Possible involvement of transcriptional activation of nuclear factor erythroid 2-related factor 2 (Nrf2) in the protective effect of caffeic acid on paraquat-induced oxidative damage in Drosophila melanogaster

In vitro antiproliferative effects of Vatairea macrocarpa (Benth.) Ducke lectin on human tumor cell lines and in vivo evaluation of its toxicity in Drosophila melanogaster

Tumor cells may develop alterations in glycosylation patterns during the initial phase of carcinogenesis. These alterations may be important therapeutic targets for lectins with antitumor action. This work aimed to evaluate the in vitro cytotoxicity of VML on tumor and non-tumor cells (concentration of 25 μg/mL and then microdiluted) and evaluate its in vivo toxicity at different concentrations (1.8, 3.5 and 7.0 μg/mL), using Drosophila melanogaster. Toxicity in D. melanogaster evaluated mortality rate, as well as oxidative stress markers (TBARS, iron levels, nitric oxide levels, protein and non-protein thiols). The cytotoxicity assay showed that VML had cytotoxic effect on leukemic lines HL-60 (IC50 = 3.5 μg/mL), KG1 (IC50 = 18.6 μg/mL) and K562 (102.0 μg/mL). In the toxicity assay, VML showed no reduction in survival at concentrations of 3.5 and 7.0 μg/mL and did not alter oxidative stress markers at any concentrations tested. Cytotoxicity of VML from HL-60, KG1 and K562 cells could arise from the interaction between the lectin and specific carbohydrates of tumor cells. In contrast, effective concentrations of VML against no-tumor cells human keratinocyte - HaCat and in the D. melanogaster model did not show toxicity, suggesting that VML is a promising molecule in vivo studies involving leukemic cells.

Natural products as non-covalent and covalent modulators of the KEAP1/NRF2 pathway exerting antioxidant effects

By controlling several antioxidant and detoxifying genes at the transcriptional level, including NAD(P)H quinone oxidoreductase 1 (NQO1), multidrug resistance-associated proteins (MRPs), UDP-glucuronosyltransferase (UGT), glutamate-cysteine ligase catalytic (GCLC) and modifier (GCLM) subunits, glutathione S-transferase (GST), sulfiredoxin1 (SRXN1), and heme-oxygenase-1 (HMOX1), the KEAP1/NRF2 pathway plays a crucial role in the oxidative stress response. Accordingly, the discovery of modulators of this pathway, activating cellular signaling through NRF2, and targeting the antioxidant response element (ARE) genes is pivotal for the development of effective antioxidant agents. In this context, natural products could represent promising drug candidates for supplementation to provide antioxidant capacity to human cells. In recent decades, by coupling in silico and experimental methods, several natural products have been characterized to exert antioxidant effects by targeting the KEAP1/NRF2 pathway. In this review article, we analyze several natural products that were investigated experimentally and in silico for their ability to modulate KEAP1/NRF2 by non-covalent and covalent mechanisms. These latter represent the two main sections of this article. For each class of inhibitors, we reviewed their antioxidant effects and potential therapeutic applications, and where possible, we analyzed the structure-activity relationship (SAR). Moreover, the main computational techniques used for the most promising identified compounds are detailed in this survey, providing an updated view on the development of natural products as antioxidant agents.

Investigating anti-inflammatory and apoptotic actions of fucoidan concentrating on computational and therapeutic applications

