The analytical approach to the nature of lipofuscin (age pigment)

An Explicit Estimated Baseline Model for Robust Estimation of Fluorophores Using Multiple-Wavelength Excitation Fluorescence Spectroscopy

Spectroscopy is a popular technique for identifying and quantifying fluorophores in fluorescent materials. However, quantifying the fluorophore of interest can be challenging when the material also contains other fluorophores (baseline), particularly if the emission spectrum of the baseline is not well-defined and overlaps with that of the fluorophore of interest. In this work, we propose a method that is free from any prior assumptions about the baseline by utilizing fluorescence signals at multiple excitation wavelengths. Despite the nonlinearity of the model, a closed-form expression of the least squares estimator is also derived. To evaluate our method, we consider the practical case of estimating the contributions of two forms of protoporphyrin IX (PpIX) in a fluorescence signal. This fluorophore of interest is commonly utilized in neuro-oncology operating rooms to distinguish the boundary between healthy and tumor tissue in a type of brain tumor known as glioma. Using a digital phantom calibrated with clinical and experimental data, we demonstrate that our method is more robust than current state-of-the-art methods for classifying pathological status, particularly when applied to images of simulated clinical gliomas. To account for the high variability in the baseline, we are examining various scenarios and their corresponding outcomes. In particular, it maintains the ability to distinguish between healthy and tumor tissue with an accuracy of up to 87%, while the ability of existing methods drops near 0%.

Lipofuscin Granule Accumulation Requires Autophagy Activation

Lipofuscins are oxidized lipid and protein complexes that accumulate during cellular senescence and tissue aging, regarded as markers for cellular oxidative damage, tissue aging, and certain aging-associated diseases. Therefore, understanding their cellular biological properties is crucial for effective treatment development. Through traditional microscopy, lipofuscins are readily observed as fluorescent granules thought to accumulate in lysosomes. However, lipofuscin granule formation and accumulation in senescent cells are poorly understood. Thus, this study examined lipofuscin accumulation in human fibroblasts exposed to various stressors. Our results substantiate that in glucose-starved or replicative senescence cells, where elevated oxidative stress levels activate autophagy, lipofuscins predominately appear as granules that co-localize with autolysosomes due to lysosomal acidity or impairment. Meanwhile, autophagosome formation is attenuated in cells experiencing oxidative stress induced by a doxorubicin pulse and chase, and lipofuscin fluorescence granules seldom manifest in the cytoplasm. As Torin-1 treatment activates autophagy, granular lipofuscins intensify and dominate, indicating that autophagy activation triggers their accumulation. Our results suggest that high oxidative stress activates autophagy but fails in lipofuscin removal, leaving an abundance of lipofuscin-filled impaired autolysosomes, referred to as residual bodies. Therefore, future endeavors in treating lipofuscin pathology-associated diseases and dysfunctions through autophagy activation demand meticulous consideration.

Aged lipid-laden microglia display impaired responses to stroke

Microglial cells of the aged brain manifest signs of dysfunction that could contribute to the worse neurological outcome of stroke in the elderly. Treatment with colony-stimulating factor 1 receptor antagonists enables transient microglia depletion that is followed by microglia repopulation after treatment interruption, causing no known harm to mice. We tested whether this strategy restored microglia function and ameliorated stroke outcome in old mice. Cerebral ischemia/reperfusion induced innate immune responses in microglia highlighted by type I interferon and metabolic changes involving lipid droplet biogenesis. Old microglia accumulated lipids under steady state and displayed exacerbated innate immune responses to stroke. Microglia repopulation in old mice reduced lipid-laden microglia, and the cells exhibited reduced inflammatory responses to ischemia. Moreover, old mice with renewed microglia showed improved motor function 2 weeks after stroke. We conclude that lipid deposits in aged microglia impair the cellular responses to ischemia and worsen functional recovery in old mice.

4-HNE Immunohistochemistry and Image Analysis for Detection of Lipid Peroxidation in Human Liver Samples Using Vitamin E Treatment in NAFLD as a Proof of Concept

Lipid peroxidation is a common feature of liver diseases, especially non-alcoholic fatty liver disease (NAFLD). There are limited validated tools to study intra-hepatic lipid peroxidation, especially for small specimen. We developed a semi-quantitative, fully automated immunohistochemistry assay for the detection of 4-hydroxynoneal (4-HNE) protein adducts, a marker of lipid peroxidation, for adaptation to clinical diagnostics and research. We used Hep G2 cells treated with 4-HNE to validate specificity, sensitivity, and dynamic range of the antibody. Staining and semi-quantitative automated readout were confirmed in human needle-biopsy liver samples from subjects with NAFLD and normal liver histology. The ability to detect changes in lipid peroxidation was tested in paired liver biopsies from NAFLD subjects, obtained before and after 4 weeks of treatment with the antioxidant vitamin E (ClinicalTrials.gov NCT01792115, n=21). The cellular calibrator was linear and NAFLD patients had significantly higher levels of 4-HNE adducts compared to controls (p=0.02). Vitamin E treatment significantly decreased 4-HNE (p=0.0002). Our findings demonstrate that 4-HNE quantification by immunohistochemistry and automated image analysis is feasible and able to detect changes in hepatic lipid peroxidation in clinical trials. This method can be applied to archival and fresh samples and should be considered for use in assessing NAFLD histology.

