Macrophage retinoblastoma deficiency leads to enhanced atherosclerosis development in ApoE‐deficient mice
Lianne S.M. BoestenA. Susanne M. ZadelaarAnita van NieuwkoopLihui HuJos JonkersBob van de WaterMarion J. GijbelsIngeborg van der MadeMenno P.J. de WintherLouis M. HavekesBart J.M. van VlijmenLianne S.M. BoestenA. Susanne M. ZadelaarAnita van NieuwkoopLihui HuJos JonkersBob van de WaterMarion J. GijbelsIngeborg van der MadeMenno P.J. de WintherLouis M. HavekesBart J.M. van Vlijmen
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Abstract:
The cellular composition of an atherosclerotic lesion is determined by cell infiltration, proliferation, and apoptosis. The tumor suppressor gene retinoblastoma (Rb) has been shown to regulate both cell proliferation and cell death in many cell types. To study the role of macrophage Rb in the development of atherosclerosis, we used apoE-deficient mice with a macrophage-restricted deletion of Rb (Rb(del) mice) and control littermates (Rb(fl) mice). After 12 wk feeding a cholesterol-rich diet, the Rb(del) mice showed a 51% increase in atherosclerotic lesion area with a 39% increase in the relative number of advanced lesions. Atherosclerotic lesions showed a 13% decrease in relative macrophage area and a 46% increase in relative smooth muscle cell area, reflecting the more advanced state of the lesions. The increase in atherosclerosis was independent of in vitro macrophage modified lipoprotein uptake or cytokine production. Whereas macrophage-restricted Rb deletion did not affect lesional macrophage apoptosis, a clear 2.6-fold increase in lesional macrophage proliferation was observed. These studies demonstrate that macrophage Rb is a suppressing factor in the progression of atherosclerosis by reducing macrophage proliferation.Keywords:
Retinoblastoma
Apolipoprotein E
Foam cell
Mycoepoxydiene (MED) is a polyketide that can be isolated from a marine fungus and is associated with various activities, including antitumor and anti-inflammatory functions. However, its effects on atherosclerosis remain unknown. Macrophage-derived foam cells play crucial roles in the initiation and progression of atherosclerotic plaques. In this study, we investigated the effects of MED on oxidized low-density lipoprotein (ox-LDL)-induced macrophage foam cell formation and activation, and on high fat diet (HFD)-induced atherosclerosis in ApoE-deficient (ApoE (-/-) ) mice.Our findings show that MED could significantly inhibit ox-LDL-induced macrophage foam cell formation and suppress the expression of lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1), which is a receptor for ox-LDL. Additionally, MED could significantly inhibit the secretion of proinflammatory cytokines, such as tumor necrosis factor (TNF-α), interleukin (IL)-6, and IL-1β. Mechanistically, MED inhibited NF-κB activation by blocking IκB-α degradation and reducing NF-κB DNA binding activity. Moreover, MED dramatically reduced the occurrence of HFD-induced atherosclerotic lesions in ApoE (-/-) mice.Our study shows that MED can inhibit macrophage foam cell formation and activation by inhibiting NF-κB activation, thereby protecting ApoE (-/-) mice from HFD-induced atherosclerosis. Our findings suggest that MED might be a potential lead compound for the development of antiatherosclerotic therapeutics.
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Proinflammatory cytokine
Apolipoprotein E
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Objective— Macrophage apoptosis plays important roles in atherosclerosis. Bcl-2 is a key cell survival molecule, but its role in macrophage apoptosis in atherosclerosis is not known. The goal herein was to determine the effect of macrophage-targeted deletion of Bcl-2 on macrophage apoptosis in atherosclerotic lesions of Apoe −/− mice. Methods and Results— Bcl2 flox -LysMCre mice were created as a model of macrophage Bcl-2 deficiency. Macrophages from these mice were more susceptible to apoptosis than those from control Bcl2 WT -LysMCre mice. The mice were bred onto the Apoe −/− background and fed a Western-type diet for 4 or 10 weeks. Apoptotic cells were equally very rare in the lesions of both groups of the 4-week-diet mice, and there was no difference in lesion area. However, Bcl2 flox -LysMCre;Apoe −/− plaques from the 10-week-diet protocol had a 40% to 45% increase in apoptotic cells and, in female mice, a ≈25% increase in plaque necrosis ( P <0.05) compared with Bcl2 WT -LysMCre lesions. Conclusions— Macrophage Bcl-2 plays a protective role against macrophage apoptosis specifically in advanced atherosclerotic lesions of Apoe −/− mice.
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Macrophages play crucial roles in development of atherosclerosis.The formation of foam cell marks the start of atherosclerosis.Macrophages are transformed to foam cells by the interruption of intracytoplasm lipid stabilization.During the transforming,many kinds of cytokines regulate the lipid stabilization through expression of certain enzymes or receptors,and the interaction between cytokines and macrophages.This review focuses on cytokine and macrophage lipid stabilization in recent researches.
