Difference between Brightens and Lighten Up

BRIGHTENS vs LIGHTEN UP: VERB

Sparkles, Glows, Softens, Warms, Freshens, Shines, Enlivens, Dims, Lightens, Darkens, Clear, Clear up, Lighten up, Light up, Lighten

Awakens, Dapples, Conjures, Lengthens, Slows, Twinkles, Glistens, Perked, Enlarges, Enriches, Fades, Rejuvenates, Sparkles, Clear, Light up

Sons are stars that brightens up the world.
Licorice extract reduces dark spots and brightens skin.
You are the sun that brightens my sky.
This hero serum visibly brightens, tightens and lifts.
What act or experience always brightens her day?
Christmas decoration brightens the house with holiday cheer.
11th June 2012 - Verali brightens up your wardrobe.
The thought of you brightens up my day.
The sun brightens the day, and the moon brightens the night, but you brighten my life.
The pink jelly base brightens, while the watermelon extract hydrates and brightens your skin.

Lighten up and introduce yourself to these little travelers.
But he was in no mood to lighten up.
Lighten up and learn to compromise on occasion.
Dude, lighten up and embrace the free publicity!
Christmas cheer that helped lighten up the screen.
Can You Lighten Up Corned Beef and Cabbage?
We must stand up against these word police and say enough is enough, lighten up people.
QUESTION so everyone should lighten up and tell me about those people up north.
Language Developing a clear style Tighten up, lighten up.
But things lighten up, as much as they can ever lighten up in the ACC, over the next three weeks.