Leupeptin protects sensory hair cells from acoustic trauma

CALPAINS, a family of calcium activated proteases, promote the breakdown of cellular proteins, kinases, phosphatases and transcription factors. Calpai n inhibitors attenuate some neurodegenerative processes in certain cell typ es. Here we show that leupeptin, a potent calpain inhibitor, protects the s ensory hair cells in the inner ear from acoustic overstimulation (48 h, 100 or 105 dB SPL, octave band noise at 4 kHz). Acoustic overstimulation cause d a significant increase in calpain immunolabeling in the sensory epitheliu m suggesting a possible role in noise-induced cochlear degeneration. Infusi on of leupeptin into the inner ear significantly reduced the amount of sens ory cell loss from acoustic overstimulation. However, leupeptin did not pro tect against hair cell loss from the ototoxic drug, carboplatin. NeuroRepor t 10:811-816 (C) 1999 Lippincott Williams & Wilkins.