Early detection of cysteine rich protein 61 (CYR61, CCN1) in urine following renal ischemic reperfusion injury

Biotherapy of experimental acute kidney injury: emerging novel therapeutic strategies

Acute kidney injury (AKI) is a complex and heterogeneous disease with high incidence and mortality, posing a serious threat to human life and health. Usually, in clinical practice, AKI is caused by crush injury, nephrotoxin exposure, ischemia-reperfusion injury, or sepsis. Therefore, most AKI models for pharmacological experimentation are based on this. The current research promises to develop new biological therapies, including antibody therapy, non-antibody protein therapy, cell therapy, and RNA therapy, that could help mitigate the development of AKI. These approaches can promote renal repair and improve systemic hemodynamics after renal injury by reducing oxidative stress, inflammatory response, organelles damage, and cell death, or activating cytoprotective mechanisms. However, no candidate drugs for AKI prevention or treatment have been successfully translated from bench to bedside. This article summarizes the latest progress in AKI biotherapy, focusing on potential clinical targets and novel treatment strategies that merit further investigation in future pre-clinical and clinical studies.

IL-6 mediates the hepatic acute phase response after prerenal azotemia in a clinically defined murine model

Prerenal azotemia (PRA) is a major cause of acute kidney injury and uncommonly studied in preclinical models. We sought to develop and characterize a novel model of PRA that meets the clinical definition: acute loss of glomerular filtration rate (GFR) that returns to baseline with resuscitation. Adult male C57BL/6J wild-type (WT) and IL-6-/- mice were studied. Intraperitoneal furosemide (4 mg) or vehicle was administered at time = 0 and 3 h to induce PRA from volume loss. Resuscitation began at 6 h with 1 mL intraperitoneal saline for four times for 36 h. Six hours after furosemide administration, measured glomerular filtration rate was 25% of baseline and returned to baseline after saline resuscitation at 48 h. After 6 h of PRA, plasma interleukin (IL)-6 was significantly increased, kidney and liver histology were normal, kidney and liver lactate were normal, and kidney injury molecule-1 immunofluorescence was negative. There were 327 differentially regulated genes upregulated in the liver, and the acute phase response was the most significantly upregulated pathway; 84 of the upregulated genes (25%) were suppressed in IL-6-/- mice, and the acute phase response was the most significantly suppressed pathway. Significantly upregulated genes and their proteins were also investigated and included serum amyloid A2, serum amyloid A1, lipocalin 2, chemokine (C-X-C motif) ligand 1, and haptoglobin; hepatic gene expression and plasma protein levels were all increased in wild-type PRA and were all reduced in IL-6-/- PRA. This work demonstrates previously unknown systemic effects of PRA that includes IL-6-mediated upregulation of the hepatic acute phase response.NEW & NOTEWORTHY Prerenal azotemia (PRA) accounts for a third of acute kidney injury (AKI) cases yet is rarely studied in preclinical models. We developed a clinically defined murine model of prerenal azotemia characterized by a 75% decrease in measured glomerular filtration rate (GFR), return of measured glomerular filtration rate to baseline with resuscitation, and absent tubular injury. Numerous systemic effects were observed, such as increased plasma interleukin-6 (IL-6) and upregulation of the hepatic acute phase response.

Proficient Novel Biomarkers Guide Early Detection of Acute Kidney Injury: A Review

The definition of acute kidney injury (AKI), despite improvements in criteria, continues to be based on the level of serum creatinine and urinary output that do not specifically indicate tubular function or injury, or glomerular function or injury that is not significant enough to warrant acute hospitalization of the patient. Finding novel biomarkers of AKI has become a major focus nowadays in nephrology to overcome the further complications of end stage renal disease (ESRD). Many compounds, such as KIM 1, IL 18, NGAL, uromodulin, calprotectin, vanin 1, galactin 3, platelet-derived growth factor (PDGF), urinary Na⁺/H⁺ exchanger isoform 3 (NHE3), retinol binding protein (RBP) and Cystatin C, are released from the renal tubules and thus any alterations in tubular function can be detected by measuring these parameters in urine. Additionally, glomerular injury can be detected by measuring immunoglobulin G, nephrin, podocalyxin, podocin, transferrin, netrin-1, pyruvate kinase M2, etc. in urine. These novel biomarkers will be useful for timing the initial insult and assessing the duration of AKI. According to available research, these biomarkers could be applied to assess the onset of AKI, distinguishing between kidney injury and dysfunction, directing the management of AKI, and enhancing disease diagnosis. Therefore, we intend to present recent developments in our understanding of significant biomarkers implicated in various aspects of renal damage. Numerous biomarkers are implicated in various pathophysiological processes that follow renal injury, and can improve prognosis and risk classification.

NIR-II Photoacoustic-Active DNA Origami Nanoantenna for Early Diagnosis and Smart Therapy of Acute Kidney Injury

Herein, we designed and synthesized a novel microRNA (miR)-responsive nanoantenna capable of early diagnosis and smart treatment of acute kidney injury (AKI). The nanoantenna was made of two miniature gold nanorods (AuNRs) (e.g., length: ∼48 nm; width: ∼9 nm) linked together by a rectangular DNA origami nanostructure (rDONs) scaffold (e.g., length: ∼90 nm; width: ∼60 nm) (rDONs@AuNR dimer). The surface plasmon resonance peak of the constructed nanoantenna is located within the NIR-II window (e.g., ∼1060 nm), thus guaranteeing photoacoustic (PA) imaging of the nanoantenna in deep tissues. Intriguingly, the nanoantenna displayed exclusive kidney retention in both healthy mice and ischemia reperfusion-induced AKI mice by leveraging the kidney-targeting ability of rDONs. Distinguished from the stable signals in the healthy mice, the PA signals of the nanoantenna would turn down in the AKI mice due to the AuNR detached from rDONs upon interaction with miR-21, which were up-expressed in AKI mice. The limit of detection toward miR-21 was down to 2.8 nM, enabling diagnosis of AKI as early as 10 min post-treatment with ischemia reperfusion, around 2 orders of magnitude earlier than most established probes. Moreover, the naked rDON scaffold generated by AKI could capture more reactive oxygen species (e.g., 1.5-fold more than rDONs@AuNR dimer), alleviating ischemic AKI. This strategy provided a new avenue for early diagnosis and smart treatment of AKI.

Polystyrene nanoplastics induce profound metabolic shift in human cells as revealed by integrated proteomic and metabolomic analysis

Nanoplastics (NPLs) are widespread in our environment. However, their impacts on human health and precise toxicity mechanisms remain poorly understood. Here we studied the internalization, release, and cytotoxicity of polystyrene nanoplastics (PSNPs) using the renal tubular epithelial cell line HKC and human derived liver cell line HL-7702. We also employed an integrated proteomic and metabolomic approach to investigate the potential biological effects of PSNPs on HKC cells. The abundances of 4770 proteins and 100 metabolites were quantified, with 785 proteins and 17 metabolites detected with altered levels in response to PSNPs. Most of the differential proteins and metabolites were enriched in a variety of metabolic pathways, for example, glycolysis, citrate cycle, oxidative phosphorylation, and amino acid metabolism, suggesting the potential effects of NPLs on global cellular metabolism shift in human cells. The altered energy metabolism induced by PSNPs was further confirmed by a Seahorse analysis. Moreover, lysosomal distribution study and western blotting showed that mTORC1 signaling, a central regulator of cellular metabolism, was inhibited upon nanoplastic exposure, likely serving as the link between lysosome dysfunction and metabolic defects. Taken together, our findings systematically mapped the key molecular changes induced by PSNPs in human cells and provide comprehensive biological insights for the risk estimation of NPLs contamination.

