Aquatic Exercise at Thermoneutral Water Temperature Enhances Antitumor Immune Responses

The effect of three types of water-based training protocols on thymus atrophy and specific indicators of cellular immune senescence in aged male rats

The collective detrimental impact of aged naive lymphocytes and thymus atrophy on the aging of the immune system can be mitigated by exercise. Hence, this research aims to explore the effects of three methods of water-based exercises on immune system aging and thymus atrophy in elderly rats. Thirty-two 24-month-old rats, with an average weight of 320 ± 5 g, were randomly allocated into four groups of endurance training (n = 8), resistance training (n = 8), combined training (n = 8), and control (n = 8).The training protocols (10 weeks) were conducted four times a week in a container measuring 50 × 50x100 cm filled with water at 30 ± 1 °C. The evaluation of naïve and memory T lymphocytes was conducted for the intervention groups based on the expression or lack of expression of the CD28 and CD57 markers in the subsets of CD4 + and CD8 + T cells. Naïve T cells were represented by CD28 + CD57- T lymphocytes, memory T cells were represented by CD28- CD57- T lymphocytes, aged naïve T cells were indicated by CD28 + CD57 + lymphocytes, and aged memory T cells were represented by CD28- CD57 + lymphocytes. The findings of the study showed that all three exercise protocols resulted in a significant decrease in levels of memory CD8, aged CD8, naive and naive CD4 and CD8, and aged memory, as well as an increase in levels of CD4, CD8, CD4 + , and naive CD8 when compared to the control group. It was observed that thymus atrophy, memory CD4, and aged CD4 had a significant decrease only in the combined exercise group compared to the control group, with no significant differences observed in these indicators for the resistance and endurance groups. Furthermore, the ratio of CD4 to CD8 remained unchanged across all groups. The findings of this study suggest greater efficacy of combined training in enhancing specific health indicators of cell immunity among elderly populations. Moreover, engaging in water exercises of all three types of combined, resistance, and endurance training are deemed safe activities for older individuals to bolster their immune system and mitigate the aging process of T cells.

Effect of exposure to disinfection by-products during swimming exercise on asthma-related immune responses

Swimming is a widely practiced exercise in modern society, where there is a heightened interest in health. The exceptional benefits of swimming are well-known, yet the issue of water quality management inevitably arises due to its nature as an aquatic exercise. Several studies reported that chlorine disinfectants commonly used in swimming pool water disinfection could degrade into toxic disinfection by-products (DBPs) and suggested that the DBPs might induce respiratory disorders, including asthma. Conversely, there were also reports that the DBPs had no significant effects on respiratory conditions. In this study, we investigated the influence of swimming exercise and DBPs on asthma. The decomposition products had little effect on the number of T cells in various immune organs. However, swimming exercise was found to increase the cell count in proportion to the exercise duration. Nevertheless, there were no significant changes in other immune cells and the secretion of asthma-related cytokines. These findings indicate that the effects of swimming pool DBPs on respiratory conditions during swimming exercise are either negligible or absent, and instead, the immunological benefits gained through consistent swimming exercise outweigh any potential drawbacks.

Effects of disinfection by-products in swimming pool environments on the immunological mechanisms of respiratory diseases

Swimming in pools is a popular and healthy recreational activity. However, potential adverse health effects from disinfection byproduct (DBP) exposure in pool water are concerning. This study evaluated how such DBP exposure affects the respiratory system. DBP exposure was simulated with an animal-specific pool environment model. Experimental animals were exposed to DBPs for a specified duration and frequency over 4 weeks. The wet and dry weights of murine lungs were measured, with no significant differences observed. There were no significant differences in interkeukin (IL)-2/4/10, and interferon-γ levels. However, IL-6 expression decreased in the experimental group. To investigate the effects of DBP exposure on immune cell response, various samples, such as bronchoalveolar lavage fluid, lymph nodes, spleen, and thymus, were collected for T-cell isolation and fluorescence-activated cell sorting. Asthma-related blood cell distribution was analyzed using a complete blood count test; no significant differences were found. Thus, DBP exposure through this model did not induce substantial lung tissue damage, major alterations in cytokine expression (besides IL-6), significant immune cell responses, or changes in asthma-associated blood cell distribution. However, considering earlier results, future studies should focus on specific types, intensity, and duration of exercise that could affect DBP exposure-related immune-inflammatory responses.

Does exercise attenuate age- and disease-associated dysfunction in unconventional T cells? Shining a light on overlooked cells in exercise immunology

Unconventional T Cells (UTCs) are a unique population of immune cells that links innate and adaptive immunity. Following activation, UTCs contribute to a host of immunological activities, rapidly responding to microbial and viral infections and playing key roles in tumor suppression. Aging and chronic disease both have been shown to adversely affect UTC numbers and function, with increased inflammation, change in body composition, and physical inactivity potentially contributing to the decline. One possibility to augment circulating UTCs is through increased physical activity. Acute exercise is a potent stimulus leading to the mobilization of immune cells while the benefits of exercise training may include anti-inflammatory effects, reductions in fat mass, and improved fitness. We provide an overview of age-related changes in UTCs, along with chronic diseases that are associated with altered UTC number and function. We summarize how UTCs respond to acute exercise and exercise training and discuss potential mechanisms that may lead to improved frequency and function.

