Rapamycin prevents concanavalin A-induced liver injury by inhibiting lymphocyte activation

Effect of rapamycin on hepatic metabolomics of non-alcoholic fatty liver rats based on non-targeted platform

Rapamycin (Rapa) is an inhibitor of mTOR complex, and its therapeutic effect on liver function was examined in non-alcoholic fatty liver disease (NAFLD) rats here. And the possible mechanism of Rapa in NAFLD was preliminarily elucidated based on the non-targeted metabolomics analysis. Adult male SD rats were fed with a high-fat and high-cholesterol diet (HFD) to establish NAFLD model. For Rapa group, 0.8 mg/(kg.d) Rapa was given to the HFD rats. Ultra-performance liquid chromatography and Q-Tof-mass spectrometry (UPLC and Q-TOF/MS) analysis were applied for the identification of metabolites in the serum of rats, which were annotated using Kyoto Encyclopedia of Genes and Genomes (KEGG). NAFLD rats presented with disturbed liver function, lipid metabolism and oxidative stress, but Rapa exerted a mitigating influence on the disorders. The metabolite profile data identified 579 metabolites that varied remarkably between the Rapa and HFD groups, with the main classes of amino acids and peptides, benzene, lipids and fatty acids. The differential metabolites were mainly involved in biosynthesis of cofactors, bile secretion, and glycerophospholipid metabolism were mainly enriched. In conclusion, Rapa has a potential protective effect against HFD-induced NAFLD, its hepatoprotective effect may achieved through mediating bile secretion and glycerophospholipid metabolism.

Mechanistic target of rapamycin complex 1 orchestrates the interplay between hepatocytes and Kupffer cells to determine the outcome of immune-mediated hepatitis

The cell-cell interaction between hepatocytes and Kupffer cells (KCs) is crucial for maintaining liver homeostasis, and the loss of KCs and hepatocytes is known to represent a common pathogenic phenomenon in autoimmune hepatitis. Until now, the mechanisms of cell-cell interaction between hepatocytes and KCs involved in immune-mediated hepatitis remains unclear. Here we dissected the impact of activated mTORC1 on the cell-cell interaction of KCs and hepatocyte in immune-mediated hepatitis. In the liver from patients with AIH and mice administrated with Con-A, mTORC1 was activated in both KCs and hepatocytes. The activated mTORC1 signal in hepatocytes with Con-A challenge caused a markedly production of miR-329-3p. Upregulated miR-329-3p inhibited SGMS1 expression in KCs through paracrine, resulting in the death of KCs. Most of maintained KCs were p-S6 positive and distributed in hepatocyte mTORC1 negative area. The activation of mTORC1 enabled KCs expressed complement factor B (CFB) to enhance the complement alternative system, which produced more complement factors to aggravate liver injury. Our findings remonstrate a heterogeneous role of mTORC1 in specific cell type for maintaining tolerogenic liver environment, and will form the basis for the development of new interventions against immune-mediated hepatitis.

Enhancement of the Tolerogenic Phenotype in the Liver by ImmTOR Nanoparticles

ImmTOR biodegradable nanoparticles encapsulating rapamycin have been shown to induce a durable tolerogenic immune response to co-administered biologics and gene therapy vectors. Prior mechanism of action studies have demonstrated selective biodistribution of ImmTOR to the spleen and liver following intravenous (IV) administration. In the spleen, ImmTOR has been shown to induce tolerogenic dendritic cells and antigen-specific regulatory T cells and inhibit antigen-specific B cell activation. Splenectomy of mice resulted in partial but incomplete abrogation of the tolerogenic immune response induced by ImmTOR. Here we investigated the ability of ImmTOR to enhance the tolerogenic environment in the liver. All the major resident populations of liver cells, including liver sinusoidal endothelial cells (LSECs), Kupffer cells (KC), stellate cells (SC), and hepatocytes, actively took up fluorescent-labeled ImmTOR particles, which resulted in downregulation of MHC class II and co-stimulatory molecules and upregulation of the PD-L1 checkpoint molecule. The LSEC, known to play an important role in hepatic tolerance induction, emerged as a key target cell for ImmTOR. LSEC isolated from ImmTOR treated mice inhibited antigen-specific activation of ovalbumin-specific OT-II T cells. The tolerogenic environment led to a multi-pronged modulation of hepatic T cell populations, resulting in an increase in T cells with a regulatory phenotype, upregulation of PD-1 on CD4⁺ and CD8⁺ T cells, and the emergence of a large population of CD4^–CD8^– (double negative) T cells. ImmTOR treatment protected mice in a concanavalin A-induced model of acute hepatitis, as evidenced by reduced production of inflammatory cytokines, infiltrate of activated leukocytes, and tissue necrosis. Modulation of T cell phenotype was seen to a lesser extent after administration by empty nanoparticles, but not free rapamycin. The upregulation of PD-1, but not the appearance of double negative T cells, was inhibited by antibodies against PD-L1 or CTLA-4. These results suggest that the liver may contribute to the tolerogenic properties of ImmTOR treatment.