Fucoidan is linked to a variety of biological processes. Differences in algae species, extraction, seasons, and locations generate structural variability in fucoidan, affecting its bioactivities. Nothing is known about fucoidan from the brown alga Dictyota bartayresiana, its anti-inflammatory properties, or its inherent mechanism. This study aimed to investigate the anti-inflammatory properties of fucoidan isolated from D. bartayresiana against LPS-induced RAW 264.7 macrophages and to explore potential molecular pathways associated with this anti-inflammatory effects. Fucoidan was first isolated and purified from D. bartayresiana, and then, MTT assay was used to determine the effect of fucoidan on cell viability. Its effects on reactive oxygen species (ROS) formation and apoptosis were also studied using the ROS assay and acridine orange/ethidium bromide fluorescence labelling, respectively. Molecular docking and molecular dynamics simulation studies were performed on target proteins NF-κB and TNF-α to identify the route implicated in these inflammatory events. It was observed that fucoidan reduced LPS-induced inflammation in RAW 264.7 cells. Fucoidan also decreased the LPS-stimulated ROS surge and was found to induce apoptosis in the cells. Molecular docking and molecular dynamics simulation studies revealed that fucoidan's potent anti-inflammatory action was achieved by obstructing the NF-κB signalling pathway. These findings were particularly noteworthy and novel because fucoidan isolated from D. bartayresiana had not previously been shown to have anti-inflammatory properties in RAW 264.7 cells or to exert its activity by obstructing the NF-κB signalling pathway. Conclusively, these findings proposed fucoidan as a potential pharmaceutical drug for inflammation-related diseases.

Dimethyl fumarate attenuates paraquat-induced pulmonary oxidative stress, inflammation and fibrosis in mice

Paraquat (PQ) is the most important cationic bipyridyl herbicide in the agricultural industry, which is very toxic to humans and animals and causes disruption in many organs, mainly in the lungs. Dimethyl fumarate (DMF) is an immune-modulating drug used in the treatment of multiple sclerosis and psoriasis shows antioxidant, anti-inflammatory, and antifibrotic effects. In this study, the ameliorative effects of DMF (10, 30 and 100 mg/kg, orally) on PQ (30 mg/kg) model of lung damage were evaluated in male mice. DMF was given daily for 7 days and PQ was administrated in the fourth day in a single dose. On the eighth day, the animals were sacrificed, and their lung tissue were removed. The results indicated that DMF can ameliorate PQ-induced the significant increase in lung index, hydroxyproline, as well as TBARS, TGF-β, NF-κB and decrease in the amount of total thiol, catalase, glutathione peroxidase, superoxide dismutase, Nrf-2, and INF-γ. The histopathological results confirmed indicated findings. The results showed that the protective effect of DMF on PQ-induced toxicity is mediated through antioxidant, anti-inflammatory and antifibrotic activities.

Pharmacological Modulation of Nrf2/HO-1 Signaling Pathway as a Therapeutic Target of Parkinson's Disease

Parkinson’s disease (PD) is a complex neurodegenerative disorder featuring both motor and nonmotor symptoms associated with a progressive loss of dopaminergic neurons in the substantia nigra pars compacta. Oxidative stress (OS) has been implicated in the pathogenesis of PD. Genetic and environmental factors can produce OS, which has been implicated as a core contributor to the initiation and progression of PD through the degeneration of dopaminergic neurons. The transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) orchestrates activation of multiple protective genes, including heme oxygenase-1 (HO-1), which protects cells from OS. Nrf2 has also been shown to exert anti-inflammatory effects and modulate both mitochondrial function and biogenesis. Recently, a series of studies have reported that different bioactive compounds were shown to be able to activate Nrf2/antioxidant response element (ARE) and can ameliorate PD-associated neurotoxin, both in animal models and in tissue culture. In this review, we briefly overview the sources of OS and the association between OS and the pathogenesis of PD. Then, we provided a concise overview of Nrf2/ARE pathway and delineated the role played by activation of Nrf2/HO-1 in PD. At last, we expand our discussion to the neuroprotective effects of pharmacological modulation of Nrf2/HO-1 by bioactive compounds and the potential application of Nrf2 activators for the treatment of PD. This review suggests that pharmacological modulation of Nrf2/HO-1 signaling pathway by bioactive compounds is a therapeutic target of PD.

