The pathogenesis of pulmonary contusion: an open chest model in the rat.
BACKGROUND
Chemokines direct leukocytes to areas of inflammation or injury. In general, CC chemokines (MCP-1, MIP-1alpha, RANTES) are chemoattractants for mononuclear cells and CXC (CINC-1, MIP-2alpha) for polymorphonuclear cells (PMNs). Herein we describe an open chest model of pulmonary contusion (PC) in a rodent (rat) and have identified a possible role for CC and CXC chemokines in the pathogenesis of PC.


METHODS
Sprague-Dawley rats (350 g) underwent thoracotomy. The exposed lung was struck with a piston at 5.2 m/s (150 J/M2). Blood, bronchoalveolar lavage (BAL), and lung tissue were collected at 3 hours and 24 hours after injury. PaO2/FiO2 (P/F) ratio was calculated at 15-minute intervals for 3 hours after contusion. Serum was evaluated for cytokine and chemokine expression using ELISA. Cell count/differential was performed on BAL, and lung tissue was obtained for histologic analysis, protein expression and wet to dry weights. Data are reported as pg/mL +/- SE. Data were analyzed using Student's t test to identify significant differences (p < or = 0.05 significant) between sham and injured animals.


RESULTS
Piston impact caused PC based upon morphologic and histologic criteria. BAL cell count and lung wet to dry weights were increased and P/F ratio was decreased after PC. Systemic levels of IL-ra, MCP-1, and the CXC chemokines MIP-2alpha and CINC-1 were significantly elevated at 3 hours when sham and injured animals were compared. All chemokines were found to be significantly elevated at 24 hours, consistent with the early PMN and subsequent mononuclear infiltration observed in the contused lung. Pulmonary expression of TNF-alpha, IL-1beta, CINC-1, MIP-2alpha, ICAM-1, and elastase were increased and activated systemic neutrophils showed increased CD-11b.


CONCLUSIONS
A model of PC is described in which innate inflammation is activated locally and systemically. Systemic levels of CC and CXC chemokines are increased after PC. This correlates with elevated PMN CD-11b expression, enhanced pulmonary ICAM-1 expression, and mononuclear and PMN infiltration into the lung and alveolar space. Elevated levels of CC and CXC chemokines are seen after PC and may be involved in the lung's inflammatory response to injury.
Hoth
J Jason
JJ
Department of General Surgery, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA. jhoth@wfubmc.edu
Stitzel
Joel D
JD
Gayzik
F Scott
FS
Brownlee
Noel A
NA
Miller
Preston R
PR
Yoza
Barbara K
BK
McCall
Charles E
CE
Meredith
J Wayne
JW
Payne
R Mark
RM
D000818:Animals; D039481:CD11b Antigen / Q000378:metabolism; D019742:Chemokines, CC / Q000097:blood; D019743:Chemokines, CXC / Q000097:blood; D003288:Contusions / Q000276:immunology* / Q000473:pathology; D004195:Disease Models, Animal; D007113:Immunity, Innate; D007249:Inflammation / Q000503:physiopathology; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D055370:Lung Injury; D008297:Male; D018375:Neutrophil Activation; D051381:Rats; D017207:Rats, Sprague-Dawley
D039481:CD11b Antigen; D019742:Chemokines, CC; D019743:Chemokines, CXC; D018799:Intercellular Adhesion Molecule-1