Effect of cholinergic denervation on hepatic fibrosis induced by carbon tetrachloride in rats

The role of hepatic sinusoidal microenvironment in NASH: pathogenesis, animal models, and therapeutic prospects

The incidence of nonalcoholic steatohepatitis (NASH) is increasing annually, posing a significant threat to human health. NASH is typified by hepatic steatosis, inflammation, and hepatocellular injury, frequently culminating in fibrosis and cirrhosis. Yet, the precise pathogenesis of NASH remains to be fully elucidated. The hepatic sinusoid, which serves as the fundamental structural and functional unit of the liver, is intricately composed of endothelial cells, Kupffer cells, and hepatic stellate cells. Consequently, the homeostasis of the hepatic sinusoidal microenvironment may exert a pivotal influence on the progression and prognosis of NASH. However, the limitations of current NASH animal models have significantly impeded advancements in understanding the disease's pathogenesis and the development of effective therapeutic interventions. In light of these challenges, this review endeavors to delve deeper into the critical role of hepatic sinusoidal microenvironment homeostasis in the pathogenesis of NASH, critically analyze the commonly employed animal models, and comprehensively summarize the most recent and promising developments in drug research and development. It is anticipated that these efforts will collectively expedite the advancement of the field of NASH research and therapeutic innovation.

The brain-liver cholinergic anti-inflammatory pathway and viral infections

Efferent cholinergic signaling is a critical and targetable source of immunoregulation. The vagus nerve (VN) is the primary source of cholinergic signaling in the body, and partially innervates hepatic functionality through the liver-brain axis. Virus-induced disruption of cholinergic signaling may promote pathogenesis in hepatotropic and neurotropic viruses. Therefore, restoring VN functionality could be a novel therapeutic strategy to alleviate pathogenic inflammation in hepatotropic and neurotropic viral infections alike. In this minireview, we discuss the physiological importance of cholinergic signaling in maintaining liver-brain axis homeostasis. Next, we explore mechanisms by which the VN is perturbed by viral infections, and how non-invasive restoration of cholinergic signaling pathways with bioelectronic medicine (BEM) might ameliorate hepatic inflammation and neuroinflammation in certain viral infections.

Functions of retinal astrocytes and Müller cells in mammalian myopia

Background

Changes in the retina and choroid blood vessels are regularly observed in myopia. However, if the retinal glial cells, which directly contact blood vessels, play a role in mammalian myopia is unknown. We aimed to explore the potential role and mechanism of retinal glial cells in form deprived myopia.

Methods

We adapted the mice form-deprivation myopia model by covering the right eye and left the left eye open for control, measured the ocular structure with anterior segment optical coherence tomography, evaluated changes in the morphology and distribution of retinal glial cells by fluorescence staining and western blotting; we also searched the online GEO databases to obtain relative gene lists and confirmed them in the form-deprivation myopia mouse retina at mRNA and protein level.

Results

Compared with the open eye, the ocular axial length (3.54 ± 0.006 mm v.s. 3.48 ± 0.004 mm, p = 0.027) and vitreous chamber depth (3.07 ± 0.005 mm v.s. 2.98 ± 0.006 mm, p = 0.007) in the covered eye became longer. Both glial fibrillary acidic protein and excitatory amino acid transporters 4 elevated. There were 12 common pathways in human myopia and anoxic astrocytes. The key proteins were also highly relevant to atropine target proteins. In mice, two common pathways were found in myopia and anoxic Müller cells. Seven main genes and four key proteins were significantly changed in the mice form-deprivation myopia retinas.

Conclusion

Retinal astrocytes and Müller cells were activated in myopia. They may response to stimuli and secretory acting factors, and might be a valid target for atropine.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-022-02643-0.

