Abstract: The present invention provides a trisulfide-compound-containing agent for inhibiting nitration of tyrosine residues in hepatocyte growth factor, the trisulfide compound being: glutathione trisulfide or a pharmaceutically acceptable salt thereof; or a compound represented by formula (1) (wherein X represents —OR1 or —NR2R3, R1 represents a hydrogen atom or an alkyl group containing 1 to 6 carbon atoms, R2 and R3 independently represent a hydrogen atom or an alkyl group containing 1 to 6 carbon atoms, and the alkyl group may have one or more substituents selected from the group consisting of amino groups and carboxy groups), a pharmaceutically acceptable salt thereof, or a cyclodextrin clathrate thereof.