Konstantinos Giannakakis

AKT2 is essential to maintain podocyte viability and function during chronic kidney disease

In chronic kidney disease (CKD), loss of functional nephrons results in metabolic and mechanical stress in the remaining ones, resulting in further nephron loss. Here we show that Akt2 activation has an essential role in podocyte protection after nephron reduction. Glomerulosclerosis and albuminuria were substantially worsened in Akt2−/− but not in Akt1−/− mice as compared to wild-type mice. Specific deletion of Akt2 or its regulator Rictor in podocytes revealed that Akt2 has an intrinsic function in podocytes. Mechanistically, Akt2 triggers a compensatory program that involves mouse double minute 2 homolog (Mdm2), glycogen synthase kinase 3 (Gsk3) and Rac1. The defective activation of this pathway after nephron reduction leads to apoptosis and foot process effacement of the podocytes. We further show that AKT2 activation by mammalian target of rapamycin complex 2 (mTORC2) is also required for podocyte survival in human CKD. More notably, we elucidate the events underlying the adverse renal effect of sirolimus and provide a criterion for the rational use of this drug. Thus, our results disclose a new function of Akt2 and identify a potential therapeutic target for preserving glomerular function in CKD.

Aberrantly glycosylated IgA1 in glomerular immune deposits of IgA nephropathy

In IgA nephropathy, abnormal O-glycosylation of IgA1 molecules contributes to mesangial IgA1 deposition and the development of glomerular injury; however, direct in situ demonstration of aberrantly O-glycosylated IgA1 within glomerular immune deposits has not been reported. This study investigated the presence of abnormally glycosylated IgA1 in situ and its spatial relationship with complement within the immune deposits and correlated these features with glomerular lesion severity. Immunofluorescence and confocal microscopy were used to evaluate 19 consecutive renal biopsies, and the severity of glomerular lesions were also scored. Aberrantly glycosylated IgA was observed within the immune deposits, and its amount was found to correlate with both the severity of glomerular lesions and the amount of C3c on the surface of the deposits. These results demonstrate that qualitative and quantitative evaluation of aberrantly glycosylated IgA can be performed on routine renal biopsy samples. Its presence in immune deposits likely influences the spatial organization of IgA and C3c, thereby contributing to the glomerular inflammatory response in IgA nephropathy.

Antiphospholipid Antibodies and Renal Involvement

Antiphospholipid antibodies are a heterogeneous group of autoantibodies associated with the hypercoagulable state affecting all vascular districts with thrombosis named antiphospholipid syndrome (APS). APS is an autoimmune disease with multifactorial etiology that includes cellular, molecular, genetic and pathogenic mechanisms. The APS clinical features are a combination of arterial and/or venous thrombosis, hematological events, recurrent fetal losses, neurological disorders and intra-abdominal manifestations. The renal involvement is associated with both primary and secondary APS. Clinical features include hypertension, renal artery stenosis, thrombotic microangiopathy and other histological manifestations of the nephropathy (APSN), venous renal thrombosis, APSN in the course of systemic lupus erythematosus and renal failure. APSN is an independent risk factor that should be included in the classification criteria for definite APS with characteristic clinical and histological features.

Histopathology of Lupus Nephritis

The spectrum of morphologic changes in lupus nephritis, either microscopic, ultrastructural, or immunohistological, closely reflects the great variety of immune complexes that are produced in the course of the disease. Every tissue component of the kidney can be affected, but glomeruli are the target structure in most patients. Several attempts have been made to correlate the clinical severity and the outcome of the nephritis with the pathologic features; the current classification and the six classes that resulted from an international study group are entirely based on glomerular changes. Major criteria of classification include the focal or diffuse involvement of the glomerulus, the site of hypercellularity, the site of immune complex deposition and the presence of active and/or sclerotic lesions. Even if less thoroughly investigated than the glomerulus, the interstitial compartment has revealed many interesting features as are vascular lesions, a common and often underestimated feature. Typing of subpopulation of lymphoid infiltrates supports the emerging evidence indicating that B cells are promoting autoimmunity in mechanisms other than autoAb secretion. Many aspects are still debated and/or poorly understood, such as the interpretation of the so-called “full house nephropathy” that closely mimic lupus nephritis in seronegative patients.

