Membranal effects of phytoestrogens and carboxy derivatives of phytoestrogens on human vascular and bone cells: new insights based on studies with carboxy-biochanin A

Growth and Osteogenic Differentiation of Discarded Gingiva-Derived Mesenchymal Stem Cells on a Commercial Scaffold

BACKGROUND

In periodontal patients with jawbone resorption, the autologous bone graft is considered a "gold standard" procedure for the placing of dental prosthesis; however, this procedure is a costly intervention and poses the risk of clinical complications. Thanks to the use of adult mesenchymal stem cells, smart biomaterials, and active biomolecules, regenerative medicine and bone tissue engineering represent a valid alternative to the traditional procedures.

AIMS

In the past, mesenchymal stem cells isolated from periodontally compromised gingiva were considered a biological waste and discarded during surgical procedures. This study aims to test the osteoconductive activity of FISIOGRAFT Bone Granular® and Matriderm® collagen scaffolds on mesenchymal stem cells isolated from periodontally compromised gingiva as a low-cost and painless strategy of autologous bone tissue regeneration.

MATERIALS AND METHODS

We isolated human mesenchymal stem cells from 22 healthy and 26 periodontally compromised gingival biopsy tissues and confirmed the stem cell phenotype by doubling time assay, colony-forming unit assay, and expression of surface and nuclear mesenchymal stem cell markers, respectively by cytofluorimetry and real-time quantitative PCR. Healthy and periodontally compromised gingival mesenchymal stem cells were seeded on FISIOGRAFT Bone Granular® and Matriderm® scaffolds, and in vitro cell viability and bone differentiation were then evaluated.

RESULTS

Even though preliminary, the results demonstrate that FISIOGRAFT Bone Granular® is not suitable for in vitro growth and osteogenic differentiation of healthy and periodontally compromised mesenchymal stem cells, which, instead, are able to grow, homogeneously distribute, and bone differentiate in the Matriderm® collagen scaffold.

CONCLUSION

Matriderm® represents a biocompatible scaffold able to support the in vitro cell growth and osteodifferentiation ability of gingival mesenchymal stem cells isolated from waste gingiva, and could be employed to develop low-cost and painless strategy of autologous bone tissue regeneration.

Perspectives Regarding the Role of Biochanin A in Humans

Biochanin A (BCA) is an isoflavone mainly found in red clover with poor solubility and oral absorption that is known to have various effects, including anti-inflammatory, estrogen-like, and glucose and lipid metabolism modulatory activity, as well as cancer preventive, neuroprotective, and drug interaction effects. BCA is already commercially available and is among the main ingredients in many types of supplements used to alleviate postmenopausal symptoms in women. The activity of BCA has not been adequately evaluated in humans. However, the results of many in vitro and in vivo studies investigating the potential health benefits of BCA are available, and the complex mechanisms by which BCA modulates transcription, apoptosis, metabolism, and immune responses have been revealed. Many efforts have been exerted to improve the poor bioavailability of BCA, and very promising results have been reported. This review focuses on the major effects of BCA and its possible molecular targets, potential uses, and limitations in health maintenance and treatment.

Estradiol-17β increases 12- and 15-lipoxygenase (type2) expression and activity and reactive oxygen species in human umbilical vascular smooth muscle cells

The net vascular effect of estrogens on the vasculature is still under debate. Here we tested the effects of estradiol- 17β (E2) as well as estrogen-receptor subtype specific and non-specific agonists and antagonists on the expression and eicosanoid production of lipoxygenase (LO) enzymes expressed in culture human umbilical vascular smooth muscle cells (VSMC), the platelet type 12LO and 15LO type 2. E2 increased 12 and 15LO mRNA expression by 2-3 folds and elicited an acute 50% increase 12 and 15 hydroxyeicosatetraenoic acid (HETE) production. Neither estrogen receptor ERα nor ERβ-specific agonists were able to reproduce the induction of LO expression, but E2-induced expression was effectively blocked by ER non-specific and receptor subtype specific antagonists. Because 12 and 15HETE can increase reactive oxygen species in other cell types, we tested the possibility that E2 could raise ROS through LO. Indeed, E2 as well as the LO products 12 and 15HETE increased reactive oxygen species (ROS) in VSMC. E2-dependent and HETE-induced ROS could be blocked by NAD (P) H-oxidase inhibitors and by the ER general antagonist ICI. E2-induced ROS was partially (∼50%) blocked by the LO inhibitor baicalein, but the LO blocker had no effect on 12 or 15HETE- induced ROS formation, thus suggesting that part of E2-dependent ROS generation resulted from E2-induced 12 and 15HETE. Collectively these findings unveil an unrecognized effect of E2 in human VSMC, to induce 12 and 15LO type 2 expression and activity and suggest that E2-dependent ROS formation in VSMC may be partially mediated by the induction of 12 and 15HETE.

