Cytoprotective induction of nitric oxide synthase in a cellular model of 5-aminolevulinic acid-based photodynamic therapy. Free Radic Biol Med 2010 May 15;48(10):1296-301
Date
02/09/2010Pubmed ID
20138143Pubmed Central ID
PMC2856718DOI
10.1016/j.freeradbiomed.2010.01.040Scopus ID
2-s2.0-77951890671 (requires institutional sign-in at Scopus site) 71 CitationsAbstract
Photodynamic therapy (PDT) employs a photosensitizing agent, molecular oxygen, and visible light to generate reactive species that kill tumor and tumor vasculature cells. Nitric oxide produced by these cells could be procarcinogenic by inhibiting apoptosis or promoting angiogenesis and tumor growth. The purpose of this study was to determine whether tumor cells upregulate NO as a cytoprotective measure during PDT. Breast tumor COH-BR1 cells sensitized in their mitochondria with 5-aminolevulinic acid (ALA)-derived protoporphyrin IX died apoptotically after irradiation, ALA- and light-only controls showing no effect. Western analysis revealed that inducible nitric oxide synthase (iNOS) was upregulated >3-fold within 4 h after ALA/light treatment, whereas other NOS isoforms were unaffected. Exposing cells to a NOS inhibitor (L-NAME or 1400W) during photochallenge enhanced caspase-3/7 activation and apoptotic killing up to 2- to 3-fold while substantially reducing chemiluminescence-assessed NO production, suggesting that this NO was cytoprotective. Consistently, the NO scavenger cPTIO enhanced ALA/light-induced caspase-3/7 activation and apoptotic kill by >2.5-fold. Of added significance, cells could be rescued from 1400W-exacerbated apoptosis by an exogenous NO donor, spermine-NONOate. This is the first reported evidence for increased tumor cell resistance due to iNOS upregulation in a PDT model. Our findings indicate that stress-elicited NO in PDT-treated tumors could compromise therapeutic efficacy and suggest NOS-based pharmacologic interventions for preventing this.
Author List
Bhowmick R, Girotti AWMESH terms used to index this publication - Major topics in bold
AdenocarcinomaAminolevulinic Acid
Apoptosis
Breast Neoplasms
Caspases
Cell Line, Tumor
Cytoprotection
Enzyme Activation
Epithelial Cells
Female
Humans
Light
NG-Nitroarginine Methyl Ester
Nitric Oxide Synthase
Photochemotherapy
