Protective Effects and Mechanisms of N-Phenethyl Caffeamide from UVA-Induced Skin Damage in Human Epidermal Keratinocytes through Nrf2/HO-1 Regulation

Abstract

The skin provides an effective barrier against physical, chemical, and microbial invasion; however, overexposure to ultraviolet (UV) radiation causes excessive cellular oxidative stress, which leads to skin damage, DNA damage, mutations, and skin cancer. This study investigated the protective effects of N-phenethyl caffeamide (K36) from UVA damage on human epidermal keratinocytes. We found that K36 reduced UVA-induced intracellular reactive oxygen species (ROS) production and induced the expression of the intrinsic antioxidant enzyme heme oxygenase-1 (HO-1) by increasing the translocation of nuclear factor erythroid 2–related factor 2 (Nrf2). K36 could inhibit the phosphorylation of extracellular-signal-regulated kinase (ERK) and c-Jun N-terminal kinases (JNK) and reduce UVA-induced matrix metalloproteinase (MMP)-1 and MMP-2 overexpression; it could also elevate the expression of tissue inhibitors of metalloproteinases (TIMP). In addition, K36 ameliorated 8-hydroxy-2′-deoxyguanosine (8-OHdG) induced by UVA irradiation. Furthermore, K36 could downregulate the expression of inducible nitric oxide synthase (iNOS) and interleukin-6 (IL-6) and the subsequent production of nitric oxide (NO) and prostaglandin E2 (PGE2). Based on our findings, K36 possessed potent antioxidant, anti-inflammatory, antiphotodamage, and even antiphotocarcinogenesis activities. Thus, K36 has the potential to be used to multifunctional skin care products and drugs.

Protection against Ultraviolet A-Induced Skin Apoptosis and Carcinogenesis through the Oxidative Stress Reduction Effects of N-(4-bromophenethyl) Caffeamide, A Propolis Derivative

“…The cells were cultured in 100-mm dishes and 24-well plates for attachment. For measurement of the survival rate of cells, an MTT assay was applied [31,32]. Various concentrations of K36H were incubated with HaCaT cells for 24 h. MTT solution was added to the plate, which was then converted to insoluble formazan crystals by cells.…”

“…The medium was removed, and phosphate-buffered saline (PBS) was added to wash the cells. The cells were exposed to UVA irradiation by using UV Crosslinkers XLE-1000A, in which the major wavelength of UVA lamps is 365 nm (Spectroline, Westbury, New York, USA) [31]. The cells were treated with UVA for approximately 45 min (10 J/cm 2 ) at a distance of 15.2 cm and were subsequently cultured in serum-free DMEM containing various concentrations of K36H for the indicated time.…”

“…To survey the ability of K36H to eliminate UVA-induced intracellular oxidative stress, the cells were cultured in 24-well plates and irradiated with UVA irradiation [31]. DMEM containing 10-μM DCFDA was added into the plates after incubation with various concentrations of K36H for 3 h. The intensity of fluorescence was excited at 488 nm and emitted at 520 nm wavelengths (Thermo Electron Corporation, Vantaa, Finland).…”

“…The NO content of the cultured medium was detected after treatment with UVA and various K36H concentrations according to the manual protocol from the Greiss reagent supplier (Promega, Madison, Wisconsin, USA) as previously described [31]. N-(1-Naphthyl) ethylenediamine solution and sulfanilamide were added to the cell culture medium and mixed.…”

“…The prostaglandin E 2 (PGE 2 ) content was measured per the manual protocol from the manufacturer as previously described (Cayman, Ann Arbor, MI, USA) [31]. A 96-well plate coated with goat polyclonal antimouse IgG secondary antibody and the cell culture medium was added.…”