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Type 1 diabetes (T1D) increases the risk of adverse coronary events. Among risk factors, dyslipidemia due to altered hepatic lipoprotein metabolism plays a central role in diabetic atherosclerosis. Nevertheless, the likely alterations in plasma lipid/lipoprotein profile remain unclear, especially in the context of spontaneously developed T1D and atherosclerosis. To address this question, we generated Ins2(+/Akita):apoE(-/-) mouse by cross-breeding Ins2(+/Akita) mouse (which has Ins2 gene mutation, causing pancreatic β-cell apoptosis and insulin deficiency) with apoE(-/-) mouse. Ins2(+/Akita):apoE(-/-) mice developed T1D spontaneously at 4-5 wk of age. At 25 wk of age and while on a standard chow diet, diabetic Ins2(+/Akita):apoE(-/-) mice exhibited an approximately threefold increase in atherosclerotic plaque in association with an approximatelty twofold increase in plasma non-HDL cholesterol, predominantly in the LDL fraction, compared with nondiabetic controls. To determine factors contributing to the exaggerated hypercholesterolemia, we assessed hepatic VLDL secretion and triglyceride content, expression of hepatic lipoprotein receptors, and plasma apolipoprotein composition. Diabetic Ins2(+/Akita):apoE(-/-) mice exhibited diminished VLDL secretion by ~50%, which was accompanied by blunted Akt phosphorylation in response to insulin infusion and decreased triglyceride content in the liver. Although the expression of hepatic LDL receptor was not affected, there was a significant reduction in the expression of lipolysis-stimulated lipoprotein receptor (LSR) by ~28%. Moreover, there was a marked decrease in plasma apoB-100 with a significant increase in apoB-48 and apoC-III levels. In conclusion, exaggerated hypercholesterolemia and atherosclerosis in spontaneously diabetic Ins2(+/Akita):apoE(-/-) mice may be attributable to impaired lipoprotein clearance in the setting of diminished expression of LSR and altered apolipoprotein composition of lipoproteins.
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Journal Article Hypothalamic-pituitary-adrenal activity during chronic central administration of interleukin-2 Get access U K Hanisch, U K Hanisch 1Douglas Hospital Research Center, Department of Psychiatry, Montreal, Quebec, Canada. Search for other works by this author on: Oxford Academic Google Scholar W Rowe, W Rowe 1Douglas Hospital Research Center, Department of Psychiatry, Montreal, Quebec, Canada. Search for other works by this author on: Oxford Academic Google Scholar S Sharma, S Sharma 1Douglas Hospital Research Center, Department of Psychiatry, Montreal, Quebec, Canada. Search for other works by this author on: Oxford Academic Google Scholar M J Meaney, M J Meaney 1Douglas Hospital Research Center, Department of Psychiatry, Montreal, Quebec, Canada. Search for other works by this author on: Oxford Academic Google Scholar R Quirion R Quirion 1Douglas Hospital Research Center, Department of Psychiatry, Montreal, Quebec, Canada. Search for other works by this author on: Oxford Academic Google Scholar Endocrinology, Volume 135, Issue 6, 1 December 1994, Pages 2465–2472, https://doi.org/10.1210/endo.135.6.7988433 Published: 01 December 1994
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The effects of lesion of the hypothalamic paraventricular nuclei (PVNx), the main thyrotrophic area, on the cold‐stimulated thyrotropin (TSH) responses to intracerebroventricular (i. c. v.) 5‐HT were studied in male rats. PVNx significantly attenuated the cold‐stimulated TSH levels, but significantly affected neither hypothalamic thyrotropin‐releasing hormone nor somatostatin content. Serum T 3 levels were significantly decreased 8 days after PVNx. Irrespective of the lesion (sham or PVNx), 5‐HT infusion (9 μg per rat) into the posterior third ventricle attenuated markedly the cold‐stimulated TSH levels, whereas infusion into the anterior third ventricle did not. Bilateral 5‐HT infusions (2 μg per side) into the hypothalamic dorsomedial nuclei significantly decreased serum TSH, but bilateral infusions into the posterior hypothalamic nuclei were without effect. Sham‐lesion and PVNx decreased serum prolactin levels without affecting the stimulation of prolactin secretion by i. c. v. 5‐HT. These results suggest that the inhibitory effect of i. c. v. 5‐HT on TSH secretion and its stimulatory action on prolactin secretion are only partially dependent on the PVN.
