Energy restriction and exercise differentially enhance components of systemic and mucosal immunity in mice

Virus Dynamics and Decay in Evaporating Human Saliva Droplets on Fomites

The transmission of most respiratory pathogens, including SARS-CoV-2, occurs via virus-containing respiratory droplets, and thus, factors that affect virus viability in droplet residues on surfaces are of critical medical and public health importance. Relative humidity (RH) is known to play a role in virus survival, with a U-shaped relationship between RH and virus viability. The mechanisms affecting virus viability in droplet residues, however, are unclear. This study examines the structure and evaporation dynamics of virus-containing saliva droplets on fomites and their impact on virus viability using four model viruses: vesicular stomatitis virus, herpes simplex virus 1, Newcastle disease virus, and coronavirus HCoV-OC43. The results support the hypothesis that the direct contact of antiviral proteins and virions within the "coffee ring" region of the droplet residue gives rise to the observed U-shaped relationship between virus viability and RH. Viruses survive much better at low and high RH, and their viability is substantially reduced at intermediate RH. A phenomenological theory explaining this phenomenon and a quantitative model analyzing and correlating the experimentally measured virus survivability are developed on the basis of the observations. The mechanisms by which RH affects virus viability are explored. At intermediate RH, antiviral proteins have optimal influence on virions because of their largest contact time and overlap area, which leads to the lowest level of virus activity.

Physical Activity and Breast Cancer Prevention: Possible Role of Immune Mediators

There is strong evidence that physical activity (PA) reduces risk, recurrence, and mortality from breast cancer. Emerging data suggest that PA induces changes in inflammatory and immune mediators that may contribute to beneficial effects on breast cancer outcomes. Thus, the goal of this review was to evaluate the evidence linking the protective benefit of PA to modulation of immune responses in breast cancer. A literature search was conducted to identify studies that evaluated the impact of PA on tumor and immune outcomes in breast cancer patients and in mammary tumor models. Nineteen studies investigated the effect of PA interventions on cancer immune outcomes using preclinical breast cancer models. Tumor growth was reduced in 11 studies, unchanged in three studies, and increased in one study. Spontaneous metastasis was reduced in two studies and survival was improved in four studies. Frequently assessed immune outcomes include splenic cell number and function, circulating inflammatory cytokines, and intratumoral immune cells and inflammatory markers. Circulating inflammatory cytokine responses were heterogeneous in preclinical models. Within the tumor microenvironment (TME), several studies documented a change in the infiltration of immune cells with an increase in effector cells and a reduction in immune suppressive cells. Twenty-three studies investigated the effect of PA interventions on immune outcomes in breast cancer patients. Thirteen studies used aerobic PA interventions and 10 studies used a combination of aerobic and resistance exercise interventions. Cycling and treadmill activities were the most commonly used PA modalities. Circulating immune cells and inflammatory cytokines were the most frequently assessed immune outcomes in the clinical studies. Among the 19 studies that evaluated a PA intervention during the post treatment period, 10 reported a reduction in the levels of at least one inflammatory cytokine. No inflammatory cytokines were quantified in the three studies that evaluated a PA intervention during treatment with chemotherapy. Immune outcomes within the tumor were assessed in only one study performing a PA intervention prior to surgery. Results from preclinical and clinical studies suggest that PA exerts heterogeneous effects on inflammatory cytokines, but may alter the gene expression profile and immune infiltrates in the tumor which may result in a reduction in immunosuppressive factors. However, additional studies are needed to better understand the effect of PA on immune outcomes in the TME.

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).

