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Regulation of Wnt signaling by nociceptive input in animal models.

Shi Y, Yuan S, Li B, Wang J, Carlton SM, Chung K, Chung JM, Tang SJ - Mol Pain (2012)

Bottom Line: In addition, Wnt3a, a prototypic Wnt ligand that activates the canonical pathway, is also enriched in the superficial layers.Furthermore, Wnt5a, a prototypic Wnt ligand for non-canonical pathways, and its receptor Ror2 are also up-regulated in the SCDH of these models.Our results suggest that Wnt signaling pathways are regulated by nociceptive input.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, TX 77555, USA.

ABSTRACT

Background: Central sensitization-associated synaptic plasticity in the spinal cord dorsal horn (SCDH) critically contributes to the development of chronic pain, but understanding of the underlying molecular pathways is still incomplete. Emerging evidence suggests that Wnt signaling plays a crucial role in regulation of synaptic plasticity. Little is known about the potential function of the Wnt signaling cascades in chronic pain development.

Results: Fluorescent immunostaining results indicate that β-catenin, an essential protein in the canonical Wnt signaling pathway, is expressed in the superficial layers of the mouse SCDH with enrichment at synapses in lamina II. In addition, Wnt3a, a prototypic Wnt ligand that activates the canonical pathway, is also enriched in the superficial layers. Immunoblotting analysis indicates that both Wnt3a a β-catenin are up-regulated in the SCDH of various mouse pain models created by hind-paw injection of capsaicin, intrathecal (i.t.) injection of HIV-gp120 protein or spinal nerve ligation (SNL). Furthermore, Wnt5a, a prototypic Wnt ligand for non-canonical pathways, and its receptor Ror2 are also up-regulated in the SCDH of these models.

Conclusion: Our results suggest that Wnt signaling pathways are regulated by nociceptive input. The activation of Wnt signaling may regulate the expression of spinal central sensitization during the development of acute and chronic pain.

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Spatial distribution of Wnt3a in mouse SCDH.A. Immunostaining of Wnt3a in mouse spinal cord. Wnt3a (red) is detected throughout the entire gray matter, with more intensive label in the superficial laminae of SCDH. B. A merged image of Wnt3a and DAPI signals to show the distribution of Wnt3a-positive cells. C-D. Wnt3a staining (C) and double-staining of Wnt3a and SP (D). Wnt3a staining is observed in the SP-labeled (green) lamina I layer and the deeper regions in the SCDH. E-F. Wnt3a staining (E) and double-staining of Wnt3a and PKCγ (F). Wnt3a staining is detected in PKCγ-labeled (green) lamina II and probably lamina III. Scattered cells with strong Wnt3a staining are also in the deep SCDH laminae (arrows, C-F). Scale bars for A and B: 300 μm; Scale bars for C-F: 100 μm.
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Figure 3: Spatial distribution of Wnt3a in mouse SCDH.A. Immunostaining of Wnt3a in mouse spinal cord. Wnt3a (red) is detected throughout the entire gray matter, with more intensive label in the superficial laminae of SCDH. B. A merged image of Wnt3a and DAPI signals to show the distribution of Wnt3a-positive cells. C-D. Wnt3a staining (C) and double-staining of Wnt3a and SP (D). Wnt3a staining is observed in the SP-labeled (green) lamina I layer and the deeper regions in the SCDH. E-F. Wnt3a staining (E) and double-staining of Wnt3a and PKCγ (F). Wnt3a staining is detected in PKCγ-labeled (green) lamina II and probably lamina III. Scattered cells with strong Wnt3a staining are also in the deep SCDH laminae (arrows, C-F). Scale bars for A and B: 300 μm; Scale bars for C-F: 100 μm.

Mentions: Next, we determined the spatial distribution of Wnt3a, a Wnt ligand that activates the canonical pathway. As shown in Figure 3 A-B, Wnt3a was detected throughout the dorsal horn, with the highest concentration in the superficial layers. In addition, some brightly stained profiles that are likely to be cell bodies in the gray matter were also detected. To determine the spatial distribution of Wnt3a, we double-labeled Wnt3a with SP or PKCγ. The results showed that Wnt3a signals were observed in regions labeled by both SP and PKCγ, indicating that Wnt3a is enriched in the laminae I and II (Figure 3 C-F). Relatively low levels of Wnt3a staining were also observed in deep SCDH layers (Figure 3 E-F). Previous studies demonstrated that Wnt3a was localized in the cell bodies and dendrites in hippocampal neurons [22,33,51]. Similarly, we found that double-staining experiments with NeuN showed that Wnt3a staining was found in NeuN-labeled cell bodies (Figure 4 A1-A2). In addition, the Wnt3a staining outside of cell bodies largely overlapped with that of MAP2, a dendritic marker (Figure 4 B1-B2). Wnt3a staining was not observed in the microglial cells (Figure 4 C1) or astrocytes (Figure 4 D1). The results suggest that Wnt3a protein is largely restricted to neurons, especially in their cell bodies and dendrites. Similarly, Wnt5a protein is also mainly expressed in neurons in the SCDH, while its co-receptor Ror2 in both neurons and astrocytes (submitted).


