Glucocorticoid-Mediated Modulation of Eosinopoiesis in Asthma: A Paradoxical Duality

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Authors provide a review focused on the molecular and cellular mechanisms underlying GC-induced eosinopoiesis, its functional link to airway inflammation, and its clinical implications for asthma management. They also explore potential therapeutic strategies aimed at selectively modulating bone marrow eosinophil output without compromising the peripheral anti-inflammatory benefits of GCs. The vast majority of observations concernig this effect of GCs have been made in animal (murine) models ans it is not clear which coud be benefits of blocking bone marrow eosinophil output in diseases, such as asthma, characterized by tissue eosinophils infiltration, activation and survival. Authors do not provide any data showing a beneficial effect of blocking bone marrow output of eosinophils in mice models of allergic asthma.

The following points need to be addressed in a revised version of the manuscript.

1-Introduction Lines 37-38 Reduction in airway eosinophilia, and promotion of apoptosis among infiltrating eosinophils are not aspect of asthma, but they are consequence of glucorticoid therapy ! Please change the sentence accordingly.

2-Lines 49-51 Authors should report if the reported observations are referred to animal or human models

3-Lines 121-2 In asthmatic patients consistently show that GC therapy restores normal  rates of eosinophil apoptosis. GC actually increase eosinophil apoptosis.

4-Lines 142 Theophylline and macrolides are not commonly used as therapy of asthma

5-Lines 169-176 Authors should report that the capacity of GCs to enhance eosinophil production in the bone marrow in allergen exposure has been observed in a murine model.

6-Lines 187-9 Authors should recognize that most of infections in humans cause eosinopenia

7-Lines 255-8 The pharmacological inhibition of STAT5 signaling partially abrogates the GC-enhanced eosinopoietic response, further confirming its functional relevance. These findings  position STAT5 as a potential molecular target for future therapeutic strategies aiming to  uncouple the anti-inflammatory benefits of GCs from their eosinopoietic side effects. The sentence does not contain any reference. STAT-5 inhibitor are presently investigated as therapy for leukemias.

8-Lines 259-269 The link between GCs and autophagy is confusing and need to be rephrased

9-Paragraph 5. The Bone Marrow Microenvironment and External Modulators of GC-Induced Eosinopoiesis. Most of the reported observations have been shown in murine models.

10-Lines 405-410 It is not clear why the increased bone marrow eosinopoiesis, promoted by GCs, should furtherly increase following withdrawal fo GCs therapy.

11-Lines 427-442 no data about increased levels of eosinophils progenitors in patients with asthma have been reported

12-Lines 469 Blocking bone marrow output by STAT-5 inhibitor is currently evaluatd for leukemias treatment. The problem in asthma is the eosinophils homing into the airways and their tissue survival and activation.

13-Conclusion. I think that the translational potential of blocking the effects of GCs on eosinopoiesis is not clear, as far as it concerns the benefits of this strategy.

Author Response

I sincerely thank the reviewer for their valuable contributions, which have undoubtedly improved the quality and clarity of this review. I carefully considered all comments and suggestions, implementing the corresponding modifications in the manuscript. All changes are highlighted in blue within the revised text for ease of reference.
Authors provide a review focused on the molecular and cellular mechanisms underlying GC-induced eosinopoiesis, its functional link to airway inflammation, and its clinical implications for asthma management. They also explore potential therapeutic strategies aimed at selectively modulating bone marrow eosinophil output without compromising the peripheral anti-inflammatory benefits of GCs. The vast majority of observations concernig this effect of GCs have been made in animal (murine) models ans it is not clear which coud be benefits of blocking bone marrow eosinophil output in diseases, such as asthma, characterized by tissue eosinophils infiltration, activation and survival. Authors do not provide any data showing a beneficial effect of blocking bone marrow output of eosinophils in mice models of allergic asthma.
Answer: I appreciate the reviewer’s insightful comment and agree that most mechanistic data regarding GC-induced eosinopoiesis are derived from murine models. I also acknowledge that direct experimental evidence demonstrating a therapeutic benefit of selectively blocking bone marrow eosinophil output in allergic asthma is lacking. My goal in this review was not to present this approach as an established therapeutic intervention but rather to highlight a potentially relevant immunoendocrine mechanism and to discuss its possible translational implications.
I have revised the clinical and translational Implications section to more clearly state that:
1.    The mechanistic framework for GC-induced eosinopoiesis is predominantly supported by murine data;
2.    Experimental manipulation of eosinophil output may produce divergent outcomes, as illustrated by Zhang et al. (2018), who showed that blocking eosinophil-derived CCL-6 exacerbated airway inflammation in a murine asthma model, underscoring the need for cautious interpretation of potential benefits;
3.    While preclinical studies suggest that bone marrow regulation significantly influences tissue eosinophil profiles, the net clinical impact of restricting eosinophil output in asthma—particularly in patients already receiving GCs—remains unproven and must be determined in future translational and clinical studies;
4.    Any therapeutic approach aiming to reduce eosinopoiesis must also consider the broader roles of eosinophils in tissue homeostasis and immune regulation, as systemic depletion could have unintended effects.
I believe these additions directly address the reviewer’s concerns by acknowledging the current evidence gap, integrating both supportive and cautionary preclinical findings, and reframing this concept as a hypothesis-generating avenue rather than a validated treatment strategy.

