Stimulation of pro-alpha(1)(I) collagen by TGF-beta(1) in mesangial cells: role of the p38 MAPK pathway

Synergistic effects of oral milk ceramide-collagen peptides mixtures in preventing UV-induced inflammation and photoaging through TGF-β and NF-κB/MAPK signaling pathways in UV-exposed hairless mice

This study investigates the synergistic effects of oral milk ceramide-collagen peptides in inhibiting UV-induced inflammation and preventing photoaging. The optimal ratio of milk ceramide to collagen peptides was determined in HaCaT cells, and the effects of oral supplementation of milk ceramide-collagen peptides were evaluated in UV-exposed hairless mice. HaCaT cells did not exhibit cytotoxicity when treated with milk ceramide and collagen peptides at concentrations up to 200 μg/mL. UVB exposure decreased cell viability, but treatment with the milk ceramide-collagen peptides mixtures (1:1, 1:3) prevented further viability loss and improved collagen peptides synthesis markers, including MMPs and TIMPs. The combination also enhanced moisture-related factors (AQP3, FLG) and reduced inflammatory cytokines (IL-6, IL-1β) and COX expression. In hairless mice, oral supplementation of milk ceramide-collagen peptides mixture (1:1 ratio) improved skin hydration, reduced erythema, TEWL, skin thickness, and wrinkle formation in a dose-dependent manner. The treatment also suppressed the expression of MMPs and TIMPs, promoting collagen peptides synthesis. Furthermore, the mixtures regulated NF-κB and MAPK signaling pathways, reducing inflammation and photoaging. These results suggest that the 1:1 milk ceramide-collagen peptides mixture effectively prevents UV-induced skin damage and photoaging by enhancing collagen peptides production and improving skin barrier function.

Understanding chronic inflammation: couplings between cytokines, ROS, NO, Cai 2+, HIF-1α, Nrf2 and autophagy

Chronic inflammation is an important component of many diseases, including autoimmune diseases, intracellular infections, dysbiosis and degenerative diseases. An important element of this state is the mainly positive feedback between inflammatory cytokines, reactive oxygen species (ROS), nitric oxide (NO), increased intracellular calcium, hypoxia-inducible factor 1-alpha (HIF-1α) stabilisation and mitochondrial oxidative stress, which, under normal conditions, enhance the response against pathogens. Autophagy and the nuclear factor erythroid 2-related factor 2 (Nrf2)-mediated antioxidant response are mainly negatively coupled with the above-mentioned elements to maintain the defence response at a level appropriate to the severity of the infection. The current review is the first attempt to build a multidimensional model of cellular self-regulation of chronic inflammation. It describes the feedbacks involved in the inflammatory response and explains the possible pathways by which inflammation becomes chronic. The multiplicity of positive feedbacks suggests that symptomatic treatment of chronic inflammation should focus on inhibiting multiple positive feedbacks to effectively suppress all dysregulated elements including inflammation, oxidative stress, calcium stress, mito-stress and other metabolic disturbances.

Crosstalk between ferroptosis and innate immune in diabetic kidney disease: mechanisms and therapeutic implications

Diabetic kidney disease (DKD) is a prevalent complication of diabetes mellitus (DM), and its incidence is increasing alongside the number of diabetes cases. Effective treatment and long-term management of DKD present significant challenges; thus, a deeper understanding of its pathogenesis is essential to address this issue. Chronic inflammation and abnormal cell death in the kidney closely associate with DKD development. Recently, there has been considerable attention focused on immune cell infiltration into renal tissues and its inflammatory response's role in disease progression. Concurrently, ferroptosis-a novel form of cell death-has emerged as a critical factor in DKD pathogenesis, leading to increased glomerular filtration permeability, proteinuria, tubular injury, interstitial fibrosis, and other pathological processes. The cardiorenal benefits of SGLT2 inhibitors (SGLT2-i) in DKD patients have been demonstrated through numerous large clinical trials. Moreover, further exploratory experiments indicate these drugs may ameliorate serum and urinary markers of inflammation, such as TNF-α, and inhibit ferroptosis in DKD models. Consequently, investigating the interplay between ferroptosis and innate immune and inflammatory responses in DKD is essential for guiding future drug development. This review presents an overview of ferroptosis within the context of DKD, beginning with its core mechanisms and delving into its potential roles in DKD progression. We will also analyze how aberrant innate immune cells, molecules, and signaling pathways contribute to disease progression. Finally, we discuss the interactions between ferroptosis and immune responses, as well as targeted therapeutic agents, based on current evidence. By analyzing the interplay between ferroptosis and innate immunity alongside its inflammatory responses in DKD, we aim to provide insights for clinical management and drug development in this area.

Oxidative stress drives endometrial fibrosis via TGF-β1/MAPK signaling pathway in breast cancer

Breast cancer patients have high serum reactive oxygen species (ROS) levels, which exert toxicity on the ovary. However, it is still unclear whether tumor-derived ROS play a role in endometrial development and function in breast cancer. Breast cancer patients and healthy controls were recruited and endometrial thickness was measured by transvaginal ultrasound (TVUS). Xenograft tumors of the breast cancer cell line MDA-MB-231 in a female BALB/c nude mice model were established, and the therapeutic mechanism of vitamin C (VC) was investigated on uterine pathology in vivo and the contribution of co-culture of breast cancer cell and endometrial epithelial cell on this process was examined in vitro. Median thickness in endometria was lower in breast cancer patients and tumor-bearing mice compared to controls. A gene signature of uteri in tumor-bearing mice demonstrated differential expression of genes (DEGs) regulating extracellular matrix (ECM) and epithelial-mesenchymal transition (EMT), and activation of TGF-β and MAPK signaling pathways. In addition, ROS, EMT- and ECM-related protein levels were enhanced in uteri in tumor-bearing mice, as well as in Ishikawa cells which were co-cultured with MDA-MB-231 cells compared to controls. Supplementation with VC reduced endometrial damage, inhibited the EMT process and collagen deposition, and maintained better histologic architecture of uteri in tumor-bearing mice via inactivation of the TGF-β1/p38MAPK pathway. In women with breast cancer oxidative stress in the endometrium results in a fibrotic response as a consequence of EMT. VC could alleviate endometrial fibrosis via TGF-β1/p38MAPK pathway and provide new predictive and therapeutic targets for fertility preservation in younger breast cancer patients.

The involvement of the Wnt/β-catenin signaling cascade in fibrosis progression and its therapeutic targeting by relaxin

Organ scarring, referred to as fibrosis, results from a failed wound-healing response to chronic tissue injury and is characterised by the aberrant accumulation of various extracellular matrix (ECM) components. Once established, fibrosis is recognised as a hallmark of stiffened and dysfunctional tissues, hence, various fibrosis-related diseases collectively contribute to high morbidity and mortality in developed countries. Despite this, these diseases are ineffectively treated by currently-available medications. The pro-fibrotic cytokine, transforming growth factor (TGF)-β1, has emerged as the master regulator of fibrosis progression, owing to its ability to promote various factors and processes that facilitate rapid ECM synthesis and deposition, whilst negating ECM degradation. TGF-β1 signal transduction is tightly controlled by canonical (Smad-dependent) and non-canonical (MAP kinase- and Rho-associated protein kinase-dependent) intracellular protein activity, whereas its pro-fibrotic actions can also be facilitated by the Wnt/β-catenin pathway. This review outlines the pathological sequence of events and contributing roles of TGF-β1 in the progression of fibrosis, and how the Wnt/β-catenin pathway contributes to tissue repair in acute disease settings, but to fibrosis and related tissue dysfunction in synergy with TGF-β1 in chronic diseases. It also outlines the anti-fibrotic and related signal transduction mechanisms of the hormone, relaxin, that are mediated via its negative modulation of TGF-β1 and Wnt/β-catenin signaling, but through the promotion of Wnt/β-catenin activity in acute disease settings. Collectively, this highlights that the crosstalk between TGF-β1 signal transduction and the Wnt/β-catenin cascade may provide a therapeutic target that can be exploited to broadly treat and reverse established fibrosis.

