Role of nitric oxide in the response to photooxidative stress in prostate cancer cells.

A continuous state of oxidative stress during inflammation contributes to the development of 25% of human cancers. Epithelial and inflammatory cells release reactive oxygen species (ROS) and reactive nitrogen species (RNS) that can damage DNA. ROS/RNS have biological implications in both chemoresistance and tumor recurrence. As several clinically employed anticancer drugs can generate ROS/RNS, we have addressed herein how inducible nitric oxide synthase and nitric oxide (iNOS/•NO) affect the molecular pathways implicated in the tumor response to oxidative stress. To mimic the oxidative stress associated with chemotherapy, we used a photosensitizer (pheophorbide a) that can generate ROS/RNS in a controlled manner. We investigated how iNOS/•NO modulates the tumor response to oxidative stress by involving the NF-κB and Nrf2 molecular pathways. We found that low levels of iNOS induce the development of a more aggressive tumor population, leading to survival, recurrence and resistance. By contrast, high levels of iNOS/•NO sensitize tumor cells to oxidative treatment, causing cell growth arrest. Our analysis showed that NF-κB and Nrf2, which are activated in response to oxidative stress, communicate with each other through RKIP. For this critical role, RKIP could be an interesting target for anticancer drugs. Our study provides insight into the complex signaling response of cancer cells to oxidative treatments as well as new possibilities for the rational design of new therapeutic strategies.

Comparative haemato-immunotoxic impacts of long-term exposure to tartrazine and chlorophyll in rats.

The haemato-immunotoxic effects of the food colourants tartrazine and chlorophyll were evaluated. Thirty adult Sprague Dawley rats were distributed into three groups and orally administered water, tartrazine (1.35 mg/kg), or chlorophyll (1.35 mg/kg) daily for 90 days. Erythrogram and leukogram profiles were evaluated. The lysozyme, nitric oxide, phagocytic activity, and immunoglobulin levels were measured. Histological and immunohistochemical evaluations of splenic tissues were conducted. Changes in the interleukin (IL) 1ß, 6, and 10 mRNA expression levels were assessed. In the tartrazine-treated rats, a significant anaemic condition and marked leukocytosis were observed. Both the innate and humoural parameters were significantly depressed. Different pathological lesions were observed, including red pulp haemorrhages, vacuolation of some splenic cells, focal hyperplasia of the white pulp, and capsular and parenchymal fibrosis. A marked increase in vascular endothelial growth factor (VEGF) and endothelial nitric oxide synthase (e-NOS) immunolabelling was evident. Marked upregulation of IL-1ß, IL-6, and IL-10 was recorded. In contrast, the chlorophyll-treated rats showed minimal haemato-immune responses. These results indicate that tartrazine exerts haematotoxic and immunotoxic effects following long-term exposure, whereas chlorophyll is a less hazardous food colourant.

Photodynamic efficiency of a chlorophyll-a derivative in vitro and in vivo.

This paper reports the antitumor activity of a chlorophyll-a derivative, 2-[1-hydroxyethyl]-2-devinylpyropheophorbide-a (HEPa). Photophysical characteristics of HEPa were measured. And its cytotoxicity, intracellular localization, biodistribution, efficiency of photodynamic therapy (PDT), histological analysis were investigated using human bile duct carcinoma cells (QBC-939) and QBC-939 tumor bearing BABL/c nude mice as animal model. The results showed that HEPa was localized mainly within the cytoplasmic region and partially in lysosome. Biodistribution of HEPa in QBC-939 tumor bearing BABL/c nude mice showed its fast rate of clearance and high tumor selectivity. In vitro, HEPa had low dark toxicity and high photoxicity against QBC-939 cells. The inhibition rate of QBC-939 tumor could increase up to 92.3%, and H&E staining confirmed that HEPa could cause serious damage to the tumor with light dose of 100J/cm(2), implying that HEPa has potential to be a new antitumor candidate for photodynamic therapy (PDT).

The sensitivity of cancer cells to pheophorbide a-based photodynamic therapy is enhanced by Nrf2 silencing.

