Expression and cell distribution of myeloid differentiation primary response protein 88 in the cerebral cortex following experimental subarachnoid hemorrhage in rats: a pilot study

Subarachnoid hemorrhage (SAH) which is mostly caused by aneurysm rupture causes a lot of death every year. Convincing evidence can be made that inflammation contributes to the poor outcome caused by SAH. Toll like receptors (TLRs), nuclear factor-kappaB (NF-κB), Interleukin 1β (IL-1β) and tumor necrosis factor-α (TNF-α) are involved in the damaging inflammation process after SAH. Myeloid differentiation primary response protein 88 (MyD88) is essential to deliver TLRs signals down to NF-κB and pro-inflammatory factors. The study aims to detect the expression level of MyD88 and know more about the role of MyD88 after SAH. Sprague Dawley (SD) rats were randomly divided into sham group and SAH groups at 2h, 6h, 12h and on day 1, day 2, day 3, day 5 and day 7. SAH groups suffered experimental subarachnoid hemorrhage by injection of 0.3 ml autoblood into the prechiasmatic cistern. MyD88 expression is measured by western blot analysis, real-time polymerase chain reaction (PCR), immunohistochemistry and immunofluorescence. The levels of TNF-α and IL-1β were measured by real-time PCR. Our results demonstrated MyD88 expression was increased after SAH, and peaked on day 1 and day 5, which showed a parallel time course to the up-regulation of IL-1β, there was a highly positive relationship between them. Immunohistochemistry and immunofluorescence results indicated up-regulated MyD88 was mainly located in neurons while over expressed MyD88 could also be found in astrocytes and microglia. These results might have important implications during the administration of specific MyD88 antagonists in order to prevent or reduce inflammatory response following SAH.