The Apelin-Apelin Receptor Axis Triggers Cholangiocyte Proliferation and Liver Fibrosis During Mouse Models of Cholestasis

Spatiotemporal evolutionary process of osteosarcoma immune microenvironment remodeling and C1QBP-driven drug resistance deciphered through single-cell multi-dimensional analysis

The tumor immune microenvironment has manifested a crucial correlation with tumor occurrence, development, recurrence, and metastasis. To explore the mechanisms intrinsic to osteosarcoma (OS) initiation and progression, this study synthesizes multiple single-cell RNA sequencing data sets, constructing a comprehensive landscape of the OS microenvironment. Integrating single-cell RNA sequencing with bulk RNA sequencing data has enabled the identification of a significant correlation between heightened expression of the fatty acid metabolism-associated gene (C1QBP) and patient survival in OS. C1QBP not only amplifies the proliferation, migration, invasion, and anti-apoptotic properties of OS but also instigates cisplatin resistance. Subsequent investigations suggest that C1QBP potentially promotes macrophage polarization from monocytes/macrophages toward M2 and M3 phenotypes. Consequently, C1QBP may emerge as a novel target for modulating OS progression and resistance therapy.

ROS-responsive nanoparticle delivery of obeticholic acid mitigate primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is a challenging cholestatic liver disease marked by progressive bile duct inflammation and fibrosis that has no FDA-approved therapy. Although obeticholic acid (OCA) has been sanctioned for PSC, its clinical utility in PSC is constrained by its potential hepatotoxicity. Here, we introduce a novel therapeutic construct consisting of OCA encapsulated within a reactive oxygen species (ROS)-responsive, biodegradable polymer, further cloaked with human placenta-derived mesenchymal stem cell (hP-MSC) membrane (MPPFTU@OCA). Using PSC patient-derived organoid models, we assessed its cellular uptake and cytotoxicity. Moreover, using a PSC mouse model induced by 3,5-diethoxycarbonyl-1,4-dihydro-collidine (DDC), we demonstrated that intravenous administration of MPPFTU@OCA not only improved cholestasis via the FXR-SHP pathway but also reduced macrophage infiltration and the accumulation of intracellular ROS, and alleviated mitochondria-induced apoptosis. Finally, we verified the ability of MPPFTU@OCA to inhibit mitochondrial ROS thereby alleviating apoptosis by measuring the mitochondrial adenosine triphosphate (ATP) concentration, ROS levels, and membrane potential (ΔΨm) using H2O2-stimulated PSC-derived organoids. These results illuminate the synergistic benefits of integrating an ROS-responsive biomimetic platform with OCA, offering a promising therapeutic avenue for PSC.

Exploring the role of ITGB6: fibrosis, cancer, and other diseases

Integrin β6 (ITGB6), a member of the integrin family of proteins, is only present in epithelial tissues and frequently associates with integrin subunit αv to form transmembrane heterodimers named integrin αvβ6. Importantly, ITGB6 determines αvβ6 expression and availability. In addition to being engaged in organ fibrosis, ITGB6 is also directly linked to the emergence of cancer, periodontitis, and several potential genetic diseases. Therefore, it is of great significance to study the molecular-biological mechanism of ITGB6, which could provide novel insights for future clinical diagnosis and therapy. This review introduces the structure, distribution, and biological function of ITGB6. This review also expounds on ITGB6-related diseases, detailing the known biological effects of ITGB6.

APLN promotes the proliferation, migration, and glycolysis of cervical cancer through the PI3K/AKT/mTOR pathway

Apelin (APLN) is an endogenous ligand of the G protein-coupled receptor APJ (APLNR). APLN has been implicated in the development of multiple tumours. Herein, we determined the effect of APLN on the biological behaviour and underlying mechanisms of cervical cancer. The expression and survival curves of APLN were determined using Gene Expression Profiling Interactive Analysis. The cellular functions of APLN were detected using CCK-8, clone formation, EdU, Transwell assays, flow cytometry, and seahorse metabolic analysis. The underlying mechanisms were elucidated using gene set enrichment analysis and Western blotting. APLN was upregulated in the samples of patients with cervical cancer and is associated with poor prognosis. APLN knockdown decreased the proliferation, migration, and glycolysis of cervical cancer cells. The opposite results were observed when APLN was overexpressed. Mechanistically, we determined that APLN was critical for activating the PI3K/AKT/mTOR pathway via APLNR. APLN receptor inhibitor ML221 reversed the effect of APLN overexpression on cervical cancer cells. Treatment with LY294002, the PI3K inhibitor, drastically reversed the oncological behaviour of APLN-overexpressing C-33A cells. APLN promoted the proliferation, migration, and glycolysis of cervical cancer cells via the PI3K/AKT/mTOR pathway.

