Drug Delivery Strategies for Curcumin and Other Natural Nrf2 Modulators of Oxidative Stress-Related Diseases

Regulation of immunomodulatory networks by Nrf2-activation in immune cells: Redox control and therapeutic potential in inflammatory diseases

Inflammatory diseases present a serious health challenge due to their widespread prevalence and the severe impact on patients' lives. In the quest to alleviate the burden of these diseases, nuclear factor erythroid 2-related factor 2 (Nrf2) has emerged as a pivotal player. As a transcription factor intimately involved in cellular defense against metabolic and oxidative stress, Nrf2's role in modulating the inflammatory responses of immune cells has garnered significant attention. Recent findings suggest that Nrf2's ability to alter the redox status of cells underlies its regulatory effects on immune responses. Our review delves into preclinical and clinical evidence that underscores the complex influence of Nrf2 activators on immune cell phenotypes, particularly in the inflammatory milieu. By offering a detailed analysis of Nrf2's role in different immune cell populations, we cast light on the potential of Nrf2 activators in shaping the immune response towards a more regulated state, mitigating the adverse effects of inflammation through modeling redox status of immune cells. Furthermore, we explore the innovative use of nanoencapsulation techniques that enhance the delivery and efficacy of Nrf2 activators, potentially advancing the treatment strategies for inflammatory ailments. We hope this review will stimulate the development and expansion of Nrf2-targeted treatments that could substantially improve outcomes for patients suffering from a broad range of inflammatory diseases.

A soy protein enzymatic digest mitigates Nrf2-related oxidative stress and attenuates depression-like behavior in a mouse model of sub-chronic restraint stress

Continuous oxidative stress conditions have been identified as a major cause of various neuropsychiatric disorders, including depression. The present study investigated the potential antidepressant-like effects of a soy protein enzymatic digest (SPD) containing soy-deprestatin, which is a soy-derived peptide with reported antidepressant-like effects, as well as its ability to mitigate oxidative stress in the brain caused by sub-chronic restraint stress. Mice were divided into two groups: a control group and restraint stress group. The restraint stress group was further divided into two groups administered water or SPD. After repeated short-time restraints over five days, we evaluated immobility times in the tail suspension test, and antioxidant enzyme activities, glutathione levels, oxidative stress maker levels, and the gene expression levels of Nrf2 and antioxidant enzymes in the brain. The results obtained showed that the oral administration of SPD reduced immobility times in mice exposed to restraint stress. In comparisons with the water-treated restraint group, the administration of SPD restored superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase activities and glutathione levels and prevented restraint stress-induced increases in malondialdehyde, carbonyl protein, and 8-OHdG levels in the restraint stress group. In addition, high expression levels of Nrf2, HO-1, NQO-1 and GCLC were observed in the SPD-treated restraint group. These results suggest that SPD attenuated repeated restraint stress-induced depression-like behaviors by mitigating oxidative stress through the activation of the Nrf2 signaling pathway.

Oxidative Stress and the Nuclear Factor Erythroid 2-Related Factor 2 (Nrf2) Pathway in Multiple Sclerosis: Focus on Certain Exogenous and Endogenous Nrf2 Activators and Therapeutic Plasma Exchange Modulation

The pathogenesis of multiple sclerosis (MS) suggests that, in genetically susceptible subjects, T lymphocytes undergo activation in the peripheral compartment, pass through the BBB, and cause damage in the CNS. They produce pro-inflammatory cytokines; induce cytotoxic activities in microglia and astrocytes with the accumulation of reactive oxygen species, reactive nitrogen species, and other highly reactive radicals; activate B cells and macrophages and stimulate the complement system. Inflammation and neurodegeneration are involved from the very beginning of the disease. They can both be affected by oxidative stress (OS) with different emphases depending on the time course of MS. Thus, OS initiates and supports inflammatory processes in the active phase, while in the chronic phase it supports neurodegenerative processes. A still unresolved issue in overcoming OS-induced lesions in MS is the insufficient endogenous activation of the Nuclear Factor Erythroid 2-Related Factor 2 (Nrf2) pathway, which under normal conditions plays an essential role in mitochondria protection, OS, neuroinflammation, and degeneration. Thus, the search for approaches aiming to elevate endogenous Nrf2 activation is capable of protecting the brain against oxidative damage. However, exogenous Nrf2 activators themselves are not without drawbacks, necessitating the search for new non-pharmacological therapeutic approaches to modulate OS. The purpose of the present review is to provide some relevant preclinical and clinical examples, focusing on certain exogenous and endogenous Nrf2 activators and the modulation of therapeutic plasma exchange (TPE). The increased plasma levels of nerve growth factor (NGF) in response to TPE treatment of MS patients suggest their antioxidant potential for endogenous Nrf2 enhancement via NGF/TrkA/PI3K/Akt and NGF/p75NTR/ceramide-PKCζ/CK2 signaling pathways.

