Design, synthesis, and characterization of novel apigenin analogues that suppress pancreatic stellate cell proliferation in vitro and associated pancreatic fibrosis in vivo

Quercetin and Related Analogs as Therapeutics to Promote Tissue Repair

Quercetin is a polyphenol of the flavonoid class of secondary metabolites that is widely distributed in the plant kingdom. Quercetin has been found to exhibit potent bioactivity in the areas of wound healing, neuroprotection, and anti-aging research. Naturally found in highly glycosylated forms, aglycone quercetin has low solubility in aqueous environments, which has heavily limited its clinical applications. To improve the stability and bioavailability of quercetin, efforts have been made to chemically modify quercetin and related flavonoids so as to improve aqueous solubility while retaining bioactivity. In this review, we provide an updated overview of the biological properties of quercetin and proposed mechanisms of actions in the context of wound healing and aging. We also provide a description of recent developments in synthetic approaches to improve the solubility and stability of quercetin and related analogs for therapeutic applications. Further research in these areas is expected to enable translational applications to improve ocular wound healing and tissue repair.

Recent research progress of Cirsium medicinal plants in China

ETHNOPHARMACOLOGICAL RELEVANCE

The species of the genus Cirsium have been used as traditional Chinese medicine for hundreds of years. It is believed that Cirsium has the efficacies of cooling blood and stopping bleeding, dispelling blood stasis, detoxifying and eliminating carbuncle. At present, they are mainly used in treatment of the hemoptysis, hematemesis, hemoptysis, hematuria, traumatic bleeding and Henoch-Schonlein purpura. They are widely used in traditional Chinese medicine.

AIM

This paper systematically collated the classification, traditional use, pharmacological action, phytochemistry and clinical application of Cirsium plants in the past ten years, intending to provide a critical appraisal of current knowledge for future in-depth study and rational development and utilization of Cirsium plants.

MATERIAL AND METHODS

This paper searched various databases (SciFinder, Science Direct, CNKI, Wiley online library, Spring Link, Web of Science, PubMed, Wanfang Data, Weipu Data), Chinese Pharmacopoeia 2020 Edition, Chinese Flora, Chinese Materia Medica and some local books on ethnopharmacology.

RESULTS

More than ten species of Cirsium have been used as folk medicine, and modern pharmacological studies have shown that Cirsium has the effects of protecting liver, antioxidation, anti-tumor, anti-inflammation, antibacterial, etc. More than 200 chemical constituents such as flavonoids, triterpenes, sterols, phenylpropanoids have been isolated from Cirsium. Some ingredients show a wide variety of bioactivities including hepatoprotective, anti-inflammatory, antioxidant, anti-tumor and other activities. At present, Cirsium medicinal plants, as traditional Chinese medicine, were mainly used to treat nephritis, Henoch-Schonlein purpura and hemorrhage, although some species used in folk lack of quality control systems.

CONCLUSION

Cirsium plants are a safe and effective medicine for cooling blood and hemostasis. Recent studies on pharmacology and phytochemistry also provide solid scientific evidences for the traditional application of this genus. It also shows significant hepatoprotective activity and may be a potential clinical candidate for the treatment of liver disease. However, the qualitative and quantitative analysis, pharmacokinetics-pharmacodynamics and mechanism of action also need in-depth study.

Computationally Assisted Lead Optimization of Novel Potent and Selective MAO-B Inhibitors

A series of dietary flavonoid acacetin 7-O-methyl ether derivatives were computationally designed aiming to improve the selectivity and potency profiles against monoamine oxidase (MAO) B. The designed compounds were evaluated for their potential to inhibit human MAO-A and -B. Compounds 1c, 2c, 3c, and 4c were the most potent with a Ki of 37 to 68 nM against MAO-B. Compounds 1c–4c displayed more than a thousand-fold selectivity index towards MAO-B compared with MAO-A. Moreover, compounds 1c and 2c showed reversible inhibition of MAO-B. These results provide a basis for further studies on the potential application of these modified flavonoids for the treatment of Parkinson’s Disease and other neurological disorders.

