Thiazolium salt mimics the non-coenzyme effects of vitamin B1 in rat synaptosomes.

Long-term studies have confirmed a causal relationship between the development of neurodegenerative processes and vitamin B1 (thiamine) deficiency. However, the biochemical mechanisms underlying the high neurotropic activity of thiamine are not fully understood. At the same time, there is increasing evidence that vitamin B1, in addition to its coenzyme functions, may have non-coenzyme activities that are particularly important for neurons. To elucidate which effects of vitamin B1 in neurons are due to its coenzyme function and which are due to its non-coenzyme activity, we conducted a comparative study of the effects of thiamine and its derivative, 3-decyloxycarbonylmethyl-5-(2-hydroxyethyl)-4-methyl-1,3-thiazolium chloride (DMHT), on selected processes in synaptosomes. The ability of DMHT to effectively compete with thiamine for binding to thiamine-binding sites on the plasma membrane of synaptosomes and to participate as a substrate in the thiamine pyrophosphokinase reaction was demonstrated. In experiments with rat brain synaptosomes, unidirectional effects of DMHT and thiamine on the activity of the pyruvate dehydrogenase complex (PDC) and on the incorporation of radiolabeled [2-14C]pyruvate into acetylcholine were demonstrated. The observed effects of thiamine and DMHT on the modulation of acetylcholine synthesis can be explained by suggesting that both compounds, which interact in cells with enzymes of thiamine metabolism, are phosphorylated and exert an inhibitory/activating effect (concentration-dependent) on PDC activity by affecting the regulatory enzymes of the complex. Such effects were not observed in the presence of structural analogues of thiamine and DMHT without a 2-hydroxyethyl substituent at position 5 of the thiazolium cycle. The effect of DMHT on the plasma membrane Ca-ATPase was similar to that of thiamine. At the same time, DMHT showed high cytostatic activity against neuroblastoma cells.

Thiamine deficiency in rats affects thiamine metabolism possibly through the formation of oxidized thiamine pyrophosphate.

BACKGROUND: Thiamine deficiency (TD) has a number of features in common with the neurodegenerative diseases development and close relationship between TD and oxidative stress (OS) has been repeatedly reported in the literature. The aim of this study is to understand how alimentary TD, accompanied by OS, affects the expression and level of two thiamine metabolism proteins in rat brain, namely, thiamine transporter 1 (THTR1) and thiamine pyrophosphokinase (TPK1), and what factors are responsible for the observed changes. METHODS: The effects of OS caused by TD on the THTR1and TPK1 expression in rat cortex, cerebellum and hippocampus were examined. The levels of active and oxidized forms of ThDP (enzymatically measured) in the blood and brain, ROS and SH-groups in the brain were also analyzed. RESULTS: TD increased the expression of THTR1 and protein level in all studied regions. In contrast, expression of TPK1 was depressed. TD-induced OS led to the accumulation of ThDP oxidized inactive form (ThDPox) in the blood and brain. In vitro reduction of ThDPox by dithiothreitol regenerates active ThDP suggesting that ThDPox is in disulfide form. A single high-dose thiamine administration to TD animals had no effect on THTR1 expression, partly raised TPK1 mRNA and protein levels, but is unable to normalize TPK1 enzyme activity. Brain and blood ThDP levels were increased in these conditions, but ThDPox was not decreased. GENERAL SIGNIFICANCE: It is likely, that the accumulation of ThDPox in tissue could be seen as a potential marker of neurocellular dysfunction and thiamine metabolic state.

[Pulmonary histological and ultrastructural changes in HIV infection concurrent with tuberculosis].

OBJECTIVE: To analyze cellular and subcellular disorders in the lung in the presence of HIV-associated tuberculosis. MATERIAL AND METHODS: The investigators made a comprehensive morphological examination of 25 autopsy specimens from patients who had died from HIV-associated tuberculosis. Lung pieces from the foci of caseous necrosis at its boundary and adjacent lung segments and from macroscopically intact perifocal pulmonary segments were microscopically explored. Plain stains and Ziehl-Neelsen histobacterioscopy were used for light microscopy. An immunohistochemical study was conducted using tuberculosis mouse monoclonal antibodies (clone 1.1/3/1, Vector). Seven early autopsy specimens (1-2 hours after statement of biological death) were investigated ultrastructurally. Ultrathin sections were contrasted with Reynolds' lead citrate and looked through a Libra-120 transmission electron microscope (Germany). Semithin sections were stained with toluidine blue. RESULTS: HIV-associated tuberculosis is a disease accompanied by dual aggressive infection. Impaired blood-air barrier integrity gives rise to structural and ultrastructural changes primarily in type I alveolocytes that are responsible for physiological gas exchange and detoxification. Type I alveolocytes have been noted to be in close contact with plasmocytes that are most ultrastructurally preserved and at the same time display the phagocytic and detoxifying functions being redistributed, which is necessary to keep cells viable and which is a characteristic sign of this comorbidity. This redistribution is due to severe damage to macrophages that are unable to ensure complete mycobacterial phagocytosis; thereby the plasma cells partly assume this function, as supported by ultrastructural examination. Severe destruction of granulocyte organelles and partial and complete cell necrosis with its preceding apoptotic changes were established. A study of vessels in the microcirculatory bed has indicated that the ultrastructural changes in the endothelial cells are polymorphic, which is characteristic of an exudative-inflammatory response of lung tissue. CONCLUSION: Cellular and subcellular changes, the pattern of intercellular relationships, and necrotic and apoptotic cell rearrangements, which are in one way or another involved in the pathophysiological processes maintaining definite hemostasis, are an important component in the pathogenesis of HIV-associated tuberculosis.

Comparative characteristic of thiamine antagonists on apoptosis induction in different types of nerve cell lines.

Abnormalities in oxidative metabolism and inflammation accompany many neurodegenerative diseases. The mechanisms of neurodegeneration induced by thiamine deficiency remain incompletely elucidated. The susceptibility of various types of nerve cells to thiamine (vitamin B) antagonists--oxythiamine (OT), pyrithiamine (PT) and amprolium (Am) was investigated. Four cell lines (neuronally differentiated rat PC-12, rat astrocytes DITNC, neuronally differentiated human SH-SY5Y and human astrocytic cells 1321N1) were used for experiments as neural cell models. When different cell types were cultivated with thiamine antagonists, a significant decrease of viability was detected in a time- and dose-dependent manner as demonstrated by the WST-1 colorimetric assay. These data were similar to those of caspase 3 activity and DNA fragmentation induced by thiamine antagonists. All tested cell lines were more vulnerable to OT and PT than to Am. Am displayed a pronounced damaging action on neuronal cells and had a modest influence on astrocytes. The last observation gives the basis to suppose, that neuronal cells need external arrival of thiamine more than astrocytes. Thus, the results testify that various types of nerve cells have different susceptibility to the thiamine antagonists and this relates to extent of apoptosis development.