Thermoneutrality and Immunity: How Does Cold Stress Affect Disease?

One of the major challenges the scientific community faces today is the lack of translational data generated from mouse trials for human health application. Housing temperature-dependent chronic cold stress in laboratory rodents is one of the key factors contributing to lack of translatability because it reveals major metabolic differences between humans and rodents. While humans tend to operate at temperatures within their thermoneutral zone, most laboratory rodents are housed at temperatures below this zone and have an increased energy demand to generate heat. This has an impact on the immune system of mice and thus affects results obtained using murine models of human diseases. A limited number of studies and reviews have shown that results obtained on mice housed at thermoneutrality were different from those obtained from mice housed in traditional housing conditions. Most of those studies, focused on obesity and cancer, found that housing mice at thermoneutrality changed the outcomes of the diseases negatively and positively, respectively. In this review, we describe how thermoneutrality impacts the immune system of rodents generally and in the context of different disease models. We show that thermoneutrality exacerbates cardiovascular and auto-immune diseases; alleviates asthma and Alzheimer’s disease; and, changes gut microbiome populations. We also show that thermoneutrality can have exacerbating or alleviating effects on the outcome of infectious diseases. Thus, we join the call of others in this field to urge researchers to refine murine models of disease and increase their translational capacity by considering housing at thermoneutrality for trials involving rodents.

Impact of physical activity and energy restriction on immune regulation of cancer

Cancer is a major public health issue worldwide. Lifestyle factors, such as body weight and physical activity (PA), significantly impact cancer risk and progression. There is strong evidence that PA reduces and obesity increases risk and mortality from numerous cancer types. Energy restriction (ER) in non-obese hosts significantly reduces tumor incidence in a variety of preclinical models, and reduces body weight and cardiometabolic risk factors in humans. Emerging data suggest that PA- and ER-induced changes in inflammatory and immune mediators may contribute to the cancer prevention effects of these interventions. A systematic literature search was conducted to identify studies that evaluated the impact of PA and ER on tumor and immune outcomes in humans and animal models. A total of 97 eligible studies were identified (68 studies reporting PA interventions and 30 studies reporting ER interventions). Thirty-one studies investigated the effect of PA on cancer immune outcomes using preclinical cancer models of breast (n=17, 55%), gastrointestinal (n=6, 19%), melanoma (n=4, 13%), and several other cancer types (n=4, 13%). Despite the heterogeneity in study designs, the majority of studies (n=23, 74%) reported positive effects of PA on tumor outcomes. Thirty-seven clinical studies investigated the effect of PA on cancer immune outcomes. None reported tumor outcomes, thus only immune outcomes were evaluated in these studies. PA studies were conducted in patients with breast (n=22, 59%), gastrointestinal (n=5, 14%), prostate (n=2, 5%), esophageal (n=1, 3%), lung (n=1, 3%) cancer, leukemia (n=1, 3%), or mixed cancer types (n=5, 14%). Twenty-two studies investigated the effect of ER interventions on cancer immune outcomes using preclinical cancer models including breast (n=5, 23%), gastrointestinal (n=5, 23%), lung (n=2, 9%), liver (n=2, 9%), pancreatic (n=2, 9%), and several other cancer types (n=6, 27%). Positive effects of ER on tumor outcomes were reported in 21 of 22 studies. Six clinical studies investigated the effect of ER (in combination with PA) on tumor immune outcomes in cancer patients with overweight or obesity. Five were conducted in breast cancer patients, and one recruited patients of a mix of cancer types. A wide range of immunological parameters including immune cell phenotype and function, cytokines, and other immune and inflammatory markers were assessed in multiple tissue compartments (blood, spleen, lymph nodes and tumor) in the included studies. Results from preclinical and clinical studies suggest that both PA and ER exert heterogeneous effects on circulating factors and systemic immune responses. PA + ER alters the gene expression profile and immune infiltrates in the tumor which may result in a reduction in immune suppressive factors. However, additional studies are needed to better understand the effect of PA and/or ER on immunomodulation, particularly in the tumor microenvironment (TME).

