We describe here a new strategy for the treatment of stroke, through the inhibition of NAALADase (N-acetylated-alpha-linked-acidic dipeptidase), an enzyme responsible for the hydrolysis of the neuropeptide NAAG (N-acetyl-aspartyl-glutamate) to N-acetyl-aspartate and glutamate. We demonstrate that the newly described NAALADase inhibitor 2-PMPA (2-(phosphonomethyl)pentanedioic acid) robustly protects against ischemic injury in a neuronal culture model of stroke and in rats after transient middle cerebral artery occlusion. Consistent with inhibition of NAALADase, we show that 2-PMPA increases NAAG and attenuates the ischemia-induced rise in glutamate. Both effects could contribute to neuroprotection. These data indicate that NAALADase inhibition may have use in neurological disorders in which excessive excitatory amino acid transmission is pathogenic.

A series of substituted phosphonate derivatives were designed and synthesized in order to study the ability of these compounds to inhibit the neuropeptidase N-acetylated alpha-linked acidic dipeptidase (NAALADase). The molecules were shown to act as inhibitors of the enzyme, with the most potent (compound 3) having a Ki of 0.275 nM. The potency of this compound is more than 1000 times greater than that of previously reported inhibitors of the enzyme. NAALADase is responsible for the catabolism of the abundant neuropeptide N-acetyl-aspartylglutamate (NAAG) into N-acetylaspartate and glutamate. NAAG has been proposed to be a neurotransmitter at a subpopulation of glutamate receptors; alternatively, NAAG has been suggested to act as a storage form of synaptic glutamate. As a result, inhibition of NAALADase may show utility as a therapeutic intervention in diseases in which altered levels of glutamate are thought to be involved.

A series of 2-(thioalkyl)pentanedioic acids were synthesized and evaluated as inhibitors of glutamate carboxypeptidase II (GCP II, EC 3.4.17.21). The inhibitory potency of these thiol-based compounds against GCP II was found to be dependent on the number of methylene units between the thiol group and pentanedioic acid. A comparison of the SAR of the thiol-based inhibitors to that of the phosphonate-based inhibitors provides insight into the role of each of the two zinc-binding groups in GCP II inhibition. The most potent thiol-based inhibitor, 2-(3-mercaptopropyl)pentanedioic acid (IC(50) = 90 nM), was found to be orally bioavailable in rats and exhibited efficacy in an animal model of neuropathic pain following oral administration.

P arkinson's disease (PD) is a chronic, progressive neurologicaldisease that affects ∼1% of the population over the age of 65. 1 It is characterized by progressive impairment in motor function that is often accompanied by disturbances in mood and cognitive function. The majority of motor impairments of PD are caused by a gradual loss of dopamine (DA) producing neurons in the ventral midbrain and concomitant loss of DA input to forebrain (striatal) motor structures. 2,3 The loss of DA input to the neostriatum leads to dysregulation of striatal function and the classic motor symptoms of PD, such as resting tremor, muscular rigidity, and bradykinesia.The majority of treatments aim to restore dopamine signaling and thereby reduce the severity of the motor symptoms. Dopamine replacement therapy using L-DOPA, the precursor to dopamine, remains the gold-standard treatment for PD. Other approaches include inhibition of DA turnover using monoamine oxidase type B (MAO-B) inhibitors, 4 catechol O-methyl-transferase (COMT) inhibitors, 5 and inhibition of dopamine reuptake 6 or direct agonists 7 of postsynaptic dopamine receptors. Although the dopamine targeted therapies work well to address the PD related motor disturbances, they all produce undesirable side effects (dyskinesia, hallucinations, onÀoff effects) that become more severe and problematic with continued treatment. Also, the aforementioned therapies typically show reduced efficacy as motor functions deteriorate and the disease progresses. Moreover, these treatments do not alter disease progression and do not address the mood, postural instability, or cognitive disturbances that frequently accompany PD.The dopamine replacement agents have significant limitations which influenced researchers to find nondopamine based treatments for PD. One nondopaminergic approach that has received considerable attention is modulation of adenosine receptors which is the topic highlighted in this Review. 8 Adenosine is a neuromodulator that coordinates responses to dopamine and other neurotransmitters in areas of the brain that are responsible for motor function, mood, and learning and memory. 9 Adenosine comprises four distinct receptor subtypes designated A 1 , A 2A , A 2B , and A 3 belonging to the G protein-coupled receptor superfamily. 10 Adenosine A 1 and A 3 receptors are coupled to inhibitory G proteins, while A 2A and A 2B receptors are coupled to stimulatory G proteins. Autoradiography studies in rodents showed that the greatest densities of A 2A receptors are found in the striatum 11 which closely matches the distribution in humans based on PET imaging. 12 As described above, loss of dopamine input into the neostriatum is a hallmark of PD and causes many of the cardinal motor symptoms of this disorder. In the striatum adenosine A 2A receptors colocalize and physically associate with dopamine D 2 receptors. ABSTRACT: This Review summarizes and updates the work on adenosine A 2A receptor antagonists for Parkinson's disease from 2006 to the present. There have been numerou...

Aberrant activation of matrix metalloproteinases (MMPs) is a common feature of pathological cascades observed in diverse disorders, such as cancer, fibrosis, immune dysregulation, and neurodegenerative diseases. MMP-9, in particular, is highly dynamically regulated in several pathological processes. Development of MMP inhibitors has therefore been an attractive strategy for therapeutic intervention. However, a long history of failed clinical trials has demonstrated that broad-spectrum MMP inhibitors have limited clinical utility, which has spurred the development of inhibitors selective for individual MMPs. Attaining selectivity has been technically challenging because of sequence and structural conservation across the various MMPs. Here, through a biochemical and structural screening paradigm, we have identified JNJ0966, a highly selective compound that inhibited activation of MMP-9 zymogen and subsequent generation of catalytically active enzyme. JNJ0966 had no effect on MMP-1, MMP-2, MMP-3, MMP-9, or MMP-14 catalytic activity and did not inhibit activation of the highly related MMP-2 zymogen. The molecular basis for this activity was characterized as an interaction of JNJ0966 with a structural pocket in proximity to the MMP-9 zymogen cleavage site near Arg-106, which is distinct from the catalytic domain. JNJ0966 was efficacious in reducing disease severity in a mouse experimental autoimmune encephalomyelitis model, demonstrating the viability of this therapeutic approach. This discovery reveals an unprecedented pharmacological approach to MMP inhibition, providing an opportunity to improve selectivity of future clinical drug candidates. Targeting zymogen activation in this manner may also allow for pharmaceutical exploration of other enzymes previously viewed as intractable drug targets. MMPs2 are a family of structurally related zinc-binding proteolytic enzymes that digest extracellular matrix proteins and participate in tissue remodeling and signaling events (1). Currently, ϳ23 MMPs have been identified, comprising secreted and membrane-bound forms, and different family members share some common structural and functional domains and have varying degrees of substrate specificity. Abnormal expression and activation of MMPs has been implicated in the pathogenesis and pathological progression of several different human diseases that are centered in many different tissues in the periphery and central nervous system (2, 3). Initial clinical exploration of synthetic MMP inhibitors was focused on oncology indications, as preventing the breakdown of tissue matrices and barriers was viewed as a potential mechanism to limit tumor metastasis.Despite intensive efforts over many years to develop synthetic MMP inhibitors, only a single MMP inhibitor, Periostat, a tetracycline derivative used in periodontal disease, has progressed into regular clinical use (4). Of the ϳ50 other clinical trials conducted with active site MMP inhibitors, all have failed due to the onset of significant dose-limiting musculoskeletal toxicity ...