The purpose of this study was to compare the performance of six candidate urinary biomarkers, kidney injury molecule 1 (KIM-1), N-acetyl-β-(D)-glucosaminidase (NAG), neutrophil gelatinaseassociated lipocalin (NGAL), interleukin 18 (IL-18), cystatin C, and α-1 microglobulin, measured 2 hours following cardiopulmonary bypass (CPB) for the early detection of acute kidney injury (AKI) in a prospective cohort of patients undergoing cardiac surgery. 103 subjects were enrolled, AKI developed in 13%. Urinary KIM-1 achieved the highest area under-the-receiver-operatorcharacteristic curve (AUC = 0.78, 95% CI 0.64-0.91), followed by IL-18 and NAG. Only urinary KIM-1 remained independently associated with AKI after adjustment for a preoperative AKI prediction score (Cleveland Clinic Foundation score; P= 0.02), or CPB perfusion time (P = 0.006). In this small pilot-cohort, KIM-1 performed best as an early biomarker for AKI. Larger studies are needed to further explore the role of biomarkers for early detection of AKI following cardiac surgery.

Pericytes regulate microvascular development and maturation through the control of endothelial cell motility, proliferation, and differentiation. The Rho GTPases have recently been described as key regulators of pericyte shape and contractile phenotype by signaling through the actin cytoskeleton in an isoactin-specific manner. In this report, we reveal that Rho GTPase-dependent signal transduction not only influences pericyte shape and contractile potential but also modulates capillary endothelial proliferative status and pericyte-endothelial interactions in vitro. We provide evidence that overexpression of mutant Rho GTPases, but not other Ras-related small GTPases, significantly alters pericyte shape, contractility, and endothelial growth state in microvascular cell co-cultures. In particular, we describe the use of a silicon substrate deformation assay to demonstrate that pericyte contractility is Rho GTP-and Rho kinase-dependent; further, we describe a novel in vitro system for examining pericyte-mediated endothelial growth arrest and show that control pericytes are capable of growtharresting capillary endothelial cells in a cell contactdependent manner, whereas pericytes overexpressing dominant-active and -negative Rho GTPase are comparably incompetent. These data strongly suggest that signaling through the pericyte Rho GTPase pathway may provide critical cues to the processes of microvascular stabilization, maturation, and contractility during development and disease.

Reactive oxygen species are important mediators of injury in acute renal failure (ARF). Although polymorphisms that affect key pro-and antioxidant enzymes might alter the susceptibility to oxidative stress-mediated injury, the use of genetic epidemiology for the study of oxidative stress-related genes has received little attention in ARF. The relationship of single-nucleotide polymorphisms in the coding region (C to T substitution at position ؉242) of the pro-oxidant enzyme NADPH oxidase p22phox subunit gene and in the promoter region (C to T substitution at position ؊262) of the antioxidant enzyme catalase gene to adverse clinical outcomes was evaluated prospectively in a cohort of 200 hospitalized patients with established ARF of mixed cause and severity. Genomic DNA was extracted from peripheral blood leukocytes and analyzed with a restriction fragment length polymorphism PCR method. Genotype-phenotype associations were characterized by measuring circulating nitrotyrosine and catalase activity. Observed and expected genotype frequencies were not significantly different, and overall baseline characteristics were not significantly different according to the various genotype groups. A genotype-phenotype association was demonstrable between the NADPH oxidase p22phox genotypes and plasma nitrotyrosine level (P ‫؍‬ 0.06), as well as between the catalase genotypes and whole-blood catalase activity (P < 0.001). Compared with the NADPH oxidase p22phox CC genotype group, the T-allele group had a higher cumulative probability of remaining hospitalized (P ‫؍‬ 0.03). Compared with the NADPH oxidase p22phox CC genotype, the T-allele carrier state was associated with 2.1-fold higher odds for dialysis requirement or hospital death (P ‫؍‬ 0.01). This association persisted with 2.0-to 2.2-fold higher odds for this composite outcome after adjustment for race; gender; age; and the Acute Physiology and Chronic Health Evaluation II score (P ‫؍‬ 0.03), the Multiple Organ Failure score (P ‫؍‬ 0.01), or presence of sepsis (P ‫؍‬ 0.02). The polymorphism in the gene that encodes the NADPH oxidase p22phox subunit at position ؉242 is associated with dialysis requirement or hospital death among patients with ARF. Larger studies are needed to confirm these relationships.

Rho family small GTPases (Rho, Rac, and Cdc42) play an important role in cell motility, adhesion, and cell division by signaling reorganization of the actin cytoskeleton. Here, we report an isoactin-specific, Rho GTPase-dependent signaling cascade in cells simultaneously expressing smooth muscle and nonmuscle actin isoforms. We transfected primary cultures of microvascular pericytes, cells related to vascular smooth muscle cells, with various Rho-related and Rho-specific expression plasmids. Overexpression of dominant positive Rho resulted in the formation of nonmuscle actin-containing stress fibers. At the same time, α-vascular smooth muscle actin (αVSMactin) containing stress fibers were disassembled, resulting in a dramatic reduction in cell size. Rho activation also yielded a disassembly of smooth muscle myosin and nonmuscle myosin from stress fibers. Overexpression of wild-type Rho had similar but less dramatic effects. In contrast, dominant negative Rho and C3 exotransferase or dominant positive Rac and Cdc42 expression failed to alter the actin cytoskeleton in an isoform-specific manner. The loss of smooth muscle contractile protein isoforms in pericyte stress fibers, together with a concomitant decrease in cell size, suggests that Rho activation influences “contractile” phenotype in an isoactin-specific manner. This, in turn, should yield significant alteration in microvascular remodeling during developmental and pathologic angiogenesis.

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