On the meta-analysis of hormetic effects.

The evidence for hormetic responses with chemical effects at doses lower than the no-observed-adverse-effect-level (sub-NOAEL) is increasing, creating a need for meta-analyses of sub-NOAEL effects across studies. However, the distinct features of hormetic responses complicate the procedures of meta-analyses aiming to study sub-NOAEL, hormetic effects, and there is no standardized methodology to serve as a guideline. In this piece, a protocol is proposed, which covers the selection of more holistic keywords to be integrated into the literature search queries, the designation of control, and the identification of NOAEL (and thus sub-NOAEL dose responses). It also considers the selection of the response indicators and the incorporation of time and dose as sources of variation. This protocol can serve as a reference point for a harmonized and more robust methodology to meta-analyze sub-NOAEL effects of chemicals on living organisms.

Low Levels of Contaminants Stimulate Harmful Algal Organisms and Enrich Their Toxins.

A widespread increase in intense phytoplankton blooms has been noted in lakes worldwide since the 1980s, with the summertime peak intensity amplifying in most lakes. Such blooms cause annual economic losses of multibillion USD and present a major challenge, affecting 11 out of the 17 United Nations Sustainable Development Goals. Here, we evaluate recent scientific evidence for hormetic effects of emerging contaminants and regulated pollutants on Microcystis sp., the most notorious cyanobacteria forming harmful algal blooms and releasing phycotoxins in eutrophic freshwater systems. This new evidence leads to the conclusion that pollution is linked to algal bloom intensification. Concentrations of contaminants that are considerably smaller than the threshold for toxicity enhance the formation of harmful colonies, increase the production of phycotoxins and their release into the environment, and lower the efficacy of algaecides to control algal blooms. The low-dose enhancement of microcystins is attributed to the up-regulation of a protein controlling microcystin release (McyH) and various microcystin synthetases in tandem with the global nitrogen regulator Ycf28, nonribosomal peptide synthetases, and several ATP-binding cassette transport proteins. Given that colony formation and phycotoxin production and release are enhanced by contaminant concentrations smaller than the toxicological threshold and are widely occurring in the environment, the effect of contaminants on harmful algal blooms is more prevalent than previously thought. Climate change and nutrient enrichment, known mechanisms underpinning algal blooms, are thus joined by low-level pollutants as another causal mechanism.

Hormesis Research in China Is More Prevalent than Previously Thought.

An analysis of China's domestic publications revealed that China's hormesis-related research was enormously underestimated. China's documented hormesis-related research spans at least four decades, covers a broad spectrum of research areas, and is more abundant than previously thought. These findings should be considered in historical assessments of the concept of hormesis. Moreover, similar to the international literature, different terms have been used to describe the same phenomenon (hormesis), which hampers communication, generalization of findings and accumulation of knowledge. Hence, we advocate that 'hormesis' should be cited as a keyword in all the relevant publications written in Chinese language.

Effective Force Generation During Mammalian Cell Migration Under Different Molecular and Physical Mechanisms.

We have developed much understanding of actin-driven cell migration and the forces that propel cell motility. However, fewer studies focused on estimating the effective forces generated by migrating cells. Since cells in vivo are exposed to complex physical environments with various barriers, understanding the forces generated by cells will provide insights into how cells manage to navigate challenging environments. In this work, we use theoretical models to discuss actin-driven and water-driven cell migration and the effect of cell shapes on force generation. The results show that the effective force generated by actin-driven cell migration is proportional to the rate of actin polymerization and the strength of focal adhesion; the energy source comes from the actin polymerization against the actin network pressure. The effective force generated by water-driven cell migration is proportional to the rate of active solute flux and the coefficient of external hydraulic resistance; the energy sources come from active solute pumping against the solute concentration gradient. The model further predicts that the actin network distribution is mechanosensitive and the presence of globular actin helps to establish a biphasic cell velocity in the strength of focal adhesion. The cell velocity and effective force generation also depend on the cell shape through the intracellular actin flow field.

