RA attenuates ISO-induced apoptosis in WT mice. (A) Tissue sections from WT mice (n = 3) were stained for TUNEL analysis and DAPI. Bottom graph shows statistical analyses of apoptotic cells from multiple random fields. P < 0.05, RA+ISO vs. ISO (Student’s t-test). (B) Caspase 3 cleavage assay. WT and CKO mice were pre-treated with RA prior to ISO treatment for 24 h (RA+ISO). Controls include vehicle (con), RA alone (RA) and ISO alone (ISO). Con and RA treatment have little effect on caspase cleavage (Cleaved Caspase 3). ISO treatment increases the cleavage in both genotypes, but RA pretreatment (RA+ISO) decreases apoptotic cleavage only in WT (upper panel), but not CKO (lower panel), mice. Statistical analyses are shown at the bottom. *P < 0.01 and **P < 0.05 (n=6, two-way ANOVA).