Biomarker and drug-target discovery using proteomics in a new rat model of sepsis-induced acute renal failure

From Acute to Chronic: Unraveling the Pathophysiological Mechanisms of the Progression from Acute Kidney Injury to Acute Kidney Disease to Chronic Kidney Disease

This article provides a thorough overview of the biomarkers, pathophysiology, and molecular pathways involved in the transition from acute kidney injury (AKI) and acute kidney disease (AKD) to chronic kidney disease (CKD). It categorizes the biomarkers of AKI into stress, damage, and functional markers, highlighting their importance in early detection, prognosis, and clinical applications. This review also highlights the links between renal injury and the pathophysiological mechanisms underlying AKI and AKD, including renal hypoperfusion, sepsis, nephrotoxicity, and immune responses. In addition, various molecules play pivotal roles in inflammation and hypoxia, triggering maladaptive repair, mitochondrial dysfunction, immune system reactions, and the cellular senescence of renal cells. Key signaling pathways, such as Wnt/β-catenin, TGF-β/SMAD, and Hippo/YAP/TAZ, promote fibrosis and impact renal function. The renin-angiotensin-aldosterone system (RAAS) triggers a cascade leading to renal fibrosis, with aldosterone exacerbating the oxidative stress and cellular changes that promote fibrosis. The clinical evidence suggests that RAS inhibitors may protect against CKD progression, especially post-AKI, though more extensive trials are needed to confirm their full impact.

Discovery of dual-target natural inhibitors of meprins α and β metalloproteases for inflammation regulation: pharmacophore modelling, molecular docking, ADME prediction, and molecular dynamics studies

Meprins, zinc-dependent metalloproteinases belonging to the metzincin family, have been associated with various inflammatory diseases due to their abnormal expression and activity. In this study, we utilized pharmacophore modelling to identify crucial features for discovering potential dual inhibitors targeting meprins α and β. We screened four pharmacophoric features against a library of 270,540 natural compounds from the Zinc database, resulting in 84,092 matching compounds. Molecular docking was then performed on these compounds, targeting the active sites of meprins α and β. Docking results revealed six compounds capable of interacting with both isoforms, with binding affinities ranging from -10.0 to -10.5 kcal/mol and -6.9 to -9.9 kcal/mol for meprin α and β, respectively. Among these compounds, ZINC000008790788 and ZINC000095099469 displayed superior docking scores and MM-GBSA binding free energy compared to reference ligands. Furthermore, these two compounds exhibited acceptable predicted pharmacokinetic properties and stable interactions with meprins α and β during molecular dynamics simulations. This study presents a comprehensive approach for identifying potential dual inhibitors of meprin α and β, offering insights into the development of therapeutic interventions for inflammatory diseases associated with meprin dysregulation.

Effects of glutamine and n-3 polyunsaturated fatty acid mixed lipid emulsion supplementation of parenteral nutrition on sepsis score and bacterial clearance in early experimental sepsis

INTRODUCTION

Glutamine (GLN) and n-3 polyunsaturated fatty acids (n-3PUFAs) have been shown to potentially possess immune-modulating and disease-modifying properties in experimental and clinical critical illness when given with parenteral nutrition (PN). However, we recently showed in experimental cancer models that combinations of GLN/n-3 PUFA may antagonize benefits of either nutrient alone. Thus, our aim was to explore the effects of PN-containing GLN and n-3PUFA mixed lipid emulsion (MLE) alone and in combination in experimental sepsis.

METHODS

Adult male rats were exposed to cecal ligation and puncture (CLP) and sacrificed at 24 h. Rats were infused with either normal saline (NS); PN + Intralipid (PNcont); PN + GLN; PN + n-3PUFA MLE; or PN + GLN/n-3PUFA MLE after CLP-sepsis for 23 h. Animals were assessed at 24 h for sepsis score, Gram (+) and Gram (-) bacterial load in blood, peritoneum, and bronchoalveolar lavage fluid (BALF).

RESULTS

Rats treated with PN + GLN or PN + n-3PUFA showed significantly lower sepsis scores compared to NS and PNcont (all p ≤ 0.016). Non-significant trends to improved sepsis scores was observed in rats treated with PN + GLN/n-3PUFA versus NS (p = 0.067) or PNcont (p = 0.093). Rats treated with PN + GLN, PN + n-3PUFA, or PN + GLN/n-3PUFA had significant improvement or trends to improved Gram (+) and Gram (-) bacterial loads in BALF versus NS (p ≤ 0.05, PN + GLN and PN + GLN/n-3PUFA for Gram (+); p = 0.057, PN + n-3PUFA for Gram (+); p ≤ 0.05, n-3PUFA and PN + GLN/n-3PUFA for Gram (-)). No differences between groups in blood or peritoneal bacterial counts observed.

CONCLUSIONS

This data describes initial evidence that nutritional-doses of GLN, n-3PUFA MLE, and GLN + n-3PUFA MLE in PN can improve bacterial load/clearance in sepsis. Further, improvements of sepsis score by PN + n-3PUFA MLE and PN + GLN was observed. Previously observed antagonism of benefits of PN-containing GLN or n-3PUFAs alone by combinations of these nutrients was not observed in experimental sepsis. These results suggest further research is needed into PN-strategies using GLN and/or n-3PUFA at nutritional-doses in sepsis.

Multi-Omics Techniques Make it Possible to Analyze Sepsis-Associated Acute Kidney Injury Comprehensively

Sepsis-associated acute kidney injury (SA-AKI) is a common complication in critically ill patients with high morbidity and mortality. SA-AKI varies considerably in disease presentation, progression, and response to treatment, highlighting the heterogeneity of the underlying biological mechanisms. In this review, we briefly describe the pathophysiology of SA-AKI, biomarkers, reference databases, and available omics techniques. Advances in omics technology allow for comprehensive analysis of SA-AKI, and the integration of multiple omics provides an opportunity to understand the information flow behind the disease. These approaches will drive a shift in current paradigms for the prevention, diagnosis, and staging and provide the renal community with significant advances in precision medicine in SA-AKI analysis.

Meprin and ADAM proteases as triggers of systemic inflammation in sepsis

Systemic inflammatory disorders (SIDs) comprise a broad range of diseases characterized by dysregulated excessive innate immune responses. Severe forms of SIDs can lead to organ failure and death, and their increasing incidence represents a major issue for the healthcare system. Protease-mediated ectodomain shedding of cytokines and their receptors represents a central mechanism in the regulation of inflammatory responses. The metalloprotease A disintegrin and metalloproteinase (ADAM) 17 is the best-characterized ectodomain sheddase capable of releasing TNF-α and soluble IL-6 receptor, which are decisive factors of systemic inflammation. Recently, meprin metalloproteases were also identified as IL-6 receptor sheddases and activators of the pro-inflammatory cytokines IL-1β and IL-18. In different mouse models of SID, particularly those mimicking a sepsis-like phenotype, ADAM17 and meprins have been found to promote disease progression. In this review, we summarize the role of ADAM10, ADAM17, and meprins in the onset and progression of sepsis and discuss their potential as therapeutic targets.

