Endothelial dysfunction (ED) plays a central role in erectile dysfunction (ED). ED reduces the bioavailability of nitric oxide (NO), which is important for relaxation of the corpus cavernosum and penile erection. Risk factors for ED and endothelial dysfunction include diabetes, smoking, hypertension, hyperlipidemia, and other conditions that promote oxidative stress and reduce NO bioavailability.

1. ENDOTHELIAL DYSFUNCTION ( ED ) in ERECTILE DYSFUNCTION( ED ) ED = ED M.Y.ABDEL_MAWLA,MD Zagazig Faculty of Medicine,EGYPT

2. Causes of Erectile Dysfunction( ED ) Endothelial dysfunction ED Smoking Hypogonadism Endocrine Disorders Hypertension Hyperlipidemia Alcohol abuse Drug abuse Anemia Trauma/surgery to pelvis or spine Peyronie’s disease Vascular surgery Depression

4. The Endothelium

5. LUMEN Tunica adventitia Tunica media Tunica intima

7. Note the individual Endothelial Cells

10. Vasoconstriction and dilatation Normal Vasoconstriction Vasodilatation

11. Vasoconstriction Vasodilatation Vasoconstriction and dilatation ↓ Resistance to flow ↑ Resistance to flow

12. Endothelial Apoptosis Normal Apoptosed

13. The Endothelium As an Endocrine Organ

14. The inner lining of our bloods vessels is the Endothelium It plays a central role in regulating the vasomotror tone & Local homeostasis & control of the coagulation process Endothelial cells have ‘Sensors’ and release ‘Mediators ’ ‘ Mediators’ are the functional molecules on the cell surface The Vascular Endothelium

15. Oxidative stress and Endothelial dysfunction Oxidative Stress leads to ED Endothelial dysfunction is mainly due to reduced bioavailability and bioactivity of Nitric Oxide (NO) It is also a physiological process Takes place gradually by age and menopause .

16. Oxidant stress and Endothelial dysfunction are major factors for atherosclerosis – the common pathway – for most of the cardiovascular risk factors including Hypertension, DM, Dyslipidemia and Smoking. Both endothelial dysfunction and oxidant stress result in clinical conditions - Heart failure, IHD and MI The Effects of ED

17. Nitric oxide (NO) Cycloxygenase (CxO) Endothelin-1 (ET-1) Endothelium Depolarisation Factor (EDF) Prostanoids Angiotensin Rho/Rho-kinase Prostaglandin E &prostacyclin (cAMP pathway). Vascular Endothelial Mediators

18. Half-life of NO, is affected by its chemical reaction and inactivation by superoxide anion NO is the most abundant free-radical in the body It is the only biological molecule in high concentrations to out-compete superoxide dismutase for superoxide NO has an anti-thrombogenic & anti-atherogenic role Nitric Oxide (NO)

19. Nitric Oxide(NO)/cGMP PATHWAY Relaxation of the smooth muscle trabeculae of the corpus cavernosum (CC)1 and of the helicine arteries leads to blood filling of the sinuses, occlusion of the venous outflow& penile erection. Nitric oxide (NO), generated by both nerves & the endothelial cells that cover the trabeculae of the CC, through stimulation of soluble guanylate cyclase and the generation of cyclic GMP play a dominant role in relaxation of smooth muscle in this tissue. Other signaling pathways involving vasoactive intestinal polypeptide/cAMP may also be operative in relaxation of the CC. Severe erectile dysfunction ((ED) in cGMP -dependent kinase 1-deficient mice, with normal cAMP signaling, shows the importance of PKG and the inability of the cAMP pathway to compensate for the absence of the cGMP signaling cascade in vivo .

20. (L-NMMA) = N(G)-mono-methyl-L-arginine

21. Endothelial NO has the following actions Smooth muscle relaxation and vasodilatation Essential for regulation of blood pressure Reduces proliferation of vascular smooth muscle Protects blood vessel intima from injurious consequences of platelet aggregation Protective actions of NO

22. NO deficiency in the vessel wall promotes Inflammation Oxidation of lipoproteins Smooth muscle proliferation Accumulation of lipid rich material Platelet activation and thrombus formation ED and NO ↓

23. NO induces synthesis of cGMP by stimulation of GC leading to relaxation of myosin (muscle protein)

25. Acetylcholine stimulates the endothelial cells to produce NO, which penetrates into and activates the muscle cells causing relaxation.

