medicinal values of snake venom

     Charles Lucien Bonaparte, younger brother of Napoleon Bonaparte, was the first to establish the proteinaceous nature of snake venom in 1843.

Proteins constitute 90-95% of venom's dry weight and they are responsible for almost all of its biological effects. Among hundreds, even thousands of proteins found in venom, there are toxins, neurotoxins in particular, as well as nontoxic proteins (which also have pharmacological properties), and many enzymes, especially hydrolytic ones.[2] Enzymes (molecular weight 13-150 KDa) make-up 80-90% of viperid and 25-70% of elapid venoms: digestive hydrolases, L-amino acid oxidase, phospholipases, thrombin-like pro-coagulant, and kallikrein-like serine proteases and metalloproteinases (hemorrhagins), which damage vascular endothelium. Polypeptide toxins (molecular weight 5-10 KDa) include cytotoxins, cardiotoxins, and postsynaptic neurotoxins (such as α-bungarotoxin and α-Cobratoxin), which bind to acetylcholine receptors at neuromuscular junctions. Compounds with low molecular weight (up to 1.5 KDa) include metals, peptides, lipids, nucleosides, carbohydrates, amines, and oligopeptides, which inhibit angiotensin converting enzyme (ACE) and potentiate bradykinin (BPP). Inter- and intra-species variation in venom chemical composition is geographical and ontogenic.[3] Phosphodiesterases interfere with the prey's cardiac system, mainly to lower the blood pressure. Phospholipase A2 causes hemolysis by lysing the phospholipid cell membranes of red blood cells.[6] Amino acid oxidases and proteases are used for digestion. Amino acid oxidase also triggers some other enzymes and is responsible for the yellow colour of the venom of some species. Hyaluronidase increases tissue permeability to accelerate absorption of other enzymes into tissues. Some snake venoms carry fasciculins, like the mambas (Dendroaspis), which inhibit cholinesterase to make the prey lose muscle control.[7]

MAIN ENZYMES OF SNAKE VENOM

TYPE	NAME	ORIGIN
Oxydoreductases	dehydrogenase lactate	Elapidae
	L-amino-acid oxidase	All species
	Catalase	All species
Transferases	Alanine amino transferase
Hydrolases	Phospholipase A2	All species
	Lysophospholipase	Elapidae, Viperidae
	Acetylcholinesterase	Elapidae
	Alkaline phosphatase	Bothrops atrox
	Acid phosphatase	Deinagkistrodon acutus
	5'-Nucleotidase	All species
	Phosphodiesterase	All species
	Deoxyribonuclease	All species
	Ribonuclease 1	All species
	Adenosine triphosphatase	All species
	Amylase	All species
	Hyaluronidase	All species
	NAD-Nucleotidase	All species
	Kininogenase	Viperidae
	Factor-X activator	Viperidae, Crotalinae
	Heparinase	Crotalinae
	α-Fibrinogenase	Viperidae, Crotalinae
	β-Fibrinogenase	Viperidae, Crotalinae
	α-β-Fibrinogenase	Bitis gabonica
	Fibrinolytic enzyme	Crotalinae
	Prothrombin activator	Crotalinae
	Collagenase	Viperidae
	Elastase	Viperidae
Lyases	Glucosamine ammonium lyase

TOXINS

NUEROTOXINS

 A) An exchange of ions (charged atoms) across the nerve cell membrane sends a depolarising current towards the end of the nerve cell (cell terminus).

B) When the depolarising current arrives at the nerve cell terminus, the neurotransmitter acetylcholine (ACh), which is held in vesicles, is released into the space between the two nerves (synapse). It moves across the synapse to the postsynaptic receptors.

C) If ACh remains at the receptor, the nerve stays stimulated, causing incontrollable muscle contractions. This condition is called tetany. An enzyme called acetylcholinesterase destroys the ACh so tetany does not occur.

Fasciculins:

These toxins attack cholinergic neurons (those that use ACh as a transmitter) by destroying acetylcholinesterase (AChE). ACh therefore cannot be broken down and stays in the receptor. This causes tetany, which can lead to death. The toxins have been called fasciculins since after injection into mice, they cause severe, generalized and long-lasting (5-7 h) fasciculations.

Snake example: found mostly in venom of Mambas and some rattlesnakes

Dendrotoxins:

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

Snake example: Mambas

α-neurotoxins:

This is a large group of toxins, with over 100 postsynaptic neurotoxins having been identified and sequenced.[8] α-neurotoxins also attack cholinergic neurons. They mimic the shape of the acetylcholine molecule and therefore fit into the receptors → they block the ACh flow → feeling of numbness and paralysis.