Associations between urinary cysteine-rich protein 61 excretion and kidney function decline in outpatients with chronic kidney disease: a prospective cohort study in Taiwan

OBJECTIVES

To examine whether urinary excretion of cysteine-rich protein 61 (Cyr61), an acknowledged proinflammatory factor in kidney pathologies, increases in chronic kidney disease (CKD) and is associated with subsequent rapid kidney function decline.

DESIGN

An observational cohort study.

SETTING

In the nephrology outpatient clinics of a tertiary hospital in Taiwan.

PARTICIPANTS

We enrolled 138 adult CKD outpatients (n=12, 32, 18, 18, 29 and 29 in stages 1, 2, 3a, 3b, 4 and 5 CKD, respectively) between February and October 2014 and followed them for 1 year. Their mean age was 60.46±13.16 years, and 51 (37%) of them were women.

PRIMARY OUTCOME MEASURES

Urinary Cyr61 levels were measured by ELISA. Rapid kidney function decline was defined as an estimated glomerular filtration rate (eGFR) decline rate ≥ 4 mL/min/1.73 m²/year or developing end-stage renal disease during subsequent 3-month or 1-year follow-up period. Models were adjusted for demographic and clinical variables.

RESULTS

The urine Cyr61-to-creatinine ratio (UCyr61CR) increased significantly in patients with stage 4 or 5 CKD. Multivariable linear regression analysis showed that log(UCyr61CR) was positively correlated with log(urine protein-to-creatinine ratio) (p<0.001) but negatively correlated with baseline eGFR (p<0.001) and hypertension (p=0.007). Complete serum creatinine data during the follow-up were available for 112 patients (81.2%). Among them, multivariable logistic regression identified log(UCyr61CR) was independently associated with rapid kidney function decline (adjusted OR 2.29, 95% CI 1.27 to 4.15) during the subsequent 3 months. UCyr61CR improved the discriminative performance of clinical models to predict 3-month rapid kidney function decline. In contrast, log(UCyr61CR) was not associated with rapid eGFR decline during the entire 1-year follow-up.

CONCLUSIONS

Elevated urinary Cyr61 excretion is associated with rapid short-term kidney function deterioration in patients with CKD. Measuring urinary Cyr61 excretion is clinically valuable for monitoring disease trajectory and may guide treatment planning.

CYR61, regulated by miR-22-3p and MALAT1, promotes autophagy in HK-2 cell inflammatory model

Background

Renal tubular epithelial cells play an important role in renal function and are a major site of injury from inflammation. Emerging evidence suggests that CYR61 is involved in the regulation of autophagy. However, there are few studies on CYR61 in nephropathy and associated inflammation. This study aimed to clarify how CYR61 regulates autophagy in human renal epithelial cells while in an inflammatory state and regulates the upstream pathway of CYR61 levels.

Methods

The human renal tubular epithelial cells (HK-2) cell line treated by lipopolysaccharide (LPS) was used as an inflammatory model of human epithelial cells. Short hairpin RNA (shRNA) was used to down-regulate CYR61, and the changes in the transcription and expression levels of related molecules, as well as the morphological changes of HK-2 cells, were detected by quantitative real time-PCR (qRT-PCR), western blot (WB), and transmission electron microscopy. Either CYR61 or MALAT1 were up-regulated by overexpression vectors, or MALAT1 was down-regulated by miR-22-3p mimics. Subsequently, the levels of CYR61, MALAT1, related inflammatory factors, and autophagy factors were measured by qPCR, WB, and enzyme-linked immunosorbent assay (ELISA). Cell apoptosis was detected by flow cytometry and acridine-orange assay.

Results

We observed that down-regulation of CYR61 could down-regulate 1B-light chain 3 (LC3) level and inhibit autophagy in the LPS-induced inflammation model of HK-2 cells. The expression levels of CYR61, Beclin1, Atg5, LC3, interleukin 6 (IL-6), and tumor necrosis factor-α (TNF-α) were significantly increased by upregulating CYR61 or MALAT1 by overexpression vector, while the expression level of p62 was significantly decreased, intracellular reactive oxygen species (ROS) content was increased, and the proportion of autophagy and apoptosis was increased. The use of miR-22-3p mimics significantly reversed the changes induced by up-regulation of CYR61 or MALAT1 at the molecular and cellular levels.

Conclusions

Our data indicated that CYR61 positively regulates autophagy of HK-2 cells under an inflammatory state, and was negatively regulated by miR-22-3p, while miR-22-3p and MALAT1 were negatively regulated by each other.

Expression of Cyr61 in ApoE-/- mice with chronic unilateral renal artery ligation

Cyr61 is a member of the CCN family of proteins that is expressed in atherosclerotic lesions and regulated by angiotensin II. It is unknown whether renal artery stenosis (RAS) increases Cyr61 expression. Male ApoE^−/− mice were randomized to surgically induced RAS, RAS + treatment with either irbesartan, aliskiren or amlodipine or sham-surgery. RAS resulted in increased plasma angiotensin II levels, a mild, sustained increase in systolic blood pressure and increased aortic lipid deposition compared to sham-surgery. Surgically induced RAS led to the formation of atheroma in the infrarenal aorta and there was consistent and intense staining for Cyr61 within the atheroma. Treatment with irbesartan, aliskiren and amlodipine were associated with decreased aortic lipid deposition and decreased staining for Cyr61 in aortic atheroma. Serum levels of Cyr61 were not increased in mice or humans with RAS. In summary, Cyr61 expression in aortic atheroma but not serum is increased by RAS in ApoE^−/− mice and is reduced by agents that lower blood pressure.

The Roles of CCN1/CYR61 in Pulmonary Diseases

CCN1 (cysteine-rich 61, connective tissue growth factor, and nephroblastoma-1), previously named CYR61 (cysteine-rich angiogenic inducer 61) belongs to the CCN family of matricellular proteins. CCN1 plays critical roles in the regulation of proliferation, differentiation, apoptosis, angiogenesis, and fibrosis. Recent studies have extensively characterized the important physiological and pathological roles of CCN1 in various tissues and organs. In this review, we summarize both basic and clinical aspects of CCN1 in pulmonary diseases, including acute lung injury (ALI), chronic obstructive pulmonary disease (COPD), lung fibrosis, pulmonary arterial hypertension (PAH), lung infection, and lung cancer. We also emphasize the important challenges for future investigations to better understand the CCN1 and its role in physiology and pathology, as well as the questions that need to be addressed for the therapeutic development of CCN1 antagonists in various lung diseases.

Anaesthetic-dependent changes in gene expression following acute and chronic exposure in the rodent brain

Anaesthesia has been predicted to affect gene expression of the memory-related regions of the brain including the primary visual cortex. It is also believed that anaesthesia causes inflammation of neural tissues, increasing elderly patients' chances of developing precursor lesions that lead to Alzheimer's disease and other neurodegeneration related diseases. We have analyzed the expression of over 22,000 genes and 129,800 transcripts using oligonucleotide microarrays to examine the brain expression profiles in Sprague Dawley rats following exposure to acute or chronic doses of the anaesthetics isoflurane, ketamine and propofol. Here we report for the first time molecular and genomic data on the effect on the rodent brain of chronic and acute exposure to isoflurane, ketamine and propofol. Our screen identified multiple genes that responded to all three anaesthetics. Although some of the genes were previously known to be anaesthesia responsive, we have for the most part identified novel genes involved in the acute and chronic rodent brain response to different anaesthesia treatments. The latter may be useful candidate genes in the search to elucidate the molecular pathways mediating anaesthetic effects in the brain and may allow us to identify mechanisms by which anaesthetics could impact on neurodegeneration.

