Releasing signals, secretory pathways, and immune function of endogenous extracellular heat shock protein 72

The inflammasome and danger associated molecular patterns (DAMPs) are implicated in cytokine and chemokine responses following stressor exposure

Exposure to stressors or trauma in the absence of pathogenic challenge can stimulate a systemic sterile inflammatory response characterized by high concentrations of blood and tissue cytokines, chemokines, and danger associated molecular patterns (DAMPs) such as heat shock protein-72 (Hsp72), and uric acid. The signaling pathways responsible for these responses remain unclear, however, the inflammasome may play a role. In vitro, DAMPs are known to stimulate the inflammasome in the presence of LPS to activate caspase-1 which cleaves immature precursors of interleukin (IL)-1β and IL-18 into their mature releasable forms. Furthermore, in vivo neutralization of the LPS selectively attenuates the stress-induced increase in the inflammasome-dependent cytokines IL-1β and IL-18. Thus, the current experiments tested the hypothesis that inflammasome-mediated processes are necessary for a systemic stress-induced inflammatory response to an acute stressor. The data presented (1) establish that male F344 rats exposed to an acute severe stressor (100 tail shocks) have elevated plasma concentrations of inflammatory proteins (IL-1β, IL-18, IL-6, IL-10, and monocyte chemotactic protein (MCP)-1), and DAMPs (uric acid and Hsp72); (2) demonstrate that inhibiting caspase-1 in vivo, using the caspase-1 inhibitor ac-YVAD-cmk, attenuates stress-induced production of IL-1β, IL-18, and IL-6 in both the circulation and peripheral tissues; and (3) implicates the DAMPs uric acid and Hsp72 as important signals contributing to inflammasome-dependent inflammatory responses using a stepwise multiple regression. The results increase our mechanistic understanding of systemic sterile inflammatory responses, and provide novel evidence that the inflammasome may be an important pharmacological target for treatment of these conditions.

Dynamics of endogenous Hsp70 synthesis in the brain of olfactory bulbectomized mice

Numerous epidemiological studies have established acute brain injury as one of the major risk factors for the Alzheimer's disease (AD). However, the lack of animal models of AD-like degeneration triggered by a defined injury hampered the development of adequate therapies. Here we report that the surgical damage of the olfactory bulbs triggers the development of several pathologies, including amyloid-β accumulation and strong decrease of neuron density in the cortex and hippocampus as well as significant disturbance of spatial memory. Characteristically, these harmful consequences of the olfactory bulbectomy (OBX) have a peculiar dynamics in time with maximal manifestation in periods of 1-1.5 months and 8 months after the surgery and, hence, exhibit biphasic pattern with almost complete recovery period taking place at 5-6 months after the operation. The quantitative determination of endogenous inducible form of Hsp70 in different brain areas of OBX mice demonstrated characteristic fluctuations of Hsp70 levels depending on the time after the operation and age of mice. Interestingly, maximal induction of Hsp70 synthesis in the hippocampus exhibits clear-cut coincidence with the recovery period in OBX animals. The observed correlation enables to suggest curing effect of Hsp70 synthesis at an earlier period of pathology development and establishes it as a possible therapeutic agent for secondary grave consequences of brain injury, such as AD-like degeneration, for which neuroprotective therapy is urgently needed.

Stress-evoked sterile inflammation, danger associated molecular patterns (DAMPs), microbial associated molecular patterns (MAMPs) and the inflammasome

Since the inception of the field of psychoneuroimmunolology research, there has been an appreciation that the physiological response to stressors includes modulation of immune function. Investigators initially focused on the effect of stress on cellular migration and immunosuppression and the resultant decreases in tumor surveillance, anti-viral T cell immunity and antigen-specific antibody responses. More recently, it has become clear that exposure to stressors also potentiate innate immune processes. Stressor exposure, for example, can change the activation status of myeloid lineage cells such as monocytes, macrophages, neutrophils, and microglia, leading to a primed state. In addition, stressor exposure increases the synthesis and release of a vast cadre' of inflammatory proteins both in the blood and within tissues (i.e., spleen, liver, adipose, vasculature and brain). The mechanisms for stress-evoked innate immune 'arousal' remain unknown. The goals of this presidential address are the following: (1) offer a personalized, brief overview of stress and immunity with a focus on 'aroused' innate immunity; (2) describe sterile inflammatory processes and the role of the inflammasome; and (3) suggest that these same processes likely contribute to primed myeloid cells and inflammatory protein responses (systemic and tissue) produced by stress in the absence of pathogens.

Commensal bacteria and MAMPs are necessary for stress-induced increases in IL-1β and IL-18 but not IL-6, IL-10 or MCP-1

Regular interactions between commensal bacteria and the enteric mucosal immune environment are necessary for normal immunity. Alterations of the commensal bacterial communities or mucosal barrier can disrupt immune function. Chronic stress interferes with bacterial community structure (specifically, α-diversity) and the integrity of the intestinal barrier. These interferences can contribute to chronic stress-induced increases in systemic IL-6 and TNF-α. Chronic stress, however, produces many physiological changes that could indirectly influence immune activity. In addition to IL-6 and TNF-α, exposure to acute stressors upregulates a plethora of inflammatory proteins, each having unique synthesis and release mechanisms. We therefore tested the hypothesis that acute stress-induced inflammatory protein responses are dependent on the commensal bacteria, and more specifically, lipopolysaccharide (LPS) shed from Gram-negative intestinal commensal bacteria. We present evidence that both reducing commensal bacteria using antibiotics and neutralizing LPS using endotoxin inhibitor (EI) attenuates increases in some (inflammasome dependent, IL-1 and IL-18), but not all (inflammasome independent, IL-6, IL-10, and MCP-1) inflammatory proteins in the blood of male F344 rats exposed to an acute tail shock stressor. Acute stress did not impact α- or β- diversity measured using 16S rRNA diversity analyses, but selectively reduced the relative abundance of Prevotella. These findings indicate that commensal bacteria contribute to acute stress-induced inflammatory protein responses, and support the presence of LPS-mediated signaling in stress-evoked cytokine and chemokine production. The selectivity of the commensal bacteria in stress-evoked IL-1β and IL-18 responses may implicate the inflammasome in this response.

Stress-induced facilitation of host response to bacterial challenge in F344 rats is dependent on extracellular heat shock protein 72 and independent of alpha beta T cells

Activation of the in vivo stress response can facilitate antibacterial host defenses. One possible mechanism for this effect is stress-induced release of heat shock protein 72 (Hsp72) into the extracellular environment. Hsp72 is a ubiquitous cellular protein that is up-regulated in response to cellular stress, and modulates various aspects of immune function including macrophage inflammatory/bactericidal responses and T-cell function when found in the extracellular environment. The current study tested the hypothesis that in vivo extracellular Hsp72 (eHsp72) at the site of inflammation contributes to stress-induced restricted development of bacteria, and facilitated recovery from bacteria-induced inflammation, and that this effect is independent of alpha beta (αβ) T cells. Male F344 rats were exposed to either inescapable electrical tail-shocks or no stress, and subcutaneously injected with Escherichia coli (ATCC 15746). The role of eHsp72 was investigated by Hsp72-immunoneutralization at the inflammatory site. The potential contribution of T cells was examined by testing male athymic (rnu/rnu) nude rats lacking mature αβ T cells and heterozygous thymic intact control (rnu/+) rats. The results were that stressor exposure increased plasma concentrations of eHsp72 and facilitated recovery from bacterial inflammation. Immunoneutralization of eHsp72 at the inflammatory site attenuated this effect. Stressor exposure impacted bacterial inflammation and eHsp72 equally in both athymic and intact control rats. These results support the hypothesis that eHsp72 at the site of inflammation, and not αβ T cells, contributes to the effect of stressor exposure on subcutaneous bacterial inflammation.

