Metallothionein plays a prominent role in the prevention of diabetic nephropathy by sulforaphane via up-regulation of Nrf2

Ranolazine as a therapeutic agent for diabetic cardiomyopathy: reducing endoplasmic reticulum stress and inflammation in type 2 diabetic rat model

BACKGROUND

Diabetic cardiomyopathy (DCM) is a significant cardiovascular complication of diabetes, characterized by structural and functional heart muscle dysfunction. Oxidative stress, endoplasmic reticulum (ER) stress, and inflammation are pivotal in the pathogenesis of DCM. Ranolazine, primarily used for angina, has demonstrated potential cardioprotective effects. This study investigates the effects of ranolazine on oxidative stress, ER stress, and inflammation in the heart tissue of type 2 diabetic rats.

METHODS

Diabetes was induced in male Wistar rats using Nicotinamide (110 mg/kg) and Streptozotocin (60 mg/kg). The rats were then divided into control and diabetic groups, with further subdivision into ranolazine-treated and untreated subgroups. Ranolazine was administered via gavage for eight weeks. Various parameters, including body weight, heart weight, serum glucose, troponin-I levels, oxidative stress markers, ER stress markers, and inflammatory markers, were assessed.

RESULTS

Diabetic rats showed increased heart weight and decreased body weight over eight weeks. Ranolazine treatment improved body weight but didn't affect serum glucose levels. The treatment significantly lowered serum troponin-I and oxidative stress markers, increased superoxide dismutase (SOD) and glutathione (GSH) levels, and decreased malondialdehyde (MDA) concentrations. Additionally, ranolazine reduced the expression of stress-related genes (GRP78, XBP1, and NLRP3) and lowered serum IL1β levels.

CONCLUSIONS

The results indicate that ranolazine protects against DCM by attenuating oxidative stress, ER stress, and inflammation. Its potential as a therapeutic agent for DCM warrants further investigation.

Keap1-independent Nrf2 regulation: A novel therapeutic target for treating kidney disease

The transcription factor NF-E2-related factor 2 (Nrf2) is a master regulator of antioxidant responses in mammals, where it plays a critical role in detoxification, maintaining cellular homeostasis, combating inflammation and fibrosis, and slowing disease progression. Kelch-like ECH-associated protein 1 (Keap1), an adaptor subunit of Cullin 3-based E3 ubiquitin ligase, serves as a critical sensor of oxidative and electrophilic stress, regulating Nrf2 activity by sequestering it in the cytoplasm, leading to its proteasomal degradation and transcriptional repression. However, the clinical potential of targeting the Keap1-dependent Nrf2 regulatory pathway has been limited. This is evidenced by early postnatal lethality in Keap1 knockout mice, as well as significant adverse events after pharmacological blockade of Keap1 in human patients with Alport syndrome as well as in those with type 2 diabetes mellitus and chronic kidney disease. The exact underlying mechanisms remain elusive, but may involve non-specific and systemic activation of the Nrf2 antioxidant response in both injured and normal tissues. Beyond Keap1-dependent regulation, Nrf2 activity is modulated by Keap1-independent mechanisms, including transcriptional, epigenetic, and post-translational modifications. In particular, GSK3β has emerged as a critical convergence point for these diverse signaling pathways. Unlike Keap1-dependent regulation, GSK3β-mediated Keap1-independent Nrf2 regulation does not affect basal Nrf2 activity but modulates its response at a delayed/late phase of cellular stress. This allows fine-tuning of the inducibility, magnitude, and duration of the Nrf2 response specifically in stressed or injured tissues. As one of the most metabolically active organs, the kidney is a major source of production of reactive oxygen and nitrogen species and also a vulnerable organ to oxidative damage. Targeting the GSK3β-mediated Nrf2 regulatory pathway represents a promising new approach for the treatment of kidney disease.

Sulforaphane alleviates renal fibrosis through dual regulation on mTOR-mediated autophagy pathway

Renal fibrosis is a common pathological process of progressive chronic kidney disease (CKD). However, effective therapy is constrained currently. Autophagy is an important mechanism in kidney injury and repairment but its exact role in renal fibrosis was discrepant according to previous studies. Sulforaphane (SFN), a natural plant compound, has been explored as a promising nutritional therapy for a variety of diseases. But the salutary effect and underlying mechanism of SFN on CKD have not been fully elucidated. In this study, we investigated the effect of SFN on renal fibrosis in unilateral ureteral obstruction (UUO) mice. Then we examined the regulatory effect of SFN on autophagy-related proteins in renal fibroblasts and renal tubular epithelial cells. Our results showed that sulforaphane could significantly alleviate renal fibrosis in UUO mice. In vitro, the expression levels of autophagy-related protein showed that SFN could upregulate the autophagy activity of renal interstitial fibroblasts and downregulate the autophagy activity of renal tubular epithelial cells. Furthermore, we found that phosphorylated mTOR protein levels was reduced in renal fibroblasts and increased in renal tubular epithelial cells after SFN treatment. Our results strongly suggested that SFN could alleviate renal fibrosis through dual regulation of mTOR-mediated autophagy pathway. This finding may provide a new perspective on the renal salutary effect of SFN and provide a preclinical rationale for exploring the therapeutic potential of SFN to slow down renal fibrosis.

Exacerbation by knocking-out metallothionein gene of obesity-induced cardiac remodeling is associated with the activation of CARD9 signaling

Obesity increases the risk of metabolic syndrome including insulin resistance, dyslipidemia, and cardiovascular disease. We demonstrated insulin resistance, cardiac hypertrophy, and cardiac inflammation in an obese mouse model induced by a high-fat diet (HFD). Caspase recruitment domain-containing protein 9 (CARD9) and B-cell lymphoma/leukemia 10 (BCL10) were upregulated, and p38 MAPK was activated in these mice. Zinc supplementation prevented these changes with upregulation of metallothionein (MT). Deletion of MT exacerbated palmitate-triggered expression of BCL10 and p38 MAPK activation and eliminated the protective benefits of zinc in palmitate-treated cardiomyocytes. Here we further investigated the mechanisms by which endogenous MT expression affects HFD-induced cardiac remodeling and the CARD9/BCL10/p38 MAPK pathway. Male MT knockout and 129S wild-type mice were assigned to receive either a normal diet or a HFD from 8-week-age for 18 weeks. MT knockout (KO) aggravated HFD-induced obesity and systemic metabolic disorder, reflected by increased body weight, perirenal white adipose tissue, and plasma cholesterol, and cardiac hypertrophy and fibrosis. Obese MT-KO mice had abundant cardiac macrophages, upregulated cardiac proinflammatory cytokines, chemokines, adhesion molecules, CARD9, and BCL10 and activated NF-κB. MT-KO exacerbated HFD-induced trace metal dyshomeostasis and oxidative stress. MT-KO combined with HFD-induced obesity synergistically promotes cardiac remodeling, possibly via trace metal dyshomeostasis-induced oxidative stress to trigger CARD9/BCL10-mediated NF-κB activation.

Sulforaphane Supplementation Did Not Modulate NRF2 and NF-kB mRNA Expressions in Hemodialysis Patients

BACKGROUND

Patients with chronic kidney disease (CKD) have reduced expression of erythroid nuclear factor-related factor 2 (NRF2) and increased nuclear factor κB (NF-κB). "Food as medicine" has been proposed as an adjuvant therapeutic alternative in modulating these factors. No studies have investigated the effects of sulforaphane (SFN) in cruciferous vegetables on the expression of these genes in patients with CKD.

OBJECTIVE

The study aimed to evaluate the effects of SFN on the expression of NRF2 and NF-κB in patients on hemodialysis (HD).

DESIGN AND METHODS

A randomized, double-blind, crossover study was performed on 30 patients on regular HD. Fourteen patients were randomly allocated to the intervention group (1 sachet/day of 2.5 g containing 1% SFN extract with 0.5% myrosinase) and 16 patients to the placebo group (1 sachet/day of 2.5 g containing corn starch colored with chlorophyll) for 2 months. After a washout period of 2 months, the groups were switched. NRF2 and NF-κB mRNA expression was evaluated by real-time quantitative polymerase chain reaction, and tumor necrosis factor alpha and interleukin-6 levels were quantified by enzyme-linked immunosorbent assay. Malondialdehyde was evaluated as a marker of lipid peroxidation.

RESULTS

Twenty-five patients (17 women, 55 [interquartile range = 19] years and 55 [interquartile range = 74] months on HD) completed the study. There was no significant difference concerning the expression of mRNA NRF2 (P = .915) and mRNA NF-κB (P = .806) after supplementation with SFN. There was no difference in pro-inflammatory and oxidative stress biomarkers.

CONCLUSION

150 μmol of SFN for 2 months had no antioxidant and anti-inflammatory effect in patients with CKD undergoing HD.

