Glucuronidation of 7-ethyl-10-hydroxycamptothecin (SN-38) by the human UDP-glucuronosyltransferases encoded at the UGT1 locus.

7-Ethyl-10-hydroxycamptothecin (SN-38) is a very promising anticancer drug used for the treatment of metastatic colonrectal cancer. SN-38 is the active metabolite of irinotecan, a semisynthetic anticancer drug derived from 20(S)camptothecin. In this study, we examined the potential for each of the UGT1-encoded isoforms (UGT1A1 and UGT1A3 through UGT1A10) to glucuronidate SN-38. The amount of specific protein for each isoform was determined by Western blot analysis. Although UGT1A1 was previously shown to metabolize this drug, the results of this study show that UGT1A7 glucuronidates this chemical at a 9- to 21-fold higher level at pH 6. 4 and pH 7.6, respectively, than that by UGT1A1. The activity of UGT1A7 is from 8.4- to 19-fold higher at pH 6.4 and 12- to 40-fold higher at pH 7.6 than that by the other 7 UGT1 encoded isoforms. UGT1A7 glucuronidates SN-38 with an apparent Km of 5 microM. Hence, the distribution of this isoform in the gastrointestinal tract has the potential to impact the effectiveness of this chemotherapeutic agent.     

Within‐generation consequences of postsettlement mortality for trait composition in wild populations: An experimental test

There is a critical need to understand patterns and causes of intraspecific variation in physiological performance in order to predict the distribution and dynamics of wild populations under natural and human‐induced environmental change. However, the usual explanation for trait differences, local adaptation, fails to account for the small‐scale phenotypic and genetic divergence observed in fishes and other species with dispersive early life stages. We tested the hypothesis that local‐scale variation in the strength of selective mortality in early life mediates the trait composition in later life stages. Through in situ experiments, we manipulated exposure to predators in the coral reef damselfish Dascyllus aruanus and examined consequences for subsequent growth performance under common garden conditions. Groups of 20 recently settled D. aruanus were outplanted to experimental coral colonies in Moorea lagoon and either exposed to natural predation mortality (52% mortality in three days) or protected from predators with cages for three days. After postsettlement mortality, predator‐exposed groups were shorter than predator‐protected ones, while groups with lower survival were in better condition, suggesting that predators removed the longer, thinner individuals. Growth of both treatment groups was subsequently compared under common conditions. We did not detect consequences of predator exposure for subsequent growth performance: Growth over the following 37 days was not affected by the prior predator treatment or survival. Genotyping at 10 microsatellite loci did indicate, however, that predator exposure significantly influenced the genetic composition of groups. We conclude that postsettlement mortality did not have carryover effects on the subsequent growth performance of cohorts in this instance, despite evidence for directional selection during the initial mortality phase.     

Molecular architecture of the ribosome‐bound Hepatitis C Virus internal ribosomal entry site RNA

Internal ribosomal entry sites (IRESs) are structured cis‐acting RNAs that drive an alternative, cap‐independent translation initiation pathway. They are used by many viruses to hijack the translational machinery of the host cell. IRESs facilitate translation initiation by recruiting and actively manipulating the eukaryotic ribosome using only a subset of canonical initiation factor and IRES transacting factors. Here we present cryo‐EM reconstructions of the ribosome 80S‐ and 40S‐bound Hepatitis C Virus (HCV) IRES. The presence of four subpopulations for the 80S•HCV IRES complex reveals dynamic conformational modes of the complex. At a global resolution of 3.9 Å for the most stable complex, a derived atomic model reveals a complex fold of the IRES RNA and molecular details of its interaction with the ribosome. The comparison of obtained structures explains how a modular architecture facilitates mRNA loading and tRNA binding to the P‐site. This information provides the structural foundation for understanding the mechanism of HCV IRES RNA‐driven translation initiation.     

Hormone-regulated expression and distribution of versican in mouse uterine tissues

Background  

Remodeling of the extracellular matrix is one of the most striking features observed in the uterus during the estrous cycle and after hormone replacement. Versican (VER) is a hyaluronan-binding proteoglycan that undergoes RNA alternative splicing, generating four distinct isoforms. This study analyzed the synthesis and distribution of VER in mouse uterine tissues during the estrous cycle, in ovariectomized (OVX) animals and after 17beta-estradiol (E2) and medroxyprogesterone (MPA) treatments, either alone or in combination.     

