Mitochondrial dysfunction in macrophages: a key to defective bacterial phagocytosis in COPD

The Role of Mitochondrial Quality Control in Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is a major cause of morbidity, mortality, and health care use worldwide with heterogeneous pathogenesis. Mitochondria, the powerhouses of cells responsible for oxidative phosphorylation and energy production, play essential roles in intracellular material metabolism, natural immunity, and cell death regulation. Therefore, it is crucial to address the urgent need for fine-tuning the regulation of mitochondrial quality to combat COPD effectively. Mitochondrial quality control (MQC) mainly refers to the selective removal of damaged or aging mitochondria and the generation of new mitochondria, which involves mitochondrial biogenesis, mitochondrial dynamics, mitophagy, etc. Mounting evidence suggests that mitochondrial dysfunction is a crucial contributor to the development and progression of COPD. This article mainly reviews the effects of MQC on COPD as well as their specific regulatory mechanisms. Finally, the therapeutic approaches of COPD via MQC are also illustrated.

Elamipretide(SS-31) Attenuates Idiopathic Pulmonary Fibrosis by Inhibiting the Nrf2-Dependent NLRP3 Inflammasome in Macrophages

Idiopathic pulmonary fibrosis (IPF) is a progressive fatal lung disease with a limited therapeutic strategy. Mitochondrial oxidative stress in macrophages is directly linked to IPF. Elamipretide(SS-31) is a mitochondrion-targeted peptide that has been shown to be safe and beneficial for multiple diseases. However, whether SS-31 alleviates IPF is unclear. In the present study, we used a bleomycin (BLM)-induced mouse model followed by SS-31 injection every other day to investigate its role in IPF and explore the possible mechanism. Our results showed that SS-31 treatment significantly suppressed BLM-induced pulmonary fibrosis and inflammation, with improved histological change, and decreased extracellular matrix deposition and inflammatory cytokines release. Impressively, the expression percentage of IL-1β and IL-18 was downregulated to lower than half with SS-31 treatment. Mechanistically, SS-31 inhibited IL-33- or lipopolysaccharide(LPS)/IL-4-induced production of IL-1β and IL-18 in macrophages by suppressing NOD-like receptor thermal protein domain associated protein 3(NLRP3) inflammasome activation. Nuclear factor erythroid 2-related factor 2(Nrf2) was dramatically upregulated along with improved mitochondrial function after SS-31 treatment in activated macrophages and BLM-induced mice. Conversely, there was no significant change after SS-31 treatment in Nrf2-/- mice and macrophages. These findings indicated that SS-31 protected against pulmonary fibrosis and inflammation by inhibiting the Nrf2-mediated NLRP3 inflammasome in macrophages. Our data provide initial evidence for the therapeutic efficacy of SS-31 in IPF.

Effects of Smoking on COVID-19 Management and Mortality: An Umbrella Review

Introduction

Smoking status appears to lead to a poor prognosis in COVID-19 patients. However, findings from the studies conducted on this topic have not been consistent, and further exploration is required.

Methods

The objective of this umbrella review was to examine the effects of smoking on COVID-19 management and mortality. Online databases that included PubMed, Embase, Scopus, and Web of Science were searched using relevant keywords up to July 27, 2022. Articles were restricted to the English language, and the PRISMA protocol was followed.

Results

A total of 27 systematic reviews, published from 2020 to 2022, were included. Individual studies included in the systematic reviews ranged from 8 to 186, with various population sizes. The consensus from the majority of systematic reviews was that COVID-19 smoker patients experience greater disease severity, disease progression, hospitalization rate, hospital admission duration, mechanical ventilation, ICU admission, and mortality rate.

Conclusions

COVID-19 patients with a history of smoking (current and former) are vulnerable to adverse hospital outcomes and worse COVID-19 progression. Effective preventive and supportive approaches are required to decrease the risk of COVID-19 morbidity and mortality in patients with a history of smoking.

The role of lung macrophages in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) as a common, preventable and treatable chronic respiratory disease in clinic, gets continuous deterioration and we can't take effective intervention at present. Lung macrophages (LMs) are closely related to the occurrence and development of COPD, but the specific mechanism is not completely clear. In this review we will focus on the role of LMs and potential avenues for therapeutic targeting for LMs in COPD.

