Mutations in human lipoyltransferase gene <Emphasis Type="Italic">LIPT1</Emphasis>cause a Leigh disease with secondary deficiency for pyruvate and alpha-ketoglutarate dehydrogenase

Background

Synthesis and apoenzyme attachment of lipoic acid have emerged as a new complex metabolic pathway. Mutations in several genes involved in the lipoic acid de novo pathway have recently been described (i.e., LIAS, NFU1, BOLA3, IBA57), but no mutation was found so far in genes involved in the specific process of attachment of lipoic acid to apoenzymes pyruvate dehydrogenase (PDHc), α-ketoglutarate dehydrogenase (α-KGDHc) and branched chain α-keto acid dehydrogenase (BCKDHc) complexes.

Methods

Exome capture was performed in a boy who developed Leigh disease following a gastroenteritis and had combined PDH and α-KGDH deficiency with a unique amino acid profile that partly ressembled E3 subunit (dihydrolipoamide dehydrogenase / DLD) deficiency. Functional studies on patient fibroblasts were performed. Lipoic acid administration was tested on the LIPT1 ortholog lip3 deletion strain yeast and on patient fibroblasts.

Results

Exome sequencing identified two heterozygous mutations (c.875C?>?G and c.535A?>?G) in the LIPT1 gene that encodes a mitochondrial lipoyltransferase which is thought to catalyze the attachment of lipoic acid on PDHc, α-KGDHc, and BCKDHc. Anti-lipoic acid antibodies revealed absent expression of PDH E2, BCKDH E2 and α-KGDH E2 subunits. Accordingly, the production of ¹⁴CO₂ by patient fibroblasts after incubation with ^14Cglucose, ^14Cbutyrate or ^14C3OHbutyrate was very low compared to controls. cDNA transfection experiments on patient fibroblasts rescued PDH and α-KGDH activities and normalized the levels of pyruvate and 3OHbutyrate in cell supernatants. The yeast lip3 deletion strain showed improved growth on ethanol medium after lipoic acid supplementation and incubation of the patient fibroblasts with lipoic acid decreased lactate level in cell supernatants.

Conclusion

We report here a putative case of impaired free or H protein-derived lipoic acid attachment due to LIPT1 mutations as a cause of PDH and α-KGDH deficiencies. Our study calls for renewed efforts to understand the mechanisms of pathology of lipoic acid-related defects and their heterogeneous biochemical expression, in order to devise efficient diagnostic procedures and possible therapies.

     

Design,synthesis, anticancer evaluation,and molecular modelling studies of novel tolmetin derivatives as potential VEGFR-2 inhibitors and apoptosis inducers

Novel tolmetin derivatives 5a–f to 8a–c were designed, synthesised, and evaluated for antiproliferative activity by NCI (USA) against a panel of 60 tumour cell lines. The cytotoxic activity of the most active tolmetin derivatives 5b and 5c was examined against HL-60, HCT-15, and UO-31 tumour cell lines. Compound 5b was found to be the most potent derivative against HL-60, HCT-15, and UO-31 cell lines with IC₅₀ values of 10.32 ± 0.55, 6.62 ± 0.35, and 7.69 ± 0.41 µM, respectively. Molecular modelling studies of derivative 5b towards the VEGFR-2 active site were performed. Compound 5b displayed high inhibitory activity against VEGFR-2 (IC₅₀ = 0.20 µM). It extremely reduced the HUVECs migration potential exhibiting deeply reduced wound healing patterns after 72 h. It induced apoptosis in HCT-15 cells (52.72-fold). This evidence was supported by an increase in the level of apoptotic caspases-3, -8, and -9 by 7.808-, 1.867-, and 7.622-fold, respectively. Compound 5b arrested the cell cycle in the G0/G1 phase. Furthermore, the ADME studies showed that compound 5b possessed promising pharmacokinetic properties.     

The lectin concanavalin-A signals MT1-MMP catalytic independent induction of COX-2 through an IKKγ/NF-κB-dependent pathway

The lectin from Canavalia ensiformis (Concanavalin-A, ConA), one of the most abundant lectins known, enables one to mimic biological lectin/carbohydrate interactions that regulate extracellular matrix protein recognition. As such, ConA is known to induce membrane type-1 matrix metalloproteinase (MT1-MMP) which expression is increased in brain cancer. Given that MT1-MMP correlated to high expression of cyclooxygenase (COX)-2 in gliomas with increasing histological grade, we specifically assessed the early proinflammatory cellular signaling processes triggered by ConA in the regulation of COX-2. We found that treatment with ConA or direct overexpression of a recombinant MT1-MMP resulted in the induction of COX-2 expression. This increase in COX-2 was correlated with a concomitant decrease in phosphorylated AKT suggestive of cell death induction, and was independent of MT1-MMP’s catalytic function. ConA- and MT1-MMP-mediated intracellular signaling of COX-2 was also confirmed in wild-type and in Nuclear Factor-kappaB (NF-κB) p65^−/− mutant mouse embryonic fibroblasts (MEF), but was abrogated in NF-κB1 (p50)^−/− and in I kappaB kinase (IKK) γ^−/− mutant MEF cells. Collectively, our results highlight an IKK/NF-κB-dependent pathway linking MT1-MMP-mediated intracellular signaling to the induction of COX-2. That signaling pathway could account for the inflammatory balance responsible for the therapy resistance phenotype of glioblastoma cells, and prompts for the design of new therapeutic strategies that target cell surface carbohydrate structures and MT1-MMP-mediated signaling. Concise summary Concanavalin-A (ConA) mimics biological lectin/carbohydrate interactions that regulate the proinflammatory phenotype of cancer cells through yet undefined signaling. Here we highlight an IKK/NF-κB-dependent pathway linking MT1-MMP-mediated intracellular signaling to the induction of cyclooxygenase-2, and that could be responsible for the therapy resistance phenotype of glioblastoma cells.     

