Cystathionine beta-synthase as a carbon monoxide-sensitive regulator of bile excretion.
Carbon monoxide (CO) is a stress-inducible gas generated by heme oxygenase (HO) eliciting adaptive responses against toxicants; however, mechanisms for its reception remain unknown. Serendipitous observation in metabolome analysis in CO-overproducing livers suggested roles of cystathionine beta-synthase (CBS) that rate-limits transsulfuration pathway and H(2)S generation, for the gas-responsive receptor. Studies using recombinant CBS indicated that CO binds to the prosthetic heme, stabilizing 6-coordinated CO-Fe(II)-histidine complex to block the activity, whereas nitric oxide (NO) forms 5-coordinated structure without inhibiting it. The CO-overproducing livers down-regulated H(2)S to stimulate HCO(3) (-)-dependent choleresis: these responses were attenuated by blocking HO or by donating H(2)S. Livers of heterozygous CBS knockout mice neither down-regulated H(2)S nor exhibited the choleresis while overproducing CO. In the mouse model of estradiol-induced cholestasis, CO overproduction by inducing HO-1 significantly improved the bile output through stimulating HCO(3) (-) excretion; such a choleretic response did not occur in the knockout mice.


CONCLUSIONS
Results collected from metabolome analyses suggested that CBS serves as a CO-sensitive modulator of H(2)S to support biliary excretion, shedding light on a putative role of the enzyme for stress-elicited adaptive response against bile-dependent detoxification processes.
Shintani
Tsunehiro
T
Department of Biochemistry and Integrative Medical Biology, Department of Surgery, School of Medicine, Keio University, Tokyo, Japan.
Iwabuchi
Takuya
T
Soga
Tomoyoshi
T
Kato
Yuichiro
Y
Yamamoto
Takehiro
T
Takano
Naoharu
N
Hishiki
Takako
T
Ueno
Yuki
Y
Ikeda
Satsuki
S
Sakuragawa
Tadayuki
T
Ishikawa
Kazuo
K
Goda
Nobuhito
N
Kitagawa
Yuko
Y
Kajimura
Mayumi
M
Matsumoto
Kenji
K
Suematsu
Makoto
M
D000818:Animals; D001646:Bile / Q000378:metabolism*; D002248:Carbon Monoxide / Q000502:physiology*; D003541:Cystathionine beta-Synthase / Q000378:metabolism*; D008297:Male; D055442:Metabolome / Q000502:physiology; D051379:Mice
D002248:Carbon Monoxide; D003541:Cystathionine beta-Synthase