Age-associated alteration in innate immune response in captive baboons

Age-associated alterations in immune and inflammatory responses in captive olive baboons (Papio anubis)

Introduction

Advanced age is a primary risk factor for many chronic diseases and conditions; however, age-related immune dysregulation is not well understood. Animal models, particularly those that resemble human age-related physiological changes, are needed to better understand immunosenescence and to improve health outcomes. Here, we explore the utility of the olive baboon (Papio anubis) in studying age-related changes to the immune system and understanding mechanisms of immunosenescence.

Methods

We examined immune cell, inflammatory responses, cytokines, and cortisol levels using hematology and flow cytometry, mitogen stimulation, multiplex cytokine assay, and cortisol immunoassay.

Results and Discussion

Our results reveal significant age effects on numerous immune and inflammatory responses. For instance, adult and aged monkeys exhibited significantly fewer monocytes than young monkeys. After stimulation with Con A and PWM (separately), we found that old baboons had higher INFγ expression compared to young baboons. Similarly, after stimulation with LPS and PWM (separately), we found that old baboons had higher TNFα expression compared to young baboons. These findings suggest that the olive baboon is a suitable model for biogerontology research, immune senescence, and development of vaccines. Though there are phenotypic and functional similarities between baboons and humans, specific differences exist in immune cell expression and immune function of lymphocytes that should be considered for better experimental outcomes in the development of therapeutics and restoring innate and adaptive immune function in aged individuals.

Insights into pathophysiology and therapeutic strategies for heat stroke: Lessons from a baboon model

Heat stroke is a perilous condition marked by severe hyperthermia and extensive multiorgan dysfunction, posing a considerable risk of mortality if not promptly identified and treated. Furthermore, the complex biological mechanisms underlying heat stroke-induced tissue and cell damage across organ systems remain incompletely understood. This knowledge gap has hindered the advancement of effective preventive and therapeutic strategies against this condition. In this narrative review, we synthesize key insights gained over a decade using a translational baboon model of heat stroke. By replicating heat stroke pathology in a non-human primate species that closely resembles humans, we have unveiled novel insights into the pathways of organ injury and cell death elicited by this condition. Here, we contextualize and integrate the lessons learned concerning heat stroke pathophysiology and recovery, areas that are inherently challenging to investigate directly in human subjects. We suggest novel research directions to advance the understanding of the complex mechanisms underlying cell death and organ injury. This may lead to precise therapeutic strategies that benefit individuals suffering from this debilitating condition.

Immunosenescence and inflammaging in the aged horse

The equine population in the United States and worldwide now includes a higher percentage of geriatric horses than ever previously recorded, and as methods to treat and manage elderly equids are developed and refined, this aging population will likely continue to expand. A better understanding of how horses age and the effect of age on immunity and disease susceptibility is needed to enable targeted preventative healthcare strategies for aged horses. This review article outlines the current state of knowledge regarding the effect of aging on immunity, vaccine responsiveness, and disease risk in the horse, highlighting similarities and differences to what is observed in aged humans. Horses show similar but milder age-related alterations in immune function to those reported in people. Decreases in lymphocyte proliferation and antibody production and diminished response to vaccination have all been documented in elderly horses, however, increased risk of infectious disease is not commonly reported. Aged horses also show evidence of a proinflammatory state (inflammaging) yet appear less susceptible to the chronic diseases of people for which inflammation is a risk factor. Information is currently lacking as to why the horse does not experience the same risk of age-related disease (e.g., cancer, heart disease, neurodegeneration) as people, although a lack of negative lifestyle habits, differences in diet, exercise, genetics and physiology may all contribute to improved health outcomes in the older horse.

Effects of Modified Electroconvulsive Therapy on Serum Cortisol, Nesfatin-1, and Pro-inflammatory Cytokine Levels in Elderly Patients With Treatment-Resistant Depression

AIM

Modified electroconvulsive therapy (MECT) is an effective strategy for treatment-resistant depression (TRD); however, the mechanism underlying effects of MECT remains unclear. Accumulating evidence suggests that TRD is closely associated with dysfunction of the hypothalamic-pituitary-adrenal (HPA) axis, anorexigenic peptides, and pro-inflammatory cytokines. However, MECT effects on the HPA axis, anorexigenic peptides, and pro-inflammatory cytokines in elderly patients with TRD remain unclear. In this study, we investigated whether the HPA axis (cortisol), anorexigenic peptides (nesfatin-1), and pro-inflammatory cytokines (C-reactive protein, tumor necrosis factor-α, and interleukin-6, and interleukin-1β) are involved in the mechanism underlying MECT effects in elderly patients with TRD.

