Limits...
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.

Show MeSH

Related in: MedlinePlus

Spatial distribution of β-catenin in normal mouse SCDH.A1-A2: Double-staining of β-catenin and SP, a marker of lamina I and outer layer of lamina II. A1. Low power images. β-catenin is detected in the gray matter of the spinal cord. In the SCDH, β-catenin displays a predominant band. A2. Higher power images of the β-catenin and SP staining in the superficial layers of the SCDH. Relatively moderate levels of β-catenin staining are detected in SP-marked layer I (I). A band with intensive β-catenin staining is observed mainly in lamina II, which partially overlaps the SP-stained outer layer of lamina II (IIo). B1-B2. Double-staining of β-catenin and IB4, a marker of the outer layer of lamina II. B1. Low power images. B2. Higher power images of the β-catenin and IB4 staining in the superficial layers of the SCDH. The outer half of the β-catenin band overlaps with IB4 (IIo), while the inner half (IIi) does not. C1-C2: Double-staining of β-catenin and PKCγ, a marker of the inner layer of lamina II (IIi). C1. Low power images. C2. Higher power images of the β-catenin and PKCγ staining in the superficial layers of the SCDH. The inner half of the β-catenin band overlaps with PKCγ. Scale bar for A1, B1 and C1: 300 μm; Scale bar for A2, B2 and C2: 50 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3472283&req=5

Figure 1: Spatial distribution of β-catenin in normal mouse SCDH.A1-A2: Double-staining of β-catenin and SP, a marker of lamina I and outer layer of lamina II. A1. Low power images. β-catenin is detected in the gray matter of the spinal cord. In the SCDH, β-catenin displays a predominant band. A2. Higher power images of the β-catenin and SP staining in the superficial layers of the SCDH. Relatively moderate levels of β-catenin staining are detected in SP-marked layer I (I). A band with intensive β-catenin staining is observed mainly in lamina II, which partially overlaps the SP-stained outer layer of lamina II (IIo). B1-B2. Double-staining of β-catenin and IB4, a marker of the outer layer of lamina II. B1. Low power images. B2. Higher power images of the β-catenin and IB4 staining in the superficial layers of the SCDH. The outer half of the β-catenin band overlaps with IB4 (IIo), while the inner half (IIi) does not. C1-C2: Double-staining of β-catenin and PKCγ, a marker of the inner layer of lamina II (IIi). C1. Low power images. C2. Higher power images of the β-catenin and PKCγ staining in the superficial layers of the SCDH. The inner half of the β-catenin band overlaps with PKCγ. Scale bar for A1, B1 and C1: 300 μm; Scale bar for A2, B2 and C2: 50 μm.

Mentions: Because the Wnt/β-catenin pathway plays important roles in synaptic plasticity such as long-term potentiation (LTP) [22,33], we were interested in testing if this pathway is involved in the regulation of central sensitization. As an initial step toward this goal, we performed fluorescent immunostaining in naïve mice to determine the spinal distribution of β-catenin and Wnt3a, two signaling proteins in the canonical pathway. We observed that β-catenin immunostaining formed a predominant band in the dorsal horn, although a low level of signal was detected throughout the gray matter of the spinal cord (Figure 1). To define further the laminar distribution of the protein in the SCDH, we used molecular markers to label the specific layers of the dorsal horn. We found that β-catenin was enriched in lamina II, both the inner (IIi) and outer (IIo) segments (Figure 1), while its staining in lamina I was relatively low (Figure 1 A1-2). Staining for isolectin B4 (IB4) and PKCγ, considered as specific markers for the outer and inner segments of lamina II, respectively, confirmed the presence of β-catenin in both the lamina IIi and IIo (Figure 1 B1-2 and C1-2). These observations indicate that the β-catenin is enriched in lamina II of the SCDH. Previous studies revealed that β-catenin is expressed in hippocampal neurons [33]. We performed double-staining experiments, using NeuN to label neuronal cell bodies. As shown in Figure 2 A-C, label for β-catenin in lamina II was observed in regions surrounding neuronal nuclei labeled by NeuN, indicating that the majority of β-catenin was in neuronal cytoplasm. On the other hand, β-catenin staining in non-neuronal cell bodies (NeuN-negative; DAPI-labeled) was detectable but relatively low.


