The effect of insulin-like growth factor-I on hepatocyte apoptosis after bile duct ligation in rat

The role of growth factors on hepatic damage in rats with obstructive jaundice

In this study, we investigated the affect and the role of growth factors on liver damage. 110 Sprague–Dawley rats were divided into 11 groups: a sham group, a control group, HGF, EGF, IGF, TGF groups of irreversible jaundiced rats and a control group and HGF, EGF, IGF, and TGF groups of reversible jaundiced rats (n = 10). In the irreversible jaundiced groups, the common bile duct was explorated, double ligated, and cut. 150 μg/kg/day HGF, 5 μg/kg/day EGF, 5 μg/kg/day IGF, and 5 μg/kg/day TGF β-1 were injected intraperitoneally after the seventh post-operative day. In the reversible jaundiced group, the common bile duct was ligated and the ligation was resolved on the seventh post-operative day. For 5 days, growth factors were injected at the same dose. Ductal proliferation scores significantly decreased after growth factor administration in the EGF-A and TGF-A groups. Furthermore, ductal proliferation was decreased in the TGF-B group. As a result of this study, HGF was effective in the irreversible jaundiced groups and ineffective in the reversible jaundice groups. EGF was effective in the reversible jaundiced groups and ineffective in the irreversible jaundiced groups. In both the irreversible jaundiced and reversible jaundiced groups, IGF was ineffective, although TGF β-1 was effective. We believe that these results arise from the positive effects of effective doses of growth factor on liver damage.

Hepatoprotective effect of ulinastatin in a rat model of major hepatectomy after obstructive jaundice

BACKGROUND

To date, major hepatectomy with obstructive jaundice is still a highly risky and difficult surgery because of the high rate of complications. An excessive inflammatory response may be the primary hindrance to postoperative recovery of liver function.

AIMS

Recent research has demonstrated that ulinastatin blocks the release of inflammatory factors and prevents the cytokine cascade reaction. This study was conducted to investigate the effect of ulinastatin on major hepatectomy after obstructive jaundice and to explore the potential mechanisms of this effect.

METHODS

Male Sprague-Dawley rats were divided into three groups: sham, control and treated groups. In the control and treated groups, obstructive jaundice was induced, and a 70 % major hepatectomy was performed with implementation of ulinastatin treatment in the treated group but not the control group. The rats were sacrificed after hepatectomy on day 1, day 3, day 5 and day 7. The survival time, liver function, inflammatory cytokine expression and the indices of proliferation activities were examined. Kupffer cells were isolated, and the mRNA and protein levels of CD14 and NF-κB P65 in the Kupffer cells were determined.

RESULTS

Compared to the control group, the survival rates, postoperative liver function, and the indices of proliferation activities were better in the treated group; in the treated group serum TNF-α and IL-6 levels were lower whereas serum IL-10 levels were higher. The expression of CD14 and NF-κB P65 in Kupffer cells at both the mRNA and protein levels was significantly higher in the control group than in the treated group.

CONCLUSIONS

Ulinastatin has a protective effect in major hepatectomy with obstructive jaundice by inhibiting Kupffer cell activation and modulating the hepatic cytokine response.

Protective effect of exogenous IGF-I on the intestinalmucosal barrier in rats with severe acute pancreatitis

BACKGROUND

Severe acute pancreatitis (SAP) can result in intestinal mucosal barrier (IMB) dysfunction. This study was undertaken to demonstrate the effect of IGF-I on the intestinal mucosal barrier in rats with SAP and its possible mechanisms.

METHODS

Seventy-two male Wistar rats were randomly divided into three groups: a sham operation (SO group, n=24), a SAP group not treated with IGF-I (SAP group, n=24), and a SAP group treated with IGF-I (IGF-I group, n=24). SAP was induced in the rats by injecting 5.0% sodium taurocholate into the biliary-pancreatic duct. The SO rats were given an infusion of normal saline instead. The rats in the IGF-I group underwent the SAP procedure and were given a subcutaneous injection of IGF-I at 30 minutes before the operation and at 3 hours after the operation. Eight rats in each group were sacrificed at 6, 12 and 24 hours after operation. Apoptosis of mucosal cells in the small intestine was determined by TUNEL. The levels of endotoxin and DAO and serum amylase were also measured. Pathologic changes in the small intestine were monitored. Changes of bax and bcl-2 mRNA expression in the small intestine were determined by reverse transcription polymerase chain reaction (RT-PCR).

