Reactive oxygen species mediate TGF-beta1-induced plasminogen activator inhibitor-1 upregulation in mesangial cells

Role of plasminogen activated inhibitor-1 in the pathogenesis of anticoagulant related nephropathy

Anticoagulant related nephropathy (ARN) is the result of glomerular hemorrhage in patients on systemic anticoagulation therapy or underlying coagulopathy. Red blood cells (RBC) that passed through the glomerular filtration barrier form RBC casts in the tubules, increase oxidative stress and result in acute tubular necrosis (ATN). The mechanisms of ARN still not completely discovered. Plasminogen activator inhibitor-1 (PAI-1) plays a significant role in the maintenance of coagulation homeostasis. We developed an animal model to study ARN in 5/6 nephrectomy (5/6NE) rats. The aim of this study was to elucidate the role of PAI-1 in the ARN pathogenesis. 5/6NE rats were treated per os with warfarin (0.75 mg/kg/day) or dabigatran (150 mg/kg/day) alone or in combination with PAI-1 antagonist TM5441 (2.5, 5.0 and 10 mg/kg/day). TM5441 in a dose dependent manner ameliorated anticoagulant-induced increase in serum creatinine in 5/6NE rats. Anticoagulant-associated increase in hematuria was no affected by TM5441. The levels of reactive oxygen species (ROS) in the kidneys were in a dose-dependent manner decreased in 5/6NE rats treated with an anticoagulant and TM5441. Our data demonstrates that PAI-1 may reduce ARN by decreasing ROS in the kidneys. Glomerular hemorrhage is not affected by anti-PAI-1 treatment. These findings indicate that while symptoms of ARN can be reduced by PAI-1 inhibition, the main pathogenesis of ARN - glomerular hemorrhage - cannot be prevented.

SMAD2/3 mediate oncogenic effects of TGF-β in the absence of SMAD4

TGF-β signaling is involved in pancreatic ductal adenocarcinoma (PDAC) tumorigenesis, representing one of the four major pathways genetically altered in 100% of PDAC cases. TGF-β exerts complex and pleiotropic effects in cancers, notably via the activation of SMAD pathways, predominantly SMAD2/3/4. Though SMAD2 and 3 are rarely mutated in cancers, SMAD4 is lost in about 50% of PDAC, and the role of SMAD2/3 in a SMAD4-null context remains understudied. We herein provide evidence of a SMAD2/3 oncogenic effect in response to TGF-β1 in SMAD4-null human PDAC cancer cells. We report that inactivation of SMAD2/3 in SMAD4-negative PDAC cells compromises TGF-β-driven collective migration mediated by FAK and Rho/Rac signaling. Moreover, RNA-sequencing analyses highlight a TGF-β gene signature related to aggressiveness mediated by SMAD2/3 in the absence of SMAD4. Using a PDAC patient cohort, we reveal that SMAD4-negative tumors with high levels of phospho-SMAD2 are more aggressive and have a poorer prognosis. Thus, loss of SMAD4 tumor suppressive activity in PDAC leads to an oncogenic gain-of-function of SMAD2/3, and to the onset of associated deleterious effects.

In pancreatic ductal adenocarcinoma cells and patient tissue, SMAD2/3 is shown to mediate oncogenic effects of TGF-β in the absence of SMAD4.

Role of urinary H2O2, 8-iso-PGF2α, and serum oxLDL/β2GP1 complex in the diabetic kidney disease

Oxidant species is reported as a major determinant in the pathophysiology of diabetic kidney disease. However, reactive oxygen species (ROS) formation in the initial phase and progressing phase of diabetic kidney disease remains unclear. Therefore, we conducted this study to find out what ROS and their modified product are associated with eGFR in type 2 diabetes mellitus (T2DM) patients. A cross-sectional study was performed on 227 T2DM patients. The study subjects were divided into three groups based on their eGFR stage (Group 1, eGFR > 89 ml/min/1.73 m2; Group 2, eGFR = 60-89 ml/min/1.73 m2; and Group 3, eGFR < 60 ml/min/1.73 m2). Enzyme-linked immunosorbent assay (ELISA) was used to measure serum oxLDL/β2GPI complex and urinary 8-iso-PGF2α, while ferrous ion oxidation xylenol orange method 1 (FOX-1) was used to measure urinary hydrogen peroxide (H2O2). H2O2 significantly decreased across the groups, whereas OxLDL/β2GPI complex increased, but not significant, and there was no trend for 8-iso-PGF2α. Consistently, in the total study population, only H2O2 showed correlation with eGFR (r = 0.161, p = 0.015). Multiple linear regression analysis showed that significant factors for increased eGFR were H2O2, diastolic blood pressure, and female. Whereas increased systolic blood pressure and age were significant factors affecting the decrease of eGFR. We also found that urinary H2O2 had correlation with serum oxLDL/β2GPI complex in total population. This finding could lead to further research on urinary H2O2 for early detection and research on novel therapies of diabetic kidney disease.

An exploratory review of Potential Adjunct Therapies for the Treatment of Coronavirus Infections

Objective

The purpose of this exploratory review c, including vitamin D, zinc, vitamin A, elderberry (S nigra), garlic (A sativum), licorice (G glabra), stinging nettle (U dioica), N-acetylcysteine, quercetin and selenium as potential adjunct therapies for the treatment of coronavirus infections.

Methods

A search of PubMed was performed for articles published from 2005 to 2021. Key words searched were zinc, vitamin A, vitamin D, Sambucus nigra, Allium sativum, Glycyrrhiza glabra, Urtica dioica, N-Acetylcysteine, quercetin, selenium and coronavirus.

Results

There were 47 articles selected for this review. Findings included that vitamin D, zinc, vitamin A, S nigra, A sativum, G glabra, U dioica, N-acetylcysteine, quercetin and selenium have been shown to produce anti-inflammatory, immunostimulatory or antiviral effects that may enhance the actions of standard therapeutics for the treatment of CoV infections. We found only research articles related to the effects of vitamin D, zinc, G glabra, quercetin and selenium against COVID-19.

Conclusion

We identified non-pharmaceutical supplements (Vitamin D, zinc, vitamin A, S nigra, A sativum, G glabra and U dioica) which may have potential to provide support for those with coronavirus infections. However, rigorous clinical studies need to be performed before any clinical recommendations can be made at this time.

Establishment of a Nanopatterned Renal Disease Model by Mimicking the Physical and Chemical Cues of a Diseased Mesangial Cell Microenvironment

Modulation of mesangial cell (MC) response by in vitro disease models offers therapeutic strategies for the treatment of several glomerular diseases. However, traditional cell culture models lack the nanostructured extracellular matrix (ECM), which has unique physical and chemical properties, so they poorly reflect the complexities of the native microenvironment. Therefore, a cell disease model with ECM nanostructures is required to better mimic the in vivo diseased nanoenvironment. To establish a renal disease model, we used a titanium dioxide-based disease-mimic nanopattern as the physical cues and transforming growth factor-beta 1 (TGF-β1) as a chemical cue. The effects of this renal disease model on proliferation and mesangial matrix (MM) component changes in the SV40MES13 (MES13) mouse mesangial cell line were evaluated. Our results showed that both the presence of the disease-mimic nanopattern and TGF-β1 intensified proliferation and resulted in increased type I collagen and fibronectin and decreased type IV collagen expressions in MES13 cells. These effects could be involved in increased TGF-β type I receptor expression in MES13 cells. The intracellular reactive oxygen species (ROS) level as a biomarker of this renal disease model indicated that the cells were in a diseased state. A small molecule A83-01 and known drug dexamethasone markedly attenuated the intracellular ROS production in MES13 that was induced by the disease-mimic nanopattern and TGF-β1. These results highlight the significant effects of physical and chemical cues in facilitating disease-like behavior in MES13 cells, providing an important theoretical basis for developing a drug screening platform for glomerular diseases.

