5-methoxytryptophan alleviates liver fibrosis by modulating FOXO3a/miR-21/ATG5 signaling pathway mediated autophagy

5-Methoxytryptophan attenuates oxidative stress-induced downregulation of PINK1 and mitigates mitochondrial damage and apoptosis in cardiac myocytes

Mitochondrial dysfunction is a hallmark of the pathogenesis of various cardiovascular diseases. 5-Methoxytryptophan (5-MTP), an intrinsic amino acid metabolite, exerts cardioprotective effects potentially through the preservation of mitochondrial integrity. This study investigates the mechanisms and contexts in which 5-MTP positively impacts mitochondrial function using cultured human cardiac myocyte cells and HL-1 cardiac cells subjected to oxidative stress (OS). We first demonstrated that 5-MTP up-regulates the expression of PINK1, a key regulator of mitochondrial homeostasis. PINK1 knockdown attenuated the beneficial effects of 5-MTP on cardiomyocyte apoptosis. Furthermore, in cells exposed to OS, 5-MTP pretreatment led to a notable decrease in mitochondrial superoxide generation. Fluorescence imaging and network analysis showed that 5-MTP preserved mitochondrial membrane potential and enhanced mitochondrial network integrity. Reduced phosphorylation of dynamin-related protein 1, which is involved in mitochondrial fission, uncovered the role of 5-MTP in maintaining mitochondrial dynamics. Notably, 5-MTP attenuated OS-induced mitophagy, as evidenced by reduced mitophagy detection dye fluorescence and lower mitochondrial Parkin levels, suggesting that mechanisms beyond the PINK1/Parkin pathway are involved. Restoration of AKT phosphorylation and reduced mitochondrial Bax localization further revealed an additional pathway contributing to mitochondrial protection. Moreover, 5-MTP attenuated pro-apoptotic Bax levels and enhanced PINK1 expression in a rat model of ischemic cardiomyopathy, corroborating its cardioprotective role. Collectively, these findings demonstrate that 5-MTP mitigates mitochondrial dysfunction through coordinated regulation of PINK1, AKT, and Bax, offering potential as a therapeutic agent to enhance cellular resilience in OS-driven mitochondrial damage.

ErTao decoction alleviates liver fibrosis by suppressing STING-mediated macrophages and NLRP3 inflammasome activation

BACKGROUND

Liver fibrosis (LF) is a common pathological process in the progression of multiple chronic liver diseases to cirrhosis, affecting millions of people worldwide annually. The incomplete understanding of its mechanisms has led to a lack of clinically effective therapeutic options. ErTao decoction (ETD, ), a derivative combining the components of Erchen Decoction and Taohong Siwu Decoction, is rooted in the traditional Chinese medicine theory of "phlegm-dampness-blood stasis". However, the precise mechanism by which ETD exerts its therapeutic effects in LF remains unclear.

PURPOSE

The purpose of study was to investigate the protective effect of ETD and elucidate its underlying molecular mechanism on LF.

METHODS

In this study, we employed a multifaceted approach to evaluate the effects of ETD on LF. We used H&E staining, Sirius red staining, immunofluorescence, immunohistochemical analysis, and Western blotting to assess the protective effects of ETD in a CCl4-induced fibrosis mouse model. In vitro validation was conducted using macrophages and hepatic stellate cells to further elucidate the mechanisms involved. STING-deficient mice were used to assess its regulatory effects on liver injury, inflammatory and activation through immunohistochemical staining and Western blotting. Furthermore, UHPLCHRMS detection and computer-aided drug analysis were employed to identify and validate potential effective components of ETD for responsible for its therapeutic effects in treating LF.

RESULTS

In our in vivo and in vitro experiments, we found that ETD effectively reduced collagen fiber deposition and alleviated LF pathological changes by inhibiting macrophage inflammatory activation and suppressing NLRP3 and STING signaling. Notably, STING deficiency exhibited a protective effect against liver tissue injury and inhibited inflammatory activation of hepatic macrophages in LF model mice. Additionally, comprehensive analysis of the active ingredients in ETD strongly suggested that Naringin served as a pivotal bioactive constituent within ETD responsible for modulating STING signaling.

CONCLUSIONS

Our study highlighted the protective effects of ETD on LF by inhibiting STING-mediated macrophage activation and NLRP3 inflammasome signaling. Notably, Naringin might serve as a promising novel STING inhibitor to effectively counteract the progression of LF. These findings represented significant advances in LF research and paved the way for the development of novel therapeutic strategies.

