A protein derived from the fusion of TAT peptide and FNK, a BCI-XL derivative, prevents cochlear hair cell death from aminoglycoside ototoxicity in vivo

We constructed a powerful artificial cytoprotective protein, FNK, from an antiapoptotic member of the BCL-2 family, Bcl-X-L. To test the efficacy of FNK in protecting cochlear hair cells (HCs) from aminoglycoside-induced cell death in vivo, we fused FNK with protein transduction domain, TAT, of the HIV/Tat protein to construct a fusion protein of TAT-FNK. We demonstrated that, after an intraperitoneal administration to guinea pigs, TAT-myc-FNK protein was diffusely distributed in the cochlea, most prominently in the HCs and supporting cells, followed by the spiral ganglion cells, 3 hr after the injection. We next demonstrated that TAT-FNK attenuated cochlear damage induced by an ototoxic combination of kanamycin sulfate (KM) and ethacrynic acid (EA) administered at 2 different dosages: 400 mg/kg KM + 50 mg/kg EA and 200 mg/kg KM + 40 mg/kg EA. TAT-FNK or vehicle was intraperitoneally injected from 3 hr before through 5 hr after inducing the ototoxic insults, 14 days after which auditory brainstem response (ABR) and HC loss were evaluated. In comparison with vehicle-administered controls, the TAT-FNK protein significantly attenuated ototoxic drug-induced ABR threshold shifts and the extent of HC death at either dosage. The TAT-FNK protein also significantly reduced the amount of cleaved poly-(ADP-ribose) polymerase-positive HCs 8 hr after the ototoxic insults compared with that in the vehicle-administered controls. These findings indicate that systemically administered TAT-FNK was successfully delivered to the guinea pig cochlea and effectively prevented apoptotic cell death of the cochlear HCs induced by KM and EA. (c) 2007 Wiley-Liss, Inc.