title: NADPH oxidase-derived superoxide impairs calcium transients and contraction in aged murine ventricular myocytes.
abstract: Since aging increases oxidative stress, we analyzed the contribution of reactive oxygen species (ROS) to the contractile dysfunction of aged ventricular myocytes and investigated whether short-term interference with ROS formation could normalize contractile performance. Isolated ventricular myocytes from young (2-4 months) and aged (24-26 months) male mice (C57BL/6) were used. We analyzed sarcomere shortening and calcium transients (Indo-1 fluorescence) of voltage clamped ventricular myocytes and myofilament ATPase activity (malachite green assay). Expression of calcium handling proteins (Western blots) and NADPH oxidase subunits (real-time PCR) was quantified, as well as NADPH oxidase activity (lucigenin chemiluminescence). We found that aged myocytes showed decelerated shortening/relengthening without changes in fractional shortening. Calcium transient decay was similarly decelerated, but the amplitude of calcium transients was increased with aging. Calcium sensitivity of myofilaments of aged myocytes was reduced. These age-dependent changes occurred without altered calcium handling protein expression but were reversed by the superoxide scavenger tiron. Aged myocytes showed increased NADPH oxidase expression and activity. Pharmacological inhibition of NADPH oxidase (diphenylene iodonium; apocynin) normalized age-dependent deceleration of shortening/relengthening. In summary, we show that increased superoxide formation by upregulated NADPH oxidase contributes significantly to age-dependent alterations in calcium handling and contractility of murine ventricular myocytes.
authors.affiliation: Julius Bernstein Institute of Physiology, Martin Luther University Halle, Germany. uwe.rueckschloss@medizin.uni-halle.de
authors.forename: Uwe
authors.initials: U
authors.lastname: Rueckschloss
authors.forename: Marten
authors.initials: M
authors.lastname: Villmow
authors.forename: Udo
authors.initials: U
authors.lastname: Klöckner
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D000818:Animals; D020013:Calcium Signaling / Q000502:physiology*; D016922:Cellular Senescence / Q000502:physiology*; D006352:Heart Ventricles / Q000166:cytology; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D009200:Myocardial Contraction / Q000502:physiology; D009206:Myocardium / Q000166:cytology*; D032383:Myocytes, Cardiac / Q000166:cytology / Q000378:metabolism*; D000074662:NADPH Oxidase 2; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases / Q000378:metabolism*; D012518:Sarcomeres / Q000378:metabolism; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism*
chemical_list: D008562:Membrane Glycoproteins; D013481:Superoxides; C488842:Cybb protein, mouse; D000074662:NADPH Oxidase 2; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases; C422943:Nox4 protein, mouse; C060505:neutrophil cytosolic factor 1; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases