Overexpression of Smad ubiquitin regulatory factor 2 suppresses transforming growth factor-β mediated liver fibrosis

Organelle stress and alterations in interorganelle crosstalk during liver fibrosis

The synchronous functioning and quality control of organelles ensure cell survival and function and are essential for maintaining homeostasis. Prolonged exposure to stressors (viruses, bacteria, parasitic infections, alcohol, drugs) or genetic mutations often disrupt the functional integrity of organelles which plays a critical role in the initiation and progression of several diseases including chronic liver diseases. One of the most important pathologic consequences of chronic liver diseases is liver fibrosis, characterized by tissue scarring due to the progressive accumulation of extracellular matrix components. Left untreated, fibrosis may advance to life-threatening complications such as cirrhosis, hepatic decompensation, and HCC, which collectively accounts for ∼1 million deaths per year worldwide. Owing to the lack of treatment options that can regress or reverse cirrhosis, liver transplantation is currently the only available treatment for end-stage liver disease. However, the limited supply of usable donor organs, adverse effects of lifelong immunosuppressive regimes, and financial considerations pose major challenges and limit its application. Hence, effective therapeutic strategies are urgently needed. An improved understanding of the organelle-level regulation of fibrosis can help devise effective antifibrotic therapies focused on reducing organelle stress, limiting organelle damage, improving interorganelle crosstalk, and restoring organelle homeostasis; and could be a potential clinical option to avoid transplantation. This review provides a timely update on the recent findings and mechanisms covering organelle-specific dysfunctions in liver fibrosis, highlights how correction of organelle functions opens new treatment avenues and discusses the potential challenges to clinical application.

Diagnosis and staging of HCV associated fibrosis, cirrhosis and hepatocellular carcinoma with target identification for miR-650, 552-3p, 676-3p, 512-5p and 147b

BACKGROUND: Chronic HCV infection progresses to fibrosis, cirrhosis and hepatocellular carcinoma (HCC). The latter represents the third most common cause for cancer mortality. Currently, there is no reliable non-invasive biomarker for diagnosis of HCV mediated disorders. OBJECTIVE: Profiling expression signature for circulatory miRNAs in the plasma of 167 Egyptian patients (40 healthy, 48 HCV fibrotic, 39 HCV cirrhotic and 40 HCV-HCC cases). METHODS: QRTPCR was used to quantify expression signature for circulatory miRNAs. RESULTS: MiR-676 and miR-650 were powerful in discriminating cirrhotic and late fibrosis from HCC. MiR-650 could distinguish mild (f0-f1) and advanced (f2-f3) fibrosis from HCC cases. MiR-650 and miR-147b could distinguish early fibrosis from healthy controls meanwhile miR-676 and miR-147b could effectively distinguish between mild chronic and (f1-f3) cases from healthy individuals. All studied miRNAs, except miR-512, can differentiate between (f0-f3) cases and healthy controls. Multivariate logistic regression revealed three potential miRNA panels for effective differentiation of HCC, cirrhotic and chronic liver cases. MiR-676-3p and miR-512-5p were significantly correlated in (f1-f3) fibrosis meanwhile miR-676 and miR-512 could differentiate between cirrhosis and (f0-f3) cases. Both miR-650 and miR-512-5p were positively correlated in the cirrhotic group and in (f0-f4) group. Putative targets for investigated miRNAs were also determined. CONCLUSIONS: Investigated miRNAs could assist in staging and diagnosis of HCV associated disorders.

