Effect In Young Mice Research Articles

Crystalline silica-induced pulmonary inflammation and autoimmunity in mature adult NZBW/f1 mice: age-related sensitivity and impact of omega-3 fatty acid intervention

Objective Occupational exposure to respirable crystalline silica (cSiO2) has been linked to lupus development. Previous studies in young lupus-prone mice revealed that intranasal cSiO2 exposure triggered autoimmunity, preventable with docosahexaenoic acid (DHA). This study explores cSiO2 and DHA effects in mature lupus-prone adult mice, more representative of cSiO2-exposed worker age. Methods Female NZBWF1 mice (14-week old) were fed control (CON) or DHA-supplemented diets. After two weeks, mice were intranasally instilled saline (VEH) or 1 mg cSiO2 weekly for four weeks. Cohorts were then analyzed 1- and 5-weeks postinstillation for lung inflammation, cell counts, chemokines, histopathology, B- and T-cell infiltration, autoantibodies, and gene signatures, with results correlated to autoimmune glomerulonephritis onset. Results VEH/CON mice showed no pathology. cSiO2/CON mice displayed significant ectopic lymphoid tissue formation in lungs at 1 week, increasing by 5 weeks. cSiO2/CON lungs exhibited elevated cellularity, chemokines, CD3+ T-cells, CD45R + B-cells, IgG + plasma cells, gene expression, IgG autoantibodies, and glomerular hypertrophy. DHA supplementation mitigated all these effects. Discussion The mature adult NZBWF1 mouse used here represents a life-stage coincident with immunological tolerance breach and one that more appropriately represents the age (20–30 yr) of cSiO2-exposed workers. cSiO2-induced robust pulmonary inflammation, autoantibody responses, and glomerulonephritis in mature adult mice, surpassing effects observed previously in young adults. DHA at a human-equivalent dosage effectively countered cSiO2-induced inflammation/autoimmunity in mature mice, mirroring protective effects in young mice. Conclusion These results highlight life-stage significance in this preclinical lupus model and underscore omega-3 fatty acids’ therapeutic potential against toxicant-triggered autoimmune responses.

Oral exposure to food grade titanium dioxide (E171) induces intestinal and behavioural alterations in adult mice but limited effects in young mice

BackgroundFood-grade titanium dioxide (E171), a white colourant widely used in ultra-processed food products, has been banned in the European Union. However, its usage is still permitted in medicines, and in several other countries. The estimated intake of E171 in children is higher than in adults, which led us to hypothesise that E171 induces differential effects depending on age, with adult mice being the most susceptible due to age, despite the lower dose. AimTo evaluate the effects of oral administration of E171 on intestinal permeability, ileum, and colon histology, and how these effects impact anxious and depressive behaviour in young and adult mice of both sexes. MethodsYoung and adult mice of both sexes C57BL/6 mice received 10 mg/kgbw E171/3 times per week for 3 months. E171 was administered orally in water by pipetting, while control groups only received drinking water, then intestinal permeability, histology and animal behaviour were analysed. ResultsE171 showed an amorphous shape, primary particles sized below 1 µm and anatase crystalline structure. Oral administration of E171 disrupted the intestinal permeability in adult male and female mice, but no effects were observed in young mice of both sexes. E171 promoted ileal adenoma formation in half of the adult female population, moreover hyperplastic crypts, and hyperplastic goblet cells at histological level in adult mice of both sexes. The colon presented hyperplastic goblet cells, hyperchromatic nuclei, increased proliferation and DNA damage in adult mice of both sexes. The anxiety and depressive behaviour were only altered in adult mice treated with E171, but no changes were detected in young animals of both sexes. ConclusionsAdult mice displayed higher susceptibility in all parameters analysed in this study compared to young mice of both sexes.

