Transforming Growth Factor-β and Long Non-coding RNA in Renal Inflammation and Fibrosis

Osthole ameliorates early diabetic kidney damage by suppressing oxidative stress, inflammation and inhibiting TGF-β1/Smads signaling pathway

BACKGROUND

Osthole is a natural active ingredient extracted from the traditional Chinese medicine Cnidium monnieri. It has been demonstrated to have anti-inflammatory, anti-fibrotic, and anti-hyperglycemic properties. However, its effect on diabetic kidney disease (DKD) remains uncertain. This study aims to assess the preventive and therapeutic effects of osthole on DKD and investigate its underlying mechanisms.

METHODS

A streptozotocin/high-fat and high-sucrose diet induced Type 2 diabetic rat model was established. Metformin served as the positive drug control. Diabetic rats were treated with metformin or three different doses of osthole for 8 weeks. Throughout the treatment period, the progression of DKD was assessed by monitoring increases in urinary protein, serum creatinine, urea nitrogen, and uric acid, along with scrutinizing kidney pathology. Enzyme-linked immunosorbent assay (ELISA) was employed to detect inflammatory factors and oxidative stress levels. At the same time, immunohistochemical staining was utilized to evaluate changes in alpha-smooth muscle actin, fibronectin, E-cadherin, and apoptosis. The alterations in TGF-β1/Smads signaling pathway were ascertained through western blot and immunofluorescence. Furthermore, we constructed a high glucose-stimulated HBZY-1 cells model to uncover its molecular protective mechanism.

RESULTS

Osthole significantly reduced fasting blood glucose, insulin resistance, serum creatinine, uric acid, blood urea nitrogen, urinary protein excretion, and glomerular mesangial matrix deposition in diabetic rats. Additionally, significant improvements were observed in inflammation, oxidative stress, apoptosis, and fibrosis levels. The increase of ROS, apoptosis and hypertrophy in HBZY-1 cells induced by high glucose was reduced by osthole. Immunofluorescence and western blot results demonstrated that osthole down-regulated the TGF-β1/Smads signaling pathway and related protein expression.

CONCLUSION

Our findings indicate that osthole exhibits potential preventive and therapeutic effects on DKD. It deserves further investigation as a promising drug for preventing and treating DKD.

Mechanisms of norcantharidin against renal tubulointerstitial fibrosis

Renal tubulointerstitial fibrosis (RTIF) is a common feature and inevitable consequence of all progressive chronic kidney diseases, leading to end-stage renal failure regardless of the initial cause. Although research over the past few decades has greatly improved our understanding of the pathophysiology of RTIF, until now there has been no specific treatment available that can halt the progression of RTIF. Norcantharidin (NCTD) is a demethylated analogue of cantharidin, a natural compound isolated from 1500 species of medicinal insect, the blister beetle (Mylabris phalerata Pallas), traditionally used for medicinal purposes. Many studies have found that NCTD can attenuate RTIF and has the potential to be an anti-RTIF drug. This article reviews the recent progress of NCTD in the treatment of RTIF, with emphasis on the pharmacological mechanism of NCTD against RTIF.

From inflammation to renal fibrosis: A one-way road in autoimmunity?

Renal fibrosis is now recognized as a main determinant of renal pathology to include chronic kidney disease. Deposition of pathological matrix in the walls of glomerular capillaries, the interstitial space, and around arterioles predicts and contributes to the functional demise of the nephron and its surrounding vasculature. The recent identification of the major cell populations of fibroblast precursors in the kidney interstitium such as pericytes and tissue-resident mesenchymal stem cells, or bone-marrow-derived macrophages, and in the glomerulus such as podocytes, parietal epithelial and mesangial cells, has enabled the study of the fibrogenic process thought the lens of involved immunological pathways. Besides, a growing body of evidence is supporting the role of the lymphatic system in modulating the immunological response potentially leading to inflammation and ultimately renal damage. These notions have moved our understanding of renal fibrosis to be recognized as a clinical entity and new main player in autoimmunity, impacting directly the management of patients.

Epigenetically regulated inflammation in vascular senescence and renal progression of chronic kidney disease

Chronic kidney disease (CKD) and its complications, including vascular senescence and progressive renal fibrosis, are associated with inflammation. Vascular senescence, in particular, has emerged as an instrumental mediator of vascular inflammation that potentially worsens renal function. Epigenetically regulated inflammation involving histone modification, DNA methylation, actions of microRNAs and other non-coding RNAs, and their reciprocal reactions during vascular senescence and inflammaging are underappreciated. Their synergistic effects can contribute to CKD progression. Vascular senotherapeutics or pharmacological anti-senescent therapies based on epigenetic machineries can therefore be plausible options for ameliorating vascular aging and even halting the worsening of renal fibrosis. These include histone deacetylase modulators, histone methyltransferase modulators, other histone modification effectors, DNA methyltransferase inhibitors, telomerase reverse transcriptase enhancers, microRNA mimic delivery, and small molecules with microRNA-regulating potentials. Some of these molecules have already been tested and have shown anecdotal evidence for treating uremic vasculopathy and renal fibrosis, supporting the feasibility of this approach.

