Research Progress on the Biological Activity of Pectolinarigenin

Wenbo ZUO, Shumei LI, Yannan LI, Hui XUE, Yu ZHANG, Tong ZHANG, Shinong WANG, Chenghao JIN*

1. College of Life Science and Technology, Heilongjiang Bayi Agricultural University, Daqing 163319, China; 2. Blood Purification Center, Daqing Oil Field General Hospital, Daqing 163001, China

Abstract Pectolinarigenin is a kind of flavonoid, which is an active ingredient in Eupatorium odoratum. Some studies have confirmed that pectolinarigenin has many biological activities, including anti-oxidation, anti-allergy, anti-inflammation, anti-tumor and so on. In this paper, the biological activity and related mechanism of pectolinarigenin were summarized in order to provide theoretical basis and reference for the further development and utilization of pectolinarigenin.

Key words Pectolinarigenin, Anti-tumor, Melanin, Anti-inflammation, Liver protection

1 Introduction

Pectolinarigenin is a kind of flavonoid mainly found inEupatoriumodoratumand other plants. Its molecular formula is C17H14O6and its molecular weight is 314.289 5.E.odoratumis a common Chinese herbal medicine in China, which has the effects of detumescence, hemostasis and anti-inflammation[1]. It is mainly used for trauma, swelling, bleeding and other diseases. Some studies have shown that pectolinarigenin has a variety of pharmacological effects, such as anti-inflammation, antioxidation, hemostasis and anti-tumor[2]. In this paper, the pharmacological effects and mechanism of pectolinarigenin were reviewed.

2 Inducing apoptosis of tumor cells

2.1InducingapoptosisofhepatomaHepG2cellsThrough MTT test, Wang Di[3]found that pectolinarigenin could inhibit the proliferation of lung cancer cells, and the killing effect was gradually enhanced with the increase of concentration. The cells were stained by Annexin-V/PI double staining and detected by flow cytometry. It was found that pectolinarigenin could induce apoptosis of tumor cells in a concentration-dependent manner. ATRA is the natural ligand of RARγ. The co-treatment of pectolinarigenin and ATRA can effectively reduce the enhancement of transcriptional activity of RARγ by ATRA. It can be inferred that pectolinarigenin is the antagonist of RARγ. After silencing RARγ by siRNA technique, it was found that the phosphorylation of Nur-77 was significantly reversed by pectolinarigenin, and Nur-77 itself was also reduced. This indicates that the phosphorylation of Nur-77 by pectolinarigenin is dependent on RARγ. Furthermore, Western blotting was used to detect the phosphorylation level of Nur-77 protein. It can be found that pectolinarigenin can activate JNK, promote Nur-77 phosphorylation, and then induce apoptosis. In addition, after HepG2 cells were treated with pectolinarigenin, the expression of p-c-jun and p-JNK proteins increased. At the same time, there was no significant change in the amount of p-c-jun and p-JNK in HepG2 cells silenced by RARγ treated with pectolinarigenin. This suggests that pectolinarigenin can effectively activate JNK signal pathway, phosphorylate Nur-77 receptor and induce apoptosis, and the whole process depends on nuclear receptor RARγ. This experiment reveals the regulatory relationship between nuclear receptor RARγ and orphan nuclear receptor Nur-77, which provides a new idea for drug research and development targeting Nur-77, and has a very broad research prospect.

2.2InducingapoptosisofnasopharyngealcarcinomaC666-1cellsNasopharyngeal carcinoma (NPC) is a polygenic hereditary tumor, which can occur not only from the squamous epithelium of the nasopharyngeal mucosa, but also from the columnar epithelium. Its incidence is extremely high in some parts of our country, which seriously endangers the health of our people[4]. Reactive oxygen species is the upstream regulatory factor of caspase family activation. Increasing or regulating the level of intracellular reactive oxygen species can lead to enhanced cytotoxic oxidative stress. After treating nasopharyngeal carcinoma C666-1 cells with pectolinarigenin for 24 h, Cheng Yin[1]found that mitochondrial membrane potential decreased and intracellular ROS level increased, and pectolinarigenin had obvious inhibitory effect on the growth and migration of C666-1 cells. The results showed that pectolinarigenin could activate apoptosis in mitochondrial pathway, and high-dose intraperitoneal injection of pectolinarigenin had no obvious side effects on nude mice.

