Sepiolite and palygorskite-underpinned regulation of mRNA expression of pro-inflammatory cytokines as determined by a murine inflammation model

Abstract

This paper shows that clay minerals, sepiolite and palygorskite collected from Torrejón El Rubio and Vallecas, Spain, respectively, altered the expression of four, namely, pro-inflammatory cytokines: interleukins IL-1 and IL-6, tumor necrosis factor (TNF-α), and interferon gamma (IFN-γ) as determined using a 12-O-tetradecanoylphorbol-13-acetate model for inflammation. Quantitative RT-PCR analyses after 4 and 24h inflammatory stimuli showed that sepiolite or palygorskite brought about a reduction in mRNA expression. Sepiolite provoked the highest mRNA expression inhibition for all cytokines, except for TNF-α, and primarily after 4h. Conversely, the anti-inflammatory effect for cytokine TNF-α was found to be true in the presence of palygorskite. Most notably, the significant reduction in mRNA expression of IL-1 registered just shortly after exposure pointed to that the anti-inflammatory effect may be important for modulation of the late inflammatory response. These clay minerals caused modifications in the mRNA expression of IL-1 and its receptor in endothelial cells and downstreaming inflammatory cascades resulting in the recruitment of neutrophils. In addition, polymorphonuclear peroxidase activity was severely reduced just after short exposure to either sepiolite or palygorskite. Evidence provided herein agree well with the idea that these clay minerals impaired neutrophils infiltration to inflamed skin, notwithstanding ear edema and deficient cell localization to skin coupled with such impairment may affect the later stages of inflammation.