Maria Franco | Oregon State University (original) (raw)

Papers by Maria Franco

Research paper thumbnail of Chronic inhibitory effect of riluzole on trophic factor production

Experimental neurology, Jan 10, 2015

Riluzole is the only FDA approved drug for the treatment of amyotrophic lateral sclerosis (ALS). ... more Riluzole is the only FDA approved drug for the treatment of amyotrophic lateral sclerosis (ALS). However, the drug affords moderate protection to ALS patients, extending life for a few months by a mechanism that remains controversial. In the presence of riluzole, astrocytes increase the production of factors protective to motor neurons. The stimulation of trophic factor production by motor neuron associated cells may contribute to riluzole's protective effect in ALS. Here, we investigated the effects of media conditioned by astrocytes and Schwann cells acutely or chronically incubated with riluzole on trophic factor-deprived motor neuron survival. While acute riluzole incubation induced CT-1 secretion by astrocytes and Schwann cells, chronic treatment stimulated a significant decrease in trophic factor production compared to untreated cultures. Accordingly, conditioned media from astrocytes and Schwann cells acutely treated with riluzole protected motor neurons from trophic fact...

Research paper thumbnail of Editorial: Mitochondrial Dynamics in Endocrine Physiology and Disease

Frontiers in Endocrinology, 2022

Research paper thumbnail of Tyrosine Nitration Supports Glioblastoma Multiforme Cell Survival and Regulates Migration

Free Radical Biology and Medicine, 2020

Research paper thumbnail of Peroxynitrite supports a metabolic reprogramming in merlin-deficient Schwann cells and promotes cell survival

Journal of Biological Chemistry, 2019

Research paper thumbnail of Molecular Basis of Redox Signaling

Oxidative Medicine and Cellular Longevity, 2019

Research paper thumbnail of Combination Therapy With c-Met and Src Inhibitors Induces Caspase-Dependent Apoptosis of Merlin-Deficient Schwann Cells and Suppresses Growth of Schwannoma Cells

Molecular cancer therapeutics, Jan 3, 2017

Neurofibromatosis type 2 (NF2) is a nervous system tumor disorder caused by inactivation of the m... more Neurofibromatosis type 2 (NF2) is a nervous system tumor disorder caused by inactivation of the merlin tumor suppressor encoded by the NF2 gene. Bilateral vestibular schwannomas (VS) are a diagnostic hallmark of NF2. Mainstream treatment options for NF2-associated tumors have been limited to surgery and radiotherapy; however, off-label uses of targeted molecular therapies are becoming increasingly common. Here we investigated drugs targeting two kinases activated in NF2-associated schwannomas, c-Met and Src. We demonstrated that merlin-deficient mouse Schwann cells (MD-MSCs) treated with the c-Met inhibitor, cabozantinib, or the Src kinase inhibitors, dasatinib and saracatinib, underwent a G1 cell cycle arrest. However, when MD-MSCs were treated with a combination of cabozantinib and saracatinib, they exhibited caspase-dependent apoptosis. The combination therapy also significantly reduced growth of MD-MSCs in an orthotopic allograft mouse model by greater than 80% of vehicle. Moreo...

Research paper thumbnail of Cellular mechanisms of peroxynitrite-induced neuronal death

Brain research bulletin, Jan 24, 2017

Peroxynitrite (ONOO(-)) is a strong biological oxidant formed by the diffusion-limited reaction o... more Peroxynitrite (ONOO(-)) is a strong biological oxidant formed by the diffusion-limited reaction of nitric oxide (NO(-)) and superoxide anion (O2(-)). It has long been theorized that peroxynitrite generation could be the cause in a number of pathological conditions ranging from atherosclerosis to inflammatory, autoimmune, heart and neurodegenerative diseases. Its relatively long biological half-life and high reactivity allows peroxynitrite to oxidize a number of different targets in the cell. In physiologically relevant conditions peroxynitrite can directly react with thiols, or the radical products of peroxynitrite decomposition may indirectly oxidize other cellular components such as lipids, proteins and DNA. Downstream, oxidative modifications caused by peroxynitrite trigger cell death by a variety of mechanisms depending on the concentration of the oxidant. Peroxynitrite stimulates necrosis, apoptosis, autophagy, parthanatos and necroptosis. Here we review the mechanisms activate...

