Bile acids initiate cholestatic liver injury by triggering a hepatocyte-specific inflammatory response
Shi-Ying Cai, … , Dhanpat Jain, James L. Boyer
Shi-Ying Cai, … , Dhanpat Jain, James L. Boyer
Published March 9, 2017
Citation Information: JCI Insight. 2017;2(5):e90780. https://doi.org/10.1172/jci.insight.90780.
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Research Article Hepatology Inflammation

Bile acids initiate cholestatic liver injury by triggering a hepatocyte-specific inflammatory response

Abstract

Mechanisms of bile acid–induced (BA-induced) liver injury in cholestasis are controversial, limiting development of new therapies. We examined how BAs initiate liver injury using isolated liver cells from humans and mice and in-vivo mouse models. At pathophysiologic concentrations, BAs induced proinflammatory cytokine expression in mouse and human hepatocytes, but not in nonparenchymal cells or cholangiocytes. These hepatocyte-specific cytokines stimulated neutrophil chemotaxis. Inflammatory injury was mitigated in Ccl2–/– mice treated with BA or after bile duct ligation, where less hepatic infiltration of neutrophils was detected. Neutrophils in periportal areas of livers from cholestatic patients also correlated with elevations in their serum aminotransferases. This liver-specific inflammatory response required BA entry into hepatocytes via basolateral transporter Ntcp. Pathophysiologic levels of BAs induced markers of ER stress and mitochondrial damage in mouse hepatocytes. Chemokine induction by BAs was reduced in hepatocytes from Tlr9–/– mice, while liver injury was diminished both in conventional and hepatocyte-specific Tlr9–/– mice, confirming a role for Tlr9 in BA-induced liver injury. These findings reveal potentially novel mechanisms whereby BAs elicit a hepatocyte-specific cytokine-induced inflammatory liver injury that involves innate immunity and point to likely novel pathways for treating cholestatic liver disease.

Authors

Shi-Ying Cai, Xinshou Ouyang, Yonglin Chen, Carol J. Soroka, Juxian Wang, Albert Mennone, Yucheng Wang, Wajahat Z. Mehal, Dhanpat Jain, James L. Boyer

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Figure 5

Bile acids induce hepatocyte mitochondrial injury and ER stress.

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Bile acids induce hepatocyte mitochondrial injury and ER stress. (A) Rep...
(A) Representative Western blot detecting leakage of mitochondrial protein cytochrome c (CytC) and ER protein Grp78 into the cytosol in mouse hepatocytes after a 24-hour treatment with chenodeoxycholic acid (CDCA, 50 μM), glycocholic acid (GCA, 200 μM), glycochenodeoxycholic acid (GCDCA, 200 μM), deoxycholic acid (DCA, 50 μM), taurocholic acid (TCA, 200 μM), and tauroursodeoxycholic acid (TUDCA, 200 μM). (B) Representative Western blot demonstrating that TCA treatment released CytC, apoptosis-inducing factor (AIF, a mitochondria-specific protein), and Grp78 from mitochondria and the ER into the cytosol in a dose- and time-dependent manner in mouse hepatocytes. (C) Representative Western blot showing reduction of mitochondrial (Mito) but not total cellular endonuclease G (Endo G) protein expression in TCA-treated mouse hepatocytes (dose and time dependency). (D) Western blot detection of GCDCA treatment (24 hours) resulting in AIF leaking into the cytosol in human hepatocytes. (E) TCA (100 μM) induction of Cxcl2 mRNA expression in mouse hepatocytes was significantly reduced by cyclosporin A (CsA, 3 μM), LY294002 (LY, 40 μM), 4,5,6,7-tetrabromobenzotriazole (TBB, 25 μM), ursodeoxycholic acid (UDCA, 250 μM), and norUDCA (norU, 500 μM). Cells were treated for 24 hours (mean ± SD, n ≥ 4). *P < 0.05 vs. TCA treatment alone by 1-way ANOVA. (F) UDCA and norUDCA treatment reduced bile acid–induced leakage of AIF and Grp78 protein into cytosol in mouse hepatocytes. All Western blots shown here have been repeated in at least 3 independent experiments.