The role of NF-kappaB signaling in impaired liver tissue repair in thioacetamide-treated type 1 diabetic rats

Anti-hypoglycemic and hepatocyte-protective effects of hyperoside from Zanthoxylum bungeanum leaves in mice with high-carbohydrate/high-fat diet and alloxan-induced diabetes

The development of diabetes mellitus (DM) is accompanied by hyperglycemia-induced oxidative stress. Hyperoside is a major bioactive component in Zanthoxylum bungeanum leaves (HZL) and is a natural antioxidant. However, the effects of HZL on DM and its mechanisms of action remain undefined. The present study evaluated the anti-hypoglycemic and hepatocyte-protective effects of HZL in mice with diabetes induced by a high-carbohydrate/high-fat diet (HFD) and alloxan. We also aimed to eludicate the underlying mechanisms. Our resutls demonstrated that the administration of HZL significantly reduced body weight gain, serum glucose levels and insulin levels in diabetic mice compared with the vehicle-treated mice. In addition, the levels of dyslipidemia markers including total cholesterol, triglyceride and low-density lipoprotein cholesterol in the HFD-treated mice were markedly decreased. Further experiments using hepatocytes from mice revealed that HZL significantly attenuated liver injury associated with DM compared with vehicle treatment, as evidenced by lower levels of alanine aminotransferase and aspartate aminotransferase in serum and by lower levels of lipid peroxidation, nitric oxide content and inducible nitric oxide synthase activity in liver tissues. Nuclear factor-κB (NF-κB) and mitogen-associated protein kinase (MAPK) signaling pathways were investigated to elucidate the molecular mechanisms responsible for the protective effects of HZL against diabetic liver injury. The results indicated that HZL inhibited the phosphorylation of p65/NF-κB, MAPK (including p38, JNK and ERK1/2) and activating transcription factor 3 protein expression, with an additional suppression of Bax, cytochrome c, caspase-9 and caspase-3 in the liver tissues of diabetic mice. Taken together, our findings suggest that HZL, which was effective in inhibiting oxidative stress-related pathways may be beneficial for use in the treatment of DM.

Diabetes mellitus and increased postoperative risk of acute renal failure after hepatectomy for hepatocellular carcinoma: a nationwide population-based study

BACKGROUND

This study aimed to determine the effects of diabetes mellitus (DM) on the risk of surgical mortality and morbidity in patients undergoing hepatectomy for hepatocellular carcinoma (HCC).

METHODS

We identified 2,962 DM patients who underwent a hepatectomy for HCC from 2000 to 2010. The non-DM control cohort consisted of 2,962 patients who also received a hepatectomy during the same period. Age, sex, comorbidities, and year of admission were all matched between the 2 cohorts.

RESULTS

The prevalence of preoperative coexisting medical conditions was comparable between the DM and non-DM cohorts, except the percentage of patients undergoing major hepatectomy (lobectomy; 18.1 % in the DM cohort vs. 20.4 % in the non-DM cohort; p = 0.02).The hazard ratio (HR) of 30-day postoperative mortality in the DM patients after hepatectomy was 1.17 [95 % confidence interval (CI) 0.75-1.84] after adjustment. The DM cohort exhibited a significantly higher risk of postoperative septicemia (adjusted hazard ratio, 1.45; 95 % CI 1.06-2.00) and acute renal failure (adjusted hazard ratio, 1.70; 95 % CI 1.01-2.84) compared with that of the non-DM cohort, but this higher risk was not associated with the increased risk of other major morbidities, including pneumonia, stroke, and myocardial infarction. Further analysis showed that major hepatectomy (lobectomy) in DM patients carried higher risks of septicemia and acute renal failure. In multiple regression models, preoperative diabetes-related comorbidities were not significantly associated with 30-day postoperative mortality.

CONCLUSIONS

DM is associated with a significantly high risk of septicemia and acute renal failure, but not with other major complications or mortality, after hepatectomy for HCC.

