Novel Curcumin C66 That Protects Diabetes-Induced Aortic Damage Was Associated with Suppressing JNK2 and Upregulating Nrf2 Expression and Function

The Role of the Dysregulated JNK Signaling Pathway in the Pathogenesis of Human Diseases and Its Potential Therapeutic Strategies: A Comprehensive Review

JNK is named after c-Jun N-terminal kinase, as it is responsible for phosphorylating c-Jun. As a member of the mitogen-activated protein kinase (MAPK) family, JNK is also known as stress-activated kinase (SAPK) because it can be activated by extracellular stresses including growth factor, UV irradiation, and virus infection. Functionally, JNK regulates various cell behaviors such as cell differentiation, proliferation, survival, and metabolic reprogramming. Dysregulated JNK signaling contributes to several types of human diseases. Although the role of the JNK pathway in a single disease has been summarized in several previous publications, a comprehensive review of its role in multiple kinds of human diseases is missing. In this review, we begin by introducing the landmark discoveries, structures, tissue expression, and activation mechanisms of the JNK pathway. Next, we come to the focus of this work: a comprehensive summary of the role of the deregulated JNK pathway in multiple kinds of diseases. Beyond that, we also discuss the current strategies for targeting the JNK pathway for therapeutic intervention and summarize the application of JNK inhibitors as well as several challenges now faced. We expect that this review can provide a more comprehensive insight into the critical role of the JNK pathway in the pathogenesis of human diseases and hope that it also provides important clues for ameliorating disease conditions.

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.

Regulation of Cellular Senescence in Type 2 Diabetes Mellitus: From Mechanisms to Clinical Applications

Cellular senescence is accelerated by hyperglycemia through multiple pathways. Therefore, senescence is an important cellular mechanism to consider in the pathophysiology of type 2 diabetes mellitus (T2DM) and an additional therapeutic target. The use of drugs that remove senescent cells has led to improvements in blood glucose levels and diabetic complications in animal studies. Although the removal of senescent cells is a promising approach for the treatment of T2DM, two main challenges limit its clinical application: the molecular basis of cellular senescence in each organ is yet to be understood, and the specific effect of removing senescent cells in each organ has to be determined. This review aims to discuss future applications of targeting senescence as a therapeutic option in T2DM and elucidate the characteristics of cellular senescence and senescence-associated secretory phenotype in the tissues important for regulating glucose levels: pancreas, liver, adipocytes, and skeletal muscle.

Efficacy of the monocarbonyl curcumin analog C66 in the reduction of diabetes-associated cardiovascular and kidney complications

Curcumin is a polyphenolic compound derived from turmeric that has potential beneficial properties for cardiovascular and renal diseases and is relatively safe and inexpensive. However, the application of curcumin is rather problematic due to its chemical instability and low bioavailability. The experimental results showed improved chemical stability and potent pharmacokinetics of one of its analogs – (2E,6E)-2,6-bis[(2-trifluoromethyl)benzylidene]cyclohexanone (C66). There are several advantages of C66, like its synthetic accessibility, structural simplicity, improved chemical stability (in vitro and in vivo), presence of two reactive electrophilic centers, and good electron-accepting capacity. Considering these characteristics, we reviewed the literature on the application of C66 in resolving diabetes-associated cardiovascular and renal complications in animal models. We also summarized the mechanisms by which C66 is preventing the release of pro-oxidative and pro-inflammatory molecules in the priming and in activation stage of cardiomyopathy, renal fibrosis, and diabetic nephropathy. The cardiovascular protective effect of C66 against diabetes-induced oxidative damage is Nrf2 mediated but mainly dependent on JNK2. In general, C66 causes inhibition of JNK2, which reduces cardiac inflammation, fibrosis, oxidative stress, and apoptosis in the settings of diabetic cardiomyopathy. C66 exerts a powerful antifibrotic effect by reducing inflammation-related factors (MCP-1, NF-κB, TNF-α, IL-1β, COX-2, and CAV-1) and inducing the expression of anti-inflammatory factors (HO-1 and NEDD4), as well as targeting TGF-β/SMADs, MAPK/ERK, and PPAR-γ pathways in animal models of diabetic nephropathy. Based on the available evidence, C66 is becoming a promising drug candidate for improving cardiovascular and renal health.