The application of omic technologies to research in sepsis-associated acute kidney injury

Acute kidney injury (AKI) is common in critically ill children and adults, and sepsis-associated AKI (SA-AKI) is the most frequent cause of AKI in the ICU. To date, no mechanistically targeted therapeutic interventions have been identified. High-throughput "omic" technologies (e.g., genomics, proteomics, metabolomics, etc.) offer a new angle of approach to achieve this end. In this review, we provide an update on the current understanding of SA-AKI pathophysiology. Omic technologies themselves are briefly discussed to facilitate interpretation of studies using them. We next summarize the body of SA-AKI research to date that has employed omic technologies. Importantly, omic studies are helping to elucidate a pathophysiology of SA-AKI centered around cellular stress responses, metabolic changes, and dysregulation of energy production that underlie its clinical features. Finally, we propose opportunities for future research using clinically relevant animal models, integrating multiple omic technologies and ultimately progressing to translational human studies focusing therapeutic strategies on targeted disease mechanisms.

Reduced Expression of Extracellular Matrix Proteins in the Heart and Kidneys of Rats with Endotoxemia under the Effect of Actinonin

We studied modulation of the expression of extracellular matrix proteins under conditions of meprin inhibition in rats with LPS-induced endotoxemia. Endotoxemia increased the expression of type I, III, IV collagens and fibronectin in the renal tissue and type III and IV collagens in the heart. Meprin inhibitor actinonin reduced expression of both meprins and genes of extracellular matrix proteins, but the intensity of this effect in the heart and kidney was different. Inhibition of meprins in endotoxemia can prevent pathological remodeling of the extracellular matrix in the heart and kidney.

Simvastatin Posttreatment Controls Inflammation and Improves Bacterial Clearance in Experimental Sepsis

Sepsis is characterized by a life-threatening organ dysfunction caused by an unbalanced host response to microbe infection that can lead to death. Besides being currently the leading cause of death in intensive care units worldwide, sepsis can also induce long-term consequences among survivors, such as cognitive impairment. Statins (lipid-lowering drugs widely used to treat dyslipidemia) have been shown to possess pleiotropic anti-inflammatory and antimicrobial effects. These drugs act inhibiting 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, an enzyme that catalyzes the conversion of HMG-CoA to mevalonate, the limiting step in cholesterol biosynthesis. In this work, we evaluated the therapeutic effects of simvastatin in an animal model of sepsis. In previous study from our group, statin pretreatment avoided cognitive damage and neuroinflammation in sepsis survivors. Herein, we focused on acute inflammation where sepsis was induced by cecal ligation and puncture (CLP), and the animals were treated with simvastatin (2 mg/kg) 6 h after surgery. We measured plasma biochemical markers of organ dysfunction, cell migration, cell activation, bacterial elimination, production of nitric oxide 24 h after CLP, survival rate for 7 days, and cognitive impairment 15 days after CLP. One single administration of simvastatin 6 h after CLP was able to prevent both liver and kidney dysfunction. In addition, this drug decreased cell accumulation in the peritoneum as well as the levels of TNF-α, MIF, IL-6, and IL-1β. Simvastatin diminished the number of bacterial colony forming units (CFU) and increased the production of nitric oxide production in the peritoneum. Simvastatin treatment increased survival for the first 24 h, but it did not alter survival rate at the end of 7 days. Our results showed that posttreatment with simvastatin hampered organ dysfunction, increased local production of nitric oxide, improved bacterial clearance, and modulated inflammation in a relevant model of sepsis.

Klotho deficiency aggravates sepsis-related multiple organ dysfunction

Sepsis-induced organ failure is characterized by a massive inflammatory response and oxidative stress. Acute kidney injury (AKI) occurs in approximately half of patients in septic shock, and the mortality associated with sepsis-induced AKI is unacceptably high. Klotho is a protein expressed by renal cells and has anti-senescence properties. Klotho has also been shown to protect the kidneys in ischemia-reperfusion injury and to have antioxidant properties. To analyze the role of Klotho in sepsis-related organ dysfunction and AKI, we used a cecal ligation and puncture (CLP) model of sepsis in heterozygous Klotho-haploinsufficient mice and their wild-type littermates (CLP- Kl/+ and CLP-WT mice, respectively). In comparison with the CLP-WT mice, CLP- Kl/+ mice showed lower survival, impaired renal function, impaired hepatic function, greater oxidative stress, upregulation of inflammatory pathways (at the systemic and kidney tissue levels), and increased NF-κB activation. It is noteworthy that CLP- Kl/+ mice also showed lower heart-rate variability, less sympathetic activity, impaired baroreflex sensitivity to sodium nitroprusside, and a blunted blood pressure response to phenylephrine. We also demonstrated that sepsis creates a state of acute Klotho deficiency. Given that low Klotho expression exacerbates sepsis and multiple organ dysfunction, Klotho might play a protective role in sepsis, especially in elderly individuals in whom Klotho expression is naturally reduced.

Urinary proteome analysis of acute hypercoagulable state in rat model induced by ε-aminocaproic acid

The hypercoagulable state occurs in a group of prothrombotic disorders associated with an increased risk for thromboembolic events, but it is difficult to diagnose due to the lack of available biomarkers. This study aimed to investigate systematic changes of urinary proteome in acute hypercoagulable state induced by certain antifibrinolytics. To reduce the effects of both genetic and environmental factors on the urinary proteome, we used a rat model of acute hypercoagulable state induced by an antifibrinolytic agent ε-aminocaproic acid, resembling human hypercoagulable state. Urine samples were collected during acute hypercoagulable state for analysis by liquid chromatography-tandem mass spectrometry (LCMS/MS). Of 65 significantly changed proteins in acute hypercoagulable state, 38 proteins had human orthologs, and 18 proteins were identified as stable in normal human urine. None of the identified proteins have been found to be clotting factors, but 4 proteins are known to be involved in the regulation of blood coagulation factors. Two proteins were verified as the markers associated with acute hypercoagulable state by Western blot analysis. In addition, four common differential urinary proteins have been found in acute hypercoagulable state induced by another antifibrinolytics tranexamic acid. These four proteins are potential biomarkers for early diagnosis of hypercoagulable state to prevent the development of thrombotic diseases.

Proteomics analysis demonstrating rosmarinic acid suppresses cell growth by blocking the glycolytic pathway in human HepG2 cells

Rosmarinic acid (RA), isolated from herbal balm mint plants, has demonstrated potent anti-tumor properties against liver cancer. However, the precise underlying mechanisms remain unclear. This study aimed to investigate the molecular mechanisms of RA in HepG2 cells. RA anti-tumor activity was assessed using 3-(4,5-dimethylthiazol-2-yl)2,5-diphenyl-tetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays, and Hoechst 33258 staining. Apoptosis and the cell cycle distribution were evaluated by flow cytometry. A proteomics approach was used to identify differentially expressed proteins following RA treatment in HepG2 cells, and quantitative reverse transcription-quantitative polymerase chain reaction was used to validate the results. Bioinformatics analysis was also implemented to further understand the identified proteins, and western blotting was used to analyze the associated proteins. Our results suggested that RA treatment significantly inhibits the viability of HepG2 cells. The MTT and LDH assays indicated dose-dependent decreases in cell proliferation following RA treatment. Hoechst 33258 staining and flow cytometry analysis showed that RA exhibits an apoptosis-inducing effect and induces cell cycle arrest in G1. The proteomics analysis successfully identified 16 differentially expressed proteins. Bioinformatics analysis indicated that the identified proteins participated in several biological processes and exhibited various molecular functions, mainly related to inactivation of the glycolytic pathway. Further western blotting analysis showed that RA could downregulate the expression of glucose transporter-1 and hexokinase-2, leading to the suppression of glucose consumption and generation of lactate and ATP. Taken together, our study found that RA exhibits significant cytotoxic effects by inhibiting cell proliferation and inducing apoptosis and cell cycle arrest, possibly by blocking the glycolytic pathway in human HepG2 cells.