Microvascular changes in young hamsters after single heterochronic blood transfusion of one unit of blood

Aging is the most significant risk factor for many chronic diseases. Studies of heterochronic blood exchange show that blood and plasma from old-age animals have senescent effects in young mice. However, the underlying mechanisms of how bloodborne factors promote aging remain largely unknown, and studies of blood transfusions' effects on donors of different ages are currently unavailable. This study aimed to compare the microcirculatory effects of blood transfusions from young or old donors in anemic young animals. Blood was collected from anesthetized young (8 weeks old) and older (52-60 weeks old) golden Syrian hamsters via cardiac puncture into CP2D (from an AS-3 blood preparation kit). The supernatant and buffy coat were removed. The AS-3 additive was added according to manufacture instructions, and packed red cells were mixed gently. For microhemodynamic studies, young golden Syrian hamsters instrumented with a dorsal window chamber were subjected to an isovolemic hemodilution of 30% of the animal's blood volume with 5% human serum albumin to induce a normovolemic anemic state. The next day, the anemic animals were randomly assigned to young or older blood and received a transfusion of a volume equivalent to a single unit of red cells. The microhemodynamics in arterioles lower and greater than 60 μm and venules between 20 and 80 μm and functional capillary density (FCD) were measured. Hemodilution acutely reduced hematocrit (Hct) to 60% of the baseline and increased microvascular blood flow in venules and arterioles while decreasing the FCD. Transfusion of young or old donors’ blood increased the Hct. There was no significant change post-transfusion in the diameter or the flow of the arterioles in the young donors' blood group compared to old donors’ blood. The animals transfused with blood from young donors restored venules flow and diameter similarly to baseline (pre-anemia). However, the old donors’ blood group did not show the same recovery. More importantly, the FCD significantly improved after younger donors' blood transfusions compared to the old ones. These results suggest that recovery from anemia is improved when using blood from younger donors, as this ensures higher FCD and supports proper tissue homeostasis. This study intentionally tried to recapitulate how blood is processed in the USA and transfuse only a conservative amount of blood into anemic animals. Studies have shown that heterochronic parabiosis (surgically joining younger and older animals in which blood, organs, and environments are shared) or a blood exchange rejuvenates old tissues. Here using a heterochronic blood transfusion, we show that the donor's age determines the recovery of FCD after transfusion. These deficits could be due to capillary collapse preventing oxygen from arriving uniformly through the tissue, as the FCD determines the microvascular oxygen diffusion field. Future studies will look at the implication of the recovery of FCD after transfusion. This study was supported by National Institutes of Health grants R01HL162120, R01HL159862 and the Department of Defense under grants W81XWH1810059. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

(m-CF3-PhSe)2 benefits against anxiety-like phenotype associated with synaptic plasticity impairment and NMDAR-mediated neurotoxicity in young mice exposed to a lifestyle model

Lifestyle habits including energy-dense foods and ethanol intake are associated with anxiety disorders. m-Trifluoromethyl-diphenyl diselenide [(m-CF3-PhSe)2] has been reported to modulate serotonergic and opioidergic systems and elicit an anxiolytic-like phenotype in animal models. This study investigated if the modulation of synaptic plasticity and NMDAR-mediated neurotoxicity contributes to the (m-CF3-PhSe)2 anxiolytic-like effect in young mice exposed to a lifestyle model. Swiss male mice (25-days old) were subjected to a lifestyle model, an energy-dense diet (20:20% lard: corn syrup) from the postnatal day (PND) 25–66 and sporadic ethanol (2 g/kg) (3 x a week, intragastrically, i.g.) from PND 45 to 60. From PND 60 to 66, mice received (m-CF3-PhSe)2 (5 mg/kg/day; i.g). The corresponding vehicle (control) groups were carried out. After, mice performed anxiety-like behavioral tests. Mice exposed only to an energy-dense diet or sporadic ethanol did not show an anxiety-like phenotype. (m-CF3-PhSe)2 abolished the anxiety-like phenotype in young mice exposed to a lifestyle model. Anxious-like mice showed increased levels of cerebral cortical NMDAR2A and 2B, NLRP3 and inflammatory markers, and decreased contents of synaptophysin, PSD95, and TRκB/BDNF/CREB signaling. (m-CF3-PhSe)2 reversed cerebral cortical neurotoxicity, the increased levels of NMDA2A and 2B, and decreased levels of synaptic plasticity-related signaling in the cerebral cortex of young mice exposed to a lifestyle model. In conclusion, the (m-CF3-PhSe)2 anxiolytic-like effect was associated with the modulation of NMDAR-mediated neurotoxicity and synaptic plasticity in the cerebral cortex of young mice exposed to the lifestyle model.

