Nf-kappa B: an important transcription factor in photobiology

Antitumor effects and potential mechanisms of aconitine based on preclinical studies: an updated systematic review and meta-analysis

Background: Herbs originating from the Aconitum L. (Ranunculaceae), such as Aconitum carmichaelii Debeaux. (Wutou), Aconitum pendulum Busch. (Tiebangchui), and Aconitum kusnezoffii Reichb. (Caowu), etc. are highly valued for their medicinal properties. The roots and tubers of these herbs are commonly used to treat an array of ailments, including joint pain and tumors. The alkaloids present in them are the primary active components, with aconitine being the most notable. Aconitine has gained attention for its exceptional anti-inflammatory and analgesic properties, as well as its potential as an anti-tumor and cardiotonic agent. However, the exact process through which aconitine hinders the growth of cancerous cells and triggers their programmed cell death remains unclear. Therefore, we have undertaken a comprehensive systematic review and meta-analysis of the current research on the potential antitumor properties of aconitine. Methods: We conducted a thorough search of relevant preclinical studies in databases including PubMed, Web of Science, VIP, WanFang Data, CNKI, Embase, Cochrane Library, and National Center for Biotechnology Information (NCBI). The search was conducted up until 15 September 2022, and the data were statistically analyzed using RevMan 5.4 software. The number of tumor cell value-added, tumor cell apoptosis rate, thymus index (TI), and Bcl-2 gene expression level were the main indicators to be analyzed. Results: After applying the final inclusion criteria, a total of thirty-seven studies, comprising both in vivo and in vitro research were analyzed. The results showed that treatment with aconitine led to a significant reduction in tumor cell proliferation, a noteworthy increase in the rate of apoptosis among tumor cells, a decrease in the thymus index, and a reduction in the expression level of Bcl-2. These results suggested that aconitine could inhibit the proliferation, invasion, and migration abilities of tumor cells by regulating Bcl-2 etc., thereby enhancing the anti-tumor effects. Conclusion: In summary, our present study demonstrated that aconitine effectively reduced tumor size and volume, indicating a strong anti-tumor effect. Additionally, aconitine could increase the expression levels of caspase-3, Bax and other targets. Mechanistically, it may regulate the expression levels of Bax and Bcl-2 through the NF-κB signaling pathway, ultimately inhibiting tumor cell proliferation through autophagy.

A randomized, controlled, feasibility study of RD-X19 in subjects with mild-to-moderate COVID-19 in the outpatient setting

The RD-X19 is an investigational, handheld medical device precisely engineered to emit blue light through the oral cavity to target the oropharynx and surrounding tissues. At doses shown to be non-cytotoxic in an in vitro 3-dimensional human epithelial tissue model, the monochromatic visible light delivered by RD-X19 results in light-initiated expression of immune stimulating cytokines IL-1α and IL-1β, with corresponding inhibition of SARS-CoV-2 replication. A single exposure of 425 nm blue light at 60 J/cm² led to >99% reductions against all SARS-CoV-2 strains tested in vitro, including the more transmissible (Alpha) and immune evasive (Beta) variants. These preclinical findings along with other studies led to a randomized, double-blind, sham-controlled early feasibility study using the investigational device as a treatment for outpatients with mild to moderate COVID-19. The study enrolled 31 subjects with a positive SARS-CoV-2 antigen test and at least two moderate COVID-19 signs and symptoms at baseline. Subjects were randomized 2:1 (RD-X19: sham) and treated twice daily for four days. Efficacy outcome measures included assessments of SARS-CoV-2 saliva viral load and clinical assessments of COVID-19. There were no local application site reactions and no device-related adverse events. At the end of study (Day 8), the mean change in log₁₀ viral load was -3.29 for RD-X19 and -1.81 for sham, demonstrating a treatment benefit of -1.48 logs [95% confidence internal (CI), -2.88 to -0.071, nominal p=0.040]. Among the clinical outcome measures, differences between RD-X19 and sham were also observed, with a 57-hour reduction of median time to sustained resolution of COVID-19 signs and symptoms (log rank test, nominal p=0.044).

Protection against UVB-induced damages in human dermal fibroblasts: efficacy of tricin isolated from enzyme-treated Zizania latifolia extract

This study was undertaken to determine the effects of enzyme-treated Zizania latifolia (ETZL) and of its major compound tricin on skin photo-aging and to investigate the mechanisms involved. It was found ETZL and tricin suppressed matrix metalloproteinase (MMP) production and increased type I-procollagen production in UVB-irradiated human dermal fibroblasts (HDFs). Furthermore, ETZL and tricin significantly up-regulated the expressions of the antioxidant enzymes HO-1 and SOD1, reduced UVB-induced reactive oxygen species (ROS) generation and mitogen-activated protein kinase (MAPK) induction by ROS and thereby attenuated activator protein-1 (AP-1) expression. In addition, ETZL and tricin both reduced the phosphorylations of IκBα and IKKα/ß and κB blocked the nuclear translocation of nuclear factor-κB (NF-κB) p65. These results show that ETZL have skin protective effects against UVB and suggest tricin as major efficacious material in ETZL protecting skin photoaging.

Cell Type-Specific Roles of NF-κB Linking Inflammation and Thrombosis

The transcription factor NF-κB is a central mediator of inflammation with multiple links to thrombotic processes. In this review, we focus on the role of NF-κB signaling in cell types within the vasculature and the circulation that are involved in thrombo-inflammatory processes. All these cells express NF-κB, which mediates important functions in cellular interactions, cell survival and differentiation, as well as expression of cytokines, chemokines, and coagulation factors. Even platelets, as anucleated cells, contain NF-κB family members and their corresponding signaling molecules, which are involved in platelet activation, as well as secondary feedback circuits. The response of endothelial cells to inflammation and NF-κB activation is characterized by the induction of adhesion molecules promoting binding and transmigration of leukocytes, while simultaneously increasing their thrombogenic potential. Paracrine signaling from endothelial cells activates NF-κB in vascular smooth muscle cells and causes a phenotypic switch to a “synthetic” state associated with a decrease in contractile proteins. Monocytes react to inflammatory situations with enforced expression of tissue factor and after differentiation to macrophages with altered polarization. Neutrophils respond with an extension of their life span—and upon full activation they can expel their DNA thereby forming so-called neutrophil extracellular traps (NETs), which exert antibacterial functions, but also induce a strong coagulatory response. This may cause formation of microthrombi that are important for the immobilization of pathogens, a process designated as immunothrombosis. However, deregulation of the complex cellular links between inflammation and thrombosis by unrestrained NET formation or the loss of the endothelial layer due to mechanical rupture or erosion can result in rapid activation and aggregation of platelets and the manifestation of thrombo-inflammatory diseases. Sepsis is an important example of such a disorder caused by a dysregulated host response to infection finally leading to severe coagulopathies. NF-κB is critically involved in these pathophysiological processes as it induces both inflammatory and thrombotic responses.

