Inhibition of matrix metalloproteinases reduces ischemia-reperfusion acute kidney injury

Protein biomarkers in assessing kidney quality before transplantation‑current status and future perspectives (Review)

To meet the demand for kidney transplants (KTx), organs are frequently retrieved not only from standard criteria donors (SCD; a donor who is aged <50 years and suffered brain death from any number of causes, such as traumatic injuries or a stroke) but also from expanded criteria donors (any donor aged >60 years or donors aged >50 years with two of the following: A history of high blood pressure, a creatinine serum level ≥1.5 mg/dl or death resulting from a stroke). This comes at the cost of a higher risk of primary non‑function (the permanent hyperkalemia, hyperuremia and fluid overload that result in the need for continuous dialysis after KTx), delayed graft function (the need for dialysis session at least once during the first week after KTx), earlier graft loss and urinary complications (vesico‑ureteral reflux, obstruction of the vesico‑ureteral anastomosis, urine leakage). At present, there are no commercially available diagnostic tools for assessing kidney quality prior to KTx. Currently available predictive models based on clinical data, such as the Kidney Donor Profile Index, are insufficient. One promising option is the application of perfusion solutions for protein biomarkers of kidney quality and predictors of short‑ and long‑term outcomes. However, to date, protein markers that can be detected with ELISA, western blotting and cytotoxic assays have not been identified to be a beneficial predictors of kidney quality. These include lactate dehydrogenases, glutathione S‑transferases, fatty acid binding proteins, extracellular histones, IL‑18, neutrophil gelatinase‑associated lipocalin, MMPs and kidney injury molecule‑1. However, novel methods, including liquid chromatography‑mass spectrometry (LC‑MS) and microarrays, allow the analysis of all renal proteins suspended/dissolved in the acellular preservation solution used for kidney storage before KTx (including hypothermic machine perfusion as one of kidney storage methods) e.g. Belzer University of Wisconsin. Recent proteomic studies utilizing LC‑MS have identified complement pathway elements (C3, C1QB, C4BPA, C1S, C1R and C1RL), desmoplakin, blood coagulation pathway elements and immunoglobulin heavy variable 2‑26 to be novel predictors of kidney quality before transplantation. This was because they were found to correlate with estimated glomerular filtration rate at 3 and 12 months after kidney transplantation. However, further proteomic studies focusing on distinct markers obtained from hypothermic and normothermic machine perfusion are needed to confirm their predictive value and to improve kidney storage methods. Therefore, the present literature review from PubMed, Scopus, Embase and Web of Science was performed with the aims of summarizing the current knowledge on the most frequently studied single protein biomarkers. In addition, novel analytical methods and insights into organ injury during preservation were documented, where future directions in assessing organ quality before kidney transplantation were also discussed.

Dual-responsive renal injury cells targeting nanoparticles for vitamin E delivery to treat ischemia reperfusion-induced acute kidney injury

Ischemia/reperfusion (I/R) is an important inducer of acute kidney injury (AKI), and triggers the generation of reactive oxygen species (ROS) and the expression of matrix metalloproteinase 2 (MMP2), exacerbating kidney damage. Given the immense potential of vitamin E (VitE) as a natural fat-soluble antioxidant in kidney protection, we designed the nanoparticles (NPs) that could dual respond to ROS and MMP2, aiming to accurately deliver VitE to renal injury cells. The NPs utilized Gel-SH as a sensitive receptor for MMP2 and diselenide as a sensitive receptor for ROS, while PEG2k modification enhanced biocompatibility and prevented phagocytosis mediated by the mononuclear phagocyte system. The amphiphilic Gel-SH and diselenide encapsulate the liposoluble VitE and self-assemble into the NPs with a hydrodynamic size of 69.92 nm. Both in vivo and in vitro experiments based on these NPs show good biocompatibility and the ability of target renal injury cells. In vivo kidney I/R injury models and in vitro cell hypoxia/reoxygenation models, the NPs have demonstrated effects in reducing oxidative stress and alleviating AKI. Notably, VitE can preferentially react with peroxyl radical (LOO•) than polyunsaturated fatty acid (PUFA), inhibiting the formation of carbon centered radical (L•), thereby blocking the chain reaction between PUFA and LOO• in ferroptosis. The NPs also inhibit the transition from AKI to chronic kidney disease, with few side effects. Thus, the NPs with dual-responsiveness to MMP2 and ROS for targeted delivery of VitE to renal injury cells exhibit remarkable effects in inhibiting ROS and the chain reactions of ferroptosis, making it a promising therapeutic agent against AKI caused by I/R.

Protective effects of pioglitazone in renal ischemia-reperfusion injury (RIRI): focus on oxidative stress and inflammation

BACKGROUND

Renal ischemia-reperfusion injury (RIRI) is a critical phenomenon that compromises renal function and is the most serious health concern related to acute kidney injury (AKI). Pioglitazone (Pio) is a known agonist of peroxisome proliferator-activated receptor-gamma (PPAR-γ). PPAR-γ is a nuclear receptor that regulates genes involved in inflammation, metabolism, and cellular differentiation. Activation of PPAR-γ is associated with antiinflammatory and antioxidant effects, which are relevant to the pathophysiology of RIRI. This study aimed to investigate the protective effects of Pio in RIRI, focusing on oxidative stress and inflammation.

METHODS

We conducted a comprehensive literature search using electronic databases, including PubMed, ScienceDirect, Web of Science, Scopus, and Google Scholar.

RESULTS

The results of this study demonstrated that Pio has antioxidant, anti-inflammatory, and anti-apoptotic activities that counteract the consequences of RIRI. The study also discussed the underlying mechanisms, including the modulation of various pathways such as TNF-α, NF-κB signaling systems, STAT3 pathway, KIM-1 and NGAL pathways, AMPK phosphorylation, and autophagy flux. Additionally, the study presented a summary of various animal studies that support the potential protective effects of Pio in RIRI.

CONCLUSION

Our findings suggest that Pio could protect the kidneys from RIRI by improving antioxidant capacity and decreasing inflammation. Therefore, these findings support the potential of Pio as a therapeutic strategy for preventing RIRI in different clinical conditions.

Complex Pathophysiology of Acute Kidney Injury (AKI) in Aging: Epigenetic Regulation, Matrix Remodeling, and the Healing Effects of H2S

The kidney is an essential excretory organ that works as a filter of toxins and metabolic by-products of the human body and maintains osmotic pressure throughout life. The kidney undergoes several physiological, morphological, and structural changes with age. As life expectancy in humans increases, cell senescence in renal aging is a growing challenge. Identifying age-related kidney disorders and their cause is one of the contemporary public health challenges. While the structural abnormalities to the extracellular matrix (ECM) occur, in part, due to changes in MMPs, EMMPRIN, and Meprin-A, a variety of epigenetic modifiers, such as DNA methylation, histone alterations, changes in small non-coding RNA, and microRNA (miRNA) expressions are proven to play pivotal roles in renal pathology. An aged kidney is vulnerable to acute injury due to ischemia-reperfusion, toxic medications, altered matrix proteins, systemic hemodynamics, etc., non-coding RNA and miRNAs play an important role in renal homeostasis, and alterations of their expressions can be considered as a good marker for AKI. Other epigenetic changes, such as histone modifications and DNA methylation, are also evident in AKI pathophysiology. The endogenous production of gaseous molecule hydrogen sulfide (H2S) was documented in the early 1980s, but its ameliorative effects, especially on kidney injury, still need further research to understand its molecular mode of action in detail. H2S donors heal fibrotic kidney tissues, attenuate oxidative stress, apoptosis, inflammation, and GFR, and also modulate the renin-angiotensin-aldosterone system (RAAS). In this review, we discuss the complex pathophysiological interplay in AKI and its available treatments along with future perspectives. The basic role of H2S in the kidney has been summarized, and recent references and knowledge gaps are also addressed. Finally, the healing effects of H2S in AKI are described with special emphasis on epigenetic regulation and matrix remodeling.

Renal macrophages and NLRP3 inflammasomes in kidney diseases and therapeutics

Macrophages are exceptionally diversified cell types and perform unique features and functions when exposed to different stimuli within the specific microenvironment of various kidney diseases. In instances of kidney tissue necrosis or infection, specific patterns associated with damage or pathogens prompt the development of pro-inflammatory macrophages (M1). These M1 macrophages contribute to exacerbating tissue damage, inflammation, and eventual fibrosis. Conversely, anti-inflammatory macrophages (M2) arise in the same circumstances, contributing to kidney repair and regeneration processes. Impaired tissue repair causes fibrosis, and hence macrophages play a protective and pathogenic role. In response to harmful stimuli within the body, inflammasomes, complex assemblies of multiple proteins, assume a pivotal function in innate immunity. The initiation of inflammasomes triggers the activation of caspase 1, which in turn facilitates the maturation of cytokines, inflammation, and cell death. Macrophages in the kidneys possess the complete elements of the NLRP3 inflammasome, including NLRP3, ASC, and pro-caspase-1. When the NLRP3 inflammasomes are activated, it triggers the activation of caspase-1, resulting in the release of mature proinflammatory cytokines (IL)-1β and IL-18 and cleavage of Gasdermin D (GSDMD). This activation process therefore then induces pyroptosis, leading to renal inflammation, cell death, and renal dysfunction. The NLRP3-ASC-caspase-1-IL-1β-IL-18 pathway has been identified as a factor in the development of the pathophysiology of numerous kidney diseases. In this review, we explore current progress in understanding macrophage behavior concerning inflammation, injury, and fibrosis in kidneys. Emphasizing the pivotal role of activated macrophages in both the advancement and recovery phases of renal diseases, the article delves into potential strategies to modify macrophage functionality and it also discusses emerging approaches to selectively target NLRP3 inflammasomes and their signaling components within the kidney, aiming to facilitate the healing process in kidney diseases.

