Grem2 mediates podocyte apoptosis in high glucose milieu

(+)-Catechins Play a Protective Role in Diabetic Kidney Disease by Alleviating EMT through Multiple Pathways

SCOPE

Diabetic nephropathy (DN), a complication of diabetes mellitus, is becoming a significant global health concern, with no complete cure currently available. Tea is regarded as an essential component of a balanced diet and contains (+)-Catechin (CE), which exert a range of pharmacological effects. Consequently, CE may be a potential treatment for DN. The objective of this study is to examine the protective effects and underlying mechanisms of CE on DN, with a particular focus on the epithelial-mesenchymal transition (EMT) process, which plays a pivotal role in regulating DN.

METHODS AND RESULTS

In this study db/db mice are treated with catechins. The results demonstrate that CE reduces obesity and hyperglycemia, improves renal dysfunction and morphological changes in diabetic mice, and inhibits the development of DN through the RAGE/NF-κB signaling pathway. Among them differentially expressed messenger RNA (mRNA) results, those related to EMT, including Cav1, grem2, macrod2, and kap, are identified. To further validate the results, the same experiments are performed on HK-2 cells.

CONCLUSIONS

The research results offer novel perspectives by emphasizing the anti-inflammatory properties of CE and their potential role in mitigating DN through the regulation of EMT-related genes such as RAGE, Cav1, grem2, macrod2, and kap.

Comprehensive analysis of the gene expression profile of the male and female BTBR mice with diabetic nephropathy

Comprehensive insight into the gender-based gene expression-related omics data in a rodent model of diabetic nephropathy (DN) is scarce. In the present study, the gender-based genes regulating different pathways involved in the progression of DN were explored through an unbiased RNA sequence of kidneys from BTBR mice with DN. We identified 17,739 and 17,981 genes in male and female DN mice; 1121 and 655 genes were expressed differentially (DEGs, differentially expressed genes) in male and female DN mice; both genders displayed only 195 DEGs. In the male DN mice, the number of upregulated genes was nearly the same as that of the down-regulated genes. In contrast, the number of upregulated genes was lesser than that of the down-regulated genes in the female DN mice, manifesting a remarkable gender disparity during the progression of DN in this animal model. Gene Ontology (GO) and KEGG-enriched results showed that most of these DEGs were related to the critical biological processes, including metabolic pathways, natural oxidation, bile secretion, and PPAR signaling; all are highly associated with DN. Notably, the DEGs significantly enriched for steroid hormone biosynthesis pathway were identified in both genders; the number of DEGs increased was 22 in male DN mice and 14 in female DN mice. Specifically, the Ugt1a10, Akr1c12, and Akr1c14 were upregulated in both genders. Interestingly, the Hsd11b1 gene was upregulated in female DN mice but downregulated in male DN mice. These results suggest that a significant gender-based variance in the gene expression occurs during the progression of DN and may be playing a role in the advancement of DN in the BTBR mouse model.

Mobilisation of jerboa kidney gene networks during dehydration and opportunistic rehydration

Desert animals have evolved systems that enable them to thrive under dry conditions. Focusing on the kidney, we have investigated the transcriptomic adaptations that enable a desert rodent, the Lesser Egyptian Jerboa (Jaculus jaculus), to withstand water deprivation and opportunistic rehydration. Analysis of the whole kidney transcriptome showed many differentially expressed genes in the Jerboa kidney, 6.4% of genes following dehydration and an even greater number (36.2%) following rehydration compared to control. Genes correlated with the rehydration condition included many ribosomal protein coding genes suggesting a concerted effort to accelerate protein synthesis when water is made available. We identify an increase in TGF-beta signaling antagonists in dehydration (e.g., GREM2). We also describe expression of multiple aquaporin and solute carrier transporters mapped to specific nephron segments. The desert adapted renal transcriptome presented here is a valuable resource to expand our understanding of osmoregulation beyond that derived from model organisms.

Nicotine exacerbates diabetic nephropathy through upregulation of Grem1 expression

BACKGROUND

Diabetic nephropathy (DN) is a major complication of diabetes mellitus. Clinical reports indicate that smoking is a significant risk factor for chronic kidney disease, and the tobacco epidemic exacerbates kidney damage in patients with DN. However, the underlying molecular mechanisms remain unclear.

