EVALUATION OF THE THERAPEUTIC OPPORTUNITIES OF PLASMAPHERESIS IN THE HEMOLYTIС DISEASE OF NEWBORNS, RELATED TO GROUP INCOMPATIBILITY, BY INDICATORS OF RED BLOOD CELL AND HEMODYNAMIC SYSTEMS

Известно, что билирубиновый обмен и степень его напряженности являются одним из ключевых элементов механизма реализации ГБН и ее возможных, вплоть до жизненно угрожающих осложнений. В статье рассматриваются возможности терапевтического воздействия плазмафереза на патогенетические механизмы ключевых гомеостатических нарушений при гемолитической болезни новорожденных, связанной с АВО-несовместимостью. Гемолиз, как пусковой механизм начальных проявлений клинической реализации ГБН, опосредуется, как известно, путем метаболизма билирубина через функциональную систему эритрон - печень. Разрушение в кровеносном русле эритроцитов - основного «источника» кислорода и последующие изменения реологии крови - магистральной кислородной системы, приводит к развитию гипоксемии и «вторичному» повреждению органов, тканей и систем, в первую очередь, наделенных высокоспециализированными функциями. Приведенные данные исследований подтверждают терапевтическую целесообразность плазмафереза, который на ранних стадиях ГБН по АБО-несовместимости обеспечивает значительный билирубин-детоксицирующий эффект, выводит из кровеносного русла метаболические эндотоксины «вторичного происхождения» It is known that bilirubin metabolism and its degree of tension is one of the key elements of the mechanism for the realization of HDN, and its possible, up to life-threatening complications. The article considers the possibilities of the therapeutic effect of plasmapheresis on the pathogenetic mechanisms of key homeostatic disorders in hemolytic disease of the newborn associated with ABO incompatibility. Hemolysis, as a trigger for the initial manifestations of the clinical realization of HDN, is mediated, as is known, by the metabolism of bilirubin through the erythron-liver functional system. The destruction in the bloodstream of red blood cells - the main "source" of oxygen and subsequent changes in blood rheology - the main oxygen system, leads to the development of hypoxemia and "secondary" damage to organs, tissues and systems in the first place, endowed with highly specialized functions. The given research data confirm the therapeutic feasibility of plasmapheresis, which in the early stages of HDN by ABO incompatibility, provides a significant bilirubin-detoxifying effect, removes metabolic endotoxins of "secondary origin" from the bloodstream

UGT1A1 (TA)n promoter genotype: Diagnostic and population pharmacogenetic marker in Serbia

The UGT1A1 enzyme is involved in the metabolism of bilirubin and numerous medications. Unconjugated hyperbilirubinemia, commonly presented as Gilbert syndrome (GS), is a result of decreased activity of the UGT1A1 enzyme, variable number of TA repeats in the promoter of theUGT1A1gene affects enzyme activity. Seven and eight TA repeats cause a decrease of UGT1A1 activity and risk GS alleles, while six TA repeats contribute to normal UGT1A1 activity and non-risk GS allele. Also, theUGT1A1(TA)npromoter genotype is recognized as a clinically relevant pharmacogenetic marker. The aim of this study was to assess diagnostic value ofUGT1A1(TA)npromoter genotyping in pediatric GS patients. Correlation of theUGT1A1(TA)ngenotypes and level of unconjugated bilirubin at diagnosis and after hypocaloric and phenobarbitone tests in these patients was analyzed. Another aim of the study was to assess pharmacogenetic potential ofUGT1A1(TA)nvariants in Serbia. Fifty-one pediatric GS patients and 100 healthy individuals were genotyped using different methodologies, polymerase chain reaction (PCR) followed by acrylamide electrophoresis, fragment length analysis and/or DNA sequencing. Concordance of theUGT1A1(TA)npromoter risk GS genotypes with GS was found in 80.0% of patients. Therefore,UGT1A1(TA)npromoter genotyping is not a reliable genetic test for GS, but it is useful for differential diagnosis of diseases associated with hyperbilirubinemia. Level of bilirubin in pediatric GS patients at diagnosis wasUGT1A1(TA)npromoter genotype-dependent. We found that the frequency of pharmacogenetic relevantUGT1A1(TA)npromoter genotypes was 63.0%, pointing out thatUGT1A1(TA)npromoter genotyping could be recommended for preemptive pharmacogenetic testing in Serbia.