Myeloid PFKFB3-mediated glycolysis promotes kidney fibrosis

Excessive renal fibrosis is a common pathology in progressive chronic kidney diseases. Inflammatory injury and aberrant repair processes contribute to the development of kidney fibrosis. Myeloid cells, particularly monocytes/macrophages, play a crucial role in kidney fibrosis by releasing their proinflammatory cytokines and extracellular matrix components such as collagen and fibronectin into the microenvironment of the injured kidney. Numerous signaling pathways have been identified in relation to these activities. However, the involvement of metabolic pathways in myeloid cell functions during the development of renal fibrosis remains understudied. In our study, we initially reanalyzed single-cell RNA sequencing data of renal myeloid cells from Dr. Denby's group and observed an increased gene expression in glycolytic pathway in myeloid cells that are critical for renal inflammation and fibrosis. To investigate the role of myeloid glycolysis in renal fibrosis, we utilized a model of unilateral ureteral obstruction in mice deficient of Pfkfb3, an activator of glycolysis, in myeloid cells (Pfkfb3 ΔMϕ ) and their wild type littermates (Pfkfb3 WT). We observed a significant reduction in fibrosis in the obstructive kidneys of Pfkfb3 ΔMϕ mice compared to Pfkfb3 WT mice. This was accompanied by a substantial decrease in macrophage infiltration, as well as a decrease of M1 and M2 macrophages and a suppression of macrophage to obtain myofibroblast phenotype in the obstructive kidneys of Pfkfb3 ΔMϕ mice. Mechanistic studies indicate that glycolytic metabolites stabilize HIF1α, leading to alterations in macrophage phenotype that contribute to renal fibrosis. In conclusion, our study implicates that targeting myeloid glycolysis represents a novel approach to inhibit renal fibrosis.

PROPHYLACTIC n CMT-3 ATTENUATES SEPSIS-INDUCED ACUTE KIDNEY INJURY IN ASSOCIATION WITH NLRP3 INFLAMMASOME ACTIVATION AND APOPTOSIS

ABSTRACT

Background: The kidney is the most common extrapulmonary organ injured in sepsis. The current study examines the ability of aerosolized nanochemically modified tetracycline 3 (nCMT-3), a pleiotropic anti-inflammatory agent, to attenuate acute kidney injury (AKI) caused by intratracheal LPS. Methods: C57BL/6 mice received aerosolized intratracheal nCMT-3 (1 mg/kg) or saline, followed by intratracheal LPS (2.5 mg/kg) to induce acute lung injury-induced AKI. Tissues were harvested at 24 h. The effects of nCMT-3 and LPS on AKI were assessed by plasma/tissue levels of serum urea nitrogen, creatinine, neutrophil gelatinase-associated lipocalin, kidney injury molecule 1, and renal histology. Renal matrix metalloproteinase (MMP) level/activity, cytochrome C, Bax, Bcl-2, caspase-3, p38 mitogen-activated protein kinase activation, NLRP3, and caspase-1 were also measured. Apoptotic cells in kidney were determined by TUNEL assay. Renal levels of IL-1β and IL-6 were measured to assess inflammation. Results: Acute lung injury-induced AKI was characterized by increased plasma blood urea nitrogen, creatinine, injury biomarkers (neutrophil gelatinase-associated lipocalin, kidney injury molecule 1), and histologic evidence of renal injury. Lipopolysaccharide-treated mice demonstrated renal injury with increased levels of inflammatory cytokines (IL-1β, IL-6), active MMP-2 and MMP-9, proapoptotic proteins (cytochrome C, Bax/Bcl-2 ratio, cleaved caspase-3), apoptotic cells, inflammasome activation (NLRP3, caspase-1), and p38 signaling. Intratracheal nCMT-3 significantly attenuated all the measured markers of renal injury, inflammation, and apoptosis. Conclusions: Pretreatment with aerosolized nCMT-3 attenuates LPS-induced AKI by inhibiting renal NLRP3 inflammasome activation, renal inflammation, and apoptosis.

Low dimensional nanomaterials for treating acute kidney injury

Acute kidney injury (AKI) is one of the most common severe complications among hospitalized patients. In the absence of specific drugs to treat AKI, hemodialysis remains the primary clinical treatment for AKI patients. AKI treatment has received significant attention recently due to the excellent drug delivery capabilities of low-dimensional nanomaterials (LDNs) and their unique therapeutic effects. Diverse LDNs have been proposed to treat AKI, with promising results and the potential for future clinical application. This article aims to provide an overview of the pathogenesis of AKI and the recent advances in the treatment of AKI using different types of LDNs. In addition, it is intended to provide theoretical support for the design of LDNs and implications for AKI treatment.

Obeticholic Acid Reduces Kidney Matrix Metalloproteinase Activation following Partial Hepatic Ischemia/Reperfusion Injury in Rats

We have previously demonstrated that the farnesoid X receptor (FXR) agonist obeticholic acid (OCA) protects the liver via downregulation of hepatic matrix metalloproteinases (MMPs) after ischemia/reperfusion (I/R), which can lead to multiorgan dysfunction. The present study investigated the capacity of OCA to modulate MMPs in distant organs such as the kidney. Male Wistar rats were dosed orally with 10 mg/kg/day of OCA (5 days) and were subjected to 60-min partial hepatic ischemia. After 120-min reperfusion, kidney biopsies (cortex and medulla) and blood samples were collected. Serum creatinine, kidney MMP-2, and MMP-9-dimer, tissue inhibitors of MMPs (TIMP-1, TIMP-2), RECK, TNF-alpha, and IL-6 were monitored. MMP-9-dimer activity in the kidney cortex and medulla increased after hepatic I/R and a reduction was detected in OCA-treated I/R rats. Although not significantly, MMP-2 activity decreased in the cortex of OCA-treated I/R rats. TIMPs and RECK levels showed no significant differences among all groups considered. Serum creatinine increased after I/R and a reduction was detected in OCA-treated I/R rats. The same trend occurred for tissue TNF-alpha and IL-6. Although the underlying mechanisms need further investigation, this is the first study showing, in the kidney, beneficial effects of OCA by reducing TNF-alpha-mediated expression of MMPs after liver I/R.

Early Treatment of Acute Myocardial Infarction with Melatonin: Effects on MMP-9 and Adverse Cardiac Events

Background: Matrix metalloproteinase-9 (MMP-9) is crucial in tissue remodeling after an adverse cardiac event. In experimental studies, melatonin has been found to attenuate MMP-9 activation. The present study assessed the effects of systemic melatonin administration on the prognosis of patients with acute myocardial infarction (AMI) successfully treated with primary percutaneous coronary intervention, and to examine the effects on MMP-9 levels. Methods: We conducted a randomized controlled trial, enrolling patients who underwent primary percutaneous coronary intervention due to AMI. They were assigned to two groups for melatonin or placebo. The primary endpoint was a combined event of mortality and heart failure readmission at 2 years. The secondary endpoint was the levels of MMP-9 after the percutaneous coronary intervention. Results: Ninety-four patients were enrolled, 45 in the melatonin group and 49 in the control group. At 2 years of follow-up, 13 (13.8%) patients suffered the primary endpoint (3 deaths and 10 readmissions due to heart failure), 3 patients in the melatonin group and 10 in the placebo group. The difference in the restricted mean survival time was 87.5 days (p = 0.02); HR = 0.3 (95% CI 0.08–1.08; p = 0.06); Log-rank test 0.04. After controlling for confounding variables, melatonin administration reduced MMP-9 levels to 90 ng/mL (95% CI 77.3–102.6). Conclusions: This pilot study demonstrated that compared to placebo, melatonin administration was associated with better outcomes in AMI patients undergoing primary percutaneous coronary intervention.

Ex-vivo Kidney Machine Perfusion: Therapeutic Potential

Kidney transplantation remains the gold standard treatment for patients suffering from end-stage kidney disease. To meet the constantly growing organ demands grafts donated after circulatory death (DCD) or retrieved from extended criteria donors (ECD) are increasingly utilized. Not surprisingly, usage of those organs is challenging due to their susceptibility to ischemia-reperfusion injury, high immunogenicity, and demanding immune regulation after implantation. Lately, a lot of effort has been put into improvement of kidney preservation strategies. After demonstrating a definite advantage over static cold storage in reduction of delayed graft function rates in randomized-controlled clinical trials, hypothermic machine perfusion has already found its place in clinical practice of kidney transplantation. Nevertheless, an active investigation of perfusion variables, such as temperature (normothermic or subnormothermic), oxygen supply and perfusate composition, is already bringing evidence that ex-vivo machine perfusion has a potential not only to maintain kidney viability, but also serve as a platform for organ conditioning, targeted treatment and even improve its quality. Many different therapies, including pharmacological agents, gene therapy, mesenchymal stromal cells, or nanoparticles (NPs), have been successfully delivered directly to the kidney during ex-vivo machine perfusion in experimental models, making a big step toward achievement of two main goals in transplant surgery: minimization of graft ischemia-reperfusion injury and reduction of immunogenicity (or even reaching tolerance). In this comprehensive review current state of evidence regarding ex-vivo kidney machine perfusion and its capacity in kidney graft treatment is presented. Moreover, challenges in application of these novel techniques in clinical practice are discussed.