Recombinant heat shock protein 70 in combination with radiotherapy as a source of tumor antigens to improve dendritic cell immunotherapy

Local radiotherapy (RT) plus intratumoral dendritic cell (DC) injection can mediate immunological response. We hypothesized that co-injection of exogenous recombinant heat shock protein 70 (rHsp70) in combination with RT-DC could be as effective as co-injection of HSP-peptide for evoking specific immune response. rHsp70-prostate-specific antigen (rHSP70C′-PSA) and α-fetoprotein (rHSP70C′-AFP) were used to compare specific response. Growth inhibition of the tumor and the systemic anti-tumor immune response were measured on CT26/PSA and CT26/AFP mice model. Intratumoral co-injection of rHsp70 and DC into the irradiated tumor site induced a more potent anti-tumor immune response than injection of DC alone. rHsp70 was as effective as rHsp70C′-PSA or rHsp70C′-AFP in inducing a tumor-specific cytotoxic T lymphocyte response or tumor growth delay. These results demonstrate that co-administration with rHsp70 and RT could be a simple and effective source of tumor antigens to achieve RT-DC immunotherapy protocol and easy to apply in clinical use.

Detection of highly curved membrane surfaces using a cyclic peptide derived from synaptotagmin-I

The generation of highly curved membranes is essential to cell growth, division, and movement. Recent research in the field is focused to answer questions related to the consequences of changes in the topology of the membrane once it is created, broadly termed as membrane curvature sensing. Most probes that are used to study curvature sensing are intact membrane active proteins such as DP1/Yop1p, ArfGAP1, BAR domains, and Synaptotagmin-I (Syt1). Taking a cue from nature, we created the cyclic peptide C2BL3C based on the membrane penetration C2B loop 3 of Syt1 via "Click" chemistry. Using a combination of spectroscopic techniques, we investigated the peptide-lipid interactions of this peptide with synthetic phospholipid vesicles and exosomes from rat blood plasma. We found that the macrocycle peptide probe was selective for lipid vesicles with highly curved surfaces (d < 100 nm). These results suggested that C2BL3C functions as a selective detector of highly curved phospholipid bilayers.

The regulation of interleukin-6 implicates skeletal muscle as an integrative stress sensor and endocrine organ

Skeletal muscle has been identified as an endocrine organ owing to its capacity to produce and secrete a variety of cytokines (myokines) and other proteins. To date, myokines have primarily been studied in response to exercise or metabolic challenges; however, numerous observations suggest that skeletal muscle may also release myokines in response to certain categories of internal or external stress exposure. Internal stress signals include oxidative or nitrosative stress, damaged or unfolded proteins, hyperthermia or energy imbalance. External stress signals, which act as indicators of organismal stress or injury in other cells, employ mediators such as catecholamines, endotoxin, alarmins, ATP and pro-inflammatory cytokines, such as tumour necrosis factor-α and interleukin-1β. External stress signals generally induce cellular responses through membrane receptor systems. In this review, we focus on the regulation of interleukin-6 (IL-6) as a prototypical stress response myokine and highlight evidence that IL-6 gene regulation in muscle is inherently organized to respond to a wide variety of internal and external stressors. Given that IL-6 can initiate protective, anti-inflammatory or restorative processes throughout the organism during life-threatening conditions, we present the argument that skeletal muscle has a physiological function as a sensor and responder to stress. Furthermore, we hypothesize that it may comprise a fundamental component of the organism's acute stress response.

Hyperthermia increases interleukin-6 in mouse skeletal muscle

Skeletal muscles produce and contribute to circulating levels of IL-6 during exercise. However, when core temperature is reduced, the response is attenuated. Therefore, we hypothesized that hyperthermia may be an important and independent stimulus for muscle IL-6. In cultured C2C12 myotubes, hyperthermia (42°C) increased IL-6 gene expression 14-fold after 1 h and 35-fold after 5 h of 37°C recovery; whereas exposure to 41°C resulted in a 2.6-fold elevation at 1 h. IL-6 protein was secreted and significantly elevated in the cell supernatant. Similar but reduced responses to heat were seen in C2C12 myoblasts. Isolated soleus muscles from mice, exposed ex vivo to 41°C for 1 h, yielded similar IL-6 gene responses (>3-fold) but without a significant effect on protein release. When whole animals were exposed to passive hyperthermia, such that core temperature increased to 42.4°C, IL-6 mRNA in soleus increased 5.4-fold compared with time matched controls. Interestingly, TNF-α gene expression was routinely suppressed at all levels of hyperthermia (40.5-42°C) in the isolated models, but TNF-α was elevated (4.2-fold) in the soleus taken from intact mice exposed, in vivo, to hyperthermia. Muscle HSP72 mRNA increased as a function of the level of hyperthermia, and IL-6 mRNA responses increased proportionally with HSP72. In cultured C2C12 myotubes, when heat shock factor was pharmacologically blocked with KNK437, both HSP72 and IL-6 mRNA elevations, induced by heat, were suppressed. These findings implicate skeletal muscle as a "heat stress sensor" at physiologically relevant hyperthermia, responding with a programmed cytokine expression pattern characterized by elevated IL-6.

Opposing roles for heat and heat shock proteins in macrophage functions during inflammation: a function of cell activation state?

Macrophages function both under normothermia and during periods of body temperature elevation (fever). Whether macrophages sense and respond to thermal signals in a manner which regulates their function in a specific manner is still not clear. In this brief review, we highlight recent studies which have analyzed the effects of mild heating on macrophage cytokine production, and summarize thermally sensitive molecular mechanisms, such as heat shock protein (HSP) expression, which have been identified. Mild, physiologically achievable, hyperthermia has been shown to have both pro- and anti-inflammatory effects on macrophage inflammatory cytokine production and overall it is not clear how hyperthermia or HSPs can exert opposing roles on macrophage function. We propose here that the stage of activation of macrophages predicts how they respond to mild heating and the specific manner in which HSPs function. Continuing research in this area is needed which will help us to better understand the immunological role of body temperature shifts. Such studies could provide a scientific basis for the use of heat in treatment of inflammatory diseases.

Effect of moxibustion pretreatment on serum levels of Helicobacter pylori IgG and eHSP72 in rats with Helicobacter pylori-induced gastritis

AIM: To investigate the effect of moxibustion pretreatment on serum levels of Helicobacter pylori (H. pylori) IgG and extracellular heat shock protein 72 (eHSP72) in rats with H. pylori-induced gastritis.

METHODS: Fifty healthy rats were randomly divided into five groups: A (normal controls), B (infected with H. pylori), C (moxibustion at acupoints), D (moxibustion at non-acupoints), and E (electroacupuncture at acupoints). Gastritis was induced in rats by oral gavage with H. pylori. The levels of serum H. pylori IgG and eHSP72 were measured by enzyme-linked immunosorbent assay.

RESULTS: Compared to group A, the ulcer index and serum levels of H. pylori IgG and eHSP72 significantly increased in group B (0.50 ± 1.00 vs 6.50 ± 4.75, 76.72 μg/L ± 11.02 μg/L vs 131.91 μg/L ± 30.04 μg/L, 152.2 ng/L ± 22.72 ng/L vs

222.59 ng/L ± 56.69 ng/L, all P < 0.01). Compared to group B, the UI and serum levels of H. pylori IgG significantly decreased (6.50 ± 4.75 vs 1.00 ± 2.00, 131.91 μg/L ± 30.04 μg/L vs 86.25 μg/L ± 18.63 μg/L, both P < 0.01) and serum levels of eHSP72 significantly increased in group C (222.59 ng/L ± 56.69 ng/L vs 285.54 ng/L ± 68.23 ng/L, P < 0.05). Compared to group D, the UI and serum levels of H. pylori IgG significantly decreased (3.00 ± 5.00 vs 1.00 ± 2.00, 116.19 μg/L ± 31.25 μg/L vs 86.25 μg/L ± 18.63 μg/L, both P < 0.01) and serum levels of eHSP72 significantly increased in group C (185.97 ng/L ± 77.62 ng/L vs 285.54 ng/L ± 68.23 ng/L, P < 0.01). Compared to group E, serum levels of H. pylori IgG significantly decreased in group C (120.25 μg/L ± 25.40 μg/L vs 86.25 μg/L ± 18.63 μg/L, P < 0.01).

