The maturing of hormesis as a credible dose-response model

Measuring herbicide (73.3 % glyphosate) exposure response in Halophila ovalis (previously johnsonii) and Halodule wrightii seagrass

We evaluated the effects of Roundup QuikPRO™ (73.3 % glyphosate) using real-world herbicide application treatments: (1) overspray (low-dose), (2) powder spill (high-dose), and (3) controls (no-dose). Seagrass and water quality were monitored to observe responses to acute herbicide application. Seagrass shoot densities significantly declined over time in high-dose treatments, whereas seagrass shoot densities in low-dose treatments were comparable to controls. In high-dose treatments, seagrass mortality increased over time, 100 % Halophila ovalis and 81 % Halodule wrightii mortality from day zero to 53. Collectively, glyphosate concentrations were negatively correlated with seagrass shoot densities, and positively correlated with water column nutrients (TN and TP). Based on these results we do not attribute local seagrass declines to low-dose glyphosate exposure, i.e., herbicide overspray events. However, we advise caution against improper herbicide handling, since glyphosate remained detectable in relatively high concentrations (<88 mg/L) after 53 days, resulting in seagrass mortality and increased water column nutrients.

Unexpected gender differences in progressive supranuclear palsy reveal efficacy for davunetide in women

Progressive supranuclear palsy (PSP) is a pure tauopathy, implicating davunetide, enhancing Tau-microtubule interaction, as an ideal drug candidate. However, pooling patient data irrespective of sex concluded no efficacy. Here, analyzing sex-dependency in a 52 week-long- PSP clinical trial (involving over 200 patients) demonstrated clear baseline differences in brain ventricular volumes, a secondary endpoint. Dramatic baseline ventricular volume-dependent/volume increase correlations were observed in 52-week-placebo-treated females (r = 0.74, P = 2.36-9), whereas davunetide-treated females (like males) revealed no such effects. Assessment of primary endpoints, by the PSP Rating Scale (PSPRS) and markedly more so by the Schwab and England Activities of Daily Living (SEADL) scale, showed significantly faster deterioration in females, starting at trial week 13 (P = 0.01, and correlating with most other endpoints by week 52). Twice daily davunetide treatments slowed female disease progression and revealed significant protection according to the SEADL scale as early as at 39 weeks (P = 0.008), as well as protection of the bulbar and limb motor domains considered by the PSPRS, including speaking and swallowing difficulties caused by brain damage, and deterioration of fine motor skills, respectably (P = 0.01), at 52 weeks. Furthermore, at 52 weeks of trial, the exploratory Geriatric Depression Scale (GDS) significantly correlated with the SEADL scale deterioration in the female placebo group and demonstrated davunetide-mediated protection of females. Female-specific davunetide-mediated protection of ventricular volume corresponded to clinical efficacy. Together with the significantly slower disease progression seen in men, the results reveal sex-based drug efficacy differences, demonstrating the neuroprotective and disease-modifying impact of davunetide treatment for female PSP patients.

Toxicity of tris(2-chloroethyl) phosphate in Daphnia magna after lifetime exposure: Changes in growth, reproduction, survival and gene transcription

In recent years, with the elimination of brominated flame retardants (BFRs), the product volume of tris(2-chloroethyl) phosphate (TCEP), as a main substitute of BFRs, was increasing and frequently detected in natural waters. However, the current toxicological studies on TCEP were mainly focused on the partial life stage assessment of model animals, and thus it might underestimate the impact of TCEP on environmental risks. Therefore, the whole-life-stage effects of TCEP on growth, reproduction, survival and gene transcription in Daphnia magna (D. magna) were studied in this study after exposure to environmentally relevant or greater concentrations (500 or 5000 ng/L). It was found that chronic exposure to TCEP at environmental relevant or greater concentrations promoted growth of D. magna and the expressions of genes involved in the pathways associated with growth were significantly up-regulated. TCEP did not affect reproduction of D. magna, but the expressions of some genes screened in reproduction stage were significantly changed. Furthermore, the expressions of genes involved in two heart disease-related pathways were down-regulated at the death stage of D. magna after TCEP exposure for 62 days, suggesting that TCEP delayed the death of D. magna by retarding their heart senility.