Characterization of TGF-β by Induced Oxidative Stress in Human Trabecular Meshwork Cells

Oxidative stress generated by reactive oxygen species (ROS) plays a critical role in the pathomechanism of glaucoma, which is a multifactorial blinding disease that may cause irreversible damage within human trabecular meshwork cells (HTMCs). It is known that the transforming growth factor-β (TGF-β) signaling pathway is an important component of oxidative stress-induced damage related to extracellular matrix (ECM) fibrosis and activates cell antioxidative mechanisms. To elucidate the dual potential roles and regulatory mechanisms of TGF-β in effects on HTMCs, we established an in vitro oxidative model using hydrogen peroxide (H₂O₂) and further focused on TGF-β-related oxidative stress pathways and the related signal transduction. Via a series of cell functional qualitative analyses to detect related protein level alterations and cell fibrosis status, we illustrated the role of TGF-β1 and TGF-β2 in oxidative stress-induced injury by shTGF-β1 and shTGF-β2 knockdown or added recombinant human TGF-β1 protein (rhTGF-β1). The results of protein level showed that p38 MAPK, TGF-β, and its related SMAD family were activated after H₂O₂ stimulation. Cell functional assays showed that HTMCs with H₂O₂ exposure duration had a more irregular actin architecture compared to normal TM cells. Data with rhTGF-β1 (1 ng/mL) pretreatment reduced the cell apoptosis rate and amount of reactive oxygen species (ROS), while it also enhanced survival. Furthermore, TGF-β1 and TGF-β2 in terms of antioxidant signaling were related to the activation of collagen I and laminin, which are fibrosis-response proteins. Succinctly, our study demonstrated that low concentrations of TGF-β1 (1 ng/mL) preserves HTMCs from free radical-mediated injury by p-p38 MAPK level and p-AKT signaling balance, presenting a signaling transduction mechanism of TGF-β1 in HTMC oxidative stress-related therapies.

PAI-1, the Plasminogen System, and Skeletal Muscle

The plasminogen system is a critical proteolytic system responsible for the remodeling of the extracellular matrix (ECM). The master regulator of the plasminogen system, plasminogen activator inhibitor-1 (PAI-1), has been implicated for its role in exacerbating various disease states not only through the accumulation of ECM (i.e., fibrosis) but also its role in altering cell fate/behaviour. Examination of PAI-1 has extended through various tissues and cell-types with recent investigations showing its presence in skeletal muscle. In skeletal muscle, the role of this protein has been implicated throughout the regeneration process, and in skeletal muscle pathologies (muscular dystrophy, diabetes, and aging-driven pathology). Needless to say, the complete function of this protein in skeletal muscle has yet to be fully elucidated. Given the importance of skeletal muscle in maintaining overall health and quality of life, it is critical to understand the alterations—particularly in PAI-1—that occur to negatively impact this organ. Thus, we provide a comprehensive review of the importance of PAI-1 in skeletal muscle health and function. We aim to shed light on the relevance of this protein in skeletal muscle and propose potential therapeutic approaches to aid in the maintenance of skeletal muscle health.

Angiotensin II Mediates High Glucose-Induced TGF-β1 and Fibronectin Upregulation in HPMC through Reactive Oxygen Species

Objective

To demonstrate the presence of an independent renin–angiotensin system (RAS) in the peritoneum and to determine the role of locally produced angiotensin (Ang) II in high glucose-induced upregulation of transforming growth factor (TGF)-β1 and fibronectin by human peritoneal mesothelial cells (HPMC).

Methods

In cultured HPMC, the expression of mRNAs for angiotensinogen, angiotensin-converting enzyme (ACE), Ang II type 1 receptor (AT1), and TGF-β1 was evaluated by real-time polymerase chain reaction; ACE, AT1, and fibronectin proteins by Western blot analysis; and Ang I, Ang II, and TGF-β1 proteins by ELISA. Dichlorofluorescein (DCF)-sensitive cellular reactive oxygen species (ROS) were measured by fluorometry.

Results

HPMC constitutively expressed all the components of RAS, and 50 mmol/L D-glucose (high glucose) significantly increased angiotensinogen, ACE, and AT1 mRNAs and ACE, AT1, and Ang II proteins. Ang II increased TGF-β1 and fibronectin protein expression and DCF-sensitive cellular ROS. Losartan prevented Ang II-induced increase in cellular ROS. Both losartan and captopril inhibited high glucose-induced upregulation of TGF-β1 and fibronectin expression in HPMC in a dose-dependent manner. Antioxidant catalase and NADPH oxidase inhibitor diphenyleneiodinium effectively inhibited Ang II-induced TGF-β1 and fibronectin protein expression.

Conclusions

The present data demonstrate that HPMC constitutively express RAS, that Ang II produced by HPMC mediates high glucose-induced upregulation of TGF-β1 and fibronectin expression, and that Ang II-induced TGF-β1 and fibronectin expression in HPMC is mediated by NADPH oxidase-dependent ROS. These data suggest that locally produced Ang II and ROS in the peritoneum may be potential therapeutic targets in peritoneal fibrosis during long-term peritoneal dialysis.

Combined treatment with benzo[a]pyrene and 1α,25-dihydroxyvitamin D3 induces expression of plasminogen activator inhibitor 1 in monocyte/macrophage-derived cells

Benzo[a]pyrene (BaP) is an environmental pollutant found in cigarette smoke and is implicated as a causative agent of tobacco-related diseases, such as arteriosclerosis. In contrast, vitamin D signaling, which is principally mediated by conversion of vitamin D to the active form, 1α,25-dihydroxyvitamin D₃ [1,25(OH)₂D₃], decreases cardiovascular disease risk. However, combined treatment with BaP and 1,25(OH)₂D₃ enhances BaP toxicity, including BaP-DNA adduct formation. We further investigated the cross-talk between BaP and 1,25(OH)₂D₃ signaling pathways, and found that combined treatment with these compounds induces mRNA and protein expression of plasminogen activator inhibitor 1 (PAI-1) in monocyte/macrophage-derived THP-1 and U937 cells. Protein synthesis inhibitor treatment did not inhibit induction of the PAI-1 gene (SERPINE1) in these cells. BaP plus 1,25(OH)₂D₃ induced differentiation markers, inhibited cellular proliferation, and induced apoptosis and oxidative stress in these cells. Reactive oxygen species scavenger treatment suppressed apoptosis but not SERPINE1 induction in cells treated with BaP plus 1,25(OH)₂D₃. Thus, combined treatment with BaP and 1,25(OH)₂D₃ induced SERPINE1 mRNA expression in these cells through a mechanism that does not require de novo protein synthesis or reactive oxygen species production. These findings suggest that induction of the proinflammatory factor PAI-1 plays a role in BaP toxicity. Interestingly, PAI-1 knockdown decreased expression of the cell surface antigen CD14, a monocytic differentiation marker, in THP-1 cells treated with BaP plus 1,25(OH)₂D₃. PAI-1 induction may also be related to a function of monocytes/macrophages in response to xenobiotic and vitamin D signaling.

Prdx6 retards senescence and restores trabecular meshwork cell health by regulating reactive oxygen species

A progressive decline in antioxidant potential and accumulation of reactive oxygen species (ROS) are major causes of pathogenesis of several diseases, including glaucoma. Trabecular meshwork (TM) dysfunction resulting in higher intraocular pressure (IOP) is a hallmark of glaucoma, but its causes are unclear. Using human (h) TM cells derived from glaucomatous and normal subjects of different ages and cells facing oxidative-stress, we showed that specific loss of moonlighting antioxidant protein Peroxiredoxin (Prdx) 6 in aging or in glaucomatous TM cells caused ROS accumulation and pathobiological changes in TM cells. Prdx6 limits the levels of ROS, thus preventing overstimulation of genes and resultant deleterious effects. We found that Prdx6 levels declined in aging and were reduced dramatically in glaucomatous and aged TM cells. Biochemical assays revealed enhanced levels of ROS, and high expression/activation of TGFβs and its responsive extracellular matrix genes α-SM, fibronectin, TGase2 and Tsp1 in aged or glaucomatous cells. Furthermore, hTM cells displayed typical features of the combined effects of TGFβs and oxidative-stress-induced cellular changes, showing increased levels of lipid peroxidation, oxidative DNA damage, and senescence markers p16, p21 and SA-βgal activity, along with reduced levels of telomerase expression and activity. Exposure to oxidative-stress (H₂O₂) or knocking down of Prdx6 (with antisense) accelerated this process. Importantly, Prdx6 delivery to sick or aged TM cells reversed the process. We propose Prdx6 as a potential therapeutic target to guard the TM from oxidative-stress and age-dependent accumulation of ROS by balancing redox-homeostasis to prevent ocular disorders, like glaucoma.

Is plasminogen activator inhibitor-1 a physiological bottleneck bridging major depressive disorder and cardiovascular disease?

