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. 2013 Jun:54:32-42.
doi: 10.1016/j.nbd.2013.02.010. Epub 2013 Mar 4.

PACAP signaling exerts opposing effects on neuroprotection and neuroinflammation during disease progression in the SOD1(G93A) mouse model of amyotrophic lateral sclerosis

Cornelia Ringer  1 , Luisa-Sybille Büning, Martin K H Schäfer, Lee E Eiden, Eberhard Weihe, Burkhard Schütz
Affiliations

PACAP signaling exerts opposing effects on neuroprotection and neuroinflammation during disease progression in the SOD1(G93A) mouse model of amyotrophic lateral sclerosis

Cornelia Ringer et al. Neurobiol Dis. 2013 Jun.

Abstract

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a pleiotropic peptide with autocrine neuroprotective and paracrine anti-inflammatory properties in various models of acute neuronal damage and neurodegenerative diseases. Therefore, we examined a possible beneficial role of endogenous PACAP in the superoxide dismutase 1, SOD1(G93A), mouse model of amyotrophic lateral sclerosis (ALS), a lethal neurodegenerative disease particularly affecting somatomotor neurons. In wild-type mice, somatomotor and visceromotor neurons in brain stem and spinal cord were found to express the PACAP specific receptor PAC1, but only visceromotor neurons expressed PACAP as a potential autocrine source of regulation of these receptors. In SOD1(G93A) mice, only a small subset of the surviving somatomotor neurons showed induction of PACAP mRNA, and somatomotor neuron degeneration was unchanged in PACAP-deficient SOD1(G93A) mice. Pre-ganglionic sympathetic visceromotor neurons were found to be resistant in SOD1(G93A) mice, while pre-ganglionic parasympathetic neurons degenerated during ALS disease progression in this mouse model. PACAP-deficient SOD1(G93A) mice showed even greater pre-ganglionic parasympathetic neuron loss compared to SOD1(G93A) mice, and additional degeneration of pre-ganglionic sympathetic neurons. Thus, constitutive expression of PACAP and PAC1 may confer neuroprotection to central visceromotor neurons in SOD1(G93A) mice via autocrine pathways. Regarding the progression of neuroinflammation, the switch from amoeboid to hypertrophic microglial phenotype observed in SOD1(G93A) mice was absent in PACAP-deficient SOD1(G93A) mice. Thus, endogenous PACAP may promote microglial cytodestructive functions thought to drive ALS disease progression. This hypothesis was consistent with prolongation of life expectancy and preserved tongue motor function in PACAP-deficient SOD1(G93A) mice, compared to SOD1(G93A) mice. Given the protective role of PACAP expression in visceromotor neurons and the opposing effect on microglial function in SOD1(G93A) mice, both PACAP agonism and antagonism may be promising therapeutic tools for ALS treatment, if stage of disease progression and targeting the specific auto- and paracrine signaling pathways are carefully considered.