2.3InducingapoptosisofosteosarcomacellsOsteosarcoma is a common malignant tumor in the bone and joint system, especially in children and adolescents, which originates from mesenchymal osteoblasts. Although some progress has been made in surgical treatment and multi-drug chemotherapy, nearly 30% of patients still die of osteosarcoma. Signal transducers and transcriptional activators (STAT3) play an important role in tumor invasiveness. With regard to osteosarcoma, the expression level of p-STAT3 is closely related to its prognosis, and the expression level of p-STAT3 is high in about 20% of osteosarcoma. Activated STAT3 pathway plays an important role in the growth and metastasis of osteosarcoma cells. Therefore, STAT3 pathway has been proved to be an attractive target for tumor therapy. Zhangetal.[2]used double luciferase assay to identify the inhibitory effect of pectolinarigenin on STAT3 activity. Studies have shown that pectolinarigenin can inhibit STAT3 signal transduction induced by IL-6 and reduce the accumulation of STAT3 in the nucleus, thus blocking the binding activity of STAT3 and DNA in osteosarcoma cells. Mechanism studies have shown that pectolinarigenin interferes with the formation of STAT3/DNA methyltransferase 1/HDAC1 histone deacetylase 1 complex in SHP-1 promoter region, and inversely mediates STAT3 signal pathway, resulting in up-regulation of SHP-1 expression in osteosarcoma. At the same time, pectolinarigenin significantly inhibited the proliferation of osteosarcoma cells and decreased the expression of STAT3 downstream proteins cyclin D1, Survirin, Bc1-2, Bcl-xl and Mcl-1, resulting in cell apoptosis. In addition, pectolinarigenin can also inhibit the migration and invasion of osteosarcoma cells. In the model of osteosarcoma xenotransplantation, intraperitoneal injection of pectolinarigenin can block the activation of STAT3 and inhibit tumor growth and metastasis, which has good pharmacodynamic properties. The results of this study suggest that pectolinarigenin may be a candidate drug for osteosarcoma intervention related to STAT3 signal inhibition activity, and there are no obvious side effectsinvivo. This provides solid evidence for the new discovery of the effect of anti-osteosarcoma.

2.4InducingapoptosisofbreastcancercellsBreast cancer is a kind of malignant tumor that seriously threatens women’s health. In recent years, the global incidence of breast cancer continues to rise. Breast cancer not only affects the long-term survival rate of patients, but also affects their appearance and mental health[6]. Lietal.[7]treated breast cancer 4T1, 231 and MCF-7 cells with pectolinarigenin, observed their inhibitory effect on proliferation, and further detected the effects of pectolinarigenin treatment on apoptosis, mitochondrial membrane potential, intracellular ROS level and cell migration ability. The results showed that pectolinarigenin could induce apoptosis and inhibit the migration ability of 4T1, 231 and MCF-7 cells through mitochondrial dependent pathway. The results show that pectolinarigenin may be a candidate drug for the treatment of breast cancer.

3 The effect of pectolinarigenin on osteoclasts

Osteoporosis (OP) is a disease characterized by decreased bone mass, destruction of bone tissue microstructure, increased bone brittleness and easy fracture[8]. The abnormal function of osteoclasts is the main cause of osteoporosis, so regulating the differentiation and function of osteoclasts is one of the strategies for the treatment of osteoporosis[9]. MAPK-activated NEATc1 and c-Fos are important downstream regulators of osteoclast formation. JNK phosphorylation activates AP-1, and c-Fos is an important part of AP-1, and c-Fos mutagenesis prevents osteoclast formation and leads to osteoporosis. Xiaoetal.[10]found that pectolinarigenin can inhibit the protein levels of NFATc1 and c-Fos. NFATc1 is the main gene expression regulator of late osteoclast formation induced by RANKL, and plays a key role in regulating osteoclast marker gene expression including Ctsk, Atp6v0d2, MMP9, Acp5 and so on. The activation of NFATc1 induced by RANKL was inhibited, and the expression of these NFATc1 targeting genes was also inhibited by pectolinarigenin, resulting in the inhibition of osteoclast formation. At the same time, pectolinarigenin can effectively inhibit the formation of F-actin ring and bone resorption of osteoclasts in a concentration-dependent manner. In addition, it was found that pectolinarigenin could inhibit the level of ROS induced by RANKL. These results suggest that pectolinarigenin can resist the disease caused by osteoclast overactivation by inhibiting the formation and function of osteoclasts and RANKL signaling pathway, and has potential application value in the treatment of osteoclast-related bone loss diseases.

