CXC chemokines: a new family of heat-shock proteins?

Modulated Electro-Hyperthermia Facilitates NK-Cell Infiltration and Growth Arrest of Human A2058 Melanoma in a Xenograft Model

Modulated electro-hyperthermia (mEHT), induced by 13.56 MHz radiofrequency, has been demonstrated both in preclinical and clinical studies to efficiently induce tumor damage and complement other treatment modalities. Here, we used a mouse xenograft model of human melanoma (A2058) to test mEHT (~42°C) both alone and combined with NK-cell immunotherapy. A single 30 min shot of mEHT resulted in significant tumor damage due to induced stress, marked by high hsp70 expression followed by significant upregulation of cleaved/activated caspase-3 and p53. When mEHT was combined with either primary human NK cells or the IL-2 independent NK-92MI cell line injected subcutaneously, the accumulation of NK cells was observed at the mEHT pretreated melanoma nodules but not at the untreated controls. mEHT induced the upregulation of the chemoattractant CXCL11 and increased the expression of the matrix metalloproteinase MMP2 which could account for the NK-cell attraction into the treated melanoma. In conclusion, mEHT monotherapy of melanoma xenograft tumors induced irreversible heat and cell stress leading to caspase dependent apoptosis to be driven by p53. mEHT could support the intratumoral attraction of distantly injected NK-cells, contributed by CXCL11 and MMP2 upregulation, resulting in an additive tumor destruction and growth inhibition. Therefore, mEHT may offer itself as a good partner for immunotherapy.

Functional differences of three CXCL10 homologues in the giant spiny frog Quasipaa spinosa

Chemokines are a superfamily of structurally related chemotactic cytokines exerting significant roles in acting as a bridge between the innate and adaptive immune responses. In this study, we identified three CXC motif chemokine 10 (CXCL10) homologues (QsCXCL10-1, QsCXCL10-2 and QsCXCL10-3) from giant spiny frog Quasipaa spinosa. All three deduced QsCXCL10 proteins contained four conserved cysteine residues as found in other known CXC chemokines. Phylogenetic analysis showed that QsCXCL10-1, 2, 3 and other CXCL10s in amphibian were grouped together to form a separate clade. These three QsCXCL10s were highly expressed in spleen and blood. Upon infection with Staphylococcus aureus or Aeromonas hydrophila, the expressions of QsCXCL10s were markedly increased in spleen and blood during biotic stresses. Meanwhile, the QsCXCL10s transcription in liver could also be up-regulated under abiotic stresses such as cold and heat stresses. The recombinant proteins of frog CXCL10 homologues were produced and purified in E. coli and possessed similar but differential bioactivities. Both rCXCL10-1 and rCXCL10-2 had strong effects on the up-regulation of pro-inflammatory cytokines (TNF-α, IL-1β and IL-8) in vivo, whereas rCXCL10-3 induced a weak expression of these cytokines. Moreover, the rCXCL10-1 and rCXCL10-2 could strongly promote splenocyte proliferation and induce lymphocytes migration, while rCXCL10-3 had limited effects on these biological processes. All three frog chemokines triggered their functional activities by engaging CXC motif chemokine receptor 3 (CXCR3). Taken together, these results revealed that the three QsCXCL10s had similar but differential functional activities in mediating immune responses and host defenses, which might contribute to a better understanding of the functional evolution of CXCL10 in vertebrates.

Roles of heat shock factor 1 beyond the heat shock response

Various stress factors leading to protein damage induce the activation of an evolutionarily conserved cell protective mechanism, the heat shock response (HSR), to maintain protein homeostasis in virtually all eukaryotic cells. Heat shock factor 1 (HSF1) plays a central role in the HSR. HSF1 was initially known as a transcription factor that upregulates genes encoding heat shock proteins (HSPs), also called molecular chaperones, which assist in refolding or degrading injured intracellular proteins. However, recent accumulating evidence indicates multiple additional functions for HSF1 beyond the activation of HSPs. Here, we present a nearly comprehensive list of non-HSP-related target genes of HSF1 identified so far. Through controlling these targets, HSF1 acts in diverse stress-induced cellular processes and molecular mechanisms, including the endoplasmic reticulum unfolded protein response and ubiquitin-proteasome system, multidrug resistance, autophagy, apoptosis, immune response, cell growth arrest, differentiation underlying developmental diapause, chromatin remodelling, cancer development, and ageing. Hence, HSF1 emerges as a major orchestrator of cellular stress response pathways.

