March 22, 2013 L ech Kiedrowski, Ph.D. UIC Department of Psychiatry lkiedr@psych.uic

1. March 22, 2013 Lech Kiedrowski, Ph.D. UIC Department of Psychiatry lkiedr@psych.uic.edu Neurodegenerative diseases

2. Knowledge Objectives: • Learn about Parkinson’s disease (PD): • Know PD statistics • Know the PD symptoms • Know the causes of PD • Know the drugs used to treat PD • Know how these drugs work • Learn about the neurodegeneration caused by stroke: • Know stroke statistics • Know the types of stroke • Know the mechanisms of brain damage caused by stroke • Know the drugs used to treat stroke • Know the prospects of new (experimental) therapies to treat stroke

3. Knowledge Objectives: Learn about Parkinson’s disease (PD): • Know PD statistics • Know the PD symptoms • Know the causes of PD • Know the drugs used to treat PD • Know how these drugs work

4. PD statistics • Affects 1% of population over the age of 60 years • Genetic factors involved in only 5-10% of cases. • Majority of cases are sporadic and may be caused by yet unknown environmental factors.

5. Symptoms of PD In 1817, James Parkinson, a physician working in London described the disease this way: “involuntary tremulous motion, with lessened muscular power, in parts not in action and even when supported; with a propensity to bend the trunk forwards, and to pass from a walking to a running pace, the senses and intellects being uninjured”

6. The MPTP Story Until early 1980 the was no animal model of PD. In 1982, an accident happened. Four young drug users in California suddenly developed PD symptoms following an injection of synthetic heroin (meperidine) contaminated with 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP). MPTP is oxidized in the brain by monoamine oxidase to MPP+. The latter is taken by dopaminergic neurons and kills them by inhibiting oxidative metabolism in the mitochondria.

7. Dopaminergic projection in the brain

8. Schematic representation of the sequence of neurons involved in parkinsonism. Top: Dopaminergic neurons (red) originating in the substantia nigra normally inhibit the GABAergic output from the striatum, whereas cholinergic neurons (orange) exert an excitatory effect. Bottom: In parkinsonism, there is a selective loss of dopaminergic neurons (dashed, red).

9. The normally high concentration of dopamine in the striatum is reduced in PD. Dopamine does not cross the blood-brain barrier and if given into the peripheral circulation has no therapeutic effect in PD. However, (–)-3-(3,4-dihydroxyphenyl)-L-alanine (levodopa), the immediate metabolic precursor of dopamine, does enter the brain (via an L-amino acid transporter, LAT), where it is decarboxylated to dopamine.

10. Levodopa Pharmacokinetics Levodopa is rapidly absorbed from the small intestine, but its absorption depends on the rate of gastric emptying and the pH of the gastric contents. Ingestion of food delays the appearance of levodopa in the plasma. Plasma concentrations usually peak between 1 and 2 hours after an oral dose, and the plasma half-life is usually between 1 and 3 hours, although it varies considerably among individuals. Unfortunately, only about 1–3% of administered levodopa actually enters the brain unaltered; the remainder is metabolized extracerebrally, predominantly by decarboxylation to dopamine, which does not penetrate the blood-brain barrier. Accordingly, levodopa must be given in large amounts when used alone. However, when given in combination with a dopa decarboxylase inhibitor that does not penetrate the blood-brain barrier, the peripheral metabolism of levodopa is reduced, plasma levels of levodopa are higher, plasma half-life is longer, and more dopa is available for entry into the brain.

11. Fate of orally administered levodopa and the effect of carbidopa, estimated from animal data. The width of each pathway indicates the absolute amount of the drug at each site, whereas the percentages shown denote the relative proportion of the administered dose. The benefits of coadministration of carbidopa include reduction of the amount of levodopa required for benefit and of the absolute amount diverted to peripheral tissues and an increase in the fraction of the dose that reaches the brain. GI, gastrointestinal.

