Platycodin D, a bioactive component of Platycodon grandiflorum, induces cancer cell death associated with extreme vacuolation

Transcriptome-based analysis of key functional genes in the triterpenoid saponin synthesis pathway of Platycodon grandiflorum

BACKGROUND

Platycodon grandiflorum (P. grandiflorum) is a commonly used medicinal plant in China. Transcriptome sequencing studies of different tissues of P. grandiflorum have been widely conducted. However, studies on transcriptome sequencing and expression patterns of key genes in the saponin synthesis pathway of Tongcheng P. grandiflorum, a high-quality medicinal resource of different years, are relatively limited.

RESULTS

This study involved transcriptome sequencing and bioinformatics analysis of the roots from annual, biennial, and triennial P. grandiflorum in the Tongcheng area. After data filtering and assembly, we obtained 111.44 Gb of clean base data, including 742,880616 clean reads. We identified 5,156 differential expression unigenes between at least two sample groups, with differences noted among annual, biennial, and triennial P. grandiflorum plants. GO enrichment analysis annotated 3509, 1819, and 1393 DEGs in comparison TC1vsTC2, TC1vsTC3, and TC2vsTC3, respectively. Furthermore, KEGG enrichment analysis identified 16 genes encoding key enzymes in the terpene skeleton biosynthesis, sesquiterpene and triterpene biosynthesis pathways, including SE, AACT, FPPS, DXR, HMGR, HMGS, and DXS. The results of qRT-PCR experiments showed that most of the genes were most highly expressed in annual P. grandiflorum.

CONCLUSIONS

The present study provided transcriptomic data from the roots of Tongcheng P. grandiflorum of different years, which provides critical bioinformatics data on the growth and development of P. grandiflorum, laying a foundation for further research on saponins and identifying key enzymes involved in this process across different growth stages.

Cellular Regulation of Macropinocytosis

Interest in macropinocytosis has risen in recent years owing to its function in tumorigenesis, immune reaction, and viral infection. Cancer cells utilize macropinocytosis to acquire nutrients to support their uncontrolled proliferation and energy consumption. Macropinocytosis, a highly dynamic endocytic and vesicular process, is regulated by a series of cellular signaling pathways. The activation of small GTPases in conjunction with phosphoinositide signaling pivotally regulates the process of macropinocytosis. In this review, we summarize important findings about the regulation of macropinocytosis and provide information to increase our understanding of the regulatory mechanism underlying it.

Platycodin D2 enhances P21/CyclinA2-mediated senescence of HCC cells by regulating NIX-induced mitophagy

BACKGROUND

Hepatocellular carcinoma (HCC) cells usually show strong resistance to chemotherapy, which not only reduces the efficacy of chemotherapy but also increases the side effects. Regulation of autophagy plays an important role in tumor treatment. Cell senescence is also an important anti-cancer mechanism, which has become an important target for tumor treatment. Therefore, it is of great clinical significance to find anti-HCC drugs that act through this new mechanism. Platycodin D2 (PD2) is a new saponin compound extracted from the traditional Chinese medicine Platycodon grandiflorum.

PURPOSE

Our study aimed to explore the effects of PD2 on HCC and identify the underlying mechanisms.

METHODS

First, the CCK8 assay was used to detect the inhibitory effect of PD2 on HCC cells. Then, different pathways of programmed cell death and cell cycle regulators were measured. In addition, we assessed the effects of PD2 on the autophagy and senescence of HCC cells by flow cytometry, immunofluorescence staining, and Western blotting. Finally, we studied the in vivo effect of PD2 on HCC cells by using a mouse tumor-bearing model.

RESULTS

Studies have shown that PD2 has a good anti-tumor effect, but the specific molecular mechanism has not been clarified. In this study, we found that PD2 has no obvious toxic effect on normal hepatocytes, but it can significantly inhibit the proliferation of HCC cells, induce mitochondrial dysfunction, enhance autophagy and cell senescence, upregulate NIX and P21, and downregulate CyclinA2. Gene silencing and overexpression indicated that PD2 induced mitophagy in HCC cells through NIX, thereby activating the P21/CyclinA2 pathway and promoting cell senescence.

