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( Hana Bak ) 대한피부과학회 2014 대한피부과학회 학술발표대회집 Vol.66 No.2
Atopic dermatitis has a complex pathophysiology, including interactions between genetic predisposition and exogenous provocation factors. Aggravating factors include psychological stress, climate, exposure to irritants and allergens. The defective barrier function can make atopic patients more prone to irritant contact dermatitis than normal population, because ordinary soaps and detergents often irritate the skin.Another triggering factors might be colonization of the skin with microorganisms, such as Staphyolcoccus aureus and Malassezia spp. Dry skin results from reduced amount of ceramides in the skin, with enhanced transepidermal water loss. Xerosis predisposes to the development of microfissures and cracks in the epithelium, which favors the entry of allergens and microorganisms. Abnormal proteins (filaggrin and related proteins) and lipid (ceramide) metabolism are responsible for the complex AD pathophysiology. It has been shown that loss-of-function mutations in the filaggrin (filament-aggregating protein) gene (FLG) predispose to AD. Filaggrin is a key component of the epidermal differentiation complex of the stratum corneum in the epidermal layer of human skin. It forms the natural moisturizing factor (NMF) in the stratum corneum and plays an important role in the barrier function of the skin. The keratohyalin granules in the granular layers are predominantly composed of profilaggrin. Filaggrin aggregates the keratin cytoskeleton system to form a dense protein.lipid matrix that is cross-linked by transglutaminases to form a cornified cell envelope. The latter prevents epidermal water loss and impedes the entry of allergens, from increased sphingomyelin deacylase activity and reduced production of ceramides by keratinocytes. Ceramides serve as important water-holding molecules in the extracellular space in the horny layer. A deficiency in ceramides results in enhanced transepidermal water loss, dry skin, and increased permeability to environmental irritants and allergens. Increased transepidermal water loss is observed in patients with AD. In addition, keratinocyte-derived antimicrobial peptides known as cathelicidins and b defensins are deficient in the skin of patients with AD. These peptides help in the host defense against bacteria, viruses, and fungi. The skin barrier In these studies, the effects on the skin barrier of a number of compounds were evaluated, including corticosteroids, immunomodulating agents (such as pimecrolimus), hydrogel, pseudoceramides, or their precursors, and NMFs. Moisturizers containing urea, a-hydroxy acids, hyaluronic acids, or ceramides have been shown to improve the integrity of the stratum corneum. More recently, ceramides,pseudoceramides, and NMFs have been studied and added to commercial moisturizers to mimic natural skin moisturizing factors and lipids. Several studies aim to show that moisturizer therapy can reduce the frequency and severity of flares and reduce the need for topical corticosteroids or topical calcineurin inhibitors. Ceramide-dominant emollients influence both transepidermal water loss and the expression of antimicrobial peptides in patients with AD. The use of ceramide-dominant emollients is associated with restoration of the permeability barrier function with concomitant improvement of antimicrobial defense in patients with AD. AD is a complex disease. To date, these randomized trials and case series have provided inadequate evidence that barrier therapy alone may cure the disease. Physicians should help patients to establish realistic therapeutic goals and to choose the most acceptable moisturizer in combination with topical, systemic, and behavioral management.
