It was previously demonstrated that Menta-FX, a mixture of
Panax quinquefolius L. (PQE),
Ginkgo biloba (GBE), and
Hypericum perforatum extracts (HPE), enhances retinal ganglion cell survival after axotomy. However, the mechanisms of neuroprotection remain
unknown. The aim of this study is to elucidate the neuroprotective mechanisms of Menta-FX. Since PQE, GBE and HPE have all
been observed to display anti-oxidative property, the involvement of anti-oxidation in Menta-FX’s neuroprotective effect was
investigated. Menta-FX lowered nitric oxide (NO) content in axotomized retinas without affecting nitric oxide synthase activity,
suggesting that Menta-FX possibly exhibited a NO scavenging property. In addition, the effect of Menta-FX on the frequency
of axotomy-induced nuclear fragmentation and caspase-3 activation was investigated. Menta-FX treatment significantly reduced
nuclear fragmentation in axotomized retinas. Surprisingly, Menta-FX had no effect on caspase-3 activation, but selectively
lowered caspase-3-independent nuclear fragmentation in axotomized retinal ganglion cells. In addition, inhibition of PI3K
activity by intravitreal injection of wortmannin, a phosphoinositide-3 kinase (PI3K) inhibitor, completely abolished the neuroprotective
effect of Menta-FX, indicating that Menta-FX’s neuroprotective effect was PI3K-dependent. Data here suggest that Menta-FX
displayed a PI3K-dependent, selective inhibition on a caspase-3-independent apoptotic pathway in axotomized RGCs, thus, highlighting
the potential use of herbal remedies as neuroprotective agents for other neurodegenerative diseases.
Keywords Ganglion cells -
Ginkgo biloba
-
Hypericum perforatum
- Optic nerve -
Panax quinquefolius L.