A novel role of LRP5 in tubulointerstitial fibrosis through activating TGF-β/Smad signaling

Association of oxidative balance score with chronic kidney disease: NHANES 1999-2018

Background

The Oxidative Balance Score (OBS), which quantifies the balance between antioxidants and pro-oxidants influenced by diet and lifestyle, is crucial given oxidative stress's significant role in Chronic Kidney Disease (CKD). This study aims to determine the association between OBS and CKD using data from the National Health and Nutrition Examination Survey (NHANES) 1999-2018.

Methods

We analyzed data from the National Health and Nutrition Examination Survey (NHANES) spanning 1999 to 2018. OBS was constructed from a detailed array of 20 factors, including dietary nutrients and lifestyle behaviors. The relationship between OBS and CKD risk was evaluated using weighted logistic regression models, adjusted for potential confounders, with a generalized additive model (GAM) examining non-linear associations. Subgroup analyses and interaction effects across diverse demographic and clinical groups, along with sensitivity analyses, were performed to validate the findings.

Results

Among 32,120 participants analyzed, 4,786 were identified with CKD. Fully adjusted weighted logistic regression analysis revealed that each unit increase in OBS was associated with a 2% reduction in CKD prevalence [OR: 0.98 (0.98-0.99), P < 0.001]. Higher OBS quartiles were significantly correlated with a decreased CKD risk [Q4 vs. Q1: OR: 0.82 (0.68-0.98), P = 0.03; P for trend = 0.01]. The GAM and smoothed curve fit indicated a linear relationship between OBS and the risk of CKD. Stratified and sensitivity analyses further substantiated the inverse relationship between OBS and CKD prevalence.

Conclusions

Our findings from the NHANES data affirm a significant inverse association between OBS and CKD risk in the U.S. population, underscoring the role of optimizing dietary and lifestyle factors in managing CKD risk. These results advocate for incorporating OBS considerations into CKD prevention and treatment strategies.

Inhibition of TGF-β1/Smad3 signaling by compound 5aa: A potential treatment for idiopathic pulmonary fibrosis

The incidence of idiopathic pulmonary fibrosis (IPF) has been steadily increasing each year, posing significant challenges in its treatment. In this study, we conducted the design and synthesis of 23 new inhibitors that specifically target the TGF-β1/Smad3 pathway. Initially, we employed a cell model of TGF-β-induced pulmonary fibrosis, using cell survival rate and HYP expression as indicators to identify the potent ingredient 5aa, which demonstrated significant anti-pulmonary fibrosis activity. Subsequently, we induced mice with bleomycin (BLM) to establish an experimental animal model of pulmonary fibrosis, and evaluated the pharmacodynamics of 5aa in vivo against pulmonary fibrosis. The alterations in HYP and collagen levels in BLM-induced pulmonary fibrosis mice were analyzed using ELISA and immunohistochemistry techniques. The results indicated that compound 5aa effectively suppressed the fibrotic response induced by TGF-β1, inhibited the expression of the fibrotic marker α-SMA, and hindered the EMT process in NIH3T3 cells. Additionally, oral administration of 5aa demonstrated significant therapeutic effects in a mouse model of IPF, comparable to the established drug Nintedanib. Moreover, compound 5aa exhibited higher bioavailability in vivo compared to Nintedanib. These collective outcomes suggest that 5aa holds promise as a potential inhibitor of TGF-β1/Smad3 signaling for the treatment of IPF.

LDL receptor-related protein 5 selectively transports unesterified polyunsaturated fatty acids to intracellular compartments

Polyunsaturated fatty acids (PUFAs), which cannot be synthesized by animals and must be supplied from the diet, have been strongly associated with human health. However, the mechanisms for their accretion remain poorly understood. Here, we show that LDL receptor-related protein 5 (LRP5), but not its homolog LRP6, selectively transports unesterified PUFAs into a number of cell types. The LDLa ligand-binding repeats of LRP5 directly bind to PUFAs and are required and sufficient for PUFA transport. In contrast to the known PUFA transporters Mfsd2a, CD36 and FATP2, LRP5 transports unesterified PUFAs via internalization to intracellular compartments including lysosomes, and n-3 PUFAs depend on this transport mechanism to inhibit mTORC1. This LRP5-mediated PUFA transport mechanism suppresses extracellular trap formation in neutrophils and protects mice from myocardial injury during ischemia-reperfusion. Thus, this study reveals a biologically important mechanism for unesterified PUFA transport to intracellular compartments.