Modulation of integrin receptor by polyphenols: Downstream Nrf2-Keap1/ARE and associated cross-talk mediators in cardiovascular diseases

As a group of heterodimeric and transmembrane glycoproteins, integrin receptors are widely expressed in various cell types overall the body. During cardiovascular dysfunction, integrin receptors apply inhibitory effects on the antioxidative pathways, including nuclear factor erythroid 2-related factor 2 (Nrf2)-Kelch like ECH Associated Protein 1 (Keap1)/antioxidant response element (ARE) and interconnected mediators. As such, dysregulation in integrin signaling pathways influences several aspects of cardiovascular diseases (CVDs) such as heart failure, arrhythmia, angina, hypertension, hyperlipidemia, platelet aggregation and coagulation. So, modulation of integrin pathway could trigger the downstream antioxidant pathways toward cardioprotection. Regarding the involvement of multiple aforementioned mediators in the pathogenesis of CVDs, as well as the side effects of conventional drugs, seeking for novel alternative drugs is of great importance. Accordingly, the plant kingdom could pave the road in the treatment of CVDs. Of natural entities, polyphenols are multi-target and accessible phytochemicals with promising potency and low levels of toxicity. The present study aims at providing the cardioprotective roles of integrin receptors and downstream antioxidant pathways in heart failure, arrhythmia, angina, hypertension, hyperlipidemia, platelet aggregation and coagulation. The potential role of polyphenols has been also revealed in targeting the aforementioned dysregulated signaling mediators in those CVDs.

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.

An update on molecular mechanisms of curcumin effect on diabetes

Owing to its prevalent nature, diabetes mellitus has become one of the most serious endocrine illnesses affecting a patient's quality of life due to the manifestation of side effects such as cardiovascular diseases, retinopathy, neuropathy, and nephropathy. Curcumin ((1E, 6E) 21, 7-bis (4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione), a major compound of turmeric, has been used in conventional medicine because of its safe nature and cost-effectiveness to meliorate diabetes and its comorbidities. These effects have also been observed in rodent models of diabetes resulting in a reduction of glycemia and blood lipids. Both the preventive and therapeutic activities of this compound are due to its antioxidant and anti-inflammatory characteristics. Furthermore, preclinical outcomes and clinical investigation demonstrate that the use of curcumin neutralizes insulin resistance, obesity, and hyperglycemia. Despite the many benefits of curcumin, its two limiting factors, solubility and bioavailability, remain a challenge for researchers; therefore, several methods such as drug formulation, nano-drug delivery, and the use of curcumin analogs have been developed to deliver curcumin and increase its bioavailability. PRACTICAL APPLICATIONS: The rise of people with type 2 diabetes has become a major concern at the global healthcare level. The best diabetes treatments today are anti-diabetic drug administration, lifestyle-related interventions (such as healthy eating and daily physical activity), arterial pressure detection, and fat control. The polyphenol curcumin, found in turmeric, can promote health by acting on a variety of cellular signaling pathways. This review article discusses curcumin and its role in the treatment of diabetes.

Nrf2-Related Therapeutic Effects of Curcumin in Different Disorders

Curcumin is a natural polyphenol with antioxidant, antibacterial, anti-cancer, and anti-inflammation effects. This substance has been shown to affect the activity of Nrf2 signaling, a pathway that is activated in response to stress and decreases levels of reactive oxygen species and electrophilic substances. Nrf2-related effects of curcumin have been investigated in different contexts, including gastrointestinal disorders, ischemia-reperfusion injury, diabetes mellitus, nervous system diseases, renal diseases, pulmonary diseases, cardiovascular diseases as well as cancers. In the current review, we discuss the Nrf2-mediated therapeutic effects of curcumin in these conditions. The data reviewed in the current manuscript indicates curcumin as a potential activator of Nrf2 and a therapeutic substance for the protection of cells in several pathological conditions.