5-Methoxytryptophan Protects against Toll-Like Receptor 2-Mediated Renal Tissue Inflammation and Fibrosis in a Murine Unilateral Ureteral Obstruction Model

INTRODUCTION

5-Methoxytryptophan (5-MTP) is a cellular metabolite with anti-inflammatory properties. Several recent reports indicate that 5-MTP protects against post-injury tissue fibrosis. It was unclear how 5-MTP controls tissue fibrosis. We postulated that 5-MTP attenuates renal interstitial fibrosis by blocking toll-like receptor 2 (TLR2) and transforming growth factor β (TGFβ) signaling pathways.

METHODS

In vivo experiments were carried out in a well-established unilateral ureteral obstruction (UUO) model in wild-type (WT) and tlr2-/- mice. The effect of 5-MTP on renal fibrosis was evaluated by pretreatment of WT UUO mice with intraperitoneal administration of 5-MTP. To determine whether 5-MTP attenuates fibrosis by inhibiting TLR2 and TGFβ signaling pathways, we evaluated the effect of 5-MTP on TLR2-induced fibroblast phenotypic switch in NRK-49F fibroblasts and TLR2 and TGFβ signaling pathways in human proximal tubular epithelial cells (HPTECs) and RAW264.7 macrophages stimulated with Pam3CSK4 (Pam3) or TGFβ1.

RESULTS

UUO-induced renal fibrosis was abrogated in tlr2-/- mice consistent with a crucial role of TLR2 in UUO-induced renal fibrosis. UUO-induced macrophage infiltration and pro-fibrotic cytokine production in renal tissues were suppressed by tlr2 knockout. 5-MTP administration attenuated renal tissue fibrosis accompanied by reduction of macrophage infiltration and IL-6 and TGFβ levels. 5-MTP inhibits TLR2 upregulation and blocks TLR2-MyD88-TRAF6 signaling pathway in macrophages. Furthermore, 5-MTP blocked Pam3- and TGFβ1-induced phenotypic switch of NRK-49F to myofibroblasts and inhibited Pam3- and TGFβ1-induced signaling pathways in HPTECs and RAW264.7 cells.

CONCLUSION

5-MTP is effective in protecting against UUO-induced renal interstitial fibrosis by blocking TLR2 and TGFβ signaling pathways.

INTRODUCTION

5-Methoxytryptophan (5-MTP) is a cellular metabolite with anti-inflammatory properties. Several recent reports indicate that 5-MTP protects against post-injury tissue fibrosis. It was unclear how 5-MTP controls tissue fibrosis. We postulated that 5-MTP attenuates renal interstitial fibrosis by blocking toll-like receptor 2 (TLR2) and transforming growth factor β (TGFβ) signaling pathways.

METHODS

In vivo experiments were carried out in a well-established unilateral ureteral obstruction (UUO) model in wild-type (WT) and tlr2-/- mice. The effect of 5-MTP on renal fibrosis was evaluated by pretreatment of WT UUO mice with intraperitoneal administration of 5-MTP. To determine whether 5-MTP attenuates fibrosis by inhibiting TLR2 and TGFβ signaling pathways, we evaluated the effect of 5-MTP on TLR2-induced fibroblast phenotypic switch in NRK-49F fibroblasts and TLR2 and TGFβ signaling pathways in human proximal tubular epithelial cells (HPTECs) and RAW264.7 macrophages stimulated with Pam3CSK4 (Pam3) or TGFβ1.

RESULTS

UUO-induced renal fibrosis was abrogated in tlr2-/- mice consistent with a crucial role of TLR2 in UUO-induced renal fibrosis. UUO-induced macrophage infiltration and pro-fibrotic cytokine production in renal tissues were suppressed by tlr2 knockout. 5-MTP administration attenuated renal tissue fibrosis accompanied by reduction of macrophage infiltration and IL-6 and TGFβ levels. 5-MTP inhibits TLR2 upregulation and blocks TLR2-MyD88-TRAF6 signaling pathway in macrophages. Furthermore, 5-MTP blocked Pam3- and TGFβ1-induced phenotypic switch of NRK-49F to myofibroblasts and inhibited Pam3- and TGFβ1-induced signaling pathways in HPTECs and RAW264.7 cells.