26. (L-NMMA) = N(G)-mono-methyl-L-arginine

27. (L-NMMA) = N(G)-mono-methyl-L-arginine (L-NMMA) = N(G)-mono-methyl-L-arginine

29. Regulatory Functions of the Endothelium Normal Dysfunction Vasodilation Vasoconstriction NO, PGI2, EDHF, BK, C-NP ROS, ET-1, TxA2, A-II, PGH2 Thrombolysis Thrombosis Platelet Disaggregation NO, PGI2 Adhesion Molecules CAMs, P,E Selectins Antiproliferation NO, PGI2, TGF-  , Hep Growth Factors ET-1, A-II, PDGF, ILGF, ILs Lipolysis Inflammation ROS, NF-  B PAI-1, TF- α , Tx-A2 tPA, Protein C, TF-I, vWF LPL Vogel R

30. Endothelium –derived vasoconstrictors vs Vasodilators Contractoion- mediating transmitters Endothelin Prostanoids Angiotensin Rho A/Rho-kinase Relaxation-mediating transmitters Nitric oxide & cGMP pathway Prostaglandin E, prostacyclin& cAMP pathway

31. Endothelium-derived vasodilators Functions relax vascular smooth muscle in both arteries and veins NO and PGI2 also inhibit platelet aggregation NO also interferes with the vascular inflammatory process by decreasing the adhesive interactions between the endothelium and circulating leukocytes, thus interfering with the atherosclerotic process

32. Endothelin peptides Endothelin-1(ET-1):synthesied by lacunar endothelium & trabecular muscle It induces contraction,via ETA receptors in penile smooth muscles( corpus cavernosa&cavernosal artery). Contraction : dependent upon increased intracellular calcium via: Transmembrane calcium flux Mobilization of inositol,1,4,5-triphosphate (IP3)-dependent calcium stores

33. Endothelin peptides Endothelin-1, a 21-amino-acid peptide, is the predominant isoform of the endothelin peptide family that includes ET-2, ET-3, and ET-4 Endothelin-1 is produced primarily by endothelial cells but can also be synthesized by vascular smooth muscle cells (VSMCs) and by macrophages The action of ET-1 are mediated by 2 receptor subtypes, ETA and E TB receptors

34. Endothelin ET A receptor mediate the vasoconstrictor effects of the peptide, ET B receptors on the endothelium stimulates synthesis of NO Increased ET-1 associated with decreased endothelium-dependent vasodilation, a reduction in the biologic actions of NO, and an increased production of oxygen-derived free radicals These effects are thought to contribute to heightened vasoconstriction and increased blood pressure increased monocyte adhesion to the vascular wall increased thrombosis a vascular inflammatory response augmented proliferation of VSMCs

35. Prostanoids Several prostanoids:PGI &thromboxane Synthesized from arachidonic acid via activity of cycloxygenase in human corpus cavernosa. Synthesis :modulated by oxygen tension &hypoxia. They are responsible for tone & spontaneous activity of trabecular muscle.

36. Rho A/Rho-kinase Rho A: a member of Ras low molecular weight of GTP-binding protein. Both Rho A &Rho –kinase :in different cellular functions including smooth muscle contraction. Human endothelial &corpus cavernosa smooth muscle cells express these proteins. RhoA/Rho-kinase signal transduction pathway:signal mediator of endothelial cell function. Rho-mediated Ca2+sensitization of cavernosal smooth muscle maintains the flaccid (contracted) state. This pathway supppresses eNOS gene expression in endothelium.