Recent progress in nanotechnology-based drug carriers for resveratrol delivery

Resveratrol is a polyphenol with diverse pharmacological activities, but its clinical efficacy is limited due to low solubility/permeability, light-induced isomerization, auto-oxidation, and rapid metabolism. Nanodelivery systems, such as liposomes, polymeric nanoparticles, lipid nanocarriers, micelles, nanocrystals, inorganic nanoparticles, nanoemulsions, protein-based nanoparticles, exosomes, macrophages, and red blood cells (RBCs) have shown great potential for improving the solubility, biocompatibility, and therapeutic efficacy of resveratrol. This review comprehensively summarizes the recent advances in resveratrol nanoencapsulation and describes potential strategies to improve the pharmacokinetics of existing nanoformulations, enhance targeting, reduce toxicity, and increase drug release and encapsulation efficiency. The article also suggests that in order to avoid potential safety issues, resveratrol nanoformulations must be tested in vivo in a wide range of diseases.

Celecoxib Oral Solution and the Benefits of Self-Microemulsifying Drug Delivery Systems (SMEDDS) Technology: A Narrative Review

INTRODUCTION

The oral route of drug delivery is the most widespread and preferred route of administration, but it has several limitations, including variable pharmacokinetics (PK), reduced dissolution and absorption, and gastrointestinal irritation. Further, many compounds have low aqueous solubility, which also limits intestinal absorption.

METHODS

For this narrative review, we conducted a literature search of PubMed until August 2022, focusing on emulsions, microemulsions, nanoemulsions, and self-emulsifying drug delivery systems.

RESULTS

The self-microemulsifying drug delivery system (SMEDDS) overcomes these limitations of hydrophobic compounds to enhance their bioavailability. A SMEDDS formulation is a clear, thermodynamically stable, oil-in-water emulsion of lipid, solubilized drug, and two surfactants, which spontaneously forms droplets < 100 nm in diameter. These components help deliver presolubilized drugs to the gastrointestinal tract, while protecting them from degradation in gastric acid or first-pass hepatic metabolism. SMEDDS formulations have improved oral drug delivery in the treatment of cancer (paclitaxel), viral infections (ritonavir), and migraine headache (ibuprofen and celecoxib oral solution). The American Headache Society recently updated their consensus statement for the acute treatment of migraine and included a selective cyclo-oxygenase-2 selective inhibitor formulated in SMEDDS, celecoxib oral solution. This SMEDDS formulation showed pronounced improvement in bioavailability compared with celecoxib capsules, allowing for a low dose of celecoxib in the oral solution to provide safe and effective acute migraine treatment. Here, we will focus on SMEDDS formulations, what differentiates them from other analogous emulsions as vehicles for poorly soluble drugs, and their clinical application in the acute treatment of migraine.

CONCLUSIONS

Oral drugs reformulated in SMEDDS have shown accelerated times to peak plasma drug concentrations and increased maximum plasma concentrations, compared with capsules, tablets, or suspensions. SMEDDS technology increases both drug absorption and bioavailability of lipophilic drugs, compared with other formulations. Clinically, this allows the use of lower doses with improved PK profiles without compromising efficacy, as shown with celecoxib oral solution for the acute treatment of migraine.

