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Stanford, CA, United States

Malkovskiy A.V.,Stanford BioADD Laboratory | Wagh D.A.,Stanford BioADD Laboratory | Longo F.M.,Stanford University | Rajadas J.,Stanford BioADD Laboratory
Analyst | Year: 2015

Phospholipids are important membrane components involved in diverse biological activities ranging from cell signaling to infection by viral particles. A thorough understanding of protein-phospholipid interaction dynamics is thus crucial for deciphering basic cellular processes as well as for targeted drug discovery. For any specific phospholipid-protein binding experiment, various groups have reported different binding constants, which are strongly dependent on applied conditions of interactions. Here, we report a method for accurate determination of the binding affinity and specificity between proteins and phospholipids using a model interaction between PLC-δ1/PH and phosphoinositide phospholipid PtdIns(4,5)P2. We developed an accurate Force Distance Spectroscopy (FDS)-based assay and have attempted to resolve the problem of variation in the observed binding constant by directly measuring the bond force. We confirm the FDS findings of a high bond strength of ∼0.19 ± 0.04 nN by Surface Plasmon Resonance (SPR) data analysis, segregating non-specific interactions, which show a significantly lower KD suggesting tight binding. © 2015 The Royal Society of Chemistry. Source


Jiang X.,Veterans Affairs Palo Alto Health Care System | Jiang X.,Stanford University | Nguyen T.T.,Veterans Affairs Palo Alto Health Care System | Nguyen T.T.,Stanford University | And 15 more authors.
American Journal of Transplantation | Year: 2015

The loss of a functional microvascular bed in rejecting solid organ transplants is correlated with fibrotic remodeling and chronic rejection; in lung allografts, this pathology is predicted by bronchoalveolar fluid neutrophilia which suggests a role for polymorphonuclear cells in microcirculatory injury. In a mouse orthotopic tracheal transplant model, cyclosporine, which primarily inhibits T cells, failed as a monotherapy for preventing microvessel rejection and graft ischemia. To target neutrophil action that may be contributing to vascular injury, we examined the effect of a neutrophil elastase inhibitor, elafin, on the microvascular health of transplant tissue. We showed that elafin monotherapy prolonged microvascular perfusion and enhanced tissue oxygenation while diminishing the infiltration of neutrophils and macrophages and decreasing tissue deposition of complement C3 and the membrane attack complex, C5b-9. Elafin was also found to promote angiogenesis through activation of the extracellular signal-regulated kinase (ERK) signaling pathway but was insufficient as a single agent to completely prevent tissue ischemia during acute rejection episodes. However, when combined with cyclosporine, elafin effectively preserved airway microvascular perfusion and oxygenation. The therapeutic strategy of targeting neutrophil elastase activity alongside standard immunosuppression during acute rejection episodes may be an effective approach for preventing the development of irreversible fibrotic remodeling. Using a mouse orthotopic tracheal transplantation model, the authors show that cyclosporine fails to protect the microvasculature of airway transplants undergoing acute rejection, but combined therapy with cyclosporine and a neutrophil elastase inhibitor, elafin, synergistically promotes the microvascular perfusion and improves the transplant structural integrity. © Copyright 2015 The American Society of Transplantation and the American Society of Transplant Surgeons. Source


Jiang X.,Stanford University | Malkovskiy A.V.,Stanford BioADD Laboratory | Tian W.,Stanford University | Sung Y.K.,Stanford University | And 8 more authors.
Biomaterials | Year: 2014

Airway tissue ischemia and hypoxia in human lung transplantation is a consequence of the sacrifice of the bronchial circulation during the surgical procedure and is a major risk factor for the development of airway anastomotic complications. Augmented expression of hypoxia-inducible factor (HIF)-1α promotes microvascular repair and alleviates allograft ischemia and hypoxia. Deferoxamine mesylate (DFO) is an FDA-approved iron chelator which has been shown to upregulate cellular HIF-1α. Here, we developed a nanoparticle formulation of DFO that can be topically applied to airway transplants at the time of surgery. In a mouse orthotopic tracheal transplant (OTT) model, the DFO nanoparticle was highly effective in enhancing airway microvascular perfusion following transplantation through the production of the angiogenic factors, placental growth factor (PLGF) and stromal cell-derived factor (SDF)-1. The endothelial cells in DFO treated airways displayed higher levels of p-eNOS and Ki67, less apoptosis, and decreased production of perivascular reactive oxygen species (ROS) compared to vehicle-treated airways. In summary, a DFO formulation topically-applied at the time of surgery successfully augmented airway anastomotic microvascular regeneration and the repair of alloimmune-injured microvasculature. This approach may be an effective topical transplant-conditioning therapy for preventing airway complications following clinical lung transplantation. © 2013 Elsevier Ltd. Source

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