Alzheimer's disease (AD) is an age-related neurodegenerative disorder. Development of AD is closely related to alterations of proteostasis including the deposition of amyloid beta (Aβ) and ...hyperphosphorylated tau in the brain. Molecular chaperones such as αB-crystallin (CryaB) can prevent aggregation of proteins and enable their correct refolding. The p38 mitogen-activated protein kinase signaling (MAPK) pathway regulates CryaB activity through phosphorylation of CryaB. Here, we examined CryaB and phospho-(p-)Ser59-CryaB protein amounts in the prefrontal cortex of the senescence-accelerated OXYS rats at different stages of the development of AD-like pathology and in Wistar rats (control). We compared this result with the changes in the expression of genes involved in the p38 MAPK signaling pathway in the prefrontal cortex of both rat strains. Manifestation and progression of AD-like pathology in OXYS rats were accompanied by an increased level of detergent-insoluble p-Ser59-CryaB in the brain cortex, while the CryaB amount did not change. p-Ser59-CryaB was absent in the detergent-soluble protein fraction of the cortex in both rat strains. Immunostaining of brain slices revealed notable colocalization of p-Ser59-CryaB with Aβ in 18-month-old OXYS rats. According to RNA sequencing data, the development of AD-like pathology in OXYS rats is accompanied in the cortex by up- and downregulation of genes involved in p38 MAPK signaling. In general, we demonstrated that the manifestation AD-like pathology in OXYS rats occurs against the background of activation of p38 MAPK–dependent CryaB phosphorylation and alterations of the p38 MAPK signaling pathway. The increased p-Ser59-CryaB amount and its colocalization with Aβ can be considered a response to the accumulation of protein aggregates and may be an important part of an endogenous mechanism of AD development.
•AD development co-occurs with increased p38-dependent CryaB phosphorylation.•p-Ser59-CryaB is only in a detergent-insoluble protein fraction of rat brain cortex.•p-Ser59-CryaB is colocalized with amyloid β in the rat brain cortex.
Neurogenesis is the key mechanism of neuronal plasticity in the adult mammalian brain. Alterations of neurogenesis happen concurrently with (and contribute to) development and progression of numerous ...neuropathological conditions including Alzheimer's disease (AD). Being the most common type of dementia, AD is studied extensively; however, the data concerning changes in neurogenesis in the pathogenesis of this disease are inconsistent. Here, using OXYS rats as a suitable model of the most common (sporadic) form of AD, we examined neurogenesis in the hippocampal dentate gyrus in early ontogenesis prior to appearance of any signs of neurodegeneration and during development and progression of AD-like pathology. We demonstrated retardation of hippocampal development in OXYS rats at an early age; this problem may contribute to the emergence of AD signs late in life. Manifestation and progression of AD-like pathology are accompanied by transcriptome changes affecting genes involved in neurogenesis in the hippocampus. These genes are associated with the extracellular matrix and angiogenesis; this observation points to alteration of a cellular microenvironment. This change along with an increased TrkA/p75NTR ratio of nerve growth factor receptors in the hippocampus may contribute to increased density of immature neurons that we observed at the progressive stage of AD-like pathology in OXYS rats. These changes may be considered a compensatory reaction intended to slow down AD-associated neurodegeneration at the progressive stage of the disease. Collectively, these data suggest that alterations of neurogenesis may not only accompany the course of Alzheimer's disease but also play a causative role in this disorder.
•Delay in hippocampal development may contribute to neurodegeneration late in life.•Changes of neurogenesis precede development of Alzheimer's disease-like pathology.•Alteration of neurogenic niche occurs during Alzheimer's disease-like pathology.•Neurodegeneration is accompanied by imbalance of hippocampal neurotrophic support.
Small non-coding RNAs are an important class of regulatory RNAs in bacteria, often regulating responses to changes in environmental conditions. OxyS is a 110 nucleotide, stable, trans-encoded small ...RNA found in Escherichia coli and is induced by an increased concentration of hydrogen peroxide. OxyS has an important regulatory role in cell stress response, affecting the expression of multiple genes. In this work, we investigated the structure of OxyS and the interaction with fhlA mRNA using nuclear magnetic resonance spectroscopy, small-angle X-ray scattering and unbiased molecular dynamics simulations. We determined the secondary structures of isolated stem-loops and confirmed their structural integrity in OxyS. Unexpectedly, stem-loop SL4 was identified in the region that was predicted to be unstructured. Three-dimensional models of OxyS demonstrate that OxyS adopts an extended structure with four solvent-exposed stem-loops, which are available for interaction with other RNAs and proteins. Furthermore, we provide evidence of base pairing between OxyS and fhlA mRNA.
