Betulinic Acid Acts in Synergism with Imatinib Mesylate, Triggering Apoptosis in MDR Leukemia Cells

Chronic myeloid leukemia (CML) is a myeloproliferative disease, characterized by the presence of the oncogene BCR-ABL. Imatinib mesylate (IMA) is the first-line treatment for CML, and some treatment resistance has been reported. Natural products are rich sources of bioactive compounds with biological effects, opening a possibility to alter cell susceptibility to drugs such as imatinib. Herein, we evaluated the interference of betulinic acid and ursolic acid in glycoprotein P (P-gp) activity and the possible synergistic effect when associated with IMA by the Chou-Talalay method. Ursolic acid presented an IC50 of 14.0 µM and 19.6 µM for K562 and Lucena 1, respectively, whilst betulinic acid presented an IC50 of 8.6 µM and 12.5 µM for these cell lines. Evaluation of the combination of terpenoids and imatinib mesylate revealed that ursolic acid or betulinic acid acts in synergism with IMA, as indicated by the combination indexes (CI<1). Analysis of annexin V labeling demonstrated that a combination of IMA with betulinic acid enhances the inhibition on cell proliferation via the apoptosis pathway, with caspases 3/7 activation after 24 hours of treatment and inhibition of the STAT5/survivin pathway, decreasing cell viability. The combination of natural products and IMA on a multidrug-resistant leukemia cell line is a promising strategy for CML treatment.

Natural compounds combined with imatinib as promising antileukemic therapy: An updated review

Natural products (NP) have been an alternative therapy for several diseases for centuries, and they also serve as an essential source of bioactive molecules, enhancing our drug discovery capacity. Among these NP, some phytochemicals have shown multiple biological effects, including anticancer activity, with higher effectiveness and less toxicity than actual treatments, suggesting their possible use on resilient human malignancies such as leukemia. Imatinib mesylate (Im) is a selective tyrosine kinase inhibitor widely used as an anticancer drug, the gold standard to attend chronic myeloid leukemia (CML). Nevertheless, resistance to this drug in patients with CML renders it insufficient to eliminate cells with Philadelphia chromosome (BCR/ABL+). Moreover, recent studies show that imatinib can induce genotoxic and chromosomic damage in some in vitro and in vivo models. These facts urge finding new therapeutic alternatives to increase the effectiveness of antileukemic treatment. Recent research has shown that the combined effects of phytochemicals with imatinib can improve the cytotoxicity or resensitized the resistant cells to this drug in diverse leukemia cell lines. Independent mechanisms of action among phytochemicals and imatinib include BCR/ABL regulation, downregulation of transcription factors, inhibition of anti-apoptotic and activation of pro-apoptotic proteins, apoptosis induction dependent- and independent of ROS-overproduction, membrane functions disruption, induction of cell cycle arrest, and cell death. This review summarizes and discusses the synergic effect of some phytochemicals combined with imatinib on leukemia cells and the mechanism of action proposed for these combinations, looking to contribute to developing new effective alternatives for leukemia treatment.

Characteristics, Isolation Methods, and Biological Properties of Aucubin

Aucubin is an iridoid glycoside widely spread in the families Cornaceae, Garryaceae, Orobanchaceae, Globulariaceae, Eucommiaceae, Scrophulariaceae, Plantaginaceae, and Rubiaceae. This review is intended to provide data on the physicochemical characteristics, isolation methods, and biological activities of aucubin and its producing plants. Aucubin is unstable and can be deglycosylated into its aglycone, aucubigenin. Various chromatographic methods (column chromatography, vacuum liquid chromatography, medium pressure liquid chromatography, and high-performance liquid chromatography) have been used together to isolate aucubin, mainly with the stationary phase C-18 and the mobile phase water-methanol solution made in gradients. In vitro and in vivo studies reveal that aucubin has a wide range of activities, including anti-inflammatory, antioxidant, anxiolytic and antidepressant, antidiabetic, antifibrotic, antimicrobial, anticancer, antihyperlipidemic, gastroprotective, cardioprotective, hepatoprotective, retinoprotective, neuroprotective, osteoprotective, and renoprotective. Even though aucubin has been extensively investigated, further research in humans is urgently needed primarily to substantiate the clinical evidence. Moreover, extensive studies on its drug delivery systems will help maximize efficacy and minimize side effects.

Potential Roles of Iridoid Glycosides and Their Underlying Mechanisms against Diverse Cancer Growth and Metastasis: Do They Have an Inhibitory Effect on Cancer Progression?