Nutrient enrichment and fisheries exploitation: interactive effects on estuarine living resources and their management

Both fisheries exploitation and increased nutrient loadings strongly affect fish and shellfish abundance and production in estuaries. These stressors do not act independently; instead, they jointly influence food webs, and each affects the sensitivity of species and ecosystems to the other. Nutrient enrichment and the habitat degradation it sometimes causes can affect sustainable yields of fisheries, and fisheries exploitation can affect the ability of estuarine systems to process nutrients. The total biomass of fisheries landings in estuaries and semi-enclosed seas tends to increase with nitrogen loadings in spite of hypoxia, but hypoxia and other negative effects of nutrient over-enrichment cause declines in individual species and in parts of systems most severely affected. More thoroughly integrated management of nutrients and fisheries will permit more effective management responses to systems affected by both stressors, including the application of fisheries regulations to rebuild stocks negatively affected by eutrophication. Reducing fishing mortality may lead to the recovery of depressed populations even when eutrophication contributes to population declines if actions are taken while the population retains sufficient reproductive potential. New advances in modeling, statistics, and technology promise to provide the information needed to improve the understanding and management of systems subject to both nutrient enrichment and fisheries exploitation. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Guest editors: J. H. Andersen & D. J. Conley Eutrophication in Coastal Ecosystems: Selected papers from the Second International Symposium on Research and Management of Eutrophication in Coastal Ecosystems, 20–23 June 2006, Nyborg, Denmark     

Treatment with apolipoprotein A-1 mimetic peptide reduces lupus-like manifestations in a murine lupus model of accelerated atherosclerosis

Introduction

The purpose of this study was to evaluate the effects of L-4F, an apolipoprotein A-1 mimetic peptide, alone or with pravastatin, in apoE^-/-Fas^-/-C57BL/6 mice that spontaneously develop immunoglobulin G (IgG) autoantibodies, glomerulonephritis, osteopenia, and atherosclerotic lesions on a normal chow diet.

Methods

Female mice, starting at eight to nine weeks of age, were treated for 27 weeks with 1) pravastatin, 2) L-4F, 3) L-4F plus pravastatin, or 4) vehicle control, followed by disease phenotype assessment.

Results

In preliminary studies, dysfunctional, proinflammatory high-density lipoproteins (piHDL) were decreased six hours after a single L-4F, but not scrambled L-4F, injection in eight- to nine-week old mice. After 35 weeks, L-4F-treated mice, in the absence/presence of pravastatin, had significantly smaller lymph nodes and glomerular tufts (P_{L, LP} < 0.05), lower serum levels of IgG antibodies to double stranded DNA (dsDNA) (P_L < 0.05) and oxidized phospholipids (oxPLs) (P_{L, LP} < 0.005), and elevated total and vertebral bone mineral density (P_{L, LP} < 0.01) compared to vehicle controls. Although all treatment groups presented larger aortic root lesions compared to vehicle controls, enlarged atheromas in combination treatment mice had significantly less infiltrated CD68⁺ macrophages (P_LP < 0.01), significantly increased mean α-actin stained area (P_LP < 0.05), and significantly lower levels of circulating markers for atherosclerosis progression, CCL19 (P_{L, LP} < 0.0005) and VCAM-1 (P_L < 0.0002).

Conclusions

L-4F treatment, alone or with pravastatin, significantly reduced IgG anti-dsDNA and IgG anti-oxPLs, proteinuria, glomerulonephritis, and osteopenia in a murine lupus model of accelerated atherosclerosis. Despite enlarged aortic lesions, increased smooth muscle content, decreased macrophage infiltration, and decreased pro-atherogenic chemokines in L-4F plus pravastatin treated mice suggest protective mechanisms not only on lupus-like disease, but also on potential plaque remodeling in a murine model of systemic lupus erythematosus (SLE) and accelerated atherosclerosis.