Nordihydroguaiaretic acid induces Nrf2 nuclear translocation in vivo and attenuates renal damage and apoptosis in the ischemia and reperfusion model

Role of Plant-Derived Compounds in the Molecular Pathways Related to Inflammation

Inflammation is the primary response to infection and injury. Its beneficial effect is an immediate resolution of the pathophysiological event. However, sustained production of inflammatory mediators such as reactive oxygen species and cytokines may cause alterations in DNA integrity and lead to malignant cell transformation and cancer. More attention has recently been paid to pyroptosis, which is an inflammatory necrosis that activates inflammasomes and the secretion of cytokines. Taking into consideration that phenolic compounds are widely available in diet and medicinal plants, their role in the prevention and support of the treatment of chronic diseases is apparent. Recently, much attention has been paid to explaining the significance of isolated compounds in the molecular pathways related to inflammation. Therefore, this review aimed to screen reports concerning the molecular mode of action assigned to phenolic compounds. The most representative compounds from the classes of flavonoids, tannins, phenolic acids, and phenolic glycosides were selected for this review. Our attention was focused mainly on nuclear factor-κB (NF-κB), nuclear factor erythroid 2-related factor 2 (Nrf2), and mitogen-activated protein kinase (MAPK) signaling pathways. Literature searching was performed using Scopus, PubMed, and Medline databases. In conclusion, based on the available literature, phenolic compounds regulate NF-κB, Nrf2, and MAPK signaling, which supports their potential role in chronic inflammatory disorders, including osteoarthritis, neurodegenerative diseases, cardiovascular, and pulmonary disorders.

Head-to-head comparison of two SGLT-2 inhibitors on AKI outcomes in a rat ischemia-reperfusion model

The CREDENCE trial testing canagliflozin and the EMPA-REG OUTCOME trial testing empagliflozin suggest different effects on acute kidney injury (AKI). AKI diagnosis was mainly made based on changes of serum creatinine (sCr) although this also reflect mode of action of SGLT-2 inhibitors. We analyzed both compounds in a rat AKI model. The renal ischemia-reperfusion injury (I/R) model was used. Four groups were analyzed: sham, I/R+placebo, I/R+canagliflozin (30 mg/kg/day), I/R+ empagliflozin (10 mg/kg/day). Glucose excretion was comparable in both treatment groups indicating comparable SGLT-2 inhibition. Comparing GFR surrogate markers after I/R (sCr and blood urea nitrogen (BUN)), sCr peaked 24 h after I/R, BUN after 48 h, respectively, in the placebo treated I/R group. At all investigated time points after I/R sCr and BUN was higher in the I/R + canagliflozin group as compared to placebo treated rats, whereas the empagliflozin group did not differ from the placebo group. I/R led to tubular dilatation and necrosis. Empagliflozin was able to reduce that finding whereas canagliflozin had no effect. Treatment with empagliflozin also resulted in a significant reduction in an improved inflammatory score (p = 0.006). Renal expression of kidney injury molecule-1 (KIM-1) increased after I/R and empagliflozin but not canagliflozin significantly alleviated KIM-1 expression. I/R reduced urinary miR-26a excretion. Empagliflozin but not canagliflozin was able to restore normal levels of urinary miR-26a. This study in an AKI model confirmed safety data in the EMPA-REG OUTCOME trial suggesting that empagliflozin might reduce AKI risk. The empagliflozin effects on KIM-1 and miR-26a might indicate beneficial regulation of inflammation. These data should stimulate clinical studies with AKI risk as primary endpoint.

Phytochemical Compounds and Pharmacological Properties of Larrea tridentata

For centuries, traditional medicine from plants (phytotherapy) was the only treatment for infectious and non-infectious diseases. Although it is still practiced in several countries with excellent therapeutic results, it is frequently underestimated because, unlike Western medicine, it is not based on an empirical scientific foundation. However, interest in the search for plant-based therapeutic resources has been stimulated by disciplines such as phytochemistry and the side effects of conventional pharmacological therapies. For example, Larrea tridentata is a perennial shrub used in traditional medicine in northern Mexico and the southern United States to treat infertility, rheumatism, arthritis, colds, diarrhea, skin problems, pain, inflammation and excess body weight. Scientific research has revealed its beneficial effects—antioxidant, antitumor, neuroprotective, regenerative, antibacterial, antiviral, antifungal, anthelmintic, antiprotozoal and insecticidal—although reports indicate that some compounds in Larrea tridentata may be hepatotoxic and nephrotoxic. Therefore, the aim of this review was to highlight the updates regarding phytochemical compounds and the pharmacological properties of Larrea tridentata.

