Chlorophyllin chemoprevention in trout initiated by aflatoxin B(1) bath treatment: An evaluation of reduced bioavailability vs. target organ protective mechanisms

Enhancing Health Benefits through Chlorophylls and Chlorophyll-Rich Agro-Food: A Comprehensive Review

Chlorophylls play a crucial role in photosynthesis and are abundantly found in green fruits and vegetables that form an integral part of our diet. Although limited, existing studies suggest that these photosynthetic pigments and their derivatives possess therapeutic properties. These bioactive molecules exhibit a wide range of beneficial effects, including antioxidant, antimutagenic, antigenotoxic, anti-cancer, and anti-obesogenic activities. However, it is unfortunate that leafy materials and fruit peels often go to waste in the food supply chain, contributing to the prevailing issue of food waste in modern societies. Nevertheless, these overlooked materials contain valuable bioactive compounds, including chlorophylls, which offer significant health benefits. Consequently, exploring the potential of these discarded resources, such as utilizing them as functional food ingredients, aligns with the principles of a circular economy and presents exciting opportunities for exploitation.

Light-Activated Biomedical Applications of Chlorophyll Derivatives

Tetrapyrroles are the basis of essential physiological functions in most living organisms. These compounds represent the basic scaffold of porphyrins, chlorophylls, and bacteriochlorophylls, among others. Chlorophyll derivatives, obtained by the natural or artificial degradation of chlorophylls, present unique properties, holding great potential in the scientific and medical fields. Indeed, they can act as cancer-preventing agents, antimutagens, apoptosis inducers, efficient antioxidants, as well as antimicrobial and immunomodulatory molecules. Moreover, thanks to their peculiar optical properties, they can be exploited as photosensitizers for photodynamic therapy and as vision enhancers. Most of these molecules, however, are highly hydrophobic and poorly soluble in biological fluids, and may display undesired toxicity due to accumulation in healthy tissues. The advent of nanomedicine has prompted the development of nanoparticles acting as carriers for chlorophyll derivatives, facilitating their targeted administration with demonstrated applicability in diagnosis and therapy. In this review, the chemical and physical properties of chlorophyll derivatives that justify their usage in the biomedical field, with particular regard to light-activated dynamics are described. Their role as antioxidants and photoactive agents are discussed, introducing the most recent nanomedical applications and focusing on inorganic and organic nanocarriers exploited in vitro and in vivo.

Cancer interception by interceptor molecules: mechanistic, preclinical and human translational studies with chlorophylls

Before 'cancer interception' was first advocated, 'interceptor molecules' had been conceived as a sub-category of preventive agents that interfered with the earliest initiation steps in carcinogenesis. Three decades ago, a seminal review cataloged over fifty synthetic agents and natural products that were known or putative interceptor molecules. Chlorophylls and their derivatives garnered much interest based on the potent antimutagenic activity in the Salmonella assay, and the subsequent mechanistic work that provided proof-of-concept for direct molecular complexes with planar aromatic carcinogens. As the 'interceptor molecule' hypothesis evolved, mechanistic experiments and preclinical studies supported the view that chlorophylls can interact with environmental heterocyclic amines, aflatoxins, and polycyclic aromatic hydrocarbons to limit their uptake and bioavailability in vivo. Support also came from human translational studies involving ultralow dose detection in healthy volunteers, as well as intervention in at-risk subjects. Antimutagenic and antigenotoxic effects of natural and synthetic chlorophylls against small alkylating agents also highlighted the fact that non-interceptor mechanisms existed. This gave impetus to investigations broadly related to free radical scavenging, anti-inflammatory effects, immune modulation and photodynamic therapy. Therapeutic aspects of chlorophylls also were investigated, with evidence for cell cycle arrest and apoptosis in human cancer cells. As the science has evolved, new mechanistic leads continue to support the use and development of chlorophylls and their porphyrin derivatives for cancer interception, beyond the initial interest as interceptor molecules.

In vitro bioassays to evaluate beneficial and adverse health effects of botanicals: promises and pitfalls

This review provides an update on the promises and pitfalls when using in vitro bioassays to evaluate beneficial and adverse health effects of botanicals and botanical preparations. Important issues addressed in the paper are: (i) the type of assays and biological effects available; (ii) false-positives, false-negatives and confounding factors; (iii) matrix and combination effects; (iv) extrapolation of in vitro data to the in vivo situation; (v) when (not) to use bioassays; and (vi) identification of active constituents. It is concluded that in vitro bioassays provide models to detect beneficial as well as adverse activities, but that linking these observations to individual ingredients and extrapolations to the in vivo situation is more complicated than generally anticipated.