Substance P promotes transforming growth factor-β-induced collagen synthesis in human corneal fibroblasts

Corneal fibroblasts maintain homeostasis of the corneal stroma by mediating the synthesis and degradation of extracellular collagen, and these actions are promoted by transforming growth factor-β (TGF-β) and interleukin-1β (IL-1β), respectively. The cornea is densely innervated with sensory nerve fibers that are not only responsible for sensation but also required for physiological processes such as tear secretion and wound healing. Loss or dysfunction of corneal nerves thus impairs corneal epithelial wound healing and can lead to neurotrophic keratopathy. The sensory neurotransmitter substance P (SP) promotes corneal epithelial wound healing by enhancing the stimulatory effects of growth factors and fibronectin. We have now investigated the role of SP in collagen metabolism mediated by human corneal fibroblasts in culture. Although SP alone had no effect on collagen synthesis or degradation by these cells, it promoted the stimulatory effect of TGF-β on collagen type I synthesis without affecting that of IL-1β on the expression of matrix metalloproteinase-1. This effect of SP on TGF-β-induced collagen synthesis was accompanied by activation of p38 mitogen-activated protein kinase (MAPK) signaling and was attenuated by pharmacological inhibition of p38 or of the neurokinin-1 receptor. Our results thus implicate SP as a modulator of TGF-β-induced collagen type I synthesis by human corneal fibroblasts, and they suggest that loss of this function may contribute to the development of neurotrophic keratopathy.NEW & NOTEWORTHY This study investigates the role of substance P (SP) in collagen metabolism mediated by human corneal fibroblasts in culture. We found that, although SP alone had no effect on collagen synthesis or degradation by corneal fibroblasts, it promoted the stimulatory effect of transforming growth factor-β on collagen type I synthesis without affecting that of interleukin-1β on the expression of matrix metalloproteinase-1.

The intervention of cannabinoid receptor in chronic and acute kidney disease animal models: a systematic review and meta-analysis

AIM

Cannabinoid receptors are components of the endocannabinoid system that affect various physiological functions. We aim to investigate the effect of cannabinoid receptor modulation on kidney disease.

METHODS

PubMed, Web of Science databases, and EMBASE were searched. Articles selection, data extraction and quality assessment were independently performed by two investigators. The SYRCLE's RoB tool was used to assess the risk of study bias, and pooled SMD using a random-effect model and 95% CIs were calculated. Subgroup analyses were conducted in preselected subgroups, and publication bias was evaluated. We compared the effects of CB1 and CB2 antagonists and/or knockout and agonists and/or genetic regulation on renal function, blood glucose levels, body weight, and pathological damage-related indicators in different models of chronic and acute kidney injury.

RESULTS

The blockade or knockout of CB1 could significantly reduce blood urea nitrogen [SMD,- 1.67 (95% CI - 2.27 to - 1.07)], serum creatinine [SMD, - 1.88 (95% CI - 2.91 to - 0.85)], and albuminuria [SMD, - 1.60 (95% CI - 2.16 to - 1.04)] in renal dysfunction animals compared with the control group. The activation of CB2 group could significantly reduce serum creatinine [SMD, - 0.97 (95% CI - 1.83 to - 0.11)] and albuminuria [SMD, - 2.43 (95% CI - 4.63 to - 0.23)] in renal dysfunction animals compared with the control group.

CONCLUSIONS

The results suggest that targeting cannabinoid receptors, particularly CB1 antagonists and CB2 agonists, can improve kidney function and reduce inflammatory responses, exerting a renal protective effect and maintaining therapeutic potential in various types of kidney disease.

Iguratimod alleviates tubulo-interstitial injury in mice with lupus

INTRODUCTION

Tubulo-interstitial injury is a poor prognostic factor for lupus nephritis (LN). Here, we tested whether iguratimod could inhibit tubulo-interstitial injury in LN.

METHODS

MRL/lpr mice, an animal model of lupus, were treated with iguratimod or vehicle solution. Pathological changes of kidney were evaluated blindly by the same pathologist. Renal type I collagen (COL-I), IgG, E-cadherin, fibroblast-specific protein 1 (FSP-1) were detected by immunofluorescence, immunohistochemical staining or quantitative real-time PCR. After treated with transforming growth factor β1 (TGF-β1) and iguratimod, E-cadherin, fibronectin, Smad2/3, p38 MAPK, p-Smad2/3, and p-p38 MAPK, β-catenin and TGF-β type II receptor (TGFβRII) in HK2 cells were measured by western blotting, quantitative real-time PCR or immunofluorescence.

RESULTS

Iguratimod reduced immune deposition along the tubular basement membrane, inhibited the tubulo-interstitial infiltration of inflammatory cells, and alleviated tubular injury in MRL/lpr mice. Moreover, Iguratimod eased the tubulo-interstitial deposition of collagen fibers, which was confirmed by decreased expression of COL-I. Furthermore, iguratimod suppressed the expression of FSP-1 and increased that of E-cadherin in renal tubular epithelial cells. In HK2 cells cultured with TGF-β1, iguratimod treatment not only reversed cellular morphological changes, but also prevented E-cadherin downregulation and fibronectin upregulation. In addition, iguratimod inhibited phosphorylation of TGFβRII, Smad2/3 and p38 MAPK in HK2 cells treated with TGF-β1, and also blocked nuclear translocation of β-catenin.

CONCLUSION

Iguratimod eased tubulo-interstitial lesions in LN, especially tubulo-interstitial fibrosis, and might have potential as a drug for inhibiting the progression of tubulo-interstitial fibrosis in LN.

Loss-of-function variants in exon 4 of TAB2 cause a recognizable multisystem disorder with cardiovascular, facial, cutaneous, and musculoskeletal involvement

PURPOSE

This study aimed to describe a multisystemic disorder featuring cardiovascular, facial, musculoskeletal, and cutaneous anomalies caused by heterozygous loss-of-function variants in TAB2.

METHODS

Affected individuals were analyzed by next-generation technologies and genomic array. The presumed loss-of-function effect of identified variants was assessed by luciferase assay in cells transiently expressing TAB2 deleterious alleles. In available patients' fibroblasts, variant pathogenicity was further explored by immunoblot and osteoblast differentiation assays. The transcriptomic profile of fibroblasts was investigated by RNA sequencing.

RESULTS

A total of 11 individuals from 8 families were heterozygotes for a novel TAB2 variant. In total, 7 variants were predicted to be null alleles and 1 was a missense change. An additional subject was heterozygous for a 52 kb microdeletion involving TAB2 exons 1 to 3. Luciferase assay indicated a decreased transcriptional activation mediated by NF-κB signaling for all point variants. Immunoblot analysis showed a reduction of TAK1 phosphorylation while osteoblast differentiation was impaired. Transcriptomic analysis identified deregulation of multiple pleiotropic pathways, such as TGFβ-, Ras-MAPK-, and Wnt-signaling networks.

CONCLUSION

Our data defined a novel disorder associated with loss-of-function or, more rarely, hypomorphic alleles in a restricted linker region of TAB2. The pleiotropic manifestations in this disorder partly recapitulate the 6q25.1 (TAB2) microdeletion syndrome and deserve the definition of cardio-facial-cutaneous-articular syndrome.

Signaling Pathways Involved in Diabetic Renal Fibrosis

Diabetic kidney disease (DKD), as the most common complication of diabetes mellitus (DM), is the major cause of end-stage renal disease (ESRD). Renal interstitial fibrosis is a crucial metabolic change in the late stage of DKD, which is always considered to be complex and irreversible. In this review, we discuss the pathological mechanisms of diabetic renal fibrosis and discussed some signaling pathways that are closely related to it, such as the TGF-β, MAPK, Wnt/β-catenin, PI3K/Akt, JAK/STAT, and Notch pathways. The cross-talks among these pathways were then discussed to elucidate the complicated cascade behind the tubulointerstitial fibrosis. Finally, we summarized the new drugs with potential therapeutic effects on renal fibrosis and listed related clinical trials. The purpose of this review is to elucidate the mechanisms and related pathways of renal fibrosis in DKD and to provide novel therapeutic intervention insights for clinical research to delay the progression of renal fibrosis.

Advanced In Vitro Modeling to Study the Paradox of Mechanically Induced Cardiac Fibrosis

In heart failure, cardiac fibrosis is the result of an adverse remodeling process. Collagen is continuously synthesized in the myocardium in an ongoing attempt of the heart to repair itself. The resulting collagen depositions act counterproductively, causing diastolic dysfunction and disturbing electrical conduction. Efforts to treat cardiac fibrosis specifically have not been successful and the molecular etiology is only partially understood. The differentiation of quiescent cardiac fibroblasts to extracellular matrix-depositing myofibroblasts is a hallmark of cardiac fibrosis and a key aspect of the adverse remodeling process. This conversion is induced by a complex interplay of biochemical signals and mechanical stimuli. Tissue-engineered 3D models to study cardiac fibroblast behavior in vitro indicate that cyclic strain can activate a myofibroblast phenotype. This raises the question how fibroblast quiescence is maintained in the healthy myocardium, despite continuous stimulation of ultimately profibrotic mechanotransductive pathways. In this review, we will discuss the convergence of biochemical and mechanical differentiation signals of myofibroblasts, and hypothesize how these affect this paradoxical quiescence. Impact statement Mechanotransduction pathways of cardiac fibroblasts seem to ultimately be profibrotic in nature, but in healthy human myocardium, cardiac fibroblasts remain quiescent, despite continuous mechanical stimulation. We propose three hypotheses that could explain this paradoxical state of affairs. Furthermore, we provide suggestions for future research, which should lead to a better understanding of fibroblast quiescence and activation, and ultimately to new strategies for the prevention and treatment of cardiac fibrosis and heart failure.