Major depressive disorder (MDD) is estimated to affect one in twenty people worldwide. MDD is highly comorbid with cardiovascular disease (CVD), itself one of the single largest causes of mortality worldwide. A number of pathological changes observed in MDD are believed to contribute to the development of cardiovascular disease, although no single mechanism has been identified. There are also no biological markers capable of predicting the future risk of developing heart disease in depressed individuals. Plasminogen activator inhibitor-1 (PAI-1) is a prothrombotic plasma protein secreted by endothelial tissue and has long been implicated in CVD. An expanding body of literature has recently implicated it in the pathogenesis of major depressive disorder as well. In this study, we review candidate pathways implicating MDD in CVD and consider how PAI-1 might act as a mediator by which MDD induces CVD development: chiefly through sleep disruption, adiposity, brain-derived neurotrophic factor (BDNF) metabolism, systemic inflammation and hypothalamic-pituitary-adrenal (HPA)-axis dysregulation. As both MDD and CVD are more prevalent in women than in men, and incidence of either condition is dramatically increased during reproductive milestones, we also explore hormonal and sex-specific associations between MDD, PAI-1 and CVD. Of special interest is the role PAI-1 plays in perinatal depression and in cardiovascular complications of pregnancy. Finally, we propose a theoretical model whereby PAI-1 might serve as a useful biomarker for CVD risk in those with depression, and as a potential target for future treatments.

Canonical Transient Receptor Potential 6 Channel: A New Target of Reactive Oxygen Species in Renal Physiology and Pathology

SIGNIFICANCE

Regulation of Ca2+ signaling cascade by reactive oxygen species (ROS) is becoming increasingly evident and this regulation represents a key mechanism for control of many fundamental cellular functions. Canonical transient receptor potential (TRPC) 6, a member of Ca2+-conductive channel in the TRPC family, is widely expressed in kidney cells, including glomerular mesangial cells, podocytes, tubular epithelial cells, and vascular myocytes in renal microvasculature. Both overproduction of ROS and dysfunction of TRPC6 channel are involved in renal injury in animal models and human subjects. Although regulation of TRPC channel function by ROS has been well described in other tissues and cell types, such as vascular smooth muscle, this important cell regulatory mechanism has not been fully reviewed in kidney cells. Recent Advances: Accumulating evidence has shown that TRPC6 is a redox-sensitive channel, and modulation of TRPC6 Ca2+ signaling by altering TRPC6 protein expression or TRPC6 channel activity in kidney cells is a downstream mechanism by which ROS induce renal damage.

CRITICAL ISSUES

This review highlights how recent studies analyzing function and expression of TRPC6 channels in the kidney and their response to ROS improve our mechanistic understanding of oxidative stress-related kidney diseases.

FUTURE DIRECTIONS

Although it is evident that ROS regulate TRPC6-mediated Ca2+ signaling in several types of kidney cells, further study is needed to identify the underlying molecular mechanism. We hope that the newly identified ROS/TRPC6 pathway will pave the way to new, promising therapeutic strategies to target kidney diseases such as diabetic nephropathy. Antioxid. Redox Signal. 25, 732-748.

Carnosic acid attenuates unilateral ureteral obstruction-induced kidney fibrosis via inhibition of Akt-mediated Nox4 expression

Fibrosis represents a common pathway to end-stage renal disease. Transforming growth factor-β (TGF-β) plays a critical role in the progression of kidney fibrosis. In the present study, we explored the effect of carnosic acid (CA) against TGF-β-induced fibroblast activation in vitro and unilateral ureteral obstruction (UUO)-induced kidney fibrosis in vivo. CA attenuated TGF-β-induced up-regulation of profibrogenic proteins, α-smooth muscle actin (α-SMA), collagen I (COLI), fibronectin (FN), and plasminogen activator inhibitor-1 (PAI-1) in kidney fibroblast cells (NRK-49F). CA inhibited TGF-β-induced hydrogen peroxide generation via inhibition of NADPH oxidase 4 (Nox4) expressions. In mice, CA-administration markedly mitigated the UUO-induced interstitial extension, collagen deposition, superoxide anion formation, hydrogen peroxide production, and lipid peroxidation. In addition, CA significantly attenuated the expression of α-SMA, COLI, FN, PAI-1, and Nox4 in UUO-induced kidneys. These results indicated that CA attenuated oxidative stress via inhibition of Nox4 expression in TGF-β-stimulated fibroblasts and UUO operated-kidneys, suggesting that CA may be useful for the treatment of fibrosis-related diseases.

Sinomenine attenuates renal fibrosis through Nrf2-mediated inhibition of oxidative stress and TGFβ signaling

Renal fibrosis is the common feature of chronic kidney disease and mainly mediated by TGFβ-associated pro-fibrogenic signaling, which causes excessive extracellular matrix accumulation and successive loss of kidney functions. Sinomenine (SIN), an alkaloid derived from medicinal herb extensively used in treatment of rheumatoid arthritis and various inflammatory disorders, displays renal protective properties in experimental animals; however its pharmacological potency against renal fibrosis is not explored. In this study we report that SIN possesses strong anti-renal fibrosis functions in kidney cell and in mouse fibrotic kidney. SIN beneficially modulated the pro-fibrogenic protein expression in TGFβ-treated kidney cells and attenuated the renal fibrotic pathogenesis incurred by unilateral ureteral obstruction (UUO), which correlated with its activation of Nrf2 signaling - the key defender against oxidative stress with anti-fibrotic potentials. Further investigation on its regulation of Nrf2 downstream events revealed that SIN significantly balanced oxidative stress via improving the expression and activity of anti-oxidant and detoxifying enzymes, and interrupted the pro-fibrogenic signaling of TGFβ/Smad and Wnt/β-catenin. Even more impressively SIN achieved its anti-fibrotic activities in an Nrf2-dependent manner, suggesting that SIN regulation of Nrf2-associated anti-fibrotic activities constitutes a critical component of SIN's renoprotective functions. Collectively our studies have demonstrated a novel anti-fibrotic property of SIN and its upstream events and provided a molecular basis for SIN's potential applications in treatment of renal fibrosis-associated kidney disorders.

Reciprocal regulation of TGF-β and reactive oxygen species: A perverse cycle for fibrosis

Transforming growth factor beta (TGF-β) is the most potent pro-fibrogenic cytokine and its expression is increased in almost all of fibrotic diseases. Although signaling through Smad pathway is believed to play a central role in TGF-β's fibrogenesis, emerging evidence indicates that reactive oxygen species (ROS) modulate TGF-β's signaling through different pathways including Smad pathway. TGF-β1 increases ROS production and suppresses antioxidant enzymes, leading to a redox imbalance. ROS, in turn, induce/activate TGF-β1 and mediate many of TGF-β's fibrogenic effects, forming a vicious cycle (see graphic flow chart on the right). Here, we review the current knowledge on the feed-forward mechanisms between TGF-β1 and ROS in the development of fibrosis. Therapeutics targeting TGF-β-induced and ROS-dependent cellular signaling represents a novel approach in the treatment of fibrotic disorders.

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TGF-β1 is the most potent ubiquitous profibrogenic cytokine.

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TGF- β 1 induces redox imbalance by ↑ ROS production and ↓ anti-oxidant defense system

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Redox imbalance, in turn, activates latent TGF-β1 and induces TGF-β1 expression.