Modulation of photochemical damage in normal and malignant cells by naturally occurring compounds

Certain phytochemicals, such as the stilbene, resveratrol (RES, found in red grapes and berries), and the triterpenoid, ursolic acid (UA, found in waxy berries and herbs such as rosemary and oregano), have antioxidant, anti-inflammatory and antiproliferative effects. Two human-derived cell lines, hTERT-RPE with a nonmalignant phenotype derived from retinal pigment epithelium, and ATCC CRL-11147 derived from a malignant skin melanoma, were used as in vitro models of photooxidative stress produced by exposure to the broadband output of a 150 W Hg vapor arc lamp at an irradiance of 19-26 mW cm(-2). In untreated cells, UV-VIS broadband light exposure produced a loss of proliferative ability, an activation of NF-κB and an increase in protein carbonyl adducts at 24 h postexposure. Pretreatment of the cells with RES or UA at 1-2 μmsignificantly reduced the amount of phosphorylated NF-κB at 24 h postexposure. RES pretreatment reduced the burden of light-induced protein carbonyl adducts by up to 25% in exposed cells. UA treatment markedly increased the sensitivity of melanoma cells to UV radiation, while conferring some photoprotection to RPE cells. These observations indicate that phytochemicals modulate the cellular response to photochemical stress by interacting with specific cell-signaling pathways.

Effect of NF-κB inhibitors on the chemotherapy-induced apoptosis of the colon cancer cell line HT-29

This study aimed to investigate the impact of the combined use of the nuclear factor-κB (NF-κB) inhibitors pyrrolidine dithiocarbamate (PDTC), bortezomib or SN50, and the chemotherapy agents arsenic acid (As₂O₃), fluorouracil (5FU), oxaliplatin or paclitaxel on the growth and apoptosis of HT-29 cells. Cell morphology was observed using inverted microscopy, and cell viability and apoptosis were assessed using the MTT assay and flow cytometry, respectively. The activities of NF-κB were analyzed by western blotting and electrophoretic mobility shift assay (EMSA). Cell growth was significantly inhibited by As₂O₃, oxaliplatin and paclitaxel in a time- and concentration-dependent manner (P<0.05), while 5FU inhibited cell growth in a time-dependent manner only (P<0.05). The growth inhibition rate and apoptosis induction ratio were increased following the combined treatment of the chemotherapy agent and NF-κB inhibitor. The expression of NF-κB p65 was upregulated when cells were treated with a chemotherapy drug, however it was downregulated following combined treatment or treatment with an NF-κB inhibitor alone. In conclusion, an NF-κB inhibitor combined with a chemotherapy drug effectively inhibited cell proliferation, induced cell apoptosis and inhibited NF-κB activity to enhance the chemotherapeutic sensitivity of HT-29 cells.

Uncaria rhynchophylla and Rhynchophylline Inhibit c-Jun N-Terminal Kinase Phosphorylation and Nuclear Factor-κB Activity in Kainic Acid-Treated Rats

Our previous studies have shown that Uncaria rhynchophylla (UR) can reduce epileptic seizures. We hypothesized that UR and its major component rhynchophylline (RH), reduce epileptic seizures in rats treated with kainic acid (KA) by inhibiting nuclear factor-κB (NF-κB) and activator-protein-1 (AP-1) activity, and by eliminating superoxide anions. Therefore, the level of superoxide anions and the DNA binding activities of NF-κB and AP-1 were measured. Sprague-Dawley (SD) rats were pre-treated with UR (1.0 g/kg, i.p.), RH (0.25 mg/kg, i.p.), or valproic acid (VA, 250 mg/kg, i.p.) for 3 days and then KA was administered intra-peritoneal (i.p.). The results indicated that UR, RH, and VA can reduce epileptic seizures and the level of superoxide anions in the blood. Furthermore, KA was demonstrated to induce the DNA binding activities of NF-κB and AP-1. However, these inductions were inhibited by pre-treatment with UR, RH, or VA for 3 days. Moreover, UR and RH were shown to be involved in the suppression of c-Jun N-terminal kinase (JNK) phosphorylation. This study suggested that UR and RH have antiepileptic effects in KA-induced seizures and are associated with the regulation of the innate immune system via a reduction in the level of superoxide anions, JNK phosphorylation, and NF-κB activation.

Photodynamic therapy in immune (non-oncological) disorders: focus on benzoporphyrin derivatives

This review examines the efficacy of photodynamic therapy in the treatment of immunological disorders. Photodynamic therapy (PDT) is a 2-step procedure. Firstly, a photosensitiser is introduced into the body, where it accumulates selectively in cells with elevated metabolism, such as cancer cells or activated cells of the immune system. Second, light is applied at a wavelength that excites the photosensitiser, producing a variety of short-lived oxygen-derived species. The effect is dependent on the doses of both photosensitiser and activating light. The mechanisms of action of PDT are multifactorial. Induction of high levels of oxidative stress results in necrotic cell death, while lower intensity oxidative stress initiates apoptosis. Sublethal doses may result in the modification of cell surface receptor expression levels and cytokine release and consequently influence cell behaviour. Immunomodulatory PDT (IPDT) utilises mainly apoptotic and sublethal doses. The studies reported here utilise verteporfin, a benzoporphyrin-derived chlorin-like photosensitiser. Veteporfin is a second generation photosensitiser, displaying rapid clearance and consequently a reduced period of skin photosensitivity compared with the first generation photosensitiser, porfimer sodium. In vivo studies showed that IPDT was effective in alleviating immunopathology in murine models of arthritis, contact hypersensitivity, experimental allergic encephalomyelitis and retention of allogeneic skin grafts. Based on these findings, early stage clinical trials with IPDT were initiated recently for the treatment of psoriasis, psoriatic arthritis and rheumatoid arthritis. While verteporfin has been the photosensitiser which pioneered IPDT, a new benzoporphyrin derivative photosensitiser, QLT0074, is under development. This has demonstrated an enhanced avidity for target cells as well as improved clearance characteristics.

A UV-responsive internal ribosome entry site enhances serine hydroxymethyltransferase 1 expression for DNA damage repair

Thymidine nucleotides are required for faithful DNA synthesis and repair, and their de novo biosynthesis is regulated by serine hydroxymethyltransferase 1 (SHMT1). The SHMT1 transcript contains a heavy chain ferritin, heterogeneous nuclear ribonucleoprotein H2, and CUG-binding protein 1-responsive internal ribosome entry site (IRES) that regulates SHMT1 translation. In this study a non-lethal dose of UVC is shown to increase SHMT1 IRES activity and protein levels in four different cell lines. The mechanism for the UV-induced activation of the SHMT1 IRES involves an increase in heavy chain ferritin and heterogeneous nuclear ribonucleoprotein H2 expression and the translocation of CUG-binding protein 1 from the nucleus to the cytoplasm. The UV-induced increase in SHMT1 translation is accompanied by an increase in the small ubiquitin-like modifier-dependent nuclear localization of the de novo thymidylate biosynthesis pathway and a decrease in DNA strand breaks, indicating a role for SHMT1 and nuclear folate metabolism in DNA repair.

A Polypodium leucotomos extract inhibits solar-simulated radiation-induced TNF-alpha and iNOS expression, transcriptional activation and apoptosis

In this report, we have examined the molecular basis of the photoprotective effect of a hydrophilic extract of the fern Polypodium leucotomos (PL) in vitro, using a solar simulator as the source of UV radiation (SSR). We found that pretreatment of human keratinocytes with PL inhibited SSR-mediated increase of tumor necrosis factor (TNF)-alpha and also abrogated nitric oxide (NO) production. Consistent with this, PL blocked the induction of inducible nitric oxide synthase (iNOS) elicited by SSR. In addition, PL inhibited the SSR-mediated transcriptional activation of NF-kappaB and AP1. Finally, we demonstrated that pretreatment with PL exerted a cytoprotective effect against SSR-induced damage, resulting in increased cell survival. Together, these data postulate a multifactor mechanism of protection not exclusively reliant on the antioxidant capability of PL, and strengthen the basic knowledge on the photoprotective effect of this botanical agent.

