Loxosceles sp (Brown Spider)
Venomous animals use their venom as tools for defense or predation. These venoms are complex mixtures, mainly enriched of proteic toxins or peptides with several, and different, biological activities. In general, spider venom is rich in biologically active molecules that are useful in experimental protocols for pharmacology, biochemistry, cell biology and immunology, as well as putative tools for biotechnology and industries (CHAIM et al, 2011).
The spiders Loxosceles intermedia (Li), Loxosceles laeta and Loxosceles gaucho belong to a group of arachnids (known as “brown spiders”), which are found in the South and South-East of Brazil and are responsible for most of the accidents by this genus (MOURA et al, 2011). Loxosceles spider bites have become an increasing public health problem in Brazil (ARAUJO et al, 2003).
 |
| Loxosceles gaucho |
The color of spiders of this genus ranges from a fawn to dark brown. The brown spiders are sedentary, non-aggressive, have nocturnal habits and prefer to inhabit dark areas. In human habitats, brown spiders are often found behind furniture, pictures and associated with clothes (CARDOSO, 1997; CHAIM et al, 2011).
Loxoscelism and dermonecrotic arachnidism are two terms used to describe the cutaneous lesions and various clinical manifestations following bites by members of the Loxosceles genus. Systemic effects, such as thrombocytopenia, disseminated intravascular coagulation and renal failure, have also been reported. Indeed, the crude venom from Loxosceles spiders can degrade the extracellular matrix and induce endogenous responses, such as platelet aggregation, hemolysis, nephrotoxicity, hepatotoxicity and cardiotoxicity (CHAIM et al, 2011; MOURA et al, 2011).
The Loxosceles Venoms
The venom of Loxosceles spiders is a complex mixture of protein and peptide toxins with a molecular mass profile ranging from 1 to 40 kDa. To date, several molecules in the Loxosceles spider crude venoms have been described, including alkaline phosphatase, 5‘-ribonucleotide phosphohydrolase, sulfated nucleosides, hyaluronidase , fosfolipases-D, metalloproteases, serine proteases and insecticide toxins (CHAIM et al, 2011).
A group of toxins from the Sphingomyelinases D (SMases D) or dermonecrotic factor (DNF) family have been characterized as responsible for most of the toxic effects of Loxosceles spider venoms. The venom is classically described as having a hemolytic action on red blood cells. This effect is calcium and complement-dependent but antibody-independent, and hemolysis is induced by native and recombinant dermonecrotic toxins (phospholipase-D).
The exact mechanism of action of the venom is not yet fully understood, thus hindering the development of effective medical treatments for loxoscelism (ARAUJO et al, 2003).
 |
| Damage after 12h from the accident with Loxosceles |
 |
| Damage after 30h from the accident |
 |
| Damage after 60h |
Biotechnological applications of brown spider venom toxins
The first biotechnological application of brown spider venom constituents is the product ARACHnase. ARACHnase is a biotechnological product usefulness like a positive control for lupus anticoagulant testing (SENFF-RIBEIRO et al, 2008).
Recombinant toxins could be useful for biotechnology as positive controls for hemolytic assays as well as for analysis of the complement system and to study new molecular mechanisms involved in such events (SENFF-RIBEIRO et al, 2008).
 |
| Loxosceles gaucho |
LPA receptors are potential targets
for Loxosceles envenomation treatment. The possibilities for
biotechnological applications in this area are enormous. Recombinant
dermonecrotic toxins could be used as reagents to establish a new model
to study the inflammatory response, as positive inducers of the inflammatory
response and edema (CHAIM et al, 2011;
SENFF-RIBEIRO et al,
2008).
Several toxins from different sources have been studied as potential insecticidal bioactives with great biotechnological possible applications. Senff-Ribeiro et al (2008) investigated the presence of insecticide toxin in the venom of L. intermedia against Spodoptera frugiperda, an insect that has caused decreased corn production of Brazil. Three new potential insecticide toxins LiTx1, LiTx2 and LiTx3 were identified containing peptides that were active against Spodoptera frugiperda. These venom-derived products open a source of insecticide toxins that could be used as substitutes for chemical defensives and lead to a decrease in environmental problems.
Brown spider venom has the presence of hyaluronidases, that are known to be involved in physiological and pathological processes ranging from fertilization to aging. Hyaluronidase-mediated degradation of hyaluronic acid (HA) increases the permeability of connective tissues and decreases the viscosity of body fluids and is also involved in bacterial pathogenesis, the spread of toxins and venoms, fertilization and cancer progression. Inhibition of HA degradation, therefore, may be crucial in reducing disease progression and the spread of venom/toxins and bacterial pathogens. Other possible applications are anti-tumor and, possibly, antibacterial and antivenom activities (SENFF-RIBEIRO et al, 2008).
Future
perspectives
Research
on the Loxosceles toxins has gained great attention. In
the last five years, using molecular biology techniques, scientists have
obtained different recombinant toxins and enough material to bring deeper
insight into the molecular action of these toxins.
Recombinant toxins have been expressed in bacteria, simple organisms that are easy to manipulate and cheap to work with (CHAIM et al, 2011).
The use of combinatorial data from proteomic and molecular biology techniques, such as mass spectrometry, transcriptome analysis and cDNA library constructions, will open possibilities for the discovery of novel toxins in complex venoms (CHAIM et al, 2011).
References:
Araujo, S. C. et al. (2003). Protection against
dermonecrotic and lethal activities of Loxosceles intermedia spider venom by
immunization with a fused recombinant protein. Toxicon
41, 261–267.
Cardoso, J. L. C.; Wen, F. H. (1997). Doenças infecciosas e parasitárias: Enfoque Amazonico. Cejup: UEPA: Instituto Evandro Chagas, 3-7.
Chaim, O. M. et al (2011). Brown Spider (Loxosceles genus) Venom Toxins: Tools for Biological Purpuses. Toxins, 3, 309-344.
Moura, J. et al (2011). Protection against the toxic effects of Loxosceles intermedia spider venom elicited by mimotope peptides. Vaccine, vol. 29, issue 45, 7992-8001.
Senff-Ribeiro, A. et al (2008). Biotechnological applications of brown spider (Loxosceles genus) venon toxins. Biotechnology Advances, vol. 26, issue 3, 210-218.