Human immunodeficiency virus-1 (HIV-1) infection is associated with numerous effects on the nervous system, including pain and peripheral neuropathies. We now demonstrate that cultured rat dorsal root ganglion (DRG) neurons express a wide variety of chemokine receptors, including those that are thought to act as receptors for the HIV-1 coat protein glycoprotein120 (gp120). Chemokines that activate all of the known chemokine receptors increased [Ca 2ϩ ] i in subsets of cultured DRG cells. Many neurons responded to multiple chemokines and also to bradykinin, ATP, and capsaicin. Immunohistochemical studies demonstrated the expression of the CXCR4 and CCR4 chemokine receptors on populations of DRG neurons that also expressed substance P and the VR1 vanilloid receptor.RT-PCR analysis confirmed the expression of CXCR4, CX3CR1, CCR4, and CCR5 mRNAs in DRG neurons. Chemokines and gp120 produced excitatory effects on DRG neurons and also stimulated the release of substance P. Chemokines and gp120 also produced allodynia after injection into the rat paw. Thus these results provide evidence that chemokines and gp120 may produce painful effects via direct actions on chemokine receptors expressed by nociceptive neurons. Chemokine receptor antagonists may be important therapeutic interventions in the pain that is associated with HIV-1 infection and inflammation.

Osteoarthritis is one of the leading causes of chronic pain, but almost nothing is known about the mechanisms and molecules that mediate osteoarthritis-associated joint pain. Consequently, treatment options remain inadequate and joint replacement is often inevitable. Here, we use a surgical mouse model that captures the long-term progression of knee osteoarthritis to longitudinally assess pain-related behaviors and concomitant changes in the innervating dorsal root ganglia (DRG). We demonstrate that monocyte chemoattractant protein (MCP)-1 (CCL2) and its high-affinity receptor, chemokine (C-C motif) receptor 2 (CCR2), are central to the development of pain associated with knee osteoarthritis. After destabilization of the medial meniscus, mice developed early-onset secondary mechanical allodynia that was maintained for 16 wk. MCP-1 and CCR2 mRNA, protein, and signaling activity were temporarily up-regulated in the innervating DRG at 8 wk after surgery. This result correlated with the presentation of movement-provoked pain behaviors, which were maintained up to 16 wk. Mice that lack Ccr2 also developed mechanical allodynia, but this started to resolve from 8 wk onwards. Despite severe allodynia and structural knee joint damage equal to wild-type mice, Ccr2-null mice did not develop movement-provoked pain behaviors at 8 wk. In wild-type mice, macrophages infiltrated the DRG by 8 wk and this was maintained through 16 wk after surgery. In contrast, macrophage infiltration was not observed in Ccr2-null mice. These observations suggest a key role for the MCP-1/CCR2 pathway in establishing osteoarthritis pain.O steoarthritis is the most common joint disorder and is one of the leading causes of chronic pain (1, 2). Osteoarthritis commonly affects knees, hips, and hands and is characterized by radiographic changes (primarily joint space narrowing, subchondral bone sclerosis, and osteophytes) accompanied by clinical symptoms, most prominently pain. Treatments that alter the progression of the structural damage in the joint are not yet available. Options for treating the pain include nonsteroidal anti-inflammatory drugs, steroids, and viscosupplementation, but analgesia is often inadequate, and uncontrolled pain is the number one reason why people with osteoarthritis undergo joint-replacement surgery (3). Despite the enormous health and economic burden of osteoarthritis and associated pain (4), very few studies have examined the molecular pathways that mediate osteoarthritis pain. As in all types of chronic pain, osteoarthritis pain is the dynamic result of a complex interaction between local tissue damage and inflammation, peripheral and central sensitization, and the brain (5-7). Joint pain associated with osteoarthritis, however, has unique clinical features that provide insight into the mechanisms that cause it. First, joint pain has a strong mechanical component: it is typically triggered by specific activities (for example, climbing stairs elicits knee pain) and is relieved by rest. As structural joint disease advance...

