Identification and biological activities of a new antiangiogenic small molecule that suppresses mitochondrial reactive oxygen species

Mitochondrial reactive oxygen species (ROS) are associated with multiple cellular functions such as cell proliferation, differentiation, and apoptosis. In particular, high levels of mitochondrial ROS in hypoxic cells regulate many angiogenesis-related diseases, including cancer and ischemic disorders. Here we report a new angiogenesis inhibitor, YCG063, which suppressed mitochondrial ROS generation in a phenotypic cell-based screening of a small molecule-focused library with an ArrayScan HCS reader. YCG063 suppressed mitochondrial ROS generation under a hypoxic condition in a dose-dependent manner, leading to the inhibition of in vitro angiogenic tube formation and chemoinvasion as well as in vivo angiogenesis of the chorioallantoic membrane (CAM) at non-toxic doses. In addition, YCG063 decreased the expression levels of HIF-1α and its target gene, VEGF. Collectively, a new antiangiogenic small molecule that suppresses mitochondrial ROS was identified. This new small molecule tool will provide a basis for a better understanding of angiogenesis driven under hypoxic conditions.     

Molecular Engineering in Hole Transport π‐Conjugated Polymers to Enable High Efficiency Colloidal Quantum Dot Solar Cells

Organic p‐type materials are potential candidates as solution processable hole transport materials (HTMs) for colloidal quantum dot solar cells (CQDSCs) because of their good hole accepting/electron blocking characteristics and synthetic versatility. However, organic HTMs have still demonstrated inferior performance compared to conventional p‐type CQD HTMs. In this work, organic π‐conjugated polymer (π‐CP) based HTMs, which can achieve performance superior to that of state‐of‐the‐art HTM, p‐type CQDs, are developed. The molecular engineering of the π‐CPs alters their optoelectronic properties, and the charge generation and collection in CQDSCs using them are substantially improved. A device using PBDTTPD‐HT achieves power conversion efficiency (PCE) of 11.53% with decent air‐storage stability. This is the highest reported PCE among CQDSCs using organic HTMs, and even higher than the reported best solid‐state ligand exchange‐free CQDSC using pCQD‐HTM. From the viewpoint of device processing, device fabrication does not require any solid‐state ligand exchange step or layer‐by‐layer deposition process, which is favorable for exploiting commercial processing techniques.     

Arabidopsis plants expressing only the redox‐regulated Rca‐α isoform have constrained photosynthesis and plant growth

Rubisco activase (Rca) facilitates the release of sugar‐phosphate inhibitors from the active sites of Rubisco and thereby plays a central role in initiating and sustaining Rubisco activation. In Arabidopsis, alternative splicing of a single Rca gene results in two Rca isoforms, Rca‐α and Rca‐β. Redox modulation of Rca‐α regulates the function of Rca‐α and Rca‐β acting together to control Rubisco activation. Although Arabidopsis Rca‐α alone less effectively activates Rubisco in vitro, it is not known how CO₂ assimilation and plant growth are impacted. Here, we show that two independent transgenic Arabidopsis lines expressing Rca‐α in the absence of Rca‐β (‘Rca‐α only’ lines) grew more slowly in various light conditions, especially under low light or fluctuating light intensity, and in a short day photoperiod compared to wildtype. Photosynthetic induction was slower in the Rca‐α only lines, and they maintained a lower rate of CO₂ assimilation during both photoperiod types. Our findings suggest Rca oligomers composed of Rca‐α only are less effective in initiating and sustaining the activation of Rubisco than when Rca‐β is also present. Currently there are no examples of any plant species that naturally express Rca‐α only but numerous examples of species expressing Rca‐β only. That Rca‐α exists in most plant species, including many C3 and C4 food and bioenergy crops, implies its presence is adaptive under some circumstances.     

yucca6, a dominant mutation in Arabidopsis, affects auxin accumulation and auxin-related phenotypes