Tubular and Glomerular Biomarkers of Acute Kidney Injury in Newborns

BACKGROUND

Acute Kidney Injury (AKI) is a sudden decrease in kidney function. In the early period, the highest percentage of AKI occurs among newborns hospitalized in the neonatal intensive care units, especially premature neonates. The prognosis of AKI depends on the type and severity of the cause of an injury, the accuracy and the time of diagnosis and treatment. The concentration of serum creatinine is still the main diagnostic test, although it changes in the course of AKI later than glomerular filtration rate GFR. In addition, the reliability of the determination of creatinine level is limited because it depends on many factors. New studies have presented other, more useful laboratory markers of renal function that can be measured in serum and/or in urine.

OBJECTIVE

The aim of the work was to present the latest data about tubular and glomerular biomarkers of acute kidney injury in newborns.

METHODS

We undertook a structured search of bibliographic databases for peer-reviewed research literature by using focused review topics. According to the conceptual framework, the main idea of research literature has been summarized and presented in this study.

RESULTS

The concentrations of some novel biomarkers are higher in serum and/or urine of term and preterm newborns with AKI, especially in the course of perinatal asphyxia.

CONCLUSION

In this systematic review of the literature, we have highlighted the usefulness of biomarkers in predicting tubular and/or glomerular injury in newborns. However, novel biomarkers need to prove their clinical applicability, accuracy, and cost-effectiveness prior to their implementation in clinical practice.

Characterization of Matricellular Protein Expression Signatures in Mechanistically Diverse Mouse Models of Kidney Injury

Fibrosis is the most common pathophysiological manifestation of Chronic Kidney Disease (CKD). It is defined as excessive deposition of extracellular matrix (ECM) proteins. Embedded within the ECM are a family of proteins called Matricellular Proteins (MCPs), which are typically expressed during chronic pathologies for ECM processing. As such, identifying potential MCPs in the pathological secretome of a damaged kidney could serve as diagnostic/therapeutic targets of fibrosis. Using published RNA-Seq data from two kidney injury mouse models of different etiologies, Folic Acid (FA) and Unilateral Ureteral Obstruction (UUO), we compared and contrasted the expression profile of various members from well-known MCP families during the Acute and Fibrotic injury phases. As a result, we identified common and distinct MCP expression signatures between both injury models. Bioinformatic analysis of their differentially expressed MCP genes revealed similar top annotation clusters from Molecular Function and Biological Process networks, which are those commonly involved in fibrosis. Using kidney lysates from FA- and UUO-injured mice, we selected MCP genes from our candidate list to confirm mRNA expression by Western Blot, which correlated with injury progression. Understanding the expressions of MCPs will provide important insight into the processes of kidney repair, and may validate MCPs as biomarkers and/or therapeutic targets of CKD.

Prognostic Value of Cysteine-Rich Protein 61 Combined with N-Terminal Pro-B-Type Natriuretic Peptide for Mortality in Acute Heart Failure Patients with and without Chronic Kidney Disease

BACKGROUND

The ability of most biomarkers, such as N-terminal pro-B-type natriuretic peptide (NT-proBNP), to predict prognosis in heart failure can be affected by the state of renal function; therefore, there is the need for a biomarker that can predict prognosis accurately without the influence of renal function. The prognostic value of cysteine-rich protein 61 (CYR61/CCN1) in acute heart failure (AHF) patients has been proven.

METHODS

A total of 248 patients hospitalized with AHF were recruited in this study, and serum CCN1 levels, NT-proBNP levels, and other necessary data of patients were collected upon admission. The correlation of serum CCN1 with estimated glomerular filtration rate (eGFR) was investigated, and the logistic regression model was used to investigate the prognostic value of serum CCN1 for 3-month mortality.

RESULTS

Fifty-four of 248 patients died (21.8%) during a 3-month follow-up. Serum CCN1 had no significant correlation with eGFR (rho = -0.088, p = 0.167). In the overall population and patients without chronic kidney disease, results showed that both serum CCN1 and NT-proBNP were significantly associated with 3-month mortality. In patients with chronic kidney disease, serum CCN1 was significantly associated with 3-month mortality in logistic regression analysis (odds ratio = 2.40, p = 0.002) while NT-proBNP was not. Further in tertile group comparison, in patients with chronic kidney disease, higher tertile levels of serum CCN1 had a significantly higher risk of 3-month mortality compared to the lower tertile ones (odds ratio = 4.17, p = 0.013), but that of NT-proBNP did not.

CONCLUSION

Serum CCN1 level is not associated with eGFR, and it maintains the prognostic value in AHF patients with chronic kidney disease. CCN1 could be a potential novel prognostic biomarker in AHF patients with chronic kidney disease.

Critical Role of Cysteine-Rich Protein 61 in Mediating the Activation of Renal Fibroblasts

Objective

To explore the expression of cysteine-rich protein 61 (Cyr61) in ischemic renal fibrosis and the role of Cyr61 in mediating the activation of renal fibroblasts.

Methods

(1) The rat model of renal fibrosis was established after ischemia-reperfusion acute renal injury (IR-AKI). We detected the renal function by biochemical test, evaluated the fibrosis by Masson staining, and detected the expression of Cyr61 by western blotting. (2) Bioinformatics technique was adopted to analyze the expression of Cyr61 in activated renal fibroblasts. (3) Normal rat kidney fibroblast cells (NRK-49F cells) with over-expression of Cyr61 (Cyr61⁺) and low-expression of it (Cyr61^--) were established by plasmid transfection. Then part of the cells were activated by TGF-β1 and NRK-49F cells were divided into control group, activated group, Cyr61⁺/Cyr61^-- group and Cyr61⁺/Cyr61^-- activated group. The expression of Cyr61 and fibrosis related factors (Col1α1, Col3α1, MMP9, and MMP13) were ascertained by PCR and western blotting. Cell proliferation was discovered by CCK8 method, cell cycle was analyzed by flow cytometry, and the transcription of cell senescence related factors (P53, P21, Rb, and P16) were ascertained by PCR method.

Results

(1) In the process of fibrosis after IR-AKI, the area of collagen fiber was most obviously at AKI 1W, while the Cyr61 protein was at the lowest level at AKI 1W. (2) Gene chip analysis showed that the expression of Cyr61 was decreased in renal fibroblasts after IR. (3) Compared with control group, Cyr61⁺ group expressed less Col1α1 or Col3α1, as well as more MMP9 and MMP13. At the same time, the proliferation of Cyr61⁺ group decreased and cells in G1 phases increased with more transcription of P53, P21, and Rb (all P < 0.05). Compared with activated group, the results of Cyr61⁺ activated group were similar to the above. The above effects of low expression group were just the opposite. In addition, there was no difference in the transcription of P16 among these groups (P > 0.05).

Conclusion

Cyr61 may not only inhibit the fibrotic phenotype of fibroblasts, but may also inhibit proliferation by promoting fibroblasts arrest in G1 phase through the P53/P21/Rb interrelated cell senescence pathway, subsequently affecting the process of ischemic renal fibrosis.

