Hepatic Stellate Cell-Derived Microvesicles Prevent Hepatocytes from Injury Induced by APAP/H2O2

Microvesicles from quiescent and TGF-β1 stimulated hepatic stellate cells: Divergent impact on hepatic vascular injury

BACKGROUND

This study evaluated the effect of microvesicles(MVs) from quiescent and TGF-β1 stimulated hepatic stellate cells (HSC-MVs, TGF-β1HSC-MVs) on H2O2-induced human umbilical vein endothelial cells (HUVECs) injury and CCl4-induced rat hepatic vascular injury.

METHODS

HUVECs were exposed to hydrogen peroxide (H2O2) to establish a model for vascular endothelial cell injury. HSC-MVs or TGF-β1HSC-MVs were co-cultured with H2O2-treated HUVECs, respectively. Indicators including cell survival rate, apoptosis rate, oxidative stress, migration, invasion, and angiogenesis were measured. Simultaneously, the expression of proteins such as PI3K, AKT, MEK1+MEK2, ERK1+ERK2, VEGF, eNOS, and CXCR4 was assessed, along with activated caspase-3. SD rats were intraperitoneally injected with CCl4 twice a week for 10 weeks to induce liver injury models. HSC-MVs or TGF-β1HSC-MVs were injected into the tail vein of rats. Liver and hepatic vascular damage were also detected.

RESULTS

In H2O2-treated HUVECs, HSC-MVs increased cell viability, reduced cytotoxicity and apoptosis, improved oxidative stress, migration, and angiogenesis, and upregulated protein expression of PI3K, AKT, MEK1/2, ERK1/2, VEGF, eNOS, and CXCR4. Conversely, TGF-β1HSC-MVs exhibited opposite effects. CCl4- induced rat hepatic injury model, HSC-MVs reduced the release of ALT and AST, hepatic inflammation, fatty deformation, and liver fibrosis. HSC-MVs also downregulated the protein expression of CD31 and CD34. Conversely, TGF-β1HSC-MVs demonstrated opposite effects.

CONCLUSION

HSC-MVs demonstrated a protective effect on H2O2-treated HUVECs and CCl4-induced rat hepatic injury, while TGF-β1HSC-MVs had an aggravating effect. The effects of MVs involve PI3K/AKT/VEGF, CXCR4, and MEK/ERK/eNOS pathways.

Unraveling the Emerging Niche Role of Hepatic Stellate Cell-derived Exosomes in Liver Diseases

Hepatic stellate cells (HSCs) play an essential role in various liver diseases, and exosomes are critical mediators of intercellular communication in local and distant microenvironments. Cellular crosstalk between HSCs and surrounding multiple tissue-resident cells promotes or inhibits the activation of HSCs. Substantial evidence has revealed that HSC-derived exosomes are involved in the occurrence and development of liver diseases through the regulation of retinoid metabolism, lipid metabolism, glucose metabolism, protein metabolism, and mitochondrial metabolism. HSC-derived exosomes are underpinned by vehicle molecules, such as mRNAs and microRNAs, that function in, and significantly affect, the processes of various liver diseases, such as acute liver injury, alcoholic liver disease, nonalcoholic fatty liver disease, viral hepatitis, fibrosis, and cancer. As such, numerous exosomes derived from HSCs or HSC-associated exosomes have attracted attention because of their biological roles and translational applications as potential targets for therapeutic targets. Herein, we review the pathophysiological and metabolic processes associated with HSC-derived exosomes, their roles in various liver diseases and their potential clinical application.

Extracellular Vesicles as Biomarkers in Liver Disease

Extracellular vesicles (EVs) are membrane-derived vesicles released by a variety of cell types, including hepatocytes, hepatic stellate cells, and immune cells in normal and pathological conditions. Depending on their biogenesis, there is a complex repertoire of EVs that differ in size and origin. EVs can carry lipids, proteins, coding and non-coding RNAs, and mitochondrial DNA causing alterations to the recipient cells, functioning as intercellular mediators of cell-cell communication (auto-, para-, juxta-, or even endocrine). Nevertheless, many questions remain unanswered in relation to the function of EVs under physiological and pathological conditions. The development and optimization of methods for EV isolation are crucial for characterizing their biological functions, as well as their potential as a treatment option in the clinic. In this manuscript, we will comprehensively review the results from different studies that investigated the role of hepatic EVs during liver diseases, including non-alcoholic fatty liver disease, non-alcoholic steatohepatitis, alcoholic liver disease, fibrosis, and hepatocellular carcinoma. In general, the identification of patients with early-stage liver disease leads to better therapeutic interventions and optimal management. Although more light needs to be shed on the mechanisms of EVs, their use for early diagnosis, follow-up, and prognosis has come into the focus of research as a high-potential source of 'liquid biopsies', since they can be found in almost all biological fluids. The use of EVs as new targets or nanovectors in drug delivery systems for liver disease therapy is also summarized.

Microvesicles Derived from TGF-β1 Stimulated Hepatic Stellate Cells Aggravate Hepatocellular Injury