Once-Daily Subcutaneous Irisin Administration Mitigates Depression- and Anxiety-like Behavior in Young Mice

Major depression is one of the most common psychiatric disorders worldwide, usually associated with anxiety. The multi-etiological nature of depression has increased the search for new antidepressant molecules, including irisin, for which, in a previous study, we tested its effect in young mice when administered intraperitoneally in a long-term intermittent manner. Here, we evaluated the effect of subcutaneous short-term irisin administration (100 µg/Kg/day/5 days) in male and female mice subjected to behavioral paradigms: Tail Suspension Test (TST), Forced Swim Test (FST), Elevated Plus Maze (EPM), and Y Maze (YM). Moreover, a qRT-PCR assay was performed to analyze the impact of irisin treatment on Pgc-1α/FNDC5 expression in the brain. A significant reduction in immobility time in TST and FST was observed in irisin-treated mice. Furthermore, irisin treatment significantly increased the number of entries and time spent in open arms, demonstrating its anxiolytic effect. Memory-enhancing effects were not reported in YM. Interestingly, no gender differences were observed in all behavioral tests. Overall, these results suggest that short-term subcutaneous irisin administration can exert an antidepressant and anxiolytic role, probably due to the activation of the Pgc-1α/FNDC5 system in the brain. Further investigation could lead to the identification of irisin as a new agent for the treatment of psychiatric disorders.

Changes in gut microbiome correlate with intestinal barrier dysfunction and inflammation following a 3-day ethanol exposure in aged mice.

Alcohol use among older adults is on the rise. This increase is clinically relevant as older adults are at risk for increased morbidity and mortality from many alcohol-related chronic diseases compared to younger patients. However, little is known regarding the synergistic effects of alcohol and age. There are intriguing data suggesting that aging may lead to impaired intestinal barrier integrity and dysbiosis of the intestinal microbiome, which could increase susceptibility to alcohol's negative effects. To study the effects of alcohol in age we exposed aged and young mice to 3 days of moderate ethanol and evaluated changes in gut parameters. We found that these levels of drinking do not have obvious effects in young mice but cause significant alcohol-induced gut barrier dysfunction and expression of the pro-inflammatory cytokine TNFα in aged mice. Ethanol-induced downregulation of expression of the gut-protective antimicrobial peptides Defa-rs1, Reg3b, and Reg3g was observed in aged, but not young mice. Analysis of the fecal microbiome revealed age-associated shifts in microbial taxa, which correlated with intestinal and hepatic inflammatory gene expression. Taken together, these data demonstrate that age drives microbiome dysbiosis, while ethanol exposure in aged mice induces changes in the expression of antimicrobial genes important for separating these potentially damaging microbes from the intestinal lumen. These changes highlight potential mechanistic targets for prevention of the age-related exacerbation of effects of ethanol on the gut.

Systemic induction of senescence in young mice after single heterochronic blood exchange.

Ageing is the largest risk factor for many chronic diseases. Studies of heterochronic parabiosis, substantiated by blood exchange and old plasma dilution, show that old-age-related factors are systemically propagated and have pro-geronic effects in young mice. However, the underlying mechanisms how bloodborne factors promote ageing remain largely unknown. Here, using heterochronic blood exchange in male mice, we show that aged mouse blood induces cell and tissue senescence in young animals after one single exchange. This induction of senescence is abrogated if old animals are treated with senolytic drugs before blood exchange, therefore attenuating the pro-geronic influence of old blood on young mice. Hence, cellular senescence is neither simply a response to stress and damage that increases with age, nor a chronological cell-intrinsic phenomenon. Instead, senescence quickly and robustly spreads to young mice from old blood. Clearing senescence cells that accumulate with age rejuvenates old circulating blood and improves the health of multiple tissues.

Accumulation of systematic TPM1 mediates inflammation and neuronal remodeling by phosphorylating PKA and regulating the FABP5/NF-κB signaling pathway in the retina of aged mice.

