Heme oxygenase-1 inhibits basophil maturation and activation but promotes its apoptosis in T helper type 2-mediated allergic airway inflammation

The Pharmacological Effect of Hemin in Inflammatory-Related Diseases: A Systematic Review

BACKGROUND

Hemin is clinically used in acute attacks of porphyria; however, recent evidence has also highlighted its capability to stimulate the heme oxygenase enzyme, being associated with cytoprotective, antioxidant, and anti-inflammatory effects. Indeed, current preclinical evidence emphasizes the potential anti-inflammatory role of hemin through its use in animal models of disease. Nevertheless, there is no consensus about the underlying mechanism(s) and the most optimal therapeutic regimens. Therefore, this review aims to summarize, analyze, and discuss the current preclinical evidence concerning the pharmacological effect of hemin.

METHODS

Following the application of the search expression and the retrieval of the articles, only nonclinical studies in vivo written in English were considered, where the potential anti-inflammatory effect of hemin was evaluated.

RESULTS

Forty-nine articles were included according to the eligibility criteria established. The results obtained show the preference of using 30 to 50 mg/kg of hemin, administered intraperitoneally, in both acute and chronic contexts. This drug demonstrates significant anti-inflammatory and antioxidant activities considering its capacity for reducing the expression of proinflammatory and oxidative markers.

CONCLUSIONS

This review highlighted the significant anti-inflammatory and antioxidant effects of hemin, providing a clearer vision for the medical community about the use of this drug in several human diseases.

Regional variations in allergen-induced airway inflammation correspond to changes in soluble guanylyl cyclase heme and expression of heme oxygenase-1

Asthma is characterized by airway remodeling and hyperreactivity. Our earlier studies determined that the nitric oxide (NO)-soluble guanylyl cyclase (sGC)-cGMP pathway plays a significant role in human lung bronchodilation. However, this bronchodilation is dysfunctional in asthma due to high NO levels, which cause sGC to become heme-free and desensitized to its natural activator, NO. In order to determine how asthma impacts the various lung segments/lobes, we mapped the inflammatory regions of lungs to determine whether such regions coincided with molecular signatures of sGC dysfunction. We demonstrate using murine models of asthma (OVA and CFA/HDM) that the inflamed segments of these murine lungs can be tracked by upregulated expression of HO1 and these regions in turn overlap with regions of heme-free sGC as evidenced by a decreased sGC-α1β1 heterodimer and an increased response to heme-independent sGC activator, BAY 60-2770, relative to naïve uninflamed regions. We also find that NO generated from iNOS upregulation in the inflamed segments has a higher impact on developing heme-free sGC as increasing iNOS activity correlates linearly with elevated heme-independent sGC activation. This excess NO works by affecting the epithelial lung hemoglobin (Hb) to become heme-free in asthma, thereby causing the Hb to lose its NO scavenging function and exposing the underlying smooth muscle sGC to excess NO, which in turn becomes heme-free. Recognition of these specific lung segments enhances our understanding of the inflamed lungs in asthma with the ultimate aim to evaluate potential therapies and suggest that regional and not global inflammation impacts lung function in asthma.

The Pharmacological Effect of Hemin in Inflammatory-Related Diseases: Protocol for a Systematic Review

BACKGROUND

Hemin is a commonly used drug in the treatment of acute attacks of porphyria, due to its capability of restoring normal levels of hemoproteins and respiratory pigments. In addition, this drug has demonstrated the capacity to induce the heme oxygenase (HO) enzyme. At the moment, there are 3 known HO isoenzymes in mammals: HO-1, HO-2, and HO-3. The first of these shows cytoprotective, antioxidant, and anti-inflammatory effects. Currently, medicines used in inflammatory disorders have increased toxicity, especially over longer time frames, which highlights the need to investigate new, safer options. Indeed, the current nonclinical evidence demonstrates the potential that hemin has a significant anti-inflammatory effect in several animal models of inflammation-related diseases, such as experimental colitis, without significant side effects. However, the underlying mechanism(s) are still not fully understood. In addition, past nonclinical studies have applied different therapeutic regimens, making it relatively difficult to understand which is optimal. According to the literature, there is a lack of review articles discussing this topic, highlighting the need for a summary and analysis of the available preclinical evidence to elucidate the abovementioned issues. Therefore, a qualitative synthesis of the current evidence is essential for the research and medical communities.

OBJECTIVE

This systematic review aims to summarize and analyze currently available nonclinical data to ascertain the potential anti-inflammatory effect of hemin in animal models.

