Temperature matters: the potential impact of thermoregulatory mechanisms in brain-body physiology.

Thermoregulation, responsible for maintaining a stable core temperature during wide fluctuations in external and internal thermal environments, is an iconic homeostatic process. However, we suggest that despite its fundamental physiological significance, the potential for required cool housing temperatures and thermoregulatory mechanisms to influence the interpretation of experimental data is not sufficiently appreciated. Moreover, although it is generally assumed that the major thermoregulatory pathways are well understood, here we discuss new research that suggests otherwise and reveals the emergence of a new wave of exciting ideas for this "old" field of research.

Association of pre-treatment lymphocyte-monocyte ratio with survival outcome in patients with head and neck cancer treated with chemoradiation.

BACKGROUND: Given the role of systematic inflammation in cancer progression, lymphocyte-monocyte ratio (LMR) from peripheral blood has been suggested as a biomarker to assess the extent of inflammation in several solid malignancies. However, the role of LMR as a prognostic factor in head and neck cancer was unclear in several meta-analyses, and there is a paucity of literature including patients in North America. We performed an observational cohort study to evaluate the association of LMR with survival outcomes in North American patients with head and neck cancer. METHODS: A single-institution, retrospective database was queried for patients with non-metastatic head and neck cancer who underwent definitive chemoradiation from June 2007 to April 2021 at the Roswell Park Comprehensive Cancer Center. Primary endpoints were overall survival (OS) and cancer-specific survival (CSS). The association of LMR with OS and CSS was examined using nonlinear Cox proportional hazard model using restricted cubic splines (RCS). Cox multivariable analysis (MVA) and Kaplan-Meier method were used to analyze OS and CSS. Pre-radiation LMR was then stratified into high and low based on its median value. Propensity scored matching was used to reduce the selection bias. RESULTS: A total of 476 patients met our criteria. Median follow up was 45.3 months (interquartile range 22.8-74.0). The nonlinear Cox regression model showed that low LMR was associated with worse OS and CSS in a continuous fashion without plateau for both OS and CSS. On Cox MVA, higher LMR as a continuous variable was associated with improved OS (adjusted hazard ratio [aHR] 0,90, 95% confidence interval [CI] 0.82-0.99, p = 0.03) and CSS (aHR 0.83, 95% CI 0.72-0.95, p = 0.009). The median value of LMR was 3.8. After propensity score matching, a total of 186 pairs were matched. Lower LMR than 3.8 remained to be associated with worse OS (HR 1.59, 95% CI 1.12-2.26, p = 0.009) and CSS (HR 1.68, 95% CI 1.08-2.63, p = 0.02). CONCLUSION: Low LMR, both as a continuous variable and dichotomized variable, was associated with worse OS and CSS. Further studies would be warranted to evaluate the role of such prognostic marker to tailor interventions.

Systemic endocrine instigation of indolent tumor growth requires osteopontin.

The effects of primary tumors on the host systemic environment and resulting contributions of the host to tumor growth are poorly understood. Here, we find that human breast carcinomas instigate the growth of otherwise-indolent tumor cells, micrometastases, and human tumor surgical specimens located at distant anatomical sites. This systemic instigation is accompanied by incorporation of bone-marrow cells (BMCs) into the stroma of the distant, once-indolent tumors. We find that BMCs of hosts bearing instigating tumors are functionally activated prior to their mobilization; hence, when coinjected with indolent cells, these activated BMCs mimic the systemic effects imparted by instigating tumors. Secretion of osteopontin by instigating tumors is necessary for BMC activation and the subsequent outgrowth of the distant otherwise-indolent tumors. These results reveal that outgrowth of indolent tumors can be governed on a systemic level by endocrine factors released by certain instigating tumors, and hold important experimental and therapeutic implications.

MEETING HIGHLIGHTS: THE THIRD MARIE SKLODOWSKA-CURIE SYMPOSIUM ON CANCER RESEARCH AND CARE AT ROSWELL PARK COMPREHENSIVE CANCER CENTER, BUFFALO, NY, SEPTEMBER 20-22, 2023.

