Roles of Ginexin – FIn the

Treatment of GlaucomaBy

Professor Kamal Eldin Hussien ElTahirDepartment of Pharmacology

College of PharmacyKing Saud University

RiyadhMarch - 2006

1•Description of the Eye

2•Formation of the Aqueous Humour

• *The Anterior chamber is filled with an aqueous fluid called The Aqueous Humour

• *It is synthesized in the ciliary Bodies in the Posterior Chamber via the enzyme carbonic anhydrase.

– H2CO H2 + CO2

• *It flows to the Anterior chamber via the Pupil.• *It provides Nutrition to the Iris, Lens and Cornea.

• *It drains out (Passes out the eye) via: a) The Trabecular meshwork .

b) Schlemm’s Canal. c) Uveosclera.

into the venous circulation

3•Intraocular Pressure (IOP)

• *The Presence of the Aqueous Humour in the Anterior Chamber creates a pressure known as the Intraocular Pressure (IOP).

• *Its normal value is 18 - 20 mmHg.• *It is regulated by the rate of synthesis and

drainage outside the eye.• *Blockage of draining systems leads to

elevation of the pressure. The fluid will be forced backward into the Posterior Chamber and the back of the eye – the site of the optic nerve and the optic disk.

4•Differences between Ocular Hypertension and

Glaucoma• *Ocular Hypertension:

• This is an increase of (IOP) without optic nerve or optic disk damage. There is no loss of the visual field.

• *Glaucoma is a disease with or without clear rises in the IOP above the normal range but it is definitely accompanied by a progressive optic neuropathy leading to a slow progressive degeneration of the Retinal Ganglion Cells and Axons resulting in loss of Vision (Blindness). It affects 66 million Subjects in the world.

• *The degeneration of neurons may extend to the Lateral Geniculate Nucleus and the Visual Cortex.

5•Causes of Glaucoma

•A) Blockage of the Drainage system for the Aqueous Humour leads to rises in the (IOP). The fluid forces its way backward and thus the pressure increases on the Retinal ganglion cells and axons. This causes compressions and deformations of these structures. As a result there is decrease in the transport of proteins nutrients and trophic factors across the retinal nerves leading to degeneration and death of the

cells .

6•Non – IOP – Factors

•B) Besides the increase in the (IOP) other factors Contribute to the Retinal Nerves damage and loss of vision:

•) 1 (Deficiency of Ocular Blood flow to the Retinal Nerves. May be due to pressure of blood clots or decreases in release of prostacyclin and [NO], the major vasodilators. The resulting ischaemia and Hypoxia damage the nerves.

•) 2 (Excessive Release of the excitatory amino acid-glutamic acid which is a neurotransmitter in the Retinal ganglionic cell and neurons. Indeed the level of glutamate increases in the Posterior Chamber in subjects with Glaucoma. Glutamate induces damage of the retinal neurons via stimulation of Release of

Intracellular Ca2+.

7•Non – IOP – Factors (Contin.)

•)3(Increase in formation of free radicals e.g .•) -. O2 ,(-. OH, -. O-O-H

• These are highly damaging to the neurons. The -. OH radicals are highly damaging to the Neuronal DNA .

•)4 (Increase in release of Inflammatory Mediators e.g. TNF, PAF, PGE2, 5-HETE, 12-HETE, LTB4 from the Glial cells and Astrocytes.

•)5 (Presence of auto antibodies against the optic nerve.•)6 (Decrease in activity of cellular Pumps. N.B. Once

Neurons are damaged they release free radicals and neurotrans mitters to damage nearby unaffected

neurons .

8•Risk Factors in Glaucoma

•) 1 (Increase in Age ( in IOP)•) 2 (High Myopia ( in IOP)

•) 3 (Increase in thickness of cornea above 555 μm ( in IOP) .•) 4 (Genetical heredity. In 3 – 4 % of glaucoma Patients there are

mutations in the Glaucoma Gene at the GLCIA locus known as (Myocilin) .

•) 5 (Systemic Hypotension.•) 6 (Defective vascular autoregulations.

•) 7 (Retinal Haemorrhages.•) 8 (Cerebral Microvascular ischaemia.

•) 9 (Hypertension.•) 10 (Migraine. (11) Retinal vessels vasospasms.

•) 12 (Smoking ( IOP) + Retinal vein occlusion.•) 13 (Alcohol ( IOP).

9•Types of Glaucoma

•)1 (Primary open Angle Glaucoma. In this Type :• *The Entrance to the Drainage System is open but there

is Blockage inside the drainage canals.• *There is an elevation in IOP (Gradual).

• *Optic Disk and Nerve Damage.• *The most common type in 90% of patients.