Matrix metalloproteinases and tissue inhibitors of matrix metalloproteinases in kidney disease

Matrix metalloproteinases (MMPs) are a group of zinc and calcium endopeptidases which cleave extracellular matrix (ECM) proteins. They are also involved in the degradation of cell surface components and regulate multiple cellular processes, cell to cell interactions, cell proliferation, and cell signaling pathways. MMPs function in close interaction with the endogenous tissue inhibitors of matrix metalloproteinases (TIMPs), both of which regulate cell turnover, modulate various growth factors, and participate in the progression of tissue fibrosis and apoptosis. The multiple roles of MMPs and TIMPs are continuously elucidated in kidney development and repair, as well as in a number of kidney diseases. This chapter focuses on the current findings of the significance of MMPs and TIMPs in a wide range of kidney diseases, whether they result from kidney tissue changes, hemodynamic alterations, tubular epithelial cell apoptosis, inflammation, or fibrosis. In addition, the potential use of these endopeptidases as biomarkers of renal dysfunction and as targets for therapeutic interventions to attenuate kidney disease are also explored in this review.

The Role of Macrophages in Kidney Fibrosis

The phenotypic heterogeneity and functional diversity of macrophages confer on them complexed roles in the development and progression of kidney diseases. After kidney injury, bone marrow-derived monocytes are rapidly recruited to the glomerulus and tubulointerstitium. They are activated and differentiated on site into pro-inflammatory M1 macrophages, which initiate Th1-type adaptive immune responses and damage normal tissues. In contrast, anti-inflammatory M2 macrophages induce Th2-type immune responses, secrete large amounts of TGF-β and anti-inflammatory cytokines, transform into αSMA+ myofibroblasts in injured kidney, inhibit immune responses, and promote wound healing and tissue fibrosis. Previous studies on the role of macrophages in kidney fibrosis were mainly focused on inflammation-associated injury and injury repair. Apart from macrophage-secreted profibrotic cytokines, such as TGF-β, evidence for a direct contribution of macrophages to kidney fibrosis is lacking. However, under inflammatory conditions, Wnt ligands are derived mainly from macrophages and Wnt signaling is central in the network of multiple profibrotic pathways. Largely underinvestigated are the direct contribution of macrophages to profibrotic signaling pathways, macrophage phenotypic heterogeneity and functional diversity in relation to kidney fibrosis, and on their cross-talk with other cells in profibrotic signaling networks that cause fibrosis. Here we aim to provide an overview on the roles of macrophage phenotypic and functional diversity in their contribution to pro-fibrotic signaling pathways, and on the therapeutic potential of targeting macrophages for the treatment of kidney fibrosis.

Key metalloproteinase-mediated pathways in the kidney

Matrix metalloproteinases (MMPs) and a disintegrin and metalloproteinases (ADAMs) belong to the metzincin family of zinc-containing multidomain molecules, and can act as soluble or membrane-bound proteases. These enzymes inactivate or activate other soluble or membrane-expressed mediator molecules, which enables them to control developmental processes, tissue remodelling, inflammatory responses and proliferative signalling pathways. The dysregulation of MMPs and ADAMs has long been recognized in acute kidney injury and in chronic kidney disease, and genetic targeting of selected MMPs and ADAMs in different mouse models of kidney disease showed that they can have detrimental and protective roles. In particular, MMP-2, MMP-7, MMP-9, ADAM10 and ADAM17 have been shown to have a mainly profibrotic effect and might therefore represent therapeutic targets. Each of these proteases has been associated with a different profibrotic pathway that involves tissue remodelling, Wnt-β-catenin signalling, stem cell factor-c-kit signalling, IL-6 trans-signalling or epidermal growth factor receptor (EGFR) signalling. Broad-spectrum metalloproteinase inhibitors have been used to treat fibrotic kidney diseases experimentally but more targeted approaches have since been developed, including inhibitory antibodies, to avoid the toxic side effects initially observed with broad-spectrum inhibitors. These advances not only provide a solid foundation for additional preclinical studies but also encourage further translation into clinical research.

The Association of Matrix Metalloproteinases With Acute Kidney Injury Following CPB-Supported Cardiac Surgery

BACKGROUND

Cardiac surgery-associated acute kidney injury (AKI) is an adverse outcome that increases morbidity and mortality in patients undergoing cardiac surgical procedures. To date, the use of serum creatinine levels as an early indicator of AKI has limitations because of its slow rise and poor predictive accuracy for renal injury. This delay in diagnosis may lead to prolonged initiation in treatment and increased risk for adverse outcomes.

OBJECTIVE

This pilot study explores serum and urine matrix metalloproteinases (MMPs)-2 and MMP-9 and their association, and potentially earlier detection of AKI in patients following cardiopulmonary bypass (CPB)-supported cardiac surgery. We hypothesize that increased activity of serum and urine levels MMP-2 and/ or MMP-9 are associated with AKI. Furthermore, MMP-2 and/ or MMP-9 may provide earlier identification of AKI as compared with serum levels of creatinine.

METHODS

During the study period, there were 150 CPB-supported surgeries, 21 of which developed AKI according to the Kidney Disease Improving Global Outcomes criteria. We then selected a sample of 21 matched cases from those patients who went through the surgery without developing AKI. Primary outcomes were the measurement via gel zymography of the serum and urine activity of MMP-2 and MMP-9 drawn at the following intervals: pre-CPB; 10-minute post-CPB; and 4-hour post-CPB time points. Secondary variables were the measurement of serum creatinine, intensive care unit (ICU) fluid balance, and length of ICU stay.

RESULTS

At the 10-minute and 4-hour post-CPB time points, the serum MMP-2 activity of AKI patients were significantly higher as compared with non-AKI patients (P < .001 and P = .004), respectively. Similarly, at the 10-minute and 4-hour post-CPB time points, the serum MMP-9 activity of AKI patients was significantly higher as compared with non-AKI patients (P = .001 and P = .014), respectively. The activity of urine MMP-2 and MMP-9 of AKI patients was significantly higher as compared with non-AKI patients at all 3 time points (P = .004, P < .001, P < .001), respectively.

CONCLUSION

Although the pilot study may have limitations, it has demonstrated that the serum and urine levels of activity of MMP-2 and MMP-9 are associated with the clinical endpoint of AKI and appear to have earlier rising levels as compared with those of serum creatinine. Furthermore, in depth, exploration is underway with a larger sample size to attempt validation of the analytical performance and reproducibility of the assay for MMP-2 and MMP-9 to aid in earlier diagnosis of AKI following CPB-supported cardiac surgery.

The Endothelial Glycocalyx as a Target of Ischemia and Reperfusion Injury in Kidney Transplantation-Where Have We Gone So Far?

The damage of the endothelial glycocalyx as a consequence of ischemia and/or reperfusion injury (IRI) following kidney transplantation has come at the spotlight of research due to potential associations with delayed graft function, acute rejection as well as long-term allograft dysfunction. The disintegration of the endothelial glycocalyx induced by IRI is the crucial event which exposes the denuded endothelial cells to further inflammatory and oxidative damage. The aim of our review is to present the currently available data regarding complex links between shedding of the glycocalyx components, like syndecan-1, hyaluronan, heparan sulphate, and CD44 with the activation of intricate immune system responses, including toll-like receptors, cytokines and pro-inflammatory transcription factors. Evidence on modes of protection of the endothelial glycocalyx and subsequently maintenance of endothelial permeability as well as novel nephroprotective molecules such as sphingosine-1 phosphate (S1P), are also depicted. Although advances in technology are making the visualization and the analysis of the endothelial glycocalyx possible, currently available evidence is mostly experimental. Ongoing progress in understanding the complex impact of IRI on the endothelial glycocalyx, opens up a new era of research in the field of organ transplantation and clinical studies are of utmost importance for the future.

Pre-arrest doxycycline protects donation after circulatory death kidneys

Kidney injury during donation after circulatory determination of death (DCDD) includes warm ischemic (WI) injury from around the time of asystole, and cold ischemic (CI) injury during cold preservation. We have previously shown that Matrix Metalloproteinases (MMPs) are involved in CI injury and that Doxycycline (Doxy), an antibiotic and known MMP inhibitor, protects the transplant kidney during CI. The purpose of our study was to determine if Doxy given before asystole can also prevent injury during WI. A rat model of DCDD was used, including Control, Preemptive Doxy (45 mg/kg iv), and Preemptive and Perfusion (100 microM) Doxy groups. Thirty minutes after asystole, both kidneys were removed. The left kidney was perfused at 4 °C for 22 h, whereas the right was used to establish the degree of warm ischemic injury prior to cold preservation. MMP-2 in the perfusate was significantly reduced in both treatment groups [Control 43.7 ± 7.2 arbitrary units, versus Preemptive Doxy group 23.2 ± 5.5 (p = 0.03), and 'Preemptive and Perfusion' group 18.0 ± 5.6 (p = 0.02)]. Reductions in NGAL, LDH, and MMP-9 were also seen. Electron microscopy showed a marked reduction in mitochondrial injury scores in the treatment groups. Pre-arrest Doxy was associated with a reduction in injury markers and morphologic changes. Doxy may be a simple and safe means of protecting transplant kidneys from both WI and CI.

Intermedin Alleviates Renal Ischemia-Reperfusion Injury and Enhances Neovascularization in Wistar Rats

Background

Ischemia-reperfusion injury (IRI) is a major cause of acute kidney injury (AKI) and increases the risk of subsequently developing chronic kidney disease. Angiogenesis has been shown to play an important role in reducing renal injury after ischemia reperfusion. In this study, we investigated whether IMD could reduce renal IRI by promoting angiogenesis.

