The Pigmentation of Blue Light is Mediated by Both Melanogenesis Activation and Autophagy Inhibition through OPN3-TRPV1.

Blue light, a high-energy radiation in the visible light spectrum, was recently reported to induce skin pigmentation. In this study, we investigated the involvement of TRPV1-mediated signaling along with OPN3 in blue light-induced melanogenesis, as well as its signaling pathway. Operating downstream target of OPN3 in blue light-induced melanogenesis, blue light activated TRPV1 and upregulated its expression, resulting in calcium influx. [Ca2+] induced activation of CaMKII and MAPK. It also downregulated clusterin expression, leading to the nuclear translocation of PAX3, ultimately affecting melanin synthesis. In addition, blue light interfered with autophagy-mediated regulation of melanosomes by decreasing not only the interaction between CLU and LC3B but the expression of ATF family. These findings demonstrate that the pigmenting effects of blue light are mediated by CaMKII- and MAPK-mediated signaling, as well as CLU-dependent inhibition of autophagy through OPN3-TRPV1-calcium influx, suggesting a new signaling pathway by which blue light regulates melanocyte biology. Furthermore, these results suggest that TRPV1 and CLU could be potential therapeutic targets for blue light-induced pigmentation due to prolonged exposure to blue light.

Anti-pollutant effect of oleic acid against urban particulate matter is mediated via regulation of AhR- and TRPV1-mediated signaling in vitro.

Urban Particulate Matter (UPM) induces skin aging and inflammatory responses by regulating skin cells through the transient receptor potential vanilloid 1 (TRPV1). Although oleic acid, an unsaturated free fatty acid (FFA), has some functional activities, its effect on UPM-induced skin damage has not been elucidated. Here, we investigated signaling pathways on how oleic acid is involved in attenuating UPM induced cell damage. UPM treatment increased XRE-promoter luciferase activity and increased translocation of AhR to the nucleus, resulting in the upregulation of CYP1A1 gene. However, oleic acid treatment attenuated the UPM effects on AhR signaling. Furthermore, while UPM induced activation of TRPV1 and MAPKs signaling which activated the downstream molecules NFκB and AP-1, these effects were reduced by cotreatment with oleic acid. UPM-dependent generation of reactive oxygen species (ROS) and reduction of cellular proliferation were also attenuated by the treatment of oleic acid. These data reveal that cell damage induced by UPM treatment occurs through AhR signaling and TRPV1 activation which in turn activates ERK and JNK, ultimately inducing NFκB and AP-1 activation. These effects were reduced by the cotreatment of oleic acid on HaCaT cells. These suggest that oleic acid reduces UPM-induced cell damage through inhibiting both the AhR signaling and activation of TRPV1 and its downstream molecules, leading to a reduction of pro-inflammatory cytokine and recovery of cell proliferation.

Anti-Pollutant Activity of Porphyra yezoensis Water Extract and Its Active Compound, Porphyra 334, against Urban Particulate Matter-Induced Keratinocyte Cell Damage.

Urban particulate matter (UPM) causes skin aging and inflammatory reactions by influencing skin cells through the aryl hydrocarbon receptor (AhR) signaling pathway. Porphyra yezoensis (also known as Pyropia yezoensis), a red alga belonging to the Bangiaceae family, is an edible red seaweed. Here, we examined the anti-pollutant effect of P. yezoensis water extract. While UPM treatment induced xenobiotic response element (XRE) promoter luciferase activity, P. yezoensis water extract reduced UPM-induced XRE activity. Next, we isolated an active compound from P. yezoensis and identified it as porphyra 334. Similar to the P. yezoensis water extract, porphyra 334 attenuated UPM-induced XRE activity. Moreover, although UPM augmented AhR nuclear translocation, which led to an increase in cytochrome P450 1A1 (CYP1A1) mRNA levels, these effects were reduced by porphyra 334. Moreover, UPM induced the production of reactive oxygen species (ROS) and reduced cell proliferation. These effects were attenuated in response to porphyra 334 treatment. Furthermore, our results revealed that the increased ROS levels induced by UPM treatment induced transient receptor potential vanilloid 1 (TRPV1) activity, which is related to skin aging and inflammatory responses. However, porphyra 334 treatment reduced this reaction by inhibiting ROS production induced by CYP1A1 activation. This indicates that porphyra 334, an active compound of P. yezoensis, attenuates UP-induced cell damage by inhibiting AhR-induced ROS production, which results in a reduction in TRPV1 activation, leading to cell proliferation. This also suggests that porphyra 334 could protect the epidermis from harmful pollutants.

