Running Head: eNOS, a target for Chinese herb Danshen in hypertension Correspondence to:

Danshen, a Chinese herb, reduces hypertension in Oriental Medicine. We hypothesized that Danshen acts partially through endothelial nitric oxide synthase (eNOS) signaling mechanisms. We tested the hypothesis using tanshinone IIA, an active ingredient of Danshen, and the 2-kidney-1-clip renovascular (2K1C) hypertension model in hamsters. Oral tanshinone (50 µg/100g of body weight) reduced mean arterial pressure (MAP) from 161.2±6.9 to 130.0±7.8 mmHg (mean±SEM; p<0.05) in hypertensive hamsters. MAP in sham-operated hamsters was 114.3±9.2 mmHg. Topical tanshinone at 1 µg/ml and 5 µg/ml increased normalized arteriolar diameter from 1.00 to 1.25±0.08 and 1.57±0.11, and increased periarteriolar nitric oxide concentration from 87.1±11.3 nM to 146.9±23.1 nM (p<0.05) at 5 µg/ml in hamster cheek pouch. NG-monomethyl-L-arginine inhibited tanshinone-induced vasodilation. Hypertension reduced eNOS protein relative to sham-operated control. Tanshinone prevented the hypertension-induced reduction of eNOS, and increased eNOS expression to levels higher than sham-operated control in hamster cheek pouch. Topical tanshinone increased normalized arteriolar diameter from 1.0 to 1.47±0.08 in the cremaster muscle of control mice and to 1.12±0.13 in cremasters of eNOS-knockout mice. In ECV 304 cells transfected with eNOS-green fluorescent protein, tanshinone increased eNOS protein expression 1.35±0.05 and 1.85±0.07-fold above control after 5 min and 1 h