Peroxisome Proliferator-Activated Receptor-γ Agonist Rosiglitazone– Induced Apoptosis in Leukemia K562 Cells and Its Mechanisms of Action

Phytochemical analysis of Artemisia kopetdaghensis: Sesquiterpene lactones with proapoptotic activity against prostate cancer cells

Phytochemical investigation of the aerial parts of Artemisia kopetdaghensis resulted in the isolation and characterization of three undescribed eudesmane-type sesquiterpene lactones, persianolide A, 4-epi-persianolide A, and 3α,4-epoxypersianolide A, together with three previously described eudesmane-type sesquiterpene lactones, 11-epi-artapshin, 1β,8α-dihydroxy-11α,13-dihydrobalchanin, and 1β-hydroxy-11-epi-colartin. The abundantly obtained 11-epi-artapshin was oxidized to undescribed 11α,13-dihydroeudesma-12,6α-olide-1,8-dione and 8β-hydroxy-11α,13-dihydroeudesma-12,6α-olide-1-one and acetylated to the undescribed 1,8-O-diacetyl-11α,13-dihydroeudesma-12,6α-olide. Structures were elucidated based on extensive spectral data analyses, including 1D and 2D NMR and HRESIMS. The absolute configuration was determined using calculated and experimental ECD spectral data. Compounds were subsequently subjected to the MTT assay to evaluate their cytotoxicity against prostate cancer cells (DU-145 and LNCaP). Related factors associated with the sequence of apoptosis were tested by ELISA, western blotting, and biochemical assay. Results suggested that 11-epi-artapshin hinders the growth of DU-145 cells through mitochondria-mediated apoptosis initiated by stimulation of ROS build-up, ΔΨm depletion, regulation of the Bax/Bcl-2 ratio, and activation of caspase 3, respectively.

Capsaicin up-regulates pro-apoptotic activity of thiazolidinediones in glioblastoma cell line

Capsaicin (N-vanillyl-8-methyl-alpha-nonenamide), a spicy, neurotoxic component of hot pepper is a ligand of vanilloid type-I (TRPV1) receptor of anti-cancer potential. However, molecular mechanism of its action is not fully understood. We found that capsaicin stimulated intrinsic and extrinsic pathway of apoptosis in human glioblastoma LN-18 cell line and this phenomenon was not dependent on TRPV1. Activation of peroxisome proliferator-activated receptor gamma (PPARγ), a ligand-dependent transcription factor, also induced apoptosis in glioblastoma cells. Although PPARγ ligands (thiazolidinediones - rosiglitazone, pioglitazone) promoted apoptosis in LN-18 cells, capsaicin augmented this effect. We found that capsaicin in a dose dependent manner induced expression of PPARγ in glioblastoma LN-18 cells. These findings suggest that capsaicin-dependent up-regulation of PPARγ represent the mechanism for augmentation of cell death by thiazolidinediones.

Astaxanthin anticancer effects are mediated through multiple molecular mechanisms: A systematic review

During the latest decades, the interest on the effectiveness of natural compounds and their impact on human health constantly increased, especially on those demonstrating to be effective on cancer. Molecules coming from nature are currently used in chemotherapy like Taxol, Vincristine or Vinblastine, and several other natural substances have been showed to be active in reducing cancer cell progression and migration. Among them, astaxanthin, a xanthophyll red colored carotenoid, displayed different biological activities including, antinflammatory, antioxidant, proapoptotic, and anticancer effects. It can induce apoptosis through downregulation of antiapoptotic protein (Bcl-2, p-Bad, and survivin) expression and upregulation of proapoptotic ones (Bax/Bad and PARP). Thanks to these mechanisms, it can exert anticancer effects towards colorectal cancer, melanoma, or gastric carcinoma cell lines. Moreover, it possesses antiproliferative activity in many experimental models and enhances the effectiveness of conventional chemotherapic drugs on tumor cells underling its potential future use. This review provides an overview of the current knowledge on the anticancer potential of astaxanthin by modulating several molecular targets. While it has been clearly demonstrated its multitarget activity in the prevention and regression of malignant cells in in vitro or in preclinical investigations, further clinical studies are needed to assess its real potential as anticancer in humans.