Pharmacological Protection against Ischemia-Reperfusion Injury by Regulating the Nrf2-Keap1-ARE Signaling Pathway

Ischemia/reperfusion (I/R) injury is associated with substantial clinical implications, including a wide range of organs such as the brain, kidneys, lungs, heart, and many others. I/R injury (IRI) occurs due to the tissue injury following the reestablishment of blood supply to ischemic tissues, leading to enhanced aseptic inflammation and stimulation of oxidative stress via reactive oxygen and nitrogen species (ROS/RNS). Since ROS causes membrane lipids’ peroxidation, triggers loss of membrane integrity, denaturation of proteins, DNA damage, and cell death, oxidative stress plays a critical part in I/R pathogenesis. Therefore, ROS regulation could be a promising therapeutic strategy for IRI. In this context, Nrf2 (NF-E2-related factor 2) is a transcription factor that regulates the expression of several factors involved in the cellular defense against oxidative stress and inflammation, including heme oxygenase-1 (HO-1). Numerous studies have shown the potential role of the Nrf2/HO-1 pathway in IRI; thus, we will review the molecular aspects of Nrf2/Kelch-like ECH-associated protein 1 (Keap1)/antioxidant response element (ARE) signaling pathway in I/R, and we will also highlight the recent insights into targeting this pathway as a promising therapeutic strategy for preventing IRI.

Treatment with catalpol protects against cisplatin-induced renal injury through Nrf2 and NF-κB signaling pathways

Cisplatin (CP) is one of the most widely used chemotherapy drugs for cancer treatment, but it often leads to nephrotoxicity. It is well known that catalpol exhibits antioxidant and anti-inflammatory functions, thus the present study aimed to investigate the potential protective effects of catalpol on CP-induced kidney injury in rats, in addition to determining the underlying mechanisms. Sprague-Dawley rats were treated with 25, 50 or 100 mg/kg catalpol for two days, injected with 20 mg/kg cisplatin and catalpol on day 3 and sacrificed on day 4. The histological analysis of isolated kidney tissues was performed using hematoxylin and eosin staining, cleaved caspase-3 expression levels were analyzed using western blotting and the expression levels of inflammatory cytokines in the tissues, including tumor necrosis factor α (TNF-α), interleukin (IL)-1β, IL-6, IL-8, IL-10 and inducible nitric oxide synthase (iNOS) were evaluated using ELISAs. Furthermore, the mRNA and protein expression levels of nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase 1 (HO-1), kelch-like ECH-associated protein 1 (Keap1), NF-κB and inhibitory κB (IκB) were determined using reverse transcription-quantitative PCR and western blotting, respectively. The results revealed that the treatment with catalpol prevented the histopathological injury and renal dysfunction caused by CP. In addition, catalpol significantly suppressed the CP-induced apoptosis of tubular cells, inhibited the CP-induced upregulation of TNF-α, IL-1β, IL-6, IL-8 and iNOS and promoted the production of the anti-inflammatory cytokine IL-10. Additionally, the mRNA and protein expression levels of Nrf2, HO-1 and IκB in the kidney tissues were increased, whereas the expression levels of Keap1 and NF-κB were significantly decreased following the treatment with catalpol. In conclusion, these results suggested that catalpol may inhibit CP-induced renal injury and suppress the associated inflammatory response through activating the Nrf2 and inhibiting the NF-κB signaling pathways, respectively.

Nordihydroguaiaretic Acid: From Herbal Medicine to Clinical Development for Cancer and Chronic Diseases

Nordihydroguaiaretic acid (NDGA) is a phenolic lignan obtained from Larrea tridentata, the creosote bush found in Mexico and USA deserts, that has been used in traditional medicine for the treatment of numerous diseases such as cancer, renal, cardiovascular, immunological, and neurological disorders, and even aging. NDGA presents two catechol rings that confer a very potent antioxidant activity by scavenging oxygen free radicals and this may explain part of its therapeutic action. Additional effects include inhibition of lipoxygenases (LOXs) and activation of signaling pathways that impinge on the transcription factor Nuclear Factor Erythroid 2-related Factor (NRF2). On the other hand, the oxidation of the catechols to the corresponding quinones my elicit alterations in proteins and DNA that raise safety concerns. This review describes the current knowledge on NDGA, its targets and side effects, and its synthetic analogs as promising therapeutic agents, highlighting their mechanism of action and clinical projection towards therapy of neurodegenerative, liver, and kidney disease, as well as cancer.