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 β-catenin in normal mouse SCDH.A1-A2: Double-staining of β-catenin and SP, a marker of lamina I and outer layer of lamina II. A1. Low power images. β-catenin is detected in the gray matter of the spinal cord. In the SCDH, β-catenin displays a predominant band. A2. Higher power images of the β-catenin and SP staining in the superficial layers of the SCDH. Relatively moderate levels of β-catenin staining are detected in SP-marked layer I (I). A band with intensive β-catenin staining is observed mainly in lamina II, which partially overlaps the SP-stained outer layer of lamina II (IIo). B1-B2. Double-staining of β-catenin and IB4, a marker of the outer layer of lamina II. B1. Low power images. B2. Higher power images of the β-catenin and IB4 staining in the superficial layers of the SCDH. The outer half of the β-catenin band overlaps with IB4 (IIo), while the inner half (IIi) does not. C1-C2: Double-staining of β-catenin and PKCγ, a marker of the inner layer of lamina II (IIi). C1. Low power images. C2. Higher power images of the β-catenin and PKCγ staining in the superficial layers of the SCDH. The inner half of the β-catenin band overlaps with PKCγ. Scale bar for A1, B1 and C1: 300 μm; Scale bar for A2, B2 and C2: 50 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3472283&req=5

Figure 1: Spatial distribution of β-catenin in normal mouse SCDH.A1-A2: Double-staining of β-catenin and SP, a marker of lamina I and outer layer of lamina II. A1. Low power images. β-catenin is detected in the gray matter of the spinal cord. In the SCDH, β-catenin displays a predominant band. A2. Higher power images of the β-catenin and SP staining in the superficial layers of the SCDH. Relatively moderate levels of β-catenin staining are detected in SP-marked layer I (I). A band with intensive β-catenin staining is observed mainly in lamina II, which partially overlaps the SP-stained outer layer of lamina II (IIo). B1-B2. Double-staining of β-catenin and IB4, a marker of the outer layer of lamina II. B1. Low power images. B2. Higher power images of the β-catenin and IB4 staining in the superficial layers of the SCDH. The outer half of the β-catenin band overlaps with IB4 (IIo), while the inner half (IIi) does not. C1-C2: Double-staining of β-catenin and PKCγ, a marker of the inner layer of lamina II (IIi). C1. Low power images. C2. Higher power images of the β-catenin and PKCγ staining in the superficial layers of the SCDH. The inner half of the β-catenin band overlaps with PKCγ. Scale bar for A1, B1 and C1: 300 μm; Scale bar for A2, B2 and C2: 50 μm.
Mentions: Because the Wnt/β-catenin pathway plays important roles in synaptic plasticity such as long-term potentiation (LTP) [22,33], we were interested in testing if this pathway is involved in the regulation of central sensitization. As an initial step toward this goal, we performed fluorescent immunostaining in naïve mice to determine the spinal distribution of β-catenin and Wnt3a, two signaling proteins in the canonical pathway. We observed that β-catenin immunostaining formed a predominant band in the dorsal horn, although a low level of signal was detected throughout the gray matter of the spinal cord (Figure 1). To define further the laminar distribution of the protein in the SCDH, we used molecular markers to label the specific layers of the dorsal horn. We found that β-catenin was enriched in lamina II, both the inner (IIi) and outer (IIo) segments (Figure 1), while its staining in lamina I was relatively low (Figure 1 A1-2). Staining for isolectin B4 (IB4) and PKCγ, considered as specific markers for the outer and inner segments of lamina II, respectively, confirmed the presence of β-catenin in both the lamina IIi and IIo (Figure 1 B1-2 and C1-2). These observations indicate that the β-catenin is enriched in lamina II of the SCDH. Previous studies revealed that β-catenin is expressed in hippocampal neurons [33]. We performed double-staining experiments, using NeuN to label neuronal cell bodies. As shown in Figure 2 A-C, label for β-catenin in lamina II was observed in regions surrounding neuronal nuclei labeled by NeuN, indicating that the majority of β-catenin was in neuronal cytoplasm. On the other hand, β-catenin staining in non-neuronal cell bodies (NeuN-negative; DAPI-labeled) was detectable but relatively low.

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