Diacerein Disrupts Testicular Homeostasis: The Essential Role of Basal Cytokines in Maintaining Sertoli Cell Integrity and the Immune Microenvironment

BACKGROUND: Pro-inflammatory cytokines, TNF and IL-1B, are essential for testicular homeostasis. Diacerein, an anti-inflammatory drug, inhibits these cytokines, impairing M2 macrophages and Leydig cells (LCs). However, its impact on Sertoli cells (SCs) and M1 (CD68) macrophages remains unknown. OBJECTIVE: To investigate the impact of diacerein-induced cytokine downregulation on SC integrity and the testicular immune profile. MATERIALS AND METHODS: Male rats were treated with diacerein (100 mg/kg) or saline for 30 days. The seminiferous epithelium was evaluated by light and transmission electron microscopy. The number of spermatocytes and Ki-67+ cells was quantified. SC structural (actin, vimentin, claudin-1, connexin-43) and functional (transferrin, Ldha) proteins, and the interstitial immunolocalization of macrophage inhibitory factor (MIF), CD68, CD45, IL-1B, iNOS, NF-κB, and karyopherin were assessed, alongside immune response genes (Tnfa, Il1b, Nfkb1, Nos2, Tgfb1) and nitrite levels. TUNEL method was also performed. RESULTS AND DISCUSSION: TNF and IL-1B were downregulated; steroidogenesis and IL-1B production by LCs decreased, coupled with reduced MIF levels. SCs exhibited electron-dense cytoplasm, disrupted filaments, and decreased blood-testis barrier proteins. Transferrin and Ldha expression were reduced, underlying reduced spermatocyte counts, arrested proliferation, and germ cell death. TUNEL-positive apoptotic bodies (probably from LCs) were found within macrophages. Despite increased CD45+ and CD68+ macrophages, a noninflammatory phenotype was observed due to NF-κB cytoplasmic sequestration and weak karyopherin expression, corroborating Tgfb1 upregulation and reduced Nos2 expression and nitrite levels. CONCLUSION: Basal cytokines are essential for SC structure and function. Despite testicular damage, diacerein shifted the immune response toward a homeostatic and immunotolerant profile, avoiding a self-destructive inflammatory process.