Protection against oxidative injury and permeability alteration in cultured alveolar epithelium by transferrin-catalase conjugate

Antioxidant strategies in respiratory medicine

Pulmonary oxidant stress plays an important pathogenetic role in disease conditions including acute lung injury/adult respiratory distress syndrome (ALI/ARDS), hyperoxia, ischemia-reperfusion, sepsis, radiation injury, lung transplantation, COPD, and inflammation. Reactive oxygen species (ROS), released from activated macrophages and leukocytes or formed in the pulmonary epithelial and endothelial cells, damage the lungs and initiate cascades of pro-inflammatory reactions propagating pulmonary and systemic stress. Diverse molecules including small organic compounds (e.g. gluthatione, tocopherol (vitamin E), flavonoids) serve as natural antioxidants that reduce oxidized cellular components, decompose ROS and detoxify toxic oxidation products. Antioxidant enzymes can either facilitate these antioxidant reactions (e.g. peroxidases using glutathione as a reducing agent) or directly decompose ROS (e.g. superoxide dismutases [SOD] and catalase). Many antioxidant agents are being tested for treatment of pulmonary oxidant stress. The administration of small antioxidants via the oral, intratracheal and vascular routes for the treatment of short- and long-term oxidant stress showed rather modest protective effects in animal and human studies. Intratracheal and intravascular administration of antioxidant enzymes are being currently tested for the treatment of acute oxidant stress. For example, intratracheal administration of recombinant human SOD is protective in premature infants exposed to hyperoxia. However, animal and human studies show that more effective delivery of drugs to cells experiencing oxidant stress is needed to improve protection. Diverse delivery systems for antioxidants including liposomes, chemical modifications (e.g. attachment of masking pegylated [PEG]-groups) and coupling to affinity carriers (e.g. antibodies against cellular adhesion molecules) are being employed and currently tested, mostly in animal and, to a limited extent, in humans, for the treatment of oxidant stress. Further studies are needed, however, in order to develop and establish effective applications of pulmonary antioxidant interventions useful in clinical practice. Although beyond the scope of this review, antioxidant gene therapies may eventually provide a strategy for the management of subacute and chronic pulmonary oxidant stress.

Efficient protection by cationized catalase against H2O2 injury in primary cultured alveolar epithelial cells

Increasing evidence suggests that hydrogen peroxide plays an important role in alveolar epithelial injury produced during many inflammatory lung diseases. In this study, the successful prevention of hydrogen peroxide (H(2)O(2))-induced injury in primary cultured rabbit alveolar epithelial cells by cationized catalase is described. Cationized catalase was synthesized by direct chemical modification to enhance its association with alveolar epithelial cells. Cationized catalase exhibited a 22.3-fold higher cellular association at 2 h than native catalase, and incubation of cationized catalase with the cells produced a 2.19-fold intracellular catalase activity, which suggested that cationized catalase distributed both to the cell membrane and into the cell interior. Cationized catalase markedly suppressed H(2)O(2)-induced cell injury. In addition, electron spin resonance spectrometry analysis revealed that cationized catalase effectively eliminated H(2)O(2) produced in the medium by glucose plus glucose oxidase. On the other hand, polyethylene glycol-modified catalase (PEG-catalase) did not have any protective effect against H(2)O(2)-induced cell injury although PEG-catalase exhibited a 2.49-fold higher cellular association at 2 h than native catalase. These results suggest that cationization of catalase is a promising strategy for the treatment of many of inflammatory lung diseases.

