Synergistic effect of chitosan and ß-carotene in inhibiting MNU-induced retinitis pigmentosa.

In this study, N-Methyl-N-nitrosourea (MNU) was intraperitoneally injected to construct a mouse retinitis pigmentosa (RP) model to evaluate the protective effect of chitosan and ß-carotene on RP. The results demonstrated that chitosan synergized with ß-carotene significantly reduced retinal histopathological structural damage in RP mice. The co-treatment group of ß-carotene and chitosan restored the retinal thickness and outer nuclear layer thickness better than the group treated with the two alone, and the thickness reached the normal level. The content of ß-carotene and retinoids in the liver of chitosan and ß-carotene co-treated group increased by 46.75 % and 20.69 %, respectively, compared to the ß-carotene group. Chitosan and ß-carotene supplement suppressed the expressions of Bax, Calpain2, Caspase3, NF-κB, TNF-α, IL-6, and IL-1ß, and promoted the up-regulation of Bcl2. Chitosan and ß-carotene interventions remarkably contributed to the content of SCFAs and enhanced the abundance of Ruminococcaceae, Rikenellaceae, Odoribacteraceae and Helicobacteraceae. Correlation analysis demonstrated a strong association between gut microbiota and improvement in retinitis pigmentosa. This study will provide a reference for the study of the gut-eye axis.

Anti-Apoptotic Effect of Chrysophanol Isolated from Cassia tora Seed Extract on Blue-Light-Induced A2E-Loaded Human Retinal Pigment Epithelial Cells.

The seeds of Cassia tora (C. tora) species mainly contain anthraquinone, anthraquinone glycoside, and naphthalene derivatives. We investigated the anti-apoptotic effects of C. tora seed extract and its isolated compounds on blue-light-induced lipofuscin (A2E)-loaded human retinal pigment epithelial (RPE) cells. For analysis of the C. tora extract, high-performance liquid chromatography method was used. A2E-loaded human retinal pigment epithelial cells and blue light were used to create excessive photo-oxidation to induce cell death. Lactate dehydrogenase (LDH) assay was used to measure cell cytotoxicity, and the mRNA expression of genes involved in apoptosis was examined to evaluate the mechanism of cell death. C. tora extract, n-hexane fraction, and chrysophanol were found to inhibit apoptotic cell death. Additionally, C. tora extract, n-hexane fraction, and chrysophanol reduced the mRNA expression of genes involved in the apoptosis pathway. C. tora and chrysophanol were considered to inhibit apoptosis and oxidative stress response. The major component of C. tora has a protective effect against apoptosis. The ingredients of C. tora can be used as therapeutic substances or to prevent diseases caused by the excessive oxidation of A2E substances in the retina, such as in age-related macular degeneration.

A Harungana madagascariensis extract with retinol-like properties: Gene upregulations and protein expressions in human fibroblasts and skin explants.

OBJECTIVE: Because they limit, even reverse, age-induced skin alterations, retinoids became a staple in cosmetology. However, their use can result in undesired secondary effects and there is a demand for natural sources of compounds with retinoid-like effects. A preliminary screening identified a Harungana madagascariensis plant extract (HME) as possibly inducing genes stimulated by retinol. We analysed its effect on gene and protein expression, comparing it to retinoids. METHODS: Gene expression was analysed by real-time qPCR on RNA from isolated fibroblasts subjected to retinol or the plant extract for 6, 48 or 96 h. Skin markers were quantified in fibroblasts cultured with retinol or extract containing medium, and UV-aged skin explants subjected to topical applications of creams containing retinol, retinaldehyde or HME. RESULTS: Real-time qPCR shows that the extract induced all RARs and RXRs, even RXRγ that was not induced by retinol. Eighty-eight per cent of the 25 early retinoid reaction genes induced by a concentration of retinol are induced by the extract. In fibroblasts, only the extract increased collagen III labelling, while collagen I and fibronectin labelling are increased by retinol and the extract, with higher levels for the extract. When topically applied to UV-aged skin explants, only the cream containing the HME led to increased labelling of CRABP1 in the epidermis. CRABP2 and Ki67 are induced by all three creams and no effect was detected on RXRs. In the dermisthe extract containing cream increased CRABP2, total collagen, procollagen I and collagen I while creams with retinol or retinaldehyde only affected some of these proteins. CONCLUSIONS: The HME induces an overall retinol-like gene induction profile in isolated fibroblasts and retinoid-like stimulation of protein synthesis in both isolated fibroblasts and photoaged skin explants.

