Astaxanthin ameliorates experimental diabetes-induced renal oxidative stress and fibronectin by upregulating connexin43 in glomerular mesangial cells and diabetic mice
Oxidative stress is the major cause of renal fibrosis in the progression of DN. Connexin43 (Cx43) exerts an anti-fibrosis effect on diabetic kidneys. The current study aimed to investigate whether astaxanthin (AST) could ameliorate the pathological progression of DN by upregulating Cx43 and activating the Nrf2/ARE signaling, which is a pivotal anti-oxidative stress system, to strengthen the cellular anti-oxidative capacity and diminish fibronectin (FN) accumulation in HG-induced glomerular mesangial cells (GMCs). Our hypothesis was verified in GMCs and the kidneys from db/db mice by western blot, immunofluorescence, immunohistochemistry, immunoprecipitation, dual luciferase reporter assay and reactive oxygen related detection kits. Results showed that AST simultaneously upregulated the Cx43 protein level and promoted the Nrf2/ARE signaling activity in the kidney of db/db mice and HG-treated GMCs. However, Cx43 depletion abrogated the Nrf2/ARE signaling activation induced by AST. AST reduced the interaction between c-Src and Nrf2 in the nuclei of GMCs cultured with HG, thereby enhancing the Nrf2 accumulation in the nuclei of GMCs. Our data suggested that AST promoted the Nrf2/ARE signaling by upregulating the Cx43 protein level to prevent renal fibrosis triggered by HG in GMCs and db/db mice. c-Src acted as a mediator in these processes.
Sinapic acid ameliorates bleomycin-induced lung fibrosis in rats
Pulmonary fibrosis is a multifaceted disease with high mortality and morbidity, and it is commonly nonresponsive to conventional therapy.
PPARγ maintains the metabolic heterogeneity and homeostasis of renal tubules
The renal tubules, which have distant metabolic features and functions in different segments, reabsorb >99% of approximately 180 l of water and 25,000 mmol of Na daily. Defective metabolism in renal tubules is involved in the pathobiology of kidney diseases. However, the mechanisms underlying the metabolic regulation in renal tubules remain to be defined.
Interleukin-18 binding protein attenuates lipopolysaccharide-induced acute lung injury in mice via suppression NF-κB and activation Nrf2 pathway
Interleukin (IL)-18 belongs to a rather large IL-1 gene family and is a proinflammatory cytokine. IL-18 plays important roles in lung injury. IL-18 binding protein (IL-18BP), a natural antagonist of IL-18, binds IL-18 with high affinity. IL-18BP is able to neutralize IL-18 biological activity and has a protective effect against renal fibrosis. The aim of this study was to evaluate the potential protective effect of IL-18BP on lipopolysaccharide (LPS)-induced acute lung injury (ALI) in mice and to illuminate the underlying mechanisms. Results indicated that pretreatment with IL-18BP significantly attenuated LPS-induced pulmonary pathological injury. Meanwhile, IL-18BP pretreatment markedly inhibited infiltration of inflammatory cell and release of inflammatory factor in ALI mice in vivo and in primary macrophages after LPS insult in vitro. IL-18BP treatment dramatically reduced oxidative stress through increasing superoxide dismutase (SOD) and glutathione (GSH) contents, and decreasing the levels of malondialdehyde (MDA) and reactive oxygen species (ROS) in LPS-induced ALI mice and primary macrophages. Additionally, IL-18BP was also observed to markedly decreased the activation of nuclear factor-kappa B (NF-κB) and upregulated the nuclear factor erythroid 2-related factor 2 (Nrf2). Taken together, IL-18BP possessed protective effect against LPS-induced ALI, which might be associated with its regulation of NF-κB and Nrf2 activities. The results rendered IL-18BP worthy of further development into a pharmaceutical drug for the treatment of ALI.
