THERAPEUTIC POTENTIAL OF

TOXINS AND VENOMS

OVERVIEW

• DEFINITIONS

• HISTORY OF POISONS

• MODERN TOXICOLOGY

• CATEGORIES OF POISONS

• PLANT TOXINS IN THERAPY

• MICROBIAL TOXINS IN THERAPY

• ANIMAL TOXINS AND VENOMS IN THERAPY

• LIMITATIONS AND PROSPECTS OF NNTA

POISON:- substance that when introduced into a living organism causes injury illness or death by chemical mechanism on a molecular scale.

TOXIN:- Naturally produced substances which act as poisons in small quantities. Homogenous structure isolated , extracted or derived from plant, animal or microbial sources , and has specific locus of action

VENOM:-

Animal toxin collected in specialized apparatus and administered by animals .

A cocktail of poisons and other organic substances

Complex mixture of proteins, enzymes , peptides and non protein inclusions.

Exist in specialized reservoirs- venom glands

HISTORY

Paracelsus:-

“All things are poisonous and there is nothing without poison. Solely the dose determines that a thing is not a poison”

Dose makes the poison.

Toxic from Toxicon ( poison arrow in greek )

• Plants animals generate toxins and venoms to discourage predators

• Poisons were discovered by witnessing the toxic effects on humans by chance/accidently

• 16000 BC – Masai tribe of Kenya used poisons in darts and arrows- strophanthin a cardiotoxic agent indigenous there

• Poisons used as a alleged means of deciding if accused was guilty, if he survived means gods were favoring him hence innocent.

• Remedies from snake venom have been reported in charaka and suchruta Samhita and Vagbhata.

• Ebers Papyrus – 1500BC – speaks of arsenic, lead, antimony, mandrake, aconite , hemlock, opium, aconite.

• Bradykinin potentiating nanopeptide from bothrops jararaca venom with ACE inhibitor action was introduced as natural method for renovascular hypertension.

Modern toxicology

• Modern methods allow minute detection of poisons

• Most important factor for toxicity is its dosage

• LD50 main statistical tool for toxicity Lower the LD50 the higher the toxicity Botulinum toxin LD50- 0.00001mg/kg

• TOXICOKINETICS- to explain the inter-individual and species difference and also particular toxicities that may be faced other than lethality

• ADME studies

CATEGORIES OF POISON

• PHYSICAL• CHEMICAL• BIOLOGICAL

Based on Source

• PLANT• ANIMAL • MICROBIAL

CHEMICAL AGENTS

INORGANICORGANIC

OXYGEN

LEAD

MERCURY

ARSENIC

WATERALCHOHOLGLYCOSIDES

CYANOGENIC COMPOUNDSINSECTICIDESHERBICIDESANALGESICS

BARBITURATEDAMPHETAMINE

COCAINEOPIATES

PHYSICAL AGENTS

NUCLEAR RADIATIONX RAYS

GAMMA RAYSULTRA VIOLET

INFRA REDMICROWAVESRADIOWAVES

ELECTROMAGNETIC FIELDS

BIOLOGICAL AGENTS

PLANTS AND MICROBESANIMALS

RICINAMANITIN

BOTULINUMENTEROTOXIN

CURARINES

BUFO TOXINSSALAMANDARIN

ALKALOIDSHOLOTHURINPUFFER TOXINCONOTOXIN

CARDIOTOXINNEUROTOXIN

HEMATOTOXINMYOTOXIN

LATROTOXINCHLOROTOXIN

BYROSTATIN

PLANT TOXINS IN THERAPEUTICSFUNGAL TOXINS

Aflatoxins - secondary metabolites of A.Flavus and A.Parasiticus-

Aflatoxin ( B1, B2 , G1 , G2 )B1 most potent environmental mutagen and carcinogen

Fusarium sp.- Zearalenone a B-resorcyclic acid lactone has hyperestrogenic activity on mice

CURARES

alkaloid arrow poisons originating from Central and South America.

competitively and reversibly inhibiting the nicotinic acetylcholine receptor (nAChR at the neuromuscular junction

weakness of the skeletal muscles and, when administered in a sufficient dose, eventual death by asphyxiation due to paralysis of the diaphragm.

tube or bamboo curare ( packing into hollow bamboo tubes - D-tubocurarine).

pot curare ( packed in terra cotta pots; - protocurarine, protocurine, and protocuridine).

calabash or gourd curare ( packed into hollow gourds; main toxin is curarine).

non-depolarizing muscle relaxant

occupies the same position on the receptor as ACh with an equal or greater affinity, and elicits no response, making it a competitive antagonist

D-tubucurarine – skeletal muscle relaxant

Griseofulvin- Toxicant from P.Griseofulvum – anti fungal

Cyclosporin A – derived from first cyclopeptides of amanita phylloides

Strychnus Nux Vomica

• Whole seed extract effectively neutralized Daboia russelli venom induced hemorrhage

• PlA2 induced neurotoxicity and cardio toxicity also reduced

• Potentiated Polyvalent snake antiserum in experimental animals

Algal toxin- Anatoxin A from blue green algae Anabaena flosaquae – strongest known agent for nicotinic receptors, more potent than carbachol.

