Zinc and Zinc Transporters in Macrophages and Their Roles in Efferocytosis in COPD

PLOS ONE, Dec 2019

Our previous studies have shown that nutritional zinc restriction exacerbates airway inflammation accompanied by an increase in caspase-3 activation and an accumulation of apoptotic epithelial cells in the bronchioles of the mice. Normally, apoptotic cells are rapidly cleared by macrophage efferocytosis, limiting any secondary necrosis and inflammation. We therefore hypothesized that zinc deficiency is not only pro-apoptotic but also impairs macrophage efferocytosis. Impaired efferocytic clearance of apoptotic epithelial cells by alveolar macrophages occurs in chronic obstructive pulmonary disease (COPD), cigarette-smoking and other lung inflammatory diseases. We now show that zinc is a factor in impaired macrophage efferocytosis in COPD. Concentrations of zinc were significantly reduced in the supernatant of bronchoalveolar lavage fluid of patients with COPD who were current smokers, compared to healthy controls, smokers or COPD patients not actively smoking. Lavage zinc was positively correlated with AM efferocytosis and there was decreased efferocytosis in macrophages depleted of Zn in vitro by treatment with the membrane-permeable zinc chelator TPEN. Organ and cell Zn homeostasis are mediated by two families of membrane ZIP and ZnT proteins. Macrophages of mice null for ZIP1 had significantly lower intracellular zinc and efferocytosis capability, suggesting ZIP1 may play an important role. We investigated further using the human THP-1 derived macrophage cell line, with and without zinc chelation by TPEN to mimic zinc deficiency. There was no change in ZIP1 mRNA levels by TPEN but a significant 3-fold increase in expression of another influx transporter ZIP2, consistent with a role for ZIP2 in maintaining macrophage Zn levels. Both ZIP1 and ZIP2 proteins were localized to the plasma membrane and cytoplasm in normal human lung alveolar macrophages. We propose that zinc homeostasis in macrophages involves the coordinated action of ZIP1 and ZIP2 transporters responding differently to zinc deficiency signals and that these play important roles in macrophage efferocytosis.

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Zinc and Zinc Transporters in Macrophages and Their Roles in Efferocytosis in COPD

et al. (2014) Zinc and Zinc Transporters in Macrophages and Their Roles in Efferocytosis in COPD. PLoS ONE 9(10): e110056. doi:10.1371/journal.pone.0110056 Zinc and Zinc Transporters in Macrophages and Their Roles in Efferocytosis in COPD Rhys Hamon 0 Claire C. Homan 0 Hai B. Tran 0 Violet R. Mukaro 0 Susan E. Lester 0 Eugene Roscioli 0 Mariea D. Bosco 0 Chiara M. Murgia 0 Margaret Leigh Ackland 0 Hubertus P. Jersmann 0 Carol Lang 0 Peter D. Zalewski 0 Sandra J. Hodge 0 Paul A. Adlard, The Florey Institute of Neuroscience and Mental Health, Australia 0 1 Discipline of Medicine, University of Adelaide, The Queen Elizabeth Hospital , Woodville, South Australia , Australia , 2 Department of Thoracic Medicine, Royal Adelaide Hospital, Lung Research Laboratory, Hanson Institute , Adelaide, South Australia , Australia , 3 Rheumatology Unit, The Queen Elizabeth Hospital , Woodville, South Australia , Australia , 4 Discipline of Surgery , University of Adelaide, The Queen Elizabeth Hospital , Woodville, South Australia , Australia , 5 CRA-NUT, Roma , Italy , 6 Centre for Cellular and Molecular Biology, School of Life and Environmental Sciences, Deakin University , Burwood, Melbourne, Victoria , Australia Our previous studies have shown that nutritional zinc restriction exacerbates airway inflammation accompanied by an increase in caspase-3 activation and an accumulation of apoptotic epithelial cells in the bronchioles of the mice. Normally, apoptotic cells are rapidly cleared by macrophage efferocytosis, limiting any secondary necrosis and inflammation. We therefore hypothesized that zinc deficiency is not only pro-apoptotic but also impairs macrophage efferocytosis. Impaired efferocytic clearance of apoptotic epithelial cells by alveolar macrophages occurs in chronic obstructive pulmonary disease (COPD), cigarette-smoking and other lung inflammatory diseases. We now show that zinc is a factor in impaired macrophage efferocytosis in COPD. Concentrations of zinc were significantly reduced in the supernatant of bronchoalveolar lavage fluid of patients with COPD who were current smokers, compared to healthy controls, smokers or COPD patients not actively smoking. Lavage zinc was positively correlated with AM efferocytosis and there was decreased efferocytosis in macrophages depleted of Zn in vitro by treatment with the membrane-permeable zinc chelator TPEN. Organ and cell Zn homeostasis are mediated by two families of membrane ZIP and ZnT proteins. Macrophages of mice null for ZIP1 had significantly lower intracellular zinc and efferocytosis capability, suggesting ZIP1 may play an important role. We investigated further using the human THP-1 derived macrophage cell line, with and without zinc chelation by TPEN to mimic zinc deficiency. There was no change in ZIP1 mRNA levels by TPEN but a significant 3-fold increase in expression of another influx transporter ZIP2, consistent with a role for ZIP2 in maintaining macrophage Zn levels. Both ZIP1 and ZIP2 proteins were localized to the plasma membrane and cytoplasm in normal human lung alveolar macrophages. We propose that zinc homeostasis in macrophages involves the coordinated action of ZIP1 and ZIP2 transporters responding differently to zinc deficiency signals and that these play important roles in macrophage efferocytosis. - Data Availability: The authors confirm that all data underlying the findings are fully available without restriction. All relevant data are within the paper and its Supporting Information files. Funding: This work was supported by National Health and Medical Research Council (NHMRC) Grant # 627223 to PDZ, and National Health and Medical Research Council (NHMRC) Peter Doherty Fellowship to CL. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. . These authors contributed equally to this work. " These authors are joint senior authors on this work. The phagocytic activity of macrophages is important not only for immune response to micro-organisms but also for removal of apoptotic cells in tissues in a process known as efferocytosis (Latin, efferre, to carry to the grave) [1]. Impairment of efferocytosis can lead to accumulation of apoptotic cells and their secondary necrosis, releasing factors that promote an inflammatory response. Efferocytosis is impaired by a number of agents including cigarette smoke and is an important pathogenic mechanism in chronic inflammatory diseases of the lung such as chronic obstructive pulmonary disease (COPD) [27]. There is interest, therefore, in factors which regulate efferocytosis. One such factor is zinc (Zn), the second most abundant metal in the body and important for many physiological and pathological processes, especially in the immune system. Increased prevalence of obstructive lung disorders [8] and lung (but not breast or prostate) cancer [9 (...truncated)


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Rhys Hamon, Claire C. Homan, Hai B. Tran, Violet R. Mukaro, Susan E. Lester, Eugene Roscioli, Mariea D. Bosco, Chiara M. Murgia, Margaret Leigh Ackland, Hubertus P. Jersmann, Carol Lang, Peter D. Zalewski, Sandra J. Hodge. Zinc and Zinc Transporters in Macrophages and Their Roles in Efferocytosis in COPD, PLOS ONE, 2014, Volume 9, Issue 10, DOI: 10.1371/journal.pone.0110056