title: Ecotoxicological assessment of cobalt using Hydra model: ROS, oxidative stress, DNA damage, cell cycle arrest, and apoptosis as mechanisms of toxicity.
abstract: The mechanisms underlying cobalt toxicity in aquatic species in general and cnidarians in particular remain poorly understood. Herein we investigated cobalt toxicity in a Hydra model from morphological, histological, developmental, and molecular biological perspectives. Hydra, exposed to cobalt (0-60 mg/L), were altered in morphology, histology, and regeneration. Exposure to standardized sublethal doses of cobalt impaired feeding by affecting nematocytes, which in turn affected reproduction. At the cellular level, excessive ROS generation, as the principal mechanism of action, primarily occurred in the lysosomes, which was accompanied by the upregulation of expression of the antioxidant genes SOD, GST, GPx, and G6PD. The number of Hsp70 and FoxO transcripts also increased. Interestingly, the upregulations were higher in the 24-h than in the 48-h time-point group, indicating that ROS overwhelmed the cellular defense mechanisms at the latter time-point. Comet assay revealed DNA damage. Cell cycle analysis indicated the induction of apoptosis accompanied or not by cell cycle arrest. Immunoblot analyses revealed that cobalt treatment triggered mitochondria-mediated apoptosis as inferred from the modulation of the key proteins Bax, Bcl-2, and caspase-3. From this data, we suggest the use of Hydra as a model organism for the risk assessment of heavy metal pollution in aquatic ecosystems.
authors.affiliation: Mahatma Gandhi-Doerenkamp Center, Bharathidasan University, Tiruchirappalli 620024, India; Dept. of Environmental Biotechnology, Bharathidasan University, Tiruchirappalli 620024, India.
authors.forename: Mohammed
authors.initials: M
authors.lastname: Zeeshan
authors.affiliation: Mahatma Gandhi-Doerenkamp Center, Bharathidasan University, Tiruchirappalli 620024, India; Dept. of Environmental Biotechnology, Bharathidasan University, Tiruchirappalli 620024, India.
authors.forename: Anbazhagan
authors.initials: A
authors.lastname: Murugadas
authors.affiliation: Developmental Biology Group, MACS-Agharkar Research Institute, Pune 411004, India.
authors.forename: Surendra
authors.initials: S
authors.lastname: Ghaskadbi
authors.affiliation: Dept. of Environmental Biotechnology, Bharathidasan University, Tiruchirappalli 620024, India.
authors.forename: Babu Rajendran
authors.initials: BR
authors.lastname: Ramaswamy
authors.affiliation: Mahatma Gandhi-Doerenkamp Center, Bharathidasan University, Tiruchirappalli 620024, India; Department of Food Science and Nutrition, College of Food and Agriculture, King Saud University, Riyadh, Saudi Arabia. Electronic address: mgdcaua@yahoo.in.
authors.forename: Mohammad Abdulkader
authors.initials: MA
authors.lastname: Akbarsha
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3 / Q000378:metabolism; D059447:Cell Cycle Checkpoints / Q000187:drug effects*; D003035:Cobalt / Q000633:toxicity*; D020552:Comet Assay; D004249:DNA Damage / Q000187:drug effects*; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D006829:Hydra / Q000187:drug effects*; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism; D019216:Metals, Heavy / Q000633:toxicity; D008928:Mitochondria; D018384:Oxidative Stress; D017382:Reactive Oxygen Species / Q000378:metabolism*
chemical_list: D000975:Antioxidants; D018840:HSP70 Heat-Shock Proteins; D019216:Metals, Heavy; D017382:Reactive Oxygen Species; D003035:Cobalt; D053148:Caspase 3
keywords: Apoptosis; Cobalt; Developmental toxicity; Histology; Hydra; Oxidative stress