On an extended understanding of the term "hormesis" for denoting alternating directions of the organism's response to increasing adverse exposures

Effective Doses of Low-Dose Naltrexone for Chronic Pain - An Observational Study

Purpose

Despite the availability of a wide variety of analgesics, many patients with chronic pain often experience suboptimal pain relief in part related to the absence of any medication to address the nociplastic component of common pain syndromes. Low-dose naltrexone has been used for the treatment of chronic pain, typically at 4.5 mg per day, even though it is also noted that effective doses of naltrexone for chronic pain presentations range from 0.1 to 4.5 mg per day. We performed an observational analysis to determine the range of effective naltrexone daily dosing in 41 patients with chronic musculoskeletal pain.

Methods

Charts of 385 patients, 115 males, 270 females, ages 18-92, were reviewed. Two hundred and sixty patients with chronic diffuse, symmetrical pain were prescribed a titrating dose of naltrexone to determine a maximally effective dose established by self-report of 1) reduction of diffuse/generalized and/or severity level of pain and/or 2) positive effects on mood, energy, and mental clarity. Brief Pain Inventory and PROMIS scales were given pre- and post-determining a maximally effective naltrexone dose.

Results

Forty-one patients met all criteria for inclusion, successfully attained a maximally effective dose, and completed a pre- and post-outcome questionnaire. Hormesis was demonstrated during the determination of the maximally effective dosing, which varied over a wide range, with statistically significant improvement in BPI.

Conclusion

The maximally effective dose of low-dose naltrexone for the treatment of chronic pain is idiosyncratic, suggesting the need for 1) dosage titration to establish a maximally effective dose and 2) the possibility of re-introduction of low-dose naltrexone to patients who had failed initial trials on a fixed dose of naltrexone.

Evaluation of Rare Earth Element-Associated Hormetic Effects in Candidate Fertilizers and Livestock Feed Additives

Rare earth elements (REEs) are recognized as emerging contaminants with implications in human and environmental health. Apart from their adverse effects, REEs have been reported as having positive effects when amended to fertilizers and livestock feed additives, thus suggesting a hormetic trend, implying a concentration-related shift from stimulation to inhibition and toxicity, with analogous trends that have been assessed for a number of xenobiotics. In view of optimizing the success of REE mixtures in stimulating crop yield and/or livestock growth or egg production, one should foresee the comparative concentration-related effects of individual REEs (e.g., Ce and La) vs. their mixtures, which may display distinct trends. The results might prompt further explorations on the use of REE mixtures vs. single REEs aimed at optimizing the preparation of fertilizers and feed additives, in view of the potential recognition of their use in agronomy and zootechny.

Hormetic Effects of Cerium, Lanthanum and Their Combination at Sub-micromolar Concentrations in Sea Urchin Sperm

Rare earth elements (REEs) cerium (Ce) and lanthanum (La) and their combination were tested across a concentration range, from toxic (10^-4 to 10^-5 M) to lower concentrations (10^-6 to 10^-8 M) for their effects on sea urchin (Sphaerechinus granularis) sperm. A significantly decreased fertilization rate (FR) was found for sperm exposed to 10^-5 M Ce, La and their combination, opposed to a significant increase of FR following 10^-7 and 10^-8 M REE sperm exposure. The offspring of REE-exposed sperm showed significantly increased developmental defects following sperm exposure to 10^-5 M REEs vs. untreated controls, while exposure to 10^-7 and 10^-8 M REEs resulted in significantly decreased rates of developmental defects. Both of observed effects-on sperm fertilization success and on offspring quality-were closely exerted by Ce or La or their combination.

Dose Dependence of the Separate and Combined Impact of Copper-Oxide and Selenium-Oxide Nanoparticles on Oxygen Consumption by Cells In Vitro With or Without the Background Action of Some Modulators of the Mitochondrial Respiratory Function

We had previously demonstrated on various stable cell cultures exposed to chemically different nanoparticles when assessing their cytotoxicity by different outcomes, dose-response relationships may be either monotonic or non-monotonic falling within an extended understanding of the hormesis paradigm. Presently, on human fibroblasts exposed to the copper-oxide and/or selenium-oxide nanoparticles, we assessed their cytotoxic effect by the inhibition of oxygen uptake against modulating the respiratory function of mitochondria (oligomycin, followed by carbonyl cyanide-4-(trifluoromethoxy) phenylhydrazone, and, finally, rotenone with antimycin A). It is hypothesized that a given type of this relationship is closely associated with the mitochondrial respiratory function. However, in only one case, this hypothesis was confirmed by finding that the monotonic dose-response relationship transformed into a non-monotonic one of the hormesis type under exposure to SeO-NP with the mitochondrial respiratory function fully inhibited by the effect of rotenone + antimycin А. In all other variants of the experiment, the shape of this relationship did not depend on the addition of the above agents to the cell culture. Neither did the effect of these modulators change the pattern of combined action of CuO-NP and SeO-NP, which was additive in all cases.

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.

Atmospheric Pb induced hormesis in the accumulator plant Tillandsia usneoides

While numerous studies reported hormesis in plants exposed to heavy metals, metals were commonly added in the growth substrate (e.g. soil or solution). The potential of heavy metals in the atmosphere to induce hormesis in plants, however, remains unknown. In this study, we exposed the widely-used accumulator plant Tillandsia usneoides to 10 atmospheric Pb concentrations (0-25.6 μg·m^-3) for 6 or 12 h. Three types of dose-response relationships between different response endpoints (biomarkers) and Pb concentrations were found for T. usneoides. The first was a monophasic dose response, in which the response increased linearly with increasing Pb concentrations, as seen for metallothionein (MT) content after a 6-h exposure. The second and dominating type was a biphasic-hormetic dose response, exhibited by malondialdehyde (MDA), superoxide anion radical (O₂^-), and superoxide dismutase (SOD) after 6 or 12 h of exposure and by glutathione (GSH) and MT content after 12 h of treatment. The third type was a triphasic dose response, as seen for leaf electric conductivity after 6 or 12 h of exposure and GSH after 6 h of exposure. This finding suggests that Pb inhibited the response of T. usneoides at very low concentrations, stimulated it at low-to-moderate concentrations, and inhibited it at higher concentrations. Our results demonstrate diverse adaptation mechanisms of plants to stress, in the framework of which alternating between up- and down-regulation of biomarkers is at play when responding to different levels of toxicants. The emergence of the triphasic dose response will further enhance the understanding of time-dependent hormesis.

New Data on Variously Directed Dose-Response Relationships and the Combined Action Types for Different Outcomes of in Vitro Nanoparticle Cytotoxicity

Spherical selenium-oxide and copper-oxide nanoparticles (SeO-NP with mean diameter 51 ± 14 nm and CuO-NP with mean diameter 21 ± 4 nm) were found to be cytotoxic for human fibroblast-like cells in vitro, as judged by decreased ATP-dependent luminescence. Compared with SeO-NP, CuO-NP produced a somewhat stronger effect of this kind. Along with cell hypertrophy developing in response to certain doses of SeO-NP and CuO-NP, our experiment also revealed doses causing a decrease in cell and cell-nucleus sizes. We observed both monotonic and different variants of nonmonotonic dose-response relationship. For the latter, we have succeeded in constructing adequate mathematical expressions based on the generalized hormesis paradigm that we had considered previously in respect of CdS-NP and PbS-NP cytotoxicity for cardiomyocites. It was demonstrated as well that combined toxicity of SeO-NP and CuO-NP is of different types depending on the outcome.