Fever, immunity, and molecular adaptations

The heat shock response (HSR) is an ancient and highly conserved process that is essential for coping with environmental stresses, including extremes of temperature. Fever is a more recently evolved response, during which organisms temporarily subject themselves to thermal stress in the face of infections. We review the phylogenetically conserved mechanisms that regulate fever and discuss the effects that febrile-range temperatures have on multiple biological processes involved in host defense and cell death and survival, including the HSR and its implications for patients with severe sepsis, trauma, and other acute systemic inflammatory states. Heat shock factor-1, a heat-induced transcriptional enhancer is not only the central regulator of the HSR but also regulates expression of pivotal cytokines and early response genes. Febrile-range temperatures exert additional immunomodulatory effects by activating mitogen-activated protein kinase cascades and accelerating apoptosis in some cell types. This results in accelerated pathogen clearance, but increased collateral tissue injury, thus the net effect of exposure to febrile range temperature depends in part on the site and nature of the pathologic process and the specific treatment provided.

Do reciprocal interactions between cell stress proteins and cytokines create a new intra-/extra-cellular signalling nexus?

Cytokine biology began in the 1950s, and by 1988, a large number of cytokines, with a myriad of biological actions, had been discovered. In 1988, the basis of the protein chaperoning function of the heat shock, or cell stress, proteins was identified, and it was assumed that this was their major activity. However, since this time, evidence has accumulated to show that cell stress proteins are secreted by cells and can stimulate cellular cytokine synthesis with the generation of pro- and/or anti-inflammatory cytokine networks. Cell stress can also control cytokine synthesis, and cytokines are able to induce, or even inhibit, the synthesis of selected cell stress proteins and may also promote their release. How cell stress proteins control the formation of cytokines is not understood and how cytokines control cell stress protein synthesis depends on the cellular compartment experiencing stress, with cytoplasmic heat shock factor 1 (HSF1) having a variety of actions on cytokine gene transcription. The endoplasmic reticulum unfolded protein response also exhibits a complex set of behaviours in terms of control of cytokine synthesis. In addition, individual intracellular cell stress proteins, such as Hsp27 and Hsp90, have major roles in controlling cellular responses to cytokines and in controlling cytokine synthesis in response to exogenous factors. While still confusing, the literature supports the hypothesis that cell stress proteins and cytokines may generate complex intra- and extra-cellular networks, which function in the control of cells to external and internal stressors and suggests the cell stress response as a key parameter in cytokine network generation and, as a consequence, in control of immunity.

Genome-wide analysis of the heat stress response in Zebu (Sahiwal) cattle

Environmental-induced hyperthermia compromises animal production with drastic economic consequences to global animal agriculture and jeopardizes animal welfare. Heat stress is a major stressor that occurs as a result of an imbalance between heat production within the body and its dissipation and it affects animals at cellular, molecular and ecological levels. The molecular mechanism underlying the physiology of heat stress in the cattle remains undefined. The present study sought to evaluate mRNA expression profiles in the cattle blood in response to heat stress. In this study we report the genes that were differentially expressed in response to heat stress using global scale genome expression technology (Microarray). Four Sahiwal heifers were exposed to 42°C with 90% humidity for 4h followed by normothermia. Gene expression changes include activation of heat shock transcription factor 1 (HSF1), increased expression of heat shock proteins (HSP) and decreased expression and synthesis of other proteins, immune system activation via extracellular secretion of HSP. A cDNA microarray analysis found 140 transcripts to be up-regulated and 77 down-regulated in the cattle blood after heat treatment (P<0.05). But still a comprehensive explanation for the direction of fold change and the specific genes involved in response to acute heat stress still remains to be explored. These findings may provide insights into the underlying mechanism of physiology of heat stress in cattle. Understanding the biology and mechanisms of heat stress is critical to developing approaches to ameliorate current production issues for improving animal performance and agriculture economics.

Fever, hyperthermia and the heat shock response

The heat shock response is a highly conserved primitive response that is essential for survival against a wide range of stresses, including extremes of temperature. Fever is a more recently evolved response, during which organisms raise their core body temperature and temporarily subject themselves to thermal stress in the face of infections. The present review documents studies showing the potential overlap between the febrile response and the heat shock response and how both activate the same common transcriptional programme (although with different magnitudes) including the stress-activated transcription factor, heat shock factor-1, to modify host defences in the context of infection, inflammation and injury. The review focuses primarily on how hyperthermia within the febrile range that often accompanies infections and inflammation acts as a biological response modifier and modifies innate immune responses. The characteristic 2-3 °C increase in core body temperature during fever activates and utilises elements of the heat shock response pathway to modify cytokine and chemokine gene expression, cellular signalling and immune cell mobilisation to sites of inflammation, infection and injury. Interestingly, typical proinflammatory agonists such as Toll-like receptor agonists modify the heat shock-induced transcriptional programme and expression of HSP genes following co-exposure to febrile range hyperthermia or heat shock, suggesting a complex reciprocal regulation between the inflammatory pathway and the heat shock response pathway.

