Macrophages in radiation injury: a new therapeutic target

Evidence of Alveolar Macrophage Metabolic Shift Following Stereotactic Body Radiation Therapy -Induced Lung Fibrosis in Mice

PURPOSE

Radiation-induced pneumopathy is the main dose-limiting factor in cases of chest radiation therapy. Macrophage infiltration is frequently observed in irradiated lung tissues and may participate in lung damage development. Radiation-induced lung fibrosis can be reproduced in rodent models using whole thorax irradiation but suffers from limits concerning the role played by unexposed lung volumes in damage development.

METHODS AND MATERIALS

Here, we used an accurate stereotactic body radiation therapy preclinical model irradiating 4% of the mouse lung. Tissue damage development and macrophage populations were followed by histology, flow cytometry, and single-cell RNA sequencing. Wild-type and CCR2 KO mice, in which monocyte recruitment is abrogated, were exposed to single doses of radiation, inducing progressive (60 Gy) or rapid (80 Gy) lung fibrosis.

RESULTS

Numerous clusters of macrophages were observed around the injured area, during progressive as well as rapid fibrosis. The results indicate that probably CCR2-independent recruitment and/or in situ proliferation may be responsible for macrophage invasion. Alveolar macrophages experience a metabolic shift from fatty acid metabolism to cholesterol biosynthesis, directing them through a possible profibrotic phenotype. Depicted data revealed that the origin and phenotype of macrophages present in the injured area may differ from what has been previously described in preclinical models exposing large lung volumes, representing a potentially interesting trail in the deciphering of radiation-induced lung damage processes.

CONCLUSIONS

Our study brings new possible clues to the understanding of macrophage implications in radiation-induced lung damage, representing an interesting area for exploration in future studies.

Therapeutic applications of stem cell-derived exosomes in radiation-induced lung injury

Radiation-induced lung injury is a common complication of chest tumor radiotherapy; however, effective clinical treatments are still lacking. Stem cell-derived exosomes, which contain various signaling molecules such as proteins, lipids, and miRNAs, not only retain the tissue repair and reconstruction properties of stem cells but also offer improved stability and safety. This presents significant potential for treating radiation-induced lung injury. Nonetheless, the clinical adoption of stem cell-derived exosomes for this purpose remains limited due to scientific, practical, and regulatory challenges. In this review, we highlight the current pathology and therapies for radiation-induced lung injury, focusing on the potential applications and therapeutic mechanisms of stem cell-derived exosomes. We also discuss the limitations of existing stem cell-derived exosomes and outline future directions for exosome-based treatments for radiation-induced lung injury.

Correlation Between Electronic Patient-Reported Outcomes and Biological Markers of Key Parameters in Acute Radiation Cystitis Among Patients With Prostate Cancer (RABBIO): Prospective Observational Study

Background

Despite advances in radiation techniques, radiation cystitis (RC) remains a significant cause of morbidity from pelvic radiotherapy, which may affect patients' quality of life (QoL). The pathophysiology of RC is not well understood, which limits the development of effective treatments.

Objective

The Radiotoxicity Bladder Biomarkers study aims to investigate the correlation between blood and urinary biomarkers and the intensity of acute RC symptoms and QoL in patients undergoing localized prostate cancer radiotherapy.

Methods

This study included patients with low- or intermediate-risk localized prostate cancer who were eligible for localized radiotherapy. Blood and urinary biomarkers were analyzed before radiotherapy was initiated and at weeks 4 and 12 of radiation therapy. Patients completed questionnaires related to RC symptoms and QoL (International Prostate Symptom Score and Functional Assessment of Cancer Therapy-Prostate [FACT-P]) using a digital remote monitoring platform. The information was processed by means of an algorithm, which classified patients according to the severity of symptoms and adverse events reported. Levels of blood and urinary biomarkers were tested with the severity of acute RC symptoms and patient-reported QoL.

Results

A total of 401 adverse events questionnaires were collected over the duration of this study from 20 patients. The most frequently reported adverse events at week 4 were pollakiuria, constipation, and diarrhea. In comparison with baseline, the mean FACT-P score decreased at week 4. A significant increase in the proportion of M2 phenotype cells (CD206+, CD163+, CD204+) at W12 compared to W0 was observed. An increase in serum and urine levels of macrophage colony-stimulating factor (M-CSF), hepatocyte growth factor, and macrophagic inflammatory protein was observed at week 12 compared to baseline levels. Baseline serum and urine M-CSF concentrations showed a significant negative correlation with FACT-P scores at weeks 4 and 12 (r=-0.65, P=.04, and r=-0.76, P=.02, respectively).

Conclusions

The Radiotoxicity Bladder Biomarkers study is the first to explore the overexpression of inflammatory proteins in blood and urine of patients with symptoms of acute RC. These preliminary findings suggest that serum and urine levels of hepatocyte growth factor, M-CSF, and macrophagic inflammatory protein, as well as macrophage polarization, are mobilized after prostate radiotherapy. The elevated M-CSF levels in serum and urine at baseline were associated with the deterioration of QoL during radiotherapy. The results of this study may help to develop mitigation strategies to limit radiation damage to the bladder.

Nervonic acid alleviates radiation-induced early phase lung inflammation by targeting macrophages activation in mice

Background

Patients receiving chest radiation therapy, or exposed to high radiation levels due to accidental nuclear leakage are at risk of radiation-induced lung injury (RILI). In innate immunity, macrophages not only exhibit certain radiation tolerance but also play an important regulatory role in the whole pathological process. Nervonic acid (NA), a long-chain unsaturated fatty acid found in nerve tissue, plays a pivotal role in maintaining normal tissue growth and repair. However, the influence of NA on RILI progression has yet to be examined.

Aim

This study aimed to assess the role of macrophage subtypes in RILI and whether NA can alleviate RILI. Specifically, whether NA can alleviate RILI by targeting macrophages and reducing the levels of inflammatory mediators in mouse models was assessed.

Methods

Mice RILI model was employed with 13 Gy whole thoracic radiation with or without administration of NA. Various assays were performed to evaluate lung tissue histological changes, cytokine expression, IκB-α expression and the number and proportion of macrophages.

Results

Radiation can lead to the release of inflammatory mediators, thereby exacerbating RILI. The specific radiation dose and duration of exposure can lead to different dynamic changes in the number of subpopulations of lung macrophages. NA can affect the changes of macrophages after irradiation and reduce inflammatory responses to alleviate RILI.

Conclusion

Macrophages play a significant role in the integrated pathological process of lung injury after irradiation which shows a dynamic change with different times. NA can protect lung tissues against the toxic effects of ionizing radiation and is a new potential functional component for targeting macrophages.

Self-Assembled EGCG Nanoparticles with Enhanced Intracellular ROS Scavenging for Skin Radioprotection

Purpose

Skin radiation damage is a prevalent form of tissue injury encountered during radiotherapy, radiation accidents, and occupational exposure. The only clinically approved radioprotective agent, amifostine, is associated with numerous side effects, underscoring the urgent need for the development of safe and effective radioprotective agents. Natural products with reductive properties possess high antioxidant activity and biocompatibility, but their low bioavailability limits their radioprotective efficacy and clinical application. To address this, we utilized epigallocatechin gallate (EGCG) as a model compound and employed nanotechnology to enhance cellular uptake of natural compounds, thereby improving their free radical scavenging capabilities.

Methods

EGCG nanoparticles (EGCG NPs) with robust intracellular reactive oxygen species (ROS) scavenging ability were prepared via self-assembly. The morphology, size distribution, and antioxidant capacity of EGCG NPs were characterized. Cytocompatibility, intracellular ROS levels and DNA damage, cell migration and immune response of EGCG NPs to macrophages were tested in vitro. The in vivo radiation protection and biocompatibility of EGCG NPs were assessed in murine model.

Results

The EGCG NPs was successfully prepared and compared to free EGCG, EGCG NPs demonstrated better cellular uptake, significantly enhancing their biocompatibility, intracellular ROS scavenging capacity, and ability to mitigate DNA damage. Furthermore, EGCG NPs facilitated fibroblast proliferation and migration, while inhibiting the polarization of macrophages towards the M1 phenotype in vitro. In animal levels, EGCG NPs exhibited markedly improved radioprotective efficacy over free EGCG, effectively reducing skin edema and ulceration, alleviating pathological conditions such as interstitial edema, dermal fluid accumulation, and inflammatory infiltration, decreasing the duration of skin injury, and promoting wound healing.

Conclusion

This work offers novel insights into the therapeutic application of EGCG NPs as a potential alternative for skin radioprotection and provides a powerful approach for developing radioprotective agents derived from natural products.

Cytological changes in radiation-induced lung injury

Radiation-induced lung injury (RILI) is a prevalent complication associated with radiotherapy for thoracic tumors. Based on the pathological progression, it can be categorized into two stages: early radiation pneumonitis and late radiation pulmonary fibrosis. The occurrence of RILI not only constrains the therapeutic dose that can be administered to the tumor target area but also significantly impairs patients' health and quality of life, thereby limiting the efficacy and applicability of radiotherapy. To effectively prevent and mitigate the development of RILI, it is crucial to disclose its underlying mechanisms. This review aims to elucidate the specific mechanisms involved in RILI and to examine the roles of various cell types, including lung parenchymal cells and different immune cells. The functions and interactions of lung epithelial cells, pulmonary vascular endothelial cells, a variety of immune cells, and fibroblasts during different stages of inflammation, tissue repair, and fibrosis following radiation-induced lung injury are analyzed. A comprehensive understanding of the dynamic changes in these cellular components is anticipated to offer new strategies for the prevention of RILI.

