Modular Approach for Rapid Identification of RNA-Based Sensors

Detection of metabolites in real time and in whole cells requires effective molecular sensors. In this regard, fluorogenic light-up RNAs have recently become important tools for small-molecule detection in cells. However, the construction of light-up RNA sensors is an arduous task that requires structural knowledge of both the sensor and reporter RNA. De novo strategies for selecting sensors from RNA libraries are limited and are mostly restricted to known aptamers and riboswitches. Here, we provide a solution to this problem by developing a capture-SELEX variant that allows the obtained libraries and aptamers to be linked to fluorogenic RNAs in a modular and allosteric manner. The approach is generally applicable and allows for rapid modular allosteric assembly with green- or red-shifted fluorogenic RNAs.

Enhancement of the therapeutic efficacy of the MAP regimen using thiamine pyrophosphate-decorated albumin nanoclusters in osteosarcoma treatment

Recent studies on osteosarcoma regimens have mainly focused on modifying the combination of antineoplastic agents rather than enhancing the therapeutic efficacy of each component. Here, an albumin nanocluster (NC)-assisted methotrexate (MTX), doxorubicin (DOX), and cisplatin (MAP) regimen with improved antitumor efficacy is presented. Human serum albumin (HSA) is decorated with thiamine pyrophosphate (TPP) to increase the affinity to the bone tumor microenvironment (TME). MTX or DOX (hydrophobic MAP components) is adsorbed to HSA-TPP via hydrophobic interactions. MTX- or DOX-adsorbed HSA-TPP NCs exhibit 20.8- and 1.64-fold higher binding affinity to hydroxyapatite, respectively, than corresponding HSA NCs, suggesting improved targeting ability to the bone TME via TPP decoration. A modified MAP regimen consisting of MTX- or DOX-adsorbed HSA-TPP NCs and free cisplatin displays a higher synergistic anticancer effect in HOS/MNNG human osteosarcoma cells than conventional MAP. TPP-decorated NCs show 1.53-fold higher tumor accumulation than unmodified NCs in an orthotopic osteosarcoma mouse model, indicating increased bone tumor distribution. As a result, the modified regimen more significantly suppresses tumor growth in vivo than solution-based conventional MAP, suggesting that HSA-TPP NC-assisted MAP may be a promising strategy for osteosarcoma treatment.

Crystal structure of Escherichia coli thiamine pyrophosphate-sensing riboswitch in the apo state

The thiamine pyrophosphate (TPP)-sensing riboswitch is one of the earliest discovered and most widespread riboswitches. Numerous structural studies have been reported for this riboswitch bound with various ligands. However, the ligand-free (apo) structure remains unknown. Here, we report a 3.1 Å resolution crystal structure of Escherichia coli TPP riboswitch in the apo state, which exhibits an extended, Y-shaped conformation further supported by small-angle X-ray scattering data and driven molecular dynamics simulations. The loss of ligand interactions results in helical uncoiling of P5 and disruption of the key tertiary interaction between the sensory domains. Opening of the aptamer propagates to the gene-regulatory P1 helix and generates the key conformational flexibility needed for the switching behavior. Much of the ligand-binding site at the three-way junction is unaltered, thereby maintaining a partially preformed pocket. Together, these results paint a dynamic picture of the ligand-induced conformational changes in TPP riboswitches that confer conditional gene regulation.

Mitochondrial transport and metabolism of the vitamin B-derived cofactors thiamine pyrophosphate, coenzyme A, FAD and NAD+ , and related diseases: A review

Multiple mitochondrial matrix enzymes playing key roles in metabolism require cofactors for their action. Due to the high impermeability of the mitochondrial inner membrane, these cofactors need to be synthesized within the mitochondria or be imported, themselves or one of their precursors, into the organelles. Transporters belonging to the protein family of mitochondrial carriers have been identified to transport the coenzymes: thiamine pyrophosphate, coenzyme A, FAD and NAD⁺ , which are all structurally similar to nucleotides and derived from different B-vitamins. These mitochondrial cofactors bind more or less tightly to their enzymes and, after having been involved in a specific reaction step, are regenerated, spontaneously or by other enzymes, to return to their active form, ready for the next catalysis round. Disease-causing mutations in the mitochondrial cofactor carrier genes compromise not only the transport reaction but also the activity of all mitochondrial enzymes using that particular cofactor and the metabolic pathways in which the cofactor-dependent enzymes are involved. The mitochondrial transport, metabolism and diseases of the cofactors thiamine pyrophosphate, coenzyme A, FAD and NAD⁺ are the focus of this review.

