TGF-β Mediates Renal Fibrosis via the Smad3-Erbb4-IR Long Noncoding RNA Axis

The long non-coding RNA PFI protects against pulmonary fibrosis by interacting with splicing regulator SRSF1

Pulmonary fibrosis (PF) is a type of interstitial pneumonia with complex etiology and high mortality, characterized by progressive scarring of the alveolar interstitium and myofibroblastic lesions. Recently, there has been growing appreciation of the importance of long non-coding RNAs (lncRNAs) in organ fibrosis. The aim of this study was to investigate the role of lncRNAs in lung fibrosis. We used a qRT-PCR assay to identify dysregulated lncRNAs in the lungs of mice with experimental, bleomycin (BLM)-induced pulmonary fibrosis, and a series of molecular assays to assess the role of the novel lncRNA NONMMUT060091, designated as pulmonary fibrosis inhibitor (PFI), which was significantly downregulated in lung fibrosis. Functionally, knockdown of endogenous PFI by smart silencer promoted proliferation, differentiation, and extracellular matrix (ECM) deposition in primary mouse lung fibroblasts (MLFs). In contrast, overexpression of PFI partially abrogated TGF-β1-induced fibrogenesis both in MLFs and in the human fetal lung fibroblast MRC-5 cells. Similarly, PFI overexpression attenuated BLM-induced pulmonary fibrosis compared with wild type (WT) mice. Mechanistically, using chromatin isolation by RNA purification-mass spectrometry (ChIRP-MS) and an RNA pull-down assay, PFI was found to directly bind Serine/arginine-rich splicing factor 1 (SRSF1), and to repress its expression and pro-fibrotic activity. Furthermore, silencing of SRSF1 inhibited TGF-β1-induced proliferation, differentiation, and ECM deposition in MRC-5 cells by limiting the formation of the EDA+Fn1 splicing isoform; whereas forced expression of SRSF1 by intratracheal injection of adeno-associated virus 5 (AAV5) ablated the anti-fibrotic effect of PFI in BLM-treated mice. Overall, these data reveal that PFI mitigated pulmonary fibrosis through negative regulation of the expression and activity of SRSF1 to decrease the formation of the EDA+Fn1 splicing isoform, and suggest that PFI and SRSF1 may serve as potential targets for the treatment of lung fibrosis.

Epigenetics and Inflammation in Diabetic Nephropathy

Diabetic nephropathy (DN) leads to high morbidity and disability. Inflammation plays a critical role in the pathogenesis of DN, which involves renal cells and immune cells, the microenvironment, as well as extrinsic factors, such as hyperglycemia, chemokines, cytokines, and growth factors. Epigenetic modifications usually regulate gene expression via DNA methylation, histone modification, and non-coding RNAs without altering the DNA sequence. During the past years, numerous studies have been published to reveal the mechanisms of epigenetic modifications that regulate inflammation in DN. This review aimed to summarize the latest evidence on the interplay of epigenetics and inflammation in DN, and highlight the potential targets for treatment and diagnosis of DN.

LncRNA lnc-ISG20 promotes renal fibrosis in diabetic nephropathy by inducing AKT phosphorylation through miR-486-5p/NFAT5

Long non‐coding RNA (lncRNA) lnc‐ISG20 has been found aberrantly up‐regulated in the glomerular in the patients with diabetic nephropathy (DN). We aimed to elucidate the function and regulatory mechanism of lncRNA lnc‐ISG20 on DN‐induced renal fibrosis. Expression patterns of lnc‐ISG20 in kidney tissues of DN patients were determined by RT‐qPCR. Mouse models of DN were constructed, while MCs were cultured under normal glucose (NG)/high glucose (HG) conditions. The expression patterns of fibrosis marker proteins collagen IV, fibronectin and TGF‐β1 were measured with Western blot assay. In addition, the relationship among lnc‐ISG20, miR‐486‐5p, NFAT5 and AKT were analysed using dual‐luciferase reporter assay and RNA immunoprecipitation. The effect of lnc‐ISG20 and miR‐486/NFAT5/p‐AKT axis on DN‐associated renal fibrosis was also verified by means of rescue experiments. The expression levels of lnc‐ISG20 were increased in DN patients, DN mouse kidney tissues and HG‐treated MCs. Lnc‐ISG20 silencing alleviated HG‐induced fibrosis in MCs and delayed renal fibrosis in DN mice. Mechanistically, miR‐486‐5p was found to be a downstream miRNA of lnc‐ISG20, while miR‐486‐5p inhibited the expression of NFAT5 by binding to its 3'UTR. NFAT5 overexpression aggravated HG‐induced fibrosis by stimulating AKT phosphorylation. However, NFAT5 silencing reversed the promotion of in vitro and in vivo fibrosis caused by lnc‐ISG20 overexpression. Our collective findings indicate that lnc‐ISG20 promotes the renal fibrosis process in DN by activating AKT through the miR‐486‐5p/NFAT5 axis. High‐expression levels of lnc‐ISG20 may be a useful indicator for DN.

LncRNA Gas5 regulates Fn1 deposition via Creb5 in renal fibrosis

Aim: Although studies on lncRNAs in renal fibrosis have focused on target genes and functions of lncRNAs, a comprehensive interaction analysis of lncRNAs is lacking. Materials & methods: Differentially expressed genes in renal fibrosis were screened, and the interaction between lncRNAs and miRNAs was searched. Results: We constructed a ceRNA network associated with renal fibrosis, by which we found the transcription factor Creb5, a target gene of lncRNA Gas5 that might regulate extracellular Fn1 deposition. Conclusion: Our study not only provides a theoretical basis for the ceRNA regulation mechanism of Gas5 but also provides experimental evidence supporting the use of Gas5 targeting in the treatment of renal fibrosis.

TGF-β1 Signaling: Immune Dynamics of Chronic Kidney Diseases

Chronic kidney disease (CKD) is a major cause of morbidity and mortality worldwide, imposing a great burden on the healthcare system. Regrettably, effective CKD therapeutic strategies are yet available due to their elusive pathogenic mechanisms. CKD is featured by progressive inflammation and fibrosis associated with immune cell dysfunction, leading to the formation of an inflammatory microenvironment, which ultimately exacerbating renal fibrosis. Transforming growth factor β1 (TGF-β1) is an indispensable immunoregulator promoting CKD progression by controlling the activation, proliferation, and apoptosis of immunocytes via both canonical and non-canonical pathways. More importantly, recent studies have uncovered a new mechanism of TGF-β1 for de novo generation of myofibroblast via macrophage-myofibroblast transition (MMT). This review will update the versatile roles of TGF-β signaling in the dynamics of renal immunity, a better understanding may facilitate the discovery of novel therapeutic strategies against CKD.

Review on Inflammation Markers in Chronic Kidney Disease

Chronic kidney disease (CKD) is one of the major health problems of the modern age. It represents an important public health challenge with an ever-lasting rising prevalence, which reached almost 700 million by the year 2017. Therefore, it is very important to identify patients at risk for CKD development and discover risk factors that cause the progression of the disease. Several studies have tackled this conundrum in recent years, novel markers have been identified, and new insights into the pathogenesis of CKD have been gained. This review summarizes the evidence on markers of inflammation and their role in the development and progression of CKD. It will focus primarily on cytokines, chemokines, and cell adhesion molecules. Nevertheless, further large, multicenter studies are needed to establish the role of these markers and confirm possible treatment options in everyday clinical practice.

Epigenetic modifications and the development of kidney graft fibrosis

PURPOSE OF REVIEW

To outline recent discoveries in epigenetic regulatory mechanisms that have potential implications in the development of renal fibrosis following kidney transplantation.

RECENT FINDINGS

The characterization of renal fibrosis following kidney transplantation has shown TGFβ/Smad signaling to play a major role in the progression to chronic allograft dysfunction. The onset of unregulated proinflammatory pathways are only exacerbated by the decline in regulatory mechanisms lost with progressive patient age and comorbidities such as hypertension and diabetes. However, significant developments in the recognition of epigenetic regulatory markers upstream of aberrant TGFβ-signaling has significant clinical potential to provide therapeutic targets for the treatment of renal fibrosis. In addition, discoveries in extracellular vesicles and the characterization of their cargo has laid new framework for the potential to evaluate patient outcomes independent of invasive biopsies.

