The Acute Respiratory Distress Syndrome affects as many as 190,000 people each year and has a mortality rate as high as 46% despite improvement in beside management of mechanical ventilation strategies. There is no specific therapy for ARDS, and novel therapeutic concepts are urgently needed. We have discovered that the zinc-dependent metallothionein pathway exerts anti-inflammatory and cytoprotective effects during cell stretch in vitro and during ventilator-induced lung injury in vivo, and in human subjects with ARDS. Our central hypothesis/premise is that lung stretch initiates zinc-dependent lung protective molecular responses. A key corollary of this hypothesis is that zinc repletion represents a low-risk, high reward therapeutic approach to prevent and/or treat ARDS. However, regulation of zinc stores/metabolism is complex. In particular, low plasma zinc levels do not necessarily reflect low tissue stores of zinc, and there is substantial heterogeneity in zinc metabolism amongst critically ill patients. Thus, tailoring a safe and effective zinc supplementation strategy for ARDS requires mechanistic and clinical data. We propose to examine the biologic and clinical endpoints of zinc deficiency and response to zinc repletion in studies spanning cells to humans.
In Aim 1, we will determine the impact of zinc repletion on the response to cell stretch in vitro, examining the pharmacokinetics, time course, and zinc import/export mechanisms underlying zinc repletion using models mirroring human ARDS.
In Aim 2, we will determine the effect of chemical rescue of zinc deficiency in response to cell stretch using murine models of human ARDS to examine the pharmacokinetics, time course, dosing strategy/interval, tissue/cellular zinc stores, and underlying mechanism of restoration of zinc deficiency in both male and female mice.
In Aim 3, we will determine the incidence and impact of zinc deficiency in human ARDS through a comprehensive analysis of zinc levels in ARDS subjects throughout the course of illness that will enable us to correlate zinc levels with clinical outcomes, as well as biomarkers of inflammation, oxidant stress, epithelial injury, zinc transporter status, and host defense. These studies will reveal, for the first time, the impact of zinc deficiency on the pathogenesis and therapy of ARDS and enable us to determine which patients might benefit from zinc repletion during ARDS. Our long-term goal is to develop the first targeted therapeutic and preventive strategy for ARDS. Importantly a Phase 1 trial recently completed enrollment testing zinc supplementation to augment the immune response in sepsis, providing a foundation for rapid clinical translation of this project.
The Acute Respiratory Distress Syndrome is a syndrome with high morbidity and mortality and for which there are no targeted treatment strategies. Mechanical ventilation can be life-saving in ARDS but also can cause high levels of lung stretch that promote additional ventilator-induced lung injury. We have discovered that the zinc-dependent metallothionein pathway is upregulated in response to mechanical stretch in cells, animals subjected to lung injury, and humans with ARDS, and is an inherently protective pathway for lung function. Exogenous activation of this endogenous pathway by zinc administration offers a novel low-risk, high-reward candidate therapeutic for ARDS. However, the regulation of zinc stores in critical illness is complex and requires mechanistic understanding prior to implementing a clinical trial in human ARDS, especially given the inherent heterogeneity of ARDS as well as highly variable patient response to clinical interventions in critical illness. We therefore propose studies that will allow us, for the first time, to determine the impact of zinc deficiency and repletion on the pathogenesis and therapy of ARDS, ideally targeted toward patients most likely to respond to zinc. Our long-term goal is to develop the first targeted therapeutic and preventive strategy for ARDS. Importantly, a Phase 1 trial has recently been completed testing zinc supplementation to augment the immune response in sepsis, providing a foundation for rapid clinical translation of this project.