Methods

The kidneys of Wistar rats were subjected to 45 min of warm ischemia followed by 24 h of reperfusion. IMD was overexpressed in vivo using the vector pcDNA3.1-IMD transfected by an ultrasound-mediated system. The renal injury after ischemia reperfusion was assessed by detection of the serum creatinine concentration and histologic examinations of renal tissues stained by PAS and H&E. Real-time PCR and Western blotting were used to determine the mRNA and protein levels, respectively. Histological examinations were used to assess the expression of CD31, MMP2, MMP9, ET-1, VEGF and VEGFR2 in tissues.

Results

Renal function and renal histological damage were significantly ameliorated in IMD-transfected rats after ischemia reperfusion. Compared to the IRI, IMD significantly promoted angiogenesis. IMD also upregulated the protein and mRNA expression levels of VEGF and VEGFR2 and downregulated the expression level of MMP2, MMP9 and ET-1.

Conclusion

IMD could protect the kidney after renal ischemia-reperfusion injury by promoting angiogenesis and reducing the destruction of the perivascular matrix.

Pre-Operative Fasting Provides Long Term Protection Against Chronic Renal Damage Induced by Ischaemia Reperfusion Injury in Wild Type and Aneurysm Prone Fibulin-4 Mice

OBJECTIVE

Renal ischaemia reperfusion injury (IRI) is inevitable during open repair of pararenal aortic aneurysms. Pre-operative fasting potently increases resistance against IRI. The effect of fasting on IRI was examined in a hypomorphic Fibulin-4 mouse model (Fibulin-4^+/R), which is predisposed to develop aortic aneurysms.

METHODS

Wild type (WT) and Fibulin-4^+/R mice were either fed ad libitum (AL) or fasted for two days before renal IRI induction by temporary clamping of the renal artery and vein of both kidneys. Six hours, 48 h, and seven days post-operatively, serum urea levels, renal histology, and mRNA expression levels of inflammatory and injury genes were determined to assess kidney function and damage. Additionally, matrix metalloproteinase activity in the kidney was assessed six months after IRI.

RESULTS

Two days of fasting improved survival the first week after renal IRI in WT mice compared with AL fed mice. Short term AL fed Fibulin-4^+/R mice showed improved survival and kidney function compared with AL fed WT mice, which could not be further enhanced by fasting. Both fasted WT and Fibulin-4^+/R mice showed improved survival, kidney function and morphology compared with AL fed mice six months after renal IRI. Fibulin-4^+/R kidneys of fasted mice showed reduced apoptosis together with increased matrix metalloprotease activity levels compared with AL fed Fibulin-4^+/R mice, indicative of increased matrix remodelling.

CONCLUSION

Fibulin-4^+/R mice are naturally protected against the short-term, but not long-term, consequences of renal IRI. Pre-operative fasting protects against renal IRI and prevents (long-term) deterioration of kidney function and morphology in both WT and Fibulin-4^+/R mice. These data suggest that pre-operative fasting may decrease renal damage in patients undergoing open abdominal aneurysm repair.

Mechanisms and therapeutic targets of ischemic acute kidney injury

Acute kidney injury (AKI) due to renal ischemia reperfusion (IR) is a major clinical problem without effective therapy and is a significant and frequent cause of morbidity and mortality during the perioperative period. Although the pathophysiology of ischemic AKI is not completely understood, several important mechanisms of renal IR-induced AKI have been studied. Renal ischemia and subsequent reperfusion injury initiates signaling cascades mediating renal cell necrosis, apoptosis, and inflammation, leading to AKI. Better understanding of the molecular and cellular pathophysiological mechanisms underlying ischemic AKI will provide more targeted approach to prevent and treat renal IR injury. In this review, we summarize important mechanisms of ischemic AKI, including renal cell death pathways and the contribution of endothelial cells, epithelial cells, and leukocytes to the inflammatory response during ischemic AKI. Additionally, we provide some updated potential therapeutic targets for the prevention or treatment of ischemic AKI, including Toll-like receptors, adenosine receptors, and peptidylarginine deiminase 4. Finally, we propose mechanisms of ischemic AKI-induced liver, intestine, and kidney dysfunction and systemic inflammation mainly mediated by Paneth cell degranulation as a potential explanation for the high mortality observed with AKI.

Anesthetic preconditioning increases sirtuin 2 gene expression in a renal ischemia reperfusion injury model

BACKGROUND

Renal transplant surgical proceedings are known to elicit periods of hypoxia and consequent blood flow reestablishment triggering ischemia-reperfusion (I-R) injury. Kidney damage induced by I-R injury associates with a higher risk of graft dysfunction and rejection. Anesthetic preconditioning exerts a beneficial effect on I-R injury by reducing oxidative stress, inflammation and apoptosis. However, the degree of renoprotection stimulated by commonly used anesthetics, as well as their mechanisms of action, are largely unknown. Sirtuins are class III histone deacetylases that reduce cellular stress, promote genome stability and regulate senescence. So far, the relationship between sirtuins and anesthetic preconditioning in the context of renal I-R has not been studied. The main objective of the present work was to determine the renal expression of sirtuins after I-R damage in rats under different anesthetic preconditioning treatments.

METHODS

Unilateral ischemia was performed via occlusion of the left renal hilum for 45 min and followed by 24 hours of reperfusion. Anesthetic preconditioning schemes (morphine 0.5 mg/kg, fentanyl 10 µg/kg, propofol 7.5 mg/kg, or dexmedetomidine 25 µg/kg) were administered 1 hour before ischemia. Creatinine levels were determined in serum, and expression of kidney injury molecule 1 and sirtuin 1, 2, 3 and 7 in kidney tissue was quantified by RT-PCR.

RESULTS

Anesthetic preconditioning with morphine, fentanyl, propofol and dexmedetomidine reduced kidney injury markers after I-R and modulated sirtuin gene expression. Opioids or dexmedetomidine administration before ischemia increased sirtuin 2 expression and correlated with improved renal function.

CONCLUSIONS

Anesthetic preconditioning is a promising strategy to prevent I-R injury associated with transplantation. Our results suggest that sirtuin 2 is involved in the protective mechanisms of some commonly used anesthetics against I-R damage.

Injectable extracellular vesicle-released self-assembling peptide nanofiber hydrogel as an enhanced cell-free therapy for tissue regeneration

Mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) have shown great potential for tissue repair, but their therapeutic capacity is limited by rapid clearance and short half-life. Herein, we purposed a hydrogel-based slow release strategy to enhance the therapeutic potency of EVs. A matrix metalloproteinase-2 (MMP2) sensitive self-assembling peptide (KMP2) hydrogel was used for the local delivery of MSC-EVs. The structure and controlled release properties of the KMP2 hydrogel were analyzed. The effects of the EV-loaded KMP2 hydrogel (KMP2-EVs) on cell apoptosis, inflammation and angiogenesis were evaluated in mice with renal ischemia-reperfusion (I/R) injury. In vitro, KMP2 formed a cross-linked nanofiber hydrogel to encapsulate MSC-EVs. KMP2 showed greater degradation and EV release in response to MMP2. The released EVs had similar structures and bioactivities as fresh, isolated EVs. In vivo, I/R mice treated with KMP2-EVs showed improved renal function by reducing tubular cell apoptosis, pro-inflammatory cytokine expression, and macrophage infiltration than mice receiving either EVs or KMP2. Moreover, KMP2-EVs showed better efficacy on promoting endothelial cell proliferation and angiogenesis than KMP2 or EVs alone, which subsequently decreased chronic renal fibrosis in I/R mice. This study highlighted that the EV-released KMP2 hydrogel is a promising cell-free therapy for tissue repair.

Pharmacological Protection of Kidney Grafts from Cold Perfusion-Induced Injury

One of the greatest challenges facing the field of organ transplantation is the shortage of donor organs for transplantation. Renal transplantation increases quality of life and survival of patients suffering from end-stage renal disease. Although kidney transplantation has evolved greatly over the past few decades, a not insignificant amount of injury occurs to the kidney during recovery, preservation, and implantation and leads to the loss of function and loss of years of dialysis-free living for many patients. The use of kidneys from expanded criteria donors (ECD) and donation after circulatory determination of death (DCDD) has been adopted partly in response to the shortage of donor kidneys; however these kidneys are even more susceptible to ischemic injury. It has been shown that matrix metalloproteinases (MMPs) and reactive oxygen species (ROS) are involved in mechanisms of injury to the transplant kidney. There is also some evidence that inhibition of MMP activity and/or ROS production can protect the kidney from injury. We review possible pharmacological strategies for protection of kidney graft from injury during recovery, preservation, and implantation.

Rat mRNA expression profiles associated with inhibition of ischemic acute kidney injury by losartan

Objective: Losartan was reported to inhibit the progression of acute kidney injury (AKI), but little is known about the underlying pharmacological mechanisms. In the present study, the mRNA expression profiles in ischemic AKI rat kidney altered by losartan treatment were analyzed by next-generation deep sequencing technology.Methods: Ischemia and reperfusion treatment was applied to induce AKI in Sprague-Dawley (SD) rats. The urea and creatinine contents in rat blood were measured. H&E staining was performed to evaluate the histological alteration of rat kidney tissues under a microscope. The TUNEL method was applied to analyze apoptosis in rat kidney tissues. The mRNA profiles in rat kidney were analyzed using next-generation deep sequencing. Differential gene expression was confirmed by quantitative qRT-PCR.Results: The rat model of AKI induced by ischemia and reperfusion showed significant increases in urea and creatinine levels, accompanied by a disrupted kidney tubular structure and renal cell apoptosis. Losartan treatment effectively inhibited the changes in urea and creatinine, tubular structure, and apoptosis in AKI rat kidney. A large number of mRNAs were found to be differentially expressed in the kidneys of AKI rats treated with losartan, which are involved in multiple processes and signaling pathways. The expression of nine differentially expressed genes such as monocyte chemoattractant protein-1 (CCL2) and suppressor of cytokine signaling 3 (SOCS3) was confirmed by qRT-PCR and Western blot.Conclusion: Losartan caused significant alterations in the gene expression profile in AKI rat kidney, which mediated its anti-AKI effects.