Gingerol suppresses sepsis-induced acute kidney injury by modulating methylsulfonylmethane and dimethylamine production

Acute kidney injury (AKI) and metabolic dysfunction are critical complications in sepsis syndrome; however, their pathophysiological mechanisms remain poorly understood. Therefore, we evaluated whether the pharmacological properties of 6-gingerol (6G) and 10-gingerol (10G) could modulate AKI and metabolic disruption in a rat model of sepsis (faecal peritonitis). Animals from the sham and AKI groups were intraperitoneally injected with 6G or 10G (25 mg/kg). Septic AKI decreased creatinine clearance and renal antioxidant activity, but enhanced oxidative stress and the renal mRNA levels of tumour necrosis factor-α, interleukin-1β, and transforming growth factor-β. Both phenol compounds repaired kidney function through antioxidant activity related to decreased oxidative/nitrosative stress and proinflammatory cytokines. Metabolomics analysis indicated different metabolic profiles for the sham surgery group, caecal ligation and puncture model alone group, and sepsis groups treated with gingerols. ¹H nuclear magnetic resonance analysis detected important increases in urinary creatine, allantoin, and dimethylglycine levels in septic rats. However, dimethylamine and methylsulfonylmethane metabolites were more frequently detected in septic animals treated with 6G or 10G, and were associated with increased survival of septic animals. Gingerols attenuated septic AKI by decreasing renal disturbances, oxidative stress, and inflammatory response through a mechanism possibly correlated with increased production of dimethylamine and methylsulfonylmethane.

Sepsis Through the Eyes of Proteomics: The Progress in the Last Decade

Sepsis is a systemic inflammatory response caused by infection whose molecular mechanisms are still not completely understood. The early detection of sepsis remains a great challenge for clinicians because no single biomarker capable of its reliable prediction, hence, delayed diagnosis frequently undermines treatment efforts, thereby contributing to high mortality. There are several experimental approaches used to reveal the molecular mechanism of sepsis progression. Proteomics coupled with mass spectrometry made possible to identify differentially expressed proteins in clinical samples. Recent advancement in liquid chromatography-based separation methods and mass spectrometers resolution and sensitivity with absolute quantitation methods, made possible to use proteomics as a powerful tool for study of clinical samples with higher coverage proteome profiles. In recent years, number of proteomic studies have been done under sepsis and/or in response to endotoxin and showed various signaling pathways, functions, and biomarkers. This review enlightened the proteomic progress in the last decade in sepsis.

Differentially expressed miRNAs in sepsis-induced acute kidney injury target oxidative stress and mitochondrial dysfunction pathways

Objective

To identify specific miRNAs involved in sepsis-induced AKI and to explore their targeting pathways.

Methods

The expression profiles of miRNAs in serum from patients with sepsis-induced AKI (n = 6), sepsis-non AKI (n = 6), and healthy volunteers (n = 3) were investigated by microarray assay and validated by quantitative PCR (qPCR). The targets of the differentially expressed miRNAs were predicted by Target Scan, mirbase and Miranda. Then the significant functions and involvement in signaling pathways of gene ontology (GO) and KEGG pathways were analyzed. Furthermore, eight miRNAs were randomly selected out of the differentially expressed miRNAs for further testing by qPCR.

Results

qPCR analysis confirmed that the expressions levels of hsa-miR-23a-3p, hsa-miR-4456, hsa-miR-142-5p, hsa-miR-22-3p and hsa-miR-191-5p were significantly lower in patients with sepsis compared with the healthy volunteers, while hsa-miR-4270, hsa-miR-4321, hsa-miR-3165 were higher in the sepsis patients. Statistically, miR-4321; miR-4270 were significantly upregulated in the sepsis-induced AKI compared with sepsis-non AKI, while only miR-4321 significantly overexpressed in the sepsis groups compared with control groups. GO analysis showed that biological processes regulated by the predicted target genes included diverse terms. They were related to kidney development, regulation of nitrogen compound metabolic process, regulation of cellular metabolic process, cellular response to oxidative stress, mitochondrial outer membrane permeabilization, etc. Pathway analysis showed that several significant pathways of the predicted target genes related to oxidative stress. miR-4321 was involved in regulating AKT1, mTOR and NOX5 expression while miR-4270 was involved in regulating PPARGC1A, AKT3, NOX5, PIK3C3, WNT1 expression. Function and pathway analysis highlighted the possible involvement of miRNA-deregulated mRNAs in oxidative stress and mitochondrial dysfunction.

Conclusion

This study might help to improve understanding of the relationship between serum miRNAs and sepsis-induced AKI, and laid an important foundation for further identification of the potential mechanisms of sepsis-induced AKI and oxidative stress and mitochondrial dysfunction.

Decreased Tissue COX5B Expression and Mitochondrial Dysfunction during Sepsis-Induced Kidney Injury in Rats

Background. Sepsis is defined as a life-threatening organ dysfunction due to a dysregulated host response to infection. Sepsis is the dominant cause of acute kidney injury (AKI), accounting for nearly 50% of episodes of acute renal failure. Signaling cascades and pathways within the kidney are largely unknown and analysis of these molecular mechanisms may enhance knowledge on pathophysiology and possible therapeutic options. Material and Methods. 26 male Wistar rats were assigned to either a sham group (control, N = 6) or sepsis group (N = 20; cecal ligature and puncture model, 24 and 48 hours after CLP). Surviving rats (n = 12) were decapitated at 24 hours (early phase; n = 6) or 48 hours (late phase; n = 6) after CLP and kidneys removed for proteomic analysis. 2D-DIGE and DeCyder 2D software (t-test, P < 0.01) were used for analysis of significantly regulated protein spots. MALDI-TOF in combination with peptide mass fingerprinting (PMF) as well as Western Blot analysis was used for protein identification. Bioinformatic network analyses (STRING, GeneMania, and PCViz) were used to describe protein-protein interactions. Results. 12 spots were identified with significantly altered proteins (P < 0.01) in the three analyzed groups. Two spots could not be identified. Four different proteins were found significantly changed among the groups: major urinary protein (MUP5), cytochrome c oxidase subunit B (COX5b), myosin-6 (MYH6), and myosin-7 (MYH7). A significant correlation with the proteins was found for mitochondrial energy production and electron transport. Conclusions. COX5B could be a promising biomarker candidate since a significant association was found during experimental sepsis in the present study. For future research, COX5B should be evaluated as a biomarker in both human urine and serum to identify sepsis.

