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Apolipoprotein A-I attenuates palmitate-mediated NF-κB activation by reducing Toll-like receptor-4 recruitment into lipid rafts.

Cheng AM, Handa P, Tateya S, Schwartz J, Tang C, Mitra P, Oram JF, Chait A, Kim F - PLoS ONE (2012)

Bottom Line: Furthermore, HDL's protective effects against saturated dietary fats have not been previously described.In this study, we used endothelial cells to demonstrate that while palmitic acid activates NF-κB signaling, apolipoprotein A-I, (apoA-I), the major protein component of HDL, attenuates palmitate-induced NF-κB activation.Further, vascular NF-κB signaling (IL-6, MCP-1, TNF-α) and macrophage markers (CD68, CD11c) induced by 24 weeks of a diabetogenic diet containing cholesterol (DDC) is reduced in human apoA-I overexpressing transgenic C57BL/6 mice compared to age-matched WT controls.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, Diabetes and Obesity Center of Excellence, University of Washington, Seattle, Washington, United States of America.

ABSTRACT
While high-density lipoprotein (HDL) is known to protect against a wide range of inflammatory stimuli, its anti-inflammatory mechanisms are not well understood. Furthermore, HDL's protective effects against saturated dietary fats have not been previously described. In this study, we used endothelial cells to demonstrate that while palmitic acid activates NF-κB signaling, apolipoprotein A-I, (apoA-I), the major protein component of HDL, attenuates palmitate-induced NF-κB activation. Further, vascular NF-κB signaling (IL-6, MCP-1, TNF-α) and macrophage markers (CD68, CD11c) induced by 24 weeks of a diabetogenic diet containing cholesterol (DDC) is reduced in human apoA-I overexpressing transgenic C57BL/6 mice compared to age-matched WT controls. Moreover, WT mice on DDC compared to a chow diet display increased gene expression of lipid raft markers such as Caveolin-1 and Flotillin-1, and inflammatory Toll-like receptors (TLRs) (TLR2, TLR4) in the vasculature. However apoA-I transgenic mice on DDC show markedly reduced expression of these genes. Finally, we show that in endothelial cells TLR4 is recruited into lipid rafts in response to palmitate, and that apoA-I prevents palmitate-induced TLR4 trafficking into lipid rafts, thereby blocking NF-κB activation. Thus, apoA-I overexpression might be a useful therapeutic tool against vascular inflammation.

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HDL or apoA-I attenuates palmitic acid dependent NF- κB signaling in endothelial cells.HMEC were pretreated with vehicle (labeled as control) or with human HDL (50 µg/ml) or ApoA-1 (50 µg/ml) for 16 hours, washed and then either treated with palmitate complexed with BSA (100 µM) for 3 hours or treated with BSA alone. A–B. ICAM-1 mRNA expression was analyzed using quantitative RT-PCR. IL-6 cytokine levels in supernatants were assessed by ELISA (n = 3). Data represents mean ± SD and *p<0.05,**p<0.01,***p<0.005. C. BAEC lysates were prepared after pretreatment with apoA-I/HDL and phopho-P65 levels were assessed by Western blot.
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pone-0033917-g002: HDL or apoA-I attenuates palmitic acid dependent NF- κB signaling in endothelial cells.HMEC were pretreated with vehicle (labeled as control) or with human HDL (50 µg/ml) or ApoA-1 (50 µg/ml) for 16 hours, washed and then either treated with palmitate complexed with BSA (100 µM) for 3 hours or treated with BSA alone. A–B. ICAM-1 mRNA expression was analyzed using quantitative RT-PCR. IL-6 cytokine levels in supernatants were assessed by ELISA (n = 3). Data represents mean ± SD and *p<0.05,**p<0.01,***p<0.005. C. BAEC lysates were prepared after pretreatment with apoA-I/HDL and phopho-P65 levels were assessed by Western blot.

Mentions: HDL/apoA-I reduces NF-κB activation mediated by many stimuli such as LPS, TNF-α, and oxidized LDL [6], [7], [13], [28]. We next asked whether HDL/apoA-I would similarly reduce palmitate-dependent activation of endothelial NF-κB. Human microvascular endothelial cells (HMECs) were pretreated with 50 µg/ml of HDL or apoA-I (50 µg/ml) for 16 hours, washed and subsequently treated them with 100 µM of palmitate for 3 hours. Pretreatment with either HDL or apoA-I significantly reduced palmitate-dependent increases in the expression of ICAM-1, and IL-6 cytokine levels compared to the vehicle-treated cells (Figure 2A, B). These observations were also found in a model of large vessel endothelial cells (BAEC). Pretreatment with apoA-I or HDL attenuated palmitate-mediated NF-κB activation, as assessed by phosphorylation of the p65 subunit of NF-κB (Figure 2C). Therefore, HDL/apoA-I is able to attenuate palmitate-mediated NF-κB-dependent inflammatory responses in endothelial cells.