The following points need to be addressed in a revised version of the manuscript.

1-Introduction Lines 37-38 Reduction in airway eosinophilia, and promotion of apoptosis among infiltrating eosinophils are not aspect of asthma, but they are consequence of glucorticoid therapy ! Please change the sentence accordingly.
Answer: I thank the reviewer for this important observation. I agree that the reduction in airway eosinophilia and the induction of apoptosis among infiltrating eosinophils are not intrinsic features of asthma, but rather consequences of glucocorticoid therapy. I have modified the sentence in the Introduction (lines 37–38) to accurately reflect this distinction.

2-Lines 49-51 Authors should report if the reported observations are referred to animal or human models
Answer: I appreciate the reviewer’s suggestion. I have revised the text in lines 49–51 to explicitly state whether the observations refer to animal models.

3-Lines 121-2 In asthmatic patients consistently show that GC therapy restores normal  rates of eosinophil apoptosis. GC actually increase eosinophil apoptosis.
Answer: I thank the reviewer for this clarification. I agree that glucocorticoid therapy in asthmatic patients does not merely restore baseline rates of eosinophil apoptosis, but actively increases apoptosis of these cells. I have revised the sentence.

4-Lines 142 Theophylline and macrolides are not commonly used as therapy of asthma
Answer: I appreciate the reviewer’s observation. I agree that theophylline and macrolides are not currently considered standard or commonly used therapies for asthma. I have revised the sentence.

5-Lines 169-176 Authors should report that the capacity of GCs to enhance eosinophil production in the bone marrow in allergen exposure has been observed in a murine model.
Answer: I thank the reviewer for this important clarification. I have revised the text to explicitly indicate that the evidence showing glucocorticoids can enhance eosinophil production in the bone marrow during allergen exposure comes from murine models.

6-Lines 187-9 Authors should recognize that most of infections in humans cause eosinopenia
Answer: I appreciate the reviewer’s observation. I have now incorporated a clarification in the manuscript acknowledging that most infections in humans are indeed associated with eosinopenia, which is commonly attributed to stress-induced endogenous glucocorticoid release and eosinophil redistribution to tissues.

7-Lines 255-8 The pharmacological inhibition of STAT5 signaling partially abrogates the GC-enhanced eosinopoietic response, further confirming its functional relevance. These findings  position STAT5 as a potential molecular target for future therapeutic strategies aiming to  uncouple the anti-inflammatory benefits of GCs from their eosinopoietic side effects. The sentence does not contain any reference. STAT-5 inhibitor are presently investigated as therapy for leukemias.
Answer: Thank you for pointing this out. I have now added appropriate references to support the statement regarding the role of STAT5 in GC-enhanced eosinopoiesis and the current investigation of STAT5 inhibitors as therapeutic agents in leukemias. 

8-Lines 259-269 The link between GCs and autophagy is confusing and need to be rephrased
Answer: I appreciate the reviewer’s feedback. I have rephrased this section to improve clarity and to clearly outline the mechanistic relationship between glucocorticoids and autophagy in the context of eosinopoiesis.

9-Paragraph 5. The Bone Marrow Microenvironment and External Modulators of GC-Induced Eosinopoiesis. Most of the reported observations have been shown in murine models.
Answer: I thank the reviewer for this important remark. I have now revised the section to clearly state that the majority of the findings described in this paragraph derive from murine experimental models, and to distinguish them from the limited data available in humans. 

10-Lines 405-410 It is not clear why the increased bone marrow eosinopoiesis, promoted by GCs, should furtherly increase following withdrawal fo GCs therapy.
Answer: I appreciate the reviewer’s observation and agree that this point required clarification. I have now rephrased the section to provide a clearer mechanistic explanation. 

