Enhanced epithelial-to-mesenchymal transition associated with lysosome dysfunction in podocytes: role of p62/Sequestosome 1 as a signaling hub

Placenta-derived mesenchymal stem cells protect against diabetic kidney disease by upregulating autophagy-mediated SIRT1/FOXO1 pathway

Diabetic kidney disease (DKD) is a common chronic microvascular complication of diabetes mellitus. Although studies have indicated the therapeutic potential of mesenchymal stem cells (MSCs) for DKD, the underlying molecular mechanisms remain unclear. Herein, we explored the renoprotective effect of placenta-derived MSCs (P-MSCs) and the potential mechanism of SIRT1/FOXO1 pathway-mediated autophagy in DKD. The urine microalbumin/creatinine ratio was determined using ELISA, and renal pathological changes were detected by special staining techniques. Immunofluorescence was used for detecting the renal tissue expression of podocin and nephrin; immunohistochemistry for the renal expression of autophagy-related proteins (LC3, Beclin-1, SIRT1, and FOXO1); and western blotting and PCR for the expression of podocyte autophagy- and pathway-related indicators. We found that P-MSCs ameliorated renal tubular injury and glomerular mesangial matrix deposition and alleviated podocyte damage in DKD rats. PMSCs enhanced autophagy levels and increased SIRT1 and FOXO1 expression in DKD rat renal tissue, whereas the autophagy inhibitor 3-methyladenine significantly attenuated the renoprotective effect of P-MSCs. P-MSCs improved HG-induced Mouse podocyte clone5(MPC5)injury, increased podocyte autophagy, and upregulated SIRT1 and FOXO1 expression. Moreover, downregulation of SIRT1 expression blocked the P-MSC-mediated enhancement of podocyte autophagy and improvement of podocyte injury. Thus, P-MSCs can significantly improve renal damage and reduce podocyte injury in DKD rats by modulating the SIRT1/FOXO1 pathway and enhancing podocyte autophagy.

Dissecting the multifaceted roles of autophagy in cancer initiation, growth, and metastasis: from molecular mechanisms to therapeutic applications

Autophagy is a cytoplasmic defense mechanism that cells use to break and reprocess their intracellular components. This utilization of autophagy is regarded as a savior in nutrient-deficient and other stressful conditions. Hence, autophagy keeps contact with and responds to miscellaneous cellular tensions and diverse pathways of signal transductions, such as growth signaling and cellular death. Importantly, autophagy is regarded as an effective tumor suppressor because regular autophagic breakdown is essential for cellular maintenance and minimizing cellular damage. However, paradoxically, autophagy has also been observed to promote the events of malignancies. This review discussed the dual role of autophagy in cancer, emphasizing its influence on tumor survival and progression. Possessing such a dual contribution to the malignant establishment, the prevention of autophagy can potentially advocate for the advancement of malignant transformation. In contrast, for the context of the instituted tumor, the agents of preventing autophagy potently inhibit the advancement of the tumor. Key regulators, including calpain 1, mTORC1, and AMPK, modulate autophagy in response to nutritional conditions and stress. Oncogenic mutations like RAS and B-RAF underscore autophagy's pivotal role in cancer development. The review also delves into autophagy's context-dependent roles in tumorigenesis, metastasis, and the tumor microenvironment (TME). It also discusses the therapeutic effectiveness of autophagy for several cancers. The recent implication of autophagy in the control of both innate and antibody-mediated immune systems made it a center of attention to evaluating its role concerning tumor antigens and treatments of cancer.

Lysosomal alkalinization in nutrient restricted cancer cells activates cytoskeletal rearrangement to enhance partial epithelial to mesenchymal transition

INTRODUCTION

Nutrient restriction in cancer cells can activate a number of stress response pathways for cell survival. We aimed to determine mechanistically how nutrient depletion in colorectal cancer (CRC) cells leads to cellular adaptation.

MATERIALS AND METHODS

Cell survival under nutrient depletion (ND) was evaluated by colony formation and in vivo tumor formation assays. Lysosomes are activated with ND; therefore, we incubated the ND cells with the V-ATPase inhibitor Bafilomycin A1 (ND+Baf). The expression of epithelial and mesenchymal markers with ND+Baf was determined by RNA sequencing and RT-qPCR while motility was determined with an in vivo Chorioallantoic membrane (CAM) assay. Reorganization of cytoskeletal network and lysosomal positioning was determined by immunocytochemistry.

RESULTS

4 different colorectal cancer (CRC) cell lines under ND showed high viability, tumor forming ability and increased expression of one or more epithelial and mesenchymal markers, suggesting the activation of partial (p)-EMT. We observed a further increase in p-EMT markers, numerous membrane protrusions, decreased cell-cell adhesion in 3D, and increased motility in ND+Baf cells. The protrusions in the ND+Baf cells were primarily mediated by microtubules and enabled the relocalization of lysosomes from the perinuclear region to the periphery.

CONCLUSIONS

ND activated p-EMT in CRC cells, which was exacerbated by lysosomal alkalinization. The ND+Baf cells also showed numerous protrusions containing lysosomes, which may lead to lysosomal exocytosis and enhanced motility.

Impaired autophagic flux and dedifferentiation in podocytes lacking Asah1 gene: Role of lysosomal TRPML1 channel

Podocytopathy and associated nephrotic syndrome have been reported in a mouse strain (Asah1fl/fl/Podocre) with a podocyte-specific deletion of α subunit (the main catalytic subunit) of acid ceramidase (Ac). However, the pathogenesis of podocytopathy in these mice remains unclear. The present study tested whether Ac deficiency impairs autophagic flux in podocytes through blockade of transient receptor potential mucolipin 1 (TRPML1) channel as a potential pathogenic mechanism of podocytopathy in Asah1fl/fl/Podocre mice. We first demonstrated that impairment of autophagic flux occurred in podocytes lacking Asah1 gene, which was evidenced by autophagosome accumulation and reduced lysosome-autophagosome interaction. TRPML1 channel agonists recovered lysosome-autophagosome interaction and attenuated autophagosome accumulation in podocytes from Asah1fl/fl/Podocre mice, while TRPML1 channel inhibitors impaired autophagic flux in WT/WT podocytes and worsened autophagic deficiency in podocytes lacking Asah1 gene. The effects of TRPML1 channel agonist were blocked by dynein inhibitors, indicating a critical role of dynein activity in the control of lysosome movement due to TRPML1 channel-mediated Ca2+ release. It was also found that there is an enhanced phenotypic transition to dedifferentiation status in podocytes lacking Asah1 gene in vitro and in vivo. Such podocyte phenotypic transition was inhibited by TRPML1 channel agonists but enhanced by TRPML1 channel inhibitors. Moreover, we found that TRPML1 gene silencing induced autophagosome accumulation and dedifferentiation in podocytes. Based on these results, we conclude that Ac activity is essential for autophagic flux and maintenance of differentiated status of podocytes. Dysfunction or deficiency of Ac may impair autophagic flux and induce podocyte dedifferentiation, which may be an important pathogenic mechanism of podocytopathy and associated nephrotic syndrome.

Applications and Mechanisms of Tripterygium Wilfordii Hook. F. and its Preparations in Kidney Diseases

Tripterygium wilfordii Hook. f. (TwHF) is a Chinese botanical drug containing a large number of metabolites. The discovered and recognized anti-inflammatory and immune-regulating effects have made it attract more and more attentions in trials and clinical researches. The extraction and processing of TwHF for pharmaceuticals is a manifestation of the role of traditional Chinese medicine. However, TwHF is toxic. Optimization of TwHF preparations has become a requirement for the development of TwHF pharmaceuticals. Our article introduces the main preparations of TwHF on the Chinese market and their characteristics. In particular, we summarize the clinical applications and influential mechanisms of TwHF and its preparations in kidney diseases. Considering that nephropathy is closely related to immune inflammation and TwHF is a botanical drug with a high number of metabolites, the application of TwHF in kidney diseases may be much more complicated. By revealing the role and mechanisms of TwHF in kidney diseases, this study aims to provide more insights to basic and clinical studies about nephropathy.

