Portal fibroblasts (PF) are fibrogenic liver cells distinct from hepatic stellate cells (HSC). Recent evidence suggests that PF may be important mediators of biliary fibrosis and cirrhosis. The cytokine monocyte chemoattractant protein-1 (MCP-1)/CCL2 is upregulated in biliary fibrosis by bile duct epithelia (BDE) and induces functional responses in HSC. Thus we hypothesized that release of MCP-1 may mediate biliary fibrosis. We report that PF express functional receptors for MCP-1 that are distinct from the receptor CCR2. MCP-1 induces proliferation, increase and redistribution of α-smooth muscle (α-SMA) expression, loss of the ectonucleotidase NTPDase2, and upregulation of α1-procollagen production in PF. BDE secretions induce α-SMA levels in PF, and this is inhibited by MCP-1 blocking antibody. Together, these data suggest that BDE regulate PF proliferation and myofibroblastic transdifferentiation in a paracrine fashion via release of MCP-1.

Background & Aims Progressive Familial Intrahepatic Cholestasis 1 (PFIC1) results from mutations in ATP8B1 (also known as FIC1), a putative aminophospholipid flippase. However conflicting hypotheses have been proposed for the pathogenesis of PFIC1. The aim of this study was to determine whether ATP8B1-deficiency produces cholestasis by altering the activity of the nuclear receptor FXR or by impairing the structure of the canalicular membrane Methods ATP8B1/Atp8b1 was knocked down in human and rat hepatocytes, and Caco2 cells using adenoviral and oligonucleotide siRNAs. Results ATP8B1 mRNA and protein expression was greatly reduced in human and rat hepatocytes and Caco2 cells. In contrast, FXR expression and several FXR dependent membrane transporters (BSEP, MRP2) were unchanged at mRNA or protein levels in ATP8B1-deficient cells, whereas Mrp3 and Mrp4 were up-regulated in rat hepatocytes. FXR activity remained intact in these cells as evidenced by 6-ECDCA mediated induction of SHP, BSEP and MDR3/Mdr2. Fluorescent substrate excretion assays indicate that Bsep function was significantly reduced in Atp8b1-deficient rat hepatocytes although Bsep remained localized to the canalicular membrane. Exposure to the hydrophobic bile acid, CDCA resulted in focal areas of canalicular membrane disruption by electron microscopy and luminal accumulation of NBD-phosphatidylserine consistent with Atp8b1’s function as an aminophospholipid flippase. Conclusion ATP8B1- deficiency predisposes to cholestasis by favoring bile acid-induced injury in the canalicular membrane, but does not directly affect FXR expression, which may occur in PFIC1 as a secondary phenomenon associated to bile acid accumulation.

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TMEPAI/PMEPA1 is a transmembrane protein that was originally identified as a prostatic RNA, the synthesis of which is induced by testosterone or its derivatives. We have recently identified TMEPAI as a direct target gene of transforming growth factor-β (TGF-β)/Smad signaling that participates in negative feedback control of the duration and intensity of TGF-β/Smad signaling. TMEPAI is constitutively and highly expressed in many types of cancer and is associated with poor prognosis. Here, we report that TMEPAI is highly expressed in the lung adenocarcinoma cell lines Calu3, NCI-H23, and RERF-LC-KJ. Expression of TMEPAI in these cancer cells was significantly suppressed by a TGF-β receptor kinase antagonist, SB208, and by TGF-β neutralizing antibodies. These results suggest that constitutive expression of TMEPAI in these cancer cells depends on autocrine TGF-β stimulation. Knockdown of TMEPAI in Calu3 and NCI-H23 cells enhanced levels of Smad2 phosphorylation and significantly suppressed cell proliferation in the presence of TGF-β, indicating that highly expressed TMEPAI suppresses levels of Smad phosphorylation in these cancer cells and reduces the growth inhibitory effects of TGF-β/Smad signaling. Furthermore, knockdown of TMEPAI in Calu3 and NCI-H23 cells suppressed sphere formation in vitro and tumor formation in s.c. tissues and in lungs after tail vein injection in NOD-SCID mice in vivo. Together, these experiments indicate that TMEPAI promotes tumorigenic activities in lung cancer cells.