The hormetic response of heart rate of fish embryos to contaminants - Implications for research and policy.

Evidence of contaminant-induced hormesis is rapidly accumulating, while the underlying mechanisms of hormesis are becoming increasingly understood. Recent developments in this research area, and especially the emergence of the nuclear factor-erythroid factor 2-related factor 2 (Nrf2) as the master mechanism, suggest that contaminants can induce cardiac hormetic responses. This paper collates significant evidence of hormetic response of the heart rate of fish embryos to contaminants, in particular antibiotics, microplastics, and herbicides, characterized by a low-dose increase (tachycardia) and a high-dose decrease (bradycardia). The increase often occurs at doses about 100-800 times smaller than the no-observed-adverse-effect-level (NOAEL). There are also indications for even triphasic responses, which include a sub-hormetic decrease of the heart rate by doses over 106 times smaller than the NOAEL. Such sub-NOAEL effects cannot be captured by linear-no-threshold (LNT) and threshold models, raising concerns about environmental health and highlighting the pressing need to consider hormetic responses in the ecological risk assessment. A visionary way forward is proposed, but addressing this research bottleneck would require improved research designs with enhanced ability and statistical power to study diphasic and triphasic responses of heart rate.

Hormesis Shifts the No-Observed-Adverse-Effect Level (NOAEL).

Data from recent dose-response toxicological studies suggest that the no-observed-adverse-effect-level (NOAEL) may depend upon whether hormesis is present. A further examination of these data supports this hypothesis by showing that the NOAEL was greater for living units (organisms or cells) showing hormesis than for living units showing no hormesis. For example, some cancer tissue cells may exhibit hormetic responses to an anticancer drug while some other cancer tissue cells may not. These findings suggest that living units showing hormesis may also be less susceptible than living units not showing hormesis. However, these findings are preliminary and cannot be generalized or assumed to be a norm yet. New studies are needed to evaluate how NOAEL shifts depending on the occurrence of hormesis.

Biphasic response of T cell activation to substrate stiffness.

T cell activation is sensitive to the mechanical properties of an activating substrate. However, there are also contrasting results on how substrate stiffness affects T cell activation, including differences between T cells of mouse and human origin. Towards reconciling these differences, this report examines the response of primary human T cells to polyacrylamide gels with stiffness between 5 and 110 kPa presenting activating antibodies to CD3 and CD28. T cell proliferation and IL-2 secretion exhibited a biphasic functional response to substrate stiffness, which can be shifted by changing density of activating antibodies and abrogated by inhibition of cellular contractility. T cell morphology was modulated by stiffness at early time points. RNA-seq indicates that T cells show differing monotonic trends in upregulated genes and pathways towards both ends of the stiffness spectrum. These studies provide a framework of T cell mechanosensing and suggest an effect of ligand density that may reconcile different, contrasting patterns of stiffness sensing seen in previous studies.

China: The New Powerhouse of Hormesis Research?

More than one third of the worldwide hormesis research has been produced at institutions in the United States (US). Although the US ranked first in terms of hormesis publication records from the mid. 1980s to the mid-late 2010s, China became the largest producer of hormesis publications in the years 2019-2020. As China is transforming into a powerhouse of hormesis research, new opportunities might arise for the research field.

Biphasic Effect of Pirfenidone on Angiogenesis.

Pirfenidone (PFD), a synthetic arsenic compound, has been found to inhibit angiogenesis at high concentrations. However, the biphasic effects of different PFD concentrations on angiogenesis have not yet been elucidated, and the present study used an in vitro model to explore the mechanisms underlying this biphasic response. The effect of PFD on the initial angiogenesis of vascular endothelial cells was investigated through a Matrigel tube formation assay, and the impact of PFD on endothelial cell migration was evaluated through scratch and transwell migration experiments. Moreover, the expression of key migration cytokines, matrix metalloproteinase (MMP)-2 and MMP-9, was examined. Finally, the biphasic mechanism of PFD on angiogenesis was explored through cell signaling and apoptosis analyses. The results showed that 10-100 µM PFD has a significant and dose-dependent inhibitory effect on tube formation and migration, while 10 nM-1 µM PFD significantly promoted tube formation and migration, with 100 nM PFD having the strongest effect. Additionally, we found that a high concentration of PFD could significantly inhibit MMP-2 and MMP-9 expression, while low concentrations of PFD significantly promoted their expression. Finally, we found that high concentrations of PFD inhibited EA.hy926 cell tube formation by promoting apoptosis, while low concentrations of PFD promoted tube formation by increasing MMP-2 and MMP-9 protein expression predominantly via the EGFR/p-p38 pathway. Overall, PFD elicits a biphasic effect on angiogenesis through different mechanisms, could be used as a new potential drug for the treatment of vascular diseases.