Protection of Cholinergic Neurons against Zinc Toxicity by Glial Cells in Thiamine-Deficient Media

Brain pathologies evoked by thiamine deficiency can be aggravated by mild zinc excess. Cholinergic neurons are the most susceptible to such cytotoxic signals. Sub-toxic zinc excess aggravates the injury of neuronal SN56 cholinergic cells under mild thiamine deficiency. The excessive cell loss is caused by Zn interference with acetyl-CoA metabolism. The aim of this work was to investigate whether and how astroglial C6 cells alleviated the neurotoxicity of Zn to cultured SN56 cells in thiamine-deficient media. Low Zn concentrations did not affect astroglial C6 and primary glial cell viability in thiamine-deficient conditions. Additionally, parameters of energy metabolism were not significantly changed. Amprolium (a competitive inhibitor of thiamine uptake) augmented thiamine pyrophosphate deficits in cells, while co-treatment with Zn enhanced the toxic effect on acetyl-CoA metabolism. SN56 cholinergic neuronal cells were more susceptible to these combined insults than C6 and primary glial cells, which affected pyruvate dehydrogenase activity and the acetyl-CoA level. A co-culture of SN56 neurons with astroglial cells in thiamine-deficient medium eliminated Zn-evoked neuronal loss. These data indicate that astroglial cells protect neurons against Zn and thiamine deficiency neurotoxicity by preserving the acetyl-CoA level.

The Changes in Antioxidant Activity of Selected Flavonoids and Caffeine Depending on the Dosage and Form of Thiamine

Phenolic compounds and thiamine may serve as therapies against oxidative stress-related neurodegenerative diseases. However, it is important to note that these components show high instability under changing conditions. The study’s aim was to determine the impact of the thiamine concentration (hydrochloride—TH and pyrophosphate—TP; in the range 0.02 to 20 mg/100 g on the indices of the chelating properties and reducing power, and free radicals scavenging indices of EGCG, EGC, ECG and caffeine added from 0.04 to 6.0 mg/100 g. Our research confirmed that higher concentrations of TH and TP can exhibit significant activity against the test antioxidant indices of all components. When above 5.0 mg/100 g of thiamine was used, the radical scavenging abilities of the compound decreased in the following order: EGCG > ECG > EGC > caffeine. The highest correlation was found for the concentration of thiamine pyrophosphate to 20.0 mg/100 g and EGCG. Knowledge of the impact of factors associated with the concentration of both EGCG, EGC, ECG or caffeine and thiamine on their activity could carry weight in regulating the quality supplemented foods, especially of nutrition support for people of all ages were oral, enteral tube feeding and parenteral nutrition).

Thiamine pyrophosphate diminishes nitric oxide synthesis in endothelial cells

Although thiamine pyrophosphate (TPP) is considered a protective agent for endothelial cells, it is still unknown if this is associated with nitric oxide (NO) synthesis. Our aim was to evaluate the synthesis of NO in endothelial cells incubated with TPP and high glucose concentrations. Endothelial cells from the umbilical cord vein from newborns (n = 20), were incubated with 5, 15 or 30 mmol/L glucose, in absence or presence of 0.625 mg/ml of TPP. Our results showed a significant increase in cell proliferation (> 40%; P < 0.05), and cell viability (> 90%; P < 0.001) after 48 h in endothelial cells cultured with glucose plus TPP. Likewise, in the presence of glucose and TPP an important rise in the consumption of glucose by the endothelial cells was observed after 24 h (> 7%; P < 0.001) and 48 h (> 10%; P < 0.05). Additionally, the levels of lactate after incubation with glucose and TPP showed only slight variations after 48 h (P < 0.05). However, these changes were clearly different from those observed in the absence of TPP. Interestingly, we found that the changes mentioned were linked with reduced levels of nitrites both at 24 h (< 171 pmol/μg protein; P < 0.001), and 48 h (< 250 pmol/μg protein; P < 0.05), which was associated with a reduced expression of mRNA of eNOS in endothelial cells incubated with TPP and high glucose. In conclusion, the presence of TPP regulates the consumption of glucose and the synthesis of NO, which would explain its protective effect in the endothelium of diabetic patients.