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Redox imbalance also mediates many of TGF-β1’s profibrogenic effects

Branched-chain amino acids attenuate early kidney injury in diabetic rats

Diabetic nephropathy (DN) is the most severe diabetic microvascular complication. The pathogenesis of diabetic nephropathy is complex, and oxidative stress plays an important role in the development of diabetic nephropathy. Elevated reactive oxygen species (ROS) levels activate various signaling pathways and influence the activities of transforming growth factor-β (TGF-β) and matrix metalloproteinase-9 (MMP-9), which contributes to glomerular hypertrophy. Branched-chain amino acids (BCAAs) are widely used in clinical treatment, and BCAAs can reduce the oxidative stress associated with the diabetic pancreas and some liver diseases. Thus, the aim of the present study was to determine whether BCAAs could attenuate oxidative stress in the kidneys of streptozotocin (STZ)-induced diabetic rats to prevent early diabetic kidney injury. Male Wistar rats were fed for two weeks with a normal chow diet or a high-fat diet in which 40% of calories were derived from fat. After this two-week period, the mice fed normal chow were injected with vehicle, while the high-fat diet group was injected intraperitoneally (i.p.) with 40 mg/kg STZ. The STZ-treated group was randomly divided into four subgroups that were treated with different doses of BCAAs or vehicle for two months by oral gavage. Plasma glucose, plasma creatinine, urinary protein and JNK, TGF-β, and MMP-9 mRNA and protein expression levels were measured in the rats. The ROS levels and proteinuria in the STZ-induced diabetic rats were significantly higher than those in the control groups. Moreover, early kidney injury occurred in the STZ-induced diabetic rats. However, BCAAs treatment decreased ROS levels, proteinuria and kidney injury. Moreover, JNK, TGF-β and MMP-9 mRNA and protein levels were significantly increased in the diabetic rats when compared with the control rats, and BCAAs treatment reversed these changes. Our results suggest that BCAAs counter oxidative stress in the kidneys of diabetic rats and alleviate diabetic kidney injury via the JNK/TGF-β/MMP-9 pathway.

Transforming growth factor β1 (TGF-β1) enhances expression of profibrotic genes through a novel signaling cascade and microRNAs in renal mesangial cells

Increased expression of transforming growth factor-β1 (TGF-β1) in glomerular mesangial cells (MC) augments extracellular matrix accumulation and hypertrophy during the progression of diabetic nephropathy (DN), a debilitating renal complication of diabetes. MicroRNAs (miRNAs) play key roles in the pathogenesis of DN by modulating the actions of TGF-β1 to enhance the expression of profibrotic genes like collagen. In this study, we found a significant decrease in the expression of miR-130b in mouse MC treated with TGF-β1. In parallel, there was a down-regulation in miR-130b host gene 2610318N02RIK (RIK), suggesting host gene-dependent expression of this miRNA. TGF-β receptor 1 (TGF-βR1) was identified as a target of miR-130b. Interestingly, the RIK promoter contains three NF-Y binding sites and was regulated by NF-YC. Furthermore, NF-YC expression was inhibited by TGF-β1, suggesting that a signaling cascade, involving TGF-β1-induced decreases in NF-YC, RIK, and miR-130b, may up-regulate TGF-βR1 to augment expression of TGF-β1 target fibrotic genes. miR-130b was down-regulated, whereas TGF-βR1, as well as the profibrotic genes collagen type IV α 1 (Col4a1), Col12a1, CTGF, and PAI-1 were up-regulated not only in mouse MC treated with TGF-β1 but also in the glomeruli of streptozotocin-injected diabetic mice, supporting in vivo relevance. Together, these results demonstrate a novel miRNA- and host gene-mediated amplifying cascade initiated by TGF-β1 that results in the up-regulation of profibrotic factors, such as TGF-βR1 and collagens associated with the progression of DN.

Oxidative exposure impairs TGF-β pathway via reduction of type II receptor and SMAD3 in human skin fibroblasts

Exposure to oxidants results in cellular alterations that are implicated in aging and age-associated diseases. Here, we report that brief, low-level oxidative exposure leads to long-term elevation of cellular reactive oxygen species (ROS) levels and oxidative damage in human skin fibroblasts. Elevated ROS impairs the transforming growth factor-β (TGF-β) pathway, through reduction of type II TGF-β receptor (TβRII) and SMAD3 protein levels. This impairment results in reduced expression of connective tissue growth factor (CTGF/CCN2) and type I collagen, which are regulated by TGF-β. Restoration of TβRII and SMAD3 together, but not separately, reinstates TGF-β signaling and increases CTGF/CCN2 and type I collagen levels. Treatment with the anti-oxidant N-acetylcysteine reduces ROS elevation and normalizes TGF-β signaling and target gene expression. These data reveal a novel linkage between limited oxidant exposure and altered cellular redox homeostasis that results in impairment of TGF-β signaling. This linkage provides new insights regarding the mechanism by which aberrant redox homeostasis is coupled to decline of collagen production, a hallmark of human skin aging.

Deficiency of growth factor midkine exacerbates necrotizing glomerular injuries in progressive glomerulonephritis

Inflammatory cell infiltration and fibrin deposition play important roles in the development of crescentic glomerulonephritis (GN). In particular, activation of coagulation is an indispensable factor in crescent formation. However, the mechanisms underlying the pathogenesis of crescent formation have not been completely elucidated. We identified the growth factor midkine (MK) as a novel key molecule in the progression of crescentic GN induced by anti-glomerular basement membrane antibody. Despite the lack of significant differences in autologous and heterologous reactions, MK-deficient (Mdk(-/-)) mice unexpectedly showed a greater number of necrotizing glomerular injuries than wild-type (Mdk(+/+)) mice. Likewise, more tubulointerstitial damage was observed in Mdk(-/-) mice, and this damage positively correlated with glomerular injury. Plasminogen activator inhibitor (PAI)-1 was strongly induced in the injured glomerulus of Mdk(-/-) mice, particularly in crescents and endothelial cells. This enhanced PAI-1 production was associated with an increase in inflammatory cell infiltration and matrix deposition in the glomerulus and the interstitium of Mdk(-/-) mice. In line with these in vivo data, primary cultured endothelial cells derived from Mdk(-/-) mice exhibited higher PAI-1 mRNA expression on fibrin challenge and less fibrinolysis than Mdk(+/+) mice. In contrast, the expression of plasminogen activators was not affected. Our combined data suggest that MK leads to a blockade of PAI-1, which is closely associated with the suppression of crescentic GN.

Dimethylfumarate attenuates renal fibrosis via NF-E2-related factor 2-mediated inhibition of transforming growth factor-β/Smad signaling

TGF-β plays a key role in the development of renal fibrosis. Suppressing the TGF-β signaling pathway is a possible therapeutic approach for preventing this disease, and reports have suggested that Nrf2 protects against renal fibrosis by inhibiting TGF-β signaling. This study examines whether dimethylfumarate (DMF), which stimulates Nrf2, prevents renal fibrosis via the Nrf2-mediated suppression of TGF-β signaling. Results showed that DMF increased nuclear levels of Nrf2, and both DMF and adenovirus-mediated overexpression of Nrf2 (Ad-Nrf2) decreased PAI-1, alpha-smooth muscle actin (α-SMA), fibronectin and type 1 collagen expression in TGF-β-treated rat mesangial cells (RMCs) and renal fibroblast cells (NRK-49F). Additionally, DMF and Ad-Nrf2 repressed TGF-β-stimulated Smad3 activity by inhibiting Smad3 phosphorylation, which was restored by siRNA-mediated knockdown of Nrf2 expression. However, downregulation of the antioxidant response element (ARE)-driven Nrf2 target genes such as NQO1, HO-1 and glutathione S-transferase (GST) did not reverse the inhibitory effect of DMF on TGF-β-induced upregulation of profibrotic genes or extracellular matrix proteins, suggesting an ARE-independent anti-fibrotic activity of DMF. Finally, DMF suppressed unilateral ureteral obstruction (UUO)-induced renal fibrosis and α-SMA, fibronectin and type 1 collagen expression in the obstructed kidneys from UUO mice, along with increased and decreased expression of Nrf2 and phospho-Smad3, respectively. In summary, DMF attenuated renal fibrosis via the Nrf2-mediated inhibition of TGF-β/Smad3 signaling in an ARE-independent manner, suggesting that DMF could be used to treat renal fibrosis.

Role of reactive oxygen species in transforming growth factor-beta1-induced extracellular matrix accumulation in renal tubular epithelial cells

Tubulointerstitial fibrosis, which is characterized by the progressive accumulation of extracellular matrix (ECM), is the main feature of chronic renal allograft dysfunction. Transforming growth factor-β1 (TGF-β1) is the key inducer of tubulointerstitial fibrosis. Plasminogen activator inhibitor-1 (PAI-1), a major inhibitor of ECM degradation, is increasingly recognized to play an important role in renal fibrosis. ECM accumulation is the net result of ECM synthesis and degradation. We previously reported that reactive oxygen species (ROS) and subsequent activation of mitogen-activated protein kinase (MAPK) are required for the TGF-β1-induced epithelial-to-mesenchymal transition in renal proximal tubular epithelial cells. In the present study, we examined the role of the ROS-MAPK pathways in TGF-β1-induced fibronectin and PAI-1 up-regulation in renal tubular epithelial cells. Growth arrested, synchronized normal rat kidney epithelial (NRK-52E) cells were stimulated with TGF-β1 (0.2-20 ng/mL) or H(2)O(2) (1-500 μmol/L) in the presence or absence of inhibitors of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (diphenyleneiodonium [DPI] and apocynin [Apo]) and MAPK (PD98059, an MEK inhibitor, or a p38 MAPK inhibitor) for up to 48 hours. Both TGF-β1 and H(2)O(2) increased fibronectin and PAI-1 secretion in dose-dependent manners. Chemical inhibition of NADPH oxidase, extracellular signal-regulated kinase (ERK), or p38 MAPK all inhibited TGF-β1-induced and H(2)O(2)-induced fibronectin and PAI-1 up-regulation. These results suggested that NADPH oxidase-mediated ROS and subsequent ERK and p38 MAPK activation play important roles in ECM accumulation in the renal tubulointerstitium.

