Background: Excessive formation of neutrophil extracellular traps (NETs) leads to NETosis, accompanied by the release of citrullinated histone H3 (CitH3), a key mediator of septic inflammation. However, the role of CitH3 in sterile inflammation, such as acute myocardial infarction (MI) and post-MI heart failure, remains incompletely understood. Methods and Results: We investigated the role of CitH3, a byproduct of NETosis, in myocardial ischemia/reperfusion (I/R) injury using a murine MI model. C57BL/6J mice were subjected to left coronary artery (LCA) occlusion followed by reperfusion and treated with either a humanized anti-CitH3 monoclonal antibody (hCitH3-mAb) or control human IgG. In mice undergoing 40 min of LCA occlusion and 24 h of reperfusion, hCitH3-mAb administered 10 min before reperfusion significantly reduced infarct size by 36% compared to control (p < 0.05). Plasma levels of CitH3, IL-1β, and interferon-β were significantly elevated following MI but were attenuated by hCitH3-mAb. In addition, plasma and cardiac tissue from treated mice showed significantly lower levels of citrate synthase, a marker of mitochondrial injury, suggesting that hCitH3-mAb preserved mitochondrial integrity after MI. In mice undergoing 50 min of LCA occlusion and 21 days of reperfusion, longitudinal echocardiography revealed preservation of left ventricular ejection fraction (LVEF) in hCitH3-mAb-treated mice, with significant improvement observed on days 7, 14, and 21 post-MI (p < 0.05 vs. control). hCitH3-mAb also mitigated myocardial fibrosis and preserved tissue architecture. Conclusions: These findings demonstrated CitH3 as a critical mediator of myocardial injury and adverse remodeling following acute MI. Neutralization of CitH3 via hCitH3-mAb attenuates I/R injury and preserves cardiac function by mitigating inflammation and protecting mitochondrial integrity. Targeting CitH3 represents a promising therapeutic strategy to prevent heart failure following MI.

TRIC-A is an intracellular cation channel enriched in excitable tissues that is recently identified as a key modulator of sarcoplasmic reticulum (SR) Ca²⁺ homeostasis through direct interaction with type 2 ryanodine receptors (RyR₂). Given the intimate anatomical and functional coupling between the SR and mitochondria, we investigated whether TRIC-A contributes to SR–mitochondrial crosstalk under cardiac stress conditions. Using a transverse aortic constriction (TAC) model, we found that TRIC-A^−/− mice developed more severe cardiac hypertrophy, underwent maladaptive remodeling, and activated apoptotic pathways compared with wild-type littermates. At the cellular level, TRIC-A-deficient cardiomyocytes were more susceptible to H₂O₂-induced mitochondrial injury and displayed abnormal mitochondrial morphology. Live-cell imaging revealed exaggerated mitochondrial Ca²⁺ uptake during caffeine stimulation and increased propensity for store-overload-induced Ca²⁺ release (SOICR). Complementary studies in HEK293 cells expressing RyR₂ demonstrated that exogenous TRIC-A expression attenuates RyR₂-mediated mitochondrial Ca²⁺ overload, preserves respiratory function, and suppresses superoxide generation. Together, these findings identify TRIC-A as a critical regulator of SR–mitochondrial Ca²⁺ signaling. By constraining mitochondrial Ca²⁺ influx and limiting oxidative stress, TRIC-A safeguards cardiomyocytes against SOICR-driven injury and confers protection against pressure overload-induced cardiac dysfunction.

Trimeric intracellular cation channel A (TRIC-A) provides counter-ion support for sarcoplasmic reticulum (SR) Ca²⁺ release, yet its physiological role in the intact heart under stress remains poorly defined. Here, we demonstrate that TRIC-A is essential for maintaining balanced SR Ca²⁺ release, mitochondrial integrity, and cardiac resilience during β-adrenergic stimulation. Tric-a^−/− cardiomyocytes exhibited Ca²⁺ transients evoked by electrical stimuli and exaggerated isoproterenol (ISO)-evoked Ca²⁺ release, consistent with SR Ca²⁺ overload. These defects were accompanied by selective upregulation of protein kinase A (PKA)-dependent phosphorylation of ryanodine receptor 2 (RyR2) (S2808) and phospholamban (PLB) (S16). Acute ISO challenge induced mitochondrial swelling, cristae disruption, and Evans Blue Dye uptake, and elevated circulating troponin T in Tric-a^−/− hearts, hallmarks of necrosis-like cell death. Mitochondrial Ca²⁺ uptake inhibition with Ru360 markedly reduced membrane injury, establishing mitochondrial Ca²⁺ overload as the proximal trigger of cardiac cell death. With sustained β-adrenergic stimulation by ISO, Tric-a^−/− hearts developed extensive interstitial and perivascular fibrosis without exaggerated hypertrophy. Cardiac fibroblasts lacked TRIC-A expression and displayed normal Ca²⁺ signaling and activation, indicating that fibrosis arises secondarily from cardiomyocyte injury rather than fibroblast-intrinsic abnormalities. These findings identify TRIC-A as a critical regulator of SR-mitochondrial Ca²⁺ coupling and a key molecular safeguard that protects the heart from catecholamine-induced injury and maladaptive remodeling.

Peptidylarginine deiminase 2 (PAD2) catalyzes protein citrullination and is implicated in inflammatory bowel disease and colorectal cancer. However, its role in regulating the intestinal epithelium and the influence of biological sex and the microbiome remain poorly defined. This study investigated the relationships among PAD2 deficiency, sex-divergent epithelial states, β-catenin regulation, and the intestinal microbiome. Global PAD2 knockout and wild-type littermate mice of both sexes were characterized under basal conditions and following dextran sodium sulfate-induced colitis. Intestinal epithelial phenotypes were assessed by histology, immunofluorescence, immunoblotting, quantitative RT-PCR, and immunoprecipitation. Gut microbial communities were evaluated by shotgun metagenomics, while broad-spectrum antibiotic treatment, fecal protein immunoblotting, and recombinant human PAD2 exposure in vitro were used to examine relationships among antibiotic-sensitive factors, β-catenin regulation, and epithelial phenotypes. PAD2 deficiency was associated with distinct epithelial states in male and female colons before injury. Male KO mice displayed increased β-catenin phosphorylation and increased susceptibility to DSS colitis, whereas female KO mice demonstrated increased total β-catenin abundance and preservation of structural epithelial features following injury. Female KO microbiota exhibited genotype-associated differences in microbial community composition by exploratory Bray-Curtis PERMANOVA. Broad-spectrum antibiotic treatment altered the female epithelial phenotype, reduced active β-catenin, and progressively depleted luminal PAD2-immunoreactive proteins. Exogenous recombinant human PAD2 increased epithelial protein citrullination and altered active β-catenin abundance in HT29 cells. Collectively, these findings demonstrate both sex-specific and sex-divergent colonic phenotypes while supporting a framework connecting PAD2 biology, epithelial architecture, and the microbial environment during intestinal maintenance and injury.