Semaphorin 3A is a new early diagnostic biomarker of experimental and pediatric acute kidney injury.

BACKGROUND: Semaphorin 3A is a secreted protein that regulates cell motility and attachment in axon guidance, vascular growth, immune cell regulation and tumor progression. However, nothing is known about its role in kidney pathophysiology. Here, we determined whether semaphorin3A is induced after acute kidney injury (AKI) and whether urinary semaphorin 3A can predict AKI in humans undergoing cardiopulmonary bypass (CPB). METHODS AND PRINCIPAL FINDINGS: In animals, semaphorin 3A is localized in distal tubules of the kidney and excretion increased within 3 hr after reperfusion of the kidney whereas serum creatinine was significantly raised at 24 hr. In humans, using serum creatinine, AKI was detected on average only 48 hours after CPB. In contrast, urine semaphorin increased at 2 hours after CPB, peaked at 6 hours (2596±591 pg/mg creatinine), and was no longer significantly elevated 12 hours after CPB. The predictive power of semaphorin 3A as demonstrated by area under the receiver-operating characteristic curve for diagnosis of AKI at 2, 6, and 12 hours after CPB was 0.88, 0.81, and 0.74, respectively. The 2-hour urine semaphorin measurement strongly correlated with duration and severity of AKI, as well as length of hospital stay. Adjusting for CPB time and gender, the 2-hour semaphorin remained an independent predictor of AKI, with an odds ratio of 2.19. CONCLUSION: Our results suggest that semaphorin 3A is an early, predictive biomarker in experimental and pediatric AKI, and may allow for the reliable early diagnosis and prognosis of AKI after CPB, much before the rise in serum creatinine

Urinary Netrin-1 Is an Early Predictive Biomarker of Acute Kidney Injury after Cardiac Surgery

Background and objectives: Netrin-1, a laminin-related axon guidance molecule, is highly induced and excreted in the urine after acute kidney injury (AKI) in animals. Here, we determined the utility of urinary netrin-1 levels to predict AKI in humans undergoing cardiopulmonary bypass (CPB)

Quantification of urine semaphorin 3A in different forms AKI and diabetes in mouse.

<p>Semaphorin 3A was quantified using ELISA kit as described in Methods. A. Semaphorin 3A in urine from animals subjected to sham surgery (0 hr) and different time after reperfusion. Ischemia reperfusion rapidly increased urinary excretion of semaphorin 3A. *<i>p</i><0.005 vs. 0 hr. B. Serum creatinine at different time after reperfusion. *<i>p</i><0.001 vs. 0 hr. C. Semaphorin 3A excretion in urine before and different time after cisplatin administration. Cisplatin administration significantly increased the excretion of semaphorin 3A at 24, 48 and 72 hr. *<i>p</i><0.005 vs. 0 hr. D. Serum creatinine at different time after administration of cisplatin. *<i>p</i><0.05. Values are mean ± SEM. n = 6–8.</p

Quantification of serum semaphorin 3A in different forms AKI and diabetes in mouse.

<p>Semaphorin 3A was quantified using ELISA kit as described in Methods. A. Circulating levels of semaphorin 3A before and different time after cisplatin administration. Cisplatin administration was significantly upregulated semaphorin 3A in the blood. *<i>p</i><0.005 vs. 0 hr. B. Circulating levels of semaphorin 3A in sham operated (0 hr) and different time after reperfusion. Ischemia reperfusion rapidly downregulated circulating semaphorin 3A. *<i>p</i><0.005 vs. 0 hr. Values are mean ± SEM. n = 4–6.</p

Regulation of semaphorin 3A expression and excretion after ischemia reperfusion injury of the kidney.

<p>A. Western blot analysis of semaphorin 3A excretion in mice urine before (0 hr) and at different time point after reperfusion. A large increase was detected at 6 hr and 24 hr after reperfusion. B. Serum creatinine levels before and different time after ischemia reperfusion of the kidney. *<i>p</i><0.001 vs. 0 hr. C. Semaphorin 3A expression in kidney tissue was analyzed by Western Blot. A single 95 KDa band was observed and increased expression seen at 24 hr. D. RT-PCR analysis of semaphorin 3A expression in the kidney after ischemia reperfusion. Semaphorin 3A mRNA expression is downregulated at 6 and 24 hr after reperfusion of the kidney. *<i>p</i><0.001 vs. sham operated. E. Graphic representation of known protease (Furin like) cleavage site and expected band of semaphorin 3A. F. Proteolytic cleavage of semaphorin 3A <i>in vitro</i>. 250 ng of recombinant semaphorin 3A-Fc chimera was incubated with 10 µl of human urine for 1 hr at 37°C (lane 1), in the presence of 20 mM EDTA (lane 2), human urine alone (lane 3) and recombinant semaphorin 3A alone. Proteolytic release of smaller fragments of semaphorin 3A was inhibited with addition of EDTA. Values are mean ± SEM. n = 3–5.</p