Utility of Whole Blood Thiamine Pyrophosphate Evaluation in TPK1-Related Diseases

TPK1 mutations are a rare, but potentially treatable, cause of thiamine deficiency. Diagnosis is challenging given the phenotypic overlap that exists with other metabolic and neurological disorders. We report a case of TPK1-related disease presenting with Leigh-like syndrome and review the diagnostic utility of thiamine pyrophosphate (TPP) blood measurement. The proband, a 35-year-old male, presented at four months of age with recurrent episodes of post-infectious encephalopathy. He subsequently developed epilepsy, learning difficulties, sensorineural hearing loss, spasticity, and dysphagia. There was a positive family history for Leigh syndrome in an older brother. Plasma lactate was elevated (3.51 mmol/L) and brain MRI showed bilateral basal ganglia hyperintensities, indicative of Leigh syndrome. Histochemical and spectrophotometric analysis of mitochondrial respiratory chain complexes I, II+III, and IV was normal. Genetic analysis of muscle mitochondrial DNA was negative. Whole exome sequencing of the proband confirmed compound heterozygous variants in TPK1: c. 426G>C (p. Leu142Phe) and c. 258+1G>A (p.?). Blood TPP levels were reduced, providing functional evidence for the deleterious effects of the variants. We highlight the clinical and bioinformatics challenges to diagnosing rare genetic disorders and the continued utility of biochemical analyses, despite major advances in DNA sequencing technology, when investigating novel, potentially disease-causing, genetic variants. Blood TPP measurement represents a fast and cost-effective diagnostic tool in TPK1-related diseases.

A reverse TCA cycle 2-oxoacid:ferredoxin oxidoreductase that makes C-C bonds from CO2

2-oxoglutarate:ferredoxin oxidoreductase (OGOR) is a thiamine pyrophosphate (TPP) and [4Fe-4S] cluster-dependent enzyme from the reductive tricarboxylic acid (rTCA) cycle that fixes CO₂ to succinyl-CoA, forming 2-oxoglutarate and CoA. Here we report an OGOR from the rTCA cycle of Magnetococcus marinus MC-1, along with all three potential ferredoxin (Fd) redox partners. We demonstrate MmOGOR operates bidirectionally (both CO₂-fixing and 2-oxoglutarate oxidizing), and that only one Fd (MmFd1) supports efficient catalysis. Our 1.94-Å and 2.80-Å resolution crystal structures of native and substrate-bound forms of MmOGOR reveal the determinants of substrate specificity and CoA-binding in an OGOR, and illuminate the [4Fe-4S] cluster environment, portraying the electronic conduit allowing MmFd1 to be wired to the bound-TPP. Structural and biochemical data further identify Glu45α as a mobile residue that impacts catalytic bias toward CO₂-fixation although it makes no direct contact with TPP-bound intermediates, indicating that reaction directionality can be tuned by second layer interactions. (149 of 150 words limit).

The Protective Effect of Thiamine Pryophosphate Against Sugar-Induced Retinal Neovascularisation in Rats

The aim of this study was to investigate the effect of thiamine pyrophosphate (TPP), administered via sugar water, on retinal neovascularisation in rats. Animals were assigned to three groups, namely the TPP sugar-water group (TPSWG, n = 12), the control group (CG, n = 12) and the healthy group (HG, n = 12). The TPSWG was injected intraperitoneally with TPP once a day for 6 months. CG and HG rats were given distilled water in the same way. TPSWG and CG rats were left free to access an additional 0.292 mmol /ml of sugar water for 6 months. The fasting blood glucose (FBG) levels of the animals were measured monthly. After 6 months, biochemical, gene expression and histopathologic analyses were carried out in the retinal tissues removed from the animals after they were killed. The measured FBG levels were 6.96 ± 0.09 mmol/ml (p < 0.0001 vs. HG), 6.95 ± 0.06 mmol/ml (p < 0.0001 vs. HG) and 3.94 ± 0.10 mmol/ml in the CG, TPSWG and HG groups, respectively. The malondialdehyde (MDA) levels were found to be 2.82 ± 0.23 (p < 0.0001 vs. HG), 1.40 ± 0.32 (p < 0.0001 vs. HG) and 1.66 ± 0.17 in the CG, TPSWG and HG, respectively. Interleukin 1 beta (IL-1β) gene expression was increased (3.78 ± 0.29, p < 0.0001) and total glutathione (tGSH) was decreased (1.32 ± 0.25, p < 0.0001) in the retinal tissue of CG compared with TPSWG (1.92 ± 0.29 and 3.18 ± 0.46, respectively). Increased vascularisation and oedema were observed in the retinal tissue of CG, while the retinal tissues of TPSWG and HG rats had a normal histopathological appearance. A carbohydrate-rich diet may lead to pathological changes in the retina even in nondiabetics, but this may be overcome by TPP administration.

