<b><i>Candida</i></b> Administration Worsens Neutrophil Extracellular Traps in Renal Ischemia Reperfusion Injury Mice: An Impact of Gut Fungi on Acute Kidney Injury

Abstract

Because of gut-barrier defect (gut-leakage) after acute kidney injury (AKI) and higher abundance of <i>Candida albicans</i> in human intestines compared with mouse guts, <i>Candida</i> administration in renal ischemia reperfusion injury (I/R) mice possibly more closely resemble patients with AKI than non-<i>Candida</i> model. Fungi in feces were detectable only in mice with <i>Candida</i> administration. <i>Candida</i> renal-I/R mice, when compared with non-<i>Candida</i> I/R, demonstrated more profound injuries, including (i) gut-leakage; FITC-dextran assay and serum (1→3)-β-D-glucan (BG), (ii) systemic inflammation (serum cytokines), and (iii) neutrophil extracellular traps (NETs); gene expression of peptidyl arginase 4 (<i>PAD4</i>) and <i>IL-1β</i>, nuclear morphology staining by 4′,6-diamidino-2-phenylindole (DAPI) and co-staining of myeloperoxidase (MPO) with neutrophil elastase (NE) in peripheral blood neutrophils. Although renal excretory function (serum creatinine) and renal histology score were nondifferent between renal-I/R mice with and without <i>Candida</i>, prominent renal NETs (<i>PAD4</i> and <i>IL-1β</i> expression with MPO and NE co-staining) was demonstrated in <i>Candida</i> renal-I/R mice. Additionally, neutrophil activation by lipopolysaccharide (LPS) plus BG (LPS + BG), when compared with LPS alone, caused (i) NETs formation; dsDNA, DAPI-stained nuclear morphology and MPO with NE co-staining, (ii) inflammatory responses; Spleen tyrosine kinase (<i>Syk</i>) and <i>NFκB</i> expression, and (iii) reduced cell energy status (maximal respiratory capacity using extracellular flux analysis). Also, LPS + BG-activated NETs formation was inhibited by a dectin-1 inhibitor, supporting an impact of BG signaling. In conclusion, <i>Candida</i>-renal I/R demonstrated more prominent serum BG and LPS from gut translocation that increased systemic inflammation and NETs through TLR-4 and dectin-1 activation. The influence of gut fungi in AKI should be concerned.