Enzyme cytochemistry combined with electron microscopy, pharmacokinetics, and clinical chemistry for the evaluation of the effects of steady-state valproic acid concentrations on the mouse

Therapeutic and Toxic Effects of Valproic Acid Metabolites

Valproic acid (VPA) and its salts are psychotropic drugs that are widely used in neurological diseases (epilepsy, neuropathic pain, migraine, etc.) and psychiatric disorders (schizophrenia, bipolar affective disorder, addiction diseases, etc.). In addition, the indications for the appointment of valproate have been expanding in recent years in connection with the study of new mechanisms of action of therapeutic and toxic metabolites of VPA in the human body. Thus, VPA is considered a component of disease-modifying therapy for multiple tumors, neurodegenerative diseases (Huntington's disease, Parkinson's disease, Duchenne progressive dystrophy, etc.), and human immunodeficiency syndrome. The metabolism of VPA is complex and continues to be studied. Known pathways of VPA metabolism include: β-oxidation in the tricarboxylic acid cycle (acetylation); oxidation with the participation of cytochrome P-450 isoenzymes (P-oxidation); and glucuronidation. The complex metabolism of VPA explains the diversity of its active and inactive metabolites, which have therapeutic, neutral, or toxic effects. It is known that some active metabolites of VPA may have a stronger clinical effect than VPA itself. These reasons explain the relevance of this narrative review, which summarizes the results of studies of blood (serum, plasma) and urinary metabolites of VPA from the standpoint of the pharmacogenomics and pharmacometabolomics. In addition, a new personalized approach to assessing the cumulative risk of developing VPA-induced adverse reactions is presented and ways for their correction are proposed depending on the patient's pharmacogenetic profile and the level of therapeutic and toxic VPA metabolites in the human body fluids (blood, urine).

Valproate-induced Fanconi syndrome in a 27-year-old woman

Valproate-induced Fanconi Syndrome (VFS) is a rare complication of this therapy that has been previously described only in children with epilepsy. We report the first known case of an adult with VFS. Metabolic derangements lead patients to present with fatigue, confusion, weakness, and even bone fractures. Identification and discontinuation of the offending agent is the treatment of choice and helps confirm the diagnosis. This case highlights the importance of surveillance for metabolic derangements among patients on long term therapy with this commonly prescribed medication.

Fanconi's Syndrome Associated with Prolonged Adefovir Dipivoxil Therapy in a Hepatitis B Virus Patient

Adefovir dipivoxil (ADV) is commonly used as an antiviral agent in the treatment of chronic hepatitis B or human immunodeficiency virus infection. Nephrotoxicity has been shown to occur at daily dosages of 60-120 mg. Fanconi's syndrome is a generalized dysfunction of the renal proximal tubular cells, which is usually accompanied by complications. Here we report a case of Fanconi's syndrome in a chronic hepatitis B patient who had been treated with a prolonged regimen of ADV at 10 mg/day. A 47-year-old man complained of severe back and chest-wall pain. He had chronic hepatitis B and had been treated with ADV at a daily dose of 10 mg for 38 months. He was hospitalized because of severe bone pain, and laboratory and radiologic findings suggested a diagnosis of Fanconi's syndrome with osteomalacia. After discontinuation of the ADV, he recovered and was discharged from hospital. His laboratory findings had normalized within 2 weeks. This case indicates that Fanconi's syndrome can be acquired by a chronic hepatitis B patient taking ADV at a conventional dosage of 10 mg/day. Therefore, patients treated with long-term ADV should be checked regularly for the occurrence of ADV-induced Fanconi's syndrome.

