Isaac Emery

Mechanisms of Urokinase Plasminogen Activator (uPA)-mediated Atherosclerosis ROLE OF THE uPA RECEPTOR AND S100A8/A9 PROTEINS

Data from clinical studies, cell culture, and animal models implicate the urokinase plasminogen activator (uPA)/uPA receptor (uPAR)/plasminogen system in the development of atherosclerosis and aneurysms. However, the mechanisms through which uPA/uPAR/plasminogen stimulate these diseases are not yet defined. We used genetically modified, atherosclerosis-prone mice, including mice with macrophage-specific uPA overexpression and mice genetically deficient in uPAR to elucidate mechanisms of uPA/uPAR/plasminogen-accelerated atherosclerosis and aneurysm formation. We found that macrophage-specific uPA overexpression accelerates atherosclerosis and causes aortic root dilation in fat-fed Ldlr−/− mice (as we previously reported in Apoe−/− mice). Macrophage-expressed uPA accelerates atherosclerosis by stimulation of lesion progression rather than initiation and causes disproportionate lipid accumulation in early lesions. uPA-accelerated atherosclerosis and aortic dilation are largely, if not completely, independent of uPAR. In the absence of uPA overexpression, however, uPAR contributes modestly to both atherosclerosis and aortic dilation. Microarray studies identified S100A8 and S100A9 mRNA as the most highly up-regulated transcripts in uPA-overexpressing macrophages; up-regulation of S100A9 protein in uPA-overexpressing macrophages was confirmed by Western blotting. S100A8/A9, which are atherogenic in mice and are expressed in human atherosclerotic plaques, are also up-regulated in the aortae of mice with uPA-overexpressing macrophages, and macrophage S100A9 mRNA is up-regulated by exposure of wild-type macrophages to medium from uPA-overexpressing macrophages. Macrophage microarray data suggest significant effects of uPA overexpression on cell migration and cell-matrix interactions. Our results confirm in a second animal model that macrophage-expressed uPA stimulates atherosclerosis and aortic dilation. They also reveal uPAR independence of these actions and implicate specific pathways in uPA/Plg-accelerated atherosclerosis and aneurysmal disease.

Plasminogen mediates the atherogenic effects of macrophage-expressed urokinase and accelerates atherosclerosis in apoE-knockout mice.

Urokinase-type plasminogen activator (uPA) is expressed at elevated levels in atherosclerotic human arteries, primarily in macrophages. Plasminogen (Plg), the primary physiologic substrate of uPA, is present at significant levels in blood and interstitial fluid. Both uPA and Plg have activities that could affect atherosclerosis progression. Moreover, correlations between increased Plg activation and accelerated atherosclerosis are reported in several human studies. However, a coherent picture of the role of the uPA/Plg system in atherogenesis has not yet emerged, with at least one animal study suggesting that Plg is atheroprotective. We used a transgenic mouse model of macrophage-targeted uPA overexpression in apolipoprotein E-deficient mice to investigate the roles of uPA and Plg in atherosclerosis. We found that macrophage-expressed uPA accelerated atherosclerotic plaque growth and promoted aortic root dilation through Plg-dependent pathways. These pathways appeared to affect lesion progression rather than initiation and to include actions that disproportionately increase lipid accumulation in the artery wall. In addition, loss of Plg was protective against atherosclerosis both in the presence and absence of uPA overexpression. Transgenic mice with macrophage-targeted uPA overexpression reveal atherogenic roles for both uPA and Plg and are a useful experimental setting for investigating the molecular mechanisms that underlie clinically established relationships between uPA expression, Plg activation, and atherosclerosis progression.

