Chitooligomers inhibit UV-A-induced photoaging of skin by regulating TGF-β/Smad signaling cascade

► Chitooligomers inhibited UV-A induced skin cell damage. ► Chitooligomers suppressed UV-A induced collagenase MMPs expression. ► Chitooligomers enhanced collagen synthesis in UV-A irradiated skin cells. ► Effect of Chitooligomers on inhibition of collagen degradation and enhancement of collagen synthesis was regulated by AP-1 and TGF-β/Smad signaling cascade.