Immunopathology of COVID-19 and its implications in the development of rhino-orbital-cerebral mucormycosis: a major review

PURPOSE

To present a literature review on various immunopathologic dysfunctions following COVID-19 infection and their potential implications in development of rhino-orbital-cerebral mucormycosis (ROCM).

METHODS

A literature search was performed via Google Scholar and PubMed with subsequent review of the accompanying references. Analogies were drawn between the immune and physiologic deviations caused by COVID-19 and the tendency of the same to predispose to ROCM.

RESULTS

Sixty-two articles were reviewed. SARS-CoV-2 virus infection leads to disruption of epithelial integrity in the respiratory passages, which may be a potential entry point for the ubiquitous Mucorales to become invasive. COVID-19 related GRP78 protein upregulation may aid in spore germination and hyphal invasion by Mucorales. COVID-19 causes interference in macrophage functioning by direct infection, a tendency for hyperglycemia, and creation of neutrophil extracellular traps. This affects innate immunity against Mucorales. Thrombocytopenia and reduction in the number of natural killer (NK) cells and infected dendritic cells is seen in COVID-19. This reduces the host immune response to pathogenic invasion by Mucorales. Cytokines released in COVID-19 cause mitochondrial dysfunction and accumulation of reactive oxygen species, which cause oxidative damage to the leucocytes. Hyperferritinemia also occurs in COVID-19 resulting in suppression of the hematopoietic proliferation of B- and T-lymphocytes.

CONCLUSIONS

COVID-19 has a role in the occurrence of ROCM due to its effects at the entry point of the fungus in the respiratory mucosa, effects of the innate immune system, creation of an environment of iron overload, propagation of hyperglycemia, and effects on the adaptive immune system.

Proteomic networks associated with tumor-educated macrophage polarization and cytotoxicity potentiated by heat-killed tuberculosis

Local administration of attenuated mycobacterium has been used as a cancer treatment adjuvant to re-boost patient immune responses with variable clinical outcomes. We aimed to clarify the impact of attenuated heat-killed tuberculosis (HKTB) on tumor-associated macrophages which play critical roles in shaping immunological regulation in the tumor microenvironment. Upon HKTB stimulation, both primary macrophages derived from the peripheral blood of healthy subjects and from lung cancer patients as well as THP1-derived classically activated macrophages (Ms) and tumor-educated macrophages (TEMs) were polarized into the proinflammatory phenotype, as characterized by increased expression cluster of differentiation 86. A quantitative proteomic analysis revealed that stimulated TEMs were unable to activate the toll-like receptor 2, signal transducer and activator of transcription 1, or nuclear factor-κB signaling. Instead, they showed distinct intercellular adhesion molecule 1 signaling, impaired cell adhesion, and mitochondrial dysfunction. These molecular mechanisms might contribute to lower cytotoxicity of HKTB-stimulated TEMs against A549 cells via the release of distinct inflammatory cytokines compared to HKTB-stimulated Ms. Our study provides an unbiased and systematic interpretation of cellular and molecular alterations of HKTB-reeducated macrophages which should help illuminate potential strategies of HKTB-stimulated macrophage-based combination therapy for cancer treatment.

SARS-CoV-2 (COVID-19) Adhesion Site Protein Upregulation in Small Airways, Type 2 Pneumocytes, and Alveolar Macrophages of Smokers and COPD – Possible Implications for Interstitial Fibrosis

Background

Smokers and patients with COPD are highly susceptible to SARS-CoV-2 infection, leading to severe COVID-19.

Methods

This cross-sectional study involved resected lung tissues from 16 patients with GOLD stage I or II COPD; of which 8 were current smokers COPD (COPD-CS), and 8 ex-smokers COPD (COPD-ES), 7 normal lung function smokers (NLFS), 9 patients with small airways disease (SAD), and 10 were never-smoking normal controls (NC). Immunostaining for ACE2, Furin, and TMPRSS2 was performed and analysed for percent expression in small airway epithelium (SAE) and counts for positively and negatively stained type 2 pneumocytes and alveolar macrophages (AMs) were done using Image ProPlus V7.0. Furthermore, primary small airway epithelial cells (pSAEC) were analysed by immunofluorescence after exposure to cigarette smoke extract (CSE).

