Silver nanoparticles inhibit the function of hypoxia-inducible factor-1 and target genes: insight into the cytotoxicity and antiangiogenesis

Abstract

Hypoxia-inducible factor-1 (HIF-1) is a transcription factor that is activated upon exposure to hypoxic stress. It modulates a number of cellular responses including proliferation, apoptosis, angiogenesis, and metabolism by activating a panel of target genes in response to hypoxia. The HIF-1 level is often upregulated in the hypoxic microenvironment of solid tumors, which contributes to cancer treatment failure. Here we report that silver nanoparticles (AgNPs), which are widely used as an antimicrobial agent, are an effective inhibitor of HIF-1. AgNPs inhibited the activation of a HIF-dependent reporter construct after the cells were exposed to hypoxic conditions or treated with cobalt chloride, a hypoxia mimetic agent. The AgNPs also interfered with the accumulation of HIF-1α protein and the induction of the endogenous HIF target genes, VEGF-A and GLUT1. Since both HIF-1 and vascular endothelial growth factor-A play an important role in angiogenesis, AgNPs also inhibited angiogenesis in vitro. Our data reveal a new mechanism of how AgNPs act on cellular function, that is, they disrupt HIF signaling pathway. This finding provides a novel insight into how AgNPs can inhibit cancer cell growth and angiogenesis.

Keywords:

• silver nanoparticles (AgNPs)
• hypoxia-inducible factor
• transcriptional activity
• vascular endothelial growth factor-A
• angiogenesis

Supplementary materials

Figure S1 pGL4.42 and pGL3 vector maps.

Notes: (A) pGL4.42, (B) pGL3.

Abbreviation: HRE, hypoxia-responsive element.

Figure S2 Raw data of AgNP-induced MCF7 apoptotic analysis using flow cytometry.

Notes: (A) Dot plot of Annexin V-FITC/PI double stained MCF7 cells. (i) Untreated cells, (ii) 100 μg/mL AgNPs treated cells, and (iii) 400 μg/mL AgNPs treated cells. (B) Representative images showing live cell (Annexin-FITC negative, PI negative), apoptotic (early apoptotic cells were Annexin-FITC positive and PI negative, late apoptotic cells were Annexin-FITC/PI double stained) and necrotic cells (PI stained only). (i) Untreated cells (ii) 100 μg/mL and (iii) 400 μg/mL AgNPs treated cells.

Abbreviations: AgNPs, silver nanoparticles; PI, propidium iodide.

Acknowledgments

This work was supported by the National Natural Science Foundation of China (No 61378088), fund for Biophotonics Innovative Personnel Base construction (101000541212011), and fund for Advanced Manufacturing Technology (101000541213504) by Beijing University of Technology. We thank Mr Weiping Zhou and Dr Anming Hu of the University of Tennessee for their thoughtful discussions.

Disclosure

The authors report no conflicts of interest in this work.