Smad7 down-regulation via ubiquitin degradation mediated by Smurf2 in fibroblasts of hypertrophic scars in burned patients

TGF-β1 (transforming growth factor β1) was considered to play a critical role in the forming of hypertrophic scars. Smad, as a kind of signal downstream mediators, can modulate the functions of TGF-β1. Smad7 can regulate TGF-β1/Smad pathway and present negative feedbacks, which prevents fibrosis mediated by TGF-β1. Nonetheless, the mechanisms related to Smad7 activity in regulating hypertrophic scarring are hardly known. The studies have shown that Smad7 decrease induced by the increase of Smurf2 (Smad ubiquitination regulatory factor 2, an E3 ubiquitin ligase of Smad7) ubiquitination degradation plays a part in fibrosis. We thus made a hypothesis that Smad7 could not inhibit TGF-β1 because Smurf2 ubiquitin degradation was increased in hypertrophic scar fibroblasts. In our research, it was discovered that there was an increase in Smad7 mRNA levels but no increase in Smad7 protein levels in the fibroblasts of hypertrophic scars after TGF-β1 treatment. The ubiquitination activity and degradation of Smad7 protein were increased in the fibroblasts of hypertrophic scars compared with the fibroblasts of normal skin. Enhanced degradation of Smad7 protein in the fibroblasts of hypertrophic scars was prevented by proteasome inhibitors MG132 / MG115. Furthermore, it was found that TGF-β1 stimulation increased Smad7 protein expression after silencing Smurf2 gene in hypertrophic scar fibroblasts, and enhanced Smad7 degradation was prevented in hypertrophic scar fibroblasts after Smurf2 was silenced. It was implied that ubiquitin degradation mediated by Smurf2 might contribute to decreased Smad7 protein levels following TGF-β1 stimulation in the fibroblasts of hypertrophic scars.

Long noncoding RNA SMUL suppresses SMURF2 production-mediated muscle atrophy via nonsense-mediated mRNA decay

As the world population grows, muscle atrophy leading to muscle wasting could become a bigger risk. Long noncoding RNAs (lncRNAs) are known to play important roles in muscle growth and muscle atrophy. Meanwhile, it has recently come to light that many putative small open reading frames (sORFs) are hidden in lncRNAs; however, their translational capabilities and functions remain unclear. In this study, we uncovered 104 myogenic-associated lncRNAs translated, in at least a small peptide, by integrated transcriptome and proteomic analyses. Furthermore, an upstream ORF (uORF) regulatory network was constructed, and a novel muscle atrophy-associated lncRNA named SMUL (Smad ubiquitin regulatory factor 2 [SMURF2] upstream lncRNA) was identified. SMUL was highly expressed in skeletal muscle, and its expression level was downregulated during myoblast differentiation. SMUL promoted myoblast proliferation and suppressed differentiation in vitro. In vivo, SMUL induced skeletal muscle atrophy and promoted a switch from slow-twitch to fast-twitch fibers. In the meantime, translation of the SMUL sORF disrupted the stability of SMURF2 mRNA. Mechanistically, SMUL restrained SMURF2 production via nonsense-mediated mRNA decay (NMD), participating in the regulation of the transforming growth factor β (TGF-β)/SMAD pathway and further regulating myogenesis and muscle atrophy. Taken together, these results suggest that SMUL could be a novel therapeutic target for muscle atrophy.

Endoplasmic reticulum stress and protein degradation in chronic liver disease

Endoplasmic reticulum (ER) stress is easily observed in chronic liver disease, which often causes accumulation of unfolded or misfolded proteins in the ER, leading to unfolded protein response (UPR). Regulating protein degradation is an integral part of UPR to relieve ER stress. The major protein degradation system includes the ubiquitin-proteasome system (UPS) and autophagy. All three arms of UPR triggered in response to ER stress can regulate UPS and autophagy. Accumulated misfolded proteins could activate these arms, and then generate various transcription factors to regulate the expression of UPS-related and autophagy-related genes. The protein degradation process regulated by UPR has great significance in many chronic liver diseases, including non-alcoholic fatty liver disease (NAFLD), alcoholic liver disease (ALD), viral hepatitis, liver fibrosis, and hepatocellular carcinoma(HCC). In most instances, the degradation of excessive proteins protects cells with ER stress survival from apoptosis. According to the specific functions of protein degradation in chronic liver disease, choosing to promote or inhibit this process is promising as a potential method for treating chronic liver disease.

