AMP-activated protein kinase activation by 5-aminoimidazole-4-carbox-amide-1-β-D-ribofuranoside (AICAR) reduces lipoteichoic acid-induced lung inflammation - PubMed (original) (raw)

AMP-activated protein kinase activation by 5-aminoimidazole-4-carbox-amide-1-β-D-ribofuranoside (AICAR) reduces lipoteichoic acid-induced lung inflammation

Arie J Hoogendijk et al. J Biol Chem. 2013.

Abstract

Adenosine monophosphate-activated protein (AMP)-activated kinase (AMPK) is a highly conserved kinase that plays a key role in energy homeostasis. Activation of AMPK was shown to reduce inflammation in response to lipolysaccharide in vitro and in vivo. 5-Aminoimidazole-4-carbox-amide-1-β-D-ribofuranoside (AICAR) is intracellularly converted to the AMP analog ZMP, which activates AMPK. Lipoteichoic acid (LTA) is a major component of the cell wall of Gram-positive bacteria that can trigger inflammatory responses. In contrast to lipopolysaccharide, little is known on the effects of AMPK activation in LTA-triggered innate immune responses. Here, we studied the potency of AMPK activation to reduce LTA-induced inflammation in vitro and in lungs in vivo. Activation of AMPK in vitro reduced cytokine production in the alveolar macrophage cell line MH-S. In vivo, AMPK activation reduced LTA-induced neutrophil influx, as well as protein leak and cytokine/chemokine levels in the bronchoalveolar space. In conclusion, AMPK activation inhibits LTA-induced lung inflammation in mice.

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Figures

FIGURE 1.

FIGURE 1.

AICAR reduces macrophage cytokine production independent of mTOR in vitro. A–D, effect of AICAR in combination or without rapamycin on cytokine responses of MH-S (alveolar macrophage cell line) on TNF-α (6 h (A), 24 h (B)) and IL-6 production (6 h (C), 24 h (D)). E, cells were stimulated with 10 μg/ml S. aureus LTA and simultaneously treated with AICAR (1 m

m

), rapamycin (100 n

m

), AICAR and rapamycin or vehicle (0.3% dimethyl sulfoxide/PBS) for 6 and 24 h. _p_ACC, _p_MTOR, _p_AMPK, AMPK, _p_P70/S6K, p70/S6K, and β-actin levels were determined by Western blotting. Data are representative for two independent experiments and expressed as mean ± S.E. (error bars), n = 4 per treatment. **, p < 0.01; ***, p < 0.001; N.D., not detectable.

FIGURE 2.

FIGURE 2.

AICAR enhances ACC phosphorylation in BAL cells. Acute lung inflammation was induced by instillation 100 μg of LTA intranasally. 500 mg/kg AICAR or vehicle (saline) was administered simultaneously intraperitoneally. After 6 and 24 h mice were sacrificed. The cell fraction obtained from pelleted BAL fluid was lysed, and _p_ACC levels were determined by Western blotting. For sham reference naïve mouse samples used. A, representative Western blot. B, bar graphs densitometric quantification of the relative amounts of _p_ACC of 4–8 mice per group normalized for β-actin. Graph data are expressed as mean ± S.E. (error bars). *, p < 0.05 versus vehicle.

FIGURE 3.

FIGURE 3.

AICAR treatment reduces cell influx into the bronchoalveolar space. Lung inflammation was induced by intranasal instillation of 100 μg of LTA. Simultaneously, 500 mg/kg AICAR or vehicle (saline) was administered intraperitoneally. After 6 and 24 h samples were harvested. For sham reference naïve mouse samples used. A, total cell count of BAL fluid. B–D, macrophage (B), polymorphonuclear (PMN) cell (C), and lymphocyte (D) counts determined by counting Giemsa-stained cytospin preparations from BAL fluid. Data are expressed as mean ± S.E. (error bars), n = 8 per group. **, p < 0.01

FIGURE 4.

FIGURE 4.

AICAR inhibits LTA-induced cytokine and chemokine release in BAL fluid. Lung inflammation was induced by intranasal instillation of 100 μg of LTA. Simultaneously, 500 mg/kg AICAR or vehicle (saline) was administered intraperitoneally. After 6 and 24 h samples were harvested. For sham reference naïve mouse samples used. TNF-α (A), IL-6 (B), KC (C), and MIP-2 (D) were measured in BAL fluid by ELISA. N.D., not detectable. Data are expressed as mean ± S.E. (error bars), n = 4–8 per group. *, p < 0.05; **, p < 0.01; ***, p < 0.001.

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