Comparative intestinal esterases amongst passerine species: Assessing vulnerability to toxic chemicals in a phylogenetically explicit context

Sources of persistent organic pollutants and their physiological effects on opportunistic urban gulls

Urbanization is associated with drastic shifts in biodiversity. While some species thrive in urban areas, the impact of inhabiting these human-altered environments on organism physiology remains understudied. We investigated how exposure to polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) affects the physiology of yellow-legged gulls (Larus michahellis) inhabiting a densely populated, industrialized city. We analyzed blood samples from 50 gulls (20 immatures and 30 adults) and assessed 27 physiological parameters and biomarkers related to xenobiotic protection, health, and feeding habits in these same individuals. We also tracked the movements of 25 gulls (15 immatures and 10 adults) to identify potential sources of persistent organic pollutants (POPs). Both adult and immature gulls primarily inhabited urban areas, followed by marine habitats. Immature gulls spent more time in freshwater, landfills, and agricultural areas. Bioaccumulated ΣPCB (median = 92.7 ng g-1 ww, 1.86-592) and ΣPBDE (median = 1.44 ng g-1 ww, 0.022-9.58) showed no significant differences between age and sex groups. Notably, immature males exhibited the highest correlations with POP concentrations, particularly with the activity of carboxylesterases (CEs), suggesting a higher sensitivity than adults. These findings highlight the potential of plasmatic CEs in immature yellow-legged gulls as effective tracers of POPs exposure and effects, offering insights into the anthropogenic impacts on urban biodiversity.

Differences in plasmatic butyrylcholinesterases (BChE) values between Pacific and Caribbean populations of terciopelo (Bothrops asper) in Costa Rica

The terciopelo (Bothrops asper) inhabits human-modified environments such as agricultural areas, becoming more prone to be exposed to organophosphate insecticides. These chemicals can inhibit plasmatic butyrylcholinesterases (BChE) activity in B. asper. Caribbean and Pacific populations of B. asper belong to two divergent lineages that exhibit robust genetic partitioning; however, differences across versants in biochemistry and hematology have not yet been examined, especially in BChE variations. This study aims to evaluate the differences of BChE plasmatic values, hematology parameters, and some biochemical analytes as biomarkers in the presence of organophosphates between the Pacific and Caribbean population of B. asper in Costa Rica. A total of 89 snakes (41 Pacific and 48 Caribbean) were used, and hematology parameter, albumin, aspartate aminotransferase (AST), total protein and BChEs were evaluated. Differences in hemoglobin content, thrombocytes, white cell count, AST, and BChE values were found between both versants. Intrinsic genetic factors might influence the variation found in BChE and AST values in the snakes sampled from both versants; moreover, understanding this variation in BChE and AST values across the B. asper's distribution can be useful in future ecotoxicology, biomonitoring, genetic and other clinical/health studies.

Comparative study of esterase activities in different tissues of marine fish species Trachurus trachurus, Merluccius merluccius and Trisopterus luscus

Pesticides are one of the most frequently anthropogenic xenobiotics detected in water. Among these, the organophosphorus pesticides (OPs) are very widely used in agriculture due to their broad spectrum of activity and their low price, but they also have high potent effects as neurotoxic compounds in non-target organisms. The aim of this study was to evaluate biomarkers acetylcholinesterase (AChE), butyrylcholinesterase (BChE), propionylcholinesterase (PChE) and carboxylesterase (CbE) in the representative Atlantic fish species Trachurus trachurus, Merluccius merluccius and Trisopterus luscus from "Rías Gallegas", a traditional Spanish fishing area. These esterase activities were evaluated in the brain, muscle and liver to determine the most adequate tissue to measure such enzymatic activities. The sensitivity of AChE and CbE activities from different tissues the widely used organophosphorus insecticide chlorpyrifos (CP), and its toxic metabolite (CP-oxon) was also tested. AChE activity was predominant in all tissues of the analysed species (particularly in brain constituting from 78.33%, 89.83% and 88.43% of total ChEs in Trachurus trachurus, Merluccius merluccius and Trisopterus luscus, respectively). Under in vitro exposure, esterases were shown to be highly sensitive to CP and especially to CP-oxon. Moreover, a similar effect observed on AChE and CbE activities could suggest that CbE activity might contribute efficiently against the toxic effects of CP, especially in muscle and the liver. The presence of BChE, PChE and upper CbE activities in muscle and the liver and their OP-sensibilities can be used to study their function in the pesticide biochemical detoxification pathways with a prominent role as a safeguarding mechanism against pesticide toxicity.

