Anti-cancer potential of persimmon (Diospyros kaki) leaves via the PDGFR-Rac-JNK pathway.

Persimmon leaves are known to have some beneficial effects, including ROS elimination, lipid circulation, and neuronal protection. However, their anti-cancer properties and the underlying mechanisms remain unclear. Herein, we show that treatment with the ethanol extract of persimmon, Diospyros kaki, leaves (EEDK) induces cancer cell death and inhibits cell proliferation. Using fluorescence resonance energy transfer (FRET) technology with genetically-encoded biosensors, we first found that EEDK stimulates a PDGFR-Rac signaling cascade in live cells. Moreover, we found that downstream of the PDGFR-Rac pathway, JNKs are activated by EEDK. In contrast, JNK-downstream inhibitors, such as CoCl2, T-5224, and pepstatin A, attenuated EEDK-induced cell death. Thus, we illustrate that the PDGFR-Rac-JNK signaling axis is triggered by EEDK, leading to cancer cell death, suggesting the extract of persimmon leaves may be a promising anti-cancer agent.

CTTNBP2 Controls Synaptic Expression of Zinc-Related Autism-Associated Proteins and Regulates Synapse Formation and Autism-like Behaviors.

Synaptic dysregulation is a critical feature of autism spectrum disorders (ASDs). Among various autism-associated genes, cortactin binding protein 2 (CTTNBP2) is a cytoskeleton regulator predominantly expressed in neurons and highly enriched at dendritic spines. Here, using Cttnbp2 knockout and ASD-linked mutant mice, we demonstrate that Cttnbp2 deficiency reduces zinc levels in the brain, alters synaptic protein targeting, impairs dendritic spine formation and ultrastructure of postsynaptic density, and influences neuronal activation and autism-like behaviors. A link to autism, the NMDAR-SHANK pathway, and zinc-related regulation are three features shared by CTTNBP2-regulated synaptic proteins. Zinc supplementation rescues the synaptic expression of CTTNBP2-regulated proteins. Moreover, zinc supplementation and administration of D-cycloserine, an NMDAR coagonist, improve the social behaviors of Cttnbp2-deficient mice. We suggest that CTTNBP2 controls the synaptic expression of a set of zinc-regulated autism-associated genes and influences NMDAR function and signaling, providing an example of how genetic and environmental factor crosstalk controls social behaviors.

Correction of aberrant NADPH oxidase activity in blood-derived mononuclear cells from type II diabetes mellitus patients by a naturally fermented papaya preparation.

UNLABELLED: Supplementation of standardized fermented papaya preparation (FPP) to adult diabetic mice improves dermal wound healing outcomes. Peripheral blood mononuclear cells (PBMC) from type II diabetes mellitus (T2DM) patients elicit a compromised respiratory burst activity resulting in increased risk of infections for the diabetic patients. AIMS: The objectives of the current study were to determine the effect of FPP supplementation on human diabetic PBMC respiratory burst activity and to understand underlying mechanisms of such action of FPP. RESULTS: When stimulated with phorbol 12-myristate 13-acetate, the production of reactive oxygen species by T2DM PBMC was markedly compromised compared to that of the PBMC from non-DM donors. FPP treated ex vivo improved respiratory burst outcomes in T2DM PBMC. FPP treatment significantly increased phosphorylation of the p47phox subunit of NADPH oxidase. In addition, the protein and mRNA expression of Rac2 was potently upregulated after FPP supplemention. The proximal human Rac2 gene promoter is G-C rich and contains consensus binding sites for Sp1 and AP-1. While FPP had no significant effect on the AP-1 DNA binding activity, the Sp1 DNA binding activity was significantly upregulated in PBMC after treatment of the cells with FPP. INNOVATION: This work provided first evidence that compromised respiratory burst performance of T2DM PBMC may be corrected by a nutritional supplement. CONCLUSION: FPP can correct respiratory burst performance of T2DM PBMC via an Sp-1-dependant pathway. Studies testing the outcome of FPP supplementation in diabetic patients are warranted.

Lipoic acid attenuates high-fat-diet-induced oxidative stress and B-cell-related immune depression.