New insights into molecular mechanisms of rosiglitazone in monotherapy or combination therapy against cancers

Rosiglitazone (ROSI), a member of thiazolidinediones (TZDs) which act as high-affinity agonists of the nuclear receptor peroxisome-proliferator-activated receptor-γ (PPARγ), is clinically used as an antidiabetic drug which could attenuate the insulin resistance associated with obesity, hypertension, and impaired glucose tolerance in humans. However, recent studies reported that ROSI had significant anticancer effects on various human malignant tumor cells. Mounting evidence indicated that ROSI could exert anticancer effects through PPARγ-dependent or PPARγ-independent ways. In this review, we summarized the PPARγ-dependent antitumor activities of ROSI, which included apoptosis induction, inhibition of cell proliferation and cancer metastasis, reversion of multidrug resistance, reduction of immune suppression, autophagy induction, and antiangiogenesis; and the PPARγ-independent antitumor activities of ROSI, which included inhibition of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathway, inhibition of prostaglandin E2 (PGE₂), increasing MAPK phosphatase 1 (MKP-1) expression and regulation of other apoptosis-related cell factors. In addition, we discussed the anti-cancer application of ROSI by monotherapy or combination therapy with present chemotherapeutic drugs in vitro and in vivo. Moreover, we reviewed the phase I cancer clinical trials related to ROSI combined with chemotherapeutics and phase II trials about the anti-cancer effects of ROSI monotherapy and the radiotherapy sensitivity of ROSI.

Anti-proliferative effect of rosiglitazone in the human T-lymphocyte leukaemia cell line Jurkat cells

Peroxisome proliferator-activated receptor γ (PPARγ) is expressed in various types of human cancer cells including leukaemia cells, and activation of PPARγ can inhibit cancer cell growth. However, whether PPARγ is expressed in Jurkat cells, a human T-lymphocyte leukaemia cell line, and whether activation of PPARγ affects cell biological behaviors remains to be clarified. In this study, we investigated the effect of a PPARγ activator rosiglitazone, under clinically relevant pharmacological concentrations, on the growth and apoptosis of Jurkat cells in vitro and explored the possible mechanism. Metformin was also included as a positive control for the anti-proliferative and pro-apoptotic effects. We found that PPARγ mRNA was transcribed in Jurkat cells. Treatment with rosiglitazone (5 µM, 10 µM, and 20 µM) or metformin (1 mM and 10 mM) inhibited cell proliferation, and induced cell cycle arrest at G0/G1 or S phase, respectively, in a dose-dependent manner. Although metformin significantly upregulated the protein levels of the pro-apoptotic markers cleaved-caspase 3 and Bax in Jurkat cells, rosiglitazone did not have such an effect. Moreover, rosiglitazone significantly upregulated the level of PPARγ, and downregulated the expression of insulin receptor (IR) and insulin-like growth factor 1 receptor (IGF-1R) in a dose-dependent manner. Our data indicate that rosiglitazone has an anti-proliferative effect in Jurkat cells, which may be at least partly mediated via downregulating IR and IGF-1R expression. Therefore, rosiglitazone may have a potential role not only for management of hyperglycaemia but also for control of tumor progression in patients with T-lymphocyte leukaemia and diabetes.

Peroxisome Proliferator-Activated Receptor Ligands and Their Role in Chronic Myeloid Leukemia: Therapeutic Strategies

Imatinib therapy remains the gold standard for treatment of chronic myeloid leukemia; however, the acquired resistance to this therapeutic agent in patients has urged the scientists to devise modalities for overcoming this chemoresistance. For this purpose, initially therapeutic agents with higher tyrosine kinase activity were introduced, which had the potential for inhibiting even mutant forms of Bcr-Abl. Furthermore, coupling imatinib with peroxisome proliferator-activated receptor ligands also showed beneficial effects in chronic myeloid leukemia cell proliferation. These combination protocols inhibited cell growth and induced apoptosis as well as differentiation in chronic myeloid leukemia cell lines. In addition, peroxisome proliferator-activated receptors ligands increased imatinib uptake by upregulating the expression of human organic cation transporter 1. Taken together, peroxisome proliferator-activated receptors ligands are currently being considered as novel promising therapeutic candidates for chronic myeloid leukemia treatment, because they can synergistically enhance the efficacy of imatinib. In this article, we reviewed the potential of peroxisome proliferator-activated receptors ligands for use in chronic myeloid leukemia treatment. The mechanism of action of these therapeutics modalities are also presented in detail.