Directed Photochemically Mediated Nickel-Catalyzed (Hetero)arylation of Aliphatic C-H Bonds.

Site-selective functionalization of unactivated C(sp3)-H centers is challenging because of the ubiquity and strength of alkyl C-H bonds. Herein, we disclose a position-selective C(sp3)-C(sp2) cross-coupling reaction. This process engages C(sp3)-H bonds and aryl bromides, utilizing catalytic quantities of a photoredox-capable molecule and a nickel precatalyst. Using this technology, selective C-H functionalization arises owing to a 1,6-hydrogen atom transfer (HAT) process that is guided by a pendant alcohol-anchored sulfamate ester. These transformations proceed directly from N-H bonds, in contrast to previous directed, radical-mediated, C-H arylation processes, which have relied on prior oxidation of the reactive nitrogen center in reactions with nucleophilic arenes. Moreover, these conditions promote arylation at secondary centers in good yields with excellent selectivity.

Clinical Application of a Solid-Phase Assay for SARS-CoV-2 IgG to Predict a Neutralizing Antibody Titer.

BACKGROUND: To assess protective immunity among a general population against severe acute respiratory syndrome coronavirus 2, the correlation of the commercially available solid-phase assay (SPA) for SARS-CoV-2 IgG with a neutralization assay must be investigated. METHODS: Both the neutralization assay and SPA were performed on samples of 143 recovered coronavirus disease 2019 (COVID-19) patients. SARS-CoV-2 IgG was measured using two SPAs for the chemiluminescence immunoassay principle with different target proteins: nucleocapsid and spike protein (Architect i2000SR [Abbott] and Liaison XL [DiaSorin], respectively). The plaque reduction neutralization test (PRNT) was conducted to obtain titers for the neutralizing antibody. RESULTS: All patients had PRNT titers ranging from 10 to 2,560. Spike Ab SPA had greater sensitivity than nucleocapsid Ab SPA (81.1% [116/143] and 70.6% [101/143], respectively, p = 0.003). The values measured for both SPAs had a positive correlation with the PRNT titers (both R = 0.77, p < 0.001). To predict a high PRNT titer (≥ 160), cutoff values of two SPAs were adjusted based on receiver-operating characteristics curve analysis. The nucleocapsid Ab SPA (cutoff index of 4.17) attained 90.3% sensitivity and 75.9% specificity, whereas the spike Ab SPA (cutoff value of 109 unit/mL) attained 87.1% sensitivity and 89.3% specificity. Therefore, the spike Ab SPA had greater specificity than the nucleocapsid Ab SPA (p = 0.003). CONCLUSIONS: The qualitative SPA for nucleocapsid Ab, as well as the quantitative SPA for spike Ab, had a modest positive correlation with the neutralization assay. However, spike Ab SPA was more suitable for neutralizing capacity.

Kinetics of neutralizing antibodies against SARS-CoV-2 infection according to sex, age, and disease severity.

Knowledge of the factors affecting the difference in kinetics and longevity of the neutralizing antibody (nAb) response to SARS-CoV-2 is necessary to properly prioritize vaccination. In the present study, from March to December 2020, of the 143 patients who recovered from COVID-19, 87 underwent study visits scheduled every 3 months. Patient demographics and blood samples were collected followed by a plaque reduction neutralization test to analyze nAb titers. A linear mixed model was used to compare the effects of sex, age, and disease severity over time. Results demonstrated a gradual reduction in nAb titers over time with a significant decrease from 6 to 9 months post-COVID-19 infection (p < 0.001). In time-to-sex, age, and disease severity comparisons, reduction in nAb titers over time was unaffected by sex (p = 0.167), age (p = 0.188), or disease severity (p = 0.081). Additionally, the nAb titer was 1.46 times significantly higher in those aged ≥ 50 years than in those aged < 50 years (p = 0.036) irrespective of time Moreover, the nAb titer was 2.41 times higher in the moderate or above than that in the below moderate disease severity group (p < 0.001). However, no significant differences were observed in terms of sex (p = 0.300). Given the reduction in nAbs over time, maintaining protective neutralizing antibodies regardless of sex, age, or disease severity is needed.