CONCLUSIONS

These results indicate that PD2 induces HCC cell death through autophagy and aging. Our findings provide a new strategy for treating HCC.

A prospective review of the health-promoting potential of Jing Si Herbal Tea

Traditional Chinese medicine (TCM) has gained considerable attention over the past few years for its multicomponent, multitarget, and multi-pathway approach to treating different diseases. Studies have shown that TCMs as adjuvant therapy along with conventional treatment may benefit in safely treating various disorders. However, investigations on finding effective herbal combinations are ongoing. A novel TCM formula, "Jing Si Herbal Tea (JSHT)," has been reported recently for their health-promoting effects in improving overall body and mental health. JSHT is a combination of eight herbs recognized in Chinese herbal pharmacopoeia for their anti-viral, anti-aging, and anti-cancer properties as well as protective effects against cardiovascular, metabolic, neural, digestive, and genitourinary diseases. Thus, to better understand the beneficial effects of the ingredients of JSHT on health, this review intends to summarize the preclinical and clinical studies of the ingredients of JSHT on human health and diseases, and possible therapeutic effects with the related mode of actions and future prospects for their application in complementary therapies.

Platycodon grandiflorum (Jacq.) A. DC.: A review of phytochemistry, pharmacology, toxicology and traditional use

BACKGROUND

The traditional Chinese medicine Platycodon grandiflorum (Jacq.) A. DC. (PG, balloon flower) has medicinal and culinary value. It consists of a variety of chemical components including triterpenoid saponins, polysaccharides, flavonoids, polyphenols, polyethylene glycols, volatile oils and mineral components, which have medicinal and edible value.

PURPOSE

The ultimate goal of this review is to summarize the phytochemistry, pharmacological activities, safety and uses of PG in local and traditional medicine.

METHODS

A comprehensive search of published literature up to March 2022 was conducted using the PubMed, China Knowledge Network and Web of Science databases to identify original research related to PG, its active ingredients and pharmacological activities.

RESULTS

Triterpene saponins are the primary bioactive compounds of PG. To date, 76 triterpene saponin compounds have been isolated and identified from PG. In addition, there are other biological components, such as flavonoids, polyacetylene and phenolic acids. These extracts possess antitussive, immunostimulatory, anti-inflammatory, antioxidant, antitumor, antiobesity, antidepressant, and cardiovascular system activities. The mechanisms of expression of these pharmacological effects include inhibition of the expression of proteins such as MDM and p53, inhibition of the activation of enzymes, such as AKT, the secretion of inflammatory factors, such as IFN-γ, TNF-α, IL-2 and IL-1β, and activation of the AMPK pathway.

CONCLUSION

This review summarizes the chemical composition, pharmacological activities, molecular mechanism, toxicity and uses of PG in local and traditional medicine over the last 12 years. PG contains a wide range of chemical components, among which triterpene saponins, especially platycoside D (PD), play a strong role in pharmacological activity, representing a natural phytomedicine with low toxicity that has applications in food, animal feed and cosmetics. Therefore, PG has value for exploitation and is an excellent choice for treating various diseases.

Platycodon grandiflorus polysaccharides deeply participate in the anti-chronic bronchitis effects of platycodon grandiflorus decoction, a representative of “the lung and intestine are related”

