nitric oxide and its role in therapeutics
TRANSCRIPT
Dr. Aditi M. Panditrao 1
Dr. Aditi M. Panditrao 2
Nitric Oxide and its role in Therapeutics
Dr. Aditi M. Panditrao
Dr. Aditi M. Panditrao 3
Nitric Oxide – A unique molecule
• Harmful and Helpful
• Discovered – 240 years ago
• Function in body – 28 years ago
Dr. Aditi M. Panditrao 4
Robert Furchgott Louis Ignarro Ferid Murad
Nobel Prize – 1998
Dr. Aditi M. Panditrao 5
What is Nitric Oxide?
• Unstable free radical gas
• Lipid Soluble, very small
• Highly reactive
Dr. Aditi M. Panditrao 6
Biosynthesis
• 3 main mechanisms:
• Via Nitric Oxide Synthase
• From Dietary Nitrates
• Nitric Oxide Donors
Major Pathway
Dr. Aditi M. Panditrao 7
Biosynthesis
via Nitric Oxide Synthase (NOS)
Dr. Aditi M. Panditrao 8
Biosynthesis
Nitric Oxide Synthase (NOS)
Neuronal NOS (nNOS)
Endothelial NOS (eNOS)
Inducible NOS (iNOS)
• Macrophages• Kupffer cells• Neutrophils• Fibroblasts• Vascular smooth
muscle
• Endothelium• Cardiac myocytes• Osteoblasts• Osteoclasts
• Neurons• Skeletal muscle
Constitutive Forms (Physiological)
Pathological
Dr. Aditi M. Panditrao 9
Biosynthesis
Activation of eNOS
Dr. Aditi M. Panditrao 10Http://www.kumc.edu/research/medicine/biochemistry/bioc800/sig02-06.htm
Dr. Aditi M. Panditrao 11
Biosynthesis
iNOS
Dr. Aditi M. Panditrao 12
Biosynthesis
Nitric Oxide Synthase (NOS)
nNOS
• Long Term Potentiation
• Cardiac function, Peristalsis, Sexual arousal
eNOS• Vascular tone,
Insulin secretion, Airway tone, Regulation of cardiac function and angiogenesis
• Embryonic heart development
iNOS• In response to
attack by parasites, bacterial infection and tumor growth
• Causes septic shock, autoimmune conditions
Dr. Aditi M. Panditrao 13
Biosynthesis
• 3 main mechanisms:
• Via Nitric Oxide Synthase
• From Dietary Nitrates
• Nitric Oxide Donors
Dr. Aditi M. Panditrao 14
Pharmacokinetics
• Absorbed systemically after inhalation
• Moves across the pulmonary capillary bed - combines with hemoglobin
• Inactivation – Haem, Oxidation, Superoxide
• Nitrate - excreted in the urine
• No known storage mechanism in humans.
Dr. Aditi M. Panditrao 15
Inactivation
• Haem –Haem + NO → Methaemoglobin + Nitrate (urine)
• Oxidation – 2NO + O2 → N2O4
N2O4 + H2O → NO2- + NO3
- + 2H+
NO2- + HbO → NO3
- + Hb
HAEM
Dr. Aditi M. Panditrao 16
Inactivation
• Superoxide –
NO(Nitric Oxide)
O2●-
(Superoxide)OONO-
(Peroxynitrite)
SOD(Superoxide Dismutase)
H2O2 + O2(Hydrogen Peroxide)
Cellular Injury
Dr. Aditi M. Panditrao 17
Mechanism of Action
Dr. Aditi M. Panditrao 18
Dr. Aditi M. Panditrao 19
Role?
• NO as a signaling molecule• NO in the nervous system• NO in the circulatory system• NO in the respiratory system• NO in the immune system• NO in the digestive system• NO in Cancer
Dr. Aditi M. Panditrao 20
NO – Signaling Molecule
1. Metalloproteins
2. Thiols
3. Tyrosine
Dr. Aditi M. Panditrao 21
Signaling Molecule
• Metalloproteins –
Dr. Aditi M. Panditrao 22
Dr. Aditi M. Panditrao 23
Signaling Molecule
• Thiols – • – SH containing• NO + Thiols → Nitrosothiols• Glutathione• Vascular Glutathione decreased in DM, Atherosclerosis
• Tyrosine Nitration – • Marker of oxidative stress and tissue damage
Dr. Aditi M. Panditrao 24
NO – Nervous System
• Neurotransmitter
• Retrograde Messenger• In learning and memory (non-declarative)
• Vasodilation – • Hypoxia
Dr. Aditi M. Panditrao 25
Dr. Aditi M. Panditrao 26
Nervous System
• Neurotransmitter?Similarities – • Present in presynaptic terminal• Natural removal from synaptic junction
Dissimilarities –
Nitric Oxide Neurotransmitters
Synthesized on demand Constant Synthesis
Diffuses out of cells Exocytosis from vesicles
Enters cell, binds to intracellular sGC
Binds to surface receptor
Dr. Aditi M. Panditrao 27
Nervous System
• Neurotransmitter?
• Assists other neurotransmitters
• Neuroprotective or Neurodegenerative?
Dr. Aditi M. Panditrao 28
NO and Pain
• In spinal cord
• Evidence of increased NO in states of Chronic Pain
• Sensitization of neurons to painful stimulus?
