Exogenous vascular endothelial growth factor supplementation can restore the podocyte barrier-forming capacity disrupted by sera of preeclamptic women

Electric cell-substrate impedance sensing in kidney research

Electric cell-substrate impedance sensing (ECIS) is a quantitative, label-free, non-invasive analytical method allowing continuous monitoring of the behaviour of adherent cells by online recording of transcellular impedance. ECIS offers a wide range of practical applications to study cell proliferation, migration, differentiation, toxicity and monolayer barrier integrity. All of these applications are relevant for basic kidney research, e.g. on endothelial cells, tubular and glomerular epithelial cells. This review gives an overview on the fundamental principles of the ECIS technology. We name strengths and remaining hurdles for practical applications, present an ECIS array reuse protocol, and review its past, present and potential future contributions to preclinical kidney research.

Nephrotoxicity induced by intravitreal vascular endothelial growth factor inhibitors: emerging evidence

Vascular endothelial growth factor (VEGF) inhibitors have emerged as powerful tools to treat malignant neoplasms and ocular diseases by virtue of their ability to inhibit angiogenesis. Recent data indicate that intravitreal injections of VEGF inhibitors can lead to significant systemic absorption as well as a measurable reduction of plasma VEGF activity. There is increasing evidence showing that vitreal absorption of these drugs is associated with cases of accelerated hypertension, worsening proteinuria, glomerular disease, thrombotic microangiopathy, and possible chronic renal function decline. In this review, the 3 most commonly used anti-VEGF agents-bevacizumab, ranibizumab, and aflibercept-are discussed, highlighting their intravitreal absorption and associated effects on the kidney as a target organ system. We provide clinical suggestions for clinicians to both better manage patients receiving anti-VEGF agents intravitreally and detect any putative systemic renal effects of these agents. While acknowledging the risks of aberrant retinal angiogenesis, it is important for clinicians to be aware of the potential for adverse renal risks with use of these agents.

Three patients with injection of intravitreal vascular endothelial growth factor inhibitors and subsequent exacerbation of chronic proteinuria and hypertension

Vascular endothelial growth factor (VEGF) receptor inhibition is a commonly used tool to prevent vascular proliferation in tumors and retinal diseases. The antiangiogenic effects of these drugs have made them potent adjunct therapies when given systemically for malignancies. They are also useful tools to ameliorate diminishing eyesight in retinopathy. Hypertension and proteinuria have been observed in systemic VEGF inhibitor therapy, with rarer presentations involving nephrotic-range proteinuria due to glomerulopathies. Pharmacokinetic studies have shown detectable blood levels of anti-VEGF inhibitors up to 30 days postintravitreal injection. Animal studies have also demonstrated binding of VEGF inhibitors in simian glomeruli 1 week after a single intravitreal injection. We report three patients who received intravitreal bevacizumab and/or aflibercept with worsening hypertension, proteinuria and renal injury. Data regarding emerging evidence of VEGF inhibitor nephrotoxicity after intravitreal injections are also presented. The clinical data and the existing literature are reviewed to support the hypothesis that intravitreal anti-VEGF agents may be unrecognized nephrotoxins. These agents are given to vulnerable patients with diabetes, hypertension and preexisting nephropathy and proteinuria. This case series is reported to spur further study of the systemic effects of intravitreal VEGF inhibitors.

Podocyte directed therapy of nephrotic syndrome-can we bring the inside out?

Several of the drugs currently used for the treatment of glomerular diseases are prescribed for their immunotherapeutic or anti-inflammatory properties, based on the current understanding that glomerular diseases are mediated by immune responses. In recent years our understanding of podocytic signalling pathways and the crucial role of genetic predispositions in the pathology of glomerular diseases has broadened. Delineation of those signalling pathways supports the hypothesis that several of the medications and immunosuppressive agents used to treat glomerular diseases directly target glomerular podocytes. Several central downstream signalling pathways merge into regulatory pathways of the podocytic actin cytoskeleton and its connection to the slit diaphragm. The slit diaphragm and the cytoskeleton of the foot process represent a functional unit. A breakdown of the cytoskeletal backbone of the foot processes leads to internalization of slit diaphragm molecules, and internalization of slit diaphragm components in turn negatively affects cytoskeletal signalling pathways. Podocytes display a remarkable ability to recover from complete effacement and to re-form interdigitating foot processes and intact slit diaphragms after pharmacological intervention. This ability indicates an active inside-out signalling machinery which stabilizes integrin complex formations and triggers the recycling of slit diaphragm molecules from intracellular compartments to the cell surface. In this review we summarize current evidence from patient studies and model organisms on the direct impact of immunosuppressive and supportive drugs on podocyte signalling pathways. We highlight new therapeutic targets that may open novel opportunities to enhance and stabilize inside-out pathways in podocytes.

