Low-Dose Radiation Therapy for Neurological Disorders: A Double-Edged Sword.

Radiation therapy targeting the central nervous system is widely utilized for the management of various brain tumors, significantly prolonging patient survival. Presently, investigations are assessing both clinical and preclinical applications of low-dose radiation (LDR) for the treatment of neuropathological conditions beyond tumor therapy. Special focus is given to refractory neurodegenerative diseases linked to neuroinflammation, such as Alzheimer's and Parkinson's diseases, where LDR has shown promising results. This comprehensive review examines the existing experimental data regarding the utilization of LDR in neurological disorders. It covers potential advantages in reducing neurodegenerative alterations and inflammation, as well as possible adverse effects, including neurological impairments. The review underscores the importance of the exposure protocol and the age at which LDR is administered in the context of the nervous system's pathological and physiological states, as these elements are crucial in determining LDR's therapeutic and toxic outcomes. The article concludes with a discussion on the future directions and challenges in optimizing LDR use, aiming to reduce toxicity while effectively managing neurological disorders.

Transcriptional Changes in Radiation-Induced Lung Injury: A Comparative Analysis of Two Radiation Doses for Preclinical Research.

In a recent stereotactic body radiation therapy animal model, radiation pneumonitis and radiation pulmonary fibrosis were observed at around 2 and 6 weeks, respectively. However, the molecular signature of this model remains unclear. This study aimed to examine the molecular characteristics at these two stages using RNA-seq analysis. Transcriptomic profiling revealed distinct transcriptional patterns for each stage. Inflammatory response and immune cell activation were involved in both stages. Cell cycle processes and response to type II interferons were observed during the inflammation stage. Extracellular matrix organization and immunoglobulin production were noted during the fibrosis stage. To investigate the impact of a 10 Gy difference on fibrosis progression, doses of 45, 55, and 65 Gy were tested. A dose of 65 Gy was selected and compared with 75 Gy. The 65 Gy dose induced inflammation and fibrosis as well as the 75 Gy dose, but with reduced lung damage, fewer inflammatory cells, and decreased collagen deposition, particularly during the inflammation stage. Transcriptomic analysis revealed significant overlap, but differences were observed and clarified in Gene Ontology and KEGG pathway analysis, potentially influenced by changes in interferon-gamma-mediated lipid metabolism. This suggests the suitability of 65 Gy for future preclinical basic and pharmaceutical research connected with radiation-induced lung injury.

Radiosensitizing effect of a novel CTSS inhibitor by enhancing BRCA1 protein stability in triple-negative breast cancer cells.

Triple-negative breast cancer (TNBC) patients harboring wild-type breast cancer susceptibility gene 1 (BRCA1) account for most TNBC patients but lack adequate targeted therapeutic options. Although radiotherapy (RT) is the primary treatment modality for TNBC patients, radioresistance is one of the major challenges. RT-induced increase in cathepsin S (CTSS) causes radioresistance through suppressing BRCA1-mediated apoptosis of tumor cells, which was induced by CTSS-mediated degradation of BRCA1. Targeting CTSS may provide a novel therapeutic opportunity for TNBC patients. Publicly available data and human tissue microarray slides were analyzed to investigate the relationship between CTSS and BRCA1 in breast cancer patients. A CTSS enzyme assay and in silico docking analysis were conducted to identify a novel CTSS inhibitor. RO5461111 was used first to confirm the concept of targeting CTSS for radiosensitizing effects. The MDA-MB-231 TNBC cell line was used for in vitro and in vivo assays. Western blotting, promoter assay, cell death assay, clonogenic survival assay, and immunohistochemistry staining were conducted to evaluate novel CTSS inhibitors. CTSS inhibitors were further evaluated for their additional benefit of inhibiting cell migration. A novel CTSS inhibitor, TS-24, increased BRCA1 protein levels and showed radiosensitization in TNBC cells with wild-type BRCA1 and in vivo in a TNBC xenograft mouse model. These effects were attributed by BRCA1-mediated apoptosis facilitated by TS-24. Furthermore, TS-24 demonstrated the additional effect of inhibiting cell migration. Our study suggests that employing CTSS inhibitors for the functional restoration of BRCA1 to enhance RT-induced apoptosis may provide a novel therapeutic opportunity for TNBC patients harboring wild-type BRCA1.