Identification of Novel Ligands for Targeted Antifibrotic Therapy of Chronic Pancreatitis

PURPOSE

Chronic pancreatitis (CP) is an inflammatory disorder of the pancreas that leads to impaired pancreatic function. The limited therapeutic options and the lack of molecular targeting ligands or non-serum-based biomarkers hinder the development of target-specific drugs. Thus, there is a need for an unbiased, comprehensive discovery and evaluation of pancreatitis-specific ligands.

METHODS

This study utilized a computational-guided in vivo phage display approach to select peptide ligands selective for cellular components in the caerulein-induced mouse model of CP. The identified peptides were conjugated to pegylated DOPC liposomes via the reverse-phase evaporation method, and the in vivo specificity and pharmacokinetics were determined. As proof of concept, CP-targeted liposomes were used to deliver an antifibrotic small molecular drug, apigenin. Antifibrotic effects determined by pancreatic histology, fibronectin expression, and collagen deposition were evaluated.

RESULTS

We have identified five peptides specific for chronic pancreatitis and demonstrated selectivity to activated pancreatic stellate cells, acinar cells, macrophages, and extracellular matrix, respectively. MDLSLKP-conjugated liposomes demonstrated an increased particle accumulation by 1.3-fold in the inflamed pancreas compared to the control liposomes. We also observed that targeted delivery of apigenin resulted in improved acini preservation, a 37.2% and 33.1% respective reduction in collagen and fibronectin expression compared to mice receiving the free drug, and reduced oxidative stress in the liver.

CONCLUSION

In summary, we have developed a systematic approach to profile peptide ligands selective for cellular components of complex disease models and demonstrated the biomedical applications of the identified peptides to improve tissue remodeling in the inflamed pancreas.

Apigenin Alleviates Renal Fibroblast Activation through AMPK and ERK Signaling Pathways In Vitro

OBJECTIVE

Renal fibrosis is a common pathway leading to the progression of chronic kidney disease. Activated fibroblasts contribute remarkably to the development of renal fibrosis. Although apigenin has been demonstrated to play a protective role from fibrotic diseases, its pharmacological effect on renal fibroblast activation remains largely unknown.

MATERIALS AND METHODS

Here, we examined the functional role of apigenin in the activation of renal fibroblasts response to transforming growth factor (TGF)-β1 and its potential mechanisms. Cultured renal fibroblasts (NRK-49F) were exposed to apigenin (1, 5, 10 and 20 μM), followed by the stimulation of TGF-β1 (2 ng/mL) for 24 h. The markers of fibroblast activation were determined. In order to confirm the anti-fibrosis effect of apigenin, the expression of fibrosis-associated genes in renal fibroblasts was assessed. As a consequence, apigenin alleviated fibroblast proliferation and fibroblastmyofibroblast differentiation induced by TGF-β1.

RESULTS

Notably, apigenin significantly inhibited the fibrosis-associated genes expression in renal fibroblasts. Moreover, apigenin treatment significantly increased the phosphorylation of AMP-activated protein kinase (AMPK). Apigenin treatment also obviously reduced TGF-β1 induced phosphorylation of ERK1/2 but not Smad2/3, p38 and JNK MAPK in renal fibroblasts.

CONCLUSION

In a summary, these results indicate that apigenin inhibits renal fibroblast proliferation, differentiation and function by AMPK activation and reduced ERK1/2 phosphorylation, suggesting it could be an attractive therapeutic potential for the treatment of renal fibrosis.

Apigenin Exerts Anti-inflammatory Effects in an Experimental Model of Acute Pancreatitis by Down-regulating TNF-α

BACKGROUND/AIM

This study investigated the anti-inflammatory effect of apigenin in an experimental model of acute pancreatitis. Inflammatory response was reflected by tissue expression of the cytokine TNF-α coupled with histological examination.

MATERIALS AND METHODS

Wistar rats were divided into three groups: Sham-group animals underwent laparotomy only, without any other interventions. Control-group animals underwent laparotomy and bilio-pancreatic duct ligation to induce pancreatitis without apigenin administration. Apigenin group animals were further treated with apigenin. Euthanasia was performed at 6, 12, 24, 48 and 72 h post-operatively.

