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Alan Daugherty

Publications and source records attributed to Alan Daugherty.

51 records · Page 3Linked to original sources
PubMed2003

Differential effects of doxycycline, a broad-spectrum matrix metalloproteinase inhibitor, on angiotensin II-induced atherosclerosis and abdominal aortic aneurysms.

OBJECTIVE: Angiotensin II (AngII) infusion into hyperlipidemic mice leads to the rapid formation of atherosclerotic lesions and abdominal aortic aneurysms (AAAs). To define the role of matrix metalloproteinases (MMPs) in the development of these vascular pathologies, we administered the broad-spectrum MMP inhibitor doxycycline to saline- and AngII-infused LDL receptor-/- mice. METHODS AND RESULTS: Mice were placed on a high-fat diet for 1 week before infusion with either saline or AngII (1000 ng x kg(-1) x min(-1)) via osmotic pumps for 28 days. Doxycycline (30 mg x kg(-1) x d(-1)) was administered in the drinking water to both saline- and AngII-infused mice. Administration of doxycycline did not significantly influence systolic blood pressure, serum cholesterol concentrations, or lipoprotein-cholesterol distribution. Doxycycline had no effect on the extent of atherosclerosis in saline- or AngII-infused mice. In contrast, doxycycline markedly reduced the incidence of AAA formation (86% vs 35%, AngII vs AngII+doxycycline, respectively; P<0.05), in addition to reducing aneurysm severity. CONCLUSIONS: These data do not imply a role for MMPs in AngII-induced atherosclerosis but provide evidence consistent with a role in AngII-induced AAA formation.

Angiotensin II↗
PubMed2003

Thalidomide inhibits early atherogenesis in apoE-deficient mice.

Inflammation is present in all stages of atherosclerosis, from fatty streaks to rupture of mature plaques. Tumour necrosis factor (TNF)-alpha is expressed in atherosclerotic lesions but its role in atherogenesis has not been defined. To clarify the role of this cytokine, we administered thalidomide, a compound known to inhibit TNF-alpha production, to homozygous apolipoprotein E-deficient (apoE-/-) mice in order to examine the effect of thalidomide on the development of early atherosclerotic lesions. Twelve apoE-/- mice were randomized to receive either sustained-release thalidomide or placebo pellets implanted subcutaneously, and the amount of atherosclerosis was quantified six weeks later. Thalidomide was well tolerated and did not result in any changes in body weight. Mice treated with thalidomide had significantly smaller mean (7986 +/- 5189 vs 19607 +/- 10353 microns 2, p = 0.05) and maximum (15800 [12777-23675] vs 37169 [28000-41351] microns 2, p = 0.03) lesion sizes than those treated with placebo. Thus, thalidomide is capable of inhibiting the early development of atherosclerosis, presumably by inhibition of TNF-alpha secretion.

Animals↗
PubMed2002

Proinflammatory properties of coplanar PCBs: in vitro and in vivo evidence.

So-called coplanar polychlorinated biphenyls (PCBs), as well as other environmental contaminants that are aryl hydrocarbon receptor (AhR) agonists, may compromise the normal functions of vascular endothelial cells by activating oxidative stress-sensitive signaling pathways and subsequent proinflammatory events critical in the pathology of atherosclerosis and cardiovascular disease. To test this hypothesis, porcine endothelial cells were exposed to PCB 153 and to three coplanar PCBs (PCB 77, PCB 126, or PCB 169). In contrast to PCB 153, which is not a ligand for the Ah receptor (AhR), all coplanar PCBs disrupted endothelial barrier function. All coplanar PCBs increased expression of the CYP1A1 gene, oxidative stress (DCF fluorescence), and the DNA-binding activity of nuclear factor kappaB (NF-kappaB). PCB-induced oxidative stress was concentration-dependent, with PCB 126 exhibiting a maximal response at the lowest concentration (0.5 microM) tested. The increase in NF-kappaB-dependent transcriptional activity was confirmed in endothelial cells by a luciferase reporter gene assay. In contrast to PCB 153, coplanar PCBs that are AhR ligands increased endothelial production of interleukin-6. At 3.4 microM, expression of the adhesion molecule VCAM-1 was most sensitive to PCB 77 and 169. We also provide in vivo evidence, suggesting that binding to the AhR is critical for the proinflammatory properties of PCBs. Twenty hours after a single administration of PCB 77, VCAM-1 expression was increased only in wild-type mice, while mice lacking the AhR gene showed no increased staining for VCAM-1. These data provide evidence that coplanar PCBs, agonists for the AhR, and inducers of cytochrome P450 1A1, produce oxidative stress and an inflammatory response in vascular endothelial cells. An intact AhR may be necessary for the observed PCB-induced responses. These findings suggest that activation of the AhR can be an underlying mechanism of atherosclerosis mediated by certain environmental contaminants.