CLC-3 regulates TGF-β/smad signaling pathway to inhibit the process of fibrosis in hypertrophic scar

Objective

To study the role and mechanism of chloride channel-3 (ClC-3) in the formation of hypertrophic scar by constructing ClC-3 interference vectors and examining their effects on human hypertrophic scar fibroblasts (HSFB).

Methods

Human HSFB and human normal skin fibroblasts (NSFB) were used in this study, and ClC-3 interference vectors were constructed to transfect cells. ClC-3 inhibitors NPPB and Tamoxifen were used to treat cells. Cell migration and the expression of TGF-β/Smad, CollagenⅠ,CollagenⅢ were examined to explore the role of ClC-3 in the formation of hypertrophic scar.

Results

Compared with the normal skin tissue, the positive expression of ClC-3 and TGF-β in the scar tissue was significantly increased. The relative expression of ClC-3 and TGF-β1 in HSFB cells was higher than that in NSFB cells. Interfering with the expression of CLC-3 can inhibit the migration of HSFB cells and the expression of TGF- β/Smad, CollagenⅠ/Ⅲ. The experiment of HSFB cells treated by CLC-3 inhibitors can also obtain similar results.

Conclusion

Inhibiting CLC-3 can reduce the formation of hypertrophic scars.

The mechanisms and therapeutic potential of long noncoding RNA NEAT1 in fibrosis

Fibrosis is the excess deposition of extracellular matrix involved in the pathogenesis of chronic diseases and finally leads to the disruption of tissue architecture and failure of organ function. Long noncoding RNAs (lncRNAs) are a class of RNAs with lengths greater than 200 nucleotides and do not code proteins, which regulate gene expression at multiple levels. Nuclear-enriched abundant transcript 1 (NEAT1) is a long noncoding RNA that is widely expressed in mammalian cells and known as essential architectural scaffold for the formation of paraspeckles. Recently, the accumulating studies demonstrated that lncRNA NEAT1 was remarkable upregulated in the development of fibrosis in different organs, such as liver fibrosis, renal fibrosis, cardiac fibrosis, and lung fibrosis. More importantly, knockdown of NEAT1 remarkably alleviated fibrosis in vitro and in vivo. In this review, we summarized current studies of NEAT1 in fibrosis and hopefully aid in a better understanding of the mechanisms of fibrosis and the potential of NEAT1 as novel therapeutic target for fibrosis.

TGF-β receptor I inhibitor may restrict the induction of EMT in inflamed intestinal epithelial cells

Despite the extensive body of research, understanding the exact molecular mechanisms governing inflammatory bowel diseases (IBDs) still demands further investigation. Transforming growth factor-β1 (TGF-β1) signaling possesses a multifacial effect on a broad range of context-dependent cellular responses. However, long-term TGF-β1 activity may trigger epithelial-mesenchymal transition (EMT), followed by fibrosis. This study aimed to determine the role of epithelial TGF-β1 signaling in inflammatory bowel disease (IBD) pathogenesis. The expression of TGF-β1 signaling components and EMT-related and epithelial tight junction markers was examined in IBD patients (n = 60) as well as LPS-induced Caco-2/RAW264.7 co-culture model using quantitative real-time polymerase chain reaction (qRT-PCR), Western blotting, and immunofluorescence staining. Furthermore, the effect of A83-01, as a TGF-β receptor I (TβRI) inhibitor, on the inflamed epithelial cells was evaluated in vitro. To evaluate the cytotoxic effects of the TβRI inhibitor, a cell viability assay was performed by the MTS method. Considering the activation of canonical and non-canonical TGF-β1 signaling pathways in IBD patients, expression results indicated that administering A83-01 in inflamed Caco-2 cells substantially blocked the expression level of TGF-β1, SMAD4, and PI3K and the phosphorylation of p-SMAD2/3, p-AKT, and p-RPS6 as well as prevented downregulation of LncGAS5 and LncCDKN2B. Further analysis revealed that the inhibition of TGF-β1 signaling in inflamed epithelial cells by the small molecule could suppress the EMT-related markers as well as improve the expression of epithelial adherens and tight junctions. Collectively, these findings indicated that the inhibition of the TGF-β1 signaling could suppress the induction of EMT in inflamed epithelial cells as well as exert a protective effect on preserving tight junction integrity. There is a pressing need to determine the exact cellular mechanisms by which TGF-β1 exerts its effect on IBD pathogenesis.