Matrix metalloproteinase-7 protects against acute kidney injury by priming renal tubules for survival and regeneration

Matrix metalloproteinase-7 (MMP-7) is a secreted endopeptidase that degrades a broad range of substrates. Recent studies have identified MMP-7 as an early biomarker to predict severe acute kidney injury (AKI) and poor outcomes after cardiac surgery; however, the role of MMP-7 in the pathogenesis of AKI is unknown. In this study, we investigated the expression of MMP-7 and the impact of MMP-7 deficiency in several models of AKI. MMP-7 was induced in renal tubules following ischemia/ reperfusion injury or cisplatin administration, and in folic acid-induced AKI. MMP-7 knockout mice experienced higher mortality, elevated serum creatinine, and more severe histologic lesions after ischemic or toxic insults. Tubular apoptosis and interstitial inflammation were more prominent in MMP-7 knockout kidneys. These histologic changes were accompanied by increased expression of FasL and other components of the extrinsic apoptotic pathway, as well as increased expression of pro-inflammatory chemokines. In a rescue experiment, exogenous MMP-7 ameliorated kidney injury in MMP-7 knockout mice after ischemia/reperfusion. In vitro, MMP-7 protected tubular epithelial cells against apoptosis by directly degrading FasL. In isolated tubules ex vivo, MMP-7 promoted cell proliferation by degrading E-cadherin and thereby liberating β-catenin, priming renal tubules for regeneration. Taken together, these results suggest that induction of MMP-7 is protective in AKI by degrading FasL and mobilizing β-catenin, thereby priming kidney tubules for survival and regeneration.

An E-selectin targeting and MMP-2-responsive dextran-curcumin polymeric prodrug for targeted therapy of acute kidney injury

Based on the overproduction of matrix metalloproteinase-2 (MMP-2) in renal tissue during acute kidney injury (AKI) occurrence, we developed a MMP-2 enzyme-triggered polymeric prodrug with sialic acid (SA) as the targeting group to the inflamed vascular endothelial cells for enhanced therapeutic outcomes. An MMP-2-responsive peptide, PVGLIG, was used to endow the polymeric prodrug with the ability to rapidly release the anti-inflammatory drug, curcumin (CUR), after the targeted site is reached and to improve the drug concentration in the target tissue. The sialic acid-dextran-PVGLIG-curcumin (SA-DEX-PVGLIG-CUR) polymeric prodrug was successfully synthesized via multi-step chemical reactions and characterized by 1H NMR. The water solubility of CUR was significantly increased in the polymeric prodrug and was approximately 23-fold higher than that of free CUR. The in vitro drug release results showed that the release rate of SA-DEX-PVGLIG-CUR was significantly enhanced compared to that of SA-DEX-CUR in a dissolving medium containing the MMP-2 enzyme, suggesting that SA-DEX-PVGLIG-CUR had rapid drug release characteristics in an inflammatory environment. A cellular uptake test confirmed that SA-DEX-PVGLIG-CUR was effectively internalized by inflamed vascular endothelial cells in comparison with that by normal cells, and the mechanism was associated with the specific interaction between SA and E-selectin receptors specifically expressed on inflamed vascular endothelial cells. Bio-distribution results further demonstrated the rapid and increased renal accumulation of SA-DEX-PVGLIG-CUR in AKI mice. Benefiting from the rapid drug release in renal tissue, SA-DEX-PVGLIG-CUR effectively ameliorated the pathological progression of AKI compared with free CUR and SA-DEX-CUR, as reflected by the improved renal functions, histopathological changes, pro-inflammatory cytokine production, oxidative stress and expression of apoptosis related proteins. Altogether, this study provided a new therapeutic strategy for the treatment of AKI.

Attenuation of Acute Renal Injury After the Post-resuscitation Administration of Doxycycline in Surviving Newborn Piglets With Severe Hypoxia-Reoxygenation

Background: Asphyxiated neonates often have myocardial dysfunction and renal insufficiency. Previously we demonstrated that doxycycline improved cardio-renal function through matrix metalloproteinase (MMP)-2 inhibition in an acute swine model of neonatal hypoxia-reoxygenation. The prolonged cardio-renal protective effects of doxycycline in neonates still remained unknown. We therefore hypothesized that the protective effects of doxycycline persisted in surviving subjects. Methods: Newborn piglets were instrumented and subjected to 1 h of hypoxia followed by reoxygenation with 21-25% oxygen and observed for 4 days. Intravenous doxycycline (30 mg/kg) or normal saline (1 mL, saline-control group) was given at 5 min of reoxygenation (n = 8/group) in a randomized, blinded fashion. Sham-operated piglets (n = 5) received no hypoxia-reoxygenation. At 96 h after reoxygenation, the left ventricular function was assessed by Millar® catheter. Renal injury was investigated by measuring plasma creatinine, urinary N-acetyl-D-glucosaminidase activity, renal tissue lactate and MMP-2 activity. Results: Both hypoxia-reoxygenation groups had similar hypoxic stress with severe lactate acidosis, and hemodynamic recovery. Doxycycline-treated piglets had higher urine output with lower urine N-acetyl-D-glucosaminidase, plasma creatinine, and renal MMP-2 activity (vs. saline-controls; all p < 0.05). These markers were all negatively correlated with urine output. Conclusions: In newborn piglets surviving hypoxia-reoxygenation, we observed a weak but significant and persistent attenuation of renal injury and improved recovery with the post-resuscitation administration of doxycycline.

Targeting enhancer of zeste homolog 2 protects against acute kidney injury

Despite the established oncogenic and profibrotic functions of enhancer of zeste homolog 2 (EZH2), a methyltransferase that induces histone H3 lysine 27 trimethylation (H3K27me3), its role in acute kidney injury (AKI) remains unclear. In this study, we demonstrated that EZH2 and H3K27me3 were upregulated in the murine kidney with AKI induced by either ischemia-reperfusion (I/R) or folic acid (FA). Pharmacologic inhibition of EZH2 with 3-deazaneplanocin A (3-DZNeP) prevented tubular injury in both models as demonstrated by reduced renal dysfunction, diminished neutrophil gelatinase-associated lipocalin expression and decreased renal tubular cell death. Injury to the kidney resulted in reduced expression of E-cadherin and ZO-1, whereas EZH2 inhibition largely preserved their expression. Moreover, 3-DZNep was effective in counteracting the increased expression of matrix metalloproteinase (MMP)-2 and MMP-9, as well as the phosphorylation of Raf-1 and ERK1/2 in the injured kidney. Conversely, blocking EZH2 reversed the decrease of tissue inhibitor of metalloproteinase (TIMP)-2 and metalloproteinase (TIMP)-3, and Raf kinase inhibitor protein (RKIP) in the kidney after acute injury. Similarly, oxidant injury to cultured kidney proximal tubular epithelial cells caused a decrease in the expression of E-cadherin, ZO-1, TIMP-2/-3, and RKIP, as well as an increase in the expression of MMP-2/9 and phosphorylation of Raf-1 ERK1/2. Blocking EZH2 with 3-DZNep or SiRNA hindered these responses. Thus, these results suggest that targeting EZH2 protects against AKI through a mechanism associated with the preservation of adhesion/junctions, reduction of matrix metalloproteinases and attenuation of the Raf-1/ERK1/2 pathway.

Doxycycline attenuates cisplatin-induced acute kidney injury through pleiotropic effects

Cisplatin (CDDP) is a widely-used chemotherapeutic drug for solid tumors, but its nephrotoxicity is a major dose-limiting factor. Doxycycline (Dox) is a tetracycline antibiotic that has been commonly used in a variety of infections. Dox has been shown to possess several other properties, including antitumor, anti-inflammatory, antioxidative, and matrix metalloproteinase (MMP)-inhibiting actions. We, therefore, investigated whether Dox exerts renoprotective effects in CDDP-induced acute kidney injury (AKI). Twelve-week-old male C57BL/6J mice were divided into the following groups: 1) control, 2) Dox (2 mg/ml in drinking water), 3) CDDP (25 mg/kg body weight, intraperitoneally), and 4) CDDP+Dox. After seven days of pretreatment with Dox, CDDP was administered and the animals were killed at day 1 or day 3. We evaluated renal function along with renal histological damage, inflammation, oxidative stress, and apoptosis. MMP and serine protease activities in the kidney tissues were assessed using zymography. Administration of CDDP exhibited renal dysfunction and caused histological damage predominantly in the proximal tubules. Dox did not affect either expression of CDDP transporters or the accumulation of CDDP in renal tissues; however, it significantly ameliorated renal dysfunction and histological changes together with reduced detrimental responses, such as oxidative stress and inflammation in the kidneys. Furthermore, Dox inhibited the activity of MMP-2 and MMP-9, as well as serine proteases in the kidney tissues. Finally, Dox markedly mitigated apoptosis in renal tubules. Thus, Dox ameliorated CDDP-induced AKI through its pleiotropic effects. Our results suggest that Dox may become a novel strategy for the prevention of CDDP-induced AKI in humans.