Targeting a cardiac abundant and fibroblasts-specific piRNA (CFRPi) to attenuate and reverse cardiac fibrosis in pressure-overloaded heart failure

Cardiac fibrosis under chronic pressure overload is an end-stage adverse remodeling of heart. However, current heart failure treatments barely focus on anti-fibrosis and the effects are limited. We aimed to seek for a cardiac abundant and cardiac fibrosis specific piRNA, exploring its underlying mechanism and therapeutic potential. Whole transcriptome sequencing and the following verification experiments identified a highly upregulated piRNA (piRNA-000691) in transverse aortic constriction (TAC) mice, TAC pig, and heart failure human samples, which was abundant in heart and specifically expressed in cardiac fibroblasts. CFRPi was gradually increased along with the progression of heart failure, which was illustrated to promote cardiac fibrosis by gain- and loss-of-function experiments in vitro and in vivo. Knockdown of CFRPi in mice alleviated cardiac fibrosis, reversed decline of systolic and diastolic functions from TAC 6 weeks to 8 weeks. Mechanistically, CFRPi inhibited APLN, a protective peptide that increased in early response and became exhausted at late stage. Knockdown of APLN in vitro notably aggravated cardiac fibroblasts activation and proliferation. In vitro and in vivo evidence both indicated Pi3k-AKT-mTOR as the downstream effector pathway of CFRPi-APLN interaction. Collectively, we here identified CFPPi as a heart abundant and cardiac fibrosis specific piRNA. Targeting CFRPi resulted in a sustainable increase of APLN and showed promising therapeutical prospect to alleviate fibrosis, rescue late-stage cardiac dysfunction, and prevent heart failure.

An On-Demand Collaborative Innate-Adaptive Immune Response to Infection Treatment

Deep tissue infection is a common clinical issue and therapeutic difficulty caused by the disruption of the host antibacterial immune function, resulting in treatment failure and infection relapse. Intracellular pathogens are refractory to elimination and can manipulate host cell biology even after appropriate treatment, resulting in a locoregional immunosuppressive state that leads to an inadequate response to conventional anti-infective therapies. Here, a novel antibacterial strategy involving autogenous immunity using a biomimetic nanoparticle (NP)-based regulating system is reported to induce in situ collaborative innate-adaptive immune responses. It is observed that a macrophage membrane coating facilitates NP enrichment at the infection site, followed by active NP accumulation in macrophages in a mannose-dependent manner. These NP-armed macrophages exhibit considerably improved innate capabilities, including more efficient intracellular ROS generation and pro-inflammatory factor secretion, M1 phenotype promotion, and effective eradication of invasive bacteria. Furthermore, the reprogrammed macrophages direct T cell activation at infectious sites, resulting in a robust adaptive antimicrobial immune response to ultimately achieve bacterial clearance and prevent infection relapse. Overall, these results provide a conceptual framework for a novel macrophage-based strategy for infection treatment via the regulation of autogenous immunity.

Chuanxiong Rhizoma extracts prevent liver fibrosis via targeting CTCF-c-MYC-H19 pathway

Objective

Hepatic fibrosis has been widely considered as a conjoint consequence of almost all chronic liver diseases. Chuanxiong Rhizoma (Chuanxiong in Chinese, CX) is a traditional Chinese herbal product to prevent cerebrovascular, gynecologic and hepatic diseases. Our previous study found that CX extracts significantly reduced collagen contraction force of hepatic stellate cells (HSCs). Here, this study aimed to compare the protection of different CX extracts on bile duct ligation (BDL)-induced liver fibrosis and investigate plausible underlying mechanisms.

Methods

The active compounds of CX extracts were identified by high performance liquid chromatography (HPLC). Network pharmacology was used to determine potential targets of CX against hepatic fibrosis. Bile duct hyperplasia and liver fibrosis were evaluated by serologic testing and histopathological evaluation. The expression of targets of interest was determined by quantitative real-time PCR (qPCR) and Western blot.

Results

Different CX extracts were identified by tetramethylpyrazine, ferulic acid and senkyunolide A. Based on the network pharmacological analysis, 42 overlap targets were obtained via merging the candidates targets of CX and liver fibrosis. Different aqueous, alkaloid and phthalide extracts of CX (CXAE, CXAL and CXPHL) significantly inhibited diffuse severe bile duct hyperplasia and thus suppressed hepatic fibrosis by decreasing CCCTC binding factor (CTCF)-c-MYC-long non-coding RNA H19 (H19) pathway in the BDL-induced mouse model. Meanwhile, CX extracts, especially CXAL and CXPHL also suppressed CTCF-c-MYC-H19 pathway and inhibited ductular reaction in cholangiocytes stimulated with taurocholate acid (TCA), lithocholic acid (LCA) and transforming growth factor beta (TGF-β), as illustrated by decreased bile duct proliferation markers.

Conclusion

Our data supported that different CX extracts, especially CXAL and CXPHL significantly alleviated hepatic fibrosis and bile duct hyperplasia via inhibiting CTCF-c-MYC-H19 pathway, providing novel insights into the anti-fibrotic mechanism of CX.

