The chemokines use G protein-coupled receptors to regulate the migratory and proadhesive responses of leukocytes. Based on observations that G protein-coupled receptors undergo heterologous desensitization, we have examined the ability of chemokines to also influence the perception of pain by cross-desensitizing opioid G protein-coupled receptors function in vitro and in vivo. We find that the chemotactic activities of both -and ␦-opioid receptors are desensitized following activation of the chemokine receptors CCR5, CCR2, CCR7, and CXCR4 but not of the CXCR1 or CXCR2 receptors. Furthermore, we also find that pretreatment with RAN-TES͞CCL5, the ligand for CCR1, and CCR5 or SDF-1␣͞CXCL12, the ligand for CXCR4, followed by opioid administration into the periaqueductal gray matter of the brain results in an increased rat tail flick response to a painful stimulus. Because chemokine administration into the periaqueductal gray matter inhibits opioidinduced analgesia, we propose that the activation of proinflammatory chemokine receptors down-regulates the analgesic functions of opioid receptors, and this enhances the perception of pain at inflammatory sites. O pioid and chemokine receptors are members of the G i protein-linked seven-transmembrane receptor family. These receptors, as well as the chemokine and endogenous opioid peptide ligands, are widely distributed in brain tissue and the periphery. Chemokines have been classified into four families: C, CC, CXC, and CX 3 C based on the position of conserved cysteines, and they interact with receptors designated CR1, CCR1-11, CXCR1-5, or CX 3 CR1, respectively (1). Three classes of receptors have been identified for the opioids, designated , , and ␦, and each of the opioid receptor genes expressed in brain tissue and immune cells has been cloned and sequenced (2-7).The -, -, and ␦-opioids are known to have inhibitory effects on both antibody and cellular immune responses (8, 9), natural killer cell activity (10), cytokine expression (11-13), and phagocytic activity (14), which may account for the decreased resistance to infections caused by morphine and heroin administration. Furthermore, pretreatment with opioids, including morphine, heroin, met-enkephalin, the selective -agonist ]enkephalin (DPDPE), leads to the inhibition of the chemotactic response of leukocytes to complement-derived chemotactic factors (15) and to the chemokines macrophage inflammatory protein (MIP-1␣)͞CCL3, regulated on activation normal T cell expressed and secreted (RANTES͞CCL5), monocyte chemotactic protein-1 (MCP-1)͞ CCL2, and IL-8͞CXCL8 (16). The latter results suggest that the activation of the -and ␦-opioid receptors leads to the desensitization of the CC chemokine receptor 2 (CCR2) and CXC chemokine receptors CXCR1 and CXCR2. In fact, the latter two receptors are phosphorylated by prior administration of opioids. Moreover, the inhibition of CCL3 and CCL5 responses following opioid pretreatment is consistent with the desensitization of either CCR1 or CCR5, or both. This receptor crosstalk r...

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Novel insights into the TRPV3mediated itch in atopic dermatitisTo the Editor:Chronic pruritus (itch) is a widespread and debilitating condition associated with dermatologic, systemic, neuropathic, or psychogenic disorders. The pathophysiologic mechanisms underpinning the transduction and potentiation of this refractory pruritus remain unclear. Current therapeutics are largely ineffective. 1 Thus, we have aimed to address this gap in knowledge by specifically focusing on clinically relevant intercellular communication in human skin cells, murine models of acute and chronic itch, and samples from human atopic dermatitis (AD) and psoriasis.In conditions of chronic dermatologic itch such as AD and psoriasis, certain members of the transient receptor potential (TRP) ion channel superfamily play an important role in the propagation of itch signaling. TRP vanilloid channel 3 (TRPV3) is a calcium-permeable cation channel that is abundantly expressed in epidermal keratinocytes. TRPV3 detects warm temperatures (>338C), is gated by a wide range of chemical stimuli, and plays an essential role in skin homeostasis and repair. Heatinduced activation of TRPV3 stimulates the release of a potent itch inducer, thymic stromal lymphopoietin (TSLP), from cultured murine keratinocytes. 2 In mice, intradermal injection of carvacrol, a TRPV3 agonist, elicits scratching behaviors. Gain-of-function mutations in TRPV3 have been confirmed in Olmsted syndrome, a rare pruritic genodermatosis in humans 3 and associated with AD-like inflammation in rodents. TRPV3 is upregulated in the skin of patients with AD. 2 Despite this, much remains unknown about the clinical relevance of TRPV3-linked pathways in human dermatitis and pruritus.Herein, real-time PCR was used to quantify TRPV3 expression in the skin of AD-like protease-activated receptor 2 (PAR2)overexpressing mouse (Grhl3PAR2 /1 mice). The level of TRPV3 transcripts was significantly increased in lesional skin of Grhl3PAR2 /1 mice versus in age-matched wild-type controls (Fig 1, A). Moreover, relative TRPV3 levels were significantly higher in lesional skin of Grhl3PAR2 /1 mice than in nonlesional Grhl3PAR2/ 1 mice (Fig 1, A), suggesting that TRPV3 expression is associated with the severity of dermatitis.Human skin samples were then examined to evaluate the clinical relevance of these murine findings. Specimens were collected from patients with AD (both lesional AD [LAD] and nonlesional AD [NLAD]), from patients with psoriasis (both lesional psoriasis [LPS] and nonlesional psoriasis [NLPS]), and from healthy controls (HC). All were analyzed by RNA sequencing, with data indicating the mean change in transcript level relative to HC. In LAD samples, TRPV3 was the only member of the TRPV family to be upregulated, with transcripts showing greater than a 2-fold increase over the HC levels (Fig 1, B). Similar to our murine model, this upregulation was absent in NLAD skin (Fig 1, C). Levels of TRPV3 transcripts were also increased in LPS skin samples versus in HC skin samples, but not in NLPS sample...

The opiates are well-established immunomodulatory factors, and recent evidence suggests that mu- and delta-opioid receptor ligands alter chemokine-driven chemotactic responses through the process of heterologous desensitization. In the present report, we sought to examine the capacity of mu- and delta-opioids to modulate the function of chemokine receptors CCR5 and CXCR4, the two major human immunodeficiency virus (HIV) coreceptors. We found that the chemotactic responses to the CCR1/5 ligand CCL5/regulated on activation, normal T expressed and secreted, but not the CXCR4 ligand stromal cell-derived factor-1alpha/CXCL12 were inhibited following opioid pretreatment. Studies were performed with primary monocytes and Chinese hamster ovary cells transfected with CCR5 and the micro-opioid receptor to determine whether cross-desensitization of CCR5 was a result of receptor internalization. Using radiolabeled-binding analysis, flow cytometry, and confocal microscopy, we found that the heterologous desensitization of CCR5 was not associated with a significant degree of receptor internalization. Despite this, we found that the cross-desensitization of CCR5 by opioids was associated with a decrease in susceptibility to R5 but not X4 strains of HIV-1. Our findings are consistent with the notion that impairment of the normal signaling activity of CCR5 inhibits HIV-1 coreceptor function. These results have significant implications for our understanding of the effect of opioids on the regulation of leukocyte trafficking in inflammatory disease states and the process of coreceptor-dependent HIV-1 infection. The interference with HIV-1 uptake by heterologous desensitization of CCR5 suggests that HIV-1 interaction with this receptor is not passive but involves a signal transduction process.