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.

Prolonged Antibiotic Use in a Preclinical Model of Gulf War Chronic Multisymptom-Illness Causes Renal Fibrosis-like Pathology via Increased micro-RNA 21-Induced PTEN Inhibition That Is Correlated with Low Host Lachnospiraceae Abundance

Gulf War (GW) veterans show gastrointestinal disturbances and gut dysbiosis. Prolonged antibiotic treatments commonly employed in veterans, especially the use of fluoroquinolones and aminoglycosides, have also been associated with dysbiosis. This study investigates the effect of prolonged antibiotic exposure on risks of adverse renal pathology and its association with gut bacterial species abundance in underlying GWI and aims to uncover the molecular mechanisms leading to possible renal dysfunction with aging. Using a GWI mouse model, administration of a prolonged antibiotic regimen involving neomycin and enrofloxacin treatment for 5 months showed an exacerbated renal inflammation with increased NF-κB activation and pro-inflammatory cytokines levels. Involvement of the high mobility group 1 (HMGB1)-mediated receptor for advanced glycation end products (RAGE) activation triggered an inflammatory phenotype and increased transforming growth factor-β (TGF-β) production. Mechanistically, TGF-β- induced microRNA-21 upregulation in the renal tissue leads to decreased phosphatase and tensin homolog (PTEN) expression. The above event led to the activation of protein kinase-B (AKT) signaling, resulting in increased fibronectin production and fibrosis-like pathology. Importantly, the increased miR-21 was associated with low levels of Lachnospiraceae in the host gut which is also a key to heightened HMGB1-mediated inflammation. Overall, though correlative, the study highlights the complex interplay between GWI, host gut dysbiosis, prolonged antibiotics usage, and renal pathology via miR-21/PTEN/AKT signaling.

Integrating Common Risk Factors with Polygenic Scores Improves the Prediction of Type 2 Diabetes

We tested associations between 13 established genetic variants and type 2 diabetes (T2D) in 1371 study participants from the Volga-Ural region of the Eurasian continent, and evaluated the predictive ability of the model containing polygenic scores for the variants associated with T2D in our dataset, alone and in combination with other risk factors such as age and sex. Using logistic regression analysis, we found associations with T2D for the CCL20 rs6749704 (OR = 1.68, P_FDR = 3.40 × 10^-5), CCR5 rs333 (OR = 1.99, P_FDR = 0.033), ADIPOQ rs17366743 (OR = 3.17, P_FDR = 2.64 × 10^-4), TCF7L2 rs114758349 (OR = 1.77, P_FDR = 9.37 × 10^-5), and CCL2 rs1024611 (OR = 1.38, P_FDR = 0.033) polymorphisms. We showed that the most informative prognostic model included weighted polygenic scores for these five loci, and non-genetic factors such as age and sex (AUC 85.8%, 95%CI 83.7-87.8%). Compared to the model containing only non-genetic parameters, adding the polygenic score for the five T2D-associated loci showed improved net reclassification (NRI = 37.62%, 1.39 × 10^-6). Inclusion of all 13 tested SNPs to the model with age and sex did not improve the predictive ability compared to the model containing five T2D-associated variants (NRI = -17.86, p = 0.093). The five variants associated with T2D in people from the Volga-Ural region are linked to inflammation (CCR5, CCL2, CCL20) and glucose metabolism regulation (TCF7L, ADIPOQ2). Further studies in independent groups of T2D patients should validate the prognostic value of the model and elucidate the molecular mechanisms of the disease development.

A natural products solution to diabetic nephropathy therapy

Diabetic nephropathy is one of the most common complications in diabetes. It has been shown to be the leading cause of end-stage renal disease. However, due to their complex pathological mechanisms, effective therapeutic drugs other than angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs), which have been used for 20 years, have not been developed so far. Recent studies have shown that diabetic nephropathy is characterized by multiple signalling pathways and multiple targets, including inflammation, apoptosis, pyroptosis, autophagy, oxidative stress, endoplasmic reticulum stress and their interactions. It definitely exacerbates the difficulty of therapy, but at the same time it also brings out the chance for natural products treatment. In the most recent two decades, a large number of natural products have displayed their potential in preclinical studies and a few compounds are under invetigation in clinical trials. Hence, many compounds targeting these singals have been emerged as a comprehensive blueprint for treating strategy of diabetic nephropathy. This review focuses on the cellular and molecular mechanisms of natural prouducts that alleviate this condition, including preclinical studies and clinical trials, which will provide new insights into the treatment of diabetic nephropathy and suggest novel ideas for new drug development.

