Abstract 223: Zinc-finger Nuclease Knockout Of Dual-specificity Protein Phosphatase-5 Enhances Myogenic Response In Autoregulation Of Cerebral Blood Flow In Fhh.1bn Rats

Abstract

We recently reported that the pressure-induced myogenic responses of afferent arteries (Af-Art) and middle cerebral arteries (MCAs) were impaired in the fawn hooded hypertensive (FHH) rats and were restored in FHH.1BN congenic strain in which chromosome 1 from the Brown Norway (BN) rats containing 11 genes including dual-specificity protein phosphatase-5 (Dusp5) was transferred into FHH genetic background. There are 4 single nucleotide polymorphisms (SNP) in Dusp5 in FHH as compared with BN rats, one of which causes G155R mutation. To determine whether Dusp5 contributes to the impaired vascular myogenic response in FHH rats, we created a Dusp5 knockout (KO) rats in the FHH.1BN genetic background using zinc-finger nuclease (ZFN) that introduced a premature stop codon at amino acid (AA) 121. The expression of Dusp5 in KO rats were significantly decreased and the level of phosphorylated ERK2 (p-ERK2) was significantly increased in multiple organs including liver, spleen and white blood cells (WBCs). The luminal diameter of the MCAs in FHH.1BN rats (n=12) decreased 20 ± 2 % when the perfusion pressure was increased from 40 to 140 mmHg, whereas it decreased 34 ± 7 % in Dusp5 KO rats (n=6) and increased 10 ± 4% in FHH strain (n=8). Autoregulation was markedly impaired and CBF increased by 54 ± 6% in FHH rats when MAP was increased from 100 to 160 mmHg. CBF was better autoregulated in FHH.1BN strain and Dusp5 KO rats increased by only 26 ± 3% and 12 ± 3% when MAP was increased over the same range. However, the range of autoregulation of CBF was extended in the FHH rats (n=7) in that CBF rose to 107 ± 6% in FHH.1BN rats (n=7) when pressure was increased to 190 mmHg versus 33 ± 4% in the Dusp5 KO animals (n=6). These results suggest that Dusp5 plays an important role in modulating of myogenic tone in the cerebral circulation. Unless the G155R mutation activates Dusp5 in FHH rats, it is unlikely that Dusp5 is responsible for the impaired myogenic response in FHH rats.