Binding site for coenzyme A revealed in the structure of pyruvate:ferredoxin oxidoreductase from Moorella thermoacetica

Pyruvate:ferredoxin oxidoreductase (PFOR) is a microbial enzyme that uses thiamine pyrophosphate (TPP), three [4Fe-4S] clusters, and coenzyme A (CoA) in the reversible oxidation of pyruvate to generate acetyl-CoA and carbon dioxide. The two electrons that are generated as a result of pyruvate decarboxylation are used in the reduction of low potential ferredoxins, which provide reducing equivalents for central metabolism, including the Wood-Ljungdahl pathway. PFOR is a member of the 2-oxoacid:ferredoxin oxidoreductase (OFOR) superfamily, which plays major roles in both microbial redox reactions and carbon dioxide fixation. Here, we present a set of crystallographic snapshots of the best-studied member of this superfamily, the PFOR from Moorella thermoacetica (MtPFOR). These snapshots include the native structure, those of lactyl-TPP and acetyl-TPP reaction intermediates, and the first of an OFOR with CoA bound. These structural data reveal the binding site of CoA as domain III, the function of which in OFORs was previously unknown, and establish sequence motifs for CoA binding in the OFOR superfamily. MtPFOR structures further show that domain III undergoes a conformational change upon CoA binding that seals off the active site and positions the thiolate of CoA directly adjacent to the TPP cofactor. These structural findings provide a molecular basis for the experimental observation that CoA binding accelerates catalysis by 10⁵-fold.

Gene expression and histopathological evaluation of thiamine pyrophosphate on optic neuropathy induced with ethambutol in rats

AIM

To compare the effects of thiamine pyrophosphate (TPP) and thiamine (TM) in oxidative optic neuropathy in rats induced by ethambutol.

METHODS

The animals were divided into four groups: a control group (CG), an ethambutol control (ETC) group, TM plus ethambutol group (TMG), and TPP plus ethambutol group (TPPG). One hour after intraperitoneal administration of TM 20 mg/kg to the TMG group and TPP 20 mg/kg to TPPG group, 30 mg/kg ethambutol was given via gavage to all the groups but the CG. This procedure was repeated once daily for 90d. After that period, all rats were exposed to high levels of anaesthesia in order to investigate the gene expression of malondialdehyde and glutathione in removed optic nerve tissue and histopathologically to examine these tissues.

RESULTS

Malondialdehyde gene expression significantly increased, whereas glutathione gene expression significantly decreased in the ETC group compared to the CG. TM could not prevent the increase of malondialdehyde gene expression and the decrease of glutathione, while TPP significantly could suppress. Histopathologically, significant vacuolization in the optic nerve, single-cell necrosis in the glial cells, and a decrease in oligodendrocytes were observed in the ETC group. Vacuolization in the optic nerve, a decrease in oligodendrocytes and single-cell necrosis were found in the TMG group, while no pathological finding was observed in the TPPG group except for mild vacuolization.

CONCLUSION

TPP protects the optic nerve against the ethambutol-induced toxicity but TM does not. TPP can be beneficial in prophilaxis of optic neuropathy in ethambutol therapy.

Quantitation of plasma thiamine, related metabolites and plasma protein oxidative damage markers in children with autism spectrum disorder and healthy controls

AIMS/HYPOTHESIS

To assess thiamine and related metabolite status by analysis of plasma and urine in autistic children and healthy controls, correlations to clinical characteristics and link to plasma protein markers of oxidative damage.

METHODS

27 children with autism (21 males and 6 females) and 21 (15 males and 6 females) age-matched healthy control children were recruited. The concentration of thiamine and related phosphorylated metabolites in plasma and urine and plasma protein content of dityrosine, N-formylkynurenine and 3-nitrotyrosine was determined.