Increased Adiposity Enhances the Accumulation of MDSCs in the Tumor Microenvironment and Adipose Tissue of Pancreatic Tumor-Bearing Mice and in Immune Organs of Tumor-Free Hosts

Obesity is associated with increased risk and reduced survival for many types of cancer. Increasing adiposity may affect the balance between immunosuppressive and antitumor mechanisms critical for dictating cancer progression or remission. The goal of the current study was to determine if increased adiposity altered tumor growth, survival, and myeloid-derived suppressor cell (MDSC) accumulation in a subcutaneous murine model of pancreatic cancer. C57BL/6 mice were placed on a 30% kcal calorie-restricted diet, 10% kcal from fat diet fed ad libitum, or 60% kcal from fat diet fed ad libitum for 16 weeks to generate lean, overweight, and obese mice, respectively; followed by subcutaneous injection with 1 × 10⁶ Panc.02 cells. We observed a significant linear relationship between increased adiposity and increased tumor growth and mortality; increased accumulation of Gr-1⁺CD11b⁺ MDSCs; and reduced CD8 T cell:MDSC ratio in multiple tissues, including tumor. Increased adiposity also increased the accumulation of MDSCs in the spleen and lymph node of tumor-free mice. These data suggest adiposity induces MDSC accumulation, which may contribute to an immunosuppressive environment promoting tumor growth. Overall, our findings provide a rationale to prevent or reverse increased body weight as a strategy to reduce the accumulation of immunosuppressive cell types.

Physical Activity Plus Energy Restriction Prevents 4T1.2 Mammary Tumor Progression, MDSC Accumulation, and an Immunosuppressive Tumor Microenvironment

Physical activity and the prevention of weight gain decrease breast cancer incidence and improve survival. Unraveling the biological mechanisms underlying these cancer prevention effects is difficult because activity and dietary restriction are often linked. The goal of this study was to determine whether physical activity (PA), preventing weight gain via energy restriction (ER), or the combination was most effective in delaying tumor growth, reducing metastatic progression, and improving survival in the 4T1.2 mammary tumor model. Furthermore, we determined whether any of these interventions prevented the expansion of protumor immunosuppressive cells and altered the tumor microenvironment (TME). Female BALB/c mice (n = 7-20/group) were randomized to sedentary (SED) or PA wheel cages and fed ad libitum (AL) or 90% of control food intake (ER). After 8 weeks on the interventions, mice were inoculated with 5 × 10⁴ 4T1.2^luc cells into the 4th mammary fat pad and continued on their respective intervention. PA+ER significantly delayed primary tumor growth (final tumor volume, 0.193 ± 0.042 vs. 0.369 ± 0.049 cm³, P < 0.001), reduced metastatic burden in the lungs (0.72 ± 0.36 vs. 16.27 ± 6.98, P = 0.054) and increased survival (median survival, 68 vs 40 days, P = 0.043) compared with SED+AL mice. PA+ER also reduced the expression level of metastatic and immunosuppressive genes and resulted in favorable changes in immune cell infiltrates in the tumor. These data suggest that both PA and ER are needed to reduce tumor growth, delay metastatic progression, and improve survival, and that this protection is associated with changes in immune-mediated mechanisms.

Srf KO and wild-type mice similarly adapt to endurance exercise

Physical exercise has important effects as secondary prevention or intervention against several diseases. Endurance exercise induces local and global effects, resulting in skeletal muscle adaptations to aerobic activity and contributes to an amelioration of muscle performance. Furthermore, it prevents muscle loss. Serum response factor (Srf) is a transcription factor of pivotal importance for muscle tissues and animal models of Srf genetic deletion/over-expression are widely used to study Srf role in muscle homeostasis, physiology and pathology. A global characterisation of exercise adaptation in the absence of Srf has not been reported. We measured body composition, muscle force, running speed, energy expenditure and metabolism in WT and inducible skeletal muscle-specific Srf KO mice, following three weeks of voluntary exercise by wheel running. We found a major improvement in the aerobic capacity and muscle function in WT mice following exercise, as expected, and no major differences were observed in Srf KO mice as compared to WT mice, following exercise. Taken together, these observations suggest that Srf is not required for an early (within 3 weeks) adaptation to spontaneous exercise and that Srf KO mice behave similarly to the WT in terms of spontaneous physical activity and the resulting adaptive responses. Therefore, Srf KO mice can be used in functional muscle studies, without the results being affected by the lack of Srf. Since lack of Srf induces premature sarcopenia, our observations suggest that the modifications due to the absence of Srf take time to occur and that young, Srf KO mice behave similarly to WT in aerobic physical activities.

