Histopathological characterization of experimentally induced cutaneous loxoscelism in rabbits inoculated with Loxosceles similis venom

Pereira NB (1), Kalapothakis E (2), Vasconcelos AC (1), Chatzaki M (3), Campos LP (1), Vieira FO (1), Verçosa BLA (1), Silva SS (1), Ferreira WM (4), Moro L (1)

(1) Department of General Pathology, Institute of Biological Sciences, Federal University of Minas Gerais (UFMG), Belo Horizonte, Minas Gerais State, Brazil; (2) Department of General Biology, Institute of Biological Sciences, Federal University of Minas Gerais (UFMG), Belo Horizonte, Minas Gerais State, Brazil; (3) Department of Molecular Biology and Genetics, Democritus University of Thrace, Dragana, Alexandroupolis, Greece; (4) Department of Animal Science, School of Veterinary Medicine, Federal University of Minas Gerais (UFMG), Belo Horizonte, Minas Gerais State, Brazil.

Abstract: Envenomation by Loxosceles bites is characterized by dermonecrotic and/or systemic features that lead to several clinical signs and symptoms called loxoscelism. Dermonecrotic lesions are preceded by thrombosis of the dermal plexus. Recent studies show that atheromatous plaque is prone to thrombosis due to endothelial cell apoptosis. To the best of our knowledge, there are no reports of microscopic dermal lesion and endothelial cell apoptosis induced by Loxosceles similis venom in the literature. Thus, the aim of the present study is to describe histological lesions induced by L. similis venom in rabbit skin and to elucidate whether apoptosis of endothelial cells is involved in the pathogenesis of loxoscelism. Forty male rabbits were split into two groups: the control group (intradermally injected with 50 μL of PBS) and the experimental group (intradermally injected with 0.5 μg of L. similis crude venom diluted in 50 μL of PBS). After 2, 4, 6 and 8 hours of injection, skin fragments were collected and processed for paraffin or methacrylate embedding. Sections of 5 μm thick were stained by HE, PAS or submitted to TUNEL reaction. Microscopically, severe edema, diffuse heterophilic inflammatory infiltrate, perivascular heterophilic infiltrate, thrombosis, fibrinoid necrosis of arteriolar wall and cutaneous muscle necrosis were observed. Two hours after venom injection, endothelial cells with apoptosis morphology were evidenced in the dermal plexus. Apoptosis was confirmed by TUNEL reaction. It seems that endothelial cell apoptosis and its consequent desquamation is an important factor that induces thrombosis and culminates in dermonecrosis, which is characteristic of cutaneous loxoscelism.

Key words: Loxosceles similis, loxoscelism, dermonecrosis, cutaneous loxoscelism, apoptosis.

COPYRIGHT

© CEVAP 2012

SUBMISSION STATUS

Received: February 14, 2012.

Accepted: June 14, 2012.

Abstract published online: June 29, 2012.

Full paper published online: August 31, 2012.

CONFLICTS OF INTEREST

The authors declare no conflicts of interest.

FINANCIAL SOURCE

The State of Minas Gerais Research Foundation (FAPEMIG), the National Council for Scientific and Technological Development (CNPq) and the Coordination for the Improvement of Higher Education Personnel (CAPES) provided the financial grants.

ETHICS COMMITTEE APPROVAL

This study was approved by the Ethics Committee in Animal Experimentation of Federal University of Minas Gerais (CETEA/UFMG 217/2007).

CORRESPONDENCE TO

Luciana Moro or Núbia Braga Pereira, Av. Antônio Carlos, 6627, Pampulha, Bloco F3-259, Belo Horizonte, MG, CEP 31270-901, Brasil. Email: moro@icb.ufmg.br or nubiologicas@yahoo.com.br.