Search

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.

Diabetic Nephropathy (DN) is a chronic complication of diabetes and the primary cause of end stage renal disease. Differential diagnosis for DN requires invasive histological investigation, thus there is need for non-invasive biomarkers to discriminate among different histological lesions in diabetic patients. With the aim to identify a pattern of differentially expressed miRNAs in kidney biopsies of DN patients, we assayed miRNA expression in kidney biopsies from DN patients, diabetic patients with membranous nephropathy and patients with normal histology. Nine miRNAs were differentially expressed among the three groups, and 2 miRNAs (miR-27b-3p and miR-1228-3p) showed interaction with an ubiquitin-conjugating E2 enzyme variant (UBE2v1). UBE2v1 mediates the formation of lysine 63-linked ubiquitin chains, a mechanism we previously showed as involved in DN kidney fibrosis. Both miRNAs were validated as down-regulated in biopsies and urines of DN patients, possibly affected by DNA methylation. Interestingly, the urinary levels of both miRNAs could also discriminate among different degrees of renal fibrosis. Finally, we showed that the combined urinary expression of both miRNAs was also able to discriminate DN patients from other glomerulonephritides in diabetic patients. In conclusion we identified two miRNAs potentially useful as candidate biomarkers of tubular-interstitial fibrosis in diabetic patients with DN.

Background: Increasing evidence demonstrates a phenotypic plasticity of endothelial cells (ECs). Endothelial-to-mesenchymal transition (EndMT) contributes to the development of tissue fibrosis. However, the pathogenic factors and signalling pathways regulating this process in ischaemia/reperfusion (I/R) injury are still poorly understood., Methods: We investigated the possible role of complement in the induction of this endothelial dysfunction in a swine model of renal I/R injury by using recombinant C1 inhibitor in vivo., Results: Here, we showed that I/R injury reduced the density of renal peritubular capillaries and induced tissue fibrosis with generation of CD31(+)/α-SMA(+) and CD31(+)/FPS-1(+) cells indicating EndMT. When we inhibited complement, the process of EndMT became rare, with preserved density of peritubular capillaries and significant reduction in renal fibrosis. When we activated ECs by anaphylatoxins in vitro, C3a and C5a led to altered endothelial phenotype with increased expression of fibroblast markers and decrease expression of specific endothelial markers. The activation of Akt pathway was pivotal for the C3a and C5a-induced EndMT in vitro. In accordance, inhibition of complement in vivo led to the abrogation of Akt signalling, with hampered EndMT and tissue fibrosis., Conclusions: Our data demonstrate a critical role for complement in the acute induction of EndMT via the Akt pathway. Therapeutic inhibition of these systems may be essential to prevent vascular damage and tissue fibrosis in transplanted kidney.

Background. The aim of this study was to investigate neutrophil activation and its role in long pentraxin-3 (PTX3) release and oxidative stress generation during haemodialysis (HD) and to correlate neutrophil PTX3 and oxidant expression with endothelial dysfunction. Methods. Forty-seven uraemic patients on stable HD, 12 healthy subjects and 15 patients with congestive heart failure (New York Heart Association classes III and IV) were enrolled. Neutrophil PTX3 protein expression was evaluated by confocal microscopy. L-selectin expression, intracellular PTX3 localization and reactive oxygen species (ROS) generation in human neutrophils were measured by flow cytometry. NADPHdependent superoxide generation was investigated by chemiluminescence. PTX3 plasma concentrations were measured by ELISA. Endothelial dysfunction was studied by flow-mediated dilation (FMD). Results. The low baseline levels of FMD significantly improved after HD, but worsened by 24 h. A significant up-regulation of PTX3 protein expression, localized within secondary granules, was detected in neutrophils isolated at 30 and 240 min of HD, along with an increase in L-selectin expression. The upregulation in intracellular PTX3 in neutrophils was associated with a significant increase in PTX3 plasma concentrations at 240 min. HD increased ROS production and NADPH oxidase activity in neutrophils. In a univariate analysis, pre-treatment with FMD was inversely correlated with PTX3 expression and ROS generation in neutrophils. In a multivariate analysis, both circulating pre-HD PTX3 and intracellular ROS generation by neutrophils were independent predictors of abnormal FMD. Conclusions. Neutrophil overexpression of PTX3 is associated with ROS overproduction and endothelial dysfunction and may represent an emerging marker of vascular damage progression in HD patients. [ABSTRACT FROM AUTHOR]