METHODS

Elderly patients with TRD were enrolled in this study between December 2019 and October 2021; all patients underwent MECT after physical examination. Serum cortisol, nesfatin-1, and pro-inflammatory cytokine levels were measured before and after the first, third, and sixth MECT sessions. The Hamilton Depression Rating Scale-24 (HAMD-24) and the Mini-Mental State Examination (MMSE) were used to evaluate depression and cognitive impairment, respectively. We compared pre- and post-MECT serum cortisol, nesfatin-1, and pro-inflammatory cytokine levels to confirm the short-term effects of MECT on these serum indices. We compared these serum indices across three time points (before the first, third, and sixth MECT sessions) to determine the long-term effects of MECT on serum cortisol, nesfatin-1, and pro-inflammatory cytokine levels.

RESULTS

We observed no statistically significant changes in the pre- and post-MECT serum cortisol, nesfatin-1, or pro-inflammatory cytokine levels. No significant changes in serum cortisol, nesfatin-1, and pro-inflammatory cytokine levels were observed across the aforementioned time points. Moreover, there were no statistically significant sex-based differences in the aforementioned serum indices. Furthermore, the serum cortisol level was negatively correlated with the serum IL-6 level before and after the first MECT session in patients with high cortisol levels (> the 50^th percentile value of all samples). Additionally, the post-MECT HAMD-24 and MMSE scores were significantly lower.

CONCLUSIONS

MECT reduced depressive symptoms despite an adverse effect on cognition and had no significant effect on the serum cortisol, nesfatin-1, and pro-inflammatory cytokine levels in elderly patients with TRD.

Effects of Chronic Viral Infection on Lymphocyte Populations in Middle-aged Baboons (Papio anubis)

Aging of the immune system is characterized by the loss of naïve T-cells, increased inflammation, and immune function impairment. Chronic infection with cytomegalovirus is thought to play a role in age-related changes in immunity. Therefore, to assess the effect of pathogens such as cytomegalovirus on the immune system, we determined lymphocyte populations and inflammatory markers over a 3-y period in captive, middle-age baboons, with various exposure to pathogens and shedding pressure. Groups included SPF (i.e., pathogen-negative; n = 14); large-group, conventionally housed (CONV LG; pathogen- positive; n = 14), and small-group, conventionally housed (CONV SM; pathogen-positive; n = 7). All baboon groups showed a decrease in CD45RA+ CD28+ (i.e., naive) cells over time during middle age, but the rate of decline appeared faster in CONV LG baboons than in the other groups. In addition, the reduction in CD45RA+ CD28+ cells in the CONV LG baboons coincided with higher IgG levels against baboon cytomegalovirus, increased serum cortisol concentration, and a greater inflammatory phenotype. The results of this project support a role for cytomegalovirus infection in immune system alterations in middle-aged baboons.

Mechanical properties of the Papio anubis tympanic membrane: Change significantly from infancy to adulthood

Mechanical properties of the tympanic membrane (TM) are important for studying the transfer function of the auditory system. However, nearly all reported human data are limited to adults because of the unavailability of temporal bones from children. In this study, we used the baboon (Papio anubis), a genetically close human relative, as a model to address the occurrence of age-dependent changes of the human TM. Forty-five baboon TMs were characterized in five age groups: <1 year, 1 to <2 years, 2 to <3 years, 3 to <5, and >5 years of age, comparable to human ages ranging from newborn to adult. The elastic properties of the baboon TMs were characterized by a micro-fringe projection technique. Volume displacement of the TM under quasi-static pressure was first determined from its micro-fringe pattern. Subsequently, these displacement values were used in a finite element model to derive mechanical properties. The Young's modulus of the baboon TM exhibited a modest decrease from 29.1 MPa to 26.0 MPa over the age groups. The average Young's modulus was ∼1.4 times higher than that of the adult human TM. This is the first time that age-related TM mechanical properties of high primate are reported. These new findings may help to explore the potential value of the baboon as a new primate model for future age-related hearing research on the normal and diseased ear.

DNA nanoparticles are safe and nontoxic in non-human primate eyes

INTRODUCTION

DNA nanoparticles (NPs) comprising polylysine conjugated to polyethylene glycol efficiently target murine photoreceptors and the retinal pigment epithelium (RPE) and lead to long-term phenotypic improvement in models of retinal degeneration. Advancing this technology requires testing in a large animal model, particularly with regard to safety. So, herein we evaluate NPs in non-human primates (baboon).

METHODS AND RESULTS

NPs with plasmids carrying GFP and a ubiquitous, RPE-specific, or photoreceptor-specific promoter were delivered by either subretinal or intravitreal injection. We detected GFP message and protein in the retina/RPE from eyes dosed with NPs carrying ubiquitously expressed and RPE-specific vectors, and GFP message in eyes injected with NPs carrying photoreceptor-specific vectors. Importantly, we observed NP DNA in the retina/RPE following intravitreal injection, indicating the inner limiting membrane does not prevent NP diffusion into the outer retina. We did not observe any adverse events in any baboon, and there were no NP-associated changes in retinal function. Furthermore, no systemic or local inflammatory reaction to the vectors/injections was observed, and no NP DNA was found outside the eye.