RESULTS

The levels of serum amylase were lower in the IGF-I group than in the SAP group at all three time points (P<0.05). The levels of endotoxin in the IGF-I group were higher than those in the SAP group at 6 hours, but lower in the IGF-I group than in the SAP group at 12 and 24 hours (P<0.05). The levels of diamine oxidase were higher in the IGF-I group at 6 hours but lower than those in the SAP group at 12 and 24 hours. The pathological score of the small intestine was lower in the IGF-I group than in the SAP group, and the difference was statistically significant at 12 and 24 hours. The pathologic changes observed under electron microscopy were better in the IGF-I group than those in the SAP group. The apoptosis index of intestinal epithelial cells was significantly decreased in the IGF-I group compared with the SAP group. Compared with the SO group, the mRNA expression levels of bax were increased at each time point in the SAP group, and were significantly decreased in the IGF-I group as compared with the SAP group at each time point (P<0.05). The expression levels of bcl-2 were weak and not different between the SO group and the SAP group (P>0.05). They were significantly increased in the IGF-I group versus the SO and SAP groups (P<0.05). The ratio of bax and bcl-2 mRNA expression levels at each time point in the SAP group were significantly higher than those in the SO group, but they were obviously decreased in the IGF-I group.

CONCLUSIONS

Exogenous IGF-I seems to protect mucosal cells in the small intestine against SAP-induced apoptosis and could alleviate SAP-induced injury of the intestinal mucosa. The underlying mechanisms include enhanced mRNA expression of bcl-2 and inhibition of bax mRNA expression.

Regulatory role of the GH-SOCS2-IGF-1 axis in the pathogenesis of intestinal mucosal barrier dysfunction in ulcerative colitis

Ulcerative colitis (UC) is a chronic, nonspecific inflammatory bowel disease usually associated with recurrent attacks. Intestinal bacterial translocation induced by intestinal mucosal barrier dysfunction may mediate abnormal immune response and chronic intestinal inflammation and therefore play an important role in the development and progression of UC. The GH-SOCS2-IGF1 axis, consisting of growth hormone (GH), suppressors of cytokine signaling 2 (SOCS2), and insulin-like growth factor-1 (IGF-1), is involved in the injury and repair of intestinal mucosal barrier. The research on the abnormal regulation of the GH-SOCS2-IGF1 axis in the pathogenesis of intestinal mucosal barrier dysfunction in UC has attracted increasing attention. This paper will briefly summarize the respective role of GH, SOCS2, and IGF-1, and discuss the regulatory role of the GH-SOCS2-IGF1 axis in the pathogenesis of intestinal mucosal barrier dysfunction in UC.

IGF-1R contributes to stress-induced hepatocellular damage in experimental cholestasis

The insulin-like growth factor type 1 receptor (IGF-1R) controls aging and cellular stress, both of which play major roles in liver disease. Stimulation of insulin-like growth factor signaling can generate cell death in vitro. Here, we tested whether IGF-1R contributes to stress insult in the liver. Cholestatic liver injury was induced by bile duct ligation in control and liver-specific IGF-1R knockout (LIGFREKO) mice. LIGFREKO mice displayed less bile duct ligation-induced hepatocyte damage than controls, while no differences in bile acid serum levels or better adaptation to cholestasis by efflux transporters were found. We therefore tested whether stress pathways contributed to this phenomenon; oxidative stress, ascertained by both malondialdehyde content and heme oxygenase-1 expression, was similar in knockout and control animals. However, together with a lower level of eukaryotic initiation factor-2 alpha phosphorylation, the endoplasmic reticulum stress protein CHOP and its downstream pro-apoptotic target Bax were induced to lesser extents in LIGFREKO mice than in controls. Expression levels of cytokeratin 19, transforming growth factor-beta1, alpha-smooth muscle actin, and collagen alpha1(I) in LIGFREKO mice were all lower than in controls, indicating reduced ductular and fibrogenic responses and increased cholestasis tolerance in these mutants. This stress resistance phenotype was also evidenced by longer post-bile duct ligation survival in mutants than controls. These results indicate that IGF-1R contributes to cholestatic liver injury, and suggests the involvement of both CHOP and Bax in this process.

