Schaefbauer, Kyle J.

Summary Background Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal lung disease characterized by aberrantly activated, apoptosis-resistant profibrotic lung (myo)fibroblasts. Prior research has demonstrated that lung fibroblasts from patients with IPF exhibit resistance to DNA damage, suggesting that this behavior contributes to their persistent survival and continuous proliferation. We propose that elevated levels of the DNA damage repair protein RAD51 regulate myofibroblast activation and apoptosis and provide a potential therapeutic target to impede fibrosis progression. Methods Human lung fibroblasts were transfected with siRNA against RAD51 or treated with RAD51-specific inhibitor B02 and markers of fibrosis, DNA damage, apoptosis, metabolic reprogramming, and mitochondrial dynamics were assessed. The preclinical efficacy of B02 was evaluated in human precision cut lung slices (PCLS) and in a mouse model of pulmonary fibrosis. Findings RAD51 expression was significantly upregulated in the lungs and lung fibroblasts of IPF patients. Knockdown or inhibition of RAD51 in fibroblasts reduced profibrotic marker expression, suppressed mTORC1 signaling and mitochondrial function, and increased apoptosis susceptibility. Pharmacological inhibition of RAD51 shifted the profibrotic phenotype towards a fibrosis-resolving state in human and mouse PCLS, and in a bleomycin-induced mouse model of lung fibrosis. Interpretation The inhibition of RAD51 exerts therapeutic benefits in lung fibrosis by promoting apoptosis. Our findings identify that inhibiting RAD51 with B02 in fibroblasts impairs DNA repair and induces metabolic reprogramming, making it a potential therapeutic target. Research in context Evidence before this study Pulmonary fibrosis (PF) is characterized by excessive fibroblast activation and subsequent deposition of extracellular matrix (ECM) proteins, which ultimately disrupt normal lung architecture. A significant contributing factor to the pathogenesis of pulmonary fibrosis is the presence of fibroblasts that are resistant to apoptosis, preventing normal wound healing. Recent studies highlight the DNA repair protein RAD51 as effective in protecting fibroblasts from death induced by chemotherapy and ionizing radiation. These finding suggested that RAD51 could have a role in fibroblast activation and apoptosis resistance in pulmonary fibrosis. Added value of this study We demonstrated that RAD51 is important for maintaining apoptosis-resistant fibrotic fibroblasts and their metabolic abnormalities. Our findings indicated that TGFβ-mediated upregulation of RAD51 reduces DNA damage, activates multiple pathways related to fibroblast activation and proliferation, and induces metabolic reprogramming, ultimately regulating apoptosis. Mechanistically, RAD51 inhibition enhanced p53 acetylation at lysine 120 and upregulated the expression proapoptotic proteins PUMA/BAK in mitochondria, promoting apoptosis. Pharmacological inhibition of RAD51 using the specific inhibitor B02 during the fibrotic phase of experimental lung disease effectively ameliorated pulmonary fibrosis. Implications of all the available evidence Our findings establish that RAD51 plays an important role in the survival of apoptosis-resistant fibrotic fibroblasts. We propose that reducing RAD51 expression leads to the metabolic reprogramming of activated fibroblasts, resulting in decreased mitochondrial respiration, reduced ATP levels, and diminished glycolysis or glutaminolysis. These observations suggest that targeting energy metabolism through RAD51 inhibition could be a viable strategy to enhance apoptosis, thereby creating a therapeutically targetable pathway in fibrotic cells. These findings highlight the potential of RAD51 as a therapeutic target for the treatment of IPF.

Abstract Description The pathophysiology of autoimmune diseases involves human leukocyte antigen (HLA)-dependent interactions between effector T and antigen presenting cells. In multiple sclerosis (MS) major histocompatibility complex (MHC) class I-restricted CD8+ T cells predominate in active lesions and are necessary and sufficient to cause axonal injury and loss of function in demyelination models. Preliminary work showed that demyelination drives presentation of neuron-specific neoantigens on axonal MHC class I and that neuroantigen-specific CD8+ T cells infiltrate the central nervous system and injure such antigen-presenting axons, supporting a pathogenic role for autoreactive anti-neuronal CD8+ T cells in MS progression. The current study investigates T cell-mediated neurotoxicity in MS patients using a coculture assay designed to address critical gaps in understanding immune-neuronal interactions. Live cell imaging showed neurite injury in cocultures of patient-dervied CD8+ T cells and autologous iPSC-derived neurons, while HLA blockade partially prevented neuronal death. To expand the utility of this assay, “universal” HLA-ABC knockout neural stem cells were reconstituted with patient-specific HLA molecules, enabling scale up of the coculture system without the need to derive neurons from each patient. Future directions include live cell reporters for granzyme B and NFAT activity, interferon signaling, and calcium transients to detect T cell activation concomitant with neuronal injury. Funding Sources NIH R01N5115126 (to Charles L. Howe) Topic Categories Neuroimmunology (NEUR)