Exosome Biogenesis and Lysosome Function Determine Podocyte Exosome Release and Glomerular Inflammatory Response during Hyperhomocysteinemia

Nucleotide-binding oligomerization domain-like receptor containing pyrin domain 3 (NLRP3) inflammasome activation in podocytes is reportedly associated with enhanced release of exosomes containing NLRP3 inflammasome products from these cells during hyperhomocysteinemia (hHcy). This study examined the possible role of increased exosome secretion during podocyte NLRP3 inflammasome activation in the glomerular inflammatory response. Whether exosome biogenesis and lysosome function are involved in the regulation of exosome release from podocytes during hHcy in mice and upon stimulation of homocysteine (Hcy) in podocytes was tested. By nanoparticle tracking analysis, treatments of mice with amitriptyline (acid sphingomyelinase inhibitor), GW4869 (exosome biogenesis inhibitor), and rapamycin (lysosome function enhancer) were found to inhibit elevated urinary exosomes during hHcy. By examining NLRP3 inflammasome activation in glomeruli during hHcy, amitriptyline (but not GW4869 and rapamycin) was shown to have an inhibitory effect. However, all treatments attenuated glomerular inflammation and injury during hHcy. In cell studies, Hcy treatment stimulated exosome release from podocytes, which was prevented by amitriptyline, GW4869, and rapamycin. Structured illumination microscopy revealed that Hcy inhibited lysosome-multivesicular body interactions in podocytes, which was prevented by amitriptyline or rapamycin but not GW4869. Thus, the data from this study shows that activation of exosome biogenesis and dysregulated lysosome function are critically implicated in the enhancement of exosome release from podocytes leading to glomerular inflammation and injury during hHcy.

PP2A protects podocytes against Adriamycin-induced injury and epithelial-to-mesenchymal transition via suppressing JIP4/p38-MAPK pathway

Protein phosphatase 2A (PP2A) is one of the major protein serine/threonine phosphatases (PPPs) with regulatory effects on several cellular processes, but its role and function in Adriamycin (ADR)-treated podocytes injury needs to be further explored. Mice podocytes were treated with ADR and PP2A inhibitor (okadaic acid, OA). After transfection, cell apoptosis was detected by flow cytometry. Expressions of podocytes injury-, apoptosis- and epithelial-to-mesenchymal transition (EMT)- and JNK-interacting protein 4/p38-Mitogen-Activated Protein Kinase (JIP4/p38-MAPK) pathway-related factors were measured using quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot as needed. Interaction between PP2A and JIP4/MAPK pathway was confirmed using co-immunoprecipitation (Co-Ip) assay. In podocytes, ADR inhibited PP2A, Nephrin and Wilms' tumor (WT) 1 expressions yet upregulated apoptosis and Desmin expression, and suppressing PP2A expressionenhanced the effects. PP2A overexpression reversed the effects of ADR on PP2A and podocyte injury-related factors expressions and apoptosis of podocytes. JIP4 was the candidate gene interacting with both PP2A and p38-MAPK pathway, and PP2A overexpression alleviated the effects of ADR on p38-MAPK pathway-related factors expressions. Additionally, in ADR-treated podocytes, PP2A suppression enhanced the effects of ADR, yet silencing of JIP4 reversed the effects of PP2A suppression on regulating p38-MAPK pathway-, apoptosis- and EMT-related factors expressions and apoptosis, with upregulations of B-cell lymphoma-2 (Bcl-2) and E-cadherin and down-regulations of Bcl-2 associated protein X (Bax), cleaved (C)-casapse-3, N-cadherin, Vimentin and Snail. PP2A protects ADR-treated podocytes against injury and EMT by suppressing JIP4/p38-MAPK pathway, showing their interaction in podocytes.

Triptolide reverses epithelial-mesenchymal transition in glioma cells via inducing autophagy

Background

To observe the effects of triptolide (TP) on the proliferation, migration, invasion, and epithelial-mesenchymal transition (EMT) of glioma cells, and to explore the possible mechanisms of phenotypic changes in EMT.

Methods

The U87 and U251 glioma cell lines were treated TP. The Cell Counting Kit-8 (CCK-8) method was used to detect the half-maximal inhibitory concentration (IC₅₀) of TP in these two cell lines and the inhibition of cell proliferation at the IC₅₀ concentration. The wound-healing experiment and Transwell invasion assay were used to detect the cells’ migration and invasion abilities, respectively. Using western blot protocol, the expression levels of the EMT markers were analyzed, and the levels of the autophagy markers were also detected. The pEGFP-C2-LC3B plasmid was transfected into glioma cells, and the effect of TP on autophagy was detected by immunofluorescence. A subcutaneous tumor model in nude mice was established to observe the effect of TP on cell proliferation in vivo, and immunohistochemistry (IHC) was used to detect the expression levels of EMT markers in mouse tumor tissues.

Results

TP significantly inhibited the proliferation of U87 and U251 cells in a dose- and time-dependent manner. TP had a significant inhibitory effect on the migration and invasion of U87 and U251 cells. Western blot showed that TP reversed the process of EMT in glioma cells, which was evidenced by the upregulated expression of the epithelial marker E-cadherin, and the downregulated expression of the mesenchymal markers N-cadherin, Vimentin, ZEB1, Snail, and Slug. TP increased autophagy in glioma cells, increased the LC3B II/I ratio, and upregulated Beclin-1 and Atg-7 expression. Immunofluorescence showed that the number of autophagosomes increased significantly after TP was applied to cells. In the nude mouse subcutaneous tumor model, experiments revealed an inhibitory effect of TP on glioma cell proliferation in vivo. IHC confirmed that the expression of E-cadherin was upregulated in mouse tumor tissues, while the expression levels of N-Cadherin and Vimentin were downregulated.

Conclusions

TP can inhibit glioma cell proliferation, migration, and invasion, and reverse EMT progression. The possible mechanism of EMT reversal in glioma cells is that TP induces autophagy.

Podocyte Sphingolipid Signaling in Nephrotic Syndrome

Podocytes play a vital role in the pathogenesis of nephrotic syndrome (NS), which is clinically characterized by heavy proteinuria, hypoalbuminemia, hyperlipidemia, and peripheral edema. The pathogenesis of NS has evolved through several hypotheses ranging from immune dysregulation theory and increased glomerular permeability theory to the current concept of podocytopathy. Podocytopathy is characterized by dysfunction or depletion of podocytes, which may be caused by unknown permeability factor, genetic disorders, drugs, infections, systemic disorders, and hyperfiltration. Over the last two decades, numerous studies have been done to explore the molecular mechanisms of podocyte injuries or NS and to develop the novel therapeutic strategies targeting podocytopathy for treatment of NS. Recent studies have shown that normal sphingolipid metabolism is essential for structural and functional integrity of podocytes. As a basic component of the plasma membrane, sphingolipids not only support the assembly of signaling molecules and interaction of receptors and effectors, but also mediate various cellular activities, such as apoptosis, proliferation, stress responses, necrosis, inflammation, autophagy, senescence, and differentiation. This review briefly summarizes current evidence demonstrating the regulation of sphingolipid metabolism in podocytes and the canonical or noncanonical roles of podocyte sphingolipid signaling in the pathogenesis of NS and associated therapeutic strategies.

Tripterygium glycoside suppresses epithelial‑to‑mesenchymal transition of diabetic kidney disease podocytes by targeting autophagy through the mTOR/Twist1 pathway

Tripterygium glycoside (TG) is a traditional Chinese medicine extract with immunosuppressive, anti-inflammatory and anti-renal fibrosis effects. Epithelial-mesenchymal transition (EMT) and cell apoptosis are considered to be the major cause of podocyte injury in diabetic kidney disease (DKD). However, it remains unknown as to whether TG is able to alleviate podocyte injury to prevent DKD progression. Therefore, the present study aimed to clarify the podocyte protective effects of TG on DKD. TG, Twist1 small interfering RNA (siRNA) and Twist1 overexpression vector were added to DKD mouse serum-induced podocytes in vitro. Autophagic and EMT activities were evaluated by immunofluorescence staining and western blot analysis. Apoptotic activity was evaluated by Annexin V-FITC/PI flow cytometric analysis. The results revealed that after treatment with DKD mouse serum, autophagy was decreased, whereas EMT and apoptotic rate were increased, in podocytes. In addition, Twist1 expression was increased in DKD-induced podocytes. Furthermore, following Twist1-small interfering RNA transfection, the DKD-induced podocyte EMT and apoptotic rate were markedly reduced, indicating that Twist1 may be a promising therapeutic target for DKD. The present results also revealed that overexpression of Twist1 increased podocyte apoptosis, although this was decreased after TG treatment, indicating that TG may exhibit a protective effect on podocytes by inhibiting the Twist1 signaling pathway. After the addition of 3-benzyl-5-((2-nitrophenoxy) methyl)-dihydrofuran-2(3H)-one, an activator of mTORC1, the effects of TG on podocyte EMT, apoptosis and the autophagy were reversed. These findings indicated that TG may alleviate EMT and apoptosis by upregulating autophagy through the mTOR/Twist1 signaling pathway in DKD.