CONCLUSION: Moxibustion at acupoints reduces H. pylori-induced gastric mucosal injury possibly via mechanisms associated with increasing serum levels of eHSP72.

Involvement of extracellular Hsp72 in wear particle-mediated osteolysis

Wear particle-mediated osteolysis is one of the major problems affecting long-term survival of orthopaedic prostheses, frequently progressing to failure of fixation and revision surgery. Upon challenging with wear particles, macrophages and various other types of cells release soluble factors that stimulate the resorptive activity of osteoclasts and impair the function and activity of osteoblasts. Extracellular Hsp72 has been reported to activate macrophages and up-regulate pro-inflammatory cytokine production, although its role in osteolysis has not been established yet. The purpose of our study was to evaluate the involvement of this protein in the inflammatory response to wear particles that leads to periprosthetic osteolysis. To this end, we used interfacial tissues and blood samples from patients undergoing revision surgery due to aseptic loosening of cementless acetabular cups. Confocal microscopy indicated that Hsp72 co-localises with CD14(+) cells of interfacial tissues. Levels of Hsp72 in the culture media from periprosthetic membranes cultured ex vivo decreased along culture time and Hsp72 levels in sera from patients were lower and under the assay detection limit compared with those from age-matched control subjects. This suggests that interfacial tissues are not actively producing the protein but likely recruit it from peripheral circulation. Incubation of human macrophages with titanium (Ti) particles decreased the release of Hsp72 into culture media. Treatment with recombinant human Hsp72 enhanced considerably IL-6 levels in culture media which were not modified after macrophage co-stimulation with Ti particles, while pre-incubation with Hsp72 increased the Ti particle-induced TNF-α and IL-1β production. Altogether, these data indicate that extracellular Hsp72 amplifies the inflammatory response to wear debris by interacting with resident macrophages in periprosthetic tissues.

Treatment with recombinant Hsp72 suppresses collagen-induced arthritis in mice

Although the level of heat shock protein (Hsp72) has been shown to be enhanced in rheumatoid arthritis (RA) synovial tissues and RA synovial fluid, it remains unclear what role extracellular Hsp72 plays in the pathogenesis of RA. This study was conducted to investigate the effects of recombinant human Hsp72 on collagen-induced arthritis (CIA) when administered therapeutically and elucidate its underlying mechanism. We demonstrated that recombinant Hsp72 significantly reduced disease severity. Hsp72-treated animals displayed significantly less cartilage and bone destruction than that in the controls. Hsp72 treatment also reduced the expression of tumor necrosis factor alpha and interleukin 6 in the sera. Furthermore, Hsp72 treatment significantly inhibited activation of nuclear factor kappa B (NF-κB) in synovial tissues of CIA mice. These findings suggest that recombinant Hsp72 effectively suppressed synovial inflammation and the development and progress of CIA, which is mediated through the reduction of production of proinflammatory cytokines and the suppression of activation of NF-κB pathway.

Recombinant human Hsp70 protects against lipoteichoic acid-induced inflammation manifestations at the cellular and organismal levels

It has been previously reported that pretreatment with exogenous heat shock protein 70 (Hsp70) is able to protect cells and animals from the deleterious effects of bacterial lipopolysaccharide (LPS) produced by Gram-negative bacteria. However, the effects of Hsp70 pretreatment on lipoteichoic acid (LTA) challenge resulted from Gram-positive bacteria infection have not been fully elucidated. In this study, we demonstrated that preconditioning with human recombinant Hsp70 ameliorates various manifestations of systematic inflammation, including reactive oxygen species, TNFα, and CD11b/CD18 adhesion receptor expression induction observed in different myeloid cells after LTA addition. Therefore, exogenous Hsp70 may provide a mechanism for controlling excessive inflammatory responses after macrophage activation. Furthermore, in a rat model of LTA-induced sepsis, we demonstrated that prophylactic administration of exogenous human Hsp70 significantly exacerbated numerous homeostatic and hemodynamic disturbances induced by LTA challenge and partially normalized the coagulation system and multiple biochemical blood parameters, including albumin and bilirubin concentrations, which were severely disturbed after LTA injections. Importantly, prophylactic intravenous injection of Hsp70 before LTA challenge significantly reduced mortality rates. Thus, exogenous mammalian Hsp70 may serve as a powerful cellular defense agent against the deleterious effects of bacterial pathogens, such as LTA and LPS. Taken together, our findings reveal novel functions of this protein and establish exogenous Hsp70 as a promising pharmacological agent for the prophylactic treatment of various types of sepsis.

Extracellular HSPA1A promotes the growth of hepatocarcinoma by augmenting tumor cell proliferation and apoptosis-resistance

Intracellular HSP70 has been implicated as a cytoprotective protein, whereas the effect of extracellular HSP70 on tumor cells has not been fully understood to date. Here we report that extracellular HSPA1A, a stress-inducible member of HSP70 family, could promote tumor growth. HSPA1A promoted the proliferation of H22 hepatocarcinoma cells through TLR2 and TLR4 signaling. The effect of HSPA1A was abolished by inhibiting NF-κB. HSPA1A also augmented the apoptosis-resistance of H22 cells by activating NF-κB, thus to promote the proliferation of H22 cells in presence of mitomycin C. Furthermore, the promoting effect of HSPA1A on tumor cell proliferation was existent after the removal of HSPA1A, which might involve HSPA1A-promoted upregulation of TLR4 expression in tumor cells and release of HMGB1 from tumor cells. These findings suggest that extracellular HSPA1A functions as endogenous ligand for TLR2 and TLR4 to facilitate tumor growth.

Pediatric Sepsis - Part V: Extracellular Heat Shock Proteins: Alarmins for the Host Immune System

Heat shock proteins (HSPs) are molecular chaperones that facilitate the proper folding and assembly of nascent polypeptides and assist in the refolding and stabilization of damaged polypeptides. Through these largely intracellular functions, the HSPs maintain homeostasis and assure cell survival. However, a growing body of literature suggests that HSPs have important effects in the extracellular environment as well. Extracellular HSPs are released from damaged or stressed cells and appear to act as local "danger signals" that activate stress response programs in surrounding cells. Importantly, extracellular HSPs have been shown to activate the host innate and adaptive immune response. With this in mind, extracellular HSPs are commonly included in a growing list of a family of proteins known as danger-associated molecular patterns (DAMPs) or alarmins, which trigger an immune response to tissue injury, such as may occur with trauma, ischemia-reperfusion injury, oxidative stress, etc. Extracellular HSPs, including Hsp72 (HSPA), Hsp27 (HSPB1), Hsp90 (HSPC), Hsp60 (HSPD), and Chaperonin/Hsp10 (HSPE) are especially attractrive candidates for DAMPs or alarmins which may be particularly relevant in the pathophysiology of the sepsis syndrome.

Comparative studies on temperature threshold for heat shock protein 70 induction in young and adult Murrah buffaloes

To know the temperature threshold for heat shock protein 70 (HSP70) induction in lymphocytes and to assess physiological changes, if any, in relation to HSP70 induction in young and adult Murrah buffaloes, this study was divided into two parts: I. In vivo study: where assay of HSP70 was performed in blood samples collected from acutely exposed young and adult Murrah buffaloes (n = 6) inside a climatic chamber at 40, 42 and 45 °C for 4 h and thermoneutral temperature (22 °C). Physiological parameters viz., rectal temperature, respiratory rate, pulse rate and skin temperature of different body parts were monitored to assess magnitude of stress in the animals owing to thermal exposure II. For in vitro study, equal numbers of lymphocyte cells were separated from blood collected from young and adult buffaloes and were subjected to four temperature treatments (38, 40, 42 and 45 °C) for 4 h. A significant increase (p < 0.05) in all the physiological parameters in both young and adult buffaloes was observed after exposure to 40, 42 and 45 °C for 4 h as compared to 38 °C. The average plasma HSP70 concentrations (ng/ml) were significantly higher (p < 0.05) at 40, 42 and 45 °C as compared to 38 °C in both young and adult and were higher in young than adult buffaloes at 38 and 45 °C. Heat shock protein 70 level in lymphocyte lysate showed highest concentration after 3-h exposure to all temperatures (40, 42 and 45 °C) in both young and adult buffaloes. The intensity of changes of all physiological parameters was more in young animals than in the adults indicating the greater susceptibility of younger animals to heat stress and was found to be changed at around 40 °C when animals were exposed to different temperatures, indicating the possibility that HSP70 production may be initiated at this temperature which is 2 or 3 °C higher than core body temperature.