Effect of temperature and food restriction on immune function in striped hamsters (Cricetulus barabensis)

Small mammals in temperate areas face seasonal fluctuations of temperature and food availability, both of which may influence their immune responses, which are critical to survival. In the present study, we tested the hypothesis that low temperature and food restriction suppress immune function in striped hamsters (Cricetulus barabensis). Thirty-seven adult male hamsters were randomly assigned to warm (23±1°C) and cold (5±1°C) treatment groups, which were further divided into fed and food-restricted groups. Body mass was not affected by cold stress, food restriction or the interaction cold stress×food restriction. Cold stress decreased total body fat mass, haematological parameters including white blood cells, lymphocytes and neutrophilic granulocytes, and immunoglobin (Ig) M titres 5 days after injecting keyhole limpet haemocyanin (KLH). However, cold temperature increased bacterial killing capacity, indicative of innate immunity, and did not affect the mass of the thymus and spleen, intermediate granulocytes, the phytohaemagglutinin (PHA) response and the levels of blood glucose and serum leptin. Corticosterone concentration was affected significantly by the interaction cold stress×food restriction but not by cold stress or food restriction alone. Food restriction reduced thymus mass, but other immunological parameters including body fat mass, spleen mass, haematological parameters, innate immunity, PHA response, the titres of IgM and IgG, and the levels of blood glucose and serum leptin were all not affected by food restriction or the interaction cold stress×food restriction. Innate immunity was positively correlated with leptin levels, whereas no significant correlations were observed in the levels of blood glucose, serum leptin, corticosterone and all the detected immune parameters. Our results show that cold stress suppressed humoral immunity but enhanced innate immunity and did not affect cellular immunity in striped hamsters. Most immunological indices were not influenced by food restriction. Blood glucose, leptin and corticosterone could not explain the changes of innate, cellular and humoral immunity upon cold stress or food restriction in striped hamsters.

Fish Oil Enhances T Cell Function and Tumor Infiltration and Is Correlated With a Cancer Prevention Effect in HER-2/neu But Not PyMT Transgenic Mice

Few studies have explored the effects of omega-3 polyunsaturated fatty acid (n-3 PUFA) supplementation on immune modulation in murine models of mammary carcinogenesis. HER-2/neu and PyMT mice were randomized to 2 dietary interventions: AIN-93G-based diet with 1) 11% of diet (per gram weight) as corn oil (CO) or 2) 10% of diet as menhaden fish oil plus 1% of diet as corn oil (FO). FO significantly reduced the incidence and multiplicity of tumors (P < 0.001) in HER-2/neu, but not PyMT mice. FO-fed mice had significantly larger splenocyte counts than CO-fed mice in both the HER-2/neu and PyMT models; and in both models this was comprised of an increase in most cell types, including Gr-1(+)/CD11b(+) cells. T cells from FO-fed HER-2/neu mice produced significantly more interleukin-2 (P = 0.004) and interferon-γ (P = 0.012) in response to in vitro stimulation with anti-CD3 (0.5 µg/ml). Lastly, FO-fed HER-2/neu mice had significantly more tumor immune infiltrates than CO-fed mice, including NK1.1(+), F4/80(+), and Gr-1(+)/CD11b(+) cells (P ≤ 0.05). Greater Th1 cytokine production and significantly more tumor immune infiltrates in FO-fed Her2/neu mice may account for the cancer prevention effect of fish oil in this model.

In vitro Production of IL-6 and IFN-γ is Influenced by Dietary Variables and Predicts Upper Respiratory Tract Infection Incidence and Severity Respectively in Young Adults