Capsaicin ameliorates renal fibrosis by inhibiting TGF-β1-Smad2/3 signaling

BACKGROUND AND PURPOSE

Chronic kidney disease (CKD), characterized by renal fibrosis, is a global refractory disease with few effective therapeutic strategies. It has been reported that capsaicin exerts many pharmacological effects including liver and cardiac fibrosis. However, whether capsaicin plays a therapeutic role in renal fibrosis remains unclear.

METHODS

We investigated antifibrotic effects of capsaicin in two mouse renal fibrosis models as follows: C57BL/6J mice were subjected to unilateral ureteral obstruction (UUO) and fed with an adenine-rich diet. We uncovered and verified the mechanisms of capsaicin in human proximal tubular epithelial cells (HK2). We mainly used histochemistry, immunohistochemistry and immunofluorescence staining, western blot assay, biochemical examination and other tools to examine the effects of capsaicin on renal fibrosis and the underlying mechanisms.

RESULTS

Capsaicin treatment significantly alleviated fibronectin and collagen depositions in the tubulointerstitium of the injured kidneys from UUO and adenine-fed mice. Meanwhile, capsaicin treatment obviously reduced α-SMA expression. Moreover, capsaicin treatment dramatically protected against the phenotypic alteration of tubular epithelial cells by increasing E-cadherin expression and decreasing vimentin expression during renal fibrosis. Mechanistically, capsaicin treatment effectively suppressed α-SMA and vimentin expressions but promoted E-cadherin expression in HK2 cells mainly through the inhibition of TGF-β1-Smad2/3 signaling.

CONCLUSION

Capsaicin significantly ameliorated renal fibrosis possibly by retarding the activation of myofibroblasts and protecting against the phenotypic alteration of tubular epithelial cells mainly through the inhibition of TGF-β1-Smad2/3 signaling. Thus, our findings may provide a new insight into the clinical application of capsaicin in renal fibrosis.

Dexmedetomidine Protects Against Kidney Fibrosis in Diabetic Mice by Targeting miR-101-3p-Mediated EndMT

Objective: Our main purpose is to explore the effect and mechanism of Dexmedetomidine (DEX)  in diabetic nephropathy fibrosis.

Methods: Diabetic model was established by intraperitoneal injection of streptozotocin (STZ) treated CD-1 mice and high glucose cultured human dermal microvascular endothelial cells (HMVECs). Immunofluorescence was used to detect renal endothelial-mesenchymal transition (EndMT); Hematoxylin and Eosin (HE) staining and Masson’s Trichrome Staining (MTS) was used to analyze renal fibrosis; CCK-8 was used to evaluate cell viability; Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was used to assess the expression of miR-101-3p; Western blots were utilized to judge the protein expression levels of EndMT, extracellular matrix and TGF-β1/Smad3 signal pathway.

Results: In this study, we first found that the protective effect of DEX on DN was related to EndMT. DEX alleviated kidney fibrosis by inhibiting EndMT in diabetic CD-1 mice. DEX could also inhibit high glucose-induced HMVECs EndMT. Then, we confirmed that miR-101-3p was the regulatory target of DEX. The expression of miR-101-3p was decreased in diabetic CD-1 mice and high glucose-induced HMVECs. After DEX treatment, the miR-101-3p increased, and the inhibition of miR-101-3p could counteract the protective effect of DEX and aggravate the EndMT. Finally, we found that the TGF- β1/Smad3 signal pathway was involved in the protective effect of DEX on DN. DEX inhibited the activation of TGF-β1/Smad3 signal pathway. On the contrary, inhibiting miR-101-3p promoted the expression of TGF-β1/Smad3.

Conclusion: DEX protects kidney fibrosis in diabetic mice by targeting miR-101-3p-mediated EndMT.