CONCLUSION

Taken together with the well-established rodent safety and efficacy data, these findings suggest that DNA NPs may be a safe and potentially clinically viable nonviral ocular therapy platform for retinal diseases.

Optimization of culture conditions for the derivation and propagation of baboon (Papio anubis) induced pluripotent stem cells

Induced pluripotent stem cells (iPSCs) offer the possibility of cell replacement therapies using patient-matched cells to treat otherwise intractable diseases and debilitations. To successfully realize this potential, several factors must be optimized including i) selection of the appropriate cell type and numbers to transplant, ii) determination of the means of transplantation and the location into which the transplanted cells should be delivered, and iii) demonstration of the safety and efficacy of the cell replacement protocol to mitigate each targeted disease state. A majority of diseases or debilitations likely to be targeted by cell-based therapeutic approaches represent complex conditions or physiologies manifest predominantly in primates including humans. Nonhuman primates afford the most clinically relevant model system for biomedical studies and testing of cell-based therapies. Baboons have 92% genomic similarity with humans overall and especially significant similarities in their immunogenetic system, rendering this species a particularly valuable model for testing procedures involving cell transplants into living individuals. To maximize the utility of the baboon model, standardized protocols must be developed for the derivation of induced pluripotent stem cells from living adults and the long-term maintenance of these cells in culture. Here we tested four commercially available culture systems (ReproFF, mTeSR1, E8 and Pluristem) for competence to maintain baboon iPSCs in a pluripotent state over multiple passages, and to support the derivation of new lines of baboon iPSCs. Of these four media only Pluristem was able to maintain baboon pluripotency as assessed by morphological characteristics, immunocytochemistry and RT-qPCR. Pluristem also facilitated the derivation of new lines of iPSCs from adult baboon somatic cells, which had previously not been accomplished. We derived multiple iPS cell lines from adult baboon peripheral blood mononuclear cells cultured in Pluristem. These were validated by expression of the pluripotency markers OCT4, NANOG, SOX2, SSEA4 and TRA181, as well as the ability to differentiate into tissues from all three germ layers when injected into immunocompromised mice. These findings further advance the utility of the baboon as an ideal preclinical model system for optimizing iPS cell-based, patient-specific replacement therapies in humans.

Dehydroepiandrosterone improves the ovarian reserve of women with diminished ovarian reserve and is a potential regulator of the immune response in the ovaries

Diminished ovarian reserve (DOR) has a high morbidity rate worldwide and has become a primary cause of infertility. DOR is a daunting obstacle in in vitro fertilization (IVF) and leads to poor ovarian response, high cancellation rates, poor IVF outcomes, and low pregnancy rates. Abnormal autoimmune function may also contribute to DOR. Dehydroepiandrosterone (DHEA) is a C19 androgenic steroid. DHEA is secreted mainly by the adrenal gland, and its secretion declines with age. DHEA has a pro-inflammatory immune function that opposes cortisol. The cortisol to DHEA ratio increases with age, which may lead to decreased immune function. DHEA supplementation helps improve this situation. A number of clinical case control studies and several prospective randomized clinical trials have observed a positive effect of DHEA supplementation in women with DOR. However, the underlying mechanism by which DHEA improves ovarian reserve remains unclear. DHEA functions as an immune regulator in many different tissues in mammals and may also play an important role in regulating the immune response in the ovaries. The conversion of DHEA to downstream sex steroids may allow it to regulate the immune response there. DHEA can also enhance the Th1 immune response and regulate the balance of the Th1/Th2 response. DHEA treatment can increase selective T lymphocyte infiltration in mice, resulting in a decline in the CD4+ T lymphocyte population and an upregulation of the CD8+ T lymphocyte population in ovarian tissue, thus regulating the balance of CD4+/CD8+ T cells. This review mainly focuses on how DHEA supplementation affects regulation of the immune response in the ovaries.

The endocannabinoid system in the baboon (Papio spp.) as a complex framework for developmental pharmacology

INTRODUCTION

The consumption of marijuana (exogenous cannabinoid) almost doubled in adults during last decade. Consumption of exogenous cannabinoids interferes with the endogenous cannabinoid (or "endocannabinoid" (eCB)) system (ECS), which comprises N-arachidonylethanolamide (anandamide, AEA), 2-arachidonoyl glycerol (2-AG), endocannabinoid receptors (cannabinoid receptors 1 and 2 (CB1R and CB2R), encoded by CNR1 and CNR2, respectively), and synthesizing/degrading enzymes (FAAH, fatty-acid amide hydrolase; MAGL, monoacylglycerol lipase; DAGL-α, diacylglycerol lipase-alpha). Reports regarding the toxic and therapeutic effects of pharmacological compounds targeting the ECS are sometimes contradictory. This may be caused by the fact that structure of the eCBs varies in the species studied.

