Murrayafoline A Induces a G0/G1-Phase Arrest in Platelet-Derived Growth Factor-Stimulated Vascular Smooth Muscle Cells

Inhibition of the RPS6KA1/FoxO1 signaling axis by hydroxycitric acid attenuates HFD-induced obesity through MCE suppression

BACKGROUND

Because obesity is associated with a hyperplasia-mediated increase in adipose tissue, inhibiting cell proliferation during mitotic clonal expansion (MCE) is a leading strategy for preventing obesity. Although (-)-hydroxycitric acid (HCA) is used to control obesity, the molecular mechanisms underlying its effects on MCE are poorly understood.

PURPOSE

This study aimed to investigate the potential effects of HCA on MCE and underlying molecular mechanisms affecting adipogenesis and obesity improvements.

METHODS

Preadipocyte cell line, 3T3-L1, were treated with HCA; oil red O, cell proliferation, cell cycle, and related alterations in signaling pathways were examined. High-fat diet (HFD)-fed mice were administered HCA for 12 weeks; body and adipose tissues weights were evaluated, and the regulation of signaling pathways in epidydimal white adipose tissue were examined in vivo.

RESULTS

Here, we report that during MCE, HCA attenuates the proliferation of the preadipocyte cell line, 3T3-L1, by arresting the cell cycle at the G0/G1 phase. In addition, HCA markedly inhibits Forkhead Box O1 (FoxO1) phosphorylation, thereby inducing the expression of cyclin-dependent kinase inhibitor 1B and suppressing the levels of cyclin-dependent kinase 2, cyclin E1, proliferating cell nuclear antigen, and phosphorylated retinoblastoma. Importantly, we found that ribosomal protein S6 kinase A1 (RPS6KA1) influences HCA-mediated inactivation of FoxO1 and its nuclear exclusion. An animal model of obesity revealed that HCA reduced high-fat diet-induced obesity by suppressing adipocyte numbers as well as epididymal and mesenteric white adipose tissue mass, which is attributed to the regulation of RPS6KA1, FoxO1, CDKN1B and PCNA that had been consistently identified in vitro.

CONCLUSIONS

These findings provide novel insights into the mechanism by which HCA regulates adipogenesis and highlight the RPS6KA1/FoxO1 signaling axis as a therapeutic target for obesity.

A low-cost, flexible extruder for liposomes synthesis and application for Murrayafoline A delivery for cancer treatment

Liposomal encapsulation is a drug delivery strategy with many advantages, such as improved bioavailability, ability to carry large drug loads, as well as controllability and specificity towards various targeted diseased tissues. Currently, most preparation techniques require an additional extrusion or filtering step to obtain monodisperse liposomes with the size of less than 100 nm. In this study, a compact liposome extruder was designed at a cost of $4.00 and used to synthesize liposome suspensions with defined particle size and high homogeneity for Murrayafoline A (Mu-A) loading and release. The synthesized MuA-loaded liposomes displayed a biphasic drug release and remained stable under the storage condition of 4°C. They also significantly reduced the viability of HepG2 cells in the cancer spheroids by 25%. The low-cost, flexible liposome extruder would allow the researchers to study liposomes and their applications in a cost-effective manner.

Anti-tumor effect of liposomes containing extracted Murrayafoline A against liver cancer cells in 2D and 3D cultured models

Murrayafoline A (MuA) is a natural compound with diverse biological activities, including cytotoxicity against cancer cells, but suffers from poor water solubility and low specificity. In order to improve the potential of MuA as a candidate for cancer treatment, MuA-loaded liposomes were prepared with the liposomal membrane consisting of dioleoylphosphatidylcholine and cholesterol. Dynamic light scattering measurements showed that the MuA-loaded liposomes had a z-average particle size of 104.3 ± 6.4 nm (mean ± SD; n = 3) and a polydispersity index of 0.15 ± 0.02 (mean ± SD; n = 3). The encapsulation efficiency was 55.3 ± 2.3% (mean ± SD; n = 3). The in vitro cytotoxicity of encapsulated MuA was attenuated at IC50 = 21.97 µg/mL compared to 6.24 µg/mL for free MuA, against HepG2. In contrast, MuA-loaded liposomes were significantly more effective at inhibiting cell growth in HepG2 cancer spheroids, which indicated that they were able to reach the interior layers of the microtumor. Taken together, these results showed that the encapsulation of MuA in liposomes is a good research direction to improve this natural compound’s potential as a candidate for cancer treatment.

