gms | German Medical Science

Objective: Semaphorins are membrane-bound or secreted glycoproteins which have important functions in regulation of axonal guidance but also in immunregulation, vascularization, in regulation of bone-matrix and oncogenesis. Single axon has the ability to extend multiple branches and form terminal arbors allowing neurons to integrate information from divergent region of the nervous system. Sema 3A is repellent axon guidance protein that functions in assembly of neuronal circuits. Recently it has been shown that this protein has a critical role in layer-specific axonal branching, which contributes to target innervation. Estrogen is known to play an important role in maintaining axonal growth and synapse formation. Zileuton, an anti-inflammatory drug (an inhibitor of Arachidonate 5-lipoxygenase), has been described to have positive effects in cerebral ischemia by inhibiting neuronal apoptosis and to restore memory impairments in a mouse model of Alzheimer’s disease. We studied the effect of zileuton on the expression of Sema 3A in brain of estrogen deficient rats.

Methods: Eight weeks after ovariectomy (Ovx) 5-month-old Sprague–Dawley rats were assigned into four groups: (1) untreated Ovx; (2-4) groups: Ovx treated with zileuton (1, 10 or 100 mg/kg body weight, respectively). Group five serves as a control group (Non-Ovx and untreated). Eleven rats per group were analyzed. After 5 weeks, the expression of protein and mRNA of Sema 3A in hippocampus and hypothalamus were defined with western-blot and real-time PCR. We have chosen these two brain region because hypothalamic neurons are targets of sex hormones and in the hippocampus sex hormones regulate neurogenesis in adults.

Results: The expression of Sema 3A-mRNA was reduced after Ovx in hypothalamus, whereas, treatment with zileuton (10 mg/kg) significantly increased it (p=0.0001) compared to other groups. The difference in total cellular protein levels (Sema 3A), between the groups were not significant. In hippocampus the changes were not detected.

Conclusion: Zileuton improved the expression of Sema 3A-mRNA which, was reduced after Ovx. This suggested a positive effect of zileuton on hypothalamic Sema 3A. A discrepancy between expression of protein and mRNA should be further analyzed. Since the axon branching occurs far from the cell body assessment of protein localization could be helpful in order to understand this.