OBJECTIVES

First: to clone and characterize the cDNAs of selected members of ECS in a non-human primate (baboon, Papio spp.), and second: to compare those cDNA sequences to known human structural variants (single nucleotide polymorphisms and haplotypes).

MATERIALS AND METHODS

Polymerase chain reaction-amplified gene products from baboon tissues were transformed into Escherichia coli. Amplicon-positive clones were sequenced, and the obtained sequences were conceptually translated into amino-acid sequences using the genetic code.

RESULTS

Among the ECS members, CNR1 was the best conserved gene between humans and baboons. The phenotypes associated with mutations in the untranslated regions of this gene in humans have not been described in baboons. One difference in the structure of CNR2 between humans and baboons was detected in the region with the only known clinically relevant polymorphism in a human receptor. All of the differences in the amino-acid structure of DAGL-α between humans and baboons were located in the hydroxylase domain, close to phosphorylation sites. None of the differences in the amino-acid structure of MAGL observed between baboons and humans were located in the area critical for enzyme function.

CONCLUSION

The evaluation of the data, obtained in non-human primate model of cannabis-related developmental exposure should take into consideration possible evolutionary-determined species-specific differences in the CB1R expression, CB2R transduction pathway, and FAAH and DAGLα substrate-enzyme interactions.

Advantages of nonhuman primates as preclinical models for evaluating stem cell-based therapies for Parkinson's disease

The derivation of dopaminergic neurons from induced pluripotent stem cells brings new hope for a patient-specific, stem cell-based replacement therapy to treat Parkinson's disease (PD) and related neurodegenerative diseases; and this novel cell-based approach has already proven effective in animal models. However, there are several aspects of this procedure that have yet to be optimized to the extent required for translation to an optimal cell-based transplantation protocol in humans. These challenges include pinpointing the optimal graft location, appropriately scaling up the graft volume, and minimizing the risk of chronic immune rejection, among others. To advance this procedure to the clinic, it is imperative that a model that accurately and fully recapitulates characteristics most pertinent to a cell-based transplantation to the human brain is used to optimize key technical aspects of the procedure. Nonhuman primates mimic humans in multiple ways including similarities in genomics, neuroanatomy, neurophysiology, immunogenetics, and age-related changes in immune function. These characteristics are critical to the establishment of a relevant model in which to conduct preclinical studies to optimize the efficacy and safety of cell-based therapeutic approaches to the treatment of PD. Here we review previous studies in rodent models, and emphasize additional advantages afforded by nonhuman primate models in general, and the baboon model in particular, for preclinical optimization of cell-based therapeutic approaches to the treatment of PD and other neurodegenerative diseases. We outline current unresolved challenges to the successful application of stem cell therapies in humans and propose that the baboon model in particular affords a number of traits that render it most useful for preclinical studies designed to overcome these challenges.

Differentiation and Characterization of Dopaminergic Neurons From Baboon Induced Pluripotent Stem Cells

: The progressive death of dopamine producing neurons in the substantia nigra pars compacta is the principal cause of symptoms of Parkinson's disease (PD). Stem cells have potential therapeutic use in replacing these cells and restoring function. To facilitate development of this approach, we sought to establish a preclinical model based on a large nonhuman primate for testing the efficacy and safety of stem cell-based transplantation. To this end, we differentiated baboon fibroblast-derived induced pluripotent stem cells (biPSCs) into dopaminergic neurons with the application of specific morphogens and growth factors. We confirmed that biPSC-derived dopaminergic neurons resemble those found in the human midbrain based on cell type-specific expression of dopamine markers TH and GIRK2. Using the reverse transcriptase quantitative polymerase chain reaction, we also showed that biPSC-derived dopaminergic neurons express PAX6, FOXA2, LMX1A, NURR1, and TH genes characteristic of this cell type in vivo. We used perforated patch-clamp electrophysiology to demonstrate that biPSC-derived dopaminergic neurons fired spontaneous rhythmic action potentials and high-frequency action potentials with spike frequency adaption upon injection of depolarizing current. Finally, we showed that biPSC-derived neurons released catecholamines in response to electrical stimulation. These results demonstrate the utility of the baboon model for testing and optimizing the efficacy and safety of stem cell-based therapeutic approaches for the treatment of PD.

SIGNIFICANCE

Functional dopamine neurons were produced from baboon induced pluripotent stem cells, and their properties were compared to baboon midbrain cells in vivo. The baboon has advantages as a clinically relevant model in which to optimize the efficacy and safety of stem cell-based therapies for neurodegenerative diseases, such as Parkinson's disease. Baboons possess crucial neuroanatomical and immunological similarities to humans, and baboon pluripotent stem cells can be differentiated into functional neurons that mimic those in the human brain, thus laying the foundation for the utility of the baboon model for evaluating stem cell therapies.

