Victor E. Laubach
- BA,BS, Pennsylvania State University, University Park, PA
- PhD, George Washington University School of Medicine
- Professor, Surgery
Mechanisms of acute lung injury after transplantation - molecular imaging, ex vivo lung perfusion, vascular inflammation, purinergic signaling, oxidative stress, innate immunity.
My laboratory conducts translational studies into mechanisms and prevention of lung ischemia-reperfusion (IR) injury following transplantation. IR injury, due to a rapid and robust inflammatory response, is a primary cause of primary graft dysfunction and remains a significant and perplexing cause of morbidity and mortality after lung transplant. IR injury also leads to an increased risk for chronic graft dysfunction and rejection. Our research utilizes both in vivo and in vitro models to explore inflammatory signaling pathways in innate immune cells, epithelial cells and endothelial cells as well as cross-talk among these cells and discovering novel therapeutic strategies to prevent or treat IR injury.
Current Research Projects: Pannexin 1 and extracellular ATP. ATP is a nucleotide released in large amounts after injury and serves as a “danger signal” to mediate inflammation. Recent studies reveal that cells can actively release ATP in a controlled manner through pannexin 1 (Panx1) channels to signal through purinergic P2X or P2Y receptors. Our data suggest that Panx1 on endothelial cells (ECs) is an important mediator of lung IR injury and may be a major source of extracellular ATP after IR. Our current NIH-funded studies are aimed at defining the role of Panx1-derived extracellular ATP (and relevant ATP-binding purinergic receptors) in mediating lung IR injury through activation of ECs, neutrophils, and alveolar macrophages.
Ex vivo lung perfusion (EVLP). EVLP is a novel technique whereby marginal (poor-quality) donor lungs undergo ex vivo perfusion in order to assess function and undergo reconditioning to allow for successful transplantation. EVLP involves keeping donor lungs ‘breathing’ outside of the body and perfusing them with nutrients and blood-substitutes. The UVA Health System is utilizing EVLP clinically, and our research lab is studying EVLP in several experimental models including murine, porcine and even human donor lungs. EVLP provides an ideal platform to apply various therapeutic strategies to the isolated organ to enhance rehabilitation of donor lungs. We are testing a variety of protective, anti-inflammatory treatments during EVLP to recondition marginal donor lungs and prevent graft failure after transplantation.
T cell-mediated IR injury. We have recently described a paradigm shift in our understanding of the role of T cells in lung IR injury by showing that the activation of invariant natural killer T (iNKT) cells is a key initiator of IR injury by producing IL-17, a key chemokine for the infiltration of neutrophils that contribute to tissue damage. We are continuing to explore the role of iNKT cells and their interaction with alveolar epithelial cells, macrophages and endothelial cells.
Non-invasive, SPECT imaging of lung inflammation after transplant. Current methods to diagnose primary graft dysfunction (PGD) in transplanted lungs are limited to x-ray, CT, and functional tests, none of which specifically address inflammation or immune cell activation; key components of PGD. The development of non-invasive, cell-specific molecular imaging methods to provide early and accurate diagnosis of lung ischemia-reperfusion injury (IRI, which leads to PGD) would permit timely and targeted therapeutic interventions. Thus our NIH-funded research aims to utilize and validate several novel molecular, cell-specific probes to image lung IRI via single photon emission computed tomography (SPECT) imaging. Molecular probes currently being investigated include probes that specifically target activated neutrophils, activated (M1) macrophages, or anti-inflammatory (M2) macrophages, with the goal of being able to image lung IRI early as well as monitor the resolution of IRI in response to therapy.
Oxidative stress. Oxidative stress is one of the key mechanisms involved in IR injury after lung transplantation. We have shown that NADPH oxidase (NOX2)-generated reactive oxygen species is a key component of immune cell activation during IR, and current studies are aimed at defining the role of NOX2 (and other NOX isoforms) in the activation of various cell populations (e.g. iNKT cells, macrophages, alveolar epithelial cells, endothelial cells) after IR.
Macrophage-mediated IR injury. We have demonstrated an important role for alveolar macrophages and macrophage-derived TNF-alpha in lung IR injury. We are continuing to explore the role of alveolar macrophages as well as their cross-talk with alveolar epithelial cells and iNKT cells.