Lignans and Their Derivatives from Plants as Antivirals

Lignans are widely produced by various plant species; they are a class of natural products that share structural similarity. They usually contain a core scaffold that is formed by two or more phenylpropanoid units. Lignans possess diverse pharmacological properties, including their antiviral activities that have been reported in recent years. This review discusses the distribution of lignans in nature according to their structural classification, and it provides a comprehensive summary of their antiviral activities. Among them, two types of antiviral lignans—podophyllotoxin and bicyclol, which are used to treat venereal warts and chronic hepatitis B (CHB) in clinical, serve as examples of using lignans for antivirals—are discussed in some detail. Prospects of lignans in antiviral drug discovery are also discussed.

miR-200a mediates protection of thymosin β-4 in cardiac microvascular endothelial cells as a novel mechanism under hypoxia-reoxygenation injury

Thymosin β-4 (Tβ4) is a ubiquitous protein, which has been suggested to regulate multiple cell signal pathways and a variety of cellular functions. However, the role Tβ4 plays in the cardiac microvascular endothelial cells (CMECs) under myocardial ischemia/reperfusion injury is currently unknown. Here we investigated the effects of Tβ4 on hypoxia/reoxygenation (H/R) induced CMECs injury and its potential molecular mechanism. Cultured CMECs were positively identified by flow cytometry using antibody against CD31 and VWF/Factor VIII, which are constitutively expressed on the surface of CMECs. Then the reduced level of Tβ4 was detected in H/R-CMECs by a real-time quantitative polymerase chain reaction. To determine the effects of Tβ4 on H/R-CMECs, we transfected the overexpression or silence vector of Tβ4 into CMECs under H/R condition. Our results indicated that H/R treatment could reduce proliferation, increased apoptosis, adhesion, and reactive oxygen species (ROS) production in CMECs, which were attenuated by Tβ4 overexpression or aggravated by Tβ4 silencing, implying Tβ4 is able to promote CMECs against H/R-induced cell injury. Furthermore, the microRNA-200a (miR-200a) level was also increased by Tβ4 in H/R-CMECs or reduced by Tβ4 small interfering RNA. To investigated the mechanism of protective effects of Tβ4 on CMECs injury, the miR-200a inhibitor was transfected into H/R-CMECs. The results indicated that inhibition of miR-200a inversed the protection of Tβ4 on H/R-CMECs, specifically including cell proliferation, cell adhesion, cell apoptosis, and ROS production, as well as nuclear factor erythroid 2-related factor 2 (Nrf2) nuclear translocation. In conclusion, our results determined that Tβ4 attenuated H/R-induced CMECs injury by miR-200a-Nrf2 signaling.

Activation of TRPC6 channels contributes to (+)-conocarpan-induced apoptotic cell death in HK-2 cells

(+)-Conocarpan (CNCP), a neolignan frequently found in many medicinal and edible plants displays a broad spectrum of bioactivity. Here, we demonstrated that CNCP induced apoptotic cell death in human kidney-2 (HK-2) cells in a concentration-dependent manner (IC₅₀ = 19.3 μM) and led to the sustained elevation of intracellular Ca²⁺ ([Ca²⁺]_i). Lower extracellular Ca²⁺ concentrations from 2.3 mM to 0 mM significantly suppressed the CNCP-induced Ca²⁺ response by 69.1%. Moreover, the depletion of intracellular Ca²⁺ stores using thapsigargin normalized CNCP-induced Ca²⁺ release from intracellular Ca²⁺ stores, suggesting that the CNCP-induced Ca²⁺ response involved both extracellular Ca²⁺ influx and Ca²⁺ release from intracellular Ca²⁺ stores. SAR7334, a TRPC3/6/7 channel inhibitor, but neither Pyr3, a selective TRPC3 channel inhibitor, nor Pico145, a TRPC1/4/5 inhibitor, suppressed the CNCP-induced Ca²⁺ response by 57.2% and decreased CNCP-induced cell death by 53.4%, suggesting a critical role for TRPC6 channels in CNCP-induced Ca²⁺ influx and apoptotic cell death. Further electrophysiological recording demonstrated that CNCP directly activated TRPC6 channels by increasing channel open probability with an EC₅₀ value of 6.01 μM. Considered together, these data demonstrate that the direct activation of TRPC6 channels contributes to CNCP-induced apoptotic cell death in HK-2 cells. Our data point out the potential risk of renal toxicity from CNCP if used as a therapeutic agent.