12. Preparations to treat PD Sinemet-25/100 (carbidopa 25 mg, levodopa 100 mg) three times daily, and gradually increased. It should be taken 30–60 minutes before meals. Sinemet-25/250 (carbidopa 25 mg, levodopa 250 mg) three or four times daily. Parcopa - A formulation of carbidopa-levodopa (10/100, 25/100, 25/250) that disintegrates in the mouth and is swallowed with the saliva is now available commercially and is best taken about 1 hour before meals. Stalevo – a combination of levodopa, carbidopa, and a catechol-O-methyltransferase (COMT) inhibitor (entacapone). Entacapone

13. CATECHOL-O-METHYLTRANSFERASE INHIBITORS – PERIPHERY Inhibition of dopa decarboxylase (by carbidopa) is associated with compensatory activation of other pathways of levodopa metabolism, especially catechol-O-methyltransferase (COMT), and this increases plasma levels of 3-O-methyldopa (3-OMD). Elevated levels of 3-OMD have been associated with a poor therapeutic response to levodopa. 3-OMD competes with levodopa for an active carrier mechanism that governs its transport across the blood-brain barrier. Selective COMT inhibitors such as tolcapone and entacapone also prolong the action of levodopa by diminishing its peripheral metabolism. Levodopa clearance is decreased, and relative bioavailability of levodopa is thus increased. Neither the time to reach peak concentration nor the maximal concentration of levodopa is increased. Stalevo consists of a combination of levodopa with both carbidopa and entacapone. It is available in three strengths: Stalevo 50 (50 mg levodopa plus 12.5 mg carbidopa and 200 mg entacapone), Stalevo 100 (100 mg, 25 mg, and 200 mg, respectively), and Stalevo 150 (150 mg, 37.5 mg, and 200 mg). Use of this preparation simplifies the drug regimen and requires the consumption of a lesser number of tablets than otherwise.

14. Levodopa Clinical Use The best results of levodopa treatment are obtained in the first few years of treatment. This is sometimes because the daily dose of levodopa must be reduced over time to avoid adverse effects at doses that were well tolerated initially. Some patients become less responsive to levodopa, perhaps because of loss of dopaminergic nigrostriatal nerve terminals or some pathologic process directly involving striatal dopamine receptors. For such reasons, the benefits of levodopa treatment often begin to diminish after about 3 or 4 years of therapy, regardless of the initial therapeutic response. Although levodopa therapy does not stop the progression of parkinsonism, its early initiation lowers the mortality rate. However, long-term therapy may lead to a number of problems including dyskinesias, which occur in up to 80% of patients receiving levodopa therapy for long periods.

15. MONOAMINE OXIDASE INHIBITORS Two types of monoamine oxidase have been distinguished in the nervous system. Monoamine oxidase A metabolizes norepinephrine, serotonin, and dopamine; monoamine oxidase B metabolizes dopamine selectively. Selegiline (deprenyl), a selective irreversible inhibitor of monoamine oxidase B at normal doses (at higher doses it inhibits MAO-A as well), retards the breakdown of dopamine; in consequence, it enhances and prolongs the antiparkinsonism effect of levodopa (thereby allowing the dose of levodopa to be reduced). The standard dose of selegiline is 5 mg with breakfast and 5 mg with lunch. Selegiline may cause insomnia when taken later during the day. Selegiline has only a minor therapeutic effect on parkinsonism when given alone. 3-MT 3-Methoxytyramine COMT 3-OMD Selegiline Rasagiline, another monoamine oxidase B inhibitor, is more potent than selegiline in preventing MPTP-induced parkinsonism and is being used for early symptomatic treatment. The standard dosage is 1 mg/d. Rasagiline is also used as adjunctive therapy at a dosage of 0.5 or 1 mg/d to prolong the effects of levodopa-carbidopa in patients with advanced disease. Rasagiline

16. CATECHOL-O-METHYLTRANSFERASE INHIBITORS - BRAIN Of two selective COMT inhibitors, tolcapone and entacapone, only tolcapone one enters the brain. In the brain, tolcapone increases dopamine levels (by preventing methylation of L-DOPA and dopamine by COMT). However the use of tolcapone has been associated with hepatotoxicity. 3-MT 3-Methoxytyramine Tolcapone COMT 3-OMD Tolcapone may cause an increase in liver enzyme levels and has been associated rarely with death from acute hepatic failure; accordingly, its use in the USA requires signed patient consent (as provided in the product labeling) plus monitoring of liver function tests every 2 weeks during the first year and less frequently thereafter. No such toxicity has been reported with entacapone. Note that entcapone is a part of the already mentioned Stalevo combination therapy (levodopa + carbidopa + entacapone).

