RhoA/ROCK pathway mediates p38 MAPK activation and morphological changes downstream of P2Y12/13 receptors in spinal microglia in neuropathic pain

• Published in: Glia Vol. 63; no. 2; pp. 216 - 228
• Main Authors: Tatsumi, Emiko, Yamanaka, Hiroki, Kobayashi, Kimiko, Yagi, Hideshi, Sakagami, Masafumi, Noguchi, Koichi
• Format: Journal Article
• Language: English
• Published: United States Blackwell Publishing Ltd 01.02.2015; Wiley Subscription Services, Inc
• Subjects: Adenosine Diphosphate - analogs & derivatives; Adenosine Diphosphate - toxicity; Animals; Calcium-Binding Proteins - metabolism; chronic pain; Disease Models, Animal; Enzyme Inhibitors - pharmacology; glial activation; Hyperalgesia - etiology; intracellular signaling cascade; Kinases; Male; Microfilament Proteins - metabolism; Microglia - drug effects; Microglia - metabolism; Microglia - pathology; Morphology; Neuralgia - pathology; P2 receptors; p38 Mitogen-Activated Protein Kinases - metabolism; Pain management; Pain Threshold - drug effects; Pain Threshold - physiology; peripheral nerve injury; Phosphorylation; Phosphorylation - drug effects; Purinergic P2Y Receptor Agonists - pharmacology; Purinergic P2Y Receptor Antagonists - pharmacology; Rats; Rats, Sprague-Dawley; Receptors, Purinergic P2Y - metabolism; rhoA GTP-Binding Protein - metabolism; Rodents; Signal Transduction - drug effects; Signal Transduction - physiology; Spinal Cord - drug effects; Spinal Cord - pathology; Spinal Cord Injuries - chemically induced; Spinal Cord Injuries - complications; Thionucleotides - toxicity; chronic pain; peripheral nerve injury; P2 receptors; intracellular signaling cascade; glial activation
• ISSN: 0894-1491; 1098-1136
• DOI: 10.1002/glia.22745

Recent studies have indicated an important role of ATP receptors in spinal microglia, such as P2Y12 or P2Y13, in the development of chronic pain. However, intracellular signaling cascade of these receptors have not been clearly elucidated. We found that intrathecal injection of 2‐(methylthio)adenosine 5′‐diphosphate (2Me‐SADP) induced mechanical hypersensitivity and p38 mitogen‐activated protein kinase (MAPK) phosphorylation in the spinal cord. Intrathecal administration of P2Y12/P2Y13 antagonists and Rho‐associated coiled‐coil‐containing protein kinase (ROCK) inhibitor H1152 suppressed not only p38 MAPK phosphorylation, but also mechanical hypersensitivity induced by 2Me‐SADP. In the rat peripheral nerve injury model, intrathecal administration of antagonists for the P2Y12/P2Y13 receptor suppressed activation of p38 MAPK in the spinal cord. In addition, subarachnoidal injection of H1152 also attenuated nerve injury‐induced spinal p38 MAPK phosphorylation and neuropathic pain behavior, suggesting an essential role of ROCK in nerve injury‐induced p38 MAPK activation. We also found that the antagonists of the P2Y12/P2Y13 receptor and H1152 had inhibitory effects on the morphological changes of microglia such as retraction of processes in both 2Me‐SADP and nerve injured rats. In contrast these treatments had no effect on the number of Iba1‐positive cells in the nerve injury model. Collectively, our results have demonstrated roles of ROCK in the spinal microglia that is involved in p38 MAPK activation and the morphological changes. Inhibition of ROCK signaling may offer a novel target for the development of a neuropathic pain treatment. GLIA 2015;63:216–228 Main Points ROCK inhibitor suppressed not only p38 MAPK phosphorylation, but also pain behavior induced by 2Me‐SADP and in a neuropathic pain model. ROCK in the spinal microglia is involved in p38 MAPK activation and the morphological changes in microglia.