SUMMARY

The current review summarizes the main findings in epigenetic machinery specific to the development of renal fibrosis and highlights therapeutic options that have significant potential to translate into clinical practice.

Non-Coding RNAs as Biomarkers and Therapeutic Targets for Diabetic Kidney Disease

Diabetic kidney disease (DKD) is the most common diabetic complication and is a leading cause of end-stage kidney disease. Increasing evidence shows that DKD is regulated not only by many classical signaling pathways but also by epigenetic mechanisms involving chromatin histone modifications, DNA methylation, and non-coding RNA (ncRNAs). In this review, we focus on our current understanding of the role and mechanisms of ncRNAs, including microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) in the pathogenesis of DKD. Of them, the regulatory role of TGF-β/Smad3-dependent miRNAs and lncRNAs in DKD is highlighted. Importantly, miRNAs and lncRNAs as biomarkers and therapeutic targets for DKD are also described, and the perspective of ncRNAs as a novel therapeutic approach for combating diabetic nephropathy is also discussed.

Long non-coding RNAs: A double-edged sword in aging kidney and renal disease

Aging as one of intrinsic biological processes is a risk factor for many chronic diseases. Kidney disease is a global problem and health care burden worldwide. The diagnosis of kidney disease is currently based on serum creatinine and urea levels. Novel biomarkers may improve diagnostic accuracy, thereby allowing early prevention and treatment. Over the past few years, advances in genome analyses have identified an emerging class of noncoding RNAs that play critical roles in the regulation of gene expression and epigenetic reprogramming. Long noncoding RNAs (lncRNAs) are pervasively transcribed in the genome and could bind DNA, RNA and protein. Emerging evidence has demonstrated that lncRNAs played an important role in all stages of kidney disease. To date, only some lncRNAs were well identified and characterized, but the complexity of multilevel regulation of transcriptional programs involved in these processes remains undefined. In this review, we summarized the lncRNA expression profiling of large-scale identified lncRNAs on kidney diseases including acute kidney injury, chronic kidney disease, diabetic nephropathy and kidney transplantation. We further discussed a number of annotated lncRNAs linking with complex etiology of kidney diseases. Finally, several lncRNAs were highlighted as diagnostic biomarkers and therapeutic targets. Targeting lncRNAs may represent a precise therapeutic strategy for progressive renal fibrosis.

Inhibition of proliferation-linked signaling cascades with atractylenolide I reduces myofibroblastic phenotype and renal fibrosis

Renal fibrosis is a frequent axis contributing to the occurrence of end-stage nephropathy. Previously, it has been reported that atractylenolide Ⅰ (ATL-1), a natural compound extracted from Atractylodes macrocephala, has anti-cancer and antioxidant effects. However, the renal anti-fibrotic effects of action remain unclear. In this study, the anti-fibrotic effects of ATL-1 were examined in fibroblasts, tubular epithelial cells (TECs) triggered by TGF-β1 in vitro, and using a unilateral ureteral obstruction (UUO) mouse model in vivo. We found that ATL-1 represses the myofibroblastic phenotype and fibrosis development in UUO kidneys by targeting the fibroblast-myofibroblast differentiation (FMD), as well as epithelial-mesenchymal transition (EMT). The anti-fibrotic effects of ATL-1 were associated with reduced cell growth in the interstitium and tubules, leading to suppression of the proliferation-linked cascades activity consisting of JAK2/STAT3, PI3K/Akt, p38 MAPK, and Wnt/β-catenin pathways. Besides, ATL-1 treatment repressed TGF-β1-triggered FMD and the myofibroblastic phenotype in fibroblasts by antagonizing the activation of proliferation-linked cascades. Likewise, TGF-β1-triggered excessive activation of the proliferation-linked signaling in TECs triggered EMT. The myofibroblastic phenotype was repressed by ATL-1. The anti-fibrotic and anti-proliferative effects of ATL-1 were linked to the inactivation of Smad2/3 signaling, partially reversing FMD, as well as EMT and the repression of the myofibroblastic phenotype. Thus, the inhibition of myofibroblastic phenotype and fibrosis development in vivo and in vitro through proliferation-linked cascades of ATL-1 makes it a prospective therapeutic bio-agent to prevent renal fibrosis.

Long Non-coding RNA LRNA9884 Promotes Acute Kidney Injury via Regulating NF-kB-Mediated Transcriptional Activation of MIF

Acute kidney injury (AKI) is one of the most common complications affecting hospitalized patients associated with an extremely high mortality rate. However, the underlying pathogenesis of AKI remains unclear that largely limits its effective management in clinic. Increasing evidence demonstrated the importance of long non-coding RNAs (lncRNAs) in the pathogenesis of AKI, because of their regulatory roles in transcription, translation, chromatin modification, and cellular organization. Here, we reported a new role of LRNA9884 in AKI. Using experimental cisplatin-induced AKI model, we found that LRNA9884 was markedly up-regulated in the nucleus of renal tubular epithelium in mice with AKI. We found that silencing of LRNA9884 effectively inhibited the production of inflammatory cytokines MCP-1, IL-6, and TNF-α in the mouse renal tubular epithelial cells (mTECs) under IL-1β stimulation in vitro. Mechanistically, LRNA9884 was involved into NF-κB-mediated inflammatory cytokines production especially on macrophage migration inhibitory factor (MIF). Collectedly, our study suggested LRNA9884 promoted MIF-triggered the production of inflammatory cytokines via NF-κB pathway after AKI injury. This study uncovered LRNA9884 has an adverse impact in AKI, and targeting LRNA9884 might represent a potential therapeutic target for AKI.

Current perspectives on inhibitory SMAD7 in health and disease

Transforming growth factor β (TGF-β) family members play an extensive role in cellular communication that orchestrates both early development and adult tissue homeostasis. Aberrant TGF-β family signaling is associated with a pathological outcome in numerous diseases, and in-depth understanding of molecular and cellular processes could result in therapeutic benefit for patients. Canonical TGF-β signaling is mediated by receptor-regulated SMADs (R-SMADs), a single co-mediator SMAD (Co-SMAD), and inhibitory SMADs (I-SMADs). SMAD7, one of the I-SMADs, is an essential negative regulator of the pleiotropic TGF-β and bone morphogenetic protein (BMP) signaling pathways. In a negative feedback loop, SMAD7 inhibits TGF-β signaling by providing competition for TGF-β type-1 receptor (TβRI), blocking phosphorylation and activation of SMAD2. Moreover, SMAD7 recruits E3 ubiquitin SMURF ligases to the type I receptor to promote ubiquitin-mediated proteasomal degradation. In addition to its role in TGF-β and BMP signaling, SMAD7 is regulated by and implicated in a variety of other signaling pathways and functions as a mediator of crosstalk. This review is focused on SMAD7, its function in TGF-β and BMP signaling, and its role as a downstream integrator and crosstalk mediator. This crucial signaling molecule is tightly regulated by various mechanisms. We provide an overview of the ways by which SMAD7 is regulated, including noncoding RNAs (ncRNAs) and post-translational modifications (PTMs). Finally, we discuss its role in diseases, such as cancer, fibrosis, and inflammatory bowel disease (IBD).

SMAD3 promotes autophagy dysregulation by triggering lysosome depletion in tubular epithelial cells in diabetic nephropathy

Macroautophagy/autophagy dysregulation has been noted in diabetic nephropathy; however, the regulatory mechanisms controlling this process remain unclear. In this study, we showed that SMAD3 (SMAD family member 3), the key effector of TGFB (transforming growth factor beta)-SMAD signaling, induces lysosome depletion via the inhibition of TFEB-dependent lysosome biogenesis. The pharmacological inhibition or genetic deletion of SMAD3 restored lysosome biogenesis activity by alleviating the suppression of TFEB, thereby protecting lysosomes from depletion and improving autophagic flux in renal tubular epithelial cells in diabetic nephropathy. Mechanistically, we found that SMAD3 directly binds to the 3'-UTR of TFEB and inhibits its transcription. Silencing TFEB suppressed lysosome biogenesis and resulted in a loss of the protective effects of SMAD3 inactivation on lysosome depletion under diabetic conditions. In conclusion, SMAD3 promotes lysosome depletion via the inhibition of TFEB-dependent lysosome biogenesis; this may be an important mechanism underlying autophagy dysregulation in the progression of diabetic nephropathy.Abbreviations: AGEs: advanced glycation end products; ATP6V1H: ATPase H+ transporting V1 subunit H; CTSB: cathepsin B; ChIP: chromatin immunoprecipitation; Co-BSA: control bovine serum albumin; DN: diabetic nephropathy; ELISA: enzyme-linked immunosorbent assay; FN1: fibronectin 1; HAVCR1/TIM1/KIM-1: hepatitis A virus cellular receptor 1; LAMP1: lysosomal associated membrane protein 1; LMP: lysosome membrane permeabilization; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; NC: negative control; SIS3: specific inhibitor of SMAD3; SMAD3: SMAD family member 3; siRNA: small interfering RNA; SQSTM1/p62: sequestosome 1; TECs: tubular epithelial cells; TFEB: transcription factor EB; TGFB1: transforming growth factor beta 1; TGFBR1: transforming growth factor beta receptor 1; UTR: untranslated region; VPS11: VPS11 core subunit of CORVET and HOPS complexes.

