Background and Aim Hepatic fibrosis is marked by activation of hepatic stellate cells (HSCs). Cholestatic injury precedes liver fibrosis and cholangiocytes interact with HSCs promoting fibrosis. Mast cells (MCs) infiltrate following liver injury and release histamine increasing biliary proliferation. We evaluated if inhibition of MC-derived histamine decreases biliary proliferation and fibrosis. Methods WT and Mdr2−/− mice (9-11 weeks) were treated with cromolyn sodium for 1 week to block MC-derived histamine. Biliary mass and proliferation were evaluated by immunohistochemistry for CK-19 and Ki-67. Bile flow, bicarbonate excretion and total bile acids were measured in all mice. Fibrosis was evaluated by Sirius Red/Fast Green staining and by qPCR for α-SMA, fibronectin, collagen type 1a and TGF-β1. HSC activation was evaluated by qPCR in total liver and immunofluorescent staining in tissues for synaptophysin 9. Histamine serum secretion was measured by EIA. Mouse liver and human liver samples from control or PSC patients were evaluated for MC markers by qPCR and immunohistochemistry. In vitro, cultured MCs were transfected with HDC shRNA to decrease histamine secretion and subsequently co-cultured with cholangiocytes or HSCs prior to measuring fibrosis markers, proliferation and TGF-β1 secretion. Results Treatment with cromolyn sodium decreased biliary proliferation, fibrosis, histamine secretion, and bile flow in Mdr2−/− mice. PSC mice and patients have increased MCs. Knockdown of MC HDC decreased cholangiocyte and HSC proliferation/activation. Conclusion MCs are recruited to proliferating cholangiocytes and promote fibrosis. Inhibition of MC-derived histamine decreases fibrosis and regulation of MC mediators may be a therapeutic for PSC.

Cholangiopathies are characterized by dysregulation of the balance between biliary growth and loss. We have shown that histamine (HA) stimulates biliary growth via autocrine mechanisms. To evaluate the paracrine effects of mast cell (MC) stabilization on biliary proliferation, sham or BDL rats were treated by IP-implanted osmotic pumps filled with saline or cromolyn sodium (24 mg/kg BW/day (inhibits MC histamine release)) for 1 week. Serum, liver blocks and cholangiocytes were collected. Histidine decarboxylase (HDC) expression was measured using real-time PCR in cholangiocytes. Intrahepatic bile duct mass (IBDM) was evaluated by IHC for CK-19. MC number was determined using toluidine blue staining and correlated to IBDM. Proliferation was evaluated by PCNA expression in liver sections and purified cholangiocytes. We assessed apoptosis using real-time PCR and IHC for BAX. Expression of MC stem factor receptor, c-kit, and the proteases chymase and tryptase were measured by real-time PCR. HA levels were measured in serum by EIA. In vitro, MCs and cholangiocytes were treated with 0.1% BSA (basal) or cromolyn (25 mM) for up to 48 h prior to assessing HDC expression, HA levels and chymase and tryptase expression. Supernatants from MCs treated with or without cromolyn were added to cholangiocytes before measuring (i) proliferation by MTT assays, (ii) HDC gene expression by real-time PCR and (iii) HA release by EIA. In vivo, cromolyn treatment decreased BDL-induced: (i) IBDM, MC number, and biliary proliferation; (ii) HDC and MC marker expression; and (iii) HA levels. Cromolyn treatment increased cholangiocyte apoptosis. In vitro, cromolyn decreased HA release and chymase and tryptase expression in MCs but not in cholangiocytes. Cromolyn-treated MC supernatants decreased biliary proliferation and HA release. These studies provide evidence that MC histamine is key to biliary proliferation and may be a therapeutic target for the treatment of cholangiopathies.