OBJECTIFS: Limitant, voire inversant les altérations cutanées induites par l'âge, les rétinoïdes sont devenus incontournables en cosmétologie. Cependant, leur application topique peut entraîner des effets secondaires indésirables et il existe une demande pour des composés naturels ayant des effets similaires à ceux des rétinoïdes. Un screening préliminaire nous avait permis d'identifier un extrait de la plante Harungana madagascariensis (HME) comme pouvant induire des gènes stimulés par le rétinol. Nous avons donc analysé son effet sur l'expression de gènes et de protéines induits par les rétinoïdes et comparé les résultats à ceux obtenus en présence de rétinoïdes. MÉTHODES: L'expression de gènes a été analysée par qPCR en temps réel réalisée sur l'ARN de fibroblastes isolés soumis au rétinol ou à l'extrait végétal pendant 6, 48 ou 96 heures. Différentes protéines cutanées ont été quantifiés dans des fibroblastes cultivés en présence de rétinol ou d'un milieu contenant l'extrait. Des quantifications ont également été faites sur des explants de peau vieillie par les UV et soumis à des applications topiques de crèmes contenant du rétinol, du rétinaldéhyde ou le HME. RESULTATS: La qPCR en temps réel montre que l'extrait induit tous les gènes RARs et RXRs, même RXRγ qui n'était pas induit par le rétinol. Quatre-vingt-huit pour cent des 25 gènes impliqués dans la réaction précoce aux rétinoïdes induits par une concentration de rétinol ont été induits par l'extrait. Dans les fibroblastes, seul l'extrait a augmenté le marquage du collagène III, tandis que le marquage du collagène I et de la fibronectine a été augmenté par le rétinol et l'extrait, avec des niveaux plus élevés pour l'extrait. En application topique sur des explants de peau vieillie par les UV, seule la crème contenant le HME a entraîné une augmentation du marquage de CRABP1 dans l'épiderme. CRABP2 et Ki67 ont été induits par les trois crèmes et aucun effet n'a été détecté sur les RXRs. Dans le derme, la crème contenant l'extrait a augmenté CRABP2, le collagène total, le procollagène I et le collagène I, tandis que les crèmes contenant du rétinol ou du rétinaldéhyde n'ont affecté que certaines de ces protéines. CONCLUSIONS: Chez les fibroblastes isolés, le HME induit un profil d'induction génique globalement similaire à celui du rétinol. Chez les fibroblastes isolés et des explants de peau photo-vieillie, il entraine une stimulation de la synthèse protéique similaire à celle des rétinoïdes.

Sulfarotene, a synthetic retinoid, overcomes stemness and sorafenib resistance of hepatocellular carcinoma via suppressing SOS2-RAS pathway.

BACKGROUND: Recurrent hepatocellular carcinoma (HCC) shows strong resistance to sorafenib, and the tumor-repopulating cells (TRCs) with cancer stem cell-like properties are considered a driver for its high recurrent rate and drug resistance. METHODS: Suppression of TRCs may thus be an effective therapeutic strategy for treating this fatal disease. We evaluated the pharmacology and mechanism of sulfarotene, a new type of synthetic retinoid, on the cancer stem cell-like properties of HCC TRCs, and assessed its preclinical efficacy in models of HCC patient-derived xenografts (PDXs). RESULTS: Sulfarotene selectively inhibited the growth of HCC TRCs in vitro and significantly deterred TRC-mediated tumor formation and lung metastasis in vivo without apparent toxicity, with an IC50 superior to that of acyclic retinoid and sorafenib, to which the recurrent HCC exhibits significant resistance at advanced stage. Sulfarotene promoted the expression and activation of RARα, which down-regulated SOS2, a key signal mediator associated with RAS activation and signal transduction involved in multiple downstream pathways. Moreover, sulfarotene selectively inhibited tumorigenesis of HCC PDXs with high expression for SOS2. CONCLUSIONS: Our study identified sulfarotene as a selective inhibitor for the TRCs of HCC, which targets a novel RARα-SOS2-RAS signal nexus, shedding light on a new, promising strategy of target therapy for advanced liver cancer.

Nutraceuticals in the Mediterranean Diet: Potential Avenues for Breast Cancer Treatment.

