Prostaglandinas dependientes de ciclooxigenasa-2: moléculas clave en el conrol funcional de los macrófagos

Resumen

Cyclooxigenase-2 (Cox-2) dependent prostaglandins (PGs) modulate many functions in a great variety of pathophysiological processes that require cell activation and cell migration. Cox-2 deficiency has been shown to decrease inflammation in mice. Here, we show that Cox-2 contributes to the development of inflammation. Accumulation of F4/80+ CD11b+ CD11c+ macrophages into the peritoneal cavity upon thioglycolate challenge was diminished in Cox-2 knockout mice compared to wild type mice. Cox-2 deficiency in macrophages resulted in a reduced expression of CD11c. Maturation of monocytes to activated macrophages was altered in the absence of Cox-2 which was related to lower levels of GM-CSF-R in Cox-2-/- macrophages and also in a decreased expression of CD11c. Cox-2 deficient macrophages showed reduced cell activation, evidenced by a reduced degradation and phosphorylation of I¿B, reduced expression of iNOS and diminished ability to clear bacteria. Besides, Cox-2-deficient macrophages had an impaired ability to activate T lymphocytes, due to reduced expression of MHCII, CD40, CD80 and CD86 molecules. We have also addressed how migration of cox-2 deficient leukocytes occur using in vivo and in vitro models. Cox-2-/- macrophages did not migrate in response to MCP-1, RANTES or MIP-1¿, and had an impaired adhesion to ICAM-1 or Fibronectin in vitro. These results were reproduced in wild type macrophages in which Cox-2 activity was blocked with pharmacological inhibitors. In vivo studies showed that cell emigration from the peritoneal cavity to lymph nodes, as well as cell adhesion to the peritoneal mesothelium was impaired in the absence of Cox-2. The defect in cox-2-/- macrophage migration was not due to changes in chemokine receptor expression. Molecular studies using cox-2-/- macrophages showed a deficiency in focal adhesion formation with reduced ability to phosphorylate paxillin (Tyr188). Phosphatydyl-3 kinase (PI3K) signalling pathway was also defective due to reduced p110¿ expression. Reduced p110 ¿ leaded to a diminished phosphorylation of Akt and a reduced activation of Cdc42 and Rac-1. Interestingly, short term inhibition of Cox-2 enzymatic activity also resulted in decreased levels of p110¿. Thus, our results indicate that cox-2-/- macrophages have a defective axis Paxillin/PI3K/Akt/Rac1-Cdc42, which results in severely impaired adhesion and migration. Finally, we studied the effects of different concentrations of PGE2 and PGF2¿ in macrophage activation, macrophage migration to different chemokines and cell adhesion to ICAM-1 and fibronectin. PGE2 and PGF2¿ affected cell adhesion and migration in a dose- dependent. PGE2 is able to increase adhesion and p110¿ expression and reverse the defective adhesion of cox-2-/- macrophages. Nonetheless, those effects varied depended on inflammatory or not PGE2 concentrations.