Elena Germani

Glycosaminoglycans co-administration enhance insulin-like growth factor-I neuroprotective and neuroregenerative activity in traumatic and genetic models of motor neuron disease: a review

In this report it is shown how glycosaminoglycans and insulin‐like growth factor‐I (IGF‐I) promote muscle reinnervation and prevent motor neuron death in experimental models of motor neuron disease. Such effect appears to be mediated by insulin‐like growth factor‐1. The glycosaminoglycan moiety of proteoglycans is a constituent of the basal lamina active on nerve regeneration by means of the interaction with laminin and with several growth factors. We have previously shown that supplementation by means of subcutaneous injections of glycosaminoglycans affects neuronal degeneration and regeneration. In this study we report that following neonatal lesion of the rat sciatic nerve, glycosaminoglycan treatment promoted extensor digitorum longus muscle reinnervation with consequent improvement of muscle morphology. In saline‐treated rats, reinnervation was only partial and there was a marked muscle fibre atrophy, whereas, glycosaminoglycan treatment of lesioned rats increased IGF‐I mRNA and protein in the reinnervated muscle, and IGF‐I and insulin‐like growth factor binding protein‐3 plasma levels. Similarly, treatment of lesioned rats with IGF‐I promoted muscle reinnervation, and prevented muscle fibre atrophy, higher levels of IGF‐I in the reinnervated muscle, of IGF‐I, and insulin‐like growth factor binding proteins in plasma. In the wobbler mouse IGF‐I and glycosaminoglycans alone promote only a partial motor neuron survival and the preservation of forelimb function decays after 3 weeks of treatment. However when glycosaminoglycans and insulin‐like growth factor are administered together the motor neuron disease in the wobbler mouse is halted and there is no more loss of motor neurons.

Long-term neuroprotective effects of glycosaminoglycans–IGF-I cotreatment in the motor neuron degeneration (mnd ) mutant mouse

This study shows that cotreatment with insulin‐like growth factor‐I (IGF‐I) and glycosaminoglycans (GAGs) prevents the onset of neuromuscular deficit in the m/m mutant mouse. These mice show a mid‐to‐late‐life onset of progressive paralysis of the hind limb, that is correlated with altered innervation and reduced nerve‐evoked isometric twitch tension in the extensor digitorum longus (EDL) muscle. Almost 50% of EDL nerve endings are negative for antisynaptophysin staining, while retrograde labelling with β‐cholera‐toxin coupled to type IV horseradish and quantitative histological analysis show a small loss of EDL and lumbar cord motor neurons. At 10 months of age also forelimb function evaluated as grip strength is significantly reduced. Animals treated either with glycosaminoglycans alone or with IGF‐I alone at low and high doses showed only a partial improvement of their condition. However, cotreatment of m/m mice with IGF‐I and GAGs fully prevented the neuromuscular abnormalities, the twitch tension loss, the motor neuron decrease and the reduction of forelimb grip strength.

Progressive and selective changes in neurotrophic factor expression and substance p axonal transport induced by perinatal diabetes: Protective action of antioxidant treatment

Diabetes‐induced embryo malformations and growth retardation are correlated with a variety of biochemical changes including oxidative stress. In this study, we show that the morphological alterations are correlated with progressive and selective changes of mRNA expression in specific neurotrophic factors. At embryological stage E‐17, diabetes affected both embryo growth and NGF mRNA expression, which was reduced by as much as 90 and 56% in target tissues of sensory system such as tongue and intestine, respectively. The reduction in retina and heart was around 50%. Conversely, the mRNA expression of low‐affinity neurotrophin receptor p75 was increased. At birth, BDNF mRNA expression was affected with a significant generalized reduction,while in vibrissae we observed a reduction of BDNF and p75 mRNAs and an increase of NGF. At postnatal day 14, pups from diabetic mothers showed reduced muscle levels of IGF‐I, while we observed a partial impairment of substance P axonal transport at postnatal day 28. Treatment of diabetic mothers with silybin, a flavonoid with antioxidant properties, prevented most of the changes in neurotrophic factor expression and substance P axonal transport with no effects on hyperglycemia and embryo growth retardation. These results indicate that oxidative stress may influence neurotrophic factor synthesis in target territories during development. In addition, these data suggest that nervous system abnormalities observed in diabetic embryopathy may also derive by insufficient neurotrophic factor biosynthesis involving sequentially NGF in the embryo and BDNF and IGF‐I in the early postnatal days. Insulin treatment of diabetic mothers normalized hyperglycemia and body growth, with consequent regular embryonic and postnatal development. J. Neurosci. Res. 57:521–528, 1999.