Photodynamic therapy (PDT) has emerged as an effective treatment for various solid tumors. The transcription factor NRF2 is known to protect against oxidative and electrophilic stress; however, its constitutive activity in cancer confers resistance to anti-cancer drugs. In the present study, we investigated NRF2 signaling as a potential molecular determinant of pheophorbide a (Pba)-based PDT by using NRF2-knockdown breast carcinoma MDA-MB-231 cells. Cells with stable NRF2 knockdown showed enhanced cytotoxicity and apoptotic/necrotic cell death following PDT along with increased levels of singlet oxygen and reactive oxygen species (ROS). A confocal microscopic visualization of fluorogenic Pba demonstrated that NRF2-knockdown cells accumulate more Pba than control cells. A subsequent analysis of the expression of membrane drug transporters showed that the basal expression of BCRP is NRF2-dependent. Among measured drug transporters, the basal expression of breast cancer resistance protein (BCRP; ABCG2) was only diminished by NRF2-knockdown. Furthermore, after incubation with the BCRP specific inhibitor, differential cellular Pba accumulation and ROS in two cell lines were abolished. In addition, NRF2-knockdown cells express low level of peroxiredoxin 3 compared to the control, which implies that diminished mitochondrial ROS defense system can be contributing to PDT sensitization. The role of the NRF2-BCRP pathway in Pba-PDT response was further confirmed in colon carcinoma HT29 cells. Specifically, NRF2 knockdown resulted in enhanced cell death and increased singlet oxygen and ROS levels following PDT through the diminished expression of BCRP. Similarly, PDT-induced ROS generation was substantially increased by treatment with NRF2 shRNA in breast carcinoma MCF-7 cells, colon carcinoma HCT116 cells, renal carcinoma A498 cells, and glioblastoma A172 cells. Taken together, these results indicate that the manipulation of NRF2 can enhance Pba-PDT sensitivity in multiple cancer cells.

Synthesis and biological evaluation of radiolabeled photosensitizer linked bovine serum albumin nanoparticles as a tumor imaging agent.

In this study, we reported on the synthesis and biological evaluation of radiolabeled fluorescent dye conjugated bovine serum albumin nanoparticles within the size range 190-210 nm. The bovine serum albumin nanoparticles (BSANPs) were prepared using a desolvation method, and chemical cross-linking was performed using gluteraldehyde. Furthermore, pheophorbide-a (PH-A) was loaded on the BSANPs. The results obtained from dynamic light scattering and electron microscopy have proved that nanoparticles are highly monodisperse and near-spherical shaped. The photo-physical properties of the PH-A-BSANPs were obtained using the spectrophotometric techniques. According to the results, PH-A and BSANPs show high non-covalent interaction. PH-A loaded nanoparticles were labeled with (99m)Tc and the radio-labeling efficiency was determined as 90 ± 1.2%. Biodistribution studies of (99m)Tc labeled PH-A-BSANPs and PH-A were carried out using female Albino Wistar rats, and (99m)Tc-PH-A-BSANPs showed a significantly higher uptake in the breast and uterus than (99m)Tc-PH-A. Cell culture study was carried out in MCF-7 cell line (human breast adenocarcinoma cell line). According to the cell culture studies, (99m)Tc-PH-A-BSANPs showed a higher uptake than (99m)Tc-PH-A. Moreover, PH-A-BSANPs demonstrated good photo-physical properties and BSANPs increased the uptake of PH-A on to the MCF-7 cell line. These results confirm that (99m)Tc labeled PH-A-BSANPs could be utilized for radioimaging.

Combining polar organic chemical integrative samplers (POCIS) with toxicity testing to evaluate pesticide mixture effects on natural phototrophic biofilms.

Polar organic chemical integrative samplers (POCIS) are valuable tools in passive sampling methods for monitoring polar organic pesticides in freshwaters. Pesticides extracted from the environment using such methods can be used to toxicity tests. This study evaluated the acute effects of POCIS extracts on natural phototrophic biofilm communities. Our results demonstrate an effect of POCIS pesticide mixtures on chlorophyll a fluorescence, photosynthetic efficiency and community structure. Nevertheless, the range of biofilm responses differs according to origin of the biofilms tested, revealing spatial variations in the sensitivity of natural communities in the studied stream. Combining passive sampler extracts with community-level toxicity tests offers promising perspectives for ecological risk assessment.

A North Sea and Baltic Sea model ensemble eutrophication assessment.

A method to combine observations and an ensemble of ecological models is suggested to produce a eutrophication assessment. Using threshold values and methodology from the Oslo and Paris Commissions (OSPAR) and the Helsinki Commission (HELCOM), four models are combined to assess eutrophication for the Baltic and North Seas for the year 2006. The assessment indicates that the entire southeastern part of the North Sea, the Kattegat, the Danish Straits, the Gulf of Finland, and the Gulf of Riga as well as parts of the Arkona Basin, the Bornholm Basin, and the Baltic proper may be classified as problem areas. The Bothnian Bay and parts of the Baltic proper, the Bornholm Basin, and the Arkona Basin are classified as potential problem areas. This method is a useful tool for the classification of eutrophication; however, the results depend on the threshold values, and further work is needed within both OSPAR and HELCOM to harmonize these values.

