Comparative study on the anti-inflammatory and protective effects of different oxygen therapy regimens on lipopolysaccharide-induced acute lung injury in mice

Abstract

Oxygen therapy after acute lung injury can regulate the inflammatory response and reduce lung tissue injury. However, the optimal exposure pressure, duration, and frequency of oxygen therapy for acute lung injury remain unclear. In the present study, after intraperitoneal injection of lipopolysaccharide in ICR mice, 1.0 atmosphere absolute (ATA) pure oxygen and 2.0 ATA hyperbaric oxygen treatment for 1 hour decreased the levels of proinflammatory factors (interleukin-1beta and interleukin-6) in peripheral blood and lung tissues. However, only 2.0 ATA hyperbaric oxygen increased the mRNA levels of anti-inflammatory factors (interleukin-10 and arginase-1) in lung tissue; 3.0 ATA hyperbaric oxygen treatment had no significant effect. We also observed that at 2.0 ATA, the anti-inflammatory effect of a single exposure to hyperbaric oxygen for 3 hours was greater than that of a single exposure to hyperbaric oxygen for 1 hour. The protective effect of two exposures for 1.5 hours was similar to that of a single exposure for 3 hours. These results suggest that hyperbaric oxygen alleviates lipopolysaccharide-induced acute lung injury by regulating the expression of inflammatory factors in an acute lung injury model and that appropriately increasing the duration and frequency of hyperbaric oxygen exposure has a better tissue-protective effect on lipopolysaccharide-induced acute lung injury. These results could guide the development of more effective oxygen therapy regimens for acute lung injury patients.

Figure 1

Experimental flow chart of different oxygen therapy regimens. Protocol 1: Experimental flow chart of different exposure pressures; gray represents the control group, the same dose of normal saline was injected; green represents the LPS (5 mg/kg) group; orange from light to dark represents the 1.0, 2.0, and 3.0 ATA exposure pressure groups, respectively. Protocol 2: Experimental flow chart of different exposure durations and continuous exposure for 1 or 3 hours under 2.0 ATA. Protocol 3: Experimental flow chart of different exposure frequencies under 2.0 ATA, a single exposure for 3 hours or two exposures for 1.5 hours. ATA: Atmosphere absolute; Con: control; Exp.: experiment; ip.: intraperitoneal injection; LPS: lipopolysaccharide.

Figure 2

Effects of different exposure pressures on inflammatory factors in the peripheral blood and lung tissues of LPS-induced ALI model mice. Note: (A) IL-1β. IL-6. and TNF-α levels in serum detected by ELISA. (B) Relative mRNA levels of the proinflammatory factors Il1b, Il6, and Tnfa in lung tissue. (C) Relative mRNA levels of the anti-inflammatory factors Il10, Arg1 and CD206 in lung tissue. The data are expressed as the mean ± SEM (n = 4–7 samples for each group). *P < 0.05, ** P < 0.01, *** P < 0.001 (one-way analysis of variance followed by Tukey’s multiple comparison test). ALI: Acute lung injury; ATA: atmosphere absolute; Con: control; IL: interleukin; LPS: lipopolysaccharide; TNF: tumor necrosis factor.

Figure 3

Exposure to different pressures of HBO results in different degrees of pathological injury to the lung tissue in an LPS-induced ALI mouse model. Note: (A) Histopathological changes in lung tissue. In the control group, lung tissue morphology was normal; in the LPS group, interstitial lung edema, neutrophil infiltration, and leakage of erythrocytes from the alveolar lumen were observed; in the LPS + 2.0 ATA HBO group, lung histopathological injuries were significantly attenuated; and in the LPS +1.0 ATA HBO group and LPS +3.0 ATA HBO group, no significant improvement was observed. Scale bars: 50 μm (upper), 5 μm (lower). (B) Lung injury scores. The data are expressed as the mean ± SEM (n = 3–5 in each group). *P < 0.05, ***P < 0.001 (one-way analysis of variance followed by Tukey’s multiple comparison test). ALI: Acute lung injury; ATA: atmosphere absolute; Con: control; HBO: hyperbaric oxygen; LPS: lipopolysaccharide.

Figure 4

Effects of different durations of HBO exposure on inflammatory factor levels in the peripheral blood and lung tissues of LPS-induced ALI model mice. Note: (A) IL-1β. IL-6. and TNF-α levels in serum detected by ELISA. (B) Relative mRNA levels of the proinflammatory factors Il1b, Il6, and Tnfa in lung tissue. (C) Relative mRNA levels of the anti-inflammatory factors Il10, Arg1 and CD206 in lung tissue. The data are expressed as the mean ± SEM (n = 4–8 samples for each group). *P < 0.05, **P < 0.01, ***P < 0.001 (one-way analysis of variance followed by Tukey’s multiple comparison test). ALI: Acute lung injury; ATA: atmosphere absolute; Con: control; HBO: hyperbaric oxygen; IL: interleukin; LPS: lipopolysaccharide; TNF: tumor necrosis factor.

Figure 5

Effects of different HBO exposure times on pathological injury to lung tissue in an LPS-induced ALI mouse model. (A) Histopathological changes in lung tissue. The LPS group exhibited pathological damage, such as capillary dilatation and congestion, interstitial edema, neutrophil infiltration, and alveolar luminal erythrocyte leakage, which were attenuated by 1 and 3 hours of 2.0 ATA HBO treatment. Scale bars: 50 μm (upper), 5 μm (lower). (B) Lung injury scores. The data are expressed as the mean ± SEM (n = 3–5 in each group). * P < 0.05, ** P < 0.01, *** P < 0.001 (one-way analysis of variance followed by Tukey’s multiple comparison test). ALI: Acute lung injury; ATA: atmosphere absolute; Con: control; HBO: hyperbaric oxygen; LPS: lipopolysaccharide.

Figure 6

Effects of different frequencies of HBO exposure on inflammatory factor levels in the peripheral blood and lung tissues of LPS-induced ALI model mice. IL-1β. IL-6. and TNF-α levels in serum detected by ELISA. (B) Relative mRNA levels of the proinflammatory factors Il1b, Il6, and Tnfa in lung tissue. (C) Relative mRNA levels of the anti-inflammatory factors Il10, Arg1 and CD206 in lung tissue. The data are expressed as the mean ± SEM (n = 4–7 samples for each group). *P < 0.05, **P < 0.01, *** P < 0.001 (one-way analysis of variance followed by Tukey’s multiple comparison test). ALI: Acute lung injury; ATA: atmosphere absolute; Con: control; HBO: hyperbaric oxygen; IL: interleukin; LPS: lipopolysaccharide; TNF: tumor necrosis factor.

Figure 7

Exposure to different frequencies of HBO similarly alleviates pathological lung tissue injury in an LPS-induced ALI mouse model. (A) Histopathological changes in lung tissue. Lung tissues in the LPS group exhibited pathological injuries, such as gross edema, neutrophil infiltration, and alveolar erythrocyte leakage, which were alleviated after two 1.5-hour and one 3-hour HBO treatments. Scale bars: 50 μm (upper), 5 μm (lower). (B) Lung injury scores. The data are expressed as the mean ± SEM (n = 3–5 in each group). ** P < 0.01, *** P < 0.001 (one-way analysis of variance followed by Tukey’s multiple comparison test). ALI: Acute lung injury; ATA: atmosphere absolute; Con: control; HBO: hyperbaric oxygen; LPS: lipopolysaccharide.