Zhenzhen Zhan

Viral infections trigger complex host defense responses, yet many key regulatory mechanisms remain undefined. Here, we identify the RNA‐binding protein RBM25 as a potent, broad‐spectrum host antiviral factor, independently of the type I interferon (IFN‐I) pathway. Viral infection downregulates RBM25 expression, and RBM25‐deficient mice exhibit enhanced susceptibility to multiple viruses and more aggravated tissue damage. In vitro, RBM25 inhibits the viral infection and replication across a spectrum of RNA and DNA viruses. Mechanistically, the antiviral activity of RBM25 is independent of IFN‐I signaling and is instead linked to an early blockade in the viral life cycle. RBM25 specifically impedes viral cell entry through the suppression of the host GTPase Rab22a, a well‐known facilitator of viral endocytosis. Virus infection‐elicited downregulation of RBM25 results in Rab22a upregulation, which consequently potentiates viral entry. Furthermore, we elucidate the post‐transcriptional mechanisms that RBM25 interacts with RC3H1 (ring finger and CCCH‐type domains 1) to form an RNA‐binding complex that binds and destabilizes Rab22a mRNA, thereby limiting its protein translation. Collectively, our work unveils the RBM25/RC3H1‐Rab22a axis as an interferon‐independent post‐transcriptional pathway that governs viral entry by modulating the mRNA stability of a critical host endocytosis factor, which presents a potential target for developing broad‐spectrum antiviral strategies.

Stimulating endogenous cardiomyocyte proliferation holds great therapeutic promise for cardiac repair, but how chromatin remodeling governs this process remains poorly understood. RNA-binding motif 22 (RBM22) participates in the regulation of various biological contexts, whereas its role in cardiac regeneration and repair is largely unknown. Here, we identify RBM22 as a pivotal regulator of cardiomyocyte proliferation. Cardiomyocyte-specific deletion of Rbm22 impairs neonatal heart regeneration and exacerbates post-infarction ventricular remodeling in adult mice. Mechanistically, RBM22 selectively binds to the proximal promoters of key cell cycle genes (Cdk4, Ccna2, and Ccne1), where it cooperates with chromatin remodeler SMARCA4 to enhance transcriptional accessibility. Furthermore, RBM22 is essential for the gene-specific recruitment of RNA Polymerase II to these gene loci to drive transcription. AAV9-mediated delivery of Rbm22 promotes cardiomyocyte proliferation in vivo following cardiac damage and increases the proliferation of human induced pluripotent stem cell-derived cardiomyocytes. Our findings establish RBM22 as a transcriptional and epigenetic regulator that overcomes cell-cycle barriers in cardiomyocytes, highlighting its therapeutic potential for cardiac injury.

Background: Tertiary lymphoid structure (TLS) is a neogenized, ectopic lymphoid aggregate found in infected, autoimmune and tumour tissues with an activated adaptive immune response. However, a comprehensive understanding of the pathological role, function, and formation of TLS in allograft rejection remains incomplete. Methods: We enrolled two large retrospective cohorts of liver biopsy (LB) after pediatric living donor liver transplantation (LDLT) and developed a deep learning pathomics (DLP) model. Gene expression profiles and corresponding clinical information of 590 cases were enrolled from three transcriptomic databases, including cohort-GSE193135 (n=337), cohort-GSE145780 (n=235), cohort-Renji (n=18). ESTIMATE, CIBERSORT, XCELL and MCP analyses were performed to visualize the immune landscape. Single-cell RNA-sequencing (scRNA-seq) analysis of 11 LBs after LDLT and multiplexed immunohistochemistry (mIHC) were performed to validate the discoveries of bioinformatics analysis. Results: We provided evidence that increased TLS in the liver was closely correlated with allograft rejection, fibrosis, and declined liver function. ScRNA-seq and in vitro co-culture analysis revealed that TLS form through the differentiation of atypical memory B (AtM B) cells via the JAK-STAT signalling pathway, stimulated by IFN-γ from exhausted CD8 ⁺ T effector memory (T _EM ) cells. The presence of TLS resulted in IgG accumulation, initiating pathological antibody-dependent cell-mediated phagocytosis (ADCP) of apoptotic hepatocytes by CD68 ⁺ macrophages. Preclinically, blocking JAK1/3 or knocking out Lta in mice limited TLS formation and attenuated allograft rejection in mouse orthotopic liver transplantation models, informing novel therapeutics for allograft rejection pathology. Conclusion: We proposed an efficient DLP model for predicting allograft rejection, and revealed an unexpected immunological mechanism of TLS in allograft rejection livers and clarified an IFN-γ-JAK-STAT-dependent circuit that could be targeted with drugs and transformed AtM B cells into potent instigators of hepatocellular injury in allograft rejection.