Temperature-induced transcription of inflammatory mediators and the influence of Hsp70 following LPS stimulation of southern bluefin tuna peripheral blood leukocytes and kidney homogenates

Temperature is known to influence inflammatory signalling in mammals, but far less understood in fish. The aim of the present study was to explore the potential effects of temperature on innate immune signalling in head kidney and leukocyte populations of the economically important southern bluefin tuna through the identification and utilization of gene expression targets in vitro. Here, we identified the mRNA sequences of five potential inflammatory mediators - TNFα (1 and 2), IL-1β, IL-8, and Cox2 - and demonstrate induction of four - TNFα (2), IL-1β, IL-8, and Cox2 - following LPS stimulation of both peripheral blood leukocytes and head kidney homogenates in vitro by real-time quantitative PCR. Comparison of transcriptional expression in cultures held at 18 and 25 °C (both within the presumed natural temperature range of this heterothermic species) showed accelerated transcription of cytokines TNFα, IL-1β and IL-8 following LPS stimulation at 25 °C in both tissue types. Peak induction reached comparable levels for each transcript at both temperatures during the 24 h test period with only limited (if any) protraction in expression resulting from cold temperature (18 °C) incubation. Partial mRNA sequences were also identified for both the constitutively expressed and heat inducible chaperone proteins Hsc70 and Hsp70, and 24 h incubation at 25 °C was sufficient to induce Hsp70 transcription in leukocyte but not in head kidney cell populations. Taken together these findings suggest that temperature exerts influence in the timing but not the degree of an innate inflammatory response in bluefin tuna and that different cell populations have differential responsiveness to heat shock in this heterothermic species. Further, LPS stimulation failed to induce Hsp70 at either incubation temperature in leukocytes; whereas 25 °C incubation caused Hsp70 up-regulation in leukocytes with or without the presence of LPS. This suggests that Hsp70 does not play a direct role in immune responsiveness for this species and that an environmental temperature of 25 °C in excess of 24 h initiates a cellular stress response in blood cells of this organism. Lastly, a strong correlation between Hsp70 and IL-8 transcriptional expression was observed following LPS/heat shock stimulation of leukocytes and five potential heat shock response elements were subsequently identified on the gene promoter region of IL-8 indicating that heat shock co-activation of this chemokine previously identified in mammals is also likely present in fish.

Airway smooth muscle as a target in asthma and the beneficial effects of bronchial thermoplasty

Airflow within the airways is determined directly by the lumenal area of that airway. In this paper, we consider several factors which can reduce airway lumenal area, including thickening and/or active constriction of the airway smooth muscle (ASM). The latter cell type can also contribute in part to inflammation, another feature of asthma, through its ability to take on a synthetic/secretory phenotype. The ASM therefore becomes a strategically important target in the treatment of asthma, given these key contributions to the pathophysiology of that disease. Pharmacological approaches have been developed to elicit relaxation of the ASM, but these are not always effective in all patients, nor do they address the long-term structural changes which impinge on the airway lumen. The recent discovery that thermal energy can be used to ablate smooth muscle has led to the development of a novel physical intervention—bronchial thermoplasty—in the treatment of asthma. Here, we review the evolution of this novel approach, consider some of the possible mechanisms that account for its salutary effects, and pose new questions which may lead to even better therapies for asthma.

Nuclear factor-kappa B is not involved in titanium dioxide-induced inflammation

Research over recent years have shown that titanium dioxide (TiO2) nanoparticles (NPs) induce inflammation in various lung, kidney, liver and brain cells. Although the mechanism of inflammation is unclear, existing literature suggests the underlying role of oxidative stress. On the other hand, it has also been shown that nuclear factor-kappa B (NF-kappaB) is activated in response to pro-inflammatory cytokines. In this study we investigated the involvement of NF-kappaB in TiO2-induced inflammation in human lung adenocarcinomic epithelial cells (A549 cells). After 24h of treatment, IL-8 protein release from A549 cells, induced by 10, 50 and 250 microg/ml of P25 TiO2 NPs, were statistically significantly raised, compared to that of the control. This finding corroborates existing literature in that TiO2 NPs induce a dose-dependent increase in the release of IL-8 protein when exposed to A549 cells. However, the binding of NF-kappaB DNA was not affected after 6 h of incubation with P25. Therefore, NF-kappaB DNA binding is not the likely transcription pathway that leads to TiO2-induced inflammation.

