Correlation between NADPH oxidase and protein kinase C in the ROS production by human granulocytes related to age

L-Carnitine in Drosophila: A Review

L-Carnitine is an amino acid derivative that plays a key role in the metabolism of fatty acids, including the shuttling of long-chain fatty acyl CoA to fuel mitochondrial β-oxidation. In addition, L-carnitine reduces oxidative damage and plays an essential role in the maintenance of cellular energy homeostasis. L-carnitine also plays an essential role in the control of cerebral functions, and the aberrant regulation of genes involved in carnitine biosynthesis and mitochondrial carnitine transport in Drosophila models has been linked to neurodegeneration. Drosophila models of neurodegenerative diseases provide a powerful platform to both unravel the molecular pathways that contribute to neurodegeneration and identify potential therapeutic targets. Drosophila can biosynthesize L-carnitine, and its carnitine transport system is similar to the human transport system; moreover, evidence from a defective Drosophila mutant for one of the carnitine shuttle genes supports the hypothesis of the occurrence of β-oxidation in glial cells. Hence, Drosophila models could advance the understanding of the links between L-carnitine and the development of neurodegenerative disorders. This review summarizes the current knowledge on L-carnitine in Drosophila and discusses the role of the L-carnitine pathway in fly models of neurodegeneration.

Which factors are associated with sarcopenia and frailty in elderly persons residing in the community?

Abstract Objective: to broaden knowledge about the factors associated with sarcopenia and frailty in elderly persons residing in the community. Method: an integrative systematic review based on the PRISMA recommendations was carried out, using articles published from 2012 to March 2017 in the PubMED, SciELO, Virtual Health Library, CINAHL and Springer electronic databases with the following descriptors: frail elderly, sarcopenia and etiology and their synonyms. The articles identified by the initial search strategy were independently assessed by two researchers, according to the eligibility criteria, and the articles selected were evaluated for methodological quality. Results: the results of this survey show that frailty may be associated with sarcopenia, low serum vitamin D levels, anemia, subclinical hyperthyroidism in men, while the greatest evolution in women was for osteoporosis. An association between sarcopenia and advanced age was also observed, with worsening quality of life, physical-functional capacity, nutritional status and comorbidities, as well as an increased risk of death in sarcopenic elderly persons. Conclusion: this systematic review showed that low serum levels of vitamin D are associated with frailty and factors that predispose this condition. It is therefore important to monitor the serum levels of this vitamin in the elderly population, and it is suggested that new studies are carried out related to supplements of this vitamin in frail elderly persons.

H2O2 accumulation mediates differentiation capacity alteration, but not proliferative decline, in senescent human fetal mesenchymal stem cells

AIMS

Mesenchymal stem cells (MSCs) with multilineage differentiation capacity and immunomodulatory properties are novel sources for cell therapy. However, in vitro expansion of these rare somatic stem cells leads to senescence, resulting in declines of differentiation and proliferative capacities. We therefore investigated the mechanisms mediating senescence in human fetal MSCs termed placenta-derived multipotent cells (PDMCs).

RESULTS

Long-term cultured PDMCs underwent senescence, with increased levels of hydrogen peroxide (H2O2; a reactive oxygen species), positive β-galactosidase staining, decreased sirtuin-1 expression, increased p21 expression, and cell cycle arrest at the G0/G1 phase. Senescent PDMCs also showed decreased osteogenic capacity. Mechanistically, increased p21 expression and proliferative decline were not due to elevated H2O2 levels nor mediated by p53. Instead, inhibition of protein kinase C (PKC)-α and -β in senescent PDMCs decreased p21 expression and reversed cell cycle arrest. H2O2 was involved in the alteration of differentiation potential, since scavenging of H2O2 restored expression of c-MAF, an osteogenic and age-sensitive transcription factor, and osteogenic capacity in senescent PDMCs.

INNOVATION

Our findings not only show the effects of senescence on MSCs, but also reveal mechanisms involved in mediating decreased proliferation and differentiation capacity. Moreover, targeting increased levels of H2O2 associated with senescence may reverse the decreased osteogenic capacity of senescent MSCs.

CONCLUSION

Our study suggests that the two biological consequences of senescence, differentiation alteration, and proliferative decline, in fetal MSCs are distinctly regulated by the H2O2-c-MAF and PKC-p21 pathways, respectively.