Green tea peptides ameliorate diabetic nephropathy by inhibiting the TGF-β/Smad signaling pathway in mice

Diabetic nephropathy (DN) is the most important cause of middle and late-stage chronic kidney disease. Green tea polypeptides are extracted from tea pomace, and exhibit various pharmacological effects. In this study, we analyzed the reno-protective effects of green tea peptides in diabetic db/db mice, and explored the underlying mechanisms. Peptide treatment for 5 weeks significantly reduced the blood glucose levels and other indices of diabetes, and alleviated renal injury measured in terms of blood creatinine, urea nitrogen and urinary albumin/urinary creatinine levels. Mechanistically, the green tea peptides downregulated p-Smad2/3, α-SMA, ZO-1 and vimentin proteins in the kidney tissues, and elevated Smad7. Thus, green tea peptides inhibited the deposition of ECM proteins by suppressing excessive activation of the TGF-β/Smad signaling pathway and reducing fibronectin levels. On the other hand, tea peptides ameliorated renal injury by inhibiting the production of inflammatory factors (iNOS and TNF-α) by suppressing the NF-κB signaling pathway. In addition, we confirmed the inhibitory effect of green tea peptides on the TGF-β/Smad signaling pathway in TGF-β1-stimulated HK-2 cells. Therefore, tea peptides can be considered as an effective candidate for alleviating DN.

Network Pharmacology and Experimental Assessment to Explore the Pharmacological Mechanism of Qimai Feiluoping Decoction Against Pulmonary Fibrosis

Pulmonary fibrosis (PF) is one of the pathologic changes in COVID-19 patients in convalescence, and it is also a potential long-term sequela in severe COVID-19 patients. Qimai Feiluoping decoction (QM) is a traditional Chinese medicine formula recommended in the Chinese national medical program for COVID-19 convalescent patients, and PF is one of its indications. Through clinical observation, QM was found to improve the clinical symptoms and pulmonary function and reduce the degree of PF of COVID-19 convalescent patients. To further explore the pharmacological mechanisms and possible active components of QM in anti-PF effect, UHPLC/Q-TOF-MS was used to analyze the composition of the QM extract and the active components that can be absorbed into the blood, leading to the identification of 56 chemical compounds and 10 active components. Then, network pharmacology was used to predict the potential mechanisms and targets of QM; it predicted that QM exerts its anti-PF effects via the regulation of the epithelial-mesenchymal transition (EMT), extracellular matrix (ECM) degradation, and TGF-β signaling pathway. Finally, TGF-β1-induced A549 cells were used to verify and explore the pharmacological effects of QM and found that QM could inhibit the proliferation of TGF-β1-induced A549 cells, attenuate EMT, and promote ECM degradation by inhibiting the TGF-β/Smad3 pathway.

LRP5-Mediated Lipid Uptake Modulates Osteogenic Differentiation of Bone Marrow Mesenchymal Stromal Cells

Nutritional microenvironment determines the specification of progenitor cells, and lipid availability was found to modulate osteogenesis in skeletal progenitors. Here, we investigated the implications of lipid scarcity in the osteogenic differentiation of bone marrow mesenchymal stromal cells (BMSCs) and the role of low-density lipoprotein receptor-related protein 5 (LRP5), a co-receptor transducing canonical Wnt/beta-catenin signals, in BMSC lipid uptake during osteogenesis. The osteogenic differentiation of murine BMSCs was suppressed by lipid scarcity and partially rescued by additional fatty acid treatment with oleate. The enhancement of osteogenesis by oleate was found to be dosage-dependent, along with the enhanced activation of beta-catenin and Wnt target genes. Conditional knockout (CKO) of Lrp5 gene in murine mesenchymal lineage using Lrp5^fl/fl;Prrx1-cre mice led to decreased bone quality and altered fat distribution in vivo. After Lrp5 ablation using adenoviral Cre-recombinase, the accumulation of lipid droplets in BMSC cytoplasm was significantly reduced, and the osteogenesis of BMSCs was suppressed. Moreover, the impaired osteogenesis due to either lipid scarcity or Lrp5 ablation could be rescued by recombinant Wnt3a protein, indicating that the osteogenesis induced by Wnt/beta-catenin signaling was independent of LRP5-mediated lipid uptake. In conclusion, lipid scarcity suppresses BMSC osteogenic differentiation. LRP5 plays a role in the uptake of lipids in BMSCs and therefore mediates osteogenic specification.

