Overexpression of Human CD55 and CD59 or Treatment with Human CD55 Protects against Renal Ischemia-Reperfusion Injury in Mice

Renovascular Disease and Mitochondrial Dysfunction in Human Mesenchymal Stem Cells

Key Points

Renovascular disease impairs the capacity of human adipose tissue–derived mesenchymal stem/stromal cells to repair ischemic murine kidneys. miR-378h modulated the capacity of renovascular disease adipose tissue–derived mesenchymal stem/stromal cells to repair ischemic kidneys in vivo .

Background

Renovascular disease leads to renal ischemia, hypertension, and eventual kidney failure. Autologous transplantation of adipose tissue–derived mesenchymal stem/stromal cells (MSCs) improves perfusion and oxygenation in stenotic human kidneys, but associated atherosclerosis and hypertension might blunt their effectiveness. We hypothesized that renovascular disease alters the human MSC transcriptome and impairs their reparative potency.

Methods

MSCs were harvested from subcutaneous abdominal fat of patients with renovascular disease and healthy volunteers (n =3 each), characterized and subsequently injected (5×105/200 μ l) into mice 2 weeks after renal artery stenosis or sham surgery (n =6/group). Two weeks later, mice underwent imaging and tissue studies. MSCs from healthy volunteers and in those with renovascular disease were also characterized by mRNA/microRNA (miRNA) sequencing. Based on these, MSC proliferation and mitochondrial damage were assessed in vitro before and after miRNA modulation and in vivo in additional renal artery stenosis mice administered with MSCs from renovascular disease pretreated with miR-378h mimic (n =5) or inhibitor (n =4).

Results

MSCs engrafted in stenotic mouse kidneys. Healthy volunteer MSCs (but not renovascular disease MSCs) decreased BP, improved serum creatinine levels and stenotic-kidney cortical perfusion and oxygenation, and attenuated peritubular capillary loss, tubular injury, and fibrosis. Genes upregulated in renovascular disease MSCs versus healthy volunteer MSCs were mostly implicated in transcription and cell proliferation, whereas those downregulated encoded mainly mitochondrial proteins. Upregulated miRNAs, including miR-378h, primarily target nuclear-encoded mitochondrial genes, whereas downregulated miRNAs mainly target genes implicated in transcription and cell proliferation. MSC proliferation was similar, but their mitochondrial structure and reparative function both in vivo and in vitro improved after miR-378h inhibition.

Conclusions

Renovascular disease impaired the reparative capacity of human MSCs, possibly by dysregulating miR-378h that targets mitochondrial genes.

Podcast

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From bench to bedside: Platelet biomimetic nanoparticles as a promising carriers for personalized drug delivery

In recent decades, there has been a burgeoning interest in cell membrane coating strategies as innovative approach for targeted delivery systems in biomedical applications. Platelet membrane-coated nanoparticles (PNPs), in particular, are gaining interest as a new route for targeted therapy due to their advantages over conventional drug therapies. Their stepwise approach blends the capabilities of the natural platelet membrane (PM) with the adaptable nature of manufactured nanomaterials, resulting in a synergistic combination that enhances drug delivery and enables the development of innovative therapeutics. In this context, we present an overview of the latest advancements in designing PNPs with various structures tailored for precise drug delivery. Initially, we describe the types, preparation methods, delivery mechanisms, and specific advantages of PNPs. Next, we focus on three critical applications of PNPs in diseases: vascular disease therapy, cancer treatment, and management of infectious diseases. This review presents our knowledge of PNPs, summarizes their advancements in targeted therapies and discusses the promising potential for clinical translation of PNPs.

Urine complement proteins are associated with kidney disease progression of type 2 diabetes in Korean and American cohorts

Background

Mechanisms of progression of diabetic kidney disease (DKD) are not completely understood. This study uses untargeted and targeted mass spectrometry-based proteomics in two independent cohorts on two continents to decipher the mechanisms of DKD in patients with type 2 diabetes.

Methods

We conducted untargeted mass spectrometry on urine samples collected at the time of kidney biopsy from Korean patients with type 2 diabetes and biopsy-proven diabetic nephropathy at Seoul National University Hospital (SNUH-DN cohort; n = 64). These findings were validated using targeted mass spectrometry in urine samples from a Chronic Renal Insufficiency Cohort subgroup with type 2 diabetes and DKD (CRIC-T2D; n = 282). Urinary biomarkers/pathways associated with kidney disease progression (doubling of serum creatinine, ≥50% decrease in estimated glomerular filtration rates, or the development of end-stage kidney disease) were identified.

Results

SNUH-DN patients had an estimated glomerular filtration rate (eGFR) of 55 mL/min/1.73 m 2 (interquartile range [IQR], 44-75) and random urine protein-to-creatinine ratio of 3.1 g/g (IQR, 1.7-7.0). Urine proteins clustered into two groups, with cluster 2 having a 4.6-fold greater hazard (95% confidence interval [CI], 1.9-11.5) of disease progression than cluster 1 in multivariable-adjusted, time-to-event analyses. Proteins in cluster 2 mapped to 10 pathways, four of the top five of which were complement or complement-related. A high complement score, constructed from urine complement protein abundance, was strongly correlated to 4 of 5 histopathologic DN features and was associated with a 2.4-fold greater hazard (95% CI, 1.0-5.4) of disease progression than a low complement score. Targeted mass spectrometry of the CRIC-T2D participants, who had an eGFR of 42 mL/min/1.73 m 2 (IQR, 37-49) and 24-hr urine protein of 0.48 g (IQR, 0.10-1.87), showed that the complement score similarly segregated them into rapid and slow DKD progression groups. In both cohorts, the complement score had a linear association with disease progression.

Conclusions

Urinary proteomic profiling confirms the association between the complement pathway and rapid DKD progression in two independent cohorts. These results suggest a need to further investigate complement pathway inhibition as a novel treatment for DKD.