Peptide DR8 suppresses epithelial-to-mesenchymal transition via the TGF-β/MAPK signaling pathway in renal fibrosis

AIMS

Renal fibrosis is a progressive disease that leads to renal dysfunction and end-stage renal failure, and there is currently no specific treatment. Our previous study showed that the 8-residue peptide DR8 (DHNNPQIR) exhibits potent antioxidant and antifibrotic properties, and accumulating evidence suggests that oxidative stress contributes greatly to fibrosis. The effects and mechanisms of DR8 on renal fibrosis remain unknown.

MATERIALS AND METHODS

The effects of DR8 were assessed in a unilateral ureteral obstruction mouse model that received a daily, single-dose subcutaneous injection of 500 μg/kg DR8 for 14 days and in cultured cells (HK-2 and NIH-3T3 cells) treated with 5 ng/mL TGF-β1 and 80 μM DR8. Western blotting, immunohistochemical staining, real-time qPCR and other tools were conducted to study the molecular mechanisms underlying antifibrotic effects.

KEY FINDINGS

DR8 improved renal function and reduced injury and extracellular matrix (ECM) deposition. Inflammation and oxidative stress were alleviated by DR8 in vivo. DR8 also inhibited the activation of fibroblasts and ECM deposition in HK-2 and NIH-3T3 cells induced by TGF-β1. In addition, epithelial-to-mesenchymal transition (EMT) was inhibited by DR8 both in vivo and in vitro. Mechanistic studies supported that DR8 inhibited ERK and p38 mitogen-activated protein kinase (MAPK) activation. These results indicate that DR8 attenuates renal fibrosis via suppression of EMT by antagonizing the MAPK pathway.

SIGNIFICANCE

We provide mechanistic details for a potential therapeutic agent and establish a foundation for peptide therapeutics.

Insights into the molecular pathogenesis of cardiospondylocarpofacial syndrome: MAP3K7 c.737-7A > G variant alters the TGFβ-mediated α-SMA cytoskeleton assembly and autophagy

Transforming growth factor beta-activated kinase 1 (TAK1) is a highly conserved kinase protein encoded by MAP3K7, and activated by multiple extracellular stimuli, growth factors and cytokines. Heterozygous variants in MAP3K7 cause the cardiospondylocarpofacial syndrome (CSCFS) which is characterized by short stature, dysmorphic facial features, cardiac septal defects with valve dysplasia, and skeletal anomalies. CSCFS has been described in seven patients to date and its molecular pathogenesis is only partially understood. Here, the functional effects of the MAP3K7 c.737-7A > G variant, previously identified in a girl with CSCFS and additional soft connective tissue features, were explored. This splice variant generates an in-frame insertion of 2 amino acid residues in the kinase domain of TAK1. Computational analysis revealed that this in-frame insertion alters protein dynamics in the kinase activation loop responsible for TAK1 autophosphorylation after binding with its interactor TAB1. Co-immunoprecipitation studies demonstrate that the ectopic expression of TAK1-mutated protein impairs its ability to physically bind TAB1. In patient's fibroblasts, MAP3K7 c.737-7A > G variant results in reduced TAK1 autophosphorylation and dysregulation of the downstream TAK1-dependent signaling pathway. TAK1 loss-of-function is associated with an impaired TGFβ-mediated α-SMA cytoskeleton assembly and cell migration, and defective autophagy process. These findings contribute to our understanding of the molecular pathogenesis of CSCFS and might offer the rationale for the design of novel therapeutic targets.

Complement component C1q is produced by isolated articular chondrocytes

OBJECTIVE

Inflammation and innate immune responses may contribute to development and progression of Osteoarthritis (OA). Chondrocytes are the sole cell type of the articular cartilage and produce extracellular-matrix molecules. How inflammatory mediators reach chondrocytes is incompletely understood. Previous studies have shown that chondrocytes express mRNA encoding complement proteins such as C1q, suggesting local protein production, which has not been demonstrated conclusively. The aim of this study is to explore C1q production at the protein level by chondrocytes.

DESIGN

We analysed protein expression of C1q in freshly isolated and cultured human articular chondrocytes using Western blot, ELISA and flow cytometry. We examined changes in mRNA expression of collagen, MMP-1 and various complement genes upon stimulation with pro-inflammatory cytokines or C1q. mRNA expression of C1 genes was determined in articular mouse chondrocytes.

RESULTS

Primary human articular chondrocytes express genes encoding C1q, C1QA, C1QB, C1QC, and secrete C1q to the extracellular medium. Stimulation of chondrocytes with pro-inflammatory cytokines upregulated C1QA, C1QB, C1QC mRNA expression, although this was not confirmed at the protein level. Extracellular C1q bound to the chondrocyte surface dose dependently. In a pilot study, binding of C1q to chondrocytes resulted in changes in the expression of collagens with a decrease in collagen type 2 and an increase in type 10. Mouse articular chondrocytes also expressed C1QA, C1QB, C1QC, C1R and C1S at the mRNA level.

CONCLUSIONS

C1q protein can be expressed and secreted by human articular chondrocytes and is able to bind to chondrocytes influencing the relative collagen expression.

TAB2 c.1398dup variant leads to haploinsufficiency and impairs extracellular matrix homeostasis

Transforming growth factor β-activated kinase 1 (TAK1) mediates multiple biological processes through the nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) and the mitogen-activated protein kinase (MAPK) signaling pathways. TAK1 activation is tightly regulated by its binding partners (TABs). In particular, binding with TAB2 is crucial for cardiovascular development and extracellular matrix (ECM) homeostasis. In our previous work, we reported a novel multisystem disorder associated with the heterozygous TAB2 c.1398dup variant. Here, we dissect the functional effects of this variant in order to understand its molecular pathogenesis. We demonstrate that TAB2 c.1398dup considerably undergoes to nonsense-mediated messenger RNA decay and encodes a truncated protein that loses its ability to bind TAK1. We also show an alteration of the TAK1 autophosphorylation status and of selected downstream signaling pathways in patients' fibroblasts. Immunofluorescence analyses and ECM-related polymerase chain reaction-array panels highlight that patient fibroblasts display ECM disorganization and altered expression of selected ECM components and collagen-related pathways. In conclusion, we deeply dissect the molecular pathogenesis of the TAB2 c.1398dup variant and show that the resulting phenotype is well explained by TAB2 loss-of-function. Our data also offer initial insights on the ECM homeostasis impairment as a molecular mechanism probably underlying a multisystem disorder linked to TAB2.

Ribes diacanthum Pall (RDP) ameliorates UUO-induced renal fibrosis via both canonical and non-canonical TGF-β signaling pathways in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Ribes diacanthum Pall (RDP), a folk medicine, has been widely used in Mongolia to treat urinary system diseases.

AIM OF THE STUDY

To investigate the effectiveness of RDP on unilateral ureteral obstruction (UUO)-induced renal interstitial fibrosis and the underlying mechanisms.

MATERIALS AND METHODS

A total of 60 mice were randomly divided into six groups: sham group, sham plus RDP (40 mg/kg) group, UUO model group, and UUO model plus RDP (10, 20 or 40 mg/kg) groups. After surgery, aqueous extract of RDP were administrated intragastrically (i.g) daily for a week and ipsilateral kidneys were collected seven days after surgery. Levels of blood urea nitrogen (BUN) and serum creatinine (Scr) were detected to reflect the kidney injury. Hematoxylin & eosin and Masson's trichrome staining were used to evaluate the kidney morphological changes and fibrosis, respectively. ELISA was used to examine the levels of pro-inflammatory cytokines. Immunohistochemistry, western blot and PCR were used to examine the expression levels of key proteins involved in transforming growth factor (TGF-β)/Smad and mitogen-activated protein kinase (MAPK) signaling pathways.

RESULTS

RDP treatment attenuates the level of BUN and kidney fibrosis in UUO mice, decreases the expressions of interleukin-6, tumor necrosis factor-α, Interleukin-1α, TGF-β1, monocyte chemotactic protein-1, α-smooth muscle actin, collagen I, fibronectin, and vimentin, while increases the expressions of E-cadherin and hepatocyte growth factor. Moreover, RDP administration significantly decreases the levels of p-Smad2/3, p-ERK1/2, p-p38 and p-JNK, while increases the expression level of Smad7 in UUO models.

CONCLUSION

These data demonstrate that RDP ameliorates renal fibrosis through TGF-β/Smad and MAPK pathways in a UUO mouse model.