•)2 (Closed Angle Glaucoma. In this type:• *The openning of the Drainage System is narrowed.

• *When the Pupil enlarges the iris branches up over the drainage canal.

• *The IOP rises quickly → Acute type or Gradual → Chronic closed or narrow Angle Glaucoma.

10•Types of Glaucoma (Contin.)

•Symptoms of closed-Angle Glaucoma:

• Headache, Eye Pain, Nausea Rainbows around lights at night and Blurred vision.

•)3 (Normal Tension Glaucoma:

• * Results from decrease in blood flow through the tiny arteries in the optic nerve.

11•Types of Glaucoma (Contin.)

•)4 (Secondary glaucoma

• *Results following:

• Eye injury, Inflammation, Tumors, Cataract, Diabetes mellitus Chronic use of steroids.

• *May be of the open-or closed-type.

12•Types of Glaucoma (contin.)

•)5 (Pigmentary Glaucoma• *This is a secondary open-angle glaucoma.

• *Results following the blockage of the drainage canals of the trabecular meshwork with small granules that break from the back of the iris and flow with the aqueous humour to close the canals and induce rise in the IOP.

•)6 (Pseudo-exfoliative Glaucoma• *This is a Secondary open-angle glaucoma.

• *It Results when a flaky material peels off the outer layer of the lens and blocks the space between the angle of the iris and the cornea of the eye resulting in inhibition of flow of aqueous humour to the trabeculator meshwork. Thus, No drainage of fluid.

• *Observed in Scandinavian .

13•Types of Glaucoma (contin.)

•)7 (Neovascular Glaucoma:•) Rubeotic Glaucoma(

• *It is a type of Secondary open-glaucoma.• *It occurs in severe diabetes mellitus.

• A retinal vein may block in one eye leading to leakage of blood which activates the Retinal cells leading to their damage and release of Vascular Endothelial Growth Factor (VEGF).

• *VEGF reaches the trabecular meshwork to stimulate growth of new blood vessels that also spread to the iris. As a result the drainage

network is blocked leading to rise in IOP .

14•Diagnosis of Glaucoma via:

•)1 (Measurement of the (IOP) using a Tonometer.

•)2 (Performance of Gonioscopy to check the openning or closure of the angle where the iris meets the cornea.

•)3 (Performance of Ophthalmoscopy to examine the optic disk and Retinal nerves using an Ophthalmoscope or preferably using Slit lamp Biomicroscope with an indirect lens or a contact lens to obtain an steroscopic view. This allows observation of optic disk curving (cupping),

haemorrhages and retinal nerve fibre layer loss .

15•Diagnosis (Contin.)

•)4 (Performance of automated Perimetry to assess the patient’s visual field.

•The peripheral field vision is affected earlier than the central visual acuity. In this test, the patient may be asked to look straight a head, then a moving light is passed and he will be asked when does the moving light pass his side vision. Alternatively, white stimuli on white background or blue stimuli against yellow backgrounds may be used.

•)5 (Measure the cornea thickness using a Pachymeter.

16•Diagnosis (Contin.)

•)6 (Performance of optic nerve and optic disk computer imaging using Optical Cohernce Tomography (OCT).

•This gives a contour map of the optic nerve, optic cup (disk) and Retinal Nerve Fibre Thickness.

•Or (7) Assess the thickness of the Retinal Nerve Fibre using Scanning Laser Polarimetry using a GDX machine.

•Or (8) Assess the Topography of the optic disk and the retinal surface to obtain Heidelberg Retinal Tomography [HRT II] using a cofocal Scanning Laser Opthalmoscope.

17•Treatment Strategy

•A) In glaucomas with elevated IOP, treatment should be directed to initially lower the IOP to 20 – 50% its initial level via drugs, laser therapy or surgery.

•B) In non-IOP- dependent glaucomas, treatment should be directed to enhance the retinal blood flow. A decrease in the IOP will also benefit the patient indirectly by enhancing blood flow to the retinal neurones.

•C) In all types of glaucomas attempts should be made to administer neuroprotectors to prevent secondary degeneration of the unaffected neurones. The neuroprotectors will act to prevent the spread of degeneration from the affected retinal ganglion cells and neurones to the yet undamaged ones. This can be obtained via administration of drugs that are: Vasodilators, antioxidants, antiglutaminergic at the N-methyl-D-Asparate receptor (NMDA), anti-inflammatory and antiplatelets.

18•Treatment with Drugs

•A) Drugs used to lower (IOP):•Group A: Prostaglandins Analogues

• Eye Drops of: (1)Latanoprost [xalatan].•) 2(Travoprost [Travatan]•) 3(Bimatoprost[Lumigan]

•) 4(Unoprostone•Mechanism of Action:

• a) They increase aqueous humour outflow through the uveoscleral pathway.