The second sodium pump: from the function to the gene

Transepithelial Na(+) transport is mediated by passive Na(+) entry across the luminal membrane and exit through the basolateral membrane by two active mechanisms: the Na(+)/K(+) pump and the second sodium pump. These processes are associated with the ouabain-sensitive Na(+)/K(+)-ATPase and the ouabain-insensitive, furosemide-inhibitable Na(+)-ATPase, respectively. Over the last 40 years, the second sodium pump has not been successfully associated with any particular membrane protein. Recently, however, purification and cloning of intestinal α-subunit of the Na(+)-ATPase from guinea pig allowed us to define it as a unique biochemical and molecular entity. The Na(+)- and Na(+)/K(+)-ATPase genes are at the same locus, atp1a1, but have independent promoters and some different exons. Herein, we spotlight the functional characteristics of the second sodium pump, and the associated Na(+)-ATPase, in the context of its role in transepithelial transport and its response to a variety of physiological and pathophysiological conditions. Identification of the Na(+)-ATPase gene (atna) allowed us, using a bioinformatics approach, to explore the tertiary structure of the protein in relation to other P-type ATPases and to predict regulatory sites in the promoter region. Potential regulatory sites linked to inflammation and cellular stress were identified in the atna gene. In addition, a human atna ortholog was recognized. Finally, experimental data obtained using spontaneously hypertensive rats suggest that the Na(+)-ATPase could play a role in the pathogenesis of essential hypertension. Thus, the participation of the second sodium pump in transepithelial Na(+) transport and cellular Na(+) homeostasis leads us to reconsider its role in health and disease.

Febrile-range hyperthermia modifies endothelial and neutrophilic functions to promote extravasation

Acute respiratory distress syndrome (ARDS) is a neutrophil (polymorphonuclear leukocyte; PMN)-driven lung injury that is associated with fever and heat-stroke, and involves approximately 40% mortality. In murine models of acute lung injury (ALI), febrile-range hyperthermia (FRH) enhanced PMN accumulation, vascular permeability, and epithelial injury, in part by augmenting pulmonary cysteine-x-cysteine (CXC) chemokine expression. To determine whether FRH increases chemokine responsiveness within the lung, we used in vivo and in vitro models that bypass the endogenous generation of chemokines. We measured PMN transalveolar migration (TAM) in mice after intratracheal instillations of the human CXC chemokine IL-8 in vivo, and of IL-8-directed PMN transendothelial migration (TEM) through human lung microvascular endothelial cell (HMVEC-L) monolayers in vitro. Pre-exposure to FRH increased in vivo IL-8-directed PMN TAM by 23.5-fold and in vitro TEM by 7-fold. Adoptive PMN transfer demonstrated that enhanced PMN TAM required both PMN donors and recipients to be exposed to FRH, suggesting interdependent effects on PMNs and endothelium. FRH exposure caused the activation of extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase in lung homogenates and circulating PMNs, with an associated increase in HSP27 phosphorylation and stress-fiber formation. The inhibition of these signaling pathways with U0126 and SB203580 blocked the effects of FRH on PMN extravasation in vivo and in vitro. Collectively, these results (1) demonstrate that FRH augments chemokine-directed PMN extravasation through direct effects on endothelium and PMNs, (2) identify ERK and p38 signaling pathways in the effect, and (3) underscore the complex effects of physiologic temperature change on innate immune function and its potential consequences for lung injury.

Heat shock protein families 70 and 90 in Duchenne muscular dystrophy and inflammatory myopathy: balancing muscle protection and destruction

Heat shock proteins are important factors in skeletal muscle physiology and stress response. We examined the effects of chronic inflammation on the distribution of heat shock protein families 70 and 90 using immunofluorescence and Western blotting, in muscle biopsies from 33 idiopathic inflammatory myopathy patients [aged 26-66 (dermatomyositis), 17-78 (polymyositis) and 57-80 (sporadic inclusion body myositis) years], and seven Duchenne muscular dystrophy patients (aged 3-19 years). Our results reveal the multifaceted role played by chaperones in inflammatory muscle tissue. On the one hand, regenerating, atrophic and vacuolated muscle fibers displayed upregulation of both protein families. Higher levels of chaperones in challenged fibers point to the myocyte's attempt to restore and regenerate. On the other hand, heat shock proteins of the 90 family were strongly upregulated in macrophages and cytotoxic T-cells actively invading nonnecrotic muscle fibers of sporadic inclusion body myositis and polymyositis, probably conferring enhanced myocytotoxic capacity. Our data provide positive arguments for exploring heat shock protein 90-based therapy in inflammatory muscle disease.