Identification of candidate lncRNA biomarkers for renal fibrosis: A systematic review

AIMS

To combine the results of dysregulated lncRNAs in individual renal fibrosis lncRNA expression profiling studies and to identify potential lncRNA biomarkers.

MATERIALS AND METHODS

We systematically searched three databases to identify lncRNA expression studies of renal fibrosis in animal models and humans. The lncRNA expression data were extracted from 24 included studies, and a lncRNA vote-counting strategy was applied to identify significant lncRNA biomarkers. The lncLocator algorithm was utilized to predict the potential subcellular localization of these lncRNAs. The predicted targets of the identified lncRNA biomarkers were obtained by searching LncBase v.2 and catRAPID. Finally, GO enrichment and KEGG pathway analyses were performed.

KEY FINDINGS

We recognized a significant lncRNA signature of 95 differentially expressed lncRNAs in 731 samples from rodent models of renal fibrosis and CKD patients, among which TCONS_01181049 and TCONS_01496394 were commonly upregulated in both urine and renal tissues, while lncRNA-Cancer Susceptibility Candidate 2 was downregulated in both blood and renal tissues. About 73.33% dysregulated lncRNAs in renal fibrosis animal models and 81.82% dysregulated lncRNAs in CKD patients were predicted to be localized to the cytoplasm. The most relevant biological processes and molecular functions associated with these lncRNAs were mRNA processing and RNA binding.

SIGNIFICANCE

The present systematic review identified 95 significantly dysregulated lncRNAs from 24 studies and future investigations should focus on exploring their potential effects on renal fibrosis and their clinical utility as biomarkers or therapeutic targets.

Norcantharidin protects against renal interstitial fibrosis by suppressing TWEAK-mediated Smad3 phosphorylation

AIMS

This study investigated the role and mechanism of action of tumor necrosis factor-like weak inducer of apoptosis (TWEAK) in the pathogenesis of renal interstitial fibrosis (RIF), and its involvement in the anti-RIF effect of norcantharidin (NCTD).

MAIN METHODS

Mice with unilateral ureteral obstruction and BUMPT mouse proximal tubular cells exposed to transforming growth factor (TGF)-β1 were used as in vivo and in vitro models of RIF, respectively. NCTD was administered to mice by intraperitoneal injection (0.075 mg kg^-1·day^-1). Hematoxylin-eosin and Masson's trichrome staining were performed to assess pathologic changes in the kidney. Immunohistochemistry, western blotting, and real-time PCR were performed to evaluate the expression of TWEAK and the fibrotic factors fibronectin (FN) and collagen type I (Col-I). The role of TWEAK in RIF and in the anti-RIF effect of NCTD was evaluated by TWEAK overexpression and neutralization with a specific antibody, and specific inhibitor of Mothers against decapentaplegic homolog (Smad)3 (SIS3) was used to examine the involvement of TGF-β1/Smad3 signaling.

KEY FINDINGS

TWEAK was mainly expressed in renal tubules in mice; the level was markedly elevated in both in vivo and in vitro RIF models. TWEAK overexpression in BUMPT cells increased the levels of phosphorylated Smad3, FN, and Col-I, which were reduced by treatment with SIS3. NCTD suppressed FN and Col-I expression by blocking TWEAK-mediated Smad3 phosphorylation.

SIGNIFICANCE

Upregulation of TWEAK contributes to RIF by promoting Smad3 phosphorylation, while NCTD inhibits this process.

Neural transcription factor Pou4f1 promotes renal fibrosis via macrophage-myofibroblast transition

Unresolved inflammation can lead to tissue fibrosis and impaired organ function. Macrophage-myofibroblast transition (MMT) is one newly identified mechanism by which ongoing chronic inflammation causes progressive fibrosis in different forms of kidney disease. However, the mechanisms underlying MMT are still largely unknown. Here, we discovered a brain-specific homeobox/POU domain protein Pou4f1 (Brn3a) as a specific regulator of MMT. Interestingly, we found that Pou4f1 is highly expressed by macrophages undergoing MMT in sites of fibrosis in human and experimental kidney disease, identified by coexpression of the myofibroblast marker, α-SMA. Unexpectedly, Pou4f1 expression peaked in the early stage in renal fibrogenesis in vivo and during MMT of bone marrow-derived macrophages (BMDMs) in vitro. Mechanistically, chromatin immunoprecipitation (ChIP) assay identified that Pou4f1 is a Smad3 target and the key downstream regulator of MMT, while microarray analysis defined a Pou4f1-dependent fibrogenic gene network for promoting TGF-β1/Smad3-driven MMT in BMDMs at the transcriptional level. More importantly, using two mouse models of progressive renal interstitial fibrosis featuring the MMT process, we demonstrated that adoptive transfer of TGF-β1-stimulated BMDMs restored both MMT and renal fibrosis in macrophage-depleted mice, which was prevented by silencing Pou4f1 in transferred BMDMs. These findings establish a role for Pou4f1 in MMT and renal fibrosis and suggest that Pou4f1 may be a therapeutic target for chronic kidney disease with progressive renal fibrosis.

Emerging role of lncRNAs in renal fibrosis

Fibrosis is the final common pathological feature of a wide variety of chronic kidney disease (CKD). However, an understanding of the mechanisms underlying the development of renal fibrosis remains challenging and controversial. As the current focus of molecular research, noncoding RNAs (ncRNAs), mainly microRNAs (miRNAs), long noncoding RNAs (lncRNAs) and circular noncoding RNAs (circRNAs), have powerful and abundant biological functions, which essentially makes them mediators of the physiological and pathological processes of various system diseases. The role of ncRNAs in renal fibrosis has also received great attention in recent years, but most research has mainly focused on miRNAs. In fact, although a large number of studies of lncRNAs have emerged recently, the role these molecules play in renal fibrosis haven't been fully understood till now. Thus, this review discusses the discovery of lncRNAs and their biological functions in different types of renal fibrosis, as well as the imminent applications of these findings in clinical use. Undoubtedly, in the future, further understanding of the function of all types of lncRNAs will reveal large breakthroughs in the treatment of renal fibrosis.

Emerging Roles of Long Non-Coding RNAs in Renal Fibrosis

Renal fibrosis is an unavoidable consequence that occurs in nearly all of the nephropathies. It is characterized by a superabundant deposition and accumulation of extracellular matrix (ECM). All compartments in the kidney can be affected, including interstitium, glomeruli, vasculature, and other connective tissue, during the pathogenesis of renal fibrosis. The development of this process eventually causes destruction of renal parenchyma and end-stage renal failure, which is a devastating disease that requires renal replacement therapies. Recently, long non-coding RNAs (lncRNAs) have been emerging as key regulators governing gene expression and affecting various biological processes. These versatile roles include transcriptional regulation, organization of nuclear domains, and the regulation of RNA molecules or proteins. Current evidence proposes the involvement of lncRNAs in the pathologic process of kidney fibrosis. In this review, the biological relevance of lncRNAs in renal fibrosis will be clarified as important novel regulators and potential therapeutic targets. The biology, and subsequently the current understanding, of lncRNAs in renal fibrosis are demonstrated—highlighting the involvement of lncRNAs in kidney cell function, phenotype transition, and vascular damage and rarefaction. Finally, we discuss challenges and future prospects of lncRNAs in diagnostic markers and potential therapeutic targets, hoping to further inspire the management of renal fibrosis.