Effects of Post Ischemia-Reperfusion Treatment with Trimetazidine on Renal Injury in Rats: Insights on Delayed Renal Fibrosis Progression

Even after recovery from acute kidney injury, glomeruli remain vulnerable to further injury by way of interstitial fibrosis. This study is aimed at elucidating the effects of post ischemia-reperfusion (I/R) treatment with trimetazidine on the progression to renal fibrosis as well as short- and intermediate-term aspects. Trimetazidine 3 mg/kg or 0.9% saline was given intraperitoneally once upon reperfusion or daily thereafter for 5 d or 8 w. Renal histologic changes and related signaling proteins were assessed. After 24 h, post I/R treatment with trimetazidine significantly reduced serum blood urea nitrogen and creatinine levels and tubular injury accompanied with upregulation of hypoxia-inducible factor- (HIF-) 1α, vascular endothelial growth factor (VEGF), and Bcl-2 expression. After 5 d, post I/R treatment with trimetazidine reduced renal tubular cell necrosis and apoptosis with upregulation of HIF-1α-VEGF and tissue inhibitors of metalloproteinase activities, attenuation of matrix metalloproteinase activities, and alteration of the ratio of Bax to Bcl-2 levels. After 8 w, however, post I/R treatment with trimetazidine did not modify the progression of renal fibrosis. In conclusion, post I/R treatment with trimetazidine allows ischemic kidneys to regain renal function and structure more rapidly compared to nontreated kidneys, but not enough to resolute renal fibrosis in long-term aspect.

Neutrophil exocytosis induces podocyte cytoskeletal reorganization and proteinuria in experimental glomerulonephritis

Acute glomerulonephritis is characterized by rapid glomerular neutrophil recruitment, proteinuria, and glomerular hypercellularity. The current study tested the hypothesis that the release of neutrophil granule contents plays a role in both the loss of filtration barrier leading to proteinuria and the increase in glomerular cells. Inhibition of neutrophil exocytosis with a peptide inhibitor prevented proteinuria and attenuated podocyte and endothelial cell injury but had no effect on glomerular hypercellularity in an experimental acute glomerulonephritis model in mice. Cultivation of podocytes with neutrophil granule contents disrupted cytoskeletal organization, an in vitro model for podocyte effacement and loss of filtration barrier. Activated, cultured podocytes released cytokines that stimulated neutrophil chemotaxis, primed respiratory burst activity, and stimulated neutrophil exocytosis. We conclude that crosstalk between podocytes and neutrophils contributes to disruption of the glomerular filtration barrier in acute glomerulonephritis. Neutrophil granule products induce podocyte injury but do not participate in the proliferative response of intrinsic glomerular cells.

Anti-CD47 monoclonal antibody therapy reduces ischemia-reperfusion injury of renal allografts in a porcine model of donation after cardiac death

We investigated whether blockade of the CD47 signaling pathway could reduce ischemia-reperfusion injury (IRI) of renal allografts donated after cardiac death (DCD) in a porcine animal model of transplantation. Renal allografts were subjected to 30 minutes of warm ischemia, 3.5 hours of cold ischemia, and then perfused with a humanized anti-CD47 monoclonal antibody (CD47mAb) in the treatment group or HTK solution in the control group (n = 4/group). The animals were euthanized five days after transplantation. At the time of reperfusion, indocyanine green-based in vivo imaging showed that CD47mAb-treated organs had greater and more uniform reperfusion. On post-transplant days 3-5, the treatment group had lower values compared to the control for creatinine and blood urea nitrogen. Histological examination of allograft tissues showed a significant decrease of acute tubular injury in the CD47mAb-treated group compared to control. Compared to the control group, CD47mAb treatment significantly decreased genes expression related to oxidative stress (sod-1, gpx-1, and txn), the inflammatory response (il-2, il-6, inf-g, and tgf-b), as well as reduced protein levels of BAX, Caspase-3, MMP2, and MMP9. These data demonstrate that CD47mAb blockade decreases IRI and subsequent tissue injury in DCD renal allografts in a large animal transplant model.

Pharmacological inhibition of Src kinase protects against acute kidney injury in a murine model of renal ischemia/reperfusion

Activation of Src kinase has been implicated in the pathogenesis of acute brain, liver, and lung injury. However, the role of Src in acute kidney injury (AKI) remains unestablished. To address this, we evaluated the effects of Src inhibition on renal dysfunction and pathological changes in a murine model of AKI induced by ischemia/reperfusion (I/R). I/R injury to the kidney resulted in increased Src phosphorylation at tyrosine 416 (activation). Administration of PP1, a highly selective Src inhibitor, blocked Src phosphorylation, improved renal function and ameliorated renal pathological damage. PP1 treatment also suppressed renal expression of neutrophil gelatinase-associated lipocalin and reduced apoptosis in the injured kidney. Moreover, Src inhibition prevented downregulation of several adherens and tight junction proteins, including E-cadherin, ZO-1, and claudins-1/−4 in the kidney after I/R injury as well as in cultured renal proximal tubular cells following oxidative stress. Finally, PP1 inhibited I/R–induced renal expression of matrix metalloproteinase-2 and -9, phosphorylation of extracellular signal–regulated kinases1/2, signal transducer and activator of transcription-3, and nuclear factor-κB, and the infiltration of macrophages into the kidney. These data indicate that Src is a pivotal mediator of renal epithelial injury and that its inhibition may have a therapeutic potential to treat AKI.

Protective effects of taurine against renal ischemia/reperfusion injury in rats by inhibition of gelatinases, MMP-2 and MMP-9, and p38 mitogen-activated protein kinase signaling

Dysregulated expression of matrix metalloproteinases (MMPs) is closely associated with the pathogenesis of renal ischemia/reperfusion injury (I/R). The production of excessive reactive oxygen species (ROS) causes tissue damage. Increased ROS production causes activation of p38 mitogen-activated protein kinase (MAPK) signaling, which participates in gene regulation of MMPs, especially MMP-2 and MMP-9 (gelatinases). Taurine (2-aminoethanesulfonic acid) in mammalian cells functions in bile acid conjugation, maintenance of calcium homeostasis, osmoregulation, membrane stabilization, and antioxidation, antiinflammatory, and antiapoptotic action. We investigated the effects of taurine and the possible role of p38 MAPK signaling on regulation of MMP-2 and MMP-9 in a renal I/R injury model in rats. Rats were divided into three groups: sham, I/R, and I/R + taurine treated. After a right nephrectomy, I/R was induced by clamping the left renal pedicle for 1 h followed by 6 h reperfusion. Taurine was administered 45 min prior to induction of ischemia. Renal function was assessed by serum creatinine and blood urea nitrogen (BUN) levels. Tubule injury and structural changes were evaluated by light microscopy. Malondialdehyde (MDA) levels were analyzed by high performance liquid chromatography (HPLC). Superoxide dismutase (SOD) activity levels were measured using a colorimetric kit. mRNA expression of MMP-2 and MMP-9 was determined by real-time polymerase chain reaction. MMP-2 and MMP-9 activities were measured using a fluorimetric kit. Phosphorylated p38 (p-p38) and total p38 MAPK protein expressions were evaluated by western blot. Taurine pretreatment significantly attenuated renal dysfunction and histologic damage, such as renal tubule dilation and loss of brush borders. The pretreatment also decreased the MDA level and attenuated the reduction of SOD activity in the kidney during I/R. Taurine pretreatment also decreased significantly both MMP-2 and MMP-9 mRNA expression and MMP-9 activity induced by I/R. In addition, the activity of p38 MAPK signaling was down-regulated significantly by taurine administration. Inhibition of MMP-2 and MMP-9 expression and MMP-9 activity caused by taurine may be associated with suppression of p38 MAPK activation during I/R induced renal injury in rats. Therefore, taurine administration may prove to be a strategy for attenuating renal I/R injury.

Magnesium isoglycyrrhizinate protects against renal‑ischemia‑reperfusion injury in a rat model via anti‑inflammation, anti‑oxidation and anti‑apoptosis

The present study aimed to investigate whether magnesium isoglycyrrhizinate protects against renal ischemia‑reperfusion injury (RIRI), and to verify the underlying mechanisms. An RIRI rat model was induced by removing the right kidney, and exposing and clamping the left kidney. RIRI model rats were administered 30 mg/kg magnesium isoglycyrrhizinate for 3 days. Blood urea nitrogen (BUN) and serum creatinine levels in the blood of RIRI model rat were examined, compared with sham‑operated controls. Magnesium isoglycyrrhizinate suppressed the activities of tumor necrosis factor‑α, interleukin (IL)‑1β, IL‑6, superoxide dismutase, glutathione peroxidase, inducible nitric oxide synthase (iNOS) and caspase‑3 in RIRI model rats. Renal iNOS, matrix metalloproteinase (MMP)‑2, phosphorylated‑signal transducers and activators of transcription 3 (STAT3) and intercellular adhesion molecule‑1 (ICAM‑1) protein expression levels were suppressed by magnesium isoglycyrrhizinate treatment in RIRI model rats. These findings suggested that magnesium isoglycyrrhizinate protects RIRI via anti‑inflammatory, ‑oxidative and ‑apoptotic mechanisms in an RIRI rat model. These results implicate magnesium isoglycyrrhizinate pretreatment as a potential approach to protect against RIRI via suppression of the iNOS, ICAM‑1, MMP‑2 and STAT3 signaling pathways.