Evaluation of the neuroprotective effect of rutin on Drosophila melanogaster about behavioral and biochemical aspects induced by mercury chloride (HgCl2)

Mercury chloride (HgCl₂) acts as a bioaccumulator capable of causing numerous neurological and physiological changes in organisms in a negative way. However, rutin has been considered a very effective antioxidant compound in the treatment of neurodegenerative diseases, as it can neutralize radicals capable of damaging neuronal cells. In this context, this study aimed to evaluate rutin as a neoprotective agent against the damage induced by HgCl₂ in Drosophila melanogaster. The exposure of the flies to the agents was carried out in triplicate, and about 150 adult flies were evaluated. To assess the antioxidant action of rutin, MTT, phenanthroline, nitric oxide, total thiols and NPSH tests were carried out in the following concentrations: Control (1500 μL of distilled water), 1 mg/g of HgCl₂, 0.5 mg/g of Rutin + HgCl₂, 1 mg/g of Rutin + HgCl₂, 2 mg/g of Rutin + HgCl₂. The locomotion test was verified by negative geotaxis, the result of which showed that flies exposed to HgCl₂ had difficulties in flight. The group treated with HgCl₂ alone had a high mortality rate, while in combination with different concentrations of rutin, it heard a moderate reduction in the number of deaths, as well as in the negative geotaxis data in which the rutin had a positive effect. An increase in iron (II) levels was observed at the highest concentrations of rutin, while at low concentrations, rutin significantly decreased nitric oxide levels. The HgCl₂ + R group (2 mg/g) showed a significant increase in the total thiols content, while for the NPSH all rutin concentrations showed a significant increase in the levels of non-protein thiols. Our results demonstrate that mercury chloride can cause oxidative stress in D. melanogaster. However, the results suggest that rutin has antioxidant and protective effects against the damage caused by HgCl₂.

Surface-modified ZrO2 nanoparticles with caffeic acid: Characterization and in vitro evaluation of biosafety for placental cells

The toxicity of hybrid nanoparticles, consisting of non-toxic components, zirconium dioxide nanoparticles (ZrO₂ NPs), and caffeic acid (CA), was examined against four different cell lines (HTR-8 SV/Neo, JEG-3, JAR, and HeLa). Stable aqueous ZrO₂ sol, synthesized by forced hydrolysis, consists of 3-4 nm in size primary particles organized in 30-60 nm in size snowflake-like particles, as determined by transmission electron microscopy and direct light scattering measurements. The surface modification of ZrO₂ NPs with CA leads to the formation of an interfacial charge transfer (ICT) complex followed by the appearance of absorption in the visible spectral range. The spectroscopic observations are complemented with the density functional theory calculations using a cluster model. The ZrO₂ NPs and CA are non-toxic against four different cell lines in investigated concentration range. Also, ZrO₂ NPs promote the proliferation of HTR-8 SV/Neo, JAR, and HeLa cells. On the other hand, hybrid ZrO₂/CA NPs induced a significant reduction of the viability of the JEG-3 cells (39 %) for the high concentration of components (1.6 mM ZrO₂ and 0.4 mM CA).

Nrf2 as a potential target for Parkinson's disease therapy

Parkinson's disease (PD) is a complex neurodegenerative disorder featuring both motor and nonmotor symptoms associated with a progressive loss of dopaminergic neurons in the substantia nigra pars compacta. Conventionally, PD treatment options have focused on dopamine replacement and provide only symptomatic relief. However, disease-modifying therapies are still unavailable. Mechanistically, genetic and environmental factors can produce oxidative stress which has been implicated as a core contributor to the initiation and progression of PD through the degeneration of dopaminergic neurons. Importantly, nuclear factor erythroid 2-related factor 2 (Nrf2) is essential for maintaining redox homeostasis by binding to the antioxidant response element which exists in the promoter regions of most genes coding for antioxidant enzymes. Furthermore, protein kinase C, mitogen-activated protein kinases, and phosphotidylinositol 3-kinase have been implicated in the regulation of Nrf2 activity during PD. Here, we review the evidence supporting the regulation of Nrf2 through Keap1-dependent and Keap1-independent mechanisms. We also address that targeting Nrf2 may provide a therapeutic option to mitigate oxidative stress-associated PD. Finally, we discuss currently known classes of small molecule activators of Nrf2, including Nrf2-activating compounds in PD.