The molecular mechanisms underlying functional decline during normal brain aging are poorly understood. Here, we identified the actin‐associated protein tropomyosin 1 (TPM1) as a new systemic pro‐aging factor associated with function deficits in normal aging retinas. Heterochronic parabiosis and blood plasma treatment confirmed that systemic factors regulated age‐related inflammatory responses and the ectopic dendritic sprouting of rod bipolar (RBC) and horizontal (HC) cells in the aging retina. Proteomic analysis revealed that TPM1 was a potential systemic molecule underlying structural and functional deficits in the aging retina. Recombinant TPM1 protein administration accelerated the activation of glial cells, the dendritic sprouting of RBCs and HCs and functional decline in the retina of young mice, whereas anti‐TPM1 neutralizing antibody treatment ameliorated age‐related structural and function changes in the retina of aged mice. Old mouse plasma (OMP) induced glial cell activation and the dendritic outgrowth of RBCs and HCs in young mice, and yet TMP1‐depleted OMP failed to reproduce the similar effect in young mice. These results confirmed that TPM1 was a systemic pro‐aging factor. Moreover, we demonstrated that systematic TPM1 was an immune‐related molecule, which elicited endogenous TPM1 expression and inflammation by phosphorylating PKA and regulating FABP5/NF‐κB signaling pathway in normal aging retinas. Interestingly, we observed TPM1 upregulation and the ectopic dendritic sprouting of RBCs and HCs in young mouse models of Alzheimer's disease, indicating a potential role of TPM1 in age‐related neurodegenerative diseases. Our data indicate that TPM1 could be targeted for combating the aging process.

Beneficial Effects of a Plasma Fraction on Inflammation and Synaptic Deficits for Age-Related Cognitive Disorders

Exercise is beneficial for physical functions across all ages. However, the response to exercise shifts from anabolism, resulting in limited gain of muscle strength and endurance. These changes likely reflect age-related alterations in transcriptional response underlying the muscular adaptation to exercise. The exact changes in gene expression accompanying exercise, however, are largely unknown, and elucidating them is of a great clinical interest for optimizing the exercise-based therapies for sarcopenia. In order to characterize the exercise-induced transcriptomic changes in aged muscle, a paired-end RNA sequencing was performed on the rRNA-depleted total RNA extracted from the gastrocnemius muscles of 24 months-old mice after 8 weeks of regimented exercise (exercise group) or sedentary activities (sedentary group). Differential gene expression analysis revealed upregulations in the group of genes involved in neurotransmission. In particular, genes encoding the transporters and receptor components of glutaminergic transmission were significantly upregulated in exercised muscles, as exemplified by Gria 1, Gria 2 and Grin2c encoding glutamate receptor 1, 2 and 2C respectively, Grin1 and Grin2b encoding N-methyl-D-aspartate receptors (NMDARs), Nptx1 responsible for glutaminergic receptor clustering, and Slc1a2 and Slc17a7 regulating synaptic uptake of glutamate. These changes were accompanied by an increase in post-synaptic NMDARs and acetylcholine receptors (AChRs), as well as their innervation at neuromuscular junctions (NMJs). These results suggest that neural responses predominate aged skeletal muscle following exercise, and indicate a possibility that glutaminergic transmission at NMJs may be responsible for synaptic protection and neural remodeling accompanying the exercise-induced functional enhancement in aged skeletal muscle.

Opioid System Contributes to the Trifluoromethyl-Substituted Diselenide Effectiveness in a Lifestyle-Induced Depression Mouse Model.

Energy-dense foods and ethanol consumption are associated with mood disorders. m-Trifluoromethyl-diphenyl diselenide [(m-CF3-PhSe)2] has been a prominent pharmacological target due to its antidepressant-like effects. This study investigated if the modulation of opioid and glucocorticoid receptors and its well-known antioxidant property contribute to the (m-CF3-PhSe)2 antidepressant-like effect in young mice subjected to an energy-dense diet and ethanol intake. Swiss male mice [postnatal day (PND) 25] were exposed to an energy-dense diet (containing 20% fat and 20% carbohydrate) or standard chow until the PND 67. Mice received ethanol (2g/kg) or water administration (3 times a week, intragastrically [i.g.]) from PND 45 to PND 60. After that, mice received (m-CF3-PhSe)2 (5mg/kg/day; i.g) or vegetal oil administration from PND 60 to 66. Mice performed the behavioral tests to evaluate the depressive-like phenotype. The results showed that individually neither an energy-dense diet nor ethanol group induced a depressive-like phenotype, but the association of both induced this phenotype in young mice. Oxidative stress was characterized by the increase of malondialdehyde, the decrease in the superoxide dismutase activity, and non-protein sulfhydryl levels in the cerebral cortex of depressive-like mice. Depressive-like mice showed an increase in the protein levels of opioid receptors and depletion in those of glucocorticoid. (m-CF3-PhSe)2 abolished depressive-like phenotype and oxidative stress as well as modulated the levels of glucocorticoid and opioid receptors. In conclusion, the modulation of opioid and glucocorticoid receptors and the antioxidant property contributed to the (m-CF3-PhSe)2 antidepressant-like effect in young mice exposed to an energy-dense diet and ethanol intake.