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The cytokine interleukin-2 (IL-2) exerts numerous effects within the immune as well as the central nervous system and is thought to serve as a humoral signal in their communication. Brain-derived or blood-borne IL-2 may also control the activity of the hypothalamic-pituitary-adrenal (HPA) axis at various levels of regulation. In this study we investigated whether persistently elevated levels of central IL-2, which are associated with several diseases or induced during immunotherapeutic use of this cytokine, could induce long term activation of the HPA axis. Adult male Sprague-Dawley rats received an intracerebroventricular infusion of the recombinant cytokine at a rate of 5 U/h (equivalent to 2.5 ng/h or 162 fmol/h) by means of osmotic minipumps. Control animals received heat-inactivated IL-2. After 7 days of continuous infusion, blood samples were taken at intervals of 4 h over a period of 24 h, and plasma levels of ACTH and corticosterone (CORT) were determined. IL-2 caused a significant increase in ACTH levels during the later portion of the dark phase of the cycle. Plasma CORT concentrations were significantly elevated over almost the whole diurnal cycle. Measurements of CORT-binding globulin concentrations revealed IL-2-induced decreases during the dark phase, resulting in a marked increase in free CORT. Additionally, after 11 days of chronic infusion, both groups of animals underwent a 20-min restraint stress. IL-2-treated animals showed stress-induced increases in plasma ACTH and CORT that were not significantly different from those of animals treated with heat-inactivated IL-2. Along with the alteration of HPA activity seen in the IL-2-treated animals, chronic delivery of the cytokine caused periventricular tissue damage and gliosis. Taken together, the data reflect the capacity of IL-2 to modulate neuroendocrine activity over an extended period of treatment. Moreover, the IL-2-induced effects on HPA activity seen here may help to explain some of the endocrine disturbances seen in patients undergoing IL-2 immunotherapy.
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Low-normal thyroid function within the euthyroid range may confer higher plasma triglycerides, but relationships with plasma apolipoprotein (apo) E, which plays an important role in the metabolism of triglyceride-rich apoB-containing lipoproteins, are unknown. We determined relationships of plasma apoE with thyroid stimulating hormone (TSH) and free thyroxine (free T4) in euthyroid subjects with and without Type 2 diabetes mellitus (T2DM). TSH, free T4, lipids, and apoE were measured in fasting plasma from 72 T2DM subjects and 82 nondiabetic subjects. The APOE genotype was also determined. Free T4 was slightly higher in T2DM (p=0.030), but TSH levels were not different vs. nondiabetic subjects. The APOE genotype distribution was not different between the groups. None of the participants had the ε2/ε2 genotype. Plasma triglycerides were higher in T2DM (p=0.037). ApoB and apoE levels were not different between the groups. In all subjects combined, multivariable analysis showed that plasma triglycerides (p=0.039), non-high density lipoprotein (non-HDL) cholesterol (p=0.030), and apoE levels (p=0.002) were each independently and positively associated with TSH after adjustment for age, sex, T2DM and the presence of the APOE ε3 allele. Furthermore, the associations of TSH with apoE remained present after adjustment for either triglycerides, non-HDL cholesterol, or apoB (p=0.005 to 0.023). The presence of T2DM did not modify the relationships of TSH with these (apo) lipoprotein variables (p=0.11 to 0.36). In conclusion, low-normal thyroid function, as indicated by higher TSH levels within the euthyroid range, may influence the metabolism of triglyceride-rich lipoproteins by affecting apoE regulation.
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Hypophysectomy of female rats has been shown to decrease the serum levels of apolipoprotein E (apoE). Continuous but not intermittent administration of GH to hypophysectomized (HX) rats increases these levels to those of normal rats, indicating that the sexually dimorphic secretion of GH is important in the regulation of apoE metabolism. In this study, these effects of GH were further investigated by studying the biosynthesis and secretion of apoE from isolated hepatocytes. Hepatocytes were isolated from HX rats as well as from HX rats that had received hormonal treatment with T4 and cortisol (C) or T4 and C together with GH given either as two daily sc injections (GH x 2) or as a continuous infusion (GHc). Hypophysectomy decreased by 47% the amount of apoE present in the culture medium after a 4-h incubation. Treatment of HX rats with T4 and C alone or in combination with GH x 2 did not influence the amount apoE present in the medium, whereas treatment with T4, C, and GHc increased the amount of apoE to that of normal controls. The different levels of apoE in the medium was not due to differences in the disappearance of apoE, indicating that it was caused by changes in the rate of apoE secretion. Consistent with this, hypophysectomy decreased the rate of intracellular accumulation of apoE measured by incubation of the cells with [35S]methionine for 0, 8, and 20 min. Treatment with T4, C, and GHc increased the rate of accumulation, but T4, C, and GH x 2 had no effect. The differences in the initial rate of intracellular accumulation of apoE were not due to variations in apoE messenger RNA pools or to differences in the degradation of apoE at a step early in the secretory pathway. These results indicate that the differences in the initial rate of accumulation of apoE results from differences in the translational rate. The major amount of apoE that was secreted to the medium appeared in the high-density lipoprotein fraction, whereas small amounts were present in the very-low-density lipoprotein fraction (VLDL). Hypophysectomy decreased the amount of newly secreted apoE in the VLDL fraction. Only therapy with T4, C, and GHc could restore the normal distribution of apoE in the VLDL fraction. In conclusion, the results indicate that the secretory pattern of GH is involved in the regulation of the apoE secretion by influencing the rate of translation.
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