Apoptosis-induced Proliferation in UV-Irradiated Human Conjunctival Epithelial Cells

A pterygium is a benign growth that develops on the conjunctiva and, in some cases, extends to the cornea and interferes with vision. Excessive exposure to ultraviolet (UV) light is one of the causes of pterygium development. We previously reported that UV-induced apoptosis is led by production of reactive oxygen species (ROS) that activate p38 mitogen-activated protein kinase (MAPK) in human conjunctival epithelial (HCE) cells. Also, ROS-dependent induction of interleukin-11 (IL-11) has been reported to upregulate MAPK pathways, which results in compensatory proliferation. In this study, we examined the effect of UV exposure on HCE cells, in terms of change in apoptosis, ROS generation, phosphorylation of c-Jun N-terminal kinase (JNK), levels of IL-11 (a key cytokine in tissue repair and compensatory proliferation), production of activator protein 1 (AP-1), and expression of c-myc, c-fos and c-jun (which provides evidence of healthy cell proliferation). Apoptosis in HCE cells was induced by UV light irradiation (312nm, 4.94mW/cm2). Apoptosis was measured using the Muse Annexin V and Dead Cell Assay Kit. ROS generation was measured by using 5-(and 6-) chloromethyl-2\u277\u27-dichlorodihydrofluorescein diacetate, acetyl ester. JNK phosphorylation, IL-11 levels and AP-1 production were measured by enzyme-linked immunosorbent assays (ELISAs). Imnunocytochemical staining was used to measure c-myc, c-fos and c-jun expression. UV irradiation increased ROS generation, phosphorylation of JNK, and apoptotic cell count. IL-11 levels and AP-1 production were significantly increased by UV irradiation. The irradiated cells had increased expression of c-myc, c-fos and c-jun, and treatment of the cells with IL-11 significantly increased expression of c-myc, c-fos and c-jun. These results suggest that the release of IL-11 from UV-induced apoptotic HCE cells and surrounding healthy cells could promote proliferation to maintain homeostasis

Quantification of (-)-epigallocatechin-3-gallate Inhibition of Migration and Invasion of Oral Squamous Cell Carcinoma Cell Lines Using Real-time Cell Analysis

Catechins found in green tea, in particular (−)-epigallocatechin-3-gallate (EGCG), have antitumor activity. The primary antitumor actions of catechins are anti-oxidative, anti-angiogenic, and anti-metastatic effects. Cell migration and invasion contribute to the metastatic potential of tumors. Real-time cell analysis (RTCA) measures cell migration and invasion in vitro. In the present study, using RTCA, we investigated whether the cell migration and invasion of oral squamous cell carcinomas (OSCCs) of the tongue and floor of the mouth were inhibited by EGCG. Studies were performed using the human SCC-4 and SAS cell lines, which are poorly differentiated OSCCs of the tongue, and the HO-1-u-1 cell line, an OSCC of the floor of the mouth. SCC-4 cells exhibited high cell migration and invasion compared with the SAS and HO-1-u-1 cells. EGCG was most effective in inhibiting the migration and invasion of SCC-4 cells, and inhibited OSCC cell invasion more strongly than it inhibited cell migration. EGCG inhibited the expression of matrix metalloproteinase (MMP)-2, MMP-9, and integrin α1 and β1 mRNA in the OSCC cell lines, particularly SCC-4 cells. The findings of the present study suggest that EGCG inhibits OSCC cell migration and invasion by inhibiting MMP-2, MMP-9, and integrin α1and β1 expression. Thus, EGCG may be a suitable agent or lead compound for the inhibition of OSCC metastasis

Suppressive Effects of Catechins in UV-Induced Cytotoxicity of Human Corneal Epithelial Cells

Photokeratitis is a disease in which the ocular surface is directly affected by oxidative stress caused by exposure to ultraviolet （UV） light and oxygen. It is speculated that the production of free radicals and reactive oxygen species （ROS） is caused by UV-induced cytotoxicity. Recent studies have reported that catechins have antioxidant, antiallergic, antitumor, and antibacterial effects. The aim of our study was to investigate the mechanism of UV-induced cytotoxicity in cultured human corneal epithelial （HCE-T） cells and evaluate the protective effects of the catechins, （?）-epigallocatechin gallate （EGCG） and （?）-epigallocatechin 3-O-（3-O-methyl） gallate （EGCG3”Me）, on apoptosis. HCE-T cells were UV irradiated at 312nm （4.94mW/cm2, 296mJ/cm2）. EGCG and EGCG3”Me were dissolved in methanol and adjusted to 5, 10, or 20?M. Absorption was measured from 250 to 400nm. EGCG and EGCG3”Me were pre-incubated for 1 hr. After UV irradiation, membrane lipid peroxide, tumor necrosis factor （TNF）-α production, ROS generation, caspase-3 and -8 activities, mitochondrial membrane potential, and cytochrome c levels were measured. Both EGCG and EGCG3”Me had UV absorption, and increased with concentration dependently. The increases in the levels of membrane lipid hyperoxidation, activation of caspase-3 and -8, production of TNF-α and ROS were found, by UV irradiation, to be significant. But these levels were significantly decreased by pretreatment with EGCG and EGCG3”Me. There were no changes in mitochondrial membrane potential and cytoplasmic cytochrome c levels after UV irradiation. Oxidative stress occurs early near the cell membrane in response to UV irradiation. As a result, TNF-α is induced, leading to apoptosis mainly through caspase-8 activation. Conversely, EGCG and EGCG3”Me absorb UV light directly and inhibit lipid peroxidation in the cell membrane. Catechins inhibit the apoptosis cascade by inactivating caspase-3 and caspase-8