Limits...
Generation of reactive oxygen species in 1-methyl-4-phenylpyridinium (MPP+) treated dopaminergic neurons occurs as an NADPH oxidase-dependent two-wave cascade.

Zawada WM, Banninger GP, Thornton J, Marriott B, Cantu D, Rachubinski AL, Das M, Griffin WS, Jones SM - J Neuroinflammation (2011)

Bottom Line: A two-wave cascade of ROS production is active in nigral dopaminergic neurons in response to neurotoxicity-induced superoxide.Our findings allow us to conclude that superoxide generated by NADPH oxidase present in nigral neurons contributes to the loss of such neurons in PD.Losartan suppression of nigral-cell superoxide production suggests that angiotensin receptor blockers have potential as PD preventatives.

View Article: PubMed Central - HTML - PubMed

Affiliation: Donald W, Reynolds Department of Geriatrics, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA. wzawada@uams.edu

ABSTRACT

Background: Reactive oxygen species (ROS), superoxide and hydrogen peroxide (H2O2), are necessary for appropriate responses to immune challenges. In the brain, excess superoxide production predicts neuronal cell loss, suggesting that Parkinson's disease (PD) with its wholesale death of dopaminergic neurons in substantia nigra pars compacta (nigra) may be a case in point. Although microglial NADPH oxidase-produced superoxide contributes to dopaminergic neuron death in an MPTP mouse model of PD, this is secondary to an initial die off of such neurons, suggesting that the initial MPTP-induced death of neurons may be via activation of NADPH oxidase in neurons themselves, thus providing an early therapeutic target.

Methods: NADPH oxidase subunits were visualized in adult mouse nigra neurons and in N27 rat dopaminergic cells by immunofluorescence. NADPH oxidase subunits in N27 cell cultures were detected by immunoblots and RT-PCR. Superoxide was measured by flow cytometric detection of H2O2-induced carboxy-H2-DCFDA fluorescence. Cells were treated with MPP+ (MPTP metabolite) following siRNA silencing of the Nox2-stabilizing subunit p22phox, or simultaneously with NADPH oxidase pharmacological inhibitors or with losartan to antagonize angiotensin II type 1 receptor-induced NADPH oxidase activation.

Results: Nigral dopaminergic neurons in situ expressed three subunits necessary for NADPH oxidase activation, and these as well as several other NADPH oxidase subunits and their encoding mRNAs were detected in unstimulated N27 cells. Overnight MPP+ treatment of N27 cells induced Nox2 protein and superoxide generation, which was counteracted by NADPH oxidase inhibitors, by siRNA silencing of p22phox, or losartan. A two-wave ROS cascade was identified: 1) as a first wave, mitochondrial H2O2 production was first noted at three hours of MPP+ treatment; and 2) as a second wave, H2O2 levels were further increased by 24 hours. This second wave was eliminated by pharmacological inhibitors and a blocker of protein synthesis.

Conclusions: A two-wave cascade of ROS production is active in nigral dopaminergic neurons in response to neurotoxicity-induced superoxide. Our findings allow us to conclude that superoxide generated by NADPH oxidase present in nigral neurons contributes to the loss of such neurons in PD. Losartan suppression of nigral-cell superoxide production suggests that angiotensin receptor blockers have potential as PD preventatives.

Show MeSH

Related in: MedlinePlus

Dopaminergic cells express subunits of the NADPH oxidase complex. (A) mRNA from untreated N27 cells was reverse transcribed and amplified using PCR primers specific to rat NADPH oxidase subunits. Nox1-4 subunits as well as p22phox, p40phox, p47phox, and p67phox were identified by their mRNA expression. Nox2, p22phox, and p47phox were also detected by their protein expression (Western immunoblot, B-D) and cellular localization (immunofluorescence, B-D). Scale bar equals 10 μm; all three micrographs were taken at the same magnification.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3198931&req=5

Figure 2: Dopaminergic cells express subunits of the NADPH oxidase complex. (A) mRNA from untreated N27 cells was reverse transcribed and amplified using PCR primers specific to rat NADPH oxidase subunits. Nox1-4 subunits as well as p22phox, p40phox, p47phox, and p67phox were identified by their mRNA expression. Nox2, p22phox, and p47phox were also detected by their protein expression (Western immunoblot, B-D) and cellular localization (immunofluorescence, B-D). Scale bar equals 10 μm; all three micrographs were taken at the same magnification.

Mentions: Expression of mRNA for all the subunits of NADPH oxidase, including NADPH oxidase subunits p22phox, p47phox, and p67phox, as well as the cytosolic regulatory NADPH oxidase subunit p40phox mRNA, which is less involved in superoxide production, and the four Nox homologues is present in the nigral dopaminergic neuronal cell line N27 (Figure 2A). Western blotting and immunofluorescence histochemistry of Nox2, p22phox, and p47phox confirmed the translation of these mRNAs in N27 (Figure 2B-D). The presence of p67phox was confirmed by fluorescence immunoreactivity in nigral dopaminergic neurons in Figure 1.


