Aug 2026· International Immunopharmacology· Vol 188, pp.
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· 0 citations· 37 references
Medicine
TL;DR
It is demonstrated that TMZ mitigates dystrophic pathology by targeting the ATP6AP2 signaling axis and dampening macrophage-mediated inflammatory responses, highlighting its potential as a novel immunopharmacological therapeutic strategy for DMD.
Abstract
Duchenne muscular dystrophy (DMD) is characterized by progressive muscle wasting and persistent chronic inflammation, yet the multi-lineage cellular drivers of its pathogenesis remain incomplete. In this study, single-cell RNA sequencing (scRNA-seq) identified Atp6ap2 as a profoundly upregulated gene across multiple skeletal muscle cell types-particularly endothelial cells, fibroblasts, and myoblasts-in both mdx and severe mdx mice. Weighted gene co-expression network analysis (WGCNA) linked Atp6ap2 expression to DMD progression, while enrichment analyses revealed that its dysregulation severely impairs vascular homeostasis and extracellular matrix integrity via the PI3K-Akt, focal adhesion, and cell cycle pathways. Utilizing Connectivity Map (CMap) analysis, we identified temozolomide (TMZ) as a top pharmacological candidate capable of reversing the ATP6AP2-associated gene signature. In vivo validation demonstrated that TMZ administration significantly enhanced motor coordination, balance, and grip strength in mdx mice, while markedly preserving dystrophic muscle architecture, reducing myofiber necrosis, and alleviating interstitial fibrosis. Mechanistically, integrated transcriptomic and metabolomic profiling revealed that TMZ induced profound metabolic and signaling shifts, modulating the Notch, MAPK, and Ras pathways, as well as autophagy and glycerophospholipid metabolism. Furthermore, scRNA-seq and cell-cell communication analyses indicated that TMZ dynamically reorganized multicellular networks, decreasing aberrant fibroblast and endothelial interactions. Crucially, immunofluorescence and Western blot validations confirmed that TMZ drastically attenuated the infiltration of F4/80-positive macrophages and suppressed their pro-inflammatory M1 polarization (indicated by reduced co-localization with iNOS and ATP6AP2), while successfully reversing the dysregulation of the ATP6AP2 axis and restoring its downstream targets MAP4K2, DGKE, and EFNA1. Collectively, our findings demonstrate that TMZ mitigates dystrophic pathology by targeting the ATP6AP2 signaling axis and dampening macrophage-mediated inflammatory responses, highlighting its potential as a novel immunopharmacological therapeutic strategy for DMD.
Efficient skeletal muscle contraction requires tight mechano‐metabolic coupling, a process regulated by AMP‐activated protein kinase (AMPK). Duchenne muscular dystrophy (DMD) is characterized by aberrant AMPK activation and disrupted metabolic signaling. This study investigates the expression and regulation of the LKB1–STRADα–MO25 heterotrimeric complex, the primary upstream activator of AMPK, in DMD models. We analyzed muscles from dystrophic mice (BL10 mdx and D2 mdx) and patient‐derived cells and found significant downregulation of the LKB1 complex across all disease stages in the DMD models, a defect not observed in an amyotrophic lateral sclerosis model. Treatment with the broad‐spectrum HDAC inhibitor vorinostat effectively restored LKB1 expression at both transcript and protein levels in D2 mdx mice. This restoration was mechanistically linked to downregulation of miR‐451, miR‐195, and miR‐17, which function as post‐transcriptional repressors of LKB1. Conversely, the selective HDAC1/2 inhibitor Rodin‐A increased Lkb1 mRNA but failed to rescue protein levels or alter miRNA expression. Our data identify the axis LKB1–STRADα–MO25 as a critical regulatory node that is disrupted in DMD, but remains responsive to epigenetic modulation. These findings suggest that restoring LKB1 activity via HDAC inhibition or miRNA targeting may represent a therapeutic avenue to address dystrophic muscle dysfunction.
Brigida Boccanegra, Lisamaura Tulimiero, R. Quarta et al.· Annals of the New York Acade...· 0 citations
Limb-girdle muscular dystrophy R2/2B (LGMDR2/2B) is an untreatable and progressive late-onset skeletal muscle disease caused by the loss of a membrane-repair protein dysferlin. Even before disease symptom onset, LGMDR2 muscles are infiltrated by pro-inflammatory macrophages (MP), implicating immune cells in disease pathogenesis. While MPs express dysferlin, defining the cell-autonomous roles of dysferlin in MP function has been challenging in vivo due to complex multicellular interactions and altered microenvironment in LGMDR2 muscle.