Effects of heat stress on proliferation, protein turnover, and abundance of heat shock protein messenger ribonucleic acid in cultured porcine muscle satellite cells

It is well established that heat stress (HS) negatively affects growth rate in swine. Although reduced feed intake undoubtedly plays a significant role in this reduction, studies in laboratory animals and other nonswine species indicate muscle growth also is affected by HS-related alterations in muscle physiology. Evidence is now emerging that heat shock proteins (Hsp), produced in response to HS and other types of cellular stress, may play an important role in regulating the rate and efficiency of muscle growth. Because muscle satellite cells play a crucial role in postnatal muscle growth, the effects of HS on rates of satellite cell proliferation, protein synthesis, and protein degradation play an important role in determining the rate and extent of muscle growth. Consequently, in the current study we have examined the effects of mild HS (40.5°C for 48 h) on the rates of proliferation, protein synthesis, and protein degradation and on quantities of Hsp90, Hsp70, and Hsp25/27 mRNA and protein in cultured porcine muscle satellite cells (PSC). Mild HS of PSC cultures resulted in 2.5-, 1.4-, and 6.5-fold increases (P < 0.05) in the abundance of Hsp90, Hsp70, and Hsp25/27 mRNA, respectively, relative to control cultures. Abundance of Hsp 90, 70, and 25/27 proteins was also increased in HS PSC cultures compared with those in control cultures. Proliferation rates in HS PSC cultures were 35% less (P < 0.05) than those in control cultures. Protein synthesis rates in HS-fused PSC cultures were 85% greater (P < 0.05) than those in control cultures, and protein degradation rates in HS-fused PSC were 23% less (P < 0.05) than those in control cultures. In light of the crucial role satellite cells play in postnatal muscle growth, the HS-induced changes we have observed in rates of proliferation, protein turnover, and abundance of Hsp mRNA and Hsp protein in PSC cultures indicate that mild HS affects the physiology of PSC in ways that could affect muscle growth in swine.

Passing the anaerobic threshold is associated with substantial changes in the gene expression profile in white blood cells

High and moderate intensity endurance exercise alters gene expression in human white blood cells (WBCs), but the understanding of how this effect occurs is limited. To increase our knowledge of the nature of this process, we investigated the effects of passing the anaerobic threshold (AnT) on the gene expression profile in WBCs of athletes. Nineteen highly trained skiers participated in a treadmill test with an incremental step protocol until exhaustion (ramp test to exhaustion, RTE). The average total time to exhaustion was 14:40 min and time after AnT was 4:50 min. Two weeks later, seven of these skiers participated in a moderate treadmill test (MT) at 80% peak O(2) uptake for 30 min, which was slightly below their AnTs. Blood samples were obtained before and immediately after both tests. RTE was associated with substantially greater leukocytosis and acidosis than MT. Gene expression in WBCs was measured using whole genome microarray expression analysis before and immediately after each test. A total of 310 upregulated genes were found after RTE, and 69 genes after MT of which 64 were identical to RTE. Both tests influenced a variety of known gene pathways related to inflammation, stress response, signal transduction and apoptosis. A large group of differentially expressed previously unknown small nucleolar RNA and small Cajal body RNA was found. In conclusion, a 15-min test to exhaustion was associated with substantially greater changes of gene expression than a 30-min test just below the AnT.

Modulatory role of calreticulin as chaperokine for dendritic cell-based immunotherapy

Heat shock proteins (HSPs) play a regulatory role for maturation of antigen-presenting cells (APCs) such as dendritic cells (DCs) and macrophages. Whereas HSP70 has been shown to enhance the maturation of human DCs via a nuclear factor kappa-B (NF-κB)-dependent pathway, the regulatory role of calreticulin (CRT), which is a HSP with similar functions to HSP70, is not well studied. To investigate the role of CRT as adjuvant in cell activation and co-stimulatory responses we determined the effects of CRT on human APC maturation in comparison to that of HSP70. To facilitate eukaryotic endotoxin-free CRT protein expression, three different methods were compared. We demonstrate that CRT induces the maturation of human DCs and increases the production of proinflammatory cytokines via the NF-κB pathway. CRT-mediated maturation was qualitatively similar to that induced by HSP70. Interestingly, priming of monocytes with HSPs showed an even more prominent effect on maturation than exposure of immature DCs to these compounds. A higher expression of CD86, CD83 and CCR7 on mature DCs were found in response to CRT. Our data provide novel insights into the role of extracellular HSPs as chaperokines in the processes of APC generation and may thus be useful to improve adoptive immunotherapy.

HSP70 expression: does it a novel fatigue signalling factor from immune system to the brain?

Integrative physiology studies have shown that immune system and central nervous system interplay very closely towards behavioural modulation. Since the 70-kDa heat shock proteins (HSP70s), whose heavy expression during exercise is well documented in the skeletal muscle and other tissues, is also extremely well conserved in nature during all evolutionary periods of species, it is conceivable that HSP70s might participate of physiologic responses such as fatigue induced by some types of physical exercise. In this way, increased circulating levels of extracellular HSP70 (eHSP70) could be envisaged as an immunomodulatory mechanism induced by exercise, besides other chemical messengers (e.g. cytokines) released during an exercise effort, that are able to binding a number of receptors in neural cells. Studies from this laboratory led us to believe that increased levels of eHSP70 in the plasma during exercise and the huge release of eHSP70 from lymphocytes during high-load exercise bouts may participate in the fatigue sensation, also acting as a danger signal from the immune system.

Characterization of two heat shock proteins (Hsp70/Hsc70) from grass carp (Ctenopharyngodon idella): evidence for their differential gene expression, protein synthesis and secretion in LPS-challenged peripheral blood lymphocytes

Two cDNAs, encoding the stress-inducible 70-kDa heat shock protein (Hsp70) and the constitutively expressed 70-kDa heat shock cognate protein (Hsc70), were isolated from grass carp. The Hsp70 and Hsc70 cDNAs were 2250 bp and 2449 bp in length and contained 1932 bp and 1953 bp open reading frames, respectively. Tissue distribution results showed that Hsp70/Hsc70 was highly expressed in gill, kidney, head kidney and peripheral blood lymphocytes (PBLs). Using grass carp PBLs as a cell model, effects of lipopolysaccharide (LPS) on the mRNA and protein levels of Hsp70/Hsc70 were examined. In this case, LPS increased the mRNA expression of Hsp70 in a time- and dose-dependent manner, but had no effect on Hsc70 mRNA expression. In agreement with this, LPS elevated the intracellular Hsp70 markedly, but not the Hsc70 protein levels in parallel experiments. Furthermore, Hsp70 protein was also detected in culture medium. Moreover, inhibition of LPS on Hsp70 release in a time-dependent manner was observed, indicating that there may be a dynamic balance between Hsp70 stores and Hsp70 release in grass carp PBLs following exposure to LPS. Taken together, these results not only shed new insights into the different regulations of LPS on Hsp70/Hsc70 gene expression, protein synthesis and release, but also provide a basis for further study on the functional role of Hsp70 in fish immune response.

