A Systematic Review of the Immune-Regulating and Anticancer Activities of Pseudolaric Acid B

Emerging trends of phytochemicals as ferroptosis modulators in cancer therapy

Ferroptosis, a novel form of regulated cell death characterized by dependence on iron and lipid peroxidation, has been implicated in a wide range of clinical conditions including neurological diseases, cardiovascular disorders, acute kidney failure, and various types of cancer. Therefore, it is critical to suppress cancer progression and proliferation. Ferroptosis can be triggered in cancer cells and some normal cells by synthetic substances, such as erastin, Ras-selective lethal small molecule-3, or clinical pharmaceuticals. Natural bioactive compounds are traditional drug discovery tools, and some have been therapeutically used as dietary additives or pharmaceutical agents against various malignancies. The fact that natural products have multiple targets and minimal side effects has led to notable advances in anticancer research. Research has indicated that ferroptosis can also be induced by natural compounds during cancer treatment. In this review, we focused on the most recent developments in emerging molecular processes and the significance of ferroptosis in cancer. To provide new perspectives on the future development of ferroptosis-related anticancer medications, we also provide a summary of the implications of natural phytochemicals in triggering ferroptosis through ROS production and ferritinophagy induction in a variety of malignancies.

New light on treatment of cervical cancer: Chinese medicine monomers can be effective for cervical cancer by inhibiting the PI3K/Akt signaling pathway

Cervical cancer (CC), as the most common malignant tumor of the female reproductive system, is infamous for its high morbidity and mortality rates. Its development and metastasis are intricate because numerous signaling pathways are involved. Since the cancer and the PI3K/Akt signaling pathway are closely intertwined, direct inhibition of either the PI3K/Akt pathway or its target genes and molecules may be remarkably constructive for treatment. Albeit remarkable advances in the treatment of CC, existing common anti-cancer medications are not without problems. These problems include myelotoxicity, cardiotoxicity, genotoxicity, and vasospasm, which are the most common and well-recognized toxicities associated with these medications. Therefore, it is necessary and urgent to develop novel, potent, secure, and more reasonably priced anticancer medications that are void of the above problems. Against this backdrop, Chinese medicine monomers have received more attention in recent years owing to their safety, low toxicity, few side effects, and anti-tumor properties. By regulating the PI3K/Akt signaling pathway, Chinese medicine monomers are effective not only in inhibiting CC growth, proliferation, apoptosis, invasion, migration, and reversing drug resistance but also in a variety of targets. Most previous earlier studies focused on the use of a single traditional Chinese medicine monomer to treat CC by regulating the PI3K/Akt signaling pathway rather than a combination of several such monomers. More importantly, to our knowledge, there has hardly been any study providing an exhaustive and comprehensive review of all the Chinese medicine monomers at CC. In response to this scarcity, we attempt in this paper to provide a comprehensive review of all the literature to date on traditional Chinese medicine monomers at cervical cancer, highlight the mechanisms and future prospects for their use in the prevention and treatment of cervical cancer.

Suppressive effect of pseudolaric acid B on Echinococcus multilocularis involving regulation of TGF-β1 signaling in vitro and in vivo