Antioxidant Activities and Mechanisms of Tomentosin in Human Keratinocytes.

Tomentosin, one of natural sesquiterpene lactones sourced from Inula viscosa L., exerts therapeutic effects in various cell types. Here, we investigated the antioxidant activities and the underlying action mechanisms of tomentosin in HaCaT cells (a human keratinocyte cell line). Specifically, we examined the involvement of tomentosin in aryl hydrocarbon receptor (AhR) and nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathways. Treatment with tomentosin for up to 60 min triggered the production of reactive oxygen species (ROS), whereas treatment for 4 h or longer decreased ROS production. Tomentosin treatment also induced the nuclear translocation of Nrf2 and upregulated the expression of Nrf2 and its target genes. These data indicate that tomentosin induces ROS production at an early stage which activates the Nrf2 pathway by disrupting the Nrf2-Keap1 complex. However, at a later stage, ROS levels were reduced by tomentosin-induced upregulation of antioxidant genes. In addition, tomentosin induced the phosphorylation of mitogen-activated protein kinases (MAPKs) including p38 MAPK and c-Jun N-terminal kinase (JNK). SB203580 (a p38 MAPK inhibitor) and SP600125 (a JNK inhibitor) attenuated the tomentosin-induced phosphorylation of Nrf2, suggesting that JNK and p38 MAPK signaling pathways can contribute to the tomentosin-induced Nrf2 activation through phosphorylation of Nrf2. Furthermore, N-acetyl-L-cysteine (NAC) treatment blocked both tomentosin-induced production of ROS and the nuclear translocation of Nrf2. These data suggest that tomentosin-induced Nrf2 signaling is mediated both by tomentosin-induced ROS production and the activation of p38 MAPK and JNK. Moreover, tomentosin inhibited the AhR signaling pathway, as evidenced by the suppression of xenobiotic-response element (XRE) reporter activity and the translocation of AhR into nucleus induced by urban pollutants, especially benzo[a]pyrene. These findings suggest that tomentosin can ameliorate skin damage induced by environmental pollutants.

Yellow Chaste Weed and Its Components, Apigenin and Galangin, Affect Proliferation and Oxidative Stress in Blue Light-Irradiated HaCaT Cells.

While harmful effects of blue light on skin cells have been recently reported, there are few studies regarding natural products that alleviate its negative effects. Therefore, we investigated ameliorating effects of yellow chaste weed (YCW) (Helichrysum arenarium) extract and its components, apigenin and galangin, on blue light-irradiated HaCaT cells. In this study, we found that YCW extract improved the reduced proliferation of HaCaT cells induced by blue light-irradiation and reduced blue light-induced production of reactive oxygen species (ROS) levels. We also found that apigenin and galangin, the main components of YCW extract, showed the same activities as YCW extract. In experiments examining molecular mechanisms of YCW extract and its components such as apigenin and galangin, they all reduced expression of transient receptor potential vanilloid member 1 (TRPV1), its phosphorylation, and calcium ion (Ca2+) influx induced by blue light irradiation. In addition, apigenin and galangin regulated phosphorylation of mitogen-activated protein kinases (MAPKs). They also reduced phosphorylation of mammalian sterile 20-like kinase-1/2 (MST-1/2), inducing phosphorylation of Akt (protein kinase B), one downstream molecule of MST-1/2. Moreover, apigenin and galangin promoted translocation of Forkhead box O3 (FoxO3a) from the nucleus to the cytosol by phosphorylating FoxO3a. Besides, apigenin and galangin interrupted blue light influences on expression of nuclear and secretory clusterin. Namely, they attenuated both upregulation of nuclear clusterin and downregulation of secretory clusterin induced by blue light irradiation. We also found that they downregulated apoptotic protein Bcl-2 associated X protein (Bax) and conversely upregulated anti-apoptotic protein B-cell lymphoma 2 (Bcl-2). Collectively, these findings indicate that YCW extract and its components, apigenin and galangin, antagonize the blue light-induced damage to the keratinocytes by regulating TRPV1/clusterin/FoxO3a and MAPK signaling.

Strategies to Generate Nitrogen-centered Radicals That May Rely on Photoredox Catalysis: Development in Reaction Methodology and Applications in Organic Synthesis.