Standigm ASK™: knowledge graph and artificial intelligence platform applied to target discovery in idiopathic pulmonary fibrosis.

Standigm ASK™ revolutionizes healthcare by addressing the critical challenge of identifying pivotal target genes in disease mechanisms-a fundamental aspect of drug development success. Standigm ASK™ integrates a unique combination of a heterogeneous knowledge graph (KG) database and an attention-based neural network model, providing interpretable subgraph evidence. Empowering users through an interactive interface, Standigm ASK™ facilitates the exploration of predicted results. Applying Standigm ASK™ to idiopathic pulmonary fibrosis (IPF), a complex lung disease, we focused on genes (AMFR, MDFIC and NR5A2) identified through KG evidence. In vitro experiments demonstrated their relevance, as TGFß treatment induced gene expression changes associated with epithelial-mesenchymal transition characteristics. Gene knockdown reversed these changes, identifying AMFR, MDFIC and NR5A2 as potential therapeutic targets for IPF. In summary, Standigm ASK™ emerges as an innovative KG and artificial intelligence platform driving insights in drug target discovery, exemplified by the identification and validation of therapeutic targets for IPF.

Mitochondria as secretory organelles and therapeutic cargos.

Mitochondria have been primarily considered intracellular organelles that are responsible for generating energy for cell survival. However, accumulating evidence suggests that mitochondria are secreted into the extracellular space under physiological and pathological conditions, and these secreted mitochondria play diverse roles by regulating metabolism, the immune response, or the differentiation/maturation in target cells. Furthermore, increasing amount of research shows the therapeutic effects of local or systemic administration of mitochondria in various disease models. These findings have led to growing interest in exploring mitochondria as potential therapeutic agents. Here, we discuss the emerging roles of mitochondria as extracellularly secreted organelles to shed light on their functions beyond energy production. Additionally, we provide information on therapeutic outcomes of mitochondrial transplantation in animal models of diseases and an update on ongoing clinical trials, underscoring the potential of using mitochondria as a novel therapeutic intervention.

Identification and Biological Evaluation of a Potent and Selective JAK1 Inhibitor for the Treatment of Pulmonary Fibrosis.

Janus kinase 1 (JAK1) plays a pivotal role in regulating inflammation and fibrosis via the JAK/STAT signaling pathway, making it a promising target for associated diseases. In this study, we explored the modification of an N-methyl 1H-pyrrolo[2,3-b]pyridine-5-carboxylate core, leading to the identification of 4-(((2S,4S)-1-(4-trifluoromethyl)-2-methylpiperidin-4-yl)amino)-N-methyl-1H-pyrrolo[2,3-b]pyridine-5-carboxamide (36b) as a highly potent and selective JAK1 inhibitor. Compound 36b exhibited an impressive IC50 value of 0.044 nM for JAK1 and demonstrated remarkable selectivity of 382-fold, 210-fold, and 1325-fold specificity over JAK2, JAK3, and TYK2, respectively. The kinase panel assays further confirmed its specificity, and cell-based experiments established its efficacy in inhibiting JAK1-STAT phosphorylation in human L-132 or SK-MES-1 cells. Pharmacokinetic studies revealed that compound 36b boasts an oral bioavailability exceeding 36%. In a bleomycin-induced fibrosis mouse model, compound 36b significantly reduced STAT3 phosphorylation, resulting in improvement in body weight and reduced collagen deposition, all achieved without significant side effects.

NXC736 Attenuates Radiation-Induced Lung Fibrosis via Regulating NLRP3/IL-1ß Signaling Pathway.