Network-based Transcriptome-wide Expression Study for Postmenopausal Osteoporosis

PURPOSE

Menopause is a crucial physiological transition during a woman's life, and it occurs with growing risks of health issues like osteoporosis. To identify postmenopausal osteoporosis-related genes, we performed transcriptome-wide expression analyses for human peripheral blood monocytes (PBMs) using Affymetrix 1.0 ST arrays in 40 Caucasian postmenopausal women with discordant bone mineral density (BMD) levels.

METHODS

We performed multiscale embedded gene coexpression network analysis (MEGENA) to study functionally orchestrating clusters of differentially expressed genes in the form of functional networks. Gene sets net correlations analysis (GSNCA) was applied to assess how the coexpression structure of a predefined gene set differs in high and low BMD groups. Bayesian network (BN) analysis was used to identify important regulation patterns between potential risk genes for osteoporosis. A small interfering ribonucleic acid (siRNA)-based gene silencing in vitro experiment was performed to validate the findings from BN analysis.

RESULT

MEGENA showed that the "T cell receptor signaling pathway" and the "osteoclast differentiation pathway" were significantly enriched in the identified compact network, which is significantly correlated with BMD variation. GSNCA revealed that the coexpression structure of the "Signaling by TGF-beta receptor complex pathway" is significantly different between the 2 BMD discordant groups; the hub genes in the postmenopausal low and high BMD group are FURIN and SMAD3 respectively. With siRNA in vitro experiments, we confirmed the regulation relationship of TGFBR2-SMAD7 and TGFBR1-SMURF2.

MAIN CONCLUSION

The present study suggests that biological signals involved in monocyte recruitment, monocyte/macrophage lineage development, osteoclast formation, and osteoclast differentiation might function together in PBMs that contribute to the pathogenesis of postmenopausal osteoporosis.

Effects of curcumin on artery blood gas index of rats with pulmonary fibrosis caused by paraquat poisoning and the expression of Smad 4, Smurf 2, interleukin-4 and interferon-γ

Effects of curcumin on artery blood gas index of rats with pulmonary fibrosis caused by paraquat poisoning and the expression of Mothers against decapentaplegic homolog 4 (Smad4), Smad ubiquitination regulatory factor 2 (Smurf2), interleukin-4 (IL-4) and interferon-γ (IFN-γ) were explored. A total of 54 Wistar rats were randomly selected, of which 36 rats were selected for paraquat poisoning pulmonary fibrosis modeling, and 18 were used in the control group for normal feeding. Then, 18 rats were randomly selected from the modeled groups and injected with curcumin and classified as the curcumin group. The remaining 18 rats were not processed and 17 were successfully modeled as the paraquat group. The expression of SMAD4, Smurf2, IL-4 and INF-γ was detected by enzyme-linked immunosorbent assay. Abdominal aortic blood was taken for determination of pH, arterial partial pressure of oxygen (PaO₂) and arterial partial pressure of carbon dioxide (PaCO₂). The artery blood PaO₂ and serum INF-γ of the curcumin and paraquat groups were significantly higher on day 1 than those on day 5 (P<0.05). The artery blood PaO₂ and serum INF-γ in the curcumin group were higher than those in the paraquat group (P<0.05). The artery blood PaCO₂, serum Smad4, Smurf2 and IL-4 in the curcumin group were significantly lower on day 1 than those on day 5 (P<0.05). The artery blood PaCO₂, serum Smad4, Smurf2 and IL-4 in the paraquat group were significantly lower on day 1 than those on day 5 (P<0.05). The PaCO₂, serum Smad4, Smurf2 and IL-4 in the curcumin group were lower than those in the paraquat group (P<0.05). In conclusion, curcumin can effectively improve pulmonary fibrosis in rats after treatment with paraquat poisoning. The results show that it is expected to be an effective drug for the treatment of paraquat, and provide effective reference and guidance for clinical treatment.