c-Flip overexpression affects satellite cell proliferation and promotes skeletal muscle aging

This study shows that forcing c-Flip overexpression in undifferentiated skeletal myogenic cells in vivo results in early aging muscle phenotype. In the transgenic mice, adult muscle histology, histochemistry and biochemistry show strong alterations: reduction of fibers size and muscle mass, mitochondrial abnormalities, increase in protein oxidation and apoptosis markers and reduced AKT/GSK3β phosphorylation. In the infant, higher levels of Pax-7, PCNA, P-ERK and active-caspase-3 were observed, indicating enhanced proliferation and concomitant apoptosis of myogenic precursors. Increased proliferation correlated with NF-κB activation, detected as p65 phosphorylation, and with high levels of embryonic myosin heavy chain. Reduced regenerative potential after muscle damage in the adult and impaired fiber growth associated with reduced NFATc2 activation in the infant were also observed, indicating that the satellite cell pool is prematurely compromised. Altogether, these data show a role for c-Flip in modulating skeletal muscle phenotype by affecting the proliferative potential of undifferentiated cells. This finding indicates a novel additional mechanism through which c-Flip might possibly control tissue remodeling.

Crescentic glomerulonephritis associated with vascular endothelial growth factor (VEGF) inhibitor and bisphosphonate administration

Bevacizumab, a vascular endothelial growth factor (VEGF) inhibitor, has been widely used in a variety of malignancies offering substantial clinical benefit. Hypertension and proteinuria are the most commonly reported manifestations of bevacizumab-related nephrotoxicity with the risk increasing along with the dose and with the concomitant use of bisphosphonates. We describe the first case of a patient with small-cell lung cancer who developed diffuse extracapillary necrotizing crescentic glomerulonephritis, temporarily necessitating haemodialysis, following administration of bevacizumab and zolendronate. Renal function improved without any specific treatment and the patient remained off dialysis after withdrawal of bevacizumab-zolendronate. Special caution is required when VEGF inhibitors are combined with bisphosphonates. Such a combination can cause crescentic necrotizing glomerular lesions. Withdrawal of the offending medications may be adequate for the alleviation of this severe glomerulonephritis.

Acute rifampicin-associated interstitial tubulopathy in a patient with pulmonary tuberculosis: a case report

IntroductionRifampicin is one of the most effective antibiotics for treating tuberculosis, but it has been associated with adverse reactions, such as nephrotoxicity, sometimes resulting in acute renal failure with oligoanuria, and hepatotoxicity. Although deterioration of renal function, determined by acute tubulointerstitial nephritis and/or acute tubular necrosis, typically appears in patients receiving intermittent rifampicin therapy, some authors have also reported cases occurring during continuous rifampicin therapy.Case presentationWe describe the case of acute renal failure with polyuria occurring in a previously healthy 50-year-old Caucasian man undergoing continuous therapy with rifampicin for culture-confirmed pulmonary tuberculosis. The patient was admitted to the L. Spallanzani National Institute for Infectious Diseases, Rome, Italy, with a 1-month history of coughing, fever and weight loss. After 6 weeks of standard antituberculous treatment, progressive deterioration of his renal function was observed: creatinine levels rose from 38.9μmol/L to 318.2μmol/L and urine volume also progressively increased to reach a state of true polyuria (8 to 10L of urine per day). He was diagnosed with suspected acute rifampicin-induced renal failure. A renal biopsy showed focal segmental glomerulosclerosis associated with acute tubulointerstitial nephritis. Rifampicin was discontinued with excellent results: after 15 days his renal function began to improve and his serum creatinine values returned to normal.ConclusionA high index of suspicion for rifampicin-associated acute renal failure should be maintained in patients with pulmonary tuberculosis who develop progressive deterioration of renal function during treatment with rifampicin. Early diagnosis and discontinuation of rifampicin are of fundamental importance for recovering renal function.