Transcriptomic analysis of the effect of remote ischaemic conditioning in an animal model of necrotising enterocolitis

Necrotising enterocolitis (NEC) has a complex pathophysiology but the common end-point is ischaemia reperfusion injury (IRI) and intestinal necrosis. We have previously reported that RIC significantly reduces the intestinal injury in a rat model of NEC. Here we describe the changes in intestinal mRNA occurring in the intestine of animals exposed to IRI, both with and without RIC. Related rat-pups were randomly assigned to four groups: SHAM, IRI only, RIC only and RIC + IRI. IRI animals, underwent 40 min of intestinal ischaemia, and 90 min of reperfusion. Animals that underwent RIC had three cycles of 5 min of alternating ischaemia/reperfusion by means of a ligature applied to the hind limb. Samples from the terminal ileum were immediately stored in RNA-preserving media for later next generation sequencing and transciptome analysis using R v 3.6.1. Differential expression testing showed that 868 genes differentially expressed in animals exposed to RIC alone compared to SHAM and 135 in the IRI and RIC group compared to IRI alone. Comparison between these two sets showed that 25 genes were differentially expressed in both groups. Pro-inflammatory molecules: NF-ĸβ2, Cxcl1, SOD2 and Map3k8 all show reduced expression in response to RIC. Targeted gene analysis revealed increased expression in PI3K which is part of the so-called RISK-pathway which is a key part of the protective mechanisms of RIC in the heart. Overall, this transcriptomic analysis shows that RIC provides a protective effect to the intestine via anti-inflammatory pathways. This could be particularly relevant to treating and preventing NEC.

Ischemia-Reperfusion Injury in Kidney Transplantation: Mechanisms and Potential Therapeutic Targets

Kidney transplantation offers a longer life expectancy and a better quality of life than dialysis to patients with end-stage kidney disease. Ischemia-reperfusion injury (IRI) is thought to be a cornerstone in delayed or reduced graft function and increases the risk of rejection by triggering the immunogenicity of the organ. IRI is an unavoidable event that happens when the blood supply is temporarily reduced and then restored to an organ. IRI is the result of several biological pathways, such as transcriptional reprogramming, apoptosis and necrosis, innate and adaptive immune responses, and endothelial dysfunction. Tubular cells mostly depend on fatty acid (FA) β-oxidation for energy production since more ATP molecules are yielded per substrate molecule than glucose oxidation. Upon ischemia-reperfusion damage, the innate and adaptive immune system activates to achieve tissue clearance and repair. Several cells, cytokines, enzymes, receptors, and ligands are known to take part in these events. The complement cascade might start even before organ procurement in deceased donors. However, additional experimental and clinical data are required to better understand the pathogenic events that take place during this complex process.

Complement System and the Kidney: Its Role in Renal Diseases, Kidney Transplantation and Renal Cell Carcinoma

The crosstalk among the complement system, immune cells, and mediators of inflammation provides an efficient mechanism to protect the organism against infections and support the repair of damaged tissues. Alterations in this complex machinery play a role in the pathogenesis of different diseases. Core complement proteins C3 and C5, their activation fragments, their receptors, and their regulators have been shown to be active intracellularly as the complosome. The kidney is particularly vulnerable to complement-induced damage, and emerging findings have revealed the role of complement system dysregulation in a wide range of kidney disorders, including glomerulopathies and ischemia-reperfusion injury during kidney transplantation. Different studies have shown that activation of the complement system is an important component of tumorigenesis and its elements have been proved to be present in the TME of various human malignancies. The role of the complement system in renal cell carcinoma (RCC) has been recently explored. Clear cell and papillary RCC upregulate most of the complement genes relative to normal kidney tissue. The aim of this narrative review is to provide novel insights into the role of complement in kidney disorders.

Targeting the Complement Pathway in Kidney Transplantation

The complement system is paramount in the clearance of pathogens and cell debris, yet is increasingly recognized as a key component in several pathways leading to allograft injury. There is thus a growing interest in new biomarkers to assess complement activation and guide tailored therapies after kidney transplantation (KTx). C5 blockade has revolutionized post-transplant management of atypical hemolytic uremic syndrome, a paradigm of complement-driven disease. Similarly, new drugs targeting the complement amplification loop hold much promise in the treatment and prevention of recurrence of C3 glomerulopathy. Although unduly activation of the complement pathway has been described after brain death and ischemia reperfusion, any clinical attempts to mitigate the ensuing renal insults have so far provided mixed results. However, the intervention timing, strategy, and type of complement blocker need to be optimized in these settings. Furthermore, the fast-moving field of ex vivo organ perfusion technology opens new avenues to deliver complement-targeted drugs to kidney allografts with limited iatrogenic risks. Complement plays also a key role in the pathogenesis of donor-specific ABO- and HLA-targeted alloantibodies. However, C5 blockade failed overall to improve outcomes in highly sensitized patients and prevent the progression to chronic antibody-mediated rejection (ABMR). Similarly, well-conducted studies with C1 inhibitors in sensitized recipients yielded disappointing results so far, in part, because of subtherapeutic dosage used in clinical studies. The emergence of new complement blockers raises hope to significantly reduce the negative effect of ischemia reperfusion, ABMR, and nephropathy recurrence on outcomes after KTx.

The Complement System in Kidney Transplantation

Kidney transplantation is the therapy of choice for patients who suffer from end-stage renal diseases. Despite improvements in surgical techniques and immunosuppressive treatments, long-term graft survival remains a challenge. A large body of evidence documented that the complement cascade, a part of the innate immune system, plays a crucial role in the deleterious inflammatory reactions that occur during the transplantation process, such as brain or cardiac death of the donor and ischaemia/reperfusion injury. In addition, the complement system also modulates the responses of T cells and B cells to alloantigens, thus playing a crucial role in cellular as well as humoral responses to the allograft, which lead to damage to the transplanted kidney. Since several drugs that are capable of inhibiting complement activation at various stages of the complement cascade are emerging and being developed, we will discuss how these novel therapies could have potential applications in ameliorating outcomes in kidney transplantations by preventing the deleterious effects of ischaemia/reperfusion injury, modulating the adaptive immune response, and treating antibody-mediated rejection.