Glycoprotein M6B Interacts with TβRI to Activate TGF-β-Smad2/3 Signaling and Promote Smooth Muscle Cell Differentiation

Smooth muscle cells (SMCs), which form the walls of blood vessels, play an important role in vascular development and the pathogenic process of vascular remodeling. However, the molecular mechanisms governing SMC differentiation remain poorly understood. Glycoprotein M6B (GPM6B) is a four-transmembrane protein that belongs to the proteolipid protein family and is widely expressed in neurons, oligodendrocytes, and astrocytes. Previous studies have revealed that GPM6B plays a role in neuronal differentiation, myelination, and osteoblast differentiation. In the present study, we found that the GPM6B gene and protein expression levels were significantly upregulated during transforming growth factor-β1 (TGF-β1)-induced SMC differentiation. The knockdown of GPM6B resulted in the downregulation of SMC-specific marker expression and repressed the activation of Smad2/3 signaling. Moreover, GPM6B regulates SMC Differentiation by Controlling TGF-β-Smad2/3 Signaling. Furthermore, we demonstrated that similar to p-Smad2/3, GPM6B was profoundly expressed and coexpressed with SMC differentiation markers in embryonic SMCs. Moreover, GPM6B can regulate the tightness between TβRI, TβRII, or Smad2/3 by directly binding to TβRI to activate Smad2/3 signaling during SMC differentiation, and activation of TGF-β-Smad2/3 signaling also facilitate the expression of GPM6B. Taken together, these findings demonstrate that GPM6B plays a crucial role in SMC differentiation and regulates SMC differentiation through the activation of TGF-β-Smad2/3 signaling via direct interactions with TβRI. This finding indicates that GPM6B is a potential target for deriving SMCs from stem cells in cardiovascular regenerative medicine. Stem Cells 2018 Stem Cells 2019;37:190-201.

Notoginsenoside R1 Protects Against Diabetic Cardiomyopathy Through Activating Estrogen Receptor α and Its Downstream Signaling

Diabetic cardiomyopathy (DCM) leads to heart failure and death in diabetic patients, no effective treatment is available. Notoginsenoside R1 (NGR1) is a novel saponin that is derived from Panax notoginseng and our previous studies have showed cardioprotective and neuroprotective effects of NGR1. However, its role in protecting against DCM remains unexplored. Herein, we examine potential effects of NGR1 on cardiac function of diabetic db/db mice and H9c2 cardiomyocytes treated by advanced glycation end products (AGEs). In vitro experiments revealed that pretreatment with NGR1 significantly decreased AGEs-induced mitochondria injury, limited an increase in ROS, and reduced apoptosis in H9c2 cells. NGR1 eliminated ROS by promoting estrogen receptor α expression, which subsequently activated Akt and Nrf2-mediated anti-oxidant enzymes. In vivo investigation demonstrated that NGR1 significantly reduced serum lipid levels, insulin resistance, the expression of enzymes related to cardiomyopathy, and the expression of apoptotic proteins. Finally, NGR1 improved cardiac dysfunction and attenuated histological abnormalities, as evidenced by elevating ejection fraction and fractional shortening, and reducing cardiac fibrosis. Mechanistically, NGR1 promoted ERα expression, which led to the activation of Akt-Nrf2 signaling and the inhibition of the TGFβ pathway. Collectively, these results strongly indicate that NGR1 exerts cardioprotective effects against DCM through its inhibition of oxidative stress and apoptosis, and eventually suppresses cardiac fibrosis and hypertrophy, which suggests that NGR1 is a potential therapeutic medicine for the treatment of DCM.

