1. 1 بسم الله الرحمن الرحيم

2. Presented By: Magd Mohamed Galal Professor Of Chest Diseases Al Azhar University Faculty Of Medicine For Girls 2012 2

3.  Discussing the relevance of genetic profiling of genes involved in mediating smoking behavior and addiction 3

4.  Although the risk of cigarette smoking is well documented, tobacco smoking continues to be the largest preventable cause of disease and premature death throughout the world.  It is estimated that there are currently still over 1.5 billion smokers worldwide, is expected to reach about 1.6–1.9 billion by 2025. 4

5.  Inhalation of (cigarette) smoke has several deleterious effects on the airways, leading to and/or influencing chronic respiratory diseases such as asthma and chronic obstructive pulmonary disease (COPD).  According to World Health Organization estimates (in 2007), 300 million people have asthma and 210 million people have COPD. 5

6.  In contrast to other common smoking- related diseases, such as cardiovascular disease and cancer, chronic respiratory diseases are the only causes of death that are still increasing.  By 2015, about 30% of the smoking-related deaths will probably be caused by chronic respiratory diseases. Mathers & Loncar,2006 6

7.  Smoke affects all people who are exposed to it, but the degree and severity is modified by many susceptibility determinants.(Martin et al2009)  Half the world’s children are involuntarily exposed to smoke 7

8.  440,000 deaths in the U.S. each year  4.8 million deaths world wide each year  10 million deaths estimated by year 2030  50,000 deaths in the U.S. due to second-hand smoke exposure  8.6 million disabled from tobacco in the U.S. alone 8

9. * Comparative Causes of Annual Deaths in the United States Number of deaths (thousands) Source: Centers for Disease Control and Prevention AIDS Alcohol Motor Homicide Drug Suicide Smoking Vehicle Induced Also suffer from mental illness and/or substance abuse * 9

10. Years of life gained Age at cessation (years) Prospective study of 34,439 male British doctors Mortality was monitored for 50 years (1951–2001) On average, cigarette smokers die approximately 10 years younger than do nonsmokers. Among those who continue smoking, at least half will die due to a tobacco-related disease. Doll et al. (2004). BMJ 328(7455):1519–1527.

11. Absorption is pH dependent  In acidic media  Ionized  poorly absorbed across membranes  In alkaline media  Non ionized  well absorbed across membranes 11 At physiologic pH (7.3–7.5), nicotine is readily absorbed.

12.  Inhaled nicotine is quickly absorbed from the large surface area of the alveoli into the pulmonary veins  Rapidly enters the arterial system  Time to arterial peak is less than 10 seconds  Easily crosses blood-brain barrier and begins to reach nAchRs in ~20 seconds  Crosses the placenta freely  Appears in breast milk in concentrations ~x2 those found in blood 12 Dani JA, et al (2009)

13. 13 Data from Henningfield et al., Drug Alcohol Depend 1993;33:23-29. Graph reprinted with permission, Rx for Change, The Regents of the University of California, University of Southern California, and Western University of Health Sciences. Arterial Venous Nicotine reaches the brain within 11 seconds

14.  Nicotine in a cigarette = 8 to 10 mg  Each cigarette delivers 1.2-2.9 mg of nicotine  A typical pack-a-day smoker absorbs 20-40mg of nicotine each day  Half-life is ~ 2hours  During a typical day, nicotine accumulates over 6-8 hours (3-4 half-lives) 14 Dani JA, et al (2009)

15.  The increment is 5-30 ng/ml after each cigarette (depending on how the cigarette is smoked)  More frequent smoking reduces fluctuations in nicotine plasma concentration  The plateau (10-50 ng/ml) is usually reached in the early afternoon 15 Dani JA, et al (2009)

16.  Biphasic action- nicotinic acetylcholine receptors  Agonist – low doses  Antagonist – high doses  Although a stimulant, it is often used to relax  Works in CNS and PNS  One of the most toxic dependence-producing psychoactive compounds overall  Nicotine acts to stimulate dopamine release in mesolimbic dopamine pathway (reward center). 16