Predictive value of soluble CD59 for poor 28-day neurological prognosis and all-cause mortality in patients after cardiopulmonary resuscitation: a prospective observatory study

BACKGROUND

sCD59, as a soluble form of CD59, is observed in multiple types of body fluids and correlated with the cell damage after ischemia/reperfusion injury. This study aims to observe the dynamic changes of serum sCD59 in patients after restoration of spontaneous circulation (ROSC) and explore the association of serum sCD59 with neurological prognosis and all-cause mortality in patients after ROSC.

METHODS

A total of 68 patients after ROSC were prospectively recruited and divided into survivors (n = 23) and non-survivors (n = 45) groups on the basis of 28-day survival. Twenty healthy volunteers were enrolled as controls. Serum sCD59 and other serum complement components, including sC5b-9, C5a, C3a, C3b, C1q, MBL, Bb, and pro-inflammatory mediators tumor necrosis factor (TNF)-α, interleukin-6 (IL-6), neurological damage biomarkers neuron-specific enolase (NSE) and soluble protein 100β (S100β) were measured by enzyme linked immunosorbent assay on day 1, 3, and 7 after ROSC. Neurologic outcome was assessed using cerebral performance category scores, with poor neurologic outcome defined as 3-5 points.

RESULTS

In the first week after ROSC, serum levels of sCD59, sC5b-9, C5a, C3a, C3b, C1q, MBL, Bb, TNF-α, IL-6, NSE and S100β were significantly elevated in patients after ROSC compared to healthy volunteers, with a significant elevation in the non-survivors compared to survivors except serum C1q and MBL. Serum sCD59 levels were positively correlated with serum sC5b-9, TNF-α, IL-6, NSE, S100β, SOFA score and APACHE II score. Moreover, serum sCD59 on day 1, 3, and 7 after ROSC could be used for predicting poor 28-day neurological prognosis and all-cause mortality. Serum sCD59 on day 3 had highest AUCs for predicting poor 28-day neurological prognosis [0.862 (95% CI 0.678-0.960)] and 28-day all-cause mortality [0.891 (95% CI 0.769-0.962)]. In multivariate logistic regression analysis, the serum level of sCD59_D1 was independently associated with poor 28-day neurological prognosis and all-cause mortality.

CONCLUSIONS

The elevated serum level of sCD59 was positively correlated with disease severity after ROSC. Moreover, serum sCD59 could have good predictive values for the poor 28-day neurological prognosis and all-cause mortality in patients after ROSC.

Inhibition of complement activation by CD55 overexpression in human induced pluripotent stem cell derived kidney organoids

End stage renal disease is an increasing problem worldwide driven by aging of the population and increased prevalence of metabolic disorders and cardiovascular disease. Currently, kidney transplantation is the only curative option, but donor organ shortages greatly limit its application. Regenerative medicine has the potential to solve the shortage by using stem cells to grow the desired tissues, like kidney tissue. Immune rejection poses a great threat towards the implementation of stem cell derived tissues and various strategies have been explored to limit the immune response towards these tissues. However, these studies are limited by targeting mainly T cell mediated immune rejection while the rejection process also involves innate and humoral immunity. In this study we investigate whether inhibition of the complement system in human induced pluripotent stem cells (iPSC) could provide protection from such immune injury. To this end we created knock-in iPSC lines of the membrane bound complement inhibitor CD55 to create a transplant-specific protection towards complement activation. CD55 inhibits the central driver of the complement cascade, C3 convertase, and we show that overexpression is able to decrease complement activation on both iPSCs as well as differentiated kidney organoids upon stimulation with anti-HLA antibodies to mimic the mechanism of humoral rejection.

Recent trends in platelet membrane-cloaked nanoparticles for application of inflammatory diseases

Platelets are multifunctional effectors of inflammatory responses and inseparable from the occurrence and development of various inflammatory diseases. The platelet membrane (PM) is integrated onto the surface of a nano-drug delivery system to form the PM-cloaked nanoparticles (PM@NPs), which can increase the biocompatibility of the nano-drug delivery system and mitigate adverse drug reactions. Owing to the strong affinity of immune regulation and adhesion-related antigens on the surface of PM to the focal sites of inflammatory diseases, which endows PM@NPs with the potential to actively target lesions and improve the therapeutic efficacy of drugs for inflammatory diseases. Based on latest developments in PM biomimetic technique and nanomedicine for the treatment of inflammatory diseases, this paper mainly elaborates three aspects: advantages of PM@NPs, experimental foundation of PM biomimetic nanotechnology, and applications of PM@NPs to the treatment of inflammatory diseases. The aim is to provide reference for the development and application of PM@NPs and novel insights into the treatment of inflammatory diseases.

