ABSTRACT
BACKGROUND: The role of Kupffer cell interleukin (IL)-1 in non-alcoholic steatohepatitis development remains unclear. AIMS: To evaluate the role of Kupffer cell IL-1α, IL-1ß or IL-1 receptor type-1 (IL-1R1) in steatohepatitis. METHODS: C57BL/6 mice were irradiated and transplanted with bone marrow-derived cells from WT, IL-1α-/-, IL-1ß-/- or IL-1R1-/- mice combined with Kupffer cell ablation with Gadolinium Chloride, and fed atherogenic diet. Plasma and liver triglycerides and cholesterol, serum alanine aminotransferase (ALT), liver histology and expression levels of inflammatory genes were assessed. RESULTS: The ablation and replacement of Kupffer cells with bone marrow-derived cells was confirmed. The atherogenic diet elevated plasma and liver cholesterol, reduced plasma and liver triglycerides and increased serum ALT levels in all groups. Steatosis and steatohepatitis were induced, but without liver fibrosis. A reduction in the severity of portal inflammation was observed only in mice with Kupffer cell deficiency of IL-1α. Accordingly, liver mRNA levels of inflammatory genes encoding for IL-1α, IL-1ß, TNFα, SAA1 and IL-6 were significantly lower in mice with Kupffer cell deficiency of IL-1α compared to WT mice. CONCLUSION: Selective deficiency of IL-1α in Kupffer cells reduces liver inflammation and expression of inflammatory cytokines, which may implicate Kupffer cell-derived IL-1α in steatohepatitis development.
Subject(s)
Cholesterol/metabolism , Fatty Liver/metabolism , Hepatitis/blood , Hypercholesterolemia/metabolism , Interleukin-1alpha/deficiency , Kupffer Cells/metabolism , Triglycerides/metabolism , Alanine Transaminase/blood , Animals , Diet, Atherogenic , Fatty Liver/genetics , Fatty Liver/pathology , Female , Gene Expression , Hepatitis/genetics , Hepatitis/pathology , Hypercholesterolemia/genetics , Interleukin-1alpha/genetics , Interleukin-1beta/deficiency , Interleukin-1beta/genetics , Interleukin-6/genetics , Male , Mice , Mice, Knockout , Portal System , RNA, Messenger/metabolism , Receptors, Interleukin-1 Type I/deficiency , Receptors, Interleukin-1 Type I/genetics , Serum Amyloid A Protein/genetics , Tumor Necrosis Factor-alpha/genetics , Vasculitis/metabolismABSTRACT
OBJECTIVES: Interleukin (IL)-1 produced by vascular and bone marrow-derived cells exerts proinflammatory effects in these cell types by binding to IL-1 receptor type-1 (IL-1R1). We have previously shown that bone marrow-derived IL-1α and IL-1ß are critical for atherogenesis in apoE knockout (KO) mice. The aim of the present study was to investigate whether IL-1R1 on vascular wall resident or bone marrow-derived cells mediates IL-1's effects in atherogenesis. METHODS AND RESULTS: We generated apoE-/-/IL-1R1-/- double knockout (DKO) mice and created radiation chimeras. Aortic sinus lesion area was 20-47% lower in DKO compared to apoE KO mice with similar plasma lipids. The production of IL-1α and IL-1ß upon stimulation with LPS was not altered in IL-1R1-/- compared to IL-1R1+/+ peritoneal macrophages. DKO mice transplanted with IL-1R1+/+ bone marrow-derived cells had reduced (48%) aortic sinus lesion compared to apoE KO mice while specific deficiency of IL-1R1 in bone marrow-derived cells did not attenuate atherosclerosis. The mRNA levels of genes that promote macrophage recruitment to the vascular wall, namely CD68, VCAM-1, ICAM-1 and MCP-1 were lower in aortas from DKO compared to apoE KO mice. Finally, blockade of IL-1R1 with IL-1R antagonist (IL-1Ra) resulted in complete abrogation of IL-1ß-induced expression of adhesion and chemotactic molecules and IL-1α, in isolated human umbilical vein endothelial cells (HUVEC). CONCLUSIONS: Vascular wall resident cells are the main targets for the pro-atherogenic effects of bone marrow-derived IL-1 through IL-1R1, partly by induction of adhesion and chemotactic molecules in endothelial cells.
Subject(s)
Aorta/immunology , Aortic Diseases/immunology , Apolipoproteins E/deficiency , Atherosclerosis/immunology , Inflammation Mediators/metabolism , Interleukin-1/metabolism , Receptors, Interleukin-1 Type I/metabolism , Animals , Aorta/metabolism , Aorta/pathology , Aortic Diseases/blood , Aortic Diseases/genetics , Aortic Diseases/pathology , Apolipoproteins E/genetics , Atherosclerosis/blood , Atherosclerosis/genetics , Atherosclerosis/pathology , Body Weight , Cells, Cultured , Disease Models, Animal , Gene Expression Regulation , Human Umbilical Vein Endothelial Cells/immunology , Human Umbilical Vein Endothelial Cells/metabolism , Humans , Interleukin-1/genetics , Lipids/blood , Macrophages/immunology , Macrophages/metabolism , Male , Mice , Mice, Inbred C57BL , Mice, Knockout , RNA, Messenger/metabolism , Radiation Chimera , Receptors, Interleukin-1 Type I/deficiency , Receptors, Interleukin-1 Type I/genetics , Time FactorsABSTRACT
BACKGROUND & AIMS: The identification of the cellular and molecular pathways that mediate the development of non-alcoholic steatohepatitis is of crucial importance. Cytokines produced by liver-resident and infiltrating inflammatory cells, play a pivotal role in liver inflammation. The role of the proinflammatory cytokines IL-1α and IL-1ß in steatohepatitis remains elusive. METHODS: We employed IL-1α and IL-1ß-deficient mice and transplanted marrow cells to study the role of liver-resident and bone marrow-derived IL-1 in steatosis and its progression to steatohepatitis. RESULTS: Atherogenic diet-induced steatohepatitis in wild-type mice was associated with 16 and 4.6 fold-elevations in mRNA levels of hepatic IL-1α and IL-1ß, respectively. In mice deficient in either IL-1α or IL-1ß the transformation of steatosis to steatohepatitis and liver fibrosis was markedly reduced. This protective effect in IL-1α-deficient mice was noted despite increased liver cholesterol levels. Deficiency of IL-1α markedly reduced plasma serum amyloid A and steady-state levels of mRNA coding for inflammatory genes (P-selectin, CXCL1, IL-6, and TNFα) as well as pro-fibrotic genes (MMP-9 and Collagen) and particularly a 50% decrease in TGFß levels (p = 0.004). IL-1α mRNA levels were two-folds lower in IL-1ß-deficient mice, and IL-1ß transcripts were three-folds lower in IL-1α-deficient compared to wild-type mice. Hepatic cell derived IL-1α rather than from recruited bone marrow-derived cells was required for steatohepatitis development. CONCLUSIONS: These data demonstrate the critical role of IL-1α and IL-1ß in the transformation of steatosis to steatohepatitis and liver fibrosis in hypercholesterolemic mice. Therefore, the potential of neutralizing IL-1α and/or IL-1ß to inhibit the development of steatohepatitis should be explored.
