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.

Potential Immunoregulatory Mechanism of Plant Saponins: A Review

Saponins are extracted from different parts of plants such as seeds, roots, stems, and leaves and have a variety of biological activities including immunomodulatory, anti-inflammatory effects, and hypoglycemic properties. They demonstrate inherent low immunogenicity and possess the capacity to effectively regulate both the innate and adaptive immune responses. Plant saponins can promote the growth and development of the body's immune organs through a variety of signaling pathways, regulate the activity of a variety of immune cells, and increase the secretion of immune-related cytokines and antigen-specific antibodies, thereby exerting the role of immune activity. However, the chemical structure of plant saponins determines its certain hemolytic and cytotoxicity. With the development of science and technology, these disadvantages can be avoided or reduced by certain technical means. In recent years, there has been a significant surge in interest surrounding the investigation of plant saponins as immunomodulators. Consequently, the objective of this review is to thoroughly examine the immunomodulatory properties of plant saponins and elucidate their potential mechanisms, with the intention of offering a valuable point of reference for subsequent research and advancement within this domain.

A review: structure-activity relationship between saponins and cellular immunity

Saponins, which exhibit many different biological and pharmacological activities, are present in a wide range of plant species and in some marine organisms. Notably, the researchers have found that saponins can activate the immune system in mammals. The strength of this function is closely related to the chemical structure of saponins. The present study of the structure-activity relationship suggests that aglycones, glycochains on aglycones and special functional groups of saponins affect the immune activity of saponins. This paper reviews the effects of different saponins on cellular immunity. As well as the structure-activity relationship of saponins. It is hoped that the information integrated in this paper will provide readers with information on the effects of saponins on cellular immunity and promote the further study of these compounds.

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.

Machine Learning-Assisted Screening of Herbal Medicine Extracts as Vaccine Adjuvants

Adjuvants are important vaccine components, composed of a variety of chemical and biological materials that enhance the vaccine antigen-specific immune responses by stimulating the innate immune cells in both direct and indirect manners to produce a variety cytokines, chemokines, and growth factors. It has been developed by empirical methods for decades and considered difficult to choose a single screening method for an ideal vaccine adjuvant, due to their diverse biochemical characteristics, complex mechanisms of, and species specificity for their adjuvanticity. We therefore established a robust adjuvant screening strategy by combining multiparametric analysis of adjuvanticity in vivo and immunological profiles in vitro (such as cytokines, chemokines, and growth factor secretion) of various library compounds derived from hot-water extracts of herbal medicines, together with their diverse distribution of nano-sized physical particle properties with a machine learning algorithm. By combining multiparametric analysis with a machine learning algorithm such as rCCA, sparse-PLS, and DIABLO, we identified that human G-CSF and mouse RANTES, produced upon adjuvant stimulation in vitro, are the most robust biological parameters that can predict the adjuvanticity of various library compounds. Notably, we revealed a certain nano-sized particle population that functioned as an independent negative parameter to adjuvanticity. Finally, we proved that the two-step strategy pairing the negative and positive parameters significantly improved the efficacy of screening and a screening strategy applying principal component analysis using the identified parameters. These novel parameters we identified for adjuvant screening by machine learning with multiple biological and physical parameters may provide new insights into the future development of effective and safe adjuvants for human use.

Future Directions for the Discovery of Natural Product-Derived Immunomodulating Drugs

Drug discovery from natural sources is going through a renaissance, having spent many decades in the shadow of synthetic molecule drug discovery, despite the fact that natural product-derived compounds occupy a much greater chemical space than those created through synthetic chemistry methods. With this new era comes new possibilities, not least the novel targets that have emerged in recent times and the development of state-of-the-art technologies that can be applied to drug discovery from natural sources. Although progress has been made with some immunomodulating drugs, there remains a pressing need for new agents that can be used to treat the wide variety of conditions that arise from disruption, or over-activation, of the immune system; natural products may therefore be key in filling this gap. Recognising that, at present, there is no authoritative article that details the current state-of-the-art of the immunomodulatory activity of natural products, this in-depth review has arisen from a joint effort between the International Union of Basic and Clinical Pharmacology (IUPHAR) Natural Products and Immunopharmacology, with contributions from a Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation number of world-leading researchers in the field of natural product drug discovery, to provide a "position statement" on what natural products has to offer in the search for new immunomodulatory argents. To this end, we provide a historical look at previous discoveries of naturally occurring immunomodulators, present a picture of the current status of the field and provide insight into the future opportunities and challenges for the discovery of new drugs to treat immune-related diseases.