How to Use Macrophages Against Cancer

Numerous studies have demonstrated the significant influence of immune cells on cancer development and treatment. This study specifically examines tumor-associated macrophages (TAMs), detailing their characteristics and roles in tumorigenesis and analyzing the impact of the ratio of TAM subtypes on patient survival and prognosis. It is established that TAMs interact with immunotherapy, radiotherapy, and chemotherapy, thereby influencing the efficacy of these treatments. Emerging therapies are explored, such as the use of nanoparticles (NPs) for drug delivery to target TAMs and modify the tumor microenvironment (TME). Additionally, novel anticancer strategies like the use of chimeric antigen receptor macrophages (CAR-Ms) show promising results. Investigations into the training of macrophages using magnetic fields, plasma stimulation, and electroporation are also discussed. Finally, this study presents prospects for the combination of TAM-based therapies for enhanced cancer treatment outcomes.

Thoracic Proton Minibeam Radiation Therapy: Tissue Preservation and Survival Advantage Over Conventional Proton Therapy

PURPOSE

Proton minibeam radiation therapy (pMBRT) is an innovative radiation therapy approach that highly modulates the spatial dimension of the dose delivery using narrow, parallel, and submillimetric proton beamlets. pMBRT has proven its remarkable healthy tissue preservation in the brain and skin. This study assesses the potential advantages of pMBRT for thoracic irradiations compared with conventional radiation therapy in terms of normal tissue toxicity. The challenge here was the influence of respiratory motion on the typical peak and valley dose patterns of pMBRT and its potential biologic effect.

METHODS AND MATERIALS

The whole thorax of naïve C57BL/6 mice received one fraction of high dose (18 Gy) pMBRT or conventional proton therapy (CPT) without any respiratory control. The development of radiation-induced pulmonary fibrosis was longitudinally monitored using cone beam computed tomography. Anatomopathologic analysis was carried out at 9 months postirradiation and focused on the reaction of the lungs' parenchyma and the response of cell types involved in the development of radiation-induced fibrosis and lung regeneration as alveolar type II epithelial cells, club cells, and macrophages.

RESULTS

pMBRT has milder effects on survival, skin reactions, and lung fibrosis compared with CPT. The pMBRT-induced lung changes were more regional and less severe, with evidence of potential reactive proliferation of alveolar type II epithelial cells and less extensive depletion of club cells and macrophage invasion than the more damaging effects observed in CPT.

CONCLUSIONS

pMBRT appears suitable to treat moving targets, holding a significant ability to preserve healthy lung tissue, even without respiratory control or precise targeting.

Tumor-associated macrophages: A sentinel of innate immune system in tumor microenvironment gone haywire

The tumor microenvironment (TME) is a critical determinant in the initiation, progression, and treatment outcomes of various cancers. Comprising of cancer-associated fibroblasts (CAF), immune cells, blood vessels, and signaling molecules, the TME is often likened to the soil supporting the seed (tumor). Among its constituents, tumor-associated macrophages (TAMs) play a pivotal role, exhibiting a dual nature as both promoters and inhibitors of tumor growth. This review explores the intricate relationship between TAMs and the TME, emphasizing their diverse functions, from phagocytosis and tissue repair to modulating immune responses. The plasticity of TAMs is highlighted, showcasing their ability to adopt either protumorigenic or anti-tumorigenic phenotypes based on environmental cues. In the context of cancer, TAMs' pro-tumorigenic activities include promoting angiogenesis, inhibiting immune responses, and fostering metastasis. The manuscript delves into therapeutic strategies targeting TAMs, emphasizing the challenges faced in depleting or inhibiting TAMs due to their multifaceted roles. The focus shifts towards reprogramming TAMs to an anti-tumorigenic M1-like phenotype, exploring interventions such as interferons, immune checkpoint inhibitors, and small molecule modulators. Noteworthy advancements include the use of CSF1R inhibitors, CD40 agonists, and CD47 blockade, demonstrating promising results in preclinical and clinical settings. A significant section is dedicated to Chimeric Antigen Receptor (CAR) technology in macrophages (CAR-M cells). While CAR-T cells have shown success in hematological malignancies, their efficacy in solid tumors has been limited. CAR-M cells, engineered to infiltrate solid tumors, are presented as a potential breakthrough, with a focus on their development, challenges, and promising outcomes. The manuscript concludes with the exploration of third-generation CAR-M technology, offering insight into in-vivo reprogramming and nonviral vector approaches. In conclusion, understanding the complex and dynamic role of TAMs in cancer is crucial for developing effective therapeutic strategies. While early-stage TAM-targeted therapies show promise, further extensive research and larger clinical trials are warranted to optimize their targeting and improve overall cancer treatment outcomes.

Copper homeostasis and cuproptosis in radiation-induced injury

Radiation therapy for cancer treatment brings about a series of radiation injuries to normal tissues. In recent years, the discovery of copper-regulated cell death, cuproptosis, a novel form of programmed cell death, has attracted widespread attention and exploration in various biological functions and pathological mechanisms of copper metabolism and cuproptosis. Understanding its role in the process of radiation injury may open up new avenues and directions for exploration in radiation biology and radiation oncology, thereby improving tumor response and mitigating adverse reactions to radiotherapy. This review provides an overview of copper metabolism, the characteristics of cuproptosis, and their potential regulatory mechanisms in radiation injury.

Resolvin D5 Protects Female Hairless Mouse Skin from Pathological Alterations Caused by UVB Irradiation

Resolvin D5 (RvD5) is a lipid mediator that has been reported to present anti-inflammatory and pro-resolution properties. Evidence also supports its capability to enhance reactive oxygen species (ROS) production during bacterial infections, which would be detrimental in diseases driven by ROS. The biological activity of RvD5 and mechanisms against UVB irradiation skin pathology have not been investigated so far. Female hairless mice were treated intraperitoneally with RvD5 before UVB stimulus. RvD5 reduced skin edema in a dose-dependent manner as well as oxidative stress by increasing antioxidants (endogenous tissue antioxidant scavenging of cationic radical, iron reduction, catalase activity and reduced glutathione levels) and decreasing pro-oxidants (superoxide anion and lipid peroxidation). RvD5 antioxidant activity was accompanied by enhancement of Nrf2, HO-1 and NQO1 mRNA expression. RvD5 reduced the production of IL-1β, TNF-α, TGF-β, and IL-10. RvD5 also reduced the inflammatory cell counts, including mast cells and neutrophils/macrophages. The reduction of oxidative stress and inflammation resulted in diminished matrix metalloproteinase 9 activity, collagen degradation, epidermal thickening and sunburn cell development. Therefore, this study demonstrates, to our knowledge, the first body of evidence that RvD5 can be used to treat UVB skin pathology and unveils, at least in part, its mechanisms of action.

Nocardia rubra cell-wall skeleton mitigates whole abdominal irradiation-induced intestinal injury via regulating macrophage function

Background

Ionizing radiation (IR)-induced intestinal injury is a major side effect and dose-limiting toxicity in patients receiving radiotherapy. There is an urgent need to identify an effective and safe radioprotectant to reduce radiation-induced intestinal injury. Immunoregulation is considered an effective strategy against IR-induced injury. The purpose of this article was to investigate the protective effect of Nocardia rubra cell wall skeleton (Nr-CWS), an immunomodulator, on radiation-induced intestinal damage and to explore its potential mechanism.

Methods

C57BL/6 J male mice exposed to 12 Gy whole abdominal irradiation (WAI) were examined for survival rate, morphology and function of the intestine and spleen, as well as the gut microbiota, to comprehensively evaluate the therapeutic effects of Nr-CWS on radiation-induced intestinal and splenetic injury. To further elucidate the underlying mechanisms of Nr-CWS-mediated intestinal protection, macrophages were depleted by clodronate liposomes to determine whether Nr-CWS-induced radioprotection is macrophage dependent, and the function of peritoneal macrophages stimulated by Nr-CWS was detected in vitro.

Results

Our data showed that Nr-CWS promoted the recovery of intestinal barrier function, enhanced leucine-rich repeat-containing G protein-coupled receptor 5+ intestinal stem cell survival and the regeneration of intestinal epithelial cells, maintained intestinal flora homeostasis, protected spleen morphology and function, and improved the outcome of mice exposed to 12 Gy WAI. Mechanistic studies indicated that Nr-CWS recruited macrophages to reduce WAI-induced intestinal damage. Moreover, macrophage depletion by clodronate liposomes blocked Nr-CWS-induced radioprotection. In vitro, we found that Nr-CWS activated the nuclear factor kappa-B signaling pathway and promoted the phagocytosis and migration ability of peritoneal macrophages.

