Recent studies indicate that oxysterols, which are ligands for the nuclear hormone liver X receptors (LXR), decrease amyloid ␤ (A␤) secretion in vitro. The effect was attributed primarily to the ATP-binding cassette transporter A1 (ABCA1) transcriptionally up-regulated by ligand-activated LXRs. We now examined the effect of the synthetic LXR ligand T0901317, which can be used in vivo, on A␤ production in vitro and in APP23 transgenic mice. T0901317 applied to a variety of in vitro models, including immortalized fibroblasts from Tangier patients, and primary embryonic mouse neurons caused a concentrationdependent decrease in A␤ secretion, and this effect was increased by the addition of apolipoprotein A-I. The inhibition of A␤ production by T0901317 was cell-type specific, being more prominent in primary neurons than in non-neuronal cells. Tangier fibroblasts lacking a functional ABCA1 secreted more A␤ than control fibroblasts, thus demonstrating the role of ABCA1 in amyloid precursor protein (APP) processing and A␤ generation. T0901317 treatment of 11-week-old APP23 mice for 6 days showed a significant increase in ABCA1 expression and a decrease in the ratio of soluble APP (sAPP)␤-to sAPP␣-cleavage products. Most importantly, the treatment caused a statistically significant reduction in the levels of soluble A␤ 40 and A␤ 42 in the brain of these mice. Our experiments demonstrate that T0901317 decreases amyloidogenic processing of APP in vitro and in vivo, thus supporting the search for potent and specific LXR ligands with properties allowing therapeutic application.

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Neuropathic pain after spinal cord injury (SCI) represents a difficult problem that is commonly refractory to conventional medical management. To determine if spinal release of gamma-amino butyric acid (GABA) could reduce below-level central neuropathic pain after SCI, we constructed a replication-incompetent herpes simplex virus (HSV)-based vector encoding one isoform of human glutamic acid decarboxylase (GAD67). Dorsal root ganglion (DRG) neurons transduced in vitro or in vivo by subcutaneous inoculation produced GAD and released GABA constitutively. T13 spinal cord hemisection resulted in central neuropathic pain manifested by mechanical allodynia and thermal hyperalgesia. Subcutaneous inoculation of the vector into both feet reduced both manifestations of below-level SCI pain; the vector-mediated effect was partially reversed by intrathecal bicuculline or phaclofen at doses that did not affect thresholds in normal or injured uninoculated animals. Vector-mediated GABA release attenuated the increase in spinal calcitonin gene-related peptide immunoreactivity caused by cord hemisection. These results suggest that HSV-mediated gene transfer to DRG could be used to treat below-level central neuropathic pain after incomplete SCI.

Objective Preclinical evidence indicates that gene transfer to the dorsal root ganglion (DRG) using replication defective herpes simplex virus (HSV)-based vectors can reduce pain-related behavior in animal models of pain. This clinical trial was carried out to assess the safety and explore the potential efficacy of this approach in humans. Methods We conducted a multicenter, dose-escalation, Phase I clinical trial of NP2, a replication defective HSV-based vector expressing human preproenkephalin (PENK) in subjects with intractable focal pain caused by cancer. NP2 was injected intradermally into the dermatome(s) corresponding to the radicular distribution of pain. The primary outcome was safety. As secondary measures, efficacy of pain relief was assessed using a numeric rating scale (NRS), the Short Form McGill Pain Questionnaire (SF-MPQ) and concurrent opiate usage. Results Ten subjects with moderate to severe intractable pain despite treatment with more than 200 mg/day of morphine (or equivalent) were enrolled into the study. Treatment was well tolerated with no study agent-related serious adverse events (SAE) observed at any point in the study. Subjects receiving the low dose of NP2 reported no substantive change in pain. Subjects in the middle and high dose cohorts reported pain relief as assessed by NRS and SF-MPQ. Interpretation Treatment of intractable pain with NP2 was well tolerated. There were no placebo controls in this relatively small study, but the dose-responsive analgesic effects suggest that NP2 may be effective in reducing pain and warrants further clinical investigation.

We tested whether transfer of the gene coding for glutamic acid decarboxylase to dorsal root ganglion using a herpes simplex virus vector to achieve release of GABA in dorsal horn would attenuate nociception in this condition. Subcutaneous inoculation of a replication-defective herpes simplex virus vector expressing glutamic acid decarboxylase (vector QHGAD67) 7 days after selective L5 spinal nerve ligation reversed mechanical allodynia and thermal hyperalgesia; the antiallodynic effect lasted 6 weeks and was reestablished by reinoculation. QH-GAD67 inoculation also suppressed induction of c-Fos and phosphorylated extracellular signal-regulated kinase 1 and 2 in the spinal cord.Peripheral neuropathic pain is a common and difficult to treat concomitant of polyneuropathy or structural nerve injury. Opioids are relatively ineffective, and their use is limited by side effects. Antidepressants and anticonvulsants have demonstrated efficacy in randomized controlled trials but provide only 50% relief in less than half of patients treated. 1 Among the complex mechanisms underlying neuropathic pain, partial nerve injury results in a selective loss of GABAergic inhibitory synaptic currents in spinal cord 2 that contribute to abnormal pain sensitivity and the phenotypic features of the neuropathic pain syndrome. GABAergic agents have not been widely used in the treatment of neuropathic pain because the therapeutic window of these agents is modest and the dose is limited by side effects.Gene transfer represents a novel and useful means to target expression of peptides to focal sites within the nervous system. We have shown that transduction of sensory neurons of the dorsal root ganglion (DRG) by footpad inoculation with herpes simplex virus (HSV)-based vectors can be used to achieve a regional antinociceptive effect. HSV vectors coding for proenkephalin or the glial cell-derived neurotrophic factor produce an antihyperalgesic and antiallodynic effect in rodent models of inflammatory pain, neuropathic pain, and pain resulting from cancer in bone, 3-6 and an HSV-vector expressing glutamic acid decarboxylase (GAD) provides an analgesic effect in the central neuropathic pain syndrome resulting from spinal cord injury. 7 In this study, we examined the antinociceptive effect of GAD expressed from an HSV-based vector in the spinal nerve ligation (SNL) model of neuropathic pain in the rat. Materials and MethodsThe nonreplicating HSV vector QHGAD67, which is defective in expression of the HSV immediate early genes ICP4, ICP22, ICP27, and ICP47 and contains the human GAD67 gene under the control of the human cytomegalovirus immediate early promoter in the U L 41 locus, has been described previously. 7 The control vector QOZHG is defective in the same HSV genes but contains the green fluorescent protein and Escherichia coli lacZ reporter genes. 7Male Sprague-Dawley rats weighing 225 to 250gm underwent selective L5 SNL, as described previously, 5 with the approval of the University Committee on Use and Care of Animals. One wee...