Matrix Metalloproteinases in Kidney Disease: Role in Pathogenesis and Potential as a Therapeutic Target

Matrix metalloproteinases (MMPs) are large family of proteinases. In addition to a fundamental role in the remodeling of the extracellular matrix, they also cleave a number of cell surface proteins and are involved in multiple cellular processes. MMP activity is regulated via numerous mechanisms, including inhibition by endogenous tissue inhibitors of metalloproteinases (TIMPs). Similar to MMPs, a role for TIMPs has been established in multiple cell signaling pathways. Aberrant expression of MMPs and TIMPS in renal pathophysiology has long been recognized, and with the generation of specific knockout mice, the mechanistic role of several MMPs and TIMPs is becoming more understood and has revealed both pathogenic and protective roles. This chapter will focus on the expression and localization of MMPs and TIMPs in the kidney, as well as summarizing the current information linking these proteins to acute kidney injury and chronic kidney disease. In addition, we will summarize studies suggesting that MMPs and TIMPs may be biomarkers of renal dysfunction and represent novel therapeutic targets to attenuate kidney disease.

An intracellular matrix metalloproteinase-2 isoform induces tubular regulated necrosis: implications for acute kidney injury

Acute kidney injury (AKI) causes severe morbidity, mortality, and chronic kidney disease (CKD). Mortality is particularly marked in the elderly and with preexisting CKD. Oxidative stress is a common theme in models of AKI induced by ischemia-reperfusion (I-R) injury. We recently characterized an intracellular isoform of matrix metalloproteinase-2 (MMP-2) induced by oxidative stress-mediated activation of an alternate promoter in the first intron of the MMP-2 gene. This generates an NH₂-terminal truncated MMP-2 (NTT-MMP-2) isoform that is intracellular and associated with mitochondria. The NTT-MMP-2 isoform is expressed in kidneys of 14-mo-old mice and in a mouse model of coronary atherosclerosis and heart failure with CKD. We recently determined that NTT-MMP-2 is induced in human renal transplants with delayed graft function and correlated with tubular cell necrosis. To determine mechanism(s) of action, we generated proximal tubule cell-specific NTT-MMP-2 transgenic mice. Although morphologically normal at the light microscopic level at 4 mo, ultrastructural studies revealed foci of tubular epithelial cell necrosis, the mitochondrial permeability transition, and mitophagy. To determine whether NTT-MMP-2 expression enhances sensitivity to I-R injury, we performed unilateral I-R to induce mild tubular injury in wild-type mice. In contrast, expression of the NTT-MMP-2 isoform resulted in a dramatic increase in tubular cell necrosis, inflammation, and fibrosis. NTT-MMP-2 mice had enhanced expression of innate immunity genes and release of danger-associated molecular pattern molecules. We conclude that NTT-MMP-2 "primes" the kidney to enhanced susceptibility to I-R injury via induction of mitochondrial dysfunction. NTT-MMP-2 may be a novel AKI treatment target.

Enhanced expression of two discrete isoforms of matrix metalloproteinase-2 in experimental and human diabetic nephropathy

BACKGROUND

We recently reported on the enhanced expression of two isoforms of matrix metalloproteinase-2 (MMP-2) in human renal transplantation delayed graft function. These consist of the conventional secreted, full length MMP-2 isoform (FL-MMP-2) and a novel intracellular N-Terminal Truncated isoform (NTT-MMP-2) generated by oxidative stress-mediated activation of an alternate promoter in the MMP-2 first intron. Here we evaluated the effect of hyperglycemia and diabetes mellitus on the in vitro and in vivo expression of the two MMP-2 isoforms.

METHODS

We quantified the abundance of the FL-MMP-2 and NTT-MMP-2 transcripts by qPCR in HK2 cells cultured in high glucose or 4-hydroxy-2-hexenal (HHE) and tested the effects of the NF-κB inhibitor pyrrolidine dithiocarbamate (PDTC). The streptozotocin (STZ) murine model of Type I diabetes mellitus and renal biopsies of human diabetic nephropathy were used in this study.

RESULTS

Both isoforms of MMP-2 in HK2 cells were upregulated by culture in high glucose or with HHE. PDTC treatment did not suppress high glucose-mediated FL-MMP-2 expression but potently inhibited NTT-MMP-2 expression. With STZ-treated mice, renal cortical expression of both isoforms was increased (FL-MMP-2, 1.8-fold; NTT-MMP-2, greater than 7-fold). Isoform-specific immunohistochemical staining revealed low, but detectable levels of the FL-MMP-2 isoform in controls, while NTT-MMP-2 was not detected. While there was a modest increase in tubular epithelial cell staining for FL-MMP-2 in STZ-treated mice, NTT-MMP-2 was intensely expressed in a basolateral pattern. FL-MMP-2 and NTT-MMP-2 isoform expression as quantified by qPCR were both significantly elevated in renal biopsies of human diabetic nephropathy (12-fold and 3-fold, respectively).

CONCLUSIONS

The expression of both isoforms of MMP-2 was enhanced in an experimental model of diabetic nephropathy and in human diabetic nephropathy. Selective MMP-2 isoform inhibition could offer a novel approach for the treatment of diabetic renal disease.

Use of Xenopus Frogs to Study Renal Development/Repair

The Xenopus genus includes several members of aquatic frogs native to Africa but is perhaps best known for the species Xenopus laevis and Xenopus tropicalis. These species were popularized as model organisms from as early as the 1800s and have been instrumental in expanding several biological fields including cell biology, environmental toxicology, regenerative biology, and developmental biology. In fact, much of what we know about the formation and maturation of the vertebrate renal system has been acquired by examining the intricate genetic and morphological patterns that epitomize nephrogenesis in Xenopus. From these numerous reports, we have learned that the process of kidney development is as unique among organs as it is conserved among vertebrates. While development of most organs involves increases in size at a single location, development of the kidney occurs through a series of three increasingly complex nephric structures that are temporally distinct from one another and which occupy discrete spatial locales within the body. These three renal systems all serve to provide homeostatic, osmoregulatory, and excretory functions in animals. Importantly, the kidneys in amphibians, such as Xenopus, are less complex and more easily accessed than those in mammals, and thus tadpoles and frogs provide useful models for understanding our own kidney development. Several descriptive and mechanistic studies conducted with the Xenopus model system have allowed us to elucidate the cellular and molecular mediators of renal patterning and have also laid the foundation for our current understanding of kidney repair mechanisms in vertebrates. While some species-specific responses to renal injury have been observed, we still recognize the advantage of the Xenopus system due to its distinctive similarity to mammalian wound healing, reparative, and regenerative responses. In addition, the first evidence of renal regeneration in an amphibian system was recently demonstrated in Xenopus laevis. As genetic and molecular tools continue to advance, our appreciation for and utilization of this amphibian model organism can only intensify and will certainly provide ample opportunities to further our understanding of renal development and repair.

Matrix Metalloproteinases in Non-Neoplastic Disorders

The matrix metalloproteinases (MMPs) are zinc-dependent endopeptidases belonging to the metzincin superfamily. There are at least 23 members of MMPs ever reported in human, and they and their substrates are widely expressed in many tissues. Recent growing evidence has established that MMP not only can degrade a variety of components of extracellular matrix, but also can cleave and activate various non-matrix proteins, including cytokines, chemokines and growth factors, contributing to both physiological and pathological processes. In normal conditions, MMP expression and activity are tightly regulated via interactions between their activators and inhibitors. Imbalance among these factors, however, results in dysregulated MMP activity, which causes tissue destruction and functional alteration or local inflammation, leading to the development of diverse diseases, such as cardiovascular disease, arthritis, neurodegenerative disease, as well as cancer. This article focuses on the accumulated evidence supporting a wide range of roles of MMPs in various non-neoplastic diseases and provides an outlook on the therapeutic potential of inhibiting MMP action.

Protection of the Transplant Kidney from Preservation Injury by Inhibition of Matrix Metalloproteinases

Background

Matrix metalloproteinases (MMPs), particularly MMP-2 and MMP-9, play an important role in ischemic injury to the heart, yet it is not known if these MMPs are involved in the injury that occurs to the transplant kidney. We therefore studied the pharmacologic protection of transplant kidneys during machine cold perfusion.

Methods

Human kidney perfusates were analyzed for the presence of injury markers such as cytochrome c oxidase, lactate dehydrogenase, and neutrophil-gelatinase associated lipocalin (NGAL), and MMP-2 and MMP-9 were measured. The effects of MMP inhibitors MMP-2 siRNA and doxycycline were studied in an animal model of donation after circulatory determination of death (DCDD).

Results

Markers of injury were present in all analyzed perfusates, with higher levels seen in perfusates from human kidneys donated after controlled DCDD compared to brain death and in perfusate from kidneys with delayed graft function. When rat kidneys were perfused at 4°C for 22 hours with the addition of MMP inhibitors, this resulted in markedly reduced levels of MMP-2, MMP-9 and analyzed injury markers.

Conclusions

Based on our study, MMPs are involved in preservation injury and the supplementation of preservation solution with MMP inhibitors is a potential novel strategy in protecting the transplant kidney from preservation injury.

Novel intracellular N-terminal truncated matrix metalloproteinase-2 isoform in skeletal muscle ischemia-reperfusion injury

Ischemia-reperfusion injury (IRI) occurs when blood returns to tissues following a period of ischemia. Reintroduction of blood flow results in the production of free radicals and reactive oxygen species that damage cells. Skeletal muscle IRI is commonly seen in orthopedic trauma patients. Experimental studies in other organ systems have elucidated the importance of extracellular and intracellular matrix metalloproteinase-2 (MMP-2) isoforms in regulating tissue damage in the setting of oxidant stress resulting from IRI. Although the extracellular full-length isoform of MMP-2 (FL-MMP-2) has been previously studied in the setting of skeletal muscle IRI, studies investigating the role of the N-terminal truncated isoform (NTT-MMP-2) in this setting are lacking. In this study, we first demonstrated significant increases in FL- and NTT-MMP-2 gene expression in C2C12 myoblast cells responding to re-oxygenation following hypoxia in vitro. We then evaluated the expression of FL- and NTT-MMP-2 in modulating skeletal muscle IRI using a previously validated murine model. NTT-MMP-2, but not FL-MMP-2 expression was significantly increased in skeletal muscle following IRI. Moreover, the expression of toll-like receptors (TLRs) -2 and -4, IL-6, OAS-1A, and CXCL1 was also significantly up-regulated following IRI. Treatment with the potent anti-oxidant pyrrolidine dithiocarbamate (PDTC) significantly suppressed NTT-MMP-2, but not FL-MMP-2 expression and improved muscle viability following IRI. This data suggests that NTT-MMP-2, but not FL-MMP-2, is the major isoform of MMP-2 involved in skeletal muscle IRI.