Nano shield: a new tetrahedral framework nucleic acids-based solution to radiation-induced mucositis

Radiation-induced oral mucositis (RIOM) is considered to be one of the most important public health problems today, affecting the overall well-being of millions of patients who have received radiotherapy. Nevertheless, the field of preventing and treating RIOM is still widely unexplored. Curcumin (Cur) with its promising anti-inflammatory and antioxidant properties is accompanied with obstacles in application, including poor dissolubility, instability and low bioavailability. In this study, a tetrahedral framework nucleic acid drug delivery system (TFNAS) was synthesized and established using a novel method to carry Cur (Cur-TFNAS) for efficient drug delivery. The results showed that Cur-TFNAS enhanced the antioxidant capacity of human oral mucosal keratin-forming cells (HOKs) compared to free Cur and TFNAS. Meanwhile, Cur-TFNAS reduced DNA damage and shielded the cells from inflammatory factors. A similar result was also well documented in vivo. Herein, we consider that Cur-TFNAS acts as a nano-shield for preventing radiation oral mucositis and shows important clinical value in the future.

Multiple mechanisms of curcumin targeting spinal cord injury

Spinal cord injury (SCI) is an irreversible disease process with a high disability and mortality rate. After primary spinal cord injury, the secondary injury may occur in sequence, which is composed of ischemia and hypoxia, excitotoxicity, calcium overload, oxidative stress and inflammation, resulting in massive death of parenchymal cells in the injured area, followed by the formation of syringomyelia. Effectively curbing the process of secondary injury can promote nerve repair and improve functional prognosis. As the main active ingredient in turmeric, curcumin can play an important role in reducing inflammation and oxidation, protecting the neurons, and ultimately reducing spinal cord injury. This article reviews the effects of curcumin on the repair of nerve injury, with emphasis on the various mechanisms by which curcumin promotes the treatment of spinal cord injury.

Curcumin intake during lactation suppresses oxidative stress through upregulation of nuclear factor erythroid 2-related factor 2 in the kidneys of fructose-loaded female rat offspring exposed to maternal protein restriction

BACKGROUND

A high-fructose diet causes the progression of chronic kidney disease. Maternal malnutrition during pregnancy and lactation increases oxidative stress, leading to chronic renal diseases later in life. We investigated whether curcumin intake during lactation could suppress oxidative stress and regulate NF-E2-related factor 2 (Nrf2) expression in the kidneys of fructose-loaded female rat offspring exposed to maternal protein restriction.

METHODS

Pregnant Wistar rats received diets containing 20% (NP) or 8% (LP) casein and 0 or 2.5 g "highly absorptive curcumin" /kg diet containing-LP diets (LP/LP or LP/Cur) during lactation. At weaning, female offspring received either distilled water (W) or 10% fructose solution (Fr) and were divided into four groups: NP/NP/W, LP/LP/W, LP/LP/Fr, and LP/Cur/Fr. At week 13, glucose (Glc), triacylglycerol (Tg), and malondialdehyde (MDA) levels in the plasma, macrophages number, fibrotic area, glutathione (GSH) levels, glutathione peroxidase (GPx) activity, protein expression levels of Nrf2, heme oxygenase-1 (HO-1), and superoxide dismutase 1 (SOD1) in the kidneys were examined.

RESULTS

The plasma levels of Glc, TG, and MDA, the number of macrophages, and the percentage of fibrotic area in the kidneys of the LP/Cur/Fr group were significantly lower than those of the LP/LP/Fr group. The expression of Nrf2 and its downstream molecules HO-1 and SOD1, GSH levels, and GPx activity in the kidneys of the LP/Cur/Fr group were significantly higher than those of the LP/LP/Fr group.

CONCLUSIONS

Maternal curcumin intake during lactation may suppress oxidative stress by upregulating Nrf2 expression in the kidneys of fructose-loaded female offspring exposed to maternal protein restriction.

