High Resolution Ultrasonography for Assessment of Renal Cysts in the PCK Rat Model of Autosomal Recessive Polycystic Kidney Disease.

BACKGROUND/AIMS: The PCK rat model of polycystic kidney disease is characterized by the progressive development of renal medullary cysts. Here, we evaluated the suitability of high resolution ultrasonography (HRU) to assess the kidney and cyst volume in PCK rats, testing three different ultrasound image analysis methods, and correlating them with kidneys weights and histological examinations. METHODS: After inducing anesthesia, PCK rats (n=18) were subjected to HRU to visualize the kidneys, to perform numeric and volumetric measurements of the kidney and any cysts observed, and to generate 3-dimensional images of the cysts within the kidney parenchyma. RESULTS: HRU provided superior information in comparison to microscopic analysis of stained kidney sections. HRU-based kidney volumes correlated strongly with kidney weights (R2=0.809; P<0.0001). CONCLUSION: HRU represents a useful diagnostic tool for kidney and cyst volume measurements in PCK rats. Sequential HRU examinations may be useful to study the effect of drugs on cyst growth without the need to euthanize experimental animals.

Inhibition of Aerobic Glycolysis Attenuates Disease Progression in Polycystic Kidney Disease.

Dysregulated signaling cascades alter energy metabolism and promote cell proliferation and cyst expansion in polycystic kidney disease (PKD). Here we tested whether metabolic reprogramming towards aerobic glycolysis ("Warburg effect") plays a pathogenic role in male heterozygous Han:SPRD rats (Cy/+), a chronic progressive model of PKD. Using microarray analysis and qPCR, we found an upregulation of genes involved in glycolysis (Hk1, Hk2, Ldha) and a downregulation of genes involved in gluconeogenesis (G6pc, Lbp1) in cystic kidneys of Cy/+ rats compared with wild-type (+/+) rats. We then tested the effect of inhibiting glycolysis with 2-deoxyglucose (2DG) on renal functional loss and cyst progression in 5-week-old male Cy/+ rats. Treatment with 2DG (500 mg/kg/day) for 5 weeks resulted in significantly lower kidney weights (-27%) and 2-kidney/total-body-weight ratios (-20%) and decreased renal cyst index (-48%) compared with vehicle treatment. Cy/+ rats treated with 2DG also showed higher clearances of creatinine (1.98±0.67 vs 1.41±0.37 ml/min), BUN (0.69±0.26 vs 0.40±0.10 ml/min) and uric acid (0.38±0.20 vs 0.21±0.10 ml/min), and reduced albuminuria. Immunoblotting analysis of kidney tissues harvested from 2DG-treated Cy/+ rats showed increased phosphorylation of AMPK-α, a negative regulator of mTOR, and restoration of ERK signaling. Assessment of Ki-67 staining indicated that 2DG limits cyst progression through inhibition of epithelial cell proliferation. Taken together, our results show that targeting the glycolytic pathway may represent a promising therapeutic strategy to control cyst growth in PKD.

Inhibition of Sodium-Glucose Cotransporter 2 with Dapagliflozin in Han: SPRD Rats with Polycystic Kidney Disease.

