The effect of oestrogen and dietary phyto-oestrogens on transepithelial calcium transport in human intestinal-like Caco-2 cells

The cytotoxicity of organophosphate flame retardants on HepG2, A549 and Caco-2 cells

In order to elucidate the cytotoxicity of organophosphate flame retardants (OPFRs), three human in vitro models, namely the HepG2 hepatoma cells, the A549 lung cancer cells and the Caco-2 colon cancer cells, were chosen to investigate the toxicity of triphenyl phosphate (TPP), tributylphosphate (TBP), tris(2-butoxyexthyl) phosphate (TBEP) and tris (2-chloroisopropyl) phosphate (TCPP). Cytotoxicity was assayed in terms of cell viability, DNA damage status, reactive oxygen species (ROS) level and lactate dehydrogenase (LDH) leakage. The results showed that all these four OPFRs could inhibit cell viability, overproduce ROS level, induce DNA lesions and increase the LDH leakage. In addition, the toxic effects of OPFRs in Caco-2 cells were relatively severer than those in HepG2 and A549 cells, which might result from some possible mechanisms apart from oxidative stress pathway. In conclusion, TBP, TPP, TBEP and TCPP could induce cell toxicity in various cell lines at relatively high concentrations as evidenced by suppression of cell viability, overproduction of ROS, induction of DNA lesions and increase of LDH leakage. Different cell types seemed to have different sensitivities and responses to OPFRs exposure, as well as the underlying potential molecular mechanisms.

Polydatin, a natural precursor of resveratrol, induces cell cycle arrest and differentiation of human colorectal Caco-2 cell

Background

Human colon adenocarcinoma cells are resistant to chemotherapeutic agents, such as anthracyclines, that induce death by increasing the reactive oxygen species. A number of studies have been focused on chemo-preventive use of resveratrol as antioxidant against cardiovascular diseases, aging and cancer. While resveratrol cytotoxic action was due to its pro-oxidant properties. In this study, we investigate whether the Resveratrol (trans-3,5,49-trihydroxystilbene) and its natural precursor Polydatin (resveratrol-3-O-b-mono- D-glucoside, the glycoside form of resveratrol) combination, might have a cooperative antitumor effect on either growing or differentiated human adenocarcinoma colon cancer cells.

Methods

The polydatin and resveratrol pharmacological interaction was evaluated in vitro on growing and differentiated Caco-2 cell lines by median drug effect analysis calculating a combination index with CalcuSyn software. We have selected a synergistic combination and we have evaluated its effect on the biological and molecular mechanisms of cell death.

Results

Simultaneous exposure to polydatin and resveratrol produced synergistic antiproliferative effects compared with single compound treatment. We demonstrated that polydatin alone or in combination with resveratrol at 3:1 molar ratio synergistically modulated oxidative stress, cell cycle, differentiation and apoptosis. Worthy of note treatment with polydatin induced a nuclear localization and decreased expression of heat shock protein 27, and vimentin redistributed within the cell.

Conclusions

From morphological, and biochemical outcome we obtained evidences that polydatin induced a transition from a proliferative morphology to cell-specific differentiated structures and caused human CaCo-2 cell death by induction of apoptosis. Our data suggest the potential use of polydatin in combination chemotherapy for human colon cancer.

Vitamin D interactions with soy isoflavones on bone after menopause: a review

Vitamin D is known to increase Ca absorption in adults. However, the threshold vitamin D status to benefit Ca absorption is lower than the target vitamin D status for higher bone mineral density and lower fracture risk, pointing to another pathway for vitamin D to benefit bone. One possibility is by affecting osteoblast and osteoclasts directly. Vitamin D-related bone metabolism may also be affected by soy isoflavones, which selectively bind to the estrogen receptor β and may reduce bone loss in postmenopausal women. We discuss a possible synergistic effect of soy isoflavones and vitamin D on bone by affecting osteoblast and osteoclast formation and activity in postmenopausal women.

