8 research outputs found
Increasing Tetrahydrobiopterin in Cardiomyocytes Adversely Affects Cardiac Redox State and Mitochondrial Function Independently of Changes in NO Production
Tetrahydrobiopterin (BH4) represents a potential strategy for the treatment of cardiac remodeling, fibrosis and/or diastolic dysfunction. The effects of oral treatment with BH4 (Sapropterin™ or Kuvan™) are however dose-limiting with high dose negating functional improvements. Cardiomyocyte-specific overexpression of GTP cyclohydrolase I (mGCH) increases BH4 several-fold in the heart. Using this model, we aimed to establish the cardiomyocyte-specific responses to high levels of BH4. Quantification of BH4 and BH2 in mGCH transgenic hearts showed age-based variations in BH4:BH2 ratios. Hearts of mice (\u3c6 \u3emonths) have lower BH4:BH2 ratios than hearts of older mice while both GTPCH activity and tissue ascorbate levels were higher in hearts of young than older mice. No evident changes in nitric oxide (NO) production assessed by nitrite and endogenous iron–nitrosyl complexes were detected in any of the age groups. Increased BH4 production in cardiomyocytes resulted in a significant loss of mitochondrial function. Diminished oxygen consumption and reserve capacity was verified in mitochondria isolated from hearts of 12-month old compared to 3-month old mice, even though at 12 months an improved BH4:BH2 ratio is established. Accumulation of 4-hydroxynonenal (4-HNE) and decreased glutathione levels were found in the mGCH hearts and isolated mitochondria. Taken together, our results indicate that the ratio of BH4:BH2 does not predict changes in neither NO levels nor cellular redox state in the heart. The BH4 oxidation essentially limits the capacity of cardiomyocytes to reduce oxidant stress. Cardiomyocyte with chronically high levels of BH4 show a significant decline in redox state and mitochondrial function
L-Carnitine and -Lipoic Acid Improve Age-Associated Decline in Mitochondrial Respiratory Chain Activity of Rat Heart Muscle
Mitochondria-Targeted Spin Traps: Synthesis, Superoxide Spin Trapping, and Mitochondrial Uptake
International audienceDevelopment of reliable methods and site-specific detection of free radicals is an active area of research. Here, we describe the synthesis and radical-trapping properties of new derivatives of DEPMPO and DIPPMPO, bearing a mitochondria-targeting triphenylphosphonium cationic moiety or guanidinium cationic group. All of the spin traps prepared have been observed to efficiently trap superoxide radical anions in a cell-free system. The superoxide spin adducts exhibited similar spectral properties, indicating no significant differences in the geometry of the cyclic nitroxide moieties of the spin adducts. The superoxide adduct stability was measured and observed to be highest (t1/2 = 73 min) for DIPPMPO nitrone linked to triphenylphosphonium moiety via a short carbon chain (Mito-DIPPMPO). The experimental results and DFT quantum chemical calculations indicate that the cationic property of the triphenylphosphonium group may be responsible for increased superoxide trapping efficiency and adduct stability of Mito-DIPPMPO, as compared to the DIPPMPO spin trap. The studies of uptake of the synthesized traps into isolated mitochondria indicated the importance of both cationic and lipophilic properties, with the DEPMPO nitrone linked to the triphenylphosphonium moiety via a long carbon chain (Mito10-DEPMPO) exhibiting the highest mitochondrial uptake. We conclude that, of the synthesized traps, Mito-DIPPMPO and Mito10-DEPMPO are the best candidates for potential mitochondria-specific spin traps for use in biologically relevant systems
Mitochondria-Targeted Spin Traps: Synthesis, Superoxide Spin Trapping, and Mitochondrial Uptake
Development of reliable methods and
site-specific detection of
free radicals is an active area of research. Here, we describe the
synthesis and radical-trapping properties of new derivatives of DEPMPO
and DIPPMPO, bearing a mitochondria-targeting triphenylphosphonium
cationic moiety or guanidinium cationic group. All of the spin
traps prepared have been observed to efficiently trap superoxide radical
anions in a cell-free system. The superoxide spin adducts exhibited
similar spectral properties, indicating no significant differences
in the geometry of the cyclic nitroxide moieties of the spin adducts.
The superoxide adduct stability was measured and observed to be highest
(<i>t</i><sub>1/2</sub> = 73 min) for DIPPMPO nitrone linked
to triphenylphosphonium moiety via a short carbon chain (Mito-DIPPMPO).
The experimental results and DFT quantum chemical calculations indicate
that the cationic property of the triphenylphosphonium group
may be responsible for increased superoxide trapping efficiency and
adduct stability of Mito-DIPPMPO, as compared to the DIPPMPO spin
trap. The studies of uptake of the synthesized traps into isolated
mitochondria indicated the importance of both cationic and lipophilic
properties, with the DEPMPO nitrone linked to the triphenylphosphonium
moiety via a long carbon chain (Mito<sub>10</sub>-DEPMPO) exhibiting
the highest mitochondrial uptake. We conclude that, of the synthesized
traps, Mito-DIPPMPO and Mito<sub>10</sub>-DEPMPO are the best candidates
for potential mitochondria-specific spin traps for use in biologically
relevant systems