Radiation-induced lung fibrosis (RILF) is a common complication of radiotherapy in lung cancer. However, to date no effective treatment has been developed for this condition. NXC736 is a novel small-molecule compound that inhibits NLRP3, but its effect on RILF is unknown. NLRP3 activation is an important trigger for the development of RILF. Thus, we aimed to evaluate the therapeutic effect of NXC736 on lung fibrosis inhibition using a RILF animal model and to elucidate its molecular signaling pathway. The left lungs of mice were irradiated with a single dose of 75 Gy. We observed that NXC736 treatment inhibited collagen deposition and inflammatory cell infiltration in irradiated mouse lung tissues. The damaged lung volume, evaluated by magnetic resonance imaging, was lower in NXC736-treated mice than in irradiated mice. NXC736-treated mice exhibited significant changes in lung function parameters. NXC736 inhibited inflammasome activation by interfering with the NLRP3-ASC-cleaved caspase-1 interaction, thereby reducing the expression of IL-1ß and blocking the fibrotic pathway. In addition, NXC736 treatment reduced the expression of epithelial-mesenchymal transition markers such as α-SMA, vimentin, and twist by blocking the Smad 2,3,4 signaling pathway. These data suggested that NXC736 is a potent therapeutic agent against RILF.

Drug like HSP27 cross linkers with chromenone structure ameliorates pulmonary fibrosis.

Background: Pulmonary fibrosis (PF) is a progressive lung disease characterized by fibroblast accumulation and collagen deposition, resulting in lung scarring and impaired gas exchange. Current treatments for idiopathic pulmonary fibrosis (IPF) have limited efficacy and significant side effects. Heat shock protein 27 (HSP27) has emerged as a potential therapeutic target for PF due to its involvement in fibrotic processes. However, effective HSP27 inhibitors for PF treatment are still lacking. Methods: To assess the anti-fibrotic effects of NA49, we utilized murine PF models induced by radiation (IR) or bleomycin (BLM). We administered NA49 to the PF mice and evaluated its impact on lung fibrosis progression. We also investigated the molecular mechanisms underlying NA49's effects, focusing on its inhibition of EMT-related signaling pathways. Results: In our study, we evaluated the potential of a novel HSP27 inhibitor, NA49, in preclinical models of PF. NA49 effectively suppressed PF development in radiation and bleomycin-induced PF models. It reduced fibrosis, inhibited NFkB signaling, and downregulated EMT-related molecules. Importantly, we evaluated the safety profile of NA49 by assessing its impact on DNA strand breakage. Compared to previous HSP27 inhibitors, NA49 showed lower levels of DNA damage in human lung epithelial cells, and suggests that NA49 may have reduced toxicity compared to other HSP27 inhibitors. Overall, our results demonstrate that NA49 effectively inhibits PF development in preclinical models. It reduces lung fibrosis, inhibits EMT-related signaling pathways, and exhibits improved safety profiles. These findings highlight the potential of NA49 as a promising candidate for the treatment of PF. Conclusion: NA49 exhibited significant anti-fibrotic effects, inhibiting fibrosis development and EMT-related signaling pathways. Moreover, NA49 showed improved safety profiles compared to previous HSP27 inhibitors.

Mitochondrial fragmentation and donut formation enhance mitochondrial secretion to promote osteogenesis.

Mitochondrial components have been abundantly detected in bone matrix, implying that they are somehow transported extracellularly to regulate osteogenesis. Here, we demonstrate that mitochondria and mitochondrial-derived vesicles (MDVs) are secreted from mature osteoblasts to promote differentiation of osteoprogenitors. We show that osteogenic induction stimulates mitochondrial fragmentation, donut formation, and secretion of mitochondria through CD38/cADPR signaling. Enhancing mitochondrial fission and donut formation through Opa1 knockdown or Fis1 overexpression increases mitochondrial secretion and accelerates osteogenesis. We also show that mitochondrial fusion promoter M1, which induces Opa1 expression, impedes osteogenesis, whereas osteoblast-specific Opa1 deletion increases bone mass. We further demonstrate that secreted mitochondria and MDVs enhance bone regeneration in vivo. Our findings suggest that mitochondrial morphology in mature osteoblasts is adapted for extracellular secretion, and secreted mitochondria and MDVs are critical promoters of osteogenesis.

The miR-15b-Smurf2-HSP27 axis promotes pulmonary fibrosis.

