Ammonium tetrathiomolybdate following ischemia/reperfusion injury: Chemistry, pharmacology, and impact of a new class of sulfide donor in preclinical injury models

Abstract

BackgroundEarly revascularization of ischemic organs is key to improving outcomes, yet consequent reperfusion injury may be harmful. Reperfusion injury is largely attributed to excess mitochondrial production of reactive oxygen species (ROS). Sulfide inhibits mitochondria and reduces ROS production. Ammonium tetrathiomolybdate (ATTM), a copper chelator, releases sulfide in a controlled and novel manner, and may offer potential therapeutic utility.Methods and findingsIn vitro, ATTM releases sulfide in a time-, pH-, temperature-, and thiol-dependent manner. Controlled sulfide release from ATTM reduces metabolism (measured as oxygen consumption) both in vivo in awake rats and ex vivo in skeletal muscle tissue, with a superior safety profile compared to standard sulfide generators. Given intravenously at reperfusion/resuscitation to rats, ATTM significantly reduced infarct size following either myocardial or cerebral ischemia, and conferred survival benefit following severe hemorrhage. Mechanistic studies (in vitro anoxia/reoxygenation) demonstrated a mitochondrial site of action (decreased MitoSOX fluorescence), where the majority of damaging ROS is produced.ConclusionsThe inorganic thiometallate ATTM represents a new class of sulfide-releasing drugs. Our findings provide impetus for further investigation of this compound as a novel adjunct therapy for reperfusion injury.

Neuroprotective effects of ammonium tetrathiomolybdate, a slow-release sulfide donor, in a rodent model of regional stroke

“…We previously described the unique sulfide-releasing properties of ATTM [23], a treatment used over many decades as an oral copper chelator to treat Wilson's disease and, more recently, investigated as an anti-cancer agent [42]. We could demonstrate organ protection and outcome benefit in reperfusion models of myocardial infarction, global brain injury, and resuscitated hemorrhage [23], and were thus keen to extend these results to a relevant preclinical stroke model. Importantly, we have recently provided evidence that ATTM acts as a targeted therapy [23].…”

“…We aimed for a minimum of 5 animals per group for histological and molecular outcome measures and 8 per group for behavioral tests. Using fixed numbers of this magnitude has previously enabled us to demonstrate clinically and statistically relevant differences [23,29].…”

“…However, all subsequent behavioral, histological, and biochemical assessments were performed by investigators unaware of the treatment allocation. We selected the quantity of ATTM administered here as this has previously conferred protection following myocardial and (global) cerebral ischemia, and hemorrhage/resuscitation [23]. Additionally, ATTM does not impact on global hemodynamics or cardiac function (mean arterial blood pressure, cardiac output, and contractility) at this dose level [23].…”

Chemistry, pharmacology, and cellular uptake mechanisms of thiometallate sulfide donors

“…In addition to the nature of the metal, the hydrolysis rates of these molecules are also determined by the cation (Lee et al, 2007). In a previous study, we showed that ATN-224, the bis-choline salt of tetrathiomolybdate, released less sulfide compared to ATTM in vitro (Dyson et al, 2017). As a result, it was less effective as a metabolic modulator in vivo.…”

Strategies for the Design of Donors and Precursors of Reactive Sulfur Species

“…While H 2 S release from TTM was not established previously it was reported that under strong acidic conditions, TTM could decompose to molybdenum disulfide and H 2 S . Recently H 2 S‐related behaviors of TTM under physiological conditions were studied by the Xian and Singer laboratories. Indeed TTM was found to produce H 2 S in a slow and sustained process.…”