title: Hyperosmotic stress reduces melanin production by altering melanosome formation.
abstract: Many tissues of the human body encounter hyperosmotic stress. The effect of extracellular osmotic changes on melanin production has not yet been elucidated. In this study, we determined that hyperosmotic stress induced by organic osmolytes results in reduced melanin production in human melanoma MNT-1 cells. Under hyperosmotic stress, few pigmented mature melanosomes were detected, but there was an increase in swollen vacuoles. These vacuoles were stained with an anti-M6PR antibody that recognizes late endosomal components and with anti-TA99 and anti-HMB45 antibodies, implying that melanosome formation was affected by hyperosmotic stress. Electron microscopic analysis revealed that the M6PR-positive swollen vacuoles were multi-layered and contained melanized granules, and they produced melanin when L-DOPA was applied, indicating that these vacuoles were still capable of producing melanin, but the inner conditions were not compatible with melanin production. The vacuolation phenomenon induced by hyperosmotic conditions disappeared with treatment with the PI3K activator 740 Y-P, indicating that the PI3K pathway is affected by hyperosmotic conditions and is responsible for the proper formation and maturation of melanosomes. The microarray analysis showed alterations of the vesicle organization and transport under hyperosmotic stress. Our findings suggest that melanogenesis could be regulated by physiological conditions, such as osmotic pressure.
authors.affiliation: Bioscience Research Institute, Amorepacific Corporation R&D Center, Yongin, Republic of Korea.
authors.forename: Bum-Ho
authors.initials: BH
authors.lastname: Bin
authors.affiliation: Department of Chemical Engineering, POSTECH, Pohang, Republic of Korea.
authors.forename: Jinhyuk
authors.initials: J
authors.lastname: Bhin
authors.affiliation: Bioscience Research Institute, Amorepacific Corporation R&D Center, Yongin, Republic of Korea.
authors.forename: Seung Ha
authors.initials: SH
authors.lastname: Yang
authors.affiliation: Gyeonggi Bio Center, Gyeonggi Institute of Science & Technology Promotion, Suwon, Republic of Korea.
authors.forename: Dong-Hwa
authors.initials: DH
authors.lastname: Choi
authors.affiliation: Gyeonggi Bio Center, Gyeonggi Institute of Science & Technology Promotion, Suwon, Republic of Korea.
authors.forename: Kyuhee
authors.initials: K
authors.lastname: Park
authors.affiliation: Bioscience Research Institute, Amorepacific Corporation R&D Center, Yongin, Republic of Korea.
authors.forename: Dong Wook
authors.initials: DW
authors.lastname: Shin
authors.affiliation: Department of Dermatology, Dongguk University Ilsan Hospital, Goyang, Republic of Korea.
authors.forename: Ai-Young
authors.initials: AY
authors.lastname: Lee
authors.affiliation: Department of Chemical Engineering, POSTECH, Pohang, Republic of Korea.
authors.forename: Daehee
authors.initials: D
authors.lastname: Hwang
authors.affiliation: Bioscience Research Institute, Amorepacific Corporation R&D Center, Yongin, Republic of Korea.
authors.forename: Eun-Gyung
authors.initials: EG
authors.lastname: Cho
authors.affiliation: Bioscience Research Institute, Amorepacific Corporation R&D Center, Yongin, Republic of Korea.
authors.forename: Tae Ryong
authors.initials: TR
authors.lastname: Lee
mesh_terms: D000978:Antiparkinson Agents / Q000494:pharmacology; D015153:Blotting, Western; D045744:Cell Line, Tumor; D016000:Cluster Analysis; D020869:Gene Expression Profiling; D006801:Humans; D007980:Levodopa / Q000494:pharmacology; D008543:Melanins / Q000096:biosynthesis*; D008544:Melanocytes / Q000187:drug effects / Q000378:metabolism; D008545:Melanoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D020460:Melanosomes / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D046529:Microscopy, Electron, Transmission; D008856:Microscopy, Fluorescence; D020411:Oligonucleotide Array Sequence Analysis; D009997:Osmotic Pressure / Q000502:physiology*; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000235:genetics; D014617:Vacuoles / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D058951:gp100 Melanoma Antigen / Q000235:genetics / Q000378:metabolism
chemical_list: D000978:Antiparkinson Agents; D008543:Melanins; D008562:Membrane Glycoproteins; C548637:PMEL protein, human; D058951:gp100 Melanoma Antigen; D007980:Levodopa; D010088:Oxidoreductases; C489799:TYRP1 protein, human; D019869:Phosphatidylinositol 3-Kinases