Increased intra-mitochondrial lipofuscin aggregates with spherical dense body formation in mitochondrial myopathy

Lipofuscin aggregation may result from incomplete degradation of damaged mitochondria by autophagy-lysosome pathway, and intra-mitochondrial lipofuscin aggregation may exacerbate mitochondrial abnormalities in mitochondrial myopathy (MM) and mitochondrial disease. We examined vastus lateralis muscle biopsies from 24 patients with pathologically diagnosed MM and clinically diagnosed chronic progressive external ophthalmoplegia, in comparison to the biopsies from 3 other groups:10 patients with inclusion body myositis (IBM), 11 younger adults, and 10 older subjects with no to minimal myopathic changes. Lipofuscin aggregation in muscle fibres was assessed on autofluorescence microscopy, some histochemical stains, and electron microscopy (EM). EM analyses demonstrated intra-mitochondrial lipofuscin aggregates, spherical dense bodies (SDBs), and paracrystalline inclusions (PCIs) which were semi-quantitatively assessed. Intra-mitochondrial lipofuscin aggregates showed no significant differences between groups of MM patients and older subjects or IBM patients, but significant differences between groups of younger adults and others with associated age-related changes. Intra-mitochondrial SDBs were significantly more in MM patients than in older subjects, IBM patients, and younger adults. There was a significant positive correlation between intra-mitochondrial lipofuscin aggregates and SDBs. These findings suggest that intra-mitochondrial formation of lipofuscin SDBs is more in MM and contributing to the pathophysiology of mitochondrial disease.

Myocardial lipofuscin accumulation in ageing and sudden cardiac death

Lipofuscin is an intracellular aggregate of highly oxidized proteins that cannot be digested in the ubiquitin-proteasome system and accumulate mainly in lysosomes, especially in aged cells and pathological conditions. However, no systematic study has evaluated the cardiac accumulation of lipofuscin during human ageing and sudden cardiac death (SCD). Age estimation in unidentified bodies and postmortem SCD diagnosis are important themes in forensics. Thus, we aimed to elucidate their correlations with myocardial lipofuscin accumulation. We collected 76 cardiac samples from autopsy patients aged 20–97 years. After histopathological examination, myocardial lipofuscin was measured using its autofluorescence. Lipofuscin accumulated mainly in the perinuclear zone, and its accumulation rate positively correlated with chronological ageing (r = 0.82). Meanwhile, no significant change in lipofuscin level was observed with different causes of death, including SCD. There was also no significant change in lipofuscin level in relation to body mass index, serum brain natriuretic peptide level, or heart weight. Moreover, we performed LC3 and p62 immunoblotting to evaluate autophagic activity, and no change was observed in ageing. Therefore, lipofuscin accumulation more directly reflects chronological ageing rather than human cardiac pathology. Our study reveals the stability and utility of cardiac lipofuscin measurement for age estimation during autopsy.

Immunotoxic effects of 4-nonylphenol on Clarias gariepinus: Cytopathological changes in hepatic melanomacrophages

Melanomacrophage centres (MMCs) play a key role in the immune response in fish. They are considered sensitive bio-monitoring structures with roles in the assessment of toxicant impacts. The aim of this study was to examine the potential histopathological effect of 4-nonylphenol (4-NP) on hepatic MMCs in Clarias gariepinus. To achieve this objective, adult male fish were divided randomly and equally into two groups: a control group and a group that was exposed to 4-NP (dissolved in water at a dose of 0.1 mg/L) for 21 days. The 4-NP-intoxicated hepatic MMCs contained numerous necrotic macrophages. Superoxide dismutase 2 was immuno-expressed in the hepatic MMCs in both groups, with no significant difference. Histomorphometric examination revealed that the sizes and numbers of MMCs were dramatically higher in the livers of 4-NP-exposed C. gariepinus than in control fish. Following 4-NP challenge, in the liver, the abundance of lipofuscin and haemosiderin pigments increased, and single-pigmented macrophages, aggregated groups of deformed red blood cells (RBCs) and macrophages were present near blood vessels and hepatic sinusoids. These results reveal that 4-NP exerts immunological effects on hepatic MMCs in C. gariepinus and support the utility of MMCs as a cytological biomarker for aquatic exposure to 4-NP.

A Sequential Study of Age-Related Lipofuscin Accumulation in Hippocampus and Striate Cortex of Rats

Background

The age-pigment, lipofuscin that accumulates in cells intrinsically and progressively with age is considered as the hallmark of aging. This accumulation is more prominent in post-mitotic cells like neurons and also appears in glia.

Purpose

The aim of the present study was to assess the age-associated occurrence and distribution pattern of lipofuscin both in neurons and microglia in various regions of hippocampus and striate cortex.

Methods

The accumulation pattern of lipofuscin in hippocampus and striate cortex was observed in the female Wistar rats of 6 age groups, that is, 3, 6, 12, 18, 24, and 30 months using the autofluorescent property of lipofuscin and its specific localization in neurons and microglia by dual immunolabeling with NeuN and Iba-1 antibodies respectively. Cytoarchitectural and the morphological age-related changes were observed with cresyl violet staining.