The TGFβ-ERK pathway contributes to Notch3 upregulation in the renal tubular epithelial cells of patients with obstructive nephropathy

Renal interstitial fibrosis is a common renal injury resulted from a variety of chronic kidney conditions and an array of factors. We report here that Notch3 is a potential contributor. In comparison to 6 healthy individuals, a robust elevation of Notch3 expression was observed in the renal tubular epithelial cells of 18 patients with obstructive nephropathy. In a rat unilateral ureteral obstruction (UUO) model which mimics the human disease, Notch3 upregulation closely followed the course of renal injury, renal fibrosis, TGFβ expression, and alpha-smooth muscle actin (α-SMA) expression, suggesting a role of Notch3 in promoting tubulointerstitial fibrosis. This possibility was supported by the observation that TGFβ, the major renal fibrogenic cytokine, stimulated Notch3 expression in human proximal tubule epithelial HK-2 cells. TGFβ enhanced the activation of ERK, p38, but not JNK MAP kinases in HK-2 cells. While inhibition of p38 activation using SB203580 did not affect TGFβ-induced Notch3 expression, inhibition of ERK activation with a MEK1 inhibitor PD98059 dramatically reduced the event. Furthermore, enforced ERK activation through overexpression of the constitutively active MEK1 mutant MEK1Q56P upregulated Notch3 expression in HK-2 cells, and PD98059 reduced ERK activation and Notch3 expression in HK-2 cells expressing MEK1Q56P. Collectively, we provide the first clinical evidence for Notch3 upregulation in patients with obstructive nephropathy; the upregulation is likely mediated through the TGFβ-ERK pathway. This study suggests that Notch3 upregulation contributes to renal injury caused by obstructive nephropathy, which could be prevented or delayed through ERK inhibition.

Rapeseed protein-derived antioxidant peptide RAP alleviates renal fibrosis through MAPK/NF-κB signaling pathways in diabetic nephropathy

Introduction

Kidney fibrosis is the main pathologic change in diabetic nephropathy (DN), which is the major cause of end-stage renal disease. Current therapeutic strategies slow down but cannot reverse the progression of renal dysfunction in DN. Plant-derived bioactive peptides in foodstuffs are widely used in many fields because of their potential pharmaceutical and nutraceutical benefits. However, this type of peptide has not yet been studied in renal fibrosis of DN. Previous studies have indicated that the peptide YWDHNNPQIR (named RAP), a natural peptide derived from rapeseed protein, has an antioxidative stress effect. The oxidative stress is believed to be associated with DN. The aim of this study was to evaluate the pharmacologic effects of RAP against renal fibrosis of DN and high glucose (HG)-induced mesangial dysfunction.

Materials and methods

Diabetes was induced by streptozotocin and high-fat diet in C57BL/6 mice and these mice were treated by subcutaneous injection of different doses of RAP (0.1 mg/kg and 0.5 mg/kg, every other day) or PBS for 12 weeks. Later, functional and histopathologic analyses were performed. Parallel experiments verifying the molecular mechanism by which RAP alleviates DN were carried out in HG-induced mesangial cells (MCs).

Results

RAP improved the renal function indices, including 24-h albuminuria, triglyceride, serum creatinine, and blood urea nitrogen levels, but did not lower blood glucose levels in DN mice. RAP also simultaneously attenuated extracellular matrix accumulation in DN mice and HG-induced MCs. Furthermore, RAP reduced HG-induced cell proliferation, but it showed no toxicity in MCs. Additionally, RAP inhibited the mitogen-activated protein kinase (MAPK) and nuclear factor κB (NF-κB) signaling pathways.

Conclusion

RAP can attenuate fibrosis in vivo and in vitro by antagonizing the MAPK and NF-κB pathways.

Triptolide Restores Autophagy to Alleviate Diabetic Renal Fibrosis through the miR-141-3p/PTEN/Akt/mTOR Pathway

Fibrosis is the major pathological feature of diabetic kidney disease (DKD). Autophagy, a process to maintain metabolic homeostasis, is obviously inhibited in DKD. Triptolide (TP) is a traditional Chinese medicine extract known for immune suppression and anti-inflammatory and anti-cancer activities. In this study, we investigated the effects of TP on autophagy and fibrosis in DKD. TP restored autophagy and alleviated fibrosis in DKD rats and high-glucose-incubated human mesangial cells. After we applied 3-methyladenine (an autophagy inhibitor) and autophagy-related gene 5-small interfering RNA (siRNA), we found that the improvement of fibrosis on TP was related to the restoration of autophagy. In addition, miR-141-3p levels were increased under high glucose but reduced after TP treatment. miR-141-3p overexpression aggravated the fibrosis and restrained the autophagy further, while miR-141-3p inhibition imitated the effects of TP. As an action target, phosphatase and tensin homolog (PTEN) showed corresponding opposite changes. After PTEN-siRNA transfection, the effects of TP on autophagy and fibrosis were inhibited. PTEN levels were downregulated, with downstream phosphorylated protein kinase B (Akt) and the mammalian target of rapamycin (mTOR) upregulated in high glucose, which were reversed by TP treatment. These findings indicate that TP alleviates fibrosis by restoring autophagy through the miR-141-3p/PTEN/Akt/mTOR pathway and is a novel therapeutic option for DKD.

ALA/LA ameliorates glucose toxicity on HK-2 cells by attenuating oxidative stress and apoptosis through the ROS/p38/TGF-β1 pathway

BACKGROUND

Growing evidence indicates that oxidative stress (OS) plays a pivotal role in Diabetic nephropathy (DN). In a previous study we demonstrated that ALA/LA protected HK-2 cells against high glucose-induced cytotoxicity. So we aimed to establish the glucose injury model of HK-2 cells and investigate the beneficial effects of ALA/LA on high glucose-induced excessive production of TGF-β1 and the possible mechanisms mediating the effects.

METHODS

The expression of OS markers in high glucose-induced HK-2 cells treated with ALA/LA., including the antioxidant enzymes and reactive oxygen species (ROS) production, as well as the apoptosis rate were assayed by ELISA and flow cytometry. The p38/transforming growth factor β1 (TGF-β1) signal pathway were measured by real-time RT-PCR and western blot.

RESULTS

The modeling condition of glucose toxicity on HK-2 cells was at the glucose concentration of 40.9 mM. ALA/LA can significantly increase the activities of antioxidant enzymes and decrease ROS production stimulated by high glucose. The study also found that ALA/LA caused a decrease in the apoptosis rate and TGF-β1 level of HK-2 cells under high glucose stress through the ROS/p38 pathway.

CONCLUSIONS

ALA/LA exerts protective effects in vitro through inhibition of ROS generation, down regulation of the activation of the p38MAPK pathway and the expression of TGF-β1 in HK-2 cells.

Alterations in the long non‑coding RNA transcriptome in mesangial cells treated with aldosterone in vitro

Clinical and experimental reports indicate that aldosterone (ALD) contributes to the progression of renal failure independent of its hemodynamic effects. However, the mechanisms remain to be completely elucidated. The aim of the present study was to investigate the alterations of long non-coding RNA (lncRNA) in mesangial cells (MCs) treated with ALD. The present study used MCs treated with 10⁻⁶ M ALD as experimental cells. Microarray techniques performed by Agilent Technologies were used to identify the profiles of differentially expressed lncRNAs between the ALD group and the control group. Pathway and gene ontology analysis were applied to determine the roles of the differentially expressed lncRNAs. Reverse transcription quantitative polymerase chain reaction (RT-qPCR) was used to quantify the differentially expressed lncRNAs. A total of 8,459 lncRNA and 13,214 mRNAs with differential expression between MCs treated with and without ALD were identified. The expression of lncRNAs was confirmed by RT-qPCR and the results were consistent with the lncRNA array. The biological functions of lncRNAs are associated with responding to external stimuli, positive regulation of biological and apoptotic processes, cell division, mitosis and nuclear division. The pathways include cell cycle and peroxisome proliferator-activated receptor signaling pathways. The present study revealed distinct sets of lncRNA expressed in MCs treated with ALD, suggesting that this class of transcripts may be involved in the pathogenesis of chronic kidney diseases.

Podocyte-specific soluble epoxide hydrolase deficiency in mice attenuates acute kidney injury

Podocytes play an important role in maintaining glomerular function, and podocyte injury is a significant component in the pathogenesis of proteinuria. Soluble epoxide hydrolase (sEH) is a cytosolic enzyme whose genetic deficiency and pharmacological inhibition have beneficial effects on renal function, but its role in podocytes remains unexplored. The objective of this study was to investigate the contribution of sEH in podocytes to lipopolysaccharide (LPS)-induced kidney injury. We report increased sEH transcript and protein expression in murine podocytes upon LPS challenge. To determine the function of sEH in podocytes in vivo we generated podocyte-specific sEH-deficient (pod-sEHKO) mice. Following LPS challenge, podocyte sEH-deficient mice exhibited lower kidney injury, proteinuria, and blood urea nitrogen concentrations than controls suggestive of preserved renal function. Also, renal mRNA and serum concentrations of inflammatory cytokines IL-6, IL-1β, and TNFα were significantly lower in LPS-treated pod-sEHKO than control mice. Moreover, podocyte sEH deficiency was associated with decreased LPS-induced NF-κB and MAPK activation and attenuated endoplasmic reticulum stress. Furthermore, the protective effects of podocyte sEH deficiency in vivo were recapitulated in E11 murine podocytes treated with a selective sEH pharmacological inhibitor. Altogether, these findings identify sEH in podocytes as a contributor to signaling events in acute renal injury and suggest that sEH inhibition may be of therapeutic value in proteinuria.