Distinct, gene-specific effect of heat shock on heat shock factor-1 recruitment and gene expression of CXC chemokine genes

The heat shock (HS) response, a phylogenetically conserved ubiquitous response to stress, is generally characterized by the induced expression of heat shock protein (HSP) genes. Our earlier studies showed that the stress-activated transcription factor, heat shock factor-1 (HSF1), activated at febrile range or HS temperatures also modified expression of non-HSP genes including cytokine and chemokine genes. We also showed by in silico analysis that 28 among 29 human and mouse CXC chemokine genes had multiple putative heat shock response elements (HSEs) present in their gene promoters. To further determine whether these potential HSEs were functional and bound HSF1, we analyzed the recruitment of HSF1 to promoters of 5 human CXC chemokine genes (CXCL-1, 2, 3, 5 and 8) by chromatin immunoprecipitation (ChIP) assay and analyzed the effect of HS exposure on tumor necrosis factor-α (TNFα)-induced expression of these genes in human lung epithelial-like A549 cells. HSF1 ChIP analysis showed that HSF1 was recruited to all but one of these CXC chemokine genes (CXCL-3) and HS caused a significant increase in recruitment of HSF1 to one or multiple HSEs present in the promoters of CXCL-1, 2, 5 and 8 genes. However, the effect of HS exposure on expression of these genes showed a variable gene-specific effect. For example, CXCL8 expression was markedly enhanced (p<0.05) whereas CXCL5 expression was significantly repressed (p<0.05) in cells exposed to HS coincident with TNFα stimulation. In contrast, expression of CXCL1 and CXCL2, despite HSF1 recruitment to their promoters, was not affected by HS exposure. Our results indicate that some, if not all, putative HSEs present in the CXC chemokine gene promoters are functional and recruit HSF1 in vivo but the effects on gene expression are variable and gene specific. We speculate, the physical proximity and interactions of other transcription factors and co-regulators with HSF1 could be critical to determining the effects of HS on the expression of these genes.

Fas ligation and tumor necrosis factor α activation of murine astrocytes promote heat shock factor-1 activation and heat shock protein expression leading to chemokine induction and cell survival

Death-inducing ligands tumor necrosis factor alpha (TNFα) and Fas ligand (FasL) do not kill cultured astrocytes; instead they induce a variety of chemokines including macrophage-inflammatory protein-1α/CC chemokine ligand 3 (CCL3), monocyte chemoattractant protein-1 (CC CCL-2), macrophage-inflammatory protein-2/CXC chemokine ligand 2 (CXCL2, a murine homologue of interleukin 8), and interferon-induced protein of 10 kDa (CXCL10). Induction is enhanced by protein synthesis inhibition suggesting the existence of endogenous inhibitors. ERK, NF-κB, heat shock factor-1 (HSF-1) and heat shock proteins were examined for their possible roles in signal transduction. Inhibition of ERK activation by PD98059 partially inhibited expression of all but FasL-induced CXCL10. Although inhibition of NF-κB DNA binding inhibited chemokine induction, PD98059 did not inhibit TNFα-induced NF-κB DNA binding suggesting that ERK serves an NF-κB-independent pathway. Heat shock itself induced astrocytic chemokine expression; both TNFα and FasL induced HSF-1 DNA binding and Hsp72 production; and Hsp72-induced chemokine expression. Inhibition of either HSF-1 binding with quercetin or heat shock protein synthesis with KNK437 compromised chemokine induction without compromising cell survival. These data suggest that the induction of heat shock proteins via HSF-1 contribute to the TNFα- and FasL-induced expression of chemokines in astrocytes.

Temporal changes in circulating levels of plasma interleukin-8 during peripartum period in Murrah buffaloes (Bubalus bubalis) under subtropical climate

The objective of this study was to elucidate the changes in circulating levels of plasma interleukin-8 (IL-8) during peripartum period in Murrah buffaloes (Bubalus bubalis). IL-8 was estimated in blood plasma of healthy peripartum Murrah buffaloes (n=6) on days ± 30, ± 15, ± 5, ± 3, ± 1 and 0 pre- and postpartum with respect to the day of parturition (day 0) in each of the two different seasons (hot-humid and spring). The mean microclimate Temperature-Humidity Index (THI) during spring season was significantly lower (p<0.01) than the corresponding THI in hot-humid season. In both the seasons, plasma IL-8 remained lower in prepartum period (≤ 46.56 ± 14.08 pg/ml during spring and ≤ 73.18 ± 18.56 pg/ml during hot-humid season) than in the postpartum period (≥ 51.41 ± 13.82 pg/ml during spring and ≥ 84.13 ± 16.97 pg/ml in hot humid season). During spring, the IL-8 levels were significantly higher (P<0.05) on days+5 and +15 postpartum in comparison to the IL-8 levels on days -30, -5, and -3 prepartum. During hot-humid season, IL-8 level was significantly higher (P<0.05) on day +30 as compared to the IL-8 levels on days -30 and -5 prepartum. The correlation between IL-8 and mean microclimate THI was significant (r=0.25, P<0.01). From the results, it is concluded that peripartum period in buffaloes is associated with an inflammatory response leading to significantly higher plasma IL-8 during parturition and postpartum period than in the pre-partum period.

