Nitric oxide regulates the expression of heme carrier protein-1 via hypoxia inducible factor-1α stabilization

Effective disruption of cancer cell membranes by photodynamic therapy with cell membrane-adhesive photosensitizer

Photodynamic therapy (PDT) is a noninvasive cancer treatment modality that involves the administration of photosensitizers and light irradiation. Previously, we established a polycation-containing hematoporphyrin (aHP) formulation that demonstrated superior antitumor efficacy in vivo, than the original hematoporphyrin (HP). In this study, we investigated underlining mechanisms of the high antitumor effect of aHP using cell experiments. Time-lapse imaging of rat gastric cancerous cell line (RGK45) treated with aHP exhibited swelling, cell rupture, and subsequent scattering of small vesicles upon light irradiation, in contrast to the small changes in morphology of RGK45 treated with HP. Furthermore, aHP presented concentrated localization on the cell membranes to a greater extent than HP. Additionally, neither aHP nor HP induced morphological changes in rat gastric mucosa cell line (RGM1). Flow cytometry analysis demonstrated a higher fluorescence of wheat germ agglutinin-conjugated dye in RGK45 than in RGM1, suggesting differential glycan expression patterns. These findings collectively suggest that the cellular toxicity of aHP may be augmented in RGK45 cells owing to its heightened affinity toward negatively charged structures on cellular membranes and its preferential localization on them. The observed membrane rupture and release of extracellular vesicles may confer an abscopal effect, in addition to direct PDT effect, thereby positioning aHP as a promising next-generation photosensitizer.

Enhancement of cytotoxic effects with ALA-PDT on treatment of radioresistant cancer cells

Radiation therapy is a lower invasive local treatment than surgery and is selected as a primary treatment for solid tumors. However, when some cancer cells obtain radiotherapy tolerance, cytotoxicity of radiotherapy for cancer cells is attenuated. Photodynamic therapy (PDT) is a non-invasive cancer therapy combined with photosensitizers and laser irradiation with an appropriate wavelength. PDT is carried out for recurrent esophageal cancer patients after radiation chemotherapy and is an effective treatment for radiation-resistant tumors. However, it is not clear why PDT is effective against radioresistant cancers. In this study, we attempted to clear this mechanism using X-ray resistant cancer cells. X-ray resistant cells produce high amounts of mitochondria-derived ROS, which enhanced nuclear translocation of NF-κB, resulting in increased NO production. Moreover, the expression of PEPT1 that imports 5-aminolevulinic acid, the precursor of photosensitizers, was upregulated in X-ray resistant cancer cells. This was accompanied by an increase in intracellular 5-aminolevulinic acid-derived porphyrin accumulation, resulting in enhancement of PDT-induced cytotoxicity. Therefore, effective accumulation of photosensitizers induced by ROS and NO may achieve PDT after radiation therapy and PDT could be a promising treatment for radioresistant cancer cells.

Photodynamic Therapy and Immunological View in Gastrointestinal Tumors

Gastrointestinal cancers are a specific group of oncological diseases in which the location and nature of growth are of key importance for clinical symptoms and prognosis. At the same time, as research shows, they pose a serious threat to a patient's life, especially at an advanced stage of development. The type of therapy used depends on the anatomical location of the cancer, its type, and the degree of progression. One of the modern forms of therapy used to treat gastrointestinal cancers is PDT, which has been approved for the treatment of esophageal cancer in the United States. Despite the increasingly rapid clinical use of this treatment method, the exact immunological mechanisms it induces in cancer cells has not yet been fully elucidated. This article presents a review of the current understanding of the mode of action of photodynamic therapy on cells of various gastrointestinal cancers with an emphasis on colorectal cancer. The types of cell death induced by PDT include apoptosis, necrosis, and pyroptosis. Anticancer effects are also a result of the destruction of tumor vasculature and activation of the immune system. Many reports exist that concern the mechanism of apoptosis induction, of which the mitochondrial pathway is most often emphasized. Photodynamic therapy may also have a beneficial effect on such aspects of cancer as the ability to develop metastases or contribute to reducing resistance to known pharmacological agents.