Effects of insulin-like growth factor -Ⅰ on bax and bcl-2 mRNA expression in intestinal mucosal epithelial cells of rats with severe acute pancreatitis

AIM: To investigate the effects of exogenous insulin-like growth factor-Ⅰ (IGF-Ⅰ) on the intestinal mucosal epithelial cell apoptosis and the associated genes bax and bcl-2 in rats with severe acute pancreatitis (SAP), and to explore the protective effect of IGF-Ⅰ on intestinal mucosal barrier function and its possible mechanisms.

METHODS: Seventy-two male Wistar rats were randomly divided into 3 groups: sham operation (SO) group, SAP group and IGF-Ⅰ treatment group. Eight rats were killed in each group at 6, 12, and 24 h, respectively. Serum amylase level was detected by iodine-starch colorimetry. Pathological changes in the small intestine were observed. Apoptosis of mucosal cells was detected by TUNEL methods, and the variation of the bax and bcl-2 gene expression in small intestinal tissue was detected by reverse transcription polymerase chain reaction (RT-PCR).

RESULTS: In the IGF-Ⅰ treatment group, the apoptosis index of intestinal epithelial cells was decreased significantly as compared with that in the SAP group (6 h: 13.88 ± 1.73 vs 19.00 ± 2.78; 12 h: 10.13 ± 1.55 vs 17.63 ± 1.60; 24 h: 9.50 ± 1.07 vs 17.25 ± 2.76; all P < 0.05), and the pathological changes in intestinal tissues were obviously improved. Compared with that in the SAP group, the bax mRNA expression was notably reduced in the IGF-Ⅰ treatment group (6 h: 1.10 ± 0.02 vs 1.19 ± 0.04; 12 h: 0.97 ± 0.04 vs 1.16 ± 0.02; 24 h, 0.87 ± 0.03 vs 1.14 ± 0.03; all P < 0.05), while, the bcl-2 mRNA expression was increased significantly in the IGF-Ⅰ treatment group (6 h: 0.65 ± 0.02 vs 0.57 ± 0.02; 12 h: 0.69 ± 0.04 vs 0.57 ± 0.01; 24 h: 0.72 ± 0.02 vs 0.58 ± 0.01; all P < 0.05).

CONCLUSION: Exogenous IGF-Ⅰ may alleviate SAP-induced injury of intestinal mucosa by altering the transcription of bax and bcl-2 genes.

Bile salts regulate proliferation and apoptosis of liver cells by modulating the IGF1 system

BACKGROUND

In different cell types, the insulin-like growth factor 1 and its receptor modulate growth, apoptosis and damage repair in cooperation with estrogen receptors.

AIM

To evaluate the involvement of the insulin-like growth factor 1 system and estrogen receptors in bile salts modulation of apoptosis/proliferation of hepatocytes and cholangiocytes. Primary cultures of rat hepatocytes and cholangiocytes were exposed to glycochenodeoxycholate or tauro-CDC in the presence or absence of insulin-like growth factor 1 receptor blocking antibody (alphaIR3), small interfering RNA for insulin-like growth factor 1, 17beta-estradiol or estrogen receptor antagonist (ICI 182,780). Proliferation was evaluated by proliferating cell nuclear antigen Western blot and apoptosis by measuring caspase-3 activity or annexin-V.

RESULTS

In hepatocytes, the insulin-like growth factor 1 receptor blocker enhanced glycochenodeoxycholate-induced apoptosis and caused tauro-CDC to promote apoptosis. 17Beta-estradiol or the estrogen receptor antagonist (ICI 182,780) did not influence the apoptotic effect of glycochenodeoxycholate. In cholangiocytes, both glycochenodeoxycholate and tauro-CDC induced proliferation at 100microM, while they induced apoptosis at 1mM with a more pronounced effect of glycochenodeoxycholate. Apoptosis induced by 1mM glycochenodeoxycholate or tauro-CDC in cholangiocytes was enhanced by blocking insulin-like growth factor 1 receptor or by silencing insulin-like growth factor 1. 17Beta-estradiol counteracts glycochenodeoxycholate-induced cholangiocyte apoptosis by enhancing insulin-like growth factor 1 secretion and activating the insulin-like growth factor 1 system.

CONCLUSIONS

Modulation of the IGF1 system could represent a potential strategy for the management of bile salts-induced liver injury.