Involvement of inflammatory chemokines in survival of human monocytes fed with malarial pigment

Hemozoin (HZ)-fed monocytes are exposed to strong oxidative stress, releasing large amounts of peroxidation derivatives with subsequent impairment of numerous functions and overproduction of proinflammatory cytokines. However, the histopathology at autopsy of tissues from patients with severe malaria showed abundant HZ in Kupffer cells and other tissue macrophages, suggesting that functional impairment and cytokine production are not accompanied by cell death. The aim of the present study was to clarify the role of HZ in cell survival, focusing on the qualitative and temporal expression patterns of proinflammatory and antiapoptotic molecules. Immunocytochemical and flow cytometric analyses showed that the long-term viability of human monocytes was unaffected by HZ. Short-term analysis by macroarray of a complete panel of cytokines and real-time reverse transcription (RT)-PCR experiments showed that HZ immediately induced interleukin-1β (IL-1β) gene expression, followed by transcription of eight additional chemokines (IL-8, epithelial cell-derived neutrophil-activating peptide 78 [ENA-78], growth-regulated oncogene α [GROα], GROβ, GROγ, macrophage inflammatory protein 1α [MIP-1α], MIP-1β, and monocyte chemoattractant protein 1 [MCP-1]), two cytokines (tumor necrosis factor alpha [TNF-α] and IL-1receptor antagonist [IL-1RA]), and the cytokine/chemokine-related proteolytic enzyme matrix metalloproteinase 9 (MMP-9). Furthermore, real-time RT-PCR showed that 15-HETE, a potent lipoperoxidation derivative generated by HZ through heme catalysis, recapitulated the effects of HZ on the expression of four of the chemokines. Intermediate-term investigation by Western blotting showed that HZ increased expression of HSP27, a chemokine-related protein with antiapoptotic properties. Taken together, the present data suggest that apoptosis of HZ-fed monocytes is prevented through a cascade involving 15-HETE-mediated upregulation of IL-1β transcription, rapidly sustained by chemokine, TNF-α, MMP-9, and IL-1RA transcription and upregulation of HSP27 protein expression.

Diverse immune mechanisms may contribute to the survival benefit seen in cancer patients receiving hyperthermia

There is increasing documentation of significant survival benefits achieved in cancer patients treated with hyperthermia in combination with radiation and/or chemotherapy. Most evidence collected regarding the mechanisms by which hyperthermia positively influences tumor control has centered on in vitro data showing the ability of heat shock temperatures (usually above 42 degrees C) to result in radio- or chemosensitization. However, these high temperatures are difficult to achieve in vivo, and new thermometry data in patients reveal that much of the tumor and surrounding region is only heated to 40-41 degrees C or less as a result of vascular drainage from the target zone of the heated tumor. Thus, there is now a growing appreciation of a role for mild hyperthermia in the stimulation of various arms of the immune system in contributing to long term protection from tumor growth. Indeed, a review of recent literature suggests the existence of an array of thermally sensitive functions which may exist naturally to help the organism to establish a new "set point" of immune responsiveness during fever. This review summarizes recent literature identifying complex effects of temperature on immune cells and potential cellular mechanisms by which increased temperature may enhance immune surveillance.

Hyperthermia in the febrile range induces HSP72 expression proportional to exposure temperature but not to HSF-1 DNA-binding activity in human lung epithelial A549 cells

Expression of heat shock proteins (HSPs) is classically activated at temperatures above the physiologic range (>or=42 degrees C) via activation of the stress-activated transcription factor, heat shock factor-1 (HSF-1). Several studies suggest that less extreme hyperthermia, especially within the febrile range, as occurs during fever and exertional/environmental hyperthemia, can also activate HSF-1 and enhance HSP expression. We compared HSP72 protein and mRNA expression in human A549 lung epithelial cells continuously exposed to 38.5 degrees C, 39.5 degrees C, or 41 degrees C or exposed to a classic heat shock (42 degrees C for 2 h). We found that expression of HSP72 protein and mRNA increased linearly as incubation temperature was increased from 37 degrees C to 41 degrees C, but increased abruptly when the incubation temperature was raised to 42 degrees C. A similar response in luciferase activity was observed using A549 cells stably transfected with an HSF-1-responsive luciferase reporter plasmid. However, activation of intranuclear HSF-1 DNA-binding activity was comparable at 38.5 degrees C, 39.5 degrees C, and 41 degrees C and only modestly greater at 42 degrees C but the mobility of HSF1 protein on a denaturing gel was altered with increasing exposure temperature and was distinctly different at 42 degrees C. These findings indicate that the proportional changes in HSF-1-dependent HSP72 expression at febrile-range temperatures are dependent upon exposure time and temperature but not on the degree of HSF-1 DNA-binding activity. Instead, HSF-1-mediated HSP expression following hyperthermia and heat shock appears to be mediated, in addition to HSF-1 activation, by posttranslational modifications of HSF-1 protein.

