Effects of Loud Noise Exposure on DNA Integrity in Rat Adrenal Gland

Loud noise is generally considered an environmental stressor causing negative effects on acoustic, cardiovascular, nervous, and endocrine systems. In this study, we investigated the effects of noise exposure on DNA integrity in rat adrenal gland evaluated by the comet assay. The exposure to loud noise (100 dBA) for 12 hr caused a significant increase of DNA damage in the adrenal gland. Genetic alterations did not decrease 24 hr after the cessation of the stimulus. We hypothesize that an imbalance of redox cell status is responsible for the induction and persistence of noise-induced cellular damage

Effects of Loud Noise Exposure on DNA Integrity in Rat Adrenal Gland

Loud noise is generally considered an environmental stressor causing negative effects on acoustic, cardiovascular, nervous, and endocrine systems. In this study, we investigated the effects of noise exposure on DNA integrity in rat adrenal gland evaluated by the comet assay. The exposure to loud noise (100 dBA) for 12 hr caused a significant increase of DNA damage in the adrenal gland. Genetic alterations did not decrease 24 hr after the cessation of the stimulus. We hypothesize that an imbalance of redox cell status is responsible for the induction and persistence of noise-induced cellular damage

A2A receptors and methamphetamine toxicity: a role of adenosine as an endogenous neurotoxin

Adenosine A2A are a class of purinergic receptors largely expressed in dopamine (DA)-rich areas of the central nervous system. In particular, they are abundant within basal ganglia, where they modulate the activity of various neurotransmitters, including DA. Despite the lack of knowledge on their fine physiological mechanisms, it is worth to mention that A2A antagonists prevent neuronal death and dyskinesia in Parkinsonism. Moreover the neuroprotective effects observed after blockade of adenosine A2A receptors in several models of neurotoxicity suggests a toxic effect for endogenous adenosine In the light of these evidences, in the present study, by using in vitro models of DA neurons, we investigated: (i) whether A2A antagonists protect DA containing neurons against methamphetamine (METH); (ii) whether activation of A2A receptors produce neurodegeneration. This was done either using A2A agonist receptor NECA or the endogenous compound adenosine; (iii) whether specific cell mechanisms are involved in these phenomena. We found that A2A antagonists protect DA cells against METH neurotoxicity. Moreover, we found that NECA and adenosine both produced a toxic effects. In the light of the key role of autophagy in modulating the survival of DA neurons we found that A2A antagonists increase, while A2A agonists decrease, autophagy. These results suggest that neuroprotection induced by A2A antagonists may be mediated by enhancement of autophagy. As expected we found that pre-treatment with a non-adenosine related inducer of autophagy produced the same protective effects obtained with A2A antagonists. Our data indicate for the first time, that A2A antagonists are protective in DA neurons against METH. Such an effect appear to be mediated by the enhancement of autophagy. On the other hand we found that activation of A2A receptor produces neurotoxicity. Interestingly these effects was reproduced by administering endogenous adenosine. This suggests that adenosine may produce neurodegeneration by inhibiting the autophagy pathway

Morphological characterization of a single knock out double transgenic mouse model of spinal muscle atrophy

Spinal muscular atrophy (SMA) is a neurogenetic autosomal recessive disorder characterized by degeneration of lower motor neurons associated with muscle atrophy and paralysis. Due to a lack of an in depth knowledge on the molecular mechanisms and fine neuropathology of SMA, validation of appropriate animal models is key in fostering SMA research. Recent studies set up an animal model showing long survival and slow disease progression. This model is knocked out for mouse SMN (Smn−/−) gene and carries a human mutation of the SMN1 gene (SMN1A2G), along with human SMN2 gene. In the present study we used this knockout double transgenic mouse as a SMA III model, to characterize the spinal cord pathology along with motor deficit at prolonged survival times (18 months). This long time interval (i.e. up to 535 days) was never analyzed before especially concerning specific motor tasks. We found that the delayed disease progression was likely to maintain fair motor activity despite a dramatic loss of large motor neurons (44.77%). At this stage, spared motor neurons showed significant cell body enlargement. Moreover, similar to what was described in patients affected by SMA we found neuronal heterotopy in the anterior white matter. Motor neuron degeneration was accompanied by the loss of SMN protein in the spinal cord. In summary, the present study validates over a long time period a SMA III mouse model showing neuropathology reminiscent of human patients and provide a useful experimental model to probe novel therapeutic strategies