Perinatal morphine exposure alters peptidergic development in the striatum

It has been reported that perinatal exposure to opiates affects mRNA synthesis, body growth and brain development in mammals, including humans. We have observed that morphine administration in drinking water during the perinatal period alters peptide development in the striatum of the rat. There is a marked increase in substance P and met‐enkephalin content, the latter is maintained even at 30 days postnatally. The transient increase or earlier maturation of substance P content is correlated by a more precocious axon terminal organization as revealed by immunocytochemical staining. The increased metenkephalin content is correlated by a higher abundance of preproenkephalin A mRNA and this correlation is particularly evident at 15 days postnatally. At earlier times both northern blotting and in situ hybridization techniques fail to show any significant difference between control and morphine exposed rats, likely because the peptide content is not very different in the two groups or at least the gap is not as wide as at later times.

Inhibition of high glucose-induced protein mono-ADP-ribosylation restores neuritogenesis and sodium-pump activity in SY5Y neuroblastoma cells.

The exposure of SY5Y neuroblastoma cells to high concentrations of glucose, fructose, or galactose is an experimental model commonly used for in vitro evaluation of typical neuronal alterations observed in diabetes mellitus. In the present study, we observed that 2 weeks of exposure to high carbohydrate concentrations caused both a significant impairment in neurite formation induced by supplementation of retinoic acid or by subtraction of fetal calf serum to the culture medium and a marked reduction in Na+–K+‐ATPase activity. However, only the exposure to high millimoles of glucose caused an enhancement of mono‐ADP‐ribosylation, typical of diabetes mellitus, affecting at leat five proteins. The concomitant exposure to high glucose and to silybin, a mono‐ADP‐ribosylation inhibitor, normalized the extent of ADP‐ribosylation of the five proteins and counteracted the inhibitory effects of high glucose on Na+‐pump activity and on neuritogenesis. Conversely, the supplementation of silybin did not prevent fructose and galactose inhibitory effects on Na+‐pump activity and neurite formation. These data confirm those of previous reports suggesting a link between excessive protein mono‐ADP‐ribosylation and the onset of diabetic complications such as diabetic neuropathy. J. Neurosci. Res. 57:663–669, 1999.

Perinatal supplementation of low doses of ethanol enhances 5-HT restoration in the central nervous system.

It has been reported that long‐term administration of ethanol has deleterious effects on the central nervous system; the alterations are particularly evident if the exposure occurs during development. Our study shows that rat perinatal administration of 3% and 6% ethanol does not alter development of serotonin (5‐HT) pathways in the central nervous system, while their reactive changes triggered by neonatal lesioning are greatly altered. The administration of 5,7‐dihydroxytriptamine (5,7‐DHT) within 6 hours from birth causes 5‐HT fiber degeneration throughout the central nervous system. The loss of 5‐HT is particularly relevant in lumbar spinal cord, occipital cortex, and hippocampus. This early decrease in 5‐HT content is followed by a slow and partial recovery. If animals are exposed to 3% ethanol during the perinatal period, there is an enhancement of the 5,7‐DHT‐induced degeneration that is, however, followed by a faster and greater recovery throughout the central nervous system. Conversely, perinatal exposure to 6% ethanol and 5,7‐DHT administration lead to an irreversible 5‐HT loss with no subsequent recovery. The deleterious effects of 6% ethanol are accompanied by a reduced expression of neurotrophin. Thus, our study suggests that chronic exposure to ethanol can influence central nervous system plasticity during development. Low doses may enhance neuronal plasticity and repair perhaps via an increased efficacy of neurotrophic factors, whereas higher doses may negatively affect neural development also by means of the impairment of the expression of neurotrophic factors. J. Neurosci. Res. 58:449–455, 1999.