11-Lines 427-442 no data about increased levels of eosinophils progenitors in patients with asthma have been reported
Answer: I appreciate the reviewer’s observation. I agree that this point required clarification. Data do exist showing the presence of eosinophil progenitors in the peripheral blood of patients with asthma. This information has now been clarified in the text, where I cite studies reporting circulating eosinophil progenitors in asthmatic patients.

12-Lines 469 Blocking bone marrow output by STAT-5 inhibitor is currently evaluatd for leukemias treatment. The problem in asthma is the eosinophils homing into the airways and their tissue survival and activation.
Answer: I agree with the reviewer. In this section, STAT5 is discussed in the context of eosinophil production. The issue of eosinophil mobilization and homing to the airways is addressed subsequently. Although the major pathogenic problem in asthma is indeed the migration of eosinophils to the lungs, bone marrow production is also relevant, and reducing production can contribute to decreasing eosinophil homing.

13-Conclusion. I think that the translational potential of blocking the effects of GCs on eosinopoiesis is not clear, as far as it concerns the benefits of this strategy.
Answer: I appreciate the reviewer’s observation. I have now revised the conclusion to better contextualize the translational implications of blocking GC-induced eosinopoiesis. The revised text acknowledges that the clinical benefits of this approach remain to be demonstrated, particularly in human asthma, and that most current evidence is derived from animal models. I also clarify that any potential therapeutic strategy should be carefully evaluated to ensure that modulation of bone marrow eosinophil output does not compromise the well-established anti-inflammatory benefits of GCs in peripheral tissues.

Reviewer 2 Report

Comments and Suggestions for Authors

The review "Glucocorticoid-Mediated Modulation of Eosinopoiesis in Asthma: A Paradoxical Duality" by Bruno Marques Vieira offers a comprehensive and well-structured overview of the molecular and cellular mechanisms underlying glucocorticoid (GC)-induced eosinopoiesis, its connection to airway inflammation, and the clinical implications for asthma management. While the review is clearly written and well organized, several areas could be improved or expanded to enhance its scientific depth and translational value.

1. Paragraph 2:
The authors may consider outlining the full sequence of eosinophil granulopoiesis, detailing the progression from myeloblast to promyelocyte, myelocyte, and metamyelocyte stages. A description of the key transcriptional programs and gene expression changes (i.e., activated and repressed genes) associated with each stage would provide a more comprehensive understanding of the differentiation process.

2. Line 391:
Given the mention of promoter usage and chromatin remodeling in the regulation of IL5RA, is there emerging evidence that GCs influence eosinopoiesis through epigenetic reprogramming of progenitor cells? If so, this aspect could be briefly discussed or cited.

3. Line 449:
The distinction between E1 and E2 eosinophil subsets is compelling. Could the author clarify whether GCs preferentially expand or suppress one of these subsets (e.g., inflammatory vs. homeostatic eosinophils)? This could have important implications for understanding disease phenotypes and treatment responses.

4. Progenitor Markers in Clinical Practice:
Would the author consider proposing a practical clinical algorithm that integrates eosinophil progenitor markers—such as CD34⁺/IL-5Rα⁺—into asthma management? For instance, if one wished to evaluate eosinophils in the sputum of glucocorticoid-treated patients, what would be the most informative surface markers to assess eosinopoietic activity or GC responsiveness?

5. Table Suggestion for Paragraph 7:
To enhance clarity and accessibility, the author could consider summarizing the key clinical and translational implications presented in paragraph 7 in the form of a table. This could help consolidate concepts such as biomarkers, risk stratification strategies, therapeutic targets, and monitoring tools.

Author Response

I sincerely thank the reviewer for their valuable contributions, which have undoubtedly improved the quality and clarity of this review. I carefully considered all comments and suggestions, implementing the corresponding modifications in the manuscript. All changes are highlighted in blue within the revised text for ease of reference.
The review "Glucocorticoid-Mediated Modulation of Eosinopoiesis in Asthma: A Paradoxical Duality" by Bruno Marques Vieira offers a comprehensive and well-structured overview of the molecular and cellular mechanisms underlying glucocorticoid (GC)-induced eosinopoiesis, its connection to airway inflammation, and the clinical implications for asthma management. While the review is clearly written and well organized, several areas could be improved or expanded to enhance its scientific depth and translational value.
1. Paragraph 2:
The authors may consider outlining the full sequence of eosinophil granulopoiesis, detailing the progression from myeloblast to promyelocyte, myelocyte, and metamyelocyte stages. A description of the key transcriptional programs and gene expression changes (i.e., activated and repressed genes) associated with each stage would provide a more comprehensive understanding of the differentiation process.
Answer: We thank the reviewer for this valuable suggestion. In the revised manuscript, we have added a dedicated paragraph providing a detailed description of the sequential stages of eosinophil development—from myeloblast to promyelocyte, myelocyte, and metamyelocyte—highlighting the key transcription factors involved, the activation and repression of specific gene programs, and the stage-specific expression of lineage markers. We have also included relevant references and indicated additional sources containing representative figures that illustrate the process.

