Suppression of ischemia‐induced fos expression and AP‐1 activity by an antisense oligodeoxynucleotide to c‐fos mRNA

Abstract

Activation of c‐fos , an immediate early gene, and the subsequent expression of the Fos protein have been noted following focal cerebral ischemia. Fos and Jun form a heterodimer as activator protein 1 (AP‐1), which transregulates the expression of several genes. To study the postischemic events related to c‐fos expression, we suppressed the expression of c‐fos by intraventricular infusion of an antisense oligodeoxynucleotide (anti‐rncfosr₁₁₅) of c‐fos mRNA. The effectiveness of anti‐rncfosr ₁₁₅ was confirmed first by its capability to block in vitro c‐fos mRNA translation. In vivo, after intraventricular infusion of ³²P‐labeled anti‐rncfosr₁₁₅, the oligodeoxynucleotide was internalized iwthin 6 hours and detectable aslo in the nucleic acids fraction up to 41 hours. Treatment of the recovered nucleic acids with RNase H separated the labeled oligodeoxynucleotide from the nucleic acid fraction, indicating an association of the antisense oligodeoxynucleotide and cellular RNA after uptake. When focal cerebral ischemia was induced 16 hours after the infusion of anti‐rncfosr₁₁₅, the postischemic increase in Fos expression and AP‐1 binding activity were suppressed. Specificity of the effect of anti‐rncfosr ₁₁₅ was suggested by its failure to suppress the DNA binding activity of nuclear cyclic AMP response elements. These results support the hypothesis that increased AP‐1 binding activity following focal cerbral ischemia is dependent on Fos expression and can be inhibited in vivo by antisense c‐fos oligodeoxy‐nucleotides.