Alzheimer’s disease (AD) is an old-age neurodegenerative disorder; however, AD predisposition may arise early in life. Vascular dysfunction makes a big contribution to AD development. Nonetheless, ...the possible role of early-life vascular dysfunction in AD development is still poorly investigated. Here, using OXYS rats as a suitable model of the most common (sporadic) type of AD, we investigated maturation of the blood–brain barrier (BBB) in the hippocampus and frontal cortex in the first 3 weeks of life. Using RNA-Seq data, we found an altered expression of BBB-associated genes in the middle of the first and second weeks of life in OXYS rats compared to control rats (Wistar strain). Moreover, by immunohistochemistry and electronic microscopy, we revealed a delay of vascularization and of subsequent pericyte coating of blood vessels in OXYS rats. These specific features were accompanied by an accelerated decrease in BBB permeability estimated using Evans blue dye. Notably, almost all of the observed differences from Wistar rats disappeared on postnatal day 20. Nonetheless, the observed features, which are characteristic of the postnatal period, may have long-term consequences and contribute to neurovascular dysfunction observed in OXYS rats late in life, thereby promoting early development of AD signs.
The hydrogen peroxide-induced small RNA OxyS has been proposed to originate from the 3' UTR of a peroxide mRNA. Unexpectedly, phylogenetic OxyS targetome predictions indicate that most OxyS targets ...belong to the category of "cell cycle," including cell division and cell elongation. Previously, we reported that
OxyS inhibits cell division by repressing expression of the essential transcription termination factor
, thereby leading to the expression of the KilR protein, which interferes with the function of the major cell division protein, FtsZ. By interfering with cell division, OxyS brings about cell-cycle arrest, thus allowing DNA damage repair. Cell division and cell elongation are opposing functions to the extent that inhibition of cell division requires a parallel inhibition of cell elongation for the cells to survive. In this study, we report that in addition to cell division, OxyS inhibits
, which encodes an essential peptidoglycan endopeptidase that is responsible for cell elongation. Our study indicates that cell-cycle arrest and balancing between cell division and cell elongation are important and conserved functions of the oxidative stress-induced sRNA OxyS.
Abstract
Small RNAs (sRNAs) are important gene regulators in bacteria, but it is unclear how new sRNAs originate and become part of regulatory networks that coordinate bacterial response to ...environmental stimuli. Using a covariance modeling-based approach, we analyzed the presence of hundreds of sRNAs in more than a thousand genomes across Enterobacterales, a bacterial order with a confluence of factors that allows robust genome-scale sRNA analyses: several well-studied organisms with fairly conserved genome structures, an established phylogeny, and substantial nucleotide diversity within a narrow evolutionary space. We discovered that a majority of sRNAs arose recently, and uncovered protein-coding genes as a potential source from which new sRNAs arise. A detailed investigation of the emergence of OxyS, a peroxide-responding sRNA, revealed that it evolved from a fragment of a peroxidase messenger RNA. Importantly, although it replaced the ancestral peroxidase, OxyS continues to be part of the ancestral peroxide-response regulon, indicating that an sRNA that arises from a protein-coding gene would inherently be part of the parental protein’s regulatory network. This new insight provides a fresh framework for understanding sRNA origin and regulatory integration in bacteria.
Translational research on Alzheimer's disease (AD) has often focused on reducing the high cerebral levels of amyloid‐β (Aβ) as a key characteristic of AD pathogenesis. There is, however, a growing ...body of evidence that synaptic dysfunction may be crucial for the development of the most common (sporadic) form of AD. The applicability of melatonin (mainly produced by the pineal gland) to the treatment of AD is actively evaluated, but usually, such studies are based on animal models of early‐onset AD, which is responsible for only ~5% of AD cases. We have shown previously that in OXYS rats (an established model of sporadic AD), accumulation of toxic forms of Aβ in the brain occurs later than does the development of signs of neurodegenerative changes and synaptic failure. In this regard, recently, we uncovered beneficial neuroprotective effects of melatonin (prophylactic dietary supplementation) in OXYS rats. Our aim here was to evaluate, starting at the age of active progression of AD‐like pathology in OXYS rats, the effects of long‐term oral administration of melatonin on the structure of synapses and on neuronal and glial cells of the hippocampus. Melatonin significantly increased hippocampal synaptic density and the number of excitatory synapses, decreased the number of inhibitory synapses, and upregulated pre‐ and postsynaptic proteins (synapsin I and PSD‐95, respectively). Furthermore, melatonin improved the ultrastructure of neuronal and glial cells and reduced glial density. Based on our past and present results, the repair of neuroplasticity by melatonin is a promising strategy against AD.