The traditional Mediterranean Diet constitutes a food model that refers to the dietary patterns of the population living in countries bordering the Mediterranean Sea in the early 1960s. A huge volume of literature data suggests that the Mediterranean-style diet provides several dietary compounds that have been reported to exert beneficial biological effects against a wide spectrum of chronic illnesses, such as cardiovascular and neurodegenerative diseases and cancer including breast carcinoma. Among bioactive nutrients identified as protective factors for breast cancer, natural polyphenols, retinoids, and polyunsaturated fatty acids (PUFAs) have been reported to possess antioxidant, anti-inflammatory, immunomodulatory and antitumoral properties. The multiple anticancer mechanisms involved include the modulation of molecular events and signaling pathways associated with cell survival, proliferation, differentiation, migration, angiogenesis, antioxidant enzymes and immune responses. This review summarizes the anticancer action of some polyphenols, like resveratrol and epigallocatechin 3-gallate, retinoids and omega-3 PUFAs by highlighting the important hallmarks of cancer in terms of (i) cell cycle growth arrest, (ii) apoptosis, (iii) inflammation and (iv) angiogenesis. The data collected from in vitro and in vivo studies strongly indicate that these natural compounds could be the prospective candidates for the future anticancer therapeutics in breast cancer disease.

Retinoids delay cell cycle progression and promote differentiation of intestinal epithelial cells exposed to nutrient deprivation.

OBJECTIVE: Vitamin A is commonly recommended as a treatment for diarrhea and undernutrition; however, little is known about the underlying cellular mechanisms. The aim of this study was to investigate the modulation of cell cycle by vitamin A derivatives (retinyl palmitate or retinol) in undernourished intestinal epithelial crypts (IEC-6). METHODS: IEC-6 cells were exposed to nutrient deprivation (no serum and no glutamine) and supplemented with retinyl palmitate or retinol at a range of 2 to 20 µM. Proliferation, apoptosis/necrosis, cell cycle process, and gene transcription were assessed. RESULTS: Nutrient deprivation for 6, 12, 24, or 48 h decreased cell proliferation, and retinyl palmitate further decreased it after 24 and 48 h. Apoptosis rates were reduced by undernourishment and further reduced by retinyl palmitate after 48 h; whereas necrosis rates were unaltered. Undernourishment induced overall cell quiescence, increased percentage of cells in G0/G1 phase and decreased percentage of cells in S phase after 12 h and in G2/M phases at 6, 12, and 24 h after treatment. Both retinoids also showed cell quiescence induction with less cells in G2/M phases after 48 h, whereas only retinol showed significant modulation of G0/G1 and S phases. Both retinoids also increased markers of cell differentiation Fabp and Iap gene transcriptions in about fivefold rates after 42 h. Furthermore, specific gene transcriptions related to MAP kinase signaling pathway regulation of cell differentiation and cell cycle regulation were triggered by retinoids in undernourished IEC-6, with higher levels of expression for Atf2 and C-jun genes. CONCLUSIONS: These findings indicated that both vitamin A derivatives induce further survival mechanisms in undernourished intestinal epithelial crypt cells. These mechanisms include increased cell quiescence, decreased apoptosis, increased cell differentiation, and transcription of genes related to MAP kinase signaling pathway.

Retinoids in Cutaneous Squamous Cell Carcinoma.

Animal studies as early as the 1920s suggested that vitamin A deficiency leads to squamous cell metaplasia in numerous epithelial tissues including the skin. However, humans usually die from vitamin A deficiency before cancers have time to develop. A recent long-term cohort study found that high dietary vitamin A reduced the risk of cutaneous squamous cell carcinoma (cSCC). cSCC is a form of nonmelanoma skin cancer that primarily occurs from excess exposure to ultraviolet light B (UVB). These cancers are expensive to treat and can lead to metastasis and death. Oral synthetic retinoids prevent the reoccurrence of cSCC, but side effects limit their use in chemoprevention. Several proteins involved in vitamin A metabolism and signaling are altered in cSCC, which may lead to retinoid resistance. The expression of vitamin A metabolism proteins may also have prognostic value. This article reviews what is known about natural and synthetic retinoids and their metabolism in cSCC.

Enhanced retinoid response by a combination of the vitamin A ester retinyl propionate with niacinamide and a flavonoid containing Ceratonia siliqua extract in retinoid responsive in vitro models.