For more than 70 years, nitrogen-centered radicals have been recognized as potent synthetic intermediates. This review is a survey designed for use by chemists engaged in target-oriented synthesis. This review summarizes the recent paradigm shift in access to and application of N-centered radicals enabled by visible-light photocatalysis. This shift broadens and streamlines approaches to many small molecules because visible-light photocatalysis conditions are mild. Explicit attention is paid to innovative advances in N-X bonds as radical precursors, where X = Cl, N, S, O, and H. For clarity, key mechanistic data is noted, where available. Synthetic applications and limitations are summarized to illuminate the tremendous utility of photocatalytically generated nitrogen-centered radicals.

Korean Guidelines for Use of Antibiotics for Intra-abdominal Infections in Adults.

The guidelines are intended to provide practical information for the correct use of antibiotics for intra-abdominal infections in Korea. With the aim of realizing evidence-based treatment, these guidelines for the use of antibiotics were written to help clinicians find answers to key clinical questions that arise in the course of patient care, using the latest research results based on systematic literature review. The guidelines were prepared in consideration of the data on the causative pathogens of intra-abdominal infections in Korea, the antibiotic susceptibility of the causative pathogens, and the antibiotics available in Korea.

Olfactory Receptor OR7A17 Expression Correlates with All-Trans Retinoic Acid (ATRA)-Induced Suppression of Proliferation in Human Keratinocyte Cells.

Olfactory receptors (ORs), which belong to the G-protein-coupled receptor family, have been widely studied as ectopically expressed receptors in various human tissues, including the skin. However, the physiological functions of only a few OR types have been elucidated in skin cells. All-trans retinoic acid (ATRA) is a well-known medication for various skin diseases. However, many studies have shown that ATRA can have adverse effects, resulting from the suppression of cell proliferation. Here, we investigated the involvement of OR7A17 in the ATRA-induced suppression of human keratinocyte (HaCaT) proliferation. We demonstrated that OR7A17 is expressed in HaCaT keratinocytes, and its expression was downregulated by ATRA. The ATRA-induced downregulation of OR7A17 was attenuated via RAR α or RAR γ antagonist treatment, indicating that the effects of ATRA on OR7A17 expression were mediated through nuclear retinoic acid receptor signaling. Moreover, we found that the overexpression of OR7A17 induced the proliferation of HaCaT cells while counteracting the antiproliferative effect of ATRA. Mechanistically, OR7A17 overexpression reversed the ATRA-induced attenuation of Ca2+ entry. Our findings indicated that ATRA suppresses cell proliferation through the downregulation of OR7A17 via RAR α- and γ-mediated retinoid signaling. Taken together, OR7A17 is a potential therapeutic target for ameliorating the anti-proliferative effects of ATRA.

Compassionate Use of GC5131 (Hyperimmunoglobulin) Therapy in Critically Ill Patients Diagnosed with COVID-19: A Case Series and Review of Literature.

Presently, the use of convalescent plasma and hyperimmunoglobulin obtained from individuals who have recovered from coronavirus disease 2019 (COVID-19) has proved to potentially provide passive antibody-based immunity, thereby leading to several clinical trials to develop an immune-based COVID-19 treatment. However, the therapeutic efficacy of hyperimmunoglobulin in critically ill patients with COVID-19 remains unknown. On 23 October 2020, we first administered GC5131 in a compassionate-use program to critically ill patients at the Kyungpook National University, Chilgok Hospital, Korea. Since then, five more critically ill patients were treated with GC5131 in this compassionate-use program in our hospital up until 17 December 2020. We retrospectively reviewed the clinical responses of six critically ill patients diagnosed with COVID-19 who received the hyperimmunoglobulin concentrate, GC5131, which was produced by the Green Cross Corporation. After the administration of GC5131, five patients died due to an exacerbation of COVID-19 pneumonia. GC5131 was ineffective when administered to critically ill patients with COVID-19. Nevertheless, we propose that to expect a therapeutic effect from GC5131, it should be administered as early as possible to avoid the excessive inflammatory response phase in patients with severe and advanced COVID-19 infection. This step was difficult to achieve in the real world due to the time required for decision making and the process of the compassionate-use program.

Protective Effects of Maclurin against Benzo[a]pyrene via Aryl Hydrocarbon Receptor and Nuclear Factor Erythroid 2-Related Factor 2 Targeting.