METHOD

In the present study, we used a diabetic mouse model to investigate the molecular mechanisms for nicotine-exacerbated DN. Twelve-week-old female mice were injected with streptozotocin (STZ) to establish a hyperglycemic diabetic model. After four months, the control and hyperglycemic diabetic mice were further divided into four groups (control, nicotine, diabetic mellitus, nicotine + diabetic mellitus) by intraperitoneal injection of nicotine or PBS. After two months, urine and blood were collected for kidney injury assay, and renal tissues were harvested for further molecular assays using RNA-seq analysis, real-time PCR, Western blot, and immunohistochemistry. In vitro studies, we used siRNA to suppress Grem1 expression in human podocytes. Then we treated them with nicotine and high glucose to compare podocyte injury.

RESULT

Nicotine administration alone did not cause apparent kidney injury, but it significantly increased hyperglycemia-induced albuminuria, BUN, plasma creatinine, and the kidney tissue mRNA expression of KIM-1 and NGAL. Results from RNA-seq analysis, real-time PCR, Western blot, and immunohistochemistry analysis revealed that, compared to hyperglycemia or nicotine alone, the combination of nicotine treatment and hyperglycemia significantly increased the expression of Grem1 and worsened DN. In vitro experiments, suppression of Grem1 expression attenuated nicotine-exacerbated podocyte injury.

CONCLUSION

Grem1 plays a vital role in nicotine-exacerbated DN. Grem1 may be a potential therapeutic target for chronic smokers with DN.

Alterations in the Circulating Proteome Associated with Albuminuria

SIGNIFICANCE STATEMENT

We describe circulating proteins associated with albuminuria in a population of African American Study of Kidney Disease and Hypertension with CKD (AASK) using the largest proteomic platform to date: nearly 7000 circulating proteins, representing approximately 2000 new targets. Findings were replicated in a subset of a general population cohort with kidney disease (ARIC) and a population with CKD Chronic Renal Insufficiency Cohort (CRIC). In cross-sectional analysis, 104 proteins were significantly associated with albuminuria in the Black group, of which 67 of 77 available proteins were replicated in ARIC and 68 of 71 available proteins in CRIC. LMAN2, TNFSFR1B, and members of the ephrin superfamily had the strongest associations. Pathway analysis also demonstrated enrichment of ephrin family proteins.

BACKGROUND

Proteomic techniques have facilitated understanding of pathways that mediate decline in GFR. Albuminuria is a key component of CKD diagnosis, staging, and prognosis but has been less studied than GFR. We sought to investigate circulating proteins associated with higher albuminuria.

METHODS

We evaluated the cross-sectional associations of the blood proteome with albuminuria and longitudinally with doubling of albuminuria in the African American Study of Kidney Disease and Hypertension (AASK; 38% female; mean GFR 46; median urine protein-to-creatinine ratio 81 mg/g; n =703) and replicated in two external cohorts: a subset of the Atherosclerosis Risk in Communities (ARIC) study with CKD and the Chronic Renal Insufficiency Cohort (CRIC).

RESULTS

In cross-sectional analysis, 104 proteins were significantly associated with albuminuria in AASK, of which 67 of 77 available proteins were replicated in ARIC and 68 of 71 available proteins in CRIC. Proteins with the strongest associations included LMAN2, TNFSFR1B, and members of the ephrin superfamily. Pathway analysis also demonstrated enrichment of ephrin family proteins. Five proteins were significantly associated with worsening albuminuria in AASK, including LMAN2 and EFNA4, which were replicated in ARIC and CRIC.

CONCLUSIONS

Among individuals with CKD, large-scale proteomic analysis identified known and novel proteins associated with albuminuria and suggested a role for ephrin signaling in albuminuria progression.

MiR-103a-3p Contributes to the Progression of Colorectal Cancer by Regulating GREM2 Expression

PURPOSE

Our research aimed to investigate the influence of miR-103a-3p on the growth and apoptosis of colorectal cancer (CRC) cells.

MATERIALS AND METHODS

Bioinformatics was employed to analyze differentially expressed microRNAs and predict target genes. qRT-PCR was applied to detect the expression of miR-103a-3p in CRC and normal cells. HCT116 and Caco-2 were chosen, and miR-103a-3p mimics, miR-103a-3p inhibitor, as well as specific siRNAs targeting GREM2, were constructed. We subsequently evaluated alternations in cell proliferation, cell cycle and cell cycle regulators, apoptosis, and related proteins (Bcl-2 and Bax) by CCK-8 testing, Western blotting, luciferase reporter, colony formation, and Annexin V-FITC/PI. Possible binding sites for miR-103a-3p on the 3'UTR of GREM2 were checked with luciferase assay, and the impact of GREM2 on miR-103a-3p activity was also validated with above biological function testing. Additionally, the effect of miR-103a-3p knockdown in CRC cells and the molecular mechanism of miR-103a-3p targeting GREM2 were also studied.

