Ezh2 emerges as an epigenetic checkpoint regulator during monocyte differentiation limiting cardiac dysfunction post-MI.

Epigenetic regulation of histone H3K27 methylation has recently emerged as a key step during alternative immunoregulatory M2-like macrophage polarization; known to impact cardiac repair after Myocardial Infarction (MI). We hypothesized that EZH2, responsible for H3K27 methylation, could act as an epigenetic checkpoint regulator during this process. We demonstrate for the first time an ectopic EZH2, and putative, cytoplasmic inactive localization of the epigenetic enzyme, during monocyte differentiation into M2 macrophages in vitro as well as in immunomodulatory cardiac macrophages in vivo in the post-MI acute inflammatory phase. Moreover, we show that pharmacological EZH2 inhibition, with GSK-343, resolves H3K27 methylation of bivalent gene promoters, thus enhancing their expression to promote human monocyte repair functions. In line with this protective effect, GSK-343 treatment accelerated cardiac inflammatory resolution preventing infarct expansion and subsequent cardiac dysfunction in female mice post-MI in vivo. In conclusion, our study reveals that pharmacological epigenetic modulation of cardiac-infiltrating immune cells may hold promise to limit adverse cardiac remodeling after MI.

Age-dependent alterations of the NMDA receptor developmental profile and adult behavior in postnatally ketamine-treated mice.

Ketamine is a NMDA receptor (NMDAR) antagonist used in pediatric anesthesia. Given the role of glutamatergic signaling during brain maturation, we studied the effects of a single ketamine injection (40 mg/kg s.c) in mouse neonates depending on postnatal age at injection (P2, P5, or P10) on cortical NMDAR subunits expression and association with Membrane-Associated Guanylate Kinases PSD95 and SAP102. The effects of ketamine injection at P2, P5, or P10 on motor activity were compared in adulthood. Ketamine increased GluN2A and GluN2B mRNA levels in P2-treated mice without change in proteins, while it decreased GluN2B protein in P10-treated mice without change in mRNA. Ketamine reduced GluN2A mRNA and protein levels in P5-treated mice without change in GluN2B and GluN1. Ketamine affected the GluN2A/PSD95 association regardless of the age at injection, while GluN2B/PSD95 association was enhanced only in P5-treated mice. Microdissection of ketamine-treated mouse cortex showed a decrease in GluN2A mRNA level in superficial layers (I-IV) and an increase in all subunit expressions in deep layers (V-VI) in P5- and P10-treated mice, respectively. Our data suggest that ketamine impairs cortical NMDAR subunit developmental profile and delays the synaptic targeting of GluN2A-enriched NMDAR. Ketamine injection at P2 or P10 resulted in hyperlocomotion in adult male mice in an open field, without change in females. Voluntary running-wheel exercise showed age- and sex-dependent alterations of the mouse activity, especially during the dark phase. Overall, a single neonatal ketamine exposure led to short-term NMDAR cortical developmental profile impairments and long-term motor activity alterations persisting in adulthood.