TRPV4 and skin disorder: Particularly, in previous studies, peroxisome proliferator-activated receptor δ (PPARδ), AMP-activated protein kinase (AMPK), and transient receptor potential cation channel subfamily V member 4 (TRPV4) participated in the maintaining of structural integrity of keratinocytes [13–17], and in general the impairment of skin permeability barrier mainly composed by keratinocytes induces dermatitis containing atopic dermatitis [18, 19].