Hyperoside and Quercitrin in Houttuynia cordata Extract Attenuate UVB-Induced Human Keratinocyte Cell Damage and Oxidative Stress via Modulation of MAPKs and Akt Signaling Pathway

Ultraviolet radiation is a major environmental harmful factor on human skin. In this paper, we investigate the potential mechanism of Houttuynia cordata extract on UVB-induced HaCaT keratinocyte cell death and inflammation. We found that Houttuynia cordata ethyl acetate extract fraction (HC-EA) protected against UVB-induced cell damage. The HPLC results indicate that quercitrin and hyperoside are the major polyphenolics in HC-EA and are responsible for providing protection against UVB-induced cell death. These responses were associated with the regulation of caspase-9 and caspase-3 activation, which rescued HaCaT cells from UVB-induced apoptosis. In addition, HC-EA, quercitrin, and hyperoside attenuated UVB-induced inflammatory mediators, including IL-6, IL-8, COX-2, and iNOS. Furthermore, the treatment of cells with HC-EA and its active compounds abolished intracellular ROS and increased levels of heme oxygenase-1 and superoxide dismutase. UVB-induced ROS production mediated Akt and mitogen activated protein kinases (MAPKs) pathways, including p38, ERK, and JNK. Our results show HC-EA, quercitrin, and hyperoside decreased UVB-induced p38 and JNK phosphorylation, while increasing ERK and Akt phosphorylation. MAPKs and Akt mediated cell survival and death were confirmed by specific inhibitors to Akt and MAPKs. Thus, HC-EA, which contains quercitrin and hyperoside, protected keratinocyte from UVB-induced oxidative damage and inflammation through the modulation of MAPKs and Akt signaling.

Identification of the circ_PRKDC/miR-20a-3p/RASA1 axis in regulating HaCaT keratinocyte migration

Migration of keratinocytes plays a crucial role in the re-epithelialization phase during wound healing. Circular RNA (circRNA) protein kinase, DNA-activated, catalytic subunit (circ_PRKDC, hsa_circ_0084443) has been identified as a regulator of keratinocyte migration. However, the molecular basis governing it remains unclear. The levels of circ_PRKDC, microRNA (miR)-20a-3p, and RAS p21 protein activator 1 (RASA1) were assessed by quantitative real-time PCR (qRT-PCR) or western blot. Subcellular localization, Actinomycin D, and Ribonuclease (RNase) R assays were performed to characterise circ_PRKDC. Cell migration was gauged by transwell and wound-healing assays. A direct relationship between miR-20a-3p and circ_PRKDC or RASA1 was verified by dual-luciferase reporter and RNA pull-down assays. Circ_PRKDC expression was reduced in wound skin during wound healing. Circ_PRKDC modulated migration of HaCaT keratinocytes. Mechanistically, circ_PRKDC directly targeted miR-20a-3p. The regulation of circ_PRKDC on HaCaT keratinocyte migration was mediated by miR-20a-3p. RASA1 was identified as a direct and functional target of miR-20a-3p, and miR-20a-3p-mediated inhibition of RASA1 impacted HaCaT keratinocyte migration. Circ_PRKDC acted as a post-transcriptional modulator of RASA1 expression through miR-20a-3p. Moreover, circ_PRKDC modulated migration of HaCaT keratinocytes by RASA1. Our findings demonstrated a novel molecular basis, the miR-20a-3p/RASA1 axis, for the regulation of circ_PRKDC on HaCaT keratinocyte migration.

Camellioside A, isolated from flowers, attenuates UVA-induced production of MMP-1 in HaCaT keratinocytes via suppression of MAPK activation

Ultraviolet (UV) radiation is responsible for various damages to the skin, collectively referred to as photoaging. A key UV-induced effect on the skin is excessive degradation of collagen and related structural abnormalities. Camellia japonica is a flowering plant with cosmeceutical properties. In the present study, Camellioside A (CMDA), a triterpene saponin, was investigated for its effects against UVA-induced photoaging in HaCaT keratinocytes. CMDA was analyzed to determine its attenuating effects against UVA-induced overproduction of the collagen degradation enzyme, matrix metalloproteinase-1 (MMP-1), in UVA-irradiated immortalized human HaCaT keratinocytes. UVA irradiation significantly increased MMP-1 release from keratinocytes in addition to suppressing type Iα1 pro-collagen production. Treatment with CMDA reversed the effects of UVA irradiation on the production of MMP-1 and type Iα1 pro-collagen. UVA irradiation also stimulated the activation of p38, ERK and JNK mitogen-activated protein kinases (MAPKs) and their downstream transcription factor activator protein 1 (a heterodimer of c-Fos and c-Jun). MAPK activation and consequent phosphorylation of c-Fos and c-Jun were also inhibited by CMDA treatment. In conclusion, the present study indicated that CMDA may have potential antiphotoaging properties due to suppression of UVA-mediated MMP-1 production.