Results

Lipofuscin pigments accumulate progressively through the normal aging process in hippocampus and striate cortex. However, in hippocampus, lipofuscin accumulates in a region-specific manner with the highest accumulation observed in cornu ammonis (CA) 1 and 3 subregions. Furthermore, the lipofuscin accumulation was also observed in microglia in the senile brains both in the hippocampus and striate cortex.

Conclusion

The progressive deposition of lipofuscin could result in cellular dysfunction. This encouraged us to forward the idea that microglia not only participate in the removal of the pigment from the neurons but also accumulate these waste products in itself. Such senescent microglia may contribute to age- related neurodegeneration as they lose the neuroprotective potential due to oxidative stress and thus may be unable to effectively phagocytose the age pigment.

Skeletal Muscle Fibrosis in Pancreatic Cancer Patients with Respect to Survival

Background

Cancer cachexia is a catabolic condition characterized by skeletal muscle wasting, consequent to tumor burden, which negatively impacts tolerance to cancer therapies and contributes to increased mortality. Partly because of the limited knowledge of the underlying mechanisms of cancer cachexia derived from human studies, however, the ability to therapeutically intervene remains elusive. The purpose of the current study was therefore to better define the phenotype of skeletal muscle obtained from patients with pancreatic ductal adenocarcinoma (PDAC), which has one of the highest rates of cachexia.

Methods

Morphological analyses were performed on rectus abdominis muscle biopsies obtained from resectable PDAC patients undergoing tumor resection surgery (N = 20) and from weight-stable non-cancer control subjects undergoing benign abdominal surgery (N = 16). PDAC patients with a body weight loss of greater than 5% during the previous 6 months were considered cachectic (N = 15). Statistical tests were two sided.

Results

Skeletal muscle from cachectic PDAC patients had increased collagen content compared with non-cancer control subjects (1.43% vs 9.66%, P = .0004, Dunn test). Across all PDAC patients, collagen content positively correlated with body weight loss (P = .0016, r = 0.672), was increased in patients with lymph node metastasis (P = .007, Mann-Whitney U test), and was associated with survival on univariate (HR = 1.08, 95% confidence interval [CI] = 1.02 to 1.04, P = .008) and multivariable analyses (HR = 1.08, 95% CI = 1.00 to 1.17, P = .038). Cachectic PDAC patients also displayed increased lipid deposition (2.63% vs 5.72%, P = .042), infiltration of CD68+ macrophages (63.6 cells/mm² vs 233.8 cells/mm², P = .0238), calcium deposition (0.21% vs 2.51%, P = .030), and evidence of deficient cellular quality control mechanisms (Mann-Whitney U test). Transcriptional profiling of all patients supported these findings by identifying gene clusters related to wounding, inflammation, and cellular response to TGF-β upregulated in cachectic PDAC patients compared with non-cancer control subjects.

Conclusions

To our knowledge, this work is the first to demonstrate increased collagen content in cachectic PDAC patients that is associated with poor survival.

Protein aggregates and proteostasis in aging: Amylin and β-cell function

The ubiquitin-proteasomal-system (UPS) and the autophagy-lysosomal-system (ALS) are both highly susceptible for disturbances leading to the accumulation of cellular damage. A decline of protein degradation during aging results in the formation of oxidatively damaged and aggregated proteins finally resulting in failure of cellular functionality. Besides protein aggregation in response to oxidative damage, amyloids are a different type of protein aggregates able to distract proteostasis and interfere with cellular functionality. Amyloids are clearly linked to the pathogenesis of age-related degenerative diseases such as Alzheimer's disease. Human amylin is one of the peptides forming fibrils in β-sheet conformation finally leading to amyloid formation. In contrast to rodent amylin, human amylin is prone to form amyloidogenic aggregates, proposed to play a role in the pathogenesis of Type 2 Diabetes by impairing β-cell functionality. Since aggregates such as lipofuscin and β-amyloid are known to impair proteostasis, it is likely to assume similar effects for human amylin. In this review, we focus on the effects of IAPP on UPS and ALS and their role in amylin degradation, since both systems play a crucial role in maintaining proteome balance thereby influencing, at least in part, cellular fate and aging.

Estrogen deficiency is associated with hippocampal morphological remodeling of early postmenopausal mice

Estrogen (E₂) deficiency is reported to involve in the impairment of cognition in postmenopausal women. However, the morphological basis is still unclear. In the present study, using transmission electron microscopy (TEM), we observed the ultrastructure of hippocampus in female C57BL/6 mice at the age of 18 months (18 M) which is considered as the early stage of postmenopause (n = 8). Compared with control mice aged 6 M (n = 8), we identified that the morphological changes in the hippocampus of these menopausal mice were mitochondrial damage, lipofuscin deposition and microtubule degradation. Notably, after E₂ was subcutaneously injected into mice aged 16 M with a dosage of 3.5 μg/kg every three days for two months in the 18 M + E₂ group (n = 8), mitochondrial damage and lipofuscin deposition in the DG region of hippocampus were prevented, but the degraded microtubules in the hippocampus of postmenopausal mice were failed to restore. These data suggest that hippocampal ultrastructure remodeling in mice can be initiated at the early stage of postmenopause, E₂ supplementation could only have an effect on mitochondrial damage and lipofuscin increase.