RESULTS

Plasma thiamine and thiamine monophosphate concentrations were similar in both study groups (median [lower-upper quartile]): autistic children - 6.60 nM (4.48-8.91) and 7.00 nM (5.51-8.55), and healthy controls - 6.82 nM (4.47-7.02) and 6.82 nM (5.84-8.91), respectively. Thiamine pyrophosphate (TPP) was decreased 24% in autistic children compared to healthy controls: 6.82 nM (5.81-8.52) versus 9.00 nM (8.41-10.71), p < .01. Urinary excretion of thiamine and fractional renal clearance of thiamine did not change between the groups. No correlation was observed between clinical markers and the plasma and urine thiamine concentration. Plasma protein dityrosine content was increased 88% in ASD. Other oxidative markers were unchanged.

CONCLUSIONS/INTERPRETATION

Autistic children had normal plasma and urinary thiamine levels whereas plasma TPP concentration was decreased. The latter may be linked to abnormal tissue handling and/or absorption from gut microbiota of TPP which warrants further investigation. Increased plasma protein dityrosine may reflect increased dual oxidase activity in response to change in mucosal immunity and host-microbe homeostasis.

One-carbon chemistry of oxalate oxidoreductase captured by X-ray crystallography

Thiamine pyrophosphate (TPP)-dependent oxalate oxidoreductase (OOR) metabolizes oxalate, generating two molecules of CO2 and two low-potential electrons, thus providing both the carbon and reducing equivalents for operation of the Wood-Ljungdahl pathway of acetogenesis. Here we present structures of OOR in which two different reaction intermediate bound states have been trapped: the covalent adducts between TPP and oxalate and between TPP and CO2. These structures, along with the previously determined structure of substrate-free OOR, allow us to visualize how active site rearrangements can drive catalysis. Our results suggest that OOR operates via a bait-and-switch mechanism, attracting substrate into the active site through the presence of positively charged and polar residues, and then altering the electrostatic environment through loop and side chain movements to drive catalysis. This simple but elegant mechanism explains how oxalate, a molecule that humans and most animals cannot break down, can be used for growth by acetogenic bacteria.

The effect of thiamine pyrophosphate on ethambutol-induced ocular toxicity

CONTEXT

Ethambutol-induced retinal oxidative damage in patients with tuberculosis is still not being adequately treated. The protective effect of thiamine pyrophosphate against oxidative damage in some tissues has been reported, but no information on the protective effects of thiamine pyrophosphate against ethambutol-induced oxidative retinal damage has been found in the medical literature.

OBJECTIVE

The objective is to investigate whether thiamine pyrophosphate has a protective effect against oxidative retinal damage in rats induced by ethambutol.

MATERIALS AND METHODS

Experimental animals divided into four groups (n = 10): the healthy group (HG), the ethambutol control group (EMB), thiamine + ethambutol group (Thi-EMB) and thiamine pyrophosphate + ethambutol group (TPP-EMB). The rats in the TPP-EMB and Thi-EMB groups were administered thiamine pyrophosphate and thiamine, respectively, at doses of 20 mg/kg intraperitoneally. Distilled water was administered intraperitoneally to the HG and the EMB groups as a solvent in the same volumes. One hour after drug injection, 30 mg/kg ethambutol was administered via an oral gavage to the TPP-EMB, Thi-EMB and EMB groups. This procedure was repeated once a day for 90 days. At the end of this period, all rats were euthanized under high-dose thiopental sodium anesthesia, and biochemical and histopathological investigations of the retinal tissue were performed.

RESULTS

Malondialdehyde (MDA) and DNA damage product 8-hydroxyguanine levels were significantly lower in the retinal tissue of TPP-EMB and HG groups compared to those of the Thi-EMB and EMB groups, and total glutathione (tGSH) was also found to be higher. In addition, severe retinal tissue vascularization, edema and loss of ganglion cells were observed in the Thi-EMB and EMB groups, whereas histopathological findings for the TPP-EMB group were observed to be close to normal.

DISCUSSION AND CONCLUSION

These findings suggest that thiamine pyrophosphate protects retinal tissues from ethambutol-induced oxidative damage, and thiamine does not. This positive effect of thiamine pyrophosphate may be useful in the prevention of ocular toxicity that occurs during ethambutol use.

