1,2,3,4,6-penta-O-galloyl-β-D-glucose protects PC12 Cells from MPP+-mediated cell death by inducing heme oxygenase-1 in an ERK- and Akt-dependent manner

Pentagalloyl Glucose: A Review of Anticancer Properties, Molecular Targets, Mechanisms of Action, Pharmacokinetics, and Safety Profile

Pentagalloyl glucose (PGG) is a natural hydrolyzable gallotannin abundant in various plants and herbs. It has a broad range of biological activities, specifically anticancer activities, and numerous molecular targets. Despite multiple studies available on the pharmacological action of PGG, the molecular mechanisms underlying the anticancer effects of PGG are unclear. Here, we have critically reviewed the natural sources of PGG, its anticancer properties, and underlying mechanisms of action. We found that multiple natural sources of PGG are available, and the existing production technology is sufficient to produce large quantities of the required product. Three plants (or their parts) with maximum PGG content were Rhus chinensis Mill, Bouea macrophylla seed, and Mangifera indica kernel. PGG acts on multiple molecular targets and signaling pathways associated with the hallmarks of cancer to inhibit growth, angiogenesis, and metastasis of several cancers. Moreover, PGG can enhance the efficacy of chemotherapy and radiotherapy by modulating various cancer-associated pathways. Therefore, PGG can be used for treating different human cancers; nevertheless, the data on the pharmacokinetics and safety profile of PGG are limited, and further studies are essential to define the clinical use of PGG in cancer therapies.

The Duration of Oxygen and Glucose Deprivation (OGD) Determines the Effects of Subsequent Reperfusion on Rat Pheochromocytoma (PC12) Cells and Primary Cortical Neurons

Reperfusion is the fundamental treatment for ischaemic stroke; however, many ischaemic stroke patients cannot undergo reperfusion treatment. Furthermore, reperfusion can cause ischaemic reperfusion injuries. This study aimed to determine the effects of reperfusion in an in vitro ischaemic stroke model-oxygen and glucose deprivation (OGD) (0.3% O2)-with rat pheochromocytoma (PC12) cells and cortical neurons. In PC12 cells, OGD resulted in a time-dependent increase in cytotoxicity and apoptosis, and reduction in MTT activity from 2 h onwards. Reperfusion following shorter periods (4 and 6 h) of OGD recovered apoptotic PC12 cells, whereas after 12 h, OGD increased LDH release. In primary neurons, 6 h OGD led to significant increase in cytotoxicity, reduction in MTT activity and dendritic MAP2 staining. Reperfusion following 6 h OGD increased the cytotoxicity. HIF-1a was stabilised by 4 and 6 h OGD in PC12 cells and 2 h OGD onwards in primary neurons. A panel of hypoxic genes were upregulated by the OGD treatments depending on the duration. In conclusion, the duration of OGD determines the mitochondrial activity, cell viability, HIF-1a stabilization, and hypoxic gene expression in both cell types. Reperfusion following OGD of short duration is neuroprotective, whereas OGD of long duration is cytotoxic.

1,2,3,4,6‑penta‑O‑galloyl‑β‑D‑glucose alleviates inflammation and oxidative stress in diabetic nephropathy rats through MAPK/NF‑κB and ERK/Nrf2/HO‑1 signaling pathways

Diabetic nephropathy (DN) is one of the main causes of chronic renal failure, which is also the final cause of mortality in ~30% of diabetic patients. 1, 2, 3, 4, 6-penta-O-galloyl-β-D-glucose (PGG) from Galla rhois has anti-inflammation, anti-oxidation and angiogenesis effects. The present study aimed to explore the protective effects on diabetic nephropathy rats by alleviating inflammation and oxidative stress and the underlying mechanism. High-fat diet/STZ induced rats and high glucose (HG) induced podocytes (MPC5) were used to simulate the DN in vivo and in vitro. The blood glucose level was measured using a blood glucose meter and renal function was determined by an automatic biochemical analyzer. The pathological changes and renal fibrosis were observed through hematoxylin and eosin, periodic acid-Schiff and Masson staining. The expression of nephrin in tissues, fibrosis-related proteins in tissues, MAPK/NF-κB and ERK/nuclear factor erythroid-derived 2-related factor 2 (Nrf2)/hemeoxygenase-1 (HO-1) signaling pathway related proteins in tissues and apoptosis related proteins in tissues and podocytes was detected by western blotting. The inflammatory response and oxidative stress in tissues and podocytes were determined by respective commercial kits and apoptosis in tissues and podocytes was detected by TUNEL assay. The viability of podocytes treated with PGG with or without HG was analyzed by CCK-8 assay. As a result, the blood glucose level, urinary albumin/creatinine ratio, blood urea nitrogen and serum creatinine in blood were all increased and nephrin expression was decreased. The pathological changes and renal fibrosis were aggravated and the inflammation, oxidative stress and apoptosis in renal tissues were enhanced. The above effects were reversed by PGG treatment dose-dependently. MAPK/NF-κB and ERK/Nrf2/HO-1 signaling pathways were activated in DN rats and were suppressed by PGG treatment. The reduced viability and increased apoptosis, inflammation and oxidative stress in MPC5 cells were shown in HG induction, which was reversed by PGG treatment. However, P79350 (p38 agonist) and LM22B-10 (ERK1/2 agonist) weakened the effect of PGG. In conclusion, PGG protects against DN kidney injury by alleviating inflammation and oxidative stress by suppressing the MAPK/NF-κB and ERK/Nrf2/HO-1 signaling pathways.