Altered neurofilament protein expression in the lateral vestibular nucleus in Parkinson's disease

A major cause of morbidity in Parkinson's disease (PD) is postural instability. The neuropathology underlying postural instability is unknown. Postural control is mediated by Deiters' neurons of the lateral vestibular nucleus (LVN), which are the brainstem origin of descending vestibulospinal reflexes. Deiters' neurons express the cytostructural protein, non-phosphorylated neurofilament protein (NPNFP). In PD, reduced expression of NPNFP in substantia nigra (SN) neurons is believed to contribute to dysfunction. It was the aim of this study to determine if there is altered expression of NPNFP in the LVN in PD. We immunolabeled NPNFP in brainstem sections of six aged controls (mean age 92 yo) and six PD donors (mean age 83 yo). Our results show there was a ~ 50% reduction in NPNFP-positive Deiters' neurons compared to controls (13 ± 2.0/section vs 25.7 ± 3.0/section; p < 0.01, repeated measures ANOVA). In contrast, there was no difference in NPNFP-positive counts in the facial nucleus between control and PD. The normalized intensity of NPNFP labeling in LVN was also reduced in PD (0.87 ± 0.05 vs 1.09 ± 0.03; p < 0.01). There was a 35% concurrent reduction in NPNFP-positive neuropil in PD relative to controls (p < 0.01). We also show there was an 84% increase (p < 0.05) in somatic lipofuscin in PD patients compared to control. Lipofuscin aggregation has been shown to increase not only with age but also with neurodegeneration. Furthermore, decreased NPNFP intensity was strongly correlated with increasing lipofuscin autofluorescence across all cases (R ² = 0.81, p < 0.01). These results show two alterations in cellular content with PD, reduced expression and intensity of NPNFP and increased lipofuscin aggregation in Deiter's neurons. These changes may contribute to degeneration of postural reflexes observed in PD.

The lysosomal storage disease continuum with ageing-related neurodegenerative disease

Lysosomal storage diseases and diseases of ageing share many features both at the physiological level and with respect to the mechanisms that underlie disease pathogenesis. Although the exact pathophysiology is not exactly the same, it is astounding how many similar pathways are altered in all of these diseases. The aim of this review is to provide a summary of the shared disease mechanisms, outlining the similarities and differences and how genetics, insight into rare diseases and functional research has changed our perspective on the causes underlying common diseases of ageing. The lysosome should no longer be considered as just the stomach of the cell or as a suicide bag, it has an emerging role in cellular signalling, nutrient sensing and recycling. The lysosome is of fundamental importance in the pathophysiology of diseases of ageing and by comparing against the LSDs we not only identify common pathways but also therapeutic targets so that ultimately more effective treatments can be developed for all neurodegenerative diseases.

Autofluorescence in samples obtained from chronic biofilm infections--"all that glitters is not gold"

When looking at tissue sections of ex vivo samples, autofluorescence can be a major cause of artifacts and misinterpretations. We here reiterate evidence that autofluorescing granules, often hemosiderin but also ceroid or mucinogen granules, are severe obstacles when imaging and diagnosing biofilm infections through fluorescent imaging techniques. We used confocal laser scanning microscopy with spectral analysis for autofluorescence detection as well as standard histological stains in order to identify the culprit and show that these granules might very well be mistaken for bacterial biofilms. Furthermore, we hypothesize that the increased amount of autofluorescing granules may be a consequence of prolonged inflammation as a consequence of chronic biofilm infections.

Defective macroautophagic turnover of brain lipids in the TgCRND8 Alzheimer mouse model: prevention by correcting lysosomal proteolytic deficits

Autophagy, the major lysosomal pathway for the turnover of intracellular organelles is markedly impaired in neurons in Alzheimer's disease and Alzheimer mouse models. We have previously reported that severe lysosomal and amyloid neuropathology and associated cognitive deficits in the TgCRND8 Alzheimer mouse model can be ameliorated by restoring lysosomal proteolytic capacity and autophagy flux via genetic deletion of the lysosomal protease inhibitor, cystatin B. Here we present evidence that macroautophagy is a significant pathway for lipid turnover, which is defective in TgCRND8 brain where lipids accumulate as membranous structures and lipid droplets within giant neuronal autolysosomes. Levels of multiple lipid species including several sphingolipids (ceramide, ganglioside GM3, GM2, GM1, GD3 and GD1a), cardiolipin, cholesterol and cholesteryl esters are elevated in autophagic vacuole fractions and lysosomes isolated from TgCRND8 brain. Lipids are localized in autophagosomes and autolysosomes by double immunofluorescence analyses in wild-type mice and colocalization is increased in TgCRND8 mice where abnormally abundant GM2 ganglioside-positive granules are detected in neuronal lysosomes. Cystatin B deletion in TgCRND8 significantly reduces the number of GM2-positive granules and lowers the levels of GM2 and GM3 in lysosomes, decreases lipofuscin-related autofluorescence, and eliminates giant lipid-containing autolysosomes while increasing numbers of normal-sized autolysosomes/lysosomes with reduced content of undigested components. These findings have identified macroautophagy as a previously unappreciated route for delivering membrane lipids to lysosomes for turnover, a function that has so far been considered to be mediated exclusively through the endocytic pathway, and revealed that autophagic-lysosomal dysfunction in TgCRND8 brain impedes lysosomal turnover of lipids as well as proteins. The amelioration of lipid accumulation in TgCRND8 by removing cystatin B inhibition on lysosomal proteases suggests that enhancing lysosomal proteolysis improves the overall environment of the lysosome and its clearance functions, which may be possibly relevant to a broader range of lysosomal disorders beyond Alzheimer's disease.

