Oral Presentation Matrix Biology Society of Australia and New Zealand Annual Meeting 2012

Damage to extracellular matrix and its main component laminin, by peroxynitrite (#39)

Georg Degendorfer 1 , Christine Y Chuang 1 , Fumiyuki Yamakura 2 , Michael J Davies 1 3
  1. The Heart Research Institute, Newtown, NSW, Australia
  2. School of Health and Nursing, Juntendo University, Tokyo, Japan
  3. Faculty of Medicine, University of Sydney, Camperdown, NSW, Australia

The extracellular matrix (ECM) provides mechanical strength and elasticity to tissues by forming a complex cross-linked scaffold of matrix proteins that provides binding sites for cells and other materials. The interaction of ECM with surrounding cells plays a key role in the regulation of cellular behaviour, and there is considerable evidence that damage to ECM components in the arterial wall plays a role in the development of atherosclerosis. Chronic inflammation, a characteristic of human atherosclerotic lesions, results in the recruitment of large numbers of activated neutrophils, monocytes and macrophages that generate reactive species such as superoxide radicals (O2•–) and nitric oxide (•NO). These species cross-react to yield peroxynitrite (ONOOH) a powerful oxidant; considerable data supports the formation of this material is human atherosclerotic lesions.

This study has examined the effects of exposure of isolated basement membrane extract and purified laminin-1 (both from murine Englebreth-Holm-Swarm tumors) to reagent ONOOH. Exposure resulted in dose-dependent protein damage, as evidenced by protein aggregation and fragmentation and loss of antibody epitope recognition. This damage was modulated by bicarbonate, a known modifier of ONOOH reactions. Loss of protein tyrosine and thiol groups, and formation of 3-nitrotyrosine and nitrotryptophans, biomarkers of reactive nitrogen species, occurred in a dose dependent manner on both isolated laminin-1 and basement membrane components.

            Overall, these studies show that ECM and in particular laminin is susceptible to oxidant-mediated protein damage induced by peroxynitrite. Furthermore, this damage leads to change in protein structures, particularly at critical cell- and protein-binding sites, which may alter the functionality of the ECM. These data are consistent with the hypothesis that peroxynitrite-mediated damage to ECM results in the weakening of its structure, and loss of function, with this potentially playing a critical role in the rupture of the fibrous cap of atherosclerotic lesions; this process is the major cause of most heart attacks and strokes.