Synthesis of endotoxin receptor CD14 protein in Kupffer cells and its role in alcohol-induced liver disease

Endotoxin Inflammatory Action on Cells by Dysregulated-Immunological-Barrier-Linked ROS-Apoptosis Mechanisms in Gut-Liver Axis

Our study highlighted the immune changes by pro-inflammatory biomarkers in the gut-liver-axis-linked ROS-cell death mechanisms in chronic and acute inflammations when gut cells are exposed to endotoxins in patients with hepatic cirrhosis or steatosis. In duodenal tissue samples, gut immune barrier dysfunction was analyzed by pro-inflammatory biomarker expressions, oxidative stress, and cell death by flow cytometry methods. A significant innate and adaptative immune system reaction was observed as result of persistent endotoxin action in gut cells in chronic inflammation tissue samples recovered from hepatic cirrhosis with the A-B child stage. Instead, in patients with C child stage of HC, the endotoxin tolerance was installed in cells, characterized by T lymphocyte silent activation and increased Th1 cytokines expression. Interesting mechanisms of ROS-cell death were observed in chronic and acute inflammation samples when gut cells were exposed to endotoxins and immune changes in the gut-liver axis. Late apoptosis represents the chronic response to injury induction by the gut immune barrier dysfunction, oxidative stress, and liver-dysregulated barrier. Meanwhile, necrosis represents an acute and severe reply to endotoxin action on gut cells when the immune system reacts to pro-inflammatory Th1 and Th2 cytokines releasing, offering protection against PAMPs/DAMPs by monocytes and T lymphocyte activation. Flow cytometric analysis of pro-inflammatory biomarkers linked to oxidative stress-cell death mechanisms shown in our study recommends laboratory techniques in diagnostic fields.

Effect of Ethanol on Exosome Biogenesis: Possible Mechanisms and Therapeutic Implications

Most eukaryotic cells, including hepatocytes, secrete exosomes into the extracellular space, which are vesicles facilitating horizontal cell-to-cell communication of molecular signals and physiological cues. The molecular cues for cellular functions are carried by exosomes via specific mRNAs, microRNAs, and proteins. Exosomes released by liver cells are a vital part of biomolecular communication in liver diseases. Importantly, exosomes play a critical role in mediating alcohol-associated liver disease (ALD) and are potential biomarkers for ALD. Moreover, alcohol exposure itself promotes exosome biogenesis and release from the livers of humans and rodent models. However, the mechanisms by which alcohol promotes exosome biogenesis in hepatocytes are still unclear. Of note, alcohol exposure leads to liver injury by modulating various cellular processes, including autophagy, ER stress, oxidative stress, and epigenetics. Evidence suggests that there is a link between each of these processes with exosome biogenesis. The aim of this review article is to discuss the interplay between ethanol exposure and these altered cellular processes in promoting hepatocyte exosome biogenesis and release. Based on the available literature, we summarize and discuss the potential mechanisms by which ethanol induces exosome release from hepatocytes, which in turn leads to the progression of ALD.

Rumex hanus by. Extract Protects Against Chronic Alcohol-Induced Liver Injury in Mice

Alcoholic liver disease (ALD) has become a global health problem. The hepatoprotective effects of bioactive ingredients extracted from Rumex hanus by. on chronic alcoholic liver injury was investigated for the first time. The extract from R. hanus by. (ERHB) was obtained by 70% ethanol extraction, and the endotoxin antagonism rate of ERHB was 88.94 ± 1.24% in vitro. The animal experiments demonstrated that ERHB promoted hepatic function by significantly enhancing the activities of alcohol dehydrogenase and acetaldehyde dehydrogenase, and by reducing the activities of cytochrome P450 proteins, alkaline phosphatase, aspartate aminotransferase, and alanine aminotransferase. Furthermore, ERHB improved alcohol-induced dyslipidemia by regulating lipid metabolism. In addition, ERHB ameliorated the alcohol-induced liver injury by inhibiting endotoxin-caused inflammation. Seven compounds with antagonistic activity on endotoxin were identified in ERHB. These results demonstrated that ERHB had protective effects on ALD and if the results can be confirmed in humans, it might be useful as a functional food supplement for ALD treatment.