• b) Activate the enzymatic activity of matrix metaloproteinases leading to remodeling of the extra cellular matrix and decrease of resistance to outflow.

•Side effects: Ocular irritation and redness, darkening of iris, macular Oedema and lengthening and darkness of eye lashes .

19•Drugs (Contin.)

•Group (B): β-Adrenoceptor Blockers.•Eye Drops:(1)Timolol [Timpotic]0.25&0.5%•) 2(Betaxolol[Betopic]0.25&0.5%

•) 3 (Cartelol.•Mechanism of Action: They inhibit production of the Aqueous humour.

•Side effects: Eye dryness & irritation.

•Group (C): Carbonic Anhydrase Inhibitors :•Eye Drops: (1) Brinzolamide [Azopt] 1%.

•) 2 (Dorzolamide.•Tablets: (1) Acetazolamide [Diamox] 500mg.

•) 2 (Menthazolamide.•Mechnism of Action: Inhibition of the enzyme cabonic anhydrase that is

involved in the production of the Aqueous humour.•Side effects: For Drops: Eye Redness & irritation.

•For Tablets: Sedation, Parethesia, Anorexia, renal calculi, diarrhoea, fever.

20•Drugs (Contin.)

•Group (D): Cholinergic Drugs:•Eye Drops: (1) Pilocarpine [Isoptocarpine] 0.5-4%.

•) 2 (Carbachol.•Mechanism of Action: They increase Aqueous humour

outflow.•Side effects: Miosis leading to blurred vision,• Myopia and Headache (due to ciliaryspasm).

•Group (E): α2 –Adrenergic Agonists:•Eye Drops: (1) Apraclonidine.

•( 2 )Primonidine.•Mechanism of Action: Reduction in secretion of Aqueous

humour and increase in its outflow.•Side effects: Sedation, Redness and irritation of the eye,

conjuntivitis.

21•Introduction

•Ginkgo biloba (Family):

•Common Name: Maidenhair tree.•Height : 30 – 40 meters.

•Circumference : 4 meters.•The Leaves : Fan – shaped

• Green to Golden Yellow•Indigenous to : Korea, China & Japan.

•Known in China for: Over 5000 Years.•Old Chinese uses : Circulation disorders• Memory Disturbance

• Asthma, Bronchitis•Introduction in Europe: 1730• in America : 1784•Start of Interest in it : 1965

• In Germany

22•Part of the Plant used: Leaves

•Constituents:• a) Flavonoidal Glycosides

•) Mono –, bio – and tri – osides of(:• Quercetin, Kaempferol, Isorhamnetin and 3´-O

methyl Myristicin .• b) Bioflavonoids:

• Bilobetin, Amentoflavone, Ginkgetin, 5-Methyl Bilobtin and Isoginkgetin .

• c) Tri Lactonic diterpenes:• Ginkgolides A, B and C

• d) Tri Lactonic Sesquiterpene:• Bilabolide

• e) Anthocyanin

23•Cinkgo Extraction: Acetone: Water and Spray Drying.

•Standardization of Extraction:•Standardized to Contain:

• 24% Flavonoid glycosides• 6% Lactonic di- and sesqui-Terpenes

• Less than 0.6 mg Ginkgolic Acid per 100gm• 1Kg Extract = 70 Kg dried Leaves

Pharmaceutical Forms: Capsules & Tablets, 40; 60; and 120 mg .

Trade Names: Ginexin – F; EGB 761;• Ginkgold; Ginkoba; GBE 24; Tebonin

•Status Classification:• In USA: Dietry Supplement

• In Canada: Food Additive• In France and Germany:As over–the Counter Drugs

•) No Prescription (•Availability : In more than 50 Countries

24•Reported Pharmacological Actions

• 1 (Blockade of Platelets-Activiting Factor (PAF) Receptors due to the Ginkgolides

and bilabolides .• 2 (Stimulation of Release of Nitric oxide [NO]

from the endothelia due to the anthocyanin.• 3 (As Anti-oxidant to scavenge oxygen free radicals

due to the flavonoids: Quercetin, Kaempferol and isorhamntin .

• 4 (Vasodilator to Blood vessels.• It increases blood flow to tissues.

• 5 (Inhibition of Cyclic Guanosine monophospho Diesterase (cGMPD) .

25•Actions (Contin.)

• 6 (Release of prostacyclin from blood vessels (PGI2).• 7 (Decrease in blood triglycerides.

• 8 (Membrane Stabiliser.• 9 (Stimulation of choline uptake by the Hippocampus ༜

Increase in Ach .• 10 )Neurone protector.