Psoriasis is a persistent inflammatory skin disease characterized by the adverse infiltration of inflammatory cells and epidermal hyperplasia. Self-RNA is the most abundant damage-associated molecular pattern (DAMP) in psoriasis tissues, which triggers and amplifies inflammatory responses through TLR7 pathway. However, the pathogenic effects of self-RNA on immune cell activation and chemotaxis during psoriasis and the underlying mechanisms remain largely unknown. Epigenetic modifications are widely acknowledged to link the environmental signals to gene expression in various immune cells, whose dysfunction tends to cause or worsen various inflammatory diseases. Through a comprehensive analysis of histone modifications in lesional skin from both psoriasis patients and mice, the significantly increased level of histone acetylation at H4 lysine 16 (H4K16ac) in macrophages was found, which was positively correlated with the accumulation of self-RNA in the dermis and psoriasis pathology. Further studies showed that lysine acetyltransferase 8 (KAT8) was responsible for self-RNA-driven H4K16ac modification and psoriasis-associated pathogenic chemokine expression in macrophages of lesional skin. Mechanistically, KAT8 was selectively recruited to the gene promoters of pathogenic chemokines including Cxcl2 and Ccl3 through interaction with AP-1 transcription complex. The auto-acetylation of KAT8 enhanced its acetyltransferase activity. KAT8-mediated H4K16ac modification at these chemokine promoters, coupling with increased chromatin accessibility, facilitated the production and secretion of pro-inflammatory chemokines CXCL2 and CCL3 for neutrophil chemotaxis, neutrophil extracellular traps (NETs) formation and aggravated inflammatory damage in psoriasis. KAT8 deficiency in macrophages or pharmacological inhibition restricted the secretion of macrophage-derived pro-inflammatory chemokines and ameliorated TLR7-dependent tissue inflammatory injury in experimental psoriasis and arthritis model. Taken together, our finding provides new insight into the role of epigenetic modification in self-RNA/TLR7 pathway-dependent immune cell activation and chemotaxis during psoriasis, which proposes the promising therapeutic strategy to control the inflammatory damage and psoriatic skin dysfunction by targeting KAT8 and KAT8-mediated H4K16ac modification in dermis macrophages.

Spliceosome dysfunction and aberrant RNA splicing underline unresolved inflammation and immunopathogenesis. Here, we revealed the misregulation of mRNA splicing via the spliceosome in the pathogenesis of rheumatoid arthritis (RA). Among them, decreased expression of RNA binding motif protein 25 (RBM25) was identified as a major pathogenic factor in RA patients and experimental arthritis mice through increased proinflammatory mediator production and increased hyperinflammation in macrophages. Multiomics analyses of macrophages from RBM25-deficient mice revealed that the transcriptional enhancement of proinflammatory genes (including Il1b, Il6, and Cxcl10) was coupled with histone 3 lysine 9 acetylation (H3K9ac) and H3K27ac modifications as well as hypoxia inducible factor-1α (HIF-1α) activity. Furthermore, RBM25 directly bound to and mediated the 14^th exon skipping of ATP citrate lyase (Acly) pre-mRNA, resulting in two distinct Acly isoforms, Acly Long (Acly L) and Acly Short (Acly S). In proinflammatory macrophages, Acly L was subjected to protein lactylation on lysine 918/995, whereas Acly S did not, which influenced its affinity for metabolic substrates and subsequent metabolic activity. RBM25 deficiency overwhelmingly increased the expression of the Acly S isoform, enhancing glycolysis and acetyl-CoA production for epigenetic remodeling, macrophage overactivation and tissue inflammatory injury. Finally, macrophage-specific deletion of RBM25 led to inflammaging, including spontaneous arthritis in various joints of mice and inflammation in multiple organs, which could be relieved by pharmacological inhibition of Acly. Overall, targeting the RBM25-Acly splicing axis represents a potential strategy for modulating macrophage responses in autoimmune arthritis and aging-associated inflammation.