Antitumor action of the peroxisome proliferator-activated receptor-γ agonist rosiglitazone in hepatocellular carcinoma

The inhibition of apoptosis in cancer cells is the major pathological feature of hepatic carcinoma. Rosiglitazone (RGZ), a ligand for peroxisome proliferator-activated receptor γ (PPAR-γ), has been shown to induce apoptosis in hepatic carcinoma cells. However, the mechanism underlying this effect remains to be elucidated. The present study aimed to investigate the effect of RGZ on cell viability and apoptosis, and its mechanisms in cultured HepG2 cells using MTT assay, flow cytometry and western blotting. The results revealed that treatment with RGZ may attenuate HepG2 cell viability and induce the apoptosis of the cells. The mechanism of RGZ-induced apoptosis involves an increase in the level of activated PPAR-γ (p-PPAR-γ) and a decrease in p85 and Akt expression. In addition, the PPAR-γ antagonist GW9662 suppressed the effect of RGZ in the HepG2 cells. Taken together, the results suggest that RGZ induces the apoptosis of HepG2 cells through the activation of PPAR-γ, suppressing the activation of the PI3K/Akt signaling pathway. Such mechanisms may contribute to the favorable effects of treatment using RGZ in HepG2 cells.

Monitoring fibrogenic progression in the liver

The clinical course of chronic liver diseases is significantly dependent on the progression rate of fibrosis which is the unstructured replacement of injured parenchyma by extracellular matrix. Despite intensive studies, the clinical opportunities for patients with fibrosing liver diseases have not improved. This will be changed by increasing knowledge of new pathogenetic mechanisms, which complement the "canonical principle" of fibrogenesis. The latter is based on the activation of hepatic stellate cells and their transdifferentiation to myofibroblasts induced by hepatocellular injury and consecutive inflammatory mediators such as TGF-β. Stellate cells express a broad spectrum of matrix components. New mechanisms indicate that the heterogeneous pool of (myo-)fibroblasts can be supplemented by epithelial-mesenchymal transition (EMT) from cholangiocytes and potentially also from hepatocytes to fibroblasts, by influx of bone marrow-derived fibrocytes in the damaged liver tissue and by differentiation of a subgroup of monocytes to fibroblasts after homing in the damaged tissue. These processes are regulated by the cytokines TGF-β and BMP-7, chemokines, colony-stimulating factors, metalloproteinases and numerous trapping proteins. They offer innovative diagnostic and therapeutic options. As an example, modulation of TGF-β/BMP-7 ratio changes the rate of EMT, and so the simultaneous determination of these parameters and of the connective tissue growth factor (CTGF) in serum might provide information on fibrogenic activity. Also, proteomic and glycomic approaches of serum are under investigation to set up specific protein profiles in patients with liver fibrosis. The aim of this article is to present the current pathogenetic concepts of liver fibrosis and to discuss established and novel diagnostic approaches to reflect the process of hepatic fibrogenesis in the medical laboratory.

PPARγ-dependent pathway in the growth-inhibitory effects of K562 cells by carotenoids in combination with rosiglitazone

BACKGROUND

Carotenoids have been found to play roles in the prevention and therapy of some cancers which PPARγ was also discovered to be involved in. The present studies were directed to determine the inhibitory effects of carotenoids in combination with rosiglitazone, a synthetic PPARγ agonist, on K562 cell proliferation and elucidate the contribution of PPARγ-dependent pathway to cell proliferation suppression.

METHODS

The effects of carotenoid and rosiglitazone combination on K562 cell proliferation were evaluated by trypan blue dye exclusion assay and MTT assay. When PPARγ has been inhibited by GW9662 and siRNA, cycle-related regulator expression in K562 cells treated with carotenoid and rosiglitazone combination was analyzed by Western blotting.

RESULTS

Rosiglitazone inhibited K562 cell proliferation and augmented the inhibitory effects of carotenoids on the cell proliferation greatly. Specific PPARγ inhibition attenuated the cell growth suppression induced by carotenoid and rosiglitazone combination. GW9662 pre-treatment attenuated the enhanced up-regulation of PPARγ expression caused by the combination treatment. Moreover, GW9662 and PPARγ siRNA also significantly attenuated the up-regulation of p21 and down-regulation of cyclin D1 caused by carotenoids and rosiglitazone.

CONCLUSIONS

PPARγ signaling pathway, via stimulating p21 and inhibiting cyclin D1, may play an important role in the anti-proliferative effects of carotenoid and rosiglitazone combination on K562 cells.

GENERAL SIGNIFICANCE

Carotenoids in combination with rosiglitazone are hopeful to provide attractive dietary or supplementation-based and pharmaceutical strategies to treat cancer diseases.

Peroxisome proliferator-activated receptor γ agonists reduce cell proliferation and viability and increase apoptosis in systemic sclerosis fibroblasts

BACKGROUND

 No study has evaluated the effect of the peroxisome proliferator-activated receptor γ (PPARγ) agonists on cell viability, proliferation and apoptosis in cultured systemic sclerosis (SSc) fibroblasts.

OBJECTIVES

The effects of two pure PPARγ agonists (rosiglitazone and pioglitazone) in cultured SSc fibroblasts were evaluated and compared with effects in normal fibroblasts.

