Modulation of the matrix redox signaling by mitochondrial Ca~(2+)

Mitochondria sense,shape and integrate signals,and thus function as central players in cellular signal transduction. Ca2+ waves and redox reactions are two such intracellular signals modulated by mitochondria. Mitochondrial Ca2+ transport is of utmost physio-pathological relevance with a strong impact on metabolism and cell fate. Despite its importance,the molecular nature of the proteins involvedin mitochondrial Ca2+ transport has been revealed only recently. Mitochondrial Ca2+ promotes energy metabolism through the activation of matrix dehydrogenases and downstream stimulation of the respiratory chain. These changes also alter the mitochondrial NAD(P)H/NAD(P)+ ratio,but at the same time will increase reactive oxygen species(ROS) production. Reducing equivalents and ROS are having opposite effects on the mitochondrial redox state,which are hard to dissect. With the recent development of genetically encoded mitochondrial-targeted redoxsensitive sensors,real-time monitoring of matrix thiol redox dynamics has become possible. The discoveries of the molecular nature of mitochondrial transporters of Ca2+ combined with the utilization of the novel redox sensors is shedding light on the complex relation between mitochondrial Ca2+ and redox signals and their impact on cell function. In this review,we describe mitochondrial Ca2+ handling,focusing on a number of newly identified proteins involved in mitochondrial Ca2+ uptake and release. We further discuss our recent findings,revealing how mitochondrial Ca2+ influences the matrix redox state. As a result,mitochondrial Ca2+ is able to modulate the many mitochondrial redox-regulated processes linked to normal physiology and disease.     

Frequency of a natural truncated allele of <Emphasis Type="Italic">MdMLO19</Emphasis> in the germplasm of <Emphasis Type="Italic">Malus domestica</Emphasis>

Podosphaera leucotricha is the causal agent of powdery mildew (PM) in apple. To reduce the amount of fungicides required to control this pathogen, the development of resistant apple cultivars should become a priority. Resistance to PM was achieved in various crops by knocking out specific members of the MLO gene family that are responsible for PM susceptibility (S-genes). In apple, the knockdown of MdMLO19 resulted in PM resistance. However, since gene silencing technologies such as RNAi are perceived unfavorably in Europe, a different approach that exploits this type of resistance is needed. This work evaluates the presence of non-functional naturally occurring alleles of MdMLO19 in apple germplasm. The screening of the re-sequencing data of 63 apple individuals led to the identification of 627 single nucleotide polymorphisms (SNPs) in five MLO genes (MdMLO5, MdMLO7, MdMLO11, MdMLO18, and MdMLO19), 127 of which were located in exons. The T-1201 insertion of a single nucleotide in MdMLO19 caused the formation of an early stop codon, resulting in a truncated protein lacking 185 amino acids, including the calmodulin-binding domain. The presence of the insertion was evaluated in 115 individuals. It was heterozygous in 64 and homozygous in 25. Twelve of the 25 individuals carrying the insertion in homozygosity were susceptible to PM. After barley, pea, cucumber, and tomato, apple would be the fifth species for which a natural non-functional mlo allele has been found.     

Towards xeno-free cultures of human limbal stem cells for ocular surface reconstruction

Isolated limbal epithelial stem cells (LESCs) were cultured with or without a 3T3 murine fibroblast feeder-layer (FL) in 4 different culture media on culture plates or on denuded human amniotic membrane (AM) support and fibrin gel support: (1) control medium supplemented with fetal bovine serum; (2) control medium supplemented with the synthetic serum “XerumFree? XF205” (XF); (3) CnT-20 medium supplemented with “XerumFree? XF205” (CnT-XF) and (4) CnT-20 medium supplemented with human AB serum (CnT-AB). The three xenogeneic media were compared to standard condition (control + FL) and parameters assessed included cell morphology, proliferative potential, number of passages, assessment of clonogenic and abortive colonies, life span, ?Np63α expression and epithelial morphology on AM. During serial cultivation of LESCs, most of the tested xeno-free media supported similar numbers of cell passages, total colony number, cumulative cell doublings (CCD) rates and expression of ?Np63α compared to control. The conditions cultivated with a FL showed a non-statistically significant higher number of cell passages and CCD rates before senescence when compared to the same conditions cultured without FL. Except for the control medium, only XF medium enabled the growth of cells on AM. The expression of ?Np63α was comparable in all the cultures grown onto AM, when compared to the controls on fibrin gel. In conclusion, the xeno-free media enabled LESC culture both on plastic and on denuded human AM. Despite the analyses were carried out in a statistically low number of samples and need re-assessment in a larger cohort, our results suggest that the production of a completely xeno-free LESC graft could be beneficial for future clinical applications.     

Through scaffold modification to 3,5-diaryl-4,5-dihydroisoxazoles: new potent and selective inhibitors of monoamine oxidase B

3,5-Diaryl-4,5-dihydroisoxazoles were synthesized and evaluated as monoamine oxidase (MAO) enzyme inhibitors and iron chelators. All compounds exhibited selective inhibitory activity towards the B isoform of MAO in the nanomolar concentration range. The best performing compound was preliminarily evaluated for its ability to bind iron II and III cations, indicating that neither iron II nor iron III is coordinated. The best compounds racemic mixtures were separated and single enantiomers inhibitory activity evaluated. Furthermore, none of the synthesised compounds exhibited activity towards MAO A. Overall, these data support our hypothesis that 3,5-diaryl-4,5-dihydroisoxazoles are promising scaffolds for the design of neuroprotective agents.     

Hypersensitivity reactions due to black henna tattoos and their components: are the clinical pictures related to the immune pathomechanism?

