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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Melatonin inhibits LPS-induced NO production in rat endothelial cells

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Tamura, Eduardo Koji [1] ; Cecon, Erika [1] ; Arantes Monteiro, Alex Willian [1] ; Martins Silva, Claudia Lucia [2] ; Markus, Regina Pekelmann [1]
Total Authors: 5
[1] Univ Sao Paulo, Dept Fisiol, Inst Biociencias, BR-05508900 Sao Paulo - Brazil
[2] Univ Fed Rio de Janeiro, Dept Farmacol Basica & Clin, Inst Ciencias Biomed, BR-21941 Rio De Janeiro - Brazil
Total Affiliations: 2
Document type: Journal article
Source: Journal of Pineal Research; v. 46, n. 3, p. 268-274, APR 2009.
Web of Science Citations: 50

Endothelial cells produce NO by activation of constitutive nitric oxide synthase (NOS) and transcription of inducible NOS (iNOS). We have previously shown that melatonin, in the nanomolar range, inhibits activation of constitutive NOS, and in the present paper, we evaluated whether it could interfere with the expression of iNOS, which is activated by lipopolysaccharide (LPS), a major component of gram-negative bacteria cell walls. Primary cultures of rat endothelial cells were loaded with fluorescent probe for NO detection. Nuclear factor kappa B (NF-kappa B) translocation in endothelial cells elicited by LPS was measured by electromobility shift assay, and the vasodilation of aortic rings was accessed by recording isometric contraction. Melatonin in a micromolar but not in a nanomolar range inhibits the NO production induced by LPS. This effect is not dependent on the activation of G protein-coupled melatonin receptors. The nuclear NF-kappa B translocation is a process necessary for iNOS transcription, and melatonin also inhibits its translocation. LPS induced vasodilation only in endothelium-intact aortic rings, and melatonin (10 mu m) inhibits the vasodilation. Here, we show that concentrations compatible with nocturnal melatonin surge (nm) did not interfere with the activity of iNOS. Considering that micromolar melatonin concentrations could be locally achieved through production by activated immune competent cells, extra-pineal melatonin could have a protective effect against tissue injury. We propose that melatonin blocked the LPS-induced vasodilation by inhibiting the NF-kappa B pathway. Finally, we propose that the effect of melatonin on vascular reactivity is one of the mechanisms that underlies the protective effect of this indolamine against LPS. (AU)

FAPESP's process: 07/07871-6 - Imune-pineal Axis: injury shifts melatonin production from endocrine to paracrine
Grantee:Regina Pekelmann Markus
Support type: Research Projects - Thematic Grants