Statins enhance rotator cuff healing by stimulating the COX2/PGE2/EP4 pathway: an in vivo and in vitro study

BACKGROUND

Statins are lipid-lowering drugs with many beneficial pleiotropic effects. Cyclooxygenase (COX2) selective inhibitors that are commonly prescribed in orthopaedic patients may effect healing. Evidence indicates that statins stimulate COX2 activity.

HYPOTHESIS

Atorvastatin (ATV) administration will enhance tendon healing by stimulating the acute inflammatory phase via increasing the production of prostaglandin E2 (PGE2).

STUDY DESIGN

Controlled laboratory study.

METHODS

After experimental rotator cuff (RC) tearing and suturing, 48 Wistar rats were randomly allocated into 4 groups: (1) ATV (20 mg/kg), (2) celecoxib (CEL; COX2 inhibitor) (10 mg/kg), (3) ATV + CEL (20 mg/kg + 10 mg/kg), and (4) saline alone. Animals were sacrificed 3 weeks after RC tears and repair, and tendon integrity was tested biomechanically in tension. To further evaluate the underlying mechanism of action, human and rat primary tenocytes were obtained from the supraspinatus tendon. Cultures were treated with a therapeutic dosage of 5 commonly used statins: CEL, ATV + CEL, PGE2, and a selective antagonist of PGE2 receptor 4 (EP4). Cell proliferation (thymidine incorporation), migration (wound healing assay), and adhesion (iCELLigence) were evaluated. The expression of all PGE2 receptors (EPs) was determined by quantitative reverse transcription polymerase chain reaction.

RESULTS

Tension testing of healed tendons demonstrated significantly higher maximal loading and stiffness in the ATV group as compared with the saline (+30% and +20%, respectively; P < .001) and CEL groups (+33% and +50%, respectively; P < .005). Celecoxib alone did not affect tendon healing (P = .88). In line with these in vivo results, tenocytes treated with statins demonstrated significantly higher proliferation rates; CEL abrogated this effect, and PGE2 treatment stimulated tenocyte proliferation even in the presence of CEL. Also, ATV stimulated the migration (wound healing) and adhesion of tenocytes. Among all PGE2 receptors, tenocytes mainly express EP4, and an EP4 selective antagonist blocked the effect of ATV.

CONCLUSION

Results indicate that ATV enhances tendon healing by stimulating tenocyte proliferation, migration, and adhesion via increased COX2 activity and autocrine/paracrine PGE2 signaling. Findings also demonstrate that this effect is mediated by EP4 signaling.

CLINICAL RELEVANCE

Although chronic inflammation contributes to the development of tendinopathy, study results advocate for a positive role of PGE2 in tendon healing during the acute inflammatory phase that follows tendon surgical repair. It is therefore suggested that ATV should be further investigated as a possible modality to improve tendon healing.

Effects of commonly used medications on bone tissue mineralisation in SaOS-2 human bone cell line: an in vitro study

We analysed the effects of commonly used medications on human osteoblastic cell activity in vitro, specifically proliferation and tissue mineralisation. A list of medications was retrieved from the records of patients aged > 65 years filed in the database of the largest health maintenance organisation in our country (> two million members). Proliferation and mineralisation assays were performed on the following drugs: rosuvastatin (statin), metformin (antidiabetic), metoprolol (β-blocker), citalopram (selective serotonin reuptake inhibitor [SSRI]), and omeprazole (proton pump inhibitor (PPI)). All tested drugs significantly stimulated DNA synthesis to varying degrees, with rosuvastatin 5 µg/ml being the most effective among them (mean 225% (SD 20)), compared with metformin 10 µg/ml (185% (SD 10)), metoprolol 0.25 µg/ml (190% (SD 20)), citalopram 0.05 µg/ml (150% (sd 10)) and omeprazole 0.001 µg/ml (145% (SD 5)). Metformin and metoprolol (to a small extent) and rosuvastatin (to a much higher extent) inhibited cell mineralisation (85% (SD 5)). Our results indicate the need to evaluate the medications prescribed to patients in terms of their potential action on osteoblasts. Appropriate evaluation and prophylactic treatment (when necessary) might lower the incidence and costs associated with potential medication-induced osteoporosis.

Rivaroxaban, a direct inhibitor of the coagulation factor Xa interferes with hormonal-induced physiological modulations in human female osteoblastic cell line SaSO2

