[Biliverdin protects the isolated lungs from ischemia/reperfusion injury via anti-apoptosis]

To observe the effect of biliverdin (BV) on the lung ischemia/reperfusion injury (LIRI), and to investigate the mechanism of BV in treatment of LIRI.

Thirty-two male Sprague-Dawley (SD) rats were randomly divided into control group, LIRI group, glutathione (GSH) group and BV-treated group, with 8 rats in each group. The rat LIRI model was reproduced by isolated lung perfusion system. Fifteen minutes after perfusion balance, lungs of control group were perfused continuously for 90 minutes, and the lungs in other groups were reperfused for 90 minutes after 1-hour ischemia, while the perfusion was added 10 μmol/L BV in BV-treated group and 4 mmol/L GSH in GSH group respectively. During the perfusion, the respiratory related indicators, such as tidal volume (VT), static compliance (Cst), arterial partial pressure of oxygen (PaO₂), airway resistance (Raw), were dynamically observed. After perfusion, the wet/dry weight ratio (W/D) of lungs was determined. Pathological changes in lung tissue were observed under light microscope. The cell apoptosis was observed by TdT-mediated dUTP nick end labeling (TUNEL) method, and the apoptosis index was calculated. The protein expression levels of heme oxygenase-1 (HO-1), phosphorylated c-Jun N-terminal kinase (p-JNK), and caspase-3 were determined by Western Blot.

Compared with control group, VT, Cst and PaO₂ in LIRI group were significantly decreased from reperfusion for 30 minutes, and Raw was significantly increased. The pathological results showed that there was different degree of hyperemia edema, inflammatory cells infiltration and bronchial endothelium injury in the lung tissue of LIRI group. The W/D ratio of LIRI group was significantly higher than that of control group (8.98±2.34 vs. 5.89±0.52, P < 0.05). TUNEL results showed that the tan apoptosis cells of LIRI group were more than control group, and the apoptosis index was significantly higher than that of the control group [(13.88±2.35)% vs. (2.26±0.60)%, P < 0.05]. Compared with control group, the protein expression levels of HO-1, p-JNK, and caspase-3 in LIRI group were significantly increased [HO-1 (gray value): 0.55±0.13 vs. 0.16±0.02, p-JNK (gray value): 0.46±0.08 vs. 0.16±0.05, caspase-3 (gray value): 0.65±0.13 vs. 0.26±0.03, all P < 0.05]. Compared with LIRI group, the respiratory indicators in BV-treated group were improved significantly, the lung tissue injury was significantly reduced, the W/D ratio was significantly decreased (6.39±0.45 vs. 8.98±2.34, P < 0.05), and the cell apoptosis index was significantly reduced [(4.49±1.10)% vs. (13.88±2.35)%, P < 0.05], as well as the protein expression levels of HO-1, p-JNK, and caspase-3 were significantly lowered [HO-1 (gray value): 0.19±0.03 vs. 0.55±0.13, p-JNK (gray value): 0.31±0.06 vs. 0.46±0.08, caspase-3 (gray value): 0.33±0.05 vs. 0.65±0.13, all P < 0.05], which indicating that BV could alleviate LIRI via anti-apoptosis. The improvement effect of BV on PaO₂, apoptosis index, protein expressions of HO-1 and caspase-3, and JNK phosphorylation were better than positive drug GSH, indicating that BV could protect LIRI ideally.

BV alleviates LIRI via its anti-JNK pathway and its anti-apoptosis property.