Genistein attenuates renal fibrosis in streptozotocin‑induced diabetic rats
The present study aimed to investigate the antifibrogenic effects of genistein (GEN) on the kidney in streptozotocin (STZ)‑induced diabetic rats and to determine the associated mechanisms. Rats were randomized into four groups: Normal control (N), STZ (S), L (STZ + low‑dose GEN) and H (STZ + high‑dose GEN). After 8 weeks, the fasting blood glucose (FBG) level, the ratio of kidney weight to body weight (renal index), 24‑h urine protein, blood urea nitrogen (BUN), serum creatinine (SCr), renal total antioxidant capacity (T‑AOC), superoxide dismutase (SOD), lipid peroxidation (LPO), malondialdehyde (MDA) and hydroxyproline (Hyp) contents were measured. The histomorphology and ultrastructure of the kidney were also assessed. In addition, mRNA expression levels of transforming growth factor‑β1 (TGF‑β1) and protein expression levels of nuclear factor erythroid 2‑related factor 2 (Nrf2), heme oxygenase‑1 (HO‑1), NAD(P)H:quinone oxidoreductase 1 (NQO1), TGF‑β1, mothers against decapentaplegic homolog 3 (Smad3), phosphorylated (p)‑Smad3 and collagen IV were estimated. Compared with group N, the levels of FBG, renal index, 24‑h urine protein, BUN, SCr, LPO, MDA and Hyp were increased, whereas the levels of T‑AOC and SOD were decreased in group S. The structure of renal tissue was damaged, and the expression of Nrf2, HO‑1 and NQO1 were reduced, whereas the expression of TGF‑β1, Smad3, p‑Smad3 and collagen IV were increased in group S. Compared with group S, the aforementioned indices were improved in groups L and H. In conclusion, GEN exhibited reno‑protective effects in diabetic rats and its mechanisms may be associated with the inhibition of oxidative stress by activating the Nrf2‑HO‑1/NQO1 pathway, and the alleviation of renal fibrosis by suppressing the TGF‑β1/Smad3 pathway.
LncRNA ENST00000453774.1 contributes to oxidative stress defense dependent on autophagy mediation to reduce extracellular matrix and alleviate renal fibrosis
Although long noncoding RNA (LncRNA) are important players in the initiation and progression of many pathological processes, the role of LncRNAENST00000453774.1 (LncRNA 74.1) in renal fibrosis still remains unclear. Lentivirus mediated LncRNA 74.1 overexpressing HK2 cells and overexpression mice models were constructed. HK2 cells induced by transforming growth factor-β (TGF-β) in vitro, and the mice UUO model in vivo were used to simulate renal fibrosis. The expression of LncRNA 74.1 was significantly downregulated in the TGF-β-induced HK-2 cell fibrosis and clinical renal fibrosis specimens. LncRNA 74.1 overexpression obviously attenuated renal fibrosis in vitro and unilateral ureteral obstruction-induced renal fibrosis in vivo. LncRNA 74.1 promoted reactive oxygen species defense by activating prosurvival autophagy then decreased ECM-related proteins fibronectin and collagen I involved in renal fibrosis. We also found that Nrf2-keap1 signaling played important roles in the remission of ECM mediated by LncRNA 74.1. This study indicates that LncRNA 74.1 downregulation would contribute to renal fibrosis and its overexpression might represent a novel anti-fibrotic treatment in renal diseases.
Thalidomide (THD) alleviates radiation induced lung fibrosis (RILF) via down-regulation of TGF-β/Smad3 signaling pathway in an Nrf2-dependent manner
Radiation-induced lung fibrosis (RILF) is a complication of radiotherapy in thoracic cancer patients. Thalidomide (THD) has a therapeutic effect on fibrotic and inflammatory disorders. The purpose of the current study was to investigate the therapeutic effect of THD on RILF in mice and better understand the underlying regulatory mechanisms of the therapeutic effect. We found that THD mitigated the fibrosis caused by irradiation in mice. The action of THD on RILF was related to the elevation of low levels reactive oxygen species (ROS), which inhibited the transforming growth factor‑β (TGF‑β)/Smad3 signaling pathway through activation of nuclear factor (erythroid-derived 2)-like 2 (Nrf2). Analysis of the therapeutic effect of THD using Nrf2-/- mouse model confirmed the role of Nrf2 in vivo. In addition, no radioprotective effect of THD on thoracic cancer cell lines was observed. In conclusion, these data showed that THD attenuated RILF in mice, which was mediated by Nrf2-dependent down-regulation of the TGF-β/Smad3 pathway, suggesting THD as a potential novel agent for RILF prevention.