Results

ACE2, Furin, and TMPRSS2 expression significantly increased in SAE and type 2 pneumocytes in all the subjects (except Furin for NLFS) compared to NC (p < 0.001). Similar significance was observed for ACE2 positive AM (p < 0.002), except COPD-ES, which decreased in ACE2 positive AMs (p < 0.003). Total type 2 pneumocytes and AMs significantly increased in the pathological groups compared to NC (p < 0.01), except SAD (p = 0.08). However, AMs are significantly reduced in COPD-ES (p < 0.003). Significant changes were observed for tissue co-expression of Furin and TMPRSS2 with ACE2 in SAE, type 2 pneumocytes and AMs. These markers also negatively correlated with lung function parameters, such as FEV₁/FVC % predicted, FEF25-75%, DLCO% predicted. A strong co-localisation and expression for ACE2 (p < 0.0001), Furin (p < 0.01), and TMPRSS2 (p < 0.0001) was observed in pSAEC treated with 1% CSE than controls.

Discussion

The increased expression of ACE2, TMPRSS2 and Furin, in the SAE, type 2 pneumocytes and AMs of smokers and COPD are detrimental to lung function and proves that these patient groups could be more susceptible to severe COVID-19 infection. Increased type 2 pneumocytes suggest that these patients are vulnerable to developing post-COVID-19 interstitial pulmonary fibrosis or fibrosis in general. There could be a silently developing interstitial pathology in smokers and patients with COPD. This is the first comprehensive study to report such changes.

Identification of Potential Key Genes in the Pathogenesis of Chronic Obstructive Pulmonary Disease Through Bioinformatics Analysis

Chronic obstructive pulmonary disease (COPD) is a common respiratory disease with high morbidity and mortality. The etiology of COPD is complex, and the pathogenesis mechanisms remain unclear. In this study, we used rat and human COPD gene expression data from our laboratory and the Gene Expression Omnibus (GEO) database to identify differentially expressed genes (DEGs) between individuals with COPD and healthy individuals. Then, protein–protein interaction (PPI) networks were constructed, and hub genes were identified. Cytoscape was used to construct the co-expressed network and competitive endogenous RNA (ceRNA) networks. A total of 198 DEGs were identified, and a PPI network with 144 nodes and 355 edges was constructed. Twelve hub genes were identified by the cytoHubba plugin in Cytoscape. Of these genes, CCR3, CCL2, COL4A2, VWF, IL1RN, IL2RA, and CCL13 were related to inflammation or immunity, or tissue-specific expression in lung tissue, and their messenger RNA (mRNA) levels were validated by qRT-PCR. COL4A2, VWF, and IL1RN were further verified by the GEO dataset GSE76925, and the ceRNA network was constructed with Cytoscape. These three genes were consistent with COPD rat model data compared with control data, and their dysregulation direction was reversed when the COPD rat model was treated with effective-component compatibility of Bufei Yishen formula III. This bioinformatics analysis strategy may be useful for elucidating novel mechanisms underlying COPD. We pinpointed three key genes that may play a role in COPD pathogenesis and therapy, which deserved to be further studied.

Mitochondrial Metabolism in Macrophages

Mitochondria are considered to be the powerhouse of the cell. Normal functioning of the mitochondria is not only essential for cellular energy production but also for several immunomodulatory processes. Macrophages operate in metabolic niches and rely on rapid adaptation to specific metabolic conditions such as hypoxia, nutrient limitations, or reactive oxygen species to neutralize pathogens. In this regard, the fast reprogramming of mitochondrial metabolism is indispensable to provide the cells with the necessary energy and intermediates to efficiently mount the inflammatory response. Moreover, mitochondria act as a physical scaffold for several proteins involved in immune signaling cascades and their dysfunction is immediately associated with a dampened immune response. In this review, we put special focus on mitochondrial function in macrophages and highlight how mitochondrial metabolism is involved in macrophage activation.