Hepatic stellate cells (HSCs) are liver-specific cells playing critical roles in liver physiological and pathophysiological processes. Transforming growth factor-β1 (TGF-β1) is an inflammatory cytokine secreted by both hepatocytes and HSCs. We have previously shown that microvesicles (MVs) derived from quiescent HSCs protect hepatocyte functions. In this study, we investigated the effects of MVs released from TGF-β1-stimulated HSCs (HSC-MVs) on xenobiotic-injured hepatocytes. Two hepatocyte cell lines (BRL-3A and HL-7702) were treated with N-acetyl-p-aminophenol or H₂O₂ to build the injury models. Different concentrations of HSC-MVs were used to coculture with injured hepatocytes. MTT, Hochest33258 staining, and flow cytometry were used to determine their effects on the viability and apoptosis of hepatocytes. Liver injury indicators, alanine aminotransferase (ALT) and aspartate amino transferase (AST), were assessed by enzyme-linked immune sorbent assay kits. The phosphoinositide 3-kinase (PI3K) activator (740Y-P) and extracelluar signal regulated kinase (Erk)1/2 activator (platelet-derived growth factor-BB) were used for pathway analysis. The expression levels of p-PI3K/PI3K, p-Akt/Akt, and activated caspase-3 were measured by western blot. Results showed that (i) HSC-MVs dose dependently impaired the viability of hepatocytes in both injury models, (ii) moreover, HSC-MVs dose dependently increased the apoptosis in those cell models, (iii) HSC-MVs also elevated the levels of ALT and AST in the coculture media, and (iv) these effects were accompanied by a decrease in p-PI3K/PI3K and p-Akt/Akt, which could be partially abolished by 740Y-P. Meanwhile, the proapoptotic effect of HSC-MVs was associated with p-Erk1/2/Erk1/2 downregulation and activated caspase-3 upregulation, and could be inhibited by Erk1/2 activation. Our findings demonstrate that HSC-MVs are involved in inflammatory hepatocytes injury probably through the PI3K/Akt, Erk1/2, and caspase-3 pathways.

Large Extracellular Vesicles: Have We Found the Holy Grail of Inflammation?

The terms microparticles (MPs) and microvesicles (MVs) refer to large extracellular vesicles (EVs) generated from a broad spectrum of cells upon its activation or death by apoptosis. The unique surface antigens of MPs/MVs allow for the identification of their cellular origin as well as its functional characterization. Two basic aspects of MP/MV functions in physiology and pathological conditions are widely considered. Firstly, it has become evident that large EVs have strong procoagulant properties. Secondly, experimental and clinical studies have shown that MPs/MVs play a crucial role in the pathophysiology of inflammation-associated disorders. A cardinal feature of these disorders is an enhanced generation of platelets-, endothelial-, and leukocyte-derived EVs. Nevertheless, anti-inflammatory effects of miscellaneous EV types have also been described, which provided important new insights into the large EV-inflammation axis. Advances in understanding the biology of MPs/MVs have led to the preparation of this review article aimed at discussing the association between large EVs and inflammation, depending on their cellular origin.

Vitronectin from brain pericytes promotes adult forebrain neurogenesis by stimulating CNTF

Vitronectin (VTN) is a glycoprotein in the blood and affects hemostasis. VTN is also present in the extracellular matrix of various organs but little is known about its function in healthy adult tissues. We show, in adult mice, that VTN is uniquely expressed by approximately half of the pericytes of subventricular zone (SVZ) where neurogenesis continues throughout life. Intracerebral VTN antibody injection or VTN knockout reduced neurogenesis as well as expression of pro-neurogenic CNTF, and anti-neurogenic LIF and IL-6. Conversely, injections of VTN, or plasma from VTN+/+, but not VTN-/- mice, increased these cytokines. VTN promoted SVZ neurogenesis when LIF and IL-6 were suppressed by co-administration of a gp130 inhibitor. Unexpectedly, VTN inhibited FAK signaling and VTN-/- mice had increased FAK signaling in the SVZ. Further, an FAK inhibitor or VTN increased CNTF expression, but not in conditional astrocytic FAK knockout mice, suggesting that VTN increases CNTF through FAK inhibition in astrocytes. These results identify a novel role of pericyte-derived VTN in the brain, where it regulates SVZ neurogenesis through co-expression of CNTF, LIF and IL-6. VTN-integrin-FAK and gp130 signaling may provide novel targets to induce neurogenesis for cell replacement therapies.

Identification of novel N-acetylcysteine derivatives for the treatment of hepatocellular injury

New anti-hepatocellular injury drugs with better curative effects and fewer side effects are urgently needed at present. In this study, a series of novel N-acetylcysteine (NAC) derivatives were designed, synthesized and biologically evaluated for their anti-hepatocellular injury activities against two different cell models. In the biological evaluation against hydrogen peroxide (H2O2)-induced LO2 hepatocytes, half of the target compounds exhibited moderate to potent activities in improving the model cell viability, and two compounds (6a and 6b) displayed more potent activities in decreasing malondialdehyde (MDA) levels than the positive control NAC. In further 4-acetamidophenol (APAP)-induced LO2 cell experiment, compounds 6a and 6b could not only improve the cell viability but also significantly reduce the secretion of MDA. Additionally, compound 6a displayed excellent Caco-2 permeability and oral bioavailability in rats. All these experimental results suggested that compounds 6a and 6b could serve as potential lead molecules for further development of anti-hepatocellular injury drugs.

Herbal Formula, Baogan Yihao (BGYH), Prevented Dimethylnitrosamine(DMN)-Induced Liver Injury in Rats

Preclinical Research Baogan Yihao (BGYH) is a traditional Chinese herbal medicine for the treatment of chronic liver diseases. In this study, the effects of BGYH on dimethylnitrosamine (DMN)-induced liver fibrosis were investigated using a rat model. BGYH alleviate liver damage, as indicated by decreased levels of AST, ALT, γ-GT, and AKP. BGYH also prevented collagen deposition and reduced pathological tissue injury in liver tissue. In fibrosis, high levels of α-SMA and TGF-β in liver tissue were markedly attenuated by BGYH. The inhibitory effect of BGYH on HSC-T6 proliferation demonstrated that BGYH exhibited significant hepatoprotective and antifibrogenic effects on DMN-induced liver injury. These findings suggest that BGYH may have therapeutic potential in the prevention and therapy of liver fibrosis. Drug Dev Res 78 : 155-163, 2017. © 2017 Wiley Periodicals, Inc.