Animals↗
PubMed2002

Interleukin-4 deficiency decreases atherosclerotic lesion formation in a site-specific manner in female LDL receptor-/- mice.

Activated lymphocytes and mast cells have been detected in human atherosclerotic lesions. Interleukin-4 (IL-4) is a prominent cytokine released during the activation of both these cell types, and its mRNA has been detected in human and mouse atherosclerotic lesions. To define the effects of IL-4 on atherogenesis, bone marrow stem cells from either IL-4-/- or IL-4+/+ mice were transplanted into lethally irradiated female low density lipoprotein (LDL) receptor-/- mice. After an interval sufficient to allow engraftment, mice were placed on a diet containing 21% saturated fat, 1.25% cholesterol, and 0.5% cholate. Hematopoietic engraftment was confirmed by the presence of the LDL receptor gene in bone marrow cells. The effect on IL-4 depletion was confirmed by quantifying cytokine release from splenocytes of reconstituted mice. The deficiency of IL-4 in bone marrow-derived cells had no effect on serum cholesterol concentrations or on the distribution of cholesterol among lipoproteins. Atherosclerotic lesion formation was not changed in the aortic root. However, deficiency of IL-4 led to reduced lesion size in the arch (9.1 +/- 1.1% versus 2.8 +/- 0.8% of intimal area, P<0.001) and the thoracic aorta (1.2 +/- 0.2% versus 0.4 +/- 0.1%, P<0.002). Therefore, IL-4 deficiency reduced atherosclerotic lesion formation in a site-specific manner in female LDL receptor-/- mice fed a high-fat diet.

Animals↗
PubMed2002

Interleukin-18 enhances atherosclerosis in apolipoprotein E(-/-) mice through release of interferon-gamma.

We have previously shown that interferon-gamma (IFN-gamma) is a potent enhancer of atherogenesis. Interleukin-18 (IL-18) promotes inflammatory responses through release of IFN-gamma, although it can also exert direct actions on other inflammatory mediators. In this present study, we determined the effects of IL-18 on atherogenesis and the role of IFN-gamma in this response. Male apolipoprotein E(-/-) mice (apoE(-/-); aged 16 weeks, n=10/group) were fed a normal diet and injected intraperitoneally for 30 days with either recombinant IL-18 (30 ng/g/day) or saline. Atherosclerotic lesion size was quantified in 2 vascular beds: the ascending aorta and the aortic arch. IL-18 administration did not affect serum cholesterol concentrations or lipoprotein-cholesterol distribution; however, exogenous IL-18 administration increased lesion size 2-fold in both the ascending aorta (50 642 +/- 12 515 versus 112 399 +/- 13 227 microm(2) P=0.004; saline versus IL-18 groups, respectively) and the aortic arch (3.1 +/- 0.3% versus 6.2 +/- 0.9% area, P=0.006). Exogenous IL-18 promoted a 4-fold increase in the number of lesion-associated T lymphocytes (11 +/- 3 versus 50 +/- 5 cells; P<0.0001) and cells expressing major histocompatability complex class II (9 +/- 3 versus 40 +/- 6 cells; P=0.0002). To determine the role of IFN-gamma production in this response, exogenous IL-18 was administered to apoE(-/-) mice that were IFN-gamma deficient. These studies demonstrated that lack of endogenous IFN-gamma ablated the effects of IL-18 on atherosclerosis. Therefore, these data strongly implicates IL-18 in the atherogenic process and suggests that IL-18 increases lesion development through enhancement of an inflammatory response involving an IFN-gamma-dependent mechanism. The full text of this article is available at http://www.circresaha.org.

Animals↗
PubMed2002

Mechanisms of abdominal aortic aneurysm formation.

Abdominal aortic aneurysms (AAA) are permanent dilations in the infra-renal area in which the arterial tissue is characterized by inflammation and medial degeneration. AAAs are a common vascular disorder and cause significant mortality in the aged population. Despite the high prevalence of this disease, there is limited knowledge on the mechanisms responsible for the vascular pathology. Therefore, current therapeutic options are restricted to surgical intervention and are predicated on the assumed propensity for rupture as the vessel enlarges. Current research focuses on inflammatory processes and their role in proteolytic degradation of the elastin and collagen fibers of the vessel wall. Definition of specific mechanisms would identify target sites for potential pharmacologic intervention and markedly improve the medical treatment and prognosis of AAA.