Overexpression of Decay Accelerating Factor Mitigates Fibrotic Responses to Lung Injury

CD55 or decay accelerating factor (DAF), a ubiquitously expressed glycosylphosphatidylinositol (GPI)-anchored protein, confers a protective threshold against complement dysregulation which is linked to the pathogenesis of idiopathic pulmonary fibrosis (IPF). Since lung fibrosis is associated with downregulation of DAF, we hypothesize that overexpression of DAF in fibrosed lungs will limit fibrotic injury by restraining complement dysregulation. Normal primary human alveolar type II epithelial cells (AECs) exposed to exogenous complement 3a or 5a, and primary AECs purified from IPF lungs demonstrated decreased membrane-bound DAF expression with concurrent increase in the endoplasmic reticulum (ER) stress protein, ATF6. Increased loss of extracellular cleaved DAF fragments was detected in normal human AECs exposed to complement 3a or 5a, and in lungs of IPF patients. C3a-induced ATF6 expression and DAF loss was inhibited using pertussis toxin (an enzymatic inactivator of G-protein coupled receptors), in murine AECs. Treatment with soluble DAF abrogated tunicamycin-induced C3a secretion and ER stress (ATF6 and BiP expression) and restored epithelial cadherin. Bleomycin-injured fibrotic mice subjected to lentiviral overexpression of DAF demonstrated diminished levels of local collagen deposition and complement activation. Further analyses showed diminished release of DAF fragments, as well as reduction in apoptosis (TUNEL and caspase 3/7 activity), and ER stress-related transcripts. Loss-of-function studies using Daf1 siRNA demonstrated worsened lung fibrosis detected by higher mRNA levels of Col1a1 and epithelial injury-related Muc1 and Snai1, with exacerbated local deposition of C5b-9. Our studies provide a rationale for rescuing fibrotic lungs via DAF induction that will restrain complement dysregulation and lung injury.

Endothelial-specific loss of Krüppel-Like Factor 4 triggers complement-mediated endothelial injury

Thrombotic microangiopathy (TMA) in the kidney represents the most severe manifestation of kidney microvascular endothelial injury. Despite the source of the inciting event, the diverse clinical forms of kidney TMA share dysregulation of endothelial cell transcripts and complement activation. Here, we show that endothelial-specific knockdown of Krüppel-Like Factor 4 (Klf4)ΔEC, an anti-inflammatory and antithrombotic zinc-finger transcription factor, increases the susceptibility to glomerular endothelial injury and microangiopathy in two genetic murine models that included endothelial nitric oxide synthase knockout mice and aged mice (52 weeks), as well as in a pharmacologic model of TMA using Shiga-toxin 2. In all models, Klf4ΔEC mice exhibit increased pro-thrombotic and pro-inflammatory transcripts, as well as increased complement factors C3 and C5b-9 deposition and histologic features consistent with subacute TMA. Interestingly, complement activation in Klf4ΔEC mice was accompanied by reduced expression of a key KLF4 transcriptional target and membrane bound complement regulatory gene, Cd55. To assess a potential mechanism by which KLF4 might regulate CD55 expression, we performed in silico chromatin immunoprecipitation enrichment analysis of the CD55 promotor and found KLF4 binding sites upstream from the CD55 transcription start site. Using patient-derived kidney biopsy specimens, we found glomerular expression of KLF4 and CD55 was reduced in patients with TMA as compared to control biopsies of the unaffected pole of patient kidneys removed due to kidney cancer. Thus, our data support that endothelial Klf4 is necessary for maintenance of a quiescent glomerular endothelial phenotype and its loss increases susceptibility to complement activation and induction of prothrombotic and pro-inflammatory pathways.

Effects of obesity on reparative function of human adipose tissue-derived mesenchymal stem cells on ischemic murine kidneys

Introduction:

Obesity is a health burden that impairs cellular processes. Mesenchymal stem/stromal cells (MSCs) are endowed with reparative properties and can ameliorate renal injury. Obesity impairs human MSC function in-vitro, but its effect on their in-vivo reparative potency remains unknown.

Subjects and Methods:

Abdominal adipose tissue-derived MSC were harvested from patients without (‘lean’) or with obesity (‘obese’) (body mass index<30 or ≥30kg/m², respectively) during kidney donation or bariatric surgery, respectively. MSC (5x10⁵/200μL) or vehicle were then injected into 129S1 mice 2 weeks after renal artery stenosis (RAS) or sham surgery (n=8/group). Two weeks later, mice underwent magnetic resonance imaging to assess renal perfusion and oxygenation in-vivo, and kidneys then harvested for ex-vivo studies.

Results:

Similar numbers of lean and obese-MSCs engrafted in stenotic mouse kidneys. Vehicle-treated RAS mice had reduced stenotic-kidney cortical and medullary perfusion and oxygenation. Lean (but not obese) MSC normalized ischemic kidney cortical perfusion, whereas both effectively mitigated renal hypoxia. Serum creatinine and blood pressure were elevated in RAS mice and lowered only by lean-MSC. Both types of MSCs alleviated stenotic-kidney fibrosis, but lean-MSC more effectively than obese-MSC. MSC senescence-associated beta-gal activity, and gene expression of p16, p21, and vascular endothelial growth factor correlated with recipient kidney perfusion and tissue injury, linking MSC characteristics with their in-vivo reparative capacity.

Discussion:

Human obesity impairs the reparative properties of adipose-tissue-derived MSCs, possibly by inducing cellular senescence. Dysfunction and senescence of the endogenous MSC repair system in patients with obesity may warrant targeting interventions to restore MSC vitality.

Role of Complement System in Kidney Transplantation: Stepping From Animal Models to Clinical Application

Kidney transplantation is a life-saving strategy for patients with end-stage renal diseases. Despite the advances in surgical techniques and immunosuppressive agents, the long-term graft survival remains a challenge. Growing evidence has shown that the complement system, part of the innate immune response, is involved in kidney transplantation. Novel insights highlighted the role of the locally produced and intracellular complement components in the development of inflammation and the alloreactive response in the kidney allograft. In the current review, we provide the updated understanding of the complement system in kidney transplantation. We will discuss the involvement of the different complement components in kidney ischemia-reperfusion injury, delayed graft function, allograft rejection, and chronic allograft injury. We will also introduce the existing and upcoming attempts to improve allograft outcomes in animal models and in the clinical setting by targeting the complement system.

