Introduction
Sepsis is defined as an organic dysfunction that threatens the life of patients due to an abnormally regulated response to infection [1]. The initial phase of sepsis is dominated by an increased production of proinflammatory cytokines, which leads to augmented capillary permeability, extravasation, hypercoagulability and myelopoiesis. One of the main sources of infection in sepsis is believed to be the intestinal microbiota via traslocation through the mucosa to the bloodstream. Systemic inflammation weakens intestinal barrier function (IBF) in animal models, resulting in increased bacterial traslocation [2]. Even if the management of sepsis has advanced in the last decades, mortality is still high and there is room for improvement. Thus, the search for effective treatments is clearly justified. Glucocorticoids (GC) constitute a therapeutic modality in sepsis, but they have only shown moderate benefit. This may be accounted for by the harmful effects of GCs on IBF, which may facilitate translocation of luminal microorganisms and molecules. Besides, GC treatment impairs epithelial healing in experimental colitis in mice [3]. Previous results of our research group have shown that mice with induced deletion of the GC receptor (GR) in intestinal epithelial cells (i.e. NR3C1ΔIEC mice) are protected against dextran sulphate sodium (DSS)-induced colitis [4].
Aims & Methods
Our aim is to understand the role of the intestinal epithelial GR and its involvement in IBF regulation in experimental sepsis, with the ultimate goal of improving the management of sepsis with GCs.
The cecal ligation and puncture (CLP) model of sepsis was applied to WT C57BL/6J and NR3C1ΔIEC mice. Caecum-exposed mice were used as control (sham). Mice were sacrificed 24 hours after surgery. Four hours before sacrifice, mice were administered 4 kD FITC-dextran, a fluorescent marker of permeability. Colon, jejunum, adrenes, kidney and liver RT-qPCRs were performed as well as determination of corticosterone plasma levels.
Results
After 24 h, CLP mice exhibited hypoglycemia and splenomegaly with elevated corticosterone plasma levels, which were associated to increased Cyp11a1 in the adrenes. Of note, both parameters were less pronounced in KO mice. Intestinal barrier function was weakened, as indicated by downregulation of Tjp1 and increased FITC-dextran plasma levels, which were similar in WT and KO mice. A modest increase in inflammatory markers was noted in the colon and jejunum. However, KO mice exhibited dampened inflammatory response in the colon, with lower expression of inflammatory markers such as S100a8 and S100a9, but not in the jejunum. Similarly, the colonic expression of Cyp11a1 and Lrh1, involved in local steroidogenesis, was lower in CLP mice, regardless of genotype. WT but not KO mice showed an increased in of tissue non-specific alkaline phosphatase (TNAP) in liver, an enzyme involved in detoxification of phosphorylated molecules such as bacterial lipopolysaccharide, but lower expression of Tsc22d3, whose role is described to be protective against sepsis [5]. Inflammation markers were also augmented in the lung and kidney.
Conclusion
In the early stages of the CLP model of sepsis the colon and jejunum are inflamed, and epithelial deletion of the glucocorticoid receptor appears to modulate colonic inflammation, but not barrier function or systemic status.
References
1. Singer, M, et al., Jama, 2016. 315(8): p. 801-10.
2. Carrico, CJ, et al., Arch Surg, 1986. 121(2): p. 196-208.
3. Ocon, B, et al., Biochem Pharmacol, 2016. 116: p. 73-88.
4. Arredondo-Amador, M, et al., Br J Pharmacol, 2021. 178(12): p. 2482-2495.
5. Ballegeer, M, et al., Shock, 2019. 52(2): p. 208-214.