Specific down-regulation of spinal μ-opioid receptor and reduced analgesic effects of morphine in mice with postherpetic pain

The analgesic effects of opioid agonists and the expression of μ-and κ-opioid receptors were compared between mice with herpetic pain and those with postherpetic pain induced by herpetic virus inoculation. Morphine inhibited herpetic pain more effectively than postherpetic pain. Intrathecal injection reduced the analgesic effects of morphine on postherpetic pain, but intracerebroventricular injection did not. The κ-opioid receptor agonist nalfurafine suppressed herpetic and postherpetic pain to similar degrees. μ-Opioid receptor-like immunoreactivities in the lumbar dorsal horn were markedly decreased at the postherpetic, but not herpetic, stage of pain. In the dorsal root ganglia, the expression of μ-opioid receptor mRNA was significantly decreased in mice with postherpetic pain, whereas the κ-opioid receptor mRNA level was not altered. These results suggest that specific down-regulation of the μ-opioid receptor in the primary sensory neurons is responsible for the reduced analgesic action of morphine on postherpetic pain. The κ-opioid receptor may be a useful target for the analgesic treatment of postherpetic neuralgia

Apoptosis-dependent externalization and involvement in apoptotic cell clearance of DmCaBP1, an endoplasmic reticulum protein of Drosophila

To elucidate the actions of Draper, a receptor responsible for the phagocytic clearance of apoptotic cells in Drosophila, we isolated proteins that bind to the extracellular region of Draper using affinity chromatography. One of those proteins has been identified to be an uncharacterized protein called Drosophila melanogaster calcium-binding protein 1 (DmCaBP1). This protein containing the thioredoxin-like domain resided in the endoplasmic reticulum and seemed to be expressed ubiquitously throughout the development of Drosophila. DmCaBP1 was externalized without truncation after the induction of apoptosis somewhat prior to chromatin condensation and DNA cleavage in a manner dependent on the activity of caspases. A recombinant DmCaBP1 protein bound to both apoptotic cells and a hemocyte-derived cell line expressing Draper. Forced expression of DmCaBP1 at the cell surface made non-apoptotic cells susceptible to phagocytosis. Flies deficient in DmCaBP1 expression developed normally and showed Draper-mediated pruning of larval axons, but a defect in the phagocytosis of apoptotic cells in embryos was observed. Loss of Pretaporter, a previously identified ligand for Draper, did not cause a further decrease in the level of phagocytosis in DmCaBP1-lacking embryos. These results collectively suggest that the endoplasmic reticulum protein DmCaBP1 is externalized upon the induction of apoptosis and serves as a tethering molecule to connect apoptotic cells and phagocytes for effective phagocytosis to occur. © 2012 by The American Society for Biochemistry and Molecular Biology, Inc

Pretaporter, a Drosophila protein serving as a ligand for Draper in the phagocytosis of apoptotic cells

金沢大学医薬保健研究域薬学系Phagocytic removal of cells undergoing apoptosis is necessary for animal development and tissue homeostasis. Draper, a homologue of the Caenorhabditis elegans phagocytosis receptor CED-1, is responsible for the phagocytosis of apoptotic cells in Drosophila, but its ligand presumably present on apoptotic cells remains unknown. An endoplasmic reticulum protein that binds to the extracellular region of Draper was isolated. Loss of this protein, which we name Pretaporter, led to a reduced level of apoptotic cell clearance in embryos, and the overexpression of pretaporter in the mutant flies rescued this defect. Results from genetic analyses suggested that Pretaporter functionally interacts with Draper and the corresponding signal mediators. Pretaporter was exposed at the cell surface after the induction of apoptosis, and cells artificially expressing Pretaporter at their surface became susceptible to Draper-mediated phagocytosis. Finally, the incubation with Pretaporter augmented the tyrosine-phosphorylation of Draper in phagocytic cells. These results collectively suggest that Pretaporter relocates from the endoplasmic reticulum to the cell surface during apoptosis to serve as a ligand for Draper in the phagocytosis of apoptotic cells. © 2009 European Molecular Biology Organization

Intradermal Nociceptin Elicits Itch-Associated Responses Through Leukotriene B4 in Mice

Nociceptin, the endogenous peptide ligand for opioid receptor like-1 (ORL1) receptor, has been implicated in the inflammation and pain in the skin. We examined whether nociceptin is a pruritogen in mice. Intradermal injections of nociceptin (1–100 nmol per site) concentration dependently increased scratching in ICR mice; the effect started within 1 min, peaked at 10–20 min, and almost subsided by 30 min. The nociceptin action was absent in ORL1 receptor-deficient (ORL1-/-) mice. Systemic, but not local, treatment with naloxone significantly inhibited scratching induced by nociceptin. The action of nociceptin was inhibited by the leukotriene B4 receptor antagonist ONO-4057 and azelastine, which inhibits the action and production of leukotriene B4 in the skin. Prepronociceptin and ORL1 receptor mRNAs were substantially expressed in the skin, whereas their expression levels were very low in the dorsal root ganglia. In the skin, nociceptin- and ORL1 receptor-like immunoreactivities were localized in the epidermis. Administration of nociceptin to primary cultures of keratinocytes from ICR and C57BL/6 (ORL1+/+) mice, but not ORL1-/- mice, produced leukotriene B4. The results suggest that nociceptin acts on ORL1 receptor on the keratinocytes to produce leukotriene B4, which induces itch-associated responses in mice