Aorta, Abdominal↗
PubMed2002

IFN-gamma deficiency exerts gender-specific effects on atherogenesis in apolipoprotein E-/- mice.

We have shown recently that administration of exogenous interferon-gamma (IFN-gamma) to apolipoprotein E (apoE)(-/-) mice augmented atherogenesis. In the present study, we examined whether deficiency of endogenous IFN-gamma would reduce atherosclerosis in apoE(-/-) mice. Compound-deficient mice were generated by crossing strain-matched IFN-gamma(-/-) and apoE(-/-) mice and comparing them to apoE(-/-) mice. Groups of both genders were fed either a normal or a high-fat diet. IFN-gamma deficiency did not affect serum cholesterol concentrations or lipoprotein-cholesterol distributions in any groups. IFN-gamma deficiency had no effect on serum triglyceride concentrations, except for an increase noted in males fed a normal diet. The extent of atherosclerosis was determined in tissue sections of the ascending aorta and on the surface of the aortic arch. During feeding of normal diets, IFN-gamma deficiency had no effect on the extent of atherosclerosis in female mice in either vascular bed. In contrast, in male mice fed normal diet, IFN-gamma deficiency markedly decreased lesion size in both vascular beds. During feeding of high-fat diets, IFN-gamma deficiency also had no effect on lesion size in females but profoundly decreased lesion size in the aortic root of male mice. IFN-gamma deficiency had no effect on the abundance of T lymphocytes or MHC class II-positive cells in aortic root lesions of females. By comparison, both these parameters were reduced in lesions of male mice. Therefore, IFN-gamma deficiency decreased atherogenesis, potentially by decreasing T lymphocyte presence and cell activation, without influencing serum cholesterol concentrations. However, this effect is strikingly restricted to male mice.

Animals↗
PubMed2002

Mouse models of atherosclerosis.

Atherosclerosis is a complex disease in which progressive cellular changes occur for decades before the acute manifestation of cardiovascular disease. Definition of atherogenic mechanisms in humans is hindered by the complexity and chronicity of the disease process, combined with the inability to sequentially characterize lesions in an individual patient because of shortcomings in noninvasive detection modalities. Therefore, there has been a reliance on animal models of the disease to define mechanistic pathways. Over the last decade, the mouse has become the predominant species used to create models of atherosclerosis. The initial interest was based on the great diversity of inbred strains with defined genetic backgrounds that provides a means of linking genes to the development of atherosclerosis. More recently, the ability to genetically modify mice to over or under express specific genes has facilitated the definition of pathways in the atherogenic process. All of the current mouse models of atherosclerosis are based on perturbations of lipoprotein metabolism through dietary and/or genetic manipulations. Although hyperlipidemia is necessary for the development of atherosclerosis, mouse models have demonstrated that many nonlipid factors can influence the severity and characteristics of lesions. This review selectively highlights some of the most commonly used mouse models of atherosclerosis and compare their lesions to those formed in the human disease.

Animals↗
PubMed2002

Abdominal aortic aneurysms: fresh insights from a novel animal model of the disease.

Abdominal aortic aneurysms (AAA) have a high prevalence in aged populations and are responsible for a large number of deaths. Despite the widespread nature of the disease, relatively little is known regarding mechanisms for formation and progression of aortic aneurysms. In part, this lack of knowledge is attributable to a paucity of animal models for this disease. This review summarizes the available animal models of AAA and focuses on a novel model of reproducible AAA generated by infusion of angiotensin II (AngII) into mice rendered hyperlipidemic by the absence of either apolipoprotein E or low-density lipoprotein receptors. AAA generated by AngII infusion have many characteristics of the human disease including marked luminal expansions, perimedial remodeling, inflammation, thrombosis and a link to hyperlipidemia. As in the human disease, male mice are more susceptible to the development of AAA than females. The vascular pathology occurs from the effects of AngII at AT1 receptors present on bone marrow-derived cells. Studies are ongoing to define the mediators responsible for AngII-induced inflammation and degradation of the medial layer of the vascular wall. The AngII-induced model of AAA has the potential to provide novel insights into the underlying mechanisms of this disease and assist with the development of pharmacological therapies.