Benzo[a]pyrene (B[a]P), a polycyclic aromatic hydrocarbon formed during the incomplete combustion of organic matter, has harmful effects. Therefore, much research is ongoing to develop agents that can mitigate the effects of B[a]P. The aim of this study was to examine the effect of maclurin, one component of the branches of Morus alba L., on the B[a]P-induced effects in HaCaT cells, a human keratinocyte cell line. Maclurin treatment inhibited aryl hydrocarbon receptor (AHR) signaling as evidenced by reduced xenobiotic response element (XRE) reporter activity, decreased expression of cytochrome P450 1A1 (CYP1A1), and reduced nuclear translocation of AHR. The B[a]P-induced dissociation of AHR from AHR-interacting protein (AIP) was suppressed by maclurin. Maclurin also inhibited the production of intracellular reactive oxygen species (ROS) induced by B[a]P. In addition, the antioxidant property of maclurin itself was demonstrated by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay. Furthermore, maclurin activated antioxidant response element (ARE) signaling through enhancement of ARE luciferase reporter activity and the expression of ARE-dependent genes including nuclear factor (erythroid-derived 2)-like 2 (Nrf2) and heme oxygenase-1 (HO-1). Nrf2 activation and its nuclear translocation were promoted by maclurin through p38 MAPK activation. These data indicate that maclurin had antagonistic activity against B[a]P effects through activation of Nrf2-mediated signaling and inhibition of AHR signaling and, suggesting its potential in protecting from harmful B[a]P-containing pollutants.

Mechanisms of Resorcinol Antagonism of Benzo[a]pyrene-Induced Damage to Human Keratinocytes.

Benzo[a]pyrene (B[a]P) is a polycyclic aromatic hydrocarbon and ubiquitous environmental toxin with known harmful effects to human health. Abnormal phenotypes of keratinocytes are closely associated with their exposure to B[a]P. Resorcinol is a component of argan oil with reported anticancer activities, but its mechanism of action and potential effect on B[a]P damage to the skin is unknown. In this study, we investigated the effects of resorcinol on B[a]P-induced abnormal keratinocyte biology and its mechanisms of action in human epidermal keratinocyte cell line HaCaT. Resorcinol suppressed aryl hydrocarbon receptor (AhR) activity as evidenced by the inhibition of B[a]P-induced xenobiotic response element (XRE)-reporter activation and cytochrome P450 1A1 (CYP1A1) expression. In addition, resorcinol attenuated B[a]P-induced nuclear translocation of AhR, and production of ROS and pro-inflammatory cytokines. We also found that resorcinol increased nuclear factor (erythroid-derived 2)-like 2 (Nrf2) activity. Antioxidant response element (ARE)-reporter activity and expression of ARE-dependent genes NAD(P)H dehydrogenase [quinone] 1 (NQO1), heme oxygenase-1 (HO-1) were increased by resorcinol. Consistently, resorcinol treatment induced nuclear localization of Nrf2 as seen by Western analysis. Knockdown of Nrf2 attenuated the resorcinol effects on ARE signaling, but knockdown of AhR did not affect resorcinol activation of Nrf2. This suggests that activation of antioxidant activity by resorcinol is not mediated by AhR. These results indicate that resorcinol is protective against effects of B[a]P exposure. The mechanism of action of resorcinol is inhibition of AhR and activation of Nrf2-mediated antioxidant signaling. Our findings suggest that resorcinol may have potential as a protective agent against B[a]P-containing pollutants.

Blue Light Irradiation Induces Human Keratinocyte Cell Damage via Transient Receptor Potential Vanilloid 1 (TRPV1) Regulation.

Although blue light has been reported to affect skin cells negatively, little is known about its action mechanisms in skin cells. Therefore, we investigated the role of the transient receptor potential vanilloid 1 (TRPV1) in blue light-induced effects on human keratinocytes and its underlying mechanisms. Blue light decreased cell proliferation and upregulated TRPV1 expression. Blue light also suppressed the epidermal growth factor receptor- (EGFR-) mediated signaling pathway by reducing the protein levels of EGFR and suppressing the EGFR/PI3K/AKT/GSK3ß/FoxO3a pathway. The blue light-induced effect in cell proliferation was reversed by TRPV1 siRNA, but not capsazepine, a TRPV1-specific antagonist. In addition, blue light irradiation increased the production of reactive oxygen species (ROS) and tumor necrosis factor-α (TNF-α). Blue light irradiation also increased both phosphorylation levels of TRPV1 and calcium influx. The blue light-induced increase in production of ROS and TNF-α was reversed by capsazepine. Furthermore, the blue light-induced increase in production of TNF-α was attenuated by SP600125 or PDTC. These findings show that blue light regulates cell survival and production of ROS and TNF-α; its effects are mediated via TRPV1. Specifically, the effects of blue light on cell proliferation are mediated by upregulating TRPV1, a negative regulator of EGFR-FoxO3a signaling. Blue light-induced production of ROS and TNF-α is also mediated through increased calcium influx via TRPV1 activation.

