Expression of the IL-2R in Human Podocytes and the Effect of Activation on Autophagy and Apoptosis.

BACKGROUND: Interleukin 2 (IL-2) treatment is associated with proteinuria. Materials and Methods: A conditionally immortalized human podocyte cell line was used to investigate expression of the podocyte specific marker podocin, IL-2R alpha (IL-2Rα), apoptosis marker Bax, and autophagy markers LC3I AND LC3II, determined by quantitative immunoblotting, following 24, 48, and 72 hours of IL-2 stimulation, comparing them to unstimulated cells. Results: Podocin was expressed at all time points. IL-2Rα expression was increased after 24 and 72 hrs (p = 0.0014, p = 0.0139) and decreased after 48 hours (p = 0.0445). Bax, LC3I, and LC3II were increased after 24 hrs (p = 0.0094, p = 0.0016, p = 0.0004) and 48 hrs (p = 0.0072, p = 0.0024, p = 0.0087). Conclusion: Human podocytes express the IL-2R and activation results in increased autophagy and apoptosis.

Increased Autophagy and Apoptosis in the Kidneys of Intrauterine Growth Restricted Rats.

BACKGROUND: IUGR has been associated with nephron loss and chronic kidney disease (CKD). MATERIALS AND METHODS: We examined autophagy and apoptosis markers in the kidneys of IUGR Sprague Dawley rats induced by maternal low protein diet (LP), comparing them to controls. The autophagy marker LC3B, the pro-apoptotic protein Bax, and the anti-apoptotic protein Bcl-2 were determined by quantitative immunoblotting. Immunohistochemical expressions of LC3B, Bax, and Bcl-2 were evaluated at 4 weeks age. Glomerular counts (by maceration techniques) were performed at 5 weeks. RESULTS: The LP diet offspring were lighter (P < 0.05). In IUGR kidneys, LC3B and Bax were increased at birth (p < 0.05, p < 0.001) and at 4 weeks (p < 0.0142, p < 0.0001), Bcl-2 was decreased at birth (p < 0.05), and there were less glomeruli (p < 0.01) at 5 weeks. CONCLUSIONS: Autophagy and apoptosis may have a role in IUGR associated decreased nephron number in Sprague rats.

Role of postnatal dietary sodium in prenatally programmed hypertension.

In this study we examined the short- and long-term impact of early life dietary sodium (Na) on prenatally programmed hypertension. Hypertension was induced in rat offspring by a maternal low protein (LP) diet. Control and LP offspring were randomized to a high (HS), standard (SS), or low (LS) Na diet after weaning. On the SS diet, the LP pups developed hypertension by 6 weeks of age. The development of hypertension was prevented by the LS diet and exacerbated by the HS diet. Kidney nitrotyrosine content, a measure of oxidative stress, was reduced by the LS diet compared with the HS diet. The modified diets had no effect on control pups. A group of animals on the SS diet was followed up to 51 weeks of age after an early life 3-week exposure to the HS or LS diet. This brief early exposure of LP animals to the LS diet prevented the later development of hypertension and ameliorated the nephrosclerosis observed after early exposure to the HS diet. The LP offspring with early exposure to LS diet had lost their salt-sensitivity when challenged with the HS diet at the age of 43-49 weeks. No effect of early life dietary Na was observed in control animals. These results show that hypertension in this model is salt sensitive and may, in part, be mediated by salt-induced renal oxidative stress and that there may exist a developmental window which allows postnatal "reprogramming" of the hypertension.

Activation of the IL-2 Receptor in Podocytes: A Potential Mechanism for Podocyte Injury in Idiopathic Nephrotic Syndrome?

The renal podocyte plays an important role in maintaining the structural integrity of the glomerular basement membrane. We have previously reported that patients with idiopathic nephrotic syndrome (INS) have increased IL-2 production. We hypothesized that podocytes express an IL-2 receptor (IL-2R) and signaling through this receptor can result in podocyte injury. To confirm the presence of the IL-2R, we tested a conditionally immortalized murine podocyte cell line by flow cytometry, qPCR, and Western blot. To test for the presence of the IL-2R in vivo, immunohistochemical staining was performed on human renal biopsies in children with FSGS and control. Podocytes were stimulated with IL-2 in vitro, to study signaling events via the JAK/STAT pathway. The results showed that stimulation with IL-2 resulted in increased mRNA and protein expression of STAT 5a, phosphorylated STAT 5, JAK 3, and phosphorylated JAK 3. We then investigated for signs of cellular injury and the data showed that pro-apoptotic markers Bax and cFLIP were significantly increased following IL-2 exposure, whereas LC3 II was decreased. Furthermore, mitochondrial depolarization and apoptosis were both significantly increased following activation of the IL-2R. We used a paracellular permeability assay to monitor the structural integrity of a podocyte monolayer following IL-2 exposure. The results showed that podocytes exposed to IL-2 have increased albumin leakage across the monolayer. We conclude that murine podocytes express the IL-2R, and that activation through the IL-2R results in podocyte injury.

