Delayed treatment with plasminogen activator inhibitor-1 decoys reduces tubulointerstitial fibrosis

Bioinformatics-integrated screening of systemic sclerosis-specific expressed markers to identify therapeutic targets

Background

Systemic sclerosis (SSc) is a rare autoimmune disease characterized by extensive skin fibrosis. There are no effective treatments due to the severity, multiorgan presentation, and variable outcomes of the disease. Here, integrated bioinformatics was employed to discover tissue-specific expressed hub genes associated with SSc, determine potential competing endogenous RNAs (ceRNA) regulatory networks, and identify potential targeted drugs.

Methods

In this study, four datasets of SSc were acquired. To identify the genes specific to tissues or organs, the BioGPS web database was used. For differentially expressed genes (DEGs), functional and enrichment analyses were carried out, and hub genes were screened and shown in a network of protein-protein interactions (PPI). The potential lncRNA-miRNA-mRNA ceRNA network was constructed using the online databases. The specifically expressed hub genes and ceRNA network were validated in the SSc mouse and in normal mice. We also used the receiver operating characteristic (ROC) curve to determine the diagnostic values of effective biomarkers in SSc. Finally, the Drug-Gene Interaction Database (DGIdb) identified specific medicines linked to hub genes.

Results

The pooled datasets identified a total of 254 DEGs. The tissue/organ-specifically expressed genes involved in this analysis are commonly found in the hematologic/immune system and bone/muscle tissue. The enrichment analysis of DEGs revealed the significant terms such as regulation of actin cytoskeleton, immune-related processes, the VEGF signaling pathway, and metabolism. Cytoscape identified six gene cluster modules and 23 hub genes. And 4 hub genes were identified, including Serpine1, CCL2, IL6, and ISG15. Consistently, the expression of Serpine1, CCL2, IL6, and ISG15 was significantly higher in the SSc mouse model than in normal mice. Eventually, we found that MALAT1-miR-206-CCL2, let-7a-5p-IL6, and miR-196a-5p-SERPINE1 may be promising RNA regulatory pathways in SSc. Besides, ten potential therapeutic drugs associated with the hub gene were identified.

Conclusions

This study revealed tissue-specific expressed genes, SERPINE1, CCL2, IL6, and ISG15, as effective biomarkers and provided new insight into the mechanisms of SSc. Potential RNA regulatory pathways, including MALAT1-miR-206-CCL2, let-7a-5p-IL6, and miR-196a-5p-SERPINE1, contribute to our knowledge of SSc. Furthermore, the analysis of drug-hub gene interactions predicted TIPLASININ, CARLUMAB and BINDARIT as candidate drugs for SSc.

The Genomic Response to TGF-β1 Dictates Failed Repair and Progression of Fibrotic Disease in the Obstructed Kidney

Tubulointerstitial fibrosis is a common and diagnostic hallmark of a spectrum of chronic renal disorders. While the etiology varies as to the causative nature of the underlying pathology, persistent TGF-β1 signaling drives the relentless progression of renal fibrotic disease. TGF-β1 orchestrates the multifaceted program of kidney fibrogenesis involving proximal tubular dysfunction, failed epithelial recovery or re-differentiation, capillary collapse and subsequent interstitial fibrosis eventually leading to chronic and ultimately end-stage disease. An increasing complement of non-canonical elements function as co-factors in TGF-β1 signaling. p53 is a particularly prominent transcriptional co-regulator of several TGF-β1 fibrotic-response genes by complexing with TGF-β1 receptor-activated SMADs. This cooperative p53/TGF-β1 genomic cluster includes genes involved in cellular proliferative control, survival, apoptosis, senescence, and ECM remodeling. While the molecular basis for this co-dependency remains to be determined, a subset of TGF-β1-regulated genes possess both p53- and SMAD-binding motifs. Increases in p53 expression and phosphorylation, moreover, are evident in various forms of renal injury as well as kidney allograft rejection. Targeted reduction of p53 levels by pharmacologic and genetic approaches attenuates expression of the involved genes and mitigates the fibrotic response confirming a key role for p53 in renal disorders. This review focuses on mechanisms underlying TGF-β1-induced renal fibrosis largely in the context of ureteral obstruction, which mimics the pathophysiology of pediatric unilateral ureteropelvic junction obstruction, and the role of p53 as a transcriptional regulator within the TGF-β1 repertoire of fibrosis-promoting genes.

