Research Article: Induction of selective liver hypothermia prevents significant ischemia/reperfusion injury in Wistar rats after 24 hours 1

Date Published: May 8, 2020

Publisher: Sociedade Brasileira para o Desenvolvimento da Pesquisa em Cirurgia

Author(s): Tomaz de Jesus Maria Grezzana, Larisse Longo, Jorge Luiz dos Santos, Gemerson Gabiatti, Carlos Boffil, Emanuel Bendo dos Santos, Carlos Thadeu Schmidt Cerski, Marcio Fernandes Chedid, Carlos Otavio Corso.

http://doi.org/10.1590/s0102-865020200020000005

Abstract

To investigate the effects of induction of selective liver hypothermia in a rodent model.

Seven male Wistar rats were subjected to 90 minutes of partial 70% liver ischemia and topic liver 26°C hypothermia (H group). Other seven male Wistar rats were subjected to 90 minutes of partial 70% normothermic liver ischemia (N group). Five additional rats underwent a midline incision and section of liver ligaments under normothermic conditions and without any liver ischemia (sham group). All animals were sacrificed 24-h after reperfusion, and livers were sampled for analyses. Pathology sections were scored for sinusoidal congestion, ballooning, hepatocelllular necrosis and the presence of neutrophilic infiltrates.

At the end of the experiment, liver tissue expressions of TNF-ɑ, IL-1β, iNOS and TNF-ɑ/IL-10 ratio were significantly reduced in the H group compared to N group, whereas IL-10 and eNOS were significantly increased in H group. Histopathological injury scores revealed a significant decrease in ischemia/reperfusion (I/R) injuries in H group.

Selective liver hypothermia prevented I/R injury by inhibiting the release of inflammatory cytokines, preserves microcirculation, prevents hepatocellular necrosis and leukocyte infiltration, allowing maintenance of the liver architecture.

Partial Text

Ischemia/reperfusion (I/R) injury remains one of the major problems in liver surgery and transplantation 1 . In liver resections, the main cause of death after hepatectomy is postoperative liver failure. This may be secondary to a small liver remnant or to an impaired liver regeneration due to underlying liver disease 2 . Transient liver biochemical dysfunction always occurs after hepatic resection with or without pedicle clamping through Pringle maneuver. Ischemia induced by prolonged Pringle maneuver may also produce postoperative liver failure in extensive resections 3 .

All procedures were reviewed and approved by HCPA Ethics Committee, which follows the rules for animal experimentation advised by the Council for International Organization of Medical Sciences (CIOMS). This study is in accordance with the ARRIVE guidelines statement.

The cytokine expression levels in the liver homogenates at the end of the experiment are shown in Figure 4 . TNF-α expression in the liver was significantly lower in the H group as compared to the N group (10,900 ± 1013 vs . 15,589 ± 823 pg/mg, respectively, P=0.044). When H and N groups were compared to sham, no differences were observed (10,900 ± 1013 and 15,589 ± 823 vs . 13,590 ± 2167 pg/mg, =0.315 and P=0.304, respectively).

As a reflection of pro- and anti-inflammatory balance, the TNF-α/IL-10 ratio (Fig. 8) was significantly higher in H group as compared to N group (1.46 ± 0.17 vs. 3.20 ± 0.41, P=0.002). I also was lower in the sham group as compared to N group (and 1.95 ± 0.21 vs . 3.20 ± 0.41, P=0.024). No significant differences were observed when H and Sham groups were compared (1.46 ± 0.17 vs . 1.95 ± 0.20, P=0.281).

Hepatic levels of eNOS were significantly higher in the H group as compared to N group (0.134 ± 0.01 vs . 0.089 ± 0.01 eNOS, P=0.039) (Fig. 9). There were no significant differences in eNOS levels between the H and sham groups (0.134 ± 0.01 vs. 0.108 ± 0.008, P=0.321). Accordingly, there were no differences between N and sham groups (0.089 ± 0.01 vs . 0.108 ± 0.008, P=0.346).

The sum of the means for all parameters evaluated was converted into a score. This score is shown in Figure 12 . There was a significant difference when the H and N groups were compared (0.71 ± 0.18 vs. 11.14 ± 2.44, P<0.001) and when the N and Sham groups were compared (11.14 ± 2.44 vs . 1.0 ± 0.44, P=0.001). No differences were observed between H and sham (0.71 ± 0.18 vs. 1.0 ± 0.44, P=0.904). In the present study, the effects of selective liver hypothermia at 24 hour after reperfusion were investigated. The present study is a continuation of our previous work, which demonstrated that selective liver hypothermia applied by topical cooling offers protection against I/R injuries in a 2-hour reperfusion model 12 . This study was the first one assessing these injury scores after 24 hours under TH. In this experimental model using prolonged clamping, liver injury was significantly attenuated by induction of selective liver hypothermia. The potential protective mechanisms involved are likely related to preservation of hepatic microcirculation, inhibition of inflammatory response, and maintenance of the liver architecture. In clinical practice, TH could be employed routinely as an adjunct to Pringle maneuver during partial liver resections.   Source: http://doi.org/10.1590/s0102-865020200020000005

 

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