Protective Role of Black Tea Extract against Nonalcoholic Steatohepatitis-Induced Skeletal Dysfunction

Aim. This paper aimed to examine the chemoprotective actions of aqueous black tea extract (BTE) against nonalcoholic steatohepatitis- (NASH-) induced skeletal changes in rats. Material. Wistar rats (body wt. 155-175 g) of both sexes, aged 4-5 months, were randomly assigned to 3 groups; Group A (control), Group B (60% high-fat diet; HFD), and Group C (HFD + 2.5% BTE). Methods. Several urinary (calcium, phosphate, creatinine, and calcium-to-creatinine ratio) serum (alkaline phosphatase and serum tartrate-resistant acid phosphatase), and molecular markers of bone turnover (receptor activator of NF-κB ligand (RANKL), osteoprotegerin (OPG), and estrogen) were tested. Also, several bone parameters (bone density, bone tensile strength, bone mineral content, and bone histology) and calcium homeostasis were checked. Results. Results indicated that HFD-induced alterations in urinary, serum, and bone parameters as well as calcium homeostasis, all could be significantly ameliorated by BTE supplementation. Conclusion. Results suggest a potential role of BTE as a protective agent against NASH-induced changes in bone metabolism in rats.

A novel quinone-based derivative (DTNQ-Pro) induces apoptotic death via modulation of heat shock protein expression in Caco-2 cells

BACKGROUND AND PURPOSE

The resistance of human colon adenocarcinoma cells to antineoplastic agents may be related to the high endogenous expression of stress proteins, including the family of heat shock proteins (HSPs). Recently, a quinone-based pentacyclic derivative, DTNQ-Pro, showed high cytotoxic activity in human colon carcinoma cell lines. The aim of the present study was to determine the precise cellular mechanisms of this cytotoxic action of DTNQ-Pro.

EXPERIMENTAL APPROACH

Using human colorectal carcinoma-derived Caco-2 cells as a model, we studied the effects of DTNQ-Pro on cellular viability and oxidative stress; HSP70 and HSP27 accumulation; and cell cycle, differentiation and apoptosis.

KEY RESULTS

Incubation of Caco-2 cells with DTNQ-Pro reduced cell growth and increased the levels of reactive oxygen species in mitochondria. After 48 h of treatment, cells surviving showed an increased expression of Mn-superoxide dismutase (SOD), nitric oxide production and membrane lipid peroxidation. Treatment with DTNQ-Pro decreased HSP70 expression, and redistributed HSP27 and vimentin within the cell. DTNQ-Pro down-regulated the expression of A and B cyclins with arrest of the cell cycle in S phase and increased cellular differentiation. A second treatment of Caco-2 cells with DTNQ-Pro induced cellular death by activation of the apoptotic pathway.

CONCLUSIONS AND IMPLICATIONS

DTNQ-Pro causes Caco-2 cell death by induction of apoptosis via inhibition of HSP70 accumulation and the intracellular redistribution of HSP27. These findings suggest the potential use of DTNQ-Pro in combination chemotherapy for colon cancer.

Influence of a low dose of dietary soybean on bone properties and mineral status in young rats

The aim of this study was to evaluate effects of dietary supplementation with genistein, daidzein stachyose, and raw or cooked soybean on mineral content, optical density, and mechanical properties of bones in growing rats. The experiment was performed on 70 male young Wistar rats (4 weeks old at the start of the experiment) divided into seven groups. Genistein, daidzein, or stachyose were administered by gavage. Raw or cooked soybean was added directly to the diet (1%) The experiment lasted 28 days. Femurs were removed postmortem and kept until analysis at -20°C. Mineral content in bones was determined by atomic absorption flame spectrometry, and inductively coupled plasma atomic emission spectrometry. Optical density was analyzed with a KODAK 1D 3.5 system. Mechanical properties were tested using INSTRON 4301 equipment. Genistein increased mineral content in bones of growing rats. Biological action of genistein and daidzein on the mineralization of bone tissues in growing rats was different. Addition of stachyose (1.9 mg/day/rat) did not affect bone tissues, nor did the addition of raw or cooked soybean. None of the studied biologically active substances: genistein (0.26 mg/day/rat), daidzein (0.104 mg/day/rat), stachyose (1.9 mg/day/rat), or soybean had an effect on bone optical density.

