Sensitivity of mechanical and metabolic functions to changes in coronary perfusion: A metabolic basis of perfusion-contraction coupling

Correlation of cardiac performance with cellular energetic components in the oxygen-deprived turtle heart

The relationship between cardiac energy metabolism and the depression of myocardial performance during oxygen deprivation has remained enigmatic. Here, we combine in vivo (31)P-NMR spectroscopy and MRI to provide the first temporal profile of in vivo cardiac energetics and cardiac performance of an anoxia-tolerant vertebrate, the freshwater turtle (Trachemys scripta) during long-term anoxia exposure (approximately 3 h at 21 degrees C and 11 days at 5 degrees C). During anoxia, phosphocreatine (PCr), unbound levels of inorganic phosphate (effective P(i)(2-)), intracellular pH (pH(i)), and free energy of ATP hydrolysis (dG/dxi) exhibited asymptotic patterns of change, indicating that turtle myocardial high-energy phosphate metabolism and energetic state are reset to new, reduced steady states during long-term anoxia exposure. At 21 degrees C, anoxia caused a reduction in pH(i) from 7.40 to 7.01, a 69% decrease in PCr and a doubling of effective P(i)(2-). ATP content remained unchanged, but the free energy of ATP hydrolysis (dG/dxi) decreased from -59.6 to -52.5 kJ/mol. Even so, none of these cellular changes correlated with the anoxic depression of cardiac performance, suggesting that autonomic cardiac regulation may override putative cellular feedback mechanisms. In contrast, during anoxia at 5 degrees C, when autonomic cardiac control is severely blunted, the decrease of pH(i) from 7.66 to 7.12, 1.9-fold increase of effective P(i)(2-), and 6.4 kJ/mol decrease of dG/dxi from -53.8 to -47.4 kJ/mol were significantly correlated to the anoxic depression of cardiac performance. Our results provide the first evidence for a close, long-term coordination of functional cardiac changes with cellular energy status in a vertebrate, with a potential for autonomic control to override these immediate relationships.

Measurements of intracellular volumes by 59Co and 2H/1H NMR and their physiological applications

Determination of the intracellular water volumes using NMR spectroscopy was performed using the NMR-visible nuclei: 59Co and 2H or 1H. Accurate measurement of intracellular water in cell suspensions and perfused organs is an important physiological parameter in the context of electrolyte homeostasis and energy metabolism, in particular when these parameters are monitored by non-invasive NMR spectroscopy. Furthermore, repeated or continuous monitoring of intracellular water provided significant insights into the physiology of cardiac muscle and sarcolemmal membrane permeability and integrity.

Display of Fas ligand protein on cardiac vasculature as a novel means of regulating allograft rejection

BACKGROUND

Fas ligand (FasL) is a potent death-inducing molecule with important functions in immune homeostasis and tolerance to self-antigens. The complex biological activities of FasL and its inefficient expression using conventional gene transfer approaches limit its use for immunomodulation to prevent allograft rejection. We have recently generated a chimeric FasL with core streptavidin (SA-FasL) with potent apoptotic activity and designed a novel approach to display it on the surface of several cell types via biotinylation. We herein tested whether SA-FasL can also be displayed on vascular endothelial cells in the heart and examined its effect on graft survival after transplantation into syngeneic and allogeneic hosts.

METHODS AND RESULTS

SA-FasL was efficiently displayed on the vasculature of BALB/c hearts with a half-life of 9 days in vivo. Transplantation of hearts displaying SA-FasL into syngeneic hosts resulted in indefinite graft survival without detectable toxicity to the grafts and hosts. In contrast, transplantation of allogeneic C57BL/10 hearts displaying SA-FasL into BALB/c recipients resulted in graft rejection, but in a delayed fashion as compared with control hearts (mean survival time=17.4+/-5 versus 9.6+/-1 days). Allograft survival was further extended to 21+/-2.6 and 24+/-3 days (P<0.05) by intravenous treatment of graft recipients with 1 dose of SA-FasL-decorated donor splenocytes on days 2 and 6 after transplantation, respectively.

CONCLUSIONS

This study shows for the first time that exogenous proteins can be displayed on the endothelium of solid organs for therapeutic purposes. This approach provides a convenient and rapid means of displaying exogenous proteins on the surface of cells, tissues, and solid organs, with broad research and therapeutic implications.