Silencing of Fas, but not caspase-8, in lung epithelial cells ameliorates pulmonary apoptosis, inflammation, and neutrophil influx after hemorrhagic shock and sepsis.

Abstract

Apoptosis and inflammation play an important role in the pathogenesis of direct/pulmonary acute lung injury (ALI). However, the role of the Fas receptor-driven apoptotic pathway in indirect/nonpulmonary ALI is virtually unstudied. We hypothesized that if Fas or caspase-8 plays a role in the induction of indirect ALI, their local silencing using small interfering RNA (siRNA) should be protective in hemorrhage-induced septic ALI. Initially, as a proof of principle, green fluorescent protein-siRNA was administered intratracheally into transgenic mice overexpressing green fluorescent protein. Twenty-four hours after siRNA delivery, lung sections revealed a significant decrease in green fluorescence. Intratracheally administered Cy-5-labeled Fas-siRNA localized primarily in pulmonary epithelial cells. Intratracheal instillation of siRNA did not induce lung inflammation via toll-like receptor or protein kinase PKR pathways as assessed by lung tissue interferon-alpha, tumor necrosis factor-alpha, and interleukin (IL)-6 levels. Mice subjected to hemorrhagic shock and sepsis received either Fas-, caspase-8-, or control-siRNA intratracheally 4 hours after hemorrhage. Fas- or caspase-8-siRNA significantly reduced lung tissue Fas or caspase-8 mRNA, respectively. Only Fas-siRNA markedly diminished lung tissue tumor necrosis factor-alpha, IL-6, IL-10, interferon-gamma, IL-12, and caspase-3 activity. Fas-siRNA also preserved alveolar architecture and reduced lung neutrophil infiltration and pulmonary epithelial apoptosis. These data indicate the pathophysiological significance of Fas activation in nonpulmonary/shock-induced ALI and the feasibility of intrapulmonary administration of anti-apoptotic siRNA in vivo.

• Authors: Mario Perl, Chun-Shiang Chung, Joanne Lomas-Neira, Tina-Marie Rachel, Walter L Biffl, William G Cioffi, Alfred Ayala
• Journal: The American journal of pathology (Am J Pathol) Vol. 167 Issue 6 Pg. 1545-59 (Dec 2005) ISSN: 0002-9440 [Print] United States
• PMID: 16314469 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• DNA Primers
• RNA, Small Interfering
• fas Receptor
• Casp8 protein, mouse
• Caspase 8
• Caspases

Topics

• Animals
• Apoptosis
• Base Sequence
• Caspase 8
• Caspases (genetics)
• DNA Primers
• Disease Models, Animal
• Gene Silencing
• Inflammation
• Lung Diseases (genetics, pathology)
• Lung Injury
• Mice
• Mice, Inbred C57BL
• Mice, Transgenic
• Neutrophils (physiology)
• RNA, Small Interfering (genetics)
• Sepsis (genetics, pathology, therapy)
• Shock, Hemorrhagic (genetics, pathology, therapy)
• fas Receptor (genetics)