Marie Sklodowska-Curie Symposia on Cancer Research and Care (MSCS-CRC) promote collaborations between cancer researchers and care providers in the United States, Canada and Central and Eastern European Countries (CEEC), to accelerate the development of new cancer therapies, advance early detection and prevention, increase cancer awareness, and improve cancer care and the quality of life of patients and their families. The third edition of MSCS-CRC, held at Roswell Park Comprehensive Cancer Center, Buffalo, NY, in September 2023, brought together 137 participants from 20 academic institutions in the US, Poland, Ukraine, Lithuania, Croatia and Hungary, together with 16 biotech and pharma entities. The key areas of collaborative opportunity identified during the meeting are a) creating of a database of available collaborative projects in the areas of early-phase clinical trials, preclinical development, and identification of early biomarkers; b) promoting awareness of cancer risks and efforts at cancer prevention; c) laboratory and clinical training; and d) sharing experience in cost-effective delivery of cancer care and improving the quality of life of cancer patients and their families. Examples of ongoing international collaborations in the above areas were discussed. Participation of the representatives of the Warsaw-based Medical Research Agency, National Cancer Institute (NCI) of the United States, National Cancer Research Institutes of Poland and Lithuania, New York State Empire State Development, Ministry of Health of Ukraine and Translational Research Cancer Center Consortium of 13 cancer centers from the US and Canada, facilitated the discussion of available governmental and non-governmental funding initiatives in the above areas.

Stimulation of an anti-tumor immune response with "chromatin-damaging" therapy.

Curaxins are small molecules that bind genomic DNA and interfere with DNA-histone interactions leading to the loss of histones and decondensation of chromatin. We named this phenomenon 'chromatin damage'. Curaxins demonstrated anti-cancer activity in multiple pre-clinical tumor models. Here, we present data which reveals, for the first time, a role for the immune system in the anti-cancer effects of curaxins. Using the lead curaxin, CBL0137, we observed elevated expression of several group of genes in CBL0137-treated tumor cells including interferon sensitive genes, MHC molecules, some embryo-specific antigens suggesting that CBL0137 increases tumor cell immunogenicity and improves recognition of tumor cells by the immune system. In support of this, we found that the anti-tumor activity of CBL0137 was reduced in immune deficient SCID mice when compared to immune competent mice. Anti-tumor activity of CBL0137 was abrogated in CD8+ T cell depleted mice but only partially lost when natural killer or CD4+ T cells were depleted. Further support for a key role for the immune system in the anti-tumor activity of CBL0137 is evidenced by an increased antigen-specific effector CD8+ T cell and NK cell response, and an increased ratio of effector T cells to Tregs in the tumor and spleen. CBL0137 also elevated the number of CXCR3-expressing CTLs in the tumor and the level of interferon-γ-inducible protein 10 (IP-10) in serum, suggesting IP-10/CXCR3 controls CBL0137-elicited recruitment of effector CTLs to tumors. Our collective data underscores a previously unrecognized role for both innate and adaptive immunity in the anti-tumor activity of curaxins.

Manipulation of Ambient Housing Temperature To Study the Impact of Chronic Stress on Immunity and Cancer in Mice.

Mice are the preeminent research organism in which to model human diseases and study the involvement of the immune response. Rapidly accumulating evidence indicates a significant involvement of stress hormones in cancer progression, resistance to therapies, and suppression of immune responses. As a result, there has been a concerted effort to model human stress in mice. In this article, we discuss recent literature showing how mice in research facilities are chronically stressed at baseline because of environmental factors. Focusing on housing temperature, we suggest that the stress of cool housing temperatures contributes to the impact of other imposed experimental stressors and therefore has a confounding effect on mouse stress models. Furthermore, we propose that manipulation of housing temperature is a useful approach for studying the impact of chronic stress on disease and the immune response and for testing therapeutic methods of reducing the negative effects of chronic stress.

Blockade of Host ß2-Adrenergic Receptor Enhances Graft-versus-Tumor Effect through Modulating APCs.