ENZYMES

Soluble epoxide hydrolase: EC 3.3.2.10.

Implication of CD38 gene in autophagic degradation of collagen I in mouse coronary arterial myocytes

Collagen deposition is a hallmark of atherosclerosis. Although compromised collagen I degradation has been implied in the pathogenesis of atherosclerosis, the molecular mechanisms are still unclear. Thus, we determined the role of CD38, an enzyme involved in cellular calcium modulation and autophagic flux, in the regulation of collagen I degradation in coronary arterial myocytes (CAMs).In primary cultured CAMs from CD38^-/- mice, collagen I protein accumulation but not mRNA abundance was significantly increased compared with cells from CD38^+/+ mice either under control or upon TGF-Beta stimulation. Pharmacological inhibition of the formation of autophagosomes with 3-methyladenine or of autophagolysosomes with a lysosomal functional blocker, bafilomycin A1, induced a similar increase in collagen protein levels, while inhibition of the proteasome by MG132 had no effects on collagen I accumulation. In addition, CD38-deficiency did not change the protein expression of matrix metalloprotein-9 (MMP-9) or tissue inhibitor of metalloproteinase-1 (TIMP-1) in CAMs. Confocal microscopy showed that collagen I deposition was mainly lied within lysosomes or autophagosomes in CD38^-/- or TGF-Beta treated CAMs. Collagen I deposition increased when CAMs lack CD38 expression or if autophagy was blocked, which is associated with impaired autophagic degradation of collagen I. This CD38 regulation of autophagic flux may represent a novel mechanism for extracellular matrix (ECM) plasticity of coronary arteries upon atherogenic stimulation.

Usp2-69 overexpression slows down the progression of rat anti-Thy1.1 nephritis

Mesangial proliferative glomerulonephritis is characterized by proliferation of mesangial cells (MCs) and transforming growth factor-β (TGF-β)-dependent stimulation of abnormal extracellular matrix (ECM) accumulation. We previously showed that Decorin--a leucine-rich proteoglycan inhibiting the progression of glomerulonephritis and glomerular sclerosis--can be degraded by the ubiquitin-proteasome pathway and deubiquitinated and stabilized by ubiquitin-specific processing protease 2-69(Usp2-69). Usp2-69 is highly expressed in the kidney and has been implicated in the regulation of cell proliferation and apoptosis. However, its role in mesangial proliferative glomerulonephritis remains unclear. Here, we explored the effect of Usp2-69 on MC proliferation and ECM deposition by transfecting Usp2-69 plasmid into rat anti-Thy1.1 nephritis model and into cultured MCs, as well as detected Usp2-69 and Decorin in rat anti-Thy1.1 nephritis model by western blot. Overexpressing Usp2-69 at the early stage, but not advanced stage, of anti-Thy1.1 nephritis alleviated cell proliferation and ECM deposition, which was shown by decreased Ki-67, Collagen IV and Fibronectin detected by immunohistochemistry. Overexpression also increased Decorin and decreased TGF-β1 and Collagen IV both in vitro and in vivo. In conclusion, our findings suggest that Usp2-69 overexpression alleviates the progression of rat anti-Thy1.1 nephritis and, therefore, that exogenous plasmid injection via the renal artery enhanced by electrotransfer technology could be a promising avenue for glomerular disease research.

Tumor Necrosis Factor-Like Weak Inducer of Apoptosis Accelerates the Progression of Renal Fibrosis in Lupus Nephritis by Activating SMAD and p38 MAPK in TGF-β1 Signaling Pathway

This study aim was to explore the effects of tumor necrosis factor-like weak inducer of apoptosis (TWEAK) in lupus nephritis and its potential underlying mechanisms. MRL/lpr mice were used for in vivo experiments and human proximal tubular cells (HK2 cells) were used for in vitro experiments. Results showed that MRL/lpr mice treated with vehicle solution or LV-Control shRNA displayed significant proteinuria and severe renal histopathological changes. LV-TWEAK-shRNA treatment reversed these changes and decreased renal expressions of TWEAK, TGF-β1, p-p38 MAPK, p-Smad2, COL-1, and α-SMA proteins. In vitro, hTWEAK treatment upregulated the expressions of TGF-β1, p-p38 MAPK, p-SMAD2, α-SMA, and COL-1 proteins in HK2 cells and downregulated the expressions of E-cadherin protein, which were reversed by cotreatment with anti-TWEAK mAb or SB431542 treatment. These findings suggest that TWEAK may contribute to chronic renal changes and renal fibrosis by activating TGF-β1 signaling pathway, and phosphorylation of Smad2 and p38 MAPK proteins was also involved in this signaling pathway.

TGF-β: the master regulator of fibrosis

Transforming growth factor-β (TGF-β) is the primary factor that drives fibrosis in most, if not all, forms of chronic kidney disease (CKD). Inhibition of the TGF-β isoform, TGF-β1, or its downstream signalling pathways substantially limits renal fibrosis in a wide range of disease models whereas overexpression of TGF-β1 induces renal fibrosis. TGF-β1 can induce renal fibrosis via activation of both canonical (Smad-based) and non-canonical (non-Smad-based) signalling pathways, which result in activation of myofibroblasts, excessive production of extracellular matrix (ECM) and inhibition of ECM degradation. The role of Smad proteins in the regulation of fibrosis is complex, with competing profibrotic and antifibrotic actions (including in the regulation of mesenchymal transitioning), and with complex interplay between TGF-β/Smads and other signalling pathways. Studies over the past 5 years have identified additional mechanisms that regulate the action of TGF-β1/Smad signalling in fibrosis, including short and long noncoding RNA molecules and epigenetic modifications of DNA and histone proteins. Although direct targeting of TGF-β1 is unlikely to yield a viable antifibrotic therapy due to the involvement of TGF-β1 in other processes, greater understanding of the various pathways by which TGF-β1 controls fibrosis has identified alternative targets for the development of novel therapeutics to halt this most damaging process in CKD.

Betulinic acid inhibits cell proliferation and fibronectin accumulation in rat glomerular mesangial cells cultured under high glucose condition

Glomerular mesangial cells (MCs) proliferation and extracellular matrix (ECM) accumulation have been recognized as major pathogenic events in the progression of diabetic nephropathy. Betulinic acid (BA), (3β-hydroxy-lup-20(29)-en-28-oic acid), is a naturally occurring pentacyclic lupane group triterpenoid, and it has been shown to possess glucose-lowering property. However, the role of BA on MC proliferation and ECM accumulation in diabetic condition remains unclear. So, in the present study, we investigated the role of BA on cell proliferation and ECM accumulation in rat glomerular MCs cultured under high glucose (HG) condition. In the current study, we demonstrated that BA suppressed HG-induced MC proliferation, arrested HG-induced cell-cycle progression, reversed HG-inhibited expression of p21(Waf1/Cip1) and p27(Kip1). It also suppressed HG-induced fibronectin (FN) expression in MCs. Furthermore, BA inhibited HG-induced phosphorylation of ERK1/2 and p38MAPK in MCs. In conclusion, our present study demonstrated that BA inhibited HG-induced cell proliferation and FN expression in MCs via inhibiting ERK1/2 and p38MAPK pathways. Thus, BA may serve as a potential drug for the treatment of diabetic nephropathy.

The renal protective effects of Anoectochilus roxburghii polysaccharose on diabetic mice induced by high-fat diet and streptozotocin

ETHNOPHARMACOLOGICAL RELEVANCE

Anoectochilus roxburghii (Wall.) Lindl. 1832 is an herbal medicine used to treat diabetes in China. Considering that Anoectochilus roxburghii polysaccharose (ARP) is the main constituent of Anoectochilus roxburghii, the present study is aimed to investigate the renal protection of ARP and its possible mechanism in diabetic mice.

MATERIALS AND METHODS

Institute of Cancer Research (ICR) mice were induced to diabetes with high-fat diet (HFD) and low-dose streptozotocin (STZ). ARP (100, 300 mg/kg) was orally administrated to diabetic mice once a day for consecutive 15 days. The fasting glucose level, expressions of key proteins of p38 MAP kinase cascade, inflammatory factors, fibronectin (FN) and the activities of matrix metalloproteinases (MMPs) were measured. Furthermore, the histological examination of the separated kidneys was also carried out.

RESULTS

Compared with the diabetic mice, ARP administration induced a significant decrease in blood glucose level and improved the body weight of diabetic mice. In addition, ARP inhibited the expression of renal p38 MAP kinase cascade and its downstream inflammatory factors including tumor necrosis factor-α (TNF-α), monocyte chemoattractant protein-1 (MCP-1), FN as well as MMP2/9. Moreover, the histological examination showed an apparent reduction of mesangial matrix deposition and damage of microvascular structure after ARP administration.

