Anticholestatic mechanisms of ursodeoxycholic acid in lipopolysaccharide-induced cholestasis

Tauroursodeoxycholate prevents estradiol 17β-d-glucuronide-induced cholestasis and endocytosis of canalicular transporters by switching off pro-cholestatic signaling pathways

AIMS

Estradiol 17β-d-glucuronide (E217G) induces cholestasis by triggering endocytosis and further intracellular retention of the canalicular transporters Bsep and Mrp2, in a cPKC- and PI3K-dependent manner, respectively. Pregnancy-induced cholestasis has been associated with E217G cholestatic effect, and is routinely treated with ursodeoxycholic acid (UDCA). Since protective mechanisms of UDCA in E217G-induced cholestasis are still unknown, we ascertained here whether its main metabolite, tauroursodeoxycholate (TUDC), can prevent endocytosis of canalicular transporters by counteracting cPKC and PI3K/Akt activation.

MAIN METHODS

Activation of cPKC and PI3K/Akt was evaluated in isolated rat hepatocytes by immunoblotting (assessment of membrane-bound and phosphorylated forms, respectively). Bsep/Mrp2 function was quantified in isolated rat hepatocyte couplets (IRHCs) by assessing the apical accumulation of their fluorescent substrates, CLF and GS-MF, respectively. We also studied, in isolated, perfused rat livers (IPRLs), the status of Bsep and Mrp2 transport function, assessed by the biliary excretion of TC and DNP-SG, respectively, and Bsep/Mrp2 localization by immunofluorescence.

KEY FINDINGS

E217G activated both cPKC- and PI3K/Akt-dependent signaling, and pretreatment with TUDC significantly attenuated these activations. In IRHCs, TUDC prevented the E217G-induced decrease in apical accumulation of CLF and GS-MF, and inhibitors of protein phosphatases failed to counteract this protection. In IPRLs, E217G induced an acute decrease in bile flow and in the biliary excretion of TC and DNP-SG, and this was prevented by TUDC. Immunofluorescence studies revealed that TUDC prevented E217G-induced Bsep/Mrp2 endocytosis.

SIGNIFICANCE

TUDC restores function and localization of Bsep/Mrp2 impaired by E217G, by preventing both cPKC and PI3K/Akt activation in a protein-phosphatase-independent manner.

A fungal P450 enzyme from Fusarium equiseti HG18 with 7β-hydroxylase activity in biosynthesis of ursodeoxycholic acid

Cytochrome P450 enzyme with 7β-hydroxylation capacity has attracted widespread attentions due to the vital roles in the biosynthesis of ursodeoxycholic acid (UDCA), a naturally active molecule for the treatment of liver and gallbladder diseases. In this study, a novel P450 hydroxylase (P450FE) was screen out from Fusarium equiseti HG18 and identified by a combination of genome and transcriptome sequencing, as well as heterologous expression in Pichia pastoris. The biotransformation of lithocholic acid (LCA) by whole cells of recombinant Pichia pastoris further confirmed the C7β-hydroxylation with 5.2% UDCA yield. It was firstly identified a fungal P450 enzyme from Fusarium equiseti HG18 with the capacity to catalyze the LCA oxidation producing UDCA. The integration of homology modeling and molecular docking discovered the substrate binding to active pockets, and the key amino acids in active center were validated by site-directed mutagenesis, and revealed that Q112, V362 and L363 were the pivotal residues of P450FE in regulating the activity and selectivity of 7β-hydroxylation. Specifically, V362I mutation exhibited 2.6-fold higher levels of UDCA and higher stereospecificity than wild-type P450FE. This advance provided guidance for improving the catalytic efficiency and selectivity of P450FE in LCA hydroxylation, indicative of the great potential in green synthesis of UDCA from biologically toxic LCA.

