Pinealectomy or light exposure exacerbates biliary damage and liver fibrosis in cholestatic rats through decreased melatonin synthesis

Melatonin, a neuroendocrine hormone synthesized by the pineal gland and cholangiocytes, decreases biliary hyperplasia and liver fibrosis during cholestasis-induced biliary injury via melatonin-dependent autocrine signaling through increased biliary arylalkylamine N-acetyltransferase (AANAT) expression and melatonin secretion, downregulation of miR-200b and specific circadian clock genes. Melatonin synthesis is decreased by pinealectomy (PINX) or chronic exposure to light. We evaluated the effect of PINX or prolonged light exposure on melatonin-dependent modulation of biliary damage/ductular reaction/liver fibrosis. Studies were performed in male rats with/without BDL for 1 week with 12:12 h dark/light cycles, continuous light or after 1 week of PINX. The expression of AANAT and melatonin levels in serum and cholangiocyte supernatant were increased in BDL rats, while decreased in BDL rats following PINX or continuous light exposure. BDL-induced increase in serum chemistry, ductular reaction, liver fibrosis, inflammation, angiogenesis and ROS generation were significantly enhanced by PINX or light exposure. Concomitant with enhanced liver fibrosis, we observed increased biliary senescence and enhanced clock genes and miR-200b expression in total liver and cholangiocytes. In vitro, the expression of AANAT, clock genes and miR-200b was increased in PSC human cholangiocyte cell lines (hPSCL). The proliferation and activation of HHStecs (human hepatic stellate cell lines) were increased after stimulating with BDL cholangiocyte supernatant and further enhanced when stimulated with BDL rats following PINX or continuous light exposure cholangiocyte supernatant via intracellular ROS generation. Conclusion: Melatonin plays an important role in the protection of liver against cholestasis-induced damage and ductular reaction.     

Donepezil attenuates high glucose-accelerated senescence in human umbilical vein endothelial cells through SIRT1 activation

Cellular senescence of endothelial cells is a damage and stress response which induces pro-inflammatory, pro-atherosclerotic, and pro-thrombotic phenotypes. Donepezil is a drug used for the treatment of mild to moderate dementia of the Alzheimer’s disease (AD). The aim of the present study was to investigate the attenuation of endothelial cell senescence by donepezil and to explore the mechanisms underlying the anti-aging effects of donepezil. Our results indicated that high glucose (HG) markedly decreased cell viability of human umbilical vein endothelial cells (HUVECs), and this phenomenon was reversed by treatment with donepezil. Importantly, our results displayed that the frequency of senescent (SA-ß-gal-positive) cells and the expression level of senescence genes (PAI-1 and p21) were significantly higher in the HG group compared with the normal glucose (NG) group, and these changes were blocked by treatment with donepezil. Also, our results showed that donepezil inhibits the generation of reactive oxygen species (ROS), which promotes cellular senescence. Pretreatment with nicotinamide (NAM), a sirtuin 1 (SIRT1) inhibitor, inhibited the reduction in senescence associated with donepezil. Indeed, our results indicated that donepezil increased the SIRT1 enzyme activity. Therefore, these results show that donepezil delays cellular senescence that is promoted under HG condition via activation of SIRT1.     

Oncogenic K-Ras Regulates Bioactive Sphingolipids in a Sphingosine Kinase 1-dependent Manner

Sphingosine kinase 1 (SK1) is an important enzyme involved in the production of the bioactive lipid sphingosine 1-phosphate (S1P). SK1 is overexpressed in many forms of cancer, however, the contribution of SK1 to cancer progression is still unclear. One of the best characterized mutations found in several forms of human cancer is an activating point mutation in the Ras oncogene, which disrupts its GTPase activity and leads to stimulation of the MEK/ERK pathway. Because SK1 activity and subcellular localization have been shown to be regulated by ERK, we wished to investigate the effect of oncogenic Ras, a potent activator of the Raf/MEK/ERK pathway, on the activity of SK1 and sphingolipid metabolism. Using HEK293T cells transiently transfected with the K-RasG12V oncogene and both wild type and Sphk1(-/-) mouse embryonic fibroblasts stably infected with retroviral K-RasG12V, we found that K-RasG12V increases the production of S1P and decreases the production of ceramide in a SK1-dependent manner. In addition, we found that expression of the K-RasG12V oncogene leads to plasma membrane localization of SK1 and a reduction in cytosolic levels of SK1. This effect is likely mediated by the Raf/MEK/ERK pathway as constitutively active B-Raf or MEK1 are able to activate SK1, but constitutively active Akt1 is not. We believe this research has important implications for how sphingolipids may be contributing to oncogenic transformation and provide some of the first evidence for oncogenes inducing specific changes in sphingolipid metabolism through SK1 regulation.     