Schwann Cells in Digestive System Disorders

Proper functioning of the digestive system is ensured by coordinated action of the central and peripheral nervous systems (PNS). Peripheral innervation of the digestive system can be viewed as intrinsic and extrinsic. The intrinsic portion is mainly composed of the neurons and glia of the enteric nervous system (ENS), while the extrinsic part is formed by sympathetic, parasympathetic, and sensory branches of the PNS. Glial cells are a crucial component of digestive tract innervation, and a great deal of research evidence highlights the important status of ENS glia in health and disease. In this review, we shift the focus a bit and discuss the functions of Schwann cells (SCs), the glial cells of the extrinsic innervation of the digestive system. For more context, we also provide information on the basic findings regarding the function of innervation in disorders of the digestive organs. We find diverse SC roles described particularly in the mouth, the pancreas, and the intestine. We note that most of the scientific evidence concerns the involvement of SCs in cancer progression and pain, but some research identifies stem cell functions and potential for regenerative medicine.

Potential Role for Combined Subtype-Selective Targeting of M1 and M3 Muscarinic Receptors in Gastrointestinal and Liver Diseases

Despite structural similarity, the five subtypes comprising the cholinergic muscarinic family of G protein-coupled receptors regulate remarkably diverse biological functions. This mini review focuses on the closely related and commonly co-expressed M₁R and M₃R muscarinic acetylcholine receptor subtypes encoded respectively by CHRM1 and CHRM3. Activated M₁R and M₃R signal via G_q and downstream initiate phospholipid turnover, changes in cell calcium levels, and activation of protein kinases that alter gene transcription and ultimately cell function. The unexpectedly divergent effects of M₁R and M₃R activation, despite similar receptor structure, distribution, and signaling, are puzzling. To explore this conundrum, we focus on the gastrointestinal (GI) tract and liver because abundant data identify opposing effects of M₁R and M₃R activation on the progression of gastric, pancreatic, and colon cancer, and liver injury and fibrosis. Whereas M₃R activation promotes GI neoplasia, M₁R activation appears protective. In contrast, in murine liver injury models, M₃R activation promotes and M₁R activation mitigates liver fibrosis. We analyze these findings critically, consider their therapeutic implications, and review the pharmacology and availability for research and therapeutics of M₁R and M₃R-selective agonists and antagonists. We conclude by considering gaps in knowledge and other factors that hinder the application of these drugs and the development of new agents to treat GI and liver diseases.

Analysis of gene expression profiling of amyloidogenic immunoglobulin light-chains on cultured rat cardiomyocytes

The present study aimed to investigate the toxic effects of different amyloidogenic light-chains (LCs) on cardiomyocytes, and demonstrate the differentially expressed genes (DEGs) and signaling pathways that participate in this process. Cultured cardiomyocytes were treated with recombinant κ LC peptide (AL-09) or with serum from a patient diagnosed with multiple myeloma (λ LC) with cardiac involvement. The 6xHis peptide or serum from healthy patients was used as peptide control or serum control, respectively. Cell viability was determined using CCK-8 assay and apoptosis was analyzed by flow cytometry. The DEGs were detected by RNA sequencing (RNA-Seq), followed by Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses. Changes in gene expression levels were confirmed by reverse transcription-quantitative PCR. The cell viability in the AL-09 peptide-treated (0.2 mg/ml) and patient serum-treated (1:10 dilution) cardiomyocytes decreased to 42 and -72% of the corresponding control groups. The extent of cell apoptosis increased in AL-09-treated cardiomyocytes compared with the control group. RNA-Seq showed 256 DEGs co-existed in the two paired groups, including 127 upregulated and 88 downregulated genes. The KEGG pathways for upregulated expressed genes included the ‘TGF-β signaling pathway’, the ‘Hedgehog signaling pathway’, the ‘ErbB signaling pathway’ and ‘lysine degradation’. The higher mRNA expression of bone morphogenetic protein (Bmp) 4, Bmp6, prostaglandin G/H synthase (Ptgs)1, Ptgs2, epiregulin, Tgfa and procollagen-lysine,2-oxoglutarate 5-dioxygenase 2 were confirmed. The KEGG pathways of downregulated expressed genes included genes involved with the ‘p53 signaling pathway’ and the ‘cell cycle’. The mRNA expression levels of E3 ubiquitin-protein ligase CCNB1IP1 showed significant downregulation in the AL-09 peptide group compared with those in the 6xHis peptide group. In conclusion, cardiomyocytes treated with amyloidogenic λ and κ LCs presented with decreased cell viability compared with controls. Cell apoptosis increased in κ LC-treated cells compared with controls. The gene expression profiles associated with transforming growth factor-β-bone morphogenetic protein, the receptor tyrosine-protein kinase erbB-2 signaling pathways, prostaglandins, collagen production, the p53 signaling pathway and the cell cycle were altered in light-chain-treated cardiomyocytes.

