Proteasome inhibitors modulate chemokine production in lung epithelial and monocytic cells

Abstract

Proteasome inhibition has become a target for antitumour and antiinflammatory therapy. The present study investigated the influence of cysteine proteinase and proteasome inhibitors on chemokine production in lung epithelial cells and monocytic cells.The lung carcinoma cell lines A549, SK-MES, NCI-H727, virus-transformed bronchial epithelial cell line BEAS-2B, primary lung epithelial cells, and the acute monocytic leukaemia cell lines Mono-Mac-6 and THP-1 were incubated withproteinase inhibitor (L-trans-Epoxysuccinyl-Leu-3-methylbutylamide-ethyl ester) and the influence on chemokine production (interleukin-8: IL-8, monocyte chemoattractant protein-1, RANTES) was quantified at protein and mRNA levels.Inhibition of proteasome activity by ALLN and b-lactone resulted in significantly increased IL-8 secretion (5-to 22-fold). Cysteine proteinase inhibitors did not influence chemokine production. The simultaneous rise in IL-8 mRNA was caused by an increased half-life of mRNA and increased RNA synthesis. Moreover, analysis of transcription factor activation revealed induction of activator protein-1 (c-Jun) activity by proteasome inhibition, whereas nuclear factor-kB (p50 and p65) was not activated. The significant increase in IL-8 production after proteasome inhibition was also observed in primary lung epithelial cells and in monocytic cells. In addition, the secreted IL-8 was biologically active as shown by the neutrophil chemotaxis assay.In conclusion, it was shown that proteasome inhibitors stimulate interleukin-8 secretion in lung epithelial cells and monocytic cells, thus recruiting neutrophils.

Oxidative Inactivation of the Proteasome in Retinal Pigment Epithelial Cells

“…Although some reports showed that proteasome inhibitors down-regulate IL-8 (83)(84)(85), others showed an increase in IL-8 expression and secretion (51)(52)(53)(54)(55). The present work reconciles these apparently conflicting reports by demonstrating that proteasome inhibition regulates IL-8 production in a time-dependent manner.…”

“…Previous studies showed that inhibition of the proteasome results in an increase in IL-8 production in other cell types (51)(52)(53)(54)(55) and that extensive oxidative stress can impair the function of the UPP (32)(33)(34)(35)(36)(37)56). To test whether oxidation-induced proteasome inactivation could be the potential mechanistic link between oxidative stress and the enhanced production of IL-8 by RPE cells, we determined the effect of oxidative stress on proteasome activity in ARPE-19 cells.…”

Proteasome dysfunction inhibits surfactant protein gene expression in lung epithelial cells: mechanism of inhibition of SP-B gene expression

“…It is possible that in proteasome inhibitor-treated cells, decreased levels of TTF-1/Nkx2.1 disrupt the formation of the transcriptional complex that is necessary for SP-B promoter activity, leading to reduced SP-B gene expression. Proteasome dysfunction is associated with endoplasmic reticulum (ER) stress response (52), oxidative stress (17), and activation of JNK MAP kinase (18). Whether such mechanisms are involved in lactacystin and MG132 decrease of TTF-1/Nkx2.1 levels and inhibition of surfactant protein gene expression in H441 cells remains to be determined.…”

“…The association between proteasome dysfunction and diseases such as neurodegenerative diseases and aging (48) and cardiac diseases (37) suggests a possible link between aberrant gene expression and pathogenesis of the diseases. In a variety of lung epithelial cell lines, proteasome inhibitors were found to increase IL-8 levels (18). In A549 lung epithelial cells, induction of IL-8 was due to both transcriptional and mRNA stabilization mechanisms (18).…”

“…On the other hand, in MLE-12 cells, lactacystin (10 M) and MG132 (1 M) inhibition of SP-B and SP-C mRNA levels was associated with low-level toxicity, suggesting that toxicity alone does not contribute to the inhibition. Other studies have found that proteasome inhibitors, including lactacystin and MG132, did not have significant toxic effects on a variety of lung cells (18,21).…”