Neopterin May Enhance TNF-α-mediated Mononuclear Cell Death in the Cerebrospinal Fluid of Patients with Bacterial Meningitis

It has been reported that levels of neopterin are elevated in the cerebrospinal fluid (CSF) of patients with bacterial meningitis, and that neopterin enhances cell death induced by H2O2 in mouse monocytes and macrophages. In the present study, we examined the relationship between the disappearance of inflammatory cells in the CSF of patients with bacterial meningitis and the effects of neopterin on cell death. We hypothesized that the rapid cell death of mononuclear leukocytes (MNs) and survival of polymorphonuclear leukocytes (PMNs) brought about by high levels of tumor necrosis factor-alpha TNF-alpha may be related to the pathophysiology of PMN predominance in the CSF of patients with bacterial meningitis. Peripheral blood leukocytes separated into two fractions (MNs and PMNs) were suspended in CSF samples from patients with bacterial meningitis, and the cell death rate was determined with MTT assay. The higher the CSF TNF-alpha level, the higher the MN mortality rate tended to be. In contrast, PMNs were able to survive high levels of TNF-alpha in the CSF. For control purposes, MNs and PMNs were also suspended in various conditioned media. The same association between TNF-alpha levels and MN mortality was observed, as was the survival of PMNs. The addition of neopterin enhanced the cytocidal effect of TNF. The present study suggests that neopterin is related to PMN predominance in the CSF of patients with bacterial meningitis via the effect of TNF-alpha on cell death.