Effects of Crystalloid, Blood and Celsior Solutions on Porcine Coronary Endothelial Function After Heart Transplantation

New strategy of endothelial protection in cardiac surgery: use of enhancer of endothelial nitric oxide synthase

BACKGROUND

Endothelial dysfunction related to the loss of nitric oxide (NO) production remains an important issue in cardiac surgery. We examined the hypothesis that AVE3085, a novel compound that enhances eNOS transcription, may protect coronary endothelium against hypoxia-reoxygenation (H-R) injury during cardioplegic arrest and the possible mechanism by which this occurs.

METHODS

Porcine coronary small arteries (600-800-microm diameter) were subjected to hypoxia (PO(2) <5 mmHg) in St. Thomas cardioplegic (ST) solution with or without AVE3085 (10 microM) or L-arginine (10 mM) at either 37 or 4 degrees C for 60 min, followed by 30-min reoxygenation. Bradykinin (-10 to -6.5 LogM)-induced, endothelium-dependent relaxation was studied in a myograph in U(46619) precontraction before and after H-R. Protein expressions of eNOS and phosphorylated eNOS at Ser-1177 (p-eNOS(Ser1177)) were also determined.

RESULTS

Exposure to ST solution with H-R at both 37 and 4 degrees C markedly reduced bradykinin-induced relaxation in coronary small arteries. Addition of AVE3085 in ST solution at 37 degrees C preserved the vasorelaxant response to bradykinin (95.7 +/- 2.1% vs. 69.2 +/- 6.6%, p < 0.01), with the protective effect comparable to that of L-arginine (96.1 +/- 3.3% vs. 70.6 +/- 8.7%, p < 0.05). eNOS and p-eNOS(Ser1177) expressions in coronary endothelial cells were significantly increased by the addition of AVE3085 in ST solution during hypoxia (p < 0.05). Protection of endothelium-dependent relaxation from H-R by AVE3085 (70.3 +/- 7.2% vs. 90.5 +/- 2.4%, p < 0.05) also reached a level similar to that by L-arginine (69.9 +/- 9.0% vs. 94.7 +/- 3.9%, p < 0.05) at 4 degrees C.

CONCLUSIONS

We have demonstrated a new mechanism to protect coronary endothelium from H-R injury by using eNOS enhancers. This may form a new strategy in the future development of cardioplegic/preservation solutions with direct targeting of eNOS expression in coronary vasculature.

Low-flow perfusion of guinea pig isolated hearts with 26 degrees C air-saturated Lifor solution for 20 hours preserves function and metabolism

BACKGROUND

Donor human hearts cannot be preserved for >5 hours between explantation and recipient implantation. A better approach is needed to preserve transplantable hearts for longer periods, ideally at ambient conditions for transport. We tested whether Lifor solution could satisfactorily preserve guinea pig isolated hearts perfused at low flow with no added oxygen at room temperature for 20 hours.

METHODS

Hearts were isolated from 18 guinea pigs and perfused initially with oxygenated Krebs-Ringer (KR) solution at 37 degrees C. Hearts were then perfused with recirculated Lifor or cardioplegia (CP) solution (K(+) 15 mmol/liter) equilibrated with room air at 20% of control flow at 26 degrees C for 20 hours. Hearts were then perfused at 100% flow with KR for 2 hours at 37 degrees C.

RESULTS

Lifor and CP arrested all hearts. During the 20-hour low-flow perfusion with Lifor coronary pressure increased by 6 +/- 2 mm Hg and percent oxygen extraction by 29 +/- 2%, whereas oxygen consumption (MVo(2)) decreased by 74 +/- 4%. Similar changes were noted for CP, except that MVo(2) was decreased by 86 +/- 7%. After 20-hour low-flow perfusion with Lifor and 2 hours of warm reperfusion with KR solution, diastolic left ventricular pressure (LVP), maximal dLVP/dt and percent oxygen extraction returned completely to baseline values, whereas heart rate returned to 80 +/- 3%, developed LVP to 76 +/- 3%, minimal dLVP/dt (relaxation) to 65 +/- 4%, coronary flow to 80 +/- 4%, oxygen consumption to 82 +/- 4% and cardiac efficiency to 85 +/- 4% of baseline values. Flow responses to adenosine and nitroprusside after Lifor treatment were 65 +/- 3% and 64 +/- 3% of their baseline values. After cardioplegia, treatment there was no cardiac activity, with a diastolic pressure of 35 +/- 14 mm Hg and a return of coronary flow to only 45 +/- 3% of baseline value.

