Molecular events associated with accelerated proliferative response in rat livers when partial hepatectomy is preceded by a sham operation

The effect of chronic iron losses on liver regeneration in male and female rats

BACKGROUND

We studied the effect of iron deficiency on liver regeneration and innate immunity - respiratory burst of PMN.

METHODS

Wistar rats, males (M) and females (F) had sham withdrawals or males (M-w) and females (F-w) had nine blood withdrawals every week. All rats were sacrificed in 10(th) week after 67% hepatectomy (PH) after (3)H-thymidin application. We determined erythrocyte and leukocyte count, respiratory burst (RB), serum prohepcidin, estradiol, iron, iron binding capacity (TIBC) and liver iron stores.

RESULTS

Liver DNA synthesis in M-w and F-w increased versus M and F (p=0.05). Serum prohepcidin after PH decreased in M, F (p=0.001) and F-w (p=0.05), but not in M-w. Blood withdrawals increased spontaneous RB (p<0.05), stimulated RB at females (p<0.01). Stimulated RB was lower in M-w then in M (p<0.01). Serum iron was lower in males than in females, but higher in rats with withdrawals than in rats without withdrawals. TIBC decreased after PH in M, F, F-w groups (p<0.001), less at M-w (p<0.05). Liver iron stores decreased in M, less in F.

CONCLUSIONS

Both genders with blood withdrawals had early beginning of liver regeneration after PH. The preconditioning (withdrawals) leads to increase in iron turnover and stores following best reactivity of PMN, rapid decrease in serum prohepcidin, and early initiation of liver regeneration, mainly in females. We assume, the females have higher iron turnover, liver iron stores more easily mobilized for blood losses, because next gravidity physio logically begin immediately after birth. Simply transfer of experimental results to human medicine is difficult.

Reperfusion stress induced during intermittent selective clamping accelerates rat liver regeneration through JNK pathway

BACKGROUND & AIMS

Liver resection includes temporal vascular inflow occlusion resulting in ischemia/reperfusion injury in the remnant liver. Here, we developed a rat model of selective lobe occlusion to isolate reperfusion stress from ischemia and to analyze its effect on liver regeneration.

METHODS

Left lateral and median lobes of liver were either mobilized or subjected twice for 10min to ischemia followed by 5min reperfusion prior to resection while the regenerative lobes were only subjected to reperfusion.

RESULTS

Although intermittent reperfusion stress induced higher levels of serum transaminases, analysis of cell cycle regulators revealed accelerated regenerative response compared to standard partial hepatectomy. The G0/G1 transition occurred before tissue resection, as evidenced by c-fos, junB, and IL-6 induction. Following hepatectomy, Cyclin D1 up-regulation, G1/S transition, and cell division occurred earlier than normal. Unexpectedly, liver mobilization, a component of the clamping procedure, also resulted in earlier G1/S transition. The shortened G1-phase was driven by the c-Jun N-terminal Kinase pathway and was associated with an oxidative stress response as evidenced by the expression of inducible nitric oxide synthase.

CONCLUSION

Intermittent selective clamping of lobes to be resected induced reperfusion stress on remnant liver that was beneficial for liver regeneration, suggesting this procedure could be applied in clinical practice.

Components of the mitogen-activated protein kinase cascade are activated in hepatic cells by Echinococcus multilocularis metacestode

AIM: To explore the effect of Echinococcus multilocularis (E. multilocularis) on the activation of mitogen-activated protein kinase (MAPK) signaling pathways and on liver cell proliferation.

METHODS: Changes in the phosphorylation of MAPKs and proliferating cell nuclear antigen (PCNA) expression were measured in the liver of patients with alveolar echinococcosis (AE). MAPKs, MEK1/2 [MAPK/extracellular signal-regulated protein kinase (ERK) kinase] and ribosomal S6 kinase (RSK) phosphorylation were detected in primary cultures of rat hepatocytes in contact in vitro with (1) E. multilocularis vesicle fluid (EmF), (2) E. multilocularis-conditioned medium (EmCM).

RESULTS: In the liver of AE patients, ERK 1/2 and p38 MAPK were activated and PCNA expression was increased, especially in the vicinity of the metacestode. Upon exposure to EmF, p38, c-Jun N-terminal kinase (JNK) and ERK1/2 were also activated in hepatocytes in vitro, as well as MEK1/2 and RSK, in the absence of any toxic effect. Upon exposure to EmCM, only JNK was up-regulated.

CONCLUSION: Previous studies have demonstrated an influence of the host on the MAPK cascade in E. multilocularis. Our data suggest that the reverse, i.e. parasite-derived signals efficiently acting on MAPK signaling pathways in host liver cells, is actually operating.

Disrupted NF- kappa B activation after partial hepatectomy does not impair hepatocyte proliferation in rats

AIM

To analyze the effects of NF- kappa B inhibition by antioxidant pyrrolidine dithiocarbamate (PDTC) or TNF inhibitor pentoxifylline (PTX) on liver regeneration after partial hepatectomy (PH).

METHODS

Saline, PDTC or PTX were injected 1 h before PH and rats were killed at 0.5 and 24 h after PH. Several control groups were used for comparison (injection control groups).

RESULTS

Compared to saline injected controls, NF- kappa B activation was absent 0.5 h after PH in rats treated with PDTC or PTX. At 24 h after PH, DNA synthesis and PCNA expression were identical in treated and control rats and thus occurred irrespectively of the status of NF- kappa B activation at 0.5 h. Signal transducer and activator of transcription 3 (Stat3) activation was observed already 0.5 h after PH in saline, PDTC or PTX group and was similar to Stat3 activation in response to injection without PH.

CONCLUSION

These data strongly suggest that (1) NF- kappa B p65/p50 DNA binding produced in response to PH is not a signal necessary to initiate the liver regeneration, (2) Stat3 activation is a stress response unrelated to the activation of NF- kappa B. In conclusion, NF- kappa B activation is not critically required for the process of liver regeneration after PH.