Natural Phytochemicals as Novel Therapeutic Strategies to Prevent and Treat Parkinson's Disease: Current Knowledge and Future Perspectives

Parkinson's disease (PD) is the second-most common neurodegenerative chronic disease affecting both cognitive performance and motor functions in aged people. Yet despite the prevalence of this disease, the current therapeutic options for the management of PD can only alleviate motor symptoms. Research has explored novel substances for naturally derived antioxidant phytochemicals with potential therapeutic benefits for PD patients through their neuroprotective mechanism, targeting oxidative stress, neuroinflammation, abnormal protein accumulation, mitochondrial dysfunction, endoplasmic reticulum stress, neurotrophic factor deficit, and apoptosis. The aim of the present study is to perform a comprehensive evaluation of naturally derived antioxidant phytochemicals with neuroprotective or therapeutic activities in PD, focusing on their neuropharmacological mechanisms, including modulation of antioxidant and anti-inflammatory activity, growth factor induction, neurotransmitter activity, direct regulation of mitochondrial apoptotic machinery, prevention of protein aggregation via modulation of protein folding, modification of cell signaling pathways, enhanced systemic immunity, autophagy, and proteasome activity. In addition, we provide data showing the relationship between nuclear factor E2-related factor 2 (Nrf2) and PD is supported by studies demonstrating that antiparkinsonian phytochemicals can activate the Nrf2/antioxidant response element (ARE) signaling pathway and Nrf2-dependent protein expression, preventing cellular oxidative damage and PD. Furthermore, we explore several experimental models that evaluated the potential neuroprotective efficacy of antioxidant phytochemical derivatives for their inhibitory effects on oxidative stress and neuroinflammation in the brain. Finally, we highlight recent developments in the nanodelivery of antioxidant phytochemicals and its neuroprotective application against pathological conditions associated with oxidative stress. In conclusion, naturally derived antioxidant phytochemicals can be considered as future pharmaceutical drug candidates to potentially alleviate symptoms or slow the progression of PD. However, further well-designed clinical studies are required to evaluate the protective and therapeutic benefits of phytochemicals as promising drugs in the management of PD.

Direct Keap1-kelch inhibitors as potential drug candidates for oxidative stress-orchestrated diseases: A review on In silico perspective

The recent outcry in the search for direct keap1 inhibitors requires a quicker and more effective drug discovery process which is an inherent property of the Computer Aided Drug Discovery (CADD) to bring drug candidates into the clinic for patient's use. This Keap1 (negative regulator of ARE master activator) is emerging as a therapeutic strategy to combat oxidative stress-orchestrated diseases. The advances in computer algorithm and compound databases require that we highlight the functionalities that this technology possesses that can be exploited to target Keap1-Nrf2 PPI. Therefore, in this review, we uncover the in silico approaches that had been exploited towards the identification of keap1 inhibition in the light of appropriate fitting with relevant amino acid residues, we found 3 and 16 other compounds that perfectly fit keap1 kelch pocket/domain. Our goal is to harness the parameters that could orchestrate keap1 surface druggability by utilizing hotspot regions for virtual fragment screening and identification of hotspot residues.

Drosophila as an emerging model organism for studies of food-derived antioxidants

Dietary supplementation with antioxidants provides health benefits by preventing diseases caused by oxidative stress and damage. Consequently, there has been growing interest in the study of antioxidative foods and their active ingredients. Oxidative stress and antioxidative responses are mechanistically conserved from Drosophila to mammals. Therefore, as a well-established model organism with a short life cycle and advantages of genetic manipulation, the fruit fly has been increasingly employed to assess functions of antioxidants in vivo. In this review, the antioxidative defense mechanisms, methods used and assays developed in Drosophila to evaluate antioxidant supplementation, are highlighted. The main manifestations of antioxidation include reduction of reactive species, up-regulation of endogenous antioxidants, inhibition on oxidative damage to biomacromolecules, enhanced resistance against oxidative stress and extension of lifespan, which are related to the activations of nuclear factor erythroid 2-related factor 2-antioxidant response element pathway and other adaptive responses. Moreover, the key considerations and future perspectives for the application of Drosophila models in the studies of food-derived antioxidants are discussed.

