A novel inhibitor of inflammatory cytokine production (CNI-1493) reduces rodent post-hemorrhagic vasospasm

Introduction: Cerebral vasospasm after aneurysmal subarachnoid hemorrhage (SAH) is a devastating complication, yet despite multiple lines of investigation an effective treatment remains lacking. Cytokine-mediated inflammation has been implicated as a causative factor in the development of posthemorrhagic vasospasm. In previous experiments using the rat femoral artery model of vasospasm, we demonstrated that elevated levels of the proinflammatory cytokine interleukin (IL)-6 are present after hemorrhage and that a polyclonal antibody against IL-6 is capable of attenuating experimental vasospasm. Methods: In the present study, we tested the ability of a novel selective proinflammatory cytokine inhibitor (CNI-1493) to protect against the occurrence of experimental vasospasm in the same rat femoral artery model. CNI-1493 was administered by injection directly into the blood-filled femoral pouches of animals at the time of their initial surgery (hemorrhage). Control animals received an equal volume of vehicle alone. Animals were killed at 8 days posthemorrhage and degree of vasospasm was assessed by image analysis of artery cross-sectional area. In a separate series of experiments, enzyme-linked immunosorbent assay (ELISA) was used to assess levels of the promflammatory cytokine IL-6 and the prototypical antiinflammatory cytokine transforming growth factor (TGF)-beta(1) after treatment with CNI-1493. Results: Pretreatment with CNI-1493 provided dose-dependent attenuation of posthemorrhagic vasospasm, with the highest dose (200 mu g in 8 mu l, dH(2)O) causing complete reversal of vasospasm (vessel cross-sectional area ratio 1.06 +/- 0.04 versus 0.87 +/- 0.06, p<0.05, one-way analysis of variance). Assessment of cytokine levels by ELISA confirmed the selectivity of CNI-1493 by demonstrating significant reductions in IL-6 levels, but no suppression of TGF-beta(1) levels. Conclusions: These findings support the conclusion that inflammatory cytokines, in particular IL-6, play an important role in development of vasospasm in the rat femoral artery model. Furthermore, these results suggest that the inhibition of inflammatory cytokines may be an appropriate strategy for the treatment of vasospasm after SAH.