Expression of genes implicated in oxidative stress in the cochlea of newborn rats.

Oxidative stress is an important mechanism inducing ototoxicity-, age- and noise-induced hearing loss. To better understand this phenomenon, we examined cochlear tissues for the expression of following genes involved directly or indirectly in the oxidative stress response: glyceraldehyde-3-phosphate dehydrogenase (Gapdh); solute carrier family-2 (facilitated glucose transporter), member-1 (Slc2a1); heme oxygenase-1 (Hmox1); heme oxygenase-2 (Hmox2); inducible nitric oxide synthase-2 (Nos2); transferrin (Tf); transferrin receptor (Tfrc); glutathione S-transferase A3 (Gsta3) and metallothionein-1a (Mt1a). Cochlear tissues were dissected from the p3-p5 Wistar rats, divided into the organ of Corti (OC), modiolus (MOD) and stria vascularis together with spiral ligament (SV + SL) and processed immediately or cultured under normoxic conditions or a short-term, mild hypoxia followed by re-oxygenation.

MRNA expression of members of the IGF system in the organ of Corti, the modiolus and the stria vascularis of newborn rats.

We analyzed the mRNA expression of the insulin-like growth factor (IGF) family genes and of selected downstream pathway genes using the Affymetrix microarray system and confirmatory RT-PCR in the freshly prepared organ of Corti (OC), modiolus (MOD) and stria vascularis (SV) from neonatal rats (3-5 days old) and after 24h in culture. Among the seven members of the IGF family analyzed in this paper, IGF1, IGF2 and IGF-binding protein (IGFBP2) had the highest basal expression in all regions. Preparatory stress and culture increased the expression of IGF2, IGFBP2, IGFBP3, IGFBP5, glucose transporterl (GLUT1), signal transducer, and activator of transcription3 (STAT3), phosphoinositide-3-kinase regulatory subunit (Pik3r1), Jun oncogene (c-jun) and decreased that of mitogen-activated protein kinases MAPK3 and MAPK14 in all regions.

Expression of apoptosis-related genes in the organ of Corti, modiolus and stria vascularis of newborn rats.

Cell death in the inner ear tissues is an important mechanism leading to hearing impairment. Here, using microarrays and real-time RT-PCR we analyzed expression of selected apoptosis-related genes in rat's inner ear. We determined the gene expression in tissues freshly isolated from neonatal rats (3-5 days old) and compared it to that of explants cultured for 24 h under normoxic or hypoxic conditions.

Up-regulation of prestin mRNA expression in the organs of Corti of guinea pigs and rats following unilateral impulse noise exposure.

Prestin is the motor protein of the outer hair cells (OHCs) and is required for both their electromotility and for cochlear amplification. We investigated the prestin mRNA expression in guinea pigs and rats in relation to the degree of noise-induced hearing loss (NIHL) induced by unilateral impulse noise exposure (167dB peak SPL) for 2.5-5 min.

Apoptosis, necrosis and hypoxia inducible factor-1 in human head and neck squamous cell carcinoma cultures.

The objective of this study was to examine the mode of cell death and the hypoxia inducible factor-1 (HIF-1) expression of human head and neck squamous cell carcinoma (HNSCC) exposed to hypoxia in vitro. Apoptosis and necrosis rates were examined using flow cytometry. The findings suggest that HNSCC cells show a considerable heterogeneity in cell size and in response to hypoxia.

Expression of prestin mRNA in the organotypic culture of rat cochlea.

To quantitate in absolute terms the prestin mRNA levels in the explant culture of rat cochlea, we used competitive RT-PCR with a synthetic internal cRNA standard. Prestin gene expression was found at levels of 100 fg specific mRNA/microg total RNA on postnatal day 3, which corresponds to about 300 copies per outer hair cell (OHC) and is indicative of an intermediate level of expression. Two days of culturing resulted in an increase of prestin mRNA levels and in the formation of an apical-basal gradient (p<0.

Expression of hypoxia-inducible factor-1 in the cochlea of newborn rats.

Hypoxia/ischemia is a major pathogenetic factor in the development of hearing loss. An important transcription factor involved in the signaling and adaptation to hypoxia/ischemia is the hypoxia-inducible factor-1 (HIF-1). To study HIF-1 expression we used an in vitro hypoxia model of explant and dissociated cultures of the stria vascularis, the organ of Corti with limbus and the modiolus from the cochlea of 3-5-day-old Wistar rats.