Dehydroepiandrosterone ameliorates H2O2-induced Leydig cells oxidation damage and apoptosis through inhibition of ROS production and activation of PI3K/Akt pathways

Dehydroepiandrosterone (DHEA) is widely used as a nutritional supplement, and administration of DHEA produces a number of beneficial effects in the elderly. Many researchers have suggested that DHEA exerts it function after conversion into more biologically active hormones in peripheral target cells. The actions of DHEA in Leydig cells, a major target cell of DHEA biotransformation in males, are not clear. The present study found that DHEA increased cell viability and decreased reactive oxygen species (ROS) and malondialdehyde contents in H₂O₂-induced Leydig cells. DHEA significantly increased the activities of superoxide dismutase, catalase and peroxidase, and decreased the DNA damage in H₂O₂-induced Leydig cells. Apoptosis was significant decreased in H₂O₂-induced Leydig cells after DHEA treatment. DHEA inhibited the loss of mitochondrial membrane potential (ΔΨm) and the upregulation of the caspase-3 protein level induced by H₂O₂ in Leydig cells. DHEA also reversed the decrease in PI3K and p-Akt protein levels induced by H₂O₂. These data showed that DHEA could ameliorate H₂O₂-induced oxidative damage by increasing anti-oxidative enzyme activities, which resulted in reduced ROS content, and decreased apoptosis, mainly by preventing the loss of ΔΨm and inhibiting caspase-3 protein levels via activation of PI3K/Akt signaling pathways. These results increase our understanding of the molecular mechanism of the anti-ageing effect of DHEA.     

Foreword: Mitochondrial Medicine

Mitochondrion is currently known to play major roles in many disease processes: neuromuscular disorders, neurodegenerative conditions (i.e. Parkinson’s and Alzheimer’s diseases), diabetes mellitus, aging, programmed cell death, and carcinogenesis, to name a few. In this background, the Department of Neuroscience of the University of Pisa (Italy) has organised a scientific meeting on October 25th, 2006, to discuss recent progress in the field of mitochondriology.     

Evolutionary perspectives on the links between mitochondrial genotype and disease phenotype

Background

Disorders of the mitochondrial respiratory chain are heterogeneous in their symptoms and underlying genetics. Simple links between candidate mutations and expression of disease phenotype typically do not exist. It thus remains unclear how the genetic variation in the mitochondrial genome contributes to the phenotypic expression of complex traits and disease phenotypes.

Scope of review

I summarize the basic genetic processes known to underpin mitochondrial disease. I highlight other plausible processes, drawn from the evolutionary biological literature, whose contribution to mitochondrial disease expression remains largely empirically unexplored. I highlight recent advances to the field, and discuss common-ground and -goals shared by researchers across medical and evolutionary domains.

Major conclusions

Mitochondrial genetic variance is linked to phenotypic variance across a variety of traits (e.g. reproductive function, life expectancy) fundamental to the upkeep of good health. Evolutionary theory predicts that mitochondrial genomes are destined to accumulate male-harming (but female-friendly) mutations, and this prediction has received proof-of-principle support. Furthermore, mitochondrial effects on the phenotype are typically manifested via interactions between mitochondrial and nuclear genes. Thus, whether a mitochondrial mutation is pathogenic in effect can depend on the nuclear genotype in which is it expressed.

General significance

Many disease phenotypes associated with OXPHOS malfunction might be determined by the outcomes of mitochondrial–nuclear interactions, and by the evolutionary forces that historically shaped mitochondrial DNA (mtDNA) sequences. Concepts and results drawn from the evolutionary sciences can have broad, but currently under-utilized, applicability to the medical sciences and provide new insights into understanding the complex genetics of mitochondrial disease. This article is part of a Special Issue entitled Frontiers of Mitochondrial Research.     

Quantification of cellular protein expression and molecular features of group 3 LEA proteins from embryos of Artemia franciscana

Late embryogenesis abundant (LEA) proteins are highly hydrophilic, low complexity proteins whose expression has been correlated with desiccation tolerance in anhydrobiotic organisms. Here, we report the identification of three new mitochondrial LEA proteins in anhydrobiotic embryos of Artemia franciscana, AfrLEA3m_47, AfrLEA3m_43, and AfrLEA3m_29. These new isoforms are recognized by antibody raised against recombinant AfrLEA3m, the original mitochondrial-targeted LEA protein previously reported from these embryos; mass spectrometry confirms all four proteins share sequence similarity. The corresponding messenger RNA (mRNA) species for the four proteins are readily amplified from total complementary DNA (cDNA) prepared from embryos. cDNA sequences of the four mRNAs are quite similar, but each has a stretch of sequence that is absent in at least one of the others, plus multiple single base pair differences. We conclude that all four mitochondrial LEA proteins are products of independent genes. Each possesses a mitochondrial targeting sequence, and indeed Western blots performed on extracts of isolated mitochondria clearly detect all four isoforms. Based on mass spectrometry and sodium dodecyl sulfate polyacrylamide gel electrophoresis migration, the cytoplasmic-localized AfrLEA2 exists primarily as a homodimer in A. franciscana. Quantification of protein expression for AfrLEA2, AfrLEA3m, AfrLEA3m_43, and AfrLEA3m_29 as a function of development shows that cellular concentrations are highest in diapause embryos and decrease during development to low levels in desiccation-intolerant nauplius larvae. When adjustment is made for mitochondria matrix volume, the effective concentrations of cytoplasmic versus mitochondrial group 3 LEA proteins are similar in vivo, and the values provide guidance for the design of in vitro functional studies with these proteins.     

