Dexmedetomidine attenuates P2X4 and NLRP3 expression in the spine of rats with diabetic neuropathic pain.

PURPOSE: To evaluate the effects of Dexmedetomidine (Dex) on spinal pathology and inflammatory factor in a rat model of Diabetic neuropathic pain (DNP). METHODS: The rats were divided into 3 groups (eight in each group): normal group (N group), diabetic neuropathic pain model group (DNP group), and DNP model with dexmedetomidine (Dex group). The rat model of diabetes was established with intraperitoneal streptozotocin (STZ) injections. Nerve cell ultrastructure was evaluated with transmission electron microscopy (TEM). The mechanical withdrawal threshold (MWT) and motor nerve conduction velocity (MNCV) tests documented that DNP rat model was characterized by a decreased pain threshold and nerve conduction velocity. RESULTS: Dex restored the phenotype of neurocytes, reduced the extent of demyelination and improved MWT and MNCV of DNP-treated rats (P=0.01, P=0.038, respectively). The expression of three pain-and inflammation-associated factors (P2X4, NLRP3, and IL-IP) was significantly upregulated at the protein level in DNP rats, and this change was reversed by Dex administration (P=0.0022, P=0.0092, P=0.0028, respectively). CONCLUSION: The P2X4/NLRP3 signaling pathway is implicated in the development and presence of DNP in vivo, and Dex protects from this disorder.

Dexmedetomidine attenuates P2X4 and NLRP3 expression in the spine of rats with diabetic neuropathic pain

Abstract Purpose: To evaluate the effects of Dexmedetomidine (Dex) on spinal pathology and inflammatory factor in a rat model of Diabetic neuropathic pain (DNP). Methods: The rats were divided into 3 groups (eight in each group): normal group (N group), diabetic neuropathic pain model group (DNP group), and DNP model with dexmedetomidine (Dex group). The rat model of diabetes was established with intraperitoneal streptozotocin (STZ) injections. Nerve cell ultrastructure was evaluated with transmission electron microscopy (TEM). The mechanical withdrawal threshold (MWT) and motor nerve conduction velocity (MNCV) tests documented that DNP rat model was characterized by a decreased pain threshold and nerve conduction velocity. Results: Dex restored the phenotype of neurocytes, reduced the extent of demyelination and improved MWT and MNCV of DNP-treated rats (P=0.01, P=0.038, respectively). The expression of three pain-and inflammation-associated factors (P2X4, NLRP3, and IL-IP) was significantly upregulated at the protein level in DNP rats, and this change was reversed by Dex administration (P=0.0022, P=0.0092, P=0.0028, respectively). Conclusion: The P2X4/NLRP3 signaling pathway is implicated in the development and presence of DNP in vivo, and Dex protects from this disorder.

Evidence for detection of rat P2X4 receptor expressed on cells by generating monoclonal antibodies recognizing the native structure.

P2X purinergic receptors are ATP-driven ionic channels expressed as trimers and showing various functions. A subtype, the P2X4 receptor present on microglial cells is highly involved in neuropathic pain. In this study, in order to prepare antibodies recognizing the native structure of rat P2X4 (rP2X4) receptor, we immunized mice with rP2X4's head domain (rHD, Gln111-Val167), which possesses an intact structure stabilized by S-S bond formation (Igawa and Abe et al. FEBS Lett. 2015), as an antigen. We generated five monoclonal antibodies with the ability to recognize the native structure of its head domain, stabilized by S-S bond formation. Site-directed mutagenesis revealed that Asn127 and Asp131 of the rHD, in which combination of these amino acid residues is only conserved in P2X4 receptor among P2X family, were closely involved in the interaction between rHD and these antibodies. We also demonstrated the antibodies obtained here could detect rP2X4 receptor expressed in 1321N1 human astrocytoma cells.

Ionotropic Purinergic Receptors P2X4 and P2X7: Proviral or Antiviral? An Insight into P2X Receptor Signaling and Hepatitis C Virus Infection.

Purinergic P2X receptors are plasma membrane bound, ATP-gated ion channels that are expressed on wide range of cells and respond to varying ATP concentrations in extracellular environment. Upon activation they increase membrane permeability for Ca(2+) ions and trigger a cascade of signaling complexes. During the course of hepatitis C virus (HCV) infection, ATP is released from the infected hepatocyte, which binds with Purinergic receptors (P2X) on peripheral blood mononuclear cells (PBMCs) and initiate downstream signaling pathways by disturbing the ionic balance of the cell. The present study investigates quantitative expression of P2X7 and P2X4 along with selected host genes PEPCK, transforming growth factor ß (TGF-ß), MAPK, Rho, and Akt in PBMCs of chronic HCV infection patients. PBMCs were isolated from collected blood samples of study subjects. Transcript analysis of P2X7, P2X4, and targeted downstream genes was done using quantitative real-time polymerase chain reaction. Relative expression analysis was performed by unpaired Student's t test on GraphPad Prism version 5. We found a notable increase of threefolds and 1.8-folds in the expression of P2X7 and P2X4 receptors in treatment naïve category while the expression of PEPCK, TGF-ß, MAPK, AKT, and Rho A increased by 2.8, 1.9, 2.2, 2.2, and 1.8-folds, respectively. In sustained virological response patients, P2X7 significantly increased up to 3.5-folds while the expression of P2X4 receptor was increased up to twofold. In third category, treatment nonresponder, the expression of P2X7, P2X4 receptors, and targeted markers remained un-altered. This study deals with two major aspects of P2X4 and P2X7 receptors in PBMCs of chronic HCV individuals. One is their role in providing antiviral immunity to host against HCV; second aspect is the role of P2X receptors in inducing HCV pathogenesis via AKT, TGF-ß, Rho A, PEPCK, and MAPK expression.

ATP release and autocrine signaling through P2X4 receptors regulate γδ T cell activation.

Purinergic signaling plays a key role in a variety of physiological functions, including regulation of immune responses. Conventional αß T cells release ATP upon TCR cross-linking; ATP binds to purinergic receptors expressed by these cells and triggers T cell activation in an autocrine and paracrine manner. Here, we studied whether similar purinergic signaling pathways also operate in the "unconventional" γδ T lymphocytes. We observed that γδ T cells purified from peripheral human blood rapidly release ATP upon in vitro stimulation with anti-CD3/CD28-coated beads or IPP. Pretreatment of γδ T cells with (10)panx-1, CBX, or Bf A reversed the stimulation-induced increase in extracellular ATP concentration, indicating that panx-1, connexin hemichannels, and vesicular exocytosis contribute to the controlled release of cellular ATP. Blockade of ATP release with (10)panx-1 inhibited Ca(2+) signaling in response to TCR stimulation. qPCR revealed that γδ T cells predominantly express purinergic receptor subtypes A2a, P2X1, P2X4, P2X7, and P2Y11. We found that pharmacological inhibition of P2X4 receptors with TNP-ATP inhibited transcriptional up-regulation of TNF-α and IFN-γ in γδ T cells stimulated with anti-CD3/CD28-coated beads or IPP. Our data thus indicate that purinergic signaling via P2X4 receptors plays an important role in orchestrating the functional response of circulating human γδ T cells.