Pituitary pars intermedia dysfunction does not necessarily impair insulin sensitivity in old horses

Equine pituitary pars intermedia dysfunction (PPID) has been associated with reduced insulin sensitivity in comparison with younger adult horses; however, the difference in insulin sensitivity between horses with PPID and aged-matched controls has not been well characterized. The objective of the study was to determine if aged horses with PPID had reduced insulin sensitivity and alterations in the insulin-mediated signaling pathways in the skeletal muscle when compared with healthy aged horses. Isoglycemic hyperinsulinemic clamp procedures were conducted in 12 horses that were classified as either PPID (n = 6; age: 25.0 ± 2.5 yr; mean ± standard deviation) or non-PPID, aged-matched controls (control) (n = 6; age: 25.7 ± 2.0 yr). Blood samples were taken before and during the clamp procedures to measure plasma glucose, insulin, and amino acid concentrations, and 2 muscle biopsies were collected from the gluteus medius muscle, one in the basal state and the second at the end of the clamp procedure (insulin-stimulated state). Plasma insulin concentrations increased ∼9-fold during the clamp compared with basal conditions (P < 0.001) in both groups. During the last 30 min of the clamp, the rate of glucose infusion required to maintain isoglycemia in horses with PPID was similar to that in the control horses (P = 0.67). The plasma concentrations of most indispensible amino acids were lower in the insulin-stimulated state than the basal state (P < 0.05). PPID status did not have an effect on the activation of factors associated with protein synthesis and breakdown; however, factors associated with protein synthesis had increased phosphorylation in the insulin-stimulated state, compared with basal. The results from this study provide evidence that PPID is not always associated with impairments in insulin sensitivity.

Age-Associated Increase in Cytokine Production During Systemic Inflammation-II: The Role of IL-1β in Age-Dependent IL-6 Upregulation in Adipose Tissue

Expression of interleukin-6 (IL-6) upon acute inflammatory stress is significantly augmented by aging in adipose tissue, a major source of this cytokine. In the present study, we examined the mechanism of age-dependent IL-6 overproduction using visceral white adipose tissue from C57BL/6 mice. Upon treatment with lipopolysaccharide (LPS) in vitro, IL-6 was produced by adipose tissue explants, and secreted levels were significantly higher in cultures from aged (24 months) mice compared to young (4 months). Interleukin 1 beta (IL-1β) and tumor necrosis factor alpha (TNFα), two inducers of IL-6, were mainly produced by the lungs and spleen rather than adipose tissue in mice after LPS injection. Treatment of adipose explants with physiological levels of IL-1β induced significant age-dependent secretion of IL-6, while treatment with TNFα had little effect, demonstrating an augmented response of adipose tissues to IL-1β in the aged. In vitro experiments utilizing a neutralizing antibody against IL-1β and in vivo experiments utilizing IL-1-receptor-1 deficient mice, confirmed that IL-6 overproduction in the aged is regulated by autocrine/paracrine action of IL-1β which specifically occurs in aged adipose tissues. These findings indicate an elevated inflammatory potential of adipose tissue in the aged and a unique IL-1β-mediated mechanism for IL-6 overproduction, which may impact age-associated vulnerability to acute inflammatory diseases such as sepsis.

Serum IL-17, IL-23, and TGF-β levels in type 1 and type 2 diabetic patients and age-matched healthy controls

Type 1 diabetes is recognized as an autoimmune inflammatory disease and low grade inflammation is also observed in type 2 diabetic patients. Interleukin 17 (IL-17) is a new player in inflammation. Th17 cells, as the main source of IL-17, require transforming growth factor β (TGF-β) and interleukin 23 (IL-23). The aim of this study was to investigate serum IL-17, IL-23 and TGF-β levels in diabetic patients and controls. In this case-control study, serum levels of IL-17, IL-23, and TGF-β were measured in 24 type 1 diabetic patients and 30 healthy controls using the ELISA method. Simultaneously, the same methodology was used to compare serum concentration of these three cytokines in 38 type 2 diabetic patients and 40 healthy controls. There was no significant difference between serum levels of IL-17 and IL-23 cytokines between cases and controls. However, TGF-β was significantly lower in type 1 diabetic patients (P < 0.001). Serum IL-17 and IL-23 levels demonstrate no association with type 1 and type 2 diabetes, but, in line with previous studies, TGF-β levels were lower in type 1 diabetic patients.