Biological activity of truncated C-terminus human heat shock protein 72

Heat shock protein 72 (Hsp72), a canonical intracellular molecular chaperone, may also function as an extracellular danger signal for the innate immune system. To further delineate the biological role of Hsp72 in the innate immune system, we generated two truncated versions of the full length human Hsp72 (N-terminus Hsp72, amino acids 1-430; and C-terminus Hsp72 amino acids 420-641) and directly compared their ability to activate cells from the macrophage/monocyte lineage. In RAW 264.7 macrophages transfected with a NF-κB-dependent luciferase reporter plasmid, C-terminus Hsp72 was a more potent inducer of NF-κB activity than N-terminus Hsp72, and this effect did not seem to be secondary to endotoxin contamination. C-terminus Hsp72-mediated activation of the NF-κB pathway was corroborated by increased activation of IκB kinase, degradation of IκBα, and increased NF-κB-DNA binding. C-terminus Hsp72 was a more potent inducer of tumor necrosis factor-α (TNFα) expression in RAW 264.7 macrophages and in primary murine peritoneal macrophages from wild-type mice. C-terminus Hsp72 did not induce TNFα expression in primary murine peritoneal macrophages from Toll-like receptor (TLR4) mutant mice, indicating a role for TLR4. In human THP-1 mononuclear cells, C-terminus Hsp72 induced tolerance to subsequent LPS stimulation, whereas N-terminus Hsp72 did not induce tolerance. Finally, control experiments using equimolar amounts of N-terminus or C-terminus Hsp72 demonstrated a higher biological potency for C-terminus Hsp72. These data demonstrate that the ability of human Hsp72 to serve as an activator for cells of the macrophage/monocyte lineage primarily lies in the C-terminus region spanning amino acids 420-641.

Extracellular heat shock proteins (eHSP70) in exercise: Possible targets outside the immune system and their role for neurodegenerative disorders treatment

The intracellular heat shock protein 70kDa (iHSP70) is a universal marker of stress protein whose expression is induced by different cell stressors, such as heat, metabolite deprivation, redox imbalances and also during physical exercise. The activation of the iHSP70 is sine qua non for the promotion of tissue repair, since the expression of this chaperone confers cytoprotection and also exerts anti-inflammatory effects. On the other hand, exercise also induces the appearance of HSP70 in the extracellular medium (eHSP70) but, so far, the eHSP70 function has been mainly attributed to the activation of the immune system, seeming to perform an opposite function from the iHSP70. Since a moderate intensity exercise bout induces a general anti-inflammatory response even in the presence of an elevated eHSP70, this protein could carry out other functions rather than immune activation. Because exercise generates heat and metabolic challenges (especially on glucose metabolism) we suggests that the motoneurons, a very active (possibly one of the most stressed cells during exercise) and also very sensitive cells to heat and glucose metabolism imbalances, could be the major sites for the eHSP70 function. Due to the importance of the iHSP70 for repair and stress adaptation, this protein must be present in abundance on the site of stress and, because of its intrinsic inability response to stress [low heat shock factor 1 (HSF-1) activation] and the structure of the motoneurons (very long cells), the iHSP70, produced on the very far nucleus, is not appropriately transported through the axon to the axon terminal, were it is required. Then, during the exercise, the released eHSP70 can be internalized by the motoneurons and act as intracellular chaperons, protecting this cell against oxidative damage, protein denaturation and many others. Since a decreased iHSP70 expression capacity is associated with neurodegeneration diseases (such as Parkinson, polyglutamine, Amyotrophic lateral sclerosis, Alzheimer's, Huntington's and many others), the understanding of the physiological function of the extracellular HSP70 could be helpful on the treatment of neurodegenerative and other neuronal diseases. Besides that, it could explain some of the beneficial effects of the pharmacological HSP70 activators and also the beneficial effects of the exercise among neuronal cells during neurodegenerative-inducing diseases.

Differential stress responses among newly received calves: variations in reductant capacity and Hsp gene expression

Bovine respiratory disease complex (BRD), a major economic concern to the beef cattle industry all over the world, is triggered by physical, biological and psychological stresses. It is becoming noticeable that the key to reducing BRD appears to be centered at reducing the response to stress. The aims of the present study were to detect individual variations in the stress response of newly received young calves through their leukocyte heat shock protein (Hsp) response, selected neutrophil-related gene expression and oxidative stress, and relate them to pulmonary adhesions at slaughter, an indicative sign of clinical and subclinical episodes of BRD at an early age. Differential expression patterns of Hsp60 and Hsp70A1A were revealed in newly received calves 1 h, 5 h and 1 day after arrival, distinguishing between stress-responsive and non-stress-responsive individuals. Plasma cortisol was also indicative of stress-responsive and non-stress-responsive individuals, 1 h and 5 h after arrival. At the longer term, β-glycan levels were highest 7 days after arrival and significantly correlated with an adhesion-free phenotype at slaughter. Oxidative stress responses, measured through the oxidation products of the exogenous linoleoyl tyrosine (LT) marker, revealed that hydroperoxidation and epoxidation of membranes may readily occur. Based on the LT oxidation products and levels of β-glycan, we present a discriminant analysis model, according to which vulnerable individuals may be predicted at near 100% probability 7 days after arrival. Since clinical signs of BRD may often go undetected in feedlot calves, such a model, after its examination in large-scale experiments, may be a reliable tool for an early prediction of subclinical signs of BRD.

Heat and exercise acclimation increases intracellular levels of Hsp72 and inhibits exercise-induced increase in intracellular and plasma Hsp72 in humans

In order to verify the effects of heat and exercise acclimation (HA) on resting and exercise-induced expression of plasma and leukocyte heat shock protein 72 (Hsp72) in humans, nine healthy young male volunteers (25.0 ± 0.7 years; 80.5 ± 2.0 kg; 180 ± 2 cm, mean ± SE) exercised for 60 min in a hot, dry environment (40 ± 0°C and 45 ± 0% relative humidity) for 11 days. The protocol consisted of running on a treadmill using a controlled hyperthermia technique in which the work rate was adjusted to elevate the rectal temperature by 1°C in 30 min and maintain it elevated for another 30 min. Before and after the HA, the volunteers performed a heat stress test (HST) at 50% of their individual maximal power output for 90 min in the same environment. Blood was drawn before (REST), immediately after (POST) and 1 h after (1 h POST) HST, and plasma and leukocytes were separated and stored. Subjects showed expected adaptations to HA: reduced exercise rectal and mean skin temperatures and heart rate, and augmented sweat rate and exercise tolerance. In HST1, plasma Hsp72 increased from REST to POST and then returned to resting values 1 h POST (REST: 1.11 ± 0.07, POST: 1.48 ± 0.10, 1 h POST: 1.22 ± 0.11 ng mL(-1); p < 0.05). In HST2, there was no change in plasma Hsp72 (REST: 0.94 ± 0.08, POST: 1.20 ± 0.15, 1 h POST: 1.17 ± 0.16 ng mL(-1); p > 0.05). HA increased resting levels of intracellular Hsp72 (HST1: 1 ± 0.02 and HST2: 4.2 ± 1.2 density units, p < 0.05). Exercise-induced increased intracellular Hsp72 expression was observed on HST1 (HST1: REST, 1 ± 0.02 vs. POST, 2.9 ± 0.9 density units, mean ± SE, p < 0.05) but was inhibited on HST2 (HST2: REST, 4.2 ± 1.2 vs. POST, 4.4 ± 1.1 density units, p > 0.05). Regression analysis showed that the lower the pre-exercise expression of intracellular Hsp72, the higher the exercise-induced increase (R = -0.85, p < 0.05). In conclusion, HA increased resting leukocyte Hsp72 levels and inhibited exercise-induced expression. This intracellular adaptation probably induces thermotolerance. In addition, the non-increase in plasma Hsp72 after HA may be related to lower stress at the cellular level in the acclimated individuals.