BACTERIAL TOXINS

Clostridium botulinum – Botulin A,B,C.D,E,F and G

Botulus- greek for sausageDeadliest nerve poison in history- oral 70ug or 1/100 inhalation is lethal Biological weapon

Toxin blocks release of Ach from presynaptic nerve terminals – generalized paralysis

• Investigational agent to study synaptic neurotransmission

• Treatment of GI smooth muscle disorders – Achalasia cardia- botulin A and B

• Treatment of chronic anal fissures

• Reduction of skin wrinkles- moderate to severe frow lines between brows- BOTOX – botulin A FDA

• Post radiotherapy masticatory spasms

• Induction of corticospinal excitability changes in patients with limb spasticity, cerebral palsy

• Involuntary muscle contractions - FDA

MARINE TOXINS

Palytoxin –

• Zoanthid Coral Palythoa toxica.

• Most active coronary vasoconstrictor.

• Acts with interaction with Ca channels.

• Most poisonous non protienaceous substance .

• Used to evaluate anti anginals.

Caribbean Tunicate- sea squirt-

• Didemins and depsipeptides

• DideminB- strong antiviral against both DNA and RNA viruses – HSV type1 ,

• Strong-immunosuppressant- potential in skin graft

• Strong activity against murine leukemia cells

• Phase2 clinical trials against adenocarcinoma kidney, advanced epithelial ovarian cancer and metastatic breast cancer

• Unfortunately high toxicity and anaphylaxis in trial patients

Sh K ( L-5 ) – amide

• Peptide analogue

• Sea anemone- stichodactyla helianthus

• Selectively blocks K channels at low levels

• Novel immunomodulator to selectively suppress memory T lymphocytes in Multiple sclerosis, Type1 DM , and Rheumatoid arthritis

ANIMAL POISONS

NNTA- Natural non herbal therapeutic alternatives

Have proven immense value in old age diseases

Agents effective at extremely low doses and mechanism of action also different from those of known therapies

Area of NNTA is scanty , largely unattended and expensive

INFLAMMATORY DISEASES

Zinconotide(prialt) non opioid non steroid alternative to pain relief

Synthetic analogue of Conotoxin MVIIA from marineConus magnus snail

Acts by blockade of presynaptic N type Ca channels on sensory neurons

Used as intrathecal analgesic in refractory to opioids

Trials have shown it has less respiratory depression, tolerance and withdrawal symptoms

Xen2174

Analogue of MrIA X conapeptide from venom of Conus marmoreus snail

Safe in phase 1 trials

Treat pain in cancer patients

Phase3 showed severe sweat reduction – suggested for hyperhidrosis treatment FDA

SNAKE VENOMS

A mixture of both protienaceous and non-protienaceous components

Proteins- enzymes, polypeptides- Myotoxic , Neurotoxic ,Hypotensine, Heamolytic , Anticoagulant , Analgesic , BactericidalCardiotoxic , Cytotoxic

NEUROTOXINS

Fasciculins:These toxins attack cholinergic neurons by destroying acetylcholinesterase (AChE). ACh therefore cannot be broken down and stays in the receptor. This causes tetany, fasciculations venom of mambas (Dendroaspis spp.) and some rattlesnakes (Crotalus spp.)

Dendrotoxins:Dendrotoxins inhibit neurotransmissions by blocking the exchange of positive and negative ions across the neuronal membrane lead to no nerve impulse, thereby paralyzing the nerves.mambas

α-neurotoxins: also MYOTOXINS

They mimic the shape of the acetylcholine → they block the ACh flow → feeling of numbness and paralysis.

king cobra (Ophiophagus hannah) (known as hannahtoxin )

sea snakes (Hydrophiinae) (known as erabutoxin),

many-banded krait (Bungarus multicinctus) (known as α-Bungarotoxin),

cobras (Naja spp.) (known as cobratoxin)

CYTOTOXINS Phospholipases:an enzyme that transforms the phospholipid molecule into a lysophospholipid (soap)the new molecule attracts and binds fat and ruptures cell membranes.Okinawan habu (Trimeresurus flavoviridis) Cardiotoxins: hey bind to particular sites on the surface of muscle cells and cause depolarisation ==> the toxin prevents muscle contraction. These toxins may cause the heart to beat irregularly or stop beating, mambas, and some cobra species