METHODS

Throughout the development of this protocol, we followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol. The comprehensive search strategy will be carried out in MEDLINE (PubMed), Web of Science, and Scopus without any filters associated with publication date. Only in vivo, nonclinical studies that evaluated the potential anti-inflammatory effect of hemin will be included. The evaluated outcomes will be the observed clinical signs, inflammatory and other biochemical markers, and macroscopic and microscopic evaluations. To analyze the potential risk of bias, we will use the risk of bias tool developed by the Systematic Review Centre for Laboratory Animal Experimentation (SYRCLE).

RESULTS

Currently, it is not possible to disclose any results since the project is still in initial steps. More specifically, we are currently engaged in the identification of eligible articles through the application of the inclusion and exclusion criteria. The work was initiated in April 2023, and it is expected to be finished at the end of 2023.

CONCLUSIONS

Concerning the major gap in the literature regarding the underlying mechanism(s) and treatment-related properties, this systematic review will be essential to clearly summarize and critically analyze the nonclinical data available, promoting a clearer vision of the potential anti-inflammatory effect of hemin.

TRIAL REGISTRATION

PROSPERO CRD42023406160; https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=406160.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

PRR1-10.2196/48368.

Immune Regulation of Heme Oxygenase-1 in Allergic Airway Inflammation

Heme oxygenase-1 (HO-1) is not only a rate-limiting enzyme in heme metabolism but is also regarded as a protective protein with an immunoregulation role in asthmatic airway inflammation. HO-1 exerts an anti-inflammation role in different stages of airway inflammation via regulating various immune cells, such as dendritic cells, mast cells, basophils, T cells, and macrophages. In addition, the immunoregulation role of HO-1 may differ according to subcellular locations.

Heme oxygenase-1 (HO-1) assists inorganic arsenic-induced immune tolerance in murine dendritic cells

Inorganic arsenic, a well-known human carcinogen, poses a major threat to global health. Given the immunosuppressive potentials of inorganic arsenic as well as limited understanding of this metalloid on antigen-presenting dendritic cells (DCs), we systematically screened the immune targets in response to arsenic treatment, as well as its possible molecular mechanism in cultured murine DCs. Our results denoted that arsenite (As) significantly induced immune tolerance by down-regulating the expression of phenotypic molecules, pro-inflammatory factors and T-lymphocyte helper (Th)1/Th17-inducible cytokines in lipopolysaccharides (LPS)-stimulated myeloid-derived dendritic cells (BMDCs). Inconsistent with dampened phosphorylation of immune-related proteins (nuclear factor kappa-B) NF-κB, p38 and JNK, the metalloid drastically induced the expression of Heme oxygenase-1 (HO-1) protein, which enlightened us to continuously explore the possible roles of HO-1 pathway in As-induced immune tolerance in BMDCs. In this respect, immunosuppressive properties of HO-1 pathway in BMDCs were firstly confirmed through pharmacological overexpression of HO-1 by both CoPP and CORM-2. By contrast, limited HO-1 expression by HO-1 inhibitor ZnPP specifically alleviated As-mediated down-regulation of CD80, chemokine factor C-C chemokine receptor 7 (CCR7), tumor necrosis factor (TNF) -α, Interleukin (IL)-23 and IL-6, which reminds us the peculiarity of HO-1 in As-induced immune tolerance in murine DCs. Based on these experimental findings, we postulated the immunosuppressive property of inorganic arsenic might be mediated partially by HO-1 in DCs, thus contributing to the interactions of DCs-polarized differentiation of T-lymphocyte subtype as well as the development of infections and malignant diseases.

Utility of basophil activation test for predicting the outcome of wheezing in children: a pilot study

BACKGROUND

No reliable biological marker for the diagnosis of asthma in younger children is currently available. In this study, we analyzed the differences in basophil activation test (BAT) results among children with recurrent wheezing episodes who had different asthma outcomes.

RESULTS

A prospective cohort study was conducted in children aged under 5 years who visited our pediatric respiratory clinic and ward for wheezing. After enrollment, the participants provided samples for a CD63-based BAT performed using an inhalant allergen mixture as a stimulant. Histories of personal allergic diseases and family allergic diseases were evaluated by using a questionnaire. All participants were followed up for 2 years, and their asthma outcomes were evaluated at the end of the follow-up period. The correlation between the BAT results and asthma outcomes was analyzed. Of the 45 originally enrolled children, 38 completed both the follow-up and a BAT. After stimulation with the inhalant mixture, the CD63 expression on basophils and the rate of positive CD63-based BAT results in children diagnosed with asthma were both significantly higher than those in children who were not diagnosed with asthma (p < 0.05 and p < 0.01, respectively). For the prediction of asthma, the positive predictive value and negative predictive value of CD63-based BAT was 71.8 and 69.2%, respectively. The positive likelihood ratio and negative likelihood ratio of CD63-based BAT were 1.70 and 0.3, respectively.

CONCLUSIONS

Our pilot study indicates that CD63-based BAT has potential clinical value for predicting asthma outcome in young children with wheezing episodes.