Curcumin-resveratrol nano-formulation counteracting hyperammonemia in rats

Malnutrition and low dietary protein intake could be risk factors for developing peripheral and central hyperammonemia, especially in pediatrics. Both curcumin and resveratrol proved to be effective against several hepatic and cerebral injuries. They were reported to be beneficial in lowering circulating ammonia levels, yet both are known for their low bioavailability. The use of pharmaceutical nano-formulations as delivery systems for these two nutraceuticals could solve the aforementioned problem. Hence, the present study aimed to investigate the valuable outcome of using a combination of curcumin and resveratrol in a nanoemulsion formulation, to counteract protein-deficient diet (PDD)-induced hyperammonemia and the consequent complications in male albino rats. Results revealed that using a nanoemulsion containing both curcumin and resveratrol at a dose of (5 + 5 mg/kg) effectively reduced hepatic and brain ammonia levels, serum ALT and AST levels, hepatic and brain nitric oxide levels, oxidative DNA damage as well as disrupted cellular energy performance. In addition, there was a substantial increase in brain levels of monoamines, and a decrease in glutamate content. Therefore, it can be concluded that the use of combined curcumin and resveratrol nanoemulsion is an effective means of ameliorating the hepatic and cerebral adverse effects resulting from PDD-induced hyperammonemia in rats.

A novel solvent-free co-grinding preparation improves curcumin bioavailability in healthy volunteers: A single-center crossover study

Curcumin, from the rhizome of turmeric (Curcuma longa L.), has a wide variety of biological activities. Unfortunately, its poor water-solubility greatly limits its bioavailability. The purpose of this study was to evaluate CUMINUP60®, a novel preparation utilizing a solvent-free, co-grinding method designed to improve curcumin's bioavailability. We performed a single-center crossover experiment to compare the new product with standard 95% curcumin in the blood plasma of twelve healthy adults (10 males, 2 females). Total bioavailability of curcumin and its sulfate and glucuronide conjugates from the test product, measured by their areas under the curve over 12 h (AUC_0-T), showed a combined increase of 178-fold over standard curcumin and its conjugates from the reference product. The new product represents a significant improvement for providing greater bioavailability of curcumin, as compared with several other branded preparations. It therefore has broad applications for preparing curcumin as a more effective health ingredient in functional foods, beverages, and nutraceuticals.

The role of Nrf2 in periodontal disease by regulating lipid peroxidation, inflammation and apoptosis

Nuclear factor E2-related factor 2(Nrf2) is a transcription factor that mainly regulates oxidative stress in the body. It initiates the expression of several downstream antioxidants, anti-inflammatory proteins and detoxification enzymes through the Kelch-like ECH-associating protein 1 (Keap1) -nuclear factor E2-related factor 2(Nrf2) -antioxidant response element (ARE) signaling pathway. Its anti-apoptosis, anti-oxidative stress and anti-inflammatory effects have gradually become the focus of periodontal disease research in recent years. In this paper, the structure and function of Nrf2 pathway and its mechanism of action in the treatment of periodontitis in recent years were analyzed and summarized, so as to further clarify the relationship between Nrf2 pathway and oxidative stress in the occurrence and development of periodontitis, and to provide ideas for the development of new treatment drugs targeting Nrf2 pathway.

Therapeutic potency of curcumin for allergic diseases: A focus on immunomodulatory actions

In light of increasing research evidence on the molecular mechanisms of allergic diseases, the crucial roles of innate and acquired immunity in the disease's pathogenesis have been well highlighted. In this respect, much attention has been paid to the modulation of unregulated and unabated inflammatory responses aiming to suppress pathologic immune responses in treating allergic diseases. One of the most important natural compounds with a high potency of immune modulation is curcumin, an active polyphenol compound derived from turmeric, Curcuma longa L. Curcumin's immunomodulatory action mainly arises from its interactions with an extensive collection of immune cells such as mast cells, eosinophils, epithelial cells, basophils, neutrophils, and lymphocytes. Up to now, there has been no detailed investigation of curcumin's immunomodulatory actions in allergic diseases. So, the present review study aims to prepare an overview of the immunomodulatory effects of curcumin on the pathologic innate immune responses and dysregulated functions of T helper (T_H) subtypes, including T_H1, T_H2, T_H17, and regulator T cells (Tregs) by gathering evidence from several studies of In-vitro and In-vivo. As the second aim of the present review, we also discuss some novel strategies to overcome the limitation of curcumin in clinical use. Finally, this review also assesses the therapeutic potential of curcumin regarding its immunomodulatory actions in allergic diseases.