Use of Accelerator Mass Spectrometry in Human Health and Molecular Toxicology

Accelerator mass spectrometry (AMS) has been adopted as a powerful bioanalytical method for human studies in the areas of pharmacology and toxicology. The exquisite sensitivity (10-18 mol) of AMS has facilitated studies of toxins and drugs at environmentally and physiologically relevant concentrations in humans. Such studies include risk assessment of environmental toxicants, drug candidate selection, absolute bioavailability determination, and more recently, assessment of drug-target binding as a biomarker of response to chemotherapy. Combining AMS with complementary capabilities such as high performance liquid chromatography (HPLC) can maximize data within a single experiment and provide additional insight when assessing drugs and toxins, such as metabolic profiling. Recent advances in the AMS technology at Lawrence Livermore National Laboratory have allowed for direct coupling of AMS with complementary capabilities such as HPLC via a liquid sample moving wire interface, offering greater sensitivity compared to that of graphite-based analysis, therefore enabling the use of lower 14C and chemical doses, which are imperative for clinical testing. The aim of this review is to highlight the recent efforts in human studies using AMS, including technological advancements and discussion of the continued promise of AMS for innovative clinical based research.

Treatment of ichthyophthiriasis with photodynamically active chlorophyllin

Water-soluble chlorophyll (chlorophyllin) exerts pronounced photodynamic activity on fish parasites. In order to determine its potential as a remedy against ectoparasites in fish carps were incubated in water with defined concentrations of chlorophyllin. The main focus of the experiments was on the ciliate Ichthyophthirius multifiliis (Fouquet) which is responsible for considerable losses in livestock in aquaculture. As malachite green, which in the past efficiently cured infected fishes, is banned because of its possible carcinogenicity; no effective remedy is presently available in aquaculture to treat ichthyophthiriasis. Using chlorophyllin, the number of trophonts was significantly reduced (more than 50 %) after 3 h incubation of infested fish at 2 and 4 mg/L and subsequent irradiation with simulated solar radiation. The lack of reinfection after light treatment indicates that also the remaining parasites have lost their multiplication capacity. In the controls (no chlorophyllin and no light, light but no chlorophyllin, or chlorophyllin but no light), no reduction of the I. multifiliis infection was observed. We propose that chlorophyllin (or other photodynamic substances) is a possible effective countermeasure against I. multifiliis and other ectoparasites in aquaculture.

Matrix-derived combination effects influencing absorption, distribution, metabolism and excretion (ADME) of food-borne toxic compounds: implications for risk assessment

Absorption, distribution, metabolism and excretion (ADME) of food-borne toxic compounds may be influenced by other compounds or constituents present in the food.

The molecular epidemiology of chronic aflatoxin driven impaired child growth

Aflatoxins are toxic secondary fungal metabolites that contaminate dietary staples in tropical regions; chronic high levels of exposure are common for many of the poorest populations. Observations in animals indicate that growth and/or food utilization are adversely affected by aflatoxins. This review highlights the development of validated exposure biomarkers and their use here to assess the role of aflatoxins in early life growth retardation. Aflatoxin exposure occurs in utero and continues in early infancy as weaning foods are introduced. Using aflatoxin-albumin exposure biomarkers, five major studies clearly demonstrate strong dose response relationships between exposure in utero and/or early infancy and growth retardation, identified by reduced birth weight and/or low HAZ and WAZ scores. The epidemiological studies include cross-sectional and longitudinal surveys, though aflatoxin reduction intervention studies are now required to further support these data and guide sustainable options to reduce the burden of exposure. The use of aflatoxin exposure biomarkers was essential in understanding the observational data reviewed and will likely be a critical monitor of the effectiveness of interventions to restrict aflatoxin exposure. Given that an estimated 4.5 billion individuals live in regions at risk of dietary contamination the public health concern cannot be over stated.

Chlorophyll-related compounds inhibit cell adhesion and inflammation in human aortic cells

The objectives of this study were to investigate the effects of chlorophyll-related compounds (CRCs) and chlorophyll (Chl) a+b on inflammation in human aortic endothelial cells. Adhesion molecule expression and interleukin (IL)-8, nuclear factor (NF)-κB p65 protein, and NF-κB and activator protein (AP)-1 DNA binding were assessed. The effects of CRCs on inflammatory signaling pathways of signal transducers and activators of transcription 3 (STAT3) and mothers against decapentaplegic homolog 4, respectively induced by IL-6 and transforming growth factor (TGF)-β, in human aortic smooth muscle cells cultured in vitro were also investigated. HAECs were pretreated with 10 μM of CRCs, Chl a+b, and aspirin (Asp) for 18 h followed by tumor necrosis factor (TNF)-α (2 ng/mL) for 6 h, and U937 cell adhesion was determined. TNF-α-induced monocyte-endothelial cell adhesion was significantly inhibited by CRCs. Moreover, CRCs and Chl a+b significantly attenuated vascular cell adhesion molecule-1, intercellular adhesion molecule-1, and IL-8 expressions. Treatments also significantly decreased in NF-κB expression, DNA binding, and AP-1 DNA binding by CRCs and Asp. Thus, CRCs exert anti-inflammatory effects through modulation of NF-κB and AP-1 signaling. Ten micromoles of CRCs and Asp upregulated the expression of mothers against decapentaplegic homolog 4 (Drosophila) (SMAD4) in the TGF-β receptor signaling pathway, and SMAD3/4 transcription activity was also increased. Ten micromoles of CRCs were able to potently inhibit STAT3-binding activity by repressing IL-6-induced STAT3 expression. Our results provide a potential mechanism that explains the anti-inflammatory activities of these CRCs.