Snake examples:

- King Cobra (known as hannahtoxin containing α-neurotoxins)[9]

- Sea snake (known as erabutoxin)

- Many-banded krait (known as α-Bungarotoxin)

- Cobras (known as cobratoxin),

Phospholipases:

Phospholipase is an enzyme that transforms the phospholipid molecule into a lysophospholipid (soap) ==> the new molecule attracts and binds fat and ruptures cell membranes.

Snake example: Japanese Habu

Cardiotoxins:

Cardiotoxins are components that are specifically toxic to the heart. They 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, causing death.

Snake example: King Cobra, Mambas, and some members of Naja genus

Hemotoxins:

The toxin causes hemolysis, or destruction of red blood cells (erythrocytes).

Snake example: most Vipers and the many members of Naja genus.

EVOLUTION

    Snake venom consists of many different toxin proteins: these can either have enzymatic activity, which typically assists in digestion, or can be shorter peptides that are used to immobilize prey. [10] Toxin proteins make up many multigene families, and arose from gene recruitment of proteins that do not code for toxins, followed by extensive evolutionary modification. [11][12][13] Toxin evolution follows the birth-and-death model of gene families, where duplication followed by functional diversification results in the creation of structurally related proteins that have slightly different functions. It is thought that venom as a way to immobilize prey was beneficial in allowing the uncoupling of feeding system and locomotion, which are coupled in the Haenophidians, which then enabled snakes with venom systems to colonize open areas.[14] Venom continue to evolve as specific toxins are modified to target a specific prey, and it is found that toxins vary according to diet in some species.[15][16]

The presence of enzymes in snake venom was once believed to be an adaptation to assist digestion. However, studies of the western diamondback rattlesnake, a snake with highly proteolytic venom, show that venom has no impact on the time required for food to pass through the gut.[17]

IMMUNITY

Among snakes

The question whether individual snakes are immune to their own venom is not yet definitely settled, though there is a known example of a cobra which self-envenomated, resulting in a large abscess requiring surgical intervention but showing none of the other effects that would have proven rapidly lethal in prey species or humans.[19] Furthermore, certain harmless species, such as the North American Lampropeltis getula and the Brazilian Rhacidelus brazili, are proof against the venom of the crotalines which frequent the same districts, and which they are able to overpower and feed upon. The Tropical Rat Snake, Spilotes variabilis, is the enemy of the Fer-de-lance in St. Lucia, and it is said[by whom?] that in their encounters the Tropical Rat Snake is invariably the victor. Repeated experiments have shown the European Common Snake, Tropidonotus natrix, not to be affected by the bite of Vipera berus and Vipera aspis, this being due to the presence, in the blood of the harmless snake, of toxic principles secreted by the parotid and labial glands, and analogous to those of the venom of these vipers. Several North American species of Rat snakes as well as King snakes have proven to be immune or highly resistant to the venom of rattlesnake species.

Among other animals

The Hedgehog, the Mongoose, the Honey Badger, the Secretary Bird and a few other birds that feed on snakes are known to be immune to a dose of snake venom. Whether the pig may be considered so is still uncertain, although it is well known that, owing to its subcutaneous layer of fat, it is often bitten without ill effect. The garden dormouse (Eliomys quercinus) has recently been added to the list of animals refractory to viper venom. Some populations of California Ground Squirrel are at least partially immune to Rattlesnake venom as adults.

Among humans

The acquisition of human immunity against snake venom is one of the oldest forms of vaccinology known to date (about AD 60, Psylli Tribe). Research into development of vaccines that will lead to immunity is ongoing. Bill Haast, owner and director of the Miami Serpentarium injected himself with snake venom during most of his adult life, in an effort to build up an immunity to a broad array of venomous snakes. It is a practice known as mithridatism. Haast lived to age 100, and survived a reported 172 snake bites. He donated his blood to be used in treating snake-bite victims when a suitable anti-venom was not available. More than twenty of those individuals recovered.[20][21][22]

MEDICINAL PROPERTY

1)   CANCER THERAPY

          Snake venoms are supposed to be the most complex of animal secretions containing a vast number of compounds with different pharmacological and biochemical activities. Literature shows that cobra venom components especially DNAase and RNAase and other enzymes inhibit cancer growth. A PROTEIN found in copperhead snake venom dramatically retards the growth of breast tumours. In studies with mice implanted with human breast cancer cells, a 60 to 70 per cent reduction in the growth rate of the breast tumours and a 90 per cent reduction of tumours that spread to the lungs was found in rodents treated with the protein. However, it will take at least 18 months before the venom protein will be ready to test on patients. The copperhead protein acts by inhibiting the development of new blood vessels to nourish the tumours and by putting tumour cells into a "suspended state of animation". Prof Markland said the dual action helped prevent the spread of cancer, a process called metastasis.