Contribution of podocyte inflammatory exosome release to glomerular inflammation and sclerosis during hyperhomocysteinemia

The nucleotide-binding oligomerization domain-like receptor containing pyrin domain 3 (NLRP3) inflammasome has been implicated in podocyte injury and glomerular sclerosis in response to hyperhomocysteinemia (hHcy). However, it remains unknown how the products of NLRP3 inflammasome in cytoplasm are secreted out of podocytes. In the present study, we tested whether exosome release serves as a critical mechanism to mediate the action of NLRP3 inflammasome activation in hHcy-induced glomerular injury. By various approaches, we found that hHcy induced NLRP3 inflammasome activation and neutrophil infiltration in glomeruli of WT/WT mice. Lysosome-MVB interaction in glomeruli remarkably decreased in WT/WT mice fed with FF diet, leading to elevation of urinary exosome excretion of these mice. Podocyte-derived exosomes containing pro-inflammatory cytokines increased in urine of WT/WT mice in response to hHcy. The release of inflammatory exosomes from podocytes was prevented by Smpd1 gene deletion but enhanced by podocyte-specific Smpd1 gene overexpression (Smpd1 encodes Asm in mice). Pathologically, hHcy-induced podocyte injury and glomerular sclerosis were blocked by Smpd1 gene knockout but amplified by podocyte-specific Smpd1 gene overexpression. Taken together, our results suggest that Asm-ceramide signaling pathway contributes to NLRP3 inflammasome activation and robust release of inflammatory exosomes in podocytes during hHcy, which together trigger local glomerular inflammation and sclerosis.

Epithelial-Mesenchymal Transition and Senescence in the Retinal Pigment Epithelium of NFE2L2/PGC-1α Double Knock-Out Mice

Age-related macular degeneration (AMD) is the most prevalent form of irreversible blindness worldwide in the elderly population. In our previous studies, we found that deficiencies in the nuclear factor, erythroid 2 like 2 (NFE2L2) and peroxisome proliferator-activated receptor gamma coactivator 1-α (PGC-1α) genes caused AMD-like pathological phenotypes in mice. In the present work, we show hijacked epithelial-mesenchymal transition (EMT) due to the common loss of PGC-1α and NFE2L2 (double knock-out, dKO) genes in aged animals. The implanted area was assessed by histology, immunohistochemistry and transmission electron microscopy. Confocal microscopy revealed altered regions in the filamentous actin ring. This contrasted with hexagonal RPE morphology in wild-type mice. The ultrastructural RPE features here illustrated loss of apical microvilli, alteration of cell-cell contact, loss of basal in-folding with deposits on Bruch’s membrane, and excessive lipofuscin deposition in dKO samples. We also found the expression of epithelial-mesenchymal transition transcription factors, such as Snail, Slug, collagen 1, vimentin and OB-cadherin, to be significantly different in dKO RPEs. An increased immunoreactivity of senescence markers p16, DEC1 and HMGB1 was also noted. These findings suggest that EMT and senescence pathways may intersect in the retinas of dKO mice. Both processes can be activated by damage to the RPE, which may be caused by increased oxidative stress resulting from the absence of NFE2L2 and PGC-1α genes, important for antioxidant defense. This dKO model may provide useful tools for studying AMD pathogenesis and evaluating novel therapies for this disease.

Lysosomal TRPML1 Channel: Implications in Cardiovascular and Kidney Diseases

Lysosomal ion channels mediate ion flux from lysosomes and regulate membrane potential across the lysosomal membrane, which are essential for lysosome biogenesis, nutrient sensing, lysosome trafficking, lysosome enzyme activity, and cell membrane repair. As a cation channel, the transient receptor potential mucolipin 1 (TRPML1) channel is mainly expressed on lysosomes and late endosomes. Recently, the normal function of TRPML1 channels has been demonstrated to be important for the maintenance of cardiovascular and renal glomerular homeostasis and thereby involved in the pathogenesis of some cardiovascular and kidney diseases. In arterial myocytes, it has been found that Nicotinic Acid Adenine Dinucleotide Phosphate (NAADP), an intracellular second messenger, can induce Ca²⁺ release through the lysosomal TRPML1 channel, leading to a global Ca²⁺ release response from the sarcoplasmic reticulum (SR). In podocytes, it has been demonstrated that lysosomal TRPML1 channels control lysosome trafficking and exosome release, which contribute to the maintenance of podocyte functional integrity. The defect or functional deficiency of lysosomal TRPML1 channels has been shown to critically contribute to the initiation and development of some chronic degeneration or diseases in the cardiovascular system or kidneys. Here we briefly summarize the current evidence demonstrating the regulation of lysosomal TRPML1 channel activity and related signaling mechanisms. We also provide some insights into the canonical and noncanonical roles of TRPML1 channel dysfunction as a potential pathogenic mechanism for certain cardiovascular and kidney diseases and associated therapeutic strategies.

Abnormal podocyte TRPML1 channel activity and exosome release in mice with podocyte-specific Asah1 gene deletion

Podocytopathy and associated nephrotic syndrome (NS) have been reported in a knockout mouse strain (Asah1^fl/fl/Podo^Cre) with a podocyte-specific deletion of α subunit (the main catalytic subunit) of acid ceramidase (Ac). However, the pathogenesis of podocytopathy of these mice remains unknown. The present study tested whether exosome release from podocytes is enhanced due to Asah1 gene knockout, which may serve as a pathogenic mechanism switching on podocytopathy and associated NS in Asah1^fl/fl/Podo^Cre mice. We first demonstrated the remarkable elevation of urinary exosome excretion in Asah1^fl/fl/Podo^Cre mice compared with WT/WT mice, which was accompanied by significant Annexin-II (an exosome marker) accumulation in glomeruli of Asah1^fl/fl/Podo^Cre mice, as detected by immunohistochemistry. In cell studies, we also confirmed that Asah1 gene knockout enhanced exosome release in the primary cultures of podocyte isolated from Asah1^fl/fl/Podo^Cre mice compared to WT/WT mice. In the podocytes from Asah1^fl/fl/Podo^Cre mice, the interactions of lysosome and multivesicular body (MVB) were demonstrated to be decreased in comparison with those from their control littermates, suggesting reduced MVB degradation that may lead to increase in exosome release. Given the critical role of transient receptor potential mucolipin 1 (TRPML1) channel in Ca²⁺-dependent lysosome trafficking and consequent lysosome-MVB interaction, we tested whether lysosomal Ca²⁺ release through TRPML1 channels is inhibited in the podocytes of Asah1^fl/fl/Podo^Cre mice. By GCaMP3 Ca²⁺ imaging, it was found that lysosomal Ca²⁺ release through TRPML1 channels was substantially suppressed in podocytes with Asah1 gene deletion. As an Ac product, sphingosine was found to rescue TRPML1 channel activity and thereby recover lysosome-MVB interaction and reduce exosome release of podocytes from Asah1^fl/fl/Podo^Cre mice. Combination of N, N-dimethylsphingosine (DMS), a potent sphingosine kinase inhibitor, and sphingosine significantly inhibited urinary exosome excretion of Asah1^fl/fl/Podo^Cre mice. Moreover, rescue of Aash1 gene expression in podocytes of Asah1^fl/fl/Podo^Cre mice showed normal ceramide metabolism and exosome secretion. Based on these results, we conclude that the normal expression of Ac importantly contributes to the control of TRPML1 channel activity, lysosome-MVB interaction, and consequent exosome release from podocytes. Asah1 gene defect inhibits TRPML1 channel activity and thereby enhances exosome release, which may contribute to the development of podocytopathy and associated NS.