Exaggerated expression of inflammatory mediators in vasoactive intestinal polypeptide knockout (VIP-/-) mice with cyclophosphamide (CYP)-induced cystitis

Vasoactive intestinal polypeptide (VIP) is an immunomodulatory neuropeptide distributed in micturition pathways. VIP(-/-) mice exhibit altered bladder function and neurochemical properties in micturition pathways after cyclophosphamide (CYP)-induced cystitis. Given VIP's role as an anti-inflammatory mediator, we hypothesized that VIP(-/-) mice would exhibit enhanced inflammatory mediator expression after cystitis. A mouse inflammatory cytokine and receptor RT2 profiler array was used to determine regulated transcripts in the urinary bladder of wild type (WT) and VIP(-/-) mice with or without CYP-induced cystitis (150 mg/kg; i.p.; 48 h). Four binary comparisons were made: WT control versus CYP treatment (48 h), VIP(-/-) control versus CYP treatment (48 h), WT control versus VIP(-/-) control, and WT with CYP treatment (48 h) versus VIP(-/-) with CYP treatment (48 h). The genes presented represent (1) greater than 1.5-fold change in either direction and (2) the p value is less than 0.05 for the comparison being made. Several regulated genes were validated using enzyme-linked immunoassays including IL-1beta and CXCL1. CYP treatment significantly (p < or = 0.001) increased expression of CXCL1 and IL-1beta in the urinary bladder of WT and VIP(-/-) mice, but expression in VIP(-/-) mice with CYP treatment was significantly (p < or = 0.001) greater (4.2- to 13-fold increase) than that observed in WT urinary bladder (3.6- to 5-fold increase). The data suggest that in VIP(-/-) mice with bladder inflammation, inflammatory mediators are increased above that observed in WT with CYP. This shift in balance may contribute to increased bladder dysfunction in VIP(-/-) mice with bladder inflammation and altered neurochemical expression in micturition pathways.

Heat shock co-activates interleukin-8 transcription

The heat shock (HS) response is a phylogenetically ancient cellular response to stress, including heat, that shifts gene expression to a set of conserved HS protein (HSP) genes. In our earlier studies, febrile-range hyperthermia (FRH) not only activated HSP gene expression, but also increased expression of CXC chemokines in mice, leading us to hypothesize that the CXC chemokine family of genes might be HS-responsive. To address this hypothesis we analyzed the effect of HS on the expression of IL-8/CXCL-8, a member of the human CXC family of ELR(+) chemokines. HS markedly enhanced TNF-alpha-induced IL-8 secretion in human A549 respiratory epithelial-like cells and in primary human small airway epithelial cells. IL-8 mRNA was also up-regulated by HS, but the stability of IL-8 mRNA was not affected. TNF-alpha-induced reporter activity of an IL-8 promoter construct IL8(-1471/+44)-luc stably transfected in A549 cells was also enhanced by HS. Electrophoretic mobility and chromatin immunoprecipitation assays showed that the stress-activated transcription factor heat shock factor-1 (HSF-1) binds to at least two putative heat shock response elements (HSE) present in the IL-8 promoter. Deletional reporter constructs lacking either one or both of these sites showed reduced HS responsiveness. Furthermore, depletion of HSF-1 using siRNA also reduced the effects HS on TNF-alpha-induced IL-8 expression, demonstrating that HSF-1 could also act to regulate IL-8 gene transcription. We speculate that during evolution the CXC chemokine genes may have co-opted elements of the HS response to amplify their expression and enhance neutrophil delivery during febrile illnesses.

Phagocytosis by human neutrophils is stimulated by a unique fungal cell wall component

Innate immunity depends upon recognition of surface features common to broad groups of pathogens. The glucose polymer beta-glucan has been implicated in fungal immune recognition. Fungal walls have two kinds of beta-glucan: beta-1,3-glucan and beta-1,6-glucan. Predominance of beta-1,3-glucan has led to the presumption that it is the key immunological determinant for neutrophils. Examining various beta-glucans for their ability to stimulate human neutrophils, we find that the minor cell wall component beta-1,6-glucan mediates neutrophil activity more efficiently than beta-1,3-glucan, as measured by engulfment, production of reactive oxygen species, and expression of heat shock proteins. Neutrophils rapidly ingest beads coated with beta-1,6-glucan while ignoring those coated with beta-1,3-glucan. Complement factors C3b/C3d are deposited on beta-1,6-glucan more readily than on beta-1,3-glucan. Beta-1,6-glucan is also important for efficient engulfment of the human pathogen Candida albicans. These unique stimulatory effects offer potential for directed stimulation of neutrophils in a therapeutic context.