The Hsp72 response in peri-parturient dairy cows: relationships with metabolic and immunological parameters

The study was aimed at assessing whether the peri-parturient period is associated with changes of intracellular and plasma inducible heat shock proteins (Hsp) 72 kDa molecular weight in dairy cows, and to establish possible relationships between Hsp72, metabolic, and immunological parameters subjected to changes around calving. The study was carried out on 35 healthy peri-parturient Holstein cows. Three, two, and one week before the expected calving, and 1, 2, 3, 4, and 5 weeks after calving, body conditions score (BCS) was measured and blood samples were collected to separate plasma and peripheral blood mononuclear cells (PBMC). Concentrations of Hsp72 in PBMC and plasma increased sharply after calving. In the post-calving period, BCS and plasma glucose declined, whereas plasma nonesterified fatty acids (NEFA) and tumor necrosis factor-alpha increased. The proliferative responses of PBMC to lipopolysaccharide (LPS) declined progressively after calving. The percentage of PBMC expressing CD14 receptors and Toll-like receptors (TLR)-4 increased and decreased in the early postpartum period, respectively. Correlation analysis revealed significant positive relationships between Hsp72 and NEFA, and between PBMC proliferation in response to LPS and the percentage of PBMC expressing TLR-4. Conversely, significant negative relationships were found between LPS-triggered proliferation of PBMC and both intracellular and plasma Hsp72. Literature data and changes of metabolic and immunological parameters reported herein authorize a few interpretative hypotheses and encourage further studies aimed at assessing possible cause and effect relationships between changes of PBMC and circulating Hsp72, metabolic, and immune parameters in dairy cows.

Hsp-72, a candidate prognostic indicator of heatstroke

Exposure of rats to environmental heat enhances the expression of heat shock protein-72 (Hsp-72) in most of their organs proportionally to heat stress severity. Pre-induction or over-expression of Hsp-72 prevents organ damage and lethality, suggesting that heat shock proteins (Hsps) may have a pathogenic role in this condition. We investigated the expression profile of Hsps in baboons subjected to environmental heat stress until the core temperature attained 42.5 degrees C (moderate heatstroke) or occurrence of hypotension associated with core temperature > or = 43.5 degrees C (severe heatstroke). Western blot analysis demonstrated a differential induction of Hsp-72 among organs of heat-stressed animals with the highest induction in the liver and the lowest in lung. Hsp-60 and Hsc-70 expression was similar between control and heat-stressed animals. ELISA studies indicated a marked release of Hsp-72 into the circulation of baboons with severe heatstroke with a peak at 24 h post-heatstroke onset and remained sustained up to 72 h. Hsp-72 release was not associated with core temperature or systolic blood pressure, but correlated with markers of liver, myocardium, and skeletal muscle tissue necrosis. Non-survivors displayed significantly higher Hsp-72 levels than survivors. No Hsp-60 was detected in the circulation. These findings add further evidence that increased expression of Hsp-72 may be an important component of the host response to severe heatstroke. They also suggest that extracellular Hsp-72 is a marker of multiple organs tissue damage. Whether extracellular Hsp-72 plays a role in the host immune response to heat stress merits further studies.

Stress for maintaining memory: HSP70 as a mobile messenger for innate and adaptive immunity

HSP are abundant and conserved proteins present in all cells. Upon temperature shock or other stress stimuli, HSP are synthesized intracellularly, which may protect cells from protein denaturation or from death. Although HSP are synthesized intracellularly, HSP can also be mobilized to the plasma membrane or even be released under stress conditions. Elucidating the roles of cell surface and extracellular HSP in immune regulation has attracted much attention in recent years. Extracellularly, HSP can serve a cytokine function to initiate both innate and adaptive immunity through activation of APC. HSP serves also a chaperone function and facilitates presentation of antigen peptide to T cells. Similarly, cell surface HSP may activate APC and promote antigen presentation through cell-cell contact. A study in this issue of the European Journal of Immunology demonstrates that cell surface HSP70 on DC induced by stress can upregulate membrane-associated IL-15, which in turn promotes the proliferation of CD4(+)CD45RA memory T cells. Moreover, a DC-CD4(+) T-cell interacting circuit formed by CD40L on T cells and CD40 on DC is proposed to play a role in the maintenance of memory homeostasis. This study has widened our view of HSP in adaptive immunity as well as their classical functions such as APC activator and antigen carrier.

C-Mannosylated peptides derived from the thrombospondin type 1 repeat interact with Hsc70 to modulate its signaling in RAW264.7 cells

The thrombospondin type 1 repeat (TSR) is a functional module of proteins called TSR superfamily proteins (e.g., thrombospondin, F-spondin, mindin, etc.) and includes a conserved Trp-x-x-Trp (W-x-x-W) motif, in which the first Trp residue is preferably modified by C-mannosylation. We previously reported that synthesized C-mannosylated TSR-derived peptides (e.g., C-Man-WSPW) specifically enhanced lipopolysaccharide-induced signaling in macrophage-like RAW264.7 cells. In this study, we searched for the proteins that bind to C-mannosylated TSR-derived peptides in RAW264.7 cells and identified heat shock cognate protein 70 (Hsc70). The binding affinity of Hsc70 for C-mannosylated peptides in solution was higher than that for the peptides without C-mannose. The binding was influenced by a nucleotide-induced conformational change of Hsc70, and C-mannosylated peptides preferred the substrate-binding domain of Hsc70. Furthermore, in RAW264.7 cells, addition of Hsc70 stimulated cellular signaling to produce tumor necrosis factor-alpha, via transforming growth factor-beta-activated kinase 1, and the Hsc70-induced signaling was enhanced more in the presence of the peptides with C-mannose than that without C-mannose, suggesting functional interaction between Hsc70 and the C-mannosylated peptides in the cells. Together, these results demonstrate a novel function of the C-mannosylation of TSR-derived peptides in terms of interaction with Hsc70 to regulate cellular signaling.

Exogenous mammalian extracellular HSP70 reduces endotoxin manifestations at the cellular and organism levels

In this study, we checked whether HSP70 preparations of different origins are able to protect model animals (rats) from endotoxic shock and modify the response of myeloid cells to lipopolysaccharide (LPS) challenge. It was shown that HSP70 preparations can effectively protect organisms from endotoxic shock by strongly decreasing mortality and restoring both homeostasis and various hemodynamic characteristics. At the cellular level, HSP70 preparations significantly inhibit LPS-induced reactive oxygen species production in various myeloid cells and decrease NO expression in macrophages, which is enhanced after LPS priming. In parallel, HSP70 preconditioning partially normalizes neutrophil apoptosis, which is disturbed as a result of LPS stimulation. These results suggest that the antiseptic actions of HSP70 preparations are probably realized at the level of receptor membrane complexes of myeloid cells, which represent the major target of LPS action. Taken together, our findings show that extracellular mammalian HSP70 may play an important role in innate immunity modulation and stimulation of endogenous protective mechanisms, both at the cellular and organism levels, which make this protein a promising base for the development of efficient antiseptic drugs.

Effects of HSP70 antisense oligonucleotide on the proliferation and apoptosis of human hepatocellular carcinoma cells

The study investigated the effects of heat shock protein 70 (HSP70) antisense oligonucleotide (ASODN) on the proliferation and apoptosis of a human hepatocellular carcinoma cell line (SMMC-7721 cells) in vitro. HSP70 oligonucleotide was transfected into SMMC-7721 cells by the mediation of Sofast transfection reagent. Inhibition rate of SMMC-7721 cells was determined by using MTT method. Apoptosis rate and cell cycle distribution were measured by flow cytometry. Immunocytochemistry staining was used to observe the expression of HSP70, Bcl-2 and Bax. The results showed that HSP70 ASODN at various concentrations could significantly inhibit the growth of SMMC-7721 cells, and the inhibition effect peaked 48 h after transfection with 400-nmol/L HSP70 ASODN. Cytometric analysis showed the apoptotic rate was increased in a dose- and time-dependent manner in the HSP70 ASODN-treated cells. The percentage of cells in the G2/M and S phases was significantly decreased and that in the G0/G1 phase increased as the HSP70 ASODN concentration was elevated and the exposure time prolonged. Immunocytochemistry showed that treatment of SMMC-7721 cells with HSP70 ASODN resulted in decreased expressions of HSP70 and Bcl-2 proteins, and an increased expression of Bax protein. It was concluded that the HSP70 ASODN can inhibit the growth of the SMMC-7721 cells and increase cell apoptosis by down-regulating the expression of HSP70. HSP70 ASODN holds promise for the treatment of hepatocellular carcinoma.

