Cholestatic interleukin-6-deficient mice succumb to endotoxin-induced liver injury and pulmonary inflammation

Protective effect of valsartan alone and in combination with neprilysin inhibitor (valsartan + sacubitril) against hepatic ischemia-reperfusion injury: targeting angiotensin II receptor-neprilysin and modulating SMAD-4/NF-κβ/JNK pathways in rats

Ischemia-reperfusion injury (IRI) is a common pathogenic situation that arises throughout all liver surgeries, including liver transplants. We aimed to compare the preventive effects of valsartan (VST) against valsartan + sacubitril (LCZ696) on hepatic injury caused by IRI. A total of thirty-six male Westar albino rats were split into six groups randomly: sham, IRI, VST + IRI, LCZ696 + IRI, VST, and LCZ696. The medicines were given orally for 10 days in a row. Hepatic tissues and blood were examined through histopathological imaging and immunohistochemical detection of hepatic SMAD-4 protein expression plus serum aminotransferase (ALT, AST) and gamma-glutamyl transferase (GGT) levels. Angiotensin II, aldosterone, and plasma renin activity were evaluated in rat serum. Liver tissue homogenate was utilized to assess reduced glutathione (GSH), myeloperoxidase (MPO), malondialdehyde (MDA), and total nitric oxide (NOx) levels. Pro-inflammatory indicators, tumor necrosis factor-alpha (TNF-α), and interleukin-1β (IL-1β), moreover with apoptosis indicators, BCL2-associated X protein (Bax), B-cell lymphoma 2 (Bcl-2), and galactine-9 (GAL9) proteins plus caspase-3, were measured in hepatic tissue homogenate. Hepatic endothelin-1 and neprilysin activity were evaluated. Western blot was done for c-Jun N-terminal kinase (JNK-7) plus nuclear factor-kappa B (NF-κβ) expressions. The study revealed that VST and LCZ696 pretreatment showed significant restoration of liver injury, correction of oxidative profile, and inhibition in the angiotensin II receptor-neprilysin pathway. Inflammatory mediators and apoptosis were significantly inhibited. The expression of SMAD-4, JNK-7, and NF-κβ proteins was notably diminished. The improvement in hepatic architecture supports these histopathological results. In conclusion, LCZ696 possesses a potentially significant protective effect against liver IRI superior to VST alone.

The Protective Effect of Sulodexide on Acute Lung Injury Induced by a Murine Model of Obstructive Jaundice

Introduction

The effect of sulodexide (SLX) on obstructive jaundice- (OJ-) induced acute lung injury (ALI) in rats was examined in this study.

Methods

In this study, 48 rats were randomly assigned to one of six groups: sham, OJ, OJ+saline, OJ+SLX (0.5 mg/ml/d), OJ+SLX (1 mg/ml/d), and OJ+SLX (2 mg/ml/d). The pathological lung injury was assessed by histological analysis and lung injury grading. ELISA kits were used to evaluate the expression of IL-6, IL-1, TNF-α, and syndecan-1 (SDC-1) in bronchoalveolar lavage fluids (BALFs). Commercial assay kits were performed to evaluate malondialdehyde (MDA) production and catalase (CAT) activity in lung tissues. The apoptosis was assessed by TUNEL assay. The lung microvascular permeability was investigated using Evans blue leakage, lung wet/dry weight (W/D) ratio, and lung permeability index (LPI). SDC-1, claudin-5, ZO-1, and VE cadherin expression levels in lung tissues were measured using Western blot.

Results

The OJ-induced ALI rats showed severe lung injury. The value of IL-6, IL-1β, TNF-α, and SDC-1 in BALFs was remarkedly increased in the OJ group. MDA content, apoptotic area, apoptotic molecules, and SDC-1 level were all higher in the OJ group's lung tissues than in the sham group. CAT activity, Evans blue leakage, W/D ratio, LPI, and expression of claudin-5, ZO-1, and VE cadherin were all lower in the OJ group compared to the sham group. The degenerative alterations in lung tissue improved after 7 days of treatment with 2 mg/ml SLX. The BALFs had lower amounts of IL-6, IL-1, TNF-α, and SDC-1. The SLX therapy reduced MDA levels while restoring CAT activity. In lung tissues, SLX reduced apoptotic area and SDC-1 expression. SLX reduced lung microvascular permeability by raising the expression of Claudin-5, ZO-1, and VE-cadherin in lung tissue when compared to the OJ group.

