Six-month partial suppression of Huntingtin is well tolerated in the adult rhesus striatum.

Huntington's disease is caused by expression of a mutant form of Huntingtin protein containing an expanded polyglutamine repeat. One possible treatment for Huntington's disease may be to reduce expression of mutant Huntingtin in the brain via RNA interference. Unless the therapeutic molecule is designed to be allele-specific, both wild-type and mutant protein will be suppressed by an RNA interference treatment. A key question is whether suppression of wild-type as well as mutant Huntingtin in targeted brain regions can be tolerated and result in a net benefit to patients with Huntington's disease. Whether Huntingtin performs essential functions in the adult brain is unclear. Here, we tested the hypothesis that the adult primate brain can tolerate moderately reduced levels of wild-type Huntingtin protein for an extended period of time. A serotype 2 adeno-associated viral vector encoding for a short hairpin RNA targeting rhesus huntingtin messenger RNA (active vector) was bilaterally injected into the striatum of four adult rhesus monkeys. Four additional animals received a comparable vector encoding a scrambled control short hairpin RNA (control vector). General health and motor behaviour were monitored for 6 months. Upon termination, brain tissues were sampled and assessed blindly for (i) huntingtin messenger RNA knockdown; (ii) Huntingtin protein expression; and (iii) neuropathological changes. Reduction in wild-type huntingtin messenger RNA levels averaging ∼30% was measured in the striatum of active vector recipients 6 months post-injection. A widespread reduction in Huntingtin protein levels was also observed by immunohistochemistry in these animals, with an average protein reduction of ∼45% relative to controls measured by western blot analysis in the putamen of active vector recipients. As with control vector recipients, no adverse effects were observed behaviourally, and no neurodegeneration was found on histological examination of active vector recipients. Our results suggest that long-term partial suppression of wild-type Huntingtin may be safe, and thus if a comparable level of suppression of mutant Huntingtin is beneficial, then partial suppression of both wild-type and mutant Huntingtin may result in a net benefit in patients with heterozygous Huntington's disease.

Effect of etanercept, a tumor necrosis factor-alpha inhibitor, on neuropathic pain in the rat chronic constriction injury model.

STUDY DESIGN: The effects of a low, local dose of a tumor necrosis factor-alpha (TNF-alpha) inhibitor on neuropathic pain behaviors in a rat chronic constriction injury model were evaluated. OBJECTIVE: To investigate whether a peripherally implanted polymer drug depot can deliver a dose of etanercept sufficient to reduce thermal hyperalgesia and mechanical allodynia in a rat model of neuropathic pain. SUMMARY OF BACKGROUND DATA: TNF-alpha inhibitors reduce pain-associated behavior in experimental models of neuropathic pain. Moreover, systemic injections of TNF-alpha inhibitors have suggested some efficacy in treating sciatic pain in limited, off-label clinical studies. Improvements in these results may be obtained by optimal dosing via targeted, sustained delivery at the site of disc-induced inflammation. METHODS: Unilateral chronic constriction injury was applied to the sciatic nerve of 56 male, Wistar rats. Four groups of animals (n = 7) received 0.5 mL phosphate-buffered saline every 3 days, 0.3 or 3 mg/kg etanercept every 3 days, or gabapentin (60 mg/kg) 1 hour before each behavioral test all via subcutaneous injection. Two groups of animals received 1.5 or 3.0 microg/h etanercept delivered by poly(lactic-co-glycolic acid) (PLGA) millicylinders (1 mm diameter x 10 mm long) implanted near the injured sciatic nerve. One group received a PLGA millicylinder implanted near the injured sciatic nerve. The final group received 3.0 microg/h etanercept via PLGA millicylinder implanted next to the uninjured, contralateral sciatic nerve. RESULTS: A low, local dose of etanercept (approximately 3 microg/h) delivered by a polymer depot significantly reduced (P < 0.05) thermal hyperalgesia for 57 days as compared to polymer depot without drug or an etanercept-loaded depot implanted near the contralateral sciatic nerve, and equivalent to a 10-fold higher dose delivered by repeat subcutaneous injection. CONCLUSION: This preclinical study indicates that delivering TNF-alpha inhibitors by means of a locally administered polymeric formulation provides long-lasting analgesia in an inflammatory neuropathic pain model.

RORalpha-mediated Purkinje cell development determines disease severity in adult SCA1 mice.

Spinocerebellar ataxia type 1 (SCA1) is one of nine inherited, typically adult onset, polyglutamine neurodegenerative diseases. To examine whether development impacts SCA1, we used a conditional transgenic mouse model of SCA1 to delay the postnatal expression of mutant ATXN1 until after completion of cerebellar development. Delayed postnatal expression of mutant ATXN1 led to a substantial reduction in severity of disease in adults in comparison with early postnatal gene expression. This was linked to a destabilization of RORalpha, a transcription factor critical for cerebellar development. In SCA1 mice, there was a depletion of RORalpha and a reduction in expression of genes controlled by RORalpha. Partial loss of RORalpha enhanced mutant ATXN1 pathogenicity. Additionally, evidence points to the existence of a complex containing ATXN1, RORalpha, and the RORalpha coactivator Tip60. These studies indicate RORalpha and Tip60 have a role in SCA1 and suggest a mechanism by which compromising cerebellar development contributes to severity of neurodegeneration in an adult.