The Specific α1-Adrenergic Receptor Antagonist Prazosin Influences the Urine Proteome

Urine, reflecting many changes in the body, is a better source than blood for biomarker discovery. However, even under physiological conditions, the urine proteome often varies. Understanding how various regulating factors affect urine proteome helps link changes to urine proteome with urinary biomarkers of physiological conditions as well as corresponding diseases. To evaluate the possible impact of α1-adrenergic receptor on urine proteome, this study investigated effects of the specific inhibitor prazosin on the urine proteome in a rat model by using tandem mass tagging and two-dimensional liquid chromatography-tandem mass spectrometry. A total of 775 proteins were identified, approximately half of which were influenced by prazosin treatment, indicating that the sympathetic nervous system exerts a significant impact on urine proteome. Eight significantly changed proteins were previously annotated as urinary candidate biomarkers. Angiotensinogen, haptoglobin, and beta-2 microglobulin, which were reported to be associated with blood pressure, were validated via Western blot. Prazosin is widely used in clinical practice; thus, these protein changes should be considered when studying corresponding diseases such as hypertension, post-traumatic stress disorder and benign prostatic hyperplasia. The related physiological activities of α1-receptors, controlling blood pressure and fear response might significantly affect the urine proteome and warrant further biomarker studies.

Proteomic analysis of apoptosis induction by lariciresinol in human HepG2 cells

Lariciresinol (LA) is a traditional Chinese medicine possessing anticancer activity, but its mechanism of action remains unclear. The present study explored the effects of LA on human HepG2 cells and the underlying mechanism. Our data indicated that LA inhibited cell proliferation and induced cell cycle arrest in S phase, subsequently resulting in apoptosis in HepG2 cells. Using a proteomics approach, eight differentially expressed proteins were identified. Among them, three proteins, glyceraldehyde-3-phosphate, UDP-glucose 4-epimerase, and annexin A1, were upregulated, while the other five proteins, heat shock protein 27, haptoglobin, tropomodulin-2, tubulin alpha-1A chain, and brain acid soluble protein 1, were downregulated; all of these proteins are involved in cell proliferation, metabolism, cytoskeletal organization, and movement. Network analysis of these proteins suggested that the ubiquitin-conjugating enzyme (UBC) plays an important role in the mechanism of LA. Western blotting confirmed downregulation of heat shock protein 27 and upregulation of ubiquitin and UBC expression levels in LA-treated cells, consistent with the results of two-dimensional electrophoresis and a STRING software-based analysis. Overall, LA is a multi-target compound with anti-cancer effects potentially related to the ubiquitin-proteasome pathway. This study will increase our understanding of the anticancer mechanisms of LA.

Genomic and Proteomic Characterization of Acute Kidney Injury

The incidence and severity of acute kidney injury (AKI) is rising globally, and the associated morbidity and mortality remain high despite promising advances in experimental therapeutics. The reasons include (a) an incomplete understanding of the complex pathophysiology, (b) an inability to reliably identify risk factors for AKI and (c) a lack of biomarkers for the early prediction of AKI and its outcomes. Functional genomics, bioinformatics and proteomics have begun to uncover candidates that are emerging as biomarkers and therapeutic targets. This review will update the reader on current technologies in genomics (including targeted sequencing, genome wide association studies and transcriptome profiling) and proteomics (including gel electrophoresis and mass spectrometry methods) and their application on human AKI.

Resveratrol attenuates lipopolysaccharide-induced acute kidney injury by suppressing inflammation driven by macrophages

SCOPE

Acute kidney injury (AKI) is the most frequent and serious complication in sepsis, a potentially deadly inflammatory response induced by bacterial, viral, or fungal infection. LPS-induced AKI is associated with an abnormal inflammatory response, including renal endothelial dysfunction and renal inflammation. Resveratrol, a natural phytoalexin with low toxicity and anti-inflammatory properties, is known to protect endothelial cells and modulate the immune response in sepsis.

METHODS AND RESULTS

This study investigates the potential protective effects of resveratrol on AKI induced by LPS exposure of mice. Resveratrol was administered as a pre- and posttreatment, or as a posttreatment alone following LPS injection and compared to control groups. Resveratrol significantly improved kidney function and lowered serum and kidney tissue inflammatory cytokine levels. Consistently, resveratrol prevented endotoxin-induced disruption of endothelial cell permeability and inhibited inflammation of kidney tissue. Resveratrol treatment attenuated the effects of LPS on macrophages, with significant inhibition of activation, cytokine release, and Toll-like receptor 4 activation. Resveratrol treatment also resulted in decreased expression of iNOS, Bcl-2, and Bcl-xL in macrophages, which was linked with induction of apoptosis in macrophages.

CONCLUSION

Our studies suggest that resveratrol might represent a novel therapeutic agent to prevent and treat sepsis-induced AKI.

Ultrasound Modulates the Splenic Neuroimmune Axis in Attenuating AKI

We showed previously that prior exposure to a modified ultrasound regimen prevents kidney ischemia-reperfusion injury (IRI) likely via the splenic cholinergic anti-inflammatory pathway (CAP) and α7 nicotinic acetylcholine receptors (α7nAChR). However, it is unclear how ultrasound stimulates the splenic CAP. Further investigating the role of the spleen in ischemic injury, we found that prior splenectomy (-7d) or chemical sympathectomy of the spleen with 6-hydroxydopamine (6OHDA; -14d) exacerbated injury after subthreshold (24-minute ischemia) IRI. 6-OHDA-induced splenic denervation also prevented ultrasound-induced protection of kidneys from moderate (26-minute ischemia) IRI. Ultrasound-induced protection required hematopoietic but not parenchymal α7nAChRs, as shown by experiments in bone marrow chimeras generated with wild-type and α7nAChR(-/-) mice. Ultrasound protection was associated with reduced expression of circulating and kidney-derived cytokines. However, splenocytes isolated from mice 24 hours after ultrasound treatment released more IL-6 ex vivo in response to LPS than splenocytes from sham mice. Adoptive transfer of splenocytes from ultrasound-treated (but not sham) mice to naïve mice was sufficient to protect kidneys of recipient mice from IRI. Ultrasound treatment 24 hours before cecal ligation puncture-induced sepsis was effective in reducing plasma creatinine in this model of AKI. Thus, splenocytes of ultrasound-treated mice are capable of modulating IRI in vivo, supporting our ongoing hypothesis that a modified ultrasound regimen has therapeutic potential for AKI and other inflammatory conditions.

Early-life course socioeconomic factors and chronic kidney disease

Kidney failure or ESRD affects approximately 650,000 Americans, whereas the number with earlier stages of CKD is much higher. Although CKD and ESRD are usually associated with adulthood, it is likely that the initial stages of CKD begin early in life. Many of these pathways are associated with low birth weight and disadvantaged socioeconomic status (SES) in childhood, translating childhood risk into later-life CKD and kidney failure. Social factors are thought to be fundamental causes of disease. Although the relationship between adult SES and CKD has been well established, the role of early childhood SES for CKD risk remains obscure. This review provides a rationale for examining the association between early-life SES and CKD. By collecting data on early-life SES and CKD, the interaction with other periods in the life course could also be studied, allowing for examination of whether SES trajectories (eg, poverty followed by affluence) or cumulative burden (eg, poverty at multiple time points) are more relevant to lifetime CKD risk.

