Antiproliferative activity of guava leaf extract via inhibition of prostaglandin endoperoxide H synthase isoforms

Prostaglandin endoperoxide H synthase (PGHS) is a key enzyme for the synthesis of prostaglandins (PGs) which play important roles in inflammation and carcinogenesis. Because the extract from Psidium guajava is known to have a variety of beneficial effects on our body including the anti-inflammatory, antioxidative and antiproliferative activities, we investigated whether the extract inhibited the catalytic activity of the two PGHS isoforms using linoleic acid as an alternative substrate. The guava leaf extract inhibited the cyclooxygenase reaction of recombinant human PGHS-1 and PGHS-2 as assessed by conversion of linoleic acid to 9- and 13-hydroxyoctadecadienoic acids (HODEs). The guava leaf extract also inhibited the PG hydroperoxidase activity of PGHS-1, which was not affected by nonsteroidal anti-inflammatory drugs (NSAIDs). Quercetin which was one of the major components not only inhibited the cyclooxygenase activity of both isoforms but also partially inhibited the PG hydroperoxidase activity. Overexpression of human PGHS-1 and PGHS-2 in the human colon carcinoma cells increased the DNA synthesis rate as compared with mock-transfected cells which did not express any isoforms. The guava leaf extract not only inhibited the PGE₂ synthesis but also suppressed the DNA synthesis rate in the PGHS-1- and PGHS-2-expressing cells to the same level as mock-transfected cells. These results demonstrate the antiproliferative activity of the guava leaf extract which is at least in part caused by inhibition of the catalytic activity of PGHS isoforms.     

Synthesis and structure–activity relationships of 2-(1,4′-bipiperidin-1′-yl)thiazolopyridine as H3 receptor antagonists

A series of 2-(1,4′-bipiperidine-1′-yl)thiazolopyridines was synthesized and evaluated as a new lead of non-imidazole histamine H₃ receptor antagonists. Introduction of diversity at the 6-position of the pyridine ring was designed to enhance in vitro potency and decrease hERG activity. The structure–activity relationships for these new thiazolopyridine antagonists are discussed.     

Mechanism for Amyloid Precursor-like Protein 2 Enhancement of Major Histocompatibility Complex Class I Molecule Degradation

Earlier studies have demonstrated interaction of the murine major histocompatibility complex (MHC) class I molecule K^d with amyloid precursor-like protein 2 (APLP2), a ubiquitously expressed member of the amyloid precursor protein family. Our current findings indicate that APLP2 is internalized in a clathrin-dependent manner, as shown by utilization of inhibitors of the clathrin pathway. Furthermore, we demonstrated that APLP2 and K^d bind at the cell surface and are internalized together. The APLP2 cytoplasmic tail contains two overlapping consensus motifs for binding to the adaptor protein-2 complex, and mutation of a tyrosine shared by both motifs severely impaired APLP2 internalization and ability to promote K^d endocytosis. Upon increased expression of wild type APLP2, K^d molecules were predominantly directed to the lysosomes rather than recycled to the plasma membrane. These findings suggest a model in which APLP2 binds K^d at the plasma membrane, facilitates uptake of K^d in a clathrin-dependent manner, and routes the endocytosed K^d to the lysosomal degradation pathway. Thus, APLP2 has a multistep trafficking function that influences the expression of major histocompatibility complex class I molecules at the plasma membrane.     

Ratio of the vitreous vascular endothelial growth factor and pigment epithelial-derived factor in Eales disease