Sauchinone Protects Renal Mesangial Cell Dysfunction against Angiotensin II by Improving Renal Fibrosis and Inflammation

Abnormal and excessive growth of mesangial cells is important in the pathophysiologic processes of diabetes-associated interstitial fibrosis and glomerulosclerosis, leading to diabetic nephropathy, which eventually turns into end-stage renal disease. Sauchinone, a biologically-active lignan isolated from aerial parts of Saururus chinensis, has anti-inflammatory and anti-viral activities effects on various cell types. However, there are no studies reporting the effects of sauchinone on diabetic nephropathy. The present study aims to investigate the role of sauchinone in mesangial cell proliferation and fibrosis induced by angiotensin II, as well as the underlying mechanisms of these processes. Human renal mesangial cells were induced by angiotensin II (AngII, 10 μM) in the presence or absence of sauchinone (0.1-1 μM) and incubated for 48 h. In this study, we found that AngII induced mesangial cell proliferation, while treatment with sauchinone inhibited the cell proliferation in a dose-dependent manner. Pre-treatment with sauchinone induced down-regulation of cyclins/CDKs and up-regulation of CDK inhibitor, p21, and p27kip1 expression. In addition, AngII-enhanced expression of fibrosis biomarkers such as fibronectin, collagen IV, and connective tissue growth factor (CTGF), which was markedly attenuated by sauchinone. Sauchinone also decreased AngII-induced TGF-β1 and Smad-2, Smad-3, and Smad-4 expression. This study further revealed that sauchinone ameliorated AngII-induced mesangial inflammation through disturbing activation of inflammatory factors, and NLRP3 inflammasome, which is composed of the NLRP3 protein, procaspase-1, and apoptosis-associated speck-like protein containing a CARD (ASC). Moreover, pretreatment of sauchinone inhibited NF-κB translocation and ROS production in AngII-exposed mesangial cells. These data suggest that sauchinone has a protective effect on renal proliferation, fibrosis and inflammation. Therefore, sauchinone might be a potential pharmacological agent in prevention of AngII-induced renal damage leading to diabetic nephropathy.

Astragaloside IV ameliorates high glucose‑induced renal tubular epithelial‑mesenchymal transition by blocking mTORC1/p70S6K signaling in HK‑2 cells

Astragaloside IV (AST) is the major active saponin in Astragalus membranaceus and, reportedly, has a variety of pharmacological activities. However, the potential of AST to ameliorate high glucose‑mediated renal tubular epithelial‑mesenchymal transition (EMT) remains undetermined. The aim of the present research was to explore the effect and mechanism of AST in EMT of renal tubular epithelial cells, as an underlying mechanism of renal fibrosis and a vital feature involved in diabetic nephropathy. The effect of AST on the EMT of renal tubular epithelial cells (HK‑2) stimulated by high glucose was investigated and it was attempted to elucidate the potential underlying mechanism. The expression of E‑cadherin and α‑smooth muscle actin were determined by western blotting and immunofluorescence assays. The expression of the mammalian target of rapamycin complex 1 (mTORC1)/ ribosomal protein S6 kinase β‑1 (p70S6K) signaling pathway and protein levels of four transcriptional factors (snail, slug, twist and zinc finger E‑box‑binding homeobox 1) were also determined by western blotting. Additionally, extracellular matrix components, including fibronectin (FN) and collagen type IV (Col IV) were detected by ELISA. The results suggested that the EMT of HK‑2 cells and the mTORC1/p70S6K pathway were activated by high glucose. The expression of snail and twist in HK‑2 cells was elevated by high glucose. Furthermore, extracellular matrix components, FN and Col IV, were increased in HK‑2 cells cultured with high glucose. In turn, treatment with AST reduced EMT features in HK‑2 cells, inhibited mTORC1/p70S6K pathway activation, downregulated expression of snail and twist, and reduced secretion of FN and Col IV. In summary, the findings suggested that AST ameliorates high glucose‑mediated renal tubular EMT by blocking the mTORC1/p70S6K signaling pathway in HK‑2 cells.

