Key role for scavenger receptor B-I in the integrative physiology of host defense during bacterial pneumonia.

Scavenger receptor B-I (SR-BI) is a multirecognition receptor that regulates cholesterol trafficking and cardiovascular inflammation. Although it is expressed by neutrophils (PMNs) and lung-resident cells, no role for SR-BI has been defined in pulmonary immunity. Herein, we report that, compared with SR-BI(+/+) counterparts, SR-BI(-/-) mice suffer markedly increased mortality during bacterial pneumonia associated with higher bacterial burden in the lung and blood, deficient induction of the stress glucocorticoid corticosterone, higher serum cytokines, and increased organ injury. SR-BI(-/-) mice had significantly increased PMN recruitment and cytokine production in the infected airspace. This was associated with defective hematopoietic cell-dependent clearance of lipopolysaccharide from the airspace and increased cytokine production by SR-BI(-/-) macrophages. Corticosterone replacement normalized alveolar neutrophilia but not alveolar cytokines, bacterial burden, or mortality, suggesting that adrenal insufficiency derepresses PMN trafficking to the SR-BI(-/-) airway in a cytokine-independent manner. Despite enhanced alveolar neutrophilia, SR-BI(-/-) mice displayed impaired phagocytic killing. Bone marrow chimeras revealed this defect to be independent of the dyslipidemia and adrenal insufficiency of SR-BI(-/-) mice. During infection, SR-BI(-/-) PMNs displayed deficient oxidant production and CD11b externalization, and increased surface L-selectin, suggesting defective activation. Taken together, SR-BI coordinates several steps in the integrated neutrophilic host defense response to pneumonia.

Evaluation of N-butylbenzenesulfonamide (NBBS) neurotoxicity in Sprague-Dawley male rats following 27-day oral exposure.

N-Butylbenzenesulfonamide (NBBS) is widely used as a plasticizer in polyacetals, polyamides, and polycarbonates and has been found in ground water and effluent from wastewater treatment sites. The compound is lipophilic and distributes rapidly to the brain but also clears rapidly and shows little evidence of accumulation. Limited studies in the literature report neurotoxicity of NBBS in rabbits and rats. Adult Sprague-Dawley male rats (Harlan) received corn oil vehicle or NBBS (100, 200, or 400mg/kg/d) via oral gavage (5 ml/kg bwt) daily/5d/week for 27 d. Deaths were observed in the 400mg/kg/d dose group in the first 5d and dosing was decreased to 300 mg/kg/d. No alterations were observed in gait, locomotor activity, and rearing behavior. No histological lesions were observed in the testis, seminal vesicles, coagulating gland, epididymis, and prostate. In the liver, minimal centrilobular hypertrophy was evident in all rats of the high dose group. Contrary to previous reports, there was no evidence of peripheral nerve lesions or gliosis in the hippocampus or cerebellum. mRNA levels for glial fibrillary acidic acid protein, interferon gamma, CXCR-3, intracellular adhesion molecule-1, and CD11b were not altered in the hippocampus while Iba-1 levels were decreased. These data do not support previous reports of neurotoxicity for NBBS within a 4-week exposure regimen; however, neuropathological injury occurring over an extended period of exposure cannot be ruled out and given the potential for human exposure requires further examination.

Expression and function of endothelial monocyte-activating polypeptide-II in acute lung inflammation.

OBJECTIVE AND DESIGN: We tested the hypothesis that total endothelial monocyte-activating polypeptide-II (EMAP-II) expression (proEMAP/p43 and mature EMAP-II) is up-regulated in lipopolysaccharide (LPS)-induced acute lung inflammation (ALI) and that mature EMAP-II induces monocyte/macrophage and granulocyte recruitment in vivo. MATERIALS: Thirty-five 10 week old, male Sprague-Dawley rats. TREATMENT: Animals were instilled intratracheally with 250 microg of E. coli LPS (N = 15) or saline (N = 5) or 20 microg of mature EMAP-II (N = 5). METHODS: Total EMAP-II was quantified using ELISA and the protein was localized with light and electron microscopic immunocytochemistry in lungs of rats at 1, 3 and 12 h (n = 5/group). RESULTS: ELISA showed increased total EMAP-II concentrations (p < 0.05) in lungs from LPS-treated rats compared to control animals. Compared to the controls, light and electron microscopic imunocytochemistry localized total EMAP-II in monocytes/macrophages and alveolar septa at 1 and 3 h and in vascular smooth muscles at 12 h post-LPS treatment. Instillation of mature EMAP-II increased lung monocytes/macrophages and granulocytes compared with control animals (p < 0.05). However, compared to the LPS treatment, mature EMAP-II instillation did not induce expression of IL-1beta and MIP-2 (p < 0.05) and provoked less vigorous recruitment of monocytes/macrophages. CONCLUSION: EMAP-II expression is increased in LPS-induced ALI, and that intra-tracheal instillation of mature EMAP-II induces recruitment of monocytes/macrophages and granulocytes into the lungs without stimulating IL-1beta or MIP-2 expression.

Toll like receptor-4 expression in lipopolysaccharide induced lung inflammation.

Bacterial lipopolysaccharides (LPS) initiate immune response through Toll-like receptor 4 (TLR4). Because many a times host is confronted with secondary bacterial challenges, it is critical to understand TLR4 expression following initial provocation. We studied TLR4 expression in rats at various times after intra-tracheal instillation of LPS. Although TLR4 mRNA was undetectable in normal lungs, it increased at 6h and 12h and declined at 36h post-LPS treatment. Western blots showed TLR4 protein at all time points. Immunohistochemistry localized TLR4 in alveolar septal cells, bronchial epithelium, macrophages and endothelium of large and peribronchial blood vessels. Dual label immunoelectron microscopy showed co-localization of TLR4 and LPS in the cytoplasm and nucleus of various lung and inflammatory cells. Nuclear localization of TLR4 was confirmed with Western blots on lung nuclear extracts. We conclude that TLR4 expression in lung is sustained up to 36 hours and that TLR4 and LPS are localized in the cytoplasm and nuclei of lung cells.