Hemotoxins:Hemotoxins cause hemolysis, the destruction of red blood cells or induce blood coagulation --vipers and many cobra species. The tropical rattlesnake Crotalus durissus produces convulxin, a coagulant.[10]

Hannalgesin

Venom of Ophiophagus Hannah

Binds to SS1 And SS2 subunit of sodium channels

Analgesia without causing neurological or muscular effects , produced sedation andmuscle relaxation

Keluoqu

Neurotoxin from Chinese cobra venom – tablets

Longer action than tramadol – analgesic

Muscle weakness and constipation – side effects

HEAMATOLOGICAL DISEASES

The venom of viperidae and crotalidae are propsects in use as anticoagulants , fibrinolytics and platelet aggregator inhibitors

Batroxobin

Serum protease from bothrops atrox moojeni venom

Thrombin like enzyme factor2A – inhibits fibrinogen to fibrin conversion

Used to study the coagulation profile in presence of heparin and PT in absence of thrombin

Used to treat vascular thrombosis

To monitor fibrinogen levels in patients on heparin therapy

Ancrod ( Viprinex)

Directly acting defibrogenating enzyme

Prevents clot formation

Reduces blood viscosity and increases flow to ischemic areas

Reperfusion agent in acute ischemic stroke

Phase3 clinical trials underway

Malayan pit viper

Lepuridin

Thrombin inhibitor derived by recombinant DNA tech from Hirudin isolated from Leech Hirudo medicinalis

Anti-thrombotic action independent of antithrombin

Inactivates fibrin bound thrombin in thrombi

Used for thromboembolic disease of arterial and venous origin

Thrombosis due to Heparin induce thrombocytopenia

Bothrojaracin

C type lectin like protein from bothrops jararaca

Has effect in protection of mice with thrombin induced thromboembolism

Action – binds to exosite 1 of fibrinogen and exosite 2 of antithrombinOn thrombin- thrombin inhibitor

Fibrolase

Directly acting plasminogen activator

From Agkistrodon copperhead snake venom

Rapidly lysis clot

Used as thrombolytic for lysis of clots in vivo

Degradation of fibrin and fibrinogenby direct action unlike streptokinase

Lebecetin

Basic protein has two alpha and two beta subunits

Dose dependently inhibits thrombin induces platelet aggregation

Does not effect TXA2 induced platelet aggregation

Also binds to GP1b/1X receptor and prevents ristocetin induced platelet aggregation

Ecarin

Is a metalloproteinase isolated from venom of echis carinatus

Prothrombin – independent group 1A prothrombin activator

Prothrombin converted to miezothrombin

Helps in detection of Von willbrands disease

RVV X and RVV V enzymes

From russels viper venom

Used to detect von Willbrans disease by determining factors X and V and prothrombin in blood

Pseutarin C

Group C prothrombin activator isolated from venom of Pseudonaja textiles

Activates prothrombin to thrombin conversion

Similar to factor Xa-Va complex

AUTOIMMUNE DISEASES

Cobra drug ( immunokine)

Nontoxic peptide called peptide E

Blocked CCR5 and CXCR4 - inhibited 90% infection tropism of HIV

Was found safe in clinical trials

Alpha Bungarotoxin

Neurotoxin

Strong affinity for muscle Ach receptor

Used to generate Ach receptor antibodies for diagnosis of myasthenia gravis

From venom of bungarus multicinctus

Acts on alpha 7 nicotinic Ach receptors in brain hence has application in neuroscience

INFECTIOUS DISEASES

L- amino oxidase

Enzyme from the venom of crotalus adamenteus shows antibacterial activity to gram positive bacteria

Agkistron halys pallus, bothrops alternatus , Trimeresurus jerdoni – against Ecoli and S.auresus

Pseudechis australis – 70 times higher than tetracycline

Peptide

From Naaja atra shown to possess antitubercular activity

Pandinins

Pim1 and Pim2 from pandinin imperator venom – activity against B.subtilus and E.coli

More against gram positive than gram negative

CARDIOVASCULAR DISEASES

BPP9a

Nanopeptide bradykinin potentiator with ACE inhibiting action

From venom of Bothrops jararaca

Synthesized as Teprotide

Later developed as oral captopril

MALIGANANT DISEASES

Salmosin

Disintegrin isolated from Korean snake venom – Agkistrodon halys brevicaudus

Blocks function of alpha2beta3 integrin

Supressed tumor progression by inhibiting tumor derived angiogenesis , adherence and proliferation.