Urinary complement proteins and risk of end-stage renal disease: quantitative urinary proteomics in patients with type 2 diabetes and biopsy-proven diabetic nephropathy

PURPOSE

To investigate the association between urinary complement proteins and renal outcome in biopsy-proven diabetic nephropathy (DN).

METHODS

Untargeted proteomic and Kyoto Encyclopedia of Genes and Genomes (KEGG) functional analyses and targeted proteomic analysis using parallel reaction-monitoring (PRM)-mass spectrometry was performed to determine the abundance of urinary complement proteins in healthy controls, type 2 diabetes mellitus (T2DM) patients, and patients with T2DM and biopsy-proven DN. The abundance of each urinary complement protein was individually included in Cox proportional hazards models for predicting progression to end-stage renal disease (ESRD).

RESULTS

Untargeted proteomic and functional analysis using the KEGG showed that differentially expressed urinary proteins were primarily associated with the complement and coagulation cascades. Subsequent urinary complement proteins quantification using PRM showed that urinary abundances of C3, C9, and complement factor H (CFAH) correlated negatively with annual estimated glomerular filtration rate (eGFR) decline, while urinary abundances of C5, decay-accelerating factor (DAF), and CD59 correlated positively with annual rate of eGFR decline. Furthermore, higher urinary abundance of CFAH and lower urinary abundance of DAF were independently associated with greater risk of progression to ESRD. Urinary abundance of CFAH and DAF had a larger area under the curve (AUC) than that of eGFR, proteinuria, or any pathological parameter. Moreover, the model that included CFAH or DAF had a larger AUC than that with only clinical or pathological parameters.

CONCLUSION

Urinary abundance of complement proteins was significantly associated with ESRD in patients with T2DM and biopsy-proven DN, indicating that therapeutically targeting the complement pathway may alleviate progression of DN.

A potent truncated form of human soluble CR1 is protective in a mouse model of renal ischemia-reperfusion injury

The complement system is a potent mediator of ischemia–reperfusion injury (IRI), which detrimentally affects the function and survival of transplanted kidneys. Human complement receptor 1 (HuCR1) is an integral membrane protein that inhibits complement activation by blocking the convertases that activate C3 and C5. We have previously reported that CSL040, a truncated form of recombinant soluble HuCR1 (sHuCR1), has enhanced complement inhibitory activity and improved pharmacokinetic properties compared to the parent molecule. Here, we compared the capacity of CSL040 and full-length sHuCR1 to suppress complement-mediated organ damage in a mouse model of warm renal IRI. Mice were treated with two doses of CSL040 or sHuCR1, given 1 h prior to 22 min unilateral renal ischemia and again 3 h later. 24 h after reperfusion, mice treated with CSL040 were protected against warm renal IRI in a dose-dependent manner, with the highest dose of 60 mg/kg significantly reducing renal dysfunction, tubular injury, complement activation, endothelial damage, and leukocyte infiltration. In contrast, treatment with sHuCR1 at a molar equivalent dose to 60 mg/kg CSL040 did not confer significant protection. Our results identify CSL040 as a promising therapeutic candidate to attenuate renal IRI and demonstrate its superior efficacy over full-length sHuCR1 in vivo.

Emerging recognition of the complement system in hepatic ischemia/reperfusion injury, liver regeneration and recovery (Review)

Hepatic ischemia/reperfusion injury (IRI) is a result of the ischemic cascade and may occur in the settings of liver trauma, resection and transplantation. Components of the complement system have been indicated to be mediators of hepatic IRI and regulators of liver regeneration. As such, their potential to mediate both beneficial and harmful effects render them key targets for therapy. In the present study, the mechanisms of complement mediating hepatic IRI were discussed with a focus on the different functions of complement in hepatic injury and liver recovery, and an explanation for this apparent paradox is provided, i.e. that the complement products C3a and C5a have an important role in liver damage; however, C3a and C5a are also necessary for liver regeneration. Furthermore, situated at the end of the complement activation cascade, the membrane attack complex is crucial in hepatic IRI and inhibiting the complex with a site-targeted murine complement inhibitor, complement receptor 2-CD59, may improve liver regeneration after partial hepatectomy, even when hepatectomy is combined with ischemia and reperfusion.

C5b-9 membrane attack complex activated NLRP3 inflammasome mediates renal tubular immune injury in trichloroethylene sensitized mice

Trichloroethylene (TCE) induced occupational medicamentosa-like dermatitis (OMLDT) in patients is accompanied, typically, by renal damage. But the role of C5b-9 and IL-1β in TCE-sensitized mouse renal tubular damage is unclear. This study aimed to investigate whether TCE-sensitized mouse renal tubular epithelial cell damage was induced by NLRP3 inflammasome and whether NLRP3 inflammasome was activated by sublytic C5b-9. In total, 52 specific pathogen-free BALB/c female mice, 6- to 8-week-old, were used for establishing the TCE-sensitized mouse model. Renal tubular epithelial cells were isolated and used for determining the sublytic level of C5b-9. Kidney histological examination, serum neutrophil gelatinase associated lipocalin (NGAL) level were used for kidney damage evaluation. Renal protein levels of C5b-9, NLRP3, ASC, Caspase-1, IL-1β, and IL-18 were measured. The renal lesions, serum NGAL level, renal NLRP3, ASC, Caspase-1 and IL-1β protein levels all increased significantly in TCE sensitized positive group. However, pretreatment with recombinant protein sCD59-Cys inhibited the expression of C5b-9, NLRP3 inflammasome, IL-1β, IL-18, and attenuated renal tubular epithelial cell damage. The sublytic C5b-9 activated NLRP3 inflammasome and aggravated renal tubular epithelial cell damage. Pretreatment with recombinant protein sCD59-Cys blocked the expression of the NLRP3 inflammasome by inhibiting the expression of C5b-9, and alleviating renal tubular epithelial cell damage.

