Precision targeting of the vagal anti-inflammatory pathway attenuates the systemic inflammatory response to burn injury

BACKGROUND

The systemic inflammatory response (SIRS) drives late morbidity and mortality after injury. The α7 nicotinic acetylcholine receptor (α7nAchR) expressed on immune cells regulates the vagal anti-inflammatory pathway that prevents an overwhelming SIRS response to injury. Nonspecific pharmacologic stimulation of the vagus nerve has been evaluated as a potential therapeutic to limit SIRS. Unfortunately, the results of clinical trials have been underwhelming. We hypothesized that directly targeting the α7nAchR would more precisely stimulate the vagal anti-inflammatory pathway on immune cells and decrease gut and lung injury after severe burn.

METHODS

C57BL/6 mice underwent 30% total body surface area steam burn. Mice were treated with an intraperitoneal injection of a selective agonist of the α7nAchR (AR-R17779) at 30 minutes postburn. Intestinal permeability to 4 kDa FITC-dextran was measured at multiple time points postinjury. Lung vascular permeability was measured 6 hours after burn injury. Serial behavioral assessments were performed to quantify activity levels.

RESULTS

Intestinal permeability peaked at 6 hours postburn. AR-R17779 decreased burn-induced intestinal permeability in a dose-dependent fashion (p < 0.001). There was no difference in gut permeability to 4 kDa FITC-dextran between sham and burn-injured animals treated with 5 mg/kg of AR-R17779. While burn injury increased lung permeability 10-fold, AR-R17779 prevented burn-induced lung permeability with no difference compared with sham (p < 0.01). Postinjury activity levels were significantly improved in burned animals treated with AR-R17779.

CONCLUSION

Directly stimulating the α7nAchR prevents burn-induced gut and lung injury. Directly targeting the α7nAChR that mediates the cholinergic anti-inflammatory response may be an improved strategy compared with nonspecific vagal agonists.

GTS-21 Protected Against LPS-Induced Sepsis Myocardial Injury in Mice Through α7nAChR

Sepsis-induced myocardial injury is a well-known cause of mortality. The cholinergic anti-inflammatory pathway (CHAIP) is a physiological mechanism by which the central nervous system regulates immune response through the vagus nerve and acetylcholine; the α7-nicotinic acetylcholine receptor (α7nAChR) is the main component of CHAIP; GTS-21, a synthetic α7nAChR selective agonist, has repeatedly shown its powerful anti-inflammatory effect. However, little is known about its effect on LPS-induced myocardial injury. We investigated the protective effects of GTS-21 on lipopolysaccharide (LPS)-induced cardiomyopathy via the cholinergic anti-inflammatory pathway in a mouse sepsis model. We constructed the model of myocardial injury in sepsis mice by C57BL/6 using LPS and determined the time of LPS treatment by hematoxylin-eosin (HE) and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL). C57BL/6 mice were randomized into five groups: blank control group, model group, α-bungarotoxin + LPS group, GTS-21 + LPS group, and α-bungarotoxin + GTS-21 + LPS group. The pathological results of myocardial tissue were detected by the HE method; the apoptosis rate was detected by the TUNEL method; the relative expressions of NF-κB p65, Caspase-3, Caspase-8, Bcl-2, Bax, p53, and a7nAChR were detected by real-time quantitative PCR (RT-PCR); and the protein expressions of IL-6, IL-1 β, TNF-α, and pSTAT3 were detected by western blot. The results showed that LPS-induced myocardial pathological and apoptosis changes were significant compared with the blank group, which was reversed by GTS-21; however, pretreatment with α-bungarotoxin obviously blocked the protective effect of GTS-21. NF-κB p65, Caspase-3, Caspase-8, Bax, p53, IL-6, IL-1β, TNF-α, and pSTAT3 were significantly increased in the model group, while a7nAChR and Bcl-2 were significantly decreased; GTS-21 treatment reversed that result, while pretreatment with α-bungarotoxin strengthened the result in the model. And pretreatment with α-bungarotoxin blocked the protective effect of GTS-21. GTS-21 can alleviate the LPS-induced damage in the heart via a7nAChR, and pretreatment with α-bungarotoxin obviously blocked the protective effect of GTS-21 on sepsis in mice.