title: Signaling events in apoptotic photokilling of 5-aminolevulinic acid-treated tumor cells: inhibitory effects of nitric oxide.
abstract: Antitumor photodynamic therapy (PDT) employs a photosensitizing agent, molecular oxygen, and visible light to produce reactive oxygen species that can destroy tumor and tumor vasculature cells. NO produced by these cells could be procarcinogenic by inhibiting apoptosis and promoting angiogenesis and tumor growth. We recently showed that NO from a chemical donor or activated macrophages makes COH-BR1 breast tumor cells more resistant to photokilling sensitized by 5-aminolevulinic acid (ALA)-generated protoporphyrin IX (PpIX). Signaling events associated with this hyperresistance have now been examined. ALA-treated COH-BR1 cells containing mitochondria-localized PpIX died mainly by apoptosis after being irradiated. Underlying redox signaling associated with MAP kinase (ERK1/2, p38, JUN) phosphorylation-activation, and heme oxygenase-1 (HO-1) upregulation was studied using immunoprecipitation and Western blot methodology. ALA/light treatment resulted in activation of proapoptotic JNK and p38 alpha, and deactivation of prosurvival p38 beta and ERK1/2. Involvement of both JNK and p38 in apoptosis was established by using a specific inhibitor for each. Spermine NONOate-derived NO, introduced immediately before irradiation, provided substantial protection against apoptosis. This was accompanied by greater HO-1 induction and a strong inhibition of each MAP kinase effect seen in the absence of NO. Downstream of JNK and p38 alpha activation, a marked upregulation/activation of proapoptotic Bax and Bid was observed along with down-regulation of antiapoptotic Bcl-xL, each response being reversed by NO. These findings provide new insights into signaling activity associated with the intrinsic apoptotic pathway in ALA-PDT and how this activity can be modulated by NO.
authors.affiliation: Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
authors.forename: Reshma
authors.initials: R
authors.lastname: Bhowmick
authors.forename: Albert W
authors.initials: AW
authors.lastname: Girotti
mesh_terms: D000622:Aminolevulinic Acid / Q000494:pharmacology* / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D019610:Cytoprotection; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D051547:Heme Oxygenase-1 / Q000235:genetics / Q000378:metabolism; D006801:Humans; D048670:MAP Kinase Kinase 4 / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000528:radiation effects; D009569:Nitric Oxide / Q000378:metabolism*; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000494:pharmacology* / Q000627:therapeutic use; D011524:Protoporphyrins / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D051017:Apoptosis Regulatory Proteins; D017319:Photosensitizing Agents; D011524:Protoporphyrins; D009569:Nitric Oxide; D000622:Aminolevulinic Acid; C028025:protoporphyrin IX; D051547:Heme Oxygenase-1; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4