Jaundice

The metabolism of bilirubin in humans is summarized in Figure 14.1 and can be divided into three sequential steps: 1 Production of unconjugated bilirubin. Red blood cells are broken down by macrophages (mainly in the spleen), which degrade haemoglobin into iron and unconjugated (water insoluble) bilirubin. The iron is stored inside transferrin proteins. Unconjugated bilirubin travels to the liver bound to albumin. In disease, unconjugated bilirubin can be produced by haemolysis of red cells intravascularly, rather than in the spleen. 2 Conjugation of bilirubin. Liver hepatocytes uptake unconjugated bilirubin and conjugate it to glucuronate, thus making water soluble, conjugated bilirubin. 3 Excretion of bilirubin. Once conjugated, bilirubin is secreted into the bile canaliculi. Conjugated bilirubin flows with bile down the bile ducts and into the duodenum. Inside the bowel, conjugated bilirubin is metabolized by bacteria into colourless products (urobilinogen, stercobilinogen). Some of these can be reabsorbed by the gut and excreted via the kidneys, but the vast majority are oxidized in the gut into coloured pigments (urobilin, stercobilin) which give faeces their brown colour. Consequently, if there is complete obstruction of the bile ducts there will be no flow of conjugated bilirubin into the gut, no conversion into urobilinogen, and therefore not even a trace of urobilinogen in the urine. The terminology is confusing because different people mean different things. If you are going to use this terminology, make sure that you and your colleagues agree on the definitions. Nonetheless, this is what people usually mean: • Prehepatic jaundice: this refers to jaundice caused by an excessive production of bilirubin. Remember that bilirubin is produced by the breakdown of haemoglobin in the blood vessels or the spleen, hence the term prehepatic. • Hepatic jaundice: for some people, this means any jaundice due to pathology in the liver (anatomically), such as points 3, 4, and 5 in Figure 14.1, and can thus include problems with hepatocytes (e.g. hepatitis) or with the bile canaliculi (e.g. primary sclerosing cholangitis, PSC).

The pharmacological features of bilirubin: the question of the century

This review looks at the toxicity and metabolism of bilirubin in terms of its pharmacological potential. Its role has gained importance as more research has revealed the functional significance and interrelationship between the gasotransmitters nitric oxide and carbon monoxide. The biological actions of bilirubin have mostly been characterized in the high micromolar range where toxic effects occur. However, it could also prove to be an important cytoprotector for brain tissue, which is inherently less equipped for antioxidant defense. Plasma bilirubin levels negatively correlate to a number of disease states. Higher levels of bilirubin that are still within the normal range provide a protective effect to the body. The effects on various disorders could be tested using controlled pharmacological upregulation of the molecule with animal models. At nanomolar concentrations, considerable benefits have been obtained when the molecule was delivered pharmacologically under in vitro or in vivo test conditions, particularly in neurodegenerative disorders and after tissue or organ transplantation. The induction of heme oxygenase-1 (HMOX-1) via the activation of nuclear factor erythroid 2-related factor or the use of bile pigments in the harvesting of diseased tissue are novel applications, and like every new therapy, should be used with caution. HMOX-1 is tissue specific, and in exceptional states, such as schizophrenia and specific types of renal disorder, the same therapy may have disastrous effects.

Organic Anion Transporter 1B1: An Important Factor in Hepatic Thyroid Hormone and Estrogen Transport and Metabolism

Sulfation is an important pathway in the metabolism of thyroid hormone and estrogens. Sulfation of estrogens is reversible by estrogen sulfatase, but sulfation of thyroid hormone accelerates its degradation by the type 1 deiodinase in liver. Organic anion transporters (OATPs) are capable of transporting iodothyronine sulfates such as T4 sulfate (T4S), T3S, and rT3S or estrogen sulfates like estrone sulfate (E1S), but the major hepatic transporter for these conjugates has not been identified. A possible candidate is OATP1B1 because model substrates for this transporter include the bilirubin mimic bromosulfophthalein (BSP) and E1S, and it is highly and specifically expressed in liver. Therefore, OATP1B1-transfected COS1 cells were studied by analysis of BSP, E1S, and iodothyronine sulfate uptake and metabolism. Two Caucasian populations (155 blood donors and 1012 participants of the Rotterdam Scan Study) were genotyped for the OATP1B1-Val174Ala polymorphism and associated with bilirubin, E1S, and T4S levels. OATP1B1-transfected cells strongly induced uptake of BSP, E1S, T4S, T3S, and rT3S compared with mock-transfected cells. Metabolism of iodothyronine sulfates by cotransfected type 1 deiodinase was greatly augmented in the presence of OATP1B1. OATP1B1-Val174 showed a 40% higher induction of transport and metabolism of these substrates than OATP1B1-Ala174. Carriers of the OATP1B1-Ala174 allele had higher serum bilirubin, E1S, and T4S levels. In conclusion, OATP1B1 is an important factor in hepatic transport and metabolism of bilirubin, E1S, and iodothyronine sulfates. OATP1B1-Ala174 displays decreased transport activity and thereby gives rise to higher bilirubin, E1S, and T4S levels in carriers of this polymorphism.

New Concepts in Hepatocellular Transport and Metabolism of Bilirubin

Determination of serum bilirubin is a widely used test for evaluation of liver function. Understanding of the bilirubin chemistry, transport, and metabolism is of the greatest importance for correct interpretation of serum bilirubin concentrations and for adequate treatment of those clinical conditions characterized by the presence of jaundice.