Phylogenetic and structural analyses of the oxa1 family of protein translocases

Mitochondrial Oxa1p homologs have been shown to function in protein export and membrane insertion in bacteria, mitochondria and chloroplasts, but their mode of action, organismal distribution and evolutionary origins are poorly understood. All sequenced homologs of Oxa1p were retrieved from the databases and multiply aligned. All organisms with a fully sequenced genome possess at least one Oxa1p homolog showing that the family is truly ubiquitous. Most prokaryotes possess just one Oxa1p homolog, but several Gram-positive bacteria and one archaeon possess two, and eukaryotes may have as many as six. Although these proteins vary in length over a 5-fold range, they exhibit a common hydrophobic core region of about 200 residues. Multiple sequence alignments reveal conserved residues and provide the basis for structural and phylogenetic analyses that serve to characterize the Oxa1 family.     

Origins, evolutionary history, and taxonomic distribution of alternative oxidase and plastoquinol terminal oxidase

Alternative oxidase (AOX) and plastoquinol terminal oxidase (PTOX) are related quinol oxidases associated with respiratory and photosynthetic electron transport chains, respectively. Contrary to previous belief, AOX is present in numerous animal phyla, as well as heterotrophic and marine phototrophic proteobacteria. PTOX appears limited to organisms capable of oxygenic photosynthesis, including cyanobacteria, algae and plants. We propose that both oxidases originated in prokaryotes from a common ancestral di-iron carboxylate protein that diversified to AOX within ancient proteobacteria and PTOX within ancient cyanobacteria. Each then entered the eukaryotic lineage separately; AOX by the endosymbiotic event that gave rise to mitochondria and later PTOX by the endosymbiotic event that gave rise to chloroplasts. Both oxidases then spread through the eukaryotic domain by vertical inheritance, as well as by secondary and potentially tertiary endosymbiotic events.     

The Miro GTPases: At the heart of the mitochondrial transport machinery

Mitochondria are organelles of elaborate structure that in addition to supplying cellular energy, have significant roles in calcium homeostasis and apoptosis. Failure to maintain mitochondrial dynamics results in neurodegenerative diseases and neuromuscular pathologies. The Miro GTPases, which constitute a unique subgroup of the Ras superfamily, have emerged as essential regulators of mitochondrial morphogenesis and trafficking along microtubules. Miro GTPases function as calcium-dependent sensors in the control of mitochondrial motility. Increased awareness of the biological function of Miro GTPases can contribute to elucidate the molecular mechanisms underlying diseases caused by deregulated mitochondrial dynamics.     

One simple,rapid and economical method for ploidy detection of Trichogramma dendrolimi Matsumura (Hymenoptera Trichogrammatidae)

Ploidy diversity provides valuable scientific information, thus making the detection technique of ploidy important. However, traditional methods of cytological observation and flow cytometry are either laborious or expensive. We here report a simple and rapid, effective and economical quantitative PCR (qPCR) approach to determine the ploidy of a parasitoid species Trichogramma dendrolimi Matsumura, an economically important biocontrol agent. We applied a mitochondrial gene cytochrome oxidase (COI) and a nuclear gene forkhead to evaluate the mitochondrial number per nuclear copy in a thelytokous Wolbachia-infected strain of T. dendrolimi and its bisexual uninfected counterparts. The 2^−ΔCq values calculated from C_q values which resulted from qPCR experiments were significantly larger in haploid males than that in diploid females. Haploid males possessed about 2.69 times mitochondrial number per nuclear copy as diploid females. Not a single significant difference was found between diploid females from thelytokous and bisexual strains. Based on the differences in relative mitochondrial content, we were allowed to distinguish between haploid males and diploid females. Moreover, the number of mitochondria significantly decreased with higher ploidy level but was not affected by Wolbachia-infection. Our study supplied an available tool to investigate the ploidy diversity in sex determination of T. dendrolimi and thelytokous manipulation of Wolbachia, which is the crucial step to further study their underlying mechanisms. This will in turn contribute to the biocontrol efficiency by enhancing the female production and hence the parasitism rate.