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Published on: April 29, 2015
Nitric oxide production by peritoneal macrophages of cirrhotic rats: a host response against bacterial peritonitis
M Morales-Ruiz1, W Jiménez, J Ros
1Hormonal Laboratory, Hospital Clínic i Provincial, University of Barcelona, Spain.
Background & Aims:
Patients and rats with cirrhosis and ascites are prone to develop peritonitis. The aim of this study was to assess whether peritoneal macrophages of cirrhotic rats without peritoneal infection produce nitric oxide and express inducible NO synthase (iNOS).
Methods:
NO2- accumulation produced by macrophages from control rats and cirrhotic rats with ascites was determined. iNOS messenger RNA and protein expression were analyzed by Northern and Western blot and immunocytochemical analysis. The in vivo effects of inhibiting iNOS were investigated by giving the specific iNOS inhibitor L-N-(1-iminoethyl)-lysine (L-NIL) or sterile saline to 9 and 7 cirrhotic rats with ascites, respectively.
Results:
Cirrhotic macrophages produced NO2- that was around fourfold greater than that of control macrophages after 30 hours in culture. Northern and Western blot and immunocytochemical analysis showed the presence of iNOS messenger RNA and protein in macrophages of cirrhotic rats. Ascites cultures were positive in all rats administered L-NIL and negative in those administered saline.
Conclusions:
Macrophages of cirrhotic rats produce NO and express iNOS messenger RNA and protein, and these changes are not a consequence of overt bacterial infection. Because iNOS inhibition results in peritoneal infection, these results suggest that iNOS induction in macrophages of cirrhotic rats is a host defense response to prevent bacterial peritonitis.
Insights
Macrophages from cirrhotic rats produce nitric oxide (NO) and express inducible NO synthase (iNOS), even without infection. This NO production is a defense mechanism against bacterial peritonitis in cirrhosis.
Area of Science:
- Immunology
- Gastroenterology
- Pathophysiology
Background:
- Cirrhosis and ascites increase susceptibility to peritonitis.
- The role of peritoneal macrophages in host defense in cirrhosis is unclear.
Purpose of the Study:
- To investigate nitric oxide (NO) production and inducible NO synthase (iNOS) expression in peritoneal macrophages of cirrhotic rats without infection.
Main Methods:
- Assessed NO2- accumulation in macrophages from control and cirrhotic rats.
- Analyzed iNOS mRNA and protein expression using Northern/Western blots and immunocytochemistry.
- Investigated the effect of iNOS inhibition (L-NIL) in vivo.
Main Results:
- Cirrhotic macrophages produced significantly higher levels of NO2- compared to controls.
- iNOS mRNA and protein were detected in macrophages of cirrhotic rats.
- Inhibition of iNOS led to peritoneal infection, while saline treatment did not.
Conclusions:
- Peritoneal macrophages in cirrhotic rats spontaneously produce NO and express iNOS.
- This iNOS induction is not due to overt infection but represents a host defense mechanism.
- iNOS plays a crucial role in preventing bacterial peritonitis in cirrhotic rats.
