Young Mice Research Articles

Loss of endogenous Nox2-NADPH oxidase does not prevent age-induced platelet activation and arterial thrombosis in mice

BackgroundReactive oxygen species are known to contribute to platelet hyperactivation and thrombosis during aging; however, the mechanistic contribution of the specific oxidative pathway remains elusive. ObjectivesWe hypothesized that during aging, endogenous Nox2-NADPH oxidase contributes to platelet reactive oxygen species accumulation and that loss of Nox2 will protect from platelet activation and thrombosis. MethodsWe studied littermates of Nox2 knockout (Nox2-KO) and -wild-type (Nox2-WT) mice at young (3-4 months) and old (18-20 months) age. Within platelets, we examined the expression of subunits of NADPH oxidase and enzyme activity, oxidant levels, activation markers, aggregation, and secretion. We also assessed susceptibility to in vivo thrombosis in 2 experimental models. ResultsWhile aged Nox2-WT mice displayed increased mRNA levels for Nox2, aged Nox2-KO mice showed an increase in Nox4 mRNA. However, neither the protein levels of several subunits nor the activity of NADPH oxidase were found to be altered by age or genotype. Both aged Nox2-WT and aged Nox2-KO mice exhibited similar enhancement in levels of platelet oxidants, granule release, αIIbβ3 activation, annexin V binding, aggregation and secretion, and a greater susceptibility to platelet-induced pulmonary thrombosis compared with young mice. In a photochemical injury model, adoptive transfer of platelets from aged Nox2-WT or Nox2-KO mice to the aged host mice resulted in a similar time to develop occlusive thrombus in the carotid artery. These findings suggest that loss of endogenous Nox2 does not protect against age-related platelet activation and arterial thrombosis in mice. ConclusionWe conclude that Nox2 is not an essential mediator of prothrombotic effects associated with aging.

Vaginal Tritrichomonas foetus infection in mice as an in vivo model for drug development against Trichomonas vaginalis.

Trichomonas vaginalis is the causative agent of the common sexually transmitted disease, trichomoniasis, which affects more than a hundred million people worldwide. Metronidazole and tinidazole, agents belonging to the 5-nitroheterocyclic class of antimicrobials, are most often used to treat infection, but increased resistance has been reported and adverse effects of these drugs can be significant. Consequently, an urgent need exists for the development of novel drug entities against trichomoniasis. Critical for antimicrobial drug development is the demonstration of in vivo efficacy. Murine models of vaginal T. vaginalis infection are unreliable for unknown reasons. Meanwhile, murine infections with the related bovine pathogen, Tritrichomonas foetus, tend to be more robust, although susceptibility to different antimicrobials might differ from T. vaginalis. Here, we explored the utility of T. foetus infection as a surrogate model for drug development against T. vaginalis. Four different T. foetus strains caused robust vaginal infection in young mice, while none of four diverse T. vaginalis strains did. Comparison of drug susceptibility profiles revealed that T. foetus and T. vaginalis were similarly susceptible to a range of 5-nitroheterocyclic and gold(I) compounds. By comparison, proteasome inhibitors were 10- to 15-fold less active against T. foetus than T. vaginalis, although one of the proteasome inhibitors, bortezomib, had low micromolar activity or better against multiple strains of both trichomonads. Different strains of T. foetus were used to demonstrate the utility of the murine vaginal infection models for in vivo efficacy testing, including for bortezomib and a gold(I) compound. The differences in susceptibility to proteasome inhibitors may be partially explained by differences in the proteasome subunit sequences between the two trichomonads, although the functional relevance of the proteasome was similar in both organisms. These findings indicate that T. foetus can serve as a reliable surrogate model for T. vaginalis in vitro and in murine infections in vivo, but caution must be exercised for specific drug classes with targets, such as the proteasome, that may display genetic divergence between the trichomonads.