The use of anticoagulants has been associated with systemic osteoporosis and increased risk for poor fracture healing but is inevitable following major orthopedic surgery of lower limbs. Rivaroxaban A (R) is an anticoagulant recently introduced in the clinical setting, which is a specific factor Xa inhibitor. We reported previously that R significantly inhibited cell growth, energy metabolism and alkaline phosphatase activity in human osteoblastic cell line SaOS2, with no effect on mineralization, indicating transient inhibition of bone formation. We now investigated the effects of R on SaOS2 response to osteoblast-modulating hormones. At sub-confluence cells were treated with: estradiol-17β (E2), the phytoestrogens daidzein (D) and biochainin A (BA), the carboxy-pytoestrogenic derivative carboxy-D (cD), the estrogen receptor α (ERα) agonist PPT, the estrogen receptor β (ERβ) agonist DPN, parathyroid hormone (PTH) and several vitamin D metabolites and analogs with/without R for 24h. All hormones tested stimulated significantly DNA synthesis (DNA), creatine kinase (CK) and alkaline phosphatase (ALP) specific activities, but all these stimulations were totally inhibited when given together with R. R had no effect on mRNA expression of ERα, ERβ and 25 Hydroxy-vitamin D3-1α hydroxylase (1OHase), but inhibited hormonal modulations of mRNA expressions. In conclusion R inhibited significantly hormonal stimulation of different parameters indicating inhibition of not only the early stages of bone formation, but also the stimulatory effects of bone modulating hormones with a yet unclear mechanism. The relevance of these findings to human bone physiology is yet to be investigated.

Age-dependent responsiveness of human female bone cells to vitamin D analog and PTH

Vitamin D less-calcemic analog JKF 1624 F2-2 (JKF) and PTH 1-34 stimulate in human female cultured osteoblasts (Ob) DNA synthesis (DNA), creatine kinase specific activity (CK), 1α, 25 vitamin D hydroxylase mRNA (1OHase) expression and 1,25(OH)2D3 (1,25) production, estrogen receptors (ER) mRNA expression and intracellular and membranal estrogen binding. In the present study, cultured Ob from different ages were subjected to hormonal stimulations and analyzed for different parameters. We found: 1) ERα expression is higher and ERβ expression is lower in pre-meno - pausal Ob (prOb), with similar intracellular and membranal binding. 2) JKF and PTH up-regulated ERα and JKF downregulated ERβ in both Ob, while PTH stimulated it in post- (poOb) and inhibited it in prOb. 3) There is higher expression of 1OHase mRNA in prOb, but 1,25 production is similar. Both parameters were hormonally stimulated to higher extent in prOb. 4) Ob express 12 and 15 lipoxygenase (LO) mRNA and produce 12- and 15-hydroxyeicosatetraenoic acid (H). 12LO expression is higher and 15LO is lower in prOb, while 12H is higher in prOb and 15H is similar in both. JKF inhibited 12LO expression in prOb and stimulated in poOb, whereas PTH stimulated it to higher extent in prOb. JKF stimulated and PTH inhibited 15LO expression in both; 12 and 15H were stimulated by both hormones in both Ob. 5. PTH and JKF stimulated DNA and CK in both Ob. In conclusion Ob demonstrate some age-dependent response to calciotrophic hormones, but the mechanism and beneficial outcome for human is unclear.

The effects of direct factor Xa inhibitor (Rivaroxaban) on the human osteoblastic cell line SaOS2

Thromboprophylaxis reduces the risk of surgery-related deep vein thrombosis, but anticoagulants were associated with systemic osteoporosis, a known risk factor for poor fracture healing. Rivaroxaban (XARELTO(®)) is a novel anticoagulant with specific ability to inhibit factor Xa, a serine endopeptidase, which plays a key role in coagulation. This study investigated the direct effects of rivaroxaban on bone biology using an in vitro cell culture model from the human female osteoblastic cell line SaOS2. Cells at subconfluence were treated for 24 hr with different concentrations of rivaroxaban and analyzed for DNA synthesis and creatine kinase- and alkaline phosphatase-specific activities, and were treated 21 days for analyzing mineralization. Rivaroxaban (0.01-50 μg/ml) dose-dependently inhibited up to 60% DNA synthesis of the cells. Creatine kinase-specific activity was also inhibited dose-dependently to a similar extent by the same concentrations. Alkaline phosphatase-specific activity was dose-dependently inhibited but only up to 30%. Cell mineralization was unaffected by 10 μg/ml rivaroxaban. This model demonstrated a significant rivaroxaban-induced reduction in osteoblastic cell growth and energy metabolism, and slight inhibition of the osteoblastic marker, alkaline phosphatase, while osteoblastic mineralization was unaffected. These findings might indicate that rivaroxaban inhibits the first stage of bone formation but does not affect later stages (i.e., bone mineralization).

Three-dimensional dynamic culture of pre-osteoblasts seeded in HA-CS/Col/nHAP composite scaffolds and treated with α-ZAL

Pre-osteoblast MC3T3-E1 cells were cultured in hyaluronic acid-modified chitosan/collagen/nano-hydroxyapatite (HA-CS/Col/nHAP) composite scaffolds and treated with phytoestrogen α-zearalanol (α-ZAL) to improve bone tissue formation for bone tissue engineering. Perfusion and dynamic strain were applied to three-dimensional (3D) cultured cells, which simulates mechanical microenvironment in bone tissue and solves mass transfer issues. The morphology of cell-scaffold constructs in vitro was then examined and markers of osteogenesis were assessed by immunohistochemistry staining and western blotting. The results showed that cells expanded their pseudopodia in an irregular manner and dispersed along the walls in 3D-dynamic culture. Osteogenic phenotype was increased or maintained by enhanced collagen I (COLI) levels, decreased osteopontin expression and having little effect on osteocalcin expression during the 12 days of in vitro culture. In response to α-ZAL, the cell-scaffold constructs showed inhibited cellular proliferation, enhanced the alkaline phosphatase (ALP) activity and increased ratio of osteoprotegerin to receptor activator of nuclear factor kappa B (NF-κB) ligand (RANKL). Application of perfusion and dynamic strain to cells-scaffold constructs treated with α-ZAL represents a promising approach in the studies of osteogenesis stimulation of bone tissue engineering.