Echinococcus multilocularis, the causative agent of alveolar echinococcosis (AE), severely threats human health and livestock farming. The first line of chemotherapeutic drug for AE is albendazole, which limits rapid extension of E. multilocularis metacestodes, but is rarely curative for AE, with severe side effects in long-term use, thus development of new anti-echinococcal drugs is mandated. Pseudolaric acid B (PAB) has long been used to treat fungal-infected dermatosis, and exerted anti-tumor, -fertility, -angiogenesis, -tubulin and antiparasitic activity. However, the effect of PAB against Echinococcus spp. remains unclear. The present study is to understand the effect of PAB against E. multilocularis in vitro and in vivo, and identify potential anti-echinococcal mechanism, as well as its toxicity. After exposure to PAB at 20 μg/ml, significant reduction of the survival rate and substantial ultrastructural destructions in E. multilocularis protoscoleces were observed in vitro. Furthermore, the wet weight of E. multilocularis cysts in the infected mice was significantly decreased after treatment with PAB (40, 20 or 10 mg/kg) for 12 weeks. Meanwhile, significant increase of both protein and mRNA expression of transforming growth factor beta 1 (TGF-β1) was detected in the serum and liver of the infected mice, whereas PAB administration lowered its expression significantly. The toxicity tests demonstrated that PAB displayed lower cytotoxicity to human liver and kidney cells (HL-7702 and HK-2 cell) with IC₅₀ = 25.29 and 42.94 μg/ml than albendazole with IC₅₀ = 3.71 and 21.22 μg/ml in vitro, and caused lower hepatoxicity and nephrotoxicity in mice than ABZ. Our findings indicated that PAB possesses potent anti-echinococcal effect, with lower toxicity than albendazole, implying a potential chemotherapeutic agent for AE. Additionally, the present study demonstrated that the suppressive effect of PAB on the parasite may involve down-regulation of TGF-β1 signaling.

Antitumor Effect of Pseudolaric Acid B Involving Regulation of Notch1/Akt Signaling Response in Human Hepatoma Cell In Vitro

Background

Liver cancer, particularly hepatocellular carcinoma (HCC), is the fourth leading cause of cancer-related death worldwide. Sorafenib is a crucial drug for the treatment of advanced HCC, but it is difficult to meet the challenge of increasing clinical demands due to its severe side effects and drug resistance. Hence, development of novel antitumor drugs is urged. Previous studies showed that pseudolaric acid B (PAB) could reduce the expression of protein kinase B (PKB/Akt), a downstream effector of Notch signaling, facilitating cell apoptosis in HCC. The disruption of Notch signaling was verified to exacerbate malignant progression and drug resistance, however, the antitumor effect of PAB on Notch signaling in HCC remains unclear. Thus, this study aims to investigate the anti-HCC effect of PAB in association with the regulation of Notch1/Akt signaling.

Methods

CCK-8 assay and transwell assay were used to examine the cell proliferation and invasion in Huh7 cells after treatment with PAB and a Notch inhibitor DAPT. Moreover, the cell cycle of Huh7 cells after treatment with PAB was analyzed using flow cytometry. Finally, the changes of Notch1, Jagged1, Hes1, and Akt expression at the protein and mRNA level in Notch1/Akt signaling in Huh7 cells after treatment with PAB and DAPT were analyzed using immunofluorescence assay and real-time qPCR.

Results

The proliferation rate of Huh7 cells exposed to PAB of 0.5, 1, 2, 4, 8, 10, 20, 40, 80, 100, and 200 μmol/L revealed a time-and dose-dependent decrease in vitro, showing cell cycle arrest at G2/M phase (P < 0.05). Furthermore, compared with the untreated group, at the concentration of 40 μmol/L, the proliferation rate and invasion rate of Huh7 cells in PAB, DAPT, and PAB-DAPT combination (PAB + DAPT) group were significantly decreased (P < 0.05), but the PAB + DAPT showed no synergistic antiproliferation and anti-invasion effect in comparison with PAB treatment alone (P > 0.05). In addition, compared with the untreated group, PAB and DAPT alone significantly downregulated the expression of Notch1, Jagged1, Hes1, Akt mRNA, or/and protein in Huh7 cells (P < 0.05), but there was no significant difference in synergistic downregulated effect between the PAB + DAPT group and the PAB group (P > 0.05).

Conclusion

PAB can suppress proliferation and invasion of HCC cells through downregulating the expression of Notch1/Akt signaling protein and mRNA, and may be a potential novel antitumor drug candidate for the clinical treatment of HCC in the future.