CONCLUSIONS

Compared with a cardioplegia solution at ambient air and temperature conditions, Lifor solution is a much better medium for long-term cardiac preservation in this model.

Endothelial dysfunction after long-term cold storage in HTK organ preservation solutions: effects of iron chelators and N-alpha-acetyl-L-histidine

BACKGROUND

To improve the rate of successful heart transplantations, organ preservation should be optimized in cardiac transplantation surgery. Iron-dependent oxidative damage and iron-independent, chloride-dependent injury of the endothelium have been described after cold ischemic storage and reperfusion, leading to an enhanced rate of complications and unfavorable outcomes. This screening study tested the effects of iron chelator supplementation in different histidine-tryptophan-ketoglutarate (HTK) organ preservation solutions on endothelial function in a long-term storage model of the isolated rat aorta.

METHODS

Isolated rat aortic rings underwent a 24-hour cold ischemic preservation in different HTK solutions supplemented with iron chelators of low (deferoxamine) and high (LK-614) membrane permeability. In vascular reactivity measurements we investigated the phenyleprine-induced contraction and both endothelium-dependent and -independent vasorelaxation by using cumulative concentrations of acetylcholine and sodium nitroprusside with and without an additional external oxidant injury during re-oxygenation.

RESULTS

Traditional HTK solution, Custodiol, failed to prevent endothelial dysfunction in our experiments. Use of chloride-poor HTK solutions containing N-alpha-acetyl-l-histidine with and without supplementation with LK-614, but not with deferoxamine, resulted in significant improvement of impaired endothelial function; moreover, complete protection of the endothelium was feasible after 24-hour cold storage. Endothelium-independent functions of vascular smooth muscle were not affected in any of the groups.

CONCLUSIONS

Our results demonstrate the important pathophysiologic role of iron-dependent oxidative injury in the development of endothelial dysfunction after cold storage, which can be prevented by cell-permeable iron chelators.

Ten-hour preservation of guinea pig isolated hearts perfused at low flow with air-saturated Lifor solution at 26°C: comparison to ViaSpan solution

There is no suitable solution to preserve hearts for longer than 5 h between donor explant and recipient implant. Lifor is a fully artificial preservation medium containing both a nonprotein oxygen and nutrient carrier (nanoparticles) and cellular nutrients, including amino acids and sugars. We proposed that recirculated Lifor solution would satisfactorily preserve guinea pig isolated hearts perfused at low flow with no added O2at room temperature for 10 h. Hearts were isolated from 21 guinea pigs and perfused with Krebs-Ringer (KR) solution (97% O2and 3% CO2) at 37°C. Heart rate, inflow and outflow O2tension, coronary flow, left ventricular pressure (LVP), and maximal and minimal rate of change in LVP (dLVP/d t) were measured. After baseline measurements, hearts were perfused with recirculated Lifor or ViaSpan equilibrated with room air at 15% of control flow at 26°C for 10 h. Hearts were then perfused at 100% flow with KR for 2 h at 37°C. A time control (untreated) group was perfused only with KR solution for 15 h. Lifor arrested and protected hearts against diastolic contracture and maintained a low O2extraction. Compared with time controls, Lifor led to a higher developed LVP and coronary flow; %O2extraction and cardiac efficiency were similar between these two groups. Hearts similarly treated with ViaSpan exhibited diastolic contracture and lower %O2extraction during treatment and, upon reperfusion with KR, exhibited continued diastolic contracture, no return of heart rate or contractility, low coronary flow, low %O2extraction, and marked infarction. For long-term cardiac protection, a suitable preservation solution recirculated at low flow and room temperature without supplemental O2would reduce the support apparatus required for transport. Lifor was far superior to ViaSpan in meeting these requirements.