Therapeutic approaches for cholestatic liver diseases: the role of nitric oxide pathway

Cholestasis describes bile secretion or flow impairment, which is clinically manifested with fatigue, pruritus, and jaundice. Neutrophils play a crucial role in many diseases such as cholestasis liver diseases through mediating several oxidative and inflammatory pathways. Data have been collected from clinical, in vitro, and in vivo studies published between 2000 and December 2021 in English and obtained from the PubMed, Google Scholar, Scopus, and Cochrane libraries. Although nitric oxide plays an important role in the pathogenesis of cholestatic liver diseases, excessive levels of NO in serum and affected tissues, mainly synthesized by the inducible nitric oxide synthase (iNOS) enzyme, can exacerbate inflammation. NO induces the inflammatory and oxidative processes, which finally leads to cell damage. We found that natural products such as baicalin, curcumin, resveratrol, and lycopene, as well as chemical likes ursodeoxycholic acid, dexamethasone, rosuvastatin, melatonin, and sildenafil, are able to markedly attenuate the NO production and iNOS expression, mainly through inducing the nuclear factor κB (NF-κB), Janus kinase and signal transducer and activator of transcription (JAK/STAT), and toll like receptor-4 (TLR4) signaling pathways. This study summarizes the latest scientific data about the bile acid signaling pathway, the neutrophil chemotaxis recruitment process during cholestasis, and the role of NO in cholestasis liver diseases. Literature review directed us to propose that suppression of NO and its related pathways could be a therapeutic option for preventing or treating cholestatic liver diseases.

Bile Acids Promote Hepatic Biotransformation and Excretion of Aflatoxin B1 in Broiler Chickens

Aflatoxin B1 (AFB1) is a hazardous mycotoxin that often contaminates animal feed and may potentially induce severe liver damage if ingested. The liver is the primary organ responsible for AFB1 detoxification through enzyme-catalyzed xenobiotic metabolism and bile acid (BA)-associated excretion. In this study, we sought to investigate whether exogenous BA improves hepatic AFB1 detoxification to alleviate AFB1-induced liver injury in broiler chickens. Five-day-old broiler chicks were randomly assigned to three groups. CON and AFB1 received a basal diet; AFB1 + BA received a basal diet with 250 mg/kg BA for 20 days. After a 3-day pre-feed, AFB1 and AFB1 + BA were daily gavaged with 250 μg/kg BW AFB1, while CON received gavage solvent for AFB1 treatment. Dietary BA supplementation protected chickens from AFB1-induced hepatic inflammation and oxidative stress. The hepatic biotransformation of AFB1 to its metabolite AFBO was improved, with accelerated excretion to the gallbladder and cecum. Accordantly, AFB1-induced down-regulation of detoxification genes, including cytochrome P450 enzymes, glutathione S-transferases, and the bile salt export pump, was rescued by BA supplementation. Moreover, liver X receptor α, suppressed by AFB1, was enhanced in BA-treated broiler chickens. These results indicate that dietary BA supplementation improves hepatic AFB1 detoxification and excretion through LXRα-involved regulation of xenobiotic enzymes.

Biological synthesis of ursodeoxycholic acid

Ursodeoxycholic acid (UDCA) is a fundamental treatment drug for numerous hepatobiliary diseases that also has adjuvant therapeutic effects on certain cancers and neurological diseases. Chemical UDCA synthesis is environmentally unfriendly with low yields. Biological UDCA synthesis by free-enzyme catalysis or whole-cell synthesis using inexpensive and readily available chenodeoxycholic acid (CDCA), cholic acid (CA), or lithocholic acid (LCA) as substrates is being developed. The free enzyme-catalyzed one-pot, one-step/two-step method uses hydroxysteroid dehydrogenase (HSDH); whole-cell synthesis, mainly uses engineered bacteria (mainly Escherichia coli) expressing the relevant HSDHs. To further develop these methods, HSDHs with specific coenzyme dependence, high enzyme activity, good stability, and high substrate loading concentration, P450 monooxygenase with C-7 hydroxylation activity and engineered strain harboring HSDHs must be exploited.