The polysaccharides from Grifola frondosa attenuate CCl4-induced hepatic fibrosis in rats via the TGF-β/Smad signaling pathway

The TGF-β1/Smad signaling pathway has been linked to hepatic fibrosis. Previous studies have shown that yellow polysaccharide can prevent the development of hepatic fibrosis. However, it is unclear whether the polysaccharide affects the TGF-β1/Smad signaling pathway. In this experiment, 50 experimental rats were randomly divided into a normal control group, model group, low GFP dose group (50 mg kg^-1), medium GFP dose group (100 mg kg^-1), and high GFP dose group (200 mg kg^-1). A cirrhotic portal hypertension rat model was established by a CCl₄ compound method. After 12 weeks of intragastric administration, the liver index of the medium dose and high dose group was significantly lower than that of the model group. The hepatic fibrosis lesions of rats in each dose group were improved to different extents, and the effect was most significant in the high dose group. The contents of ALT, AST, TBIL and CIV, PCIII, LN and HA in serum were significantly decreased. The activity of SOD and GSH-Px in the liver tissue of GFP medium and high dose groups was significantly increased and the content of MDA was significantly decreased. The contents of TNF-α, IL-1β and IL-6 were significantly decreased. The western blot results showed that the expressions of p-Smad 2/3, Smad4, PAI-1, Imp7 and Imp8 in medium dose and high dose groups were significantly lower than those in the model group, while the expression of Smad7 was significantly higher than that of the model group. The GFP-treated group was able to reduce the expression level of mi R-154 in liver tissue and increase the expression level of miR-146a. GFP has a significant intervention effect on rat hepatic fibrosis, and its mechanism may inhibit the progression of hepatic fibrosis by inhibiting oxidative stress and inflammatory response and regulating TGF-β1/Smad signaling pathway and mi RNA expression.

Age-dependent modulation of fasting and long-term dietary restriction on acetylcholinesterase in non-neuronal tissues of mice

Dietary restriction (DR) without malnutrition is a robust intervention that extends lifespan and slows the onset of nervous system deficit and age-related diseases in diverse organisms. Acetylcholinesterase (AChE), a thoroughly studied enzyme better known for hydrolyzing acetylcholine (ACh) in neuronal tissues, has recently been linked with multiple unrelated biological functions in different non-neuronal tissues. In the present study, the activity and protein expression level of AChE in liver, heart, and kidney of young (1 month), adult (6 month), and aged (18 month) mice were investigated. We also studied age- and tissue-specific changes in AChE activity and protein expression level after the mice were subjected to 24-h fasting and long-term DR. Our results showed that AChE activity and protein expression in kidney and heart of aged mice decreased significantly in comparison with young mice. On the contrary, long-term DR decreases the AChE activity and the protein expression level in all tissues irrespective of ages studied. We summarized that changes in AChE with age in different tissues studied reflects its different roles at different phases of an organism's life. Conversely, the cumulative modulation manifested in the form of lowering AChE by long-term DR may prevent the futile synthesis and accumulation of unwanted AChE besides the added compensatory benefit of enhanced ACh availability needed during the period of starvation. This, in turn, may help in preventing the declining homeostatic roles of this important neurotransmitter in different tissues.

The myofibroblast, a key cell in normal and pathological tissue repair

Myofibroblasts are characterized by their expression of α-smooth muscle actin, their enhanced contractility when compared to normal fibroblasts and their increased synthetic activity of extracellular matrix proteins. Myofibroblasts play an important role in normal tissue repair processes, particularly in the skin where they were first described. During normal tissue repair, they appear transiently and are then lost via apoptosis. However, the chronic presence and continued activity of myofibroblasts characterize many fibrotic pathologies, in the skin and internal organs including the liver, kidney and lung. More recently, it has become clear that myofibroblasts also play a role in many types of cancer as stromal or cancer-associated myofibroblast. The fact that myofibroblasts are now known to be key players in many pathologies makes understanding their functions, origin and the regulation of their differentiation important to enable them to be regulated in normal physiology and targeted in fibrosis, scarring and cancer.

