FIR pathways and effects in skin photoaging.

<p>FIR inhibits MMPs and leads to interference with collagen degradation. Furthermore, FIR increases collagen synthesis through the TGF-β/Smad pathway. In addition, FIR-induced autophagy may be mediated by inhibition of the Akt/mTOR signaling pathway. Autophagy can block the epidermal hyperproliferative response to UV and may suppress photoaging.