Senescence-accelerated mouse (SAM) with special references to neurodegeneration models, SAMP8 and SAMP10 mice

Saponins from Astragalus membranaceus (Fisch.) Bge Alleviated Neuronal Ferroptosis in Alzheimer's Disease by Regulating the NOX4/Nrf2 Signaling Pathway

Alzheimer's disease (AD) is a chronic neurodegenerative disease of the central nervous system caused by loss of neuronal or myelin function, accompanied by ferroptosis. Astragalus membranaceus (Fisch.) Bge. (A. membranaceus) is one of China's homologous lists of medicines and food, and its active component saponins have neuroprotective effects. This study examines the mechanism of saponins from A. membranaceus (AS) in treating AD. UPLC-Q-TOF-MS analyzed the composition of AS. Ferroptosis models were established to evaluate the anti-AD efficacy. As a result, AS treatment inhibited ferroptosis in SAMP8 mice by restoring iron homeostasis and lipid peroxidation (LPO) balance in the brain, thereby improving cognitive impairment and pathological damage. Mechanistically, AS treatment reduced Fe2+, MDA, and ROS levels and enhanced protein levels of SLC7A11, GPX4, FTH1, and FPN1. NADPH oxidase 4 (NOX4) overexpression revealed that AS treatment inhibited NOX4, thereby reducing NOX4 stability and regulating the NOX4/Nrf2 pathway in erastin-injured HT22 cells and significantly alleviating ferroptosis. Therefore, AS inhibited ferroptosis and improved AD by rebuilding iron homeostasis and LPO balance in the brain. AS has the potential to be a promising candidate medicine for AD.

Age-related increase in the excitability of mouse layer V pyramidal neurons in the primary motor cortex is accompanied by an increased persistent inward current

Sarcopenia, or pathological age-related loss of muscle strength and mass, contributes to physical function impairment in older adults. While current understanding of sarcopenia is centered mostly on neuromuscular mechanisms, mounting evidence supports that deficits at the level of the primary motor cortex (PMC) play a significant role. Despite the importance of the PMC to initiate movement, understanding of how age affects the excitability of layer V pyramidal neurons (LVPNs) of the PMC is limited. To address this, we used the whole-cell patch clamp technique to measure the excitability of LVPNs of the PMC in young, late adulthood, and old mice. Old LVPNs had increased firing frequency and membrane input resistance, but no differences in action potential kinetics versus young and late adulthood mice. Since changes in the persistent inward current (PIC) are known to contribute to changes in motor neuron excitability, we measured LVPN PICs as a putative contributor to LVPN excitability. The PIC amplitude was increased in old LVPN via increases in Na+ and Ca2+ PICs, in addition to being active across a wider voltage range. Given that LVPN function is integral to initiation of voluntary muscle contraction, altered LVPN excitability likely contributes to age-related impairment of physical function.

Murine Non-Transgenic Models of Alzheimer's Disease Pathology: Focus on Risk Factors

Alzheimer's disease (AD) represents a significant challenge among neurodegenerative disorders, as effective treatments and therapies remain largely undeveloped. Despite extensive research efforts employing various methodologies and diverse genetic models focused on amyloid-β (Aβ) pathology, the research for effective therapeutic strategies remains inconclusive. The key pathological features of AD include Aβ senile plaques, neurofibrillary tangles (NFTs), and the activation of neuroinflammatory pathways. Presently, investigations into AD and assessing potential treatments predominantly utilize Aβ transgenic models. Conversely, non-transgenic models may provide valuable insights into the multifaceted pathological states associated with AD. Thus, these models may serve as practical complementary tools for evaluating therapeutic and intervention strategies, since the primary AD risk factors are most frequently modeled. This review aims to critically assess the existing literature on AD non-transgenic models induced by streptozotocin, scopolamine, aging, mechanical stress, metals, and dietary patterns to enhance their application in AD research.

Deciphering the role of IGFBP5 in delaying fibrosis and sarcopenia in aging skeletal muscle: therapeutic implications and molecular mechanisms

Introduction

Sarcopenia is a condition characterized by the loss of muscle fibers and excessive deposition of extracellular matrix proteins. The interplay between muscle atrophy and fibrosis is a central feature of sarcopenia. While the mechanisms underlying skeletal muscle aging and fibrosis remain incompletely understood, cellular senescence has emerged as a key contributor. This study investigates the role of D-galactose (D-gal) in inducing fibroblasts senescence and skeletal muscle fibrosis, and aims to find the key regulator of the process to serve as a therapeutical target.

Methods

To discover the role of D-gal in inducing cellular senescence and fibrosis, the senescence markers and the expression of fibrosis-related proteins were assessed after introducing D-gal among fibroblasts, and muscle strength and mass. The severity of muscle atrophy and fibrosis were also verified by using H&E staining and Masson trichrome staining after D-gal treatment via subcutaneous injection among mice. Subsequently, mRNA sequencing (RNA-seq) was performed and the differential expressed genes were identified between under D-gal or control treatment, to discover the key regulator of D-GAL-driven fibroblasts senescence and fibrosis. The role of the key regulator IGFBP5 were then validated in D-GAL treated IGFBP5-knockdown fibroblasts in vitro by analyzing the level of senescence and fibrosis-related markers. And the results were further confirmed in vivo in IGFBP5-knockdown SAMP8 mice with histological examinations.

Results

D-gal treatment effectively induced cellular senescence and fibrosis in fibroblasts, as well as skeletal muscle atrophy, fibrosis and loss in muscle mass and function in mice. IGFBP5 was identified as a key regulator of D-GAL induced senescence and fibrosis among fibroblasts using RNA-seq. And further validation tests showed that IGFBP5-knockdown could alleviate D-GAL-induced fibroblast cellular senescence and fibrosis, as well as the severity of muscle atrophy and fibrosis in SAMP8 mice.

Discussion

IGFBP5 emerging as a key regulator of D-GAL-induced fibroblast cellular senescence and fibrosis. The findings provide new insights into the molecular mechanisms underlying age-related skeletal muscle fibrosis and highlight IGFBP5 as a potential therapeutic target. Further research is needed to validate these findings and explore related clinical applications.

Targeting farnesoid X receptor as aging intervention therapy

Environmental toxicants have been linked to aging and age-related diseases. The emerging evidence has shown that the enhancement of detoxification gene expression is a common transcriptome marker of long-lived mice, Drosophila melanogaster, and Caenorhabditis elegans. Meanwhile, the resistance to toxicants was increased in long-lived animals. Here, we show that farnesoid X receptor (FXR) agonist obeticholic acid (OCA), a marketed drug for the treatment of cholestasis, may extend the lifespan and healthspan both in C. elegans and chemical-induced early senescent mice. Furthermore, OCA increased the resistance of worms to toxicants and activated the expression of detoxification genes in both mice and C. elegans. The longevity effects of OCA were attenuated in Fxr -/- mice and Fxr homologous nhr-8 and daf-12 mutant C. elegans. In addition, metabolome analysis revealed that OCA increased the endogenous agonist levels of the pregnane X receptor (PXR), a major nuclear receptor for detoxification regulation, in the liver of mice. Together, our findings suggest that OCA has the potential to lengthen lifespan and healthspan by activating nuclear receptor-mediated detoxification functions, thus, targeting FXR may offer to promote longevity.

Qiangji decoction mitigates neuronal damage, synaptic and mitochondrial dysfunction in SAMP8 mice through the regulation of ROCK2/Drp1-mediated mitochondrial dynamics

ETHNOPHARMACOLOGICAL RELEVANCE

Qiangji Decoction (QJD), a Chinese medicine, is widely used in Traditional Chinese Medicine to treat amnesia and Alzheimer's disease (AD), showing significant anti-AD effects. However, the precise mechanisms behind these effects are not well understood and require more research.

AIM OF THE STUDY

This study aims to elucidate the mechanisms by which QJD ameliorates neuronal damage, synaptic dysfunction, and mitochondrial impairment in AD through the regulation of ROCK2/Drp1-mediated mitochondrial dynamics.

MATERIALS AND METHODS

UPLC-Q-TOF-MS/MS was used to identify active components in QJD extract. The study used SAMP8 mice for AD modeling and SAMR1 mice as controls. Cognitive function in SAMP8 mice was assessed with the Morris Water Maze after following treatment with QJD and the mitochondrial fission inhibitor Mdivi-1. Nissl and FJB staining evaluated QJD's effect on hippocampal injury. Synaptic integrity was examined with Golgi-Cox staining, transmission electron microscopy, and immunofluorescence. Mitochondrial function in hippocampal neurons was assessed using electron microscopy, JC-1 staining, and reagent kits. Western blot analyzed expression of proteins related to mitochondrial fission (ROCK2, Drp1, Fis1, Mff) and fusion (Mfn1, Mfn2, OPA1).