Eales disease (ED) is an idiopathic inflammatory venous occlusion of the peripheral retina. As neovascularization is prominent in ED, this study attempts to look at the ratio of VEGF, the angiogenic factor, and PEDF, an anti-angiogenic factor in the vitreous of ED patients in comparison with the macular hole (MH) and Proliferative Diabetic Retinopathy (PDR). Vitreous levels of VEGF and PEDF were determined in the undiluted vitreous specimen obtained from 26 ED cases, 17 PDR, and seven patients with MH. The vitreous levels of VEGF and PEDF were estimated by ELISA. The immunohistochemistry (IHC) for VEGF and PEDF were done in the epiretinal membrane of ED and PDR case. The VEGF/PEDF ratio was found to be significantly increased in ED (p = 0.014) and PDR (p = 0.000) compared to MH. However the ratio was 3.5-fold higher in PDR than ED (p = 0.009). The IHC data on the ERM specimen from ED showed the presence of VEGF and PEDF similar to PDR. The high angiogenic potential seen as the ratio of VEGF/PEDF correlates with the peak clinical onset of the disease in the age group 21–30 years and the diseases usually self-resolves above the age of 40, which is reflected by the low ratio of VEGF/PEDF. The study shows that the VEGF/PEDF ratio is significantly increased in ED though the angiogenic potential is higher in PDR than in ED. Clinically Eales Disease is known as a self-limiting disease, while PDR is a progressive disease.     

Alternatives for Reintroducing a Rare Ecotone Species: Manually Thinned Forest Edge versus Restored Habitat Remnant

Species native to ecotones are often overlooked in restoration efforts despite the increasing rarity of ecotone habitat. In fragmented, fire-suppressed landscapes, true ecotone may no longer exist. Restoration biologists interested in reintroducing ecotone species must decide whether to plant them in historic ecotones maintained by manual thinning or whether to opt for discrete restoration areas that are easier to maintain. We investigated these two alternatives with Lantana canescens , a rare tropical shrub native to the ecotone between pine and hardwood forests of Miami-Dade County, Florida, U.S.A. Our short-term findings show that after 15 and 18 months, survival of transplants was 69% in a restored site and 65% and 84% in two historic ecotone sites. The restored site had significantly higher photosynthetically active radiation (PAR) (75%) than the historic ecotones (25–39%). Correspondingly, 267 seedlings have recruited at the restored site, whereas only 8 have emerged at both historic ecotone sites. Seedling establishment was associated with higher PAR at the restored site. We found that overall population sustainability was higher at the restored site where there is the additional benefit of less maintenance. Our work suggests that, by reducing succession, a discrete restoration area can approach the historic conditions of hardwood/pine forest ecotone more closely than degraded historic ecotones themselves. We present a viable solution for conserving rare ecotone species when their natural habitat and the processes that maintained it no longer exist.     

Rapid Global Expansion of the Fungal Disease Chytridiomycosis into Declining and Healthy Amphibian Populations

The fungal disease chytridiomycosis, caused by Batrachochytrium dendrobatidis, is enigmatic because it occurs globally in both declining and apparently healthy (non-declining) amphibian populations. This distribution has fueled debate concerning whether, in sites where it has recently been found, the pathogen was introduced or is endemic. In this study, we addressed the molecular population genetics of a global collection of fungal strains from both declining and healthy amphibian populations using DNA sequence variation from 17 nuclear loci and a large fragment from the mitochondrial genome. We found a low rate of DNA polymorphism, with only two sequence alleles detected at each locus, but a high diversity of diploid genotypes. Half of the loci displayed an excess of heterozygous genotypes, consistent with a primarily clonal mode of reproduction. Despite the absence of obvious sex, genotypic diversity was high (44 unique genotypes out of 59 strains). We provide evidence that the observed genotypic variation can be generated by loss of heterozygosity through mitotic recombination. One strain isolated from a bullfrog possessed as much allelic diversity as the entire global sample, suggesting the current epidemic can be traced back to the outbreak of a single clonal lineage. These data are consistent with the current chytridiomycosis epidemic resulting from a novel pathogen undergoing a rapid and recent range expansion. The widespread occurrence of the same lineage in both healthy and declining populations suggests that the outcome of the disease is contingent on environmental factors and host resistance.     