Generation of a novel decay accelerating factor (DAF) knock-out rat model using clustered regularly-interspaced short palindromic repeats, (CRISPR)/associated protein 9 (Cas9), genome editing

Decay accelerating factor (DAF), a key complement activation control protein, is a 70 kDa membrane bound glycoprotein which controls extent of formation of the C3 and C5 convertases by accelerating their decay. Using clustered regularly-interspaced short palindromic repeats, (CRISPR)/associated protein 9 (Cas9) genome editing we generated a novel DAF deficient (Daf^-/-) rat model. The present study describes the renal and extrarenal phenotype of this model and assesses renal response to complement-dependent injury induced by administration of a complement-fixing antibody (anti-Fx1A) against the glomerular epithelial cell (podocyte). Rats generated were healthy, viable and able to reproduce normally. Complete absence of DAF was documented in renal as well as extra-renal tissues at both protein and mRNA level compared to Daf^+/+ rats. Renal histology in Daf^-/- rats showed no differences regarding glomerular or tubulointerstitial pathology compared to Daf^+/+ rats. Moreover, there was no difference in urine protein excretion (ratio of urine albumin to creatinine) or in serum creatinine and urea levels. In Daf^-/- rats, proteinuria was significantly increased following binding of anti-Fx1A antibody to podocytes while increased C3b deposition was observed. The DAF knock-out rat model developed validates the role of this complement cascade regulator in immune-mediated podocyte injury. Given the increasing role of dysregulated complement activation in various forms of kidney disease and the fact that the rat is the preferred animal for renal pathophysiology studies, the rat DAF deficient model may serve as a useful tool to study the role of this complement activation regulator in complement-dependent forms of kidney injury.

Inhibition of BRD4 Reduces Neutrophil Activation and Adhesion to the Vascular Endothelium Following Ischemia Reperfusion Injury

Renal ischemia reperfusion injury (IRI) is associated with inflammation, including neutrophil infiltration that exacerbates the initial ischemic insult. The molecular pathways involved are poorly characterized and there is currently no treatment. We performed an in silico analysis demonstrating changes in NFκB-mediated gene expression in early renal IRI. We then evaluated NFκB-blockade with a BRD4 inhibitor on neutrophil adhesion to endothelial cells in vitro, and tested BRD4 inhibition in an in vivo IRI model. BRD4 inhibition attenuated neutrophil adhesion to activated endothelial cells. In vivo, IRI led to increased expression of cytokines and adhesion molecules at 6 h post-IRI with sustained up-regulated expression to 48 h post-IRI. These effects were attenuated, in part, with BRD4 inhibition. Absolute neutrophil counts increased significantly in the bone marrow, blood, and kidney 24 h post-IRI. Activated neutrophils increased in the blood and kidney at 6 h post-IRI and remained elevated in the kidney until 48 h post-IRI. BRD4 inhibition reduced both total and activated neutrophil counts in the kidney. IRI-induced tubular injury correlated with neutrophil accumulation and was reduced by BRD4 inhibition. In summary, BRD4 inhibition has important systemic and renal effects on neutrophils, and these effects are associated with reduced renal injury.

Vascular Signaling in Allogenic Solid Organ Transplantation - The Role of Endothelial Cells

Graft rejection remains the major obstacle after vascularized solid organ transplantation. Endothelial cells, which form the interface between the transplanted graft and the host’s immunity, are the first target for host immune cells. During acute cellular rejection endothelial cells are directly attacked by HLA I and II-recognizing NK cells, macrophages, and T cells, and activation of the complement system leads to endothelial cell lysis. The established forms of immunosuppressive therapy provide effective treatment options, but the treatment of chronic rejection of solid organs remains challenging. Chronic rejection is mainly based on production of donor-specific antibodies that induce endothelial cell activation—a condition which phenotypically resembles chronic inflammation. Activated endothelial cells produce chemokines, and expression of adhesion molecules increases. Due to this pro-inflammatory microenvironment, leukocytes are recruited and transmigrate from the bloodstream across the endothelial monolayer into the vessel wall. This mononuclear infiltrate is a hallmark of transplant vasculopathy. Furthermore, expression profiles of different cytokines serve as clinical markers for the patient’s outcome. Besides their effects on immune cells, activated endothelial cells support the migration and proliferation of vascular smooth muscle cells. In turn, muscle cell recruitment leads to neointima formation followed by reduction in organ perfusion and eventually results in tissue injury. Activation of endothelial cells involves antibody ligation to the surface of endothelial cells. Subsequently, intracellular signaling pathways are initiated. These signaling cascades may serve as targets to prevent or treat adverse effects in antibody-activated endothelial cells. Preventive or therapeutic strategies for chronic rejection can be investigated in sophisticated mouse models of transplant vasculopathy, mimicking interactions between immune cells and endothelium.

Hypoxia-induced complement dysregulation is associated with microvascular impairments in mouse tracheal transplants

BACKGROUND

Complement Regulatory Proteins (CRPs), especially CD55 primarily negate complement factor 3-mediated injuries and maintain tissue homeostasis during complement cascade activation. Complement activation and regulation during alloimmune inflammation contribute to allograft injury and therefore we proposed to investigate a crucial pathological link between vascular expression of CD55, active-C3, T cell immunity and associated microvascular tissue injuries during allograft rejection.

METHODS

Balb/c→C57BL/6 allografts were examined for microvascular deposition of CD55, C3d, T cells, and associated tissue microvascular impairments during rejection in mouse orthotopic tracheal transplantation.

RESULTS

Our findings demonstrated that hypoxia-induced early activation of HIF-1α favors a cell-mediated inflammation (CD4⁺, CD8⁺, and associated proinflammatory cytokines, IL-2 and TNF-α), which proportionally triggers the downregulation of CRP-CD55, and thereby augments the uncontrolled release of active-C3, and Caspase-3 deposition on CD31⁺ graft vascular endothelial cells. These molecular changes are pathologically associated with microvascular deterioration (low tissue O₂ and Blood flow) and subsequent airway epithelial injuries of rejecting allografts as compared to non-rejecting syngrafts.

