Macrophages-induced neovascularization in a murine model of accute inflammation induced by LPS

EULALIA DE LA TORRE, EUGENIA HOVSEPIAN, NORA GOREN, MARÍA ELENA SALES

Viña del Mar, Chile.

Congreso; 9th Latin American Congress of Immunology (ALAI); 2009

Septic shock (SS) induced by bacterial infections affects mainly the cardiovascular system. This damage is caused either by bacteria or by its endotoxins, ie: lypopolysaccharide (LPS). We have previously observed that LPS generates “angiogenic cardiomyocytes” in BALB/c mice. The role of macrophages (MP) in inflammatory angiogenesis during SS is almost unknown. Taking into account that angiogenesis could be improving or impairing the damage in cardiovascular tissue induced by SS, the aims of this study were to investigate the production of inflammatory mediators by MP and to evaluate its angiogenicity in a BALB/c mice model of SS induced by LPS. MP treated in vitro with LPS (10 ug/ml) produced higher levels of nitric oxide (NO) measured as nitrite (uM) than untreated MP  (MP: 3.73±0,15; MP+LPS: 10.51±0.18; control: p<0.05) concomitantly with an increase in nitric oxide synthase 2 expression by Western blot (Wb) (D.O.) (MP: N.D.;MP+LPS: 14.4±0.5) via NF-kB activation. We also observed an increment in metalloprotease-9 (MMP-9) activity induced by LPS vs. untreated MP (p<0.05). LPS also generated MP capable to induce neovascularization in vivo (Nº vessels/mm2 skin) (MP: 1.35±0.13; MP+LPS: 2.18±0.19; p<0.01). By Wb we also demonstrated that LPS produced an increment in the expression of MMP-9 (control: 3.96±0.02; LPS: 6.6±0.05; p<0.05), CD-31 (control: 23.00±0.03; LPS: 28.00±0,11; p<0.05) and vascular endothelial growth factor-A (VEGF-A) (control: 0.90±0.07; LPS: 1.80±0.04; p<0.05) in the angiogenic site. Thus we observed that MP obtained from BALB/c mice after 24h treatment with LPS i.p. (1 ug/g) up-regulated the expression of pro-angiogenic proteins respect to MP from untreated animals (control): VEGF-A (control: ND; LPS: 8.82±0.09; p<0.05) and MMP-9 (control: 2.9±0.1; LPS: 14.8±0.1; p<0.05). In conclusion murine MP are able to respond to LPS increasing the production of inflammatory mediators as NO, MMP-9 and VEGF-A in vitro and also can induce neovascularization, these effects would enable MP to be modulators of  cardiac angiogenesis during SS.