The Not So ‘Mighty Chondrion’: Emergence of Renal Diseases due to Mitochondrial Dysfunction

Mitochondria are intracellular organelles with a variety of vital functions, including the provision of energy in the form of adenosine 5'-triphosphate. Increasingly, we are becoming more aware of the importance of mitochondrial dysfunction in a number of common medical conditions. In this review and overview, we focus on the growing evidence that mitochondrial dysfunction is involved in either the etiology or underlying pathophysiology of a broad spectrum of renal diseases, including acute renal injury due to ischemia-reperfusion injury, renal Fanconi syndrome, and glomerular disorders such as focal segmental glomerulosclerosis. In addition, mitochondrial dysfunction may also contribute to the growing burden of chronic kidney disease seen in our aging population, which is still largely unexplained. Unfortunately, at present, our ability to diagnose and treat renal disorders related to mitochondrial dysfunction is limited, and further work in this field is needed.

Renal injury from valproic acid: case report and literature review

A child with developmental delay and epilepsy developed glucosuria approximately 16 months after starting valproic acid therapy. Laboratory evaluation revealed global defects in proximal tubule function consistent with the De Toni-Debré-Fanconi syndrome. Discontinuation of valproate led to complete recovery 5 months later. Review of previously reported cases indicates that this complication is unique to children and reversible when the medication is discontinued.

Valproate, but not lamotrigine, induces ovarian morphological changes in Wistar rats

Valproate (VPA) medication is associated with development of polycystic ovaries, menstrual disorders and hormonal changes in women with epilepsy. We sought to determine if changes in the ovaries also occurred in an animal model without epilepsy, and whether this effect could be related to a carcinogenic effect expressed by overexpression of p53. A potentially alternative antiepileptic drug, lamotrigine (LTG), was evaluated simultaneously. To this end, female Wistar rats were fed perorally with VPA 400 mg/kg/day (n = 15), VPA 600 mg/kg/day (n = 20), LTG 10 mg/kg/day (n = 15) or control solution (n = 15) for 90-95 days. There was a significant, dose-dependent increase in the number of follicular cysts, reduction in the number of corpora lutea and reduction of ovarian weight in the VPA group. No ovarian pathology was observed in the LTG group. In neither of the groups were morphological changes seen in other organs, nor was there any overexpression of the tumor suppressor gene p53 found. An alternative antiepileptic drug, LTG, showed no ovarian pathology, and there were no light microscopic changes in other organs, or evidence of pathologic p53 overexpression in the LTG-treated animals.

Effects of long-term administration of the antiepileptic drug--sodium valproate upon the ultrastructure of hepatocytes in rats

Chronic intragastric application (1, 3, 6, 9 and 12 months) of the antiepileptic drug--sodium valproate (VPA; Vupral "Polfa") to rats in the effective dose of 200 mg/kg b.w./day exerts hepatotoxic effect after 9 and 12 months of the experiment. The first ultrastructural changes in hepatocytes were observed after 3 months of the drug administration. These became more intense in the subsequent stages of the experiment, to be most pronounced after 12 months. The most striking changes were in the mitochondria (significant swelling, an increase in their number, degeneration of matrix and cristae, disruption of the outer mitochondrial membrane) and in peroxisomes (proliferation, enlargement and the presence of distinct nucleoids). Further alterations in hepatocytes manifested themselves in: microvesicular fatty change with cholesterolosis (cholesterol clefts), damage to the cellular membrane of the sinusoidal pole with dilation of the perisinusoidal space of Disse, presence of cystern-like cytoplasmic vacuoles in the sinusoidal region, filled with plasma-like material and focal cytoplasmic necrosis. The changes in hepatocytes coexisted with the swelling and activation of sinusoidal cells, endothelial cells and Kupffer cells. The author suggests that mitochondria and peroxisomes considerably contribute to the morphogenesis of hepatocyte damage by VPA in the chronic experimental model.