Alteration of N6-methyladenosine epitranscriptome profile in unilateral ureteral obstructive nephropathy

Aim: To reveal the alterations of N⁶-methyladenosine (m⁶A) epitranscriptome profile in kidney after unilateral ureteral obstruction in mice. Materials & methods: Total renal m⁶A and expressions of methyltransferases and demethylases were detected by colorimetric quantification method, real-time PCR and western blot, respectively. Methylated RNA immunoprecipitation sequencing was performed to map epitranscriptome-wide m⁶A profile. Results: Total m⁶A levels were time-dependent decreased within 1 week, with the lowest level detected at day 7. A total of 823 differentially methylated transcripts in 507 genes were identified. Specifically, demethylated mRNAs selectively acted on multiple pathways, including TGF-β and WNT. Conclusion: m⁶A modification has a functional importance in renal interstitial fibrosis during obstructive nephropathy and might be a promising therapeutic target.

The Mincle/Syk/NF-κB Signaling Circuit Is Essential for Maintaining the Protumoral Activities of Tumor-Associated Macrophages

Tumor-associated macrophages (TAM) have important roles in cancer progression, but the signaling behind the formation of protumoral TAM remains understudied. Here, by single-cell RNA sequencing, we revealed that the pattern recognition receptor Mincle was highly expressed in TAM and significantly associated with mortality in patients with non-small cell lung cancer. Cancer cells markedly induced Mincle expression in bone marrow-derived macrophages (BMDM), thus promoting cancer progression in invasive lung carcinoma LLC and melanoma B16F10 in vivo and in vitro Mincle was predominately expressed in the M2-like TAM in non-small cell lung carcinoma and LLC tumors, and silencing of Mincle unexpectedly promoted M1-like phenotypes in vitro Mechanistically, we discovered a novel Mincle/Syk/NF-κB signaling pathway in TAM needed for executing their TLR4-independent protumoral activities. Adoptive transfer of Mincle-silenced BMDM significantly suppressed TAM-driven cancer progression in the LLC-bearing NOD/SCID mice. By modifying our well-established ultrasound microbubble-mediated gene transfer protocol, we demonstrated that tumor-specific silencing of Mincle effectively blocked Mincle/Syk/NF-κB signaling, therefore inhibiting the TAM-driven cancer progression in the syngeneic mouse cancer models. Thus, our findings highlight the function of Mincle as a novel immunotherapeutic target for cancer via blocking the Mincle/Syk/NF-κB circuit in TAM.

The Emerging Role of Innate Immunity in Chronic Kidney Diseases

Renal fibrosis is a common fate of chronic kidney diseases. Emerging studies suggest that unsolved inflammation will progressively transit into tissue fibrosis that finally results in an irreversible end-stage renal disease (ESRD). Renal inflammation recruits and activates immunocytes, which largely promotes tissue scarring of the diseased kidney. Importantly, studies have suggested a crucial role of innate immunity in the pathologic basis of kidney diseases. This review provides an update of both clinical and experimental information, focused on how innate immune signaling contributes to renal fibrogenesis. A better understanding of the underlying mechanisms may uncover a novel therapeutic strategy for ESRD.

Potential Roles of Long Noncoding RNAs as Therapeutic Targets in Renal Fibrosis

Many studies have made clear that most of the genome is transcribed into noncoding RNAs, including microRNAs (miRNAs) and long noncoding RNAs (lncRNAs), both of which can affect different cell features. LncRNAs are long heterogeneous RNAs that regulate gene expression and a variety of signaling pathways involved in cellular homeostasis and development. Several studies have demonstrated that lncRNA is an important class of regulatory molecule that can be targeted to change cellular physiology and function. The expression or dysfunction of lncRNAs is closely related to various hereditary, autoimmune, and metabolic diseases, and tumors. Specifically, recent work has shown that lncRNAs have an important role in kidney pathogenesis. The effective roles of lncRNAs have been recognized in renal ischemia, injury, inflammation, fibrosis, glomerular diseases, renal transplantation, and renal-cell carcinoma. The present review focuses on the emerging role and function of lncRNAs in the pathogenesis of kidney inflammation and fibrosis as novel essential regulators. Although lncRNAs are important players in the initiation and progression of many pathological processes, their role in renal fibrosis remains unclear. This review summarizes the current understanding of lncRNAs in the pathogenesis of kidney fibrosis and elucidates the potential role of these novel regulatory molecules as therapeutic targets for the clinical treatment of kidney inflammation and fibrosis.

Gallic acid and ferulic acid protect the liver from thioacetamide-induced fibrosis in rats via differential expression of miR-21, miR-30 and miR-200 and impact on TGF-β1/Smad3 signaling

This study evaluates the possible protective effects of gallic acid (GaA) and ferulic acid (FeA) against an experimentally induced liver fibrosis by thioacetamide (TAA) in rats. Animals were divided into: Control group, GaA group (20 mg/kg/day, p.o), FeA (20 mg/kg/day, p.o), TAA group (receiving 250 mg/kg twice/week, I.P), TAA + GaA group, TAA + FeA group (received the same previous doses) and TAA+silymarin group (received silymarin at 100 mg/kg/day+TAA as mentioned above). After 6 consecutive weeks, animals were sacrificed and the assessment of liver functions, oxidative stress biomarkers and histopathological examination of the liver tissues were performed. In addition, the effect on TGF-β1/Smad3 signaling and the expression of miR-21, miR-30 and miR-200 were evaluated. The results showed that administration of GaA or FeA with TAA induced a significant reduction in serum ALT, AST and ALP activities and protected the integrity of liver tissues. Furthermore, they increased the activities of the hepatic antioxidant enzymes; superoxide dismutase and catalase while decreased malondialdehyde content to a normal level. The hepatic expression of TGF-β1, phosphorylated and total Smad3 proteins were significantly decreased. In addition, miR-21 expression was downregulated while miR-30 and miR-200 expressions were upregulated by administration of gallic acid or ferulic acid. In conclusion, gallic and ferulic acids exhibit hepatoprotective and antioxidant effects against TAA-induced liver fibrosis in rats. These effects are mediated through inhibition of TGF-β1/Smad3 signaling and differentially regulating the hepatic expression level of miR-21, miR-30 and miR-200.

TGF-β in renal fibrosis: triumphs and challenges

Renal fibrosis is a hallmark of chronic kidney disease. Although considerable achievements in the pathogenesis of renal fibrosis have been made, the underlying mechanisms of renal fibrosis remain largely to be explored. Now we have reached the consensus that TGF-β is a master regulator of renal fibrosis. Indeed, TGF-β regulates renal fibrosis via both canonical and noncanonical TGF-β signaling. Moreover, ongoing renal inflammation promotes fibrosis as inflammatory cells such as macrophages, conventional T cells and mucosal-associated invariant T cells may directly or indirectly contribute to renal fibrosis, which is also tightly regulated by TGF-β. However, anti-TGF-β treatment for renal fibrosis remains ineffective and nonspecific. Thus, research into mechanisms and treatment of renal fibrosis remains highly challenging.

Elevated intracellular copper contributes a unique role to kidney fibrosis by lysyl oxidase mediated matrix crosslinking

Copper ions play various roles in mammalian cells, presumably due to their involvement in different enzymatic reactions. Some studies indicated that serum copper correlates with fibrosis in organs, such as liver and lung. However, the mechanism is unknown. Here, we explored the role of copper in kidney fibrosis development and possible underlying mechanisms. We found that copper transporter 1 (CTR1) expression was increased in the kidney tissues in two fibrosis models and in patients with kidney fibrosis. Similar results were also found in renal tubular epithelial cells and fibroblast cells treated with transforming growth factor beta (TGF-β). Mechanistically, the upregulation of CTR1 required Smads-dependent TGF-β signaling pathway and Smad3 directly binded to the promoter of CTR1 in renal fibroblast cells using chromatin immunoprecipitation. Elevated CTR1 induced increase of copper intracellular influx. The elevated intracellular copper ions activated lysyl oxidase (LOX) to enhance the crosslinking of collagen and elastin, which then promoted kidney fibrosis. Reducing intracellular copper accumulation by knocking down CTR1 ameliorated kidney fibrosis in unilateral ureteral obstruction induced renal fibrosis model and renal fibroblast cells stimulated by TGF-β. Treatment with copper chelator tetrathiomolybdate (TM) also alleviated renal fibrosis in vivo and in vitro. In conclusion, intracellular copper accumulation plays a unique role to kidney fibrosis by activating LOX mediated collagen and elastin crosslinking. Inhibition of intracellular copper overload may be a potential portal to alleviate kidney fibrosis.