Conclusion

The results suggested that SLX attenuates OJ-induced ALI in rats by protecting the pulmonary microvascular endothelial barrier.

Predictive Power of Preoperative Serum Total Bilirubin for the Outcomes Following Pancreaticoduodenectomy

Background: The high levels of bilirubin in patients with periampullary cancers may increase the morbidity or mortality after curative surgery. Objectives: We aimed at evaluating the predictive power of preoperative serum total bilirubin for the outcomes after pancreaticoduodenectomy (PD) in resectable periampullary cancers. Methods: The data of 80 patients, who had undergone PD, were retrospectively analyzed. Regarding the preoperative bilirubin, we opted for 20 mg/dL as the cut-off value to divide patients into two groups to be subjected to simple and multiple logistic regression. Results: A total of 80 patients with a mean age of 54.90 ± 14.33 years underwent PD. The median preoperative bilirubin level was 4.7 mg/dL and the majority of cases (88.8%) had bilirubin < 20 mg/dL. While there was no significant difference in the mortality between bilirubin groups (P = 0.266), bilirubin≥20 mg/dL remarkably increased the postoperative morbidity (P = 0.012, Odds ratio = 3.04); 57.5% of cases underwent biliary drainage before surgery, which did not impact the mortality and morbidity. Multiple analysis by a logistic regression model disclosed that the only statistically significant variable for mortality was the total operative time (P = 0.038) and among all factors, total bilirubin level was the only independent predictor for the morbidity status (P = 0.009). Conclusions: This study suggested that preoperative biliary drainage should only be limited to patients with high bilirubin levels (≥ 20 mg/dL) or expected delayed surgeries.

Folic acid and RAAS blockers in ischemia/reperfusion-induced hepatic injury: A current mechanistic concept for understanding the incidence, significance & outcome

Hepatic ischemia-reperfusion injury (IRI) is not only one of the pathophysiological process involving the liver, but also a complex systemic process affecting multiple tissues and organs. IRI after liver transplant occurs due to in major resections and occlusion of vessels, or during the perioperative period, leads to acute liver failure which shows the dynamic process that involves two interrelated phases of local ischemic insult and inflammation-mediated reperfusion injury and has an impact on morbidity and mortality. The renin-angiotensin-aldosterone system (RAAS) is activated locally in the injured cells by the occurrence of I/R, which plays an essential role in the fate of the damaged tissue. However, a preclinical study explores the protective role of RAAS inhibitor in acute liver injury in a model of inflammation caused by ischemia and reperfusion. In-addition to RAAS blockers in monotherapy does not effectively block the complete pathway. Thus, the present study is designed to explore the effect of combined folic acid with RAAS blockers in combination, produce a synergistic effect. Moreover, in this review, we will describe the understanding of the possible incidence of downregulatory molecular mechanisms associated with renin-angiotensin-aldosterone system and the significance & outcome of the combination of folic acid and RAAS blockers in liver injury due to ischemia/reperfusion.

Platelet activating factor receptor acts to limit colitis-induced liver inflammation