Assessment of immune responses in healthy adults following dietary or lifestyle interventions is challenging due to significant inter-individual variability. Thus, gaining a better understanding of host factors that contribute to the heterogeneity in immunity is necessary. To address this question, healthy adults [n = 36, 18-40 years old, body mass index (BMI) 20-35 kg/m(2)] were recruited. Dietary intake was obtained via 3-day dietary recall records, physical activity level was evaluated using the International Physical Activity Questionnaire, and peripheral blood mononuclear cells were isolated from peripheral blood. Expression of activation markers on unstimulated immune subsets was assessed by flow cytometry. T-cell proliferation and cytokine secretion was assessed following in vitro stimulation with anti-CD3 or lipopolysaccharide. Furthermore, the incidence and severity of cold or flu symptoms were obtained from self-reported upper respiratory tract infection (URTI) questionnaires. The relationship between activation marker expression on T cells and T-cell effector functions; and in vitro cytokine secretion and URTI was determined by linear or logistic regression. CD69 and CD25 expression on unstimulated T cells was significantly associated with T-cell proliferation and interleukin-2 secretion. Incidence and severity of cold or flu symptoms was significantly associated with in vitro interleukin-6 and interferon-gamma secretion, respectively. Furthermore, host factors (e.g., age, BMI, physical activity, and diet) contributed significantly to the relationship between activation marker expression and T-cell effector function, and cytokine secretion and cold and flu status. In conclusion, these results suggest that lifestyle and dietary factors are important variables that contribute to immune responses and should be included in human clinical trials that assess immune endpoints.

Quantitative feed restriction rather than caloric restriction modulates the immune response of growing rabbits

BACKGROUND

Short-term feed restriction strategies are used in rabbits to reduce postweaning digestive disorders, but little is known about the involvement of the immune system in these beneficial effects.

OBJECTIVE

In the present study, the consequences of feed and energy restriction on immune response were investigated.

METHODS

At weaning, 320 male and female rabbits were assigned to 4 groups differing in dietary digestible energy (DE) concentrations and intake levels: a low-energy ad libitum-feed (LE100) group, a low-energy restricted-feed (LE75) group, a high-energy ad libitum-feed (HE100) group, and a high-energy restricted-feed (HE75) group. The high-energy groups consumed 10.13 MJ DE/kg of feed, whereas the low-energy groups consumed 9.08 MJ DE/kg (formulated values). Intake amounts for the restricted groups were 75% those of the ad libitum groups. Rabbits consumed these diets until age 63 d, after which they consumed feed ad libitum for 9 d. Ten rabbits per group and per age were killed at ages 42, 50, 63, and 72 d. Spleens and appendixes were weighed; Peyer's patch surface area was determined by image analysis; plasma total immunoglobulin (Ig) G and anti-ovalbumin IgG; and fecal and plasma IgA concentrations were determined by ELISA; and ileal expressions of cytokines were measured by quantitative reverse transcriptase-polymerase chain reaction at ages 50 and 63 d.

RESULTS

The relative weight and size of the lymphoid organs were not affected by treatments. Concentrations of plasma total IgA (-41% at 63 d and -29% at 72 d), IgG (-22% at 72 d), and anti-ovalbumin IgG (-41% at 63 d) were lower with feed restriction. Fecal IgA concentrations were lower with quantitative restriction (-40%, -52%, and -65% at age 42, 50, and 63 d, respectively) and energy restriction (-56%, -46%, and -73% at ages 50, 63, and 72 d, respectively). Feed-restricted rabbits tended to have greater expressions of interleukin (IL) 1β and IL-2 and lower expressions of tumor necrosis factor α (P < 0.1).

CONCLUSION

These results demonstrated that, in rabbits, restriction and, to a lesser extent, dietary energy concentration modulate gut immunity.

Dietary methionine restriction inhibits prostatic intraepithelial neoplasia in TRAMP mice

BACKGROUND

Prostate cancer (PCa) is a major aging-related disease for which little progress has been made in developing preventive strategies. Over the past several years, methionine restriction (MR), the feeding of a diet low in methionine (Met), has been identified as an intervention which significantly extends lifespan and reduces the onset of chronic diseases, including cancer, in laboratory animals. We, therefore, hypothesized that MR may be an effective strategy for inhibiting PCa.

METHODS

Control (0.86% Met) or MR (0.12% Met) diets were fed to 5-week old TRansgenic Adenocarcinoma of the Mouse Prostate (TRAMP) mice, a well-characterized model for PCa. The mice were sacrificed at 16 weeks of age and prostate and other tissues were harvested for histological and biochemical analyses.