RESULTS

The analysis of QJD extract via UPLC-Q-TOF-MS/MS led to the identification of 46 active compounds. In SAMP8 mice, administration of QJD resulted in decreased escape latency, increased platform crossings, and extended duration in the target quadrant. Additionally, QJD exhibited neuroprotective effects on the hippocampus of SAMP8 mice, effectively preventing neuronal loss and damage. QJD also facilitated the extension and thickening of dendritic spines, enhanced the ultrastructure of hippocampal synapses, and upregulated synaptic function-related proteins, including PSD95 and SYN1. Furthermore, QJD ameliorated mitochondrial damage, improved mitochondrial membrane potential and ATP content, and reduced ROS expression in hippocampal neurons of SAMP8 mice. These effects were mediated through the downregulation of ROCK2, phosphorylated Drp1 (Ser616), Fis1, and Mff, as well as the upregulation of Mfn1, Mfn2, and OPA1.

CONCLUSIONS

QJD may reduce neuronal damage, synaptic dysfunction, and mitochondrial impairment in SAMP8 mice by regulating mitochondrial dynamics through the ROCK2/Drp1 pathway.

Characterization of a natural model of adult mice with different rate of aging

Aging is a heterogeneous process, so individuals of the same age may be aging at a different rate. A natural model of premature aging in mice have been proposed based on the poor response to the T-maze. Those that take longer to cross the intersection are known as Prematurely Aging Mice (PAM), while those that show an exceptional response are known as Exceptional non-PAM (E-NPAM), being the rest non-PAM (NPAM). Although many aspects of PAM and E-NPAM have been described, some aspects of their brain aging have not been studied. Similarly, it is known that PAM, NPAM and E-NPAM show a different rate of aging and longevity, but the differences between these three groups in behavior, immune function and oxidative-inflammatory state are unknown. The present study aims to deepen the study of brain aging in PAM and E-NPAM, and to study the differences in behavior, immunity, and oxidative-inflammatory state of peritoneal leukocytes between PAM, NPAM and E-NPAM. Results show deteriorated brains in PAM. Moreover, NPAM show an oxidative state similar to E-NPAM, an anxiety similar to PAM, and an intermediate immunity and lifespan between PAM and E-NPAM. In conclusion, immune function seems to be more associated with the longevity achieved.

High-fat diet-induced obesity accelerates the progression of spontaneous osteoarthritis in senescence-accelerated mouse prone 8

OBJECTIVES

Ageing and obesity are major risk factors for osteoarthritis (OA), a widespread disease currently lacking efficient treatments. Senescence-accelerated mouse prone 8 (SAMP8) display early onset ageing phenotypes, including OA. This study investigates the impacts of high-fat diet (HFD)-induced obesity on OA development in SAMP8.

METHODS

SAMP8 at 5 weeks were fed either a normal chow diet or an HFD for 10 weeks to induce obesity. Parameters related to obesity, liver function, and lipid and glucose metabolism were analysed. At 14 weeks of age, knee joint pathology, bone mineral density, and muscle strength were assessed. Immunohistochemistry and TUNEL staining were performed to evaluate markers for cartilage degeneration and chondrocyte apoptosis.

RESULTS

At 14 weeks of age, HFD-induced obesity increased liver and adipose tissue inflammation in SAMP8 without further exacerbating diabetes. Histological scoring revealed aggravated cartilage, menisci deterioration, and synovitis, while no further loss of bone mineral density or muscle strength was observed. Increased chondrocyte apoptosis was detected in knee joints following HFD feeding.

CONCLUSIONS

Ten weeks of HFD feeding promotes spontaneous OA progression in 14-week-old SAMP8, potentially via liver damage that subsequently leads to chondrocyte apoptosis. This ageing-obese mouse model may prove valuable for further exploration of spontaneous OA pathophysiology.

More than a number: Incorporating the aged phenotype to improve in vitro and in vivo modeling of neurodegenerative disease

Age is the number one risk factor for developing a neurodegenerative disease (ND), such as Alzheimer's disease (AD) or Parkinson's disease (PD). With our rapidly ageing world population, there will be an increased burden of ND and need for disease-modifying treatments. Currently, however, translation of research from bench to bedside in NDs is poor. This may be due, at least in part, to the failure to account for the potential effect of ageing in preclinical modelling of NDs. While ageing can impact upon physiological response in multiple ways, only a limited number of preclinical studies of ND have incorporated ageing as a factor of interest. Here, we evaluate the aged phenotype and highlight the critical, but unmet, need to incorporate aspects of this phenotype into both the in vitro and in vivo models used in ND research. Given technological advances in the field over the past several years, we discuss how these could be harnessed to create novel models of ND that more readily incorporate aspects of the aged phenotype. This includes a recently described in vitro panel of ageing markers, which could help lead to more standardised models and improve reproducibility across studies. Importantly, we cannot assume that young cells or animals yield the same responses as seen in the context of ageing; thus, an improved understanding of the biology of ageing, and how to appropriately incorporate this into the modelling of ND, will ensure the best chance for successful translation of new therapies to the aged patient.

Protein Oxidation in Aging and Alzheimer's Disease Brain

Proteins are essential molecules that play crucial roles in maintaining cellular homeostasis and carrying out biological functions such as catalyzing biochemical reactions, structural proteins, immune response, etc. However, proteins also are highly susceptible to damage by reactive oxygen species (ROS) and reactive nitrogen species (RNS). In this review, we summarize the role of protein oxidation in normal aging and Alzheimer's disease (AD). The major emphasis of this review article is on the carbonylation and nitration of proteins in AD and mild cognitive impairment (MCI). The oxidatively modified proteins showed a strong correlation with the reported changes in brain structure, carbohydrate metabolism, synaptic transmission, cellular energetics, etc., of both MCI and AD brains compared to the controls. Some proteins were found to be common targets of oxidation and were observed during the early stages of AD, suggesting that those changes might be critical in the onset of symptoms and/or formation of the pathological hallmarks of AD. Further studies are required to fully elucidate the role of protein oxidation and nitration in the progression and pathogenesis of AD.

Optical development in the murine eye lens of accelerated senescence-prone SAMP8 and senescence-resistant SAMR1 strains

The eye lens is responsible for focusing objects at various distances onto the retina and its refractive power is determined by its surface curvature as well as its internal gradient refractive index (GRIN). The lens continues to grow with age resulting in changes to the shape and to the GRIN profile. The present study aims to investigate how the ageing process may influence lens optical development. Murine lenses of accelerated senescence-prone strain (SAMP8) aged from 4 to 50 weeks; senescence-resistant strain (SAMR1) aged from 5 to 52 weeks as well as AKR strain (served as control) aged from 6 to 70 weeks were measured using the X-ray interferometer at the SPring-8 synchrotron Japan within three consecutive years from 2020 to 2022. Three dimensional distributions of the lens GRIN were reconstructed using the measured data and the lens shapes were determined using image segmentation in MatLab. Variations in the parameters describing the lens shape and the GRIN profile with age were compared amongst three mouse strains. With advancing age, both the lens anterior and posterior surface flattens and the lens sagittal thickness increase in all three mouse strains (Anterior radius of curvature increase at 0.008 mm/week, 0.007 mm/week and 0.002 mm/week while posterior radius of curvature increase at 0.002 mm/week, 0.007 mm/week and 0.003 mm/week respectively in AKR, SAMP8 and SAMR1 lenses). Compared with the AKR strain, the SAMP8 samples demonstrate a higher rate of increase in the posterior curvature radius (0.007 mm/week) and the thickness (0.015 mm/week), whilst the SAMR1 samples show slower increases in the anterior curvature radius (0.002 mm/week) and its thickness (0.013 mm/week). There are similar age-related trends in GRIN shape in the radial direction (in all three types of murine lenses nr2 and nr6 increase with age while nr4 decrease with age consistently) but not in the axial direction amongst three mouse strains (nz1 of AKR lens decrease while of SAMP8 and SAMR1 increase with age; nz2 of all three models increase with age; nz3 of AKR lens increase while of SAMP8 and SAMR1 decrease with age). The ageing process can influence the speed of lens shape change and affect the GRIN profile mainly in the axial direction, contributing to an accelerated decline rate of the optical power in the senescence-prone strain (3.5 D/week compared to 2.3 D/week in the AKR control model) but a retardatory decrease in the senescence-resistant strain (2.1 D/week compared to the 2.3D/week in the AKR control model).

