Biological Effects Induced by Ultraviolet Radiation in Human Fibroblasts (original) (raw)

2012, Flow Cytometry - Recent Perspectives

Flow Cytometry-Recent Perspectives 440 stress. Fortunately, UVC is prevented from reaching the earth, as it is largely absorbed by atmospheric ozone layer (Afag, 2011). It has already been proposed that programmed cell death (apoptosis) can be induced by UV light in various cell types (reviewed in Schwarz, 1998). The cellular responses to injuries or stresses are important in determining cell fate (Aylon & Oren, 2007). Many signaling pathways participate in this process, with the mitogen-activated protein kinase (MAPK) cascades and p53 pathway being two of the major pathways implicated (Aylon & Oren, 2007; Li et al., 2009). The cellular response to DNA damage is focused on p53, which can induce the cell to apoptosis by the protein PUMA (p53 up-regulated modulator of apoptosis), a member of the Bcl-2 homology (BH)3-only Bcl-2 family proteins. Recent studies suggest that Bcl-2 family members play an essential role in regulating apoptosis initiation through the mitochondria (Zhang et al., 2009). UV irradiation induces permeabilization of the lysosomal membrane with release of cathepsin B and D to the cytosol, translocation of the proapoptotic Bcl-2 proteins Bax and Bid to mitochondriallike structures. Subsequently, there is cytochrome c release and activation of caspase-3 (Bivik et al., 2006). p38 MAPK, one of the four MAPK subfamilies in mammalian cells, is activated by proinflammatory cytokines and environmental stress (Brown & Benchimol, 2006; Johnson & Lapadat, 2002). p38 is not only reported to be phosphorylated and activated to mediate cell apoptosis and the differentiation process (Thornton & Rincon, 2009), but also to have cell protective effects under certain circumstances (Chouinard et al., 2002). MAPK pathways mediate cellular responses to many different extracellular signaling molecules such as the ones involved in differentiation, gene expression, regulation of proliferation, apoptosis, development, motility or metabolism. The typical MAPK pathways, characterized by the ERK1/2, ERK5, JNK, and p38 MAPK components, comprise a cascade of three successive phosphorylation events exerted by a MAPK kinase kinase (MAPKKK), a MAPK kinase (MAPKK), and a MAPK (Kostenko et al., 2011).