Optimization of Murrayafoline A ethanol extraction process from the roots of Glycosmis stenocarpa, and evaluation of its Tumorigenesis inhibition activity on Hep-G2 cells

Glycosmis stenocarpa is a species of shrub found in the Northern provinces of Vietnam. Its roots contain different carbazolic derivatives, mainly Murrayafoline A (Mu-A), which exhibits valuable biological activities. In this study, we performed an extraction of Mu-A from the roots of G. stenocarpa and optimized this process using response surface methodology (RSM) according to a central composite design, with three independent parameters including extraction time (min), extraction temperature (°C), and solvent/material ratio (mL/g). Two dependent variables were the Mu-A content (mg/g raw materials) and extraction efficiency (%). The optimal conditions to extract Mu-A were found to be as follows: extraction temperature, 67°C; extraction time, 165 min; and solvent/material ratio, 5:1. Under these conditions, the Mu-A content and extraction efficiency were 38.94 ± 1.31 mg/g raw materials and 34.98 ± 1.18%, respectively. Mu-A exhibited antiproliferation and antitumor-promoting activity against the HepG-2 cell line. The present optimization work of Mu-A extraction from G. stenocarpa roots contributed to the attempt of designing a large-scale extraction process for the compound and further exploitation of its potential in vivo applications.

Plant-Derived Products for Treatment of Vascular Intima Hyperplasia Selectively Inhibit Vascular Smooth Muscle Cell Functions

Natural products are used widely for preventing intimal hyperplasia (IH), a common cardiovascular disease. Four different cells initiate and progress IH, namely, vascular smooth muscle, adventitial and endothelial cells, and circulation or bone marrow-derived cells. Vascular smooth muscle cells (VSMCs) play a critical role in initiation and development of intimal thickening and formation of neointimal hyperplasia. In this review, we describe the different originating cells involved in vascular IH and emphasize the effect of different natural products on inhibiting abnormal cellular functions, such as VSMC proliferation and migration. We further present a classification for the different natural products like phenols, flavonoids, terpenes, and alkaloids that suppress VSMC growth. Abnormal VSMC physiology involves disturbance in MAPKs, PI3K/AKT, JAK-STAT, FAK, and NF-κB signal pathways. Most of the natural isolate studies have revealed G1/S phase of cell cycle arrest, decreased ROS production, induced cell apoptosis, restrained migration, and downregulated collagen deposition. It is necessary to screen optimal drugs from natural sources that preferentially inhibit VSMC rather than vascular endothelial cell growth to prevent early IH, restenosis following graft implantation, and atherosclerotic diseases.

Vascular smooth muscle cell proliferation as a therapeutic target. Part 2: Natural products inhibiting proliferation

Many natural products have been so far tested regarding their potency to inhibit vascular smooth muscle cell proliferation, a process involved in atherosclerosis, pulmonary hypertension and restenosis. Compounds studied in vitro and in vivo as VSMC proliferation inhibitors include, for example indirubin-3'-monoxime, resveratrol, hyperoside, plumericin, pelargonidin, zerumbone and apamin. Moreover, taxol and rapamycin, the most prominent compounds applied in drug-eluting stents to counteract restenosis, are natural products. Numerous studies show that natural products have proven to yield effective inhibitors of vascular smooth muscle cell proliferation and ongoing research effort might result in the discovery of further clinically relevant compounds.

Curcumol induces cell cycle arrest in colon cancer cells via reactive oxygen species and Akt/ GSK3β/cyclin D1 pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Curcuma kwangsiensis S. G. Lee & C. F. Liang (Guangxi ezhu, in Chinese) belongs to the Zingiberaceae family, has been used as a traditionally Chinese medicine nearly 2000 year. Curcumol is one of the guaiane-type sesquiterpenoid hemiketal isolated from medicine plant Curcuma kwangsiensis S. G. Lee & C. F. Liang, which has been reported possesses anti-cancer effects. Our previous study found that the most contribution to inhibit nasopharyngeal carcinoma cell growth was curcumol.

AIM OF THE STUDY

To assess the effect of curcumol on cell cycle arrest against human colon cancer cells (CRC) cells (LoVo and SW480) and explore its mechanism in vitro and in vivo.