Long non-coding RNA lnc-CHAF1B-3 promotes renal interstitial fibrosis by regulating EMT-related genes in renal proximal tubular cells

Renal interstitial fibrosis (RIF) is a common pathological manifestation of chronic kidney diseases. Epithelial-mesenchymal transition (EMT) of tubular epithelial cells is considered a major cause of RIF. Although long non-coding RNAs (lncRNAs) are reportedly involved in various pathophysiological processes, the roles and underlying molecular mechanisms of lncRNAs in the progression of RIF are poorly understood. In this study, we investigated the function of lncRNAs in RIF. Microarray assays showed that expression of the lncRNA lnc-CHAF1B-3 (also called claudin 14 antisense RNA 1) was significantly upregulated in human renal proximal tubular cells by both transforming growth factor-β1 (TGF-β1) and hypoxic stimulation, accompanied with increased expression of EMT-related genes. Knockdown of lnc-CHAF1B-3 significantly suppressed TGF-β1-induced upregulated expression of collagen type I alpha 1, cadherin-2, plasminogen activator inhibitor-1, snail family transcriptional repressor I (SNAI1) and SNAI2. Quantitative reverse transcriptase PCR analyses of paraffin-embedded kidney biopsy samples from IgA nephropathy patients revealed lnc-CHAF1B-3 expression was correlated positively with urinary protein levels and correlated negatively with estimated glomerular filtration rate. In situ hybridization demonstrated that lnc-CHAF1B-3 is expressed only in proximal tubules. These findings suggest lnc-CHAF1B-3 affects the progression of RIF by regulating EMT-related signaling. Thus, lnc-CHAF1B-3 is a potential target in the treatment of RIF.

Functions and therapeutic interventions of non-coding RNAs associated with TLR signaling pathway in atherosclerosis

Nowadays, emerging data demonstrate that the toll-like receptor (TLR) signaling pathway plays an important role in the progression of inflammatory atherosclerosis. Indeed, dysregulated TLR signaling pathway could be a cornerstone of inflammation and atherosclerosis, which contributes to the development of cardiovascular diseases. It is interesting to note that this pathway is heavily controlled by several mechanisms, such as epigenetic factors in which the role of non-coding RNAs (ncRNAs), particularly microRNAs and long noncoding RNAs as well as circular RNAs in the pathogenesis of atherosclerosis has been well studied. Recent years have seen a significant surge in the amount of research exploring the interplay between ncRNAs and TLR signaling pathway downstream targets in the development of atherosclerosis; however, there is still considerable room for improvement in this field. The current study was designed to review underlying mechanisms of TLR signaling pathway and ncRNA interactions to shed light on therapeutic implications in patients with atherosclerosis.

Renal Fibrosis in Lupus Nephritis

Fibrosis can be defined as a pathological process in which deposition of connective tissue replaces normal parenchyma. The kidney, like any organ or tissue, can be impacted by this maladaptive reaction, resulting in persistent inflammation or long-lasting injury. While glomerular injury has traditionally been regarded as the primary focus for classification and prognosis of lupus nephritis (LN), increasing attention has been placed on interstitial fibrosis and tubular atrophy as markers of injury severity, predictors of therapeutic response, and prognostic factors of renal outcome in recent years. This review will discuss the fibrogenesis in LN and known mechanisms of renal fibrosis. The importance of the chronicity index, which was recently added to the histological categorization of LN, and its role in predicting treatment response and renal prognosis for patients with LN, will be explored. A better understanding of cellular and molecular pathways involved in fibrosis in LN could enable the identification of individuals at higher risk of progression to chronic kidney disease and end-stage renal disease, and the development of new therapeutic strategies for lupus patients.

Protective effect of quercetin on kidney diseases: From chemistry to herbal medicines

Kidney injuries may trigger renal fibrosis and lead to chronic kidney disease (CKD), but effective therapeutic strategies are still limited. Quercetin is a natural flavonoid widely distributed in herbal medicines. A large number of studies have demonstrated that quercetin may protect kidneys by alleviating renal toxicity, apoptosis, fibrosis and inflammation in a variety of kidney diseases. Therefore, quercetin could be one of the promising drugs in the treatment of renal disorders. In the present study, we review the latest progress and highlight the beneficial role of quercetin in kidney diseases and its underlying mechanisms. The pharmacokinetics and bioavailability of quercetin and its proportion in herbal medicine will also be discussed.