Novel photosensitizer-protein nanoparticles for photodynamic therapy: photophysical characterization and in vitro investigations.

In this work two types of pheophorbide-HSA (Pheo-HSA) nanoparticles, PHSA40 and PHSA100, were prepared and their photophysical and photosensitizing properties were investigated. Due to intramolecular interactions the singlet oxygen quantum yield of PHSA40 and PHSA100 is very low (less than 0.1). Intracellular uptake and phototoxicity of pheophorbide a as well as of the Pheo-HSA nanoparticles were studied in Jurkat cells. The HSA nanoparticles do not influence the amount of dye accumulation in cells. After 24h incubation, PHSA40 and PHSA100 showed a higher phototoxicity than Pheo. The reason for this behavior is an efficient nanoparticle decomposition in the cellular lysosomes. The process of drug release during incubation of cells with Pheo-HSA nanoparticles was illustrated by fluorescence lifetime imaging (FLIM) and confocal laser scanning microscopy (CLSM). The final phototoxicity of Pheo-HSA is at the same scale as induced by free Pheo. The drug release ability of HSA nanoparticles shows the possibility to use such formulations as drug carriers in PDT treatment. Therefore, this work constructs a standard for further investigation and optimization of photosensitizer-HSA drug carrier system.

Monomeric pheophorbide(a)-containing poly(ethyleneglycol-b-epsilon-caprolactone) micelles for photodynamic therapy.

Incorporation of unaggregated monomeric molecules of pheophorbide(a) into micelles of poly(ethyleneoxide-b-epsilon-caprolactone) has been characterized by fluorescence spectroscopy, dynamic light scattering, transmission electron microscopy and asymmetric flow field flow fractionation. It was shown that the method used leads to 20 nm micelles, corresponding to approximately 200 molecules of polymer and 4 molecules of monomeric pheophorbide(a) per nano-object which was able to generate (1)O(2) in the medium. They have been used thereafter as nanocarriers for photosensitizers in photodynamic therapy against cancer cells. The encapsulation of photosensitizer has been verified and in vitro tests on human cancerous cells have revealed a ca. 2-fold enhanced photocytotoxicity and cellular uptake compared to free pheophorbide(a).

Cellular phototoxicity evoked through the inhibition of human ABC transporter ABCG2 by cyclin-dependent kinase inhibitors in vitro.

PURPOSE: The physiological importance of the human ATP-binding cassette (ABC) transporter ABCG2 has been recognized with regard to porphyrin-mediated photosensitivity. Functional impairment owing to inhibition of ABCG2 by drugs or its genetic polymorphisms may lead to the disruption of porphyrin homeostasis, which in turn causes cellular toxicity. MATERIALS AND METHODS: We evaluated the impact on photosensitivity of the inhibition by cyclin-dependent kinase (CDK) inhibitors of ABCG2 function. For this purpose, we established new methods for photosensitivity assays by using Flp-In-293 cells and plasma membrane vesicles prepared from Sf9 insect cells. With the new methods, we subsequently tested CDK inhibitors, i.e., purvalanol A, WHI-P180, bohemine, roscovitine, and olomoucine. RESULTS: Among CDK inhibitors tested, purvalanol A was found to be the most potent inhibitor (IC50=3.5 microM) for ABCG2-mediated hematoporphyrin transport. At a concentration of 2.5 microM, it evoked the photosensitivity of ABCG2-expressing Flp-In-293 cells treated with pheophorbide a. WHI-P180 moderately inhibited ABCG2 function, exhibiting weak phototoxicity. In contrast, the phototoxicity of bohemine, roscovitine, and olomoucine were minimal in our assay system. CONCLUSIONS: It is suggested that the planar structure is an important factor for interactions with the active site of ABCG2. The present study provides a new approach to studying drug-induced phototoxicity in vitro.

In vitro evaluation of photosensitivity risk related to genetic polymorphisms of human ABC transporter ABCG2 and inhibition by drugs.