Effect of Curcumin on Interleukin-6 Expression and Malondialdehyde Levels in Liver Fibrosis

BACKGROUND: Chronic inflammation and excessive oxidative stress are the main mechanisms causing liver fibrosis. It releases anti-inflammatory cytokines, namely, interleukin 6 (IL-6), nitric oxide, and malondialdehyde (MDA). Curcumin acts as an anti-inflammatory, antioxidant, and antifibrotic. AIM: This study is aimed to analyze differences in IL-6 expression and MDA levels in (Deutschland, Denken, and Yoken) DDY mice with liver fibrosis after common bile duct ligation between the curcumin-treated and control groups. METHODS: This research is an experimental study with a post-test-only control group design. Seventy-five male DDY mice 20–30g were used in this study (n = 5). Mice were randomly divided into five groups, each consisting of 15 mice. The first group healthy control (HC) was the HC group given phosphate-buffered saline (PBS) solution and did not perform the CBDL. The second group negative control (NC) was a NC group given PBS solution and completed the CBDL. The third group positive control (PC) was a PC group given oral ursodeoxycholic acid (UDCA) and performed CBDL. The fourth group (P1) was assigned oral curcumin and performed the CBDL. The fifth group (P2) was given oral curcumin and UDCA and performed the CBDL. Seven, fourteen, and 21 days after ligation, liver samples were taken to examine IL-6 expression and MDA levels. RESULTS: There was a significant difference between the NC and PC groups (p = 0.00), NC and P1 (p = 0.00), NC with P2 (p = 0.00), PC with P1 (p = 0.04), PC with P2 (p = 0.04), on day 21 between the NC and PC groups (p = 0.00), NC with P1 (p = 0.00), and PC with P2 (p = 0.00). Statistical analysis of the comparison of MDA levels on days 7 and 14 found no significant difference. On day 21, there was a substantial difference between the NC group and P1 (p = 0.02). CONCLUSION: This study concluded that curcumin effectively reduced IL-6 expression and MDA levels in liver fibrosis.

Impact of Ursodeoxycholic Acid in Critically Ill Patients With Sepsis: A Retrospective Study

Background: Using ursodeoxycholic acid (UDCA) in critically ill patients as adjunctive therapy for sepsis/septic shock in neonates and children is controversial, while it has not been extensively investigated in adults. This study aims to assess the effect of UDCA use on the early resolution of sepsis/septic shock in critically ill adult patients. Method: A retrospective study of critically ill adult patients in the intensive care unit (ICU) admitted with sepsis/septic shock at King Abdulaziz Medical City. Based on their usage of UDCA, patients were categorized into two groups. A total of 88 patients were included for analysis after matching, based on severity of illness scores within 24-hours of ICU admission. The primary outcome was to assess the effect of UDCA on the severity and resolution of shock at day three of ICU admission. The secondary outcomes were 30-day in-hospital mortality, mechanical ventilation (MV) duration, and ICU length of stay (LOS). Results: Out of the 88 patients matched, 44 patients (50%) received UDCA during the study period. Using UDCA was neither associated with improvement in Sequential Organ Failure Assessment (SOFA) score ( p-value: 0.32), inotropes/vasopressors requirement ( p-value: 0.79), Glasgow Coma Scale (GCS) ( p-value: 0.59) nor total bilirubin levels ( p-value: 0.79) at day three compared with the control. There was a significant association between using UDCA and improvement in PaO2/FiO2 ratio ( p-value: 0.01) and early extubation at day three ( p-value: 0.04). Conclusion: Using UDCA in critically ill patients with sepsis/septic shock was not associated with improvement in shock severity and resolution. However, patients who received UDCA were more likely to be extubated and not require MV on day three of ICU admission.

