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Induction of nitric oxide production in mouse macrophages by Shiga toxin
1Felsenstein Medical Research Center, Petah Tikva, Israel.
Abstract:
Host mediators play an important role in the pathogenesis of shigellosis and Shiga toxin toxicity. Nitric oxide (NO) production in mouse peritoneal macrophages and in the macrophage J744 cell line in response to purified Shiga toxin and lipopolysaccharide (LPS) from Shigella flexneri were studied. Shiga toxin induced NO production in a dose-dependent manner up to 800 ng/ml. Detectable levels of NO were present as early as 4 h after induction and continued to increase during 72 h; Shiga toxin induced greater NO production with time than did LPS. Pre-treatment of Shiga toxin (400 ng/ml) or LPS (10 ng/ml) with polymyxin B, which inactivates LPS, reduced their ability to induce NO by 28% and 96%, respectively. Induction in the presence of anti-TNF alpha antibodies did not reduce the amount of NO in the supernate. These studies showed that Shiga toxin induces NO production in murine macrophages.
Insights
Shiga toxin triggers nitric oxide (NO) production in mouse macrophages, a key mediator in shigellosis pathogenesis. This NO release is time- and dose-dependent, exceeding that induced by lipopolysaccharide (LPS).
Area of Science:
- Immunology
- Microbiology
- Pathogenesis
Background:
- Host mediators are crucial in shigellosis and Shiga toxin toxicity.
- Nitric oxide (NO) is a significant mediator in inflammatory responses.
Purpose of the Study:
- To investigate the role of Shiga toxin in inducing nitric oxide (NO) production in murine macrophages.
- To compare NO induction by Shiga toxin versus lipopolysaccharide (LPS) from Shigella flexneri.
Main Methods:
- Murine peritoneal macrophages and J774 cell line were stimulated with purified Shiga toxin and LPS.
- Nitric oxide production was measured over time (up to 72 hours).
- The effect of polymyxin B and anti-TNF-alpha antibodies on NO induction was assessed.
Main Results:
- Shiga toxin induced NO production in a dose-dependent manner.
- NO levels increased with time, with Shiga toxin showing greater induction than LPS.
- Polymyxin B significantly reduced NO induction by LPS (96%) and Shiga toxin (28%).
- Anti-TNF-alpha antibodies did not affect NO production.
Conclusions:
- Shiga toxin directly induces nitric oxide production in murine macrophages.
- This NO production is a significant factor in the host response to Shiga toxin.
- The mechanism of NO induction by Shiga toxin differs partly from that of LPS.