Lnc-Ang362 is a pro-fibrotic long non-coding RNA promoting cardiac fibrosis after myocardial infarction by suppressing Smad7

BACKGROUND

Cardiac fibrosis following myocardial infarction (MI) leads to cardiac remodeling and dysfunction. Dysregulation of Smad7 which negatively regulates the profibrotic transforming growth factor-β1 (TGF-β1)/Smad signaling promotes cardiac fibrosis. However, the molecular mechanisms underlying TGF-β1/Smad7 dysregulation remain elusive. Long non-coding RNAs (lncRNAs) are recently emerging as important regulators of cardiac diseases. Here, we report lnc-Ang362 is a novel lncRNA mediating MI-induced fibrosis through TGF-β1/Smad7 signaling pathway.

METHODS AND RESULTS

The MI model was established by artificial coronary artery occlusion in rats. Microarray analysis identified 215 lncRNAs (fold change > 2.0, P < 0.05) differentially expressed between MI hearts and the sham group 4 weeks after MI. Lnc-Ang362 had the highest fold upregulation and the change was validated by reverse transcription polymerase chain reaction. Also, MI caused a marked increase in TGF-β1 and collagen I/III expression, but significantly downregulated Smad7 expression. Adult rat cardiac fibroblasts (RCFs) treated with TGF-β1 showed increased lnc-Ang362 expression and decreased Smad7 expression. Moreover, overexpression and knockdown of lnc-Ang362 by small interfering RNAs reduced and increased Smad7 expression, respectively. Importantly, this result was negatively correlated with the expression of collagen I/III in RCFs. Furthermore, the luciferase reporter assays confirmed that Smad7 was a validated lnc-Ang362 target. Further silencing Smad7 attenuated the effects of lnc-Ang362 knockdown on decreasing collagen I/III expression in RCFs.

CONCLUSIONS

These results suggested lnc-Ang362 promoted cardiac fibrosis after MI via directly suppressing Smad7, which may decrease the inhibitory feedback regulation of TGF-β1/Smad signaling pathway. Thus, lnc-Ang362 may be a novel profibrotic lncRNA in the regulation of cardiac fibrosis post MI.

Effects of endothelial progenitor cells transplantation on hyperlipidemia associated kidney damage in ApoE knockout mouse model

Background

Hyperlipidaemia causes kidney damage over the long term. We investigated the effect of the administration of endothelial progenitor cells (EPCs) on the progression of kidney damage in a mouse model of hyperlipidaemia.

Methods

Apolipoprotein E-knockout (ApoE^−/−) mice were treated with a high-cholesterol diet after spleen resection. Twenty-four weeks later, the mice were divided into two groups and intravenously injected with PBS or EPCs. Six weeks later, the recruitment of EPCs to the kidney was monitored by immunofluorescence. The lipid, endothelial cell, and collagen contents in the kidney were evaluated by specific immunostaining. The protein expression levels of transforming growth factor-β (TGF-β), Smad2/3, and phospho-Smad3 (p-smad3) were detected by western blot analysis.

Results

ApoE^−/− mice treated with a high-fat diet demonstrated glomerular lipid deposition, enlargement of the glomerular mesangial matrix, endothelial cell enlargement accompanied by vacuolar degeneration and an area of interstitial collagen in the kidney. Six weeks after EPC treatment, only a few EPCs were detected in the kidney tissues of ApoE^−/− mice, mainly in the kidney interstitial area. No significant differences in TGF-β, p-smad3 or smad2/3 expression were found between the PBS group and the EPC treatment group (TGF-β expression, PBS group: 1.06 ± 0.09, EPC treatment group: 1.09 ± 0.17, P = 0.787; p-smad3/smad2/3 expression: PBS group: 1.11 ± 0.41, EPC treatment group: 1.05 ± 0.33, P = 0.861).

Conclusions

Our findings demonstrate that hyperlipidaemia causes basement membrane thickening, glomerulosclerosis and the vascular degeneration of endothelial cells. The long-term administration of EPCs substantially has limited effect in the progression of kidney damage in a mouse model of hyperlipidaemia.

lncRNA Erbb4-IR is downregulated in prostate carcinoma and predicts prognosis

Long non-coding (lnc) RNA Erbb4-IR has been associated with diabetic renal injury; however, its roles in other diseases remain unknown. Therefore, the present study investigated the involvement of Erbb4-IR in prostate carcinoma. Reverse transcription-quantitative PCR was used to analyze gene expression in tissue samples collected from patients with prostate carcinoma. Overexpression experiments via cell transfection were performed to determine the association between Erbb4-IR and microRNA (miR)-21. Furthermore, Cell Counting Kit-8 and cell apoptosis assays were performed to assess cell proliferation and apoptotic rate, respectively. The results revealed that Erbb4-IR was downregulated in prostate carcinoma tissues compared with adjacent non-cancerous tissues, and that low expression of Erbb4-IR in tumor tissues was closely associated with poor survival. Furthermore, miR-21 was upregulated in prostate carcinoma tissues compared with adjacent non-cancerous tissues and was inversely associated with Erbb4-IR expression in tumor tissues. In vitro cell experiments revealed that Erbb4-IR overexpression resulted in the downregulation of miR-21, while miR-21 overexpression did not significantly affect the expression of Erbb4-IR. Moreover, Erbb4-IR overexpression increased apoptosis and inhibited the proliferation of prostate carcinoma cells. miR-21 overexpression resulted in the opposite effect and attenuated the effects of Erbb4-IR overexpression. Therefore, the results of the present study suggested that lncRNA Erbb4-IR is downregulated in prostate carcinoma and may inhibit cancer development by downregulating miR-21.

The long noncoding RNA Ptprd-IR is a novel molecular target for TGF-β1-mediated nephritis

The role of microRNAs (miRNAs) in chronic kidney disease (CKD) is relatively well established, but much less is known about the role(s) of long noncoding RNAs (lncRNAs). Transforming growth factor β1 (TGF-β1) mediates inflammatory and fibrogenic signaling in CKD via the transcription factor Smad3; however, the extent of lncRNAs-based regulation of TGF-β1 signaling in CKD remains unknown. Herein, we identified np_4334, a lncRNA we named Ptprd-IR, whose promoter contains a highly-conserved site for Smad3 binding. Smad3 knockout (KO) eliminated Ptprd-IR upregulation in a murine model of obstructive nephropathy. Furthermore, Ptprd-IR KO in renal tubular epithelial cell cultures blocked TGF-β1- and interleukin-1β (IL-1β)-mediated NF-κB inflammatory signaling but did not impact TGF-β1-triggered Smad3 pathway activity and fibrosis. Accordingly, Ptprd-IR overexpression (OE) upregulated TGF-β1- and IL-1β-mediated NF-κB pathway activation and production of pro-inflammatory cytokines but did not influence TGF-β1-mediated fibrogenic signaling. Additionally, transfection of obstructed kidneys with Ptprd-IR-directed shRNA attenuated the inflammatory response via NF-κB but did not impact TGF-β1/Smad3-mediated fibrogenesis. Overall, our findings demonstrate that the lncRNA Ptprd-IR stimulates the inflammatory response in kidneys and advocate Ptprd-IR as a possible therapeutic target for CKD.

Diverse Role of TGF-β in Kidney Disease

Inflammation and fibrosis are two pathological features of chronic kidney disease (CKD). Transforming growth factor-β (TGF-β) has been long considered as a key mediator of renal fibrosis. In addition, TGF-β also acts as a potent anti-inflammatory cytokine that negatively regulates renal inflammation. Thus, blockade of TGF-β inhibits renal fibrosis while promoting inflammation, revealing a diverse role for TGF-β in CKD. It is now well documented that TGF-β1 activates its downstream signaling molecules such as Smad3 and Smad3-dependent non-coding RNAs to transcriptionally and differentially regulate renal inflammation and fibrosis, which is negatively regulated by Smad7. Therefore, treatments by rebalancing Smad3/Smad7 signaling or by specifically targeting Smad3-dependent non-coding RNAs that regulate renal fibrosis or inflammation could be a better therapeutic approach. In this review, the paradoxical functions and underlying mechanisms by which TGF-β1 regulates in renal inflammation and fibrosis are discussed and novel therapeutic strategies for kidney disease by targeting downstream TGF-β/Smad signaling and transcriptomes are highlighted.