Effect of exposition to chlorpyrifos upon plasmatic cholinesterases, hematology and blood biochemistry values in Bothrops asper (Serpentes: Viperidae)

The terciopelo (Bothrops asper), is one of the most important venomous snakes in Costa Rica and common on agriculture where insecticides are frequently used for pest control. To assess the exposure to organophosphates on captive B. asper, an experiment using chlorpyrifos and butyrylcholinesterase (BChE), as a biomarker was conducted. In addition to BChE, hematology, aspartate aminotransferase (AST), total proteins (TP) and albumin were measured after exposure. Different concentrations of chlorpyrifos were used in Group A (0.1%) and B (1%), while the Control Group received distilled water; each group was composed of 5 snakes. Values of BChE, AST, TP, and albumin were measured before exposure, and at 6, 12, 24, 196, 360 and 528 h post-exposure. Hematology values were measured after 24 h post-exposure. As result, an important variation between subjects in all groups before exposure was obtained. Moreover, BChE activity showed 37% inhibition of Group A when compared to Control Group at 12 h post-exposure, and a higher inhibition of Group B (97%) related to Control Group, at 6 h post-exposure. Recovery of BChE occurred towards 528 h, never reaching initial values. Despite some variation in the rest of parameters used, a marked relative lymphopenia and monocytosis occurred at 24 h, assuming stress as the main cause.

Reference intervals for B-esterases in gull, Larus michahellis (Nauman, 1840) from Northwest Spain: influence of age, gender, and tissue

Over the last years, cholinesterase (ChE) and carboxylesterase (CbE) activities have been increasingly used in environmental biomonitoring to detect the exposure to anticholinesterase insecticides such as organophosphorates (OPs) and carbamates (CBs). The aim of this study was to determine ChE and CbE enzymatic activities present in liver and muscle of yellow-legged gulls (Larus michahellis), a seabird species considered suitable to monitor environmental pollution. In order to provide reference data for further biomonitoring studies, the influence of different factors, such as gender, age, sampling mode, and tissue, was considered in the present study. Our data report a statistically significant difference in CbE enzymatic activity comparing liver and muscle samples (P < 0.05) along with an age-related CbE activity in liver samples (P < 0.05). Moreover, according to our results, capture method might influence CbE and ChE activity in both liver and muscle samples (P < 0.05). These findings underline the importance to assess basal levels of ChE and CbE activity considering, among other factors, gender-, age- and organ-related differences and confirm the suitability of Larus michahellis as a sentinel species especially within an urban environment.

Effect of diet on carboxylesterase activity of tadpoles (Rhinella arenarum) exposed to chlorpyrifos

An outdoor microcosm was performed with tadpoles (Rhinella arenarum) exposed to 125μgL^-1 chlorpyrifos and fed two types of food, i.e., lettuce (Lactuca sativa) and a formulated commercial pellet. Acetylcholinesterase (AChE) and carboxylesterase (CbE) activities were measured in liver and intestine after 10 days of pesticide exposure. Non-exposed tadpoles fed lettuce had an intestinal AChE activity almost two-fold higher than that of pellet-fed tadpoles. No significant differences were observed, however, in liver AChE activity between diets. Likewise, intestinal CbE activity - measured using two substrates, i.e. 1-naphthyl acetate (1-NA) and 4-nitrophenyl valerate (4-NPV) - was higher in tadpoles fed lettuce than in those fed pellets. However, the diet-dependent response of liver CbE activity was opposite to that in the intestine. Chlorpyrifos caused a significant inhibition of both esterase activities, which was tissue- and diet-specific. The highest inhibition degree was found in the intestinal AChE and CbE activities of lettuce-fed tadpoles (42-78% of controls) compared with pellet-fed tadpoles (<60%). Although chlorpyrifos significantly inhibited liver CbE activity of the group fed lettuce, this effect was not observed in the group fed pellets. In general, intestinal CbE activity was more sensitive to chlorpyrifos inhibition than AChE activity. This finding, together with the high levels of basal CbE activity found in the intestine, may be understood as a detoxification system able to reduce intestinal OP uptake. Moreover, the results of this study suggest that diet is a determinant factor in toxicity testing with tadpoles to assess OP toxicity, because it modulates levels of this potential detoxifying enzyme activity.