Conclusions

Our study suggests the therapeutic effect of Nr-CWS on radiation-induced intestinal injury, and provides possible therapeutic strategy and potential preventive and therapeutic drugs to alleviate it.

Cytokine, chemokine alterations and immune cell infiltration in Radiation-induced lung injury: Implications for prevention and management

Radiation therapy is one of the primary treatments for thoracic malignancies, with radiation-induced lung injury (RILI) emerging as its most prevalent complication. RILI encompasses early-stage radiation pneumonitis (RP) and the subsequent development of radiation pulmonary fibrosis (RPF). During radiation treatment, not only are tumor cells targeted, but normal tissue cells, including alveolar epithelial cells and vascular endothelial cells, also sustain damage. Within the lungs, ionizing radiation boosts the intracellular levels of reactive oxygen species across various cell types. This elevation precipitates the release of cytokines and chemokines, coupled with the infiltration of inflammatory cells, culminating in the onset of RP. This pulmonary inflammatory response can persist, spanning a duration from several months to years, ultimately progressing to RPF. This review aims to explore the alterations in cytokine and chemokine release and the influx of immune cells post-ionizing radiation exposure in the lungs, offering insights for the prevention and management of RILI.

Cellular RNA and DNA sensing pathways are essential for the dose-dependent response of human monocytes to ionizing radiation

Circulating monocytes are important players of the inflammatory response to ionizing radiation (IR). These IR-resistant immune cells migrate to radiation-damaged tissues and differentiate into macrophages that phagocytize dying cells, but also facilitate inflammation. Besides the effect of damage-associated molecular patterns, released from irradiated tissues, the inflammatory activation of monocytes and macrophages is largely dependent on IR-induced DNA damage and aberrant transcriptional activity, which may facilitate expression of type I interferons (IFN-I) and numerous inflammation-related genes. We analyzed the accumulation of dsRNA, dsDNA fragments, and RNA:DNA hybrids in the context of induction of RNA-triggered MAVS-mediated and DNA-triggered STING-mediated signaling pathways, in primary human monocytes and a monocytic cell line, THP1, in response to various doses of gamma IR. We found that exposure to lower doses (<7.5 Gy) led to the accumulation of dsRNA, along with dsDNA and RNA:DNA hybrids and activated both MAVS and STING pathway-induced gene expression and signaling activity of IFN-I. Higher doses of IR resulted in the reduced dsRNA level, degradation of RNA-sensing mediators involved in MAVS signaling and coincided with an increased accumulation of dsDNA and RNA:DNA hybrids that correlated with elevated STING signaling and NF-κB-dependent gene expression. While both pathways activate IFN-I expression, using MAVS- and STING-knockout THP1 cells, we identified differences in the spectra of interferon-stimulated genes (ISGs) that are associated with each specific signaling pathway and outlined a large group of STING signaling-associated genes. Using the RNAi technique, we found that increasing the dose of IR activates STING signaling through the DNA sensor cGAS, along with suppression of the DDX41 helicase, which is known to reduce the accumulation of RNA:DNA hybrids and thereby limit cGAS/STING signaling activity. Together, these results indicate that depending on the applied dose, IR leads to the activation of either dsRNA-induced MAVS signaling, which predominantly leads to the expression of both pro- and anti-inflammatory markers, or dsDNA-induced STING signaling that contributes to pro-inflammatory activation of the cells. While RNA:DNA hybrids boost both MAVS- and STING-mediated signaling pathways, these structures being accumulated upon high IR doses promote type I interferon expression and appear to be potent enhancers of radiation dose-dependent pro-inflammatory activation of monocytes.

The effects of radiation on myeloid lineage immune cells within the rodent urinary bladder: a systematic review

PURPOSE

Radiotherapy is a prominent therapy for many malignant and non-malignant disorders, though it can cause side effects such as radiation-induced cystitis. Current research has highlighted a role for mast cells and macrophages in the prognosis of such radiation-induced toxicities. However, the prognostic value of these immune cells in the pathophysiology of radiation-induced cystitis is not clear. As such, a systematic review was conducted to assess myeloid-lineage immune cells for their prognostic value in radiation-induced cystitis to address this gap in literature.

METHODS

The protocol was registered in PROSPERO, and searches were performed in PubMed, Embase and Web of Science databases for pre-clinical rodent studies on radiation-induced cystitis.

RESULTS

After de-duplication, 153 articles were screened for relevancy by title and abstract. Title and abstract screening deemed 64 studies irrelevant. The remaining 85 studies were full-text screened, yielding seven unique articles for data extraction. Most included studies had an unclear risk of bias. The findings of this systematic review suggest that the prognostic value of myeloid-lineage immune cells in radiation-induced cystitis is still unclear, indicating a need for further research in this field.

CONCLUSION

Although the studies reviewed provide some insight into the role of these immune cells in disease pathology, the limited number of studies and unclear risk of bias further highlights a need for additional, high-quality research in this area. In summary, this systematic review highlights a need to understand the involvement of immune cells in radiation-induced cystitis pathophysiology and lay the groundwork for further research in this area.

TRIAL REGISTRATION

PROSPERO registration: CRD42022345960.

CSF1R-dependent macrophages in the salivary gland are essential for epithelial regeneration after radiation-induced injury

The salivary glands often become damaged in individuals receiving radiotherapy for head and neck cancer, resulting in chronic dry mouth. This leads to detrimental effects on their health and quality of life, for which there is no regenerative therapy. Macrophages are the predominant immune cell in the salivary glands and are attractive therapeutic targets due to their unrivaled capacity to drive tissue repair. Yet, the nature and role of macrophages in salivary gland homeostasis and how they may contribute to tissue repair after injury are not well understood. Here, we show that at least two phenotypically and transcriptionally distinct CX3CR1+ macrophage populations are present in the adult salivary gland, which occupy anatomically distinct niches. CD11c+CD206-CD163- macrophages typically associate with gland epithelium, whereas CD11c-CD206+CD163+ macrophages associate with blood vessels and nerves. Using a suite of complementary fate mapping systems, we show that there are highly dynamic changes in the ontogeny and composition of salivary gland macrophages with age. Using an in vivo model of radiation-induced salivary gland injury combined with genetic or antibody-mediated depletion of macrophages, we demonstrate an essential role for macrophages in clearance of cells with DNA damage. Furthermore, we show that epithelial-associated macrophages are indispensable for effective tissue repair and gland function after radiation-induced injury, with their depletion resulting in reduced saliva production. Our data, therefore, provide a strong case for exploring the therapeutic potential of manipulating macrophages to promote tissue repair and thus minimize salivary gland dysfunction after radiotherapy.

MiR-223-3p attenuates radiation-induced inflammatory response and inhibits the activation of NLRP3 inflammasome in macrophages

Macrophage pyroptosis plays an important role in the development of radiation-induced cell and tissue damage, leading to acute lung injury. However, the underlying mechanisms of NOD-like receptor thermal protein domain-associated protein 3 (NLRP3)-mediated macrophage pyroptosis and the regulatory factors involved in radiation-induced pyroptosis are unclear. In this study, the expression of the NLRP3 inflammasome and pyroptosis-associated factors in murine macrophage cell lines was investigated after ionizing radiation. High-throughput RNA sequencing was performed to identify and characterize miRNAs and mRNA transcripts associated with NLRP3-mediated cell death. Our results demonstrated that cleaved-caspase-1 (p10) and N-terminal domain of gasdermin-D (GSDMD-N) were upregulated, and the number of NLRP3 inflammasomes and pyroptotic cells increased in murine macrophage cell lines after irradiation (8 Gy). Comparativeprofiling of 300miRNAs revealed that 41 miRNAsexhibited significantly different expression after 8 Gy of irradiation. Granulocyte-specific microRNA-223-3p (miR-223-3p) is a negative regulator of NLRP3. In vitro experiments revealed that the expression of miR-223-3p was significantly altered by irradiation. Moreover, miR-223-3p decreased the expression of NLRP3 and proinflammatory factors, resulting in reduced pyroptosis in irradiated murine macrophages. Subsequently, in vivo experiments revealed the efficacy of miR-223-3p supplementation in ameliorating alveolar macrophage (AM) pyroptosis, attenuating the infiltration of inflammatory monocytes, and significantly alleviating the severity of acute radiation-induced lung injury (ARILI). Our findings suggest that the miR-223-3p/NLRP3/caspase-1 axis is involved in radiation-induced AM pyroptosis and ARILI.

Pharmacology and Rationale for Seralutinib in the Treatment of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a complex disorder characterized by vascular remodeling and a consequent increase in pulmonary vascular resistance. The histologic hallmarks of PAH include plexiform and neointimal lesions of the pulmonary arterioles, which are composed of dysregulated, apoptosis-resistant endothelial cells and myofibroblasts. Platelet-derived growth factor receptors (PDGFR) α and β, colony stimulating factor 1 receptor (CSF1R), and mast/stem cell growth factor receptor kit (c-KIT) are closely related kinases that have been implicated in PAH progression. In addition, emerging data indicate significant crosstalk between PDGF signaling and the bone morphogenetic protein receptor type 2 (BMPR2)/transforming growth factor β (TGFβ) receptor axis. This review will discuss the importance of the PDGFR-CSF1R-c-KIT signaling network in PAH pathogenesis, present evidence that the inhibition of all three nodes in this kinase network is a potential therapeutic approach for PAH, and highlight the therapeutic potential of seralutinib, currently in development for PAH, which targets these pathways.