Liver inflammation is a common extraintestinal manifestation in inflammatory bowel disease (IBD), yet, the mechanisms driving gut-liver axis inflammation remain poorly understood. IBD leads to a breakdown in the integrity of the intestinal barrier causing an increase in portal and systemic gut-derived antigens, which challenge the liver. Here, we examined the role of platelet activating factor receptor (PAFR) in colitis-associated liver damage using dextran sulfate sodium (DSS) and anti-CD40-induced colitis models. Both DSS and anti-CD40 models exhibited liver inflammation associated with colitis. Colitis reduced global PAFR protein expression in mouse livers causing an exclusive re-localization of PAFR to the portal triad. The global decrease in liver PAFR was associated with increased sirtuin 1 while relocalized PAFR expression was limited to Kupffer cells (KCs) and co-localized with toll-like receptor 4. DSS activated the NLRP3-inflammasome and increased interleukin (IL)-1β in the liver. Antagonism of PAFR amplified the inflammasome response by increasing NLRP3, caspase-1, and IL-1β protein levels in the liver. LPS also increased NLRP3 response in human hepatocytes, however, overexpression of PAFR restored the levels of NLPR3 and caspase-1 proteins. Interestingly, KCs depletion also increased IL-1β protein in mouse liver after DSS challenge. These data suggest a protective role for PAFR-expressing KCs during colitis and that regulation of PAFR is important for gut-liver axis homeostasis.

Pathogenesis of Kupffer Cells in Cholestatic Liver Injury

Kupffer cells are the resident macrophages in the liver. They are located in hepatic sinusoid, which allows them to remove foreign materials, pathogens, and apoptotic cells efficiently. Activated Kupffer cells secrete various mediators, including cytokines and chemokines, to initiate immune responses, inflammation, or recruitment of other liver cells. Bile duct ligation (BDL) surgery in rodents is often studied as an animal model of cholestatic liver disease, characterized by obstruction of bile flow. BDL mice show altered functional activities of Kupffer cells compared with sham-operated mice, including elevated cytokine secretion and impaired bacterial clearance. Various mediators produced by other liver cells can regulate Kupffer cell activation, which suggest that Kupffer cells orchestrate with other liver cells to relay inflammatory signals and to maintain liver homeostasis during BDL-induced liver injury. Blocking or depletion of Kupffer cells, an approach for the treatment of liver diseases, has shown controversial implications. Procedures in Kupffer cell research have limitations and may produce various results in Kupffer cell research. It is important, however, to reveal underlying mechanisms of activation and functions of Kupffer cells, followed by hepatic inflammation and fibrosis. This review summarizes present Kupffer cell studies in cholestatic liver injury.

Should preoperative biliary drainage be routinely performed for obstructive jaundice with resectable tumor?

Obstructive jaundice is a common clinical manifestation of malignant lesions adjacent to extrahepatic bile duct, ampulla or pancreatic head. Animal experiments and some clinical observations have demonstrated that preoperative biliary drainage could improve liver function as well as reduce endotoxemia, thereby reducing the incidence of perioperative complications. However, a number of randomized, controlled studies have found that preoperative biliary drainage failed to improve prognosis or reduce the incidence of perioperative complications; in contrast, it might increase the incidence of complications and cause extra financial burden on patients. Thus, whether preoperative biliary drainage should be performed or not is controversial. Since clinical randomized controlled studies are more relevant in clinical setting, we believe that preoperative biliary drainage should not be routinely performed for obstructive jaundice with resectable tumors. More randomized, controlled, prospective studies should be conducted for further exploration.

Efficacy of dynamic indices in predicting fluid responsiveness in patients with obstructive jaundice

Previous studies have shown that the stroke volume variation (SVV), the pulse pressure variation (PPV) and the pleth variability index (PVI) could be successfully used for predicting fluid responsiveness (FR) in surgical patients. The aim of this study was to validate the ability of SVV, PPV and PVI to predict intraoperative FR in mechanically ventilated patients with obstructive jaundice (OJ). Thirty-two patients with OJ (mean serum total bilirubin 190.5 ± 95.3 µmol L(-1)) received intraoperative volume expansion (VE) with 250 ml colloids immediately after an exploratory laparotomy had been completed and after a 5 min period of hemodynamic stability. Hemodynamic variables were recorded before and after VE. FR was defined as an increase in stroke volume index > 10% after VE. The ability of SVV, PPV and PVI to predict FR was assessed by calculation of the area under the receiver operating characteristic curve. Eleven (34%) patients were responders and 21 patients were nonresponders to VE. The PPV was the unique dynamic index that had the moderate ability to predict FR during surgical procedures, the area under the curve was 0.71 (95% CI, 0.523 to 0.856; P = 0.039) and the threshold (sensitivity and specificity) discriminated responders was 7.5% (63.6%/71.4%). The present study concluded that SVV and PVI were not reliable predictors of FR, but PPV has some value predicting FR in patients with OJ intraoperatively.

