In vitro differences between astrocytes of control and wobbler mice spinal cord

Long-term effects of the glucocorticoid receptor modulator CORT113176 in murine motoneuron degeneration

The Wobbler mouse spinal cord shows vacuolated motoneurons, glial reaction, inflammation and abnormal glutamatergic parameters. Wobblers also show deficits of motor performance. These conditions resemble amyotrophic lateral sclerosis (ALS). Wobbler mice also show high levels of corticosterone in blood, adrenals and brain plus adrenal hypertrophy, suggesting that chronically elevated glucocorticoids prime spinal cord neuroinflammation. Therefore, we analyzed if treatment of Wobbler mice with the glucocorticoid receptor (GR) antagonist CORT113176 mitigated the mentioned abnormalities. 30 mg/kg CORT113176 given daily for 3 weeks reduced motoneuron vacuolation, decreased astro and microgliosis, lowered the inflammatory mediators high mobility group box 1 protein (HMGB1), toll-like receptor 4, myeloid differentiation primary response 88 (MyD88), p50 subunit of nuclear factor kappa B (NFκB), tumor necrosis factor (TNF) receptor, and interleukin 18 (IL18) compared to untreated Wobblers. CORT113176 increased the survival signal pAKT (serine-threonine kinase) and decreased the death signal phosphorylated Junk-N-terminal kinase (pJNK), symptomatic of antiapoptosis. There was a moderate positive effect on glutamine synthase and astrocyte glutamate transporters, suggesting decreased glutamate excitotoxicity. In this pre-clinical study, Wobblers receiving CORT113176 showed enhanced resistance to fatigue in the rota rod test and lower forelimb atrophy at weeks 2-3. Therefore, long-term treatment with CORT113176 attenuated degeneration and inflammation, increased motor performance and decreased paw deformity. Antagonism of the GR may be of potential therapeutic value for neurodegenerative diseases.

The selective glucocorticoid receptor modulator CORT108297 restores faulty hippocampal parameters in Wobbler and corticosterone-treated mice

Mutant Wobbler mice are models for human amyotrophic lateral sclerosis (ALS). In addition to spinal cord degeneration, Wobbler mice show high levels of blood corticosterone, hyperactivity of the hypothalamic-pituitary-adrenal axis and abnormalities of the hippocampus. Hypersecretion of glucocorticoids increase hippocampus vulnerability, a process linked to an enriched content of glucocorticoid receptors (GR). Hence, we studied if a selective GR antagonist (CORT108297) with null affinity for other steroid receptors restored faulty hippocampus parameters of Wobbler mice. Three months old genotyped Wobbler mice received s.c. vehicle or CORT108297 during 4 days. We compared the response of doublecortin (DCX)+ neuroblasts in the subgranular layer of the dentate gyrus (DG), NeuN+ cells in the hilus of the DG, glial fibrillary acidic protein (GFAP)+ astrocytes and the phenotype of Iba1+ microglia in CORT108297-treated and vehicle-treated Wobblers. The number of DCX+ cells in Wobblers was lower than in control mice, whereas CORT108297 restored this parameter. After CORT108297 treatment, Wobblers showed diminished astrogliosis, and changed the phenotype of Iba1+ microglia from an activated to a quiescent form. These changes occurred without alterations in the hypercorticosteronemia or the number of NeuN+ cells of the Wobblers. In a separate experiment employing control NFR/NFR mice, treatment with corticosterone for 5 days reduced DCX+ neuroblasts and induced astrocyte hypertrophy, whereas treatment with CORT108297 antagonized these effects. Normalization of neuronal progenitors, astrogliosis and microglial phenotype by CORT108297 indicates the usefulness of this antagonist to normalize hippocampus parameters of Wobbler mice. Thus, CORT108297 opens new therapeutic options for the brain abnormalities of ALS patients and hyperadrenocorticisms.

