GsMTx4-D is a cardioprotectant against myocardial infarction during ischemia and reperfusion

Abstract

GsMTx4 is a selective inhibitor of cationic mechanosensitive ion channels (MSCs) and has helped establish the role of MSCs in cardiac physiology. Inhomogeneous local mechanical stresses due to hypercontracture and swelling during ischemic reperfusion injury (IRI) likely induce elevated MSC activity that can contribute to cation imbalance. The aim of this study was to determine if the D enantiomer of GsMTx4 can act as a cardioprotectant in a mouse IRI model. Ischemia and reperfusion involved ligating a coronary artery followed by release of the ligature. GsMTx4-D was tested by either acute intravenous injection during the ischemic event or by two day pretreatment by intraperitoneal injection, both methods achieving similar results. Based on pharmacokinetic studies, GsMTx4-D dosage was set to achieve expected plasma concentrations between 50 and 5000 nM and heart tissue concentrations between 1 and 200 nM by intravenous injection. Relative to vehicle injected animals, GsMTx4-D reduced infarct area by ~40% for acute and pretreated animals for both 20 and 45 min ischemic challenges. Many indicators of cardiac output were indistinguishable from sham-treated control hearts after GsMTx4-D treatment showing improvement at both 4 and 48 h post ischemia, and premature ventricular beats immediately following reperfusion were also significantly reduced. To determine if GsMTx4-D cardioprotection could act directly at the level of cardiomyocytes, we tested its effects in vitro on indicators of IRI damage like cation influx and activation of inflammatory kinases in isolated myocytes cultured under hypoxic conditions. Hypoxia challenged cardiomyocytes treated with 10 μM GsMTx4-D showed improved contractility and near normal contraction-related Ca2+ influx. GsMTx4-D inhibited indicators of ischemic damage such as the apoptotic signaling system JNK/c-Jun, but also inhibited the energy response signaling system Akt kinase. We conclude that GsMTx4-D is a potent cardioprotectant in vivo that may act directly on cardiomyocytes and potentially be useful in multidrug strategies to treat IRI.

Inhibition of Piezo1 attenuates demyelination in the central nervous system

“…The 34-amino acid peptide (Alomone labs, STG-100) is a member of the Inhibitory Cysteine Knot family with six cysteines, is a nontoxic component of tarantula venom, and functions as a negative allosteric modulator of mechanoreceptors (Suchyna et al, 2000). The D and L enantiomers of GsMTx4 have almost identical activity (Wang, Ma, Sachs, Li, & Suchyna, 2016) which suggests that its mechanism is not reliant on direct stereo-chemical interactions (Gnanasambandam et al, 2017). Instead, it has high affinity for lipid bilayers and its ability to partition into membranes and inhibit mechanosensitive ion channel opening appears key to its mechanism of action as a gating modifier of Piezo1 (Gottlieb, Suchyna, & Sachs, 2007).…”

Piezo channels and GsMTx4: Two milestones in our understanding of excitatory mechanosensitive channels and their role in pathology

“…The D-form of GsMTx4 has now been tested in vivo in mouse models of cardiac ischemic reperfusion injury [106] and muscular dystrophy [107], and shown to be an effective muscle protectant. In a mouse model of ischemic reperfusion injury GsMTx4-D was injected by intravenous administration during the ischemic event and pretreatment subcutaneously for a two day prior to ischemic challenge.…”

“…GsMTx4 has revealed that MSCS “apparently” contribute significantly to normal short-term and developmental physiology (examples: arterial pressure regulation [110, 111, 119, 120], skeletal muscle pressor reflex [121], cardiac stretch induced slow force response [122], RBC volume regulation [123, 124], neuronal touch and pain sensation [125–127], mechanotransduction of sound by OHCs [128, 129], serotonin release by gut epithelium [130], renal epithelium luminal pressure detection [131], etc.). Interestingly, when injected over 6 weeks, the GsMTx4 exposure reached concentrations in most tissues that would inhibit MSCs (nervous system is an exception – GsMTx4 does not appear to cross the blood brain barrier [106, 107]), but with no detectable effect on normal physiology [107]. We also showed that IV injection into telemetered free-roaming ferrets had no acute effect on normal cardiac hemodynamic or electrical properties [106].…”

“…Interestingly, when injected over 6 weeks, the GsMTx4 exposure reached concentrations in most tissues that would inhibit MSCs (nervous system is an exception – GsMTx4 does not appear to cross the blood brain barrier [106, 107]), but with no detectable effect on normal physiology [107]. We also showed that IV injection into telemetered free-roaming ferrets had no acute effect on normal cardiac hemodynamic or electrical properties [106]. And subcutaneous injection into mice over 2 weeks that were housed with, or without, running wheels showed a 2–3 fold increased muscle concentration in the animals with running wheels, but no change in running distance [107].…”

Na+/Ca2+ exchanger 1 is a key mechanosensitive molecule of the esophageal myenteric neurons

“…The concentration of KB-R7943 (10 µmol/L) was applied for cell study; however, for the whole animal study, a higher concentration (30 µmol/L) was used similar to what is cited in the literature. [54][55][56] The other chemicals were obtained from Fisher Scientific (Santa Clara, CA, USA).…”