Deficiency of prion protein induces impaired autophagic flux in neurons

Normal cellular prion protein (PrP^C) is highly expressed in the central nervous system. The Zürich I Prnp-deficient mouse strain did not show an abnormal phenotype in initial studies, however, in later studies, deficits in exploratory behavior and short- and long-term memory have been revealed. In the present study, numerous autophagic vacuoles were found in neurons from Zürich I Prnp-deficient mice. The autophagic accumulation in the soma of cortical neurons in Zürich I Prnp-deficient mice was observed as early as 3 months of age, and in the hippocampal neurons at 6 months of age. Specifically, there is accumulation of electron dense pigments associated with autophagy in the neurons of Zürich I Prnp-deficient mice. Furthermore, autophagic accumulations were observed as early as 3 months of age in the CA3 region of hippocampal and cerebral cortical neuropils. The autophagic vacuoles increased with age in the hippocampus of Zürich I Prnp-deficient mice at a faster rate and to a greater extent than in normal C57BL/6J mice, whereas the cortex exhibited high levels that were maintained from 3 months old in Zürich I Prnp-deficient mice. The pigmented autophagic accumulation is due to the incompletely digested material from autophagic vacuoles. Furthermore, a deficiency in PrP^C may disrupt the autophagic flux by inhibiting autophagosome-lysosomal fusion. Overall, our results provide insight into the protective role of PrP^C in neurons, which may play a role in normal behavior and other brain functions.

Distinct types of lipofuscin pigment in the hippocampus and cerebellum of aged cheirogaleid primates

The formation of autofluorescent lipopigment or lipofuscin is a highly consistent and reliable cytological change that correlates with cellular aging in postmitotic cells. One causal factor of lipofuscinogenesis involves free radical-induced lipid peroxidation. In mammals, dentate gyrus neurons and Purkinje cells are usually affected widely. In this study, we investigated the ultrastructure of lipofuscin deposits in large neurons of the dentate gyrus and in Purkinje cells of aged fat-tailed dwarf lemurs (Cheirogaleus medius Geoffroy, 1812) with electron and confocal microscopy and compared it with previous observations in other species. Cheirogaleid primates such as mouse and dwarf lemurs are archaic primates that provide interesting nonhuman models of aging. Our study revealed region-specific as well as species-specific characteristics of lipofuscin ultrastructure. This suggests differences in cellular metabolism and/or in organelles involved in lipofuscin production in cerebellar Purkinje cells and in hippocampal dentate gyrus neurons.

Effect of temperature on the rate of ageing: an experimental study of the blowfly Calliphora stygia

All organisms age, the rate of which can be measured by demographic analysis of mortality rates. The rate of ageing is thermally sensitive in ectothermic invertebrates and we examined the effects of temperature on both demographic rates of ageing and on cellular senescence in the blowfly, Calliphora stygia. The short lifespan of these flies is advantageous for demographic measurements while their large body size permits individual-based biochemical characterisation. Blowflies maintained at temperatures from 12°C to 34°C had a five to six-fold decrease in maximum and average longevity, respectively. Mortality rates were best described by a two-phase Gompertz relation, which revealed the first-phase of ageing to be much more temperature sensitive than the second stage. Flies held at low temperatures had both a slower first-phase rate of ageing and a delayed onset of second-phase ageing, which significantly extended their longevity compared with those at high temperatures. Blowflies that were transferred from 29°C to 15°C had higher first-phase mortality rates than those of flies held at constant 15°C, but their onset of second-phase ageing was deferred beyond that of flies held constantly at this temperature. The accumulation of fluorescent AGE pigment, a measure of cellular oxidative damage, increased steadily over time in all blowflies, irrespective of the temporal pattern of mortality. Pigment accumulated steadily during periods of 'negligible senescence', as measured by minimal rate of mortality, and the rate of accumulation was significantly affected by temperature. Thus accumulation of AGE pigment is more representative of chronological age than a reflection of biological age or a cause of mortality.