OBJECTIVES: Retinoids have been used for decades as efficacious topical agents to treat photoaged skin. The purpose of our present research is to evaluate whether the activity of the vitamin A ester retinyl propionate (RP) can be enhanced by niacinamide (Nam) and a flavonoid containing Ceratonia siliqua (CS) fruit extract in retinoid responsive in vitro models. METHODS: Retinyl propionate was tested alone and in combination with Nam and CS in an RARα reporter cell line for promoter activation and compared to trans-retinoic acid (tRA) activation. These treatments were also tested in keratinocytes for gene expression profiling by qPCR using a panel of 40 retinoid responsive genes. RESULTS: tRA or RP elicited RARα reporter activation in a dose-dependent manner. The combination of 0.5 µM or 2 µM RP with 10 mM Nam had a 56% and 95% signal increase compared to RP, respectively. The addition of 1% CS to 0.5 µM or 2 µM RP with 10 mM Nam elicited a further increase of 114% and 156%, respectively, over RP and Nam combinations. All retinoids elicited an increase in expression of 40 retinoid sensitive genes over control levels. Of the 40 genes, 27 were enhanced by either 0.1 µM RP or 0.5 µM RP with 10 mM Nam and 1% CS. Nam or CS had very modest activity in both models. CONCLUSION: The combination of RP with Nam and CS showed a higher retinoid response than RP in two separate retinoid responsive in vitro models. We hypothesize Nam and CS enhances RP activity by modulating metabolism to tRA via increasing NAD+ pools and inhibiting reduction of retinal (RAL) back to retinol, respectively. The findings provide evidence that this combination may have enhanced efficacy for treating the appearance of photoaged skin.

OBJECTIFS: Les rétinoïdes sont utilisés depuis des décennies comme agents topiques efficaces pour traiter la peau photo-âgée. Le but de notre recherche actuelle est d'évaluer si l'activité du propionate rétinyl ester de vitamine A (RP) peut être augmentée par le niacinamide (Nam) et un flavonoïde contenant un extrait de fruit de Ceratonia Siliqua (CS) dans les modèles in vitro sensibles aux rétinoïdes. MÉTHODES: RP a été testé seul et en combinaison avec Nam et CS dans une ligne de cellule rapporteur de RARα pour l'activation du promoteur et par rapport à l'activation de l'acide transrétinoïque(tRA). Ces traitements ont également été testés dans les kératinocytes pour le profilage d'expression génique par qPCR à l'aide d'un panel de 40 gènes rétinoïdes sensibles. RÉSULTATS: tRA ou RP ont provoqué l'activation du promoteur RARα d'une manière dépendante de la dose. La combinaison de 0,5 µM ou 2 µM de RP avec 10 mM de Nam a permis une augmentation respectivement de 56% et 95% du signal par rapport à RP. L'ajout de 1 % de CS à 0,5 µM ou 2 µM de RP avec 10 mM de Nam a permis une nouvelle augmentation de 114 % et 156 %, respectivement, qu'avec la combinaison RP et Nam. Tous les rétinoïdes ont provoqué une augmentation de l'expression de 40 gènes sensibles aux rétinoïdes sur les niveaux de contrôle. Sur les 40 gènes, 27 ont été améliorés soit par 0,1 µM de RP ou 0.5 µM de RP avec 10 mM de Nam et 1% de CS. Nam ou CS avaient une activité très modeste dans les deux modèles. CONCLUSION: La combinaison de RP avec Nam et CS a montré une réponse rétinoïde plus élevée que RP dans deux modèles in vitro séparés sensibles aux rétinoïdes. Nous émettons l'hypothèse que Nam et CS améliorent l'activité RP en modulant le métabolisme de tRA par l'augmentation des groupement NAD+ et en inhibant la réduction du rétinal (RAL) en rétinol, respectivement. Les résultats fournissent la preuve que cette combinaison peut améliorer l'efficacité du traitement de l'aspect de la peau photo-âgée.

Methods to Assess Activity and Potency of Rexinoids Using Rapid Luciferase-Based Assays: A Case Study with NEt-TMN.

