Inflammatory pathways in liver homeostasis and liver injury

Clin Rev Allergy Immunol. 2009 Feb;36(1):4-12. doi: 10.1007/s12016-008-8091-0.

Abstract

The liver is a unique organ with respect to its anatomical location, allowing continuous blood flow from the gastrointestinal tract through the sinusoids, and its cellular composition, comprising metabolically active hepatocytes, nonhepatocytic parenchymal cells, and various immune cell populations. Cytokines are key mediators within the complex interplay of intrahepatic immune cells and hepatocytes, as they can activate effector functions of immune cells, as well as hepatocytic intracellular signaling pathways controlling cellular homeostasis. Kupffer cells and liver-infiltrating monocyte-derived macrophages are primary sources of cytokines such as tumor-necrosis factor-alpha (TNF-alpha) and interleukin-6. The liver is also enriched in natural killer (NK) and NK T cells, which fulfill functions in pathogen defense, T cell recruitment, and modulation of liver injury. TNF-alpha can activate specific intracellular pathways in hepatocytes that influence cell fate in different manners, e.g., proapoptotic signals via the caspase cascade, but also survival pathways, namely the nuclear factor (NF)-kappaB pathway. NF-kappaB regulates important functions in liver physiology and pathology. Recent experiments with genetically modified mice demonstrated important and partly controversial functions of this pathway, e.g., in cytokine-mediated hepatocyte apoptosis or ischemia-reperfusion injury. The exact dissection of the contribution of recruited and resident immune cells, their soluble cytokine and chemokine mediators, and the intracellular hepatocytic response in liver homeostasis and injury could potentially identify novel targets for the treatment of acute and chronic liver disease, liver fibrosis, or cirrhosis.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Animals
  • Apoptosis Regulatory Proteins / immunology
  • Apoptosis Regulatory Proteins / metabolism
  • Cytokines / immunology*
  • Cytokines / metabolism
  • Hepatocytes / immunology
  • Hepatocytes / metabolism
  • Homeostasis / immunology
  • Humans
  • Inflammation / immunology*
  • Inflammation / metabolism
  • Killer Cells, Natural / immunology
  • Killer Cells, Natural / metabolism
  • Kupffer Cells / immunology
  • Kupffer Cells / metabolism
  • Liver / immunology*
  • Liver / metabolism
  • Liver Diseases / immunology*
  • Liver Diseases / metabolism
  • Mice
  • NF-kappaB-Inducing Kinase
  • Natural Killer T-Cells / immunology
  • Natural Killer T-Cells / metabolism
  • Protein Serine-Threonine Kinases / immunology
  • Protein Serine-Threonine Kinases / metabolism
  • Receptors, Cytokine / immunology*
  • Receptors, Cytokine / metabolism
  • Signal Transduction / immunology
  • Tumor Necrosis Factor-alpha / immunology
  • Tumor Necrosis Factor-alpha / metabolism

Substances

  • Apoptosis Regulatory Proteins
  • Cytokines
  • Receptors, Cytokine
  • Tumor Necrosis Factor-alpha
  • Protein Serine-Threonine Kinases