In chronic schistosomiasis, hepatic fibrosis is linked to the portal hypertension that causes morbidity in Schistosoma mansoni infection. Silymarin (SIL) is a hepatoprotective and antioxidant medicament largely prescribed against liver diseases that has previously been shown to prevent fibrosis during acute murine schistosomiasis. Here we employed silymarin to try to reverse established hepatic fibrosis in chronic schistosomiasis. Silymarin or vehicle was administered to BALB/c mice every 48 h, starting on the 40th (80 days of treatment), 70th (50 days), or 110th (10 days) day postinfection (dpi). All mice were sacrificed and analyzed at 120 dpi. Treatment with silymarin reduced liver weight and granuloma sizes, reduced the increase in alanine aminotransferase and aspartate aminotransferase levels, and reduced the established hepatic fibrosis (assessed by hydroxyproline contents and picrosirius staining). Treatment with silymarin also reduced the levels of interleukin-13 (IL-13) in serum and increased the gamma interferon (IFN-␥)/IL-13 ratio. There was a linear correlation between IL-13 levels in serum and hydroxyproline hepatic content in both infected untreated and SIL-treated mice, with decreased IL-13 levels corresponding to decreased hydroxyproline hepatic contents. Treatment with either SIL or N-acetylcysteine reduced both proliferation of fibroblast cell lines and basal/IL-13-induced production of collagen I, indicating that besides inhibiting IL-13 production during infection, SIL antioxidant properties most likely contribute to inhibition of collagen production downstream of IL-13. These results show that silymarin interferes with fibrogenic cytokines, reduces established fibrosis, and inhibits downstream effects of IL-13 on fibrogenesis, indicating the drug as a safe and cheap treatment to liver fibrotic disease in schistosomiasis.
Schistosomiasis is a chronic disease of high prevalence and wide distribution around the world (1) caused by worms that parasitize the vascular system. The morbidity in schistosomiasis is associated with the arrival of worm eggs to the liver and the stimulation of a granulomatous reaction (2). Chronic liver pathology is closely associated to the nature of the host inflammatory response. The immunological progression of this disease is frequently divided in distinct phases: prepostural acute Th1 phase, postural acute Th2 phase, and chronic Th2 downmodulated phase (3). The control of this Th response throughout the chronic phase may be associated with the reduction of morbidity in schistosomiasis. During acute murine infection, administration of antioxidant drugs such as curcumin (4), resveratrol (5), n-acetylcysteine (6), artemether (7), and silymarin (8) is used to reduce morbidity and prevent hepatic fibrosis. The reversal of established hepatic fibrosis at the chronic stage is directly linked to the portal hypertension, the major cause of morbidity in Schistosoma mansoni infection, and was not attained in any of these previous works. Currently, there is no medical treatmen...