Renal protection of in vivo administration of tempol in streptozotocin-induced diabetic rats

The present study was carried out to investigate the protective effects of tempol on renal function and the underlying mechanism in streptozotocin-induced diabetic rats. The diabetic rats were randomly divided into the model group (without tempol) and tempol group (1 mM tempol in drinking water for 6 weeks). Nondiabetic rats were served as the Control group. The mRNA expression of canonical transient receptor potential 6 (TRPC6), transforming growth factor (TGF)-β1, and type IV collagen (Col IV) were examined. The malondialdehyde (MDA) level, activities of superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) in renal tissues were measured to assess redox status in kidneys. We found that tempol significantly reduced 24-h urine output and urine albuminuria excretion in the diabetic rats. Compared with the model group, the concentration of MDA was significantly lower in the tempol group. In addition, diabetes decreased activities of SOD and GSH-Px and these responses were prevented by tempol treatment. Moreover, in diabetic rats, the mRNA expression levels of TGF-β1 and Col IV were upregulated. TRPC6 mRNA expression level was down-regulated in diabetic kidneys. However, all of these diabetic effects were significantly suppressed by tempol treatment. These results suggest that chronic treatment of diabetic rats with tempol can protect kidneys, possibly by reducing expression of TGF-β1, Col IV, and upregulating TRPC6 expression level.

Therapeutic potential and anti-amyloidosis mechanisms of tert-butylhydroquinone for Alzheimer's disease

Alzheimer's disease (AD) is a major cause of dementia in the elderly with no effective treatment. Accumulation of amyloid-β peptide (Aβ) in the brain, one of the pathological features of AD, is considered to be a central disease-causing and disease-promoting event in AD. In this study, we showed that feeding male AβPP/PS1 transgenic mice, a well established mouse model of AD, with a diet containing phenolic antioxidant tert-butylhydroquinone (TBHQ) dramatically reduced brain Aβ load with no significant effect on the amounts of alpha- and beta-C-terminal fragments or full-length AβPP. Further studies showed that TBHQ diet inhibited the expression of plasminogen activator inhibitor-1 (PAI-1), a protease inhibitor which plays a critical role in brain Aβ accumulation in AD, accompanied by increases in the activities of tissue type and urokinase type plasminogen activators (tPA and uPA) as well as plasmin. Moreover, we showed that TBHQ diet increased the expression of low density lipoprotein related protein-1, a multi ligand endocytotic receptor involved in transporting Aβ out of the brain, and plasma Aβ(40) and Aβ(42) levels. We also showed that TBHQ diet increased the concentration of glutathione, an important antioxidant, and suppressed the expression of NADPH oxidase 2 as well as lipid peroxidation. Collectively, our data suggest that TBHQ may have therapeutic potential for AD by increasing brain antioxidant capacity/reducing oxidative stress level and by stimulating Aβ degradation/clearance pathways.

Poly(ADP-ribose) polymerase 1 is indispensable for transforming growth factor-β Induced Smad3 activation in vascular smooth muscle cell

Background

Transforming growth factor type-β (TGF-β)/Smad pathway plays an essential role in vascular fibrosis. Reactive oxygen species (ROS) generation also mediates TGF-β signaling-induced vascular fibrosis, suggesting that some sort of interaction exists between Smad and redox pathways. However, the underlying molecular mechanism is largely unknown. This study aims to investigate the influence of poly(ADP-ribose) polymerase 1 (PARP1), a downstream effector of ROS, on TGF-β signaling transduction through Smad3 pathway in rat vascular smooth muscle cells (VSMCs).

Methods and Results

TGF-β1 treatment promoted PARP1 activation through induction of ROS generation in rat VSMCs. TGF-β1-induced phosphorylation and nuclear accumulation of Smad3 was prevented by treatment of cells with PARP inhibitor, 3-aminobenzamide (3AB) or N-(6-oxo-5,6-dihydrophenanthridin-2-yl)-2-(N,N-dimethylamino)acetami (PJ34), or PARP1 siRNA. TGF-β1 treatment promoted poly(ADP-ribosy)lation of Smad3 via activation of PARP1 in the nucleus. Poly(ADP-ribosy)lation enhanced Smad-Smad binding element (SBE) complex formation in nuclear extracts and increased DNA binding activity of Smad3. Pretreatment with 3AB, PJ34, or PARP1 siRNA prevented TGF-β1-induced Smad3 transactivation and expression of Smad3 target genes, including collagen Iα1, collagen IIIα1 and tissue inhibitor of metalloproteinase 1, in rat VSMCs.

Conclusions

PARP1 is indispensable for TGF-β1 induced Smad3 activation in rat VSMCs. Targeting PARP1 may be a promising therapeutic approach against vascular diseases induced by dysregulation of TGF-β/Smad3 pathway.

Hypertensive nephropathy treatment by heart-protecting musk pill: a study of anti-inflammatory therapy for target organ damage of hypertension

This study was designed to investigate the protective effect of the heart-protecting musk pill (HMP) on inflammatory injury of kidney from spontaneously hypertensive rat (SHR). Male SHRs aged 4 weeks were divided into SHR model group, HMP low-dosage group (13.5 mg/kg), and HMP high-dosage group (40 mg/kg). Age-matched Wistar–Kyoto rats were used as normal control. All rats were killed at 12 weeks of age. Tail-cuff method and enzyme-linked immunosorbent assay were used to determine rat systolic blood pressure and angiotensin II (Ang II) contents, respectively. Renal inflammatory damage was evaluated by the following parameters: protein expressions of inflammatory cytokines, carbonyl protein contents, nitrite concentration, infiltration of monocytes/macrophages in interstitium and glomeruli, kidney pathological changes, and excretion rate of urinary protein. HMP did not prevent the development of hypertension in SHR. However, this Chinese medicinal compound decreased renal Ang II content. Consistent with the change of renal Ang II, all the parameters of renal inflammatory injury were significantly decreased by HMP. This study indicates that HMP is a potent suppressor of renal inflammatory damage in SHR, which may serve as a basis for the advanced preventive and therapeutic investigation of HMP in hypertensive nephropathy.

Rescue of mesangial cells from high glucose-induced over-proliferation and extracellular matrix secretion by hydrogen sulfide

BACKGROUND

Hydrogen sulfide (H(2)S) is considered as the third gasotransmitter after nitric oxide and carbon monoxide. This gas molecule participates in the regulation of renal function. Diabetic nephropathy (DN) is one of the major chronic complications of diabetes. The present study aimed to explore the changes in H(2)S metabolism in the early stage of DN and the effects of H(2)S on cultured rat renal glomerular mesangial cells (MCs).

METHODS

Cultured rat MCs and streptozotocin (STZ)-induced diabetic rats were used in this study. Expression levels of cystathionine γ-lyase (CSE), transforming growth factor-β1 (TGF-β1) and collagen IV in rat renal cortex and in cultured MCs were determined by quantitative real-time PCR and western blot. Reactive oxygen species (ROS) released from rat MCs was assessed by fluorescent probe assays. MCs proliferation was analyzed by 5'-bromo-2'-deoxyuridine incorporation assay.

