This allodynia created at 3 h and lasted for a lot more than 48 h (Fig

This allodynia created at 3 h and lasted for a lot more than 48 h (Fig

This allodynia created at 3 h and lasted for a lot more than 48 h (Fig.1B). a peptide inhibitor of c-Jun N-terminal kinase (JNK), D-JNKI-1. Of be aware a short publicity of astrocytes to TNF- for a quarter-hour dramatically elevated the appearance and release from the chemokine monocyte chemoattractant proteins-1 (MCP-1), 3 hours after TNF- drawback also, within a JNK-dependent way. In parallel, intrathecal administration of TNF- induced MCP-1 appearance in spinal-cord astrocytes. Specifically, mechanised allodynia induced by TNF–activated astrocytes was reversed by a MCP-1 neutralizing antibody. Finally, pretreatment of astrocytes with MCP-1 siRNA attenuated astrocytes-induced mechanical allodynia. Taken together, our results suggest that activated astrocytes are sufficient to produce persistent pain symptom in na?ve mice by releasing MCP-1. Keywords: TNF-, MCP-1, JNK, astrocytes, central sensitization Introduction Chronic pain, such as nerve injury-induced neuropathic pain, is an unmet clinical challenge (Campbell and Meyer, 2006; Costigan et al., Solifenacin succinate 2009; Dworkin et al., 2003). Chronic pain can manifest as spontaneous pain, such as burning pain, and evoked pain, such as hyperalgesia (increased responsiveness to noxious stimuli). Chronic Rabbit Polyclonal to MYO9B pain is also characterized by allodynia, in particular mechanical allodynia or tactile allodynia, so that normally non-painful low threshold mechanical stimuli can induce painful responses. Mechanical allodynia is usually a cardinal and intractable symptom of chronic pain (Campbell and Meyer, 2006). It is not only produced in the injured region, but also spread to the adjacent non-injured regions and even contralateral side of body parts (Baron, 2009; Campbell et al., 1988). It is generally believed that hyperactivity in the spinal cord pain circuit, i.e. central sensitization, contributes to the generation of mechanical allodynia and spread of pain (Ji et al., 2003; Woolf and Salter, 2000). Recent progress in pain research has pointed to an important role of glial cells in the generation of chronic pain. Many lines of evidence indicate that glial cells such as microglia and astrocytes in the spinal cord become reactive in chronic pain conditions and contribute to the development and maintenance of chronic pain by inducing central sensitization (DeLeo and Yezierski, 2001; Garrison et al., 1994; Ji and Strichartz, 2004; McMahon and Malcangio, 2009; Milligan and Watkins, 2009; Ren and Dubner, 2008; Scholz and Woolf, 2007). Accumulating evidence demonstrates that activation of microglia in the spinal cord induces neuropathic pain by producing Solifenacin succinate proinflammatory cytokines and the brain-derived neurotrophic factor (BDNF) (Coull et al., 2005; Inoue and Tsuda, 2009; Suter et al., 2007; Tsuda et al., 2005; Tsuda et al., 2003). The role Solifenacin succinate of astrocytes in chronic pain and the underlying mechanisms have also been investigated (Ji et al., 2006). Astrocytes are organized in gap junction-coupled networks. They not only transmit Ca2+ signaling in the form of oscillations or waves through the networks (Haydon, 2000), but also form a tripartite synapse with pre- and post-synaptic membranes and through which modulate synaptic strength (Haydon and Carmignoto, 2006; Jourdain et al., 2007). After injuries, reactive astrocytes express the c-Jun-N-terminal kinase (JNK), a member of the mitogen-activated protein kinase (MAPK), and produce the proinflammatory cytokine interleukin-1beta (IL-1) and chemokine MCP-1, enhancing and maintaining central sensitization and chronic pain says (Gao et al., 2009; Guo et al., 2007; Kawasaki et al., 2008a; Kawasaki et al., 2008b; Ren and Dubner, 2008; Zhuang et al., 2006). Spinal injection of ATP-activated microglia has been shown to produce mechanical allodynia via releasing BDNF (Coull et al., 2005; Tsuda et al., 2003). It remains unclear whether and how activated astrocytes are sufficient to induce this persistent pain symptom. Our recent study showed that TNF- induced a dramatic increase of MCP-1 in astrocytes via the activation of JNK (Gao et al., 2009). In this study we further examined whether TNF–activated astrocytes would induce mechanical allodynia by releasing MCP-1. Materials and Methods Animals CD1 mice, obtained from Charles River Laboratories, were used for most experiments. Adult CD1 mice (male, 25C32 g) were used for behavioral studies. Neonatal CD1 mice (P2) were used to prepare primary cultures of astrocytes. TNF receptor (R1/R2) double knockout mice (TNFR1/R2?/?, male, 25C32 g), obtained from Jackson Laboratories, and C57BL/6 wild-type control mice were also used in some experiment. All animal procedures performed in this study were approved by the Animal Care Committee of Harvard Medical School. Reagents TNF- was purchased from R&D. MCP-1 neutralizing antibody and control serum were purchased from Millipore and Invitrogen, respectively. The.