Level of Macrophage uPA Expression Is an Important Determinant of Atherosclerotic Lesion Growth in Apoe −/− Mice

Objective—Enhanced plasminogen activation, mediated by overexpression of urokinase-type plasminogen activator (uPA), accelerates atherosclerosis in apolipoprotein E–null mice. However, the mechanisms through which uPA acts remain unclear. In addition, although elevated uPA expression can accelerate murine atherosclerosis, there is not yet any evidence that decreased uPA expression would retard atherosclerosis. Methods and Results—We used a bone marrow transplant (BMT) approach and apolipoprotein E–deficient (Apoe−/−) mice to investigate cellular mechanisms of uPA-accelerated atherosclerosis, aortic dilation, and sudden death. We also used BMT to determine whether postnatal loss of uPA expression in macrophages retards atherosclerosis. BMT from uPA-overexpressing mice yielded recipients with macrophage-specific uPA overexpression; whereas BMT from uPA knockout mice yielded recipients with macrophage-specific loss of uPA expression. Recipients of uPA-overexpressing BM acquired all the vascular phenotypes (accelerated atherosclerosis, aortic medial destruction and dilation, severe coronary stenoses) as well as the sudden death phenotype of uPA-overexpressing mice. Moreover, fat-fed 37-week-old recipients of uPA-null BM had significantly less atherosclerosis than recipients of uPA wild-type marrow (40% less aortic surface lesion area; P=0.03). Conclusions—The level of uPA expression by macrophages—over a broad range—is an important determinant of atherosclerotic lesion growth in Apoe−/− mice.

Direct emission of methane and nitrous oxide from switchgrass and corn stover: implications for large-scale biomass storage.

Little is known about the contributions of biomass feedstock storage to the net greenhouse gas emissions from cellulosic biofuels. Direct emissions of methane and nitrous oxide during decomposition in storage may contribute substantially to the global warming potential of biofuels. In this study, laboratory‐scale bales of switchgrass and corn stover were stored under a range of moisture (13.0–32.9%) and temperature (5–35 °C) conditions and monitored for O2 consumption and CO2, CH4, and N2O production over 8 weeks. Gas concentrations and emissions rates were highly variable within and between experimental groups. Stover bales produced higher CO2 concentrations (P = 0.0002) and lower O2 (P < 0.0001) during storage than switchgrass bales. Methane concentrations (1.8–2100 ppm) were inversely correlated with bale moisture (P < 0.05), with emissions rates ranging from 4.4–914.9 μg kg−1 DM day−1. Nitrous oxide concentrations ranged from 0 to 31 ppm, and emissions from switchgrass bales inversely correlated with temperature and moisture (P < 0.0001). Net global warming potential from each treatment (0–2.4 gCO2e kg−1 DM) suggests that direct emission of methane and nitrous oxide from aerobically stored feedstocks have a small effect on net global warming potential of cellulosic biofuels.

Evaluating the Potential of Marginal Land for Cellulosic Feedstock Production and Carbon Sequestration in the United States

Land availability for growing feedstocks at scale is a crucial concern for the bioenergy industry. Feedstock production on land not well-suited to growing conventional crops, or marginal land, is often promoted as ideal, although there is a poor understanding of the qualities, quantity, and distribution of marginal lands in the United States. We examine the spatial distribution of land complying with several key marginal land definitions at the United States county, agro-ecological zone, and national scales, and compare the ability of both marginal land and land cover data sets to identify regions for feedstock production. We conclude that very few land parcels comply with multiple definitions of marginal land. Furthermore, to examine possible carbon-flow implications of feedstock production on land that could be considered marginal per multiple definitions, we model soil carbon changes upon transitions from marginal cropland, grassland, and cropland-pastureland to switchgrass production for three marginal land-rich counties. Our findings suggest that total soil organic carbon changes per county are small, and generally positive, and can influence life-cycle greenhouse gas emissions of switchgrass ethanol.

Grassland soil microbial respiration responses to urea and litter applications

Abstract Ground ryegrass (Lolium perenne L., 5300 kg C ha‐1, 12 g C kg‐1 (soil)) and urea were applied to a grassland soil with the same dose of nitrogen (N), 500 kg N ha‐1, 1.1 g N kg‐1 soil, and microbial respiration responses measured in the laboratory. Microbial respiration rate in control, ryegrass‐ and urea‐amended soil averaged 2.1 ± 0.2, 25.0 ± 1.7 and 10.6 ± 0.7 μg CO2 kg‐1 soil s‐1, 1.5 h after treatment applications. Microbial respiration rates in ryegrass‐ and urea‐amended soil were significantly greater than the controls for 17 and 6 days, respectively (P = 0.05), after treatment application. Integrated over the 24‐day‐long study, microbial respiration in ryegrass‐ and urea‐amended soil increased 9.9 and 0.2 g CO2 kg‐1 soil over the controls, excluding CO2 production by carbonate hydrolysis. After ryegrass application, a multi‐component, time‐response model fitted the data well including rapid and, 2 days later, delayed, up‐regulation responses of the microbial community followed by a protracted asymptote.