RESULTS

As previously reported, MR was associated with a decrease in body weight which was not associated with lowered food intake. MR led to significant reductions in the development of Prostatic Intraepithelial Neoplasia (PIN) lesions, specifically in the anterior and dorsal lobes of the prostate where the incidence of high-grade PIN was reduced by ∼50% (P < 0.02). The reduction in PIN severity was associated with 46-64% reductions in cell proliferation rates (P < 0.02) and plasma IGF-1 levels (P < 0.0001), which might, in part, explain the effects on carcinogenesis. Additionally, no adverse consequences of MR on immune function were observed in the TRAMP mice.

CONCLUSIONS

Overall, these findings indicate that MR is associated with a reduction in prostate cancer development in the TRAMP model and supports the continued development of MR as a potential PCa prevention strategy.

Intermittent fasting promotes bacterial clearance and intestinal IgA production in Salmonella typhimurium-infected mice

The impact of intermittent fasting versus ad libitum feeding during Salmonella typhimurium infection was evaluated in terms of duodenum IgA levels, bacterial clearance and intestinal and extra-intestinal infection susceptibility. Mice that were intermittently fasted for 12 weeks or fed ad libitum were infected with S. typhimurium and assessed at 7 and 14 days post-infection. Next, we evaluated bacterial load in the faeces, Peyer's patches, spleen and liver by plate counting, as well as total and specific intestinal IgA and plasmatic corticosterone levels (by immunoenzymatic assay) and lamina propria IgA levels in plasma cells (by cytofluorometry). Polymeric immunoglobulin receptor, α- and J-chains, Pax-5 factor, pro-inflammatory cytokine (tumour necrosis factor-α and interferon-γ) and anti-inflammatory cytokine (transforming growth factor-β) mRNA levels were assessed in mucosal and liver samples (by real-time PCR). Compared with the infected ad libitum mice, the intermittently fasted infected animals had (1) lower intestinal and systemic bacterial loads; (2) higher SIgA and IgA plasma cell levels; (3) higher mRNA expression of most intestinal parameters; and (4) increased or decreased corticosterone levels on day 7 and 14 post-infection, respectively. No contribution of liver IgA was observed at the intestinal level. Apparently, the changes following metabolic stress induced by intermittent fasting during food deprivation days increased the resistance to S. typhimurium infection by triggering intestinal IgA production and presumably, pathogen elimination by phagocytic inflammatory cells.

HMB attenuates muscle loss during sustained energy deficit induced by calorie restriction and endurance exercise

OBJECTIVE

To investigate the efficacy and underlying mechanisms of β-hydroxy-β-methylbutyrate (HMB) on body composition, muscle mass and physical performance under catabolic versus normal training conditions.

MATERIALS/METHODS

Mice were divided into four groups (n=10/group): (1) ALT=ad libitum+trained (1 h/d for 3 d/wk); (2) ALTH=ALT+HMB (0.5 g/kg BW/d); (3) C=calorie restricted (-30%)+trained (6 h/d, 6 d/wk); and (4) CH=C+HMB. Repeated in vivo assessments included body composition, grip strength and sensorimotor coordination before and after the experimental protocol, while in vitro analyses included muscle wet weights, expression of selected genes and proteins regulating muscle mass, and myofiber cross-sectional area. ANOVAs were used with significance set at p<0.05.

RESULTS

ALTH had greater lean mass than ALT and sensorimotor function increased in ALTH, but decreased in ALT under normal training conditions. Grip strength decreased only in C, but was maintained in CH. Gastrocnemius mass and myofiber CSA were greater in CH than C following catabolic conditions. Gastrocnemius atrogin-1 mRNA expression was elevated in C but not in CH compared to all other groups whereas atrogin-1 protein levels showed no significant changes.

CONCLUSION

HMB improves body composition and sensorimotor function during normal training and attenuates muscle mass and strength loss during catabolic conditions.