MATERIALS AND METHODS

Curcumol was dissolved in absolute ethyl alcohol. The concentration of absolute ethyl alcohol in the control group or in experimental samples was always 1/500 (v/v) of the final medium volume. LoVo and SW480 cells were treated with different concentrations of curcumol (0, 53, 106, 212 and 424μM). And then the cell cycle of each group was examined by flow cytometry. The protein levels of PI3K, p-Akt, cyclin D1, cyclin E, CDK2, CDK4 and GSK3β were determined by Western blot. The mRNA expression of PI3K, Akt, cyclin D1, CDK4, P27, p21, and P16 in the treated cells were analyzed by real-time RT-PCR. In addition, the antitumor activity of curcumol was evaluated in nude mice bearing orthotopic tumor implants.

RESULTS

Curcumol induced cell cycle arrest in G1/S phase. RT-qPCR and Western blot data showed that curcumol enhanced the expression of GSK3β, P27, p21 and P16, and decreased the levels of PI3K, phosphorylated Akt (p-Akt), cyclin D1, CDK4, cyclin E and CDK2. Furthermore, curcumol induced reactive oxygen species (ROS) generation in LoVo cells, and ROS scavenger N-acetylcysteine (NAC) significantly reversed curcumol-induced cell growth inhibition. Besides, curcumol also prevented the growth of human colon cancer cells xenografts in nude mouse, accompanied by the reduction of PI3K, Akt, cyclin D1, CDK4, cycln E and significant increase of GSK3β.

CONCLUSIONS

Curcumol caused cell cycle arrest at the G0/G1 phase by ROS production and Akt/ GSK3β/cyclin D1 pathways inactivation, indicating the potential of curcumol in the prevention of colon cancer carcinogenesis.

Inhibition of Collagen-Induced Platelet Aggregation by the Secobutanolide Secolincomolide A from Lindera obtusiloba Blume

Atherothrombosis is one of the main underlying cause of cardiovascular diseases. In addition to treating atherothrombosis with antithrombotic agents, there is growing interest in the role of natural food products and biologically active ingredients for the prevention and treatment of cardiovascular diseases. This study aimed to investigate the effect of secolincomolide A (3) isolated from Lindera obtusiloba Blume on platelet activity and identify possible signaling pathways. In our study, the antiplatelet activities of 3 were measured by collagen-induced platelet aggregation and serotonin secretion in freshly isolated rabbit platelets. Interestingly, 3 effectively inhibited the collagen-induced platelet aggregation and serotonin secretion via decreased production of diacylglycerol, arachidonic acid, and cyclooxygenase-mediated metabolites such as thromboxane B₂ (TXB₂), and prostaglandin D₂ (PGD₂). In accordance with the antiplatelet activities, 3 prolonged bleeding time and attenuated FeCl₃-induced thrombus formation in arterial thrombosis model. Notably, 3 abolished the phosphorylation of phospholipase Cγ2 (PLCγ2), spleen tyrosine kinase (Syk), p47, extracellular signal-regulated kinase 1/2 (ERK1/2), protein kinase B (Akt) by inhibiting the activation of the collagen receptor, glycoprotein VI (GPVI). Taken together, our results indicate the therapeutic potential of 3 in antiplatelet action through inhibition of the GPVI-mediated signaling pathway and the COX-1-mediated AA metabolic pathways.

Arborinane Triterpenoids from Rubia philippinensis Inhibit Proliferation and Migration of Vascular Smooth Muscle Cells Induced by the Platelet-Derived Growth Factor

The abnormal proliferation and migration of vascular smooth muscle cells (VSMCs) are associated with cardiovascular diseases and related complications. Such deleterious proliferation and migration events are triggered by cytokines and growth factors, and among them, platelet-derived growth factor (PDGF) is recognized as the most potent inducer. Despite the genus Rubia being researched to identify valuable commercial and medicinal virtues, Rubia philippinensis has rarely been investigated. Nine arborinane-type triterpenoids (1-9) were identified from this underutilized plant species. In particular, 4 was identified as the first arborinane derivative carrying a ketocarbonyl motif at C-19. The presence of the cyclopentanone moiety and the associated configurational assignment were determined by utilizing NOE and coupling constant analysis. These compounds were assessed for their inhibitory potential on PDGF-induced proliferation and the migration of VSMCs. Treatment with 5 μM compound 5 (62.6 ± 10.7%) and compound 9 (41.1 ± 4.7%) impeded PDGF-stimulated proliferation without exerting cytotoxicity. Compound 7 exhibited antimigration activity in a dose-dependent manner (38.5 ± 3.0% at 10 μM, 57.6 ± 3.2% at 30 μM). These results suggest that the arborinane-type triterpenoids may be a pertinent starting point for the development of cardiovascular drugs capable of preventing the intimal accumulation of VSMCs.