M1 muscarinic receptor activation reverses age-related memory updating impairment in mice

Previously consolidated memories can become temporarily labile upon reactivation.Reactivation-based memory updating is chiefly studied in young subjects, so we aimed to assess this process across the lifespan. To do this, we developed a behavioural paradigm wherein a reactivated object memory is updated with contextual information; 3-month-old and 6-month-old male C57BL/6 mice displayed object memory updating, but 12-month-old mice did not. We found that M1 muscarinic acetylcholine receptor signaling during reactivation was necessary for object memory updating in the young mice. Next, we targeted this mechanism in an attempt to facilitate object memory updating in aging mice. Remarkably, systemic pharmacological M1 receptor activation reversed the age-related deficit. Quantification of cholinergic system markers within perirhinal cortex revealed subtle cellular changes that may contribute to differential performance across age groups. These findings suggest that natural cholinergic change across the lifespan contributes to inflexible memory in the aging brain.

Mild forced exercise in young mice prevents anergia induced by dopamine depletion in late adulthood: Relation to CDNF and DARPP-32 phosphorylation patterns in nucleus accumbens

Mesolimbic dopamine (DA) plays a critical role in behavioral activation and exertion of effort in motivated behaviors. DA antagonism and depletion in nucleus accumbens (Nacb) induces anergia in effort-based decision-making tasks. Exercise improves motor function in Parkinson's disease (PD). However, the beneficial effects of physical exercise on anergia, a symptom present in many psychiatric and neurological pathologies needs to be studied. During 9 weeks, young CD1 male mice were trained to run at a moderate speed in automatically turning running wheels (RW) (forced exercise group) or locked in static RWs (control group) in 1 h daily sessions. Both groups were tested in a 3-choice-T-maze task developed for the assessment of preference between active (RW) vs. sedentary reinforcers, and vulnerability to DA depletion-induced anergia was studied after tetrabenazine administration (TBZ; VMAT-2 blocker). Exercise did not change spontaneous preferences, did not affect body weight, plasma corticosterone levels or measures of anxiety, but it increased the cerebral DA neurotrophic factor (CDNF) in Nacb core, suggesting a neuroprotective effect in this nucleus. After TBZ administration, only the non-trained group showed a shift in relative preferences from active to sedentary options, reducing time running but increasing consumption of pellets, thus showing a typical anergic but not anhedonic effect. Moreover, only in the non-trained group, phosphorylation of DARPP-32(Thr34) increased after TBZ administration. These results are the first to show that mild forced exercise carried out from a young age to adulthood could act on Nacb-related functions, and prevent the anergia-inducing effects of DA depletion.

Motor Function And Muscle Mass Are Reduced In Hindlimbs After Short Term Immobilization In Young Mice

Motor Function And Muscle Mass Are Reduced In Hindlimbs After Short Term Immobilization In Young Mice

Loss of Hdac4 in Osteoprogenitors Impairs Postnatal Trabecular and Cortical Bone Formation, Resulting in a Dwarfism and Osteopenia Phenotype in Mice

HDAC4 is a class II histone deacetylation protein with a well-characterized role in chondrocyte differentiation and skeletal development, and dysregulated expression or haploinsufficiency of Hdac4 leads to skeletal formation and malformation disorders. The early lethality of hdac4 ablation mice hindered further investigation of its role in postnatal bone growth and development. Therefore, this study aims to investigate the significant role of Hdac4 in postnatal endochondral bone development using two mouse models with conditional deletion of Hdac4 in Sp7-expressing osteoprogenitors or chondrocytes and monitored postnatal bone development. The phenotype of Acan-CreERT2; Hdac4fl/fl mice largely resembled that of conventional Hdac4-/- mice. But phenotypic characterizations of mice with Hdac4 inactivation in Sp7-expressing osteoprogenitors (Sp7-Cre; Hdac4fl/fl) showed dwarfism with body and limb shortening and remarkable skeletal defects. Micro-computed tomography analysis of tibias further demonstrated that loss of Hdac4 expression impaired bone formation and microarchitecture, mainly characterized by dysplasia of trabecular and cortical bone in young mice. Our in vivo and in vitro data support a crucial role for Hdac4 in regulating osteoblast proliferation and differentiation, bone matrix protein production, angiogenesis, and ultimately trabecular and cortical bone formation. Moreover, RNA-seq analysis implicated Hdac4 in the regulation of key genes and pathways necessary to affect the accumulation of extracellular matrix, biological processes related to signal transduction, and skeletal growth. Collectively, our data show that postnatal expression of Hdac4 in Sp7-expressing osteoprogenitors provides essential regulatory oversight of endochondral bone formation, bone morphology, and homeostasis.