RAGE/HMGB1 axis. We have shown that macrophage-derived HMGB1 mediates lung IR injury by binding RAGE on iNKT cells and inducing IL-17 production, and we are continuing to study these signaling mechanisms. One potential mechanism being explored is whether RAGE-mediated IL-17 production requires NOX2 activation. In addition, we are exploring how alveolar macrophages release HMGB1 and whether this involves Toll-like Receptor (TLR) signaling in an autocrine fashion.
Sphingosine 1-phospate (S1P). S1P binds to a family of G-protein-coupled receptors (S1PR1-5) and plays a central role in maintaining endothelial barrier integrity. Circulating S1P is synthesized largely by red blood cells (RBCs) via SphK1. SphK1 and SphK2 synthesize tissue S1P, but S1P lyase maintains low tissue S1P levels. Preservation of endothelial barrier requires this steep differential across the endothelium, termed vascular S1P gradient (circulating S1P levels much higher than tissue). We have demonstrated that S1P-mediated protection from lung IR injury is mediated by S1PR1 receptor activation and that selective S1PR1 agonists may provide a novel therapeutic strategy to prevent lung IR injury after transplantation. Our current research is aimed at defining methods to protect the pulmonary endothelium after IR by increasing the vascular S1P gradient via pharmacologic methods.
Adenosine receptors in lung IR injury.. In organ injury such as IR injury, adenosine is a retaliatory metabolite with largely protective, anti-inflammatory effects. Adenosine binds to a family of G protein-coupled purinergic receptors (A1R, A2AR, A2BR, A3R), which are all expressed in the lung. We have shown that A2AR agonists potently attenuate lung IR injury largely due to the inactivation of NOX2 to block IL-17 production by iNKT cells. In contrast to A2AR, the role of A2BR in inflammation seems to vary depending on model as it has been shown to play both anti- and pro-inflammatory roles in injury. We have demonstrated that A2BR is proinflammatory after IR (lungs of A2BR-/- mice are protected), which is mediated by A2BRs on resident pulmonary (non-bone marrow-derived) cells such as epithelia. We also demonstrated that treatment with an selective A2BR antagonist attenuates lung IR injury in mice. Ongoing studies are aimed at further defining the therapeutic potential of A2AR agonists and A2BR antagonists in preventing lung IRI after transplant. In fact, research from our laboratory over the past decade has led to a recent clinical trial here at UVA (NIH R01HL128492) to test the use of A2AR agonist in lung transplant recipients.
Models used in the lab: We heavily utilize a mouse model of IR injury involving various knockout, transgenic and chimeric mice, immune cell ablation studies and adoptive transfer studies. We also utilize an in vitro model of IR using various pulmonary and immune cells, in isolated or co-culture conditions, to answer specific questions about cellular signaling after IR. Finally, our laboratory utilizes a large animal, porcine model of EVLP and lung transplantation as a pre-clinical model.
Techniques used in the lab: Routine techniques we use in the laboratory include cell culture, purification of primary cells, quantitative RT-PCR, flow cytometry, FACS, ELISA, multiplex (bead-array) cytokine assay, Western blot, ELISPOT assay, gene array, immunohistochemistry, confocal microscopy biochemical assays, and oxidative stress evaluation. Some murine methods we use include thoracic surgery, bone marrow transplantation, immune cell ablation, adoptive transfer of immune cells, pulmonary function measurements using an isolated mouse lung system, bronchoalveolar lavage, and measurement of pulmonary microvascular permeability.
