Repeated concanavalin a challenge in mice induces an interleukin 10–producing phenotype and liver fibrosis

✍ Scribed by Hubert Louis; Alain Le Moine; Eric Quertinmont; Marie-Odile Peny; Albert Geerts; Michel Goldman; Olivier Le Moine; Jacques Devière

• Book ID: 102851472
• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 593 KB
• Volume: 31
• Category: Article
• ISSN: 0270-9139
• DOI: 10.1002/hep.510310218

✦ Synopsis

Weekly injections of Concanavalin A (Con

A) were performed in BALB/c mice to evaluate the pattern of cytokine production and liver injury. High serum levels of tumor necrosis factor ␣ (TNF-␣), interleukin 2 (IL-2), IL-4, and interferon gamma (IFN-␥) were found in the serum after the first 2 injections of Con A but rapidly decreased from the third injection. Conversely, IL-10 serum levels after repeated Con A challenge increased by 7 times from week 1 to 20. In vivo depletion studies indicated that CD4 ؉ T cells are essential in IL-10 production. Hepatocyte necrosis was only observed after the first injections of Con A whereas centrilobular inflammatory infiltrates persisted up to 20 weeks. Perisinusoidal liver fibrosis was also increasingly detected in BALB/c mice, whereas no fibrous change was observed in nude mice after 6 weeks of Con A challenge. The number of stellate cells, detected by immunostaining, increased after 20 weeks of Con A injections. Liver cytokine messenger RNA (mRNA) expression after 20 weeks showed expression of transforming growth factor ␤1 (TGF-␤1), IL-10, and IL-4 whereas IL-2 was no more expressed. The present study shows that mice repeatedly injected with Con A develop liver fibrosis. The cytokinerelease pattern observed after 1 injection of Con A is rapidly shifted towards an immunomodulatory phenotype characterized by the systemic production of large amounts of IL-10. (HEPATOLOGY 2000;31:381-390.)

Hepatic diseases are a major health problem worldwide. In many chronic liver diseases including viral hepatitis 1,2 and autoimmune disorders, 3 activated T cells can be found infiltrating, and progressively destroying, the liver parenchyma. Fibrosis is a common feature complicating chronic liver inflammation that eventually leads to cirrhosis. Furthermore, evidence is now provided that increased cytokine production within the liver may be involved in liver injury. 4,5 However, few models of chronic T-cell-dependent liver injury have been developed. These are, in fact, of major interest for the understanding of immunological mechanisms involved in the development of hepatitis, fibrosis, and for the assessment of new treatments.

Recently, a model of acute T-cell-mediated liver injury was described when the plant lectin Concanavalin A (Con A) was injected in mice. 6 This well-known polyclonal mitogen stimulates a large proportion of T lymphocytes, irrespective of the antigenic specificity of the cells. 7 Injected intravenously (IV) in mice, Con A induces a cytokine secretion syndrome that leads to an organ-specific liver injury. 6 Among the endogenous cytokines secreted after Con A administration, tumor necrosis factor ␣ (TNF-␣), 8,9 interferon gamma (IFN-␥), 10,11 and interleukin 4 (IL-4) 12 play a critical role in the development of this experimental liver disease. Con A injection is followed up by lymphoid infiltration of the liver mostly with CD4 ϩ T cells, 8 these cells being crucially involved in the development of the toxicity. 6 CD4 ϩ T cells can be differentiated into 2 different subsets of lymphocytes depending on their cytokine production pattern: Th1 clones producing IL-2, IFN-␥, and TNF-␤; and Th2 clones producing IL-4, IL-5, IL-6, IL-10, and IL-13. 13 IL-10 is a potent anti-inflammatory cytokine that can be produced by Th0 and Th2 cells, monocytes/macrophages, including Kupffer cells, and B cells. 14,15 IL-10 inhibits the synthesis of proinflammatory cytokines by Th-1 T cells, 16,17 and reduces T-cell activation. 18 In a previous report, we stated that IL-10 is produced within the liver after Con A challenge, and that endogenously produced IL-10 has a protective role in Con A-induced hepatitis, through its suppressive property on proinflammatory cytokine production. 19 The aim of the present study was to evaluate the effects of chronic exposure to Con A on the development of liver injury in mice. We show that this experimental model leads to a long-lasting IL-10-producing phenotype, liver inflammatory infiltrates and fibrosis, and might serve as a new tool in the understanding of chronic liver diseases.

Methods

Animals. Ten to 15-week-old female BALB/c and athymic nude mice were purchased from Bantin & Kingman (Grimston Aldbrough, Hull, UK). They were maintained in our animal facilities on standard laboratory chow. All animals received care in compliance with the national legal requirements and with the National Institutes of Health guidelines.