Photomechanic can do it for ages, but Lightroom cannot import the Nikon lock key setting.
chflags uchg test.jpg
As even dedicated LR plugins have serious problems, here is some code to do it from the command line
find /Volumes/WJSTDE32GB -name "*" -flags uchg -exec chflags nouchg {} \; -exec exiftool -rating=1 '{}' \;