Allogeneic hematopoietic cell transplantation is a potential curative therapy for hematologic malignancies. Host APCs are pivotal to the desired graft-versus-tumor (GVT) effect. Recent studies have shown that ß2-adrenergic receptor (ß2AR) signaling can have an important impact on immune cell function, including dendritic cells (DCs). In this article, we demonstrate that pretreatment of host mice with a ß2AR blocker significantly increases the GVT effect of donor CD8+ T cells by decreasing tumor burden without increasing graft-versus-host disease. ß2AR-deficient host mice have significantly increased effector memory and central memory CD8+ T cells and improved reconstitution of T cells, including CD4+Foxp3+ regulatory T cells. Notably, ß2AR deficiency induces increased CD11c+ DC development. Also, ß2AR-deficient bone marrow-derived DCs induce higher CD8+ T cell proliferation and improved tumor killing in vitro. Metabolic profiling shows that ß2AR deficiency renders DCs more immunogenic through upregulation of mTOR activity and reduction of STAT3 phosphorylation. Altogether, these findings demonstrate an important role for host ß2AR signaling in suppressing T cell reconstitution and GVT activity.

Contribution of Immune Cells to Glucocorticoid Receptor Expression in Breast Cancer.

Breast cancer (BC) patients experience increased stress with elevated cortisol levels, increasing risk of cancer recurrence. Cortisol binds to a cytoplasmic receptor, glucocorticoid receptor (GR) encoded by GR gene (NR3C1). We hypothesized that not only cancer cells, but even immune cells in the tumor microenvironment (TME) may contribute to GR expression in bulk tumor and influence prognosis. To test this, mRNA expression data was accessed from METABRIC and TCGA. "High" and "low" expression was based on highest and lowest quartiles of NR3C1 gene expression, respectively. Single-cell sequencing data were obtained from GSE75688 and GSE114725 cohorts. Computer algorithms CIBERSORT, Gene Set Enrichment Analysis and TIMER were used. GR-high BC has better median disease-free and disease-specific survival. Single cell sequencing data showed higher GR expression on immune cells compared to cancer and stromal cells. Positive correlation between GR-high BC and CD8+ T-cells was noted. In GR-high tumors, higher cytolytic activity (CYT) with decreased T-regulatory and T-follicular helper cells was observed. High GR expression was associated with lower proliferation index Ki67, enriched in IL-2_STAT5, apoptosis, KRAS, TGF-ß signaling, and epithelial-to-mesenchymal transition. Immune cells significantly contribute to GR expression of bulk BC. GR-high BC has a favorable TME with higher CYT with favorable outcomes.

ß-Adrenergic signaling blocks murine CD8+ T-cell metabolic reprogramming during activation: a mechanism for immunosuppression by adrenergic stress.

Primary and secondary lymphoid organs are heavily innervated by the autonomic nervous system. Norepinephrine, the primary neurotransmitter secreted by post-ganglionic sympathetic neurons, binds to and activates ß-adrenergic receptors expressed on the surface of immune cells and regulates the functions of these cells. While it is known that both activated and memory CD8+ T-cells primarily express the ß2-adrenergic receptor (ß2-AR) and that signaling through this receptor can inhibit CD8+ T-cell effector function, the mechanism(s) underlying this suppression is not understood. Under normal activation conditions, T-cells increase glucose uptake and undergo metabolic reprogramming. In this study, we show that treatment of murine CD8+ T-cells with the pan ß-AR agonist isoproterenol (ISO) was associated with a reduced expression of glucose transporter 1 following activation, as well as decreased glucose uptake and glycolysis compared to CD8+ T-cells activated in the absence of ISO. The effect of ISO was specifically dependent upon ß2-AR, since it was not seen in adrb2-/- CD8+ T-cells and was blocked by the ß-AR antagonist propranolol. In addition, we found that mitochondrial function in CD8+ T-cells was also impaired by ß2-AR signaling. This study demonstrates that one mechanism by which ß2-AR signaling can inhibit CD8+ T-cell activation is by suppressing the required metabolic reprogramming events which accompany activation of these immune cells and thus reveals a new mechanism by which adrenergic stress can suppress the effector activity of immune cells.