Molecular biomarkers of Graves' ophthalmopathy

Graves' ophthalmopathy (GO), a complication of Graves' disease (GD), is typified by orbital inflammation, ocular tissue expansion and remodeling and, ultimately, fibrosis. Orbital fibroblasts are key effectors of GO pathogenesis exhibiting exaggerated inflammatory and fibroproliferative responses to cytokines released by infiltrating immune cells. Activated orbital fibroblasts also produce inflammatory mediators that contribute to disease progression, facilitate the orbital trafficking of monocytes and macrophages, promote differentiation of matrix-producing myofibroblasts and stimulate accumulation of a hyaluronan-rich stroma, which leads to orbital tissue edema and fibrosis. Proteomic and transcriptome profiling of the genomic response of ocular and non-ocular fibroblasts to INF-γ and TGF-β1 focused on identification of translationally-relevant therapeutic candidates. Induction of plasminogen activator inhibitor-1 (PAI-1, SERPINE1), a clade E member of the serine protease inhibitor (SERPIN) gene family and a prominent regulator of the pericellular proteolytic microenvironment, was one of the most highly up-regulated proteins in INF-γ- or TGF-β1-stimulated GO fibroblasts as well as in severe active GD compared to patients without thyroid disease. PAI-1 has multifunctional roles in inflammatory and fibrotic processes that impact tissue remodeling, immune cell trafficking and survival as well as signaling through several receptor systems. This review focuses on the pathophysiology of the GO fibroblast and possible targets for effective drug therapy.

Sitagliptin ameliorates diabetic nephropathy by blocking TGF-β1/Smad signaling pathway

Diabetic nephropathy (DN) is the leading cause of end-stage failure of the kidney, but the efficacy of current strategies available for the prevention of DN remains unsatisfactory. The purpose of this study was to assess whether sitagliptin (SIT) has therapeutic potential for prevention of DN and to investigate its possible mechanism. The effects of SIT on DN were investigated in rats with type 2 diabetes mellitus (T2DM) and rat mesangial cells (MCs) induced by high glucose. T2DM rats were administered at a dose of 10 mg/kg SIT. The kidney index, 24 h urinary protein, blood urea nitrogen (BUN), serum creatinine (Cr), accumulation of glycogen and collagens were investigated by different methods. MCs were administered with SIT at doses of 0.1, 1 and 10 µmol/ml. The possible mechanism of SIT on protection of diabetic kidney injury was examined by expression of transforming growth factor-β1 (TGF-β1)/Smad pathway. The results showed that the SIT-treated diabetic rats significantly reduced diabetic kidney injury by inhibiting the kidney index and attenuating 24 h urinary protein, reducing BUN and serum creatinine, inhibiting progressive renal fibrosis and increassing extracellular matrix including collagen IV and fibronectin. Further studies showed that inhibition of renal fibrosis in SIT-treated diabetic rats and MCs were associated with rebalancing of TGF-β1/Smad pathway. Sitagliptin may be a potent agent for preventing the progression of DN through inhabiting TGF-β1/Smad-mediated renal fibrosis.

TGF-β1/p53 signaling in renal fibrogenesis

Fibrotic disorders of the renal, pulmonary, cardiac, and hepatic systems are associated with significant morbidity and mortality. Effective therapies to prevent or curtail the advancement to organ failure, however, remain a major clinical challenge. Chronic kidney disease, in particular, constitutes an increasing medical burden affecting >15% of the US population. Regardless of etiology (diabetes, hypertension, ischemia, acute injury, urologic obstruction), persistently elevated TGF-β1 levels are causatively linked to the activation of profibrotic signaling networks and disease progression. TGF-β1 is the principal driver of renal fibrogenesis, a dynamic pathophysiologic process that involves tubular cell injury/apoptosis, infiltration of inflammatory cells, interstitial fibroblast activation and excess extracellular matrix synthesis/deposition leading to impaired kidney function and, eventually, to chronic and end-stage disease. TGF-β1 activates the ALK5 type I receptor (which phosphorylates SMAD2/3) as well as non-canonical (e.g., src kinase, EGFR, JAK/STAT, p53) pathways that collectively drive the fibrotic genomic program. Such multiplexed signal integration has pathophysiological consequences. Indeed, TGF-β1 stimulates the activation and assembly of p53-SMAD3 complexes required for transcription of the renal fibrotic genes plasminogen activator inhibitor-1, connective tissue growth factor and TGF-β1. Tubular-specific ablation of p53 in mice or pifithrin-α-mediated inactivation of p53 prevents epithelial G₂/M arrest, reduces the secretion of fibrotic effectors and attenuates the transition from acute to chronic renal injury, further supporting the involvement of p53 in disease progression. This review focuses on the pathophysiology of TGF-β1-initiated renal fibrogenesis and the role of p53 as a regulator of profibrotic gene expression.