Histone deacetylase inhibitor suberoylanilide hydroxamic acid suppresses the pro-oncogenic effects induced by hepatitis B virus pre-S2 mutant oncoprotein and represents a potential chemopreventive agent in high-risk chronic HBV patients

Chronic hepatitis B virus (HBV) infection is the major cause of hepatocellular carcinoma (HCC). The pre-S(2) mutant large HBV surface antigen (LHBS) in type II ground glass hepatocytes (GGHs) has been recognized as an emerging viral oncoprotein; it directly interacts with the c-Jun activation domain-binding protein 1 (JAB1) and subsequently causes hyperphosphorylation of the tumor-suppressor retinoblastoma and, consequently, leads to disturbed cell cycle progression. The interaction of the pre-S(2) mutant LHBS with JAB1 could provide a potential target for chemoprevention. In this study, we found that the preneoplastic type II GGHs showed a significant decrease of the cyclin-dependent kinase inhibitor p27(Kip1), which serves as a marker for pre-S(2) mutant-JAB1 complex formation. The histone deacetylase (HDAC) inhibitor suberoylanilide hydroxamic acid (SAHA) elevated expression of the tumor-suppressor thioredoxin-binding protein 2 (TBP2), which subsequently enhanced the JAB1-TBP2 interaction and abolished the pre-S(2) mutant LHBS-induced degradation of p27(Kip1), which, in turn, recovered the normal cell cycle checkpoint. The pre-S(2) mutant LHBS-induced pro-oncogenic effects: increased cell proliferation, nuclear/cytoplasmic ratio and proliferating cell nuclear antigen expression, were all greatly ameliorated after SAHA treatments, which suggested SAHA as a promising chemopreventive agent for the pre-S(2) mutant oncoprotein-induced HCC. In conclusion, this study provides the mechanism of histone deacetylase (HDAC) inhibitor in preventing the pre-S(2) mutant-induced oncogenic phenotype. The HDAC inhibitor SAHA is therefore a potential chemopreventive agent for high-risk chronic HBV patients who may develop HCC.

Dietary modulation of the biotransformation and genotoxicity of aflatoxin B(1)

Diet and its various components are consistently identified as among the most important 'risk factors' for cancer worldwide, yet great uncertainty remains regarding the relative contribution of nutritive (e.g., vitamins, calories) vs. non-nutritive (e.g., phytochemicals, fiber, contaminants) factors in both cancer induction and cancer prevention. Among the most potent known human dietary carcinogens is the mycotoxin, aflatoxin B(1) (AFB). AFB and related aflatoxins are produced as secondary metabolites by the molds Aspergillus flavus and Aspergillus parasiticus that commonly infect poorly stored foods including peanuts, pistachios, corn, and rice. AFB is a potent hepatocarcinogenic agent in numerous animal species, and has been implicated in the etiology of human hepatocellular carcinoma. Recent research has shown that many diet-derived factors have great potential to influence AFB biotransformation, and some efficiently protect from AFB-induced genotoxicity. One key mode of action for reducing AFB-induced carcinogenesis in experimental animals was shown to be the induction of detoxification enzymes such as certain glutathione-S-transferases that are regulated through the Keap1-Nrf2-ARE signaling pathway. Although initial studies utilized the dithiolthione drug, oltipraz, as a prototypical inducer of antioxidant response, dietary components such as suforaphane (SFN) are also effective inducers of this pathway in rodent models. However, human GSTs in general do not appear to be extensively induced by SFN, and GSTM1 - the only human GST with measurable catalytic activity toward aflatoxin B(1)-8,9-epoxide (AFBO; the genotoxic metabolite of AFB), does not appear to be induced by SFN, at least in human hepatocytes, even though its expression in human liver cells does appear to offer considerable protection against AFB-DNA damage. Although induction of detoxification pathways has served as the primary mechanistic focus of chemoprevention studies, protective effects of chemoprotective dietary components may also arise through a decrease in the rate of activation of AFB to AFBO. Dietary consumption of apiaceous vegetables inhibits CYP1A2 activity in humans, and it has been demonstrated that some compounds in those vegetables act as potent inhibitors of human CYP1A2 and cause reduced hCYP1A2-mediated mutagenicity of AFB. Other dietary compounds of different origin (e.g., constituents of brassica vegetables and hops) have been shown to modify expression of human hepatic enzymes involved in the oxidation of AFB. SFN has been shown to protect animals from AFB-induced tumors, to reduce AFB biomarkers in humans in vivo and to reduce efficiently AFB adduct formation in human hepatocytes, although it appears that this protective effect is the result of repression of human hepatic CYP3A4 expression, rather than induction of protective GSTs, at least in human hepatocytes. If this mechanism were to occur in vivo in humans, it would raise safety concerns for the use of SFN as a chemoprotective agent as it may have important implications for drug-drug interactions in humans. A dietary chemoprevention pathway that is independent of AFB biotransformation is represented by the potential for dietary components, such as chlorophyllin, to tightly bind to and reduce the bioavailability of aflatoxins. Chlorophyllin has been shown to significantly reduce genotoxic AFB biomarkers in humans, and it therefore holds promise as a practical means of reducing the incidence of AFB-induced liver cancer. Recent reports have demonstrated that DNA repair mechanisms are inducible in mammalian systems and some diet-derived compounds elevated significantly the gene expression of enzymes potentially involved in nucleotide excision repair of AFB-DNA adducts. However, these are initial observations and more research is needed to determine if dietary modulation of DNA repair is a safe and effective approach to chemoprevention of AFB-induced liver cancer.

