59 research outputs found
High Density Lipoprotein-Binding Proteins in Liver
In one of the oldest civilizations we know, that of ancient Egypt, thoughts
about the heart reflected a certain duality. On the one hand, the heart was
associated with concepts like virtue, or soul. A central passage in the Book
of the Dead of the ancient Egyptians is the description and illustration of the
weighing of the soul (Fig. 1). The heart of the diseased was put on a pair of
scales and balanced against the hieroglyphic symbol of virtue, the feather
maat. If the ibis god of scribes, Thot, could register a favourable verdict, the
dead man or woman was presented to the god of the dead, Osiris, and was
allowed entrance into the world of the dead. If not, the heart was devoured
by a horrifying beast, which event was described as the
Regenerative medicine funding policies in Europe and The Netherlands
Stem cells & developmental biolog
Ubiquitous expression of the rtTA2S-M2 inducible system in transgenic mice driven by the human hnRNPA2B1/CBX3 CpG island
Background. A sensitive, ubiquitously expressed tetracycline inducible system would be a valuable tool in mouse transgenesis. However, this has been difficult to obtain due to position effects observed at different chromosomal sites of transgene integration, which negatively affect expression in many tissues. The aim of this study was to test the utility of a mammalian methylation-free CpG island to drive ubiquitous expression of the sensitive doxycycline (Dox) inducible rtTA2S-M2 Tet-transactivator in transgenic mice. Results. An 8 kb genomic fragment from the methylation-free CpG island of the human hnRNPA2B1-CBX3 housekeeping gene locus was tested. In a number of transgenic mouse lines obtained, rtTA2S-M2 expression was detected in many tissues examined. Characterisation of the highest expressing rtTA2S-M2 transgenic mouse line demonstrated Dox-inducible GFP transgene expression in many tissues. Using this line we also show highly sensitive quantitative induction wit
Elevation of plasma phospholipid transfer protein in transgenic mice increases VLDL secretion
Two lipid transfer proteins are active in human plasma, cholesteryl ester
transfer protein (CETP), and phospholipid transfer protein (PLTP). Mice by
nature do not express CETP. Additional inactivation of the PLTP gene
resulted in reduced secretion of VLDL and subsequently in decreased
susceptibility to diet-induced atherosclerosis. The aim of this study is
to assess possible effects of differences in PLTP expression on VLDL
secretion in mice that are proficient in CETP and PLTP. We compared human
CETP transgenic (huCETPtg) mice with mice expressing both human lipid
transfer proteins (huCETPtg/huPLTPtg). Plasma cholesterol in huCETPtg mice
was 1.5-fold higher compared with huCETPtg/huPLTPtg mice (P < 0.001). This
difference was mostly due to a lower HDL level in the huCETPtg/huPLTPtg
mice, which subsequently could lead to the somewhat decreased CETP
activity and concentration that was found in huCETPtg/huPLTPtg mice (P <
0.05). PLTP activity was 2.8-fold increased in these animals (P < 0.001).
The human PLTP concentration was 5 microg/ml. Moderate overexpression of
PLTP resulted in a 1.5-fold higher VLDL secretion compared with huCETPtg
mice (P < 0.05). The composition of nascent VLDL was similar in both
strains. These results indicate that elevated PLTP activity in huCETPtg
mice results in an increase in VLDL secretion. In addition, PLTP
overexpression decreases plasma HDL cholesterol as well as CETP
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Female resistance to pneumonia identifies lung macrophage nitric oxide synthase-3 as a therapeutic target
To identify new approaches to enhance innate immunity to bacterial pneumonia, we investigated the natural experiment of gender differences in resistance to infections. Female and estrogen-treated male mice show greater resistance to pneumococcal pneumonia, seen as greater bacterial clearance, diminished lung inflammation, and better survival. In vitro, lung macrophages from female mice and humans show better killing of ingested bacteria. Inhibitors and genetically altered mice identify a critical role for estrogen-mediated activation of lung macrophage nitric oxide synthase-3 (NOS3). Epidemiologic data show decreased hospitalization for pneumonia in women receiving estrogen or statins (known to activate NOS3). Pharmacologic targeting of NOS3 with statins or another small-molecule compound (AVE3085) enhanced macrophage bacterial killing, improved bacterial clearance, and increased host survival in both primary and secondary (post-influenza) pneumonia. The data identify a novel mechanism for host defense via NOS3 and suggest a potential therapeutic strategy to reduce secondary bacterial pneumonia after influenza. DOI: http://dx.doi.org/10.7554/eLife.03711.00
Evaluation of phospholipid transfer protein and cholesteryl ester transfer protein as contributors to the generation of pre beta-high-density lipoproteins
High-density lipoproteins (HDLs) are considered anti-atherogenic because
they mediate peripheral cell cholesterol transport to the liver for
excretion and degradation. An important step in this reverse
cholesterol-transport pathway is the uptake of cellular cholesterol by a
specific subclass of small, lipid-poor apolipoprotein A-I particles
designated pre beta-HDL. The two lipid-transfer proteins present in human
plasma, cholesteryl ester transfer protein (CETP) and phospholipid
transfer protein (PLTP), have both been implicated in the formation of pre
beta-HDL. In order to investigate the relative contribution of each of
these proteins, we used transgenic mouse models. Comparisons were made
between human CETP transgenic mice (huCETPtg), human PLTP transgenic mice
(huPLTPtg) and mice transgenic for both lipid-transfer proteins
(huCETPtg/huPLTPtg). These animals showed elevated plasma levels of CETP
activity, PLTP activity or both activities, respectively. We evaluated the
generation of pre beta-HDL in mouse plasma by immunoblotting and crossed
immuno-electrophoresis. Generation of pre beta-HDL was equal in huCETPtg
and wild-type mice. In contrast, in huPLTPtg and huCETPtg/huPLTPtg mice,
pre beta-HDL generation was 3-fold higher than in plasma from either
wild-type or huCETPtg mice. Our findings demonstrate that, of the two
plasma lipid-transfer proteins, PLTP rather than CETP is responsible for
the generation of pre beta-HDL. These data support the hypothesis of a
role for PLTP in the initial stage of reverse cholesterol transport
Human plasma phospholipid transfer protein increases the antiatherogenic potential of high density lipoproteins in transgenic mice
Plasma phospholipid transfer protein (PLTP) transfers phospholipids
between lipoprotein particles and alters high density lipoprotein (HDL)
subfraction patterns in vitro, but its physiological function is poorly
understood. Transgenic mice that overexpress human PLTP were generated.