Noradrenaline increases the expression and release of Hsp72 by human neutrophils

The blood concentration of extracellular 72kDa heat shock protein (eHsp72) increases under conditions of stress, including intense exercise. However, the signal(s), source(s), and secretory pathways in its release into the bloodstream have yet to be clarified. The aim of the present study was to evaluate the role of noradrenaline (NA) as a stress signal on the expression and release of Hsp72 by circulating neutrophils (as a source), all within a context of the immunophysiological regulation during exercise-induced stress in sedentary and healthy young (21-26years) women. The expression of Hsp72 on the surface of isolated neutrophils was determined by flow cytometry, and its release by cultured isolated neutrophils was determined by ELISA. Incubation with cmHsp70-FITC showed that neutrophils express Hsp72 on their surface under basal conditions. In addition, cultured isolated neutrophils (37 degrees C and 5% CO(2)) also released Hsp72 under basal conditions, with this release increasing from 10min to 24h in the absence of cell damage. NA at 10(-9)-10(-5)M doubled the percentage of neutrophils expressing Hsp72 after 60min and 24h incubation. NA also stimulated (by about 20%) the release of Hsp72 after 10min of incubation.

IN CONCLUSION

(1) Hsp72 is expressed on the surface of isolated neutrophils under basal conditions, and this expression is augmented by NA. (2) Isolated neutrophils can also release Hsp72 under cultured basal conditions in the absence of cell death, and NA can increase this release. These results may contribute to confirming the hypothesis that NA can act as a "stress signal" for the increased eHsp72 in the context of exercise stress, with a role for neutrophils as a source for the expression and, to a lesser degree, the release of Hsp72 after activation by NA.

Neonatal bacterial infection alters fever to live and simulated infections in adulthood

Fever is a critical component of the host immune response to infection. An emerging literature demonstrates that experience with infectious organisms early in life, during the perinatal period, may permanently program immune responses later in life, including fever. We explored the influence of neonatal infection with Escherichia coli on fever responses to lipopolysaccharide (LPS) and E. coli in adulthood. Fever to a low dose of LPS in adulthood did not significantly differ as a consequence of early-life infection. Eight days after the LPS injection, the same group of rats received a high dose of live E. coli. This time, neonatally infected rats exhibited a markedly longer fever than controls. In a subsequent experiment, fever to a single high dose of E. coli without prior LPS in adulthood did not differ by group, suggesting that the previous difference was a lack of tolerance to the dual challenges in early-infected rats. Finally, both groups exhibited decreased tumor necrosis factor (TNF)-alpha and toll-like-receptor (TLR) 4 production to dual LPS challenges in isolated splenocytes, whereas only rats infected as neonates exhibited increased cyclooxygenase-2 within the hypothalamus in response to adult infection, suggesting that early infection-induced changes in fever regulation may involve a change in central mechanisms. Taken together, these data indicate that early-life infection is associated with marked changes in host temperature regulation in adulthood.

HSP72 inhibits Smad3 activation and nuclear translocation in renal epithelial-to-mesenchymal transition

Although heat shock protein 72 (HSP72) ameliorates renal tubulointerstitial fibrosis by inhibiting epithelial-to-mesenchymal transition (EMT), the underlying mechanism is unknown. Because Smad proteins transduce TGF-beta signaling from the cytosol to the nucleus and HSP72 assists in protein folding and facilitates nuclear translocation, we investigated whether HSP72 inhibits TGF-beta-induced EMT by modulating Smad expression, activation, and nuclear translocation. To evaluate the roles of distinct HSP72 structural domains in these processes, we constructed vectors that expressed wild-type HSP72 or mutants lacking either the peptide-binding domain (HSP72-DeltaPBD), which is responsible for substrate binding and refolding, or the nuclear localization signal (HSP72-DeltaNLS). Overexpression of wild-type HSP72 or HSP72-DeltaNLS inhibited TGF-beta1-induced EMT, but HSP72-DeltaPBD did not, suggesting a critical role for the PBD in this inhibition. HSP72 overexpression inhibited TGF-beta1-induced phosphorylation and nuclear translocation of Smad3 and p-Smad3, but not Smad2; these inhibitory effects required the PBD but not the NLS. Coimmunoprecipitation assays suggested a physical interaction between Smad3 and the PBD. siRNA knockdown of endogenous HSP72 enhanced both TGF-beta1-induced Smad3 phosphorylation and EMT and confirmed the interaction of HSP72 with both Smad3 and p-Smad3. In vivo, induction of HSP72 by geranylgeranylacetone suppressed Smad3 phosphorylation in renal tubular cells after unilateral ureteral obstruction. In conclusion, HSP72 inhibits EMT in renal epithelial cells primarily by exerting domain-specific effects on Smad3 activation and nuclear translocation.

Ingestion of bacteria overproducing DnaK attenuates Vibrio infection of Artemia franciscana larvae

Feeding of bacterially encapsulated heat shock proteins (Hsps) to invertebrates is a novel way to limit Vibrio infection. As an example, ingestion of Escherichia coli overproducing prokaryotic Hsps significantly improves survival of gnotobiotically cultured Artemia larvae upon challenge with pathogenic Vibrio campbellii. The relationship between Hsp accumulation and enhanced resistance to infection may involve DnaK, the prokaryotic equivalent to Hsp70, a major molecular chaperone in eukaryotic cells. In support of this proposal, heat-stressed bacterial strains LVS 2 (Bacillus sp.), LVS 3 (Aeromonas hydrophila), LVS 8 (Vibrio sp.), GR 8 (Cytophaga sp.), and GR 10 (Roseobacter sp.) were shown in this work to be more effective than nonheated bacteria in protecting gnotobiotic Artemia larvae against V. campbellii challenge. Immunoprobing of Western blots and quantification by enzyme-linked immunosorbent assay revealed that the amount of DnaK in bacteria and their ability to enhance larval resistance to infection by V. campbellii are correlated. Although the function of DnaK is uncertain, it may improve tolerance to V. campbellii via immune stimulation, a possibility of significance from a fundamental perspective and also because it could be applied in aquaculture, a major method of food production.

Short-term highly intense physiological stress causes an increase in the expression of heat shock protein in human leukocytes

Extracellular heat shock protein with molecular weight of 70 kDa is a signal molecule of the immune system. It is secreted by the peripheral blood, liver and muscle cells in response to physiological, thermal, and mental stresses. The main goal of our study was to compare the levels of expression of heat shock protein (70 kDa) matrix ribonucleic acid in leukocytes and serum concentrations of the protein before and after physiological stress. In order to solve this problem, we developed enzyme immunoassay of serum heat shock (70 kDa) protein concentration and a method for evaluating the expression of matrix ribonucleic acid of this protein in leukocytes by the real time PCR. The concentration of 70 kDa heat shock protein in the serum increased 1.7 times as a result of even a short-term highly intense physiological stress, while the expression of its matrix ribonucleic acid in leukocytes increased 1.5 times. The individual features determine the response to physiological stress. Probable sources of 70 kDa heat shock protein are discussed.