Morphological features of encephalopathy after chronic administration of the antiepileptic drug valproate to rats. A transmission electron microscopic study of capillaries in the cerebellar cortex

Long-term intragastric application of the antiepileptic drug sodium valproate (Vupral "Polfa") at the effective dose of 200 mg/kg b. w. once daily to rats for 1, 3, 6, 9 and 12 months revealed neurological disorders indicating cerebellum damage ("valproate encephalopathy"). The first ultrastructural changes in structural elements of the blood-brain-barrier (BBB) in the cerebellar cortex were detectable after 3 months of the experiment. They became more severe in the later months of the experiment, and were most severe after 12 months, located mainly in the molecular layer of the cerebellar cortex. Lesions of the capillary included necrosis of endothelial cells. Organelles of these cells, in particular the mitochondria (increased number and size, distinct degeneration of their matrix and cristae) and Golgi apparatus were altered. Reduced size of capillary lumen and occlusion were caused by swollen endothelial cells which had luminal protrusions and swollen microvilli. Pressure on the vessel wall was produced by enlarged perivascular astrocytic processes. Fragments of necrotic endothelial cells were in the vascular lumens and in these there was loosening and breaking of tight cellular junctions. Damage to the vascular basement lamina was also observed. Damage to the capillary was accompanied by marked damage to neuroglial cells, mainly to perivascular processes of astrocytes. The proliferation of astrocytes (Bergmann's in particular) and occasionally of oligodendrocytes was found. Alterations in the structural elements of the BBB coexisted with marked lesions of neurons of the cerebellum (Purkinje cells are earliest). In electron micrographs both luminal and antiluminal sides of the BBB of the cerebellar cortex had similar lesions. The possible influence of the hepatic damage, mainly hyperammonemia, upon the development of valproate encephalopathy is discussed.

Reversible Fanconi syndrome associated with valproate therapy

Two children with developmental delay and seizure disorders had Fanconi syndrome associated with valproate therapy. Both recovered normal proximal tubular function within 4 months of discontinuing valproate therapy.

Lesions and repair of cells of maternal mice after valproic acid (VPA) treatment on day 8 of pregnancy: an enzyme histochemical analysis

Mice received a single teratogenic dose of the antiepileptic drug valproic acid (VPA; 500 mg/kg i.p.) on 8th d of pregnancy. The effects of VPA were studied primarily by enzyme histochemical means over a period of 48 h. Plasma membrane-associated hydrolases were more affected than lysosome-associated ones. Lesions were not found in the spleen, but a slight response, without morphological damages, was observed in the lung and thymus. Comparatively more severe injuries, which were not accompanied by clear-cut structural changes either, occurred in the liver. The most severe damages including morphological lesions were noticed especially in the proximal tubules of the kidney. The first damages were already seen after 3 h and concerned primarily the liver. After 12 h, a maximal response to VPA was detected in all organs. Repair of most of the enzymatic lesions set in after 24 h. After 48 h, lesions were not longer seen in the lung and thymus. In contrast, enzymatically and morphologically injured proximal renal tubules could still be found after this period as a response to a single dose of VPA; in the liver only enzymatic lesions were present at this stage.

Effect of valproate on renal metabolism in the intact dog

Valproate is an antiepileptic drug known to induce hyperammonemia in humans. This hyperammonemia might result from a reduced detoxification of ammonium in the liver and/or from an accelerated renal ammoniagenesis. Six dogs with normal acid-base equilibrium and eight dogs with chronic metabolic acidosis were infused with valproate directly into their left renal artery in order to obtain arterial concentrations around 3 to 4 mM. The arterial ammonium concentration rose only in chronically acidotic dogs, whereas the lactate concentration and the lactate/pyruvate ratio increased in both groups. The urinary excretion of lactate and pyruvate increased markedly but the urinary excretion of other relevant metabolites remained minimal. Renal glutamine utilization and ammonium production were not changed by valproate administration in normal dogs but increased modestly in acidotic dogs. However, renal lactate utilization was drastically reduced and in fact, changed into a net production of lactate. Valproate strikingly reduced the renal cortical concentrations of glutamine, glutamate, alphaketoglutarate and citrate, and more modestly those of malate, oxaloacetate, aspartate, alanine and ATP. By contrast, the tissue lactate concentration and the lactate/pyruvate ratio were markedly increased. In experiments with brush border membrane vesicles, valproate inhibited the lactate transporter. These results suggest that high concentrations of valproate drastically inhibited the proximal reabsorption and the proximal and distal oxidation of lactate and pyruvate. Valproate probably became itself a significant energetic substrate for the kidney.

