Shikonin protects skin cells against oxidative stress and cellular dysfunction induced by fine particulate matter.

Shikonin, an herbal naphthoquinone, demonstrates a broad spectrum of pharmacological properties. Owing to increasingly adverse environmental conditions, human skin is vulnerable to harmful influences from dust particles. This study explored the antioxidant capabilities of shikonin and its ability to protect human keratinocytes from oxidative stress induced by fine particulate matter (PM2.5). We found that shikonin at a concentration of 3 µM was nontoxic to human keratinocytes and effectively scavenged reactive oxygen species (ROS) while increasing the production of reduced glutathione (GSH). Furthermore, shikonin enhanced GSH level by upregulating glutamate-cysteine ligase catalytic subunit and glutathione synthetase mediated by nuclear factor-erythroid 2-related factor. Shikonin reduced ROS levels induced by PM2.5, leading to recovering PM2.5-impaired cellular biomolecules and cell viability. Shikonin restored the GSH level in PM2.5-exposed keratinocytes via enhancing the expression of GSH-synthesizing enzymes. Notably, buthionine sulphoximine, an inhibitor of GSH synthesis, diminished effect of shikonin against PM2.5-induced cell damage, confirming the role of GSH in shikonin-induced cytoprotection. Collectively, these findings indicated that shikonin could provide substantial cytoprotection against the adverse effects of PM2.5 through direct ROS scavenging and modulation of cellular antioxidant system.

The inhibitory effect of chlorogenic acid on oxidative stress and apoptosis induced by PM2.5 in HaCaT keratinocytes.

Exposure to fine particulate matter with an aerodynamic diameter of less than 2.5 µm (PM2.5) can cause oxidative damage and apoptosis in the human skin. Chlorogenic acid (CGA) is a bioactive polyphenolic compound with antioxidant, antifungal, and antiviral properties. The objective of this study was to identify the ameliorating impact of CGA that might protect human HaCaT cells against PM2.5. CGA significantly scavenged the reactive oxygen species (ROS) generated by PM2.5, attenuated oxidative cellular/organelle damage, mitochondrial membrane depolarization, and suppressed cytochrome c release into the cytosol. The application of CGA led to a reduction in the expression levels of Bcl-2-associated X protein, caspase-9, and caspase-3, while simultaneously increasing the expression of B-cell lymphoma 2. In addition, CGA was able to reverse the decrease in cell viability caused by PM2.5 via the inhibition of extracellular signal-regulated kinase (ERK). This effect was further confirmed by the use of the mitogen-activated protein kinase kinase inhibitor, which acted upstream of ERK. In conclusion, CGA protected keratinocytes from mitochondrial damage and apoptosis via ameliorating PM2.5-induced oxidative stress and ERK activation.

Rosmarinic Acid Protects Skin Keratinocytes from Particulate Matter 2.5-Induced Apoptosis.

Background: The exposure of the human skin to particulate matter 2.5 (PM2.5) results in adverse health outcomes, such as skin aging, wrinkle formation, pigment spots, and atopic dermatitis. It has previously been shown that rosmarinic acid (RA) can protect keratinocytes from ultraviolet B radiation by enhancing cellular antioxidant systems and reducing oxidative damage; however, its protective action against the adverse effects of PM2.5 on skin cells remains unclear. Therefore, in this study, we explored the mechanism underlying the protective effects of RA against PM2.5-mediated oxidative stress in HaCaT keratinocytes. Methods: HaCaT keratinocytes were pretreated with RA and exposed to PM2.5. Thereafter, reactive oxygen species (ROS) production, protein carbonylation, lipid peroxidation, DNA damage, and cellular apoptosis were investigated using various methods, including confocal microscopy, western blot analysis, and flow cytometry. Results: RA significantly inhibited PM2.5-induced lipid peroxidation, protein carbonylation, DNA damage, increases in intracellular Ca2+ level, and mitochondrial depolarization. It also significantly attenuated PM2.5-induced apoptosis by downregulating Bcl-2-associated X, cleaved caspase-9, and cleaved caspase-3 protein levels, while upregulating B-cell lymphoma 2 protein level. Further, our results indicated that PM2.5-induced apoptosis was associated with the activation of the mitogen-activated protein kinase (MAPK) signaling pathway and that MAPK inhibitors as well as RA exhibited protective effects against PM2.5-induced apoptosis. Conclusion: RA protected HaCaT cells from PM2.5-induced apoptosis by lowering oxidative stress.

