Tubulin and actin mRNAs in the young-adult and the aged rat brain: effects of repeated administration with bifemelane hydrochloride

Age-related sex differences in the expression of important disease-linked mitochondrial proteins in mice

The prevalence and progression of many illnesses, such as neurodegenerative and cardiovascular diseases, obesity, and cancer, vary between women and men, often in an age-dependent manner. A joint hallmark of these diseases is some type of mitochondrial dysfunction. While several mitochondrial proteins are known to be regulated by sex hormones, the levels of those proteins have not been systematically analyzed with regard to sex and age, and studies that consider sex and/or age differences in the protein expression are very rare. In this study, we compared the expression patterns of physiologically important mitochondrial proteins in female and male C57BL/6N mice of age cohorts frequently used in experiments. We found that sex-related differences in the expression of uncoupling proteins 1 and 3 (UCP1 and UCP3) occur in an age-dependent manner. The sex-specific expression of UCP1 and UCP3 in brown adipose tissue (BAT) was inversely correlated with differences in body weight. Expression of UCP4 in the brain, Complex I in the spleen, and Complex II in the brain and BAT was least affected by the sex of the mouse. We further demonstrated that there are serious limitations in using VDAC1 and actin as markers in western blot analyses, due to their sex- and age-specific fluctuations. Our results confirm that sex and age are important parameters and should be taken into account by researchers who examine the mechanistic aspects of diseases. HIGHLIGHTS: I.The levels of UCP1 and UCP3 protein expression differ between females and males in an age-dependent manner.II.Pre-pubertal expression of almost all proteins tested in this study does not depend on the sex of the mouse.III.Expression of VDAC1 and actin, which are often used as loading control proteins in western blot analysis, is tissue-specifically influenced by sex and age.

A small molecule screening to detect potential therapeutic targets in human podocytes

WIDMEIER E, TAN W, AIRIK M, HILDEBRANDT F

A small molecule screening to detect potential therapeutic targets in human podocytes. Am J Physiol Renal Physiol 312: F157-F171, 2017. First published October 19, 2016; doi:10.1152/ajprenal.00386.2016. Steroid-resistant nephrotic syndrome (SRNS) inevitably progresses to end-stage kidney disease, requiring dialysis or transplantation for survival. However, treatment modalities and drug discovery remain limited. Mutations in over 30 genes have been discovered as monogenic causes of SRNS. Most of these genes are predominantly expressed in the glomerular epithelial cell, the podocyte, placing it at the center of the pathogenesis of SRNS. Podocyte migration rate (PMR) represents a relevant intermediate phenotype of disease in monogenic causes of SRNS. We therefore adapted PMR in a high-throughput manner to screen small molecules as potential therapeutic targets for SRNS. We performed a high-throughput drug screening of a National Institutes of Health Clinical Collection (NCC) library (n = 725 compounds) measuring PMR by videomicroscopy. We used the Woundmaker to perform individual 96-well scratch wounds and screened compounds using a quantitative kinetic live cell imaging migration assay using IncuCyte ZOOM technology. Using a normal distribution for the average PMR in wild-type podocytes with a vehicle control (DMSO), we applied a 90% confidence interval to define "distinct" compounds (5% faster/slower PMR) and found that 12 of 725 compounds (at 10 μM) reduced PMR. Clusters of drugs that alter PMR included actin/tubulin modulators such as the azole class of antifungals and antineoplastic vinca-alkaloids. We hereby identify compounds that alter PMR. The PMR assay provides a new avenue to test therapeutics for nephrotic syndrome. Positive results may reveal novel pathways in the study of glomerular diseases such as SRNS.

Age-associated changes in synaptic lipid raft proteins revealed by two-dimensional fluorescence difference gel electrophoresis

Brain aging is associated with a progressive decline in cognitive function though the molecular mechanisms remain unknown. Functional changes in brain neurons could be due to age-related alterations in levels of specific proteins critical for information processing. Specialized membrane microdomains known as 'lipid rafts' contain protein complexes involved in many signal transduction processes. This study was undertaken to determine if two-dimensional fluorescence difference gel electrophoresis (2D DIGE) analysis of proteins in synaptic membrane lipid rafts revealed age-dependent alterations in levels of raft proteins. Five pairs of young and aged rat synaptic membrane rafts were subjected to DIGE separation, followed by image analysis and identification of significantly altered proteins. Of 1046 matched spots on DIGE gels, 94 showed statistically significant differences in levels between old and young rafts, and 87 of these were decreased in aged rafts. The 41 most significantly altered (p<0.03) proteins included several synaptic proteins involved in energy metabolism, redox homeostasis, and cytoskeletal structure. This may indicate a disruption in bioenergetic balance and redox homeostasis in synaptic rafts with brain aging. Differential levels of representative identified proteins were confirmed by immunoblot analysis. Our findings provide novel pathways in investigations of mechanisms that may contribute to altered neuronal function in aging brain.

Proteomics analyses of specific protein oxidation and protein expression in aged rat brain and its modulation by L-acetylcarnitine: insights into the mechanisms of action of this proposed therapeutic agent for CNS disorders associated with oxidative stress

Impaired function of the central nervous system (CNS) in aged animals is associated with increased susceptibility to the development of many neurodegenerative diseases. Age-related functional deterioration in brain is consistent with the free radical theory of aging that predicts, among other things, that free radical reactions with and damage to biomolecules, such as proteins and membrane lipid bilayers, leads to loss of neurons and subsequently diminished cognition. These oxidatively modified biomolecules are believed to contribute to the decreased antioxidant content, mitochondrial dysfunction, and impaired plasticity in aged brains. Treatment of rodents with L-acetylcarnitine (LAC; gamma-trimethyl-beta-acetylbutyrobetaine) can improve these functional losses. Although it is well established that administration of LAC can decrease protein oxidation in aged brains, it is not clear which proteins are decreased in their level of oxidation in the brains of aged rats treated with LAC. The current study used a parallel redox proteomics approach to identify the proteins that are oxidized in aged rat cortex and hippocampus of aged rats. Moreover, those proteins that are reduced in oxidation status were identified in aged brains from rats treated in vivo with LAC. The findings are discussed in reference to brain aging and age-related cognitive impairment.

Comparison of hippocampal synaptosome proteins in young-adult and aged rats

The hippocampus is important in learning and memory functions but its ability to aid in these functions declines during aging. In this study, we examined hippocampal proteins whose expressions changed in the aging process. A comparison of synaptosome proteins of hippocampus prepared from young-adult (9-week-old) rats with those from aged (30-month-old) rats by two-dimensional fluorescence difference gel electrophoresis revealed 24 spots that were expressed differently among about 1000 spots detected in both young-adult and aged rat samples. Nineteen of these 24 spots were identified by peptide mass fingerprinting. These proteins included chaperone proteins and proteins related to the cytoskeleton, neurotransmission, signal transduction and energy supply. The cytoskeleton-related proteins included actin and T-complex 1, which is thought to play a role in actin folding. Actin was up-regulated but T-complex 1 was down-regulated in aged rat synapses. These results suggest that age-dependent changes of actin filament formation are related to neuronal dysfunction associated with aging.