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

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. To investigate the impact of diacerein-induced cytokine downregulation on SC integrity and the testicular immune profile. 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. 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. 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.