[Influence of P2Y12 receptor inhibitor on pain threshold and spinal p38MAPK in rat bone cancer pain model].

Abstract

OBJECTIVE:

To investigate the role of P2Y12 receptor in rat bone cancer pain model and its influence on p38MAPK (Mitogen-activated protein kinase).

METHOD:

A total of forty female SD rats, weighting 200 - 250 g, were randomly divided into 5 groups (n = 8): normal group (group N), sham group (group S), vehicle group (group DA), cancer group (group A), and analgesia group (group MA). Rats in group N were untreated, rats in group S were injected with Hank's solution 10 µl into the left tibial metaphysis; rats in group DA, group A and group MA were injected with Walker 256 cancer cells (10 µl, 2×10⁷ cells/ml) into the left tibial metaphysic to establish the model of bone cancer pain. Catheterization was simultaneously made in four groups between L3 and L4 vertebra except group N. Saline (0.9%, 15 µl) was injected in group S and group A, DMSO (5%, 15 µl) was injected in group DA, and MRS2395 (400 pmol/µl, 15 µl) was injected in group MA on day 9 to 12 post-inoculation. Mechanical withdrawal thresholds were measured on left hind paw before and every 10 min after intrathecal injection. Rats were euthanized after measuring mechanical withdrawal threshold at day 12 post-inoculation. L4-6 sections of spinal cord were collected to determine the expression of p-p38MAPK by immunohistochemistry and immunofluorescent.

RESULT:

Compared to that in group N (36.1 g ± 4.0 g) and group S (38.9 g ± 5.2 g), mechanical withdrawal thresholds in group MA (19.8 g ± 5.0 g) were decreased on day 9 post-inoculation (P < 0.01), and the expression of p-p38MAPK in spinal cord was increased on day 12 (P < 0.01). Compared to that in group DA (17.7 g ± 3.0 g) and group A (19.1 g ± 2.5 g), mechanical withdrawal threshold in group MA was obviously increased after intrathecal injection, peaked at (26.5 g ± 4.7 g) (P < 0.05); compared with group DA (number 43.4 ± 3.8, IOD 569 ± 27) and group A(number 45.0 ± 2.6, IOD 594 ± 22), the expression level of p-p38MAPK in spinal cord in group MA at day 12 was significantly decreased (number 20.9 ± 2.2, IOD 246 ± 25) (P < 0.01); Mechanical withdrawal threshold in group MA was still lower than group N and group S, while the expression of p-p38MAPK was higher than group N (number 9.9 ± 2.4, IOD 82 ± 28) and group S (number 10.9 ± 2.2, IOD 109 ± 25) (P < 0.01). Immunofluorescent showed that p-p38MAPK was colocalized with microglia in spinal dorsal horn, but not with neurons and astrocytes.

CONCLUSIONS:

These results demonstrate rat bone cancer pain could partially relieved after intrathecal injection of P2Y12 receptor inhibitor MRS2395 through inhibiting the phosphorylation of p38MAPK in spinal dorsal horn.

• Authors: Yan-li Zhu, Ming-juan Liu, Hua-dong Ni, Ming Yao, Bing Huang, Xu-yan Zhou, Jian-liang Sun, Qing-quan Lian
• Journal: Zhonghua yi xue za zhi (Zhonghua Yi Xue Za Zhi) Vol. 92 Issue 39 Pg. 2785-8 (Oct 23 2012) ISSN: 0376-2491 [Print] China
• PMID: 23290170 (Publication Type: English Abstract, Journal Article, Research Support, U.S. Gov't, Non-P.H.S.)

Chemical References

• 2,2-dimethylpropionic acid 3-(2-chloro-6-methylaminopurin-9-yl)-2-(2,2-dimethylpropionyloxymethyl)propyl ester
• Purinergic P2Y Receptor Antagonists
• Valerates
• p38 Mitogen-Activated Protein Kinases
• Adenine

Topics

• Adenine (analogs & derivatives, pharmacology)
• Animals
• Bone Neoplasms (metabolism, physiopathology)
• Disease Models, Animal
• Female
• Pain (drug therapy, metabolism, physiopathology)
• Pain Threshold
• Purinergic P2Y Receptor Antagonists (pharmacology)
• Rats
• Rats, Sprague-Dawley
• Spinal Cord (metabolism)
• Valerates (pharmacology)
• p38 Mitogen-Activated Protein Kinases (metabolism)