The effect of progesterone on the electron emission and degradation of testosterone.

Based on recent findings that hormones can emit electrons () from their excited singlet state in polar media, it was of importance to study a possible mutual interaction of progesterone (PRG) and testosterone (TES) in this respect. Hormones of highest purity were dissolved in an air-free mixture of 40% triply distilled water and 60% ethanol, because the hormones are unsoluble in water. As energy source for substrate excitation in singlet state served a monochromatic UV-light (254 nm), the emitted electrons were scavenged by chloroethanol, whereby the quantum yield of produced Cl⁻ ions, Q (Cl⁻), is equal to Q(e⁻(aq)). Hormone degradation initiated by the electron emission was studied by HPLC method, using a Zorbax Eclipse XDB-C18 column (150 mm x 4.6 mm, 5 µm). The quantum yield of emitted e⁻(aq), Q(e⁻(aq)), from TES was 3.6 times higher than that from PRG, which is explained by the different molecular structures of the hormones. Observed 2nd and 3rd maxima of electron emission indicate the ability of TES and PRG products to also eject e⁻(aq), but with lower yield. It can be stated that a part of the emitted electrons from TES are consumed by PRG⁺ leading to a partial regeneration of hormone. The present results offer a deeper insight in the biological behavior of hormones.

Electron emission and product analysis of estrone: progesterone interactions studied by experiments in vitro.

Recent studies showed that hormones like progesterone, testosterone, etc. can eject [Formula: see text] (solvated electrons). By means of electron transfer processes via the brain, the hormones communicate with other biological systems in the organism. The present study proves that also estrone is able to emit electrons. Their yield strongly depends on the concentration of the hormone, temperature and on the absorbed energy. The metabolites resulting from this process are likewise able to generate electrons, however with much smaller yields. The formation of the estrone metabolites is studied by HPLC-analyses. In vitro experiments with MCF-7 cells demonstrate the distinct effect of progesterone on the carcinogenity of estrone metabolites. Probable reaction mechanisms for explanation of the observed effects are postulated.

Photo-induced regeneration of hormones by electron transfer processes: Potential biological and medical consequences.

Based on the previous results concerning electron transfer processes in biological substances, it was of interest to investigate if hormone transients resulting by e.g. electron emission can be regenerated.The presented results prove for the first time that the hormone transients originating by the electron emission process can be successfully regenerated by the transfer of electrons from a potent electron donor, such as vitamin C (VitC). Investigations were performed using progesterone (PRG), testosterone (TES) and estrone (E1) as representatives of hormones. By irradiation with monochromatic UV light (λ=254 nm) in a media of 40% water and 60% ethanol, the degradation as well as the regeneration of the hormones was studied with each hormone individually and in the mixture with VitC as a function of the absorbed UV dose, using HPLC. Calculated from the obtained initial yields, the determined regeneration of PRG amounted to 52.7%, for TES to 58.6% and for E1 to 90.9%. The consumption of VitC was determined in the same way.The reported results concerning the regeneration of hormones by the transfer of electrons from an electron donor offer a new, promising method for the therapy with hormones. As a consequence of the regeneration of hormones, a decreased formation of carcinogenic metabolites is expected.

17beta-estradiol acting as an electron mediator: experiments in vitro.

BACKGROUND: The present work reports on the effect of oxidizing (OH, O(2)(*-)) and reducing free radicals (e(-)(aq), H) on 17beta-estradiol (17betaE2) in respect to breast cancer initiation. The objectives of the study were based on the following premise: the ability of 17betaE2 to emit electrons (e(-)(aq)) as well as to transfer them to other biological systems. Thereby, the resulting transient hormone products are leading to the formation of metabolites, some of which may initiate the neoplastic process. The present work considers the effect of the simultaneously generated oxidizing and reducing free radicals on the carcinogenic properties of the 17betaE2 metabolites. MATERIALS AND METHODS: Water-soluble 17betaE2 with incorporated 2-hydroxypropyl-beta-cyclodextrin (HBC) in various aqueous media (pH ~7.4), saturated with air, N(2)O or argon, as well as HBC alone, were exposed to the action of free radicals produced by gamma-ray. Escherichia coli bacteria (AB 1157) were used as a model for living systems. RESULTS: From the survival curves obtained under different conditions, the derived DeltaD(37) values (representing the radiation dose at which N/N(0)=0.37; N/N(0) ratio: N(0)=starting number of colonies, N=number after irradiation treatment) illustrate that 17betaE2 as well as HBC act as very powerful scavengers of OH and O(2)(*-) radicals. On the other hand, 17betaE2 and HBC intermediates resulting from attack of the reducing species (e(-)(aq), H) have strong anticancer properties. CONCLUSION: It is stated that DeltaD(37) values strongly depend on the reactivity of the individual free radicals. Oxidizing free radicals lead to positive DeltaD(37) values, illustrating the strongly pronounced radiation protecting ability of the systems. On the contrary, the primary reducing free radicals result in negative DeltaD(37) values, indicating anticancer effect.