Losartan Affects Glomerular AKT and mTOR Phosphorylation in an Experimental Model of Type 1 Diabetic Nephropathy

The AKT-mTOR pathway is activated in diabetic nephropathy. Renin-angiotensin system modulators exert beneficial effects on the diabetic kidney. We explored the action of losartan on AKT-mTOR phosphorylation in glomeruli and podocytes. Diabetes mellitus was induced to Sprague-Dawley rats by streptozotocin. Five months later, the rats were commenced on losartan and euthanized 2 months later. Kidneys were processed for immunofluorescence studies. Glomeruli were isolated for Western blot analysis. Diabetes increased activated forms of AKT and mTOR both in glomeruli and podocytes. In diabetic rats, losartan decreased phosphorylated/activated forms of AKT (Thr308) and mTOR (Ser2448) in glomeruli but decreased only activated mTOR in podocytes. However, in both glomeruli and podocytes of healthy animals, an inverse pattern was evident. In conclusion, a new body of evidence indicates the differential activation of AKT-mTOR in glomeruli and podocytes of healthy and diabetic animals in response to losartan.

Clinical and histological outcome predictors in renal limited pauci-immune crescentic glomerulonephritis: A single centre experience

Renal-limited vasculitis is a pauci-immune crescentic glomerulonephritis with no signs of systemic involvement, representing one of the most common causes of rapidly progressive glomerulonephritis. The study aims to examine clinical and histological features in twenty-four patients with RLV diagnosed by the Nephrology Department of Sapienza University of Rome, Italy, evaluating the role of these parameters in predicting renal survival. Patients details, clinical and histological features and outcomes were recorded at the time of renal biopsy and over a mean follow-up period of 36±6 months. In our study, serum creatinine at presentation was significantly higher in patients who had a poor outcome than in those who survived with independent renal function (6.3±2.47 mg/dl vs 2.84±2.01 mg/dl, P= 0.002). The presence of C3c was found in the area of glomerular fibrinoid necrosis and in small arteries and arterioles with fibrinoid necrosis in 17 patients (P= 0.018). In conclusion, serum creatinine at presentation and focal C3c depositions in areas of glomerular and arteriolar fibrinoid necrosis were the best determinants of poor renal outcome, maybe underlining the pathogenic role of alternative pathway activation of complement system but also demonstrating the focal distribution of necrotizing lesions.

Phosphodiesterase-5 inhibition preserves renal hemodynamics and function in mice with diabetic kidney disease by modulating miR-22 and BMP7

Diabetic Nephropathy (DN) is the leading cause of end-stage renal disease. Preclinical and experimental studies show that PDE5 inhibitors (PDE5is) exert protective effects in DN improving perivascular inflammation. Using a mouse model of diabetic kidney injury we investigated the protective proprieties of PDE5is on renal hemodynamics and the molecular mechanisms involved. PDE5i treatment prevented the development of DN-related hypertension (P < 0.001), the increase of urine albumin creatinine ratio (P < 0.01), the fall in glomerular filtration rate (P < 0.001), and improved renal resistive index (P < 0.001) and kidney microcirculation. Moreover PDE5i attenuated the rise of nephropathy biomarkers, soluble urokinase-type plasminogen activator receptor, suPAR and neutrophil gelatinase-associated lipocalin, NGAL. In treated animals, blood vessel perfusion was improved and vascular leakage reduced, suggesting preserved renal endothelium integrity, as confirmed by higher capillary density, number of CD31+ cells and pericyte coverage. Analysis of the mechanisms involved revealed the induction of bone morphogenetic protein-7 (BMP7) expression, a critical regulator of angiogenesis and kidney homeostasis, through a PDE5i-dependent downregulation of miR-22. In conclusion PDE5i slows the progression of DN in mice, improving hemodynamic parameters and vessel integrity. Regulation of miR-22/BMP7, an unknown mechanism of PDE5is in nephrovascular protection, might represent a novel therapeutic option for treatment of diabetic complications.