Activation of autophagy inhibits epithelial to mesenchymal transition process of human lens epithelial cells induced by high glucose conditions

Subcapsular cataracts are common phenotype of diabetic cataracts, and abnormal lens epithelial cells (LECs) under the lens capsules have been considered to involve in the pathogenesis. Our previous studies have shown that the epithelial to mesenchymal transition (EMT), which is responsible for the LECs to lose their original polarity and tight junctions, occurs in a diabetic cataract mouse model. Autophagy is known to function in the EMT process in multiple tissues. However, the relationship between autophagy and EMT process in LECs has not yet been fully demonstrated. We found that high glucose retreatment reducing expression level of E-cadherin, an epithelial marker, but increasing that of α-smooth muscle actin (α-SMA), a mesenchymal marker, by Western blot and immunoflurence staining assays, and increased the cell migration by Transwell assay in human lens epithelial cell line HLE-B3. High glucose retreatment also led to impairment of autophagy, representing by downregulation of Beclin, LC3II/LC3I, and reducing the number of autophagosomes. Activation of autophagy by rapamycin could prevent high glucose-induced EMT. In addition, the levels of p62 and Snail were increased in high glucose-treated HLE-B3 cells, and their interactions were demonstrated by co-immunoprecipitation and immunoflurence staining, but all these changes were attenuated by application of rapamycin. These findings delineated a novel autophagy-mediated mechanism, p62 might mediate Snail underlying high glucose-induced EMT in LECs, suggesting a potential therapeutic approach for diabetic cataract by regulating autophagy.

EMT and EndMT: Emerging Roles in Age-Related Macular Degeneration

Epithelial–mesenchymal transition (EMT) and endothelial–mesenchymal transition (EndMT) are physiological processes required for normal embryogenesis. However, these processes can be hijacked in pathological conditions to facilitate tissue fibrosis and cancer metastasis. In the eye, EMT and EndMT play key roles in the pathogenesis of subretinal fibrosis, the end-stage of age-related macular degeneration (AMD) that leads to profound and permanent vision loss. Predominant in subretinal fibrotic lesions are matrix-producing mesenchymal cells believed to originate from the retinal pigment epithelium (RPE) and/or choroidal endothelial cells (CECs) through EMT and EndMT, respectively. Recent evidence suggests that EMT of RPE may also be implicated during the early stages of AMD. Transforming growth factor-beta (TGFβ) is a key cytokine orchestrating both EMT and EndMT. Investigations in the molecular mechanisms underpinning EMT and EndMT in AMD have implicated a myriad of contributing factors including signaling pathways, extracellular matrix remodelling, oxidative stress, inflammation, autophagy, metabolism and mitochondrial dysfunction. Questions arise as to differences in the mesenchymal cells derived from these two processes and their distinct mechanistic contributions to the pathogenesis of AMD. Detailed discussion on the AMD microenvironment highlights the synergistic interactions between RPE and CECs that may augment the EMT and EndMT processes in vivo. Understanding the differential regulatory networks of EMT and EndMT and their contributions to both the dry and wet forms of AMD can aid the development of therapeutic strategies targeting both RPE and CECs to potentially reverse the aberrant cellular transdifferentiation processes, regenerate the retina and thus restore vision.

p62/SQSTM1 accumulation due to degradation inhibition and transcriptional activation plays a critical role in silica nanoparticle-induced airway inflammation via NF-κB activation

BACKGROUND

Most nanoparticles (NPs) reportedly block autophagic flux, thereby upregulating p62/SQSTM1 through degradation inhibition. p62 also acts as a multifunctional scaffold protein with multiple domains, and is involved in various cellular processes. However, the autophagy substrate-independent role of p62 and its regulation at the transcriptional level upon NPs exposure remain unclear.

RESULTS

In this work, we exposed BEAS-2b cells and mice to silica nanoparticles (SiNPs), and found that SiNPs increased p62 protein levels in vivo and vitro. Then, we further explored the role and mechanism of SiNPs-stimulated p62 in vitro, and found that p62 degradation was inhibited due to autophagic flux blockade. Mechanistically, SiNPs blocked autophagic flux through impairment of lysosomal capacity rather than defective autophagosome fusion with lysosomes. Moreover, SiNPs stimulated translocation of NF-E2-related factor 2 (Nrf2) to the nucleus from the cytoplasm, which upregulated p62 transcriptional activation through direct binding of Nrf2 to the p62 promoter. Nrf2 siRNA dramatically reduced both the mRNA and protein levels of p62. These two mechanisms led to p62 protein accumulation, thus increasing interleukin (IL)-1 and IL-6 expression. SiNPs activated nuclear factor kappa B (NF-κB), and this effect could be alleviated by p62 knockdown.

CONCLUSION

SiNPs caused accumulation of p62 through both pre- and post-translational mechanisms, resulting in airway inflammation. These findings improve our understanding of SiNP-induced pulmonary damage and the molecular targets available to mitigate it.

Podocytopathy and Nephrotic Syndrome in Mice with Podocyte-Specific Deletion of the Asah1 Gene: Role of Ceramide Accumulation in Glomeruli

Lysosomal acid ceramidase (Ac) has been shown to be critical for ceramide hydrolysis and regulation of lysosome function and cellular homeostasis. In the present study, we generated a knockout mouse strain (Asah1^fl/fl/Podo^Cre) with a podocyte-specific deletion of the α subunit (main catalytic subunit) of Ac. Although no significant morphologic changes in glomeruli were observed in these mice under light microscope, severe proteinuria and albuminuria were found in these podocyte-specific knockout mice compared with control genotype littermates. Transmission electron microscopic analysis showed that podocytes of the knockout mice had distinctive foot process effacement and microvillus formation. These functional and morphologic changes indicate the development of nephrotic syndrome in mice bearing the Asah1 podocyte-specific gene deletion. Ceramide accumulation determined by liquid chromatography-tandem mass spectrometry was demonstrated in isolated glomeruli of Asah1^fl/fl/Podo^Cre mice compared with their littermates. By crossbreeding Asah1^fl/fl/Podo^Cre mice with Smpd1^-/- mice, we also produced a double knockout strain, Smpd1^-/-/Asah1^fl/fl/Podo^Cre, that also lacks Smpd1, the acid sphingomyelinase that hydrolyzes sphingomyelin to ceramide. These mice exhibited significantly lower levels of glomerular ceramide with decreased podocyte injury compared with Asah1^fl/fl/Podo^Cre mice. These results strongly suggest that lysosomal Ac in podocytes is essential for the maintenance of the structural and functional integrity of podocytes.

Podocyte Lysosome Dysfunction in Chronic Glomerular Diseases

Podocytes are visceral epithelial cells covering the outer surface of glomerular capillaries in the kidney. Blood is filtered through the slit diaphragm of podocytes to form urine. The functional and structural integrity of podocytes is essential for the normal function of the kidney. As a membrane-bound organelle, lysosomes are responsible for the degradation of molecules via hydrolytic enzymes. In addition to its degradative properties, recent studies have revealed that lysosomes may serve as a platform mediating cellular signaling in different types of cells. In the last decade, increasing evidence has revealed that the normal function of the lysosome is important for the maintenance of podocyte homeostasis. Podocytes have no ability to proliferate under most pathological conditions; therefore, lysosome-dependent autophagic flux is critical for podocyte survival. In addition, new insights into the pathogenic role of lysosome and associated signaling in podocyte injury and chronic kidney disease have recently emerged. Targeting lysosomal functions or signaling pathways are considered potential therapeutic strategies for some chronic glomerular diseases. This review briefly summarizes current evidence demonstrating the regulation of lysosomal function and signaling mechanisms as well as the canonical and noncanonical roles of podocyte lysosome dysfunction in the development of chronic glomerular diseases and associated therapeutic strategies.

