Giovanni Pertosa

Mitochondrial dysregulation and oxidative stress in patients with chronic kidney disease

BackgroundChronic 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.ResultsTo 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.ConclusionTaken 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.

A specific immune transcriptomic profile discriminates chronic kidney disease patients in predialysis from hemodialyzed patients

BackgroundChronic kidney disease (CKD) patients present a complex interaction between the innate and adaptive immune systems, in which immune activation (hypercytokinemia and acute-phase response) and immune suppression (impairment of response to infections and poor development of adaptive immunity) coexist. In this setting, circulating uremic toxins and microinflammation play a critical role. This condition, already present in the last stages of renal damage, seems to be enhanced by the contact of blood with bioincompatible extracorporeal hemodialysis (HD) devices. However, although largely described, the cellular machinery associated to the CKD- and HD-related immune-dysfunction is still poorly defined. Understanding the mechanisms behind this important complication may generate a perspective for improving patients outcome.MethodsTo better recognize the biological bases of the CKD-related immune dysfunction and to identify differences between CKD patients in conservative (CKD) from those in HD treatment, we used an high-throughput strategy (microarray) combined with classical bio-molecular approaches.ResultsImmune transcriptomic screening of peripheral blood mononuclear cells (1030 gene probe sets selected by Gene-Ontology) showed that 275 gene probe sets (corresponding to 213 genes) discriminated 9 CKD patients stage III-IV (mean ± SD of eGFR: 32.27±14.7 ml/min) from 17 HD patients (p < 0.0001, FDR = 5%). Seventy-one genes were up- and 142 down-regulated in HD patients. Functional analysis revealed, then, close biological links among the selected genes with a pivotal role of PTX3, IL-15 (up-regulated in HD) and HLA-G (down-regulated in HD). ELISA, performed on an independent testing-group [11 CKD stage III-IV (mean ± SD of eGFR: 30.26±14.89 ml/min) and 13 HD] confirmed that HLA-G, a protein with inhibition effects on several immunological cell lines including natural killers (NK), was down-expressed in HD (p = 0.04). Additionally, in the testing-group, protein levels of CX3CR1, an highly selective chemokine receptor and surface marker for cytotoxic effector lymphocytes, resulted higher expressed in HD compared to CKD (p < 0.01).ConclusionTaken together our results show, for the first time, that HD patients present a different immune-pattern compared to the un-dialyzed CKD patients. Among the selected genes, some of them encode for important biological elements involved in proliferation/activation of cytotoxic effector lymphocytes and in the immune-inflammatory cellular machinery. Additionally, this study reveals new potential diagnostic bio-markers and therapeutic targets.

Pre-existing type 2 diabetes mellitus is an independent risk factor for mortality and progression in patients with renal cell carcinoma.

AbstractMalignancies are one of the main causes of mortality in diabetic patients; however, to date, very limited data have been reported on the specific influence of type 2 diabetes mellitus (T2DM) on the survival of patients with renal cell carcinoma (RCC). In the present long-term retrospective study, we investigated whether T2DM may influence the overall survival (OS), cancer-specific survival (CSS), and progression-free survival (PFS) in patients with surgically treated RCC.Medical records of 924 patients treated by radical or partial nephrectomy for sporadic, unilateral RCC were reviewed. Patients with type-1 DM and with T2 DM receiving insulin treatment were excluded. Survival estimates were calculated according to the Kaplan–Meier method and compared with the log-rank test. Univariate and multivariate analyses were performed using the Cox regression model.Of the 924 RCC patients, 152 (16.5%) had T2DM. Mean follow-up was 68.5 months. Mean OS was 41.3 and 96.3 months in T2DM and non-T2DM patients, respectively (P < 0.0001).The estimated CSS rates at 1, 3, and 5 years in T2DM versus non-T2DM patients were 63.4% versus 76.7%, 30.4% versus 56.6%, and 16.3% versus 48.6%, respectively (P = 0.001). Mean PFS was significantly lower (31.5 vs 96.3 months; P < 0.0001) in the T2DM group. At multivariate analysis, T2DM was an independent adverse prognostic factor for OS (hazard ratio [HR] = 3.44; 95% confidence interval [CI]:2.40–4.92), CSS (HR = 6.39; 95% CI: 3.78–10.79), and PFS (HR = 4.71; 95% CI: 3.11–7.15).In conclusion, our findings suggest that patients with RCC and pre-existing T2DM have a shorter OS, increased risk of recurrence, and higher risk for kidney cancer mortality than those without diabetes.

