Spatial and temporal analysis of nociception-related spinal cord matrix metalloproteinase expression in a murine neuropathic pain model.

BACKGROUND: Although the mammalian central nervous system contains numerous matrix metalloproteinases (MMPs), the significance of each MMP relative to nociception remains obscure. Working from the hypothesis that MMPs may be involved in activity-dependent reorganization during neuronal modulation, we explored the role of each MMP following neuropathological injury by establishing MMP expression profiles in a murine model for neuropathic pain. METHODS: Sciatic nerves of adult male C57BL/6C mice were partially ligated, and their responses to mechanical and radiant heat stimulations were observed at 1, 3, 7, and 14 days. The expression of several nociception-related MMPs (MMP-2, MMP-9, MMP-12, MMP-17, and MMP-24) in the spinal cord was detected by immunohistochemical analysis, Western blotting, and real-time polymerase chain reaction. In addition, the potential of GM6001, a general inhibitor of MMP peritoneal administration, to modulate nociceptive pain responses in a chronic neuropathic pain model in mice was also investigated. RESULTS: MMP-2, 9, 17, and 24, but not MMP-12, were expressed in the murine spinal cord. MMP-9 was constitutively expressed in neurons and microglial cells, immediately upregulated after nerve injury, and returned to baseline levels at day 3. Expression of MMP-2, MMP-17, and MMP-24 gradually increased after nerve injury. Morphologically, MMP-2-positive cells were glial-like cells. MMP-17 and MMP-24 expression was widespread in gray matter, neurons, and microglial cells, and concentrated in the marginal zone of the dorsal horn and in small capillaries. Peritoneal administration of GM6001 resulted in significantly attenuated thermal hyperalgesia and tactile allodynia induced by nerve injury. CONCLUSION: Expression of several nociception-related MMPs was differentially regulated both temporally and spatially following nerve injury. These results suggest that neuronal remodeling requires concerted expression of particular MMPs in specific temporal and spatial patterns, which may be necessary for neuronal plasticity and/or recovery.

Peritoneal administration of Met-RANTES attenuates inflammatory and nociceptive responses in a murine neuropathic pain model.

UNLABELLED: The C-C motif chemokine ligand 5 (CCL5; also known as regulated on activation, normal T expressed and secreted, or RANTES) is a member of the CC family of chemokines that specifically attract and activate leukocytes to sites of inflammation. Although CCL5 has been implicated in the processing of pain, its detailed mechanisms of action are still unknown. In this study, we investigated the potential of the Met-RANTES, a selective CCL5 receptor antagonist, via peritoneal administration to modulate the recruitment of inflammatory cells in injured sites and attenuate nociceptive responses in a neuropathic pain model in mice. Nociceptive sensitization, immune cell infiltration, multiple cytokine secretion, and opioid peptide expression in damaged nerves were studied. Our results indicated that Met-RANTES-treated mice had less behavioral hypersensitivity after partial sciatic nerve ligation. Macrophage infiltration, pro-inflammatory cytokine (TNFα, IL-1ß, IL-6, and IFNγ) protein secretion, and enkephalin, ß-endorphin, and dynorphin mRNA expression in damaged nerves following partial sciatic nerve ligation were significantly decreased, and anti-inflammatory cytokine (IL-10) protein was significantly increased in Met-RANTES-treated mice. These results suggest that CCL5 is capable of regulating the microenvironment that controls behavioral hypersensitivity at the level of the peripheral injured site in a murine chronic neuropathic pain model. PERSPECTIVE: The present study identifies the potent pro-inflammatory potential of CCL5 and verifies the possible role of selective CCL5 receptor inhibitor in a murine neuropathic pain model.

Absence of C-C motif chemokine ligand 5 in mice leads to decreased local macrophage recruitment and behavioral hypersensitivity in a murine neuropathic pain model.

Accumulated evidence suggests that the C-C motif chemokine ligand 5 (CCL5) modulates migration of inflammatory cells in several pathological conditions. This study tested the hypothesis that lack of CCL5 would modulate the recruitment of inflammatory cells to painful, inflamed sites and could attenuate pain in a murine chronic neuropathic pain model. Nociceptive sensitization, immune cell infiltration, multiple cytokine expression, and opioid peptide expression in damaged nerves were studied in wild-type (CCL5 +/+) and CCL5-deficient (CCL5 -/-) mice after partial sciatic nerve ligation (PSNL). Results indicated that CCL5 -/- mice had less behavioral hypersensitivity after PSNL. Macrophage infiltration and proinflammatory cytokines (tumor necrosis factor-α, interleukin [IL]-1ß, IL-6, and interferon-γ) in damaged nerves following PSNL were significantly decreased in CCL5 -/- mice. Conversely, several antiinflammatory cytokine (IL-4 and IL-10) proteins were significantly increased in CCL5 -/- animals and the expression of enkephalin, ß-endorphin, and dynorphin mRNA was significantly lower than in wild-type control mice. These results represent the first evidence that CCL5 is capable of regulating the pathway that controls hyperalgesia at the level of the peripheral injured site in a murine chronic neuropathic pain model. We demonstrated that lack of CCL5 modulated cell infiltration and the proinflammatory milieu within the injured nerve. Attenuated behavioral hypersensitivity in CCL5 -/- mice observed in the current study could be a result of decreased macrophage infiltration, mobilization, and functional ability at injured sites. Collectively, the present study results suggest that CCL5 receptor antagonists may ultimately provide a novel class of analgesics for therapeutic intervention in chronic neuropathic pain.

