Melatonin inhibits LPS‐induced NO production in rat endothelial cells

Abstract

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-kappaB) 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-kappaB 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 mum) 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-kappaB 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.

Gene regulation by melatonin linked to epigenetic phenomena

“…Also, the regulation of IL-2 and IL-6 production by human mononuclear immune cells seems to be mediated through this mechanism (Carrillo-Vico et al, 2005b). As recently documented by Esposito et al (2008b) and others (Deng et al, 2006;Ozbek et al, 2009;Tamura et al, 2009), melatonin suppresses NF-κB binding to DNA via a NR cross-talk and decreases TNF-α, iNOS, COX-2 and PGE2 levels. Deng et al (2006) noted that melatonin inhibits p300 HAT activity and abrogates p300-augmented COX-2 and iNOS expression.…”

Impact of melatonin on immunity: a review

“…Melatonin acts as their inhibitor; its inhibitory effect can significantly contribute to a melatonin-linked anti-inflammatory mechanism. Owing to inflammation, inhibition of inducible NOS (iNOS) activation is an extensive effect observable for melatonin presented in nanomolar concentrations [34]. In another review paper, inhibition of iNOS was described: melatonin synthetic analogs were compared as candidates for novel drugs [35].…”

Pathological Effect of Melatonin on Vascular Endothelial Cell Detachment

“…혈관내피세포의 탈착을 야기하는 요인 중 하나는 산화질소 생산의 감소이다 [23]. 따라서 일차적으로 본 논문에서는 산 화질소의 생산이 melatonin에 의해 어떻게 조절되는지 규명 하였다 [20]. 또한 melatonin이 병리적 기능 중의 하나인 혈 관내피세포 탈착에 어떤 영향을 미치는지 관찰하여, melatonin이 혈관의 병리적 기능에 미치는 영향 및 역할을 본 논 문을 통하여 보고한다.…”