CONCLUSION

5-MTP is effective in protecting against UUO-induced renal interstitial fibrosis by blocking TLR2 and TGFβ signaling pathways.

Predictive Value of 5-Methoxytryptophan on Long-Term Clinical Outcome after PCI in Patients with Acute Myocardial Infarction-a Prospective Cohort Study

BACKGROUND

In recent years, 5-Methoxytryptophan (5-MTP) has been identified as an endothelial factor with vaso-protective and anti-inflammatory properties.

METHODS

In this prospective cohort study, a total of 407 patients with acute myocardial infarction (AMI) who underwent percutaneous coronary intervention (PCI) successfully were enrolled. A 1-year follow-up Kaplan-Meier survival analysis was used for evaluating the correlation between 5-MTP and major adverse cardiovascular event (MACE) while Cox proportional-hazards regression was used to identify predictive values of 5-MTP on MACE after AMI.

RESULTS

Increased 5-MTP level led to a significant downtrend in the incidence of MACE (All Log-rank p < 0.05). Thus, a high baseline 5-MTP could reduce the 1-year incidence of MACE (HR = 0.33, 95%Cl 0.17-0.64, p = 0.001) and heart failure (HF) (HR = 0.28, 95% Cl 0.13-0.62, p = 0.002). Subgroup analysis indicated the predictive value of 5-MTP was more significant in patients aged ≤ 65 years and those with higher baseline NT-proBNP, T2DM, STEMI, and baseline HF with preserved LVEF (HFpEF) characteristics.

CONCLUSIONS

Plasma 5-MTP is an independent and protective early biomarker for 1-year MACE and HF events in patients with AMI, especially in younger patients and those with T2DM, STEMI, and baseline HFpEF characteristics.

Autophagy in hepatic progenitor cells modulates exosomal miRNAs to inhibit liver fibrosis in schistosomiasis

Schistosoma infection is one of the major causes of liver fibrosis. Emerging roles of hepatic progenitor cells (HPCs) in the pathogenesis of liver fibrosis have been identified. Nevertheless, the precise mechanism underlying the role of HPCs in liver fibrosis in schistosomiasis remains unclear. This study examined how autophagy in HPCs affects schistosomiasis-induced liver fibrosis by modulating exosomal miRNAs. The activation of HPCs was verified by immunohistochemistry (IHC) and immunofluorescence (IF) staining in fibrotic liver from patients and mice with Schistosoma japonicum infection. By coculturing HPCs with hepatic stellate cells (HSCs) and assessing the autophagy level in HPCs by proteomic analysis and in vitro phenotypic assays, we found that impaired autophagy degradation in these activated HPCs was mediated by lysosomal dysfunction. Blocking autophagy by the autophagy inhibitor chloroquine (CQ) significantly diminished liver fibrosis and granuloma formation in S. japonicum-infected mice. HPC-secreted extracellular vehicles (EVs) were further isolated and studied by miRNA sequencing. miR-1306-3p, miR-493-3p, and miR-34a-5p were identified, and their distribution into EVs was inhibited due to impaired autophagy in HPCs, which contributed to suppressing HSC activation. In conclusion, we showed that the altered autophagy process upon HPC activation may prevent liver fibrosis by modulating exosomal miRNA release and inhibiting HSC activation in schistosomiasis. Targeting the autophagy degradation process may be a therapeutic strategy for liver fibrosis during Schistosoma infection.

Critical role of miR-21/exosomal miR-21 in autophagy pathway

Activation of autophagy, a process of cellular stress response, leads to the breakdown of proteins, organelles, and other parts of the cell in lysosomes, and can be linked to several ailments, such as cancer, neurological diseases, and rare hereditary syndromes. Thus, its regulation is very carefully monitored. Transcriptional and post-translational mechanisms domestically or in whole organisms utilized to control the autophagic activity, have been heavily researched. In modern times, microRNAs (miRNAs) are being considered to have a part in post-translational orchestration of the autophagic activity, with miR-21 as one of the best studied miRNAs, it is often more than expressed in cancer cells. This regulatory RNA is thought to play a major role in a plethora of processes and illnesses including growth, cancer, cardiovascular disease, and inflammation. Different studies have suggested that a few autophagy-oriented genes, such as PTEN, Rab11a, Atg12, SIPA1L2, and ATG5, are all targeted by miR-21, indicating its essential role in the regulation.

