title: Violet/blue light activates Nrf2 signaling and modulates the inflammatory response of THP-1 monocytes.
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-1LPS, 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.
authors.affiliation: Augusta University, Dept. of Oral Biology, 1120 15th St., Augusta, GA 30912-1126, USA. lewisj@westernu.edu.
authors.forename: L A
authors.initials: LA
authors.lastname: Trotter
authors.forename: D
authors.initials: D
authors.lastname: Patel
authors.forename: S
authors.initials: S
authors.lastname: Dubin
authors.forename: C
authors.initials: C
authors.lastname: Guerra
authors.forename: V
authors.initials: V
authors.lastname: McCloud
authors.forename: P
authors.initials: P
authors.lastname: Lockwood
authors.forename: R
authors.initials: R
authors.lastname: Messer
authors.forename: J C
authors.initials: JC
authors.lastname: Wataha
authors.forename: J B
authors.initials: JB
authors.lastname: Lewis
mesh_terms: D002478:Cells, Cultured; D006801:Humans; D007249:Inflammation / Q000378:metabolism*; D008027:Light; D051267:NF-E2-Related Factor 2 / Q000378:metabolism*; D015398:Signal Transduction / Q000528:radiation effects*; D000074084:THP-1 Cells
chemical_list: D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human