Related Experiment Videos
High levels of nitric oxide production decrease early but increase late survival of Brucella abortus in macrophages
1Animal Health and Biomedical Sciences, University of Wisconsin-Madison, Madison, WI 53706-1581, U.S.A.
Microbial Pathogenesis
|November 17, 2001
Summary
Nitric oxide (NO) aids in killing Brucella abortus within macrophages, but the bacteria prevent apoptosis for survival and replication. NO production is enhanced by Escherichia coli LPS and IFN-gamma.
Area of Science:
- Immunology
- Microbiology
- Cell Biology
Background:
- Nitric oxide (NO) acts as a defense mechanism against pathogens and induces apoptosis.
- Apoptosis is a host protective mechanism against intracellular bacteria.
- Brucella abortus is an intracellular bacterium that survives within macrophages.
Purpose of the Study:
- To investigate the intracellular survival of Brucella abortus in RAW264.7 macrophages under conditions of NO-induced apoptosis.
- To determine the effect of NO on B. abortus survival and macrophage apoptosis.
- To explore potential therapeutic strategies to enhance NO production.
Main Methods:
- RAW264.7 macrophages were infected with B. abortus.
- Nitric oxide synthase (iNOS) expression and NO production were modulated using Escherichia coli LPS and IFN-gamma.
- Nitrite concentration was measured using a colorimetric assay.
- Bacterial survival and macrophage apoptosis were assessed.
Main Results:
- Enhanced NO production (up to 140 microM) was achieved using E. coli LPS and IFN-gamma.
- Infection with B. abortus led to a significant decrease in NO production (60 microM) compared to controls.
- NO accumulation reduced the number of surviving B. abortus from 6 to 24 hours post-infection.
- High NO levels induced apoptosis in macrophages, but B. abortus infection decreased macrophage apoptosis.
- B. abortus survived and replicated after 24 hours despite NO presence.
Conclusions:
- NO accelerates the killing of intracellular B. abortus, but does not eliminate it completely within 24 hours.
- B. abortus employs mechanisms to prevent macrophage apoptosis, facilitating its survival and intracellular replication.
- The Brucella genome may contain genes for nitric and nitrous oxide reductases, potentially allowing utilization of NO as a nitrogen source or counteraction of its effects.