Acute kidney injury (AKI) in children is associated with increased mortality and prolonged length of hospital stay and may also be associated with long-term chronic kidney disease development. Despite encouraging results on AKI treatment in animal studies, no specific treatment has yet been successful in humans. One of the important factors contributing to this problem is the lack of an early AKI diagnostic test. Serum creatinine, the current main diagnostic test for AKI, rises late in AKI pathophysiology and is an inaccurate marker of acute changes in glomerular filtration rate. Therefore, new biomarkers of AKI are needed. With great advancements in genomics, proteomics, and metabolomics, new AKI biomarkers, mainly consisting of urinary proteins that appear in response to renal tubular cell injury, have been, and continue to be, discovered. These new biomarkers offer promise for early AKI diagnosis and for the depiction of severity of renal injury occurring with AKI. This review provides a summary of what a biomarker is, why we need new biomarkers of AKI, and how biomarkers are discovered and should be evaluated. The review also provides a summary of selected AKI biomarkers that have been studied in children.

Our previous linkage studies indicated that there might be a blood pressure (BP) quantitative trait locus (QTL) on chromosome 3 (Chr 3) contrasting between the Dahl salt-sensitive (S) strain and the Lewis (LEW) strain. To prove and then to narrow down the segment containing this QTL, five congenic strains have been generated by replacing various segments of the S rats with the homologous segments of the LEW rats. They are designated as S.L1, S.L2, S.L3, S.L4, and S.L5, respectively. S.L2, S.L3, S.L4, and S.L5 are substrains of S.L1, i.e., they contain substitutions of smaller sections within the large fragment defined by S.L1. The construction of these congenic strains was facilitated by a genome-wide marker screening process. BPs of the rats were measured by telemetry. S.L2 and S.L3 shared a fragment of Chr 3 in common and both showed a BP-lowering effect, indicating the existence of "-BP" QTL alleles from LEW compared with S. In contrast, S.L4 involves a section with no overlap with either S.L2 or S.L3, and S.L4 showed a BP significantly higher than that of S rats, indicating the presence of "+BP" QTL alleles from LEW compared with S. Interestingly, the combined effect of the -BP QTL and +BP QTL alleles was "-" in S.L1, implying that the "-" QTL is epistatic to "+" QTL.

Abstract-Chromosome mapping based on congenic strains can restrict quantitative trait loci (QTLs) for blood pressure (BP) into small intervals that are otherwise indistinguishable in linkage analysis. Also, congenic strains can be created to test a candidate gene to be a BP QTL. Taking full advantage of these features, we produced 10 congenic strains by replacing various segments of chromosome (Chr) 10 of the Dahl salt-sensitive (DSS) rat with those of the Lewis (LEW) rat. These strains were made to systematically cover an entire section of Chr 10. Three of the strains were designed to narrow the intervals that harbor previously mapped QTL1 and QTL2. Two of the strains were designed for the express purpose of testing the QTL candidacy of loci for inducible nitric oxide synthase (Nos2) and angiotensin-converting enzyme (Ace) genes. BPs of these strains were measured by telemetry and compared with those of the DSS rat. Consequently, QTL1 and QTL2 were narrowed to segments of 53.5 and 100.4 centiRays, respectively. A new QTL, QTL3, was found between QTL1 and QTL2. Both Nos2 and Ace have been disqualified as QTLs in the DSS and LEW comparison. Therefore, there are no obvious candidate genes in the segments that harbor these 3 QTLs, which represent genes previously not thought to be involved in BP regulation. These QTLs will likely have an influence on studies of human hypertension because of their homology with the human CHR 17 region in which QTLs for BP have been found.

