Premature aging in behavior and immune functions in tyrosine hydroxylase haploinsufficient female mice. A longitudinal study

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

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

In Response to a Punctual Stress Male and Female Tyrosine Hydroxylase Haploinsufficient Mice Show a Deteriorated Behavior, Immunity, and Redox State

An inadequate stress response is associated with impaired neuroimmunoendocrine communication, increasing morbidity and mortality. Since catecholamines (CA) constitute one of the acute stress response pathways, female mice with an haploinsufficiency of the tyrosine hydroxylase gene (TH-HZ), the main limiting enzyme in CA synthesis, show low CA amounts, exhibiting an impairment of homeostatic systems. The aim of this study was to investigate the effect of a punctual stress in TH-HZ mice, determining the differences with wild-type (WT) mice and those due to sex by restraint with a clamp for 10 min. After restraint, a behavioral battery was performed, and several immune functions, redox state parameters, and CA amounts were evaluated in peritoneal leukocytes. Results show that this punctual stress impaired WT behavior and improved female WT immunity and oxidative stress, whereas in TH-HZ mice, all parameters were impaired. In addition, different responses to stress due to sex were observed, with males having a worse response. In conclusion, this study confirms that a correct CA synthesis is necessary to deal with stress, and that when a positive stress (eustress) occurs, individuals may improve their immune function and oxidative state. Furthermore, it shows that the response to the same stressor is different according to sex.

Positive effects of pulsed electromagnetic fields on behavior, immune function, and oxidative and inflammatory state in old mice

The establishment of chronic oxidative and inflammatory stress with aging leads to the deterioration of the nervous and immune systems and, consequently, to the loss of health. The aim of this work was to study the effect of exposure to low-frequency pulsed electromagnetic fields (PEMFs) produced by the NEURALTER® system (15 min/day for 4 weeks) in the behavior, immune functions, and oxidative and inflammatory state of old mice. Female old CD1 mice were divided into three groups: control group, handling control group and Neuralter group. Then, behavioral tests were performed, and peritoneal leukocytes were extracted to analyze function, oxidative and inflammatory parameters. In peritoneal leukocytes from old mice, the effects in vitro of 15 min with NEURALTER® were studied on function and oxidative parameters. The results show that after this type of treatment, old mice had greater coordination and locomotion, better immune function, and an oxidative-inflammatory state. Similarly, the immune function and oxidative state of leukocytes showed an improvement when these cells were exposed directly to the NEURALTER® system. In conclusion, the exposure to low-frequency PEMFs produced by the NEURALTER® system has beneficial effects on health in aging. In addition, this effect is direct, at least in part, on immune cells.

[Improved immunity and mean lifespan in mature mice genetically deficient in catecholamine synthesis after living with wild type for two months]

INTRODUCTION

Mice hemizygous in tyrosine hydroxylase (TH-HZ), the limiting enzyme in catecholamine synthesis, show premature immunosenescence, which in females is associated with a shorter lifespan than the corresponding controls (WT). The coexistence of TH-Hz with WT improves the immune function in both males and females in adulthood.

OBJECTIVE

To test whether cohabitation for two months of mature male TH-HZ with WT improves the immune function of the former and whether this impacts the lifespan.

MATERIAL AND METHODS

Mature male ICR-CD1 mice (13 ± 1 months) TH-HZ coexisted with WT (2:4 ratio in each cage) for two months. Peritoneal leukocytes were extracted from all animals at baseline, one month, and two months after cohabitation, and macrophage phagocytic capacity, macrophage and lymphocyte chemotaxis, natural killer (NK) antitumor activity, and lymphoproliferative capacity in response to the mitogens concanavalin A and lipopolysaccharide (LPS) were assessed. The animals were maintained under these conditions until their natural death.

RESULTS

The TH-HZ, which start, in general, with lower values than the WT in the immune functions studied, improved them after two months of cohabitation, becoming similar to those of the controls. This improvement was already observed in NK activity after one month of cohabitation. The TH-HZ presented lower mean longevity than WT, but when they cohabited with WT, it was similar to the latter.

