Effects of Propranolol on Growth, Lipids and Energy Metabolism and Oxidative Stress Response of Phaeodactylum tricornutum

Abstract

Present demographic trends suggest a rise in the contributions of human pharmaceuticals into coastal ecosystems, underpinning an increasing demand to evaluate the ecotoxicological effects and implications of drug residues in marine risk assessments. Propranolol, a non-selective β-adrenoceptor blocker, is used worldwide to treat high blood pressure conditions and other related cardiovascular conditions. Although diatoms lack β-adrenoceptors, this microalgal group presents receptor-like kinases and proteins with a functional analogy to the animal receptors and that can be targeted by propranolol. In the present work, the authors evaluated the effect of this non-selective β-adrenoceptor blocker in diatom cells using P. tricornutum as a model organism, to evaluate the potential effect of this compound in cell physiology (growth, lipids and energy metabolism and oxidative stress) and its potential relevance for marine ecosystems. Propranolol exposure leads to a significant reduction in diatom cell growth, more evident in the highest concentrations tested. This is likely due to the observed impairment of the main primary photochemistry processes and the enhancement of the mitochondrial respiratory activity. More specifically, propranolol decreased the energy transduction from photosystem II (PSII) to the electron transport chain, leading to an increase in oxidative stress levels. Cells exposed to propranolol also exhibited high-dissipated energy flux, indicating that this excessive energy is efficiently diverted, to some extent, from the photosystems, acting to prevent irreversible photoinhibition. As energy production is impaired at the PSII donor side, preventing energy production through the electron transport chain, diatoms appear to be consuming storage lipids as an energy backup system, to maintain essential cellular functions. This consumption will be attained by an increase in respiratory activity. Considering the primary oxygen production and consumption pathways, propranolol showed a significant reduction of the autotrophic O2 production and an increase in the heterotrophic mitochondrial respiration. Both mechanisms can have negative effects on marine trophic webs, due to a decrease in the energetic input from marine primary producers and a simultaneous oxygen production decrease for heterotrophic species. In ecotoxicological terms, bio-optical and fatty acid data appear as highly efficient tools for ecotoxicity assessment, with an overall high degree of classification when these traits are used to build a toxicological profile, instead of individually assessed.

Ecoengineering Solutions for the Impairment of Spreading and Growth of Invasive Spartina patens in Mediterranean Salt Marshes

“…Using multivariate analysis of the assessed biophysical and biochemical traits it was possible to observe that techniques, such as PAM and infrared thermography, are the most efficient tools to evaluate in situ the success of the intervention and the stress levels imposed on the plants targeted to be removed. As in previous ecological studies in response to stress (Cruz de Carvalho et al, 2020a,b;Duarte et al, 2020), the use of bio-optical techniques (e.g., Kautsky plot) allowed an efficient identification of the waterlogged plants and, thus, provide efficient and reliable tools to monitor the success of control interventions, without disturbing the process itself and allowing repeated measures over the intervention period.…”

Artificial Intelligence Meets Marine Ecotoxicology: Applying Deep Learning to Bio-Optical Data from Marine Diatoms Exposed to Legacy and Emerging Contaminants

“…In the present work, the authors aim to study the applicability of the obtained fluorescence data in automatic machine-learning-based systems, for ecotoxicological classification of marine diatoms-based exposure trials, and, thus, the physiological responses of the cells will not be discussed in the present work, as this is out of the scope of the present work. The physiological effects of each contaminant are discussed elsewhere [6][7][8]16,23,24]. Nevertheless, and in order to better understand the magnitude of the ecotoxicological effects observed in the cultures, relative growth inhibition and half-maximal inhibitory concentrations were also determined as proxy measures of the toxicity effects observed in the cultures, that are unequivocally connected with the photochemical results (Table 2).…”

“…Table 1 contains some details regarding this dataset, including the identification of the contaminants and different concentrations used, and the distribution of samples between contaminants and concentrations. Further details on the techniques and protocols used for obtaining the data can be found in [6][7][8]16,24]. Cell density was evaluated in all experimental reactors at the end of the exposure trials and the percentage of growth inhibition towards the respective control condition was calculated, as well as the half-maximal inhibitory concentration (IC50), according to the OECD (2011) guidelines.…”

“…These facts are the cornerstone of the pioneering research field of toxicophenomics, which merges plant phenomics, measuring traits, such as plant growth and performance using non-invasive technologies, with ecotoxicology, shifting the use of these phenotyping tools to address contaminant induced stress in autotrophs. Optical techniques to disclose different groups of samples exposed to different degrees of contamination has been applied in marine phototrophs with a high degree of efficiency, in both ecotoxicological trials and under field conditions [6,8,16], and using communities as meta-organisms instead of single species [17]. The application of these bio-optical technologies produces large data packages with physiological interest, regarding the effects of a given compound in an autotrophic organism, and also with a high volume of data points that can be used by machine learning techniques, to produce classifiers of the toxicity degree to which organisms are exposed [18].…”

Evaluation of Multivariate Biomarker Indexes Application in Ecotoxicity Tests with Marine Diatoms Exposed to Emerging Contaminants

“…In the present work, the suitability of the three different multivariate indexes (BAI, IBR, and PCA-based indexes) was tested through application of previously obtained oxidative stress biomarker data, using marine diatoms as a study model. The impacts of pharmaceuticals (propranolol [22], fluoxetine [23], ibuprofen [24], detergents (SDS) [25], and herbicides (glyphosate [15])) on primary production and physiological fitness of the marine diatom Phaeodactylum tricornutum were used to understand the suitability of multivariate indexes in depicting dose responses and contaminant types, as well as to evaluate the performance and accuracy of each approach for future ecotoxicological trials. In sum, we intended to produce an index that allows to better communicate toxicity results, providing an easy-to-understand framework, which is accessible to managers and the general public.…”