Current Status of Novel Biomarkers for the Diagnosis of Acute Kidney Injury: A Historical Perspective

Acute kidney injury (AKI) is a common and serious medical condition associated with significant increases in morbidity, mortality, and cost of care. Because of the high incidence and poor outcomes associated with AKI, there has been significant interest in the development of new therapies for the prevention and treatment of the disease. A lack of efficacy in drug trials led to the concern that AKI was not being diagnosed early enough for an effective intervention and that a rise in serum creatinine itself is not a sensitive-enough marker. Researchers have been searching for novel biomarkers that can not only assess a decline in kidney function but also demonstrate structural damage to the kidney and at time points earlier than increases in serum creatinine measurements allow. Over the past 10 years, there have been 3300 new publications and hundreds of new biomarkers investigated, yet concern still remains regarding AKI biomarker performance. The AKI biomarkers are yet to be widely utilized in clinical practice, leading some to question whether AKI biomarkers will ever reach their initial promise. However, we believe that biomarkers are an important part of current and future AKI research and clinical management. In this review, we compare the historical contexts of acute myocardial ischemia and AKI biomarker development to illustrate the progress that has been made within AKI biomarker research in a relatively short period of time and also to point out key differences between the disease processes that have been barriers to widespread AKI biomarker adoption. Finally, we discuss potential paths by which biomarkers can lead to appropriate AKI treatment responses that lower morbidity and mortality.

Validity of Klotho, CYR61 and YKL-40 as ideal predictive biomarkers for acute kidney injury: review study

CONTEXT AND OBJECTIVE:

Acute kidney injury (AKI) is still a headache for clinicians and scientists as a possible reason for increased death among intensive care unit (ICU) patients after invasive cardiac surgery. Furthermore, the diagnostic process for AKI using conventional biomarkers is not sufficient to ensure early warning of this condition because of the morbid influence of non-renal factors that definitively delay the time for the prognosis. These imposed limitations have led to significant amounts of research targeted towards identifying novel biomarkers for AKI with a sustained degree of sensitivity and specificity. Here, we reviewed previous studies conducted on the Klotho, CYR61 and YKL-40 biomarkers in relation to AKI.

DESIGN AND SETTING:

Review of the literature conducted in the Institute of Clinical Chemistry & Biochemistry, Ljubljana University Medical Center, Slovenia.

METHODS:

The literature was searched in PubMed and the Cochrane Library. From the database of this specialty, we selected 17 references that matched our context for detailed analysis and further investigation.

RESULTS:

The studies reviewed showed notable differences in their results relating to the diagnostic impact of Klotho, CYR61 and YKL-40 on early prediction of AKI.

CONCLUSIONS:

The results regarding the Klotho, CYR61 and YKL-40 biomarkers showed markedly equivocal performance in the previous studies and did not fulfill the expectations that these factors would form valid possible biomarkers for AKI.

7,8-DHF Treatment Induces Cyr61 Expression to Suppress Hypoxia Induced ER Stress in HK-2 Cells

Acute kidney injury (AKI) is a common syndrome which is strongly linked to high morbidity and mortality. Hypoxia is the leading cause of AKI and the proximal renal tubular cells are the most damaged part in the kidney during this period. It has been observed that 7,8-dihydroxyflavone (7,8-DHF) plays a protective role by acting on antiapoptosis and antioxidative stress. In this study we explored functions of 7,8-DHF in protecting human proximal tubular cell line HK-2 from hypoxia insults. We observed that treatment of 7,8-DHF could improve the viability of ischemic cell. Mechanistically, we found that 7,8-DHF could elevate the expression of cysteine-rich protein 61 (Cyr61), a protective immediate early gene in AKI. In addition, treatment of 7,8-DHF decreased CCAAT/enhancer-binding protein homologous protein (CHOP) expression, which is a marker protein during endoplasmic reticulum (ER) stress activation. Intriguingly, overexpression of Cyr61 significantly reduced CHOP expression. Taken together, our results provide novel insights into the possible protective role of 7,8-DHF by activating Cyr61 signaling and suppressing ER stress in hypoxic HK-2 cells which have potential clinical implications for the treatment of AKI.

Klotho and S100A8/A9 as Discriminative Markers between Pre-Renal and Intrinsic Acute Kidney Injury

Early detection and accurate differentiation of the cause of AKI may improve the prognosis of the patient. However, to date, there are few reliable biomarkers that can discriminate between pre-renal and intrinsic AKI. In this study, we determined whether AKI is associated with altered serum and urinary levels of Klotho, S100A8/A9 (an endogenous ligand of toll-like receptor 4), and neutrophil gelatinase-associated lipocalin (NGAL), which may allow differentiation between pre-renal and intrinsic AKI. A volume-depleted pre-renal AKI model was induced in male Sprague Dawley rats fed a low-salt diet (0.03%) without water 96 h before two intraperitoneal (IP) injections of furosemide (20 mg/kg) at a 24 h interval. In contrast, in the cisplatin-induced intrinsic AKI model, animals were given a single IP injection of cisplatin (5 mg/kg). All of the animals were euthanized 72 h after the first IP injection. Serum and urinary levels of Klotho, S100A8/A9, and NGAL were measured using an enzyme-linked immunosorbent assay. We also performed a proof-of-concept cross-sectional study to measure serum and urinary biomarkers in 61 hospitalized patients with established AKI. Compared to the intrinsic AKI group, the pre-renal AKI group showed a marked depression in urinary Klotho levels (13.21±17.32 vs. 72.97±17.96 pg/mL; P = 0.002). In addition, the intrinsic AKI group showed marked elevation of S100A8/A9 levels compared to the pre-renal AKI group (2629.97±598.05 ng/mL vs. 685.09±111.65 ng/mL; P = 0.002 in serum; 3361.11±250.86 ng/mL vs. 741.72±101.96 ng/mL; P = 0.003 in urine). There was no difference in serum and urinary NGAL levels between the pre-renal and intrinsic AKI groups. The proof-of-concept study with the hospitalized AKI patients also demonstrated decreased urinary Klotho in pre-renal AKI patients and increased urinary S100A8/A9 concentrations in intrinsic AKI patients. The attenuation of urinary Klotho and increase in urinary S100A8/A9 may allow differentiation between pre-renal and intrinsic AKI.

Regulation of CCN1 (Cyr61) in a porcine model of intestinal ischemia/reperfusion

Intestinal ischemia is a serious condition that may lead to both local and systemic inflammatory responses. Restoration of blood supply (reperfusion) to ischemic tissues often increases the extent of the tissue injury. Cysteine-rich angiogenic inducer 61 (Cyr61)/CCN1 is an extracellular matrix-associated signaling protein that has diverse functions. CCN1 is highly expressed at sites of inflammation and wound repair, and may modify cell responses. This study aimed to investigate regulation and cellular distribution of CCN1 in intestinal ischemia/reperfusion (I/R) injury in pigs. After intestinal I/R, increased expression of CCN1 was detected by quantitative RT-PCR, Western blot analysis and immunohistochemistry compared with non-ischemic intestine. Immunoflorescence staining revealed that CCN1 was mainly up-regulated in intestinal mucosa after intestinal I/R. Microvillus epithelial cells and vascular endothelial cells were strongly positive for CCN1 in intestinal I/R, while natural killer cells and/or subsets of neutrophils were only modestly positive for CCN1. Furthermore, blood samples taken from the portal and caval veins during ischemia and after reperfusion showed no change of the CCN1 levels, indicating that CCN1 was locally regulated. In conclusion, these observations show, for the first time, that the CCN1 molecule is up-regulated in response to intestinal I/R in a local manner.

Acute kidney injury induced by various pneumoperitoneum pressures in a rabbit model of mild and severe hydronephrosis

OBJECTIVE

Increased pneumoperitoneum pressure during laparoscopic surgery can result in acute kidney injury. We aimed to clarify whether intraabdominal pressure tolerance is modified in various degrees of unilateral kidney hydronephrosis in rabbits.

