Proteins involved in the antioxidant and inflammatory response in rutin-treated human skin fibroblasts exposed to UVA or UVB irradiation.

BACKGROUND: Rutin, due to its polyphenolic structure, has antioxidant properties and can be used as a cytoprotective compound against UV-induced effects on skin cells. OBJECTIVE: The aim of this study was to examine the effect of rutin on proteomic profile in human skin fibroblasts irradiated with UV dose that induces apoptosis. METHODS: Proteome analysis based on the results obtained by the QExactive OrbiTrap mass spectrometer. RESULTS: Results show that rutin treatment more strongly protects against UVA-induced rather than UVB-induced increases in the total expression of proteins involved in antioxidant (such as SOD, TrxR, and Prxs 1/2) and inflammatory response (e.g., IL-17F, PAK2, and YWHAZ). However, in the case of UVB-irradiated cells, rutin additionally enhances the levels of disulfide-isomerase - an enzyme that is responsible for the formation and breakage of disulfide bonds. Moreover, UVB radiation promotes rutin-Keap1 adduct formation, which leads to the activation of Nrf2, a factor that is responsible for the synthesis of cytoprotective proteins. Furthermore, rutin partially prevents UV-induced apoptosis by restoring the physiological levels of p53, cytochrome c, and cell cycle and apoptosis regulator protein 2 that were increased following irradiation. CONCLUSION: In conclusion, our results show that rutin effectively prevents UV-induced damages associated with proinflammatory and prooxidative activity and protects cells against apoptosis.

Slug inhibition upregulates radiation-induced PUMA activity leading to apoptosis in cholangiocarcinomas.

Resistance of cholangiocarcinoma to irradiation therapy is a major problem in cancer treatment. Slug, a snail family transcription factor, is a suppressor of PUMA (p53 upregulated modulator of apoptosis), which has been shown to be involved in the control of apoptosis. In this study, we investigated whether the modulation of Slug expression, using adeno-associated-virus-mediated transfer of siRNA targeting Slug gene (rAAV2-Slug siRNA), affects cholangiocarcinoma sensitivity to radiation. In the present study, we used rAAV2-Slug siRNA to downregulate the expression of Slug in QBC939 cholangiocarcinoma cell lines in vitro before γ-irradiation. In vivo studies were done with orthotopic cholangiocarcinoma, and radiosensitivity was evaluated both in vitro and in vivo. rAAV2-Slug siRNA transfection resulted in downregulation of the levels of Slug in QBC939 cells. In addition, rAAV2-Slug siRNA, in combination with radiation, increased levels of the PUMA, which contributes to the radiosensitivity of cholangiocarcinomas. Finally, treatment with rAAV2-Slug siRNA plus γ-irradiation completely regressed tumor growth in orthotopic cholangiocarcinomas model. In summary, integrating gene therapy with radiotherapy could have a synergistic effect, thereby improving the survival of patients with cholangiocarcinomas.

XPB induces C1D expression to counteract UV-induced apoptosis.

Although C1D has been shown to be involved in DNA double-strand break repair, how C1D expression was induced and the mechanism(s) by which C1D facilitates DNA repair in mammalian cells remain poorly understood. We and others have previously shown that expression of xeroderma pigmentosum B (XPB) protein efficiently compensated the UV irradiation-sensitive phenotype of 27-1 cells, which lack functional XPB. To further explore XPB-regulated genes that could be involved in UV-induced DNA repair, differential display analysis of mRNA levels from CHO-9, 27-1, and 27-1 complemented with wild-type XPB was done and C1D gene was identified as one of the major genes whose expression was significantly upregulated by restoring XPB function. We found that XPB is essential to induce C1D transcription after UV irradiation. The increase in C1D expression effectively compensates for the UV-induced proteolysis of C1D and thus maintains cellular C1D level to cope with DNA damage inflicted by UV irradiation. We further showed that although insufficient to rescue 27-1 cells from UV-induced apoptosis by itself, C1D facilitates XPB DNA repair through direct interaction with XPB. Our findings provided direct evidence that C1D is associated with DNA repair complex and may promote repair of UV-induced DNA damage.

Identifying apoptosis-evasion proteins/pathways in human hepatoma cells via induction of cellular hormesis by UV irradiation.