Nucleolin identified by comparative mass‑spectra analysis is a potential marker for invasive progression of hepatocellular carcinoma

At present, the diagnosis and prognosis of hepatocellular carcinoma (HCC) metastasis remains poor. Recently, a number of proteins associated with the metastasis and invasion of HCC were identified; however, the effective markers require further elucidation. In the current study, a nucleolin expression was observed in MHCC97L and HCCLM9 HCC cell lines, with low and high metastatic potentials respectively, using comparative proteomics. The data indicated that nucleolin expression in the nucleus was significantly higher in HCCLM9 cells, and it primarily influenced the migration of HCC cells in vitro. Thus, to the best of our knowledge this is the first study to hypothesize that nucleolin may be a novel marker for HCC invasive progression.

The role of proteomics in understanding biological mechanisms of sepsis

Sepsis is a systemic inflammatory state caused by infection. Complications of this infection with multiple organ failure lead to more lethal conditions, such as severe sepsis and septic shock. Sepsis is one of the leading causes of US deaths. Novel biomarkers with high sensitivity and specificity may be helpful for early diagnosis of sepsis and for improvement of patient outcomes through the development of new therapies. Mass spectrometry-based proteomics offers powerful tools to identify such biomarkers and furthermore to give insight to fundamental mechanisms of this clinical condition. In this review, we summarize findings from proteomics studies of sepsis and how their applications have provided more understanding into the pathogenesis of septic infection. Literatures related to "proteomics", "sepsis", "systemic inflammatory response syndrome", "severe sepsis", "septic infection", and "multiple organ dysfunction syndrome" were searched using PubMed. Findings about neonatal and adult sepsis are discussed separately. Within the adult sepsis studies, results are grouped based on the models (e.g., human or animal). Across investigations in clinical populations and in rodent and mammalian animal models, biological pathways, such as inflammatory and acute phase response, coagulation, complement, mitochondrial energy metabolism, chaperones, and oxidative stress, are altered at the protein level. These proteomics studies have discovered many novel biomarker candidates of septic infection. Validation the clinical use of these biomarker candidates may significantly impact the diagnosis and prognosis of sepsis. In addition, the molecular mechanisms revealed by these studies may also guide the development of more effective treatments.

(Pro)renin receptor blocker improves survival of rats with sepsis

BACKGROUND

The renin-angiotensin system (RAS) affects inflammatory responses during sepsis. Nonproteolytic activation of prorenin by the (pro)renin receptor has recently been shown to stimulate the tissue RAS. In the present study, the effect of (pro)renin receptor blocker (PRRB) pretreatment on sepsis in a rat cecal ligation and puncture (CLP) model was investigated.

MATERIALS AND METHODS

Male Sprague-Dawley rats underwent CLP and were randomly divided into two groups: PRRB-treated group and control peptide-treated group. Survival was analyzed for 7 d after CLP. The serum concentrations of cytokines and high-mobility group box chromosomal protein 1 (HMGB1) were measured at three time points (0, 3, and 6 h after CLP). Hematoxylin-eosin staining and immunohistochemical staining for nonproteolytically activated prorenin and HMGB1 were performed on the cecum to assess pathologic changes found 6 h after CLP.

RESULTS

Treatment with PRRB improved the survival rate of the post-CLP septic rats (P = 0.023). PRRB also significantly reduced serum tumor necrosis factor-α, interleukin-1β, and HMGB1 levels 6 h after CLP. In CLP rats that were treated with control peptide, the expression of activated prorenin was elevated in peritoneal foam cells. Moreover, expression of HMGB1 was increased in peritoneal inflammatory cells. In contrast, both were markedly suppressed in CLP rats that were treated with PRRB.

CONCLUSIONS

PRRB significantly improved the survival rate of rats with clinically relevant sepsis, possibly by attenuating a sepsis-induced systemic inflammatory response. We propose that overactivation of the RAS by activation of prorenin in foam cells may be a significant contributor to sepsis.

The metalloproteases meprin α and meprin β: unique enzymes in inflammation, neurodegeneration, cancer and fibrosis

The metalloproteases meprin α and meprin β exhibit structural and functional features that are unique among all extracellular proteases. Although meprins were discovered more than 30 years ago, their precise substrates and physiological roles have been elusive. Both enzymes were originally found to be highly expressed in kidney and intestine, which focused research on these particular tissues and associated pathologies. Only recently it has become evident that meprins exhibit a much broader expression pattern, implicating functions in angiogenesis, cancer, inflammation, fibrosis and neurodegenerative diseases. Different animal models, as well as proteomics approaches for the identification of protease substrates, have helped to reveal more precise molecular signalling events mediated by meprin activity, such as activation and release of pro-inflammatory cytokines. APP (amyloid precursor protein) is cleaved by meprin β in vivo, reminiscent of the β-secretase BACE1 (β-site APP-cleaving enzyme 1). The subsequent release of Aβ (amyloid β) peptides is thought to be the major cause of the neurodegenerative Alzheimer's disease. On the other hand, ADAM10 (a disintegrin and metalloprotease domain 10), which is the constitutive α-secretase, was shown to be activated by meprin β, which is itself shed from the cell surface by ADAM10. In skin, both meprins are overexpressed in fibrotic tumours, characterized by massive accumulation of fibrillar collagens. Indeed, procollagen III is processed to its mature form by meprin α and meprin β, an essential step in collagen fibril assembly. The recently solved crystal structure of meprin β and the unique cleavage specificity of these proteases identified by proteomics will help to generate specific inhibitors that could be used as therapeutics to target meprins under certain pathological conditions.

Ischemic preconditioning attenuates lipid peroxidation and apoptosis in the cecal ligation and puncture model of sepsis

Sepsis and septic shock are are among the major causes of mortality in intensive care units. The lung and kidney are the organs most affected by sepsis. Evidence exists that lipid peroxidation and apoptosis may be responsible for the high mortality due to sepsis. Ischemic preconditioning (IP) is a method for the protection of tissues and organs against ischemia/reperfusion injury by reducing reactive oxygen species levels, lipid peroxidation and apoptosis. In the present study, the effects of IP were investigated in cecal ligation and puncture (CLP)-induced sepsis in rats. The three groups of animals used in the present controlled study were the sham-operated group (sham, n=7), which only underwent a laparotomy; the sepsis group (sepsis, n=7), which underwent cecal ligation and perforation; and the IP + sepsis group (IP+sepsis, n=7), which underwent CLP immediately prior to the application of three cycles of IP to the hind limb. The study was terminated at 6 h after the induction of CLP. Blood, kidney and lung tissue samples were collected for the determination of serum creatinine, blood urea nitrogen (BUN), neutrophil gelatinase-associated lipocalin (NGAL) and lung tissue malondialdehyde (MDA) levels, as well as histological examination. The serum creatinine, plasma NGAL and lung tissue MDA levels in the sepsis group were significantly increased compared with those in the sham and the IP+sepsis groups (P<0.05). Alveolar macrophage counts, histological kidney and lung injury scores, kidney (caspase 3) and lung tissue immuonreactivity (M30) scores in the sepsis group were also significantly increased compared with those in the sham and IP+sepsis groups (P<0.05). The alveolar macrophage count in the IP+sepsis group was increased compared with that in the sham group (P<0.05). In conclusion, IP inhibits lipid peroxidation and attenuates histological injury and apoptosis in the lung and kidney during sepsis.

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.

Small interfering RNA targeting Toll-like receptor 9 protects mice against polymicrobial septic acute kidney injury

BACKGROUND/AIMS

Although recent reports suggest that Toll-like receptor (TLR) 9 is associated with the pathogenesis of polymicrobial septic acute kidney injury (AKI), it is still unclear whether and how renal TLR9 is involved in the development of polymicrobial septic AKI. This study aimed to determine whether the expression of TLR9 in mouse renal cells is related to the development of polymicrobial septic AKI.