Endocrine regulation of calcium transport in epithelia

1. Calcium (re)absorption occurs in epithelia, including the intestine, kidney, mammary glands, placenta and gills (in the case of fish). 2. Calcium is transported across epithelia by two transport mechanisms, paracellular and transcellular, and the movement is regulated by a complex array of transport processes that are mediated by hormonal, developmental and physiological factors involving the gastrointestinal tract, bone, kidney and the parathyroids. 3. Clear understanding of the calcium transport pathways and their endocrine regulation is critical for minimizing various metabolic and health disorders at different physiological stages. Here, we first briefly review the calcium transport mechanisms before discussing in detail the endocrine factors that regulate calcium transport in the epithelia.

Soy phytoestrogens: impact on postmenopausal bone loss and mechanisms of action

Due to their ability to mimic the actions of mammalian estrogens, soy phytoestrogens have been proposed as potential therapeutic agents to aid in preventing postmenopausal bone loss. In vitro, phytoestrogens promote osteoblastogenesis and inhibit osteoclastogenesis. Although a relatively large number of intervention studies have been undertaken in animals and humans, the efficacy of phytoestrogens as bone-protective agents in vivo remains unclear. Differences in the bioactivities of individual phytoestrogens, differences in phytoestrogen metabolism and bioavailability within different study populations, and imprecise reporting of the dose of phytoestrogens administered in intervention studies may have contributed to the disparity in study findings.

Effect of 17beta-oestradiol on transepithelial calcium transport in human intestinal-like Caco-2 cells and its interactions with 1,25-dihydroxycholecalciferol and 9-cis retinoic acid

BACKGROUND

Oestrogen therapy helps prevent bone loss in postmenopausal women and corrects a decline in Ca absorption efficiency at the onset of menopause. However, the mechanism by which 17beta-oestradiol (17beta-E2) stimulates Ca absorption is unclear. Oestrogen may exert its effect indirectly via increasing 1,25-dihydroxycholeciferol (1,25 (OH)2D3) or its receptor, or act more directly on the intestines via the oestrogen receptor (OR). Since oestrogen also increases retinol levels, this may influence Ca absorption.

AIM

To investigate the effect of 17beta-E2 alone and in combination with 1,25 (OH)2D3 on intestinal Ca uptake and absorption in Caco-2 cells cultured under deplete- and replete-9-cis retinoic acid (9-cis RA) conditions.

METHODS

Twenty-one day-old Caco-2 cell monolayers (n 9 wells per treatment) were exposed to 9-cis RA-deplete and -replete media containing dimethyl sulfoxide (control), 10 nM-1,25 (OH)2D3, 10 nM-17beta-E2, or 10 nM-1,25 (OH)2D3 plus 10 nM-17beta-E2, for 48 h.

RESULTS

1,25 (OH)2D3 stimulated Ca uptake, total Ca transport, calbindin D(9K) and CaT1 mRNA levels, while 17beta-E2 and 9-cis RA had no effect on Ca absorption or uptake. Nor did they augment the stimulatory effect of 1,25 (OH)2D3.

CONCLUSION

These in vitro findings suggest that oestrogen does not have a direct effect on intestinal Ca absorption.

