Effects of vascular endothelial growth factor (VEGF) on motor neuron degeneration.

Both in mice and humans, low expression levels of vascular endothelial growth factor (VEGF) are linked to adult-onset motor neuron disease or amyotrophic lateral sclerosis (ALS). The mechanism through which reduced VEGF levels result in this phenotype is unknown. We therefore examined the direct effects of VEGF on motor neurons and found VEGF to have a direct neurotrophic effect on motor neurons in vitro. Survival and vulnerability to excitotoxicity of motor neurons from VEGF(delta/delta) mice was however similar to that of motor neurons from non-transgenic littermates. The VEGF concentration in the spinal cord of mutant (G93A) SOD1 mice was not different from that found in wild-type SOD1 overexpressing mice. Upregulation of VEGF in the spinal cord, by housing mutant (G93A) SOD1 mice in hypoxic conditions, did not affect their life span. Our results show that VEGF is a neurotrophic factor for motor neurons in vitro, and shortage of this neurotrophic factor may contribute to the motor neuron death observed in humans and animals with low VEGF expression levels.

Upregulation of HSP27 in a transgenic model of ALS.

Mutations of the SOD1 gene underlie 1 form of familial amyotrophic lateral sclerosis (ALS). Their pathogenic mechanism remains uncertain, but is thought to involve oxidative stress and abnormal protein aggregation, 2 processes known to induce heat shock proteins (HSPs). We studied the expression of 3 HSPs (alphaB-crystallin, HSP27, and HSP70) in transgenic mice overexpressing human mutant (G93A and G37R) SOD1, using a combination of immunohistochemistry and immunoblotting. Quantitative Western blot analysis demonstrated alphaB-crystallin and HSP27 to be upregulated in the spinal cord of mutant SOD1 mice compared to mice overexpressing wild-type SOD1. HSP70 levels were normal. Immunocytochemical studies of the ventral horn of the spinal cord demonstrated HSP27 to be localized in the nucleus of neurons and glial cells in presymptomatic and early symptomatic animals, where it often was punctate in pattern. In the later stages of the disease, HSP27 was predominantly present in the cytoplasm of reactive glial cells. The early nuclear localization was confirmed by Western blot analysis of spinal cord nuclear and cytoplasmic fractions. In contrast to HSP27, alphaB-crystallin was localized exclusively in the cytoplasm of reactive glial cells.