Suppression of ROS generation by 4,4-diaminodiphenylsulfone in non-phagocytic human diploid fibroblasts

The action mode of 4,4-diaminodiphenylsulfone (DDS) is still under debate, although it has long been used in treatment of several dermatologic diseases including Hansens disease. In this study, we tested the effect of DDS as an antioxidant on paraquat-induced oxidative stress in non-phagocytic human diploid fibroblasts (HDFs). Overall, preincubation of HDFs with DDS prevented the oxidative stress and the resulting cytotoxic damages caused by paraquat in these cells. The specific effects of DDS in paraquat-treated HDFs are summarized as follows: a) reducing the expression of NADPH oxidase 4 (NOX4) by inhibiting paraquat-induced activation of PKC; b) inhibiting paraquat-induced decreases in mitochondrial complex protein levels as well as in membrane potentials; c) consequently, inhibiting the generation of cytosolic and mitochondrial superoxide anions. Taken together, these findings suggest that DDS would suppress the radical generation in non-phagocytic HDFs during oxidative stress, and that DDS might have the extended potential to be used further in prevention of other oxidative stress-related pathologies.

Phosphorylated extracellular signal-regulated protein kinases 1 and 2 phosphorylate Sp1 on serine 59 and regulate cellular senescence via transcription of p21Sdi1/Cip1/Waf1

Expression of p21(Sdi1) downstream of p53 is essential for induction of cellular senescence, although cancer cell senescence can also occur in the p53 null condition. We report herein that senescence-associated phosphorylated extracellular signal-regulated protein kinases 1 and 2 (SA-pErk1/2) enhanced p21(Sdi1) transcription by phosphorylating Sp1 on Ser(59) downstream of protein kinase C (PKC) alpha. Reactive oxygen species (ROS), which was increased in cellular senescence, significantly activated both PKCalpha and PKCbetaI. However, PKCalpha, but not PKCbetaI, regulated ROS generation and cell proliferation in senescent cells along with activation of cdk2, proven by siRNAs. PKCalpha-siRNA also reduced SA-pErk1/2 expression in old human diploid fibroblast cells, accompanied with changes of senescence phenotypes to young cell-like. Regulation of SA-pErk1/2 was also confirmed by using catalytically active PKCalpha and its DN-mutant construct. These findings strongly suggest a new pathway to regulate senescence phenotypes by ROS via Sp1 phosphorylation between PKCalpha and SA-pErk1/2: employing GST-Sp1 mutants and MEK inhibitor analyses, we found that SA-pErk1/2 regulated Sp1 phosphorylation on the Ser(59) residue in vivo, but not threonine, in cellular senescence, which regulated transcription of p21(Sdi1) expression. In summary, PKCalpha, which was activated in senescent cells by ROS strongly activated Erk1/2, and the SA-pErk1/2 in turn phosphorylated Sp1 on Ser(59). Sp1-enhanced transcription of p21(Sdi1) resulted in regulation of cellular senescence in primary human diploid fibroblast cells.

Malaria circumsporozoite protein inhibits the respiratory burst in Kupffer cells

After transmission by infected mosquitoes, malaria sporozoites rapidly travel to the liver. To infect hepatocytes, sporozoites traverse Kupffer cells, but surprisingly, the parasites are not killed by these resident macrophages of the liver. Here we show that Plasmodium sporozoites and recombinant circumsporozoite protein (CSP) suppress the respiratory burst in Kupffer cells. Sporozoites and CSP increased the intracellular concentration of cyclic adenosyl mono-phosphate (cAMP) and inositol 1,4,5-triphosphate in Kupffer cells, but not in hepatocytes or liver endothelia. Preincubation with cAMP analogues or inhibition of phosphodiesterase also inhibited the respiratory burst. By contrast, adenylyl cyclase inhibition abrogated the suppressive effect of sporozoites. Selective protein kinase A (PKA) inhibitors failed to reverse the CSP-mediated blockage and stimulation of the exchange protein directly activated by cAMP (EPAC), but not PKA inhibited the respiratory burst. Both blockage of the low-density lipoprotein receptor-related protein (LRP-1) with receptor-associated protein and elimination of cell surface proteoglycans inhibited the cAMP increase in Kupffer cells. We propose that by binding of CSP to LRP-1 and cell surface proteoglycans, malaria sporozoites induce a cAMP/EPAC-dependent, but PKA-independent signal transduction pathway that suppresses defence mechanisms in Kupffer cells. This allows the sporozoites to safely pass through these professional phagocytes and to develop inside neighbouring hepatocytes.