Design, synthesis, and biological evaluation of dibromotyrosine analogues inspired by marine natural products as inhibitors of human prostate cancer proliferation, invasion, and migration

Bioactive secondary metabolites originating from dibromotyrosine are common in marine sponges, such as sponges of the Aplysina species. Verongiaquinol (1), 3,5-dibromo-1-hydroxy-4-oxocyclohexa-2,5-diene-1-acetamide, and aeroplysinin-1 are examples of such bioactive metabolites. Previous studies have shown the potent antimicrobial as well as cytotoxic properties of verongiaquinol and the anti-angiogenic activity of aeroplysinin-1. The work presented herein shows the design and synthesis of dibromotyrosine-inspired phenolic ester and ether analogues with anti-angiogenic, anti-proliferative and anti-migratory properties and negligible cytotoxicity. Several analogues were synthesized based on docking experiments in the ATP binding site of VEGFR2 and their anti-angiogenic potential and ability to inhibit angiogenesis and prostate cancer proliferation, migration and invasion were evaluated using the chick chorioallantoic membrane (CAM) assay, MTT, wound-healing, and Cultrex® BME cell invasion assay models, respectively. Analogues with high docking scores showed promising anti-angiogenic activity in the CAM assay. In general, ester analogues (5, 6, and 8–10) proved to be of higher anti-migratory activity whereas ether analogues (11–14) showed better anti-proliferative activity. These results demonstrate the potential of dibromotyrosines as promising inhibitory scaffolds for the control of metastatic prostate cancer proliferation and migration.     

Synthesis of novel 4-substituted-7-trifluoromethylquinoline derivatives with nitric oxide releasing properties and their evaluation as analgesic and anti-inflammatory agents

Six derivatives of the general formula 2- or 4-(7-trifluoromethylquinolin-4-ylamino) benzoic acid N'-(nitrooxyacetyl or propionyl) hydrazide and an oxime of the formula 1-[4-(7-trifluoromethylquinolin-4-ylamino)phenyl]ethanone oxime were synthesized and tested for their in vivo anti-inflammatory, analgesic, and ulcerogenic properties, as well as their in vitro nitric oxide release ability. Compound 2-(7-trifluoromethylquinolin-4-ylamino)benzoic acid N'-(2-nitrooxy propionyl)hydrazide 12 showed an anti-inflammatory activity comparable to that of indomethacin in the carrageenan-induced rat paw edema test, and equipotency to glafenine in the acetic acid mice induced writhing model at 100mg/kg p.o., respectively. All the final compounds showed no tendency to induce stomach ulceration in rats; nitric oxide seems to contribute to their excellent safety profile.     

Microextraction of bacterial lipid A: easy and rapid method for mass spectrometric characterization

Endotoxins (lipopolysaccharides) are the main components of Gram-negative bacterial outer membranes. A quick and simple way to isolate their lipid region (lipid A) directly from whole bacterial cells was devised. This method using hot ammonium-isobutyrate solvent was applied to small quantities of cells and proved to be indispensable when a rapid characterization of lipid A structure by mass spectrometry was required. Biological activities of endotoxins are directly related to the lipid A structures, which vary greatly with cell growth conditions. This method is suitable for rough- and smooth-type bacteria and very efficient for screening variations in lipid A structures. Data are acquired in a few hours and avoid the use of phenol in extraction.     

Pantoprazole attenuates tumorigenesis via inhibition of exosomal secretion in a rat model of hepatic precancerous lesion induced by diethylnitrosamine and 2-acetamidofluorene

The present study aimed to evaluate the potential therapeutic effect of pantoprazole, a proton-pump inhibitor, on precancerous lesion (PCL) in rats. diethylnitrosamine and 2-acetylaminofluorene were used to induce PCL in rats, in vivo. The rats were treated with three doses of pantoprazole (100, 50, and 25  mg/kg; three times weekly) during the last 4 weeks of the total 10 weeks of the experiment. Blood and liver tissue samples were collected for measurement of the exosomal abundance and exosomal competing endogenous RNA markers. Results revealed that pantoprazole administration had an ameliorating effect on liver function tests and microscopic features of the liver; and decreased exosome abundance in the liver tissue samples and sera of the rats. Meanwhile, the treatment also resulted in a dose-dependent decrease in exosomal RAB11A mRNA and long noncoding RNA RP11-513I15.6, which is an important participant in th exosomal secretion process with an increase in exosomal miRNA-1262. Based on these results, we postulated that pantoprazole has the potential to attenuate liver tumorigenesis in this rat model.