CONCLUSION

Together, these findings establish a pathological correlation between complement dysregulation, T cell immunity, and microvascular associated injuries during alloimmune inflammation in transplantation.

Kidney injury enhances renal G-CSF expression and modulates granulopoiesis and human neutrophil CD177 in vivo

Kidney injury significantly increases overall mortality. Neutrophilic granulocytes (neutrophils) are the most abundant human blood leukocytes. They are characterized by a high turnover rate, chiefly controlled by granulocyte colony stimulating factor (G‐CSF). The role of kidney injury and uremia in regulation of granulopoiesis has not been reported. Kidney transplantation, which inherently causes ischemia–reperfusion injury of the graft, elevated human neutrophil expression of the surface glycoprotein CD177. CD177 is among the most G‐CSF‐responsive neutrophil genes and reversibly increased on neutrophils of healthy donors who received recombinant G‐CSF. In kidney graft recipients, a transient rise in neutrophil CD177 correlated with renal tubular epithelial G‐CSF expression. In contrast, CD177 was unaltered in patients with chronic renal impairment and independent of renal replacement therapy. Under controlled conditions of experimental ischemia–reperfusion and unilateral ureteral obstruction injuries in mice, renal G‐CSF mRNA and protein expression significantly increased and systemic neutrophilia developed. Human renal tubular epithelial cell G‐CSF expression was promoted by hypoxia and proinflammatory cytokine interleukin 17A in vitro. Clinically, recipients of ABO blood group‐incompatible kidney grafts developed a larger rise in neutrophil CD177. Their grafts are characterized by complement C4d deposition on the renal endothelium, even in the absence of rejection. Indeed, complement activation, but not hypoxia, induced primary human endothelial cell G‐CSF expression. Our data demonstrate that kidney injury induces renal G‐CSF expression and modulates granulopoiesis. They delineate differential G‐CSF regulation in renal epithelium and endothelium. Altered granulopoiesis may contribute to the systemic impact of kidney injury.

Complement regulatory protein CD59a plays a protective role in immune liver injury of trichloroethylene-sensitized BALB/c mice

Trichloroethylene (TCE) is a major occupational and environmental chemical compound which causes occupational dermatitis medicamentosa-like of TCE with severe liver damage. Our previous studies showed that complement activation was a newly recognized mechanism for TCE-induced liver damage. The objective of this study was to explore the role of the key complement regulatory protein, CD59a, in TCE-induced immune liver injury. We firstly evaluated the changes of CD59a expression in liver tissue and then investigated if the changes were associated with membrane attack complex (MAC) formation, nuclear factor kappa B (NF-κB) activation and liver damage in BALB/c mice model of TCE-induced skin sensitization in the absence or presence of soluble recombinant rat CD59-Cys. The results showed that low expression of CD59a accompanied by MAC deposition in the liver of TCE-sensitized BALB/c mice, which was consistent in time. In addition, activation of NF-κB pathway, upregulation of inflammatory cytokine and liver damage also occured. Additional experiment showed that recombinant rat sCD59-Cys alleviated inflammation and liver damage in TCE-sensitized BALB/c mice. Moreover, recombinant rat sCD59-Cys reduced MAC formation and inhibited NF-κB activation measured by P-IκBα and nuclear NF-κB p65 in the liver of TCE-sensitized BALB/c mice. In conclusion, recombinant rat sCD59-Cys plays a protective role in immune liver injury of TCE-sensitized BALB/c mice.

Caspase Inhibition During Cold Storage Improves Graft Function and Histology in a Murine Kidney Transplant Model

BACKGROUND

Prolonged cold ischemia is a risk factor for delayed graft function of kidney transplants, and is associated with caspase-3-mediated apoptotic tubular cell death. We hypothesized that treatment of tubular cells and donor kidneys during cold storage with a caspase inhibitor before transplant would reduce tubular cell apoptosis and improve kidney function after transplant.

METHODS

Mouse tubular cells were incubated with either dimethyl sulfoxide (DMSO) or Q-VD-OPh during cold storage in saline followed by rewarming in normal media. For in vivo studies, donor kidneys from C57BL/6 mice were perfused with cold saline, DMSO (vehicle), or QVD-OPh. Donor kidneys were then recovered, stored at 4°C for 60 minutes, and transplanted into syngeneic C57BL/6 recipients.

RESULTS

Tubular cells treated with a caspase inhibitor had significantly reduced capsase-3 protein expression, caspase-3 activity, and apoptotic cell death compared with saline or DMSO (vehicle) in a dose-dependent manner. Treatment of donor kidneys with a caspase inhibitor significantly reduced serum creatinine and resulted in significantly less tubular cell apoptosis, BBI, tubular injury, cast formation, and tubule lumen dilation compared with DMSO and saline-treated kidneys.

CONCLUSIONS

Caspase inhibition resulted in decreased tubular cell apoptosis and improved renal function after transplantation. Caspase inhibition may be a useful strategy to prevent cold ischemic injury of donor renal grafts.

Complement-mediated Damage to the Glycocalyx Plays a Role in Renal Ischemia-reperfusion Injury in Mice

Background

Complement activation plays an important role in the pathogenesis of renal ischemia-reperfusion (IR) injury (IRI), but whether this involves damage to the vasculoprotective endothelial glycocalyx is not clear. We investigated the impact of complement activation on glycocalyx integrity and renal dysfunction in a mouse model of renal IRI.

Methods

Right nephrectomized male C57BL/6 mice were subjected to 22 minutes left renal ischemia and sacrificed 24 hours after reperfusion to analyze renal function, complement activation, glycocalyx damage, endothelial cell activation, inflammation, and infiltration of neutrophils and macrophages.