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Figures

Fig. 1
Fig. 1
PACAP ligand-receptor systems in wild-type (WT) somatomotor and visceromotor nuclei. (A) Giemsa-stained paramedian section through the caudal brain medulla. X = dorsal nucleus of the vagus nerve (visceromotor) and XII = hypoglossal nucleus (somatomotor). (B–E) Dark-field images from double in situ hybridization histochemistry to simultaneously detect VAChT mRNA (digoxygenin-label, black signals) in combination with PACAP, PAC1, VPAC1, and VPAC2 mRNA (radioactive-label, white dots), respectively. Note the presence of PACAP transcripts in visceromotor neurons, PAC1 in viscero- and somatomotor neurons, VPAC1 in glial cells within these nuclei but absence from both motor neuron pools, and VPAC2 in somatomotor, but not visceromotor neurons. Scale bar in (A) equals 100 μm and accounts for all panels.
Fig. 2
Fig. 2
Induction of PACAP mRNA in single somatomotor neurons at end-stage in SOD1 mice. Double in situ hybridization histochemistry for VAChT mRNA (Digoxigenin-labeled riboprobe, left panels) and PACAP mRNA (radioactive-labeled riboprobe, right panels) on the same section. VAChT labels all somatomotor (facial, VII; hypoglossal, XII) and visceromotor (vagal, X) neurons. At P40 (A, B + E, F), somatomotor neurons in the hypoglossal (XII) and facial (VII) nucleus did not express PACAP (B + F), while all visceromotor neurons of the vagal nucleus (X) displayed uniform PACAP mRNA expression (B). In end-stage SOD1 mice (C, D + G, H), PACAP-expression in X apparently was unchanged (D), and only a few of the remaining somatomotor neurons (arrows) had induced PACAP expression in both XII (D) and VII (H). Scale bar in (A) equals 200 μm and accounts for all panels.
Fig. 3
Fig. 3
Neuropathology of the pre-ganglionic parasympathetic and sympathetic systems in SOD1 mice. (A + B) Giemsa-stained para-median sections through the vagal (X) and hypoglossal (XII) nuclei from P120 WT and end-stage SOD1 mice. The dashed lines indicate the border between the two nuclei. Note vacuolization in the neuropil of end-stage SOD1 mice (B) that is present in both nuclei. (C + D) Giemsa-stained transverse sections of the intermediolateral cell column (IML) in the thoracic spinal cord. In P120 WT mice (C), groups of IML neurons are separated by dense and uniform neuropil. In SOD1 mice at disease end-stage (D), the IML center is characterized by presence of pathologic vacuoles, which have displaced the IML neurons. Scale bar in (A) equals 100 μm and accounts for pictures A + B; scale bar in (C) equals 50 μm and accounts for C + D.
Fig. 4
Fig. 4
Somatomotor and visceromotor neurodegeneration in SOD1 and SOD1:PACAP−/− mice. (A–H) ChAT immunolabeling of the vagal/hypoglossal nuclei (upper panel) and of the IML (lower panel) from end-stage mice. Note ChAT-immunoreactivity surrounding pathologic vacuoles in SOD1-harboring genotypes. Scale bar in (A) equals 100 μm and accounts for pictures (A–D); scale bar in (E) equals 50 μm and accounts for (E–H). (I–K) Quantification of somatomotor hypoglossal (XII), parasympathetic vagal (X) and sympathetic (IML) neurons based on ChAT-immunoreactivities. ***p < 0.001 SOD1 compared to respective WT (WT or PACAP−/−, respectively); ns = no significant difference to respective WT group, or between SOD1 and SOD1:PACAP−/−; # p < 0.05 between SOD1 and SOD1:PACAP−/−.
Fig. 5
Fig. 5
(A) Survival analysis of SOD1 mice, revealing a significant extension of mean life expectancy of SOD1:PACAP−/− mice (139.5 days; n = 16) when compared to SOD1 mice (132.0 days; n = 11; p = 0.0022). Body weight (B) and motor functions (C + D) of all study groups (WT, n = 18; PACAP−/−, n = 12; SOD1, n = 11; and SOD1:PACAP−/−, n = 16) were monitored weekly starting at P49. Data were analyzed by two-way ANOVA with Bonferroni post hoc testing and results shown as means with SEM. Differences between SOD1 and SOD1:PACAP−/− mice at a given age are indicated by asterisks; *p < 0.05; **p < 0.01.
Fig. 6
Fig. 6
Iba1 immunohistochemistry revealing different microglia morphology depending on SOD1 and PACAP genotypes and brain region, respectively. (A, D, G, J) Low magnifications of medullary brain stem. (B, E, H, K) High magnifications of single microglial cells located in the brain stem. (C, F, I, L) High magnifications of single microglial cells located in the motor cortex. In WT (A–C) and PACAP−/− (D–F) mice at P120, microglia showed ramified, resting morphologies, although the processes were hardly visible in the brain stem neuropil. In end-stage SOD1 mice (G–I), microglia in brain stem (G and H) were mostly hypertrophic to degenerating, resulting in weak Iba1 staining. In the cortex (I), microglia exhibited amoeboid morphology. In end-stage SOD1:PACAP−/− animals (J–L), microglia in brain stem (J and K) were strongly labeled by Iba1 and showed a predominantly amoeboid morphology. In the cortex (L), microglia with ramified morphology and clearly visible processes dominated. Scale bar in (A) equals 50 μm and applies to all low magnifications (A, D, G, J), and scale bar in (B) equals 5 μm and applies to all high magnifications (B, C, E, F, H, I, K, L).
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References

    1. Abad C, Tan YV, Lopez R, Nobuta H, Dong H, Phan P, Feng JM, Campagnoni AT, Waschek JA. Vasoactive intestinal peptide loss leads to impaired CNS parenchymal T-cell infiltration and resistance to experimental autoimmune encephalomyelitis. Proc Natl Acad Sci U S A. 2010;107:19555–19560. - PMC - PubMed
    1. Appel SH, Beers DR, Henkel JS. T cell-microglial dialogue in Parkinson’s disease and amyotrophic lateral sclerosis: are we listening? Trends Immunol. 2010;31:7–17. - PMC - PubMed
    1. Arimura A, Somogyvári-Vigh A, Miyata A, Mizuno K, Coy DH, Kitada C. Tissue distribution of PACAP as determined by RIA: highly abundant in the rat brain and testes. Endocrinology. 1991;129:2787–2789. - PubMed
    1. Armstrong BD, Hu Z, Abad C, Yamamoto M, Rodriguez WI, Cheng J, Tam J, Gomariz RP, Patterson PH, Waschek JA. Lymphocyte regulation of neuropeptide gene expression after neuronal injury. J Neurosci Res. 2003;74:240–247. - PubMed
    1. Armstrong BD, Abad C, Chhith S, Cheung-Lau G, Hajji OE, Nobuta H, Waschek JA. Impaired nerve regeneration and enhanced neuroinflammatory response in mice lacking pituitary adenylyl cyclase activating peptide. Neuroscience. 2008;151:63–73. - PMC - PubMed

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