Dexmedetomidine Leads to the Mitigation of Myocardial Ischemia/Reperfusion-Induced Acute Lung Injury in Diabetic Rats Via Modulation of Hypoxia-Inducible Factor-1α

Abstract

Introduction: The objective of this study is to investigate the protective mechanism of dexmedetomidine (Dex) in myocardial ischemia/reperfusion (MIR)-induced acute lung injury (ALI) of diabetic rats by inhibiting hypoxia-inducible factor-1α (HIF-1α).

Methods: Initially, healthy male Sprague Dawley rats were treated with streptozocin to induce diabetes. Then, three weeks after the induction, Dex or lentiviral vector (LV)-HIF-1α was injected into the rats 30 minutes prior to the MIR modeling. After four weeks, lung tissues were harvested for pathological changes observation and the wet/dry weight (W/D) ratio determination. Afterwards, oxidative stress indicators and pro-inflammatory factors were measured. In addition, HIF-1α expression was assessed by immunohistochemistry and western blot analysis.

Results: Dex could suppress inflammatory cell infiltration, improve lung tissue structure, reduce pathological score and the W/D ratio, and block oxidative stress and inflammatory response in MIR-induced ALI of diabetic rats. Besides, Dex could also inhibit HIF-1α expression. Moreover, Dex + LV-HIF-1α reversed the protective role of Dex on diabetic MIR-induced ALI.

Conclusion: Our study has made it clear that Dex inhibited the upregulation of HIF-1α in diabetic MIR-induced ALI, and thus protect lung functions by quenching the accumulation of oxygen radical and reducing lung inflammatory response.

Keywords: Acute Lung Injury; Dexmedetomidine; Diabetes; Hypoxia-Inducible Factor 1; Myocardial Ischemia Reperfusion; Up-Regulation.

Fig. 1

Timeline of the treatment of the studied rats. The figure shows the diabetes induction period, ischemia/reperfusion period, Dex administration time points, animal sacrifice time points, and test indicators of each time point. ELISA=enzyme-linked immunosorbent assay; HE=hematoxylin and eosin; IHC=immunohistochemistry; LVDP=left ventricular developed pressure; STZ=streptozocin; TTC=2, 3, 5-triphenyltetrazolium chloride; W/D=wet/dry weight.

Fig. 2

Identification of myocardial ischemia/reperfusion (MIR) injury in diabetic mouse models. A-B) Glucose (A) and body weights (B) of diabetic rats at three days, one week, two weeks, and three weeks after streptozocin induction. C) Left ventricular developed pressure (LVDP) level in each group after MIR (n=6). D) Infarct’s size of each group after MIR observed by 2, 3, 5-triphenyltetrazolium chloride staining (n=3). One-way analysis of variance (ANOVA) and repeated ANOVA were employed to verify statistical significance. * P<0.05, compared with the non-diabetic sham (NS) group; # P<0.05, compared with the diabetic sham (DS) group; & P<0.05, compared with the diabetic + ischemia/reperfusion (DIR) group. Dex=dexmedetomidine; NIR=non-diabetic + ischemia/reperfusion.

Fig. 3

Dexmedetomidine (Dex) relieves diabetic myocardial ischemia/reperfusion-induced acute lung injury. A-C) Representative hematoxylin and eosin staining images (A), pathological injury score (B), and wet/dry weight (W/D) ratio (C) of lung tissue sections from rats treated with Dex for four weeks (×200) (n=6). One-way analysis of variance was employed to verify statistical significance. *P<0.05, compared with the non-diabetic sham (NS) group; #P<0.05, compared with the diabetic sham (DS) group; & P<0.05, compared with the diabetic + ischemia/reperfusion (DIR) group. NIR=non-diabetic + ischemia/reperfusion.

Fig. 4

Dexmedetomidine (Dex) suppresses oxidative stress (oxygen radical) and inflammatory response in diabetic myocardial ischemia/reperfusion-induced acute lung injury. A-C) Levels of oxidative stress indicators including malondialdehyde (MDA) (A), superoxide dismutase (SOD) (B), and nitric oxide (NO) (C) in lung tissues from each group after being treated by Dex for four weeks. D-F) Levels of pro-inflammatory factors including tumor necrosis factor-α (TNF-α) (D), interleukin (IL)-1β (E), and IL-6 (F) in lung tissues from each group after being treated with Dex for four weeks (n=6). One-way analysis of variance was employed to verify statistical significance. *P<0.05, compared with the non-diabetic sham (NS) group; #P<0.05, compared with the diabetic sham (DS) group; & P<0.05, compared with the diabetic + ischemia/reperfusion (DIR) group. NIR=non-diabetic + ischemia/reperfusion.

Fig. 5

Dexmedetomidine (Dex) inhibits hypoxia-inducible factor-1α (HIF-1α) in lung tissues from the diabetic myocardial ischemia/reperfusion-induced acute lung injury rats. A-B) HIF-1α expression (A) and positive rate (B) in lung tissues from each group after being treated by Dex for four weeks examined by immunohistochemistry. C-D) HIF-1α expression (C) and grey value (D) in lung tissues from each group after being treated by Dex for four weeks tested by western blot analysis. *P<0.05, compared with the non-diabetic sham (NS) group;^#P<0.05, compared with the diabetic sham (DS) group; & P<0.05, compared with the diabetic + ischemia/reperfusion (DIR) group. NIR=non-diabetic + ischemia/reperfusion.

Fig. 6

Dexmedetomidine (Dex) attenuates diabetic myocardial ischemia/reperfusion-induced acute lung injury by limiting hypoxia-inducible factor-1α (HIF-1α). A-B) HIF-1α expression (A) and grey value (B) in lung tissues from each group after being treated by Dex + lentiviral vector (LV)-HIF-1α for four weeks detected by western blot analysis. C-E) Representative hematoxylin and eosin staining images (×200) (C), pathological score (D), and the wet/dry weight (W/D) ratio in lung tissues from each group after being treated with Dex + LV-HIF-1α for four weeks. F-H) Levels of oxidative stress indicators including malondialdehyde (MDA) (F), superoxide dismutase (SOD) (G), and nitric oxide (NO) (H) in lung tissues from each group after being treated with Dex + LV-HIF-1α for four weeks. I-K) Tumor necrosis factor-α (TNF-α) (I), interleukin (IL)-1β (J), and IL-6 (K) in lung tissues from each group after being treated with Dex + LV-HIF-1α for four weeks (n=6). The t-test was employed to verify statistical significance. *P<0.05, compared with the Dex + LV-negative control (NC) group. DIR=diabetic + ischemia/reperfusion; DS=diabetic sham; NIR=non-diabetic + ischemia/reperfusion; NS=non-diabetic sham.