- Charles E, Huerter M, Wagner C, Sharma A, Zhao Y, Stoler M, Mehaffey J, Isbell J, Lau C, Tribble C, Laubach V, Kron I. Donation After Circulatory Death Lungs Transplantable Up to Six Hours After Ex Vivo Lung Perfusion. The Annals of thoracic surgery. 2016;102(6): 1845-1853. PMID: 27614736 | PMCID: PMC5112144
- Huerter M, Sharma A, Zhao Y, Charles E, Kron I, Laubach V. Attenuation of Pulmonary Ischemia-Reperfusion Injury by Adenosine A2B Receptor Antagonism. The Annals of thoracic surgery. 2016;102(2): 385-93. PMID: 27109193 | PMCID: PMC4958568
- Laubach V, Sharma A. Mechanisms of lung ischemia-reperfusion injury. Current opinion in organ transplantation. 2016. PMID: 26945320 | PMCID: PMC4861054
- Sharma A, LaPar D, Stone M, Zhao Y, Mehta C, Kron I, Laubach V. NOX2 Activation of Natural Killer T Cells Is Blocked by the Adenosine A2A Receptor to Inhibit Lung Ischemia-Reperfusion Injury. American journal of respiratory and critical care medicine. 2016;193(9): 988-99. PMID: 26757359 | PMCID: PMC4872653
- Stone M, Sharma A, Mas V, Gehrau R, Mulloy D, Zhao Y, Lau C, Kron I, Huerter M, Laubach V. Ex Vivo Perfusion With Adenosine A2A Receptor Agonist Enhances Rehabilitation of Murine Donor Lungs After Circulatory Death. Transplantation. 2015;99(12): 2494-503. PMID: 26262504 | PMCID: PMC4668207
- Stone M, Sharma A, Zhao Y, Charles E, Huerter M, Johnston W, Kron I, Lynch K, Laubach V. Sphingosine-1-phosphate receptor 1 agonism attenuates lung ischemia-reperfusion injury. American journal of physiology. Lung cellular and molecular physiology. 2015;308(12): L1245-52. PMID: 25910934 | PMCID: PMC4587601
- Sharma A, LaPar D, Stone M, Zhao Y, Kron I, Laubach V. Receptor for advanced glycation end products (RAGE) on iNKT cells mediates lung ischemia-reperfusion injury. American journal of transplantation : official journal of the American Society of Transplantation and the American Society of Transplant Surgeons. 2013;13(9): 2255-67. PMID: 23865790 | PMCID: PMC3776006
- Sharma A, Mulloy D, Le L, Laubach V. NADPH oxidase mediates synergistic effects of IL-17 and TNF-α on CXCL1 expression by epithelial cells after lung ischemia-reperfusion. American journal of physiology. Lung cellular and molecular physiology. 2013;306(1): L69-79. PMID: 24186876 | PMCID: PMC3920214
- Mulloy D, Stone M, Crosby I, Lapar D, Sharma A, Webb D, Lau C, Laubach V, Kron I. Ex vivo rehabilitation of non-heart-beating donor lungs in preclinical porcine model: delayed perfusion results in superior lung function. The Journal of thoracic and cardiovascular surgery. 2012;144(5): 1208-15. PMID: 22944084 | PMCID: PMC3477251
- Lapar D, Hajzus V, Zhao Y, Lau C, French B, Kron I, Sharma A, Laubach V. Acute hyperglycemic exacerbation of lung ischemia-reperfusion injury is mediated by receptor for advanced glycation end-products signaling. American journal of respiratory cell and molecular biology. 2011;46(3): 299-305. PMID: 21980055 | PMCID: PMC3326427
- Sharma A, LaPar D, Zhao Y, Li L, Lau C, Kron I, Iwakura Y, Okusa M, Laubach V. Natural killer T cell-derived IL-17 mediates lung ischemia-reperfusion injury. American journal of respiratory and critical care medicine. 2011;183(11): 1539-49. PMID: 21317314 | PMCID: PMC3137143
- Gazoni L, Walters D, Unger E, Linden J, Kron I, Laubach V. Activation of A1, A2A, or A3 adenosine receptors attenuates lung ischemia-reperfusion injury. The Journal of thoracic and cardiovascular surgery. 2010;140(2): 440-6. PMID: 20398911 | PMCID: PMC2906677
- Laubach V, French B, Okusa M. Targeting of adenosine receptors in ischemia-reperfusion injury. Expert opinion on therapeutic targets. 2010;15(1): 103-18. PMID: 21110787 | PMCID: PMC3075429
- Sharma A, Linden J, Kron I, Laubach V. Protection from pulmonary ischemia-reperfusion injury by adenosine A2A receptor activation. Respiratory research. 2009;10 58. PMID: 19558673 | PMCID: PMC2711962
- Yang Z, Sharma A, Linden J, Kron I, Laubach V. CD4+ T lymphocytes mediate acute pulmonary ischemia-reperfusion injury. The Journal of thoracic and cardiovascular surgery. 2009;137(3): 695-702; discussion 702. PMID: 19258091 | PMCID: PMC2670927