Muscarinic receptor mediated signaling pathways in hepatocytes from CCL4 - induced liver fibrotic rat

The activation of M 3 muscarinic receptor reverses liver injuryvia the Sp1/lncRNA Gm2199/miR-212 axis

Muscarinic acetylcholine receptors (MRs) play important roles in the regulation of hepatic fibrosis and the receptor agonists and antagonists can affect hepatocyte proliferation. However, little is known about the impact of M ₃R subtypes and associated signaling pathways on liver injury. The aim of this study is to explore the function and mechanism of M ₃R in the regulation of liver injury. We evaluate liver injury and detect the changes in related indexes, including alanine aminotransferase (ALT), aspartate aminotransferase (AST), hydroxyproline (HYP), and transforming growth factor-β1 (TGF-β1), after administration of an M ₃R agonist. Western blot analysis and qRT-PCR show that the transcription factor Sp1 and long noncoding RNA (lncRNA) Gm2199 are also changed significantly. Rescue assay is performed to further confirm that M ₃R contributes to the progression of hepatocyte proliferation through regulating Sp1 and Gm2199. The activated M ₃R can specifically regulate Gm2199 by inhibiting the expression of Sp1. Meanwhile, Gm2199 directly regulates miR-212, and ERK is a potential target of miR-212. Collectively, these findings define a novel mechanism for activating M ₃R to reverse liver injury, which affects hepatocyte proliferation through the Sp1/Gm 2199/miR-212/ERK axis.

The protective effect of hederagenin on renal fibrosis by targeting muscarinic acetylcholine receptor

Hederagenin (HE) plays a protective role by inhibiting cell proliferation and ameliorating fibrosis. The current therapy for Chronic kidney disease (CKD) often result in the risks of side effects. The present study aimed to explore whether it can protect against renal fibrosis and unveil the underlying mechanism. Transforming growth factor (TGF)-β was used to induce the fibroblasts NRK-49 F for the simulation of renal fibrosis. The cell viability and expression of fibrosis-related proteins in TGF-β-treated NRK-49 F cells was, respectively, measured by Cell Counting Kit-8 (CCK-8) and western blot. After predicting the target genes of HE, M3 receptor was measured in NRK-49 F cells treated with TGF-β alone or in combination with HE. Then, M3 receptor was silenced in TGF-β-treated NRK-49 F cells for the detection of its role in proliferation and fibrosis. Muscarinic acetylcholine receptor M3 (M3 receptor) agonist pilocarpine was further added to determine the role of M3 receptor involved. HE inhibited the proliferation and fibrosis of TGF-β-treated NRK-49 F cells. M3 receptor was predicted to be a target of HE. Moreover, interference of M3 receptor improved the proliferation and fibrosis of TGF-β-treated NRK-49 F cells. Further addition of pilocarpine reversed the inhibitory effect of HE on proliferation and fibrosis of TGF-β-treated NRK-49 F cells. HE protects against renal fibrosis in NRK-49 F cells by targeting Muscarinic acetylcholine receptor, which will provide theoretical basis for the clinical use of HE for kidney-related disease treatment.

Group II muscarinic acetylcholine receptors attenuate hepatic injury via Nrf2/ARE pathway

Parasympathetic nervous system dysfunction is common in patients with liver disease. We have previously shown that muscarinic acetylcholine receptors (mAchRs) play an important role in the regulation of hepatic fibrosis and that the receptor agonists and antagonists affect hepatocyte proliferation. However, little is known about the impact of the different mAchR subtypes and associated signaling pathways on liver injury. Here, we treated the human liver cell line HL7702 with 10 mmol/L carbon tetrachloride (CCL4) to induce hepatocyte damage. We found that CCL4 treatment increased the protein levels of group I mAchRs (M1, M3, M5) but reduced the expression of group II mAchRs (M2, M4) and activated the Nrf2/ARE and MAPK signaling pathways. Although overexpression of M1, M3, or M5 led to hepatocyte damage with an intact Nrf2/ARE pathway, overexpression of M2 or M4 increased, and siRNA-mediated knockdown of either M2 or M4 decreased the protein levels of Nrf2 and its downstream target genes. Moreover, CCL4 treatment increased serum ALT levels more significantly, but only induced slight changes in the expression of mAchRs, NQO1 and HO1, while reducing the expression of M2 and M4 in liver tissues of Nrf2-/- mice compared to wild type mice. Our findings suggest that group II mAchRs, M2 and M4, activate the Nrf2/ARE signaling pathway, which regulates the expression of M2 and M4, to protect the liver from CCL4-induced injury.