SPAG5-AS1 inhibited autophagy and aggravated apoptosis of podocytes via SPAG5/AKT/mTOR pathway

Objectives

Podocyte injury is a prediction marker of diabetic nephropathy (DN), and AKT/mTOR pathway–mediated inhibition of autophagy is widely reported to contribute to podocyte damage. Recent study stated that sperm‐associated antigen 5 (SPAG5) activated AKT/mTOR signalling in bladder urothelial carcinoma, indicating SPAG5 might regulate autophagy and play a role in podocyte damage.

Materials and methods

Apoptosis and autophagy of human podocytes (HPCs) were detected by flow cytometry and immunofluorescence (IF). Gene level was assessed by Western blot and RT‐qPCR. Molecular interactions were determined by pulldown, RNA immunoprecipitation (RIP), co‐immunoprecipitation (co‐IP), chromatin immunoprecipitation (ChIP) and luciferase reporter assays.

Results

SPAG5 mRNA and protein levels were upregulated under high glucose treatment in HPCs. Silencing SPAG5 reversed the increase of apoptosis and decrease of autophagy in high glucose–treated HPCs. Later, we found a long non‐coding RNA (lncRNA) SPAG5 antisense RNA1 (SPAG5‐AS1) as a neighbour gene to SPAG5. Mechanistically, YY1 transcriptionally upregulated SPAG5‐AS1 and SPAG5 in high glucose–treated podocytes. SPAG5‐AS1 acted as a competitive endogenous RNA (ceRNA) to regulate miR‐769‐5p/YY1 axis and induce SPAG5. SPAG5‐AS1 interacted with ubiquitin‐specific peptidase 14 (USP14) and leads to de‐ubiquitination and stabilization of SPAG5 protein.

Conclusions

This study revealed that SPAG5‐AS1 inhibited autophagy and aggravated apoptosis of podocytes via SPAG5/AKT/mTOR pathway, indicating SPAG5‐AS1/SPAG5 as a potential target for the alleviation of podocyte injury and offering new thoughts for the treatments of DN.

Cudraxanthone D Regulates Epithelial-Mesenchymal Transition by Autophagy Inhibition in Oral Squamous Cell Carcinoma Cell Lines

Cudraxanthone D (CD), derived from the root bark of Cudrania tricuspidata, is a natural xanthone compound. However, the biological activity of CD in terms of human metabolism has been barely reported to date. Autophagy is known as a self-degradation process related to cancer cell viability and metastasis. Herein, we investigated the effects of CD on human oral squamous cell carcinoma (OSCC) metastatic related cell phenotype. We confirmed that CD effectively decreased proliferation and viability in a time- and dose-dependent manner in human OSCC cells. In addition, OSCC cell migration, invasion, and EMT were inhibited by CD. To further determine the underlying mechanism of CD's inhibition of cell metastatic potential, we established the relationship between EMT and autophagy in OSCC cells. Thus, our findings indicated that CD inhibited the potential metastatic abilities of OSCC cells by attenuating autophagy.

p66Shc regulates podocyte autophagy in high glucose environment through the Notch-PTEN-PI3K/Akt/mTOR pathway

BACKGROUND AND AIMS

Autophagy has been found to be involved in podocyte injury, which is a key factor in the progression of diabetic kidney disease (DKD). p66Shc is an important protein adaptor that regulates production of reactive oxygen species (ROS) and induction of apoptosis, and is a novel biomarker for oxidative damage of renal tubules. Our preliminary studies showed that p66Shc expression in podocytes of DKD patients is increased, while autophagic flux and podocyte number is decreased in DKD patients. The mechanism by which p66Shc may regulate podocyte autophagy and injury remains unknown. The present study aimed to investigate the molecular function of p66Shc under high glucose condition and its possible therapeutic utility in DKD.

METHODS

We histologically evaluated kidney injury in a streptozocin (STZ)-induced mouse model of diabetes using HE, PAS, PASM, and Masson staining and assessed glomerular structure by transmission electron microscopy. The apoptosis rate of high glucose-treated podocytes was assessed by TUNEL and Annexin V/PI staining. Markers of podocyte autophagy were measured by immunofluorescence and western blotting. DHE/ET fluorescence quantification was used for ROS detection and quantification.

RESULTS

Urine creatinine, serum creatinine, urinary microalbumin, and p66Shc expression were significantly increased in STZ-induced diabetic mice. Cultured MPC5 podocytes subjected to high glucose showed reduced viability, and p66Shc overexpression further accelerated apoptosis. p66Shc knockdown enhanced HG-induced autophagy, while p66Shc overexpression reduced the expression of PTEN and increased the expression of mTOR and phospho-mTOR. LC3 protein expression was higher in cells with p66Shc knockdown, indicating that activation of p66Shc inhibits podocyte autophagy. DAPT, an inhibitor of the Notch pathway, downregulated the expression of p66Shc.

CONCLUSION

These findings indicate that p66Shc inhibits podocyte autophagy and induces apoptosis through the Notch -PTEN-PI3K/Akt/ mTOR signaling pathway in high glucose environment, providing novel evidence for its potential role in DKD treatment.

C/EBPα deficiency in podocytes aggravates podocyte senescence and kidney injury in aging mice

Kidney aging leads to an increased incidence of end-stage renal disease (ESRD) in the elderly, and aging is a complex biological process controlled by signaling pathways and transcription factors. Podocyte senescence plays a central role in injury resulting from kidney aging. Here, we demonstrated the critical role of C/EBPα in podocyte senescence and kidney aging by generating a genetically modified mouse model of chronological aging in which C/EBPα was selectively deleted in podocytes and by overexpressing C/EBPα in cultured podocytes, in which premature senescence was induced by treatment with adriamycin. Moreover, we illuminated the mechanisms by which podocyte senescence causes tubular impairment by stimulating HK-2 cells with bovine serum albumin (BSA) and chloroquine. Our findings suggest that C/EBPα knockout in podocytes aggravates podocyte senescence through the AMPK/mTOR pathway, leading to glomerulosclerosis, and that subsequent albuminuria exacerbates the epithelial-mesenchymal transdifferentiation of senescent tubular cells by suppressing autophagy. These observations highlight the importance of C/EBPα as a new potential target in kidney aging.

Role of Podocyte Injury in Glomerulosclerosis

Finding new therapeutic targets of glomerulosclerosis treatment is an ongoing quest. Due to a living environment of various stresses and pathological stimuli, podocytes are prone to injuries; moreover, as a cell without proliferative potential, loss of podocytes is vital in the pathogenesis of glomerulosclerosis. Thus, sufficient understanding of factors and underlying mechanisms of podocyte injury facilitates the advancement of treating and prevention of glomerulosclerosis. The clinical symptom of podocyte injury is proteinuria, sometimes with loss of kidney functions progressing to glomerulosclerosis. Injury-induced changes in podocyte physiology and function are actually not a simple passive process, but a complex interaction of proteins that comprise the anatomical structure of podocytes at molecular levels. This chapter lists several aspects of podocyte injuries along with potential mechanisms, including glucose and lipid metabolism disorder, hypertension, RAS activation, micro-inflammation, immune disorder, and other factors. These aspects are not technically separated items, but intertwined with each other in the pathogenesis of podocyte injuries.

Control of lysosomal TRPML1 channel activity and exosome release by acid ceramidase in mouse podocytes

The transient receptor potential mucolipin 1 (TRPML1) channel has been reported to mediate lysosomal Ca2+ release that is involved in Ca2+-dependent lysosome trafficking and autophagic flux. However, this regulatory mechanism of lysosomal TRPML1 channel activity in podocytes remains poorly understood. In the present study, we tested whether the TRPML1 channel in podocytes mediates lysosome trafficking, which is essential for multivesicular body (MVB) degradation by lysosomes. We first demonstrated the abundant expression of TRPML1 channel in podocytes. By GCaMP3 Ca2+ imaging, we characterized the lysosomal specificity of TRPML1 channel-mediated Ca2+ release in podocytes. Given the important role of acid ceramidase (AC) in lysosome function and podocyte injury, we tested whether AC regulates this TRPML1 channel-mediated Ca2+ release and consequent lysosome-dependent MVB degradation in podocytes. Pharmacologically, it was found that TRPML1 channel activity was remarkably attenuated by the AC inhibitor carmofur. Sphingosine, as an AC product, was demonstrated to induce TRPML1-mediated Ca2+ release, which was inhibited by a TRPML1 blocker, verapamil. Using a Port-a-Patch planar patch-clamp system, we found that AC-associated sphingolipids, sphingomyelin, ceramide, and sphingosine had different effects on TRPML1 channel activity in podocytes. Functionally, the inhibition of AC or blockade of TRPML1 channels was found to suppress the interaction of lysosomes and MVBs, leading to increased exosome release from podocytes. These results suggest that AC is critical for TRPML1 channel-mediated Ca2+ release, which controls lysosome-MVB interaction and exosome release in podocytes.

