In animals, sporadic injections of the mitochondrial toxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) selectively damage dopaminergic neurons but do not fully reproduce the features of human Parkinson's disease. We have now developed a mouse Parkinson's disease model that is based on continuous MPTP administration with an osmotic minipump and mimics many features of the human disease. Although both sporadic and continuous MPTP administration led to severe striatal dopamine depletion and nigral cell loss, we find that only continuous administration of MPTP produced progressive behavioral changes and triggered formation of nigral inclusions immunoreactive for ubiquitin and ␣-synuclein. Moreover, only continuous MPTP infusions caused long-lasting activation of glucose uptake and inhibition of the ubiquitin-proteasome system. In mice lacking ␣-synuclein, continuous MPTP delivery still induced metabolic activation, but induction of behavioral symptoms and neuronal cell death were almost completely alleviated. Furthermore, the inhibition of the ubiquitinproteasome system and the production of inclusion bodies were reduced. These data suggest that continuous low-level exposure of mice to MPTP causes a Parkinson-like syndrome in an ␣-synucleindependent manner.neurodegeneration ͉ mitochondria ͉ neuronal inclusions ͉ Lewy bodies

High amounts of glutamate are found in the brains of people with multiple sclerosis, an inflammatory disease marked by progressive demyelination. Glutamate might affect neuroinflammation via effects on immune cells. Knockout mice lacking metabotropic glutamate receptor-4 (mGluR4) were markedly vulnerable to experimental autoimmune encephalomyelitis (EAE, a mouse model of multiple sclerosis) and developed responses dominated by interleukin-17-producing T helper (T(H)17) cells. In dendritic cells (DCs) from those mice, defective mGluR4 signaling-which would normally decrease intracellular cAMP formation-biased T(H) cell commitment to the T(H)17 phenotype. In wild-type mice, mGluR4 was constitutively expressed in all peripheral DCs, and this expression increased after cell activation. Treatment of wild-type mice with a selective mGluR4 enhancer increased EAE resistance via regulatory T (T(reg)) cells. The high amounts of glutamate in neuroinflammation might reflect a counterregulatory mechanism that is protective in nature and might be harnessed therapeutically for restricting immunopathology in multiple sclerosis.

Knowing that expression of metabotropic glutamate 2 (mGlu2) receptors in the dorsal root ganglia is regulated by acetylation mechanisms, we examined the effect of two selective and chemically unrelated histone deacetylase (HDAC) inhibitors, N- (2-aminophenyl)-4-[N-(pyridine-3-ylmethoxy-carbonyl)aminomethyl]benzamide (MS-275) and suberoylanilide hydroamic acid (SAHA), in a mouse model of persistent inflammatory pain. Although a single subcutaneous injection of MS-275 (3 mg/kg) or SAHA (5-50 mg/kg) was ineffective, a 5-day treatment with either of the two HDAC inhibitors substantially reduced the nociceptive response in the second phase of the formalin test, which reflects the development of central sensitization in the dorsal horn of the spinal cord. Analgesia was abrogated by a single injection of the mGlu2/3 receptor antagonist (␣S)-␣-amino-␣-[(1S,2S)-2-carboxycyclopropyl]-9H-xantine-9-propanoic acid (LY341495; 1 mg/kg, i.p.), which was inactive per se. Both MS-275 and SAHA upregulated the expression of mGlu2 receptors in the dorsal root ganglion (DRG) and spinal cord under conditions in which they caused analgesia, without changing the expression of mGlu1a, mGlu4, or mGlu5 receptors. Induction of DRG mGlu2 receptors in response to SAHA was associated with increased acetylation of p65/RelA on lysine 310, a process that enhances the transcriptional activity of p65/RelA at nuclear factor-B-regulated genes. Transcription of the mGlu2 receptor gene is known to be activated by p65/RelA in DRG neurons. We conclude that HDAC inhibition produces analgesia by up-regulating mGlu2 receptor expression in the DRG, an effect that results from the amplification of NF-B transcriptional activity. These data provide the first evidence that HDAC inhibitors cause analgesia and suggest that HDACs are potential targets for the epigenetic treatment of pain.Histone deacetylase (HDAC) inhibitors are known to modulate gene expression by increasing acetylation of histone proteins, thus remodeling chromatin structure (Strahl and Allis, 2000). Eighteen HDAC isoenzymes have been identified and divided into four classes based on their homology to yeast deacetylase proteins. Class I HDACs include the HDAC1, -2, -3, and -8 isoforms. These enzymes are ubiquitously expressed and have a predominant nuclear localization. Class II HDACs, which include HDAC4, -5, -6, -7, -9, and -10, are cytosolic enzymes and have a more restricted tissue pattern of expression. Class III HDACs include sirtuins, whereas HDAC11 is the only member of class IV HDAC and shares properties of both class I and II HDACs (Xu et al., 2007;Yang and Seto, 2007).In addition to histones, a number of nonhistone proteins, mainly transcription factors, are regulated by acetylation and are specifically targeted by HDACs (Spange et al., 2009). In particular, members of the nuclear factor-B (NF-B) family of transcription factors are known to be regulated by reversible acetylation (Chen et al., 2001). The NF-B/Rel family consists of p50, p52, p65/RelA, c-Rel, and RelB, which Arti...