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BAK, HANA,LEE, HYUN JU,CHANG, SUNG-EUN,CHOI, JEE-HO,KIM, MYEUNG NAM,KIM, BEOM JOON Blackwell Publishing Inc 2009 Dermatologic surgery Vol.35 No.8
<P>BACKGROUND</P><P>Characteristic clinical features of melasma are symmetry of hyperpigmentation and distribution related to trigeminal nerves, which suggest that the neural involvement could play a part in the pathogenic mechanisms of pigmentation.</P><P>OBJECTIVE</P><P>To evaluate whether some neuropeptides and neurotrophins and their receptors were associated with the pathogenesis of melasma.</P><P>METHODS</P><P>To investigate the involvement of neuronal system and neuropeptides in melasma, we examined the expression of nerve growth factor receptor (NGFR) and neural endopeptidase (NEP) in melasma lesional and nonlesional skin. Skin biopsies were obtained from lesional and nonlesional facial skin of six Korean women with melasma. Confocal laser scanning microscopic examination and western blot were performed.</P><P>RESULTS</P><P>Melasma lesions showed markedly greater expression of NGFR and NEP than nonlesional skin.</P><P>CONCLUSION</P><P>We suggest that neuroactive molecules, including NGF, is one of the critical factors for the pathogenesis of melasma, which may directly affect the microenvironment around melanocytes through a NGFR immunoreactivity (NGFR-IR) nerve fiber pathway, and higher levels of NEP in melasma has an important role in regulation of melanogenesis.</P>
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Altered epidermal lipid layers induced by long‐term exposure to suberythemal‐dose ultraviolet
Bak, Hana,Hong, Seung‐,phil,Jeong, Se‐,Kyoo,Choi, Eung‐,Ho,Lee, Sang E.,Lee, Seung‐,Hun,Ahn, Sung‐,Ku Blackwell Publishing Ltd 2011 International journal of dermatology Vol.50 No.7
<P><B>Abstract</B></P><P><B>Background </B> Although several studies have reported on the biological effects of ultraviolet (UV) radiation, there have been only a few reports on the changes in epidermal lipids following long‐term UV irradiation at suberythemal dose (SED), to which people are usually exposed during their lifetime.</P><P><B>Objectives </B> To investigate the changes of epidermal lipid properties after long‐term UV radiation with SED.</P><P><B>Materials and methods </B> Hairless mice were irradiated three times weekly for 15 weeks at an SED of UV (UVB: 20 mJ/cm<SUP>2</SUP>; UVA: 14 J/cm<SUP>2</SUP>). Every three weeks, transepidermal water loss (TEWL) was measured by a Tewameter. The morphological alterations of stratum corneum (SC) lipid lamellae were examined by electron microscopy (EM). Activities of three key enzymes for mRNA of serine palmitoyl transferase, fatty acid synthase, and HMG CoA reductase were analyzed with real time reverse transcriptase‐polymerase chain reaction. We also measured the amount of ceramide, cholesterol sulfate, and free fatty acid in the SC by high‐performance thin‐layer chromatography with exposed times.</P><P><B>Results </B> The SED UV‐irradiated group showed increased TEWL after 12 weeks. Following the irradiation period, EM revealed incomplete and separated lamellae at SC intercellular space. mRNA of three key enzymes was increased until six weeks of UV irradiation and decreased thereafter. However, three major lipid amounts gradually decreased throughout the exposed period, with a notable decrease in ceramide.</P><P><B>Conclusions </B> Long‐term UV irradiation even with SED influences skin barrier function and structure with prominent ceramide decrease in SC intercellular lipid.</P>
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Therapeutic Moisturizers for Skin Diseases
( Hana Bak ) 한국피부장벽학회 2014 한국피부장벽학회지 Vol.16 No.1
Daily moisturizers are recommended by dermatologists as an important part of the management of patients with atopic dermatitis and other dry skin diseases. However, it is true that manyhealthcare professionals and patients overlook the importance of moisturizers and consider them not to be ‘active’ treatments.Moisturizers have multiple functions executed by a great variety of ingredients.Apart from moistening the skin, they affect the structure and barrier function of diseased and healthy looking skin. Application of moisturizers to the skin induces changes in its superficial as well as deep layers. The chemical and physical characteristics of individual ingredients determine the performance of the formulation. In order to have proper effect, it is conceivable that moisturizers should be tailored with respect to many diseases that contributesto the different symptoms of dryness. This article reviews the role of different therapeutic moisturizers in the treatment of common skin barrier disorders including atopic dermatitis, psoriasis, acne and rosacea.
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조하나(Hana Jo),최성만(Seongman Choi),박경수(Kyungsu Bak),양계병(Gyaebyung Yang) 한국추진공학회 2016 한국추진공학회 학술대회논문집 Vol.2016 No.12
덕티드팬 항공기에 적용 가능한 터보샤프트 엔진에 대한 사이클 해석을 Gasturb 12 소프트웨어를 이용하여 수행하였다. 덕티드 팬 항공기의 임무별 동력요구조건에 대한 터보샤프트 엔진의 추력과 비연료소모율(SFC) 특성을 도출하였다. 항공기의 순항조건에서 비연료소모율 향상을 위하여 VGV(Variable Guide Vane)을 도입하여 그 효과를 검토하였고, 탈 설계점에서의 엔진성능향상을 위하여 여러 가지 설계점 변경을 통하여 그 특성을 연구하였다. The cycle analysis of the turboshaft engine for the ducted-fan rotorcraft was performed using Gasturb 12 software. The characteristics of the thrust and specific fuel consumption with mission requirements of the ducted-fan rotorcraft were deducted. To enhance the specific fuel consumption performance in cruise flight condition, variable guide vane system is adopted and the effect was analyzed. Also several design points were studied for improving off design engine performance.
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