Involvement of extracellular vesicles in the progression, diagnosis, treatment, and prevention of whole-body ionizing radiation-induced immune dysfunction

Acute radiation syndrome (ARS) develops after exposure to high doses of ionizing radiation and features immune suppression and organ failure. Currently, there are no diagnostics to identify the occurrence or severity of exposure and there are limited treatments and preventative strategies to mitigate ARS. Extracellular vesicles (EVs) are mediators of intercellular communication that contribute to immune dysfunction across many diseases. We investigated if EV cargo can identify whole body irradiation (WBIR) exposure and if EVs promote ARS immune dysfunction. We hypothesized that beneficial EVs derived from mesenchymal stem cells (MSC-EVs) would blunt ARS immune dysfunction and might serve as prophylactic radioprotectants. Mice received WBIR (2 or 9 Gy) with assessment of EVs at 3 and 7 days after exposure. LC-MS/MS proteomic analysis of WBIR-EVs found dose-related changes as well as candidate proteins that were increased with both doses and timepoints (34 total) such as Thromboxane-A Synthase and lymphocyte cytosolic protein 2. Suprabasin and Sarcalumenin were increased only after 9 Gy suggesting these proteins may indicate high dose/lethal exposure. Analysis of EV miRNAs identified miR-376 and miR-136, which were increased up to 200- and 60-fold respectively by both doses of WBIR and select miRNAs such as miR-1839 and miR-664 were increased only with 9 Gy. WBIR-EVs (9 Gy) were biologically active and blunted immune responses to LPS in RAW264.7 macrophages, inhibiting canonical signaling pathways associated with wound healing and phagosome formation. When given 3 days after exposure, MSC-EVs slightly modified immune gene expression changes in the spleens of mice in response to WBIR and in a combined radiation plus burn injury exposure (RCI). MSC-EVs normalized the expression of certain key immune genes such as NFκBia and Cxcr4 (WBIR), Map4k1, Ccr9 and Cxcl12 (RCI) and lowered plasma TNFα cytokine levels after RCI. When given prophylactically (24 and 3 hours before exposure), MSC-EVs prolonged survival to the 9 Gy lethal exposure. Thus, EVs are important participants in ARS. EV cargo might be used to diagnose WBIR exposure, and MSC-EVs might serve as radioprotectants to blunt the impact of toxic radiation exposure.

Influence of the irradiated pulmonary microenvironment on macrophage and T cell dynamics

BACKGROUND

The lung is sensitive to radiation, increasing normal tissue toxicity risks following radiation therapy. Adverse outcomes include pneumonitis and pulmonary fibrosis, which result from dysregulated intercellular communication within the pulmonary microenvironment. Although macrophages are implicated in these pathogenic outcomes, the impact of their microenvironment is not well understood.

MATERIALS AND METHODS

C57BL/6J mice received 6Gyx5 irradiation to the right lung. Macrophage and T cell dynamics were investigated in ipsilateral right lungs, contralateral left lungs and non-irradiated control lungs 4-26wk post exposure. Lungs were evaluated by flow cytometry, histology and proteomics.

RESULTS

Following uni-lung irradiation, focal regions of macrophage accumulation were noted in both lungs by 8wk, however by 26wk fibrotic lesions were observed only in ipsilateral lungs. Infiltrating and alveolar macrophages populations expanded in both lungs, however transitional CD11b + alveolar macrophages persisted only in ipsilateral lungs and expressed lower CD206. Concurrently, arginase-1 + macrophages accumulated in ipsilateral but not contralateral lungs at 8 and 26wk post exposure, while CD206 + macrophages were absent from these accumulations. While radiation expanded CD8 + T cells in both lungs, T regulatory cells only increased in ipsilateral lungs. Unbiased proteomics analysis of immune cells revealed a substantial number of differentially expressed proteins in ipsilateral lungs when compared to contralateral lungs and both differed from non-irradiated controls.

CONCLUSIONS

Pulmonary macrophage and T cell dynamics are impacted by the microenvironmental conditions that develop following radiation exposure, both locally and systemically. While macrophages and T cells infiltrate and expand in both lungs, they diverge phenotypically depending on their environment.

Correlation Between Serum and Urine Biomarkers and the Intensity of Acute Radiation Cystitis in Patients Treated With Radiation Therapy for Localized Prostate Cancer: Protocol for the Radiotoxicity Bladder Biomarkers (RABBIO) Study

BACKGROUND

Despite improvements in radiation techniques, pelvic radiotherapy is responsible for acute and delayed bladder adverse events, defined as radiation cystitis. The initial symptoms of bladder injury secondary to pelvic irradiation are likely to occur during treatment or within 3 months of radiotherapy in approximately 50% of irradiated patients, and have a significant impact on their quality of life. The pathophysiology of radiation cystitis is not well understood, particularly because of the risk of complications associated with access to bladder tissue after irradiation, which limits our ability to study this process and develop treatments.

OBJECTIVE

It is an original study combining digital data collection to monitor patients' symptoms and biological markers during irradiation. The main objective of our study is to evaluate the correlation of biological biomarkers with the intensity of acute radiation cystitis and the quality of life of patients, assessed with the digital telemonitoring platform Cureety.

METHODS

Patients with intermediate-risk localized prostate cancer who are eligible for localized radiotherapy will be included. Inflammatory biomarkers will be analyzed in urine and blood samples before the start of radiotherapy and at weeks 4, 12, and 48 of irradiation, through quantitative methods such as a multiplex Luminex assay, flow cytometry, and enzyme-linked immunosorbent assay. We will also characterize the patients' gut and urine microbiota composition using 16S ribosomal RNA sequencing technology. Between sample collection visits, patients will complete various questionnaires related to radiation cystitis symptoms (using the International Prostate Symptom Score), adverse events, and quality of life (using the Functional Assessment of Cancer Therapy-Prostate questionnaire), using the Cureety digital remote monitoring platform. Upon receipt of the questionnaires, an algorithm will process the information and classify patients in accordance with the severity of symptoms and adverse events reported on the basis of Common Terminology Criteria for Adverse Events and International Prostate Symptom Score standards. This will allow us to correlate levels of urinary, blood, and fecal biomarkers with the severity of acute radiation cystitis symptoms and patient-reported quality of life.

RESULTS

The study started in March 2022. We estimate a recruitment period of approximately 18 months, and the final results are expected in 2024.

CONCLUSIONS

This prospective study is the first to explore the overexpression of inflammatory proteins in fluid biopsies from patients with symptoms of acute radiation cystitis. In addition, the 1-year follow-up after treatment will allow us to predict which patients are at risk of late radiation cystitis and to refer them for radioprotective treatment. The results of this study will allow us to develop strategies to limit radiation damage to the bladder and improve the quality of life of patients.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05246774; https://clinicaltrials.gov/ct2/show/NCT05246774?term=NCT05246774.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/38362.

Clinical Radiobiology for Radiation Oncology

This chapter is focused on radiobiological aspects at the molecular, cellular, and tissue level which are relevant for the clinical use of ionizing radiation (IR) in cancer therapy. For radiation oncology, it is critical to find a balance, i.e., the therapeutic window, between the probability of tumor control and the probability of side effects caused by radiation injury to the healthy tissues and organs. An overview is given about modern precision radiotherapy (RT) techniques, which allow optimal sparing of healthy tissues. Biological factors determining the width of the therapeutic window are explained. The role of the six typical radiobiological phenomena determining the response of both malignant and normal tissues in the clinic, the 6R’s, which are Reoxygenation, Redistribution, Repopulation, Repair, Radiosensitivity, and Reactivation of the immune system, is discussed. Information is provided on tumor characteristics, for example, tumor type, growth kinetics, hypoxia, aberrant molecular signaling pathways, cancer stem cells and their impact on the response to RT. The role of the tumor microenvironment and microbiota is described and the effects of radiation on the immune system including the abscopal effect phenomenon are outlined. A summary is given on tumor diagnosis, response prediction via biomarkers, genetics, and radiomics, and ways to selectively enhance the RT response in tumors. Furthermore, we describe acute and late normal tissue reactions following exposure to radiation: cellular aspects, tissue kinetics, latency periods, permanent or transient injury, and histopathology. Details are also given on the differential effect on tumor and late responding healthy tissues following fractionated and low dose rate irradiation as well as the effect of whole-body exposure.

Radiotherapy induced immunogenic cell death by remodeling tumor immune microenvironment

Emerging evidence indicates that the induction of radiotherapy(RT) on the immunogenic cell death (ICD) is not only dependent on its direct cytotoxic effect, changes in the tumor immune microenvironment also play an important role in it. Tumor immune microenvironment (TIME) refers to the immune microenvironment that tumor cells exist, including tumor cells, inflammatory cells, immune cells, various signaling molecules and extracellular matrix. TIME has a barrier effect on the anti-tumor function of immune cells, which can inhibit all stages of anti-tumor immune response. The remodeling of TIME caused by RT may affect the degree of immunogenicity, and make it change from immunosuppressive phenotype to immunostimulatory phenotype. It is of great significance to reveal the causes of immune escape of tumor cells, especially for the treatment of drug-resistant tumor. In this review, we focus on the effect of RT on the TIME, the mechanism of RT in reversing the TIME to suppress intrinsic immunity, and the sensitization effect of the remodeling of TIME caused by RT on the effectiveness of immunotherapy.

