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Pre-exposure to zymosan enhances lung defense mechanisms and accelerates the pulmonary clearance of a bacterial pathogen in rats.

Young-S; Roberts-JR; Antonini-JM
Toxicologist 2006 Mar; 90(1):212
Although bacteria and fungi are common etiological agents which are known to induce pulmonary inflammation, complicated interactions may exist when the lungs are exposed to both concurrently. The objective of the present investigation was to determine the effects of pre-exposure to zymosan (a 1-->3-glucan from baker yeast) on bacterial (Listeria monocytogenes) infection in male Sprague-Dawley rats. On day 0, rats received a single dose of zymosan A (2.5 mg/kg body weight) via intratracheal instillation or vehicle control (saline). On day 3, rats were intratracheally inoculated with 5x105 bacteria, and bacterial clearance was determined by measuring colony-forming units cultured from the left lungs. Rats were euthanized on days 6, 8, and 10, and bronchoalveolar lavage (BAL) was performed on the right lungs. Inflammation and lung injury were assessed by measuring (1) neutrophil (PMN) infiltration and (2) albumin, total protein and lactate dehydrogenase levels in BAL fluid. Alveolar macrophage activation was determined by chemiluminescence. Immune response was assessed by immunophenotyping of lymphocytes and lymphokine production. Immunophenotyping was performed on BAL cells and lung-associated lymph node cells. Lymphokine production was measured using lymph node cells treated with or without concanavalin A stimulation. Zymosan pre-exposure accelerated the clearance of the bacteria from the lungs compared to the control group. Zymosan-treated rats also had a smaller PMN infiltration in the lung compared to control, however, a greater number of lymphocytes was present in lymph nodes of the rats. Lung injury parameters were lower in zymosan-treated rats at days 6 and 8. Activation of macrophages recovered from zymosan-treated rats was elevated at day 6 compared to control. These results strongly suggest that pre-exposure to zymosan enhances the lung immune response and attenuates pulmonary infection in rats.
Bacteria; Laboratory-animals; Animals; Animal-studies; Fungi; Fungicides; Exposure-levels; Exposure-assessment; Lung-disorders; Immune-reaction; Pulmonary-system-disorders; Respiratory-system-disorders
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Work Environment and Workforce: Mixed Exposures
Source Name
The Toxicologist. Society of Toxicology 45th Annual Meeting and ToxExpo, March 5-9, 2006, San Diego, California