Exosome secreted from adipose-derived stem cells attenuates diabetic nephropathy by promoting autophagy flux and inhibiting apoptosis in podocyte

Background

It is confirmed that adipose-derived stem cells (ADSCs) transplantation effectively relieves kidney fibrosis and type 2 diabetes disease in mice. Currently, exosome from urine-derived stem cells (USCs) can protect type 1 diabetes-mediated kidney injury and attenuate podocyte damage in diabetic nephropathy (DN). Exosome derived from USCs has evolved into the strategy for DN treatment, but the role of ADSCs-derived exosome (ADSCs-Exo) in DN remains unclear. The present study is aimed to investigate the therapeutic action and molecular mechanism of ADSCs-derived exosome on DN.

Methods

ADSCs and exosome were authenticated by immunofluorescence and flow cytometry. Morphology and the number of exosome were evaluated by electron microscope and Nanosight Tracking Analysis (NTA), respectively. Cell apoptosis was assessed using flow cytometry. Podocyte autophagy and signaling transduction were measured by immunofluorescence and immunoblotting. Dual Luciferase Reporter assay was employed to detect the regulatory relationship between miR-486 and Smad1.

Results

ADSCs-Exo attenuated spontaneous diabetes by reducing levels of urine protein, serum creatinine (Scr), blood urea nitrogen (BUN), and podocyte apoptosis in mice. In in vitro experiment, ADSCs-Exo also reversed high glucose-induced decrease of cell viability and the increase of cell apoptosis in MPC5 cells. In terms of mechanism, ADSCs-Exo could enhance autophagy flux and reduce podocyte injury by inhibiting the activation of mTOR signaling in MPC5 and spontaneous diabetic mice. Eventually, we found that miR-486 was the key factors in ADSCs and in the process of ADSCs-Exo-mediated improvement of DN symptom in vivo and in vitro. miR-486 reduced Smad1 expression by target regulating Smad1 whose reduction could inhibit mTOR activation, leading to the increase of autophagy and the reduction of podocyte apoptosis.

Conclusions

In conclusion, we illustrated that ADSCs-Exo vividly ameliorated DN symptom by enhancing the expression of miR-486 which led to the inhibition of Smad1/mTOR signaling pathway in podocyte. Possibly, ADSCs-Exo was used as a main therapeutic strategy for DN in future.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1177-1) contains supplementary material, which is available to authorized users.

EMT Regulation by Autophagy: A New Perspective in Glioblastoma Biology

Epithelial-to-mesenchymal transition (EMT) and its reverse process MET naturally occur during development and in tissue repair in vertebrates. EMT is also recognized as the crucial event by which cancer cells acquire an invasive phenotype through the activation of specific transcription factors and signalling pathways. Even though glial cells have a mesenchymal phenotype, an EMT-like process tends to exacerbate it during gliomagenesis and progression to more aggressive stages of the disease. Autophagy is an evolutionary conserved degradative process that cells use in order to maintain a proper homeostasis, and defects in autophagy have been associated to several pathologies including cancer. Besides modulating cell resistance or sensitivity to therapy, autophagy also affects the migration and invasion capabilities of tumor cells. Despite this evidence, few papers are present in literature about the involvement of autophagy in EMT-like processes in glioblastoma (GBM) so far. This review summarizes the current understanding of the interplay between autophagy and EMT in cancer, with special regard to GBM model. As the invasive behaviour is a hallmark of GBM aggressiveness, defining a new link between autophagy and EMT can open a novel scenario for targeting these processes in future therapeutical approaches.

Astragaloside IV inhibits glucose-induced epithelial-mesenchymal transition of podocytes through autophagy enhancement via the SIRT-NF-κB p65 axis

Both autophagy and podocyte epithelial-mesenchymal transition (EMT) are critical factors in glomerular diseases that involve proteinuria and fibrosis. Here, we sought to determine whether plant-derived saponin astragaloside IV (AS-IV) was able to reverse renal fibrosis and improve renal function through regulation of autophagy and podocyte EMT. Cultured immortalized mouse podocytes and KK-Ay mice models of diabetes were exposed to AS-IV. Western blotting, real-time PCR, immunofluorescence and histochemistry were used to analyze markers of autophagy and podocyte EMT. We observed that AS-IV inhibited glucose-induced podocyte EMT and enhanced autophagy by decreasing NF-κB subunit p65 acetylation as well as increasing Sirtuin1 (SIRT1) expression. Treatment of the cells and animal models with a SIRT1 inhibitor EX527 was able to reverse these effects. The SIRT1 activator SRT1720 was also found to decrease p65 acetylation and enhance autophagy in glucose-induced podocyte EMT. Additionally, further treatment with autophagy inhibitor 3-methyladenine was able to reverse the effects of AS-IV on podocyte EMT, while the autophagy activator rapamycin or the NF-κB pathway inhibitor ammonium pyrrolidinedithiocarbamate (PDTC) were able to reverse glucose-induced podocyte EMT. Notably, both renal fibrosis and renal function in diabetic KK-Ay mice were improved after treatment with AS-IV. These findings support AS-IV as a renoprotective agent that likely exerts its effects on podocyte EMT through modulation of the SIRT1-NF-κB pathway and autophagy activation. Further studies are required to clarify the role of AS-IV as a potential therapeutic agent in glomerular diseases.

Contribution of p62/SQSTM1 to PDGF-BB-induced myofibroblast-like phenotypic transition in vascular smooth muscle cells lacking Smpd1 gene

Accumulating evidence indicates a critical role of autophagy in regulating vascular smooth muscle cell (SMC) homeostasis in atherogenesis. However, little is known about the modulatory role of autophagy in PDGF-BB-induced SMC transition towards the synthetic phenotype and extracellular matrix remodeling. We recently demonstrated that acid sphingomyelinase (ASM, encoded by Smpd1 gene) controls autophagy maturation in coronary arterial SMCs. Here, we demonstrate that PDGF-BB stimulation causes a myofibroblast-like non-canonical synthetic phenotype transition in Smpd1^−/− SMCs. These non-canonical phenotypic changes induced by PDGF-BB in Smpd1^−/− SMCs were characterized by increased expression of fibroblast-specific protein (FSP-1), massive deposition of collagen type I, decreased cell size, elevated inflammatory status with enhanced cytokine release and adhesion molecule expression. Mechanistically, PDGF-BB induces prolonged Akt activation that causes decreased autophagosome biogenesis and thereby exaggerates p62/SQSTM1 accumulation in Smpd1^−/− SMCs. More importantly, Akt inhibition or p62/SQSTM1 gene silencing attenuates PDGF-BB-induced phenotypic changes in Smpd1^−/− SMCs. This first demonstration of a p62/SQSTM1-dependent myofibroblast-like phenotypic transition in Smpd1^−/− SMCs suggests that ASM-mediated autophagy pathway contributes to maintaining the arterial smooth muscle homeostasis in situation of vascular remodeling during atherosclerosis.

A Role for βA3/A1-Crystallin in Type 2 EMT of RPE Cells Occurring in Dry Age-Related Macular Degeneration

Purpose

The RPE cells have a major role in the development of dry age-related macular degeneration (AMD). We present novel evidence that βA3/A1-crystallin, encoded by the Cryba1 gene, a protein known to be important for lysosomal clearance in the RPE, also has a role in epithelial-to-mesenchymal transition (EMT) of RPE cells.

