2015-2016 KURE Cohort

 

Howard Cha¹, Zhengrong Guan, MD, PhD², and Edward W. Inscho, PhD²; ¹University of California, Merced; ²Medicine, Division of Nephrology, University of Alabama at Birmingham

 

Inflammation contributes to renal microvascular autoregulatory impairment associated with hypertension. Our laboratory recently found that anti-inflammatory treatment with pentosan polysulfate prevents impairment of renal autoregulation in mineralocorticoid-induced hypertensive rats despite persistent hypertension. Whether the autoregulatory impairment arises from inflammation, elevated arterial pressure, or directly from mineralocorticoid treatment is unclear. We hypothesize that suppression of hypertension with hydralazine, hydrochlorothiazide, and reserpine treatment protects renal autoregulatory function in deoxycorticosterone acetate-salt (DOCA-salt) rats. DOCA-salt treatment was induced by subcutaneous implantation of DOCA pellets in uninephrectomized rats (UNx) receiving HHR in the drinking water along with 1% NaCl and 0.2% KCl for three weeks. Systolic blood pressure was monitored weekly. 24-hour urine output was measured weekly using metabolic cages. Renal autoregulatory function was assessed in vitro using the blood-perfused juxtamedullary nephron preparation on day 21. Systolic blood pressure remained stable when compared to UNx rats. DOCA-salt rats treated with HHR did not develop hypertension, did not display signs of glomerular damage, and have a pressure-diameter profile of normal autoregulatory behavior. These results support our hypothesis that autoregulatory impairment in DOCA-salt hypertensive rats is caused by elevated arterial pressure rather than a direct effect of the mineralocorticoid-salt treatment.

 

Jocelyne Fadiga¹, Colin Reily², Stacy Hall², Audra Laube², Bruce A. Julian², Matthew B. Renfrow², and Jan Novak, PhD²; ¹University of California, Merced; ²Division of Gastroenterology and Hepatology, University of Alabama at Birmingham

 

IgA nephropathy (IgAN) is a chronic kidney disease with up to 40% patients progressing to end-stage renal disease (ESRD). IgAN is characterized by IgA1-contaning immunodeposits in the mesangium. These immunodeposits, enriched for galactose-deficient IgA1 (Gd-IgA1), likely originate from the circulating immune complexes consisting of Gd-IgA1 bound by anti-glycan autoantibodies. Gd-IgA1 is produced by IgA1-producing cells due to abnormal expression of key glycosylation enzymes. Serum levels of Gd-IgA1 are associated with disease progression. Serum IgA1 is predominantly monomeric, with only about 10% in the polymeric form, as dimers or higher polymers. To better characterize the autoantigen, we analyzed the O-glycosylation of polymeric and monomeric IgA1 from serum and secreted by IgA1-producing cells. METHODS: IgA1 in serum and media of immortalized cells derived from healthy controls and patients with IgAN, and the mono/polymeric forms were isolated by affinity and size-exclusion chromatography. The molecular form of IgA1 was assessed by non-reducing SDS-PAGE and the degree of galactose deficiency by enzyme linked immunosorbent assay (ELISA) with lectin from Helix aspersa (HAA) and mass spectrometry. RESULTS: We tested separation of polymeric and monomeric IgA1 using several matrices at low-pressure vs. standard high-pressure liquid chromatography. We hypothesize that the lectin-reactive serum IgA1 (Gd-IgA1) is predominantly in immune complexes and free polymeric form and that most Gd-IgA1 produced by IgA1-secreting cells is a polymer. CONCLUSION: In IgAN, polymeric IgA1 forms are more reactive with Gd-IgA1-specific lectin. These finding will need to be validated using a larger cohort of subjects and analyses expanded by mass spectrometry profiling. KEY WORDS: IgA nephropathy, glycosylation, IgA1, O-glycans, chronic renal disease

 

Marcos Lucero¹, Joshua S. Speed², and David M. Pollock, PhD²; ¹University of California, Merced; ²Medicine-Nephrology, University of Alabama at Birmingham

 

Loss of renal endothelin B receptor (ETB) function results in salt-sensitive hypertension and genetic mutation of the ETB receptor impairs the ability to excrete an acute salt load in rats. In order to probe the mechanisms, we designed experiments to develop a mouse model to determine whether loss of ETB function impairs the ability to excrete an acute salt load. Mice were treated with vehicle or the ETB antagonist, A-192621 (15 mg/kg given 3X at 24, 12, and 1 hour before start an acute salt load). At the onset of their inactive period (lights on) mice were given 65 mg of NaCl in 300 µL of H2O by oral gavage and urine was collected hourly for 8 hours. After gavage, mice treated with vehicle had a significant increase in Na+ excretion compared to mice given vehicle (H2O) at 2 hours (7.5±1.2 vs. 0.03±0.03 mg/2 hours respectively) and 4 hours (8.9±2.0 vs. 0.2±0.1 mg/2 hours respectively, n=4) post gavage. Interestingly, blockade of ETB receptors delayed the natriuretic response to a NaCl load, with the peak response of 9.3±1.4 mg/2hours occurring during hour 6. The peak response occurred at 2.5±0.3 hrs in untreated mice vs. 5.0±0.3 hrs in mice given the ETB antagonist. These data indicate that loss of ETB function in mice impairs the ability to excrete an acute salt load and provide evidence that genetically engineered mice may be an ideal model to probe the mechanisms by which ETB receptors maintain proper salt and H2O homeostasis.

 

Iris D. Montes^1,2, Carmen De Miguel¹, and Jennifer S. Pollock, PhD¹; ¹Section of Cardio-Renal Physiology and Medicine, Division of Nephrology, Department of Medicine, University of Alabama at Birmingham; ²Department of Biology, University of California, Merced

 

Dietary sodium intake is one of the main culprits in hypertension and kidney disease. Its effects are more prevalent in men than in pre-menopausal women of the same age. To assess sex differences in the role that vasoactive peptide endothelin-1 (ET-1) has in the development of hypertension and kidney damage, vascular endothelial cell ET-1 knockout (VEET KO) mice of both sexes (12 weeks old; n=5-7/group) were placed on high salt diets (4% NaCl) for 3 weeks. We hypothesized that the lack of ET-1 in the vasculature decreases the development of renal damage and this effect would be more prevalent in males. Water consumption, urine excretion, and urinary markers of renal damage were assessed at the end of the high salt period. Water consumption was uniform in both genotypes and sexes; however, urine production in male and female VEET KO mice was significantly reduced compared to Flox controls (Flox vs. VEET KO; Males: 2.6 ± 0.5 vs. 1.2± 0.4 ml/day; Females 3.0 ± 0.2 vs. 1.4 ± 0.2 ml/day; p<0.05). KIM-1 excretion, a marker of proximal tubule damage, was significantly decreased in female VEET KO mice, compared to female Flox controls (6426.1 ± 1432.6 pg/day vs. 2539.0 ± 796.4 pg/day; p<0.05), while there was no significant difference in both male genotypes. Results suggest that vascular endothelial ET-1 plays a larger role in the development of high salt-induced renal damage in males than in females.