Pediatric acute lymphoblastic leukemia management using multitargeting bioactive natural compounds: A systematic and critical review

Pediatric acute lymphoblastic leukemia (pALL), a malignancy of the lymphoid line of blood cells, accounts for a large percentage of all childhood leukemia cases. Although the 5-year survival rate for children with ALL has greatly improved over years, using chemotherapeutics as its first-line treatment still causes short- and long-term side effects. Furthermore, induction of toxicity and resistance, as well as the high cost, limit their application. Phytochemicals, with remarkable cancer preventive and chemotherapeutic characteristics, may serve as old solutions to new challenges. Bioactive plant secondary metabolites have exhibited promising antileukemic and adjunctive effects by targeting various molecular processes, including autophagy, cell cycle, angiogenesis, and extrinsic/intrinsic apoptotic pathways. Although numerous reports have shown that numerous plant secondary metabolites can interfere with the progression of malignancies, including leukemia, there was no comprehensive review article on the effect of phytochemicals on pALL. This systematic review aims to provide critical and cohesive analysis of the potential of various naturally-occurring metabolites in the management of pALL with the understanding of underlying molecular and cellular mechanisms of action.

Pseudolaric Acid B Attenuates High Salt Intake-Induced Hypertensive Left Ventricular Remodeling by Modulating Monocyte/Macrophage Phenotypes

Background

Studies in ApoE knockout mice have shown that pseudolaric acid B (PB) can act as an immunomodulatory drug and attenuate atherosclerosis progression by modulating monocyte/macrophage phenotypes. Our previous study demonstrated that high salt intake could shift the phenotype of monocytes/macrophages to an inflammatory phenotype, and that this shift was related to hypertension and hypertensive left ventricular (LV) remodeling. However, no comprehensive assessment of the effects of PB on hypertensive LV remodeling has been conducted.

Material/Methods

In this study, RAW264.7 macrophages cultured with different concentrations of NaCl were used to investigate the modulating effects of PB on macrophage phenotype. Furthermore, N-nitro-l-arginine methyl ester hypertensive mice were used to investigate the modulating effects of PB on monocyte phenotype. LV remodeling was investigated by echocardiography. LV morphologic staining (for cardiomyocyte hypertrophy and collagen deposition) was performed at the time of sacrifice.

Results

The results showed that PB significantly improved the viability of RAW264.7 cells, suppressed their phagocytic and migration abilities, and inhibited their phenotypic shift to M1 macrophages. In addition, the blood pressure of PB-treated mice was significantly decreased relative to that of control mice. Furthermore, after PB treatment, the percentage of Ly6C^hi monocytes was significantly decreased while that of Ly6C^lo monocytes was apparently increased. Moreover, PB preserved LV function and alleviated myocardial fibrosis and cardiomyocyte hypertrophy as measured at the end of the experimental period. The transfer of monocytes from PB-treated mice to hypertensive mice achieved the same effects.

Conclusions

Together, these findings indicate that PB exerts its protective effects on hypertensive LV remodeling by modulating monocyte/macrophage phenotypes and warrants further investigation.

Synergistic Effect of Pseudolaric Acid B with Fluconazole Against Resistant Isolates and Biofilm of Candida tropicalis

Purpose

Candida tropicalis (C. tropicalis) has emerged as an important fungal pathogen due to its increasing resistance to conventional antifungal agents, especially fluconazole (FLC). Pseudolaric acid B (PAB), a herbal-originated diterpene acid from Pseudolarix kaempferi Gordon, has been reported to possess inhibitory activity against fungus. The present study aims to investigate the antifungal effect of PAB alone and in combination with FLC on planktonic and biofilm cells of C. tropicalis.

Methods

The antifungal activity of PAB against planktonic isolates was evaluated alone and in combination with FLC using the chequerboard microdilution method and growth curve assay. The anti-biofilm effects were quantified by tetrazolium (XTT) reduction assay, which were further confirmed by scanning electron microscopy (SEM) and fluorescent microscope to observe morphological changes of biofilm treated with PAB and FLC.

Results

It was revealed that PAB alone exhibited similar inhibitory activity against FLC-resistant and FLC-susceptible strains with median MIC ranging from 8 to 16 µg/mL. When administered in combination, synergism was observed in all (13/13) FLC-resistant and (2/9) FLC-susceptible strains with FICI ranging from 0.070 to 0.375. Moreover, the concomitant use of PAB and FLC exhibited a strong dose-dependent synergistic inhibitory effect on the early and mature biofilm, eliminating more than 80% biofilm formation. SEM found that PAB, different from azoles, could significantly inhibit spore germination and destroy the cell integrity causing cell deformation, swelling, collapse and outer membrane perforation.