The effects of age and cytomegalovirus on markers of inflammation and lymphocyte populations in captive baboons

The human immune system undergoes age-related changes that can lead to increased disease susceptibility. Using the baboon as a model for human immune system aging, we examined age-related changes in relative and absolute numbers of T cell subpopulations, cytomegalovirus (CMV) titer and markers of inflammation. In addition, the effect of gender, social status and peer group on lymphocyte subpopulations was determined. Relative and absolute numbers of total lymphocytes (CD3+), T helper cells (CD4+), and cytotoxic T cells (CD8+) increased with age. The proportion of naïve T cells (CD45RA+) decreased, while the total number of cells negative for the co-stimulatory receptor, CD28 (CD28-) increased in an age-dependent manner. Furthermore, CMV titers were negatively correlated with the number of naive CD4+ cells. IL-6 and cortisol concentration were also negatively associated with T cell subpopulations. Additionally, socially dominant baboons exhibited decreases in naïve CD4+ and CD8+ cells (by 65% and 52%, respectively) compared to subordinate animals. These results suggest that factors such as CMV exposure and inflammation may contribute to the age-related decline in immune health and indicate that factors like social status should be considered when studying immunosenescence in animal models.

Age- and gender-associated changes in the concentrations of serum TGF-1β, DHEA-S and IGF-1 in healthy captive baboons (Papio hamadryas anubis)

Age-related changes in the concentration of factors like TGF-1β, DHEA-S and IGF-1 may increase the risk of disease and illnesses in advanced life. A better understanding of these changes would aid in the development of more appropriate treatments and/or preventative care for many conditions associated with age. Due to their similar immune system and vulnerability to pathogens, baboons are an ideal model for humans. However, little research has been done examining the general effects of age in baboons. Therefore, we wanted to further examine the effects of aging in baboons by determining the age-dependent changes in serum TGF-1β, DHEA-S and IGF-1 concentrations. Blood samples were collected during routine health checks in 113-118 captive baboons. In addition, longitudinal samples from 23 to 27 adult individuals were collected an average of 10.7years apart. Both age and gender influenced the concentrations of serum TGF-1β and IGF-1. When both genders were analyzed together, TGF-1β increased 16.1% as adults, compared to younger and older animals, but male and female baboons showed a slightly different temporal pattern of change. IGF-1 decreased with increasing age and males had a 30% greater concentration of IGF-1 than did females. While there was no effect of gender among our population, serum DHEA-S was negatively correlated with age, decreasing by 51.6% in the oldest animals. There were no effects of age or gender on serum IGFBP-3. In longitudinal samples collected from the same individuals, the concentrations of TGF-1β, DHEA-S and IGF-1 were reduced with age. The results presented herein provide additional knowledge of the aging process in baboons and further validate the use of this species as an appropriate model for aging in humans.

Aging-induced dysregulation of dicer1-dependent microRNA expression impairs angiogenic capacity of rat cerebromicrovascular endothelial cells

Age-related impairment of angiogenesis is likely to play a central role in cerebromicrovascular rarefaction and development of vascular cognitive impairment, but the underlying mechanisms remain elusive. To test the hypothesis that dysregulation of Dicer1 (ribonuclease III, a key enzyme of the microRNA [miRNA] machinery) impairs endothelial angiogenic capacity in aging, primary cerebromicrovascular endothelial cells (CMVECs) were isolated from young (3 months old) and aged (24 months old) Fischer 344 × Brown Norway rats. We found an age-related downregulation of Dicer1 expression both in CMVECs and in small cerebral vessels isolated from aged rats. In aged CMVECs, Dicer1 expression was increased by treatment with polyethylene glycol-catalase. Compared with young cells, aged CMVECs exhibited altered miRNA expression profile, which was associated with impaired proliferation, adhesion to vitronectin, collagen and fibronectin, cellular migration (measured by a wound-healing assay using electric cell-substrate impedance sensing technology), and impaired ability to form capillary-like structures. Overexpression of Dicer1 in aged CMVECs partially restored miRNA expression profile and significantly improved angiogenic processes. In young CMVECs, downregulation of Dicer1 (siRNA) resulted in altered miRNA expression profile associated with impaired proliferation, adhesion, migration, and tube formation, mimicking the aging phenotype. Collectively, we found that Dicer1 is essential for normal endothelial angiogenic processes, suggesting that age-related dysregulation of Dicer1-dependent miRNA expression may be a potential mechanism underlying impaired angiogenesis and cerebromicrovascular rarefaction in aging.

The effect of season on inflammatory response in captive baboons

INTRODUCTION

Highly seasonal animals demonstrate predictable changes in immune function that coincide with changes in photoperiod. Little is known about the effect of season on immune response in baboons. The objective of this study was to determine the effect of season on inflammatory response in baboons.

MATERIALS AND METHODS

Peripheral blood mononuclear cell cytokine response following immune stimulation and serum markers of inflammation were assessed during each season in two groups of young male baboons: one housed under natural light and one in a controlled environment of 12 hours light:12 hours dark.

RESULTS

A seasonal immune rhythm was evident in both groups, with a greater TNF-α and IL-6 response to stimulation and serum CRP concentration in June and September compared with December.

CONCLUSIONS

Season is an important experimental confounder, and therefore, time of year should be controlled when designing studies and analyzing data from immune studies in baboons.

