Biphasic Dose-Response Induced by Phytochemicals: Experimental Evidence

Ginkgo biloba in the management of the COVID-19 severity

The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection is linked with inflammatory disorders and the development of oxidative stress in extreme cases. Therefore, anti-inflammatory and antioxidant drugs may alleviate these complications. Ginkgo biloba L. folium extract (EGb) is a herbal medicine containing various active constituents. This review aims to provide a critical discussion on the potential role of EGb in the management of coronavirus disease 2019 (COVID-19). The antiviral effect of EGb is mediated by different mechanisms, including blocking SARS-CoV-2 3-chymotrypsin-like protease that provides trans-variant effectiveness. Moreover, EGb impedes the development of pulmonary inflammatory disorders through the diminution of neutrophil elastase activity, the release of proinflammatory cytokines, platelet aggregation, and thrombosis. Thus, EGb can attenuate the acute lung injury and acute respiratory distress syndrome in COVID-19. In conclusion, EGb offers the potential of being used as adjuvant antiviral and symptomatic therapy. Nanosystems enabling targeted delivery, personalization, and booster of effects provide the opportunity for the use of EGb in modern phytotherapy.

Hormetic effect of an Ethanolic Graviola Leaf Extract on HGF-1 cells survival

Plant-extracted compounds have been used for centuries in traditional pharmacopeia. Some of them have proven to be excellent drug alternatives for cancer treatment as they target metabolic pathways that are key to cancer cells such as apoptosis, energy-producing catabolic pathways, and the response to oxidative stress. Since some anticancer drugs have been shown to produce dose dependent biologically opposite effects, it is crucial to determine the range of doses for which the compounds have maximum therapeutic benefits. Annona muricata or Graviola is a tropical tree that is common in the Puerto Rican landscape. Although a plethora of studies conducted in vitro and in vivo studies have indeed reported that extracts prepared from the Graviola root, fruit, bark, and leaves possess antiproliferative activities in a large variety of cancer cells, the efficiency of Graviola extracts to curb the progression of head and neck cancers has been overlooked. Furthermore, the bioactivity of Graviola extracts on sane/non-cancerous cells has largely been ignored. The present work reports the in vitro antiproliferative/anticancer behavior of an ethanolic Graviola leaf extract on squamous cell carcinoma cell lines 9 and 25 vs. a sane/non-cancerous human gingival fibroblast cell line-1. Our results show that the Graviola extract induces cell death in the squamous cell carcinoma cell lines at all concentrations tested and a dose-dependent biphasic concentration-dependent/hormetic effect on the fibroblastic cells. This suggests that, at low doses, the phytochemicals present in the prepared Graviola extract could offer potential therapeutic avenues for curbing the progression of head and neck cancers.

Potential of Sulforaphane and Broccoli Membrane Vesicles as Regulators of M1/M2 Human Macrophage Activity

Macrophages have emerged as important therapeutic targets in many human diseases. The aim of this study was to analyze the effect of broccoli membrane vesicles and sulphoraphane (SFN), either free or encapsulated, on the activity of human monocyte-derived M1 and M2 macrophage primary culture. Our results show that exposure for 24 h to SFN 25 µM, free and encapsulated, induced a potent reduction on the activity of human M1 and M2 macrophages, downregulating proinflammatory and anti-inflammatory cytokines and phagocytic capability on C. albicans. The broccoli membrane vesicles do not represent inert nanocarriers, as they have low amounts of bioactive compounds, being able to modulate the cytokine production, depending on the inflammatory state of the cells. They could induce opposite effects to that of higher doses of SFN, reflecting its hormetic effect. These data reinforce the potential use of broccoli compounds as therapeutic agents not only for inflammatory diseases, but they also open new clinical possibilities for applications in other diseases related to immunodeficiency, autoimmunity, or in cancer therapy. Considering the variability of their biological effects in different scenarios, a proper therapeutic strategy with Brassica bioactive compounds should be designed for each pathology.