Effects of Apelin on the fibrosis of retinal tissues and Müller cells in diabetes retinopathy through the JAK2/STAT3 signalling pathway

Retinal fibrosis was a key characteristic of diabetes retinopathy (DR). Apelin was found to be a candidate for tissue fibrosis. Nevertheless, the role of Apelin in the Müller cells in DR remains unclear. This study identified the function and mechanism of Apelin in Müller cells and the fibrosis of retinal tissue. Western blot was carried out to detect the Apelin, GFAP, Collagen I, α-SMA, JAK2 and STAT3 protein levels. Masson staining was performed to display the histopathological changes in retinal tissue of diabetic mellitus (DM) rats. The immunofluorescence staining was conducted to evaluate the Apelin levels in the retinal tissue. The levels of GFAP, Collagen I and α-SMA in the retinal tissue of DM rats was visualised by the immunohistochemistry staining. The results showed that Apelin, GFAP, Collagen I andα-SMA expression was prominently elevated in the retinal tissue of DM rats and high glucose (HG)-exposed Müller cells. The results of Masson staining showed that the epiretinal fibrotic membrane was observed in DM rats. Apelin knockdown declined the GFAP, Collagen I andα-SMA levels. Besides, the protein levels of p-JAK2 and p-STAT3 were elevated in the HG-treated Müller cells, while Apelin knockdown declined them. FLLL32 treatment neutralised the role of Apelin. In conclusion, Apelin facilitated the fibrogenic activity of Müller cells through activating the JAK2/STAT3 signalling pathway, and thus inducing the retinal fibrosis in DR.

JNKs protect from cholestatic liver disease progression by modulating Apelin signalling

Background & Aims

Cholestatic liver injury is associated with c-Jun N-terminal kinases (JNK) activation in distinct cell types. Its hepatocyte-specific function during cholestasis, however, has not yet been established. Therefore, in our present study, we investigated the role of JNK1/2 during cholestasis and dissected its hepatocyte-specific function.

Methods

A cohort of patients with primary biliary cholangitis (n = 29) and primary sclerosing cholangitis (n = 37) was examined. Wild-type, hepatocyte-specific knockout mice for Jnk2 (Jnk2Δhepa) or Jnk1 and Jnk2 (Jnk1Δhepa/2Δhepa) were generated. Mice were subjected to bile duct ligation (BDL) or carbon tetrachloride (CCl4) treatment. Finally, Apelin signalling was blocked using a specific inhibitor. As an interventional approach, Jnk1/2 were silenced in wild-type mice using lipid nanoparticles for small interfering RNA delivery.

Results

JNK activation was increased in liver specimens from patients with chronic cholestasis (primary biliary cholangitis and primary sclerosing cholangitis) and in livers of Mdr2-/- and BDL-treated animals. In Jnk1Δhepa/2Δhepa animals, serum transaminases increased after BDL, and liver histology demonstrated enhanced cell death, compensatory proliferation, hepatic fibrogenesis, and inflammation. Furthermore, microarray analysis revealed that hepatocytic Jnk1/2 ablation induces JNK-target genes involved in oxidative stress and Apelin signalling after BDL. Consequently, blocking Apelin signalling attenuated BDL-induced liver injury and fibrosis in Jnk1Δhepa/2Δhepa mice. Finally, we established an interventional small interfering RNA approach of selective Jnk1/2 targeting in hepatocytes in vivo, further demonstrating the essential protective role of Jnk1/2 during cholestasis.

Conclusions

Jnk1 and Jnk2 work together to protect hepatocytes from cholestatic liver disease by controlling Apelin signalling. Dual modification of JNK signalling in hepatocytes is feasible, and enhancing its expression might be an attractive therapeutic approach for cholestatic liver disease.

Impact and Implications

The cell-specific function of Jnk genes during cholestasis has not been explicitly explored. In this study, we showed that combined Jnk1/2, but not Jnk2 deficiency, in hepatocytes exacerbates liver damage and fibrosis by enhancing Apelin signalling, which contributes to cholestasis progression. Combined cell-specific Jnk targeting may be a new molecular strategy for treating cholestatic liver disease.

FOXC2-AS1/FOXC2 axis mediates matrix stiffness-induced trans-differentiation of hepatic stellate cells into fibrosis-promoting myofibroblasts

Matrix stiffness is a central modulator of hepatic stellate cells (HSCs) activation and hepatic fibrogenesis. However, the long non-coding RNAs (lncRNAs)-regulated transcriptional factors linking matrix stiffness to alterations in HSCs phenotype are not completely understood. In this study, we investigated the effects of matrix stiffness on HSCs activation and its potential mechanism. Through analysis the RNA-seq data with human primary HSCs cultured on 0.4 kPa and 25.6 kPa hydrogel, we identified that forkhead box protein C2 (FOXC2) and its antisense lncRNA FXOC2-AS1 as the new mechanosensing transcriptional regulators that coordinate HSCs responses to the matrix stiffness, moreover, FOXC2 and FOXC2-AS1 expression were also elevated in human fibrosis and cirrhosis tissues. The matrix stiffness was sufficient to activate HSCs into myofibroblasts, resulting in nuclear accumulation of FOXC2. Disrupting FOXC2 and FOXC2-AS1 level abrogated stiffness-induced activation of HSCs. Further mechanistic studies displayed that stiffness-upregulated lncRNA FOXC2-AS1 had no influence on transcription of FOXC2. FOXC2-AS1 exerted its biological function through maintaining the RNA stability of FOXC2, and protecting FOXC2 mRNA from degradation by RNA exosome complex. Additionally, rescue assays confirmed that reintroduction of FOXC2 in FOXC2-AS1-depleted HSCs reversed the repression of FOXC2-AS1 knockdown on stiffness-induced HSCs activation. In AAV6-treated mice fibrotic models, targeting FOXC2 in vivo lead to a reduced degree of liver fibrosis. In sum, our study uncovers a reciprocal crosstalk between matrix stiffness and FOXC2-AS1/FOXC2 axis leading to modulation of HSCs mechanoactivation and liver fibrosis, and present AAV6 shRNA as an effective strategy that targets FOXC2 leading to the resolution of liver fibrosis.

