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Lippincott, Williams & Wilkins, Critical Care Medicine, 6(41), p. e85-e92, 2013

DOI: 10.1097/ccm.0b013e31827c0b05

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Peripheral Neural Detection of Danger–Associated and Pathogen–Associated Molecular Patterns

This paper is available in a repository.
This paper is available in a repository.

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Abstract

OBJECTIVE:: Bidirectional links between the nervous and immune systems modulate inflammation. The cellular mechanisms underlying the detection of danger-associated molecular patterns and pathogen-associated molecular patterns by the nervous system are not well understood. We hypothesized that the carotid body, a tissue of neural crest origin, detect pathogen associated molecular patterns and danger associated molecular patterns via an inflammasome-dependent mechanism similar to that described in immune cells. DESIGN:: Randomized, controlled laboratory investigation. SETTING:: University laboratory. SUBJECTS:: C57Bl/6J mice; juvenile Sprague-Dawley rats, primary human neutrophils. INTERVENTIONS:: Rat carotid body chemosensitive cells, and human neutrophils, were treated with TLR agonists to activate inflammasome-dependent pathways. In mice, systemic inflammation was induced by the pathogen associated molecular pattern zymosan (intraperitoneal injection; 500mg/kg). Isolated carotid body/carotid sinus nerve preparations were used to assess peripheral chemoafferent activity. Ventilation was measured by whole-body plethysmography. MEASUREMENTS AND MAIN RESULTS:: Chemosensitive carotid body glomus cells exhibited toll-like receptor (TLR-2 and TLR-4), NLRP1, and NLRP3 inflammasome immunoreactivities. Zymosan increased NLRP3 inflammasome and interleukin-1β expression in glomus cells (p < 0.01). Human neutrophils demonstrated similar LPS-induced changes in inflammasome expression. Carotid body glomus cells also expressed IL-1 receptor and responded to application of IL-1β with increases in intracellular [Ca]. Four hours after injection of zymosan carotid sinus nerve chemoafferent discharge assessed in vitro (i.e., in the absence of acidosis/circulating inflammatory mediators) was increased five-fold (p < 0.001). Accordingly, zymosan-induced systemic inflammation was accompanied by enhanced respiratory activity. CONCLUSIONS:: In carotid body chemosensitive glomus cells, activation of toll-like receptors increases NLRP3 inflammasome expression, and enhances IL-1β production, which is capable of acting in an autocrine manner to enhance peripheral chemoreceptor drive.