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Background Thioredoxin 2 (Trx2) is a key mitochondrial protein which regulates cellular redox and survival by suppressing mitochondrial ROS generation and by inhibiting apoptosis stress kinase-1 (ASK1)-dependent apoptotic signaling. To date, the role of the mitochondrial Trx2 system in heart failure pathogenesis has not been investigated. Methods and Results Western blot and histological analysis revealed that Trx2 protein expression levels were reduced in hearts from patients with dilated cardiomyopathy (DCM), with a concomitant increase in increased ASK1 phosphorylation/activity. Cardiac-specific Trx2 knockout mice (Trx2-cKO). Trx2-cKO mice develop spontaneous DCM at 1 month of age with increased heart size, reduced ventricular wall thickness, and a progressive decline in left ventricular (LV) contractile function, resulting in mortality due to heart failure by ~4 months of age. The progressive decline in cardiac function observed in Trx2-cKO mice was accompanied by disruption of mitochondrial ultrastructure, mitochondrial membrane depolarization, increased mitochondrial ROS generation and reduced ATP production, correlating with increased ASK1 signaling and increased cardiomyocyte apoptosis. Chronic administration of a highly selective ASK1 inhibitor improved cardiac phenotype and reduced maladaptive LV remodeling with significant reductions in oxidative stress, apoptosis, fibrosis and cardiac failure. Cellular data from Trx2-deficient cardiomyocytes demonstrated that ASK1 inhibition reduced apoptosis and reduced mitochondrial ROS generation. Conclusions Our data support an essential role for mitochondrial Trx2 in preserving cardiac function by suppressing mitochondrial ROS production and ASK1-dependent apoptosis. Inhibition of ASK1 represents a promising therapeutic strategy for the treatment of dilated cardiomyopathy and heart failure.

Cerebral cavernous malformations (CCMs) are vascular malformations that affect the central nervous system and result in cerebral hemorrhage, seizure and stroke. CCM arises from loss-of-function mutations in one of three genes: CCM1, CCM2 and CCM3 (PDCD10). CCM3 mutations in human often result in a more severe form of the disease, and CCM3 knockout mice show severe phenotypes with yet-to-be defined mechanisms. We have recently reported that CCM3 regulates UNC13 family-mediated exocytosis. Here we investigate endothelial cells (EC) exocytosis in CCM disease progression. We find that CCM3 suppresses UNC13B/VAMP3-dependent exocytosis of angiopoietin-2 (ANGPT2) in brain endothelial cells. CCM3 ablation in EC augments exocytosis and secretion of ANGPT2, correlating with destabilized EC junctions, enlarged lumen formation, and endothelial cell-pericyte dissociations. UNC13B deficiency that blunts ANGPT2 secretion from EC or an ANGPT2 neutralization antibody normalizes the defects caused by CCM3 deficiency. More importantly, ANGPT2 neutralization antibody treatment or UNC13B deficiency blunts the CCM lesion phenotypes, including disruption of EC junctions, vessel dilation and pericyte dissociation, in the brains and retinas caused by endothelial cell-specific CCM3 inactivation. Our study reveals that enhanced secretion of ANGPT2 in endothelial cells contributes to the progression of the CCM disease, providing a novel therapeutic approach to treat this devastating pathology.

SUMMARY The regenerative capacity of the human endometrium requires a population of local stem cells. However, the phenotypes, locations, and origin of these cells are still unknown. In a mouse menstruation model, uterine stromal SM22α + -derived CD34 + KLF4 + stem cells are activated and integrate into the regeneration area, where they differentiate and incorporate into the endometrial epithelium; this process is correlated with enhanced protein SUMOylation in CD34 + KLF4 + cells. Mice with a stromal SM22α-specific SENP1 deletion (SENP1smKO) exhibit accelerated endometrial repair in the regeneration model and develop spontaneous uterine hyperplasia. Mechanistic studies suggest that SENP1 deletion induces SUMOylation of ERα, which augments ERα transcriptional activity and proliferative signaling in SM22α + CD34 + KLF4 + cells. These cells then transdifferentiate to the endometrial epithelium. Our study reveals that CD34 + KLF4 + stromal-resident stem cells directly contribute to endometrial regeneration, which is regulated through SENP1-mediated ERα suppression.