Potential drugs which activate nuclear factor E2-related factor 2 signaling to prevent diabetic cardiovascular complications: A focus on fumaric acid esters

A review of how the saffron (Crocus sativus) petal and its main constituents interact with the Nrf2 and NF-κB signaling pathways

The primary by-product of saffron (Crocus sativus) processing is saffron petals, which are produced in large quantities but are discarded. The saffron petals contain a variety of substances, including alkaloids, anthocyanins, flavonoids, glycosides, kaempferol, and minerals. Pharmacological investigations revealed the antibacterial, antidepressant, antidiabetic, antihypertensive, antinociceptive, antispasmodic, antitussive, hepatoprotective, immunomodulatory, and renoprotective properties of saffron petals, which are based on their antioxidant, anti-inflammatory, and antiapoptotic effects. The nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway protects against oxidative stress, carcinogenesis, and inflammation. Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-ĸB) is a protein complex involved in approximately all animal cells and participates in different biological procedures such as apoptosis, cell growth, development, deoxyribonucleic acid (DNA) transcription, immune response, and inflammation. The pharmacological properties of saffron and its compounds are discussed in this review, along with their associated modes of action, particularly the Nrf2 and NF-ĸB signaling pathways. Without considering a time constraint, our team conducted this review using search engines or electronic databases like PubMed, Scopus, and Web of Science. Saffron petals and their main constituents may have protective effects in numerous organs such as the brain, colon, heart, joints, liver, lung, and pancreas through several mechanisms, including the Nrf2/heme oxygenase-1 (HO-1)/Kelch-like ECH-associated protein 1 (Keap1) signaling cascade, which would then result in its antioxidant, anti-inflammatory, antiapoptotic, and therapeutic effects.

Response to fumaric acid esters for plaque type psoriasis in real-world practice is largely independent of patient characteristics at baseline - a multivariable regression analysis from the German psoriasis registry PsoBest

OBJECTIVES

Fumaric acid esters (FAEs) are a well-established treatment option for long-term therapy of moderate to severe plaque psoriasis. This study examines effectiveness of FAEs for the treatment of plaque psoriasis in real-world practice at 12 months and if patient characteristics affect the odds of clinical response.

METHODS

A descriptive, multivariable logistic regression analysis was conducted in a cohort drawn from the German registry PsoBest. Baseline patient characteristics were assessed as potential treatment effect modifiers.

RESULTS

444 patients (mean age 47.0 years, 39.0% female) were eligible for response analysis using nonresponder imputation at month 12. Of these, 39.6% achieved clinical response, i.e., Psoriasis Area and Severity Index (PASI) ≤3 or skin clearance. In logistic regression analysis (R² = 0.114), only baseline PASI was a significant factor: patients with PASI <10 had a 4 times higher odds (p ≤ 0.001, OR 4.088), patients with PASI of 10-20 a twofold higher odds of response (p ≤ 0.044, OR 1.961) compared to those with PASI >20. Neither sex, age, body weight, disease duration, comorbidity nor pre-treatment had an impact on the odds of response (p > 0.05).

CONCLUSIONS

FAEs showed a favorable response at 12 months, largely independent of patient characteristics.

Repurposing Dimethyl Fumarate for Cardiovascular Diseases: Pharmacological Effects, Molecular Mechanisms, and Therapeutic Promise

Dimethyl fumarate (DMF) is a small molecule that has been shown to assert potent in vivo immunoregulatory and anti-inflammatory therapeutic actions. The drug has been approved and is currently in use for treating multiple sclerosis and psoriasis in the USA and Europe. Since inflammatory reactions have been significantly implicated in the etiology and progression of diverse disease states, the pharmacological actions of DMF are presently being explored and generalized to other diseases where inflammation needs to be suppressed and immunoregulation is desirable, either as a monotherapeutic agent or as an adjuvant. In this review, we focus on DMF, and present an overview of its mechanism of action while briefly discussing its pharmacokinetic profile. We further discuss in detail its pharmacological uses and highlight its potential applications in the treatment of cardiovascular diseases. DMF, with its unique combination of anti-inflammatory and vasculoprotective effects, has the potential to be repurposed as a therapeutic agent in patients with atherosclerotic cardiovascular disease. The clinical studies mentioned in this review with respect to the beneficial effects of DMF in atherosclerosis involve observations in patients with multiple sclerosis and psoriasis in small cohorts and for short durations. The findings of these studies need to be assessed in larger prospective clinical trials, ideally with a double-blind randomized study design, investigating the effects on cardiovascular endpoints as well as morbidity and mortality. The long-term impact of DMF therapy on cardiovascular diseases also needs to be confirmed.