METHODS

The efficacy of small interfering RNA (siRNA) targeting TLR9 was tested in a cultured murine macrophage cell line (RAW264.7 cells). The most potent siRNA was transfected into mice using the hydrodynamic method prior to the induction of polymicrobial septic AKI being induced by cecal ligation and puncture (CLP). TLR9 knockdown was determined by real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting in RAW264.7 cells and kidney tissues. The levels of serum creatinine and blood urea nitrogen (BUN) and the renal histopathology assessment were determined at 6-, 12-, and 24-hour time points after CLP, and renal cell apoptosis was studied at 24 h. The 4- and 7-day survival rates of mice were also observed.

RESULTS

We found that mice developed AKI in our model of polymicrobial sepsis, despite fluid and antibiotic resuscitation, which resembles human sepsis. siRNA to TLR9 successfully silenced the induction of renal TLR9 gene and protein expression following CLP. Effective silencing of renal TLR9 expression decreased renal cell apoptosis, mitigated the severity of AKI, and increased the survival of mice.

CONCLUSIONS

Our data demonstrates the induction of TLR9 expression in mouse kidney tissue following CLP. Renal cell apoptosis and AKI in our model of polymicrobial sepsis are dependent on TLR9. Thus, TLR9 may play a critical role in the pathophysiology of polymicrobial septic AKI.

Meprin A metalloproteinase and its role in acute kidney injury

Meprin A, composed of α- and β-subunits, is a membrane-associated neutral metalloendoprotease that belongs to the astacin family of zinc endopeptidases. It was first discovered as an azocasein and benzoyl-l-tyrosyl-p-aminobenzoic acid hydrolase in the brush-border membranes of proximal tubules and intestines. Meprin isoforms are now found to be widely distributed in various organs (kidney, intestines, leukocytes, skin, bladder, and a variety of cancer cells) and are capable of hydrolyzing and processing a large number of substrates, including extracellular matrix proteins, cytokines, adherens junction proteins, hormones, bioactive peptides, and cell surface proteins. The ability of meprin A to cleave various substrates sheds new light on the functional properties of this enzyme, including matrix remodeling, inflammation, and cell-cell and cell-matrix processes. Following ischemia-reperfusion (IR)- and cisplatin-induced acute kidney injury (AKI), meprin A is redistributed toward the basolateral plasma membrane, and the cleaved form of meprin A is excreted in the urine. These studies suggest that altered localization and shedding of meprin A in places other than the apical membranes may be deleterious in vivo in acute tubular injury. These studies also provide new insight into the importance of a sheddase involved in the release of membrane-associated meprin A under pathological conditions. Meprin A is injurious to the kidney during AKI, as meprin A-knockout mice and meprin inhibition provide protective roles and improve renal function. Meprin A, therefore, plays an important role in AKI and potentially is a unique target for therapeutic intervention during AKI.

Redox proteomics in study of kidney-associated hypertension: new insights to old diseases

SIGNIFICANCE

The kidney helps to maintain low blood pressure in the human body, and impaired kidney function is a common attribute of aging that is often associated with high blood pressure (hypertension). Kidney-related pathologies are important contributors (either directly or indirectly) to overall human mortality. In comparison with other organs, kidney has an unusually wide range of oxidative status, ranging from the well-perfused cortex to near-anoxic medulla.

RECENT ADVANCES

Oxidative stress has been implicated in many kidney pathologies, especially chronic kidney disease, and there is considerable research interest in oxidative stress biomarkers for earlier prediction of disease onset. Proteomics approaches have been taken to study of human kidney tissue, serum/plasma, urine, and animal models of hypertension.

CRITICAL ISSUES

Redox proteomics, in which oxidative post-translational modifications can be identified in protein targets of oxidative or nitrosative stress, has not been very extensively pursued in this set of pathologies.

FUTURE DIRECTIONS

Proteomics studies of kidney and related tissues have relevance to chronic kidney disease, and redox proteomics, in particular, represents an under-exploited toolkit for identification of novel biomarkers in this commonly occurring pathology.

Severity of sepsis-induced acute kidney injury in a novel mouse model is age dependent

OBJECTIVE

Despite extensive research, the mortality rate of patients with sepsis-induced acute kidney injury (AKI) is unacceptably high, especially in the elderly. Current sepsis models have difficulties in reproducing AKI. This study aimed to develop a novel, clinically relevant mouse model for sepsis-induced AKI by uterine ligation and inoculation of bacteria. In addition, the age dependency of the severity of sepsis and sepsis-induced AKI was studied by validating this model in three different age categories.

DESIGN

Experimental animal investigation.

SETTING

University research laboratory.

SUBJECTS

Young (12-14 wks), aged (46-48 wks), and old (70-72 wks) C57BL/6 female mice were used as models for adolescent, adult premenopausal, and elderly postmenopausal women, respectively.

INTERVENTIONS

Uterine ligation and inoculation with 10 colony forming unit Escherichia coli or saline (sham) was performed; in vivo imaging with a luminescent Escherichia coli strain documented the course of infection.

MEASUREMENTS AND MAIN RESULTS

All mice had established Escherichia coli sepsis at 48 hrs postinfection, with higher mortality rate in old (43%) compared to aged (23%) or young (9%) mice. Infected mice had elevated serum or plasma cytokine, chemokine (tumor necrosis factor, interleukin-6, keratinocyte-derived chemokine, monocyte chemoattractant protein 1, and interleukin-10), and NOx concentrations compared to sham mice. AKI was confirmed by renal histology. Serum creatinine concentrations at 48 hrs increased with age (mean ± SEM; controls 0.18 ± 0.03 mg/dL, young 0.28 ± 0.03 mg/dL, aged 0.38 ± 0.05 mg/dL, and old 0.44 ± 0.06 mg/dL).

CONCLUSION

The uterine ligation and inoculation model for sepsis-induced AKI starts from a real infectious focus and shows an age-dependent severity of septic AKI that resembles AKI in humans.

Proteomics-based investigations of animal models of disease

Cells contain a large yet, constant genome, which contains all the coding information necessary to sustain cellular physiology. However, proteins are the end products of genes, and hence dictate the phenotype of cells and tissues. Therefore, proteomics can provide key information for the elucidation of physiological and pathophysiological mechanisms by identifying the protein profile from cells and tissues. The relatively novel techniques used for the study of proteomics thus have the potential to improve diagnostic, prognostic, as well as therapeutic avenues. In this review, we first discuss the benefits of animal models over the use of human samples for the proteomic analysis of human disease. Next, we aim to demonstrate the potential of proteomics in the elucidation of disease mechanisms that may not be possible by other conventional technologies. Following this, we describe the use of proteomics for the analysis of PTM and protein interactions in animal models and their relevance to the study of human disease. Finally, we discuss the development of clinical biomarkers for the early diagnosis of disease via proteomic analysis of animal models. We also discuss the development of standard proteomes and relate how this data will benefit future proteomic research. A comprehensive review of all animal models used in conjunction with proteomics is beyond the scope of this manuscript. Therefore, we aimed to cover a large breadth of topics, which together, demonstrate the potential of proteomics as a powerful tool in biomedical research.