2. Line 391:
Given the mention of promoter usage and chromatin remodeling in the regulation of IL5RA, is there emerging evidence that GCs influence eosinopoiesis through epigenetic reprogramming of progenitor cells? If so, this aspect could be briefly discussed or cited.
Answer: I thank the reviewer for this valuable suggestion. I have now incorporated a discussion addressing the potential role of epigenetic reprogramming in modulating eosinophil responses to GCs, considering differences across maturation stages. As described in the revised manuscript, evidence indicates that eosinophil sensitivity to GC-induced apoptosis varies according to their activation and maturation status, with IL-5–primed eosinophils exhibiting reduced pro-apoptotic responses and less activated or immature cells being more susceptible. In humans, GC exposure regulates transcriptional programs related to apoptosis, migration, and receptor signaling, but these responses vary with activation context. Although direct studies in eosinophils are lacking, findings in other cell type (B cells) demonstrate that epigenetic changes occur during maturation and influence responsiveness to external stimuli. 

3. Line 449:
The distinction between E1 and E2 eosinophil subsets is compelling. Could the author clarify whether GCs preferentially expand or suppress one of these subsets (e.g., inflammatory vs. homeostatic eosinophils)? This could have important implications for understanding disease phenotypes and treatment responses.
Answer: I thank the reviewer for raising this important point. Current research does not provide strong evidence that GCs directly induce a specific eosinophil phenotype. As noted in the revised manuscript, GCs can upregulate certain surface proteins, which may modulate eosinophil activation and cytokine secretion. However, this does not correspond to a definitive shift between E1/E2 or inflammatory/resident phenotypes. At present, the potential for GCs to selectively expand, suppress, or reprogram these subsets remains an open question that warrants further investigation.

4. Progenitor Markers in Clinical Practice:
Would the author consider proposing a practical clinical algorithm that integrates eosinophil progenitor markers—such as CD34⁺/IL-5Rα⁺—into asthma management? For instance, if one wished to evaluate eosinophils in the sputum of glucocorticoid-treated patients, what would be the most informative surface markers to assess eosinopoietic activity or GC responsiveness?
Answer: I thank the reviewer for this very interesting suggestion. Developing a practical clinical algorithm integrating eosinophil progenitor markers into asthma management goes beyond the scope of this review. While I agree that such an approach holds potential clinical relevance, integrating these markers into a decision-making framework would require validation in prospective studies. My primary aim in this review is to shed light on an underexplored topic that may have important clinical implications. Throughout the manuscript, I have cited studies reporting markers expressed by eosinophils at different stages of differentiation, so that clinicians interested in this area can consult these references to further explore the dynamics and potential applications of these markers.

5. Table Suggestion for Paragraph 7:
To enhance clarity and accessibility, the author could consider summarizing the key clinical and translational implications presented in paragraph 7 in the form of a table. This could help consolidate concepts such as biomarkers, risk stratification strategies, therapeutic targets, and monitoring tools.
Answer: I thank the reviewer for this valuable suggestion. I agree that summarizing the key clinical and translational implications could improve clarity and accessibility. Following this recommendation, I have incorporated a new table entitled "Summary of Key Clinical and Translational Considerations in GC-Induced Eosinopoiesis", which consolidates the main points discussed in paragraph 7, including relevant biomarkers, potential risk stratification strategies, therapeutic targets, and monitoring approaches. While my intention with this review was not to provide a prescriptive clinical algorithm, I believe this addition will help readers integrate these concepts into their own research or clinical reasoning.

Reviewer 3 Report

Comments and Suggestions for Authors

General comments:

This is a very thorough review covering an intriguing subject of paradoxical contrary influence of GCS on eosinopoiesis in the bone marrow and in peripheral tissues.

The introduction provides all information which may be required to familiarize the reader with the subject and justification for tackling on this topic is convincingly provided.

Bidirectional and different influence of GCS on eosinopoiesis is broadly covered. It is, however, puzzling and intriguing, that most references included in the review do not seem to be the recent ones and they’re mainly reflecting animal or experimental studies. It looks like the subject of dual influence of GCS on eosinophilia has not been stirring much clinical interest over last years. Interestingly, the authors put forward some suppositions and indicate possible strategies for clinical research which is interesting and inspiring. PLase clarify, however, if there are no more recent experimental or clinical data on the topic. This would render the review more credible, up-to-date and appealing.