Biological and clinical relevance of metastasis-associated long noncoding RNAs in esophageal squamous cell carcinoma: A systematic review

Esophageal squamous cell carcinoma (ESCC) is a foremost cancer-related death worldwide owing to rapid metastasis and poor prognosis. Metastasis, as the most important reason for death, is biologically a multifaceted process involving a range of cell signaling pathways. Long noncoding RNAs (lncRNAs), as transcriptional regulators, can regulate numerous genomic processes and cellular processes such as cell proliferation, migration, and invasion. LncRNAs have also been shown to involve in/regulate the cancer metastasis-related signaling pathways. Hence, they have increasingly been brought to international attention in molecular oncology research. A number of researchers have attempted to reveal the biological and clinical relevance of lncRNAs in ESCC tumourigenesis and metastasis. The aberrant expression of these molecules in ESCC has regularly been reported to involve in various cellular processes and clinical features, including diagnosis, prognosis, and therapeutic responses. Here, we especially consider the pathways in which lncRNAs act as metastasis-mediated effectors, mainly by interacting with epithelial-mesenchymal transition-associated factors. We review the biological roles of lncRNAs through involving in ESCC metastasis as well as the clinical significance of the metastasis-related lncRNAs in cancer diagnosis and prognosis.

Long non-coding RNAs as novel diagnostic and therapeutic targets in kidney disease

Long non-coding RNAs (lncRNAs) have critical roles in the development of many diseases including kidney disease. An increasing number of studies have shown that lncRNAs are involved in kidney development and that their dysregulation can result in distinct disease processes, including acute kidney injury (AKI), chronic kidney disease (CKD), and renal cell carcinoma (RCC). Understanding the roles of lncRNAs in kidney disease may provide new diagnostic and therapeutic opportunities in the clinic. This review provides an overview of lncRNA characteristics, biological function and discusses specific studies that provide insight into the function and potential application of lncRNAs in kidney disease treatment.

Renoprotective Effect of Formononetin by Suppressing Smad3 Expression in Db/Db Mice

PURPOSE

Glomerular sclerosis and renal interstitial fibrosis are the most important pathologies in the development of kidney damage under diabetic conditions. Smad3 plays antagonistic roles in high glucose-induced renal tubular fibrosis, which is an important treatment target for diabetic nephropathy (DN). Formononetin (FMN) has multiple effects on diabetic vascular complications including DN. However, whether it plays an anti-fibrosis role by regulating smad3 is unclear. The purpose of this study was to evaluate the renoprotective effect of FMN by suppressing smad3 expression in db/db mice.

METHODS

FMN was orally administered to db/db mice with a dose of 25 or 50 mg/kg/day for 8 weeks. At the end of the study, serum, urine, and kidney samples were collected for biochemical and pathological examinations. The expressions of proteins and mRNA associated with renal fibrosis were determined by biochemical, histological, immunofluorescence, and real-time PCR analysis.

RESULTS

The results showed that FMN substantially improved the glucolipid metabolism, reduced the oxidative stress, and protected renal function in db/db mice. Meanwhile, protein and mRNA expression of smad3 and related regulatory factor of extracellular matrix deposition were significantly suppressed.

CONCLUSION

The present study suggested that FMN has a good renoprotective effect in DN, which plays an anti-fibrosis role in db/db mice by suppressing the expression of smad3.

LncRNA GAS5 exacerbates renal tubular epithelial fibrosis by acting as a competing endogenous RNA of miR-96-5p

Renal fibrosis is at the core of various renal diseases, including diabetic kidney disease (DKD). Long noncoding RNAs (lncRNAs) are known players in the regulation of renal fibrosis. However, their expression and function in DKD still need to be elucidated. The purpose of this study was to assess how lncRNA GAS5 regulates fibrosis and its mechanism in TGF-β1-treated renal proximal tubular cell.In this study, the lncRNA GAS5 was upregulated in both TGF-β1-treated HK-2 cells and the kidneys of HDF/STZ mice. Knockdown of GAS5 relieved renal tubular epithelial fibrosis. This effect was mediated by the downregulation and functional inactivation of miR-96-5p. Furthermore, miR-96-5p was downregulated in DKD mice, and this downregulation attenuated the repression of FN1(fibronectin, FN) and led to its upregulation. The decrease in miR-96-5p was partially attributed to the miRNA-sponge action of GAS5.Our research demonstrates that knockdown of lncRNA GAS5 leads to antifibrosis by competitively binding miR-96-5p, which inhibits the expression of FN1. These results indicate that targeting lncRNA GAS5 may be a promising therapeutic strategy for preventing DKD.

Circulating Long Noncoding RNA LIPCAR Predicts Heart Failure Outcomes in Patients Without Chronic Kidney Disease

The plasma levels of long noncoding RNA LIPCAR are elevated in heart failure (HF) patients with reduced ejection fraction and associated with left ventricular remodeling and poor outcomes. We studied whether the presence of chronic kidney disease (CKD), as defined by an estimated glomerular filtration rate value <60mL/(min·1.73m2) modified the associations of plasma LIPCAR with left ventricular remodeling and outcomes in HF patients. Two hundred and thirty-four patients (mean age 74 [9.14] years, 50% male) were enrolled and followed for 4.73 (0.24-7.25) years. Plasma LIPCAR was detected by real-time quantitative polymerase chain reaction. LIPCAR was increased ( P=0.005) in patients compared with 17 age- and sex-matched controls, directly correlated with age ( P=0.001) and with the maximal early transmitral flow velocity to the mean peak early diastolic velocity of the mitral annulus displacement ratio ( P=0.001) and inversely correlated with estimated glomerular filtration rate ( P<0.001). LIPCAR was associated with hospitalization for HF, cardiovascular death, and a composite of hospitalization for HF or cardiovascular death ( P≤0.010), these associations being dependent of estimated glomerular filtration rate. The interactions between estimated glomerular filtration rate and LIPCAR with respect to these outcomes were statistically significant or of borderline significance ( P≤0.060). LIPCAR was increased in CKD patients compared with non-CKD patients ( P=0.021). LIPCAR was independently associated with hospitalization for HF ( P≤0.039) only in non-CKD patients, but its addition to traditional risk factors did not improve risk prediction in these patients. In conclusion, plasma LIPCAR prognosticates outcomes in elderly HF patients without CKD. Thus, there is an effect modification of CKD on the association of circulating LIPCAR with outcomes in HF patients.

TGF-β1-p53 cooperativity regulates a profibrotic genomic program in the kidney: molecular mechanisms and clinical implications

Chronic kidney disease affects >15% of the U.S. population and >850 million individuals worldwide. Fibrosis is the common outcome of many chronic renal disorders and, although the etiology varies (i.e., diabetes, hypertension, ischemia, acute injury, and urologic obstructive disorders), persistently elevated renal TGF-β1 levels result in the relentless progression of fibrotic disease. TGF-β1 orchestrates the multifaceted program of renal fibrogenesis involving proximal tubular dysfunction, failed epithelial recovery and redifferentiation, and subsequent tubulointerstitial fibrosis, eventually leading to chronic renal disease. Recent findings implicate p53 as a cofactor in the TGF-β1-induced signaling pathway and a transcriptional coregulator of several TGF-β1 profibrotic response genes by complexing with receptor-activated SMADs, which are homologous to the small worms (SMA) and Drosophilia mothers against decapentaplegic (MAD) gene families. The cooperative p53-TGF-β1 genomic cluster includes genes involved in cell growth control and extracellular matrix remodeling [e.g., plasminogen activator inhibitor-1 (PAI-1; serine protease inhibitor, clade E, member 1), connective tissue growth factor, and collagen I]. Although the molecular basis for this codependency is unclear, many TGF-β1-responsive genes possess p53 binding motifs. p53 up-regulation and increased p53 phosphorylation; moreover, they are evident in nephrotoxin- and ischemia/reperfusion-induced injury, diabetic nephropathy, ureteral obstructive disease, and kidney allograft rejection. Pharmacologic and genetic approaches that target p53 attenuate expression of the involved genes and mitigate the fibrotic response, confirming a key role for p53 in renal disorders. This review focuses on mechanisms whereby p53 functions as a transcriptional regulator within the TGF-β1 cluster with an emphasis on the potent fibrosis-promoting PAI-1 gene.-Higgins, C. E., Tang, J., Mian, B. M., Higgins, S. P., Gifford, C. C., Conti, D. J., Meldrum, K. K., Samarakoon, R., Higgins, P. J. TGF-β1-p53 cooperativity regulates a profibrotic genomic program in the kidney: molecular mechanisms and clinical implications.

