DESCRIPTION (provided by applicant): In spite of decades of study, it is still not clear how otitis media impacts the inner ear to cause sensorineural hearing loss. Thus, it is impossible to predict who is at risk or what markers can be used to determine if inner ear inflammation is occurring, making effective diagnosis and management difficult. Therefore, our bng-term goal is to identify how inflammation in the middle ear causes cochlear pathology. The PI and his colleagues, has recently developed an acute otitis media mouse model, as well as described chronic otitis media in the C3H/HeJ mouse that has a defect in its toll like receptor 4 (TLR4). These collaborations have led to the development of new methods to characterize both middle ear and inner ear cytokine expression, nuclear factor-kB (NF-kB)-mediated inflammatory processes, nitric oxide-mediated cochlear damage, and quantitative immune cell pathology. The proposed studies will capitalize on both these acute and chronic middle ear disease mouse models to establish the correlative middle ear and inner ear immune profiles. This will describe for the first time the molecular immune mechanisms by which otitis media can directly cause inner ear pathology. Therefore, this research has the potential to significantly advance our understanding of inner ear inflammatory processes elicited by both acute and chronic otitis media and lay the groundwork for development of new procedures for the detection and therapy of sensorineural hearing loss. The proposed studies will utilize BALB/c mice inoculated in the middle ear with heat-killed Haemophilous influenza or Streptococcus pneumoniae (acute otitis media) and C3H/HeJ mice defective for TLR4 (chronic otitis media) to characterize inner ear pathology, physiology, cytokine gene expression, cytokine levels, NF- kB activated inflammatory processes, and reactive oxygen species. The specific aims of this proposal are: Aim 1: To characterize the inner ear inflammatory profile in acute otitis media. This will test the hypothesis that acute otitis media causes a transient inner ear immune response characterized by Thl inflammatory processes. Aim 2: To characterize the inner ear inflammatory profile in chronic otitis media. This will test the hypothesis that chronic otitis media causes a persistent and destructive inner ear immune response characterized by expanded Th1 inflammatory processes. Inner ear pathology will be measured with auditory brainstem response audiometry, the endocochlear potential, light and electron microscopy, and immunohistochemistry of inflammatory mediators. Cochlear immune-mediated processes will be assessed by measurement of inflammatory cytokines, cytokine gene expression, and ELISA of transcription factors, vascular related factors, and reactive oxygen species.