DC32, a Dihydroartemisinin Derivative, Ameliorates Collagen-Induced Arthritis Through an Nrf2-p62-Keap1 Feedback Loop

Artemisinins have been reported to have diverse functions, such as antimalaria, anticancer, anti-inflammation, and immunoregulation activities. DC32 [(9α,12α-dihydroartemisinyl) bis(2′-chlorocinnmate)], a dihydroartemisinin derivative possessing potent immunosuppressive properties, was synthesized in our previous study. Collagen-induced arthritis (CIA) in DBA/1 mice and inflammatory model in NIH-3T3 cells were established to evaluate the effect of DC32 on RA and discover the underlying mechanisms. The results showed that DC32 could markedly alleviate footpad inflammation, reduce cartilage degradation, activate the Nrf2/HO-1 signaling pathway, and increase the transcription of p62 in DBA/1 mice with CIA. Further mechanistic exploration with NIH-3T3 cells indicated that DC32 could increase the transcription, expression, and nuclear translocation of Nrf2. In addition, DC32 promoted degradation of Keap1 protein and upregulated HO-1 and p62 expression. Furthermore, the effect of DC32 on Keap1 degradation could be prevented by p62 knockdown using siRNA. Administration of DC32 could inhibit the activation of Akt/mTOR and ERK, and pretreatment of NIH-3T3 cells with the autophagy inhibitor 3-methyladenine (3-MA) attenuated the degradation of Keap1 induced by DC32. These results suggest that DC32 inhibits the degradation of Nrf2 by promoting p62-mediated selective autophagy and that p62 upregulation contributed to a positive feedback loop for persistent activation of Nrf2. In summary, our present study demonstrated that DC32 significantly suppressed rheumatoid arthritis (RA) via the Nrf2-p62-Keap1 feedback loop by increasing the mRNA and protein levels of Nrf2 and inducing p62 expression. These findings provide new mechanisms for artemisinins in RA treatment and a potential strategy for discovering antirheumatic drugs.

Antitumor Effects of Nordihydroguaiaretic Acid (NDGA) in Bladder T24 Cancer Cells are Related to Increase in ROS Production and Mitochondrial Leak Respiration

The aim of this study was to evaluate the effect of nordihydroguaiaretic acid (NDGA) on tumor bladder T24 cells. Bladder cancer T24 cells were cultured on Dulbecco's Modified Eagle Medium in presence of NDGA. Cell viability and apoptosis were evaluated after 24, 48 and 72 h by using fluorescein diacetate (FDA) and Alexa fluor 488 annexin-V/propidium iodide solution, respectively. To determine the mitochondrial effects of NDGA (0-24 h), reactive oxygen species (ROS) levels by dihydroethidium fluorescence, mitochondrial membrane potential (ΔΨm) by 5,5’,6,6'-tetrachloro-1,1’,3,3'-tetraethyl-imidacarbocyanine iodide (JC-1) dual fluorescence and cellular respiration states by high resolution respirometry were evaluated. It was found that NDGA reduced T24 cell viability after 72 h of incubation in a concentration-dependent manner and apoptosis increased at 48 h. Furthermore, 20 μM NDGA increased ROS levels, decreased ΔΨm and promoted leak of respiration from mitochondrial respiratory chain in T24 cells which was associated to the death of tumor cells. Taken together these results suggested that antitumor effects of NDGA in T24 cells are related to its ability to induce mitochondrial alteration.

Curcumin: An effective adjunct in patients with statin-associated muscle symptoms?

In spite of the unequivocal efficacy of statins in reducing primary and secondary cardiovascular events, the use of these drugs in a considerable number of patients is limited because of statin intolerance, mainly statin-associated muscle symptoms (SAMS). SAMS encompass a broad spectrum of clinical presentations, including mild muscular aching and other types of myalgias, myopathy with the significant elevation of creatine kinase, and the rare but life-threatening rhabdomyolysis. Among several pathophysiologic mechanisms of SAMS, mitochondrial dysfunction is thought to be one of the main one. Curcumin is the polyphenolic ingredient of Curcuma longa L., which has various pharmacological properties against a vast range of diseases. Curcumin has several mechanisms of actions relevant to the treatment of SAMS. These effects include the capacity to prevent and reduce delayed onset muscle soreness by blocking the nuclear factor inflammatory pathway, attenuation of muscular atrophy, enhancement of muscle fibre regeneration following injury, and analgesic and antioxidant effects. Curcumin can also increase the levels of cyclic adenosine monophosphate, which leads to an increase in the number of mitochondrial DNA duplicates in skeletal muscle cells. Finally, owing to its essential lipid-modifying properties, curcumin might serve as an adjunct to statin therapy in patients with SAMS, allowing for effective lowering of low-density lipoprotein cholesterol and possibly for statin dose reduction. Owing to the paucity of effective treatments, and the safety of curcumin in clinical practice, proof-of-concept trials are recommended to assess the potential benefit of this phytochemical in the treatment of SAMS.