Regulation of signal transduction and role of platelets in liver regeneration

Among all organs, the liver has a unique regeneration capability after sustaining injury or the loss of tissue that occurs mainly due to mitosis in the hepatocytes that are quiescent under normal conditions. Liver regeneration is induced through a cascade of various cytokines and growth factors, such as, tumor necrosis factor alpha, interleukin-6, hepatocyte growth factor, and insulin-like growth factor, which activate nuclear factor κB, signal transducer and activator of transcription 3, and phosphatidyl inositol 3-kinase signaling pathways. We previously reported that platelets can play important roles in liver regeneration through a direct effect on hepatocytes and collaborative effects with the nonparenchymal cells of the liver, including Kupffer cells and liver sinusoidal endothelial cells, which participate in liver regeneration through the production of various growth factors and cytokines. In this paper, the roles of platelets and nonparenchymal cells in liver regeneration, including the associated cytokines, growth factors, and signaling pathways, are described.

Protective effect of ligustrazine on residual liver tissue in rats after hepatectomy

AIM: To investigate the effect of ligustrazine in alleviating inflammation and inhibiting the activation of NF-κB in rats after liver trauma.

METHODS: Sixty rats which underwent 2/3 hepatectomy were randomly and equally divided into three groups. Group A was intraperitoneally injected with normal saline, and groups B and C were injected with PDTC and ligustrazine, respectively. The general status of the rats was observed, and changes in serum levels of aminotransferases were measured. Hepatic pathological changes were examined, and the activation of NF-κB was investigated by Western blot.

RESULTS: Cellular swelling was milder in group C than in group A. Serum levels of ALT at 6 and 10 h after the operation were significantly lower in group C than in group A (6 h: 488.9 U/L ± 59.2 U/L vs 651.6 ± 65.3 U/L; 10 h: 670.0 U/L ± 73.4 U/L vs 930.0 U/L ± 62.9 U/L; both P < 0.05). Serum levels of AST at 6 and 10 h were also significantly lower in group C than in group A (6 h: 1113.1 U/L ± 138.7 U/L vs 1315.0 U/L ± 111.0 U/L; 10 h: 1388.2 U/L ± 209.6 U/L vs 1728.4 U/L ± 87.3 U/L; both P < 0.05). The levels of activated NF-κB in group C (0.78 ± 0.04, 0.75 ± 0.07) were lower than those in group A (both were 1), higher than those in group B (0.68 ± 0.09, 0.66 ± 0.04) at 2 and 10 h (all P < 0.05), but were comparable to that in group B at 6 h (0.71 ± 0.07 vs 0.64 ± 0.09, P > 0.05).

CONCLUSION: Ligustrazine protects the posttraumatic liver tissue possibly by inhibiting the activation of NF-κB.

Platelets promote liver regeneration under conditions of Kupffer cell depletion after hepatectomy in mice

BACKGROUND

Platelets have been proven to promote liver regeneration after hepatectomy. Kupffer cells produce inflammatory cytokines and also promote liver regeneration. In the present study, we examined whether platelets promote liver regeneration after hepatectomy under conditions of Kupffer cell depletion.

METHODS

Seventy percent hepatectomy was carried out in mice, which were subsequently divided into four groups: (1) a normal group without any treatment, (2) a Kupffer cell depleted (KD) group, (3) a thrombocytotic group, and (4) a combined thrombocytotic and Kupffer cell depleted (TKD) group. Growth kinetics in the liver regeneration, growth factors, inflammatory cytokines, and signal transduction relating to hepatocyte proliferation were analyzed.

RESULTS

In the KD group, liver regeneration was significantly delayed compared to the normal group 48 h after hepatectomy. On the other hand, liver regeneration of the TKD group increased significantly compared to KD group, to a level that was the same as that recorded in the normal group. In the thrombocytotic group, liver regeneration increased significantly compared to the normal group. Tumor necrosis factor alpha (TNF-alpha) expression was lower in the KD and TKD groups than in the normal group after hepatectomy, but, in the TKD group, hepatocyte growth factor and Akt phosphorylation were higher than in the normal and KD groups.

CONCLUSIONS

After hepatectomy, liver regeneration in the Kupffer cell depleted group was delayed because of lower TNF-alpha expression. Platelets promote liver regeneration even under condition of Kupffer cell depletion by stimulating hepatocyte growth factor and insulin-like growth factor-1 expression, and they activate Akt.