Alternative model organisms for toxicological fingerprinting of relevant parameters in food and nutrition

In the field of (food) toxicology, there is a strong trend of replacing animal trials with alternative methods for the assessment of adverse health effects in humans. The replacement of animal trials is not only driven by ethical concerns but also by the number of potential testing substances (food additives, packaging material, contaminants, and toxicants), which is steadily increasing. In vitro 2D cell culture applications in combination with in silico modeling might provide an applicable first response. However, those systems lack accurate predictions of metabolic actions. Thus, alternative in vivo models could fill the gap between cell culture and animal trials. In this review, we highlight relevant studies in the field and spotlight the applicability of alternative models, including C. elegans, D. rerio, Drosophila, HET-CAM and Lab-on-a-chip.

Neuroprotective Effects of Coffee Bioactive Compounds: A Review

Coffee is one of the most widely consumed beverages worldwide. It is usually identified as a stimulant because of a high content of caffeine. However, caffeine is not the only coffee bioactive component. The coffee beverage is in fact a mixture of a number of bioactive compounds such as polyphenols, especially chlorogenic acids (in green beans) and caffeic acid (in roasted coffee beans), alkaloids (caffeine and trigonelline), and the diterpenes (cafestol and kahweol). Extensive research shows that coffee consumption appears to have beneficial effects on human health. Regular coffee intake may protect from many chronic disorders, including cardiovascular disease, type 2 diabetes, obesity, and some types of cancer. Importantly, coffee consumption seems to be also correlated with a decreased risk of developing some neurodegenerative conditions such as Alzheimer's disease, Parkinson's disease, and dementia. Regular coffee intake may also reduce the risk of stroke. The mechanism underlying these effects is, however, still poorly understood. This review summarizes the current knowledge on the neuroprotective potential of the main bioactive coffee components, i.e., caffeine, chlorogenic acid, caffeic acid, trigonelline, kahweol, and cafestol. Data from both in vitro and in vivo preclinical experiments, including their potential therapeutic applications, are reviewed and discussed. Epidemiological studies and clinical reports on this matter are also described. Moreover, potential molecular mechanism(s) by which coffee bioactive components may provide neuroprotection are reviewed.

Cymbopogon citratus (DC.) Stapf mitigates ER-stress induced by streptozotocin in rats via down-regulation of GRP78 and up-regulation of Nrf2 signaling

ETHNOPHARMACOLOGICAL RELEVANCE

Endoplasmic reticulum (ER) stress plays a role in the pathogenesis of diabetes mellitus, contributing to pancreatic dysfunction and insulin resistance. Ameliorating ER stress may be a viable therapeutic approach in the proper management of diabetes mellitus. Cymbopogon citratus (C.citratus) has been used in traditional medicine in the management of diabetes mellitus. Although well known for its anti-diabetic effect, the mechanism underlying this effect remains unclear.

AIM OF THE STUDY

This study was designed to investigate the effect of C. citratus methanolic leaves extract on ER stress induced by streptozotocin (STZ) in wistar rats.

MATERIALS AND METHODS

STZ (60 mg/kg) was used to induce ER stress in the pancreas of rats. The rats were administered C. citratus methanolic leaves extract via gastric gavage at doses 100, 200 and 400 mg/kg for two weeks while metformin (100 mg/kg) was used as positive control. Fasting blood glucose (FBG), expression of ER-stress related genes (GRP78, CHOP, ATF4, TRB3, PERK, IRE1), antioxidant (Nrf2 and AhR) and pro-inflammatory (TNF-α) genes were determined. Possible compounds responsible for this effect were also predicted through molecular docking.

