HISTOCHEMICAL LOCALIZATION OF CERTAIN OXIDATIVE ENZYMES IN THE RAT TESTIS

The localization and distribution of β-hydroxybutyrate dehydrogenase, succinic dehydrogenase, malic dehydrogenase, and lactic dehydrogenase in the rat testis have been studied histochemically. Intense enzyme activity in the interstitium as well as tubules was observed. However, malic dehydrogenase was found to be more active in the interstitium than in the tubules. The distribution pattern of enzyme activity appeared in four different phases in the seminiferous tubules corresponding to the gradient in the spermatogenetic wave, thereby indicating a metabolic adaptation at subcellular level.

Paragangliomas in patients with mutations of the SDHD gene

OBJECTIVE:

Paragangliomas represent neoplasms of neural crest origin that arise from paraganglia. Mutations in the gene encoding succinate dehydrogenase subunit D (SDHD) are responsible for a percentage of hereditary paragangliomas. We previously described a group of 271 pheochromocytoma patients, 11 of whom had mutations of the SDHD gene. The objective of this study was to find out whether those 11 patients had additional paragangliomas.

STUDY DESIGN:

Ten patients participated in our clinical screening program that included MRI of the skull base and neck, thorax, and abdomen, as well as an 18Fluoro-DOPA positron emission tomography (DOPA-PET).

RESULTS:

Five patients presented with head and neck paragangliomas, 1 patient with a thoracic paraganglioma, and 2 patients with intraabdominal paragangliomas.

CONCLUSIONS:

The screening for paragangliomas in patients with mutations of the SDHD gene offers the chance to diagnose those tumors in an early stage.

SIGNIFICANCE:

Because morbidity after surgical resection increases with tumor size, early surgery will minimize the potential risks.

Neuroprotective activities of curcumin and quercetin with potential relevance to mitochondrial dysfunction induced by oxaliplatin

Peripheral neurotoxicity is one of the serious dose-limiting side effects of oxaliplatin (Oxa) when used in the treatment of malignant conditions. It is documented that it elicits major side effects specifically neurotoxicity due to oxidative stress forcing the patients to limit its clinical use in long-term treatment. Oxidative stress has been proven to be involved in Oxa-induced toxicity including neurotoxicity. The mitochondria have recently emerged as targets for anticancer drugs in various kinds of toxicity including neurotoxicity that can lead to neoplastic disease. However, there is paucity of literature involving the role of the mitochondria in mediating Oxa-induced neurotoxicity and its underlying mechanism is still debatable. The purpose of this study was to investigate the dose-dependent damage caused by Oxa on isolated brain mitochondria under in vitro conditions. The study was also designed to investigate the neuroprotective effects of nutraceuticals, curcumin (CMN), and quercetin (QR) on Oxa-induced mitochondrial oxidative stress and respiratory chain complexes in the brain of rats. Oxidative stress biomarkers, levels of nonenzymatic antioxidants, activities of enzymatic antioxidants, and mitochondrial complexes were evaluated against the neurotoxicity induced by Oxa. Pretreatment with CMN and QR significantly replenished the mitochondrial lipid peroxidation levels and protein carbonyl content induced by Oxa. CMN and QR ameliorated altered nonenzymatic and enzymatic antioxidants and complex enzymes of mitochondria. We conclude that CMN and QR, by attenuating oxidative stress as evident by mitochondrial dysfunction, hold promise as agents that can potentially reduce Oxa-induced adverse effects in the brain.

[Gastrointestinal stromal tumor (GIST): advances in 2013]

Gastrointestinal stromal tumors (GIST) are currently regarded as a heterogenous group of tumors sharing common histological appearance, KIT immunopositivity and supposed origin from tissue progenitor cells capable of differentiation into the phenotype of Cajal interstitial cells. GISTs can be divided according to immunoexpression of the beta subunit of mitochondrial enzyme succinate dehydrogenase (SDHB) to SDHB-positive (encompassing KIT, PDGFRA and NF1 mutated GISTs), and SDHB-deficient GISTs (including Carney-Stratakis syndrome, Carney triad, sporadic pediatric GISTs, and a small subset of sporadic adult GISTs). The individual molecular subtypes differ in biological behavior and in their response to systemic targeted therapy, which is indicated in metastatic GISTs or in tumors with high risk of recurrence. Although several risk-stratification classifications have been developed, strictly defined criteria to identify patients at risk are still lacking. Pharmacogenomics have been successful in designing drugs to overcome not only the primary resistance of GISTs to the action of imatinib (e.g. GISTs with a substitution of Asp842Val in exon 18 PDGFRA or SDHB-deficient GISTs), but also the secondary resistance caused by secondary mutation of a gene encoding either the receptor tyrosine kinase or other molecules involved in the respective signalling cascade. Future directions concentrate on rational molecular targeting for systemic therapy based on complex genetic investigation of the tumor. Peripheral blood is planned to be used as a source of information for genetic events responsible for the secondary resistance of metastatic tumors.

