The NF-κB essential modulator (NEMO) controls podocyte cytoskeletal dynamics independently of NF-κB

Swollen Feet: Considering the Paradoxical Roles of Interleukins in Nephrotic Syndrome

Interleukins are a family of 40 bioactive peptides that act through cell surface receptors to induce a variety of intracellular responses. While interleukins are most commonly associated with destructive, pro-inflammatory signaling in cells, some also play a role in promoting cellular resilience and survival. This review will highlight recent evidence of the cytoprotective actions of the interleukin 1 receptor (IL-1R)- and common gamma chain receptor (IL-Rγc)-signaling cytokines in nephrotic syndrome (NS). NS results from the injury or loss of glomerular visceral epithelial cells (i.e., podocytes). Although the causes of podocyte dysfunction vary, it is clear that pro-inflammatory cytokines play a significant role in regulating the propagation, duration and severity of disease. Pro-inflammatory cytokines signaling through IL-1R and IL-Rγc have been shown to exert anti-apoptotic effects in podocytes through the phosphoinositol-3-kinase (PI-3K)/AKT pathway, highlighting the potential utility of IL-1R- and IL-Rγc-signaling interleukins for the treatment of podocytopathy in NS. The paradoxical role of interleukins as drivers and mitigators of podocyte injury is complex and ill-defined. Emerging evidence of the cytoprotective role of some interleukins in NS highlights the urgent need for a nuanced understanding of their pro-survival benefits and reveals their potential as podocyte-sparing therapeutics for NS.

The podocytes' inflammatory responses in experimental GN are independent of canonical MYD88-dependent toll-like receptor signaling

Podocytes form the kidney filtration barrier and continuously adjust to external stimuli to preserve their integrity even in the presence of inflammation. It was suggested that canonical toll-like receptor signaling, mediated by the adaptor protein MYD88, plays a crucial role in initiating inflammatory responses in glomerulonephritis (GN). We explored the influence of podocyte-intrinsic MYD88 by challenging wild-type (WT) and podocyte-specific Myd88 knockout (MyD88pko) mice, with a model of experimental GN (nephrotoxic nephritis, NTN). Next-generation sequencing revealed a robust upregulation of inflammatory pathways and changes in cytoskeletal and cell adhesion proteins in sorted podocytes from WT mice during disease. Unchallenged MyD88pko mice were healthy and showed no proteinuria, normal kidney function and lacked morphological changes. During NTN, MyD88pko exhibited a transient increase in proteinuria in comparison to littermates, while histological damage, podocyte ultrastructure in STED imaging and frequencies of infiltrating immune cells by flow cytometry were unchanged. MYD88-deficiency led to subtle changes in the podocyte transcriptome, without a significant impact on the overall podocyte response to inflammation, presumably through MYD88-independent signaling pathways. In conclusion, our study reveals a comprehensive analysis of podocyte adaptation to an inflammatory environment on the transcriptome level, while MYD88-deficiency had only limited impact on the course of GN suggesting additional signaling through MYD88-independent signaling.

MicroRNA-181a-3p as a Diagnostic and Prognostic Biomarker for Acute Myeloid Leukemia

Background

Micro (mi) RNAs play an important role in the pathogenesis and development of acute myeloid leukemia (AML), and their abnormal expression may be sufficient to predict the prognosis and outcomes in AML patients. We evaluated the clinical diagnostic value of miRNA-181a-3p in predicting prognosis and outcomes in patients with AML.

Methods

A total of 119 newly diagnosed adult patients with AML and 60 healthy controls were recruited. Blood specimens were obtained from all AML patients at diagnosis, and 10 blood specimens were obtained on day 28 after induction chemotherapy. The controls also provided blood samples. Relative gene expression was quantified by PCR and determined using the comparative Ct method. Publicly available clinical data and gene expressions for 188 patients with AML were downloaded from TCGA data portal.

Results

Compared with healthy controls, the expression of miRNA-181a-3p was significantly increased in patients with AML. MiR-181a-3p expression could be used to discriminate AML patients from controls, with up-regulated expression correlating with favorable prognosis. Moreover, miRNA-181a-3p expression was significantly decreased in patients who achieved a complete response after induction chemotherapy. The multivariate Cox analysis highlighted the prognostic value of miR-181a-3p for patients with AML. Finally, we found that miR-181a-3p expression was negatively correlated with the expression of the NF-κB essential modulator (NEMO/IKBKG).

Conclusions

MiR-181a-3p may be clinically useful as a disease marker for AML, and enhanced the prediction of patient outcomes to chemotherapy.

NFκB and Kidney Injury

The global burden of chronic kidney disease will increase during the next century. As NFκB, first described more than 30 years ago, plays a major role in immune and non-immune-mediated diseases and in inflammatory and metabolic disorders, this review article summarizes current knowledge on the role of NFκB in in vivo kidney injury and describes the new and so far not completely understood crosstalk between canonical and non-canonical NFκB pathways in T-lymphocyte activation in renal disease.