Diabetic cardiomyopathy: molecular mechanisms, detrimental effects of conventional treatment, and beneficial effects of natural therapy
Diabetic complications are among the largely exigent health problems currently. Cardiovascular complications, including diabetic cardiomyopathy (DCM), account for more than 80% of diabetic deaths. Investigators are exploring new therapeutic targets to slow or abate diabetes because of the growing occurrence and augmented risk of deaths due to its complications. Research on rodent models of type 1 and type 2 diabetes mellitus, and the use of genetic engineering techniques in mice and rats have significantly sophisticated for our understanding of the molecular mechanisms in human DCM. DCM is featured by pathophysiological mechanisms that are hyperglycemia, insulin resistance, oxidative stress, left ventricular hypertrophy, damaged left ventricular systolic and diastolic functions, myocardial fibrosis, endothelial dysfunction, myocyte cell death, autophagy, and endoplasmic reticulum stress. A number of molecular and cellular pathways, such as cardiac ubiquitin proteasome system, FoxO transcription factors, hexosamine biosynthetic pathway, polyol pathway, protein kinase C signaling, NF-κB signaling, peroxisome proliferator-activated receptor signaling, Nrf2 pathway, mitogen-activated protein kinase pathway, and micro RNAs, play a major role in DCM. Currently, there are a few drugs for the management of DCM and some of them have considerable adverse effects. So, researchers are focusing on the natural products to ameliorate it. Hence, in this review, we discuss the pathogical, molecular, and cellular mechanisms of DCM; the current diagnostic methods and treatments; adverse effects of conventional treatment; and beneficial effects of natural product-based therapeutics, which may pave the way to new treatment strategies. Graphical Abstract.
Impaired Endothelial Autophagy Promotes Liver Fibrosis By Aggravating The Oxidative Stress Response During Acute Liver Injury
Endothelial dysfunction plays an essential role in initiation and progression of liver injury, yet phenotypic regulation of liver endothelial cells remains unknown. Autophagy is an endogenous protective system whose loss could undermine LSEC integrity and phenotype. The aim of our study was to investigate the role of autophagy in the regulation of endothelial dysfunction and the impact of its manipulation during liver injury.
Downregulation of HMGB1 is required for the protective role of Nrf2 in EMT-mediated PF
Epithelial-mesenchymal transition (EMT) is considered to be the key event in the formation of pulmonary fibrosis (PF). High-mobility group box 1 (HMGB1) is a novel mediator of EMT. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a critical transcription factor for protecting against PF. However, it is unknown the relationship between Nrf2 and HMGB1 in EMT-mediated PF. Bleomycin (BLM)-induced PF in Nrf2-knockout (Nrf2 ) and wild-type (WT) mice and transforming growth factor β1 (TGF-β1)-induced EMT in rat type II alveolar epithelial cell line (RLE-6TN) and human alveolar epithelial cell line (A549) were established to observe the relationship among Nrf2, HMGB1, and EMT by western blot and immunohistochemistry. BLM-induced EMT was more severe and the expression of HMGB1 was more increased in Nrf2 mice compared with WT mice. In vitro, Nrf2 activation attenuated TGF-β1-induced EMT and ROS production accompanied by the downregulation of HMGB1. In contrast, silencing Nrf2 enhanced TGF-β1-induced EMT and ROS production along with increased the protein expression and the release of HMGB1. Moreover, HMGB1 activation aggravated TGF-β1-induced EMT and HMGB1 deficiency alleviated TGF-β1-induced EMT. Furthermore, HMGB1 silence attenuated the protective effect of Nrf2 on EMT. These findings suggest downregulation of HMGB1, which is required for the protective role of Nrf2 in EMT-mediated PF and provide an important therapeutic target for PF.