Platycodon grandiflorus (Jacq.) A. DC. (PG) root is one of the most commonly used medicine-food materials for respiratory discomfort in Asia, usually in the form of a decoction or leaching solution. As everyone knows, both of decoction and leaching solution is a polyphase dispersion system, containing low-molecular-weight water-soluble active ingredients and hydrophilic macromolecules. This study aimed to discuss the synergistic effect of Platycodon grandiflorus polysaccharide (PGP) and platycodin D (PD) in PG decoction against chronic bronchitis (CB) and the mechanism underlying. A series of PGP, PD, and PGD + PD suspensions were administrated to CB model rats, on the levels of whole animal and in situ intestinal segment with or without mesenteric lymphatic vessels ligation. It exhibited that PGP exhibited synergistic effects with PD, on improving the histopathological abnormity, mucus secretion excess, and immunological imbalance in lung of CB model rat, closely associated with its modulations on the mucosal immunity status in small intestine. The polysaccharide macromolecules in PG decoction or leaching solution should be responsible for the modulation of pulmonary immune state, possibly through the common mucosal immune between small intestine and lung. These results might be a new perspective that illustrates the classical theory of “the lung and intestine are related” in traditional Chinese medicine.

Identification of key amino acid residues toward improving the catalytic activity and substrate specificity of plant-derived cytochrome P450 monooxygenases CYP716A subfamily enzyme for triterpenoid production in Saccharomyces cerevisiae

Triterpenoids constitute a group of specialized plant metabolites with wide structural diversity and high therapeutic value for human health. Cytochrome P450 monooxygenases (CYP) are a family of enzymes important for generating the structural diversity of triterpenoids by catalyzing the site-specific oxidization of the triterpene backbone. The CYP716 enzyme family has been isolated from various plant families as triterpenoid oxidases; however, their experimental crystal structures are not yet available and the detailed catalytic mechanism remains elusive. Here, we address this challenge by integrating bioinformatics approaches with data from other CYP families. Medicago truncatula CYP716A12, the first functionally characterized CYP716A subfamily enzyme, was chosen as the model for this study. We performed homology modeling, structural alignment, in silico site-directed mutagenesis, and molecular docking analysis to search and screen key amino acid residues relevant to the catalytic activity and substrate specificity of the CYP716A subfamily enzyme in triterpenoid biosynthesis. An in vivo functional analysis using engineered yeast that endogenously produced plant-derived triterpenes was performed to elucidate the results. When the amino acids in the signature region and substrate recognition sites (SRSs) were substituted, the product profile of CYP716A12 was modified. We identified amino acid residues that control the substrate contraction of the enzyme (D292) and engineered the enzyme to improve its catalytic activity and substrate specificity (D122, I212, and Q358) for triterpenoid biosynthesis. In addition, we demonstrated the versatility of this strategy by changing the properties of key residues in SRSs to improve the catalytic activity of Arabidopsis thaliana CYP716A1 (S356) and CYP716A2 (M206, F210) at C-28 on the triterpene backbone. This research has the potential to help in the production of desired triterpenoids in engineered yeast by increasing the catalytic activity and substrate specificity of plant CYP716A subfamily enzymes.

The Role and Therapeutic Potential of Macropinocytosis in Cancer

Macropinocytosis, a unique endocytosis pathway characterized by nonspecific internalization, has a vital role in the uptake of extracellular substances and antigen presentation. It is known to have dual effects on cancer cells, depending on cancer type and certain microenvironmental conditions. It helps cancer cells survive in nutrient-deficient environments, enhances resistance to anticancer drugs, and promotes invasion and metastasis. Conversely, overexpression of the RAS gene alongside drug treatment can lead to methuosis, a novel mode of cell death. The survival and proliferation of cancer cells is closely related to macropinocytosis in the tumor microenvironment (TME), but identifying how these cells interface with the TME is crucial for creating drugs that can limit cancer progression and metastasis. Substantial progress has been made in recent years on designing anticancer therapies that utilize the effects of macropinocytosis. Both the induction and inhibition of macropinocytosis are useful strategies for combating cancer cells. This article systematically reviews the general mechanisms of macropinocytosis, its specific functions in tumor cells, its occurrence in nontumor cells in the TME, and its application in tumor therapies. The aim is to elucidate the role and therapeutic potential of macropinocytosis in cancer treatment.