Sitagliptin ameliorates high glucose-induced cell proliferation and expression of the extracellular matrix in glomerular mesangial cells

Diabetic nephropathy (DN) is one of the most important causes that leads to end-stage renal disease and the efficacy of strategies currently available for the prevention of DN remains unsatisfactory. Sitagliptin (SIT), which is a dipeptidyl peptidase-4 inhibitor, exhibited a modest beneficial effect on glycated hemoglobin levels and is capable of ameliorating renal ischemia reperfusion injury. By determining the expression of transforming growth factor-β1 (TGF-β1), connective tissue growth factor (CTGF), collagen type IV (ColIV) and fibronectin (FN) levels in high glucose-cultured glomerular mesangial cells (MCs), the present study aimed to assess the anti-proliferative and anti-fibrotic effects of SIT on the therapeutic potential for the prevention of DN and its mechanism. Specifically, cell proliferation was determined via cell counting kit-8 assay, and the expression levels of TGF-β1 and CTGF mRNA were detected by reverse transcription polymerase chain reaction analysis. Furthermore, the secretion of TGF-β1, CTGF, ColIV and FN proteins was measured via enzyme-linked immunosorbent assays. The results demonstrated that high glucose induced the proliferation of MCs and enhanced the expression of TGF-β1, CTGF, ColIV and FN. Furthermore, treatment with SIT inhibited cell proliferation and the expression of TGF-β1, CTGF, ColIV and FN induced by high glucose. In conclusion, SIT inhibits cell proliferation and the expression of the major extracellular matrix proteins induced by high glucose, indicating its value for treating or relieving DN.

Effects of Free Anthraquinones Extract from the Rhubarb on Cell Proliferation and Accumulation of Extracellular Matrix in High Glucose Cultured-Mesangial Cells

Diabetic nephropathy (DN) is the leading cause of end-stage failure of the kidney, but the efficacy of currently available strategies for the prevention of DN remains unsatisfactory. In this study, we investigated the effects of free anthraquinones (FARs) extract, which was extracted from the rhubarb and purified by macroporous resin DM130 with gradient mixtures of ethanol/water as the lelution solvents, in high glucose-cultured glomerular mesangial cells (MCs). The cell proliferation was determined by CCK-8 assay, the levels of TGF-β₁, CTGF, ColIV and FN proteins in the supernatant of MCs were measured by ELISA assays, and the mRNA levels of these four genes were detected by RT-PCR. The results showed that the increased proliferation of MCs, the mRNA levels and protein expression of TGF-β₁, CTGF, ColIV and FN induced by high glucose were inhibited after the treatment with the FARs extract. This indicated that FARs extract could inhibit cell proliferation and the expression of main extracellular matrix induced by high glucose in MCs. The FARs extract exhibited potential values for prophylaxis and therapy of DN.

Oxidative Stress and Skin Fibrosis

Fibrosis is defined as increased fibroblast proliferation and deposition of extracellular matrix components with potential clinical ramifications including organ dysfunction and failure. Fibrosis is a characteristic finding of various skin diseases which can have life-threatening consequences. These implications call for research into this topic as only a few treatments targeting fibrosis are available. In this review, we discuss oxidative stress and its role in skin fibrosis. Recent studies have implicated the importance of oxidative stress in a variety of cellular pathways directly and indirectly involved in the pathogenesis of skin fibrosis. The cellular pathways by which oxidative stress affects specific fibrotic skin disorders are also reviewed. Finally, we also describe various therapeutic approaches specifically targeting oxidative stress to prevent skin fibrosis. We believe oxidative stress is a relevant target, and understanding the role of oxidative stress in skin fibrosis will enhance knowledge of fibrotic skin diseases and potentially produce targeted therapeutic options.