Increased hydrogen sulfide turnover serves a cytoprotective role during the development of replicative senescence

The mammalian gasotransmitter hydrogen sulfide (H2S) is produced by enzymes such as cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE), 3-mercaptopyruvate sulfurtransferase (3-MST). Prior studies suggest that H2S may have cytoprotective and anti-aging effects. This project explores the regulation and role of endogenous H2S in a murine model of replicative senescence. H2S and polysulfide levels in RAW 264.7 murine macrophages (control cells: passage 5–10; senescent cells: passage 30–40) were measured using fluorescent probes. The expression of H2S-related enzymes and the activity of senescence marker beta-galactosidase (SA-β-Gal) were also analyzed. CBS, CSE, and 3-MST were inhibited using selective pharmacological inhibitors. Senescence led to a moderate upregulation of CBS and in a significant increase in CSE and 3-MST. H2S degradation enzymes were also elevated in senescence. Inhibition of H2S-producing enzymes reduced H2S levels but increased polysulfides. Inhibition of H2S production during senescence suppressed cell proliferation, and elevated SA-β-Gal and p21 levels. Comparing young and old mice spleens revealed downregulation of CBS and ETHE1 and upregulation of rhodanese and SUOX in older mice. The results demonstrate that increased reactive sulfur turnover occurs in senescent macrophages and that reactive sulfur species supports cell proliferation and regulate cellular senescence

Exerkine irisin mitigates cognitive impairment by suppressing gut-brain axis-mediated inflammation

IntroductionExercise has been recognized to improve cognitive performance by optimizing gut flora and up-regulating exerkine irisin. ObjectiveAlthough exercise-induced irisin is beneficial to cognitive improvement, whether this benefit is achieved by optimizing gut microbiota and metabolites is not fully explored. MethodsAfter aerobic exercise and exogenous irisin interventions for 12 weeks, the 16S rRNA and metabolites in feces of 21-month-old mice were analyzed. Meanwhile, the differential miRNAs and mRNAs in hippocampal tissues were screened by high-throughput sequencing. Relevant mRNAs and proteins were evaluated by RT-PCR, Western blot, and immunofluorescence. ResultsCompared with the young control mice, irisin levels and cognitive capacity of aged mice revealed a significant reduction, while aerobic exercise and intraperitoneal injection of exogenous irisin reversed aging-induced cognitive impairment. Similarly, 147 up-regulated and 173 down-regulated metabolites were detected in aged mice, while 64 and 45 up-regulated and 225 and 187 down-regulated metabolites were detected in aged mice with exercise and irisin interventions, respectively. Moreover, during hippocampal miRNA and mRNA sequencing analysis, 9 differential gut flora and 35 differential genes were identified to be correlated with the inflammatory signaling mediated by the TLR4/MyD88 signal pathway. ConclusionAging-induced cognitive impairment is due to insulin resistance induced by TLR4/MyD88 signaling activation in hippocampal tissues mediated by gut microbiota and metabolite changes. Myokine irisin may be an important mediator in optimizing gut microbiota and metabolism for an improved understanding of mitigated aging process upon exercise interventions.

Effects of deep-sea water on training efficiency, locomotor function and respiratory metabolism in young and aged mice

Deep sea water (DSW) contains many trace minerals, and its applications, which include its use as drinking water, have gradually been expanding. Generally, humans tend to be lacking in mineral intake and deficiencies of trace minerals may increase the risk of several health problems. In recent years, the lack of exercise among the elderly has become an issue, leading to the onset of frailty and sarcopenia, which in turn increases the risk of dementia. Therefore, we investigated whether the daily intake of DSW-extract-added water (DSW; hardness 300 mg/L) impacted the training effect in aged mice. Treatment with DSW significantly induced a training effect in aged mice subjected to treadmill exercise. Locomotor function and metabolic capacity were also significantly increased in aged mice after DSW treatment. The results indicate that daily intake of DSW may enhance the training effect of exercise and affect locomotor performance.

Aging reveals a sex-dependent susceptibility of sarcospan-deficient mice to cardiometabolic disease.

