Ultrastructure of astrocytes in the cortex of the hippocampal gyrus and in the neocortex of the temporal lobe in experimental valproate encephalopathy and after valproate withdrawal

Rat hippocampal CA3 neuronal injury induced by limb ischemia/reperfusion: A possible restorative effect of alpha lipoic acid

Limb ischemia reperfusion (I/R) injury is associated with serious local and systemic effects. Reperfusion may augment tissue injury in excess of that produced by ischemia alone. The hippocampus has been reported to be vulnerable to I/R injury. Alpha lipoic acid (ALA) is an endogenous antioxidant with a powerful antioxidative, anti-inflammatory, and antiapoptotic properties. We studied the probable restorative effect of ALA on limb I/R-induced structural damage of rat hippocampus. Forty adult male albino rats were divided equally into four groups: group I (sham); group II (I/R-1 day) has undergone bilateral femoral arteries occlusion (3 h), then reperfusion for 1 day; group III (I/R-7 days) has undergone reperfusion for seven days; group IV (I/R-ALA) has undergone I/R as group III and received an intraperitoneal injection of ALA (100 mg/kg) for 7 days. I/R groups revealed degenerative changes in the pyramidal neuronal perikarya of CA3 field in the form of dark-stained cytoplasm, dilated RER cisternae, mitochondrial alterations, and dense bodies' accumulation. Their dendrites showed disorganized microtubules. Astrogliosis is featured by an increased number and increased immunoreactivity of astrocytes for glial fibrillary acid protein. Morphometric data revealed significant reduction of light neurons, surface area of neurons, and thickness of the CA3 layer. Most blood capillaries exhibited narrow lumen and irregular basal lamina. ALA ameliorated the neuronal damage. Pyramidal neurons revealed preservation of normal structure. Significant increase in the thickness of pyramidal layer in CA3 field and surface area and number of light neurons was observed but astrogliosis persisted. Limb I/R had a deleterious remote effect on the hippocampus aggravated with longer period of reperfusion. This work may encourage the use of ALA in the critical clinical settings with I/R injury.

Altered cortical thickness following prenatal sodium valproate exposure

Prenatal exposure to sodium valproate (VPA) is associated with neurodevelopmental impairments. Cortical thickness was measured in 16 children exposed prenatally to VPA and 16 controls. We found increased left inferior frontal gyrus (IFG; BA45) and left pericalcarine sulcus (BA18) thickness, an association between VPA dose and right IFG thickness, and a close relationship between verbal skills and left IFG thickness. A significant interaction between group and hemispheric IFG thickness showed absence of the normal asymmetry in the IFG region of VPA-exposed children. These data provide preliminary insights into the putative neural basis of difficulties experienced by some VPA-exposed children.

Valproate (VPA)-associated hyperammonemic encephalopathy independent of elevated serum VPA levels: 21 cases in China from May 2000 to May 2012

Valproate (VPA) is a medication that is widely used in the treatment of neurological and psychiatric disorders, such as epilepsy and bipolar disorder. Valproate-induced hyperammonemic encephalopathy (VHE) is a rare central nervous system adverse effect of this medication that is characterized by impaired consciousness, which can range from drowsiness to coma; increased seizure frequency; acute cognitive symptoms; and gastrointestinal symptoms. In this manuscript, we report a single case and also review previous cases of VHE (n=20) in Chinese patients to identify risk factors for VHE. Increasing clinicians' awareness of VHE during concomitant VPA therapy is of utmost importance. Serum ammonia level is a useful and important diagnostic test. The discontinuation of VPA is currently the mainstay of treatment for VHE.

