Molecular and Cellular Mechanisms of Propolis and Its Polyphenolic Compounds against Cancer

In recent years, interest in natural products such as alternative sources of pharmaceuticals for numerous chronic diseases, including tumors, has been renewed. Propolis, a natural product collected by honeybees, and polyphenolic/flavonoid propolis-related components modulate all steps of the cancer progression process. Anticancer activity of propolis and its compounds relies on various mechanisms: cell-cycle arrest and attenuation of cancer cells proliferation, reduction in the number of cancer stem cells, induction of apoptosis, modulation of oncogene signaling pathways, inhibition of matrix metalloproteinases, prevention of metastasis, anti-angiogenesis, anti-inflammatory effects accompanied by the modulation of the tumor microenvironment (by modifying macrophage activation and polarization), epigenetic regulation, antiviral and bactericidal activities, modulation of gut microbiota, and attenuation of chemotherapy-induced deleterious side effects. Ingredients from propolis also "sensitize" cancer cells to chemotherapeutic agents, likely by blocking the activation of the transcription factor nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). In this review, we summarize the current knowledge related to the the effects of flavonoids and other polyphenolic compounds from propolis on tumor growth and metastasizing ability, and discuss possible molecular and cellular mechanisms involved in the modulation of inflammatory pathways and cellular processes that affect survival, proliferation, invasion, angiogenesis, and metastasis of the tumor.

Consumption of soy isoflavones during the prepubertal phase delays puberty and causes hypergonadotropic hypogonadism with disruption of hypothalamic-pituitary gonadotropins regulation in male rats

Isoflavones are phytoestrogens with recognized estrogenic activity but may also affect testosterone, corticosterone and thyroid hormone levels in experimental models. However, the molecular mechanisms involved in these alterations are still unclear. Isoflavones are present in soy-based infant formula, in breast milk after the consumption of soy by the mother and are widely used for the preparation of beverages consumed by toddlers and teenagers. In this sense, we proposed to investigate the effects of soy isoflavone exposure during the prepubertal period, a recognized window of sensitivity for endocrine disruption, over the hypothalamic-pituitary-testicular (HPT) axis. For this, 42 3-week-old male Wistar rats were exposed to 0.5, 5 or 50 mg of soy isoflavones/kg from postnatal day (PND) 23 to PND60. We evaluated body growth, age at puberty, serum concentrations of LH, FSH, testosterone and estradiol, and the expression of the transcripts (mRNA) of genes encoding key genes controlling the hypothalamic-pituitary-testicular (HPT) axis. In the hypothalamus, we observed an increase in Esr1 mRNA expression (0.5 and 5 mg). In the pituitary, we observed an increase in Gnrhr mRNA expression (50 mg), a reduction in Lhb mRNA expression (0.5 mg), and a reduction in Ar mRNA expression. In the testis, we observed an increase in Lhcgr mRNA expression (50 mg) and a reduction in Star mRNA expression (0.5 and 5 mg). The serum levels of LH (5 and 50 mg) and FSH (0.5 mg) were increased, while testosterone and estradiol were reduced. Puberty was delayed in all groups. Taken together, these results suggest that prepubertal consumption of relevant levels of soy isoflavones disrupts the HPT axis, causing hypergonadotropic hypogonadism and altered expression levels of key genes regulating the axis.

Influence of synthetic isoflavones on selected urinary steroid biomarkers: Relevance to doping control

In this work we have investigated the influence of the intake of two synthetic isoflavones, methoxyisoflavone and ipriflavone, on the urinary concentration of endogenous steroids, and on their relative ratios, of doping relevance. Specifically, the concentrations of testosterone (T), epitestosterone (E), androsterone (A), etiocholanolone (Etio), 5α-androstan-3α,17α-diol (5αAdiol), 5β-androstan-3α,17α-diol (5βAdiol), and the ratios T/E, A/T, A/Etio, 5αAdiol/5βAdiol, 5αAdiol/E, were considered, in the framework of the Steroidal Module of the Athlete Biological Passport (ABP). The above set of parameters were complemented by the urinary levels of luteinizing hormone (total LH) and the ratio between T and LH (T/total LH), to assess the possible effects on the biosynthesis of the mentioned steroids. Five healthy Caucasian male volunteers were selected for the study. Urine samples were collected before and during the administration of (i) methoxyisoflavone (Methoxyisoflavone, MyProtein) and (ii) ipriflavone (Osteofix ®, Chiesi Farmaceutici). For the analysis of the urinary steroid profile, after enzymatic hydrolysis with β-glucuronidase from Escherichia Coli (E. Coli) and liquid-liquid extraction with tert-buthylmethyl ether, all samples were analyzed by gas chromatography coupled to tandem mass spectrometry (GC-MS/MS), while for the determination of total LH all urine samples were directly analyzed by a chemiluminescent immunometric assay technique (Siemens Immulite 2000 LH). Our results show that the administration of either methoxyisoflavone or ipriflavone causes an alteration of the urinary concentrations and concentration ratios of the investigated steroids, in the range 55-80% from the baseline values. Furthermore, an oversecretion of LH after the daily intake of methoxyisoflavone or ipriflavone was also recorded in all volunteers, corresponding to an increase in the biosynthesis and excretion of T and some of its metabolites. These changes trigger a disregulation in the pattern of urinary excretion of the steroids included in the Steroidal Module of the ABP, which makes more difficult the interpretation of the longitudinal steroid profile based on the definition of individual normality ranges for each athlete. Our data are also consistent with previous evidence regarding the in vitro effects of natural and synthetic isoflavones, suggesting that their monitoring in doping control routine analysis would be very beneficial for the result management activities.