37. Angiotesin Renin-angiotensinsystem maintains penile smooth muscle tone. Angiotensin 11 evokes smoth muscle contraction of human corpus cavernosa muscle via relevent receptor & increased IP3 &increased intracellular calcium

38. Nitric Oxide(NO)/cGMP PATHWAY Relaxation of the smooth muscle trabeculae of the corpus cavernosum (CC)1 and of the helicine arteries leads to blood filling of the sinuses, occlusion of the venous outflow& penile erection. Nitric oxide (NO), generated by both nerves & the endothelial cells that cover the trabeculae of the CC, through stimulation of soluble guanylate cyclase and the generation of cyclic GMP play a dominant role in relaxation of smooth muscle in this tissue. Other signaling pathways involving vasoactive intestinal polypeptide/cAMP may also be operative in relaxation of the CC. Severe erectile dysfunction in cGMP-dependent kinase 1-deficient mice, with normal cAMP signaling, also demonstrated the importance of PKG and the inability of the cAMP pathway to compensate for the absence of the cGMP signaling cascade in vivo .

39. Endothelial production of vasoactive factors Normal endothelium is pivotal in the maintenance of normal vascular homeostasis through a balanced production of vasodilator and vasoconstrictor substances Endothelium-derived vasodilators Endothelium-derived vasoconstrictors

40. Endothelium-derived vasodilators Nitric oxide (NO) Adrenomedullin Endothelium-derived hyperpolarizing factors Prostacyclin (PGI2) relax vascular smooth muscle in both arteries and veins NO and PGI2 also inhibit platelet aggregation NO also interferes with the vascular inflammatory process by decreasing the adhesive interactions between the endothelium and circulating leukocytes, thus interfering with the atherosclerotic process

41. Vasoconstrictors From the sympathetic nerves, circulation, endothelium Norepinephrine (NE) Angiotensin II Thromoxane A2 5-hydroxyeicosatetaraenoic acid (5-HETE) Endothelin (ET)-1

42. Endothelium-dependent vasodilator and vasoconstrictor mechanisms

43. Endothelium-derived NO & vascular tone NO-a potent mediator of vascular relaxation through action on soluble cGMP in VSMC to inhibit ca-dependent contraction NO synthesis & release occurs continuously under basal conditions & can be increased through activation of muscarinic, thrombin, purinergic, and ET B receptors in the endothelial-cell plasma membrane that mediate the actions of acetylcholine, thrombin, ADP, and ET-1 respectively Changes in vascular wall shear forces associated with increased flow also increase NO release Sustained increase in BP-by continuous administration of stereoselective inhibitors of NO synthase further indicates-NO is important in maintenance a vasodilated state.

49. ENOTHELIUM DYSFUNCTION(ED)

51. The Mechanism of the Assocation Between Endothelium&Erectile Dysfunction

53. The roles of two forms of nitric oxide synthase in cavernosal smooth muscle relaxation and the initiation and maintenance of penile erection Watts Permission obtained from National Academy of Sciences © Hurt KJ et al . (2002) Proc Natl Acad Sci USA 99: 4061–4066.

54. Risk Factors for Development of Endothelium& Erectile Dysfunction Diabetes Mellitus (DM) Insulin Resistance Syndrome. Cigarette Smoking Hypertension Atherosclerosis &Hyperlipidemia

55. Endothelial dysfunction in DM

56. NO and endothelial dysfunction in diabetes Type 1 diabetes- -impaired endothelium-dependent vasodilation in response to acetylcholine and similar agonists that stimulate the release of NO Type 1 and 2 diabetes—endothelium-dependent vasodilatory responses to brachial artery infusions of acetylcholine, methacholine, and similar agonists are impaired in the forearm In normotensive type 2 diabetes—demonstration of blunted endothelium-dependent vasodilation suggests that the endothelial abnormalities cannot be ascribed solely to the impaired endothelium-dependent vasodilation Contribution of prostaglandins to abnormalities in endothelial function is minimal

58. Mechanisms of impaired endothelium-derived vasodilation in diabetes Biologic actions of NO are diminished in diabetes, but production of NO is actually increased Increase in the production of ROS by several vascular components in diabetics Interactions of NO & superoxide anion within the microenvironment of the vessel wall-- inactivation of NO & formation of the potent oxidant radical, peroxynitrite (OONO - )

59. Mechanisms of impaired endothelium-derived vasodilation in diabetes The ratio of NADH/NAD+ :increased in diabetes reducing the levels of NADPH which is an essential cofactor for NO synthesase & increase levels of calcium elevating messengers, thus increasing smooth muscle contractility. Decreased endothelium –derived hyperpolarization factor( EDHF ) in human penile arteries,hence reduction of endothelium-dependent relaxation

60. Hyperglycemia in DM Associated with diminished biologic actions of NO Tesfamariam: impaired vasodilatory responses to high glucose levels- -caused by increased oxygen-derived free radicals through a protein kinase C-mediated mechanism that stimulates the formation of vasoconstrictor prostanoids The vasoconstrictor effect can be abolished by aldose reductase inhibitors High glucose increase both NO synthase expression & superoxide anion generation by aortic endothelial cells.

