Therapeutic effects and anti-inflammatory mechanisms of heparin on acute lung injury in rabbits

Objectives: The objectives were to investigate the potential beneficial effects and molecular mechanisms of heparin and low-molecular-weight heparin (LMWH) on acute lung injury (ALI). Methods: Forty-eight rabbits were randomized into four groups: normal control group (Group A), lipopolysaccharide (LPS) group (Group 13), LPS + heparin group (Group Q, and LPS + LMWH group (Group D). The rabbit ALI model was established by intravenous (IV) injection with LPS. Alveolar-arterial O-2 difference (PA-aO2), serum tumor necrosis factor alpha (TNF-alpha), circulating p38 mitogen-activated protein kinase (p38 MAPK) levels, lung nuclear factor (NF)-kappa B levels, and lung dry/wet (D/W) ratio were measured, and the lung injury scores were calculated. Results: Lipopolysaccharide caused significant increases in PA-aO2, serum TNF-alpha, expression of p38 MAPK in polymorphonuclear neutrophils (PMNs), the lung injury scores, and nuclear factor-kappa B (NF-kappa B) activity in the lung tissue and caused a decrease in lung D/W ratio. A positive linear correlation was found between p38 MAPK and TNF-alpha at 1, 2, 4, and 6 hours (r = 0.68, 0.92, 0.93, and 0.93, respectively) and between NF-kappa B and p38 MAPK and TNF-alpha at 6 hours (r = 0.94 and 0.83, respectively). IV heparin or LMWH given after LPS treatment attenuated these changes in inflammatory response, oxygenation, p38 MAPK expression, and NF-kappa B activation. Conclusions: The anti-inflammatory mechanisms of heparin in ALI may be inhibiting p38 MAPK and NF-kappa B activities, and then TNF-alpha overexpression, thus alleviating the inflammatory reaction.