Kuraishi Y. Gabapentin antinociception in mice with acute herpetic pain induced by herpes simplex virus infection. J Pharmacol Exp Ther

ABSTRACT The effects of systemic and local injections of gabapentin, a novel anticonvulsant agent, were tested on nociceptive behaviors in mice with acute herpetic pain. Transdermal infection with herpes simplex virus type-1 (HSV-1) produced nociceptive hypersensitivity of the infected hind paw to innocuous (allodynia) and noxious mechanical stimulation (hyperalgesia) with von Frey filaments. Systemic administration of gabapentin (10 -100 mg/kg, peroral) produced a dose-dependent inhibition of both allodynia and hyperalgesia; gabapentin (30 -300 mg/kg) did not affect locomotor activity. Intrathecal injection of gabapentin (10 -100 g/animal) also attenuated dose dependently both nociceptive hypersensitivities. In contrast, intraplantar, intracisternal, and intracerebroventricular administration of gabapentin (10 -100 g/animal) had no effect on the HSV-1-induced nociceptive hypersensitivities. Pretreatment with naltrexone (1 mg/ kg) inhibited antinociceptive effect of morphine (5 mg/kg), but not gabapentin (100 mg/kg). Repeated administration of morphine (5 mg/kg, four times) led to tolerance of antinociceptive action, whereas gabapentin (100 mg/kg, four times) had antinociceptive effect even after the forth administration. The present results suggest that gabapentin is effective in the treatment of acute herpetic pain without apparent adverse effects, and analgesic action of gabapentin is mainly mediated by actions on the spinal cord. Gabapentin [1-(aminomethyl)cyclohexaneacetic acid], a novel anticonvulsant agent, is currently in clinical use as an "add-on" therapy in patients with partial seizures resistant to conventional therapies Recently, we have developed a mouse model of acute herpetic pain Materials and Methods Animals. Female BALB/c mice weighing about 20 g (6 weeks old at the start of experiments; Japan SLC, Shizuoka, Japan) were used. They were housed six per cage under controlled temperature (22 Ϯ 1°C) and humidity (55 Ϯ 10%). The room was lighted from 7:00 AM to 7:00 PM and during the behavioral test. Food and water were freely available. HSV-1 inoculation and behavioral experiments were done in the infection roo

Different roles of capsaicin-sensitive and H-1 histamine receptor-expressing sensory neurones in itch of mosquito allergy in mice

Although mosquito allergy induces the release of histamine, the itch-related response, scratching, is not effectively suppressed by blockade of H, histamine receptors. To address this question, we examined the effects of neonatal capsaicin treatment on allergic reactions and H, histamine receptor-expressing sensory neurones in mice. Neonatal capsaicin treatment almost completely abolished allergy-associated scratching, without effects on plasma extravasation or increase in serum concentrations of immunoglobulins E and G,. An injection of edema contents from an animal exhibiting allergic reaction elicited scratching in naive animals, suggesting the production of pruritogen(s) by allergic reaction; this production was not suppressed by neonatal capsaicin treatment. This treatment markedly decreased the number of sensory neurones immunoreactive for TRPV1 capsaicin receptor, with little effect on sensor), neurones immunoreactive for neurofilament 200, a marker of myelinated A-fibre neurones. In addition, there was a trend towards a reduction in numbers of sensory neurones immunoreactive for H, histamine receptor. The results suggest that capsaicin-sensitive sensory neurones that lack H, histamine receptors play a key role in signalling of allergic itch

Peripheral gabapentin regulates mosquito allergy-induced itch in mice

The antipruritic activity of gabapentin, an anticonvulsant, was studied in a mouse model of allergic itch. In mice sensitized by an extract of the salivary glands of the mosquito (ESGM), an intradermal injection of ESGM elicited scratching and increased peripheral nerve firing. Oral or intradermal administration of gabapentin at the ESGM injection site inhibited ESGM-induced scratching and peripheral nerve firing. However, gabapentin did not affect histamine-induced scratching. The distributions of immunoreactivity to the voltage-dependent calcium channel α2δ-1 subunit, a site of gabapentin action, and the histamine H1 receptor differed in the mouse dorsal root ganglia. The α2δ-1 subunit was mainly found in neurons that were 15–20 µm in diameter, whereas the H1 receptor was mainly in 20–30 µm neurons. In addition, α2δ-1 subunit immunoreactivity co-localized with that of transient receptor potential vanilloid 1 (TRPV1). These results suggest that gabapentin regulates allergic itch by acting on the calcium channel α2δ-1 subunit in peripheral TRPV1-positive neurons