Anticarcinogenic effect of probiotic fermented milk and chlorophyllin on aflatoxin-B1-induced liver carcinogenesis in rats

The present investigation was carried out to evaluate the hepatoprotective effect of probiotic fermented milk (FM) containing Lactobacillus rhamnosus GG and Lactobacillus casei strain Shirota, alone as well as in combination with chlorophyllin (CHL) as an antioxidant agent in male Wistar rats administered aflatoxin-B1 (AFB1). AFB1 was injected intraperitoneally at the rate of 450 μg/kg body weight per animal twice a week for 6 weeks, maintaining an equal time interval between the two consecutive AFB1 administrations. A total of 125 male Wistar rats were randomly allocated to five groups, each group having twenty-five animals. Group I was offered FM containing L. rhamnosus GG and L. casei strain Shirota. Group II was administered AFB1 and served as the control group; group III was administered FM-AFB1, in which besides administering AFB1, FM was also offered. Group IV was offered CHL and AFB1, and group V was offered both FM and CHL along with AFB1. The rats were euthanised at the 15th and 25th week of the experiment and examined for the biochemical and hepatopathological profile. A significant reduction in thiobarbituric acid-reactive substances (TBARS) was observed in the FM–CHL–AFB1 group compared with the AFB1 control group. FM alone or in combination with CHL was found to show a significant (P < 0·05) hepatoprotective effect by lowering the levels of TBARS and by enhancing the activities of antioxidant enzymes such as glutathione peroxidase, superoxide dismutase, catalase and glutathione-S-transferase, indicating that probiotic FM alone or in combination with CHL possesses a potent protective effect against AFB1-induced hepatic damage.

Preventive and therapeutic methods against the toxic effects of mycotoxins - a review

Ingredients used in animal feeds and their contamination with undesirable substances, such as mycotoxins, are fundamentally important both in terms of the quality of animal products and the potential human health impacts associated with the animal-based food production chain. Feed ingredients contaminated with mycotoxins may have a wide range of toxicological effects on animals. Therefore, mycotoxin contamination of feed ingredients constituting complete feed products represents an important potential hazard in farm animal production. This review summarises the potential effects of some preventive methods used during the storage of cereal grains as well as of nutritive (e.g. antioxidants, amino acids, fats) or non-nutritive compounds (e.g. pharmacological substances, carbon- or silica-based polymers) and detoxifying enzymes recommended for use against the toxic effects of different mycotoxins.

Effects of chlorophyll and chlorophyllin on low-dose aflatoxin B(1) pharmacokinetics in human volunteers

Chlorophyll (Chla) and chlorophyllin (CHL) were shown previously to reduce carcinogen bioavailability, biomarker damage, and tumorigenicity in trout and rats. These findings were partially extended to humans, where CHL reduced excretion of aflatoxin B(1) (AFB(1))-DNA repair products in Chinese unavoidably exposed to dietary AFB(1). However, neither AFB(1) pharmacokinetics nor Chla effects were examined. We conducted an unblinded crossover study to establish AFB(1) pharmacokinetic parameters among four human volunteers, and to explore possible effects of CHL or Chla cotreatment in three of those volunteers. For protocol 1, fasted subjects received an Institutional Review Board-approved dose of 14C-AFB(1) (30 ng, 5 nCi) by capsule with 100 mL water, followed by normal eating and drinking after 2 hours. Blood and cumulative urine samples were collected over 72 hours, and 14C- AFB(1) equivalents were determined by accelerator mass spectrometry. Protocols 2 and 3 were similar except capsules also contained 150 mg of purified Chla or CHL, respectively. Protocols were repeated thrice for each volunteer. The study revealed rapid human AFB(1) uptake (plasma k(a), 5.05 + or - 1.10 h(-1); T(max), 1.0 hour) and urinary elimination (95% complete by 24 hours) kinetics. Chla and CHL treatment each significantly impeded AFB(1) absorption and reduced Cmax and AUCs (plasma and urine) in one or more subjects. These initial results provide AFB(1) pharmacokinetic parameters previously unavailable for humans, and suggest that Chla or CHL co-consumption may limit the bioavailability of ingested aflatoxin in humans, as they do in animal models.