Research paper thumbnail of Copper delivery to the CNS by CuATSM effectively treats motor neuron disease in SOD(G93A) mice co-expressing the copper-chaperone-for-SOD

Neurobiology of disease, Jan 27, 2016

Over-expression of mutant copper, zinc superoxide dismutase (SOD) in mice induces ALS and has bec... more Over-expression of mutant copper, zinc superoxide dismutase (SOD) in mice induces ALS and has become the most widely used model of neurodegeneration. However, no pharmaceutical agent in 20years has extended lifespan by more than a few weeks. The Copper-Chaperone-for-SOD (CCS) protein completes the maturation of SOD by inserting copper, but paradoxically human CCS causes mice co-expressing mutant SOD to die within two weeks of birth. Hypothesizing that co-expression of CCS created copper deficiency in spinal cord, we treated these pups with the PET-imaging agent CuATSM, which is known to deliver copper into the CNS within minutes. CuATSM prevented the early mortality of CCSxSOD mice, while markedly increasing Cu, Zn SOD protein in their ventral spinal cord. Remarkably, continued treatment with CuATSM extended the survival of these mice by an average of 18months. When CuATSM treatment was stopped, these mice developed ALS-related symptoms and died within 3months. Restoring CuATSM trea...

Research paper thumbnail of Reactive nitrogen species in cellular signaling

Experimental biology and medicine (Maywood, N.J.), Jan 16, 2015

The transduction of cellular signals occurs through the modification of target molecules. Most of... more The transduction of cellular signals occurs through the modification of target molecules. Most of these modifications are transitory, thus the signal transduction pathways can be tightly regulated. Reactive nitrogen species are a group of compounds with different properties and reactivity. Some reactive nitrogen species are highly reactive and their interaction with macromolecules can lead to permanent modifications, which suggested they were lacking the specificity needed to participate in cell signaling events. However, the perception of reactive nitrogen species as oxidizers of macromolecules leading to general oxidative damage has recently evolved. The concept of redox signaling is now well established for a number of reactive oxygen and nitrogen species. In this context, the post-translational modifications introduced by reactive nitrogen species can be very specific and are active participants in signal transduction pathways. This review addresses the role of these oxidative m...

Research paper thumbnail of Tyrosine nitration as mediator of cell death

Cellular and Molecular Life Sciences, 2014

Nitrotyrosine is used as a marker for the production of peroxynitrite and other reactive nitrogen... more Nitrotyrosine is used as a marker for the production of peroxynitrite and other reactive nitrogen species. For over 20 years the presence of nitrotyrosine was associated with cell death in multiple pathologies. Filling the gap between correlation and causality has proven to be a difficult task. Here, we discuss the evidence supporting tyrosine nitration as a specific posttranslational modification participating in the induction of cell death signaling pathways.

Research paper thumbnail of Akt1 Intramitochondrial Cycling Is a Crucial Step in the Redox Modulation of Cell Cycle Progression

Research paper thumbnail of Cell H2O2 Steady-State Concentration and Mitochondrial Nitric Oxide

Methods in Enzymology, 2005

For many years, mitochondrial respiration was thought to follow an &a... more For many years, mitochondrial respiration was thought to follow an "all or nothing" paradigm supporting the notion that in the normal O2 concentration range, respiration is mainly controlled by tissue demands. However, nitric oxide produced by cytosol or mitochondrial nitric oxide synthases adapts respiration to different physiologic conditions and increases the mitochondrial production of O2 active species that contributes to NO clearance. Because mitochondrial NO utilization is sensitive to environmental or hormonal modulation, and because diffusible active species, like H2O2, are able to regulate genes related to proliferation, quiescence, and death, we surmised that the two mechanisms converge to elicit the different responses in cell physiology.