Effect of PPARγ Inhibition on Bone in Aged Animals

Aging is accompanied by bone loss and marrowfat accumulation. PPARg is a key factor regulating adipocyte differentiation. Marrowfat secretes large quantities of factors including adipokines, cytokines and chemokines that contribute to bone loss. We hypothesized that inhibition of PPARg would reduce adipocytes and adipose-generated inflammatory factors, and thus decrease aging-induced bone loss. To test this hypothesis, we treated young (6mo) and old (23mo) female C57BL/6 mice with a PPARg antagonist GW9662 (1mg/kg body weight, IP injection for 6wks) and examined the effects on bone, immune cell lineage skewing, and the expression of inflammation related genes. DXA analysis data showed that GW treatment had no effect on vertebral and femoral BMD and BMC in young or old mice. u-CT analysis showed that GW treatment reduced BV/TV in old mice but had no effect in young mice. FACS analysis data showed that GW treatment significantly increased lymphoid (CD3) and decreased myeloid (CD11b) lineage cells only in young mice. GW treatment significantly decreased CD4 and CD8 T cell subpopulations in young mice, but had no effect in old mice. Interestingly, Nanostring analysis of inflammation genes revealed an opposite effects of GW treatment in young vs. old mice, i.e., genes whose expression were downregulated by GW in bone cells of the young mice were upregulated in the old mice. These results suggested that systemic inhibition of PPARg, while enhancing CD3 and reducing CD11b cell populations in the bone marrow of young mice, may have a negative effect on bone architecture in old mice.

Marrow aspiration in aged mice: intramedullary osteogenesis, reduced mechano-adaptation, increased marrow fat

ABSTRACT Introduction: With age, the number of adipocytes and osteoclasts increases, the number of osteoblasts decreases, and mechano-adaptation is impaired. Objectives: Using marrow aspiration, which has a known osteogenic effect in young mice, we sought to recruit osteoblast progenitors to mediate the mechano-adaptive response to in vivo tibial loading. Methods: First, we assessed bone formation and marrow adiposity in the tibiae of old mice (>20 months) sacrificed 1, 2, and 4 weeks after unilateral marrow aspiration. Then, we examined the effects of marrow aspiration on mechano-adaptation in aged mice using tibial loading. Results: Two weeks after aspiration, aspirated tibiae had more bone than contralateral tibiae due to the formation of bone in the medullary canal. Two weeks and four weeks after marrow aspiration, the volume of marrow adipose tissue was higher in the aspirated tibiae, compared to contralateral tibiae. Histomorphometry indicated that aspiration increased non-periosteal (endosteal, intracortical, intramedullary) bone formation, compared to the contralateral tibia. Mice with marrow aspiration had reduced periosteal bone formation in the contralateral tibia, compared to mice that had loading alone. Loading-induced periosteal bone formation was higher in mice that had loading alone, compared to mice that had aspiration + loading, indicating that aspiration further reduced the mechano-adaptive response. Conclusion: These data demonstrate that, in old mice, bone forms in the medullary canal following aspiration. Adiposity is increased following marrow aspiration, and periosteal mechano-adaptation is reduced.

