Skin hyperpigmentation is one of the most common skin disorders caused by abnormal melanogenesis. The mechanism and key factors at play are not fully understood. Previous reports have indicated that cystamine (CTM) inhibits melanin synthesis, though its molecular mechanism in melanogenesis remains unclear. In the present study, we investigated the effect of CTM on melanin production using ELISA reader and the expression of proteins involved in melanogenesis by Western blotting, and examined the involvement of transglutaminase-2 (Tgase-2) in SK-MEL-2 human melanoma cells by gene silencing. In the results, CTM dose-dependently suppressed melanin production and dendrite extension in alpha-MSH-induced melanogenesis of SK-MEL-2 human melanoma cells. CTM also suppressed alpha-MSH-induced chemotactic migration as well as the expressions of melanogenesis factors TRP-1, TRP-2 and MITF in alpha-MSH-treated SK-MEL-2 cells. Meanwhile, gene silencing of Tgase-2 suppressed dendrite extension and the expressions of TRP-1 and TRP-2 in alpha-MSH-treated SK-MEL-2 cells. Overall, these findings suggested that CTM suppresses alpha-MSH-induced melanogenesis via Tgase-2 inhibition and that therefore, Tgase-2 might be a new target in hyperpigmentation disorder therapy.
Blotting, Western ; Cystamine ; Dendrites ; Enzyme-Linked Immunosorbent Assay ; Gene Silencing ; Humans ; Hyperpigmentation ; Melanins ; Melanoma* ; Skin

The stiffness of cancer cells is attributable to intermediate filaments such as keratin. Perinuclear reorganization via phosphorylation of specific serine residue in keratin is implicated in the deformability of metastatic cancer cells including the human pancreatic carcinoma cell line (PANC-1). 12-O-Tetradecanoylphorbol-13-acetate (TPA) is a potent tumor promoter and protein kinase C (PKC) activator. However, its effects on phosphorylation and reorganization of keratin 8 (K8) are not well known. Therefore, we examined the underlying mechanism and effect of TPA on K8 phosphorylation and reorganization. TPA induced phosphorylation and reorganization of K8 and transglutaminase-2 (Tgase-2) expression in a time- and dose-dependent manner in PANC-1 cells. These effects peaked after 45 min and 100 nM of TPA treatment. We next investigated, using cystamine (CTM), Tgase inhibitor, and Tgase-2 gene silencing, Tgase-2's possible involvement in TPA-induced K8 phosphorylation and reorganization. We found that Tgase-2 gene silencing inhibited K8 phosphorylation and reorganization in PANC-1 cells. Tgase-2 gene silencing, we additionally discovered, suppressed TPA-induced migration of PANC-1 cells and Tgase-2 overexpression induced migration of PANC-1 cells. Overall, these results suggested that TPA induced K8 phosphorylation and reorganization via Tgase-2 expression in PANC-1 cells.
Cell Line ; Cystamine ; Gene Silencing ; Humans ; Intermediate Filaments ; Keratin-8* ; Phosphorylation* ; Protein Kinase C ; Serine

Osteoprotegerin (OPG) is a secreted glycoprotein and a member of the tumor necrosis factor receptor superfamily. It usually functions in bone remodeling, by inhibiting osteoclastogenesis through interaction with a receptor activator of the nuclear factor kappaB (RANKL). Transglutaminases-2 (Tgase-2) is a group of multifunctional enzymes that plays a role in cancer cell metastasis and bone formation. However, relationship between OPG and Tgase-2 is not studied. Therefore, we investigated the involvement of 12-O-Tetradecanoylphorbol 13-acetate in the expression of OPG in MG-63 osteosarcoma cells. Interleukin-1beta time-dependently induced OPG and Tgase-2 expression in cell lysates and media of the MG-63 cells by a Western blot. Additional 110 kda band was found in the media of MG-63 cells. 12-O-Tetradecanoylphorbol 13-acetate also induced OPG and Tgase-2 expression. However, an 110 kda band was not found in TPA-treated media of MG-63 cells. Cystamine, a Tgase-2 inhibitor, dose-dependently suppressed the expression of OPG in MG-63 cells. Gene silencing of Tgase-2 also significantly suppressed the expression of OPG in MG-63 cells. Next, we examined whether a band of 110 kda of OPG contains an isopeptide bond, an indication of Tgase-2 action, by monoclonal antibody specific for the isopeptide bond. However, we could not find the isopeptide bond at 110 kda but 77 kda, which is believed to be the band position of Tgase-2. This suggested that 110 kda is not the direct product of Tgase-2's action. All together, OPG and Tgase-2 is induced by IL-1beta or TPA in MG-63 cells and Tgase-2 is involved in OPG expression in MG-63 cells.
Blotting, Western ; Bone Remodeling ; Cystamine ; Gene Silencing ; Glycoproteins ; Interleukin-1beta ; Multifunctional Enzymes ; Neoplasm Metastasis ; Osteogenesis ; Osteoprotegerin* ; Osteosarcoma* ; Receptors, Tumor Necrosis Factor

