Cellular metabolic rates in the kidney are critical for maintaining renal function. In a hypoxic milieu, cells rely on glycolysis to meet energy needs, resulting in the generation of pyruvate and NADH. In the absence of oxidative phosphorylation, the continuation of glycolysis is dependent on the regeneration of NAD+ from NADH accompanied by the fermentation of pyruvate to lactate. This reaction is catalyzed by lactate dehydrogenase (LDH) isoform A (LDHA), while isoform B (LDHB) catalyzes the opposite reaction. LDH is widely used as a potential injury marker, yet the precise isoform-specific cellular localization of the enzyme along the nephron has not been characterized. By combining immunohistochemistry and single-cell RNA sequencing data on healthy mouse kidneys we identified that LDHA is primarily expressed in proximal segments while LDHB is expressed in the distal parts of the nephron. In vitro studies in mouse and human renal proximal tubule cells show an increase in LDHA following hypoxia with no change in LDHB. We observed that the overall expression of both LDHA and LDHB decreased following renal ischemia-reperfusion injury (IRI) as well as in the adenine-diet induced model of chronic kidney disease. Single-nucleus RNA sequencing analyses of kidneys following IRI revealed a significant decline in the number of cells expressing Ldha and Ldhb, however, cells that were positive showed increased average expression post-injury which subsided during the recovery phase. These data provide information on the cell-specific expression of LDHA and LDHB in the normal kidney as well as following acute and chronic kidney disease.

Given the abundance of heme proteins (cytochromes) in the mitochondrion, it is evident that a meticulously orchestrated iron metabolism is essential for cardiac health. Here, we examined the functional significance of myocardial ferritin heavy chain (FtH) in a model of acute myocardial infarction. We report that FtH deletion did not alter either the mitochondrial regulatory and surveillance pathways (fission and fusion) or mitochondrial bioenergetics in response to injury. Furthermore, deletion of myocardial FtH did not affect cardiac function, assessed by measurement of left ventricular ejection fraction, on days 1, 7, and 21 post injury. To identify the modulated pathways providing cardiomyocyte protection coincident with FtH deletion, we performed unbiased transcriptomic analysis. We found that following injury, FtH deletion was associated with upregulation of several genes with anti-ferroptotic properties, including heme oxygenase-1 (HO-1) and the cystine/glutamate anti-porter (Slc7a11). These results suggested that HO-1 overexpression mitigates ferroptosis via upregulation of Slc7a11. Indeed, using transgenic mice with HO-1 overexpression, we demonstrate that overexpressed HO-1 is coupled with increased Slc7a11 expression. In conclusion, we demonstrate that following injury, myocardial FtH deletion leads to a compensatory upregulation in a number of anti-ferroptotic genes, including HO-1. Such HO-1 induction leads to overexpression of Slc7a11 and protects the heart against ischemia-reperfusion-mediated ferroptosis, preserves mitochondrial function, and overall function of the myocardium.

Expansion of renal lymphatic networks, or lymphangiogenesis (LA) is well-recognized during development, and is now being implicated in kidney diseases. Though LA is associated with multiple pathological conditions, very little is known about its role in acute kidney injury (AKI). The purpose of this study was to evaluate the role of LA in a model of cisplatin-induced nephrotoxicity. LA is predominately regulated by VEGF-C and VEGF-D, ligands that exert their function through their cognate receptor VEGFR3. We demonstrate the use of MAZ51, a selective VEGFR3 inhibitor, which caused significantly worse structural and functional kidney damage in cisplatin nephrotoxicity. Apoptotic cell death and inflammation were also increased in the MAZ51 treated animals compared to vehicle-treated animals following cisplatin administration. Notably, MAZ51 caused significant upregulation of intrarenal phospho-NF-kB, phospho-JNK, and IL-6. Cisplatin nephrotoxicity is associated with vascular congestion due to endothelial dysfunction. Using three-dimensional tissue cytometry, a novel approach to explore lymphatics in the kidney, we detected significant vascular autofluorescence attributed to erythrocytes in cisplatin alone treated animals. Interestingly, no such congestion was detected in MAZ51 treated animals. We found increased renal vascular damage in MAZ51 treated animals, whereby MAZ51 caused a modest decrease in endothelial markers Emcn and vWF, with a modest increase in VEGFR2. Our findings identify a protective role for de novo LA in cisplatin nephrotoxicity and provide a rationale for the development of therapeutic approaches targeting LA. Our studies also suggest off target effects of MAZ51 on the vasculature in the setting of cisplatin nephrotoxicity.