This mini-review describes the role of different mitochondrial components in the formation of rea... more This mini-review describes the role of different mitochondrial components in the formation of reactive oxygen species under normal and pathological conditions and the effect of inhibitors and uncouplers on superoxide formation.
The enzyme NADH-fumarate reductase is not found in mammalian cells but it is present in several p... more The enzyme NADH-fumarate reductase is not found in mammalian cells but it is present in several parasitic protozoa including Trypanosoma cruzi, the parasite that causes Chagas' disease. This study shows that the drug 2-mercaptopyridine-Noxide (MPNO) inhibits NADH-fumarate reductase purified from T. cruzi (ID SH = 35 WM). When added to intact cells, MPNO inhibited the growth of T. cruzi epimastigotes in culture (ID SH = 0.08 WM) as well as the infection of mammalian myoblasts by T. cruzi trypomastigotes (ID SH = 20 WM). At a concentration of 2.4 WM, MPNO also inhibited the growth of amastigotes (intracellular dividing forms) in cultured mammalian myoblasts. Supplementation of culture media with 5 mM succinate, the product of fumarate reductase, partially protected against the inhibition of the growth of epimastigotes by MPNO. Moreover, MPNO inhibited the accumulation of succinate in cultures of epimastigotes, as measured by high performance liquid chromatography. Although MPNO may have other intracellular targets in addition to fumarate reductase, these results support the hypothesis that compounds which inhibit the enzyme fumarate reductase may be potential chemotherapeutic agents against Chagas' disease. z
1. Mol Biochem Parasitol. 1998 May 15;93(1):135-7. Rotenone at high concentrations inhibits NADH-... more 1. Mol Biochem Parasitol. 1998 May 15;93(1):135-7. Rotenone at high concentrations inhibits NADH-fumarate reductase and the mitochondrial respiratory chain of Trypanosoma brucei and T. cruzi. Hernandez FR, Turrens JF. ...
The enzyme NADH-fumarate reductase is not found in mammalian cells but it is present in several p... more The enzyme NADH-fumarate reductase is not found in mammalian cells but it is present in several parasitic protozoa including Trypanosoma cruzi, the parasite that causes Chagas' disease. This study shows that the drug 2-mercaptopyridine-N-oxide (MPNO) inhibits NADH-fumarate reductase purified from T. cruzi (ID50=35 μM). When added to intact cells, MPNO inhibited the growth of T. cruzi epimastigotes in culture (ID50=0.08 μM) as well as the infection of mammalian myoblasts by T. cruzi trypomastigotes (ID50=20 μM). At a concentration of 2.4 μM, MPNO also inhibited the growth of amastigotes (intracellular dividing forms) in cultured mammalian myoblasts. Supplementation of culture media with 5 mM succinate, the product of fumarate reductase, partially protected against the inhibition of the growth of epimastigotes by MPNO. Moreover, MPNO inhibited the accumulation of succinate in cultures of epimastigotes, as measured by high performance liquid chromatography. Although MPNO may have other intracellular targets in addition to fumarate reductase, these results support the hypothesis that compounds which inhibit the enzyme fumarate reductase may be potential chemotherapeutic agents against Chagas' disease.
tein oxidation. In addition, this study confirms that Tris buffer is a target for strong oxidants... more tein oxidation. In addition, this study confirms that Tris buffer is a target for strong oxidants and shows Bovine serum albumin oxidation by peroxynitrite is that its oxidation also is accompanied by light emisaccompanied by chemiluminescence (Watts et al.,
Comparative Biochemistry and Physiology Part C: Comparative Pharmacology, 1987
1. The antitumor drug lonidamine inhibited growth of promastigotes of Leishmunia mexicana in axen... more 1. The antitumor drug lonidamine inhibited growth of promastigotes of Leishmunia mexicana in axenic culture.