β-Sitosterol stimulates ceramide metabolism in differentiated Caco2 cells

Previous studies from our laboratory on tumor cells suggest that phytosterols stimulate ceramide production, which was associated with cell growth inhibition and stimulation of apoptosis. The objective of the present study was to examine the effect of phytosterols on ceramide metabolism in small intestinal cells that represent the first cells in contact with dietary phytosterols. Caco(2) cells, an accepted model for human intestinal epithelial cells, were used in this study. Ceramide and ceramide-containing lipids were examined by labeling the ceramide pool with (3)H-serine. Cells were supplemented with 16 microM of sterols (cholesterol, beta-sitosterol or campesterol) for 16 days postconfluence and continued to differentiate. Of the two phytosterols, beta-sitosterol, but not campesterol, induced more than double the serine labeling when compared with cholesterol. This increase was uniform in sphingomyelin (SM), ceramide and sphingosine labeling. Sterols had no effect on SM concentration in the cells. In addition, sterol had no effect on the activity of SM synthase or sphingomyelinases. There was an inhibition of ceramidases with campesterol supplementation. These data suggest that the observed increases in SM and sphingosine labeling were due to an increase in ceramide turnover. The increase in ceramide turnover with beta-sitosterol supplementation was not associated with growth inhibition but was with increases in ceramide glycosylation products such as cerebrosides and gangliosides. It was concluded that beta-sitosterol has no effect on differential Caco(2), a model of normal small intestinal cells. The increase in the glycosylated ceramide products may offer a means to protect the cells from the harmful effect of ceramide by excreting them with lipoproteins.

Dietary additions of lactose, casein and soy protein exerted only moderate effects on calcium homeostasis in calcitriol deficient piglets

It has been reported from rats and mice that blood and bone calcium can be normalised in the absence of Vitamin D hormone or its receptor by dietary means. It was the aim of this study to test, whether a similar result can be obtained with pigs. Piglets with inherited calcitriol deficiency were fed with high calcium and Pi diets and supplemented with soy protein or casein and lactose or corn starch, which have been shown to normalise plasma and bone calcium in Vitamin D deficient rats and in mice. In the calcitriol deficient piglets none of the diets was capable to prevent the development of hypocalcemia. However, additions of lactose and soy protein improved somewhat plasma calcium (P < 0.001). Feeding of soy protein also had a significant positive effect on plasma phosphate concentration (P < 0.001). The study shows that in contrast to rats, calcitriol is essential for maintaining a normal plasma and bone calcium status. Responses of this type, when obtained with rats or mice can probably not directly be transferred to pigs and perhaps also not to humans.

Lack of dose-responsive effect of dietary phyto-oestrogens on transepithelial calcium transport in human intestinal-like Caco-2 cells

Ca absorption has been shown to be unaffected by high luminal concentrations of two commonly consumed soyabean phyto-oestrogens (PO) (genistein and daidzein) in Caco-2 cells grown under oestrogen-depleted conditions. However, these compounds exhibit dose-dependent biphasic effects in some tissues, such as reproductive tissue and bone. Thus, in light of this biphasic activity, the effect of lower concentrations of genistein and daidzein on Ca absorption requires further investigation. Therefore, the aim of the present study was to investigate the effect of a range of concentrations of genistein and daidzein on Ca absorption in the human Caco-2 intestinal-like cell model. Caco-2 cells were seeded onto permeable filter supports and allowed to differentiate into monolayers. On day 21, the Caco-2 monolayers (n 12 per treatment), grown in oestrogen-deplete media, were then exposed to 10 nm-1,25-dihydroxycholecalciferol (1,25 (OH)2D3), or 1, 10 and 50 microm-genistein or -daidzein for 24 h. After exposure, transepithelial and transcellular transport of (45)Ca and fluorescein transport were measured. As expected, 1,25 (OH)2D3 stimulated Ca absorption in Caco-2 cells, by up regulating transcellular transport. Ca absorption was unaffected by either PO at luminal concentrations of 1, 10 or 50 microm, typical of intakes by Western and Asian populations as well as supplemental levels, respectively. The results of this model suggest that the proposed beneficial effects of supplemental levels of these PO compounds on bone mass in postmenopausal women more probably arise from direct effects on bone cells, and not by an indirect effect of these compounds on Ca absorption.