HDAC1 Mediates High Salt Impaired Endothelial NO Signaling

Abstract

High salt diet (HS) impairment of endothelial nitric oxide (NO) signaling has been described in human and rodents. The mechanisms which mediate this dysfunction remain unknown. We and others have previously shown histone deacetylase 1 (HDAC1) decreases endothelial NO production. We therefore sought to investigate the mechanisms by which HS initiates endothelial dysfunction and if it is HDAC1-dependent. We first investigated if HS induced endothelial dysfunction is acutely regulated by a circulating factor. Male Sprague Dawley rats were fed normal salt diet (NS; 0.49% NaCl) or 2 weeks of HS (4.0% NaCl). Afferent arteriole vasoconstrictor responses to the NOS inhibitor, L-NAME, were monitored using the in vitro, blood perfused juxtamedullary nephron preparation. Arterioles from HS fed rats perfused with blood from HS fed rats demonstrated blunted constriction to L-NAME (96 ± 2% of Con) compared to arterioles from NS fed rats perfused with blood from NS fed rats (76.2 ± 2% of Con; P=0.0017). Perfusing arterioles from NS fed rats with blood HS fed rats blunted constriction to L-NAME (88 ± 1% of Con) compared to perfusing with blood from NS fed rats (P=0.0003), but not to the same extent as arterioles from HS fed rats perfused with blood from HS fed rats (P=0.0095). HS arterioles perfused with blood from NS fed rats had similar L-NAME-induced constriction (75 ± 2% of Con) compared to arterioles from NS fed rats perfused with blood from NS fed rats (P=0.9107). In short, the impaired constriction to L-NAME is dependent up on the diet of the blood donor and not the diet of the arteriole donor suggesting HS impairs endothelial function through an acute-acting circulating factor. This was not due to increased plasma arginase activity (NS: 7.96 ± 3.73 U/L vs HS: 5.42 ± 1.83 U/L P=0.5813), changes in plasma tetrahydrobiopterin (NS: 65.09 ± 11.57 pmol/ml vs HS: 53.54 ± 5.59 pmol/ml, P=0.311) or changes in plasma dihydrobiopterin (NS: 98.18 ± 7.84 pmol/ml vs HS: 87.45 ± 13.28 pmol/ml, P=0.530). We then investigated if HS increased endothelial HDAC1 activity. Renal endothelial cells were isolated from NS and HS fed rats and incubated in plasma from the same rat. HDAC1 activity was defined as the MS-275 (HDAC1 specific inhibitor) inhibitable portion of total HDAC activity. We found HS significantly increased renal endothelial HDAC1 activity (NS: 0.38 ± 0.03 pmol/min vs HS:0.94 ± 0.19 pmol/min, P=0.01). Furthermore, in vitro HDAC1 inhibition with 300 nM MS-275 restored the arteriolar vasoconstrictor responses in HS rats (79 ± 3% of Con) to values similar to NS fed rats (P=0.969) and to NS rats + MS-275 (79 ± 1% of Con; P>0.998). When plasma from HS fed rats was combined with erythrocytes from NS fed rats and perfused through arterioles from NS fed rats, constriction to L-NAME was blunted (85 ± 3% of Con; P=0.0129). Under these same conditions, HDAC1 inhibition restored constriction (75.7 ± 0.95 % of Con) similar to controls (P=0.979). We conclude that HS disruption of renal microvascular NO signaling is initiated by a circulating factor(s) that increases endothelial HDAC1 activity.