From the iTunes Help file:
Use subtitles and alternative audio tracks
Some videos feature subtitles, closed captioning, and alternative audio tracks (in other languages, for example).
Here are ways to use subtitles and alternative audio tracks:
- To change the default language used for subtitles and audio, choose iTunes > Preferences, click Playback, and choose a language from the Audio Language and Subtitle Language pop-up menus.
- To turn closed captioning on or off, choose iTunes > Preferences, click Playback, and select “Show closed captioning when available.”
- To change settings while you’re playing a movie in iTunes, choose Controls > Audio & Subtitles > Option.
- To quickly turn subtitles on or off while a movie is playing, move the pointer over the movie until the controls appear, and then click the Subtitles button .
There's no mention of using a remote.