61. Dyslipidemia in DM (1) Elevated TG, low HDL-c, and elevated IDL—insulin resistance syndrome Hypercholesterolemia is associated with impaired endothelium-dependent vasodilation in human forearm & pig coronary arteries & rabbit aorta These functional vascular changes associated with Increase generation of ROS Persistence of endothelial NO release Increased generation of OONO- Oxidative modification of LDL

62. Dyslipidemia in DM (2) The extent of ROS formation-also be a determinant of endothelial NO release-it may affect the proportion of circulating and tissue cholesterol that has been oxidized Oxidatively modified LDL- -impair endothelium-dependent vasodialtion more than native LDL in vascular ring Hypertriglyceridemia -independent risk factor for CAD Postprandial hypertriglyceridemia--cause a transient impairment of endothelium-dependent vasodilation in normal volunteers Postprandial hypertriglyceridemia is more exaggerated in type 2 diabetics & associated with higher forearm venous free radical & greater impairment of flow-dependent vasodilation

63. Increased oxidative stress in diabetes Oxidative stress—imbalance between the production of ROS and the numerous antioxidant defense mechanisms present in biologic systems Reactive oxygen species (ROS) include superoxide anion that is converted to hydrogen peroxide both enzymatically and by several isoforms of the enzyme superoxide dismutase In diabetes, overproduction of ROS overwhelms normal antioxidant defenses with consequent alterations in both the function and the structure of the CV system

64. Insulin resistance syndrome and endothelial dysfunction Syndrome of insulin resistance may precede the onset of overt type 2 diabetes The clinical features include hyperinsulinemia, truncal obesity, hypertension, and dyslipidemia characterized by elevated serum TG, low HDL-C, and increased IDL These hallmarks are thought to result from relative insensitivity of selected tissues, particularly skeletal muscle, to the action of insulin

65. Insulin resistance syndrome It is hypothesized that compensatory hyperinsulinemia maintains the serum glucose within the normal range until pancreatic islet  -cells can no longer produce sufficient insulin, and overt type 2 diabetes occur Insulin resistance is associated with a clustering of CV risk factors that predispose patients with this metabolic syndrome to later CV events There is evidence of sympathetic nervous system activation that may contribute to the hypertension that develops.

66. Insulin resistance syndrome Insulin itself promotes vasodilation , in part through stimulation of endothelial NO release This vasodilatory action may be counterbalanced in the insulin resistance syndrome by the development of hypertension, which independently impairs endothelium-dependent vasodilation

67. Endothelin and endothelial dysfunction in diabetes Endothelin-1, a 21-amino-acid peptide, is the predominant isoform of the endothelin peptide family that includes ET-2, ET-3, and ET-4 Endothelin-1 is produced primarily by endothelial cells but can also be synthesized by vascular smooth muscle cells (VSMCs) and by macrophages The action of ET-1 are mediated by 2 receptor subtypes, ET A and E T B receptors

68. Endothelin in DM Plasma ET-1 are increased in type 2 diabetes Most of the ET-1 cause vasoconstriction of VSMCs through a paracrine effect mediated by ET A receptors Infusion of ET-1 cause sustained increases in BP Nonselective ET A /ET B antagonist, bosentan, lowers BP in patients with essential hypertension Plasma ET-1-may be a marker for atherosclerotic disease in type 2 diabetic patients ET-1 participate in the fibrotic process--an essential component of the glomerulosclerosis, cardiac and vascular remodling, and atherosclerosis that occur at an accelerated rate in hypertensive type 2 diabetics.

