Both MAPK and STAT3 signal transduction pathways are necessary for IL-6-dependent hepatic stellate cells activation

• Published in: PloS one Vol. 12; no. 5; p. e0176173
• Main Authors: Kagan, Polina, Sultan, Maya, Tachlytski, Irina, Safran, Michal, Ben-Ari, Ziv
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 04.05.2017; Public Library of Science (PLoS)
• Subjects: Actin; Activation analysis; Acute phase proteins; Acute phase substances; Analysis; Animals; Attenuation; Autocrine signalling; Biochemistry; Biology and life sciences; Buffers; Cancer; Carbon dioxide; Carbon tetrachloride; CCL4 protein; Cell activation; Cell density; Cellular signal transduction; Cholangitis; Cytokines; Cytoskeleton; Defensive behavior; Differentiation; Dilution; Diseases; Hepatic Stellate Cells - metabolism; Hepatitis; Hepatocytes; Hepatology; Homeostasis; Immune system; Infections; Inflammation; Inhibition; Inhibitors; Interferon; Interleukin 6; Interleukin-6 - metabolism; Kinases; Laboratories; Leukocytes; Liver; Liver cirrhosis; Liver diseases; Mathematical models; Medicine; Medicine and Health Sciences; Mice; Mice, Inbred ICR; Mitogen-activated protein kinases; Mitogen-Activated Protein Kinases - metabolism; Oxidative stress; Platelets; Probes; Protein kinase; Proteins; Rats; Ribonucleic acid; RNA; Rodents; Salts; Signal Transduction; Smooth muscle; STAT3; STAT3 Transcription Factor - metabolism; Steel; Synthesis; Temperature; Temperature effects; Thrombin; Transcription factors; Transducers; Tubes; Vascular endothelial growth factor; Wound healing; Tel Aviv Israel; Israel
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0176173

During liver injury, hepatic stellate cells (HSCs) can undergo activation and transform into alpha-smooth muscle actin (αSMA)-expressing contractile myofibroblast-like cells, leading to deposition of excessive scar matrix. We have recently demonstrated that depletion of adenosine deaminase acting on double-stranded RNA (ADAR1) from mouse hepatocytes leads to HSC activation and induction of inflammation and hepatic fibrosis that is mediated by interleukin 6 (IL-6). Our aim was to identify and characterize the molecular pathways involved in the direct, inflammation-independent activation of HSCs by IL-6. Primary HSCs were isolated from mouse livers. mRNA levels of αSMA and Col1a were analyzed using qRT-PCR. Protein levels of αSMA, MAPK, p-MAPK, p38, p-p38, STAT3 and p-STAT3 were assessed by Western Blot analysis. The effect of specific signal transduction pathway inhibitors (i.e., SB203580 (P-38 inhibitor), U0126 (MAPK inhibitor), S3I-201 (STAT3 inhibitor) and Ruxolitinib (Jak1/2 inhibitor)) was also studied. Primary HSCs treated with IL-6 demonstrated upregulation of αSMA and Col1a mRNA levels as well as increased αSMA protein levels. Moreover, the phenotypic transition of quiescent HSCs toward myofibroblast-like cells was noted upon administration of IL-6 and not in untreated samples. In addition, the phosphorylation levels of p38, MAPK and STAT3 increased 30 minutes after treatment, and was followed by a decline in the phosphorylation levels 2-4 hours post-treatment. However, addition of specific signal transduction pathway inhibitors curbed this effect, and resulted in αSMA and Col1a expression levels similar to those measured in untreated control samples. IL-6 can directly induce the transition of HSCs toward myofibroblast-like cells. The effect is mediated by the activation of both MAPK and JAK/STAT signaling pathways. Elimination of either MAPK or JAK/STAT signaling pathways inhibits HSC stimulation. These results might pave the road toward the development of potential therapeutic interventions for hepatic fibrosis.