METHODS

A total 90 rabbits were randomly allocated to three groups (group PN, PM and PS, i.e. rabbits with no, mild and severe hydronephrosis, respectively, subjected to intraabdominal pressures). Rabbits in group PM (n=30) and group PS (n=30) underwent a surgical procedure inducing a mild or severe left hydronephrosis. Rabbits in all groups were then allocated to 5 subgroups. Then, they were subjected to intraabdominal pressures of 0, 6, 9, 12, and 15 mm Hg, respectively. Acute kidney injury was assessed by measuring serum creatinine (Scr), blood urea nitrogen (BUN), tubular cell apoptosis, kidney injury molecule-1 (KIM-1) and cysteine-rich 61 (Cyr-61/CCN1) expression.

RESULTS

Acute kidney injury with increased tubular apoptosis and KIM-1 and Cyr-61 expression occurred when intraabdominal pressure reached 15, 15 and 9 mm Hg in PN, PM and PS groups, respectively. The Scr and BUN levels were similar in all groups.

CONCLUSIONS

In rabbits, kidneys with severe hydronephrosis were more likely to suffer acute injury when they were exposed to pneumoperitoneal pressure.

Blockade of cysteine-rich protein 61 attenuates renal inflammation and fibrosis after ischemic kidney injury

Emerging data have suggested that acute kidney injury (AKI) is often incompletely repaired and can lead to chronic kidney disease (CKD), which is characterized by tubulointerstitial inflammation and fibrosis. However, the underlying mechanisms linking AKI to CKD remain obscure. The present study aimed to investigate the role of cysteine-rich protein 61 (Cyr61) after unilateral kidney ischemia-reperfusion injury (IRI) in mice. After IRI, increased expression of Cyr61 was detected, predominately in the proximal tubular epithelium. This was confirmed by in vitro experiments, which showed that hypoxia stimulated Cyr61 expression in cultured proximal tubular epithelial cells. The proinflammatory property of Cyr61 was indicated by its ability to upregulate monocyte chemoattractant protein-1 and IL-6. Additionally, we found elevated urinary Cyr61 excretion in patients with AKI. Notably, treatment of mice with an anti-Cyr61 antibody attenuated the upregulation of kidney monocyte chemoattractant protein-1, IL-6, IL-1β, and macrophage inflammatory protein-2 and reduced the infiltration of F4/80-positive macrophages on days 7 and 14 after IRI. In addition, blockade of Cyr61 reduced the mRNA expression of collagen, transforming growth factor-β, and plasminogen activator inhibitor-I as well as the degree of collagen fibril accumulation, as evaluated by picrosirius red staining, and levels of α-smooth muscle actin proteins by day 14. Concurrently, in the treated group, peritubular microvascular density was more preserved on day 14. We conclude that Cyr61 blockade inhibits the triad of inflammation, interstitial fibrosis, and capillary rarefaction after severe ischemic AKI. The results of this study expand the knowledge of the mechanisms underlying the AKI-to-CKD transition and suggest that Cyr61 is a potential therapeutic target.

Evaluation of molecular profiles in calcineurin inhibitor toxicity post-kidney transplant: input to chronic allograft dysfunction

The molecular basis of calcineurin inhibitor toxicity (CNIT) in kidney transplantation (KT) and its contribution to chronic allograft dysfunction (CAD) with interstitial fibrosis (IF) and tubular atrophy (TA) were evaluated by: (1) identifying specific CNIT molecular pathways that associate with allograft injury (cross-sectional study) and (2) assessing the contribution of the identified CNIT signature in the progression to CAD with IF/TA (longitudinal study). Kidney biopsies from well-selected transplant recipients with histological diagnosis of CNIT (n = 14), acute rejection (n = 13) and CAD with IF/TA (n = 10) were evaluated. Normal allografts (n = 18) were used as controls. To test CNIT contribution to CAD progression, an independent set of biopsies (n = 122) from 61 KT patients collected at 3 and ~12 months post-KT (range = 9-18) were evaluated. Patients were classified based on 2-year post-KT graft function and histological findings as progressors (n = 30) or nonprogressors to CAD (n = 31). Molecular signatures characterizing CNIT samples were identified. Patients classified as progressors showed an overlap of 7% and 22% with the CNIT signature at 3 and at ~12 months post-KT, respectively, while the overlap was <1% and 1% in nonprogressor patients, showing CNIT at the molecular level as a nonimmunological factor involved in the progression to CAD.

Pathogenesis of renal failure in multiple myeloma: any role of contrast media?

The spectrum of kidney disease-associated monoclonal immunoglobulin and plasma cell malignancies is remarkably broad and encompasses nearly all nephropathologic entities. Multiple myeloma with kidney impairment at presentation is a medical emergency since the recovery of kidney function is associated with survival benefits. In most cases, kidney impairment may be the first clinical manifestation of malignant plasma cell dyscrasias like multiple myeloma and light chain amyloidosis. Multiple myeloma per se cannot be considered a main risk factor for developing acute kidney injury following intravascular administration of iodinated contrast media. The risk is increased by comorbidities such as chronic kidney disease, diabetes, hypercalcemia, dehydration, and use of nephrotoxic drugs. Before the administration of contrast media, the current recommended laboratory tests for assessing kidney function are serum creatinine measurement and the estimation of glomerular filtration rate by using the CKD-EPI equation. The assessment of Bence Jones proteinuria is unnecessary for evaluating the risk of kidney failure in patients with multiple myeloma, since this test cannot be considered a surrogate biomarker of kidney function.

Nephroscreen™: a diagnostic test for predicting acute renal failure?

Acute renal failure is a frequent and often fatal complication of hospitalized patients. While the risk of acute renal failure among select patient groups is well recognized, physicians currently rely on diagnostic tests such as changes of serum creatinine and indirect assessment of the glomerular filtration rate to diagnose acute renal failure. Although these parameters capture the degree of kidney function lost, they are not warning signs of evolving kidney injury. While the clinical emergence of acute renal failure is sudden, the pathologic changes preceding loss of kidney function are not so sudden. Nephroscreen is a fast and easy-to-use urine enzyme-linked immunosorbent assay test designed to quantify specific pathologic events preceding death of renal proximal tubule cells. It detects acute kidney damage days before serum creatinine rises and may open new avenues to defining acute renal failure as well as treating acute renal failure patients earlier and more effectively.

Acute kidney injuries induced by various irrigation pressures in rat models of mild and severe hydronephrosis

OBJECTIVE

To clarify whether tolerance to irrigation pressure could be modified over varying degrees of kidney obstruction during the endoscopic treatment of kidney stones in a rat model.

METHODS

A total of 126 rats were randomly allocated into 2 experimental groups and a control group. The experimental groups underwent a surgical procedure to induce mild (group M, n = 60) or severe (group S, n = 60) hydronephrosis. In each group, the rats were then randomly allocated into 4 subgroups (M0 to M3 and S0 to S3) of respectively 6, 18, 18, and 18 rats. Groups 0 to 3 were respectively perfused with 0 (no irrigation), 20, 60, and 100 mm Hg pressure fluid. The control group underwent no surgical procedures and was only perfused with 100 mm Hg pressure fluid. Acute kidney injuries were assessed by analyzing the kidney microstructure, tubular cell apoptosis, kidney injury molecule-1, and cysteine-rich 61 (Cyr61/CCN1) expression using immunohistochemistry.

RESULTS

No abnormalities were observed for the control group, groups 0, or 1. In group 2, abnormalities were observed only in the S group, whereas all kidneys in group 3 suffered acute kidneys injuries, along with occurrence of tubular cells necrosis, increased apoptosis, and increased expression of kidney injury molecule-1 and Cyr61.

