Elevated plasma
homocysteine levels are considered an independent risk factor for
cardiovascular diseases. Experimental evidence has shown that
hydrogen sulfide anion (HS(-)) protects the myocardium from
ischemia/reperfusion (IR) injury. Both
homocysteine levels and endogenous HS(-) production are mainly regulated by two transsulfuration
enzymes,
cystathionine β-synthase (CBS) and
cystathionine γ-
lyase (CTH). We hypothesized that the transsulfuration pathway plays essential roles in the development of cardiac adaptive responses against
ischemia, and investigated the roles of
homocysteine, HS(-), and transsulfuration
enzymes in fasting-induced cardioprotection against IR injury utilizing hyperhomocysteinemic Cbs (-/-) and Cth (-/-) mice. Langendorff-perfused hearts were subjected to 25-min global
ischemia, followed by 60-min reperfusion. Two-day fasting ameliorated
left ventricular dysfunction after reperfusion via
propargylglycine- and
glibenclamide-sensitive pathways in wild-type mice but not in Cbs (-/-) or Cth (-/-) mice, although fasting induced cardiac expression of several Nrf2 target
antioxidant genes in both wild-type and Cth (-/-) mice. Intraperitoneal administration of
sodium hydrosulfide (a HS(-) donor) at 24 h prior to IR improved myocardial recovery in wild-type mice but not in Cth (-/-) or high-
methionine-diet-fed (thus intermediately hyperhomocysteinemic) wild-type mice. Quantitative analysis of reactive
sulfur species using
monobromobimane derivatization methods revealed that
homocysteine efficiently captures HS(-) to form
homocysteine persulfide in the hearts as well as in the in vitro reactions. Here we propose a novel molecular and pathophysiological basis for
hyperhomocysteinemia; excessive circulatory
homocysteine interferes with HS(-)-related cardioprotection against IR injury by capturing endogenous HS(-) to form
homocysteine persulfide.
KEY MESSAGE: Two-day fasting of mice ameliorates
ischemia/reperfusion injury in Langendorff hearts. H2S-producing
enzymes, CBS and CTH, are essential in fasting-induced cardioprotection. Administration of a H2S donor (
NaHS) confers cardioprotection against IR injury.
NaHS effects are absent in Cth (-/-), Cbs (-/-), and dietary hyperhomocysteinemic mice.
Homocysteine captures cardioprotective HS(-) to form
homocysteine persulfide.