Oxidative stress inhibition and oxidant activity by fibrous clays

Our plain-English summary of Oxidative stress inhibition and oxidant activity by fibrous clays, by J. Cervini-Silva, A. Nieto-Camacho, V. Gómez-Vidales (Colloids and Surfaces. B, Biointerfaces, 2015).

The study

• Authors: J. Cervini-Silva, A. Nieto-Camacho, V. Gómez-Vidales
• Journal: Colloids and Surfaces. B, Biointerfaces
• Published: 2015;133:32-5
• Cited by: 10 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Fibrous clays (sepiolite, palygorskite) are produced at 1.2m tonnes per year and have a wide range of industrial applications needing to replace long-fibre length asbestos. However, information on the beneficial effects of fibrous clays on health remains scarce. This paper reports on the effect of sepiolite (Vallecas, Spain) and palygorskite (Torrejón El Rubio, Spain) on cell damage via oxidative stress (determined as the progress of lipid peroxidation, LP). The extent of LP was assessed using the Thiobarbituric Acid Reactive Substances assay. The oxidant activity by fibrous clays was quantified using Electron-Paramagnetic Resonance. Sepiolite and palygorskite inhibited LP, whereby corresponding IC50 values were 6557±1024 and 4250±289μgmL(-1). As evidenced by dose-response experiments LP inhibition by palygorskite was surface-controlled. Fibrous clay surfaces did not stabilize HO species, except for suspensions containing 5000μgmL(-1). A strong oxidant (or weak anti-oxidant) activity favours the inhibition of LP by fibrous clays.

Copyright © 2015 Elsevier B.V. All rights reserved.

In plain English

This short laboratory report tested two fibrous clays: sepiolite from Vallecas, Spain, and palygorskite from Torrejón El Rubio, Spain. The authors describe these clays as used in applications needing to replace long-fibre asbestos. No asbestos was tested. The authors measured whether the clays reduced lipid peroxidation, a form of oxidative damage to fats, in lipids taken from rat brain, with iron added to trigger the damage. Sepiolite reduced lipid peroxidation by 65% and palygorskite by 75%. Both reduced it less than the two comparison substances, a tubular halloysite clay (85%) and quercetin (97%). The concentration needed to cut the damage by half was 6557 plus or minus 1024 micrograms per millilitre for sepiolite and 4250 plus or minus 289 for palygorskite. In a second test for hydroxyl radicals, a reactive oxygen species, dispersions containing 5000 micrograms per millilitre of palygorskite showed radicals forming, while all other dispersions showed a weak signal. The authors concluded that both clays inhibited lipid peroxidation effectively. They interpreted this as related to a strong oxidant (or weak anti-oxidant) activity of the clay surfaces.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory (in vitro) experiment on lipids from rat brain homogenate, using a lipid peroxidation (TBARS) assay and electron paramagnetic resonance measurements
• Who was studied: Clay samples: sepiolite (Vallecas, Spain), palygorskite (Torrejón El Rubio, Spain) and, for comparison, halloysite CLA-1 (South Australia), tested on rat brain lipids. No human subjects.
• Exposure: Fibrous clays sepiolite and palygorskite, which the authors describe as used in applications needing to replace long-fibre length asbestos. Lipid damage was triggered with iron (FeSO4). Hydroxyl radical tests used clay concentrations of 5000 and 1000 micrograms per millilitre. No asbestos was tested.
• Main results:
  • Sepiolite inhibited lipid peroxidation by 65% and palygorskite by 75%. Neither surpassed tubular halloysite CLA-1 (85%) or quercetin (97%).
  • Concentrations reducing the response by half (IC50), in micrograms per millilitre: sepiolite 6557 plus or minus 1024; palygorskite 4250 plus or minus 289; tubular halloysite 2023 plus or minus 99 (a value cited from an earlier study); quercetin 0.51 plus or minus 0.01.
  • Dose-response experiments for palygorskite showed that lipid peroxidation inhibition was surface mediated.
  • Across sepiolite, palygorskite and tubular halloysite, lipid peroxidation inhibition decreased as the total number of surface sites increased. The authors call this a signature of specific adsorption.
  • Hydroxyl radicals formed in dispersions containing 5000 micrograms per millilitre of palygorskite. All other dispersions showed a weak EPR signal.
• The authors' conclusion: The authors concluded that sepiolite and palygorskite inhibited lipid peroxidation effectively, though less than tubular halloysite or quercetin. They interpreted the coincidence between poor stabilization of hydroxyl radicals and lipid peroxidation inhibition to mean that the inhibition related to a strong oxidant (or weak anti-oxidant) activity.

Topics

Medical terms in this study, explained in our Lexicon: Oxidative Stress, Sepiolite, Palygorskite (Attapulgite), Dose-response relationship.

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