Since porphyrins are regarded as endogenous substrates for the ATP-binding cassette (ABC) transporter ABCG2, it is hypothesized that functional impairment owing to genetic polymorphisms or inhibition of ABCG2 by drugs may result in a disruption of cellular porphyrin homeostasis. In the present study, we expressed ABCG2 genetic variants, i.e., V12M, Q141K, S441N, and F489L, as well as the wild type (WT) in Flp-In-293 cells to examine the hypothesis. Cells expressing S441N and F489L variants exhibited high levels of both cellularly accumulated pheophorbide a and photosensitivity, when those cells were incubated with pheophorbide a and irradiated with visible light. To further elucidate the significance of ABCG2 in cellular porphyrin homeostasis, we observed cellular accumulation and compartmentation of porphyrin and pheophorbide a by means of a new fluorescence microscopy technology, and found that accumulation of porphyrin and pheophorbide a in the cytoplasm compartment was maintained at low levels in Flp-In-293 cells expressing ABCG2 WT, V12M, or Q141K. When ABCG2 was inhibited by imatinib or novobiocin, however, those cells became sensitive to light. Based on these results, it is strongly suggested that certain genetic polymorphisms and/or inhibition of ABCG2 by drugs can enhance the potential risk of photosensitivity.

Cyclodextrin/chlorophyll a complexes as supramolecular photosensitizers.

The interactions between chlorophyll a, and three cyclodextrins, hydroxypropyl-beta-cyclodextrin heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin and hydroxypropyl-gamma-cyclodextrin, were studied in aqueous solutions by means of absorption, emission and circular dichroism spectroscopy. Nanosecond laser flash photolysis and steady-state singlet oxygen generation experiments were performed to clarify the photoactivity of chlorophyll a in these systems. Moreover the photosensitizing activity of these complexes towards human leukemia T-lymphocytes (Jurkat cells) was tested and compared with that of the free sensitizer, chlorophyll a. The results obtained indicate that each cyclodextrin is able to carry the pigment in monomeric form inside of cells producing singlet oxygen.

Investigation of genotoxic and antigenotoxic activities of Melampodium divaricatum in Salmonella typhimurium.

Melampodium divaricatum is a member of the Asteraceae and in Brazil is known as false-calendula, its flowers being used in anti-inflammatory preparations, substituting the true calendula or marigold (Calendula officinalis L.). The flower extract was investigated for mutagenic and antimutagenic effect in the Salmonella/microsome assay. The tested extract was not mutagenic in the strains TA100, TA98, TA97a and TA102 and decreased the mutagenicity of aflatoxin B1, benzo(a)pyrene and daunomycin. Chlorophyll and triterpenes were detected in the extract, and they might have contributed to the observed effect. Our data suggest that these medicinal plants possess cancer chemopreventive properties.

Avaliação in vitro da citotoxicidade do extrato da clorofila / In vitro evaluation of the cytotoxicity of extrect of clorophyll

Introdução: A clorofila tem demonstrado apresentar capacidade de limpeza, aumentando a permeabilidade de túbulos dentinários in vitro. No uso endodôntico, essa substância poderia entrar em contato com o tecido periodontal. Portanto, para indicar a aplicação da clorofila na clínica odontológica se faz necessário analisar sua citotoxicidade primeiramente em cultivo celular, antes dos testes in vivo. O objetivo deste trabalho é analisar a citotoxicidade do extrato da clorofila utilizando cultura de fibroblastos. Método - Foi utilizada a técnica da exclusão de células coradas pelo azul de Trypan em linhagem de fibroblastos de ligamento periodontal humano (linhagem FI3). A clorofila foi diluída na proporção de 1: 1 em meio Eagle modificado por Dulbecco (DME) e aplicada sobre monocamadas confluentes de células FL3. As porcentagens de viabilidade celular foram calculadas após O, 6, 12, 24 horas do contato das células com a clorofila. Resultados - A viabilidade celular das culturas tratadas variou de 70 a 87%, enquanto a viabilidade das culturas-controles tratadas com meio DME sem clorofila variou de 82 a 94%. Portanto, não houve diferença significante entre a viabilidade de células tratadas com a clorofila e células-controle. Conclusão - Os resultados demonstram que a clorofila é uma substância biocompatível no nível in vitro.

The breast cancer resistance protein protects against a major chlorophyll-derived dietary phototoxin and protoporphyria.