Temperature as a modulator of the gut microbiome: what are the implications and opportunities for thermal medicine?

There is substantial research being conducted on the relationships between the gut microbiome, the immune response and health and disease. Environmental temperature and heat stress are known to modify the gut microbiome. Changes in core temperature have been linked, in multiple phyla, to altered microbiome composition and function. This raises the question of whether local/regional or whole body thermal therapies which target tumors in the abdomen, peritoneal cavity, or pelvis influence the gut microbiome. To date, there is little information on whether thermal therapy exerts positive or negative effects on the microbiome. This is an intriguing question since there is growing interest in the immunological impact of various thermal therapies. The goal of this brief review is to highlight research on how environmental conditions, particularly temperature (internal as well as external temperatures) influences the gut microbiome. Given the potential for temperature shifts to modulate gut microbe function and composition, it is likely that various forms of thermal therapy, including hyperthermic intraperitoneal chemotherapy (HIPEC), deep regional, and whole body hyperthermia influence the microbiome in ways that are currently not appreciated. More research is needed to determine whether thermal therapy induced changes in the microbiome occur, and whether they are beneficial or detrimental to the host. Currently, although approaches to microbiome modification such as dietary intervention, fecal transfer, probiotics and prebiotics are being developed, the potential of temperature manipulation has, as yet, not been explored. Therefore, new research could reveal whether perturbations of the microbiome composition that have negative health consequences (dysbiosis) could be an important target for treatment by thermal medicine.

Host-Derived Serine Protease Inhibitor 6 Provides Granzyme B-Independent Protection of Intestinal Epithelial Cells in Murine Graft-versus-Host Disease.

Graft-versus-host disease (GVHD) is a serious complication after allogeneic hematopoietic cell transplantation (allo-HCT) that limits the therapeutic potential of this treatment. Host antigen-presenting cells (APCs) play a vital role in activating donor T cells that subsequently use granzyme B (GzmB) and other cytotoxic molecules to damage host normal tissues. Serine protease inhibitor 6 (Spi6), known as the sole endogenous inhibitor of GzmB, has been implicated in protecting T cells and APCs against GzmB-inflicted damage. In this study we used murine models to examine the previously unknown role of host-derived Spi6 in GVHD pathogenesis. Our results indicated that host Spi6 deficiency exacerbated GVHD as evidenced by significantly increased lethality and clinical and histopathologic scores. Using bone marrow chimera system, we found that Spi6 in nonhematopoietic tissue played a dominant role in protecting against GVHD and was significantly upregulated in intestinal epithelial cells after allo-HCT, whereas Spi6 in hematopoietic APCs surprisingly suppressed alloreactive T cell response. Interestingly, the protective effect of Spi6 and its expression in intestinal epithelial cells appeared to be independent of donor-derived GzmB. We used in silico modeling to explore potential targets of Spi6. Interaction tested in silico demonstrated that Spi6 could inhibit caspase-3 and caspase-8 with the same functional loop that inhibits GzmB but was not capable of forming stable interaction with caspase-1 or granzyme A. Using an in vitro co-culture system, we further identified that donor T cell-derived IFN-γ was important for inducing Spi6 expression in an intestinal epithelial cell line. Altogether, our data indicate that host Spi6 plays a novel, GzmB-independent role in regulating alloreactive T cell response and protecting intestinal epithelial cells. Therefore, enhancing host-derived Spi6 function has the potential to reduce GVHD.

An overview of the role of sympathetic regulation of immune responses in infectious disease and autoimmunity.