RESULTS

H(2)S levels in the plasma and renal cortex and the levels of CSE messenger RNA (mRNA) and protein in renal cortex were significantly reduced, while the levels of TGF-β1 and collagen IV increased 3 weeks after STZ injection. Administration of NaHS, a H(2)S donor, reversed the increases in TGF-β1 and collagen IV in diabetic rats. By contrast, NaHS did not alter the TGF-β1 and collagen IV levels in non-diabetic rats. But NaHS lowered the CSE mRNA level in renal cortex. Exposure to high glucose promoted ROS generation and cell proliferation, up-regulated the expression of TGF-β1 and collagen IV but decreased the CSE expression in cultured MCs. Treatment of cultured MCs with NaHS reversed the effect of high glucose. NaHS did not change ROS generation, cell proliferation, TGF-β1 and collagen IV expression in the cells cultured with normal glucose. Reduction of endogenous H(2)S generation by DL-propargylglycine, a CSE inhibitor, produced similar cellular effects as high glucose, including increases in cell proliferation, TGF-β1 and collagen IV expressions and ROS generation.

CONCLUSION

Suppressed CSE-catalyzed endogenous H(2)S production in the kidney by hyperglycemia may play an important role in the pathogenesis of DN.

Plasminogen activator inhibitor-1 antisense oligodeoxynucleotides abrogate mesangial fibronectin accumulation

Excessive extracellular matrix (ECM) accumulation is the main feature of chronic renal disease including diabetic nephropathy. Plasminogen activator inhibitor (PAI)-1 is known to play an important role in renal ECM accumulation in part through suppression of plasmin generation and matrix metalloproteinase (MMP) activation. The present study examined the effect of PAI-1 antisense oligodeoxynucleotide (ODN) on fibronectin upregulation and plasmin/MMP suppression in primary mesangial cells cultured under high glucose (HG) or transforming growth factor (TGF)-β1, major mediators of diabetic renal ECM accumulation. Growth arrested and synchronized rat primary mesangial cells were transfected with 1 µM phosphorothioate-modified antisense or control mis-match ODN for 24 hours with cationic liposome and then stimulated with 30 mM D-glucose or 2 ng/ml TGF-β1. PAI-1 or fibronectin protein was measured by Western blot analysis. Plasmin activity was determined using a synthetic fluorometric plasmin substrate and MMP-2 activity analyzed using zymography. HG and TGF-β1 significantly increased PAI-1 and fibronectin protein expression as well as decreased plasmin and MMP-2 activity. Transient transfection of mesangial cells with PAI-1 antisense ODN, but not mis-match ODN, effectively reversed basal as well as HG- and TGF-β1-induced suppression of plasmin and MMP-2 activity. Both basal and upregulated fibronectin secretion were also inhibited by PAI-1 antisense ODN. These data confirm that PAI-1 plays an important role in ECM accumulation in diabetic mesangium through suppression of protease activity and suggest that PAI-1 antisense ODN would be an effective therapeutic strategy for prevention of renal fibrosis including diabetic nephropathy.

Epithelial-mesenchymal transition of rat peritoneal mesothelial cells via Rhoa/Rock pathway

The objective of this study was to investigate the role of the RhoA/Rock signaling pathway in the epithelial-mesenchymal transition (EMT) of rat peritoneal mesothelial cells (RPMCs). Primary SD rat peritoneal mesothelial cells were cultured in vitro. RPMCs were randomly assigned to four groups: group A (control), group B (TGF-β1, 10 μg/L), group C (10 μg/L TGF-β1 + 10 μmol/L Y-27632, an inhibitor of Rock that was pre-applied for 2 h before TGF-β1 stimulation), and group D (Y-27632 alone, 10 μmol/L). Our results were as follows: (1) TGF-β1 stimulation elicited a robust increase in RhoA activity in a time-dependent manner; the increase was 2.57 ± 0.52 times larger than the activity observed for the control group (P < 0.05) after 10 min of stimulation. RhoA activity peaked at 1 h and was 4.35 ± 0.41 times the value observed for the control group (P < 0.05). (2) TGF-β1 up-regulated mRNA and/or protein expression of α-SMA, vimentin, and collagen and down-regulated mRNA and protein expression of E-cadherin in RPMCs. (3) The Rock inhibitor Y-27632 effectively reduced TGF-β1-induced expression of α-SMA, collagen, and vimentin; the mRNA levels of α-SMA and collagen decreased by 53.8% and 55.7%, respectively, and the protein levels of α-SMA, vimentin, and collagen decreased by 42.6%, 60.1%, and 58.1%, respectively, as compared to TGF-β1-stimulated groups (P < 0.05). However, the Rock inhibitor Y-27632 had no effect on the level of E-cadherin. In conclusion, the RhoA/Rock signaling pathway may mediate EMT induced by TGF-β1 in rat peritoneal mesothelial cells. The RhoA/Rock pathway may be a potential therapeutic target for the treatment of peritoneal fibrosis.

Regulation of plasminogen activator inhibitor-1 expression in endothelial cells with exposure to metal nanoparticles

Recent studies demonstrated that exposure to nanoparticles could enhance the adhesion of endothelial cells and modify the membrane structure of vascular endothelium. The endothelium plays an important role in the regulation of fibrinolysis, and imbalance of the fibrinolysis system potential contributes to the development of thrombosis. Plasminogen activator inhibitor-1 (PAI-1) is the most potent endogenous inhibitor of fibrinolysis and is involved in the pathogenesis of several cardiovascular diseases. The aim of this study was to investigate the alteration of PAI-1 expression in mouse pulmonary microvascular endothelial cells (MPMVEC) exposed to the metal nanoparticles that are known to be reactive, and the potential underlying mechanisms. We compared the alteration of PAI-1 expression in MPMVEC exposed to non-toxic doses of nano-size copper (II) oxide (Nano-CuO) and nano-size titanium dioxide (Nano-TiO(2)). Our results showed that Nano-CuO caused a dose- and time-dependent increase in PAI-1 expression. Moreover, exposure of MPMVEC to Nano-CuO caused reactive oxygen species (ROS) generation that was abolished by pre-treatment of cells with ROS scavengers or inhibitors, DPI, NAC and catalase. Exposure of MPMVEC to Nano-CuO also caused a dose- and time-dependent increase in p38 phosphorylation by Western blot. These effects were significantly attenuated when MPMVEC were pre-treated with DPI, NAC and catalase. To further investigate the role of p38 phosphorylation in Nano-CuO-induced PAI-1 overexpression, the p38 inhibitor, SB203580, was used to pre-treat cells prior to Nano-CuO exposure. We found that Nano-CuO-induced overexpression of PAI-1 was attenuated by p38 inhibitor pre-treatment. However, Nano-TiO(2) did not show the same results. Our results suggest that Nano-CuO caused up-regulation of PAI-1 in endothelial cells is mediated by p38 phosphorylation due to oxidative stress. These findings have important implications for understanding the potential health effects of metal nanoparticle exposure.

Oxidative modification of nuclear mitogen-activated protein kinase phosphatase 1 is involved in transforming growth factor beta1-induced expression of plasminogen activator inhibitor 1 in fibroblasts

Transforming growth factor beta (TGF-beta) stimulates reactive oxygen species (ROS) production in various cell types, which mediates many of the effects of TGF-beta. The molecular mechanisms whereby TGF-beta increases ROS production and ROS modulate the signaling processes of TGF-beta, however, remain poorly defined. In this study, we show that TGF-beta1 stimulates NADPH oxidase 4 (Nox4) expression and ROS generation in the nucleus of murine embryo fibroblasts (NIH3T3 cells). This is associated with an increase in protein thiol modification and inactivation of MAPK phosphatase 1 (MKP-1), a nuclear phosphatase. Furthermore, knockdown of MKP-1 using small interfering RNA enhances TGF-beta1-induced phosphorylation of JNK and p38 as well as the expression of plasminogen activator inhibitor 1 (PAI-1), a TGF-beta-responsive gene involved in the pathogenesis of many diseases. Knockdown of Nox4 with Nox4 small interfering RNA, on the other hand, reduces TGF-beta1-stimulated ROS production, p38 phosphorylation, and PAI-1 expression. TGF-beta also increased the nuclear level of Nox4 protein as well as PAI-1 expression in human lung fibroblasts (CCL-210 cells), suggesting that TGF-beta may induce PAI-1 expression by a similar mechanism in human lung fibroblasts. In summary, in this study we have identified nuclear MAPK phosphatase MKP-1 as a novel molecular target of ROS in TGF-beta signaling pathways. Our data suggest that increased generation of ROS by Nox4 mediates TGF-beta1-induced PAI-1 gene expression at least in part through oxidative modification and inhibition of MKP-1 leading to a sustained activation of JNK and p38 MAPKs.