The nootropic and anticholinesterase activities of Clitoria ternatea Linn. root extract: Potential treatment for cognitive decline

BACKGROUND

Clitoria ternatea (CT) is an herbal plant that has been used as a memory booster in folk medicine. CT root extract has been proven to restore chronic cerebral hypoperfusion (CCH)-induced memory deficits in a rat model, but the underlying mechanisms and the toxicity profile following repeated exposure have yet to be explored.

THE AIM OF THE STUDY

To investigate the effects of the chronic (28 days) oral administration of CT root extract on CCH-induced cognitive impairment, neuronal damage and cholinergic deficit, and its toxicity profile in the CCH rat model.

MATERIALS AND METHODS

The permanent bilateral occlusion of common carotid arteries (PBOCCA) surgery method was employed to develop a CCH model in male Sprague Dawley (SD) rats. Then, these rats were given oral administration of CT root extract at doses of 100, 200, and 300 mg/kg, respectively for 28 days and subjected to behavioural tests. At the end of the experiment, the brain was harvested for histological analysis and cholinesterase activities. Then, blood samples were collected and organs such as liver, kidney, lung, heart, and spleen were procured for toxicity assessment.

RESULTS

Chronic treatment of CT root extract at doses of 200 and 300 mg/kg, restored memory impairments induced by CCH. CT root extract was also found to diminish CCH-induced neuronal damage in the CA1 region of the hippocampus. High dose (300 mg/kg) of the CT root extract was significantly inhibited the increased acetylcholinesterase (AChE) activity in the frontal cortex and hippocampus of the PBOCCA rats. In toxicity study, repeated doses of CT root extract were found to be safe in PBOCCA rats after 28 days of treatment.

CONCLUSIONS

Our findings provided scientific evidence supporting the therapeutic potential of CT root extract in the treatment of vascular dementia (VaD)-related cholinergic abnormalities and subsequent cognitive decline.

The anti-angiogenic tyrosine kinase inhibitor Pazopanib kills cancer cells and disrupts endothelial networks in biomimetic three-dimensional renal tumouroids

Pazopanib is a tyrosine kinase inhibitor used to treat renal cell carcinoma. Few in vitro studies investigate its effects towards cancer cells or endothelial cells in the presence of cancer. We tested the effect of Pazopanib on renal cell carcinoma cells (CAKI-2,786-O) in two-dimensional and three-dimensional tumouroids made of dense extracellular matrix, treated in normoxia and hypoxia. Finally, we engineered complex tumouroids with a stromal compartment containing fibroblasts and endothelial cells. Simple CAKI-2 tumouroids were more resistant to Pazopanib than 786-O tumouroids. Under hypoxia, while the more 'resistant' CAKI-2 tumouroids showed no decrease in viability, 786-O tumouroids required higher Pazopanib concentrations to induce cell death. In complex tumouroids, Pazopanib exposure led to a reduction in the overall cell viability (p < 0.0001), disruption of endothelial networks and direct killing of renal cell carcinoma cells. We report a biomimetic multicellular tumouroid for drug testing, suitable for agents whose primary target is not confined to cancer cells.

Differential sensitivity to the antifouling chemical medetomidine between wood frog and American toad tadpoles with evidence for low-dose stimulation and high-dose inhibition of metamorphosis