Mechanism of cholangiocellular damage and repair during cholestasis

The mechanism of damage of the biliary epithelium remains partially unexplored. However, recently many works have offered new evidence regarding the cholangiocytes' damage process, which is the main target in a broad spectrum of pathologies ranging from acute cholestasis, cholangiopathies to cholangiocarcinoma. This is encouraging since some works addressed this epithelium's relevance in health and disease until a few years ago. The biliary tree in the liver, comprised of cholangiocytes, is a pipeline for bile flow and regulates key hepatic processes such as proliferation, regeneration, immune response, and signaling. This review aimed to compile the most recent advances on the mechanisms of cholangiocellular damage during cholestasis, which, although it is present in many cholangiopathies, is not necessarily a common or conserved process in all of them, having a relevant role cAMP and PKA during obstructive cholestasis, as well as Ca²⁺-dependent PKC in functional cholestasis. Cholangiocellular damage could vary according to the type of cholestasis, the aggressor, or the bile ducts' location where it develops and what kind of damage can favor cholangiocellular carcinoma development.

Oxidative Stress and Localization Status of Hepatocellular Transporters: Impact on Bile Secretion and Role of Signaling Pathways

Significance: Most hepatopathies are primarily or secondarily cholestatic in nature. Oxidative stress (OS) is a frequent trait among them, and impairs the machinery to generate bile by triggering endocytic internalization of hepatocellular transporters, thus causing cholestasis. This is critical, since it leads to accelerated transporter degradation, which could explain the common post-transcriptional downregulation of transporter expression in human cholestatic diseases. Recent Advances: The mechanisms involved in OS-induced hepatocellular transporter internalization are being revealed. Filamentous actin (F-actin) cytoskeleton disorganization and/or detachment of crosslinking actin proteins that afford transporter stability have been characterized as causal factors. Activation of redox-sensitive signaling pathways leading to changes in phosphorylation status of these structures is involved, including Ca²⁺-mediated activation of "classical" and "novel" protein kinase C (PKC) isoforms or redox-signaling cascades downstream of NADPH oxidase. Critical Issues: Despite the well-known occurrence of hepatocellular transporter internalization in human hepatopathies, the cholestatic implications of this phenomenon have been overlooked. Accordingly, no specific treatment has been established in the clinical practice for its prevention/reversion. Future Directions: We need to improve our knowledge on the pro-oxidant triggering factors and the multiple signaling pathways that mediate this oxidative injury in each cholestatic hepatopathy, so as to envisage tailor-made therapeutic strategies for each case. Meanwhile, administration of antioxidants or heme oxygenase-1 induction to elevate the hepatocellular levels of the endogenous scavenger bilirubin are promising alternatives that need to be re-evaluated and implemented. They may complement current treatments in cholestasis aimed to enhance transcriptional carrier expression, by providing membrane stability to the newly synthesized carriers. Antioxid. Redox Signal. 35, 808-831.

Nifuroxazide mitigates cholestatic liver injury by synergistic inhibition of Il-6/Β-catenin signaling and enhancement of BSEP and MDRP2 expression

Cholestasis is a complex hepatic disorder underlined with retention of the highly toxic bile components within the hepatocytes. Nifuroxazide (NIF); a nitrofuran derivative, is widely used drug for treatment of acute and chronic diarrhea. The current study was performed to investigate the curative effect of NIF (25 and 50 mg/kg) on lithocholic acid (LCA)-induced cholestasis and compare the observed impact to that of ursodeoxycholic acid (UDCA). Intriguingly, NIF significantly attenuated LCA-induced cholestatic injury. NIF successfully reversed cholestatic injury to a similar extent compared to the mainstay drug, UDCA. NIF administration remarkably attenuated liver/body index and restored liver functions. Moreover, it restored the disrupted balance in oxidative homeostasis. On the other hand, NIF induced a marked improvement in histopathological and immuno-histochemical analysis of liver specimens. Ultimately, NIF mitigated inflammatory response and proliferative ability of hepatocytes with significant reduction in hepatic expression of proliferatingcellnuclearantigen(PCNA), cluster of differentiation 68 (CD68), interlukin-6 (Il-6) and β-catenin. Interestingly, NIF successfully increased bile transformation with increased the hepatic expression of bile salt export pump (BSEP) and multidrug resistance-associated protein 2 (MDRP2). Nevertheless, molecular docking of NIF with β-catenin and BSEP showed a better alignment inside the pocket with strong interaction for both protein binding sites. In conclusion, NIF attenuated experimentally-induced cholestatic dysfunction with an underlined synergistic inhibition of Il-6/Β-catenin pathways and direct enhancement of bile acids transporters gene expression.