Efficacy and safety of dietary polyphenol supplementation in the treatment of non-alcoholic fatty liver disease: A systematic review and meta-analysis

Background

Dietary polyphenol treatment of non-alcoholic fatty liver disease (NAFLD) is a novel direction, and the existing clinical studies have little effective evidence for its therapeutic effect, and some studies have inconsistent results. The effectiveness of dietary polyphenols in the treatment of NAFLD is still controversial. The aim of this study was to evaluate the therapeutic efficacy of oral dietary polyphenols in patients with NAFLD.

Methods

The literature (both Chinese and English) published before 30 April 2022 in PubMed, Cochrane, Medline, CNKI, and other databases on the treatment of NAFLD with dietary polyphenols was searched. Manual screening, quality assessment, and data extraction of search results were conducted strictly according to the inclusion and exclusion criteria. RevMan 5.3 software was used to perform the meta-analysis.

Results

The RCTs included in this study involved dietary supplementation with eight polyphenols (curcumin, resveratrol, naringenin, anthocyanin, hesperidin, catechin, silymarin, and genistein) and 2,173 participants. This systematic review and meta-analysis found that 1) curcumin may decrease body mass index (BMI), Aspartate aminotransferase (AST), Alanine aminotransferase (ALT), Triglycerides (TG) total cholesterol (TC), and Homeostasis Model Assessment-Insulin Resistance (HOMA-IR) compared to placebo; and curcumin does not increase the occurrence of adverse events. 2) Although the meta-analysis results of all randomized controlled trials (RCTs) did not reveal significant positive changes, individual RCTs showed meaningful results. 3) Naringenin significantly decreased the percentage of NAFLD grade, TG, TC, and low-density lipoprotein cholesterol (LDL-C) and increased high-density lipoprotein cholesterol (HDL-C) but had no significant effect on AST and ALT, and it is a safe supplementation. 4) Only one team presents a protocol about anthocyanin (from Cornus mas L. fruit extract) in the treatment of NAFLD. 5) Hesperidin may decrease BMI, AST, ALT, TG, TC, HOMA-IR, and so on. 6) Catechin may decrease BMI, HOMA-IR, and TG level, and it was well tolerated by the patients. 7) Silymarin was effective in improving ALT and AST and reducing hepatic fat accumulation and liver stiffness in NAFLD patients.

Conclusion

Based on current evidence, curcumin can reduce BMI, TG, TC, liver enzymes, and insulin resistance; catechin can reduce BMI, insulin resistance, and TG effectively; silymarin can reduce liver enzymes. For resveratrol, naringenin, anthocyanin, hesperidin, and catechin, more RCTs are needed to further evaluate their efficacy and safety.

Normal and Pathological NRF2 Signalling in the Central Nervous System

The nuclear factor erythroid 2-related factor 2 (NRF2) was originally described as a master regulator of antioxidant cellular response, but in the time since, numerous important biological functions linked to cell survival, cellular detoxification, metabolism, autophagy, proteostasis, inflammation, immunity, and differentiation have been attributed to this pleiotropic transcription factor that regulates hundreds of genes. After 40 years of in-depth research and key discoveries, NRF2 is now at the center of a vast regulatory network, revealing NRF2 signalling as increasingly complex. It is widely recognized that reactive oxygen species (ROS) play a key role in human physiological and pathological processes such as ageing, obesity, diabetes, cancer, and neurodegenerative diseases. The high oxygen consumption associated with high levels of free iron and oxidizable unsaturated lipids make the brain particularly vulnerable to oxidative stress. A good stability of NRF2 activity is thus crucial to maintain the redox balance and therefore brain homeostasis. In this review, we have gathered recent data about the contribution of the NRF2 pathway in the healthy brain as well as during metabolic diseases, cancer, ageing, and ageing-related neurodegenerative diseases. We also discuss promising therapeutic strategies and the need for better understanding of cell-type-specific functions of NRF2 in these different fields.