Dopaminergic neuron loss in mice due to increased levels of wild-type human α-Synuclein only takes place under conditions of accelerated aging

Understanding the intricate pathogenic mechanisms behind Parkinson's disease (PD) and its multifactorial nature presents a significant challenge in disease modeling. To address this, we explore genetic models that better capture the disease's complexity. Given that aging is the primary risk factor for PD, this study investigates the impact of aging in conjunction with overexpression of wild-type human α-synuclein (α-Syn) in the dopaminergic system. This is achieved by introducing a novel transgenic mouse strain overexpressing α-Syn under the TH-promoter within the senescence-accelerated SAMP8 (P8) genetic background. Behavioral assessments, conducted at both 10 and 16 months of age, unveil motor impairments exclusive to P8 α-SynTg mice, a phenomenon conspicuously absent in α-SynTg mice. These findings suggest a synergistic interplay between heightened α-Syn levels and the aging process, resulting in motor deficits. These motor disturbances correlate with reduced dopamine (DA) levels, increased DA turnover, synaptic terminal loss, and notably, the depletion of dopaminergic neurons in the substantia nigra and noradrenergic neurons in the locus coeruleus. Furthermore, P8 α-SynTg mice exhibit alterations in gut transit time, mirroring early PD symptoms. In summary, P8 α-SynTg mice effectively replicate parkinsonian phenotypes by combining α-Syn transgene expression with accelerated aging. This model offers valuable insights into the understanding of PD and serves as a valuable platform for further research.

DNA Mutagenicity of Hydroxyhydroquinone in Roasted Coffee Products and Its Suppression by Chlorogenic Acid, a Coffee Polyphenol, in Oxidative-Damage-Sensitive SAMP8 Mice

Hydroxyhydroquinone (HHQ) is an oxidative component produced by roasting coffee beans and has been reported to generate relatively large amounts of reactive oxygen species (ROS). In this study, we used senescence-accelerated mouse prone 8 (SAMP8) mice to determine whether HHQ consumption increases oxidative-stress-induced injury, because in SAMP8 mice, the activity of 8-oxoguanine DNA glycosylase 1, which repairs oxidative modifications in DNA, is decreased. The results showed that two out of twelve (16.7%) HHQ-treated mice presented polyuria and glucosuria around 2 months after the start of treatment, indicating that HHQ may act as a mutagen against SAMP8 mice, which is sensitive to oxidative damage. No abnormalities were observed in the chlorogenic acid (coffee polyphenol, CPP)-treated group. The concentration of hydrogen peroxide in the serum of SAMP8 mice was significantly higher than that in SAMR1 (senescence-resistant) control mice, and the concentration was further increased in the HHQ-treated group. CPP, when coexisting with HHQ at the rate contained in roasted coffee, decreased the amount of hydrogen peroxide in the serum of SAMP8 mice. Although CPP can act both oxidatively and antioxidatively as a polyphenol, CPP acts more antioxidatively when coexisting with HHQ. Thus, the oxidative effect of HHQ was shown to be counteracted by CPP.

Feasibility of administration of calcitonin gene-related peptide receptor antagonist on attenuation of pain and progression in osteoarthritis

Suppressing inflammation and abnormal subchondral bone turnover is essential for reducing osteoarthritis (OA) progression and pain relief. This study focused on calcitonin gene-related peptide (CGRP), which is involved in inflammation and bone metabolism, and investigated whether a CGRP receptor antagonist (rimegepant) could suppress OA progression and relieve pain in two OA models. C57BL/6 mice (10-week-old) underwent surgical destabilization of the medial meniscus, and Rimegepant (1.0 mg/kg/100 μL) or phosphate-buffered saline (100 μL) was administered weekly intraperitoneally after OA surgery and evaluated at 4, 8, and 12 weeks. In the senescence-accelerated mice (SAM)-prone 8 (SAMP8), rimegepant was administered weekly before and after subchondral bone sclerosis and sacrificed at 9 and 23 weeks, respectively. Behavioral assessment and immunohistochemical staining (CGRP) of the dorsal root ganglion (DRG) were conducted to assess pain. In DMM mice, synovitis, cartilage degeneration, and osteosclerosis were significantly suppressed in the rimegepant group. In SAMP8, synovitis, cartilage degeneration, and osteosclerosis were significantly suppressed by rimegepant at 9 weeks; however, not at 23 weeks. Behavioral assessment shows the traveled distance and the number of standings in the rimegepant group were significantly longer and higher. In addition, CGRP expression of the DRG was significantly lower in the rimegepant group at 8 and 12 weeks of DMM and 9 weeks of SAMP8 treatment. No adverse effects were observed in either of the mouse models. Inhibition of CGRP signaling has the potential to be a therapeutic target to prevent OA progression and suppress pain through the attenuation of subchondral bone sclerosis and synovitis.

Differential Epigenetic Changes in the Dorsal Hippocampus of Male and Female SAMP8 Mice: A Preliminary Study

Alzheimer's disease (AD) is the most common age-related neurodegenerative disease characterized by memory loss and cognitive impairment. The causes of the disease are not well understood, as it involves a complex interaction between genetic, environmental, and epigenetic factors. SAMP8 mice have been proposed as a model for studying late-onset AD, since they show age-related learning and memory deficits as well as several features of AD pathogenesis. Epigenetic changes have been described in SAMP8 mice, although sex differences have never been evaluated. Here we used western blot and qPCR analyses to investigate whether epigenetic markers are differentially altered in the dorsal hippocampus, a region important for the regulation of learning and memory, of 9-month-old male and female SAMP8 mice. We found that H3Ac was selectively reduced in male SAMP8 mice compared to male SAMR1 control mice, but not in female mice, whereas H3K27me3 was reduced overall in SAMP8 mice. Moreover, the levels of HDAC2 and JmjD3 were increased, whereas the levels of HDAC4 and Dnmt3a were reduced in SAMP8 mice compared to SAMR1. In addition, levels of HDAC1 were reduced, whereas Utx and Jmjd3 were selectively increased in females compared to males. Although our results are preliminary, they suggest that epigenetic mechanisms in the dorsal hippocampus are differentially regulated in male and female SAMP8 mice.

Pregnane X receptor agonist nomilin extends lifespan and healthspan in preclinical models through detoxification functions

Citrus fruit has long been considered a healthy food, but its role and detailed mechanism in lifespan extension are not clear. Here, by using the nematode C. elegans, we identified that nomilin, a bitter-taste limoloid that is enriched in citrus, significantly extended the animals' lifespan, healthspan, and toxin resistance. Further analyses indicate that this ageing inhibiting activity depended on the insulin-like pathway DAF-2/DAF-16 and nuclear hormone receptors NHR-8/DAF-12. Moreover, the human pregnane X receptor (hPXR) was identified as the mammalian counterpart of NHR-8/DAF-12 and X-ray crystallography showed that nomilin directly binds with hPXR. The hPXR mutations that prevented nomilin binding blocked the activity of nomilin both in mammalian cells and in C. elegans. Finally, dietary nomilin supplementation improved healthspan and lifespan in D-galactose- and doxorubicin-induced senescent mice as well as in male senescence accelerated mice prone 8 (SAMP8) mice, and induced a longevity gene signature similar to that of most longevity interventions in the liver of bile-duct-ligation male mice. Taken together, we identified that nomilin may extend lifespan and healthspan in animals via the activation of PXR mediated detoxification functions.

LC-MS/MS quantitation of elastin crosslinker desmosines and histological analysis of skin aging characteristics in mice

Elastic fibers consist of an insoluble inner core of elastin, which confers elasticity and resilience to vertebral organs and tissues. Desmosine (DES) and isodesmosine (IDES) are potential biomarkers of pathologies that lead to decreased elastin turnover. Mice are commonly used in research to mimic humans because of their similar genetics, physiology, and organ systems. The present study thus used senescent accelerated prone (SAMP10) and senescent accelerated resistant (SAMR1) mice to examine the connection between aging and histological or biomolecular changes. Mice were divided into three groups: SAMP10 fed a control diet (CD), SAMP10 fed a high-fat diet (HFD), and SAMR1 fed a CD. The percent liver to total body weight ratio (%LW/BW), desmosines (DESs or DES/IDES) content, and histological alterations in skin samples were evaluated. DESs were quantified using an isotope-dilution liquid chromatography-tandem mass spectrometry method with isodesmosine-¹³C₃,¹⁵N₁ as the internal standard (ISTD). The assays were repeatable, reproducible, and accurate, with %CV values ≤ (1.90, 1.77, and 3.03), ISTD area %RSD of (1.54, 0.92, and 1.13), and %AC of (99.02 ± 1.86, 101.00 ± 2.30, and 101.30 ± 2.90) for the calibrations (equimolar DES/IDES, DES, and IDES, respectively). The average DESs content per dry-weight abdominal skin and %LW/BW were similar between the three groups. Histological analyses revealed elastin fibers in five randomly selected samples. The epidermis and dermal white adipose tissue layers were thicker in SAMP10 mice than SAMR1 mice. Thus, characteristic signs of aging in SAMP10 and SAMR1 mice could not be differentiated based on measurement of DESs content of the skin or %LW/BW, but aging could be differentiated based on microscopic analysis of histological changes in the skin components of SAMP10 and SAMR1 mice.

