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Posts Tagged ‘iron transport’


Author: Dr. Tilda Barliya PhD

 

One of the latest posts address to issue of immunoreactivity and nanotechnology and I wanted to take advantage of this stage to address this topic again. On the many, potentially good effects and goals of nanotechnology, we have emerging side effects and human health issues that needs to be addressed.

It is estimated that the average person in a developed country consumes between 10xE12 and 10xE14 man-made fine (diameter, 0.1–1 mm) to ultrafine (diameter, ,100 nm) particles every day. These dietary particles are mainly TiO2, silicates and aluminosilicates derived from food additives such as stabilizers and anticaking agents . Because most of these micro- and nanoparticles have negatively charged surfaces, they can bind to biomolecules in the gut lumen, absorb across the gastrointestinal tract and accumulate at the base of Peyer’s patches, where a large concentration of M cells are found. M cells transport microorganisms and particles from the gut lumen to immune cells across the intestinal epithelium, and are important for defending the body against ingested toxic substances and stimulating mucosal immunity.

In a research collaboration led by Michael Shuler, the Samuel B. Eckert Professor of Chemical Engineering and the James and Marsha McCormick Chair of Biomedical Engineering, studied how large doses of polystyrene nanoparticles — a common, FDA-approved material found in substances from food additives to vitamins — affected how well chickens absorbed iron, an essential nutrient, into their cells (http://www.nature.com/nnano/journal/v7/n4/full/nnano.2012.3.html).

The researchers tested both acute and chronic nanoparticle exposure using human gut cells in petri dishes as well as live chickens and reported matching results. They chose chickens because these animals absorb iron into their bodies similarly to humans, and they are also similarly sensitive to micronutrient deficiencies.

More so, the authors chose iron absorption as a subject because iron is an example of an essential nutrient that is transported across the intestinal epithelium by means of complex, highly regulated, protein-assisted vesicular and non-vesicular mechanisms.

The researchers used commercially available, 50-nanometer polystyrene carboxylated particles that are generally considered safe for human consumption. They found that following acute exposure, a few minutes to a few hours after consumption, both the absorption of iron in the in vitro cells and the chickens decreased. But following exposure of 2 milligrams per kilogram for two weeks — a slower, more chronic intake — the structure of the intestinal villi began to change and increase in surface area. This was an effective physiological remodeling that led to increased iron absorption.

The increased iron uptake by monolayers exposed to +50 nm particles is probably due to the increased tight junction permeability, as increased transcytosis of luminal material often accompanies tight junction dysfunction.

The in vivo experiments indicate that nanoparticle exposure causes a disruption in iron transport and that the intestinal villi remodel to increase the surface area available for absorption. This increased area compensates for the disruption in iron transport caused by the nanoparticles.

Ferritin levels were analysed in all samples to exclude pre-existing differences in iron status as a cause for differences in iron transport or uptake. Ferritin levels in all nanoparticle-exposed and control cultures were not significantly different. 

The authors concluded that The intestinal epithelial layer represents the initial gate that ingested nanoparticles must pass to reach the body. The polystyrene particles used in these experiments are generally considered non-toxic, but their interaction with a normal physiological process suggests a potential mechanism for a chronic, harmful, but subtle response.

Similar disruptions in nutrient absorption could be possible in relation to other inorganic elements such as calcium, copper and zinc, which require passive or active transport systems for them to be absorbed through the intestinal epithelium. Fat-soluble vitamins such as vitamins A, D, E and K are absorbed only after micellization by pancreatic lipase.

oral exposure to polystyrene nanoparticles can disrupt iron transport and chronic exposure can cause remodelling of the intestinal villi. Remodelling of the villi increases the surface area available for iron absorption. Nanoparticle size, concentration and charge can influence iron uptake and iron transport at doses that represent potential human exposure.

 

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