Activated mast cells (MCs) release histamine (HA) and MCs infiltrate the liver following bile duct ligation (BDL) increasing intrahepatic bile duct mass (IBDM) and fibrosis. We evaluated the effects of BDL in MC deficient mice. Methods: WT and KitW-sh mice were subjected to sham or BDL for up to 7 days and KitW-sh mice were injected with cultured mast cells or 1X PBS before collecting serum, liver blocks and cholangiocytes. Liver damage was assessed by H&E and ALT levels. IBDM was detected by CK-19 expression and proliferation by Ki-67 immunohistochemistry. Fibrosis was detected by immunohistochemistry, hydroxyproline content and by qPCR for fibrotic markers. Hepatic stellate cell (HSC) activation and TGF-β1 expression/secretion were evaluated. HDC and histamine receptor (HR) expression were detected by qPCR and HA secretion by EIA. To evaluate vascular cells, Von Willebrand (vWF) and VEGF-C expression were measured. In vitro, cultured HSCs were stimulated with cholangiocyte supernatants and α-SMA measured. Results: BDL-induced liver damage was reduced in the BDL KitW-sh mice, whereas injection of MCs did not mimic BDL-induced damage. In BDL KitW-sh mice, IBDM, proliferation, HSC activation/fibrosis and TGF-β1 expression/secretion were decreased. The HDC/HA/HR axis was ablated in sham and BDL KitW-sh mice. vWF and VEGF-C expression decreased in BDL KitW-sh mice. In KitW-sh mice injected with MCs, IBDM, proliferation, fibrosis and vascular cell activation increased. Stimulation with cholangiocyte supernatants from BDL WT or KitW-sh mice injected with MCs increased HSC activation, which decreased with supernatants from BDL KitW-sh mice. Conclusion: MCs promote hyperplasia, fibrosis and vascular cell activation. Knockout of MCs decreases BDL-induced damage. Modulation of MCs may be important in developing therapeutics for cholangiopathies.

Inhibition of H1/H2HR reverses PSC-associated damage and decreases CCA growth, angiogenesis, and EMT; because PSC patients are at risk of developing CCA, using HR blockers may be therapeutic for these diseases. (Hepatology 2018).

The tumor microenvironment of cholangiocarcinoma (CCA) is composed of numerous cells, including mast cells (MCs). MCs release histamine, which increases CCA progression and angiogenesis. Cholangiocytes secrete stem cell factor, which functions via the MC growth factor receptor c-Kit. Here, we show that cholangiocytes express histidine decarboxylase and its inhibition reduces CCA growth. MC recruitment in the tumor microenvironment increased CCA growth. MC infiltration and MC markers were detected by toluidine blue staining and real-time PCR in human biopsies and in tumors from athymic mice treated with saline, histamine, histidine decarboxylase inhibitor, or cromolyn sodium. Tumor growth, angiogenesis, and epithelial-mesenchymal transition (EMT)/extracellular matrix (ECM) markers were measured in mice treated with cromolyn sodium. In vitro, human CCA cells were treated with MC supernatant fluids before evaluating angiogenesis and EMT/ECM expression. Migration assays were performed with CCA cells treated with the stem cell factor inhibitor. MC supernatant fluids increased CCA histidine decarboxylase, vascular endothelial growth factor, and MC/EMT/ECM expression that decreased with pretreatment of cromolyn sodium. MCs were found in human biopsies. In mice treated with cromolyn sodium, MC infiltration and tumor growth decreased. Inhibition of CCA stem cell factor blocked MC migration and MC/EMT/ECM in CCA. MCs migrate into CCA tumor microenvironment via c-Kit/stem cell factor and increase tumor progression, angiogenesis, EMT switch, and ECM degradation. Cholangiocarcinoma (CCA) cancers are primary tumors that arise from the neoplastic transformation of cholangiocytes, the epithelial cells lining the intrahepatic and extrahepatic bile ducts of the liver.1 CCA is the second most prevalent liver tumor after hepatocellular carcinoma and accounts for 10% to 20% of deaths caused by hepatobiliary malignancies.2 Increased risk of developing CCA is associated with primary sclerosing cholangitis, liver fluke infestation, hepatitis C virus infection, and other diseases that lead to chronic biliary obstruction and inflammation.3 CAA is a metastatic cancer, and studies have found its potential to migrate outside of the biliary tract. 4 We have found that histamine via the H4 histamine receptor (HR)