CONCLUSION

The coexistence of TH-HZ male mice with WT mice for two months at mature age improves these genetically modified animals' immune response and longevity.

Investigating population-level immunosenescence: From bench to bedside

The immune response is remodeled with aging in a process called immunosenescence. Some immunologists conceive immunosenescence as an adaptation of immunity to the aged immune-environment rather than a merely collapsed reactivity of immune cells against microbes and tumor cells. Others believe on an uninterrupted activation of the innate immune system with aging, leading to a low grade, sterile and chronic proinflammatory state called inflammaging. For instance, it is possible that chronic infection by cytomegalovirus leads to persistent production of viral load. This phenomenon offers periodic stimuli to the immune system that ultimately contribute to the remodeling of the immune response. If investigating immunosenescence at the cellular level is already a difficult task, considering the population level is much more complex. However, by studying immunosenescence at the population level, we can extract valuable results with viable applications. While studies with animal models allow scientists to deepen their understanding of the mechanisms of immunosenescence, studying large populations can bring practical innovations to medicine and the health system. Many researchers and funders have dedicated themselves to producing methods for the evaluation of immunosenescence on a large scale, aiming to elucidate new mechanisms by which diseases are established in the elderly. The description of how the immune response is remodeled with aging emerges as a new tool to identify the subset of subjects in which unhealthy aging is a matter of time, to help better individualize clinical management and select patients who may benefit. of early interventions. This review focuses on functional assays as valuable methods for measuring the remodeling of the immune response with aging and discuss their clinical impact. We also recall fundamental concepts for understanding the aging process of the immune response. In addition, we highlight future prospects for immunosenescence research.

Mitochondrial DNA insertions into nuclear DNA affecting chromosome segregation: Insights for a novel mechanism of immunosenescence in mice

Mitochondrial DNA sequences were found inserted in the nuclear genome of mouse peritoneal T lymphocytes that increased progressively with aging. These insertions were preferentially located at the pericentromeric heterochromatin. In the same individuals, binucleated T-cells with micronuclei showed a significantly increased frequency associated with age. Most of them were positive for centromere sequences, reflecting the loss of chromatids or whole chromosomes. The proliferative capacity of T lymphocytes decreased with age as well as the glutathione reductase activity, whereas the oxidized glutathione and malondialdehyde concentrations exhibited a significant increase. These results may point to a common process that provides insights for a new approach to understanding immunosenescence. We propose a novel mechanism in which mitochondrial fragments, originated by the increased oxidative stress status during aging, accumulate inside the nuclear genome of T lymphocytes in a time-dependent way. The primary entrance of mitochondrial fragments at the pericentromeric regions may compromise chromosome segregation, causing genetic loss that leads to micronuclei formation, rendering aneuploid cells with reduced proliferation capacity, one of the hallmark of immunosenescence. Future experiments deciphering the mechanistic basis of this phenomenon are needed.

SOCIAL ENVIRONMENT IMPROVES THE CYTOKINE PROFILE AND LYMPHOPROLIFERATIVE RESPONSE IN CHRONOLOGICALLY OLD AND PREMATURELY AGING MICE

Among the age-associated changes in the immune system, the most evident is the decrease in proliferative responses of lymphocytes to mitogenic stimuli, which is accompanied by the loss of cytokine network homeostasis. Chronic low-grade inflammatory stress, termed as sterile inflammation, is also observed during aging. In chronologically and prematurely aging mice, cohabitation with adult animals for two months favored improvements in several immune functions. This study aimed to determine whether cohabitation could restore several cytokine networks, improve lymphoproliferative responses to mitogens, and diminish sterile inflammation. Chronologically old mice (76±4 weeks) and prematurely aging mice (33±4 weeks) (PAM and TH-HZ) were cohabited with adults (without premature aging) for two months. Subsequently, lymphoproliferation in both basal (unstimulated) conditions and in the presence of mitogenic stimuli lipopolysaccharide A (LPS) or concanavalin A (ConA) was analyzed in cultures of peritoneal leukocytes for 48h. Cytokine secretions (IL-1β, TNF-α, IL-6, IL-10, and IL-17) in these cultures were also evaluated. The results showed that cohabitation restored the levels of these cytokines in old and prematurely aging mice and improved the subsequent lymphoproliferative responses. In addition, this social strategy diminished sterile inflammation and decreased inflammatory stress in unstimulated conditions. Therefore, this strategy seems to be capable of restoring the relevant immune function of lymphocytes and reducing the inflammatory stress, which are the improvements required for an adequate immune response.

