Secretin/Secretin Receptor (Sct/SR) Signaling Promotes Biliary Senescence and Liver Fibrosis During Alcoholic Liver Disease
Authors: Kennedy Lindsey , Wu Nan , Venter Julie , Zhou Tianhao , Ceci Ludovica , Kyritsi Konstantina , Francis Heather , Guillot Adrien , Meng Fanyin , Gao Bin , Alpini Gianfranco , Glaser Shannon 
Published: June 2021

Chronic alcohol consumption can cause alcoholic liver disease (ALD) which evolves to cirrhosis at later stages. Ductular reaction characterized by extensive biliary cell proliferation, portal inflammation and fibrosis is observed in such conditions. Biliary senescence is increased during cholangiopathies, and leads to paracrine activation of hepatic stellate cells (HSCs) and increased liver fibrosis by changes in the Sct/MicroRNA (miR)‐125b‐dependent biliary release of TGF‐b1. Sct and SR are only expressed by cholangiocytes and the Sct/SR axis promotes biliary senescence through increased TGF‐b1 signaling. Damage to cholangiocytes and the role of Sct/SR signaling during ALD is unknown. Our aim is to characterize biliary cell damage, fibrosis, and the potential implications of biliary Sct/SR signaling during ALD.MethodsHuman samples from healthy and alcoholic steatohepatitis (ASH) patients were evaluated for: (i) Sct/SR/miR‐125b/TGF‐b1 axis and Sct serum levels, (ii) bile duct mass (IBDM), (iii) biliary senescence, (iv) Kupffer cell number, and (v) liver fibrosis as described below. In human samples, serum Sct levels were correlated with serum levels of total bilirubin (TBIL) and aspartate aminotransferase (AST), and MELD score. For in vivo studies, female wild‐type (WT), Sct−/−, SR−/− and Sct−/−/SR−/− (DKO) were ad libitum fed a 5% ethanol (EtOH) diet for 8 wks with a 31.5% EtOH gavage 1X/wk. Liver damage and steatosis were evaluated by H&E and Oil Red O staining. Biliary Sct/SR expression was visualized by immunostaining, and serum Sct levels by EIA. IBDM was evaluated by CK‐19 (biliary‐specific marker) staining. Biliary senescence was determined by immunostaining for p16, p21 and SA‐b‐Galactosidase. Kupffer cell number was evaluated by staining for F4/80. Liver fibrosis was determined by Sirius Red staining, and immunostaining for Collagen‐1a. HSC activation was visualized by staining for desmin (HSC marker) and a‐smooth muscle actin (a‐SMA, increased in activated HSCs). Biliary miR‐125b levels were determined by qPCR, and TGF‐b1 expression by staining.ResultsHuman ASH had increased biliary Sct/SR/miR‐125b/TGF‐b1 signaling, Sct secretion, IBDM, Kupffer cell number and liver fibrosis. Increased Sct serum levels positively correlated with serum TBIL and AST levels, and MELD score in ASH patients. WT EtOH mice had increased (i) liver damage/steatosis, (ii) biliary Sct/SR/miR‐125b/TGF‐b1 signaling and Sct secretion, (iii) IBDM and biliary senescence, (iv) Kupffer cell number, and (v) liver fibrosis/HSC activation compared to pair‐fed animals. These parameters were decreased in Sct−/−, SR−/− and DKO EtOH mice.ConclusionEnhanced biliary Sct/SR expression promotes biliary senescence and subsequent liver fibrosis during ALD progression via miR‐125b/TGF‐b1 signaling. Increased biliary Sct/SR expression correlates with increased liver damage in patients with ASH, eluding to the importance of biliary activation during ALD. Blocking Sct/SR signaling may be a therapeutic option for patients with ALD.Support or Funding InformationNIH NIDDK, NIH NIAAA, VA MeritThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.