Numerous genes including sarcospan (SSPN) have been designated as obesity-susceptibility genes by human genome-wide association studies. Variants in the SSPN locus have been linked with sex-dependent obesity-associated traits; however, this association has not been investigated in vivo. To delineate the role SSPN plays in regulating metabolism with potential to impact cardiac function, we subjected young and aged global SSPN-deficient (SSPN-/-) male and female mice to obesogenic conditions (60% fat diet). We hypothesized that loss of SSPN combined with metabolic stress would increase susceptibility of mice to cardiometabolic disease. Baseline and end-point assessments of several anthropometric parameters were performed including weight, glucose tolerance, and fat distribution of mice fed control (CD) and high-fat (HFD) diet. Doppler echocardiography was used to monitor cardiac function. White adipose and cardiac tissues were assessed for inflammation by histological, gene expression, and cytokine analysis. Overall, SSPN deficiency protected both sexes and ages from diet-induced obesity, with a greater effect in females. SSPN-/- HFD mice gained less weight than wild-type (WT) cohorts, while SSPN-/- CD groups increased weight. Furthermore, aged SSPN-/- mice developed glucose intolerance regardless of diet. Echocardiography showed preserved systolic function for all groups; however, aged SSPN-/- males exhibited significant increases in left ventricular mass (CD) and signs of diastolic dysfunction (HFD). Cytokine analysis revealed significantly increased IL-1α and IL-17Α in white adipose tissue from young SSPN-/- male mice, which may be protective from diet-induced obesity. Overall, these studies suggest that several sex-dependent mechanisms influence the role SSPN plays in metabolic responses that become evident with age.NEW & NOTEWORTHY Young and aged sarcospan (SSPN)-deficient mice were examined to assess the role of SSPN in obesity and cardiometabolic disease. Both sexes displayed a "leaner" phenotype in response to high-fat diet (HFD). Notably, several sex differences were identified in aged SSPN-deficient mice: 1) females developed glucose intolerance (control and HFD) and 2) males exhibited increased left ventricular mass (control) and diastolic dysfunction (HFD). Therefore, we conclude that SSPN exerts a sex-dependent influence on obesity-associated diseases.

Late-life Attenuation of Cytomegalovirus-mediated CD8 T Cell Memory Inflation: Shrinking of the Cytomegalovirus Latency Niche.

CMV drives the accumulation of virus-specific, highly differentiated CD8 memory T cells (memory inflation [MI]). In mice, MI was shown to directly correlate with the CMV infection dose, yet the CMV-associated CD8 MI plateaus over time. It is unclear how MI is regulated with aging. We infected young mice with 102, 104, and 106 PFU of murine CMV and confirmed that MI magnitude was directly proportional to the infectious dose, reaching a setpoint by midlife. By old age, MI subsided, most prominently in mice infected with 106 PFU, and reached statistical parity between groups in 26-mo-old mice. This corresponded to an age-related loss in lymphatic endothelial cells in lymph nodes, recently shown to be sufficient to drive MI in mice. We propose that MI size and persistence over the lifespan is controlled by the size of the lymphatic endothelial cell niche, whose shrinking leads to reduced MI with aging.

Differences in motor learning-related structural plasticity of layer 2/3 parvalbumin-positive interneurons of the young and aged motor cortex.

Changes to neuronal connectivity are believed to be a key factor in cognitive impairments associated with normal aging. Because of its effect on activities of daily living, deficient motor control is a critical type of cognitive decline to understand. Diminished inhibitory networks in the cortex are implicated in such motor control deficits, pointing to the connectivity of inhibitory cortical interneurons as an important area for study. Here, we used chronic two-photon microscopy to track the structural plasticity of en passant boutons (EPBs) of parvalbumin-positive interneurons in the mouse motor cortex in the first longitudinal, in vivo study of inhibitory interneuron synapses in the context of aging. Young (3-5months) and aged (23-28months) mice underwent training on the accelerating rotarod to evoke motor learning-induced structural plasticity. Our analysis reveals that, in comparison with axons from young mice, those from aged mice have fewer EPBs at baseline that also tend to be larger in size. Aged axons also express learning-related structural plasticity-like new bouton stabilization and bouton enlargement-that is less persistent than that of young axons. This study reveals striking baseline differences in young and aged axon morphology as well as differences in the deployment of learning-related structural plasticity across axons.

