Search

Impaired mitochondria cause an impressive decrease in ATP production becoming a common condition of cardiovascular diseases. Myxomatous mitral valve disease (MMVD) is characterized by mitochondrial dysfunction. By a non-invasive procedure of metabolism analysis on peripheral blood mononuclear cells, we exploit ex-vivo studies that directly constitute a translational approach to evaluate the cell bioenergetics. Cell ATP production decreased in the presence of MMVD, whereas glycolysis was unaffected. In MMVD, the mitochondrial activity underwent a significant reduction of basal respiration, maximal respiration, and ATP production. Our results depicted a pathological condition of MMVD characterized by cell metabolism deprived of mitochondrial energy support., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Salvatore Nesci reports financial support was provided by University of Bologna. Chiara Bernardini reports financial support was provided by University of Bologna. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The foetal bovine serum (FBS) concentration could influence functional parameters of IPEC-J2 cells. IPEC-J2 is a non-transformed continuous epithelial cell line that represents an established in vitro model to study porcine gut inflammation and alterations of intestinal integrity. This cell line also represents a good translational model thanks to the high similitudes between pig and human gastrointestinal tract. With the aim to assess if the FBS-dependent functional variations are linked to the bioenergetic aspects, the addition of 5% and 10% FBS in the IPEC-J2 culture medium were tested. Doubling time and TEER measurement indicated that cells cultured at higher FBS dose grow faster and as a more compact monolayer. 10% FBS increases ATP production and mitochondrial oxidative phosphorylation (OxPhos) and does not affect glycolysis. Both at 5% and 10% FBS ATP production mainly comes from OxPhos and FBS concentration does not affect the cell respiration bioenergetic parameters. Noteworthy, IPEC-J2 treated with 5% and 10% FBS have a metabolic potential since both OxPhos and glycolysis increase by > 100% and < 50%, respectively in comparison with baseline metabolism. Moreover, glucose, fatty acids and glutamine constitute the preferred metabolic fuel for mitochondrial respiration at both FBS conditions tested. Accordingly, the cells flexibility to oxidize these substrates shows that IPEC-J2 mitochondria cannot maintain the basal ATP production without oxidizing all the substrates available irrespective of FBS concentration. To sum up, in IPEC-J2 cells OxPhos increases with the FBS-stimulated functional physiological parameters to fulfil ATP requirements., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Of the two main sectors of the F-type ATP synthase, the membrane-intrinsic F O domain is the one which, during evolution, has undergone the highest structural variations and changes in subunit composition. The F O complexity in mitochondria is apparently related to additional enzyme functions that lack in bacterial and thylakoid complexes. Indeed, the F-type ATP synthase has the main bioenergetic role to synthesize ATP by exploiting the electrochemical gradient built by respiratory complexes. The F O membrane domain, essential in the enzyme machinery, also participates in the bioenergetic cost of synthesizing ATP and in the formation of the cristae , thus contributing to mitochondrial morphology. The recent enzyme involvement in a high-conductance channel, which forms in the inner mitochondrial membrane and promotes the mitochondrial permeability transition, highlights a new F-type ATP synthase role. Point mutations which cause amino acid substitutions in F O subunits produce mitochondrial dysfunctions and lead to severe pathologies. The F O variability in different species, pointed out by cryo-EM analysis, mirrors the multiple enzyme functions and opens a new scenario in mitochondrial biology.

The properties of the mitochondrial F 1 F O -ATPase catalytic site, which can bind Mg 2+ , Mn 2+ , or Ca 2+ and hydrolyze ATP, were explored by inhibition kinetic analyses to cast light on the Ca 2+ -activated F 1 F O -ATPase connection with the permeability transition pore (PTP) that initiates cascade events leading to cell death. While the natural cofactor Mg 2+ activates the F 1 F O -ATPase in competition with Mn 2+ , Ca 2+ is a noncompetitive inhibitor in the presence of Mg 2+ . Selective F 1 inhibitors (Is-F 1 ), namely NBD-Cl, piceatannol, resveratrol, and quercetin, exerted different mechanisms (mixed and uncompetitive inhibition) on either Ca 2+ - or Mg 2+ -activated F 1 F O -ATPase, consistent with the conclusion that the catalytic mechanism changes when Mg 2+ is replaced by Ca 2+ . In a partially purified F 1 domain preparation, Ca 2+ -activated F 1 -ATPase maintained Is-F 1 sensitivity, and enzyme inhibition was accompanied by the maintenance of the mitochondrial calcium retention capacity and membrane potential. The data strengthen the structural relationship between Ca 2+ -activated F 1 F O -ATPase and the PTP, and, in turn, on consequences, such as physiopathological cellular changes., (© 2019 New York Academy of Sciences.)