Thaliporphine derivative improves acute lung injury after traumatic brain injury

Abstract

Acute lung injury (ALI) occurs frequently in patients with severe traumatic brain injury (TBI) and is associated with a poor clinical outcome. Aquaporins (AQPs), particularly AQP1 and AQP4, maintain water balances between the epithelial and microvascular domains of the lung. Since pulmonary edema (PE) usually occurs in the TBI-induced ALI patients, we investigated the effects of a thaliporphine derivative, TM-1, on the expression of AQPs and histological outcomes in the lung following TBI in rats. TM-1 administered (10 mg/kg, intraperitoneal injection) at 3 or 4 h after TBI significantly reduced the elevated mRNA expression and protein levels of AQP1 and AQP4 and diminished the wet/dry weight ratio, which reflects PE, in the lung at 8 and 24 h after TBI. Postinjury TM-1 administration also improved histopathological changes at 8 and 24 h after TBI. PE was accompanied with tissue pathological changes because a positive correlation between the lung injury score and the wet/dry weight ratio in the same animal was observed. Postinjury administration of TM-1 improved ALI and reduced PE at 8 and 24 h following TBI. The pulmonary-protective effect of TM-1 may be attributed to, at least in part, downregulation of AQP1 and AQP4 expression after TBI.

Figure 1

TM-1 administered 3 or 4 h after injury reduced the TBI-induced lung wet/dry weight ratio measured 8 and 24 h after TBI. Decrease in the wet/dry weight ratio at 3 or 4 h after injury with TM-1 administration (10 mg/kg) when the rats were sacrificed at 8 or 24 h after injury, respectively. Data are expressed as mean ± SD (n = 5/group). ^*** P < 0.001 TBI + veh group compared with the sham-operated group; ^### P < 0.001 TM-1 treated groups compared with the TBI + veh groups; ⁺ P < 0.05, comparison between wet/dry weight ratios of rats sacrificed at 24 h following TM-1 administration (10 mg/kg) at 3 and 4 h after injury.

Figure 2

TM-1 administered 3 or 4 h after injury reduced the TBI-induced AQP1 mRNA expression measured 8 and 24 h after TBI. Relative AQP1 mRNA expression was measured by reverse transcription Q-PCR using β-actin (a) and Gapdh (b) as reference genes. AQP1 mRNA expression significantly decreased following TM-1 administration (10 mg/kg) at 3 and 4 h after injury in the rats sacrificed 8 or 24 h after injury, respectively. Compared with the TBI + veh groups, the TM-1 treated groups exhibited significantly decreased mRNA expression. Data are expressed as mean ± SD (n = 5/group). ^*** P < 0.001 TBI + veh group compared with the sham-operated group; ^# P < 0.05 and ^### P < 0.0001 TM-1 treated group compared with the TBI + veh groups; ⁺⁺⁺ P < 0.001, comparison between mRNA expression following TM-1 administration (10 mg/kg) 3 and 4 h after injury in the rats sacrificed 8 or 24 h after TBI.

Figure 3

TM-1 administered 3 or 4 h after injury reduced TBI-induced lung AQP1 protein expression levels measured 8 and 24 h after TBI. The AQP1 protein level showed a marked decrease following TM-1 administration 3 or 4 h after injury (10 mg/kg), respectively. Rats were sacrificed 8 or 24 h after TBI. Data are expressed as mean ± SD (n = 5/group). ^*** P < 0.001 compared with the sham-operated group; ^# P < 0.05 compared with the untreated groups; ⁺⁺⁺ P < 0.001, comparison between mRNA expression following TM-1 administration (10 mg/kg) 3 and 4 h after injury in the rats sacrificed 8 and 24 h after TBI; ⁺ P < 0.05, comparison between protein levels following TM-1 administration (10 mg/kg) 3 and 4 h after injury in the rats sacrificed 24 h after TBI.

Figure 4

TM-1 administered 3 or 4 h after injury reduced the TBI-induced AQP4 mRNA expression measured 8 and 24 h after TBI. (a) β-actin and (b) Gapdh as reference genes. AQP4 mRNA expression significantly decreased following TM-1 administration (10 mg/kg) 3 and 4 h after injury in the rats sacrificed 8 or 24 h after injury, respectively. Compared with the TBI + veh groups, the TM-1 treated groups exhibited significantly decreased mRNA expression. Data are expressed as mean ± SD (n = 5/group). ^*** P < 0.001 TBI + veh group compared with the sham-operated group; ^## P < 0.01 and ^### P < 0.001 compared with the TBI + veh groups; ⁺ P < 0.05, comparison between mRNA expression following TM-1 administration (10 mg/kg) 3 and 4 h after injury in the rats sacrificed 8 or 24 h after TBI.

Figure 5

TM-1 administered 3 or 4 h after injury reduced the TBI-induced AQP4 protein level measured 8 and 24 h after TBI. The AQP4 protein level showed a marked decrease following TM-1 administration (10 mg/kg) 3 and 4 h after injury, respectively. Rats were sacrificed 8 or 24 h after TBI. Data are expressed as mean ± SD (n = 5/group). ^** P < 0.01 and ^*** P < 0.001 TBI + veh group compared with the sham-operated group; ^# P < 0.05 TM-1 treated groups compared with the TBI + veh groups; no significance in AQP4 protein expression following TM-1 administration (10 mg/kg) at 3 and 4 h after injury in the rats sacrificed at 8 or 24 h after TBI.

Figure 6

TM-1 administered 3 or 4 h after injury reduced alveolar swelling with infiltration of inflammatory cells 8 and 24 h after TBI by H&E staining. The vehicle-treated sham-operated group showed a normal alveolar morphology. Alveolar swelling and infiltration of inflammatory cells increased 8 and 24 h in vehicle-treated TBI rats. Alveolar swelling and infiltration of inflammatory cells decreased following TM-1 administration 3 and 4 h after injury. Rats were sacrificed 8 or 24 h after TBI. Bar = 25 μm.

Figure 7

TM-1 administered 3 or 4 h after injury reduced the TBI-induced lung injury score 8 and 24 h after TBI. Significant difference was observed between the sham-operated and TBI groups. The lung injury score decreased with TM-1 administration (10 mg/kg) 3 and 4 h after injury. Rats were sacrificed 24 h after TBI. The lung injury score decreased following TM-1 administration (10 mg/kg) 3 and 4 h after injury. Rats were sacrificed 24 h after TBI. Data are expressed as mean ± SD (n = 5/group). ^*** P < 0.001 compared with the sham-operated group; ^### P < 0.001 compared with the untreated groups.

Figure 8

Rats administered TM-1 3 or 4 h after injury showed a positive correlation between the wet/dry weight ratio and the lung injury score. (a) The wet/dry weight ratio and the lung injury score in rats sacrificed at 8 h after TBI exhibited a positive correlation (df = 13, r = 0.72224) and a significant difference (P < 0.01) in the three groups. (b) The wet/dry weight ratio and the lung injury score in rats sacrificed at 24 h after TBI exhibited a positive correlation (df = 13, r = 0.72633) and a significant difference (P < 0.01) in the three groups.