Insights into the Therapeutic uses of Plant Derive Phytocompounds onDiabetic Nephropathy

Diabetic nephropathy (DN) is one of the primary consequences of diabetes mellitus, affecting many people worldwide and is the main cause of death under the age of sixty. Reactive oxygen species (ROS) production rises during hyperglycemia and is crucial to the development of diabetic complications. Advanced glycation end products (AGEs) are produced excessively in a diabetic state and are accumulated in the kidney, where they change renal architecture and impair renal function. Another important targeted pathway for the formation of DN includes nuclear factor kappa-B (NF-kB), Nuclear factor E2-related factor 2 (Nrf2), NLR family pyrin domain containing 3 (NLRP3), protein kinase B/mammalian target of rapamycin (Akt/mTOR), and autophagy. About 40% of individuals with diabetes eventually acquire diabetic kidney disease and end-stage renal disease that needs hemodialysis, peritoneal dialysis, or kidney transplantation to survive. The current state of acceptable therapy for this kidney ailment is limited. The studies revealed that some naturally occurring bioactive substances might shield the kidney by controlling oxidative stress, renal fibrosis, inflammation, and autophagy. In order to provide new potential therapeutic lead bioactive compounds for contemporary drug discovery and clinical management of DN, this review was designed to examine the various mechanistic pathways by which conventional plants derive phytocompounds that are effective for the control and treatment of DN.

Oxidative Stress Induced by Lipotoxicity and Renal Hypoxia in Diabetic Kidney Disease and Possible Therapeutic Interventions: Targeting the Lipid Metabolism and Hypoxia

Oxidative stress, a hallmark pathophysiological feature in diabetic kidney disease (DKD), arises from the intricate interplay between pro-oxidants and anti-oxidants. While hyperglycemia has been well established as a key contributor, lipotoxicity emerges as a significant instigator of oxidative stress. Lipotoxicity encompasses the accumulation of lipid intermediates, culminating in cellular dysfunction and cell death. However, the mechanisms underlying lipotoxic kidney injury in DKD still require further investigation. The key role of cell metabolism in the maintenance of cell viability and integrity in the kidney is of paramount importance to maintain proper renal function. Recently, dysfunction in energy metabolism, resulting from an imbalance in oxygen levels in the diabetic condition, may be the primary pathophysiologic pathway driving DKD. Therefore, we aim to shed light on the pivotal role of oxidative stress related to lipotoxicity and renal hypoxia in the initiation and progression of DKD. Multifaceted mechanisms underlying lipotoxicity, including oxidative stress with mitochondrial dysfunction, endoplasmic reticulum stress activated by the unfolded protein response pathway, pro-inflammation, and impaired autophagy, are delineated here. Also, we explore potential therapeutic interventions for DKD, targeting lipotoxicity- and hypoxia-induced oxidative stress. These interventions focus on ameliorating the molecular pathways of lipid accumulation within the kidney and enhancing renal metabolism in the face of lipid overload or ameliorating subsequent oxidative stress. This review highlights the significance of lipotoxicity, renal hypoxia-induced oxidative stress, and its potential for therapeutic intervention in DKD.

A mechanistic overview of sulforaphane and its derivatives application in diabetes and its complications

Sulforaphane (SFN) is a type of phytochemical found in many cruciferous vegetables that has been shown to positively benefit the control of Type 2 Diabetes Mellitus (T2DM). The search was done from 2000 until December 2022 using PubMed, Scopus, Web of Sciences, and Google Scholar databases. We included all in vitro, in vivo, and clinical trials. Sulforaphane has been demonstrated to activate the PI3K/AKT and AMP-activated protein kinase pathways and the glucose transporter type 4 to increase insulin production and reduce insulin resistance. Interestingly, SFN possesses protective effects against diabetes complications, such as diabetic-induced hepatic damage, vascular inflammation and endothelial dysfunction, nephropathy, and neuropathy via nuclear factor erythroid 2-related factor 2 activation that leads to the translation of several anti-oxidant enzymes and regulation glycolysis, pentose phosphate pathway, fatty acid metabolism, glutamine metabolism, and glutathione metabolism. Furthermore, multiple clinical trial studies emphasized the ameliorating effects of SFN on T2DM patients. This review provides sufficient evidence for further research and development of sulforaphane as a hypoglycemic drug.

Sulforaphane: A nutraceutical against diabetes-related complications

There is an increasing interest in the use of nutraceuticals and plant-derived bioactive compounds from foods for their potential health benefits. For example, as a major active ingredient found from cruciferous vegetables like broccoli, there has been growing interest in understanding the therapeutic effects of sulforaphane against diverse metabolic complications. The past decade has seen an extensive growth in literature reporting on the potential health benefits of sulforaphane to neutralize pathological consequences of oxidative stress and inflammation, which may be essential in protecting against diabetes-related complications. In fact, preclinical evidence summarized within this review supports an active role of sulforaphane in activating nuclear factor erythroid 2-related factor 2 or effectively modulating AMP-activated protein kinase to protect against diabetic complications, including diabetic cardiomyopathy, diabetic neuropathy, diabetic nephropathy, as well as other metabolic complications involving non-alcoholic fatty liver disease and skeletal muscle insulin resistance. With clinical evidence suggesting that foods rich in sulforaphane like broccoli can improve the metabolic status and lower cardiovascular disease risk by reducing biomarkers of oxidative stress and inflammation in patients with type 2 diabetes. This information remains essential in determining the therapeutic value of sulforaphane or its potential use as a nutraceutical to manage diabetes and its related complications. Finally, this review discusses essential information on the bioavailability profile of sulforaphane, while also covering information on the pathological consequences of oxidative stress and inflammation that drive the development and progression of diabetes.

RIG-I contributes to keratinocyte proliferation and wound repair by inducing TIMP-1 expression through NF-κB signaling pathway

Epithelial keratinocyte proliferation is an essential element of wound repair, and chronic wound conditions, such as diabetic foot, are characterized by aberrant re-epithelialization. In this study, we examined the functional role of retinoic acid inducible-gene I (RIG-I), a key regulator of epidermal keratinocyte proliferation, in promoting TIMP-1 expression. We found that RIG-I is overexpressed in keratinocytes of skin injury and underexpressed in skin wound sites of diabetic foot and streptozotocin-induced diabetic mice. Moreover, mice lacking RIG-I developed an aggravated phenotype when subjected to skin injury. Mechanistically, RIG-I promoted keratinocyte proliferation and wound repair by inducing TIMP-1 via the NF-κB signaling pathway. Indeed, recombinant TIMP-1 directly accelerated HaCaT cell proliferation in vitro and promoted wound healing in Ddx58-/- and diabetic mice in vivo. In summary, we demonstrated that RIG-I is a crucial factor that mediates epidermal keratinocyte proliferation and may be a potential biomarker for skin injury severity, thus making it an attractive locally therapeutic target for the treatment of chronic wounds such as diabetic foot.

Nrf2 signaling in diabetic nephropathy, cardiomyopathy and neuropathy: Therapeutic targeting, challenges and future prospective

Western lifestyle contributes to an overt increase in the prevalence of metabolic anomalies including diabetes mellitus (DM) and obesity. Prevalence of DM is rapidly growing worldwide, affecting many individuals in both developing and developed countries. DM is correlated with the onset and development of complications with diabetic nephropathy (DN), diabetic cardiomyopathy (DC) and diabetic neuropathy being the most devastating pathological events. On the other hand, Nrf2 is a regulator for redox balance in cells and accounts for activation of antioxidant enzymes. Dysregulation of Nrf2 signaling has been shown in various human diseases such as DM. This review focuses on the role Nrf2 signaling in major diabetic complications and targeting Nrf2 for treatment of this disease. These three complications share similarities including the presence of oxidative stress, inflammation and fibrosis. Onset and development of fibrosis impairs organ function, while oxidative stress and inflammation can evoke damage to cells. Activation of Nrf2 signaling significantly dampens inflammation and oxidative damage, and is beneficial in retarding interstitial fibrosis in diabetic complications. SIRT1 and AMPK are among the predominant pathways to upregulate Nrf2 expression in the amelioration of DN, DC and diabetic neuropathy. Moreover, certain therapeutic agents such as resveratrol and curcumin, among others, have been employed in promoting Nrf2 expression to upregulate HO-1 and other antioxidant enzymes in the combat of oxidative stress in the face of DM.

Sulforaphane exhibits potent renoprotective effects in preclinical models of kidney diseases: A systematic review and meta-analysis

AIMS

Sulforaphane (SFN), a naturally occurring isothiocyanate found in cruciferous vegetables, has received extensive attention as a natural activator of the Nrf2/Keap1 cytoprotective pathway. In this review, a meta-analysis and systematic review of the renoprotective effects of SFN were performed in various preclinical models of kidney diseases.