Lipofuscin in human glaucomatous optic nerves

Lipofuscin accumulation has been observed in a number of neurodegenerative diseases. We recently found that autofluorescent particles also occur in the aged human optic nerve. In this study we sought to determine the nature of these particles and their correlation with aging, age-related macular degeneration (AMD) and primary open angle glaucoma (POAG). Groups of eight optic nerves from patients diagnosed with primary open angle glaucoma, age-related macular degeneration, age-matched controls and four optic nerves derived from controls younger than 42 years were used for the study. All samples were fixed in paraformaldehyde and frozen frontal sections were prepared. Sections were analyzed with fluorescence microscopy, bright field microscopy, Sudan black staining and spectrofluorometry using a confocal laser scanning microscope. Sections were photographed and analyzed to establish the distribution, quantity, and size of the autofluorescent particles. Additionally, transmission electron microscopy was used to determine the ultrastructural location of the granules. On unstained sections under light microscopy granules are detectable as pale brown inclusions and are easily stained with oil-soluble dyes, such as Sudan black. Granules fluoresce when excited at all tested wavelengths but lose their fluorescence after staining with Sudan black. These particles are distributed throughout the axonal columns, but not in the septa, and appear to be located within the glia ensheathing optic nerve axons. The histologic properties of the granules seen in the optic nerve sections correspond to lipofuscin aggregates, a result of incomplete degradation of oxidized proteins. Our morphometric analyses indicate that overall the optic nerves from control, glaucoma, and AMD donors contain similar amounts of lipofuscin. However, optic nerves derived from donors with glaucoma contain lipofuscin particles that are larger than those observed in the age-matched control and AMD groups. Furthermore optic nerves from glaucoma donors display a smaller diameter than those from age-matched controls resulting in a higher concentration of lipofuscin in glaucomatous optic nerves.

Protein damage, repair and proteolysis

Proteins are continuously affected by various intrinsic and extrinsic factors. Damaged proteins influence several intracellular pathways and result in different disorders and diseases. Aggregation of damaged proteins depends on the balance between their generation and their reversal or elimination by protein repair systems and degradation, respectively. With regard to protein repair, only few repair mechanisms have been evidenced including the reduction of methionine sulfoxide residues by the methionine sulfoxide reductases, the conversion of isoaspartyl residues to L-aspartate by L-isoaspartate methyl transferase and deglycation by phosphorylation of protein-bound fructosamine by fructosamine-3-kinase. Protein degradation is orchestrated by two major proteolytic systems, namely the lysosome and the proteasome. Alteration of the function for both systems has been involved in all aspects of cellular metabolic networks linked to either normal or pathological processes. Given the importance of protein repair and degradation, great effort has recently been made regarding the modulation of these systems in various physiological conditions such as aging, as well as in diseases. Genetic modulation has produced promising results in the area of protein repair enzymes but there are not yet any identified potent inhibitors, and, to our knowledge, only one activating compound has been reported so far. In contrast, different drugs as well as natural compounds that interfere with proteolysis have been identified and/or developed resulting in homeostatic maintenance and/or the delay of disease progression.

Near-to-perfect homeostasis: examples of universal aging rule which germline evades

Aging is considered to be a progressive decline in an organism's functioning over time and is almost universal throughout the living world. Currently, many different aging mechanisms have been reported at all levels of biological organization, with a variety of biochemical, metabolic, and genetic pathways involved. Some of these mechanisms are common across species, and others work different, but each of them is constitutive. This review describes the common characteristics of the aging processes, which are consistent changes over time that involve either the accumulation or depletion of particular system components. These accumulations and depletions may result from imperfect homeostasis, which is the incomplete compensation of a particular biological process with another process evolved to compensate it. In accordance with disposable-soma theory, this imperfection in homeostasis may originate as a function of cell differentiation as early as in yeasts. It may result either from antagonistic pleiotropy mechanisms, or be simply negligible as a subject of natural selection if an adverse effect of the accumulation phenotypically manifests in organism's post-reproductive age. If this phenomenon holds true for many different functions it would lead to the occurrence of a wide variety of aging mechanisms, some of which are common among species, while others unique, because aging is the inherent property of most biological processes that have not yet evolved to be perfectly in balance. Examples of imperfect homeostasis mechanisms of aging, the ways in which germ line escapes from them, and the possibilities of anti-aging treatment are discussed in this review.

Lipofuscin-like pigment in gonads of Sea Urchin Strongylocentrotus intermedius as a potential biomarker of marine pollution: a field study

Accumulation of lipofuscin-like pigments (LLPs) has been shown to be an appropriate index of both age and stress in some aquatic invertebrates. In the present study, LLP was quantified by measuring its autofluorescence intensity (ex 450 nm/em 512 nm) in nutritive phagocytes (NPs) of sea urchins Strongylocentrotus intermedius inhabiting polluted and relatively clean areas of Japan Sea. To avoid variations in LLP content related to sea urchin reproductive condition, only developing gonads with acini occupied mostly by NPs were used for LLP quantification as well as semiquantitative histopathological analysis. LLP concentrations ranged from 0.0 to 4.57 ± 0.53% area fraction in female gonads and from 0.0 to 4.61 ± 0.35% in male gonads. The presence of specimens with extremely high LLP concentrations (>1.5%) in all examined samples, including specimens from the reference station, as well as the absence of strong correlations between LLP concentrations and several parameters related to pollution (heavy-metal concentrations in sea urchin gonads and concentrations of heavy metals, DDT, hexachlorocyclohexane, and total petroleum hydrocarbons in sediments), allow us to conclude that LLP content in sea urchin NPs can not be used as a biomarker in marine pollution monitoring.

