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Endothelial NO/cGMP/VASP signaling attenuates Kupffer cell activation and hepatic insulin resistance induced by high-fat feeding.

Tateya S, Rizzo NO, Handa P, Cheng AM, Morgan-Stevenson V, Daum G, Clowes AW, Morton GJ, Schwartz MW, Kim F - Diabetes (2011)

Bottom Line: We sought to determine whether reduced endothelial nitric oxide (NO) signaling contributes to the effect of high-fat feeding to increase hepatic inflammatory signaling and if so, whether this effect 1) involves activation of Kupffer cells and 2) is ameliorated by increased NO signaling.Targeted deletion of vasodilator-stimulated phosphoprotein (VASP), a key downstream target of endothelially derived NO, similarly predisposes to hepatic and Kupffer cell inflammation and abrogates the protective effect of NO signaling in both macrophages and hepatocytes studied in a cell culture model.Our findings also identify the NO/VASP pathway as a novel potential target for the treatment of obesity-associated liver insulin resistance.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, University of Washington, Seattle, Washington, USA.

ABSTRACT

Objective: Proinflammatory activation of Kupffer cells is implicated in the effect of high-fat feeding to cause liver insulin resistance. We sought to determine whether reduced endothelial nitric oxide (NO) signaling contributes to the effect of high-fat feeding to increase hepatic inflammatory signaling and if so, whether this effect 1) involves activation of Kupffer cells and 2) is ameliorated by increased NO signaling.

Research design and methods: Effect of NO/cGMP signaling on hepatic inflammation and on isolated Kupffer cells was examined in C57BL/6 mice, eNos(-/-) mice, and Vasp(-/-) mice fed a low-fat or high-fat diet.

Results: We show that high-fat feeding induces proinflammatory activation of Kupffer cells in wild-type mice coincident with reduced liver endothelial nitric oxide synthase activity and NO content while, conversely, enhancement of signaling downstream of endogenous NO by phosphodiesterase-5 inhibition protects against high fat-induced inflammation in Kupffer cells. Furthermore, proinflammatory activation of Kupffer cells is evident in eNos(-/-) mice even on a low-fat diet. Targeted deletion of vasodilator-stimulated phosphoprotein (VASP), a key downstream target of endothelially derived NO, similarly predisposes to hepatic and Kupffer cell inflammation and abrogates the protective effect of NO signaling in both macrophages and hepatocytes studied in a cell culture model.

Conclusions: These results collectively imply a physiological role for endothelial NO to limit obesity-associated inflammation and insulin resistance in hepatocytes and support a model in which Kupffer cell activation during high-fat feeding is dependent on reduced NO signaling. Our findings also identify the NO/VASP pathway as a novel potential target for the treatment of obesity-associated liver insulin resistance.

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The effect of VASP signaling on RAW cell inflammatory responses to LPS. RAW cells were transduced with VASP (VASP-OE) or control (Con) vector. A: VASP Western blot. B: RAW cells were stimulated with LPS (5 ng/mL) and IFN-γ (12 ng/mL) for 4 h and then analyzed for TNF-α, IL-6, and iNOS mRNA expression (n = 3). *P < 0.05. C: Peritoneal macrophages from VASP−/− and wild-type (WT) control mice were stimulated with LPS (5 ng/mL) and IFN-γ (12 ng/mL) for 4 h in the presence or absence of DETA-NO (10 μmol/L for 4 h) or 8Br-cGMP (10 μmol/L for 4 h). *P < 0.05. IB, immunoblot; kD, kilodalton.
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Figure 5: The effect of VASP signaling on RAW cell inflammatory responses to LPS. RAW cells were transduced with VASP (VASP-OE) or control (Con) vector. A: VASP Western blot. B: RAW cells were stimulated with LPS (5 ng/mL) and IFN-γ (12 ng/mL) for 4 h and then analyzed for TNF-α, IL-6, and iNOS mRNA expression (n = 3). *P < 0.05. C: Peritoneal macrophages from VASP−/− and wild-type (WT) control mice were stimulated with LPS (5 ng/mL) and IFN-γ (12 ng/mL) for 4 h in the presence or absence of DETA-NO (10 μmol/L for 4 h) or 8Br-cGMP (10 μmol/L for 4 h). *P < 0.05. IB, immunoblot; kD, kilodalton.

Mentions: To more directly investigate whether VASP is a determinant of macrophage activation phenotype, we next asked whether signaling via this protein plays a tonic role to limit inflammatory responses of macrophages in a cell culture system. First, we overexpressed VASP in RAW cells by retroviral gene transfer (Fig. 5A) and observed that VASP overexpression is associated with an attenuation of lipopolysaccharide (LPS)-dependent induction of TNF-α, IL-6, and iNOS mRNA (Fig. 5B) compared with control RAW cells transduced with empty vector. Thus, increased VASP signaling appears to attenuate inflammatory signaling in macrophages.


