leukotriene-b4 and Klebsiella-Infections

In prior studies, we demonstrated that 1) CXCL1/KC is essential for NF-κB and MAPK activation and expression of CXCL2/MIP-2 and CXCL5/LPS-induced CXC chemokine in Klebsiella-infected lungs, and 2) CXCL1 derived from hematopoietic and resident cells contributes to host immunity against Klebsiella. However, the role of CXCL1 in mediating neutrophil leukotriene B(4) (LTB(4)), reactive oxygen species (ROS), and reactive nitrogen species (RNS) production is unclear, as is the contribution of these factors to host immunity. In this study, we investigated 1) the role of CXCL1 in LTB(4), NADPH oxidase, and inducible NO synthase (iNOS) expression in lungs and neutrophils, and 2) whether LTB(4) postinfection reverses innate immune defects in CXCL1(-/-) mice via regulation of NADPH oxidase and iNOS. Our results demonstrate reduced neutrophil influx, attenuated LTB(4) levels, and decreased ROS and iNOS production in the lungs of CXCL1(-/-) mice after Klebsiella pneumoniae infection. Using neutrophil depletion and repletion, we found that neutrophils are the predominant source of pulmonary LTB(4) after infection. To treat immune defects in CXCL1(-/-) mice, we intrapulmonarily administered LTB(4). Postinfection, LTB(4) treatment reversed immune defects in CXCL1(-/-) mice and improved survival, neutrophil recruitment, cytokine/chemokine expression, NF-κB/MAPK activation, and ROS/RNS production. LTB(4) also enhanced myeloperoxidase, H(2)O(2,) RNS production, and bacterial killing in K. pneumoniae-infected CXCL1(-/-) neutrophils. These novel results uncover important roles for CXCL1 in generating ROS and RNS in neutrophils and in regulating host immunity against K. pneumoniae infection. Our findings suggest that LTB(4) could be used to correct defects in neutrophil recruitment and function in individuals lacking or expressing malfunctional CXCL1.

Topics: Animals; Chemokine CXCL1; Chemotaxis, Leukocyte; Drug Evaluation, Preclinical; Female; Klebsiella Infections; Klebsiella pneumoniae; Leukotriene B4; Lung; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; NADPH Oxidases; Neutrophils; Nitric Oxide Synthase Type II; Peroxidase; Pneumonia, Bacterial; Reactive Nitrogen Species; Reactive Oxygen Species

Leukotriene (LT) B(4) is generated in response to engagement of the Fc gamma receptor (Fc gamma R) and potently contributes to Fc gamma R-mediated antimicrobial functions in pulmonary alveolar macrophages. In this study, we report that the LTB(4) receptor leukotriene B(4) receptor 1 (BLT1) redistributes from nonlipid raft (LR) to LR membrane microdomains upon immunoglobulin G-red blood cell, but not LTB(4), challenge. Cholesterol depletion to disrupt LRs abolished LTB(4)-induced enhancement of phagocytosis, microbicidal activity, and signaling. The dependence on LR integrity for BLT1 signaling correlated with formation of a complex consisting of BLT1, its primary coupled G protein G alpha i3, Src kinase, and Fc gamma RI within LRs. This association was dependent on Src-mediated phosphorylation of BLT1. These data identify a novel form of regulation in which engagement of a macrophage immunoreceptor recruits a stimulatory G protein-coupled receptor into a LR microdomain with resultant enhanced antimicrobial signaling.

Topics: Animals; Cholesterol; GTP-Binding Protein alpha Subunits, Gi-Go; Immunoglobulin G; Immunologic Capping; Klebsiella Infections; Klebsiella pneumoniae; Leukotriene B4; Macrophages, Alveolar; Membrane Microdomains; Mice; Mice, Knockout; Phagocytosis; Phosphorylation; Rats; Rats, Wistar; Receptors, IgG; Receptors, Leukotriene B4; Signal Transduction; src-Family Kinases

The effect of combined administration of flunixin meglumine (FM) and nordihydroguaiaretic acid (NDGA) on milk prostaglandin F2 alpha (PGF2 alpha) and leukotriene B4 (LTB4) concentrations, and inflammatory indicators of bovine mastitis was examined. Mastitis was induced in six Holstein cows by the inoculation of Klebsiella pneumoniae via the teat canal. Four cows were intravenously treated with FM (1.1 mg/kg) and NDGA (10 mg/kg) 1 hour prior to bacterial inoculation and again at post inoculation hour (PIH) 11. Two control cows were intravenously treated with equivalent volume doses of sterile isotonic saline solution at the same post inoculation time points. Combined use of FM and NDGA was effective in reducing elevations in milk PGF2 alpha levels and slightly effective in reducing elevations in milk LTB4 levels in the mastitic cows. Elevations in milk bovine serum albumin (BSA) levels were partially reduced during the early post inoculation time period in the FM and NDGA treated cows as compared to the saline treated control cows. Milk somatic cell counts from inoculated quarters were not significantly altered by FM and NDGA treatment. Elevations in rectal temperature were not reduced by FM and NDGA treatment, but clinical signs of quarter inflammation (warmth and swelling) were reduced by FM and NDGA treatment.

Topics: Animals; Cattle; Clonixin; Dinoprost; Female; Klebsiella Infections; Klebsiella pneumoniae; Leukotriene B4; Masoprocol; Mastitis, Bovine

Mastitis was induced in 4 lactating cows by inoculation of Klebsiella pneumoniae (10(7) organisms/ml) via the teat canal. Sterile isotonic saline solution (1 ml) was instilled into designated control quarters via the teat canal. Changes in milk leukotriene B4 and C4 (LTB4, LTC4) concentrations, milk somatic cell counts, and milk bovine serum albumin concentration were monitored over a 24-hour postinoculation period. Milk LTB4 concentration before inoculation in control quarters and quarters later to be infected was 376 +/- 45 and 326 +/- 56 pg/ml of milk, respectively. A significant (P less than 0.05) increase in milk LTB4 concentration in the infected quarters was first observed at postinoculation hour 6, and milk LTB4 concentration in infected quarters generally remained significantly high through postinoculation hour 14. Thereafter, milk LTB4 concentration in infected quarters was not significantly different from the concentration in control quarters. Measurable amounts of LTC4 were not detected in the milk of either control or infected quarters. Milk bovine serum albumin concentration in the infected quarters generally was high throughout the study, as were milk somatic cell counts. The results of this study suggested that LTB4 contributes to the pathogenesis of bovine mastitis.

Topics: Animals; Cattle; Cell Count; Female; Klebsiella Infections; Klebsiella pneumoniae; Leukotriene B4; Mastitis, Bovine; Milk; Serum Albumin, Bovine; SRS-A; Time Factors