Photodynamic Therapy for X-ray-Induced Radiation-Resistant Cancer Cells

Radiotherapy, in which X-rays are commonly used, is one of the most effective procedures for treating cancer. However, some cancer cells become resistant to radiation therapy, leading to poor prognosis. Therefore, a new therapeutic method is required to prevent cancer cells from acquiring radiation resistance. Photodynamic therapy (PDT) is a cancer treatment that uses photosensitizers, such as porphyrin compounds, and low-powered laser irradiation. We previously reported that reactive oxygen species (ROS) derived from mitochondria induce the expression of a porphyrin transporter (HCP1) and that laser irradiation enhances the cytotoxic effect. In addition, X-ray irradiation induces the production of mitochondrial ROS. Therefore, radioresistant cancer cells established with continuous X-ray irradiation would also overexpress ROS, and photodynamic therapy could be an effective therapeutic method. In this study, we established radioresistant cancer cells and examined the therapeutic effects and mechanisms with photodynamic therapy. We confirmed that X-ray-resistant cells showed overgeneration of mitochondrial ROS and elevated expression of HCP1, which led to the active accumulation of porphyrin and an increase in cytotoxicity with laser irradiation. Thus, photodynamic therapy is a promising treatment for X-ray-resistant cancers.

Singlet oxygen-generating cell-adhesive glass surfaces for the fundamental investigation of plasma membrane-targeted photodynamic therapy

Recently, plasma membrane-targeted photodynamic therapy has attracted attention as an effective cancer immunotherapeutic strategy. However, the released photosensitizers do not only adhere to the plasma membrane but may also be internalized in the cytosol, in endosomes/lysosomes, hindering investigations of the effects of photosensitizers attached to the plasma membrane. In this study, we developed a cell culture dish with singlet oxygen-generating cell-adhesive glass surfaces that allows investigation of the effects of photosensitizers attached to the plasma membrane. For cell adhesion, poly[N-(3-aminopropyl)methacrylamide] conjugated with hematoporphyrin PA-HpD was immobilized on the glass surfaces. Singlet oxygen was produced from the PA-HpD-immobilized glass surface upon laser irradiation at 635 nm. When murine colon adenocarcinoma 26 (Colon-26) cells were cultured on the PA-HpD-immobilized surface, the cells were swollen and ruptured, leading to effective apoptotic cell death using laser irradiation at 635 nm. In addition, microvesicles of approximately 10 μm in diameter were released from the plasma membrane into the culture medium. These phenomena were due to the oxidation of lipids in the cellular membrane, caused by the plasma membrane-targeted photodynamic therapy. In contrast, these phenomena were not observed on poly[N-(3-aminopropyl)methacrylamide]-immobilized glass surfaces. These results indicate that cell culture dishes with singlet oxygen-generating cell-adhesive glass surfaces can be used to investigate fundamental mechanisms in plasma membrane-targeted photodynamic therapy.

Nanoparticle-mediated therapeutic management in cholangiocarcinoma drug targeting: Current progress and future prospects

Patients with cholangiocarcinoma (CCA) often have an unfavorable prognosis because of its insidious nature, low resectability rate, and poor response to anticancer drugs and radiotherapy, which makes early detection and treatment difficult. At present, CCA has a five-year overall survival rate (OS) of only 5%, despite advances in therapies. New an increasing number of evidence suggests that nanoplatforms may play a crucial role in enhancing the pharmacological effects and in reducing both short- and long-term side effects of cancer treatment. This document reviews the advantages and shortcomings of nanoparticles such as liposomes, polymeric nanoparticle，inorganic nanoparticle, nano-metals and nano-alloys, carbon dots, nano-micelles, dendrimer, nano-capsule, bio-Nanomaterials in the diagnosis and treatment of CCA and discuss the current challenges in of nanoplatforms for CCA.

Acetic acid enhances the effect of photodynamic therapy in gastric cancer cells via the production of reactive oxygen species

Acetic acid is a major component of vinegar and is reported to have beneficial health effects. Notably, it causes oxidative stress and enhances the production of reactive oxygen species (ROS) in gastric cancer cells. ROS play important roles in cellular signal transduction, resulting in the regulation of protein expression and apoptosis. We previously reported that ROS upregulate heme carrier protein 1 (HCP1). Moreover, ROS increase the cellular uptake of porphyrins, which are precursors of heme and substrates for uptake by HCP1. Therefore, we hypothesized that photodynamic therapy (PDT) for cancer treatment using laser irradiation and photosensitizers, such as porphyrin, is enhanced via ROS produced by acetic acid. Herein, we used the rat gastric mucosal cells, RGM1, its cancer-like mutated cells, RGK1, and a manganese superoxide dismutase (MnSOD)-overexpressing RGK cell line, RGK-MnSOD. We confirmed that cancer-specific cellular uptake of porphyrin is increased upon acetic acid treatment and enhances the PDT cytotoxicity in RGK-1, not in RGM-1 and RGK-MnSOD. We believe that this occurs because of the overproduction of ROS and subsequent upregulation of HCP1 in cancerous cells. In conclusion, acetic acid can elevate the effect of PDT by inducing cancer-specific HCP1 expression via ROS production.

