Impact of Intermittent Hypoxia on Sepsis Outcomes in a Murine Model

Abstract

Sleep apnea has been associated with a variety of diseases, but its impact on sepsis outcome remains unclear. This study investigated the effect of intermittent hypoxia [IH]-the principal feature of sleep apnea-on murine sepsis. 5-week-old male C57BL6 mice were assigned to groups receiving severe IH (O2 fluctuating from room air to an O2 nadir of 5.7% with a cycle length of 90 seconds), mild IH (room air to 12%, 4 minutes/cycle), or room air for 3 weeks. Sepsis was induced by cecal ligation and puncture and survival was monitored. Sepsis severity was evaluated by murine sepsis scores, blood bacterial load, plasma tumor necrosis factor-α [TNF-α]/interleukin-6 [IL-6] levels and histopathology of vital organs. Compared with normoxic controls, mice subjected to severe IH had earlier mortality, a lower leukocyte count, higher blood bacterial load, higher plasma TNF-α and IL-6 levels, more severe inflammatory changes in the lung, spleen and small intestine. Mice subjected to mild IH did not differ from normoxic controls, except a higher IL-6 level after sepsis induced. The adverse impact of severe IH was reversed following a 10-day normoxic recovery. In conclusion, severe IH, not mild IH, contributed to poorer outcomes in a murine sepsis model.

Figure 1

The study design.

Figure 2

Profile of Intermittent hypoxia of the IH1 and IH2 protocols.

Figure 3

Levels of Inflammatory biomarkers and sepsis severity in mice. (A) leukocyte count, (B) TNF-α, (C) IL-6 (D)bacterial load, (E) sepsis scores. Post-CLP IH2 and control groups: n = 6; other groups: n = 5. *p < 0.05; ^#p < 0.05 for comparison between before and after CLP in each of the three groups (IH1/IH2/control).

Figure 4

Survival after cecal ligation and puncture. In comparison to normoxic controls, the IH1 group had significantly earlier mortality. The difference between IH1 and IH2 showed a trend toward statistical significance. p = 0.008 for three-group comparison. IH1 vs control: p = 0.002, IH1 vs IIH2: p = 0.056. n = 12 for each group.

Figure 5

Histopathologic evaluation with hematoxylin-eosin staining (magnification 40×). showed more prominent inflammatory changes in the lung, small intestine and spleen in the IH1 group than in the IH2 group and normoxic controls. Bar: 200 μm.

Figure 6

Histopathologic evaluation with hematoxylin-eosin staining (magnification 100×). The IH1 group had more severe inflammatory change than the IH group or normoxic controls. Scores of organ damage were shown on the last row. Bar: 100 μm.

Figure 7

Normoxic recovery. With a 10-day normoxic recovery following the IH1 protocol, sepsis severity (A) and mortality (B) did not differ significantly between the IH1 group and normoxic controls. n = 6 for each group.