Enhanced Liver Autophagic Activity Improves Survival of Septic Mice Lacking Surfactant Proteins A and D

Enhanced Liver Autophagic Activity Improves Survival of Septic Mice Lacking Surfactant Proteins A and D

ZHE TANG,^1,2 LAN NI,^1,3 SARA JAVIDIPARSIJANI,¹ FENGQI HU,¹ LOUIS A GATTO,^1,4 ROBERT COONEY¹ and GUIRONG WANG¹

¹Department of Surgery, SUNY Upstate Medical University, Syracuse, NY, USA
²Department of Surgery of Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, P.R. China
³Department of Respiratory Diseases of Renmin Hospital, and Department of Respiratory Diseases of Zhongnan Hospital, Wuhan University, Wuhan, Hubei, P.R. China
⁴Department of Biological Sciences, SUNY Cortland, Cortland, NY, USA

Autophagy is a protective cellular mechanism in response to various stresses, including sepsis. Sepsis is defined as systemic inflammation by infection. Surfactant protein A and D (SP-A and SP-D) are involved in host defense, regulation of inflammation, and homeostasis, but their roles in the autophagic activity and relevant gene expression in sepsis are unclear. In this study, mice lacking SP-A and SP-D (SP-A/D KO mice) and background-matched wild-type (WT) C57BL/6 mice underwent either cecal ligation and puncture (CLP) or sham surgery. The results showed that SP-A/D KO mice had lower mortality than WT mice in CLP sepsis. Liver tissues showed marked pathological changes in both septic SP-A/D KO and WT mice 24 hrs after CLP treatment; and quantitative analysis of liver histopathology revealed significant difference between septic SP-A/D and septic WT mice. SP-A/D KO mice had higher basal and sepsis-induced level of autophagy than WT mice (p < 0.05), as judged by Western blot and electron microscopic analyses. The expression of 84 autophagy-related genes revealed differential basal and sepsis-induced gene expression between SP-A/D KO and WT mice. The expression increased in three genes and decreased in four genes in septic WT mice, as compared to septic SP-A/D KO mice (p < 0.05). Furthermore, differential responses to sepsis between SP-A/D KO and WT mice were found in six signaling pathways related to autophagy and apoptosis. Therefore, enhanced autophagic activity improves the survival of septic SP-A/D KO mice through the regulation of liver autophagy/apoptosis-related gene expression and signaling pathway activation.

keywords —— autophagy; innate immunity; sepsis; signaling pathway; surfactant protein

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Tohoku J. Exp. Med., 2013, 231, 127-138

Correspondence: Guirong Wang, Ph.D., Department of Surgery, UH Room 8715, SUNY Upstate Medical University, 750 E Adams St., Syracuse, NY 13210, USA.

e-mail: wangg@upstate.edu