Effects of dietary restriction or swimming on lymphocytes and macrophages functionality from old rats

Although aging compromises the functionality of macrophages (MΦ) and lymphocytes (LY), and dietary restriction (DR) and exercise partially counterbalance immunosenescence, it is unknown what effects of both strategies have on the functionality of these immune cells. Rats were randomly distributed into adult control (AD), older group (OLD), older submitted to 50% of DR (DR) and older submitted to swimming (EX) (n = 10 in each group). The function of immune cells (proliferative index, phagocytic capacity and H₂O₂ production), the weight and protein content of lymphoid organs (thymus and spleen), plasma glutamine concentration, interleukins (IL-1, IL-2, IL-6) and, immunoglobulins (IgA and IgG) were analysed. There was an increase of 74% in body weight in aged animals as compared with the AD group, while body weight reduced 19% in the DR as compared with the OLD group. Swimming training stimulated MΦ phagocytosis, while the EX group presented a decrease of the proliferative capacity of LY from the mesenteric lymph nodes (44% and 62%, respectively), when stimulated with ConA and LPS as compared with the old rats. These data demonstrated that DR and exercise affects differentially MΦ and LY function.

Neuroimmunological effects of physical exercise in depression

The search for an extended understanding of the causes of depression, and for the development of additional effective treatments is highly significant. Clinical and pre-clinical studies suggest stress is a key mediator in the pathophysiology of depression. Exercise is a readily available therapeutic option, effective as a first-line treatment in mild to moderate depression. In pre-clinical models exercise attenuates stress-related depression-like behaviours. Cellular and humoral neuroimmune mechanisms beyond inflammation and oxidative stress are highly significant in understanding depression pathogenesis. The effects of exercise on such mechanisms are unclear. When clinical and pre-clinical data is taken together, exercise may reduce inflammation and oxidation stress via a multitude of cellular and humoral neuroimmune changes. Astrocytes, microglia and T cells have an antiinflammatory and neuroprotective functions via a variety of mechanisms. It is unknown whether exercise has effects on specific neuroimmune markers implicated in the pathogenesis of depression such as markers of immunosenescence, B or T cell reactivity, astrocyte populations, self-specific CD4+ T cells, T helper 17 cells or T regulatory cells.

Benefits of exercise training on breast cancer progression and inflammation in C3(1)SV40Tag mice

Many observational epidemiologic studies suggest an association between exercise and breast cancer risk. However, the lack of controlled experimental studies that examine this relationship and the mechanisms involved weaken the basis for inferring a causal relationship. Inflammation plays a role in breast cancer progression and exercise has been reported to reduce inflammation; however, the anti-inflammatory effects of exercise in breast cancer have yet to be established. We examined the relationship between exercise training and systemic inflammation in relation to breast cancer progression in C3(1)SV40Tag mice. Female C3(1)SV40Tag mice were assigned to either exercise (Ex) or sedentary (Sed) treatment (n=12-14/group). Beginning at 4 wks of age mice (Ex) were run on a treadmill for 60 min/d (20 m/min and 5% grade), 6 d/wk for a period of 20 wks. Mice were examined weekly for palpable tumors, and tumor number and volume were recorded. At 24 wks of age mice were sacrificed and a more direct measure of tumor number and volume, and spleen weight was recorded. Plasma was analyzed for MCP-1 and IL-6 concentration using ELISA. Ex reduced palpable tumor number at sacrifice (24 wks) by approximately 70% (P<0.05). Tumor volume was also reduced in Ex at 21-23 wks (P<0.05). This reduction in tumor progression by Ex was associated with a reduction in plasma concentration of MCP-1 and IL-6, and spleen weight (P<0.05). These data provide strong support for a beneficial effect of exercise training on tumor progression in the C3(1)SV40Tag mouse model of breast cancer that may be partly mediated by its anti-inflammatory potential.

