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Post-translational modification of manganese superoxide dismutase in acutely rejecting cardiac transplants: role of inducible nitric oxide synthase. J Heart Lung Transplant 2005 Oct;24(10):1591-9

Date

10/08/2005

Pubmed ID

16210135

DOI

10.1016/j.healun.2005.01.009

Scopus ID

2-s2.0-25844454887   35 Citations

Abstract

BACKGROUND: Nitration of a critical tyrosine residue in the active site of manganese superoxide dismutase (MnSOD) can lead to enzyme inactivation. In this study, we examined the effect of inducible nitric oxide synthase (iNOS) on MnSOD expression, activity and nitration in acutely rejecting cardiac transplants.

METHODS: Lewis (isograft) or Wistar-Furth (allograft) donor hearts were transplanted into Lewis recipient rats. Some rats received L-N6-(1-iminoethyl) lysine (l-NIL), a specific iNOS inhibitor. Protein nitration was determined by immunohistochemical, Western blot and slot-blot analyses. MnSOD enzyme activity and gene expression were determined using Western, reverse transcriptase-polymerase chain reaction (RT-PCR) and immunoprecipitation techniques.

RESULTS: MnSOD protein levels were decreased 50% by post-operative day 6 (POD 6), which was prevented by L-NIL. RT-PCR analysis indicated that this decrease could not be explained by any changes in MnSOD mRNA. MnSOD enzyme activity but not protein was decreased at POD 5 in untreated allografts. The loss of MnSOD activity at POD 5 was also prevented by L-NIL. Immunoreactive nitrotyrosine was apparent in untreated allografts at POD 6. Slot-blot analysis indicated that nitrotyrosine formation in allografts could be blocked by L-NIL. Nitration of MnSOD was evident upon immunoprecipitation of MnSOD followed by Western blotting for nitrotyrosine.

CONCLUSIONS: These results suggest that the decreased MnSOD enzyme activity in acutely rejecting cardiac allografts can be attributed to a post-translational modification related to nitration arising via an iNOS-dependent pathway. This could be a potential major source of amplified oxidative stress in acute graft rejection.

Author List

Nilakantan V, Halligan NL, Nguyen TK, Hilton G, Khanna AK, Roza AM, Johnson CP, Adams MB, Griffith OW, Pieper GM

Authors

Christopher P. Johnson MD Professor in the Surgery department at Medical College of Wisconsin
Allan M. Roza MD Professor in the Surgery department at Medical College of Wisconsin




MESH terms used to index this publication - Major topics in bold

Acute Disease
Animals
Disease Models, Animal
Enzyme Inhibitors
Gene Expression
Graft Rejection
Heart Transplantation
Lysine
Nitric Oxide Synthase Type II
Oxidative Stress
Peroxynitrous Acid
Protein Processing, Post-Translational
Rats
Rats, Inbred Lew
Rats, Inbred WF
Superoxide Dismutase
Tyrosine
jenkins-FCD Prod-478 d1509cf07a111124a2d122fd3df854cc0b993c00