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.

Natural Antioxidant and Anti-Inflammatory Compounds in Foodstuff or Medicinal Herbs Inducing Heme Oxygenase-1 Expression

Heme oxygenase-1 (HO-1) is an inducible antioxidant enzyme that catalyzes heme group degradation. Decreased level of HO-1 is correlated with disease progression, and HO-1 induction suppresses development of metabolic and neurological disorders. Natural compounds with antioxidant activities have emerged as a rich source of HO-1 inducers with marginal toxicity. Here we discuss the therapeutic role of HO-1 in obesity, hypertension, atherosclerosis, Parkinson's disease and hepatic fibrosis, and present important signaling pathway components that lead to HO-1 expression. We provide an updated, comprehensive list of natural HO-1 inducers in foodstuff and medicinal herbs categorized by their chemical structures. Based on the continued research in HO-1 signaling pathways and rapid development of their natural inducers, HO-1 may serve as a preventive and therapeutic target for metabolic and neurological disorders.

Effects of Mycoplasmas on the Host Cell Signaling Pathways

Mycoplasmas are the smallest free-living organisms. Reduced sizes of their genomes put constraints on the ability of these bacteria to live autonomously and make them highly dependent on the nutrients produced by host cells. Importantly, at the organism level, mycoplasmal infections may cause pathological changes to the host, including cancer and severe immunological reactions. At the molecular level, mycoplasmas often activate the NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells) inflammatory response and concomitantly inhibit the p53-mediated response, which normally triggers the cell cycle and apoptosis. Thus, mycoplasmal infections may be considered as cancer-associated factors. At the same time, mycoplasmas through their membrane lipoproteins (LAMPs) along with lipoprotein derivatives (lipopeptide MALP-2, macrophage-activating lipopeptide-2) are able to modulate anti-inflammatory responses via nuclear translocation and activation of Nrf2 (the nuclear factor-E2-related anti-inflammatory transcription factor 2). Thus, interactions between mycoplasmas and host cells are multifaceted and depend on the cellular context. In this review, we summarize the current information on the role of mycoplasmas in affecting the host’s intracellular signaling mediated by the interactions between transcriptional factors p53, Nrf2, and NF-κB. A better understanding of the mechanisms underlying pathologic processes associated with reprogramming eukaryotic cells that arise during the mycoplasma-host cell interaction should facilitate the development of new therapeutic approaches to treat oncogenic and inflammatory processes.

Protective effects of delphinidin against H2O2-induced oxidative injuries in human retinal pigment epithelial cells

Age-related macular degeneration (AMD) is now one of the leading causes of blindness in the elderly population and oxidative stress-induced damage to retinal pigment epithelial (RPE) cells occurs as part of the pathogenesis of AMD. In the present study, we evaluated the protective effect of delphinidin (2-(3,4,5-trihydroxyphenyl) chromenylium-3,5,7-triol) against hydrogen peroxide (H₂O₂)-induced toxicity in human ARPE-19 cells and its molecular mechanism. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and flow cytometry demonstrated that pretreatment of ARPE-19 cells with delphinidin (25, 50, and 100 μg/ml) significantly increased cell viability and reduced the apoptosis from H₂O₂ (0.5 mM)-induced oxidative stress in a concentration-dependent manner, which was achieved by the inhibition of Bax, cytochrome c, and caspase-3 protein expression and enhancement of Bcl-2 protein. The same tendency was observed in ARPE-19 cells pre-treated with 15 mM of N-acetylcysteine (NAC) before the addition of H₂O₂. Furthermore, pre-incubation of ARPE-19 cells with delphinidin markedly inhibited the intracellular reactive oxygen species (ROS) generation and Nox1 protein expression induced by H₂O₂. Moreover, the decreased antioxidant enzymes activities of superoxide dismutase (SOD), catalase (CAT), and glutathione-peroxidase (GSH-PX) and elevated (MDA) level in H₂O₂-treated cells were reversed to the normal standard by the addition of delphinidin, which was regulated by increasing nuclear Nrf2 protein expression in ARPE-19 cells. Our results suggest that delphinidin effectively protects human ARPE-19 cells from H₂O₂-induced oxidative damage via anti-apoptotic and antioxidant effects.