When first diagnosed with breast cancer, many women already have metastatic disease, which means that the cancer has spread to another site such as the lymph nodes, brain or bone.

Called contortrostatin, CN, the protein is purified from the venom of the southern copperhead and is one of a cocktail used by the snake to immobilise prey, keeping blood fluid so that other damaging proteins can spread through the body.  Snake venoms in general are loaded with proteins, many of which lead to tissue destruction at the site of the bite. The mice trials had not revealed any side-effects other than local bleeding. CN belongs to a class of proteins known as disintegrins, so named because they disrupt the function of certain other proteins, called integrins, on the surface of cells that enable them to stick together.

CN should be administered periodically over time in the hope of shrinking the tumour to a size is effective in retarding the spread of tumour cells because it inhibits their adhesion to and invasion of normal cells. CN would need to be administered per where treatment could be scaled back or stopped.

2)   IN STROKE

      A stroke happens when blood flow to the brain is interrupted. Lack of oxygen and food to the brain can lead to serious central nervous system impairments and even death. Snake venom has been found to have properties that can be useful in the treatment of strokes. A substance called ANCROD, derived from snake venom, allows stroke victims to recover their mental and physical abilities. Researchers found that more than 40% of patients who received ANCROD recovered all of their mental faculties versus more than 30% for placebo patients. The researchers hope that snake venom may provide an alternative to Tissue Plasminogen Activator (TPA) which currently is the only FDA-approved treatment for acute stokes.

ANCROD is a substance formulated from the venom of the Malayan pit viper. In previous observations, scientists had noted that the blood of people bitten by the snake failed to clot. Since stokes are caused by blood clots, researchers were hopeful that this anticoagulant might have applications in stoke victims.

The most striking difference between ANCROD and TPA is the method of administration. TPA is normally injected in a single dose, preferably in the first three hours after the onset of a stroke. ANCROD, on the other hand, is administered by IV over a 3 to 5 day period.

While TPA dissolves clots that cause strokes, ANCROD works by reducing the level of fibrinogen in the blood. Since fibrinogen is the clotting factor in the body, lower levels allow the blood to flow more freely through the blood vessels, thereby reducing the chances for clotting.

Scientists found that those patients whose fibrinogen was reduced and maintained at a target level had the most successful treatment after a stroke. The amount necessary to produce this result was determined by both the body weight of the patient and the relative amount of fibrinogen in the patient's blood. During the treatment period, the additional amount of ANCROD needed was based on the relative level of fibrinogen present in the blood at that time.

The target level was 40-70 milligrams of fibrinogen per deciliter of blood. Doctors found that if this level was maintained in the body, the patients regained their mental faculties after the stroke, had less chance of bleeding, and had less chance of another stroke during the therapy period.

Researchers hope to provide an alternative to the use of TPA. They speculate that having a wider range of treatments will benefit patients. Depending on the kind of stoke and the particular patient, one of the two could be more effective than the other.

Patients participated in a follow-up three months after the stroke. Various mental and physical tests were performed to gauge whether these patients had returned to normal and regained their mental faculties. Researchers noted that patients who received ANCROD were more likely to have a higher risk of bleeding in the brain compared to TPA patients.

3)   BRAIN DISORDERS

   The paralyzing effects of the venom of African mamba snakes can be so powerful that bites from these snakes have been known to topple giraffes and lions, and can kill a person within 20 minutes. But that hasn’t stopped biochemist Dr. Krishna Baksi of the Universidad Central Del Caribe in Puerto Rico from working with the venom of these snakes. With funding from the NIH National Institute of General Medical Sciences, Dr. Baksi is trying to figure out what enables proteins in the mamba venom from latching on so tightly and specifically to certain structures called receptors, which jut out of the surface of brain and nerve cells. The brain uses certain kinds of these receptors to receive the chemical signals that let it learn, form memories, perceive pain, and do many other functions. Nerve cells use the same receptor type to pass on signals to neighboring muscles that trigger them to contract or stay at rest, and affect breathing and heart beat rates. There are five known subtypes of these receptors, each of which are thought to play a role in various diseases, including asthma, Parkinson’s disease, Alzheimer’s disease and certain pain disorders. So researchers are eager to find drugs that can alter the actions of these receptors.