Circulating factors induced by caloric restriction in the nonhuman primate Macaca mulatta activate angiogenic processes in endothelial cells

Moderate caloric restriction (CR) without malnutrition increases healthspan in virtually every species studied, including nonhuman primates. In mice, CR exerts significant microvascular protective effects resulting in increased microvascular density in the heart and the brain, which likely contribute to enhanced tolerance to ischemia and improved cardiac performance and cognitive function. Yet, the underlying mechanisms by which CR confer microvascular protection remain elusive. To test the hypothesis that circulating factors triggered by CR regulate endothelial angiogenic capacity, we treated cultured human endothelial cells with sera derived from Macaca mulatta on long-term (over 10 years) CR. Cells treated with sera derived from ad-libitum-fed control monkeys served as controls. We found that factors present in CR sera upregulate vascular endothelial growth factor (VEGF) signaling and stimulate angiogenic processes, including endothelial cell proliferation and formation of capillary-like structures. Treatment with CR sera also tended to increase cellular migration (measured by a wound-healing assay using electric cell-substrate impedance sensing [ECIS] technology) and adhesion to collagen. Collectively, we find that circulating factors induced by CR promote endothelial angiogenic processes, suggesting that increased angiogenesis may be a potential mechanism by which CR improves cardiac function and prevents vascular cognitive impairment.

Testing the oxidative stress hypothesis of aging in primate fibroblasts: is there a correlation between species longevity and cellular ROS production?

The present study was conducted to test predictions of the oxidative stress theory of aging assessing reactive oxygen species production and oxidative stress resistance in cultured fibroblasts from 13 primate species ranging in body size from 0.25 to 120 kg and in longevity from 20 to 90 years. We assessed both basal and stress-induced reactive oxygen species production in fibroblasts from five great apes (human, chimpanzee, bonobo, gorilla, and orangutan), four Old World monkeys (baboon, rhesus and crested black macaques, and patas monkey), three New World monkeys (common marmoset, red-bellied tamarin, and woolly monkey), and one lemur (ring-tailed lemur). Measurements of cellular MitoSox fluorescence, an indicator of mitochondrial superoxide (O2(·-)) generation, showed an inverse correlation between longevity and steady state or metabolic stress-induced mitochondrial O2(·-) production, but this correlation was lost when the effects of body mass were removed, and the data were analyzed using phylogenetically independent contrasts. Fibroblasts from longer-lived primate species also exhibited superior resistance to H(2)O(2)-induced apoptotic cell death than cells from shorter-living primates. After correction for body mass and lack of phylogenetic independence, this correlation, although still discernible, fell short of significance by regression analysis. Thus, increased longevity in this sample of primates is not causally associated with low cellular reactive oxygen species generation, but further studies are warranted to test the association between increased cellular resistance to oxidative stressor and primate longevity.

Age-dependent changes in innate immune phenotype and function in rhesus macaques (Macaca mulatta)

Aged individuals are more susceptible to infections due to a general decline in immune function broadly referred to as immune senescence. While age-related changes in the adaptive immune system are well documented, aging of the innate immune system remains less well understood, particularly in nonhuman primates. A more robust understanding of age-related changes in innate immune function would provide mechanistic insight into the increased susceptibility of the elderly to infection. Rhesus macaques have proved a critical translational model for aging research, and present a unique opportunity to dissect age-dependent modulation of the innate immune system. We examined age-related changes in: (i) innate immune cell frequencies; (ii) expression of pattern recognition receptors (PRRs) and innate signaling molecules; (iii) cytokine responses of monocytes and dendritic cells (DC) following stimulation with PRR agonists; and (iv) plasma cytokine levels in this model. We found marked changes in both the phenotype and function of innate immune cells. This included an age-associated increased frequency of myeloid DC (mDC). Moreover, we found toll-like receptor (TLR) agonists lipopolysaccharide (TLR4), fibroblast stimulating ligand-1 (TLR2/6), and ODN2006 (TLR7/9) induced reduced cytokine responses in aged mDC. Interestingly, with the exception of the monocyte-derived TNFα response to LPS, which increased with age, TNFα, IL-6, and IFNα responses declined with age. We also found that TLR4, TLR5, and innate negative regulator, sterile alpha and TIR motif containing protein (SARM), were all expressed at lower levels in young animals. By contrast, absent in melanoma 2 and retinoic acid-inducible gene I expression was lowest in aged animals. Together, these observations indicate that several parameters of innate immunity are significantly modulated by age and contribute to differential immune function in aged macaques.