BACKGROUND: Heat shock protein 27 (HSP27) is overexpressed during pulmonary fibrosis (PF) and exacerbates PF; however, the upregulation of HSP27 during PF and the therapeutic strategy of HSP27 inhibition is not well elucidated. METHODS: We have developed a mouse model simulating clinical stereotactic body radiotherapy (SBRT) with focal irradiation and validated the induction of RIPF. HSP25 (murine form of HSP27) transgenic (TG) and LLC1-derived orthotropic lung tumor models were also used. Lung tissues of patients with RIPF and idiopathic pulmonary fibrosis, and lung tissues from various fibrotic mouse models, as well as appropriated cell line systems were used. Public available gene expression datasets were used for therapeutic response rate analysis. A synthetic small molecule HSP27 inhibitor, J2 was also used. RESULTS: HSP27 expression with its phosphorylated form (pHSP27) increased during PF. Decreased mRNA expression of SMAD-specific E3 ubiquitin-protein ligase 2 (Smurf2), which is involved in ubiquitin degradation of HSP27, was responsible for the increased expression of pHSP27. In addition, increased expression of miRNA15b was identified with decreased expression of Smurf2 mRNA in PF models. Inverse correlation between pHSP27 and Smurf2 was observed in the lung tissues of PF animals, an irradiated orthotropic lung cancer models, and PF tissues from patients. Moreover, a HSP27 inhibitor cross-linked with HSP27 protein to ameliorate PF, which was more effective when targeting the epithelial to mesenchymal transition (EMT) stage of PF. CONCLUSIONS: Our findings identify upregulation mechanisms of HSP27 during PF and provide a therapeutic strategy for HSP27 inhibition for overcoming PF.

Design, synthesis, and biological evaluation of novel HSP27 inhibitors to sensitize lung cancer cells to clinically available anticancer agents.

Expression of heat shock protein (HSP) correlates with the oncogenic status of malignant cells and plays an important role in tumorigenesis. HSP27 is constitutively expressed at specific stages of cancer development, and several clinical trials have reported correlations between HSP27 expression and tumor progression, metastasis, and chemoresistance in various types of cancer cells. These findings indicate that HSP27 is a major drug target, particularly in chemo-resistant cancers. As part of our ongoing efforts to improve the previously identified J2, a HSP27 cross-linker, we, in this study, report the identification of NK16 as a novel inducer of abnormal HSP27 dimers that did not affect the expression of HSP90 in an NCI-H460 lung cancer cell model. When NCI-H460 cells were treated with NK16 in combination with the anticancer drug cisplatin or paclitaxel, cleavage of PARP and caspase-3 was increased compared to administration of cisplatin or paclitaxel alone. Similar results were obtained in an NCI-H460-xenografted mouse model, in which tumor growth was suppressed more by co-administration of NK16 and paclitaxel than by paclitaxel alone. We propose NK16 as a meaningful strategy to improve the anticancer efficacy of cisplatin and paclitaxel.

BRCA1 deficiency in triple-negative breast cancer: Protein stability as a basis for therapy.

Mutations in breast cancer-associated 1 (BRCA1) increase the lifetime risk of developing breast cancer by up to 51% over the risk of the general population. Many aspects of this multifunctional protein have been revealed, including its essential role in homologous recombination repair, E3 ubiquitin ligase activity, transcriptional regulation, and apoptosis. Although most studies have focused on BRCA1 deficiency due to mutations, only a minority of patients carry BRCA1 mutations. A recent study has suggested an expanded definition of BRCA1 deficiency with reduced BRCA1 levels, which accounts for almost half of all triple-negative breast cancer (TNBC) patients. Reduced BRCA1 levels can result from epigenetic modifications or increased proteasomal degradation. In this review, we discuss how this knowledge of BRCA1 function and regulation of BRCA1 protein stability can help overcome the challenges encountered in the clinic and advance current treatment strategies for BRCA1-related breast cancer patients, especially focusing on TNBC.

Effects of intermediate frequency electromagnetic fields: a review of animal studies.