miRNA‑21 promotes the progression of acute liver failure via the KLF6/autophagy/IL‑23 signaling pathway

Acute liver failure (ALF) is a complex syndrome characterized by overactivation of innate immunity, and the recruitment and differentiation of immune cells at inflammatory sites. The present study aimed to explore the role of microRNA (miRNA/miR)‑21 and its potential mechanisms underlying inflammatory responses in ALF. Baseline serum miR‑21 was analyzed in patients with ALF and healthy controls. In addition, miR‑21 antagomir was injected via the tail vein into C57BL/6 mice, and lipopolysaccharide/D‑galactosamine (LPS/GalN) was injected into mice after 48 h. The expression levels of miR‑21, Krüppel‑like‑factor‑6 (KLF6), autophagy‑related proteins and interleukin (IL)‑23, and hepatic pathology were then assessed in the liver tissue. Furthermore, THP‑1‑derived macrophages were transfected with a miRNA negative control, miR‑21 inhibitor, miR‑21 mimics or KLF6 overexpression plasmid, followed by treatment with or without rapamycin, and the expression levels of miR‑21, KLF6, autophagy‑related proteins and IL‑23 were evaluated. The results revealed that baseline serum miR‑21 levels were significantly upregulated in patients with ALF. In addition, LPS/GalN‑induced ALF was attenuated in the antagomir‑21 mouse group. KLF6 was identified as a target of miR‑21‑5p with one putative seed match site identified by TargetScan. A subsequent luciferase activity assay demonstrated a direct interaction between miR‑21‑5p and the 3'‑UTR of KLF6 mRNA. Further experiments suggested that miR‑21 promoted the expression of IL‑23 via inhibiting KLF6, which regulated autophagy. In conclusion, in the present study, baseline serum miR‑21 levels were highly upregulated in patients with ALF, antagomir‑21 attenuated LPS/GalN‑induced ALF in a mouse model, and miR‑21 could promote the expression of IL‑23 via inhibiting KLF6.

Exosomes from adipose-derived mesenchymal stem cells improve liver fibrosis by regulating the miR-20a-5p/TGFBR2 axis to affect the p38 MAPK/NF-κB pathway

OBJECTIVE

Human adipose-derived mesenchymal stem cell exosomes (ADSC-Exos) are active constituents for treating liver fibrosis. This paper attempted to preliminarily explain the functional mechanism of ADSC-Exos in liver fibrosis through the p38 MAPK/NF-κB pathway.

METHODS

The cell models of hepatic fibrosis were established by inducing LX-2 cells with TGF-β1. Mouse models of liver fibrosis were established by treating mice with CCl4. The in vivo and in vitro models of liver fibrosis were treated with ADSC-Exos. ADSCs were identified by flow cytometry/Alizarin red/oil red O/alcian blue staining. ADSC-Exos were identified by transmission electron microscopy, nanoparticle tracking analysis, and Western blot. LX-2 cell proliferation/viability were evaluated by MTT/BrdU assays. Exosomes were tracked in vivo and body weight changes in mice were monitored. Hepatic pathological changes were observed by HE/Masson staining. α-SMA/collagen I levels in liver tissues were assessed by immunohistochemistry. HA/PIIINP concentrations were measured using the magnetic particle chemiluminescence method. Liver function was assessed using an automatic analyzer. miR-20a-5p level was measured by RT-qPCR. The mRNA levels of fibrosis markers were determined by RT-qPCR, and their protein levels and levels of MAPK/NF-κB pathway-related proteins, as well as TGFBR2 protein level were measured by Western blot. The P65 nuclear expression in mouse liver tissues was quantified by immunofluorescence.

RESULTS

ADSC-Exos suppressed TGF-β1-induced LX-2 cell proliferation and fibrosis and reduced mRNA and protein levels of fibrosis markers in vitro. ADSC-Exos ameliorated liver fibrosis by inhibiting the p38 MAPK/NF-κB pathway activation. ADSC-Exos inhibited activation of the p38 MAPK/NF-κB pathway via regulating the miR-20a-5p/TGFBR2 axis. The in vivo experiment asserted that ADSC-Exos were mainly distributed in the liver, and ADSC-Exos relieved liver fibrosis in mice, which was evidenced by alleviating decreased body weight, reducing collagen and enhancing liver function, and repressed the activation of the p38 MAPK/NF-κB pathway via the miR-20a-5p/TGFBR2 axis.

