Problem: This study examined the effect of intraperitoneal administration of lipopolysaccharide (LPS) to adult male mouse on the expression levels of interleukin-18 (IL-18), IL-18 receptor (IL-18R) and the IL-1beta converting enzyme (ICE) (IL-18 family) in their testes and spleen (control).
Method of study: Adult mice were injected (intraperitoneally; i.p.) with saline (control) or LPS (2, 20, 100 microg/mL; 100 microL/mouse). After 3 and 24 hr, testes and spleen were collected. Testicular tissue was examined for IL-18 (by ELISA, real time PCR, and western blot analysis), IL-18R and ICE (western blot and real time PCR analysis) and spleen tissue was examined for the IL-18 family by real time PCR analysis. Student's t-test was used for statistical analysis.
Results: Homogenates of mouse testes contain and express basal levels of IL-18, ICE and IL-18 R. The expression levels of IL-18, ICE and IL-18R were significantly increased 3 and 24 hr after intraperitoneal injection of LPS to mature mouse, as examined by ELISA, western blot and real time PCR analysis. However, the expression levels of IL-18, ICE and IL-18Ralpha in the spleen increased significantly only after 24 hr of LPS stimulation, as examined by real time PCR.
Conclusion: Our results demonstrate that LPS increases the expression levels of the IL-18 family in mouse testis and spleen, but the time of expression differs between the two organs. The presence of IL-18 in the testes might be involved in the regulation of physiological and infection/inflammatory processes, and may be part of the autocrine/paracrine factors that control spermatogenesis. Further studies should be performed to confirm this possibility.