The long noncoding RNA Tug1 connects metabolic changes with kidney disease in podocytes

Astragaloside IV/lncRNA-TUG1/TRAF5 signaling pathway participates in podocyte apoptosis of diabetic nephropathy rats

Objective

This study aims to figure out the mechanism of astragaloside IV (AS-IV) in the protection of podocyte apoptosis in diabetic nephropathy (DN) rats.

Materials and methods

Streptozotocin (STZ) was used to induce diabetes in rats, and the diabetic rats were treated with 5 mg/kg/d of AS-IV for 12 weeks. Albuminuria level, relative TUG1 and TRAF5 levels, and TRAF5 and cleaved-caspase-3 protein levels were examined by ELISA, quantitative reverse transcription (qRT)-PCR, and Western blot analyses, respectively. The interaction between TUG1 and TRAF5 was confirmed by RNA pull-down and RNA precipitation. TUNEL assay was used to detect podocyte apoptosis.

Results

Compared with control rats, DN rats had higher albuminuria and TRAF5 levels and lower TUG1 level. AS-IV treatment attenuated albuminuria and TRAF5 levels and improved TUG1 level in DN rats. TUG1 was downregulated and TRAF5 was upregulated in high-glucose-treated MPC5 cells, and AS-IV ameliorated the TUG1 level. In addition, TUG1 interacted with TRAF5, and TUG1 overexpression promoted degradation of TRAF5 protein. Besides, AS-IV modulated TRAF5 expression through regulating TUG1. AS-IV decreased podocyte apoptosis via the TUG1/TRAF5 pathway. Finally, in vivo experiment proved that si-TUG1 abrogated the protective effect of AS-IV on DN.

Conclusion

AS-IV attenuated podocyte apoptosis and protected diabetic rats from DN via the lncRNA-TUG1/TRAF5 pathway.

Long noncoding RNA TUG1 facilitates osteogenic differentiation of periodontal ligament stem cells via interacting with Lin28A

Periodontal ligament stem cells (PDLSCs) are mesenchymal stem cells derived from dental tissues with multidirectional differentiation potential and excellent self-renewing ability. Recently, long noncoding RNAs (lncRNAs) have been shown to play important roles in MSC osteogenic differentiation. In this study, we found that taurine upregulated gene 1 (TUG1), an evolutionarily conserved and widely present lncRNA was significantly upregulated in osteogenically induced PDLSCs compared to their undifferentiated counterparts. Further investigation demonstrated that the expression of TUG1 was positively correlated with the osteogenic differentiation of PDLSCs following the induction, as evidenced by the increase in cellular alkaline phosphatase (ALP) level, formation of calcium nodules, and the upregulation of several osteogenic-related gene markers such as ALP, osteocalcin (OCN), and runt-related transcription factor 2 (Runx2). Conversely, TUG1 knockdown was demonstrated to inhibit the potential of PDLSCs for osteogenic differentiation. Using bioinformatics analysis, we identified lin-28 homolog A (Lin28A) as a potential target of TUG1 during osteogenic differentiation of PDLSCs. Lin28A was found to be significantly downregulated in TUG1-repressed PDLSCs and contained multiple binding sites for lncRNA TUG1. Moreover, suppression of Lin28A was shown to be able to inhibit osteogenic differentiation and decreased the expression of several osteogenic genes. Taken together, these results could help researchers better understand the mechanism that governs the osteogenic differentiation of PDLSCs, and also serve as a stepping stone for the development of novel therapeutic strategies that can be used to regenerate dental tissues.

Novel lncRNA Erbb4-IR Promotes Diabetic Kidney Injury in db/db Mice by Targeting miR-29b

Transforming growth factor-β/Smad signaling plays an important role in diabetic nephropathy. The current study identified a novel Smad3-dependent long noncoding RNA (lncRNA) Erbb4-IR in the development of type 2 diabetic nephropathy (T2DN) in db/db mice. We found that Erbb4-IR was highly expressed in T2DN of db/db mice and specifically induced by advanced glycosylation end products (AGEs) via a Smad3-dependent mechanism. The functional role of Erbb4-IR in T2DN was revealed by kidney-specific silencing of Erbb4-IR to protect against the development of T2DN, such as elevated microalbuminuria, serum creatinine, and progressive renal fibrosis in db/db mice, and to block AGE-induced collagen I and IV expression in mouse mesangial cells (mMCs) and mouse tubular epithelial cells (mTECs). Mechanistically, we identified that the Erbb4-IR-microRNA (miR)-29b axis was a key mechanism of T2DN because Erbb4-IR was able to bind the 3' untranslated region of miR-29b genomic sequence to suppress miR-29b expression at transcriptional level. In contrast, silencing of renal Erbb4-IR increased miR-29b and therefore protected the kidney from progressive renal injury in db/db mice and prevented mTECs and mMCs from AGE-induced loss of miR-29b and fibrotic response in vitro. Collectively, we identify that Erbb4-IR is a Smad3-dependent lncRNA that promotes renal fibrosis in T2DN by suppressing miR-29b. Targeting Erbb4-IR may represent a novel therapy for T2DN.