Protective Effect of Fermented Sea Tangle Extract on Skin Cell Damage Caused by Particulate Matter.

The skin is directly exposed to atmospheric pollutants, especially particulate matter 2.5 (PM2.5) in the air, which poses significant harm to skin health. However, limited research has been performed to identify molecules that can confer resistance to such substances. Herein, we analyzed the effect of fermented sea tangle (FST) extract on PM2.5-induced human HaCaT keratinocyte damage. Results showed that FST extract, at concentrations less than 800 µg/mL, exhibited non-significant toxicity to cells and concentration-dependent inhibition of PM2.5-induced reactive oxygen species (ROS) production. PM2.5 induced oxidative stress by stimulating ROS, resulting in DNA damage, lipid peroxidation, and protein carbonylation, which were inhibited by the FST extract. FST extract significantly suppressed the increase in calcium level and apoptosis caused by PM2.5 treatment and significantly restored the reduced cell viability. Mitochondrial membrane depolarization occurred due to PM2.5 treatment, however, FST extract recovered mitochondrial membrane polarization. PM2.5 inhibited the expression of the anti-apoptotic protein Bcl-2, and induced the expression of pro-apoptotic proteins Bax and Bim, the apoptosis initiator caspase-9, as well as the executor caspase-3, however, FST extract effectively protected the changes in the levels of these proteins caused by PM2.5. Interestingly, pan-caspase inhibitor Z-VAD-FMK treatment enhanced the anti-apoptotic effect of FST extract in PM2.5-treated cells. Our results indicate that FST extract prevents PM2.5-induced cell damage via inhibition of mitochondria-mediated apoptosis in human keratinocytes. Accordingly, FST extract could be included in skin care products to protect cells against the harmful effects of PM2.5.

Butin Protects Keratinocytes From Particulate Matter 2.5 and Ultraviolet B-Mediated Damages.

BACKGROUND: Butin is a naturally occurring compound with a wide range of medicinal properties, including anti-inflammatory, anti-arthritic, and antioxidant properties. Particulate matter 2.5 (PM2.5) and ultraviolet B (UVB) radiation contribute to skin cell damage via the induction of oxidative stress. METHODS: This study sought to assess the protective effects of butin against damage triggered by PM2.5 and UVB in human HaCaT keratinocytes. Assessments were performed to evaluate cell viability, apoptosis, and cellular component damage. RESULTS: Butin exhibited its protective ability via the inhibition of PM2.5-induced reactive oxygen species generation, lipid peroxidation, DNA damage, protein carbonylation, and mitochondrial damage. Butin reduced the PM2.5-induced c-Fos and phospho-c-Jun protein levels as well as mitogen-activated protein kinase. Furthermore, butin mitigated PM2.5- and UVB-induced apoptosis. CONCLUSION: Butin had the potential as a pharmaceutical candidate for treating skin damage caused by PM2.5 and UVB exposure.

Silver nanoparticle-induced cell damage via impaired mtROS-JNK/MnSOD signaling pathway.

This study investigated the mechanism of silver nanoparticle (AgNP) cytotoxicity from a mitochondrial perspective. The effect of AgNP on manganese superoxide dismutase (MnSOD), a mitochondrial antioxidant enzyme, against oxidative stress has not been studied in detail. We demonstrated that AgNP decreased MnSOD mRNA level, protein expression, and activity in human Chang liver cells in a time-dependent manner. AgNP induced the production of mitochondrial reactive oxygen species (mtROS), particularly superoxide anion. AgNP was found to increase mitochondrial calcium level and disrupt mitochondrial function, leading to reduced ATP level, succinate dehydrogenase activity, and mitochondrial permeability. AgNP induced cytochrome c release from the mitochondria into the cytoplasm, attenuated the expression of the anti-apoptotic proteins phospho Bcl-2 and Mcl-1, and induced the expression of the pro-apoptotic proteins Bim and Bax. In addition, c-Jun N-terminal kinase (JNK) phosphorylation was significantly increased by AgNP. Treatment with elamipretide (a mitochondria-targeted antioxidant) and SP600125 (a JNK inhibitor) showed the involvement of MnSOD and JNK in these processes. These results indicated that AgNP damaged human Chang liver cells by destroying mitochondrial function through the accumulation of mtROS.