Summary of Natural Products Ameliorate Concanavalin A-Induced Liver Injury: Structures, Sources, Pharmacological Effects, and Mechanisms of Action

Liver diseases represent a threat to human health and are a significant cause of mortality and morbidity worldwide. Autoimmune hepatitis (AIH) is a progressive and chronic hepatic inflammatory disease, which may lead to severe complications. Concanavalin A (Con A)-induced hepatic injury is regarded as an appropriate experimental model for investigating the pathology and mechanisms involved in liver injury mediated by immune cells as well as T cell-related liver disease. Despite the advances in modern medicine, the only available strategies to treat AIH, include the use of steroids either solely or with immunosuppressant drugs. Unfortunately, this currently available treatment is associated with significant side-effects. Therefore, there is an urgent need for safe and effective drugs to replace and/or supplement those in current use. Natural products have been utilized for treating liver disorders and have become a promising therapy for various liver disorders. In this review, the natural compounds and herbal formulations as well as extracts and/or fractions with protection against liver injury caused by Con A and the underlying possible mechanism(s) of action are reviewed. A total of 53 compounds from different structural classes are discussed and over 97 references are cited. The goal of this review is to attract the interest of pharmacologists, natural product researchers, and synthetic chemists for discovering novel drug candidates for treating immune-mediated liver injury.

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.

Bioactive platycodins from Platycodonis Radix: Phytochemistry, pharmacological activities, toxicology and pharmacokinetics

Platycodonis Radix, the root of Platycodon grandiflorum (Jacq.) A. DC., is a well-known edible herbal medicine. It is a common vegetable used for the preparation of side dish, kimchi, dessert, and tea. Besides, it has been used to treat respiratory disease including cough, excessive phlegm, and sore throat for a long history. In the past decades, the bioactive components and the pharmacological activities of Platycodonis Radix have been widely investigated. Thereinto, platycodins, the oleanane-type triterpenoid saponins were demonstrated to be the main bioactive components in Platycodonis Radix, and more than 70 platycodins have been identified up to date. This paper mainly reviewed the phytochemistry, pharmacological activities (apophlegmatic, anti-tussive, anti-inflammatory, anti-cancer, anti-obesity, anti-diabetic, immunomodulatory, cardiovascular protective, and hepatoprotective activities, etc.), toxicology and pharmacokinetics of platycodins isolated from Platycodonis Radix, aiming to promote further investigation on therapeutic potential of these platycodins.

A Systems-Level Analysis of Mechanisms of Platycodon grandiflorum Based on A Network Pharmacological Approach

Platycodon grandiflorum (PG) is widely used in Asia for its various beneficial effects. Although many studies were conducted to understand the molecular mechanisms of PG, it is still unclear how the combinations of multiple ingredients work together to exert its therapeutic effects. The aim of the present study was to provide a comprehensive review of the systems-level mechanisms of PG by adopting network pharmacological analysis. We constructed a compound⁻target⁻disease network for PG using experimentally validated and machine-leaning-based prediction results. Each target of the network was analyzed based on previously known pharmacological activities of PG. Gene ontology analysis revealed that the majority of targets were related to cellular and metabolic processes, responses to stimuli, and biological regulation. In pathway enrichment analyses of targets, the terms related to cancer showed the most significant enrichment and formed distinct clusters. Degree matrix analysis for target⁻disease associations of PG suggested the therapeutic potential of PG in various cancers including hepatocellular carcinoma, gastric cancer, prostate cancer, small-cell lung cancer, and renal cell carcinoma. We expect that network pharmacological approaches will provide an understanding of the systems-level mechanisms of medicinal herbs and further develop their therapeutic potentials.

Platycoside O, a new triterpenoid saponin from the roots of Platycodon grandiflorum

A new unusual minor triterpenoid saponin, platycoside O (1), was isolated from the 75% EtOH extract obtained from the roots of Platycodon grandiflorum, together with four known saponins: platycoside M-3 (2), platycoside J (3), platycoside F (4) and platycoside B (5). The structure of 1 was determined as 3-O-β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl-2β,3β,16α,23-tetrahydroxyolean-12-en-24-methoxyl, 24-oxo-28-oic acid 28-O-β-D-xylopyranosyl-(1→4)-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranoside on the basis of spectral analysis and chemical evidence.

Advances in effective vaccine development against hepatitis B: focus on mucosal vaccine delivery strategies

Hepatitis B virus causes chronic necroinflammatory liver disease, which is known as hepatitis B. This inflammatory condition may further aggravate liver cirrhosis or hepatocellular carcinoma. Currently available conventional hepatitis B vaccine contains one of the viral envelope proteins, hepatitis B surface antigen, which develops a humoral immune response and hence protects against the infection. However, it fails in developing the desired cellular immune response, which is one of the most important bioresponses contributing to virus elimination from infected hepatocytes. At the same time, moderate humoral response developed following conventional vaccination do not protect the mucosal surfaces through serosal response. The mucosa is a predominant entry site for most of the infectious pathogens. Several strategies, including the use of adjuvants, development of surface functionalized novel antigen carriers and mucosal immunization for example, have been explored to investigate their role in addressing the limitations associated with the current hepatitis B vaccine. This review focuses on recent advances that have been made in order to develop an effective vaccine against hepatitis B.