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Unique Toll-Like Receptor 4 Activation by NAMPT/PBEF Induces NFκB Signaling and Inflammatory Lung Injury.

Camp SM, Ceco E, Evenoski CL, Danilov SM, Zhou T, Chiang ET, Moreno-Vinasco L, Mapes B, Zhao J, Gursoy G, Brown ME, Adyshev DM, Siddiqui SS, Quijada H, Sammani S, Letsiou E, Saadat L, Yousef M, Wang T, Liang J, Garcia JG - Sci Rep (2015)

Bottom Line: Although VILI severity is attenuated by reduced NAMPT/PBEF bioavailability, the precise contribution of NAMPT/PBEF and excessive mechanical stress to VILI pathobiology is unknown.Unlike MD-2, whose TLR4 binding alone is insufficient to initiate TLR4 signaling, NAMPT/PBEF alone produces robust TLR4 activation, likely via a protruding region of NAMPT/PBEF (S402-N412) with structural similarity to LPS.The identification of this unique mode of TLR4 activation by NAMPT/PBEF advances the understanding of innate immunity responses as well as the untoward events associated with mechanical stress-induced lung inflammation.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine and Arizona Respiratory Center, The University of Arizona.

ABSTRACT
Ventilator-induced inflammatory lung injury (VILI) is mechanistically linked to increased NAMPT transcription and circulating levels of nicotinamide phosphoribosyl-transferase (NAMPT/PBEF). Although VILI severity is attenuated by reduced NAMPT/PBEF bioavailability, the precise contribution of NAMPT/PBEF and excessive mechanical stress to VILI pathobiology is unknown. We now report that NAMPT/PBEF induces lung NFκB transcriptional activities and inflammatory injury via direct ligation of Toll-like receptor 4 (TLR4). Computational analysis demonstrated that NAMPT/PBEF and MD-2, a TLR4-binding protein essential for LPS-induced TLR4 activation, share ~30% sequence identity and exhibit striking structural similarity in loop regions critical for MD-2-TLR4 binding. Unlike MD-2, whose TLR4 binding alone is insufficient to initiate TLR4 signaling, NAMPT/PBEF alone produces robust TLR4 activation, likely via a protruding region of NAMPT/PBEF (S402-N412) with structural similarity to LPS. The identification of this unique mode of TLR4 activation by NAMPT/PBEF advances the understanding of innate immunity responses as well as the untoward events associated with mechanical stress-induced lung inflammation.

No MeSH data available.


Related in: MedlinePlus

Extracellular NAMPT/PBEF mediates rapid NFκB activation in murine lungs.(Panel A) Paraffin-embedded lung tissue was sectioned (10 μm) and immunostained with p-NFκB antibody. Shown are representative images where prominent NFκB activation is evident in VILI-challenged mice, compared to spontaneously breathing (SB) mice, with prominent p-NFκB expression in capillary endothelium and alveolar epithelium. Scale bar = 100 μm. See Supplemental Figure 1 for IHC staining isotype controls. (Panel B) Heat maps reflecting the highly upregulated expression of NFκB pathway genes in response to rPBEF (40 μg/mouse, 4.5 hr), LPS (2.5 mg/kg, 4 hr), and VILI challenge (30 ml/kg tidal volume, 4 hr). VILI-mediated increases in NFκB pathway gene expression were markedly reduced in heterozygous PBEF+/− mice. Blue color indicates reduced gene expression, red color reflects increased gene expression.
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f2: Extracellular NAMPT/PBEF mediates rapid NFκB activation in murine lungs.(Panel A) Paraffin-embedded lung tissue was sectioned (10 μm) and immunostained with p-NFκB antibody. Shown are representative images where prominent NFκB activation is evident in VILI-challenged mice, compared to spontaneously breathing (SB) mice, with prominent p-NFκB expression in capillary endothelium and alveolar epithelium. Scale bar = 100 μm. See Supplemental Figure 1 for IHC staining isotype controls. (Panel B) Heat maps reflecting the highly upregulated expression of NFκB pathway genes in response to rPBEF (40 μg/mouse, 4.5 hr), LPS (2.5 mg/kg, 4 hr), and VILI challenge (30 ml/kg tidal volume, 4 hr). VILI-mediated increases in NFκB pathway gene expression were markedly reduced in heterozygous PBEF+/− mice. Blue color indicates reduced gene expression, red color reflects increased gene expression.

Mentions: Extracellular NAMPT/PBEF-mediated NFκB activation was next evaluated in preclinical models of ARDS/VILI. Phospho-NFκB immunostaining of murine lung tissues from VILI-exposed mice revealed prominent VILI-induced NFκB phosphorylation/activation in vascular endothelium and alveolar epithelium (Fig. 2A). Genome–wide gene expression analysis in wild type mice revealed marked similarities in NFκB Toll receptor pathway signaling gene upregulation evoked by rPBEF, LPS, and VILI, with heterozygous PBEF+/− mice exhibiting dramatic attenuation of VILI-mediated NFκB pathway gene expression (Fig. 2B). These studies provide compelling evidence for extracellular NAMPT/PBEF involvement in induction of the NFκB transcriptome and in lung innate immunity directly contributing to ARDS/VILI pathobiology.