The inducing and inhibiting effects of sodium valproate in vivo on the biotransformation systems of xenobiotics in isolated rat hepatocytes

1. The induction and inhibition of some biotransformation enzymes by valproate have been studied in hepatocytes isolated from rats treated with sodium valproate either i.p. or by subcutaneous implantation of osmotic pumps. 2. When valproate was given i.p., the cytochromes P-450 and b5, and aldrin epoxidase and glutathione S-transferase activities were significantly induced. 3. In contrast, valproate administered by osmotic pumps induced 7-ethoxycoumarin-O-deethylase activity, whereas aldrin expoxidase and glutathione S-transferase activities were significantly inhibited. At a valproate serum concentration of about 100 micrograms/ml for 2 weeks a significant induction of the cytochromes P-450 and b5 was observed. 4. Since there is a large difference between the half-lives of valproate in man and rodent, constant-rate delivery of valproate represents a better model for induction studies than i.p. injection.

Enzyme cytochemistry of rat organs after uremia with special reference to proteases

Wistar rat organs and tissues were investigated after acute and chronic uremia using enzyme cytochemical means whereby special attention was paid to plasma membrane and lysosomal proteases. Heart muscle, pancreas, spleen, stomach, duodenum, jejunum, colon and skeletal muscle did not show any clear-cut indications of alterations. After acute uremia activities of dipeptidyl peptidase IV, glutamyl aminopeptidase and microsomal alanyl aminopeptidase were decreased in the extraorbital gland and that of dipeptidyl peptidase IV in the submandibular gland. The thymus showed an increased staining for glutamyl aminopeptidase and lysosomal proteases. An activity increase of dipeptidyl peptidase IV, acid phosphatase and beta-N-acetyl-D-glucosaminidase occurred in bronchial lavage cells among which the alveolar macrophages predominated. In addition, their number was comparatively higher. Non-specific esterase activity was lowered in these cells. Alkaline phosphatase activity was drastically enhanced at the biliary pole of hepatocytes. Following chronic uremia all effects were less pronounced except for the lavage cells which were positive for glutamyl aminopeptidase, microsomal alanyl aminopeptidase and gamma-glutamyl transpeptidase and showed increased staining for lysosomal proteases, glycosidases and nonspecific phosphatases.

Protease cytochemistry in the murine rodent, guinea-pig and marmoset placenta

Plasma membrane and lysosomal proteases, gamma-glutamyl transferase and extracellular matrix proteases were investigated by qualitative cytochemical means in the mature placenta of mice, rats, guinea-pigs and marmosets. These studies revealed similarities, which concerned primarily the lysosomal proteases in different structures of the placenta and all proteases and gamma-glutamyl transferases in the zone of placental shedding. However, species differences predominated. They were observed especially for amino-peptidase A and M, dipeptidyl peptidase IV and gamma-glutamyl transferase in the plasma membranes and extracellular matrix of the placental barrier and decidual cells of all species and the cells of the basal zone in rats and mice. Plasma membrane and extracellular matrix proteases in other parts of the placenta, e.g. the placenta stem of guinea-pigs and basal plate, amniotic and chorionic plate of marmosets occurred only in these species. Elastase substrates hydrolysing endopeptidase I and kallikrein-, thrombin-, plasmin-, plasminogen- and cathepsin B substrates hydrolysing endopeptidase II were not observed in any of these species. A general comparison of the species revealed similarities for the mouse, rat and guinea-pig placental barrier, but not for that of marmosets. The proteases of this zone in the marmoset placenta are more similar to the human situation, but do not correspond to it completely.