Regulation of Wnt signaling by nociceptive input in animal models.

Shi Y, Yuan S, Li B, Wang J, Carlton SM, Chung K, Chung JM, Tang SJ - Mol Pain (2012)

Spatial distribution of Wnt3a in mouse SCDH.A. Immunostaining of Wnt3a in mouse spinal cord. Wnt3a (red) is detected throughout the entire gray matter, with more intensive label in the superficial laminae of SCDH. B. A merged image of Wnt3a and DAPI signals to show the distribution of Wnt3a-positive cells. C-D. Wnt3a staining (C) and double-staining of Wnt3a and SP (D). Wnt3a staining is observed in the SP-labeled (green) lamina I layer and the deeper regions in the SCDH. E-F. Wnt3a staining (E) and double-staining of Wnt3a and PKCγ (F). Wnt3a staining is detected in PKCγ-labeled (green) lamina II and probably lamina III. Scattered cells with strong Wnt3a staining are also in the deep SCDH laminae (arrows, C-F). Scale bars for A and B: 300 μm; Scale bars for C-F: 100 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Figure 3: Spatial distribution of Wnt3a in mouse SCDH.A. Immunostaining of Wnt3a in mouse spinal cord. Wnt3a (red) is detected throughout the entire gray matter, with more intensive label in the superficial laminae of SCDH. B. A merged image of Wnt3a and DAPI signals to show the distribution of Wnt3a-positive cells. C-D. Wnt3a staining (C) and double-staining of Wnt3a and SP (D). Wnt3a staining is observed in the SP-labeled (green) lamina I layer and the deeper regions in the SCDH. E-F. Wnt3a staining (E) and double-staining of Wnt3a and PKCγ (F). Wnt3a staining is detected in PKCγ-labeled (green) lamina II and probably lamina III. Scattered cells with strong Wnt3a staining are also in the deep SCDH laminae (arrows, C-F). Scale bars for A and B: 300 μm; Scale bars for C-F: 100 μm.
Mentions: Next, we determined the spatial distribution of Wnt3a, a Wnt ligand that activates the canonical pathway. As shown in Figure 3 A-B, Wnt3a was detected throughout the dorsal horn, with the highest concentration in the superficial layers. In addition, some brightly stained profiles that are likely to be cell bodies in the gray matter were also detected. To determine the spatial distribution of Wnt3a, we double-labeled Wnt3a with SP or PKCγ. The results showed that Wnt3a signals were observed in regions labeled by both SP and PKCγ, indicating that Wnt3a is enriched in the laminae I and II (Figure 3 C-F). Relatively low levels of Wnt3a staining were also observed in deep SCDH layers (Figure 3 E-F). Previous studies demonstrated that Wnt3a was localized in the cell bodies and dendrites in hippocampal neurons [22,33,51]. Similarly, we found that double-staining experiments with NeuN showed that Wnt3a staining was found in NeuN-labeled cell bodies (Figure 4 A1-A2). In addition, the Wnt3a staining outside of cell bodies largely overlapped with that of MAP2, a dendritic marker (Figure 4 B1-B2). Wnt3a staining was not observed in the microglial cells (Figure 4 C1) or astrocytes (Figure 4 D1). The results suggest that Wnt3a protein is largely restricted to neurons, especially in their cell bodies and dendrites. Similarly, Wnt5a protein is also mainly expressed in neurons in the SCDH, while its co-receptor Ror2 in both neurons and astrocytes (submitted).

Bottom Line: In addition, Wnt3a, a prototypic Wnt ligand that activates the canonical pathway, is also enriched in the superficial layers.Furthermore, Wnt5a, a prototypic Wnt ligand for non-canonical pathways, and its receptor Ror2 are also up-regulated in the SCDH of these models.Our results suggest that Wnt signaling pathways are regulated by nociceptive input.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, TX 77555, USA.

ABSTRACT

Background: Central sensitization-associated synaptic plasticity in the spinal cord dorsal horn (SCDH) critically contributes to the development of chronic pain, but understanding of the underlying molecular pathways is still incomplete. Emerging evidence suggests that Wnt signaling plays a crucial role in regulation of synaptic plasticity. Little is known about the potential function of the Wnt signaling cascades in chronic pain development.

Results: Fluorescent immunostaining results indicate that β-catenin, an essential protein in the canonical Wnt signaling pathway, is expressed in the superficial layers of the mouse SCDH with enrichment at synapses in lamina II. In addition, Wnt3a, a prototypic Wnt ligand that activates the canonical pathway, is also enriched in the superficial layers. Immunoblotting analysis indicates that both Wnt3a a β-catenin are up-regulated in the SCDH of various mouse pain models created by hind-paw injection of capsaicin, intrathecal (i.t.) injection of HIV-gp120 protein or spinal nerve ligation (SNL). Furthermore, Wnt5a, a prototypic Wnt ligand for non-canonical pathways, and its receptor Ror2 are also up-regulated in the SCDH of these models.

Conclusion: Our results suggest that Wnt signaling pathways are regulated by nociceptive input. The activation of Wnt signaling may regulate the expression of spinal central sensitization during the development of acute and chronic pain.

Show MeSH
Related in: MedlinePlus