Immobilization stress induces cell death through production of reactive oxygen species in the mouse cerebral cortex

Prolonged stress has been shown to impair brain function and increase vulnerability to neuronal injury. To elucidate the in vivo response of neuronal cells to induced stress, we immobilized mice by binding their legs. Levels of reactive oxygen species (ROS) in the cerebral cortex were increased after stress induction. NADPH oxidase, interleukin-1beta (IL-1beta) and cyclooxygenase 2 mRNA (COX-2) expression levels were upregulated, and Fas levels were also increased. The increased expression of these factors was associated with neuronal death, which was confirmed by TUNEL and NeuN staining. OX42 staining was also evident around the TUNEL-stained lesions. From these findings, it appears that immobilization stress induces neuronal death in the mouse cerebral cortex, a process mediated by NADPH oxidase, IL-1beta, COX-2, ROS and Fas. However, this could be inhibited by pretreating the animals with antioxidants such as ebselen or pyrrolidine dithiocarbamate.

Mitochondrial uncoupling proteins: new perspectives for evolutionary ecologists

Reactive oxygen species (ROS)-induced damage on host cells and molecules has been considered the most likely proximal mechanism responsible for the age-related decline in organismal performance. Organisms have two possible ways to reduce the negative effect of ROS: disposing of effective antioxidant defenses and minimizing ROS production. The unbalance between the amount of ROS produced and the availability of antioxidant defenses determines the intensity of so-called oxidative stress. Interestingly, most studies that deal with the effect of oxidative stress on organismal performance have focused on the antioxidant defense compartment and, surprisingly, have neglected the mechanisms that control ROS production within mitochondria. Uncoupling proteins (UCPs), mitochondrial transporters of the inner membrane, are involved in the control of redox state of cells and in the production of mitochondrial ROS. Given their function, UCPs might therefore represent a major mechanistic link between metabolic activity and fitness. We suggest that by exploring the role of expression and function of UCPs both in experimental as well as in comparative studies, evolutionary biologists may gain better insight into this link.

Free Radical Mechanisms of Aging Processes Under Physiological Conditions

Free radical theory of aging predicts crucial role for free radicals produced by external factors (environmental contamination, irradiation, etc.) or pathological disorders (hereditary diseases or infections) in the initiation of aging. Does it mean that under hypothetical completely physiological conditions aging processes could be fully suppressed? To answer this question, we will consider the possible mechanisms of free radical formation in such hypothetical state. There are two major mechanisms, which are responsible for free radical-mediated damage in a living organism: superoxide overproduction by mitochondria and nonenzymatic lipid peroxidation. Superoxide overproduction causes the inhibition of nitric oxide formation and bioavailability, one of principal characteristics of aging, while nonenzymatic lipid peroxidation, which is already demonstrated at physiological conditions, produces toxic isoprostanes. We suggest that major initiators of free radical-mediated damaging processes leading to aging at physiological state are oxidizable components of diet. The possibility of inhibition of aging processes by supplementation of nontoxic antioxidants and calorie restriction is discussed. Scheme demonstrating the potential mechanisms of starting the free radical-mediated aging processes is presented, which are discussed on the grounds of known literature data.

Peritoneal macrophages function modulation by L-carnitine in aging rats

BACKGROUND AND AIMS

The aging process is associated with a progressive decline in physiological functions involving immune response in most species. The aim of the present study was to determine the effect of L-carnitine on impaired macrophages function in aged rats.

METHODS

Superoxide anion production, chemotaxis and phagocytic activity were studied in peritoneal macrophages obtained from young (2 months old) and aged (24 months old) rats. L-carnitine (50 mg/kg bw) or control vehicle was orally gavaged into young and aged rats for 30 consecutive days.

RESULTS

The peritoneal macrophages of the aged rats exhibited an increase in superoxide anion generation and a decline in chemotaxis and phagocytic index by comparison with the young rats. Superoxide anion production in aged rats was significantly reduced by L-carnitine treatment, as accompanied by a significant enhancement of chemotactic activity, which was restored to control levels observed in young rats. The age-related reduction in phagocytic index was only slightly, but not significantly, restored by L-carnitine administration, however.

CONCLUSION

The findings suggest that L-carnitine administration may be useful in reversing some age-related changes.