Exploring the role of the NLRP3 inflammasome in epididymitis: consequences for tissue damage and cell death pathways.

• Grant number: 24/19000-5
• Support Opportunities: Scholarships in Brazil - Master
• Start date: April 01, 2025
• End date: September 30, 2026
• Field of knowledge: Biological Sciences - Pharmacology - Biochemical and Molecular Pharmacology
• Principal Investigator: Erick José Ramo da Silva
• Grantee: Juliana Quintaneiro Bizzotto
• Host Institution: Instituto de Biociências (IBB). Universidade Estadual Paulista (UNESP). Campus de Botucatu. Botucatu , SP, Brazil
• Associated research grant: 21/06718-7 - Translational studies on the sperm-binding protein EPPIN as a male contraceptive drug target, AP.JP2

Abstract

Upon release from the seminiferous tubules, spermatozoa undergo essential post-testicular maturation in the epididymis to acquire full motility and fertilization capacity. The epididymis, a single, highly coiled, and convoluted tubule, hosts spermatozoa in a luminal compartment surrounded by a pseudostratified epithelium composed of various cell types. The interaction between immune cells (e.g., mononuclear phagocytes and T and B lymphocytes) with other epididymal cells, including epithelial cells and sperm, is crucial in shaping dynamic region-specific microenvironments that support sperm maturation, protection, and storage. Disruptions in the immune environment are detrimental to epididymal function and, thus, male fertility. The epididymis is vulnerable to infections, which can lead to epididymitis, a common urological condition and a significant cause of male infertility. Rodent models of epididymitis induced by the retrograde luminal of uropathogenic E. coli (UPEC) infection or other inflammatory stimuli (e.g., lipopolysaccharide; LPS) showed that the epididymis displays a highly regionalized response. Specifically, the distal regions (corpus and cauda) appear more susceptible to injury than the proximal regions (initial segment and caput). These alterations have been linked with higher production of cytokines and chemokines in the distal epididymal regions via the TLR4/NF-¿B pathway following LPS) stimulation. LPS activation of the TLR4/NF-¿B pathway is known to activate the NLRP3 inflammasome complex, which promotes pro-inflammatory cytokines IL1B and IL18 release. The NLRP3 inflammasome also drives the activation of other molecules that intensify inflammation and pyroptosis, a form of programmed cell death. We hypothesize that the differential activation of the NLRP3 inflammasome complex contributes to the regionalized epididymal responses to LPS, leading to tissue damage associated with epididymitis. This project aims to investigate the role of the NLRP3 inflammasome complex during epididymitis. Adult mice will be treated with ultrapure LPS from E. coli (1.0 mg/kg; i.p.) to induce systemic endotoxemia in the presence or absence of pretreatment with NFKB inhibitors (BAY-11-7082) or NLRP3 inhibitors (MCC950). At specified time points, mice will be euthanized, and their epididymis will be dissected into initial segment, caput, corpus, and cauda regions for analysis. We will evaluate the expression and activation of elements of the NLRP3 inflammasome complex (NLRP3, PYCARD, CASP1, and NEK7), cytokines (IL1B, IL18, IL6, TNF, and IL10), and other inflammatory and cell death mediators (BCL2, BAX, BAK, GSDMD, CASP8, and CASP3). We expect to unravel the involvement of the NLRP3 inflammasome in epididymal inflammation, paving the way to improve our understanding of the pathophysiology of epididymitis and potentially uncover novel adjuvant strategies to protect the epididymis and preserve male fertility.