Senescence in immune priming and attractiveness in a beetle

Age‐related decline in immune activity is referred to as immunosenescence and has been observed for both the adaptive immune response of vertebrates and the innate immune system of invertebrates. Because maintaining a basic level of immune defence and mounting an immune response is costly, optimal investment in immune function should vary over a wide range of individual states such as the individual’s age. In this study, we tested whether the immune response and immunological priming within individuals become less efficient with age using mealworm beetles, Tenebrio molitor, as a model organism. We also tested whether ageing and immunological priming affected the odours produced by males. We found that young males of T. molitor were capable of mounting an immune response a sterile nylon monofilament implant with the potential to exhibit a simple form of immune memory through mechanisms of immune priming. Older males did not increase their immune response to a second immune challenge, which negatively affected their sexual attractiveness and remaining life span. Our results indicate that the immune system of older males in T. molitor is less effective, suggesting complex evolutionary trade‐offs between ageing, immune response and sexual attractiveness.     

Factors influencing soay sheep survival: a Bayesian analysis

This article presents a Bayesian analysis of mark-recapture-recovery data on Soay sheep. A reversible jump Markov chain Monte Carlo technique is used to determine age classes of common survival, and to model the survival probabilities in those classes using logistic regression. This involves environmental and individual covariates, as well as random effects. Auxiliary variables are used to impute missing covariates measured on individual sheep. The Bayesian approach suggests different models from those previously obtained using classical statistical methods. Following model averaging, features that were not previously detected, and which are of ecological importance, are identified.     

Control of isoperoxidases involved in chlorophyll degradation of stored broccoli (Brassica oleracea) florets by heat treatment

Changes in isoperoxidases involved in chlorophyll (Chl) degradation of stored broccoli (Brassica oleracea L.) florets and their control by heat treatment (HT) were determined. Chl a and b contents in non-heat-treated broccoli florets decreased greatly after 2 days at 15 degrees C, whereas the contents in heat-treated florets (50 degrees C for 2 h) showed almost no change. Three isoperoxidases involved in Chl degradation were detected by means of molecular exclusion chromatography and the molecular weights of those isoperoxidases were about 95 (Type I), 67 (Type II) and 56 (Type III) kDa, respectively. Only Type I was detected in broccoli florets immediately after harvest, and its activity in non-heat-treated broccoli increased greatly during storage. Both Type II and Type III were present in non-heat-treated broccoli with floret senescence. HT suppressed the enhancement of all of the isoperoxidase activities. Cycloheximide treatment also effectively retarded the increase in Types I, II and III isoperoxidase activities concomitant with the suppression of floret yellowing. The K(m) values corresponding to Chl a of Type II and Type III were lower than Type I, and the V(max)/K(m) values corresponding to Chl a of Type II and Type III were higher than Type I. This suggests that both Types II and III could be closely associated with Chl degradation in broccoli florets and that HT might inhibit floret senescence by suppression of isoperoxidase activities.     

Decline in ascorbate peroxidase activity--a prerequisite factor for tepal senescence in gladiolus