OBJECTIVE: This study investigated whether spleen oxidative stress induced by a high-fat diet (HFD) influences the expression of genes involved in B-cell activation, thus leading to B-cell-related immunosuppression. METHODS: Male C57BL/6 mice were randomly assigned to one of three groups with eight mice in each group. The control group consumed an ordinary diet (4.9% fat, w/w). The other two groups were fed an HFD (21.2% fat) and an HFD plus 0.1% lipoic acid (LA). After 10 wk, plasma and spleen oxidative stress biomarkers including superoxide dismutase, catalase, glutathione peroxidase, total antioxidant capacity, reduced glutathione/oxidized glutathione ratio, and malondialdehyde were examined. The B-cell-related immune function was evaluated by examining the number of B cells, and the apoptotic percentages of splenic lymphocytes were determined by flow cytometry. Furthermore, the B-cell activation and reactive oxygen species scavenger-related genes differentially expressed between mice fed an HFD and those fed an HFD supplemented with LA were identified through complementary DNA microarray. RESULTS: The HFD induced marked decreases in the number of B cells and significantly increased the apoptotic percentages of splenic lymphocytes, accompanied by oxidative stress and increased oxidative damage, in the plasma and spleen. In addition, complementary DNA array analysis results showed that the HFD induced the decreased expression of genes associated with antioxidant defense, such as superoxide dismutase-3 (1.5-fold), metallothionein-1 (3.03-fold), glutathione peroxidase-5 (17.15-fold), and peroxiredoxin-4 (1.5), and B-cell activation, such as immunoglobulin heavy chain 6 (2.46-fold), immunoglobulin κ-chain (1.74-fold), Fc receptor (1.41-fold), and RAS-related C3 botulinum substrate-1 (7.46). The LA supplement prevented the buildup of oxidative stress and upregulated related gene expressions. CONCLUSION: These results indicate a role for LA as a possible effective supplement with an HFD to prevent the development of oxidative stress and to attenuate B-cell damnification by increasing the gene expression of the B-cell receptor signaling pathway.

Cryptotanshinone inhibits lymphatic endothelial cell tube formation by suppressing VEGFR-3/ERK and small GTPase pathways.

Cryptotanshinone (CPT), isolated from the plant Salvia miltiorrhiza Bunge, is a potential anticancer agent. However, the underlying mechanism remains to be defined. Here, we show that CPT inhibited lymphangiogenesis in an in vitro model (tube formation). This effect was partly attributed to inhibiting expression of VEGF receptor 3 (VEGFR-3) in murine lymphatic endothelial cells (LEC), as overexpression of VEGFR-3 conferred resistance to CPT inhibition of the tube formation, whereas downregulation of VEGFR-3 mimicked the effect of CPT, blocking the tube formation. Furthermore, CPT inhibited phosphorylation of the extracellular signal-related kinase 1/2 (ERK1/2). Overexpression of VEGFR-3 attenuated CPT inhibition of ERK1/2 phosphorylation, whereas downregulation of VEGFR-3 inhibited ERK1/2 phosphorylation in LECs. Expression of constitutively active MKK1 resulted in activation of ERK1/2 and partially prevented CPT inhibition of LEC tube formation. In addition, CPT also inhibited protein expression and activities of Rac1 and Cdc42 but not RhoA. Expression of constitutively active Rac1 and Cdc42 concurrently, but not Rac1 or Cdc42 alone, conferred resistance to CPT inhibition of LEC tube formation. Taken together, the results suggest that CPT inhibits LEC tube formation, in part, by inhibiting VEGFR-3-mediated ERK1/2 phosphorylation and, in part, by inhibiting expression of the small GTPases.

Green tea (-)-epigallocatechin-3-gallate down-regulates VASP expression and inhibits breast cancer cell migration and invasion by attenuating Rac1 activity.

(-)-Epigallocatechin-3-gallate (EGCG) is a polyphenolic compound from green tea that has been shown to have anti-tumor activities such as inhibiting adhesion, migration, and proliferation of tumor cells. However, the delicate mechanisms and signaling pathways underlying the potential anticancer effects of EGCG in breast cancer cells remain unclear. The goal of this study was to examine the effects of EGCG on the migration and invasion of MCF-7 cells and to identify the signaling pathway(s) underlying the cellular response to EGCG exposure. In a concentration-dependent manner, EGCG decreased the migratory and invasive potential of MCF-7 cells with a concomitant down-regulation of vasodilator-stimulated phosphoprotein (VASP) expression and Rac1 activity. Using specific siRNAs to block the expression of VASP and Rac1 in MCF-7 cells that were previously treated with epidermal growth factor (EGF), we demonstrated that the regulation of cell migration and invasion was associated with Rac1 activity and VASP expression. In addition, siRNA mediated knock-down of Rac1 decreased the amount of VASP expression at the mRNA level while VASP specific siRNA revealed no effect on the expression of Rac1 in MCF-7 cells. These findings suggest that the inhibitory effect of EGCG on MCF-7 cell migration and invasion may be produced by a down regulation of VASP expression via the Rac1 pathway.

Epoxycyclopentenone-containing oxidized phospholipids restore endothelial barrier function via Cdc42 and Rac.

After an acute phase of inflammation or injury, restoration of the endothelial barrier is important to regain vascular integrity and to prevent edema formation. However, little is known about mediators that control restoration of endothelial barrier function. We show here that oxidized phospholipids that accumulate at sites of inflammation and tissue damage are potent regulators of endothelial barrier function. Oxygenated epoxyisoprostane-containing phospholipids, but not fragmented oxidized phospholipids, exhibited barrier-protective effects mediated by small GTPases Cdc42 and Rac and their cytoskeletal, focal adhesion, and adherens junction effector proteins. Oxidized phospholipid-induced cytoskeletal rearrangements resulted in a unique peripheral actin rim formation, which was mimicked by coexpression of constitutively active Cdc42 and Rac, and abolished by coexpression of dominant-negative Rac and Cdc42. Thus, oxidative modification of phospholipids during inflammation leads to the formation of novel regulators that may be critically involved in restoration of vascular barrier function.