Research paper thumbnail of P140. iNOS translocation to mitochondria and septic organ failure

Research paper thumbnail of Temporal patterns of tyrosine nitration in embryo heart development

Free Radical Biology and Medicine, 2013

Tyrosine nitration is a biomarker for the production of peroxynitrite and other reactive nitrogen... more Tyrosine nitration is a biomarker for the production of peroxynitrite and other reactive nitrogen species. Nitrotyrosine immunoreactivity is present in many pathological conditions including several cardiac diseases. Because the events observed during heart failure may recapitulate some aspects of development, we tested whether nitrotyrosine is present during normal development of the rat embryo heart and its potential relationship in cardiac remodeling through apoptosis. Nitric oxide production is highly dynamic during development, but whether peroxynitrite and nitrotyrosine are formed during normal embryonic development has received little attention. Rat embryo hearts exhibited strong nitrotyrosine immunoreactivity in endocardial and myocardial cells of the atria and ventricles from E12 to E18. After E18, nitrotyrosine staining faded and disappeared entirely by birth. Tyrosine nitration in the myocardial tissue coincided with elevated protein expression of nitric oxide synthases (eNOS and iNOS). The immunoreactivity for these NOS isoforms remained elevated even after nitrotyrosine had disappeared. Tyrosine nitration did not correlate with cell death or proliferation of cardiac cells. Analysis of tryptic peptides by MALDI-TOF showed that nitration occurs in actin, myosin, and the mitochondrial ATP synthase α chain. These results suggest that reactive nitrogen species are not restricted to pathological conditions but may play a role during normal embryonic development.

Research paper thumbnail of Nitrated Hsp90 Decreases Mitochondrial Membrane Potential and Oxygen Consumption

Free Radical Biology and Medicine, 2011

Research paper thumbnail of Nitrated Hsp90 Induces Apoptosis in Motor Neurons by a Fas-Dependent Mechanism

Free Radical Biology and Medicine, 2011

Research paper thumbnail of IL-9 promotes anti-Mycobacterium leprae cytotoxicity: involvement of IFN?

Clinical and Experimental Immunology, 2006

Interleukin 9 (IL-9) is a T-cell derived factor preferentially expressed by CD4+ Th2 cells and it... more Interleukin 9 (IL-9) is a T-cell derived factor preferentially expressed by CD4+ Th2 cells and it has been characterized both in human and murine systems. It is a pleiotropic cytokine with multiple functions on cells of the lymphoid, myeloid and mast cell lineages, as well as on lung epithelial cells. Other activities described for IL-9 support its contribution to asthma and its important role in helminthic infections, where a Th2 response can be protective and IL-9 enhances resistance or is responsible for elimination of the nematode. Nevertheless, until recently there were no studies on its role in bacterial infections in man. We have demonstrated that cytokines can modulate the specific cytotoxicity generation in peripheral blood mononuclear cells from leprosy patients and normal controls. In the present report we studied the effect of IL-9 in this experimental model. Our results indicate that IL-9 can counteract the negative effect mediated by IL-4 on the generation of M. leprae-induced cytotoxic T lymphocytes. Moreover, it can increase this lytic activity in controls and enhance the stimulatory effect of IL-2 or IL-6 in cells from leprosy patients and controls. IL-9 is also able to revert the inhibitory effect of IL-10 and IL-13 on the M. leprae-induced cytotoxic activity. Although the exact mechanism of action of IL-9 remains to be determined, interferon gamma seems to be required for the effect of IL-9 in this experimental model. These data suggest that IL-9 may have an atypical Th2 behaviour and play a role in the modulation of the immune response to mycobacterial infections.