Potential Molecular Mechanisms behind the Ultra-High Dose Rate "FLASH" Effect

FLASH radiotherapy, or the delivery of a dose at an ultra-high dose rate (>40 Gy/s), has recently emerged as a promising tool to enhance the therapeutic index in cancer treatment. The remarkable sparing of normal tissues and equivalent tumor control by FLASH irradiation compared to conventional dose rate irradiation—the FLASH effect—has already been demonstrated in several preclinical models and even in a first patient with T-cell cutaneous lymphoma. However, the biological mechanisms responsible for the differential effect produced by FLASH irradiation in normal and cancer cells remain to be elucidated. This is of great importance because a good understanding of the underlying radiobiological mechanisms and characterization of the specific beam parameters is required for a successful clinical translation of FLASH radiotherapy. In this review, we summarize the FLASH investigations performed so far and critically evaluate the current hypotheses explaining the FLASH effect, including oxygen depletion, the production of reactive oxygen species, and an altered immune response. We also propose a new theory that assumes an important role of mitochondria in mediating the normal tissue and tumor response to FLASH dose rates.

A novel approach for the prevention of ionizing radiation-induced bone loss using a designer multifunctional cerium oxide nanozyme

The disability, mortality and costs due to ionizing radiation (IR)-induced osteoporotic bone fractures are substantial and no effective therapy exists. Ionizing radiation increases cellular oxidative damage, causing an imbalance in bone turnover that is primarily driven via heightened activity of the bone-resorbing osteoclast. We demonstrate that rats exposed to sublethal levels of IR develop fragile, osteoporotic bone. At reactive surface sites, cerium ions have the ability to easily undergo redox cycling: drastically adjusting their electronic configurations and versatile catalytic activities. These properties make cerium oxide nanomaterials fascinating. We show that an engineered artificial nanozyme composed of cerium oxide, and designed to possess a higher fraction of trivalent (Ce³⁺) surface sites, mitigates the IR-induced loss in bone area, bone architecture, and strength. These investigations also demonstrate that our nanozyme furnishes several mechanistic avenues of protection and selectively targets highly damaging reactive oxygen species, protecting the rats against IR-induced DNA damage, cellular senescence, and elevated osteoclastic activity in vitro and in vivo. Further, we reveal that our nanozyme is a previously unreported key regulator of osteoclast formation derived from macrophages while also directly targeting bone progenitor cells, favoring new bone formation despite its exposure to harmful levels of IR in vitro. These findings open a new approach for the specific prevention of IR-induced bone loss using synthesis-mediated designer multifunctional nanomaterials.

MRTF may be the missing link in a multiscale mechanobiology approach toward macrophage dysfunction in space

Macrophages exhibit impaired phagocytosis, adhesion, migration, and cytokine production in space, hindering their ability to elicit immune responses. Considering that the combined effect of spaceflight microgravity and radiation is multiscale and multifactorial in nature, it is expected that contradictory findings are common in the field. This theory paper reanalyzes research on the macrophage spaceflight response across multiple timescales from seconds to weeks, and spatial scales from the molecular, intracellular, extracellular, to the physiological. Key findings include time-dependence of both pro-inflammatory activation and integrin expression. Here, we introduce the time-dependent, intracellular localization of MRTF-A as a hypothetical confounder of macrophage activation. We discuss the mechanosensitive MRTF-A/SRF pathway dependence on the actin cytoskeleton/nucleoskeleton, microtubules, membrane mechanoreceptors, hypoxia, oxidative stress, and intracellular/extracellular crosstalk. By adopting a multiscale perspective, this paper provides the first mechanistic answer for a three-decade-old question regarding impaired cytokine secretion in microgravity—and strengthens the connection between the recent advances in mechanobiology, microgravity, and the spaceflight immune response. Finally, we hypothesize MRTF involvement and complications in treating spaceflight-induced cardiovascular, skeletal, and immune disease.

Tumor cell-based vaccine contributes to local tumor irradiation by eliciting a tumor model-dependent systemic immune response

Multimodal treatment approaches, such as radio-immunotherapy, necessitate regimen optimization and the investigation of the interactions of different modalities. The aim of this study was two-fold. Firstly, to select the most effective combination of irradiation and the previously developed tumor cell-based vaccine and then to provide insight into the immune response to the selected combinatorial treatment. The study was performed in immunologically different murine tumor models: B16F10 melanoma and CT26 colorectal carcinoma. The most effective combinatorial treatment was selected by comparing three different IR regimens and three different vaccination regimens. We determined the local immune response by investigating immune cell infiltration at the vaccination site and in tumors. Lastly, we determined the systemic immune response by investigating the amount of tumor-specific effector lymphocytes in draining lymph nodes. The selected most effective combinatorial treatment was 5× 5 Gy in combination with concomitant single-dose vaccination (B16F10) or with concomitant multi-dose vaccination (CT26). The combinatorial treatment successfully elicited a local immune response at the vaccination site and in tumors in both tumor models. It also resulted in the highest amount of tumor-specific effector lymphocytes in draining lymph nodes in the B16F10, but not in the CT26 tumor-bearing mice. However, the amount of tumor-specific effector lymphocytes was intrinsically higher in the CT26 than in the B16F10 tumor model. Upon the selection of the most effective combinatorial treatment, we demonstrated that the vaccine elicits an immune response and contributes to the antitumor efficacy of tumor irradiation. However, this interaction is multi-faceted and appears to be dependent on the tumor immunogenicity.

Re-Du-Ning injection ameliorates radiation-induced pneumonitis and fibrosis by inhibiting AIM2 inflammasome and epithelial-mesenchymal transition

BACKGROUND

Radiation-induced lung injury (RILI) is a common side effect in chest radiotherapy patients, and there is no good medicine to treat it. Re-Du-Ning (RDN) injection is a traditional Chinese medicine that is clinically used to treat upper respiratory tract infections and acute bronchitis. RDN has the advantage of high safety and mild side effects. The mechanism of most traditional Chinese medicine preparations is unknown.

PURPOSE

To illustrate the mechanisms of RDN for the treatment of RILI.

METHODS

Female C57BL/6 mice were used to establish a RILI model via irradiation, and RDN injection was intraperitoneally administered at doses of 5, 10, and 20 ml/kg. The cytokines were measured by ELISA and qPCR. The data related to Absent in melanoma 2 (AIM2) inflammasome were analyzed via ELISA and a network pharmacological approach. In addition, the data related to epithelial-mesenchymal transition (EMT) were analyzed via immunofluorescence, Western blotting, and a network pharmacological approach.

RESULTS

RDN robustly alleviated RILI. Meanwhile, RDN downregulated inflammatory cells' infiltration and the expression of pro-inflammatory cytokines, such as IL-1β, IL-6, and TNF-α. Next, the potential molecular mechanisms of RDN were predicted through network pharmacology analysis. RDN may ameliorate radiation pneumonitis (RP) by inhibiting AIM2-mediated pyroptosis. Moreover, RDN treatment inhibited EMT and phosphoinositide-3-kinase (PI3K)/protein kinase B (AKT) pathway. The active compounds from Lonicera japonica Thunb. decreased the phosphorylation of Akt.

CONCLUSION

These findings demonstrate that RDN, as a traditional Chinese medicine preparation, will be a candidate drug for treating RILI.

Targeted Accumulation of Macrophages Induced by Microbeam Irradiation in a Tissue-Dependent Manner

Radiation therapy (RT) is a vital component of multimodal cancer treatment, and its immunomodulatory effects are a major focus of current therapeutic strategies. Macrophages are some of the first cells recruited to sites of radiation-induced injury where they can aid in tissue repair, propagate radiation-induced fibrogenesis and influence tumour dynamics. Microbeam radiation therapy (MRT) is a unique, spatially fractionated radiation modality that has demonstrated exceptional tumour control and reduction in normal tissue toxicity, including fibrosis. We conducted a morphological analysis of MRT-irradiated normal liver, lung and skin tissues as well as lung and melanoma tumours. MRT induced distinct patterns of DNA damage, reflecting the geometry of the microbeam array. Macrophages infiltrated these regions of peak dose deposition at variable timepoints post-irradiation depending on the tissue type. In normal liver and lung tissue, macrophages clearly demarcated the beam path by 48 h and 7 days post-irradiation, respectively. This was not reflected, however, in normal skin tissue, despite clear DNA damage marking the beam path. Persistent DNA damage was observed in MRT-irradiated lung carcinoma, with an accompanying geometry-specific influx of mixed M1/M2-like macrophage populations. These data indicate the unique potential of MRT as a tool to induce a remarkable accumulation of macrophages in an organ/tissue-specific manner. Further characterization of these macrophage populations is warranted to identify their organ-specific roles in normal tissue sparing and anti-tumour responses.