Diesel exhaust particulate matter impairs Toll-like receptor signaling and host defense against staphylococcal cutaneous infection in mice.

Air pollution is an emerging cause of mortality, affecting nearly 5 million people each year. Exposure to diesel exhaust fine particulate matter (PM2.5) aggravates respiratory and skin conditions. However, its impact on the protective immunity of the skin remains poorly understood. This study aimed to investigate the underlying molecular mechanism for adverse effects of PM2.5 on the host protective immunity using in vitro cell and in vivo mouse model. Intracellular translocation of Toll-like receptor 9 (TLR9) and CpG-DNA internalization were assessed in dendritic cells without or with PM2.5 treatment using immunofluorescence staining. Cytokine and nitric oxide production were measured in dendritic cells and macrophages without or with PM2.5 treatment. NF-κB and MAPK signaling was determined using western blotting. Skin disease severity, bacterial loads, and cytokine production were assessed in cutaneous Staphylococcus aureus (S. aureus) infection mouse model. PM2.5 interfered with TLR9 activation by inhibiting both TLR9 trafficking to early endosomes and CpG-DNA internalization via clathrin-mediated endocytosis. In addition, exposure to PM2.5 inhibited various TLR-mediated nitric oxide and cytokine production as well as MAPK and NF-κB signaling. PM2.5 rendered mice more susceptible to staphylococcal skin infections. Our results suggest that exposure to PM impairs TLR signaling and dampens the host defense against staphylococcal skin infections. Our data provide a novel perspective into the impact of PM on protective immunity which is paramount to revealing air pollutant-mediated toxicity on the host immunity.

Spermidine Attenuates High Glucose-Induced Oxidative Damage in Retinal Pigment Epithelial Cells by Inhibiting Production of ROS and NF-κB/NLRP3 Inflammasome Pathway.

Diabetic retinopathy (DR) is the leading cause of vision loss and a critical complication of diabetes with a very complex etiology. The build-up of reactive oxygen species (ROS) due to hyperglycemia is recognized as a primary risk factor for DR. Although spermidine, a naturally occurring polyamine, has been reported to have antioxidant effects, its effectiveness in DR has not yet been examined. Therefore, in this study, we investigated whether spermidine could inhibit high glucose (HG)-promoted oxidative stress in human retinal pigment epithelial (RPE) cells. The results demonstrated that spermidine notably attenuated cytotoxicity and apoptosis in HG-treated RPE ARPE-19 cells, which was related to the inhibition of mitochondrial ROS production. Under HG conditions, interleukin (IL)-1ß and IL-18's release levels were markedly increased, coupled with nuclear factor kappa B (NF-κB) signaling activation. However, spermidine counteracted the HG-induced effects. Moreover, the expression of nucleotide-binding oligomerization domain-like receptor (NLR) protein 3 (NLRP3) inflammasome multiprotein complex molecules, including TXNIP, NLRP3, ASC, and caspase-1, increased in hyperglycemic ARPE-19 cells, but spermidine reversed these molecular changes. Collectively, our findings demonstrate that spermidine can protect RPE cells from HG-caused injury by reducing ROS and NF-κB/NLRP3 inflammasome pathway activation, indicating that spermidine could be a potential therapeutic compound for DR treatment.

Induction of apoptosis through inactivation of ROS-dependent PI3K/Akt signaling pathway by platycodin D in human bladder urothelial carcinoma cells.