Conclusion

PAB was highly active against FLC-resistant isolates and biofilm of C. tropicalis, particularly when combined with FLC. These findings suggest that PAB may have potential as a novel antifungal agent with different targets from azole drugs.

Pseudolaric acid B induces mitotic arrest and apoptosis in both imatinib-sensitive and -resistant chronic myeloid leukaemia cells

The selective BCR-ABL tyrosine kinase inhibitor imatinib is one of the first-line therapies in the management of chronic myeloid leukaemia (CML). However, acquired resistance to this inhibitor, which is especially conferred by the T315I point mutation in BCR-ABL, impedes the efficacy of imatinib therapy. Therefore, the discovery and development of novel agents to overcome imatinib resistance is urgently needed. Pseudolaric acid B (PAB), a small molecule isolated from the traditional Chinese medicine Cortex pseudolaricis, has been reported to be a potential candidate for immune disorders and cancer treatment. However, its effects on CML and the involved molecular mechanism have not been reported. In the current study, by performing both in vitro and in vivo experiments in CML cells, we showed that PAB blocked the cell cycle at G₂/M phase and subsequently activated the caspase pathway, cleaved the BCR-ABL protein and inhibited the BCR-ABL downstream pathways, ultimately leading to cell proliferation inhibition, cytotoxicity and apoptosis. These events were observed in both imatinib-sensitive and imatinib-insensitive CML cell lines. Moreover, PAB decreased the viability of primary blood mononuclear cells from CML patients and induced apoptosis in these cells. Our findings suggest that PAB could be used as a novel agent to sensitize imatinib-resistant CML.

The anti-inflammatory effects of Pseudorlaric acid D on atherosclerosis

Atherosclerosis is regarded as a chronic inflammatory disease which immune response is regulated by multiple factors. Pseudorlaric acid D (PLAD) is the main bioactive component of Pseudolarix kaempferi Gorden, but little of its property has been found in the literature. We aimed to investigate the anti-inflammatory activity and the underlying mechanisms of PLAD on atherosclerosis. In this study, atherosclerosis model was established by feeding with a high-fat diet in ApoE^-/- mice. PLAD was administered intragastrically at a dose of 5 mg/kg for four weeks. We found that PLAD could significantly improve the lipid metabolism and decrease atherosclerotic lesion areas as well as mitigate atherosclerotic changes on vessel walls. Besides, PLAD could markedly inhibit the inflammatory response by down-regulating the levels of Ly6C^hi monocytes and NETs, and restraining NETs formation. The expression of pro-inflammatory cytokines IL-1β and IL-18 was also evidently reduced by PLAD. These results indicated that modulating the activation and recruitment of Ly6C^hi monocytes and NETs could be the potential anti-inflammatory mechanisms of PLAD on atherosclerosis. PLAD might be a promising therapeutic strategy for the treatment of atherosclerosis and inflammation-related diseases.

Pseudolaric Acid B Induces Growth Inhibition and Caspase-Dependent Apoptosis on Head and Neck Cancer Cell lines through Death Receptor 5

Pseudolaric Acid B (PAB), diterpenoid isolated from the root bark of Pseudolarix kaempferi Gordon tree (Pinaceae), exhibits an anti-proliferative and apoptotic activity in various cancer cell lines but to date, the effects of PAB on head and neck cancer (HNC) cell lines remain to be elucidated. In this study, we showed that PAB significantly inhibited the viability and caspase-dependent apoptosis in HN22 cell line. PAB-induced apoptosis is through inducing death receptor 5 (DR5) together with the increase in the expression of cleaved caspase-8. It also inhibited the proliferations and induced apoptosis through DR5 in other three HNC cell lines (HSC3, Ca9.22, and HSC4). Extending our in vitro findings, we found that ethanol extract of Pseudolarix kaempferi (2.5 mg/kg/day) reduced tumor growth in a xenograft model bearing HN22 cell line without any change in body weight. DR5 were also found to be increased in tumors tissue of PAB-treated mice without any apparent histopathological changes in liver or kidney tissues. Taken together, PAB may be a potential lead compound for chemotherapeutic agents against head and neck cancer.

