Pretreatment with FK506 up-regulates insulin receptors in regenerating rat liver

Abstract

This report examines the effect of FK506 pretreatment on liver insulin receptor expression in partially (70%) hepatectomized rats. FK506 pretreatment led to an increased insulin receptor number 24 hours after hepatectomy, detected by means of insulin binding and crosslinking procedures. This increase was related to enhanced insulin receptor expression determined by in vitro mRNA translation and Western blot techniques. We also tested the functionality of the expressed insulin receptors by [ 3 H] thymidine incorporation into DNA in insulin-stimulated hepatocytes. The results show that FK506 pretreatment elicits an increase in the amount of insulin receptor ␣-subunits as measured by Western blot. Maximum ␣-subunit expression recorded 24 hours after surgery was preceded by increased insulin receptor mRNA levels, which were detected 6 hours after hepatectomy. Moreover, in FK506 -pretreated rat hepatocytes, obtained from remnant livers 24 hours after partial hepatectomy (PH), the increase in insulin receptor number was associated with improved sensitivity to the hormone. However, in both experimental groups (FK506-pretreated and nonpretreated rats), the sensitivity of hepatocytes toward epidermal growth factor (EGF) showed no significant change, which suggests a specific effect of FK506 on insulin receptor expression. In conclusion, our findings suggest that FK506 pretreatment induces insulin receptor expression in regenerating rat liver and promotes liver regeneration in hepatectomized rats. (HEPATOLOGY 2002;36:555-561.) P retreatment with immunosuppressive drugs, such as FK506 and cyclosporin A (CsA), increases the liver regenerative response after partial hepatectomy (PH) in rats. 1 Several research efforts have tried to determine the factors involved in the proliferative response associated with drug treatment. FK506 or CsA could modulate the liver response by (1) increasing the expression of local mitogens such as hepatocyte growth factor 2 or insulin-like growth factor I 3 ; (2) decreasing the production of inhibitory cytokines such as transforming growth factor ␤ 1 2 or interleukin 2 4 ; (3) inhibiting natural killer activity 4 ; or (4) predisposing the liver to regenerative signals. This last hypothesis has been suggested but not shown. Insulin is considered a secondary mitogen that enhances liver sensitivity to mitogens during its regeneration. 5 Administering insulin to 70% PH rats increases [ 3 H] thymidine labeling of DNA in hepatic parenchyma cells. 6 Insulin induces a specific peak in [ 3 H] thymidine incorporation 24 hours after PH, which is not observed in insulin-untreated or glucagon-treated animals. 6 This 24-hour period after PH also coincides with maximal effects of FK506 1 or CsA 2 on the liver regenerative response. Moreover, the role of insulin in liver regeneration is supported by its blunting of the immediate-early gene response after PH in diabetic animals. 7 In a very recent study performed in 70% PH/50% pancreatectomized rats, it was shown that liver mass recovery in these animals was del...

Liver Xeno-Repopulation with Human Hepatocytes in Fah−/−Rag2−/− Mice after Pharmacological Immunosuppression

“…14,15,17,23 We found that pharmacological depletion of NK cells by anti-asialo GM1 treatment was sufficient for liver xeno-repopulation in Fah Ϫ/Ϫ Rag2 Ϫ/Ϫ mice. However, the level of xeno-repopulation was not comparable to those found in Fah…”

“…16 FK506 was also found to induce hepatocyte proliferation and promote liver regeneration in partial hepatectomized rats. 17 We tested the potential effect of FK506 on promoting liver xeno-repopulation in Fah Ϫ/Ϫ Rag2 Ϫ/Ϫ recipients, along with treatment of anti-asialo GM1. FK506 was administered to mouse recipients at a dose of 1 g/g body weight per day.…”

“…24,25 Besides immunosuppression, FK506 modulates liver responses by increasing expression of local mitogens such as insulin-like growth factor-I, increasing expression of insulin receptor, and decreasing production of inhibitory cytokines such as interleukin 2, to promote liver regeneration. 17,26 Without treatment with Asialo-GM antibody, NK cells likely inhibit xeno-engraftment of human hepatocytes. We did find, however, that FK506 treatment alone could promote the proliferation of engrafted hepatocytes in nodules, which were significantly enlarged compared with treatment without FK506.…”

Xeno-repopulation of Fah−/−Nod/Scid mice livers by human hepatocytes

“…The use of FK506 played an important role by improving the efficiency of liver xeno-repopulation in Fah −/− Nod/Scid mice. In addition to immunosuppression, FK506 modulates liver responses by increasing the expression of local mitogens, such as insulin-like growth factor-I, and insulin receptors while, at the same time, decreasing the production of inhibitory cytokines such as interleukin 2, to promote liver regeneration [18][19][20]. FK506 reduces macrophage recruitment and attenuates leukocyte accumulation, neutrophil infiltration and the activation of resident immunocompetent hepatic NK cells [21,22].…”

Modelos de regeneração hepática em animais em crescimento: estudos histológicos, moleculares e avaliação de efeitos de imunossupressores

“…observaram que o tratamento com tacrolimus antes da ressecção de 70% do parênquima hepático em ratos adultos promove a regeneração por aumento da expressão dos receptores de insulina nos hepatócitos. 33 Considerando-se a importância do estudo dos efeitos das drogas imunossupressoras sobre a regeneração e remodelação do parênquima hepático em crianças submetidas a transplante de fígado, despertou-se o interesse pela pesquisa no animal de experimentação em crescimento, dadas as óbvias restrições éticas ao estudo em humanos. Por outro lado, do ponto de vista prático é inexeqüível a realização de transplante de fígado em animais de pequeno porte em crescimento, o que impossibilita a pesquisa com este modelo.…”