This chapter outlines the materials, methods, and procedures for the in vitro biological evaluation of retinoid-X-receptor (RXR) agonists including 6-(ethyl(5,5,8,8-tetramethyl-5,6,7,8-tetrahydronaphthalen-2-yl)amino)nicotinic acid (NEt-TMN), as well as several NEt-TMN analog compounds recently reported by our group. These methods have general applicability beyond this NEt-TMN case study, and can be employed to characterize and biologically evaluate other putative RXR agonists (rexinoids), and benchmarked against perhaps the most common rexinoid known as bexarotene (Bex), a drug awarded FDA approval for the treatment of cutaneous T-cell lymphoma in 1999 but that is also prescribed for non-small cell lung cancer and continues to be explored in multiple human cancer types. The side-effect profile of Bex treatment includes hypothyroidism and hypertriglyceridemia arising from the inhibition or activation of additional nuclear receptors that partner with RXR. Because rexinoids often exhibit selectivity for RXR activation, versus activating the retinoic-acid-receptor (RAR), rexinoid treatment avoids the cutaneous toxicity commonly associated as a side effect with retinoids. There are many examples of other potent rexinoids, where biological evaluation has contributed useful insight into qSAR studies on these compounds, often also benchmarked to Bex, as potential treatments for cancer. Because of differential pleiotropy in other pathways, even closely related rexinoids display unique side-effect and activity profiles. Notable examples of potent rexinoids in addition to Bex and NEt-TMN include CD3254, LGD100268, and 9-cis-UAB30. Indeed, the methods described herein to evaluate NEt-TMN and analogous rexinoids are generally applicable to a wider variety of potent, moderate, and even weak RXR ligands.In terms of in vitro biological evaluation, methods for a rapid and preliminary assessment of rexinoid activity are described by employing a biologically relevant, RXR-responsive element (RXRE)-mediated transcription assay in mammalian cells. In addition, a second, more sensitive assay is also detailed that utilizes activation of RXR-RXR homodimers in the context of a mammalian two-hybrid (M2H) luciferase assay. Methods for applying the M2H assay at different rexinoid concentrations are further described for the determination of EC50 values for rexinoids from dose-response curves.

An Overview of Carotenoids, Apocarotenoids, and Vitamin A in Agro-Food, Nutrition, Health, and Disease.

Carotenoids are fascinating compounds that can be converted into many others, including retinoids that also play key roles in many processes. Although carotenoids are largely known in the context of food science, nutrition, and health as natural colorants and precursors of vitamin A (VA), evidence has accumulated that even those that cannot be converted to VA may be involved in health-promoting biological actions. It is not surprising that carotenoids (most notably lutein) are among the bioactives for which the need to establish recommended dietary intakes have been recently discussed. In this review, the importance of carotenoids (including apocarotenoids) and key derivatives (retinoids with VA activity) in agro-food with relevance to health is summarized. Furthermore, the European Network to Advance Carotenoid Research and Applications in Agro-Food and Health (EUROCAROTEN) is introduced. EUROCAROTEN originated from the Ibero-American Network for the Study of Carotenoids as Functional Food Ingredients (IBERCAROT).

Nonclinical and human pharmacology of the potent and selective topical retinoic acid receptor-γ agonist trifarotene.

BACKGROUND: First- and third-generation retinoids are the main treatment for acne. Even though efficacious, they lack full selectivity for retinoic acid receptor (RAR) γ, expressed in the epidermis and infundibulum. OBJECTIVES: To characterize the in vitro metabolism and the pharmacology of the novel retinoid trifarotene. MATERIALS AND METHODS: In vitro assays determined efficacy, potency and selectivity on RARs, as well as the activity on the expression of retinoid target genes in human keratinocytes and ex vivo cultured skin. In vivo studies investigated topical comedolytic, anti-inflammatory and depigmenting properties. The trifarotene-induced gene expression profile was investigated in nonlesional skin of patients with acne and compared with ex vivo and in vivo models. Finally, the metabolic stability in human keratinocytes and hepatic microsomes was established. RESULTS: Trifarotene is a selective RARγ agonist with > 20-fold selectivity over RARα and RARß. Trifarotene is active and stable in keratinocytes but rapidly metabolized by human hepatic microsomes, predicting improved safety. In vivo, trifarotene 0·01% applied topically is highly comedolytic and has anti-inflammatory and antipigmenting properties. Gene expression studies indicated potent activation of known retinoid-modulated processes (epidermal differentiation, proliferation, stress response, retinoic acid metabolism) and novel pathways (proteolysis, transport/skin hydration, cell adhesion) in ex vivo and in vivo models, as well as in human skin after 4 weeks of topical application of trifarotene 0·005% cream. CONCLUSIONS: Based on its RARγ selectivity, rapid degradation in human hepatic microsomes and pharmacological properties including potent modulation of epidermal processes, topical treatment with trifarotene could result in good efficacy and may present a favourable safety profile in acne and ichthyotic disorders.