Moringa oleifera leaf extract induces osteogenic-like differentiation of human osteosarcoma SaOS2 cells

Introduction

Moringa oleifera is known as a ‘natural nutrition of the tropics’ because it provides vital nutritional supplements and a variety of pharmacological benefits. The focus of this study was to elucidate the dose dependent effects of Moringa oleifera leaf (MOL) extract on the growth of the human osteoblast-like osteosarcoma SaOS-2 cell line and primary osteoblast cells.

Methods

Trypan blue & tetrazolium assay, intracellular ROS generation, chromatin condensation, cell cycle analysis, alkaline phosphatase (ALP), mineralization, and osteogenic gene expression were tested on both treated and untreated osteosarcoma SaOS-2 cells.

Results

As revealed by cell viability assay, growth activity was observed at concentrations 25 and 50 μg/mL of MOL extract, whereas 100 and 200 μg/mL doses decreased the proliferation activity, resulting in ROS production and chromatin condensation. Cell cycle study revealed that MOL extract at 50 and 100 μg/mL concentrations arrested the cells in the G2/M phase. Low doses increased the ALP levels, mineralization, and expression of the bone morphogenetic protein 2 (BMP2) and runt-related transcription factor 2 (Runx2) genes in osteoblast-like SaOS-2 cells, however, high doses inhibited the proliferation properties of MOL extract. Through AutoDock Vina and iGEMDOCK 2.1, the interaction of active components of MOL, such as β-sitosterol, quercetin and kaempferol, with BMP2 and Runx2 proteins revealed a reasonable binding affinity. Moreover, these components did not show any Lipinski's rule of five violation and showed predictable pharmacokinetic properties.

Conclusion

The results of the biphasic dose-response of MOL extract on the growth activity of osteoblast-like SaOS-2 cells and in silico binding interface, may provide a therapeutic and/or preventive implication in prospective drug development.

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Low doses of Moringa oleifera leaf (MOL) extract increased the cell viability of SaOS-2 cells and primary osteoblasts.

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High doses decreased the growth, resulting in ROS production and chromatin condensation and cell cycle arrest.

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Small doses increased the ALP levels, mineralization, and BMP2 and Runx2 genes expression, and vice versa.

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In silico analysis showed good binding interaction of active components of MOL with BMP2 and Runx2 proteins.

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The biphasic dose-response of MOL and in silico analysis may provide an implication for prospective drug development.

Alpinumisoflavone against cancer pro-angiogenic targets: In silico, In vitro, and In ovo evaluation

BACKGROUND

Breast cancer is currently the world's most predominant malignancy. In cancer progression, angiogenesis is a requirement for tumor growth and metastasis.Alpinumisoflavone (AIF), a bioactive isoflavonoid, exhibited good binding affinity with the angiogenesis pathway's druggable target through molecular docking.

OBJECTIVES

To confirm AIF's angiogenesis inhibitory activity, cytotoxic potential toward breast cancer cells, and druggability.

METHODS

Antiangiogenic activity was evaluated in six pro-angiogenic proteins in vitro, duck chorioallantoic membrane (CAM) in ovo, molecular docking and druggability in silico.

RESULTS

Findings showed that AIF significantly inhibited (p =  < 0.001) the HER2(IC50 = 2.96 µM), VEGFR-2(IC50 = 4.80 µM), MMP-9(IC50 = 23.00 µM), FGFR4(IC50 = 57.65 µM), EGFR(IC50 = 92.06 µM) and RET(IC50 =  > 200 µM) activity in vitro.AIF at 25 µM-200 µM significantly inhibited (p =  < 0.001) the total number of branch points (IC50 = 14.25 μM) and mean length of tubule complexes (IC50 = 3.52 μM) of duck CAM comparable (p =  > 0.001) with the positive control 200 µM celecoxib on both parameters.AIF inhibited the growth of the estrogen-receptor-positive (ER +) human breast cancer cells (MCF-7) by 44.92 ± 1.79% at 100 µM while presenting less toxicity to human dermal fibroblast neonatal (HDFn) normal cells.The positive control 100 µM doxorubicin showed 86.66 ± 0.93% and 92.97 ± 1.27% inhibition with MCF-7 (IC50 = 3.62 μM) and HDFn, (IC50 = 27.16 μM) respectively.In docking, AIF has the greatest in silico binding affinity on HER2 (-10.9 kcal/mol) among the key angiogenic molecules tested. In silico rat oral LD50 calculation indicates that AIF is moderate to slightly toxic at 146.4 mg/kg with 1.1 g/kg and 20.1 mg/kg upper and lower 95% confidence limits. Lastly, it sufficiently complies with Lipinski's, Veber's, Egan's, Ghose's, and Muegge's Rule, supporting its oral drug-like property.