Evading apoptosis is pivotal in both of carcinogenesis and resistance to anticancer therapy. We investigated the molecules and pathways of apoptosis evasion in human hepatoma cells by irradiating hepatoma cells with optimized UV (so-called "hormetic responses"). Proteins and pathways related to hormetic responses were identified via proteomic approaches followed by reconstruction of function-networks. Of the 2326 defined protein spots, 42 distinct proteins significantly changed their expression. Eleven hormetic response proteins (HINT1, PHB, CTSD, ANXA1, LGASL1, TPT1, NPM, PRDX2, UCHL1, CERK, and C1QBP) were involved in 5 death-regulatory pathways, including the p53-dependent apoptotic pathway, protein ubiquinization, cellular redox, calcium-mediated signaling pathway, and sphingomyelin-metabolism pathway. Knockdown of HINT1 expression via RNA interference increased tumor cell resistance to apoptosis induction, while silencing NPM, UCHL1, or CERK greatly sensitized tumor cells to apoptosis induction. In conclusion, NPM, UCHL1, and CERK act as apoptosis-evasion proteins that may serve as therapeutic targets for hepatoma. Silencing their expression would increase therapeutic efficacy, thereby reducing the corresponding doses and side-effects of anticancer therapy. This model of induction of cellular hormetic responses to identify apoptosis-evasion molecules/pathways via proteomic approaches can be applied to other modalities of anticancer therapy.

A recombinant MnSOD is radioprotective for normal cells and radiosensitizing for tumor cells.

Organisms exposed to ionizing radiation are mainly damaged by free radicals, which are generated by the radiolysis of water contained in the cells. Recently a significant reduction of tissue injury from irradiation damage was demonstrated by using MnSOD-plasmid/liposome treatments in the protection of murine lung. In this study we show that a new active recombinant human MnSOD (rMnSOD), easily administered in vivo, not only exerts the same radioprotective effect on normal cells and organisms as any MnSOD, but it is also radiosensitizing for tumor cells. In addition, we show how healthy animals, exposed to lethal doses of ionizing radiation and daily injections with rMnSOD, were protected from radiodamage and were still alive 30 days after the irradiation, while animals treated with only PBS solution, in the absence of rMnSOD, died after 7-8 days from the radiotreatments. The molecular analysis of all irradiated tissues revealed that the antiapoptotic AVEN gene appeared activated only in the animals treated in the presence of rMnSOD. The data suggest that rMnSOD deserves to be considered as a pharmaceutical tool for making radiotherapy more selective on cancer cells and to prevent and/or cure the accidental damage derived from exposure to ionizing radiation.

Effect of 6mT static magnetic field on the bcl-2, bax, p53 and hsp70 expression in freshly isolated and in vitro aged human lymphocytes.

An increasing number of evidence indicates that static magnetic fields (SMFs) are capable of altering apoptosis, mainly through modulation of Ca(2+) influx. Here we present data that suggest apoptotic-related gene expression as an alternative pathway, through which exposure to 6milliTesla (mT) SMF can interfere with apoptosis. Exposure to 6mT SMF affects the apoptotic rate (spontaneous and drug-induced) and [Ca(2+)](i) in isolated human lymphocytes; the aged cells are more susceptible to exposure than fresh ones. The exposure to 6mT exerted a protective effect on chemical or physical-induced apoptosis, irrespective of the age of the cells. The investigation of the gene expression of bcl-2, bax, p53 and hsp70 in freshly isolated and in culture-aged human lymphocytes indicates that these genes are modulated by SMF exposure in the experimental conditions used, in a gene-, age- and time-dependent manner. The exposure of isolated lymphocytes to SMF for up to 24h modulated increased bax and p53 and decreased hsp70, and bcl-2. The amount of increment and/or decrement of the proteins varied for each gene examined and was independent of the apoptotic inducers. Finally, the same stress applied to freshly isolated or aged lymphocytes resulted in different modulation of bcl-2, bax and hsp70.

p53 Binding to the p21 promoter is dependent on the nature of DNA damage.

p53 Is a tumor suppressor that integrates signals from different stress induced signalling pathways, regulates cell cycle arrest, senescence, apoptosis and DNA repair. How p53 dictates cell fate is unclear. As a major transcriptional target of p53 in response to cellular stress, p21 is a key component in cell cycle control and apoptosis, directing an anti-apoptotic response following DNA damage. It is therefore likely that p53-dependent regulation of p21 contributes, at least in part, how p53 influences cellular outcome upon DNA damage. Here we compare the p53-dependent transcriptional regulation of p21 in response to DNA damage by ultraviolet (UV) radiation and ionizing radiation (IR). We demonstrate that despite comparable levels of p53 accumulation by both types of DNA damage, IR causes significant, early accumulation of p21 not seen in UV-damaged cells, with a substantially different cell cycle profile. Whereas UV and IR both target p21 protein for degradation immediately after DNA damage, differential post-damage p21 transcription is accountable for the disparity in p21 protein levels. Chromatin immunoprecipitation studies reveal that p53 displays a clear bias against the p21 promoter in UV-damaged cells compared to IR-damaged cells. We note differential post-translational modifications of nuclear p53 between UV and IR treatment. Furthermore we demonstrate that this disparity correlated with reduced histone acetylation on the TATA box within the p21 promoter following UV treatment. This suggests that the nature of DNA damage enables p53 to selectively discriminate between promoters in the induction of target genes, thereby regulating their expression and subsequent cellular outcome.