Stress in patients and pre-clinical research animals plays a critical role in disease progression Activation of the sympathetic nervous system (SNS) by stress results in secretion of the catecholamines epinephrine (Epi) and norepinephrine (NE) from the adrenal gland and sympathetic nerve endings. Adrenergic receptors for catecholamines are present on immune cells and their activity is affected by stress and the accompanying changes in levels of these neurotransmitters. In this short review, we discuss how this adrenergic stress impacts two categories of immune responses, infections and autoimmune diseases. Catecholamines signal primarily through the ß2-adrenergic receptors present on innate and adaptive immune cells which are critical in responding to infections caused by pathogens. In general, this adrenergic input, particularly chronic stimulation, suppresses lymphocytes and allows infections to progress. On the other hand, insufficient adrenergic control of immune responses allows progression of several autoimmune diseases.

Housing Temperature-Induced Stress Is Suppressing Murine Graft-versus-Host Disease through ß2-Adrenergic Receptor Signaling.

Graft-versus-host disease (GVHD) is the major complication of allogeneic hematopoietic cell transplantation, a potentially curative therapy for hematologic diseases. It has long been thought that murine bone marrow-derived T cells do not mediate severe GVHD because of their quantity and/or phenotype. During the course of experiments testing the impact of housing temperatures on GVHD, we discovered that this apparent resistance is a function of the relatively cool ambient housing temperature. Murine bone marrow-derived T cells have the ability to mediate severe GVHD in mice housed at a thermoneutral temperature. Specifically, mice housed at Institutional Animal Care and Use Committee-mandated, cool standard temperatures (∼ 22°C) are more resistant to developing GVHD than are mice housed at thermoneutral temperatures (∼ 30°C). We learned that the mechanism underlying this housing-dependent immunosuppression is associated with increased norepinephrine production and excessive signaling through ß-adrenergic receptor signaling, which is increased when mice are cold stressed. Treatment of mice housed at 22°C with a ß2-adrenergic antagonist reverses the norepinephrine-driven suppression of GVHD and yields similar disease to mice housed at 30°C. Conversely, administering a ß2-adrenergic agonist decreases GVHD in mice housed at 30°C. In further mechanistic studies using ß2-adrenergic receptor-deficient (ß2-AR(-/-)) mice, we found that it is host cell ß2-AR signaling that is essential for decreasing GVHD. These data reveal how baseline levels of ß-adrenergic receptor signaling can influence murine GVHD and point to the feasibility of manipulation of ß2-AR signaling to ameliorate GVHD in the clinical setting.

The Impact of Housing Temperature-Induced Chronic Stress on Preclinical Mouse Tumor Models and Therapeutic Responses: An Important Role for the Nervous System.

In the last 10-15 years, there has been a recognition that the catecholamines (norepinephrine, NE, and epinephrine, Epi) released by the sympathetic nervous system under stressful conditions promote tumor growth through a variety of mechanisms. Tumors recruit autonomic nerves during their development and NE is then released locally in the tumor microenvironment (TME). Acting through adrenergic receptors present on a variety of cells in the TME, NE and Epi induce proliferation, resistance to apoptosis, epithelial to mesenchymal transition, metastasis of tumor cells, angiogenesis, and inflammation in the TME. These pre-clinical studies have been conducted in mouse models whose care and housing parameters are outlined in "The Guide for the Care and Use of Laboratory Animals [1]. In particular, the Guide mandates that mice be housed at standardized sub-thermoneutral temperatures; however, this causes a state of chronic cold-stress and elevated levels of NE. Although mice are able to maintain a normal body temperature when kept at these cool temperatures, it is becoming clear that this cold-stress is sufficient to activate physiological changes which affect experimental outcomes. We find that when mice are housed under standard, sub-thermoneutral temperatures (~22 °C, ST), tumor growth is significantly greater than when mice are housed at thermoneutrality (~30 °C TT). We also find that the anti-tumor immune response is suppressed at ST and this immunosuppression can be reversed by housing mice at TT or by administration of propranolol (a ß-adrenergic receptor antagonist) to mice housed at ST. Furthermore, at ST tumors are more resistant to therapy and can also be sensitized to cytotoxic therapies by housing mice at TT or by treating mice with propranolol. The implications of these observations are particularly relevant to the way in which experiments conducted in preclinical models are interpreted and the findings implemented in the clinic. It may be that the disappointing failure of many new therapies to fulfill their promise in the clinic is related to an incomplete preclinical assessment in mouse models. Further, an expanded understanding of the efficacy of a therapy alone or in combination obtained by testing under a wider range of conditions would better predict how patients, who are under various levels of stress, might respond in a clinical setting. This may be particularly important to consider since we now appreciate that long term outcome of many therapies depends on eliciting an immune response.It is clear that the outcome of metabolic experiments, immunological investigations and therapeutic efficacy testing in tumors of mice housed at ST is restricted and expanding these experiments to include results obtained at TT may provide us with valuable information that would otherwise be overlooked.

