Related Experiment Videos
Increase in histamine synthesis by liver macrophages in CCl4-injured mast cell-deficient W/Wv mice
Abstract:
This study set out to examine the possible role of liver macrophages in histamine synthesis in the injured liver. The effects of the hepatotoxins Escherichia coli lipopolysaccharide (LPS) and CCl4 on histamine synthesis in the liver of mice were evaluated. C3H/HeJ mice were resistant to LPS in including histidine decarboxylase (HDC) in the liver compared with C3H/HeN mice and mast cell-deficient W/Wv mice. However, C3H/HeJ mice did respond strongly to another hepatotoxin, CCl4, leading to a significant increase in HDC activity. CCl4 also caused a marked increase in HDC activity and histamine levels in the liver of W/Wv mice. In addition, injection of CCl4 produced a large increase in the activity of HDC in the spleen and lung of W/Wv mice. HDC activity was confined to the nonparenchymal cells, with parenchymal cells expressing essentially no HDC activity. The CCl4-induced increase in HDC activity was confined, at least in part, to the liver macrophages. These results indicate that the macrophages are responsible for the increase in HDC-dependent histamine production in the liver caused by the injection of hepatotoxins. The possible role of histamine in liver regeneration after injury is discussed.
Insights
Liver macrophages are key to histamine production following liver injury. These immune cells increase histidine decarboxylase (HDC) activity, boosting histamine synthesis in response to toxins like CCl4.
Area of Science:
- Immunology
- Hepatology
- Biochemistry
Background:
- Histamine plays a role in immune responses and tissue repair.
- Liver injury can trigger inflammatory processes involving immune cells.
- Histidine decarboxylase (HDC) is the enzyme responsible for histamine synthesis.
Purpose of the Study:
- To investigate the role of liver macrophages in histamine synthesis after liver injury.
- To determine the effects of hepatotoxins, lipopolysaccharide (LPS) and carbon tetrachloride (CCl4), on histamine production in mouse livers.
Main Methods:
- Evaluation of histidine decarboxylase (HDC) activity and histamine levels in mouse livers following administration of LPS and CCl4.
- Comparison of responses in different mouse strains (C3H/HeJ, C3H/HeN) and mast cell-deficient mice (W/Wv).
- Localization of HDC activity within liver cell populations.
Main Results:
- Hepatotoxin CCl4 significantly increased HDC activity and histamine levels in mouse livers, particularly in mast cell-deficient mice.
- HDC activity was primarily located in nonparenchymal liver cells, with a notable contribution from liver macrophages.
- CCl4 also elevated HDC activity in the spleen and lungs of W/Wv mice.
Conclusions:
- Liver macrophages are the primary source of increased histamine production in the injured liver.
- HDC-dependent histamine synthesis by macrophages is a significant response to hepatotoxin-induced liver injury.
- Histamine may play a role in liver regeneration processes post-injury.