Oxidative stress is associated with a variety of pathological processes of clinical relevance. So... more Oxidative stress is associated with a variety of pathological processes of clinical relevance. Some of the intermediates generated during the chain reactions associated with oxidation of lipids and proteins are electronically excited and decay emitting photons, which may be detected with the help of sensitive photomultipliers. This technique has been used to monitor oxidative stress in a variety of scenarios including intact organs in vivo or in vitro, and simple models such as proteins and lipids exposed to oxidants. The main drawback of this technique is that the emission of light is extremely weak and it is subjected to substantial interference from spurious sources. In addition, the quantum efficiency of photomultipliers varies with wavelength making it even more difficult to collect reliable data using photomultipliers sensitive to relatively broad spectral ranges. In order to identify the peak emission wavelengths in the visible region, we exposed model systems (proteins, lipids and amino acids) to peroxynitrite and sources of hydroxyl and alcoxyl radicals, analyzing the emission of light with interference filters. The results indicate that the peak emission for most biological models occurs between 450 and 700 nm. The emission at higher wavelengths (lower energy levels) was observed mostly in the presence of less powerful oxidants such as tert-butyl hydroperoxide.
Much evidence indicates that superoxide is generated from Oz in a cyanide-sensitive reaction invo... more Much evidence indicates that superoxide is generated from Oz in a cyanide-sensitive reaction involving a reduced component of complex III of the mitochondrial respiratory chain, particularly when antimycin A is present. Although it is generally believed that ubisemiquinone is the electron donor to Oz, little experimental evidence supporting this view has been reported. Experiments with succinate as electron donor in the presence of antimycin A in intact rat heart mitochondria, which contain much superoxide dismutase but little catalase, showed that myxothiazol, which inhibits reduction of the Rieske iron-sulfur center, prevented formation of hydrogen peroxide, determined spectrophotometrically as the HzOz-peroxidase complex. Similarly, depletion of the mitochondria of their cytochrome c also inhibited formation of Hz02, which was restored by addition of cytochrome c. These observations indicate that factors preventing the formation of ubisemiquinone also prevent Hz02 formation. They also exclude ubiquinol, which remains reduced under these conditions, as the reductant of Oz. Since cytochrome b also remains fully reduced when myxothiazol is added to succinate-and antimycin A-supplemented mitochondria, reduced cytochrome b may also be excluded as the reductant of OZ. These observations, which are consistent with the Q-cycle reactions, by exclusion of other possibilities leave ubisemiquinone as the only reduced electron carrier in complex III capable of reducing Oz to 0;. o 1985 Academic Press, Inc.
This mini-review describes the role of different mitochondrial components in the formation of rea... more This mini-review describes the role of different mitochondrial components in the formation of reactive oxygen species under normal and pathological conditions and the effect of inhibitors and uncouplers on superoxide formation.
The enzyme NADH-fumarate reductase is not found in mammalian cells but it is present in several p... more The enzyme NADH-fumarate reductase is not found in mammalian cells but it is present in several parasitic protozoa including Trypanosoma cruzi, the parasite that causes Chagas' disease. This study shows that the drug 2-mercaptopyridine-Noxide (MPNO) inhibits NADH-fumarate reductase purified from T. cruzi (ID SH = 35 WM). When added to intact cells, MPNO inhibited the growth of T. cruzi epimastigotes in culture (ID SH = 0.08 WM) as well as the infection of mammalian myoblasts by T. cruzi trypomastigotes (ID SH = 20 WM). At a concentration of 2.4 WM, MPNO also inhibited the growth of amastigotes (intracellular dividing forms) in cultured mammalian myoblasts. Supplementation of culture media with 5 mM succinate, the product of fumarate reductase, partially protected against the inhibition of the growth of epimastigotes by MPNO. Moreover, MPNO inhibited the accumulation of succinate in cultures of epimastigotes, as measured by high performance liquid chromatography. Although MPNO may have other intracellular targets in addition to fumarate reductase, these results support the hypothesis that compounds which inhibit the enzyme fumarate reductase may be potential chemotherapeutic agents against Chagas' disease. z
1. Mol Biochem Parasitol. 1998 May 15;93(1):135-7. Rotenone at high concentrations inhibits NADH-... more 1. Mol Biochem Parasitol. 1998 May 15;93(1):135-7. Rotenone at high concentrations inhibits NADH-fumarate reductase and the mitochondrial respiratory chain of Trypanosoma brucei and T. cruzi. Hernandez FR, Turrens JF. ...