Antifouling chemicals are legacy contaminants in aquatic ecosystems. Previous experiments have shown that a 14-day exposure to the antifouling chemical medetomidine delays metamorphosis and reduces body mass in wood frog tadpoles. In the present study, we exposed wood frog tadpoles to medetomidine for 3, 7, and 10 days at 100 nM, 1 μM, and 10 μM. We also exposed American toad tadpoles to medetomidine for 3 days at four concentrations (10 nM, 100 nM, 1 μM, and 10 μM) in static renewal experiments. In each experiment, we measured growth, frequency and time to metamorphosis, and mass at metamorphosis. In both species, medetomidine significantly slowed development as measured by the Gosner stage. After 34 days in culture, wood frog tadpoles exposed to 1 and 10 μM medetomidine for as few as 3 days were significantly less developed compared to controls. Toads exposed to 1 μM medetomidine for 3 days were also significantly less developed on day 27, but by day 34, there was no difference from controls. For wood frogs, medetomidine significantly affected time to metamorphosis with a trend for tadpoles at lower concentrations metamorphosing sooner than those at higher concentrations. While medetomidine affected time to metamorphosis in wood frogs, it did not affect fresh mass, dry mass, or mortality compared to controls. Wood frog tadpoles that did not metamorphose after over 90 days in culture were more frequent in high-concentration groups than in the control. In toads, 10 μM medetomidine was 100% lethal within 23 days, but at the same concentration and duration, no wood frog tadpoles died. Lower concentrations were also significantly lethal to toads compared to controls, but tadpoles that survived in 10 and 100 nM metamorphosed sooner than those in 1 μM. Fresh mass of toad tadpoles exposed to 1 μm was significantly smaller at metamorphosis compared to that of controls. Medetomidine also affected the behavior of tadpoles. In toads, medetomidine significantly reduced both percent activity and startle response. In wood frogs, medetomidine significantly reduced percent activity, but increased startle response. We discuss our finding of low-dose stimulation and high-dose inhibition of different life history endpoints in terms of hormetic mechanisms. The differential sensitivity between species in terms of mortality, frequency of metamorphosis, and behavior highlights the potential negative environmental effects of medetomidine to amphibians.

The role of declining adaptive homeostasis in ageing

Adaptive homeostasis is "the transient expansion or contraction of the homeostatic range for any given physiological parameter in response to exposure to sub-toxic, non-damaging, signalling molecules or events, or the removal or cessation of such molecules or events" (Davies, 2016). Adaptive homeostasis enables biological systems to make continuous short-term adjustments for optimal functioning despite ever-changing internal and external environments. Initiation of adaptation in response to an appropriate signal allows organisms to successfully cope with much greater, normally toxic, stresses. These short-term responses are initiated following effective signals, including hypoxia, cold shock, heat shock, oxidative stress, exercise-induced adaptation, caloric restriction, osmotic stress, mechanical stress, immune response, and even emotional stress. There is now substantial literature detailing a decline in adaptive homeostasis that, unfortunately, appears to manifest with ageing, especially in the last third of the lifespan. In this review, we present the hypothesis that one hallmark of the ageing process is a significant decline in adaptive homeostasis capacity. We discuss the mechanistic importance of diminished capacity for short-term (reversible) adaptive responses (both biochemical and signal transduction/gene expression-based) to changing internal and external conditions, for short-term survival and for lifespan and healthspan. Studies of cultured mammalian cells, worms, flies, rodents, simians, apes, and even humans, all indicate declining adaptive homeostasis as a potential contributor to age-dependent senescence, increased risk of disease, and even mortality. Emerging work points to Nrf2-Keap1 signal transduction pathway inhibitors, including Bach1 and c-Myc, both of whose tissue concentrations increase with age, as possible major causes for age-dependent loss of adaptive homeostasis.

Hormetic Response by Silver Nanoparticles on In Vitro Multiplication of Sugarcane (Saccharum spp. Cv. Mex 69-290) Using a Temporary Immersion System

Background:

Hormesis is considered a dose–response phenomenon characterized by growth stimulation at low doses and inhibition at high doses. The hormetic response by silver nanoparticles (AgNPs) on in vitro multiplication of sugarcane was evaluated using a temporary immersion system.

Methods:

Sugarcane shoots were used as explants cultured in Murashige and Skoog medium with AgNPs at concentrations of 0, 25, 50, 100, and 200 mg/L. Shoot multiplication rate and length were used to determine hormetic response. Total content of phenolic compounds of sugarcane, mineral nutrition, and reactive oxygen species (ROS) was determined.

Results:

Results were presented as a dose–response curve. Stimulation phase growth was observed at 50 mg/L AgNPs, whereas inhibition phase was detected at 200 mg/L AgNPs. Mineral nutrient analysis showed changes in macronutrient and micronutrient contents due to the effect of AgNPs. Moreover, AgNPs induced ROS production and increased total phenolic content, with a dose-dependent effect.

Conclusion:

Results suggested that the production of ROS and mineral nutrition are key mechanisms of AgNP-induced hormesis and that phenolic accumulation was obtained as a response of the plant to stress produced by high doses of AgNPs. Therefore, small doses of AgNPs in the culture medium could be an efficient strategy for commercial micropropagation.