The quandary of preresection biliary drainage for pancreatic cancer

Surgery in patients with obstructive jaundice caused by a tumor in the pancreatic head area is associated with a higher risk of postoperative complications. Preoperative biliary drainage was introduced in an attempt to improve the general condition and reduce morbidity and mortality. Extensive experimental studies have been performed to analyze the beneficial effect of biliary drainage and showed improvement in liver function, nutritional status, and cell-mediated immune function as well as reduction in mortality. However, despite the results seen in the experimental studies, clinical studies reported both beneficial and adverse effects, and most studies advised against routinely performing preoperative biliary drainage. To add clarity to the ongoing controversy, a recent randomized controlled trial was performed and reported more overall complications in patients with jaundice who underwent preoperative biliary drainage followed by surgery compared to those who underwent surgery alone. Many of these complications were stent related. Like most clinical studies, a plastic stent was used to initiate biliary drainage. Patients with jaundice because of a tumor in the pancreatic head area without locoregional irresectability or metastases should be candidates for early surgery. Preoperative biliary drainage should not be performed routinely. However, some selected patients might benefit from preoperative biliary drainage, in cases of severe jaundice, neoadjuvant therapy, or postponed surgery due to logistics. In these cases, the use of metal biliary stents is indicated.

Regulatory T cells suppress sickness behaviour development without altering liver injury in cholestatic mice

BACKGROUND & AIMS

Cholestatic liver diseases are commonly accompanied by debilitating symptoms, collectively termed sickness behaviours. Regulatory T cells (T(regs)) can suppress inflammation; however, a role for T(regs) in modulating sickness behaviours has not been evaluated.

METHODS

A mouse model of cholestatic liver injury due to bile duct ligation (BDL) was used to study the role of T(regs) in sickness behaviour development.

RESULTS

BDL mice developed reproducible sickness behaviours, as assessed in a social investigation paradigm, characterized by decreased social investigative behaviour and increased immobility. Depletion of peripheral T(regs) in BDL mice worsened BDL-associated sickness behaviours, whereas infusion of T(regs) improved these behaviours; however, liver injury severity was not altered by T(reg) manipulation. Hepatic IL-6 mRNA and circulating IL-6 levels were elevated in BDL vs. control mice, and were elevated further in T(reg)-depleted BDL mice, but were decreased after infusion of T(regs) in BDL mice. IL-6 knock out (KO) BDL mice exhibited a marked reduction in sickness behaviours, compared to wildtype BDL mice. Furthermore, IL-6 KO BDL mice injected with rmIL-6 displayed sickness behaviours similar to wildtype BDL mice, whereas saline injection did not alter behaviour in IL-6 KO BDL mice. BDL was associated with increased hippocampal cerebral endothelial cell p-STAT3 expression, which was significantly reduced in IL-6 KO BDL mice.

CONCLUSIONS

T(regs) modulate sickness behaviour development in the setting of cholestatic liver injury, driven mainly through T(reg) inhibition of circulating monocyte and hepatic IL-6 production, and subsequent signalling via circulating IL-6 acting at the level of the cerebral endothelium.

Effect of salvia miltiorrhizae on pulmonary apoptosis of rats with severe acute pancreatitis or obstructive jaundice

To investigate the effect of apoptosis about Salvia miltiorrhizae injection on the lungs of SAP and OJ rats. Total 288 rats were used for SAP-associated experiments and OJ-associated experiments, respectively. The rats were randomly divided into sham-operated, model control and treated group. According to the difference of time points after operation, the SAP rats in each group were subdivided into 3, 6 and 12 h groups while the OJ rats were divided into 7, 14, 21 and 28 days groups. The pathological changes, expression levels of Bax protein and apoptotic indexes in the lungs of SAP or OJ rats were observed, and the mortality rates of SAP or OJ rats were recorded, respectively. The numbers of dead SAP and OJ rats in treated groups declined. The pathological changes in the lungs of SAP or OJ rats in treated groups were relieved to varying degrees. There was no marked difference in pathological severity scores and the positive staining intensity of Bax protein between treated groups and model control groups (all P > 0.05). Salvia miltiorrhizae has some protective effect on the lungs of rats with SAP or OJ which may be related apoptosis although our results can not find significant difference between treated groups and model control groups.