Nicaraven mitigates radiation-induced lung injury by downregulating the NF-κB and TGF-β/Smad pathways to suppress the inflammatory response

Radiation-induced lung injury (RILI) is commonly observed in patients receiving radiotherapy, and clinical prevention and treatment remain difficult. We investigated the effect and mechanism of nicaraven for mitigating RILI. C57BL/6 N mice (12-week-old) were treated daily with 6 Gy X-ray thoracic radiation for 5 days in sequences (cumulative dose of 30 Gy), and nicaraven (50 mg/kg) or placebo was injected intraperitoneally in 10 min after each radiation exposure. Mice were sacrificed and lung tissues were collected for experimental assessments at the next day (acute phase) or 100 days (chronic phase) after the last radiation exposure. Of the acute phase, immunohistochemical analysis of lung tissues showed that radiation significantly induced DNA damage of the lung cells, increased the number of Sca-1+ stem cells, and induced the recruitment of CD11c+, F4/80+ and CD206+ inflammatory cells. However, all these changes in the irradiated lungs were effectively mitigated by nicaraven administration. Western blot analysis showed that nicaraven administration effectively attenuated the radiation-induced upregulation of NF-κB, TGF-β, and pSmad2 in lungs. Of the chronic phase, nicaraven administration effectively attenuated the radiation-induced enhancement of α-SMA expression and collagen deposition in lungs. In conclusion we find that nicaraven can effectively mitigate RILI by downregulating NF-κB and TGF-β/pSmad2 pathways to suppress the inflammatory response in the irradiated lungs.

Radiation-Induced Macrophage Senescence Impairs Resolution Programs and Drives Cardiovascular Inflammation

Radiation is associated with tissue damage and increased risk of atherosclerosis, but there are currently no treatments and a very limited mechanistic understanding of how radiation impacts tissue repair mechanisms. We uncovered that radiation significantly delayed temporal resolution programs that were associated with decreased efferocytosis in vivo. Resolvin D1 (RvD1), a known proresolving ligand, promoted swift resolution and restored efferocytosis in sublethally irradiated mice. Irradiated macrophages exhibited several features of senescence, including increased expression of p16^INK4A and p21, heightened levels of SA-β-gal, COX-2, several proinflammatory cytokines/chemokines, and oxidative stress (OS) in vitro, and when transferred to mice, they exacerbated inflammation in vivo. Mechanistically, heightened OS in senescent macrophages led to impairment in their ability to carry out efficient efferocytosis, and treatment with RvD1 reduced OS and improved efferocytosis. Sublethally irradiated Ldlr ^-/- mice exhibited increased plaque necrosis, p16^INK4A cells, and decreased lesional collagen compared with nonirradiated controls, and treatment with RvD1 significantly reduced necrosis and increased lesional collagen. Removal of p16^INK4A hematopoietic cells during advanced atherosclerosis with p16-3MR mice reduced plaque necrosis and increased production of key intraplaque-resolving mediators. Our results demonstrate that sublethal radiation drives macrophage senescence and efferocytosis defects and suggest that RvD1 may be a new therapeutic strategy to limit radiation-induced tissue damage.

Multifaceted roles of a bioengineered nanoreactor in repressing radiation-induced lung injury

Radiation-induced lung injury (RILI) is a potentially fatal and dose-limiting complication of thoracic cancer radiotherapy. However, effective therapeutic agents for this condition are limited. Here, we describe a novel strategy to exert additive effects of a non-erythropoietic EPO derivative (ARA290), along with a free radical scavenger, superoxide dismutase (SOD), using a bioengineered nanoreactor (SOD@ARA290-HBc). ARA290-chimeric nanoreactor makes SOD present in a confined reaction space by encapsulation into its interior to heighten stability against denaturing stimuli. In a RILI mouse model, intratracheal administration of SOD@ARA290-HBc was shown to significantly ameliorate acute radiation pneumonitis and pulmonary fibrosis. Our investigations revealed that SOD@ARA290-HBc performs its radioprotective effects by protecting against radiation induced alveolar epithelial cell apoptosis and ferroptosis, suppressing oxidative stress, inhibiting inflammation and by modulating the infiltrated macrophage phenotype, or through a combination of these mechanisms. In conclusion, SOD@ARA29-HBc is a potential therapeutic agent for RILI, and given its multifaceted roles, it may be further developed as a translational nanomedicine for other related disorders.

Small Endogeneous Peptide Mitigates Myocardial Remodeling in a Mouse Model of Cardioselective Galectin-3 Overexpression

BACKGROUND

Myocardial Gal3 (galectin-3) expression is associated with cardiac inflammation and fibrosis. Increased Gal3 portends susceptibility to heart failure and death. There are no data reporting the causative role of Gal3 to mediate cardiac fibro-inflammatory response and heart failure.

METHODS

We developed a cardioselective Gal3 gain-of-function mouse (Gal3+/+) using α-myosin heavy chain promotor. We confirmed Gal3-transgene expression with real-time polymerase chain reaction and quantified cardiac/circulating Gal3 with Western blot and immunoassays. We used echocardiogram and cardiac magnetic resonance imaging to measure cardiac volumes, function, and myocardial velocities. Ex vivo, we studied myocardial inflammation/fibrosis and downstream TGF (transforming growth factor) β1-mRNA expression. We examined the effects of acute myocardial ischemia in presence of excess Gal3 by inducing acute myocardial infarction in mice. Two subsets of mice including mice treated with N-acetyl-seryl-aspartyl-lysyl-proline (a Gal3-inhibitor) and mice with genetic Gal3 loss-of-function (Gal3-/-) were studied for comparative analysis of Gal3 function.

RESULTS

Gal3+/+ mice had increased cardiac/circulating Gal3. Gal3+/+ mice showed excess pericardial fat pad, dilated ventricles and cardiac dysfunction, which was partly normalized by N-acetyl-seryl-aspartyl-lysyl-proline. Cardiac magnetic resonance imaging showed reduced myocardial contractile velocities in Gal3+/+. The majority of Gal3+/+ mice did not survive acute myocardial infarction, and the survivors had profound cardiac dysfunction. Myocardial histology of Gal3+/+ mice showed macrophage/mast-cell infiltration, fibrosis and higher TGFβ1-mRNA expression, which were mitigated by both Gal3 gene deletion and N-acetyl-seryl-aspartyl-lysyl-proline administration.

CONCLUSIONS

Our study shows that cardioselective Gal3 overexpression leads to multiple cardiac phenotypic defects including ventricular dilation and cardiac dysfunction. Pharmacological Gal3 inhibition conferred protective effects with reduction of inflammation and fibrosis. Our study highlights the importance of translational studies to counteract Gal3 function and prevent cardiac dysfunction.

Dual oxidase 1 limits the IFNγ-associated antitumor effect of macrophages

Background

Macrophages play pivotal roles in tumor progression and the response to anticancer therapies, including radiotherapy (RT). Dual oxidase (DUOX) 1 is a transmembrane enzyme that plays a critical role in oxidant generation.

Methods

Since we found DUOX1 expression in macrophages from human lung samples exposed to ionizing radiation, we aimed to assess the involvement of DUOX1 in macrophage activation and the role of these macrophages in tumor development.

Results

Using Duox1^−/− mice, we demonstrated that the lack of DUOX1 in proinflammatory macrophages improved the antitumor effect of these cells. Furthermore, intratumoral injection of Duox1^−/− proinflammatory macrophages significantly enhanced the antitumor effect of RT. Mechanistically, DUOX1 deficiency increased the production of proinflammatory cytokines (IFNγ, CXCL9, CCL3 and TNFα) by activated macrophages in vitro and the expression of major histocompatibility complex class II in the membranes of macrophages. We also demonstrated that DUOX1 was involved in the phagocytotic function of macrophages in vitro and in vivo. The antitumor effect of Duox1^−/− macrophages was associated with a significant increase in IFNγ production by both lymphoid and myeloid immune cells.

Conclusions

Our data indicate that DUOX1 is a new target for macrophage reprogramming and suggest that DUOX1 inhibition in macrophages combined with RT is a new therapeutic strategy for the management of cancers.

SPM Receptor Expression and Localization in Irradiated Salivary Glands

Radiation therapy-mediated salivary gland destruction is characterized by increased inflammatory cell infiltration and fibrosis, both of which ultimately lead to salivary gland hypofunction. However, current treatments (e.g., artificial saliva and sialagogues) only promote temporary relief of symptoms. As such, developing alternative measures against radiation damage is critical for restoring salivary gland structure and function. One promising option for managing radiation therapy-mediated damage in salivary glands is by activation of specialized proresolving lipid mediator receptors due to their demonstrated role in resolution of inflammation and fibrosis in many tissues. Nonetheless, little is known about the presence and function of these receptors in healthy and/or irradiated salivary glands. Therefore, the goal of this study was to detect whether these specialized proresolving lipid mediator receptors are expressed in healthy salivary glands and, if so, if they are maintained after radiation therapy-mediated damage. Our results indicate that specialized proresolving lipid mediator receptors are heterogeneously expressed in inflammatory as well as in acinar and ductal cells within human submandibular glands and that their expression persists after radiation therapy. These findings suggest that epithelial cells as well as resident immune cells represent potential targets for modulation of resolution of inflammation and fibrosis in irradiated salivary glands.

