Post-Cardiac Surgery Acute Kidney Injury Prevention by Administration of Proton Pump Inhibitor (P2 Trial)

Each year more than 500,000 cardiac surgeries are performed in the USA alone. AKI is a common complication following cardiac surgery and is associated with poor patient outcome and increased health care cost. Therefore, there is an urgent need to identify medical interventions and treatments that prevent AKI or mitigate its severity when it occurs after cardiac surgery. One of the main causes of AKI following cardiac surgery involves renal hypoperfusion/ischemia and reperfusion injury. Hypoxia inducible factors (HIFs) are key transcription factors responsible for tissue adaptation to low oxygen, which orchestrate the expression of a wide variety of genes including a set of microRNAs. MicroRNAs are endogenous single-stranded noncoding miRNAs of nucleotides that participate in physiological and pathological functions via regulating post-transcription of target genes. During ischemic injury, hypoxia upregulates endothelial MicroRNAs that have a potential in renal protection through vascular integrity and regeneration. Additionally, microRNAs exert protective effects via decreasing apoptosis and promoting tubular cell proliferation during ischemic AKI. Moreover, decreased serum levels of MicroRNAs are highly correlated with AKI severity in the intensive care unit (ICU) patients. Our preliminary study identified ATP4A as the downstream target gene of MicroRNAs in the kidney. ATP4A (catalytic α subunit of H+/K+ ATPase) is located in intercalated cells in the distal tubules and cortical collecting ducts, which regulates urine acidification through secretion of hydrogen and reabsorption of potassium from urine. Proton pump inhibitors (PPIs) block the ATP hydrolysis of the H+/K+ ATPase via binding its active site of ATP4A and further enhance this endogenous kidney protection pathway. Despite robust animal model data, randomized controlled trial aiming to test the effectiveness of PPI in post-cardiac surgery AKI prevention is lacking. If proven to be effective, our studies could be easily implemented in clinical practice and serve as an effective treatment for perioperative AKI.