title: Rabbits with elevated serum C-reactive protein exhibit diminished neutrophil infiltration and vascular permeability in C5a-induced alveolitis.
abstract: In previous studies, we have shown that C-reactive protein (CRP) inhibits chemotaxis of neutrophils to complement fragments in vitro. To evaluate the effect of CRP on C5a-induced inflammation in vivo, a rabbit model of alveolitis was used. Rabbits pretreated with subcutaneous injections of croton oil had serum CRP increase from undetectable levels to 270 +/- 70 micrograms/ml 48 hours later. Rabbits were intubated and C5a des arg (10 micrograms/ml) instilled directly into the lungs via an endotracheal tube. Four to six hours later, the animals were killed and bronchoalveolar lavage performed. Rabbits pretreated with croton oil had significantly (P < 0.01) reduced C5a des arg-stimulated neutrophil infiltration (30 +/- 5%) into alveolar air spaces compared to untreated rabbits (64 +/- 9%). Increased numbers of total leukocytes in the alveolar washes coincided with increased neutrophil numbers whereas alveolar macrophages remained unchanged in all groups. Rabbits pretreated with croton oil also had a significant decrease (P < 0.05) in total protein (320 +/- 50 micrograms/ml) in lavage fluid after C5a instillation compared with untreated animals (850 +/- 140 micrograms/ml). In vitro, rabbit CRP (50 micrograms/ml) added to normal rabbit serum significantly (P < 0.05) inhibited chemotaxis of human neutrophils by 41%. Finally, direct intravenous pretreatment of rabbits with purified CRP also significantly reduced C5a-induced alveolitis. The CRP-C5a group had 33 +/- 10% neutrophil infiltration, a significant (P < 0.01) reduction from the C5a group (71 +/- 6%). The total protein content of the CRP-C5a rabbits was 986 +/- 165 micrograms/ml in the lavage fluid, which was significantly (P < 0.05) lower than the C5a group (1645 +/- 363 micrograms/ml). Therefore, CRP inhibits the development of neutrophil alveolitis and protein leakage in vivo and inhibits neutrophil chemotaxis in vitro. These data indicate that CRP offers a protective effect in neutrophil-mediated lung injury by reducing neutrophil influx and protein leak.
authors.affiliation: Cell and Molecular Biology Program, St. Louis University School of Medicine, Missouri.
authors.forename: R M
authors.initials: RM
authors.lastname: Heuertz
authors.forename: C A
authors.initials: CA
authors.lastname: Piquette
authors.forename: R O
authors.initials: RO
authors.lastname: Webster
mesh_terms: D000818:Animals; D002097:C-Reactive Protein / Q000008:administration & dosage / Q000378:metabolism* / Q000502:physiology; D002199:Capillary Permeability / Q000187:drug effects*; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology; D002634:Chemotaxis, Leukocyte / Q000187:drug effects; D015937:Complement C5a, des-Arginine / Q000494:pharmacology*; D003436:Croton Oil / Q000008:administration & dosage / Q000494:pharmacology; D006801:Humans; D009504:Neutrophils / Q000187:drug effects / Q000473:pathology*; D011817:Rabbits; D012130:Respiratory Hypersensitivity / Q000097:blood* / Q000473:pathology
chemical_list: D015937:Complement C5a, des-Arginine; D003436:Croton Oil; D002097:C-Reactive Protein