title: Why is rose bengal more phototoxic to fibroblasts in vitro than in vivo?
abstract: Photosensitized protein cross-linking has been recently developed to seal wounds and strengthen tissue. Although the photosensitizing dye, Rose Bengal (RB), is phototoxic to cultured cells, cytotoxicity does not accompany RB-photosensitized tissue repair in vivo. We investigated whether the environment surrounding cells in tissue or the high irradiances used for photo-cross-linking inhibited RB phototoxicity. Fibroblasts (FB) grown within collagen gels to mimic a tissue environment and monolayer cultured FB were treated with RB (0.01-1 mm) and the high 532 nm laser irradiances used in vivo for tissue repair (0.10-0.50 W cm(-2)). Monolayer FB were substantially more sensitive to RB photosensitization: the LD50 was >200-fold lower than that in collagen gels. Collagen gel protection was associated with increased Akt phosphorylation, a prosurvival pathway. RB phototoxicity in collagen gels was 25-fold greater at low (0.030 W cm(-2)) that at high (0.50 W cm(-2)) irradiances. Oxygen depletion at high irradiance only partially accounted for the irradiance dependence of phototoxicity as replacing air with nitrogen only increased the LD50 by four-fold in monolayers. These results indicate that the lack of RB phototoxicity during in vivo tissue repair results from upregulation of prosurvival pathways in tissue cells, oxygen depletion and irradiance-dependent RB photochemistry.
authors.affiliation: Wellman Center for Photomedicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA.
authors.forename: Min
authors.initials: M
authors.lastname: Yao
authors.forename: Chuan
authors.initials: C
authors.lastname: Gu
authors.forename: Francis J
authors.initials: FJ
authors.lastname: Doyle
authors.forename: Hong
authors.initials: H
authors.lastname: Zhu
authors.forename: Robert W
authors.initials: RW
authors.lastname: Redmond
authors.forename: Irene E
authors.initials: IE
authors.lastname: Kochevar
mesh_terms: D002478:Cells, Cultured; D003094:Collagen / Q000378:metabolism; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D006801:Humans; D066298:In Vitro Techniques; D008027:Light; D012395:Rose Bengal / Q000633:toxicity*
chemical_list: D012395:Rose Bengal; D003094:Collagen