Regulation of basal promoter activity of the human thiamine pyrophosphate transporter SLC44A4 in human intestinal epithelial cells

Microbiota of the large intestine synthesize considerable amount of vitamin B1 in the form of thiamine pyrophosphate (TPP). There is a specific high-affinity regulated carrier-mediated uptake system for TPP in human colonocytes (product of the SLC44A4 gene). The mechanisms of regulation of SLC44A4 gene expression are currently unknown. In this study, we characterized the SLC44A4 minimal promoter region and identified transcription factors important for basal promoter activity in colonic epithelial cells. The 5'-regulatory region of the SLC44A4 gene (1,022 bp) was cloned and showed promoter activity upon transient transfection into human colonic epithelial NCM460 cells. With the use of a series of 5'- and 3'-deletion luciferase reporter constructs, the minimal genomic region that required basal transcription of the SLC44A4 gene expression was mapped between nucleotides -178 and +88 (using the distal transcriptional start site as +1). Mutational analysis performed on putative cis-regulatory elements established the involvement of ETS/ELF3 [E26 transformation-specific sequence (ETS) proteins], cAMP-responsive element (CRE), and SP1/GC-box sequence motifs in basal SLC44A4 promoter activity. By means of EMSA, binding of ELF3 and CRE-binding protein-1 (CREB-1) transcription factors to the SLC44A4 minimal promoter was shown. Contribution of CREB into SLC44A4 promoter activity was confirmed using NCM460 cells overexpressing CREB. We also found high expression of ELF3 and CREB-1 in colonic (NCM460) compared with noncolonic (ARPE19) cells, suggesting their possible contribution to colon-specific pattern of SLC44A4 expression. This study represents the first characterization of the SLC44A4 promoter and reports the importance of both ELF3 and CREB-1 transcription factors in the maintenance of basal promoter activity in colonic epithelial cells.

Rapid reversal of severe lactic acidosis after thiamine administration in critically ill adults: a report of 3 cases

BACKGROUND

Thiamine plays a critical role in energy metabolism. Critically ill patients may have thiamine deficiency and increased mortality due to potentially irreversible consequences. The aim of this study was to show the impact of thiamine deficiency in a series of patients and the rapid response to thiamine replacement, showing the changes in clinical and metabolic conditions over time.

METHODS

We described 3 cases of hospitalized patients who had received parenteral nutrition (PN) without vitamin supplementation. All the patients were admitted to the ICU between 2010 and 2011 with a severe form of lactic acidosis, an unstable circulatory state, and a different neurological disorder (a lethargic state, a severe form of impaired near-coma consciousness, and Wernicke encephalopathy).

RESULTS

Intravenous (IV) administration of thiamine was associated with a rapid and marked restoration of acid-base balance, hemodynamic stability and the disappearance of neurological disturbances, and normalization of the clinical and biochemical conditions of all the patients within the following hours.

CONCLUSIONS

The 3 cases demonstrated the rapidity of the reversal of severe thiamine deficiency, achieved by appropriate replacement in different hospitalized patients. The regression of clinical and biochemical disorders requires a prompt diagnosis and treatment based on the IV administration of thiamine and magnesium sulfate. In hospitalized patients at risk, thiamine deficiency is prevented by the integration of thiamine supplementation into PN and other forms of nutrition support.

Examination of the effects of thiamine and thiamine pyrophosphate on Doxorubicin-induced experimental cardiotoxicity

BACKGROUND AND PURPOSE

To investigate the effect of thiamine and thiamine pyrophosphate on doxorubicin-induced cardiotoxicity biochemically and histopathologically and to examine whether doxorubicin cardiotoxicity is related to the conversion of thiamine into thiamine pyrophosphate and inhibition of thiamine pyrophosphokinase (TPK) enzyme.

EXPERIMENTAL APPROACH

A total of 48 Albino Wistar male rats were used. Rats were divided into groups as thiamine + doxorubicin (TIA + DOX), thiamine pyrophosphate + doxorubicin (TPP + DOX), DOX, and healthy (HEA) groups. One hour after the administration of thiamine and TPP in 25 mg/kg doses, 5 mg/kg doxorubicin were injected to all groups except HEA group during 7 days. Then, the samples were collected for biochemical (glutathione [GSH], malondialdehyde [MDA], DNA damage, creatine kinase (CK), CK-MB, and troponine I [TP-I]), molecular (TPK), and histopathological examinations.

KEY RESULTS

Oxidant parameters (MDA and DNA damage) decreased and antioxidant parameter (GSH) increased in TPP + DOX group. In addition, levels of CK, CK-MB, and TP-I were low in the TPP + DOX group and high in the TIA + DOX and DOX groups. Cardiac tissue was protected in TPP + DOX group, and no protective effect was observed in TIA + DOX and DOX groups. Messenger RNA expression of TPK was decreased in DOX and TIA + DOX groups.