Involvement of reactive oxygen species in TGF-beta1-induced tropoelastin expression by human dermal fibroblasts

Chronic exposure to solar UV radiation causes marked changes in the dermal extracellular matrix that underlie the loss of resiliency and increased laxity observed in photoaged skin. In particular, the dermal elastin content increases substantially and the normal, well-organized elastic fibers are replaced by amorphous elastotic material. Transforming growth factor-beta1 (TGF-beta1) stimulates synthesis of elastin by dermal fibroblasts and may mediate the increase in elastin in chronically photodamaged skin. We investigated pathways involved in the TGF-beta1-induced increase in tropoelastin (TE), the soluble elastin monomer and assessed the role of reactive oxygen species (ROS) in the regulation of TE mRNA. Antioxidants and an inhibitor of NADPH oxidase blocked TGF-beta1-induced TE mRNA increase even when added 1.5 h after TGF-beta1, although ROS were detected for only 30 min. The TE mRNA increase required activation of Smad4, shown using Smad4 siRNA, and also involved the ERK1/2, p38 and JNK MAP kinases but not PI3K. ROS did not enhance signaling through Smad2 but did enhance activation of p38 and ERK1/2 at 10 min after TGF-beta1. These results indicate that Smad and MAPK pathways mediate TGF-beta1-induced TE expression and that ROS are required for both early signal transduction and later steps that increase elastin.

Inactivation of sestrin 2 induces TGF-beta signaling and partially rescues pulmonary emphysema in a mouse model of COPD

Chronic obstructive pulmonary disease (COPD) is a leading cause of morbidity and mortality worldwide. Cigarette smoking has been identified as one of the major risk factors and several predisposing genetic factors have been implicated in the pathogenesis of COPD, including a single nucleotide polymorphism (SNP) in the latent transforming growth factor (TGF)-beta binding protein 4 (Ltbp4)-encoding gene. Consistent with this finding, mice with a null mutation of the short splice variant of Ltbp4 (Ltbp4S) develop pulmonary emphysema that is reminiscent of COPD. Here, we report that the mutational inactivation of the antioxidant protein sestrin 2 (sesn2) partially rescues the emphysema phenotype of Ltbp4S mice and is associated with activation of the TGF-beta and mammalian target of rapamycin (mTOR) signal transduction pathways. The results suggest that sesn2 could be clinically relevant to patients with COPD who might benefit from antagonists of sestrin function.

Oxidative stress and glutathione in TGF-beta-mediated fibrogenesis

Transforming growth factor beta (TGF-beta) is the most potent and ubiquitous profibrogenic cytokine, and its expression is increased in almost all the fibrotic diseases and in experimental fibrosis models. TGF-beta increases reactive oxygen species production and decreases the concentration of glutathione (GSH), the most abundant intracellular free thiol and an important antioxidant, which mediates many of the fibrogenic effects of TGF-beta in various types of cells. A decreased GSH concentration is also observed in human fibrotic diseases and in experimental fibrosis models. Although the biological significance of GSH depletion in the development of fibrosis remains obscure, GSH and N-acetylcysteine, a precursor of GSH, have been used in clinics for the treatment of fibrotic diseases. This review summarizes recent findings in the field to address the potential mechanism whereby oxidative stress mediates fibrogenesis induced by TGF-beta and the potential therapeutic value of antioxidant treatment in fibrotic diseases.

Oral hydrogen water prevents chronic allograft nephropathy in rats

Reactive oxygen species (ROS) contribute to the development of interstitial fibrosis and tubular atrophy seen in chronic allograft nephropathy (CAN). As molecular hydrogen gas can act as a scavenger of ROS, we tested the effect of treatment with hydrogen water (HW) in a model of kidney transplantation, in which allografts from Lewis rats were orthotopically transplanted into Brown Norway recipients that had undergone bilateral nephrectomy. Molecular hydrogen was dissolved in water and recipients were given HW from day 0 until day 150. Rats that were treated with regular water (RW) gradually developed proteinuria and their creatinine clearance declined, ultimately leading to graft failure secondary to CAN. In contrast, treatment with HW improved allograft function, slowed the progression of CAN, reduced oxidant injury and inflammatory mediator production, and improved overall survival. Inflammatory signaling pathways, such as mitogen-activated protein kinases, were less activated in renal allografts from HW-treated rats as compared with RW-treated rats. Hence, oral HW is an effective antioxidant and antiinflammatory agent that prevented CAN, improved survival of rat renal allografts, and may be of therapeutic value in the setting of transplantation.

Expression and activity of phosphodiesterase isoforms during epithelial mesenchymal transition: the role of phosphodiesterase 4

Epithelial-mesenchymal transition (EMT) has emerged as a critical event in the pathogenesis of organ fibrosis and cancer and is typically induced by the multifunctional cytokine transforming growth factor (TGF)-beta1. The present study was undertaken to evaluate the potential role of phosphodiesterases (PDEs) in TGF-beta1-induced EMT in the human alveolar epithelial type II cell line A549. Stimulation of A549 with TGF-beta1 induced EMT by morphological alterations and by expression changes of the epithelial phenotype markers E-cadherin, cytokeratin-18, zona occludens-1, and the mesenchymal phenotype markers, collagen I, fibronectin, and alpha-smooth muscle actin. Interestingly, TGF-beta1 stimulation caused twofold increase in total cAMP-PDE activity, contributed mostly by PDE4. Furthermore, mRNA and protein expression demonstrated up-regulation of PDE4A and PDE4D isoforms in TGF-beta1-stimulated cells. Most importantly, treatment of TGF-beta1 stimulated epithelial cells with the PDE4-selective inhibitor rolipram or PDE4 small interfering RNA potently inhibited EMT changes in a Smad-independent manner by decreasing reactive oxygen species, p38, and extracellular signal-regulated kinase phosphorylation. In contrast, the ectopic overexpression of PDE4A and/or PDE4D resulted in a significant loss of epithelial marker E-cadherin but did not result in changes of mesenchymal markers. In addition, Rho kinase signaling activated by TGF-beta1 during EMT demonstrated to be a positive regulator of PDE4. Collectively, the findings presented herein suggest that TGF-beta1 mediated up-regulation of PDE4 promotes EMT in alveolar epithelial cells. Thus, targeting PDE4 isoforms may be a novel approach to attenuate EMT-associated lung diseases such as pulmonary fibrosis and lung cancer.

Tempol or candesartan prevents high-fat diet-induced hypertension and renal damage in spontaneously hypertensive rats

BACKGROUND

Obesity has been strongly associated with the development and aggravation of hypertension and chronic kidney disease. To date, the systemic renin-angiotensin system (RAS) has been known to involve in obesity-induced tissue damage and hypertension. However, the intrarenal mechanism whereby obesity induces and aggravates hypertension and renal disease remains poorly understood. Therefore, we investigated the role of intrarenal RAS and oxidative stress in diet-induced hypertension and renal inflammation in spontaneously hypertensive rats (SHR) fed a high-fat diet.

METHODS

Male SHR and Wistar-Kyoto rats (WKY) were divided into eight groups: normal-fat diet-fed WKY (WKY-NF), high-fat diet-fed WKY (WKY-HF), high-fat diet-fed tempol-treated WKY (WKY-HF/T), high-fat diet-fed candesartan-treated WKY (WKY-HF/C), normal-fat diet-fed SHR (SHR-NF), high-fat diet-fed SHR (SHR-HF), high-fat diet-fed tempol-treated SHR (SHR-HF/T) and high-fat diet-fed candesartan-treated SHR (SHR-HF/C). After 12 weeks of treatment, haemodynamic measurements and histological assessment of the kidney were performed.

RESULTS

At the end of week 12, the high-fat fed SHR gained more body weight, their systolic blood pressure was further elevated and glucose intolerance induced. There was no significant difference in the insulin resistance index, serum lipid profile, plasma renin activity and serum aldosterone levels according to diet. However, the high-fat diet resulted in increases in immunohistochemical stains of renin and angiotensin II in the kidney. The real-time PCR also demonstrated significant increases in mRNA levels of renin, angiotensinogen and angiotensin-converting enzyme in the kidney, reflecting enhanced activation of the intrarenal RAS, which findings were also shown by Western blot analysis for renin and angiotensin II type 1 receptor. The expression of ED-1, osteopontin and TGF-beta1 in the renal cortex were prominently enhanced in the SHR-HF group with the increased intrarenal lipid concentrations and oxidative stress. Administration of tempol or candesartan in the high-fat diet-induced SHR inhibited the elevation of the systolic blood pressure, intrarenal lipid concentrations, oxidative stress and the degree of renal inflammation to the levels of, or more than, the SHR-NF with no differences in the body weight and periepididymal fat weight, compared to those in the SHR-HF group without such treatment.