CONCLUSION

This study revealed that AIF possesses characteristics of a phytoestrogen compound with significant binding affinity, inhibitory activity against pro-angiogenic proteins, and cytotoxic potential against ER + breast cancer cells.The acceptable and considerable safety and drug-likeness profiles of AIF are worthy of further confirmation in vivo and advanced pre-clinical studies so that AIF can be elevated as a promising molecule for breast cancer therapy.

Assessment of Systemic Toxicity, Genotoxicity, and Early Phase Hepatocarcinogenicity of Iron (III)-Tannic Acid Nanoparticles in Rats

Iron-tannic acid nanoparticles (Fe-TA NPs) presented MRI contrast enhancement in both liver cancer cells and preneoplastic rat livers, while also exhibiting an anti-proliferative effect via enhanced autophagic death of liver cancer cells. Hence, a toxicity assessment of Fe-TA NPs was carried out in the present study. Acute and systemic toxicity of intraperitoneal Fe-TA NPs administration was investigated via a single dose of 55 mg/kg body weight (bw). Doses were then repeated 10 times within a range of 0.22 to 5.5 mg/kg bw every 3 days in rats. Furthermore, clastogenicity was assessed by rat liver micronucleus assay. Carcinogenicity was evaluated by medium-term carcinogenicity assay using glutathione S-transferase placental form positive foci as a preneoplastic marker, while three doses ranging from 0.55 to 17.5 mg/kg bw were administered 10 times weekly via intraperitoneum. Our study found that the LD50 value of Fe-TA NPs was greater than 55 mg/kg bw. Repeated dose administration of Fe-TA NPs over a period of 28 days and 10 weeks revealed no obvious signs of systemic toxicity, clastogenicity, and hepatocarcinogenicity. Furthermore, Fe-TA NPs did not alter liver function or serum iron status, however, increased liver iron content at certain dose in rats. Notably, antioxidant response was observed when a dose of 17.5 mg/kg bw was given to rats. Accordingly, our study found no signs of toxicity, genotoxicity, and early phase hepatocarcinogenicity of Fe-TA NPs in rats.

Reconceptualization of Hormetic Responses in the Frame of Redox Toxicology

Cellular adaptive mechanisms emerging after exposure to low levels of toxic agents or stressful stimuli comprise an important biological feature that has gained considerable scientific interest. Investigations of low-dose exposures to diverse chemical compounds signify the non-linear mode of action in the exposed cell or organism at such dose levels in contrast to the classic detrimental effects induced at higher ones, a phenomenon usually referred to as hormesis. The resulting phenotype is a beneficial effect that tests our physiology within the limits of our homeostatic adaptations. Therefore, doses below the region of adverse responses are of particular interest and are specified as the hormetic gain zone. The manifestation of redox adaptations aiming to prevent from disturbances of redox homeostasis represent an area of particular interest in hormetic responses, observed after exposure not only to stressors but also to compounds of natural origin, such as phytochemicals. Findings from previous studies on several agents demonstrate the heterogeneity of the specific zone in terms of the molecular events occurring. Major factors deeply involved in these biphasic phenomena are the bioactive compound per se, the dose level, the duration of exposure, the cell, tissue or even organ exposed to and, of course, the biomarker examined. In the end, the molecular fate is a complex toxicological event, based on beneficial and detrimental effects, which, however, are poorly understood to date.