Mild cold-stress depresses immune responses: Implications for cancer models involving laboratory mice.

Physiologically accurate mouse models of cancer are critical in the pre-clinical development of novel cancer therapies. However, current standardized animal-housing temperatures elicit chronic cold-associated stress in mice, which is further increased in the presence of tumor. This cold-stress significantly impacts experimental outcomes. Data from our lab and others suggest standard housing fundamentally alters murine physiology, and this can produce altered immune baselines in tumor and other disease models. Researchers may thus underestimate the efficacy of therapies that are benefitted by immune responses. A potential mediator, norepinephrine, also underlies stress pathways common in mice and humans. Therefore, research into mechanisms connecting cold-stress and norepinephrine signaling with immune depression in mice could highlight new combination therapies for humans to simultaneously target stress while stimulating anti-tumor immunity.

Baseline tumor growth and immune control in laboratory mice are significantly influenced by subthermoneutral housing temperature.

We show here that fundamental aspects of antitumor immunity in mice are significantly influenced by ambient housing temperature. Standard housing temperature for laboratory mice in research facilities is mandated to be between 20-26 °C; however, these subthermoneutral temperatures cause mild chronic cold stress, activating thermogenesis to maintain normal body temperature. When stress is alleviated by housing at thermoneutral ambient temperature (30-31 °C), we observe a striking reduction in tumor formation, growth rate and metastasis. This improved control of tumor growth is dependent upon the adaptive immune system. We observe significantly increased numbers of antigen-specific CD8(+) T lymphocytes and CD8(+) T cells with an activated phenotype in the tumor microenvironment at thermoneutrality. At the same time there is a significant reduction in numbers of immunosuppressive MDSCs and regulatory T lymphocytes. Notably, in temperature preference studies, tumor-bearing mice select a higher ambient temperature than non-tumor-bearing mice, suggesting that tumor-bearing mice experience a greater degree of cold-stress. Overall, our data raise the hypothesis that suppression of antitumor immunity is an outcome of cold stress-induced thermogenesis. Therefore, the common approach of studying immunity against tumors in mice housed only at standard room temperature may be limiting our understanding of the full potential of the antitumor immune response.

A pilot study of the effects of mild systemic heating on human head and neck tumour xenografts: Analysis of tumour perfusion, interstitial fluid pressure, hypoxia and efficacy of radiation therapy.

PURPOSE: The tumour microenvironment is frequently hypoxic, poorly perfused, and exhibits abnormally high interstitial fluid pressure. These factors can significantly reduce efficacy of chemo and radiation therapies. The present study aims to determine whether mild systemic heating alters these parameters and improves response to radiation in human head and neck tumour xenografts in SCID mice. MATERIALS AND METHODS: SCID mice were injected with FaDu cells (a human head and neck carcinoma cell line), or implanted with a resected patient head and neck squamous cell carcinoma grown as a xenograft, followed by mild systemic heating. Body temperature during heating was maintained at 39.5 ± 0.5 °C for 4 h. Interstitial fluid pressure (IFP), hypoxia and relative tumour perfusion in the tumours were measured at 2 and 24 h post-heating. Tumour vessel perfusion was measured 24 h post-heating, coinciding with the first dose of fractionated radiotherapy. RESULTS: Heating tumour-bearing mice resulted in significant decrease in intratumoural IFP, increased the number of perfused tumour blood vessels as well as relative tumour perfusion in both tumour models. Intratumoural hypoxia was also reduced in tumours of mice that received heat treatment. Mice bearing FaDu tumours heated 24 h prior to five daily radiation treatments exhibited significantly enhanced tumour response compared to tumours in control mice. CONCLUSIONS: Mild systemic heating can significantly alter the tumour microenvironment of human head and neck tumour xenograft models, decreasing IFP and hypoxia while increasing microvascular perfusion. Collectively, these effects could be responsible for the improved response to radiotherapy.

