Abstract P223: Identification of Chromosome 2 Differentially Expressed Genes Linked to Vascular Inflammation Using Congenic Rats Fed a Normal and High-Salt Diet

Abstract

Background: The immune system plays an important role in hypertension. Chromosome 2 (Chr2) introgression from normotensive Brown Norway (BN) rats into hypertensive Dahl salt sensitive (SS) background (consomic SB2) reduced blood pressure (BP), and vascular inflammation under a normal-salt diet (NSD). We hypothesized that BN Chr2 contains anti-inflammatory genes that could prevent BP elevation and vascular inflammation in rats fed NSD and high-salt diet (HSD). These genes will be identified using microRNA (miRNA) and total RNA sequencing in aorta of congenic rats containing different portions of BN Chr2 under NSD and HSD. Methods and Results: Four-to-6 week-old male SS and congenic SB2a and SB2b rats were fed a NSD or HSD (4% NaCl) for 8 weeks. Telemetry systolic BP (SBP) was lower in SB2a and SB2b compared to SS (125±3, 127±6 vs 146±2 mm Hg, P <0.05) under NSD and tended to be higher in SB2b but not in SB2a when compared to SS (185±8, 167±7 vs 168±5 mm Hg) under HSD. RNA was extracted from aorta and used for small and total RNA sequencing using Illumina HiSeq-2500. Differentially expressed (DE) miRNAs and genes (mRNAs and non-coding RNAs [ncRNAs]) encoded in BN Chr2 introgressed portions were identified with fold change ≤ or ≥1.5 and FDR<0.05 in SB2a vs SS (miRNAs: 2 up (↑) and 2 down (↓), mRNAs: 8 ↑ and 10 ↓, ncRNA: 1 ↓) under NSD and (miRNAs: 12 ↑ and 14 ↓; mRNAs: 188↑ and 259 ↓, ncRNAs: 1 ↑ and 11 ↓) under HSD; and SB2b vs SS (miRNAs: 2 ↑ and 4 ↓, mRNAs: 26 ↑ and 85 ↓; ncRNAs: 1 ↑ and 2 ↓) under NSD and (mRNAs: 6 ↑ and 11 ↓, ncRNAs: 1 ↑ and 3 ↓) under HSD. Ddah1 was down-regulated in SB2a vs SS rats fed NSD and HSD, while Acad9 , Agtr1b, ncRNA AABR07012047.1 , Fbxw7, Ptgfrn were down-regulated and ncRNA AABR07012585.3 , Bbs12, Kcnab1 were up-regulated in SB2b vs SS rats fed NSD and HSD. DE RNAs were confirmed by reverse transcription-quantitative PCR (RT-qPCR). Correlation between RNA-sequencing and RT-qPCR data was demonstrated for 6 of 9 tested RNAs: Kcnab1 (r=0.86, P <3.3E-9), Agtr1b (r=0.85, P <6E-9), Ddah1 (r=0.78 , P <5.0E-7) , Bbs12 (r=0.72, P <6.4E-6), Ptgfrn (r=0.54, P <0.005), and AABR07012047.1 (r=0.48, P <0.05). Conclusions: BN Chr2 encoded DE genes were identified in aorta of congenic SB2a and SB2b rats fed NSD and HSD. Whether these genes play a role in vascular inflammation remains to be determined.