Elucidating the antibiofilm activity of Frangula emodin against Staphylococcus aureus biofilms

AIMS

Because the Staphylococcus aureus is one of the most well-known pathogens associated with medical devices and nosocomial infections, the aim of the study was to examine antibiofilm potential of emodin against it.

METHODS AND RESULTS

Antibacterial activity was examined through microdilution assay. Antibiofilm testing included crystal violet staining of biofilm biomass and morphology analysis by Atomic force microscopy (AFM). Furthermore, aerobic respiration was monitored using the Micro-Oxymax respirometer. For investigation of gene expression qRT-PCR was performed. Emodin demonstrated strong antibacterial activity and ability to inhibit biofilm formation of all tested strains. The effect on preformed biofilms was spotted in few strains. AFM revealed that emodin affects biofilm structure and roughness. Monitoring of respiration under emodin treatment in planktonic and biofilm form revealed that emodin influenced aerobic respiration. Moreover, qRT-PCR showed that emodin modulates expression of icaA, icaD, srrA and srrB genes, as well as RNAIII, and that this activity was strain-specific.

CONCLUSION

The results obtained in this study indicate the novel antibiofilm activity of emodin and its multiple pathways of action.

SIGNIFICANCE AND IMPACT OF STUDY

This is the first study that examined pathways through which emodin expressed its antibiofilm activity.

Resveratrol-Based Nanoformulations as an Emerging Therapeutic Strategy for Cancer

Resveratrol is a polyphenolic stilbene derivative widely present in grapes and red wine. Broadly known for its antioxidant effects, numerous studies have also indicated that it exerts anti-inflammatory and antiaging abilities and a great potential in cancer therapy. Regrettably, the oral administration of resveratrol has pharmacokinetic and physicochemical limitations such as hampering its effects so that effective administration methods are demanding to ensure its efficiency. Thus, the present review explores the published data on the application of resveratrol nanoformulations in cancer therapy, with the use of different types of nanodelivery systems. Mechanisms of action with a potential use in cancer therapy, negative effects, and the influence of resveratrol nanoformulations in different types of cancer are also highlighted. Finally, the toxicological features of nanoresveratrol are also discussed.

Association between Dietary Intake of Flavonoids and Cancer Recurrence among Breast Cancer Survivors

Intake of flavonoids is associated with the incidence of breast cancer, but the association between the intake of flavonoids and cancer recurrence is unclear. This study aimed to investigate the hypothesis that intake of flavonoids and flavonoid-rich foods is negatively associated with cancer recurrence. Among 572 women who underwent breast cancer surgery, 66 patients had a cancer recurrence. Dietary data were collected using a structured 24-h dietary recall, and intake of flavonoids was calculated based on the Korea Rural Development Administration flavonoid database. Among overweight and obese patients, disease-free survival was associated with intake of flavonoids (p = 0.004) and flavonoid-rich foods (p = 0.003). Intake of flavonoids (hazard ratio (HR) = 0.249, 95% confidence interval (CI): 0.09–0.64) and flavonoid-rich foods (HR = 0.244, 95% CI: 0.09–0.66) was negatively associated with cancer recurrence after adjusting for confounding factors in overweight and obese patients. Consumption of flavonoids and flavonoid-rich foods was lower in overweight and obese patients with cancer recurrence than those without recurrence and in normal-weight patients. This study suggests that intake of flavonoids and flavonoid-rich foods could have beneficial effects on cancer recurrence in overweight and obese breast cancer survivors.