17. 17

18. 18

19. 19

20.  Nicotine rises the stimulation of nicotinic receptors. The excessive and chronic activation of these receptors is balanced by a down- regulation in the number of active receptors.  The reduction of the number of active receptors reduces the psychotropic effect of nicotine. Due to the phenomenon of tolerance, the smoker needs to smoke more and more cigarettes to keep a constant effect. 20

21.  The first cigarette of the day is the most pleasant because the sensibility of the dopamine receptors is maximal. Then, the receptors are soon desensitized and the pleasure wears off. 21

22. 22 Tuberoinfundibular pathway Hypothalamus to Pituitary gland. Hormonal regulation. Maternal behavior (nurturing). Pregnancy. Sensory processes Mesolimbic and Mesocortical pathways Ventral Tegmental Area to Nucleus Accumbens, Amygdala & Hippocampus, and Prefrontal Cortex. Memory. Motivation and emotional response. Reward and desire. Addiction. Can cause hallucinations and schizophrenia if not functioning properly Nigrostriatal pathway Substantia Nigra to Striatum. Motor control. Death of neurons in this pathway can result in Parkinson's Disease

23. Nicotine enters brain Stimulation of nicotine receptors Dopamine release Dopamine Reward Pathway Prefrontal cortex Nucleus accumbens Ventral tegmental area 23

24. Dopamine Pathways Functions  reward (motivation)  pleasure,euphoria  motor function (fine tuning)  compulsion  perserveration  decision making Serotonin Pathways Functions  mood  memory processing  sleep  cognition nucleus accumbens hippocampus striatum frontal cortex substantia nigra/VTA raphe 24

25. Neuronal structure (receiving) (sending) 25

26. Vmat transporter stimulation DA How some drugs of abuse cause dopamine release: opioids narcotics (activate opioid receptors) nicotine (activate nicotine receptors) How some drugs of abuse cause dopamine release: opioids narcotics (activate opioid receptors) nicotine (activate nicotine receptors) vesicle Neuronal terminal 26

27. 27 Perry et al. J Pharmacol Exp Ther 1999;289:1545–1552. Nonsmoker Smoker Human smokers have increased nicotine receptors in the prefrontal cortex. High Low Image courtesy of George Washington University / Dr. David C. Perry

28. 28 Reprinted from Med Clin N Am 76(2), Benowitz NL, Cigarette smoking and nicotine addiction, pp. 415–437, Copyright 1992, with permission from Elsevier.

29. Hedonic Scale Normal Affective Response to Drugs/Alcohol Altered Dysregulated Set-Point following chronic drug use (Koob, Science, 1997) Hedonic Set Point is Altered with Chronic Drug Use Initially use to get high… Now use to “get normal” “ Cravings ” “Feel good” “Feel bad” Slide from Pating,D.

30. Metabolized and excreted in urine 30 CH 3 N H 10–20% excreted unchanged in urine Adapted and reprinted with permission. Benowitz et al. J Pharmacol Exp Ther 1994;268:296–303. 70–80% cotinine ~ 10% other metabolites N

31.  The CYP2A6 enzyme is responsible for 90% of nicotine metabolism  80% of nicotine becomes cotinine, which becomes 3 hydroxy-cotinine  Several genetic variants for the CYP2A6 enzyme have been identified 31 Hukkanen et al., 2005

32. 32

33.  The amine function of nicotine may react with nitrogen monoxide or with nitrous acid in order to form a "nitrosonium" type molecule.  This compound may then be transformed by the body, which means oxidized and opened. This opening leads to two isomers, two "nitrosamino" type molecules (R 2 N-N=O) where one of the two R group is a methyl. 33

