cord-factors and Peritonitis

Sepsis is a systemic inflammatory response to bacterial infection. The therapeutic options for treating sepsis are limited. Impaired neutrophil recruitment into the infection site is directly associated with severe sepsis, but the precise mechanism is unclear. Here, we show that Mincle plays a key role in neutrophil migration and resistance during polymicrobial sepsis. Mincle-deficient mice exhibited lower survival rates in experimental sepsis from cecal ligation and puncture and Escherichia coli-induced peritonitis. Mincle deficiency led to higher serum inflammatory cytokine levels and reduced bacterial clearance and neutrophil recruitment. Transcriptome analyses revealed that trehalose dimycolate, a Mincle ligand, reduced the expression of G protein-coupled receptor kinase 2 (GRK2) in neutrophils. Indeed, GRK2 expression was upregulated, but surface expression of the chemokine receptor CXCR2 was downregulated in blood neutrophils from Mincle-deficient mice with septic injury. Moreover, CXCL2-mediated adhesion, chemotactic responses, and F-actin polymerization were reduced in Mincle-deficient neutrophils. Finally, we found that fewer Mincle-deficient neutrophils infiltrated from the blood circulation into the peritoneal fluid in bacterial septic peritonitis compared with wild-type cells. Thus, our results indicate that Mincle plays an important role in neutrophil infiltration and suggest that Mincle signaling may provide a therapeutic target for treating sepsis.

Topics: Animals; Cell Movement; Coinfection; Cord Factors; Escherichia coli; G-Protein-Coupled Receptor Kinase 2; Gene Expression Regulation; Humans; Lectins, C-Type; Membrane Proteins; Mice; Neutrophil Infiltration; Neutrophils; Peritonitis; Receptors, Interleukin-8B; Sepsis; Transcriptome

Intraperitoneal injections of cord factor (trehalose dimycolate, TDM) provides a model for interstitial and hemorrhagic lung disease that is produced by a chemically defined substance. A single injection of 10 micrograms of TDM, in light mineral oil or hexadecane, into C57BL/6 mice produces interstitial and hemorrhagic pneumonitis. Following injection of TDM the pulmonary lesions increase gradually and become maximal by the seventh to ninth day, at which time 70% of the mice show both gross hemorrhages and dense mononuclear infiltrates; an additional 20% of the mice show only microscopic lesions. From day 14 onward the incidence and severity of the lesions decrease, and by day 28 the lungs are normal by both gross and light-microscopy examination. Only 5% of the mice succumb. Except for peritonitis other organs are not affected. Doses of 3.3 and 10 micrograms of TDM are equally effective in producing the lesions, but a dose of 1.0 microgram of TDM causes only mild interstitial inflammation and lesser doses do not induce lesions. A single subcutaneous injection of 10 micrograms of TDM causes lesions in only 20% of mice. Vehicle-injected mice do not develop lesions. Electron microscopy revealed that the majority of the infiltrating cells are monocytes and macrophages and that extensive interstitial damage is produced. The mechanism of the effects of TDM are unknown and is currently under study. Our preliminary data suggests that the phenomenon is dependent upon T-lymphocytes.

Topics: Animals; Cord Factors; Glycolipids; Hemorrhage; Injections, Intraperitoneal; Lung; Macrophages; Male; Mice; Mice, Inbred C57BL; Microscopy, Electron; Monocytes; Mycobacterium tuberculosis; Peritonitis; Pneumonia; T-Lymphocytes; Time Factors