Immunotargeting of catalase to the pulmonary endothelium alleviates oxidative stress and reduces acute lung transplantation injury

Abstract

Vascular immunotargeting may facilitate the rapid and specific delivery of therapeutic agents to endothelial cells. We investigated whether targeting of an antioxidant enzyme, catalase, to the pulmonary endothelium alleviates oxidative stress in an in vivo model of lung transplantation. Intravenously injected enzymes, conjugated with an antibody to platelet-endothelial cell adhesion molecule-1, accumulate in the pulmonary vasculature and retain their activity during prolonged cold storage and transplantation. Immunotargeting of catalase to donor rats augments the antioxidant capacity of the pulmonary endothelium, reduces oxidative stress, ameliorates ischemia-reperfusion injury, prolongs the acceptable cold ischemia period of lung grafts, and improves the function of transplanted lung grafts. These findings validate the therapeutic potential of vascular immunotargeting as a drug delivery strategy to reduce endothelial injury. Potential applications of this strategy include improving the outcome of clinical lung transplantation and treating a wide variety of endothelial disorders.

Factors modulating the delivery and effect of enzymatic cargo conjugated with antibodies targeted to the pulmonary endothelium

“…Most likely, lag between peak anti-TM/GOX targeting and manifestation of its effect reveals the time interval that is necessary to generate sufficiently toxic amount of H 2 O 2 in the pulmonary vasculature and cause the oxidative stress that takes a few hours to develop into vascular edema. Consistent with the fact that endothelium degrades delivered conjugates within a few hours [46,49,53], a more prolonged hyperoxia did not aggravate further the injury: enhanced supply of the substrate makes no difference when the targeted enzyme is gone.…”

“…We tested distribution of the radiolabeled TM antibodies and GOX conjugates one hour after IV injection. Previous studies of immunotargeting of radiolabeled conjugates directed to highly accessible endothelial determinants such as TM, angiotensin-converting enzyme (ACE), PECAM-1, intercellular adhesion molecule 1 (ICAM-1) and GP90 showed that their maximum uptake in the lungs occurs within 15-30 min, followed by a short 15-30 min stable period and subsequent reduction of the pulmonary level observed at times more than one hour after IV injection [22,25,27,[46][47][48][49][50][51][52]. Therefore, the kinetics of lung edema development showing a maximum 4 hour after injection of a lower dose of the conjugate selected to avoid overt early lethality (Fig.4C) is not due to delayed accumulation of GOX in the lungs.…”

Targeting of Drugs to ICAM for Treatment of Acute Lung Injury

“…In particular, intemalization of anti-ICAM-1 or anti-PECAM-1 conjugates was dependent on antigen clustering, and a critical parameter for intemalization was conjugate size (100 [211] and induces acute oxidative endothelial injury in murine lungs after IV injection [212]. Recent studies indicate that anti-CAM/catalase conjugates bind to and enter EC, which protects endothelium against oxidant stress in cell cultures [75,213] and in animals [214].…”

“…This intemalization pathway delivers materials to lysosomal compartments with unusually slow kinetics (around 3 h) [253]. Conjugation of catalase to anti-ICAM-1 or anti-PECAM-1 antibodies permits intracellular delivery of the active enzyme to EC, and provides anti-oxidant protection for a relatively prolonged window time due to the slow kinetics of delivery to lysosomes [214,253].…”

Targeted Delivery of Nucleic Acid-Based Therapeutics to the Pulmonary Circulation

“…These studies have important implications as endothelial dysfunction plays an important role in a number of pulmonary diseases such as pulmonary hypertension, adult respiratory distress syndrome, or metastatic disease to the lung. For example, targeted delivery of catalase to pulmonary ECs has been shown to offer lung protection in several models of lung injury (7)(8). Nucleic acidbased drugs are currently being explored as novel therapeutics, and they also hold promise for the treatment of pulmonary vascular diseases (9).…”