A new class of synthetic retinoid antibiotics effective against bacterial persisters.

A challenge in the treatment of Staphylococcus aureus infections is the high prevalence of methicillin-resistant S. aureus (MRSA) strains and the formation of non-growing, dormant 'persister' subpopulations that exhibit high levels of tolerance to antibiotics and have a role in chronic or recurrent infections. As conventional antibiotics are not effective in the treatment of infections caused by such bacteria, novel antibacterial therapeutics are urgently required. Here we used a Caenorhabditis elegans-MRSA infection screen to identify two synthetic retinoids, CD437 and CD1530, which kill both growing and persister MRSA cells by disrupting lipid bilayers. CD437 and CD1530 exhibit high killing rates, synergism with gentamicin, and a low probability of resistance selection. All-atom molecular dynamics simulations demonstrated that the ability of retinoids to penetrate and embed in lipid bilayers correlates with their bactericidal ability. An analogue of CD437 was found to retain anti-persister activity and show an improved cytotoxicity profile. Both CD437 and this analogue, alone or in combination with gentamicin, exhibit considerable efficacy in a mouse model of chronic MRSA infection. With further development and optimization, synthetic retinoids have the potential to become a new class of antimicrobials for the treatment of Gram-positive bacterial infections that are currently difficult to cure.

[The influence of retinoids on the regeneration of an open osteal wound]. / Vliianie retinoidov na regeneratsiiu otkrytoi kostnoi rany.

The objective of the present study was to elucidate the influence of retinoid-based pharmaceutical products on the process of regeneration of the tissues surrounding an open osteal wound under the experimental conditions. The experiments were carried out using 20 'Sovetskaya shinshilla' rabbits (12 males and 8 females). The animals with the modelled open osteal wound underwent daily treatment by the placement of the dressings impregnated with a mixture of dioxo-methyltetrahydropyrimidine and chloramphenicol ointments supplemented by 0.05% retinoic acid (1:1:1). The rabbits of the control group were treated using the dressings impregnated only with a mixture of dioxo-methyltetrahydropyrimidine and chloramphenicol ointments containing no retinoic acid. The study has demonstrated that the application of the retinoid-based medications for the treatment of the open osteal wound resulted in the well apparent positive dynamics of the wound process in comparison with that in the control animals. It is concluded that the data obtained give evidence that retinoid-based preparations can be used as an adjuvant treatment for the acceleration and promotion of the wound healing process in the trepanation cavity following sanation surgery on the middle ear.

Hepatic Detoxification of Bisphenol A is Retinoid-Dependent.

Bisphenol A (BPA, 2,2-bis(4-hydroxyphenyl) propane) is a widely used industrial chemical. The extensive distribution of BPA in the environment poses risks to humans. However, the molecular mechanisms underlying BPA toxicity as well as its effective detoxification and elimination are not well understood. We have investigated specifically for BPA the notion raised in the literature that the optimal sensing, detoxification, and elimination of xenobiotics requires retinoid (natural derivatives and synthetic analogs of vitamin A) actions. The objective of the study was to explore how retinoids, both those stored in the liver and those originating from recent oral intake, help maintain an optimal xenobiotic detoxification response, affecting mRNA expression and activities of elements of xenobiotic detoxification system upon BPA administration to mice. Wild-type and mice lacking hepatic retinoid stores (Lrat-/-) were acutely treated with BPA (50 mg/kg body weight), with or without oral supplementation with retinyl acetate. Hepatic mRNA expression levels of the genes encoding nuclear receptors and their downstream targets involved in xenobiotic biotransformation, phase I and phase II enzyme activities, and levels of oxidative damage to cellular proteins and lipids in hepatic microsomes, mitochondria and cytosol, were assessed. BPA treatment induced hepatic activities needed for its detoxification and elimination in wild-type mice. However, BPA failed to induce these activities in the livers of Lrat-/- mice. Oral supplementation with retinyl acetate restored phase I and phase II enzyme activities, but accelerated BPA-induced oxidative damage through enhancement of non-mitochondrial ROS production. Thus, the activities of the enzymes involved in the hepatic elimination of BPA require hepatic retinoid stores. The extent of hepatic damage that arises from acute BPA intoxication is directly affected by retinoid administration during the period of BPA exposure and hepatic retinoid stores that have accumulated over the lifetime of the organism.

