Novel Delivery of Antioxidant Enzyme Catalase to Alveolar Macrophages by Fc Receptor-Mediated Endocytosis

Jeannine Harrison, Xianglin Shi, Li Ying Wang, Joseph K.H. Ma, Yongyut Rojanasakul

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


Excessive production of reactive oxygen species by alveolar macrophages (AMs) in response to inhaled toxic substances is a major cause of oxidative lung injury. Therapeutic approaches designed to protect the lungs from oxidative injury by administering native antioxidant enzymes such as catalase and superoxide dismutase have been suggested. However, problems associated with poor penetration of these enzymes to the intracellular target sites have limited their effective use. The present study reports a drug targeting method based on receptor-mediated endocytosis of the antioxidant enzyme catalase to the AMs. This method employs molecular conjugate consisting of a cognate moiety, in this case IgG which recognizes the macrophage Fc receptor, covalently linked to the enzyme catalase via the reversible disulfide linkage. The uptake efficiency of the enzyme conjugate and its protection against oxidative injury were evaluated microfluorometrically using the intracellular oxidative probe dichlorodihydrofluorescein BSA: anti BSA antibody complex (DCHF-IC), and the cell viability indicator propidium iodide. The DCHF-IC-stimulated macrophages exhibited a dose- and time-dependent increase in intracellular fluorescence with a half maximal response dose of approximately 120 µg/ml. Free catalase (50–500 U/ml) failed to inhibit the DCHF-IC-induced oxidative burst and had only a marginal protective effect on AM injury. In contrast, the catalase-IgG conjugate (50–500 U/ml) strongly inhibited both the DCHF-IC-induced oxidation and injury in a dose-dependent manner. Effective inhibition was shown to require both the antioxidant catalase moiety and the cognate moiety for the cell surface receptor. Specific internalization of the conjugate through the Fc receptor was also investigated by competitive inhibition using free IgG. Under this condition, the conjugate showed a much reduced protective effect on intracellular oxidation, indicating conjugate internalization through the Fc endocytosis pathway. Thus, the enzyme-IgG conjugate system may be used as an effective and selective means to deliver antioxidant enzymes to the intracellular oxidative targets of the AMs.

Original languageEnglish
Pages (from-to)1110-1114
Number of pages5
JournalPharmaceutical Research
Issue number8
StatePublished - Aug 1994


  • catalase
  • endocytosis
  • immune complex
  • macrophages
  • oxidation

ASJC Scopus subject areas

  • Biotechnology
  • Molecular Medicine
  • Pharmacology
  • Pharmaceutical Science
  • Organic Chemistry
  • Pharmacology (medical)


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