A 5-hydroxytryptamine receptor antagonist, sarpogrelate, reduces renal tubulointerstitial fibrosis by suppressing PAI-1

A selective 5-hydroxytryptamine (5-HT) 2A receptor antagonist sarpogrelate (SG) blocks serotonin-induced platelet aggregation. It has been used clinically for the treatment of peripheral arterial disease. SG might be able to improve chronic ischemia, which contributes to renal fibrosis progression by maintaining renal microcirculation. This study investigated whether SG suppresses renal fibrosis. C57BL/6 mice fed a 0.2% adenine-containing diet for 6 wk developed severe tubulointerstitial fibrosis with kidney dysfunction. Subsequent SG treatment (30 mg·kg(-1)·day(-1)) for 4 wk improved these changes significantly by increasing peritubular blood flow in the fibrotic area, as evaluated by intravital microscopy and decreasing fibrin deposition. Urinary L-type fatty acid-binding protein, up-regulated by renal hypoxia, was also reduced by SG. Additionally, results showed that mRNA expression of plasminogen activator inhibitor-1 (PAI-1), which is known to promote fibrosis by mediating and enhancing transforming growth factor (TGF)-β1 signaling, was suppressed by SG treatment in the kidney. In vitro experiments using cultured murine proximal tubular epithelial (mProx) cells revealed that incubation with TGF-β1 and 5-HT increased PAI-1 mRNA expression; SG significantly reduced it. In conclusion, SG reduces renal fibrosis not only by the antithrombotic effect of maintaining peritubular blood flow but also by suppressing PAI-1 expression in renal tubular cells.

Dual effect of chemokine CCL7/MCP-3 in the development of renal tubulointerstitial fibrosis

Most end-stage renal disease kidneys display accumulation of extracellular matrix (ECM) in the renal tubular compartment (tubular interstitial fibrosis - TIF) which is strongly correlated with the future loss of renal function. Although inflammation is a key event in the development of TIF, it can also have a beneficial anti-fibrotic role depending in particular on the stage of the pathology. Chemokines play an important role in monocyte extravasation in the inflammatory process. CCL2 has already been shown to be involved in the development of TIF but CCL7, a close relative of CCL2 and able to bind to similar receptors, has not been studied in renal disease. We therefore studied chemokine CCL7 in a model of unilateral ureteral obstruction (UUO)-induced TIF. We observed that the role of CCL7 differs depending on the stage of the pathology. In early stages (0-8 days), CCL7 deficient (CCL7-KO) mice displayed attenuated TIF potentially involving two mechanisms: an early (0-3 days) decrease of inflammatory cell infiltration followed (3-8 days) by a decrease in tubular ECM production independent of inflammation. In contrast, during later stages of obstruction (10-14 days), CCL7-KO mice displayed increased TIF which was again associated with reduced inflammation. Interestingly, the switch between this anti- to profibrotic effect was accompanied by an increased influx of immunosuppressive regulatory T cells. In conclusion, these results highlight for the first time a dual role for CCL7 in the development of renal TIF, deleterious in early stages but beneficial during later stages.

TGF-β signaling in tissue fibrosis: redox controls, target genes and therapeutic opportunities

During development of TGF-β1-initiated fibroproliferative disorders, NADPH oxidases (NOX family members) generate reactive oxygen species (ROS) resulting in downstream transcription of a subset genes encoding matrix structural elements and profibrotic factors. Prominent among the repertoire of disease-implicated genes is the TGF-β1 target gene encoding the potent profibrotic matricellular protein plasminogen activator inhibitor-1 (PAI-1 or SERPINE1). PAI-1 is the major physiologic inhibitor of the plasmin-based pericellular cascade and a causative factor in the development of vascular thrombotic and fibroproliferative disorders. ROS generation in response to TGF-β1 stimulation is rapid and precedes PAI-1 induction; engagement of non-SMAD (e.g., EGFR, Src kinase, MAP kinases, p53) and SMAD2/3 pathways are both required for PAI-1 expression and are ROS-dependent. Recent findings suggest a novel role for p53 in TGF-β1-induced PAI-1 transcription that involves ROS generation and p53/SMAD interactions. Targeting ROS and ROS-activated cellular events is likely to have therapeutic implications in the management of fibrotic disorders, particularly in the context of prolonged TGF-β1 signaling.