Integrated metabolomic and transcriptomic analysis reveals variation in the metabolites and genes of Platycodon grandiflorus roots from different regions

INTRODUCTION

Platycodon grandiflorum root (PG), a popular traditional Chinese medicine, contains considerable chemical components with broad pharmacological activities. The complexity and diversity of the chemical components of PG from different origins contribute to its broad biological activities. The quality of southern PG is superior to that of northern PG, but the mechanisms underlying these differences remain unclear.

OBJECTIVES

In order to study variation in the differentially accumulated metabolites (DAMs), differentially expressed genes (DEGs), as well as their interactions and signalling pathways among PG from Anhui and Liaoning.

METHODS

The metabolomes based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) and the transcriptome based on high-throughput sequencing technology were combined to comprehensively analyse PGn and PGb.

RESULTS

A total of 6515 DEGs and 83 DAMs from the comparison of PG from Anhui and Liaoning were detected. Integrated analysis of metabolomic and transcriptomic data revealed that 215 DEGs and 57 DAMs were significantly enriched in 48 pathways according to KEGG pathway enrichment analysis, and 15 DEGs and 10 DAMs significantly enriched in the main pathway sesquiterpenoid and triterpenoid and phenylpropanoid biosynthesis might play a key role in complex response or regulatory processes.

CONCLUSION

Differences in PG from southern and northern China might thus stem from differences in environmental factors, such as precipitation, light duration, and humidity. The results of our study provide new insight into geographic variation in gene expression and metabolite accumulation and will enhance the utilisation of PG resources.

High-yield bioactive triterpenoid production by heterologous expression in Nicotiana benthamiana using the Tsukuba system

Oleanolic acid is a pentacyclic triterpenoid found in numerous plant species and is a precursor to several bioactive triterpenoids with commercial potential. However, oleanolic acid accumulates at low levels in plants, and its chemical synthesis is challenging. Here, we established a method for producing oleanolic acid in substantial quantities via heterologous expression of pathway enzymes in Nicotiana benthamiana. The "Tsukuba system" is one of the most efficient agroinfiltration-based transient protein expression systems using the vector pBYR2HS, which contains geminiviral replication machinery and a double terminator for boosting expression. Additionally, the pBYR2HS vector contains an expression cassette for the gene-silencing suppressor p19 protein from tomato bushy stunt virus, which can also contribute to enhancing the expression of target proteins. In this study, we evaluated the applicability of this system to heterologous triterpenoid production in N. benthamiana. Medicago truncatula cytochrome P450 monooxygenase (CYP) 716A12 is the first enzyme to be functionally characterized as β-amyrin C-28 oxidase producing oleanolic acid. A mutant CYP716A12 (D122Q) with improved catalytic activity engineered in our previous study was co-expressed with other enzymes in N. benthamiana leaves. Using pBYR2HS, oleanolic acid yield was increased 13.1-fold compared with that using the conventional binary vector, indicating the advantage of the Tsukuba system. We also demonstrated the efficacy of co-expressing a mutant Arabidopsis thaliana HMGR1 catalytic domain, additional NADPH-cytochrome P450 reductase (CPR) transferring electrons to heterologous CYPs, and application of ascorbic acid for preventing leaf necrosis after agroinfiltration, to improve product yield. As a result, the product yields of both simple (β-amyrin) and oxidized (oleanolic acid and maslinic acid) triterpenoids were significantly improved compared with the previously reported yield in heterologous triterpenoid production in N. benthamiana leaves.