Acetylcholine induces fibrogenic effects via M2/M3 acetylcholine receptors in non-alcoholic steatohepatitis and in primary human hepatic stellate cells

BACKGROUND

The parasympathetic nervous system (PNS), via neurotransmitter acetylcholine (ACh), modulates fibrogenesis in animal models. However, the role of ACh in human hepatic fibrogenesis is unclear.

AIMS

We aimed to determine the fibrogenic responses of human hepatic stellate cells (hHSC) to ACh and the relevance of the PNS in hepatic fibrosis in patients with non-alcoholic steatohepatitis (NASH).

METHODS

Primary hHSC were analyzed for synthesis of endogenous ACh and acetylcholinesterase and gene expression of choline acetyltransferase and muscarinic ACh receptors (mAChR). Cell proliferation and fibrogenic markers were analyzed in hHSC exposed to ACh, atropine, mecamylamine, methoctramine, and 4-diphenylacetoxy-N-methylpiperidine methiodide. mAChR expression was analyzed in human NASH scored for fibrosis.

RESULTS

We observed that hHSC synthesize ACh and acetylcholinesterase and express choline acetyltransferase and M1-M5 mAChR. We also show that M2 was increased during NASH progression, while both M2 and M3 were found upregulated in activated hHSC. Furthermore, endogenous ACh is required for hHSC basal growth. Exogenous ACh resulted in hHSC hyperproliferation via mAChR and phosphoinositide 3-kinase and Mitogen-activated protein kinase kinase (MEK) signaling pathways, as well as increased fibrogenic markers.

CONCLUSION

We show that ACh regulates hHSC activation via M2 and M3 mAChR involving the phosphoinositide 3-kinase and MEK pathways in vitro. Finally, we provide evidence that the PNS may be involved in human NASH fibrosis.

M1 Muscarinic Receptor Deficiency Attenuates Azoxymethane-Induced Chronic Liver Injury in Mice

Cholinergic nervous system regulates liver injury. However, the role of M1 muscarinic receptors (M1R) in modulating chronic liver injury is uncertain. To address this gap in knowledge we treated M1R-deficient and WT mice with azoxymethane (AOM) for six weeks and assessed liver injury responses 14 weeks after the last dose of AOM. Compared to AOM-treated WT mice, M1R-deficient mice had attenuated liver nodularity, fibrosis and ductular proliferation, α-SMA staining, and expression of α1 collagen, Tgfβ-R, Pdgf-R, Mmp-2, Timp-1 and Timp-2. In hepatocytes, these findings were associated with reductions of cleaved caspase-3 staining and Tnf-α expression. In response to AOM treatment, M1R-deficient mice mounted a vigorous anti-oxidant response by upregulating Gclc and Nqo1 expression, and attenuating peroxynitrite generation. M1R-deficient mouse livers had increased expression of Trail-R2, a promotor of stellate cell apoptosis; dual staining for TUNNEL and α-SMA revealed increased stellate cells apoptosis in livers from M1R-deficient mice compared to those from WT. Finally, pharmacological inhibition of M1R reduced H₂O₂-induced hepatocyte apoptosis in vitro. These results indicate that following liver injury, anti-oxidant response in M1R-deficient mice attenuates hepatocyte apoptosis and reduces stellate cell activation, thereby diminishing fibrosis. Therefore, targeting M1R expression and activation in chronic liver injury may provide therapeutic benefit.