Cell release during perfusion reflects cold ischemic injury in rat livers

The global shortage of donor organs has made it crucial to deeply understand and better predict donor liver viability. However, biomarkers that effectively assess viability of marginal grafts for organ transplantation are currently lacking. Here, we showed that hepatocytes, sinusoidal endothelial, stellate, and liver-specific immune cells were released into perfusates from Lewis rat livers as a result of cold ischemia and machine perfusion. Perfusate comparison analysis of fresh livers and cold ischemic livers showed that the released cell profiles were significantly altered by the duration of cold ischemia. Our findings show for the first time that parenchymal cells are released from organs under non-proliferative pathological conditions, correlating with the degree of ischemic injury. Thus, perfusate cell profiles could serve as potential biomarkers of graft viability and indicators of specific injury mechanisms during organ handling and transplantation. Further, parenchymal cell release may have applications in other pathological conditions beyond organ transplantation.

[Effects of Panax notoginseng saponins on liver graft rejection in rats and the mechanisms]

OBJECTIVE

To investigate the effects of Panax notoginseng saponins (PNS) on the functional status of Kupffer cells (KCs) and immune environment after liver transplantation and explore the possible mechanisms.

METHODS

KCs were isolated from rats and assessed for phagocytic activity and viability using ink and Trypan blue staining. The cells were exposed to lipopolysaccharide (LPS) alone or in combination with PNS treatment at 0, 10 or 20 μmol/L. The expressions of the inflammatory factors and the oxidative stress products in the cells and the supernatant were assayed with Western blotting and ELISA; the expression of CD206 was detected using immunofluorescence assay, and the expressions of NF-κB and Keap1-Nrf2-ARE pathway proteins were detected using Western blotting. We established an orthotopic liver transplantation (LT) model in rats and assessed the effect of 200 mg/kg PNS on the graft function, inflammatory factors, pathology of the liver tissue, hepatocyte apoptosis and survival time of the rats in comparison with those in rats receiving a sham operation or PBS treatment following LT.

RESULTS

Treatment with PNS significantly lowered the levels of inflammatory factors and oxidative stress products and increased the levels of interleukin-10 (IL-10) and SOD in a concentration-dependent manner in the KCs (P < 0.05). Immunofluorescence assay showed that PNS treatment obviously increased the expression of CD206 in the KCs. PNS treatment also significantly reduced the expressions of IRAK4, p-IKKα, p-IκBα, p-p65 and Keap1 proteins and increased the expression levels of Nrf2 and ARE proteins in the KCs (P < 0.05). In the rat models of LT, PNS treatment significantly improved the liver graft function, lowered the expression of the pro-inflammatory factors, and reduced hepatocyte apoptosis as compared with PBS treatment. PNS treatment obviously alleviated pathological changes in the liver graft and significantly prolonged the survival time of the rats following LT (P < 0.05). In addition, injection of GdCl3 to block KC function resulted in severe acute graft rejection in the rats regardless of PNS treatment (P > 0.05).

CONCLUSIONS

PNS can reduce inflammatory response and oxidative stress in activated KCs by inhibiting NF-κB and Keap1-Nrf2-ARE pathways and promote the polarization of KCs into M2 phenotype to prolong the survival time of rats after LT.

