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

Relationship of Grade of Malignant Brain Tumor to Cancer Stem Cells and Survivin Expression

Glioblastoma (GBM) is difficult to completely cure by surgical treatment alone, and it is generally treated with a combination of surgery, radiotherapy, and chemotherapy. However, GBM is resistant to radiotherapy and chemotherapy, and complete cure cannot be achieved. Cancer stem cells (CSC) and survivin, which inhibit apoptosis, are considered as factors underlying tumor recurrence and the radiation- and drug-resistance of these tumors. We analyzed CSC and survivin expression in surgically excised specimens of malignant brain tumors to establish the relationships between the grades and CSC and survivin expression and between MIB-1 (Ki-67) expression and resistance. No relationship was noted between the grades and CSC or survivin expression, or between MIB-1 and CSC expression or between Grade 3 and 4 MIB-1 and survivin expression, although a correlation was noted between MIB-1 and survivin expression in Grade II tumors. These findings suggested that CSC are consistently contained in tumor tissue at a specific rate regardless of the histological grade, and the apoptosis of cells with low-level proliferative and cell cycling activities does not occur because these cells do not respond to chemotherapy or radiation, being resistant to treatment

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