Dendrobium Mixture Ameliorates Diabetic Nephropathy in db/db Mice by Regulating the TGF-β1/Smads Signaling Pathway

Dendrobium mixture (DMix) is an effective treatment for diabetic nephropathy (DN), but the molecular mechanism underlying its action remains unclear. In this study, we investigated whether DMix regulates the transforming growth factor-β1 (TGF-β1)/Smads signal transduction pathway. Twenty-four db/db mice were randomly divided into three groups: the model, DMix, and gliquidone groups, while eight db/m mice were selected as the normal control group. The drug was administered by continuous gavage for 8 weeks. Body weight (BW), kidney weight (KW), kidney index, fasting blood glucose (FBG), blood lipid, 24-hour urinary albumin excretion rate, blood urea nitrogen, and serum creatinine levels were measured. Pathological changes in the renal tissue were observed under a light microscope. Real-time quantitative PCR and immunohistochemical staining were used to detect the mRNA and protein expression levels of TGF-β1 and alpha-smooth muscle actin (α-SMA), respectively, in renal tissues. TGF-β1, Smad2, p-Smad2, Smad3, p-Smad3, and α-SMA expression levels were measured using western blotting. The results showed that DMix significantly reduced the FBG level, BW, KW, and blood lipid level and improved renal function in db/db mice. Histopathology showed that DMix alleviated glomerular mesangial cell proliferation and renal interstitial fibrosis in db/db mice. Additionally, DMix reduced the protein and mRNA expression levels of TGF-β1 and α-SMA and inhibited Smad2 and Smad3 phosphorylation. We conclude that DMix may inhibit renal fibrosis and delay the progression of DN by regulating the TGF-β1/Smads signaling pathway.

Alpha-lipoic acid could attenuate the effect of chemerin-induced diabetic nephropathy progression

Objective(s):

Chemerin is associated with insulin resistance, obesity, and metabolic syndrome. α-lipoic acid (α-LA) is a potent antioxidant involved in the reduction of diabetic symptoms. This study aimed to investigate the relationship between chemerin and P38 MAPK in the progression of diabetic nephropathy (DN) and examine the effects of α-LA on chemerin-treated human mesangial cells (HMCs).

Materials and Methods:

HMCs were transfected with a chemerin-overexpressing plasmid. HMCs were also treated with high-glucose, chemerin, α-LA, PDTC (pyrrolidine dithiocarbamate ammonium, NF-κB p65 inhibitor), and/or SB203580 (P38 MAPK inhibitor). Cell proliferation was tested using the Cell Counting Kit-8 assay. Collagen type IV and laminin were tested by ELISA. Chemerin expression was detected by qRT-PCR. The chemerin receptor was detected by immunohistochemistry. Interleukin-6 (IL-6), tumor necrosis factor-a (TNF-α), nuclear factor-κBp-p65 (NF-κB p-p65), transforming growth factor-β (TGF-β), and p-P38 mitogen-activated protein kinase (p-P38 MAPK) were evaluated by western blot.

Results:

High-glucose culture increased the expression of the chemerin receptor. α-LA inhibited HMC proliferation. Chemerin overexpression increased collagen type IV and laminin expression. P38 MAPK signaling was activated by chemerin, resulting in up-regulation of IL-6, TNF-α, NF-κB p-p65, and TGF-β. SB203580, PDTC, and α-LA reversed the effects of chemerin, reducing IL-6, TNF-α, NF-κB p-p65, and TGF-β expression.

Conclusion:

Chemerin might be involved in the occurrence and development of DN. α-LA might prevent the effects of chemerin on the progression of DN, possibly via the P38 MAPK pathway.

Icariin Ameliorates Diabetic Renal Tubulointerstitial Fibrosis by Restoring Autophagy via Regulation of the miR-192-5p/GLP-1R Pathway

Tubulointerstitial fibrosis is one of the most common pathological features of diabetic nephropathy. Autophagy, an intracellular mechanism to remove damaged or dysfunctional cell parts and maintain metabolic homeostasis, is inhibited in diabetic neuropathy. Icariin is a traditional Chinese medicine extract known for nourishing the kidney and reinforcing Yang. In this study, we investigated the effects and mechanism of Icariin on renal function, autophagy, and fibrosis in type 2 diabetic nephropathic rats and in high-glucose-incubated human renal tubular epithelial cells and rat renal fibroblasts (in vitro). Icariin improved diabetes, renal function, restored autophagy, and alleviated fibrosis in type 2 diabetic neuropathic rats and in vitro. After we applied autophagy-related gene 5-small interfering RNA, we found that fibrosis improvement by Icariin was related to autophagy restoration. By detecting serum sex hormone levels, and using dihydrotestosterone, siRNA for androgen receptor, and the androgen receptor antagonist Apalutamide (ARN-509), we found that Icariin had an androgen-like effect and restored autophagy and reduced fibrosis by regulating the androgen receptor. In addition, miR-192-5p levels were increased under high glucose but reduced after dihydrotestosterone and Icariin treatment. Furthermore, dihydrotestosterone and Icariin inhibited miR-192-5p overexpression-induced fibrosis production and autophagy limitation. Glucagon-like peptide-1 receptor (GLP-1R) was downregulated by high glucose and overexpression of miR-192-5p and could be restored by dihydrotestosterone and Icariin. By using ARN-509, we found that Icariin increased GLP-1R expression by regulating the androgen receptor. GLP-1R-siRNA transfection weakened the effects of Icariin on autophagy and fibrosis. These findings indicate that Icariin alleviates tubulointerstitial fibrosis by restoring autophagy through the miR-192-5p/GLP-1R pathway and is a novel therapeutic option for diabetic fibrosis.