Decreased immune response in monkeys administered a human T-effector cell agonist (OX40) antibody.

The OX40 receptor plays a crucial co-stimulatory role in T effector cell survival, expansion, cytokine production, and cytotoxicity to tumor cells; therefore, OX40 agonists are being evaluated as anti-cancer immunotherapies, especially in combination with checkpoint inhibitors. To support clinical development of BMS-986178 (an OX40 agonist antibody), two repeat-dose toxicity studies were conducted in cynomolgus monkeys. In the first study, BMS-986178 was administered intravenously (IV) once weekly for one month at doses from 30 to 120 mg/kg. BMS-986178 was well tolerated; surprisingly, immune function was suppressed rather than increased based on pharmacodynamic (PD) and flow cytometry readouts (e.g. T-cell dependent antibody response [TDAR]). To determine whether immune suppression was due to a bi-phasic response, a follow-up study was conducted at lower doses (1 and 10 mg/kg). Although receptor engagement was confirmed, immune function was still suppressed at both doses. In addition, treatment-emergent anti-drug antibodies (ADAs) at 1 mg/kg resulted in hypersensitivity reactions and reduced BMS-986178 exposure after repeated dosing, which precluded a full PD assessment at this dose. In conclusion, BMS-986178 was clinically well-tolerated by monkeys at weekly IV doses from 10 to 120 mg/kg (AUC[0-168] ≤ 712,000 µg●h/mL). However, despite target engagement, PD assays and other immune endpoints demonstrated immune suppression, not stimulation. Due to the inverted immune response at higher doses and the onset of ADAs, additional repeat-dose toxicity studies of BMS-986178 in monkeys (that would typically be required to support Phase 3 clinical trials and registration) would not add value for human safety assessment.

Chlorophyll hormesis: Are chlorophylls major components of stress biology in higher plants?

High oxidative stress inhibits the synthesis and accumulation of chlorophylls, the pigments that absorb and use light. We collated evidence from a diverse array of studies demonstrating that chlorophyll concentration increases in response to low-level stress and decreases in response to high-level stress. These observations were from 33 species, >20 stress-inducing agents, 43 experimental setups and 177 dose responses, suggesting generality. Data meta-analysis indicated that the maximum stimulatory response did not differ significantly among species and agents. The stimulatory response maximized within a defined time window (median = 150-160% of the control response), after which it decreased but remained elevated (median = 120-130% of control response). The common stimulation of chlorophylls by low-level stress indicates that chlorophylls are major components of stress biology, with their increased concentration at low-level stress suggestive of their requirement for normal functioning and health. Increased chlorophyll concentration in response to low-level stress may equip systems with an enhanced capacity for defense against high-level (health-threatening) challenges within defined time windows, such as pollution or herbivores. These developments have wide-ranging implications in ecophysiology, biotic interactions and evolution.

Hormesis: The dose response for the 21st century: The future has arrived.

Dose-response is the backbone of toxicology, and one of the most debated scientific issues over the 20th century. It was in the last century that the scientific community applauded the discovery of the proportionality rule, so called linear non-threshold dose-response relationship. It was also in the same century that all the regulatory standards were framed around threshold and linear non-threshold models. At the same time, hormesis was a marginalized dose-response relationship often viewed as the extreme values of a data distribution in a Box and Whiskers plot. However, an analysis of bibliometric data indicates that the future has arrived, and hormesis is now revolutionizing toxicology and most research areas of biology. Hormesis celebrates its rebirth some 150 years after its discovery.