Serum fetuin a in hemodialysis: a link between derangement of calcium-phosphorus homeostasis and progression of atherosclerosis?

BACKGROUND Fetuin A, a circulating inhibitor of ectopic calcification, is downregulated in hemodialysis and has been shown to predict cardiovascular mortality in this setting. The association of altered calcium-phosphorus with serum fetuin A levels is still a matter of debate. Although carotid intima-media thickness (cIMT) is a strong predictor of major cardiovascular events, its association with serum fetuin A levels is poorly defined. STUDY DESIGN Cohort study. PARTICIPANTS & SETTINGS 174 uremic patients on long-term hemodialysis therapy enrolled in 4 university hospitals. PREDICTORS Serum fetuin A levels at the beginning of the study (T0) and after 12 months (T12). OUTCOMES Progression of atherosclerosis assessed by means of cIMT measurements at 24 months (T24); cardiovascular morbidity and mortality at 36 months. RESULTS Serum fetuin A concentrations at T0 and T12 were 282.3 +/- 79.4 and 290.0 +/- 92.2 microg/mL, respectively. Mean T0 and T24 cIMT values were 1.02 +/- 0.2 and 1.06 +/- 0.2 mm, respectively (P < 0.001). Fatal and nonfatal cardiovascular disease occurred in 36 and 86 patients by 36 months, respectively. In multivariate logistic regression, higher calcium-phosphorus product was associated with lower serum fetuin A level (odds ratio, 0.96; 95% confidence interval [CI], 0.93 to 1.00; P = 0.02). Multiple regression analysis showed that T0 serum fetuin A level was associated with T24 cIMT (P = 0.01) after adjustments for age, cholesterol level, high-sensitivity C-reactive protein level, previous cardiovascular events, and T0 cIMT. In a multivariate Cox regression analysis, cardiovascular mortality was independently associated with a 1-tertile lower T0 serum fetuin A level, and a 1-tertile higher T0 cIMT value was independently associated with greater cardiovascular mortality (hazard ratio, 0.45; 95% CI, 0.15 to 0.65; P = 0.007 and hazard ratio, 10.00; 95% CI, 3.16 to 31.73; P < 0.001, respectively) after adjustment for age and previous cardiovascular events. LIMITATION Length of follow-up. CONCLUSION Calcium-phosphorus product in hemodialysis patients inversely correlated with serum fetuin A level, which, in turn, was associated inversely with progression of atherosclerotic lesions and cardiovascular mortality in this study population.

BMP-2 induces a profibrotic phenotype in adult renal progenitor cells through Nox4 activation

Adult renal progenitor cells (ARPCs) isolated from the human kidney may contribute to repair featuring acute kidney injury (AKI). Bone morphogenetic proteins (BMPs) regulate differentiation, modeling, and regeneration processes in several tissues. The aim of this study was to evaluate the biological actions of BMP-2 in ARPCs in vitro and in vivo. BMP-2 was expressed in ARPCs of normal adult human kidneys, and it was upregulated in vivo after delayed graft function (DGF) of renal transplantation, a condition of AKI. ARPCs expressed BMP receptors, suggesting their potential responsiveness to BMP-2. Incubation of ARPCs with this growth factor enhanced reactive oxygen species (ROS) production, NADPH oxidase activity, and Nox4 protein expression. In vivo, Nox4 was localized in BMP-2-expressing CD133+ cells at the tubular level after DGF. BMP-2 incubation induced α-smooth muscle actin (SMA), collagen I, and fibronectin protein expression in ARPCs. Moreover, α-SMA colocalized with CD133 in vivo after DGF. The oxidative stimulus (H(2)O(2)) induced α-SMA expression in ARPCs, while the antioxidant N-acetyl-cysteine inhibited BMP-2-induced α-SMA expression. Nox4 silencing abolished BMP-2-induced NADPH oxidase activation and myofibroblastic induction. We showed that 1) ARPCs express BMP-2, 2) this expression is increased in a model of AKI; 3) BMP-2 may induce the commitment of ARPCs toward a myofibroblastic phenotype in vitro and in vivo; and 4) this profibrotic effect is mediated by Nox4 activation. Our findings suggest a novel mechanism linking AKI with progressive renal damage.