RESULTS

Over-expression of TNF-α in relation to postoperative time was observed in the control group (p<0.001). In the apigenin group, under-expression of TNF-α in relation to postoperative time was observed (p<0.013). At 72 h, apigenin reduced pancreatic TNF-α expression and prevented pancreatic necrosis.

CONCLUSION

Apigenin slows progression and reduces severity of acute pancreatitis. Apigenin may serve as an adjunct to a more successful therapeutic strategy in acute pancreatitis.

Transforming growth factor-β in pancreatic diseases: Mechanisms and therapeutic potential

Pancreatic diseases, such as acute pancreatitis, chronic pancreatitis, and pancreatic cancer, are common gastrointestinal diseases resulting in the development of local and systemic complications with a high risk of death. Numerous studies have examined pancreatic diseases over the past few decades; however, the pathogenesis remains unclear, and there is a lack of effective treatment options. Recently, emerging evidence has suggested that transforming growth factor beta (TGF-β) exerts controversial functions in apoptosis, inflammatory responses, and carcinogenesis, indicating its complex role in the pathogenesis of pancreas-associated disease. Therefore, a further understanding of relevant TGF-β signalling will provide new ideas and potential therapeutic targets for preventing disease progression. This is the first systematic review of recent data from animal and human clinical studies focusing on TGF-β signalling in pancreas damage and diseases. This information may aid in the development of therapeutic agents for regulating TGF-β in this pathology to prevent or treat pancreatic diseases.

Apigenin Decreases Acinar Cell Damage in Pancreatitis

OBJECTIVE

Chronic pancreatitis is the consequence of multiple episodes of recurrent acute pancreatitis (RAP). We hypothesized that apigenin can minimize the sequelae of RAP by limiting acinar cells' proinflammatory signaling pathways.

METHODS

AR42J acinar cells were treated in vitro with transforming growth factor β (TGF-β), apigenin, and other inhibitors. Dual luciferase reporter assay measured parathyroid hormone-related protein (PTHrP) promoter activity. MAPK/ERK pathway activity was assessed by immunoblotting and in vivo by immunohistochemistry with a cerulein-induced RAP mouse model. Nuclear factor κ B nuclear localization was analyzed in vitro in cells stimulated with tumor necrosis factor α. Primary acini were isolated and treated with cerulein; interleukin 6 messenger RNA was measured comparing PTHrP wild-type and knockout mice.

RESULTS

Apigenin and PD98059 each downregulated TGF-β stimulation of PTHrP P3 promoter activity. In a RAP mouse model, apigenin reduced pERK nuclear localization in acinar cells and preserved acinar cell architecture. Apigenin suppressed tumor necrosis factor α-mediated signaling by decreasing nuclear factor κ B nuclear localization and decreased interleukin 6 messenger RNA levels via a PTHrP-dependent mechanism.

CONCLUSIONS

Apigenin reduced inflammatory responses in experimental models of RAP. The mechanisms mediating the actions of apigenin, in part, are owing to attenuation of PTHrP and TGF-β proinflammatory signaling.

Postgenomic Properties of Natural Micronutrients

Modern medical approaches to the therapy of various diseases, including cancer, are based on the use of toxic drugs. The unfavorable side effects of traditional medicine could be counterbalanced by addition of natural bioactive substances to conventional therapy due to their mild action on cells combined with the multitargeted effects. To elucidate the real mechanisms of their biological activity, versatile approaches including a number of "omics" such as genomics, transcriptomics, proteomics, and metabolomics are used. This review highlights inclusion of bioactive natural compounds into the therapy of chronic diseases from the viewpoint of modern omics-based nutritional biochemistry. The recently accumulated data argue for necessity to employ nutrigenetic and nutrimetabolomic analyses to prevent or diminish the risk of chronic diseases.

