Ascorbic acid for amelioration of reperfusion injury in a lung autotransplantation model in sheep

The effects of vitamin C on respiratory, allergic and immunological diseases: an experimental and clinical-based review

Vitamin C is used in modern medicine supplements for treatment of various disorders associated with oxidative stress, inflammation and immune dysregulation. In this review article, experimental and clinical results regarding the effects of vitamin C on respiratory immunologic, and allergic diseases are reviewed. Various databases and appropriate keywords are used to search the effect of vitamin C on respiratory diseases until the end of May 2022. Books, theses and articles were included. These studies assessed the effects of vitamin C on respiratory disorders including asthma, chronic obstructive pulmonary disease (COPD), lung infection and lung cancer. Vitamin C showed relaxant effect on tracheal smooth muscle via various mechanisms. The preventive effects of vitamin C were mediated by antioxidant, immunomodulatory and anti-inflammatory mechanisms in the experimental animal models of different respiratory diseases. Some clinical studies also indicated the effect of vitamin C on lung cancer and lung infections. Therefore, vitamin C could be used a preventive and/or relieving therapy in respiratory diseases.

Ascorbic acid prolongs the viability and stability of isolated perfused lungs: A mechanistic study using 31P and hyperpolarized 13C nuclear magnetic resonance

Ex vivo lung perfusion (EVLP) has recently shown promise as a means of more accurately gauging the health of lung grafts and improving graft performance post-transplant. However, reperfusion of ischemic lung promotes the depletion of high-energy compounds and a progressive loss of normal mitochondrial function, and it remains unclear how and to what extent the EVLP approach contributes to this metabolic decline. Although ascorbate has been used to mitigate the effects of ischemia-reperfusion injury, the nature of its effects during EVLP are also not clear. To address these uncertainties, this study monitored the energy status of lungs during EVLP and after the administration of ascorbate using (31)P and hyperpolarized (13)C NMR (nuclear magnetic resonance). Our experiments demonstrated that the oxidative phosphorylation capacity and pyruvate dehydrogenase flux of lungs decline during ex vivo perfusion. The addition of ascorbate to the perfusate prolonged lung viability by 80% and increased the hyperpolarized (13)C bicarbonate signal by a factor of 2.7. The effect of ascorbate is apparently due not to its antioxidant quality but rather to its ability to energize cellular respiration given that it increased the lung's energy charge significantly, whereas other antioxidants (glutathione and α-lipoic acid) did not alter energy metabolism. During ascorbate administration, inhibition of mitochondrial complex I with rotenone depressed energy charge and shifted the metabolic state of the lung toward glycolysis; reenergizing the electron transport chain with TMPD (N,N,N',N'-tetramethyl-p-phenylenediamine) recovered metabolic activity. This indicates that ascorbate slows the decline of the ex vivo perfused lung's mitochondrial activity through an independent interaction with the electron transport chain complexes.

Ischaemia-reperfusion injury of rat ovary and the effects of vitamin C, mannitol and verapamil

BACKGROUND

In this prospective controlled study, the aim was to examine the effects of vitamin C, mannitol and verapamil on adnexial ischaemia-reperfusion injury in the rat ovary.

METHODS

Thirty-six female Wistar rats were used. In the controls (group 1), only laparotomy was performed. In group 2, ovarian ischaemia was produced and the bilateral ovaries were surgically removed 4 h later. In group 3, an ischaemic period of 4 h was followed by reperfusion for 1 h; the bilateral ovaries were then removed. In groups 4, 5 and 6, after 4 h of ischaemia, either vitamin C, mannitol or verapamil respectively was infused before reperfusion; after 1 h of reperfusion the ovaries were removed. Thiobarbituric acid reactive substance (TBARS) levels were measured in all ovary tissues.

RESULTS

TBARS levels of the reperfusion group were significantly higher than those of groups treated with vitamin C or mannitol (P = 0.013 and P = 0.045 respectively), but not of the verapamil group.

CONCLUSIONS

Vitamin C and mannitol were found to be effective in reducing ischaemia-reperfusion injury of the ovary during its early stages, but verapamil was ineffective.

C1-esterase inhibitor reduces reperfusion injury after lung transplantation

BACKGROUND

Activation of the complement system and polymorphonuclear neutrophilic leukocytes plays a major role in mediating reperfusion injury after lung transplantation. We hypothesized that early interference with complement activation would reduce lung reperfusion injury after transplantation.

METHODS

Unilateral left lung autotransplantation was performed in 6 sheep. After hilar stripping the left lung was flushed with Euro-Collins solution and preserved for 2 hours in situ at 15 degrees C. After reperfusion the right main bronchus and pulmonary artery were occluded, leaving the animal dependent on the reperfused lung (reperfused group). C1-esterase inhibitor group animals (n = 6) received 200 U/kg body weight of C1-esterase inhibitor as a short infusion, half 10 minutes before, the other half 10 minutes after reperfusion. Controls (n = 6) underwent hilar preparation only. Pulmonary function was assessed by alveolar-arterial oxygen difference and pulmonary vascular resistance. The release of beta-N-acetylglucosaminidase served as indicator of polymorphonuclear neutrophilic leukocyte activation. Extravascular lung water was an indicator for pulmonary edema formation. Biopsy specimens were taken from all groups 3 hours after reperfusion for light and electron microscopy.

RESULTS

In the reperfused group, alveolar-arterial oxygen difference and pulmonary vascular resistance were significantly elevated after reperfusion. All animals developed frank alveolar edema. The biochemical marker beta-N-acetylglucosaminidase showed significant leukocyte activation. In the C1-esterase inhibitor group, alveolar-arterial oxygen difference, pulmonary vascular resistance, and the level of polymorphonuclear neutrophilic leukocyte activation were significantly lower.

CONCLUSIONS

Treatment with C1-esterase inhibitor reduces reperfusion injury and improves pulmonary function in this experimental model.