MAIN METHODS

The primary outcome was the impact of SFN on renal function biomarkers (uremia, creatininemia, proteinuria or creatinine clearance) and secondary outcomes were kidney lesion histological indices/kidney injury molecular biomarkers. The effects of SFN were evaluated according to the standardized mean differences (SMDs). A random-effects model was applied to estimate the overall summary effect.

KEY FINDINGS

Twenty-five articles (out of 209 studies) were selected from the literature. SFN administration significantly increased creatinine clearance (SMD +1.88 95 % CI: [1.09; 2.68], P < 0.0001, I² = 0 %) and decreased the plasma creatinine (SMD -1.24, [-1.59; -0.88], P < 0.0001, I² = 36.0 %) and urea (SMD -3.22 [-4.42, -2.01], P < 0.0001, I² = 72.4 %) levels. SFN administration (median dose: 2.5 mg/kg, median duration: 3 weeks) significantly decreased urinary protein excretion (SMD -2.20 [-2.68; -1.73], P < 0.0001, I² = 34.1 %). It further improved two kidney lesion histological indices namely kidney fibrosis (SMD -3.08 [-4.53; -1.63], P < 0.0001, I² = 73.7 %) and glomerulosclerosis (SMD -2.24 [-2.96; -1.53], P < 0.0001, I² = 9.7 %) and decreased kidney injury molecular biomarkers (SMD -1.51 [-2.00; -1.02], P < 0.0001, I² = 0 %).

SIGNIFICANCE

These findings provide new insights concerning preclinical strategies for treating kidney disease or kidney failure with SFN supplements and should stimulate interest in clinical evaluations of SFN in patients with kidney disease.

Oxidative Stress and NRF2/KEAP1/ARE Pathway in Diabetic Kidney Disease (DKD): New Perspectives

Diabetes mellitus (DM) is one of the most debilitating chronic diseases worldwide, with increased prevalence and incidence. In addition to its macrovascular damage, through its microvascular complications, such as Diabetic Kidney Disease (DKD), DM further compounds the quality of life of these patients. Considering DKD is the main cause of end-stage renal disease (ESRD) in developed countries, extensive research is currently investigating the matrix of DKD pathophysiology. Hyperglycemia, inflammation and oxidative stress (OS) are the main mechanisms behind this disease. By generating pro-inflammatory factors (e.g., IL-1,6,18, TNF-α, TGF-β, NF-κB, MCP-1, VCAM-1, ICAM-1) and the activation of diverse pathways (e.g., PKC, ROCK, AGE/RAGE, JAK-STAT), they promote a pro-oxidant state with impairment of the antioxidant system (NRF2/KEAP1/ARE pathway) and, finally, alterations in the renal filtration unit. Hitherto, a wide spectrum of pre-clinical and clinical studies shows the beneficial use of NRF2-inducing strategies, such as NRF2 activators (e.g., Bardoxolone methyl, Curcumin, Sulforaphane and their analogues), and other natural compounds with antioxidant properties in DKD treatment. However, limitations regarding the lack of larger clinical trials, solubility or delivery hamper their implementation for clinical use. Therefore, in this review, we will discuss DKD mechanisms, especially oxidative stress (OS) and NRF2/KEAP1/ARE involvement, while highlighting the potential of therapeutic approaches that target DKD via OS.

tBHQ attenuates podocyte injury in diabetic nephropathy by inhibiting NADPH oxidase-derived ROS generation via the Nrf2/HO-1 signalling pathway

Aims

Oxidative stress plays a crucial role in podocyte injury in diabetic nephropathy (DN). tert-Butylhydroquinone (tBHQ) is an activator of Nrf2 that exerts protective effects in diabetic mice, but the underlying mechanism of tBHQ in the podocytes of DN is not fully understood.

Materials and methods

A high glucose (HG)-induced HK2 cell model and streptozotocin-induced rat model of DN were established and treated with tBHQ or apocynin. The expression levels of Nrf2, HO-1, NOX2 and NOX4 were determined by Western blot or immunohistochemical staining. The level of oxidative stress in podocytes or kidney tissues was assessed using DCFH-DA or dihydroethidium (DHE) staining. Cell injury was assessed by F-actin staining and flow cytometry analysis.

Key findings

We showed that HG treatment increased the expressions of NOX2 and NOX4 and enhanced ROS production in podocytes. Inhibition of NADPH oxidase activity by apocynin dramatically attenuated HG-induced ROS production and further alleviated cell injury and apoptosis in podocytes. Moreover, we found that HG inhibited the Nrf2/HO-1 signalling pathway in podocytes; however, tBHQ treatment significantly activated the Nrf2 signalling pathway, inhibited NADPH oxidase activity, and attenuated ROS production and cell injury in HG-treated podocytes. Furthermore, we observed that tBHQ treatment partially attenuated renal injury, activated the Nrf2 signalling pathway, inhibited NADPH oxidase activity and reduced ROS generation in the kidneys of STZ-induced diabetic rats.

Significance

These results suggest that tBHQ exerts a protective role in hyperglycaemia-induced podocyte injury, and that the potential protective mechanism of tBHQ involves inhibiting NADPH oxidase-derived ROS generation by activating the Nrf2/HO-1 signalling pathway.

Knowledge domain and emerging trends in diabetic cardiomyopathy: A scientometric review based on CiteSpace analysis

Objective

To review the literature related to diabetic cardiomyopathy (DCM), and investigate research hotspots and development trends of this field in the relevant studies based on CiteSpace software of text mining and visualization in scientific literature.

Methods

The relevant literature from the last 20 years was retrieved from the Web of Science (WoS) Core Collection database. After manual selection, each document record includes title, authors, year, organization, abstract, keywords, citation, descriptors, and identifiers. We imported the downloaded data into CiteSpace V (version 5.8.R2) to draw the knowledge map and conduct cooperative network analysis, cluster analysis, burst keyword analysis, and co-citation analysis.

Results

After manual screening, there were 3,547 relevant pieces of literature published in the last 18 years (from 2004 to 2021), including 2,935 articles and reviews, which contained 15,533 references, and the number was increasing year by year. The publications of DCM were dedicated by 778 authors of 512 institutions in 116 countries. The People's Republic of China dominated this field (1,117), followed by the USA (768) and Canada (176). In general, most articles were published with a focus on “oxidative stress,” “heart failure,” “diabetic cardiomyopathy,” “dysfunction,” “cardiomyopathy,” “expression,” “heart,” “mechanism,” and “insulin resistance.” Then, 10 main clusters were generated with a modularity Q of 0.6442 and a weighted mean silhouette of 0.8325 by the log-likelihood ratio (LLR) algorithm, including #0 heart failure, #1 perfused heart, #2 metabolic disease, #3 protective effect, #4 diabetic patient, #5 cardiac fibrosis, #6 vascular complication, #7 mitochondrial dynamics, #8 sarcoplasmic reticulum, and #9 zinc supplementation. The top five references with the strongest citation bursts include “Boudina and Abel”, “Jia et al.”, “Fang et al.”, “Poornima et al.”, and “Aneja et al.”.

Conclusion

The global field of DCM has expanded in the last 20 years. The People's Republic of China contributes the most. However, there is little cooperation among authors and institutions. Overall, this bibliometric study identified the hotspots in DCM research, including “stress state,” “energy metabolism,” “autophagy,” “apoptosis,” “inflammation,” “fibrosis,” “PPAR,” etc. Thus, further research focuses on these topics that may be more helpful to identify, prevent DCM and improve prophylaxis strategies to bring benefit to patients in the near future.

Traditional uses, phytochemistry, transformation of ingredients and pharmacology of the dried seeds of Raphanus sativus L. (Raphani Semen), A comprehensive review

ETHNOPHARMACOLOGICAL RELEVANCE

Raphani Semen (Lai Fu-zi in Chinese, RS), the dried seeds of Raphanus sativus L., is a traditional Chinese herbal medicine. RS has long been used for eliminating bloating and digestion, antitussive, expectorant and anti-asthmatic in clinical treatment of traditional Chinese medicine.

AIM OF THE STUDY

This review provides a critical and comprehensive summary of traditional uses, phytochemistry, transformation of ingredients and pharmacology of RS based on research data that have been reported, aiming at providing a basis for further study on RS.

MATERIALS AND METHODS

The search terms "Raphani Semen", "the seeds of Raphanus sativus L." and "radish seed" were used to obtain the information from electronic databases such as Web of Science, China National Knowledge Infrastructure, PubMed and other web search instruments. Traditional uses, phytochemistry, transformation of ingredients and pharmacology of RS were summarized.

