Pramanicin analog induces apoptosis in human colon cancer cells: critical roles for Bcl-2, Bim, and p38 MAPK signaling

Asiatic Acid Alleviates Myocardial Ischemia-Reperfusion Injury by Inhibiting the ROS-Mediated Mitochondria-Dependent Apoptosis Pathway

Myocardial ischemia-reperfusion injury (MIRI) is a major cause of heart failure in patients with coronary heart disease (CHD). Mitochondrial dysfunction is the crucial factor of MIRI; oxidative stress caused by mitochondrial reactive oxygen species (ROS) aggravates myocardial cell damage through the mitochondria-dependent apoptosis pathway. Asiatic acid (AA) is a type of pentacyclic triterpene compound purified from the traditional Chinese medicine Centella asiatica, and its protective pharmacological activities have been reported in various disease models. This study is aimed at investigating the protective effects of AA and the underlying mechanisms in MIRI. To achieve this goal, an animal model of MIRI in vivo and a cell model of oxygen-glucose deprivation/reperfusion (OGD/R) in vitro were established. The results show that AA exerts a protective effect on MIRI by improving cardiac function and reducing cardiomyocyte damage. Due to its antioxidant properties, AA alleviates mitochondrial oxidative stress, as evidenced by the stable mitochondrial structure, maintained mitochondrial membrane potential (MMP), and reduced ROS generation, otherwise due to its antiapoptotic properties. AA inhibits the mitogen-activated protein kinase (MAPK)/mitochondria-dependent apoptosis pathway, as evidenced by the limited phosphorylation of p38-MAPK and JNK-MAPK, balanced proportion of Bcl-2/Bax, reduced cytochrome c release, inhibition of caspase cascade, and reduced apoptosis. In conclusion, our study confirms that AA exerts cardiac-protective effects by regulating ROS-induced oxidative stress via the MAPK/mitochondria-dependent apoptosis pathway; the results provide new evidence that AA may represent a potential treatment for CHD patients.

A Review: Mechanism of Phyllanthus urinaria in Cancers-NF-κB, P13K/AKT, and MAPKs Signaling Activation

Phyllanthus urinaria has been characterized for its several biological and medicinal effects such as antiviral, antibacterial, anti-inflammatory, anticancer, and immunoregulation. In recent years, Phyllanthus urinaria has demonstrated potential to modulate the activation of critical pathways such as NF-κB, P13K/AKT, and ERK/JNK/P38/MAPKs associated with cell growth, proliferation, metastasis, and apoptotic cell death. To date, there is much evidence indicating that modulation of cellular signaling pathways is a promising approach to consider in drug development and discovery. Thus, therapies that can regulate cancer-related pathways are longed-for in anticancer drug discovery. This review's focus is to provide comprehensive knowledge on the anticancer mechanisms of Phyllanthus urinaria through the regulation of NF-κB, P13K/AKT, and ERK/JNK/P38/MAPKs signaling pathways. Thus, the review summarizes both in vitro and in vivo effects of Phyllanthus urinaria extracts or bioactive constituents with emphasis on tumor cell apoptosis. The literature information was obtained from publications on Google Scholar, PubMed, Web of Science, and EBSCOhost. The key words used in the search were "Phyllanthus" or "Phyllanthus urinaria" and cancer. P. urinaria inhibits cancer cell proliferation via inhibition of NF-κB, P13K/AKT, and MAPKs (ERK, JNK, P38) pathways to induce apoptosis and prevents angiogenesis. It is expected that understanding these fundamental mechanisms may help stimulate additional research to exploit Phyllanthus urinaria and other natural products for the development of novel anticancer therapies in the future.