Wnt9a Promotes Renal Fibrosis by Accelerating Cellular Senescence in Tubular Epithelial Cells

Cellular senescence is associated with renal disease progression, and accelerated tubular cell senescence promotes the pathogenesis of renal fibrosis. However, the underlying mechanism is unknown. We assessed the potential role of Wnt9a in tubular cell senescence and renal fibrosis. Compared with tubular cells of normal subjects, tubular cells of humans with a variety of nephropathies and those of several mouse models of CKD expressed high levels of Wnt9a that colocalized with the senescence-related protein p16^INK4A Wnt9a expression level correlated with the extent of renal fibrosis, decline of eGFR, and expression of p16^INK4A Furthermore, ectopic expression of Wnt9a after ischemia-reperfusion injury (IRI) induced activation of β-catenin and exacerbated renal fibrosis. Overexpression of Wnt9a exacerbated tubular senescence, evidenced by increased detection of p16^INK4A expression and senescence-associated β-galactosidase activity. Conversely, shRNA-mediated knockdown of Wnt9a repressed IRI-induced renal fibrosis in vivo and impeded the growth of senescent tubular epithelial cells in culture. Notably, Wnt9a-induced renal fibrosis was inhibited by shRNA-mediated silencing of p16^INK4A in the IRI mouse model. In a human proximal tubular epithelial cell line and primary renal tubular cells, Wnt9a remarkably upregulated levels of senescence-related p16^INK4A, p19^ARF, p53, and p21 and decreased the phosphorylation of retinoblastoma protein. Wnt9a also induced senescent tubular cells to produce TGF-β1, which promoted proliferation and activation in normal rat kidney fibroblasts. Thus, Wnt9a drives tubular senescence and fibroblast activation. Furthermore, the Wnt9a-TGF-β pathway appears to create a reciprocal activation loop between senescent tubular cells and activated fibroblasts that promotes and accelerates the pathogenesis of renal fibrosis.

LncRNA AK054921 and AK128652 are potential serum biomarkers and predictors of patient survival with alcoholic cirrhosis

Alcoholic liver disease (ALD) is one of the leading causes of chronic liver disease. Recent studies have demonstrated the roles of long noncoding RNAs (lncRNAs) in the pathogenesis of several disease processes. However, the roles of lncRNAs in patients with ALD remain unexplored. Global profiling for human lncRNAs from peripheral blood RNA was performed in a well‐characterized cohort of healthy controls (HC; n = 4), excessive drinkers (ED) without liver disease (n = 4), and those with alcoholic cirrhosis (AC) with different severities (n = 12). The expression of unique lncRNA signatures were validated in a separate cohort of HC (n = 17), ED (n = 19), AC (n = 48), and human liver tissues with ALD (n = 19). A detailed analysis of plasma lncRNAs in AC subjects with different severities compared with HC identified 244 commonly up‐regulated lncRNAs and 181 commonly down‐regulated lncRNAs. We further validated top 20 most differentially up‐ and down‐regulated lncRNAs in ED and AC compared with HC and also determined the expression of selected lncRNAs in human liver tissues with or without AC. Among those lncRNAs, AK128652 and AK054921 were two of the most abundantly expressed lncRNAs in normal human plasma and liver, and their levels were significantly elevated in AC. The prognostic significance of AK128652 and AK054921 was determined in 48 subjects with AC who were followed prospectively for 520 days. The expression of AK128652 and AK054921 was inversely associated with survival in patients with AC. Conclusion: lncRNAs AK054921 and AK128652 are potential biomarkers to predict the progression to ALD in individuals with excessive alcohol consumption and are predictors of survival in patients with AC. (Hepatology Communications 2017;1:513–523)

Increasing the level of peroxisome proliferator-activated receptor γ coactivator-1α in podocytes results in collapsing glomerulopathy

Inherited and acquired mitochondrial defects have been associated with podocyte dysfunction and chronic kidney disease (CKD). Peroxisome proliferator-activated receptor γ coactivator-1α (PGC1α) is one of the main transcriptional regulators of mitochondrial biogenesis and function. We hypothesized that increasing PGC1α expression in podocytes could protect from CKD. We found that PGC1α and mitochondrial transcript levels are lower in podocytes of patients and mouse models with diabetic kidney disease (DKD). To increase PGC1α expression, podocyte-specific inducible PGC1α-transgenic mice were generated by crossing nephrin-rtTA mice with tetO-Ppargc1a animals. Transgene induction resulted in albuminuria and glomerulosclerosis in a dose-dependent manner. Expression of PGC1α in podocytes increased mitochondrial biogenesis and maximal respiratory capacity. PGC1α also shifted podocytes towards fatty acid usage from their baseline glucose preference. RNA sequencing analysis indicated that PGC1α induced podocyte proliferation. Histological lesions of mice with podocyte-specific PGC1α expression resembled collapsing focal segmental glomerular sclerosis. In conclusion, decreased podocyte PGC1α expression and mitochondrial content is a consistent feature of DKD, but excessive PGC1α alters mitochondrial properties and induces podocyte proliferation and dedifferentiation, indicating that there is likely a narrow therapeutic window for PGC1α levels in podocytes.