Hydrophobicity and antioxidant activity acting together for the beneficial health properties of nordihydroguaiaretic acid

Nordihydroguaiaretic acid (NDGA) and rosmarinic acid (RA), phenolic compounds found in various plants and functional foods, have known antioxidant and anti-inflammatory properties. In the present study, we comparatively investigated the importance of hydrophobicity and oxidisability of NDGA and RA, regarding their antioxidant and pharmacological activities. Using a panel of cell-free antioxidant protocols, including electrochemical measurements, we demonstrated that the anti-radical capacities of RA and NDGA were similar. However, the relative capacity of NDGA as an inhibitor of NADPH oxidase (ex vivo assays) was significantly higher compared to RA. The inhibitory effect on NADPH oxidase was not related to simple scavengers of superoxide anions, as confirmed by oxygen consumption by the activated neutrophils. The higher hydrophobicity of NDGA was also a determinant for the higher efficacy of NDGA regarding the inhibition of the release of hypochlorous acid by PMA-activated neutrophil and cytokine (TNF-α and IL-10) production by Staphylococcus aureus-stimulated peripheral blood mononuclear cells. In conclusion, although there have been extensive studies about the pharmacological properties of NDGA, our study showed, for the first time, the importance not only of its antioxidant activity, but also its hydrophobicity as a crucial factor for pharmacological action.

Protective effect of Wuzhi tablet (Schisandra sphenanthera extract) against cisplatin-induced nephrotoxicity via Nrf2-mediated defense response

Cisplatin is a potent anti-cancer agent for various types of tumors. However, the clinical use of cisplatin is often limited by its nephrotoxicity. This study reports that WZ tablet (WZ, a preparation of an ethanol extract of Schisandra sphenanthera) mitigates cisplatin-induced toxicity in renal epithelial HK-2 cells and in mice. Pretreatment of HK-2 cells with WZ ameliorated cisplatin-induced cytotoxicity caused by oxidative stress, as was demonstrated by reductions in the levels of reactive oxygen species (ROS) and increased levels of glutathione (GSH). WZ facilitated the nuclear accumulation of the transcription factor NF-E2-related factor 2 (Nrf2) and the subsequent expression of its target genes such as

NAD(P)H

quinine oxidoreductase 1 (NQO1), heme oxygenase-1 (HO-1) and glutamate cysteine ligase (GCL). Protective effects of WZ on cisplatin-induced nephrotoxicity were also observed in mice. WZ attenuated cisplatin-induced renal dysfunction, structural damage and oxidative stress. The nuclear accumulation of Nrf2 and its target genes were increased by WZ treatment. Taken together, these findings demonstrated WZ have a protective effect against cisplatin-induced nephrotoxicity by activation of the Nrf2 mediated defense response, which is of significant importance for therapeutic intervention in cisplatin induced renal injury.

Cytotoxic activity of butane type of 1,7-seco-2,7'-cyclolignanes and apoptosis induction by Caspase 9 and 3

All stereoisomers of methoxybutane and fluorobutane type of 1,7-seco-2,7'-cyclolignane were synthesized and cytotoxic activities of these compounds were compared with those of all stereoisomers of butane and butanol type compounds. Both enantiomers of butane type secocyclolignane showed higher cytotoxic activity (IC50=16-20 μM) than methoxy type compounds, whereas none was observed for all the stereoisomers of butanol type secocyclolignane, however, (-)-Kadangustin J showed stereospecific cytotoxic activity (IC50=47-67 μM). Since (R)-9'-fluoro derivative 23 was most potent (IC50=19 μM) among the corresponding fluoro stereoisomers, (R)-9'-alkyl derivatives were synthesized, hydrophobic 9'-heptyl derivative 27 showing highest activity (IC50=3.7 μM against HL-60, IC50=3.1 μM against HeLa) in this experiment. Apoptosis induction caused by Caspase 3 and 9 for (R)-9'-heptyl derivative 27 was observed in the research on the mechanism. A degradation of DNA into small fragments was also shown by DNA ladder assay.