Ubiquitination in Scleroderma Fibrosis and Its Treatment

Scleroderma (systemic sclerosis, SSc) is a highly heterogeneous rheumatic disease, and uncontrolled fibrosis in visceral organs is the major cause of death in patients. The transforming growth factor-β (TGF-β) and WNT/β-catenin signaling pathways, along with signal transducer and activator of transcription 3 (STAT3), play crucial roles in this fibrotic process. Currently, no therapy is available that effectively arrests or reverses the progression of fibrosis in patients with SSc. Ubiquitination is an important post-translational modification that controls many critical cellular functions. Dysregulated ubiquitination events have been observed in patients with systemic lupus erythematosus, rheumatoid arthritis and fibrotic diseases. Inhibitors targeting the ubiquitination pathway have considerable potential for the treatment of rheumatic diseases. However, very few studies have examined the role and mechanism of ubiquitination in patients with SSc. In this review, we will summarize the molecular mechanisms of ubiquitination in patients with SSc and explore the potential targets for treatment.

Smurf2, an E3 ubiquitin ligase, interacts with PDE4B and attenuates liver fibrosis through miR-132 mediated CTGF inhibition

We previously reported that Smad ubiquitin regulatory factor 2 (Smurf2) activity was decreased in human fibrotic livers. Here, we overexpressed Smurf2 in livers of transgenic mice and observed inhibited collagen deposition and hepatic stellate cell activation in fibrotic model induced by carbon tetrachloride treatment or bile duct ligation. Hepatic Smurf2 overexpression also inhibited the production of connective tissue growth factor (CTGF), a central mediator of liver fibrosis. Using miRNA array and bioinformatics analyses, we identified miR-132 as a mediator of this inhibitory effect. miR-132 directly targets the 3'-untranslated region of CTGF and was transcriptionally upregulated by cAMP-PKA-CREB signaling. In addition, Smurf2 activated cAMP-PKA-CREB pathway by interacting with phosphodiesterase 4B (PDE4B) and facilitating its degradation. Thus, we have demonstrated a previously unrecognized anti-fibrotic pathway controlled by Smurf2.

Molecular mechanism of smurf2 in regulating the expression of SnoN in diabetic nephropathy

The aim of the present study was to examine the regulatory mechanism underlying the depression in Ski-related novel protein N (SnoN) in diabetic nephrology (DN). NRK-52E cells, a rat primary renal tubular epithelial cell line, were cultured to clarify the effect of small mothers against decapentaplegic (Smad) ubiquitination regulatory factor 2 (smurf2) on SnoN in a low glucose environment in vitro. NRK-52E cells and DM rats were injected with adenoviruses AD-smurf2 and AD-shsmurf2, respectively, and the protein expression profiles of SnoN, smurf2 and phosphorylated (p)-Smad2 were then detected. In addition, the protein levels of smurf2, p-Smad2 and SnoN were analyzed following treatment with transforming growth factor (TGF)-β1 or TGF-β1 inhibitor to validate the effect of the TGF-β1/Smad signaling pathway. The effect of smurf2 on the degradation of SnoN by ubiquitination was found to be a key factor in DN, which was mediated by the TGF-β1/Smad signaling pathway.

E3 ubiquitin ligase: A potential regulator in fibrosis and systemic sclerosis

Systemic sclerosis (SSc) is an autoimmune disease characterized by fibrosis in the skin and internal organs. The pathogenesis of SSc is not completely understood until now. Recently, many studies have focused on the role of E3 ubiquitin ligases in organ fibrosis. However, the possible regulatory mechanisms of E3 ubiquitin ligases in fibrosis and SSc are not well documented. In this review, we summarized that E3 ubiquitin ligases regulated fibrosis through ubiquitin-mediated degradation of TGF-β/Smad signaling pathway. Moreover, E3 ubiquitin ligases participated in regulating fibrosis by other methods, such as inducing epithelial transition to mesenchymal cell, enhancing the production of TGF-β and protecting activated hepatic stellate cells from apoptosis. However, the specific regulatory mechanisms of E3 ubiquitin ligases in scleroderma is still not fully understood. There are more works to be done to specify the mechanism of E3 ubiquitin ligases in regulation of fibrosis in SSc.