Prognostic and clinicopathological role of long non-coding RNA taurine upregulated 1 in various human malignancies: A systemic review and meta-analysis

The aberrant dysregulation of taurine upregulated 1, a novel discovered long non-coding RNA, was ubiquitous in different human solid tumors. Accumulating researches have indicated that taurine upregulated 1 is an independent prognostic indicator in cancer patients. This investigation aimed to further explore the prognostic and clinical significance of taurine upregulated 1 in various types of cancers. Eligible studies were systematically searched in PubMed, Embase, Medline, and Web of Science databases. A total of 12/14 studies with 1303/1228 individuals were included to evaluate the association of taurine upregulated 1 with overall survival and clinicopathological features by pooled hazard ratio and odds ratio in malignancies. The meta-analysis suggested overexpression of taurine upregulated 1 was significantly correlated with unfavorable overall survival in patients with cancer (pooled hazard ratio = 1.63, 95% confidence interval: 1.29-2.06). There was also a significantly positive correlation between high level of taurine upregulated 1 and high pathological grade carcinoma (pooled odds ratio = 4.41, 95% confidence interval: 3.07-6.43) and positive lymphatic metastasis (pooled odds ratio = 2.00, 95% confidence interval: 1.31-3.06). In summary, upregulated taurine upregulated 1 is correlated with more advanced clinicopathological characteristics and poor prognosis, suggesting that taurine upregulated 1 may serve as a novel predictive biomarker of patients with numerous tumors.

WT1 ameliorates podocyte injury via repression of EZH2/β-catenin pathway in diabetic nephropathy

Epigenetic modulation of podocyte injury plays a pivotal role in diabetic nephropathy (DN). Wilm's tumor 1 (WT1) has been found to have opposing roles with β-catenin in podocyte biology. Herein, we asked whether the histone methyltransferase enzyme enhancer of zeste homolog 2 (EZH2) promotes WT1-induced podocyte injury via β-catenin activation and the underlying mechanisms. We found that WT1 antagonized EZH2 and ameliorated β-catenin-mediated podocyte injury as demonstrated by attenuated podocyte mesenchymal transition, maintenance of podocyte architectural integrity, decreased podocyte apoptosis and oxidative stress. Further, we provided mechanistical evidence that EZH2 was required in WT1-mediated β-catenin inactivation via repression of secreted frizzled-related protein 1 (SFRP-1), a Wnt antagonist. Moreover, EZH2-mediated silencing of SFRP-1 was due to increased histone 3 lysine 27 trimethylation (H3K27me3) on its promoter region. WT1 favored renal function and decreased podocyte injury in diabetic rats and DN patients. Notably, WT1 exhibited clinical and biological relevance as it was linked to dropped serum creatinine, decreased proteinuria and elevated estimated glomerular filtration rate (eGFR). We propose an epigenetic process via the WT1/EZH2/β-catenin axis in attenuating podocyte injury in DN. Targeting WT1 and EZH2 could be potential therapeutic approaches for DN.

p53/Drp1-dependent mitochondrial fission mediates aldosterone-induced podocyte injury and mitochondrial dysfunction

Mitochondrial dysfunction is increasingly recognized as an important factor in glomerular diseases. Previous study has shown that mitochondrial fission contributed to mitochondrial dysfunction. However, the mechanism of mitochondrial fission on mitochondrial dysfunction in aldosterone-induced podocyte injury remains ambiguous. This study aimed to investigate the pathogenic effect of mitochondrial fission both in vivo and in vitro. In an animal model of aldosterone-induced nephropathy, inhibition of the mitochondrial fission protein dynamin-related protein 1 (Drp1) suppressed aldosterone-induced podocyte injury. In cultured podocytes, aldosterone dose dependently induced Drp1 expression. Knockdown of Drp1 inhibited aldosterone-induced mitochondrial fission, mitochondrial dysfunction, and podocyte apoptosis. Furthermore, aldosterone dose dependently induced p53 expression. Knockdown of p53 inhibited aldosterone-induced Drp1 expression, mitochondrial dysfunction, and podocyte apoptosis. These findings implicated that aldosterone induced mitochondrial dysfunction and podocyte injury mediated by p53/Drp1-dependent mitochondrial fission, which may provide opportunities for therapeutic intervention for podocyte injury.