Naturally occurring chlorophyll derivatives inhibit aflatoxin B1-DNA adduct formation in hepatoma cells

The inhibitory effects of four chlorophyll derivatives (chlorophyllide [Chlide] a and b and pheophorbide [Pho] a and b) on aflatoxin B1 (AFB1)-DNA adduct formation, and on the modulation of hepatic glutathione S-transferase (GST) were evaluated in murine hepatoma (Hepa-1) cells. Enzyme-linked immunosorbent assay showed that pretreatment with Chlide or Pho significantly reduced the formation of AFB1-DNA adducts, and that Pho was the most potent inhibitor. However, wash-out prior to adding AFB1 totally eliminated inhibition by Childe and partially eliminated inhibition by Pho, indicating that the inhibitory effect of Chlide, and to some extent Pho, was mediated through direct trapping of AFB1. Furthermore, spectrophotometric analysis showed that Pho treatment could increase GST activity in Hepa-1 cells. These observations indicate that the chlorophyll derivatives studied may attenuate AFB1-induced DNA damage in the Hepa-1 cell by direct trapping of AFB1. Pho provided additional protection not only by direct trapping, but also by increasing GST activity against hepatic AFB1 metabolites.

Protective effect of dietary tomatine against dibenzo[a,l]pyrene (DBP)-induced liver and stomach tumors in rainbow trout

The potential anti-carcinogenic effects of tomatine, a mixture of commercial tomato glycoalkaloids alpha-tomatine and dehydrotomatine (10:1), were examined in the rainbow trout chemoprevention model. Prior to the chemoprevention study, a preliminary toxicity study revealed that tomatine in the diet fed daily at doses from 100 to 2000 parts per million (ppm) for 4 weeks was not toxic to trout. For the tumor study, replicate groups of 105 trout were fed diets containing dibenzo[a,l]pyrene (DBP) alone (224 ppm), (N = 3), DBP plus tomatine at 2000 ppm (N = 2), tomatine alone (N = 2), or control diet (N = 2) for 4 weeks. The fish were then returned to control diet for 8 months and necropsied for histopathology. Dietary tomatine was found to reduce DBP-initiated liver tumor incidence from 37.0 to 19.0% and stomach tumor incidence from 46.4 to 29.4%. Tomatine also reduced stomach tumor multiplicity. The tomatine-containing diets did not induce mortality, change in fish weights, or liver weights. No adverse pathological effects in the tissues of the fish on the tomatine diets were observed. Dose-response and chemopreventive mechanisms for tomatine protection remain to be examined. This is the first report on the anticarcinogenic effects of tomatine in vivo.

Low-dose dietary chlorophyll inhibits multi-organ carcinogenesis in the rainbow trout

We recently reported that chlorophyll (Chl) strongly inhibits aflatoxin B(1) preneoplasia biomarkers in rats when administered by co-gavage (Simonich et al., 2007. Natural chlorophyll inhibits aflatoxin B1-induced multi-organ carcinogenesis in the rat. Carcinogenesis 28, 1294-1302.). The present study extends this by examining the effects of dietary Chl on tumor development, using rainbow trout to explore ubiquity of mechanism. Duplicate groups of 140 trout were fed diet containing 224 ppm dibenzo[a,l]pyrene (DBP) alone, or with 1000-6000 ppm Chl, for 4 weeks. DBP induced high tumor incidences in liver (51%) and stomach (56%), whereas Chl co-fed at 2000, 4000 or 6000 ppm reduced incidences in stomach (to 29%, 23% and 19%, resp., P<0.005) and liver (to 21%, 28% and 26%, resp., P<0.0005). Chlorophyllin (CHL) at 2000 ppm gave similar protection. Chl complexed with DBP in vitro (2Chl:DBP, K(d1)=4.44+/-0.46 microM, K(d2)=3.30+/-0.18 microM), as did CHL (K(d1)=1.38+/-0.32 microM, K(d2)=1.17+/-0.05 microM), possibly explaining their ability to inhibit DBP uptake into the liver by 61-63% (P<0.001). This is the first demonstration that dietary Chl can reduce tumorigenesis in any whole animal model, and that it may do so by a simple, species-independent mechanism.

Lack of preventive effects of dietary fibers or chlorophyllin against acrylamide toxicity in rats

Dietary fibers and chlorophyllin have shown to exert anti-carcinogenic effects against co-administered carcinogens. To test the possibility of chemoprevention by such dietary supplements on subacutely induced acrylamide (ACR) toxicity, Sprague-Dawley male rats were administered 2.5% sodium alginate, 5% glucomannan, 5% digestion resistant maltodextrin, 2.5% chitin or 1% chlorophyllin in the diet, and starting one week later, co-administered 0.02% ACR in the drinking water for 4 weeks. For comparison, untreated control animals given basal diet and tap water were also included. Neurotoxicity was examined with reference to gait abnormalities and by quantitative assessment of histopathological changes in the sciatic and trigeminal nerves, as well as aberrant dot-like immunoreactivity for synaptophysin in the cerebellar molecular layer. Testicular toxicity was assessed by quantitation of seminiferous tubules with exfoliation of germ cells into the lumen and cell debris in the ducts of the epididymides. Development of testicular toxicity as well as neurotoxicity was evident with ACR-treatment, but was not suppressed by dietary addition of fibers or chlorophyllin, suggesting no apparent beneficial influence of these dietary supplements on experimentally induced subacute ACR toxicity.