Unique Toll-Like Receptor 4 Activation by NAMPT/PBEF Induces NFκB Signaling and Inflammatory Lung Injury.

Camp SM, Ceco E, Evenoski CL, Danilov SM, Zhou T, Chiang ET, Moreno-Vinasco L, Mapes B, Zhao J, Gursoy G, Brown ME, Adyshev DM, Siddiqui SS, Quijada H, Sammani S, Letsiou E, Saadat L, Yousef M, Wang T, Liang J, Garcia JG - Sci Rep (2015)

Extracellular NAMPT/PBEF mediates rapid NFκB activation in murine lungs.(Panel A) Paraffin-embedded lung tissue was sectioned (10 μm) and immunostained with p-NFκB antibody. Shown are representative images where prominent NFκB activation is evident in VILI-challenged mice, compared to spontaneously breathing (SB) mice, with prominent p-NFκB expression in capillary endothelium and alveolar epithelium. Scale bar = 100 μm. See Supplemental Figure 1 for IHC staining isotype controls. (Panel B) Heat maps reflecting the highly upregulated expression of NFκB pathway genes in response to rPBEF (40 μg/mouse, 4.5 hr), LPS (2.5 mg/kg, 4 hr), and VILI challenge (30 ml/kg tidal volume, 4 hr). VILI-mediated increases in NFκB pathway gene expression were markedly reduced in heterozygous PBEF+/− mice. Blue color indicates reduced gene expression, red color reflects increased gene expression.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4536637&req=5

f2: Extracellular NAMPT/PBEF mediates rapid NFκB activation in murine lungs.(Panel A) Paraffin-embedded lung tissue was sectioned (10 μm) and immunostained with p-NFκB antibody. Shown are representative images where prominent NFκB activation is evident in VILI-challenged mice, compared to spontaneously breathing (SB) mice, with prominent p-NFκB expression in capillary endothelium and alveolar epithelium. Scale bar = 100 μm. See Supplemental Figure 1 for IHC staining isotype controls. (Panel B) Heat maps reflecting the highly upregulated expression of NFκB pathway genes in response to rPBEF (40 μg/mouse, 4.5 hr), LPS (2.5 mg/kg, 4 hr), and VILI challenge (30 ml/kg tidal volume, 4 hr). VILI-mediated increases in NFκB pathway gene expression were markedly reduced in heterozygous PBEF+/− mice. Blue color indicates reduced gene expression, red color reflects increased gene expression.
Mentions: Extracellular NAMPT/PBEF-mediated NFκB activation was next evaluated in preclinical models of ARDS/VILI. Phospho-NFκB immunostaining of murine lung tissues from VILI-exposed mice revealed prominent VILI-induced NFκB phosphorylation/activation in vascular endothelium and alveolar epithelium (Fig. 2A). Genome–wide gene expression analysis in wild type mice revealed marked similarities in NFκB Toll receptor pathway signaling gene upregulation evoked by rPBEF, LPS, and VILI, with heterozygous PBEF+/− mice exhibiting dramatic attenuation of VILI-mediated NFκB pathway gene expression (Fig. 2B). These studies provide compelling evidence for extracellular NAMPT/PBEF involvement in induction of the NFκB transcriptome and in lung innate immunity directly contributing to ARDS/VILI pathobiology.

Bottom Line: Although VILI severity is attenuated by reduced NAMPT/PBEF bioavailability, the precise contribution of NAMPT/PBEF and excessive mechanical stress to VILI pathobiology is unknown.Unlike MD-2, whose TLR4 binding alone is insufficient to initiate TLR4 signaling, NAMPT/PBEF alone produces robust TLR4 activation, likely via a protruding region of NAMPT/PBEF (S402-N412) with structural similarity to LPS.The identification of this unique mode of TLR4 activation by NAMPT/PBEF advances the understanding of innate immunity responses as well as the untoward events associated with mechanical stress-induced lung inflammation.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine and Arizona Respiratory Center, The University of Arizona.

ABSTRACT
Ventilator-induced inflammatory lung injury (VILI) is mechanistically linked to increased NAMPT transcription and circulating levels of nicotinamide phosphoribosyl-transferase (NAMPT/PBEF). Although VILI severity is attenuated by reduced NAMPT/PBEF bioavailability, the precise contribution of NAMPT/PBEF and excessive mechanical stress to VILI pathobiology is unknown. We now report that NAMPT/PBEF induces lung NFκB transcriptional activities and inflammatory injury via direct ligation of Toll-like receptor 4 (TLR4). Computational analysis demonstrated that NAMPT/PBEF and MD-2, a TLR4-binding protein essential for LPS-induced TLR4 activation, share ~30% sequence identity and exhibit striking structural similarity in loop regions critical for MD-2-TLR4 binding. Unlike MD-2, whose TLR4 binding alone is insufficient to initiate TLR4 signaling, NAMPT/PBEF alone produces robust TLR4 activation, likely via a protruding region of NAMPT/PBEF (S402-N412) with structural similarity to LPS. The identification of this unique mode of TLR4 activation by NAMPT/PBEF advances the understanding of innate immunity responses as well as the untoward events associated with mechanical stress-induced lung inflammation.

No MeSH data available.


Related in: MedlinePlus