Signaling Pathways Related to Oxidative Stress in Diabetic Cardiomyopathy

Diabetes is a chronic metabolic disease that is increasing in prevalence and causes many complications. Diabetic cardiomyopathy (DCM) is a complication of diabetes that is associated with high mortality, but it is not well defined. Nevertheless, it is generally accepted that DCM refers to a clinical disease that occurs in patients with diabetes and involves ventricular dysfunction, in the absence of other cardiovascular diseases, such as coronary atherosclerotic heart disease, hypertension, or valvular heart disease. However, it is currently uncertain whether the pathogenesis of DCM is directly attributable to metabolic dysfunction or secondary to diabetic microangiopathy. Oxidative stress (OS) is considered to be a key component of its pathogenesis. The production of reactive oxygen species (ROS) in cardiomyocytes is a vicious circle, resulting in further production of ROS, mitochondrial DNA damage, lipid peroxidation, and the post-translational modification of proteins, as well as inflammation, cardiac hypertrophy and fibrosis, ultimately leading to cell death and cardiac dysfunction. ROS have been shown to affect various signaling pathways involved in the development of DCM. For instance, OS causes metabolic disorders by affecting the regulation of PPARα, AMPK/mTOR, and SIRT3/FOXO3a. Furthermore, OS participates in inflammation mediated by the NF-κB pathway, NLRP3 inflammasome, and the TLR4 pathway. OS also promotes TGF-β-, Rho-ROCK-, and Notch-mediated cardiac remodeling, and is involved in the regulation of calcium homeostasis, which impairs ATP production and causes ROS overproduction. In this review, we summarize the signaling pathways that link OS to DCM, with the intention of identifying appropriate targets and new antioxidant therapies for DCM.

The potential role of Keap1-Nrf2 pathway in the pathogenesis of Alzheimer's disease, type 2 diabetes, and type 2 diabetes-related Alzheimer's disease

Kelch-like ECH associated-protein 1 (Keap1)-nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway is thought to be the key regulatory process defensing oxidative stress in multiple organs. Type 2 diabetes mellitus (T2DM) and Alzheimer's disease (AD) are both serious global health problems with high prevalence. A growing number of literatures have suggested a possible link between Keap1-Nrf2 signaling pathway and the pathological changes of T2DM, AD as well as T2DM-related AD. The current review mainly discusses how the damaged Keap1-Nrf2 signaling pathway leads to dysregulated redox molecular signaling, which may contribute to the pathogenesis of AD and T2DM-related cognitive dysfunction, as well as some compounds targeting this pathway. The further exploration of the mechanisms of this pathway could provide novel therapeutic strategies to improve cognitive function, through restoration of expression or translocation of Nrf2 and scavenging excessive free radicals.

Curcumin Activates the Nrf2 Pathway and Induces Cellular Protection Against Oxidative Injury

Curcumin is a naturally occurring polyphenol that is isolated from the rhizome of Curcuma longa (turmeric). This medicinal compound has different biological activities, including antioxidant, antibacterial, antineoplastic, and anti-inflammatory. It also has therapeutic effects on neurodegenerative disorders, renal disorders, and diabetes mellitus. Curcumin is safe and well-tolerated at high concentrations without inducing toxicity. It seems that curcumin is capable of targeting the Nrf2 signaling pathway in protecting the cells against oxidative damage. Besides, this strategy is advantageous in cancer therapy. Accumulating data demonstrates that curcumin applies four distinct ways to stimulate the Nrf2 signaling pathway, including inhibition of Keap1, affecting the upstream mediators of Nrf2, influencing the expression of Nrf2 and target genes, and finally, improving the nuclear translocation of Nrf2. In the present review, the effects of curcumin on the Nrf2 signaling pathway to exert its therapeutic and biological activities has been discussed.

