Extracellular inosine participates in tumor necrosis factor-alpha induced nitric oxide production in cultured Sertoli cells

Recent reports have described purinergic modulation of tumor necrosis factor-alpha (TNF-α) signaling in neutrophils and astrocytes. In Sertoli cells, both TNF-R1 and TNF-R2 TNF-α receptors are present and this cytokine modulates many functions of these cells related to the maintenance of spermatogenesis. Sertoli cells express distinct purinoreceptors and previous work has shown that these cells secrete extracellular nucleotides and their metabolites. In this work, we studied the possible role of extracellular purines in TNF-α signaling in cultured Sertoli cells. This cytokine increased inosine concentration from 30 min to 6 h, with no effect at 24 h. Both TNF-α and inosine increased nitrite accumulation and nitric oxide synthase activity. Erythro-9-(2-hydroxy-3-nonyl)adenine (EHNA), an adenosine deaminase inhibitor, abolished the TNF-α induced inosine increase, nitrite accumulation and nitric oxide synthase activity. These results suggest that extracellular inosine acts as intermediary in TNF-α stimulated nitric oxide production in cultured Sertoli cells.