Impaired telomere pathway and fertility in Senescence-Accelerated Mice Prone 8 females with reproductive senescence

Ovarian aging is the main cause of infertility and telomere attrition is common to both aging and fertility disorders. Senescence-Accelerated Mouse Prone 8 (SAMP8) model has shortened lifespan and premature infertility, reflecting signs of reproductive senescence described in middle-aged women. Thus, our objective was to study SAMP8 female fertility and the telomere pathway at the point of reproductive senescence. The lifespan of SAMP8 and control mice was monitored. Telomere length (TL) was measured by in situ hybridization in blood and ovary. Telomerase activity (TA) was analyzed by telomere-repeat amplification protocol, and telomerase expression, by real-time quantitative PCR in ovaries from 7-month-old SAMP8 and controls. Ovarian follicles at different stages of maturation were evaluated by immunohistochemistry. Reproductive outcomes were analyzed after ovarian stimulation. Unpaired t-test or Mann-Whitney test were used to calculate p-values, depending on the variable distribution. Long-rank test was used to compare survival curves and Fisher's exact test was used in contingency tables. Median lifespan of SAMP8 females was reduced compared to SAMP8 males (p = 0.0138) and control females (p < 0.0001). In blood, 7-month-old SAMP8 females presented lower mean TL compared to age-matched controls (p = 0.041). Accordingly, the accumulation of short telomeres was higher in 7-month-old SAMP8 females (p = 0.0202). Ovarian TA was lower in 7-month-old SAMP8 females compared to controls. Similarly, telomerase expression was lower in the ovaries of 7-month-old SAMP8 females (p = 0.04). Globally, mean TL in ovaries and granulosa cells (GCs) were similar. However, the percentage of long telomeres in ovaries (p = 0.004) and GCs (p = 0.004) from 7-month-old SAMP8 females was lower compared to controls. In early-antral and antral follicles, mean TL of SAMP8 GCs was lower than in age-matched controls (p = 0.0156 for early-antral and p = 0.0037 for antral follicles). Middle-aged SAMP8 showed similar numbers of follicles than controls, although recovered oocytes after ovarian stimulation were lower (p = 0.0068). Fertilization rate in oocytes from SAMP8 was not impaired, but SAMP8 mice produced significantly more morphologically abnormal embryos than controls (27.03% in SAMP8 vs. 1.22% in controls; p < 0.001). Our findings suggest telomere dysfunction in SAMP8 females, at the time of reproductive senescence.

Mouse Models with SGLT2 Mutations: Toward Understanding the Role of SGLT2 beyond Glucose Reabsorption

The sodium–glucose cotransporter 2 (SGLT2) mainly carries out glucose reabsorption in the kidney. Familial renal glycosuria, which is a mutation of SGLT2, is known to excrete glucose in the urine, but blood glucose levels are almost normal. Therefore, SGLT2 inhibitors are attracting attention as a new therapeutic drug for diabetes, which is increasing worldwide. In fact, SGLT2 inhibitors not only suppress hyperglycemia but also reduce renal, heart, and cardiovascular diseases. However, whether long-term SGLT2 inhibition is completely harmless requires further investigation. In this context, mice with mutations in SGLT2 have been generated and detailed studies are being conducted, e.g., the SGLT2−/− mouse, Sweet Pee mouse, Jimbee mouse, and SAMP10-ΔSglt2 mouse. Biological changes associated with SGLT2 mutations have been reported in these model mice, suggesting that SGLT2 is not only responsible for sugar reabsorption but is also related to other functions, such as bone metabolism, longevity, and cognitive functions. In this review, we present the characteristics of these mutant mice. Moreover, because the relationship between diabetes and Alzheimer’s disease has been discussed, we examined the relationship between changes in glucose homeostasis and the amyloid precursor protein in SGLT2 mutant mice.

Emerging role of aging in the progression of NAFLD to HCC

With the aging of global population, the incidence of nonalcoholic fatty liver disease (NAFLD) has surged in recent decades. NAFLD is a multifactorial disease that follows a progressive course, ranging from simple fatty liver, nonalcoholic steatohepatitis (NASH) to liver cirrhosis and hepatocellular carcinoma (HCC). It is well established that aging induces pathological changes in liver and potentiates the occurrence and progression of NAFLD, HCC and other age-related liver diseases. Studies of senescent cells also indicate a pivotal engagement in the development of NAFLD via diverse mechanisms. Moreover, nicotinamide adenine dinucleotide (NAD⁺), silence information regulator protein family (sirtuins), and mechanistic target of rapamycin (mTOR) are three vital and broadly studied targets involved in aging process and NAFLD. Nevertheless, the crucial role of these aging-associated factors in aging-related NAFLD remains underestimated. Here, we reviewed the current research on the roles of aging, cellular senescence and three aging-related factors in the evolution of NAFLD to HCC, aiming at inspiring promising therapeutic targets for aging-related NAFLD and its progression.

Impact of aging on tendon homeostasis, tendinopathy development, and impaired healing

Aging is a complex and progressive process where the tissues of the body demonstrate a decreased ability to maintain homeostasis. During aging, there are substantial cellular and molecular changes, with a subsequent increase in susceptibility to pathological degeneration of normal tissue function. In tendon, aging results in well characterized alterations in extracellular matrix (ECM) structure and composition. In addition, the cellular environment of aged tendons is altered, including a marked decrease in cell density and metabolic activity, as well as an increase in cellular senescence. Collectively, these degenerative changes make aging a key risk factor for the development of tendinopathies and can increase the frequency of tendon injuries. However, inconsistencies in the extent of age-related degenerative impairments in tendons have been reported, likely due to differences in how "old" and "young" age-groups have been defined, differences between anatomically distinct tendons, and differences between animal models that have been utilized to study the impact of aging on tendon homeostasis. In this review, we address these issues by summarizing data by well-defined age categories (young adults, middle-aged, and aged) and from anatomically distinct tendon types. We then summarize in detail how aging affects tendon mechanics, structure, composition, and the cellular environment based on current data and underscore what is currently not known. Finally, we discuss gaps in the current understanding of tendon aging and propose key avenues for future research that can shed light on the specific mechanisms of tendon pathogenesis due to aging.

Proteomic Signature and mRNA Expression in Hippocampus of SAMP8 and SAMR1 Mice during Aging

Aging is a complex process often accompanied by cognitive decline that represents a risk factor for many neurodegenerative disorders including Alzheimer's and Parkinson's disease. The molecular mechanisms involved in age-related cognitive decline are not yet fully understood, although increased neuroinflammation is considered to play a significant role. In this study, we characterized a proteomic view of the hippocampus of the senescence-accelerated mouse prone-8 (SAMP8), a model of enhanced senescence, in comparison with the senescence-accelerated-resistant mouse (SAMR1), a model of normal aging. We additionally investigated inflammatory cytokines and cholinergic components gene expression during aging in the mouse brain tissues. Proteomic data defined the expression of key proteins involved in metabolic and cellular processes in neuronal and glial cells of the hippocampus. Gene Ontology revealed that most of the differentially expressed proteins are involved in the cytoskeleton and cell motility regulation. Molecular analysis results showed that both inflammatory cytokines and cholinergic components are differentially expressed during aging, with a downward trend of cholinergic receptors and esterase enzymes expression, in contrast to an upward trend of inflammatory cytokines in the hippocampus of SAMP8. Together, our results support the important role of the cholinergic and cytokine systems in the aging of the murine brain.

Salidroside Alleviates Renal Fibrosis in SAMP8 Mice by Inhibiting Ferroptosis

Renal fibrosis progression is closely associated with aging, which ultimately leads to renal dysfunction. Salidroside (SAL) is considered to have broad anti-aging effects. However, the roles and mechanisms of SAL in aging-related renal fibrosis remain unclear. The study aimed to evaluate the protective effects and mechanisms of SAL in SAMP8 mice. SAMP8 mice were administered with SAL and Ferrostatin-1 (Fer-1) for 12 weeks. Renal function, renal fibrosis, and ferroptosis in renal tissue were detected. The results showed that elevated blood urea nitrogen (BUN) and serum creatinine (SCr) levels significantly decreased, serum albumin (ALB) levels increased, and mesangial hyperplasia significantly reduced in the SAL group. SAL significantly reduced transforming growth factor-β (TGF-β) and α-smooth muscle actin (α-sma) levels in SAMP8 mice. SAL treatment significantly decreased lipid peroxidation in the kidneys, and regulated iron transport-related proteins and ferroptosis-related proteins. These results suggested that SAL delays renal aging and inhibits aging-related glomerular fibrosis by inhibiting ferroptosis in SAMP8 mice.