Visible light regulates neurite outgrowth of nerve cells

The neurite outgrowth of PC12 cells on collagen-coated glass plates under light emitting diode (LED) irradiation at several wavelengths (i.e., 455, 470, 525, 600, 630, 880 and 945 nm) was investigated. No neurite outgrowth was observed during cultivation under irradiation from the lamp of an inverted light microscope through filters (yielding mixed light at ca. 525 nm and more than 800 nm), whereas neurite outgrowth was observed during cultivation in the dark. When these cells were irradiated with monochromatic LED light, neurite outgrowth was slightly, but not completely, suppressed at 455, 525, 600, 630, 880 and 945 nm, as was observed in the case of mixed light. Long connected neuronal outgrowths (e.g., 3 mm length) were observed with LED light at 470 nm and 1.8 mW/cm(2) intensity. No such outgrowths were observed at other LED light wavelengths (i.e., 455, 525, 600, 630, 880 and 945 nm). Irradiation at 470 nm may have caused specific responses to transductional signals in these cells that led to the connection of neuronal outgrowths between cells. Not only suppressed neurite outgrowth but also long connected neurite outgrowths were observed when PC12 cells were cultured under several different wavelengths of light.

Detection of UV-induced activation of NF-kappaB in a recombinant human cell line by means of Enhanced Green Fluorescent Protein (EGFP)

The cellular protection reaction known as ultraviolet (UV) response leads to increased transcription of several genes. Parts of this transcriptional response are transmitted via activation of the Nuclear factor kappaB (NF-kappaB). The contribution of different UV radiation qualities to this process is not yet known. In a previous work, a stably transfected human cell line was developed which indicates activation of the NF-kappaB pathway by fluorescence of the reporters Enhanced Green Fluorescent Protein (EGFP) and its destabilized variant (d2EGFP) thereby allowing a fast and reliable monitoring of UV effects on the NF-kappaB pathway. Cells were exposed to a mercury low-pressure lamp or to simulated sunlight of different wavelength ranges and subjected to flow cytometric analysis after different post-irradiation periods. Growth capacity of cells after UV irradiation was quantified using a luminance measurement of crystal violet stained cell layers. In contrast to UVC and UVB, UVA radiation induced d2EGFP expression and NF-kappaB activation in a non-cytotoxic dose range. These results show that NF-kappaB plays a role in the UVA-induced gene activation in a non-cytotoxic dose range in a human epithelial cell line.

Ultraviolet B light stimulates interleukin-20 expression by human epithelial keratinocytes

The proinflammatory cytokine interleukin-20 (IL-20) may exert the majority of its activity in the skin. We examined the effect of various treatments including several forms of phototherapy on IL-20 expression using cultured normal human epithelial keratinocytes (NHEK). Broadband UVB light, recombinant (r) IL-1 and rIL-8 increased, while hydrocortisone reduced, NHEK supernatant IL-20 levels. Elevation of NHEK IL-20 mRNA and maximal supernatant IL-20 levels occurred with a UVB light dose (40 mJ cm(-2)) that reduced cell viability by approximately 50%. While this UVB light dose also elevated supernatant IL-1 alpha and IL-8 levels, antibody neutralization studies indicated that neither of these cytokines was directly responsible for this increase in IL-20 expression. However, the elevation in IL-20 levels was fully inhibited by the p38 mitogen-activated protein kinase (MAPK) inhibitor SB-203580, suggesting involvement of this stress signaling pathway in this UVB light response. Photodynamic therapy (PDT) with the photosensitizer lemuteporfin, UVA light, cisplatin, lipopolysaccharide (LPS), tumor necrosis factor-alpha (TNF-alpha) or recombinant interferon-gamma (rIFN-gamma) either had little effect or decreased NHEK supernatant IL-20 levels. Reduced IL-20 levels paralleled the cytotoxic actions of PDT, UVA light or cisplatin and the antiproliferative effect of rIFN-gamma. Neither rIL-20 supplementation nor anti-IL-20 antibody treatments affected cell viability indicating that soluble IL-20 did not affect the short-term survival of UVB light-irradiated NHEK. Stimulation of IL-20 expression in keratinocytes by UVB light suggests that this cytokine might participate in skin responses to this ever-present environmental factor and potentially has a role in UV light-associated dermatoses.

Calcium/calmodulin-dependent protein kinases as potential targets in cancer therapy

In this review the authors discuss the expression and activation of a family of protein kinases known as the calcium/calmodulin-dependent kinases (CaM-kinase) and the role that these kinases have in the activation of antiapoptotic signalling pathways. In addition, the authors outline a novel mechanism of activation of these kinases by oxidative stress. Founded on this novel mechanism of activation and the role that these kinases have in activating antiapoptotic signalling pathways, the authors propose that the CaM-kinases would make very good targets for sensitising cancer cells to certain therapeutic treatments. Furthermore, the authors discuss the role that these kinases have in cell transformation and in the regulation of the cell cycle. Based on these roles the authors suggest that inhibition of the CaM-kinases not only has the potential to sensitise cancer cells, but also has the potential to induce cytostasis in these cells.

Poly (ADP-ribose) polymerase inhibitor 3-aminobenzamide rescues N-methyl-N-nitrosourea-induced photoreceptor cell apoptosis in Sprague-Dawley rats through preservation of nuclear factor-kappaB activity

The activation of poly (ADP-ribose) polymerase (PARP) plays a pivotal role in mediating N-methyl-N-nitrosourea (MNU)-induced photoreceptor cell apoptosis. We examined the retinoprotective effects of the PARP inhibitor 3-aminobenzamide (3-AB) against MNU-induced retinal damage in relation to dose and timing of prescription, and the involvement of the transcription factor nuclear factor (NF)-kappaB. Female Sprague-Dawley rats were intraperitoneally injected with 60 mg/kg MNU at 50 days of age, and were then immediately given a subcutaneous injection of 0, 1, 5, 10, 30 or 50 mg/kg of 3-AB, or were injected with 50 mg/kg 3-AB 12h before, concurrently, or 4, 6 or 12h after MNU. Rats were killed 3 and 7 days after MNU, and MNU-treated and 3-AB-injected retinas were compared with MNU-untreated control retinas or MNU-treated/3-AB-uninjected retinas. Apoptosis in photoreceptor cells was detected by performing formamide-induced DNA denaturation and staining with anti-single-stranded DNA antibody. Retinal morphologies were compared and evaluated morphometrically using the photoreceptor cell ratio and retinal damage ratio as indices to evaluate the efficacy of 3-AB. We examined expression of the phosphorylated form of NF-kappaB and IkappaBalpha (p-NF-kappaB and p-IkappaBalpha, respectively) in retinas of MNU-treated rats concurrently treated with or without 50mg/kg 3-AB, compared with MNU-untreated control retinas. 3-AB dose-dependently suppressed photoreceptor cell apoptosis: 50mg/kg 3-AB injected concurrently with MNU completely rescued photoreceptor cell damage; 30 mg/kg 3-AB significantly reduced photoreceptor cell damage; 10 mg/kg 3-AB tended to suppress photoreceptor cell damage; <or=5mg/kg 3-AB was ineffective. When 50mg/kg 3-AB was injected 12h before or >or=4h after MNU, it did not exert a retinoprotective effect. p-NF-kappaB levels of MNU-treated rat retinas were significantly lower than those of MNU-untreated control retinas, while 50 mg/kg 3-AB injected concurrently with MNU preserved the p-NF-kappaB levels; p-IkappaBalpha levels tended to decrease after MNU injection, compared with untreated control retinas, but the difference was not significant. Thus, 3-AB dose-dependently suppressed MNU-induced retinal damage, and 50mg/kg 3-AB injected concurrently with MNU completely rescued photoreceptor cell apoptosis via preservation of NF-kappaB activity.