Immunology and the elder eye

AbstractSeveral eye diseases occur more frequently in the elderly, such as age‐related macular degeneration (AMD), primary open angle glaucoma and intraocular melanoma. Inflammation has become an important player, and while in the past AMD was considered purely a vessel disease, it has become clear that macrophages and complement play an important role in the development of the leaky vessels. The function of macrophages changes when we age. As Makitie and Kivela had shown that macrophages have a prognostic value in uveal melanoma, we started to investigate the role of aging in the development of ocular tumors in a mouse model. Ly observed that depletion of macrophages had no effect in young mice, but prevented intraocular tumor growth in old mice. Maat, Bronkhorst and Brouwer showed that specific chromosomal abnormalities in a uveal melanoma are associated with prognosis, influx of macrophages and a high vessel density.While working on this, I learned about a patient with glaucoma who had the impression that her visual field had decreased when she had the flu. Around the same time, Dr Dong Feng Chen of the Schepens Eye Research Institute in Boston developed a murine glaucoma model. A Dutch PhD student, Dr Khanh Vu, set out to determine whether inflammation plays a role in glaucoma, and indeed, glaucomatous damage following high eye pressure increased through the induction of immune responses. High eye pressure led to influx of macrophages and T cells into the retina, and the induction of specific antibodies and T cell responses. The T cells are directed against heat shock proteins, which become expressed after trauma. Blocking T cell immune response limited the loss of retinal ganglion cells and axons in the mouse after glaucoma induction. The anti‐heat shock immune response did not develop when the mouse lacked a microbiome. Patients with glaucoma also showed anti‐heat shock protein antibodies and T cell responses.These data show that inflammation plays a role in several age‐related eye disease, including age‐related macular degeneration, uveal melanoma and glaucoma.Makitie T. et al. Tumor‐infiltrating macrophages (CD68+ cells) and prognosis in malignant uveal melanoma. Invest Ophthalmol Vis Sci 2001; 42: 1414‐1421. Bronkhorst I.H. et al. Detection of M2 macrophages in uveal melanoma and relation with survival. Invest Ophtalmol Vis Sci 2011; 52: 643‐650. Doi: 10.1167/iovs.10‐5979. Ly L.V. et al. In aged mice, outgrowth of intraocular melanoma depends on proangiogenic.M2 type macrophages. J Immunol. 2010; 185: 3481‐3488. Chen H. et al. Commensal microflora‐induced T cell responses mediate progressive neurodegeneration in glaucoma. Nat Commun 2018; Aug 10;9(1): 3209. Doi: 10.1038/s41467‐018‐05681‐9

BENEFICIAL EFFECTS OF A PLASMA FRACTION ON NEUROGENESIS FOR AGE-RELATED COGNITIVE DISORDERS

The process of aging is multifactorial and therefore single interventions may be unlikely to attenuate the myriad pathologies. Plasma contains many beneficial factors which have been shown in animal models to ameliorate multiple age-related deficits across varied organ systems, including the brain. We demonstrated that human plasma from young 18-22-year-old donors reverses age-related cognitive decline and enhances hippocampal neurogenesis and cell survival in aged immunocompromised mice, while plasma from aged individuals (62-68 years old) has detrimental effects in young mice. Utilizing cell-based assays we identified a human plasma fraction (PF) which enhanced neuronal outgrowth and synaptic connectivity. We demonstrate that PF administration provides benefits beyond those observed with whole plasma treatment, resulting in decreased brain inflammation, increased synaptic density and neuronal activation. We evaluated longitudinal treatment of PF and observed no depletion in stem cell populations while maintaining an enhanced level of neurogenesis. We examined PF in an α-synuclein mouse model of Parkinson’s disease, where treatment significantly reversed functional, inflammatory, and neuronal deficits. To further our understanding of interplay between multiple mechanisms inducing neurogenesis, we examined the effect of exercise on PF treated mice and observed a synergistic increase in neurogenesis. Proteomic analysis of mouse plasma following PF treatment demonstrates differential protein levels compared to running or the combination of running and PF, suggesting that PF is mechanistically different from the effect of running. In summary, we demonstrate that PF is a multifactorial and multimodal, clinically-relevant, intervention for the treatment of global changes induced by aging.

The Dipeptidyl Peptidase 4 Substrate CXCL12 Has Opposing Cardiac Effects in Young Mice and Aged Diabetic Mice Mediated by Ca2+ Flux and Phosphoinositide 3-Kinase γ.

Blood glucose-lowering therapies can positively or negatively affect heart function in type 2 diabetes, or they can have neutral effects. Dipeptidyl peptidase 4 (DPP-4) inhibitors lower blood glucose by preventing the proteolytic inactivation of glucagon-like peptide 1 (GLP-1). However, GLP-1 is not the only peptide substrate of DPP-4. Here, we investigated the GLP-1-independent cardiac effects of DPP-4 substrates. Pointing to GLP-1 receptor (GLP-1R)-independent actions, DPP-4 inhibition prevented systolic dysfunction equally in pressure-overloaded wild-type and GLP-1R knockout mice. Likewise, DPP-4 inhibition or the DPP-4 substrates substance P or C-X-C motif chemokine ligand 12 (CXCL12) improved contractile recovery after no-flow ischemia in the hearts of otherwise healthy young adult mice. Either DPP-4 inhibition or CXCL12 increased phosphorylation of the Ca2+ regulatory protein phospholamban (PLN), and CXCL12 directly enhanced cardiomyocyte Ca2+ flux. In contrast, hearts of aged obese diabetic mice (which may better mimic the comorbid patient population) had diminished levels of PLN phosphorylation. In this setting, CXCL12 paradoxically impaired cardiac contractility in a phosphoinositide 3-kinase γ-dependent manner. These findings indicate that the cardiac effects of DPP-4 inhibition primarily occur through GLP-1R-independent processes and that ostensibly beneficial DPP-4 substrates can paradoxically worsen heart function in the presence of comorbid diabetes.