Potential neuroprotective role of transforming growth factor β1 (TGFβ1) in the brain

TGFβ1 is a growth factor that is known to be expressed in most neurodegenerative diseases and after vascular accidents in the brain. TGFβ1 downregulates the activity of activated microglia and promotes astrogliosis. It also prevents cell death by a known mechanism dependant on astrocytes and the secretion of the plasminogen activator inhibitor 1 (PAI-1). This mechanism can provide light on what is the mechanism of action of TGFβ1 as a protective factor and it can provide the pharmacological principles in which this pathway could be used with therapeutic purposes. TGFβ1 is upregulated in most neurodegenerative diseases, however, its expression appears dramatically blocked in Huntington's disease, the fastest of those diseases in progress after the onset. This fact suggests that TGFβ1 slows down the neurodegenerative process, preventing tissue damage and neural apoptotic death. However, the exact details of TGFβ1 action are still unknown and the physiological roles on the diseases are still mysterious. Interestingly, all the data regarding the roles of TGFβ1 in health and disease have been also confirmed with the use of transgenic knockouts and TGFβ1 overexpressing mice. What possibly came as a surprise from the study of TGFβ1 overexpressing models is that combining its neuroprotective and antiproliferative effects, this cytokine generates a significant disruption in the hippocampal circuitry with its consequent learning and memory deficit.

Progesterone attenuates several hippocampal abnormalities of the Wobbler mouse

It is now recognised that progesterone plays a protective role for diseases of the central nervous system. In the Wobbler mouse, a model of motoneurone degeneration, progesterone treatment prevents spinal cord neuropathology and clinical progression of the disease. However, neuropathological and functional abnormalities have also been discovered in the brain of Wobbler mice and patients with amyotrophic lateral sclerosis. The present study examined the hippocampus of control and afflicted Wobbler mice and the changes in response to progesterone treatment. Mice received either a single progesterone implant (20 mg for 18 days). We found that the hippocampal pathology of the untreated Wobblers involved a decreased expression of brain-derived neurotrophic factor (BDNF) mRNA, decreased astrogliosis in the stratum lucidum, stratum radiatum and stratum lacunosum-moleculare, decreased doublecortin (DCX)-positive neuroblasts in the subgranular zone of the dentate gyrus and a decreased density of GABA immunoreactive hippocampal interneurones and granule cells of the dentate gyrus. Although progesterone did not change the normal parameters of control mice, it attenuated several hippocampal abnormalities in Wobblers. Thus, progesterone increased hippocampal BDNF mRNA expression, decreased glial fibrillary acidic protein-positive astrocytes and increased the number of GABAergic interneurones and granule cells. The number of DCX expressing neuroblasts and immature neurones remained impaired in both progesterone-treated and untreated Wobblers. In conclusion, progesterone treatment exerted beneficial effects on some aspects of hippocampal neuropathology, suggesting its neuroprotective role in the brain, in agreement with previous data obtained in the spinal cord of Wobbler mice.

Plasma and Cerebrospinal Fluid-Based Protein Biomarkers for Motor Neuron Disease

Motor neuron diseases (MNDs) and, in particular, amyotrophic lateral sclerosis (ALS), are a heterogeneous group of neurologic disorders characterized by the progressive loss of motor function. In ALS, a selective and relentless degeneration of both upper and lower motor neurons occurs, culminating in mortality typically within 5 years of symptom onset. However, survival rates vary among individual patients and can be from a few months to >10 years from diagnosis. Inadequacies in disease detection and treatment, along with a lack of diagnostic and prognostic tools, have prompted many to turn to proteomics-based biomarker discovery efforts. Proteomics refers to the study of the proteins expressed by a genome at a particular time, and the proteome can respond to and reflect the status of an organism, including health and disease states. Although an emerging field, proteomic applications promise to uncover biomarkers critical for differentiating patients with ALS and other MNDs from healthy individuals and from patients affected by other diseases. Ideally, these studies will also provide mechanistic information to facilitate identification of new drug targets for subsequent therapeutic development. In addition to proper experimental design, standard operating procedures for sample acquisition, preprocessing, and storage must be developed. Biological samples typically analyzed in proteomic studies of neurologic diseases include both plasma and cerebrospinal fluid (CSF). Recent studies have identified individual proteins and/or protein panels from blood plasma and CSF that represent putative biomarkers for ALS, although many of these proteins are not unique to this disease. Continued investigations are required to validate these initial findings and to further pursue the role of these proteins as diagnostic biomarkers or surrogate markers of disease progression. Protein biomarkers specific to ALS will additionally function to evaluate drug efficacy in clinical trials and to identify novel targets for drug design. It is hoped that proteomic technologies will soon integrate the basic biology of ALS with mechanistic disease information to achieve success in the clinical setting.