RESULTS

RS has been traditionally used to treat food dyspeptic retention, distending pain in the epigastrium and abdomen, constipation, diarrhea and dysentery, panting, and cough with phlegm congestion in the clinical practice. The chemical constituents of RS include glucosinolates and sulfur-containing derivatives, phenylpropanoid sucrosides, small organic acids and derivatives, flavone glycosides, alkaloids, terpenoids, steroids, oligosaccharides and others. Among them, glucosinolates can be transformated to isothiocyanates by plant myrosinase or the intestinal flora, which display a variety of activities, such as anti-tumor, anti-inflammatory, antioxidant, antibacterial, treatment of metabolic diseases, central nervous system protection, anti-osteoporosis. RS has a variety of pharmacological activities, including treatment of metabolic diseases, anti-inflammatory, anti-tumor, antioxidant, antibacterial, antihypertensive, central nervous system protection, anti-osteoporosis, etc. This review will provide useful insight for exploration, further study and precise medication of RS in the future.

CONCLUSIONS

According to its traditional uses, phytochemistry, transformation of ingredients and pharmacology, RS is regarded as a promising medical plant with various chemical compounds and numerous pharmacological activities. However, the material bases and mechanisms of traditional effect of RS need further study.

MBTPS2 exacerbates albuminuria in streptozotocin-induced type I diabetic nephropathy by promoting endoplasmic reticulum stress-mediated renal damage

BACKGROUND

The membrane-bound transcription factor protease site 2 (MBTPS2) is an intramembranous metalloprotease involved in the regulation of ER stress response, however, whether it is associated with DN is unknown.

RESULTS

We report that MBTPS2 expression is upregulated in the renal cortex of diabetic mice induced by streptozotocin (STZ), a murine model of insulinopenic type 1 DN. Functionally, in vivo, MBTPS2 overexpression exacerbates and its knockdown attenuates albuminuria, which indicate a detrimental role of MBTPS2 played in albuminuria development in DN mice. We further show that MBTPS2 promotes ER stress and renal damage in DN mice, and that reducing ER stress via a chemical chaperone 4-phenylbutyric acid (4-PBA) markedly rescues MBTPS2-exacerbated renal damage and albuminuria severity.

CONCLUSIONS

Collectively, our study associates the function of MBTPS2 in DN albuminuria with ER stress regulation, thus underscoring the notorious role of maladaptive ER response in influencing DN albuminuria.

Metals and Metallothionein Expression in Relation to Progression of Chronic Kidney Disease of Unknown Etiology (CKDu) in Sri Lanka

Chronic kidney disease of unknown etiology was investigated for metal relations in an endemic area by a cross-sectional study with CKD stages G1, G2, G3a, G3b, G4, G5 (ESRD), and endemic and nonendemic controls (EC and NEC) as groups. Subjects with the medical diagnosis were classified into groups by eGFR (SCr, CKD-EPI) and UACR of the study. It determined 24 metals/metalloids in plasma (ICPMS) and metallothionein (MT) mRNA in blood (RT-PCR). MT1A at G3b and MT2A throughout G2−G5 showed increased transcription compared to NEC (ANOVA, p < 0.01). Both MT1A and MT2A remained metal-responsive as associations emerged between MT2A and human MT inducer Cr (in EC: r = 0.54, p < 0.05, n = 14), and between MT1A and MT2A (in EC pooled with G1−G5: r = 0.58, p < 0.001, n = 110). Human MT (hMT)-inducers, namely Zn, Cu, As, Pb, and Ni; Σ hMT-inducers; 14 more non-inducer metals; and Σ MT-binding metals remained higher (p < 0.05) in EC as compared to NEC. Declining eGFR or CKD progression increased the burden of Be, Mg, Al, V, Co, Ni, Rb, Cs, Ba, Mn, Zn, Sr, Σ hMT-inducers, and Σ MT-binding metals in plasma, suggesting an MT role in the disease. MT1A/2A mRNA followed UACR (PCA, Dendrogram: similarity, 57.7%). The study provides evidence that proteinuric chronic renal failure may increase plasma metal levels where blood MT2A could be a marker.

Research advances in the protective effect of sulforaphane against kidney injury and related mechanisms

Kidney injury and related diseases have become quite common in recent years, and have attracted more attention. Sulforaphane, a kind of isothiocyanate, is widely distributed in cruciferous plants and it is a common antioxidant. Specifically, sulforaphane can reduce oxidative damage by preventing cells from freeradical damage, preventing cells from degeneration, and acting as an anti-inflammation, etc. This study summarized the investigations of the effects of sulforaphane on kidney injury. This study discussed the mechanisms of sulforaphane on immune, renal ischemia-reperfusion, diabetic nephropathy, age-related, and other factors-induced kidney injury models and discussed the potential and relative mechanisms of sulforaphane for kidney injury protection.

Sulforaphane Targets TRA-1/GLI Upstream of DAF-16/FOXO to Promote C. elegans Longevity and Healthspan

Broccoli-derived isothiocyanate sulforaphane inhibits inflammation and cancer. Sulforaphane may support healthy aging, but the underlying detailed mechanisms are unclear. We used the C. elegans nematode model to address this question. Wild-type and 4 mutant C. elegans worm strains were fed in the presence or absence of sulforaphane and E. coli food bacteria transfected with RNA interference gene constructs. Kaplan-Meier survival analysis, live imaging of mobility and pharyngeal pumping, fluorescence microscopy, RT-qPCR, and Western blotting were performed. In the wild type, sulforaphane prolonged lifespan and increased mobility and food intake because of sulforaphane-induced upregulation of the sex-determination transcription factor TRA-1, which is the ortholog of the human GLI mediator of sonic hedgehog signaling. In turn, the tra-1 target gene daf-16, which is the ortholog of human FOXO and the major mediator of insulin/IGF-1 and aging signaling, was induced. By contrast, sulforaphane did not prolong lifespan and healthspan when tra-1 or daf-16 was inhibited by RNA interference or when worms with a loss-of-function mutation of the tra-1 or daf-16 genes were used. Conversely, the average lifespan of C. elegans with hyperactive TRA-1 increased by 8.9%, but this longer survival was abolished by RNAi-mediated inhibition of daf-16. Our data suggest the involvement of sulforaphane in regulating healthy aging and prolonging lifespan by inducing the expression and nuclear translocation of TRA-1/GLI and its downstream target DAF-16/FOXO.

Sulforaphane Ameliorates Diabetes-Induced Renal Fibrosis through Epigenetic Up-Regulation of BMP-7

BACKGROUND

The dietary agent sulforaphane (SFN) has been reported to reduce diabetes-induced renal fibrosis, as well as inhibit histone deacetylase (HDAC) activity. Bone morphologic protein 7 (BMP-7) has been shown to reduce renal fibrosis induced by transforming growth factor-beta1. The aim of this study was to investigate the epigenetic effect of SFN on BMP-7 expression in diabetes-induced renal fibrosis.

METHODS

Streptozotocin (STZ)-induced diabetic mice and age-matched controls were subcutaneously injected with SFN or vehicle for 4 months to measure the in vivo effects of SFN on the kidneys. The human renal proximal tubular (HK11) cell line was used to mimic diabetic conditions in vitro. HK11 cells were transfected to over-express HDAC2 and treated with high glucose/palmitate (HG/Pal) to explore the epigenetic modulation of BMP-7 in SFN-mediated protection against HG/Pal-induced renal fibrosis.

RESULTS

SFN significantly attenuated diabetes-induced renal fibrosis in vivo. Among all of the HDACs we detected, HDAC2 activity was markedly elevated in the STZ-induced diabetic kidneys and HG/Pal-treated HK11 cells. SFN inhibited the diabetes-induced increase in HDAC2 activity which was associated with histone acetylation and transcriptional activation of the BMP-7 promoter. HDAC2 over-expression reduced BMP-7 expression and abolished the SFN-mediated protection against HG/Pal-induced fibrosis in vitro.

CONCLUSION

Our study demonstrates that the HDAC inhibitor SFN protects against diabetes-induced renal fibrosis through epigenetic up-regulation of BMP-7.