The enhanced monocyte adhesiveness after UVB exposure requires ROS and NF-kappaB signaling in human keratinocyte

The infiltration of both monocyte and activated T cells in the skin is one of critical steps in the development of UVB-induced inflammation. Upregulation of adhesion molecules such as intercellular adhesion molecule 1 (ICAM-1) on the surface of keratinocytes plays an important role in this process. In this study, we examined the molecular mechanism responsible for UVB-induced expression of ICAM-1 and subsequent monocyte adhesion by keratinocyte. We observed that (1) UVB induced protein and mRNA expression of ICAM-1 in a dose- and time-dependent manner in human keratinocyte cell HaCaT; (2) UVB induced the translocation of NF-kappaB and inhibition of NF-kappaB by NF-kappaB inhibitors suppressed UVB-induced mRNA and protein expression of ICAM-1; (3) UVB increased the intracellular level of reactive oxygen species (ROS) by HaCaT cells; (4) UVB-induced increase of intracellular ROS level was suppressed by pretreatment with diphenyl iodonium (DPI) and N-acetyl cysteine (NAC); and (5) inhibition of UVB-induced ROS production by DPI or NAC suppressed UVB-mediated translocation of NF-kappaB, expression of ICAM-1 and subsequent monocyte adhesion in HaCaT cells. These results suggest that UVB-induced ROS is involved in the translocation of NF-kappaB which is responsible for expression of ICAM-1 and subsequent increased monocyte adhesion in human keratinocyte.

Epidermal growth factor receptor is a critical mediator of ultraviolet B irradiation-induced signal transduction in immortalized human keratinocyte HaCaT cells

Epidermal growth factor receptor (EGFR) is a critical mediator of several types of epithelial cancers. Skin cancer arising from exposure to ultraviolet B irradiation (UVB) from the sun is a prominent form of human cancer. Recent data indicate that in addition to cognate ligands, EGFR is activated by UVB irradiation. We used pharmacological and genetic approaches to investigate the function of EGFR in mediating UVB-induced signal transduction in human skin keratinocyte HaCaT cells. Pharmacological inhibition of EGFR tyrosine kinase significantly inhibited UVB-mediated induction of ERK, p38, and JNK MAP kinases, and their effectors, transcription factors c-Fos and c-Jun. Inhibition of UVB activation of EGFR also suppressed activation of AKT-, PKC-, and PKA-dependent signal transduction pathways. B82 mouse L cells devoid of EGFR were used to further investigate EGFR dependence of UVB-induced signal transduction. UVB failed to induce ERK, and JNK activation was reduced 60% in B82 cells compared to B82K+ cells, which express EGFR. In addition, UVB induced both c-Fos and c-Jun proteins in B82K+ cells, whereas neither were induced in B82 cells. Taken together, these data demonstrate that EGFR is required for UVB-mediated induction of multiple signaling pathways that are known to mediate tumor formation in skin.

The ubiquitin-proteasome system at the crossroads of stress-response and ageing pathways: a handle for skin care?

The regulation of gene expression at the transcriptional level has been considered for long as the main mechanism of cellular adaptive responses. Since the turn of the century, however, it is becoming clear that higher organisms developed a complex, sensitive and maybe equally important network of regulatory pathways, relying largely on protein interactions, post-translational modifications and proteolysis. Here we review the involvement of the ubiquitin-proteasome pathway of protein degradation at different levels of cellular life in relation with ageing, and with a special focus on skin. It comes out that the ubiquitin system plays a major role in signal transduction associated with stress and ageing, in skin in particular through the control of retinoid and NF-kappaB pathways. The understanding of specific proteolytic targeting by E3 ubiquitin-ligases paves the way for a new generation of active molecules that may control particular steps of normal and pathological ageing.

Cellular UV damage responses--functions of tumor suppressor p53

DNA damage, provoked by ultraviolet (UV) radiation, evokes a cellular damage response composed of activation of stress signaling and DNA checkpoint functions. These are translated to responses of replicative arrest, damage repair, and apoptosis aimed at cellular recovery from the damage. p53 tumor suppressor is a central stress response protein, activated by multiple endogenous and environmental insults, including UV radiation. The significance of p53 in the DNA damage responses has frequently been reviewed in the context of ionizing radiation or other double strand break (DSB)-inducing agents. Despite partly similar patterns, the molecular events following UV radiation are, however, distinct from the responses induced by DSBs and are profoundly coupled with transcriptional stress. These are illustrated, e.g., by the UV damage-specific translocations of Mdm2, promyelocytic leukemia protein, and nucleophosmin and their interactions with p53. In this review, we discuss UV damage-provoked cellular responses and the functions of p53 in damage recovery and cell death.

Tetramethylpyrazine protected photoreceptor cells of rats by modulating nuclear translocation of NF-kappaB

AIM

To evaluate the effect of tetramethylpyrazine (TMP) injection on retinal damage induced by N-methyl-N-nitrosourea (MNU) in rats and on nuclear factor-kappa B (NF-kappaB) family members.

METHODS

Female Sprague-Dawley (SD) rats were randomly divided into groups: (i), control group; (ii), model group; and (iii), TMP-injection groups, in which the rats were subdivided into 40 mg/kg, 80 mg/kg and 160 mg/kg groups. Drugs were injected ip into 47-day-old SD rats once a day. At 50 days of age, all rats in the model group and drug groups also received a single ip injection of 60 mg/kg MNU. Rats in group 1 received ip injection of physiological saline. All rats were killed at different times after MNU or physiological saline treatment. The apoptotic index of photoreceptor cells was calculated by TUNEL labeling; retinal damage was evaluated based on retinal thickness and the expression of NF-kappaB family members was detected by Western blot.

RESULTS

TMP injections, in a dose-dependent manner, suppressed photoreceptor cell apoptosis and decreased its loss in the peripheral retina. As compared with the MNU-treated group, TMP injection at a dose of 160 mg/kg also time-dependently upregulated the NF-kappaB/p65 protein level in the nucleus and downregulated the IkappaBalpha protein level in the cytoplasm. However, no protective effect of TMP injection on MNU-induced central retinal damage was found.

CONCLUSION

TMP injection partially protects against MNU-induced retinal damage by upregulating the nuclear translocation of p65 to inhibit photoreceptor cells apoptosis.

Blue light generates reactive oxygen species (ROS) differentially in tumor vs. normal epithelial cells

OBJECTIVES

Blue light of high intensity is commonly used in dentistry to activate polymerization of resin restorative materials. Other than its effects on the retina, the biological effects of blue light (380-500nm wavelengths) are poorly studied. Limited evidence suggests that blue light acts by forming intracellular reactive oxygen species (ROS) that then affect critical cell functions. If the biological effects of blue light are redox-mediated, antioxidants might be used to mitigate unwanted side effects of blue light during clinical use, or blue light might be used therapeutically to modulate redox-sensitive cell signaling responses.