Web-based weight management programs in an integrated health care setting: a randomized, controlled trial

Objective: To assess the efficacy of a Web‐based tailored behavioral weight management program compared with Web‐based information‐only weight management materials. Research Methods and Procedures: Participants, 2862 eligible overweight and obese (BMI = 27 to 40 kg/m²) members from four regions of Kaiser Permanente's integrated health care delivery system, were randomized to receive either a tailored expert system or information‐only Web‐based weight management materials. Weight change and program satisfaction were assessed by self‐report through an Internet‐based survey at 3‐ and 6‐month follow‐up periods. Results: Significantly greater weight loss at follow‐up was found among participants assigned to the tailored expert system than among those assigned to the information‐only condition. Subjects in the tailored expert system lost a mean of 3 ± 0.3% of their baseline weight, whereas subjects in the information‐only condition lost a mean of 1.2 ± 0.4% (p < 0.0004). Participants were also more likely to report that the tailored expert system was personally relevant, helpful, and easy to understand. Notably, 36% of enrollees were African‐American, with enrollment rates higher than the general proportion of African Americans in any of the study regions. Discussion: The results of this large, randomized control trial show the potential benefit of the Web‐based tailored expert system for weight management compared with a Web‐based information‐only weight management program.     

The Involvement of Lipid Peroxide-Derived Aldehydes in Aluminum Toxicity of Tobacco Roots