Ligand-dependent corepressor LCoR was identified as a protein that interacts with the estrogen receptor ␣ (ER␣) ligand binding domain in a hormone-dependent manner. LCoR also interacts directly with histone deacetylase 3 (HDAC3) and HDAC6. Notably, HDAC6 has emerged as a marker of breast cancer prognosis. However, although HDAC3 is nuclear, HDAC6 is cytoplasmic in many cells. We found that HDAC6 is partially nuclear in estrogen-responsive MCF7 cells, colocalizes with LCoR, represses transactivation of estrogen-inducible reporter genes, and augments corepression by LCoR. In contrast, no repression was observed upon HDAC6 expression in COS7 cells, where it is exclusively cytoplasmic. LCoR binds to HDAC6 in vitro via a central domain, and repression by LCoR mutants lacking this domain was attenuated. Kinetic chromatin immunoprecipitation assays revealed hormone-dependent recruitment of LCoR to promoters of ER␣-induced target genes in synchrony with ER␣. HDAC6 was also recruited to these promoters, and repeat chromatin immunoprecipitation experiments confirmed the corecruitment of LCoR with ER␣ and with HDAC6. Remarkably, however, although we find evidence for corecruitment of LCoR and ER␣ on genes repressed by the receptor, LCoR and HDAC6 failed to coimmunoprecipitate, suggesting that they are part of distinct complexes on these genes. Although small interfering RNA-mediated knockdown of LCoR or HDAC6 augmented expression of an estrogen-sensitive reporter gene in MCF7 cells, unexpectedly their ablation led to reduced expression of some endogenous estrogen target genes. Taken together, these data establish that HDAC6 can function as a cofactor of LCoR but suggest that they may act in enhance expressing some target genes.Nuclear receptors are ligand-regulated transcription factors whose activities are controlled by a variety of lipophilic extracellular signals, including steroid and thyroid hormones, metabolites of vitamins A (retinoids) and D (1, 2). DNA-bound nuclear receptors regulate transcription by recruiting complexes of coregulatory proteins, classified as coactivators or corepressors depending on whether they act to stimulate or repress transcription (2-4). Many coactivators interact with receptors through signature LXXLL motifs, known as NR boxes, which are oriented within a hydrophobic pocket of agonist-bound receptor ligand binding domains (5). Several coactivators or their associated cofactors possess histone acetyltransferase activity, which essentially caps positively charged lysine residues and loosens their association with DNA, facilitating chromatin remodeling and subsequent access of the transcriptional machinery to promoters.Nuclear receptor corepressors NCoR 7 and SMRT were isolated as factors that interacted with hormone-free but not hormone-bound thyroid and retinoid receptors (6, 7). They bind to receptor ligand binding domains through extended LXXX-IXXX(L/I) motifs known as CoRNR boxes (8, 9) and recruit multiprotein complexes implicated in transcriptional repression and histone deacetylatio...

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Background Early accurate acute kidney injury (AKI) diagnosis is needed to pursue AKI treatment trials. We evaluated Cystatin C (CysC) as an early biomarker of serum creatinine (SCr)-AKI and as an alternative to define AKI. Methods 160 non-cardiac children admitted to our intensive care unit (ICU) were prospectively studied. We measured daily CysC and SCr. AKI was staged according to the Kidney Disease: Improving Global Outcomes (KDIGO) SCr criteria and by similarly applied criteria, using CysC (CysC-AKI) We calculated area under the curve (AUC) for 1) neutrophil gelatinase associated lipocalin (NGAL), interleukin-18 (IL-18), kidney injury molecule-1 (KIM-1) and urine cystatin C (uCysC) to diagnose SCr- and CysC-AKI and 2) for CysC to diagnose SCr-AKI. We evaluated the relation of each AKI definition with length of stay and mechanical ventilation duration. Results 44% of patients developed SCr-AKI; 32% developed CysC-AKI. Whether AKI was defined by SCr or CysC, NGALwas associated with AKI severity. CysC-AKI was not more strongly associated with clinical outcomes. However, early ICU admission CysC predicted SCr-AKI development within 48 hours (AUC=0.70 [95% CI 0.53 – 0.89]). Conclusions Our findings do not support replacing SCr by CysC to define AKI. However, CysC may be used for predicting AKI development when obtained early in ICU admission.

AKI is independently associated with higher hospitalizations and physician visits postdischarge.

Ligand-dependent corepressor LCoR interacts with the progesterone receptor (PR) and estrogen receptor ER␣ in the presence of hormone. LCoR contains tandem N-terminal PXDLS motifs that recruit C-terminal-binding protein (CtBP) corepressors as well as a C-terminal helix-turn-helix (HTH) domain. Here, we analyzed the function of these domains in coregulation of PR-and ER␣-regulated gene expression. LCoR and CtBP1 colocalize in nuclear bodies that also contain CtBP-interacting protein CtIP and polycomb group repressor complex marker BMI1. Coexpression of CtBP1 in MCF7 or T47D breast cancer cells augmented corepression by LCoR, whereas coexpression of CtIP did not, consistent with direct interaction of LCoR with CtBP1, but not CtIP. The N-terminal region containing the PXDLS motifs is necessary and sufficient for CTBP1 recruitment and essential for full corepression. However, LCoR function was also strongly dependent on the helix-turn-helix domain, as its deletion completely abolished corepression. LCoR, CtBP, and CtIP were recruited to endogenous PR-and ER␣-stimulated genes in a hormone-dependent manner. Similarly, LCoR was recruited to estrogen-repressed genes, whereas hormone treatment reduced CtBP1 binding. Small interfering RNA-mediated knockdown of LCoR or CtBP1 augmented expression of progesterone-and estrogen-stimulated reporter genes as well as endogenous progesterone-stimulated target genes. In contrast, their ablation had gene-specific effects on ER␣-regulated transcription that generally led to reduced gene expression. Taken together, these results show that multiple domains contribute to LCoR function. They also reveal a role for LCoR and CtBP1 as attenuators of progesterone-regulated transcription but suggest that LCoR and CtBP1 can act to enhance transcription of some genes.