Proteomic updates on sepsis

The increased knowledge regarding proteomic analysis techniques has allowed for better understanding of the molecular bases related to the identification of cell signaling, modifying protein, and post-translational modification pathways, in addition to the characterization of specific biological markers. Thus, documenting certain proteins expressed in sepsis is a promising approach to elucidate pathophysiological, diagnostic, therapeutic, and prognostic aspects in this condition with a purpose of applying them to clinical practice. Although the studies are still preliminary, proteomics may offer good benefits for the better management of septic patients. Thus, this article aims to introduce a short review of the applications of proteomic studies to sepsis.

Chemical proteomics: terra incognita for novel drug target profiling

The growing demand for new therapeutic strategies in the medical and pharmaceutic fields has resulted in a pressing need for novel druggable targets. Paradoxically, however, the targets of certain drugs that are already widely used in clinical practice have largely not been annotated. Because the pharmacologic effects of a drug can only be appreciated when its interactions with cellular components are clearly delineated, an integrated deconvolution of drug-target interactions for each drug is necessary. The emerging field of chemical proteomics represents a powerful mass spectrometry (MS)-based affinity chromatography approach for identifying proteome-wide small molecule-protein interactions and mapping these interactions to signaling and metabolic pathways. This technique could comprehensively characterize drug targets, profile the toxicity of known drugs, and identify possible off-target activities. With the use of this technique, candidate drug molecules could be optimized, and predictable side effects might consequently be avoided. Herein, we provide a holistic overview of the major chemical proteomic approaches and highlight recent advances in this area as well as its potential applications in drug discovery.

Pharmacological targets in the renal peritubular microenvironment: implications for therapy for sepsis-induced acute kidney injury

One of the most frequent and serious complications to develop in septic patients is acute kidney injury (AKI), a disorder characterized by a rapid failure of the kidneys to adequately filter the blood, regulate ion and water balance, and generate urine. AKI greatly worsens the already poor prognosis of sepsis and increases cost of care. To date, therapies have been mostly supportive; consequently there has been little change in the mortality rates over the last decade. This is due, at least in part, to the delay in establishing clinical evidence of an infection and the associated presence of the systemic inflammatory response syndrome and thus, a delay in initiating therapy. A second reason is a lack of understanding regarding the mechanisms leading to renal injury, which has hindered the development of more targeted therapies. In this review, we summarize recent studies, which have examined the development of renal injury during sepsis and propose how changes in the peritubular capillary microenvironment lead to and then perpetuate microcirculatory failure and tubular epithelial cell injury. We also discuss a number of potential therapeutic targets in the renal peritubular microenvironment, which may prevent or lessen injury and/or promote recovery.

Erythropoietin prevents sepsis-related acute kidney injury in rats by inhibiting NF-κB and upregulating endothelial nitric oxide synthase

The pathophysiology of sepsis involves complex cytokine and inflammatory mediator networks, a mechanism to which NF-κB activation is central. Downregulation of endothelial nitric oxide synthase (eNOS) contributes to sepsis-induced endothelial dysfunction. Erythropoietin (EPO) has emerged as a major tissue-protective cytokine in the setting of stress. We investigated the role of EPO in sepsis-related acute kidney injury using a cecal ligation and puncture (CLP) model. Wistar rats were divided into three primary groups: control (sham-operated); CLP; and CLP+EPO. EPO (4,000 IU/kg body wt ip) was administered 24 and 1 h before CLP. Another group of rats received N-nitro-l-arginine methyl ester (l-NAME) simultaneously with EPO administration (CLP+EPO+l-NAME). A fifth group (CLP+EPOtreat) received EPO at 1 and 4 h after CLP. At 48 h postprocedure, CLP+EPO rats presented significantly higher inulin clearance than did CLP and CLP+EPO+l-NAME rats; hematocrit levels, mean arterial pressure, and metabolic balance remained unchanged in the CLP+EPO rats; and inulin clearance was significantly higher in CLP+EPOtreat rats than in CLP rats. At 48 h after CLP, creatinine clearance was significantly higher in the CLP+EPO rats than in the CLP rats. In renal tissue, pre-CLP EPO administration prevented the sepsis-induced increase in macrophage infiltration, as well as preserving eNOS expression, EPO receptor (EpoR) expression, IKK-α activation, NF-κB activation, and inflammatory cytokine levels, thereby increasing survival. We conclude that this protection, which appears to be dependent on EpoR activation and on eNOS expression, is attributable, in part, to inhibition of the inflammatory response via NF-κB downregulation.

Chitinase-like proteins are candidate biomarkers for sepsis-induced acute kidney injury

Sepsis-induced acute kidney injury (AKI) is a frequent complication of critically ill patients and leads to high mortality rates. The specificity of currently available urinary biomarkers for AKI in the context of sepsis is questioned. This study aimed to discover urinary biomarkers for septic AKI by contemporary shotgun proteomics in a mouse model for sepsis and to validate these in individual urine samples of mice and human septic patients with and without AKI. At 48 h after uterine ligation and inoculation of Escherichia coli, aged mice (48 weeks) became septic. A subgroup developed AKI, defined by serum creatinine, blood urea nitrogen, and renal histology. Separate pools of urine from septic mice with and without AKI mice were collected during 12 h before and between 36-48 h after infection, and their proteome compositions were quantitatively compared. Candidate biomarkers were validated by Western blot analysis of urine, plasma, and renal tissue homogenates from individual mice, and a limited number of urine samples from human septic patients with and without AKI. Urinary neutrophil gelatinase-associated lipocalin, thioredoxin, gelsolin, chitinase 3-like protein 1 and -3 (CHI3L3) and acidic mammalian chitinase were the most distinctive candidate biomarkers selected for septic AKI. Both neutrophil gelatinase-associated lipocalin and thioredoxin were detected in urine of septic mice and increased with severity of AKI. Acidic mammalian chitinase was only present in urine of septic mice with AKI. Both urinary chitinase 3-like protein 1 and -3 were only detected in septic mice with severe AKI. The human homologue chitinase 3-like protein 1 was found to be more excreted in urine from septic patients with AKI than without. In summary, urinary chitinase 3-like protein 1 and -3 and acidic mammalian chitinase discriminated sepsis from sepsis-induced AKI in mice. Further studies of human chitinase proteins are likely to lead to additional insights in septic AKI.

Searching for mechanisms that matter in early septic acute kidney injury: an experimental study

Introduction

In almost half of all sepsis patients, acute kidney injury (AKI) develops. However, the pathobiologic differences between sepsis patients with and without AKI are only poorly understood. We used a unique opportunity to examine dynamic inflammatory, renal hemodynamic, and microvascular changes in two clinically relevant large-animal models of sepsis. Our aim was to assess variability in renal responses to sepsis and to identify both hemodynamic and nonhemodynamic mechanisms discriminating individuals with AKI from those in whom AKI did not develop.

Methods

Thirty-six pigs were anesthetized, mechanically ventilated, and instrumented. After a recovery period, progressive sepsis was induced either by peritonitis (n = 13) or by continuous intravenous infusion of live Pseudomonas aeruginosa (n = 15). Eight sham operated-on animals served as time-matched controls. All animals received standard intensive care unit (ICU) care, including goal-directed hemodynamic management. Before, and at 12, 18, and 22 hours of sepsis, systemic and renal (ultrasound flow probe) hemodynamics, renal cortex microcirculation (laser Doppler), inflammation (interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), oxidative stress (thiobarbituric acid reactive species (TBARS), nitrite/nitrate concentrations (NOx), and renal oxygen kinetics and energy metabolism were measured.

