Association studies on human mitochondrial DNA: methodological aspects and results in the most common age-related diseases

Mitochondrial DNA (mtDNA) follows direct maternal inheritance and, as such, can be used in phylogenetic studies to determine a human lineage tree. The presence of common polymorphisms allows a classification of mtDNA in haplogroups and sub-haplogroups, according to the branch they belong to. Thanks to the rapidly growing number of mtDNA sequences available, this classification is being corrected and redefined to be more accurate. In parallel with this process, several studies are trying to identify an association between common mtDNA polymorphisms and common complex traits, as hypothesized by the common disease-common variant theory. Here we review the associations already reported with the main age-related complex diseases and we identify the critical points (sample size, size of the recruiting area, careful matching between cases and controls regarding geographical origin and ethnicity, data quality checking) to be taken in account in planning such studies. On the whole, this research area is opening a new perspective as an important component of "mitochondrial medicine", capable of identifying new molecular targets for the diagnosis, prevention and treatment of common complex diseases.     

Caspase-independent Mitochondrial Cell Death Results from Loss of Respiration,Not Cytotoxic Protein Release

In apoptosis, mitochondrial outer membrane permeabilization (MOMP) triggers caspase-dependent death. However, cells undergo clonogenic death even if caspases are blocked. One proposed mechanism involved the release of cytotoxic proteins (e.g., AIF and endoG) from mitochondria. To initiate MOMP directly without side effects, we created a tamoxifen-switchable BimS fusion protein. Surprisingly, even after MOMP, caspase-inhibited cells replicated DNA and divided for ∼48 h before undergoing proliferation arrest. AIF and endoG remained in mitochondria. However, cells gradually lost mitochondrial membrane potential and ATP content, and DNA synthesis slowed to a halt by 72 h. These defects resulted from a partial loss of respiratory function, occurring 4–8 h after MOMP, that was not merely due to dispersion of cytochrome c. In particular, Complex I activity was completely lost, and Complex IV activity was reduced by ∼70%, whereas Complex II was unaffected. Later, cells exhibited a more profound loss of mitochondrial protein constituents. Thus, under caspase inhibition, MOMP-induced clonogenic death results from a progressive loss of mitochondrial function, rather than the release of cytotoxic proteins from mitochondria.     

Anti-Apoptotic Genes in the Survival of Monocytic Cells During Infection

Macrophages are cells of the immune system that protect organisms against invading pathogens by fulfilling critical roles in innate and adaptive immunity and inflammation. They originate from circulating monocytes and show a high degree of heterogeneity, which reflects the specialization of function given by different anatomical locations. Differentiation of monocytes towards a macrophage phenotype is also accompanied by an increase of resistance against various apoptotic stimuli, a required characteristic that allows macrophages to accomplish their function in a stressful environment.Apoptosis, a form of programmed cell death, is a tightly regulated process, needed to maintain homeostasis by balancing proliferation with cellular demise. Caspases, a family of cysteine proteases that are highly conserved in multicellular organisms, function as central regulators of apoptosis. FLIP (FLICE-inhibitory protein), anti-apoptotic members of the Bcl2 family and inhibitors of apoptosis (IAP) are the main three groups of anti-apoptotic genes that counteract caspase activation through both the extrinsic and intrinsic apoptotic pathways.Modulation of the apoptotic machinery during viral and bacterial infections, as well as in various malignancies, is a wellestablished mechanism that promotes the survival of affected cells. The involvement of anti-apoptotic genes in the survival of monocytes/macrophages, either physiological or pathological, will be described in this review. How viral and bacterial infections that target cells of the monocytic lineage affect the expression of anti-apoptotic genes is important in understanding the pathological mechanisms that lead to manifested disease. The latest therapeutic approaches that target anti-apoptotic genes will also be discussed.Key Words: Apoptosis, monocytes/macrophages, HIV, anti-apoptotic genes, tuberculosis.     

Immunoproteasome LMP2 60HH Variant Alters MBP Epitope Generation and Reduces the Risk to Develop Multiple Sclerosis in Italian Female Population

Background

Albeit several studies pointed out the pivotal role that CD4+T cells have in Multiple Sclerosis, the CD8+ T cells involvement in the pathology is still in its early phases of investigation. Proteasome degradation is the key step in the production of MHC class I-restricted epitopes and therefore its activity could be an important element in the activation and regulation of autoreactive CD8+ T cells in Multiple Sclerosis.

Methodology/Principal Findings

Immunoproteasomes and PA28-αβ regulator are present in MS affected brain area and accumulated in plaques. They are expressed in cell types supposed to be involved in MS development such as neurons, endothelial cells, oligodendrocytes, macrophages/macroglia and lymphocytes. Furthermore, in a genetic study on 1262 Italian MS cases and 845 controls we observed that HLA-A*02+ female subjects carrying the immunoproteasome LMP2 codon 60HH variant have a reduced risk to develop MS. Accordingly, immunoproteasomes carrying the LMP2 60H allele produce in vitro a lower amount of the HLA-A*0201 restricted immunodominant epitope MBP_111–119.

Conclusion/Significance

The immunoproteasome LMP2 60HH variant reduces the risk to develop MS amongst Italian HLA-A*02+ females. We propose that such an effect is mediated by the altered proteasome-dependent production of a specific MBP epitope presented on the MHC class I. Our observations thereby support the hypothesis of an involvement of immunoproteasome in the MS pathogenesis.     

