Delia Recalde

Human Apolipoprotein A-IV Reduces Secretion of Proinflammatory Cytokines and Atherosclerotic Effects of a Chronic Infection Mimicked by Lipopolysaccharide

Objective—Expression of human apolipoprotein (h-apo) A-IV in apoE-deficient (apoE0) mice (h-apoA-IV/E0) reduces susceptibility to atherosclerosis. Chronic infection mimicked by exposure to lipopolysaccharide (LPS) increases the size of atherosclerosis lesions in apoE0 mice. Thus, we used h-apoA-IV/E0 mice to determine whether h-apoA-IV plays a protective role after LPS administration. Methods and Results—We injected apoE0, h-apoA-IV/E0, and C57Bl/6 (wild-type) mice intraperitoneally with either LPS or phosphate-buffered saline (PBS) every week for 10 weeks. Atherosclerotic lesions were significantly smaller in h-apoA-IV/E0 mice treated with LPS than in their apoE0 counterparts. The titers of IgG2a and IgG2b autoantibodies to oxidized low-density lipoprotein (LDL) were higher in the LPS-group of h-apoA-IV/E0 mice than in apoE0 mice, suggesting that the Th1 response is stronger in the presence of h-apoA-IV. Lymphocytes from the blood, liver, spleen, and thymus of h-apoA-IV/E0 mice treated with LPS produced less IL-4, INF-&ggr;, and TNF-&agr; proinflammatory cytokines than their apoE0 counterparts. Furthermore, we demonstrated that recombinant h-apoA-IV blocks the LPS-induced stimulation of monocytes. Conclusions—The expression of h-apoA-IV in apoE0 mice reduces the susceptibility to atherogenesis and decreases the secretion of proinflammatory cytokines after LPS administration.

Individual Variation of Scavenger Receptor Expression in Human Macrophages with Oxidized Low-Density Lipoprotein Is Associated with a Differential Inflammatory Response

Atherosclerosis is an inflammatory disease in which oxidized low-density lipoprotein (oxLDL) plays important roles. Scavenger receptors (SR) CD36, SR-A, and LOX-1 uptake over 90% of the oxLDL leading to foam cell formation and secretion of inflammatory cytokines. To investigate whether the interindividual differences in macrophage SR gene expression could determine the inflammatory variability in response to oxLDL, we quantified the gene and protein expression of SR and inflammatory molecules from macrophages isolated from 18 volunteer subjects and incubated with oxLDL for 1, 3, 6, and 18 h. The individual gene expression profile of the studied SR at 1 h of incubation was highly variable, showing a wide fold-change range: CD36: −3.57–4.22, SR-A: −5.0–4.43, and LOX-1: −1.56–75.32. We identified subjects as high and low responders depending on whether their SR gene expression was above or below the median, showing a different inflammation response pattern. CD36 and LOX-1 gene expression correlated positively with IL-1β; SR-A correlated negatively with IL-8 and positively with PPARγ and NF-κBΙA. These results were confirmed in the same subjects 3 mo after the first sampling. Furthermore, a negative correlation existed between CD36 and SR-A at protein level after 18 h of oxLDL incubation (R = −0.926, p = 0.024). These data would suggest that the type of SR could determine the macrophage activation: more proinflammatory when associated to CD36 and LOX-1 than when associated with SR-A.

Enhanced fractional catabolic rate of apo A-I and apo A-II in heterozygous subjects for apo A-IZaragoza (L144R)

We have recently reported a new apolipoprotein (apo) A-I variant (apo A-I(Zaragoza) L144R) in a Spanish family with HDL-C levels below the 5th percentile for age and sex and low apo A-I concentrations. All the apo A-I(Zaragoza) subjects were heterozygous and none of them showed evidence of coronary artery disease (CAD). Mean plasma HDL-C, apo A-I, and apo A-II levels were lower in apo A-I(Zaragoza) carriers as compared to control subjects (40, 60, and 50%, respectively). Lipid composition analysis revealed that apo A-I(Zaragoza) carriers had HDL particles with a higher percentage of HDL triglyceride and a lower percentage of HDL esterified cholesterol as compared to those of control subjects. Lecithin:cholesterol acyltransferase (LCAT) activity and cholesterol esterification rate of apo A-I(Zaragoza) carriers were normal. Apo A-I and apo A-II metabolic studies were performed on two heterozygous apo A-I(Zaragoza) carriers and on six control subjects. We used a primed constant infusion of [5,5,5-2H3]leucine and HDL apo A-I and apo A-II tracer/tracee ratios were determined by gas chromatography mass spectrometry and fitted to a monoexponential equation using SAAM II software. Both subjects carrying apo A-I(Zaragoza) variant showed mean apo A-I fractional catabolic rate (FCR) values more than two-fold higher than mean FCR values of their controls (0.470+/-0.0792 vs. 0.207+/-0.0635 x day(-1), respectively). Apo A-I secretion rate (SR) of apo A-I(Zaragoza) subjects was slightly increased compared with controls (17.32+/-0.226 vs. 12.76+/-3.918 mg x kg(-l) x day(-1), respectively). Apo A-II FCR was also markedly elevated in both subjects with apo A-I(Zaragoza) when compared with controls (0.366+/-0.1450 vs. 0.171+/-0.0333 x day(-1), respectively) and apo A-II SR was normal (2.31+/-0.517 vs. 2.1+/-0.684 mg x kg(-l) x day(-1), respectively). Our results show that the apo A-I(Zaragoza) variant results in heterozygosis in abnormal HDL particle composition and in enhanced catabolism of apo A-I and apo A-II without affecting significantly the secretion rates of these apolipoproteins and the LCAT activation.

Análisis de las regiones reguladoras de la expresión de apo A-I en sujetos con hipoalfalipoproteinemia

Introduccion/Objetivos La concentracion de apolipoproteina (apo) A-I esta directamente relacionada con la concentracion de colesterol ligado a HDL (cHDL) e inversamente relacionada con el riesgo de padecer enfermedad coronaria. El gen de apo A-I forma parte de la agrupacion genica A-I/C-III/A-IV, localizada en el cromosoma 11. La expresion de la proteina se encuentra regulada por una region promotora y una region exaltadora, situadas en 5’ de los genes de apo A-I y apo C-III, respectivamente. Se han descrito varios sitios polimorficos, que podrian afectar la expresion de la proteina: g.(–78)G>A, en 5’ del gen de apo A-I, g.(–636)C>A, g.(–625)G>A, g.(–620)T>del, g.(–479)C>T y g.(–452)T>C, en 5’ del gen de apo C-III; SstI, en 3’ de apo C-III Metodos Hemos analizado el genotipo de los polimorfismos y la presencia de nuevas mutaciones en las regiones reguladoras del gen de apo A-I en un grupo de 66 sujetos espanoles no relacionados con hipoalfalipoproteinemia (HALP) (cHDL Resultados Las frecuencias alelicas observadas para los polimorfismos fueron similares a las descritas en sujetos normolipemicos. Solamente se observo una asociacion significativa entre el alelo menor del polimorfismo g.(–452)T>C con concentraciones bajas de cLDL (p Conclusiones Nuestros resultados sugieren que la variabilidad genetica del promotor y exaltador del gen de apo A-I no justifica un porcentaje significativo de casos de HALP en poblacion espanola