Nrf2 Regulation by Curcumin: Molecular Aspects for Therapeutic Prospects

Nuclear factor erythroid 2 p45-related factor (2Nrf2) is an essential leucine zipper protein (bZIP) that is primarily located in the cytoplasm under physiological conditions. Nrf2 principally modulates endogenous defense in response to oxidative stress in the brain.In this regard, Nrf2 translocates into the nucleus and heterodimerizes with the tiny Maf or Jun proteins. It then attaches to certain DNA locations in the nucleus, such as electrophile response elements (EpRE) or antioxidant response elements (ARE), to start the transcription of cytoprotective genes. Many neoplasms have been shown to have over activated Nrf2, strongly suggesting that it is responsible for tumors with a poor prognosis. Exactly like curcumin, Zinc-curcumin Zn (II)-curc compound has been shown to induce Nrf2 activation. In the cancer cell lines analyzed, Zinc-curcumin Zn (II)-curc compound can also display anticancer effects via diverse molecular mechanisms, including markedly increasing heme oxygenase-1 (HO-1) p62/SQSTM1 and the Nrf2 protein levels along with its targets. It also strikingly decreases the levels of Nrf2 inhibitor, Kelch-like ECH-associated protein 1 (Keap1) protein.As a result, the crosstalk between p62/SQSTM1 and Nrf2 could be used to improve cancer patient response to treatments. The interconnected anti-inflammatory and antioxidative properties of curcumin resulted from its modulatory effects on Nrf2 signaling pathway have been shown to improve insulin resistance. Curcumin exerts its anti-inflammatory impact through suppressing metabolic reactions and proteins such as Keap1 that provoke inflammation and oxidation. A rational amount of curcumin-activated antioxidant Nrf2 HO-1 and Nrf2-Keap1 pathways and upregulated the modifier subunit of glutamate-cysteine ligase involved in the production of the intracellular antioxidant glutathione. Enhanced expression of glutamate-cysteine ligase, a modifier subunit (GLCM), inhibited transcription of glutamate-cysteine ligase, a catalytic subunit (GCLC). A variety of in vivo, in vitro and clinical studies has been done so far to confirm the protective role of curcumin via Nrf2 regulation. This manuscript is designed to provide a comprehensive review on the molecular aspects of curcumin and its derivatives/analogs via regulation of Nrf2 regulation.

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.

JNK signaling pathway in metabolic disorders: An emerging therapeutic target

Metabolic Syndrome is a multifactorial disease associated with increased risk of cardiovascular disorders, type 2 diabetes mellitus, fatty liver disease, etc. Various stress stimuli such as reactive oxygen species, endoplasmic reticulum stress, mitochondrial dysfunction, increased cytokines, or free fatty acids are known to aggravate progressive development of hyperglycemia and hyperlipidemia. Although the exact mechanism contributing to altered metabolism is unclear. Evidence suggests stress kinase role to be a crucial one in metabolic syndrome. Stress kinase, c-jun N-terminal kinase activation (JNK) is involved in various metabolic manifestations including obesity, insulin resistance, fatty liver disease as well as cardiometabolic disorders. It emerged as a foremost mediator in regulating metabolism in the liver, skeletal muscle, adipose tissue as well as pancreatic β cells. It has three isoforms each having a unique and tissue-specific role in altered metabolism. Current findings based on genetic manipulation or chemical inhibition studies identified JNK isoforms to play a central role in the regulation of whole-body metabolism, suggesting it to be a novel therapeutic target. Hence, it is imperative to elucidate its role in metabolic syndrome onset and progression. The purpose of this review is to elucidate in vitro and in vivo implications of JNK signaling along with the therapeutic strategy to inhibit specific isoform. Since metabolic syndrome is an array of diseases and complex pathway, carefully examining each tissue will be important for specific treatment strategies.

