UVA irradiation of dysplastic keratinocytes: oxidative damage versus antioxidant defense.

UVA affects epidermal cell physiology in a complex manner, but the harmful effects have been studied mainly in terms of DNA damage, mutagenesis and carcinogenesis. We investigated UVA effects on membrane integrity and antioxidant defense of dysplastic keratinocytes after one and two hours of irradiation, both immediately after exposure, and 24 h post-irradiation. To determine the UVA oxidative stress on cell membrane, lipid peroxidation was correlated with changes in fatty acid levels. Membrane permeability and integrity were assessed by propidium iodide staining and lactate dehydrogenase release. The effects on keratinocyte antioxidant protection were investigated in terms of catalase activity and expression. Lipid peroxidation increased in an exposure time-dependent manner. UVA exposure decreased the level of polyunsaturated fatty acids, which gradually returned to its initial value. Lactate dehydrogenase release showed a dramatic loss in membrane integrity after 2 h minimum of exposure. The cell ability to restore membrane permeability was noted at 24 h post-irradiation (for one hour exposure). Catalase activity decreased in an exposure time-dependent manner. UVA-irradiated dysplastic keratinocytes developed mechanisms leading to cell protection and survival, following a non-lethal exposure. The surviving cells gained an increased resistance to apoptosis, suggesting that their pre-malignant status harbors an abnormal ability to control their fate.

Telocytes in human term placenta: morphology and phenotype.

In the last few years, a new cell type - interstitial Cajal-like cell (ICLC) - has been described in digestive and extra-digestive organs. The name has recently been changed to telocytes (TC) and their typical thin, long processes have been named telopodes (TP). To support the hypothesis that TC may also be present in human placenta and add to the information already available, we provide evidence on the ultrastructure, immunophenotype, distribution, and interactions with the surrounding stromal cells of TC in the villous core of human term placenta. We used phase-contrast microscopy, light microscopy of semithin sections, transmission electron microscopy, immunohistochemistry, and immunofluorescence of tissue sections or cell cultures, following a pre-established diagnostic algorithm. Transmission electron microscopy showed cells resembling TC, most (∼76%) having 2-3 very thin, longprocesses (tens to hundreds of micrometers), with an uneven calibre(≤0.5 µm thick) and typical branching pattern. The dilations of processes accommodate caveolae, endoplasmic reticulum cisternae, and mitochondria. These TC have close contacts with perivascular SMC in stem villi. In situ, similar cells are positive for c-kit, CD34, vimentin, caveolin-1, vascular endothelial growth factor (VEGF), and inducible nitric oxide synathase (iNOS). The c-kit-positive cells inconsistently co-express CD34, CD44, αSMA, S100, neuron-specific enolase, and nestin. Among cells with a morphologic TC profile in cell cultures, about 13% co-express c-kit, vimentin, and caveolin-1; 70% of the c-kit-positive cells co-express CD34 and 12% co-express iNOS or VEGF. In conclusion, this study confirms the presence of TC in human term placenta and provides their ultrastructural and immunophenotypic characterization.

Human NK cells express Fc receptors for IgA which mediate signal transduction and target cell killing.

Receptors for the Fc region of IgG (FcgammaRIIIa, FcgammaRIIc) and IgM (FcmicroR) were previously described on NK cells. In this work the expression of Fc receptors for IgA (FcalphaR) on human NK cells and the signaling events were investigated. The FcalphaR was demonstrated by flow cytometry using secretory IgA (sIgA) and anti-human IgA antibody. The percentage of NK cells (CD3(-)CD56(+)CD16(+)) expressing FcalphaR ranged between 55.7% and 95.7%, with a mean +/- SD of 75.2+/-11.8. The association constant and the number of (125)I-labeled sIgA ((125)I-sIgA) molecules bound per cell, calculated by Scatchard analysis, were 2 x 10(7) M(-1) and 1.7 x 10(4), respectively. The binding specificity was proved by inhibition experiments. Cold sIgA but not IgA Fab fragments were able to inhibit (125)I-sIgA binding in a concentration-dependent manner. Binding of sIgA to NK cells was neither inhibited by anti-mannose receptor antibody, nor by L-fucose, D-galactose, D-glucose, D-mannose or N-acetyl-D-glucosamine. Pretreatment of NK cells with polymeric IgA inhibited their capacity to kill (51)Cr-labeled K562 target cells by 34.8%, whereas with monomeric IgA only by 13.1%. Ligand-induced clustering of the FcalphaR resulted in activation of tyrosine kinases Lck, Syk and phosphatidylinositol 3-kinase. The present studies support the concept that human NK cells bind preferentially sIgA and polymeric IgA with moderate affinity via FcalphaR, which is different from the FcalphaRI/CD89 and other carbohydrate-recognizing receptors like mannose receptor/CD206. This novel structure mediates signal transduction and cell killing.