Accelerated lipofuscinosis and ubiquitination in granulin knockout mice suggest a role for progranulin in successful aging

Progranulin (PGRN) is involved in wound repair, inflammation, and tumor formation, but its function in the central nervous system is unknown. Roles in development, sexual differentiation, and long-term neuronal survival have been suggested. Mutations in the GRN gene resulting in partial loss of the encoded PGRN protein cause frontotemporal lobar degeneration with ubiquitin immunoreactive inclusions. We sought to understand the neuropathological consequences of loss of PGRN function throughout the lifespan of GRN-deficient ((-/+) and (-/-)) mice. An aged series of GRN-deficient and wild-type mice were compared by histology, immunohistochemistry, and electron microscopy. Although GRN-deficient mice were viable, GRN(-/-) mice were produced at lower than predicted frequency. Neuropathologically, GRN(-/+) were indistinguishable from controls; however, GRN(-/-) mice developed age-associated, abnormal intraneuronal ubiquitin-positive autofluorescent lipofuscin. Lipofuscin was noted in aged GRN(+/+) mice at levels comparable with those of young GRN(-/-) mice. GRN(-/-) mice developed microgliosis, astrogliosis, and tissue vacuolation, with focal neuronal loss and severe gliosis apparent in the oldest GRN(-/-) mice. Although no overt frontotemporal lobar degeneration with ubiquitin immunoreactive inclusions type- or TAR DNA binding protein-43-positive lesions were observed, robust lipofuscinosis and ubiquitination in GRN(-/-) mice is strikingly similar to changes associated with aging and cellular decline in humans and animal models. Our data suggests that PGRN plays a key role in maintaining neuronal function during aging and supports the notion that PGRN is a trophic factor essential for long-term neuronal survival.

Glial fibrillary acidic protein is elevated in the lysosomal storage disease classical late-infantile neuronal ceroid lipofuscinosis, but is not a component of the storage material

Classical late-infantile neuronal ceroid lipofuscinosis (LINCL) is a fatal neurodegenerative disease of children caused by mutations in TPP1, the gene encoding the lysosomal protease tripeptidyl peptidase 1. LINCL is characterized by lysosomal accumulation of storage material of which only a single protein component, subunit c of mitochondrial ATP synthase, has been well established to date. Identification of other protein constituents of the storage material could provide useful insights into the pathophysiology of disease and the natural substrates for TPP1. We have therefore initiated a proteomic analysis of storage material in brain from a LINCL mouse model. One protein, GFAP (glial fibrillary acidic protein), was found to be elevated in the LINCL mice compared with normal controls in both isolated storage bodies and a lysosome-enriched subcellular fraction that contains storage material. To determine whether GFAP accumulates within the lysosome in LINCL, we examined its intracellular distribution using subcellular fractionation and morphological methods. These experiments demonstrate that GFAP is not a component of the storage material in LINCL, suggesting that reports of GFAP storage in other NCLs may need to be re-examined. A number of other proteins were elevated in the storage material and/or lysosome-enriched fraction from the LINCL mice, but it remains unclear whether these proteins are true constituents of the storage material or, like GFAP, whether they associate with this material upon purification.

Age-related differences in oxidative protein-damage in young and senescent fibroblasts

Aging is accompanied by an accumulation of oxidized proteins and cross-linked modified protein material. The intracellular formation and accumulation of highly oxidized and cross-linked proteins, the so-called lipofuscin, is a typical sign of senescence. However, little is known whether the lipofuscin accumulation during aging is related to environmental conditions, as oxidative stress, and whether the accumulation of oxidized proteins and lipofuscin is preferentially taking place in the cytosol or the nucleus and finally, what is the role of lysosomes in this process. Therefore, we investigated human skin fibroblasts in an early stage of proliferation ("young cells") and in a late stage ("senescent cells"). Such cells were compared for the amount of protein carbonyls and lipofuscin and their distribution within the cytosol and the nucleus. Furthermore, cells were exposed to single and repeated doses of hydrogen peroxide and paraquat, measuring the same set of parameters. In addition to that the role of the proteasome to degrade oxidized proteins in young and senescent cells was tested. Furthermore, detailed microscopic analysis was performed testing the intracellular distribution of lipofuscin. The results clearly demonstrated that repeated/chronic oxidative stress induces a senescence-like phenotype of the distribution of oxidized proteins as well as of lipofuscin. It could be demonstrated that most of the lipofuscin is located in lysosomes and that senescent cells contain less lysosomes not lipofuscin-laden in comparison to young cells.

Food inequality negatively impacts cardiac health in rabbits

BACKGROUND

Individuals with lower socioeconomic status experience higher rates of mortality and are more likely to suffer from numerous diseases. While some studies indicate that humans who suffer from social inequality suffer generally worse health, to our knowledge no controlled experiments of this nature have been done in any species. Lipofuscin is a highly oxidized cross-linked aggregate consisting of oxidized protein and lipid clusters. This eminent terminal oxidation outcome accumulates within cells during aging process.

METHODOLOGY/PRINCIPAL FINDINGS

Thirty two rabbits were assigned into four groups randomly of eight each. The first group encountered food deprivation for eight weeks and was kept in an isolated situation. The second group was food deprived for eight weeks but encountered to other groups continuously. The third group suffered two weeks of deprivation and then received free access to food. The fourth group had free access to diet without any deprivation. All hearts were removed for histopathological evaluation. Cross-sections of hearts were examined by light microscopy for the presence of yellow-brown Lipofuscin pigment granules. Here we show that relative food deprivation can cause accumulation of Lipofuscin pigmentation. We find that cardiac Lipofuscin deposition increases the most in the inequitable condition in which food deprived individuals observe well-fed individuals.