Pathogenesis, clinical features of asthma COPD overlap (ACO), and therapeutic modalities

Both asthma and COPD are heterogeneous diseases identified by characteristic symptoms and functional abnormalities, with airway obstruction common in both diseases. Asthma COPD overlap (ACO) does not define a single disease but is a descriptive term for clinical use that includes several overlapping clinical phenotypes of chronic airways disease with different underlying mechanisms. This literature review was initiated to describe published studies, identify gaps in knowledge, and propose future research goals regarding the disease pathology of ACO, especially the airway remodelling changes and inflammation aspects. Airway remodelling occurs in asthma and COPD, but there are differences in the structures affected and the prime anatomic site at which they occur. Reticular basement membrane thickening and cellular infiltration with eosinophils and T-helper (CD4+) lymphocytes are prominent features of asthma. Epithelial squamous metaplasia, airway wall fibrosis, emphysema, bronchoalveolar lavage (BAL) neutrophilia and (CD8+) T-cytotoxic lymphocyte infiltrations in the airway wall are features of COPD. There is no universally accepted definition of ACO, nor are there clearly defined pathological characteristics to differentiate from asthma and COPD. Understanding etiological concepts within the purview of inflammation and airway remodelling changes in ACO would allow better management of these patients.

Pulmonary macrophages and their different roles in health and disease

Macrophages are a heterogeneous population of myeloid cells with phenotype and function modulated according to the microenvironment in which they are found. The lung resident macrophages known as Alveolar Macrophages (AM) and Interstitial Macrophages (IM) are localized in two different compartments. During lung homeostasis, macrophages can remove inhaled particulates, cellular debris and contribute to some metabolic processes. Macrophages may assume a pro-inflammatory phenotype after being classically activated (M1) or anti-inflammatory when being alternatively activated (M2). M1 and M2 have different transcription profiles and act by eliminating bacteria, viruses and fungi from the host or repairing the damage triggered by inflammation, respectively. Nevertheless, macrophages also may contribute to lung damage during persistent inflammation or continuous exposure to antigens. In this review, we discuss the origin and function of pulmonary macrophages in the context of homeostasis, infectious and non-infectious lung diseases.

The Role of Smoking and Nicotine in the Transmission and Pathogenesis of COVID-19

Coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 virus, is turning out to be one of the most devastating global pandemics in the history of humankind. There is a shortage of effective therapeutic strategies or preventative vaccines for this disease to date. A rigorous investigation is needed for identifying and developing more effective therapeutic strategies for COVID-19. Angiotensin-converting enzyme 2 (ACE2), a crucial factor in COVID-19 pathogenesis, has been identified as a potential target for COVID-19 treatment. Smoking and vaping are potential risk factors for COVID-19 that are also shown to upregulate ACE2 expression. In this review, we have discussed the pathobiology of COVID-19 in the lungs and brain and the role of ACE2 in the transmission and pathobiology of this disease. Furthermore, we have shown possible interactions between nicotine/smoking and ACE2 in the lungs and brain, which could aggravate the transmission and pathobiology of COVID-19, resulting in a poor disease outcome. SIGNIFICANCE STATEMENT: This review addresses the present global pandemic of coronavirus disease 2019 (COVID-19) with respect to its pathobiology in the lungs and brain. It focuses on the potential negative impact of tobacco and nicotine exposure on the outcomes of this disease by interaction with the angiotensin-converting enzyme 2 receptor. It adds to the time-sensitive and critically important growing knowledge about the risk factors, transmission, pathobiology, and prognosis of COVID-19.