Targeting endothelial coagulation signaling ameliorates liver obstructive cholestasis and dysfunctional angiogenesis

Cholestatic fibrogenesis is a pathobiological process in which cumulative injury to the bile ducts coincides with progressive liver fibrosis. The pathobiologic mechanisms underlying fibrogenesis and disease progression remain poorly understood. Currently, there is no effective treatment for liver fibrosis. In this study, we discovered that components of the coagulation cascade were associated with the advanced progression of obstructive cholestasis, and anticoagulant therapy could improve liver cholestasis-induced fibrosis. In a mouse model of common bile duct ligation (BDL), which mimics cholestatic liver injury, RNA sequencing analysis revealed an increased expression of coagulation factors in endothelial cells. Pharmacological targeting of the coagulation signaling by hirudin, an anticoagulatory antagonist of thrombin, ameliorated obstructive cholestasis, and attenuated liver fibrosis symptoms. Hirudin attenuated fibrosis-associated angiogenesis, endothelial-to-mesenchymal transition (EndMT), and tissue hypoxia and reduced liver inflammation after BDL. Furthermore, hirudin suppressed YAP (Yes-associated protein) signaling and its downstream effectors in vascular endothelial cells, which are considered with profibrotic characteristics. In conclusion, we demonstrated that pharmacological targeting of coagulation signaling by hirudin has the potential to alleviate liver obstructive cholestasis and fibrosis.

P4HA2 induces hepatic ductular reaction and biliary fibrosis in chronic cholestatic liver diseases

BACKGROUNDS

Prolyl-4-hydroxylases (P4Hs) are key enzymes in collagen synthesis. The P4HA subunit (P4HA1, P4HA2, and P4HA3) contains a substrate binding and catalyzation domain. We postulated that P4HA2 would play a key role in the cholangiocyte pathology of cholestatic liver diseases.

METHODS

We studied humans with primary biliary cholangitis (PBC) and Primary sclerosing cholangitis (PSC), P4HA2 -/- mice injured by DDC, and P4HA2 -/- /MDR2 -/- double knockout mice. A parallel study was performed in patients with PBC, PSC, and controls using immunohistochemistry and immunofluorescence. In the murine model, the level of ductular reaction and biliary fibrosis were monitored by histology, qPCR, immunohistochemistry, and Western blotting. Expression of Yes1 Associated Transcriptional Regulator (YAP) phosphorylation was measured in isolated mouse cholangiocytes. The mechanism of P4HA2 was explored in RBE and 293T cell lines by using qPCR, Western blot, immunofluorescence, and co-immunoprecipitation.

RESULTS

The hepatic expression level of P4HA2 was highly elevated in patients with PBC or PSC. Ductular reactive cholangiocytes predominantly expressed P4HA2. Cholestatic patients with more severe liver injury correlated with levels of P4HA2 in the liver. In P4HA2 -/- mice, there was a significantly reduced level of ductular reaction and fibrosis compared with controls in the DDC-induced chronic cholestasis. Decreased liver fibrosis and ductular reaction were observed in P4HA2 -/- /MDR2 -/- mice compared with MDR2 -/- mice. Cholangiocytes isolated from P4HA2 -/- /MDR2 -/- mice displayed a higher level of YAP phosphorylation, resulting in cholangiocytes proliferation inhibition. In vitro studies showed that P4HA2 promotes RBE cell proliferation by inducing SAV1 degradation, eventually resulting in the activation of YAP.

CONCLUSIONS

P4HA2 promotes hepatic ductular reaction and biliary fibrosis by regulating the SAV1-mediated Hippo signaling pathway. P4HA2 is a potential therapeutic target for PBC and PSC.

Ductular reaction in non-alcoholic fatty liver disease: When Macbeth is perverted

Non-alcoholic fatty liver disease (NAFLD) or metabolic (dysfunction)-associated fatty liver disease is the leading cause of chronic liver diseases defined as a disease spectrum comprising hepatic steatosis, non-alcoholic steatohepatitis (NASH), liver fibrosis, cirrhosis, and hepatic carcinoma. NASH, characterized by hepatocyte injury, steatosis, inflammation, and fibrosis, is associated with NAFLD prognosis. Ductular reaction (DR) is a common compensatory reaction associated with liver injury, which involves the hepatic progenitor cells (HPCs), hepatic stellate cells, myofibroblasts, inflammatory cells (such as macrophages), and their secreted substances. Recently, several studies have shown that the extent of DR parallels the stage of NASH and fibrosis. This review summarizes previous research on the correlation between DR and NASH, the potential interplay mechanism driving HPC differentiation, and NASH progression.