Compared with wild-type mice, these mice show a 2.5- to 4.5-fold increase
in PLTP activity in plasma. This results in a 30% to 40% decrease of
plasma levels of HDL cholesterol. Incubation of plasma from transgenic
animals at 37 degrees C reveals a 2- to 3-fold increase in the formation
of pre-beta-HDL compared with plasma from wild-type mice. Although
pre-beta-HDL is normally a minor subfraction of HDL, it is known to be a
very efficient acceptor of peripheral cell cholesterol and a key mediator
in reverse cholesterol transport. Further experiments show that plasma
from transgenic animals is much more efficient in preventing the
accumulation of intracellular cholesterol in macrophages than plasma from
wild-type mice, despite lower total HDL concentrations. It is concluded
that PLTP can act as an antiatherogenic factor preventing cellular
cholesterol overload by generation of pre-beta-HDL
Reduction of blood pressure, plasma cholesterol, and atherosclerosis by elevated endothelial nitric oxide.
In the vascular system, nitric oxide is generated by endothelial NO synthase (eNOS). NO has pleiotropic effects, most of which are believed to be atheroprotective. Therefore, it has been argued that patients suffering from cardiovascular disease could benefit from an increase in eNOS activity. However, increased NO production can cause oxidative damage, cell toxicity, and apoptosis and hence could be atherogenic rather than beneficial. To study the in vivo effects of increased eNOS activity, we created transgenic mice overexpressing human eNOS. Aortic blood pressure was approximately 20 mm Hg lower in the transgenic mice compared with control mice because of lower systemic vascular resistance. The effects of eNOS overexpression on diet-induced atherosclerosis were studied in apolipoprotein E-deficient mice. Elevation of eNOS activity decreased blood pressure ( approximately 20 mm Hg) and plasma levels of cholesterol (approximately 17%), resulting in a reduction in atherosclerotic lesions by 40%. We conclude that an increase in eNOS activity is beneficial and provides protection against atherosclerosis
Elevation of plasma phospholipid transfer protein increases the risk of atherosclerosis despite lower apolipoprotein B-containing lipoproteins.
Plasma phospholipid transfer protein (PLTP) transfers phospholipids
between lipoproteins and mediates HDL conversion. PLTP-overexpressing mice
have increased atherosclerosis. However, mice do not express cholesteryl
ester transfer protein (CETP), which is involved in the same metabolic
pathways as PLTP. Therefore, we studied atherosclerosis in heterozygous
LDL receptor-deficient (LDLR(+/-)) mice expressing both human CETP and
human PLTP. We used two transgenic lines with moderately and highly
elevated plasma PLTP activity. In LDLR(+/-)/huCETPtg mice, cholesterol is
present in both LDL and HDL. Both are decreased in
LDLR(+/-)/huCETPtg/huPLTPtg mice (>50%). An atherogenic diet resulted in
high levels of VLDL+LDL cholesterol. PLTP expression caused a strong PLTP
dose-dependent decrease in VLDL and LDL cholesterol (-26% and -69%) and a
decrease in HDL cholesterol (-70%). Surprisingly, atherosclerosis was
increased in the two transgenic lines with moderately and highly elevated
plasma PLTP activity (1.9-fold and 4.4-fold, respectively), indicating
that the adverse effect of the reduction in plasma HDL outweighs the
beneficial effect of the reduction in apolipoprotein B (apoB)-containing
lipoproteins. The activities of the antiatherogenic enzymes paraoxonase
and platelet-activating factor acetyl hydrolase were both PLTP
dose-dependently reduced ( approximately -33% and -65%, respectively). We
conclude that expression of PLTP in this animal model results in increased
atherosclerosis in spite of reduced apoB-containing lipoproteins, by
reduction of HDL and of HDL-associated antioxidant enzyme activities
Increased risk of atherosclerosis by elevated plasma levels of phospholipid transfer protein.
Plasma phospholipid transfer protein (PLTP) is thought to be involved in
the remodeling of high density lipoproteins (HDL), which are
atheroprotective. It is also involved in the metabolism of very low
density lipoproteins (VLDL). Hence, PLTP is thought to be an important
factor in lipoprotein metabolism and the development of atherosclerosis.
We have overexpressed PLTP in mice heterozygous for the low density
lipoprotein (LDL) receptor, a model for atherosclerosis. We show that
increased PLTP activity results in a dose-dependent decrease in HDL, and a
moderate stimulation of VLDL secretion (</=1.5-fold). The mice were given
a high fat, high cholesterol diet, which resulted in hypercholesterolemia
in all animals. HDL concentrations were dramatically reduced in
PLTP-overexpressing animals when compared with LDL receptor controls,
whereas VLDL + LDL cholesterol levels were identical. Susceptibility to
atherosclerosis was increased in a PLTP dose-responsive manner. We
conclude that PLTP increases susceptibility to atherosclerosis by lowering
HDL concentrations, and therefore we suggest that an increase in PLTP is a
novel, long term risk factor for atherosclerosis in humans
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