Relationship between oxidative stress and nuclear factor-erythroid-2-related factor 2 signaling in diabetic cardiomyopathy (Review)

Diabetic cardiomyopathy (DCM) is the leading cause of death worldwide, and oxidative stress was discovered to serve an important role in the pathophysiology of the condition. An imbalance between free radicals and antioxidant defenses is known to be associated with cellular dysfunction, leading to the development of various types of cardiac disease. Nuclear factor-erythroid-2-related factor 2 (NRF2) is a transcription factor that controls the basal and inducible expression levels of various antioxidant genes and other cytoprotective phase II detoxifying enzymes, which are ubiquitously expressed in the cardiac system. Kelch-like ECH-associated protein 1 (Keap1) serves as the main intracellular regulator of NRF2. Emerging evidence has revealed that NRF2 is a critical regulator of cardiac homeostasis via the suppression of oxidative stress. The activation of NRF2 was discovered to enhance specific endogenous antioxidant defense factors, one of which is antioxidant response element (ARE), which was subsequently illustrated to detoxify and counteract oxidative stress-associated DCM. The NRF2 signaling pathway is closely associated with the development of various types of cardiac disease, including ischemic heart disease, heart failure, myocardial infarction, atrial fibrillation and myocarditis. Therefore, it is hypothesized that drugs targeting this pathway may be developed to inhibit the activation of NRF2 signaling, thereby preventing the occurrence of DCM and effectively treating the disease.

Therapeutic and biological activities of berberine: The involvement of Nrf2 signaling pathway

Since the beginning of the 21st century, studies have focused on developing drugs from naturally occurring compounds. Berberine (Brb) as a plant-derived compound is of interest. It is an isoquinone alkaloid which is derived from Berberis aristata, Berberis aquifolium and Berberis vulgaris. This plant-derived compound has a variety of pharmacological effects such as antioxidant, anti-inflammatory, antidiabetic, antidiarrheal, antitumor, antimicrobial, and anti-inflammatory. Various studies have demonstrated the therapeutic and biological activities of Brb, but there is a lack of a precise review to manifest the signaling pathway of action of Brb. The nuclear factor erythroid 2-related factor 2 (Nrf2) is a highly conserved pathway which mainly involves in preservation of redox balance. At the present review, we describe the therapeutic and biological activities of Brb as well as the relevant mechanisms specially focused on the Nrf2 signaling pathway.

Current Status and Challenges of NRF2 as a Potential Therapeutic Target for Diabetic Cardiomyopathy

Diabetic cardiomyopathy is one of the main causes of heart failure and death in patients with diabetes mellitus. Reactive oxygen species produced excessively in diabetes mellitus cause necrosis, apoptosis, ferroptosis, inflammation, and fibrosis of the myocardium as well as impair the cardiac structure and function. It is increasingly clear that oxidative stress is a principal cause of diabetic cardiomyopathy. The transcription factor nuclear factor-erythroid 2 p45-related factor 2 (NRF2) activates the transcription of more than 200 genes in the human genome. Most of the proteins translated from these genes possess anti-oxidant, anti-inflammatory, anti-apoptotic, anti-ferroptotic, and anti-fibrotic actions. There is a growing body of evidence indicating that NRF2 and its target genes are crucial in preventing high glucose-induced oxidative damage in diabetic cardiomyopathy. Recently, many natural and synthetic activators of NRF2 are shown to possess promising therapeutic effects on diabetic cardiomyopathy in animal models of diabetic cardiomyopathy. Targeting NRF2 signaling by pharmacological entities is a potential approach to ameliorating diabetic cardiomyopathy. However, the persistent high expression of NRF2 in cancer tissues also protects the growth of cancer cells. This "dark side" of NRF2 increases the challenges of using NRF2 activators to treat diabetic cardiomyopathy. In addition, some NRF2 activators were found to have off-target effects. In this review, we summarize the current status and challenges of NRF2 as a potential therapeutic target for diabetic cardiomyopathy.

The protective effect of kaempferol on heart via the regulation of Nrf2, NF-κβ, and PI3K/Akt/GSK-3β signaling pathways in isoproterenol-induced heart failure in diabetic rats