METHODS

Intracellular ROS were estimated using HFLUOR-DA (dihydrofluorescein diacetate), a vital fluorescein-based, redox-sensitive dye. ROS were measured in normal (NHEK) and oral squamous carcinoma (OSC2) epithelial cells, shown previously to respond differentially to blue light irradiation. Two-hour cumulative levels of ROS and approximate ROS lifetimes were measured after irradiation doses of 5-30 J/cm(2). The blue light-induced generation of ROS was further tested by the ability of the antioxidants N-acetylcysteine (NAC) and vitamin E to mitigate intracellular ROS levels.

RESULTS

Dose-dependent ROS levels were generated in both NHEK and OSC2 cells, but cumulative levels were higher and persisted longer in the OSC2 cells. Both vitamin E and NAC significantly reduced blue-light-induced levels of ROS, but were more effective in the OSC2 cells.

SIGNIFICANCE

The induction of intracellular ROS by blue light implies that redox effects may mediate cellular responses to blue light. This result suggests the opportunity to mitigate any effects of direct or coincident exposure during dental treatment via antioxidants, and the opportunity to exploit differences in redox processing among cells for possible treatment of epithelial cancer or wound healing.

Blue light differentially alters cellular redox properties

Blue light (lambda = 380-500 nm) historically has been used to initiate polymerization of biomaterials and recently has been proposed as a therapeutic agent. New evidence suggests that cell-type-specific responses result from redox changes induced by exposure to blue light. Cultured cells were exposed to defined doses of blue light, equivalent to exposure times of 10 s and 2 min, to achieve energies of 5 J/cm2 and 60 J/cm2, respectively, after which (a) viable cell number, (b) cellular protein profiles, (c) mitochondrial succinate dehydrogenase (SDH) activity, (d) total reactive oxygen species (ROS), and (e) induction of apoptosis were compared to that of nonexposed control cultures. Results showed that blue-light exposure arrested monocyte cell growth and increased levels of peroxiredoxins. SDH activity of normal epidermal keratinocytes (NHEK) was slightly enhanced by blue light, whereas identical treatment of OSC2 oral tumor cells resulted in significant suppression of SDH activity. Blue-light exposure generally induced higher levels of total ROS in OSC2 cells than in NHEK. Finally, only OSC2 cells exhibited signs of apoptosis via Annexin V staining following exposure to blue light. These data support the central hypothesis that blue light induces an oxidative stress response in cultured cells resulting in cell-type-specific survival outcomes. The identification of oxidative stress as a mediator of the effects of blue light is a critical first step in defining its biological risks and therapeutic opportunities.

Molecular characterization of two CuZn-superoxide dismutases in a sea anemone

Cnidarians living in symbiosis with photosynthetic cells--called zooxanthellae--are submitted to high oxygen levels generated by photosynthesis. To cope with this hyperoxic state, symbiotic cnidarians present a high diversity of superoxide dismutases (SOD) isoforms. To understand better the mechanism of resistance of cnidarian hosts to hyperoxia, we studied copper- and zinc-containing SOD (CuZnSOD) from Anemonia viridis, a temperate symbiotic sea anemone. We cloned two CuZnSOD genes that we call AvCuZnSODa and AvCuZnSODb. Their molecular analysis suggests that the AvCuZnSODa transcript encodes an extracellular form of CuZnSOD, whereas the AvCuZnSODb transcript encodes an intracellular form. Using in situ hybridization, we showed that both AvCuZnSODa and AvCuZnSODb transcripts are expressed in the endodermal and ectodermal cells of the sea anemone, but not in the zooxanthellae. The genomic flanking sequences of AvCuZnSODa and AvCuZnSODb revealed different putative binding sites for transcription factors, suggesting different modes of regulation for the two genes. This study represents a first step in the understanding of the molecular mechanisms of host animal resistance to permanent hyperoxia status resulting from the photosynthetic symbiosis. Moreover, AvCuZnSODa and AvCuZnSODb are the first SODs cloned from a diploblastic animal, contributing to the evolutionary understanding of SODs.

Role for retinoblastoma protein family members in UV-enhanced expression from the human cytomegalovirus immediate early promoters

The expression from a reporter construct driven by a cytomegalovirus (CMV) immediate early (IE) promoter is strongly inducible by UV in human fibroblasts. This response is induced at lower UV fluences in transcription-coupled repair (TCR)-deficient fibroblasts compared with normal fibroblasts and is absent in their simian virus 40-transformed counterparts. In this study we demonstrate that expression of human papilloma virus (HPV) E7 (but not of HPV E6) can attenuate UV-induced expression from the human CMV-IE-driven reporter construct in human fibroblasts. Furthermore, UV-induced expression from the reporter construct appears impaired in murine fibroblasts harboring inactivating mutations in the retinoblastoma (Rb) gene family members p107 and pRb but not in fibroblasts harboring such mutations in the p53 gene. Taken together, these data suggest that one or more members of the pRb family (but not p53) play an essential role in mediating UV-induced expression from the CMV-IE promoter. In this study we report normal UV-upregulation of reporter expression in xeroderma pigmentosum (XP) group E fibroblasts, consistent with normal TCR. Because XP-E cells deficient in the p48 subunit of the damaged DNA-binding protein are impaired in E2F-1-activated transcription, these results also suggest that the (pRb-regulated) transcription factor E2F-1 does not play an essential role in UV-enhanced expression from the CMV-IE promoter.

Downregulation of NF-kappaB activation in human keratinocytes by melanogenic inhibitors

BACKGROUND

Exposure of skin cells, particularly keratinocytes to various nuclear factor-kappaB (NF-kappaB) activators (e.g. tumor necrosis factor-alpha, interleukin-1, lipopolysaccharides, and ultraviolet light) leads to phosphorylation and degradation of the inhibitory protein, IkappaB. Liberated NF-kappaB is translocated into the nucleus where it can change or alter expression of target genes, resulting in the secretion of extracellular signaling molecules including melanotrophic factors affecting melanocyte.

OBJECTIVE

In order to demonstrate the possible role of NF-kappaB activation on the synthesis of melanotrophic factors from the keratinocytes, the activities of NF-kappaB induced by melanogenic inhibitors (MIs) were determined in human HaCaT keratinocytes transfected with pNF-kappaB-SEAP-NPT plasmid. Transfectant cells released the secretory alkaline phosphatase (SEAP) as a transcription reporter in response to the NF-kappaB activity and contain the neomycin phosphotransferase (NPT) gene for the dominant selection marker for geneticin resistance.

METHODS

MIs such as niacinamide, kojic acid, hydroquinone, resorcinol, arbutin, and glycolic acid were preincubated with transfectant HaCaT cells for 3 h and then ultraviolet B (UVB) was irradiated. NF-kappaB activation was measured with the SEAP reporter gene assay using a fluorescence detection method.

RESULTS

Of the MIs tested, kojic acid (IC(50)=60 microM) was found to be the most potent inhibitor of UVB-upregulating NF-kappaB activation in transfectant HaCaT cells, which is followed by niacinamide (IC(50)=540 microM). Pretreatment of the transfectant HaCaT cells with the MIs, especially kojic acid and niacinamide, effectively lowered NF-kappaB binding measured by electrophoretic mobility shift assay. Furthermore, these two inhibitors remarkably reduced the secretion level of IL-6, one of melanotrophic factors, triggered by UV-radiation of the HaCaT cells.