The antioxidant and antiapoptotic effect of boric acid on hepatoxicity in chronic alcohol-fed rats

The harmful use of alcohol is a worldwide problem involving all ages. This study aims to investigate chronic alcohol exposure related hepatotoxicity on the rat liver and possible hepatoprotective effects of boric acid. Rats were separated into 4 different groups: control, ethanol, ethanol+boric acid, and boric acid. We measured (i) malondialdehyde (MDA), total sialic acid (TSA), superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) levels, which are known to be the markers of alcohol damage; and also (ii) caspase-3, tumor necrosis factor-alpha (TNF-α), and the terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) as the markers of apoptosis. In the ethanol group, MDA, TSA, and TNF-α levels increased whereas SOD and CAT levels decreased compared with the control group. Ethanol+boric acid group MDA, TSA, caspase-3, and TNF-α levels decreased whereas SOD and CAT levels increased compared with the ethanol group. Using histopathological evaluation of light microscope images, immunohistochemical caspase-3 and TNF-α activity in the ethanol+boric acid group were shown to be decreased compared with that in the ethanol group. Our results revealed that ethanol is capable of triggering oxidative stress and apoptosis in the rat liver. We propose that boric acid is an effective compound in protecting the rat liver against ethanol.

Low-Dose Pulsatile Interleukin-6 As a Treatment Option for Diabetic Peripheral Neuropathy

Diabetic peripheral neuropathy (DPN) remains one of the most common and serious complications of diabetes. Currently, pharmacological agents are limited to treating the pain associated with DPN, and do not address the underlying pathological mechanisms driving nerve damage, thus leaving a significant unmet medical need. Interestingly, research conducted using exercise as a treatment for DPN has revealed interleukin-6 (IL-6) signaling to be associated with many positive benefits such as enhanced blood flow and lipid metabolism, decreased chronic inflammation, and peripheral nerve fiber regeneration. IL-6, once known solely as a pro-inflammatory cytokine, is now understood to signal as a multifunctional cytokine, capable of eliciting both pro- and anti-inflammatory responses in a context-dependent fashion. IL-6 released from muscle in response to exercise signals as a myokine and as such has a unique kinetic profile, whereby levels are transiently elevated up to 100-fold and return to baseline levels within 4 h. Importantly, this kinetic profile is in stark contrast to long-term IL-6 elevation that is associated with pro-inflammatory states. Given exercise induces IL-6 myokine signaling, and exercise has been shown to elicit numerous beneficial effects for the treatment of DPN, a causal link has been suggested. Here, we discuss both the clinical and preclinical literature related to the application of IL-6 as a treatment strategy for DPN. In addition, we discuss how IL-6 may directly modulate Schwann and nerve cells to explore a mechanistic understanding of how this treatment elicits a neuroprotective and/or regenerative response. Collectively, studies suggest that IL-6, when administered in a low-dose pulsatile strategy to mimic the body's natural response to exercise, may prove to be an effective treatment for the protection and/or restoration of peripheral nerve function in DPN. This review highlights the studies supporting this assertion and provides rationale for continued investigation of IL-6 for the treatment of DPN.

[Effect of inhibiting TIM-4 function in Kupffer cells on liver graft rejection in mice]

OBJECTIVE

To investigate the effects of inhibiting TIM-4 function in Kupffer cells (KCs) on liver graft rejection in mice and explore the underlying mechanism.

METHODS

Mouse models of orthotopic liver transplantation were treated with a control mAb group and TIM-4 mAb. The activated KCs were assayed with immunohistochemistry after operation. The expression of TIM-4 in KCs were assayed with Western blotting and RT-PCR and the levels of AST, ALT, TBIL, TNF-α, IFN-γ and CCL2 were assayed detected. The expression of TIM-4 in KCs was observed with laser confocal microscopy. HE staining was used to observe the microstructure of the liver tissues, and the number of CD25⁺Foxp3⁺T cells was determined using with flow cytometry; the proteins levels of p-P65and p-P38 were assayed with Western blotting. The donor mice were treated with clodronate liposomes to destroy the KCs in the liver before transplantation, and the liver grafts were examined for graft rejection.