CONCLUSIONS

Our study suggests that a high-fat diet induces fatty kidneys, aggravation of blood pressure and renal inflammation in the SHR. Blockade of oxidative stress by tempol or of RAS by candesartan ameliorates the increase in blood pressure and renal inflammation and improves intrarenal lipid accumulation. Therefore, antioxidants or angiotensin receptor blockers can prevent diet-induced hypertension and renal inflammation in hypertensive rats.

The role of plasminogen activator inhibitor 1 in renal and cardiovascular diseases

The 50 kDa glycoprotein plasminogen activator inhibitor 1 (PAI-1) is the major physiological inhibitor of tissue-type and urokinase-type plasminogen activator. These two molecules convert inactive plasminogen into its fibrin-degrading form, plasmin. Plasma and tissue concentrations of PAI-1 are extremely low under normal circumstances but increase under pathologic conditions. This increase is mediated by many factors, including reactive oxygen species. Increased PAI-1 activity is associated with an increased risk of ischemic cardiovascular events and tissue fibrosis. Whereas the antifibrinolytic property of PAI-1 derives mainly from its inhibition of serine proteases, its profibrotic actions seem to derive from a capacity to stimulate interstitial macrophage recruitment and increase transcription of profibrotic genes, as well as from inhibition of serine proteases. Despite studies in mice that lack or overexpress PAI-1, the biological effects of this molecule in humans remain incompletely understood because of the complexity of the PAI-1-plasminogen-activator-plasmin system. The cardioprotective and renoprotective properties of some currently available drugs might be attributable in part to inhibition of PAI-1. The development of an orally active, high-affinity PAI-1 inhibitor will provide a potentially important pharmacological tool for further investigation of the role of PAI-1 and might offer a novel therapeutic strategy in renal and cardiovascular diseases.

Alveolar oxidative stress is associated with elevated levels of nonenzymatic low-molecular-weight antioxidants in patients with different forms of chronic fibrosing interstitial lung diseases

Increasing evidence indicates that disequilibrium of the alveolar oxidant-antioxidant balance may play a role in the pathogenesis of chronic fibrosing lung diseases. Excessive production of oxidants and a differential regulation of antioxidant enzymes have been described under these conditions. We characterized for the first time numerous nonenzymatic low-molecular-weight antioxidants in bronchoalveolar lavage fluids from patients with different forms of lung fibrosis initiated either by injury to the alveolar epithelium (idiopathic pulmonary fibrosis, IPF) or by inflammation (chronic sarcoidosis/hypersensitivity pneumonitis). Footprints of oxidative stress accompanied by an increase in the majority of antioxidants assessed were observed in all patient groups: elevated levels of uric acid, ascorbic acid, retinol, and alpha-tocopherol were noted, whereas glutathione levels were unchanged. The expression of Nrf2, an important redox-sensitive transcriptional regulator of antioxidants, was increased in IPF lungs. Our findings were corroborated in the bleomycin model of lung fibrosis where--aside from uric acid--nonenzymatic antioxidants were elevated during the fibrotic phase. In conclusion, alveolar levels of nonenzymatic antioxidants are elevated in fibrosing lung diseases, but are incapable of restoring oxidative balance. This increase may be part of an adaptive response to oxidative stress. However, a leakage from the blood may also contribute to our findings.

Hypoxia/reoxygenation induces CTGF and PAI-1 in cultured human retinal pigment epithelium cells

Early age-related macular degeneration (AMD) is characterized by thickening of Bruch's membrane due to the accumulation of extracellular matrix (ECM). This finding could be related to hypoxia of the retinal pigment epithelium (RPE). In the present study, we investigated the effects of hypoxia and reoxygenation on the expression of connective tissue growth factor (CTGF), plasminogen activator inhibitor-1 (PAI-1), collagen type IV (Col IV) and fibronectin (Fn) in cultured human RPE cells. Cultured human RPE cells were kept for 12-36h under hypoxic conditions (1% O(2)). Reoxygenation was conducted for 24h. Hypoxia-mediated CTGF and PAI-1 expression were analyzed by using immunohistochemistry, Northern and Western blot analysis. Actinomycin D was added to examine whether hypoxia induces the transcription of CTGF and PAI-1 mRNA. Furthermore, cells were transfected with siRNA against hypoxia-inducible factor-1alpha (HIF-1alpha) and kept under hypoxic conditions. The effects of antioxidants on hypoxia/reoxygenation-mediated CTGF and PAI-1 expression were tested by real-time PCR analysis. Production of Col IV and Fn were investigated by real-time PCR and Western blot analysis. Both hypoxia and hypoxia/reoxygenation increased the expression of CTGF, PAI-1, Col IV and Fn. Actinomycin D prevented the new transcription of CTGF and PAI-1 mRNA by hypoxia. Using siRNA against HIF-1alpha, the hypoxia-mediated increase of CTGF and PAI-1 was inhibited. Antioxidants attenuated the reoxygenation-mediated increase of CTGF and PAI-1. The process of hypoxia/reoxygenation in the RPE may lead to an increase of ECM in the RPE and thus may contribute to the accumulation of ECM in Bruch's membrane.

Role of reactive oxygen species in the pathogenesis of diabetic nephropathy

There is an increasing evidence that reactive oxygen species (ROS) play a major role in the development of diabetic complications. Oxidative stress is increased in diabetes and the overproduction of ROS in diabetes is a direct consequence of hyperglycemia. Various types of vascular cells including renal cells are able to produce ROS under hyperglycemic condition. Both NADPH oxidase and mitochondrial electron gradient play roles in hyperglycemia-induced ROS generation. In addition to their ability to directly inflict macromolecular damage, ROS can function as signaling molecules. ROS mediate hyperglycemia-induced activation of signal transduction cascades and transcription factors leading to transcriptional activation of profibrotic genes in the kidney. Furthermore, ROS-activated signaling molecules generate and signal through ROS and thus ROS act as a signal amplifier. Intensive glycemic control and inhibition of angiotensin II delay the onset and progression of diabetic nephropathy, in part, through prevention of overproduction of ROS. Conventional and catalytic antioxidants have been shown to prevent or delay the onset of diabetic nephropathy. Combination of strategies to prevent overproduction of ROS and to increase the removal of preformed ROS may prove to be effective in preventing the development and progression of diabetic nephropathy.

Oxidative and nitrosative stress and fibrogenic response

Uncontrolled production of collagen I is the main feature of liver fibrosis. Following a fibrogenic stimulus such as alcohol, hepatic stellate cells (HSC) transform into an activated collagen-producing cell. In alcoholic liver disease, numerous changes in gene expression are associated with HSC activation, including the induction of several intracellular signaling cascades, which help maintain the activated phenotype and control the fibrogenic and proliferative state of the cell. Detailed analyses for understanding the molecular basis of the collagen I gene regulation have revealed a complex process involving reactive oxygen species (ROS) as key mediators. Less is known, however, about the contribution of reactive nitrogen species (RNS). In addition, a series of cytokines, growth factors, and chemokines, which activate extracellular matrix (ECM)-producing cells through paracrine and autocrine loops, contribute to the fibrogenic response.

NOX enzymes and diabetic complications

Several molecular mechanisms have been identified that mediate the tissue-damaging effects of hyperglycemia. These are increased flux through the polyol and hexosamine pathways, increased formation of advanced glycation end products, activation of protein kinase C, and augmented generation of reactive oxygen species (ROS). Increased production of ROS not only causes cellular damage but also activates the signal transduction cascade that activates specific target genes. Based on recent experimental data, it is now accepted that increased NADPH oxidase activity in tissues vulnerable to hyperglycemia takes place downstream of the advanced glycation end products and protein kinase C pathways, two of the primary mechanisms involved in the pathogenesis of diabetic complications. Thus, compounds that suppress NADPH oxidase activity may offer therapeutic benefits to ameliorate diabetic complications, highlighting the significance of NADPH oxidase as a new therapeutic target.