Engagement of phytoestrogens in breast cancer suppression: Structural classification and mechanistic approach

Cancer is the world's devastating disease, and breast cancer is the most common reason for the death of women worldwide. Many synthetic drugs and medications are provided with their beneficial actions, but all of these have side effects and resistance problems. Natural remedies are coming forward to overcome the disadvantages of synthetic drugs. Among the natural categories, phytoestrogens having a structural similarity of mammalian oestradiol proves its benefit with various mechanisms not only in the treatment of breast cancer but even to prevent the occurrence of postmenopausal symptoms. Phytoestrogens are plant-derived compounds that were utilized in ancient medications and traditional knowledge for its sex hormone properties. Phytoestrogens exert pleiotropic effects on cellular signalling and show effects on estrogen-dependent diseases. However, because of activation/inhibition of steroid hormonal receptor ER-α or ER-β, these compounds induce or inhibit steroid hormonal (estrogen) action and, therefore, have the potential to disrupt hormone (estrogen) signalling pathway. In this review, we have discussed and summarize the effect of certain phytoestrogens and their possible mechanisms that can substantiate advantageous benefits for the treatment of post-menopausal symptoms as well as for breast cancer.

Inhibitory effect of chrysin on estrogen biosynthesis by suppression of enzyme aromatase (CYP19): A systematic review

The cytochrome P450 enzyme functions as the rate-limiting enzyme in changing androgens to estrogens. Inhibition of aromatase is one of the significant objectives of treatment of hormone-dependent diseases such as breast cancer, especially in post-menopausal women. Natural compounds like chrysin, as a flavor that has a high concentration in honey and propolis, are rich sources of them can be useful in inhibiting aromatase for chemoprevention following treatment or in women at risk of acquiring breast cancer. This study intended to summarize the existing evidence on the effect of chrysin on aromatase activity. We systematically searched Science Direct, PubMed and Google Scholar and hand searched the reference lists of identified relevant articles, up to 5 February, 2019. Articles with English abstracts that reported the effect of chrysin on aromatase inhibition and without publication date restriction were investigated. Twenty relevant articles were chosen from a total of 1721 articles. Only one study was performed on humans and two studies were assayed on rats, while other studies were evaluated in vitro. All the studies except one showed that chrysin had the potency of aromatase inhibition; however, only one study performed on endometrial stromal cells showed that chrysin and naringenin did not indicate aromatase inhibitory properties. Various assay methods and experimental conditions were the important aspects leading to different results between the studies. Chrysin has potency in inhibition of the aromatase enzyme and thus can be useful in preventing and treating the hormone-dependent breast cancer and as an adjuvant therapy for estrogen-dependent diseases.

An investigation on the metabolic pathways of synthetic isoflavones by gas chromatography coupled to high accuracy mass spectrometry

RATIONALE

Isoflavones are a group of flavonoids that may be of interest in sport doping because they can be used by athletes in the recovery periods after the administration of anabolic steroids, with the aim of increasing the natural production of luteinizing hormone (LH) and, consequently, the biosynthesis of endogenous androgens.

METHODS

The in vivo metabolism of methoxyisoflavone (5-methyl-7-methoxyisoflavone) and ipriflavone (7-isopropoxyisoflavone), respectively present in a dietary supplement and in a pharmaceutical preparation, was investigated. The study was carried out by the analysis of urinary samples collected from male Caucasian subjects before, during and after the oral administration of methoxyisoflavone or ipriflavone. After enzymatic hydrolysis and liquid-liquid extraction, all urinary samples were analyzed by gas chromatography/quadrupole time-of-flight (qTOF MS system/qTOF) electron ionization mass spectrometry (EI-MS).

RESULTS

Eight metabolites of methoxyisoflavone and six metabolites of ipriflavone were isolated. The corresponding accurate mass spectra are specific for isoflavone structures and revealed also a retro-Diels-Alder fragmentation.

CONCLUSIONS

When excreted in large amounts, the urinary metabolites of methoxyisoflavone and ipriflavone can be traced to potential confounding factors in doping analysis. As methoxyisoflavone and ipriflavone have been shown to inhibit the enzyme aromatase, thus interfering with the normal metabolic pathways of testosterone, the detection of their intake, by screening for the presence of their main metabolites in urine, might be helpful in routine doping control analysis.