Sulforaphane exposure impairs contractility and mitochondrial function in three-dimensional engineered heart tissue

Sulforaphane (SFN) is a phytochemical compound extracted from cruciferous plants, like broccoli or cauliflower. Its isothiocyanate group renders SFN reactive, thus allowing post-translational modification of cellular proteins to regulate their function with the potential for biological and therapeutic actions. SFN and stabilized variants recently received regulatory approval for clinical studies in humans for the treatment of neurological disorders and cancer. Potential unwanted side effects of SFN on heart function have not been investigated yet. The present study characterizes the impact of SFN on cardiomyocyte contractile function in cardiac preparations from neonatal rat, adult mouse and human induced-pluripotent stem cell-derived cardiomyocytes. This revealed a SFN-mediated negative inotropic effect, when administered either acutely or chronically, with an impairment of the Frank-Starling response to stretch activation. A direct effect of SFN on myofilament function was excluded in chemically permeabilized mouse trabeculae. However, SFN pretreatment increased lactate formation and enhanced the mitochondrial production of reactive oxygen species accompanied by a significant reduction in the mitochondrial membrane potential. Transmission electron microscopy revealed disturbed sarcomeric organization and inflated mitochondria with whorled membrane shape in response to SFN exposure. Interestingly, administration of the alternative energy source l-glutamine to the medium that bypasses the uptake route of pyruvate into the mitochondrial tricarboxylic acid cycle improved force development in SFN-treated EHTs, suggesting indeed mitochondrial dysfunction as a contributor of SFN-mediated contractile dysfunction. Taken together, the data from the present study suggest that SFN might impact negatively on cardiac contractility in patients with cardiovascular co-morbidities undergoing SFN supplementation therapy. Therefore, cardiac function should be monitored regularly to avoid the onset of cardiotoxic side effects.

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Sulforaphane has negative inotropic effects and increases diastolic tension.

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Sulforaphane exposure increases lactate levels and mitochondrial ROS production and reduces mitochondrial membrane potential.

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l-glutamine supplementation rescues the sulforaphane-mediated reduction in force development.

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Sulforaphane plasma levels and cardiac function should be monitored to avoid unwanted cardiac side effects in patients.

Yeast grown in continuous culture systems can detect mutagens with improved sensitivity relative to the Ames test

Continuous culture systems allow for the controlled growth of microorganisms over a long period of time. Here, we develop a novel test for mutagenicity that involves growing yeast in continuous culture systems exposed to low levels of mutagen for a period of approximately 20 days. In contrast, most microorganism-based tests for mutagenicity expose the potential mutagen to the biological reporter at a high concentration of mutagen for a short period of time. Our test improves upon the sensitivity of the well-established Ames test by at least 20-fold for each of two mutagens that act by different mechanisms (the intercalator ethidium bromide and alkylating agent methyl methanesulfonate). To conduct the tests, cultures were grown in small, inexpensive continuous culture systems in media containing (potential) mutagen, and the resulting mutagenicity of the added compound was assessed via two methods: a canavanine-based plate assay and whole genome sequencing. In the canavanine-based plate assay, we were able to detect a clear relationship between the amount of mutagen and the number of canavanine-resistant mutant colonies over a period of one to three weeks of exposure. Whole genome sequencing of yeast grown in continuous culture systems exposed to methyl methanesulfonate demonstrated that quantification of mutations is possible by identifying the number of unique variants across each strain. However, this method had lower sensitivity than the plate-based assay and failed to distinguish the different concentrations of mutagen. In conclusion, we propose that yeast grown in continuous culture systems can provide an improved and more sensitive test for mutagenicity.

Protopine/Gemcitabine Combination Induces Cytotoxic or Cytoprotective Effects in Cell Type-Specific and Dose-Dependent Manner on Human Cancer and Normal Cells