Platycodin D (PD) is a triterpenoid saponin, a major bioactive constituent of the roots of Platycodon grandiflorum, which is well known for possessing various pharmacological properties. However, the anti-cancer mechanism of PD in bladder cancer cells remains poorly understood. In the current study, we investigated the effect of PD on the growth of human bladder urothelial carcinoma cells. PD treatment significantly reduced the cell survival of bladder cancer cells associated with induction of apoptosis and DNA damage. PD inhibited the expression of inhibitor of apoptosis family members, activated caspases, and induced cleavage of poly (ADP-ribose) polymerase. PD also increased the release of cytochrome c into the cytoplasm by disrupting the mitochondrial membrane potential while upregulating the expression ratio of Bax to Bcl-2. The PD-mediated anti-proliferative effect was significantly inhibited by pre-treatment with a pancaspase inhibitor, but not by an inhibitor of necroptosis. Moreover, PD suppressed the phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) signaling pathway, and the apoptosis-inducing effect of PD was further enhanced by a PI3K inhibitor. In addition, PD increased the accumulation of reactive oxygen species (ROS), whereas N-acetyl cysteine (NAC), an ROS inhibitor, significantly attenuated the growth inhibition and inactivation of the PI3K/Akt/mTOR signaling caused by PD. Furthermore, NAC significantly suppressed apoptosis, DNA damage, and decreased cell viability induced by PD treatment. Collectively, our findings indicated that PD blocked the growth of bladder urothelial carcinoma cells by inducing ROS-mediated inactivation of the PI3K/Akt/mTOR signaling.

Hesperidin Exhibits Protective Effects against PM2.5-Mediated Mitochondrial Damage, Cell Cycle Arrest, and Cellular Senescence in Human HaCaT Keratinocytes.

Particulate matter 2.5 (PM2.5) exposure can trigger adverse health outcomes in the human skin, such as skin aging, wrinkles, pigment spots, and atopic dermatitis. PM2.5 is associated with mitochondrial damage and the generation of reactive oxygen species (ROS). Hesperidin is a bioflavonoid that exhibits antioxidant and anti-inflammatory properties. This study aimed to determine the mechanism underlying the protective effect of hesperidin on human HaCaT keratinocytes against PM2.5-induced mitochondrial damage, cell cycle arrest, and cellular senescence. Human HaCaT keratinocytes were pre-treated with hesperidin and then treated with PM2.5. Hesperidin attenuated PM2.5-induced mitochondrial and DNA damage, G0/G1 cell cycle arrest, and SA-ßGal activity, the protein levels of cell cycle regulators, and matrix metalloproteinases (MMPs). Moreover, treatment with a specific c-Jun N-terminal kinase (JNK) inhibitor, SP600125, along with hesperidin markedly restored PM2.5-induced cell cycle arrest and cellular senescence. In addition, hesperidin significantly reduced the activation of MMPs, including MMP-1, MMP-2, and MMP-9, by inhibiting the activation of activator protein 1. In conclusion, hesperidin ameliorates PM2.5-induced mitochondrial damage, cell cycle arrest, and cellular senescence in human HaCaT keratinocytes via the ROS/JNK pathway.

5-Bromo-3,4-dihydroxybenzaldehyde Promotes Hair Growth through Activation of Wnt/ß-Catenin and Autophagy Pathways and Inhibition of TGF-ß Pathways in Dermal Papilla Cells.

Various studies addressing the increasing problem of hair loss, using natural products with few side effects, have been conducted. 5-bromo-3,4-dihydroxybenzaldehyde (BDB) exhibited anti-inflammatory effects in mouse models of atopic dermatitis and inhibited UVB-induced oxidative stress in keratinocytes. Here, we investigated its stimulating effect and the underlying mechanism of action on hair growth using rat vibrissa follicles and dermal papilla cells (DPCs), required for the regulation of hair cycle and length. BDB increased the length of hair fibers in rat vibrissa follicles and the proliferation of DPCs, along with causing changes in the levels of cell cycle-related proteins. We investigated whether BDB could trigger anagen-activating signaling pathways, such as the Wnt/ß-catenin pathway and autophagy in DPCs. BDB induces activation of the Wnt/ß-catenin pathway through the phosphorylation of GSG3ß and ß-catenin. BDB increased the levels of autophagic vacuoles and autophagy regulatory proteins Atg7, Atg5, Atg16L, and LC3B. We also investigated whether BDB inhibits the TGF-ß pathway, which promotes transition to the catagen phase. BDB inhibited the phosphorylation of Smad2 induced by TGF-ß1. Thus, BDB can promote hair growth by modulating anagen signaling by activating Wnt/ß-catenin and autophagy pathways and inhibiting the TGF-ß pathway in DPCs.

