Effect of tumour necrosis factor-α receptor 1 genetic deletion on carrageenan-induced acute inflammation:: a comparison with etanercept

In the present study, we used tumour necrosis factor-alpha receptor 1 knock-out mice (TNF-alpha R1KO) to evaluate an in vivo role of TNF-alpha R1 on the pathogenesis of inflammatory diseases. We used a murine model of carrageenan-induced acute inflammation (pleurisy), a preclinical model of airway inflammation. The data proved that TNF-alpha R1KO were resistant to carrageenan-induced acute inflammation compared with TNF-alpha wild-type mice. TNF-alpha R1KO showed a significant reduction in accumulation of pleural exudate and in the number of inflammatory cells, in lung infiltration of polymorphonuclear leucocytes and lipid peroxidation and showed a decreased production of nitrite/nitrate in pleural exudates. Furthermore, the intensity and degree of the adhesion molecule intercellular adhesion molecule-1 and P-selectin, Fas ligand (FasL), inducible nitric oxide sythase and nitrotyrosine determined by immunohistochemical analysis were reduced markedly in lung tissues from TNF-alpha R1KO at 4 h and 24 h after carrageenan injection. Moreover, TNF-alpha and interleukin-1 beta concentrations were reduced in inflamed areas and in pleural exudates from TNF-alpha R1KO. To support the results generated using pleural inflammation, carrageenan-induced paw oedema models were also performed. In order to elucidate whether the observed anti-inflammatory effects were related to the inhibition of TNF-alpha, we also investigated the effect of etanercept, a TNF-alpha soluble receptor construct, on carrageenan-induced pleurisy. The treatment with etanercept (5 mg/kg subcutaneously 2 h before the carrageenan injection) reduces markedly both laboratory and histological signs of carrageenan-induced pleurisy. Our results showed that administration of etanercept resulted in the same outcome as that of deletion of the TNF-alpha R1 receptor, adding a new insight to TNF-alpha as an excellent target by therapeutic applications.