An insight into the mechanism and molecular basis of dysfunctional immune response involved in cholestasis

Cholestasis is one of the most common clinical symptom of liver diseases. If patients do not receive effective treatment, cholestasis can evolve into liver fibrosis, cirrhosis and ultimately liver failure requiring liver transplantation. Currently, only ursodeoxycholic acid, obeticholic acid and bezafibrate are FDA-approved drugs, thereby requiring a breakthrough in new mechanisms and therapeutic development. Inflammation is one of the common complications of cholestasis. Hepatic accumulation of toxic hydrophobic bile acids is a highly immunogenic process involving both resident and immigrating immune cells. And the resulting inflammation may further aggravate hepatocyte injury. Though, great investigations have been made in the immune responses during cholestasis, the relationship between immune responses and cholestasis remains unclear. Moreover, scarce reviews summarize the immune responses during cholestasis and the efficacy of therapies on immune response. The main purpose of this paper is to review the existing literature on dysfunctional immune response during cholestasis and the effect of treatment on immune response which may provide an insight for researchers and drug development.

The effects of ursodeoxycholic acid on sepsis-induced cholestasis management in an animal model

Objectives

Cholestasis refers to a reduction in bile flow from the liver into the biliary system. Ursodeoxycholic acid (UDCA) is commonly used for the treatment of hepatic cholestasis. This study aimed to explore the role of UDCA in the treatment and prevention of lipopolysaccharide (LPS)-induced cholestasis.

Methods

Sixty male albino rats were randomly classified into five groups of 12 rats each: the control group (received saline and water), UDCA group (received UDCA), LPS group (received LPS), treatment group (received LPS followed by UDCA), and prevention group (received UDCA followed by LPS). Changes in gamma-glutamyl transferase (GGT), plasma aspartate transferase (AST), plasma alkaline transferase (ALT), plasma alkaline phosphatase (ALP), total bilirubin (TBIL), hepatocyte apoptosis, immunomodulatory activity, plasma pro-inflammatory cytokines (TNF-α, IL-1α, and IL-4), and liver histology were assessed.

Results

UDCA improved serum liver chemical markers (GGT, ALP, and AST) in both the prevention and treatment groups (p < 0.05 and p < 0.05, respectively). CD3 count was higher in the UDCA treatment group compared to the LPS group (p < 0.001). UDCA caused a reduction in plasma TNF-α in the prevention group (P < 0.05); however, it had no effect on the treatment group, as compared to the LPS group. Similarly, UDCA had no effect on IL-1α or IL-4. UDCA treatment resulted in improved liver histological features and a significant reduction in liver tissue apoptosis in both the treatment and prevention groups, as compared to the LPS group (p = 0.013 and p = 0.002, respectively).

Conclusions

This study provides evidence of the effectiveness of UDCA for the treatment and prevention of sepsis-induced cholestasis.