Carotenoids: biochemistry, pharmacology and treatment.

Carotenoids and retinoids have several similar biological activities such as antioxidant properties, the inhibition of malignant tumour growth and the induction of apoptosis. Supplementation with carotenoids can affect cell growth and modulate gene expression and immune responses. Epidemiological studies have shown a correlation between a high carotenoid intake in the diet with a reduced risk of breast, cervical, ovarian, colorectal cancers, and cardiovascular and eye diseases. Cancer chemoprevention by dietary carotenoids involves several mechanisms, including effects on gap junctional intercellular communication, growth factor signalling, cell cycle progression, differentiation-related proteins, retinoid-like receptors, antioxidant response element, nuclear receptors, AP-1 transcriptional complex, the Wnt/ß-catenin pathway and inflammatory cytokines. Moreover, carotenoids can stimulate the proliferation of B- and T-lymphocytes, the activity of macrophages and cytotoxic T-cells, effector T-cell function and the production of cytokines. Recently, the beneficial effects of carotenoid-rich vegetables and fruits in health and in decreasing the risk of certain diseases has been attributed to the major carotenoids, ß-carotene, lycopene, lutein, zeaxanthin, crocin (/crocetin) and curcumin, due to their antioxidant effects. It is thought that carotenoids act in a time- and dose-dependent manner. In this review, we briefly describe the biological and immunological activities of the main carotenoids used for the treatment of various diseases and their possible mechanisms of action. LINKED ARTICLES: This article is part of a themed section on Principles of Pharmacological Research of Nutraceuticals. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.11/issuetoc.

Antagonizing Retinoic Acid Receptors Increases Myeloid Cell Production by Cultured Human Hematopoietic Stem Cells.

Activities of the retinoic acid receptor (RAR)α and RARγ are important to hematopoiesis. Here, we have investigated the effects of receptor selective agonists and antagonists on the primitive human hematopoietic cell lines KG1 and NB-4 and purified normal human hematopoietic stem cells (HSCs). Agonizing RARα (by AGN195183) was effective in driving neutrophil differentiation of NB-4 cells and this agonist synergized with a low amount (10 nM) of 1α,25-dihydroxyvitamin D3 to drive monocyte differentiation of NB-4 and KG1 cells. Treatment of cultures of human HSCs (supplemented with stem cell factor ± interleukin 3) with an antagonist of all RARs (AGN194310) or of RARα (AGN196996) prolonged the lifespan of cultures, up to 55 days, and increased the production of neutrophils and monocytes. Slowing down of cell differentiation was not observed, and instead, hematopoietic stem and progenitor cells had expanded in number. Antagonism of RARγ (by AGN205728) did not affect cultures of HSCs. Studies of CV-1 and LNCaP cells transfected with RAR expression vectors and a reporter vector revealed that RARγ and RARß are activated by sub-nM all-trans retinoic acid (EC50-0.3 nM): ~50-fold more is required for activation of RARα (EC50-16 nM). These findings further support the notion that the balance of expression and activity of RARα and RARγ are important to hematopoietic stem and progenitor cell expansion and differentiation.

Genetic and pharmacological inhibition of retinoic acid receptor γ function promotes endochondral bone formation.

The nuclear retinoic acid receptors (RARs) play key roles in skeletal development and endochondral ossification. Previously, we showed that RARγ regulates chondrogenesis and that pharmacological activation of RARγ blocked heterotopic ossification (HO), pathology in which endochondral bone forms in soft tissues. Thus, we reasoned that pharmacological inhibition of RARγ should enhance endochondral ossification, leading to a potential therapeutic strategy for bone deficiencies. We created surgical bone defects in wild type and RARγ-null mice and monitored bone healing. Fibrous, cartilaginous, and osseous tissues formed in both groups by day 7, but more cartilaginous tissue formed in mutants within and around the defects compared to controls. Next, we implanted a mixture of Matrigel and rhBMP2 subdermally to induce ectopic endochondral ossification. Administration of RARγ antagonists significantly stimulated ectopic bone formation in wild type but not in RARγ-null mice. The antagonist-induced increases in bone formation were preceded by increases in cartilage formation and were accompanied by higher levels of phosphorylated Smad1/5/8 (pSmad1/5/8) compared to vehicle-treated control. Higher pSmad1/5/8 levels were also observed in cartilaginous tissues forming in healing bone defects in RARγ-null mice, and increases in pSmad1/5/8 levels and Id1-luc activity were observed in RARγ antagonist-treated chondrogenic cells in culture. Our data show that genetic or pharmacological interference with RARγ stimulates endochondral bone formation and does so at least in part by stimulating canonical BMP signaling. This pharmacologic strategy could represent a new tool to enhance endochondral bone formation in the setting of various orthopedic surgical interventions and other skeletal deficiencies. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1096-1105, 2017.