Results

Ischemia-reperfusion induced severe renal injury, manifested by significantly increased serum creatinine and urea, complement activation and deposition, loss of glycocalyx, endothelial activation, inflammation, and innate cell infiltration. Treatment with the anti-C5 antibody BB5.1 protected against IRI as indicated by significantly lower serum creatinine (P = 0.04) and urea (P = 0.003), tissue C3b/c and C9 deposition (both P = 0.004), plasma C3b (P = 0.001) and C5a (P = 0.006), endothelial vascular cell adhesion molecule-1 expression (P = 0.003), glycocalyx shedding (tissue heparan sulfate [P = 0.001], plasma syndecan-1 [P = 0.007], and hyaluronan [P = 0.02]), inflammation (high mobility group box-1 [P = 0.0003]), and tissue neutrophil (P = 0.0009) and macrophage (P = 0.004) infiltration.

Conclusions

Together, our data confirm that the terminal pathway of complement activation plays a key role in renal IRI and demonstrate that the mechanism of injury involves shedding of the glycocalyx.

Complement Inhibitor CRIg/FH Ameliorates Renal Ischemia Reperfusion Injury via Activation of PI3K/AKT Signaling

Complement activation is involved in the pathogenesis of ischemia reperfusion injury (IRI), which is an inevitable process during kidney transplantation. Therefore, complement-targeted therapeutics hold great potential in protecting the allografts from IRI. We observed universal deposition of C3d and membrane attack complex in human renal allografts with delayed graft function or biopsy-proved rejection, which confirmed the involvement of complement in IRI. Using FB-, C3-, C4-, C5-, C5aR1-, C5aR2-, and C6-deficient mice, we found that all components, except C5aR2 deficiency, significantly alleviated renal IRI to varying degrees. These gene deficiencies reduced local (deposition of C3d and membrane attack complex) and systemic (serum levels of C3a and C5a) complement activation, attenuated pathological damage, suppressed apoptosis, and restored the levels of multiple local cytokines (e.g., reduced IL-1β, IL-9, and IL-12p40 and increased IL-4, IL-5, IL-10, and IL-13) in various gene-deficient mice, which resulted in the eventual recovery of renal function. In addition, we demonstrated that CRIg/FH, which is a targeted complement inhibitor for the classical and primarily alternative pathways, exerted a robust renoprotective effect that was comparable to gene deficiency using similar mechanisms. Further, we revealed that PI3K/AKT activation, predominantly in glomeruli that was remarkably inhibited by IRI, played an essential role in the CRIg/FH renoprotective effect. The specific PI3K antagonist duvelisib almost completely abrogated AKT phosphorylation, thus abolishing the renoprotective role of CRIg/FH. Our findings suggested that complement activation at multiple stages induced renal IRI, and CRIg/FH and/or PI3K/AKT agonists may hold the potential in ameliorating renal IRI.

Aging Is Associated With Impaired Activation of Protein Homeostasis-Related Pathways After Cardiac Arrest in Mice

Background The mechanisms underlying worse outcome at advanced age after cardiac arrest ( CA ) and resuscitation are not well understood. Because protein homeostasis (proteostasis) is essential for cellular and organismal health, but is impaired after CA , we investigated the effects of age on proteostasis-related prosurvival pathways activated after CA . Methods and Results Young (2-3 months old) and aged (21-22 months old) male C57Bl/6 mice were subjected to CA and cardiopulmonary resuscitation ( CPR ). Functional outcome and organ damage were evaluated by assessing neurologic deficits, histological features, and creatinine level. CA / CPR -related changes in small ubiquitin-like modifier conjugation, ubiquitination, and the unfolded protein response were analyzed by measuring mRNA and protein levels in the brain, kidney, and spinal cord. Thiamet-G was used to increase O-linked β-N-acetylglucosamine modification. After CA / CPR , aged mice had trended lower survival rates, more severe tissue damage in the brain and kidney, and poorer recovery of neurologic function compared with young mice. Furthermore, small ubiquitin-like modifier conjugation, ubiquitination, unfolded protein response, and O-linked β-N-acetylglucosamine modification were activated after CA / CPR in young mice, but their activation was impaired in aged mice. Finally, pharmacologically increasing O-linked β-N-acetylglucosamine modification after CA improved outcome. Conclusions Results suggest that impaired activation of prosurvival pathways contributes to worse outcome after CA / CPR in aged mice because restoration of proteostasis is critical to the survival of cells stressed by ischemia. Therefore, a pharmacologic intervention that targets aging-related impairment of proteostasis-related pathways after CA / CPR may represent a promising therapeutic strategy.

Biochemical targets of drugs mitigating oxidative stress via redox-independent mechanisms

Acute or chronic oxidative stress plays an important role in many pathologies. Two opposite approaches are typically used to prevent the damage induced by reactive oxygen and nitrogen species (RONS), namely treatment either with antioxidants or with weak oxidants that up-regulate endogenous antioxidant mechanisms. This review discusses options for the third pharmacological approach, namely amelioration of oxidative stress by 'redox-inert' compounds, which do not inactivate RONS but either inhibit the basic mechanisms leading to their formation (i.e. inflammation) or help cells to cope with their toxic action. The present study describes biochemical targets of many drugs mitigating acute oxidative stress in animal models of ischemia-reperfusion injury or N-acetyl-p-aminophenol overdose. In addition to the pro-inflammatory molecules, the targets of mitigating drugs include protein kinases and transcription factors involved in regulation of energy metabolism and cell life/death balance, proteins regulating mitochondrial permeability transition, proteins involved in the endoplasmic reticulum stress and unfolded protein response, nuclear receptors such as peroxisome proliferator-activated receptors, and isoprenoid synthesis. The data may help in identification of oxidative stress mitigators that will be effective in human disease on top of the current standard of care.