Discovery of novel negletein derivatives as potent anticancer agents for acute myeloid leukemia

Baicalin and its aglycone baicalein derived from Scutellaria baicalensis exhibited potent anticancer effects in various types of cancer cell lines. However, the unfavorable pharmaceutical properties became the main obstacle for their potential clinical development. With the aim of development of novel anticancer agents based on the skeleton of baicalin, a series of novel negletein derivatives were designed and synthesized. Among them, compound 8 (FZU-02,006) with an N,N-dimethylamino ethoxyl moiety at the C-6 position exhibited significant enhanced antiproliferative effect against HL-60 cells in vitro through regulating multisignaling pathways. These results revealed that compound 8 with the improved aqueous solubility (as HCl salt, >1 mg/ml) and enhanced antileukemia potency might serve as a promising lead for further development.

Transcriptome-based repurposing of apigenin as a potential anti-fibrotic agent targeting hepatic stellate cells

We have used a computational approach to identify anti-fibrotic therapies by querying a transcriptome. A transcriptome signature of activated hepatic stellate cells (HSCs), the primary collagen-secreting cell in liver, and queried against a transcriptomic database that quantifies changes in gene expression in response to 1,309 FDA-approved drugs and bioactives (CMap). The flavonoid apigenin was among 9 top-ranked compounds predicted to have anti-fibrotic activity; indeed, apigenin dose-dependently reduced collagen I in the human HSC line, TWNT-4. To identify proteins mediating apigenin's effect, we next overlapped a 122-gene signature unique to HSCs with a list of 160 genes encoding proteins that are known to interact with apigenin, which identified C1QTNF2, encoding for Complement C1q tumor necrosis factor-related protein 2, a secreted adipocytokine with metabolic effects in liver. To validate its disease relevance, C1QTNF2 expression is reduced during hepatic stellate cell activation in culture and in a mouse model of alcoholic liver injury in vivo, and its expression correlates with better clinical outcomes in patients with hepatitis C cirrhosis (n = 216), suggesting it may have a protective role in cirrhosis progression.These findings reinforce the value of computational approaches to drug discovery for hepatic fibrosis, and identify C1QTNF2 as a potential mediator of apigenin's anti-fibrotic activity.

Efficient Preparation of Various O-Methylquercetins by Selective Demethylation

penta-O-Methylquercetin (2) was prepared by permethylation of quercetin (1). Selective demethylation of 2 using either BBr3 or BCl3/TBAI ( tetra-butylammonium iodide) gave five O-methylquercetins (3-6), with satisfactory yields. The reaction can be easily scaled-up. We established an efficient and large-scale preparation of O-methylquercetins.

Polyelectrolyte multilayers assembled from IL-10 plasmid DNA and TGF-β siRNA facilitate chronic pancreatitis treatment

Nanoparticles assembled with IL-10 plasmid DNA and TGF-β siRNA can reduce inflammation and fibrosis in mice with chronic pancreatitis (CP).

Pancreatic stellate cell: physiologic role, role in fibrosis and cancer

PURPOSE OF REVIEW

Ever since the first descriptions of methods to isolate pancreatic stellate cells (PSCs) from rodent and human pancreas 17 years ago, rapid advances have been made in our understanding of the biology of these cells and their functions in health and disease. This review updates recent literature in the field, which indicates an increasingly complex role for the cells in normal pancreas, pancreatitis and pancreatic cancer.

RECENT FINDINGS

Work reported over the past 12 months includes improved methods of PSC immortalization, a role for PSCs in islet fibrosis, novel factors causing PSC activation as well as those inducing quiescence, and translational research aimed at inhibiting the facilitatory effects of PSCs on disease progression in chronic pancreatitis as well as pancreatic cancer.

SUMMARY

Improved understanding of the role of PSCs in pancreatic pathophysiology has prompted a focus on translational studies aimed at developing novel approaches to modulate PSC function in a bid to improve clinical outcomes of two major fibrotic diseases of the pancreas: chronic pancreatitis and pancreatic cancer.

Evolution in medicinal chemistry of ursolic acid derivatives as anticancer agents

Currently, there is a renewed interest in common dietaries and plant-based traditional medicines for the prevention and treatment of cancer. In the search for potential anticancer agents from natural sources, ursolic acid (UA), a pentacyclic triterpenoid widely found in various medicinal herbs and fruits, exhibits powerful biological effects including its attractive anticancer activity against various types of cancer cells. However, the limited solubility, rapid metabolism and poor bioavailability of UA restricted its further clinical applications. In the past decade, with substantial progress toward the development of new chemical entities for the treatment of cancer, numerous UA derivatives have been designed and prepared to overcome its disadvantages. Despite extensive effort, discovery of effective UA derivatives has so far met with only limited success. This review summarizes the current status of the structural diversity and evolution in medicinal chemistry of UA analogues and provides a detailed discussion of future direction for further research in the chemical modifications of UA.

