Photodynamic action of porphyrin on Ca2+ influx in endoplasmic reticulum: a comparison with mitochondria

The dynamic properties of protein and lipid regions of mitochondrial membranes during the permeability transition (PT) process were studied by following the anisotropy changes of hematoporphyrin (HP) and 1,6-diphenyl-1,3,5-hexatriene (DPH), respectively. We show that opening of the PT pore is accompanied by a remarkable increase of mitochondrial membrane fluidity which is specifically localized to protein sites, while lipid domains are unaffected. The increased membrane fluidity is not related to the collapse of transmembrane potential that follows the PT, as demonstrated by a comparison between the anisotropy properties of permeabilized mitochondria and impermeable, depolarized organelles. Parameters such as osmotic swelling and temperature, which are shown to affect the mitochondrial membrane dynamics in the absence of permeability transition, cannot alone account for the pore dynamical properties. We suggest that the observed increase in fluidity is mainly due to a conformational change of pore-forming protein(s) during the "assembly" of the PT pore.

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Tacrolimus and sirolimus decrease oxidative phosphorylation of isolated rat kidney mitochondria

Simon¹,

Morin

Urien

et al. 2003

British J Pharmacology

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1 Tacrolimus and sirolimus are potent immunosuppressors used in transplantation. Tacrolimus has been suspected to alter mitochondrial respiration of di erent tissues but sirolimus has not been evaluated. 2 We evaluated the in vitro e ect of tacrolimus and sirolimus on oxidative phosphorylation of isolated rat kidney mitochondria. 3 Oxygen consumption was measured with a Clark-type electrode. Tacrolimus and sirolimus increased the resting rate (state 4) and had no signi®cant e ect on ADP-stimulated respiration (state 3). The decrease of respiratory control ratio was concentration-dependent with a biphasic curve for tacrolimus. The EC 50 s were 3.4610 711 M and 2.3610 78 M for tacrolimus and 4.4610 710 M for sirolimus. The maximal inhibition was 20 and 14% for tacrolimus and sirolimus, respectively. 4 Tacrolimus and sirolimus had an uncoupling e ect on oxidative phosphorylation related to a decrease of the inner membrane¯uidity. At the opposite of cyclosporin A, no e ect on swelling or Ca 2+¯u xes was observed. 5 All events occurred at therapeutic concentrations and then could appear during long-term treatment. Cellular consequences such as chronic nephrotoxicity with tacrolimus are suggested. The risk of cyclosporin A nephrotoxicity potentiation by sirolimus is discussed.

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Photodynamic action of porphyrin on Ca2+ influx in endoplasmic reticulum: a comparison with mitochondria

Cited by 8 publications

References 37 publications

Са2+- and NF-κB-dependent generation of NO in the photosensitized neurons and satellite glial cells

Са2+- and NF-κB-dependent generation of NO in the photosensitized neurons and satellite glial cells

Changes of the Fluidity of Mitochondrial Membranes Induced by the Permeability Transition

Tacrolimus and sirolimus decrease oxidative phosphorylation of isolated rat kidney mitochondria

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