CONCLUSION

These observations suggest that MIs working at the in vivo level might act partially through the modulation of the synthesis of melanotrophic factors in keratinocyte.

Prosurvival and antiapoptotic effects of PGE2 in radiation injury are mediated by EP2 receptor in intestine

The biological activities of PGE(2) are mediated through EP receptors (EP(1)-EP(4)), plasma membrane G protein-coupled receptors that differ in ligand binding and signal-transduction pathways. We investigated gastrointestinal EP(2) receptor expression in adult mice before and after radiation injury and evaluated intestinal stem cell survival and crypt epithelial apoptosis after radiation injury in EP(2) null mice. EP(2) was expressed throughout the gut. Intestinal EP(2) mRNA increased fivefold after gamma-irradiation. Crypt survival was diminished in EP(2)-/- mice (4.06 crypts/cross section) compared with wild-type littermates (8.15 crypts/cross section). Radiation-induced apoptosis was significantly increased in EP(2)-/- mice compared with wild-type littermates. Apoptosis was 1.6-fold higher in EP(2) (-/-) mice (5.9 apoptotic cells/crypt) than in wild-type mice (3.5 apoptotic cells/crypt). The EP(2) receptor is expressed in mouse gastrointestinal epithelial cells and is upregulated following radiation injury. The effects of PGE(2) on both crypt epithelial apoptosis and intestinal crypt stem cell survival are mediated through the EP(2) receptor.

Inhibition of ultraviolet B-mediated activation of nuclear factor kappaB in normal human epidermal keratinocytes by green tea Constituent (-)-epigallocatechin-3-gallate

Epigallocatechin-3-gallate (EGCG), the major constituent of green tea, possesses significant anti-inflammatory and cancer chemopreventive properties. Studies have shown the photochemopreventive effects of green tea and EGCG in cell culture, animal models, and human skin. The molecular mechanism(s) of photochemopreventive effects of EGCG are incompletely understood. We recently showed that EGCG treatment of the normal human epidermal keratinocytes (NHEK) inhibits ultraviolet (UV)B-mediated activation of the mitogen-activated protein kinase (MAPK) pathway. In this study, we evaluated the effect of EGCG on UVB-mediated modulation of the nuclear factor kappa B (NF-kappaB) pathway, which is known to play a critical role in a variety of physiological functions and is involved in inflammation and development of cancer. Immunoblot analysis demonstrated that the treatment of NHEK with EGCG (10-40 microM) for 24 h resulted in a significant inhibition of UVB (40 mJ/cm(2))-mediated degradation and phosphorylation of IkappaBalpha and activation of IKKalpha, in a dose-dependent manner. UVB-mediated degradation and phosphorylation of IkappaBalpha and activation of IKKalpha was also observed in a time-dependent protocol (15 and 30 min, 1, 2, 3, 6, 12 h post-UVB exposure). Employing immunoblot analysis, enzyme-linked immunosorbent assay, and gel shift assay, we demonstrate that EGCG treatment of the cells resulted in a significant dose- and time-dependent inhibition of UVB-mediated activation and nuclear translocation of a NF-kappaB/p65. Our data suggest that EGCG protects against the adverse effects of UV radiation via modulations in NF-kappaB pathway, and provide a molecular basis for the photochemopreventive effect of EGCG.

Activation of Poly(adenosine diphosphate–ribose) Polymerase in Mouse Tumors Treated by Photodynamic Therapy¶

Poly(adenosine diphosphate-ribose) polymerase (PARP) has recently been characterized as a key regulator of cell death-survival transcriptional programs associated with stress and inflammation. Possible participation of this enzyme in the response of tumors to photodynamic therapy (PDT) was investigated in this study. Immunohistochemical analysis of mouse FsaR tumors treated by PDT based on photosensitizers Photofrin or 5,10,15,20-tetra-(m-hydroxyphenyl)chlorine (mTHPC) revealed a strong positive staining for PARP product poly(ADP-ribose) at 30 min and 1 h after PDT, respectively, and even more intense positivity at 2 h after PDT with both photosensitizers. Flow cytometry-based examination showed the induction of poly-ADP-ribosylation in FsaR tumors at 30 min after PDT, with a trend for a further increase in the intensity by 2 h after PDT in both cancer cells and tumor-associated leukocytes. In FsaR cells treated in vitro by mTHPC-based PDT, flow cytometric analysis indicated that the activation of PARP concentrated in cells undergoing apoptosis and reached a maximum by 30 min after PDT. The administration of PARP inhibitors, 3-aminobenzamide or 1,5-isoquinolinediol, to FsaR tumor-bearing mice before PDT light treatment increased the resistance of these tumors to PDT. PARP appears to control the balance between apoptotic and necrotic cell death in PDT-treated tumors and regulate the progression of PDT-induced inflammatory or innate immune response.

[The Rel/NF-kappa-B transcription factors: complex role in cell regulation]

The transcription factor NF-kappa B has attracted widespread attention among researchers. NF-kappa B displays some original characteristics including rapid regulation, the wide range of genes that it controls and its probable involvement in several diseases. In resting cells, NF-kappa B is kept in an inactive form in the cytoplasm where it is bound to a member of the I kappa B family of inhibitory proteins. NF-kappa B can be activated by exposure of cells to physiological as well as non physiological stimuli. Upon cell activation, the inhibitors are modified through site specific phosphorylations which target them for subsequent ubiquitination and proteolytic degradation by the proteasome. Removal of the inhibitor unmasks the nuclear localization signals on subunits of NF-kappa B. Free NF-kappa B moves to the nucleus where it binds to target DNA elements and activate transcription of genes encoding proteins involved in immune responses, inflammation or cell proliferation. NF-kappa B could be considered as a co-ordinating element in the body's responses to situations of stress, infection or inflammation. A tight regulation of NF-kappa B seems to be crucial since a dysfunction could promote pathogenic processes including AIDS (acquired immunodeficiency syndrome), rheumatoid arthritis and cancer. Additionally, it will be important to understand the exact roles for NF-kappa B in regulating apoptosis. NF-kappa B is now regarded as a good therapeutic target and the development of specific inhibitors should lead in the next future to novel therapeutics.

Gamma-glutamyl transpeptidase activity mediates NF-kappaB activation through lipid peroxidation in human leukemia U937 cells

Gamma-glutamyl transpeptidase (GGT) is a key enzyme in the catabolism of glutathione (GSH). Recently, it has been reported that the extracellular cleavage of GSH by GGT induced the production of reactive oxygen species (ROS), suggesting that GGT plays a pro-oxidant role. In the present study, we investigated the nature of the oxidative stress generate by glutathione and GGT and the possibility that this stress affects the activity of NF-kappaB a prototypical oxidant-stress-responsive transcription factor. We found that, in the presence of iron, a natural substrate of GGT, glutathione induces lipid peroxidation in U937 cells. This induction depends on GGT activity as it is prevented by the Serine/Borate complex, a GGT inhibitor. We found that y-glutamyl transpeptidase activity induces NF-kappaB DNA binding activity, an effect which is significantly reduced by the addition of GGT inhibitors (Serine/Borate complex and Acivicin). Moreover, we show that lipid peroxidation is involved in GGT-dependent NF-kappaB activation since vitamin E, which completely inhibits GGT-induced generation of lipid peroxides, prevents the GGT-dependent NF-kappaB activation. Finally, inhibition of GGT by either the Serine/Borate complex or by Acivicin resulted in cell apoptosis. This finding suggests that GGT-mediated NF-kappaB activation plays a role in the control of apoptosis in U937 cells.