BACKGROUND/AIMS: Dapagliflozin (DAPA) is a selective inhibitor of the sodium-glucose cotransporter 2 (SGLT2) which induces glucosuria and osmotic diuresis. The therapeutic effect of DAPA in progressing stages of polycystic kidney disease (PKD) has not been studied. METHODS: We examined the effect of DAPA in the Han: SPRD rat model of PKD. DAPA (10 mg/kg/day) or vehicle (VEH) was administered orally via gavage to 5 week old male Han: SPRD (Cy/+) or control (+/+) rats (n = 8-9 per group) for 5 weeks. Blood and urine were collected at baseline and after 2.5 and 5 weeks of treatment to assess renal function and albuminuria. At the end of the treatment, rats were sacrificed and kidneys were excised for histological analysis. RESULTS: After 5 weeks of treatment, DAPA-treated Cy/+ and +/+ rats exhibited significantly higher glucosuria, water intake and urine output than VEH-treated rats. DAPA-treated Cy/+ rats also exhibited significantly higher clearances for creatinine and BUN and less albuminuria than VEH-treated Cy/+ rats. DAPA treatment for 5 weeks resulted in a significant increase of the kidney weight in Cy/+ rats but no change in cyst growth. The degree of tubular epithelial cell proliferation, macrophage infiltration and interstitial fibrosis was also similar in DAPA-and VEH-treated Cy/+ rats. CONCLUSION: The induction of glucosuria with the SGLT2-specific inhibitor DAPA was associated with improved renal function and decreased albuminuria, but had no effect on cyst growth in Cy/+ rats. Overall the beneficial effects of DAPA in this PKD model were weaker than the previously described effects of the combined SGLT1/2 inhibitor phlorizin.

Effect of Sodium-Glucose Cotransport Inhibition on Polycystic Kidney Disease Progression in PCK Rats.

The sodium-glucose-cotransporter-2 (SGLT2) inhibitor dapagliflozin (DAPA) induces glucosuria and osmotic diuresis via inhibition of renal glucose reabsorption. Since increased diuresis retards the progression of polycystic kidney disease (PKD), we investigated the effect of DAPA in the PCK rat model of PKD. DAPA (10 mg/kg/d) or vehicle was administered by gavage to 6 week old male PCK rats (n=9 per group). Renal function, albuminuria, kidney weight and cyst volume were assessed after 6 weeks of treatment. Treatment with DAPA markedly increased glucose excretion (23.6 ± 4.3 vs 0.3 ± 0.1 mmol/d) and urine output (57.3 ± 6.8 vs 19.3 ± 0.8 ml/d). DAPA-treated PCK rats had higher clearances for creatinine (3.1 ± 0.1 vs 2.6 ± 0.2 ml/min) and BUN (1.7 ± 0.1 vs 1.2 ± 0.1 ml/min) after 3 weeks, and developed a 4-fold increase in albuminuria. Ultrasound imaging and histological analysis revealed a higher cyst volume and a 23% higher total kidney weight after 6 weeks of DAPA treatment. At week 6 the renal cAMP content was similar between DAPA and vehicle, and staining for Ki67 did not reveal an increase in cell proliferation. In conclusion, the inhibition of glucose reabsorption with the SGLT2-specific inhibitor DAPA caused osmotic diuresis, hyperfiltration, albuminuria and an increase in cyst volume in PCK rats. The mechanisms which link glucosuria to hyperfiltration, albuminuria and enhanced cyst volume in PCK rats remain to be elucidated.

Targeting of sodium-glucose cotransporters with phlorizin inhibits polycystic kidney disease progression in Han:SPRD rats.

Renal tubular epithelial cell proliferation and transepithelial cyst fluid secretion are key features in the progression of polycystic kidney disease (PKD). As the role of the apical renal sodium-glucose cotransporters in these processes is not known, we tested whether phlorizin inhibits cyst growth and delays renal disease progression in a rat model of PKD. Glycosuria was induced by subcutaneous injection of phlorizin in male heterozygous (Cy/+) and wild-type Han:SPRD rats. Phlorizin induced immediate and sustained glycosuria and osmotic diuresis in these rats. Cy/+ rats treated with phlorizin for 5 weeks showed a significant increase in creatinine clearance, a lower 2-kidneys/body weight ratio, a lower renal cyst index, and reduced urinary albumin excretion as compared with vehicle-treated Cy/+ rats. Measurement of Ki67 staining found significantly lower cell proliferation in dilated tubules and cysts of Cy/+ rats treated with phlorizin, as well as a marked inhibition of the activated MAP kinase pathway. In contrast, the mTOR pathway remained unaltered. Phlorizin dose dependently inhibited MAP kinase in cultured tubular epithelial cells from Cy/+ rats. Thus, long-term treatment with phlorizin significantly inhibits cystic disease progression in a rat model of PKD. Hence, induction of glycosuria and osmotic diuresis (glycuresis) by renal sodium-glucose cotransporters inhibition could have a therapeutic effect in polycystic kidney disease.