Lectin-mediated drug delivery: binding and uptake of BSA-WGA conjugates using the Caco-2 model

To examine whether the dietary lectin wheat germ agglutinin (WGA) can facilitate binding and uptake of protein drugs due to its cytoadhesive and cytoinvasive properties, conjugates were prepared by covalent coupling of fluorescein-labeled bovine serum albumin (F-BSA) to WGA using divinylsulfone for crosslinking. Increasing the molar ratio of F-BSA/WGA resulted in 2.6-8.7 times higher Caco-2 binding as compared with glycyl-F-BSA. About 75% of F-BSA-WGA were bound specifically to Caco-2 cells according to inhibition studies in presence of the complementary carbohydrate. The Caco-2 association of F-BSA-WGA was temperature-dependent indicating active uptake of membrane bound conjugate, which was confirmed by confocal microscopy. The conjugate accumulated within lysosomal compartments followed by proteolytic degradation of F-BSA-WGA 1-4 h after conjugate loading as observed by equilibrating the intracellular pH with monensin. Finally low molecular weight degradation products of the proteinaceous prodrug appear in the extracellular medium. Contrary to Caco-2 single cells, a minor part of the conjugate is degraded by brush border proteases already 30 min after exposure to Caco-2 monolayers. But most of the conjugate is taken up into differentiated cells and processed as in single cells. Though the enzymic barrier remains to be surmounted, WGA-mediated drug delivery is a promising strategy for peroral delivery of even high molecular weight drugs to overcome the mucosal barrier.

Oxidant injury in coronary heart disease (Part-I)

Oxidative stress damages the heart through a series of reactions beginning with lipid peroxidation, the main process behind atherosclerosis. Antioxidant supplementation has some beneficial effects by binding with metal ions or catalysts to prevent oxidative lipid peroxidation and chain production.

Delivery of antioxidant enzyme proteins to the lung

Protection of alveolar epithelial cells (alveolocytes) and vascular endothelial cells against pulmonary oxidative stress is an important problem. An inadequate delivery to the target cells limits the protective utility of the antioxidant enzymes, superoxide dismutase (SOD) and catalase. SOD and catalase modifications, such as coupling with polyethylene glycol and encapsulation in liposomes, prolong the life span of the active enzymes in vivo. The airway administration of SOD and catalase protects alveolocytes against hyperoxic oxidative stress. Although pulmonary endothelium is poorly accessible from the airways, it is accessible from circulation. However, antioxidant enzymes and their derivatives display poor targeting to pulmonary endothelium. To improve the targeting and provide intracellular delivery to endothelium, the enzymes can be conjugated with antibodies against endothelial antigens, such as angiotensin-converting enzyme and adhesion molecules [intercellular adhesion molecule-1 (ICAM-1) or platelet-endothelial cell adhesion molecule-1 (PECAM-1)]. These immunoconjugates accumulate in the pulmonary vasculature in intact animals, enter endothelium, and augment the antioxidant defenses. The immunoconjugates directed against ICAM-1 and PECAM-1 may also provide a secondary therapeutic benefit by blocking of sequestration and infiltration of leukocytes in the lungs. Further investigations are necessary to evaluate the therapeutic effectiveness of the vascular immunotargeting of antioxidant enzymes and solve technical problems associated with production of safe, clinically useful conjugates.

Exercise and the immune system: regulation, integration, and adaptation

Stress-induced immunological reactions to exercise have stimulated much research into stress immunology and neuroimmunology. It is suggested that exercise can be employed as a model of temporary immunosuppression that occurs after severe physical stress. The exercise-stress model can be easily manipulated experimentally and allows for the study of interactions between the nervous, the endocrine, and the immune systems. This review focuses on mechanisms underlying exercise-induced immune changes such as neuroendocrinological factors including catecholamines, growth hormone, cortisol, beta-endorphin, and sex steroids. The contribution of a metabolic link between skeletal muscles and the lymphoid system is also reviewed. The mechanisms of exercise-associated muscle damage and the initiation of the inflammatory cytokine cascade are discussed. Given that exercise modulates the immune system in healthy individuals, considerations of the clinical ramifications of exercise in the prevention of diseases for which the immune system has a role is of importance. Accordingly, drawing on the experimental, clinical, and epidemiological literature, we address the interactions between exercise and infectious diseases as well as exercise and neoplasia within the context of both aging and nutrition.