The natural alkaloid protopine (PRO) exhibits pharmacological properties including anticancer activity. We investigated the effects of PRO, alone and in combination with the chemotherapeutic gemcitabine (GEM), on human tumor cell lines and non-tumor human dermal fibroblasts (HDFs). We found that treatments with different PRO/GEM combinations were cytotoxic or cytoprotective, depending on concentration and cell type. PRO/GEM decreased viability in pancreatic cancer MIA PaCa-2 and PANC-1 cells, while it rescued the GEM-induced viability decline in HDFs and in tumor MCF-7 cells. Moreover, PRO/GEM decreased G1, S and G2/M phases, concomitantly with an increase of subG1 phase in MIA PaCa-2 and PANC-1 cells. Differently, PRO/GEM restored the normal progression of the cell cycle, altered by GEM, and decreased cell death in HDFs. PRO alone increased mitochondrial reactive oxygen species (ROS) in MIA PaCa-2, PANC-1 cells and HDFs, while PRO/GEM increased both intracellular and mitochondrial ROS in the three cell lines. These results indicate that specific combinations of PRO/GEM may be used to induce cytotoxic effects in pancreatic tumor MIA PaCa-2 and PANC-1 cells, but have cytoprotective or no effects in HDFs.

Tavarua Deoxyriboside A and Jasplakinolide as Potential Neuroprotective Agents: Effects on Cellular Models of Oxidative Stress and Neuroinflammation

The oceans harbor a great reservoir of molecules with unknown bioactivities, which could be useful for the treatment of illnesses that nowadays have no cure, such as neurodegenerative diseases. In this work, we evaluated the neuroprotective potential of the marine Fijian compounds tavarua deoxyriboside A and jasplakinolide against oxidative stress and neuroinflammation, crucial mechanisms in neurodegeneration. Both metabolites protected SH-SY5Y human neuroblastoma cells from H₂O₂ damage, improving mitochondrial function and activating the antioxidant systems of cells. These effects were mediated by their ability of inducing Nrf2 translocation. In BV2 microglial cells activated with lipopolysaccharide, Fijian metabolites also displayed promising results, decreasing the release of proinflammatory mediators (ROS, NO, cytokines) through the reduction of gp91 and NFkB-p65 expression. Finally, we performed a coculture among both cell lines, in which treatment with compounds protected SH-SY5Y cells from activated microglia, corroborating their neuroprotective effects. These results suggest that tavarua deoxyriboside A and jasplakinolide could be used as candidate molecules for further studies against neurodegeneration.

Cardioprotective effects and concentration-response relationship of aminoalcohol-diterpenoid alkaloids from Aconitum carmichaelii

Fuzi, a well-known traditional Chinese medicine developed from the lateral roots of Aconitum carmichaelii Debx., has been widely used for the treatment of heart failure. In order to search for active compounds from Fuzi, a phytochemical study was performed, which resulted in the isolation of 14 aminoalcohol-diterpenoid alkaloids, including one new compound (1). Their cardioprotective effects against doxorubicin-induced toxicity in H9c2 cells were evaluated. All of the alkaloids showed cardioprotective effects in a nonmonotonic concentration-response manner, with the maximum protection rates ranging from 17.96 ± 2.93% to 98.31 ± 0.35%. Compound 5 exhibited the most potent cardioprotective activity. Taking the maximum protection rate as an indicator, the preliminary structure-activity relationship analysis indicated that the substitutions of C-1, C-13, C-15, C-16, and N and the configurations of OMe-6 and OH-15 are important structural features for the cardioprotective activities of the aminoalcohol-diterpenoid alkaloids.

Inhibitory effect of flavonoid xanthomicrol on triple-negative breast tumor via regulation of cancer-associated microRNAs

Breast cancer is the leading cause of cancer death in women worldwide. Due to the side effects of current chemo-reagents on healthy tissues, it is essential to search for alternative compounds with less toxicity and better efficacy. In the present study, we have investigated the anticancer effects of flavonoid xanthomicrol on the mice breast cancer model using MTT assay, cell cycle and Annexin/PI analysis, colony formation assay, H&E staining, immunohistochemistry, and miRNA analysis. Our results demonstrated that xanthomicrol decreased the cell viability and clonogenic capability, induced G1-arrest and apoptosis in the breast cancer cells in vitro, and caused a significant reduction in the volume and weight of mice tumors in vivo. In addition, xanthomicrol reduced the expression of TNFα, VEGF, MMP9, and Ki67, while upregulating the expression of apoptotic markers such as Bax, caspase3, and caspase9. Finally, the expression of miR21, miR27, and miR125, known as oncomirs, decreased significantly after xanthomicrol administration, while the expression of miR29 and miR34, functioning as tumor suppressors, increased significantly (p < .001). Our data demonstrated that xanthomicrol can induce apoptosis and suppress angiogenesis in breast cancer cells due to its inhibitory effect on oncomirs and its stimulatory effect on tumor suppressor miRNAs.