Mechanisms and outcomes of drug- and toxicant-induced liver toxicity in diabetes

Increase dincidences of hepatotoxicity have been observed in diabetic patients receiving drug therapies. Neither the mechanisms nor the predisposing factors underlying hepatotoxicity in diabetics are clearly understood. Animal studies designed to examine the mechanisms of diabetes-modulated hepatotoxicity have traditionally focused only on bioactivation/detoxification of drugs and toxicants. It is becoming clear that once injury is initiated, additional events determine the final outcome of liver injury. Foremost among them are two leading mechanisms: first, biochemical mechanisms that lead to progression or regression of injury; and second, whether or not timely and adequate liver tissue repair occurs to mitigate injury and restore liver function. The liver has a remarkable ability to repair and restore its structure and function after physical or chemical-induced damage. The dynamic interaction between biotransformation-based liver injury and compensatory tissue repair plays a pivotal role in determining the ultimate outcome of hepatotoxicity initiated by drugs or toxicants. In this review, mechanisms underlying altered hepatotoxicity in diabetes with emphasis on both altered bioactivation and liver tissue repair are discussed. Animal models of both marked sensitivity (diabetic rats) and equally marked protection (diabetic mice) from drug-induced hepatotoxicity are described. These examples represent a remarkable species difference. Availability of the rodent diabetic models offers a unique opportunity to uncover mechanisms of clinical interest in averting human diabetic sensitivity to drug-induced hepatotoxicities. While the rat diabetic models appear to be suitable, the diabetic mouse models might not be suitable in preclinical testing for potential hepatotoxic effects of drugs or toxicants, because regardless of type 1 or type2 diabetes, mice are resistant to acute drug-or toxicant-induced toxicities.

Mechanisms of inhibited liver tissue repair in toxicant challenged type 2 diabetic rats

Liver injury initiated by non-lethal doses of CCl(4) and thioacetamide (TA) progresses to hepatic failure and death of type 2 diabetic (DB) rats due to failed advance of liver cells from G(0)/G(1) to S-phase and inhibited tissue repair. Objective of the present study was to investigate cellular signaling mechanisms of failed cell division in DB rats upon hepatotoxicant challenge. In CCl(4)-treated non-diabetic (non-DB) rats, increased IL-6 levels, sustained activation of extracellular regulated kinases 1/2 (ERK1/2) MAPK, and sustained phosphorylation of retinoblastoma protein (p-pRB) via cyclin D1/cyclin-dependent kinase (cdk) 4 and cyclin D1/cdk6 complexes stimulated G(0)/G(1) to S-phase transition of liver cells. In contrast to the non-DB rats, CCl(4) administration led to lower plasma IL-6, decreased ERK1/2 activation, lower cyclin D1, and cdk 4/6 expression resulting in decreased p-pRB and inhibition of liver cell division in the DB rats. Furthermore, higher TGFbeta1 expression and p21 activation may also contribute to decreased p-pRB in DB rats compared to non-DB rats. Similarly, after TA administration to DB rats, down-regulation of cyclin D1 and p-pRB leads to markedly decreased advance of liver cells from G(0)/G(1) to S-phase and tissue repair compared to the non-DB rats. Hepatic ATP levels did not differ between the DB and non-DB rats obviating its role in failed tissue repair in the DB rats. In conclusion, decreased p-pRB may contribute to blocked advance of cells from G(0)/G(1) to S-phase and failed cell division in DB rats exposed to CCl(4) or TA, leading to progression of liver injury and hepatic failure.

Prior administration of a low dose of thioacetamide protects type 1 diabetic rats from subsequent administration of lethal dose of thioacetamide

Previously, we reported that an ordinarily non-lethal dose of thioacetamide (TA, 300 mg/kg) causes 90% mortality in type 1 diabetic rats due to inhibited liver tissue repair, whereas 30 mg TA/kg allows 100% survival due to stimulated although delayed tissue repair. Objective of this investigation was to test whether prior administration of a low dose of TA (30 mg/kg) would lead to sustainable stimulation of liver tissue repair in type 1 diabetic rats sufficient to protect from a subsequently administered lethal dose of TA. Therefore, in the present study, the hypothesis that preplacement of tissue repair by a low dose of TA (30 mg TA/kg, ip) can reverse the hepatotoxicant sensitivity (autoprotection) in type 1 diabetic rats was tested. Preliminary studies revealed that a single intraperitoneal (ip) administration of TA causes 90% mortality in diabetic rats with as low as 75 mg/kg. To establish an autoprotection model in diabetic condition, diabetic rats were treated with 30 mg TA/kg (priming dose). Administration of priming dose stimulated tissue repair that peaked at 72h, at which time these rats were treated with a single ip dose of 75 mg TA/kg. Our results show that tissue repair stimulated by the priming dose enabled diabetic rats to overexpress, calpastatin, endogenous inhibitor of calpain, to inhibit calpain-mediated progression of liver injury induced by the subsequent administration of lethal dose, resulting in 100% survival. Further investigation revealed that protection observed in these rats is not due to decreased bioactivation. These studies underscore the importance of stimulation of tissue repair in the final outcome of liver injury (survival/death) after hepatotoxicant challenge. Furthermore, these results also suggest that it is possible to stimulate tissue repair in diabetics to overcome the enhanced sensitivity of hepatotoxicants.

