Therapeutic modulation of metabolism to mitigate global ischaemia-reperfusion injury

Abstract

Ischaemia–reperfusion injury (IRI) is a major contributor to mortality and organ dysfunction after haemorrhagic shock, cardiac arrest, myocardial infarction and stroke. Although restoration of perfusion is essential to salvage ischaemic tissue, reperfusion itself triggers mitochondrial reactive oxygen species (ROS) generation, redox imbalance, inflammation and secondary cellular injury. This thesis investigated whether therapeutic modulation of metabolism and redox biology at the onset of reperfusion could attenuate global IRI in clinically relevant non-clinical models.

Two distinct interventions were evaluated. The first was diethylamine tetrathiomolybdate (DEATTM), a novel, soluble thiometallate sulfide donor with improved physicochemical properties compared with the parent compound ammonium tetrathiomolybdate (ATTM). DEATTM suppresses mitochondrial respiration, limits mitochondrial ROS formation and scavenges ROS that escape metabolic control. The second was pF48, a recombinant haemoglobin-based oxygen carrier (HBOC) engineered to improve vascular retention, reduce nitric oxide (NO) scavenging and influence redox balance.

A rat haemorrhage-reperfusion model was used as the principal platform for therapeutic testing. Global ischaemia was induced by controlled withdrawal of 40% of estimated blood volume, followed by 90 minutes of ischaemia and subsequent resuscitation with or without the treatment of interest. Physiological monitoring included invasive blood pressure, echocardiography, arterial blood gas analysis, tissue oxygen tension, urine output, organ function biomarkers, oxidative stress indices and inflammatory mediators.

In vivo pharmacokinetic/pharmacodynamic assessment showed that DEATTM produced effects consistent with biologically relevant sulfide release and modulation of mitochondrial metabolism (e.g. hyperlactataemia and increased tissue oxygen tension). In the haemorrhage-reperfusion model, DEATTM significantly improved survival (p<0.05), preserved renal and hepatic function, and reduced oxidative injury and pro-inflammatory responses. These findings support a protective effect mediated by early suppression of mitochondrial oxidative injury, combined with direct ROS scavenging.

The second therapeutic strategy, pF48, was evaluated in the same haemorrhage–reperfusion model. pF48 rapidly improved blood pressure recovery, increased tissue oxygen tension, enhanced diuresis, preserved organ function, maintained tissue glutathione levels and reduced lipid peroxidation in surviving animals. However, pF48 also increased methaemoglobin and nitrate/nitrite levels and was associated with complement activation, indicating that potential immunological and redox-related liabilities require further investigation.

Overall, this thesis identifies early reperfusion as a critical therapeutic window in global IRI and demonstrates that interventions targeting metabolism, oxidative injury and oxygen handling can modify short-term outcome. DEATTM and pF48 provide complementary proof-of-concept strategies that justify further mechanistic, comparative and translational evaluation in longer-term and larger-animal models.