Synapses on demand require dendrites at the ready: How defining stages of dendritic development in vitro could inform studies of behaviorally driven information storage in the brain

Bill Greenoughs work provides a framework for thinking about synaptogenesis not only as a key step in the initial wiring of neural systems according to a species typical plan (i.e., experience-expectant development), but also as a mechanism for storing information based an individuals unique experience over its lifetime (i.e., experience-dependent plasticity). Analysis of synaptic development in vitro brings a new opportunity to test the limits of expectant-expectant development at the level of the individual neuron. We analyzed dendritic growth, synapse formation, and the development of specialized cytoplasmic microdomains during development in cultured hippocampal neurons, to determine if the timing of each of these events is correlated. Taken together, the findings reported here support the hypotheses that (1) dendritic development is rate limiting in synapse formation and (2) synaptic circuits are assembled in a step-wise fashion consistent with a stage-specific shift from genomically pre-programmed to activity-dependent mechanisms.

Without animals, US farmers would reduce feed crop production

In “Nutritional and greenhouse gas impacts of removing animals from US agriculture,” White and Hall (1) imagine a future without animal agriculture but fail to address perhaps the single most influential aspect of livestock on US agriculture: land use for feed crops. The authors unrealistically assume that without livestock, Americans would continue to grow … [↵][1]1Email: isaace{at}gfi.org. [1]: #xref-corresp-1-1

Life cycle assessment of drop-in biofuels from prairie cordgrass

Abstract. This study uses the life cycle assessment framework to compare the effects on human health and the environment of drop-in biofuels produced from switchgrass and prairie cordgrass using a variety of low-input farming methods. Biofuel scenarios were developed using experimental data from South Dakota State Universitys Felt Farm, pretreatment and biomass conversion testing through South Dakota State University, and process models of biomass catalytic fast pyrolysis to biogasoline and biodiesel from the National Renewable Energy Laboratory. In particular, we examined the influence of low-input cropping systems, biomass densification and pretreatment (such as pelleting and AFEX) at regional biomass preprocessing depots, and transportation distance on net greenhouse gas emissions, human health, and ecotoxicity. Results show that greenhouse gas emissions from biogasoline from catalytic fast pyrolysis of prairie grasses provide emissions reductions of up to 80% compared to fossil fuels, though the extent of emissions reductions vary greatly by scenario. Biomass pretreatment and preprocessing steps, particularly drying biomass prior to catalytic fast pyrolysis, can have large contributions to net greenhouse gas emissions. Notably, differences in biomass composition between crop species could play a large role in the energy requirements, fuel yield, and carbon balance of catalytic fast pyrolysis. We conclude that biogasoline from both prairie cordgrass and switchgrass has potential to provide substantial emissions reductions. Catalytic fast pyrolysis is the primary contributor to human health and ecotoxicity metrics. This conversion process, for which little data is available, should be a key target for improved modeling of environmental outcomes from drop-in biofuels.

Lettuce to Reduce Greenhouse Gases: A Comparative Life Cycle Assessment of Conventional and Community Agriculture

One of the most frequently touted benefits of community gardens and the local food movement is the potential to reduce greenhouse gas emissions through local low input production. Commercially grown foods, grown as monocultures on large acreage typically require large inputs of fertilizers, water and pesticides along with long transport distances and refrigerated storage to reach consumers. What impact can we have when labor, water, and nutrients are supplied locally? To evaluate this, we used life cycle assessment to compare the greenhouse gas emissions of supplying lettuce to customers in Seattle with either conventionally grown lettuce from central California or with lettuce grown in a community garden (Figs. 1 and 2).