Reduction of renal tubular injury with a RAGE inhibitor FPS-ZM1, valsartan and their combination in streptozotocin-induced diabetes in the rat
Receptor for advanced glycation end-products (RAGE) is involved in the pathogenesis of diabetic nephropathy. FPS-ZM1, a selective RAGE inhibitor, in combination with valsartan were investigated for their protective potentials on the renal markers of tubular injury in streptozotocin-induced diabetic rats. Rats were assigned into groups of receiving FPS-ZM1 (1 mg/kg/day), valsartan (100 mg/kg/day), and FPS-ZM1 plus valsartan (1 mg/kg/day and 100 mg/kg/day, respectively) for one month. Kidney histology, renal inflammation and oxidative stress, and renal and urinary markers of tubular injury were investigated. FPS-ZM1 and valsartan in combination more significantly attenuated renal expressions of tumor necrosis factor-alpha and interleukin-6 genes and reduced urinary levels of interleukin-6. Moreover, the combination elevated renal NAD/NADH ratios and Sirt1 activities, and mitigated nuclear acetylated NF-κB p65 levels. In addition to alleviating indices of oxidative stress i.e. malondialdehyde, superoxide dismutase and glutathione peroxidase, the combination of FPS-ZM1 and valsartan more effectively upregulated the renal levels of master antioxidant proteins Nrf2, heme oxygenase-1, and NAD(P)H:quinone oxidoreductase-1. Additionally, this dual therapy ameliorated more efficiently the indices of renal tubular injuries as indicated by decreased renal kidney injury molecule-1 levels as well as reduced urinary levels of cystatin C, retinol binding protein, and beta-2-microglobulin. While FPS-ZM1 alone had no appreciable effects on the renal fibrosis, the combination treatment ameliorated fibrosis better than valsartan in the kidneys. Collectively, these findings underline the extra benefits of FPS-ZM1 and valsartan dual administrations in obviating the renal tubular cell injury in streptozotocin-induced diabetic rats partly by suppressing renal inflammation and oxidative stress.
Stevia rebaudiana tea prevents experimental cirrhosis via regulation of NF-κB, Nrf2, transforming growth factor beta, Smad7, and hepatic stellate cell activation
Ziziphus spina-christi leaf extract ameliorates schistosomiasis liver granuloma, fibrosis, and oxidative stress through downregulation of fibrinogenic signaling in mice
Schistosomiasis is a widespread parasitic infection that affects humans, as well as wild and domestic animals. It ranks second after malaria, with a significant health and socio-economic impact in the developing countries. The objective of this study was to assess the anti-schistosomal impact of Ziziphus spina-christi leaf extract (ZLE) on Schistosoma mansoni-induced liver fibrosis in CD-1 Swiss male albino mice. S. mansoni infection was achieved by dipping of mouse tails in schistosomal cercariae. ZLE treatment was initiated at 46 days post-infection by administering a dose of the extract on a daily basis for 10 consecutive days. S. mansoni infection resulted in liver granuloma and fibrosis, with a drastic elevation in liver function factors, nitric oxide, and lipid peroxidation, which were associated with a reduction in glutathione content and substantial inhibition of antioxidant enzyme activities compared to those of the control. Induction of hepatic granuloma, oxidative stress, and fibrosis in the liver was controlled by ZLE administration, which also produced inhibition of matrix metalloproteinase-9, alpha-smooth muscle actin, transforming growth factor-β, and tissue inhibitors of metalloproteinases expressions. In addition, the S. mansoni-infected group exhibited an increase in Bax and caspase-3 levels and a decrease in Bcl-2 level. However, treatment with ZLE mainly mitigated apoptosis in the liver. Thus, the findings of this study revealed that Ziziphus spina-christi had anti-apoptotic, anti-fibrotic, antioxidant, and protective effects on S. mansoni-induced liver wounds. The benefits of Ziziphus spina-christi extract on S. mansoni were partly partially mediated by enhancing anti-fibrinogenic and nuclear factor erythroid 2-related factor 2 (Nrf2) pathways.