Fibrinogen as a damage-associated mitogenic signal for the renal fibroblast

Fibroblast proliferation is central to the evolution of renal tubulointerstitial fibrosis. Using both in vivo and in vitro approaches, Sörensen et al. describe a role for fibrinogen as a cell-surface-receptor-mediated mitogen for renal fibroblasts. This interaction, likely to be initiated by injury and extravasation and to signal principally via Toll-like receptors, implicates fibrinogen in renal fibrosis beyond its textbook description as a scaffold precursor at the end of the coagulation cascade.

TGF-β1 → SMAD/p53/USF2 → PAI-1 transcriptional axis in ureteral obstruction-induced renal fibrosis

Chronic kidney disease constitutes an increasing medical burden affecting 26 million people in the United States alone. Diabetes, hypertension, ischemia, acute injury, and urological obstruction contribute to renal fibrosis, a common pathological hallmark of chronic kidney disease. Regardless of etiology, elevated TGF-β1 levels are causatively linked to the activation of profibrotic signaling pathways initiated by angiotensin, glucose, and oxidative stress. Unilateral ureteral obstruction (UUO) is a useful and accessible model to identify mechanisms underlying the progression of renal fibrosis. Plasminogen activator inhibitor-1 (PAI-1), a major effector and downstream target of TGF-β1 in the progression of several clinically important fibrotic disorders, is highly up-regulated in UUO and causatively linked to disease severity. SMAD and non-SMAD pathways (pp60(c-src), epidermal growth factor receptor [EGFR], mitogen-activated protein kinase, p53) are required for PAI-1 induction by TGF-β1. SMAD2/3, pp60(c-src), EGFR, and p53 activation are each increased in the obstructed kidney. This review summarizes the molecular basis and translational significance of TGF-β1-stimulated PAI-1 expression in the progression of kidney disease induced by ureteral obstruction. Mechanisms discussed here appear to be operative in other renal fibrotic disorders and are relevant to the global issue of tissue fibrosis, regardless of organ site.

Plasminogen activator inhibitor-1 antisense oligodeoxynucleotides abrogate mesangial fibronectin accumulation

Excessive extracellular matrix (ECM) accumulation is the main feature of chronic renal disease including diabetic nephropathy. Plasminogen activator inhibitor (PAI)-1 is known to play an important role in renal ECM accumulation in part through suppression of plasmin generation and matrix metalloproteinase (MMP) activation. The present study examined the effect of PAI-1 antisense oligodeoxynucleotide (ODN) on fibronectin upregulation and plasmin/MMP suppression in primary mesangial cells cultured under high glucose (HG) or transforming growth factor (TGF)-β1, major mediators of diabetic renal ECM accumulation. Growth arrested and synchronized rat primary mesangial cells were transfected with 1 µM phosphorothioate-modified antisense or control mis-match ODN for 24 hours with cationic liposome and then stimulated with 30 mM D-glucose or 2 ng/ml TGF-β1. PAI-1 or fibronectin protein was measured by Western blot analysis. Plasmin activity was determined using a synthetic fluorometric plasmin substrate and MMP-2 activity analyzed using zymography. HG and TGF-β1 significantly increased PAI-1 and fibronectin protein expression as well as decreased plasmin and MMP-2 activity. Transient transfection of mesangial cells with PAI-1 antisense ODN, but not mis-match ODN, effectively reversed basal as well as HG- and TGF-β1-induced suppression of plasmin and MMP-2 activity. Both basal and upregulated fibronectin secretion were also inhibited by PAI-1 antisense ODN. These data confirm that PAI-1 plays an important role in ECM accumulation in diabetic mesangium through suppression of protease activity and suggest that PAI-1 antisense ODN would be an effective therapeutic strategy for prevention of renal fibrosis including diabetic nephropathy.

Review: Therapeutic potential of plasminogen activator inhibitor-1 inhibitors

Plasminogen activator inhibitor-1 (PAI-1) is the major physiological inhibitor of fibrinolysis and regulates cell migration and fibrosis. Preclinical studies using genetically altered mice and biological or small molecule inhibitors have elucidated a role for PAI-1 in the pathogenesis of thrombosis, vascular remodeling, renal injury, and initiation of diabetes. Inhibition of PAI-1 is a potential therapeutic strategy in these diseases.