17. DOPAMINE RECEPTOR AGONISTS Dopamine receptor agonists may have a beneficial effect in addition to that of levodopa. Unlike levodopa, they do not require enzymatic conversion to an active metabolite, have no potentially toxic metabolites, and do not compete with other substances for active transport into the blood and across the blood-brain barrier. The older dopamine agonists (bromocriptine and pergolide) are ergot (ergoline) derivatives, and their side effects are of more concern than those of the newer agents (pramipexole and ropinirole).

18. DOPAMINE RECEPTOR AGONISTS Pramipexole Pramipexole has preferential affinity for the D3 family of receptors. It is effective as monotherapy for mild parkinsonism and is also helpful in patients with advanced disease, permitting the dose of levodopa to be reduced and smoothing out response fluctuations. Pramipexole may ameliorate affective symptoms. A possible neuroprotective effect has been suggested by its ability to scavenge hydrogen peroxide and enhance neurotrophic activity in mesencephalic dopaminergic cell cultures. Pramipexole is rapidly absorbed after oral administration, reaching peak plasma concentrations in approximately 2 hours, and is excreted largely unchanged in the urine. It is started at a dosage of 0.125 mg three times daily, doubled after 1 week, and again after another week. Further increments in the daily dose are by 0.75 mg at weekly intervals, depending on response and tolerance. Most patients require between 0.5 and 1.5 mg three times daily. Renal insufficiency may necessitate dosage adjustment.

19. DOPAMINE RECEPTOR AGONISTS Ropinirole Another nonergoline derivative, ropinirole (now available in a generic preparation) is a relatively pure D2 receptor agonist that is effective as monotherapy in patients with mild disease and as a means of smoothing the response to levodopa in patients with more advanced disease and response fluctuations. It is introduced at 0.25 mg three times daily, and the total daily dose is then increased by 0.75 mg at weekly intervals until the fourth week and by 1.5 mg thereafter. In most instances, a dosage between 2 and 8 mg three times daily is necessary.

20. Symptoms of PD result in part from an excessive activation of pathways that are innervated by acetylcholinergic fibers. Therefore, PD therapy may also includes acetylcholine-blocking (anti-muscarinic) agents. However, these drugs have a number of undesirable central nervous system and peripheral effects and are poorly tolerated by the elderly.

21. PD treatment - Summary • PD therapy consists of : • Increasing dopamine supply • Inhibiting dopamine metabolism • Enhancing activation of dopamine receptors 3-MT

22. Knowledge Objectives: Learn about the neurodegeneration caused by stroke: • Know stroke statistics • Know the types of stroke • Know the mechanisms of brain damage caused by stroke • Know the drugs used to treat stroke • Know the prospects of new (experimental) therapies to treat stroke

23. Stroke statistics • About795,000 cases each year • Every 40 seconds someone in the USA has a stroke and every 3 min someone dies of it • Stroke is the third leading cause of death, after heart disease and cancer • Stroke is the leading cause of long-term disability (60% of survivors become handicapped) • The estimated direct and indirect cost of stroke for 2009 was $68.9 billion. American Heart Association 2009

24. Two types of stroke 13% 87%

25. Stroke and brain damage The only FDA-approved therapy for stroke is intravenous injection of t-PA (Tissue Plasminogen Activator, a clot-dissolving agent) However, t-PA must be applied during the first 3 hours of stroke and during this time it has to be determined that the stroke is not hemorrhagic Often stroke victims arrive at the hospital or are diagnosed too late to apply t-PA

26. The sensitivity of brain to ischemic damage • Brain damage can start to occur just 4-6 minutes after the blood supply is arrested • When the blood supply to the brain is arrested for more than 12 min, the survival rate is only 2%