Mutual interaction of special phytoestrogenic compounds, their synthetic carboxy-derivatives and the less-calcemic vitamin D analog activities in human derived female cultured osteoblasts

Cultured female-derived human bone cells (hObs) responded by different parameters to different phytoestrogenic and vitamin D compounds. Pre- and post-menopausal hObs express ERα and ERβ mRNA with higher abundance of ERα. Pre-treatment with the less-calcemic vitamin D analog JKF 1624F(2)-2 (JKF) upregulated responsiveness to estrogens via modulation of ERs expression. These estrogenic compounds induce the expression and activity of 25 hydroxy-vitamin D(3)-1α hydroxylase (1OHase). We now analyzed the effects of carboxy-genistein (cG), carboxy-biocainin A (cBA) and carboxy-daidzein (cD), of BA, D or G and of licorice derived compounds glabridin (Glb) and glabrene (Gla) and estradiol-17β (E(2)) on DNA synthesis, creatine kinase specific activity (CK), intracellular and membranal E(2) binding and their modulations by JKF in hObs. We also analyzed modulation by phytoestrogenic compounds of 1OHase mRNA expression and activity. We showed that: (1) all compounds stimulated DNA synthesis and CK. (2) JKF and all estrogenic compounds modulated ERα and ERβ mRNA expression. (3) Pre-treatment with JKF increased DNA synthesis and CK responses only to E(2), D, G and Gla. (4) JKF increased the intracellular competitive binding only of E(2), D and G. (5) JKF abolished the membranal binding of all protein-bound estrogens. (6) JKF and all estrogenic compounds except the protein-bound ones up-regulated 1OHase expression and activity. In conclusion phytoestrogens and their analogs increase DNA synthesis and CK, and lead to increased production of 1,25(OH)(2)D(3) in hObs, while pre-treatment with JKF modulates the effect of estrogenic compounds via regulation of ERs mRNA expression in a yet unclear mechanism.

Anti-thyroid cancer properties of a novel isoflavone derivative, 7-(O)-carboxymethyl daidzein conjugated to N-t-Boc-hexylenediamine in vitro and in vivo

The incidence of thyroid cancer is up to 3 folds higher in women than in men, suggesting that estrogenic effects may be involved in the pathogenesis of this malignancy. Here, we explore whether or not human thyroid cancer cell growth can be curbed by a novel isoflavone derivative generated in our laboratory, the N-t-Boc-hexylenediamine derivative of 7-(O)-carboxymethyl daidzein (cD-tboc). With the exception of the follicular cancer cell line WRO, estrogen receptor (ER)α mRNA was only marginally expressed in cell lines derived from papillary (NPA), follicular (MRO), anaplastic thyroid carcinoma (ARO) such that the expression of estrogen receptor (ER) βmRNA was more abundant than that of ERα mRNA in these cell types. Estradiol-17β (E2; 0.03-300nmol/l) per se increased proliferation in all four cell-types. The ERβ-specific agonist DPN increased [(3)H]-thymidine incorporation in all four thyroid cancer cell lines, whereas the ERα-specific agonist PPT increased growth only in NPA and WRO. By contrast, cD-tboc, derived from the weak estrogen daidzein, did not cause cell growth and dose-dependently diminished cell growth in all four cell lines via apoptosis and not necrosis, as detected by the release of histone-DNA fragments. The cytotoxic growth inhibitory effect of cD-tboc in these cells was modulated by E2 and the general caspase inhibitor Z-VAD-FMK, and the magnitude of this salvage was cell type-and dose-dependent. When nude mice carrying ARO thyroid xenografts were treated with cD-tboc, tumor volume decreased significantly, and no apparent toxicity was observed. These results suggest that cD-tboc may be a promising agent for therapy of thyroid carcinoma either alone or in combination with existing cytotoxic drugs.

