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Infection and Immunity, April 2009, p. 1569-1578, Vol. 77, No. 4
0019-9567/09/$08.00+0     doi:10.1128/IAI.01505-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

RICK Promotes Inflammation and Lethality after Gram-Negative Bacterial Infection in Mice Stimulated with Lipopolysaccharide{triangledown}

Jong-Hwan Park, Yun-Gi Kim, and Gabriel Núñez*

Department of Pathology, University of Michigan Medical School, and University of Michigan Comprehensive Cancer Center, Ann Arbor, Michigan 48109

Received 10 December 2008/ Returned for modification 19 January 2009/ Accepted 23 January 2009

RICK (receptor-interacting protein-like interacting caspase-like apoptosis regulatory protein kinase), a serine-threonine kinase, functions downstream of the pattern recognition receptors Nod1 and Nod2 to mediate NF-{kappa}B and mitogen-activated protein kinase (MAPK) activation in response to specific microbial stimuli. However, the function of RICK in the recognition and host defense of gram-negative bacteria remains poorly understood. We report here that infection of wild-type and RICK-deficient macrophages with Pseudomonas aeruginosa and Escherichia coli elicited comparable activation of NF-{kappa}B and MAPKs as well as secretion of proinflammatory cytokines. However, production of interleukin 6 (IL-6) and IL-1β induced by these gram-negative bacteria was impaired in RICK-deficient macrophages when the cells had previously been stimulated with lipopolysaccharide (LPS) or E. coli. The diminished proinflammatory response of RICK-deficient macrophages to bacteria was associated with reduced activation of NF-{kappa}B and MAPKs. Importantly, mutant mice deficient in RICK were less susceptible than wild-type mice to P. aeruginosa infection when the animals had previously been stimulated with LPS. The reduced lethality of RICK-deficient mice infected with P. aeruginosa was independent of pathogen clearance but was associated with diminished production of proinflammatory molecules in vivo. These results demonstrate that RICK contributes to the induction of proinflammatory responses and susceptibility to gram-negative bacteria after exposure to LPS, a condition that is associated with reduced Toll-like receptor signaling.

* Corresponding author. Mailing address: Department of Pathology, University of Michigan Medical School, and University of Michigan Comprehensive Cancer Center, 1500 E. Medical Center Dr., Ann Arbor, MI 48109. Phone: (734) 764-8514. Fax: (734) 647-9654. E-mail: bclx{at}umich.edu

{triangledown} Published ahead of print on 2 February 2009.

Editor: B. A. McCormick

Infection and Immunity, April 2009, p. 1569-1578, Vol. 77, No. 4
0019-9567/09/$08.00+0     doi:10.1128/IAI.01505-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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