Flower senescence was studied in Gladiolus cv. "Snow Princess" over five arbitrarily divided developmental stages (stage 1, half bloom; stage 2, full bloom; stage 3, beginning of wilting; stage 4, 50% wilting; stage 5, complete wilting) in terms of changes in fresh weight, antioxidant enzymes (superoxide dismutase, SOD; ascorbate peroxidase, APX; glutathione reductase, GR) activities and membrane integrity. A significant decrease in tepal fresh weight was observed over the senescence period (after stage 2). Membrane integrity was studied by measuring lipid peroxidation [in terms of thiobarbituric acid reactive substances (TBARS) content] and membrane stability index (MSI) percentage. Maximum TBARS content was recorded in stage 4 (50% wilting). This increase in lipid peroxidation over the senescence period was in close association with high degree of membrane deterioration expressed as decrease in membrane stability index percentage. A significant decrease (two and half-fold) in MSI% in stage 5 (as compared to stage 1) indicates complete membrane deterioration. Progressive increase in endogenous H2O2 level was recorded over senescence period. Maximum H2O2 content (19.7+/-1.4 micromol g(-1) DW) was recorded at stage 5 (complete wilting). Three different patterns were observed in antioxidant enzymes behavior over the senescence period. APX activity was declined significantly as, the flower entered stage 3 (beginning of wilting) from full bloom condition (stage 2). Progressive and significant increase in SOD activity was measured as a function of time. Maximum SOD activity (24.2+/-0.8 U mg(-1) DW) was recorded in stage 5 (three-fold increase over stage 1). GR activity initially increased up to stage 4 (50% wilting) and declined significantly thereafter (approximately seven-fold). An increase in endogenous H2O2 level during senescence may be the result of a programmed down-regulation of APX enzyme activity, which seems to be the prerequisite factor for initiating senescence process in gladiolus tepal.     

G-protein gamma subunit GNG11 strongly regulates cellular senescence

GNG11 is a member of the gamma subunit family of heteromeric G-protein, but its function is entirely unknown. Here, we successfully characterized its specific role in cellular senescence. We have found that overexpression of GNG11 immediately induces cellular senescence in normal human fibroblasts, and its down-regulation by antisense cDNA extends their lifespan. Surprisingly, this gene is very rapidly induced by senescence-inducing agents such as H(2)O(2). Furthermore, overexpression of GNG11 activated ERK1/2 of the MAP kinase family, but did not Ras. Collectively, these results suggest a novel senescence pathway mediated by GNG11 in response to environmental cues.     

Damage of PS II during senescence of Spirodela polyrrhiza explants under long-day conditions and its prevention by 6-benzyladenine

The chlorophyll a (Chl a) fluorescence technique was applied to investigate damage of PS II during senescence of excised half-fronds in Spirodela polyrrhiza P143. The green explants showed a typical Chl a fluorescence transient, OJIP. After cultivation of explants under long-day conditions for 8 days, all the J, I, and P steps disappeared, but a clear K band, an indication of senescence, was observed. JIP-test showed that at this time point, the photosynthetic performance index (PI) dropped to zero and the active reaction center (RC) per leaf cross-section (RC/CS) declined to 18%. As the oxygen-evolving complex (OEC) and the chlorophyll content all remained above 42%, it is proposed that the decline in RC contributes more to the appearance of the K band. Supplementation of 6-benzyladenine (6-BA) into the medium at the beginning of cultivation caused dramatic increase in PI, OEC, RC/CS, and chlorophyll content, and at any time before the 8th day reversed the senescence process of the explants. When 6-BA was added after 8 days of cultivation, the PI did not increase anymore, RC/CS and OEC were maintained at 22% and above 40%, respectively, and chlorophyll content decreased continuously further. These data support a view that the decline in RC is crucial for initiation of the irreversible senescence phase of explants cultivated under long-day conditions.     

Integrating evolutionary and molecular genetics of aging

Aging or senescence is an age-dependent decline in physiological function, demographically manifest as decreased survival and fecundity with increasing age. Since aging is disadvantageous it should not evolve by natural selection. So why do organisms age and die? In the 1940s and 1950s evolutionary geneticists resolved this paradox by positing that aging evolves because selection is inefficient at maintaining function late in life. By the 1980s and 1990s this evolutionary theory of aging had received firm empirical support, but little was known about the mechanisms of aging. Around the same time biologists began to apply the tools of molecular genetics to aging and successfully identified mutations that affect longevity. Today, the molecular genetics of aging is a burgeoning field, but progress in evolutionary genetics of aging has largely stalled. Here we argue that some of the most exciting and unresolved questions about aging require an integration of molecular and evolutionary approaches. Is aging a universal process? Why do species age at different rates? Are the mechanisms of aging conserved or lineage-specific? Are longevity genes identified in the laboratory under selection in natural populations? What is the genetic basis of plasticity in aging in response to environmental cues and is this plasticity adaptive? What are the mechanisms underlying trade-offs between early fitness traits and life span? To answer these questions evolutionary biologists must adopt the tools of molecular biology, while molecular biologists must put their experiments into an evolutionary framework. The time is ripe for a synthesis of molecular biogerontology and the evolutionary biology of aging.