Mutual interaction of 17beta-estradiol and progesterone: electron emission. Free radical effect studied by experiments in vitro.

BACKGROUND: Based on the different behaviour of 17beta-estradiol (17betaE(2)) and progesterone (PRG), it was of interest to investigate the interaction of both hormones in respect of their electron emission and cytotoxicity by experiments in vitro. MATERIALS AND METHODS: The studies include determination of emitted electrons (e(-)(aq)) by the individual hormones as well as by their mixtures, all complexed with cyclodextrin (HBC). Experiments in vitro (Escherichia coli bacteria) were performed for a better understanding of the mechanisms involved. Survival ratios, DeltaD(37)(Gy), were calculated. RESULTS: Aqueous HBC as well as 17betaE(2) and PRG, individually as well as in mixtures, are able to emit e(-)(aq). The resulting transients can lead to the formation of metabolites, some of which can initiate cancer. It was established that both hormones, 17betaE(2) and PRG, interact in respect to their electron emission property. In the frame of experiments in vitro, it was found that oxidizing radicals (OH, O(2)(-)) lead to negative DeltaD(37)(Gy) values, indicating cytostatic properties. On the other hand, the primary reducing radicals (e(-)(aq), H) lead to positive DeltaD(37)(Gy) values, indicating a radical-scavenging effect. CONCLUSION: The main outcome of this work is that PRG in combination with 17betaE(2) can strongly reduce the number of carcinogenic 17betaE(2)-metabolites. This fact offers a new pathway for application of hormones in medical treatment of patients.

Vitamin free radicals and their anticancer action. Review.

The antimumor effect of antioxidant vitamins (C, E and beta-carotene) as well as of the vitamins B1 up to B6 and B11 under the action of oxidizing (OH, O(2)(*-)) and reducing free radicals (e(aq)(-), H) is discussed. In addition, the synergistic action of vitamins on cytostatic agents under the influence of free radicals and the involved reaction mechanisms are briefly discussed. The very fast kinetics of electron transfer taking place within a biological molecule (vitamin B11) is shown for demonstration of the complicated free radical processes in the organism.

Photo-induced electron emission from 17beta-estradiol and progesterone and possible biological consequences.

It was established for the first time, that the sexual hormones 17beta-estradiol (17betaE2) and progesterone (PRG) are able to emit electrons from their excited single state in water-ethanol mixtures. The yield of the "solvated electrons" (e(s)(-)) depends on the substrate concentration, the ratio of water-alcohol-mixtures and the temperature. The e(s)(-) yield obtained from 17betaE2 is by two orders of magnitude higher than this of PRG. The possible relationship of the resulting hormone transients from 17betaE2 leading via specific metabolites to breast cancer is discussed.

Radiation-induced antitumor properties of vitamin B5 (pantothenic acid) and its effect on mitomycin C activity: experiments in vitro.

Vitamin B5 (pantothenic acid) shows a strongly pronounced antitumor effect under the influence of ionizing radiation. In the frame of experiments in vitro (model: Escherichia coli bacteria, AB1157) performed under the exact knowledge of concentration and kind of the free radicals acting in the various aqueous media (pH 7.4) the following was established: (i) vitamin B5 possesses a very intense antitumor property, (ii) it exerts a strong synergistic effect on mitomycin C (MMC), (iii) the oxidizing species (OH*, O2*-) appears to be most important in the initiation of the observed effect. The generated radiolytic products from vitamin B5 very likely also play an important role in this respect.

Radiation-induced effect of adenine (vitamin B4) on mitomycin C activity. In vitro experiments.

