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Prevention of endotoxin-induced lethality in mice by calmodulin kinase activator
1Department of Oral Microbiology, Asahi University School of Dentistry, 1851-1 Hozumi-cho, Motosu-gun, Gifu, Japan.
Abstract:
Porphyromonas gingivalis strain 381 lipid A showed lower activity in inducing interleukin (IL)-1alpha and IL-1beta production and cytokine mRNA expression than synthetic Escherichia coli lipid A (compound 506) in alveolar macrophages of C57BL/6 mice. Both the lipid As induced tumor necrosis factor alpha in alveolar macrophages and IL-6 in peritoneal macrophages. A calmodulin (CaM) antagonist, W-7, inhibited IL-1beta production and its mRNA expression induced by P. gingivalis lipid A but not compound 506 in alveolar macrophages. A CaM kinase activator reduced the induction of IL-1beta in the serum of mice when administered with compound 506, and protected the mice against the lethal toxicity. The modulation of a variety of intracellular enzymes including the CaM kinase may result in clinical control of endotoxic sepsis.
Insights
Porphyromonas gingivalis lipid A is less potent than E. coli lipid A in stimulating certain immune responses. Calmodulin kinase modulation offers potential for controlling endotoxic sepsis.
Area of Science:
- Immunology
- Microbiology
- Biochemistry
Background:
- Lipid A from Gram-negative bacteria is a potent endotoxin that triggers inflammatory responses.
- Different strains of bacteria possess distinct Lipid A structures, potentially leading to varied immune-stimulating activities.
Purpose of the Study:
- To compare the immunomodulatory effects of Porphyromonas gingivalis (Pg) lipid A and synthetic Escherichia coli (Ec) lipid A.
- To investigate the role of calmodulin (CaM) and CaM kinase in mediating the inflammatory responses induced by these lipid A compounds.
Main Methods:
- Primary cultures of alveolar and peritoneal macrophages from C57BL/6 mice were used.
- Interleukin (IL)-1alpha, IL-1beta, tumor necrosis factor alpha (TNF-alpha), and IL-6 production and mRNA expression were measured.
- The effects of a CaM antagonist (W-7) and a CaM kinase activator were assessed.
Main Results:
- Pg lipid A exhibited lower activity in inducing IL-1alpha and IL-1beta production compared to Ec lipid A (compound 506).
- Both lipid A types induced TNF-alpha in alveolar macrophages and IL-6 in peritoneal macrophages.
- CaM antagonism inhibited IL-1beta induction by Pg lipid A but not Ec lipid A.
- CaM kinase activation, particularly with compound 506, reduced IL-1beta in serum and protected against lethal toxicity.
Conclusions:
- Pg lipid A is less potent in inducing certain pro-inflammatory cytokines than Ec lipid A.
- Calmodulin signaling pathways are differentially involved in the response to different lipid A structures.
- Targeting intracellular enzymes like CaM kinase presents a potential therapeutic strategy for managing endotoxic sepsis.