Oxidative injury of the root elongation zone is a primary event in aluminum (Al) toxicity in plants, but the injuring species remain unidentified. We verified the hypothesis that lipid peroxide-derived aldehydes, especially highly electrophilic α,β-unsaturated aldehydes (2-alkenals), participate in Al toxicity. Transgenic tobacco (Nicotiana tabacum) overexpressing Arabidopsis (Arabidopsis thaliana) 2-alkenal reductase (AER-OE plants), wild-type SR1, and an empty vector-transformed control line (SR-Vec) were exposed to AlCl₃ on their roots. Compared with the two controls, AER-OE plants suffered less retardation of root elongation under AlCl₃ treatment and showed more rapid regrowth of roots upon Al removal. Under AlCl₃ treatment, the roots of AER-OE plants accumulated Al and H₂O₂ to the same levels as did the sensitive controls, while they accumulated lower levels of aldehydes and suffered less cell death than SR1 and SR-Vec roots. In SR1 roots, AlCl₃ treatment markedly increased the contents of the highly reactive 2-alkenals acrolein, 4-hydroxy-(E)-2-hexenal, and 4-hydroxy-(E)-2-nonenal and other aldehydes such as malondialdehyde and formaldehyde. In AER-OE roots, accumulation of these aldehydes was significantly less. Growth of the roots exposed to 4-hydroxy-(E)-2-nonenal and (E)-2-hexenal were retarded more in SR1 than in AER-OE plants. Thus, the lipid peroxide-derived aldehydes, formed downstream of reactive oxygen species, injured root cells directly. Their suppression by AER provides a new defense mechanism against Al toxicity.Aluminum (Al) is the most abundant metal in the earth''s crust and is a major factor limiting plant growth and productivity in acid soils, which cover about 50% of the world''s potentially arable land surface (Kochian, 1995; Kochian et al., 2004). The primary site of Al accumulation and toxicity is the root meristem, and inhibition of root elongation is the most notable symptom of Al toxicity (Delhaize and Ryan, 1995; Yamamoto et al., 2003). Al causes various adverse effects, such as disruption of signal transduction pathways, inhibition of cell division and ion fluxes, disruption of cytoskeletal dynamics, induced generation of reactive oxygen species (ROS), and disturbance of plasma membrane stability and function (Jones and Kochian, 1995; Blancaflor et al., 1998; Yamamoto et al., 2001, 2002; Kochian et al., 2004; Ma et al., 2007). Of all these toxic effects, the generation of ROS is observed rapidly and sustainably in roots after Al exposure. Al-induced generation of ROS has been shown in maize (Zea mays) and Allium cepa roots (Jones et al., 2006; Achary et al., 2008). Tahara et al. (2008) showed that ROS generated to a greater degree in Al-sensitive species than in Al-tolerant species. Yamamoto et al. (2002, 2003) have shown a correlation between ROS level and inhibition of growth capacity in cultured tobacco (Nicotiana tabacum) cells. Furthermore, ROS generation increases with increasing Al concentration (Achary et al., 2008; Xue et al., 2008). Generation of ROS appears to be a cause, rather than a result, of Al-induced cell injury, because high ROS scavenging ability resulted in enhanced Al tolerance (Devi et al., 2003; Ezaki et al., 2008). In addition, overexpression of genes encoding antioxidant enzymes (peroxidase and superoxide dismutase) conferred Al tolerance to the transgenic plants (Ezaki et al., 2000; Basu et al., 2001). Thus, ROS appears to be the primary factors that cause growth inhibition in Al-stressed roots.Downstream of ROS generation, lipid peroxidation is a common symptom of Al toxicity (Yamamoto et al., 2001), and it increases with increasing Al concentration (Achary et al., 2008). From animal cell studies, it is now recognized that the toxicity of lipid peroxide (LOOH) is largely ascribable to LOOH-derived aldehydes. In particular, α,β-unsaturated aldehydes, such as 4-hydroxy-(E)-2-nonenal (HNE) and acrolein, are strong electrophiles and readily modify proteins and nucleic acids (Esterbauer et al., 1991; Taylor et al., 2002; O''Brien et al., 2005; Møller et al., 2007). HNE causes depletion of glutathione, a decrease in protein thiols, disturbance of calcium homeostasis, inhibition of DNA, RNA, and protein synthesis, lactate release, morphological changes of cells, and finally leading to cell death (Esterbauer et al., 1991; Burcham, 1998). Increase of HNE has been observed in a wide range of human diseases, including Alzheimer''s disease, Parkinson''s disease, and mitochondrial complex 1 deficiency (Poli and Schaur, 2000).In plants, too, a close correlation between the level of LOOH-derived aldehydes (determined as thiobarbituric acid-reactive substances [TBARS]) and cellular damage has been shown under environmental stresses caused by heat, chilling, UV-B radiation, salinity, heavy metals, and Al (Ma et al., 2007; Ezaki et al., 2008). Their involvement in cellular damage has been demonstrated by the protective effects of the aldehyde-scavenging enzymes aldehyde dehydrogenase (Sunkar et al., 2003; Kotchoni et al., 2006) and aldehyde reductase (Oberschall et al., 2000; Hideg et al., 2003; Hegedüs et al., 2004) to confer tolerance against various environmental stresses when they were overexpressed in plants. In barley (Hordeum vulgare) roots, the formation of HNE in association with Al treatment was observed (Sakihama and Yamasaki, 2002). Occurrence of HNE in Arabidopsis (Arabidopsis thaliana) leaves under oxidative stress has been also deduced by detection of modified proteins in the mitochondria (Winger et al., 2007). HNE rapidly inhibited respiration in isolated potato (Solanum tuberosum) mitochondria by inactivating pyruvate dehydrogenase, 2-oxoglutarate dehydrogenase, NAD-malic enzyme (Millar and Leaver, 2000), and alternative oxidase (Winger et al., 2005). HNE and other 2-alkenals also inactivated photosynthesis in isolated chloroplasts (Mano et al., 2009). Arabidopsis contains 2-alkenal reductase (AER; E.C. 1.3.1.74) that catalyzes the reduction of the α,β-unsaturated bond of 2-alkenals to produce n-alkanals (Mano et al., 2002). Overexpression of AER in tobacco (Mano et al., 2005) and in Arabidopsis (Papdi et al., 2008) improved the tolerance to photooxidative stress and NaCl stress, respectively. Thus, accumulated observation indicates that LOOH-derived aldehydes, especially 2-alkenals, are commonly involved in oxidative damage in plant cells. Considering the critical importance of ROS in Al toxicity to roots, it is expected that 2-alkenals are produced and mediate damage in the stressed root cells.To evaluate the roles of LOOH-derived aldehydes in root injury under Al stress, we employed transgenic tobacco plants that overexpress the AER gene (AER-OE plants; Mano et al., 2005). With Al treatment, the roots of AER-OE accumulated Al and H₂O₂ to the same levels as those of the wild type, but they showed resistance to inhibition of elongation. Aldehyde analysis revealed that the Al treatment increased the contents of several toxic aldehydes, including HNE and acrolein in wild-type plants, but these aldehydes were significantly suppressed in the AER-OE plants. On the basis of these results, we propose that the inhibition of root growth by Al ions is induced by toxic aldehydes generated with ROS.