Methods

RPE from dry AMD globes, genetically engineered mice lacking Cryba1 globally or specifically in the RPE, spontaneous mutant rats (Nuc1) with a loss-of-function mutation in Cryba1, and the melanoma OCM3 cell line were used. Spatial localization of proteins was demonstrated with immunofluorescence, gene expression levels were determined by quantitative PCR (qPCR), and protein levels by Western blotting. Cell movement was evaluated using wound healing and cell migration assays. Co-immunoprecipitation was used to identify binding partners of βA3/A1-crystallin.

Results

βA3/A1-crystallin is upregulated in polarized RPE cells compared to undifferentiated cells. Loss of βA3/A1-crystallin in murine and human RPE cells resulted in upregulation of Snail and vimentin, downregulation of E-cadherin, and increased cell migration. βA3/A1-crystallin binds to cortactin, and loss of βA3/A1-crystallin resulted in increased P-cortactin^Y421. The RPE from AMD samples had increased Snail and vimentin, and decreased E-cadherin, compared to age-matched controls.

Conclusions

We introduced a novel concept of dry AMD initiation induced by lysosomal clearance defects in the RPE and subsequent attempts by RPE cells to avoid the resulting stress by undergoing EMT. We demonstrate that βA3/A1-crystallin is a potential therapeutic target for AMD through rejuvenation of lysosomal dysfunction and potentially, reversal of EMT.

Novel oncogene COPS3 interacts with Beclin1 and Raf-1 to regulate metastasis of osteosarcoma through autophagy

Background

Expression of COP9 signalosome subunit 3 (COPS3), an oncogene overexpressed in osteosarcoma, has been demonstrated to be significantly correlated with tumor metastasis. However, the underlying mechanism by which COPS3 promotes metastasis of osteosarcoma and its role in autophagy remain unknown.

Methods

The expression of COPS3 was detected in primary osteosarcoma tissues and matching lung metastasis tissues by immunohistochemistry (IHC). The effect of COPS3 on the metastasis of osteosarcoma cells was investigated by transwell, wound healing assays and animal studies. Indicated proteins was analyzed by western blotting when COPS3 was knockdown or overexpressed. The COPS3 Interacting protein was determined by immunoprecipitation assay. The relationship between COPS3 and autophagy was detected by western blotting and immunofluorescence.

Results

We found that knockdown of COPS3 significantly reduced the lung metastasis of osteosarcoma cells in a mouse model, coinciding with downregulation of mitogen-activated protein kinase (MEK) and extracellular signal-regulated kinase (ERK) signaling. The silencing of COPS3 also inhibited the epithelial–mesenchymal transition (EMT) through the 90 kDa ribosomal S6 kinases (RSK), a family of signal transduction proteins downstream of MEK/ERK. Reciprocal immunoprecipitation assays revealed that COPS3 directly interacts with Raf-1, an upstream regulator of MEK/ERK. Surprisingly, Beclin1, an important autophagic protein, appeared in the COPS3-immunoprecipitates, along with the autophagic markers LC3-I and LC3-II. Loss of COPS3 completely inhibited H₂O₂-induced autophagic flux and reduced Beclin1 expression. Additionally, autophagy inhibitor or silencing of Beclin1 both decreased cell metastasis.

Conclusions

Taken together, these data reveal a novel function of COPS3 in the regulation of autophagy and highlight the relationship between autophagy and metastasis in osteosarcoma cells.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0791-6) contains supplementary material, which is available to authorized users.

DRAM1 regulates the migration and invasion of hepatoblastoma cells via autophagy-EMT pathway

DNA-damage regulated autophagy modulator 1 (DRAM1) is known as a target of TP53-mediated autophagy, and has been reported to promote the migration and invasion abilities of glioblastoma stem cells. However, the precise contribution of DRAM1 to cancer cell invasion and migration, and the underlying mechanisms remain unclear. In the present study, small interfering (si)RNA or short hairpin RNA mediated knockdown of DRAM1 was performed in hepatoblastoma cells and the migration and invasion abilities were detected in vitro and in vivo. To investigate the underlying mechanisms, western blotting and immunofluorescence were used to detect the expression of autophagy-associated proteins and epithelial-mesenchymal-transition (EMT)-associated markers. The results showed that DRAM1 knockdown by specific siRNA abrogated cell autophagy, as well as inhibited the migration and invasion of HepG2 cells in Transwell assays, which may be reversed by rapamycin treatment. In addition, DRAM1 knockdown increased the expression of E-Cadherin while decreased the expression of vimentin in HepG2 cells, which was also be reversed by rapamycin treatment. Taken together, these results suggest that DRAM1 is involved in the regulation of the migration and invasion of HepG2 cells via autophagy-EMT pathway.

Non-genetic mechanisms of diabetic nephropathy

Diabetic nephropathy (DN) is one of the most common microvascular complications in diabetes mellitus patients and is characterized by thickened glomerular basement membrane, increased extracellular matrix formation, and podocyte loss. These phenomena lead to proteinuria and altered glomerular filtration rate, that is, the rate initially increases but progressively decreases. DN has become the leading cause of end-stage renal disease. Its prevalence shows a rapid growth trend and causes heavy social and economic burden in many countries. However, this disease is multifactorial, and its mechanism is poorly understood due to the complex pathogenesis of DN. In this review, we highlight the new molecular insights about the pathogenesis of DN from the aspects of immune inflammation response, epithelial-mesenchymal transition, apoptosis and mitochondrial damage, epigenetics, and podocyte-endothelial communication. This work offers groundwork for understanding the initiation and progression of DN, as well as provides ideas for developing new prevention and treatment measures.

Autophagy as a potential therapeutic target during epithelial to mesenchymal transition in renal cell carcinoma: An in vitro study

Cancer progression toward invasive and metastatic disease is aided by reactivation of epithelial-mesenchymal transition (EMT), involving transdifferentiation of epithelial cells into mesenchymal phenotype. This leads to increased migratory and stem cell-like features in the cells. These EMT cells are more resistant to chemotherapy and it is hypothesized that the phenomenon of autophagy induces resistance, providing a survival strategy for cells. In the present study, we induced EMT-like phenotype in renal carcinoma cells and identified corresponding higher autophagy flux in these cells. The EMT transformed cells may be a representative of the resistant cancer stem cell(CSC)-like phenotype. Autophagy was identified as a potential mechanism of cell survival in these cells thus implying that autophagy inhibition can lead to enhanced cell death. We also observed that tumor cells especially EMT transformed cells, have been 'primed' to undergo autophagy by mTOR inhibition. We observed that combined use of autophagy inhibitor and temsirolimus (TEM) improved antitumor activity against RCC in EMT transformed metastatic cells. One of the approaches for inhibiting autophagy was the use of lysosomotropic anti-malarial drug, chloroquine (CQ) and we explored the therapeutic potential of combination of CQ and the mTOR inhibitor, TEM. EMT transformed cells showed increased cell cytotoxicity when autophagy was impaired by addition CQ with TEM. This led us to conclude that inhibition of autophagy with the current therapeutic regimen could be useful in targeting the EMT transformed cells along with the bulk tumor cells in RCC.

Overexpression of dishevelled 2 is involved in tumor metastasis and is associated with poor prognosis in hepatocellular carcinoma

PURPOSE

Although hepatocellular carcinoma (HCC) is one of the most common malignant tumors, its molecular mechanism is still unknown. Dishevelled 2 (Dvl2) is one of the downstream targets of non-canonical Wnt signaling, which has been demonstrated to be of great importance in the progression of cancers. Nevertheless, the expression mechanisms and physiological significance of Dvl2 in HCC remain unclear.

METHODS

Western blotting and immunohistochemistry were used to measure Dvl2 protein expression in HCC and adjacent normal tissues of 101 patients. Wound healing and transwell assays were used to determine cell migration and invasion.

RESULTS

Dvl2 expression was upregulated in HCC tissues compared to the adjacent normal tissues. Moreover, its expression level was significantly correlated with histological grade (P = 0.042), metastasis (P = 0.005) and vein invasion (P = 0.009) in patients with HCC. Wound healing and transwell assays showed that knockdown of Dvl2 reduced cell migration and invasion in HepG2 cells. Finally, we confirmed that Dvl2 could regulate the migration and invasion of HCC cells by interacting with P62 in non-canonical Wnt signaling.