Two preferentially expressed proteins protect vascular endothelial cells from an attack by peptide-specific CTL.

Vascular endothelial cells (EC) are an exposed tissue with intimate contact with circulating Ag-specific CTL. Experimental in vitro and clinical data suggested that endothelial cells present a different repertoire of MHC class I-restricted peptides compared with syngeneic leukocytes or epithelial cells. This endothelial-specific peptide repertoire might protect EC from CTL-mediated cell death. The HLA-A*02-restricted peptide profile of human EC and syngeneic B lymphoblastoid cells was biochemically analyzed and compared. For EC selective peptides, source protein expression, peptide binding affinity, and peptide-HLA-A*02 turnover were measured. The significance of abundant peptide presentation for target cell recognition by immunodominant CTL was tested by small interfering RNA treatment of EC to knock down the source proteins. High amounts of two peptides, PTRF(56-64) and CD59(106-114), were consistently detected in EC. This predominance of two endothelial peptides was explained by cell type-specific source protein expression that compensated for poor HLA-A*02 binding affinity and short half-live of peptide/HLA-A*02 complexes. Knocking down the source proteins containing the abundant endothelial peptide motifs led to a nearly 100-fold increase of surface expression of SMCY(311-319), an immunodominant minor histocompatibility Ag, as detected by cytotoxicity assays using SMCY(311-319)-specific CTL. We conclude that EC express and present preferentially two distinct HLA-A*02-restricted peptides at extraordinary high levels. These abundant self-peptides may protect EC from CTL-mediated lysis by competing for HLA-A*02 binding sites with immunodominant scarcely expressed antigenic peptides.

Apoptosis induction by Maackia amurensis agglutinin in childhood acute lymphoblastic leukemic cells.

Malignant transformation is known to be associated with changes in cell surface carbohydrate-architecture, which can be detected by lectins. In the present study, Maackia amurensis agglutinin (MAA), specific for NeuNAcalpha(2-->3)Gal/GalNAc showed strong binding with lymphoblasts of children having acute lymphoblastic leukemia (ALL) as compared to cells from children with non-hematological disorders ("Controls"). MAA recognized a 66 kDa sialoglycoprotein present in membrane fraction of ALL cells. Moreover, MAA induced apoptosis in ALL cells was found to be reduced significantly in presence of GM2/IgG(MAA). Thus, MAA has a potential to be used as diagnostic and therapeutic agent in case of childhood-ALL.

Anaerobiosis induced virulence of Salmonella typhi.

BACKGROUND & OBJECTIVES: Anaerobic conditions are frequently encountered by pathogens invading the gastrointestinal tract due to low/limiting oxygen conditions prevalent in the small intestine. This anaerobic stress has been suggested to enhance the virulence of gut pathogens. In the present study, we examined the effect of anaerobiosis on the virulence of Salmonella Typhi, a Gram negative bacteria which invades through the gut mucosa and is responsible for typhoid fever. METHODS: Salmonella Typhi (ty2) was cultured in aerobic and anaerobic conditions to compare its virulence by rabbit ileal loop assay, hydrophobicity assay, expression of outer membrane proteins (OMPs) and antioxidant enzymes assay. RESULTS: Anaerobically grown S. Typhi showed significantly higher cell surface hydrophobicity as compared to aerobic bacteria. In vivo toxin production by rabbit ileal loop assay also showed significantly higher fluid accumulation with anaerobic S. Typhi. Expression of OMPs in anaerobic S. Typhi showed a distinct induction of five outer membrane proteins. We observed that exposure of anaerobic S. Typhi to aerobic conditions induced significantly higher level of antioxidant enzymes like superoxide dismutase (SOD) and catalase. INTERPRETATION & CONCLUSION: Our results suggest that exposure of S. Typhi to anaerobic conditions enhances its virulence.