A rac-like small G-protein from Brassica campestris activates a PKC-dependent phospholipase D.

A cDNA clone encoding a rac-like small GTP binding protein was isolated from a cDNA library of Chinese cabbage (Brassica campestris L. ssp. pekinensis) flower buds and named Brac1. The Brac1 cDNA contains an open reading frame encoding 198 amino acid residues with an estimated molecular mass of 21,690 Da and this coding region has conserved residues and motifs unique to the Rho subfamily of proteins. The deduced amino acid sequence of the Brac1 protein is closely related to that of Arabidopsis thaliana Arac3 (91%), but it shares relatively little homology with other members of the Ras superfamily (about 30% identity). To further characterize Brac1, a pGBrac1 expression vector consisting of PCR-amplified Brac1 cDNA plus glutathione S-transferase (GST) and pBKS(+)II was used to purify the protein. Using a PEI-cellulose/TLC plate, GTPase activity of this protein was confirmed and competition binding studies, using the guanine nucleotides, ATP, UTP and CTP, revealed that the di- and triphosphate forms of guanine nucleotides strongly bind Brac1. Membrane-bound PLD activity was synergistically enhanced by Brac1 in the presence of protein kinase C, but not in the presence of ARF (ADP-ribosylation factor). Genomic analysis indicated that Brac1 belongs to a multigene family. Brac1 transcripts were expressed in all the organs of Brassica, but were especially prevalent in flower buds.

Regulation of pollen tube growth by Rac-like GTPases.

Plant Rac-like GTPases have been classified phylogenetically into two major groups-class I and class II. Several pollen-expressed class I Rac-like GTPases have been shown to be important regulators of polar pollen tube growth. The functional participation by some of the class I and all of the class II Arabidopsis Rac-like GTPases in pollen tube growth remains to be explored. It is shown that at least four members of the Arabidopsis Rac GTPase family are expressed in pollen, including a class II Rac, AtRac7. However, when over-expressed as fusion proteins with GFP, both pollen- and non-pollen-expressed AtRacs interfered with the normal pollen tube tip growth process. These observations suggest that these AtRacs share similar biochemical activities and may integrate into the pollen cellular machinery that regulates the polar tube growth process. Therefore, the functional contribution by individual Rac GTPase to the pollen tube growth process probably depends to a considerable extent on their expression characteristics in pollen. Among the Arabidopsis Racs, GFP-AtRac7 showed association with the cell membrane and Golgi bodies, a pattern distinct from all previously reported localization for other plant Racs. Over-expressing GFP-AtRac7 also induced the broadest spectrum of pollen tube growth defects, including pollen tubes that are bifurcated, with diverted growth trajectory or a ballooned tip. Transgenic plants with multiple copies of the chimeric Lat52-GFP-AtRac7 showed severely reduced seed set, probably many of these defective pollen tubes were arrested, or reduced in their growth rates that they did not arrive at the ovules while they were still receptive for fertilization. These observations substantiate the importance of Rac-like GTPases to sexual reproduction.

A genome-wide analysis of Arabidopsis Rop-interactive CRIB motif-containing proteins that act as Rop GTPase targets.

The plant-specific Rop family GTPases are versatile molecular switches in many processes during plant growth, development, and responses to the environment. To understand how Rop achieves its functional versatility in signaling, we performed a genome-wide identification of putative Rop targets using a combination of the yeast two-hybrid method, bioinformatic tools, and a robust functional assay in pollen. In this study, we have identified 11 Arabidopsis genes encoding novel proteins, termed RICs (for Rop-interactive CRIB motif-containing proteins), that contain a CRIB (for Cdc42/Rac-interactive binding) motif required for their specific interaction with GTP-bound Rop1. RICs are divergent and classified into five groups that share little sequence homology outside of the conserved Rop-interactive domain. Overexpression in tobacco pollen tubes of the nine Ric genes that are expressed in Arabidopsis pollen causes distinct phenotypes, implying distinct functions for various RICs. RIC3 (group III) and RIC4 (group V) both cause depolarized growth like Rop1 and display Rop1-enhanced localization to the tip of pollen tubes, suggesting that these RICs may be two distinct targets of Rop1. In contrast, RIC10 (group I) promotes pollen tube elongation but does not affect pollen tube growth polarity and shows Rop1-independent localization to the cytoplasm, suggesting that RIC10 may participate in a Rop1-independent pathway probably controlled by a different Rop. Expression of all other RICs causes various degrees of growth inhibition in pollen tubes. Furthermore, these inhibitory RICs also exhibit distinct patterns of localization in pollen tubes. Our results suggest that various RICs have evolved to interact with Rops differentially and to perform distinct functions in pollen tubes. Reverse transcriptase-mediated polymerase chain reaction analysis showed that six of the nine RICs are expressed in various parts of Arabidopsis plants. On the basis of these observations, we propose that RICs function as Rop GTPase targets that control various Rop-dependent signaling pathways in plants.