Generation of reactive oxygen species in 1-methyl-4-phenylpyridinium (MPP+) treated dopaminergic neurons occurs as an NADPH oxidase-dependent two-wave cascade.

Zawada WM, Banninger GP, Thornton J, Marriott B, Cantu D, Rachubinski AL, Das M, Griffin WS, Jones SM - J Neuroinflammation (2011)

Dopaminergic cells express subunits of the NADPH oxidase complex. (A) mRNA from untreated N27 cells was reverse transcribed and amplified using PCR primers specific to rat NADPH oxidase subunits. Nox1-4 subunits as well as p22phox, p40phox, p47phox, and p67phox were identified by their mRNA expression. Nox2, p22phox, and p47phox were also detected by their protein expression (Western immunoblot, B-D) and cellular localization (immunofluorescence, B-D). Scale bar equals 10 μm; all three micrographs were taken at the same magnification.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3198931&req=5

Figure 2: Dopaminergic cells express subunits of the NADPH oxidase complex. (A) mRNA from untreated N27 cells was reverse transcribed and amplified using PCR primers specific to rat NADPH oxidase subunits. Nox1-4 subunits as well as p22phox, p40phox, p47phox, and p67phox were identified by their mRNA expression. Nox2, p22phox, and p47phox were also detected by their protein expression (Western immunoblot, B-D) and cellular localization (immunofluorescence, B-D). Scale bar equals 10 μm; all three micrographs were taken at the same magnification.
Mentions: Expression of mRNA for all the subunits of NADPH oxidase, including NADPH oxidase subunits p22phox, p47phox, and p67phox, as well as the cytosolic regulatory NADPH oxidase subunit p40phox mRNA, which is less involved in superoxide production, and the four Nox homologues is present in the nigral dopaminergic neuronal cell line N27 (Figure 2A). Western blotting and immunofluorescence histochemistry of Nox2, p22phox, and p47phox confirmed the translation of these mRNAs in N27 (Figure 2B-D). The presence of p67phox was confirmed by fluorescence immunoreactivity in nigral dopaminergic neurons in Figure 1.

Bottom Line: A two-wave cascade of ROS production is active in nigral dopaminergic neurons in response to neurotoxicity-induced superoxide.Our findings allow us to conclude that superoxide generated by NADPH oxidase present in nigral neurons contributes to the loss of such neurons in PD.Losartan suppression of nigral-cell superoxide production suggests that angiotensin receptor blockers have potential as PD preventatives.

View Article: PubMed Central - HTML - PubMed

Affiliation: Donald W, Reynolds Department of Geriatrics, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA. wzawada@uams.edu

ABSTRACT

Background: Reactive oxygen species (ROS), superoxide and hydrogen peroxide (H2O2), are necessary for appropriate responses to immune challenges. In the brain, excess superoxide production predicts neuronal cell loss, suggesting that Parkinson's disease (PD) with its wholesale death of dopaminergic neurons in substantia nigra pars compacta (nigra) may be a case in point. Although microglial NADPH oxidase-produced superoxide contributes to dopaminergic neuron death in an MPTP mouse model of PD, this is secondary to an initial die off of such neurons, suggesting that the initial MPTP-induced death of neurons may be via activation of NADPH oxidase in neurons themselves, thus providing an early therapeutic target.

Methods: NADPH oxidase subunits were visualized in adult mouse nigra neurons and in N27 rat dopaminergic cells by immunofluorescence. NADPH oxidase subunits in N27 cell cultures were detected by immunoblots and RT-PCR. Superoxide was measured by flow cytometric detection of H2O2-induced carboxy-H2-DCFDA fluorescence. Cells were treated with MPP+ (MPTP metabolite) following siRNA silencing of the Nox2-stabilizing subunit p22phox, or simultaneously with NADPH oxidase pharmacological inhibitors or with losartan to antagonize angiotensin II type 1 receptor-induced NADPH oxidase activation.

Results: Nigral dopaminergic neurons in situ expressed three subunits necessary for NADPH oxidase activation, and these as well as several other NADPH oxidase subunits and their encoding mRNAs were detected in unstimulated N27 cells. Overnight MPP+ treatment of N27 cells induced Nox2 protein and superoxide generation, which was counteracted by NADPH oxidase inhibitors, by siRNA silencing of p22phox, or losartan. A two-wave ROS cascade was identified: 1) as a first wave, mitochondrial H2O2 production was first noted at three hours of MPP+ treatment; and 2) as a second wave, H2O2 levels were further increased by 24 hours. This second wave was eliminated by pharmacological inhibitors and a blocker of protein synthesis.

Conclusions: A two-wave cascade of ROS production is active in nigral dopaminergic neurons in response to neurotoxicity-induced superoxide. Our findings allow us to conclude that superoxide generated by NADPH oxidase present in nigral neurons contributes to the loss of such neurons in PD. Losartan suppression of nigral-cell superoxide production suggests that angiotensin receptor blockers have potential as PD preventatives.

Show MeSH
Related in: MedlinePlus