Puma: mauling the intestinal crypt.

Cancer therapies utilizing chemotherapy or radiotherapy are constrained by risk of intestinal stem cell death. In this issue of Cell Stem Cell, Qiu et al. report that Puma deletion prevents intestinal degeneration following DNA damage, thus offering a target protein for the design of enhanced cancer treatments.

Orally administered epigallocatechin gallate attenuates light-induced photoreceptor damage.

EGCG, a major component of green tea, has a number of properties which includes it being a powerful antioxidant. The purpose of this investigation was to deduce whether inclusion of EGCG in the drinking water of albino rats attenuates the effect of a light insult (2200lx, for 24h) to the retina. TUNEL-positive cells were detected in the outer nuclear layer of the retina, indicating the efficacy of the light insult in inducing photoreceptor degeneration. Moreover, Ret-P1 and the mRNA for rhodopsin located at photoreceptors were also significantly reduced as well as the amplitude of both the a- and b-waves of the electroretinogram was also reduced showing that photoreceptors in particular are affected by light. An increase in protein/mRNA of GFAP located primarily to Müller cells caused by light shows that other retinal components are also influenced by the light insult. However, antigens associated with bipolar (alpha-PKC), ganglion (Thy-1) and amacrine (GABA) cells, in contrast, appeared unaffected. The light insult also caused a change in the content of various proteins (caspase-3, caspase-8, PARP, Bad, and Bcl-2) involved in apoptosis. A number of the changes to the retina caused by a light insult were significantly attenuated when EGCG was in the drinking water. The reduction of the a- and b-waves and photoreceptor specific mRNAs/protein caused by light were significantly less. In addition, EGCG attenuated the changes caused by light to certain apoptotic proteins (especially at after 2 days) but did not appear to significantly influence the light-induced up-regulation of GFAP protein/mRNA. It is concluded that orally administered EGCG blunts the detrimental effect of light to the retina of albino rats where the photoreceptors are primarily affected.

5-Aminolevulinic acid-based photodynamic therapy suppressed survival factors and activated proteases for apoptosis in human glioblastoma U87MG cells.

Glioblastoma is the most common astrocytic brain tumor in humans. Current therapies for this malignancy are mostly ineffective. Photodynamic therapy (PDT), an exciting treatment strategy based on activation of a photosensitizer, has not yet been extensively explored for treating glioblastoma. We used 5-aminolevulinic acid (5-ALA) as a photosensitizer for PDT to induce apoptosis in human malignant glioblastoma U87MG cells and to understand the underlying molecular mechanisms. Trypan blue dye exclusion test showed a decrease in cell viability after exposure to increasing doses of 5-ALA for 4h followed by PDT with a broad spectrum blue light (400-550 nm) at a dose of 18J/cm(2) for 1h and then incubation at 37 degrees C for 4h. Following 0.5 and 1mM 5-ALA-based PDT (5-ALA-PDT), Wright staining and ApopTag assay showed occurrence of apoptosis morphologically and biochemically, respectively. After 5-ALA-PDT, down regulation of nuclear factor kappa B (NFkappaB) and baculovirus inhibitor-of-apoptosis repeat containing-3 (BIRC-3) protein indicated inhibition of survival signals. Besides, 5-ALA-PDT caused increase in Bax:Bcl-2 ratio and mitochondrial release of cytochrome c and apoptosis-inducing factor (AIF). Activation of calpain, caspase-9, and caspase-3 occurred in course of apoptosis. Calpain and caspase-3 activities cleaved alpha-spectrin at specific sites generating 145kD spectrin breakdown product (SBDP) and 120kD SBDP, respectively. The results suggested that 5-ALA-PDT induced apoptosis in U87MG cells by suppression of survival signals and activation of proteolytic pathways. Thus, 5-ALA-PDT can be an effective strategy for inducing apoptosis in glioblastoma.

Switch between apoptosis and autophagy: radiation-induced endoplasmic reticulum stress?

The induction of cell death by radiation has largely been attributed to pro-apoptotic mechanisms. Autophagy, an alternative form of programmed cell death, has recently been shown to contribute significantly to anti-neoplastic effects of radiation therapy. In light of this, ER stress has been shown to trigger both apoptosis and autophagy, and act as an important mediator linking the two programmed cell death pathways. Recent data reveal that ER stress leads to activation of autophagosome formation with LC3 conversion via either PERK-eIF2a pathway or IRE1-JNK pathway. In this focused review, we summarize the main molecular mediators that control cellular "switches" between apoptosis and autophagy pathways by utilizing radiation therapy as a model.