Social status predicts wound healing in wild baboons

Social status can have striking effects on health in humans and other animals, but the causes often are unknown. In male vertebrates, status-related differences in health may be influenced by correlates of male social status that suppress immune responses. Immunosuppressive correlates of low social status may include chronic social stress, poor physical condition, and old age; the immunosuppressive correlates of high status may include high testosterone and energetic costs of reproduction. Here we test whether these correlates could create status-related differences in immune function by measuring the incidence of illness and injury and then examining healing rates in a 27-y data set of natural injuries and illnesses in wild baboon males. We found no evidence that the high testosterone and intense reproductive effort associated with high rank suppress immune responses. Instead, high-ranking males were less likely to become ill, and they recovered more quickly than low-ranking males, even controlling for differences in age. Notably, alpha males, who experience high glucocorticoids, as well as the highest testosterone and reproductive effort, healed significantly faster than other males, even other high-ranking males. We discuss why alpha males seem to escape from the immunosuppressive costs of glucocorticoids but low-ranking males do not, including the idea that glucocorticoids' effects depend on an individual's physiological and social context.

Role of aging on innate responses to viral infections

Older people exhibit increased morbidity and mortality after viral infections than younger people. Additionally, vaccines are less protective in older people than in younger people. As the immune system is critical for host defense to viral infections and for vaccine efficacy, the implications are that aging negatively affects immunity. The immune system is broadly categorized into adaptive and innate systems. The innate immune system acts as a first line of defense to pathogen invasion. In this review, I focus on how aging affects the innate immune response to viral infection.

Age-associated proinflammatory secretory phenotype in vascular smooth muscle cells from the non-human primate Macaca mulatta: reversal by resveratrol treatment

There is increasing evidence that age-associated chronic low-grade inflammation promotes the development of both large-vessel disease (myocardial infarction, stroke, peripheral arterial disease) and small-vessel pathologies (including vascular cognitive impairment) in older persons. However, the source of age-related chronic vascular inflammation remains unclear. To test the hypothesis that cell-autonomous mechanisms contribute to the proinflammatory changes in vascular phenotype that accompanies advancing age, we analyzed the cytokine secretion profile of primary vascular smooth muscle cells (VSMCs) derived from young (∼13 years old) and aged (∼21 years old) Macaca mulatta. Aged VSMCs cultured in the absence of systemic factors exhibited significantly increased secretion of interleukin-1β, MCP-1, and tumor necrosis factorα compared with young control cells. Secretion of interleukin-6 also tended to increase in aged VSMCs. This age-associated proinflammatory shift in the cellular secretory phenotype was associated with an increased mitochondrial O(2)(-) production and nuclear factor κ-light-chain-enhancer of activated B cells activation. Treatment of aged VSMCs with a physiologically relevant concentration of resveratrol (1 μM) exerted significant anti-inflammatory effects, reversing aging-induced alterations in the cellular cytokine secretion profile and inhibiting nuclear factor κ-light-chain-enhancer of activated B cells. Resveratrol also attenuated mitochondrial O(2)(-) production and upregulated the transcriptional activity of Nrf2 in aged VSMCs. Thus, in non-human primates, cell-autonomous activation of nuclear factor κ-light-chain-enhancer of activated B cells and expression of an inflammatory secretome likely contribute to vascular inflammation in aging. Resveratrol treatment prevents the proinflammatory properties of the aged VSMC secretome, an effect that likely contributes to the demonstrated vasoprotective action of resveratrol in animal models of aging.

Growth hormone and IGF-1 deficiency exacerbate high-fat diet-induced endothelial impairment in obese Lewis dwarf rats: implications for vascular aging

Previous studies suggest that the age-related decline in circulating growth hormone (GH) and insulin-like growth factor-1 (IGF-1) levels significantly contribute to vascular dysfunction in aging by impairing cellular oxidative stress resistance pathways. Obesity in elderly individuals is increasing at alarming rates, and there is evidence suggesting that elderly individuals are more vulnerable to the deleterious cardiovascular effects of obesity than younger individuals. However, the specific mechanisms through which aging, GH/IGF-1 deficiency, and obesity interact to promote the development of cardiovascular disease remain unclear. To test the hypothesis that low circulating GH/IGF-1 levels exacerbate the pro-oxidant and proinflammatory vascular effects of obesity, GH/IGF-1-deficient Lewis dwarf rats and heterozygous control rats were fed either a standard diet or a high-fat diet (HFD) for 7 months. Feeding an HFD resulted in similar relative weight gains and increases in body fat content in Lewis dwarf rats and control rats. HFD-fed Lewis dwarf rats exhibited a relative increase in blood glucose levels, lower insulin, and impaired glucose tolerance as compared with HFD-fed control rats. Analysis of serum cytokine expression signatures indicated that chronic GH/IGF-1 deficiency exacerbates HFD-induced inflammation. GH/IGF-1 deficiency also exacerbated HFD-induced endothelial dysfunction, oxidative stress, and expression of inflammatory markers (tumor necrosis factor-α, ICAM-1) in aortas of Lewis dwarf rats. Overall, our results are consistent with the available clinical and experimental evidence suggesting that GH/IGF-1 deficiency renders the cardiovascular system more vulnerable to the deleterious effects of obesity.