Remote effects of acute kidney injury in a porcine model

Acute kidney injury (AKI) is a common and serious condition with no specific treatment. An episode of AKI may affect organs distant from the kidney, further increasing the morbidity associated with AKI. The mechanism of organ cross talk after AKI is unclear. The renal and immune systems of pigs and humans are alike. Using a preclinical animal (porcine) model, we tested the hypothesis that early effects of AKI on distant organs is by immune cell infiltration, leading to inflammatory cytokine production, extravasation, and edema. In 29 pigs exposed to either sham surgery or renal ischemia-reperfusion (control, n = 12; AKI, n = 17), we assessed remote organ (liver, lung, brain) effects in the short (from 2- to 48-h reperfusion) and longer term (5 wk later) using immunofluorescence (for leukocyte infiltration, apoptosis), a cytokine array, tissue elemental analysis (e.g., electrolytes), blood hematology and chemistry (e.g., liver enzymes), and PCR (for inflammatory markers). AKI elicited significant, short-term (∼24 h) increments in enzymes indicative of acute liver damage (e.g. , AST: ALT ratio; P = 0.02) and influenced tissue biochemistry in some remote organs (e.g., lung tissue [Ca(2+)] increased; P = 0.04). These effects largely resolved after 48 h, and no further histopathology, edema, apoptosis, or immune cell infiltration was noted in the liver, lung, or hippocampus in the short and longer term. AKI has subtle biochemical effects on remote organs in the short term, including a transient increment in markers of acute liver damage. These effects resolved by 48 h, and no further remote organ histopathology, apoptosis, edema, or immune cell infiltration was noted.