Sex specific response of cultured human bone cells to ERα and ERβ specific agonists by modulation of cell proliferation and creatine kinase specific activity

We have previously reported that human cultured bone cells (hObs) respond to estradiol-17β (E2) by stimulating DNA synthesis, creatine kinase BB specific activity (CK) and other parameters sex-specifically. We now investigate the sex specificity of the response of these hObs to estrogen receptor (ER) α and ERβ specific agonists. Real time PCR revealed that all cells express mRNA for both ERs. ERα mRNA but not ERβ mRNA was stimulated by all estrogenic compounds in both pre- and post-menopausal hObs with no effect in male hObs. Cells treated with E2, 2,3-bis (4-hydroxyphenyl)-propionitrile (DPN; ERβ specific agonist) and 4,4',4″-[4-propyl-(1H)-pyrazol-1,3,5-triyl] tris-phenol (PPT; ERα specific agonist) showed increased DNA synthesis and CK in all female but not male hObs. Raloxifene (Ral), a specific ERα antagonist, inhibited the stimulation of DNA synthesis and CK by E2 or PPT, but not by DPN. DPN and PPT like E2 modulated the expression of both 12 and 15 lipooxygenase (LO) mRNA in both female but not male hObs. 12 and 15 HETE production was modulated only by DPN and PPT in these cells. The LO inhibitor baicaleine inhibited only E2 and PPT but not DPN effects in both female hObs. In conclusion, we provide herein evidence for the separation of age- and sex-dependent mediation via both ERα and ERβ pathways in the effects of estrogens on hObs, with a yet unknown mechanism.

The effects of estrogen receptors α- and β-specific agonists and antagonists on cell proliferation and energy metabolism in human bone cell line

In cultured human osteoblasts estradiol-17β (E2) modulated DNA synthesis, the specific activity of creatine kinase BB (CK), 12 and 15 lipoxygenase (LO) mRNA expression and formation of 12- and 15-hydroxyeicosatetraenoic acid (HETE). We now investigate the response of human bone cell line (SaOS2) to phytoestrogens and estrogen receptors (ER)-specific agonists and antagonists. Treatment of SaSO2 with E2, 2,3-bis (4-hydroxyphenyl)-propionitrile (DPN; ERβ-specific agonist), 4,4',4″-[4-propyl-(1H)-pyrazol-1,3,5-triyl] tris-phenol (PPT; ERα-specific agonist), biochainin A (BA), daidzein (D), genistein (G) and raloxifene (Ral) showed increased DNA synthesis and CK. Ral inhibited completely all stimulations except DPN and to some extent D. The ERα-specific antagonist methyl-piperidino-pyrazole (MPP) and the ERβ-specific antagonist 4-[2-phenyl-5,7-bis (tri-fluoro-methyl) pyrazolo [1,5-a]pyrimidin-3-yl] phenol (PTHPP) inhibited DNA synthesis, CK and reactive oxygen species (ROS) formation induced by estrogens according to their receptors affinity. The LO inhibitor baicaleine inhibited only E2, DPN and G's effects. E2 and Ral unlike all other compounds had no effect on ERα mRNA expression, while ERβ mRNA expression was stimulated by all compounds. All compounds modulated the expression of 12LO and 15LO mRNA, except E2, PPT and Ral for 12LO, and 12- and 15-HETE productions and stimulated ROS formation which was inhibited by NADPH oxidase inhibitors diphenyleneiodonium chloride (DPI) and N-acetyl cysteine and the estrogen inhibitor ICI. DPI did not affect hormonal-induced DNA and CK. In conclusion, we provide evidence for the separation of mediation via ERα and ERβ pathways in the effects of estrogenic compounds on osteoblasts, but the role of LO/HETE/ROS is unclear.

DT56a (Femarelle), contrary to estradiol-17β, is effective in human derived female osteoblasts in hyperglycemic condition

We have reported previously, that female-derived cultured osteoblasts (hObs) responded to DT56a (Femarelle) measured by the stimulation of creatine kinase specific activity (CK), which is a marker for hormone responsiveness and (3)[H] thymidine incorporation into DNA (DNA synthesis). Since the skeletal protective effects of estrogens are not discernable in hyperglycemic diabetic women, we sought to analyze the effect of estrogenic compounds on CK and DNA synthesis in hObs when grown in high glucose concentration (HG). Cells were grown either in normal glucose (NG) (4.5g/L; 22mM) or HG (9.0g/L; 44mM) for 7 days. HG increased constitutive CK but, the response of CK activity and DNA synthesis to estradiol-17β (E(2)) treatment was reduced. In contrary, DT56a was found to be active (as measured by CK activity and DNA synthesis) in both NG and HG. HG decreases the hormonal responsiveness and might block important effects of estrogenic compounds, most likely contributing to their decreased skeletal preserving properties in hyperglycemic women. In hObs from post-menopausal women grown in HG, ERs mRNA expressions were unchanged. On the other hand, in hObs from pre-menopausal women HG increased ERs mRNA expressions. Since DT56a unlike E(2) is active in HG environment as well as in normal glucose, it may be an effective bone restoring agent in diabetic post-menopausal women.