Peroxiredoxin I deficiency increases keratinocyte apoptosis in a skin tumor model via the ROS-p38 MAPK pathway.

Keratinocyte hyperproliferation is an essential link in skin cancer pathogenesis. Peroxiredoxin I (Prx I) is known to regulate cancer cell proliferation, differentiation, and apoptosis, but its role in skin cancer remains unclear. This study aimed to elucidate the role and mechanism of Prx I in skin cancer pathogenesis. Dimethylbenz[a]anthracene (DMBA) and 12-O-tetradecanoyl-phorbol-13-acetate (TPA) were used to create a skin tumor model of the initiation/promotion stage of cancer. The role of Prx I in H2O2-induced keratinocyte apoptosis was also investigated. After DMBA/TPA treatment, Prx I deficiency was significantly associated with less skin tumors, lower Bcl-2 expression, and higher p-p38 and cleaved caspase-3 expressions in Prx I knockout tumors than in wild-type controls. H2O2 stimulation caused more cellular apoptosis in Prx I knockdown HaCaT cells than in normal HaCaT cells. The signaling study revealed that Bcl-2, p-p38, and cleaved caspase-3 expressions were consistent with the results in the tumors. In conclusion, the deletion of Prx I triggered the DMBA/TPA-induced skin tumor formation in vivo and in vitro by regulating the reactive oxygen species (ROS)-p38 mitogen-activated protein kinase (MAPK) pathway. These findings provide a theoretical basis for treating skin cancer.

Hemistepsin A protects human keratinocytes against hydrogen peroxide-induced oxidative stress through activation of the Nrf2/HO-1 signaling pathway.

Hemistepsin A, a sesquiterpene lactone compound isolated from Hemistepta lyrata, has been identified a variety of pharmacological actions including anti-hepatotoxic, anti-inflammatory and anti-cancer activities. Nevertheless, the antioxidant effects of hemistepsin A and the underlying mechanisms have not been investigated properly. Therefore, in the present study, we investigated the protective effect of hemistepsin A against oxidative stress in HaCaT human keratinocytes. The results demonstrated that hemistepsin A suppressed 500 µM hydrogen peroxide (H2O2)-induced cytotoxicity and DNA damage by blocking ROS accumulation. 10 µM Hemistepsin A also prevented apoptosis by preventing the mitochondrial dysfunction and the cytosolic release of cytochrome c, reducing the rate of Bax/Bcl-2 expression, and decreasing the activation of caspase-9 and caspase-3, suggesting that hemistepsin A protected cells from H2O2-induced mitochondria-mediated apoptosis. In addition, hemistepsin A markedly promoted the activation of nuclear factor-erythroid-2-related factor 2 (Nrf2), which was associated with the enhanced expression and activity of heme oxygenase-1 (HO-1) in the presence of 500 µM H2O2. However, inhibiting the expression of HO-1 by artificially blocking the expression of Nrf2 or HO-1 using siRNA significantly eliminated the protective effect of hemistepsin A, indicating that hemistepsin A activates the Nrf2/HO-1 signaling pathway in HaCaT cells to protect against oxidative stress. Therefore, these results suggest that hemistepsin A may be useful as a potential therapeutic agent against various oxidative stress-related skin diseases.

Extract of Cornus officinalis Protects Keratinocytes from Particulate Matter-induced Oxidative Stress.