A mitohormetic response to pro-oxidant exposure in the house mouse

Mitochondria are hypothesized to display a biphasic response to reactive oxygen species (ROS) exposure. In this study, we evaluated the time course changes in mitochondrial performance and oxidative stress in house mice following X-irradiation. Forty-eight mice were equally divided among six groups, including a nonirradiated control and five experimental groups that varied in time between X-ray exposure and euthanasia (1 h and 1, 4, 7, and 10 days after X-irradiation). We measured parameters associated with mitochondrial respiratory function and ROS emission from isolated liver and skeletal muscle mitochondria and levels of oxidative damage and antioxidants in liver, skeletal muscle, and heart tissues. Mitochondrial function dropped initially after X-irradiation but recovered quickly and was elevated 10 days after the exposure. Hydrogen peroxide production, lipid peroxidation, and protein carbonylation showed inverse U-shaped curves, with levels returning to control or lower than control, 10 days after X-irradiation. Enzymatic antioxidants and markers for mitochondrial biogenesis exhibited a tissue-specific response after irradiation. These data provide the first chronological description of the mitohormetic response after a mild dose of irradiation and highlight the protective response that cells display to ROS exposure. This study also provides valuable information and application for future mitochondrial and oxidative stress studies in numerous physiological settings.

Temporal Responses to X-Radiation Exposure in Spleen in the pKZ1 Mouse Recombination Assay

The in vivo mouse transgenic pKZ1 chromosomal inversion assay is a sensitive assay that responds to very low doses of DNA-damaging agents. pKZ1 inversions are measured as the frequency of cells expressing E. coli β-galactosidase protein, which can only be produced from an inverted pKZ1 transgene. In previous studies we reported that a single whole-body low dose of 0.01 mGy X rays alone caused an increase in pKZ1 chromosomal inversions in spleen when analyzed 3 days postirradiation, and yet this same dose could protect from high-dose-induced inversions when delivered as a conditioning dose 4 h before or after a 1 Gy challenge dose. In an attempt to explain these results, we performed temporal studies over a wide radiation dose range to determine if the inversion response was temporally different at different doses. pKZ1 mice were irradiated with a single whole-body X-ray dose of 0.01 mGy, 1 mGy or 1 Gy, and spleen sections were then analyzed for pKZ1 inversions at 7 h, 1 day or 7 days after exposure. No change in inversion frequency was observed at the 7 h time point at any dose. At day 1, an increase in inversions was observed in response to the 0.01 mGy dose, whereas a decrease in inversions below sham-treated frequency was observed for the 1 mGy dose. Inversion frequency for both doses returned to sham-treated inversion frequency by day 7. To our knowledge, this is the first reported study to examine the temporal nature of a radiation response spanning a wide dose range, including doses relevant to occupational exposure, and the results are dynamic and dose specific. The results suggest that inversions induced after low-dose irradiation are removed by homeostatic mechanisms within a short time frame, and underscore the importance of studying responses over a period of time when interpreting radiation effects.

Serrulatane Diterpenoid from Eremophila neglecta Exhibits Bacterial Biofilm Dispersion and Inhibits Release of Pro-inflammatory Cytokines from Activated Macrophages

The purpose of this study was to assess the biofilm-removing efficacy and inflammatory activity of a serrulatane diterpenoid, 8-hydroxyserrulat-14-en-19-oic acid (1), isolated from the Australian medicinal plant Eremophila neglecta. Biofilm breakup activity of compound 1 on established Staphylococcus epidermidis and Staphylococcus aureus biofilms was compared to the antiseptic chlorhexidine and antibiotic levofloxacin. In a time-course study, 1 was deposited onto polypropylene mesh to mimic a wound dressing and tested for biofilm removal. The ex-vivo cytotoxicity and effect on lipopolysaccharide-induced pro-inflammatory cytokine release were studied in mouse primary bone-marrow-derived macrophage (BMDM) cells. Compound 1 was effective in dispersing 12 h pre-established biofilms with a 7 log10 reduction of viable bacterial cell counts, but was less active against 24 h biofilms (approximately 2 log10 reduction). Compound-loaded mesh showed dosage-dependent biofilm-removing capability. In addition, compound 1 displayed a significant inhibitory effect on tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6) secretion from BMDM cells, but interleukin-1 beta (IL-1β) secretion was not significant. The compound was not cytotoxic to BMDM cells at concentrations effective in removing biofilm and lowering cytokine release. These findings highlight the potential of this serrulatane diterpenoid to be further developed for applications in wound management.

