Ultraviolet (UV) irradiation induces detrimental changes in human skin which result in photoaging. UV-induced intracellular changes cause degradation of extracellular matrix (ECM). UV-stimulated cleavage of collagen in ECM occurs via matrix metalloproteinases (MMPs). (±)-syringaresinol (SYR), a phytochemical which belongs to the lignan group of polyphenols, was investigated for its ability to reverse the UVA-induced changes in human HaCaT keratinocytes and dermal fibroblasts (HDFs) in vitro. Effect of SYR on UVA-induced changes was investigated by production and activation of MMPs and its transcriptional upstream effectors; mitogen-activated protein kinases (MAPKs) and pro-inflammatory mediators. Levels of expression were determined using ELISA, RT-PCR and immunoblotting. UVA irradiation stimulated the production of MMP-1 and inhibited collagen production. SYR treatment suppressed MMP-1 and enhanced collagen production in UVA-irradiated HaCaT keratinocytes and HDFs. SYR repressed the UV-induced phosphorylation of p38, ERK and JNK MAPKs in HaCaT keratinocytes while only suppressing JNK phosphorylation in HDFs. In addition, SYR was able to inhibit UVA-induced production of inflammatory cytokines; TNF-α, COX-2, IL-1β and IL-6. Moreover, SYR suppressed the activator protein-1 (AP-1), a heterodimer of phosphorylated transcription factors c-Jun and c-Fos. SYR-treatment decreased nuclear levels of activated c-Fos and c-Jun as a mechanism to inhibit UVA-induced transcriptional activities leading to MMP-1 production. In conclusion, current results demonstrated that SYR could inhibit UVA-induced upregulation of MMP-1 by suppressing MAPK/AP-1 signaling in HaCaT keratinocytes and HDFs. Therefore, SYR was suggested as a potential compound with antiphotoaging properties against UVA-induced skin aging.

Overproduction and stimulation of tyrosinase result in increased melanogenesis of which several skin disorders such as freckles, spots, and hyperpigmentation appear as complications. Limonium tetragonum is a halophyte well-known for its antioxidative properties. This study investigated the anti-melanogenic effects of solvent-partitioned L. tetragonum extracts (LTEs) and its bioactive constituents, two isolated flavonoid glycosides. Current study followed a set of experiments on B16-F10 mouse melanoma cell model with a focus on tyrosinase activity and production. The anti-melanogenic capacity of LTEs was confirmed by their tyrosinase inhibitory effects, prevention of DOPA oxidation, and suppression of melanin production. The inhibition of tyrosinase and DOPA oxidation by LTEs was suggested to be related with the downregulation of microphthalmia-associated transcription factor, tyrosinase, tyrosinase-related protein-1, and tyrosinase-related protein-2, verified with mRNA and protein expression levels. Among all tested LTEs, 85% aq. MeOH and n-BuOH were found to be the most active fractions which later yielded the two known compounds, myricetin 3-galactoside and quercetin 3-O-β-galactopyronaside. The anti-melanogenic potential of the compounds were confirmed by their tyrosinase inhibitory effects. These results suggested that L. tetragonum may serve as a potential source of bioactive substances with effective anti-melanogenesis properties.

UV irradiation is one of the main causes of extrinsic skin aging. UV-mediated skin aging, also known as photoaging, causes excessive breakdown of extracellular matrix which leads skin to lose its elasticity and strength. Several phytochemicals are known to exert anti-photoaging effects via different mechanisms, partly due to their antioxidant properties. The current study has been carried out to determine the potential anti-photoaging properties of myricetin 3-O-β-d-galacto-pyranoside (M3G), a flavonol glycoside isolated from L. tetragonum, in UVA-irradiated in vitro models; HaCaT keratinocytes and human dermal fibroblasts (HDFs). UVA-induced changes in MMP-1 and collagen production have been observed in HaCaT keratinocytes and HDFs. Further, UVA-induced activation of MAPK signaling, and pro-inflammatory cytokine production have been investigated. TGFβ/Smad pathway has also been analyzed in UVA-irradiated HDFs. Treatment with M3G reversed the UVA-induced changes in MMP-1 and collagen production both in HaCaT keratinocytes and HDFs. UVA-mediated activation of p38, ERK and JNK MAPK activation was also inhibited by M3G treatment in HaCaT keratinocytes. In HDFs, M3G was able to upregulate the TGFβ/Smad pathway activation. In addition, M3G downregulated the UVA-induced pro-inflammatory cytokines in keratinocytes and HDFs. It has been suggested that the M3G has exerted potential antiphotoaging properties in vitro, by attenuating UVA-induced changes in MMP-1 and collagen production in keratinocytes and dermal fibroblasts.

Chronic UVA exposure results in elevated reactive oxygen species in skin which leads to photoaging characterized as upregulated matrix metalloproteinase (MMP)-1 and loss of collagen. Therefore, natural antioxidants are hailed as promising agents to be utilized against photoaging. In the current study, reynosin and santamarine, two known sesquiterpene lactones isolated from Artemisia scoparia, were analyzed for their anti-photoaging properties in UVA-irradiated human dermal fibroblasts (HDFs). Results showed that UVA irradiation (8 J/cm²) upregulated the MMP-1 secretion and expression, and suppressed collagen production, which were significantly reverted by santamarine treatment (10 µM). Although both reynosin and santamarine exhibited ROS scavenging abilities, reynosin failed to significantly diminish UVA-stimulated MMP-1 release. UVA-irradiated HDFs showed increased collagen production when treated with santamarine. As a mechanism to suppress MMP-1, santamarine significantly suppressed the UVA-induced phosphorylation of p38 and JNK and nuclear translocation of p-c-Fos and p-c-Jun. Santamarine promoted collagen I production via relieving the UVA-induced suppression on TGF-β and its downstream activator Smad2/3 complex. Antioxidant properties of santamarine were also shown to arise from stimulating Nrf2-dependent expression of antioxidant enzymes SOD-1 and HO-1 in UVA-irradiated HDFs. In conclusion, santamarine was found to be a promising natural antioxidant with anti-photoaging properties against UVA-induced damages in HDFs.