Identification by cDNA microarray technology of genes modulated by artificial ultraviolet radiation in normal human melanocytes: relation to melanocarcinogenesis

Target genes of ultraviolet stress response in cutaneous melanocytes, potentially associated with solar-induced melanocarcinogenesis, were characterized by cDNA microarray technology. In cultured normal human melanocytes, 198 genes out of approximately 9000 arrayed were found modulated > or = 1.9 times following artificial ultraviolet minus sign mainly ultraviolet-B minus sign irradiation (100 mJ per cm(2)). Among them, 159 corresponded to known sequences, the encoded proteins being mostly involved in DNA or RNA binding/synthesis/modification, or ribosomal proteins. The others were transcription factors, receptors, tumor suppressors, and (proto)oncogenes. Members of these families have already been linked to melanoma. In addition, some of the modulated genes were borne by chromosomes harboring candidate melanoma loci. Comparisons with genes modified in melanoma samples reported in previous studies with similar microarray platform showed that 59% of the known genes sensitive to ultraviolet were modulated in the same way. Furthermore, 39 expressed sequence tags were modulated, and preliminary experiments showed that two expressed sequence tags displayed differential expressions both in melanoma cell lines and in melanoma tumors. These results provide a basis for further studies on the role of modulated genes in ultraviolet-induced melanoma. Because some of these genes are potential markers of the disease, they might help for developing new molecular-based strategies for risk prediction in patients.

Kojic acid, a potential inhibitor of NF-kappaB activation in transfectant human HaCaT and SCC-13 cells

The activation of NF-kappaB induced by kojic acid, an inhibitor of tyrosinase for biosynthesis of melanin in melanocytes, was investigated in human transfectant HaCaT and SCC-13 cells. These two keratinocyte cell lines transfected with pNF-kappaB-SEAP-NPT plasmid were used to determine the activation of NF-kappaB. Transfectant cells release the secretory alkaline phosphatase (SEAP) as a transcription reporter in response to the NF-kappaB activity and contain the neomycin phosphotransferase (NPT) gene for the dominant selective marker of geneticin resistance. NF-kappaB activation was measured in the SEAP reporter gene assay using a fluorescence detection method. Kojic acid showed the inhibition of cellular NF-kappaB activity in both human keratinocyte transfectants. It could also downregulate the ultraviolet ray (UVR)-induced activation of NF-kappaB expression in transfectant HaCaT cells. Moreover, the inhibitory activity of kojic acid in transfectant HaCaT cells was found to be more potent than known antioxidants, e.g., vitamin C and N-acetyl-L-cysteine. These results indicate that kojic acid is a potential inhibitor of NF-kappaB activation in human keratinocytes, and suggest the hypothesis that NF-kappaB activation may be involved in kojic acid induced anti-melanogenic effect.

Dietary eicosapentaenoic acid prevents systemic immunosuppression in mice induced by UVB radiation

Moison, R. M. W. and Beijersbergen van Henegouwen, G. M. J. Dietary Eicosapentaenoic Acid Prevents Systemic Immunosuppression in Mice Induced by UVB Radiation. Radiat. Res. 156, 36-44 (2001). Reactive oxygen species (ROS) contribute to the immunosuppression induced by UVB radiation. Omega-3 fatty acids in fish oil, e.g. eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), can modulate immunoresponsiveness, but because of their susceptibility to ROS-induced damage, they can also challenge the epidermal antioxidant defense system. The influence of dietary supplementation with different omega-3 fatty acids on systemic immunosuppression induced in mice by UVB radiation was studied using the contact hypersensitivity response to trinitrochlorobenzene. In an attempt to study the mechanisms involved, UVB-radiation-induced changes in epidermal antioxidant status were also studied. Mice received high-fat (25% w/w) diets enriched with either oleic acid (control diet), EPA, DHA, or EPA + DHA (MaxEPA). Immunosuppression induced by UVB radiation was 53% in mice fed the oleic acid diet and 69% in mice fed the DHA diet. In contrast, immunosuppression was only 4% and 24% in mice fed the EPA and MaxEPA diets, respectively. Increased lipid peroxidation and decreased vitamin E levels (P < 0.05) were found in unirradiated mice fed the MaxEPA and DHA diets. For all diets, exposure to UVB radiation increased lipid peroxidation (P < 0.05), but levels of glutathione (P < 0.05) and vitamin C (P > 0.05) decreased only in the mice given fish oil. UVB irradiation did not influence vitamin E levels. In conclusion, dietary EPA, but not DHA, protects against UVB-radiation-induced immunosuppression in mice. The degree of protection appears to be related to the amount of EPA incorporated and the ability of the epidermis to maintain an adequate antioxidant level after irradiation.

A cell-based assay system for monitoring NF-kappaB activity in human HaCat transfectant cells

A cell-based assay system for monitoring NF-kappaB activity was developed to determine the influence of activated NF-kappaB in human HaCaT cells. The pNF-kappaB-SEAP-NPT plasmid that permits expression of the secretory alkaline phosphatase (SEAP) reporter gene in response to the NF-kappaB activity and contains the neomycin phosphotransferase (NPT) gene for geneticin resistance in host cells was constructed and transfected into the human keratinocyte cell line HaCaT. Human HaCaT transfectant cells were demonstrated to secrete the SEAP enzyme into the culture medium in a time-dependent manner until 72 h. NF-kappaB activities were measured by the SEAP reporter gene assay using a fluorescence detection method. HaCaT cell transfectants treated with antioxidants [e.g., N-acetyl-l-cysteine and vitamin C] showed reduction of NF-kappaB activity in a time- and concentration-dependent manner, whereas phorbol 12-myristate 13-acetate known as a stimulator of NF-kappaB expression increased NF-kappaB activity in a time- and concentration-dependent manner. This assay system could be used to determine the quantitative measurement of NF-kappaB activity in the human skin and allow the screening of anti-inflammatory agents for dermatological purpose from various synthetic chemicals and natural products.

Glutaredoxin protects cerebellar granule neurons from dopamine-induced apoptosis by activating NF-kappa B via Ref-1

The neurotransmitter dopamine (DA) induces apoptosis via its oxidative metabolites. This study shows that glutaredoxin 2 (Grx2) from Escherichia coli and human glutaredoxin could protect cerebellar granule neurons from DA-induced apoptosis. E. coli Grx2, which catalyzes glutathione-disulfide oxidoreduction via its -Cys-Pro-Tyr-Cys- active site, penetrates into cerebellar granule neurons and exerts its activity via NF-kappaB activation. Analysis of single and double cysteine to serine substitutions in the active site of Grx2 showed that both cysteine residues were essential for activity. Although DA significantly reduced NF-kappaB binding activity, Grx2 could stimulate the binding of NF-kappaB to DNA by: (i) translocating NF-kappaB from the cytoplasm to the nucleus after promoting the phosphorylation and degradation of I-kappaBalpha, and (ii) activating the binding of pre existing nuclear NF-kappaB. The DNA binding activity of NF-kappaB itself was essential for neuronal survival. Overexpression of I-kappaB dominant negative gene (I-kappaB-DeltaN) in granule neurons significantly reduced their viability, irrespective of the presence of Grx2. Ref-1 expression was down-regulated by DA but up-regulated by Grx2, while treatment of neurons with Ref-1 antisense oligonucleotide reduced the ability of Grx2 to activate NF-kappaB binding activity. These results show that Grx2 exerts its anti apoptotic activity through the activation of Ref-1, which then activates NF-kappaB.

