Project description:In order to elucidate molecular mechanisms of noise-induced hearing loss in the cochlea (inner ear), transcriptome of the cochlear sample was analyzed after induction of hearing loss by exposure to intense noise in mice. Cochlear transcriptome was analyzed at 3 hours following the noise exposure.
Project description:In order to elucidate molecular mechanisms of noise-induced hearing loss and dexamethasone therapy in the cochlea (inner ear), transcriptome of cochlear samples was analyzed after induction of hearing loss by exposure to intense noise in mice. Dexamethasone was intraperitoneally injected immediately following the noise trauma. Cochlear transcriptome was analyzed at 12h and 24h following the noise trauma and dexamethasone administration.
Project description:The cochlea possesses a robust circadian clock machinery that regulates auditory function. How the cochlear clock is influenced by the circadian system remains unknown. Here we show that cochlear rhythms are system-driven and require local Bmal1 as well as central input from the suprachiasmatic nuclei (SCN). SCN ablations disrupted the circadian expression of the core clock genes in the cochlea. Since the circadian secretion of glucocorticoids (GCs) is controlled by the SCN and that GCs are known to modulate auditory function, we assessed their influence on circadian gene expression. Removal of circulating GCs by adrenalectomy (ADX) did not have a major impact on core clock gene expression in the cochlea. Rather it abolished the transcription of clock-controlled genes involved in inflammation. ADX abolished the known differential auditory sensitivity to day and night noise trauma and prevented the induction of GABA-ergic and glutamate receptors mRNA transcripts. However, these improvements were unrelated to changes at the synaptic level suggesting other cochlear functions may be involved. Due to this circadian regulation of noise sensitivity by GCs, we evaluated the actions of the synthetic glucocorticoid dexamethasone (DEX) at different times of the day. DEX was effective in protecting from acute noise trauma only when administered during daytime, when circulating glucocorticoids are low, indicating that chronopharmacological approaches are important for obtaining optimal treatment strategies for hearing loss. GCs appear as a major regulator of the differential sensitivity to day or night noise trauma, a mechanism likely involving the circadian control of inflammatory responses.
Project description:Six month-old wild type and Igf1 heterozygous mice were exposed to a violet swept sine noise (frequency range 2–20 kHz) at 110 dB SPL for 30 minutes. Cochlear samples were taken at 2 and 24 hours post-noise exposure to study the evolution of the expression of inflammation genes by using PCR arrays and RT-qPCR. Six month-old wild type and Igf1 heterozygous mice not exposed to noise were used as control.
Project description:Six month-old wild type and Igf1 heterozygous mice were exposed to a violet swept sine noise (frequency range 2–20 kHz) at 110 dB SPL for 30 minutes. Cochlear samples were taken at 2 and 24 hours post-noise exposure to study the evolution of the expression of inflammation genes by using PCR arrays and RT-qPCR. Six month-old wild type and Igf1 heterozygous mice not exposed to noise were used as control.
Project description:The molecular mechanisms underlying the great differences in susceptibility to noise-induced hearing loss (NIHL) exhibited by both humans and laboratory animals are unknown. Using microarray technology, the present study demonstrates that the effects of noise overexposure on the expression of molecules likely to be important to the development of NIHL differ among inbred mice that have distinctive susceptibilities to NIHL including B6.CAST, 129X1/SvJ, and 129S1/SvImJ. The noise-exposure protocol produced, on average, a permanent loss of about 40 dB in sensitivity for auditory brainstem responses in susceptible B6.CAST mice, but no threshold elevations for the two resistant 129S1/SvImJ and 129X1/SvJ substrains. Measurements of noise-induced gene expression changes 6 h after the noise exposure revealed significant alterations in the expression levels of 48 genes in the resistant mice, while by these same criteria, there were seven differentially expressed genes in the susceptible B6.CAST mice. Differentially expressed genes in both groups of mice included subsets of transcription factors. However, only in the resistant mice was there a significant induction of proteins involved in cell-survival pathways such as HSP70, HSP40, p21, GADD45ï¢, Ier3, and Nfï«ï¢iïº. Moreover, increased expression of three of these factors after noise was confirmed at the protein level. Drastically enhanced HSP70, GADD45ï¢, and p21 immunostaining were detected 6 h after the noise exposure in subsets of cells of the lateral wall, spiral limbus, and organ of Corti as well as in cochlear nerve fibers. Upregulation of these proteins after noise exposure likely contributes to the prevalence of survival cellular pathways and thus to the resistance to NIHL that is characteristic of the 129X1/SvJ mice. Experiment Overall Design: Female 10-wk-old mice of the B6.CAST and 129X1/SvJ strains were divided randomly into non-noise control and noise-exposure groups. The non-noise mice served as controls in the gene-profiling experiments to control for the stress induced by experimenter handling and/or confinement of the mice in the noise-exposure chamber that was not directly related to the noise. This mice were in the noise chamber for a sham exposure. In contrast, the ânoiseâ groups were exposed to a 105-dB SPL, 10-kHz octave band of noise for 1 h and sacrificed 6 h after the exposure. Of each of these major groups, eight mice were used for each of three 129X1/SvJ control and three noise-exposed 129X1/SvJ arrays and two B6.CAST control and two noise-exposed B6.CAST arrays. Consequently within each subgroup the arrays are biological replicates.
Project description:Noise-induced hidden hearing loss (HHL) is a new type of hearing loss that has been identified in recent years and leads to insidious damage to the cochlea, unlike the well-known noise-induced hearing loss (NIHL). However, the cellular and molecular basis for it remains to be elucidated. Here, we established a single-cell transcriptome profile of the C57BL/6J mouse cochlea, in which we describe the transcriptome changes of individual cell types within the cochlea with HHL and NIHL. Mice in the HHL group were exposed to 110 dB of noise for 2 hours, and those in the NIHL group were exposed to 115 dB of noise for 4 hours for 3 days. The cochlea was taken 6 hours after the last noise exposure. The control group was not exposed to noise, with other conditions being the same as those in the noise-exposed group. The results of sequencing at the single-cell level help us gain a deeper understanding of the mechanisms of the development of HHL and NIHL.
Project description:The effect of IV-administered Vitamin C on the plasma proteome in the pig trauma model was investigated with label free proteomics. Plasma samples were drawn from 9 male Sinclair swine at baseline, post-trauma, and 0.25, 2, and 4 hours post resuscitation with 500 mL of hydroxyethyl starch. Swine were randomized to receive either saline, low-dose VitC (50 mg/kg), or high-dose VitC (200 mg/kg) during volume resuscitation (N = 3/treatment). High performance LC-MS/MS proteomics was then used to quantitatively measure plasma protein levels over time.