Abstract Overgrowth of the fungus Wallemia mellicola in the intestines of mice enhances the severity of asthma. Wallemia mellicola interacts with the immune system through Dectin-2 expressed on the surface of myeloid and intestinal epithelial cells. Using Dectin-2-deficient mice, we show that the interaction of W. mellicola with Dectin-2 is essential for the gut-lung pathways, enhancing the severity of asthma in mice with W. mellicola intestinal dysbiosis. These findings offer better insight into dysbiosis-associated inflammation and highlight the role pattern recognition receptors have in immune recognition of commensal fungi in the gut, leading to alterations in immune function in the lungs.

ObjectivesThe aim of this study was to assess bleomycin‐induced pulmonary fibrosis on ex vivo mouse lungs using ultrasound image grading and texture analysis.MethodsExcised mouse lungs were divided into 3 groups: control, mild fibrosis, and severe fibrosis based on the monitored indicators of health. B‐mode ultrasound images were obtained via scanning the mouse lungs ex vivo. The surface smoothness, echo density, and angle of lesions or the lung margin were graded, and the imaging contrast, correlation, homogeneity, and entropy were assessed via texture analysis.ResultsThe grades of surface smoothness, echo density, and angle were statistically higher for the severe fibrosis group compared with those of the control and mild fibrosis groups (P < .05). In addition, statistically significant differences in the contrast, correlation, and homogeneity between mild and severe fibrosis groups were observed (P < .05).ConclusionsThe results obtained in this study suggest that ultrasound image grading and texture analysis are valuable and meaningful methods for assessing pulmonary fibrosis in a bleomycin mouse model.

One key bottleneck in understanding the human genome is the relative under-characterization of 90% of protein coding regions. We report a collection of 1200 transgenic zebrafish strains made with the gene-break transposon (GBT) protein trap to simultaneously report and reversibly knockdown the tagged genes. Protein trap-associated mRFP expression shows previously undocumented expression of 35% and 90% of cloned genes at 2 and 4 days post-fertilization, respectively. Further, investigated alleles regularly show 99% gene-specific mRNA knockdown. Homozygous GBT animals in ryr1b , fras1 , tnnt2a , edar and hmcn1 phenocopied established mutants. 204 cloned lines trapped diverse proteins, including 64 orthologs of human disease-associated genes with 40 as potential new disease models. Severely reduced skeletal muscle Ca 2+ transients in GBT ryr1b homozygous animals validated the ability to explore molecular mechanisms of genetic diseases. This GBT system facilitates novel functional genome annotation towards understanding cellular and molecular underpinnings of vertebrate biology and human disease.

Abstract In the current work we show that the profibrotic actions of TGF‐β are mediated, at least in part, through a metabolic maladaptation in glutamine metabolism and how the inhibition of glutaminase 1 (GLS1) reverses pulmonary fibrosis. GLS1 was found to be highly expressed in fibrotic vs normal lung fibroblasts and the expression of profibrotic targets, cell migration, and soft agar colony formation stimulated by TGF‐β required GLS1 activity. Moreover, knockdown of SMAD2 or SMAD3 as well as inhibition of PI3K, mTORC2, and PDGFR abrogated the induction of GLS1 by TGF‐β. We further demonstrated that the NAD‐dependent protein deacetylase, SIRT7, and the FOXO4 transcription factor acted as endogenous brakes for GLS1 expression, which are inhibited by TGF‐β. Lastly, administration of the GLS1 inhibitor CB‐839 attenuated bleomycin‐induced pulmonary fibrosis. Our study points to an exciting and unexplored connection between epigenetic and transcriptional processes that regulate glutamine metabolism and fibrotic development in a TGF‐β‐dependent manner.

TGF-β–dependent metabolic dysregulation contributes to lung fibrosis.