PURPOSE: Many novel devices such as induction cookers or wireless power transfer produce electromagnetic fields (EMFs) in the intermediate frequency (IF) range (300 Hz to 10 MHz) and it is very meaningful for summarizing the bioeffects of IF-EMF research, particularly animal studies. This review takes into account experimental studies that used murine models to study the health effects of exposure to IF-EMF. The analyses included here use data available in the literature published from January 1988 to August 2021 including the animal studies about general adverse effects, tumorigenic effects, and effects on developmental stages. The studies that linked IF-EMF exposure during pregnancy or neonatal stage to behavioral and cognition changes were included. Additionally, this review also covers the effects of IF-EMF on gene expression patterns in the brain, behavior patterns associated with learning and memory, and immune function. CONCLUSIONS: Although most studies have suggested that IF-EMF is harmless, some adverse effects have been reported after exposure at developmental stages and prolonged exposure. Compared to extremely low frequency (ELF) or radiofrequency (RF) EMF bands, studies on health effects with more diverse perspectives of IF-EMF have not been conducted. Therefore, performing more research should be necessary using the latest biomedical tools. From this point of view, a comprehensive review of IF-EMF studies, particularly animal studies, will provide a valuable basis for further risk analysis in humans.

Regulation of BRCA1 stability through the tandem UBX domains of isoleucyl-tRNA synthetase 1.

Aminoacyl-tRNA synthetases (ARSs) have evolved to acquire various additional domains. These domains allow ARSs to communicate with other cellular proteins in order to promote non-translational functions. Vertebrate cytoplasmic isoleucyl-tRNA synthetases (IARS1s) have an uncharacterized unique domain, UNE-I. Here, we present the crystal structure of the chicken IARS1 UNE-I complexed with glutamyl-tRNA synthetase 1 (EARS1). UNE-I consists of tandem ubiquitin regulatory X (UBX) domains that interact with a distinct hairpin loop on EARS1 and protect its neighboring proteins in the multi-synthetase complex from degradation. Phosphomimetic mutation of the two serine residues in the hairpin loop releases IARS1 from the complex. IARS1 interacts with BRCA1 in the nucleus, regulates its stability by inhibiting ubiquitylation via the UBX domains, and controls DNA repair function.

Reactivation of Bone Lining Cells are Attenuated Over Repeated Anti-sclerostin Antibody Administration.

Reactivation of bone lining cells (BLCs) is a crucial mechanism governing the anabolic action of anti-sclerostin antibody (Scl-Ab) via modeling-based bone formation; however, it remains unclear whether this reactivation can be attenuated after persistent administration of Scl-Ab. Here, we aimed to investigate the reproducibility of persistent Scl-Ab administration for the reactivation of BLCs, and to elucidate the relationship between the activity of BLCs and serum levels of N-terminal procollagen type I (P1NP) during chronic Scl-Ab administration. We conducted an osteoblast lineage tracing study. Briefly, Dmp1-CreERt2(+):Rosa26R mice were injected with 1 mg of 4-hydroxy-tamoxifen weekly from postnatal weeks four to eight. Mice were treated twice with either vehicle or Scl-Ab (25 mg/kg) at weeks 12, 16, and 20, and were euthanized at weeks 8, 12, 13, 16, 17, 20, and 21 (4-6 mice in each group). After euthanization, the number and thickness of X-gal (+) cells on the periosteum of the femoral bones and the serum levels of P1NP were quantified at each time point. Scl-Ab induced a significant increase in the thickness of X-gal (+) cells on periosteal bone surfaces at postnatal weeks 13 (after 1st dose), 17 (after 2nd dose), and 21 (after 3rd dose) compared to that in vehicle-treated mice (all P < 0.001). In the Scl-Ab group, significant increases in the thickness of labeled cells were observed between weeks 16 and 17 and weeks 20 and 21 (both P < 0.001). The percentage increase in X-gal (+) cell thickness was 108.9% from week 12 to week 13, 54.6% from week 16 to week 17, and 49.2% from week 20 to week 21 in the Scl-Ab group. Although Scl-Ab treatment increased the serum levels of P1NP at postnatal weeks 13 and 17 compared with those at week 12 (P = 0.017 and P = 0.038, respectively), the same was not observed at week 21 (P = 0.296). A significant increase in P1NP levels was observed between weeks 16 and 17 and weeks 20 and 21 in the Scl-Ab group (P = 0.005 and P = 0.007, respectively). The percentage increase in P1NP levels was 141.7% from weeks 12 to 13, 114.8% from weeks 16 to 17, and 99.4% from weeks 20 to 21. Serum P1NP levels were positively correlated with X-gal (+) cell thickness (R2 = 0.732, P < 0.001). Reactivation of BLCs is modestly attenuated, but reproducible, during persistent Scl-Ab administration. Serum P1NP levels appear to be an indicator of the impact of Scl-Ab on the conversion of BLCs into mature osteoblasts on periosteal bone surfaces, thus contributing to modeling-based bone formation.