Human umbilical cord mesenchymal stem cell-derived exosomal miR-335-5p attenuates the inflammation and tubular epithelial-myofibroblast transdifferentiation of renal tubular epithelial cells by reducing ADAM19 protein levels

BACKGROUND

Renal tubular epithelial-myofibroblast transdifferentiation (EMT) plays a key role in the regulation of renal fibrosis. Exosomes derived from human umbilical cord mesenchymal stem cells (hucMSCs) play a crucial role in alleviating renal fibrosis and injury. Additionally, hucMSC-derived exosomes contain numerous microRNAs (miRNAs). However, it is unclear whether mesenchymal stem cells can regulate the transforming growth factor (TGF)-β1-induced EMT of human renal tubular epithelial cells (RTECs) through exosomal miRNAs.

METHOD

HK-2, a human RTEC line, was co-treated with TGF-β1 and hucMSC-derived exosomes. Additionally, TGF-β1-treated HK-2 cells were transfected with a miR-335-5p mimic and disintegrin and metalloproteinase domain-containing protein 19 (ADAM19)-overexpression plasmid. miR-335-5p expression and ADAM19 protein and inflammation levels were measured via quantitative reverse transcription polymerase chain reaction, western blotting, and enzyme-linked immunosorbent assays, respectively.

RESULTS

TGF-β1 treatment changed the shape of HK-2 cells from a cobblestone morphology to a long spindle shape, accompanied by an increase in interleukin (IL)-6, tumor necrosis factor-α, IL-1β, collagen I, collagen III, α-smooth muscle actin, vimentin, and N-cadherin protein levels, whereas E-cadherin protein levels were reduced in these HK-2 cells, suggesting that TGF-β1 treatment induced the inflammation and EMT of HK-2 cells. HucMSC-exosomes improved the inflammation and EMT phenotype of TGF-β1-induced HK-2 cells by transferring miR-335-5p. miR-335-5p was found to bind the ADAM19 3'-untranslated region to reduce ADAM19 protein levels. Additionally, miR-335-5p improved the inflammation and EMT phenotype of HK-2 cells by reducing ADAM19 protein levels with TGF-β1 induction.

CONCLUSIONS

HucMSC-derived exosomal miR-335-5p attenuates the inflammation and EMT of HK-2 cells by reducing ADAM19 protein levels upon TGF-β1 induction. This study provides a potential therapeutic strategy and identifies targets for clinically treating renal fibrosis.

Salvia miltiorrhiza Bunge (Danshen) and Bioactive Compound Tanshinone IIA Alleviates Cisplatin-Induced Acute Kidney Injury Through Regulating PXR/NF-κB Signaling

Objective: The present study aims to provide evidence on the potential protective role of Salvia miltiorrhiza Bunge (Danshen) and its bioactive compound Tanshinone IIA (TanIIA) in AKI and to reveal the specific regulatory function of PXR/NF-κB signaling in AKI-induced renal inflammation. Methods: A network pharmacological analysis was used to study target genes and regulatory networks in the treatment of Salvia miltiorrhiza on AKI. Further experiments with in vivo AKI mouse model and in vitro studies were applied to investigate the renal protective effect of TanIIA in AKI. The mechanisms of TanIIA regulating PXR/NF-κB signaling in renal inflammation were also studied. Results: Network pharmacology had suggested the nuclear receptor family as new therapeutic targets of Salvia miltiorrhiza in AKI treatment. The in vivo studies had demonstrated that TanIIA improved renal function and inflammation by reducing necrosis and promoting the proliferation of tubular epithelial cells. Improved renal arterial perfusion in AKI mice with TanIIA treatment was also recorded by ultrasonography. In vitro studies had shown that TanIIA ameliorated renal inflammation by activating the PXR while inhibiting PXR-mediated NF-κB signaling. The results had suggested a role of PXR activation against AKI-induced renal inflammation. Conclusion: Salvia miltiorrhiza Bunge (Danshen) may protect the kidneys against AKI by regulating nuclear receptors. TanIIA improved cell necrosis proliferation and reduced renal inflammation by upregulating the expression of the PXR and inhibiting NF-κB signaling in a PXR-dependent manner. The PXR may be a potential therapeutic target for AKI treatment.