CONCLUSIONS/SIGNIFICANCE

Our findings demonstrate that a sense of inequality in food intake can promote aging more than food deprivation alone. These findings should be considered as a basis for further studies on the physiological mechanisms by which inequality negatively impacts health and well-being.

Neuronal pigmented autophagic vacuoles: lipofuscin, neuromelanin, and ceroid as macroautophagic responses during aging and disease

The most striking morphologic change in neurons during normal aging is the accumulation of autophagic vacuoles filled with lipofuscin or neuromelanin pigments. These organelles are similar to those containing the ceroid pigments associated with neurologic disorders, particularly in diseases caused by lysosomal dysfunction. The pigments arise from incompletely degraded proteins and lipids principally derived from the breakdown of mitochondria or products of oxidized catecholamines. Pigmented autophagic vacuoles may eventually occupy a major portion of the neuronal cell body volume because of resistance of the pigments to lysosomal degradation and/or inadequate fusion of the vacuoles with lysosomes. Although the formation of autophagic vacuoles via macroautophagy protects the neuron from cellular stress, accumulation of pigmented autophagic vacuoles may eventually interfere with normal degradative pathways and endocytic/secretory tasks such as appropriate response to growth factors.

Mitochondrially encoded cysteine predicts animal lifespan

The role of genetic factors in the determination of lifespan is undisputed. However, numerous successful efforts to identify individual genetic modulators of longevity have not yielded yet a quantitative measure to estimate the lifespan of a species from scratch, merely based on its genomic constitution. Here, we report on a meta-examination of genome sequences from 248 animal species with known maximum lifespan, including mammals, birds, fish, insects, and helminths. Our analysis reveals that the frequency with which cysteine is encoded by mitochondrial DNA is a specific and phylogenetically ubiquitous molecular indicator of aerobic longevity: long-lived species synthesize respiratory chain complexes which are depleted of cysteine. Cysteine depletion was also found on a proteome-wide scale in aerobic versus anaerobic bacteria, archaea, and unicellular eukaryotes; in mitochondrial versus hydrogenosomal sequences; and in the mitochondria of free-living, aerobic versus anaerobic-parasitic worms. The association of longevity with mitochondrial cysteine depletion persisted after correction for body mass and phylogenetic interdependence, but it was uncoupled in helminthic species with predominantly anaerobic lifestyle. We conclude that protein-coding genes on mitochondrial DNA constitute a quantitative trait locus for aerobic longevity, wherein the oxidation of mitochondrially translated cysteine mediates the coupling of trait and locus. These results provide distinct support for the free radical theory of aging.

Neurolipofuscin is a measure of age in Panulirus argus, the Caribbean spiny lobster, in Florida

Accurate age estimates for Panulirus argus, the commercially important Caribbean spiny lobster, would greatly enhance life history and population analyses. Most age approximations of P. argus are based on size and growth data, but size is generally considered a poor proxy for age of crustaceans in the field because of numerous environmental, density-dependent, and fishery-related factors. An established technique for aging crustaceans, employing histologically determined lipofuscin content in the nervous system, was investigated using known-age lobsters reared in the laboratory at ambient temperatures. We verified the presence of lipofuscin in eyestalk neural tissue by using autofluorescence and Sudan black staining and described its distribution in cell cluster A of the hemiellipsoid body. Neurolipofuscin accumulated with age; the overall trend was linear with indications of seasonal oscillation, whereas growth began to approach an asymptote after 3 years. Differences in the neurolipofuscin concentrations in the two eyestalks from the same animal were statistically insignificant. There was also no difference in the neurolipofuscin concentrations of males and females of the same age. The present data suggest a maximum potential lifespan for P. argus of about 20 years. These results also suggest that the neurolipofuscin technique will be valuable for estimating age of wild-caught specimens of P. argus.

The origin of fluorescence in the neuronal ceroid lipofuscinoses (Batten disease) and neuron cultures from affected sheep for studies of neurodegeneration

Lipofuscin and ceroid are usually held responsible for impaired cellular performance, via oxidative damage and the irreversible accumulation of fluorescent products of lipid peroxidation. The neuronal ceroid lipofuscinoses (NCLs, Batten disease) are inherited neurodegenerative diseases characterized by intracellular accumulation of fluorescent lipofuscin-like bodies. However these bodies are lysosomes packed with a particular protein, subunit c of mitochondrial ATP synthase; not the result of oxidative damage. No individual storage body component was fluorescent nor were solutions of total storage bodies. UV-vis spectra confirmed the lack of a fluorophor. Crystals of non-fluorescent albumin and reconstituted storage bodies were fluorescent in glycerol suspensions. This fluorescence is probably caused by interference of light reflected from the protein array, as is often observed in protein crystals. Other lipofuscins may be secondary lysosomes with a high protein content and the source of fluorescence the same. The neurodegeneration associated with lipofuscin accumulation may be caused by that accumulation, or may be a separate manifestation of aging. Neuronal cell cultures offer a way to study these processes. Subunit c accumulation has been observed in cerebral bipolar neurons cultured from 90 day NCL affected sheep foetuses. Neurons from different parts of the brain behave differently. Normal 108 day cerebellar granule neurons migrated into clumps when cultured with tri-iodothyronine, but affected cerebellar neurons did not, nor did normal or affected cerebral neurons.