RESULTS

The number of activated KCs in the liver graft increased progressively over time. Compared with the sham-operated group, the liver graft showed significantly increased TIM-4 protein and mRNA levels at 1, 3, and 7 days after transplantation (P<0.05) and increased levels of AST, ALT, TBIL, TNF-α, IFN-γ and CCL2 at 7 days (P<0.05). The graft in TIM-4 mAb group showed mild pathological changes with a mean RAI score of 2.67∓0.75, which was significantly lower than that in control mAb group (P<0.05). The mean survival time of the recipient mice was 53.8∓6.4 days in TIM-4 mAb group, significantly longer than that in the control mAB group (14.5∓2.9 days, P<0.05). Donor treatment with clodronate liposomes resulted in comparable RAI scores in TIM-4 mAb and control mAb groups (8.01∓0.64 vs 7.93∓0.56, P>0.05). The protein levels of p-P65 and p-P38 in TIM-4 mAb group were significantly lower than those in control mAb group (P<0.05), and CD25⁺Foxp3⁺T cells in the liver graft increased significantly in TIM-4 mAb group.

CONCLUSION

Inhibition of TIM-4 function in KCs reduces the production of inflammatory factors after liver transplantation possibly by inhibiting the NF-κB and MAPK signaling pathways and promoting the proliferation of Foxp3⁺Treg cells to induce allograft tolerance.

Molecular mechanisms of hepatic apoptosis

Apoptosis is a prominent feature of liver diseases. Causative factors such as alcohol, viruses, toxic bile acids, fatty acids, drugs, and immune response, can induce apoptotic cell death via membrane receptors and intracellular stress. Apoptotic signaling network, including membrane death receptor-mediated cascade, reactive oxygen species (ROS) generation, endoplasmic reticulum (ER) stress, lysosomal permeabilization, and mitochondrial dysfunction, is intermixed each other, but one mechanism may dominate at a particular stage. Mechanisms of hepatic apoptosis are complicated by multiple signaling pathways. The progression of liver disease is affected by the balance between apoptotic and antiapoptotic capabilities. Therapeutic options of liver injury are impacted by the clear understanding toward mechanisms of hepatic apoptosis.

Molecular mechanisms of hepatic apoptosis

Apoptosis is a prominent feature of liver diseases. Causative factors such as alcohol, viruses, toxic bile acids, fatty acids, drugs, and immune response, can induce apoptotic cell death via membrane receptors and intracellular stress. Apoptotic signaling network, including membrane death receptor-mediated cascade, reactive oxygen species (ROS) generation, endoplasmic reticulum (ER) stress, lysosomal permeabilization, and mitochondrial dysfunction, is intermixed each other, but one mechanism may dominate at a particular stage. Mechanisms of hepatic apoptosis are complicated by multiple signaling pathways. The progression of liver disease is affected by the balance between apoptotic and antiapoptotic capabilities. Therapeutic options of liver injury are impacted by the clear understanding toward mechanisms of hepatic apoptosis.

Alcoholic liver disease and the gut-liver axis

Alcoholic liver disease (ALD) is one of the leading causes of liver diseases and liver-related death worldwide. Of the many factors that contribute to the pathogenesis of ALD, gut-derived lipopolysaccharide (LPS) plays a central role in induction of steatosis, inflammation, and fibrosis in the liver. In this review, we discuss the mechanisms by which alcohol contributes to increased gut permeability, the activation of Kupffer cells, and the inflammatory cascade by LPS. The role of the Toll-like receptor 4 (TLR4) complex in LPS recognition and the importance of the TLR4-induced signaling pathways are evaluated in ALD.

Betaine inhibits Toll-like receptor 4 expression in rats with ethanol-induced liver injury

AIM: To test whether ethanol feeding could induce Toll-like receptor 4 (TLR4) responses, assess the hepatoprotective effect of betaine and its inhibitive effect on TLR4 in animal models of alcoholic liver injury.