The skin is one of the large organs in the human body and the most exposed to outdoor contaminants such as particulate matter < 2.5 µm (PM2.5). Recently, we reported that PM2.5 induced cellular macromolecule disruption of lipids, proteins, and DNA, via reactive oxygen species, eventually causing cellular apoptosis of human keratinocytes. In this study, the ethanol extract of Cornus officinalis fruit (EECF) showed anti-oxidant effect against PM2.5-induced cellular oxidative stress. EECF protected cells against PM2.5-induced DNA damage, lipid peroxidation, and protein carbonylation. PM2.5 up-regulated intracellular and mitochondrial Ca2+ levels excessively, which led to mitochondrial depolarization and cellular apoptosis. However, EECF suppressed the PM2.5-induced excessive Ca2+ accumulation and inhibited apoptosis. The data confirmed that EECF greatly protected human HaCaT keratinocytes from PM2.5-induced oxidative stress.

Inhibitory effect of particulate matter on toll-like receptor 9 stimulated dendritic cells by downregulating mitogen-activated protein kinase and NF-κB pathway.

Ambient particulate matter (PM) is associated with adverse health consequences. However, the influence of PM on the innate immune system is poorly understood. The aim of the present study was to examine the effect of diesel particulate matter 2.5 µm (PM2.5, SRM1650b) on dendritic cells. PM2.5 significantly reduced cytokine levels of interleukin (IL)-12 p40, IL-6 and TNF-α levels in CpG-DNA (TLR9 ligand)-stimulated dendritic cells. To determine the mechanisms underlying this observed inhibition induced by PM2.5, western blot analysis was conducted. PM2.5 was found to downregulate ERK1/2, JNK1/2, p38 MAPKs, and NF-κB pathways. PM2.5 exposure decreased TLR9-dependent NF-κB and activator protein (AP-1) reporter luciferase activities. Our findings demonstrate that PM2.5 reduced the production of cytokines which may be associated with inhibition of MAPK and NF-κB signaling pathway. Further, data suggest the immunosuppressive effect of PM2.5 on the innate immune cells may lead to serious damage to the host immune system.

HNG, A Humanin Analogue, Promotes Hair Growth by Inhibiting Anagen-to-Catagen Transition.

The hair follicle goes through repetitive cycles including anagen, catagen, and telogen. The interaction of dermal papilla cells (DPCs) and keratinocytes regulates the hair cycle and hair growth. Humanin was discovered in the surviving brain cells of patients with Alzheimer's disease. HNG, a humanin analogue, activates cell growth, proliferation, and cell cycle progression, and it protects cells from apoptosis. This study was performed to investigate the promoting effect and action mechanisms of HNG on hair growth. HNG significantly increased DPC proliferation. HNG significantly increased hair shaft elongation in vibrissa hair follicle organ culture. In vivo experiment showed that HNG prolonged anagen duration and inhibited hair follicle cell apoptosis, indicating that HNG inhibited the transition from the anagen to catagen phase mice. Furthermore, HNG activated extracellular signal-regulated kinase (Erk)1/2, Akt, and signal transducer and activator of transcription (Stat3) within minutes and up-regulated vascular endothelial growth factor (VEGF) levels on DPCs. This means that HNG could induce the anagen phase longer by up-regulating VEGF, which is a Stat3 target gene and one of the anagen maintenance factors. HNG stimulated the anagen phase longer with VEGF up-regulation, and it prevented apoptosis by activating Erk1/2, Akt, and Stat3 signaling.

Norgalanthamine Stimulates Proliferation of Dermal Papilla Cells via Anagen-Activating Signaling Pathways.

Norgalanthamine has been shown to possess hair-growth promoting effects, including increase in hair-fiber length in cultured rat vibrissa follicles and increase in dermal papilla cell (DPC) proliferation. However, the intracellular mechanisms that underlie the action of norgalanthamine in DPCs have not been investigated. In this study, we addressed the ability of norgalanthamine to trigger anagen-activating signaling pathways in DPCs. Norgalanthamine significantly increased extracellular signal-regulated kinase (ERK) 1/2 phosphorylation at 0.1 µM, a concentration at which DPC proliferation was also induced. Furthermore, the increases in norgalanthamine-induced ERK 1/2 activation and subsequent DPC proliferation were suppressed by the mitogen-activated protein kinase/ERK kinase (MEK) 1/2 inhibitor, U0126. A 0.1 µM dose of norgalanthamine also increased phosphorylation of AKT, which was followed by an increase in glycogen synthase kinase 3ß phosphorylation and nuclear translocation of ß-catenin. In addition, LY294002, a phosphatidylinositol 3 kinase (PI3K) inhibitor, blocked the effect of norgalanthamine on DPC proliferation. These results suggest that norgalanthamine can stimulate the anagen phase of the hair cycle in DPCs via activation of the ERK 1/2, PI3K/AKT, and Wnt/ß-catenin pathways.