Genetic Analysis for Type 1 Diabetes Genes in Juvenile Dermatomyositis Unveils Genetic Disease Overlap

OBJECTIVES

Juvenile dermatomyositis (JDM) is a serious autoimmune and complex genetic disease. Another autoimmune genetic disease, type 1 diabetes (T1D), has been observed for significantly increased prevalence in families with JDM, while increased JDM risk has also been observed in T1D cases. This study aimed to study whether these two autoimmune diseases, JDM and T1D, share common genetic susceptibility.

METHODS

From 169 JDM families, 121 unrelated cases with European ancestry (EA) were identified by genome-wide genotyping, principal component analysis (PCA), and identical-by-descent (IBD) analysis. T1D genetic risk score (GRS) were calculated in these cases, and were compared with 361 EA T1D cases and 1943 non-diabetes EA controls. 113 cases of the 121 unrelated European cases were sequenced by whole exome sequencing (WES).

RESULTS

We observed increased T1D GRS in JDM cases (P=9.42E-05). Using whole exome sequencing (WES), we uncovered the T1D genes, phospholipase B1 (PLB1), cystic fibrosis transmembrane conductance regulator (CFTR), tyrosine hydroxylase (TH), CD6 molecule (CD6), perforin 1 (PRF1), and dynein axonemal heavy chain 2 (DNAH2), potentially associated with JDM by the burden test of rare functional coding variants.

CONCLUSION

Novel mechanisms of JDM related to these T1D genes are suggested by this study, which may imply novel therapeutic targets for JDM and warrant further study.

A short social interaction between adult and old mice improves the homeostatic systems and increases healthy longevity

The aging process can be influenced by environmental factors, such as the social environment. The continuous cohabitation of the chronologically old mice with adult animals improves them at the behavioral level, immune function, oxidative stress and longevity, but causes a deterioration of these parameters in adults. Therefore, the objective of the study was to study whether the coexistence for only 15 min a day of old mice with adult mice, can produce that improvement and greater longevity in old animals without causing deterioration in adults. For that, old and adult CD1 female mice, after two months of that social interaction, were submitted to a behavioral battery and then peritoneal leukocytes were collected to assess several immune functions, oxidative and inflammatory stress parameters as well as catecholamine concentrations. When the adult mice reached old age, the same parameters were again analyzed. The life span of each animal was also recorded. Plasmatic concentration of oxytocin was also studied. The results showed that old mice presented better behavioral capacity, immunity and oxi-inflammatory state after this social interaction with adult animals, and consequently an extended life span. Adult mice, in general, did not show any changes after social interaction with old animals, but when they achieved old age, improvements of some parameters and of longevity were observed in comparison with animals that never had a that social interaction. In conclusion, a short social interaction between old and adult individuals can be an excellent strategy for improving in both the health state and longevity.

Pro-Aging Effects of Xanthine Oxidoreductase Products

The senescence process is the result of a series of factors that start from the genetic constitution interacting with epigenetic modifications induced by endogenous and environmental causes and that lead to a progressive deterioration at the cellular and functional levels. One of the main causes of aging is oxidative stress deriving from the imbalance between the production of reactive oxygen (ROS) and nitrogen (RNS) species and their scavenging through antioxidants. Xanthine oxidoreductase (XOR) activities produce uric acid, as well as reactive oxygen and nitrogen species, which all may be relevant to such equilibrium. This review analyzes XOR activity through in vitro experiments, animal studies and clinical reports, which highlight the pro-aging effects of XOR products. However, XOR activity contributes to a regular level of ROS and RNS, which appears essential for the proper functioning of many physiological pathways. This discourages the use of therapies with XOR inhibitors, unless symptomatic hyperuricemia is present.