4 Inhibition of melanin production

Melanin is produced by the oxidation and polymerization of tyrosine, two special cell groups of melanocytes and melanoma cells. It widely exists in the skin, eyes and hair of human and higher animals, and plays a role in protecting the skin and resisting ultraviolet rays. At the same time, it can also be used as ultraviolet absorber, antioxidant and new natural drug carrier to treat some nervous system diseases related to melanin deficiency[11]. Leeetal.[12]treated melanin a cell with pectolinarigenin, and detected melanin content by Western blotting, real-time fluorescence quantitative analysis and other methods. The results showed that melanin content decreased after pectolinarigenin treated cells. MITF is the most important transcription factor regulating the expression of melanin biosynthesis related genes. Further, Western blotting detection showed that pectolinarigenin could reduce the protein expression of tyrosinase, TRP1 and TRP and significantly inhibit the expression of MITF protein. In addition, the reconstructed human skin model was treated with pectolinarigenin, and melanin content was found to decrease. To sum up, it is suggested that pectolinarigenin is an anti-melanotic substance, which can treat melanin a cells and has no cytotoxicity. It can also inhibit the expression of tyrosinase-related genes and has important application value in the field of human skin problems.

5 Hepatoprotective effect

The liver is the most important place for drug metabolism in the body, and it is the most vulnerable organ affected by drugs. Due to the wide use of various drugs, drug-induced liver injury has become a serious health problem. In-depth study of its mechanism is of great help to the prevention and treatment of drug-induced liver injury[13]. In order to identify the protective effect of pectolinarigenin extracted fromCirsiumsetidenson liver, Yooetal.[14]used column chromatography to separate the butanol (BuOH) part of the methanol (MeOH) extract fromCirsiumsetidens. The pectolinarin was obtained and hydrolyzed in acid solution to obtain pectolinarigenin. The rat liver injury induced by D-galactosamine (GaIN) was used as a model to study its protective effect on liver. Glutathione metabolism was measured by glutathione (GSH), glutathione reductase (GR), glutamine cysteine synthetase (GCS), glutathione S-transferase (GST) and superoxide dismutase (SOD). The results showed that the activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline aminotransferase (ALP) and lactate dehydrogenase (LDH) decreased significantly, while the activities of GSH, GR, GCS, GST and SOD increased, and the increase of lipid peroxidation induced by GaIN was inhibited. This shows that pectolinarigenin has a protective effect on the liver and can protect the liver from GAIN-induced injury by blocking the antioxidant mechanism.

6 Anti-inflammatory effect

Inflammation is a complex physiological and pathological process, which can occur in tissues and organs in various parts of the body. The inflammatory response usually results in activation or phagocytosis of neutrophils or macrophages, causing tissue damage to the human body[15-16]. Limetal.[17]separated ethyl acetate fraction from methanol extract ofPhyllanthusangustifoliaby column chromatography under the guidance of biological activity, and obtained pectolinarigenin. COX and LOX inhibitors could inhibit AA-induced ear edema and cgn-induced foot edema, while steroidal anti-inflammatory drugs such as 5-LOX inhibitors and prednisolone could inhibit PCA. Pectolinarigenin has a strong inhibitory effect on COX-2-mediated PGE and 5-LOX-mediated LI production, indicating that it may also act as a dual inhibitor of COX and LOX in vivo. However, pectolinarigenin did not affect the expression of COX-2 or the activation of nuclear transcription factor (NF-κB). In addition, in vivo studies showed that pectolinarigenin (taken orally at 20 mg/kg) had similar inhibitory effects on arachidonic acid-induced ear edema, carrageenan-induced foot edema and passive skin anaphylaxis in mice, and may inhibit the formation of eicosanoid in inflammatory lesions, promoting the anti-inflammatory effect of pectolinarigenin to some extent. Erukainureetal.[18]separated dichloromethane (DCM), a methanol extract from lichen leaves, by silica gel column chromatography, and further obtained pectolinarigenin through separation to study its effects on respiratory oxidation burst of neutrophils and inhibition of T cell proliferation. From the results, it is found that pectolinarigenin has significant immunomodulatory activity, indicating that it has a strong immunosuppressive effect and can effectively inhibit the respiratory oxidation burst of polymorphonuclear neutrophils. In addition, pectolinarigenin has an inhibitory effect on respiratory oxidation burst and T cell proliferation, which further indicates that this flavonoid has the potential of immune regulation. To sum up, pectolinarigenin has significant anti-inflammatory activity and is expected to become a new anti-inflammatory and anti-allergic drug.

7 Conclusion

Pectolinarigenin has the effects of anti-inflammation, hemostasis and antioxidation. At the same time, it has cytotoxic effect on many kinds of tumor cells, and it can promote the apoptosis of tumor cells and inhibit the formation of melanin. However, it is not clear what signal pathway it regulates to induce cell apoptosis, and further experimental exploration is needed. In accordance with the relevant theories of traditional Chinese medicine, this paper made a more comprehensive and in-depth study of pectolinarigenin from the animal (such as the construction of nude mouse tumor model), cell (each tumor cell as the experimental model) and molecular levels. This provides a strong basis for the treatment of tumor and lays a foundation for further promoting its development into a common antineoplastic drug.