In vivo immunomodulation of IL6 signaling in a murine multiple trauma model

Abstract

A significant number of trauma patients die during the ICU phase of care because of a severe immune response. Interleukin-6 (IL6) plays a central role within that immune response, signaling through a membrane-bound (IL6-R) and a soluble IL6 receptor (sIL6-R). IL6 and the sIL6-R can form an agonistic IL6/sIL6-R-complex, activating numerous cells that are usually not IL6 responsive, a process called trans-signaling. We attempted to demonstrate that modulation of the IL6 signaling (classic signaling and trans-signaling) can attenuate the devastating immune response after trauma in a murine multiple trauma model. Mice were allocated to three study arms: sham, fracture or polytrauma. Half of the animals had the application of an IL6-R antibody following an intervention. After a pre-set time, blood samples were analysed for IL6 and sIL6-R serum levels, organs were analysed for neutrophil infiltration and end organ damage was evaluated. IL6 and sIL6-R showed a rapid peak after fracture, and much more markedly after polytrauma. These parameters were reduced significantly by globally blocking IL6 signaling via IL6-R antibody (Mab) application. Shock organ analysis also illustrated significant neutrophil infiltration following polytrauma, which was also abated via IL6-R Mab application. Furthermore, end organ damage was reduced by IL6-R Mab application. The study results prove the regulatory role of IL6 signaling pathways in polytrauma, with haemorrhagic shock being a major trigger of inflammatory response. Modulation of IL6 signaling shows promise in the prevention of adverse events like organ failure following major trauma and might be a target for in vivo immunomodulation to reduce mortality in severely injured patients, but further evaluation regarding classic IL6 signaling and IL6 trans-signaling is needed.

Keywords: IL6; Immunomodulation; Polytrauma; Trans-signaling; sIL6-R.

Fig. 1

IL6 signaling via membrane-bound IL6 receptor and trans-signaling via soluble IL6 receptor

Fig. 2

IL6 serum levels following fracture without immunomodulation (group IIa) and polytrauma without immunomodulation (group IIIa). Group Ia represents sham mice. * represents p ≤ 0.05

Fig. 3

Trans-signaling ratio (TSR) following fracture without immunomodulation (group IIa) and polytrauma without immunomodulation (group IIIa). Group Ia represents sham mice. * represents p ≤ 0.05

Fig. 4

Liver Ly6G stain of group IIIa at 6 h (polytrauma without immunomodulation)

Fig. 5

Liver Ly6G stain of group IIIb at 6 h (polytrauma with immunomodulation)

Fig. 6

Neutrophil granulocytes in the liver following fracture without immunomodulation (group IIa) and polytrauma without immunomodulation (group IIIa). Group Ia represents sham mice. * represents p ≤ 0.05

Fig. 7

Neutrophil granulocytes in the liver following polytrauma with immunomodulation (group IIIb) and without immunomodulation (group IIIa). Group Ia represents sham mice. * represents p ≤ 0.05

Fig. 8

Difference in lung weight following polytrauma with and without immunomodulation (groups IIIa and IIIb). * represents p ≤ 0.05