METHODS: Forty-eight female Sprague-Dawley rats were randomly divided into four groups as control, model, low and high dose betaine groups. Except control group, all rats were fed with high fat-containing diet plus ethanol and fish oil gavages for 8 wk. Betaine was administered intragastrically after exposure of ethanol for 4 wk. The changes of liver histology were examined. The expression of TLR4 mRNA and protein was detected by RT-PCR and Western blotting, respectively. The serum aminotransferase activity [alanine transarninase (ALT), aspartate aminotransferase (AST)], serum endotoxin, and liver inflammatory factors [tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), interleukin-18 (IL-18)] were also assayed.

RESULTS: Compared with control group, rats of model group developed marked liver injury, accompanied by an increase of ALT (159.41 ± 7.74 U/L vs 59.47 ± 2.34 U/L, P < 0.0001), AST (248.25 ± 1.40 U/L vs 116.89 ± 3.48 U/L, P < 0.0001), endotoxin (135.37 ± 30.17 ng/L vs 44.15 ± 7.54 ng/L, P < 0.0001), TNF-α (20.81 ± 8.58 pg/mL vs 9.34 ± 2.57 pg/mL, P = 0.0003), IFN-γ (30.18 ± 7.60 pg/mL vs 16.86 ± 9.49 pg/mL, P = 0.0039) and IL-18 (40.99 ± 8.25 pg/mL vs 19.73 ± 9.31 pg/mL, P = 0.0001). At the same time, the expression of TLR4 mRNA and protein was markedly induced in the liver after chronic ethanol consumption (1.45 ± 0.07 vs 0.44 ± 0.04, P < 0.0001; 1.83 ± 0.13 vs 0.56 ± 0.08, P < 0.0001). Compared with model group, betaine feeding resulted in significant decreases of ALT (64.93 ± 6.06 U/L vs 159.41 ± 7.74 U/L, P < 0.0001), AST (188.73 ± 1.11 U/L vs 248.25 ± 1.40 U/L, P < 0.0001), endotoxin (61.80 ± 12.56 ng/L vs 135.37 ± 30.17 ng/L, P < 0.0001), TNF-α (9.79 ± 1.32 pg/mL vs 20.81 ± 8.58 pg/mL, P = 0.0003), IFN-γ (18.02 ± 5.96 pg/mL vs 30.18 ± 7.60 pg/mL, P = 0.0008) and IL-18 (18.23 ± 7.01 pg/mL vs 40.99 ± 8.25 pg/mL, P < 0.0001). Betaine also improved liver steatosis. The expression levels of TLR4 mRNA or protein in liver tissues were significantly lowered (0.62 ± 0.04 vs 1.45 ± 0.07, P < 0.0001; and 0.65 ± 0.06 vs 1.83 ± 0.13, P < 0.0001). There was a statistical difference of TLR4 mRNA and protein expression between high- and low-dose betaine groups (0.62 ± 0.04 vs 0.73 ± 0.05, P < 0.0001, and 0.65 ± 0.06 vs 0.81 ± 0.09, P < 0.0001).

CONCLUSION: Betaine can prevent the alcohol-induced liver injury effectively and improve the liver function. The expression of TLR4 increases significantly in ethanol-fed rats and betaine administration can inhibit TLR4 expression.

Prostacyclin in liver disease: a potential therapeutic option

Complex molecular and cellular mechanisms are involved in the initiation and progression of hepatic fibrosis. Recent studies have shown that hepatic stellate cells, endothelin, cytokines and prostacyclin play crucial roles in this pathology. Prostacyclin exerts vasorelaxant, antioxidant and antifibrotic properties that prevent the development of fibrosis and cirrhosis in liver diseases. In this editorial, the authors discuss some of the molecular and cellular mechanisms involved in the initiation and progression of liver fibrosis and the role played by prostacyclin in counteracting it. At the moment, however, only limited information is available from clinical studies demonstrating the effectiveness of prostacyclin in liver diseases and this makes it difficult to draw any conclusions; further efforts are necessary to verify whether prostacyclin, alone or in combination with other drugs, may be a valid therapeutic option in liver diseases.