Nrf2 Activation Attenuates Acrylamide-Induced Neuropathy in Mice

Acrylamide is a well characterized neurotoxicant known to cause neuropathy and encephalopathy in humans and experimental animals. To investigate the role of nuclear factor erythroid 2-related factor 2 (Nrf2) in acrylamide-induced neuropathy, male C57Bl/6JJcl adult mice were exposed to acrylamide at 0, 200 or 300 ppm in drinking water and co-administered with subcutaneous injections of sulforaphane, a known activator of the Nrf2 signaling pathway at 0 or 25 mg/kg body weight daily for 4 weeks. Assessments for neurotoxicity, hepatotoxicity, oxidative stress as well as messenger RNA-expression analysis for Nrf2-antioxidant and pro-inflammatory cytokine genes were conducted. Relative to mice exposed only to acrylamide, co-administration of sulforaphane protected against acrylamide-induced neurotoxic effects such as increase in landing foot spread or decrease in density of noradrenergic axons as well as hepatic necrosis and hemorrhage. Moreover, co-administration of sulforaphane enhanced acrylamide-induced mRNA upregulation of Nrf2 and its downstream antioxidant proteins and suppressed acrylamide-induced mRNA upregulation of tumor necrosis factor alpha (TNF-α) and inducible nitric oxide synthase (iNOS) in the cerebral cortex. The results demonstrate that activation of the Nrf2 signaling pathway by co-treatment of sulforaphane provides protection against acrylamide-induced neurotoxicity through suppression of oxidative stress and inflammation. Nrf2 remains an important target for the strategic prevention of acrylamide-induced neurotoxicity.

The Influence of Plant Extracts and Phytoconstituents on Antioxidant Enzymes Activity and Gene Expression in the Prevention and Treatment of Impaired Glucose Homeostasis and Diabetes Complications

Diabetes is a complex metabolic disorder resulting either from insulin resistance or an impaired insulin secretion. Prolonged elevated blood glucose concentration, the key clinical sign of diabetes, initiates an enhancement of reactive oxygen species derived from glucose autoxidation and glycosylation of proteins. Consequently, chronic oxidative stress overwhelms cellular endogenous antioxidant defenses and leads to the acute and long-standing structural and functional changes of macromolecules resulting in impaired cellular functioning, cell death and organ dysfunction. The oxidative stress provoked chain of pathological events over time cause diabetic complications such as nephropathy, peripheral neuropathy, cardiomyopathy, retinopathy, hypertension, and liver disease. Under diabetic conditions, accompanying genome/epigenome and metabolite markers alterations may also affect glucose homeostasis, pancreatic β-cells, muscle, liver, and adipose tissue. By providing deeper genetic/epigenetic insight of direct or indirect dietary effects, nutrigenomics offers a promising opportunity to improve the quality of life of diabetic patients. Natural plant extracts, or their naturally occurring compounds, were shown to be very proficient in the prevention and treatment of different pathologies associated with oxidative stress including diabetes and its complications. Considering that food intake is one of the crucial components in diabetes’ prevalence, progression and complications, this review summarizes the effect of the major plant secondary metabolite and phytoconstituents on the antioxidant enzymes activity and gene expression under diabetic conditions.

Eat Your Broccoli: Oxidative Stress, NRF2, and Sulforaphane in Chronic Kidney Disease

The mainstay of therapy for chronic kidney disease is control of blood pressure and proteinuria through the use of angiotensin-converting enzyme inhibitors (ACE-Is) or angiotensin receptor blockers (ARBs) that were introduced more than 20 years ago. Yet, many chronic kidney disease (CKD) patients still progress to end-stage kidney disease—the ultimate in failed prevention. While increased oxidative stress is a major molecular underpinning of CKD progression, no treatment modality specifically targeting oxidative stress has been established clinically. Here, we review the influence of oxidative stress in CKD, and discuss regarding the role of the Nrf2 pathway in kidney disease from studies using genetic and pharmacologic approaches in animal models and clinical trials. We will then focus on the promising therapeutic potential of sulforaphane, an isothiocyanate derived from cruciferous vegetables that has garnered significant attention over the past decade for its potent Nrf2-activating effect, and implications for precision medicine.

Protective Role of Nrf2 in Renal Disease

Chronic kidney disease (CKD) is one of the fastest-growing causes of death and is predicted to become by 2040 the fifth global cause of death. CKD is characterized by increased oxidative stress and chronic inflammation. However, therapies to slow or prevent CKD progression remain an unmet need. Nrf2 (nuclear factor erythroid 2-related factor 2) is a transcription factor that plays a key role in protection against oxidative stress and regulation of the inflammatory response. Consequently, the use of compounds targeting Nrf2 has generated growing interest for nephrologists. Pre-clinical and clinical studies have demonstrated that Nrf2-inducing strategies prevent CKD progression and protect from acute kidney injury (AKI). In this article, we review current knowledge on the protective mechanisms mediated by Nrf2 against kidney injury, novel therapeutic strategies to induce Nrf2 activation, and the status of ongoing clinical trials targeting Nrf2 in renal diseases.

Cruciferous vegetables: rationale for exploring potential salutary effects of sulforaphane-rich foods in patients with chronic kidney disease

Sulforaphane (SFN) is a sulfur-containing isothiocyanate found in cruciferous vegetables (Brassicaceae) and a well-known activator of nuclear factor-erythroid 2-related factor 2 (Nrf2), considered a master regulator of cellular antioxidant responses. Patients with chronic diseases, such as diabetes, cardiovascular disease, cancer, and chronic kidney disease (CKD) present with high levels of oxidative stress and a massive inflammatory burden associated with diminished Nrf2 and elevated nuclear transcription factor-κB-κB expression. Because it is a common constituent of dietary vegetables, the salutogenic properties of sulforaphane, especially it’s antioxidative and anti-inflammatory properties, have been explored as a nutritional intervention in a range of diseases of ageing, though data on CKD remain scarce. In this brief review, the effects of SFN as a senotherapeutic agent are described and a rationale is provided for studies that aim to explore the potential benefits of SFN-rich foods in patients with CKD.

Role of Nrf2 dysfunction in the pathogenesis of diabetic nephropathy: Therapeutic prospect of epigallocatechin-3-gallate

Diabetic nephropathy (DN), a progressive kidney disease afflicts more than 20 and up to 40% of the diabetic population and it is characterized by persistent microalbuminuria declined glomerular filtration rate. The interesting feature associated with DN is that, even though the progression of the disease correlates with oxidative stress, Nrf2, the master regulator of antioxidant defense system involved in counteracting oxidative stress is also upregulated in the diabetic kidneys of both human as well as experimental animals in early stages of DN. Despite the increased expression, the ability of this protein to get translocated into the nucleus is diminished signifying the functional impairment of Nrf2, implying redox imbalance. Hence, it is understood that agents that boost the translocation of Nrf2 might be beneficial rather than those that quantitatively overexpress Nrf2 in treating DN. The deleterious effects of synthetic Nrf2 activators have instigated the researchers to search for phytochemicals that have ambient Nrf2 boosting ability with no side effects, one such phytochemical is Epigallocatechin-3-gallate (EGCG) and it has shown beneficial effects by preventing the progression of DN via influencing Nrf2/ARE pathway, however, the modus operandi is unclear, despite speculations. This study was designed to find out whether supplementation of Nrf2 booster like EGCG at the crucial time of Nrf2 dysfunction can mitigate the progression of DN. Based on the findings of the present study, it might be concluded that the beneficial effect of EGCG in mitigating DN is mediated mainly through its ability to activate the Nrf2/ARE signaling pathway at multiple stages i.e., by downregulating Keap1 and boosting the nuclear Nrf2 level by disrupting Nrf2-Keap1 interaction. These results emphasize that supplementation of EGCG might be more beneficial at an early stage of DN, where dysfunctional Nrf2 accumulation occurs, which should be further validated.

Sulforaphane prevents type 2 diabetes-induced nephropathy via AMPK-mediated activation of lipid metabolic pathways and Nrf2 antioxidative function

Sulforaphane (SFN) prevents diabetic nephropathy (DN) in type 2 diabetes (T2D) by up-regulating nuclear factor (erythroid-derived 2)-like 2 (Nrf2). AMP-activated protein kinase (AMPK) can attenuate the pathogenesis of DN by improving renal lipotoxicity along with the activation of Nrf2-mediated antioxidative signaling. Therefore, we investigated whether AMPKα2, the central subunit of AMPK in energy metabolism, is required for SFN protection against DN in T2D, and whether potential cross-talk occurs between AMPKα2 and Nrf2. AMPKα2 knockout (Ampkα2-/-) mice and wildtype (WT) mice were fed a high-fat diet (HFD) or a normal diet (ND) to induce insulin resistance, followed by streptozotocin (STZ) injection to induce hyperglycemia, as a T2D model. Both T2D and control mice were treated with SFN or vehicle for 3 months. At the end of the 3-month treatment, all mice were maintained only on HFD or ND for an additional 3 months without SFN treatment. Mice were killed at sixth month after T2D onset. Twenty-four-hour urine albumin at third and sixth months was significantly increased as renal dysfunction, along with significant renal pathological changes and biochemical changes including renal hypertrophy, oxidative damage, inflammation, and fibrosis in WT T2D mice, which were prevented by SFN in certain contexts, but not in Ampkα2-/- T2D mice. SFN prevention of T2D-induced renal lipotoxicity was associated with AMPK-mediated activation of lipid metabolism and Nrf2-dependent antioxidative function in WT mice, but not in SFN-treated Ampkα2-/- mice. Therefore, SFN prevention of DN is AMPKα2-mediated activation of probably both lipid metabolism and Nrf2 via AMPK/AKT/glycogen synthase kinase (GSK)-3β/Src family tyrosine kinase (Fyn) pathways.