Preclinical evidence of Yinchenhao decoction on cholestasis: A systematic review and meta-analysis of animal studies

Cholestasis is an important cause of liver fibrosis and cirrhosis. Yinchenhao decoction has been used as a well-known traditional Chinese medicine used in the treatment of cholestasis for over 2,000 years. The purpose of this systematic review is to evaluate the preclinical evidence of Yinchenhao decoction on cholestasis models. The following databases were searched from inception to February 2020. Chinese National Knowledge Infrastructure, VIP medicine information system, Wanfang Database, PubMed, Web of Science, Embase and the Cochrane Library were searched. The content concerned Yinchenhao decoction on different animal model experiments for the treatment of cholestasis. The methodological quality of the included studies was assessed based on the SYstematic Review Center for Laboratory animal Experimentation Animal Experiment Bias Risk Assessment Tool. A meta-analysis was conducted with RevMan 5.3 software according to the Cochrane tool. Nineteen studies on a total of 404 animals were included with five kinds of experimental animal models. The results showed that serum total bilirubin (TBIL), direct bilirubin (DBIL), indirect bilirubin and total bile acid in the group treated with Yinchenhao decoction were significantly lower than those in the model group (P < 0.00001). The alanine aminotransferase (ALT), aspartate aminotransferase and alkaline phosphatase levels in the Yinchenhao decoction group were also significantly reduced (P < 0.00001). The subgroup analysis of the different models showed that Yinchenhao decoction had a significant effect on the bile duct ligation model, and there was a significant reduction in TBIL, DBIL and ALT levels (P < 0.00001) in ANIT-induced cholestasis. After 24 hours of Yinchenhao decoction treatment, there was no significant difference in TBIL levels (P = 0.34), but after 48 and 72 hours of treatment, the TBIL levels were significantly reduced compared with the model group (P < 0.00001). There was no significant difference in DBIL after 48 hours of administration (P = 0.26), but compared with the model group, Yinchenhao decoction could significantly reduce the DBIL levels after 48 hours of treatment (P < 0.0003). Yinchenhao decoction could significantly reduce the ALT levels after 24, 48 and 72 hours (P < 0.006). Yinchenhao decoction was able to significantly reduce the levels of TBIL, DBIL and ALT on different rat species: Wistar and Sprague Dawley (P = 0.0001; P = 0.0002). The preclinical evidence indicated that Yinchenhao decoction might be a potent and promising agent for cholestasis. Moreover, this conclusion should be further confirmed with more well-designed researches.

Ursodeoxycholic acid abrogates gentamicin-induced hepatotoxicity in rats: Role of NF-κB-p65/TNF-α, Bax/Bcl-xl/Caspase-3, and eNOS/iNOS pathways

AIM

The present study focused on the possible underlying protective mechanisms of UDCA against GNT-induced hepatic injury.

METHODS

For achieving this goal, adult male rats were allocated into 4 groups: normal control (received vehicle), GNT (100 mg/kg, i.p. for 8 days), UDCA (60 mg/kg, P.O. for 15 days), and GNT + UDCA (received UDCA for 15 days and GNT started from the 7th day and lasted for 8 days).

RESULTS

The results revealed that UDCA significantly improved GNT-induced hepatic injury, oxidative stress, apoptosis, and inflammatory response. Interestingly, UDCA inhibited apoptosis by marked down-regulation of the Bax gene, Caspase-3, and cleaved Caspase-3 protein expressions while the level of Bcl-xL gene significantly increased. Moreover, UDCA strongly inhibited the inflammatory response through the down-regulation of both NF-κB-p65 and TNF-α accompanied by IL-10 elevation. Furthermore, the obtained results ended with the restored of mitochondria function that confirmed by electron microscopy. Histological analysis showed that UDCA remarkably ameliorated the histopathological changes induced by GNT.

SIGNIFICANCE

UDCA may be a promising agent that can be used to prevent hepatotoxicity observed in GNT treatment. This effect could be attributed to, at least in part, the ability of UDCA to modulate NF-κB-p65/TNF-α, Bax/Bcl-xl/Caspase-3, and eNOS/iNOS signaling pathways.