Sustained expression of osteopontin is closely associated with calcium deposits in the rat hippocampus after transient forebrain ischemia

The present study was designed to evaluate the extent and topography of osteopontin (OPN) protein expression in the rat hippocampus 4 to 12 weeks following transient forebrain ischemia, and to compare OPN expression patterns with those of calcium deposits and astroglial and microglial reactions. Two patterns of OPN staining were recognized by light microscopy: 1) a diffuse pattern of tiny granular deposits throughout the CA1 region at 4 weeks after ischemia and 2) non-diffuse ovoid to round deposits, which formed conglomerates in the CA1 pyramidal cell layer over the chronic interval of 8 to 12 weeks. Immunogold-silver electron microscopy and electron probe microanalysis demonstrated that OPN deposits were indeed diverse types of calcium deposits, which were clearly delineated by profuse silver grains indicative of OPN expression. Intracellular OPN deposits were frequently observed within reactive astrocytes and neurons 4 weeks after ischemia but rarely at later times. By contrast, extracellular OPN deposits progressively increased in size and appeared to be gradually phagocytized by microglia or brain macrophages and some astrocytes over 8 to 12 weeks. These data indicate an interaction between OPN and calcium in the hippocampus in the chronic period after ischemia, suggesting that OPN binding to calcium deposits may be involved in scavenging mechanisms.

Histone deacetylase inhibition promotes Caspase-independent cell death of ventral midbrain neurons

Inhibition of histone deacetylase (HDAC) activity results in dedifferentiation of various neural precursor cell populations, but is also known to promote neuronal differentiation. We sought to determine the effects of HDAC inhibition on differentiated and non-differentiated midbrain cells in order to examine more closely the consequences of HDAC inhibition on cell fate in a heterogeneous population. We demonstrate that HDAC inhibitor (HDACi) treatment causes a significant attenuation in the numbers of neurons, but not astrocytes, within 48h, with no evidence of neuronal dedifferentiation. The loss of neurons is due to an initial morphological destabilization, which is not recoverable upon inhibitor removal, and ultimately leads to cell death. HDACi treatment results in progenitor cell cycle arrest and Caspase-dependent apoptosis. In contrast, the loss of midbrain neurons does not correlate with activated Caspase-3 expression. Treating cultures transiently with Caspase inhibitors blocks overall HDACi-induced cell death in the cultures, but does not prevent the loss of neurons. These data suggest that HDACi treated midbrain neurons undergo Caspase-independent cell death. Finally, we demonstrate that cortical neurons do not undergo cell death in response to HDACi treatment, suggesting that there may be tissue-specific or microenvironmental factors that promote the susceptibility of midbrain neurons to the neurotoxic effects of HDAC inhibition.

HDAC inhibitor trichostatin A-inhibited survival of dopaminergic neuronal cells

Histone deacetylase (HDAC) inhibitors have been shown associated with neurodegenerative diseases. However, their effects on survival of dopaminergic neurons remain uncertain. In the present study, the HDAC inhibitor trichostatin A (TSA) was tested in following dopaminergic neuronal cell lines: rat N27, mouse MN9D, and human SH-SY5Y cells. Results demonstrated that a single TSA treatment resulted in decreased cell survival and increased apoptosis in dopaminergic neuronal cells. Pre-treatment with TSA resulted in exacerbated neurotoxic damage to dopaminergic neurons induced by 1-methyl-4-phenylpyridinium and rotenone. These results suggest that HDAC inhibitors may influence Parkinson's disease pathogenesis by inhibiting survival and increasing vulnerability of dopaminergic neurons to neurotoxins. Our data also suggested the importance of prudent use of HDAC inhibitors in therapy.

Juvenile absence epilepsy exacerbated by valproic acid

Valproic acid is commonly and effectively used in the treatment of idiopathic generalized epilepsies, including juvenile absence epilepsy. Although several adverse effects are associated with this drug, it has only rarely been known to exacerbate seizures. Similar to antiarrhythmic drugs aggravating particular arrhythmias, antiepileptic drugs can paradoxically induce new seizure types or exacerbate existing ones. This reaction is better known with carbamazepine and phenytoin, but is less common with broad-spectrum antiepileptic drugs such as valproic acid. This report describes a case of paradoxical, intravenous valproic acid-induced seizure exacerbation in a child with juvenile absence epilepsy, documented by video-electroencephalography.