RESULTS

Induction of ER stress using STZ significantly increased FBG while administration of C. citratus methanolic extract restored it to normal control level (p < 0.05). Significant down-regulation of ER stress genes was observed upon treatment of ER stress induced rats with C. citratus methanolic extract when compared to ER-stress untreated rats. Significant up-regulation (p < 0.05) of genes coding for Nrf2 and AhR was also noticed upon treatment of ER stress induced rats with C. citratus methanolic extract. Molecular docking suggests that apigenin targets GRP78 with binding affinity of -9.3 kcal/mol while kaempferol and quercetin target Keap1 with binding affinity of -9.5 kcal/mol and may be responsible for this ameliorative effect on ER stress.

CONCLUSION

These observations suggest that C. citratus mitigate ER stress induced by STZ via its down-regulative effect on GRP78 and up-regulative effect on NRF2 signaling.

The Nrf2-Keap1 pathway: A secret weapon against pesticide persecution in Drosophila Kc cells

Nrf2-Keap1 pathway defends organisms against the detrimental effects of oxidative stress, and play pivotal roles in preventing xenobiotic-related toxicity. We designed experiments to explore and verify its role and function under deltamethrin (DM) stress. In experiments, DM was selected as the inducer, and Drosophila Kc cells were treated as the objects. The result showed the oxidative stress of cells proliferated in a very short time after DM treatment, reaching the maximum after one hour of treatment. The experimental data showed Nrf2 could be up-regulated and activated by DM which were manifested by the increase of Nrf2 mRNA, Nrf2 protein in the nucleus and the expression of detoxification enzyme genes. We further tested the activity of all groups, and found the survival rate of cells was basically proportional to the expression of Nrf2. Based on the above experimental results, Keap1 overexpression (K+), Nrf2 overexpression (N+) or interference (N-) cells were used to verified the relationship between Nrf2, cell survival and detoxification enzymes expression. We found the cell survival rate of N+ group was significantly higher than that of other groups and the expression of detoxification enzymes were increased compared to the control group. These results demonstrated that Nrf2 is related to cell detoxification and associated with the tolerance to DM. Our evidence suggested Nrf2 is a potential therapeutic target for oxidative stress and a potential molecular target gene of resistance control.

Caffeic acid reduces A53T α-synuclein by activating JNK/Bcl-2-mediated autophagy in vitro and improves behaviour and protects dopaminergic neurons in a mouse model of Parkinson's disease

The human A53T mutant of α-synuclein tends to aggregate and leads to neurotoxicity in familial Parkinson's disease (PD). The aggregation of α-synuclein is also found in sporadic PD. Thus, targeting α-synuclein clearance could be used as a drug-discovery strategy for PD treatment. Caffeic acid (CA) has shown neuroprotection in Alzheimer's disease or cerebral ischaemia; however, it is unclear whether CA confers neuroprotection in α-synuclein-induced PD models. Here we focus on whether and how A53T α-synuclein is affected by CA. We assessed the effect of CA on cell viability in SH-SY5Y cells overexpressing A53T α-synuclein. Pathway-related inhibitors were used to identify the autophagy mechanisms. Seven-month-old A53T α-synuclein transgenic mice (A53T Tg mice) received CA daily for eight consecutive weeks. Behaviour tests including the buried food pellet test, the pole test, the Rotarod test, open field analysis, and gait analysis were used to evaluate the neuroprotective effect of CA. Tyrosine hydroxylase and α-synuclein were assessed by immunohistochemistry or western blot in the substantia nigra (SN). We found that CA alleviated the cell damage induced by overexpressing A53T α-synuclein and that CA reduced A53T α-synuclein by activating the JNK/Bcl-2-mediated autophagy pathway. The efficacy of CA on A53T α-synuclein degradation was reversed by the autophagy inhibitor bafilomycin A1 and the JNK inhibitor SP600125. In A53T Tg mice, CA improved behavioural impairments, attenuated loss of dopaminergic neurons, enhanced autophagy and reduced α-synuclein in the SN. Thus, the results provide scientific evidence for the neuroprotective effect of CA in PD. Our work lays the foundation for CA clinical trials to treat PD in the future.

