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.
戴維在一家商店裏發現了這款粉色絲綢燈罩,覺得它會讓房間亮麗起來。
4V-ERG (使)好轉;(使)變得樂觀 If someone or something brightens a situation or the situation brightens, it becomes more pleasant, enjoyable, or favourable. (使)好轉;(使)變得樂觀 [Also VERBPREPOSITION]
That does not do much to brighten the prospects of kids in the city. [VERB noun]
那並不能使城裏孩子們的前途更光明些。
It is undeniable that the economic picture is brightening. [VERB]