This study was designed to delineate the effect of kaempferol (KF) on heart failure (HF) in diabetic rats. Streptozotocin-induced male diabetic rats received KF orally at 10 and 20 mg/kg for 42 consecutive days. In last 2 days of the experimental period, isoproterenol was subcutaneously injected at 85 mg/kg to induce HF. The hearts were processed for hemodynamic, biochemical, molecular, and histological investigations. Systolic blood pressure, diastolic blood pressure, and mean arterial blood pressure were elevated in KF-treated HF-induced diabetic rats. Moreover, KF treatment resulted in decreased fasting blood glucose and glycosylated hemoglobin levels with increased serum insulin levels. Besides, serum cardiac injury markers like troponin-I, creatine kinase-muscle/brain, lactate dehydrogenase, and brain natriuretic peptide levels were significantly reduced in KF treatment. KF treatment has shown decrease in cardiac heme oxygenase-1, nuclear factor erythroid 2-related factor 2 (Nrf-2), and γ-glutamylcysteine synthetase with increased Keap1 mRNA levels. The cardioprotection of KF was improved by inhibition of apoptosis via blocking phosphorylation of Akt/glycogen synthase kinase (GSK)-3β and p38 mitogen-activated protein-kinase/extracellular signal-regulated kinases signaling pathways in HF-induced diabetic rats. Moreover, reduced cardiac apoptosis in KF treatment was confirmed by decreased terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) positive cells, histopathological changes in HF-induced diabetic rats. Therefore, the cardioprotective effect of KF is attributed to the regulation of Nrf2, nuclear factor kappa-light-chain-enhancer of activated B cells, and Akt/GSK-3β signaling pathways in HF-induced diabetic rats.

Kaempferol attenuates hyperglycemia-induced cardiac injuries by inhibiting inflammatory responses and oxidative stress

PURPOSE

Suppression of inflammation and oxidative stress is an attractive strategy to against diabetic cardiomyopathy (DCM). Kaempferol (KPF) exerts both anti-inflammatory and antioxidant pharmacological properties. However, little is known about the effect of KPF on protecting myocardial injury in diabetes. The present study aimed to investigate the effect of KPF on DCM and underlying mechanism.

METHODS

Anti-inflammation and anti-oxidative stress activities of KPF were evaluated in H9c2 cells or primary cardiomyocytes by real-time quantitate PCR, immunoblotting, immunofluorescence, ELISA, and FACS. Streptozotocin (STZ)-induced type 1 diabetes mellitus mice were constructed. Corresponding to experiments in vitro, the therapeutic effect of KPF was also assessed using heart tissues from mice.

RESULTS

KPF significantly inhibited high glocose (HG) induced expression of inflammatory cytokines and generation of ROS, leading to reduced fibrotic responses and cell apoptosis in vitro. KPF mediated DCM protective effects through inhibiting nuclear factor-κB (NF-κB) nucleus translocation and activating nuclear factor-erythroid 2 p45-related factor-2 (Nrf-2). In STZ-induced type 1 diabetic mouse model, KPF prevented diabetes-induced cardiac fibrosis and apoptosis. These changes were also accompanied by reducing inflammation and oxidative stress in diabetic mice hearts.

CONCLUSION

KPF is a potential therapeutic agent for the treatment of DCM, mechanically linked to inhibition of NF-κB and Nrf-2 activation.

Nrf2 at the heart of oxidative stress and cardiac protection

The NFE2L2 gene encodes the transcription factor Nrf2 best known for regulating the expression of antioxidant and detoxification genes. Gene knockout approaches have demonstrated its universal cytoprotective features. While Nrf2 has been the topic of intensive research in cancer biology since its discovery in 1994, understanding the role of Nrf2 in cardiovascular disease has just begun. The literature concerning Nrf2 in experimental models of atherosclerosis, ischemia, reperfusion, cardiac hypertrophy, heart failure, and diabetes supports its cardiac protective character. In addition to antioxidant and detoxification genes, Nrf2 has been found to regulate genes participating in cell signaling, transcription, anabolic metabolism, autophagy, cell proliferation, extracellular matrix remodeling, and organ development, suggesting that Nrf2 governs damage resistance as well as wound repair and tissue remodeling. A long list of small molecules, most derived from natural products, have been characterized as Nrf2 inducers. These compounds disrupt Keap1-mediated Nrf2 ubquitination, thereby prohibiting proteasomal degradation and allowing Nrf2 protein to accumulate and translocate to the nucleus, where Nrf2 interacts with sMaf to bind to ARE in the promoter of genes. Recently alternative mechanisms driving Nrf2 protein increase have been revealed, including removal of Keap1 by autophagy due to p62/SQSTM1 binding, inhibition of βTrCP or Synoviolin/Hrd1-mediated ubiquitination of Nrf2, and de novo Nrf2 protein translation. We review here a large volume of literature reporting historical and recent discoveries about the function and regulation of Nrf2 gene. Multiple lines of evidence presented here support the potential of dialing up the Nrf2 pathway for cardiac protection in the clinic.

