Research Article

Antioxidant role of human haptoglobin

  1. Chi Feng Tseng,
  2. Chia Ching Lin,
  3. Hsing Yi Huang,
  4. Huei Chun Liu,
  5. Ph.D., Professor and Dean Simon J. T. Mao*

Article first published online: 9 JUN 2004

DOI: 10.1002/pmic.200300787

Issue

PROTEOMICS

PROTEOMICS

Special Issue: UNDERSTANDING BIOLOGICAL SYSTEMS THROUGH PROTEOMICS – SPS Proceedings 3rd Annual Congress, Basel, Switzerland 2–4 December 2003

Volume 4, Issue 8, pages 2221–2228, August 2004

Additional Information

How to Cite

Tseng, C. F., Lin, C. C., Huang, H. Y., Liu, H. C. and Mao, S. J. T. (2004), Antioxidant role of human haptoglobin. PROTEOMICS, 4: 2221–2228. doi: 10.1002/pmic.200300787

Author Information

  1. Institute of Biochemical Engineering, College of Biological Science and Technology, National Chiao Tung University, Hsinchu, Taiwan

*Department of Biological Science and Technology, College of Biological Science and Technology, National Chiao Tung University, 75 PO-Ai Street, Hsinchu, Taiwan Fax: 886-3-572-9288

Publication History

  1. Issue published online: 20 JUL 2004
  2. Article first published online: 9 JUN 2004
  3. Manuscript Received: 16 DEC 2003

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Keywords:

  • Antioxidant;
  • Haptoglobin cDNA;
  • Haptoglobin phenotypes;
  • Hemoglobin;
  • Physiologic role

Abstract

Human plasma haptoglobin (Hp) is classified according to three phenotypes: Hp 1-1, 2-1, and 2-2 attributed by their two common alleles 1 and 2. Clinically, the 2–2 phenotype is associated with the risk of cardiovascular diseases and diabetes mellitus in patients. In this study, we demonstrate that Hp is an extremely potent antioxidant, which directly protects low density lipoprotein from Cu2+-induced oxidation. Its potency was markedly superior to probucol (one of the most potent antioxidants). Ranking of the IC50 of antioxidant activity was as follows: Hp 1-1 ≳ Hp 2-1 ≳ Hp 2-2 ≳ probucol ≳ vitamin E. Blockage of disulfide linkages between Hp subunits, not only abolished the α-helical content but also diminished the ability of Hp to form a complex with hemoglobin. The modified Hp subunits exerted almost 4 times greater antioxidant activity than that of native Hp. To investigate the antioxidant role of Hp on the cellular level, the cDNA of Hp 1-1 was cloned, introduced into the pcDNA3.0 vector which contains the cytomega lovirus promoter and transfected into chinese hamster ovary (CHO)-K1 cells. Following transfection, CHO cells were able to express Hp 1–1 protein and significantly (p < 0.001) elevated cell tolerance against oxidative stress. Transfected cells showed 2-fold higher resistance to hydrogen peroxide exposure for 24 h compared to control cells. Thus, Hp plays a provocative antioxidant role as demonstrated by our in vitro and ex vivo studies.

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