Chemoprevention of hepatocellular carcinoma in aflatoxin endemic areas

Hepatocellular carcinoma is one of the most common cancers worldwide. Infection with hepatitis B virus and exposure to aflatoxins in the diet act synergistically to amplify risk. From a public health perspective, hepatitis virus vaccination programs and efforts to both reduce aflatoxin exposures and to attenuate the toxicological consequences of unavoidable exposures should have major impacts on the global incidence of this disease. Experimentally, aflatoxin-induced hepatocarcinogenesis can be inhibited by over a score of different chemopreventive agents with multiple mechanisms of action. One agent, oltipraz, is a potent inducer of phase 2 enzymes involved in the detoxication of carcinogens including aflatoxin. A second agent, chlorophyllin, impedes the bioavailability of carcinogens by forming molecular complexes and enhances their elimination in the fecal stream. This review highlights the findings of recent randomized clinical trials with oltipraz and chlorophyllin conducted in individuals exposed to dietary aflatoxins and at high risk for development of liver cancer. Both chemopreventive agents modulated levels of aflatoxin biomarkers in the study participants in manners consonant with protection. Although pharmacological approaches establish proof of principle and help identify key molecular targets for interventions, food-based approaches that also use these molecular targets may be the most practical for widespread application in high-risk populations.

Effects of chlorophyllin on transport of dibenzo(a, l)pyrene, 2-amino-1-methyl-6-phenylimidazo-[4,5-b]pyridine, and aflatoxin B1 across Caco-2 cell monolayers

Chlorophyllin (CHL) is a sodium copper derivative of chlorophyll that is capable of forming strong non-covalent complexes with several known carcinogens. Antimutagenic and anticarcinogenic effects, including reduced DNA adduct and tumor formation have been demonstrated for CHL against aflatoxin B(1) (AFB(1)), dibenzo(a,l)pyrene (DBP) and 2-amino-1-methyl-6-phenylimidazo-[4,5-b]pyridine (PhIP). Alterations in uptake and/or metabolism of planar molecules with at least partial ring structure have been proposed as mechanisms of action for CHL chemoprevention. The Caco-2 cell model of intestinal epithelial transport was used to evaluate the absorption of 1 microM DBP, AFB(1) and PhIP across cell monolayers in the presence of 0, 1, 10, and 100 microM CHL. No significant differences were observed in the permeability (P(e)) of DBP and AFB(1) from the basolateral-to-apical (BL --> AP) compared to apical-to-basolateral (AP --> BL) compartments for DBP and AFB(1), however, the P(e) of PhIP from BL --> AP, 1.26 x 10(5) +/- 2.10 x 10(6) cm/s, was significantly higher than AP --> BL, 5.83 x 10(6) +/- 7.56 x 10(7) cm/s, (P<0.001) suggesting an active efflux pathway. Transport of DBP from AP --> BL compartments was significantly reduced at all CHL concentrations (P<0.05). AP --> BL transport of AFB(1) was significantly reduced by the addition of 100 microM CHL (P<0.05) while 1 microM or 10 microM CHL had no effect. Complexation studies revealed a higher binding affinity (K(b)) for DBP to CHL compared to AFB(1) to CHL in transport buffer. AP --> BL transport of PhIP, which has a lower binding affinity for CHL than AFB(1) or DBP, was not significantly altered by the addition of CHL. These data suggest that the transport of AFB(1) and DBP can be inhibited by CHL, which supports a model of direct binding in the intestinal tract of CHL to these carcinogens with resultant reduction of bioavailability as one mechanism of action as a cancer chemopreventive agent.

Dietary aflatoxin exposure and chemoprevention of cancer: a clinical review

Exposure to dietary aflatoxins is considered to be an important risk factor for the development of hepatocellular carcinoma in certain regions of the world. Significant advances have recently been made in understanding the clinical toxicology of aflatoxins. These include the development and validation of biomarkers of exposure and genotoxic effect. These biomarkers are currently being utilized to explore the potential that pharmaceutical interventions may have in modifying the toxicokinetics of dietary aflatoxin exposure. Preliminary results of clinical trials with the drug oltipraz suggest that it may modify the genotoxic effects of aflatoxin B1 by inhibiting bioactivation pathways and stimulating detoxification pathways. More recent results of a clinical trial with chlorophyllin suggest that this drug may have a role in preventing dietary exposure to aflatoxin B1 by reducing its oral bioavailability. The preliminary results of these chemoprevention studies may ultimately have implications for cancer prevention in high-risk populations in the future.