Human Keratinocyte UVB-Protective Effects of a Low Molecular Weight Fucoidan from Sargassum horneri Purified by Step Gradient Ethanol Precipitation

Ultraviolet B (UVB) radiation-induced oxidative skin cell damage is a major cause of photoaging. In the present study, a low molecular weight fucoidan fraction (SHC4) was obtained from Sargassum horneri by Celluclast-assisted extraction, followed by step gradient ethanol precipitation. The protective effect of SHC4 was investigated in human keratinocytes against UVB-induced oxidative stress. The purified fucoidan was characterized by Fourier-transform infrared spectroscopy (FTIR), ¹H nuclear magnetic resonance (NMR), agarose gel-based molecular weight analysis and monosaccharide composition analysis. SHC4 had a mean molecular weight of 60 kDa, with 37.43% fucose and 28.01 ± 0.50% sulfate content. The structure was mainly composed of α-L-Fucp-(1→4) linked fucose units. SHC4 treatment dose-dependently reduced intracellular reactive oxygen species (ROS) levels and increased the cell viability of UVB exposed HaCaT keratinocytes. Moreover, SHC4 dose-dependently inhibited UVB-induced apoptotic body formation, sub-G₁ accumulation of cells and DNA damage. Inhibition of apoptosis was mediated via the mitochondria-mediated pathway, re-establishing the loss of mitochondrial membrane potential. The UVB protective effect of SHC4 was facilitated by enhancing intracellular antioxidant defense via nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) signaling. Further studies may promote the use of SHC4 as an active ingredient in cosmetics and nutricosmetics.

Anticatabolic and Anti-Inflammatory Effects of Myricetin 3-O-β-d-Galactopyranoside in UVA-Irradiated Dermal Cells via Repression of MAPK/AP-1 and Activation of TGFβ/Smad

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.

A Novel Butylated Caffeic Acid Derivative Protects HaCaT Keratinocytes from Squalene Peroxidation-Induced Stress

Squalene is a major sebum lipid which is easily peroxidized by ultraviolet A (UVA) irradiation, generating products that can stress keratinocytes. Prevention of squalene photooxidation with antioxidants could potentially help defend skin from environmental stress. Previously, we have systematically characterized butylated caffeic acid (BCA) as a more lipophilic alternative of caffeic acid (CA). The current study aimed to test the hypothesis that the lipophilic property of BCA makes it a good candidate as a skin antioxidant. The UVA-induced peroxidation of squalene and the antioxidative activity of CA and BCA were measured for peroxide value and further characterized with ultraperformance liquid chromatography coupled with ultraviolet and mass spectrometry analysis. Both CA and BCA showed strong antioxidant capacity during squalene peroxidation under direct UVA challenge. In HaCaT keratinocyte culture, BCA's and CA's impact on the damage induced by peroxidized squalene (P-SQ) was investigated through quantification of reactive oxygen species (ROS) generation and expression of interleukin-1 (IL-1) cytokines. Both BCA and CA decreased P-SQ-induced IL-1β secretion in HaCaT cells. However, only BCA could reduce P-SQ-induced ROS generation as well as expression of inflammatory cytokines in the IL-1 family. This advantage in biological efficacy could have been attributed to BCA's superior intracellular bioavailability due to its higher lipophilicity compared with CA, as indicated by higher intracellular concentration of BCA. Based on this observation, we propose using BCA as a functional antioxidant to prevent sebum lipid from peroxidation and its detrimental effect to skin.

