The 27-kDa heat shock protein (HSP27) is a reliable hippocampal marker of full development of pilocarpine-induced status epilepticus.

Purpose: The pilocarpine-induced status epilepticus (SE) in rodents provides a valuable animal model of temporal lobe epilepsy. Since not all animals enter SE following pilocarpine injection, we aimed to find a biomarker for full development of pilocarpine-induced SE using a proteomic approach.

Methods: Two-dimensional gel electrophoresis and Western blot analysis were performed with protein extracts from hippocampal tissue taken from four different groups of animals: pilocarpine-treated rats with full development of SE, pilocarpine-treated rats without seizures, pilocarpine-treated rats with seizures but without SE, and saline-injected rats.

Results: 2D gel electrophoresis revealed two protein spots which were only present after full development of pilocarpine-induced SE, but neither in gels from pilocarpine-treated rats without seizures nor in those of saline-injected animals. The protein in both spots was identified as the small 27-kDa heat shock protein (HSP27) by MALDI-TOF mass spectrometry. Subsequent Western blot analyses confirmed that HSP27 immunoreactivity was only observed with the hippocampal protein extracts in the status epilepticus group, but in none of the other groups. Furthermore, immunocytochemistry showed that HSP27 expression following pilocarpine-induced SE was localized in astrocytes.

Conclusion: We propose that HSP27 is a highly sensitive and specific hippocampal marker for full development of pilocarpine-induced status epilepticus.