CONCLUSION

Rats with severely obstructed kidneys were more likely to suffer acute kidney injuries than those with less obstructed kidneys when exposed to higher kidney irrigation pressures. This suggests that the pressure should be controlled and reduced when performing endourologic procedures in the context of kidney obstruction.

Organic anion transporter 5 renal expression and urinary excretion in rats with vascular calcification

It has been described renal damage in rats with vascular calcification. The organic anion transporter 5 (Oat5) is only expressed in kidney, and its urinary excretion was proposed as potential early biomarker of renal injury. The aim of this study was to evaluate the Oat5 renal expression and its urinary excretion in an experimental model of vascular calcification in comparison with traditional markers of renal injury. Vascular calcification was obtained by the administration of an overdose of vitamin D₃ (300,000 IU/kg, b.w., i.m.) to male Wistar rats. Oat5 urinary abundance was evaluated by Western blotting. Traditional markers of renal injury, such as creatinine and urea plasma levels, urinary protein levels, and urinary alkaline phosphatase (AP) activity, were determined using commercial kits. Histology was assessed by hematoxylin/eosin staining. Oat5 renal expression was evaluated by Western blotting and by immunohistochemistry. An increased expression of Oat5 in renal homogenates, in apical membranes, and in its urinary excretion was observed in rats with vascular calcification. The traditional parameters used to evaluate renal function were not modified, with the exception of histology. It is possible to postulate the urinary excretion of Oat5 as a potential noninvasive biomarker of renal injury associated with vascular calcification.

Hippo signaling disruption and Akt stimulation of ovarian follicles for infertility treatment

Primary ovarian insufficiency (POI) and polycystic ovarian syndrome are ovarian diseases causing infertility. Although there is no effective treatment for POI, therapies for polycystic ovarian syndrome include ovarian wedge resection or laser drilling to induce follicle growth. Underlying mechanisms for these disruptive procedures are unclear. Here, we explored the role of the conserved Hippo signaling pathway that serves to maintain optimal size across organs and species. We found that fragmentation of murine ovaries promoted actin polymerization and disrupted ovarian Hippo signaling, leading to increased expression of downstream growth factors, promotion of follicle growth, and the generation of mature oocytes. In addition to elucidating mechanisms underlying follicle growth elicited by ovarian damage, we further demonstrated additive follicle growth when ovarian fragmentation was combined with Akt stimulator treatments. We then extended results to treatment of infertility in POI patients via disruption of Hippo signaling by fragmenting ovaries followed by Akt stimulator treatment and autografting. We successfully promoted follicle growth, retrieved mature oocytes, and performed in vitro fertilization. Following embryo transfer, a healthy baby was delivered. The ovarian fragmentation-in vitro activation approach is not only valuable for treating infertility of POI patients but could also be useful for middle-aged infertile women, cancer patients undergoing sterilizing treatments, and other conditions of diminished ovarian reserve.

Novel biomarkers for early diagnosis of acute kidney injury

BACKGROUND

Acute kidney injury (AKI) is a common and serious problem in critically ill patients. Tests currently used to detect AKI (i.e., serum creatinine, serum urea and various urinary indices) often result in serious delays in detection of clinically relevant injury. This delayed detection translates into a potential missed opportunity for therapeutic interventions at a time when kidney damage may be limitable or reversible. This is also recognized as a potential reason for the poor clinical outcomes often associated with AKI.

OBJECTIVES

To appraise the recent literature characterizing several novel serum and urinary biomarkers, including neutrophil gelatinase-associated lipocalin, IL-18 and kidney injury molecule-1, which are capable of detecting AKI at an earlier phase of injury. Also to discuss the pitfalls of current conventional testing in kidney injury.

METHOD

Narrative literature review.

CONCLUSIONS

These novel biomarkers can detect injury when damage may still be reversible, allow for early risk stratification and/or prognostication, and are associated in early clinical studies with important outcomes such as severity of AKI, need for renal replacement therapy and survival. There is optimism that these novel biomarkers will discriminate the underlying pathophysiology of AKI (i.e., ischemia, sepsis, toxins or multifactorial), discriminate AKI from other renal disease (i.e., chronic kidney disease) and aid in localizing the site of acute injury in the kidney. As such, the future may entail development of an 'AKI biomarker panel' (i.e., analogous to a cardiac or liver enzyme panel) for use in clinical practice.

Cysteine-rich protein 61 plays a proinflammatory role in obstructive kidney fibrosis

Cysteine-rich protein 61 (Cyr61) is a secreted matrix-associated protein that regulates a broad spectrum of biological and cellular activities. This study aimed to investigate the role of Cyr61 in progressive kidney fibrosis induced by unilateral ureteral obstruction (UUO) surgery in mice. The expression of Cyr61 transcripts and proteins in the obstructed kidneys were increased from day 1 and remained high until day 10 after surgery. Immunohistochemistry indicated that Cyr61 was expressed mainly in renal tubular epithelial cells. The upregulated Cyr61 in UUO kidneys was reduced in mice treated with pan-transforming growth factor-β (TGF-β) antibody. The role of TGF-β in tubular Cyr61 upregulation after obstructive kidney injury was further supported by experiments showing that TGF-β1 stimulated Cyr61 expression in cultured tubular epithelial cells. Notably, the upregulation of Cyr61 in UUO kidneys was followed by a marked increase in monocyte chemoattractant protein 1 (MCP-1) transcripts and macrophage infiltration, which were attenuated in mice treated with anti-Cyr61 antibodies. This proinflammatory property of Cyr61 in inducing MCP-1 expression was further confirmed in tubular epithelial cells cultured with Cyr61 protein. The anti-Cyr61 antibody in UUO mice also reduced the levels of collagen type 1-α1 transcripts, collagen fibril accumulation evaluated by picrosirius red staining, and the levels of α-smooth muscle actin (α-SMA) transcripts and proteins on day 4 after surgery; however, the antifibrotic effect was not sustained. In conclusion, the TGF-β-mediated increase in tubular Cyr61 expression involved renal inflammatory cell infiltration through MCP-1 induction during obstructive kidney injury. The Cyr61 blockade attenuated kidney fibrosis in the early phase, but the antifibrotic effect could not be sustained.

Gene expression changes in melanoma metastases in response to high-dose chemotherapy during isolated limb perfusion

Despite recent advances in melanoma therapy, disseminated melanoma still lacks effective treatment, and recurrence of the tumor frequently occurs, even after high-dose chemotherapy. The mechanisms responsible for this chemoresistance or for the formation of new relapses remain poorly understood. Using a human 'model', in which the isolated limb is perfused with high doses of the chemotherapeutic melphalan (ILP), we identified a five-gene set (ATF3, CYR61, IER5, IL6, and PTGS2) of stress-induced genes that was consistently upregulated after ILP in all in-transit metastatic melanoma samples as well as in three melphalan-treated melanoma cell lines. Early post-ILP relapses retained these elevated expressions, whereas the expression of these genes returned to their original levels in late post-ILP recurrences. In addition, we identified upregulation of these genes in the A375 cell line's side population (SP) and melanospheres, established methods to enrich for candidate cancer stem cells (CSCs), which are considered chemoresistant and tumorigenic, and thus proposed to be responsible for tumor relapse. Our data identify an immediate and short-term upregulation of early stress-responsive genes that are potentially linked to chemoresistance and CSCs.