The MT1G Gene in LUHMES Neurons Is a Sensitive Biomarker of Neurotoxicity

Identification of toxicants that underlie neurological diseases is a neglected area awaiting a valid strategy to identify such toxicants. We sought biomarkers that respond to known neurotoxicants in LUHMES immortalized neurons and evaluated these biomarkers for use in screening libraries of environmental toxicants. LUHMES immortalized human dopaminergic neurons were surveyed by RNA sequencing following challenge with parkinsonian toxicants rotenone, 6-hydroxydopamine, MPP+, and ziram (zinc dimethyldithiocarbamate; Zn²⁺DDC₂), as well as additional toxicants paraquat, MS275, and methylmercury. The metallothionein gene MT1G was the most dynamic gene expression response to all seven toxicants. Multiple toxicants also increased transcripts for SLC30A1 and SLC30A2 zinc secretion transporters, the SLC7A11 xCT cystine/glutamate antiporter important for glutathione synthesis, DNA damage inducible transcript 3 (DDIT3), and secreted growth factors FIBIN and CXCL12, whereas several toxicants decreased expression of the apelin growth factor (APLN). These biomarker genes revealed stress responses to many toxicants at sub-cytotoxic concentrations. Since several of these biomarker genes and prior neurological disease studies implicated disruption of metal distribution, we tested metal chelator thiram (dimethyldithiocarbamate, DDC), ziram, and several other metals and metal chelates for cytotoxicity and induction of MT1G expression. Metals and chelators that caused dynamic increases in MT1G expression also caused cytotoxicity, except Ni²⁺DDC₂ induced MT1G at 5 μM, but lacked cytotoxicity up to 100 μM. These results bolster prior work suggesting that neurons are characteristically sensitive to depletion of glutathione or to disruption of cellular metal distribution and provide biomarkers to search for such neurotoxicants in chemical libraries.

Protective role of mitoquinone against impaired mitochondrial homeostasis in metabolic syndrome

Mitochondria control various processes in cellular metabolic homeostasis, such as adenosine triphosphate production, generation and clearance of reactive oxygen species, control of intracellular Ca²⁺ and apoptosis, and are thus a critical therapeutic target for metabolic syndrome (MetS). The mitochondrial targeted antioxidant mitoquinone (MitoQ) reduces mitochondrial oxidative stress, prevents impaired mitochondrial dynamics, and increases mitochondrial turnover by promoting autophagy (mitophagy) and mitochondrial biogenesis, which ultimately contribute to the attenuation of MetS conditions, including obesity, insulin resistance, hypertension and cardiovascular disease. The regulatory effect of MitoQ on mitochondrial homeostasis is mediated through AMPK and its downstream signaling pathways, including MTOR, SIRT1, Nrf2 and NF-κB. However, there are few reviews focusing on the critical role of MitoQ as a therapeutic agent in the treatment of MetS. The purpose of this review is to summarize the mitochondrial role in the pathogenesis of MetS, especially in obesity and type 2 diabetes, and discuss the effect and underlying mechanism of MitoQ on mitochondrial homeostasis in MetS.

Sulforaphane suppresses obesity-related glomerulopathy-induced damage by enhancing autophagy via Nrf2

AIMS

Obesity-related glomerulopathy (ORG) is characterized by glomerulomegaly with or without focal and segmental glomerulosclerosis lesions. Isothiocyanate sulforaphane (SFN) can protect kidneys from ORG-related damages. In this study, we investigated the effects of SFN as a preventive therapy or intervention for ORG to reveal its mechanism of action.

MAIN METHODS

We established a mouse obesity model with preventive SFN or N-acetylcysteine treatment for 2 months. Thereafter, we used nuclear factor erythroid 2-related factor 2-deficient (Nrf2^-/-) and wild type mice in our ORG model with SFN treatment. Finally, we generated a corresponding mouse podocyte model in vitro. The body weight, wet weight of perirenal-and peritesticular fat, and urinary albumin/creatinine ratio were assessed. We used periodic acid-Schiff staining and electron microscopy to assess the function of the kidneys and podocytes. In addition, we evaluated the expression of Nrf2 and podocyte-specific proteins by western blotting.

KEY FINDINGS

Treatment with SFN reduced body weight, organ-associated fat weight, and urinary albumin/creatinine ratio in both the preventive treatment and disease intervention regimens. SFN treated mice exhibited higher expression levels of podocyte-specific proteins and better podocyte function. However, treatment with SFN did not affect these parameters in obese Nrf2^-/- mice. Light chain 3 of microtubule-associated protein 1-II and metallothionein had higher expression in the wild type than in the Nrf2^-/- mice.

SIGNIFICANCE

Treatment with SFN limited ORG-induced damage by enhancing podocyte autophagy via Nrf2.

Protective role of NRF2 in macrovascular complications of diabetes

Macrovascular complications develop in over a half of the diabetic individuals, resulting in high morbidity and mortality. This poses a severe threat to public health and a heavy burden to social economy. It is therefore important to develop effective approaches to prevent or slow down the pathogenesis and progression of macrovascular complications of diabetes (MCD). Oxidative stress is a major contributor to MCD. Nuclear factor (erythroid‐derived 2)‐like 2 (NRF2) governs cellular antioxidant defence system by activating the transcription of various antioxidant genes, combating diabetes‐induced oxidative stress. Accumulating experimental evidence has demonstrated that NRF2 activation protects against MCD. Structural inhibition of Kelch‐like ECH‐associated protein 1 (KEAP1) is a canonical way to activate NRF2. More recently, novel approaches, such as activation of the Nfe2l2 gene transcription, decreasing KEAP1 protein level by microRNA‐induced degradation of Keap1 mRNA, prevention of proteasomal degradation of NRF2 protein and modulation of other upstream regulators of NRF2, have emerged in prevention of MCD. This review provides a brief introduction of the pathophysiology of MCD and the role of oxidative stress in the pathogenesis of MCD. By reviewing previous work on the activation of NRF2 in MCD, we summarize strategies to activate NRF2, providing clues for future intervention of MCD. Controversies over NRF2 activation and future perspectives are also provided in this review.

Nrf2 participates in the anti-apoptotic role of zinc in Type 2 diabetic nephropathy through Wnt/β-catenin signaling pathway

Zinc (Zn), as an essential trace element, has been approved to serve many roles in diabetic studies. Also Zn deficiency will aggravate renal damage in diabetes through suppression of nuclear factor-erythroid 2-related factor 2 (Nrf2) expression and function. The purpose of this study was to illustrate the role of Zn in renal apoptosis in diabetes and whether Nrf2 participated in the process. Type 2 diabetes mice model was induced by a single dose of streptozotocin (STZ) injection after high-fat diet (HFD) feeding for 3 months, then the mice were given diets supplemented with different concentrations of Zn (control, 30 ppm; low-concentration, 0.85 ppm). After 12-week treatment, morphology and associated protein expressions were examined. The results showed that low Zn diet significantly aggravated the level of renal apoptosis during diabetes, performed as the upregulation of caspase-3 expression. In addition, either low Zn diet or diabetes or both dramatically decreased the expression of Nrf2 and P-AKT in kidney. Moreover, the expression of β-catenin in kidney was increased markedly in diabetic groups. Mechanistic study applying human renal tubular epithelial cells (HK11) confirmed the role of Nrf2, as silencing Nrf2 expression abolished Zn supplementation protection against high sugar + high fat + low Zn-induced apoptosis and downregulation of β-catenin expression. All these results suggest that Nrf2 plays a key role in Zn protection against Type 2 diabetes induced renal apoptosis, which might be through Wnt/β-catenin signaling pathway.

Sulforaphane attenuates angiotensin II-induced human umbilical vein endothelial cell injury by modulating ROS-mediated mitochondrial signaling

The study aimed to investigate whether sulforaphane (SFN) protects against angiotensin II (Ang II)-mediated human umbilical vein endothelial cell (HUVEC) injury. Ang II treatment decreased HUVEC viability, increased cell apoptosis, decreased mitochondria membrane potential (MMP), impaired cytochrome c release, activated caspase 3/9, and induced reactive oxygen species (ROS) production, and nicotinamide adenine dinucleotide phosphate oxidase activity. Moreover, SFN treatment blunted Ang II-stimulated oxidative stress and mitochondria-related apoptosis in HUVECs. The ROS scavenger N-acetyl-l-cysteine reduced Ang II-induced oxidative stress and apoptosis, indicating that ROS generation is involved in the Ang II-induced mitochondria-mediated apoptotic pathway. SFN induced nuclear factor erythroid 2 (Nrf2) activation and expression in Ang II-stimulated HUVECs. Downregulation of Nrf2 expression by a target-specific siRNA revealed an Nrf2-dependent effect on the SFN-mediated attenuation of Ang II-induced apoptosis in HUVECs. Pretreatment with brusatol, an Nrf2-specific inhibitor, reversed the protective effects of SFN on Ang II-induced HUVEC injury. SFN treatment protected HUVECs from Ang II-induced damage by decreasing oxidative stress and ameliorating mitochondrial injury.