Characterizing age-related changes in intact mitochondrial proteoforms in murine hearts using quantitative top-down proteomics

BackgroundCardiovascular diseases (CVDs) are the leading cause of death worldwide, and the prevalence of CVDs increases markedly with age. Due to the high energetic demand, the heart is highly sensitive to mitochondrial dysfunction. The complexity of the cardiac mitochondrial proteome hinders the development of effective strategies that target mitochondrial dysfunction in CVDs. Mammalian mitochondria are composed of over 1000 proteins, most of which can undergo post-translational modifications (PTMs). Top-down proteomics is a powerful technique for characterizing and quantifying proteoform sequence variations and PTMs. However, there are still knowledge gaps in the study of age-related mitochondrial proteoform changes using this technique. In this study, we used top-down proteomics to identify intact mitochondrial proteoforms in young and old hearts and determined changes in protein abundance and PTMs in cardiac aging.MethodsIntact mitochondria were isolated from the hearts of young (4-month-old) and old (24-25-month-old) mice. The mitochondria were lysed, and mitochondrial lysates were subjected to denaturation, reduction, and alkylation. For quantitative top-down analysis, there were 12 runs in total arising from 3 biological replicates in two conditions, with technical duplicates for each sample. The collected top-down datasets were deconvoluted and quantified, and then the proteoforms were identified.ResultsFrom a total of 12 LC-MS/MS runs, we identified 134 unique mitochondrial proteins in the different sub-mitochondrial compartments (OMM, IMS, IMM, matrix). 823 unique proteoforms in different mass ranges were identified. Compared to cardiac mitochondria of young mice, 7 proteoforms exhibited increased abundance and 13 proteoforms exhibited decreased abundance in cardiac mitochondria of old mice. Our analysis also detected PTMs of mitochondrial proteoforms, including N-terminal acetylation, lysine succinylation, lysine acetylation, oxidation, and phosphorylation. Data are available via ProteomeXchange with the identifier PXD051505.ConclusionBy combining mitochondrial protein enrichment using mitochondrial fractionation with quantitative top-down analysis using ultrahigh-pressure liquid chromatography (UPLC)-MS and label-free quantitation, we successfully identified and quantified intact proteoforms in the complex mitochondrial proteome. Using this approach, we detected age-related changes in abundance and PTMs of mitochondrial proteoforms in the heart.

Sirtuin 3 reinforces acylcarnitine metabolism and maintains thermogenesis in brown adipose tissue of aging mice.

Acylcarnitine (ACar) is a novel fuel source for activating thermogenesis in brown adipose tissue (BAT). However, whether ACar metabolism underlies BAT thermogenesis decline with aging remain unclear. Here, the L-carnitine-treated young and aging mice were used to investigate the effects of activation of ACar metabolism on BAT thermogenesis during aging. We showed that long term L-carnitine feeding, which results in an elevation in circulating ACar levels, failed to improve cold sensitivity of aging mice, which still displayed impaired thermogenesis and ACar metabolism in interscapular BAT (iBAT). The RNA-sequencing was used to identify the key regulator for the response of aging mice to LCar induced activation of ACar metabolism in BAT, and we identified Sirt3 as a key regulator for the response of aging mice to L-carnitine induced activation of ACar metabolism in iBAT. Then the adipose-specific Sirt3 knockout (Sirt3 AKO) mice were used to investigate the role of Sirt3 in ACar metabolism and thermogenesis of BAT and explore the underlying mechanism, and the results showed that Sirt3 AKO mice displayed defective ACar metabolism and thermogenesis in iBAT. Mechanically, Sirt3 regulated ACar metabolism via HIF1α-PPARα signaling pathway to promote iBAT thermogenesis, and knockdown or inhibition of HIF1α ameliorated impaired ACar metabolism and thermogenesis of iBAT in the absence of Sirt3. Collectively, we propose that Sirt3 regulated ACar metabolism is critical in maintaining thermogenesis in BAT of aging mice, which can promote the development of anti-aging intervention strategy.

Ionizing Radiation Dose Differentially Affects the Host-Microbe Relationship over Time.

