Abstract P150: Genes of a Brown Norway Chromosome 2 Fragment Introgressed Into Hypertensive Dahl Salt-Sensitive Background Exert Pro-Inflammatory Effects When Stimulated by a High-Salt Diet

Abstract

Background: Chromosome 2 (Chr2) introgression from normotensive Brown Norway (BN) rats into hypertensive Dahl salt-sensitive (SS) background (consomic S B 2) reduced blood pressure (BP) and vascular inflammation under normal-salt diet (NSD). We hypothesized that BN Chr2 contains anti-inflammatory genes that could reduce BP elevation and vascular inflammation in rats fed NSD and high-salt diet (HSD). Method: Four- to 6-week old male SS and congenic rats containing the BN Chr2 distal portion (S B 2a) and middle segment (S B 2b) were fed NSD or HSD (4% NaCl) for 8 weeks. We determined systolic BP (SBP) by telemetry, reactive oxygen species (ROS) generation using dihydroethidium staining, and vascular cell adhesion molecule 1 (VCAM-1), monocyte chemoattractant protein-1 (MCP-1) expression and monocyte/macrophage (MoMϕ) infiltration by immunofluorescence in aorta or perivascular fat (PVAT). RNA was extracted from aorta and used for small and total RNA sequencing and data were analyzed using a systems biology approach. Differentially expressed genes (DEGs) were identified with fold change >1.3 and fold discovery rate <0.05 and some of them were validated with RT-qPCR. Results: SS SBP was 145±2 mm Hg under NSD and 168±1 mm Hg under HSD, which was lower in S B 2a and S B 2b SBP (125±3 and 127±6, P <0.05) under NSD but similar under HSD. Examination of ROS generation, VCAM-1 and MCP-1 expression and MoMϕ infiltration revealed that S B 2a present less and more inflammation under NSD and HSD, respectively, compared to SS. DEGs were identified in S B 2a vs SS uniquely under NSD (15↑ and 8↓) and HSD (318↑ and 221↓) and under both diet (3↑ and 3↓), and in S B 2b vs SS uniquely under NSD (43↑ and 65↓) and HSD (4↑ and 7 ↓) and under both diet (3↑ and 4 ↓). DEGs encoded within BN Chr2a were uniquely identified under NSD (1↑ and 1↓) and HSD (6↑ and 1↓), and in both diets (1↑ and 1↓). Gene enrichment analysis revealed that under NSD, 2 BN Chr2a DEGs are involved in regulation of BP, and under HSD, 7 BN Chr2a DEGs in cell proliferation, cell differentiation, signal transduction and the immune system. RT-qPCR validated DEGs encoded within BN Chr2a under NSD (2) and HSD (4). Conclusions: DEGs encoded within BN Chr2a fragment are associated with anti- and pro-inflammatory effects under NSD and HSD, respectively.