RESULTS

Bioinformatics analysis revealed that miR-103a-3p expression increased remarkably in CRC, and targeted regulatory correlation existed between miR-103a-3p and GREM2. MiR-103a-3p inhibitor significantly impeded proliferative capacity and caused cell cycle arrest, as well as apoptosis, in HCT116 and Caco-2 cells. Consistent with this finding, overexpression of GREM2 showed similar effects to miR-103a-3p inhibition. Moreover, we demonstrated that miR-103a-3p connected target GREM2 and GREM2 knockdown reversed the effects of miR-103a-3p inhibitor on HCT116 and Caco-2 cell proliferation, cell cycle, and apoptosis. Further study showed that miR-103a-3p targeting GREM2 appeared to affect CRC progression via the transforming growth factor-β pathway.

CONCLUSION

MiR-103a-3p could augment CRC progression by targeting GREM2 and that miR-103a-3p/GREM2 could be potential novel targets for CRC therapy.

BMP-7 ameliorates partial epithelial-mesenchymal transition by restoring SnoN protein level via Smad1/5 pathway in diabetic kidney disease

Tubulointerstitial fibrosis (TIF) is involved in the development of diabetic kidney disease (DKD). Transforming growth factor β1 (TGF-β1) is involved in the extensive fibrosis of renal tissue by facilitating the partial epithelial-mesenchymal transition (EMT), increasing the synthesis of extracellular matrix (ECM), inhibiting degradation, inducing apoptosis of renal parenchyma cells, and activating renal interstitial fibroblasts and inflammatory cells. Recent studies indicated that bone morphogenetic protein-7 (BMP-7) upregulated the expression of endogenous SnoN against renal TIF induced by TGF-β1 or hyperglycemia. Nevertheless, the mechanisms underlying the BMP-7-mediated restoration of SnoN protein level remains elusive. The present study demonstrated the increased expression of BMP-7 in diabetic mellitus (DM) mice by hydrodynamic tail vein injection of overexpressed BMP-7 plasmid, which attenuated the effects of DM on kidney in mice. Partial tubular EMT and the accumulation of Collagen-III were resisted in DM mice that received overexpressed BMP-7 plasmid. Similar in vivo results showed that BMP-7 was competent to alleviate NRK-52E cells undergoing partial EMT in a high-glucose milieu. Furthermore, exogenous BMP-7 activated the Smad1/5 pathway to promote gene transcription of SnoN and intervened ubiquitination of SnoN; both effects repaired the SnoN protein level in renal tubular cells and kidney tissues of DM mice. Therefore, these findings suggested that BMP-7 could upregulate SnoN mRNA and protein levels by activating the classical Smad1/5 pathway to refrain from the partial EMT of renal tubular epithelial cells and the deposition of ECM in DKD-induced renal fibrosis.

Sulfuretted hydrogen ameliorates high dose glucose-induced podocyte apoptosis via orchestrating AMPK/mTOR cascade-mediated anti-apoptotic effects

Background

Podocytes play a pivotal role in the glomerular filtration barrier and contribute to proteinuria and glomerulosclerosis through abnormal apoptosis. Longitudinal studies have indicated the protective properties of hydrogen sulfide (H₂S) against neuronal cell apoptosis, whereas the biological function and the underlying molecular mechanism on glucose-induced podocyte apoptosis are largely unknown.

Methods

Herein, we conducted multifaceted biological analyses to verify the potential function of H₂S in glucose-induced podocyte apoptosis by examining apoptotic proteins and markers (e.g., caspase 3, Hoechst) and antioxidative effects [e.g., reactive oxygen species (ROS), lipid peroxidation, superoxide dismutase (SOD), catalase (CAT)]. Then, we took advantage of transcriptome sequencing and biological analyses to further determine the potential influence of H₂S as well as the accompanying molecular mechanism.

Results

In this study, we found that glucose-induced podocyte apoptosis could be largely rescued by H₂S via antioxidative responses, which was further confirmed by transcriptome sequencing and bioinformatics analyses. According to apoptotic signaling analysis, the over-activated AMPK/mTOR signaling cascade in glucose-treated podocytes was effectively restrained.

Conclusions

For the first time, we indicated the protective effect and mechanism of H₂S in podocytes by restricting glucose-induced apoptosis and suppressing the abnormally activated AMPK/mTOR signaling cascade. Our findings provide new references for podocyte apoptosis-associated diseases and also indicate the potential of H₂S administration in clinical trials.

