Cr(VI)-stimulated STAT3 tyrosine phosphorylation and nuclear translocation in human airway epithelial cells requires Lck

Abstract

Chronic inhalation of low amounts of Cr(VI) promotes pulmonary diseases and cancers through poorly defined mechanisms. SFKs (Src family kinases) in pulmonary airway cells may mediate Cr(VI) signalling for lung injury, although the downstream effectors of Cr(VI)-stimulated SFKs and how they relate to pathogenic gene induction are unknown. Therefore SFK-dependent activation of transcription factors by non-cytotoxic exposure of human bronchial epithelial cells to Cr(VI) was determined. Protein–DNA binding arrays demonstrated that exposing BEAS 2B cells to 5 μM Cr(VI) for 4 and 24 h resulted in increased protein binding to 25 and 43 cis-elements respectively, while binding to 12 and 16 cis-elements decreased. Of note, Cr(VI) increased protein binding to several STAT (signal transducer and activator of transcription) cis-elements. Cr(VI) stimulated acute tyrosine phosphorylation and nuclear translocation of STAT1 over a 4 h period and a prolonged activation of STAT3 that reached a peak between 48 and 72 h. This prolonged activation was observed for both STAT3α and STAT3β. Immunofluorescent confocal microscopy confirmed that Cr(VI) increased nuclear localization of phosphorylated STAT3 for more than 72 h in both primary and BEAS 2B human airway cells. Cr(VI) induced transactivation of both a STAT3-driven luciferase reporter construct and the endogenous inflammatory gene IL-6 (interleukin-6). Inhibition with siRNA (small interfering RNA) targeting the SFK Lck, but not dominant-negative JAK (Janus kinase), prevented Cr(VI)-stimulated phosphorylation of both STAT3 isoforms and induction of IL-6. The results suggest that Cr(VI) activates epithelial cell Lck to signal for prolonged STAT3 activation and transactivation of IL-6, an important immunomodulator of lung disease progression.

Nickel Mobilizes Intracellular Zinc to Induce Metallothionein in Human Airway Epithelial Cells

“…These studies used the BEAS-2B cells to model the terminal bronchiolar epithelial responses to Ni. While these cells are SV40 immortalized, we have demonstrated that their responses to metals are nearly identical to primary normal human bronchiolar epithelial cells cultured on an air/liquid interface (27) and mouse bronchiolar epithelium in vivo (29). Induction of MT after Ni exposure in these cells closely matches responses observed in mouse lungs (33), and thus the mechanisms for this induction in BEAS-2B cells are likely to be broadly applicable.…”

“…The medium was changed 12 to 16 hours before the experiment. Under these conditions, the BEAS-2B responses to metals are similar to responses in primary human bronchial epithelial cells grown in air/ liquid interface cultures (27). Dko7 cells are SV-40 immortalized mouse embryonic fibroblasts (MEF) derived from MTF-1 double knockout embryonic stem cells (28).…”

Hexavalent chromium induces malignant transformation of human lung bronchial epithelial cells via ROS-dependent activation of miR-21-PDCD4 signaling

“…Previous studies showed that Cr(VI) stimulates IL-6 mRNA levels and STAT3 phosphorylation in human airway epithelial cells [34]. STAT3 binding to the miR-21 promoter upon IL-6 induction has been reported previously [30].…”

Luteolin inhibits Cr(VI)-induced malignant cell transformation of human lung epithelial cells by targeting ROS mediated multiple cell signaling pathways

“…Moreover, STAT3 is upregulated in both premalignant tumors (papillomas) and squamous cell carcinomas of mouse skin induced by topical treatment with DMBA + TPA (Chan et al , 2004). Cr(VI)-induced transactivation of STAT3 has been reported in human airway epithelial cells (O’hara et al , 2007). Cr(VI) exposure in BEAS-2B cells increased Stat3 activation and phosphorylation whereas treatment of luteolin suppressed them.…”

“…STAT3 is linked to inflammation-associated oncogenic transformation, by promoting pro-oncogenic inflammatory pathways, including nuclear factor-κB (NF-κB) and interleukin-6 (IL-6) (Yu et al , 2009). Previous studies demonstrated a prolonged STAT3 activation and transactivation of IL-6, with Cr(VI) exposure in human epithelial cells (O’hara et al , 2007). Inducible nitric oxide synthase (iNOS), one of the three isoforms of nitric oxide synthase, catalyzes the oxidative deamination of l-arginine to produce citrulline and nitric oxide (Chen et al , 2005).…”