The ubiquitin ligase Smurf2 suppresses TGFβ-induced epithelial-mesenchymal transition in a sumoylation-regulated manner

Epithelial-mesenchymal transition (EMT) is a fundamental cellular process in epithelial tissue development, and can be reactivated in cancer contributing to tumor invasiveness and metastasis. The cytokine transforming growth factor-β (TGFβ) is a key inducer of EMT, but the mechanisms that regulate TGFβ-induced EMT remain incompletely understood. Here, we report that knockdown of the ubiquitin ligase Smurf2 promotes the ability of TGFβ to induce EMT in a three-dimensional cell culture model of NMuMG mammary epithelial cells. In other studies, we identify Smurf2 as a target of the small ubiquitin like modifier (SUMO) pathway. We find that the SUMO-E2 conjugating enzyme Ubc9 and the SUMO E3 ligase PIAS3 associate with Smurf2 and promote its sumoylation at the distinct sites of Lysines 26 and 369. The sumoylation of Smurf2 enhances its ability to induce the degradation of the TGFβ receptor and thereby suppresses EMT in NMuMG cells. Collectively, our data reveal that Smurf2 acts in a sumoylation-regulated manner to suppress TGFβ-induced EMT. These findings have significant implications for our understanding of epithelial tissue development and cancer.

The nanomechanical signature of liver cancer tissues and its molecular origin

Patients with cirrhosis are at higher risk of developing hepatocellular carcinoma (HCC), the second most frequent cause of cancer-related deaths. Although HCC diagnosis based on conventional morphological characteristics serves as the "gold standard" in the clinic, there is a high demand for more convenient and effective diagnostic methods that employ new biophysical perspectives. Here, we show that the nanomechanical signature of liver tissue is directly correlated with the development of HCC. Using indentation-type atomic force microscopy (IT-AFM), we demonstrate that the lowest elasticity peak (LEP) in the Young's modulus distribution of surgically removed liver cancer tissues can serve as a mechanical fingerprint to evaluate the malignancy of liver cancer. Cirrhotic tissues shared the same LEP as normal tissues. However, a noticeable downward shift in the LEP was detected when the cirrhotic tissues progressed to a malignant state, making the tumor tissues more prone to microvascular invasion. Cell-level mechanistic studies revealed that the expression level of a Rho-family effector (mDia1) was consistent with the mechanical trend exhibited by the tissue. Our findings indicate that the mechanical profiles of liver cancer tissues directly varied with tumor progression, providing an additional platform for the future diagnosis of HCC.

Expression of Smad7 and Smad ubiquitin regulatory factor 2 in a rat model of chronic pancreatitis

OBJECTIVE

To quantify the expressions of Smad7 and Smad ubiquitin regulatory factor 2 (Smurf2) in the pancreas in rats with chronic pancreatitis (CP).

METHODS

A total of 16 male Wistar rats were randomly divided into the control group and the CP group, with 8 rats in each group. CP was induced in vivo with dibutyltin dichloride (DBTC). Four weeks after DBTC administration, histological assessment and the measurement of hydroxyproline content in the pancreatic tissues were performed to assess the inflammation and fibrosis of the pancreas. Immunohistochemistry and reverse transcription polymerase chain reaction (RT-PCR) for transforming growth factor (TGF)-β1 and α-smooth muscle actin (α-SMA) were applied to assess activated pancreatic stellate cells (PSC) and TGF-β1 expression. Smad7 and Smurf2 expressions in the pancreas were measured using Western blot and RT-PCR.

RESULTS

Typical histopathological characteristics of DBTC-induced CP in the rats with extensively activated PSC. Compared with the control group, the expressions of TGF-β1, α-SMA and hydroxyproline content in the pancreatic tissues in the CP group were significantly increased. Meanwhile, the mRNA and protein expressions of Smad7 and Smurf2 were significant increased in the fibrotic pancreas, in which the expressions of Smad7 proteins showed an obvious reduction compared with controls.