Morphological effects of chronic excitotoxicity depend on autophagy activation failure

It is well known that exposure to excitatory amino acid in specific experimental conditions might produce a defect in the autophagy pathway. Such an effect was observed in motor neurons exposed chronically to glutamate agonists. In particular, it is well known that glutamate induces motor neuron death and this is supposed to play a key role in the physiopathology of motor neuron loss in amyotrophic lateral sclerosis (ALS). Similarly, a defective recruitment of autophagy was recently documented in ALS. In the present study, we used primary motor neuron cultures to analyzed whether AMPA receptor stimulation via kainic acid produces activation of autophagy and whether this is defective compared with what it is required to rescue motor neurons. In particular we found that exposure of motor neurons to kainic acid produces intracellular alterations associated with defective autophagy. The ultrastructural alterations consist of increased motor neurons size, damaged mitochondria, protein accumulation, large cytoplasmic vacuoles placed in perinuclear positions These cellular alterations is reminiscent of ALS, which in turn is characterized by a defective autophagy. Once we confirmed that excitotoxicity recruits autophagy, which remains defective to clear altered proteins and organelles, we provided a pharmacological stimulation of such a pathway in order to ameliorate motor neuron survival. In this experimental conditions, We observe that pharmacological activation of the autophagy machinery is able to counteract kainic acid-mediated motor neuron damage

Parallelism between central and enteric nervous system damage in experimental parkinsonism

Parkinson’s disease (PD) is a neurodegenerative condition which affects dopaminergic neurons of the substantia nigra (SN), leading to a movement disorder. Non motor alterations occur in several viscera, in particular the gastrointestinal tract. In 9-week old C57BL mice we examined the effects of the parkinsonism-inducing neurotoxin 1-methyl, 4-phenyl, 1,2,3,6,-tetrahydropyridine (MPTP, administered either acutely or chronically) in SN and striatum, as well as in duodenum. Motor tests (open field and PaGE) were performed. One week after treatment with MPTP (acute: 20 mg/KgX3, 2h apart or chonic: 5 mg/kg x2/die, for 3 weeks), histological investigations, immunohistochemistry and immunoblotting for tyrosine hydroxylase (TH), and α-synuclein (α-syn) were carried out. Immunocytochemical investigations were analyzed under electron microscopy. Motor tests showed a failure of the PaGE test in all MPTP-treated animals, whereas no difference was found in open field test in comparison with controls. Analysis of histological sections showed some alterations consisting of slight atrophy of duodenal mucosa and glandular disarrangement only after chronic treatment. Under electron microscopy the brush border appeared discontinuous. In all MPTP-administered mice, TH immunopositivity was reduced in SN and striatum, confirming its central dopaminergic neurotoxicity. At duodenal level, TH immunostaining was lost following all MPTP treatments with a slight variation in chronic compared with acute administrations. This was confirmed by semiquantitative immunoblotting. Moreover, α-syn immunostaining was enhanced by MPTP treatment but this was way more evident following chronic administration both at central and peripheral level. Following chronic treatment α-Syn immunopositive structures were investigated under electron microscopy. Our study shows that chronic more than acute administration of MPTP induces alterations at duodenal level reminiscent of dopaminergic damage in SN and striatum. Moreover, this experimental model of parkinsonism features gastrointestinal dysfunction observed in PD patients. These findings lend substance to the concept of the enteric nervous system as a double brain which recapitulates and is an ancestry of the central nervous system

Plastic changes in the spinal cord in motor neuron disease.

In the present paper, we analyze the cell number within lamina X at the end stage of disease in a G93A mouse model of ALS; the effects induced by lithium; the stem-cell like phenotype of lamina X cells during ALS; the differentiation of these cells towards either a glial or neuronal phenotype. In summary we found that G93A mouse model of ALS produces an increase in lamina X cells which is further augmented by lithium administration. In the absence of lithium these nestin positive stem-like cells preferentially differentiate into glia (GFAP positive), while in the presence of lithium these cells differentiate towards a neuronlike phenotype (III-tubulin, NeuN, and calbindin-D28K positive). These effects of lithium are observed concomitantly with attenuation in disease progression and are reminiscent of neurogenetic effects induced by lithiumin the subependymal ventricular zone of the hippocampus