CONCLUSION

ADSC-Exos attenuated liver fibrosis by suppressing the activation of the p38 MAPK/NF-κB pathway via the miR-20a-5p/TGFBR2 axis.

5-Methoxytryptophan ameliorates endotoxin-induced acute lung injury in vivo and in vitro by inhibiting NLRP3 inflammasome-mediated pyroptosis through the Nrf2/HO-1 signaling pathway

BACKGROUND AND AIM

Endotoxin-induced acute lung injury (ALI) is a complicated and fatal condition with no specific or efficient clinical treatments. 5-Methoxytryptophan (5-MTP), an endogenous metabolite of tryptophan, was revealed to block systemic inflammation. However, the specific mechanism by which 5-MTP affects ALI still needs to be clarified. The purpose of this study was to determine whether 5-MTP protected the lung by inhibiting NLRP3 inflammasome-mediated pyroptosis through the Nrf2/HO-1 signaling pathway.

METHODS AND RESULTS

We used lipopolysaccharide (LPS)-stimulated C57BL/6 J mice and MH-S alveolar macrophages to create models of ALI, and 5-MTP (100 mg/kg) administration attenuated pathological lung damage in LPS-exposed mice, which was associated with decreased inflammatory cytokines and oxidative stress levels, upregulated protein expression of Nrf2 and HO-1, and suppressed Caspase-1 activation and NLRP3-mediated pyroptosis protein levels. Moreover, Nrf2-deficient mice or MH-S cells were treated with 5-MTP to further confirm the protective effect of the Nrf2/HO-1 pathway on lung damage. We found that Nrf2 deficiency partially eliminated the beneficial effect of 5-MTP on reducing oxidative stress levels and inflammatory responses and abrogating the inhibition of NLRP3-mediated pyroptosis induced by LPS.

CONCLUSION

These findings suggested that 5-MTP could effectively ameliorate ALI by inhibiting NLRP3-mediated pyroptosis via the Nrf2/HO-1 signaling pathway.

Liver Fibrosis Resolution: From Molecular Mechanisms to Therapeutic Opportunities

The liver is a critical system for metabolism in human beings, which plays an essential role in an abundance of physiological processes and is vulnerable to endogenous or exogenous injuries. After the damage to the liver, a type of aberrant wound healing response known as liver fibrosis may happen, which can result in an excessive accumulation of extracellular matrix (ECM) and then cause cirrhosis or hepatocellular carcinoma (HCC), seriously endangering human health and causing a great economic burden. However, few effective anti-fibrotic medications are clinically available to treat liver fibrosis. The most efficient approach to liver fibrosis prevention and treatment currently is to eliminate its causes, but this approach's efficiency is too slow, or some causes cannot be fully eliminated, which causes liver fibrosis to worsen. In cases of advanced fibrosis, the only available treatment is liver transplantation. Therefore, new treatments or therapeutic agents need to be explored to stop the further development of early liver fibrosis or to reverse the fibrosis process to achieve liver fibrosis resolution. Understanding the mechanisms that lead to the development of liver fibrosis is necessary to find new therapeutic targets and drugs. The complex process of liver fibrosis is regulated by a variety of cells and cytokines, among which hepatic stellate cells (HSCs) are the essential cells, and their continued activation will lead to further progression of liver fibrosis. It has been found that inhibiting HSC activation, or inducing apoptosis, and inactivating activated hepatic stellate cells (aHSCs) can reverse fibrosis and thus achieve liver fibrosis regression. Hence, this review will concentrate on how HSCs become activated during liver fibrosis, including intercellular interactions and related signaling pathways, as well as targeting HSCs or liver fibrosis signaling pathways to achieve the resolution of liver fibrosis. Finally, new therapeutic compounds targeting liver fibrosis are summarized to provide more options for the therapy of liver fibrosis.