Bile acid-mediated signaling in cholestatic liver diseases

Chronic cholestatic liver diseases, such as primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC), are associated with bile stasis and gradually progress to fibrosis, cirrhosis, and liver failure, which requires liver transplantation. Although ursodeoxycholic acid is effective in slowing the disease progression of PBC, it has limited efficacy in PSC patients. It is challenging to develop effective therapeutic agents due to the limited understanding of disease pathogenesis. During the last decade, numerous studies have demonstrated that disruption of bile acid (BA) metabolism and intrahepatic circulation promotes the progression of cholestatic liver diseases. BAs not only play an essential role in nutrition absorption as detergents but also play an important role in regulating hepatic metabolism and modulating immune responses as key signaling molecules. Several excellent papers have recently reviewed the role of BAs in metabolic liver diseases. This review focuses on BA-mediated signaling in cholestatic liver disease.

Apelin Receptor Can Act as a Specific Marker and Promising Therapeutic Target for Infantile Hemangioma

Infantile hemangioma (IH), the most common benign tumor in infancy, is generally sensitive to propranolol treatment. However, the challenge remains because resistance or recurrence could occur in some patients, and the mechanism or target of propranolol remains unknown. Therefore, advancement in the drug development is needed. In this study, we explored whether apelin receptor (APJ) can become a candidate target. We found that APJ is expressed only in endothelial cells of IH (HemECs) but not in other vascular anomalies, and its antagonist, ML221, can negatively regulate cellular viability and functions of HemECs. This inhibitory effect could be replicated in a murine hemangioma model. Importantly, in vitro experiments also indicated that ML221 failed to affect the proliferation or angiogenesis of normal endothelial cells or APJ-knockout HemECs. Through analysis of the phosphoantibody microarray data, ML221 was revealed to have an inhibitory effect on HemECs by suppressing the activation of mitogen-activated protein kinase/extracellular signal-regulated kinase pathway. These results verified the distinctive expression of APJ in IH and specific inhibition of HemEC activity caused by ML221. In addition, APJ was also detected in propranolol-resistant IH. Collectively, we propose that APJ can act as a specific marker and a promising therapeutic target for IH, which will facilitate further drug development.

Identification of AKR1B10 as a key gene in primary biliary cholangitis by integrated bioinformatics analysis and experimental validation

Background: Primary biliary cholangitis (PBC) is a chronic autoimmune liver disease that eventually progresses to cirrhosis and hepatocellular carcinoma (HCC) in the absence of proper treatment. However, Gene expression and molecular mechanisms involved in the pathogenesis of PBC have not been completely elucidated. Methods: Microarray expression profiling dataset GSE61260 was downloaded from the Gene Expression Omnibus (GEO) database. Data were normalized to screen differentially expressed genes (DEGs) using the limma package in R. Moreover, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes pathway (KEGG) enrichment analyses were performed. A protein-protein interaction (PPI) network was constructed to identify hub genes and an integrative regulatory network of transcriptional factor-DEG-microRNA was established. Gene Set Enrichment Analysis (GSEA) was used to analyze differences in biological states for groups with different expressions of aldo-keto reductase family 1 member B10 (AKR1B10). Immunohistochemistry (IHC) analysis was performed to validate the expression of hepatic AKR1B10 in patients with PBC. The association of hepatic AKR1B10 levels with clinical parameters was evaluated using one-way analysis of variance (ANOVA) and Pearson's correlation analysis. Results: This study identified 22 upregulated and 12 downregulated DEGs between patients with PBC and healthy controls. GO and KEGG analysis revealed that DEGs were mainly enriched in immune reactions. AKR1B10 was identified as a key gene and was further analyzed by screening out hub genes from the PPI network. GSEA analysis indicated that high expression of AKR1B10 might promote PBC to develop into HCC. Immunohistochemistry results verified the increased expression of hepatic AKR1B10 in patients with PBC and demonstrated its positive correlation with the severity of PBC. Conclusion: AKR1B10 was identified as a hub gene in PBC by integrated bioinformatics analysis and clinical validation. The increase of AKR1B10 expression in patients with PBC was associated with disease severity and might promote the progression of PBC to HCC.

Targeting adipokines in polycystic ovary syndrome and related metabolic disorders: from experimental insights to clinical studies

Polycystic ovary syndrome (PCOS) affects approximately 15% of women of reproductive age worldwide. It is the most prevalent endocrine disorder with marked risks for female infertility, type 2 diabetes mellitus (T2DM), psychiatric disorders and gynecological cancers. Although the pathophysiology of PCOS remains largely elusive, growing evidence suggests a close link with obesity and its related metabolic disorders. As a highly active endocrine cell population, hypertrophic adipocytes in obesity have disturbed production of a vast array of adipokines, biologically active peptides that exert pleiotropic effects on homeostatic regulation of glucose and lipid metabolism. In parallel with their crucial roles in the pathophysiology of obesity-induced metabolic diseases, adipokines have recently been identified as promising targets for novel therapeutic strategies for multiple diseases. Current treatments for PCOS are suboptimal with insufficient alleviation of all symptoms. Novel findings in adipokine-targeted agents may provide important insight into the development of new drugs for PCOS. This Review presents an overview of the current understanding of mechanisms that link PCOS to obesity and highlights emerging evidence of adipose-ovary crosstalk as a pivotal mediator of PCOS pathogenesis. We summarize recent findings of preclinical and clinical studies that reveal the therapeutic potential of adipokine-targeted novel approaches to PCOS and its related metabolic disorders. We also discuss the critical gaps in knowledge that need to be addressed to guide the development of adipokine-based novel therapies for PCOS.

