RESUMO
<p><b>OBJECTIVE</b>To investigate whether the p38 mitogen-activated protein kinase (MAPK) signaling pathway mediates advanced oxidation protein products (AOPPs)-induced epithelial-to-mesenchymal transition (EMT) in tubular cells.</p><p><b>METHODS</b>Human proximal tubular cells (HK-2 cells) exposed to AOPP-bovine serum albumin (BSA) were examined for expressions of p38 MAPK and phosphorylated p38 MAPK using Western blotting. Western blotting and quantitative RT-PCR were used to examine the protein and mRNA expressions of EMT markers E-cadherin and vimentin and endoplasmic reticulum stress marker glucose-regulated protein (GRP) 78 in cells treated with SB203580 (an inhibitor of the p38 MAPK signaling pathway) prior to AOPP exposure. The cells treated with AOPPs following pretreatment with salubrinal (an inhibitor of endoplasmic reticulum stress) were also examined for expressions of p38 MAPK and phosphorylated p38 MAPK.</p><p><b>RESULTS</b>AOPP treatment induced the phosphorylation of p38 MAPK in HK-2 cells. AOPP-induced decrease in E-cadherin expression and overexpression of vimentin and GRP78 were partly inhibited by pretreatment of the cells with SB203580. Salubrina partly suppressed AOPP-induced phosphorylation of p38 MAPK in the cells.</p><p><b>CONCLUSION</b>p38 MAPK signaling pathway, which is regulated by endoplasmic reticulum stress, might mediate AOPP-induced EMT in HK-2 cells.</p>
RESUMO
<p><b>OBJECTIVE</b>To investigate the effect of arctiin on advanced oxidation protein product (AOPP)-induced epithelial-to-mesenchymal transition (EMT) in tubular cells and explore the mechanisms underlying this effect.</p><p><b>METHODS</b>Human proximal tubular cells (HK-2 cells) were treated with bovine serum albumin (BSA) or AOPPs in the presence or absence of arctiin. The expressions of E-cadherin, vimentin, and GRP78 at the protein and mRNA levels in the cells were examined using Western blotting and quantitative real-time PCR. The level of reactive oxygen species (ROS) was measured by flow cytometry with DCFH-DA as the fluorescent probe.</p><p><b>RESULTS</b>Compared with BSA-treated cells, the cells treated with AOPPs showed decreased expression of epithelial cell marker E-cadherin and overexpression of mesenchymal marker vimentin and endoplasmic reticulum stress marker GRP78 with an increased ROS level. These changes induced by AOPPs were partly inhibited by arctiin.</p><p><b>CONCLUSION</b>Arctiin can ameliorate AOPP-induced EMT in tubular cells by inhibiting endoplasmic reticulum stress, and oxidative stress response may participate in this process.</p>