Research paper thumbnail of Nitration of Hsp90 on tyrosine 33 regulates mitochondrial metabolism

Journal of Biological Chemistry, 2015

Research paper thumbnail of Nitration of Hsp90 induces cell death

Proceedings of the National Academy of Sciences, 2013

Research paper thumbnail of Hypothyroid Phenotype is Contributed by Mitochondrial Complex I Inactivation Due to Translocated Neuronal Nitric-Oxide Synthase

Journal of Biological …, 2006

Although transcriptional effects of thyroid hormones have substantial influence on oxidative meta... more Although transcriptional effects of thyroid hormones have substantial influence on oxidative metabolism, how thyroid sets basal metabolic rate remains obscure. Compartmental localization of nitric-oxide synthases is important for nitric oxide signaling. We therefore examined liver neuronal nitric-oxide synthase-␣ (nNOS) subcellular distribution as a putative mechanism for thyroid effects on rat metabolic rate. At low 3,3,5-triiodo-L-thyronine levels, nNOS mRNA increased by 3-fold, protein expression by one-fold, and nNOS was selectively translocated to mitochondria without changes in other isoforms. In contrast, under thyroid hormone administration, mRNA level did not change and nNOS remained predominantly localized in cytosol. In hypothyroidism, nNOS translocation resulted in enhanced mitochondrial nitric-oxide synthase activity with low O 2 uptake. In this context, NO utilization increased active O 2 species and peroxynitrite yields and tyrosine nitration of complex I proteins that reduced complex activity. Hypothyroidism was also associated to high phospho-p38 mitogenactivated protein kinase and decreased phospho-extracellular signal-regulated kinase 1/2 and cyclin D1 levels. Similarly to thyroid hormones, but without changing thyroid status, nitric-oxide synthase inhibitor N-nitro-L-arginine methyl ester increased basal metabolic rate, prevented mitochondrial nitration and complex I derangement, and turned mitogen-activated protein kinase signaling and cyclin D1 expression back to control pattern. We surmise that nNOS spatial confinement in mitochondria is a significant downstream effector of thyroid hormone and hypothyroid phenotype.

Research paper thumbnail of Chronic inhibitory effect of riluzole on trophic factor production

Experimental neurology, Jan 10, 2015

Riluzole is the only FDA approved drug for the treatment of amyotrophic lateral sclerosis (ALS). ... more Riluzole is the only FDA approved drug for the treatment of amyotrophic lateral sclerosis (ALS). However, the drug affords moderate protection to ALS patients, extending life for a few months by a mechanism that remains controversial. In the presence of riluzole, astrocytes increase the production of factors protective to motor neurons. The stimulation of trophic factor production by motor neuron associated cells may contribute to riluzole's protective effect in ALS. Here, we investigated the effects of media conditioned by astrocytes and Schwann cells acutely or chronically incubated with riluzole on trophic factor-deprived motor neuron survival. While acute riluzole incubation induced CT-1 secretion by astrocytes and Schwann cells, chronic treatment stimulated a significant decrease in trophic factor production compared to untreated cultures. Accordingly, conditioned media from astrocytes and Schwann cells acutely treated with riluzole protected motor neurons from trophic fact...

Research paper thumbnail of Editorial: Mitochondrial Dynamics in Endocrine Physiology and Disease

Frontiers in Endocrinology, 2022

Research paper thumbnail of Tyrosine Nitration Supports Glioblastoma Multiforme Cell Survival and Regulates Migration

Free Radical Biology and Medicine, 2020

Research paper thumbnail of Peroxynitrite supports a metabolic reprogramming in merlin-deficient Schwann cells and promotes cell survival

Journal of Biological Chemistry, 2019

Research paper thumbnail of Molecular Basis of Redox Signaling

Oxidative Medicine and Cellular Longevity, 2019

Research paper thumbnail of Combination Therapy With c-Met and Src Inhibitors Induces Caspase-Dependent Apoptosis of Merlin-Deficient Schwann Cells and Suppresses Growth of Schwannoma Cells