Endogenous reactive oxygen species and nitric oxide have opposite roles in regulating HIF-1alpha expression in hypoxic astrocytes

Ischemic stroke results in cerebral tissue hypoxia and increased expression of hypoxia-inducible factor (HIF), which is critically implicated in ischemic brain injury. Understanding the mechanisms of HIF-1alpha regulation in the ischemic brain has been an important research focus. The generation of both nitric oxide (NO) and reactive oxygen species (ROS) is increased under hypoxic/ischemic conditions and each of them has been independently shown to regulate HIF-1alpha expression. In this study, we investigated the cross-effects of NO and ROS on the expression of HIF-1alpha in hypoxic astrocytes. Exposure of astrocytes to 2 h-hypoxia remarkably increased HIF-1alpha protein levels, which was accompanied by increased NO and ROS production. Decreasing ROS with NAC, NADPH oxidase inhibitor DPI, or SOD mimetic MnTMPyP decreased hypoxia-induced HIF-1alpha protein accumulation and increased NO level in hypoxic astrocytes. The NO synthase (NOS) inhibitor L-NAME inhibited ROS generation, which led to a reduction in hypoxia-induced HIF-1alpha protein expression. Although NOS inhibitor or ROS scavengers alone reduced HIF-1alpha protein levels, the reduction was reversed when NOS inhibitor and ROS scavenger present together. The NO scavenger PTIO increased hypoxia-induced HIF-1alpha protein expression and ROS production, while HIF-1alpha protein level was decreased in the presence of NO scavenger and ROS scavenger together. These results suggest that ROS, NO, and their interaction critically contribute to the regulation of hypoxia-induced HIF-1alpha protein accumulation under hypoxic condition. Furthermore, our results indicate that hypoxia-induced NO generation may represent an endogenous mechanism for balancing ROS-mediated hypoxic stress, as reflected by inhibiting hypoxia-induced HIF-1alpha protein accumulation.

SLC46A1 contributes to hepatic iron metabolism by importing heme in hepatocytes

BACKGROUND

Iron is finely regulated due to its vital roles in organisms and the peroxidase reactivity if excess. Solute Carrier Family 46 Member 1 (SLC46A1), also named PCFT or HCP1, is the main importer of heme‑iron in the intestine, but has a high abundance in the liver. Since the liver has a central role in iron homeostasis, whether SLC46A1 regulates hepatic iron metabolism is of interest to be identified.

METHODS

The recombinant adeno-associated virus vectors were used to hepatic-specifically inhibit SLC46A1 expression to observe its effects on hepatic iron metabolism. Then the abilities of SLC46A1 in importing heme and folate, and consequent alterations of iron content in hepatocytes were determined. Furthermore, effects of iron on SLC46A1 expression were investigated both in vitro and in vivo.

RESULTS

The hepatocyte-specific inhibition of SLC46A1 decreases iron content in the liver and increases iron content in serum. Expressions of iron-related molecules, transferrin receptor 1, hepcidin and ferroportin, are correspondingly altered. Interestingly, free heme concentration in serum is increased, indicating a decreased import of heme by the liver. In hepatocytes, SLC46A1 is capable of importing hemin, increasing intracellular iron content. The import of hemin by SLC46A1 is unaffected by its other substrate, folate. Instead, hemin treatment decreases SLC46A1 expression, reducing the import of folate. In addition, SLC46A1 itself shows to be iron-responsive both in vivo and in vitro, making it available for regulating iron metabolism.

CONCLUSION

The results elucidate that SLC46A1 regulates iron metabolism in the liver through a folate-independent manner of importing heme. The iron-responsive characters of SLC46A1 give us a new clue to link heme or iron overload with folate deficiency diseases.