G Protein-Coupled Receptor Kinase 2 as Novel Therapeutic Target in Fibrotic Diseases

G protein-coupled receptor kinase 2 (GRK2), an important subtype of GRKs, specifically phosphorylates agonist-activated G protein-coupled receptors (GPCRs). Besides, current research confirms that it participates in multiple regulation of diverse cells via a non-phosphorylated pathway, including interacting with various non-receptor substrates and binding partners. Fibrosis is a common pathophysiological phenomenon in the repair process of many tissues due to various pathogenic factors such as inflammation, injury, drugs, etc. The characteristics of fibrosis are the activation of fibroblasts leading to myofibroblast proliferation and differentiation, subsequent aggerate excessive deposition of extracellular matrix (ECM). Then, a positive feedback loop is occurred between tissue stiffness caused by ECM and fibroblasts, ultimately resulting in distortion of organ architecture and function. At present, GRK2, which has been described as a multifunctional protein, regulates copious signaling pathways under pathophysiological conditions correlated with fibrotic diseases. Along with GRK2-mediated regulation, there are diverse effects on the growth and apoptosis of different cells, inflammatory response and deposition of ECM, which are essential in organ fibrosis progression. This review is to highlight the relationship between GRK2 and fibrotic diseases based on recent research. It is becoming more convincing that GRK2 could be considered as a potential therapeutic target in many fibrotic diseases.

USF2 knockdown downregulates THBS1 to inhibit the TGF-β signaling pathway and reduce pyroptosis in sepsis-induced acute kidney injury

OBJECTIVE

Acute kidney injury (AKI) is a serious complication of sepsis. This study was performed to explore the mechanism that THBS1 mediated pyroptosis by regulating the TGF-β signaling pathway in sepsis-induced AKI.

METHODS

Gene expression microarray related to sepsis-induced AKI was obtained from the GEO database, and the mechanism in sepsis-induced AKI was predicted by bioinformatics analysis. qRT-PCR and ELISA were performed to detect expressions of THBS1, USF2, TNF-α, IL-1β, and IL-18 in sepsis-induced AKI patients and healthy volunteers. The mouse model of sepsis-induced AKI was established, with serum creatinine, urea nitrogen, 24-h urine output measured, and renal tissue lesions observed by HE staining. The cell model of sepsis-induced AKI was cultured in vitro, with expressions of TNF-α, IL-1β, and IL-18, pyroptosis, Caspase-1 and GSDMD-N, and activation of TGF-β/Smad3 pathway detected. The upstream transcription factor USF2 was knocked down in cells to explore its effect on sepsis-induced AKI.

RESULTS

THBS1 and USF2 were highly expressed in patients with sepsis-induced AKI. Silencing THBS1 protected mice against sepsis-induced AKI, and significantly decreased the expressions of NLRP3, Caspase-1, GSDMD-N, IL-1β, and IL-18, increased cell viability, and decreased LDH activity, thus partially reversing the changes in cell morphology. Mechanistically, USF2 promoted oxidative stress responses by transcriptionally activating THBS1 to activate the TGF-β/Smad3/NLRP3/Caspase-1 signaling pathway and stimulate pyroptosis, and finally exacerbated sepsis-induced AKI.

CONCLUSION

USF2 knockdown downregulates THBS1 to inhibit the TGF-β/Smad3 signaling pathway and reduce pyroptosis and further ameliorate sepsis-induced AKI.

Assessing and counteracting fibrosis is a cornerstone of the treatment of CKD secondary to systemic and renal limited autoimmune disorders

Chronic kidney disease (CKD) is an increasing cause of morbidity and mortality worldwide. Besides the higher prevalence of diabetes, hypertension and aging worldwide, immune mediated disorders remain an important cause of kidney disease and are especially prevalent in young adults. Regardless of the initial insult, final pathway to CKD and kidney failure is always the loss of normal tissue and fibrosis development, in which the dynamic equilibrium between extracellular matrix synthesis and degradation is disturbed, leading to excessive production and accumulation. During fibrosis, a multitude of cell types intervene at different levels, but myofibroblasts and inflammatory cells are considered critical in the process. They exert their effects through different molecular pathways, of which transforming growth factor β (TGF-β) has demonstrated to be of particular importance. Additionally, CKD itself promotes fibrosis due to the accumulation of toxins and hormonal changes, and proteinuria is simultaneously a manifestation of CKD and a specific driver of renal fibrosis. Pathways involved in renal fibrosis and CKD are closely interrelated, and although important advances have been made in our knowledge of them, it is still necessary to translate them into clinical practice. Given the complexity of this process, it is highly likely that its treatment will require a multi-target strategy to control the origin of the damage but also the mechanisms that perpetuate it. Fortunately, rapid technology development over the last years and new available drugs in the nephrologist's armamentarium give reasons for optimism that more personalized assistance for CKD and renal fibrosis will appear in the future.