Background High dietary salt intake is strongly correlated with cardiovascular (CV) diseases and it is regarded as a major risk factor associated with the pathogenesis of hypertension. The CV control centres in the brainstem (the nucleus tractus solitarii (NTS) and the rostral ventrolateral medulla (RVLM)) and hypothalamic forebrain (the subfornical organ, SFO; the supraoptic nucleus, SON and the paraventricular nucleus, PVN) have critical roles in regulating CV autonomic motor outflows, and thus maintaining blood pressure (BP). Growing evidence has implicated autonomic regulatory networks in salt-sensitive HPN (SSH), but the genetic basis remains to be delineated. We hypothesized that the development and/ or maintenance of SSH is reliant on the change in the expression of genes in brain regions controlling the CV system. Methodology We used RNA-Sequencing (RNA-Seq) to describe the differential expression of genes in SFO, SON, PVN, NTS and RVLM of rats being chronically fed with high-salt (HS) diet. Subsequently, a selection of putatively regulated genes was validated with quantitative reverse transcription polymerase chain reaction (qRT-PCR) in both Spontaneously Hypertensive rats (SHRs) and Wistar Kyoto (WKY) rats. Results The findings enabled us to identify number of differentially expressed genes in SFO, SON, PVN, NTS and RVLM; that are either up-regulated in both strains of rats (SON- Caprin2, Sctr), down-regulated in both strains of rats (PVN- Orc, Gkap1), up-regulated only in SHRs (SFO- Apopt1, Lin52, AVP, OXT; SON- AVP, OXT; PVN- Caprin2, Sclt; RVLM- A4galt, Slc29a4, Cmc1) or down-regulated only in SHRs (SON- Ndufaf2, Kcnv1; PVN- Pi4k2a; NTS- Snrpd2l, Ankrd29, St6galnac6, Rnf157, Iglon5, Csrnp3, Rprd1a; RVLM- Ttr, Faim). Conclusions These findings demonstrated the adverse effects of HS diet on BP, which may be mediated via modulating the signaling systems in CV centers in the hypothalamic forebrain and brainstem.

27An increase in blood pressure (BP) by a high-salt (HS) diet may involve the 28 changes in the expression of epithelium sodium channels (ENaCs) and aquaporins 29 (AQPs) in the kidney which affect the sodium-and water-handling mechanisms. In the 30 present study, spontaneously hypertensive rats (SHRs) and Wistar Kyoto (WKY) rats 31 were exposed to HS and regular-salt (RS) diets for 6 weeks and fluid intake was 32 monitored. After 6 weeks, mean arterial pressure (MAP) and plasma hormonal activity 33 of atrial natriuretic peptide (ANP), levels of angiotensin II (Ang II), aldosterone and 34 arginine vasopressin (AVP) were determined. The expression of mRNA and protein 35 levels of ENaC and AQP subunits in kidneys were quantified by real-time PCR and 36 Western blotting. High-salt diet caused higher MAP only in SHRs and higher fluid 37 intake in both strains of rats when compared with their respective controls on RS diet.38 The plasma levels of Ang II and aldosterone were low in both SHRs and WKY rats fed 39 with HS diet. Meanwhile, plasma ANP activity was high in both strains of rats on HS 40 diet; whilst the AVP showed vice versa effects. The renal expression of mRNA and 41 protein levels of α-and γ-ENaCs was lowered by HS diet in both SHRs and WKY rats.42 Although β-ENaC mRNA and protein expression levels were depressed in SHRs but 43 they were enhanced in WKY rats. On the other hand, AQP-1, 2 and 7 mRNA and 44 protein expression levels were lowered in both strains of rats fed with HS diet, while 45 that of AQP-3, 4 and 6 showed no significant changes. The suppression of mRNA and 46 protein expression levels of ENaC and AQP subunits suggests that the HS-induced 47 increase in the MAP of SHRs may not be due to the renal sodium and water retention 48 solely. 49 3 50 Introduction 51 Dietary salt (i.e. sodium chloride, NaCl) intake is the most remarkably modifiable 52 environmental risk factor that attracts many studies on hypertension (HPN). It has been 53 acknowledged as an important contributing factor of the aetiology and progression of 54 HPN [1]. Despite the abundant experimental, interventional and epidemiological 55 observations demonstrating an association between dietary salt and HPN, scepticism 56 remains as to how high salt (HS) intake can be mechanistically linked to the increase in 57 blood pressure (BP). Knowing the heterogeneity of HPN, it is likely to involve the 58 intricate integration of multiple regulatory systems and the kidneys have long been 59 implicated to play a central role in regulating BP. Defects in the kidneys sodium-and 60 water-handling mechanisms have been mooted as one of the primary causes of HPN in 61 HS intake [2]. 62The kidneys have the capacity to return altered BP to baseline level by 63 increasing or decreasing sodium and water excretion in response to elevated or reduced 64 BP [3]. This is accomplished in the kidney by the presence of renal membrane-bound 65 protein i.e. epithelial sodium channel (ENaC) that fine-tune sodium reabsorption [4] 66 and aquaporins (AQPs) that ...