[Kidney injury biomarkers]

Over the last few decades, prevalence of renal diseases has grown continuously in occidental societies due to life conditions (age, life style, chronic disease, etc.) or potential exposure to nephrotoxic agents (drugs and environmental chemicals). Today, the knowledge of the nephropatology mechanism is improving. Nevertheless, considering it is a complex and multifunctional structure, the clinical strategy of this issue (prognostic, diagnostic or therapy) keeps posing a major challenge for clinicians mostly because classical markers are not sensitive enough and require hours before reaching significant levels. Furthermore, most of these markers provide information on function and not on structural integrity of the tissue. Identification and development of new biomarkers share promise of improvement in the rapid diagnostic of kidney diseases and development of new cures in order to optimize the clinical strategy associated to the renal failure.

Pathophysiology of acute kidney injury

Acute kidney injury (AKI) is the leading cause of nephrology consultation and is associated with high mortality rates. The primary causes of AKI include ischemia, hypoxia, or nephrotoxicity. An underlying feature is a rapid decline in glomerular filtration rate (GFR) usually associated with decreases in renal blood flow. Inflammation represents an important additional component of AKI leading to the extension phase of injury, which may be associated with insensitivity to vasodilator therapy. It is suggested that targeting the extension phase represents an area potential of treatment with the greatest possible impact. The underlying basis of renal injury appears to be impaired energetics of the highly metabolically active nephron segments (i.e., proximal tubules and thick ascending limb) in the renal outer medulla, which can trigger conversion from transient hypoxia to intrinsic renal failure. Injury to kidney cells can be lethal or sublethal. Sublethal injury represents an important component in AKI, as it may profoundly influence GFR and renal blood flow. The nature of the recovery response is mediated by the degree to which sublethal cells can restore normal function and promote regeneration. The successful recovery from AKI depends on the degree to which these repair processes ensue and these may be compromised in elderly or chronic kidney disease (CKD) patients. Recent data suggest that AKI represents a potential link to CKD in surviving patients. Finally, earlier diagnosis of AKI represents an important area in treating patients with AKI that has spawned increased awareness of the potential that biomarkers of AKI may play in the future.

Use of urinary biomarkers of renal ischemia in a lamb preclinical left ventricular assist device model

Evaluation of thrombogenicity is a critical component in the preclinical testing and development of blood pumps. Left ventricular assist devices (LVADs), because of their device routing, can produce thromboembolic showers to the kidney resulting in renal cortical ischemia or infarctions. Although postmortem evaluation of renal pathology can confirm ischemic events and infarctions, there are no validated and highly sensitive real-time measures of renal ischemia in the preclinical models. In this article, we report the evaluation of urinary biomarkers of ischemic tubular damage in a lamb preclinical LVAD model. We found that urinary excretion of glutathione-S-transferase-π, heat shock protein 1B, and hepatitis A virus cellular receptor 1 homologue precursor (HAVCR1/kidney injury molecule 1) were upregulated in toxic ischemic renal injury as well as in the immediate postoperative period in an LVAD-implanted lamb. These markers were consistent with both gross and histologic pathology, and proved far more sensitive for renal injury than serum blood urea nitrogen or creatinine concentrations.

Cysteine-rich 61 (CYR61) is up-regulated in proliferative diabetic retinopathy

BACKGROUND

To investigate the role of CYR61 as a retinal angiogenic factor in proliferative diabetic retinopathy (PDR).

METHODS

Effects of CYR61 on RF/6A cell proliferation, migration and angiogenesis were observed by MTT assay, Transwell assay, and tube formation assay. The expression and distribution of CYR61 on retina layers of diabetic mouse were demonstrated by immunohistochemistry. The expression of Cyr61 mRNA in diabetic mouse retina was evaluated by reverse transcription-polymerase chain reaction (RT-PCR). Vitreous CYR61 levels of PDR and non-diabetic patients were measured by enzyme-linked immunosorbent assay (ELISA). Expression and distribution of CYR61 on epiretinal membrane of PDR, proliferative vitreoretinopathy (PVR) and idiopathic epiretinal membrane were evaluated by immunohistochemistry.

RESULTS

RF/6A cell proliferation, migration and tube formation capacity increased with increased concentration of CYR61 (p = 0.000). Anti-CYR61 antibody could inhibit cell migration and tube formation promoted by CYR61. In diabetic mouse, CYR61 was expressed in retina layers just as normal mouse, but the staining was stronger than normal in ganglion cell layer and inner plexiform layer. The Cyr61 mRNA expression in retina of diabetic mouse was more than that in normal mouse (p = 0.009). Vitreous CYR61 level was higher in patients with PDR than non-diabetic patients (p = 0.000). PDR patients with plenty of neovasculature on retina and epiretinal membranes had higher level of vitreous CYR61 than patients with little neovasculature (p = 0.001). CYR61 expressed in the cytoplasm of epiretinal membranes in PDR, especially in the wall cells of the tube-like structure.

CONCLUSIONS

CYR61 are likely to be involved in the pathogenesis of diabetic retinopathy, and may play a role in the course of neovasculation.

Neutrophil Gelatinase Associated Lipocalin: An Emerging Biomarker for Acute Kidney Injury in Cardiovascular Disease

Acute kidney injury (AKI) commonly occurs in hospitalised patients resulting in short and long-term morbidity and mortality. A subset of patients especially those with cardiovascular diseases appear particularly vulnerable. The diagnosis of AKI currently depends on changes in serum creatinine and is usually made at least 24 to 48 hours after the initial renal insult. This hinders formulation of possible early therapeutic strategies which could otherwise reduce the clinical sequelae of AKI. Neutrophil gelatinase-associated lipocalin (NGAL) is released in both serum and urine, and has shown great promise in identifying AKI as early as two to four hours after renal injury. NGAL has been demonstrated to be both specific and sensitive in a variety of renal conditions associated with AKI, compared to serum creatinine. This article discusses the emerging role of NGAL in the diagnostic and prognostic evaluation of AKI secondary to cardiovascular diseases and interventions including its benefits and pitfalls. NGAL has been shown to be useful in the diagnosis of AKI particularly for contrast induced nephropathy (CIN) after percutaneous coronary intervention (PCI) and renal dysfunction complicating acute and chronic heart failure. Larger prospective outcome studies with therapeutic interventions are warranted to further validate the role of NGAL in the diagnosis of AKI and in cardiorenal syndrome.

Biomarkers of immunosuppressant organ toxicity after transplantation: status, concepts and misconceptions

INTRODUCTION

A major challenge in transplantation is improving long-term organ transplant and patient survival. Immunosuppressants protect the transplant organ from alloimmune reactions, but sometimes also exhibit limiting side effects. The key to improving long-term outcome following transplantation is the selection of the correct immunosuppressive regimen for an individual patient for minimizing toxicity while maintaining immunosuppressive efficacy.

AREAS COVERED

Proteomics and metabolomics have the potential to develop sensitive and specific diagnostic tools for monitoring early changes in cell signal transduction, regulation and biochemical pathways. Here, we review the steps required for the development of molecular markers from discovery, mechanistic and clinical qualification to regulatory approval, and present a critical discussion of the current status of molecular marker development as relevant for the management and individualization of immunosuppressive drug regimens.

EXPERT OPINION

Although metabolomics and proteomics-based studies have yielded several candidate molecular markers, most published studies are poorly designed, statistically underpowered and/or often have not gone beyond the discovery stage. Most molecular marker candidates are still at an early stage. Due to the high complexity of and the resources required for diagnostic marker development, initiatives and consortia organized and supported by funding agencies and regulatory agencies will be critical.