The early transcriptional response of human granulocytes to infection with Candida albicans is not essential for killing but reflects cellular communications

Candida albicans is a polymorphic opportunistic fungus that can cause life-threatening systemic infections following hematogenous dissemination in patients susceptible to nosocomial infection. Neutrophils form part of the innate immune response, which is the first line of defense against microbes and is particularly important in C. albicans infections. To compare the transcriptional response of leukocytes exposed to C. albicans, we investigated the expression of key cytokine genes in polymorphonuclear and mononuclear leukocytes after incubation with C. albicans for 1 h. Isolated mononuclear cells expressed high levels of genes encoding proinflammatory signaling molecules, whereas neutrophils exhibited much lower levels, similar to those observed in whole blood. The global transcriptional profile of neutrophils was examined by using an immunology-biased human microarray to determine whether different morphological forms or the viability of C. albicans altered the transcriptome. Hyphal cells appeared to have the broadest effect, although the most strongly induced genes were regulated independently of morphology or viability. These genes were involved in proinflammatory cell-cell signaling, cell signal transduction, and cell growth. Generally, genes encoding known components of neutrophil granules showed no upregulation at this time point; however, lactoferrin, a well-known candidacidal peptide, was secreted by neutrophils. Addition to inhibitors of RNA or protein de novo synthesis did not influence the killing activity within 30 min. These results support the general notion that neutrophils do not require gene transcription to mount an immediate and direct attack against microbes. However, neutrophils exposed to C. albicans express genes involved in communication with other immune cells.

RANK ligand expression in heat shock factor-2 deficient mouse bone marrow stromal/preosteoblast cells

Heat Shock Proteins (HSP) are molecular chaperones activated upon cellular stress/stimuli. HSP gene expression is regulated by Heat Shock Factors (HSF). We have recently demonstrated a functional role for heat shock factor-2 (HSF-2) in fibroblast growth factor-2 (FGF-2)-induced RANK ligand (RANKL), a critical osteoclastogenic factor expression on stromal/preosteoblast cells. In the present study, we show that FGF-2 treatment did not induce RANKL expression in HSF-2-/-stromal/preosteoblast cells. Interestingly, HSF-2 deficiency resulted in rapid induction of alkaline phosphatase (ALP) activity and osteocalcin mRNA expression in these cells. Furthermore, FGF-2 did not induce osteoclast formation in co-culture of normal mouse spleen cells and HSF-2-/-stromal/preosteoblast cells. Electron microscopy analysis demonstrated that osteoclasts from HSF-2-/-mice have poorly developed ruffled borders. These data further confirm that HSF-2 plays an important role in FGF-2-induced RANKL expression in stromal/preosteoblast cells. HSF-2 deficiency has pleotropic effects on gene expression during osteoblast differentiation and osteoclastogenesis in the bone microenvironment. Novel therapeutic agents that modulate HSF-2 activation may have therapeutic utility against increased levels of FGF-2 and bone destruction associated with pathologic conditions.

Expression of fractalkine and fractalkine receptor in urinary bladder after cyclophosphamide (CYP)-induced cystitis

Alterations in the expression of the chemokine, fractalkine (CX3CL1), were examined in the urinary bladder after cyclophosphamide (CYP)-induced cystitis of varying duration: acute (4 h or 48 h), or chronic (10 day). CYP-induced cystitis significantly (p<or=0.01) increased fractalkine protein expression in the urinary bladder with acute (48 h) and chronic CYP treatment. Western blot analysis also demonstrated significantly (p<or=0.01) increased fractalkine expression in the whole urinary bladder with acute (1.5-2.2-fold) and chronic (3-fold) CYP-induced cystitis. Immunohistochemistry for fractalkine-immunoreactivity revealed little fractalkine-IR in control or acute (4 h) CYP-treated rat urinary bladders except in a vascular bed but showed no colocalization with nerve fibers in the suburothelial plexus in any experimental group. However, expression was significantly (p<or=0.001) upregulated in the urothelium with 48 h or chronic CYP treatment. Similarly, fractalkine receptor (CX3CR1)-IR was significantly (p<or=0.001) upregulated in the urothelium with 48 h or chronic CYP treatment. These studies demonstrated upregulation of the chemokine, fractalkine, in the urinary bladder and specifically in the urothelium with CYP-induced cystitis. Chemokines, and specifically, fractalkine, may be another class of neuromodulatory agents upregulated in the urinary bladder that can affect micturition function and sensory processing with cystitis and may represent novel, drug targets for cystitis.