Tetratricopeptide repeat domain 36 deficiency mitigates renal tubular injury by inhibiting TGF-β1-induced epithelial-mesenchymal transition in a mouse model of chronic kidney disease

Advances in the study of key cells and signaling pathways in renal fibrosis and the interventional role of Chinese medicines

Renal fibrosis (RF) is a pathological process characterized by the excessive accumulation of extracellular matrix (ECM), which triggers a repair cascade in response to stimuli and pathogenic factors, leading to the activation of molecular signaling pathways involved in fibrosis. This article discusses the key cells, molecules, and signaling pathways implicated in the pathogenesis of RF, with a particular focus on tubular epithelial cells (TECs), cellular senescence, ferroptosis, autophagy, epithelial-mesenchymal transition (EMT), and transforming growth factor-β(TGF-β)/Smad signaling. These factors drive the core and regulatory pathways that significantly influence RF. A comprehensive understanding of their roles is essential. Through a literature review, we explore recent advancements in traditional Chinese medicine (TCM) aimed at reducing RF and inhibiting chronic kidney disease (CKD). We summarize, analyze, and elaborate on the important role of Chinese herbs in RF, aiming to provide new directions for their application in prevention and treatment, as well as scientific guidance for clinical practices.

A single-cell profile reveals the transcriptional regulation responded for Abelmoschus manihot (L.) treatment in diabetic kidney disease

BACKGROUND

Huangkui capsule (HKC), as an ethanol extract of Abelmoschus manihot (L.), has a significant efficacy in treatment of the patients with diabetic kidney disease (DKD). The bioactive ingredients of HKC mainly include the flavonoids such as rutin, hyperoside, hibifolin, isoquercetin, myricetin, quercetin and quercetin-3-O-robinobioside.

PURPOSE

To explore the molecular mechanisms of A. manihot in treatment of DKD.

STUDY DESIGN

A single-cell RNA sequencing analysis of kidneys in db/db mice with and without HKC administration.

METHODS

Urinary biochemical and histopathological examination in C57BL/6 and db/db mice of DKD and HKC groups was done. Single-cell RNA sequencing pipeline was then performed. The regulatory mechanisms of seven flavonoids in HKC were revealed by cell communication, prediction of transcription factor regulatory network, and molecular docking.

RESULTS

By constructing ligand-receptor regulatory network and performing molecular docking between 75 receptors with different activities and seven flavonoids. 11 key receptors in 4 cell types (segment 3 proximal convoluted tubular cell, ascending limbs of the loop of Henle, distal convoluted tubule, and T cell) in kidneys were found to be directly interacted with HKC. The interactions regulated 8 downstream regulons. The docking receptors in T cell led to transcriptional event differences in the regulons such as Cebpb, Rel, Tbx21 and Klf2 and consequently affected the activation, differentiation, and infiltration of T cell, while the receptors Tgfbr1 and Ldlr in stromal cells of kidneys were closely associated with the downstream transcriptional events of renal injury and proteinuria in DKD.

CONCLUSION

The current study provides novel information of the key receptors and regulons in renal cells for a better understanding of the cell type specific molecular mechanisms of A. manihot in treatment of DKD.

Epithelial-mesenchymal plasticity in kidney fibrosis

Epithelial-mesenchymal transition (EMT) is an important biological process contributing to kidney fibrosis and chronic kidney disease. This process is characterized by decreased epithelial phenotypes/markers and increased mesenchymal phenotypes/markers. Tubular epithelial cells (TECs) are commonly susceptible to EMT by various stimuli, for example, transforming growth factor-β (TGF-β), cellular communication network factor 2, angiotensin-II, fibroblast growth factor-2, oncostatin M, matrix metalloproteinase-2, tissue plasminogen activator (t-PA), plasmin, interleukin-1β, and reactive oxygen species. Similarly, glomerular podocytes can undergo EMT via these stimuli and by high glucose condition in diabetic kidney disease. EMT of TECs and podocytes leads to tubulointerstitial fibrosis and glomerulosclerosis, respectively. Signaling pathways involved in EMT-mediated kidney fibrosis are diverse and complex. TGF-β1/Smad and Wnt/β-catenin pathways are the major venues triggering EMT in TECs and podocytes. These two pathways thus serve as the major therapeutic targets against EMT-mediated kidney fibrosis. To date, a number of EMT inhibitors have been identified and characterized. As expected, the majority of these EMT inhibitors affect TGF-β1/Smad and Wnt/β-catenin pathways. In addition to kidney fibrosis, these EMT-targeted antifibrotic inhibitors are expected to be effective for treatment against fibrosis in other organs/tissues.

