Effects of UVB-induced oxidative stress on protein expression and specific protein oxidation in normal human epithelial keratinocytes: a proteomic approach

Oxidative stress in HPV-driven viral carcinogenesis: redox proteomics analysis of HPV-16 dysplastic and neoplastic tissues

Genital infection by high risk Human Papillomavirus (HR-HPV), although recognized as the main etio-pathogenetic factor of cervical cancer, is not per se sufficient to induce tumour development. Oxidative stress (OS) represents an interesting and under-explored candidate as a promoting factor in HPV-initiated carcinogenesis. To gain insight into the role of OS in cervical cancer, HPV-16 positive tissues were collected from patients with invasive squamous cervical carcinoma, from patients with High Grade dysplastic HPV lesions and from patients with no clinical evidence of HPV lesions. After virological characterization, modulation of proteins involved in the redox status regulation was investigated. ERp57 and GST were sharply elevated in dysplastic and neoplastic tissues. TrxR2 peaked in dysplastic samples while iNOS was progressively reduced in dysplastic and neoplastic samples. By redox proteomic approach, five proteins were found to have increased levels of carbonyls in dysplastic samples respect to controls namely: cytokeratin 6, actin, cornulin, retinal dehydrogenase and GAPDH. In carcinoma samples the peptidyl-prolyl cis-trans isomerase A, ERp57, serpin B3, Annexin 2 and GAPDH were found less oxidized than in dysplastic tissues. HPV16 neoplastic progression seems associated with increased oxidant environment. In dysplastic tissues the oxidative modification of DNA and proteins involved in cell morphogenesis and terminal differentiation may provide the conditions for the neoplastic progression. Conversely cancer tissues seem to attain an improved control on oxidative damage as shown by the selective reduction of carbonyl adducts on key detoxifying/pro-survival proteins.

Involvement of P2Y receptors in the protective effect of ATP towards the cell damage in HaCaT cells exposed to H₂O₂

It has recently been reported that activation of P2Y(1) receptor, one of the purine receptors, by extracellular nucleotides induces cytoprotection against oxidative stress. In this study, we examined the protective effect of ATP on the cell damage in human epidermal keratinocyte HaCaT cells exposed to H(2)O(2) via the P2Y receptor-mediated induction of intracellular antioxidants. The cells were damaged by exposure to H(2)O(2) in a dose- and time-dependent manner. The damage induced by 7.5 mM H(2)O(2) was blocked by pretreatment of the cells with ATP (1-10 µM). The protective effect of ATP was significantly reduced by P2Y receptor antagonists. Exogenously added ATP induced various intracellular antioxidants, including thiol-containing proteins, Cu/Zn superoxide dismutase (SOD) and thioredoxin-1, in HaCaT cells. In conclusion, it was found that ATP protected the cells from the H(2)O(2)-induced cell damages via the P2Y receptor-mediated induction of intracellular antioxidants.

Mechanism of hydrogen peroxide-induced keratinocyte migration in a scratch-wound model

Recent studies have shown that low concentrations of H(2)O(2) are produced endogenously by nonphagocytes after wounding. We observed that H(2)O(2) at such concentrations can stimulate proliferation as well as migration of keratinocytes in a scratch-wound assay. Both wounding and H(2)O(2) can induce phosphorylation of ERK1/2 via EGFR, but the activation of ERK1/2 by H(2)O(2) is more sustained and can last more than 8h. Sustained ERK1/2 activation is required for the increased proliferation and migration induced by H(2)O(2). The p38 MAPK was also found to be phosphorylated upon treatment with H(2)O(2) but it was not required for H(2)O(2)-induced migration or proliferation. Furthermore, it was observed that there is a cross talk between the ERK1/2 and the p38 pathways whereby inhibition of either pathway can lead to activation of the other. As a result, the motogenic effects of H(2)O(2) were further enhanced when p38 was inhibited. Our data are consistent with the view that H(2)O(2) may play an important signaling role in wound healing.

Kindlin-1 and -2 have overlapping functions in epithelial cells implications for phenotype modification

Kindlins are a novel family of intracellular adaptor proteins in integrin-containing focal adhesions. Kindlin-1 and -2 are expressed in the skin, but whether and how they cooperate in adult epithelial cells have remained elusive. We uncovered the overlapping roles of kindlin-1 and -2 in maintaining epithelial integrity and show that the phenotype of kindlin-1-deficient cells can be modulated by regulating kindlin-2 gene expression and vice versa. The experimental evidence is provided by use of human keratinocyte cell lines that express both kindlins, just kindlin-1 or kindlin-2, or none of them. Double deficiency of kindlin-1 and -2 had significant negative effects on focal adhesion formation and actin cytoskeleton organization, cell adhesion, survival, directional migration, and activation of β(1) integrin, whereas deficiency of one kindlin only showed variable perturbation of these functions. Cell motility and formation of cell-cell contacts were particularly affected by lack of kindlin-2. These results predict that kindlin-1 and -2 can functionally compensate for each other, at least in part. The high physiologic and pathologic significance of the compensation was emphasized by the discovery of environmental regulation of kindlin-2 expression. UV-B irradiation induced loss of kindlin-2 in keratinocytes. This first example of environmental regulation of kindlin expression has implications for phenotype modulation in Kindler syndrome, a skin disorder caused by kindlin-1 deficiency.

Tangeretin reduces ultraviolet B (UVB)-induced cyclooxygenase-2 expression in mouse epidermal cells by blocking mitogen-activated protein kinase (MAPK) activation and reactive oxygen species (ROS) generation

The present study examined the effects of tangeretin, a polymethoxylated flavonone present in citrus fruits, on ultraviolet B (UVB)-induced cyclooxygenase-2 (COX-2) expression in JB6 P+ mouse skin epidermal cells. Tangeretin suppressed UVB-induced COX-2 expression and transactivation of nuclear factor-κB and activator protein-1 in JB6 P+ cells. Moreover, tangeretin blocked UVB-induced phosphorylation of Akt and mitogen-activated protein kinases (MAPKs), including extracellular signal-regulated protein kinase, c-Jun N-terminal kinase, and p38, and attenuated the phosphorylation of MAPK kinases 1/2, 3/6, and 4. Tangeretin also limited the endogenous generation of reactive oxygen species (ROS), thereby protecting the cells against oxidative stress. However, tangeretin did not scavenge the stable 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and influence the nicotinamide adenine dinucleotide phosphate oxidase activity. These results suggest that the anti-inflammatory effects of tangeretin stem from its modulation of cell signaling and suppression of intracellular ROS generation. Tangeretin may have a potent chemopreventive effect in skin cancer.

An in vitro Survey on the Apoptotic Effects of UVB Ray in Bacillus anthracis

OBJECTIVES

Bacillus anthracis as the bacterial agent of anthrax, is spread in different geographical zones around the world.The purpose of this survey was to observe eventual apoptotic reactions in total genomic DNA of UVB irradiated colonies of Bacillus anthracis.

MATERIALS AND METHODS

The colonies of Bacillus anthracis were exposed to UVB ray for 10 minutes; then, the DNA molecules of control and irradiated colonies were extracted. Finally, the DNA samples mixed in loading dye, were run in 1% agarose gel containing fluorescent dye of ethidium bromide to produce visible DNA bands.

OUTCOMES

Neither smear nor DNA laddering band were detected upon the agarose gel.

CONCLUSIONS

According to the present protocol, the UVB ray can not induce apoptosis feature in colonies of Bacillus anthracis. It seems that the recovery and protection systems in Bacillus anthracis can resist against eventual UVB disorders.