Mitochondria-targeted antioxidant therapy with MitoQ ameliorates aortic stiffening in old mice.

Aortic stiffening is a major independent risk factor for cardiovascular diseases, cognitive dysfunction, and other chronic disorders of aging. Mitochondria-derived reactive oxygen species are a key source of arterial oxidative stress, which may contribute to arterial stiffening by promoting adverse structural changes—including collagen overabundance and elastin degradation—and enhancing inflammation, but the potential for mitochondria-targeted therapeutic strategies to ameliorate aortic stiffening with primary aging is unknown. We assessed aortic stiffness [pulse-wave velocity (aPWV)], ex vivo aortic intrinsic mechanical properties [elastic modulus (EM) of collagen and elastin regions], and aortic protein expression in young (~6 mo) and old (~27 mo) male C57BL/6 mice consuming normal drinking water (YC and OC) or water containing mitochondria-targeted antioxidant MitoQ (250 µM; YMQ and OMQ) for 4 wk. Both baseline and postintervention aPWV values were higher in OC vs. YC (post: 482 ± 21 vs. 420 ± 5 cm/s, P < 0.05). MitoQ had no effect in young mice but decreased aPWV in old mice (OMQ, 426 ± 20, P < 0.05 vs. OC). MitoQ did not affect age-associated increases in aortic collagen-region EM, collagen expression, or proinflammatory cytokine expression, but partially attenuated age-associated decreases in elastin region EM and elastin expression. Our results demonstrate that MitoQ reverses in vivo aortic stiffness in old mice and suggest that mitochondria-targeted antioxidants may represent a novel, promising therapeutic strategy for decreasing aortic stiffness with primary aging and, possibly, age-related clinical disorders in humans. The destiffening effects of MitoQ treatment may be at least partially mediated by attenuation/reversal of age-related aortic elastin degradation.NEW & NOTEWORTHY We show that 4 wk of treatment with the mitochondria-specific antioxidant MitoQ in mice completely reverses the age-associated elevation in aortic stiffness, assessed as aortic pulse-wave velocity. The destiffening effects of MitoQ treatment may be at least partially mediated by attenuation of age-related aortic elastin degradation. Our results suggest that mitochondria-targeted therapeutic strategies may hold promise for decreasing arterial stiffening with aging in humans, possibly decreasing the risk of many chronic age-related clinical disorders.

Dantrolene suppresses spontaneous Ca2+release without altering excitation-contraction coupling in cardiomyocytes of aged mice

Cardiac dysfunction in the aged heart reflects abnormalities in cardiomyocyte Ca(2+) homeostasis including altered Ca(2+) cycling through the sarcoplasmic reticulum (SR). The ryanodine receptor antagonist dantrolene exerts antiarrhythmic effects by preventing spontaneous diastolic Ca(2+) release from the SR. We tested the hypothesis that dantrolene prevents spontaneous Ca(2+) release without altering excitation-contraction coupling in aged myocardium. Left ventricular cardiomyocytes isolated from young (3 to 4 mo) and aged (24-26 mo) C57BL/6 mice were loaded with the Ca(2+) indicator fluo-4. Amplitudes of action potential-induced Ca(2+) transients at 1-Hz pacing were similar between young and aged mice, yet cell shortening was impaired in aged mice. Isoproterenol (1 μM) increased Ca(2+) transient amplitude and cell shortening to identical levels in young and aged; dantrolene (1 μM) had no effect on Ca(2+) transients or cell shortening during pacing. Under Ca(2+) overload conditions induced with 10 mM extracellular Ca(2+) concentration, spontaneous Ca(2+) waves were of diminished amplitude and associated with lower SR Ca(2+) content in aged versus young mice. Despite no effect in young mice, dantrolene increased SR Ca(2+) content and Ca(2+) wave amplitude in aged mice. In the presence of isoproterenol following rest from 1-Hz pacing, Ca(2+) spark frequency was elevated in aged mice, yet the time to spontaneous Ca(2+) wave was similar between young and aged mice; dantrolene decreased Ca(2+) spark frequency and prolonged the time to Ca(2+) wave onset in aged mice with no effect in young mice. Thus dantrolene attenuates diastolic Ca(2+) release in the aged murine heart that may prove useful in preventing cardiac dysfunction.