Senescence-accelerated mice prone 8 (SAMP8) in male as a spontaneous osteoarthritis model

BACKGROUND

Animal models of spontaneous osteoarthritis (OA) are sparse and not well characterized. The purpose of the present study is to examine OA-related changes and mechanisms in senescence-accelerated mouse prone 8 (SAMP8) that displays a phenotype of accelerated aging.  METHODS: Knees of male SAMP8 and SAM-resistant 1 (SAMR1) mice as control from 6 to 33 weeks of age were evaluated by histological grading systems for joint tissues (cartilage, meniscus, synovium, and subchondral bone), and µCT analysis. Gene expression patterns in articular cartilage were analyzed by real-time PCR. Immunohistochemistry was performed for OA-related factors, senescence markers, and apoptosis.

RESULTS

Starting at 14 weeks of age, SAMP8 exhibited mild OA-like changes such as proteoglycan loss and cartilage fibrillation. From 18 to 33 weeks of age, SAMP8 progressed to partial or full-thickness defects with exposure of subchondral bone on the medial tibia and exhibited synovitis. Histological scoring indicated significantly more severe OA in SAMP8 compared with SAMR1 from 14 weeks [median (interquartile range): SAMR1: 0.89 (0.56-1.81) vs SAMP8: 1.78 (1.35-4.62)] to 33 weeks of age [SAMR1: 1.67 (1.61-1.04) vs SAMP8: 13.03 (12.26-13.57)]. Subchondral bone sclerosis in the medial tibia, bone mineral density (BMD) loss of femoral metaphysis, and meniscus degeneration occurred much earlier than the onset of cartilage degeneration in SAMP8 at 14 weeks of age.

CONCLUSIONS

SAMP8 are a spontaneous OA model that is useful for investigating the pathogenesis of primary OA and evaluating therapeutic interventions.

Bibliometric review of 1992–2022 publications on acupuncture for cognitive impairment

Objective

To explore the development context, research hotspots, and frontiers of acupuncture therapy for cognitive impairment (CI) from 1992 to 2022 by visualization analysis.

Methods

Articles about acupuncture therapy for cognitive impairment were retrieved from the Web of Science Core Collection (WoSCC) until 1 March 2022. Basic information was collected by Excel 2007, and VOSviewer 1.6.17 was used to analyze the co-occurrence of countries, institutes, and authors. Co-citation maps of authors and references were analyzed by CiteSpace V.5.8.R3. In addition, CiteSpace was used to analyze keyword clusters and forecast research frontiers.

Results

A total of 279 articles were retrieved, including articles from 19 countries, 334 research institutes, and 101 academic journals. The most published country and institutes were the People's Republic of China (217) and the Fujian University of Traditional Chinese Medicine (40). Ronald C Petersen owned the highest co-citations (56). Keywords and co-cited references cluster showed the main research directions in this area, including “ischemic stroke,” “cerebral ischemia/reperfusion,” “mild cognitive impairment,” “Alzheimer's disease,” “vascular dementia,” “vascular cognitive impairment with no dementia,” “multi-infarct dementia,” “synaptic injury,” “functional MRI,” “glucose metabolism,” “NMDA,” “nuclear factor-kappa b pathway,” “neurotrophic factor,” “matrix metalloproteinase-2 (MMP-2),” “tumor necrosis factor-alpha,” “Bax,” “Caspase-3,” and “Noxa”. Trending keywords may indicate frontier topics, such as “randomized controlled trial,” “rat model,” and “meta-analysis.”

Conclusion

This research provides valuable information for the study of acupuncture. Diseases focus on mild cognitive impairment (MCI), Alzheimer's disease (AD), and vascular dementia (VaD). Tauopathies with hyperphosphorylation of Tau protein as the main lesions also need to be paid attention to. The development of functional magnetic resonance imaging (fMRI) will better explain the therapeutic effect of acupuncture treatment. The effect of acupuncture on a single point is more convincing, and acupuncture on Baihui (GV20) may be needed in the future. Finally, the implementation of high-quality multicenter randomized controlled trials (RCTs) requires increased collaboration among experts from multiple fields and countries.

Buckwheat Flour and Its Starch Prevent Age-Related Cognitive Decline by Increasing Hippocampal BDNF Production in Senescence-Accelerated Mouse Prone 8 Mice

Buckwheat is an important pseudo-cereal crop worldwide. This study investigated whether long-term administration of buckwheat can suppress age-related cognitive decline in senescence-accelerated mouse prone 8 (SAMP8) mice. For 26 weeks, 18-week-old male SAMP8 mice were fed a standard diet containing 5% (w/w) buckwheat, Tartary buckwheat, wheat, or rice flour. In the Barnes maze and passive avoidance tests, mice fed buckwheat whole flour (BWF) showed improved cognitive performance compared to those fed a control diet, while no improvement was noticed in case of the other diets. Analysis of the gut microbiota showed that BWF and buckwheat outer flour administration increased the abundance of Lactococcus and Ruminiclostridium, respectively, at the genus level. The expression levels of brain-derived neurotrophic factor (BDNF), postsynaptic Arc and PSD95, and the mature neuronal marker NeuN in the hippocampus were increased after BWF administration, which was induced by the activation of the ERK/CREB signaling pathway and histone H3 acetylation. A similar increase in cognitive performance-related hippocampal BDNF expression in SAMP8 mice was observed after the oral administration of starch prepared from BWF. Therefore, the long-term administration of BWF suppresses cognitive decline by increasing hippocampal BDNF production in SAMP8 mice.

Coffee Polyphenol, Chlorogenic Acid, Suppresses Brain Aging and Its Effects Are Enhanced by Milk Fat Globule Membrane Components

Mice feed with coffee polyphenols (CPP, chlorogenic acid) and milk fat globule membrane (MFGM) has increased survival rates and helps retain long-term memory. In the cerebral cortex of aged mice, CPP intake decreased the expression of the proinflammatory cytokine TNF-α, and lysosomal enzyme cathepsin B. The suppression of inflammation in the brain during aging was thought to result in the suppression of the repressor element 1-silencing transcription factor (REST) and prevention of brain aging. In contrast, CPP increased the expression of REST, cAMP-responsive element binding (CREB) and transforming growth factor β1 (TGF-β1) in the young hippocampus. The increased expression of these factors may contribute to the induction of neuronal differentiation and the suppression of memory decline with aging. Taken together, these results suggest that CPP increases CREB in the young hippocampus and suppresses inflammation in the old brain, resulting in a preventive effect on brain aging. The endotoxin levels were not elevated in the serum of aged mice. Although the mechanism of action of MFGM has not yet been elucidated, the increase in survival rate with both CPP and MFGM intake suggests that adding milk to coffee may improve not only the taste, but also the function.

Discovery and In Vivo Proof of Concept of a Highly Potent Dual Inhibitor of Soluble Epoxide Hydrolase and Acetylcholinesterase for the Treatment of Alzheimer's Disease

With innumerable clinical failures of target-specific drug candidates for multifactorial diseases, such as Alzheimer's disease (AD), which remains inefficiently treated, the advent of multitarget drug discovery has brought a new breath of hope. Here, we disclose a class of 6-chlorotacrine (huprine)-TPPU hybrids as dual inhibitors of the enzymes soluble epoxide hydrolase (sEH) and acetylcholinesterase (AChE), a multitarget profile to provide cumulative effects against neuroinflammation and memory impairment. Computational studies confirmed the gorge-wide occupancy of both enzymes, from the main site to a secondary site, including a so far non-described AChE cryptic pocket. The lead compound displayed in vitro dual nanomolar potencies, adequate brain permeability, aqueous solubility, human microsomal stability, lack of neurotoxicity, and it rescued memory, synaptic plasticity, and neuroinflammation in an AD mouse model, after low dose chronic oral administration.

White matter-associated microglia: New players in brain aging and neurodegenerative diseases

There has been growing interest in brain aging and rejuvenation. It is well known that brain aging is one of the leading causes of neurodegenerative diseases, such as Alzheimer's disease, but brain aging alone can cause cognitive decline. Microglia are thought to act as 'conductors' of white matter aging by modulating diverse glial cells and phagocytosing white matter-derived myelin debris. A recent study identified a specific subpopulation of microglia in the white matter of aged mice, termed white matter-associated microglia (WAM). Additionally, senescent microglia show impaired phagocytic function and altered lipid metabolism, which cause accumulation of lipid metabolites and eventually lead to myelin sheath degeneration. These results suggest that senescent WAM could be pivotal players in axonal loss during brain aging. The aim of this review is to assess the current state of knowledge on brain aging, with an emphasis on the roles of the white matter and microglia, and suggest potential approaches for rejuvenating the aged brain.