Quelques considérations sur une possibilité de stimulation biologique du champignon Eremothecium ashbyii

Résumé La variabilité et l'instabilité des caractères biologiques du champignonEremothecium ashbyii, créent des difficultés dans la production industrielle de la riboflavine. Un mélange du miel d'abeille et de la levure-facteurs complexes à des potences multiples sur le métabolisme-permet qu'on obtient des résultats intéressants, par la stimulation de la croissance et la multiplication du microorganisme, répercutées favorablement sur la riboflavinogénèse.

---

Summary The variability and instability of the biological character of the fungusEremothecium ashbyii account for the difficulties encountered in the large scale production of riboflavine. A mixture of honey and yeast — complex factors of many metabolic potencies — has been used and interesting results have been obtained following stimulation of growth and multiplication favourably affecting riboflavinogenesis.

     

GLYCOPROTEINS IN BRAIN TISSUE OF THE O-VARIANT OF GM2 GANGLIOSIDOSIS

Abstract— The dialysableglycopeptide preparation recovered from the glycoproteins in cerebral gray matter of a case of the O-variant form of G_M2 gangliosidosis contained four fold more N -acetylglucosamine and mannose than a similar preparation from normal gray matter. In the O-variant form of G_M2 gangliosidosis, the enzymes β - N -acetylhexosaminidases A and B are missing. A three- and four-fold elevation, respectively, of N -acetylglucosamine and mannose in the dialysable glycopeptide preparation from a case of Tay-Sachs disease (B-variant form of G_M2 gangliosidosis) was noted. The B-variant lacks hexosaminidase A but has ample supplies of hexosaminidase B. The brain level of glycosaminoglycans was not affected in the O- and B-variant forms of G_M2 gangliosidosis.     

Inflammatory and Phagocytic Response to Experimental Campylobacter jejuni Infection in Mice

After intraperitoneal inoculation with Campylobacter jejuni BALB/c, Swiss and DBA mice show a peritoneal inflammatory response of different intensity. Only BALB/c mice have a strong peritoneal response. Simultaneous intraperitoneal inoculation of C. jejuni plus FeCl₃ increase both inflammatory response and phagocytic activity in Swiss mice, without production of diarrhea. Some thermostable compounds of C. jejuni have a very strong chemotactic activity against peritoneal cells of mice, whereas a diffusible, thermolabile and glutaraldehyde-resistant factor has an inhibitory effect over murine peritoneal cell phagocytosis. Bactericidal activity of peritoneal cells increased after in vitro re-challenge with C. jejuni. Bacteremia is present in all the mice strains tested, but the clearance is quick in DBA and slow in BALB/c and Swiss mice. These experiments confirm that in mice, peritoneal non-specific mechanisms of defense, such as macrophages, play an important role in order to control C. jejuni infection.     

Influence of endogenous opioids on atrial natriuretic factor release during exercise in man

To evaluate to what extent opioid secretion in exercise induces the release of atrial natriuretic factor (ANF), six healthy male volunteers who were trained subjects, were submitted to two maximal exercise tests with and without (control) opioid receptor blockade by Naltrexone. Blood samples were drawn before (rest) and after exercise (post-exercise) in order to measure human ANF (alpha h ANF), beta-endorphin, plasma aldosterone concentration (PAC) plasma renin activity (PRA) and adreno-cortico trophic hormone (ATCH) by radio-immunological methods. Expired gas was collected during exercise to measure oxygen consumption. On average, the same maximal oxygen consumption (VO2max) during exercise was reached by all subjects with and without treatment. Plasma ANF level at rest slightly decreased after administration of Naltrexone; the response to physical exercise was significantly reduced by Naltrexone. There was no statistical difference between plasma levels of beta-endorphin, PRA and ACTH at rest nor in the post-exercise situation under the influence of Naltrexone. The PAC increased significantly at rest after Naltrexone administration but there was no statistical difference between both values after exercise. These data demonstrate that: (1) ANF secretion during exercise is influenced by the level of beta-endorphin in the plasma; (2) the possible inhibitory role of ANF on aldosterone secretion during exercise is probably over-ruled by the increase in plasma ACTH and PRA.     

Molecular identification of the advanced third-stage larvae (ADV L3) of Gnathostoma lamothei in Tabasco,Mexico

Advanced third-stage larvae (ADV L₃) of Gnathostoma spp. were collected from the muscle tissue of three species of freshwater fish (i.e., Gobiomorus dormitor, Petenia splendida, and Parachromis managuensis) in Swamps of Centla, Tabasco, Mexico. Nine sequences of the ITS2 of the ribosomal DNA of Gnathostoma spp. were compared with sequences obtained from GenBank for G. binucleatum, G. lamothei, G. miyazakii, G. spinigerum, and G. turgidum. Sequences of the ADV L₃ from P. splendida (Isla Chinal), P. managuensis (Isla Chinal), and of two of the six larvae collected from G. dormitor (Tres Brazos), were identical to that of G. binucleatum (GenBank). Sequences from the other four larvae from G. dormitor (Tres Brazos) are identical to the sequence of G. lamothei (GenBank). This is the first record of the intermediate host of G. lamothei. The only species documented to cause human gnathostomiasis in the Americas is G. binucleatum. Our finding of G. binucleatum, and G. lamothei parasitizing the commercially important fish species, G. dormitor in Centla swamps, indicates the possibility of G. lamothei causing human gnathostomiasis in Mexico as well.