FOXO3 est un facteur de transcription important pour la réponse au stress, la régulation de la différenciation et de la survie cellulaires qui a des effets neuroprotecteurs dans plusieurs modèles de maladies neurodégénératives, dont la maladie de Huntington (MH). Les effets neuroprotecteurs de FOXO3 sont réprimés dans la MH par une activité anormale de Ryk, un récepteur Wnt important pour la neurogenèse, par la liaison du domaine intracellulaire de Ryk à la ?-caténine, un co-facteur de FOXO3. L'objectif principal de ce travail est d'étudier les effets de la huntingtine mutée (mHTT) sur le répertoire des cibles directes humaines de FOXO3 à l'aide d'un modèle des phases développementales de la MH, à savoir des cellules souches neurales isogéniques issues de cellules souches pluripotentes induites. En formant un complexe tripartite avec la ?-caténine et FOXO3, Ryk agit comme un co-régulateur de FOXO3 en conditions normales ou pathologiques. L'analyse des cibles directes de FOXO3 montre une reprogrammation de ces cibles avec des pertes et des gains dans des voies de signalisation qui sont connues pour leur rôle dans la MH, notamment les voies de régulation de la prolifération cellulaire. Ces résultats montrent que la régulation des gènes par FOXO3 est fortement modifiée dans les cellules qui expriment la mHTT. Cela ouvre la voie à l'étude des mécanismes d'homéostase cellulaire sous contrôle de FOXO3 dans les neurones en différenciation et leur impact sur l'activité des neurones adultes. Plus largement, ces résultats permettent de mieux comprendre la dynamique moléculaire de la MH et les effets de reprogrammation moléculaire sur la différenciation et l'activité neuronale. / FOXO3 is an important transcription factor for stress response, the regulation of differentiation and cell survival that has neuroprotective effects in several models of neurodegenerative diseases, including Huntington’s disease (HD). The neuroprotective effects of FOXO3 in HD are repressed by abnormal signaling from the Wnt receptor Ryk by the binding of the intracellular domain of Ryk to the β-catenin, a cofactor of FOXO3.The aim of this work was to explore the effect of the mutant huntingtin (mHTT) on the repertoire of direct FOXO3 targets (F3Ts) using a model of developmental stage of HD, namely HD isogenic neural stem cells derived from Huntington’s Induced Pluripotent Stem cells. Forming a tripartite complex with β-catenin and FOXO3, Ryk acts as a co-regulator of FOXO3 in normal or pathological condition. Analysis of direct FOXO3 targets shows reprogramming of these targets with losses and gains in signaling pathways that are known to role in HD, including regulatory pathways of cell proliferation. These results show that gene regulation by FOXO3 is heavily modified in cells expressing the mutant huntingtin. Our findings open the way for a comprehensive study of cellular homeostasis mechanisms under the control of FOXO3 in neural differentiation and their impact on the activity of adult neurons. More broadly, these results provide insight into the molecular dynamics of MH and the effects of molecular reprogramming in differentiation and neuronal activity.

After the findings were reported for the Women’s Health Initiative (WHI) study in the past decade, there has been a significant decline in the overall use of hormone replacement therapy (HRT) among women. However, there are still millions of middle-aged, menopausal women in the U.S. who are currently undergoing hormone therapy. Their reasons for continuing treatment include relief of severe menopausal symptoms, aid in the management of osteoporosis and reduction in the risk of colon cancer (Ness et al., 2005). The purpose of the following investigation was to evaluate the impact of HRT on the central and peripheral auditory systems both during and after treatment. Over the course of the study, hormone treatments were administered to female aging CBA/CaJ mice to observe what effects estrogen (E) and progestin (P) have on the peripheral and central auditory systems. Female CBA/CaJ middle age mice were ovariectomized and placed into 4 HRT groups (E, P, E+P and Placebo [Pb]). Hormone treatment lasted 6 months followed by a recovery/washout period of 1 month. During this time, electrophysiology tests such as auditory brainstem responses (ABR) and ABR gap in noise (GIN) were used to measure neural activity for the auditory nerve and brainstem. Distortion product otoacoustic emission (DPOAE) testing was also implemented to assess the functional status of the outer hair cells (OHC) and their ability to amplify sound in the cochlea. After 6 months of treatment, animals treated with E exhibited the least amount of changes in ABR thresholds and ABR GIN amplitudes than any other subject groups. Interestingly, P animals exhibited an abrupt increase in ABR thresholds only 3 months after treatment; however, for ABR GIN amplitude levels a progressive reduction observed throughout the study. E+P and Pb animals showed signs of accelerated age-related hearing loss (ARHL) with significantly elevated ABR thresholds and dwindling ABR GIN amplitude levels. No significant signs of recovery were observed for any of the hormone groups. Therefore, in the present murine investigation, the effects of HRT were long lasting. To further expand on the results obtained for the electrophysiology tests, molecular biology experiments were performed to evaluate the expression of IGF-1R and FoxO3 in the cochlea during hormone therapy, from both in vitro and in vivo perspectives. Both genes play significant roles in the PI3K/AKT pathway and were specifically chosen because of their role in anti-apoptotic responses and cell survival. It was hypothesized that E attenuates the effects of ARHL via the PI3K/AKT pathway by up-regulating IGF-1R and FoxO3 to counteract the effects of oxidative stress in the aging mammalian cochlea. qPCR experiments were performed with stria vascularis (SV) lateral wall cells extracted from the cochlea of each animal in the hormone groups post-treatment (in vivo) and in SVK-1 cells treated with HRT over various lengths of time (in vitro) to evaluate the expression levels of IGF-1R and FoxO3. In-vivo experiments showed that the E-treated animals had significantly higher IG-1R levels compared to the other subject groups after treatment was discontinued. Similarly, IGF-1R levels steadily increased for E-treated SVK-1 cells over the course of hormone therapy, compared to P and E+P cells. FoxO3 expression, on the other hand, declined for all of the hormone-treated cells groups, relative to control SVK-1 cells (in vitro), and no statistical differences were detected for FoxO3 levels among the post-treatment animals (in vivo). These findings indicate that there is cross talk between E and IGF-1R involving the PI3K/AKT pathway, which contributes to the delayed onset of ARHL observed during HRT with E. Meanwhile, FoxO3 may not play a role in neuro-protective properties in the cochlea during HRT, as initially hypothesized.