The effects of second-hand smoke on biological processes important in atherogenesis

BACKGROUND: Atherosclerosis is the leading cause of death in western societies and cigarette smoke is among the factors that strongly contribute to the development of this disease. The early events in atherogenesis are stimulated on the one hand by cytokines that chemoattract leukocytes and on the other hand by decrease in circulating molecules that protect endothelial cells (ECs) from injury. Here we focus our studies on the effects of "second-hand" smoke on atherogenesis. METHODS: To perform these studies, a smoking system that closely simulates exposure of humans to second-hand smoke was developed and a mouse model system transgenic for human apoB(100 )was used. These mice have moderate lipid levels that closely mimic human conditions that lead to atherosclerotic plaque formation. RESULTS: "Second-hand" cigarette smoke decreases plasma high density lipoprotein levels in the blood and also decreases the ratios between high density lipoprotein and low density lipoprotein, high density lipoprotein and triglyceride, and high density lipoprotein and total cholesterol. This change in lipid profiles causes not only more lipid accumulation in the aorta but also lipid deposition in many of the smaller vessels of the heart and in hepatocytes. In addition, mice exposed to smoke have increased levels of Monocyte Chemoattractant Protein–1 in circulation and in the heart/aorta tissue, have increased macrophages in the arterial walls, and have decreased levels of adiponectin, an EC-protective protein. Also, cytokine arrays revealed that mice exposed to smoke do not undergo the switch from the pro-inflammatory cytokine profile (that develops when the mice are initially exposed to second-hand smoke) to the adaptive response. Furthermore, triglyceride levels increase significantly in the liver of smoke-exposed mice. CONCLUSION: Long-term exposure to "second-hand" smoke creates a state of permanent inflammation and an imbalance in the lipid profile that leads to lipid accumulation in the liver and in the blood vessels of the heart and aorta. The former potentially can lead to non-alcoholic fatty liver disease and the latter to heart attacks

Heat Shock Proteins and Amateur Chaperones in Amyloid-Beta Accumulation and Clearance in Alzheimer’s Disease

The pathologic lesions of Alzheimer’s disease (AD) are characterized by accumulation of protein aggregates consisting of intracellular or extracellular misfolded proteins. The amyloid-β (Aβ) protein accumulates extracellularly in senile plaques and cerebral amyloid angiopathy, whereas the hyperphosphorylated tau protein accumulates intracellularly as neurofibrillary tangles. “Professional chaperones”, such as the heat shock protein family, have a function in the prevention of protein misfolding and subsequent aggregation. “Amateur” chaperones, such as apolipoproteins and heparan sulfate proteoglycans, bind amyloidogenic proteins and may affect their aggregation process. Professional and amateur chaperones not only colocalize with the pathological lesions of AD, but may also be involved in conformational changes of Aβ, and in the clearance of Aβ from the brain via phagocytosis or active transport across the blood–brain barrier. Thus, both professional and amateur chaperones may be involved in the aggregation, accumulation, persistence, and clearance of Aβ and tau and in other Aβ-associated reactions such as inflammation associated with AD lesions, and may, therefore, serve as potential targets for therapeutic intervention

Uptake of chemically modified low density lipoproteins in vivo is mediated by specific endothelial cells

ABSTRACT Acetoacetylated (AcAc) and acetylated (Ac) low density lipoproteins (LDL) are rapidly cleared from the plasma (t,/2 ~ 1 min). Because macrophages, Kupffer cells, and to a lesser extent, endothelial cells metabolize these modified lipoproteins in vitro, it was of interest to determine whether endothelial cells or macrophages could be responsible for the in vivo uptake of these lipoproteins. As previously reported, the liver is the predominant site of the uptake of AcAc LDL; however, we have found that the spleen, bone marrow, adrenal, and ovary also participate in this rapid clearance. A histological examination of tissue sections, undertaken after the administration of AcAc LDL or Ac LDL (labeled with either ~2Sl or a fluorescent probe) to rats, dogs, or guinea pigs, was used to identify the specific cells binding and internalizing these lipoproteins in vivo. With both techniques, the sinusoidal endothelial cells of the liver, spleen, bone marrow, and adrenal were labeled. Less labeling was noted in the ovarian endothelia. Uptake of AcAc LDL by endothelial cells of the liver, spleen, and bone marrow was confirmed by transmission electron microscopy. These data suggest uptake through coated pits. Uptake of AcAc LDL was not observed in the endothelia of arteries (including the coronaries and aorta), veins, or capillaries of the heart, testes, kidney, brain