PPARγ Mediates the Anti-Epithelial-Mesenchymal Transition Effects of FGF1ΔHBS in Chronic Kidney Diseases via Inhibition of TGF-β1/SMAD3 Signaling

Podocytes are essential components of the glomerular basement membrane. Epithelial-mesenchymal-transition (EMT) in podocytes results in proteinuria. Fibroblast growth factor 1 (FGF1) protects renal function against diabetic nephropathy (DN). In the present study, we showed that treatment with an FGF1 variant with decreased mitogenic potency (FGF1^ΔHBS) inhibited podocyte EMT, depletion, renal fibrosis, and preserved renal function in two nephropathy models. Mechanistic studies revealed that the inhibitory effects of FGF1^ΔHBS podocyte EMT were mediated by decreased expression of transforming growth factor β1 via upregulation of PPARγ. FGF1^ΔHBS enhanced the interaction between PPARγ and SMAD3 and suppressed SMAD3 nuclei translocation. We found that the anti-EMT activities of FGF1^ΔHBS were independent of glucose-lowering effects. These findings expand the potential uses of FGF1^ΔHBS in the treatment of diseases associated with EMT.

LRP5 and LRP6 in Wnt Signaling: Similarity and Divergence

The canonical Wnt/β-catenin signaling plays a fundamental role in regulating embryonic development, injury repair and the pathogenesis of human diseases. In vertebrates, low density lipoprotein receptor-related proteins 5 and 6 (LRP5 and LRP6), the single-pass transmembrane proteins, act as coreceptors of Wnt ligands and are indispensable for Wnt signal transduction. LRP5 and LRP6 are highly homologous and widely co-expressed in embryonic and adult tissues, and they share similar function in mediating Wnt signaling. However, they also exhibit distinct characteristics by interacting with different protein partners. As such, each of them possesses its own unique functions. In this review, we systematically discuss the similarity and divergence of LRP5 and LRP6 in mediating Wnt and other signaling in the context of kidney diseases. A better understanding of the precise role of LRP5 and LRP6 may afford us to identify and refine therapeutic targets for the treatment of a variety of human diseases.

Distinct roles of LRP5 and LRP6 in Wnt signaling regulation in the retina

Dysregulation of Wnt signaling is implicated in multiple ocular disorders. The roles of Wnt co-receptors LRP5 and LRP6 in Wnt signaling regulation remain elusive, as most retinal cells express both of the co-receptors. To address this question, LRP5 and LRP6 were individually knocked-out in a human retinal pigment epithelium cell line using the CRISPR-Cas9 technology. Wnt signaling activity induced by various Wnt ligands was measured using wild-type and the KO cell lines. The results identified three groups of Wnt ligands based on their co-receptor specificity: 1) activation of Wnt signaling only through LRP6, 2) through both LRP5 and LRP6 and 3) predominantly through LRP5. These results indicate that LRP5 and LRP6 have differential roles in Wnt signaling regulation.

Exosomes: Biomarkers and Therapeutic Targets of Diabetic Vascular Complications

Diabetic vascular complications (DVC) including macrovascular and microvascular lesions, have a significant impact on public health, and lead to increased patient mortality. Disordered intercellular cascades play a vital role in diabetic systemic vasculopathy. Exosomes participate in the abnormal signal transduction of local vascular cells and mediate the transmission of metabolic disorder signal molecules in distant organs and cells through the blood circulation. They can store different signaling molecules in the membrane structure and release them into the blood, urine, and tears. In recent years, the carrier value and therapeutic effect of exosomes derived from stem cells have garnered attention. Exosomes are not only a promising biomarker but also a potential target and tool for the treatment of DVC. This review explored changes in the production process of exosomes in the diabetic microenvironment and exosomes' early warning role in DVC from different systems and their pathological processes. On the basis of these findings, we discussed the future direction of exosomes in the treatment of DVC, and the current limitations of exosomes in DVC research.

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.