Activation of cyclic adenosine monophosphate-dependent protein kinase a signaling prevents liver ischemia/reperfusion injury in mice

Abstract

Hepatic ischemia and reperfusion injury (IRI) occurs in multiple clinical settings including liver transplantation. Cyclic adenosine monophosphate (cAMP)-dependent protein kinase A (PKA) pathway inhibits hepatocellular apoptosis and regulates TLR4-triggered inflammation responses in vitro. Here, we examined the function and therapeutic potential of cAMP-PKA activation in a murine (C57/BL6) model of liver warm ischemia (90 min) followed by reperfusion. Liver IRI triggered cAMP-PKA activation, whereas administration of its specific inhibitor, H-89, exacerbated hepatocellular damage. Conversely, Forskolin therapy, which activates PKA by elevating cAMP levels, protected livers from IRI, evidenced by diminished serum ALT and well-preserved tissue architecture. Liver protection rendered by cAMP-PKA stimulation was accompanied by diminished neutrophil and macrophage infiltration/activation, reduced hepatocyte necrosis/apoptosis, yet increased cAMP response element-binding protein (CREB) and augmented IL-10 expression. Neutralization of IL-10 restored liver damage in otherwise IR-resistant Forskolin-treated mice. In vitro, cAMP-PKA activation diminished macrophage TNF-α/IL-6/IL-12 in an IL-10-dependent manner, and prevented necrosis/apoptosis in primary mouse hepatocyte cultures. Our novel findings in a mouse model of liver IRI document the importance of cAMP-PKA signaling in hepatic homeostasis and cytoprotection in vivo. Activation of cAMP-PKA signaling differentially regulates local inflammation and prevents hepatocyte death, providing the rationale for novel therapeutic approaches to combat liver IRI in transplant recipients.

Targeting TIM-1 on CD4 T Cells Depresses Macrophage Activation and Overcomes Ischemia-Reperfusion Injury in Mouse Orthotopic Liver Transplantation

“…), or ConA-activated TIM-1 Hi CD4+ vs. TIM-1 Lo CD4+ T cells (2.5×10 6 i.v.). The animals were anesthetized, injected with heparin (100 U/kg) and an atraumatic clip was used to interrupt the arterial/portal venous blood supply to the cephalad liver lobes (18, 19). After 90 min of warm ischemia, the clip was removed, and recipients were sacrificed at 6 h of reperfusion.…”

“…Liver specimens (4μm), stained with hematoxylin and eosin (H&E), were analyzed by modified Suzuki’s criteria (18). Primary mAb against mouse neutrophils Ly-6G (1A8; BD Biosciences, San Jose, CA) and macrophages CD68 (FA-11; AbD Serotec, Raleigh, NC) were used (18).…”

“…Primary mAb against mouse neutrophils Ly-6G (1A8; BD Biosciences, San Jose, CA) and macrophages CD68 (FA-11; AbD Serotec, Raleigh, NC) were used (18). In addition, TIM-4 expressing macrophages were identified by immunofluorescence double staining using rat anti-mouse TIM-4 mAb (RMT4-53; Bio X Cell) with goat anti-rat IgG-Alexa Fluor® 555, followed by rat anti-mouse CD68-Alexa Fluor® 488 (FA-11; AbD Serotec).…”

“…The presence of myeloperoxidase (MPO) was used as an index of neutrophil accumulation in the liver (18). One absorbance unit (U) of MPO activity was defined as the quantity of enzyme degrading 1mol peroxide/min at 25°C/gram of tissue.…”

Sleeping Beauty Insertional Mutagenesis in Mice Identifies Drivers of Steatosis-Associated Hepatic Tumors

“…The PKA/cAMP signaling pathway regulates glucose and lipid metabolism, proliferation, and hepatocyte survival. (43–45) The PKA catalytic subunit, PRKACA , is commonly activated by mutations in adrenocortical tumors(32) and recurrent translocations in fibrolamellar HCC. (32,46) β-adrenergic receptors activate PKA/cAMP signaling in many cell types including hepatocytes and regulate many cancer-relevant cellular processes including growth, metabolism, DNA damage repair, cell motility, survival, and inflammation.…”