CONCLUSION AND IMPLICATIONS

The cardiotoxic effect of doxorubicin originated from the inhibition of TPK enzyme resulting in insufficient production of thiamine pyrophosphate.

Damage induced by paracetamol compared with N-acetylcysteine

BACKGROUND

This study investigated the effect of thiamine pyrophosphate (TPP) on oxidative liver damage induced in rats with high-dose paracetamol.

METHODS

Rats for this experiment were divided into the following groups: healthy control, paracetamol control, thiamine + paracetamol, TPP + paracetamol, and N-acetylcysteine + paracetamol. Oxidant and antioxidant parameters and liver function test levels were compared between the groups.

RESULTS

The results show that TPP and N-acetylcysteine with paracetamol equally prevented a rise in oxidants such as malondialdehyde and nitric oxide. They also prevented a decrease in enzymatic and nonenzymatic antioxidants such as glutathione, glutathione peroxidase, glutaredoxin, glutathione S-transferase, superoxide dismutase, and catalase in the rat liver.

CONCLUSION

Thiamine pyrophosphate and N-acetylcysteine had a similar positive effect on oxidative damage caused by paracetamol hepatotoxicity. These findings show that TPP may be beneficial in paracetamol hepatotoxicity.

Effect of thiamine pyrophosphate on ischemia-reperfusion induced oxidative damage in rat kidney

Objectives:

The biochemical effects of thiamine pyrophosphate on ischemia-reperfusion (IR) induced oxidative damage and DNA mutation in rat kidney tissue were investigated, and compared to thiamine.

Materials and Methods:

Rats were divided into four groups: Renal ischemia-reperfusion (RIR); thiamine pyrophosphate + RIR (TPRIR); thiamine + RIR (TRIR); and sham group (SG).

Results:

The results of biochemical experiments have shown that malondialdehyde (MDA) levels in rat kidney tissue after TRIR and TPRIR treatment were 7.2 ± 0.5 (P > 0.05) and 3.3 ± 0.3 (P < 0.0001) μmol/g protein, respectively. The MDA levels in the SG rat kidney tissue and in RIR group were 3.6 ± 0.2 (P < 0.0001) and 7.6 ± 0.6 μmol/g protein, respectively. Total glutathione (tGSH) levels in TRIR, TPRIR, SG, and RIR animal groups were 2.2 ± 0.3 (P > 0.05), 5.8 ± 0.4 (P < 0.0001), 6.2 ± 0.2 (P < 0.0001), and 1.7 ± 0.2 nmol/g protein, respectively. In the TRIR, TPRIR, SG, and RIR animal groups; 8-hydroxyguanine (8-OHGua)/Gua levels, which indicate mutagenic DNA, were 1.75 ± 0.12 (P > 0.05), 0.93 ± 0.1 (P < 0.0001), 0.85 ± 0.08 (P < 0.0001), and 1.93 ± 0.24 pmol/L, respectively.

Conclusions:

It has been shown that thiamine pyrophosphate prevents increase in mutagenic DNA in IR induced oxidative damage, whereas thiamine does not have this effect.

A possible role for the chloroplast pyruvate dehydrogenase complex in plant glycolate and glyoxylate metabolism

Glyoxylate is a peroxisomal intermediate of photorespiration, the recycling pathway for 2-phosphoglycolate (2-PG) produced by the oxygenase activity of Rubisco. Under hot and dry growth conditions, photorespiratory intermediates can accumulate and must be detoxified by alternative pathways, including plastidal reactions. Moreover, there is evidence that chloroplasts are capable of actively producing glyoxylate from glycolate. Further metabolic steps are unknown, but probably include a CO2 release step. Here, we report that CO2 production from glycolate and glyoxylate in isolated tobacco chloroplasts can be inhibited by pyruvate, but not related compounds. We isolated a protein fraction that was enriched for the chloroplast pyruvate dehydrogenase complex (PDC). The fraction contained a protein complex of several MDa in size that included all predicted subunits of the chloroplast PDC and a so far unidentified HSP93-V/ClpC1 heat shock protein. Glyoxylate competitively inhibited NADH formation from pyruvate in this fraction. The Km for pyruvate and the Ki for glyoxylate were 330 and 270 μM, respectively. Glyoxylate decarboxylation was also enriched in this fraction and could be in turn inhibited by pyruvate. Based on these data, we suggest that the chloroplast PDC might be part of a pathway for glycolate and/or glyoxylate oxidation in chloroplasts.

