Cerebrospinal fluid of postherpetic neuralgia patients induced interleukin-6 release in human glial cell-line T98G

Chronic intractable pain caused by postherpetic neuralgia (PHN) can be alleviated by intrathecal (i.t.) steroid therapy. We investigated the possibility that interleukin-6 (IL-6) release in an in vitro system could be a potential marker for evaluating the effectiveness of i.t. steroid therapy in PHN patients. We studied 32 patients who received a course of i.t. injection of water-soluble dexamethasone. Their therapeutic index was calculated as such: ((Pain score before treatment - Pain score after treatment) ÷ Pain score before treatment) × 100%, and they were divided into two groups, therapy effective (index > 50%) and ineffective (index < 50%). Cerebrospinal fluid (CSF) from the patients was used to stimulate cultures of T98G glioblastoma cells, and the subsequent IL-6 release was measured by enzyme-linked immunosorbent assay (ELISA). Our results showed that the CSF triggered IL-6 release from T98G cells in a volume-dependent manner. IL-6 release was significantly lower when using CSF from the therapy effective patient group (p < 0.001) compared to the therapy ineffective group. In particular, therapy effective patients had less IL-6 release even before treatment as compared to therapy ineffective patients. In the therapy effective group, in vitro steroid treatment suppressed the CSF's IL-6 releasing effect almost completely, whereas in the therapy ineffective group, the IL-6 release was significantly reduced but remained detectable. These in vitro tests may provide an objective evaluation on the efficacy of i.t. steroid therapy administered to PHN patients.