PUVA (psoralen + UVA) photochemotherapy: processes triggered in the cells

Photochemotherapy using psoralens and UVA is a treatment used widely in some skin diseases, in cutaneous lymphomas and in autoimmune diseases. This review has selected recent publications dealing with the photochemical processes triggered in the cells by UVA radiation and psoralen treatment. The photochemical changes initiated in the cell membranes were described.

Signaling pathways in cell death and survival after photodynamic therapy

Photodynamic therapy (PDT) is a cytotoxic treatment, which can induce cells to initiate a rescue response, or to undergo cell death, either apoptosis or necrosis. The many signaling pathways involved in these processes are the topic of this review. The subcellular localization of the photosensitizer has been shown to be a key factor in the outcome of PDT. Mitochondrial localized photosensitizers are able to induce apoptosis very rapidly. Lysosomal localized photosensitizers can elicit either a necrotic or an apoptotic response. In the plasma membrane, a target for various photosensitizers, rescue responses, apoptosis and necrosis is initiated. Several protein phosphorylation cascades are involved in the regulation of the response to PDT. Finally, a number of stress-induced proteins play a role in the rescue response after PDT. Notably, the induction of apoptosis by PDT might not be crucial for an optimal outcome. Recent studies indicate that abrogation of the apoptotic pathway does alter the clonogenic survival of the cells after PDT. Further studies, both in vitro and especially in vivo could lead to more efficient combination therapies in which signaling pathways, involved in cell death or rescue, are either up- or downregulated before PDT.

Differential developmental expression and cell type specificity of Dictyostelium catalases and their response to oxidative stress and UV-light

Cells of Dictyostelium discoideum are highly resistant to DNA damaging agents such as UV-light, gamma-radiation and chemicals. The genes encoding nucleotide excision repair (NER) and base excision repair (BER) enzymes are rapidly upregulated in response to UV-irradiation and DNA-damaging chemicals, suggesting that this is at least partially responsible for the resistance of this organism to these agents. Although Dictyostelium is also unusually resistant to high concentrations of H(2)O(2), little is known about the response of this organism to oxidative stress. To determine if transcriptional upregulation is a common mechanism for responding to DNA-damaging agents, we have studied the Dictyostelium catalase and Cu/Zn superoxide dismutase antioxidant enzymes. We show that there are two catalase genes and that each is differentially regulated both temporally and spatially during multicellular development. The catA gene is expressed throughout growth and development and its corresponding enzyme is maintained at a steady level. In contrast, the catB gene encodes a larger protein and is only expressed during the final stages of morphogenesis. Cell type fractionation showed that the CatB enzyme is exclusively localized to the prespore cells and the CatA enzyme is found exclusively in the prestalk cells. Each enzyme has a different subcellular localization. The unique developmental timing and cell type distribution suggest that the role for catB in cell differentiation is to protect the dormant spores from oxidative damage. We found that exposure to H(2)O(2) does not result in the induction of the catalase, superoxide dismutase, NER or BER mRNAs. A mutant with greatly reduced levels of catA mRNA and enzyme has greatly increased sensitivity to H(2)O(2) but normal sensitivity to UV. These results indicate that the natural resistance to oxidative stress is not due to an ability to rapidly raise the level of antioxidant or DNA repair enzymes and that the response to UV-light is independent from the response to reactive oxygen compounds.

Early physiological and cytological events induced by wounding in potato tuber

The response of potato tuber (Solanum tuberosum L. cv. Kennebec) to mechanical wounding was investigated at different times. Changes in the levels of indole-3-acetic acid (IAA), polyunsaturated fatty acids (PUFAs) and lipid hydroperoxides (LOOHs) were monitored up to 120 min after wounding and related to the cytological events occurring up to 24 h. Twenty minutes after injury, an increase in IAA and LOOH levels and a decrease in the levels of PUFAs was observed. Wounding induced mitoses in differentiated (parenchyma) cells starting at 120 min, and promoted an increase of mitotic activity in the meristematic cells (procambium and bud dome), after 360 min. The inhibition of the increase in LOOHs and IAA by lipoxygenase (LOX) inhibitors, as well as the ability of in vitro peroxidated linoleic acid to enhance IAA production, suggest a close relationship among lipoperoxidation, IAA and mitotic activity in the response of potato tuber cells to injury, resulting in a specific growth response, i.e. bud growth and periderm formation.

Cytotoxicity and cytotoxic molecules in invertebrates

Although lacking the components that characterize the acquired immunity systems of vertebrates, invertebrates nevertheless possess effective general innate immune mechanisms which exhibit striking parallels with those of vertebrates. These innate immune systems include both cellular and humoral elements. Invertebrate phagocytes synthesize both oxygen-dependent and oxygen-independent molecules to combat infectious agents. Cytotoxic substances employed by invertebrates include reactive intermediates of oxygen and nitrogen, antimicrobial peptides, lectins, cytokine- and complement-like molecules, and quinoid intermediates of melanin. The signal transduction pathways that are involved in mediating the production of these substances appear to be very similar among animal species, suggesting a common ancestral origin for the innate immune systems.

Influence of photodynamic therapy on immunological aspects of disease - an update

Photodynamic therapy (PDT) utilises light-absorbing compounds combined with directed photo-irradiation to produce clinical effects. This review updates advances in the understanding of the biochemical pathways triggered by PDT within cells, its influence upon different immune parameters and progress in the use of PDT against human immune-mediated disease. Several works have further defined the notable capacity of PDT to foster anticancer immunity.

Nuclear factor-κB activation by the photochemotherapeutic agent verteporfin

The nuclear factor-kappa B (NF-κB) gene transactivator serves in the formation of immune, inflammatory, and stress responses. In quiescent cells, NF-κB principally resides within the cytoplasm in association with inhibitory κ (IκB) proteins. The status of IκB and NF-κB proteins was evaluated for promyelocytic leukemia HL-60 cells treated at different intensities of photodynamic therapy (PDT). The action of the potent photosensitizer, benzoporphyrin derivative monoacid ring A (verteporfin), and visible light irradiation were assessed. At a verteporfin concentration that produced the death of a high proportion of cells after light irradiation, evidence of caspase-3 and caspase-9 processing and of poly(ADP-ribose) polymerase cleavage was present within whole cell lysates. The general caspase inhibitor Z-Val-Ala-Asp-fluoromethylketone (ZVAD.fmk) effectively blocked these apoptosis-related changes. Recent studies indicate that IκB proteins may be caspase substrates during apoptosis. However, the level of IκBβ was unchanged for HL-60 cells undergoing PDT-induced apoptosis. IκB levels decreased during PDT-induced apoptosis, though ZVAD.fmk did not affect this change. At a less intensive level of photosensitization, cellular IκB levels were transiently depressed after PDT. At these times, p50 and RelA NF-κB species were increased within nuclear extracts, as revealed by electrophoretic mobility supershift assays. HL-60 cells transiently transfected with a κB-luciferase reporter construct exhibited elevated luciferase activity after PDT or treatment with tumor necrosis factor-, a well-characterized NF-κB activator. Productive NF-κB activation and associated gene transcription may influence the phenotype and behavior of cells exposed to less intensive PDT regimens. However, IκB is not subject to caspase-mediated degradation as a component of PDT-induced apoptosis. (Blood. 2000;95:256-262)