BACKGROUND: Reparative macrophages play a crucial role in limiting excessive fibrosis and promoting cardiac repair after myocardial infarction (MI), highlighting the significance of enhancing their reparative phenotype for wound healing. Metabolic adaptation orchestrates the phenotypic transition of macrophages; however, the precise mechanisms governing metabolic reprogramming of cardiac reparative macrophages remain poorly understood. In this study, we investigated the role of NPM1 (nucleophosmin 1) in the metabolic and phenotypic shift of cardiac macrophages in the context of MI and explored the therapeutic effect of targeting NPM1 for ischemic tissue repair. METHODS: Peripheral blood mononuclear cells were obtained from healthy individuals and patients with MI to explore NPM1 expression and its correlation with prognostic indicators. Through RNA sequencing, metabolite profiling, histology, and phenotype analyses, we investigated the role of NPM1 in postinfarct cardiac repair using macrophage-specific NPM1 knockout mice. Epigenetic experiments were conducted to study the mechanisms underlying metabolic reprogramming and phenotype transition of NPM1-deficient cardiac macrophages. The therapeutic efficacy of antisense oligonucleotide and inhibitor targeting NPM1 was then assessed in wild-type mice with MI. RESULTS: NPM1 expression was upregulated in the peripheral blood mononuclear cells from patients with MI that closely correlated with adverse prognostic indicators of MI. Macrophage-specific NPM1 deletion reduced infarct size, promoted angiogenesis, and suppressed tissue fibrosis, in turn improving cardiac function and protecting against adverse cardiac remodeling after MI. Furthermore, NPM1 deficiency boosted the reparative function of cardiac macrophages by shifting macrophage metabolism from the inflammatory glycolytic system to oxygen-driven mitochondrial energy production. The oligomeric NPM1 recruited histone demethylase KDM5b to the promoter of Tsc1 ( TSC complex subunit 1 ), the mTOR (mechanistic target of rapamycin kinase) complex inhibitor, reduced histone H3K4me3 modification, and inhibited TSC1 expression, which then facilitated mTOR-related inflammatory glycolysis and antagonized the reparative function of cardiac macrophages. The in vivo administration of antisense oligonucleotide targeting NPM1 or oligomerization inhibitor NSC348884 substantially ameliorated tissue injury and enhanced cardiac recovery in mice after MI. CONCLUSIONS: Our findings uncover the key role of epigenetic factor NPM1 in impeding postinfarction cardiac repair by remodeling metabolism pattern and impairing the reparative function of cardiac macrophages. NPM1 may serve as a promising prognostic biomarker and a valuable therapeutic target for heart failure after MI.

Epigenetic regulation of inflammatory macrophages governs inflammation initiation and resolution in the pathogenesis of rheumatoid arthritis (RA). Nevertheless, the mechanisms underlying macrophage‐mediated arthritis injuries remain largely obscure. Here, we found that increased expression of lysine acetyltransferase 2A (KAT2A) in synovial tissues was closely correlated with inflammatory joint immunopathology in both RA patients and experimental arthritis mice. Administration of MB‐3, the KAT2A‐specific chemical inhibitor, significantly ameliorated the synovitis and bone destruction in collagen‐induced arthritis model. Both pharmacological inhibition and siRNA silencing of KAT2A, not only suppressed innate stimuli‐triggered proinflammatory gene (such as Il1b and Nlrp3) transcription but also impaired NLR family pyrin domain containing 3 (NLRP3) inflammasome activation in vivo and in vitro. Mechanistically, KAT2A facilitated macrophage glycolysis reprogramming through suppressing nuclear factor‐erythroid 2‐related factor 2 (NRF2) activity as well as downstream antioxidant molecules, which supported histone 3 lysine 9 acetylation (H3K9ac) and limited NRF2‐mediated transcriptional repression of proinflammatory genes. Our study proves that acetyltransferase KAT2A licenses metabolic and epigenetic reprogramming for NLRP3 inflammasome activation in inflammatory macrophages, thereby targeting KAT2A represents a potential therapeutic approach for patients suffering from RA and relevant inflammatory diseases.