Improvement of mitochondrial function by Tapinanthus globifer (A.Rich.) Tiegh. Against hepatotoxic agent in isolated rat's liver mitochondria

ETHNOPHARMACOLOGICAL RELEVANCE

Disturbed mitochondrial function and energy crisis serve as key mechanisms for the development of liver injury. Hence, targeting cellular mitochondria in liver diseases might serve as a therapeutic option. Tapinanthus globifer (A.Rich.) Tiegh. has been used in traditional medicine in the management of liver disease. However, there is no scientific evidence supporting such use.

AIM OF THE STUDY

The current investigation was designed to evaluate the protective role of Tapinanthus globifer treatment on the liver mitochondrial function after the induction of hepatotoxicity by the hepatotoxic agent Fe²⁺in vitro.

MATERIALS AND METHODS

In this study, isolated mitochondria from rats' liver was incubated with Fe²⁺ (10 μM) for 1 h in the absence or presence of T. globifer (50, 100 and 200 μg/mL) metanolic extract (MVA). Mitochondrial viability, mitochondrial membrane potential (ΔΨm), mitochondrial swelling (MPTP)., total thiol content, lipid peroxidation (TBARS) and reactive oxygen species (ROS) production were measured. HPLC-DAD was used to identify potential phytochemicals in MVA.

RESULTS

(MVA) was able to improve mitochondrial dysfunction induced by Fe²⁺, by attenuating MTT reduction, increased ΔΨm and mitochondrial swelling. Reduced total thiol and non-protein thiol contents which were associated with increased lipid peroxidation and ROS generation in Fe²⁺-treated mitochondria were significantly improved by MVA co-treatment. HPLC-DAD analysis revealed the presence of gallic acid, catechin, epigallocatechin, caffeic acid, rutin, glycoside flavonoid and quercetin in MVA that can be responsible for its beneficial effect.

CONCLUSION

MVA phyto-compounds enhance mitochondrial redox signaling and possess mitochondrial function improving potential, thereby, providing scientific basis for its use in traditional medicine.

ERK/Nrf2 pathway activation by caffeic acid in HepG2 cells alleviates its hepatocellular damage caused by t-butylhydroperoxide-induced oxidative stress

Background

Several studies have found that caffeic acid (CA), a well-known phytochemical, displays important antioxidant and anti-cancer activities. However, no evidence exists on the protective effect and its mechanisms that CA treatment alone has against oxidative stress induced by tert-butyl hydroperoxide (t-BHP) in HepG2 cells.

Methods

Hepatoprotective activities such as cell viability, mRNA expression, and report gene assay were measured using HepG2 cell. Three types of genes and proteins related with detoxification in liver were used for measuring the hepatoprotective effects. Statistical analysis was performed using one-way ANOVA test and differences among groups were evaluated by Tukey’s studentized range tests.

Results

The present study indicate that treatment with CA up-regulates heme oxygenase-1 (HO-1) and glutamate-cysteine ligase (GCL) mRNA and protein expressions in a CA-dose-dependent manner. In addition, translocation of nuclear factor-E2 p45-related factor (Nrf2) from the cytoplasm to the nucleus and phosphorylation of extracellular signal-regulated kinase, ERK and c-Jun N-terminal kinase, JNK which have been shown to be involved in mitogen-activated protein kinases, MAPKs are significantly enhanced by CA treatment. Furthermore, in cell nuclei, CA enhances the 5′-flanking regulatory region of human antioxidant response element (ARE) and activates the ARE binding site.

Conclusion

Therefore, CA proved to be a stimulant of the expression of detoxification enzymes such as HO-1, GCLC, and GCLM through the ERK/Nrf2 pathway, and it may be an effective chemoprotective agent for protecting liver damage against oxidative damage.

Graphical abstract

Electronic supplementary material

The online version of this article (10.1186/s12906-019-2551-3) contains supplementary material, which is available to authorized users.