The radiation-induced biological behavior of adenine (vitamin B4) was investigated in vitro under various conditions, implementing breast cancer cells (MCF-7 line) as a model. In aerated media (46% OH and 54% O2*-) at pH=7.4, adenine at low concentration (2 micromol) acted as an efficient radiation-protecting agent. At higher concentration, however, it inhibited cytostatic properties with regard to cancer cells. This double-track activity is based on its chemical structure. Similar features of adenine were also observed in air-free (46% OH, 44% e- aq, 10% H) as well as in media saturated with N2O (90% OH, 10% H), but with different efficiencies. In the presence of mitomycin C (MMC), adenine retained its double-track behavior. Hence, adenine and MMC compete for the e- aq, but the electronically excited adenine molecules can transfer electrons to MMC, leading to the additional formation of active MMC-. By implementation of formate for the conversion of OH and H into the transient *COO-, which subsequently transfers electron to MMC, a highest efficiency of MMC- was obtained.

Effect of resveratrol and mixtures of resveratrol and mitomycin C on cancer cells under irradiation.

The radiation-biological effects of resveratrol (Res) alone or with mitomycin C (MMC) were investigated under various conditions in human breast cancer cells (MCF-7). The data of the survival curves obtained in aerated media (acting species: 42% OH, 54% 02*-) showed that Res possesses antitumor activity and also acts as an efficient radical scavenger. This property was extremely enhanced in the presence of MMC. In media saturated with N2O (90% OH, 10% H) Res at low concentrations acted as a radiation-protecting agent, but at higher concentrations its cytostatic effect predominated. At the same time, the MMC-activity was reduced. In anaerobic media, Res demonstrated its radiation-protecting ability, but in mixtures the MMC-ability was reduced in comparison to that of pure MMC due to competition reactions between Res and MMC for the available free radicals. Finally, in a cell suspension containing formate as a specific scavenger for OH and H radicals (pH = 7.4), Res successfully competed for these species and showed antitumor activity. Considering the reaction rate constants of the involved substrates and the implemented concentrations in each medium, the kinetic probability of each survival curve was calculated. Based on these data it was evident that the bifunctional property of Res (acting as radiation protector and also having antitumor activity) was based on an electron ejection process from its excited single state and on its reactivity with the primary radicals (OH, H, e(aq)-).

Pulse Radiolysis Using Very-high-energy Ions for Optimizing Cancer Therapy.

Cancer therapy by means of high-energy ions is very efficient. As a consequence of the linear-energy-transfer effect only a negligible part of the produced free radicals can escape combination processes to form molecular products and to cause undesired side processes. Positrons (e⁺) and γ-rays, generated by the nuclear interaction of high-energy ions in the medium, serve in monitoring the radiation dose absorbed by the tumor. However, due to the dipole nature of water molecules a small proportion of thermalized positrons (e⁺th) can become solvated (e⁺aq). Hence, they are stabilized, live longer and can initiate side reactions. In addition, positronium (Ps), besides solvated electrons (e⁺aq), can be generated and involved in the reaction mechanisms. For a better understanding of the reaction mechanisms involved and to improve cancer therapy, a time-resolved pulse radiolysis instrument using high-energy particles is discussed here. The proposed method is examined and recommended by CERN experts. It is planned to be realized at the MedAustron Radiation Therapy and Research Centre in Wiener Neustadt, Austria.

Transient absorption spectra and kinetics of folic acid (vitamin B11) and some kinetic data of folinic acid and methotrexate.

Folic acid (FA; vitamin B11) exhibits antitumor properties. Its transients, resulting from reaction with OH radicals, are of special interest and were studied by pulse radiolysis. The complex composition of FA offers the formation of numerous transients having different electronic structure stability (lifetime). Investigating their kinetic profiles of decay at various wavelengths, it was established that transients with very unstable electron structure (very short-lived radicals) tend to convert into more stable electronic structures (longer lived) by intramolecular electron transfer process. The biological importance of a FA radical depends on its concentration and on its specific reaction rate constant (k value) for a given process. The rate constant for the OH attack is k(OH + FA) = 1.1 x 10(10) L mol(-1) s(-1). Superimposed absorption spectra of FA radicals as well as formation and decay rate constants of total processes are presented. The primary spectrum is characterized by lambda = 425 nm, epsilon = 1.64 x 10(4) L mol(-1) s(-1). The chemical structure of FA is similar to that of folinic acid (FNA) and of methotrexate (MTX), but their biological properties are different. Therefore, their rate constants for the reactions with e-aq and OH were also determined for comparison: k(FNA + e-aq) = 3.1 x 10(10) L mol(-1) s(-1), k(FNA + OH) = 0.8 x 10(10) L mol(-1) s(-1), k(MTX + e-aq) = 1 x 10(10) L mol(-1) s(-1); k(MTX + OH) = 2.3 x 10(10) L mol(-1) s(-1), and k(FA + e-aq) = 1.9 x 10(10) L mol(-1) s(-1).