Molecular biomarker candidates of acute kidney injury in zero-hour renal transplant needle biopsies

The aim of this study was to assess gene expression levels of four biomarker candidates [lipocalin 2 (LCN2), the kidney injury molecule 1 (HAVCR1), netrin 1, and the cysteine-rich, angiogenic inducer, 61] in the tubulointerstitial and the glomerular compartment of zero-hour kidney biopsies in order to predict developing delayed graft function (DGF). Thirty-four needle kidney biopsy samples of deceased donors were manually microdissected. Relative gene expression levels were determined by real-time RT-PCR. For the validation of the biomarker candidates, we calculated a mixed model comparing kidneys with DGF, primary function and control samples from the healthy parts of tumor nephrectomies. Significant biomarker candidates were analyzed together with donor age in multivariable regression models to determine the prognostic value. Expression levels of LCN2 and HAVCR1 in the tubulointerstitium were significantly upregulated in the DGF group (LCN2: fold change = 3.78, P = 0.031 and HAVCR1: fold change = 3.44, P = 0.010). Odds ratios of both genes could not reach significance in the multivariable model together with donor age. The area under the curve of the receiver operating characteristic ranges between 0.75 and 0.83. LCN2 and HAVCR1 gene expression levels in zero-hour biopsies show potential to act as early biomarkers for DGF.

Urinary parameters predictive of cisplatin-induced acute renal injury in dogs

A 28-day study was conducted to evaluate changes in urinary cytokine/chemokine expression levels in dogs with renal injury due to administration of cisplatin. Animals (n=17) were administered cisplatin at 0.75 mg/kg/day (i.v.) for five consecutive days. Urine/serum were collected at pre-dosing, 4h post-dosing and on days 2, 3, 4, 8, 10, 14, 16, 18, 21, 23, 25, 28 and unscheduled terminations. Animals were euthanized when serum creatinine (sCr) levels measured at ≥ 1.9 mg/dL, indicating significant loss of renal function (decreased glomerular filtration rate). Relevant clinical observations included lethargy and dehydration. Pre-study sCr levels ranged from 0.6 to 0.8 mg/dL; on days 1 through 4, sCr levels ranged from 0.5 and 1.1mg/dL; and terminal sCr levels ranged from 0.6 and 6.6 mg/dL. Histologically, cisplatin-related renal changes were characterized as proximal tubule dilatation, vacuolization, degeneration, regeneration, and interstitial inflammation. Increased interleukin (IL)-2, IL-8, monocyte chemoattractant protein-1 (MCP-1), granulocyte-macrophage colony-stimulating factor (GMCSF) and keratinocyte-derived chemokine (KC) occurred on days 3 through 4. Increased IL-7 occurred on day 4. This study showed for the first time that inflammatory cytokines/chemokines in urine positively identified acute renal tubular injury in dogs at time points earlier than sCr, a traditional marker of nephrotoxicity.

Biomarkers in renal transplantation ischemia reperfusion injury

Ischemia reperfusion injury (IRI) is a choreographed process leading to delayed graft function (DGF) and reduced long-term patency of the transplanted organ. Early identification of recipients of grafts at risk would allow modification of the posttransplant management, and thereby potentially improve short- and long-term outcomes. The recently emerged "omics" technologies together with bioinformatics workup have allowed the integration and analysis of IRI-associated molecular profiles in the context of DGF. Such a systems biological approach promises qualitative information about interdependencies of complex processes such as IRI regulation, rather than offering descriptive tables of differentially regulated features on a transcriptome, proteome, or metabolome level leaking the functional, biological framework. In deceased-donor kidney transplantation as the primary causative factor resulting in IRI and DGF, a distinct signature and choreography of molecular events in the graft before harvesting seems to be associated with subsequent DGF. A systems biological assessment of these molecular changes suggests that processes along inflammation are of pivotal importance for the early stage of IRI. The causal proof of this association has been tested by a double-blinded, randomized, controlled trial of steroid or placebo infusion into deceased donors before the organs were harvested. Thorough systems biological analysis revealed a panel of biomarkers with excellent discrimination. In summary, integrated analysis of omics data has brought forward biomarker candidates and candidate panels that promise early assessment of IRI. However, the clinical utility of these markers still needs to be established in prospective trials in independent patient populations.

Histogenomics: association of gene expression patterns with histological parameters in kidney biopsies

BACKGROUND

Several studies investigated the association of histologic scores of donor kidney biopsies obtained before engraftment with posttransplant outcomes. Discrimination and goodness of fit of these scores, however, is low.

METHODS

Thus, we sought to identify and elucidate the performance of molecular rather than histologic markers for this purpose using whole genome gene expression microarray experiments.

RESULTS

We identified 80 unique differentially regulated genes in 82 samples, showing no histologic damage versus those with histologic damage, based on the Chronic Allograft Damage Index (CADI) and acute tubular injury. Main biological categories enriched with up-regulated genes in damaged tissue were "immunity and defense," "cell communication," or "apoptosis." Interestingly, genes involved in cell structure, cell adhesion, and protein trafficking were specific for tubular atrophy. Histology (CADI score) explained only 14% of the variability of 1 year creatinine (adjusted R2 for panel-reactive antibodies, biopsy confirmed acute rejection, and sum of human leukocyte antigen mismatches) whereas a combination of three biomarkers without clinical covariables explained 28%. The three molecular markers are the NLR family, pyrin domain containing 2 (NLRP2), immunoglobulin J polypeptide, and the regulator of G-protein signaling 5.

CONCLUSION

In summary, we identified biomarkers in transplant kidney biopsies, which are predictive for medium-term allograft function.

The role of extracorporeal blood purification therapies in the prevention of radiocontrast-induced nephropathy

Radiocontrast-induced nephropathy (RCIN) is a common and potentially serious complication following diagnostic and therapeutic cardiology procedures using radiocontrast media. The first and most important step in reducing the likelihood of RCIN is to identify patients at risk, by medical history and measurement of serum creatinine concentration to allow calculation of estimated glomerular filtration rate (GFR). Extracorporeal blood purification effectively removes radiocontrast media from the circulation. Periprocedural extracorporeal blood purification (hemodialysis or continuous renal replacement therapy) does not reduce the incidence of RCIN compared with standard medical therapy, and cannot be recommended at this time. The potential benefit of continuous venovenous hemofiltration published by a single center should be confirmed with further studies before it can be recommended or disregarded, and higher doses of continuous renal replacement therapy may also merit further investigation.

Acute kidney injury: epidemiology and assessment

An evolving understanding of epidemiology and pathophysiology of acute organ dysfunction in the setting of critical illness has given rise to new concepts and terminology for a syndrome once known as either acute tubular necrosis or acute renal failure. Indeed, the clinical syndrome known as acute tubular necrosis does not actually manifest the morphological changes that the name implies. Similarly, a precise biochemical definition of acute renal failure was never proposed, and until recently there has been no consensus on the diagnostic criteria or clinical definition. The RIFLE criteria were developed to achieve diagnostic standardization and the term acute kidney injury (AKI) has been proposed to encompass the entire spectrum of the syndrome from minor changes in renal function to requirement for renal replacement therapy. AKI is not acute tubular necrosis nor is it acute renal failure. Small changes in kidney function in hospitalized patients are important and are associated with significant changes in short and possibly long-term outcomes. The RIFLE criteria provide a uniform definition of AKI and have now been validated in numerous studies. The population incidence of AKI is approximately 2000-3000 patients per million population per year. The incidence of AKI is increasing and ICU patients with AKI have a longer length of stay and therefore generate greater costs. In addition, AKI is associated with increased mortality, even after correction for covariates. Patients with AKI who are treated with RRT, still have a mortality of 50-60 %. Of surviving patients, 5-20 % remain dialysis-dependent at hospital discharge.