Intestinal microbiota in pediatric patients with end stage renal disease: a Midwest Pediatric Nephrology Consortium study.

BACKGROUND: End-stage renal disease (ESRD) is associated with uremia and increased systemic inflammation. Alteration of the intestinal microbiota may facilitate translocation of endotoxins into the systemic circulation leading to inflammation. We hypothesized that children with ESRD have an altered intestinal microbiota and increased serum levels of bacterially derived uremic toxins. METHODS: Four groups of subjects were recruited: peritoneal dialysis (PD), hemodialysis (HD), post-kidney transplant and healthy controls. Stool bacterial composition was assessed by pyrosequencing analysis of 16S rRNA genes. Serum levels of C-reactive protein (CRP), D-lactate, p-cresyl sulfate and indoxyl sulfate were measured. RESULTS: Compared to controls, the relative abundance of Firmicutes (P = 0.0228) and Actinobacteria (P = 0.0040) was decreased in PD patients. The relative abundance of Bacteroidetes was increased in HD patients (P = 0.0462). Compared to HD patients the relative abundance of Proteobacteria (P = 0.0233) was increased in PD patients. At the family level, Enterobacteriaceae was significantly increased in PD patients (P = 0.0020) compared to controls; whereas, Bifidobacteria showed a significant decrease in PD and transplant patients (P = 0.0020) compared to control. Alpha diversity was decreased in PD patients and kidney transplant using both phylogenetic and non-phylogenetic diversity measures (P = 0.0031 and 0.0003, respectively), while beta diversity showed significant separation (R statistic = 0.2656, P = 0.010) between PD patients and controls. ESRD patients had increased serum levels of p-cresyl sulfate and indoxyl sulfate (P < 0.0001 and P < 0.0001, respectively). The data suggests that no significant correlation exists between the alpha diversity of the intestinal microbiota and CRP, D-lactate, or uremic toxins. Oral iron supplementation results in expansion of the phylum Proteobacteria. CONCLUSIONS: Children with ESRD have altered intestinal microbiota and increased bacterially derived serum uremic toxins.

Kidney immune cell infiltration and oxidative stress contribute to prenatally programmed hypertension.

BACKGROUND: Prenatal environment has been shown to modify adult blood pressure profile, but the underlying mechanisms are not well understood. The role of renal immune cell infiltration, oxidative stress, and nitric oxide bioavailability in the pathogenesis was investigated. METHODS: Adult hypertension in rat offspring was induced by maternal low protein diet. Oxidative stress was determined by quantitative immunoblotting for nitrotyrosine, and T-cell and macrophage content by immunostaining, in offspring kidneys before and after the onset of hypertension. Nitric oxide metabolites (NOx) were measured in 24-hour urines. A group of offspring was treated with the immunosuppressive drug mycophenolate mofetil (MMF) to reduce inflammation, or with the superoxide dismutase mimetic Tempol to reduce oxidative stress, for a 3-week period before the onset of hypertension. RESULTS: During the prehypertensive stage, at 4 weeks of age, the low protein diet pups exhibited an increase in kidney nitrotyrosine content and in number of immune cells, both of which persisted in untreated animals after hypertension was established, at 8 weeks of age. Urine NOx was increased at 4 weeks and unchanged at 8 weeks of age. Both MMF and Tempol treatment prevented the immune cell infiltration, the increase in kidney nitrotyrosine abundance, and the development of hypertension. The effect on blood pressure persisted throughout the 4- to 10-week observation period after discontinuation of the treatments. CONCLUSION: Renal oxidative stress and infiltrating immune cells may play a pathogenetic role in prenatally programmed hypertension. Nitric oxide bioavailability does not appear impaired.

Kidney angiotensin and angiotensin receptor expression in prenatally programmed hypertension.

Adult hypertension may be programmed by the prenatal environment in humans and in experimental animals. The potential role of the intrarenal renin-angiotensin system (RAS) in prenatally programmed hypertension was investigated. Hypertension in rat offspring was induced by maternal protein restriction during pregnancy. The offspring were studied on day 1 of life and immediately preceding the development of hypertension on day 28. ANG I and II contents were determined by radioimmunoassy. Angiotensin receptor protein and mRNA levels were quantified by immunoblotting and real-time RT-PCR, respectively. Plasma and kidney ANG I and II were unchanged in the offspring from low-protein pregnancies (LP). ANG II type 1 receptor (AT(1)R) protein abundance was low in the newborn LP kidney (P < 0.05) but rose above control values by 28 days of age (P < 0.05); the rise was associated with an increase in AT(1)R subtype A (P < 0.01), but not subtype B, mRNA level. ANG II type 2 receptor protein expression was decreased on day 1 (P < 0.05) and increased on day 28 (P < 0.05) in LP kidneys. The results show that prenatal programming of hypertension is associated with an abnormal pattern of intrarenal RAS ontogeny that may play a pathogenetic role, for instance, by constitutively altering renal hemodynamics or Na reabsorption.