Clinicopathologic and Transcriptomic Analysis of Radiation-Induced Lung Injury in Nonhuman Primates

PURPOSE

Radiation-induced lung injury (RILI) is a progressive condition with an early phase (radiation pneumonitis) and a late phase (lung fibrosis). RILI may occur after partial-body ionizing radiation exposures or internal radioisotope exposure, with wide individual variability in timing and extent of lung injury. This study aimed to provide new insights into the pathogenesis and progression of RILI in the nonhuman primate (NHP) rhesus macaque model.

METHODS AND MATERIALS

We used an integrative approach to understand RILI and its evolution at clinical and molecular levels in 17 NHPs exposed to 10 Gy of whole-thorax irradiation in comparison with 3 sham-irradiated control NHPs. Clinically, we monitored respiratory rates, computed tomography (CT) scans, plasma cytokine levels, and bronchoalveolar lavage (BAL) over 8 months and lung samples collected at necropsy for molecular and histopathologic analyses using RNA sequencing and immunohistochemistry.

RESULTS

Elevated respiratory rates, greater CT density, and more severe pneumonitis with increased macrophage content were associated with early mortality. Radiation-induced lung fibrosis included polarization of macrophages toward the M2-like phenotype, TGF-β signaling, expression of CDKN1A/p21 in epithelial cells, and expression of α-SMA in lung stroma. RNA sequencing analysis of lung tissue revealed SERPINA3, ATP12A, GJB2, CLDN10, TOX3, and LPA as top dysregulated transcripts in irradiated animals. In addition to transcriptomic data, we observed increased protein expression of SERPINA3, TGF-β1, CCL2, and CCL11 in BAL and plasma samples.

CONCLUSIONS

Our combined clinical, imaging, histologic, and transcriptomic analysis provides new insights into the early and late phases of RILI and highlights possible biomarkers and potential therapeutic targets of RILI. Activation of TGF-β and macrophage polarization appear to be key mechanisms involved in RILI.

Tissue-Resident and Recruited Macrophages in Primary Tumor and Metastatic Microenvironments: Potential Targets in Cancer Therapy

Macrophages within solid tumors and metastatic sites are heterogenous populations with different developmental origins and substantially contribute to tumor progression. A number of tumor-promoting phenotypes associated with both tumor- and metastasis-associated macrophages are similar to innate programs of embryonic-derived tissue-resident macrophages. In contrast to recruited macrophages originating from marrow precursors, tissue-resident macrophages are seeded before birth and function to coordinate tissue remodeling and maintain tissue integrity and homeostasis. Both recruited and tissue-resident macrophage populations contribute to tumor growth and metastasis and are important mediators of resistance to chemotherapy, radiation therapy, and immune checkpoint blockade. Thus, targeting various macrophage populations and their tumor-promoting phenotypes holds therapeutic promise. Here, we discuss various macrophage populations as regulators of tumor progression, immunity, and immunotherapy. We provide an overview of macrophage targeting strategies, including therapeutics designed to induce macrophage depletion, impair recruitment, and induce repolarization. We also provide a perspective on the therapeutic potential for macrophage-specific acquisition of trained immunity as an anti-cancer agent and discuss the therapeutic potential of exploiting macrophages and their traits to reduce tumor burden.

15-PGDH inhibition activates the splenic niche to promote hematopoietic regeneration

The splenic microenvironment regulates hematopoietic stem and progenitor cell (HSPC) function, particularly during demand-adapted hematopoiesis; however, practical strategies to enhance splenic support of transplanted HSPCs have proved elusive. We have previously demonstrated that inhibiting 15-hydroxyprostaglandin dehydrogenase (15-PGDH), using the small molecule (+)SW033291 (PGDHi), increases BM prostaglandin E₂ (PGE₂) levels, expands HSPC numbers, and accelerates hematologic reconstitution after BM transplantation (BMT) in mice. Here we demonstrate that the splenic microenvironment, specifically 15-PGDH high-expressing macrophages, megakaryocytes (MKs), and mast cells (MCs), regulates steady-state hematopoiesis and potentiates recovery after BMT. Notably, PGDHi-induced neutrophil, platelet, and HSPC recovery were highly attenuated in splenectomized mice. PGDHi induced nonpathologic splenic extramedullary hematopoiesis at steady state, and pretransplant PGDHi enhanced the homing of transplanted cells to the spleen. 15-PGDH enzymatic activity localized specifically to macrophages, MK lineage cells, and MCs, identifying these cell types as likely coordinating the impact of PGDHi on splenic HSPCs. These findings suggest that 15-PGDH expression marks HSC niche cell types that regulate hematopoietic regeneration. Therefore, PGDHi provides a well-tolerated strategy to therapeutically target multiple HSC niches, promote hematopoietic regeneration, and improve clinical outcomes of BMT.

Untangling Local Pro-Inflammatory, Reparative, and Regulatory Damage-Associated Molecular-Patterns (DAMPs) Pathways to Improve Transplant Outcomes

Detrimental inflammatory responses after solid organ transplantation are initiated when immune cells sense pathogen-associated molecular patterns (PAMPs) and certain damage-associated molecular patterns (DAMPs) released or exposed during transplant-associated processes, such as ischemia/reperfusion injury (IRI), surgical trauma, and recipient conditioning. These inflammatory responses initiate and propagate anti-alloantigen (AlloAg) responses and targeting DAMPs and PAMPs, or the signaling cascades they activate, reduce alloimmunity, and contribute to improved outcomes after allogeneic solid organ transplantation in experimental studies. However, DAMPs have also been implicated in initiating essential anti-inflammatory and reparative functions of specific immune cells, particularly Treg and macrophages. Interestingly, DAMP signaling is also involved in local and systemic homeostasis. Herein, we describe the emerging literature defining how poor outcomes after transplantation may result, not from just an over-abundance of DAMP-driven inflammation, but instead an inadequate presence of a subset of DAMPs or related molecules needed to repair tissue successfully or re-establish tissue homeostasis. Adverse outcomes may also arise when these homeostatic or reparative signals become dysregulated or hijacked by alloreactive immune cells in transplant niches. A complete understanding of the critical pathways controlling tissue repair and homeostasis, and how alloimmune responses or transplant-related processes disrupt these will lead to new immunotherapeutics that can prevent or reverse the tissue pathology leading to lost grafts due to chronic rejection.

Response of human macrophages to gamma radiation is mediated via expression of endogenous retroviruses

Ionizing radiation-induced tissue damage recruits monocytes into the exposed area where they are differentiated to macrophages. These implement phagocytic removal of dying cells and elicit an acute inflammatory response, but can also facilitate tumorigenesis due to production of anti-inflammatory cytokines. Using primary human monocyte-derived macrophages (MDMs) and the THP1 monocytic cell line, we demonstrate that gamma radiation triggers monocyte differentiation toward the macrophage phenotype with increased expression of type I interferons (IFN-I) and both pro- and anti-inflammatory macrophage activation markers. We found that these changes correlate with significantly upregulated expression of 622 retroelements from various groups, particularly of several clades of human endogenous retroviruses (HERVs). Elevated transcription was detected in both sense and antisense directions in the HERV subgroups tested, including the most genetically homogeneous clade HML-2. The level of antisense transcription was three- to five-fold higher than of the sense strand levels. Using a proximity ligation assay and immunoprecipitation followed by RNA quantification, we identified an increased amount of the dsRNA receptors MDA-5 and TLR3 bound to an equivalent number of copies of sense and antisense chains of HERVK HML-2 RNA. This binding triggered MAVS-associated signaling pathways resulting in increased expression of IFN-I and inflammation related genes that enhanced the cumulative inflammatory effect of radiation-induced senescence. HML-2 knockdown was accompanied with reduced expression and secretion of IFNα, pro-inflammatory (IL-1β, IL-6, CCL2, CCL3, CCL8, and CCL20) and anti-inflammatory (IL10) modulators in irradiated monocytes and MDMs. Taken together, our data indicate that radiation stress-induced HERV expression enhances the IFN-I and cytokine response and results in increased levels of pro-inflammatory modulators along with expression of anti-inflammatory factors associated with the macrophage tumorigenic phenotype.

Ionizing radiation is a powerful stressogenic factor that induces massive cell damage. The signals released from radiation-damaged tissues recruit the monocytes, which are differentiated into macrophages that remove dying cells via phagocytosis and facilitate inflammation but can also contribute to tumorigenesis through anti-inflammatory and regenerative activities. The mechanism of this dual response of macrophages to irradiation is not fully understood. Using primary human macrophages and a monocytic cell line, we demonstrated that gamma radiation doses activate expression of various human endogenous retroviruses (HERVs). At the molecular level, we have shown that increased numbers of sense and antisense transcripts of tested HERV subgroups bind to double-stranded RNA receptors inducing the expression of type I interferons, multiple pro-inflammatory and some anti-inflammatory factors. At the phenotypic level, polarized macrophages exhibit a potent inflammatory response along with potentially tumorigenic characteristics. Our data suggest that endogenous retroviruses represent an important contributor of the macrophage-mediated inflammation in response to radiation-induced stress but may also indirectly influence tumorigenesis via biased macrophage polarization.