Endothelial NO/cGMP/VASP signaling attenuates Kupffer cell activation and hepatic insulin resistance induced by high-fat feeding.

Tateya S, Rizzo NO, Handa P, Cheng AM, Morgan-Stevenson V, Daum G, Clowes AW, Morton GJ, Schwartz MW, Kim F - Diabetes (2011)

The effect of VASP signaling on RAW cell inflammatory responses to LPS. RAW cells were transduced with VASP (VASP-OE) or control (Con) vector. A: VASP Western blot. B: RAW cells were stimulated with LPS (5 ng/mL) and IFN-γ (12 ng/mL) for 4 h and then analyzed for TNF-α, IL-6, and iNOS mRNA expression (n = 3). *P < 0.05. C: Peritoneal macrophages from VASP−/− and wild-type (WT) control mice were stimulated with LPS (5 ng/mL) and IFN-γ (12 ng/mL) for 4 h in the presence or absence of DETA-NO (10 μmol/L for 4 h) or 8Br-cGMP (10 μmol/L for 4 h). *P < 0.05. IB, immunoblot; kD, kilodalton.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC3198085&req=5

Figure 5: The effect of VASP signaling on RAW cell inflammatory responses to LPS. RAW cells were transduced with VASP (VASP-OE) or control (Con) vector. A: VASP Western blot. B: RAW cells were stimulated with LPS (5 ng/mL) and IFN-γ (12 ng/mL) for 4 h and then analyzed for TNF-α, IL-6, and iNOS mRNA expression (n = 3). *P < 0.05. C: Peritoneal macrophages from VASP−/− and wild-type (WT) control mice were stimulated with LPS (5 ng/mL) and IFN-γ (12 ng/mL) for 4 h in the presence or absence of DETA-NO (10 μmol/L for 4 h) or 8Br-cGMP (10 μmol/L for 4 h). *P < 0.05. IB, immunoblot; kD, kilodalton.
Mentions: To more directly investigate whether VASP is a determinant of macrophage activation phenotype, we next asked whether signaling via this protein plays a tonic role to limit inflammatory responses of macrophages in a cell culture system. First, we overexpressed VASP in RAW cells by retroviral gene transfer (Fig. 5A) and observed that VASP overexpression is associated with an attenuation of lipopolysaccharide (LPS)-dependent induction of TNF-α, IL-6, and iNOS mRNA (Fig. 5B) compared with control RAW cells transduced with empty vector. Thus, increased VASP signaling appears to attenuate inflammatory signaling in macrophages.

Bottom Line: We sought to determine whether reduced endothelial nitric oxide (NO) signaling contributes to the effect of high-fat feeding to increase hepatic inflammatory signaling and if so, whether this effect 1) involves activation of Kupffer cells and 2) is ameliorated by increased NO signaling.Targeted deletion of vasodilator-stimulated phosphoprotein (VASP), a key downstream target of endothelially derived NO, similarly predisposes to hepatic and Kupffer cell inflammation and abrogates the protective effect of NO signaling in both macrophages and hepatocytes studied in a cell culture model.Our findings also identify the NO/VASP pathway as a novel potential target for the treatment of obesity-associated liver insulin resistance.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, University of Washington, Seattle, Washington, USA.

ABSTRACT

Objective: Proinflammatory activation of Kupffer cells is implicated in the effect of high-fat feeding to cause liver insulin resistance. We sought to determine whether reduced endothelial nitric oxide (NO) signaling contributes to the effect of high-fat feeding to increase hepatic inflammatory signaling and if so, whether this effect 1) involves activation of Kupffer cells and 2) is ameliorated by increased NO signaling.

Research design and methods: Effect of NO/cGMP signaling on hepatic inflammation and on isolated Kupffer cells was examined in C57BL/6 mice, eNos(-/-) mice, and Vasp(-/-) mice fed a low-fat or high-fat diet.

Results: We show that high-fat feeding induces proinflammatory activation of Kupffer cells in wild-type mice coincident with reduced liver endothelial nitric oxide synthase activity and NO content while, conversely, enhancement of signaling downstream of endogenous NO by phosphodiesterase-5 inhibition protects against high fat-induced inflammation in Kupffer cells. Furthermore, proinflammatory activation of Kupffer cells is evident in eNos(-/-) mice even on a low-fat diet. Targeted deletion of vasodilator-stimulated phosphoprotein (VASP), a key downstream target of endothelially derived NO, similarly predisposes to hepatic and Kupffer cell inflammation and abrogates the protective effect of NO signaling in both macrophages and hepatocytes studied in a cell culture model.

Conclusions: These results collectively imply a physiological role for endothelial NO to limit obesity-associated inflammation and insulin resistance in hepatocytes and support a model in which Kupffer cell activation during high-fat feeding is dependent on reduced NO signaling. Our findings also identify the NO/VASP pathway as a novel potential target for the treatment of obesity-associated liver insulin resistance.

Show MeSH
Related in: MedlinePlus