Transgenic expression of Hsc70 in pancreatic islets enhances autoimmune diabetes in response to beta cell damage

Inflammation following tissue damage promotes lymphocyte recruitment, tissue remodeling, and wound healing while maintaining self tolerance. Endogenous signals associated with tissue damage and cell death have been proposed to initiate and instruct immune responses following injury. In this study, we have examined the effects of elevated levels of a candidate endogenous danger signal, heat shock cognate protein 70 (hsc70), on stimulation of inflammation and autoimmunity following cell damage. We find that damage to pancreatic beta cells expressing additional cytosolic hsc70 leads to an increased incidence of diabetes in a transgenic mouse model. Steady-state levels of activated APC and T cell populations in the draining lymph node were enhanced, which further increased following streptozotocin-induced beta cell death. In addition, proinflammatory serum cytokines, and lymphocyte recruitment were increased in hsc70 transgenic mice. Islet Ag-specific T cells underwent a greater extent of proliferation in the lymph nodes of mice expressing hsc70 following beta cell damage, suggesting elevated Ag presentation following release of Ag in the presence of hsc70. These findings suggest that an elevated content of hsc70 in cells undergoing necrotic or apoptotic cell death can increase the extent of sterile inflammation and increase the susceptibility to autoimmunity.

Exercise-induced extracellular 72 kDa heat shock protein (Hsp72) stimulates neutrophil phagocytic and fungicidal capacities via TLR-2

This study evaluated the role of toll like receptor 2 (TLR-2) in the interaction of 72 kDa extracellular heat shock protein (Hsp72, a stress-inducible protein) with neutrophils and the participation on TLR-2 in the stimulation of neutrophil phagocytic and fungicidal capacities by post-exercise physiological concentrations of Hsp72. Human peripheral blood neutrophils were incubated with fluorescein isothiocyanate-conjugated Hsp72, and were analyzed by immunofluorescence microscopy and flow cytometry. Both methods revealed an interaction of Hsp72 with neutrophils. In addition, when neutrophils were pre-incubated with an anti-TLR-2 antibody this interaction was clearly decreased. Post-exercise circulating concentration of Hsp72 (8.6 ng/ml) stimulated the phagocytic and fungicidal capacities of neutrophils and this effect could be also blocked using an antibody against TLR-2. Phosphatidylinositol-3-kinase (PI3K), extracellular signal-regulated kinase (ERK) and the nuclear transcription factor kappa beta (NF-kappabeta) were found to be involved in the signaling process, confirming the participation of TLR-2 in the stimulation of neutrophil function by Hsp72. In conclusion, TLR-2 is involved at least in part, in the stimulation of neutrophil phagocytic and fungicidal capacities induced by post-exercise physiological concentrations of Hsp72.

Heat shock protein 70 enhances vascular bone morphogenetic protein-4 signaling by binding matrix Gla protein

RATIONALE

Matrix Gla protein (MGP) is a calcification inhibitor, which binds and inhibits bone morphogenetic protein (BMP)-2 and -4.

OBJECTIVE

The objective was to determine whether MGP also binds other proteins, which could interfere with its function.

METHODS AND RESULTS

We transfected bovine aortic endothelial cells with N-terminally FLAG-tagged MGP and used immunoprecipitation and liquid chromatographic-tandem mass spectrometric analysis to identify MGP-binding proteins. Heat shock protein (HSP)70, a stress-induced protein expressed in atherosclerotic lesions and soluble in serum, was identified as a novel MGP-binding protein. The interaction between MGP and HSP70 was confirmed by coimmunoprecipitation and chemical crosslinking, and blocked the interaction between MGP and BMP-4. In endothelial cells, HSP70 enhanced BMP-4-induced proliferation and tube formation, and in calcifying vascular cells, HSP70 enhanced BMP-induced calcium deposition. In addition, HSP70 mediated the procalcific effect of interleukin-6 on calcifying vascular cells. In apolipoprotein E-null mice, a model for atherosclerosis, levels of BMP-4, HSP70, MGP, and interleukin-6 were elevated in the aortic wall. Levels of BMP-4, HSP70, and interleukin-6 were also elevated in serum, and anti-HSP70 antibodies diminished its procalcific effect on calcifying vascular cells.

CONCLUSION

HSP70 binds MGP and enhances BMP activity, thereby functioning as a potential link between cellular stress, inflammation, and BMP signaling.

Stress proteins and oxidative damage in a renal derived cell line exposed to inorganic mercury and lead

A close link between stress protein up-regulation and oxidative damage may provide a novel therapeutic tool to counteract nephrotoxicity induced by toxic metals in the human population, mainly in children, of industrialized countries. Here we analysed the time course of the expression of several heat shock proteins, glucose-regulated proteins and metallothioneins in a rat proximal tubular cell line (NRK-52E) exposed to subcytotoxic doses of inorganic mercury and lead. Concomitantly, we used morphological and biochemical methods to evaluate metal-induced cytotoxicity and oxidative damage. In particular, as biochemical indicators of oxidative stress we detected reactive oxygen species (ROS) and nitrogen species (RNS), total glutathione (GSH) and glutathione-S-transferase (GST) activity. Our results clearly demonstrated that mercury increases ROS and RNS levels and the expressions of Hsp25 and inducible Hsp72. These findings are corroborated by evident mitochondrial damage, apoptosis or necrosis. By contrast, lead is unable to up-regulate Hsp72 but enhances Grp78 and activates nuclear Hsp25 translocation. Furthermore, lead causes endoplasmic reticulum (ER) stress, vacuolation and nucleolar segregation. Lastly, both metals stimulate the over-expression of MTs, but with a different time course. In conclusion, in NRK-52E cell line the stress response is an early and metal-induced event that correlates well with the direct oxidative damage induced by mercury. Indeed, different chaperones are involved in the specific nephrotoxic mechanism of these environmental pollutants and work together for cell survival.

Increased intracellular, cell surface, and secreted inducible heat shock protein 70 responses are triggered during the monocyte to dendritic cell (DC) transition by cytokines independently of heat stress and infection and may positively regulate DC growth

Physiologic triggers and functional consequences of endogenous heat shock protein (HSP) responses in dendritic cells (DC) are poorly defined. In this study, we show that even in the absence of heat stress and infection, a specific cohort of DC/proinflammatory cytokines (IL-4-IL-13/IL-6/GM-CSF) institutes an enhanced inducible (i)HSP70 intracellular and extracellular response in human monocyte-derived DC, especially during the monocyte to DC transition. Interestingly, whereas heat stress alone initiated an intracellular iHSP70 response in monocyte DC precursors, it did not promote cell surface or secreted iHSP70 responses, both of which were induced by cytokines independently of heat. The cytokine-induced iHSP70 response, which did not occur in lymphocytes, or monocytes-macrophages generated with M-CSF, was instituted within 48 h of cytokine exposure, and peaked upon commitment to DC growth at 72 h. Although a return to baseline levels was noted after this period, a distinct rise in iHSP70 occurred again during terminal DC maturation. Chemical inhibition of the iHSP70 response with either triptolide or KNK-437 was coupled with inhibition of DC differentiation and yielded cells displaying features of monocytes-macrophages. Exogenously supplied riHSP70 amplified events associated with cytokine-advanced DC differentiation/maturation, most notably the up-regulation of antiapoptotic proteins (Bcl-x(L)). Engaging the HSP receptor CD40 with CD40L produced identical results as extracellular riHSP70, and, moreover, an enhanced iHSP70 response. Thus, distinct iHSP70 and HSP receptor-mediated responses are triggered by cytokines irrespective of heat stress and infection in monocyte-derived DC and may function to positively regulate monocyte-derived DC, especially during critical periods of their growth.

Unconventional secretion of tubby and tubby-like protein 1

Tubby-like proteins (Tulps) with no signal peptide have been characterized as cytoplasmic proteins with various intracellular functions, including binding to phosphatidylinositol-4,5-bisphosphate [PI(4,5)P(2)]. PI(4,5)P(2) has been implicated in unconventional secretion of fibroblast growth factor-2 without a signal peptide. Here, we show that all Tulps are expressed intracellularly and extracellularly. Tubby secretion is partially dependent on its PI(4,5)P(2)-binding activity with an essential secretory signal in the N-terminus. Pathogenic mutation in Tubby mice has no impact on tubby extracellular trafficking. Moreover, unconventional secretion of tubby and Tulp1 is independent of endoplasmic reticulum-Golgi pathway. These data implicate that Tulps may function extracellularly as well.