Apigenin inhibits pancreatic stellate cell activity in pancreatitis

BACKGROUND

Chronic pancreatitis (CP) is characterized by recurrent pancreatic injury, resulting in inflammation, necrosis, and fibrosis. There are currently no drugs limiting pancreatic fibrosis associated with CP, and there is a definite need to fill this void in patient care.

MATERIALS AND METHODS

Pancreatitis was induced in C57/BL6 mice using supraphysiologic doses of cerulein, and apigenin treatment (once daily, 50 μg per mouse by oral gavage) was initiated 1 wk into the recurrent acute pancreatitis (RAP) protocol. Pancreata were harvested after 4 wk of RAP. Immunostaining with fibronectin antibody was used to quantify the extent of pancreatic fibrosis. To assess how apigenin may decrease organ fibrosis, we evaluated the effect of apigenin on the proliferation and apoptosis of human pancreatic stellate cells (PSCs) in vitro. Finally, we assessed apigenin's effect on the gene expression in PSCs stimulated with parathyroid hormone-related protein, a profibrotic and proinflammatory mediator of pancreatitis, using reverse transcription-polymerase chain reaction.

RESULTS

After 4 wk of RAP, apigenin significantly reduced the fibrotic response to injury while preserving acinar units. Apigenin inhibited viability and induced apoptosis of PSCs in a time- and dose-dependent manner. Finally, apigenin reduced parathyroid hormone-related protein-stimulated increases in the PSC messenger RNA expression levels of extracellular matrix proteins collagen 1A1 and fibronectin, proliferating cell nuclear antigen, transforming growth factor-beta, and interleukin-6.

CONCLUSIONS

These in vivo and in vitro studies provide novel insights regarding apigenin's mechanism(s) of action in reducing the severity of RAP. Additional preclinical testing of apigenin analogs is warranted to develop a therapeutic agent for patients at risk for CP.

Anti-inflammation and anti-fibrosis with PEGylated, apigenin loaded PLGA nanoparticles in chronic pancreatitis disease

In this work, apigenin, a drug that can inhibit pancreatic stellate cell fibrosis, is loaded into PEGylated PLGA nanoparticles to treat the inflammation and fibrosis associated with chronic pancreatitis (CP).

Exploring therapeutic potentials of baicalin and its aglycone baicalein for hematological malignancies

Despite tremendous advances in the targeted therapy for various types of hematological malignancies with successful improvements in the survival rates, emerging resistance issues are startlingly high and novel therapeutic strategies are urgently needed. In addition, chemoprevention is currently becoming an elusive goal. Plant-derived natural products have garnered considerable attention in recent years due to the potential dual functions as chemotherapeutics and dietary chemoprevention. One of the particularly ubiquitous families is the polyphenolic flavonoids. Among them, baicalin and its aglycone baicalein have been widely investigated in hematological malignancies because both of them exhibit remarkable pharmacological properties. This review focuses on the recent achievements in drug discovery research associated with baicalin and baicalein for hematological malignancy therapies. The promising anticancer activities of these two flavonoids targeting diverse signaling pathways and their potential biological mechanisms in different types of hematological malignancies, as well as the combination strategy with baicalin or baicalein as chemotherapeutic adjuvants for recent therapies in these intractable diseases are discussed. Meanwhile, the biotransformation of baicalin and baicalein and the relevant approaches to improve their bioavailability are also summarized.

Development of a Concise Synthetic Approach to Access Oroxin A

A novel environment-friendly method to access bioactive oroxin A through a one-pot/two-step process from naturally abundant and inexpensive baicalin is described. The procedure presented here has several advantages including clean, one-pot, synthetic ease, and large-scale feasibility. This work also provides a model strategy for rapid and diverse access to natural molecules sharing the common skeleton of this family.