The effects of superoxide dismutase in gerbils with bacterial meningitis

BACKGROUND: Inflammatory products, such as oxygen radicals generated during the course of bacterial meningitis, can damage nerve endings, hair cells, and/or supporting cells in the cochlea. Superoxide dismutase (SOD), an O-2-scavenger, has been shown to play an important role in the protection against radical toxicity in various animal experiments. OBJECTIVE. To study the antioxidant effects of SOD on the inflammatory response of gerbils with bacterial meningitis. STUDY DESIGN: Meningitis was induced in three groups of 10 gerbils by intrathecal (IT) injection of Streptococcus pneumoniae into the cisterna magna. Group 1 received IT SOD, group 2 received intramuscular (IM) SOD, and group 3, the control group, received IM normal saline. Histologic data and auditory brainstem responses (ABR) were obtained from each gerbil. RESULTS: Fibrosis and/or neo-ossification were near absent in the IT SOD group and significantly less fibrosis occurred in the IM group (IT vs. IM: P = 0.010; IT vs. control group: P = 0.001). The amount of surviving spiral ganglion cells correlated inversely with the extent of fibrosis (r = -0.753, P < 0.00001). CONCLUSIONS: IT injection of SOD significantly reduced cochlear fibrosis and neo-ossification, reduced the spiral ganglion cell loss, and decreased damage of the cochlear components following bacterial meningitis.