Dihydrotestosterone and estradiol-17beta mutually neutralize their inhibitory effects on human vascular smooth muscle cell growth in vitro

We reported previously that high concentrations of either estradiol-17beta (E(2)) or dihydrotestosterone (DHT) inhibit growth of human cultured vascular smooth muscle cells (VSMC), mediated by cell membrane receptors and MAP-kinase-kinase activity (MEK). We now tested whether the presence of the opposite gender's dominant sex hormone modifies these effects. We incubated VSMC with various concentrations of E(2) and DHT or protein bound hormones (E(2)-BSA or T-BSA), alone or in various combinations. High concentration of E(2) or E(2)-BSA inhibited VSMC growth and stimulated MEK. In the presence of 3 nM DHT, high concentration of E(2) no longer inhibited (3)[H] thymidine incorporation or increased MEK. Moreover, when high DHT concentration (300 nM) was added to VSMC exposed to high E(2), VSMC growth actually increased without change in MEK. DHT at 300 nM suppressed VSMC growth and increased MEK while 0.3 nM E(2) had only marginal effect on this interaction, and 30 nM E(2) reversed the inhibitory effect of DHT on cell growth. The inhibitory effects of both E(2) and DHT on VSMC cell growth and the stimulation of MEK was apparently mediated by cell membrane receptors, as it persisted when bovine serum albumin (BSA)-bound hormones were used. Further, inhibition of VSMC growth induced by E(2)-BSA was reversed in the presence of T-BSA and vice versa. These results suggest that while female and male sex hormones affect VSMC growth similarly, they interfere in a dose-, hormone- and MEK-dependent manner with each other's effect.

Regulation of cellular signals from nutritional molecules: a specific role for phytochemicals, beyond antioxidant activity

Phytochemicals (PhC) are a ubiquitous class of plant secondary metabolites. A "recommended" human diet should warrant a high proportion of energy from fruits and vegetables, therefore providing, among other factors, a huge intake of PhC, in general considered "health promoting" by virtue of their antioxidant activity and positive modulation, either directly or indirectly, of the cellular and tissue redox balance. Diet acts through multiple pathways and the association between the consumption of specific food items and the risk of degenerative diseases is extremely complex. Recent literature suggests that molecules having a chemical structure compatible with a putative antioxidant capacity can actually "perform" activities and roles independent of such capacity, interacting with cellular functions at different levels, such as affecting enzyme activities, binding to membrane or nuclear receptors as either an elective ligand or a ligand mimic. Inductive or signaling effects may occur at concentrations much lower than that required for effective antioxidant activity. Therefore, the "antioxidant hypothesis" is to be considered in some cases an intellectual "shortcut" possibly biasing the real understanding of the molecular mechanisms underlying the beneficial effects of various classes of food items. In the past few years, many exciting new indications elucidating the mechanisms of polyphenols have been published. Here, we summarize the current knowledge of the mechanisms by which specific molecules of nutritional interest, and in particular polyphenols, play a role in cellular response and in preventing pathologies. In particular, their direct interaction with nuclear receptors and their ability to modulate the activity of key enzymes involved in cell signaling and antioxidant responses are presented and discussed.

A daidzein-daunomycin conjugate improves the therapeutic response in an animal model of ovarian carcinoma

The use of daunomycin against neoplasms is limited due to its severe cardiotoxicity. The cytotoxicity of daunomycin can be minimized by linking it to an affinity tag. Since ovarian cancer cells are sensitive to isoflavone action, we synthesized a daidzein daunomycin conjugate. In MLS human ovarian cancer cells, the conjugate was shown to have a larger cytotoxic effect than daunomycin per se at a low concentration. The conjugate was then tested in vivo in mice carrying MLS xenografts. Tumour growth in the groups of conjugate and daunomycin was inhibited by >50% as compared to vehicle treated mice. In contrast to daunomycin treated mice, no weight reduction or death was seen in mice treated with the conjugate. In vivo imaging of the fluorescence signal generated by daunomycin indicated uptake of both conjugate and daunomycin by the tumour. Tumour fluorescence was, however, higher in the conjugate treated mice than in the daunomycin treated mice, thus suggesting specific delivery of the drug to the tumour. Histological examination of myocardial tissue indicated that only the daunomycin, but not conjugate treated mice showed cardiac damage. These results indicate that targeting of daunomycin via carboxymethyldaidzein retains daunomycin's cytotoxic effects while averting its toxicity in an ovarian xenograft.