Selective activation of tumor-suppressive MAPKP signaling pathway by triptonide effectively inhibits pancreatic cancer cell tumorigenicity and tumor growth

The mitogen-activated protein kinase (MAPK, 1K) family members ERK, JNK, and p38 play a divergent role in either promoting tumorigenesis or tumor-suppression. Activation of ERK and JNK promotes tumorigenesis; whereas, escalation of p38 inhibits carcinogenesis. As these three MAPK members are controlled by the common up-stream MAPK signaling proteins which consist of MAPK kinases (2K) and MAPK kinase kinases (3K), how to selectively actuate tumor-suppressive p38, not concurrently stimulate tumorigenic ERK and JNK, in cancer cells is a challenge for cancer researchers, and a new opportunity for novel anti-cancer drug discovery. Using human pancreatic cancer cells and xenograft mice as models, we found that a small molecule triptonide first discerningly activated the up-stream MAPK kinase kinase MEKK4, not the other two 3K members ASK1 and GADD45; and then selectively actuated the middle stream MAPK kinase MKK4, not the other two 2K members MKK3 and MKK6; and followed by activation of the MAPK member p38, not the other two members ERK and JNK. These data suggest that triptonide is a selective MEKK4-MKK4-p38 axis agonist. Consequently, selective activation of the MEKK4-MKK4-p38 signaling axis by triptonide activated tumor suppressor p21 and inhibited CDK3 expression, resulting in cancer cell cycle arrest at G2/M phase and marked inhibition of pancreatic cancer cell tumorigenic capability in vitro and tumor growth in xenograft mice. Our findings support the notion that selective activation of tumor-suppressive MEKK4-MKK4-p38-p21signaling pathway by triptonide is a new approach for pancreatic cancer therapy, providing a new drug candidate for development of novel anti-cancer therapeutics.

Induction of Apoptosis Scutellaria baicalensis Georgi Root Extract by Inactivation of the Phosphatidyl Inositol 3-kinase/Akt Signaling Pathway in Human Leukemia U937 Cells

Background

The roots of Scutellaria baicalensis Georgi (Labiatae) have been widely used in traditional medicine for treatment of various diseases. In this study, we investigated the effects of ethanol extracts of S. baicalensis roots (EESB) on the growth ofn human leukemia U937 cells.

Methods

The effect of EESB on cell viability was measured by the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide assay. Apoptosis was determined using 4,6-diamidino-2-phenyllindile staining and flow cytometry. The effects of EESB on the expression of regulatory proteins of apoptosis and phosphatidyl inositol 3-kinase (PI3K)/Akt signaling were determined by Western blotting. Caspase activity and mitochondrial membrane potential (MMP) were measured using flow cytometric analysis.

Results

EESB significantly inhibited the growth of U937 cells and induced apoptosis, which was associated with down-regulation of anti-apoptotic Bcl-2, up-regulation of pro-apoptotic Bax, the loss of MMP and activation of caspase-9 and -3. We also found that EESB enhanced the expression of death receptors (DRs) and their associated ligands and induced the activation of caspase-8 and truncation of Bid. In addition, EESB suppressed PI3K/Akt signaling and EESB-induced apoptosis and growth inhibition were further increased by inhibition of PI3K activity.

Conclusions

Our results indicated that the pro-apoptotic effect of EESB was mediated through the activation of DR-mediated intrinsic and mitochondria-mediated extrinsic apoptosis pathways and inhibition of the PI3K/Akt signaling in U937 cells.

Correlation of ERK/MAPK signaling pathway with proliferation and apoptosis of colon cancer cells

The role of extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK/MAPK) signaling pathway in the proliferation and apoptosis of human colon cancer cells was studied. The transduction process of ERK/MAPK signaling pathway was inhibited using methyl ethyl ketone (MEK) inhibitor U0126. Promoting effect of hepatocyte growth factor (HGF) on proliferation of human colon cancer cells was detected via Cell Counting Kit 8 (CCK8), the cycle and apoptosis of human colon cancer cells were detected via flow cytometry, and the migration of human colon cancer cells was detected via wound healing assay. The results revealed that after drug treatment for 48 h, there were statistically significant differences in 4 and 8 µmol/l U0126 experimental group compared with control group (P<0.05). Compared with those in control group, G1 phase, S phase, G2 phase and proliferation index (PI) in 2, 4 and 8 µmol/l U0126 group had statistically significant differences (P<0.05). There were statistically significant differences in comparison of G1 phase, S phase, G2 phase and PI between control and 8 µmol/l U0126 group (P<0.05). Compared with that in control group, the cell migration distance in 8 µmol/l U0126 group had a statistically significant difference after drug treatment for 24 h (P<0.05). After drug treatment for 48 and 72 h, the cell migration distance in 4 and 8 µmol/l U0126 group was significantly reduced, and the differences were statistically significant compared with that in control group (P<0.05). In conclusion, ERK/MAPK signaling pathway is involved in the effects of HGF of promoting proliferation and regulating cell cycle and apoptosis of human colon cancer cells, providing a new approach for the treatment of colon cancer.