The treatment of cystamine, a transglutaminase (TGase) inhibitor, has beneficial effects in several diseases including CAG-expansion disorders and cataract. We compared the inhibition characteristics of cystamine with those of cysteamine, a reduced form of cystamine expected to be present inside cells. Cystamine is a more potent inhibitor for TGase than cysteamine with different kinetics pattern in a non- reducing condition. By contrast, under reducing conditions, the inhibitory effect of cystamine was comparable with that of cysteamine. However, cystamine inhibited intracellular TGase activity more strongly than cysteamine despite of cytoplasmic reducing environment, suggesting that cystamine itself inhibits in situ TGase activity by forming mixed disulfides.
Cell Line, Tumor ; Comparative Study ; Cystamine/*pharmacology ; Cysteamine/*pharmacology ; Enzyme Inhibitors/*pharmacology ; Humans ; Research Support, Non-U.S. Gov't ; Transglutaminases/*antagonists & inhibitors

BACKGROUND: Transglutaminase-2 (TG-2) has been reported to play an important role in the process of fibrosis. However, TG-2 studies on fibroproliferation of acute lung injury (ALI) are absent. The purpose of this study was to investigate the role of TG-2 in the fibroproliferation of lipopolysaccharide (LPS)-induced ALI. METHODS: The male C57BL/6 mice of 5 weeks age were divided into 3 groups; control group (n=30) in which 50 microL of saline was given intratracheally (IT), LPS group (n=30) in which LPS 0.5 mg/kg/50 microL of saline was given IT, and LPS+Cyst group treated with intraperitoneal 200 mg/kg of cystamine, competitive inhibitor of TG-2, after induction of ALI by LPS. TG-2 activity and nuclear factor (NF)-kappaB were measured in lung tissue homogenate. Tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-6, myeloperoxidase (MPO), and transforming growth factor (TGF)-beta1 were measured using bronchoalveolar lavage fluids. Histopathologic ALI score and Mallory's phosphotunistic acid hematoxylin (PTAH) for collagen and fibronectin deposition were performed. RESULTS: The TG-2 activities in the LPS group were significantly higher than the control and LPS+Cyst groups (p<0.05). The TNF-alpha and IL-1beta concentrations and NF-kappaB activity were lower in the LPS+Cyst group than the LPS group (p<0.05). The LPS+Cyst group showed lower MPO, ALI score, TGF-beta1 concentration, and Mallory's PTAH stain than the LPS group, but the differences were not significant (p>0.05). CONCLUSION: Inhibition of TG-2 activity in the LPS-induced ALI prevented early inflammatory parameters, but had limited effects on late ALI and fibroproliferative parameters.
Acute Lung Injury ; Animals ; Bronchoalveolar Lavage Fluid ; Collagen ; Cystamine ; Fibronectins ; Fibrosis ; Hematoxylin ; Humans ; Inflammation ; Interleukin-6 ; Interleukins ; Lipopolysaccharides ; Lung ; Male ; Mice ; NF-kappa B ; Peroxidase ; Transforming Growth Factor beta1 ; Transforming Growth Factors ; Tumor Necrosis Factor-alpha

This study was performed to examine the role of transglutaminase 2 (TG2) in ventilator-induced lung injury (VILI). C57BL/6 mice were divided into six experimental groups: 1) control group; 2) lipopolysaccharide (LPS) group; 3) lung protective ventilation (LPV) group; 4) VILI group; 5) VILI with cystamine, a TG2 inhibitor, pretreatment (Cyst+VILI) group; and 6) LPV with cystamine pretreatment (Cyst+LPV) group. Acute lung injury (ALI) score, TG2 activity and gene expression, inflammatory cytokines, and nuclear factor-kappaB (NF-kappaB) activity were measured. TG2 activity and gene expression were significantly increased in the VILI group (P < 0.05). Cystamine pretreatment significantly decreased TG2 activity and gene expression in the Cyst+VILI group (P < 0.05). Inflammatory cytokines were higher in the VILI group than in the LPS and LPV groups (P < 0.05), and significantly lower in the Cyst+VILI group than the VILI group (P < 0.05). NF-kappaB activity was increased in the VILI group compared with the LPS and LPV groups (P < 0.05), and significantly decreased in the Cyst+VILI group compared to the VILI group (P = 0.029). The ALI score of the Cyst+VILI group was lower than the VILI group, but the difference was not statistically significant (P = 0.105). These results suggest potential roles of TG2 in the pathogenesis of VILI.
Acute Lung Injury/pathology ; Animals ; Cystamine/therapeutic use ; Cytokines/analysis ; Enzyme Inhibitors/therapeutic use ; Enzyme-Linked Immunosorbent Assay ; GTP-Binding Proteins/*antagonists & inhibitors/genetics/metabolism ; Gene Expression ; Lipopolysaccharides/toxicity ; Male ; Mice ; Mice, Inbred C57BL ; NF-kappa B/metabolism ; Respiration, Artificial ; Transglutaminases/*antagonists & inhibitors/genetics/metabolism ; Ventilator-Induced Lung Injury/*enzymology/pathology/prevention & control