Thermodynamic analysis of ligand binding and ligand binding-induced tertiary structure formation by the thiamine pyrophosphate riboswitch

The thi-box riboswitch regulates gene expression in response to the intracellular concentration of thiamine pyrophosphate (TPP) in archaea, bacteria, and eukarya. To complement previous biochemical, genetic, and structural studies of this phylogenetically widespread RNA domain, we have characterized its interaction with TPP by isothermal titration calorimetry. This shows that TPP binding is highly dependent on Mg(2+) concentration. The dissociation constant decreases from approximately 200 nM at 0.5 mM Mg(2+) concentration to approximately 9 nM at 2.5 mM Mg(2+) concentration. Binding is enthalpically driven, but the unfavorable entropy of binding decreases as Mg(2+) concentration rises, suggesting that divalent cations serve to pre-organize the RNA. Mutagenesis, biochemical analysis, and a new crystal structure of the riboswitch suggest that a critical element that participates in organizing the riboswitch structure is the tertiary interaction formed between the P3 and L5 regions. This tertiary contact is distant from the TPP binding site, but calorimetric analysis reveals that even subtle mutations in L5 can have readily detectable effects on TPP binding. The thermodynamic signatures of these mutations, namely decreased favorable enthalpy of binding and small effects on entropy of binding, are consistent with the P3-L5 association contributing allosterically to TPP-induced compaction of the RNA.

Ligand binding and gene control characteristics of tandem riboswitches in Bacillus anthracis

Most riboswitches are composed of a single metabolite-binding aptamer and a single expression platform that function together to regulate genes in response to changing metabolite concentrations. In rare instances, two aptamers or sometimes two complete riboswitches reside adjacent to each other in untranslated regions (UTRs) of mRNAs. We have examined an example of a tandem riboswitch in the Gram-positive bacterium Bacillus anthracis that includes two complete riboswitches for thiamine pyrophosphate (TPP). Unlike other complex riboswitch systems described recently, tandem TPP riboswitches do not exhibit cooperative ligand binding and do not detect two different types of metabolites. In contrast, both riboswitches respond independently to TPP and are predicted to function in concert to mimic the more "digital" gene control outcome observed when two aptamers bind ligands cooperatively. Our findings further demonstrate that simple gene control elements made only of RNA can be assembled in different architectures to yield more complex gene control outcomes.

A Korean female patient with thiamine-responsive pyruvate dehydrogenase complex deficiency due to a novel point mutation (Y161C)in the PDHA1 gene

Pyruvate dehydrogenase complex (PDHC) deficiency is mostly due to mutations in the X-linked E1alpha subunit gene (PDHA1). Some of the patients with PDHC deficiency showed clinical improvements with thiamine treatment. We report the results of biochemical and molecular analysis in a female patient with lactic acidemia. The PDHC activity was assayed at different concentrations of thiamine pyrophosphate (TPP). The PDHC activity showed null activity at low TPP concentration (1 x 10(-3) mM), but significantly increased at a high TPP concentration (1 mM). Sequencing analysis of PDHA1 gene of the patient revealed a substitution of cysteine for tyrosine at position 161 (Y161C). Thiamine treatment resulted in reduction of the patient's serum lactate concentration and dramatic clinical improvement. Biochemical, molecular, and clinical data suggest that this patient has a thiamine-responsive PDHC deficiency due to a novel mutation, Y161C. Therefore, to detect the thiamine responsiveness it is necessary to measure activities of PDHC not only at high but also at low concentration of TPP.

Metabolite-binding RNA domains are present in the genes of eukaryotes

Genetic control by metabolite-binding mRNAs is widespread in prokaryotes. These riboswitches are typically located in noncoding regions of mRNA, where they selectively bind their target compound and subsequently modulate gene expression. We have identified mRNA elements in fungi and in plants that match the consensus sequence and structure of thiamine pyrophosphate-binding domains of prokaryotes. In Arabidopsis, the consensus motif resides in the 3'-UTR of a thiamine biosynthetic gene, and the isolated RNA domain binds the corresponding coenzyme in vitro. These results suggest that metabolite-binding mRNAs are possibly involved in eukaryotic gene regulation and that some riboswitches might be representatives of an ancient form of genetic control.