Silencing of Fas, Fas-Associated via Death Domain, or Caspase 3 Differentially Affects Lung Inflammation, Apoptosis, and Development of Trauma-Induced Septic Acute Lung Injury

Abstract

Activation of Fas signaling is a potentially important pathophysiological mechanism in the development of septic acute lung injury (ALI). However, so far the optimal targets within this signaling cascade remain elusive. Thus, we tested the hypothesis that in vivo gene silencing of Fas, Fas-associated via death domain (FADD), or caspase 3 by intratracheal administration of small interfering RNA would ameliorate ALI in a clinically relevant double-hit mouse model of trauma induced septic lung injury. Male C57Bl/6 mice received small interfering (Fas, FADD, caspase 3) or control RNA 24 h before and 12 h after blunt chest trauma or sham procedures. Polymicrobial sepsis was induced by cecal ligation and puncture 24 h after chest trauma. Twelve or 24 h later, lung tissue, plasma, and bronchoalveolar lavage fluid were harvested. During ALI, lung apoptosis (active caspase 3 Western blotting, TUNEL staining) was substantially increased when compared with sham. Silencing of caspase 3 or FADD both markedly reduced pulmonary apoptosis. Fas- and FADD-small interfering RNA administration substantially decreased lung cytokine concentration, whereas caspase 3 silencing did not reduce lung inflammation. In addition, Fas silencing markedly decreased lung neutrophil infiltration. Interestingly, only in response to caspase 3 silencing, ALI-induced lung epithelial barrier dysfunction was substantially improved, and histological appearance was beneficially affected. Taken together, downstream inhibition of lung apoptosis via caspase 3 silencing proved to be superior in mitigating ALI when compared with upstream inhibition of apoptosis via Fas or FADD silencing, even in the presence of additional anti-inflammatory effects. This indicates a major pathophysiological role of lung apoptosis and suggests the importance of other than Fas-driven apoptotic pathways in trauma-induced septic ALI.

The caspase inhibitor zVAD increases lung inflammation in pneumovirus infection in mice

“…; Messer et al. ). Our study adds to the body of literature on this topic, however, by showing inefficient and even unfavorable responses to treatment with the caspase inhibitor zVAD in severe pneumovirus‐induced lung injury.…”

“…; Messer et al. ). The various treatment strategies to inhibit apoptosis used in these studies include silencing of caspases and death receptor signaling by small interfering RNA (Perl et al.…”

“…; Messer et al. ), as well as blockade by decoy receptors and fusion proteins instilled in the lungs (Matute‐Bello et al. ).…”

“…From the above, one can hypothesize that treatment strategies to block apoptosis in the lung may protect the lung epithelium and thus improve the outcome of severe RSV-LRTD. Indeed, experimental studies in animals modeling human ARDS have shown that inhibition of apoptosis in the lungs can be beneficial in terms of survival, lung permeability, and histopathological alterations (Kawasaki et al 2000;Matute-Bello et al 2005;Lipke et al 2010;Messer et al 2013). The various treatment strategies to inhibit apoptosis used in these studies include silencing of caspases and death receptor signaling by small interfering RNA (Perl et al 2005;Messer et al 2013), as well as blockade by decoy receptors and fusion proteins instilled in the lungs .…”

“…Indeed, experimental studies in animals modeling human ARDS have shown that inhibition of apoptosis in the lungs can be beneficial in terms of survival, lung permeability, and histopathological alterations (Kawasaki et al 2000;Matute-Bello et al 2005;Lipke et al 2010;Messer et al 2013). The various treatment strategies to inhibit apoptosis used in these studies include silencing of caspases and death receptor signaling by small interfering RNA (Perl et al 2005;Messer et al 2013), as well as blockade by decoy receptors and fusion proteins instilled in the lungs . Interestingly, systemic administration of the synthetic peptide Z-VAD(OMe)-FMK (zVAD), a widely used irreversible pan-caspase inhibitor, reduced lung epithelial cell apoptosis (Kawasaki et al 2000;Le Berre et al 2004;Herrero et al 2013), lung permeability (Le Berre et al 2004;Lipke et al 2010;Herrero et al 2013), and mortality (Kawasaki et al 2000) in several animal models of lung injury.…”