A Model for the Acrosome Reaction in Mammalian Sperm.

The acrosome reaction is a complex, calcium-dependent reaction that results in an exocytotic event required for successful fertilization of the egg. It has long been thought that the acrosome reaction occurs upon sperm binding to the zona pellucida, a viscoelastic layer surrounding the oocyte. Recent studies have suggested that the reaction may even occur before the sperm encounters the zona, perhaps mediated by progesterone or some other agonist. It has been particularly difficult to understand differences between progesterone-induced and zona-induced reactions experimentally and whether one substance is the more biologically relevant trigger. Until this present work, there has been little effort to mathematically model the acrosome reaction in sperm as a whole. Instead, attention has been paid to modeling portions of the pathways involved in other cell types. Here we present a base model for the acrosome reaction which characterizes the known biochemical reactions and behaviors of the system. Our model allows us to analyze several pathways that may act as a stabilizing mechanism for avoiding sustained oscillatory calcium responses often observed in other cell types. Such an oscillatory regime might otherwise prevent acrosomal exocytosis and therefore inhibit fertilization. Results indicate that the acrosome reaction may rely upon multiple redundant mechanisms to avoid entering an oscillatory state and instead maintain a high resting level of calcium, known to be required for successful acrosomal exocytosis and, ultimately, fertilization of the oocyte.

Osmotic Compounds Enhance Antibiotic Efficacy against Acinetobacter baumannii Biofilm Communities.

Biofilm-associated infections are a clinical challenge, in part because a hydrated matrix protects the bacterial community from antibiotics. Herein, we evaluated how different osmotic compounds (maltodextrin, sucrose, and polyethylene glycol [PEG]) enhance antibiotic efficacy against Acinetobacter baumannii biofilm communities. Established (24-h) test tube biofilms (strain ATCC 17978) were treated with osmotic compounds in the presence or absence of 10× the MIC of different antibiotics (50 µg/ml tobramycin, 20 µg/ml ciprofloxacin, 300 µg/ml chloramphenicol, 30 µg/ml nalidixic acid, or 100 µg/ml erythromycin). Combining antibiotics with hypertonic concentrations of the osmotic compounds for 24 h reduced the number of biofilm bacteria by 5 to 7 log (P < 0.05). Increasing concentrations of osmotic compounds improved the effect, but there was a trade-off with increasing solution viscosity, whereby low-molecular-mass compounds (sucrose, 400-Da PEG) worked better than higher-mass compounds (maltodextrin, 3,350-Da PEG). Ten other A. baumannii strains were similarly treated with 400-Da PEG and tobramycin, resulting in a mean 2.7-log reduction in recoverable bacteria compared with tobramycin treatment alone. Multivariate regression models with data from different osmotic compounds and nine antibiotics demonstrated that the benefit from combining hypertonic treatments with antibiotics is a function of antibiotic mass and lipophilicity (r2 > 0.82; P < 0.002), and the relationship was generalizable for biofilms formed by A. baumannii and Escherichia coli K-12. Augmenting topical antibiotic therapies with a low-mass hypertonic treatment may enhance the efficacy of antibiotics against wound biofilms, particularly when using low-mass hydrophilic antibiotics.IMPORTANCE Biofilms form a barrier that protects bacteria from environmental insults, including exposure to antibiotics. We demonstrated that multiple osmotic compounds can enhance antibiotic efficacy against Acinetobacter baumannii biofilm communities, but viscosity is a limiting factor, and the most effective compounds have lower molecular mass. The synergism between osmotic compounds and antibiotics is also dependent on the hydrophobicity and mass of the antibiotics. The statistical models presented herein provide a basis for predicting the optimal combination of osmotic compounds and antibiotics against surface biofilms communities.

Carbon black nanoparticles induce biphasic gene expression changes associated with inflammatory responses in the lungs of C57BL/6 mice following a single intratracheal instillation.