Apelin-13 Protects Neurons by Attenuating Early-Stage Postspinal Cord Injury Apoptosis In Vitro

Apelin is a 77-amino-acid peptide that is an endogenous ligand for the G protein-coupled receptor APJ (Apelin receptor, APJ). Apelin-13, as the most bioactive affinity fragment of apelin, plays a role in energy metabolism, myocardial ischemia-reperfusion injury, and the regulation of the inflammatory response during oxidative stress, but its role in spinal cord injury is still unclear. This research identified and verified the differential expression of apelin in rat spinal cord injured tissues and normal spinal cord tissues by transcriptome sequencing in vivo and proved that apelin-13 protects neurons by strengthening autophagy and attenuating early-stage postspinal cord injury apoptosis in vitro. After constructing the model concerning a rat spinal cord hemisection damage, transcriptome sequencing was performed on the injured and normal spinal cord tissues of rats, which identified the differentially expressed gene apelin, with qRT-PCR detecting the representative level of apelin. The oxygen-glucose deprivation (OGD) model of PC12 cells was constructed in vitro to simulate spinal cord injury. The OGD injury times were 2 h, 4 h, 6 h, 8 h, and 12 h, and the non-OGD injury group was used as the control. The expression of apelin at each time point was observed by Western blotting. The expression of apelin was the lowest in the 6 h OGD injury group (p < 0.05). Therefore, the OGD injury time of 6 h was used in subsequent experiments. The noncytotoxic drug concentration of apelin-13 was determined with a Cell Counting Kit-8 (CCK-8) assay. An appropriate dose of apelin-13 (1 μM) significantly improved cell survival (p < 0.05). Thus, subsequent experiments selected a concentration of 1 μM apelin-13 as it significantly increased cell viability. Finally, we divided the experimental groups into four groups according to whether they received drugs (1 μM apelin-13, 24 h) or OGD (6 h): (1) control group: without apelin-13 or OGD injury; (2) apelin-13 group: with apelin-13 but no OGD injury; (3) OGD group: with OGD injury but without apelin-13; and (4) OGD + apelin-13 group: with apelin-13 and OGD injury. The TUNEL assay and flow cytometry results showed that compared with the OGD group, apoptosis in the OGD+Apelin-13 group was significantly reduced (p < 0.001). Determination of cell viability under different conditions by CCK-8 assay results displays that Apelin-13 can significantly improve the cell viability percentage under OGD conditions (p < 0.001). Western blotting results showed that apelin-13 decreased the expression ratios of apoptosis-related proteins Bax/Bcl-2 and cleaved-caspase3/caspase3 (p < 0.05), increasing the key to Beclin1-dependent autophagy pathway expression of the protein Beclin1. This finding indicates that apelin-13 protects neurons by strengthening autophagy and attenuating early-stage postspinal cord injury apoptosis in vitro.

ERK inhibition reduces neuronal death and ameliorates inflammatory responses in forebrain-specific Ppp2cα knockout mice

It has been shown that PP2A is critical for apoptosis in neural progenitor cells. However, it remains unknown whether PP2A is required for neuronal survival. To address this question, we generated forebrain-specific Ppp2cα knockout (KO) mice. We show that Ppp2cα KO mice display robust neuronal apoptosis and inflammatory responses in the postnatal cortex. Previous evidence has revealed that PD98059 is a potent ERK inhibitor and may protect the brain against cell death after cardiac arrest. To study whether PD98059 may have any effects on Ppp2cα KO mice, the latter was treated with this inhibitor. We demonstrated that the total number of cleaved caspase3 positive (+) cells in the cortex was significantly reduced in Ppp2cα KO mice treated with PD98059 compared with those without PD98059 treatment. We observed that the total number of IBA1+ cells in the cortex was significantly decreased in Ppp2cα KO mice treated with PD98059. Mechanistic analysis reveals that deletion of PP2Aca causes DNA damage, which may be attenuated by PD98059. Together, this study suggests that inhibition of ERK may be an effective strategy to reduce cell death in brain diseases with abnormal neuronal apoptosis.

The Apelin-APJ axis alleviates LPS-induced pulmonary fibrosis and endothelial mesenchymal transformation in mice by promoting Angiotensin-Converting Enzyme 2

Fibrotic alterations resulting from abnormal tissue repair after lung injury are responsible for the high mortality observed after acute respiratory distress syndrome. Therefore, the prevention and treatment of pulmonary fibrosis has been widely concerned. The Apelin-APJ axis plays an important role in the prevention and treatment of respiratory diseases and organ fibrosis. However, its underlying mechanism remains to be further studied. The aim of this study was to investigate whether the anti-pulmonary fibrosis effect of apelin-APJ axis is related to the activation of angiotensin-converting Enzyme 2 (ACE2). Here, we found that exogenous activation of the Apelin-APJ axis alleviates lipopolysaccharide (LPS)-induced pulmonary fibrosis in mice. In vitro studies revealed that Apelin-13 inhibited LPS-induced endothelial mesenchymal transition in lung microvascular endothelial cells, whereas [Ala13]-Apelin-13 (Apelin-APJ axis inhibitor) accelerated LPS-induced endothelial interstitial transformation in lung microvascular endothelial cells. Notably, angiotensin-converting enzyme 2 (ACE2) inhibitor blocks the beneficial effect of the Apelin-APJ axis activation on LPS-induced pulmonary fibrosis. This finding suggests that the Apelin-APJ axis inhibits pulmonary fibrosis by activating ACE2. Simultaneously, accumulating evidence suggests that ubiquitination may contribute to pulmonary fibrosis. Our study found that LPS increased the ubiquitination of ACE2 protein, whereas Apelin-13 inhibited it. In conclusion, exogenous activation of the Apelin-APJ axis improves LPS-induced pulmonary fibrosis in mice and may be a viable therapeutic target for pulmonary fibrosis.

