title: Effects of diode 808 nm GaAlAs low-power laser irradiation on inhibition of the proliferation of human hepatoma cells in vitro and their possible mechanism.
abstract: Low-power laser irradiation (LPLI) has come into a wide range of use in medical field. Considering basic research, LPLI can enhance DNA synthesis and increases proliferation rate of human cells. But only a few data about the effects of LPLI on human liver or hepatoma cells are available. The cytoskeleton plays important roles in cell function and therefore is implicated in the pathogenesis of many human liver diseases, including malignant tumors. In our previous study, we found the stability of cytokeratin molecules in human hepatocytes was related to the intact microtubule network that was influenced by colchicine. In this study, we are going to search the effect of LPLI on proliferation of human hepatoma cell line HepG2 and J-5 cells. In addition, the stability of cytokeratin and synemin (one of the intermediate filament-associated proteins) were analyzed under the action of LPLI to evaluate the possible mechanism of LPLI effects on proliferation of human hepatoma cells. In experiment, HepG2 and J-5 cells were cultured in 24-well plate for 24 hours. After irradiation by 130 mW diode 808 nm GaAlAs continue wave laser in different time intervals, the cell numbers were counted. Western blot and immunofluorescent staining examined the expression and distribution of PCNA, cytokeratin and synemin. The cell number counting and PCNA expression were evaluated to determine the proliferation. The organization and expression of cytokeratin and synemin were studied to identify the stability of cytoskeleton affected by LPLI. The results revealed that proliferation of HepG2 and J-5 cells was inhibited by LPLI since the cell number and PCNA expression was reduced. Maximal effect was achieved with 90 and 120 seconds of exposure time (of energy density 5.85 J/cm2 and 7.8 J/cm2, respectively) for HepG2 and J-5, respectively. The decreased ratio of cell number by this dose of irradiation was 72% and 66% in HepG2 and J-5 cells, respectively. Besides that, the architecture of intermediate filaments in these cells was disorganized by laser irradiation. The expression of intermediate filament-associated protein, synemin, was also reduced. Two significant findings are raised in this study: (1) Diode 808 nm GaAlAs continuous wave laser has an inhibitory effect on the proliferation of human hepatoma cells line HepG2 and J-5. (2) The mechanism of inhibition might be due to down-regulation of synemin expression and alteration of cytokeratin organization that was caused by laser irradiation.
authors.affiliation: Center for Research and Development, Chung-tai Institute of Health Sciences and Technology, Taichung, Taiwan.
authors.forename: Yi-Hsiang
authors.initials: YH
authors.lastname: Liu
authors.forename: Chiung-Chi
authors.initials: CC
authors.lastname: Cheng
authors.forename: Chin-Chin
authors.initials: CC
authors.lastname: Ho
authors.forename: Ren-Jeng
authors.initials: RJ
authors.lastname: Pei
authors.forename: Karen Ying
authors.initials: KY
authors.lastname: Lee
authors.forename: Kun-Tu
authors.initials: KT
authors.lastname: Yeh
authors.forename: You
authors.initials: Y
authors.lastname: Chan
authors.forename: Yih-Shyong
authors.initials: YS
authors.lastname: Lai
mesh_terms: D000704:Analysis of Variance; D015153:Blotting, Western; D006528:Carcinoma, Hepatocellular / Q000473:pathology / Q000532:radiotherapy*; D002452:Cell Count; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000528:radiation effects*; D016650:Fluorescein-5-isothiocyanate; D019084:Fluorescent Antibody Technique, Indirect; D005456:Fluorescent Dyes; D006801:Humans; D066298:In Vitro Techniques; D007381:Intermediate Filament Proteins / Q000528:radiation effects; D007633:Keratins / Q000528:radiation effects; D008113:Liver Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D028022:Low-Level Light Therapy; D010590:Phalloidine; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D011829:Radiation Dosage; D013997:Time Factors
chemical_list: D005456:Fluorescent Dyes; D007381:Intermediate Filament Proteins; D018809:Proliferating Cell Nuclear Antigen; C430456:desmuslin; D010590:Phalloidine; D007633:Keratins; D016650:Fluorescein-5-isothiocyanate