I don’t know that you need a regex to filter this. Use a complex filter and then in the Include (Or Exclude if that’s what you’re trying to do)
The Complex filter provides 2 text boxes for Include and 2 for Exclude.
Put this string in 1st box: “%LINK-3-UPDOWN: Interface”
Then put this string in the 2nd box: “changed to up”
That should be read by the filter as “%LINK-3-UPDOWN: Interface” AND “changed to up”