Apolipoprotein A-I attenuates palmitate-mediated NF-κB activation by reducing Toll-like receptor-4 recruitment into lipid rafts.

Cheng AM, Handa P, Tateya S, Schwartz J, Tang C, Mitra P, Oram JF, Chait A, Kim F - PLoS ONE (2012)

HDL or apoA-I attenuates palmitic acid dependent NF- κB signaling in endothelial cells.HMEC were pretreated with vehicle (labeled as control) or with human HDL (50 µg/ml) or ApoA-1 (50 µg/ml) for 16 hours, washed and then either treated with palmitate complexed with BSA (100 µM) for 3 hours or treated with BSA alone. A–B. ICAM-1 mRNA expression was analyzed using quantitative RT-PCR. IL-6 cytokine levels in supernatants were assessed by ELISA (n = 3). Data represents mean ± SD and *p<0.05,**p<0.01,***p<0.005. C. BAEC lysates were prepared after pretreatment with apoA-I/HDL and phopho-P65 levels were assessed by Western blot.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3316516&req=5

pone-0033917-g002: HDL or apoA-I attenuates palmitic acid dependent NF- κB signaling in endothelial cells.HMEC were pretreated with vehicle (labeled as control) or with human HDL (50 µg/ml) or ApoA-1 (50 µg/ml) for 16 hours, washed and then either treated with palmitate complexed with BSA (100 µM) for 3 hours or treated with BSA alone. A–B. ICAM-1 mRNA expression was analyzed using quantitative RT-PCR. IL-6 cytokine levels in supernatants were assessed by ELISA (n = 3). Data represents mean ± SD and *p<0.05,**p<0.01,***p<0.005. C. BAEC lysates were prepared after pretreatment with apoA-I/HDL and phopho-P65 levels were assessed by Western blot.
Mentions: HDL/apoA-I reduces NF-κB activation mediated by many stimuli such as LPS, TNF-α, and oxidized LDL [6], [7], [13], [28]. We next asked whether HDL/apoA-I would similarly reduce palmitate-dependent activation of endothelial NF-κB. Human microvascular endothelial cells (HMECs) were pretreated with 50 µg/ml of HDL or apoA-I (50 µg/ml) for 16 hours, washed and subsequently treated them with 100 µM of palmitate for 3 hours. Pretreatment with either HDL or apoA-I significantly reduced palmitate-dependent increases in the expression of ICAM-1, and IL-6 cytokine levels compared to the vehicle-treated cells (Figure 2A, B). These observations were also found in a model of large vessel endothelial cells (BAEC). Pretreatment with apoA-I or HDL attenuated palmitate-mediated NF-κB activation, as assessed by phosphorylation of the p65 subunit of NF-κB (Figure 2C). Therefore, HDL/apoA-I is able to attenuate palmitate-mediated NF-κB-dependent inflammatory responses in endothelial cells.

Bottom Line: Furthermore, HDL's protective effects against saturated dietary fats have not been previously described.In this study, we used endothelial cells to demonstrate that while palmitic acid activates NF-κB signaling, apolipoprotein A-I, (apoA-I), the major protein component of HDL, attenuates palmitate-induced NF-κB activation.Further, vascular NF-κB signaling (IL-6, MCP-1, TNF-α) and macrophage markers (CD68, CD11c) induced by 24 weeks of a diabetogenic diet containing cholesterol (DDC) is reduced in human apoA-I overexpressing transgenic C57BL/6 mice compared to age-matched WT controls.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, Diabetes and Obesity Center of Excellence, University of Washington, Seattle, Washington, United States of America.

ABSTRACT
While high-density lipoprotein (HDL) is known to protect against a wide range of inflammatory stimuli, its anti-inflammatory mechanisms are not well understood. Furthermore, HDL's protective effects against saturated dietary fats have not been previously described. In this study, we used endothelial cells to demonstrate that while palmitic acid activates NF-κB signaling, apolipoprotein A-I, (apoA-I), the major protein component of HDL, attenuates palmitate-induced NF-κB activation. Further, vascular NF-κB signaling (IL-6, MCP-1, TNF-α) and macrophage markers (CD68, CD11c) induced by 24 weeks of a diabetogenic diet containing cholesterol (DDC) is reduced in human apoA-I overexpressing transgenic C57BL/6 mice compared to age-matched WT controls. Moreover, WT mice on DDC compared to a chow diet display increased gene expression of lipid raft markers such as Caveolin-1 and Flotillin-1, and inflammatory Toll-like receptors (TLRs) (TLR2, TLR4) in the vasculature. However apoA-I transgenic mice on DDC show markedly reduced expression of these genes. Finally, we show that in endothelial cells TLR4 is recruited into lipid rafts in response to palmitate, and that apoA-I prevents palmitate-induced TLR4 trafficking into lipid rafts, thereby blocking NF-κB activation. Thus, apoA-I overexpression might be a useful therapeutic tool against vascular inflammation.

Show MeSH
Related in: MedlinePlus