Delay of photoreceptor cell degeneration in rd mice by systemically administered phenyl-N-tert-butylnitrone.

PURPOSE To study the effect of systemic administration of phenyl-N-tert-butylnitrone (PBN) on the degeneration of photoreceptor cells in rd mice. METHODS PBN was injected intraperitoneally into FVB/rd mice on postnatal days (P) 5 to 14 (group A), and P10 to 18 (group B). At days P14, 16, 18, 20 and 27, morphological changes and apoptosis were analyzed by staining with hematoxylin and eosin or DAPI. The effect of PBN on apoptosis was analyzed in retinal pigment epithelial (RPE) cells by the measurement of caspase-3 activity. RESULTS In control and group B mice, the outer nuclear layer (ONL) of the retina was composed of 8-10 rows at P12, and rapidly decreased to one row at P18. In group A mice, the ONL was preserved with 5-7 rows at P18, and decreased to one row at P22. PBN inhibited caspase-3 activity in cultured RPE cells. CONCLUSIONS PBN delayed, but did not block, the degeneration of photoreceptor cells in rd mice. PBN may exert its inhibitory effect during the early phase of photoreceptor cell degeneration.