Schistosoma mansoni eggs modulate lipid metabolism in hepatocytes

Introduction:

Schistosomiasis is a prevalent parasitic disease causing severe clinical symptoms as well as socioeconomic problems and more than 200,000 deaths per year. During infection with S. mansoni, paired adult worms produce approximately 300 eggs per day per couple. Eggs-secreted and immunologically active antigens are involved in the recruitment of inflammatory and immune cells, leading to the formation of granulomas and eventually progressing fibrosis.

Methods:

In the present study, liver tissue of S. mansoni-infected hamsters was examined by Western blot (WB) and immunohistochemistry (IHC) to analyse hepatic lipid metabolism during S. mansoni infection. Monosex infection with cercariae of one sex was used as control to mimic worm infection without egg production.

Results:

IHC analyses showed increased Perilipin2, FAS (fatty acid synthase), and ACC1 (Acetyl-CoA carboxylase 1) expression in hepatocytes around granulomas in bisex infected livers. Additionally, WB demonstrated increased FAS and ACC1 expression in the livers of bisex-infected hamsters as compared to monosex. On the other hand, enzymes involved in lipid catabolism, e.g. hepatic lipase (LIPC), were found to be downregulated in hepatocytes around granulomas.

Conclusions:

In conclusion, our data demonstrated for the first time enhanced lipid synthesis and accumulation as well as reduced lipid catabolism in hepatocytes around granulomas in infected liver tissue. These results suggest that eggs might not only benefit from the host"s lipids as they cannot produce these lipids by themselves but, moreover, that eggs are able to actively drive the process of lipid synthesis and supply. Since it is not clear if this processes are controlled directly by egg-secreted factors or indirectly by the induction of granulomatous inflammation we aim to analyse whether these effects can be induced by eggs or egg-secreted factors in cell culture.