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Violet/blue light activates Nrf2 signaling and modulates the inflammatory response of THP-1 monocytes

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Abstract

Several studies suggest that light in the UVA range (320–400 nm) activates signaling pathways that are anti-inflammatory and antioxidative. These effects have been attributed to Nrf2-mediated upregulation of “phase 2” genes such as heme oxygenase-1 (HO-1) that neutralize oxidative stress and metabolize electrophiles. Proteomics analysis previously had shown that small doses of blue light (400–500 nm) increased levels of peroxiredoxin phase 2 proteins in THP-1 monocytes, which led to our hypothesis that blue light activates Nrf2 signaling and thus may serve as an anti-inflammatory agent. THP-1 monocytes were treated with doses of blue light with and without lipopolysaccharide (LPS) inflammatory challenge. Cell lysates were tested for Nrf2 activation and HO-1 production. Treated cells were assessed for viability/mitochondrial activity via trypan blue exclusion and MTT assay, and secretion of two major pro-inflammatory cytokines, interleukin 8 (IL8) and tumor necrosis factor alpha (TNFα) was measured using ELISA. Blue light activated the phase 2 response in cultured THP-1 cells and was protective against LPS-induced cytotoxicity. Light pre-treatment also significantly reduced cytokine secretion in response to 0.1 μg ml−1 LPS, but had no anti-inflammatory effect at high LPS levels. This study is the first to report these effects using a light source that is approved for routine use on dental patients. Cellular responses to these light energies are worth further study and may provide therapeutic interventions for inflammation.

Graphical abstract: Violet/blue light activates Nrf2 signaling and modulates the inflammatory response of THP-1 monocytes

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Publication details

The article was received on 15 Aug 2016, accepted on 25 Mar 2017 and first published on 28 Mar 2017


Article type: Paper
DOI: 10.1039/C6PP00299D
Citation: Photochem. Photobiol. Sci., 2017, Advance Article
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    Violet/blue light activates Nrf2 signaling and modulates the inflammatory response of THP-1 monocytes

    L. A. Trotter, D. Patel, S. Dubin, C. Guerra, V. McCloud, P. Lockwood, R. Messer, J. C. Wataha and J. B. Lewis, Photochem. Photobiol. Sci., 2017, Advance Article , DOI: 10.1039/C6PP00299D

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