34.  In acidic medium, the oxygen of the "nitrosamine" group is protonated and the double bond moves to the central nitrogen, which becomes positively charged. This new molecule is a methyl source. The "nitrosamine" group can then react with another amine, which removes the positive charge from the nitrogen.  If the amine that reacts is a part of the structure of the DNA, an irreversible alkylation of the DNA occurs  This alkylation is really noxious and may help in the development of cancer as it prevents the normal development of the cell. 34

35. 35

36.  Tobacco smoking is believed to be a complex, multi factorial behavior with both genetic and environmental determinants.  More recent studies have found significant genetic influences on several aspects of smoking behavior. 36

37.  It has been demonstrated that genetic factors account for approximately  40–75% of the variation in smoking initiation,  70–80% of the variation in smoking maintenance,  about 50% of the variance in cessation success  and 30–50% of the variance in risk of withdrawal symptoms. ( Xian 2003- Pergadia 2006) 37

38.  Variations in several genes have been suggested to contribute to smoking behavior, and research has been focused on two broad classes of candidate genes:  Genes that may influence the response to nicotine  Nicotine metabolism,  Nicotinic receptors  Genes that may predispose to addictive behavior due to their effects on key neurotransmitter pathways  Dopamine and  Serotonin. (MacLeod 2006-Batra 2003) 38

39. 39

40.  The major genes responsible for the metabolism of nicotine are the hepatic enzymes  cytochrome P450 2A6 (CYP2A6) and  cytochrome P450 2D6 (CYP2D6). 40

41.  CYP2A6 genetic variants predict level of smoking and nicotine dependence, and severity of withdrawal 41 Malaiyandi et al., 2006; Kubota et al., 2006 Nicotine Dependence Smoking Rate Withdrawal Symptoms

42.  3HC/cotinine ratio represents rate of metabolism (smaller value = slower metabolism)  Those with genetic variants thought to slow metabolism have a lower 3/HC/cotinine ratio  Proof of principle and verification of 3HC/cotinine as a phenotypic marker of CYP2A6 genetic variants 42 Malaiyandi et al., 2006; Lerman et al., 2006

43. 43

44. 44

45. 45 Nicotine-d2 Clearance (ml/min/kg) Duplication (*1x2)  clearance Inactive alleles (*4)  clearance Hukkanen et al., 2005

46.  Ultra metabolisers were found to be more likely to be heavy smokers 46

47. (Benowitz et al 2002). 47

48.  The rate of nicotine metabolism is faster in women than men (Benowitz et al 2006).  Among women, nicotine metabolism is faster in women taking estrogen-containing oral contraceptives, and is even faster during pregnancy, compared with other women. 48

49. 49

50. 1 Schnoll et al. (2007) Curr Psychiatry Rep, 9:349-357. 2 Hutchison et al. (2007) Arch Gen Psychiatry, 64(9):1078-1086. 50

51. 51

52.  Investigators have examined the association between smoking behavior and variations in several genes involved in the dopamine pathway, such as  Dopamine receptors,  The dopamine transporter and  Enzymes involved in dopamine synthesis and metabolism. 52 (Balfour 2004)

53. 53

54. 54 ( Laucht et al 2005)

55. (Lerman et al 1999)55

56. (Zhang et al, 2006) 56

57.  In addition to direct and indirect stimulation of neurotransmitter release, chronic cigarette smoking (but not nicotine administration) reduces brain monoamine oxidase A and B (MAO A and MAO B) activity, which would be expected to increase mono aminergic neurotransmitter levels such as dopamine and nor epinephrine in synapses, thus augmenting the effects of nicotine and contributing to addiction. 57 MansvelderHD,&McGeheeDS.2002.

58. 58

59. 59

60. 60

61. 61

62.  Smoke affects all people who are exposed to it, but the degree and severity is modified by many susceptibility determinants  Genetic factors account for approximately,40–75% of the variation in smoking initiation, 70–80% of the variation in smoking maintenance, about 50% of the variance in cessation success and 30–50% of the variance in risk of withdrawal symptoms. 62

63. Presented by Prof. Magd Mohamed Galal