Effects of Propranolol on Bone, White Adipose Tissue, and Bone Marrow Adipose Tissue in Mice Housed at Room Temperature or Thermoneutral Temperature

Growing female mice housed at room temperature (22°C) weigh the same but differ in body composition compared to mice housed at thermoneutrality (32°C). Specifically, mice housed at room temperature have lower levels of white adipose tissue (WAT). Additionally, bone marrow adipose tissue (bMAT) and cancellous bone volume fraction in distal femur metaphysis are lower in room temperature-housed mice. The metabolic changes induced by sub-thermoneutral housing are associated with lower leptin levels in serum and higher levels of Ucp1 gene expression in brown adipose tissue. Although the precise mechanisms mediating adaptation to sub-thermoneutral temperature stress remain to be elucidated, there is evidence that increased sympathetic nervous system activity acting via β-adrenergic receptors plays an important role. We therefore evaluated the effect of the non-specific β-blocker propranolol (primarily β₁ and β₂ antagonist) on body composition, femur microarchitecture, and bMAT in growing female C57BL/6 mice housed at either room temperature or thermoneutral temperature. As anticipated, cancellous bone volume fraction, WAT and bMAT were lower in mice housed at room temperature. Propranolol had small but significant effects on bone microarchitecture (increased trabecular number and decreased trabecular spacing), but did not attenuate premature bone loss induced by room temperature housing. In contrast, propranolol treatment prevented housing temperature-associated differences in WAT and bMAT. To gain additional insight, we evaluated a panel of genes in tibia, using an adipogenesis PCR array. Housing temperature and treatment with propranolol had exclusive as well as shared effects on gene expression. Of particular interest was the finding that room temperature housing reduced, whereas propranolol increased, expression of the gene for acetyl-CoA carboxylase (Acacb), the rate-limiting step for fatty acid synthesis and a key regulator of β-oxidation. Taken together, these findings provide evidence that increased activation of β₁ and/or β₂ receptors contributes to reduced bMAT by regulating adipocyte metabolism, but that this pathway is unlikely to be responsible for premature cancellous bone loss in room temperature-housed mice.

Thermoneutral housing attenuates premature cancellous bone loss in male C57BL/6J mice

Mice are a commonly used model to investigate aging-related bone loss but, in contrast to humans, mice exhibit cancellous bone loss prior to skeletal maturity. The mechanisms mediating premature bone loss are not well established. However, our previous work in female mice suggests housing temperature is a critical factor. Premature cancellous bone loss was prevented in female C57BL/6J mice by housing the animals at thermoneutral temperature (where basal rate of energy production is at equilibrium with heat loss). In the present study, we determined if the protective effects of thermoneutral housing extend to males. Male C57BL/6J mice were housed at standard room temperature (22°C) or thermoneutral (32°C) conditions from 5 (rapidly growing) to 16 (slowly growing) weeks of age. Mice housed at room temperature exhibited reductions in cancellous bone volume fraction in distal femur metaphysis and fifth lumbar vertebra; these effects were abolished at thermoneutral conditions. Mice housed at thermoneutral temperature had higher levels of bone formation in distal femur (based on histomorphometry) and globally (serum osteocalcin), and lower global levels of bone resorption (serum C-terminal telopeptide of type I collagen) compared to mice housed at room temperature. Thermoneutral housing had no impact on bone marrow adiposity but resulted in higher abdominal white adipose tissue and serum leptin. The overall magnitude of room temperature housing-induced cancellous bone loss did not differ between male (current study) and female (published data) mice. These findings highlight housing temperature as a critical experimental variable in studies using mice of either sex to investigate aging-related changes in bone metabolism.

Anti-oxidant and Anti-inflammatory Effects of Aquatic Exercise in Allergic Airway Inflammation in Mice

Oxidative stress and inflammation are key pathways responsible for the pathogenesis of asthma. Aquatic exercise (AE) has been proven to elicit a variety of biological activities such as anti-oxidant and anti-inflammatory effects. However, although proper forms of AE provide beneficial health effects, incorrect forms and types of AE are potentially injurious to health. Several studies have investigated AE, but the relationship between types of AE and asthma has not been fully elucidated. This study evaluated the effects of two types of AE according to resistance on ovalbumin (OVA)-induced allergic airway inflammation in mice. BALB/c mice were subjected to OVA sensitization and challenge, and then to different types of AE including, walking and swimming, in a pool filled with water to a height of 2.5 and 13 cm for 30 min, respectively. AE reduced OVA-induced eosinophilic inflammation, airway hyperresponsiveness, and serum immunoglobulin E level. AE significantly inhibited increases in interleukin (IL)-4, IL-5, IL-13, histamine, leukotriene D4, and tryptase levels in bronchoalveolar lavage fluid (BALF). AE also effectively suppressed mucus formation, lung fibrosis, and hypertrophy of airway smooth muscle within the lung tissues. This exercise markedly reduced the levels of malondialdehyde while increased glutathione and superoxide dismutase (SOD) activity in lung tissues. Furthermore, AE significantly decreased tumor necrosis factor-α, IL-6 levels, and prostaglandin E2 production in BALF. The inhibitory effects of swimming on the levels of biomarkers related to oxidative stress and inflammation were greater than that of walking. These effects may have occurred through upregulation of NF-E2-related factor 2/heme oxygenase-1 signaling and suppression of mitogen-activated protein kinase/nuclear factor-κB pathway. Cumulative results from this study suggest that AE might be beneficial in mitigating the levels of biomarkers related to oxidative stress and inflammation. Thus, this therapy represents a crucial non-pharmacological intervention for treatments of allergic airway inflammation.