The preventive effect of deep sea water on the development of cancerous skin cells through the induction of autophagic cell death in UVB-damaged HaCaT keratinocyte

Ultraviolet light (UV) is a major inducer of skin cancer. Therefore, recovery and removal of UV-damaged skin cells are important in the prevention of skin carcinogenesis. Here, we investigated the effect of deep sea water (DSW) in HaCaT keratinocyte exposed by UVB (λ = 290∼320 nm). The result showed that UVB-induced cell death was reinforced by DSW treatment in a hardness-dependent manner. Furthermore, the increase of cell death by DSW was associated with the down-regulation of survivin and RAD51 expressions induced by UVB. Moreover, we confirmed the inhibition of H2 A.X phosphorylation, a marker for double-stranded DNA damage, and the enhancement of LC3-II and SQSTM1/p62 expressions by DSW administration in UVB-radiated HaCaT keratinocyte. The results imply that the enhancement of UVB-induced cell death by DSW is associated with autophagy. Therefore, we further explored the regulation of autophagy-regulating proteins and apoptosis-related factors expression. Phosphorylation of mammalian target of rapamycin (mTOR), ribosomal protein S6, and S6 kinase by UVB radiation were regressed via DSW treatment, underlying the increase of AMP-activated protein kinase (AMPK) phosphorylation. Furthermore, UVB-enhanced nuclear factor κB (NF-κB) and c-Jun N-terminal kinase (JNK) phosphorylations were increased with DSW treatment. Contrastingly, DSW lessened the Ser15 phosphorylation of p53 and cleavage of poly (ADP-ribose) polymerase induced by UVB radiation. Consequently, the results demonstrate that DSW enhances UVB-damaged skin cell clearance through the activation of autophagic cell death underlying the regulation of AMP-activated protein kinase (AMPK)/mTOR signaling as well as NF-κB and JNK phosphorylations. In conclusion, this investigation suggests that DSW is a potent candidate for the prevention of UV-induced skin cancer development.

TNIP1 reduction sensitizes keratinocytes to post-receptor signalling following exposure to TLR agonists

Cell level inflammatory signalling is a combination of initiation at cell membrane receptors and modulation by cytoplasmic regulatory proteins. For keratinocytes, the predominant cell type in the epidermis, this would include toll-like receptors (TLR) and cytoplasmic proteins that propagate or dampen post-receptor signalling. We previously reported that increased levels of tumor necrosis factor α induced protein 3-interacting protein 1 (TNIP1) in HaCaT keratinocytes leads to decreased expression of stress response and inflammation-associated genes. This finding suggested decreased TNIP1 levels, as seen in some cutaneous disease states, may produce the opposite effect, sensitizing cells to triggers of inflammatory signalling including those sensed by TLR. In this study of TNIP1-deficient HaCaT keratinocytes we examined intracellular signalling consequences especially those expected to produce gene expression changes downstream of TLR3 or TLR2/6 activation by Poly (I:C) or FSL-1, agonists modeling skin relevant pathogens. We found TNIP1-deficient keratinocytes are hyper-sensitive to TLR activation compared to control cells with a normal complement of TNIP1 and receiving the same agonist stimulation. TNIP1-deficient keratinocytes have increased levels of activated (phosphorylated) cytoplasmic mediators such as JNK and p38 and greater nuclear translocation of NF-κB and phospho-p38 when exposed to TLR ligands. This is consistent with significantly increased expression of several inflammatory cytokines and chemokines, such as IL-6 and IL-8. These results describe how decreased TNIP1 levels promote a hyper-sensitive state in HaCaT keratinocytes evidenced by increased activation of signalling molecules downstream of TLR agonists and increased expression of pro-inflammatory mediators. TNIP1 keratinocyte deficiency as reported for some skin diseases may predispose these cells to excessive inflammatory signalling upon exposure to viral or bacterial ligands for TLR.

MCP-1 produced by keratinocytes is associated with leucocyte recruitment during elicitation of nickel-induced occupational allergic contact dermatitis