Social Environment Ameliorates Behavioral and Immune Impairments in Tyrosine Hydroxylase Haploinsufficient Female Mice

The social environment can influence the functional capacity of nervous and immune systems, and consequently the state of health, especially in aged individuals. Adult female tyrosine hydroxylase haploinsufficient (TH-HZ) mice exhibit behavioral impairments, premature immunosenescence and oxidative- inflammatory stress. All these deteriorations are associated with a lower lifespan than wild type (WT) counterparts. The aim was to analyze whether the cohabitation with WT animals could revert or at least ameliorate the deterioration in the nervous and immune systems that female TH-HZ mice show at adult age. Female TH-HZ and WT mice at age of 3-4 weeks were divided into following groups: control TH-HZ (5 TH-HZ mice in the cage; TH-HZ100%), control WT (5 WT mice in the cage; WT100%), TH-HZ > 50% and WT < 50% (5 TH-HZ with 2 WT mice in each cage) as well as TH-HZ < 50% and WT > 50% (2 TH-HZ and 5 WT mice in each cage). At the age of 37-38 weeks, all mice were submitted to a battery of behavioral tests, evaluating sensorimotor abilities, exploratory capacities and anxiety-like behaviors. Subsequently, peritoneal leukocytes were extracted and several immune functions as well as oxidative and inflammatory stress parameters were analyzed. The results showed that the TH-HZ < 50% group had improved behavioral responses, especially anxiety-like behaviors, and the immunosenescence and oxidative stress of their peritoneal leukocytes were ameliorated. However, WT mice that cohabited with TH-HZ mice presented higher anxiety-like behaviors and deterioration in immune functions and in their inflammatory stress parameters. Thus, this social environment is capable of ameliorating the impairments associated with a haploinsufficiency of the th gene. Graphical Abstract.

Remodeling of the Immune Response With Aging: Immunosenescence and Its Potential Impact on COVID-19 Immune Response

Elderly individuals are the most susceptible to an aggressive form of coronavirus disease (COVID-19), caused by SARS-CoV-2. The remodeling of immune response that is observed among the elderly could explain, at least in part, the age gradient in lethality of COVID-19. In this review, we will discuss the phenomenon of immunosenescence, which entails changes that occur in both innate and adaptive immunity with aging. Furthermore, we will discuss inflamm-aging, a low-grade inflammatory state triggered by continuous antigenic stimulation, which may ultimately increase all-cause mortality. In general, the elderly are less capable of responding to neo-antigens, because of lower naïve T cell frequency. Furthermore, they have an expansion of memory T cells with a shrinkage of the T cell diversity repertoire. When infected by SARS-CoV-2, young people present with a milder disease as they frequently clear the virus through an efficient adaptive immune response. Indeed, antibody-secreting cells and follicular helper T cells are thought to be effectively activated in young patients that present a favorable prognosis. In contrast, the elderly are more prone to an uncontrolled activation of innate immune response that leads to cytokine release syndrome and tissue damage. The failure to trigger an effective adaptive immune response in combination with a higher pro-inflammatory tonus may explain why the elderly do not appropriately control viral replication and the potential clinical consequences triggered by a cytokine storm, endothelial injury, and disseminated organ injury. Enhancing the efficacy of the adaptive immune response may be an important issue both for infection resolution as well as for the appropriate generation of immunity upon vaccination, while inhibiting inflamm-aging will likely emerge as a potential complementary therapeutic approach in the management of patients with severe COVID-19.