The enzyme NADH-fumarate reductase is not found in mammalian cells but it is present in several p... more The enzyme NADH-fumarate reductase is not found in mammalian cells but it is present in several parasitic protozoa including Trypanosoma cruzi, the parasite that causes Chagas' disease. This study shows that the drug 2-mercaptopyridine-N-oxide (MPNO) inhibits NADH-fumarate reductase purified from T. cruzi (ID50=35 μM). When added to intact cells, MPNO inhibited the growth of T. cruzi epimastigotes in culture (ID50=0.08 μM) as well as the infection of mammalian myoblasts by T. cruzi trypomastigotes (ID50=20 μM). At a concentration of 2.4 μM, MPNO also inhibited the growth of amastigotes (intracellular dividing forms) in cultured mammalian myoblasts. Supplementation of culture media with 5 mM succinate, the product of fumarate reductase, partially protected against the inhibition of the growth of epimastigotes by MPNO. Moreover, MPNO inhibited the accumulation of succinate in cultures of epimastigotes, as measured by high performance liquid chromatography. Although MPNO may have other intracellular targets in addition to fumarate reductase, these results support the hypothesis that compounds which inhibit the enzyme fumarate reductase may be potential chemotherapeutic agents against Chagas' disease.
tein oxidation. In addition, this study confirms that Tris buffer is a target for strong oxidants... more tein oxidation. In addition, this study confirms that Tris buffer is a target for strong oxidants and shows Bovine serum albumin oxidation by peroxynitrite is that its oxidation also is accompanied by light emisaccompanied by chemiluminescence (Watts et al.,
Comparative Biochemistry and Physiology Part C: Comparative Pharmacology, 1987
1. The antitumor drug lonidamine inhibited growth of promastigotes of Leishmunia mexicana in axen... more 1. The antitumor drug lonidamine inhibited growth of promastigotes of Leishmunia mexicana in axenic culture.
Oxidative stress is associated with a variety of pathological processes of clinical relevance. So... more Oxidative stress is associated with a variety of pathological processes of clinical relevance. Some of the intermediates generated during the chain reactions associated with oxidation of lipids and proteins are electronically excited and decay emitting photons, which may be detected with the help of sensitive photomultipliers. This technique has been used to monitor oxidative stress in a variety of scenarios including intact organs in vivo or in vitro, and simple models such as proteins and lipids exposed to oxidants. The main drawback of this technique is that the emission of light is extremely weak and it is subjected to substantial interference from spurious sources. In addition, the quantum efficiency of photomultipliers varies with wavelength making it even more difficult to collect reliable data using photomultipliers sensitive to relatively broad spectral ranges. In order to identify the peak emission wavelengths in the visible region, we exposed model systems (proteins, lipids and amino acids) to peroxynitrite and sources of hydroxyl and alcoxyl radicals, analyzing the emission of light with interference filters. The results indicate that the peak emission for most biological models occurs between 450 and 700 nm. The emission at higher wavelengths (lower energy levels) was observed mostly in the presence of less powerful oxidants such as tert-butyl hydroperoxide.
Much evidence indicates that superoxide is generated from Oz in a cyanide-sensitive reaction invo... more Much evidence indicates that superoxide is generated from Oz in a cyanide-sensitive reaction involving a reduced component of complex III of the mitochondrial respiratory chain, particularly when antimycin A is present. Although it is generally believed that ubisemiquinone is the electron donor to Oz, little experimental evidence supporting this view has been reported. Experiments with succinate as electron donor in the presence of antimycin A in intact rat heart mitochondria, which contain much superoxide dismutase but little catalase, showed that myxothiazol, which inhibits reduction of the Rieske iron-sulfur center, prevented formation of hydrogen peroxide, determined spectrophotometrically as the HzOz-peroxidase complex. Similarly, depletion of the mitochondria of their cytochrome c also inhibited formation of Hz02, which was restored by addition of cytochrome c. These observations indicate that factors preventing the formation of ubisemiquinone also prevent Hz02 formation. They also exclude ubiquinol, which remains reduced under these conditions, as the reductant of Oz. Since cytochrome b also remains fully reduced when myxothiazol is added to succinate-and antimycin A-supplemented mitochondria, reduced cytochrome b may also be excluded as the reductant of OZ. These observations, which are consistent with the Q-cycle reactions, by exclusion of other possibilities leave ubisemiquinone as the only reduced electron carrier in complex III capable of reducing Oz to 0;. o 1985 Academic Press, Inc.
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Papers by Julio Turrens