Chronic Inflammation and Radiation-Induced Cystitis: Molecular Background and Therapeutic Perspectives

Radiation cystitis is a potential complication following the therapeutic irradiation of pelvic cancers. Its clinical management remains unclear, and few preclinical data are available on its underlying pathophysiology. The therapeutic strategy is difficult to establish because few prospective and randomized trials are available. In this review, we report on the clinical presentation and pathophysiology of radiation cystitis. Then we discuss potential therapeutic approaches, with a focus on the immunopathological processes underlying the onset of radiation cystitis, including the fibrotic process. Potential therapeutic avenues for therapeutic modulation will be highlighted, with a focus on the interaction between mesenchymal stromal cells and macrophages for the prevention and treatment of radiation cystitis.

Ameliorative effect of 2-methoxyestradiol on radiation-induced lung injury

AIMS

Radiation-induced lung injury (RILI) is a serious complication of radiation therapy. Development of an effective drug that selectively protects normal lung tissues and sensitizes tumor cells to radiotherapy is an unmet need. 2-Methoxyestradiol (2ME2) possesses polypharmacological properties, which qualifies it as an effective radioprotector. Our aim is to explore the potential protective effects of 2ME2 against early and late stages of RILI and the underlying mechanisms.

MAIN METHODS

BALB/c mice were either treated with 2ME2 (50 mg/kg/day i.p., for 4 weeks); or received a single dose of 10 Gy ionizing radiation (IR) delivered to the lungs; or 10 Gy IR and 2ME2. Animal survival and pulmonary functions were evaluated. Immune-phenotyping of alveolar macrophages (AM) in the broncho-alveolar lavage fluids (BALF) was determined by flow cytometry. ELISA was used to evaluate the expression levels of TNF-α, TGF-β; and IL-10 in BALF. Lung tissues were used for histopathological examination or immunofluorescence staining for CD68 (pan-macrophage marker), Arginase-1 (Arg1, M2-specific marker), inducible nitric oxide synthase (iNOS, M1-specific marker) and HIF-1α. VEGF and γH2AX expression in lung tissues were detected by western blot.

KEY FINDINGS

The results demonstrated that 2ME2 improved the survival, lung functions and histopathological parameters of irradiated mice. Additionally, it attenuated the radiation-induced AM polarization and reduced the pneumonitis and fibrosis markers in lung tissues. Significant reduction of TNF-α and TGF-β with concomitant increase in IL-10 concentrations were observed. Moreover, the expression of HIF-1α, VEGF and γH2AX declined.

SIGNIFICANCE

2ME2 is a promising radioprotectant with fewer anticipated side effects.

Wee1 kinase inhibitor AZD1775 potentiates CD8+ T cell-dependent antitumour activity via dendritic cell activation following a single high dose of irradiation

As standard treatments for cancer, DNA-damaging chemotherapeutic agents and irradiation therapy improve survival in patients with various cancers. Wee1, a kinase associated with the cell cycle, causes G2/M cell cycle arrest to allow repair of injured DNA in cancer cells, and a Wee1 inhibitor has been confirmed to lead to apoptosis in cancer cells. Recently, there has been renewed interest in exploring the immune environment which plays a significant role in tumour suppression. A Wee1 inhibitor combined with radiotherapy has been tested in lung, pancreatic, and prostate cancer and melanoma in vivo or in vitro. There is still no research evaluating the immunoregulatory effects of AZD1775 plus high-dose irradiation (IR) in vivo. T cell killing and CD8+ T cell depletion assays demonstrated that the combination of AZD1775 and IR delayed tumour growth in breast cancer mouse models. Additionally, combination treatment also suppressed the expression of PD-L1, a co-inhibitor, through the STAT3-IRF1 axis. The importance and originality of this study are that it explores the internal and external mechanisms of AZD1775 combined with a single high dose of IR and provides a rationale for applying the combination therapy described above in a clinical trial.

Radiotherapy-immunotherapy combinations - perspectives and challenges

Ionizing radiation has historically been used to treat cancer by killing tumour cells, in particular by inducing DNA damage. This view of radiotherapy (RT) as a simple cytotoxic agent has dramatically changed in recent years, and it is now widely accepted that RT can deeply reshape the tumour environment by modulating the immune response. Such evidence gives a strong rationale for the use of immunomodulators to boost the therapeutic value of RT, introducing the era of ‘immunoradiotherapy’. The increasing amount of preclinical and clinical data concerning the combination of RT with immunomodulators, in particular with immune checkpoint inhibitors such as anti‐PD‐1/PD‐L1 and anti‐CTLA4, reflects the interest of the scientific and medical community concerning immunoradiotherapy. The expectations are enormous since the rationale for performing such combinations is strong, with the possibility to use a local treatment such as RT to amplify a systemic antitumour response, as illustrated by the case of the abscopal effect. Nevertheless, several points remain to be addressed such as the need to find biomarkers to identify patients who will benefit from immunoradiotherapy, the identification of the best sequences/schedules for combination with immunomodulators and mechanisms to overcome resistance. Additionally, the effects of immunoradiotherapy on healthy tissues and related toxicity remain largely unexplored. To answer these critical questions and make immunoradiotherapy keep its promising qualities, large efforts are needed from both the pharmaceutical industry and academic/governmental research. Moreover, because of the work of both these entities, the arsenal of available immunomodulators is quickly expanding, thus opening the field to increasing combinations with RT. We thus forecast that the field of immunoradiotherapy will further expand in the coming years, and it needs to be supported by appropriate investment plans.

The Role of NLRP3 Inflammasome in Radiation-Induced Cardiovascular Injury

The increasing risk of long-term adverse effects from radiotherapy on the cardiovascular structure is receiving increasing attention. However, the mechanisms underlying this increased risk remain poorly understood. Recently, the nucleotide-binding domain and leucine-rich-repeat-containing family pyrin 3 (NLRP3) inflammasome was suggested to play a critical role in radiation-induced cardiovascular injury. However, the relationship between ionizing radiation and the NLRP3 inflammasome in acute and chronic inflammation is complex. We reviewed literature detailing pathological changes and molecular mechanisms associated with radiation-induced damage to the cardiovascular structure, with a specific focus on NLRP3 inflammasome-related cardiovascular diseases. We also summarized possible therapeutic strategies for the prevention of radiation-induced heart disease (RIHD).

CDX-301: a novel medical countermeasure for hematopoietic acute radiation syndrome in mice

Bone marrow failure and hematopoietic damage is one of the major consequences of irradiation-induced lethality. There is an immediate need to develop medical countermeasures (MCMs) to combat irradiation-induced lethality. We tested the efficacy of CDX-301, developed by Celldex Therapeutics Inc., in mice exposed to Co-60 gamma total body irradiation (TBI). The drug demonstrated its efficacy both as a prophylactic countermeasure and a mitigator in CD2F1 mice exposed to TBI. A single dose of CDX-301 administered 24 h prior to 24 h post–exposure conferred significant survival. Accelerated recovery from irradiation-induced peripheral blood cytopenia, bone marrow damage as well as apoptosis in sternum was observed in mice pre-treated with CDX-301. Analysis of splenocytes revealed alterations in T cell profiles that were dependent on the time of drug administration. Prophylactic treatment of CDX-301 resulted in increased splenic CD3+ T cells, specifically CD4+T helper cells, compared to splenocytes from non-irradiated mice. These results indicate that CDX-301 is a promising radiation countermeasure and demonstrate its capability to protect cells within hematopoietic organs. These data support potential use of CDX-301, both pre- and post-radiation, against hematopoietic acute radiation syndrome with a broad window for medical management in a radiological or nuclear event.

Inhibition of AIM2 inflammasome-mediated pyroptosis by Andrographolide contributes to amelioration of radiation-induced lung inflammation and fibrosis

Radiation-induced lung injury (RILI) is one of the most common and fatal complications of thoracic radiotherapy, whereas no effective interventions are available. Andrographolide, an active component extracted from Andrographis paniculate, is prescribed as a treatment for upper respiratory tract infection. Here we report the potential radioprotective effect and mechanism of Andrographolide on RILI. C57BL/6 mice were exposed to 18 Gy of whole thorax irradiation, followed by intraperitoneal injection of Andrographolide every other day for 4 weeks. Andrographolide significantly ameliorated radiation-induced lung tissue damage, inflammatory cell infiltration, and pro-inflammatory cytokine release in the early phase and progressive fibrosis in the late phase. Moreover, Andrographolide markedly hampered radiation-induced activation of the AIM2 inflammasome and pyroptosis in vivo. Furthermore, bone marrow-derived macrophages (BMDMs) were exposed to 8 Gy of X-ray radiation in vitro and Andrographolide significantly inhibited AIM2 inflammasome mediated-pyroptosis in BMDMs. Mechanistically, Andrographolide effectively prevented AIM2 from translocating into the nucleus to sense DNA damage induced by radiation or chemotherapeutic agents in BMDMs. Taken together, Andrographolide ameliorates RILI by suppressing AIM2 inflammasome mediated-pyroptosis in macrophage, identifying Andrographolide as a novel potential protective agent for RILI.