Anti-semaphorin 3A Antibodies Rescue Retinal Ganglion Cells from Cell Death following Optic Nerve Axotomy

Abstract

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 functionblocking 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.

The brain within the tumor: new roles for axon guidance molecules in cancers

“…Such molecules have already been successfully used on developing neurons 164,165 but still have to be tested on tumors. Moreover, the 3D-structure of several of these axon guidance proteins, in particular semaphorins and neuropilins, have been recently solved, which should help designing new molecules.…”

Cranial expression of class 3 secreted semaphorins and their neuropilin receptors

“…This effect is apparently not mediated by Sema3A (Ohta et al, 1999;Shepherd et al, 1996); therefore, it would be interesting to see whether Sema3D can repel RGCs. In addition to chemorepulsion, Sema3A has been shown to promote apoptosis, including that of RGCs (Bagnard et al, 2001;Shirvan et al, 2002). This is an important process in the developing lens (Jean et al, 1998) to which Sema3A may, …”

A Novel Role for Sema3A in Neuroprotection from Injury Mediated by Activated Microglia

“…We provide evidence in vitro and in vivo for upregulation of both Plexin-A1 and Npn-1 after activation of microglia. Recent reports also implicate semaphorin-mediated neuronal and neuronal progenitor apoptotic cell death (Gagliardini and Fankhauser, 1999;Shirvan et al, 1999Shirvan et al, , 2002Bagnard et al, 2001). We therefore examined whether semaphorin has a similar effect on microglia.…”

“…After a 1 h blocking step in 3% normal goat serum (NGS), 30 m sections were incubated overnight with primary antibody in Tris-buffered saline (TBS) containing 0.2% Triton X-100 (Sigma) with 1% NGS. The following antibodies were used: OX42 (1:400; Serotec, Oxford, UK), Plexin-A1 culture supernatant (a gift from H. Fujisawa, National Institute of Genetics, Mishima, Japan) Npn-1 (1:200) (Kolodkin et al, 1997;Pasterkamp et al, 1999), Sema3A (1:250; a gift from A. Barzilai, Tel Aviv University, Tel Aviv, Israel) (Shirvan et al, 2002), and NeuN (1:200; Chemicon, Hampshire, UK). After washing in TBS, sections were incubated in biotinylated secondary antibodies (1:200) for 3 h at room temperature.…”