TGF-β/Smad and Renal Fibrosis

Renal fibrosis is characterized by excessive deposition of extracellular matrix (ECM) that disrupts and replaces functional parenchyma, which leads to organ failure. It is known as the major pathological mechanism of chronic kidney disease (CKD). Although CKD has an impact on no less than 10% of the world population, therapeutic options are still limited. Regardless of etiology, elevated TGF-β levels are highly correlated with the activated pro-fibrotic pathways and disease progression. TGF-β, the key driver of renal fibrosis, is involved in a dynamic pathophysiological process that leads to CKD and end-stage renal disease (ESRD). It is becoming clear that epigenetics regulates renal programming, and therefore, the development and progression of renal disease. Indeed, recent evidence shows TGF-β1/Smad signaling regulates renal fibrosis via epigenetic-correlated mechanisms. This review focuses on the function of TGF-β/Smads in renal fibrogenesis, and the role of epigenetics as a regulator of pro-fibrotic gene expression.

Effect of mycophenolate and rapamycin on renal fibrosis in lupus nephritis

Lupus nephritis (LN) leads to chronic kidney disease (CKD) through progressive fibrosis. Mycophenolate inhibits inosine monophosphate dehydrogenase and is a standard treatment for LN. The mammalian or mechanistic target of rapamycin (mTOR) pathway is activated in LN. Rapamycin inhibits mTOR and is effective in preventing kidney transplant rejection, with the additional merits of reduced incidence of malignancies and viral infections. The effect of mycophenolate or rapamycin on kidney fibrosis in LN has not been investigated. We investigated the effects of mycophenolate and rapamycin in New Zealand Black and White first generation (NZB/W F1) murine LN and human mesangial cells (HMCs), focusing on mechanisms leading to kidney fibrosis. Treatment of mice with mycophenolate or rapamycin improved nephritis manifestations, decreased anti-double stranded (ds) DNA antibody titer and reduced immunoglobulin G (IgG) deposition in the kidney. Both mycophenolate and rapamycin, especially the latter, decreased glomerular mTOR Ser2448 phosphorylation. Renal histology in untreated mice showed mesangial proliferation and progressive glomerulosclerosis with tubular atrophy, and increased expression of transforming growth factor β1 (TGF-β1), monocyte chemoattractant protein-1 (MCP-1), α-smooth muscle actin (α-SMA), fibronectin (FN) and collagen. Both mycophenolate and rapamycin ameliorated the histopathological changes. Results from in vitro experiments showed that both mycophenolate and rapamycin decreased mesangial cell proliferation and their binding with anti-dsDNA antibodies. Mycophenolate and rapamycin also down-regulated mTOR and extracellular signal-regulated kinase (ERK) phosphorylation and inhibited fibrotic responses in mesangial cells that were induced by anti-dsDNA antibodies or TGF-β1. Our findings suggest that, in addition to immunosuppression, mycophenolate and rapamycin may reduce fibrosis in LN, which has important implications in preventing CKD in patients with LN.

LRNA9884, a Novel Smad3-Dependent Long Noncoding RNA, Promotes Diabetic Kidney Injury in db/db Mice via Enhancing MCP-1-Dependent Renal Inflammation

Transforming growth factor-β/Smad3 signaling plays an important role in diabetic nephropathy, but its underlying working mechanism remains largely unexplored. The current study uncovered the pathogenic role and underlying mechanism of a novel Smad3-dependent long noncoding RNA (lncRNA) (LRNA9884) in type 2 diabetic nephropathy (T2DN). We found that LRNA9884 was significantly upregulated in the diabetic kidney of db/db mice at the age of 8 weeks preceding the onset of microalbuminuria and was associated with the progression of diabetic renal injury. LRNA9884 was induced by advanced glycation end products and tightly regulated by Smad3, and its levels were significantly blunted in db/db mice and cells lacking Smad3. More importantly, kidney-specific silencing of LRNA9884 effectively attenuated diabetic kidney injury in db/db mice, as shown by the reduction of histological injury, albuminuria excretion, and serum creatinine. Mechanistically, we identified that LRNA9884 promoted renal inflammation-driven T2DN by triggering MCP-1 production at the transcriptional level, and its direct binding significantly enhanced the promoter activity of MCP-1. Thus, LRNA9884 is a novel Smad3-dependent lncRNA that is highly expressed in db/db mice associated with T2DN development. Targeting of LRNA9884 effectively blocked MCP-1-dependent renal inflammation, therefore suppressing the progressive diabetic renal injury in db/db mice. This study reveals that LRNA9884 may be a novel and precision therapeutic target for T2DN in the future.

LncRNA: Shedding light on mechanisms and opportunities in fibrosis and aging

Fibrosis is universally observed in multiple aging-related diseases and progressions and is characterized by excess accumulation of the extracellular matrix. Fibrosis occurs in various human organs and eventually results in organ failure. Noncoding RNAs (ncRNAs) have emerged as essential regulators of cellular signaling and relevant human diseases. In particular, the enigmatic class of long noncoding RNAs (lncRNAs) is a kind of noncoding RNA that is longer than 200 nucleotides and does not possess protein coding ability. LncRNAs have been identified to exert both promotive and inhibitory effects on the multifaceted processes of fibrosis. A growing body of studies has revealed that lncRNAs are involved in fibrosis in various organs, including the liver, heart, lung, and kidney. As lncRNAs have been increasingly identified, they have become promising targets for anti-fibrosis therapies. This review systematically highlights the recent advances regarding the roles of lncRNAs in fibrosis and sheds light on the use of lncRNAs as a potential treatment for fibrosis.

Petchiether A attenuates obstructive nephropathy by suppressing TGF-β/Smad3 and NF-κB signalling

Obstructive nephropathy is the end result of a variety of diseases that block drainage from the kidney(s). Transforming growth factor‐β1 (TGF‐β1)/Smad3‐driven renal fibrosis is the common pathogenesis of obstructive nephropathy. In this study, we identified petchiether A (petA), a novel small‐molecule meroterpenoid from Ganoderma, as a potential inhibitor of TGF‐β1‐induced Smad3 phosphorylation. The obstructive nephropathy was induced by unilateral ureteral obstruction (UUO) in mice. Mice received an intraperitoneal injection of petA/vehicle before and after UUO or sham operation. An in vivo study revealed that petA protected against renal inflammation and fibrosis by reducing the infiltration of macrophages, inhibiting the expression of proinflammatory cytokines (interleukin‐1β and tumour necrosis factor‐α) and reducing extracellular matrix deposition (α‐smooth muscle actin, collagen I and fibronectin) in the obstructed kidney of UUO mice; these changes were associated with suppression of Smad3 and NF‐κB p65 phosphorylation. Petchiether A inhibited Smad3 phosphorylation in vitro and down‐regulated the expression of the fibrotic marker collagen I in TGF‐β1‐treated renal epithelial cells. Further, we found that petA dose‐dependently suppressed Smad3‐responsive promoter activity, indicating that petA inhibits gene expression downstream of the TGF‐β/Smad3 signalling pathway. In conclusion, our findings suggest that petA protects against renal inflammation and fibrosis by selectively inhibiting TGF‐β/Smad3 signalling.

LncRNA FEZF1-AS1 Promotes TGF-β2-Mediated Proliferation and Migration in Human Lens Epithelial Cells SRA01/04

Posterior capsule opacification (PCO) is a common complication after cataract surgery attributed to the proliferation and migration of postoperative residual lens epithelial cells (LECs). The long noncoding RNA (lncRNA) FEZ family zinc finger 1 antisense RNA 1 (FEZF1-AS1) promotes the proliferation and migration of multiple types of cancer cells. Here, we discovered that FEZF1-AS1 is markedly upregulated in TGF-β2-treated SRA01/04 cells. In addition, the proliferation and migration of SRA01/04 cells were enhanced following TGF-β2 treatment. FEZF1-AS1 knockdown inhibited the TGF-β2-induced proliferation and migration of SRA01/04 cells. Accordingly, FEZF1-AS1 overexpression promoted the TGF-β2-induced proliferation and migration of SRA01/04 cells. Finally, FEZF1-AS1 upregulated TGF-β2-induced SRA01/04 cell proliferation and migration via boosting FEZF1 protein levels. Our findings indicate that the dysregulation of FEZF1-AS1 participates in the TGF-β2-induced proliferation and migration of human lens epithelial cells (HLECs), which might be achieved, at least in part, through the induction of FEZF1 expression.