Diet, exercise and gut mucosal immunity

Diet and exercise are primary strategies recommended for the control of the obesity epidemic. Considerable attention is being paid to the effect of both on the immune system. However, little research has been done on the effect of diet, nutrients or exercise on the mucosal immune system. The gastrointestinal tract (gut) is not only responsible for the entry of nutrients into the organism, but also for triggering the primary immune response to orally ingested antigens. The gut-associated lymphoid tissue contains a large amount of immune cells, disseminated all along the intestine in Peyer's patches and lamina propria. Specific nutrients or their combinations, as well as the microflora, are capable of modulating the immune system through cell activation, production of signalling molecules or gene expression. We have observed an increase in T-cells as well as a decrease in B-cells from Peyer's patches, induced by diets high in fats or carbohydrates in Balb/c mice. It has also been demonstrated that exercise modulates the immune system, where moderate levels may improve its function by increasing the proliferation of lymphocytes from various sites, including gut-associated lymphoid tissue, whereas exhaustive acute exercise may cause immunosuppression. High-fat diets combined with exercise are able to induce an increase in CD3+ lymphocytes due to increased CD8+ cells and a decrease in B-cells. Explanations and consequences of the effects of diet and exercise on the gut mucosal immunity are still being explored.

Intestinal tumours, colonic butyrate and sleep in exercised Min mice

There is strong epidemiological evidence that more physical activity is associated with reduced risk of colon cancer, but the amount or type of activity necessary to invoke this protection is disputed, and the mechanism that is responsible has not been elucidated. The present study compared the effects of two contrasting exercise regimens on intestinal tumourigenesis in Min mice, and investigated two novel mechanistic factors: colonic butyrate and sleep. From 5 weeks of age, Min mice were exercised by running on a treadmill (TR; < or = 21 m/min, 30-60 min/d, 5 d/week, < or = 12 weeks). Additional groups of mice were provided with an exercise wheel (WH) or no exercise (CON). Mice had free access to a Western-style, high-fat diet. WH mice ran 3.97 km (females) and 1.92 km (males) daily (P = 0.002). There were no differences in body weight gain or body composition between treatment groups. Treadmill running reduced the numbers of larger ( > or = 2 mm diameter) tumours (P = 0.042), and tended to reduce tumour multiplicity in the colon (P = 0.049). TR mice had a higher molar proportion of butyrate in colonic digesta than CON mice (P = 0.030), and when treatment groups were combined, there was a weak negative correlation (r - 0.174, P = 0.061) between butyrate molar proportion and total tumour number. In a subset of animals in which non-exercise physical activity was monitored, there were strong positive correlations between sleep duration and both tumour multiplicity (P < 0.001) and tumour burden (P = 0.001). More studies of the effects of sleep and of colonic butyrate in mediating the effects of physical activity on intestinal tumourigenesis are warranted.

Physical activity and hematologic cancer prevention

This chapter presents the epidemiologic evidence on the association between physical activity and hematologic cancers and related hypothesized biologic mechanisms. Some preliminary indications of a protective role for physical activity for non-Hodgkin's lymphoma, leukemia, multiple myeloma, and Hodgkin's lymphoma exist, but the level of epidemiologic evidence is still insufficient to make any definitive conclusions regarding the nature of these associations. Several plausible biologic mechanisms underlying the possible associations between physical activity and hematologic cancers have been proposed, including enhancement of immune function, reduction in obesity, improvement of antioxidant defense systems, impact on metabolic hormones, and anti-inflammatory effects. Future studies should improve the estimation of physical activity by using more reliable, valid, and comprehensive measurement tools, assessing all components of physical activity (type, intensity, and time period), and conducting intervention studies to evaluate the effect of physical activity on various biomarkers of cancer in order to provide further insight into plausible biologic mechanisms underlying the possible association between physical activity and hematologic cancers.

Swim training suppresses tumor growth in mice

The present study was designed to determine the effects of physical training on the development of cancer induced by the injection of Ehrlich tumor cells in mice. Male Swiss mice were subjected to a swim training protocol (5 days/wk for 6 wk, 1 h at 50% of maximal capacity-trained groups) or remained sedentary in their cages (sedentary groups). The inoculation of Ehrlich tumor cells was performed at the end of the fourth week, and animals were killed after 6 wk of training. Heart and solid tumor weights were recorded, and tumor volumes were calculated. Portions of the tumors were used for the evaluation of macrophages and neutrophil accumulation or fixed in neutral 10% buffered formalin for histological analysis. The tumor volume and weight were, respectively, ∼270% and 280% greater in sedentary mice than in trained mice. Macrophage infiltration in the tumor tissue was significantly lower in trained mice (0.65 ± 0.16 vs. 1.78 ± 0.43 macrophages × 103 in the sedentary group). Moreover, neutrophil accumulation in tumors was slightly reduced after exercise training, and the amount of tumor cells was reduced in trained mice. Exercise capacity was substantially increased in trained mice, as determined by a 440% increase in the exercise time at 50% of maximal capacity. In summary, swim training retarded the development of Ehrlich tumors in mice, accompanied by a reduction in macrophage infiltration and neutrophil accumulation. These findings provide conceptual support for clinical observations that controlled physical activities may be a therapeutically important approach to preventing cancer progression and may improve the outcome of cancer treatment.

