The effect of copper on tight junctional permeability in a human intestinal cell line (Caco-2)

Artificial Digestion of Polydisperse Copper Oxide Nanoparticles: Investigation of Effects on the Human In Vitro Intestinal Co-Culture Model Caco-2/HT29-MTX

Copper oxide nanoparticles (CuO-NP) are increasingly used in consumer-related products, which may result in increased oral ingestion. Digestion of particles can change their physicochemical properties and toxicity. Therefore, our aim was to simulate the gastrointestinal tract using a static in vitro digestion model. Toxic properties of digested and undigested CuO-NP were compared using an epithelial mono-culture (Caco-2) and a mucus-secreting co-culture model (Caco-2/HT29-MTX). Effects on intestinal barrier integrity, permeability, cell viability and apoptosis were analyzed. CuO-NP concentrations of 1, 10 and 100 µg mL−1 were used. Particle characterization by dynamic light scattering and transmission electron microscopy showed similar mean particle sizes before and after digestion, resulting in comparable delivered particle doses in vitro. Only slight effects on barrier integrity and cell viability were detected for 100 µg mL−1 CuO-NP, while the ion control CuCl2 always caused significantly higher adverse effects. The utilized cell models were not significantly different. In summary, undigested and digested CuO-NP show comparable effects on the mono-/co-cultures, which are weaker than those of copper ions. Only in the highest concentration, CuO-NP showed weak effects on barrier integrity and cell viability. Nevertheless, a slightly increased apoptosis rate indicates existing cellular stress, which gives reason for further investigations.

Effect of preventive supplementation with zinc and other micronutrients on non-malarial morbidity in Tanzanian pre-school children: a randomized trial

BACKGROUND

The efficacy of preventive zinc supplementation against diarrhea and respiratory illness may depend on simultaneous supplementation with other micronutrients. We aimed to assess the effect of supplementation with zinc and multiple micronutrients on diarrhea and other causes of non-malarial morbidity.

METHODS AND FINDINGS

Rural Tanzanian children (n = 612) aged 6-60 months and with height-for-age z-score < -1.5 SD were randomized to daily supplementation with zinc (10 mg) alone, multi-nutrients without zinc, multi-nutrients with zinc, or placebo. Children were followed for an average of 45 weeks. During follow-up, we recorded morbidity episodes. We found no evidence that concurrent supplementation with multi-nutrients influenced the magnitude of the effect of zinc on rates of diarrhea, respiratory illness, fever without localizing signs, or other illness (guardian-reported illness with symptoms involving skin, ears, eyes and abscesses, but excluding trauma or burns). Zinc supplementation reduced the hazard rate of diarrhea by 24% (4%-40%). By contrast, multi-nutrients seemed to increase this rate (HR; 95% CI: 1.19; 0.94-1.50), particularly in children with asymptomatic Giardia infection at baseline (2.03; 1.24-3.32). Zinc also protected against episodes of fever without localizing signs (0.75; 0.57-0.96), but we found no evidence that it reduced the overall number of clinic visits.

CONCLUSIONS

We found no evidence that the efficacy of zinc supplements in reducing diarrhea rates is enhanced by concurrent supplementation with other micronutrients. By reducing rates of fever without localizing signs, supplementation with zinc may reduce inappropriate drug use with anti-malarial medications and antibiotics.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00623857.

Effect of preventive supplementation with zinc and other micronutrients on non-malarial morbidity in Tanzanian pre-school children: a randomized trial

Background

The efficacy of preventive zinc supplementation against diarrhea and respiratory illness may depend on simultaneous supplementation with other micronutrients. We aimed to assess the effect of supplementation with zinc and multiple micronutrients on diarrhea and other causes of non-malarial morbidity.

Methods and Findings

Rural Tanzanian children (n = 612) aged 6–60 months and with height-for-age z-score < –1.5 SD were randomized to daily supplementation with zinc (10 mg) alone, multi-nutrients without zinc, multi-nutrients with zinc, or placebo. Children were followed for an average of 45 weeks. During follow-up, we recorded morbidity episodes. We found no evidence that concurrent supplementation with multi-nutrients influenced the magnitude of the effect of zinc on rates of diarrhea, respiratory illness, fever without localizing signs, or other illness (guardian-reported illness with symptoms involving skin, ears, eyes and abscesses, but excluding trauma or burns). Zinc supplementation reduced the hazard rate of diarrhea by 24% (4%–40%). By contrast, multi-nutrients seemed to increase this rate (HR; 95% CI: 1.19; 0.94–1.50), particularly in children with asymptomatic Giardia infection at baseline (2.03; 1.24–3.32). Zinc also protected against episodes of fever without localizing signs (0.75; 0.57–0.96), but we found no evidence that it reduced the overall number of clinic visits.

Conclusions

We found no evidence that the efficacy of zinc supplements in reducing diarrhea rates is enhanced by concurrent supplementation with other micronutrients. By reducing rates of fever without localizing signs, supplementation with zinc may reduce inappropriate drug use with anti-malarial medications and antibiotics.