Lipoxygenase metabolites are mediators of PTH-dependent human osteoblast growth

PTH-induced osteoblast proliferation may contribute to its anabolic effects in bone. Since PTH-dependent osteoblast-like cell (Ob) growth is mediated via protein kinase C (PKC) and MAP kinase-kinase (MEK) and since lipoxygenase (LO) products activate PKC in a number of cell types, we assessed the expression of LO pathways in primary human cultured Ob. Ob from pre- or post-menopausal women were cultured and were treated with PTH and assayed for the expression of 12-LO and both type I and type II 15-LO mRNA and for the release their enzymatic products, 12- and 15-hydroxyeicosatetraenoic acid (HETE). Cells were also treated with PTH for stimulation DNA synthesis. First, Ob express platelet type- 12-LO and both type I and type II 15-LO mRNA and release their enzymatic products, 12- and 15-hydroxyeicosatetraenoic acid (HETE). Second, in female Ob, PTH induced a rapid increase in 12-HETE (50 fold increase) and 15-HETE (80 fold increase) and increased the expression of 12-LO mRNA but not of the two isoforms of 15-LO. PTH as well as 12 and 15-HETE stimulated DNA synthesis in Ob. The LO inhibitor baicalein inhibited PTH-stimulated DNA synthesis, which was reversed in the presence of either 12- or 15-HETE. A PKC inhibitor (bisindolylmaleimide I) as well as a MEK inhibitor (PD 98059) completely inhibited the stimulation of DNA synthesis by PTH, 12-HETE and the combination of PTH and 12-HETE. In contrast, 15-HETE-induced DNA synthesis was not abolished by these inhibitors. Further, 15-HETE partially restored the stimulatory effect of PTH on DNA synthesis in cells treated with PKC or MEK inhibitors. Finally, PTH- induced ERK1/2 phosphorylation, was blocked by a MEK inhibitor. These results demonstrate a novel mechanism of PTH-induced human bone cell proliferation operating through LO enzymes.

Diabetes modulates differentially creatine kinase-specific activity responsiveness to estradiol-17beta and to raloxifene in rat organs

Diabetes mellitus increases the risk for CVD in women. While there is considerable evidence suggesting beneficial effects of estrogen on decreasing lipid peroxidation, atherosclerotic processes, and cardiovascular diseases, diabetes negates most estrogen protective effects as well as the skeletal protective effects of estrogens, which are not discernable in diabetic women. In the present study, we examined the in vivo effects of estradiol-17beta (E2), on creatine kinase (CK)-specific activity, in estrogen-responsive organs from healthy and diabetic rats. Healthy or diabetic (streptozotocin-induced) female rats were injected with either E2 (10-50 microg/rat) or raloxifene (Ral; 500-1,000 microg/rat). Twenty-four hours following the injection, animals were sacrificed; their organs removed and assayed for CK-specific activity. CK-specific activity in different organs [Left ventricle of heart (Lv), uterus (Ut), aorta (Ao), para uterine adipose tissue (Ad), epiphyseal cartilage (Ep), and diaphyseal bone (Di)] from healthy animals, was stimulated with increased doses of E2, with maximum at 20 microg/rat. Age-matched diabetic female rats exhibited a remarkable decreased response to E2 in all organs except Ut. In contrast, the response to Ral was not altered in diabetic rats. Similar results were observed in organs from ovariectomized female rats (Ovx), healthy or diabetic. These results support our previous in vitro findings, demonstrating that hyperglycemia decreases CK response to E2 but not to Ral in cultured human vascular and bone cells. In summary, diabetes mellitus decreases CK response to E2 but not that of Ral in skeletal and vascular tissues. The decreased response to E2 detected in organs derived from diabetic rats might be due to changes in nuclear and/or membrane estrogen receptors and/or other genomic and non-genomic pathways, as was shown in in vitro cellular models.

Responsiveness to estradiol-17beta and to phytoestrogens in primary human osteoblasts is modulated differentially by high glucose concentration

We have reported previously, that female-derived bone cells responded to 17beta-estradiol (E(2)) and to raloxifene (Ral), whereas male-derived cells responded only to dihydrotestosterone (DHT) when the stimulation of creatine kinase specific activity (CK), which is a marker for hormone responsiveness, was measured. In cells derived from pre-menopausal women, E(2), G, D and Ral stimulated CK to higher extent compared to post-menopausal bone cells, whereas quecertin (Qu), carboxy-biochainin A (cBA) and carboxy-genistein (cG) stimulated CK in both age groups similarly, and biochainin A (BA) stimulated post-menopausal cells to a bit higher extent than pre-menopausal cells. Since the skeletal protective effects of estrogens are not discernable in diabetic women, we tested in this study, the effects of high glucose concentration in the growth medium, on the effects of estrogenic compounds on CK in human-derived bone cells (hObs). Female-derived hObs were grown either in normal (4.5 g/l; 22 mM, NG) or high glucose (9.0 g/l; 44 mM, HG) for 7 days. HG increased constitutive CK, but attenuated E(2)- and DHT-induced CK in female or male hObs, respectively. HG also inhibited genistein (G) and daidzein (D) stimulated CK in female hObs, but not the effects of biochainin A (BA), quecertin (Qu) or Ral. Intracellular, mainly nuclear binding of (3)[H]E(2) was characteristic of the different phytoestrogens in female hObs, was abolished by HG. Membranal binding of Eu-Ov-E(2), was displaced only by E(2)-Ov, ICI, cG-Ov or cD-Ov but decreased total binding of Eu-Ov-E(2) in both age groups and completely abolished the competition with E(2)-Ov or ICI in both age groups, but the competition with cD-Ov and cG-Ov was decreased only slightly but not statistically significant. HG also abolished Eu-BSA-T, which bound similarly male-derived hObs. All hObs expressed mRNA for ERalpha and ERbeta with higher abundance of ERalpha. HG increased mRNA for both ERs in female-derived hObs, but decreased mRNA for both ERs in male-derived hObs. Hence, human bone cells, which express specific nuclear and membranal binding sites for estrogenic compounds, are modulated by HG, leading to altered hormonal responsiveness, which might block important effects of estrogenic compounds, contributing probably to their decreased skeletal preserving properties under hyperglycemia.