A nervous tumor microenvironment: the impact of adrenergic stress on cancer cells, immunosuppression, and immunotherapeutic response.

Long conserved mechanisms maintain homeostasis in living creatures in response to a variety of stresses. However, continuous exposure to stress can result in unabated production of stress hormones, especially catecholamines, which can have detrimental health effects. While the long-term effects of chronic stress have well-known physiological consequences, recent discoveries have revealed that stress may affect therapeutic efficacy in cancer. Growing epidemiological evidence reveals strong correlations between progression-free and long-term survival and ß-blocker usage in cancer patients. In this review, we summarize the current understanding of how the catecholamines, epinephrine and norepinephrine, affect cancer cell survival and tumor progression. We also highlight new data exploring the potential contributions of stress to immunosuppression in the tumor microenvironment and the implications of these findings for the efficacy of immunotherapies.

Elevating body temperature enhances hematopoiesis and neutrophil recovery after total body irradiation in an IL-1-, IL-17-, and G-CSF-dependent manner.

Neutropenia is a common side effect of cytotoxic chemotherapy and radiation, increasing the risk of infection in these patients. Here we examined the impact of body temperature on neutrophil recovery in the blood and bone marrow after total body irradiation (TBI). Mice were exposed to either 3 or 6 Gy TBI followed by a mild heat treatment that temporarily raised core body temperature to approximately 39.5°C. Neutrophil recovery was then compared with control mice that received either TBI alone heat treatment alone. Mice that received both TBI and heat treatment exhibited a significant increase in the rate of neutrophil recovery in the blood and an increase in the number of marrow hematopoietic stem cells and neutrophil progenitors compared with that seen in mice that received either TBI or heat alone. The combination treatment also increased G-CSF concentrations in the serum, bone marrow, and intestinal tissue and IL-17, IL-1ß, and IL-1α concentrations in the intestinal tissue after TBI. Neutralizing G-CSF or inhibiting IL-17 or IL-1 signaling significantly blocked the thermally mediated increase in neutrophil numbers. These findings suggest that a physiologically relevant increase in body temperature can accelerate recovery from neutropenia after TBI through a G-CSF-, IL-17-, and IL-1-dependent mechanism.

Housing temperature influences the pattern of heat shock protein induction in mice following mild whole body hyperthermia.

PURPOSE: Researchers studying the murine response to stress generally use mice housed under standard, nationally mandated conditions as controls. Few investigators are concerned whether basic physical aspects of mouse housing could be an additional source of stress, capable of influencing the subsequent impact of an experimentally applied stressor. We have recently become aware of the potential for housing conditions to impact important physiological and immunological properties in mice. MATERIALS AND METHODS: Here we sought to determine whether housing mice at standard temperature (ST; 22 °C) vs. thermoneutral temperature (TT; 30 °C) influences baseline expression of heat shock proteins (HSPs) and their typical induction following a whole body heating. RESULTS: There were no significant differences in baseline expression of HSPs at ST and TT. However, in several cases, the induction of Hsp70, Hsp110 and Hsp90 in tissues of mice maintained at ST was greater than at TT following 6 h of heating (which elevated core body temperature to 39.5 °C). This loss of HSP induction was also seen when mice housed at ST were treated with propranolol, a ß-adrenergic receptor antagonist, used clinically to treat hypertension and stress. CONCLUSIONS: Taken together, these data show that housing temperature significantly influences the expression of HSPs in mice after whole body heating and thus should be considered when stress responses are studied in mice.