Enhanced expression of type I interferon and toll-like receptor-3 in primary biliary cirrhosis

Abstract

The pathogenesis of primary biliary cirrhosis (PBC) remains enigmatic. In order to address this issue, we analyzed by laser capture microdissection and real-time reverse transcription-polymerase chain reaction the site-specific expression of messenger RNA (mRNA) for cytokines (interferon (IFN)-a, -b, -c, interleukin (IL)-1b, -4, -6, -10, -12p40, -18, tumor necrosis factor-a) and toll-like receptors (TLRs) (TLR-2, -3, -4, -7, -9) in portal tract and liver parenchyma from patients with early-stage PBC. Expression of IFN-a, -b and TLR-3 proteins was also studied by immunohistochemistry. Autoimmune hepatitis (AIH) and chronic hepatitis C (CHC) served as disease controls. The expression levels of type I IFN (IFN-a, -b) and TLR-3 mRNAs, which are known to induce type I IFN, were significantly higher in portal tract and liver parenchyma as compared to AIH and CHC. A strong positive correlation between the mRNA levels of type I IFN and TLR-3 was also seen in both areas. Immunohistologically, IFN-a is present in the mononuclear cells in portal tract and sinusoidal cells. Macrophages in portal tract and hepatocytes expressed IFN-b and TLR-3. Furthermore, the level of IFN-a mRNA in the portal tract was positively correlated with serum alkaline phosphatase. In conclusion, these data indicate that TLR-3 and type I IFN signaling pathways are active in both the portal tract and liver parenchyma of early-stage PBC, and form the basis for our hypothesis that these signaling pathways are involved in the pathophysiology of PBC. Laboratory Investigation (2005) 85, 908-920.

The type I interferon system in systemic lupus erythematosus

“…In addition, expression of IFN␣ genes in islets precedes the lymphocyte infiltration and islet cell destruction observed in experimental diabetes, which moreover can be prevented by neutralizing anti-IFN␣ antibodies. Recently, increased IFN␣ mRNA expression was also noted in liver biopsy specimens obtained from patients with primary biliary cirrhosis (98).…”

Increased expression of Toll-like receptor 3 in intrahepatic biliary epithelial cells at sites of ductular reaction in diseased livers

“…Mouse monoclonal antibodies specific for cytokeratin (CK) 7 and CK 19 were purchased from DAKO (DAKO Japan, Kyoto, Japan). Frozen sections, 4 mm in thickness, were stained with anti-TLR and anti-CK7 or -CK19 antibodies as described elsewhere [17]. Briefly, frozen sections were first fixed in 50 and 100% acetone for 30 s and 3 min, respectively, followed by treatment with Peroxidase Blocking agent (DAKO) for 10 min.…”

“…Immunostaining of these cultured cells was then performed in a similar manner as that described for frozen sections of liver biopsies [17]. In brief, HIBECs were fixed with acetone, treated with peroxidase-blocking agent, and incubated with anti-TLR (anti-TLR1, -2, -3, -4, and -6) and anti-CK7 or anti-CK19 monoclonal antibodies followed by visualization of bound antibodies using a standard 2-step method with ENVISION+ (DAKO).…”

“…We previously found that the expression of TLR3 and IFN-b mRNAs is significantly increased in both the portal areas and parenchyma of livers diseased with PBC [17]. There was a positive correlation between TLR3 and IFN-b mRNA levels in both areas, indicating that TLR3-type 1 IFN signaling pathway is activated in PBC; the TLR3-expressing and/or IFN-b-producing cells, however, remain unknown [17]. This prompted us to investigate TLR3 expression and IFN-b production in human intrahepatic biliary epithelial cells (HIBECs).…”

“…The intracellular RNA sensors RIG-I/MDA5 also serve as IFN inducers acting via the mitochondrial antiviral signaling protein (MAVS)-IRF3 signaling pathway, thus protecting host cells against the spread of viral invasion [2,3]. We previously found that the expression of TLR3 and IFN-b mRNAs is significantly increased in both the portal areas and parenchyma of livers diseased with PBC [17]. There was a positive correlation between TLR3 and IFN-b mRNA levels in both areas, indicating that TLR3-type 1 IFN signaling pathway is activated in PBC; the TLR3-expressing and/or IFN-b-producing cells, however, remain unknown [17].…”