Metallothionein induction attenuates the progression of lung injury in mice exposed to long-term intermittent hypoxia

BACKGROUND

Intermittent hypoxia (IH), a hallmark of obstructive sleep apnea (OSA), is prevalent in older adults and associated with inflammation. We previously showed that IH induces renal fibrosis and cardiomyopathy and hypothesized that lung inflammatory changes may underlie deficits in pulmonary function in OSA.

METHODS

Pulmonary inflammatory and oxidative markers were assessed in metallothionein KO (MT-KO) mice and WT 129S1 controls exposed to IH or to normoxia for 8 weeks.

RESULTS

MT expression increased at 3 days in WT, falling back at 1 week. Pro-fibrotic markers CTGF and PAI-1 were unchanged in WT, but increased at 3 or 8 weeks, with enhanced Sirius Red staining at 8 weeks, in IH-exposed MT-KO. Cellular infiltration, TNF-α and IL-6 increased earlier in IH-exposed MT-KO than in WT. Oxidative markers, 3-nitrotyrosine and 4-hydroxynonenal increased in both but persisted in MT-KO. Antioxidant Nrf2, HO-1 and NQO1, increased at 3 days in WT mice and at 8 weeks IH in MT-KO. While early Nrf2 induction required MT, its later increase at 8 weeks in MT-KO was independent from MT.

CONCLUSIONS

We conclude that early MT and antioxidant gene response protects from fibrotic changes in long-term IH-exposed mouse lung. Without this response, pulmonary fibrosis may develop with longer IH exposure.

Theophylline exerts complex anti-ageing and anti-cytotoxicity effects in human skin ex vivo

OBJECTIVE

Theophylline is a phosphodiesterase inhibitor that is being used clinically for asthma therapy. In addition, it is recognized as a cosmetic agent with possible anti-ageing and anti-oxidative properties. Nevertheless, how it affects human skin is still poorly examined.

METHODS

Theophylline (10 or 100 µM) was administered to the culture medium of full-thickness human skin ex vivo for 24 or 72 h.

RESULTS

Theophylline stimulated protein expression of the anti-oxidant metallothionein-1 and mRNA levels of collagen I and III. Assessment of fibrillin-1 immunohistology revealed enhanced structural stability of dermal microfibrils. Theophylline also exerted extracellular matrix-protective effects by decreasing MMP-2 and MMP-9 mRNA levels, partially antagonizing the effects of menadione, the potent, toxic ROS donor. In addition, it decreased menadione-stimulated epidermal keratinocytes apoptosis. Interestingly, theophylline also increased the level of intracutaneously produced melatonin, that is the most potent ROS-protective and DNA damage repair neuromediator, and tendentially increased protein expression of MT1, the melatonin receptor. Theophylline also increased the expression of keratin 15, the stem cell marker, in the epidermal basal layer but did not change mitochondrial activity or epidermal pigmentation.

CONCLUSION

This ex vivo pilot study in human skin shows that theophylline possesses several interesting complex skin-protective properties. It encourages further examination of theophylline as a topical candidate for anti-ageing treatment.

Protection against diabetic cardiomyopathy is achieved using a combination of sulforaphane and zinc in type 1 diabetic OVE26 mice

Sulforaphane (SFN) can effectively induce nuclear factor E2-related factor 2 (Nrf2), and zinc (Zn) can effectively induce metallothionein (MT), both of which have been shown to protect against diabetic cardiomyopathy (DCM). However, it is unclear whether combined treatment with SFN and Zn offers better cardiac protection than either one alone. Here, we treated 5-week-old OVE mice that spontaneously develop type 1 diabetes with SFN and/or Zn for 18 weeks. Cardiac dysfunction, by echocardiography, and pathological alterations and remodelling, shown by cardiac hypertrophy, fibrosis, inflammation and oxidative damage, examined by histopathology, Western blotting and real-time PCR, were observed in OVE mice. All these dysfunction and pathological abnormalities seen in OVE mice were attenuated in OVE mice with treatment of either SFN, Zn or SFN/Zn, and the combined treatment with SFN/Zn was better than single treatments at ameliorating DCM. In addition, combined SFN and Zn treatment increased Nrf2 function and MT expression in the heart of OVE mice to a greater extent than SFN or Zn alone. This indicates that the dual activation of Nrf2 and MT by combined treatment with SFN and Zn may be more effective than monotherapy at preventing the development of DCM via complementary, additive mechanisms.

Contrast media (meglumine diatrizoate) aggravates renal inflammation, oxidative DNA damage and apoptosis in diabetic rats which is restored by sulforaphane through Nrf2/HO-1 reactivation

Diabetes mellitus is an independent risk factor for renal impairment in patients exposed to contrast media. It doubles the risk and decreases survival rate of contrast induced nephropathy (CIN). Sulforaphane has antioxidant properties via Nrf2 activation. The interaction of diabetes and/or sulforaphane with contrast media on Nrf2 regulation is not yet understood. Herein, diabetes was induced by a single intra-peritoneal injection of streptozotocin. Animals were then divided into five groups; control non-diabetic group; diabetic group; diabetic/sulforaphane group; diabetic/CIN group; diabetic/CIN/sulforaphane group. Animals were assessed 24 h after CIN induction. Sulforaphane improved the impaired nephrotoxicity parameters, histopathological features, and oxidative stress markers induced by contrast media (meglumine diatrizoate) in diabetic rats. Immunofluorescence detection revealed increased Nrf2 expression in kidney sections after sulforaphane pretreatment. Moreover, gene expression of Nrf2 and HO-1 were up-regulated, while IL-6 and caspase3 were down-regulated in kidney tissues of animals pretreated with sulforaphane. In NRK-52E cells, sulforaphane pretreatment significantly ameliorated the cytotoxicity of meglumine diatrizoate. However, silencing Nrf2 using small interfering RNA (siRNA) abolished the cytoprotective effects of sulforaphane. Collectively, the results of this study suggest that Nrf2/HO-1 pathway has a protective role against CIN and support the clinical implication of Nrf2 activators, such as sulforaphane, in CIN particularly in diabetic patients.

4-O-methylhonokiol ameliorates type 2 diabetes-induced nephropathy in mice likely by activation of AMPK-mediated fatty acid oxidation and Nrf2-mediated anti-oxidative stress

Diabetic nephropathy (DN) is one of the most serious long-term complications of type 2 diabetes (T2D). 4-O-methylhonokiol (MH) is one of the biologically active ingredients extracted from the Magnolia stem bark. In this study, we aim to elucidate whether treatment with MH can ameliorate or slow-down progression of DN in a T2D murine model and, if so, whether the protective response of MH correlates with AMPK-associated anti-oxidant and anti-inflammatory effects. To induce T2D, mice were fed normal diet (ND) or high fat diet (HFD) for 3 months to induce insulin resistance, followed by an intraperitoneal injection of STZ to induce hyperglycemia. Both T2D and control mice received gavage containing vehicle or MH once diabetes onset for 3 months. Once completing 3-month MH treatment, five mice from each group were sacrificed as 3 month time-point. The rest mice in each group were sacrificed 3 months later as 6 month time-point. In T2D mice, the typical DN symptoms were induced as expected, reflected by increased proteinuria, renal lipid accumulation and lipotoxic effects inducing oxidative stress, and inflammatory reactions, and final fibrosis. However, these typical DN changes were significantly prevented by MH treatment for 3 months and even at 3 months post-MH withdrawal. Mechanistically, MH renal-protection from DN may be related to lipid metabolic improvement and oxidative stress attenuation along with increases in AMPK/PGC-1α/CPT1B-mediated fatty acid oxidation and Nrf2/SOD2-mediated anti-oxidative stress. Results showed the preventive effect of MH on the renal oxidative stress and inflammation in DN.

