Liver-Specific Ablation of Integrin-Linked Kinase in Mice Results in Enhanced and Prolonged Cell Proliferation and Hepatomegaly after Phenobarbital Administration

Abstract

We have recently demonstrated that disruption of extracellular matrix (ECM)/integrin signaling via elimination of integrin-linked kinase (ILK) in hepatocytes interferes with signals leading to termination of liver regeneration. This study investigates the role of ILK in liver enlargement induced by phenobarbital (PB). Wild-type (WT) and ILK:liver-/- mice were given PB (0.1% in drinking water) for 10 days. Livers were harvested on 2, 5, and 10 days during PB administration. In the hepatocyte-specific ILK/liver-/- mice, the liver:body weight ratio was more than double as compared to 0 h at day 2 (2.5 times), while at days 5 and 10, it was enlarged three times. In the WT mice, the increase was as expected from previous literature (1.8 times) and seems to have leveled off after day 2. There were slightly increased proliferating cell nuclear antigen-positive cells in the ILK/liver-/- animals at day 2 as compared to WT after PB administration. In the WT animals, the proliferative response had come back to normal by days 5 and 10. Hepatocytes of the ILK/liver-/- mice continued to proliferate up until day 10. ILK/liver-/- mice also showed increased expression of key genes involved in hepatocyte proliferation at different time points during PB administration. In summary, ECM proteins communicate with the signaling machinery of dividing cells via ILK to regulate hepatocyte proliferation and termination of the proliferative response. Lack of ILK in the hepatocytes imparts prolonged proliferative response not only to stimuli related to liver regeneration but also to xenobiotic chemical mitogens, such as PB.

Liver-Specific Deletion of Integrin-Linked Kinase in Mice Attenuates Hepatotoxicity and Improves Liver Regeneration After Acetaminophen Overdose

“…Previous studies show that ILK mediated ECM signaling inhibits hepatocyte proliferation and ILK deletion results in enhanced proliferation after PHX or treatment with nuclear receptor agonists (1,9,11). Changes in ECM occur after toxin-induced liver injury and ILK signaling has been reported to play a role in process of injury development, and subsequent recovery and survival response (12,13,28).…”

“…ILK-mediated ECM signaling is known to exert inhibitory effects on hepatocyte proliferation and is one of the major ‘termination signals’ for liver regeneration. ILK-KO mice, which lack this inhibitory signal and thus have proliferative advantage due to termination defect, exhibit increased liver regeneration after partial hepatectomy as well as after administration of nuclear receptor agonists (1,9,11). Both these models do not involve massive liver injury.…”

“…Liver-specific deletion of ILK results in increased hepatocyte proliferation along with defect in termination of liver regeneration after PHX resulting in mice with increased liver size (1). Further, enhanced and prolonged liver regeneration was observed in liver-specific ILK KO mice after administration of nuclear receptor agonists, such as TCBOPOP and phenobarbital (9,11). …”

Analysis of the role of the integrin signaling pathway in hepatocytes during rat liver regeneration

“…In addition, the E t of path 3 was higher than the control, too. Integrins combined with ILK, and then regulated expression of cyclin D1 by activation of the ERK→MSK1/2→CREB pathway (path 3) [7]. Transfer of ILKoverexpressing hepatocytes resulted in continued high levels of expression of cyclin D1 and cyclin A proteins, indicating that, when overexpressed, ILK induces signaling pathways resulting in the stimulation of G1/S cyclin-Cdk activities, finally leading to hepatocytes entering S phase [8,10].…”

“…Previous studies showed that hepatocyte differentiation and proliferation are greatly affected by extracellular matrix (ECM) through the integrin signaling pathway [6]. Recent research demonstrated that disruption of ECM/integrin signaling via elimination of integrin-linked kinase (ILK) in hepatocytes interferes with signals, leading to termination of liver regeneration [7]. However, the ECM/integrin signaling pathway is a complex signaling transduction network which is made up of many branches.…”