Abstract P010: Specific Renal Outer Medulla Upregulation of α-and β-Adrenergic Receptor Subtypes in Spontaneously Hypertensive African Green Monkeys

The African Green Monkey ( Chlorocebus aethiops sabaeus ) is a highly translational model of spontaneous hypertension (HT). Within the cohort of measured colony animals, 33% (98 of 300) of adult African Green Monkeys exhibit systolic blood pressures (SBP)> 140 mmHg, assessed by forearm cuff plethysmography. Heart rate is elevated in HT vs. normotensive (NT) animals (121±2 bpm vs. 134±2 bpm, p<0.05) suggesting that sympathetic nerve activity is likely elevated in the HT African Green Monkey, similar to patients with essential hypertension. This study assessed mRNA expression of adrenergic receptor subtypes in the renal cortex, outer medulla, and inner medulla of male HT and NT African Green Monkeys. Primers were custom designed and evaluated for appropriate specificities and efficiencies (95-105%) for α 1a , α 1d , α 2c , β 1 and β 2 adrenoceptors. Gene expression was measured with qRT-PCR and normalized to RPS32 expression in the liver of each animal. The HT cohort of African Green Monkeys (n=18) assessed an averaged SBP of 168.24 ± 7.25mmHg compared with NT animals (n=18) that averaged 96.61 ± 3.20mmHg. Expression of α 1a , α 1d and α 2c genes were all increased in the renal outer medulla of HT animals (α 1a : NT RQ 0.24 ± 0.15 vs. HT RQ 0.89 ± 0.22, p<0.05; α 1d : NT RQ 0.43 ± 0.24 vs. HT RQ 1.99 ± 0.74, p<0.05; and α 2c : NT RQ 1.11 ± 0.53 vs HT RQ 1.41 ± 0.35, p<0.05). β 1 adrenergic receptor expression in the outer medulla was similar in NT and HT animals (β 1 : NT RQ 0.75 ± 0.30 vs. HT RQ 1.82 ± 0.64, p>0.05), but β 2 adrenoceptor expression was upregulated in HT animals (β 2 : NT RQ 0.36 ± 0.13 vs HT RQ 2.05 ± 0.82; p<0.05). Expression of each adrenoceptor subtype was similar in the renal cortex and inner medulla of HT animals (p>0.05, all groups compared with Mann-Whitney U Test). These data suggest that the renal outer medulla of HT African Green Monkey may be sensitized to sympathetic nerve activity via elevated adrenergic receptor gene expression. Thus, subtle changes in renal sympathetic outflow may elicit renal medullary vasoconstriction and contribute to the development of the spontaneous hypertensive phenotype in the African Green Monkey.

Abstract 570: Characteristics of Long Non-coding RNAs in the Brown Norway Rat and Alterations in the Dahl Salt-Sensitive Rat

Long non-coding RNAs (lncRNAs) are emerging as important mediators of genomic regulation. lncRNAs, however, remain poorly characterized in the rat model organism, which is widely used in hypertension research. Using poly(A)-independent and strand-specific RNA-seq, we identified approximately 1,500 to 1,800 lncRNAs expressed in each of the following tissues of Brown Norway rats: the renal cortex, renal outer medulla, liver, cardiac left ventricle, adrenal gland, and hypothalamus. Expression patterns and the binding of histone H3K4me3 to promoter regions were confirmed for several of the identified lncRNAs. Patterns of rat lncRNA expression appeared to be more tissue-specific than mRNA. Rat lncRNAs, on average, had similar lengths to mRNA but substantially fewer exons. The median abundance of rat lncRNAs was approximately 40% of that of mRNA. Approximately 28% of the lncRNAs identified in the renal outer medulla appeared to lack a poly(A) tail. Differential expression of 74 lncRNAs was detected in the renal outer medulla between Dahl salt-sensitive SS rats and salt-insensitive, congenic SS.13BN26 rats fed a high-salt diet. Two of the differentially expressed lncRNAs, which were confirmed, were located within the substituted congenic region. The study identified genome-wide characteristics of lncRNAs in the rat model and suggested a role of lncRNAs in hypertension.

Gene expression reveals vulnerability to oxidative stress and interstitial fibrosis of renal outer medulla to nonhypertensive elevations of ANG II

The present study was designed to determine whether nonhypertensive elevations of plasma ANG II would modify the expression of genes involved in renal injury that could influence oxidative stress and extracellular matrix formation in the renal medulla using microarray, Northern, and Western blot techniques. Sprague-Dawley rats were infused intravenously with either ANG II (5 ng · kg−1 · min−1) or vehicle for 7 days ( n = 6/group). Mean arterial pressure averaged 110 ± 0.6 mmHg during the control period and 113 ± 0.4 mmHg after ANG II. The mRNA of 1,751 genes (∼80% of all currently known rat genes) that was differentially expressed (ANG II vs. saline) in renal outer and inner medulla was determined. The results of 12 hybridizations indicated that in response to ANG II, 11 genes were upregulated and 25 were downregulated in the outer medulla, while 11 were upregulated and 13 were downregulated in the inner medulla. These differentially expressed genes, most of which were not known previously to be affected by ANG II in the renal medulla, were found to group into eight physiological pathways known to influence renal injury and kidney function. Particularly, expression of several genes would be expected to increase oxidative stress and interstitial fibrosis in the outer medulla. Western blot analyses confirmed increased expression of transforming growth factor-β1 and collagen type IV proteins in the outer medulla. Results demonstrate that nonhypertensive elevations of plasma ANG II can significantly alter the expression of a variety of genes in the renal outer medulla and suggested the vulnerability of the renal outer medulla to the injurious effect of ANG II.