METHODS

 The study included evaluation of cell viability and proliferation (based on the cleavage of tetrazolium salts and measurement of absorbance of the cell proliferation reagent WST-1), and determination of cell apoptosis (by means of the Hoechst dye uptake).

RESULTS

Rosiglitazone or pioglitazone (20μmolL(-1) ) significantly reduced cell proliferation (cell count of 75% and 83% compared with baseline, respectively, after 2h) and cell viability (absorbance reductions of 25% and 22% compared with baseline, respectively, after 2 h), and increased apoptosis (apoptotic cell percentages 9·9% and 8·6%, respectively, after 48h of incubation) in SSc fibroblasts, whereas they did not present a significant influence on control fibroblasts.

CONCLUSIONS

The effects of rosiglitazone or pioglitazone shown on SSc fibroblasts raise the hypothesis of a therapeutic role for PPARγ agonists in patients affected by SSc.

Troglitazone suppresses telomerase activity independently of PPARgamma in estrogen-receptor negative breast cancer cells

Background

Breast cancer is one the highest causes of female cancer death worldwide. Many standard chemotherapeutic agents currently used to treat breast cancer are relatively non-specific and act on all rapidly dividing cells. In recent years, more specific targeted therapies have been introduced. It is known that telomerase is active in over 90% of breast cancer tumors but inactive in adjacent normal tissues. The prevalence of active telomerase in breast cancer patients makes telomerase an attractive therapeutic target. Recent evidence suggests that telomerase activity can be suppressed by peroxisome proliferator activated receptor gamma (PPARγ). However, its effect on telomerase regulation in breast cancer has not been investigated.

Methods

In this study, we investigated the effect of the PPARγ ligand, troglitazone, on telomerase activity in the MDA-MB-231 breast cancer cell line. Real time RT-PCR and telomerase activity assays were used to evaluate the effect of troglitazone. MDA-MB-231 cells had PPARγ expression silenced using shRNA interference.

Results

We demonstrated that troglitazone reduced the mRNA expression of hTERT and telomerase activity in the MDA-MB-231 breast cancer cell line. Troglitazone reduced telomerase activity even in the absence of PPARγ. In agreement with this result, we found no correlation between PPARγ and hTERT mRNA transcript levels in breast cancer patients. Statistical significance was determined using Pearson correlation and the paired Student's t test.

Conclusions

To our knowledge, this is the first time that the effect of troglitazone on telomerase activity in breast cancer cells has been investigated. Our data suggest that troglitazone may be used as an anti-telomerase agent; however, the mechanism underlying this inhibitory effect remains to be determined.

Protein kinase C-zeta mediates apoptosis of mouse Kupffer cells via ERK-1/2: a novel mechanism

BACKGROUND

We have demonstrated that activated Kupffer cells undergo accelerated apoptosis via Toll-like receptor (TLR)-4 and protein kinase C (PKC)-ζ-dependent nuclear factor (NF)-κB activation. Because PKC-ζ plays a pivotal role in cell signaling, we sought to determine the signaling pathway of PKC-ζ in Kupffer cell apoptosis.

METHODS

Mouse Kupffer cell line (MKCL3-2) were transfected with PKC-ζ small interfering RNA (siRNA) and then treated with elastase alone or elastase along with the extracellular signal-regulated kinase (ERK) inhibitor U0126. Cell extracts were assayed for PKC-ζ (protein and activity), TLR-4, NF-κB nuclear translocation, phosphorylated ERK-1/2, activated caspase-3, and DNA fragmentation. All n ≥3; data are expressed as mean values ± standard deviations; means were compared using the t test; P < .05 was considered significant.

RESULTS

Elastase upregulated TLR-4, PKC-ζ, NF-κB, ERK-1/2, caspase-3, and DNA fragmentation (all P < .01 versus control). Transfection with PKC-ζ siRNA attenuated the elastase-induced upregulation of PKC-ζ activity, NF-κB, ERK-1/2, caspase-3, and DNA fragmentation (all P < .01 versus control). The interaction of PKC-ζ with ERK-1/2 was increased by elastase and was attenuated by PKC-ζ siRNA as confirmed by co-immunoprecipitation and immunofluorescent staining.

CONCLUSION

Activation of Kupffer cells upregulates PKC-ζ activity, increases apoptosis, and induces nuclear translocation of NF-κB via ERK-1/2-dependent pathways. Inhibiting the activity of PKC-ζ significantly attenuates Kupffer cell apoptosis, NF-κB, and ERK-1/2 activation. The interaction of PKC-ζ and ERK-1/2 warrants further investigation.