Detection of apoptosis by RT–PCR array in mefloquine–induced cochlear damage

Objective: To investigate the occurrence and possible mechanisms of apoptosis in cochlear epithelium and spiral ganglion neurons after mefloquine treatment. Methods: We used quantitative RT–PCR apoptosis–focused gene arrays (96–well, 84 apoptosis related genes) to assess changes of gene expression in the cochlear basilar membrane (hair cells–supporting cells) and spiral ganglion neurons of rat cochlear organotypic cultures treated with 100 μM mefloquine for 3 h. Results: Significant up–or down–regulation in gene expression was detected in 23 genes in the cochlear basilar membrane, and in 32 genes in the spiral ganglion neurons compared with time–matched controls. The responding genes could be classified as pro–or anti–apoptotic, and were mainly implicated in the Bcl–2, Caspase, Card, IAP, TNF ligand/TNF receptor, Death domain/Death effector domain, DNA damage/p53, and NF–kappa B families. Synthetic analysis suggested that these families could be revised to two major pathways mainly involved in the death receptor–mediated signaling pathway and apoptotic mitochondrial pathway. In addition, it was found that numerous anti–apoptotic genes such as Bcl2a1, Birc1b, Birc3, Birc4, Bnip1, Cflar, Il10, Lhx4, Mcl1, Nfkb1, Prlr, Prok2, and TNF were greatly up–regulated in the cochlear tissue, which might imply the co–existence of protective response in the cells at the early stage of mefloquine–induced damage.