Effect of undissolved Nb carbides on mechanical properties of hydrogen-precharged tempered martensitic steel.

Nb carbides have attracted significant attention to enhance the resistance of tempered martensitic (TM) steel to hydrogen embrittlement (HE). However, previous studies have elucidated the role of Nb carbides in HE resistance without categorizing their types (i.e., undissolved and newly precipitated). This study focuses on the effect of "undissolved" Nb carbides on the tensile and fatigue properties of hydrogen-precharged TM steels. It validated the following two factors for the HE resistance of the TM steels containing undissolved Nb carbides: hydrogen-trapping by the carbides and refinement of prior austenite grain. The former factor rarely affected the HE resistance owing to the interfacial incoherency between the undissolved carbides and ferritic matrix. Such results are distinguished from previous studies focusing on the newly precipitated carbides. In contrast, the latter factor contributed significantly to the HE resistance via the decrease in hydrogen contents per unit surface of prior austenite grain boundaries.

Antagonizing Effects of Clematis apiifolia DC. Extract against Benzo[a]pyrene-Induced Damage to Human Keratinocytes.

Background. Benzo[a]pyrene (B[a]P), a polycyclic aromatic hydrocarbon present in the atmosphere, has cytotoxic and carcinogenic effects. There have been no reports to demonstrate involvement of Clematis apiifolia DC. extract (CAE) in B[a]P-induced effects. This study was conducted to investigate the effect of CAE on B[a]P-induced effects and to elucidate its mechanism of action in HaCaT human keratinocytes. CAE inhibited aryl hydrocarbon receptor (AhR) signaling by decreasing both XRE reporter activity and expression of cytochrome P450 1A1 (CYP1A1) induced by B[a]P treatment in HaCaT cells. We also found that B[a]P-induced nuclear translocation of AhR and production of reactive oxygen species (ROS) and proinflammatory cytokines were attenuated by CAE treatment. CAE treatment suppressed B[a]P-induced phosphorylation of Src (Tyr416). In addition, dasatinib, a Src inhibitor, also inhibited B[a]P-induced nuclear translocation of AhR, similar to CAE treatment. In addition, CAE activated antioxidant response element (ARE) signaling by increasing ARE luciferase reporter activity and expression of ARE-dependent genes such as nuclear factor (erythroid-derived 2)-like 2 (Nrf2), NAD(P)H dehydrogenase [quinone] 1 (NQO1), and heme oxygenase-1 (HO-1). Nuclear translocation of Nrf2 by CAE was demonstrated by Western blot analysis and immunocytochemistry. The effects of CAE on ARE signaling were attenuated by knockdown of the Nrf2 gene. Inhibition of AhR signaling and activation of antioxidant activity by CAE operated in a reciprocally independent manner as evidenced by AhR and Nrf2 siRNA experiments. These findings indicate that CAE exerts protective effects against B[a]P by inhibiting AhR signaling and activating Nrf2-mediated signaling, suggesting its potential in protection from harmful B[a]P-containing pollutants.

p44/42 MAPK signaling is a prime target activated by phenylethyl resorcinol in its anti-melanogenic action.