Major issues:

Several data from clinical studies are briefly mentioned. They are really interesting and may highlight the directions for future research but do not seem to be clearly referenced. These examples include:

Lines 408 through 410 : “This phenomenon may underlie the clinical observation that some patients experience exacerbations shortly after tapering corticosteroid therapy, despite achieving prior control.”

Lines 425 through 431, a paragraph starting with: „A growing body of evidence………….”

Lines 432 through 437 – the whole paragraph (as above , interesting data but not referenced)

Minor issues:

In this type pf the review, I’d suggest to rephrase/rename subsections 8 and 9 to highlight the fact that they contain „research gaps” and „Future research directions”, as it is often seen in reviews aiming at drawing attention to the interesting and/or emerging, yet not elucidated topic.

Author Response

I sincerely thank the reviewer for their valuable contributions, which have undoubtedly improved the quality and clarity of this review. I carefully considered all comments and suggestions, implementing the corresponding modifications in the manuscript. All changes are highlighted in blue within the revised text for ease of reference.

This is a very thorough review covering an intriguing subject of paradoxical contrary influence of GCS on eosinopoiesis in the bone marrow and in peripheral tissues.

The introduction provides all information which may be required to familiarize the reader with the subject and justification for tackling on this topic is convincingly provided.

Bidirectional and different influence of GCS on eosinopoiesis is broadly covered. It is, however, puzzling and intriguing, that most references included in the review do not seem to be the recent ones and they’re mainly reflecting animal or experimental studies. It looks like the subject of dual influence of GCS on eosinophilia has not been stirring much clinical interest over last years. Interestingly, the authors put forward some suppositions and indicate possible strategies for clinical research which is interesting and inspiring. PLase clarify, however, if there are no more recent experimental or clinical data on the topic. This would render the review more credible, up-to-date and appealing.

Answer: I thank the reviewer for this pertinent comment. In preparing the revised version, I have incorporated a substantial number of new and updated references. However, it is important to note that research specifically addressing human eosinopoiesis remains scarce, largely due to the inherent challenges in obtaining human bone marrow samples and the technical difficulties associated with their culture. Consequently, most of the available evidence still derives from murine models. Recently, a few studies have sought to explore eosinopoiesis in humans, and these have been included in the present review; however, they remain limited in number. One of my goals with this work is precisely to stimulate the scientific community to further investigate human eosinopoiesis, particularly given the growing interest and expanding discussions on eosinophils in recent years.

 

Major issues:

Several data from clinical studies are briefly mentioned. They are really interesting and may highlight the directions for future research but do not seem to be clearly referenced. These examples include:

Lines 408 through 410 : “This phenomenon may underlie the clinical observation that some patients experience exacerbations shortly after tapering corticosteroid therapy, despite achieving prior control.”

Lines 425 through 431, a paragraph starting with: „A growing body of evidence………….”

Lines 432 through 437 – the whole paragraph (as above , interesting data but not referenced)

Answer: I thank the reviewer for pointing this out. I have now reviewed all the mentioned sections (Lines 408–410, 425–431, and 432–437) and added the appropriate references to support each of the statements. These citations include recent and relevant literature, ensuring that the clinical observations and experimental findings discussed are properly substantiated and clearly traceable to their original sources.

Minor issues:

In this type pf the review, I’d suggest to rephrase/rename subsections 8 and 9 to highlight the fact that they contain „research gaps” and „Future research directions”, as it is often seen in reviews aiming at drawing attention to the interesting and/or emerging, yet not elucidated topic.

Answer: I thank the reviewer for this constructive suggestion. I have now rephrased the subsection titles to clearly convey their focus: subsection 8 is now titled “Research Gaps in Glucocorticoid–Eosinopoiesis Interactions”, and subsection 9 is now titled “Future Research Directions”. These revised titles more explicitly highlight that these sections address areas where evidence is lacking and where further investigation could yield significant advances, aligning with the structure often seen in reviews that aim to encourage research in emerging topics.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The revised version of the manuscript is much improved and it addresses most of the relevant critical points.

Reviewer 2 Report

Comments and Suggestions for Authors

The authors significantly improved their manuscript, and it is now suitable for publication in Allergies.

Reviewer 3 Report

Comments and Suggestions for Authors

My remarks have been addressed accorodingly and relevant feedback has been provided by the Author. The manuscript is comprehensive and clearly described the scientific problem, highlighting knowledge gaps and shaling future possible research paths.

I have no more remarks on my behalf.