C9 staining in substantia nigra specimens. Fig. 2A: Sta

Complement activation in the Parkinson's disease substantia nigra: an immunocytochemical study.

Loeffler DA, Camp DM, Conant SB -Journal of neuroinflammation(2006)

C9 staining in substantia nigra specimens. Fig. 2A: Staining of multiple Lewy bodies within a melanized neuron in a PD specimen; adjacent melanized neuron (arrow) and its axon are also C9-positive; Fig. 2B: immunoreactivity for C9 in a Lewy body (arrowhead) and in melanin-depleted neurons (arrows) in a different PD specimen; Fig. 2C: staining of melanized neuron (arrow) and its processes in a DLB specimen; Fig 2D: multiple immunoreactive melanized neurons in an aged normal specimen. (Fig. 2A, bar = 10 μm; Figs. 2B–D, bar = 50 μm; immunoreactive structures are dark blue or gray, in contrast to brown melanin and yellow background).

F2:C9 staining in substantia nigra specimens. Fig. 2A: Staining of multiple Lewy bodies within a melanized neuron in a PD specimen; adjacent melanized neuron (arrow) and its axon are also C9-positive; Fig. 2B: immunoreactivity for C9 in a Lewy body (arrowhead) and in melanin-depleted neurons (arrows) in a different PD specimen; Fig. 2C: staining of melanized neuron (arrow) and its processes in a DLB specimen; Fig 2D: multiple immunoreactive melanized neurons in an aged normal specimen. (Fig. 2A, bar = 10 μm; Figs. 2B–D, bar = 50 μm; immunoreactive structures are dark blue or gray, in contrast to brown melanin and yellow background).

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Affiliation:Division of Neurology, William Beaumont Hospital Research Institute, Royal Oak, MI 48073, USA. DLoeffler@beaumont.edu

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Bottom Line:The long-term use of nonsteroidal anti-inflammatory drugs has been associated, in retrospective studies, with decreased risk for PD, suggesting that inflammation may contribute to development of this disorder.C9 immunoreactivity was significantly increased in PD vs.AD specimens, but unlike iC3b, the increased C9 staining in PD and young normal specimens did not achieve statistical significance vs. aged normal specimens. iC3b and C9 staining in PD specimens was not correlated with the numbers of remaining melanized neurons, nor with the duration of PD.

Abstract

Background: Inflammatory processes are increased in the Parkinson's disease (PD) brain. The long-term use of nonsteroidal anti-inflammatory drugs has been associated, in retrospective studies, with decreased risk for PD, suggesting that inflammation may contribute to development of this disorder. The objective of this study was to determine the extent of complement activation, a major inflammatory mechanism, in PD.

Methods: Substantia nigra specimens from young normal subjects (n = 11-13), aged normal subjects (n = 24-28), and subjects with PD (n = 19-20), Alzheimer's disease (AD; n = 12-13), and dementia with Lewy bodies (DLB; n = 9) were stained for iC3b and C9, representing early- and late-stage complement activation, respectively. Numbers of iC3b+, C9+, and total melanized neurons in each section were counted in a blinded fashion. Nonparametric analyses were used to evaluate differences between groups and to evaluate correlations between complement staining, numbers of melanized neurons, and the duration of PD.

Results: Lewy bodies in both PD and DLB specimens stained for iC3b and C9. Staining was also prominent on melanized neurons. The percentage of iC3b+ neurons was significantly increased in PD vs. aged normal and AD specimens, and in young normal vs. aged normal specimens. C9 immunoreactivity was significantly increased in PD vs. AD specimens, but unlike iC3b, the increased C9 staining in PD and young normal specimens did not achieve statistical significance vs. aged normal specimens. iC3b and C9 staining in PD specimens was not correlated with the numbers of remaining melanized neurons, nor with the duration of PD.

Conclusion: Complement activation occurs on Lewy bodies and melanized neurons in the PD substantia nigra. Early complement activation (iC3b) is increased on melanized neurons in PD vs. aged normal specimens, and late-stage complement activation (C9) also tends to increase. This latter finding suggests that complement activation may contribute to loss of dopaminergic neurons in some individuals with PD. Complement activation on melanized neurons appears to decrease with normal aging, suggesting a possible neuroprotective role for this process in the normal substantia nigra.

Mentions

Lewy bodies were immunoreactive for both iC3b (7 of 20 PD specimens, 6 of 9 DLB specimens) and C9 (11 of 19 PD specimens, 9 of 9 DLB specimens). Staining was also detected on melanized neurons (cell bodies, axons, and melanin fragments), occasional non-melanized neurons, glia, and, in AD specimens, senile plaques. In PD specimens, many of the iC3b+ and C9+ melanized neurons had few remaining melanin granules. No cellular staining was present in negative controls, although faint vascular staining was observed in a few specimens. Staining for iC3b and C9 is shown in Figs. 1 and 2, respectively. There was marked variation in the percentages of immunoreactive melanized neurons for different specimens within each group, with little or no staining in some specimens and more than 25% staining in others; staining even exceeded 50% of melanized neurons in a few specimens. Complement immunoreactivity of melanized neurons generally was not localized to a particular sector (lateral, middle, or medial) of the substantia nigra.

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