Iridoids are glycosides found in plants, having inherent roles in defending them against infection by viruses and microorganisms, and in the rapid repair of damaged areas. The emerging roles of iridoid glycosides on pharmacological properties have aroused the curiosity of many researchers, and studies undertaken indicate that iridoid glycosides exert inhibitory effects in numerous cancers. This review focuses on the roles and the potential mechanism of iridoid glycosides at each stage of cancer development such as proliferation, epithelial mesenchymal transition (EMT), migration, invasion and angiogenesis. Overall, the reviewed literature indicates that iridoid glycosides inhibit cancer growth by inducing cell cycle arrest or by regulating apoptosis-related signaling pathways. In addition, iridoid glycosides suppress the expression and activity of matrix metalloproteinases (MMPs), resulting in reduced cancer cell migration and invasiveness. The antiangiogenic mechanism of iridoid glycosides was found to be closely related to the transcriptional regulation of pro-angiogenic factors, i.e., vascular endothelial growth factors (VEGFs) and cluster of differentiation 31 (CD31). Taken together, these results indicate the therapeutic potential of iridoid glycosides to alleviate or prevent rapid cancer progression and metastasis.

Aucubin Promotes Differentiation of Neural Precursor Cells into GABAergic Neurons

Aucubin is a small compound naturally found in traditional medicinal herbs with primarily anti-inflammatory and protective effects. In the nervous system, aucubin is reported to be neuroprotective by enhancing neuronal survival and inhibiting apoptotic cell death in cultures and disease models. Our previous data, however, suggest that aucubin facilitates neurite elongation in cultured hippocampal neurons and axonal regrowth in regenerating sciatic nerves. Here, we investigated whether aucubin facilitates the differentiation of neural precursor cells (NPCs) into specific types of neurons. In NPCs cultured primarily from the rat embryonic hippocampus, aucubin significantly elevated the number of GAD65/67 immunoreactive cells and the expression of GAD65/67 proteins was upregulated dramatically by more than three-fold at relatively low concentrations of aucubin (0.01 µM to 10 µM). The expression of both NeuN and vGluT1 of NPCs, the markers for neurons and glutamatergic cells, respectively, and the number of vGluT1 immunoreactive cells also increased with higher concentrations of aucubin (1 µM and 10 µM), but the ratio of the increases was largely lower than GAD expression and GAD immunoreactive cells. The GABAergic differentiation of pax6-expressing late NPCs into GABA-producing cells was further supported in cortical NPCs primarily cultured from transgenic mouse brains, which express recombinant GFP under the control of pax6 promoter. The results suggest that aucubin can be developed as a therapeutic candidate for neurodegenerative disorders caused by the loss of inhibitory GABAergic neurons.

Effect of aucubin on neural precursor cell survival during neuronal differentiation

PURPOSE OF THE STUDY

Aucubin (ACB) is an iridoid glycoside with various biological activities. Previously, it is reported that ACB reduces cell survival and proliferation in many human tumors, whereas it facilitates cell survival and neuroprotection in damaged neuronal cells and disease models. However, its effects on cell survival in the non-proliferating or differentiated neurons are not known.

MATERIALS AND METHODS

We examined whether ACB facilitated cell survival in differentiating neural precursor cells, HiB5, compared with the proliferating HiB5 cells at various concentrations.

RESULTS

The cell viabilities were evaluated by measuring MTT values, cell numbers, amounts of neurotransmittersD1 and protein amounts of neuronal markers. Here, we showed that ACB promotes cell survival in differentiated neurons (10-200 μg/mL), but reduces it in proliferating NPCs (200-400 μg/mL). Protein amounts of neurofilament proteins, NF-H, NF-M, PSD-95 in post-synaptic density, GAP-43 in growing neurites and NeuN in differentiated neurons were upregulated by addition of ACB, indicating that cell survival increased in differentiated neurons, shown by immunoblot analysis. Especially, when PDGF was added into N2 media to facilitate neuronal differentiation of HiB5 cells, the viability of differentiated HiB5 cells was significantly elevated following the increase of ACB concentration. Furthermore, ACB promoted cell survival of specific neuron types, such as GABAergic neurons and glutamatergic neurons. When differentiated neurons were immunostained with markers for specific neurons, neuronal subtypes producing GABA and GAD 65/67 were immunostained more than subtypes producing glutamate and vGluT1.

CONCLUSION

These results indicate that ACB improves neuronal cell survival in differentiated cells, suggesting it may be a therapeutic compound for neurodegenerative disorders.

Nepeta deflersiana attenuates isoproterenol-induced myocardial injuries in rats: Possible involvement of oxidative stress, apoptosis, inflammation through nuclear factor (NF)-κB downregulation

BACKGROUND

Nepeta deflersiana (Lamiaceae) is a perennial herb used in the Saudi and Yemeni folk medicine as an anti-inflammatory, carminative, and antirheumatic agent.

