Morphological and Functional Alterations Induced by Two Ecologically Relevant Concentrations of Lead on Danio rerio Gills

Abstract

Lead (Pb), due to its high toxicity and bioaccumulation tendency, is one of the top three pollutants of concern for both humans and wildlife and occupies second place in the Priority List of Hazardous Substances. In freshwater fish, Pb is mainly absorbed through the gills, where the greatest accumulation occurs. Despite the crucial role of gills in several physiological functions such as gas exchange, water balance, and osmoregulation, no studies evaluated the effects of environmentally relevant concentrations of Pb on this organ, and existing literature only refers to high levels of exposure. Herein we investigated for the first time the molecular and morphological effects induced by two low and environmentally relevant concentrations of Pb (2.5 and 5 μg/L) on the gills of Danio rerio, a model species with a high translational value for human toxicity. It was demonstrated that Pb administration at even low doses induces osmoregulatory dysfunctions by affecting Na+/K+-ATPase and AQP3 expression. It was also shown that Pb upregulates MTs as a protective response to prevent cell damage. Modulation of SOD confirms that the production of reactive oxygen species is an important toxicity mechanism of Pb. Histological and morphometric analysis revealed conspicuous pathological changes, both dose- and time-dependent.

Morphological and Functional Alterations in Zebrafish (Danio rerio) Liver after Exposure to Two Ecologically Relevant Concentrations of Lead

“…The analytical verification of the actual concentrations was performed throughout the experiment (starting from time 0 every 24 h) (Table S1). No evident variation was recorded, and such a result is in agreement with the data from previous studies ( [25] and the references therein).…”

“…An increase in MT expression has been demonstrated in the liver of both marine and freshwater fish after dietary exposure to Pb, and in fish coming from Pb-contaminated areas [49,79]. Furthermore, our recent study reported an increase in the expression of mtf1 in zebrafish gills after Pb exposure [25]. Although MT induction has been demonstrated in several fish organs after exposure to heavy metals, the liver is one of the organs that first responds to the toxic input [79].…”

“…Fish assimilate Pb through direct ingestion (i.e., in food and water), ion exchange across lipophilic membranes (e.g., the gills), or adsorption across specific tissue and membrane surfaces [3]. In fish, numerous detrimental effects induced by Pb have been reported, including genotoxicity [16], oxidative stress induction [17][18][19][20], change in the activities of immune-related enzymes and genes [8,21,22], and histological changes in some tissues and organs [16,[23][24][25].…”

Environmentally relevant lead alters nuclear integrity in erythrocytes and generates oxidative stress in liver of Anabas testudineus: Involvement of Nrf2‐Keap1 regulation and expression of biomarker genes

“…Huang et al (2014) reported that Pb may be present in a high concentration in storm water runoff ranging from 75 to 926 ppm. According to Curcio et al (2022), Pb is present in water bodies within the range of 0.05 to 566.2 ppm. Hence the selected dose (43.3 ppm of Pb) used in the present study may be considered as environmentally relevant.…”

Regulation of PGC-1α of the Mitochondrial Energy Metabolism Pathway in the Gills of Indian Medaka (Oryzias dancena) under Hypothermal Stress

“…Being exposed directly to external environments, the gill is one of the primary organs for osmoregulation in fish and is sensitive to physical and chemical changes in aquatic environments such as temperature, acidification of water supplies, salts and heavy metals and water borne toxicants [14,15]. The gill has several functions, including gas exchange and osmoregulation [16,17]. It has been claimed that fish osmoregulation requires a substantial amount of metabolic energy [18,19].…”