Pathophysiological Fundamentals of Diabetic Cardiomyopathy

Diabetic cardiomyopathy (DCM) was first recognized more than four decades ago and occurred independent of cardiovascular diseases or hypertension in both type 1 and type 2 diabetic patients. The exact mechanisms underlying this disease remain incompletely understood. Several pathophysiological bases responsible for DCM have been proposed, including the presence of hyperglycemia, nonenzymatic glycosylation of large molecules (e.g., proteins), energy metabolic disturbance, mitochondrial damage and dysfunction, impaired calcium handling, reactive oxygen species formation, inflammation, cardiac cell death, and cardiac hypertrophy and fibrosis, leading to impairment of cardiac contractile functions. Increasing evidence also indicates the phenomenon called "metabolic memory" for diabetes-induced cardiovascular complications, for which epigenetic modulation seemed to play an important role, suggesting that the aforementioned pathogenic bases may be regulated by epigenetic modification. Therefore, this review aims at briefly summarizing the current understanding of the pathophysiological bases for DCM. Although how epigenetic mechanisms play a role remains incompletely understood now, extensive clinical and experimental studies have implicated its importance in regulating the cardiac responses to diabetes, which are believed to shed insight into understanding of the pathophysiological and epigenetic mechanisms for the development of DCM and its possible prevention and/or therapy. © 2017 American Physiological Society. Compr Physiol 7:693-711, 2017.

Oxidative Stress-Related Mechanisms and Antioxidant Therapy in Diabetic Retinopathy

Diabetic retinopathy (DR) is one of the most common microvascular complications of diabetes and is the leading cause of blindness in young adults. Oxidative stress has been implicated as a critical cause of DR. Metabolic abnormalities induced by high-glucose levels are involved in the development of DR and appear to be influenced by oxidative stress. The imbalance between reactive oxygen species (ROS) production and the antioxidant defense system activates several oxidative stress-related mechanisms that promote the pathogenesis of DR. The damage caused by oxidative stress persists for a considerable time, even after the blood glucose concentration has returned to a normal level. Animal experiments have proved that the use of antioxidants is a beneficial therapeutic strategy for the treatment of DR, but more data are required from clinical trials. The aims of this review are to highlight the improvements to our understanding of the oxidative stress-related mechanisms underlying the development of DR and provide a summary of the main antioxidant therapy strategies used to treat the disease.

Chemical-induced coordinated and reciprocal changes in heme metabolism, cytochrome P450 synthesis and others in the liver of humans and rodents

A wide variety of drugs and chemicals have been shown to produce induction and inhibition of heme-metabolizing enzymes, and of drug-metabolizing enzymes, including cytochrome P450s (P450s, CYPs), which consist of many molecular species with lower substrate specificity. Such chemically induced enzyme alterations are coordinately or reciprocally regulated through the same and/or different signal transductions. From the toxicological point of view, these enzymatic changes sometimes exacerbate inherited diseases, such as precipitation of porphyrogenic attacks, although the induction of these enzymes is dependent on the animal species in response to the differences in the stimuli of the liver, where they are also metabolized by P450s. Since P450s are hemoproteins, their induction and/or inhibition by chemical compounds could be coordinately accompanied by heme synthesis and/or inhibition. This review will take a retrospective view of research works carried out in our department and current findings on chemical-induced changes in hepatic heme metabolism in many places, together with current knowledge. Specifically, current beneficial aspects of induction of heme oxygenase-1, a rate-limiting heme degradation enzyme, and its relation to reciprocal and coordinated changes in P450s, with special reference to CYP2A5, in the liver are discussed. Mechanistic studies are also summarized in relation to current understanding on these aspects. Emphasis is also paid to an example of a single chemical compound that could cause various changes by mediating multiple signal transduction systems. Current toxicological studies have been developing by utilizing a sophisticated "omics" technology and survey integrated changes in the tissues produced by the administration of a chemical, even in time- and dose-dependent manners. Toxicological studies are generally carried out step by step to determine and elucidate mechanisms produced by drugs and chemicals. Such approaches are correct; however, current "omics" technology can clarify overall changes occurring in the cells and tissues after treating animals with drugs and chemicals, integrate them and discuss the results. In the present review, we will discuss chemical-induced similar changes of heme synthesis and degradation, and of P450s and finally convergence to similar or different directions.