Pseudolaric acid B inhibits PAX2 expression through Wnt signaling and induces BAX expression, therefore promoting apoptosis in HeLa cervical cancer cells

Objectives

Pseudolaric acid B (PAB) has been shown to inhibit the growth of various tumor cells, but the molecular details of its function are still unknown. This study investigated the molecular mechanisms by which PAB induces apoptosis in HeLa cells.

Methods

The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays were performed to investigate the effect of PAB treatment in various cervical cancer cell lines. Annexin V/propidium iodide staining combined with flow cytometry and Hoechst 33258 staining were used to assess PAB-induced apoptosis. Additionally, we performed bioinformatics analyses and identified a paired box 2 (PAX2) binding site on the BAX promoter. We then validated the binding using luciferase and chromatin immunoprecipitation assays. Finally, western blotting assays were used to investigate PAB effect on the Wnt signaling and the involved signaling molecules.

Results

PAB promotes apoptosis and downregulates PAX2 expression in HeLa cells in a time- and concentration-dependent manner. PAX2 binds to the promoter of BAX and inhibits its expression; therefore, PAX2 inhibition is associated with increased levels of BAX, which induces apoptosis of HeLa cells via the mitochondrial pathway. Additionally, PAB inhibits classical Wnt signaling.

Conclusion

PAB effectively inhibits Wnt signaling and PAX2 expression, and increases BAX levels, which induce apoptosis in HeLa cells. Therefore, PAB is a promising natural molecule for the treatment of cervical cancer.

Pseudolaric acid B exhibits anti-cancer activity on human hepatocellular carcinoma through inhibition of multiple carcinogenic signaling pathways

BACKGROUND

Pseudolaric acid B (PAB), a diterpene acid isolated from the root bark of Pseudolarix kaempferi, exhibits a potent anti-cancer activity in a variety of tumor cells.

PURPOSE

The present study was designed to evaluate the anti-cancer effects of PAB on hepatocellular carcinoma (HCC) cell lines in vitro, and to explore the underlying mechanism.

METHODS

The anti-proliferative activity of PAB on HCC cells were assessed via sulforhodamine B staining, colony formation, cell cycle analysis, respectively. Apoptosis was detected using Annexin V/propidium iodide double staining and diamidino-phenyl-indole staining, respectively. Protein expression regulated by PAB treatment was tested by western blotting.

RESULTS

The present results showed that PAB significantly inhibited the proliferation of HepG2, SK-Hep-1, and Huh-7 HCC cell lines in vitro with IC₅₀ values of 1.58, 1.90, and 2.06 μM, respectively. Furthermore, PAB treatment repressed the colony formation in HepG2, SK-Hep-1, and Huh-7 HCC cell lines. Flow cytometry analysis revealed that PAB caused an obvious cell cycle arrest in G2/M phase and induced apoptosis with the induction of p21, Bax, cleaved-caspase-3, and cleaved-PARP in human HepG2 and SK-Hep-1 cells. Mechanistically, PAB treatment down-regulated the phosphorylation of STAT3, ERK1/2, and Akt. Moreover, abnormal GSK-3β/β-catenin signaling in HepG2 cells was remarkably suppressed by PAB treatment. Finally, proliferation markers including cyclin D1 and c-Myc, and anti-apoptosis proteins such as Bcl-2 and survivin were also down-regulated by PAB treatment in HepG2 cells.

CONCLUSION

Taken together, our results suggest that PAB exerts anti-cancer activity in HCC cells through inhibition of STAT3, ERK1/2, Akt, and GSK-3β/β-catenin carcinogenic signaling pathways, and may be used as a phytomedicine in the treatment of HCC.