Antagonistic Effects of Endogenous Nitric Oxide in a Glioblastoma Photodynamic Therapy Model.
Gliomas are aggressive brain tumors that are resistant to conventional chemotherapy and radiotherapy. Much of this resistance is attributed to endogenous nitric oxide (NO). Recent studies revealed that 5-aminolevulinic acid (ALA)-based photodynamic therapy (PDT) has advantages over conventional treatments for glioblastoma. In this study, we used an in vitro model to assess whether NO from glioblastoma cells can interfere with ALA-PDT. Human U87 and U251 cells expressed significant basal levels of neuronal NO synthase (nNOS) and its inducible counterpart (iNOS). After an ALA/light challenge, iNOS level increased three- to fourfold over 24 h, whereas nNOS remained unchanged. Elevated iNOS resulted in a large increase in intracellular NO. Extent of ALA/light-induced apoptosis increased substantially when an iNOS inhibitor or NO scavenger was present, implying that iNOS/NO was acting cytoprotectively. Moreover, cells surviving a photochallenge exhibited a striking increase in proliferation, migration and invasion rates, iNOS/NO again playing a dominant role. Also observed was a large iNOS/NO-dependent increase in matrix metalloproteinase-9 activity, decrease in tissue inhibitor of metalloproteinase-1 expression and increase in survivin and S100A4 expression, each effect being consistent with accelerated migration/invasion as a prelude to metastasis. Our findings suggest introduction of iNOS inhibitors as pharmacologic adjuvants for glioblastoma PDT.
Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI.
Jonathan M
JM
Fahey
Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI.
Joseph V
JV
Emmer
Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI.|Department of Biophysics, Jagiellonian University, Krakow, Poland.
Witold
W
Korytowski
Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI.
Neil
N
Hogg
Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI.
Albert W
AW
Girotti
D000277:Adjuvants, Pharmaceutic / Q000494:pharmacology / Q000627:therapeutic use*; D000622:Aminolevulinic Acid / Q000494:pharmacology / Q000627:therapeutic use*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D005909:Glioblastoma / Q000628:therapy*; D006801:Humans; D009569:Nitric Oxide / Q000037:antagonists & inhibitors*; D052247:Nitric Oxide Synthase Type II / Q000037:antagonists & inhibitors*; D010778:Photochemotherapy
D000277:Adjuvants, Pharmaceutic; D009569:Nitric Oxide; D000622:Aminolevulinic Acid; D052247:Nitric Oxide Synthase Type II