Vagotomy attenuates bleomycin-induced pulmonary fibrosis in mice

The progression of pulmonary fibrosis (PF) entails a complex network of interactions between multiple classes of molecules and cells, which are closely related to the vagus nerve. Stimulation of the vagus nerve increases fibrogenic cytokines in humans, therefore, activation of the nerve may promote PF. The hypothesis was tested by comparing the extent and severity of fibrosis in lungs with and without vagal innervation in unilaterally vagotomized mice. The results show that in vagotomized lungs, there were less collagen staining, less severe fibrotic foci (subpleural, peri-vascular and peri-bronchiolar lesions) and destruction of alveolar architecture; decreased collagen deposition (denervated vs intact: COL1α1, 19.1 ± 2.2 vs 22.0 ± 2.6 ng/mg protein; COL1α2, 4.5 ± 0.3 vs 5.7 ± 0.5 ng/mg protein; p < 0.01, n = 21) and protein levels of transforming growth factor beta and interleukin 4; and fewer myofibroblast infiltration (denervated vs intact: 1.2 ± 0.2 vs 3.2 ± 0.6 cells/visual field; p < 0.05, n = 6) and M2 macrophages [though the infiltration of macrophages was increased (denervated vs intact: 112 ± 8 vs 76 ± 9 cells/visual field; p < 0.01, n = 6), the percentage of M2 macrophages was decreased (denervated vs intact: 31 ± 4 vs 57 ± 9%; p < 0.05, n = 5)]. It indicated that the vagus nerve may influence PF by enhancing fibrogenic factors and fibrogenic cells.

Non-alcoholic fatty liver induces insulin resistance and metabolic disorders with development of brain damage and dysfunction

In the present study we investigated the effect of the non-alcoholic fatty liver disease (NAFLD) on the alterations in the activity of neurotransmitters catabolizing enzymes and energy catabolising enzymes, prooxidants, endogenous antioxidants and proinflammatory cytokines in brain tissue of NAFLD rats. Rats were intraperitonealy injected with CCl4 solution at a dose of (0.021 mole/Kg, 20 μL, body weight) three times weekly for four weeks. Acetylcholine esterase (AChE), monoamine oxidase (MAO), prooxidant/ antioxidants status, ATPase, lipid profile and glucose level were estimated spectrophotometrically while inflammatory markers; interleukin 6 and tumor necrosis factor alpha (IL6 and TNF-α) and insulin were assessed by ELISA technique. Our results showed that the induced NAFLD and insulin resistance (IR) were accompanied with hyperglycemia and hyperlipidemia and lowered brain glucose level with elevated ATPase activity, prooxidant status (TBARS level, xanthine oxidase and cytochrome 2E1 activities), and inflammatory markers. Through the induction period AChE activity was significantly increased compared to control in blood, liver and brain tissues. Also, MAO activity was significantly increased in both brain and liver tissue but decreased in serum compared with control. These biochemical data were supported with pathophysiological analysis that showed severe neurodegeneration, pyknosis acuolations and cavitations. These observations warrant the reassessment of the conventional concept that the NAFLD with IR progression may induce disturbances in activities of neurotransmitters catabolising enzymes and energy production accompanied with oxidative stress and metabolic disorders, acting as relative risk factors for brain dysfunction and damage with the development of age-associated neurodegenerative diseases such as Alzheimer's disease.

Protective effect of quercetin on liver damage induced by chronic toluene exposure in rats

The aim of this study was to evaluate the possible protective effects of quercetin (QE) on liver injury caused by chronic toluene exposure in rats. The rats were randomly allotted into one of three experimental groups: control, toluene treated and toluene treated with QE; each group contained 10 animals. The control group received 1 ml physiologic serum, and toluene treatment was performed by inhalation of 3000 ppm toluene, for 8 h/day and 6 days/week for 12 weeks. The rats in the QE-treated groups were given QE (15 mg/kg, intraperitoneal) once a day for 12 weeks starting just after toluene exposure. Tissue samples were obtained for histopathological investigation. To date, no histopathological changes in the liver of rats after chronic toluene exposure by QE treatment have been reported. Light microscopic evaluation of liver tissue samples of toluene-exposed rats revealed enlarged sinusoids filled with blood. In addition, some of the hepatocytes showed loss of cytoplasm, and some had a hyperchromatic nucleus. QE treatment attenuated alterations in liver histology. The alpha smooth muscle actin, transforming growth factor beta-positive cells and the activity of terminal deoxynucleotidyl transferase dUTP nick end labeling in the toluene-treated group were observed to be reduced with QE treatment. The data indicate that QE attenuates toluene-induced liver injury, but further investigation is still absolutely necessary.