Hypothermic Machine Perfusion Reduced Inflammatory Reaction by Downregulating the Expression of Matrix Metalloproteinase 9 in a Reperfusion Model of Donation After Cardiac Death

The exact mechanism by which hypothermic machine perfusion (HMP) improves the graft quality in kidney transplantation of donation after cardiac death (DCD) remains unclear. The aim of this study was to investigate the correlation between the expression of matrix metalloproteinase 9 (MMP-9) and inflammatory reaction in kidney ischemia-reperfusion (I/R) injury injury followed by cold storage (CS) or HMP model of DCD. New Zealand white rabbit kidneys were subjected to 35 min of warm ischemia and 1 h reperfusion, then preserved by either 1 h reperfusion (sham-operated group), 4 h CS or 4 h HMP in vivo. Kidneys were reperfused 24 h followed by further analysis. No treatment was given to rabbits in the normal control group. The expression of MMP-9, nuclear factor-κB (NF-κB), and MMP-2 mRNA were detected by real-time PCR (RT-PCR). MMP-9 was located by immunohistochemistry and immunofluorescence methods. Tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), myeloperoxidase (MPO), superoxide dismutase (SOD), and malondialdehyde (MDA) were measured by kits for each groups. Compared with the CS group, the expression of MMP-9 and NF-κB mRNA were downregulated in HMP group (P < 0.05). In contrast, expression of MMP-2 mRNA had no statistical significance between CS group and HMP group (P > 0.05). In normal control and sham-operated groups, a low level of MMP-9 expression was detected in glomeruli. However, positive signals of MMP-9 were mostly located in the tubulointerstitium and the vascular wall of CS and HMP groups. Expression of TNF-α, IL-6, MDA, and activity of MPO decreased while activity of SOD in the HMP group increased in contrast to the CS group (P < 0.05). In conclusion, inflammatory cytokines mediated MMP-9 expression through NF-κB band to MMP-9 promoter region, resulting in renal injury. Therefore, HMP reduced inflammatory reaction by downregulating the expression of MMP-9, which may be the mechanism of kidney protection in I/R injury.

Matrix Metalloproteinase-2 Knockout and Heterozygote Mice Are Protected from Hydronephrosis and Kidney Fibrosis after Unilateral Ureteral Obstruction

Matrix Metalloproteinase-2 (Mmp2) is a collagenase known to be important in the development of renal fibrosis. In unilateral ureteral obstruction (UUO) the obstructed kidney (OK) develops fibrosis, while the contralateral (CL) does not. In this study we investigated the effect of UUO on gene expression, fibrosis and pelvic remodeling in the kidneys of Mmp2 deficient mice (Mmp2-/-), heterozygous animals (Mmp2+/-) and wild-type mice (Mmp2+/+). Sham operated animals served as controls (Cntrl). UUO was prepared under isoflurane anaesthesia, and the animals were sacrificed after one week. UUO caused hydronephrosis, dilation of renal tubules, loss of parenchymal thickness, and fibrosis. Damage was most severe in Mmp2+/+ mice, while both Mmp2-/- and Mmp2+/- groups showed considerably milder hydronephrosis, no tubular necrosis, and less tubular dilation. Picrosirius red quantification of fibrous collagen showed 1.63±0.25% positivity in OK and 0.29±0.11% in CL (p<0.05) of Mmp2+/+, Mmp2-/- OK and Mmp2-/- CL exhibited only 0.49±0.09% and 0.23±0.04% (p<0.05) positivity, respectively. Mmp2+/- OK and Mmp2+/- CL showed 0.43±0.09% and 0.22±0.06% (p<0.05) positivity, respectively. Transcriptomic analysis showed that 26 genes (out of 48 examined) were differentially expressed by ANOVA (p<0.05). 25 genes were upregulated in Mmp2+/+ OK compared to Mmp2+/+ CL: Adamts1, -2, Col1a1, -2, -3a1, -4a1, -5a1, -5a2, Dcn, Fbln1, -5, Fmod, Fn1, Itga2, Loxl1, Mgp, Mmp2, -3, Nid1, Pdgfb, Spp1, Tgfb1, Timp2, Trf, Vim. In Mmp2-/- and Mmp2+/- 18 and 12 genes were expressed differentially between OK and CL, respectively. Only Mmp2 was differentially regulated when comparing Mmp2-/- OK and Mmp2+/- OK. Under stress, it appears that Mmp2+/- OK responds with less Mmp2 upregulation than Mmp2+/+ OK, suggesting that there is a threshold level of Mmp2 necessary for damage and fibrosis to occur. In conclusion, reduced Mmp2 expression during UUO protects mice against hydronephrosis and renal fibrosis.

Two Distinct Isoforms of Matrix Metalloproteinase-2 Are Associated with Human Delayed Kidney Graft Function

Delayed graft function (DGF) is a frequent complication of renal transplantation, particularly in the setting of transplantation of kidneys derived from deceased donors and expanded-criteria donors. DGF results from tubular epithelial cell injury and has immediate and long term consequences. These include requirement for post-transplantation dialysis, increased incidence of acute rejection, and poorer long-term outcomes. DGF represents one of the clearest clinical examples of renal acute ischemia/reperfusion injury. Experimental studies have demonstrated that ischemia/reperfusion injury induces the synthesis of the full length secreted isoform of matrix metalloproteinase-2 (FL-MMP-2), as well as an intracellular N-terminal truncated MMP-2 isoform (NTT-MMP-2) that initiates an innate immune response. We hypothesized that the two MMP-2 isoforms mediate tubular epithelial cell injury in DGF. Archival renal biopsy sections from 10 protocol biopsy controls and 41 cases with a clinical diagnosis of DGF were analyzed for the extent of tubular injury, expression of the FL-MMP-2 and NTT-MMP-2 isoforms by immunohistochemistry (IHC), in situ hybridization, and qPCR to determine isoform abundance. Differences in transcript abundance were related to tubular injury score. Markers of MMP-2-mediated injury included TUNEL staining and assessment of peritubular capillary density. There was a clear relationship between tubular epithelial cell expression of both FL-MMP-2 and NTT-MMP-2 IHC with the extent of tubular injury. The MMP-2 isoforms were detected in the same tubular segments and were present at sites of tubular injury. qPCR demonstrated highly significant increases in both the FL-MMP-2 and NTT-MMP-2 transcripts. Statistical analysis revealed highly significant associations between FL-MMP-2 and NTT-MMP-2 transcript abundance and the extent of tubular injury, with NTT-MMP-2 having the strongest association. We conclude that two distinct MMP-2 isoforms are associated with tubular injury in DGF and offer novel therapeutic targets for the prevention of this disorder.

Loss of matrix metalloproteinase-8 is associated with worsened recovery after ischemic kidney injury

Acute kidney injury (AKI) leads to chronic kidney disease. The mechanisms involved with recovery from AKI are poorly understood and molecular mediators responsible for healing and restoration of kidney function are understudied. We previously discovered differential expression of matrix metalloproteinase-8 (MMP-8) mRNA and protein in patients with severe sepsis associated AKI versus sepsis without AKI. Here, we demonstrate the involvement of MMP-8 in purely ischemic AKI. Mice subjected to 30 min of bilateral renal ischemia developed increased plasma creatinine and MMP-8 expression within 24 h versus sham controls. After an initial surge and subsequent return toward baseline, both kidney MMP-8 expression and activity exhibited a late increase (Days 5-7 post-ischemia reperfusion) in mice subjected to AKI. Neutrophil infiltration of the kidney was significantly higher after AKI in wild-type mice than in MMP-8 null mice, starting at 4 days. Additionally, MMP-8 null mice subjected to AKI demonstrated a persistent histopathologic and functional injury and worsened health (greater overall weight loss) versus wild-type cohorts after seven days. Taken together, our findings suggest that MMP-8 is involved with restoration of baseline kidney health after ischemic kidney injury and that a potential mechanism involves the interaction of MMP-8 and neutrophil recruitment to the site of injury.

Biomarkers in post-reperfusion syndrome after acute lower limb ischaemia

Ischaemia reperfusion (I/R) injury refers to tissue damage caused when blood supply returns to the tissue after a period of ischaemia. Matrix metalloproteinases (MMPs), neutrophil gelatinase-associated lipocalin (NGAL) and cytokines are biomarkers involved in several vascular complications. The aim of this study was to evaluate the role of MMPs, NGAL and inflammatory cytokines in I/R syndrome. We conducted an open label, multicentric, parallel group study, between January 2010 and December 2013. Patients with acute limb ischaemia were enrolled in this study and were divided into two groups: (i) those subjected to fasciotomy and (ii) those not subjected to fasciotomy, according to the onset of compartment syndrome. Plasma and tissue values of MMPs and NGAL as well as plasma cytokines were evaluated. MMPs, NGAL and cytokine levels were higher in patients with compartment syndrome. Biomarkers evaluated in this study may be used in the future as predictors of I/R injury severity and its possible evolution towards post-reperfusion syndrome.