Coagulation Cascade Activation Causes CC Chemokine Receptor-2 Gene Expression and Mononuclear Cell Activation in Hemodialysis Patients

Priming of the coagulation cascade during hemodialysis (HD) leads to the release of activated factor X (FXa). The binding of FXa to its specific receptors, effector protease receptor-1 (EPR-1) and protease-activated receptor-2 (PAR-2), may induce the activation of peripheral blood mononuclear cells (PBMC) and promote a chronic inflammatory state that is responsible for several HD-related morbidities. In the attempt to elucidate the mechanisms underlying the coagulation-associated inflammation in HD, 10 HD patients were randomized to be treated subsequently with a cellulose acetate membrane (CA) and Ethylen-vinyl-alcohol (EVAL), a synthetic membrane that has been shown to reduce FXa generation. At the end of each experimental period, surface FXa and thrombin receptors (EPR-1 and PAR-1, -2, and -4) and CCR2 (monocyte chemoattractant protein-1 receptor) gene expression in isolated PBMC were examined. the ability of dialytic membranes to activate protein-tyrosine kinases and the stress-activated kinase JNK and to modulate the generation of terminal complement complex (TCC) was also investigated. EPR-1 and PAR-2 and -4 mRNA expression, barely detectable in normal PBMC, were significantly upregulated in HD patients, particularly in those who were treated with CA. A striking increase of tyrosine-phosphorylated proteins and JNK activation was observed at the end of HD only in CA-treated patients. Simultaneously, an increased gene expression for both splicing isoforms of CCR2, A and B, only in PBMC from CA-treated patients was demonstrated. The increased CCR-2 mRNA abundance was followed by a significant increase in its protein synthesis. The high expression of CCR2 was associated with an increased generation of plasma TCC and a significant drop in leukocyte and monocyte count. By contrast, EVAL treatment slightly lowered TCC generation and normalized leukocyte count. In vitro FXa induced CCR2 A and B expression and JNK activation in freshly isolated PBMC. FXa-induced CCR2 mRNA expression was completely abolished by JNK and tyrosine kinase inhibition. In conclusion, these data suggest that subclinical clotting activation may cause an increased CCR2 gene and protein expression on uremic PBMC, contributing to HD-related chronic microinflammation. The use of the less coagulation-activating membrane, EVAL, may reduce PBMC activation through the modulation of the stress-activated kinase JNK.

Complement Modulation of Anti-Aging Factor Klotho in Ischemia/Reperfusion Injury and Delayed Graft Function.

Klotho is an anti‐aging factor mainly produced by renal tubular epithelial cells (TEC) with pleiotropic functions. Klotho is down‐regulated in acute kidney injury in native kidney; however, the modulation of Klotho in kidney transplantation has not been investigated. In a swine model of ischemia/reperfusion injury (IRI), we observed a remarkable reduction of renal Klotho by 24 h from IRI. Complement inhibition by C1‐inhibitor preserved Klotho expression in vivo by abrogating nuclear factor kappa B (NF‐kB) signaling. In accordance, complement anaphylotoxin C5a led to a significant down‐regulation of Klotho in TEC in vitro that was NF‐kB mediated. Analysis of Klotho in kidneys from cadaveric donors demonstrated a significant expression of Klotho in pre‐implantation biopsies; however, patients affected by delayed graft function (DGF) showed a profound down‐regulation of Klotho compared with patients with early graft function. Quantification of serum Klotho after 2 years from transplantation demonstrated significant lower levels in DGF patients. Our data demonstrated that complement might be pivotal in the down‐regulation of Klotho in IRI leading to a permanent deficiency after years from transplantation. Considering the anti‐senescence and anti‐fibrotic effects of Klotho at renal levels, we hypothesize that this acquired deficiency of Klotho might contribute to DGF‐associated chronic allograft dysfunction.