CB1 receptor blockade ameliorates hepatic fat infiltration and inflammation and increases Nrf2-AMPK pathway in a rat model of severely uncontrolled diabetes
Previous studies have shown that the CB1 receptor antagonist reverses steatohepatitis and its related features of metabolic syndrome, such as obesity and type 2 diabetes. However, the beneficial effects of CB1 receptor blockade on hepatic steatosis and inflammation have not been investigated independently of its effects on body weight and glycemic control. At 32 weeks of age, OLETF rats were administered with rimonabant (10 mg·kg-1·day-1) by oral gavage for 6 weeks. No significant changes in body weight, OGTT, and serum glucose were observed in spite of rimonabant-decreased food intake. Moreover, there was a significant difference between initial and final body weight, regardless of rimonabant administration, indicating that OLETF rats were severely diabetic rats. Rimonabant administration significantly decreased serum liver enzyme levels such as ALT and AST, hepatic fat accumulation, lipid peroxidation, and cell death as demonstrated by the number of TUNEL-positive cells in severely uncontrolled diabetic OLETF rats. Significant decreases in hepatic gene expression of proinflammatory cytokines (CD11b, F4/80, MCP1, and TNFα), negative inflammatory mediators (SOCS1 and SOCS3), and fibrosis-related proteins (TGFβ, collagen 1, and TIMP1) were found in rimonabant-treated OLETF rats. Six-week administration of rimonabant significantly upregulated mRNA levels of CPT1α and PPARα related to β-oxidation. Moreover, significant increases in Nrf2 gene expression and its downstream genes, NQO1, GSAT, HO-1, and TXNRD1 along with increased AMPK phosphorylation were noted in uncontrolled diabetic rats treated with rimonabant. The observed potent inhibitory effects of CB1 receptor blockade on hepatic fat infiltration and cellular death in severely uncontrolled diabetic rats indicate that CB1 receptor is a possible therapeutic target. Increased Nrf2 and AMPK phosphorylation may play a role in the mechanism of rimonabant action.
Inhibitory Effects of Momordicine I on High-Glucose-Induced Cell Proliferation and Collagen Synthesis in Rat Cardiac Fibroblasts
Diabetes-associated cardiac fibrosis is a severe cardiovascular complication. Momordicine I, a bioactive triterpenoid isolated from bitter melon, has been demonstrated to have antidiabetic properties. This study investigated the effects of momordicine I on high-glucose-induced cardiac fibroblast activation. Rat cardiac fibroblasts were cultured in a high-glucose (25 mM) medium in the absence or presence of momordicine I, and the changes in collagen synthesis, transforming growth factor-1 (TGF-1) production, and related signaling molecules were assessed. Increased oxidative stress plays a critical role in the development of high-glucose-induced cardiac fibrosis; we further explored momordicine I's antioxidant activity and its effect on fibroblasts. Our data revealed that a high-glucose condition promoted fibroblast proliferation and collagen synthesis and these effects were abolished by momordicine I (0.3 and 1 M) pretreatment. Furthermore, the inhibitory effect of momordicine I on high-glucose-induced fibroblast activation may be associated with its activation of nuclear factor erythroid 2-related factor 2 (Nrf2) and the inhibition of reactive oxygen species formation, TGF-1 production, and Smad2/3 phosphorylation. The addition of brusatol (a selective inhibitor of Nrf2) or Nrf2 siRNA significantly abolished the inhibitory effect of momordicine I on fibroblast activation. Our findings revealed that the antifibrotic effect of momordicine I was mediated, at least partially, by the inhibition of the TGF-1/Smad pathway, fibroblast proliferation, and collagen synthesis through Nrf2 activation. Thus, this work provides crucial insights into the molecular pathways for the clinical application of momordicine I for treating diabetes-associated cardiac fibrosis.