Ethanol Upregulates Glucocorticoid-Induced Leucine Zipper Expression and Modulates Cellular Inflammatory Responses in Lung Epithelial Cells

Abstract

Alcohol abuse is associated with immunosuppressive and infectious sequelae. Particularly, alcoholics are more susceptible to pulmonary infections. In this report, gene transcriptional profiles of primary human airway epithelial cells exposed to varying doses of alcohol (0, 50, and 100 mM) were obtained. Comparison of gene transcription levels in 0 mM alcohol treatments with those in 50 mM alcohol treatments resulted in 2 genes being upregulated and 16 genes downregulated by at least 2-fold. Moreover, 0 mM and 100 mM alcohol exposure led to the upregulation of 14 genes and downregulation of 157 genes. Among the upregulated genes, glucocorticoid-induced leucine zipper (GILZ) responded to alcohol in a dose-dependent manner. Moreover, GILZ protein levels also correlated with this transcriptional pattern. Lentiviral expression of GILZ small interfering RNA in human airway epithelial cells diminished the alcohol-induced upregulation, confirming that GILZ is indeed an alcohol-responsive gene. Gene silencing of GILZ in A549 cells resulted in secretion of significantly higher amounts of inflammatory cytokines in response to IL-1β stimulation. The GILZ-silenced cells were more resistant to alcohol-mediated suppression of cytokine secretion. Further data demonstrated that the glucocorticoid receptor is involved in the regulation of GILZ by alcohol. Because GILZ is a key glucocorticoid-responsive factor mediating the anti-inflammatory and immunosuppressive actions of steroids, we propose that similar signaling pathways may play a role in the anti-inflammatory and immunosuppressive effects of alcohol.

Glucocorticoid‐induced leucine zipper is downregulated in human alveolar macrophages upon Toll‐like receptor activation

“…We found indeed that absence of GILZ enhanced NF-κB activity and TNF-α mRNA induction upon LPS-treatment. Our findings are in line with previous reports of increased cytokine production upon IL-1β-mediated activation in GILZ-silenced lung A549 cells [13], indicating that decreased levels of GILZ within the cell promote an inflammatory response.…”

“…We found indeed that absence of GILZ enhanced NF-κB activity and TNF-α mRNA induction upon LPS-treatment. Our findings are in line with previous reports of increased cytokine production upon IL-1β-mediated activation in GILZ-silenced lung A549 cells [13], indicating that decreased levels of GILZ within the cell promote an inflammatory response.As we speculated that downregulation of GILZ was not an effect specific for TLR4 activation, we also explored effects of other TLR ligands. Indeed, activation of all TLRs, with the exception of TLR3, diminished GILZ mRNA in AMs.…”

“…Glucocorticoids are widely used for the treatment of inflammatory pathologies, including inflammatory lung diseases, such as asthma. The induction of GILZ has been suggested to contribute to the antiinflammatory actions of glucocorticoids in different cells, such as T cells, mast cells, and epithelial cells [9][10][11][12][13]. The binding to and inhibition of NF-κB by GILZ seems essential for its antiinflammatory action [9,10,14,15].…”

Glucocorticoid-Induced Leucine Zipper: A Critical Factor in Macrophage Endotoxin Tolerance

“…GILZ impairs inflammation via inhibition of the nuclear translocation of NF-kB and AP-1 by direct binding. In this manner, GILZ decreases the expression of proinflammatory mediators, such as MIP-1a, TNF-a, or IFN-g, and inhibits TLR2 upregulation (1,3,4,8,14,35,36).…”

“…Silencing of GILZ in A549 epithelial cells or endothelial cells results in secretion of significantly higher amounts of inflammatory mediators in response to inflammatory stimuli (36). Likewise, investigations on the functional significance of GILZ downregulation in macrophages performed by siRNA-facilitated GILZ knockdown revealed a proinflammatory response, as indicated by increased cytokine expression and NF-kB activity (4).…”