The Alzheimer's disease drug candidate J147 decreases blood plasma fatty acid levels via modulation of AMPK/ACC1 signaling in the liver

J147 is a novel drug candidate developed to treat neurological dysfunction. Numerous studies have demonstrated the beneficial effects of J147 in cellular and animal models of disease which has led to the transitioning of the compound into human clinical trials. However, no biomarkers for its target engagement have been identified. Here, we determined if specific metabolites in the plasma could be indicative of J147's activity in vivo. Plasma lipidomics data from three independent rodent studies were assessed along with liver lipidomics data from one of the studies. J147 consistently reduced plasma free fatty acid (FFA) levels across the independent studies. Decreased FFA levels were also found in the livers of J147-treated mice that correlated well with those in the plasma. These changes in the liver were associated with activation of the AMP-activated protein kinase/acetyl-CoA carboxylase 1 signaling pathway. A reduction in FFA levels by J147 was confirmed in HepG2 cells, where activation of the AMPK/ACC1 pathway was seen along with increases in acetyl-CoA and ATP levels which correlated with enhanced cellular bioenergetics. Our data show that J147 targets liver cells to activate the AMPK/ACC1 signaling pathway and preserve energy at the expense of inhibiting FFA synthesis.

Systems approaches to investigate the role of NF-κB signaling in aging

The nuclear factor-κB (NF-κB) signaling pathway is one of the most well-studied pathways related to inflammation, and its involvement in aging has attracted considerable attention. As aging is a complex phenomenon and is the result of a multi-step process, the involvement of the NF-κB pathway in aging remains unclear. To elucidate the role of NF-κB in the regulation of aging, different systems biology approaches have been employed. A multi-omics data-driven approach can be used to interpret and clarify unknown mechanisms but cannot generate mechanistic regulatory structures alone. In contrast, combining this approach with a mathematical modeling approach can identify the mechanistics of the phenomena of interest. The development of single-cell technologies has also helped clarify the heterogeneity of the NF-κB response and underlying mechanisms. Here, we review advances in the understanding of the regulation of aging by NF-κB by focusing on omics approaches, single-cell analysis, and mathematical modeling of the NF-κB network.

Administration of miR-195 Inhibitor Enhances Memory Function Through Improving Synaptic Degradation and Mitochondrial Dysfunction of the Hippocampal Neurons in SAMP8 Mice

BACKGROUND

Mitochondrial dysfunction is an early feature of Alzheimer's disease (AD) and miR-195 is involved in mitochondrial disorder through targeting MFN-2 protein in hippocampal neurons of AD.

OBJECTIVE

To clarify if administration of miR-195 inhibitor could enhance the memory deficits through improving hippocampal neuron mitochondrial dysfunction in SAMP8 mice.

METHODS

The expression of miR-195 was detected by RT-qPCR in primary hippocampal neurons and HT-22 cells treated with Aβ 1-42. Morris water maze (MWM) was used to assess the learning and memory function in SAMP8 mice administrated with antagomir-195. Transmission electron microscopy was employed to determine the morphological changes of synapses and mitochondria of hippocampus in SAMP8 mice. Mitochondrial respiration was measured using a high-resolution oxygraph.

RESULTS

The expression of miR-195 were upregulated in the primary hippocampal neurons and HT-22 cells induced by Aβ 1-42. Inhibition of miR-195 ameliorated the mitochondrial dysfunction in HT-22 cells induced by Aβ 1-42, including mitochondrial morphologic damages, mitochondrial membrane potential, respiration function, and ATP production. Administration of antagomir-195 by the third ventricle injection markedly ameliorated the cognitive function, postsynaptic density thickness, length of synaptic active area, mitochondrial aspect ratio, and area in hippocampus of SAMP8 mice. Finally, antagomir-195 was able to promote an increase in the activity of respiratory chain complex CI and II in SAMP8 mice.

CONCLUSION

This study demonstrated that miR-195 inhibitor ameliorated the cognitive impairment of AD mice by improving mitochondrial structure damages and dysfunction in the hippocampal neurons, which provide an experimental basis for further exploring the treatment strategy of AD.

From virtual screening hits targeting a cryptic pocket in BACE-1 to a nontoxic brain permeable multitarget anti-Alzheimer lead with disease-modifying and cognition-enhancing effects

Starting from six potential hits identified in a virtual screening campaign directed to a cryptic pocket of BACE-1, at the edge of the catalytic cleft, we have synthesized and evaluated six hybrid compounds, designed to simultaneously reach BACE-1 secondary and catalytic sites and to exert additional activities of interest for Alzheimer's disease (AD). We have identified a lead compound with potent in vitro activity towards human BACE-1 and cholinesterases, moderate Aβ42 and tau antiaggregating activity, and brain permeability, which is nontoxic in neuronal cells and zebrafish embryos at concentrations above those required for the in vitro activities. This compound completely restored short- and long-term memory in a mouse model of AD (SAMP8) relative to healthy control strain SAMR1, shifted APP processing towards the non-amyloidogenic pathway, reduced tau phosphorylation, and increased the levels of synaptic proteins PSD95 and synaptophysin, thereby emerging as a promising disease-modifying, cognition-enhancing anti-AD lead.

Principles of brain aging: Status and challenges of modeling human molecular changes in mice

Due to the extension of human life expectancy, the prevalence of cognitive impairment is rising in the older portion of society. Developing new strategies to delay or attenuate cognitive decline is vital. For this purpose, it is imperative to understand the cellular and molecular events at the basis of brain aging. While several organs are directly accessible to molecular analysis through biopsies, the brain constitutes a notable exception. Most of the molecular studies are performed on postmortem tissues, where cell death and tissue damage have already occurred. Hence, the study of the molecular aspects of cognitive decline largely relies on animal models and in particular on small mammals such as mice. What have we learned from these models? Do these animals recapitulate the changes observed in humans? What should we expect from future mouse studies? In this review we answer these questions by summarizing the state of the research that has addressed cognitive decline in mice from several perspectives, including genetic manipulation and omics strategies. We conclude that, while extremely valuable, mouse models have limitations that can be addressed by the optimal design of future studies and by ensuring that results are cross-validated in the human context.

Hallmarks of Testicular Aging: The Challenge of Anti-Inflammatory and Antioxidant Therapies Using Natural and/or Pharmacological Compounds to Improve the Physiopathological Status of the Aged Male Gonad

The evolutionary theory of aging supports a trade-off relationship between reproduction and aging. Aging of the male reproductive system primarily affects the testes, leading to a decrease in the levels of sexual hormones, alterations in sperm quality and production, and a decline in fertility that does not necessarily involve a complete cessation of spermatogenesis. Inflammation, oxidation, and apoptosis are events considered as predictors of pathogenesis and the development of age-related diseases that are frequently observed in aged testes. Although the molecular mechanisms are still poorly understood, accumulating evidence points toward pro-inflammatory molecules and reactive oxygen species as primary contributing factors for testicular aging. However, the real impact of aging-related testicular alterations on fertility, reproductive health, and life span is far from being fully revealed. This work discusses the current knowledge on the impact of aging in the testis, particularly of aging-related dysregulated inflammation and oxidative damage on the functioning of its different cell populations. More interestingly, this review covers the potential benefits of anti-aging interventions and therapies using either pharmacological compounds (such as non-selective non-steroidal anti-inflammatory medication) or more natural alternatives (such as various nutraceuticals or even probiotics) that exhibit anti-inflammatory, antioxidant, and anti-apoptotic properties. Some of these are currently being investigated or are already in clinical use to delay or prevent testicular aging.

Synergistic Neuroprotective Effects of a Natural Product Mixture against AD Hallmarks and Cognitive Decline in Caenorhabditis elegans and an SAMP8 Mice Model

The study of different natural products can provide a wealth of bioactive compounds, and more interestingly, their combination can exert a new strategy for several neurodegenerative diseases with major public health importance, such as Alzheimer’s disease (AD). Here, we investigated the synergistic neuroprotective effects of a mixed extract composed of docosahexaenoic acid, Ginkgo biloba, D-pinitol, and ursolic acid in several transgenic Caenorhabditis elegans (C. elegans) and a senescence-accelerated prone mice 8 (SAMP8) model. First, we found a significantly higher survival percentage in the C. elegans group treated with the natural product mixture compared to the single extract-treated groups. Likewise, we found a significantly increased lifespan in group of C. elegans treated with the natural product mixture compared to the other groups, suggesting synergistic effects. Remarkably, we determined a significant reduction in Aβ plaque accumulation in the group of C. elegans treated with the natural product mixture compared to the other groups, confirming synergy. Finally, we demonstrated better cognitive performance in the group treated with the natural product mixture in both AD models (neuronal Aβ C. elegans strain CL2355 and the SAMP8 mice model), confirming the molecular results and unraveling the synergist effects of this combination. Therefore, our results proved the potential of this new natural product mixture for AD therapeutic strategies.