Membrane damage precedes DNA damage in hydroxychavicol treated E. coli cells and facilitates cooperativity with hydrophobic antibiotics

Hydroxychavicol (HC), found abundantly in Piper betle leaves is credited with antimicrobial property. Previously we had shown HC induces reactive oxygen species mediated DNA damage in bacterial cells. HC also resulted in membrane compromise revealing its pleiotropic effects on cellular targets. The kinetics and exact sequence of events leading to inhibition of growth and cell death in E. coli after HC treatment remains poorly understood. We show that sub-lethal concentration (125 μg/mL) of HC causes cellular filamentation within 1 h of treatment, while a higher concentration (750 μg/mL) induces cell breakage. HC-treated cells were found to experience oxidative stress as early as 10 min, while evidence of membrane damage was apparent at 30 min. DNA damage repair genes were found to be activated at 60 min. Interestingly, HC-induced cell permeabilization was inhibited and enhanced by external Mg²⁺ and EDTA, respectively, suggesting that HC damages the outer membrane. Kinetic experiments revealed that HC-treated cells underwent oxidative stress, membrane damage and DNA damage in that order. Because gram negative bacteria such as E. coli are refractory to several antibiotics due to the presence of the outer membrane, we hypothesized that HC pretreatment would sensitize E. coli to hydrophobic antibiotics. Our study reveals for the first time that HC could sensitize bacteria to clinically used antibiotics due to its outer membrane damaging property.

The phytoprotective agent sulforaphane prevents inflammatory degenerative diseases and age-related pathologies via Nrf2-mediated hormesis

In numerous experimental models, sulforaphane (SFN) is shown herein to induce hormetic dose responses that are not only common but display endpoints of biomedical and clinical relevance. These hormetic responses are mediated via the activation of nuclear factor erythroid- derived 2 (Nrf2) antioxidant response elements (AREs) and, as such, are characteristically biphasic, well integrated, concentration/dose dependent, and specific with regard to the targeted cell type and the temporal profile of response. In experimental disease models, the SFN-induced hormetic activation of Nrf2 was shown to effectively reduce the occurrence and severity of a wide range of human-related pathologies, including Parkinson's disease, Alzheimer's disease, stroke, age-related ocular damage, chemically induced brain damage, and renal nephropathy, amongst others, while also enhancing stem cell proliferation. Although SFN was broadly chemoprotective within an hormetic dose-response context, it also enhanced cell proliferation/cell viability at low concentrations in multiple tumor cell lines. Although the implications of the findings in tumor cells are largely uncertain at this time and warrant further consideration, the potential utility of SFN in cancer treatment has not been precluded. This assessment of SFN complements recent reports of similar hormesis-based chemoprotections by other widely used dietary supplements, such as curcumin, ginkgo biloba, ginseng, green tea, and resveratrol. Interestingly, the mechanistic profile of SFN is similar to that of numerous other hormetic agents, indicating that activation of the Nrf2/ARE pathway is probably a central, integrative, and underlying mechanism of hormesis itself. The Nrf2/ARE pathway provides an explanation for how large numbers of agents that both display hormetic dose responses and activate Nrf2 can function to limit age-related damage, the progression of numerous disease processes, and chemical- and radiation- induced toxicities. These findings extend the generality of the hormetic dose response to include SFN and many other chemical activators of Nrf2 that are cited in the biomedical literature and therefore have potentially important public health and clinical implications.