To investigate the expression profile of monocyte chemoattractant peptide-1 (MCP-1) by keratinocytes after nickel exposure and to identify its role for leucocyte migration during nickel-induced occupational allergic contact dermatitis (OACD), 26 workers diagnosed with nickel-induced OACD were enrolled. Skin biopsies from the positive nickel-challenged sites at different time points were assessed by immunohistochemistry (IHC) for MCP-1, CD68, CD45RO, and in situ hybridization (ISH) for MCP-1, using chronic periumbilical dermititis as controls. The expressions of MCP-1 in HaCaT cell culture after nickel treatment were quantified by enzyme-linked immunosorbent assay. The results showed that at positive nickel-challenged sites, strong expressions of MCP-1, both messenger RNA (mRNA) and protein, were detected in the basal keratinocytes during the early phase (24-48 h after nickel application), paralleled by the recruitment of CD68⁺ and CD45RO⁺ cells to the skin compartments. The expressions of MCP-1 declined gradually in the late phase (72-96 h after nickel application). Treatment with nickel sulfate at noncytotoxic concentrations (0.01-100 µM) induced a concentration-related elevation of MCP-1 expression by HaCaT cells compared to the untreated cells. The data indicated that a temporal expression pattern of MCP-1 produced by keratinocytes after nickel exposure was involved in the complex process of mononuclear cell infiltration during elicitation of nickel-induced OACD. Targeting MCP-1 might be a potential therapeutic strategy for OACD.

Protective Effects of Minor Components of Curcuminoids on Hydrogen Peroxide-Treated Human HaCaT Keratinocytes

Hydrogen peroxide, one of the reactive oxygen species (ROS), can cause intracellular oxidative stress associated with skin aging and/or photoaging. Curcumin, a polyphenol in turmeric, has been reported to exhibit biological activity. In this study, five naturally occurring curcuminoids [curcumin, demethoxycurcumin (DMC), bisdemethoxycurcumin (BDMC), monohydroxy-DMC, and monohydroxy-BDMC] were used to investigate their protective roles against hydrogen peroxide-induced oxidative stress in the immortalized human keratinocyte cell lines (HaCaT cells). These five curcuminoids at 10 μM, but not at 5 μM, were shown to exhibit cytotoxicities toward HaCaT keratinocytes. Therefore, a 5 μM concentration of the five curcuminoids was selected for further investigations. Cells were pretreated with or without curcuminoids for 2.5 h before 24-h hydrogen peroxide (150 μM) treatments. Pretreatments with the minor components monohydroxy-DMC or monohydroxy-BDMC, but not curcumin, DMC, and BDMC, showed protective activity, elevating cell viability compared to cells with direct hydrogen peroxide treatments. Pretreatments with monohydroxy-DMC and monohydroxy-BDMC showed the best protective effects, reducing apoptotic cell populations and intracellular ROS, as demonstrated by flow cytometry, as well as reducing the changes of the mitochondrial membrane potential compared to cells with direct hydrogen peroxide treatments. The pretreatments with monohydroxy-DMC and monohydroxy-BDMC reduced c-jun and c-fos mRNA expression and p53 tumor suppressor protein expression and increased HO-1 protein expression and glutathione peroxidase (GPx) activity, respectively, compared to cells with direct hydrogen peroxide treatments. The five curcuminoids exhibited similar hydrogen peroxide-scavenging activity in vitro. It was proposed that monohydroxy-DMC and monohydroxy-BDMC could induce antioxidant defense systems better than curcumin, DMC, or BDMC could against hydrogen peroxide-induced oxidative stress and apoptosis of HaCaT keratinocytes and that they may have potential as ingredients in antiaging cosmetics for skin care.

6'-o-galloylpaeoniflorin protects human keratinocytes against oxidative stress-induced cell damage

6'-O-galloylpaeoniflorin (GPF) is a galloylated derivate of paeoniflorin and a key chemical constituent of the peony root, a perennial flowering plant that is widely used as an herbal medicine in East Asia. This study is the first investigation of the cytoprotective effects of GPF against hydrogen peroxide (H₂O₂)-induced cell injury and death in human HaCaT keratinocytes. GPF demonstrated a significant scavenging capacity against the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical, H₂O₂-generated intracellular reactive oxygen species (ROS), the superoxide anion radical (O₂^-), and the hydroxyl radical (•OH). GPF also safeguarded HaCaT keratinocytes against H₂O₂-provoked apoptotic cell death and attenuated oxidative macromolecular damage to DNA, lipids, and proteins. The compound exerted its cytoprotective actions in keratinocytes at least in part by decreasing the number of DNA strand breaks, the levels of 8-isoprostane (a stable end-product of lipid peroxidation), and the formation of carbonylated protein species. Taken together, these results indicate that GPF may be developed as a cytoprotector against ROS-mediated oxidative stress.