Many studies have shown that transplanted or endogenous neural progenitor cells will migrate toward damaged areas of the brain. However, the mechanism underlying this effect is not clear. Here we report that, using hippocampal slice cultures, grafted neural progenitor cells (NPs) migrate toward areas of neuroinflammation and that chemokines are a major regulator of this process. Migration of NPs was observed after injecting an inflammatory stimulus into the area of the fimbria and transplanting enhanced green fluorescent protein (EGFP)-labeled NPs into the dentate gyrus of cultured hippocampal slices. Three to 7 d after transplantation, EGFP-NPs in control slices showed little tendency to migrate and had differentiated into neurons and glia. In contrast, in slices injected with inflammatory stimuli, EGFP-NPs migrated toward the site of the injection. NPs in these slices also survived less well. The inflammatory stimuli used were a combination of the cytokines tumor necrosis factor-␣ and interferon-␥, the bacterial toxin lipopolysaccharide, the human immunodeficiency virus-1 coat protein glycoprotein 120, or a ␤-amyloid-expressing adenovirus. We showed that these inflammatory stimuli increased the synthesis of numerous chemokines and cytokines by hippocampal slices. When EGFP-NPs from CC chemokine receptor CCR 2 knock-out mice were transplanted into slices, they exhibited little migration toward sites of inflammation. Similarly, wild-type EGFP-NPs exhibited little migration toward inflammatory sites when transplanted into slices prepared from monocyte chemoattractant protein-1 (MCP-1) knock-out mice. These data indicate that factors secreted by sites of neuroinflammation are attractive to neural progenitors and suggest that chemokines such as MCP-1 play an important role in this process.

We previously demonstrated that chemokine receptors are expressed by neural progenitors grown as cultured neurospheres. To examine the significance of these findings for neural progenitor function in vivo, we investigated whether chemokine receptors were expressed by cells having the characteristics of neural progenitors in neurogenic regions of the postnatal brain. Using in situ hybridization we demonstrated the expression of CCR1, CCR2, CCR5, CXCR3, and CXCR4 chemokine receptors by cells in the dentate gyrus (DG), subventricular zone of the lateral ventricle, and olfactory bulb. The pattern of expression for all of these receptors was similar, including regions where neural progenitors normally reside. In addition, we attempted to colocalize chemokine receptors with markers for neural progenitors. In order to do this we used nestin-EGFP and TLXLacZ transgenic mice, as well as labeling for Ki67, a marker for dividing cells. In all three areas of the brain we demonstrated colocalization of chemokine receptors with these three markers in populations of cells. Expression of chemokine receptors by neural progenitors was further confirmed using CXCR4-EGFP BAC transgenic mice. Expression of CXCR4 in the DG included cells that expressed nestin and GFAP as well as cells that appeared to be immature granule neurons expressing PSA-NCAM, calretinin, and Prox-1. CXCR4-expressing cells in the DG were found in close proximity to immature granule neurons that expressed the chemokine SDF-1/CXCL12. Cells expressing CXCR4 frequently coexpressed CCR2 receptors. These data support the hypothesis that chemokine receptors are important in regulating the migration of progenitor cells in postnatal brain. Indexing terms stem cells; development; chemotaxis; brain repairDuring embryogenesis, neural stem/progenitor cells must migrate long distances from the germinal epithelia where they are born to their final destinations (Hatten, 1999;Alvarez-Buylla et al., 2001). During migration, stem cells may continue to divide and also become restricted in terms of their ultimate phenotypes. Thus, the timing of neuro-and gliogenesis in the developing embryo is precisely controlled (Rallu et al., 2002). The factors that determine the migration, proliferation, and differentiation of embryonic stem cells have been widely investigated and numerous factors have been shown to influence these processes (Lindvall et al., 2004). One group of molecules that has recently been shown to control progenitor cell migration in the nervous system are the chemokines (CHEMO-tactic cytoKINES) (Tran and © NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript Miller, 2003). The chemokines are a family of small secreted proteins that are known to be important regulators of leukocyte trafficking under both normal conditions and during inflammatory responses (Moser et al., 2004). Furthermore, it is now known that chemokine signaling has an important role to play in the developing embryo. Deletion of the genes for the CXCR4 chemokine receptor or f...

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