Age Factors↗
PubMed2002

Overexpression of SR-BI by adenoviral vector promotes clearance of apoA-I, but not apoB, in human apoB transgenic mice.

Scavenger receptor BI (SR-BI) is a multi-ligand lipoprotein receptor that mediates selective lipid uptake from HDL, and plays a central role in hepatic HDL metabolism. In this report, we investigated the extent to which SR-BI selective lipid uptake contributes to LDL metabolism. As has been reported for human LDL, mouse SR-BI expressed in transfected cells mediated selective lipid uptake from mouse LDL. However, LDL-cholesteryl oleoyl ester (CE) transfer relative to LDL-CE bound to the cell surface (fractional transfer) was approximately 18-fold lower compared with HDL-CE. Adenoviral vector-mediated SR-BI overexpression in livers of human apoB transgenic mice ( approximately 10-fold increased expression) reduced plasma HDL-cholesterol (HDL-C) and apolipoprotein (apo)A-I concentrations to nearly undetectable levels 3 days after adenovirus infusion. Increased hepatic SR-BI expression resulted in only a modest depletion in LDL-C that was restricted to large LDL particles, and no change in steady-state concentrations of human apoB. Kinetic studies showed a 19% increase in the clearance rate of LDL-CE in mice with increased SR-BI expression, but no change in LDL apolipoprotein clearance. Quantification of hepatic uptake of LDL-CE and LDL-apolipoprotein showed selective uptake of LDL-CE in livers of human apo B transgenic mice. However, such uptake was not significantly increased in mice over-expressing SR-BI. We conclude that SR-BI-mediated selective uptake from LDL plays a minor role in LDL metabolism in vivo.

Adenoviridae↗
PubMed2002

Interleukin-4 deficiency promotes gallstone formation.

Feeding interleukin-4 (IL-4) deficient C57BL/6 LDL receptor (LDLr)(-/-) mice a modified diet to investigate the role of this cytokine in cholesterol metabolism led to an unexpected phenotype. IL-4(-/-) --> LDLr(-/-) mice had enlarged gallbladders and an increased mortality that was preceded by acute body weight loss. To determine if IL-4 deficiency accounted for these findings, C57BL/6 IL-4(+/+) and IL-4(-/-) mice were fed either a normal or modified diet. IL-4 deficiency did not alter bile composition or cause liver toxicity in mice fed a fat-enriched diet. Following 8 weeks of feeding a fat-enriched diet, no gallstones were detected in IL-4(+/+) mice, and only 20% had cholesterol crystals. In contrast, IL-4(-/-) mice had a 100% incidence of gallstones and cholesterol crystals. IL-4(-/-) deficiency also increased serum concentrations of bilirubin following feeding a fat-enriched diet. Therefore, these studies revealed an unexpected finding that IL-4 deficiency predisposes to gallstone formation.

Alanine Transaminase↗
PubMed2002

Macrophage-specific expression of class A scavenger receptors in LDL receptor(-/-) mice decreases atherosclerosis and changes spleen morphology.

Class A scavenger receptors (SR-A) have been implicated in the atherogenic process, although there have been conflicting reports as to their specific effect on the development of lesions. In part, this discord may arise because of the variable contribution of SR-A in the several cell types known to express this protein. To determine the effects of macrophage-specific SR-A expression in the atherogenic process, transgenic mice were created using the chicken lysozyme (lyso) promoter to drive expression of bovine SR-A (bSR-A). To express this gene in an atherosclerosis-susceptible strain, bone marrow cells from transgenic and non-transgenic littermates were used to repopulate lethally-irradiated female LDL receptor (LDLr)(-/-) mice. Following hematopoietic engraftment, mice were placed on a diet enriched in saturated fat and cholesterol. After 8 weeks, there was a modest, but statistically significant reduction in serum total cholesterol in LDLr(-/-) mice repopulated with lyso-bSR-A transgenic cells, due to decreased LDL-cholesterol. The extent of atherosclerosis was reduced in both cross-sectional analysis of the aortic root and en face analysis of the intimal surface of the aortic arch. In addition to changes in atherosclerosis, lyso-bSR-A repopulated LDLr(-/-) mice had a marked increase (3.6x) in spleen weights and a disruption of spleen white pulp formation. Therefore, macrophage-specific overexpression of SR-A resulted in reduced atherosclerosis in two vascular beds, reduced serum cholesterol concentrations, and changed the morphology of the spleen.

Animals↗