Circadian clock disruption by selective removal of endogenous carbon monoxide

Abstract

Circadian rhythms are regulated by transcription-translation feedback loops (TTFL) of clock genes. Previous studies have demonstrated that core transcriptional factors, NPAS2 and CLOCK, in the TTFL can reversibly bind carbon monoxide (CO) in vitro. However, little is known about whether endogenous CO, which is continuously produced during a heme metabolic process, is involved in the circadian system. Here we show that selective removal of endogenous CO in mice considerably disrupts rhythmic expression of the clock genes. A highly selective CO scavenger, hemoCD1, which is a supramolecular complex of an iron(II)porphyrin with a per-O-methyl-β-cyclodextrin dimer, was used to remove endogenous CO in mice. Intraperitoneal administration of hemoCD1 to mice immediately reduced the amount of internal CO. The removal of CO promoted the bindings of NPAS2 and CLOCK to DNA (E-box) in the murine liver, resulting in up-regulation of the E-box-controlled clock genes (Per1, Per2, Cry1, Cry2, and Rev-erbα). Within 3 h after the administration, most hemoCD1 in mice was excreted in the urine, and heme oxygenase-1 (HO-1) was gradually induced in the liver. Increased endogenous CO production due to the overexpression of HO-1 caused dissociation of NPAS2 and CLOCK from E-box, which in turn induced down-regulation of the clock genes. The down-regulation continued over 12 h even after the internal CO level recovered to normal. The late down-regulation was ascribed to an inflammatory response caused by the endogenous CO reduction. The CO pseudo-knockdown experiments provided the clear evidence that endogenous CO contributes to regulation in the mammalian circadian clock.

Supramolecular Complexation in Biological Media: NMR Study on Inclusion of an Anionic Tetraarylporphyrin into a Per‐O‐Methylated β‐Cyclodextrin Cavity in Serum, Blood, and Urine

“…Pharmacokinetic application of 1D HMQC : In previous studies, we injected animals (rats and mice) with the inclusion complexes of TPPS and its iron complex (FeTPPS) with methylated β‐CD derivatives. The complexes administered either intravenously or intraperitoneally were filtered through the renal glomeruli; thus partially excreted in the urine.…”

“…In our laboratory, highly specific intermolecular interaction between TMCD and water‐soluble porphyrins such as 5,10,15,20‐tetrakis(4‐sulphonatophenyl)porphyrin (TPPS) has been studied . In particular, the iron complex of TPPS included by a per‐ O ‐methylated β‐CD dimer having a pyridine linker has been utilized in vivo as an artificial oxygen carrier, cyanide antidote, and carbon monoxide removal agent . In these previous investigations, however, we did not provide satisfactory evidence to indicate that the inclusion complexes of CDs with porphyrins were sustained in the biological media.…”

Heme binding to human CLOCK affects interactions with the E-box

“…In the case of particular circadian proteins, several-including REV-ERB, PER2, NPAS2-are shown to bind heme (12,15,20,21,(31)(32)(33)(34)(35)(36)(37)(38)(39)(40) and complex formation with partner proteins can be affected by heme or CO binding (34,41,42). And there are precedents for a circadian control mechanism that occurs through binding to PAS domain proteins, because of other regulatory PAS domain proteins that are known to bind heme [for example FixL in the histidine kinase family, the phosphodiesterases EcDOS and PDEA1 (43) Structure and Heme Ligation in hCLOCK.…”

Regulation and function of extra‐SCN circadian oscillators in the brain

“…The diurnal activity of core clock genes as well as of CCG s is therefore controlled through binding of different protein regulators to E‐boxes , D‐boxes or ROREs . To adapt these molecular oscillations to external time, the circadian TTFL can be reset by light as a main stimulus, but also other stimuli such as polyunsaturated fatty acids (PUFAs), carbon monoxide (CO) and nitric oxide (NO) were described to have resetting functions (Figure ) . Light stimulates the transcription of Per genes in the suprachiasmatic nucleus (SCN) resulting in entrainment of the circadian pacemaker to the day‐night cycle .…”