Synergistic Antioxidant Activity and Enhanced Stability of Curcumin Encapsulated in Vegetal Oil-Based Microemulsion and Gel Microemulsions

Curcumin, due to its antioxidant, antibacterial, anti-inflammatory, and antitumoral activity, has attracted huge attention in applications in many fields such as pharmacy, medicine, nutrition, cosmetics, and biotechnology. The stability of curcumin-based products and preservation of antioxidant properties are still challenges in practical applications. Stability and antioxidant properties were studied for curcumin encapsulated in O/W microemulsion systems and three related gel microemulsions. Only biodegradable and biocompatible ingredients were used for carriers: grape seed oil as oily phase, Tween 80, and Plurol^® Diisostearique CG as a surfactant mix, and ethanol as a co-solvent. For the gel microemulsions, water-soluble polymers, namely Carbopol^® 980 NF, chitosan, and sodium hyaluronate were used. The influence of UVC irradiation and heat treatment on the degradation kinetics of curcumin in the formulations was studied. Because of the antioxidant character of the microemulsion oily phase, the possibility of a synergistic effect between grape seed oil and curcumin was explored. In this study, the high efficiency of the studied drug delivery systems to ensure protection from external degradative factors was confirmed. Also, the influence of the encapsulation in microemulsion and derived gel microemulsion systems on the antioxidant capacity curcumin was studied, and a synergistic effect with vegetal oil was demonstrated.

Oxidative Stress, Inflammation and Connexin Hemichannels in Muscular Dystrophies

Muscular dystrophies (MDs) are a heterogeneous group of congenital neuromuscular disorders whose clinical signs include myalgia, skeletal muscle weakness, hypotonia, and atrophy that leads to progressive muscle disability and loss of ambulation. MDs can also affect cardiac and respiratory muscles, impairing life-expectancy. MDs in clude Duchenne muscular dystrophy, Emery-Dreifuss muscular dystrophy, facioscapulohumeral muscular dystrophy and limb-girdle muscular dystrophy. These and other MDs are caused by mutations in genes that encode proteins responsible for the structure and function of skeletal muscles, such as components of the dystrophin-glycoprotein-complex that connect the sarcomeric-actin with the extracellular matrix, allowing contractile force transmission and providing stability during muscle contraction. Consequently, in dystrophic conditions in which such proteins are affected, muscle integrity is disrupted, leading to local inflammatory responses, oxidative stress, Ca²⁺-dyshomeostasis and muscle degeneration. In this scenario, dysregulation of connexin hemichannels seem to be an early disruptor of the homeostasis that further plays a relevant role in these processes. The interaction between all these elements constitutes a positive feedback loop that contributes to the worsening of the diseases. Thus, we discuss here the interplay between inflammation, oxidative stress and connexin hemichannels in the progression of MDs and their potential as therapeutic targets.

Protective Effects of Curcumin in Cardiovascular Diseases—Impact on Oxidative Stress and Mitochondria

Cardiovascular diseases (CVDs) contribute to a large part of worldwide mortality. Similarly, two of the major risk factors for these diseases, aging and obesity, are also global problems. Aging, the gradual decline of body functions, is non-modifiable. Obesity, a modifiable risk factor for CVDs, also predisposes to type 2 diabetes mellitus (T2DM). Moreover, it affects not only the vasculature and the heart but also specific fat depots, which themselves have a major impact on the development and progression of CVDs. Common denominators of aging, obesity, and T2DM include oxidative stress, mitochondrial dysfunction, metabolic abnormalities such as altered lipid profiles and glucose metabolism, and inflammation. Several plant substances such as curcumin, the major active compound in turmeric root, have been used for a long time in traditional medicine and for the treatment of CVDs. Newer mechanistic, animal, and human studies provide evidence that curcumin has pleiotropic effects and attenuates numerous parameters which contribute to an increased risk for CVDs in aging as well as in obesity. Thus, curcumin as a nutraceutical could hold promise in the prevention of CVDs, but more standardized clinical trials are required to fully unravel its potential.