Carbocisteine promotes phagocytosis of apoptotic cells by alveolar macrophages

Clinical Efficacy of Carbocysteine in COPD: Beyond the Mucolytic Action

Chronic obstructive pulmonary disease (COPD) is a heterogeneous disease with a versatile and complicated profile, being the fourth most common single cause of death worldwide. Several research groups have been trying to identify possible therapeutic approaches to treat COPD, such as the use of mucoactive drugs, which include carbocysteine. However, their role in the treatment of patients suffering from COPD remains controversial due to COPD's multifaceted profile. In the present review, 72 articles, published in peer-reviewed journals with high impact factors, are analyzed in order to provide significant insight and increase the knowledge about COPD considering the important contribution of carbocysteine in reducing exacerbations via multiple mechanisms. Carbocysteine is in fact able to modulate mucins and ciliary functions, and to counteract viral and bacterial infections as well as oxidative stress, offering cytoprotective effects. Furthermore, carbocysteine improves steroid responsiveness and exerts anti-inflammatory activity. This analysis demonstrates that the use of carbocysteine in COPD patients represents a well-tolerated treatment with a favorable safety profile, and might contribute to a better quality of life for patients suffering from this serious illness.

Extracellular HMGB1 Impairs Macrophage-Mediated Efferocytosis by Suppressing the Rab43-Controlled Cell Surface Transport of CD91

High-mobility group box 1 (HMGB1) protein can impair phagocyte function by suppressing the macrophage-mediated clearance of apoptotic cells (ACs), thereby delaying inflammation resolution in the lungs and allowing the progression of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). However, the precise mechanism underlying this HMGB1-mediated inhibition of efferocytosis remains unknown. The aim of this study was to determine the effect of HMGB1 on macrophage-mediated efferocytosis. We discovered that HMGB1 prevented efferocytosis by bone marrow-derived macrophages (BMDMs) and suppressed the expression of Ras-related GTP-binding protein 43 (Rab43), a member of the Ras-associated binding (Rab) family. The downregulation of Rab43 expression resulted in impaired clearance of apoptotic thymocytes by BMDMs. Subsequent analysis of HMGB1-treated and Rab43-deficient BMDMs revealed the inhibited transport of cluster of differentiation 91 (CD91), a phagocyte recognition receptor, from the cytoplasm to the cell surface. Notably, Rab43 directly interacted with CD91 to mediate its intercellular trafficking. Furthermore, Rab43 knockout delayed the inflammation resolution and aggravated the lung tissue damage in mice with ALI. Therefore, our results provide evidence that HMGB1 impairs macrophage-mediated efferocytosis and delays inflammation resolution by suppressing the Rab43-regulated anterograde transport of CD91, suggesting that the restoration of Rab43 levels is a promising strategy for attenuating ALI and ARDS in humans.

S-Carboxymethyl-l-cysteine: a multiple dosing study using pharmacokinetic modelling

S-Carboxymethyl-l-cysteine is a mucolytic agent used as adjunctive therapy in the treatment of respiratory disorders. Various mechanisms of action have been proposed but few studies have attempted to link the required in vitro concentrations with those achieved actually in vivo during clinical therapy.The data from several published studies has been re-analysed by WinNonlin using non-compartmental analysis modelling, Phoenix modelling and Classic PK compartmental modelling for both single (500-1500 mg) and multiple oral administration of the drug.Multiple dose modelling indicated maximum peak concentrations (C_max) ranging from 1.29 to 11.22 μg/ml and those at steady state (C_ss(av)) from 1.30 to 8.40 μg/ml. For the standard therapeutic regimen of 3 × 750 mg (2250 mg/day) these values were 1.29-5.22 μg/ml (C_max) and 1.30-3.50 μg/ml (C_ss(av)). No accumulation was observed.Hence, only the pharmacodynamic studies reporting significant effects below c.10 μg/ml were likely to occur in vivo and these were mainly gene-related mechanisms. The majority of events, although demonstrable in vitro, required levels much greater than possible to achieve in the clinical situation.Such unappreciated disregard for in vitro-in vivo 'concentration matching' may lead to erroneous conclusions regarding mechanisms of action for many drugs as well as for S-carboxymethyl-l-cysteine.

Clinical relevance of serum α-l-fucosidase activity in the SARS-CoV-2 infection

Background and aims

The reduced fucosylation in the spike glycoprotein of SARS-CoV-2 and the IgG antibody has been observed in COVID-19. However, the clinical relevance of α-l-fucosidase, the enzyme for defucosylation has not been discovered.

Materials and methods

585 COVID-19 patients were included to analyze the correlations of α-l-fucosidase activity with the nucleic acid test, IgM/IgG, comorbidities, and disease progression.

Results

Among the COVID-19 patients, 5.75% were double-negative for nucleic acid and antibodies. All of them had increased α-l-fucosidase, while only one had abnormal serum amyloid A (SAA) and C-reactive protein (CRP). The abnormal rate of α-l-fucosidase was 81.82% before the presence of IgM, 100% in the presence of IgM, and 66.2% in the presence of IgG. 73.42% of patients with glucometabolic disorders had increased α-l-fucosidase activity and had the highest mortality of 6.33%. The increased α-l-fucosidase was observed in 55.8% of non-severe cases and 72.9% of severe cases, with an odds ratio of 2.118. The α-l-fucosidase mRNA was irrelevant to its serum activity.

Conclusion

The change in α-l-fucosidase activity in COVID-19 preceded the IgM and SAA and showed a preferable relation with glucometabolic disorders, which may be conducive to virus invasion or invoke an immune response against SARS-CoV-2.