Nobiletin inhibits breast cancer via p38 mitogen-activated protein kinase, nuclear transcription factor-κB, and nuclear factor erythroid 2-related factor 2 pathways in MCF-7 cells

INTRODUCTION

Breast cancer is one of the most commonly diagnosed cancers in women, with a high mortality rate.

OBJECTIVE

In the present study, we evaluated the anticancer effect of nobiletin, a flavone glycoside, on the breast cancer cell line MCF-7.

RESULT

Cell viability and proliferation decreased and cell morphology changed from diamond to round after being treated with nobiletin. Nobiletin induced apoptosis of breast cancer MCF-7 cells via regulating the protein expression of Bax, Bcl-2, cleaved caspase-3, and p53. The expression of Bcl-2 decreased, while the expression of Bax and p53 increased in MCF-7 cells treated with nobiletin. Meanwhile, nobiletin inhibited cell migration by downregulating the protein expression of matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9). Moreover, phosphorylation of p38 was increased, and the translocation of p65 and nuclear factor erythroid 2-related factor 2 (Nrf2) to the nucleus was decreased, which suggested that the anticancer effects of nobiletin might at least partially rely on mediating the p38 mitogen-activated protein kinase, nuclear transcription factor-κB, and Nrf2 pathways in MCF-7 breast cancer cells.

CONCLUSION AND RECOMMENDATION

Our data showed that nobiletin was a potential antitumor drug, and it provided some experimental basis for the clinical application of tumor therapy.

Calreticulin is a fine tuning molecule in epibrassinolide-induced apoptosis through activating endoplasmic reticulum stress in colon cancer cells

Epibrassinolide (EBR), a member of brassinostreoids plant hormones with cell proliferation promoting role in plants, is a natural polyhydroxysteroid with structural similarity to steroid hormones of vertebrates. EBR has antiproliferative and apoptosis-inducing effect in various cancer cells. Although EBR has been shown to affect survival and mitochondria-mediated apoptosis pathways in a p53-independent manner, the exact molecular targets of EBR are still under investigation. Our recent SILAC (Stable Isotope Labeling by Amino Acids in Cell Culture) data showed that the most significantly altered protein after EBR treatment was calreticulin (CALR). CALR, a chaperone localized in endoplasmic reticulum (ER) lumen, plays role in protein folding and buffering Ca²⁺ ions. The alteration of CALR may cause ER stress and unfolded protein response correspondingly the induction of apoptosis. Unfolded proteins are conducted to 26S proteasomal degradation following ubiquitination. Our study revealed that EBR treatment caused ER stress and UPR by altering CALR expression causing caspase-dependent apoptosis in HCT 116, HT29, DLD-1, and SW480 colon cancer cells. Furthermore, 48 h EBR treatment did not caused UPR in Fetal Human Colon cells (FHC) and Mouse Embryonic Fibroblast cells (MEF). In addition our findings showed that HCT 116 colon cancer cells lacking Bax and Puma expression still undergo UPR and related apoptosis. CALR silencing and rapamycin co-treatment prevented EBR-induced UPR and apoptosis, whereas 26S proteasome inhibition further increased the effect of EBR in colon cancer cells. All these findings showed that EBR is an ER stress and apoptotic inducer in colon cancer cells without affecting non-malignant cells.

Mimics of pramanicin derived from pyroglutamic acid and their antibacterial activity

Mono and dihydroxypyrrolidinones are readily available by direct oxygenation of a pyroglutamate-derived bicyclic lactam with high diastereoselectivity, and these may be manipulated further in protected or unprotected form by Grignard addition to a pendant Weinreb amide to give acylhydroxypyrrolidinones.