Smoking and COVID-19: Adding Fuel to the Flame

The coronavirus disease 2019 (COVID-19) pandemic, an infection caused by the severe acute respiratory syndrome coronavirus (SARS-CoV-2), has led to more than 771,000 deaths worldwide. Tobacco smoking is a major known risk factor for severe illness and even death from many respiratory infections. The effects of smoking on COVID-19 are currently controversial. Here, we provide an overview of the current knowledge on the effects of smoking on the clinical manifestations, disease progression, inflammatory responses, immunopathogenesis, racial ethnic disparities, and incidence of COVID-19. This review also documents future directions of smoking related research in COVID-19. The current epidemiological finding suggests that active smoking is associated with an increased severity of disease and death in hospitalized COVID-19 patients. Smoking can upregulate the angiotensin-converting enzyme-2 (ACE-2) receptor utilized by SARS-CoV-2 to enter the host cell and activate a ‘cytokine storm’ which can lead to worsen outcomes in COVID-19 patients. This receptor can also act as a potential therapeutic target for COVID-19 and other infectious diseases. The COVID-19 pandemic sheds light on a legacy of inequalities regarding gender, racial, and ethnic health disparities associated with active smoking, thus, smoking cessation may help in improving outcomes. In addition, to flatten the COVID-19 curve, staying indoors, avoiding unnecessary social contact, and bolstering the immune defense system by maintaining a healthy diet/living are highly desirable.

Covid-19 Kills More Men Than Women: An Overview of Possible Reasons

The high mortality observed in Covid-19 patients may be related to unrecognized pulmonary embolism, pulmonary thrombosis, or other underlying cardiovascular diseases. Recent data have highlighted that the mortality rate of Covid-19 seems to be higher in male patients compared to females. In this paper, we have analyzed possible factors that may underline this sex difference in terms of activity of the immune system and its modulation by sex hormones, coagulation pattern, and preexisting cardiovascular diseases as well as effects deriving from smoking and drinking habits. Future studies are needed to evaluate the effects of sex differences on the prevalence of infections, including Covid-19, its outcome, and the responses to antiviral treatments.

Immunopathogenesis and therapeutic potential of macrophage influx in diffuse parenchymal lung diseases

INTRODUCTION

The diffuse parenchymal lung diseases (DPLD)/interstitial lung diseases (ILD) are progressive lung disorders with usually unclear etiology, poor long-term survival and no effective treatment. Their pathogenesis is characterized by alveolar epithelial cell injury, inflammation, epithelial-mesenchymal transition, and parenchymal fibrosis. Macrophages play diverse roles in their development, both in the acute phase and in tissue repair.

AREAS COVERED

In this review, we summarize the current state of knowledge regarding the role of macrophages and their phenotypes in the immunopathogenesis of DPLDs; CVD-ILD, UIP, NSIP, DIP, RB-ILD, AIP, HP, Sarcoidosis, etc. Our goal is to update the understanding of the immune mechanisms underlying the initiation and progression of fibrosis in DPLDs. This will help in identification of biomarkers and in developing novel therapeutic strategies for DPLDs. A thorough literature search of the published studies in PubMed (from 1975 to 2020) was done.

EXPERT OPINION

The macrophage associated inflammatory markers needs to be explored for their potential as biomarkers of disease activity and progression. Pharmacological targeting of macrophage activation may reduce the risk of macrophage activation syndrome (MAS) and help improving the survival and prognosis of these patients.

Smoking Upregulates Angiotensin-Converting Enzyme-2 Receptor: A Potential Adhesion Site for Novel Coronavirus SARS-CoV-2 (Covid-19)

The epicenter of the original outbreak in China has high male smoking rates of around 50%, and early reported death rates have an emphasis on older males, therefore the likelihood of smokers being overrepresented in fatalities is high. In Iran, China, Italy, and South Korea, female smoking rates are much lower than males. Fewer females have contracted the virus. If this analysis is correct, then Indonesia would be expected to begin experiencing high rates of Covid-19 because its male smoking rate is over 60% (Tobacco Atlas). Smokers are vulnerable to respiratory viruses. Smoking can upregulate angiotensin-converting enzyme-2 (ACE2) receptor, the known receptor for both the severe acute respiratory syndrome (SARS)-coronavirus (SARS-CoV) and the human respiratory coronavirus NL638. This could also be true for new electronic smoking devices such as electronic cigarettes and "heat-not-burn" IQOS devices. ACE2 could be a novel adhesion molecule for SARS-CoV-2 causing Covid-19 and a potential therapeutic target for the prevention of fatal microbial infections, and therefore it should be fast tracked and prioritized for research and investigation. Data on smoking status should be collected on all identified cases of Covid-19.