CONCLUSIONS

The protective effects of ARP on diabetic renal damage may be attributed to the inhibition of p38 MAP kinase cascade and then attenuating the inflammatory responses and high glucose-induced renal damage.

Fuzheng Huayu Recipe Ameliorates Liver Fibrosis by Restoring Balance between Epithelial-to-Mesenchymal Transition and Mesenchymal-to-Epithelial Transition in Hepatic Stellate Cells

Activation of hepatic stellate cells (HSCs) depending on epithelial-to-mesenchymal transition (EMT) reflects the key event of liver fibrosis. Contrastively, mesenchymal-to-epithelial transition (MET) of HSCs facilitates the fibrosis resolution. Here we investigated the effect of Fuzheng Huayu (FZHY) recipe, a Chinese herbal decoction made of Radix Salviae Miltiorrhizae, Semen Persicae, Cordyceps sinensis, Pollen Pini, and Gynostemma pentaphyllum, on liver fibrosis concerning the balance of EMT and MET in HSCs. In contrast to the increased TGF-β 1/BMP-7 ratio in activated HSCs, FZHY administration induced significant upregulation of BMP-7 and downregulation of TGF-β 1 at both transcription and translation levels. Restoration of TGF-β 1/BMP-7 ratio inhibited the expression of p38 MAPK and phosphorylated p38 MAPK, resulting in the reversal of epithelial-to-mesenchymal transition (EMT) to mesenchymal-to-epithelial transition (MET) as characterized by the abolishment of EMT markers (α-SMA and desmin) and reoccurrence of MET marker (E-cadherin). In vivo treatment of FZHY recipe also demonstrated the statistical reduction of activated HSCs with EMT phenotype, which attenuated the carbon tetrachloride- (CCl4-) induced liver fibrosis in a dose-dependent manner. These findings may highlight a novel antifibrotic role of FZHY recipe on the basis of rebalancing EMT and MET in HSCs.

Mini-review: emerging roles of microRNAs in the pathophysiology of renal diseases

MicroRNAs (miRNA) are endogenously produced short noncoding regulatory RNAs that can repress gene expression by posttranscriptional mechanisms. They can therefore influence both normal and pathological conditions in diverse biological systems. Several miRNAs have been detected in kidneys, where they have been found to be crucial for renal development and normal physiological functions as well as significant contributors to the pathogenesis of renal disorders such as diabetic nephropathy, acute kidney injury, lupus nephritis, polycystic kidney disease, and others, due to their effects on key genes involved in these disease processes. miRNAs have also emerged as novel biomarkers in these renal disorders. Due to increasing evidence of their actions in various kidney segments, in this mini-review we discuss the functional significance of altered miRNA expression during the development of renal pathologies and highlight emerging miRNA-based therapeutics and diagnostic strategies for early detection and treatment of kidney diseases.

MicroRNAs in diabetic nephropathy: functions, biomarkers, and therapeutic targets

MicroRNAs (miRNAs) are short noncoding RNAs that regulate gene expression by posttranscriptional and epigenetic mechanisms and thereby affect many cellular processes and disease states. Over 2,000 human mature miRNAs have been identified, and at least 60% of all human protein-coding genes are known to be regulated by miRNAs. MicroRNA biogenesis involves classical transcription regulation and processing by key ribonucleases, as well as other protein factors and epigenetic mechanisms. Diabetic nephropathy (DN), a severe microvascular complication frequently associated with diabetes mellitus, is a major cause of renal failure. Although several mechanisms of regulation of key renal genes implicated in DN pathogenesis have been identified, a greater understanding is needed to develop better treatment modalities. Recent studies show that miRNAs induced in renal cells in vivo and in vitro under diabetic conditions can promote the accumulation of extracellular matrix proteins related to fibrosis and glomerular dysfunction. In this review, we highlight the significance of the expression of miRNAs in various stages of DN and emerging approaches to exploit them as biomarkers for early detection or novel therapeutic targets to prevent progression of DN.

Circulating TGF-β1-Regulated miRNAs and the Risk of Rapid Progression to ESRD in Type 1 Diabetes

We investigated whether circulating TGF-β1-regulated miRNAs detectable in plasma are associated with the risk of rapid progression to end-stage renal disease (ESRD) in a cohort of proteinuric patients with type 1 diabetes (T1D) and normal eGFR. Plasma specimens obtained at entry to the study were examined in two prospective subgroups that were followed for 7-20 years (rapid progressors and nonprogressors), as well as a reference panel of normoalbuminuric T1D patients. Of the five miRNAs examined in this study, let-7c-5p and miR-29a-3p were significantly associated with protection against rapid progression and let-7b-5p and miR-21-5p were significantly associated with the increased risk of ESRD. In logistic analysis, controlling for HbA1c and other covariates, let-7c-5p and miR-29a-3p were associated with more than a 50% reduction in the risk of rapid progression (P ≤ 0.001), while let-7b-5p and miR-21-5p were associated with a >2.5-fold increase in the risk of ESRD (P ≤ 0.005). This study is the first prospective study to demonstrate that circulating TGF-β1-regulated miRNAs are deregulated early in T1D patients who are at risk for rapid progression to ESRD.

Gallic acid ameliorates renal functions by inhibiting the activation of p38 MAPK in experimentally induced type 2 diabetic rats and cultured rat proximal tubular epithelial cells

Diabetic nephropathy (DN) is one of the leading causes of morbidity and mortality in diabetic patients that accounts for about 40% of deaths in type 2 diabetes. p38 mitogen activated protein kinase (p38 MAPK), a serine-threonine kinase, plays an important role in tissue inflammation and is known to be activated under conditions of oxidative stress and hyperglycemia. The role of p38 MAPK has been demonstrated in DN, and its inhibition has been suggested as an alternative approach in the treatment of DN. In the present study, we investigated the nephroprotective effects of an anti-inflammatory phenolic compound, gallic acid (GA, 3,4,5-trihydroxybenzoic acid), in high fat diet/streptozotocin (HFD/STZ) induce type 2 diabetic wistar albino rats. GA (25 mg/kgbw and 50 mg/kgbw, p.o.) treatment for 16 weeks post induction of diabetes led to a significant reduction in the levels of blood glucose, HbA1c, serum creatinine, blood urea nitrogen and proteinuria as well as a significant reduction in the levels of creatinine clearance. GA significantly inhibited the renal p38 MAPK and nuclear factor kappa B (N-κB) activation as well as significantly reduced the levels of renal transforming growth factor beta (TGF-β) and fibronectin. Treatment with GA resulted in a significant reduction in the serum levels of proinflammatory cytokines viz. interleukin 1 beta (IL-1β), IL-6 and tumor necrosis factor alpha (TNF-α). Moreover, GA significantly lowered renal pathology and attenuated renal oxidative stress. In cultured rat NRK 52E proximal tubular epithelial cells, GA treatment inhibited high glucose induced activation of p38 MAPK and NF-κB as well as suppressed proinflammatory cytokine synthesis. The results of the present study provide in vivo and in vitro evidences that the p38 MAPK pathway plays an important role in the pathogenesis of DN, and GA attenuates the p38 MAPK-mediated renal dysfunction in HFD/STZ induced type 2 diabetic rats.

Inhibition to DRP1 translocation can mitigate p38 MAPK-signaling pathway activation in GMC induced by hyperglycemia

Diabetic nephropathy (DN) is a serious complication of diabetes with a poorly defined etiology and limited treatment options. Early intervention is a key to preventing the progression of DN. Dynamin-related protein 1 (DRP1) regulates mitochondrial morphology by promoting its fission and is involved in the pathogenesis of numerous diseases. Furthermore, DRP1 is also closely associated with the development of diabetes, but its functional role in DN remains unknown. This study investigated the effect of DRP1 on early stage of DN. DRP1 expression has increased significantly in glomerular mesangial cell (GMC), which is cultivated in high glucose (HG). Ultra-microstructural changes of nephrons, expression of collagen IV and phosph-p38, ROS production, and mitochondrial function were evaluated and, at the same time, were compared with glomerular mesangial cell (GMC) cultured in normal-glucose (NG), mannitol, and a medium with mitochondrial division inhibitor 1 (Midivi-1). Endogenous DRP1 expression increased in DN. Compared to the control groups ofNG and mannitol, overexpression of DRP1 destroyed pathological changes typical of the GMC, like accumulation of extracellular matrix, and an increase in mitochondria division. In addition, Overexpression of DRP1 promoted the activation of p38, the accumulation of ROS, mitochondrial dysfunction, and the synthesis of collagen IV, and all these changes are suppressed by Midivi-1. This study demonstrates that DRP1 overexpression can accelerate pathological changes in the GMC cultured in HG. Further studies are needed to clarify the underlying mechanism of this destructive function.