Characterization of motor neuron loss in animal models featuring prolonged disease duration

Motor neuron loss is a feature of amyotrophic lateral sclerosis (ALS), spinal muscle atrophy (SMA) and it is recently described in other neurodegenerative disorders. In humans these disorders vary from dramatically short up to long disease duration. A short disease duration in humans ranges from some months up to 1 or 2 years. In contrast animal models commonly used to evaluate motor neuron disorders are extremely short lasting, where motor impairment lasts about a few weeks. This is the case of the G93A mouse model which is expected to reproduce ALS in humans. Despite commonalities, this condensed time interval is likely to produce different pathological correlates. Therefore, it is not surprising that experimental morphology and therapeutics fail to detect some hallmarks of human disorders in these animal models. This temporal discrepancy is often missed out and genetic background as well as evolution-based structural differences in motor systems are considered as critical determinants instead. The present communication wish to introduce the benefits of a long-lasting animal model of motor neuron disorders. In detail, we had been able to characterize the motor failure, the biochemical abnormalities and the morphological alterations which develop only at prolonged time interval (18 months) using a single knock out double transgenic mouse model of human SMAIII. In these mice we had been able to dissect for the first time morphological alterations typical of human disorders such as motor neuron heterotopy as well as motor neuron loss. This is correlated with a profound loss of the survival motor neuron (SMN) protein. There was a remarkable somatotopic correlation between the specific motor deficit (proximal vs distal limb muscles) and the severity of motor neuron loss in the corresponding pool (medial vs lateral) of motor neurons in the spinal cord. This ideal experimental context provides the chance to evaluate the therapeutic effects of specific drugs administered in the long run ruling out bias due to experimental variability when the drugs are administered only for a few weeks. In this way it is also easy to discern symptomatic vs disease modifying effects. In line with this, we compared the effects of GSK3 beta inhibitors and/or autophagy activators and we found a remarkable induction in the SMN protein which was in line with protection from motor neuron loss and a steady effect counteracting the long term progressive motor deterioration

Morphology demonstrates similar autophagy alterations in neurodegeneration and brain tumors

Malignant glioma are the most malignant brain tumors. Frequent genetic alterations involve PTEN (Phosphatase homolog deleted on chromosome Tensin and Ten), a lipid phosphatase that after mutation is not able to convert phosphatidylinositol (3,4,5)-triphosphate (PIP3) into phosphatidylinositol (4,5)-bisphosphate (PIP2) and thereby inhibiting AKT, which in turn activates the apoptotic factors, mutations of p53 and retinoblastoma, both responsible of controlling the phase transition G1 / S of cell cycle under physiological conditions and prevent the replication of DNA when the cell is altered. Recently a dramatic uptake of the amino acid glutamine was reported in malignant glioma. This amino acid produces a marked inhibition of the autophagy pathway. Consistently, autophagy is defective in human glioblastoma similar to neurodegeneration. Autophagy is the main clearing system to remove damaged or potentially harmful organelles and misfolded proteins. Autophagy progresses through several stages: (i) the phagophore (ii) the autophagosome (iii) the amphisomes; (iv) the autophagolysosome and (v) the autophagoproteasome. The last stages involves the fusion of amphisome with lysosome which originates autophagolysosome that contains the elements to be removed and lytic enzymes necessary for this degradation process, while the autophagoproteasome derives from the fusion with component of the proteasome. The autophagy machinery can be measured by several specific markers such as beclin1 and LC3, the occurrence of stagnant autophagy vacuoles. In the present study we characterized the consistency and relevance of autophagy failure in glioblastoma by using human cell lines, primary human cell cultures and in vivo human glioblastoma cells implanted in the brain of nude mice. In baseline conditions we observed in cells obtained from surgery of human patients a marked inhibition of the autophagy pathway. This was associated with an increase in autophagy substrates overlapping with neurodegenerative disorders. In keeping with the ongoing autophagy inhibition we found that activation of the autophagy pathway reduced cell proliferation and promoted cell differentiation dose-dependently in vitro while the systemic administration of a powerful autophagy activator reduced the volume of brain tumor in vivo by 96.6%. These data indicate a relevant role of autophagy failure in glioblastoma and suggest potential approaches to contrast tumor growth