Comprehensive review on signaling pathways of dietary saponins in cancer cells suppression

Nutrigenomics utilizes high-throughput genomic technologies to reveal changes in gene and protein levels. Excitingly, ever-growing body of scientific findings has provided sufficient evidence about the interplay between diet and genes. Cutting-edge research and advancements in genomics, epigenetics and metabolomics have deepened our understanding on the role of dietary factors in the inhibition of carcinogenesis and metastasis. Dietary saponins, a type of triterpene glycosides, are generally found in Platycodon grandifloras, Dioscorea oppositifolia, asparagus, legumes, and sea cucumber. Wealth of information has started to shed light on pleiotropic mechanistic roles of dietary saponins in cancer prevention and inhibition. In this review, we have attempted to summarize the in vitro research of dietary saponins in the last two decades by searching common databases such as Google Scholar, PubMed, Scopus, and Web of Science. The results showed that dietary saponins exerted anti-cancer activities via regulation of apoptosis, autophagy, arrest cell cycle, anti-proliferation, anti-metastasis, and anti-angiogenesis, by regulation of several critical signaling pathways, including MAPK, PI3K/Akt/mTOR, NF-κB, and VEGF/VEGFR. However, there is no data about the dosage of dietary saponins for practical anti-cancer effects in human bodies. Extensive clinical studies are needed to confirm the effectiveness of dietary saponins for further commercial and medical applications.

Terpenoids' anti-cancer effects: focus on autophagy

Terpenoids are the largest class of natural products, most of which are derived from plants. Amongst their numerous biological properties, their anti-tumor effects are of interest for they are extremely diverse which include anti-proliferative, apoptotic, anti-angiogenic, and anti-metastatic activities. Recently, several in vitro and in vivo studies have been dedicated to understanding the 'terpenoid induced autophagy' phenomenon in cancer cells. Light has already been shed on the intricacy of apoptosis and autophagy relationship. This latter crosstalk is driven by the delicate balance between activating or silencing of certain proteins whereby the outcome is expressed via interrelated signaling pathways. In this review, we focus on nine of the most studied terpenoids and on their cell death and autophagic activity. These terpenoids are grouped in three classes: sesquiterpenoid (artemisinin, parthenolide), diterpenoids (oridonin, triptolide), and triterpenoids (alisol, betulinic acid, oleanolic acid, platycodin D, and ursolic acid). We have selected these nine terpenoids among others as they belong to the different major classes of terpenoids and our extensive search of the literature indicated that they were the most studied in terms of autophagy in cancer. These terpenoids alone demonstrate the complexity by which these secondary metabolites induce autophagy via complex signaling pathways such as MAPK/ERK/JNK, PI3K/AKT/mTOR, AMPK, NF-kB, and reactive oxygen species. Moreover, induction of autophagy can be either destructive or protective in tumor cells. Nevertheless, should this phenomenon be well understood, we ought to be able to exploit it to create novel therapies and design more effective regimens in the management and treatment of cancer.

Platycodon grandiflorum extract: chemical composition and whitening, antioxidant, and anti-inflammatory effects

Whitening cosmetics have a large market scale and broad development prospects, while whitening products of traditional Chinese medicine have always been a research hotspot. In this study, the whitening active extract of Platycodon grandiflorum (PGE) was isolated and purified for the first time, and the whitening activity mechanism and chemical composition of PGE were elucidated. A total of 45 components were identified via high-performance liquid chromatography-mass spectrometry (HPLC-MS) analysis, including arbutin, syringin, chlorogenic acid, platycoside E, platycodin D₃, baicalin, platycodin D, and luteolin. The scavenging rates of PGE toward DPPH and ABTS free radicals were 98.03% and 84.30%, respectively. The inhibition rate of PGE toward tyrosinase was up to 97.71%. The PGE had significant anti-inflammatory effects on RAW264.7 macrophages stimulated by lipopolysaccharide (LPS) and had significant inhibition effects on tyrosinase and melanin generation of B16F10 cells stimulated by α-MSH. The results showed that the PGE achieved a synergistic whitening effect by inhibiting the activation of oxygen free radicals on tyrosinase, antioxidation, anti-inflammatory effect, enzyme activity, and melanin generation. As a whitening agent extracted from natural plants, PGE has great potential in the research and development of plant whitening cosmetics, which lays a foundation for the further development and utilization of Platycodon grandiflorum resources and also provides a theoretical basis for the development of green and organic whitening cosmetics.