To address this, we generated human induced pluripotent stem cell (hiPSC)-derived macrophages (iMPs) from three healthy and three LGMDR2 donors to delineate cell-autonomous roles of dysferlin in macrophage: 1) polarization, 2) transcriptional profile, 3) secretome, and 4) phagocytotic and endocytic function.
Despite exhibiting comparable polarization under well-characterized pro- and anti-inflammatory cues, RNAseq analyses revealed downregulation of Gene Ontology terms related to cytokine secretion, phagocytosis, and receptor-mediated endocytosis in LGMDR2 iMPs. Proteomic analysis of iMP conditioned media revealed significant differences in 72 secreted proteins, including numerous chemokines, cytokines, and growth factors, suggesting an altered secretory phenotype. Functional assays found no significant differences in the phagocytosis of E. coli bioparticles or fluorescent myotube debris. However, receptor-mediated endocytosis of AcLDL was significantly lower in both M0 and M2 LGMDR2 vs. healthy iMPs. Pharmacological screens identified clathrin-dependent endocytosis as the primary pathway for AcLDL uptake in both genotypes, with altered clathrin trafficking and reduced scavenger receptor expression likely underlying LGMDR2 endocytic deficits.
Overall, dysferlin loss in iMPs results in cell-autonomously altered transcriptome, secretome, and endocytic function, which may contribute to LGMDR2 muscle pathology and disease progression.
Jain Foundation grant, NIH grant 1R01AR082979-01, National Science Foundation Graduate Research Fellowship
Immune Mechanisms of Human Disease (HUM)
Amber Detwiler, Rachel Luner, Alex Schneider et al.· Journal of Immunology· 0 citations
Sarcopenia, an age-related degenerative disease of skeletal muscle, is closely associated with osteoporosis and other bone disorders, partly due to dysregulated endocrine function of skeletal muscle. However, the specific cellular sources and molecular mechanisms driving this pathological secretory phenotype remain poorly defined. Using three distinct aging murine models, including sedentary controls, treadmill exercise-trained (TE) mice, and botulinum toxin A (BTXA)-induced muscle atrophy, combined with human cohort analysis, we investigated muscle-bone crosstalk. Fluorescence-activated cell sorting (FACS) was used to isolate fibro-adipogenic progenitors (FAPs). FAP-specific genetic manipulations, including conditional knockout (cKO) mice and adeno-associated virus-mediated knockdown, together with pharmacological inhibition of YAP1, were employed to dissect the mechanistic link between muscle secretory dysfunction and bone metabolism. We demonstrate that pathogenic activation of FAPs serves as a critical cellular source of bone-catabolic myokines during muscle atrophy. In a human cohort of older individuals with sarcopenia, osteoporosis, or osteosarcopenia, FAP numbers were significantly increased and correlated positively with sarcopenia traits and IL-6 and FGF21 levels. In mice, muscle wasting drives FAP accumulation through YAP1-mediated mechanotransduction, characterized by enhanced proliferation, suppressed apoptosis, and acquisition of a profibrotic phenotype concomitant with elevated IL-6 and FGF21 secretion. Using FAP-specific Il6 or Fgf21 knockdown, we showed that genetic ablation of these myokines in FAPs rescued trabecular bone loss despite persistent muscle atrophy. Mechanistically, YAP1 functions as a central regulator of this pathogenic secretory phenotype; FAP-specific Yap1 overexpression may contribute to the myokine dysfunction and bone loss, while FAP-specific Yap1 deletion or pharmacological inhibition diminished bone-loss-related myokine production and ameliorated bone deterioration. FAP-specific Yap1 cKO mice demonstrated that endogenous YAP1 is essential for pathogenic FAP activation and subsequent bone loss. Furthermore, therapeutic targeting of the FAP-YAP1-myokine axis provided robust skeletal protection in ovariectomy-induced postmenopausal osteoporosis. These findings reveal that dysregulated endocrine function of skeletal muscle promotes bone loss through YAP1-driven pathogenic FAPs secreting IL-6 and FGF21, identifying FAP-derived IL-6 and FGF21 as key mediators of muscle-bone crosstalk and establishing the YAP1-FAP-myokine axis as a therapeutic target for preventing bone loss in sarcopenia and osteoporosis.
Xiaoyu Cai, Tao Xu, R. Ma et al.· Advancement of science· 0 citations
OBJECTIVE
Fibro-adipogenic progenitor (FAP) dysfunction drives skeletal muscle fibrosis in type 2 diabetes mellitus (T2DM), yet the underlying metabolic-epigenetic mechanisms remain poorly understood. This study investigates how metabolite fluctuations regulate the cell fate of CD90+ FAPs in the diabetic skeletal muscles.