CONCLUSION

The dysregulation of Smad7 and Smurf2 may be associated with the pathogenesis of pancreatic fibrosis through the TGF-β signaling pathway.

Increased Transforming Growth Factor-β Levels Associated With Cardiac Adverse Events in Hypertrophic Cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is a common genetic heart disease characterized by ventricular hypertrophy, myocardial fibrosis, and impaired ventricular relaxation. The exact mechanisms by which fibrosis is caused remain unknown.

HYPOTHESIS

Circulating TGF-β is related to poor prognosis in HCM.

METHODS

We compared TGF-β levels of 49 HCM patients with those of 40 non-HCM patients. We followed the patients with HCM for 18 months and divided them into 2 groups: low TGF-β (≤ 4877 pg/mL) and high TGF-β (> 4877 pg/mL). We compared the 2 groups in terms of brain natriuretic peptide (BNP), echocardiographic parameters, and clinical outcomes including myocardial infarction, arrhythmias, implantable cardioverter-defibrillator implantation, hospitalization, New York Heart Association (NYHA) class, acute heart failure, and mortality.

RESULTS

The HCM patients had higher TGF-β levels than those in the control group (P = 0.005). In the follow-up, those in the high TGF-β group had higher BNP levels, larger left-atrial size, thicker interventricular septum, NYHA class, more hospitalizations, and a greater number of clinical adverse events (P < 0.001, P = 0.01, P < 0.001, P = 0.002, P < 0.001 and P = 0.003, respectively). TGF-β level of > 4877 pg/mL can predict adverse events with a specificity of 75% and a sensitivity of 72% (P = 0.014). In multivariate regression analysis, TGF-β, BNP, and interventricular septum thickness were significantly associated with adverse events (P = 0.028, P = 0.030, and P = 0.034, respectively).

CONCLUSIONS

The TGF-β level is higher in HCM patients and associated with a poor prognosis in HCM.

AKT regulation of mesothelial-to-mesenchymal transition in peritoneal dialysis is modulated by Smurf2 and deubiquitinating enzyme USP4

Background

Transforming growth factor-β1 (TGF-β1) plays a key role in mesothelial-to-mesenchymal transition (MMT) during peritoneal dialysis (PD). However, the role of Akt in MMT transformation in PD is not clear.

Results

In this study, we observed that the phosphorylated form of protein kinase B (Akt), termed as pAkt, was up-regulated in the peritoneum of mice undergoing PD. It was associated with thickening of the peritoneum and up-regulation of TGF-β1. Upregulation of pAkt paralleled with the increased expression of Smad ubiquitination regulatory factor 2 (Smurf2), Vimentin and fibronectin (FN), and decreased expression of mothers against decapentaplegic homolog 7 (Smad7) and Zonula Occludens protein 1(ZO-1) in mice undergoing PD treatment and in TGF-β1 induced human peritoneal mesothelial cells (HPMCs). These changes were reversed with the treatment of a PI3K/Akt inhibitor LY294002 in vivo or in cells transfected with Akt dominant-negative (Akt-DN) plasmids in vitro. Increased Smurf2 expression in HPMCs, induced by TGF-β1 was accompanied with altered expression of Transforming growth factor receptor I (TβR-I), Smad7, ZO-1, Vimentin and FN via Akt modulation. In addition, inhibition of Ubiquitin carboxyl-terminal hydrolase 4 (USP4) decreased TGF- β1-induced expression of TβR-I and reversed the altered expression of Smad7, Smurf2, ZO-1 and Vimentin. Moreover, TGF-β1 accentuated the interactions between Smurf2 and Smad7, while reduced the association between TβR-I and Smurf2. These interactions were reversed by the treatment of Akt-DN and USP4 siRNA, respectively.

Conclusions

These data implied that Akt mediated MMT in PD via Smurf2 modulation/and or Smad7 degradation while conceivably maintaining the TβRI stability, most likely by the USP4.