Sporadic amyotrophic lateral sclerosis: new hypothesis regarding its etiology and pathogenesis suggests that astrocytes might be the primary target hosting a still unknown external agent

This article briefly describes the already known clinical features and pathogenic mechanisms underlying sporadic amyotrophic lateral sclerosis, namely excitoxicity, oxidative stress, protein damage, inflammation, genetic abnormalities and neuronal death. Thereafter, it puts forward the hypothesis that astrocytes may be the cells which serve as targets for the harmful action of a still unknown environmental agent, while neuronal death may be a secondary event following the initial insult to glial cells. The article also suggests that an emergent virus or a misfolded infectious protein might be potential candidates to accomplish this task.

Stage dependent effects of progesterone on motoneurons and glial cells of wobbler mouse spinal cord degeneration

In the Wobbler mouse, a mutation in the Vps54 gene is accompanied by motoneuron degeneration and astrogliosis in the cervical spinal cord. Previous work has shown that these abnormalities are greatly attenuated by progesterone treatment of clinically afflicted Wobblers. However, whether progesterone is effective at all disease stages has not yet been tested. The present work used genotyped (wr/wr) Wobbler mice at three periods of the disease: early progressive (1-2 months), established (5-8 months) or late stages (12 months) and age-matched wildtype controls (NFR/NFR), half of which were implanted with a progesterone pellet (20 mg) for 18 days. In untreated Wobblers, degenerating vacuolated motoneurons were initially abundant, experienced a slight reduction at the established stage and dramatically diminished during the late period. In motoneurons, the cholinergic marker choline acetyltransferase (ChAT) was reduced at all stages of the Wobbler disease, whereas hyperexpression of the growth-associated protein (GAP43) mRNA preferentially occurred at the early progressive and established stages. Progesterone therapy significantly reduced motoneuron vacuolation, enhanced ChAT immunoreactive perikarya and reduced the hyperexpression of GAP43 during the early progressive and established stages. At all stage periods, untreated Wobblers showed high density of glial fibrillary acidic protein (GFAP)+ astrocytes and decreased number of glutamine synthase (GS) immunostained cells. Progesterone treatment down-regulated GFAP+ astrocytes and up-regulated GS+ cell number. These data reinforced the usefulness of progesterone to improve motoneuron and glial cell abnormalities of Wobbler mice and further showed that therapeutic benefit seems more effective at the early progressive and established periods, rather than on advance stages of spinal cord neurodegeneration.

Interleukin-1beta mediates GDNF up-regulation upon dopaminergic injury in ventral midbrain cell cultures

We recently proposed the involvement of diffusible modulators in signalling astrocytes to increase glial cell line-derived neurotrophic factor (GDNF) expression after selective dopaminergic injury by H2O2 or L-DOPA. Here we report that interleukin-1beta (IL-1beta) is involved in this crosstalk between injured neurons and astrocytes. IL-1beta was detected only in the media from challenged neuron-glia cultures. Exogenous IL-1beta did not change GDNF protein levels in astrocyte cultures, and diminished GDNF levels in neuron-glia cultures. This decrease was not due to cell loss, as assessed by the MTT assay and immunocytochemistry. Neither H2O2 nor L-DOPA induced microglia proliferation or appeared to change its activation state. The IL-1 receptor antagonist (IL-1ra) prevented GDNF up-regulation in challenged cultures, showing that IL-1beta is involved in the signalling between injured neurons and astrocytes. Since IL-1ra decreased the number of dopaminergic neurons in H2O2-treated cultures, we propose that IL-1 has a neuroprotective role in this system involving GDNF up-regulation.

Increased plasma TGF-beta1 in patients with amyotrophic lateral sclerosis

OBJECTIVES

To investigate the levels of transforming growth factor-beta1 (TGF-beta1) in plasma of patients with amyotrophic lateral sclerosis (ALS).

MATERIAL AND METHODS

The TGF-beta1 plasma concentrations were measured with an enzyme-linked immunosorbent assay from 11 patients with ALS and 13 age matched healthy controls.

RESULTS

The mean TGF-beta1 plasma concentration in the patients with ALS (2.15 +/- 0.80 ng/ml, mean +/- SD) was significantly higher than in the healthy controls (1.59 +/- 0.32 ng/ml) (P=0.031). There was a significant positive correlation between the TGF-beta1 plasma concentration in the patients with ALS and the duration of illness (r=0.66, P=0.028).

