Activation of JAK-STAT3 signaling pathway in chronic subdural hematoma outer membranes

Chronic subdural hematoma (CSDH) is an inflammatory disease, the mechanism of which still remains to be elucidated. Interleukin-6 (IL-6), one of the inflammatory cytokines regulating janus kinase (JAK)-signal transducer and activator of transcription (STAT) signaling pathway, is expressed in human CSDH fluid. The status of this signaling pathway in human CSDH outer membranes was examined in the present study using outer membranes obtained during trepanation surgery. Concentrations of IL-6 in human CSDH fluids were measured using an enzyme immuno-assay kit. Expression patterns of JAK1, STAT1, phosphorylated (p)-STAT1 at Tyr(701) and at Ser(727), STAT3, p-STAT3 at Tyr(705) and at Ser(727) and actin in outer membranes were examined by Western blot analysis and immunohistochemistry. IL-6 is significantly expressed in human CSDH fluids compared with control cerebrospinal fluid. JAK1, STAT1 and STAT3 were detected in all cases. The expression of p-STAT3 at Tyr(705) is more significant compared with that of p-STAT1 at Tyr(701). In some cases, p-STAT3 at Ser(727) could also be detected, while p-STAT1 at Ser(727) could not. The localizations of STAT1 and STAT3 were revealed to be present in fibroblasts in human CSDH outer membranes, especially when p-STAT3 at Tyr(705) was in the nuclei of fibroblasts. These findings suggest that JAK1-STAT3 signaling is dominantly activated in fibroblasts of human CSDH outer membranes compared with STAT1 and indicate the possibility that this JAK1-STAT3 pathway might be activated by IL-6 and play a critical role in progression of human CSDH.