Trial Registration

ClinicalTrials.gov NCT00623857

Cell growing density affects the structural and functional properties of Caco-2 differentiated monolayer

The human intestinal Caco-2 cell line has been extensively used as a model of the intestinal barrier. However, it is widely reported in literature that culture-related conditions, as well as the different Caco-2 cell lines utilized in different laboratories, often lead to problems of reproducibility making difficult to compare results. We developed a new cell-maintenance protocol in which Caco-2 cells were subcultured at 50% of confluence instead of 80% of confluence, as usually suggested. Using this new protocol, Caco-2 cells retained a higher proliferation potential resulting in a cell population, which, on reaching confluence, was able to differentiate almost synchronously, forming a more homogeneous and polarized cell monolayer, as compared to that obtained using a high cell growing density. This comparison has been done by analyzing the gene expression and the structural characteristics of the 21-days differentiated monolayers by microarrays hybridization and by confocal microscopy. We then investigated if these differences could also modify the effects of toxicants on 21-days-differentiated cells. We analyzed the 2 h-acute toxicity of CuCl(2) in terms of actin depolymerization and metallothionein 2A (MT2A) and heat shock protein 70 (HSPA1A) genes induction. Copper treatment resulted in different levels of actin depolymerization and gene expression induction in relationship with culture protocol, the low-density growing cells showing a more homogeneous and stronger response. Our results suggest that cell growing density could influence a number of morphological and physiological properties of differentiated Caco-2 cells and these effects must be taken in account when these cells are used as intestinal model.

Increased functional expression of P-glycoprotein in Caco-2 TC7 cells exposed long-term to cadmium

The objective of this study was to investigate whether P-glycoprotein (P-gp) functional expression in intestinal cells is modified after long-term exposure to the food contaminant cadmium (Cd). The Caco-2 cell line, clone TC7, was first validated as a cellular model for long-term exposure to cadmium. Cytotoxicity tests after acute exposure of 24 h showed a significant concentration-dependent decrease in cellular viability at cadmium levels higher than 10 microM and led us to select the cadmium ranges for long-term exposure: 1, 5, and 10 microM. Intestinal cells were exposed to these cadmium concentrations for four consecutive weeks without inducing DNA condensation or fragmentation. In the second part of this work, we studied the functional expression of the drug efflux pump multidrug resistance P-glycoprotein after long-term exposure to cadmium by immunoblotting with the monoclonal antibody F4 and measurement of calcein-AM+/-the P-gp inhibitor verapamil. Western blot analysis with the F4 antibody detected a single band of 170 to 180 kDa which is the size previously reported for P-gp. Calcein-AM assay showed that four weeks exposure of intestinal cells to 1, 5, and 10 microM Cd increased P-gp functional expression in proportion to the Cd concentration.

Sodium-sensitive and -insensitive copper accumulation by isolated intestinal cells of rainbow troutOncorhynchus mykiss

The pathway for copper (Cu) uptake across the mucosal membrane into intestinal cells has not been elucidated in fish. Copper accumulation in freshly isolated intestinal cells from rainbow trout Oncorhynchus mykiss was measured after exposure to 0–800 μmol l–1 CuSO4 for 15 min. With external Cu concentration (Cuo) of 800 μmol l–1, the rate of Cu accumulation by cells was 1.88±0.52 nmol Cu mg–1cell protein h–1 compared to 0.05±0.01 nmol Cu mg–1 cell protein h–1 with no added Cuo (means ± s.e.m., N=6). Deduction of a rapid Cu accumulation measured on/in cells at time zero (about 12% of the total Cu uptake when Cuo was 800 μmol l–1)revealed a saturable uptake curve, which reached a plateau at 400 μmol l–1 Cuo (Km=216 μmol l–1 Cuo; Vmax=1.09 nmol Cu mg–1 cell protein h–1; 140 mmol l–1 NaCl throughout). Incubation of cells at 4°C did not prevent Cu accumulation. Lowering external [Na+] to 11 mmol l–1 (low Na+o) generally did not alter the rate of Cu accumulation into the cells over a 15 min period. Under low Na+o conditions Cu accumulation was exponential(non-saturable). Na+-insensitive Cu accumulation dominated (59% of total Cu accumulation) when Cuo was 400 μmol l–1 or less. At high Cuo (800 μmol l–1), removal of Na+ caused a 45% increase in Cu accumulation. Pre-incubation of cells with blocking agents of epithelial Na+ channel (ENaC) for 15 min (normal [NaCl] throughout) caused Cu accumulation rates to increase by 40-fold (100 μmol l–1phenamil), 21-fold (10 μmol l–1 CDPC) or 12-fold (2 mmol l–1 amiloride) when Cuo was 800 μmol l–1 compared to those in drug-free controls. Lowering the external chloride concentration [Cl–]o from 131.6 to 6.6 mmol l–1 (replaced by sodium gluconate) caused the rate of Cu accumulation to increase 11-fold when Cuo was 800μmol l–1. Application of 0.1 mmol l–1DIDS (normal Cl–o) caused a similar effect. Lowering external pH from 7.4 to pH 5.5 produced a 17-fold, saturable,increase in Cu accumulation rate, which was not explained by increased instantaneous Cu accumulation on/in cells at low pH. We conclude that Cu accumulation by intestinal cells is mainly Na+-insensitive and more characteristic of a pH- and K+-sensitive Ctr1-like pathway than Cu uptake through ENaCs.