Effects of kindled seizures upon hematopoiesis in rats

Anticonvulsant activity of bone marrow cells in electroconvulsive seizures in mice

Background

Bone marrow is an accessible source of progenitor cells, which have been investigated as treatment for neurological diseases in a number of clinical trials. Here we evaluated the potential benefit of bone marrow cells in protecting against convulsive seizures induced by maximum electroconvulsive shock (MES), a widely used model for screening of anti-epileptic drugs. Behavioral and inflammatory responses were measured after MES induction in order to verify the effects promoted by transplantation of bone marrow cells. To assess the anticonvulsant effects of bone marrow cell transplantation, we measured the frequency and duration of tonic seizure, the mortality rate, the microglial expression and the blood levels of cytokine IL-1, IL-6, IL-10 and TNF-α after MES induction. We hypothesized that these behavioral and inflammatory responses to a strong stimulus such as a convulsive seizure could be modified by the transplantation of bone marrow cells.

Results

Bone marrow transplanted cells altered the convulsive threshold and showed anticonvulsant effect by protecting from tonic seizures. Bone marrow cells modified the microglial expression in the analyzed brain areas, increased the IL-10 and attenuate IL-6 levels.

Conclusions

Bone marrow cells exert protective effects by blocking the course of electroconvulsive seizures. Additionally, electroconvulsive seizures induced acute inflammatory responses by altering the pattern of microglia expression, as well as in IL-6 and IL-10 levels. Our findings also indicated that the anticonvulsant effects of these cells can be tested with the MES model following the same paradigm used for drug testing in pharmacological screening. Studies on the inflammatory reaction in response to acute seizures in the presence of transplanted bone marrow cells might open a wide range of discussions on the mechanisms relevant to the pathophysiology of epilepsies.

Tac1 regulation by RNA-binding protein and miRNA in bone marrow stroma: Implication for hematopoietic activity

Hematopoiesis is the process by which immune and blood cells are produced from a finite number of relatively few hematopoietic stem cells (HSCs). In adults, hematopoiesis occurs in the adult bone marrow (BM), with the support of stromal cells. This support partly occurs through the production of hematopoietic regulators belonging to the families of cytokines and neuropeptides/neurotransmitters, which mediate their actions through specific receptors. Thus, stromal cells could be central to the neural-hematopoietic-immune axis. This study focuses on Tac1, which encodes hematopoietic regulators belonging to the tachykinin family of neuropeptides. We examined post-transcriptional regulation of Tac1 in BM stroma. Since this gene is inducible in stroma, we selected cytokines with varying hematopoietic effects: stimulator Stem Cell Factor (SCF), broad-acting IL-11 and suppressive TGF-beta1. RNA shift with Tac1 mRNA and cytoplasmic extracts from IL-11 and SCF-stimulated stroma showed RNA shift after 15min at 37 degrees C, whereas a shift was detected with extracts from TGF-beta1-stimulated stroma after 5min at room temperature. Another level of post-transcriptional regulation was observed by the detection of miRNAs that interact with the 3' untranslated region of Tac1 mRNA. In summary, this study showed that cytokine induced miRNA downregulation and RNA-binding protein(s) are involved in post-transcriptional regulation of Tac1 in BM stroma. The broad categories of cytokines as hematopoietic stimulators or inhibitors might depend on the avidity of RNA-binding protein(s) for Tac1 mRNA, as well as the ability to degrade or stabilize the specific miRNAs.

Long-term kindled seizures induce alterations in hematopoietic functions: role of serum leptin

Recent studies conducted in our laboratory have demonstrated marked increases in both serum leptin levels and colony numbers in bone marrow progenitor cells following long-term kindled seizures in rats. The present study sought to determine whether such changes in hematopoietic functions following kindling are linked to increased serum leptin levels. Kindled stage V seizures were induced for 30 days in Sprague-Dawley rats by stimulation of the basal complex of amygdala. The results revealed colony numbers in colony forming units-granulocyte/macrophage (CFU-GM) cultures from kindled rats increased significantly, an effect that was blocked by the presence of an anti-leptin antibody. The results further demonstrated that the addition of serum obtained from kindled rats to CFU-GM cultures from control rats significantly increased the numbers of colonies relative to non-serum added cultures. Moreover, the proliferative effects of serum from kindled rats were also blocked by adding an anti-leptin antibody. These findings were confirmed from the observations that the long isoform of the leptin receptor, which is capable of signal transduction, was present only in kindled, but not in control rats. Thus, the results provide evidence that the hematopoietic changes observed following long-term kindling are directly associated with elevated serum leptin levels.