Kyoung Mi Moon

Anti-Wrinkle and Anti-Inflammatory Effects of Active Garlic Components and the Inhibition of MMPs via NF-κB Signaling

Skin aging is a multisystem degenerative process caused by several factors, such as, UV irradiation, stress, and smoke. Furthermore, wrinkle formation is a striking feature of photoaging and is associated with oxidative stress and inflammatory response. In the present study, we investigated whether caffeic acid, S-allyl cysteine, and uracil, which were isolated from garlic, modulate UVB-induced wrinkle formation and effect the expression of matrix-metalloproteinase (MMP) and NF-κB signaling. The results obtained showed that all three compounds significantly inhibited the degradation of type І procollagen and the expressions of MMPs in vivo and attenuated the histological collagen fiber disorder and oxidative stress in vivo. Furthermore, caffeic acid and S-allyl cysteine were found to decrease oxidative stress and inflammation by modulating the activities of NF-κB and AP-1, and uracil exhibited an indirect anti-oxidant effect by suppressing cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) expressions levels and downregulating transcriptional factors. These results suggest that the anti-wrinkle effects of caffeic acid, S-allyl cysteine, and uracil are due to anti-oxidant and/or anti-inflammatory effects. Summarizing, caffeic acid, S-allyl cysteine, and uracil inhibited UVB-induced wrinkle formation by modulating MMP via NF-κB signaling.

The roles of FoxOs in modulation of aging by calorie restriction

FoxO activity and modifications, such as its phosphorylation, acetylation, and methylation, may help drive the expression of genes involved in combating oxidative stress by causing the epigenetic modifications, and thus, preserve cellular function during aging and age-related diseases, such as diabetes, cancer, and Alzheimer disease. Insulin signaling has been postulated to influence the aging process by increasing resistance to oxidative stress, and slowing the accumulation of oxidative damage. Some antioxidative effects are mediated by a conserved family of forkhead box transcription factors (FoxOs), which in the absence of insulin signaling freely bind to promoters of antioxidant enzymes, superoxide dismutase, and catalase. On the other hand, calorie restriction (CR) extends the lifespans of several species via the insulin pathway, and extends longevity and healthspan in diverse species via a conserved mechanism. CR enhances adaptive stress responses at the cellular and organism levels and extends lifespan in a FoxO-independent manner. Thus, increased modification of FoxO is modulated via the hyperinsulinemia-induced PI3K/Akt pathway during aging, and CR reverses this process. Accordingly, FoxO plays an important role in maintenance of metabolic homeostasis and removal of oxidative stress in the aging process and in the effect of CR on lifespan.

The underlying mechanism of proinflammatory NF-κB activation by the mTORC2/Akt/IKKα pathway during skin aging.

Mammalian target of rapamycin complex 2 (mTORC2), one of two different enzymatic complexes of mTOR, regulates a diverse set of substrates including Akt. mTOR pathway is one of well-known mediators of aging process, however, its role in skin aging has not been determined. Skin aging can be induced by physical age and ultraviolet (UV) irradiation which are intrinsic and extrinsic factors, respectively. Here, we report increased mTORC2 pathway in intrinsic and photo-induced skin aging, which is implicated in the activation of nuclear factor-κB (NF-κB). UVB-irradiated or aged mice skin revealed that mTORC2 activity and its component, rictor were significantly upregulated which in turn increased Akt activation and Akt-dependent IκB kinase α (IKKα) phosphorylation at Thr23 in vivo. We also confirmed that UVB induced the mTORC2/Akt/IKKα signaling pathway with HaCaT human normal keratinocytes. The increased mTORC2 signaling pathway during skin aging were associated to NF-κB activation. Suppression of mTORC2 activity by the treatment of a mTOR small inhibitor or knockdown of RICTOR partially rescued UVB-induced NF-κB activation through the downregulation of Akt/IKKα activity. Our data demonstrated the upregulation of mTORC2 pathway in intrinsic and photo-induced skin aging and its role in IKKα/NF-κB activation. These data not only expanded the functions of mTOR to skin aging but also revealed the therapeutic potential of inhibiting mTORC2 in ameliorating both intrinsic skin aging and photoaging.

(Z)-5-(2,4-Dihydroxybenzylidene)thiazolidine-2,4-dione Prevents UVB-Induced Melanogenesis and Wrinkle Formation through Suppressing Oxidative Stress in HRM-2 Hairless Mice

