Effect of insulin-like growth factor-I on Leishmania amazonensis promastigote arginase activation and reciprocal inhibition of NOS2 pathway in macrophage in vitro.

We showed previously that insulin-like growth factor (IGF)-I induces an exacerbation of the lesion development in experimental cutaneous leishmaniasis favouring parasite growth within host macrophages. Here we studied the effect of IGF-I in vitro in BALB/c mouse peritoneal macrophages infected with stationary phase Leishmania amazonensis promastigotes. IGF-I was used to pre-incubate either macrophage or parasite before infection of the macrophages or adding it at the start of the Leishmania-macrophage culture and maintaining it throughout the experimental period. Independent of stimulation protocol, IGF-I induced significantly increased parasite growth within macrophages. Arginase activation considered as a key factor in Leishmania growth was studied, and its expression and activity were increased in Leishmania-infected macrophages but significantly more in infected cells upon IGF-I stimulus, an effect specifically inhibited by NOHA. Arginase known to be present on Leishmania was also studied, and its expression and activity were seen in the absence of any stimulus but significantly increased after 5 min of incubation with IGF-I. In addition, Leishmania was pre-incubated with NOHA for 5 min, washed, then macrophages infected observing a significantly reduced parasite burden in both IGF-I-stimulated and non-stimulated macrophages. Reciprocal decrease in the nitric oxide (NO) level and inhibition of nitric oxide synthase (NOS2) expression were also observed in IGF-I-stimulated infected macrophages. Our data strongly suggest that IGF-I induces preferential expression and activation of Leishmania promastigote arginase, contributes to the alternative activation of macrophages in the context of innate immunity and interferes with NOS pathway in infected macrophages probably as a reciprocal effect.

Evaluation of anti-Schistosoma mansoni IgG antibodies in patients with chronic schistosomiasis mansoni before and after specific treatment.

The circumoval precipitin test (COPT), enzyme-linked immunosorbent assay (ELISA) and the immunoblotting anti-adult worm antigen (AWA) and soluble egg antigen (SEA) tests were applied to 17 chronically schistosome-infected patients for the detection of anti-Schistosoma mansoni antibodies before and on four occasions after oxamniquine administration over a period of six months. Compared to a control group, schistosomiasis patients showed high levels of IgG antibodies in AWA and SEA-ELISA. A decrease in IgG levels was observed six months after treatment, although negative reactions were not obtained. Significant decreases in IgG1, IgG3 and, mainly, IgG4, but not anti-SEA IgG2 levels were observed six months after treatment, again without negativity. Analysis of anti-AWA IgG antibodies by immunoblotting before treatment showed a 31 kDa strand in 14 patients (82%) which disappeared in three cases up to six months after treatment; furthermore, anti-SEA IgG antibodies showed the same band in nine patients (53%) before treatment, which disappeared in only four cases up to six months after treatment.

Lipoproteins modify the macrophage uptake of triacylglycerol emulsion and of zymosan particles by similar mechanisms.

The uptake of lipids and formation of foam cells are key events in atherosclerosis and in eruptive xanthomata formation in primary hyperchylomicronemia. Here we have compared the influence of low density lipoprotein (LDL), oxidized LDL (oxLDL), high density lipoprotein (HDL), and delipidated HDL (apoHDL) on the uptake by macrophages of zymosan (an insoluble fraction of yeast cell walls) and of triglyceride-rich emulsion (EM) particles that resemble chylomicrons, but, like zymosan, are equally devoid of protein components. Zymosan internalization is known to occur through unspecific phagocytosis, whereas natural chylomicrons are taken up by several specific lipoprotein receptors. We found that phagocytosis is not promoted as much by oxLDL as by normal LDL. HDL-coated zymosan was found to be inert and apoHDL slightly enhanced phagocytosis. LDL and apoHDL promoted the uptake of EM while oxLDL and HDL significantly inhibited the uptake. Therefore, the data support that HDL, and not apoHDL, particles inhibit EM uptake. We concluded that by using lipoprotein-coated zymosan particles, we could demonstrate different biological effects of LDL, oxLDL, HDL, and apoHDL on macrophage phagocytosis and that this method could be useful to delineate components of the various lipoproteins important for the propagation or inhibition of the formation of foam cells.

Zymosan phagocytosis by mouse peritoneal macrophages is increased by apoHDL- and not by intact HDL-covered particles.

The uptake of lipids and lipoprotein particles by macrophages undergoes phagocytic activation and the formation of foam cells are key events in atherosclerosis. In this study we determined how intact high density lipoproteins (HDL) and apolipoproteins-HDL (removal of the lipid component from HDL, i.e., apoHDL) influence the phagocytosis of zymosan by mouse peritoneal macrophages. Zymosan particles preincubated together with lipoproteins or alone (control) were incubated with the macrophages. Phagocytosis activity was reported as the percent of macrophages that internalized three or more zymosan particles. HDL co-incubated with zymosan did not influence the over-all uptake of zymosan particles compared to apoHDL, which greatly enhanced the ability of the particle to be phagocytized (P<0.001). Part of this effect might be related to a greater binding of apoHDL to the particles compared to that of HDL (P<0.05). We conclude that this can be a useful method to study the ability of lipoproteins, including modified lipoproteins obtained from subjects with genetic forms of hyperlipidemia, to opsonize particles such as red blood cells and thus to investigate the processes that control the formation of foam cells and the mechanisms of atherogenesis.