Hypersensitivity to para-phenylenediamine (PPD) and related compounds induced by temporary black henna tattoos has become a serious health problem worldwide. Different patterns of sensitization with various clinical aspects are described in literature due to PPD associated to henna tattoo and these manifestations are likely correlated with the immunological and dermatological pathomechanisms involved. Henna is the Persian name of the plant Lawsonia inermis, Fam. Lythraceae. It is a woody shrub that grow in regions of North Africa, South Asia, India and Sri Lanka. Nowadays it is rather frequent to see temporary “tattoos” performed with henna. To make tattoos darker and long-lasting PPD has been associated to henna in tattoo drawings mixtures, so obtaining “black henna”. In these years there has been a rise of contact sensitization to PPD and in medical literature an increased number of cases have been reported on temporary henna tattoo application. Here we review the various clinical patterns related to PPD and henna tattoo, to investigate the possible link between clinic-morphological pictures and the immunological response to PPD and henna. The literature underlines that different clinical manifestations are related to black henna containing PPD, and its derivative products may cause delayed-type as well as immediate-type reactions. Further studies are needed to investigate the relationship between clinical and morphological aspects of PPD contact dermatitis and the T cell subsets predominance.     

MAR‐Mediated transgene integration into permissive chromatin and increased expression by recombination pathway engineering

Untargeted plasmid integration into mammalian cell genomes remains a poorly understood and inefficient process. The formation of plasmid concatemers and their genomic integration has been ascribed either to non‐homologous end‐joining (NHEJ) or homologous recombination (HR) DNA repair pathways. However, a direct involvement of these pathways has remained unclear. Here, we show that the silencing of many HR factors enhanced plasmid concatemer formation and stable expression of the gene of interest in Chinese hamster ovary (CHO) cells, while the inhibition of NHEJ had no effect. However, genomic integration was decreased by the silencing of specific HR components, such as Rad51, and DNA synthesis‐dependent microhomology‐mediated end‐joining (SD‐MMEJ) activities. Genome‐wide analysis of the integration loci and junction sequences validated the prevalent use of the SD‐MMEJ pathway for transgene integration close to cellular genes, an effect shared with matrix attachment region (MAR) DNA elements that stimulate plasmid integration and expression. Overall, we conclude that SD‐MMEJ is the main mechanism driving the illegitimate genomic integration of foreign DNA in CHO cells, and we provide a recombination engineering approach that increases transgene integration and recombinant protein expression in these cells. Biotechnol. Bioeng. 2017;114: 384–396. © 2016 The Authors. Biotechnology and Bioengineering published by Wiley Periodicals, Inc.     

Clinical applications of NGF in ocular diseases

Nerve Growth Factor (NGF) and its receptors TrkA and p75 are expressed in physiological states in the anterior and posterior segments of the human eye, where they exert several tissue-specific functions. The roles played by NGF in the homeostasis of the eye and in vision are, therefore, crucial and have been widely investigated both in vitro and in vivo, with growing evidence of an NGF-pathway alteration in several ocular diseases. In this review we describe the functions of NGF in health and diseases states of the eye, and discuss the potential therapeutic effectiveness of NGF in preliminary clinical reports performed in severe ocular diseases unresponsive to any standard treatment. In fact, pharmacodynamic studies showing that NGF administered topically on the ocular surface affects not only the ocular surface but is also able to reach the retina, optic nerve and brain, recently opened new perspectives for the treatment of challenging ocular surface diseases, optic nerve diseases, and degenerative diseases of the retina currently lacking an effective therapy.     

Zinc inhibition of bacterial cytochrome bc(1) reveals the role of cytochrome b E295 in proton release at the Q(o) site

The cytochrome (cyt) bc(1) complex (cyt bc(1)) plays a major role in the electrogenic extrusion of protons across the membrane responsible for the proton motive force to produce ATP. Proton-coupled electron transfer underlying the catalysis of cyt bc(1) is generally accepted, but the molecular basis of coupling and associated proton efflux pathway(s) remains unclear. Herein we studied Zn(2+)-induced inhibition of Rhodobacter capsulatus cyt bc(1) using enzyme kinetics, isothermal titration calorimetry (ITC), and electrochemically induced Fourier transform infrared (FTIR) difference spectroscopy with the purpose of understanding the Zn(2+) binding mechanism and its inhibitory effect on cyt bc(1) function. Analogous studies were conducted with a mutant of cyt b, E295, a residue previously proposed to bind Zn(2+) on the basis of extended X-ray absorption fine-structure spectroscopy. ITC analysis indicated that mutation of E295 to valine, a noncoordinating residue, results in a decrease in Zn(2+) binding affinity. The kinetic study showed that wild-type cyt bc(1) and its E295V mutant have similar levels of apparent K(m) values for decylbenzohydroquinone as a substrate (4.9 ± 0.2 and 3.1 ± 0.4 μM, respectively), whereas their K(I) values for Zn(2+) are 8.3 and 38.5 μM, respectively. The calorimetry-based K(D) values for the high-affinity site of cyt bc(1) are on the same order of magnitude as the K(I) values derived from the kinetic analysis. Furthermore, the FTIR signal of protonated acidic residues was perturbed in the presence of Zn(2+), whereas the E295V mutant exhibited no significant change in electrochemically induced FTIR difference spectra measured in the presence and absence of Zn(2+). Our overall results indicate that the proton-active E295 residue near the Q(o) site of cyt bc(1) can bind directly to Zn(2+), resulting in a decrease in the electron transferring activity without changing drastically the redox potentials of the cofactors of the enzyme. We conclude that E295 is involved in proton efflux coupled to electron transfer at the Q(o) site of cyt bc(1).