Cholinergic neuron-like D-U87 cells promote polarization of allergic rhinitis T-helper 2 cells

BACKGROUND

Parasympathetic nerve hypersensitivity contributes to the severity of allergic rhinitis (AR), but the precise mechanism underlying neuroimmune regulation in patients with AR remains unclear. This study investigated the effect of cholinergic nerve inhibition on AR CD4⁺ T-helper (Th)2-cell polarization and the underlying regulatory mechanism in vitro.

METHODS

An in-vitro neuroimmune coculture model of D-U87 cells and CD4⁺ T cells was established. D-U87 cells with cholinergic neuron characteristics were used as cholinergic neuron models. CD4⁺ T cells were derived from peripheral blood monocytes from AR patients (n = 60) and control subjects (n = 40). Th1- and Th2-cell percentages were measured by flow cytometry. Proteins involved in related signaling pathways were analyzed by protein chip assay and Western blotting.

RESULTS

The Th2-cell percentage among CD4⁺ T cells from AR patients was significantly increased after coculture with D-U87 cells and was decreased by ipratropium bromide (IB) treatment. In contrast, the Th1-cell percentage among control CD4⁺ T cells was significantly increased after coculture with D-U87 cells, but was unaltered by IB treatment. Furthermore, phosphorylated Akt (p-Akt) protein levels increased in CD4⁺ T cells from both controls and AR patients after coculture with D-U87 cells and decreased after IB treatment. However, higher p-Akt levels were observed in cells from AR patients than in cells from control subjects. Moreover, Akt inhibition decreased Th2-cell percentage in AR patients.

CONCLUSION

In-vitro cholinergic nerve inhibition with IB decreased AR CD4⁺ T-cell polarization into Th2 cells partially through an Akt-dependent mechanism.

Differentiation of human glioblastoma U87 cells into cholinergic neuron

To facilitate research methodologies for investigating the role of cholinergic nerves in many diseases, establishing an in vitro cholinergic neuron model is necessary. In this study, we investigated whether human glioblastoma U87 cells could be differentiated into cholinergic neurons in vitro. Sodium butyrate was used as the differentiation agent. The differentiated cells established by inducing U87 cells with sodium butyrate were named D-U87 cells. Immunofluorescence was used to label the neuronal markers MAP2, NF-M, and ChAT and the glial marker GFAP in D-U87 cells. Flow cytometry was used to measure cell cycle distribution in D-U87 cells. PCR, protein chip, and western blot assays were used to measure the expression levels of muscarinic cholinergic receptor 1 (M1), M4, ChAT, SYP and Akt. ELISA was used to measure neurotransmitter levels. As a result, we found that sodium butyrate induced U87 cell differentiation into cells with neuronal characteristics and increased not only the expression levels of the cholinergic neuron-related proteins M1, M4, ChAT and SYP in D-U87 cells but also the acetylcholine neurotransmitters in D-U87 cells. Moreover, the Akt protein expression in D-U87 cells was increased compared with that in U87 cells. Finally, we found that M1, M4, ChAT and SYP protein expression and acetylcholine secretion levels were significantly decreased in D-U87 cells after treatment with the Akt inhibitor MK-2206. These results demonstrate that D-U87 cells exhibit cholinergic neuron characteristics and that sodium butyrate induced U87 cell differentiation into cholinergic neuron partially through Akt signaling.

Fucoidan Alleviates Acetaminophen-Induced Hepatotoxicity via Oxidative Stress Inhibition and Nrf2 Translocation

Acetaminophen (APAP) is a widely used analgesic and antipyretic drug that leads to severe hepatotoxicity at excessive doses. Fucoidan, a sulfated polysaccharide derived from brown seaweeds, possesses a wide range of pharmacological properties. However, the impacts of fucoidan on APAP-induced liver injury have not been sufficiently addressed. In the present study, male Institute of Cancer Research (ICR) mice aged 6 weeks were subjected to a single APAP (500 mg/kg) intraperitoneal injection after 7 days of fucoidan (100 or 200 mg/kg/day) or bicyclol intragastric administration. The mice continued to be administered fucoidan or bicyclol once per day, and were sacrificed at an indicated time. The indexes evaluated included liver pathological changes, levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in the serum, levels of reactive oxygen species (ROS), malondialdehyde (MDA), superoxide dismutase (SOD), glutathione (GSH) and catalase (CAT) in the liver, and related proteins levels (CYP2E1, pJNK and Bax). Furthermore, human hepatocyte HL-7702 cell line was used to elucidate the potential molecular mechanism of fucoidan. The mitochondrial membrane potential (MMP) and nuclear factor-erythroid 2-related factor (Nrf2) translocation in HL-7702 cells were determined. The results showed that fucoidan pretreatment reduced the levels of ALT, AST, ROS, and MDA, while it enhanced the levels of GSH, SOD, and CAT activities. Additionally, oxidative stress-induced phosphorylated c-Jun N-terminal protein kinase (JNK) and decreased MMP were attenuated by fucoidan. Although the nuclear Nrf2 was induced after APAP incubation, fucoidan further enhanced Nrf2 in cell nuclei and total expression of Nrf2. These results indicated that fucoidan ameliorated APAP hepatotoxicity, and the mechanism might be related to Nrf2-mediated oxidative stress.