Background. Uncontrolled melanogenesis and wrinkle formation are an indication of photoaging. Our previous studies demonstrated that (Z)-5-(2,4-dihydroxybenzylidene)thiazolidine-2,4-dione (MHY498) inhibited tyrosinase activity and melanogenesis in vitro. Objective. To examine in vivo effects of MHY498 as an antiaging compound on UVB-induced melanogenesis and wrinkle formation, we topically applied MHY498 on dorsal skin of HRM-2 hairless mice. Methods. Using histological analysis, we evaluated effects of MHY498 on melanogenesis and wrinkle formation after UVB exposure. In addition, related molecular signaling pathways were examined using western blotting, fluorometric assay, and enzyme-linked immunosorbent assay. Results. MHY498 suppressed UVB-induced melanogenesis by inhibiting phosphorylation of CREB and translocation of MITF protein into the nucleus, which are key factors for tyrosinase expression. Consistently, tyrosinase protein levels were notably reduced in the dorsal skin of the hairless mice by MHY498 treatment. Furthermore, MHY498 inhibited UVB-induced wrinkle formation and collagen fiber destruction by increasing type 1 procollagen concentration and decreasing protein expression levels of MMPs, which play an essential role in collagen fiber degradation. As a mechanism, MHY498 notably ameliorated UVB-induced oxidative stress and NF-κB activation in the dermal skin of the hairless mice. Conclusion. Our study suggests that MHY498 can be used as a therapeutic or cosmetic agent for preventing uncontrolled melanogenesis and wrinkle formation.

(Z)-2-(Benzo[d]thiazol-2-ylamino)-5-(substituted benzylidene)thiazol-4(5H)-one Derivatives as Novel Tyrosinase Inhibitors

Inhibiting tyrosinase is an important goal to prevent melanin accumulation in skin and thereby to inhibit pigmentation disorders. Therefore, tyrosinase inhibitors are an attractive target in cosmetics and treatments for pigmentation disorders. However, only a few tyrosinase inhibitors are currently available because of their toxic effects to skin or lack of selectivity and stability. Here, we newly synthesized thirteen (Z)-2-(benzo[d]thiazol-2-ylamino)-5-(substituted benzylidene)thiazol-4(5H)-one derivatives and examined their effect on melanogenesis. Of these compounds, MHY2081 had the strongest inhibitory effect on tyrosinase without cytotoxicity in B16F10 melanoma cells. Consistently, melanogenesis was notably decreased by MHY2081 treatment. As an underlying mechanism, docking simulation showed that compared to kojic acid, a well-known competitive tyrosinase inhibitor which forms a hydrogen bond and aromatic interaction with tyrosinase, MHY2081 has stronger affinity with tyrosinase by forming three hydrogen bonds and a hydrophobic interaction with residues of tyrosinase. In parallel with this, Lineweaver-Burk plot analysis showed that MHY2081 is a strong competitive inhibitor of tyrosinase. In conclusion, MHY2081 may be a novel tyrosinase inhibitor for prevention and treatment of pigmentation disorders.

A novel synthetic compound, (Z)-5-(3-hydroxy-4-methoxybenzylidene)-2-iminothiazolidin-4-one (MHY773) inhibits mushroom tyrosinase

Abstract As part of continued efforts for the development of new tyrosinase inhibitors, (Z)-5-(substituted benzylidene)-2-iminothiazolidin-4-one derivatives (1a – 1l) were rationally synthesized and evaluated for their inhibitory potential in vitro. These compounds were designed and synthesized based on the structural attributes of a β-phenyl-α,β-unsaturated carbonyl scaffold template. Among these compounds, (Z)-5-(3-hydroxy-4-methoxybenzylidene)-2-iminothiazolidin-4-one (1e, MHY773) exhibited the greatest tyrosinase inhibition (IC50 = 2.87 μM and 8.06 μM for monophenolase and diphenolase), and outperformed the positive control, kojic acid (IC50 = 15.59 and 31.61 μM). The kinetic and docking studies demonstrated that MHY773 interacted with active site of tyrosinase. Moreover, a melanin quantification assay demonstrated that MHY773 attenuates α-melanocyte-stimulating hormone (α-MSH) and 3-isobutyl-1-methylxanthine (IBMX)-induced melanin contents in B16F10 melanoma cells. Taken together, these data suggest that MHY773 suppressed the melanin production via the inhibition of tyrosinase activity. MHY773 is a promising for the development of effective pharmacological and cosmetic agents for skin-whitening. Binding mode and affinity of MHY773 with tyrosinase was investigated by enzyme kinetics and docking simulations. MHY773 showed potent tyrosinase inhibitory activity.

2-(3, 4-dihydroxybenzylidene)malononitrile as a novel anti-melanogenic compound

Tyrosinase is a key player in ultraviolet-induced melanogenesis. Because excessive melanin accumulation in the skin can induce hyperpigmentation, the development of tyrosinase inhibitors has attracted attention in cosmetic-related fields. However, side effects including toxicity and low selectivity have limited the use of many tyrosinase inhibitors in cosmetics. We synthesized 12 novel 2-(substituted benzylidene)malononitrile derivatives and investigated their anti-melanogenic activities. Of these 12 compounds, 2-(3, 4-dihydroxy benzylidene)malononitrile (BMN11) exhibited the strongest inhibitory activity against tyrosinase (IC50 = 17.05 μM). In parallel with this, BMN11 treatment notably decreased alpha-melanocyte-stimulating hormone-induced melanin accumulation in B16F10, cells without toxicity and also decreased melanin accumulation in a human skin model. As a mechanism underlying the BMN11-mediated anti-melanogenic effect, docking simulation showed that BMN11 can directly bind to tyrosinase by forming two hydrogen bonds with GLY281 and ASN260 residues, and via three hydrophobic interactions with VAL283, PHE264, and ALA286 residues in the tyrosinase binding pocket, and this likely contributes to its inhibitory effect on tyrosinase. Consistently, Lineweaver-Burk and Cornish-Bowden plots showed that BMN11 is a competitive inhibitor of tyrosinase. We concluded that BMN11 may be a novel tyrosinase inhibitor that could be used in cosmetics.