Inhibition of lipopolysaccharide-induced inflammation via the protective role of T regulatory cells in the fetal liver in a late-pregnancy preterm mouse model

OBJECTIVES

This study intended to explore the effect of T regulatory cells (Tregs) in the perinatal liver against LPS-induced inflammation in a preterm birth mouse model. Moreover, the role of adoptive Tregs on the inflammatory response induced by LPS was also studied.

METHODS

Female BALB/C mice were injected intraperitoneally (IP) with LPS dissolved in normal saline solution at a dose of 50 µg/kg. Spleens from pregnant mice were used to obtain Tregs. The expression of Forkhead family transcription factor-3 (Foxp3), Interleukin-6 (IL-6), Toll-like receptor-4 (TLR-4), and Heme oxygenase-1 (HO-1) were assessed from fetal liver tissues by polymerase chain reaction and western blotting.

RESULTS

LPS administered to mice induced an inflammatory response in the perinatal liver, and this inflammatory response was negatively regulated by Tregs in the experimental group. Maternal-fetal tolerance was maintained by Tregs. Transmission of Tregs was estimated in different experimental groups based on the mRNA expression of TLR-4, IL-6, HO-1, and Foxp3.

CONCLUSIONS

After analysis of the experimental data, it was determined that Tregs exhibited regulatory potential against LPS-induced inflammatory response. Further, it was concluded that the transmission of Tregs improved the mother's immune tolerance against LPS-induced inflammation in the fetal liver.

Mechanism of colorectal carcinogenesis triggered by heme iron from red meat

Colorectal cancer (CRC) is one of the major tumor entities worldwide, with an increasing incidence in younger people. CRC formation is causally linked to various genetic, life-style and dietary risk factors. Among the ladder, the consumption of red meat has emerged as important risk factor contributing to CRC. A large body of evidence shows that heme iron is the critical component of red meat, which promotes colorectal carcinogenesis. In this review, we describe the uptake and cellular fate of both heme and inorganic iron in intestinal epithelial cells. Next, an overview on the DNA damaging properties of heme iron is provided, highlighting the DNA adducts relevant for CRC etiology. Moreover, heme triggered mechanisms leading to colonic hyperproliferation are presented, which are intimately linked to changes in the intestinal microbiota induced by heme. A special focus was set on the impact of heme iron on innate and adaptive immune cells, which could be relevant in the context of CRC. Finally, we recapitulate in vivo studies providing evidence for the tumor-promoting potential of dietary heme iron. Altogether, heme iron affects numerous key pathways involved in the pathogenesis of CRC.

Heme Catabolic Pathway in Inflammation and Immune Disorders

In recent years, the heme catabolic pathway is considered to play an important regulatory role in cell protection, apoptosis, inflammation, and other physiological and pathological processes. An appropriate amount of heme forms the basic elements of various life activities, while when released in large quantities, it can induce toxicity by mediating oxidative stress and inflammation. Heme oxygenase (HO) -1 can catabolize free heme into carbon monoxide (CO), ferrous iron, and biliverdin (BV)/bilirubin (BR). The diverse functions of these metabolites in immune systems are fascinating. Decades work shows that administration of degradation products of heme such as CO and BV/BR exerts protective activities in systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), multiple sclerosis (MS) and other immune disorders. This review elaborates the molecular and biochemical characterization of heme catabolic pathway, discusses the signal transduction and immunomodulatory mechanism in inflammation and summarizes the promising therapeutic strategies based on this pathway in inflammatory and immune disorders.

Airway epithelial TSLP production of TLR2 drives type 2 immunity in allergic airway inflammation

Epithelial cells (ECs)-derived cytokines are induced by different stimuli through pattern recognition receptors (PRRs) to mount a type-2-cell-mediated immune response; however, the underlying mechanisms are poorly characterized. Here, we demonstrated asthmatic features in both primary bronchial epithelial cells (pBECs) and mouse model using several allergens including ovalbumin (OVA), house dust mite (HDM), or Alternaria alternata. We found that toll-like receptor 2 (TLR2) was highly induced in ECs but not dendritic cells (DCs) by various allergens, leading to recruitment of circulating basophils into the lung via C-C chemokine ligand-2 (CCL2). TLR2 expression increased thymic stromal lymphopoietin (TSLP) production through the NF-κB and JNK signaling pathways to extend the survival of recruited basophils and resident DCs in the lung, predisposing a type-2-cell-mediated airway inflammation. Conversely, TLR2 deficiency impaired secretion of TSLP and CCL2, decreased infiltration of lung basophils, and increased resistance to Th2 response. Blocking TSLP also phenocopied these phenomena. Our findings reveal a pro-inflammatory role of airway ECs through a TLR2-dependent TSLP production, which may have implication for treating allergic asthma.