Lithium Enolates Derived from Pyroglutaminol: Aggregation, Solvation, and Atropisomerism

Lithium enolates derived from protected pyroglutaminols were characterized by using (6)Li, (13)C, and (19)F NMR spectroscopies in conjunction with the method of continuous variations. Mixtures of tetrasolvated dimers and tetrasolvated tetramers in different proportions depend on the steric demands of the hemiaminal protecting group, tetrahydrofuran concentration, and the presence or absence of an α-fluoro moiety. The high steric demands of the substituted bicyclo[3.3.0] ring system promote dimers to an unusual extent and allow solvents and atropisomers in cubic tetramers to be observed in the slow-exchange limit. Pyridine used as a (6)Li chemical shift reagent proved useful in assigning solvation numbers.

AMP-activated protein kinase couples 3-bromopyruvate-induced energy depletion to apoptosis via activation of FoxO3a and upregulation of proapoptotic Bcl-2 proteins

Most tumors primarily rely on glycolysis rather than mitochondrial respiration for ATP production. This phenomenon, also known as Warburg effect, renders tumors more sensitive to glycolytic disturbances compared to normal cells. 3-bromopyruvate is a potent inhibitor of glycolysis that shows promise as an anticancer drug candidate. Although investigations revealed that 3-BP triggers apoptosis through ATP depletion and subsequent AMPK activation, the underlying molecular mechanisms coupling AMPK to apoptosis are poorly understood. We showed that 3-BP leads to a rapid ATP depletion which was followed by growth inhibition and Bax-dependent apoptosis in HCT116 cells. Apoptosis was accompanied with activation of caspase-9 and -3 while pretreatment with a general caspase inhibitor attenuated cell death. AMPK, p38, JNK, and Akt were phosphorylated immediately upon treatment. Pharmacological inhibition and silencing of AMPK largely inhibited 3-BP-induced apoptosis and reversed phosphorylation of JNK. Transcriptional activity of FoxO3a was dramatically increased subsequent to AMPK-mediated phosphorylation of FoxO3a at Ser413. Cell death analysis of cells transiently transfected with wt or AMPK-phosphorylation-deficient FoxO3 expression plasmids verified the contributory role of AMPK-FoxO3a axis in 3-BP-induced apoptosis. In addition, expression of proapoptotic Bcl-2 proteins Bim and Bax were upregulated in an AMPK-dependent manner. Bim was transcriptionally activated in association with FoxO3a activity, while Bax upregulation was abolished in p53-null cells. Together, these data suggest that AMPK couples 3-BP-induced metabolic disruption to intrinsic apoptosis via modulation of FoxO3a-Bim axis and Bax expression. © 2015 Wiley Periodicals, Inc.

Cigarette smoke extract-induced BEAS-2B cell apoptosis and anti-oxidative Nrf-2 up-regulation are mediated by ROS-stimulated p38 activation

Cigarette smoke contains reactive oxygen (ROS) that can cause oxidative stress. It increases the number of apoptotic and necrotic lung cells and further induces the development of chronic airway disease. In this study, we investigated the effects of cigarette smoke extract (CSE) on apoptosis in human bronchial epithelial cells (BEAS-2B). CSE exposure induced ROS generation and p38 mitogen-activated protein kinase (MAPK) activation that are associated with the activation of apoptosis-regulating signal kinase 1 (ASK-1). N-acetylcysteine (a general antioxidant) attenuated the CSE-induced ASK-1 and p38 MAPK activation and cell apoptosis, suggesting a triggering role of ROS in ASK-1/p38 MAPK activation during apoptotic progression. In contrast, the inhibition and knockdown of p38 attenuated the expression of anti-oxidant master NF-E2-related factor 2 (Nrf-2) and CSE-induced apoptosis, suggesting that p38 MAPK modulates Nrf-2 expression and presumably prevents cell apoptosis. Taken together, the data presented in this manuscript demonstrate that the ROS-dependent ASK-1/p38 signaling cascade regulates CSE-induced BEAS-2B cell apoptosis. In addition, anti-oxidative Nrf-2 is also up-regulated by the ROS/p38 signaling cascade in this progression.