Cholestasis downregulate hepcidin expression through inhibiting IL-6-induced phosphorylation of signal transducer and activator of transcription 3 signaling

Hepcidin is downregulated during progressive cholestasis in biliary atresia, but the mechanism is unknown. To verify whether downregulation of hepcidin is specific to cholestasis irrespective of the patient's age, we first analyzed liver hepcidin mRNA and protein expression in adults with primary biliary cirrhosis (PBC) (n=4), non-cholestatic cirrhosis (n=19) and in controls (n=9). We evaluated the tyrosine phosphorylation of signal transducer and activator of transcription 3 (pSTAT3) expressions in the liver sections. A rat model of cholestasis by ligation of the extrahepatic bile duct (BDL) was created, and lipopolysaccharide (LPS)-induced cholangitis in cholestatic rats 2 weeks after BDL was also established to study the modulation of hepcidin by interleukin-6 (IL-6) and STAT3 signaling pathway in these models, using real-time quantitative reverse transcription-PCR, immunohistochemistry, western blotting and enzyme-linked immunosorbent assay (ELISA). An in vitro study of the effect of bile acids on hepcidin expression was carried out to re-confirm the in vivo findings. There was significantly lower hepcidin mRNA and pSTAT3 protein expression in cholestatic cirrhosis compared with non-cholestatic cirrhosis in adults. BDL caused significant decrease in hepcidin and gp130 mRNA expression compared with sham-operated group and normal control. Furthermore, there was significantly lower pSTAT3 protein expression and nuclear translocation in the cholestatic liver from the patients and the BDL rats, which was comparable to lower liver hepcidin mRNA and plasma hepcidin expression. Furthermore, BDL for 2 weeks attenuated the upregulation of hepcidin expression induced by LPS. Hydrophobic bile acid glycochenodeoxycholate inhibited IL-6-induced pSTAT3 expression in primary hepatocytes and resulted in the downregulation of hepcidin mRNA expression. In conclusion, the study shows that cholestasis or its important component-hydrophobic bile acids-can downregulate hepcidin expression through inhibiting IL-6-induced STAT3 phosphorylation and pSTAT3 protein nuclear translocation.

Protective effects of Salvia miltiorrhizae on multiple organs of rats with obstructive jaundice

PURPOSE

we aim to explore the protective effects of Salvia miltiorrhizae injection on multiple organs of obstructive jaundice (OJ) rats through observing the impact of this injection on the pathological alterations in these organs and the contents of endotoxin, PLA(2), and TNF-alpha in the blood.

METHODS

A total of 90 mice were randomly divided into sham-operated group, model-control group, and Salvia miltiorrhizae-treated group (n = 30). According to the duration of postoperative administration, each group was further divided into two subgroups, namely, 21 d subgroup (consecutive administration for 21 d, n = 15) and 28 d subgroup (consecutive administration for 28 d, n = 15). After administration, the pathological alterations in multiple organs were observed and the contents of endotoxin, PLA(2), and TNF-alpha in the blood were determined.

RESULTS

Compared to model control group, the number of dead rats in treated group decreased though there was no statistical difference between the two groups. The pathological alterations in the liver, kidney, and spleen in treated group showed varying degrees of mitigation. At all time points, the contents of plasma endotoxin declined significantly. On day 28, plasma PLA(2) content in treated group was significantly lower than that in model-control group.

CONCLUSION

Salvia miltiorrhizae injection is able to obviously reduce the contents of inflammatory mediators in the blood of OJ rats and exert some protective effects on multiple organs of these rats.