Ginnalin A from Kujin tea (Acer tataricum subsp. ginnala) exhibits a colorectal cancer chemoprevention effect via activation of the Nrf2/HO-1 signaling pathway

Ginnalin A (also known as acertannin) is one of the most important phenolic compounds of several beverage Acer plants. In this study, it is reported for the first time that ginnalin A is an activator of the Nrf2 signaling pathway in human colon cancer cells. Ginnalin A, isolated from the leaves of Acer tataricum subsp. ginnala, exhibited promising preventive activity against colon cancer cells (HCT116, SW480 and SW620) with IC50 values of 24.8 μM, 22.0 μM and 39.7 μM, respectively. In addition, it significantly reduced the colony formation of these cells. Flow cytometry analysis indicated that ginnalin A suppressed cancer proliferation via the induction of cell cycle arrest at the S-phase. Real time PCR analysis demonstrated that ginnalin A can upregulate the mRNA expression levels of Nrf2-related antioxidant genes Nrf2, HO-1 and NQO1. Western blotting analysis revealed that ginnalin A promoted the Nrf2 nuclear translocation and upregulated the proteins Nrf2, HO-1 and NQO1. Moreover, the upregulation of p62 and the inhibition of Keap1 were also found by Western blotting analysis. Therefore, the activation of the Nrf2 signaling pathway was probably induced through the upregulation of p62 and the inhibition of Keap1.

Pinostrobin Exerts Neuroprotective Actions in Neurotoxin-Induced Parkinson's Disease Models through Nrf2 Induction

The aim of the present study was to assess the neuroprotective effects of pinostrobin (PSB), a dietary bioflavonoid, and its underlying mechanisms in neurotoxin-induced Parkinson's disease (PD) models. First, PSB could attenuate 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced loss of dopaminergic neurons and improve behavior deficiency in zebrafish, supporting its potential neuroprotective actions in vivo. Next, PSB could decreased apoptosis and death in the 1-methyl-4-phenylpyridinium (MPP⁺)-intoxicated SH-SY5Y cells, evidenced by MTT, LDH, Annexin V-FITC/PI, and DNA fragmentation assay. PSB also blocked MPP⁺-induced apoptotic cascades, including loss of mitochondrial membrane potential, activation of caspase 3, and reduced ratio of Bcl-2/Bax. In addition, PSB suppressed MPP⁺-induced oxidative stress but increased antioxidant enzymes, evidenced by decrease of reactive oxygen species generation and lipid peroxidation and up-regulation of GSH-Px, SOD, CAT, GSH/GSSG, and NAD/NADH. Further investigations showed that PSB significantly enhanced Nrf2 expression and nuclear accumulation, improved ARE promoter activity and up-regulated expression of HO-1 and GCLC. Furthermore, Nrf2 knockdown via specific Nrf2 siRNA abolished PSB-induced antioxidative and antiapoptotic effects against MPP⁺ insults. Interestingly, we then found that PSB promoted phosphorylation of PI3K/AKT and ERK, and pharmacological inhibition of PI3K/AKT or ERK signaling diminished PSB-induced Nrf2/ARE activation and protective actions. In summary, PSB confers neuroprotection against MPTP/MPP⁺-induced neurotoxicity in PD models. Promoting activation of Nrf2/ARE signaling contributes to PSB-mediated antioxidative and neuroprotective actions, which, in part, is mediated by PI3K/AKT and ERK.

Mycoplasma fermentans MALP-2 induces heme oxygenase-1 expression via mitogen-activated protein kinases and Nrf2 pathways to modulate cyclooxygenase 2 expression in human monocytes

Heme oxygenase-1 (HO-1) is a stress-inducible rate-limiting enzyme in heme degradation that confers cytoprotection against oxidative injury and performs a vital function in the maintenance of cell hemostasis. Increasing numbers of reports have indicated that mycoplasma-derived membrane lipoproteins/lipopeptides, such as macrophage-activating lipopeptide-2 (MALP-2), function as agents that stimulate the immune system by producing various inflammatory mediators, such as cytokines and cyclooxygenase 2 (COX-2), which play roles in the pathogenesis of inflammatory responses during mycoplasma infection. Here, we report that MALP-2 induced HO-1 mRNA and protein expression and upregulated HO-1 enzyme activity in THP-1 cells. Specific inhibitors of mitogen-activated protein kinases (MAPKs), SB203580, PD98059, and SP600125, significantly abolished HO-1 expression. In addition, MALP-2 also induced NF-E2-related factor 2 (Nrf2) translocation, and the silencing of Nrf2 expression in THP-1 cells decreased the levels of MALP-2-mediated HO-1 expression. Furthermore, COX-2 protein expression levels were upregulated in THP-1 cells in response to MALP-2, and transfection with small interfering RNAs of HO-1 significantly increased COX-2 accumulation. These results demonstrate that MALP-2 induces HO-1 expression via MAPKs and Nrf2 pathways and, furthermore, that MALP-2-induced COX-2 expression was modulated by HO-1 in THP-1 cells.