Brighten up means the same as brighten .brighten up同brighten
David spotted the pink silk lampshade in a shop and thought it would brighten up the room.
戴维在一家商店里发现了这款粉色丝绸灯罩,觉得它会让房间亮丽起来。
4V-ERG (使)好转;(使)变得乐观 If someone or something brightens a situation or the situation brightens, it becomes more pleasant, enjoyable, or favourable. (使)好转;(使)变得乐观 [Also VERBPREPOSITION]
That does not do much to brighten the prospects of kids in the city. [VERB noun]
那并不能使城里孩子们的前途更光明些。
It is undeniable that the economic picture is brightening. [VERB]