Zinc deficiency primes the lung for ventilator-induced injury
Francis Boudreault, Miguel Pinilla-Vera, Joshua A. Englert, Alvin T. Kho, Colleen Isabelle, Antonio J. Arciniegas, Diana Barragan-Bradford, Carolina Quintana, Diana Amador-Munoz, Jiazhen Guan, Kyoung Moo Choi, MICU Registry, Lynette Sholl, Shelley Hurwitz, Daniel J. Tschumperlin, Rebecca M. Baron
Francis Boudreault, Miguel Pinilla-Vera, Joshua A. Englert, Alvin T. Kho, Colleen Isabelle, Antonio J. Arciniegas, Diana Barragan-Bradford, Carolina Quintana, Diana Amador-Munoz, Jiazhen Guan, Kyoung Moo Choi, MICU Registry, Lynette Sholl, Shelley Hurwitz, Daniel J. Tschumperlin, Rebecca M. Baron
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Research Article Inflammation Pulmonology

Zinc deficiency primes the lung for ventilator-induced injury

Abstract

Mechanical ventilation is necessary to support patients with acute lung injury, but also exacerbates injury through mechanical stress–activated signaling pathways. We show that stretch applied to cultured human cells, and to mouse lungs in vivo, induces robust expression of metallothionein, a potent antioxidant and cytoprotective molecule critical for cellular zinc homeostasis. Furthermore, genetic deficiency of murine metallothionein genes exacerbated lung injury caused by high tidal volume mechanical ventilation, identifying an adaptive role for these genes in limiting lung injury. Stretch induction of metallothionein required zinc and the zinc-binding transcription factor MTF1. We further show that mouse dietary zinc deficiency potentiates ventilator-induced lung injury, and that plasma zinc levels are significantly reduced in human patients who go on to develop acute respiratory distress syndrome (ARDS) compared with healthy and non-ARDS intensive care unit (ICU) controls, as well as with other ICU patients without ARDS. Taken together, our findings identify a potentially novel adaptive response of the lung to stretch and a critical role for zinc in defining the lung’s tolerance for mechanical ventilation. These results demonstrate that failure of stretch-adaptive responses play an important role in exacerbating mechanical ventilator–induced lung injury, and identify zinc and metallothionein as targets for lung-protective interventions in patients requiring mechanical ventilation.

Authors

Francis Boudreault, Miguel Pinilla-Vera, Joshua A. Englert, Alvin T. Kho, Colleen Isabelle, Antonio J. Arciniegas, Diana Barragan-Bradford, Carolina Quintana, Diana Amador-Munoz, Jiazhen Guan, Kyoung Moo Choi, MICU Registry, Lynette Sholl, Shelley Hurwitz, Daniel J. Tschumperlin, Rebecca M. Baron

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Figure 2

Mt1/2-deficient mice exhibit enhanced lung injury in response to ventilator-induced lung injury.

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Mt1/2-deficient mice exhibit enhanced lung injury in response to ventila...
(A) WT mice were subjected to mechanical ventilation using a Flexivent ventilator with a tidal volume of 24 ml/kg, followed by lung harvest and assessment of Mt1 (black circles) and Mt2 levels (blue squares) using real-time quantitative PCR (qPCR) (n = 3–5 mice per time point). *P < 0.001 versus baseline by 1-way ANOVA with Newman-Keuls post-hoc test. (B) WT mice subjected to mechanical ventilation as in panel A were assessed for metallothionein (MT) lung protein levels, with β-actin as a loading control (pooled from 4 mice/time point). (C) Mt1/2(–/–) (red squares) and Mt1/2(+/+) control mice (black circles) were subjected to mechanical ventilation and lung stiffness (elastance, H) was measured hourly. The percentage change in elastance was determined over the time course of mechanical ventilation (n = 19–25 at 0–6 hours, n = 8–12 at 8 hours for each genotype). *P < 0.05 versus Mt1/2(+/+) by 2-way ANOVA with Bonferroni’s post-hoc test. (D–F) After 8 hours of mechanical ventilation (n = 4–8/group, denoted MV 24 ml/kg), bronchoalveolar lavage (BAL) fluid was collected and analyzed for total and differential cell counts (D), IL-6 levels by ELISA (E), and BAL total protein levels (F). *P < 0.05 versus Mt1/2(+/+) ventilation-induced lung injury (VILI) at 8 hours by 2-way ANOVA, with Bonferroni post-hoc test. No difference in baseline levels for any of these outcomes was observed between the 2 groups prior to mechanical ventilation. (G and H) After 8 hours of mechanical ventilation lungs were harvested and fixed at 30 cmH2O, paraffin embedded, and then stained with H&E (G), or with antibody against Gr1 to visualize neutrophils (H). Original magnification ×200. Histologic lung injury was quantified using a lung injury score as referenced in the text (I), and neutrophil infiltration was quantified by counting the Gr1-positive neutrophils per high-power field (hpf) (J). (I and J) n = 4/group, with each data point representing 1 mouse and the average of 9 hpfs expressed as mean ± SEM. *P < 0.05 versus Mt1/2(+/+) by Mann-Whitney U test.