Astragalus and Paeoniae Radix Rubra extract (APE) inhibits hepatic stellate cell activation by modulating transforming growth factor-β/Smad pathway

Previous studies have shown that Astragalus and Paeoniae Radix Rubra extract (APE) is capable of protecting against liver fibrosis in rats. The hypothesis of the present study was that APE exerts its anti‑fibrotic effect by mediating the transforming growth factor β (TGF‑β)/Smad signaling pathway. In order to investigate this hypothesis, a series of assays were designed to detect the effects of APE on cell proliferation, cell invasion and the activation of hepatic stellate cells (HSCs). In addition, the effects of APE on the TGF‑β/Smad signaling pathway were explored, with the aim of elucidating the underlying mechanisms. HSCs were initially isolated from normal rat liver. A number of assays were then employed in order to evaluate the effects of APE on the function of these cells. Cell proliferation was investigated using an MTT assay and cell invasion was observed with the use of transwell invasion chambers. Collagen synthesis was measured with a 3H‑proline incorporation assay and expression of α‑smooth muscle actin was used to determine the extent of HSC activation. Protein expression induced by TGF‑β1 in HSCs was investigated by western blot and immunofluorescence analyses. Plasminogen activator inhibitor type1 (PAI‑1) and urokinase‑type plasminogen activator (uPA) transcriptional activity was measured using reverse transcription polymerase chain reaction. The results demonstrated that APE (5‑80 µg/ml) significantly inhibited fetal bovine serum‑induced cell proliferation in a dose‑dependent manner. Cell invasion and activation of HSCs induced by TGF‑β1 were disrupted by treatment with APE in a dose‑dependent manner. TGF‑β1 was observed to increase the phosphorylation of Smad2/3, while APE administered at higher doses produced inhibitory effects on Smad2/3 phosphorylation. In addition, administration of APE abrogated the TGF‑β1‑induced reduction in Smad‑7 expression in a dose‑dependent manner. The results further indicated that APE treatment not only reduced PAI‑1 expression, but also increased uPA expression in a dose‑dependent manner. In conclusion, APE exerted inhibitory effects on cell proliferation, invasion and activation of HSCs, and the mechanisms underlying these effects may involve the TGF‑β1/Smad pathway.

Significance of expression of Smad ubiquitination regulatory factors in liver fibrosis

AIM: To observe the expression of Smad ubiquitination regulatory factor (Smurf)1, Smurf2, Smad3 and Smad7 proteins in liver fibrosis and to evaluate their interactions.

METHODS: Immunohistochemistry was applied to detect the expression of Smurf1, Smurf2, Smad3 and Smad7 in 9 normal liver tissue samples and 38 chronic HBV infection tissue samples.

RESULTS: Smurf1, Smurf2, Smad3 and Smad7 showed widespread expression in the liver parenchymal cells and nonparenchymal cells. Compared with normal liver tissue, the positive rates of Smad3 and Smurf2 expression increased significantly (66.7% vs 100%, 66.7% vs 92.1%, P < 0.01 for both) and the positive rate of Smad7 expression decreased significantly in liver fibrosis (77.8% vs 39.5%, P < 0.01), although the positive rate of Smurf1 expression had no significant change (77.8% vs 63.2%, P > 0.05). There were significant positive correlations between Smad3 and Smurf2 expression and the degree of fibrosis (P < 0.01 for both). Smad7 expression was negatively correlated with the degree of fibrosis (P < 0.01). There was no significant correlation between Smurf1 expression and liver fibrosis (P > 0.05). Smurf2 expression was positively correlated with Smad3 expression (P < 0.01) and negatively with Smad7 expression (P < 0.01). There was no significant relationship between Smurf1 and Smurf2, Smad3, Smad7 expression (P > 0.05 for all). There was a negative correlation between expression of Smad3 and that of Smad7 (P < 0.01).

CONCLUSION: The increase of Smad3 signal and decrease of Smad7 signal may lead to the development of liver fibrosis, and Smurf2 may play a bidirectionally regulatory role in the progression of liver fibrosis.