Molecular cloning, chromosomal location, and expression analysis of porcine CD14

CD14 is a membrane-associated glycosylphosphatidylinositol (GPI)-anchored protein that binds lipopolysaccharide (LPS) of Gram-negative bacteria and enables LPS-dependent responses in a variety of cells. In this study a cDNA containing the porcine CD14 coding sequence has been cloned and its complete sequence determined. The amino acid sequence deduced from pig CD14 cDNA encodes a 373 amino acid polypeptide that exhibits 75%, 72%, 69%, 66%, 57% and 56% similarity to CD14 from cow, horse, human, rabbit, mouse and rat, respectively. Structural analysis showed that the porcine CD14 is a membrane glycoprotein with a GPI-anchor site and an extracellular domain containing 11 leucine-rich repeats. In addition, the LPS-binding regions identified in the human CD14 are highly conserved in the N-terminal domain of the porcine sequence. Fluorescence in situ hybridization was used to locate the CD14 gene on the pig chromosome 2, band q28. Expression analysis revealed that porcine CD14 transcripts were detected in all tissues and cells examined, suggesting that the expression of porcine CD14 gene is not restricted to myeloid cell lineage. Finally, we report that LPS stimulation significantly up-regulated CD14 gene expression in porcine alveolar macrophages.

Time to abandon dogma: CD14 is expressed by non‐myeloid lineage cells

CD14 is a pattern recognition receptor; its important role in innate immunity is reviewed here. Since its discovery and subsequent classification at the first leucocyte typing workshop in 1982, CD14 has been thought of as a leucocyte differentiation antigen. However, it has become clear that CD14 is also expressed by many non-myeloid cells, and the evidence for this is presented. The possible role of the presence of low copy number CD14 on non-myeloid cells is discussed. It is time to acknowledge CD14 as an ubiquitous molecule and abandon the position that it is expressed by myeloid cells alone.

CD14 expression in Kupffer cells of ischemia-reperfusion injury after rat liver transplantation

AIM: To study the expression of lipopolysaccharide receptor CD14 mRNA and protein in Kupffer cells and its role in ischemia-reperfusion injury (IRI) in rat liver graft.

METHODS: The Kupffer cells were isolated and divided into control, ischemia-reperfusion (IR), and anti CD14 antibody groups. The CD14 mRNA, CD14 protein, nuclear factor kappa B (NF-κB) activity, and TNF-α and IL-1 level in the culture supernatant were measured.

RESULTS: The CD14 mRNA, and protein in IR group were significantly higher than those in control group (mRNA 1.28±0.12 vs 0.42±0.02, protein 23.7±2.36 vs 6.3±1.27, P < 0.01). The NF-κB activity, TNF-α and IL-1 level in IR group were significantly higher than those in control group (NF-κB 2.79±0.48 vs 0.27±0.01, TNF-α 205.9±12.04 ng/L vs 57.4±4.35 ng/L, IL-1 176.8±8.94 ng/L vs 37.6±3.47 ng/L, P < 0.01), and they greatly decreased after anti-CD14 antibody treatment compared with IR group (NF-κB 1.34±0.24 vs 2.79±0.48, TNF-α 129.6±6.48 ng/L vs 205.9±12.04 ng/L, IL-1 103.4±5.74 ng/L vs 176.8±8.94 ng/L, P < 0.05), but still significantly higher than those in control group (NF-κB 1.34±0.24 vs 0.27±0.01, TNF-α 129.6±6.48 ng/L vs 57.4±4.35 ng/L, IL-1 103.4±5.74 ng/L vs 37.6±3.47 ng/L, P < 0.01).

CONCLUSION: LPS following IR can up-regulate the expression of CD14 mRNA and protein in Kupffer cells, and subsequently activate NF-κB to produce cytokines. But other signal transduction pathways might also participate in the NF-κB activation and IRI.