Effect of Fermented Fish Oil on Fine Particulate Matter-Induced Skin Aging.

Skin is exposed to various harmful environmental factors such as air pollution, which includes different types of particulate matter (PM). Atmospheric PM has harmful effects on humans through increasing the generation of reactive oxygen species (ROS), which have been reported to promote skin aging via the induction of matrix metalloproteinases (MMPs), which in turn can cause the degradation of collagen. In this study, we investigated the effect of fermented fish oil (FFO) derived from mackerel on fine PM (particles with a diameter < 2.5 µm: PM2.5)-induced skin aging in human keratinocytes. We found that FFO inhibited the PM2.5-induced generation of intracellular ROS and MMPs, including MMP-1, MMP-2, and MMP-9. In addition, FFO significantly abrogated the elevation of intracellular Ca2+ levels in PM2.5-treated cells and was also found to block the PM2.5-induced mitogen-activated protein kinase/activator protein 1 (MAPK/AP-1) pathway. In conclusion, FFO has an anti-aging effect on PM2.5-induced aging in human keratinocytes.

Diphlorethohydroxycarmalol Attenuates Fine Particulate Matter-Induced Subcellular Skin Dysfunction.

The skin, the largest organ in humans, is exposed to major sources of outdoor air pollution, such as fine particulate matter with a diameter ≤ 2.5 µm (PM2.5). Diphlorethohydroxycarmalol (DPHC), a marine-based compound, possesses multiple activities including antioxidant effects. In the present study, we evaluated the protective effect of DPHC on PM2.5-induced skin cell damage and elucidated the underlying mechanisms in vitro and in vivo. The results showed that DPHC blocked PM2.5-induced reactive oxygen species generation in human keratinocytes. In addition, DPHC protected cells against PM2.5-induced DNA damage, endoplasmic reticulum stress, and autophagy. HR-1 hairless mice exposed to PM2.5 showed lipid peroxidation, protein carbonylation, and increased epidermal height, which were inhibited by DPHC. Moreover, PM2.5 induced apoptosis and mitogen-activated protein kinase (MAPK) protein expression; however, these changes were attenuated by DPHC 5. MAPK inhibitors were used to elucidate the molecular mechanisms underlying these actions, and the results demonstrated that MAPK signaling pathway may play a key role in PM2.5-induced skin damage.

Marine Compound 3-bromo-4,5-dihydroxybenzaldehyde Protects Skin Cells against Oxidative Damage via the Nrf2/HO-1 Pathway.

In this study, we aimed to illustrate the potential bio-effects of 3-bromo-4,5-dihydroxybenzaldehyde (3-BDB) on the antioxidant/cytoprotective enzyme heme oxygenase-1 (HO-1) in keratinocytes. The antioxidant effects of 3-BDB were examined via reverse transcription PCR, Western blotting, HO-1 activity assay, and immunocytochemistry. Chromatin immunoprecipitation analysis was performed to test for nuclear factor erythroid 2-related factor 2 (Nrf2) binding to the antioxidant response element of the HO-1 promoter. Furthermore, the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay showed that the cytoprotective effects of 3-BDB were mediated by the activation of extracellular signal-regulated kinase (ERK) and protein kinase B (PKB, Akt) signaling. Moreover, 3-BDB induced the phosphorylation of ERK and Akt, while inhibitors of ERK and Akt abrogated the 3-BDB-enhanced levels of HO-1 and Nrf2. Finally, 3-BDB protected cells from H2O2- and UVB-induced oxidative damage. This 3-BDB-mediated cytoprotection was suppressed by inhibitors of HO-1, ERK, and Akt. The present results indicate that 3-BDB activated Nrf2 signaling cascades in keratinocytes, which was mediated by ERK and Akt, upregulated HO-1, and induced cytoprotective effects against oxidative stress.