Curcumin and cardiovascular diseases: Focus on cellular targets and cascades

Cardiovascular diseases (CVDs) are one of the leading causes of the most considerable mortality globally, and it has been tried to find the molecular mechanisms and design new drugs that triggered the molecular target. Curcumin is the main ingredient of Curcuma longa (turmeric) that has been used in traditional medicine for treating several diseases for years. Numerous investigations have indicated the beneficial effect of Curcumin in modulating multiple signaling pathways involved in oxidative stress, inflammation, apoptosis, and proliferation. The cardiovascular protective effects of Curcumin against CVDs have been indicated in several studies. In the current review study, we provided novel information on Curcumin's protective effects against various CVDs and potential molecular signaling targets of Curcumin. Nonetheless, more studies should be performed to discover the exact molecular target of Curcumin against CVDs.

Curcumin derivatives for Type 2 Diabetes management and prevention of complications

Type 2 diabetes Mellitus (T2DM) is characterized by chronically increased blood glucose levels, which is associated with impairment of the inflammatory and oxidative state and dyslipidaemia. Although it is considered a world heath concern and one of the most studied diseases, we are still pursuing an effective therapy for both the pathophysiological mechanisms and the complications. Curcumin, a natural compound found in the rhizome of Curcuma longa, is well known for its numerous biological activities, as demonstrated by several studies supporting that curcumin possesses hypoglycaemic, hypolipidemic, anti-inflammatory and antioxidant properties, among others. These effects have been explored to the attenuation of hyperglycaemia and progression of DM complications, being appointed as a potential therapeutic approach. Besides its strong intrinsic activity, the polyphenol has low bioavailability, compromising its therapeutic efficacy. In order to overcome this limitation, several chemical strategies have been applied to curcumin, such as drug delivery systems, chemical manipulation and the use of adjuvant therapies. Given the promising results obtained with curcumin derivative, in this review we discuss not only the therapeutic targets of curcumin, but also its most recently developed analogues and their efficacy in the management of T2DM pathophysiology and complications.

Endoplasmic reticulum stress and destruction of pancreatic β cells in type 1 diabetes

Type 1 diabetes (T1D) results from dysfunction of pancreatic islets β cells. Recent studies supported that endoplasmic reticulum (ER) stress takes an important role in pancreatic β cell excessive loss, resulting in T1D. Here, we aimed to review the relationship between ER stress and T1D. Additionally, we also reviewed the potential mechanisms underlying ER stress mediated T1D. Studies have shown that severe ER stress is directly involved in the pancreatic β cells destruction and pathogenesis of T1D. ER stress plays a key part in pancreatic β cells and T1D, which will help in developing new effective therapeutics for T1D.

Curcumin and arterial function in health and disease: impact on oxidative stress and inflammation

PURPOSE OF REVIEW

The purpose of this review is to provide a concise overview of the polyphenol curcumin for improving arterial health, specifically endothelial function and arterial stiffness, to reduce cardiovascular disease (CVD) risk and to highlight potential mechanisms of action by which curcumin may improve artery function.

RECENT FINDINGS

The primary findings of this review support the notion for curcumin to improve arterial health both with aging and obesity. There are few clinical trials on curcumin, and those that currently exist are small in scale but provide evidence for curcumin to improve endothelial function in older adults and reduce arterial stiffness in young, obese men. The antioxidant and anti-inflammatory properties of curcumin appear to be important targets of curcumin that are related to improved arterial health. Mechanistic studies have revealed superoxide dismutase, heme oxygenase-1 and nuclear factor erythroid 2-related factor 2 as emerging targets for the beneficial effects of curcumin on the vasculature.

SUMMARY

In summary, the efficacy of curcumin for improving arterial function is promising in the limited number of clinical studies performed to date. Still, much investigation is needed to elucidate the effectiveness of curcumin for improving arterial health to lower CVD risk.