Rapamycin attenuates liver injury caused by vinyl chloride metabolite chloroethanol and lipopolysaccharide in mice

Vinyl chloride (VC) is a prevalent environmental toxicant that is rapidly metabolized within the liver. Its metabolites have been shown to directly cause hepatic injury at high exposure levels. We have previously reported that VC metabolite, chloroethanol (CE), potentiates liver injury caused by lipopolysaccharide (LPS). Importantly, that study showed that CE alone, while not causing damage per se, was sufficient to alter hepatic metabolism and increase mTOR phosphorylation in mice, suggesting a possible role for the mTOR pathway. Here, we explored the effect of an mTOR inhibitor, rapamycin, in this model. C57BL/6 J mice were administered CE, followed by rapamycin 1 h and LPS 24 h later. As observed previously, the combination of CE and LPS significantly enhanced liver injury, inflammation, oxidative stress, and metabolic dysregulation. Rapamycin attenuated not only inflammation, but also restored the metabolic phenotype and protected against CE + LPS-induced oxidative stress. Importantly, rapamycin protected against mitochondrial damage and subsequent production of reactive oxygen species (ROS). The protective effect on mitochondrial function by rapamycin was mediated, by restoring the integrity of the electron transport chain at least in part, by blunting the deactivation of mitochondrial c-src, which is involved mitochondrial ROS production by electron transport chain leakage. Taken together, these results further demonstrate a significant role of mTOR-mediated pathways in VC-metabolite induced liver injury and provide further insight into VC-associated hepatic damage. As mTOR mediated pathways are very complex and rapamycin is a more global inhibitor, more specific mTOR (i.e. mTORC1) inhibitors should be considered in future studies.

Erzhi Pill® Repairs Experimental Liver Injury via TSC/mTOR Signaling Pathway Inhibiting Excessive Apoptosis

The present study aimed to investigate the mechanism of hepatoprotective effect of Erzhi Pill (EZP) on the liver injury via observing TSC/mTOR signaling pathway activation. The experimental liver injury was induced by 2-acetylaminofluorene (2-AAF) treatment combined with partial hepatectomy (PH). EZP treated 2-AAF/PH-induced liver injury by the therapeutic and prophylactic administration. After the administration of EZP, the activities of aspartic transaminase (AST), alanine aminotransferase (ALT), alkaline phosphatase (AKP), and gamma-glutamyl transpeptidase (γ-GT) were decreased, followed by the decreased levels of hepatocyte apoptosis and caspase-3 expression. However, the secretion of albumin, liver weight, and index of liver weight were elevated. Microscopic examination showed that EZP restored pathological liver injury. Meanwhile, Rheb and mammalian target of rapamycin (mTOR) activation were suppressed, and tuberous sclerosis complex (TSC) expression was elevated in liver tissues induced by 2-AAF/PHx and accompanied with lower-expression of Bax, Notch1, p70S6K, and 4E-EIF and upregulated levels of Bcl-2 and Cyclin D. Hepatoprotective effect of EZP was possibly realized via inhibiting TSC/mTOR signaling pathway to suppress excessive apoptosis of hepatocyte.

Preparation and antioxidant activity of PEGylated chitosans with different particle sizes

The preparation of water-soluble chitosans such as polyethylene glycol (PEG)-grafted derivatives is essential for improving the biocompatibility and water solubility of these types of polysaccharides. In this study, chitosans (CS1; 22 kDa, CS2; 38 kDa, CS3; 52 kDa) with different molecular weights were modified with a succinyl ester derivative of monomethoxypolyethylene glycol (mPEG-COONSu; 2 kDa), and the properties of the resulting conjugates (mPEG-CS1, mPEG-CS2, mPEG-CS3) were investigated. The antioxidant properties of these mPEG-CSs were examined using (1) N-centered radicals derived from 1,1'-diphenyl-2-picrylhydrazyl (DPPH), (2) reducing power, based on their ability to reduce Cu2+ and (3) hydroxyl radicals via the use of ESR spectrometry. The order of their effectiveness was mPEG-CS1>mPEG-CS2>mPEG-CS3, i.e. mPEG-CS1 with a low particle size had the highest scavenging activity of the mPEG-CSs tested. In an in vivo study, we examined the effect of mPEG-CS1 on liver injury, caused by injecting mice with Concanavalin A (Con A). The livers of mice that were treated with mPEG-CS1 were protected from Con A-induced injury. Further, pre-treatment with mPEG-CS1 dramatically reduced the mortality associated with Con A-induced mortality. These findings suggest that mPEG-CS1 could be potentially useful in the treatment of immune-mediated liver injury.