69. Advanced glycation end products (AGEs)in Diabetes AGEs formed by the nonenzymatic binding of glucose to lipids or to free amino groups on proteins The formation of AGEs is inhibited by NO, whose biologic actions are blunted in diabetics The increased stiffness of the arterial wall contributes to isolated hypertension The increased systolic pressure in turn produces an increased workload on the left ventricle, resulting in increased left ventricular mass Reduction arterial wall compliance linked to increased CV risk in type 1 & 2 diabetics and occur early in the course of DM before vascular disease is clinically apparent

70. Adverse consequences associated with endothelial dysfunction in diabetes mellitus Decreased NO formation, release, and action Increased formation of reactive oxygen species Decreased prostacyclin formation and release Increased formation of vasoconstrictor prostanoid Increased formation and release of ET-1 Increased lipid oxidation Increased cytokine and growth factor production Increased adhesion molecule expression Hypertension Changes in heart and vessel wall structure Acceleration of the atherosclerotic process

71. HYPERTENSION and Risk of Endothelium & Erectile Dysfuction CVS complications of hypertension is associated wit ED. In ED due to arterial insufficiency: low oxygen tensionin corporal blood,reduced PGE1 &PGE2, Increased tranformation of transforming growth factor(TGF)-B-induced fibrillar collagen synthesis in corpus cavernosa. Diffused venous leakage & failure of veno-occlusive mechanisms. Endothelial –dependent vasodilation:impaired. Age dependent &independent decrease of NO synthesis.

72. Endothelium in Hypertension

73. Endothelial mechanoreceptors changes in hypertension –induced stress

74. Cigarette Smoking Free radicles&aromatic compounds released from cigarette smoke: decrease endothelial NO Synthesae activity and elicit superoxide –mediated NO degradation ,tending to increased penilemisculature & promoting ED. Direct toxic effects of nicotine & CO2 on penile vasculature. Increased hyper- coaglulability agents

75. ATHEROSCLEOSIS & HYPERLIPIDEMIA :Effect on penile endothelium Chronic ischaemia:reduced NOS activity,reduced enothelium-dependent & neurogenic NO-mediated relaxation of cavernosal tissue together with elevated thromboxane-mediated contractions. High LDL : elevated contraction due to increased intracellular inositol & calcium. Chronic hypercholestraemia : Reduced endothelium dependent relaxation in cavernous tissue. 2.Impaired NO/cGMP pathway due to elevated superoxides & NOS inhibitors (eg.nitromonomethyl l arginine L_NMMA).

76. Can We Measure Endothelial Function ??

77. Clinical Methods for Assessing Endothelium - Dependent Dilation Forearm Brachial Artery Diameter  with Arterial Occlusion FMD Forearm Blood Flow with ACh

79. Penile/Brachial Index (PBI) 0.7 - 1.0 = normal 0.6 - 0.7 = borderline abnormal <0.6 = abnormal

80. What is the Treatment. for Endothelial Dysfunction ??

81. Control of all the known CV risk factors Main focus on the big six – DM, HTN, Lipids, Obesity, Smoking, Sedentary life style Diet and physical activity are vital in Rx of ED Statins are the first line treatment for ED Insulin and Rx. Insulin resistance improves ED What is the Treatment for Endothelial Dysfunction?

82. Erectile Dysfunction – Today’s concept Penis is the barometer of Endothelial Health Erectile Dysfunction is a mirror of Cardiovascular Risk ED = ED

84. Targeting Endothelium Dysfunction in Erectile Dysfunction Treating risk factors &disorders. Cessation of smoking. Long term phosohodiesterase-5 inhibitors therapy Antioxidant therapy Future directions Corporal tissue engeneering Gene therapy(eg Rho A/Rho A-kinase antisense gene therapy) .

86. Type 5 Phosphodiesterase (PDE5) Inhibitors Viagra (Sildenafil) Tabs: 25, 50, 100 mg. Levitra (Vardenafil) Tabs: 2.5, 5, 10, 20 mg. Cialis (Tadalafil) Tabs: 5, 10, 20 mg.

87. Take Home Messages Common under laying pathology is ED & ED . Endothelial Dysfunction can be measured Endothelium is the largest endocrine gland ED is diagnostic and prognostic ED can be treated and monitored ED = ED – So careful evaluation is needed Penis is the barometer of CV Risk

88. THANK YOU