Valproate-induced hyperammonemic encephalopathy

Valproate-induced hyperammonemic encephalopathy (VHE) is an unusual complication characterized by a decreasing level of consciousness, focal neurological deficits, cognitive slowing, vomiting, drowsiness, and lethargy. We have thoroughly reviewed the predisposing factors and their screening, the biochemical and physiopathological mechanisms involved, the different treatments described, and those that are being investigated. Etiopathogenesis is not completely understood, although hyperammonemia has been postulated as the main cause of the clinical syndrome. The increase in serum ammonium level is due to several mechanisms, the most important one appearing to be the inhibition of carbamoylphosphate synthetase-I, the enzyme that begins the urea cycle. Polytherapy with several drugs, such as phenobarbital and topiramate, seems to contribute to hyperammonemia. Hyperammonemia leads to an increase in the glutamine level in the brain, which produces astrocyte swelling and cerebral edema. There are several studies that suggest that treatment with supplements of carnitine can lead to an early favorable clinical response due to the probable carnitine deficiency induced by a valproate (VPA) treatment. Development of the progressive confusional syndrome, associated with an increase in seizure frequency after VPA treatment onset, obliges us to rule out VHE by screening for blood ammonium levels and the existence of urea cycle enzyme deficiency, such as ornithine carbamoyltransferase deficiency. Electroencephalography (EEG) is characterized by signs of severe encephalopathy with continuous generalized slowing, a predominance of theta and delta activity, occasional bursts of frontal intermittent rhythmic delta activity, and triphasic waves. These EEG findings, as well as clinical manifestations and hyperammonemia, tend to normalize after VPA withdrawal.

Aggravation of epilepsy by antiepileptic drugs

Antiepileptic drugs may paradoxically worsen seizure frequency or induce new seizure types in some patients with epilepsy. The mechanisms of seizure aggravation by antiepileptic drugs are mostly unknown and may be related to specific pharmacodynamic properties of these drugs. This article provides a review of the various clinical circumstances of seizure exacerbation and aggravation of epilepsy by antiepileptic drugs as well as a discussion of possible mechanisms underlying the occasional paradoxical effect of these drugs. Antiepileptic drug-induced seizure aggravation can occur virtually with all antiepileptic medications. Drugs that aggravate seizures are more likely to have only one or two mechanisms of action, either enhanced gamma-aminobutyric acid-mediated transmission or blockade of voltage-gated sodium channels. Antiepileptic drug-induced seizure exacerbation should be considered and the accuracy of diagnosis of the seizure type should be questioned whenever there is seizure worsening or the appearance of new seizure types after the introduction of any antiepileptic medication.

A transmission electron microscopic study of microglia/macrophages in the hippocampal cortex and neocortex following chronic exposure to valproate

In chronic administration of sodium valproate to rats, significant disorders of structural integrity of the hippocampal gyrus and the neocortex of the temporal lobe, observed in the last two stages of the experiment (after 9 and 12 months), coexisted with increased number of microglial cells and, especially after 12 months, with intense phagocytic activity within these cells. At the ultrastructural level, phagocyte microglial cells were hypertrophied with several broadened processes. Their cytoplasm contained rich lysosomal apparatus, numerous lipofuscin-like structures, lipid droplets and multilaminated bodies. The nuclei of these cells were characteristic oval or round and sometimes triangle in shape with dense and highly clumped heterochromatin, distinctly accumulated under nuclear envelope, and sparse euchromatin. Microglia/macrophages were frequently present in a close vicinity of changed neuronal somata and also close to the altered elements of the neuropil pyramidal layer of the cortex. Microglial response may, together with abnormalities in neurones, astroglia and blood-brain barrier, play a significant role in the development of experimental valproate encephalopathy.