Inhalation of carbon black nanoparticles (CBNPs) causes pulmonary inflammation; however, time course data to evaluate the detailed evolution of lung inflammatory responses are lacking. Here we establish a time-series of lung inflammatory response to CBNPs. Female C57BL/6 mice were intratracheally instilled with 162 µg CBNPs alongside vehicle controls. Lung tissues were examined 3h, and 1, 2, 3, 4, 5, 14, and 42 days (d) post-exposure. Global gene expression and pulmonary inflammation were assessed. DNA damage was evaluated in bronchoalveolar lavage (BAL) cells and lung tissue using the comet assay. Increased neutrophil influx was observed at all time-points. DNA strand breaks were increased in BAL cells 3h post-exposure, and in lung tissues 2-5d post-exposure. Approximately 2600 genes were differentially expressed (± 1.5 fold; p ≤ 0.05) across all time-points in the lungs of exposed mice. Altered transcript levels were associated with immune-inflammatory response and acute phase response pathways, consistent with the BAL profiles and expression changes found in common respiratory infectious diseases. Genes involved in DNA repair, apoptosis, cell cycle regulation, and muscle contraction were also differentially expressed. Gene expression changes associated with inflammatory response followed a biphasic pattern, with initial changes at 3h post-exposure declining to base-levels by 3d, increasing again at 14 d, and then persisting to 42 d post-exposure. Thus, this single CBNP exposure that was equivalent to nine 8-h working days at the current Danish occupational exposure limit induced biphasic inflammatory response in gene expression that lasted until 42 d post-exposure, raising concern over the chronic effects of CBNP exposure.

Biphasic response of a tecto-mesencephalic pilocytic astrocytoma after Gamma Knife surgery--A case report.

Biphasic response (shrinkage-regrowth-shrinkage) of tumors has never previously been reported in the postoperative course, neither after microsurgery, nor after Gamma Knife surgery (GKS). We present the case of an adult with dorsal midbrain syndrome resulting from a pilocytic astrocytoma centered on the mesencephalic tectum. The tumor extended to the third ventricle and the thalamus. Initially, due to tumor growth, a biopsy was performed and histology established. Later, a ventriculocisternostomy for obstructive hydrocephalus was performed. Finally, GKS was performed, as the tumor continued to grow. After GKS, the lesion exhibited a biphasic response, with a major shrinkage at 3 months, regrowth within the target volume at 6 and 9 months and a second phase of important shrinkage at 12 months, which persisted for the next two years. The possible mechanisms for this particular response pattern are discussed.

Role of mast cell in the late phase of contact hypersensitivity induced by trimellitic anhydride.

Mast cells are known as effector cells of IgE-mediated allergic responses, but role of mast cells in contact hypersensitivity (CHS) has been considered controversial. In this study, we investigated role of mast cell in trimellitic anhydride (TMA)-induced CHS. The mice were sensitized to TMA on the back and repeatedly challenged with TMA on the left ear at 1-week intervals. The ear after challenge showed biphasic responses. The repetition of TMA challenge shifted in time course of ear response and enlarged the extent of early and late phase reactions in proportion to the frequency of TMA challenges in C57BL/6 mice. In late phase reaction, peak of ear response by single challenge showed at 24 hours after challenge, but the peak by repeat challenges at 8 hours after the last challenge. Number of mast cells and eosinophils per unit area increased in proportion to frequency of TMA challenges. However, mast cell-deficient WBB6F1/J-Kit(W)/Kit(W-v) mice developed the late phase reaction without the early phase reaction. The repetition of TMA challenge shifted in time course of ear response and enlarged the extent of ear response and the infiltration of eosinophils. The magnitude of these responses observed according to the frequency of the TMA challenge in mast cell-deficient WBB6F1/J-Kit(W)/Kit(W-v) mice was significantly lower than that in C57BL/6 mice. Also TMA elicited mast cell degranulation and histamine release from rat peritoneal mast cells in a concentration-dependent manner. Conclusively, TMA induces the early and late phase reactions in CHS, and mast cells may be required for TMA-induced CHS.