Recent discoveries in microbiota dysbiosis, cholangiocytic factors, and models for studying the pathogenesis of primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is a cholangiopathy caused by genetic and microenvironmental changes, such as bile homeostasis disorders and microbiota dysbiosis. Therapeutic options are limited, and proven surveillance strategies are currently lacking. Clinically, PSC presents as alternating strictures and dilatations of biliary ducts, resulting in the typical “beaded” appearance seen on cholangiography. The pathogenesis of PSC is still unclear, but cholangiocytes play an essential role in disease development, wherein a reactive phenotype is caused by the secretion of neuroendocrine factors. The liver–gut axis is implicated in the pathogenesis of PSC owing to the dysbiosis of microbiota, but the underlying mechanism is still poorly understood. Alterations in cholangiocyte responses and related signalling pathways during PSC progression were elucidated by recent research, providing novel therapeutic targets. In this review, we summarise the currently known underlying mechanisms of PSC pathogenesis caused by the dysbiosis of microbiota and newly reported information regarding cholangiocytes in PSC. We also summarise recently reported in vitro and in vivo models for studying the pathogenesis of PSC.

Cellular senescence in the cholangiopathies

PURPOSE OF REVIEW

Cellular senescence (i.e. permanent withdrawal from the cell cycle) is increasingly recognized as a pathologic feature in a variety of inflammatory liver diseases, including primary sclerosing cholangitis (PSC), primary biliary cholangitis (PBC) and additional cholangiopathies. Herein, we provide an update on the interplay between cholangiocytes, cellular senescence and the cholangiopathies.

RECENT FINDINGS

The themes covered by this review include novel models for studying the role of senescent cholangiocytes and the cholangiopathies, identification and modulation of key pathways or molecules regulating cholangiocyte senescence, and discovery of druggable targets to advance therapeutic options for the cholangiopathies. Most recent studies focused on PSC; however, the concepts and findings may be applied to additional cholangiopathies.

SUMMARY

Cholangiopathies present unique and divergent clinicopathological features, causes and genetic backgrounds, but share several common disease processes. Cholangiocyte senescence in the cholestatic cholangiopathies, primarily PSC and PBC, is regarded as a key pathogenetic process. Importantly, senescent cholangiocytes exhibit phenotypic features including the senescence-associated secretory phenotype (SASP) and resistance to apoptosis that provide new directions for basic research and new prognostic and therapeutic approaches for clinical practice.

Predictive and Diagnostic Value of Serum Adipokines in Pregnant Women with Intrahepatic Cholestasis

The objective of this study was to assess the value of serum leptin, adiponectin, apelin, and ghrelin as biomarkers for the prediction and diagnosis of intra-hepatic cholestasis (ICP). This prospective study included pregnant women in the third trimester of pregnancy: 63 with ICP, 48 and 15 of whom had mild and severe disease, respectively, and 32 as controls. ICP women had increased median levels of serum leptin, adiponectin, apelin, and ghrelin compared to the controls (p < 0.05). These biomarkers meaningfully changed regarding the severity of ICP: While leptin was reduced, apelin and ghrelin were increased, and adiponectin was increased somewhat. To predict and diagnose ICP, the predictive values of serum leptin, adiponectin, and apelin need to be accepted as comparable, with moderate to high sensitivity and specificity; however, the predictive value of serum ghrelin was somewhat lower. More research is needed to clarify the potential properties of adipokines to gain acceptance as a predictive or diagnostic biomarker for ICP.

NOX4: a potential therapeutic target for pancreatic cancer and its mechanism

Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 4 (NOX4) is one of the seven isoforms of NOX family, which is upregulated in pancreatic cancer cell, mouse model of pancreatic cancer and human pancreatic cancer tissue. NOX4 is a constitutively active enzyme that primarily produces hydrogen peroxide, which exhibits completely different properties from other subtypes of NOX family. More importantly, recent studies illuminate that NOX4 promotes pancreatic cancer occurrence and development in different ways. This review summarizes the potential roles and its mechanism of NOX4 in pancreatic cancer and explores NOX4 as the potential therapeutic target in pancreatic cancer.

Elevated reactivity of Apelin inhibited renal fibrosis induced by chronic intermittent hypoxia

BACKGROUND

Apelin and its receptor angiotensin receptor - like 1 (APJ) are closely related to renal fibrosis, but their specific roles in renal fibrosis are still controversial. In this article, we discussed the role of Apelin/APJ system in renal fibrosis and its mechanism.