Sex-specific regulation of growth plate chondrocytes by estrogen is via multiple MAP kinase signaling pathways

Both male and female rat growth plate cartilage cells possess estrogen receptors (ERs), but 17beta-estradiol (E(2)) activates protein kinase C (PKC) and PKC-dependent biological responses to E(2) only in cells from female animals. PKC signaling can elicit genomic responses via mitogen activated protein kinase (MAPK) and E(2) has been shown to activate ERK MAPK in many cells, suggesting that MAPK may play a role in growth plate chondrocytes as well. We tested if E(2) increases MAPK activity and if so, whether the response is limited to female cells, if it is PKC-dependent, and if the mechanism involves traditional ER pathways. We also determined the contribution of MAPK to the biological response of growth plate chondrocytes and assessed the relative contributions of ERK, p38 and JNK MAPKs. Female rat costochondral cartilage cells were treated with E(2) and MAPK-specific activity determined in cell layer lysates. The mechanism of MAPK activation was determined by treating the cells with E(2) conjugated to bovine serum albumin (E(2)-BSA) to assess if membrane receptors were involved; stereospecificity was determined using 17alpha-estradiol; PKC and phospholipase C (PLC) dependence was determined using specific inhibitors; and the ER agonist diethylstilbestrol, the ER antagonist ICI 182780, and tamoxifen were used to assess the role of traditional ER pathways. E(2) regulation of ERK1/2 MAPK was assessed and the relative roles of ERK1/2, p38 and JNK MAPKs determined using specific inhibitors. E(2) caused a rapid dose-dependent activation of MAPK that was greatest in cells treated for 9 min with 10(-9) M hormone; activity remained elevated for 3 h. E(2)'s effect on MAPK was stereospecific and comparable to that of E(2)-BSA. It was insensitive to DES and ICI 182780, dependent on PKC and PLC, blocked by tamoxifen and it did not require gene transcription or translation. E(2) had no effect on ERK1 or ERK2 mRNA or protein but it caused a rapid phosphorylation of ERK1/2 at 9 min. Inhibition of ERK1/2 and p38 MAPK reduced the stimulatory effects of E(2) on alkaline phosphatase activity and [(35)S]-sulfate incorporation. These results suggest that E(2) regulates MAPK through a sex-specific membrane-mediated mechanism that does not involve cytosolic ERs in a traditional sense and that ERK1/2 and p38 mediate the downstream biological effects of the hormone.

25-hydroxyvitamin D3-1alpha-hydroxylase is expressed in human vascular smooth muscle cells and is upregulated by parathyroid hormone and estrogenic compounds

BACKGROUND

1,25(OH)2 vitamin D3 exerts multiple effects in human vascular smooth muscle cells (VSMCs). We therefore tested the possibility that VSMCs possess an endogenous 25-hydroxyvitamin D3-1alpha-hydroxylase system, the final enzyme in the biosynthetic pathway of 1,25(OH)2D3.

METHODS AND RESULTS

We assessed the expression and activity of 25-hydroxyvitamin D3-1alpha-hydroxylase by real-time polymerase chain reaction and the conversion of 25(OH)D3 into 1,25(OH)2D3. First, 25-hydroxyvitamin D3-1alpha-hydroxylase mRNA was identified in cultured VSMCs by real-time polymerase chain reaction. Second, in cells treated daily (3 days) with parathyroid hormone (66 nmol/L), estradiol-17beta (30 nmol/L), raloxifene (3 micromol/L), and the phytoestrogens genistein (3 micromol/L), biochainin A (3 micromol/L), and 6-carboxy biochainin A (30 nmol/L), 25-hydroxyvitamin D3-1alpha-hydroxylase mRNA increased by 43+/-13%, (P<0.05) 7+/-24% (P=NS), 176+/-28% (P<0.01), 65+/-11% (P<0.05), 152+/-24% (P<0.01), and 71+/-9% (P<0.05), respectively. Third, production of 1,25(OH)2D3 from 25(OH)D3 was seen with a Km of 25 ng/mL and increased dose dependently after treatment with parathyroid hormone, genistein, and the phytosetrogen derivative 6-carboxy biochainin A. Estradiol-17beta and biochainin A also increased the generation of 1,25(OH)2D3 by 40+/-23% (P<0.05) and 55+/-13% (P<0.05), respectively.

CONCLUSIONS

We provide here the first evidence for the expression of an enzymatically active 25(OH)D3-1alpha-hydroxylase system in human VSMCs, which can be upregulated by parathyroid hormone and estrogenic compounds. Because exogenous vitamin D inhibits VSMC proliferation, the role of this system as an autocrine mechanism to curb changes in VSMC proliferation and phenotype is a subject for future investigation.