Effect of betaine on hepatic insulin resistance through FOXO1-induced NLRP3 inflammasome

In the present study, we attempted to elucidate whether molecular modulation of inflammation by betaine through the forkhead box O1 (FOXO1)-induced NLRP3 inflammasome improves insulin resistance. Betaine is a major water-soluble component of Lycium chinense. It mainly functions as an oxidative metabolite of choline by suppressing superoxide-induced free radicals by donating methyl groups. The FOXO1 transcription factor regulates various genes involved in cellular metabolic processes related to cell death as well as oxidative stress responses through binding to the thioredoxin-interacting protein (TXNIP). Betaine is known to inhibit FOXO1 phosphorylation through phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) in liver cells exposed to insulin. To elucidate the molecular mechanism of inactivation of insulin-induced FOXO1 by the antioxidant betaine, we used HepG2 cells and the liver of db/db mice treated with betaine at a dose of 50 mg/kg/day for 3 weeks. We found that the activation of NLRP3 inflammasome genes was reduced by betaine, which resulted in the suppression of reactive species (RS) production in liver cells. In addition, betaine inhibited insulin-induced PI3K/AKT and FOXO1 activation. Therefore, betaine suppressed the cytokine interleukin-1β production by inhibiting the activation of the NLRP3 inflammasome via interaction of FOXO1 and TXNIP. Our results suggest that betaine inhibits the FOXO1 binding to TXNIP, leading to the suppression of RS-induced NLRP3 inflammasome activation in a diabetic liver.

Physiological characterization of a novel PPAR pan agonist, 2-(4-(5,6-methylenedioxybenzo[ d ]thiazol-2-yl)-2-methylphenoxy)-2-methylpropanoic acid (MHY2013)

Recently, agonists targeting multiple peroxisome proliferator-activated receptors (PPARs) have been developed to improve metabolic disorders and minimize the side effects of selective PPAR agonists such as weight gain and dyslipidemia. We newly synthesized six 2-methyl-2-(o-tolyloxy)propanoic acid derivatives based on the structure of a well-known PPAR pan agonist, bezafibrate. Of six compounds, MHY2013 was screened as the strongest activator of three PPAR subtypes based on protein docking simulation and luciferase assays. When treated orally in db/db mice, MHY2013 ameliorated obesity-induced insulin resistance, dyslipidemia, and hepatic steatosis without changes of the body weight and levels of liver and kidney injury markers. MHY2013 decreased the serum triglyceride and fatty acid levels, which is associated with an increase in fatty acid oxidation signaling in the liver and thermogenic signaling on white adipose tissue, respectively. Furthermore, MHY2013 markedly increased serum levels of insulin-sensitizing hormones including fibroblast growth factor 21 (FGF21) and adiponectin. In conclusion, this study suggests that, MHY2013 is a novel PPAR pan agonist that improves obesity-induced insulin resistance, dyslipidemia and hepatic steatosis and elevates insulin-sensitizing hormones in the blood.

Swertiajaponin inhibits skin pigmentation by dual mechanisms to suppress tyrosinase

Many skin-whitening compounds target tyrosinase because it catalyzes two rate-limiting steps in melanin synthesis. Although many tyrosinase inhibitors are currently available for a skin–whitening purpose, undesirable adverse effects are also reported. Thus, numerous efforts have been made to develop safer tyrosinase inhibitors from natural products. In line with this, we tested fifty flavonoids, a group of naturally occurring antioxidants and metal chelators, and screened swertiajaponin as the strongest tyrosinase inhibitor in cell-free experiments. Swertiajaponin did not show cytotoxicity in B16F10, HaCat, and Hs27 cells and exhibited strong anti oxidative activity in experiments using the cell-free system and B16F10 cells. It markedly inhibited αMSH- or UVB-induced melanin accumulation in B16F10 cells and suppressed skin pigmentation in a human skin model. As underlying mechanisms, in silico and Lineweaver-Burk plot analyses exhibited that swertiajaponin may directly bind to and inhibit tyrosinase activity by forming multiple hydrogen bonds and hydrophobic interactions with the binding pocket of tyrosinase. In addition, western blotting results indicated that swertiajaponin inhibited oxidative stress-mediated MAPK/MITF signaling, leading to decrease in tyrosinase protein level. Together, swertiajaponin suppresses melanin accumulation by inhibiting both activity and protein expression levels of tyrosinase. Thus, it would be a novel additive for whitening cosmetics.