The search for anti-oxytotic/ferroptotic compounds in the plant world

Oxytosis/ferroptosis is a form of non-apoptotic regulated cell death characterized by glutathione (GSH) depletion and dysregulated production of mitochondrial ROS that results in lethal lipid peroxidation. As the significance of oxytosis/ferroptosis to age-associated human diseases is now beginning to be appreciated, the development of innovative approaches to identify novel therapeutics that target the oxytosis/ferroptosis pathway could not be more timely. Due to their sessile nature, plants are exposed to a variety of stresses that trigger physiological changes similar to those found in oxytosis/ferroptosis. As such, they have evolved a rich array of chemical strategies to deal with those challenging conditions. This review details a drug discovery approach for identifying potent inhibitors of oxytosis/ferroptosis from plants for the treatment of Alzheimer's disease and related dementias, thereby highlighting the tremendous potential of plant-based research for developing new medicines while simultaneously being a catalyst for sustainability.

Senescent accelerated prone 8 (SAMP8) mice as a model of age dependent neuroinflammation

BACKGROUND

Aging and age-related diseases are strong risk factors for the development of neurodegenerative diseases. Neuroinflammation (NIF), as the brain's immune response, plays an important role in aged associated degeneration of central nervous system (CNS). There is a need for well characterized animal models that will allow the scientific community to understand and modulate this process.

METHODS

We have analyzed aging-phenotypical and inflammatory changes of brain myeloid cells (bMyC) in a senescent accelerated prone aged (SAMP8) mouse model, and compared with their senescence resistant control mice (SAMR1). We have performed morphometric methods to evaluate the architecture of cellular prolongations and determined the appearance of Iba1⁺ clustered cells with aging. To analyze specific constant brain areas, we have performed stereology measurements of Iba1⁺ cells in the hippocampal formation. We have isolated bMyC from brain parenchyma (BP) and choroid plexus plus meningeal membranes (m/Ch), and analyzed their response to systemic lipopolysaccharide (LPS)-driven inflammation.

RESULTS

Aged 10 months old SAMP8 mice present many of the hallmarks of aging-dependent neuroinflammation when compared with their SAMR1 control, i.e., increase of protein aggregates, presence of Iba1⁺ clusters, but not an increase in the number of Iba1⁺ cells. We have further observed an increase of main inflammatory mediator IL-1β, and an augment of border MHCII⁺Iba1⁺ cells. Isolated CD45⁺ bMyC from brain parenchyma (BP) and choroid plexus plus meningeal membranes (m/Ch) have been analyzed, showing that there is not a significant increase of CD45⁺ cells from the periphery. Our data support that aged-driven pro-inflammatory cytokine interleukin 1 beta (IL-1β) transcription is enhanced in CD45⁺BP cells. Furthermore, LPS-driven systemic inflammation produces inflammatory cytokines mainly in border bMyC, sensed to a lesser extent by the BP bMyC, showing that IL-1β expression is further augmented in aged SAMP8 compared to control SAMR1.

CONCLUSION

Our data validate the SAMP8 model to study age-associated neuroinflammatory events, but careful controls for age and strain are required. These animals show morphological changes in their bMyC cell repertoires associated to age, corresponding to an increase in the production of pro-inflammatory cytokines such as IL-1β, which predispose the brain to an enhanced inflammatory response after LPS-systemic challenge.

Interleukin-1β Modulates Synaptic Transmission and Synaptic Plasticity During the Acute Phase of Sepsis in the Senescence-Accelerated Mouse Hippocampus

Background

Aging and pre-existing cognitive impairment are considered to be independent risk factors for sepsis-associated encephalopathy. This study aimed to investigate the manner in which aging and pre-existing cognitive dysfunction modified neuroinflammation, synaptic plasticity, and basal synaptic transmission during the acute phase of sepsis using Senescence-Accelerated Mice Prone 8 (SAMP8) and Senescence-Accelerated Resistant Mice 1 (SAMR1).

Methods

We used 6-month-old SAMP8 and SAMR1. Sepsis was induced using cecal ligation and puncture (CLP). The animal's hippocampi and blood were collected for subsequent investigations 24 h after surgery.

Results

Long-term potentiation (LTP) was impaired in the Shaffer-collateral (SC)-CA1 pathway of the hippocampus in SAMP8 without surgery compared to the age-matched SAMR1, which was reflective of cognitive dysfunction in SAMP8. CLP impaired the SC-CA1 LTP in SAMR1 compared to the sham-operated controls, but not in SAMP8. Moreover, CLP decreased the input-output curve and increased the paired-pulse ratio in SAMP8, suggesting the reduced probability of basal synaptic transmission due to sepsis. Immunohistochemical analysis revealed that CLP elevated IL-1β levels, especially in the hippocampi of SAMP8 with microglial activation. In vivo peripheral IL-1 receptor antagonist (IL-1ra) administration in the septic SAMP8 revealed that the neuroinflammation was not correlated with the peripheral elevation of IL-1β. Ex vivo IL-1ra administration to the hippocampus ameliorated LTP impairment in SAMR1 and the reduction in basal transmission in SAMP8 after sepsis.

Conclusions

The mechanism of the modulation of synaptic transmission and synaptic plasticity by the acute stage of sepsis differed between SAMR1 and SAMP8. These changes were related to centrally derived IL-1 receptor-mediated signaling and were accompanied by microglial activation, especially in SAMP8.

Geroprotective effects of Alzheimer's disease drug candidates

Geroprotectors are compounds that slow the biological aging process in model organisms and may therefore extend healthy lifespan in humans. It is hypothesized that they do so by preserving the more youthful function of multiple organ systems. However, this hypothesis has rarely been tested in any organisms besides C. elegans and D. melanogaster. To determine if two life-extending compounds for Drosophila maintain a more youthful phenotype in old mice, we asked if they had anti-aging effects in both the brain and kidney. We utilized rapidly aging senescence-accelerated SAMP8 mice to investigate age-associated protein level alterations in these organs. The test compounds were two cognition-enhancing Alzheimer's disease drug candidates, J147 and CMS121. Mice were fed the compounds in the last quadrant of their lifespan, when they have cognitive deficits and are beginning to develop CKD. Both compounds improved physiological markers for brain and kidney function. However, these two organs had distinct, tissue-specific protein level alterations that occurred with age, but in both cases, drug treatments restored a more youthful level. These data show that geroprotective AD drug candidates J147 and CMS121 prevent age-associated disease in both brain and kidney, and that their apparent mode of action in each tissue is distinct.

Motor Dyscoordination and Alteration of Functional Correlation Between DGKγ and PKCγ in Senescence-Accelerated Mouse Prone 8 (SAMP8)

Senescence-accelerated mouse prone 8 (SAMP8) is an animal model of age-related central nervous system (CNS) disorders. Although SAMP8 shows deficits in learning, memory, and emotion, its motor coordination has not been clarified. We have recently reported that DGKγ-regulated PKCγ activity is important for cerebellar motor coordination. However, involvement of the functional correlation between the kinases in age-related motor dyscoordination still remains unknown. Therefore, we have investigated the motor coordination in SAMP8 and involvement of the functional correlation between DGKγ and PKCγ in the age-related motor dyscoordination. Although 6 weeks old SAMP8 showed equivalent motor coordination with control mice (SAMR1) in the rotarod test, 24 weeks old SAMP8 exhibited significantly less latency in the rotarod test and more frequent slips in the beam test compared to the age-matched SAMR1. Furthermore, 24 weeks old SAMP8 showed the higher locomotor activity in open field test and Y-maze test. Western blotting revealed that DGKγ expression decreased in the cerebellum of 24 weeks old SAMP8, while PKCγ was upregulated. These results suggest that SAMP8 is a useful model of age-related motor dysfunction and that the DGKγ-regulated PKCγ activity is involved in the age-related motor dyscoordination.

Neuronal and glial region dependent changes in female mice from a model of premature aging

Adult Premature Aging Mice (PAM) show premature immunosenescence, oxidative and inflammatory stress and consequently a shorter lifespan than Exceptional Non-Prematurely Aging Mice (E-NPAM) at the same age. Indeed, adult female PAM exhibit behavioral age-related declines and abnormalities in its brain neurochemistry. Nevertheless, it is not clear whether these impairments might be accompanied by previous changes related to the neuroinflammation process in their central nervous system (CNS). Therefore, the aim of the present work was to determine if adult female PAM may show brain neuroinflammation processes comparable to those observed in chronologically old female mice. Accordingly, ICR-CD1 female mice were classified in PAM, Regular Non-Prematurely Aging Mice (R-NPAM) and E-NPAM and compared to a group of chronologically old female mice (OLD) (24±1 months). Through the application of immunohistochemical techniques we evaluated changes in the expression of NeuN (a neuronal marker), Iba-1 (a microglia marker) and GFAP (an astrocyte marker) in brain areas related to the behavioral alterations previously detected in both PAM and chronologically old mice. In general, PAM showed a lower NeuN expression and a higher GFAP and Iba1 expression mainly in the Anterior Frontal Cortex and in the Medial Hippocampal Formation, when compared to E-NPAM; similar changes were observed in OLD. Other brain areas, such as the Hypothalamic Nuclei and Motor Cortex were less affected. In conclusion, adult PAM and OLD female mice share some region-dependent neuronal and glial changes that may underlie, at least in part, some of the behavioral abnormalities previously reported in these animals.