Molecular cancer therapeutics, Jan 3, 2017

Neurofibromatosis type 2 (NF2) is a nervous system tumor disorder caused by inactivation of the m... more Neurofibromatosis type 2 (NF2) is a nervous system tumor disorder caused by inactivation of the merlin tumor suppressor encoded by the NF2 gene. Bilateral vestibular schwannomas (VS) are a diagnostic hallmark of NF2. Mainstream treatment options for NF2-associated tumors have been limited to surgery and radiotherapy; however, off-label uses of targeted molecular therapies are becoming increasingly common. Here we investigated drugs targeting two kinases activated in NF2-associated schwannomas, c-Met and Src. We demonstrated that merlin-deficient mouse Schwann cells (MD-MSCs) treated with the c-Met inhibitor, cabozantinib, or the Src kinase inhibitors, dasatinib and saracatinib, underwent a G1 cell cycle arrest. However, when MD-MSCs were treated with a combination of cabozantinib and saracatinib, they exhibited caspase-dependent apoptosis. The combination therapy also significantly reduced growth of MD-MSCs in an orthotopic allograft mouse model by greater than 80% of vehicle. Moreo...

Research paper thumbnail of Cellular mechanisms of peroxynitrite-induced neuronal death

Brain research bulletin, Jan 24, 2017

Peroxynitrite (ONOO(-)) is a strong biological oxidant formed by the diffusion-limited reaction o... more Peroxynitrite (ONOO(-)) is a strong biological oxidant formed by the diffusion-limited reaction of nitric oxide (NO(-)) and superoxide anion (O2(-)). It has long been theorized that peroxynitrite generation could be the cause in a number of pathological conditions ranging from atherosclerosis to inflammatory, autoimmune, heart and neurodegenerative diseases. Its relatively long biological half-life and high reactivity allows peroxynitrite to oxidize a number of different targets in the cell. In physiologically relevant conditions peroxynitrite can directly react with thiols, or the radical products of peroxynitrite decomposition may indirectly oxidize other cellular components such as lipids, proteins and DNA. Downstream, oxidative modifications caused by peroxynitrite trigger cell death by a variety of mechanisms depending on the concentration of the oxidant. Peroxynitrite stimulates necrosis, apoptosis, autophagy, parthanatos and necroptosis. Here we review the mechanisms activate...

Research paper thumbnail of Copper delivery to the CNS by CuATSM effectively treats motor neuron disease in SOD(G93A) mice co-expressing the copper-chaperone-for-SOD

Neurobiology of disease, Jan 27, 2016

Over-expression of mutant copper, zinc superoxide dismutase (SOD) in mice induces ALS and has bec... more Over-expression of mutant copper, zinc superoxide dismutase (SOD) in mice induces ALS and has become the most widely used model of neurodegeneration. However, no pharmaceutical agent in 20years has extended lifespan by more than a few weeks. The Copper-Chaperone-for-SOD (CCS) protein completes the maturation of SOD by inserting copper, but paradoxically human CCS causes mice co-expressing mutant SOD to die within two weeks of birth. Hypothesizing that co-expression of CCS created copper deficiency in spinal cord, we treated these pups with the PET-imaging agent CuATSM, which is known to deliver copper into the CNS within minutes. CuATSM prevented the early mortality of CCSxSOD mice, while markedly increasing Cu, Zn SOD protein in their ventral spinal cord. Remarkably, continued treatment with CuATSM extended the survival of these mice by an average of 18months. When CuATSM treatment was stopped, these mice developed ALS-related symptoms and died within 3months. Restoring CuATSM trea...