27. Arch. Neurol. Psych. 50 (1943) 510-528

28. The Kabat-Rossen-Anderson apparatus

29. Arch. Neurol. Psych. 50 (1943) 510-528

30. Dramatic Symptoms Arch. Neurol. Psych. 50 (1943) 510-528

31. Even More Dramatic Symptoms Arch. Neurol. Psych. 50 (1943) 510-528

32. After release of pressure in the cuff, consciousness is rapidly restored Arch. Neurol. Psych. 50 (1943) 510-528

33. Conclusion: 7 seconds of brain ischemia will make you unconscious, but will not damage your brain Arch. Neurol. Psych. 50 (1943) 510-528

34. EEG is flat within 10 sec of global brain ischemia Ischemic depolarization (high elevation in external K+) takes place about 2 min after the onset of ischemia. Hansen, Acta Physiol. Scand. (1978) 102: 324-329.

35. Sagital section through rat brain Hippocampus

36. Selective vulnerability of CA1 neurons to ischemia CA1 CA = Cornu Ammonis (Ammon’s horn) DG = Dentate Gyrus Sham operated DG CA3 CA1 neurons die CA3 and DG neurons survive 3 days after 10-min ischemia 7 days after 10-min ischemia Yokota et al. Stroke (1995) 26: 1901-1907.

37. Ischemia has to last over 2 min to kill CA1 neurons 2 min of ischemia 3 min of ischemia Hippocampal CA1 region in gerbil brain 7 days after ischemia Kato et al. Brain Res. (1991) 553: 238-242.

38. What kills the CA1 neurons?

39. The Pulsinelli et al. experiment

40. Denervation protects CA1 neurons from ischemic death Pulsinelli (1985) Prog Brain Res 63: 29-37

41. ? ? ? Death

42. Extracellular glutamate during ischemia and reperfusion Baseline Ischemia Reperfusion 10 20 30 10 2010 20 30 60 120 Glutamate (µM) sampled from various brain regions of the rat subjected to 20-min ischemia. Globus et al. (1988) J Neurochem 51:1455-1464

43. Glutamate is neurotoxic Olney, J.W., Brain lesions, obesity, and other disturbances in mice treated with monosodium glutamate. Science, 1969. 164: p. 719-721. A single subcutaneous injection of glutamate (4 mg/g) produces brain lesions and kills 2 – 9 day-old mice within 1 to 48 hours

44. Receptor Glutamate ? Death

45. The sequence of ischemic events in the brain From Ugarte and Osborne, Progress Neurobiol 64 (2001) 219-249

46. In cultured spinal neurons, glutamate deregulates Ca2+ homeostasis in a Ca-dependent manner Tymianski et al. J. Neurosci. 13 (1993) 2085-2104

47. Blocking NMDA receptors prevents glutamate-induced deregulation of Ca2+ homeostasis and neuronal death Ca2+ deregulation Dead Neurons Fraction deregulated/dead APV – NMDA receptor inhibitor CNQX – AMPA/kainate receptor inhibitor NIM – voltage-gated Ca channel inhibitor Conclusion: Inhibiting NMDA receptors is sufficient to protect the neurons against glutamate-induced death Tymianski et al. J. Neurosci. 13 (1993) 2085-2104

48. Failure of clinical stroke trials with glutamate receptor antagonist Drugs Mode of action Result Selfotel competitive NMDA antagonist trial discontinued Aptiganel noncompetitive NMDA antagonist adverse effects MK-801 noncompetitive NMDA antagonist adverse effects Dextrorfan noncompetitive NMDA antagonist adverse effects GV150526 glycine site antagonist of NMDA rec. no efficacy Eliprodil polyamine site antagonist of NMDA rec. no efficacy NBQX competitive AMPA receptor antagonist trial discontinued adverse effects renal toxicity Cerebrovasc. Dis. 11, suppl 1 (2001) 60-70

50. CaEDTA but not ZnEDTA protects CA1 neurons against ischemic death The role of zinc in ischemic neuronal death Zinc-specific fluorescence in rat hippocampus before ischemia CA1 region 3 days after 10-min ischemia Zinc-specific fluorescence Fuchsin staining (pink) of degenerating neurons Koh et al. Science 272 (1996) 1013-1016