METHODS AND RESULTS
Re-analysis of single-cell RNA sequencing data from human diabetic skeletal muscle, combined with immunofluorescence staining of biopsy specimens, revealed a significant expansion of CD90+ FAPs characterized by aberrant asymmetric cell division (ACD) associated polarity and a profibrotic phenotype. Using LC-MS, we identified a marked metabolic shift in insulin-resistant CD90+ FAPs, with reduced alpha-ketoglutarate (α-KG) and elevated L-2-hydroxyglutarate (L-2HG) levels. Reduced α-KG availability, together with competitive inhibition by accumulated L-2HG, suppresses TET2 activity and shifts DNA cytosine modification toward increased 5mC and decreased 5hmC. Specifically, epigenetic remodeling at the promoters of polarity-related genes-Pard3b, Pard6b, and Prkcz-was associated with activation of an ACD-related polarity program in CD90+ FAPs. This lineage bias promotes fibrogenic differentiation, ultimately exacerbating collagen accumulation and impairing muscle function. Dietary α-KG supplementation restored the α-KG/L-2HG ratio, restrained aberrant ACD-related polarity program, and effectively prevented or alleviated muscle fibrosis in T2DM mice. Conversely, TET2 knockdown attenuated the protective effects of α-KG on DNA hydroxymethylation and profibrotic activation of CD90+ FAPs, supporting a TET2-dependent mechanism underlying the epigenetic effects of α-KG.
CONCLUSION
Our findings demonstrate that dysregulation of α-KG and L-2HG drives diabetic muscle fibrosis by disrupting TET2-dependent DNA hydroxymethylation and FAP division symmetry. Restoring this metabolic-epigenetic axis represents a promising therapeutic strategy for treating diabetic skeletal muscle fibrosis.
Zhou-Jie Tong, Yihui Li, Ming Song et al.· Metabolism: Clinical and Exp...· 1 citation
Traumatic brain injury (TBI) is a leading cause of severe disability, frequently resulting in persistent cognitive dysfunction. Microglial M1/M2 polarization is critically involved in TBI pathogenesis, yet its molecular regulatory mechanisms remain poorly understood. TIM-4, a TIM family member implicated in cerebral ischemia-reperfusion injury, has an unknown function in TBI—particularly regarding its regulation of neuronal death.
We employed a comprehensive multi-omics strategy integrating bulk RNA-seq, publicly available single-cell RNA sequencing (scRNA-seq; GEO: GSE101901), weighted gene co-expression network analysis (WGCNA), quantitative proteomics, phosphoproteomics, and epigenomic profiling (ATAC-seq and H3K27ac ChIP-seq) to systematically investigate TIM-4 in TBI. Functional validation included TIM-4 knockdown experiments, TUNEL apoptosis detection, Golgi staining for dendritic spine analysis, and behavioral assessments.
TIM-4 was the most significantly upregulated gene and protein across all omics layers, with expression positively correlated with pro-inflammatory factors and negatively correlated with anti-inflammatory markers. ScRNA-seq revealed TIM-4 upregulation was restricted to activated M1-like microglia, and pseudotime trajectory analysis demonstrated TIM-4-driven M1 polarization. WGCNA identified a TIM-4-associated co-expression module strongly correlated with TBI severity and behavioral outcomes (r = 0.92, p < 0.001). Phosphoproteomics identified TIM-4 Y
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hyper-phosphorylation as a key post-translational regulatory event, and ATAC-seq/ChIP-seq revealed NF-κB-driven chromatin remodeling at the TIM-4 locus. Multi-omics integration ranked TIM-4 as the master regulatory hub (composite evidence score = 0.89). Functionally, TIM-4 knockdown promoted microglial M2 polarization, reduced neuronal apoptosis and dendritic spine loss, and significantly improved spatial memory deficits and motor coordination following TBI.
TIM-4 is established as a critical driver of neuroinflammation-associated neuronal death in TBI, representing a promising therapeutic target for TBI-related cognitive dysfunction.
Liang Chen, Yan-Yan Li, Li Han et al.· Frontiers in Cell and Develo...· 0 citations
Combination therapies targeting multiple of these glucose signaling pathway proteins, together with glucose and N-acetylcysteine, yielded superior therapeutic benefit in complex I disease cell and C. elegans models.
Kelsey Keith, Min Peng, Cristina Remes et al.· bioRxiv· 0 citations