|Elsasser, Theodore - Ted|
Submitted to: Experimental Biology and Medicine
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2006
Publication Date: 7/15/2007
Citation: Cattin, I., Christen, S., Shaw, S.G., Blum, J.W., Elsasser, T.H. 2007. Protein s-nitrosylation in the neonate:immunoreactivity is differentially encountered among tissues and correlates with age-patterned changes in plasma nitrate concentration and tissue s-nitrosothiol localization. Experimental Biology and Medicine 232(2):309-322. Interpretive Summary: The sudden switch from uterine to extrauterine life is recognized as a significant stress on the neonate. We have modeled using the infant calf, the presence and development of post-translational modifications in proteins in organs and plasma suggesting that nitrosylation is an important adaptive mechanism for the delivery of nitric oxide to tissues for the purposes of immunodefense and maintenance of vascular function in delicate regulatory organs such as the liver and intestine. The discovery of this phenomenon in calves is unique and indicates that arginine utilization and status is important to this phase for the neonate since it is from arginine that the nitrosylation reaction stems. Improved vascular delivery of oxygen and nutrients to tissues may be possible with modulation of these neonatal tissue nitrosylations and potentially achievable through maternal nutrition prior to term.
Technical Abstract: Relative to mature subjects, neonates have several hundreds times the plasma concentration of nitrite and nitrate (NOx¯), the stable decay products of nitric oxide (NO) suggesting a high level of activation of the NO axis at birth. While the half-life of NO is short (milliseconds), the functionality of this vascular regulatory and signal transduction molecule can be prolonged when it reacts to form S-nitrosothiols (RSNO) from which NO can be re-released. Using the calf as a model, we tested the hypothesis that circulating levels of RSNOs are also elevated at birth and are selectively generated in critical tissue beds. Plasma samples were collected from calves on days 0, 1, 7 and 112 of life (n=13) and from mature cattle (n=8) and analyzed for NOx¯, RSNO and for S-nitrosylated albumin (SNALB, the major circulating RSNO protrein). As with NOx¯, RSNO and SNALB levels were highest on day-0 and progressively decreased with age. S-nitrosocysteine (SNC, a validated marker for S-nitrosylated proteins) and inducible (iNOS) and the phosphorylation-activated endothelial (SER1177PO4-eNOS) nitric oxide synthase isoforms were identified by immunohistochemical localization in tissues harvested from another group of calves at 4 and 24 h and two weeks after birth. Tissue SNC, iNOS and phosphor-eNOS were detected in liver and ileum at 4 h after birth, increased between 4 and 24 h and then declined to negative status by 2 weeks of life. Collectively, the data suggest that the localization of S-nitrosylation reaction products differs between tissues in the neonate and is consistent with time-related changes in immunoreactivity of iNOS and eNOS in those tissues.