Long Noncoding RNA: Genomics and Relevance to Physiology

The mammalian cell expresses thousands of long noncoding RNAs (lncRNAs) that are longer than 200 nucleotides but do not encode any protein. lncRNAs can change the expression of protein-coding genes through both cis and trans mechanisms, including imprinting and other types of transcriptional regulation, and posttranscriptional regulation including serving as molecular sponges. Deep sequencing, coupled with analysis of sequence characteristics, is the primary method used to identify lncRNAs. Physiological roles of specific lncRNAs can be examined using genetic targeting or knockdown with modified oligonucleotides. Identification of nucleic acids or proteins with which an lncRNA interacts is essential for understanding the molecular mechanism underlying its physiological role. lncRNAs have been reported to contribute to the regulation of physiological functions and disease development in several organ systems, including the cardiovascular, renal, muscular, endocrine, digestive, nervous, respiratory, and reproductive systems. The physiological role of the majority of lncRNAs, many of which are species and tissue specific, remains to be determined. © 2019 American Physiological Society. Compr Physiol 9:933-946, 2019.

The protective effect of the TUG1/miR‑197/MAPK1 axis on lipopolysaccharide‑induced podocyte injury

The podocyte, a type of glomerular epithelial cell, is the key constituent of the filtration barrier layer in the kidney. Previous studies have shown that long non‑coding RNA (lncRNA)‑taurine‑upregulated gene 1 (TUG1) served a protective role in diabetes‑induced podocyte damage. The aim of the present study was to investigate the potential role of TUG1 in the progress of podocyte injury induced by lipopolysaccharide (LPS), and explore the underlying mechanisms. The results showed that TUG1 expression was suppressed in LPS‑induced podocytes. Enhanced TUG1 expression by exogenous recombinant vector regulated the expression of podocyte associated proteins [Nephrin, Podocin and CCAAT/enhancer‑binding protein (CHOP)]. A marked decrease was observed in the level the albumin influx in cells transfected with TUG1. Further study indicated that microRNA (miR)‑197 is a potential target of TUG1. The enhanced level of miR‑197 induced by LPS was inhibited in cells transfected with TUG1. The decreased Nephrin and Podocin expression, upregulated CHOP expression and the increased albumin influx were slightly enhanced by miR‑197 mimic transfection, while markedly suppressed by miR‑197 inhibitor transfection in LPS‑induced podocytes. Mitogen‑activated protein kinase (MAPK) protein was predicted as a potential target of miR‑197. The downregulated expression of phosphorylated‑MAPK/MAPK induced by LPS was significantly suppressed by TUG1 transfection in podocytes. In addition to this, autophagy was promoted by TUG1 transfection via the elevation of the Beclin1 and light chain (LC)3 II/LC3 I levels, and suppressing p62 expression. However, the p38 MAPK inhibitor SB203580 reversed the changes that TUG1 induced in the levels of Beclin1, LC3 II/LC3 I and p62. Taken together, these results demonstrated that LPS‑induced podocyte injury could be alleviated by the TUG1/miR‑197/MAPK1 axis.

Non-Coding RNAs as New Therapeutic Targets in the Context of Renal Fibrosis

Fibrosis, or tissue scarring, is defined as the excessive, persistent and destructive accumulation of extracellular matrix components in response to chronic tissue injury. Renal fibrosis represents the final stage of most chronic kidney diseases and contributes to the progressive and irreversible decline in kidney function. Limited therapeutic options are available and the molecular mechanisms governing the renal fibrosis process are complex and remain poorly understood. Recently, the role of non-coding RNAs, and in particular microRNAs (miRNAs), has been described in kidney fibrosis. Seminal studies have highlighted their potential importance as new therapeutic targets and innovative diagnostic and/or prognostic biomarkers. This review will summarize recent scientific advances and will discuss potential clinical applications as well as future research directions.

Non-coding RNAs in kidney injury and repair

Acute kidney injury (AKI) is a major kidney disease featured by a rapid decline of renal function. Pathologically, AKI is characterized by tubular epithelial cell injury and death. Besides its acute consequence, AKI contributes critically to the development and progression of chronic kidney disease (CKD). After AKI, surviving tubular cells regenerate to repair. Normal repair restores tubular integrity, while maladaptive or incomplete repair results in renal fibrosis and eventually CKD. Non-coding RNAs (ncRNAs) are functional RNA molecules that are transcribed from DNA but not translated into proteins, which mainly include microRNAs (miRNAs), long non-coding RNAs (lncRNAs), circular RNAs (circRNAs), small nucleolar RNAs (snoRNAs), and tRNAs. Accumulating evidence suggests that ncRNAs play important roles in kidney injury and repair. In this review, we summarize the recent advances in the understanding of the roles of ncRNAs, especially miRNAs and lncRNAs in kidney injury and repair, discuss the potential application of ncRNAs as biomarkers of AKI as well as therapeutic targets for treating AKI and impeding AKI-CKD transition, and highlight the future research directions of ncRNAs in kidney injury and repair.

Epigenetic regulation in AKI and kidney repair: mechanisms and therapeutic implications

Acute kidney injury (AKI) is a major public health concern associated with high morbidity and mortality. Despite decades of research, the pathogenesis of AKI remains incompletely understood and effective therapies are lacking. An increasing body of evidence suggests a role for epigenetic regulation in the process of AKI and kidney repair, involving remarkable changes in histone modifications, DNA methylation and the expression of various non-coding RNAs. For instance, increases in levels of histone acetylation seem to protect kidneys from AKI and promote kidney repair. AKI is also associated with changes in genome-wide and gene-specific DNA methylation; however, the role and regulation of DNA methylation in kidney injury and repair remains largely elusive. MicroRNAs have been studied quite extensively in AKI, and a plethora of specific microRNAs have been implicated in the pathogenesis of AKI. Emerging research suggests potential for microRNAs as novel diagnostic biomarkers of AKI. Further investigation into these epigenetic mechanisms will not only generate novel insights into the mechanisms of AKI and kidney repair but also might lead to new strategies for the diagnosis and therapy of this disease.

Metformin Inhibits the Expression of Biomarkers of Fibrosis of EPCs In Vitro

Endothelial progenitor cells (EPCs) are a group of circulating cells with important functions in vascular repair and treatment of cardiovascular diseases. However, in patients with atrial fibrillation (AF), the number and function of EPCs reportedly are decreased. TGF-β is highly expressed in AF patients. In this study, we examined the effect of TGF-β1 on EPCs and the therapeutic outcome of metformin treatment on TGF-β1-induced EPCs. EPCs were induced with TGF-β1 at different concentrations (5 ng/ml, 10 ng/ml, and 20 ng/ml) for 48 h followed by western blot, qPCR, and immunofluorescence analyses to investigate changes in the levels of the fibrosis-related proteins, α-SMA, Col I, Col III, CTGF, and MMP-1. Live-dead cell staining was used to evaluate cell apoptosis. Compared with the control, TGF-β1 treatment significantly (p < 0.05) enhanced the levels of α-SMA, Col I, Col III, CTGF, and MMP-1 in a dose-dependent manner. The most effective concentration of TGF-β1 (20 ng/ml) was then used to induce fibrosis biomarker expression in EPCs, followed by treatment with metformin at different concentrations (0.5, 1, and 2 mmol/l). Metformin treatment suppressed TGF-β-induced expression of all above factors, with the effect at 2 mmol/l being significant (p < 0.05). Live-dead cell staining showed no difference among the control, TGF-β1-treated, and metformin-treated groups. In conclusion, our study showed that TGF-β1 induces the expression of fibrosis biomarkers in EPCs, which is attenuated by treatment with metformin. Thus, metformin may have therapeutic potential for improving EPC function in cardiovascular diseases.