Comparative analysis of changes of myocardial angiogenesis and energy metabolism in postinfarction and diabetic damage of rat heart

Comparative study of changes in myocardial activity of lactate dehydrogenase (LDH), succinate dehydrogenase (SDH), and capillary density distribution in the experimental models of diabetic and postinfarction damage of rat heart was performed. Data showed that decrease in LDH and SDH activities was observed in both pathologies which can suggest abnormal processes of glycolysis and oxidative phosphorylation in cardiac mitochondria. Activity of LDH and SDH in combined pathologies was comparative with the corresponding values of these parameters in control group. The authors hypothesize that these differences can be caused by specifics of myocardial vascularization. The results of the study showed that an increase in capillary density was found in all groups of rats with pathologies compared with control group. However, no significant differences in the intensity of angiogenesis processes were found between groups with pathologies.

DNA microarray gene expression profile of Mycobacterium tuberculosis when exposed to osthole

Tuberculosis (TB), affecting one-third of the global population, kills an estimated two to three million people every year. The development of drug resistance is becoming a serious threat to any attempt to control this disease, which underscores the need for new agents targeting Mycobacterium tuberculosis (M. tuberculosis). Osthole (7-methoxy-8-isopentenoxycoumarin) is a coumarin derivative present in many medicinal plants. Previous studies have shown that osthole possesses antimycobacterial effects, however, the action mechanism of osthole is unclear. In the study, we used a commercial oligonucleotide microarray to determine the overall transcriptional response of M. tuberculosis H37Rv triggered by exposure to osthole. Analysis of the microarray data revealed that a total of 478 genes were differentially regulated by osthole. Of these, 241 genes were upregulated, and 237 genes were downregulated. Some of the important genes that were significantly regulated are related to different pathways such as fumarate reductase, class I peroxidase, cell wall, nitrate respiration, and protein synthesis. Real-time quantitative RT-PCR was performed for chosen genes to validate the microarray results. To our knowledge, this genome-wide transcriptomics approach has produced the first insights into the response of M. tuberculosis when exposed to osthole.

[The mutations of germline succinate dehydrogrnase subunit B (SDHB) in sporadic paragangliomas]

PURPOSE

The purpose of this study was to investigate the somatic mutations of human mitochondria succinate dehydrogenase subunit B (SDHB) in sporadic paragangliomas.

METHODS

Eight exons of SDHB gene in 8 sporadic paragangliomas cases were amplified by PCR and sequenced, respectively. The sequences were analyzed to find mutations compared with human homology sequence in Genebank and SNP database.

RESULTS

Nine sequence variations were found in 8 cases, in which one mutation was found in one case (1/8, 12.5%). The mutation was identified as the sixty four base pair in exon 2 of SDHB(c.136C>T), resulting in a change from a arginine to a stop codon (p.Arg90X). The left 8 variations were polymorphisms.

CONCLUSIONS

The mutation of SDHB exists in sporadic paragangliomas patients and it might play a significant role in paragangliomas tumorigenesis.

Mitochondrial targeting of vitamin E succinate enhances its pro-apoptotic and anti-cancer activity via mitochondrial complex II

Mitochondrial complex II (CII) has been recently identified as a novel target for anti-cancer drugs. Mitochondrially targeted vitamin E succinate (MitoVES) is modified so that it is preferentially localized to mitochondria, greatly enhancing its pro-apoptotic and anti-cancer activity. Using genetically manipulated cells, MitoVES caused apoptosis and generation of reactive oxygen species (ROS) in CII-proficient malignant cells but not their CII-dysfunctional counterparts. MitoVES inhibited the succinate dehydrogenase (SDH) activity of CII with IC(50) of 80 μM, whereas the electron transfer from CII to CIII was inhibited with IC(50) of 1.5 μM. The agent had no effect either on the enzymatic activity of CI or on electron transfer from CI to CIII. Over 24 h, MitoVES caused stabilization of the oxygen-dependent destruction domain of HIF1α fused to GFP, indicating promotion of the state of pseudohypoxia. Molecular modeling predicted the succinyl group anchored into the proximal CII ubiquinone (UbQ)-binding site and successively reduced interaction energies for serially shorter phytyl chain homologs of MitoVES correlated with their lower effects on apoptosis induction, ROS generation, and SDH activity. Mutation of the UbQ-binding Ser(68) within the proximal site of the CII SDHC subunit (S68A or S68L) suppressed both ROS generation and apoptosis induction by MitoVES. In vivo studies indicated that MitoVES also acts by causing pseudohypoxia in the context of tumor suppression. We propose that mitochondrial targeting of VES with an 11-carbon chain localizes the agent into an ideal position across the interface of the mitochondrial inner membrane and matrix, optimizing its biological effects as an anti-cancer drug.

[Research advances in molecular biology of carotid body tumor]

The carotid body (CB) is a highly specialized small organ located at the bifurcation of the common carotid artery in the neck and plays an important role in acute adaptation to hypoxia, which is the most common tumor site in head and neck paragangliomas. Although carotid body tumors (CBTs) are mostly slow-growing and benign, they can cause significant morbidity because of their proximity to major arteries and nerves in the head and neck. CBTs can be caused by a genetic predisposition and by chronic hypoxic stimulation. Currently, inactivating germline mutations in the mitochondrial complex II subunits SDHB, SDHC, and SDHD have been identified as genetic risk factors for CB tumors (CBTs). Another locus at chromosome 11q13, identified by linkage analysis in a single family, may harbor a fourth susceptibility gene. This paper highlights the recent research advances in etiologic mechanism of molecular biological aspect of CBT.