Pentraxin 3 and complement cascade activation in the failure of arteriovenous fistula

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.

Interaction between parathyroid hormone and the Charlson comorbidity index on survival of incident haemodialysis patients

BACKGROUND Haemodialysis patients are ageing and have with a high rate of comorbidities. The impact of this novel clinical setting on intact parathyroid hormone (iPTH) is not well established. METHODS For this observational, prospective multicentre cohort study, incident haemodialysis patients were recruited in 40 Italian centres and followed up for a mean period of 18 +/- 6.7 months. Clinical characteristics and biochemistry were recorded at baseline. Comorbid conditions were scored by the Charlson comorbidity index (CCI). RESULTS Data of 411 patients (mean age: 66.5 +/- 14.8 years; 17.3% >80 years old) were recorded. The mean CCI was 4.17 +/- 2.8. In patients with CCI >0, an inverse correlation was observed between CCI (excluding age) and iPTH (P = 0.00002). Independently of CCI, patients with iPTH <150 pg/ml had 76% as high as the risk of all-cause mortality. After multivariable adjustment, the combination of the first tertile of iPTH with second and third tertiles of CCI was significantly associated with all-cause mortality (RR = 3.83, P = 0.02; RR = 3.79, P = 0.01, respectively). CONCLUSIONS Incident haemodialysis patients suffer from a high rate of clinical complications. In these patients, low iPTH and high CCI are often associated and very likely responsible for an adverse outcome.

Endothelial dysfunction and renal fibrosis in endotoxemia-induced oliguric kidney injury: possible role of LPS-binding protein

IntroductionThe pathophysiology of endotoxemia-induced acute kidney injury (AKI) is characterized by an intense activation of the host immune system and renal resident cells by lipopolysaccharide (LPS) and derived proinflammatory products. However, the occurrence of renal fibrosis in this setting has been poorly investigated. The aim of the present study was to investigate the possible association between endothelial dysfunction and acute development of tissue fibrosis in a swine model of LPS-induced AKI. Moreover, we studied the possible effects of coupled plasma filtration adsorption (CPFA) in this setting.MethodsAfter 9 hours from LPS infusion and 6 hours of CPFA treatment, histologic and biochemical changes were analyzed in pigs. Apoptosis and endothelial dysfunction were assessed on renal biopsies. The levels of LPS-binding protein (LBP) were quantified with enzyme-linked immunosorbent assay (ELISA). Endothelial cells (ECs) were stimulated in vitro with LPS and cultured in the presence of swine sera and were analyzed with FACS and real-time RT-PCR.ResultsIn a swine model of LPS-induced AKI, we observed that acute tubulointerstitial fibrosis occurred within 9 hours from LPS injection. Acute fibrosis was associated with dysfunctional alpha-smooth muscle actin (α-SMA)+ ECs characterized by active proliferation (Ki-67+) without apoptosis (caspase-3-). LPS led to EC dysfunction in vitro with significant vimentin and N-cadherin expression and increased collagen I mRNA synthesis. Therapeutic intervention by citrate-based CPFA significantly prevented acute fibrosis in endotoxemic animals, by preserving the EC phenotype in both peritubular capillaries and renal arteries. We found that the removal of LBP from plasma was crucial to eliminate the effects of LPS on EC dysfunction, by blocking LPS-induced collagen I production.ConclusionsOur data indicate that EC dysfunction might be pivotal in the acute development of tubulointerstitial fibrosis in LPS-induced AKI. Selective removal of the LPS adaptor protein LBP might represent a future therapeutic option to prevent EC dysfunction and tissue fibrosis in endotoxemia-induced AKI.