A novel immune-based therapy for stroke induces neuroprotection and supports neurogenesis.

The ability of the central nervous system to cope with stressful conditions was shown to be dependent on proper T-cell-mediated immune response. Because the therapeutic window for neuroprotection after acute insults such as stroke is relatively narrow, we searched for a procedure that would allow the relevant T cells to be recruited rapidly. Permanent middle cerebral artery occlusion was induced in adult rats. To facilitate a rapid poststroke T cell activity, rats were treated with poly-YE using different regimens. Control and poly-YE-treated rats were assessed for functional recovery using neurological severity score and Morris water maze. Neuroprotection, neurogenesis, growth factor expression, and microglial phenotype were assessed using histological and immunofluorescence methods. Administration of poly-YE as late as 24 hours after middle cerebral artery occlusion yielded a beneficial effect manifested by better neurological performance, reduced neuronal loss, attenuation of behavioral deficits, and increased hippocampal and cortical neurogenesis. This compound affected the subacute phase by modulating microglial response and by increasing local production of insulin-like growth factor-I, known to be a key player in neuronal survival and neurogenesis. The relative wide therapeutic window, coupled with its efficacy in attenuating further degeneration and enhancing restoration, makes poly-YE a promising immune-based candidate for stroke therapy.

Up-regulation of semaphorin expression in retina of glaucomatous rabbits.

BACKGROUND: Glaucoma is a term encompassing a variety of diseases that end in the death of retinal ganglion cells (RGC). Although a variety of factors can initiate the disease onset, increased intraocular pressure (IOP) is one of the major risk factors. In our previous study we found that semaphorins were causally involved in RGC death following axotomy. Since a common feature of all retinal neuropathies is axonal damage, we hypothesized that semaphorins are involved in glaucoma-induced RGC death. The purpose of this study was to analyze the effect of increased IOP on RGC viability and to analyze semaphorin expression pattern in glaucomatous retinas. METHODS: Utilizing retrograde-labeled dye (4-Di-10-Asp) and hematoxylin-eosin staining, we investigated the effect of elevated levels of IOP on RGC viability. In addition, immunohistochemical analysis and western blotting were used to study the pattern of semaphorin expression in retinas of rabbits with genetically developed increased IOP and subsequently glaucoma. RESULTS: Using specific anti-semaphorin antibodies, the expression of a single protein with the size of a semaphorin protein, 110 kDa, was detected; its expression was up-regulated in glaucomatous rabbits compared with controls. Time-course analysis revealed that semaphorin expression peaked between 2 and 6 months of age and declined thereafter. Immunohistochemical analysis revealed that semaphorin expression was up-regulated specifically in the ganglion cell layer, which is a structure that is highly affected in glaucoma. CONCLUSION: Deciphering the molecular mechanisms of glaucoma-induced death and its mediators is a crucial step towards designing new therapeutic strategies to treat this incurable disease.

Anti-semaphorin 3A antibodies rescue retinal ganglion cells from cell death following optic nerve axotomy.

Damage to the optic nerve in mammals induces retrograde degeneration and apoptosis of the retinal ganglion cell (RGC) bodies. The mechanisms that mediate the response of the neuronal cells to the axonal injury are still unknown. We have previously shown that semaphorins, axon guidance molecules with repulsive cues, are capable of mediating apoptosis in cultured neuronal cells (Shirvan, A., Ziv, I., Fleminger, G., Shina, R., He, Z., Brudo, I., Melamed, E., and Brazilai, A. (1999) J. Neurochem. 73, 961-971). In this study, we examined the involvement of semaphorins in an in vivo experimental animal model of complete axotomy of the rat optic nerve. We demonstrate that a marked induction of type III semaphorin proteins takes place in ipsilateral retinas at early stages following axotomy, well before any morphological signs of RGC apoptosis can be detected. Time course analysis revealed that a peak of expression occurred after 2-3 days and then declined. A small conserved peptide derived from semaphorin 3A that was previously shown to induce neuronal death in culture was capable of inducing RGC loss upon its intravitreous injection into the rat eye. Moreover, we demonstrate a marked inhibition of RGC loss when axotomized eyes were co-treated by intravitreous injection of function-blocking antibodies against the semaphorin 3A-derived peptide. Marked neuronal protection from degeneration was also observed when the antibodies were applied 24 h post-injury. We therefore suggest that semaphorins are key proteins that modulate the cell fate of axotomized RGC. Neutralization of the semaphorin repulsive function may serve as a promising new approach for treatment of traumatic injury in the adult mammalian central nervous system or of ophthalmologic diseases such as glaucoma and ischemic optic neuropathy that induce apoptotic RGC death.