Epigallocatechin-3-gallate reduces tubular cell apoptosis in mice with ureteral obstruction

BACKGROUND

Tubular cell apoptosis plays a crucial role in different kinds of renal diseases. Epigallocatechin-3-gallate (EGCG), a polyphenol extracted from green tea, has been shown to inhibit renal fibrosis in unilateral ureteral obstruction (UUO) mice, but its role in preventing tubular cell apoptosis and the underlying signaling mechanisms still remains unclear.

MATERIALS AND METHODS

Mice subjected to UUO were intraperitoneally administered EGCG (5 mg/kg) for 14 d. Normal rat kidney proximal tubular epithelial cell line NRK-52E was induced by transforming growth factor β1 (TGF-β1). Periodic acid-schiff and Masson's trichrome staining was used for histologic study. TUNEL, Hoechst staining, and flow cytometry analysis were used to measure the apoptotic status of tubular cells. Western blotting was used to determine the expression of apoptotic-associated proteins and mitogen-activated protein kinase pathway proteins.

RESULTS

EGCG significantly attenuated tubular injury and renal tubulointerstitial fibrosis in the obstructed kidneys of UUO mice. In addition, EGCG prevented UUO and TGF-β1-induced tubular apoptosis in a dose-dependent manner. In parallel, protein expression of B-clell lymphoma-2 (Bcl-2) was upregulated and protein expressions of Bcl-2 accosiated X protein (Bax), cleaved caspase 3, and cleaved poly ADP-ribose polymerase (PARP) were downregulated by EGCG. Furthermore, UUO and TGF-β1-stimulated phosphorylation of mitogen-activated protein kinase was inhibited by EGCG.

CONCLUSIONS

EGCG effectively reduces tubular cell apoptosis induced by UUO and may have potential as a clinical treatment in patients with chronic kidney disease.

Ursolic acid attenuates diabetic mesangial cell injury through the up-regulation of autophagy via miRNA-21/PTEN/Akt/mTOR suppression

OBJECTIVE

To investigate the effect of ursolic acid on autophagy mediated through the miRNA-21-targeted phosphoinositide 3 kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) pathway in rat mesangial cells cultured under high glucose (HG) conditions.

METHODS

Rat glomerular mesangial cells were cultured under normal glucose, HG, HG with the PI3K inhibitor LY294002 or HG with ursolic acid conditions. Cell proliferation and hypertrophy were assayed using an MTT assay and the ratio of total protein to cell number, respectively. The miRNA-21 expression was detected using RT-qPCR. The expression of phosphatase and tensin homolog (PTEN)/AKT/mTOR signaling signatures, autophagy-associated protein and collagen I was detected by western blotting and RT-qPCR. Autophagosomes were observed using electron microscopy.

RESULTS

Compared with mesangial cells cultured under normal glucose conditions, the cells exposed to HG showed up-regulated miRNA-21 expression, down-regulated PTEN protein and mRNA expression, up-regulated p85PI3K, pAkt, pmTOR, p62/SQSTMI, and collagen I expression and down-regulated LC3II expression. Ursolic acid and LY294002 inhibited HG-induced mesangial cell hypertrophy and proliferation, down-regulated p85PI3K, pAkt, pmTOR, p62/SQSTMI, and collagen I expression and up-regulated LC3II expression. However, LY294002 did not affect the expression of miRNA-21 and PTEN. Ursolic acid down-regulated miRNA-21 expression and up-regulated PTEN protein and mRNA expression.

CONCLUSIONS

Ursolic acid inhibits the glucose-induced up-regulation of mesangial cell miRNA-21 expression, up-regulates PTEN expression, inhibits the activation of PI3K/Akt/mTOR signaling pathway, and enhances autophagy to reduce the accumulation of the extracellular matrix and ameliorate cell hypertrophy and proliferation.

Oxidative stress mediates the conversion of endothelial cells into myofibroblasts via a TGF-β1 and TGF-β2-dependent pathway

During the pathogenesis of systemic inflammation, reactive oxygen species (ROS) circulate in the bloodstream and interact with endothelial cells (ECs), increasing intracellular oxidative stress. Although endothelial dysfunction is crucial in the pathogenesis of systemic inflammation, little is known about the effects of oxidative stress on endothelial dysfunction. Oxidative stress induces several functions, including cellular transformation. A singular process of cell conversion is tendothelial-to-mesenchymal transition, in which ECs become myofibroblasts, thus losing their endothelial properties and gaining fibrotic behavior. However, the participation of oxidative stress as an inductor of conversion of ECs into myofibroblasts is not known. Thus, we studied the role played by oxidative stress in this conversion and investigated the underlying mechanism. Our results show that oxidative stress induces conversion of ECs into myofibroblasts through decreasing the levels of endothelial markers and increasing those of fibrotic and ECM proteins. The underlying mechanism depends on the ALK5/Smad3/NF-κB pathway. Oxidative stress induces the expression and secretion of TGF-β1 and TGF-β2 and p38 MAPK phosphorylation. Downregulation of TGF-β1 and TGF-β2 by siRNA technology abolished the H2O2-induced conversion. To our knowledge, this is the first report showing that oxidative stress is able to induce conversion of ECs into myofibroblasts via TGF-β secretion, emerging as a source for oxidative stress-based vascular dysfunction. Thus, oxidative stress emerges as a decisive factor in inducing conversion of ECs into myofibroblasts through a TGF-β-dependent mechanism, changing the ECs protein expression profile, and converting normal ECs into pathological ones. This information will be useful in designing new and improved therapeutic strategies against oxidative stress-mediated systemic inflammatory diseases.

Diabetic nephropathy--emerging epigenetic mechanisms

Diabetic nephropathy (DN), a severe microvascular complication frequently associated with both type 1 and type 2 diabetes mellitus, is a leading cause of renal failure. The condition can also lead to accelerated cardiovascular disease and macrovascular complications. Currently available therapies have not been fully efficacious in the treatment of DN, suggesting that further understanding of the molecular mechanisms underlying the pathogenesis of DN is necessary for the improved management of this disease. Although key signal transduction and gene regulation mechanisms have been identified, especially those related to the effects of hyperglycaemia, transforming growth factor β1 and angiotensin II, progress in functional genomics, high-throughput sequencing technology, epigenetics and systems biology approaches have greatly expanded our knowledge and uncovered new molecular mechanisms and factors involved in DN. These mechanisms include DNA methylation, chromatin histone modifications, novel transcripts and functional noncoding RNAs, such as microRNAs and long noncoding RNAs. In this Review, we discuss the significance of these emerging mechanisms, how they mediate the actions of growth factors to augment the expression of extracellular matrix and inflammatory genes associated with DN and their potential usefulness as diagnostic biomarkers or novel therapeutic targets for DN.

Endotoxin-induced endothelial fibrosis is dependent on expression of transforming growth factors β1 and β2

During endotoxemia-induced inflammatory disease, bacterial endotoxins circulate in the bloodstream and interact with endothelial cells (ECs), inducing dysfunction of the ECs. We previously reported that endotoxins induce the conversion of ECs into activated fibroblasts. Through endotoxin-induced endothelial fibrosis, ECs change their morphology and their protein expression pattern, thereby suppressing endothelial markers and upregulating fibrotic proteins. The most commonly used fibrotic inducers are transforming growth factor β1 (TGF-β1) and TGF-β2. However, whether TGF-β1 and TGF-β2 participate in endotoxin-induced endothelial fibrosis remains unknown. We have shown that the endotoxin-induced endothelial fibrosis process is dependent on the TGF-β receptor, ALK5, and the activation of Smad3, a protein that is activated by ALK5 activation, thus suggesting that endotoxin elicits TGF-β production to mediate endotoxin-induced endothelial fibrosis. Therefore, we investigated the dependence of endotoxin-induced endothelial fibrosis on the expression of TGF-β1 and TGF-β2. Endotoxin-treated ECs induced the expression and secretion of TGF-β1 and TGF-β2. TGF-β1 and TGF-β2 downregulation inhibited the endotoxin-induced changes in the endothelial marker VE-cadherin and in the fibrotic proteins α-SMA and fibronectin. Thus, endotoxin induces the production of TGF-β1 and TGF-β2 as a mechanism to promote endotoxin-induced endothelial fibrosis. To the best of our knowledge, this is the first report showing that endotoxin induces endothelial fibrosis via TGF-β secretion, which represents an emerging source of vascular dysfunction. These findings contribute to understanding the molecular mechanism of endotoxin-induced endothelial fibrosis, which could be useful in the treatment of inflammatory diseases.