Whitening cosmetics have a large market scale and broad development prospects, while whitening products of traditional Chinese medicine have always been a research hotspot.

Drying characteristics and bioactivity evolution of Platycodon grandiflorum as affected by different microwave combined drying methods

This study was to investigate the effect of different drying methods on the drying kinetics, physical properties, and bioactivity of Platycodon grandiflorum (PG). Four drying methods were employed to conduct the dehydrated process, namely, hot air drying (AD), vacuum drying (VD), microwave hot airflow rolling-bed drying (MHARD), and pulse-spouted microwave vacuum drying (PSMVD). PSMVD showed the highest drying rate among four drying methods based on the result of fitting first-order reaction model. And PSMVD-dried product showed higher rehydration ratio and better mechanical properties, suggesting a better rehydration characteristic. In addition, considering the content of Platycodin D, PSMVD is a promising drying technology for the dehydration of PG.

Suppressive effect of platycodin D on bladder cancer through microRNA-129-5p-mediated PABPC1/PI3K/AKT axis inactivation

Platycodin D (PD) is a major constituent of Platycodon grandiflorum and has multiple functions in disease control. This study focused on the function of PD in bladder cancer cell behaviors and the molecules involved. First, we administered PD to the bladder cancer cell lines T24 and 5637 and the human uroepithelial cell line SV-HUC-1. Cell viability and growth were evaluated using MTT, EdU, and colony formation assays, and cell apoptosis was determined using Hoechst 33342 staining and flow cytometry. The microRNAs (miRNAs) showing differential expression in cells before and after PD treatment were screened. Moreover, we altered the expression of miR-129-5p and PABPC1 to identify their functions in bladder cancer progression. We found that PD specifically inhibited the proliferation and promoted the apoptosis of bladder cancer cells; miR-129-5p was found to be partially responsible for the cancer-inhibiting properties of PD. PABPC1, a direct target of miR-129-5p, was abundantly expressed in T24 and 5637 cell lines and promoted cell proliferation and suppressed cell apoptosis. In addition, PABPC1 promoted the phosphorylation of PI3K and AKT in bladder cancer cells. Altogether, PD had a concentration-dependent suppressive effect on bladder cancer cell growth and was involved in the upregulation of miR-129-5p and the subsequent inhibition of PABPC1 and inactivation of PI3K/AKT signaling.

Proposed mechanisms for the extracellular release of PD-L1 by the anticancer saponin platycodin D

Platycodin D (PTD) is an oleanane-type terpenoid saponin, isolated from the plant Platycodon grandiflorus. PTD displays multiple pharmacological effects, notably significant anticancer activities in vitro and in vivo. Recently, PTD was shown to trigger the extracellular release of the immunologic checkpoint glycoprotein PD-L1. The reduction of PD-L1 expression at the surface of cancer cells leads to interleukin-2 secretion and T cells activation. In the present review, we have analyzed the potential origin of this atypical PTD-induced PD-L1 release to propose a mechanistic explanation. For that, we considered all published scientific information, as well as the physicochemical characteristics of the natural product (a modeling analysis of PTD and the related saponin β -escin is provided). On this basis, we raise the hypothesis that the capacity of PTD to induce PD-L1 extracellular release derives from two main mechanisms: (i) a drug-promoted shedding of membrane PD-L1 by metalloproteases or more likely, (ii) a cholesterol binding-related effect, that would lead to perturbation of membrane raft domains, limiting the recruitment of proteins like TLR4. The drug-induced membrane effects (frequently observed with saponin drugs), associated with a production of interferon-γ,can favor the release of proteins like PD-L1 into membrane vesicles. Our analysis supports the hypothesis that PTD is a cholesterol-dependent lipid raft-modulating agent able to promote the formation of PD-L1 containing extracellular vesicles. The anticancer potential of PTD and its capacity to modulate the functioning of the PD-1/PD-L1 checkpoint should be further considered.