The antitumor and immunoadjuvant effects of IFN-alpha in combination with recombinant poxvirus vaccines

PURPOSE

IFN-alpha is a pleiotropic cytokine possessing immunomodulatory properties that may improve the efficacy of therapeutic cancer vaccines. The aim of this study was to evaluate the effectiveness and compatibility of combining recombinant IFN-alpha with poxvirus vaccines targeting the human carcinoembryonic antigen (CEA) in murine models of colorectal and pancreatic adenocarcinomas, where CEA is a self-antigen.

EXPERIMENTAL DESIGN

The phenotypic and functional effects of IFN-alpha were evaluated in the draining inguinal lymph nodes of tumor-free mice. We studied the effect of the site of IFN-alpha administration (local versus distal) on antigen-specific immune responses to poxvirus vaccination. Mechanistic studies were conducted to assess the efficacy of IFN-alpha and CEA-directed poxvirus vaccines in tumor-bearing CEA transgenic mice.

RESULTS

We identified a dose and schedule of IFN-alpha that induced a locoregional expansion of the draining inguinal lymph nodes and improved cellular cytotoxicity (natural killer and CD8(+)) and antigen presentation. Suppression of the vaccinia virus was avoided by administering IFN-alpha distal to the site of vaccination. The combination of IFN-alpha and vaccine inhibited tumor growth, improved survival, and elicited CEA-specific CTL responses in mice with CEA(+) adenocarcinomas. In mice with pancreatic tumors, IFN-alpha slowed tumor growth, induced CTL activity, and increased CD8(+) tumor-infiltrating lymphocytes.

CONCLUSIONS

These data suggest that IFN-alpha can be used as a biological response modifier with antigen-directed poxvirus vaccines to yield significant therapeutic antitumor immune responses. This study provides the rationale and mechanistic insights to support a clinical trial of this immunotherapeutic strategy in patients with CEA-expressing carcinomas.

Age-dependent spatial memory loss can be partially restored by immune activation

Aging is often associated with a decline in hippocampus-dependent spatial memory. Here, we show that functional cell-mediated immunity is required for the maintenance of hippocampus-dependent spatial memory. Sudden imposition of immune compromise in young mice caused spatial memory impairment, whereas immune reconstitution reversed memory deficit in immune-deficient mice. Analysis of hippocampal gene expression suggested that immune-dependent spatial memory performance was associated with the expression of insulin-like growth factor (Igf1) and of genes encoding proteins related to presynaptic activity (Syt10, Cplx2). We further showed that memory loss in aged mice could be attributed to age-related attenuation of the immune response and could be reversed by immune system activation. Homeostatic-driven proliferation of lymphocytes, which expands the existing T cell repertoire, restored spatial memory deficits in aged mice. Thus, our results identify a novel function of the immune system in the maintenance of spatial memory and suggest an original approach for arresting or reversing age-associated memory loss.

Exercise enhances vaccine-induced antigen-specific T cell responses

Regular moderate exercise has been proposed to enhance immune function, but its effects on immunity and their consequences have not been well studied. Mice without (AL) or with access (AL+EX) to voluntary running wheels were vaccinated with a model antigen (ovalbumin (OVA)) via intranasal or subcutaneous routes to target the mucosal and systemic immune compartments, respectively. EX enhanced OVA-specific CD4(+) T cell cytokine production and proliferation in all lymphoid organs examined without changes in cell distribution in any organ. These results suggest that coupling moderate exercise with vaccination may enhance vaccine efficacy for the prevention and/or therapy of numerous diseases.