Nitric oxide regulates the expression of heme carrier protein-1 via hypoxia inducible factor-1? stabilization.
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ABSTRACT: Photodynamic therapy (PDT) is a cancer therapy that capitalizes on cancer-specific porphyrin accumulation. We have investigated this phenomenon to propose the following three conclusions: 1) the mechanism underlying this phenomenon is closely related to both nitric oxide (NO) and heme carrier protein-1 (HCP-1), 2) NO inactivates ferrochelatase, and thus, the intracellular porphyrin levels in the cells are increased by the administration of an NO donor after 5-aminolevulinic acid treatment, 3) HCP-1 transports not only heme but also other porphyrins. Since NO stabilizes hypoxia-inducible factor (HIF)-1?, resulting in the upregulation of heme biosynthesis, HCP-1 expression can be increased by HIF-1? stabilization. In this study, we determined whether NO regulates HCP-1 expression by stabilizing HIF-1? expression. For this purpose, rat gastric cancer cell line RGK36 was treated with L-arginine or N6-(1-iminoethyl)-L-lysine (L-NIL). L-arginine treatment increased the intracellular NO concentration, and both HCP-1 and HIF-1? expression, while L-NIL treatment decreased them. Cytotoxicity of PDT was enhanced by L-arginine, following intracellular hemato-porphyrin dihydrochloride (HpD) accumulation. Both Cytotoxicity of PDT and HpD accumulation were decreased by L-NIL. The HCP-1 and HIF-1? expression, intracellular HpD accumulation and PDT cytotoxicity were decreased by 2-methoxyestradiol, which is a HIF-1? inhibitor. Moreover, these phenomena were not increased by a combination of both L-arginine and 2-Me. Thus, HCP-1 can be a downstream target of HIF-1?. These effects were also induced in the human gastric cancer cell line MKN45. Taken together, we conclude that HCP-1 expression is regulated by NO via HIF-1? stabilization.
SUBMITTER: Kurokawa H
PROVIDER: S-EPMC6742216 | biostudies-literature | 2019
REPOSITORIES: biostudies-literature
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