The ratio of prematurely aging to non-prematurely aging mice cohabiting, conditions their behavior, immunity and lifespan

Adult prematurely aging mice (PAM) show behavioral deterioration, premature immunosenescence and increased oxidative stress, impairments that are associated with their shorter lifespan, compared to the corresponding exceptional non-prematurely aging mice (ENPAM). When PAM live in a predominantly ENPAM environment (2/5, respectively) they exhibit an improvement of immunity and redox state in their spleen and thymus leukocytes, and an increased lifespan. Nevertheless, it is unknown if other PAM/ENPAM ratios could affect behavioral and peritoneal leukocyte functions of PAM and change their lifespan. ENPAM and PAM were divided into the following groups: C-ENPAM (8 ENPAM in the cage); C-PAM (8 PAM in the cage); ENPAM>50% and PAM<50% (5 ENPAM/2 PAM in each cage); ENPAM = 50% and PAM = 50% (4 ENPAM/4 PAM in each cage), and PAM>50% and ENPAM<50% (5 PAM/2 ENPAM in each cage). After two months, mice were submitted to a battery of behavioral tests. Several functions and oxidative stress parameters were then assessed in their peritoneal leukocytes. Animals were maintained in these conditions to analyze their lifespan. The results showed that PAM>50%, PAM = 50% and PAM<50% exhibited better behavioral responses, immunity and redox states in their peritoneal leukocytes than C-PAM. This improvement was higher when the number of ENPAM in the cage was increased, with most of the parameters in PAM<50% reaching similar values to those in C-ENPAM, and an increased lifespan. However, ENPAM that cohabited with PAM showed, in general, an impairment of parameters studied. In conclusion, the PAM/ENPAM cohabitation ratio is relevant to behavior and immunity.

Impacts of the late adulthood diet-induced obesity onset on behavior, immune function, redox state and life span of male and female mice

The aim of the present study was to investigate whether the late onset of diet-induced obesity (DIO) in middle-aged mice affected behavioral, immunological and oxidative stress parameters as well as life span of male and female mice. Also, it was analyzed whether the late DIO onset aggravated immunosenescence in old female mice. Late-adult male and female ICR/CD1 mice (28 weeks old) were fed either a high-fat diet or a standard diet during 14 weeks. After that, in these middle-aged (42 weeks old) diet-induced obese (DIO) and non-DIO controls, behavior as well as functions and redox state of peritoneal leukocytes were evaluated. These same parameters (excepting behavioral tests) were repeated when female mice were old (72 weeks old). The results showed lower exploratory activity and higher anxiety-like behavior in middle-aged male and female DIO than in controls. Moreover, these DIO animals from both sexes exhibited statistically significant impaired immune cell functions, such as chemotaxis of macrophages and lymphocytes, phagocytosis of macrophages, natural killer activity and lymphoproliferation in response to ConA and LPS, as well as an oxidative stress state in comparison with controls. Male DIO mice exhibited higher impairments in a variety of the evaluated parameters and a shorter life span than their female counterparts. In addition, female DIO mice, at old age, showed aggravated immunosenescence. In conclusion, the late DIO onset leads to impairments in behavior as well as in immune system functions of middle-aged male and female mice, males being significantly more affected than females.

Oxidative-Inflammatory Stress in Immune Cells from Adult Mice with Premature Aging

Oxidative and inflammatory stresses are closely related processes, which contribute to age-associated impairments that affect the regulatory systems such as the immune system and its immunosenescence. Therefore, the aim of this work was to confirm whether an oxidative/inflammatory stress occurs in immune cells from adult mice with premature aging, similar to that shown in leukocytes from chronologically old animals, and if this results in immunosenescence. Several oxidants/antioxidants and inflammatory/anti-inflammatory cytokines were analyzed in peritoneal leukocytes from adult female CD1 mice in two models of premature aging—(a) prematurely aging mice (PAM) and (b) mice with the deletion of a single allele (hemi-zygotic: HZ) of the tyrosine hydroxylase (th) gene (TH-HZ), together with cells from chronologically old animals. Several immune function parameters were also studied in peritoneal phagocytes and lymphocytes. The same oxidants and antioxidants were also analyzed in spleen and thymus leukocytes. The results showed that the immune cells of PAM and TH-HZ mice presented lower values of antioxidant defenses and higher values of oxidants/pro-inflammatory cytokines than cells from corresponding controls, and similar to those in cells from old animals. Moreover, premature immunosenescence in peritoneal leukocytes from both PAM and TH-HZ mice was also observed. In conclusion, adult PAM and TH-HZ mice showed oxidative stress in their immune cells, which would explain their immunosenescence.