CONCLUSIONS

Our data showed that Dvl2 was overexpressed in HCC tissues and was also correlated with poor prognosis, suggesting that Dvl2 is a novel therapeutic target for HCC.

Knocking down TCF8 inhibits high glucose- and angiotensin II-induced epithelial to mesenchymal transition in podocytes

Epithelial to mesenchymal transition (EMT) is a physiological phenomenon in mammalian embryogenesis by which epithelial cells become mesenchymal stem cells. Studies have indicated that an inappropriate EMT plays a key role in a variety of pathogenic processes such as embryonic development and tumor metastasis. Moreover, recent studies have indicated EMT also plays an important role in renal fibrosis. In the current study, glucose and angiotensin II promoted EMT in podocytes as well as changes in the cellular morphology of podocytes. A high concentration of glucose and angiotensin II also promoted podocyte movement and migration. Moreover, a high concentration of glucose and angiotensin II promoted TCF8 expression. Inhibiting TCF8 expression with siRNA reversed EMT in podocytes in the presence of a high concentration of glucose and angiotensin. Inhibiting TCF8 expression also reversed changes in cellular morphology and podocyte movement and migration. Therefore, glucose and angiotensin II may promote EMT in podocytes via TCF8.

Contribution of p62 to Phenotype Transition of Coronary Arterial Myocytes with Defective Autophagy

Background:

Autophagy disorder contributes to dedifferentiation of arterial smooth muscle cells, but the mechanisms are poorly understood. Here, we sought to investigate the role of scaffolding adaptor p62/SQSTM1 (p62) in phenotype switching of mouse coronary arterial myocytes (CAMs) induced by CD38 gene deficiency or lysosomal dysfunction which blocks autophagic flux in the cells.

Methods:

Protein expression was measured by western blot analysis and immunofluorescent staining. Cell cycle and proliferation rate were analyzed by flow cytometry and MTS assay respectively. mRNA abundance was tested by qRT-PCR.

Results:

CD38 gene deficiency or bafilomycin A1 (baf), a selective lysosomal inhibitor treatment increased proliferation rate and vimentin expression in CAMs which was prevented by p62 gene silencing. Cell percentage in G₂/M and G₀/G₁ phase was decreased and increased by CD38 deficiency or baf treatment, respectively which was accompanied by accrual of cyclin-dependent kinase 1 (CDK1) protein. Although free ubiquitin content was increased, the colocalization of it to CDK1 was markedly decreased in CD38^−/− or baf treated CAMs. Furthermore, the changes in both cell cycle and CDK1 ubiquitinylation could be restored by p62 gene silencing.

Conclusion:

The results suggest in CD38^−/− or baf treated CAMs, p62 accumulation promotes phenotype transition and proliferation by accelerating cell cycle progress through G₂/M which might relate to the compromised ubiquitinylation and degradation of CDK1.

Autophagy and epithelial-mesenchymal transition: an intricate interplay in cancer

Autophagy and epithelial to mesenchymal transition (EMT) are major biological processes in cancer. Autophagy is a catabolic pathway that aids cancer cells to overcome intracellular or environmental stress, including nutrient deprivation, hypoxia and drugs effect. EMT is a complex transdifferentiation through which cancer cells acquire mesenchymal features, including motility and metastatic potential. Recent observations indicate that these two processes are linked in a complex relationship. On the one side, cells that underwent EMT require autophagy activation to survive during the metastatic spreading. On the other side, autophagy, acting as oncosuppressive signal, tends to inhibit the early phases of metastasization, contrasting the activation of the EMT mainly by selectively destabilizing crucial mediators of this process. Currently, still limited information is available regarding the molecular hubs at the interplay between autophagy and EMT. However, a growing number of evidence points to the functional interaction between cytoskeleton and mitochondria as one of the crucial regulatory center at the crossroad between these two biological processes. Cytoskeleton and mitochondria are linked in a tight functional relationship. Controlling mitochondria dynamics, the cytoskeleton cooperates to dictate mitochondria availability for the cell. Vice versa, the number and structure of mitochondria, which are primarily affected by autophagy-related processes, define the energy supply that cancer cells use to reorganize the cytoskeleton and to sustain cell movement during EMT. In this review, we aim to revise the evidence on the functional crosstalk between autophagy and EMT in cancer and to summarize the data supporting a parallel regulation of these two processes through shared signaling pathways. Furthermore, we intend to highlight the relevance of cytoskeleton and mitochondria in mediating the interaction between autophagy and EMT in cancer.

Protective Effect of Tempol on Acute Kidney Injury Through PI3K/Akt/Nrf2 Signaling Pathway

BACKGROUND/AIMS

Tempol is a protective antioxidant against ischemic injury in many animal models. The molecular mechanisms are not well understood. Nuclear factor erythroid 2-related factor (Nrf2) is a master transcription factor during oxidative stress, which is enhanced by activation of protein kinase C (PKC) pathway. Another factor, tubular epithelial apoptosis, is mediated by activation of phosphoinositide 3-kinase (PI3K)/protein kinase B (PKB, Akt) signaling pathway during renal ischemic injury. We tested the hypothesis that tempol activates PKC or PI3K/Akt/Nrf2 pathways to transcribe many genes that coordinate endogenous antioxidant defense.

METHODS

The right renal pedicle was clamped for 45 minutes and the left kidney was removed to study renal ischemia/reperfusion (I/R) injury in C57BL/6 mice. The response was assessed from serum parameters, renal morphology and renal expression of PKC, phosphorylated-PKC (p-PKC), Nrf2, heme oxygenase-1 (HO-1), Akt, phosphorylated-Akt (p-Akt), pro-caspase-3 and cleaved caspase-3 in groups of sham and I/R mice given vehicle, or tempol (50 or 100 mg/kg, intraperitoneal injection).

RESULTS

The serum malondialdehyde (MDA, marker of reactive oxygen species) doubled and the BUN and creatinine increased 5- to 10-fold after I/R injury. Tempol (50 or 100 mg/kg) prevented the increases in MDA but only tempol (50 mg/kg) lessened the increases in BUN and creatinine and moderated the acute tubular necrosis. I/R did not change expression of PKC or p-PKC but reduced renal expression of Nrf2, p-Akt, HO-1 and pro-caspase-3 and increased cleaved caspase-3. Tempol (50 mg/kg) prevented these changes produced by I/R whereas tempol (100 mg/kg) had lesser or inconsistent effects.

CONCLUSION

Tempol (50 mg/kg) prevents lipid peroxidation and attenuates renal damage after I/R injury. The beneficial pathway apparently is not dependent on upregulation or phosphorylation of PKC, at lower tempol doses, does implicate upregulation of Akt with expression of Nrf2 that could account for the increase in the antioxidant gene HO-1 and a reduction in the cleavage of the cellular damage marker pro-caspase-3.

Autophagy regulates hepatocyte identity and epithelial-to-mesenchymal and mesenchymal-to-epithelial transitions promoting Snail degradation

Epithelial-to-mesenchymal transition (EMT) and the reverse process mesenchymal-to-epithelial transition (MET) are events involved in development, wound healing and stem cell behaviour and contribute pathologically to cancer progression. The identification of the molecular mechanisms underlying these phenotypic conversions in hepatocytes are fundamental to design specific therapeutic strategies aimed at optimising liver repair. The role of autophagy in EMT/MET processes of hepatocytes was investigated in liver-specific autophagy-deficient mice (Alb-Cre;ATG7^fl/fl) and using the nontumorigenic immortalised hepatocytes cell line MMH. Autophagy deficiency in vivo reduces epithelial markers' expression and increases the levels of mesenchymal markers. These alterations are associated with an increased protein level of the EMT master regulator Snail, without transcriptional induction. Interestingly, we found that autophagy degrades Snail in a p62/SQSTM1 (Sequestosome-1)-dependent manner. Moreover, accordingly to a pro-epithelial function, we observed that autophagy stimulation strongly affects EMT progression, whereas it is necessary for MET. Finally, we found that the EMT induced by TGFβ affects the autophagy flux, indicating that these processes regulate each other. Overall, we found that autophagy regulates the phenotype plasticity of hepatocytes promoting their epithelial identity through the inhibition of the mesenchymal programme.