Minimal change disease onset observed after bevacizumab administration

This is a report of a patient with minimal change disease (MCD) onset after bevacizumab administration. A 72-year-old man with inoperable Grade 3 astrocytoma was treated with a combination of temozolomide and the vascular endothelial growth factor monoclonal antibody bevacizumab. After two biweekly treatments, he developed nephrotic syndrome. Despite cessation of bevacizumab, his renal function deteriorated and a renal biopsy disclosed MCD. Thereafter, he was started on high-dose oral prednisone and renal function immediately improved. Within weeks, the nephrotic syndrome resolved. Although rare, biologic agents can cause various glomerulopathies that can have important therapeutic implications. MCD should be considered in patients who develop nephrotic syndrome while exposed to antiangiogenic agents.

The optimization of a chronic nitric oxide synthase (NOS) inhibition model of pre-eclampsia by evaluating physiological changes

OBJECTIVES

In order to address the gap in our understanding of the pathogenesis and pathophysiology of PE, we optimized the NOS inhibition animal model by comparing changes in different parameters at various time frames during pregnancy, in both early and late-onset PE.

STUDY DESIGN

120 nulliparous Sprague-Dawley rats were divided into 5 groups (n=24). A pregnant control, two groups that represented early and late-onset PE and two groups that were treated with sildenafil citrate (SC) to show reversal of the pre-eclamptic-like symptoms.

RESULTS

Our results showed that treatment with L-NAME caused significant changes in physiological parameters for both early and late-onset PE groups. There was a significant increase in systolic blood pressure (SBP) levels in the early-onset PE group (128.5±5.71 mmHg) and late-onset PE group (128.3±6.15 mmHg) on day 19 compared to the SBPs on day 0, (p<0.01). Urine excretion volumes in the early-onset PE group (13.62±3.18 mL) and in the late-onset PE (13.28±2.60 mL), compared to the pregnant control group (11.96±1.9 mL) were also increased (p<0.05). There was also an increase in total urinary protein in the early-onset PE group (0.62±0.08 g/L and the late-onset PE group (0.45±0.05 g/L), when compared to the pregnant control group (0.38±0.07) (p<0.05). We also found a decrease in fetal numbers in the PE group in comparison to the pregnant control and SC treated groups. The remission of these signs was seen after delivery of the fetuses. We also demonstrated that treatment of this syndrome with SC prevented the development of these signs.

CONCLUSIONS

The NOS inhibition model can be used for the study of the pathogenesis and pathophysiology of PE, since the pathogenic changes mimic those of early and late-PE.

Proteinuria in preeclampsia from a podocyte injury perspective

Preeclampsia is a frequent cause of maternal and fetal morbidity and mortality worldwide. The underlying causes of this hypertensive complication have remained elusive. The placenta seems to be at the origin of the disease, as its removal appears to be the only effective treatment available. Many organs can potentially be affected. Nonetheless, kidney alterations are always present: proteinuria is one of the hallmarks for a preeclampsia diagnosis. VEGF is pivotal for maintaining glomerular filtration barrier function; hence, the elevated concentrations of placental-derived VEGF inhibitors, such as sFlt-1, may largely explain the renal alterations observed. Classically, glomerular endothelial injury was considered responsible for the renal impairment present in preeclampsia. Recent findings, however, have shown that podocytes are crucial in explaining the loss of filtration capacity of the preeclamptic kidney. The aims of this manuscript are to detail the main findings that associate podocyte injury with proteinuria in preeclampsia, and discuss the eventual applications of podocyte damage biomarkers in clinical practice.