Abstract 560: Cardiac Gene Transfer with nNOS into Sympathetic Nerves Reverses Abnormal Neurotransmission in Spontaneous Hypertension Rats
Sympathetic hyper-responsiveness seen in hypertension may result from oxidative stress impairing the nitric oxide (NO) - cGMP pathway. We tested the hypothesis that gene transfer with neuronal NO synthase (nNOS) could restore sympathetic balance in the spontaneously hypertensive rat (SHR). Percutaneous gene transfer to the right atrial wall was performed in 16 - 20 weeks old male SHRs and Wistar-Kyoto (WKY) rats, using 5×1010 particles of adenovirus constructed with a noradrenergic neuron-specific promoter (PRS×8) encoding nNOS (Ad.PRS-nNOS) or enhanced green fluorescence protein (Ad.PRS-eGFP). Five days after transduction, isolated right atria were removed and evoked [3H]norephinephrine (NE) release, NOS activity and cGMP was measured. Tissue levels of cGMP were significantly reduced in Ad.PRS-eGFP treated SHR (0.37 ± 0.01 pmol/mg protein, n=6) compared to Ad.PRS-eGFP treated WKY atria (0.44 ± 0.02 pmol/mg protein, n=6, p<0.05). In the SHR (Ad.PRS-eGFP treated, n=6) NE release was greater compared to WKY atria (Ad.PRS-eGFP treated, n=5, p<0.05); sGC inhibitor 1H-(1,2,4)oxadiazolo(4,3-a)quinoxaline-1-one (ODQ, 10 μmol/L) did not effect Ad.PRS-eGFP treated SHR. Atria treated with Ad.PRS-nNOS had enhanced nNOS activity when compared to Ad.PRS-eGFP treated atria (SHR increased by 40.08 ± 10.03 %; WKY increased by 24.90 ± 8.85 %; n=6 in each group). Gene transfer with Ad.PRS-nNOS (n=6) in WKY rats caused a 16.12 ± 3.13 % reduction in NE release compared to Ad.PRS-eGFP treated atria (n=5, p<0.01). ODQ significantly enhanced the NE release in Ad.PRS-nNOS or Ad.PRS-eGFP treated WKY atria. Gene transfer with Ad.PRS-nNOS in SHR (n=6) attenuated the NE release by 21.24 ± 3.97 % compared to Ad.PRS-eGFP (n=5, p<0.05). This attenuation was reversed by ODQ. Gene transfer with Ad.PRS-nNOS also restored cGMP levels in SHR (0.50 ± 0.05 pmol/mg protein, n=6) to those seen in WKY atria. We conclude that artificial up-regulation of cardiac nNOS via gene transfer with noradrenergic cell specific nNOS may provide a novel mechanism for correcting peripheral sympathetic hyperactivity in hypertension.