Anthocyanins improve liver fibrosis in mice by regulating the autophagic flux level of hepatic stellate cells by mmu_circ_0000623

Liver fibrosis is a key step in the progression of various chronic liver diseases to liver cirrhosis and even liver cancer, it is also an important link affecting prognosis. Therefore, this study aimed to investigate the therapeutic effect of anthocyanins on liver fibrosis and the molecular mechanism of mmu_circ_0000623 in anthocyanin therapy. In this study, CCL4 was used to build a mouse liver fibrosis model, and the treatment groups were treated with 100 and 200 mg/kg of anthocyanins daily by gavage. Liver fibrosis indicators, macrophage polarization markers, and liver injury markers were further detected by real-time quantitative PCR (qRT-PCR), western blotting (WB), and enzyme-linked immunosorbent assay. Morphological verification of liver injury in different treatment groups was performed by histopathological method. A mouse hepatic stellate cell (HSC) model and a mouse liver fibrosis model were constructed to verify the expression of circ_0000623, miR-351-5p, and TFEB. Transfected with mRFP-GFP-LC3 to detect the autophagic flux of HSCs. We found that 100 mg/kg or 200 mg/kg of anthocyanins could significantly reduce the degree of liver fibrosis in mice. In addition, anthocyanins can inhibit the proliferation, activation, and migration ability of HSCs. circ_0000623 was lowly expressed in mice with liver fibrosis, and anthocyanin treatment could promote its increased expression. Further testing found that anthocyanins could reverse the blocked autophagic flux induced by PDGF or CCL4. This effect is achieved by regulating the expression of TFEB by competitive adsorption of miR-351-5p. Anthocyanins could treat liver fibrosis by modulating circ_0000623/miR-351-5p/TFEB-mediated changes in HSC autophagic flux.

Kinsenoside Alleviates Alcoholic Liver Injury by Reducing Oxidative Stress, Inhibiting Endoplasmic Reticulum Stress, and Regulating AMPK-Dependent Autophagy

Background:Anoectochilus roxburghii (Orchidaceae) is a traditional Chinese medicinal herb with anti-inflammatory, antilipemic, liver protective, immunomodulatory, and other pharmacological activities. Kinsenoside (KD), which shows protective effects against a variety types of liver damage, is an active ingredient extracted from A. roxburghii. However, the liver protective effects and potential mechanisms of KD in alcoholic liver disease (ALD) remain unclear. This study aimed to investigate the liver protective activity and potential mechanisms of KD in ALD.

Methods: AML12 normal mouse hepatocyte cells were used to detect the protective effect of KD against ethanol-induced cell damage. An alcoholic liver injury model was induced by feeding male C57BL/6J mice with an ethanol-containing liquid diet, in combination with intraperitoneal administration of 5% carbon tetrachloride (CCl₄) in olive oil. Mice were divided into control, model, silymarin (positive control), and two KD groups, treated with different doses. After treatment, hematoxylin–eosin and Masson’s trichrome staining of liver tissues was performed, and serum alanine aminotransferase (ALT) and aspartate transaminase (AST) levels were determined to assess the protective effect of KD against alcoholic liver injury. Moreover, proteomics techniques were used to explore the potential mechanism of KD action, and ELISA assay, immunohistochemistry, TUNEL assay, and western blotting were used to verify the mechanism.

Results: The results showed that KD concentration-dependently reduced ethanol-induced lipid accumulation in AML12 cells. In ALD mice model, the histological examination of liver tissues, combined with the determination of ALT and AST serum levels, demonstrated a protective effect of KD in the alcoholic liver injury mice. In addition, KD treatment markedly enhanced the antioxidant capacity and reduced the endoplasmic reticulum (ER) stress, inflammation, and apoptosis compared with those in the model group. Furthermore, KD increased the phosphorylation level of AMP-activated protein kinase (AMPK), inhibited the mechanistic target of rapamycin, promoted the phosphorylation of ULK1 (Ser555), increased the level of the autophagy marker LC3A/B, and restored ethanol-suppressed autophagic flux, thus activating AMPK-dependent autophagy.

Conclusion: This study indicates that KD alleviates alcoholic liver injury by reducing oxidative stress and ER stress, while activating AMPK-dependent autophagy. All results suggested that KD may be a potential therapeutic agent for ALD.