Targeting TAM-secreted S100A9 effectively enhances the tumor-suppressive effect of metformin in treating lung adenocarcinoma

Metformin's effect on tumor treatment was complex, because it significantly reduced cancer cell proliferation in vitro, but made no difference in prognosis in several clinical cohorts. Our transcriptome sequencing results revealed that tumor-associated macrophage (TAM) infiltration significantly increased in active lung adenocarcinoma (LUAD) patients with long-term metformin use. We further identified that the tumor suppressive effect of metformin was more significant in mice after the depletion of macrophages, suggesting that TAMs might play an important role in metformin's effects in LUAD. Combining 10X Genomics single-cell sequencing of tumor samples, transcriptome sequencing of metformin-treated TAMs, and the ChIP-Seq data of the Encode database, we identified and validated that metformin significantly increased the expression and secretion of S100A9 of TAMs through AMPK-CEBP/β pathway. For the downstream, S100A9 binds to RAGE receptors on the surface of LUAD cells, and then activates the NF-κB pathway to promote EMT and progression of LUAD, counteracting the inhibitory effect of metformin on LUAD cells. In cell-derived xenograft models (CDX) and patient-derived xenograft models (PDX) models, our results showed that neutralizing antibodies targeting TAM-secreted S100A9 effectively enhanced the tumor suppressive effect of metformin in treating LUAD. Our results will enable us to better comprehend the complex role of metformin in LUAD, and advance its clinical application in cancer treatment.

The CaMKII Inhibitory Peptide AIP Alleviates Renal Fibrosis Through the TGF-β/Smad and RAF/ERK Pathways

Renal fibrosis is characterized by the excessive deposition of extracellular matrix that destroys and replaces the functional renal parenchyma, ultimately leading to organ failure. It is a common pathway by which chronic kidney disease can develop into end-stage renal disease, which has high global morbidity and mortality, and there are currently no good therapeutic agents available. Calcium/calmodulin-dependent protein kinase II (CaMKII) has been indicated to be closely related to the occurrence of renal fibrosis, and its specific inhibitory peptide, autocamtide-2-related inhibitory peptide (AIP), was shown to directly bind the active site of CaMKII. In this study, we examined the effect of AIP on the progression of renal fibrosis and its possible mechanism. The results showed that AIP could inhibit the expression of the fibrosis markers fibronectin, collagen I, matrix metalloproteinase 2, and α-smooth muscle actin in vivo and in vitro. Further analysis revealed that AIP could inhibit the expression of various epithelial-to-mesenchymal transformation-related markers, such as vimentin and Snail 1, in vivo and in vitro. Mechanistically, AIP could significantly inhibit the activation of CaMKII, Smad 2, Raf, and extracellular regulated protein kinases (ERK) in vitro and in vivo and reduce the expression of transforming growth factor-β (TGF-β) in vivo. These results suggested that AIP could alleviate renal fibrosis by inhibiting CaMKII and blocking activation of the TGF-β/Smad2 and RAF/ERK pathways. Our study provides a possible drug candidate and demonstrates that CaMKII is a potential pharmacological target for the treatment of renal fibrosis. SIGNIFICANCE STATEMENT: We have demonstrated that AIP significantly attenuated transforming growth factor-β-1-induced fibrogenesis and ameliorated unilateral ureteral obstruction-induced renal fibrosis through the CaMKII/TGF-β/Smad and CaMKII/RAF/ERK signaling pathways in vitro and in vivo. Our study provides a possible drug candidate and demonstrates that CaMKII can be a potential pharmacological target for the treatment of renal fibrosis.

Astragaloside IV Blunts Epithelial-Mesenchymal Transition and G2/M Arrest to Alleviate Renal Fibrosis via Regulating ALDH2-Mediated Autophagy

Previous studies show that astragaloside IV (ASIV) has anti-renal fibrosis effects. However, its mechanism remains elusive. In this study, we investigated the anti-fibrosis mechanisms of ASIV on chronic kidney disease (CKD) in vivo and in vitro. A CKD model was induced in rats with adenine (200 mg/kg/d, i.g.), and an in vitro renal fibrosis model was induced in human kidney-2 (HK-2) cells treated with TGF-β1. We revealed that ASIV significantly alleviated renal fibrosis by suppressing the expressions of epithelial-mesenchymal transition (EMT)-related proteins, including fibronectin, vimentin, and alpha-smooth muscle actin (α-SMA), and G2/M arrest-related proteins, including phosphorylated p53 (p-p53), p21, phosphorylated histone H3 (p-H3), and Ki67 in both of the in vivo and in vitro models. Transcriptomic analysis and subsequent validation showed that ASIV rescued ALDH2 expression and inhibited AKT/mTOR-mediated autophagy. Furthermore, in ALDH2-knockdown HK-2 cells, ASIV failed to inhibit AKT/mTOR-mediated autophagy and could not blunt EMT and G2/M arrest. In addition, we further demonstrated that rapamycin, an autophagy inducer, reversed the treatment of ASIV by promoting autophagy in TGF-β1-treated HK-2 cells. A dual-luciferase report assay indicated that ASIV enhanced the transcriptional activity of the ALDH2 promoter. In addition, a further molecular docking analysis showed the potential interaction of ALDH2 and ASIV. Collectively, our data indicate that ALDH2-mediated autophagy may be a novel target in treating renal fibrosis in CKD models, and ASIV may be an effective targeted drug for ALDH2, which illuminate a new insight into the treatment of renal fibrosis and provide new evidence of pharmacology to elucidate the anti-fibrosis mechanism of ASIV in treating renal fibrosis.