Inflammation confers dual effects on nociceptive processing in chronic neuropathic pain model.

BACKGROUND: Although inflammation induces pain, immune cells also produce mediators that can effectively counteract it. To further elucidate the role of the immune response, we analyzed the relationship of pain behavior, several inflammatory signals, and opioid peptides using partial sciatic nerve ligation in mice at different levels of immunocompromise. METHODS: Sciatic nerves of C57BL/6C, nonobese diabetic (NOD), or nonobese diabetic-severe combined immune deficiency (NOD-SCID) mice were partially ligated. Responses to mechanical and radiant heat stimuli were observed. Inflammation was detected by immunohistochemistry and flow cytometry. Inflammatory cytokines and opioid peptides were analyzed using real-time polymerase chain reaction and enzyme-linked immunosorbent assay or immunostaining. RESULTS: Inflammation in immunocompromised mice was subordinate when compared with that seen in C57BL/6C mice. In addition, immunocompromised mice had less pain hypersensitivity at early stages. Whereas proinflammatory tumor necrosis factor-α (TNF-α), interleukin 1ß (IL-1ß), interleukin 6 (IL-6), and interferon-γ (IFN-γ), as well as antiinflammatory interleukin 1 receptor antagonist (IL-1Ra), interleukin 4 (IL-4), interleukin 10 (IL-10), and interleukin 13 (IL-13) cytokine expression and protein were increased in C57BL/6C mice, they were lower in immunocompromised mice. Although enkephalin, dynorphin, and ß-endorphin messenger RNA expression also increased in C57BL/6C mice, peaking on day 14, this result was not observed in immunocompromised mice. CONCLUSION: The contribution of inflammation to nerve injury is complex with biphasic modulation. During the early phase, a wide range of proinflammatory cytokines are released, leading to enhanced pain. In contrast, the analgesic effect of opioid peptides and antiinflammatory cytokines was more predominate in the later phases of injury, leading to attenuated pain responses.

Exogenous granulocyte colony-stimulating factor exacerbate pain-related behaviors after peripheral nerve injury.

Previous studies have demonstrated that inflammatory cells produce several mediators that can effectively counteract pain. This study was designed to test the hypothesis that exogenous administration of recombinant mouse granulocyte-colony-stimulating factor (rmG-CSF) to enhance the recruitment of inflammatory cells to painful inflamed sites could attenuate pain in a chronic neuropathic pain model in mice. Our results indicate that treatment with rmG-CSF increased several cytokines and opioid peptides content; however, it did not attenuate but exacerbate neuropathic pain. Our study highlights the potent pro-inflammatory potential of G-CSF and suggests they may be targets for therapeutic intervention in chronic neuropathic pain.

Effects of lotus plumule supplementation before and following systemic administration of lipopolysaccharide on the splenocyte responses of BALB/c mice.

To determine whether lotus plumule supplementation alleviates acute systemic inflammation in vivo, the BALB/c mice were continuously supplemented with lotus plumule for 3 weeks, following administration with an intraperitoneal (i.p.) injection of lipopolysaccharide (LPS) at a concentration of 10mg/kg body weight (BW) to induce acute systemic inflammation. At 24h after injection of LPS, the mice were sacrificed and the visceral organ weight and splenocyte responses were measured. The results showed that lotus plumule supplementation did not significantly affect body weights and IL-6 secretion of splenocyte cultures from BALB/c mice. LPS challenge significantly increased the relative organ weights of the lungs, liver, and spleen, however low dose supplementation (40 mg/kg BW/day) with lotus plumule significantly decreased the relative organ weights of the inflammatory liver, spleen and kidney. Low dose supplementation with lotus plumule significantly increased IL-10 production of splenocyte cultures, however high dose supplementation (800 mg/kg BW/day) significantly decreased IL-10 production. These results suggest that low dose and 3-week supplementation of lotus plumule might alleviate acute systemic inflammation in vivo via decreasing the visceral organ inflammation and increasing the production of anti-inflammatory cytokine IL-10 from splenocytes. These results are valuable for developing future nutraceuticals and anti-inflammatory agents from traditional medicinal foods.