Activation of the HSP27-AKT axis contributes to gefitinib resistance in non-small cell lung cancer cells independent of EGFR mutations.

PURPOSE: Although epidermal growth factor receptor (EGFR)-activating mutations in non-small cell lung cancer (NSCLC) usually show sensitivity to first-generation EGFR-tyrosine kinase inhibitors (TKIs), most patients relapse because of drug resistance. Heat shock protein 27 (HSP27) has been reported to be involved in the resistance of EGFR-TKIs, although the underlying mechanism is unclear. Here, we explore the mechanisms of HSP27-mediated EGFR TKI resistance and propose novel therapeutic strategies. METHODS: To determine the mechanism of HSP27 associated gefitinib resistance, differences were assessed using gefitinib-sensitive and -resistant NSCLC cell lines. In vivo xenograft experiments were conducted to elucidate the combinatorial effects of J2, a small molecule HSP27 inhibitor, and gefitinib. Analyses of human NSCLC tissues and PDX tissues were also used for comparison of HSP27 and phosphorylated AKT expression. RESULTS: Large-scale cohort analysis of NSCLC cases revealed that HSP27 expression correlated well with the incidence of EGFR mutations and affected patient survival. Increased pAKT and HSP27 was observed in gefitinib-resistant cells compared with gefitinib-sensitive cells. Moreover, increased phosphorylation of HSP27 by gefitinib augmented its protein stability and potentiated its binding activity with pAKT, which resulted in increased gefitinib resistance. However, in gefitinib-sensitive cells, stronger binding activity between EGFR and HSP27 was observed. Moreover, these phenomena occurred regardless of EGFR mutation including secondary mutations, such as T790M. AKT knockdown switched HSP27-pAKT binding to HSP27-EGFR, which promoted gefitinib sensitivity in gefitinib-resistant cells. Functional inhibition of HSP27 yielded sensitization to gefitinib in gefitinib-resistant cells by inhibiting the interaction between HSP27 and pAKT. CONCLUSIONS: Our results indicate that combination of EGFR-TKIs with HSP27 inhibitors may represent a good strategy to overcome resistance to EGFR-TKIs, especially in cancers exhibiting AKT pathway activation.

Hypoxia-induced ELF3 promotes tumor angiogenesis through IGF1/IGF1R.

Epithelial ovarian cancer (EOC) is one of the most lethal gynecological cancers despite a relatively low incidence. Angiogenesis, one of the hallmarks of cancer, is essential for the pathogenesis of EOC, which is related to the induction of angiogenic factors. We found that ELF3 was highly expressed in EOCs under hypoxia and functioned as a transcription factor for IGF1. The ELF3-mediated increase in the secretion of IGF1 and VEGF promoted endothelial cell proliferation, migration, and EOC angiogenesis. Although this situation was much exaggerated under hypoxia, ELF3 silencing under hypoxia significantly attenuated angiogenic activity in endothelial cells by reducing the expression and secretion of IGF1 and VEGF. ELF3 silencing attenuated angiogenesis and tumorigenesis in ex vivo and xenograft mouse models. Consequently, ELF3 plays an important role in the induction of angiogenesis and tumorigenesis in EOC as a transcription factor of IGF1. A detailed understanding of the biological mechanism of ELF3 may both improve current antiangiogenic therapies and have anticancer effects for EOC.

