Ursodeoxycholyl lysophosphatidylethanolamide inhibits cholestasis- and hypoxia-induced apoptosis by upregulating antiapoptosis proteins

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.

Ursodeoxycholyl Lysophosphatidylethanolamide Protects Against CD95/FAS-Induced Fulminant Hepatitis

Increased activation of CD95/Fas by Fas ligand in viral hepatitis and autoimmunity is involved in pathogenesis of fulminant hepatitis and liver failure. We designed a bile-acid phospholipid conjugate ursodeoxycholyl lysophosphatidylethanolamide (UDCA-LPE with LPE containing oleate at the sn-1) as a hepatoprotectant that was shown to protect against fulminant hepatitis induced by endotoxin. We herein further assessed the ability of UDCA-LPE to prevent death receptor CD95/Fas-induced fulminant hepatitis. C57BL/6 mice were intravenously administered with CD95/Fas agonistic monoclonal antibody (Jo-2) with or without 1 h pretreatment with 50 mg/kg UDCA-LPE. Jo-2 administration caused massive hepatocyte damage as seen by histology, and this was associated with a significant decrease in hepatic phosphatidylcholine (PC), lysoPC, and lysophosphatidylethanolamine levels. By histology, UDCA-LPE pretreatment improved hepatocyte damage and restored the loss of these phospholipids in part by a mechanism involving an inhibition of cytosolic phospholipaseA2 expression. Accordingly, Jo-2 treatment increased hepatic expression of cleaved caspase 8, caspase 3, and poly (ADP-Ribose) polymerase-1, and on the other hand decreased that of anti-apoptotic cellular FLICE-inhibitory protein. UDCA-LPE pretreatment was able to reverse all these changes. Moreover, UDCA-LPE attenuated inflammatory response by lowering the levels of Jo-2-induced proinflammatory cytokines TNF-α, IL-6, and IL-1β in liver and serum. UDCA-LPE was also able to decrease the levels of stimulated Th1/Th17 cytokines in Jo-2-primed isolated splenocytes. Taken together, UDCA-LPE exhibited potent anti-inflammatory effects against CD95/Fas-induced fulminant hepatitis.

Ursodeoxycholyl lysophosphatidylethanolamide negatively regulates TLR-mediated lipopolysaccharide response in human THP-1-derived macrophages

The bile acid-phospholipid conjugate ursodeoxycholyl oleoyl-lysophophatidylethanolamide (UDCA-18:1LPE) is an anti-inflammatory and anti-fibrotic agent as previously shown in cultured hepatocytes and hepatic stellate cells as well as in in vivo models of liver injury. We hypothesize that UDCA-18:1LPE may directly inhibit the activation of immune cells. We found that UDCA-18:1LPE was capable of inhibiting the migration of phorbol ester-differentiated human THP-1 cells. We examined anti-inflammatory activity of UDCA-18:1LPE during activation of THP1-derived macrophages. Treatment of these macrophages by bacterial lipopolysaccharide (LPS) for 24 h induced the release of pro-inflammatory cytokines TNF-α, IL-6 and IL-1β. This release was markedly inhibited by pretreatment with UDCA-18:1LPE by ~ 65-90%. Derivatives with a different fatty-acid chain in LPE moiety also exhibited anti-inflammatory property. Western blotting and indirect immunofluorescence analyses revealed that UDCA-18:1LPE attenuated the expression of phosphorylated p38, MKK4/MKK7, JNK1/2, and c-Jun as well as nuclear translocation of NF-κB by ~ 22-86%. After LPS stimulation, the Toll-like receptor adaptor proteins, myeloid differentiation factor 88 and TNF receptor associated factor 6, were recruited into lipid rafts and UDCA-18:1LPE inhibited this recruitment by 22% and 58%, respectively. Moreover, LPS treatment caused a decrease of the known cytoprotective lysophosphatidylcholine species containing polyunsaturated fatty acids by 43%, and UDCA-18:1LPE co-treatment reversed this decrease. In conclusion, UDCA-18:1LPE and derivatives inhibited LPS inflammatory response by interfering with Toll-like receptor signaling in lipid rafts leading to an inhibition of MAPK and NF-κB activation. These conjugates may represent a class of lead compounds for development of anti-inflammatory drugs.