The polyacetylenes falcarinol and falcarindiol affect stress responses in myotube cultures in a biphasic manner

The effects of the bioactive polyacetylenes, falcarinol and falcarindiol, present in carrots, celery, celeriac and other umbelliferous vegetables, on the stress responses in primary myotube cultures, were studied. Biphasic responses on cellular stress responses in myotube cultures were investigated by exposing them to various concentrations of falcarinol and falcarindiol for 24 h before testing effects of 100 microM H(2)O(2) on the intracellular formation of reactive oxygen species (ROS), transcription of the antioxidative enzyme cytosolic glutathione peroxidase (cGPx), and the heat shock proteins (HSP) HSP70 and HO1. At low concentrations (1.6 to 25 microM) polyacetylenes caused a slightly accelerated intra-cellular ROS formation, increased cGPx transcription and decreased HSP70 and HO1 transcription. The increased cGPx transcription may be interpreted as an adaptive response to the increased ROS formation and may have caused a reduced demand for the protective functions of the HSPs. ROS formation, however, was substantially decreased after pre-incubation with both polyacetylenes at 50 and 100 microM, the cGPx transcription was reduced and the HSP70 and HO1 transcription increased, indicating a need for the protective and repairing functions of the HSPs. In conclusion, pre-incubation with low concentrations of both polyacetylenes prior to H(2)O(2) exposure induced a cytoprotective effect whereas higher concentrations had adverse effects.

Hormesis and toxic torts

Policy implementation of hormesis has to date focused on regulatory applications. Toxic-tort litigation may provide an alternative policy venue for real-world applications of hormesis. Businesses and government entities, who are sued by individuals claiming to have been injured by exposure to very low levels of toxic substances may defend those cases by deploying hormesis to argue that such exposures were unlikely to be harmful. The threshold issue in using hormesis in toxic-tort defense is whether such evidence will be admissible under applicable standards for scientific evidence, which will likely turn on whether hormesis is deemed to be ;generally accepted' in the relevant scientific community. Given the relatively novel status of hormesis, its admissibility will likely be a close call, but is likely to be held admissible in favorable circumstances. If admissible, hormesis is likely to receive a fairer and more even-handed consideration than in regulatory decisions, where regulatory agencies are bound by policy-based default assumptions that limit their receptivity to new concepts such as hormesis. The perception of hormesis by juries will likely be the critical factor for determining the utility of hormesis in toxic-tort litigation, and this perception is likely to be affected by the presentation and circumstances in the individual case.

Hormetic Mechanisms of Anti-Aging and Rejuvenating Effects of Repeated Mild Heat Stress on Human Fibroblasts in Vitro

The phenomenon of hormesis is represented by mild stress-induced stimulation of maintenance and repair pathways, resulting in beneficial effects for cells and organisms. We have reported that repeated mild heat stress (RMHS) has anti-aging hormetic effects on growth and various cellular and biochemical characteristics of human skin fibroblasts undergoing aging in vitro. These effects of RMHS include the maintenance of the stress protein profile, reduction in the accumulation of oxidatively and glycoxidatively damaged proteins, stimulation of the activities of the proteasome and its 11S activator, improvement in cellular resistance to ethanol, hydrogen peroxide, and ultraviolet rays, and increased antioxidative activity of the cells. We have also reported that RMHS prolongs the lifespan of Drosophila. Others have reported anti-aging and life prolonging effects of a wide variety of so-called stressors, such as pro-oxidants, aldehydes, calorie restriction, irradiation, heat shock, and hypergravity. Although molecular mechanisms of hormesis are yet to be elucidated, there are indications that relatively small hormetic effects become biologically amplified, resulting in significant improvement of cellular and organic functions and survival. Hormesis, therefore, can be an effective approach for modulating aging, for preventing or delaying the onset of age-related diseases, and for improving the quality of life in old age.