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Research
Phalguni Anand Alladi
National Institute of Mental Health and Neuro Sciences
Corresponding Author
ORCiD: https://orcid.org/0000-0002-2876-3478
License:
This work is licensed under a CC BY 4.0 License. Read Full License
Background
Both astroglia and microglia show region-specific distribution pattern in the central nervous system and often maladapt to age-associated alterations within their niche. Studies on autopsied substantia nigra of Parkinson’s disease (PD) patients and experimental models propose gliosis as a trigger for neuronal loss. Epidemiological studies propose an ethnic bias in PD prevalence, since Caucasians are more susceptible than non-whites living in Asia and Africa. Similarly, different mice strains are variably sensitive to the neurotoxin MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine). We had earlier likened divergent MPTP-sensitivity of C57BL/6J and CD-1 mice with differential susceptibility to PD, based on differences in neuronal numbers.
Methods
Here we examined whether the variable susceptibility was also incumbent to inter-strain differences in the glial features in the substantia nigra pars compacta (SNpc) of C57BL/6J and CD-1 mice. We performed unbiased stereology to quantify iba-1 immunoreactive microglia and s100β immunopositive astroglia on immunohistochemically stained sections. Further, ELISA based estimation of pro- inflammatory and anti-inflammatory cytokines was supplemented with estimation of enzymes like fractalkine, hemeoxygenase, and monoamine oxidases A and B. Electron microscopy was performed to compare the effects on the organelles.
Results
Stereological counts showed more microglia and fewer astrocytes in the substantia nigra of MPTP-susceptible normal C57BL/6J mice, which suggests persistence of an immune-vigilant state. MPTP caused induction of microgliosis and astrogliosis in both strains, suggesting the involvement of these cells in pathogenesis. ELISA of pro-inflammatory cytokines in the ventral-midbrain revealed augmentation of TNF-α and IL-6 at middle-age in both strains that reduced at old-age, suggesting middle-age as a critical, inflamm-aging associated time-point. TNF-α levels were persistently high in C57BL/6J, through aging and post-MPTP; while IL-6 and IL-1β were upregulated at old-age. CD-1 had higher levels of anti-inflammatory cytokine TGF-β. MPTP-challenge caused upregulation of enzymes MAO-A, MAO-B and iNOS in both strains. Post-MPTP enhancement in fractalkine and hemeoxygenase-1, may be neuronal compensatory signals. Lastly, ultrastructural observations of elongated mitochondria in astroglia and microglia vis-à-vis the shrunken ones in neurons, suggest upscaling of their functions with neurotoxic consequences.
Conclusions
Thus, astroglia and microglia play a critical role in modulating aging and the susceptibility of an individual to PD.
Keywords
Parkinson’s disease, 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP), Cytokine ELISA, Neuroinflammation, Monoamine oxidases A&B, Unbiased stereology, C57BL/6J, CD-1 white mice, substantia nigra pars compacta, Fecal microbiome
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A new preprint design is coming!
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This is a preprint, a preliminary version of a manuscript that has not completed peer review at a journal. Research Square does not conduct peer review prior to posting preprints. The posting of a preprint on this server should not be interpreted as an endorsement of its validity or suitability for dissemination as established information or for guiding clinical practice.
Research
Phalguni Anand Alladi
National Institute of Mental Health and Neuro Sciences
Corresponding Author
ORCiD: https://orcid.org/0000-0002-2876-3478
Badges
Prescreen
This manuscript passed our Prescreen assessment
Complete author information
Appropriate declaration statements
Potential risks to human health
Prescreen
History
CURRENT STATUS: Posted
Version 1
Posted 12 Feb, 2021
No community comments so far
Metrics
Comments: 0
PDF Downloads: ...
HTML Views: ...
Subject Areas
Neurobiology of Disease
License:
This work is licensed under a CC BY 4.0 License. Read Full License
Background
Both astroglia and microglia show region-specific distribution pattern in the central nervous system and often maladapt to age-associated alterations within their niche. Studies on autopsied substantia nigra of Parkinson’s disease (PD) patients and experimental models propose gliosis as a trigger for neuronal loss. Epidemiological studies propose an ethnic bias in PD prevalence, since Caucasians are more susceptible than non-whites living in Asia and Africa. Similarly, different mice strains are variably sensitive to the neurotoxin MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine). We had earlier likened divergent MPTP-sensitivity of C57BL/6J and CD-1 mice with differential susceptibility to PD, based on differences in neuronal numbers.
Methods
Here we examined whether the variable susceptibility was also incumbent to inter-strain differences in the glial features in the substantia nigra pars compacta (SNpc) of C57BL/6J and CD-1 mice. We performed unbiased stereology to quantify iba-1 immunoreactive microglia and s100β immunopositive astroglia on immunohistochemically stained sections. Further, ELISA based estimation of pro- inflammatory and anti-inflammatory cytokines was supplemented with estimation of enzymes like fractalkine, hemeoxygenase, and monoamine oxidases A and B. Electron microscopy was performed to compare the effects on the organelles.
Results
Stereological counts showed more microglia and fewer astrocytes in the substantia nigra of MPTP-susceptible normal C57BL/6J mice, which suggests persistence of an immune-vigilant state. MPTP caused induction of microgliosis and astrogliosis in both strains, suggesting the involvement of these cells in pathogenesis. ELISA of pro-inflammatory cytokines in the ventral-midbrain revealed augmentation of TNF-α and IL-6 at middle-age in both strains that reduced at old-age, suggesting middle-age as a critical, inflamm-aging associated time-point. TNF-α levels were persistently high in C57BL/6J, through aging and post-MPTP; while IL-6 and IL-1β were upregulated at old-age. CD-1 had higher levels of anti-inflammatory cytokine TGF-β. MPTP-challenge caused upregulation of enzymes MAO-A, MAO-B and iNOS in both strains. Post-MPTP enhancement in fractalkine and hemeoxygenase-1, may be neuronal compensatory signals. Lastly, ultrastructural observations of elongated mitochondria in astroglia and microglia vis-à-vis the shrunken ones in neurons, suggest upscaling of their functions with neurotoxic consequences.
Conclusions
Thus, astroglia and microglia play a critical role in modulating aging and the susceptibility of an individual to PD.
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 8
Figure 9
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