Elevated cholesterol levels have a poor prognosis in a cholestasis scenario

Cholestasis results from defective bile flow through the biliary ducts leading to the accumulation of bile acids (BAs) in hepatocytes and serum. It has been seen that cholestasis is associated with hypercholesterolemia, which is a prerequisite for gallstone formation and primary biliary cirrhosis, being some of the most common gastrointestinal disorders in Western societies. Cytotoxic BAs induce proinflammatory mediators, oxidative stress, and apoptosis in hepatocytes, whereas cytoprotective BAs prevent them; they can also modify the plasmatic membrane structure of cells or mitochondrial outer membrane properties as well as the distribution of cholesterol, altering various proteins involved in BAs homeostasis.

ER stress contributes to alpha-naphthyl isothiocyanate-induced liver injury with cholestasis in mice

Endoplasmic reticulum (ER) stress is involved in the development of several liver diseases and tumors. This study investigated the underlying mechanisms of α-naphthyl isothiocyanate (ANIT)-induced liver injury with cholestasis in mice and found ER stress contributes to the injury. All animals were randomly divided into three groups. In the ANIT-intoxicated group, mice were intragastrically given 100mg/kg ANIT (dissolved in corn oil), while the other groups received an equal volume of vehicle as control. After 24 and 48h of ANIT administration, blood samples and liver tissues of all animals were collected for serum biochemistry and hepatic histopathological examinations to evaluate liver injuries with cholestasis. Hepatocellular apoptosis was assessed by the terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay. The expression of hepatic ER stress-related markers was determined by real-time PCR, immunohistochemical assay and Western blot. ANIT was found to significantly induce liver injury with cholestasis compared with control mice as evidenced by the increase of serum transaminases and total bilirubin (TBil), and histopathological changes in mice. ANIT remarkably induced hepatocellular apoptosis, upregulated the expression of caspase-9 and cytochrome c, and inhibited the gene and protein expression of proliferating cell nuclear antigen (PCNA). The gene expression of ER stress-related markers, including glucose-regulated protein 78 (GRP78), protein kinase R-like ER kinase (PERK), eukaryotic initiation factor 2α (eIF2α), inositol requiring enzyme-1α (IRE-1α) and activating transcription factor 6 (ATF6) was upregulated by ANIT in mice. ANIT also upregulated the protein expression of GRP78 and activated the phosphorylation of IRE1. These results suggested that ANIT induced liver injury with cholestasis partly due to its ability to activate the ER stress pathway.

Protein tyrosine phosphatase 1B (PTP1B): A key regulator and therapeutic target in liver diseases

Phosphorylation of tyrosine residues within proteins, which is controlled by the reciprocal action of protein tyrosine kinases and protein tyrosine phosphatases, plays a key role in regulating almost all physiological responses. Therefore, it comes as no surprise that once the balance of tyrosine phosphorylation is disturbed, drastic effects can occur. Protein tyrosine phosphatase 1B (PTP1B), a classical non-transmembrane tyrosine phosphatase, is a pivotal regulator and promising drug target in type 2 diabetes and obesity. Recently it has received renewed attention in liver diseases and represents an intriguing opportunity as a drug target by modulating hepatocyte death and survival, hepatic lipogenesis and so on. Here, the multiple roles of PTP1B in liver diseases will be presented, with respect to liver regeneration, drug-induced liver disease, non-alcoholic fatty liver disease (NAFLD) and hepatocellular carcinoma.

Long-term hypoxia exposure enhanced IGFBP-3 protein synthesis and secretion resulting in cell apoptosis in H9c2 myocardial cells

Myocardial infarction (MI) usually results in myocardial ischemia, remodeling and hypoxia that lead to cell death. To date, the insulin-like growth factor binding protein-3 (IGFBP3) is known to play an important role in insulin growth factor (IGF) bioavailability. Previous studies have found that hypoxia results in cell apoptosis. However, the detailed mechanism and roles of IGFBP3 in long-term hypoxia (LTH) regulated heart cell apoptosis remains unknown. In this study H9c2 cardiomyoblast cells were treated with investigated long-term hypoxic exposure with the possible mechanisms involved. The results showed that LTH enhanced IGFBP3 protein synthesis and induced its secretion. The accumulated IGFBP3 sequestered Insulin growth factor 1 (IGF-1) away from the type I IGF receptor (IGF-1 R), which blocked the IGF1R/PI3K/Akt survival signaling pathway, resulting in cell apoptosis. According to our findings, IGFBP3 could be a valuable target for developing treatments for cardiac diseases in long-term hypoxia exposure patients.