Role of mast cell in the late phase of contact hypersensitivity induced by trimellitic anhydride / 대한해부학회지

Mast cells are known as effector cells of IgE-mediated allergic responses, but role of mast cells in contact hypersensitivity (CHS) has been considered controversial. In this study, we investigated role of mast cell in trimellitic anhydride (TMA)-induced CHS. The mice were sensitized to TMA on the back and repeatedly challenged with TMA on the left ear at 1-week intervals. The ear after challenge showed biphasic responses. The repetition of TMA challenge shifted in time course of ear response and enlarged the extent of early and late phase reactions in proportion to the frequency of TMA challenges in C57BL/6 mice. In late phase reaction, peak of ear response by single challenge showed at 24 hours after challenge, but the peak by repeat challenges at 8 hours after the last challenge. Number of mast cells and eosinophils per unit area increased in proportion to frequency of TMA challenges. However, mast cell-deficient WBB6F1/J-Kit(W)/Kit(W-v) mice developed the late phase reaction without the early phase reaction. The repetition of TMA challenge shifted in time course of ear response and enlarged the extent of ear response and the infiltration of eosinophils. The magnitude of these responses observed according to the frequency of the TMA challenge in mast cell-deficient WBB6F1/J-Kit(W)/Kit(W-v) mice was significantly lower than that in C57BL/6 mice. Also TMA elicited mast cell degranulation and histamine release from rat peritoneal mast cells in a concentration-dependent manner. Conclusively, TMA induces the early and late phase reactions in CHS, and mast cells may be required for TMA-induced CHS.

The hidden switches underlying RORα-mediated circuits that critically regulate uncontrolled cell proliferation.

Prostaglandin E2 (PGE2) is known to have a key role in the development of colorectal cancer, but previous experiments showed its contrasting (i.e. tumor-promoting or tumor-suppressive) roles depending on experimental conditions. To elucidate the mechanisms underlying such contrasting roles of PGE2 in tumorigenesis, we investigated all the previous experiments and found a new signal transduction pathway mediated by retinoic acid receptor-related orphan receptor (ROR)α, in which PGE2/PKCα-dependent phosphorylation of RORα attenuates Wnt target gene expression in colon cancer cells. From mathematical simulations combined with biochemical experimentation, we revealed that RORα induces a biphasic response of Wnt target genes to PGE2 stimulation through a regulatory switch formed by an incoherent feedforward loop, which provides a mechanistic explanation on the contrasting roles of PGE2 observed in previous experiments. More interestingly, we found that RORα constitutes another regulatory switch formed by coupled positive and negative feedback loops, which regulates the hysteretic response of Wnt signaling and eventually converts a proliferative cellular state into an anti-proliferative state in a very delicate way. Our results indicate that RORα is the key regulator at the center of these hidden switches that critically regulate cancer cell proliferation and thereby being a promising anti-cancer therapeutic target.

Regulatory-Science: Biphasic Cancer Models or the LNT-Not Just a Matter of Biology!

There is no doubt that prudence and risk aversion must guide public decisions when the associated adverse outcomes are either serious or irreversible. With any carcinogen, the levels of risk and needed protection before and after an event occurs, are determined by dose-response models. Regulatory law should not crowd out the actual beneficial effects from low dose exposures-when demonstrable-that are inevitably lost when it adopts the linear non-threshold (LNT) as its causal model. Because regulating exposures requires planning and developing protective measures for future acute and chronic exposures, public management decisions should be based on minimizing costs and harmful exposures. We address the direct and indirect effects of causation when the danger consists of exposure to very low levels of carcinogens and toxicants. The societal consequences of a policy can be deleterious when that policy is based on a risk assumed by the LNT, in cases where low exposures are actually beneficial. Our work develops the science and the law of causal risk modeling: both are interwoven. We suggest how their relevant characteristics differ, but do not attempt to keep them separated; as we demonstrate, this union, however unsatisfactory, cannot be severed.