Autophagy regulates TGF-β expression and suppresses kidney fibrosis induced by unilateral ureteral obstruction

Autophagy is an evolutionarily conserved process that cells use to degrade and recycle cellular proteins and remove damaged organelles. During the past decade, there has been a growing interest in defining the basic cellular mechanism of autophagy and its roles in health and disease. However, the functional role of autophagy in kidney fibrosis remains poorly understood. Here, using GFP-LC3 transgenic mice, we show that autophagy is induced in renal tubular epithelial cells (RTECs) of obstructed kidneys after unilateral ureteral obstruction (UUO). Deletion of LC3B (LC3(-/-) mice) resulted in increased collagen deposition and increased mature profibrotic factor TGF-β levels in obstructed kidneys. Beclin 1 heterozygous (beclin 1(+/-)) mice also displayed increased collagen deposition in the obstructed kidneys after UUO. We also show that TGF-β1 induces autophagy in primary mouse RTECs and human renal proximal tubular epithelial (HK-2) cells. LC3 deficiency resulted in increased levels of mature TGF-β in primary RTECs. Under conditions of TGF-β1 stimulation and autoinduction, inhibition of autolysosomal protein degradation by bafilomycin A1 increased mature TGF-β protein levels without alterations in TGF-β1 mRNA. These data suggest a novel intracellular mechanism by which mature TGF-β1 protein levels may be regulated in RTECs through autophagic degradation, which suppresses kidney fibrosis induced by UUO. The dual functions of TGF-β1, as an inducer of TGF-β1 autoinduction and an inducer of autophagy and TGF-β degradation, underscore the multifunctionality of TGF-β1.

Wld(S) ameliorates renal injury in a type 1 diabetic mouse model

Diabetic nephropathy (DN) is the leading cause of end-stage kidney disease worldwide. The purpose of this study is to investigate whether the Wld(S) (slow Wallerian degeneration; also known as Wld) gene plays a renoprotective role during the progression of DN. Diabetes was induced in 8-wk-old male wild-type (WT) and C57BL/Wld(S) mice by streptozotocin (STZ) injection. Blood and urinary variables including blood glucose, glycated hemoglobin (GHb), insulin, urea nitrogen, and albumin/creatinine ratio were assessed 4, 7, and 14 wk after STZ injection. Periodic acid-Schiff staining, Masson staining, and silver staining were performed for renal pathological analyses. In addition, the renal ultrastructure was observed by electron microscope. The activities of p38 and ERK signaling in renal cortical tissues were evaluated by Western blotting. NAD(+)/NADH ratio and NADPH oxidase activity were also measured. Moreover, the expressions of TNF-α, IL-1, and IL-6 were examined. We provide experimental evidence demonstrating that the Wld(S) gene is expressed in kidney cells and protects against the early stage of diabetes-induced renal dysfunction and extracellular matrix accumulation through delaying the reduction of the NAD(+)/NADH ratio, inhibiting the activation of p38 and ERK signaling, and suppressing oxidative stress as evidenced by the decreased NADPH oxidase activity and lower expression of TNF-α, IL-1, and IL-6.

The physical basis of renal fibrosis: effects of altered hydrodynamic forces on kidney homeostasis

Healthy kidneys are continuously exposed to an array of physical forces as they filter the blood: shear stress along the inner lumen of the tubules, distension of the tubular walls in response to changing fluid pressures, and bending moments along both the cilia and microvilli of individual epithelial cells that comprise the tubules. Dysregulation of kidney homeostasis via underlying medical conditions such as hypertension, diabetes, or glomerulonephritis fundamentally elevates the magnitudes of each principle force in the kidney and leads to fibrotic scarring and eventual loss of organ function. The purpose of this review is to summarize the progress made characterizing the response of kidney cells to pathological levels of mechanical stimuli. In particular, we examine important, mechanically responsive signaling cascades and explore fundamental changes in renal cell homeostasis after cyclic strain or fluid shear stress exposure. Elucidating the effects of these disease-related mechanical imbalances on endogenous signaling events in kidney cells presents a unique opportunity to better understand the fibrotic process.

Regulation of autophagy by TGF-β: emerging role in kidney fibrosis

Autophagy is a highly conserved homoeostatic mechanism for cell survival under conditions of stress, and is widely implicated as an important pathway in many biological processes and diseases. In progressive kidney diseases, fibrosis represents the common pathway to end-stage kidney failure. Transforming growth factor-β1 (TGF-β1) is a pleiotropic cytokine that has been established as a central mediator of kidney fibrosis. A recently emerging body of evidence from studies in renal cells in culture and experimental animal models suggests that TGF-β1 regulates autophagy and that autophagy regulates many critical aspects of normal and disease conditions associated with kidney fibrosis, such as tubulointerstitial fibrosis, glomerulosclerosis, and diabetic nephropathy. Here, we review the recent advances exploring the process of autophagy, its regulation by TGF-β1, and the implication in the pathogenesis of progressive kidney fibrosis and injury responses. Understanding the cellular and molecular bases of this process is crucial for identifying potential new diagnostic and therapeutic targets of kidney fibrosis.

The role of angiogenic factors in fibroid pathogenesis: potential implications for future therapy

BACKGROUND

It is well established that tumors are dependent on angiogenesis for their growth and survival. Although uterine fibroids are known to be benign tumors with reduced vascularization, recent work demonstrates that the vasculature of fibroids is grossly and microscopically abnormal. Accumulating evidence suggests that angiogenic growth factor dysregulation may be implicated in these vascular and other features of fibroid pathophysiology.

METHODS

Literature searches were performed in PubMed and Google Scholar for articles with content related to angiogenic growth factors and myometrium/leiomyoma. The findings are hereby reviewed and discussed.

RESULTS

Multiple growth factors involved in angiogenesis are differentially expressed in leiomyoma compared with myometrium. These include epidermal growth factor (EGF), heparin-binding-EGF, vascular endothelial growth factor, basic fibroblast growth factor, platelet-derived growth factor, transforming growth factor-β and adrenomedullin. An important paradox is that although leiomyoma tissues are hypoxic, leiomyoma feature down-regulation of key molecular regulators of the hypoxia response. Furthermore, the hypoxic milieu of leiomyoma may contribute to fibroid development and growth. Notably, common treatments for fibroids such as GnRH agonists and uterine artery embolization (UAE) are shown to work at least partly via anti-angiogenic mechanisms.

CONCLUSIONS

Angiogenic growth factors play an important role in mechanisms of fibroid pathophysiology, including abnormal vasculature and fibroid growth and survival. Moreover, the fibroid's abnormal vasculature together with its aberrant hypoxic and angiogenic response may make it especially vulnerable to disruption of its vascular supply, a feature which could be exploited for treatment. Further experimental studies are required in order to gain a better understanding of the growth factors that are involved in normal and pathological myometrial angiogenesis, and to assess the potential of anti-angiogenic treatment strategies for uterine fibroids.

Huangkui capsule, an extract from Abelmoschus manihot (L.) medic, ameliorates adriamycin-induced renal inflammation and glomerular injury via inhibiting p38MAPK signaling pathway activity in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Abelmoschus manihot (L.) medic (AM) is a natural medicinal plant used for the treatment of inflammatory diseases in China. Huangkui capsule (HKC), an extract from AM, has been proved clinically effective in improving renal inflammation and glomerular injury in chronic kidney disease (CKD). However, the dose-effects and the mechanisms involved in vivo are still unclear.

AIM OF THE STUDY

This study was performed to examine the dose-effects of HKC on renal inflammation and glomerular lesion in adriamycin-induced nephropathy (ADRN), then to clarify the mechanisms in vivo of HKC by investigating its actions on modulating the activation of p38 mitogen-activated protein kinase (p38MAPK) signaling pathway.

MATERIALS AND METHODS

The rats with chronic ADRN, created by the unilateral nephrectomy and twice adriamycin injections (ADR, 4 mg/kg and 2mg/kg) within 4 weeks, were divided into four groups, a Sham group, a Vehicle group, a high-dose HKC group, and a low-dose HKC group, and that, sacrificed at the end of the 4th week after the administration. The rat's general status, renal morphological appearance, proteinuria, blood biochemical parameters, glomerular morphological changes, podocyte shape, and macrophage (ED1(+) and ED3(+) cells) infiltration in glomeruli were examined, respectively. The protein expressions of inflammatory cytokines including tumor necrosis factor (TNF)-α and interleukin (IL)-2, as well as p38MAPK signaling molecules such as transforming growth factor (TGF)-β1, p38MAPK, and phosphorylated-p38MAPK (p-p38MAPK), were also evaluated individually.

RESULTS

HKC at high dose of 2g/kg/d not only significantly ameliorated the rat's general status, renal morphological appearance, proteinuria, albumin, and glomerulosclerosis, but also obviously reduced the infiltrated ED1(+) and ED3(+) macrophages in glomeruli and TNF-α protein expression in the kidney, in addition to these, evidently down-regulated TGF-β1 and p-p38MAPK protein expressions in ADRN rats, but had no influence on podocyte shape and renal function.

CONCLUSION

HKC could dose-dependently ameliorate renal inflammation and glomerular injury in ADRN rats, by way of reducing the infiltration and the activation of macrophages in glomeruli, and TNF-α protein expression in the kidney, as well as inhibiting p38MAPK signaling pathway activity via the down-regulation of p-p38MAPK and TGF-β1 protein expressions in vivo.