Abstract 17888: Heart Failure Alters Slack Sarcomere Length and Z-disc width in Single Human Cardiomyocytes
In vitro exposure of cardiomyocytes (CMs) to oxidative agents induces contractile dysfunction because of oxidative damage of sarcomeric Z-disc proteins. Oxidative modification of titin-actin interaction close to the Z-discs can also have an impact on an altered Z-disc structure and slack sarcomere length (SL) by presetting a higher intrasarcomeric tension. To explore in vivo relevance of these effects, Z-disc widths and slack SLs of isolated human CMs were determined. LV myocardial samples were obtained from 3 explanted donor hearts (Con) and from transvascular endomyocardial biopsies of 6 heart failure (HF) patients. All patients were free of coronary artery disease. All CMs were Triton-permeabilized. To investigate the role of titin-actin interaction half of the CMs were treated with gelsolin, which induced extraction of actin and consequent disruption of titin-actin overlap. CMs were labelled with antibody against alpha-actinin to localize the Z-discs and with rhodamine-phalloidin to stain F-actin. High quality, 3D stacks of optical sections of CMs were obtained with digital imaging fluorescence microscopy (Figure). Linescans of alpha-actinin signal drawn perpendicularly to the Z-discs were used to create histograms of fluorescence intensity peaks, which allowed slack SL and Z-disc width determinations (Figure). Slack SLs of HF CMs were shorter compared to Con (13±0.5 a.u. vs. 14.9±0.6 a.u.; p=0.031). This was accompanied by larger Z-disc widths in HF than in Con (3.63±0.15 a.u. vs. 3.16±0.11 a.u.; p=0.032). Gelsolin treatment further shortened slack SL in HF (11.15±0.52 a.u.; p=0.048 vs. HF no gelsolin)(Figure).
Conclusions: slack SL and Z-disc width are altered upon HF, possibly due to oxidative damage of the Z-discs and of proteins in their immediate proximity. Structural and adjoining molecules of the Z-discs represent target proteins of oxidative modification, which may contribute to contractile dysfunction in HF.
- © 2010 by American Heart Association, Inc.