Oxidative stress and macrophages: driving forces behind exacerbations of asthma and chronic obstructive pulmonary disease?

Oxidative stress is a common feature of obstructive airway diseases like asthma and chronic obstructive pulmonary disease (COPD). Lung macrophages are key innate immune cells that can generate oxidants and are known to display aberrant polarization patterns and defective phagocytic responses in these diseases. Whether these characteristics are linked in one way or another and whether they contribute to the onset and severity of exacerbations in asthma and COPD remain poorly understood. Insight into oxidative stress, macrophages, and their interactions may be important in fully understanding acute worsening of lung disease. This review therefore highlights the current state of the art regarding the role of oxidative stress and macrophages in exacerbations of asthma and COPD. It shows that oxidative stress can attenuate macrophage function, which may result in impaired responses toward exacerbating triggers and may contribute to exaggerated inflammation in the airways.

Restoring cigarette smoke-induced impairment of efferocytosis in alveolar macrophages

Cigarette smoke has been associated with susceptibility to different pulmonary and airway diseases. Impaired alveolar macrophages (AMs) that are major phagocytes in the lung have been associated with patients with airway diseases and active smokers. In the current report, we show that exposure to second-hand cigarette smoke (SHS) significantly reduced efferocytosis in vivo. More importantly, delivery of recombinant granulocyte-macrophage colony-stimulating factor (GM-CSF) to the alveolar space restored and refurbished the efferocytosis capability of AMs. Exposure to SHS significantly reduced expression of CD16/32 on AMs, and treatment with GM-CSF not only restored but also significantly increased the expression of CD16/32 on AMs. GM-CSF treatment increased uptake and digestion/removal of apoptotic cells by AMs. The latter was attributed to increased expression of Rab5 and Rab7. Increased efferocytosis of AMs was also tested in a disease condition. AMs from GM-CSF-treated, influenza-infected, SHS-exposed mice showed significantly better efferocytosis activity, and mice had significantly less morbidity compared with phosphate-buffered saline-treated group. GM-CSF-treated mice had increased amphiregulin levels in the lungs, which in addition to efferocytosis of AMs may have attributed to their protection against influenza. These results will have great implications for developing therapeutic approaches by harnessing mucosal innate immunity to treat lung and airway diseases and protect against pneumonia.

Modulation of expression in BEAS-2B airway epithelial cells of α-L-fucosidase A1 and A2 by Th1 and Th2 cytokines, and overexpression of α-L-fucosidase 2

Chronic Th2-driven airway inflammation with excessive mucus production occurs in asthma. The regulation of FUCA1 and FUCA2 gene expression and enzyme activity in response to asthma-associated Th2 cytokines and, for contrast, Th1 cytokine IFN-γ, were investigated in a human airway cell line. BEAS-2B cells were supplemented with Th2-derived cytokines (IL-13, IL-4, IL-5) or/and IFN-γ. RNA and cell supernatants from stimulated and unstimulated cells were collected over a period of 3 h. Alpha-L-fucosidase A1 and A2 gene expression were assessed using real time RT-PCR, while enzymatic activities were measured using a fluorescent assay. To characterise α-L-fucosidase A2, CHO-K1 and BEAS-2B cell lines were transiently transfected, the FUCA2 gene was overexpressed, and the protein was immunoprecipitated. The transcription of FUCA1 was upregulated (p < 0.01) in response to IFN-γ, suggesting that FUCA1 transcription and fucosidase activity are regulated in a Th1-dependent manner. The gene expression was the highest for 30 min after IFN-γ stimulation (>twofold induction), whereas secreted enzyme activity in BEAS-2B cells was significantly increased 1 h after IFN-γ addition. IL-4, IL-5 and IL-13 had no effect on FUCA1 and FUCA2 expression and activity. The IFN-γ-induced increase in expression and activity was repressed by the presence of the Th2 cytokine IL-5. Enzymatically active α-L-fucosidase 2 was immunoprecipitated from BEAS-2B cells, with highest activity at pH 4.9. IL-13, IL-4 and IL-5 have no effect on the expression of FUCA1 and FUCA2, but its expression is upregulated by IFN-γ, a Th1 cytokine. Active α-L-fucosidase 2 was overexpressed in BEAS-2B cells.

Efferocytosis and lung disease

In healthy individuals, billions of cells die by apoptosis each day. Clearance of these apoptotic cells, termed "efferocytosis," must be efficient to prevent secondary necrosis and the release of proinflammatory cell contents that disrupt tissue homeostasis and potentially foster autoimmunity. During inflammation, most apoptotic cells are cleared by macrophages; the efferocytic process actively induces a macrophage phenotype that favors tissue repair and suppression of inflammation. Several chronic lung diseases, particularly airways diseases such as chronic obstructive lung disease, asthma, and cystic fibrosis, are characterized by an increased lung burden of uningested apoptotic cells. Alveolar macrophages from individuals with these chronic airways diseases have decreased efferocytosis relative to alveolar macrophages from healthy subjects. These two findings have led to the hypothesis that impaired apoptotic cell clearance may contribute causally to sustained lung inflammation and that therapies to enhance efferocytosis might be beneficial. This review of the English-language scientific literature (2006 to mid-2012) explains how such existing therapies as corticosteroids, statins, and macrolides may act in part by augmenting apoptotic cell clearance. However, efferocytosis can also impede host defenses against lung infection. Thus, determining whether novel therapies to augment efferocytosis should be developed and in whom they should be used lies at the heart of efforts to differentiate specific phenotypes within complex chronic lung diseases to provide appropriately personalized therapies.