Melatonin: Free Radicals and Metabolites Resulting by Emission and Consumption of Solvated Electrons (eaq-): Reaction Mechanisms.

BACKGROUND/AIM: Melatonin not only regulates circadian rhythm, but also induces apoptosis in tumor cells. Hence, elucidation of the basic reaction mechanisms of melatonin and its metabolites is a matter of interest. MATERIAL AND METHODS: Melatonin dissolved in a mixture of water/ethanol=40/60 form associates (unstable complexes). For simulation of biological processes, melatonin was excited by UV light into the singlet state. RESULTS: By using monochromatic UV light (λ=254 nm) melatonin ejects solvated electrons (eaq (-)), a part of which is scavenged by melatonin in ground state contained in the associates. Consequently, with increase of melatonin concentration a decrease of the determined quantum yield of emitted eaq (-), Q(eaq (-)), is obtained. The complex molecular structure of melatonin contains functional groups which can emit eaq (-), as well such consuming eaq (-). As a succession of these processes various types of metabolites are generated, as well as degradation products, with lower molecular weight, are formed. CONCLUSION: Not melatonin per se, but the ejected eaq (-) and thereby resulting various metabolites are responsible for different biological properties of melatonin.

Effect of antioxidant vitamins on radiation-induced apoptosis in cells of a human lymphoblastic cell line.

Modulating the amount of radiation-induced apoptosis by administering antioxidant vitamins offers a possible way to influence radiation-induced side effects in normal tissues. Therefore, we investigated the effect of beta-carotene, vitamin C and alpha-tocopherol on radiation-induced apoptosis in cells in culture. Human T-lymphoblastic MOLT-3 cells were irradiated with a dose of 3 Gy 1 h after or immediately prior to the addition of vitamins in three concentrations (0.01 microM, 1 microM and 100 microM). Eight hours later, apoptosis was scored morphologically by staining the nuclear DNA with Hoechst 33342. When given prior to irradiation, beta-carotene and vitamin E reduced the amount of radiation-induced apoptosis significantly at concentrations of 0.01 microM and 1 microM. In contrast, vitamin C did not show any protective effect when given at these two concentrations and caused a slight but significant radiosensitization at 100 microM. At 0.01 microM, all combinations of two vitamins showed a protective effect. This was also observed for the combination of all three vitamins at concentrations of 0.01 and 1 microM. When given immediately after irradiation, each of the three vitamins showed a protective effect at 0.01 microM. In addition, the combination of alpha-tocopherol and vitamin C reduced radiation-induced apoptosis slightly when given at 1 microM. In all other cases, no statistically significant modulation of radiation-induced apoptosis was observed. In our experimental system, the protective effect of beta-carotene and vitamin E was dependent on concentration and occurred only in the micromolar and sub-micromolar concentration range, while vitamin C alone, but not in combinations, had a sensitizing effect, thus arguing for a careful consideration of vitamin concentrations in clinical settings.

Radiation-induced sensitizing effect of folic acid (vitamin B11) and its synergistic action to mitomycin C: in vitro experiments and radiolysis.

Folic acid (FA; vitamin B11) is found to exhibit very strong cytostatic effects upon gamma-irradiation in neutral media. This effect depends on the FA concentration, pH of the media, and on the presence of air. The largest cytostatic efficiency of FA was observed in an air-free environment (pH 7.4), where deltaD37 = -90 for 10(-4) mol/dm3 FA and deltaD37 = -160 for 10(-3) mol/dm3 FA was found. FA also acts as a very efficient electron donor and is therefore able, in air-free neutral media, to enhance the efficiency of 7.5 x 10(-7) mol/dm3 mitomycin C (MMC) from deltaD37 = -80 up to deltaD37 = -200 in the presence of 5 x 10(-5) mol/dm3 FA, respectively. This synergistic effect offers a new pathway for more efficient radiation therapy by joint implementation of MMC and FA. Additionally, FA radiolysis was studied in the absence and presence of air as well as in media saturated with N20 (conversion of e(aq)- into OH). As a result of these investigations, various products were detected: ammonia, aldehydes, and a mixture of carboxylic acids, in addition to some not yet identified compounds. Their individual yields could not be identified at present.