Cerebrovascular dysfunction plays a critical role in the pathogenesis of Alzheimer's disease (AD): the most common cause of dementia in the elderly. The involvement of neurovasculature disorders in ...the progression of AD is now increasingly appreciated, but whether they represent initial factors or late-stage pathological changes during the disease is unclear. Using senescence-accelerated OXYS rats, which simulate key characteristics of sporadic AD, we evaluated contributions of cerebrovascular alterations to the disease development. At preclinical, early, and advanced stages of AD-like pathology, in the hippocampus of OXYS and Wistar (control) rats, we evaluated (i) the blood vessel state by histological and electron-microscopic analyses; (ii) differences in gene expression according to RNA sequencing (RNA-Seq) to identify the metabolic processes and pathways associated with blood vessel function; (iii) the amount of vascular endothelial growth factor (VEGF) by western blot and immunohistochemical analysis.
We observed a loss of hippocampal blood vessel density and ultrastructural changes of those blood vessels in OXYS rats at the early stage of AD-like pathology. There were significant alterations in the vessels and downregulation of VEGF with an increased amount of amyloid β
there at the advanced stage of the disease. According to RNA-Seq data analysis, major alterations in cerebrovascular processes of OXYS rats were associated with blood vessel development, circulatory system processes, the VEGF signaling pathway, and vascular smooth muscle contraction. At preclinical and early stages of the AD-like pathology, these processes were upregulated and then downregulated with age. At the advanced stage in OXYS rats, differentially expressed genes (DEGs) were associated with downregulation of cerebrovascular function as compared to Wistar rats. Among the 46 DEGs at the preclinical stage of the disease, 28 DEGs at the early stage, and among 85 DEGs at the advanced stage, using functional analysis and gene network construction, we identified genes (Nos1, P2rx4, Pla2g6, and Bdkrb2) probably playing a significant role in the development of cerebrovascular dysfunction in OXYS rats.
Changes in expression of the genes functionally associated with cerebrovascular processes already in the early period of life may contribute to the development of AD-like pathology in OXYS rats.
Antibiotics have been one of the most successful forms of therapy in medicine. However, the efficiency of antibiotics is compromised by the emergence of antibiotic-resistant pathogens. To reduce ...antibiotic resistance, complete understanding of bacterial tactics to defend themselves against antibiotics is necessary. Small-noncoding RNAs (sRNAs) modulate gene expression by base-pairing with multiple target mRNAs. Cellular levels of Hfq-dependent sRNAs influence antibiotic resistance by modulating expression of specific target genes; therefore, such sRNAs could be a good tool to identify target mRNAs that modulate antibiotic susceptibility and may themselves be used as druggable molecules. Here, we report the identification of genes and pathways associated with OxyS RNA-mediated cephalothin resistance using phenotypic and expression analyses of OxyS-regulated genes identified by RNA-seq, literature mining, or predictions. From our studies we found that the differential expression of 27 OxyS-regulated genes was involved in cephalothin susceptibility. Among them, 17 gene knockouts showed resistance to the drug and nine from them is associated with cAMP receptor protein (CRP), a transcriptional dual regulator in E. coli. Moreover, levels of OxyS and OxyS-modulated genes (cycA and cysH) were also altered in multidrug-resistant (MDR) E. coli strains. Together, our data suggest that OxyS extensively modulates gene expression in multiple pathways to develop cephalothin resistance. In addition, OxyS and its regulated target genes, either individually or in combination, could be used as molecular markers and targets for the identification and eradication of cephalothin-resistant strains.
•Expression profile of E. coli mRNAs regulated by OxyS RNA was analyzed.•Influence of OxyS-regulated genes on cephalothin susceptibility was tested.•17 CRP-associated pathway genes are involved in the cephalothin resistance.•The expression pattern of OxyS-mediated cephalothin resistance was similarly identified in multidrug-resistant strains.•OxyS RNA and its target mRNAs could be used as molecular markers to detect cephalothin resistance in E. coli.
Age-related macular degeneration (AMD) is the leading cause of irreversible visual impairment worldwide. Age is the greatest risk factor for AMD but the underlying mechanism remains unascertained, ...resulting in a lack of effective therapies. Growing evidence shows that dysregulation of the p38 MAPK signaling pathway (SP) contributes to aging and neurodegenerative diseases; however, information about its alteration in the retina with age and during AMD development is limited. To assess the contribution of alterations in p38 MAPK signaling to AMD, we compared age-associated changes in p38 MAPK SP activity in the retina between Wistar rats (control) and OXYS rats, which develop AMD-like retinopathy spontaneously. We analyzed changes in the mRNA levels of genes of this SP in the retina (data of RNA-seq) and evaluated the phosphorylation/activation of key kinases using Western blotting at different stages of AMD-like pathology including the preclinical stage. p38 MAPK SP activity increased in the retinas of healthy Wistar rats with age. The manifestation and dramatic progression of AMD-like pathology in OXYS rats was accompanied by hyperphosphorylation of p38 MAPK and MK2 as key p38 MAPK SP kinases. Retinopathy progression co-occurred with the enhancement of p38 MAPK-dependent phosphorylation of CryaB at Ser59 in the retina.
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