Diazoxide decreases ischemia-reperfusion injury in a rat model of lung transplantation

Ex Vivo Lung Perfusion with K(ATP) Channel Modulators Antagonize Ischemia Reperfusion Injury

Ex vivo lung perfusion (EVLP) has been implemented to increase the number of donor lungs available for transplantation. The use of K(ATP) channel modulators during EVLP experiments may protect against lung ischemia-reperfusion injury and may inhibit the formation of reactive oxygen species. In a rat model of donation after circulatory death with 2 h warm ischemic time, we evaluated rat lungs for a 4-hour time in EVLP containing either mitochondrial-specific or plasma membrane and/or sarcolemmal-specific forms of K(ATP) channel modulators. Lung physiological data were recorded, and metabolic parameters were assessed. When compared to the control group, in the EVLP performed with diazoxide or 5-hydroxydecanoic acid (5-HD) we recorded significantly lower pulmonary vascular resistance and only in the diazoxide group recorded significant lung weight loss. In the perfusate of the 5-HD group, interleukin-1β and interleukin-1α were significantly lower when compared to the control group. Perfusate levels of calcium ions were significantly higher in both 5-HD and cromakalim groups, whereas the levels of calcium, potassium, chlorine and lactate were reduced in the diazoxide group, although not significantly when compared to the control. The use of a diazoxide mitochondrial-specific K(ATP) channel opener during EVLP improved lung physiological and metabolic parameters and reduced edema.

Effects of hyperbaric oxygen on intestinal mucosa apoptosis caused by ischemia-reperfusion injury in rats

BACKGROUND

Hyperbaric oxygen (HBO) is an effective adjuvant therapy for ischemia- reperfusion (I/R) injury of the brain, small intestine and testis in addition to crushing injury. Studies have shown that HBO increases the activity of villi of the ileum 30 minutes after I/R injury. The present study aimed to observe the effect of HBO on apoptosis of epithelial cells in the small intestine during different periods of I/R and to elucidate the potential mechanisms.

METHODS

Rats were subjected to 60-minute ischemia by clamping the superior mesenteric artery and 60-minute reperfusion by removal of clamping. The rats were randomly divided into four groups: I/R group, HBO precondition or HBO treatment before ischemia (HBO-P), HBO treatment during ischemia period (HBO-I), and HBO treatment during reperfusion (HBO-R). After 60-minute reperfusion, samples of the small intestine were prepared to measure the level of ATP by using the colorimetric method and immunochemical expression of caspase-3. The levels of TNF-α in intestinal tissue were measured using the enzyme-linked immunosorbent assay method (Elisa).

RESULTS

TNF-α levels were significantly lower in the HBO-I group than in the HBO-P (P<0.05), HBO-R and I/R groups; there was no significant difference between the HBO-R and I/R groups (P>0.05). The expression of caspas-3 was significantly lower in the HBO-I group than in the HBO-P group (P<0.05); it was also significantly lower in the HBO-P group than in the I/R and HBO-R groups (P<0.05). ATP level was significantly lower in the HBO-I group than in the HBO-P group (P<0.05), and also it was significantly lower in the HBO-P group than in the I/R and HBO-R groups (P<0.05).

CONCLUSIONS

There is an association between HBO, small intestinal I/R injury, and mucosa apoptosis. HBO maintains ATP and aerobic metabolism, inhibites TNF-α production, and thus prevents intestinal mucosa from apoptosis. Best results can be obtained when HBO is administered to patients in the period of ischemia, and no side effects are produced when HBO is given during the period of reperfusion.

Effect of dexmedetomidine on lung ischemia‑reperfusion injury

Dexmedetomidine, a specific selective α₂-adrenergic agonist, does not only have the characteristics of being a sedative and analgesic, but also exhibits a protective role in brain ischemia-reperfusion injury and inhibits the inflammation in animals with sepsis. The objective of the present study was to investigate whether dexmedetomidine is capable of attenuating rat pulmonary damage induced by ischemia-reperfusion injury, which is a type of acute sterile lung injury. Sprague-Dawley rats were randomly assigned into six groups: The sham-operated (sham) group, the lung ischemia-reperfusion (I/R) group, intravenous injection of dexmedetomidine 2.5 μg/kg/h (Dex2.5) or 5 μg/kg/h (Dex5) for 1 h prior to ischemia, combination of α₂-adrenergic antagonist yohimbine prior to dexmedetomidine pre-treatment (Dex+Yoh) and pre-administration of yohimbine alone (Yoh) prior to ischemia. Lung injury was assessed by the histopathological changes, arterial blood gas, wet/dry (w/d) weight ratio and myeloperoxidase (MPO) activity of the lung. The concentration of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and monocyte chemoattractant protein-1 (MCP-1) in bronchoalveolar lavage fluid (BALF) was measured by an enzyme-linked immunosorbent assay. The expression of toll-like receptor-4 (TLR4) and myeloid differentiation factor 88 (MyD88) mRNA in the lung were determined by quantitative PCR, and phosphorylated levels of c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK)1/2 were determined by western blotting. Pre-treatment with dexmedetomidine significantly reduced the lung injury, w/d weight ratio and MPO activity, and decreased the concentration of TNF-α, IL-6 and MCP-1 in BALF compared with the I/R group. The expression of TLR4 and MyD88 mRNA and the levels of phosphorylated JNK and ERK1/2 in the lung tissue were markedly downregulated by intravenous injection of dexmedetomidne for 1 h prior to lung I/R. The protective effects of dexmedetomidine on the lung were not completely reversed by the α₂-adrenergic antagonist, yohimbine. Pre-treatment with dexmedetomidine is capable of reducing pulmonary damage and inhibiting sterile inflammation induced by lung I/R injury. TLR4/MyD88/mitogen-activated protein kinase (MAPK) signaling is involved in the protective mechanism of dexmedetomidine through α₂-adrenoceptor independence.