Sulforaphane ameliorates high-fat diet-induced spermatogenic deficiency in mice†

Sulforaphane (SFN), a dietary isothiocyanate that is mainly found in cruciferous vegetables, possesses anti-oxidative and anticancer activity and modulates inflammation. However, little is known about the role of SFN in obesity-related male reproductive defects. The present study aimed to investigate the effects of SFN on high-fat diet (HFD)-induced male spermatogenic impairment and further clarify the possible underlying mechanisms. In this study, 8-week-old mice were randomly divided into four groups. Mice were fed a normal diet or an HFD with or without SFN supplementation. Sulforaphane was subcutaneously injected at a dose of 0.5 mg/kg 5 days/week for 4 weeks beginning 8 weeks after initiation of the HFD. The results demonstrated that SFN could protect against HFD-induced reproductive dysfunction in male mice. Moreover, SFN also improved reproductive ability, as demonstrated by an increased pregnancy rate and decreased embryo resorption rate in comparison to the corresponding HFD group. We also observed a decrease in apoptosis and an attenuation of endoplasmic reticulum (ER) stress after SFN treatment. In vitro studies of mouse and human sperm samples also revealed that SFN protects against the palmitic acid-induced reduction in sperm viability and motility by inhibiting ER stress in an AMP-activated protein kinase (AMPK)-dependent manner. AMPK-dependent ER stress attenuation by SFN was further confirmed using AMPK knockout mice. Taken together, these data show that SFN protects against HFD-induced male reproductive dysfunction by inhibiting ER stress and apoptosis. These findings may be helpful for identifying new therapeutic methods to treat male infertility.

Moringa Isothiocyanate Activates Nrf2: Potential Role in Diabetic Nephropathy

Moringa isothiocyanate (MIC-1) is the main active isothiocyanate found in Moringa oleifera, a plant consumed as diet and traditional herbal medicine. Compared to sulforaphane (SFN), MICs are less studied and most work have focused on its anti-inflammatory activity. The purpose of this study is to better understand the Nrf2-ARE antioxidant activity of MIC-1 and its potential in diabetic nephropathy. MIC-1 showed little toxicity from 1.25-5 μM. MIC-1 activated Nrf2-ARE at similar levels to SFN. MIC-1 also increased gene expression of downstream Nrf2 genes NQO1, HO-1, and GCLC. Protein expression of HO-1 and GCLC was elevated in MIC-1-treated cells versus control. MIC-1 suppressed pro-inflammatory cytokines in LPS-stimulated macrophages. MIC-1 reduced levels of reactive oxygen species in high glucose (HG)-treated human renal proximal tubule HK-2 cells. RNA-seq was performed to examine the transcriptome in HK-2 cells exposed to HG with or without MIC-1. Ingenuity Pathway Analysis (IPA) of RNA-seq on HK-2 cells exposed to HG identified TGFβ1 and NQO1 regulation as potentially impacted and treatment of HG-exposed HK-2 cells with MIC-1 reversed the gene expression of these two pathways. Results implicate that the transcriptional regulator TGFβ1 signaling is activated by HG and that MIC-1 can inhibit HG-stimulated TGFβ1 activation. In summary, MIC-1 activates Nrf2-ARE signaling, increases expression of Nrf2 target genes, and suppresses inflammation, while also reducing oxidative stress and possibly TGFβ1 signaling in high glucose induced renal cells. Taken together, it appears that one potential therapeutic strategy for managing DN and is currently under development in clinic is Nrf2 activation.

Beneficial Role of Some Natural Products to Attenuate the Diabetic Cardiomyopathy Through Nrf2 Pathway in Cell Culture and Animal Models

Diabetic cardiomyopathy, as one of the main cardiac complications in diabetic patients, is identified to connect with oxidative stress that is due to interruption in balance between reactive oxygen species or/and reactive nitrogen species generation and their clearance by antioxidant protection systems. Transcription factor the nuclear factor erythroid 2-related factor 2 (Nrf2) plays a significant role in maintaining the oxidative homeostasis by regulating multiple downstream antioxidants. The Nrf2 plays a significant role in ARE-mediated basal and inducible expression of more than 200 genes that can be grouped into numerous categories as well as antioxidant genes and phase II detoxifying enzymes. On the other hand, activation of Nrf2 by natural and synthetic therapeutics or antioxidants has been revealed effective for the prevention and treatment of toxicities and diseases connected with oxidative stress. Hence, recently focus has been shifted toward plants and plant-based medicines in curing such chronic diseases, as they are supposed to be less toxic. In this review, we focused on the role of some natural products on diabetic cardiomyopathy through Nrf2 pathway.

Clopidogrel Reduces Fibronectin Accumulation and Improves Diabetes-Induced Renal Fibrosis

Hyperglycemia-induced renal fibrosis causes end-stage renal disease. Clopidogrel, a platelet inhibitor, is often administered to decrease cardiovascular events in diabetic patients. We investigated whether clopidogrel can reduce diabetes-induced renal fibrosis in a streptozotocin-induced type 1 diabetes murine model and fibronectin involvement in this protective response. Diabetic and age-matched controls were sacrificed three months after the onset of diabetes, and additional controls and diabetic animals were further treated with clopidogrel or vehicle for three months. Diabetes induced renal morphological changes and fibrosis after three months. Clopidogrel, administered during the last three months, significantly decreased blood glucose, collagen and fibronectin expression compared to vehicle-treated diabetic mice. Diabetes increased TGF-β expression, inducing fibrosis via Smad-independent pathways, MAP kinases, and Akt activation at three months but returned to baseline at six months, whereas the expression of fibronectin and collagen remained elevated. Our results suggest that activation of TGF-β, CTGF, and MAP kinases are early profibrotic signaling events, resulting in significant fibronectin accumulation at the early time point and returning to baseline at a later time point. Akt activation at the three-month time point may serve as an adaptive response in T1D. Mechanisms of clopidogrel therapeutic effect on the diabetic kidney remain to be investigated as this clinically approved compound could provide novel approaches to prevent diabetes-induced renal disease, therefore improving patients' survival.

Enhanced Oxidative Damage and Nrf2 Downregulation Contribute to the Aggravation of Periodontitis by Diabetes Mellitus

Diabetes mellitus is a well-recognized risk factor for periodontitis. The goal of the present study was to elucidate whether oxidative stress and nuclear factor erythroid 2-related factor 2 (Nrf2) participate in the aggravation of periodontitis by diabetes. For this purpose, we assigned Wistar rats to control, periodontitis, diabetes, and diabetic periodontitis groups. Two weeks after induction of diabetes by streptozotocin, periodontitis was induced by ligation. Two weeks later, periodontal tissues and blood were harvested and analyzed by stereomicroscopy, immunohistochemistry, and real-time polymerase chain reaction. We found that ligation induced more severe bone loss and periodontal cell apoptosis in diabetic rats than in normal rats (p < 0.05). Compared with the control group, periodontitis significantly enhanced local oxidative damage (elevated expression of 3-nitrotyrosine, 4-hydroxy-2-nonenal, and 8-hydroxy-deoxyguanosine), whereas diabetes significantly increased systemic oxidative damage and suppressed antioxidant capacity (increased malondialdehyde expression and decreased superoxide dismutase activity) (p < 0.05). Simultaneous periodontitis and diabetes synergistically aggravated both local and systemic oxidative damage (p < 0.05); this finding was strongly correlated with the more severe periodontal destruction in diabetic periodontitis. Furthermore, gene and protein expression of Nrf2 was significantly downregulated in diabetic periodontitis (p < 0.05). Multiple regression analysis indicated that the reduced Nrf2 expression was strongly correlated with the aggravated periodontal destruction and oxidative damage in diabetic periodontitis. We conclude that enhanced local and systemic oxidative damage and Nrf2 downregulation contribute to the development and progression of diabetic periodontitis.

Dimethyl fumarate accelerates wound healing under diabetic condition

Impaired wound healing is a common complication among patients with diabetes mellitus (DM), resulting in high rates of disability and mortality. Recent findings highlighted the critical role of nuclear factor erythroid 2-related factor 2 (NRF2) - a master of cellular antioxidants scavenging excessive DM-induced free radicals - in accelerating diabetic wound healing. Dimethyl fumarate (DMF) is a potent NRF2 activator used for the treatment of multiple sclerosis. However, the effect of DMF on wound healing has not been determined. The present study investigated the effect of DMF on the diabetic and the non-diabetic wound healing in streptozotocin-induced diabetic mice and non-diabetic control mice. DMF activated NRF2 signaling under both conditions. Interestingly, DMF attenuated oxidative damage and inflammation, and accelerated wound closure in the diabetic mice. However, this effect was not observed in non-diabetic mice. Keratinocytes were treated with normal glucose (NG), high glucose (HG), or hydrogen peroxide (H2O2), in the presence or absence of DMF to assess the role of reactive oxygen species (ROS) - inducible in DM - in mediating DMF-induced protection. Both HG and H2O2 elevated ROS, oxidative damage, and inflammation, the effects of which were similarly blunted by DMF. However, in spite of the activation of NRF2, DMF lost this capability under the NG condition. The findings of this study demonstrate that ROS activate the protective effect of DMF on the diabetic wound healing.