Microorganisms that colonize in or on a host play significant roles in regulating the host's immunological fitness and bioenergy production, thus controlling the host's stress responses. Radiation elicits a pro-inflammatory and bioenergy-expensive state, which could influence the gut microbial compositions and, therefore, the host-microbe bidirectional relationship. To test this hypothesis, young adult mice were exposed to total body irradiation (TBI) at doses of 9.5 Gy and 11 Gy, respectively. The irradiated mice were euthanized on days 1, 3, and 9 post TBI, and their descending colon contents (DCCs) were collected. The 16S ribosomal RNAs from the DCCs were screened to find the differentially enriched bacterial taxa due to TBI. Subsequently, these data were analyzed to identify the metagenome-specific biofunctions. The bacterial community of the DCCs showed increased levels of diversity as time progressed following TBI. The abundance profile was the most divergent at day 9 post 11 Gy TBI. For instance, an anti-inflammatory and energy-harvesting bacterium, namely, Firmicutes, became highly abundant and co-expressed in the DCC with pro-inflammatory Deferribacteres at day 9 post 11 Gy TBI. A systems evaluation found a diverging trend in the regulation profiles of the functional networks that were linked to the bacteria and metabolites of the DCCs, respectively. Additionally, the network clusters associated with lipid metabolism and bioenergy synthesis were found to be activated in the DCC bacteria but inhibited in the metabolite space at day 9 post 11 Gy. Taking these results together, the present analysis indicated a disrupted mouse-bacteria symbiotic relationship as time progressed after lethal irradiation. This information can help develop precise interventions to ameliorate the symptoms triggered by TBI.

Single cell RNA sequencing provides novel cellular transcriptional profiles and underlying pathogenesis of presbycusis

Age-related hearing loss (ARHL) or presbycusis is associated with irreversible progressive damage in the inner ear, where the sound is transduced into electrical signal; but the detailed mechanism remains unclear. Here, we sought to determine the potential molecular mechanism involved in the pathogeneses of ARHL with bioinformatics methods. A single-cell transcriptome sequencing study was performed on the cochlear samples from young and aged mice. Detection of identified cell type marker allowed us to screen 18 transcriptional clusters, including myeloid cells, epithelial cells, B cells, endothelial cells, fibroblasts, T cells, inner pillar cells, neurons, inner phalangeal cells, and red blood cells. Cell-cell communications were analyzed between young and aged cochlear tissue samples by using the latest integration algorithms Cellchat. A total of 56 differentially expressed genes were screened between the two groups. Functional enrichment analysis showed these genes were mainly involved in immune, oxidative stress, apoptosis, and metabolic processes. The expression levels of crucial genes in cochlear tissues were further verified by immunohistochemistry. Overall, this study provides new theoretical support for the development of clinical therapeutic drugs.

High iron in mouse olfactory ensheathing cells at the glia limitans in the olfactory bulb underlies MRI T2* hypointensity

Abstract Brain iron is important for normal function, and aberrantly high iron is often associated with neuroinflammation and neurodegeneration. Oligodendrocytes are a major source of iron in brain as are iron-laden activated macrophages and microglia. T2*-weighted MRI detected a large decrease in signal at the olfactory nerve layer (ONL) in normal young mice over the period of 3 to 12 weeks of age, consistent with iron accumulation in this region. This signal change was most prominent in the inner nerve fiber layer (iNFL). Iron histochemistry, ferritin immunohistology, and electron microscopy showed that there was high iron and ferritin in the olfactory ensheathing cells (OECs) in the iNFL of ONL. The iron concentration in the iNFL was calculated to be approximately 2–3 mM based on MRI T2* relaxivity. The glomerular region near the high-iron iNFL had evidence of neuroinflammation markers of activated microglia and lipofuscin. Lipofuscin was found within the activated microglia as early as 6 weeks. In rats, MRI T2* signal loss in the ONL and high iron levels and lipofuscin were only detected in older rats (11 months) but not in young rats. These results indicate that mouse OECs develop high levels of iron at an early age. It is not clear if this iron is important for mouse OEC function or a result of phagocytic activity of OECs. The relation between iron and inflammation may be interesting to study in these young, healthy mice.

Dysregulated miR-124 mediates impaired social memory behavior caused by paternal early social isolation.