Short-Term Treatment With Rapamycin and Dietary Restriction Have Overlapping and Distinctive Effects in Young Mice

Because rapamycin, an inhibitor of the nutrient sensor mammalian target of rapamycin, and dietary restriction both increase life span of mice, it has been hypothesized that they act through similar mechanisms. To test this hypothesis, we compared various biological parameters in dietary restriction mice (40% food restriction) and mice fed rapamycin (14 ppm). Both treatments led to a significant reduction in mammalian target of rapamycin signaling and a corresponding increase in autophagy. However, we observed striking differences in fat mass, insulin sensitivity, and expression of cell cycle and sirtuin genes in mice fed rapamycin compared with dietary restriction. Thus, although both treatments lead to significant downregulation of mammalian target of rapamycin signaling, these two manipulations have quite different effects on other physiological functions suggesting that they might increase life span through a common pathway as well as pathways that are altered differently by dietary restriction and rapamycin.

Reversal of Age‐Related Mitochondrial Dysfunction In Vivo by Treatment with the Mitochondrially Targeted Therapeutic SS‐ 31

In vivo mitochondrial function and energy homeostasis in skeletal muscle declines with age. The ability to reverse this dysfunction with an acute treatment would represent a new paradigm for improving skeletal muscle function in the elderly. Here we test whether the novel, mitochondrially‐targeted peptide SS‐31 restores mitochondrial energetics in aged mouse skeletal muscle in vivo. We treated young and old mice with an acute 3mg/kg dose of SS‐31 and assessed in vivo mitochondrial function and energetic state after one hour using a unique combined magnetic resonance and optical spectroscopy system. In vivo mitochondrial coupling (P/O), phosphorylation capacity, and energy state (PCr/ATP) significantly declined with age. SS‐31 significantly improved all three measures of mitochondrial energetics in skeletal muscle of aged mice, but had no observed effect in young mice. Reversal of the age‐related decline in capacity and energy state may be due to both SS‐31's antioxidant activity and a more direct facilitation of mitochondrial respiratory activity in aged muscle. These results suggest that short‐term treatment with mitochondrially targeted therapeutics may represent a new approach to reverse the effects of aging on skeletal muscle energetics. This was supported by NIH grants AG001751 and AG028455.

Aerobic exercise reverses arterial inflammation with aging in mice

We tested the hypothesis that regular aerobic exercise reverses arterial inflammation with aging. When compared with young controls (6.2 ± 0.4 mo; n = 7), old (31.3 ± 0.5 mo; n = 11) male B6D2F1 cage-restricted mice demonstrated increased arterial activation of the proinflammatory transcription factor NF-κB, as indicated by greater aortic phosphorylation of both the inhibitor of NF-κB kinase (IKK) and the p65 subunit of NF-κB (both P < 0.05). Similarly, aortic expression of the proinflammatory cytokines IL-1 and IL-6, IFN-γ, and TNF-α were greater in the old mice (all P < 0.05). Macrophage and T lymphocyte abundance was unchanged with age in the aortic intima and media but was markedly increased in the adventitia and perivascular fat tissue of old mice (all P < 0.05). This proinflammatory arterial phenotype with aging was associated with vascular dysfunction, as reflected by impaired nitric oxide-mediated endothelium-dependent dilation. Voluntary wheel running (10-14 wk) normalized aortic IKK-NF-κB activation, cytokine expression, adventitial and perivascular macrophage infiltration, and vascular function in old mice (32.4 ± 0.3 mo; n = 8) while having no consistent effects in young mice. Short-term voluntary wheel running started late in life reverses arterial inflammation with aging in mice possibly via outside-in actions. These anti-inflammatory effects may play an important role in the amelioration of age-associated vascular dysfunction by regular aerobic exercise.