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Updated: Aug 20, 2025
Colon Ascendens Stent Peritonitis CASP - a Standardized Model for Polymicrobial Abdominal Sepsis
Published on: December 18, 2010
FK506 impairs neutrophil migration that results in increased polymicrobial sepsis susceptibility
Vanessa de Fátima Borges1,2, Leticia Selinger Galant1,2, Alexandre Kanashiro1,2
1Department of Pharmacology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil.
Objective:
This study aimed to investigate the effects of FK506 on experimental sepsis immunopathology. It investigated the effect of FK506 on leukocyte recruitment to the site of infection, systemic cytokine production, and organ injury in mice with sepsis.
Methods:
Using a murine cecal ligation and puncture (CLP) peritonitis model, the experiments were performed with wild-type (WT) mice and mice deficient in the gene Nfat1 (Nfat1-/-) in the C57BL/6 background. Animals were treated with 2.0 mg/kg of FK506, subcutaneously, 1 h before the sepsis model, twice a day (12 h/12 h). The number of bacteria colony forming units (CFU) was manually counted. The number of neutrophils in the lungs was estimated by the myeloperoxidase (MPO) assay. The expression of CXCR2 in neutrophils was determined using flow cytometry analysis. The expression of inflammatory cytokines in macrophage was determined using ELISA. The direct effect of FK506 on CXCR2 internalization was evaluated using HEK-293T cells after CXCL2 stimulation by the BRET method.
Results:
FK506 treatment potentiated the failure of neutrophil migration into the peritoneal cavity, resulting in bacteremia and an exacerbated systemic inflammatory response, which led to higher organ damage and mortality rates. Failed neutrophil migration was associated with elevated CXCL2 chemokine plasma levels and lower expression of the CXCR2 receptor on circulating neutrophils compared with non-treated CLP-induced septic mice. FK506 did not directly affect CXCL2-induced CXCR2 internalization by transfected HEK-293 cells or mice neutrophils, despite increasing CXCL2 release by LPS-treated macrophages. Finally, the CLP-induced response of Nfat1-/- mice was similar to those observed in the Nfat1+/+ genotype, suggesting that the FK506 effect is not dependent on the NFAT1 pathway.
Conclusion:
Our data indicate that the increased susceptibility to infection of FK506-treated mice is associated with failed neutrophil migration due to the reduced membrane availability of CXCR2 receptors in response to exacerbated levels of circulating CXCL2.
Insights
FK506 treatment impairs neutrophil migration in experimental sepsis, increasing susceptibility to infection. This occurs due to reduced CXCR2 receptor availability, leading to higher mortality rates in septic mice.
Area of Science:
- Immunology
- Pharmacology
- Microbiology
Background:
- Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection.
- Understanding the immunopathology of sepsis is crucial for developing effective treatments.
- FK506 (Tacrolimus) is an immunosuppressant with potential effects on immune responses during sepsis.
Purpose of the Study:
- To investigate the impact of FK506 on experimental sepsis immunopathology in mice.
- To determine FK506's effects on leukocyte recruitment, cytokine production, and organ injury during sepsis.
Main Methods:
- A murine cecal ligation and puncture (CLP) model of peritonitis was used.
- Wild-type and Nfat1-deficient mice were treated with FK506.
- Neutrophil migration, bacterial load, cytokine levels, and CXCR2 expression were assessed.
- HEK-293T cells were used to evaluate FK506's direct effect on CXCR2 internalization.
Main Results:
- FK506 treatment exacerbated sepsis, leading to increased bacteremia, organ damage, and mortality.
- Neutrophil migration to the infection site was impaired in FK506-treated mice.
- This impairment was linked to elevated CXCL2 levels and reduced CXCR2 expression on neutrophils.
- FK506's effects were independent of the NFAT1 pathway.
Conclusions:
- FK506 treatment increases susceptibility to sepsis by inhibiting neutrophil migration.
- Reduced membrane availability of CXCR2 receptors, in the context of high CXCL2 levels, underlies this effect.
- These findings highlight a novel mechanism of FK506-induced immunodeficiency in sepsis.
