Bioenergetikai változások glutamát excitotoxicitásban és oxidatív stresszben = Bioenergetical changes in glutamate excitotoxicity and oxidative stress

Munkánk egyfelől az ischemia és számos neurodegenerativ betegség pathomechanizmusában meghatározó szerepet játszó oxidativ stressz akut hatásaival, másfelől az oxidativ stressz keletkezésével kapcsolatban hozott uj eredményeket. Megállapitások: 1) Enyhe oxidativ stressz potencirozza a Na-terhelésre bekövetkező glutamat felszabadulást és csökkenti a gluthation mennyiségét izolált idegvégződésekben. 2) Az oxidativ stressz gátolja a pH regulációt és a mitokondriumok kalcium háztartást reguláló szerepét az agy-vér gátat alkotó kapillárisokból tenyésztett endothel sejtekben. 3) A mitokondriális légzési lánc komponensei közül a ROS keletkezésében a meghatározó a komplex I gátlása, amely már kis mértékű gátlás esetén olyan mennyiségű ROS képzéssel jár, hogy gátolja az endogén akonitázt. 4) A légési lánc mellett fontos általunk leirt új forrása a ROS keletkezésnek az alpha-ketoglutarát enzim, amely normál katalitikus működése során szuperoxidot és hidrogén peroxidot termel, amit a NADH/NAD arány regulál. 5) Agykéregből származó sejttenyészeten a glutamat excitotoxikus hatásában szerepet játszanak a transient receptor potential csatornák és a pathomechanizmus fontos része a sejtek NADH szintjének csökkenése. 6) Megtörtént az eddig ismeretlen funkciójú kalcium-aktiválta nem-szelektiv kation csatornák részletes jellemzése agyi kapilláris endothel sejt tenyészetben. | The findings of this research project show, on one hand, sensitive processes that are impaired by oxidative stress in neurons and rat brain capillary endothelial cells (RBCE), on the other hand, mechanisms involved in the generation of oxidative stress. Major findings: i) Hydrogen peroxide potentiate the release of glutamate induced by a sodium load in isolated nerve terminals. ii) Oxidative stress impairs the intracellular pH regulation and the mitochondrial calcium regulation in RBCE cells. iii) Physiologically the most relevant site of reactive oxygen species (ROS) production in the respiratory chain is at complex I; when this complex is inhibited by 25-30 %, relevant to Parkinson?s disease, ROS is generated in sufficient amount to inhibit endogenous mitochondrial aconitase. iv) In addition to the respiratory chain, alpha-ketoglutarate dehydrogenase could be a significant source of ROS generation in mitochondria under conditions when the NADH/NAD ratio is increased (ischemia, Parkinson?s disease). v) Transient receptor potential (TRP) channels are involved in the delayed calcium deregulation (DCD) associated with glutamate excitotoxicity in cortical cell cultures. DCD is accompanied by a significant drop in the intracellular NADH level. vi) Calcium-activated non-selective cation channels, which are abundant in RBCE cells, have been characterized; the gating characteristics as well as the regulation by nucleotides have been described in details

Comparative analysis on the structural features of the 5' flanking region of κ-casein genes from six different species

κ-casein plays an essential role in the formation, stabilisation and aggregation of milk micelles. Control of κ-casein expression reflects this essential role, although an understanding of the mechanisms involved lags behind that of the other milk protein genes. We determined the 5'-flanking sequences for the murine, rabbit and human κ-casein genes and compared them to the published ruminant sequences. The most conserved region was not the proximal promoter region but an approximately 400 bp long region centred 800 bp upstream of the TATA box. This region contained two highly conserved MGF/STAT5 sites with common spacing relative to each other. In this region, six conserved short stretches of similarity were also found which did not correspond to known transcription factor consensus sites. On the contrary to ruminant and human 5' regulatory sequences, the rabbit and murine 5'-flanking regions did not harbour any kind of repetitive elements. We generated a phylogenetic tree of the six species based on multiple alignment of the κ-casein sequences. This study identified conserved candidate transcriptional regulatory elements within the κ-casein gene promoter

Comparative analysis on the structural features of the 5' flanking region of <it>κ</it>-casein genes from six different species

Abstract κ-casein plays an essential role in the formation, stabilisation and aggregation of milk micelles. Control of κ-casein expression reflects this essential role, although an understanding of the mechanisms involved lags behind that of the other milk protein genes. We determined the 5'-flanking sequences for the murine, rabbit and human κ-casein genes and compared them to the published ruminant sequences. The most conserved region was not the proximal promoter region but an approximately 400 bp long region centred 800 bp upstream of the TATA box. This region contained two highly conserved MGF/STAT5 sites with common spacing relative to each other. In this region, six conserved short stretches of similarity were also found which did not correspond to known transcription factor consensus sites. On the contrary to ruminant and human 5' regulatory sequences, the rabbit and murine 5'-flanking regions did not harbour any kind of repetitive elements. We generated a phylogenetic tree of the six species based on multiple alignment of the κ-casein sequences. This study identified conserved candidate transcriptional regulatory elements within the κ-casein gene promoter.</p