Results

In 14 (50%) pigs, AKI developed (62% in peritonitis, 40% in bacteria infusion model). Fecal peritonitis resulted in hyperdynamic circulation, whereas continuous bacteria infusion was associated with normodynamic hemodynamics. Despite insults of equal magnitude, comparable systemic hemodynamic response, and uniform supportive treatment, only those pigs with AKI exhibited a progressive increase in renal vascular resistance. This intrarenal vasoconstriction occurred predominantly in the live-bacteria infusion model. In contrast to AKI-free animals, the development of septic AKI was preceded by early and remarkable inflammatory response (TNF-α, IL-6) and oxidative stress (TBARS).

Conclusions

The observed variability in susceptibility to septic AKI in our models replicates that of human disease. Early abnormal host response accompanied by subsequent uncoupling between systemic and renal vascular resistance appear to be major determinants in the early phase of porcine septic AKI. Nonuniform and model-related renal hemodynamic responses that are unpredictable from systemic changes should be taken into consideration when evaluating hemodynamic therapeutic interventions in septic AKI.

Actinonin, a meprin A inhibitor, protects the renal microcirculation during sepsis

Sepsis-induced acute kidney injury occurs in 20% to 50% of septic patients and nearly doubles the mortality rate of sepsis. Because treatment in the septic patient is usually begun only after the onset of symptoms, therapy that is effective even when delayed would have the greatest impact on patient survival. The metalloproteinase meprin A, an oligomeric complex made of α- and β-subunits, is highly expressed at the brush-border membranes of the kidney and capable of degrading numerous substrates including extracellular matrix proteins and cytokines. The goal of the present study was to compare the therapeutic potential of actinonin, an inhibitor of meprin A, when administered before and after the onset of sepsis. Mice were treated with actinonin at 30 min before or 7 h after induction of sepsis by cecal ligation and puncture (CLP). Intravital videomicroscopy was used to image renal peritubular capillary perfusion and reactive nitrogen species. Actinonin treatment 30 min before CLP reduced IL-1β levels and prevented the fall in renal capillary perfusion at 7 and 18 h. Actinonin also prevented the fall in renal capillary perfusion even when administered at 7 h after CLP. In addition, even late administration of actinonin preserved renal morphology and lowered blood urea nitrogen and serum creatinine concentrations. These data suggest that agents such as actinonin should be evaluated further as possible therapeutic agents because targeting both the early systemic and later organ-damaging effects of sepsis should have the highest likelihood of success.

FLNA and PGK1 are two potential markers for progression in hepatocellular carcinoma

BACKGROUND/AIMS

Hepatocellular carcinoma (HCC) is one of the most deadly diseases; metastasis and recurrence are the most important factors that affect the therapy of HCC chronically. Until now, the prognosis for the metastasis of HCC had not improved. Recently, several proteins that are related to metastasis and invasion of HCC were identified, but the effective markers still remain to be elucidated.

METHODS

In this study, comparative proteomics was used to study the differentially expressed proteins in two HCC cell lines MHCC97L and HCCLM9, which have low and high metastatic potentials, respectively.

RESULTS

Our findings indicated that filamin A (FLNA) and phosphoglycerate kinase 1 (PGK1) were two significantly differentially expressed proteins, with high expression in HCCLM9 cells, and may influence the metastasis of HCC cells.

CONCLUSION

Taken together with the confirmation of expression on the mRNA level, we propose the use of FLNA and PGK1 as potential markers for the progression of HCC.

Identification of diagnostic urinary biomarkers for acute kidney injury

Acute kidney injury (AKI) is an important cause of death among hospitalized patients. The 2 most common causes of AKI are acute tubular necrosis (ATN) and prerenal azotemia (PRA). Appropriate diagnosis of the disease is important but often difficult. We analyzed urine proteins by 2-dimensional gel electrophoresis from 38 patients with AKI. Patients were randomly assigned to a training set, an internal test set, or an external validation set. Spot abundances were analyzed by artificial neural networks to identify biomarkers that differentiate between ATN and PRA. When the trained neural network algorithm was tested against the training data, it identified the diagnosis for 16 of 18 patients in the training set and all 10 patients in the internal test set. The accuracy was validated in the novel external set of patients where conditions of 9 of 10 patients were correctly diagnosed including 5 of 5 with ATN and 4 of 5 with PRA. Plasma retinol-binding protein was identified in 1 spot and a fragment of albumin and plasma retinol-binding protein in the other. These proteins are candidate markers for diagnostic assays of AKI.

Animal models of sepsis and sepsis-induced kidney injury

Sepsis is characterized by a severe inflammatory response to infection, and its complications, including acute kidney injury, can be fatal. Animal models that correctly mimic human disease are extremely valuable because they hasten the development of clinically useful therapeutics. Too often, however, animal models do not properly mimic human disease. In this Review, we outline a bedside-to-bench-to-bedside approach that has resulted in improved animal models for the study of sepsis - a complex disease for which preventive and therapeutic strategies are unfortunately lacking. We also highlight a few of the promising avenues for therapeutic advances and biomarkers for sepsis and sepsis-induced acute kidney injury. Finally, we review how the study of drug targets and biomarkers are affected by and in turn have influenced these evolving animal models.

Recent progress of proteomics in critical illness

Critical illness, such as sepsis or septic shock with multiple organ dysfunction syndrome, is the leading cause of morbidity and mortality in intensive care units. The complexity of critical illness requires a robust methodology to explore the underlying mechanisms. Proteomics represents a powerful postgenomic biotechnology used for simultaneous examination of a large number of proteins or the proteome. Recent progress in proteomic techniques allows thorough evaluation of molecular changes associated with critical illness, thereby permitting to identify novel biomarkers and therapeutic targets. This review provides an update on the recent progress and potential of rapidly evolving proteomics approach to facilitate new discoveries in the field of critical care medicine.

Interpreting the proteome and peptidome in transplantation

Publication of the human proteome has prompted efforts to develop high-throughput techniques that can catalogue and quantify proteins and peptides present in different tissue types. The field of proteomics aims to identify, quantify, analyze, and functionally define a large number of proteins in cellular processes in different disease states on a global scale. Peptidomics, a newer name in the -omics world, measures and identifies naturally occurring low molecular weight peptides, also providing an insight into enzymatic processes and molecular events occurring in the system of interest. One area of major interest is the use of proteomics to identify diagnostic and prognostic biomarkers for different diseases as well as for various clinical phenotypes in organ transplantation that can advance targeted therapy for various forms of graft injury. Outcomes in organ transplantation can be potentially improved by identifying noninvasive biomarkers that will serve as triggers that predate graft injury, and can offer a means to customize patient treatment by differentiating among causes of acute and chronic graft injury. Proteomic and peptidomic strategies can be harnessed for frequent noninvasive measurements in tissue fluids, allowing for serial monitoring of organ disease. In this review, we describe the basic techniques used in proteomic and peptidomic approaches, point out special considerations in using these methods, and discuss their applications in recently published studies in organ transplantation.