Early social isolation (SI) leads to various abnormalities in emotion and behavior during adulthood. However, the negative impact of SI on offspring remains unclear. This study has discovered that paternal early SI causes social memory deficits and anxiety-like behavior in F1 young adult mice, with alterations of myelin and synapses in the medial prefrontal cortex (mPFC). The 2-week SI in the F1 progeny exacerbates social memory impairment and hypomyelination in the mPFC. Furthermore, the down-regulation of miR-124, a key inhibitor of myelinogenesis, or over-expression of its target gene Nr4a1 in the mPFC of the F1 mice improves social interaction ability and enhances oligodendrocyte maturation and myelin formation. Mechanistically, elevated levels of miR-124 in the sperm of paternal SI mice are transmitted epigenetically to offspring, altering the expression levels of miR-124/Nr4a1/glucocorticoid receptors in mPFC oligodendrocytes. This, in turn, impedes the establishment of myelinogenesis-dependent social behavior. This study unveils a novel mechanism through which miR-124 mediates the intergenerational effects of early isolation stress, ultimately impairing the establishment of social behavior and neurodevelopment.

A biocompatible polydopamine platform for targeted delivery of nicotinamide mononucleotide and boosting NAD+ levels in the brain.

Nicotinamide mononucleotide (NMN), a precursor of the coenzyme nicotinamide adenine dinucleotide (NAD+), has gained wide attention as an anti-aging agent, which plays a significant role in intracellular redox reactions. However, its effectiveness is limited by easy metabolism in the liver and subsequent excretion as nicotinamide, resulting in low bioavailability, particularly in the brain. Additionally, the blood-brain barrier (BBB) further hinders NMN supply to the brain, compromising its potential anti-aging effects. Herein, we developed a biocompatible polydopamine (PDA) platform to deliver NMN for boosting NAD+ levels in the brain for the first time. The lactoferrin (Lf) ligand was covalently attached to the PDA spheres to improve BBB transport efficiency. The resultant PDA-based system, referred to as PDA-Lf-NMN, not only exhibited superior BBB penetration ability but also improved the utilization rate of brain NMN in elevating NAD+ levels compared to NMN alone for both young (3 months) and old (21 months) mice. Moreover, after the old mice were treated with low-dose PDA-Lf-NMN (8 mg kg-1 day-1), they exhibited improved spatial cognition. Importantly, these nanomedicines did not induce any cellular necrosis or apoptosis. It provides a promising avenue for delivering NMN specifically to the brain, boosting NAD+ levels for promoting longevity and treating brain aging-related diseases.

GDF3 promotes adipose tissue macrophage-mediated inflammation via altered chromatin accessibility during aging.

Age-related susceptibility to sepsis and endotoxemia is poorly defined, although hyperactivation of the immune system and the expansion of the visceral adipose as an immunological reservoir are underlying features. Macrophages from older organisms exhibit substantial changes, including chronic NLRP3 inflammasome activation, genomic remodeling and a dysfunctional, amplified inflammatory response upon new exposure to pathogen. However, the mechanisms by which old macrophages maintain their inflammatory phenotype during endotoxemia remains elusive. We previously identified Gdf3 , a TGFβ superfamily cytokine, as a top-regulated gene by age and the NLRP3 inflammasome in adipose tissue macrophages (ATMs). Here, we demonstrate that endotoxemia increases inflammatory (CD11c + ) ATMs in a Gdf3- dependent manner in old mice. Lifelong systemic or myeloid-specific deletion of Gdf3 leads to reduced endotoxemia- induced inflammation, with decreased CD11c + ATMs and inflammatory cytokines, and protection from hypothermia. Moreover, acute blockade of Gdf3 using JQ1, a BRD4 inhibitor, phenocopies old mice with lifelong Gdf3- deficiency. We show that GDF3 promotes the inflammatory phenotype in ATMs by phosphorylating SMAD2/3. Mechanistically, the differential chromatin landscape of ATMs from old mice with or without myeloid-driven Gdf3 indicates that GDF3- SMAD2/3 signaling axis shifts the chromatin accessibility of ATMs towards an inflammatory state during aging. Furthermore, pharmaceutical inhibition of SMAD3 with a specific inhibitor of SMAD3 (SIS3) mimics Gdf3 deletion. SIS3 reduces endotoxemia-mediated inflammation with fewer CD11c + ATMs and less severe hypothermia in old, but not young mice, as well as reduced mortality. In human adipose tissue, age positively correlates with GDF3 level, while inflammation correlates with pSMAD2/3 level. Overall, these results highlight the importance of GDF3-SMAD2/3 axis in driving inflammation in older organisms and identify this signaling axis as a promising therapeutic target for mitigating endotoxemia-related inflammation in the aged.