Sirtuin3 deficiency exacerbates carbon tetrachloride-induced hepatic injury in mice

Sirtuin3 (SIRT3) plays an important role in maintaining normal mitochondrial function and alleviating oxidative stress. After carbon tetrachloride (CCl₄ ) administration, the expression of SIRT3 decreased in the liver of mice, which indicated that the SIRT3 might play a crucial role during chemical-induced acute hepatic injury. To verify the hypothesis, CCl ₄ was given to induce acute hepatic injury in SIRT3 knockout (KO) mice and wild-type (WT) mice. CCl ₄ -induced liver injury was more severe in SIRT3 KO mice compared with the WT mice. In addition, the oxidative stress induced by CCl ₄ was enhanced in the SIRT3 KO mice. Furthermore, the increased expression of dynamin-related protein 1 was also aggravated in SIRT3 KO mice after CCl ₄ administration. In conclusion, our study demonstrated that SIRT3 deficiency exacerbated CCl ₄ -induced impairment of the liver in mice, and the mechanism might be related to enhanced oxidative stress.

Recent Update on the Pharmacological Effects and Mechanisms of Dihydromyricetin

As the most abundant natural flavonoid in rattan tea, dihydromyricetin (DMY) has shown a wide range of pharmacological effects. In addition to the general characteristics of flavonoids, DMY has the effects of cardioprotection, anti-diabetes, hepatoprotection, neuroprotection, anti-tumor, and dermatoprotection. DMY was also applied for the treatment of bacterial infection, osteoporosis, asthma, kidney injury, nephrotoxicity and so on. These effects to some extent enrich the understanding about the role of DMY in disease prevention and therapy. However, to date, we still have no outlined knowledge about the detailed mechanism of DMY, which might be related to anti-oxidation and anti-inflammation. And the detailed mechanisms may be associated with several different molecules involved in cellular apoptosis, oxidative stress, and inflammation, such as AMP-activated protein kinase (AMPK), mitogen-activated protein kinase (MAPK), protein kinase B (Akt), nuclear factor-κB (NF-κB), nuclear factor E2-related factor 2 (Nrf2), ATP-binding cassette transporter A1 (ABCA1), peroxisome proliferator-activated receptor-γ (PPARγ) and so on. Here, we summarized the current pharmacological developments of DMY as well as possible mechanisms, aiming to push the understanding about the protective role of DMY as well as its preclinical assessment of novel application.

Autophagy inhibition attenuates the induction of anti-inflammatory effect of catalpol in liver fibrosis

Autophagy has been regarded as an inflammation-associated defensive mechanism against chronic liver disease, which has been highlighted as a novel therapeutic target for the treatment of liver fibrosis. We herein aimed to study the effects of catalpol on liver fibrosis in vivo and in vitro, and to elucidate the role of autophagy in catalpol-induced anti-inflammation. Catalpol protected the liver against CCl₄-induced injury, as evidenced by mitigated hepatic steatosis, necrosis, and fibrotic septa. Catalpol decreased the serum levels of alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase and bilirubin as well as the liver/body weight ratio. Masson and sirius red staining along with hydroxyproline detection showed that catalpol decreased collagen deposition significantly compared to that of the model group. Catalpol inhibited CCl₄-induced liver fibrosis, manifested as decreased expressions of α-SMA, fibronectin and α1(I)-procollagen at both transcriptional and translational levels. Inflammatory factors, such as IL-1β, TNF-α, IL-18, IL-6 and COX-2, were significantly elevated in rats receiving CCl₄ and down-regulated by catalpol in a dose-dependent manner in vivo. Western blot and immunofluorescence assay revealed that catalpol activated the autophagy of rats with CCl₄-caused liver fibrosis, as indicated by up-regulation of LC3-II and beclin1 and down-regulation of P62. The results of in vitro experiments were consistent. Interestingly, inhibition or depletion of autophagy by LY294002 or Atg5 siRNA significantly attenuated catalpol-induced anti-inflammatory effects on activated hepatic stellate cells in vitro. In conclusion, catalpol relieved liver fibrosis mainly by inhibiting inflammation, and autophagy inhibition attenuated the catalpol-induced anti-inflammatory effect on liver fibrosis.