Preoperative biliary drainage in patients with obstructive jaundice: history and current status

RATIONALE

Preoperative biliary drainage (PBD) has been introduced to improve outcome after surgery in patients suffering from obstructive jaundice due to a potentially resectable proximal or distal bile duct/pancreatic head lesion. In experimental models, PBD is almost exclusively associated with beneficial results: improved liver function and nutritional status; reduction of systemic endotoxemia; cytokine release; and, as a result, an improved immune response. Mortality was significantly reduced in these animal models. Human studies show conflicting results.

FINDINGS

For distal obstruction, currently the "best-evidence" available clearly shows that routine PBD does not yield the appreciated improvement in postoperative morbidity and mortality in patients undergoing resection. Moreover, PBD harbors its own complications. However, most of the available data are outdated or suffer from methodological deficits.

CONCLUSION

The highest level of evidence for PBD to be performed in proximal obstruction, as well as over the preferred mode, is lacking but, nevertheless, assimilated in the treatment algorithm for many centers. Logistics and waiting lists, although sometimes inevitable, could be factors that might influence the decision to opt for PBD, as well as an extended diagnostic workup with laparoscopy (on indication) or scheduled preoperative chemotherapy.

Endocrine and paracrine role of bile acids

Bile acids are not only important for the absorption of dietary lipids and fat soluble vitamins but are signalling molecules with diverse endocrine and paracrine functions. Bile acids regulate bile acid, lipid and glucose metabolism and modulate temperature and energy homeostasis. Furthermore, bile acids can not only promote cell proliferation and liver regeneration but can also induce programmed cell death. Bile acid functions are mediated through different pathways which comprise the activation of nuclear hormone receptors, of intracellular kinases and of the plasma membrane-bound, G-protein coupled bile acid receptor TGR5/Gpbar-1.

Liver fibrosis: a balance of ACEs?

There is an increasing body of evidence to suggest that the RAS (renin–angiotensin system) contributes to tissue injury and fibrosis in chronic liver disease. A number of studies have shown that components of a local hepatic RAS are up-regulated in fibrotic livers of humans and in experimental animal models. Angiotensin II, the main physiological effector molecule of this system, mediates liver fibrosis by stimulating fibroblast proliferation (myofibroblast and hepatic stellate cells), infiltration of inflammatory cells, and the release of inflammatory cytokines and growth factors such as TGF (transforming growth factor)-β1, IL (interleukin)-1β, MCP (monocyte chemoattractant protein)-1 and connective tissue growth factor. Furthermore, blockade of the RAS by ACE (angiotensin-converting enzyme) inhibitors and angiotensin type 1 receptor antagonists significantly attenuate liver fibrosis in experimental models of chronic liver injury. In 2000 ACE2 (angiotensin-converting enzyme 2), a human homologue of ACE, was identified. ACE2 efficiently degrades angiotensin II to angiotensin-(1–7), a peptide which has recently been shown to have both vasodilatory and tissue protective effects. This suggests that ACE2 and its products may be part of an alternate enzymatic pathway in the RAS, which counterbalances the generation and actions of angiotensin II, the ACE2–angiotensin-(1–7)–Mas axis. This review focuses on the potential roles of the RAS, angiotensin II and ACE2 in chronic liver injury and fibrogenesis.

[Cytokines and other immunological parameters as markers of distant organ involvement in acute pancreatitis]

BACKGROUND AND OBJECTIVE

There is a role of immunologic proinflammatory mediators in pathogenesis of distant organ disfunction in acute pancreatitis (AP). The aim is to evaluate the relationship between those mediators and liver, kidney and lung disfunction in patients with AP.

PATIENTS AND METHOD

On the day of admission in 34 patients with AP, biochemical parameters of liver function, creatinine and arterial partial pressure of oxygen (PO2) were determined, and cut points were established. Soluble tumor necrosis factor receptor I (sTNFRI), interleukin (IL) 1 receptor antagonist (IL-1Ra), IL-6, soluble IL-6 receptor (sIL-6R), IL-18, and intercellular adhesion molecule-1 (ICAM-1) were determined on days 1, 2, 3 and 7, and were compared between patients with biochemical parameters and PO2 on admission higher or lower than an established cut point.

