OBJECTIVES Type 2 diabetes causes mitochondrial dysfunction, which increases myocardial susceptibility to ischaemia–reperfusion injury. We investigated the efficacy of transplantation of mitochondria isolated from diabetic or non-diabetic donors in providing cardioprotection from warm global ischaemia and reperfusion in the diabetic rat heart. METHODS Ex vivo perfused hearts from Zucker diabetic fatty (ZDF fa/fa) rats (n = 6 per group) were subjected to 30 min of warm global ischaemia and 120 min reperfusion. Immediately prior to reperfusion, vehicle alone (VEH) or vehicle containing mitochondria isolated from either ZDF (MTZDF) or non-diabetic Zucker lean (ZL +/?) (MTZL) skeletal muscle were delivered to the coronary arteries via the aortic cannula. RESULTS Following 30-min global ischaemia and 120-min reperfusion, left ventricular developed pressure was significantly increased in MTZDF and MTZL groups compared to VEH group (MTZDF: 92.8 ± 5.2 mmHg vs MTZL: 110.7 ± 2.4 mmHg vs VEH: 44.3 ± 5.9 mmHg; P < 0.01 each); and left ventricular end-diastolic pressure was significantly decreased (MTZDF 12.1 ± 1.3 mmHg vs MTZL 8.6 ± 0.8 mmHg vs VEH: 18.6 ± 1.5 mmHg; P = 0.016 for MTZDF vs VEH and P < 0.01 for MTZL vs VEH). Total tissue ATP content was significantly increased in both MT groups compared to VEH group (MTZDF: 18.9 ± 1.5 mmol/mg protein/mg tissue vs MTZL: 28.1 ± 2.3 mmol/mg protein/mg tissue vs VEH: 13.1 ± 0.5 mmol/mg protein/mg tissue; P = 0.018 for MTZDF vs VEH and P < 0.01 for MTZL vs VEH). Infarct size was significantly decreased in the MT groups (MTZDF: 11.8 ± 0.7% vs MTZL: 9.9 ± 0.5% vs VEH: 52.0 ± 1.4%; P < 0.01 each). CONCLUSIONS Mitochondrial transplantation significantly enhances post-ischaemic myocardial functional recovery and significantly decreases myocellular injury in the diabetic heart.

Acute kidney injury (AKI) is a common clinical disorder and one of the major causes of morbidity and mortality in the postoperative period. In this study, the safety and efficacy of autologous mitochondrial transplantation by intra-arterial injection for renal protection in a swine model of bilateral renal ischemia-reperfusion injury (IRI) was investigated. Female Yorkshire pigs underwent percutaneous bilateral temporary occlusion of the renal arteries with balloon-catheters. Following 60 minutes ischemia, the balloon catheters were deflated and the animals received either autologous mitochondria suspended in vehicle or vehicle alone, delivered as a single bolus to the renal arteries. The injected mitochondria were rapidly taken up by the kidney and were distributed throughout the tubular epithelium of cortex and medulla. There were no safety related issues detected with mitochondrial transplantation. Following 24 hours of reperfusion, estimated glomerular filtration rate and urine output were significantly increased while serum creatinine and blood urea nitrogen were significantly decreased in swine receiving mitochondria as compared to those receiving vehicle. Gross anatomy, histopathological analysis, acute tubular necrosis scoring and transmission electron microscopy showed that the renal cortex of vehicle group had extensive coagulative necrosis of primarily proximal tubules, while the mitochondrial transplanted kidney showed only patchy mild acute tubular injury. Renal cortex IL-6 expression was significantly increased in Vehicle kidneys as compared to the kidneys receiving mitochondrial transplantation. These results demonstrate that mitochondrial transplantation by intra-arterial injection provides renal protection from IRI, significantly enhancing renal function and reducing renal damage.

Kynurenic acid (KynA) is tissue protective in cardiac, cerebral, renal, and retinal ischemia models, but the mechanism is unknown. KynA can bind to multiple receptors, including the aryl hydrocarbon receptor, the a7 nicotinic acetylcholine receptor (a7nAChR), multiple ionotropic glutamate receptors, and the orphan G protein–coupled receptor GPR35. Here, we show that GPR35 activation was necessary and sufficient for ischemic protection by KynA. When bound by KynA, GPR35 activated G i - and G 12/13 -coupled signaling and trafficked to the outer mitochondria membrane, where it bound, apparantly indirectly, to ATP synthase inhibitory factor subunit 1 (ATPIF1). Activated GPR35, in an ATPIF1-dependent and pertussis toxin–sensitive manner, induced ATP synthase dimerization, which prevented ATP loss upon ischemia. These findings provide a rationale for the development of specific GPR35 agonists for the treatment of ischemic diseases.