PURPOSE

This study explores the phytochemistry of the plant and the cardioprotective effect of N. deflersiana ethanolic extract (NDEE) against isoproterenol (ISP)-induced myocardial injury in rats.

DESIGN/METHODS

Cardiac function, serum cardiac enzymes, myocardial antioxidants, inflammatory, and apoptotic biomarkers, and histopathological parameters were studied in ISP-injured Wistar rat heart tissues.

RESULTS

To the best of our knowledge, this is the first study to report the isolation of nine secondary metabolites from this plant: 1α-hydroxy-7α,14α,18-triacetoxy-isopimara-8,15-diene (1), β-sitosterol (2), lupeol (3), ursolic acid (4), 2,3-dihydroxy ursolic acid (5), caffeic acid (6), methyl rosmarinate (7), rosmarinic acid (8), and an irridoid glucoside 8-epi-7-deoxyloganic acid (9). To explain the mechanisms underlying the cardioprotective effect of NDEE, we evaluated the redox-sensitivity of NDEE in ISP-induced cardiac injury. The oral administration of NDEE (50 and 100 mg/kg b.w) prevented the depletion of endogenous antioxidants (CAT, SOD, NP-SH, and NO) and myocyte injury marker enzymes and inhibited lipid peroxidation (MDA, MPO). Moreover, NDEE downregulated the expression of pro-inflammatory cytokines (TNFα, IL-6, and IL-10) and apoptotic markers (caspase-3 and Bax) and upregulated the anti-apoptotic protein Bcl2. Furthermore, NDEE pretreatment significantly downregulated cardiac NF-κB (p65) expression, NF-κB-DNA binding activity, and MPO activity. Histological data showed that NDEE pretreatment reduced myonecrosis, edema, and infiltration of inflammatory cells and restored the architecture of cardiomyocytes.

CONCLUSION

NDEE demonstrated strong antioxidant, cardioprotective, anti-inflammatory, and anti-apoptotic potential against myocardial damage. This further endorses the use of N. deflersiana in Yemeni folk medicine against cardiovascular diseases.

Aucubin promotes angiogenesis via estrogen receptor beta in a mouse model of hindlimb ischemia

Aucubin (AU) is an iridoid glycoside that has been shown to display estrogenic properties and has various pharmacological effects. Herein, we described the angiogenic properties of AU. In the study, hindlimb ischemia was induced by ligation of femoral artery on the right leg of ovariectomized mice. AU treatment significantly accelerated perfusion recovery and reduced tissue injury in mice muscle. Quantification of CD31-positive vessels in hindlimb muscles provided evidences that AU promoted angiogenesis in peripheral ischemia. In addition, results from quantitative PCR and western blot suggested AU induced angiogenesis via vascular endothelial cell growth factor (VEGF)/Akt/endothelial nitric oxide synthase (eNOS) signaling pathway. More interestingly, AU's angiogenic effects could be completely abolished in estrogen receptor beta (ERβ) knockout mice. In conclusion, the underlying mechanisms were elucidated that AU produced pro-angiogenic effects through ERβ-mediated VEGF signaling pathways. These results expand knowledge about the beneficial effects of AU in angiogenesis and blood flow recovery. It might provide insight into the ERβ regulating neovascularisation in hindlimb ischemia and identify AU as a potent new compound used for the treatment of peripheral vascular disease.

Cytotoxic and Apoptotic Activities of Methanolic Subfractions of Scrophularia oxysepala against Human Breast Cancer Cell Line

Herbs have played a positive role in medicine for thousands of years. In the current study, we investigated the cytotoxicity effects of Scrophularia oxysepala methanolic subfractions and the underlying mechanism responsible for cell death in human breast carcinoma (MCF-7 cells) and mouse fibrosarcoma (WEHI-164 cells). From 60% and 80% methanolic fractions, four subfractions (Fa, Fb, Fc, and Fd), yielded from size exclusion by Sephadex-LH20 column chromatography, were chosen. MTT assay revealed that all subfractions significantly reduced cell viability after 24 h and 36 h in a dose-dependent manner; it is worth noting that Fa and Fb subfractions had the highest cytotoxicity, with IC50 values of 52.9 and 61.2 μg/mL in MCF-7 at 24 h, respectively. ELISA, TUNEL, and DNA fragmentation assay revealed that antiproliferative effects of all subfractions were associated with apoptosis on cancer cells, without any significant effect on L929 normal cells. qRT-PCR data showed that, after 24 h treatment with IC50 concentrations of the subfractions, caspase-3 expression was increased in cancer cells while the expression of Bcl-2 was decreased. S. oxysepala methanolic subfractions induce apoptosis in MCF-7 and WEHI-164 cells and could be considered as a source of natural anticancer agents.