But their efforts have been hampered by an inability to find compounds that act specifically on only one type of receptor--you don’t want a drug that acts on the receptor involved with Alzheimer’s disease if you have Parkinson’s disease, for example. And that’s where the mamba snake comes in. Its venom has proteins that are highly specific for which receptors they will latch on to. By studying the structure of these proteins, Dr. Baksi hopes to have results that drug makers can use to design new and more selective drugs for a wide range of neurological disorders.

4)   AIDS

  

Snake venom contains Phospholipase A2 (PLA2)[11,16], which protect human primary blood leukocytes from the replication of various macrophage and T cell-tropic human immunodeficiency virus 1 (HIV-1) strains. PLA2 which is found in the venom of many snakes has been shown to block viral entry into cells before virion uncoating through prevention of intracellular release of viral capsid protein [16]. This is mainly due to the specific interaction of PLA2 to host cells and not due to catalytic activity.

       Immunokine - an oxidized derivative of alpha - cobra toxin (Naja naja siamensis), has been shown to inhibit the infection of lymphocytes by HIV and Feline immunodeficiency virus (FIV) through chemokine receptors (CCR 5 and CXCR 4).

   L- amino acid oxidase (LAO), present in the venom of Trimeresurus stejnegeri[18], C. Atrox, P. australis[19]; inhibits infection and replication of HIV virus through P24 antigen in a dose dependant manner[18]. P24 antigen is a core protein of HIV and its level associates with viral load[20]. Besides the binding of protein to cell membrane, hydrogen peroxide (H2O2) produced as a free radical could inhibit the infection/replication of HIV, thereby further enhancing the anti viral activity. In contrast, catalase - a scavenger of H2O2, reduces the anti- viral activity [18].

    Protein fragment isolated from Oxyuranus scutellatus snake venom is a potent inhibitor of p24 antigen and blocks viral replication of resistant strains [21].

 Snake venom contains metalloprotease inhibitors[16,22] which could prevent the production of new viruses through inhibition of protease enzymes. HIV infects a CD4 cell of a person's body and then it copies its own genetic code into the cell's DNA. Then, CD4 cell is "programmed" to make new HIV genetic material and proteins. These proteins are degraded by HIV protease enzyme and again these proteins are used to make functional new HIV particles. Protease inhibitors are used to block the protease enzyme and prevent the cell from producing new viruses.

P-glycoprotein (P-gp), a membrane protein, is an energy-dependent efflux transporter driven by ATP hydrolysis[23]. P-gp transports a wide range of substances with diverse chemical structures. In general, P-gp substrates appear to be lipophilic and amphiphatic, and are recognized to play an important role in processes of absorption, distribution, metabolism, and excretion of many clinically important drugs in humans [23]. Because of its importance in pharmacokinetics, inhibition or induction of P-gp by various components of snake venom can lead to significant drug-drug interactions, thereby changing the systemic or target tissue exposure of the protease inhibitors. At the same time one has to remember genetic polymorphism of P-gp,[23] which has also been recorded recently, because it may affect drug disposition and produce variable drug effects.

5)   Analgesic effect

 Scientists have used the venom of Africa's lethal black mamba to produce an effective pain relief without toxic side effects. peptides isolated from black mamba venom may be a safer pain killer than morphine.

In mice at least, the peptides bypass the receptors in the brain that are targeted by morphine and other opioid compounds which sometimes cause side-effects like breathing difficulties or nausea.

Nor do the peptides pose the same risk of addiction or drug abuse. natural peptides, mambalgins, from the venom of the snake Black Mamba that are able to significantly reduce pain in mice without toxic effect, It is remarkable that this was made possible from the deadly venom of one of the most venomous snakes," she says.

"(It) is surprising that mambalgins, which represent less than 0.5 per cent of the total venom protein content, has analgesic (pain-relief) properties without neurotoxicity in mice, whereas the total venom of black mamba is lethal and among the most neurotoxic ones."

Morphine is often regarded as the best drug to relieve severe pain and suffering, but it has several side effects and can be habit-forming.

The black mamba's venom is among the fastest acting of any snake species, and a bite will be fatal if not treated with antivenom - the poison attacking the central nervous system and causing respiratory paralysis.

Mice are among the agile adder's favourite prey in the wild in eastern and southern Africa.

6)   ANTI AGING

  A topical treatment incorporating imitation snake venom is being marketed as an alternative to Botox. The results of this product, called Wrinkle Defence, are typical of topical treatments in their cumulative effect. While Botox injections are immediately active on the facial muscles, the “freezing” results of this topical begin to appear after about two weeks. It is claimed that Wrinkle Defence visibly reduces wrinkles by 52%.