Research paper thumbnail of Reactive nitrogen species in cellular signaling

Experimental biology and medicine (Maywood, N.J.), Jan 16, 2015

The transduction of cellular signals occurs through the modification of target molecules. Most of... more The transduction of cellular signals occurs through the modification of target molecules. Most of these modifications are transitory, thus the signal transduction pathways can be tightly regulated. Reactive nitrogen species are a group of compounds with different properties and reactivity. Some reactive nitrogen species are highly reactive and their interaction with macromolecules can lead to permanent modifications, which suggested they were lacking the specificity needed to participate in cell signaling events. However, the perception of reactive nitrogen species as oxidizers of macromolecules leading to general oxidative damage has recently evolved. The concept of redox signaling is now well established for a number of reactive oxygen and nitrogen species. In this context, the post-translational modifications introduced by reactive nitrogen species can be very specific and are active participants in signal transduction pathways. This review addresses the role of these oxidative m...

Research paper thumbnail of Tyrosine nitration as mediator of cell death

Cellular and Molecular Life Sciences, 2014

Nitrotyrosine is used as a marker for the production of peroxynitrite and other reactive nitrogen... more Nitrotyrosine is used as a marker for the production of peroxynitrite and other reactive nitrogen species. For over 20 years the presence of nitrotyrosine was associated with cell death in multiple pathologies. Filling the gap between correlation and causality has proven to be a difficult task. Here, we discuss the evidence supporting tyrosine nitration as a specific posttranslational modification participating in the induction of cell death signaling pathways.

Research paper thumbnail of Akt1 Intramitochondrial Cycling Is a Crucial Step in the Redox Modulation of Cell Cycle Progression

Research paper thumbnail of Cell H2O2 Steady-State Concentration and Mitochondrial Nitric Oxide

Methods in Enzymology, 2005

For many years, mitochondrial respiration was thought to follow an &a... more For many years, mitochondrial respiration was thought to follow an "all or nothing" paradigm supporting the notion that in the normal O2 concentration range, respiration is mainly controlled by tissue demands. However, nitric oxide produced by cytosol or mitochondrial nitric oxide synthases adapts respiration to different physiologic conditions and increases the mitochondrial production of O2 active species that contributes to NO clearance. Because mitochondrial NO utilization is sensitive to environmental or hormonal modulation, and because diffusible active species, like H2O2, are able to regulate genes related to proliferation, quiescence, and death, we surmised that the two mechanisms converge to elicit the different responses in cell physiology.

Research paper thumbnail of P140. iNOS translocation to mitochondria and septic organ failure

Research paper thumbnail of Temporal patterns of tyrosine nitration in embryo heart development

Free Radical Biology and Medicine, 2013

Tyrosine nitration is a biomarker for the production of peroxynitrite and other reactive nitrogen... more Tyrosine nitration is a biomarker for the production of peroxynitrite and other reactive nitrogen species. Nitrotyrosine immunoreactivity is present in many pathological conditions including several cardiac diseases. Because the events observed during heart failure may recapitulate some aspects of development, we tested whether nitrotyrosine is present during normal development of the rat embryo heart and its potential relationship in cardiac remodeling through apoptosis. Nitric oxide production is highly dynamic during development, but whether peroxynitrite and nitrotyrosine are formed during normal embryonic development has received little attention. Rat embryo hearts exhibited strong nitrotyrosine immunoreactivity in endocardial and myocardial cells of the atria and ventricles from E12 to E18. After E18, nitrotyrosine staining faded and disappeared entirely by birth. Tyrosine nitration in the myocardial tissue coincided with elevated protein expression of nitric oxide synthases (eNOS and iNOS). The immunoreactivity for these NOS isoforms remained elevated even after nitrotyrosine had disappeared. Tyrosine nitration did not correlate with cell death or proliferation of cardiac cells. Analysis of tryptic peptides by MALDI-TOF showed that nitration occurs in actin, myosin, and the mitochondrial ATP synthase α chain. These results suggest that reactive nitrogen species are not restricted to pathological conditions but may play a role during normal embryonic development.