Formation of Factor Va by Atherosclerotic Rabbit Aorta Mediates Factor Xa-catalyzed Prothrombin Activation

Vascular cell procoagulant activity may be important in the pathogenesis of atherosclerosis. In previous studies, we described the ability of the atherogenic metabolite homocysteine to activate endothelial cell Factor V, a key coagulation cofactor for thrombin generation. The present study was designed to investigate Factor V activity and Factor X.-catalyzed prothrombin activation by control and atherosclerotic aorta from normal and hypercholesterolemic rabbits. Factor X. generated ninefold more thrombin on atherosclerotic aortic segments than on control segments. Atherosclerotic segments activated '25I-prothrombin with Factor X. in the presence of the thrombin inhibitor dansyl arginine4-ethylpiperidine amide and cleaved 125I-Factor V. This suggests that increases in vessel-wall Factor V activity and Factor X.-catalyzed prothrombin activation result from activation of vessel-wall Factor V. 125I_ Factor V. peptides generated by atherosclerotic aorta were very similar in molecular weight to those generated by homocysteine-treated cells. When vascular endothelium was mechanically removed by brushing, atherosclerotic vessels still generated four- to fivefold more thrombin than control vessels. These data and results from immunocytochemical studies suggest that Factor V in atherosclerotic vessels is associated with both endothelium and other cells of the lesion. In contrast, Factor V in control vessels is associated primarily with endothelium. The increases in Factor V activity and thrombin formation in the blood vessel wall of hypercholesterolemic rabbits may contribute to the development of atherosclerosis and its complications

Expression of human apolipoprotein E3 or E4 in the brains of ApoE�/� mice: isoformspecific effects on neurodegeneration

Apolipoprotein (apo) E isoforms are key determinants of susceptibility to Alzheimer’s disease. The apoE4 isoform is the major known genetic risk factor for this disease and is also associated with poor outcome after acute head trauma or stroke. To test the hypothesis that apoE3, but not apoE4, protects against age-related and excitotoxin-induced neurodegeneration, we analyzed apoE knockout (Apoe �/ � ) mice expressing similar levels of human apoE3 or apoE4 in the brain under control of the neuron-specific enolase promoter. Neuronal apoE expression was widespread in the brains of these mice. Kainic acid-challenged wild-type or Apoe �/ � mice had a significant loss of synaptophysin-positive presynaptic terminals and microtubule-associated protein 2-positive neuronal dendrites in the neocortex and hippocampus, and a disruption of neurofilament-positive axons in the hippocampus. Expression of apoE3, but not of apoE4, protected against this excitotoxininduced neuronal damage. ApoE3, but not apoE4, also protected against the age-dependent neurodegeneration seen in Apoe �/ � mice. These differences in the effects of apoE isoforms on neuronal integrity may relate to the increased risk of Alzheimer’s disease and to the poor outcome after head trauma and stroke associated with apoE4 in humans. Key words: apolipoprotein E; Alzheimer’s disease; apoE transgenic mice; excitotoxicity; apoE knockout mice; neurodegeneration Apolipoprotein (apo) E is a 34 kDa protein that participates in the transport of plasma lipids and in the redistribution of lipids among cells (Mahley, 1988). Of the three common apoE isoforms in humans (Utermann et al., 1977), apoE4 is a major risk factor for Alzheimer’s disease (AD) (Corder et al., 1993; Strittmatter e