Conventional, but not remote ischemic preconditioning, reduces iNOS transcription in liver ischemia/reperfusion

Abstract

Aim: To study the effects of preconditioning on inducible nitric oxide synthase (iNOS) and interleukin 1 (IL-1) receptor transcription in rat liver ischemia/reperfusion injury (IRI).

Methods: Seventy-two male rats were randomized into 3 groups: the one-hour segmental ischemia (IRI, n = 24) group, the ischemic preconditioning (IPC, n = 24) group or the remote ischemic preconditioning (R-IPC, n = 24) group. The IPC and R-IPC were performed as 10 min of ischemia and 10 min of reperfusion. The iNOS and the IL-1 receptor mRNA in the liver tissue was analyzed with real time PCR. The total Nitrite and Nitrate (NOx) in continuously sampled microdialysate (MD) from the liver was analyzed. In addition, the NOx levels in the serum were analyzed.

Results: After 4 h of reperfusion, the iNOS mRNA was significantly higher in the R-IPC (ΔCt: 3.44 ± 0.57) group than in the IPC (ΔCt: 5.86 ± 0.82) group (P = 0.025). The IL-1 receptor transcription activity was reduced in the IPC group (ΔCt: 1.88 ± 0.53 to 4.81 ± 0.21), but not in the R-IPC group, during reperfusion (P = 0.027). In the MD, a significant drop in the NOx levels was noted in the R-IPC group (12.3 ± 2.2 to 4.7 ± 1.2 μmol/L) at the end of ischemia compared with the levels in early ischemia (P = 0.008). A similar trend was observed in the IPC group (11.8 ± 2.1 to 6.4 ± 1.5 μmol/L), although this difference was not statistically significant. The levels of NOx rose quickly during reperfusion in both groups.

Conclusion: IPC, but not R-IPC, reduces iNOS and IL-1 receptor transcription during early reperfusion, indicating a lower inflammatory reaction. NOx is consumed in the ischemic liver lobe.

Keywords: Inducible nitric oxide synthase; Interleukin-1 receptor; Ischemia-reperfusion injury; Liver ischemia; Liver surgery; Microdialysis; Nitric oxide; Preconditioning; Remote preconditioning.

Figures

Figure 1

Nitrite and nitrate in serum or in microdialysis (mean ± SE) in rats subjected to 60 min of segmental (left lateral lobe) ischemia (shaded area) of the liver and 4 h of reperfusion after conventional or remote ischemic preconditioning. A: Nitrite and Nitrate in serum. Initially, a significant rise was observed during the ischemia followed by a significant fall during the reperfusion in both the IPC and the R-IPC groups. For the IPC group, the fall started immediately after ischemia, but in the R-IPC group, a rise was observed during the first 60 min of reperfusion; B: Nitrite and Nitrate in microdialysis. In both the IPC and R-IPC groups, the NOx levels dropped significantly during ischemia in the ischemic lobes, but during reperfusion there was an upward trending movement. In the control lobes, no fall was observed during ischemia. IPC: Ischemic preconditioning; R-IPC: Remote ischemic preconditioning; NOx: Nitrite and nitrate; IRI: Ischemia/reperfusion injury.

Figure 2

Inducible nitric oxide synthase or interleukin-1R mRNA in liver tissue (mean ± SE) in rats previously subjected to 60 min of ischemia/reperfusion injury after ischemic preconditioning or remote ischemic preconditioning. A: iNOS transcription. The iNOS transcription was significantly increased in the R-IPC group (n = 8) after 4 h of reperfusion compared with the IPC group (n = 8), aP < 0.05 vs IPC group; B: IL-1R transcription. The IL-1R transcription decreased in the IPC group during reperfusion (P = 0.027) but did not change in the R-IPC group. The transcription after ischemia was higher in the IPC group than in the R-IPC group; bP < 0.01, IPC group vs R-IPC group. iNOS: Inducible nitric oxide synthase; IL-1R: Interleukin-1R; IPC: Ischemic preconditioning; R-IPC: Remote ischemic preconditioning.