Efferocytosis and enhanced FPR2 expression following apoptotic cell instillation attenuate radiation-induced lung inflammation and fibrosis.

Lung inflammation and fibrosis are common side effects of radiotherapy that can lead to serious reduction in the quality of life of patients. However, no effective treatment is available, and the mechanisms underlying its pathophysiology are poorly understood. Irradiation increases formyl peptide receptor 2 (FPR2) expression in lung tissue, and FPR2 agonists are known to promote the uptake of apoptosis cells, referred to as efferocytosis that is a hallmark of the resolution of inflammation. Herein, in a mouse model of radiation-induced lung injury (RILI), efferocytosis was induced by injecting apoptotic cells into the lung through the trachea, and its correlation with FPR expression and the effect of efferocytosis and FPR expression on RILI were assessed. Interestingly, when apoptotic cells were injected into the lung, the radiation-induced increase in FPR2 expression was further amplified. In the mouse model of RILI, apoptotic cell instillation reduced the volume of the damaged lung and prevented the decrease in lung function. Additionally, the expression of inflammatory cytokines, fibrosis-related markers, and oxidative stress-related markers was reduced by apoptotic cell instillation. Co-administration of apoptotic Jurkat cells and WRW4, the FPR2 antagonist, reversed these effects. These findings suggest that efferocytosis induced by apoptotic cell instillation and enhanced FPR2 expression attenuate RILI, thereby alleviating lung inflammation and fibrosis.

Therapeutic potential of targeting cathepsin S in pulmonary fibrosis.

Cathepsin S (CTSS), a lysosomal protease, belongs to a family of cysteine cathepsin proteases that promote degradation of damaged proteins in the endolysosomal pathway. Aberrant CTSS expression and regulation are associated with the pathogenesis of several diseases, including lung diseases. CTSS overexpression causes a variety of pathological processes, including pulmonary fibrosis, with increased CTSS secretion and accelerated extracellular matrix remodeling. Compared to many other cysteine cathepsin family members, CTSS has unique features that it presents limited tissue expression and retains its enzymatic activity at a neutral pH, suggesting its decisive involvement in disease microenvironments. In this review, we investigated the role of CTSS in lung disease, exploring recent studies that have indicated that CTSS mediates fibrosis in unique ways, along with its structure, substrates, and distinct regulation. We also outlined examples of CTSS inhibitors in clinical and preclinical development and proposed CTSS as a potential therapeutic target for pulmonary fibrosis.

HSPB1 inhibitor J2 attenuates lung inflammation through direct modulation of Ym1 production and paracrine signaling.

Heat shock protein beta-1 (HSPB1) is a multifaceted protein that controls cellular stress, modulates cell differentiation and development, and inhibits apoptosis of cancer cells. Increased HSPB1 expression is highly associated with poor outcomes in lung cancer by enhancing cell migration and invasion; therefore, targeting HSPB1 may be a promising therapeutic for lung cancer and fibrosis. Although the HSPB1 inhibitor J2 has been reported to exhibit potent antifibrotic effects, it remains unclear whether and how J2 directly modulates inflammatory immune responses in pulmonary fibrosis. In this study, we found that J2 potently attenuated irradiation or bleomycin-induced pulmonary fibrosis by significantly inhibiting the infiltration and activation of T cells and macrophages. J2 inhibited T-cell proliferation and subsequently suppressed T helper cell development. Although there was no significant effect of J2 on cell proliferation of M1 and M2 macrophages, J2 specifically increased the expression of Ym1 in M2 macrophages without affecting the expression of other M2 markers. Interestingly, J2 increased lysosomal degradation of HSPB1 and inhibited HSPB1-induced repression of signal transducer and activator of transcription 6 (STAT6), which simultaneously increased STAT6 and Ym1 expression. Ym1 production and secretion by J2-treated M2 macrophages substantially decreased IL-8 production by airway epithelial cells in vitro and in vivo, resulting in attenuation of airway inflammation. Taken together, we suggest that J2 has potential as a therapeutic agent for pulmonary fibrosis with increased HSPB1 expression through direct immune suppression by Ym1 production by M2 macrophages as well as T-cell suppression.