Discovery of Soluble Epoxide Hydrolase Inhibitors from Chemical Synthesis and Natural Products

Soluble epoxide hydrolase (sEH) is an α/β hydrolase fold protein and widely distributed in numerous organs including the liver, kidney, and brain. The inhibition of sEH can effectively maintain endogenous epoxyeicosatrienoic acids (EETs) levels and reduce dihydroxyeicosatrienoic acids (DHETs) levels, resulting in therapeutic potentials for cardiovascular, central nervous system, and metabolic diseases. Therefore, since the beginning of this century, the development of sEH inhibitors is a hot research topic. A variety of potent sEH inhibitors have been developed by chemical synthesis or isolated from natural sources. In this review, we mainly summarized the interconnected aspects of sEH with cardiovascular, central nervous system, and metabolic diseases and then focus on representative inhibitors, which would provide some useful guidance for the future development of potential sEH inhibitors.

Relevance of endoplasmic reticulum and mitochondria interactions in age-associated diseases

Although the elixir of youth remains in the darkness, medical and scientific advances have succeeded in increasing human longevity; however, the predisposition to disease and its high economic cost are raising. Different strategies (e.g., antioxidants) and signaling pathways (e.g., Nrf2) have been identified to help regulate disease progression, nevertheless, there are still missing links that we need to understand. Contact sites called mitochondria-associated membranes (MAM) allow bi-directional communication between organelles as part of the essential functions in the cell to maintain its homeostasis. Different groups have deeply studied the role of MAM in aging; however, it's necessary to analyze their involvement in the progression of age-related diseases. In this review, we highlight the role of contact sites in these conditions, as well as the morphological and functional changes of mitochondria and ER in aging. We emphasize the intimate relationship between both organelles as a reflection of the biological processes that take place in the cell to try to regulate the deterioration characteristic of the aging process; proposing MAM as a potential target to help limit the disease progression with age.

I2 imidazoline receptor modulation protects aged SAMP8 mice against cognitive decline by suppressing the calcineurin pathway

Brain aging and dementia are current problems that must be solved. The levels of imidazoline 2 receptors (I₂-IRs) are increased in the brain in Alzheimer's disease (AD) and other neurodegenerative diseases. We tested the action of the specific and selective I₂-IR ligand B06 in a mouse model of accelerated aging and AD, the senescence-accelerated mouse prone 8 (SAMP8) model. Oral administration of B06 for 4 weeks improved SAMP8 mouse behavior and cognition and reduced AD hallmarks, oxidative stress, and apoptotic and neuroinflammation markers. Likewise, B06 regulated glial excitatory amino acid transporter 2 and N-methyl-D aspartate 2A and 2B receptor subunit protein levels. Calcineurin (CaN) is a phosphatase that controls the phosphorylation levels of cAMP response element-binding (CREB), apoptotic mediator BCL-2-associated agonist of cell death (BAD) and GSK3β, among other molecules. Interestingly, B06 was able to reduce the levels of the CaN active form (CaN A). Likewise, CREB phosphorylation, BAD gene expression, and other factors were modified after B06 treatment. Moreover, phosphorylation of a target of CaN, nuclear factor of activated T-cells, cytoplasmic 1 (NFAT_C1), was increased in B06-treated mice, impeding the transcription of genes related to neuroinflammation and neural plasticity. In summary, this I₂ imidazoline ligand can exert its beneficial effects on age-related conditions by modulating CaN pathway action and affecting several molecular pathways, playing a neuroprotective role in SAMP8 mice.

Sugarcane (Saccharum officinarum L.) Top Extract Ameliorates Cognitive Decline in Senescence Model SAMP8 Mice: Modulation of Neural Development and Energy Metabolism

Age-related biological alterations in brain function increase the risk of mild cognitive impairment and dementia, a global problem exacerbated by aging populations in developed nations. Limited pharmacological therapies have resulted in attention turning to the promising role of medicinal plants and dietary supplements in the treatment and prevention of dementia. Sugarcane (Saccharum officinarum L.) top, largely considered as a by-product because of its low sugar content, in fact contains the most abundant amounts of antioxidant polyphenols relative to the rest of the plant. Given the numerous epidemiological studies on the effects of polyphenols on cognitive function, in this study, we analyzed polyphenolic constituents of sugarcane top and examined the effect of sugarcane top ethanolic extract (STEE) on a range of central nervous system functions in vitro and in vivo. Orally administrated STEE rescued spatial learning and memory deficit in the senescence-accelerated mouse prone 8 (SAMP8) mice, a non-transgenic strain that spontaneously develops a multisystemic aging phenotype including pathological features of Alzheimer's disease. This could be correlated with an increased number of hippocampal newborn neurons and restoration of cortical monoamine levels in STEE-fed SAMP8 mice. Global genomic analysis by microarray in cerebral cortices showed multiple potential mechanisms for the cognitive improvement. Gene set enrichment analysis (GSEA) revealed biological processes such as neurogenesis, neuron differentiation, and neuron development were significantly enriched in STEE-fed mice brain compared to non-treated SAMP8 mice. Furthermore, STEE treatment significantly regulated genes involved in neurotrophin signaling, glucose metabolism, and neural development in mice brain. Our in vitro results suggest that STEE treatment enhances the metabolic activity of neuronal cells promoting glucose metabolism with significant upregulation of genes, namely PGK1, PGAM1, PKM, and PC. STEE also stimulated proliferation of human neural stem cells (hNSCs), regulated bHLH factor expression and induced neuronal differentiation and astrocytic process lengthening. Altogether, our findings suggest the potential of STEE as a dietary intervention, with promising implications as a novel nutraceutical for cognitive health.

Aging-Related Phenotypic Conversion of Medullary Microglia Enhances Intraoral Incisional Pain Sensitivity

Activated microglia involved in the development of orofacial pain hypersensitivity have two major polarization states. The aim of this study was to assess the involvement of the aging-related phenotypic conversion of medullary microglia in the enhancement of intraoral pain sensitivity using senescence-accelerated mice (SAM)-prone/8 (SAMP8) and SAM-resistant/1 (SAMR1) mice. Mechanical head-withdrawal threshold (MHWT) was measured for 21 days post palatal mucosal incision. The number of CD11c-immunoreactive (IR) cells [affective microglia (M1)] and CD163-IR cells [protective microglia (M2)], and tumor-necrosis-factor-α (TNF-α)-IR M1 and interleukin (IL)-10-IR M2 were analyzed via immunohistochemistry on days 3 and 11 following incision. The decrease in MHWT observed following incision was enhanced in SAMP8 mice. M1 levels and the number of TNF-α-IR M1 were increased on day 3 in SAMP8 mice compared with those in SAMR1 mice. On day 11, M1 and M2 activation was observed in both groups, whereas IL-10-IR M2 levels were attenuated in SAMP8 mice, and the number of TNF-α-IR M1 cells increased, compared to those in SAMR1 mice. These results suggest that the mechanical allodynia observed following intraoral injury is potentiated and sustained in SAMP8 mice due to enhancement of TNF-α signaling, M1 activation, and an attenuation of M2 activation accompanying IL-10 release.

Pharmacological Inhibition of Soluble Epoxide Hydrolase as a New Therapy for Alzheimer's Disease

The inhibition of the enzyme soluble epoxide hydrolase (sEH) has demonstrated clinical therapeutic effects in several peripheral inflammatory-related diseases, with 3 compounds in clinical trials. However, the role of this enzyme in the neuroinflammation process has been largely neglected. Herein, we disclose the pharmacological validation of sEH as a novel target for the treatment of Alzheimer's disease (AD). Evaluation of cognitive impairment and pathological hallmarks were used in 2 models of age-related cognitive decline and AD using 3 structurally different and potent sEH inhibitors as chemical probes. sEH is upregulated in brains from AD patients. Our findings supported the beneficial effects of central sEH inhibition, regarding reducing cognitive impairment, neuroinflammation, tau hyperphosphorylation pathology, and the number of amyloid plaques. This study suggests that inhibition of inflammation in the brain by targeting sEH is a relevant therapeutic strategy for AD.