Effects of chlorophyllin on mouse embryonic and fetal development in vivo

Chlorophyllin (CHL) has proven that there is antimutagenic and anticarcinogenic activity in several organisms without causing lethal effects. However, there is no information about its effects when it is administered in gestation. In the present study, we assessed possible effects of CHL when it was administered to CD-1 mice on the 8th day of gestation using the same doses and administration route used in ours previous antimutagenic and antigenotoxic studies. Females were exposed to a single dose of CHL by i.p. injection (20, 40, 50, or 100mg/kg b.w.). On day 18 all dams were subjected to cesarean section and the fetuses were examined with common teratological methods. Results show that CHL-treatment induced total litter loss and is dose-dependent, probably due to either the interaction between CHL and some general control mechanisms of embryo development or by an impairment of maternal-fetal interactions. The analysis of uterine horns of the CHL-treated females with total litter loss revealed the presence of green rings in the uterus. Results show the inverse relationship between the number of live implants and the frequency of green rings, indicating implantation sites where embryo death and early resorptions occurred. Although CHL was given in a single dose on day 8 in this study, the results indicate that CHL is associated with significant embryo lethality.

Dietary butylated hydroxytoluene protects against aflatoxicosis in Turkeys

Turkeys are among the most sensitive species to the toxic effects of the mycotoxin aflatoxin B(1) (AFB(1)). In mammals, dietary antioxidants, such as butylated hydroxytoluene (BHT), have been shown to lessen the toxic effects of AFB(1) by various mechanisms. To test whether BHT protects against aflatoxicosis in turkeys, we supplemented the feed of 10-day-old male white turkeys with low (1000 ppm) and high (4000 ppm) BHT for 20 days. AFB(1) (1 ppm) was then added to the diets and continued for another 10 days. Birds in the AFB(1)-only group had a lower weight gain, a condition that had returned to near control in groups fed diets containing AFB(1) + BHT. Significant elevations in serum aspartate transaminase, alanine aminotransferase, and lactate dehydrogenase, which were evident in the AFB(1) group, were reversed in the AFB(1) + BHT groups. Histopathology revealed hepatic submassive necrotic lesions and biliary hyperplasia, the severity of which was lessened in the AFB(1) + BHT-treated birds. Hepatocellular hydropic degeneration was observed in the BHT-only group, but not in the AFB(1) + BHT groups. This condition associated with BHT treatment was found in a separate study to be reversible and without any long-term adverse effects. These results indicate that BHT counteracts many of the deleterious effects caused by AFB(1) and that this antioxidant may prove to be a viable feed additive for the reduction of aflatoxicosis in turkeys.

Chlorophyllin intervention reduces aflatoxin-DNA adducts in individuals at high risk for liver cancer

Residents of Qidong, People's Republic of China, are at high risk for development of hepatocellular carcinoma, in part from consumption of foods contaminated with aflatoxins. Chlorophyllin, a mixture of semisynthetic, water-soluble derivatives of chlorophyll that is used as a food colorant and over-the-counter medicine, has been shown to be an effective inhibitor of aflatoxin hepatocarcinogenesis in animal models by blocking carcinogen bioavailability. In a randomized, double-blind, placebo-controlled chemoprevention trial, we tested whether chlorophyllin could alter the disposition of aflatoxin. One hundred and eighty healthy adults from Qidong were randomly assigned to ingest 100 mg of chlorophyllin or a placebo three times a day for 4 months. The primary endpoint was modulation of levels of aflatoxin-N(7)-guanine adducts in urine samples collected 3 months into the intervention measured by using sequential immunoaffinity chromatography and liquid chromatography-electrospray mass spectrometry. This aflatoxin-DNA adduct excretion product serves as a biomarker of the biologically effective dose of aflatoxin, and elevated levels are associated with increased risk of liver cancer. Adherence to the study protocol was outstanding, and no adverse events were reported. Aflatoxin-N(7)-guanine could be detected in 105 of 169 available samples. Chlorophyllin consumption at each meal led to an overall 55% reduction (P = 0.036) in median urinary levels of this aflatoxin biomarker compared with those taking placebo. Thus, prophylactic interventions with chlorophyllin or supplementation of diets with foods rich in chlorophylls may represent practical means to prevent the development of hepatocellular carcinoma or other environmentally induced cancers.

Effect of chlorophyllin on chromium trioxide-induced micronuclei in polychromatic erythrocytes in mouse peripheral blood