BACKGROUND: Melanin plays a crucial role in protecting human skin against exposure to ultraviolet (UV) radiation. However, its overproduction induces hyperpigmentation disorders of the skin. PURPOSE: To investigate effects of phenylethyl resorcinol as one resorcinol derivative on melanogenesis and its mechanisms using B16F10 mouse melanoma cells and human epidermal melanocytes. METHODS: Effects of phenylethyl resorcinol on melanogenesis and its mechanism of action were examined using several in vitro assays (i.e., cell survival, melanin content, cellular tyrosinase activity, real-time PCR analysis, luciferase-reporter assay, Western blot analysis, and ELISAs for cyclic AMP (cAMP), protein kinase A (PKA), cAMP response element binding (CREB) protein, and mitogen-activated protein kinases (MAPKs)). RESULTS: Phenylethyl resorcinol reduced both melanin content and tyrosinase activity in these cells. Phenylethyl resorcinol also suppressed tyrosinase activity in cell-free tyrosinase enzyme assay. Although phenylethyl resorcinol decreased mRNA levels of tyrosinase and tyrosinase-related protein (TRP)-2, it did not affect mRNA levels of melanogenic gene microphthalmia-associated transcriptional factor (MITF) or TRP-1. Phenylethyl resorcinol had no effects on cAMP signaling or NF-κB signaling based on results of cyclic AMP response element (CRE)-luciferase reporter assay, cAMP production, protein kinase A (PKA) activity, Western blot assays for phosphorylated CRE-binding protein (CREB), NF-κB-luciferase reporter assay, and Western blot assays for phosphorylated NF-κB. However, phenylethyl resorcinol induced activation of activator protein-1 (AP-1) signaling. Specifically, phenylethyl resorcinol increased AP-1 reporter activity and increased phosphorylation of p44/42 MAPK, but not p38 MAPK or c-Jun N-terminal kinase (JNK). MEK1/2 and Src, upstream molecules of p44/42 MAPK were also phosphorylated by phenylethyl resorcinol. In addition, phenylethyl resorcinol-induced decreases in melanin content, tyrosinase activity, and MITF protein levels were attenuated by PD98059, a p44/42 MAPK inhibitor. CONCLUSION: These data indicate that the anti-melanogenic activity of phenylethyl resorcinol is mediated by activation of p44/42 MAPK, indicating that phenylethyl resorcinol may be a potential therapeutic agent for treating hyperpigmentation skin disorders.

Enhanced Activation of Rac1/Cdc42 and MITF Leads to Augmented Osteoclastogenesis in Autosomal Dominant Osteopetrosis Type II.

The autosomal dominant osteopetrosis type II (ADOII) caused by the mutation of chloride channel 7 (ClC-7) gene is the most common form of adult-onset osteopetrosis. Despite dysfunctional bone resorption, an augmented osteoclast differentiation was reported recently in ADOII patients. DNA sequencing analysis of the ADOII patient's ClC-7 gene identified a known heterozygous mutation, c.643G>A in exon 7, encoding p.Gly215Arg. In vitro osteoclast differentiation from the ADOII patient's peripheral blood mononuclear cells (PBMCs) increased compared with control despite their dysfunctional bone resorbing capacity. Osteoclasts from the ADOII patient's PBMCs and ClC-7 knockdown bone marrow monocytes (BMMs) showed an enhanced Ser-71 phosphorylation of Rac1/Cdc42 and increase of the microphthalmia-associated transcription factor (MITF) and receptor activator of NF-κB (RANK) that can be responsible for the enhanced osteoclast differentiation. © 2018 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research.

Melanogenic Effects of Maclurin Are Mediated through the Activation of cAMP/PKA/CREB and p38 MAPK/CREB Signaling Pathways.

Melanogenesis is the biological process which the skin pigment melanin is synthesized to protect the skin against ultraviolet irradiation and other external stresses. Abnormal biology of melanocytes is closely associated with depigmented skin disorders such as vitiligo. In this study, we examined the effects of maclurin on melanogenesis and cytoprotection. Maclurin enhanced cellular tyrosinase activity as well as cellular melanin levels. We found that maclurin treatment increased the expression of microphthalmia-associated transcription factor (MITF), tyrosinase-related protein- (TRP-) 1, TRP-2, and tyrosinase. Mechanistically, maclurin promoted melanogenesis through cyclic adenosine monophosphate (cAMP) response element binding (CREB) protein-dependent upregulation of MITF. CREB activation was found to be mediated by p38 mitogen-activated protein kinase (MAPK) or cAMP-protein kinase A (PKA) signaling. In addition, maclurin-induced CREB phosphorylation was mediated through the activation of both the cAMP/PKA and the p38 MAPK signaling pathways. Maclurin-induced suppression of p44/42 MAPK activation also contributed to its melanogenic activity. Furthermore, maclurin showed protective effects against H2O2 treatment and UVB irradiation in human melanocytes. These findings indicate that the melanogenic effects of maclurin depend on increased MITF gene expression, which is mediated by the activation of both p38 MAPK/CREB and cAMP/PKA/CREB signaling. Our results thus suggest that maclurin could be useful as a protective agent against hypopigmented skin disorders.