Relapse of nephrotic syndrome triggered by Kawasaki disease

Minor infections, allergies, insect bites, and bee stings are commonly reported causes of nephrotic syndrome (NS). Herein, we report, to the best of our knowledge, the first case of NS relapse due to Kawasaki disease (KD). An 8-year-old boy presented with high fever of 4-day duration. He had developed steroid-dependent NS at the age of 4 years and remained in remission after steroid and mizonbin therapy. Renal biopsy, performed at the age of four, showed minimal change (MC) disease. Upon examination, the patient fulfilled 5 of 6 criteria for KD under the Japanese diagnostic guidelines, with positive proteinuria. He was diagnosed with NS relapse caused by KD. Proteinuria resolved after treatment with intravenous immunoglobulin and cyclosporine A. We present the case of an 8-year-old boy, whose NS relapsed due to KD. To the best of our knowledge, this is the first case report. It is necessary to recognize that KD can trigger relapse of MCNS.

Protein tyrosine phosphatase Shp2 deficiency in podocytes attenuates lipopolysaccharide-induced proteinuria

Podocytes are specialized epithelial cells that play a significant role in maintaining the integrity of the glomerular filtration barrier and preventing urinary protein leakage. We investigated the contribution of protein tyrosine phosphatase Shp2 to lipopolysaccharide (LPS)-induced renal injury. We report increased Shp2 expression in murine kidneys and cultured podocytes following an LPS challenge. To determine the role of podocyte Shp2 in vivo, we generated podocyte-specific Shp2 knockout (pod-Shp2 KO) mice. Following administration of LPS, pod-Shp2 KO mice exhibited lower proteinuria and blood urea nitrogen concentrations than controls indicative of preserved filter integrity. In addition, renal mRNA and serum concentrations of inflammatory cytokines IL-1β, TNFα, INFγ and IL-12 p70 were significantly decreased in LPS-treated knockout mice compared with controls. Moreover, the protective effects of podocyte Shp2 deficiency were associated with decreased LPS-induced NF-κB and MAPK activation, nephrin phosphorylation and attenuated endoplasmic reticulum stress. These effects were recapitulated in differentiated E11 murine podocytes with lentiviral-mediated Shp2 knockdown. Furthermore, Shp2 deficient podocytes displayed reduced LPS-induced migration in a wound healing assay. These findings identify Shp2 in podocytes as a significant contributor to the signaling events following LPS challenge and suggest that inhibition of Shp2 in podocytes may present a potential therapeutic target for podocytopathies.

Podocyte-specific NF-κB inhibition ameliorates proteinuria in adriamycin-induced nephropathy in mice

BACKGROUND

Podocytes play a central role in the formation of the glomerular filtration barrier in the kidney, and their dysfunction has been shown to result in proteinuria. In the present study, we sought to determine the cell-autonomous role of NF-κB, a proinflammatory signaling, within podocytes in proteinuric kidney disease.

METHODS

Podocyte-specific IκBΔN transgenic (Pod-IκBΔN) mice, in which NF-κB was inhibited specifically in podocytes, were generated by the Cre-loxP technology, and their phenotype was compared with control mice in adriamycin-induced nephropathy.

RESULTS

Pod-IκBΔN mice were phenotypically normal and did not exhibit proteinuria at the physiological condition. By the intravenous administration of adriamycin, overt proteinuria appeared in Pod-IκBΔN mice, as well as in control mice. However, of interest, the amount of proteinuria was significantly lower in adriamycin-injected Pod-IκBΔN mice (373 ± 122 mg albumin/g creatinine), compared with adriamycin-injected control mice (992 ± 395 mg albumin/g creatinine). Expression of podocyte-selective slit diaphragm-associated proteins, such as nephrin and synaptopodin, was markedly decreased by adriamycin injection in control mice, whereas the reduction was attenuated in Pod-IκBΔN mice. Adriamycin-induced reduction in synaptopodin expression was also seen in cultured podocytes derived from control mice, but not in those from Pod-IκBΔN mice.

CONCLUSIONS

Because nephrin and synaptopodin are essential for the maintenance of the slit diaphragm in podocytes, these results suggest that proteinuria in adriamycin-induced nephropathy is caused by the reduction in expression of these proteins. The results also suggest that the NF-κB signalling in podocytes cell-autonomously contributes to proteinuria through the regulation of these proteins.

Podocytes

Podocytes are highly specialized cells of the kidney glomerulus that wrap around capillaries and that neighbor cells of the Bowman’s capsule. When it comes to glomerular filtration, podocytes play an active role in preventing plasma proteins from entering the urinary ultrafiltrate by providing a barrier comprising filtration slits between foot processes, which in aggregate represent a dynamic network of cellular extensions. Foot processes interdigitate with foot processes from adjacent podocytes and form a network of narrow and rather uniform gaps. The fenestrated endothelial cells retain blood cells but permit passage of small solutes and an overlying basement membrane less permeable to macromolecules, in particular to albumin. The cytoskeletal dynamics and structural plasticity of podocytes as well as the signaling between each of these distinct layers are essential for an efficient glomerular filtration and thus for proper renal function. The genetic or acquired impairment of podocytes may lead to foot process effacement (podocyte fusion or retraction), a morphological hallmark of proteinuric renal diseases. Here, we briefly discuss aspects of a contemporary view of podocytes in glomerular filtration, the patterns of structural changes in podocytes associated with common glomerular diseases, and the current state of basic and clinical research.