title: Modulation of cadmium-induced mitochondrial dysfunction and volume changes by temperature in rainbow trout (Oncorhynchus mykiss).
abstract: We investigated how temperature modulates cadmium (Cd)-induced mitochondrial bioenergetic disturbances, metal accumulation and volume changes in rainbow trout (Oncorhynchus mykiss). In the first set of experiments, rainbow trout liver mitochondrial function and Cd content were measured in the presence of complex I substrates, malate and glutamate, following exposure to Cd (0-100 μM) at three (5, 13 and 25 °C) temperatures. The second set of experiments assessed the effect of temperature on Cd-induced mitochondrial volume changes, including the underlying mechanisms, at 15 and 25 °C. Although temperature stimulated both state 3 and 4 rates of respiration, the coupling efficiency was reduced at temperature extremes due to greater inhibition of state 3 at low temperature and greater stimulation of state 4 at the high temperature. Cadmium exposure reduced the stimulatory effect of temperature on state 3 respiration but increased that on state 4, consequently exacerbating mitochondrial uncoupling. The interaction of Cd and temperature yielded different responses on thermal sensitivity of state 3 and 4 respiration; the Q10 values for state 3 respiration increased at low temperature (5-13 °C) while those for state 4 increased at high temperature (13-25 °C). Importantly, the mitochondria accumulated more Cd at high temperature suggesting that the observed greater impairment of oxidative phosphorylation with temperature was due, at least in part, to a higher metal burden. Cadmium-induced mitochondrial volume changes were characterized by an early phase of contraction followed by swelling, with temperature changing the kinetics and intensifying the effects. Lastly, using specific modulators of mitochondrial ion channels, we demonstrated that the mitochondrial volume changes were associated with Cd uptake via the mitochondrial calcium uniporter (MCU) without significant contribution of the permeability transition pore and/or potassium channels. Overall, it appears that high temperature exacerbates Cd-induced mitochondrial dysfunction and volume changes in part by increasing metal uptake through the MCU.
authors.affiliation: Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE, Canada C1A 4P3.
authors.forename: John O
authors.initials: JO
authors.lastname: Onukwufor
authors.affiliation: Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE, Canada C1A 4P3.
authors.forename: Fred
authors.initials: F
authors.lastname: Kibenge
authors.affiliation: Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE, Canada C1A 4P3.
authors.forename: Don
authors.initials: D
authors.lastname: Stevens
authors.affiliation: Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE, Canada C1A 4P3. Electronic address: ckamunde@upei.ca.
authors.forename: Collins
authors.initials: C
authors.lastname: Kamunde
mesh_terms: D000818:Animals; D002104:Cadmium / Q000032:analysis / Q000633:toxicity*; D015220:Calcium Channels / Q000378:metabolism; D019069:Cell Respiration / Q000187:drug effects; D004734:Energy Metabolism / Q000187:drug effects; D008099:Liver / Q000737:chemistry / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects*; D017686:Oncorhynchus mykiss / Q000502:physiology*; D013696:Temperature; D014874:Water Pollutants, Chemical / Q000633:toxicity
chemical_list: D015220:Calcium Channels; D014874:Water Pollutants, Chemical; C034703:mitochondrial calcium uniporter; D002104:Cadmium
keywords: Cadmium; Interactions; Mitochondrial bioenergetics; Mitochondrial volume; Rainbow trout; Temperature