Microarray analysis of thioacetamide-treated type 1 diabetic rats

It is well known that diabetes imparts high sensitivity to numerous hepatotoxicants. Previously, we have shown that a normally non-lethal dose of thioacetamide (TA, 300 mg/kg) causes 90% mortality in type 1 diabetic (DB) rats due to inhibited tissue repair allowing progression of liver injury. On the other hand, DB rats exposed to 30 mg TA/kg exhibit delayed tissue repair and delayed recovery from injury. The objective of this study was to investigate the mechanism of impaired tissue repair and progression of liver injury in TA-treated DB rats by using cDNA microarray. Gene expression pattern was examined at 0, 6, and 12 h after TA challenge, and selected mechanistic leads from microarray experiments were confirmed by real-time RT-PCR and further investigated at protein level over the time course of 0 to 36 h after TA treatment. Diabetic condition itself increased gene expression of proteases and decreased gene expression of protease inhibitors. Administration of 300 mg TA/kg to DB rats further elevated gene expression of proteases and suppressed gene expression of protease inhibitors, explaining progression of liver injury in DB rats after TA treatment. Inhibited expression of genes involved in cell division cycle (cyclin D1, IGFBP-1, ras, E2F) was observed after exposure of DB rats to 300 mg TA/kg, explaining inhibited tissue repair in these rats. On the other hand, DB rats receiving 30 mg TA/kg exhibit delayed expression of genes involved in cell division cycle, explaining delayed tissue repair in these rats. In conclusion, impaired cyclin D1 signaling along with increased proteases and decreased protease inhibitors may explain impaired tissue repair that leads to progression of liver injury initiated by TA in DB rats.

Type 2 diabetic rats are sensitive to thioacetamide hepatotoxicity

Previously, we reported high hepatotoxic sensitivity of type 2 diabetic (DB) rats to three dissimilar hepatotoxicants. Additional work revealed that a normally nonlethal dose of CCl4 was lethal in DB rats due to inhibited compensatory tissue repair. The present study was conducted to investigate the importance of compensatory tissue repair in determining the final outcome of hepatotoxicity in diabetes, using another structurally and mechanistically dissimilar hepatotoxicant, thioacetamide (TA), to initiate liver injury. A normally nonlethal dose of TA (300 mg/kg, ip), caused 100% mortality in DB rats. Time course studies (0 to 96 h) showed that in the non-DB rats, liver injury initiated by TA as assessed by plasma alanine or aspartate aminotransferase and hepatic necrosis progressed up to 48 h and regressed to normal at 96 h resulting in 100% survival. In the DB rats, liver injury rapidly progressed resulting in progressively deteriorating liver due to rapidly expanding injury, hepatic failure, and 100% mortality between 24 and 48 h post-TA treatment. Covalent binding of 14C-TA-derived radiolabel to liver tissue did not differ from that observed in the non-DB rats, indicating similar bioactivation-based initiation of hepatotoxicity. S-phase DNA synthesis measured by [3H]-thymidine incorporation, and advancement of cells through the cell division cycle measured by PCNA immunohistochemistry, were substantially inhibited in the DB rats compared to the non-DB rats challenged with TA. Thus, inhibited cell division and compromised tissue repair in the DB rats resulted in progressive expansion of liver injury culminating in mortality. In conclusion, it appears that similar to type 1 diabetes, type 2 diabetes also increases sensitivity to dissimilar hepatotoxicants due to inhibited compensatory tissue repair, suggesting that sensitivity to hepatotoxicity in diabetes occurs in the absence as well as presence of insulin.