The breast cancer resistance protein (BCRPABCG2) is a member of the ATP-binding cassette family of drug transporters and confers resistance to various anticancer drugs. We show here that mice lacking Bcrp1Abcg2 become extremely sensitive to the dietary chlorophyll-breakdown product pheophorbide a, resulting in severe, sometimes lethal phototoxic lesions on light-exposed skin. Pheophorbide a occurs in various plant-derived foods and food supplements. Bcrp1 transports pheophorbide a and is highly efficient in limiting its uptake from ingested food. Bcrp1(-/-) mice also displayed a previously unknown type of protoporphyria. Erythrocyte levels of the heme precursor and phototoxin protoporphyrin IX, which is structurally related to pheophorbide a, were increased 10-fold. Transplantation with wild-type bone marrow cured the protoporphyria and reduced the phototoxin sensitivity of Bcrp1(-/-) mice. These results indicate that humans or animals with low or absent BCRP activity may be at increased risk for developing protoporphyria and diet-dependent phototoxicity and provide a striking illustration of the importance of drug transporters in protection from toxicity of normal food constituents.

Investigation of genotoxic and antigenotoxic activities of chlorophylls and chlorophyllin in cultured V79 cells.

Chlorophyll and its derivatives are examples of plant compounds (purified and/or extracted) which appear to protect DNA from damage caused by chemical or physical agents, although some studies have identified clastogenic activity of these compounds. This study was carried out to assess the genotoxic activity of chlorophyll-a (Chl-a), -b (Chl-b) and chlorophyllin (Chl) and their antigenotoxic activity against the DNA damage induced by methyl methanesulphonate (MMS) under conditions of simultaneous, pre-, post-treatment, and simultaneous treatment after pre-incubation of the chemical with MMS. The micronucleus (MN) test was used in binucleated cells (induced by cytochalasin-B) of a mammalian cell line (V79). The three concentrations of Chl-a, Chl-b or Chl (0.1375, 0.275, 0.55microM) were not genotoxic and the genotoxic action of MMS (400microM) decreased (74-117%) under all treatment conditions. The results showed that there was no significant difference among the treatment types, the concentration or the nature of chlorophyll used. The data obtained suggest that Chl-a, Chl-b and Chl when associated with the DNA damaging agent, MMS, may protect the DNA by desgenotoxic action and/or by bio-antigenotoxic mechanisms, with the similar efficiency.

Cytotoxic pheophorbide-related compounds from Clerodendrum calamitosum and C. cyrtophyllum.

Three pheophorbide-related compounds (1-3) were isolated from the leaves and stems of Clerodendrum calamitosum. The methyl ester of 3 (6) and the known (10S)-hydroxypheophytin a (7) also were isolated from leaves of the related plant Clerodendrum cyrtophyllum. Compounds 1 and 6 were isolated for the first time as naturally occurring products from a plant source. All structures were elucidated by detailed spectroscopic analysis. Biological evaluation showed that 1 and 2 exhibited strong cytotoxicity against human lung carcinoma (A549), ileocecal carcinoma (HCT-8), kidney carcinoma (CAKI-1), breast adenocarcinoma (MCF-7), malignant melanoma (SK-MEL-2), ovarian carcinoma (1A9), and epidermoid carcinoma of the nasopharynx (KB), and its etoposide- (KB-7d), vincristine- (KB-VCR), and camptothecin-resistant (KB-CPT) subclones. Compound 3 was less cytotoxic than 1 and 2. Compounds 4-6, the methyl esters of 1-3, showed strongly increased cytotoxicity compared with the parent acids. Interestingly, 6 was the most active derivative among these compounds. Compound 7 was inactive.

[A 13-week subchronic oral toxicity study of chlorophyll in F344 rats].

A 13-week subchronic toxicity study of chlorophyll (containing 40% oil) was performed in both sexes of F344 rats by feeding of CRF-1 powder diet containing 0, 0.18%, 0.55%, 1.66% and 5%, and vehicle (oil) alone. No animals died during the administration period and no changes in body weights and food intakes were found in any dosed groups. Some hematological, serum biochemical and histopathological changes were observed for the 5%-treated group, but these did not suggest obvious toxicity. These findings indicate that the treatment with 1.66% chlorophyll in diet for 13 weeks does not cause any changes in rats and the 5% feeding is not obviously toxic.

Chlorophyll and chlorophyllin as modifiers of genotoxic effects.

Reports on an inverse relationship between the consumption of fresh vegetables and human gastrointestinal cancer have been followed by screening for the protective activity of a large number of plant extracts, including leafy vegetables. Chlorophyll is ubiquitous in all green plant parts. Chlorophyllins are derivatives of chlorophyll in which the central magnesium atom is replaced by other metals, such as cobalt, copper or iron. An attempt has been made in this article to review the relative efficacy of chlorophyll and chlorophyllin in modifying the genotoxic effects of various known toxicants.