Auxin plays critical roles in many aspects of plant growth and development. Although a number of auxin biosynthetic pathways have been identified, their overlapping nature has prevented a clear elucidation of auxin biosynthesis. Recently, Arabidopsis (Arabidopsis thaliana) mutants with supernormal auxin phenotypes have been reported. These mutants exhibit hyperactivation of genes belonging to the YUCCA family, encoding putative flavin monooxygenase enzymes that result in increased endogenous auxin levels. Here, we report the discovery of fertile dominant Arabidopsis hypertall1-1D and hypertall1-2D (yucca6-1D, -2D) mutants that exhibit typical auxin overproduction phenotypic alterations, such as epinastic cotyledons, increased apical dominance, and curled leaves. However, unlike other auxin overproduction mutants, yucca6 plants do not display short or hairy root phenotypes and lack morphological changes under dark conditions. In addition, yucca6-1D and yucca6-2D have extremely tall (>1 m) inflorescences with extreme apical dominance and twisted cauline leaves. Microarray analyses revealed that expression of several indole-3-acetic acid-inducible genes, including Aux/IAA, SMALL AUXIN-UP RNA, and GH3, is severalfold higher in yucca6 mutants than in the wild type. Tryptophan (Trp) analog feeding experiments and catalytic activity assays with recombinant YUCCA6 indicate that YUCCA6 is involved in a Trp-dependent auxin biosynthesis pathway. YUCCA6:GREEN FLUORESCENT PROTEIN fusion protein indicates YUCCA6 protein exhibits a nonplastidial subcellular localization in an unidentified intracellular compartment. Taken together, our results identify YUCCA6 as a functional member of the YUCCA family with unique roles in growth and development.     

Hypoxia/reoxygenation-induced cytotoxicity in cultured human lymphocytes

Reactive oxygen species (ROS) generated after exposure to hypoxia and reoxygenation (H/R) play a pivotal role in the stimulation of cell death. In this study, we explored H/R-induced cytotoxicity in human lymphocytes. Compared to cells under normoxic conditions, H/R-treated cells exhibited significantly decreased viability and increased DNA breakage. Western blotting analysis demonstrated that H/R-induced the accumulation of p53 and p63 proteins. H/R also led to the activation of caspase-3 and -9, accompanied by the cleavage of PARP (poly(ADP-ribose)polymerase). Because apoptosis is usually accompanied by ROS generation and collapse of the mitochondrial membrane potential (MMP, Deltapsi(m)), we examined ROS and MMP levels in H/R-treated lymphocytes. Cells subjected to H/R exhibited significantly increased ROS and decreased MMP, compared with normoxic cells. Taken together, these results indicate that H/R treatment of human lymphocytes induces rapid ROS generation and MMP collapse, which triggers apoptosis.     

Molecular and functional characterization of a cyclophilin with antifungal activity from Chinese cabbage

An antifungal protein that inhibits the growth of filamentous fungal pathogens was isolated from Chinese cabbage (Brassica campestris L. ssp. pekinensis) by affinity chromatography on Affi-gel blue gel and ion exchange chromatography on CM-Sepharose. The N-terminal amino acid sequence of the protein was highly homologous to that of plant cyclophilins and consequently the protein was denoted as C-CyP. To understand the antifungal activity of C-CyP, we isolated a cDNA encoding its gene from a Chinese cabbage leaf cDNA library. The Chinese cabbage genome bears more than one C-CyP gene copy and C-CyP mRNA is highly expressed in all tissues except the seeds. Recombinant C-CyP catalyzed the cis-trans inter-conversion of the Ala-Pro bond of the substrate, which indicates this protein has peptidyl-prolyl cis-trans isomerase activity. It also inhibited the growth of several fungal pathogens.     

Heat shock protein 27 is associated with irinotecan resistance in human colorectal cancer cells

Heat shock protein (Hsp) in tumor cells has been proposed to enhance their resistance to chemotherapeutic agents. In the present study, we investigated the influence of Hsp expression on the irinotecan resistance of human colorectal cancer cells. Among eight Hsp genes tested in this study, we confirmed that the expression of Hsp27 correlated with irinotecan resistance in colorectal cancer cells. Specific inhibition of Hsp27 expression using an antisense oliogodeoxynucleotide increased the irinotecan sensitivity. On the contrary, an overexpression of Hsp27 decreased the irinotecan sensitivity in colorectal cancer cells. Elevated expression of Hsp27 decreased caspase-3 activity in colorectal cancer cells. The expression level of Hsp27 determined by immunohistochemical analysis correlated with the clinical response to irinotecan in colorectal cancer patients. Hsp27 expression levels of irinotecan-non-responder (mean staining score, 6.28; proportion of high staining score, 64.2%) were significantly higher compared to those of irinotecan-responder (mean staining score, 3.16; proportion of high staining score, 33.3%) (P for t-test=0.045). These findings suggest that Hsp27 is involved in the irinotecan resistance of colorectal cancer cells possibly by reducing caspase-3 activity.