Incidence of apoptosis after retinoids and insulin-like growth factor-I (IGF-I) supplementation during goat in vitro embryo production.

The addition of growth factors and vitamins enhances goat embryonic development in vitro. However, few attempts have been reported trying to identify supplementation regimens for oocyte maturation or embryo culture with additive properties. The present report was aimed to evaluate if retinoids [0.3 µM retinyl acetate (RAc) and 0.5 µM 9-cis-retinoic acid (RA)] supplementation during goat oocyte maturation and retinoids and/or 50 ng mL-1 IGF-I during embryo culture synergically enhanced embryonic development while diminishing the incidence of apoptosis. All combinations of RAc and RA treatment produced blastocysts with similar efficiencies, while IGF-I enhanced embryos yields irrespectively of retinoid addition. Moreover, retinoids and IGF-I supplementation showed similar caspase activity or DNA fragmentation indexes in blastocysts. In conclusion, supplementation with retinoids and IGF-I during goat embryo culture enhances blastocysts development without synergic reduction of apoptosis.

Retinoids have therapeutic action in type 2 diabetes.

OBJECTIVE: Uncontrolled diabetes is associated with a compromised antioxidant state of the body. Consequentially, the reactive oxygen species generated lead to oxidative insult and associated complications. Based on this paradigm, exogenous antioxidant supplementation is thought to exert a therapeutic role in type 2 diabetes (T2-D) biology. METHODS: In the present study, the effect of vitamin A supplementation was assessed on disease progression in T2-D BALB/c mice. Animals were divided into three groups. With the exception of control, the mice in remaining groups were induced with experimental T2-D. After a 15-day treatment protocol, the mice were sacrificed and various parameters were analyzed. RESULTS: The treated group evidenced a considerable improvement in total antioxidant potential and glycemic control. A therapeutic effect on beta cell degeneration as compared to the diabetic group was also found. CONCLUSIONS: The study illustrates the antihyperglycemic and antioxidant potential of vitamin A in vivo, which has potential to serve as a dietary intervention in T2-D.

Characterization of total retinoid-like activity of compounds produced by three common phytoplankton species.

Phytoplankton can produce various bioactive metabolites, which may affect other organisms in the aquatic environment. This study provides the first information on the total retinoid-like activity associated with both intracellular and extracellular metabolites produced by selected phytoplankton species that could play a role in teratogenic effects and developmental disruption in exposed organisms. The studied species included a coccoid cyanobacteria (Microcystis aeruginosa), a filamentous cyanobacteria (Aphanizomenon gracile) and a green alga (Desmodesmus quadricauda), all of which commonly occur in freshwater bodies in Europe. Methanolic extracts from cellular material and extracellular exudates were prepared from cultures cultivated in two light-intensity variants with five replicates for each species. The retinoid-like activity was evaluated by in vitro assays along with chemical analyses of two potent retinoic acids (all-trans retinoic acid (ATRA) and 9cis-RA). The mean total retinoid-like activity of metabolites produced by the three studied species representing different phytoplankton taxonomic groups ranged from 705 to 5572ng ATRA equivalent/g dry matter corresponding to 0.064-0.234ng ATRA/106 cells. Retinoid-like activity was found in the cellular extracts of all species, while only the extracellular exudates of cyanobacteria exhibited detectable activity (41-1081ng ATRA/L). The greatest extracellular as well as total (extra- and intra- cellular together) retinoid-like activity was detected for Microcystis aeruginosa. The two potent retinoic acids studied were more frequently detected in cellular extracts than in extracellular exudates of all species. Their contribution to observed in vitro effects was relatively low for all tested samples (<10%), indicating a substantial contribution of other retinoid-like compounds to the overall activity. The results indicate possible influence of light intensity and cell density on the production of metabolites with retinoid-like activity and the cyanotoxin microcystin by the studied species. The recalculation of the results per dry weight, water volume, per 106 cells and biovolume enables a direct comparison of the retinoid-like activity distribution between extracts and exudates and the use of the data for risk assessment in water bodies.