Gremlin2 Activates Fibroblasts to Promote Pulmonary Fibrosis Through the Bone Morphogenic Protein Pathway

Idiopathic pulmonary fibrosis (IPF) is a progressive lung disease causing unremitting extracellular matrix deposition. Transforming growth factor-β (TGF-β) superfamily involves bone morphogenetic proteins (BMPs) and TGF-β, and the balance between the activation of TGF-β-dependent SMADs (Smad2/3) and BMP-dependent SMADs (Smad1/5/8) is essential for fibrosis process. GREM2, initially identified as a TGF-β-inducible gene, encodes a small secreted glycoprotein belonging to a group of matricellular proteins, its role in lung fibrosis is not clear. Here, we identified Gremlin2 as a key regulator of fibroblast activation. Gremlin2 was highly expressed in the serum and lung tissues in IPF patients. Bleomycin-induced lung fibrosis model exhibited high expression of Gremlin2 in the bronchoalveolar lavage fluid (BALF) and lung tissue. Isolation of primary cells from bleomycin-induced fibrosis lung showed a good correlation of Gremlin2 and Acta2 (α-SMA) expressions. Overexpression of Gremlin2 in human fetal lung fibroblast 1 (HFL-1) cells increased its invasion and migration. Furthermore, Gremlin2 regulates fibrosis functions through mediating TGF-β/BMP signaling, in which Gremlin2 may activate TGF-β signaling and inhibit BMP signaling. Therefore, we provided in vivo and in vitro evidence to demonstrate that Gremlin2 may be a potential therapeutic target for the treatment of IPF.

EDA2R mediates podocyte injury in high glucose milieu

EDA2R is a member of the large family of tumor necrosis factor receptor (TNFR). Previous studies suggested that EDA2R expression might be increased in the kidneys of diabetic mice. However, its mRNA and protein expression in kidneys were not analyzed; moreover, its role in the development of diabetic kidney disease was not explored. Here we analyzed the mRNA and protein expressions of EDA2R in diabetic kidneys and examined its role in the podocyte injury in high glucose milieu. By analysis with real-time PCR, Western blotting, we found that both the mRNA and protein levels of EDA2R were increased in the kidneys of diabetic mice. Immunohistochemical studies revealed that EDA2R expression was enhanced in both glomerular and tubular cells of diabetic mice and humans. In vitro studies, high glucose increased EDA2R expression in cultured human podocytes. Overexpression of EDA2R in podocytes promoted podocyte apoptosis and decreased nephrin expression. Moreover, ED2AR increased ROS generation in podocytes, while inhibiting ROS generation attenuates EDA2R-mediated podocyte injury. In addition, EDA2R silencing partially suppressed high glucose-induced ROS generation, apoptosis, and nephrin decrease. Our study demonstrated that high glucose increases EDA2R expression in kidney cells and that EDA2R induces podocyte apoptosis and dedifferentiation in high glucose milieu partially through enhanced ROS generation.

Altered renal hemodynamics is associated with glomerular lipid accumulation in obese Dahl salt-sensitive leptin receptor mutant rats

The present study examined whether development of renal injury in the nondiabetic obese Dahl salt-sensitive leptin receptor mutant (SS^LepRmutant) strain is associated with elevations in glomerular filtration rate and renal lipid accumulation. Baseline mean arterial pressure at 6 wk of age was similar between Dahl salt-sensitive wild-type (SS_WT) and SS^LepRmutant rats. However, by 18 wk of age, the SS^LepRmutant strain developed hypertension, while the elevation in mean arterial pressure was not as severe in SS_WT rats (192 ± 4 and 149 ± 6 mmHg, respectively). At baseline, proteinuria was fourfold higher in SS^LepRmutant than SS_WT rats and remained elevated throughout the study. The early development of progressive proteinuria was associated with renal hyperfiltration followed by a decline in renal function over the course of study in the SS^LepRmutant compared with SS_WT rats. Kidneys from the SS^LepRmutant strain displayed more glomerulosclerosis and glomerular lipid accumulation than SS_WT rats. Glomeruli were isolated from the renal cortex of both strains at 6 and 18 wk of age, and RNA sequencing was performed to identify genes and pathways driving glomerular injury. We observed significant increases in expression of the influx lipid transporters, chemokine (C-X-C motif) ligand 16 (Cxcl16) and scavenger receptor and fatty acid translocase (Cd36), respectively, and a significant decrease in expression of the efflux lipid transporter, ATP-binding cassette subfamily A member 2 (Abca2; cholesterol efflux regulatory protein 2), in SS^LepRmutant compared with SS_WT rats at 6 and 18 wk of age, which were validated by RT-PCR analysis. These data suggest an association between glomerular hyperfiltration and glomerular lipid accumulation during the early development of proteinuria associated with obesity.