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HIV‐1‐related proteins decrease Nrf2 expression and alter tight junction protein localization in the plasma membranes of cultured alveolar epithelial cells
Author(s) -
Fan Xian,
Joshi Pratibha,
Koval Mike,
Guidot David M
Publication year - 2010
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.24.1_supplement.612.22
Subject(s) - occludin , tight junction , western blot , oxidative stress , microbiology and biotechnology , gene expression , biology , gene silencing , transcription factor , chemistry , immunology , gene , biochemistry
There is abundant evidence that HIV‐1‐related proteins can directly induce oxidative stress and impair tight junction (TJ) protein expression, causing serious consequences for the blood‐brain endothelial barrier and the alveolar epithelial air‐liquid barrier. Nrf2 is the redox‐sensitive transcription factor that regulates the expression of multiple antioxidants. We hypothesized that HIV‐1‐induced oxidative stress and barrier dysfunction could involve changes in Nrf2 expression. To test this hypothesis, we first determined that the gene and protein expression of Nrf2 and of the TJ proteins, occludin and ZO‐1, were significantly decreased in primary alveolar epithelial cells (AECs) isolated from HIV‐1 transgenic rats when compared to AECs from wild type (WT) littermates as assessed by real‐time PCR and western blot analysis. In parallel, exposing rat lung epithelial L2 cells to HIV‐1‐related proteins in vitro significantly inhibited Nrf2 gene expression. We then employed RNA silencing of Nrf2 in AECs isolated from WT rats to determine how this affected occludin and ZO‐1 expression. Consistent with our hypothesis, transfecting these cells with Nrf2 siRNA decreased the membrane localization of occludin and ZO‐1as assessed by immunocytochemistry, even though gene expression of occludin and ZO‐1 did not appear to be affected. Taken together, these data suggest that HIV‐1‐related proteins inhibit the expression of Nrf2 in the alveolar epithelium, and that as a consequence, tight junction assembly in the plasma membrane is somehow impaired. Whether this effect on TJ is mediated by oxidative stress is as yet unknown, but we speculate that Nrf2 expression is a redox‐sensitive target of HIV‐1‐related proteins that could mediate some of the cellular dysfunction in cells that are not directly infected by HIV‐1.