Research paper thumbnail of Nitrated Hsp90 Decreases Mitochondrial Membrane Potential and Oxygen Consumption

Free Radical Biology and Medicine, 2011

Research paper thumbnail of Nitrated Hsp90 Induces Apoptosis in Motor Neurons by a Fas-Dependent Mechanism

Free Radical Biology and Medicine, 2011

Research paper thumbnail of IL-9 promotes anti-Mycobacterium leprae cytotoxicity: involvement of IFN?

Clinical and Experimental Immunology, 2006

Interleukin 9 (IL-9) is a T-cell derived factor preferentially expressed by CD4+ Th2 cells and it... more Interleukin 9 (IL-9) is a T-cell derived factor preferentially expressed by CD4+ Th2 cells and it has been characterized both in human and murine systems. It is a pleiotropic cytokine with multiple functions on cells of the lymphoid, myeloid and mast cell lineages, as well as on lung epithelial cells. Other activities described for IL-9 support its contribution to asthma and its important role in helminthic infections, where a Th2 response can be protective and IL-9 enhances resistance or is responsible for elimination of the nematode. Nevertheless, until recently there were no studies on its role in bacterial infections in man. We have demonstrated that cytokines can modulate the specific cytotoxicity generation in peripheral blood mononuclear cells from leprosy patients and normal controls. In the present report we studied the effect of IL-9 in this experimental model. Our results indicate that IL-9 can counteract the negative effect mediated by IL-4 on the generation of M. leprae-induced cytotoxic T lymphocytes. Moreover, it can increase this lytic activity in controls and enhance the stimulatory effect of IL-2 or IL-6 in cells from leprosy patients and controls. IL-9 is also able to revert the inhibitory effect of IL-10 and IL-13 on the M. leprae-induced cytotoxic activity. Although the exact mechanism of action of IL-9 remains to be determined, interferon gamma seems to be required for the effect of IL-9 in this experimental model. These data suggest that IL-9 may have an atypical Th2 behaviour and play a role in the modulation of the immune response to mycobacterial infections.

Research paper thumbnail of Nitration of Hsp90 on tyrosine 33 regulates mitochondrial metabolism

Journal of Biological Chemistry, 2015

Research paper thumbnail of Nitration of Hsp90 induces cell death

Proceedings of the National Academy of Sciences, 2013

Research paper thumbnail of Hypothyroid Phenotype is Contributed by Mitochondrial Complex I Inactivation Due to Translocated Neuronal Nitric-Oxide Synthase

Journal of Biological …, 2006

Although transcriptional effects of thyroid hormones have substantial influence on oxidative meta... more Although transcriptional effects of thyroid hormones have substantial influence on oxidative metabolism, how thyroid sets basal metabolic rate remains obscure. Compartmental localization of nitric-oxide synthases is important for nitric oxide signaling. We therefore examined liver neuronal nitric-oxide synthase-␣ (nNOS) subcellular distribution as a putative mechanism for thyroid effects on rat metabolic rate. At low 3,3,5-triiodo-L-thyronine levels, nNOS mRNA increased by 3-fold, protein expression by one-fold, and nNOS was selectively translocated to mitochondria without changes in other isoforms. In contrast, under thyroid hormone administration, mRNA level did not change and nNOS remained predominantly localized in cytosol. In hypothyroidism, nNOS translocation resulted in enhanced mitochondrial nitric-oxide synthase activity with low O 2 uptake. In this context, NO utilization increased active O 2 species and peroxynitrite yields and tyrosine nitration of complex I proteins that reduced complex activity. Hypothyroidism was also associated to high phospho-p38 mitogenactivated protein kinase and decreased phospho-extracellular signal-regulated kinase 1/2 and cyclin D1 levels. Similarly to thyroid hormones, but without changing thyroid status, nitric-oxide synthase inhibitor N-nitro-L-arginine methyl ester increased basal metabolic rate, prevented mitochondrial nitration and complex I derangement, and turned mitogen-activated protein kinase signaling and cyclin D1 expression back to control pattern. We surmise that nNOS spatial confinement in mitochondria is a significant downstream effector of thyroid hormone and hypothyroid phenotype.