Rhodostomin

Disintegrin from venom of Calloselasma rhodostoma

Inhibits angiogenesis induced by fibroblast GF

Suppressed murine melanoma growth

The anti angiogenic activity is related to integrin alpha5beta3 blockade

Contorstrostatin

Disintegrin from Agkistrodon contortrix

Strongly inhibited metastatic melanoma adhesion to extracellular matrix

Lung colonization by M-24 met cells prevented

Inhibited tumor growth and angiogenesis and prolonged survival in mice glioma

Liposomal delivery proved promising in human breast cancer

Longer half life and gets accumulated in tumor cells and is devoid of platelet reactivity

Toxin CM-28

Protien from Russels viper venom

BM-T2- nonprotien from Bufo melanostictus

Pronounced reduction in proliferation of cancer cell cultures

Decreased PCNA expression and exhibited cytotoxicity

Dr-CT-1

Heat stable protein from daboia russelli venom

Significant decrease in human leukemic cell lines in mice

Antiproliferation due to reduction in MTT values

Cell cycle arrest in G1 phase

PSYCHOTIC DISEASES

POVRVP

Photo-oxidized product – generated by exposure of russels viper venom to UV radiation

Seadtive, analgesic and anti-inflammatory actions in pre clinical models

Cardiac stimulant properties in isolated rat heart perfusion

It is lately proved for use in chronic psychotic hyperactive disorders

POECVP

From Echis carinatus venom showed anti-depressant and nootropic properties

POESVP

From Enhydrina schistose showed CNS stimulant,. Analgesic and anticoagulant nootropic properties

Both above used for chronic psychotic depressive disorders

SCORPION TOXINS

Used very commonly as part of Chinese medicine

Treating neural diseases like apoplexy, epilepsy, facial paralysis, hemiplegia

Soothe nerves and relieve pain of meningitis cerebral palsy and rheumatism

Anti-nociceptive activity

Peptide from Bothus martense shows strong inhibition of visceral and somatic pain and also anti-tumour activity

Beta toxins of scorpion venom used to study voltage activated Na+ channels

Vasosensory response by indian red scorpion venom is similar to vasosensory response of capsaicin

SPIDER TOXINS

Spider toxins are neurotoxins

Co-agatoxin IV A from funnel web spider venom- can be used in opiod dependant or tolerant patients for nociception

Psalmotoxin- from south American tarantula Psalmopoeus cambridgei- blocks H+ gated cataionic channels- important role in brain ischeamia or epilepsy

Black widow spider

LIZARD TOXINS

Gila monster venom- Heloderma suspectum

Peptide is similar to GLP1- Exendin 4

Stimulated insulin secretion and agonist of GLP1 receptor

Synthetic exendin4 is Exanatide

Gila monster saliva and extraction

FROG TOXINS

Batrachotoxins from Phyllobates sp. Is a neurotoxin

Similar to digitalis

In PNS causes activation of Na+ channels- blocks nerve signals

Biochemical tool to study Na+ channels

Epibatidine

Alkaloid from skin of frog Epipedobatus tricolor

Binds to Nicotinic Ach receptors at NMJ

200 times more potent than morphine for pain relief

Bufodienolides

Glycosides from central Asian green toad venom bufo viridis

Inhibit endogenous myocardial Na-K-ATPase. Increase force of contraction and to some extent heart rate

Frog atrial trabecular contractionsalso increased

Similar to strophanthin k, and digitoxinum

Histrionicotoxin

Piperidine alkaloid from skin of dentrobates histrionicus

Non competitive inhibition of nicotinic receptors- biochemical probe in NMJ transmission

Dermorphine

From Phyllomedusa species

Heptapeptide chain , high affinity for opioid receptors

Produce anti-nociception, catalepsy, rigidity and sedation

Intrathecal 100 times more potent than morphine

FISH AND MOLLUSCS TOXINS

Tetrodotoxin

From ovary and liver of tetradoxitidae sp.

Used in biochemical research

100 times more toxic than cyanide

Urotensin1

Peptide from many fishes- sustained hypotension in mammalian species

TmC447.2

Myotoxin from toadfish Thalassophzyne maculosa- depolarizes skeletal muscle

HONEY BEE TOXINSOpitoxin From honey bee Apis mellifera - Polypeptide neurotoxin

Used in research to study electrical properties of small conductance Ca+ activated K+ channels( SK channels)

Apamin blocks these channels in brain and spinal cord- role in memory processMultiple sclerosis

Has therapeutic applications in peripheral cells like pancreas- insulin releasing cells

PROSPECTS OF NNTA

• High scope for newer Molecule discovery

• Known effects can be easily tested

• Physiological actions are easier to observe in pre clinical studies

• Some of the natural products available in abundance

LIMITATIONS OF NNTA

HIGH cost of extraction and research

A huge variety of poisons to choose from

Avaialbility of individual species- extinction

Time lag in research

Dose limitations doesn’t hold true for all poisons

Highly delicate nature of poisons

Ethics and social stigma

THANK YOU