RESULTS

Levels of sTNFRI, IL-18 and ICAM-1 were significantly higher and sustained, and IL-6 only the first day, in patients with parameters of liver function above the cut point. sTNFRI, IL-1Ra and ICAM-1 early showed significantly higher levels in relation with serum creatinine, and these and also IL-6 in those with PO2 below 60 mmHg.

CONCLUSIONS

sTNFRI, IL-6, IL-18 and ICAM-1 behaved as early markers of hepatic alteration, sTNFRI, IL-1Ra and ICAM-1 of renal disfunction and these and IL-6 of lung injury.

Up-regulation of interleukin-6 gene expression in cyclophosphamide-induced cystitis in mice: An in situ hybridization histochemical study

AIM

To determine the time course and the cellular sources of interleukin (IL)-6 in the bladder during experimental cystitis, the expression of the IL-6 gene and IL-6 protein was examined in the bladder during cyclophosphamide (CP)-induced cystitis.

METHODS

Mice were killed at 0, 1, 2, 6, 12 and 48 h after the intraperitoneal administration of 0.9% saline containing either CP (200 mg/kg) or saline. The expression of IL-6 gene and IL-6 protein were detected using in situ hybridization histochemistry and immunocytochemistry, respectively.

RESULTS

In situ hybridization histochemistry showed that IL-6 gene expression was significantly up-regulated in the bladder at 1 h in comparison to that at 0 h after CP administration. The levels of IL-6 gene expression peaked at 6 h after CP administration and then declined thereafter. In contrast, only a few IL-6 transcripts were expressed in the bladder but they remained unchanged following the administration of saline at all time points examined. The IL-6 transcripts were predominantly distributed in the perivascular area of the submucosal layers during CP-induced cystitis. Immunocytochemistry demonstrated IL-6 immunoreactivity in the spindle-shaped cells located in the vicinity of the dilated vessels of the submucosal layers during CP-induced cystitis.

CONCLUSION

IL-6 gene expression was up-regulated in the submucosal layer of the bladder and peaked at 6 h after CP administration, suggesting that the primary source of IL-6 may be fibroblasts in the bladder during CP-induced cystitis.

Bile acids inhibit interleukin-6 signaling via gp130 receptor-dependent and -independent pathways in rat liver

Interleukin-6 (IL-6) is a major regulator of the acute phase reaction in the liver and is thought to mediate protective effects in response to hepatotoxins. In this study, the influence of bile acids on IL-6 signal transduction was analyzed. It was shown that hydrophobic bile acids such as glycochenodeoxycholate (GCDC) inhibited IL-6-induced tyrosine phosphorylation of signal transducer and activator of transcription (STAT) 3 in hepatocytes and in perfused rat liver. This inhibition was accompanied by GCDC-mediated downregulation of glycoprotein (gp) 130 expression, whereas gp130 and suppressor of cytokine signaling 3 messenger RNA and gp80 protein levels remained unaffected. The GCDC-induced downregulation of gp130 protein expression was insensitive to inhibition of proteasomal or lysosomal protein degradation but turned out to be sensitive to inhibition of caspase-3 or caspase-8 activity. Accordingly, treatment of cell extracts with active recombinant caspase-3 led to a decay of immunoreactive gp130. Moreover, activation of caspases by CD95 ligand or hyperosmotic stress also resulted in a downregulation of gp130 levels. This indicates that caspase activation antagonizes IL-6 signaling by decay of gp130 levels. However, caspase inhibition did not prevent GCDC-dependent inhibition of IL-6-induced STAT3 activation, which turned out to be at least partially sensitive to suppression of p38(MAPK) activation. In conclusion, hydrophobic bile acids compromise IL-6 signaling through both a caspase-mediated downregulation of gp130 and a p38(MAPK)-dependent inhibition of STAT3 phosphorylation. This may contribute to bile acid-induced hepatotoxicity in cholestasis through counteracting the known hepatoprotective effects of IL-6.