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Aberrant eNOS phosphorylation in Idiopathic Pulmonary Arterial Hypertension
Author(s) -
Ghosh Sudakshina,
Mavrakis Lori,
Janocha Allison J.,
Comhair Suzy A.A.,
Erzurum Serpil C.
Publication year - 2010
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.24.1_supplement.1023.4
Subject(s) - enos , phosphorylation , nitric oxide , medicine , endocrinology , bradykinin , vasodilation , nitric oxide synthase type iii , nitric oxide synthase , endothelial nos , chemistry , biochemistry , receptor
Based upon its critical role in mediating vasodilation, nitric oxide (NO) deficiency has been implicated in the pathogenesis of Idiopathic Pulmonary Arterial Hypertension (IPAH). We have shown that NO production by pulmonary artery endothelial cells (PAEC) derived from IPAH lungs is lower than control lungs. We hypothesized that the low NO production by IPAH PAEC is due to reduced activity of the endothelial nitric oxide synthase (eNOS). Agonist‐induced (Bradykinin, BK, 1 mM) NO production nearly doubled in control PAEC (n = 4) [nitrite pmol/ml‐min, nonstimulated: 0.14 ± 0.01; stimulated: 0.24±0.01, p < 0.0001] whereas NO production increased only minimally in IPAH PAECs (n=6) [pmol/ml‐min, nonstimulated: 0.15 ± 0.01, stimulated: 0.18 ± 0.01, p = 0.01]. Dimerization of eNOS, which is required for active enzyme, was similar among control and IPAH PAECs. Activity of dimeric eNOS is determined by phosphorylation; Serine 1177 (S1177) phosphorylation is required for enzyme synthesis of NO and Threonine 495 (T495) phosphorylation inhibits activity. BK stimulation caused phosphorylation of S1177 in IPAH PAEC, but less than control cells (pS1177/total eNOS, control: 1.25 ± 0.01, IPAH: 0.92 ± 0.03, p = 0.01). BK also rapidly induced dephosphorylation of T495 in control PAEC, but not in IPAH PAEC (pT495/total eNOS, control: 0.11 ± 0.01, IPAH: 2.1 ± 0.06, p = 0.01). These findings point to abnormalities in eNOS phosphorylation in the decreased NO synthesis of IPAH cells.