CONCLUSION

Our findings provide evidence that in ALS the plasma concentration of TGF-beta1 increases significantly with the duration of illness. These results suggest that TGF-beta1 is involved in the disease process of ALS.

Toluene inhalation induces glial cell line-derived neurotrophic factor, transforming growth factor and tumor necrosis factor in rat cerebellum

Rats were exposed to toluene (1500 ppm for 4 h per day) for 7 days. After toluene inhalation, only granule cells in the dentate gyrus of the hippocampus were slightly shrunken. In the cerebellum, several Purkinje cells were shrunken and lost, and the white matter was thinner than in controls. Microtubule-associated protein 2 (MAP2)-immunopositive filaments of neuronal processes were slightly disarrayed in the radial layer of the hippocampus, and were fragmented in the molecular layer of the cerebellum. It was considered that toluene induced neuronal changes both in the cerebellum and the hippocampus. To elucidate the effect of neurotrophic factors on those neuronal changes, glial cell line-derived neurotrophic factor (GDNF), transforming growth factor (TGF) and tumor necrosis factor (TNF) in rat brain were examined immunohistochemically. In control rats, TNF-alpha was not stained in either the hippocampus or the cerebellum, while TGF-beta1 was scarcely expressed in the cerebellum. GDNF was minimally expressed in the Purkinje cells in the cerebellum. After toluene-treatment, TGF-beta1 was over-expressed in the endothelium of the capillary vessel walls in both regions. In the cerebellum, TNF-alpha was induced only in the granule cells, while GDNF expression was enhanced in the Purkinje cells. These data suggest that toluene induces astrocyte activation through TGF-beta1 upregulation, which then induces GDNF in the Purkinje cells and TNF-alpha in the granule cells of the cerebellum. The differences in the expression of the neurotrophic factors may account for neurobehavioral changes after toluene exposure.

Cellular basis of steroid neuroprotection in the wobbler mouse, a genetic model of motoneuron disease

1. The Wobbler mouse suffers an autosomal recessive mutation producing severe motoneuron degeneration and astrogliosis in the spinal cord. It has been considered a suitable model of human motoneuron disease, including the sporadic form of amyotrophic lateral sclerosis (ALS). 2. Evidences exist demonstrating increased oxidative stress in the spinal cord of Wobbler mice, whereas antioxidant therapy delayed neurodegeneration and improved muscle trophism. 21-Aminosteroids are glucocorticoid-derived hydrophobic compounds with antioxidant potency 3 times higher than vitamin E and 100 times higher than methylprednisolone. They do not bind to intracellular receptors, and prevent lipid peroxidation by insertion into membrane lipid bilayers. 3. In common with the spinal cord of ALS patients, Wobbler mice present astrocytosis with hyperexpression of glial fibrillary acidic protein (GFAP), and increased expression of nitric oxide synthase (NOS) and growth-associated protein (GAP-43) in motoneurons. Here, we review our studies on the effects of a 21-aminosteroid on GFAP, NOS, and GAP-43. 4. First, we showed that 21-aminosteroid treatment further increased GFAP-expressing astrocytes in gray matter of the Wobbler spinal cord. This effect may provide neuroprotection if one considers a trophic and beneficial function of astrocytes during the course of degeneration. Other neuroprotectans used in Wobbler mice (T-588) also increased pre-existing astrocytosis. 5. Second, histochemical determination of NADPH-diaphorase, a parameter indicative of neuronal NOS activity, showed that the 21-aminosteroid down-regulated the high activity of this enzyme in ventral horn motoneurons. Therefore, suppression of nitric oxide by decreasing NADPH-diaphorase (NOS) activity may provide neuroprotection considering that excess NO is highly toxic to motoneurons. 6. Finally, 21-aminosteroid treatment significantly attenuated the aberrant expression of both GAP-43 protein and mRNA in Wobbler motoneurons. Hyperexpression of GAP-43 possibly indicated abnormal synaptogenesis, denervation, and muscle atrophy, parameters which may return to normal following antioxidant steroid treatment. 7. Besides 21-aminosteroids, other steroids also behave as neuroprotectans. In this regard, degenerative diseases may constitute potential targets of these hormones, based on the fact that the spinal cord expresses in a regional and cell-specific fashion, receptors for androgens. progesterone, adrenal steroids, and estrogens.