Abstracts

Rationale: The chemokine C-C motif recepor 2 (CCR2, also designated as CD192, CC-CKR-2; CKR2; CMKBR2; MCP-1-R) is the chemokine monocyte chemoattractant protein-1 (MCP-1) receptor. These are integral membrane proteins that specifically bind and respond to cytokines of the CC chemokine family, and are involved with immune infiltration of the CNS by inflammatory cells, (i.e., monocytes) in various brain diseases. It is known that brain inflammation occurs after seizures, and can contribute to a pro-epileptogenic neural system. We aimed to investigate if CCR2 was altered in the hippocampus following status epilepsticus (SE) induced by pilocarpine (PILO) injection. Methods: Adult Sprague Dawley rats were treated with methylscopolamine (2 mg/kg) 30 min before PILO i.p. injection (320 mg/kg; n=4). Ninety minutes after SE onset rats received diazepam (10 mg/kg). Control rats (n=4) were injected with saline instead of PILO. Five days after SE induction rats were transcardially perfused and brain sections of 40 µm were immunohistochemistry processed for CCR2 and glial fibrillary acidic protein (GFAP), a marker of astrocytes. The number of CCR2 positive cells was counted in the hippocampal dentate gyrus and CA1 region in three sections per rat (Bregma range: -2.52 and -5.40). Results: Rats with PILO-induced SE presented up-regulation of CCR2 expression in the dentate gyrus granular cell layer (GCL; 64 ± 16.09; mean ± SEM) and in the CA1 area (97 ± 14.95) when compared with control rats (20 ± 4.10, 33.25 ± 7.11, GCL and CA1, respectively; p < 0.05, t-test). We observed that the majority of CCR2 cells in the hippocampal dentate gyrus were located in the subgranular zone of the GCL. Interestingly, in CA1 region, SE rats also presented a robust population of CCR2 positive processes that was almost inexistent in control rats, and moreover, many of these CCR2 process were double labeled with GFAP. Conclusions: These results show that CCR2 is up-regulated in the hippocampus after PILO-induced seizures indicating that this chemokine receptor may play an important role in the brain inflammation after prolonged seizures. The increased CCR2 expression by astrocytes suggests that it may mediate the inflammatory response through monocyte infiltration especially in the CA1 region, an area usually damaged after seizures. Additionally, the fact that most of CCR2 cells in the hippocampal dentate gyrus appear to be located in the subgranular zone of the GCL is very interesting since it is in this region that newly born neurons are concentrated after seizures, therefore supporting the idea that brain inflammation and neurogenesis are closely related and can contribute to epileptogenesis.