Dr. Aditi M. Panditrao 29
Neurotoxicity
• CNS dementia during AIDS• Multiple Sclerosis• Bacterial Meningitis• Migraine• Alzheimer’s Disease• Huntington’s Disease
Dr. Aditi M. Panditrao 30
NO – Circulatory System
• Vasodilator
• Antiatherosclerotic
• Antithrombotic
• Aids gas exchange between haemoglobin and cells
Dr. Aditi M. Panditrao 31
Smooth Muscle Contraction
Dr. Aditi M. Panditrao 32
Circulatory System
• Vasodilator -
Dr. Aditi M. Panditrao 33
Dr. Aditi M. Panditrao 34
Circulatory System
• Antiatherosclerotic & Antithrombotic
Dr. Aditi M. Panditrao 35
Dr. Aditi M. Panditrao 36
Circulatory System
• Heart • Depresses all cardiac functions
• Pre-eclampsia
• Sickle cell disease
Dr. Aditi M. Panditrao 37
NO – Immune System
• iNOS in phagocytes – NO
• Antibacterial, antiparasitic
• Formation of Reactive species
Dr. Aditi M. Panditrao 38
Dr. Aditi M. Panditrao 39
NO – Septic Shock
• Increased iNOS or NO
• Hypotension, cardiodepression, edema, vascular hypoactivity
• Tyrosine nitration?
Dr. Aditi M. Panditrao 40
NO – Respiratory System
• Bronchodilation
• Increased blood flow
• Shunting
• NO2 – Acute Lung Injury, Pneumothorax
Dr. Aditi M. Panditrao 41
Respiratory System
• Asthma –
• Inflammatory hyperreactivity of airway
• Increased NO production
• Exhaled NO – Biomarker
Dr. Aditi M. Panditrao 42
Dr. Aditi M. Panditrao 43
Dr. Aditi M. Panditrao 44
NO – Digestive System
• Stretching of stomach
• Gut motility
• Protective mechanisms
• Protective in NSAID induced injury?
Dr. Aditi M. Panditrao 45
NO – Cancer
• Pro Cancer –
• Angiogenesis• Invasion• Metastasis• Apoptosis of macrophages
Dr. Aditi M. Panditrao 46
NO - Cancer
• Anti Cancer –
• Cytotoxic
• Suppresses Cellular respiration
• Apoptotic
• Inhibits viral replication
Dr. Aditi M. Panditrao 47
Dr. Aditi M. Panditrao 48
NO - Miscellanous
• Impotence
• Infantile Hypertrophic Pyloric Stenosis
• Wound Healing
• Osteoarthritis
Dr. Aditi M. Panditrao 49
Dr. Aditi M. Panditrao 50
Therapeutic Applications
• Neonatal Hypoxic Respiratory Failure
• Pulmonary Hypertension (Adults)
• Adult Respiratory Distress Syndrome?
• Inhaled NO
Dr. Aditi M. Panditrao 51
Dr. Aditi M. Panditrao 52
Therapeutic Applications
• Inhaled NO – • Selective pulmonary vasodilator• Decrease Pulmonary Vascular Resistance• Improve oxygenation• Reduce inflammation• Antibacterial
• Unsatisfactory results from trials
Dr. Aditi M. Panditrao 53
Therapeutic Applications
• iNO Problems – • Disproportionate vascular selectivity• Systemic effects• Reacts with Oxygen• Methemoglobin• Prolongation of PT• Rebound Pulm. HTN and Hypoxemia• Infection
Dr. Aditi M. Panditrao 54
Therapeutic Applications
• Neonatal Respiratory Failure – • Start at 20 ppm• 5-14 days
• Pulmonary HTN • Heart and Lung Surgery• Asthma• Sickle Cell disease
Dr. Aditi M. Panditrao 55
NO Supplements
• Vasodilatory properties
• Side effects
• Not harmful in prescribed quantities
Dr. Aditi M. Panditrao 56
Dr. Aditi M. Panditrao 57
NO Donors
• Organic Nitrates – Nitroglycerin
• Organic Nitrites – Amyl nitrite
• Sodium Nitroprusside
• Beetroot
• NO releasers – Propofol, Nebivolol
Dr. Aditi M. Panditrao 58
• NO Inhibitors• NMMA (N- mono methyl arginine)• ADMA (Assymetric dimethyl arginine)• L-NAME (N-nitro-l-argenine methyl ester)
• NO potentiators – • PDE V Inhibitors• Statins, ACE-I, Insulin, Estrogens
Dr. Aditi M. Panditrao 59
Recent
• Use of iNO in neonates with surfactant dysfunction
• N-iminomethyl-L-lysine – selective iNOS inhibitor
• 7-nitroindazole-S-methyl-L-thiocitruline – selective nNOS inhibitor
• S-nitrosoglutathione (SNOG)• S-nitrosoacetylpenicillamine (SNAP)
Dr. Aditi M. Panditrao 60
Recent
• Epoprostenol (PGI2) – alternative to iNO
• Diazeniumdiolates – Anticancer(Nanoparticles)
• NO topical
• NO saliva test
• COX – inhibiting NO Donors – Naproxcinod
Dr. Aditi M. Panditrao 61
Thank You!!
Dr. Aditi M. Panditrao 62