The influence of interleukin-1 receptor antagonist transgene on spiral ganglion neurons

The cytokine interleukin-1 beta (IL-1) has been shown to induce the secreti on of NGF and GDNF in several types of neuronal populations. IL-1 has also been shown to mediate immune response following trauma or presence of forei gn antigens. We investigated the influence of an IL-1 antagonist on the sur vival of spiral ganglion neurons in inner ears in which hair cells have bee n eliminated. We used a replication-deficient adenoviral vector containing the human IL-1 receptor antagonist (IL-1ra) cDNA. Guinea pigs were bilatera lly deafened with ototoxic drugs. One week later their left cochleae were i noculated with the IL-1ra vector, designated Ad.IL-1ra. The vector was deli vered by injection through the cochlear round window. IL-1ra protein levels within the perilymph of Ad.IL-1ra-injected animals were measured with ELIS A and found to be significantly elevated compared to our controls. Spiral g anglion cell counts in experimental ears revealed a lower density of neuron s after Ad.IL-1ra inoculation. Taken together, the data suggest that the Ad .IL-1ra-infected cochlear cells synthesized the transgenic human IL-1ra pro tein, which was then secreted by the cells into the perilymph, resulting in an accelerated neuronal degeneration in hair cell-depleted ears. (C) 1999 Elsevier Science B.V. All rights reserved.