Influence of vitamin B1 on sanazole activity under irradiation. A study in vitro.

The effect of vitamin B1 (thiamine) on sanazole (AK-2123) efficiency was investigated in vitro under irradiation, using E. coli bacteria (AB 1157) as a model. In order to get a deeper insight into the reaction mechanisms, the experiments were performed in media saturated with argon, air or N20. In the first case vitamin B1 acts as a cytostatic, but in the presence of air or N20 it shows strongly pronounced antioxidant action and leads to an essential increase of sanazole efficiency.

Vitamins B6 and C and mitomycin C-efficiency under irradiation.

The radiation-induced effect of Vitamin B6 (Vit. B6) on mitomycin C (MMC) was investigated by using Escherichia coli bacteria AB 1157 as a model in air-free media as well as in media saturated with nitrous oxide (N20) or air, respectively. In all three types of media Vit.B6 showed cytostatic abilities. The highest synergistic effect of Vit.B6 on MMC was observed in an air-free environment. It decreased 2.8-fold in aerated solution and showed the opposite effect in solutions saturated with N20. The addition of Vitamin C (Vit.C) to the Vit.B6/MMC-mixture in air-free media reduced the MMC-efficiency by a factor of 3.6, whereas the presence of air led to a MMC enhancement of 1.6-fold. Considerations based on the involvement of the primary transients of water radiolysis were made in order to explain the observed effects.

Procarbacine radiolysis and experiments in vitro.

Steady-state radiolysis of aqueous procarbazine (PC) was studied in air-free, aerated and solutions saturated with N2O. The corresponding Gi(-PC)-values obtained at pH=7.4 were: 2.85, 5.60 and 3.45, respectively. The investigations in vitro, using E. coli (AB 1157) as a model for living systems, demonstrated that PC acts as a cytostatic in air-free as well as in aerated media. However, it shows radiation protecting ability in the presence of N2O, where OH-radicals are the predominant reactants. Similar results were observed at pH=6.2. The experimental data contribute to a better understanding of the many-sided and frequently contradictory behavior of PC.

Vitamin B2 (riboflavin) and a mixture of vitamin B2 and C affects MMC efficiency in aerated media under irradiation.

Vitamin B2 (Riboflavin) acts as a strong radiation protecting agent in Escherichia coli bacteria (AB1157) in aerated media. This ability is reinforced by the addition of vitamin C. Under the influence of gamma-radiation, vitamin B2 completely suppresses the cytostatic activity of mitomycin C (MMC). In the presence of both vitamins, B2 and C, MMC is converted from an efficient cytostatic to a rather strong radiation protecting agent. This effect opens a new pathway for specific protection of normal mammalian cells (with a high O2-content) under treatment with ionizing radiation.

Mitomycin C radical cation studied by pulse radiolysis.

The formation of the radical cation of mitomycin C (MMC.+) was investigated in aqueous solution by a pulse radiolysis method using SO4.- species as one electron oxidizing agent. The spectroscopic and kinetic characteristics of MMC.+ transients were determined, namely: absorption maxima at 295, 400 and 500 nm, the corresponding molar extinction coefficients are [symbol: see text] 295 = 5.63 x 10(3) dm3 mol-1 cm-1, [symbol: see text] 400 = 2.9 x 10(3) dm3 mol-1 cm-1, [symbol: see text] 500 = 2.32 x 10(3) dm3 mol-1 cm-1; the rate constant for formation of MMC.+ is k = (1.2 +/- 0.2) x 10(10) dm3 mol-1 s-1 and for decay 2k = (4.6 +/- 0.4) x 10(8) dm-3 mol-1 s-1. Based on this fact it can be assumed that not only the well-known mitomycin C radical anion (semiquinone, MMC.-) is efficiently involved in the radiotherapy process, but in a given oxidation environment the MMC.+ species could also play a role in this respect.