Differential Cellular Responses to Class I and II Sphingomyelinase D: Unraveling the Mechanisms of Loxosceles Venom-Induced Dermonecrosis and Potential Therapeutic Targets

Author(s)

Pinto, Bruna Fernandes ; Lopes, Priscila Hess ; Trufen, Carlos Eduardo Madureira ; Ching, Ana Tung Ching ; de Azevedo, Inacio de Loyola M. Junqueira ; Nishiyama-Jr, Milton Yutaka ; de Souza, Marcelo Medina ; Pohl, Paula C. ; Tambourgi, Denise V.

• Document type: Journal article
• Source: INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES; v. 26, n. 7, p. 20-pg., 2025-03-26.

Abstract

Dermonecrosis resulting from Loxosceles spider envenomation, primarily driven by the enzyme sphingomyelinase D (SMase D), is characterized by severe inflammation and nonhealing wounds. SMases can be classified as Class I or II based on their structural characteristics. Class I exhibits greater dermonecrotic activity than Class II; however, the intracellular mechanisms responsible for this difference remain poorly understood. The differential transcriptomics analysis of human keratinocytes treated with each toxin revealed that Class I primarily activates pathways associated with proteolytic activity and apoptosis. In contrast, Class II uniquely upregulates key genes, including PIM-1, MCL-1, PAI-1, p21, and c-FOS, which support cell survival and inhibit apoptosis. These pathways also facilitate tissue repair and keratinocyte proliferation during wound healing, particularly through signaling mechanisms involving Substance P and VEGF-A. RT-qPCR confirmed these findings, with protein level evaluations indicating the sustained upregulation of VEGF-A exclusively in keratinocytes treated with Class II. We identified Substance P and VEGF-A as potential therapeutic targets for managing cutaneous loxoscelism, providing valuable insights into the cellular mechanisms underlying the distinct toxic effects of the two SMase D isoforms. By elucidating these pathways, this study enhances our understanding of loxoscelism's pathophysiology and highlights strategies for therapeutic intervention in dermonecrotic injuries caused by spider venom. (AU)

• FAPESP's process: 20/03718-3 - Understanding the local reactions induced by Loxosceles venoms and their main toxins
• Grantee: Bruna Fernandes Pinto
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 13/07467-1 - CeTICS - Center of Toxins, Immune-Response and Cell Signaling
• Grantee: Hugo Aguirre Armelin
• Support Opportunities: Research Grants - Research, Innovation and Dissemination Centers - RIDC