• 11 )Inhibition of age-induced decrease in brain muscarinic receptors .

• 12 )Suppression of cerebral cortex and Retina Oedemas .

• 13 )It increases brain O2 and blood supply.• 14 )It stimulates glucose influx and ATP production in

cells.• 15 )It helps the brain to record Information,

communicate ideas and recall concepts

26•Ginexin – F As a Neuroprotector

•Properties that Qualify Ginexin – F to be as a Neuroprotector in Glaucomas:

•)1 (Ability to vasodilate peripheral and central blood vessels. Thus, it •a) enhances blood flow to various organs.•)This is due to its non-flavone component(

•Via release of [NO] and [PGI2].•b) Antagonises ischaemia – induced inflammation and cellular

damage.•c) Antagonises hypoxia – induced decrease in ATP and membranes

break down.•d) Antagonises ichaemia-induced decrease in Plasminogen

activating factor and increase in Plasmingen activator inhibition. Thus, it enhance fibrinolytic activity.

•e) Enhances glucose uptake by cells.•f) Antagonises the retinal artery occlusion-induced oedema and

necrosis.

27•Ginexin-F properties

•)2 (Inhibits formation of O2 Radicals & scavenging them via its flavonoidal components: Quercetin, Kaempferol and isorhamnetin. Furthermore, it

•a)Stimulates production of reduced glutathione that protects cell membranes from the damaging action of lipid & other peroxides.

•b)It increases the level of glutathione disulphide redctase (GDS) that acts to regenerate reduced glutathione as follows:

•4 -. O-O-H Reduced glutathione 2H2O + O2 • peroxides +peroxidase+

• Glutathione disulphide(GDS)

•Reduced Glutathione GDS – Reductase

•c) prevents conversion of low density lipoprotein cholestrol to the cytotoxic oxysterols.

28•Ginexin-F (properties)

•d) Inhibits oxidative stress-induced mitochondrial aging and damage leading to maintenance of ATP production.

•)3 (Antagonises PAF-induced Platelets aggregation and enhances blood fluidity i.e. it decreases its viscosity and thus helps in blood flow to organs.

•)4 (Decreases glutamic acid-induced neuronal damage and elevation of the harmful intracellular Ca2+ levels via antagonism of PAF that enhaces glutamic acid actions.

29•Ginexin-F (properties)

•)5 (Inhibits glutamate-induced elevation of intracellular Ca2+ ions that damage cells and neurones. This is attributed to the flavonoids and bilobalide components.

•)6 (Enhances regeneration of damaged nerves via its bilobalide component.

•)7 (Antagonises proteolytic enzymes-induced retinal cell damage.

•)8 (Inhibits PAF-induced inflammation due to its ginkogolides and bilabolide.

•)9 (Protects retinal ganglion cells from cautery-induced retinal degeneration.

30•Use of Ginexin-F in Glaucoma

•)1 (Intake of 40 mg 3x daily for 4weeks by glaucoma patients produced significant improvement in the visual field indices but did not decrease (IOP).

•)2 (Treatment of glaucoma patients with Ginexin-F 40mg 3x daily for 2 days significantly increased the velocity of blood flow in the ophthalmic artery by 23% but did not affect (IOP).

31•Treatment of Glaucoma (Contin.)

•B] Laser treatment:•) 1 (In primary open Angle glaucoma, Laser

Traberculoplasty Techniques are used. The Laser rays are directed to the Trabecular meshwork to reduce their resistance to the Aqueous humour outflow.

•) 2 (In advanced cases of primary open Angle glaucoma, the laser rays are applied to the white sclera to damage the ciliary bodies to reduce Aqueous humour secretion.

•) 3 (In closed Angle glaucoma, the cornea is anaesthetized, a contact lens is placed on the eye and a laser shot is given to make a hole in the iris to allow passage of fluid from the posterior chamber to the anterior chamber & hence to outside the eye.

32•Concluding Remark

•Ginexin-F seemed to have a high potential in treating of glaucomas if combined with IOP lowering drugs. It has a high potential to act as a Neuroprotector to prevent the spread of the damage that occurred in some retinal ganglion cells & neurones to unaffected cells. Its benefit will be high if it is started early as soon as the neuronal damage is detected. It is hoped that further clinical trials and studies will establish its

role as a neuroprotector .

33•Summary of Glaucoma’s Treatments

Glaucoma TypeTreatment

1 (Closed AngleInitially Eye drops + a few days later Laser

2 (PigmentryEye drops + Surgery

3 (NeovascularEye drops + Laser. Laser stops prodction of VEGF in Retina cells

4 (PseudoexfoliativeEye drops + Surgery

34