Impact of intravenous iron on cardiac and skeletal oxidative stress and cardiac mitochondrial function in experimental uraemia chronic kidney disease

Introuction: Uraemia leads to changes in cardiac structure, metabolic remodeling and anaemia, key factors in the development of heart failure in patients with chronic kidney disease. Previous studies have identified abnormalities in mitochondrial function, potentially impairing energy provision and enhancing oxidative stress. This study characterised oxidant status and changes in mitochondrial function in uraemia and the impact of correcting anaemia via intravenous iron therapy. Methods: Experimental uraemia was induced in male Sprague-Dawley rats via a subtotal nephrectomy and parenteral iron administration given 6 weeks post-surgery. Oxidative stress from tissue samples was evaluated by measuring pro-oxidant activities and anti-oxidant capacities in both sham and uraemic animals with and without iron supplementation. Thiobarbituric acid-reactive substances (TBARS), aconitase activity and cardiolipin were measured. Mitochondrial function was assessed using the Seahorse XFp analyser on isolated mitochondria excised from cardiac tissue. Results: Oxidative stress in this uraemic model was increased in cardiac tissue (increased GSSG/GSH ratio, TBARS and increased activities of pro-oxidant enzymes). There was no impact on skeletal tissue. Parenteral iron ameliorated oxidative stress by enhancing the anti-oxidant defense system in cardiac tissue and skeletal tissue. Examination of respiratory reserve in cardiac mitochondria demonstrated that parenteral iron restored mitochondrial function. This experimental model of uraemia demonstrated a specific oxidative stress on the heart muscle without significant changes in skeletal oxidant status. Iron therapy improved anti-oxidant defence system, consequently reducing oxidative stress in the heart and skeletal tissue. There was an improvement in cardiac mitochondrial function. Conclusions: This experimental evidence indicates that iron therapy could reduce vulnerability to oxidative stress and potentially improve both cardiac and skeletal functional capacity from improvements in mitochondrial function.

Keywords

Anaemia

Cardiac

Chronic kidney disease

Iron

Mitochondria

Oxidative stress

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Fig. 1.

Mitochondrial coupling (A) and electron flow (B) experiments. (A) Mitochondrial coupling experiment. Injections are as follows: port A, 40 $\mu{}$ M adenosine diphosphate (ADP) (4 $\mu{}$ M final); port B, 25 $\mu{}$ g/mL oligomycin (2.5 $\mu{}$ g/mL final); port C, 40 $\mu{}$ M phenylhydrazone (FCCP) (4 $\mu{}$ M final); and port D, 40 $\mu{}$ M antimycin A (4 $\mu{}$ M final). OCR, oxygen consumption ratio. (B) Mitochondrial electron flow experiment: port A, 20 $\mu{}$ M rotenone (2 $\mu{}$ M final); port B, 100 mM succinate (10 mM final); port C, 40 $\mu{}$ M antimycin A (4 $\mu{}$ M final); port D, 100 mM ascorbate plus 1 mM N,N,N9,N9-Tetramethylp- phenylenediamine (TMPD, 10 mM and 100 $\mu{}$ M final, respectively). Initial condition: 0.6 $\mu{}$ g mitochondrial, 10 mM pyruvate, 2 mM malate and 4 $\mu{}$ M FCCP with (blue) or without (orange) 10 mM malonate.

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Front. Biosci. (Landmark Ed) Print ISSN 2768-6701 Electronic ISSN 2768-6698