Co-expression of fibrotic genes in inflammatory bowel disease; A localized event?

INTRODUCTION

Extracellular matrix turnover, a ubiquitous dynamic biological process, can be diverted to fibrosis. The latter can affect the intestine as a serious complication of Inflammatory Bowel Diseases (IBD) and is resistant to current pharmacological interventions. It embosses the need for out-of-the-box approaches to identify and target molecular mechanisms of fibrosis.

METHODS AND RESULTS

In this study, a novel mRNA sequencing dataset of 22 pairs of intestinal biopsies from the terminal ileum (TI) and the sigmoid of 7 patients with Crohn's disease, 6 with ulcerative colitis and 9 control individuals (CI) served as a validation cohort of a core fibrotic transcriptomic signature (FIBSig), This signature, which was identified in publicly available data (839 samples from patients and healthy individuals) of 5 fibrotic disorders affecting different organs (GI tract, lung, skin, liver, kidney), encompasses 241 genes and the functional pathways which derive from their interactome. These genes were used in further bioinformatics co-expression analyses to elucidate the site-specific molecular background of intestinal fibrosis highlighting their involvement, particularly in the terminal ileum. We also confirmed different transcriptomic profiles of the sigmoid and terminal ileum in our validation cohort. Combining the results of these analyses we highlight 21 core hub genes within a larger single co-expression module, highly enriched in the terminal ileum of CD patients. Further pathway analysis revealed known and novel inflammation-regulated, fibrogenic pathways operating in the TI, such as IL-13 signaling and pyroptosis, respectively.

DISCUSSION

These findings provide a rationale for the increased incidence of fibrosis at the terminal ileum of CD patients and highlight operating pathways in intestinal fibrosis for future evaluation with mechanistic and translational studies.

Carvacrol preserves antioxidant status and attenuates kidney fibrosis via modulation of TGF-β1/Smad signaling and inflammation

Chronic kidney disease (CKD) with diverse aetiologies is emerging as a challenging kidney disorder associated with inflammation and interstitial fibrosis. Carvacrol (CVL) is a bioactive monoterpenoid found abundantly in oregano, thyme, and bergamot, having diverse pharmacological benefits. However, the effect of CVL against fibrotic changes in the kidneys is poorly defined. In the current study, a robust mouse model of renal fibrosis induced through unilateral ureteral obstruction (UUO) is used to investigate the anti-fibrotic activity of CVL. The mice were treated with two different oral doses of CVL (25 mg kg^-1 and 50 mg kg^-1 body weight) for 14 consecutive days. The UUO induction resulted in impaired renal function, severe histological damage, and collagen deposition in the obstructed kidney. Our findings revealed profound activation of transforming growth factor-β1 (TGF-β1) and NF-κB (p65) signaling along with the downregulation of antioxidant proteins, nuclear factor-erythroid factor 2-related factor 2 (Nrf2), NAD(P)H: quinone oxidoreductase 1 (NQO1), and superoxide dismutase (SOD) in the obstructed kidney. CVL administration markedly recovered antioxidant proteins and kidney histological changes. In addition, CVL blunted the NF-κB (p65) phosphorylation and reduced the levels of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, and cyclooxygenase 2 (COX-2) compared to the UUO control group. CVL also alleviated the increased fibrotic protein levels of TGF-β1, pSmad2/3, collagen I, collagen III, fibronectin, and myofibroblast activation and epithelial-mesenchymal transition (EMT) markers, including alpha-smooth muscle actin (α-SMA), E-cadherin, and vimentin in the kidneys. Findings from in vitro study also confirmed that CVL inhibits the EMT process in TGF-β1 stimulated renal tubular epithelial cells (NRK 52E cells). Collectively, our findings indicate that CVL administration attenuates kidney fibrosis by targeting oxidative stress and inflammation.