Faculty of Medicine, University of Tsukuba, Ibaraki, Japan.
Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan.
PLoS One. 2019 Sep 12;14(9):e0222074. doi: 10.1371/journal.pone.0222074. eCollection 2019.
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)-1α, resulting in the upregulation of heme biosynthesis, HCP-1 expression can be increased by HIF-1α stabilization. In this study, we determined whether NO regulates HCP-1 expression by stabilizing HIF-1α 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-1α 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-1α expression, intracellular HpD accumulation and PDT cytotoxicity were decreased by 2-methoxyestradiol, which is a HIF-1α 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-1α. 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-1α stabilization.
光动力疗法（PDT）是一种利用癌症特异性卟啉积累的癌症治疗方法。我们已经研究了这一现象，并提出了以下三个结论：1）这种现象的机制与一氧化氮（NO）和血红素载体蛋白-1（HCP-1）密切相关，2）NO 使亚铁螯合酶失活，因此，在用 5-氨基酮戊酸处理后给予 NO 供体，细胞内卟啉水平增加，3）HCP-1 不仅转运血红素，还转运其他卟啉。由于 NO 稳定缺氧诱导因子（HIF）-1α，导致血红素生物合成上调，HCP-1 表达可以通过 HIF-1α 稳定化增加。在这项研究中，我们确定了 NO 是否通过稳定 HIF-1α 表达来调节 HCP-1 表达。为此，用 L-精氨酸或 N6-（1-亚氨基乙基）-L-赖氨酸（L-NIL）处理大鼠胃癌细胞系 RGK36。L-精氨酸处理增加了细胞内 NO 浓度，以及 HCP-1 和 HIF-1α 的表达，而 L-NIL 处理则降低了它们。L-精氨酸处理后，细胞内血红素-卟啉二盐酸盐（HpD）积累后，PDT 的细胞毒性增强。L-NIL 处理降低了 PDT 的细胞毒性和 HpD 积累。2-甲氧基雌二醇，一种 HIF-1α 抑制剂，降低了 HCP-1 和 HIF-1α 的表达、细胞内 HpD 积累和 PDT 细胞毒性。此外，这些现象并没有因 L-精氨酸和 2-Me 的组合而增加。因此，HCP-1 可以是 HIF-1α 的下游靶标。这些现象也在人胃癌细胞系 MKN45 中诱导。综上所述，我们得出结论，HCP-1 的表达受 NO 通过 HIF-1α 稳定化的调节。
