High mobility group box protein 1 (HMGB1) plays an important role in onset and progression of autoimmune diseases. This nucleosomal protein is actively secreted during inflammation and acts as a late phase cytokine. Targeting HMGB1 by ethyl pyruvate (EP) significantly reduces its pro-inflammatory effects. Experimental autoimmune orchitis (EAO) serves as a rodent model to study autoimmune based chronic testicular inflammation characterized by elevated levels of pro-inflammatory cytokines, lymphocytic infiltrates in the interstitium, germ cell loss, and subsequent infertility.
EAO was induced in Wistar rats by immunization with testicular homogenate. To block HMGB1 action, EAO and control animals received EP (40 mg/kg, i.p.). HMGB1 localization in testis was analyzed by immunostaining. Levels of HMGB1, IL6, and TNFα were measured using ELISA and real-time qRT-PCR. Interaction of HMGB1 with its receptors RAGE and TLR4 was determined by in situ proximity ligation assay. Activation of MAPK kinases was investigated in isolated testicular macrophages (TM), peritubular (PTC), and Sertoli cells (SC) by western blot.
HMGB1 was translocated from the nuclei in EAO testis followed by significant elevation of HMGB1 levels during the chronic phase of the disease. HMGB1 receptors TLR4 and RAGE were differentially expressed in testicular somatic cells. Binding of HMGB1 to TLR4 was significantly higher in TM compared to SC and PTC with higher levels of HMGB1RAGE interaction. In support, HMGB1 triggered RAGE-dependent ERK1/2 and CREB activation in SC and PTC. In vivo treatment of EAO animals with EP successfully reduced disease progression. Inhibiting HMGB1s action during the course of testicular inflammation could be a promising therapeutical approach to prevent loss of spermatogenesis.
02 - 04 Sep 2014
World Congress of Reproductive Biology