Liver regeneration biology: Implications for liver tumour therapies

The liver has remarkable regenerative potential, with the capacity to regenerate after 75% hepatectomy in humans and up to 90% hepatectomy in some rodent models, enabling it to meet the challenge of diverse injury types, including physical trauma, infection, inflammatory processes, direct toxicity, and immunological insults. Current understanding of liver regeneration is based largely on animal research, historically in large animals, and more recently in rodents and zebrafish, which provide powerful genetic manipulation experimental tools. Whilst immensely valuable, these models have limitations in extrapolation to the human situation. In vitro models have evolved from 2-dimensional culture to complex 3 dimensional organoids, but also have shortcomings in replicating the complex hepatic micro-anatomical and physiological milieu. The process of liver regeneration is only partially understood and characterized by layers of complexity. Liver regeneration is triggered and controlled by a multitude of mitogens acting in autocrine, paracrine, and endocrine ways, with much redundancy and cross-talk between biochemical pathways. The regenerative response is variable, involving both hypertrophy and true proliferative hyperplasia, which is itself variable, including both cellular phenotypic fidelity and cellular trans-differentiation, according to the type of injury. Complex interactions occur between parenchymal and non-parenchymal cells, and regeneration is affected by the status of the liver parenchyma, with differences between healthy and diseased liver. Finally, the process of termination of liver regeneration is even less well understood than its triggers. The complexity of liver regeneration biology combined with limited understanding has restricted specific clinical interventions to enhance liver regeneration. Moreover, manipulating the fundamental biochemical pathways involved would require cautious assessment, for fear of unintended consequences. Nevertheless, current knowledge provides guiding principles for strategies to optimise liver regeneration potential.

Control of Tissue Fibrosis by 5-Methoxytryptophan, an Innate Anti-Inflammatory Metabolite

Tissue fibrosis causes debilitating human diseases such as liver cirrhosis, heart failure, chronic kidney disease and pulmonary insufficiency. It is a dynamic process orchestrated by specific subsets of monocyte-macrophages, fibroblasts, pericytes and hepatic stellate cells. Fibrosis is linked to tissue inflammation. Pro-inflammatory macrophages promote fibrosis by driving myofibroblast differentiation and macrophage myofibroblast transition. Myofibroblasts express α-smooth muscle cell actin (α-SMA) and secrete extracellular matrix (ECM) proteins notably collagen I and III. Deposition of ECM proteins at injury sites and interstitial tissues distorts normal structure and impairs vital functions. Despite advances in the mechanisms of fibrosis at cellular, molecular and genetic levels, prevention and treatment of fibrotic diseases remain poorly developed. Recent reports suggest that 5-methoxytryptophan (5-MTP) is effective in attenuating injury-induced liver, kidney, cardiac and pulmonary fibrosis. It inhibits macrophage activation and blocks fibroblast differentiation to myofibroblasts. Furthermore, it inhibits hepatic stellate cell differentiation into myofibroblasts. As 5-MTP is an endogenous molecule derived from tryptophan catabolism via tryptophan hydroxylase pathway, it is well-suited as a lead compound for developing new anti-fibrotic drugs. This article provides an overview of 5-MTP synthesis, and a critical review of its anti-fibrotic activities. Its mechanisms of actions and potential therapeutic value will be discussed.

Anti-inflammation treatment for protection of hepatocytes and amelioration of hepatic fibrosis in rats

Chronic inflammation is considered as an important pathophysiologic mechanism of hepatic cirrhosis, which induces hepatocyte injury and activates hepatic stellate cells (HSCs), thus resulting in hepatic fibrosis. Previous studies have reported that cyclooxygenase-2 (COX-2) inhibitor can effectively treat liver fibrosis, while somatostatin (SST) analogues inhibit the activation of HSCs. The present study aimed to investigate the effects of a COX-2 inhibitor, celecoxib, combined with a SST analogue, octreotide, for protection of hepatocytes and prevention of fibrosis in a rat model of hepatic fibrosis. Therefore, a hepatic fibrosis rat model was established following peritoneal injection of thioacetamide (TAA), and the rats were then treated with a combination of celecoxib and octreotide (TAA + C). Immunohistochemistry and western blotting assays were used to assess the expression levels of proteins associated with inflammation, epithelial-mesenchymal transition (EMT), proliferation, apoptosis and autophagy. H&E staining, transmission electron microscopy and scanning electron microscopy were used to evaluate the destruction of hepatocytes. Masson's Trichrome and Sirius Red were used to measure the degree of liver fibrosis. The results demonstrated that, compared with those of the control group, the degree of liver fibrosis and the expression of the intrahepatic inflammation factors were aggravated in the TAA group. Furthermore, the apoptosis rate, EMT and autophagy of hepatocytes were also increased in the TAA group. However, treatment with TAA + C restored the aforementioned increased levels compared with the TAA group. In conclusion, treatment of rats with the combination of celecoxib and octreotide could attenuate the progress of hepatic fibrosis via protection of hepatocytes by reducing apoptosis, EMT and autophagy in hepatocytes.