Substance P (SP) is involved in the proliferation of cholangiocytes in bile duct ligated (BDL) mice and human cholangiocarcinoma growth by interacting with the neurokinin-1 receptor (NK-1R). To identify whether SP regulates liver fibrosis during cholestasis, wild type (WT) or NK-1R knockout (NK-1R−/−) mice that received BDL or sham surgery and Mdr2−/− mice treated with either an NK-1R antagonist (L-733,060) or saline were used. Additionally, WT mice were treated with SP or saline intraperitoneally. In vivo, there was increased expression of TAC1 (coding SP) and NK-1R in both BDL and Mdr2−/− mice compared to WT mice. The expression of TAC1 and NK-1R was significantly higher in liver samples from PSC patients compared to healthy controls. Knockout of NK-1R decreased BDL-induced liver fibrosis and treatment with L-733,060 resulted in decreased liver fibrosis in Mdr2−/− mice, which was shown by decreased Sirius red staining, fibrosis gene and protein expression and reduced transforming growth factor-β1 levels in serum and cholangiocytes supernatants. Furthermore, we observed that reduced liver fibrosis in NK-1R−/− mice with BDL surgery or Mdr2−/− mice treated with L-733,060 was associated with enhanced cellular senescence of hepatic stellate cells (HSCs) and decreased senescence of cholangiocytes. In vitro, L-733,060 inhibited SP-induced expression of fibrotic genes in HSCs and cholangiocytes. Treatment with L-733,060 partially reversed SP-induced decrease of senescence genes expression in cultured HSCs and SP-induced increase of senescence-related genes expression in cultured cholangiocytes. Collectively, our results demonstrated the regulatory effects of the SP/NK-1R axis on liver fibrosis through changes in cellular senescence during cholestatic liver injury.

Melatonin therapy or prolonged exposure to complete darkness reduces biliary hyperplasia and liver fibrosis in bile-duct-ligated (BDL) rats; however, no information exists in primary sclerosing cholangitis (PSC). Thus, we aimed to determine the therapeutic effects of prolonged dark therapy or melatonin administration on hepatic fibrosis in the multidrug resistance gene 2-knockout (Mdr2) mouse model of PSC. Melatonin levels, biliary mass, liver fibrosis, angiogenesis and miR-200b expression were evaluated in wild-type and Mdr2 mice exposed to darkness or melatonin treatment or in male patients with PSC and healthy controls. Mdr2 mice were also treated with miR-200b inhibitor or control before evaluating biliary mass, liver fibrosis, and angiogenesis. After overexpression of arylalkylamine -acetyltransferase (AANAT; the enzyme regulating melatonin synthesis) or inhibition of miR-200b in cholangiocytes and hepatic stellate cells, we evaluated angiogenesis and fibrosis gene expression. After exposure to darkness or administration of melatonin, Mdr2 mice show elevated serum melatonin levels and inhibition of biliary mass, along with reduction of liver fibrosis and angiogenesis. MicroRNA PCR analysis demonstrated that miR-200b expression increased in Mdr2 mice and patients with PSC compared with controls and decreased in Mdr2 mice subjected to dark exposure or melatonin treatment. Inhibition of miR-200b in Mdr2 ablates biliary proliferation, liver fibrosis, and angiogenesis. , overexpression of AANAT or inhibition of miR-200b in cholangiocytes and hepatic stellate cells decreased the expression of miR-200b, angiogenesis, and fibrosis genes. Dark therapy or targeting melatonin/miR-200b axis may be important in the management of biliary damage and liver fibrosis in cholangiopathies including PSC.-Wu, N., Meng, F., Zhou, T., Han, Y., Kennedy, L., Venter, J., Francis, H., DeMorrow, S., Onori, P., Invernizzi, P., Bernuzzi, F., Mancinelli, R., Gaudio, E., Franchitto, A., Glaser, S., Alpini G. Prolonged darkness reduces liver fibrosis in a mouse model of primary sclerosing cholangitis by miR-200b down-regulation.

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