Aims. Our group investigated albumin gene expression in human adipocytes, its regulation by inflammation and the possible contribution of adipose tissue to albumin circulating levels. Methods. Both inflamed and healthy subjects provided adipose tissue samples. RT-PCR, Real-Time PCR, and Western Blot analysis on homogenates of adipocytes and pre-adipocytes were performed. In sixty-three healthy subjects and fifty-four micro-inflamed end stage renal disease (ESRD) patients circulating levels of albumin were measured by nephelometry; all subjects were also evaluated for body composition, calculated from bioelectrical measurements and an thropometric data. Results. A clear gene expression of albumin was showed in pre-adipocytes and, for the first time, in mature adipocytes. Albumin gene expression resulted significantly higher in pre-adipocytes than in adipocytes. No significant difference in albumin gene expression was showed between healthy controls and inflamed patients. A significant negative correlation was observed between albumin levels and fat mass in both healthy subjects and inflamed ESRD patients. Conclusions. In the present study we found first time evidence that human adipocytes express albumin. Our results also showed that systemic inflammation does not modulate albumin gene expression. The negative correlation between albumin and fat mass seems to exclude a significant contributing role of adipocyte in plasma albumin. [ABSTRACT FROM AUTHOR]

Background: Chronic renal disease (CKD) is characterized by complex changes in cell metabolism leading to an increased production of oxygen radicals, that, in turn has been suggested to play a key role in numerous clinical complications of this pathological condition. Several reports have focused on the identification of biological elements involved in the development of systemic biochemical alterations in CKD, but this abundant literature results fragmented and not exhaustive. Results: To better define the cellular machinery associated to this condition, we employed a high-throughput genomic approach based on a whole transcriptomic analysis associated with classical molecular methodologies. The genomic screening of peripheral blood mononuclear cells revealed that 44 genes were up-regulated in both CKD patients in conservative treatment (CKD, n = 9) and hemodialysis (HD, n = 17) compared to healthy subjects (HS, n = 8) (p < 0.001, FDR = 1%). Functional analysis demonstrated that 11/44 genes were involved in the oxidative phosphorylation system. Western blotting for COXI and COXIV, key constituents of the complex IV of oxidative phosphorylation system, performed on an independent testing-group (12 healthy subjects, 10 CKD and 14 HD) confirmed an higher synthesis of these subunits in CKD/HD patients compared to the control group. Only for COXI, the comparison between CKD and healthy subjects reached the statistical significance. However, complex IV activity was significantly reduced in CKD/HD patients compared to healthy subjects (p < 0.01). Finally, CKD/HD patients presented higher reactive oxygen species and 8-hydroxydeoxyguanosine levels compared to controls. Conclusion: Taken together these results suggest, for the first time, that CKD/HD patients may have an impaired mitochondrial respiratory system and this condition may be both the consequence and the cause of an enhanced oxidative stress. [ABSTRACT FROM AUTHOR]

Abstract: Objective: Pentraxin-3 (PTX3) has been suggested to play a role in the development of vascular pathology. Stenosis of arteriovenous fistula (AVF) leading to its failure is the major cause of morbidity in hemodialysis patients. To date, little is known on the pathogenesis of AVF stenosis. The aim of the present study was to investigate the potential role of PTX3 in this setting. Methods and results: A sample of venous wall was collected at the time of AVF formation in 44 patients with end stage renal disease. Ten patients developed AVF stenosis and from these patients a second portion of the venous wall was obtained during surgical revision of the AVF. Confocal laser scanning microscopy demonstrated that PTX3 immunostaining, hardly detectable in native AVF, was significantly increased in failed AVF, showing a specific co-localization with endothelial cell markers. Circulating mononuclear cells isolated at the time of AVF revision presented a significantly higher PTX3 mRNA expression than those collected during AVF creation. Interestingly, a significant deposition of C5b-9 on endothelial cells, co-localizing with PTX3, was observed in stenotic AVF. Conclusion: The present study demonstrates for the first time a close association between PTX3 deposition and complement activation at the endothelial cell level in failed AVF and suggests a role for PTX3 in modulating innate immunity in the pathogenesis of AVF stenosis. [Copyright &y& Elsevier]