Stress relief for the inner ear

Mechanosensory hair cells in the inner ear transduce mechanical stimuli into neural signals to mediate hearing and balance. Hair cell death is caused by a variety of stresses, including exposure to ototoxic drugs, which causes hearing loss for an estimated 500,000 Americans each year. Heat shock proteins (HSPs) are induced in response to cellular stress, and induction of HSP70 was previously shown to protect against the ototoxic effects of aminoglycoside antibiotics. To determine the molecular mechanisms that underlie HSP70's protective effects, Lindsey May and colleagues utilized cultured utricles from adult mouse ears to examine stress responses in hair cells. They found that HSP70 was expressed by glia-like supporting cells that surround hair cells in response to heat shock stress. Moreover, expression of HSP70 in supporting cells or application of exogenous HSP70 inhibited aminoglycoside antibiotic-induced hair cell death. The data indicate that supporting cells protect sensory hair cells by secreting HSP70.