Effects of TNF-α and IL-1β on iron metabolism by A549 cells and influence on cytotoxicity

Abstract

Extracellular iron, which is predominantly bound by transferrin, is present in low concentrations within alveolar structures, and concentrations are increased in various pulmonary disorders. Iron accumulation by cells can promote oxidative injury. However, the synthesis of ferritin stimulated by metal exposure for intracellular iron storage is normally protective. The cytokines tumor necrosis factor (TNF)-α and interleukin (IL)-1β may alter iron metabolism by alveolar cells. In this study, we assessed the effects of TNF-α and IL-1β on iron metabolism with a cell line with properties of type 2 alveolar epithelial cells (A549) exposed to non-transferrin-bound (NTBI; FeSO4) or transferrin-bound (TBI) iron. In addition, we assessed the cytotoxicity of these exposures by measuring the cell accumulation of malondialdehyde (MDA), a product of lipid peroxidation, and cell death (MTT assay and lactate dehydrogenase release). A549 cells treated with NTBI or TBI in concentrations up to 40 μM accumulated iron and synthesized predominantly L-type ferritin without accumulation of MDA or cell death. Treatment of A549 cells with TNF-α (20 ng) or IL-1β (20 ng) decreased cell transferrin-receptor expression and induced synthesis of H-type ferritin. TNF-α and IL-1β decreased the uptake of TBI; however, the uptake of NTBI was increased. Both cytokines enhanced total ferritin synthesis (H plus L types) in response to iron treatments due to enhanced synthesis of H-type ferritin. Coexposure to TNF-α and NTBI, but not to TBI, induced MDA accumulation and greater cytotoxicity (MTT and lactate dehydrogenase release) than TNF-α alone. These findings indicate that TNF-α and IL-1β modulate iron uptake by A549 cells, with differing effects on TBI and NTBI, as well as on H-ferritin synthesis. Enhanced iron uptake induced by TNF-α and NTBI was also associated with increased cytotoxicity to A549 cells.

Variable tissue expression of transferrin receptors: relevance to acute respiratory distress syndrome

“…Several studies have demonstrated decreased expression of TfR in response to pro-inflammatory stimuli such as LPS in combination with c-interferon, tumour necrosis factor, interleukin-1 and combinations of chemokines applied to isolated epithelial cells and or macrophages [19][20][21]. Indeed, nitric oxide-mediated degradation of IRP-2 is a key regulatory component under such circumstances [22,23].…”

Regulation of ferritin genes and protein

“…In contrast, treatment with iron alone (transferrin-bound or nontransferrin-bound iron) induced the synthesis of L ferritin. 82 Overexpression of myotonic dystrophy protein kinase in C2C12 24,193,194,195,196,197,198,199,200,201,202,203 Ferritin L non-IRE mutations Neuroferritinopathy 64…”

Development of Budesonide Microparticles Using Spray-Drying Technology for Pulmonary Administration: Design, Characterization, In Vitro Evaluation, and In Vivo Efficacy Study

“…BUD is reported to exhibit anti-inflammatory activity via the inhibition of inflammatory mediators TNF-α and IL-6. In order to prove that the spray-drying process, polymers, and excipients did not alter the therapeutic activity of drug, BUD and developed formulations were tested against TNF-α and IL-6 in A549 alveolar epithelial cells (27).…”