Probing the Portal System as the Source of Inflammation in An Acute Systemic Burn Model
*Fatemeh Adiliaghdam, *Florian Kuehn, *Laurence Rahme, Richard Hodin
Massachusetts General Hospital, Boston, MA
Objective: Our previous data has shown that in mice subjected to a severe cutaneous burn,there is an impaired gut barrier leading to a systemic inflammatory response syndrome.The portal system sits at the interface between the host and the inflammatory mediators in the gut.Identifying the mediators that cross the gut barrier under conditions of barrier dysfunction could lead to novel therapeutic targets to prevent gut-derived sepsis.
Design and Intervention:Mice were subjected to a 30% back burn+/-oral supplementation with the brush border enzyme intestinal alkaline phosphatase(IAP),given its role in maintaining the gut barrier. Mouse portal vein serum was removed and tested in an ex-vivo model by application to primary mouse macrophages.
Main Outcome Measures:Inflammatory gene expression was assessed using qPCR.Mass spectrometry was used on the portal serum to identify protein mediators that cross the gut barrier in response to the burn insult.
Results:Compared to sham controls,the portal serum from burned-mice contained more LPS(10.4 vs 4.2EU/L,p<0.01)and had a much higher (3.3-fold,p<0.001)pro-inflammatory impact on the macrophages.This effect was largely preserved even after Polymixin-B incubation(LPS depletion),suggesting the presence of non-LPS mediators in portal serum.IAP markedly decreased the portal LPS (approx.40% decrease, p<0.05)and blocked the pro-inflammatory effect of portal serum on the target cells(1.8-fold, p<0.01).A proteomic screen identified two mouse-derived proteins(Ig-kappa light chain and enolase)and two bacterially-derived proteins(Flagellin Listeria monocytogenes and Flagellar P-ring protein)that were markedly enriched in the burn compared to sham and burn+IAP mice.
Conclusions:Portal vein is highly enriched in pro-inflammatory mediators following cutaneous burn insult.These molecules are derived from both the bacteria and the host tissues. Oral IAP therapy may represent a novel approach to promoting gut barrier function and blocking specific mediators from entering the portal system, thus preventing gut-induced systemic inflammation.