The effect of chlorophyllin on micronucleated polychromatic erythrocytes (MN-PCE) induction by chromium trioxide (CrO(3)) exposure in peripheral blood of mice was studied. Animals were treated with a single intraperitoneal dose of chlorophyllin (CHL) (20mg/kg), CrO(3) (20mg/kg), and CHL (20mg/kg) 4h before (CHL-CrO(3)) or 4h before and 20h after chromium treatments (20mg/kg; CHL-CrO(3)-CHL). Peripheral blood samples were drawn from the caudal vein at 0, 12 and 48h, and analyzed by the acridine orange (AO) technique. The results obtained in present study shown that CHL injection did not modify the number of MN-PCE. CrO(3) treatment resulted in a significantly increases 12 and 48h after the injection, reaching a four-fold increase 48h after CrO(3) administration. Whereas treatment with 20mg/kg of CHL prior to chromium, decreased the MN frequency induced by chromium in the 12h samples. When the samples were analyzed 48h after CrO(3) injection, no significant differences between CHL-CrO(3) and CHL-CrO(3)-CHL in comparison with CrO(3) treatment, were observed. These results indicate that increase of MN-PCE by CrO(3) is CHL-blocked in both protocols used (CHL-CrO(3) and CHL-CrO(3)-CHL) at 12h after treatment, but it was unable to modify the frequency of MN-PCE measured 48h after CrO(3) injection. The absence of a protective effect by CHL in the MN-PCE induction by CrO(3) at 48h, show that CHL has action only on one of the times of MN induction and suggests the possible action of CrO(3) by two different mechanisms, and not by CHL time-limited in vivo.

Inhibition of dibenzo[a,l]pyrene-induced multi-organ carcinogenesis by dietary chlorophyllin in rainbow trout

Cancer chemoprevention by dietary chlorophyllin (CHL) was investigated in a rainbow trout multi-organ tumor model. In study 1, duplicate groups of 130 juvenile trout were treated for 2 weeks with control diet, 500 p.p.m. dibenzo[a,l]pyrene (DB[a,l]P) or 500 p.p.m. DB[a,l]P + 2052 p.p.m. CHL, then returned to control diet. DB[a,l]P alone proved somewhat toxic but induced high tumor incidences in liver (61%), stomach (91%) and swimbladder (53%) 11 months after initiation. CHL co-feeding abrogated DB[a,l]P acute toxicity and reduced tumor incidences to 18% in liver, 34% in stomach and 3% in swimbladder (P Collapse

Key Words

• chlorophyllin
• aflatoxin b1
• heterocyclic amine
• trout
• salmonella assay
• dna adduct
• anticarcinogen

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MESH Headings

• Animals
• Anticarcinogenic Agents/administration & dosage
• Anticarcinogenic Agents/pharmacology
• Benzopyrenes/toxicity
• Carcinogens/toxicity
• Chlorophyllides/administration & dosage
• Chlorophyllides/pharmacology
• Diet
• Mutagenicity Tests
• Neoplasms, Experimental/chemically induced
• Neoplasms, Experimental/prevention & control
• Oncorhynchus mykiss

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Grants

• ES00210 NIEHS NIH HHS
• P30 ES003850 NIEHS NIH HHS
• R29 CA065525 NCI NIH HHS
• ES03850 NIEHS NIH HHS
• R01 CA065525 NCI NIH HHS
• ES04766 NIEHS NIH HHS
• R01 CA065525-06A1 NCI NIH HHS
• P30 ES000210 NIEHS NIH HHS

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Affiliation(s)

A P Reddy Department of Environmental Toxicology, Oregon State University, Corvallis, OR 97331, USA
U Harttig
M C Barth
W M Baird
M Schimerlik
J D Hendricks
G S Bailey

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Mechanisms of chlorophyllin anticarcinogenesis: dose-responsive inhibition of aflatoxin uptake and biodistribution following oral co-administration in rainbow trout

Chlorophyllin (CHL) is a potent blocking agent against aflatoxin B(1) DNA adduction and tumorigenesis in the trout model, but mechanisms responsible for this chemoprotection in vivo are not well established. This study employed aflatoxin B(2) (AFB(2)), a structural analogue of AFB(1) that cannot be metabolized directly to the 8,9-exo-epoxide electrophile, to investigate CHL effects on carcinogen uptake and distribution kinetics following oral exposure in trout. CHL was shown to form an AFB(2) complex in vitro with a dissociation constant (K(d) = 1.92 +/- 0.13 microM) comparable to that with AFB(1). Following gavage, [(3)H]AFB(2) equivalents distributed rapidly from the stomach to other organs including blood, liver, and eventually to bile as a major repository. Bile was found to contain almost entirely parent AFB(2) 1 h after gavage, with a single metabolite dominating 3-24 h and an additional metabolite prominent by 48 h after gavage. Addition of sufficient CHL (>/=13.9 mM) to assure >99% complexation of AFB(2) (0.906 microM) in the gavage mix resulted in 80-90% reduction in AFB(2) equivalents in liver and bile 3 h after gavage. In three separate kinetic studies of up to 120 h postgavage, addition of >/=13.9 mM CHL to the gavage mix reproducibly and markedly delayed the rate of AFB(2) loss from stomach, retarded its appearance in blood, liver, and bile, and reduced peak AFB(2) concentrations in those tissues by up to 60%. Introduction of a food bolus immediately after gavage prolonged AFB(2) residence in stomach and intestine but did not abrogate the inhibitory effects of CHL on AFB(2) uptake and distribution. These results demonstrate that oral co-treatment with CHL under conditions where complex formation is initially assured, substantially reduces AFB(2) systemic uptake and target organ bioavailability in the trout.