METHODS

Chronic intermittent hypoxia (CIH) rat model was established to induce the environment of renal fibrosis and a competitive antagonist of the APJ receptor ML221 was administered to CIH rats. The rats were divided into Control, CIH and ML221 groups. HE staining was used to detect the inflammatory injury and fibrosis of renal tissue. The expressions of renal fibrosis-related indicators transforming growth factor-β (TGF-β), α-smooth muscle actin (α-SMA) and Human type I collagen (Col-Ⅰ) were detected by immunohistochemistry. The levels of oxidative stress indexes reactive oxygen species (ROS), Malondialdehyde (MDA), Superoxide Dismutase (SOD) and inflammation-related indexes Interleukin (IL) -6, tumor necrosis factor-α (TNF-α) and IL-1β were detected by ELISA. At the same time, the levels of Apelin-13 and AngiotensinII (AngⅡ) were also measured by ELISA. Finally, western blot was used to detect the expression of Apelin pathway and renal fibrosis-related proteins. In addition, at the cellular level, we divided the cells into Control, CIH, Apelin-13 and Apelin-13+ML-221 groups to further verify the specific mechanisms at the cellular level.

RESULTS

The expression of Apeline-13 and its related pathways was significantly increased after the induction of CIH in rats. However, the degree of renal fibrosis in ML221 group was further significantly increased after inhibiting the expression of Apelin. At the cellular level, CIH model cells treated with Apelin-13 significantly reduced cell proliferation, oxidative stress and inflammatory response, and decreased the expression of fibrosis-related proteins, which can be reversed by ML221 administration.

CONCLUSION

The increased reactivity of Apelin may be one of the protective mechanisms against renal fibrosis induced by CIH.

METTL3/N6-methyladenosine/ miR-21-5p promotes obstructive renal fibrosis by regulating inflammation through SPRY1/ERK/NF-κB pathway activation

Renal fibrosis induced by urinary tract obstruction is a common clinical occurrence; however, effective treatment is lacking, and a deeper understanding of the mechanism of renal fibrosis is needed. Previous studies have revealed that miR-21 impacts liver and lung fibrosis progression by activating the SPRY1/ERK/NF-kB signalling pathway. However, whether miR-21 mediates obstructive renal fibrosis through the same signalling pathway has not been determined. Additionally, studies have shown that N6-methyladenosine (m⁶ A) modification-dependent primary microRNA (pri-microRNA) processing is essential for maturation of microRNAs, but its role in the maturation of miR-21 in obstructive renal fibrosis has not yet been investigated in detail. To address these issues, we employed a mouse model of unilateral ureteral obstruction (UUO) in which the left ureters were ligated for 3, 7 and 14 days to simulate the fibrotic process. In vitro, human renal proximal tubular epithelial (HK-2) cells were transfected with plasmids containing the corresponding sequence of METTL3, miR-21-5p mimic or miR-21-5p inhibitor. We found that the levels of miR-21-5p and m⁶ A modification in the UUO model groups increased significantly, and as predicted, the SPRY1/ERK/NF-kB pathway was activated by miR-21-5p, confirming that miR-21-5p plays an important role in obstructive renal fibrosis by enhancing inflammation. METTL3 was found to play a major catalytic role in m⁶ A modification in UUO mice and drove obstructive renal fibrosis development by promoting miR-21-5p maturation. Our research is the first to demonstrate the role of the METTL3-m⁶ A-miR-21-5p-SPRY1/ERK/NF-kB axis in obstructive renal fibrosis and provides a deeper understanding of renal fibrosis.

New insights on the role of vascular endothelial growth factor in biliary pathophysiology

The family of vascular endothelial growth factors (VEGFs) includes 5 members (VEGF-A to -D, and placenta growth factor), which regulate several critical biological processes. VEGF-A exerts a variety of biological effects through high-affinity binding to tyrosine kinase receptors (VEGFR-1, -2 and -3), co-receptors and accessory proteins. In addition to its fundamental function in angiogenesis and endothelial cell biology, VEGF/VEGFR signalling also plays a role in other cell types including epithelial cells. This review provides an overview of VEGF signalling in biliary epithelial cell biology in both normal and pathologic conditions. VEGF/VEGFR-2 signalling stimulates bile duct proliferation in an autocrine and paracrine fashion. VEGF/VEGFR-1/VEGFR-2 and angiopoietins are involved at different stages of biliary development. In certain conditions, cholangiocytes maintain the ability to secrete VEGF-A, and to express a functional VEGFR-2 receptor. For example, in polycystic liver disease, VEGF secreted by cystic cells stimulates cyst growth and vascular remodelling through a PKA/RAS/ERK/HIF1α-dependent mechanism, unveiling a new level of complexity in VEFG/VEGFR-2 regulation in epithelial cells. VEGF/VEGFR-2 signalling is also reactivated during the liver repair process. In this context, pro-angiogenic factors mediate the interactions between epithelial, mesenchymal and inflammatory cells. This process takes place during the wound healing response, however, in chronic biliary diseases, it may lead to pathological neo-angiogenesis, a condition strictly linked with fibrosis progression, the development of cirrhosis and related complications, and cholangiocarcinoma. Novel observations indicate that in cholangiocarcinoma, VEGF is a determinant of lymphangiogenesis and of the immune response to the tumour. Better insights into the role of VEGF signalling in biliary pathophysiology might help in the search for effective therapeutic strategies.