ABSTRACT
The activation of neurotrophic signaling pathways following the upregulation of glial cell line-derived neurotrophic factor (GDNF), a member of the transforming growth factor-β family, has a potential neuroprotective effect in the adult brain. Herein, we report that hippocampal transduction of adeno-associated virus serotype 1 (AAV1) with a constitutively active form of ras homolog enriched in brain [Rheb(S16H)], which can stimulate the production of brain-derived neurotrophic factor (BDNF) in hippocampal neurons, induces the increases in expression of GDNF and GDNF family receptor α-1 (GFRα-1), in neurons and astrocytes in the hippocampus of rat brain in vivo . Moreover, upregulation of GDNF and GFRα-1 contributes to neuroprotection against thrombin-induced neurotoxicity in the hippocampus. These results suggest that AAV1-Rheb(S16H) transduction of hippocampal neurons, resulting in neurotrophic interactions between neurons and astrocytes, may be useful for neuroprotection in the adult hippocampus.
ABSTRACT
We recently reported that adeno-associated virus serotype 1 (AAV1) transduction of murine nigral dopaminergic (DA) neurons with constitutively active ras homolog enriched in brain with a mutation of serine to histidine at position 16 [Rheb(S16H)] induced the production of neurotrophic factors, resulting in neuroprotective effects on the nigrostriatal DA system in animal models of Parkinson’s disease (PD). To further investigate whether AAV1-Rheb(S16H) transduction has neuroprotective potential against neurotoxic inflammation, which is known to be a potential event related to PD pathogenesis, we examined the effects of Rheb(S16H) expression in nigral DA neurons under a neurotoxic inflammatory environment induced by the endogenous microglial activator prothrombin kringle-2 (pKr-2). Our observations showed that Rheb(S16H) transduction played a role in the neuroprotection of the nigrostriatal DA system against pKr-2-induced neurotoxic inflammation, even though there were similar levels of pro-inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-α) and interleukin-1-beta (IL-1β), in the AAV1-Rheb(S16H)-treated substantia nigra (SN) compared to the SN treated with pKr-2 alone; the neuroprotective effects may be mediated by the activation of neurotrophic signaling pathways following Rheb(S16H) transduction of nigral DA neurons. We conclude that AAV1-Rheb(S16H) transduction of neuronal populations to activate the production of neurotrophic factors and intracellular neurotrophic signaling pathways may offer promise for protecting adult neurons from extracellular neurotoxic inflammation.