Protective role of heat stress in burn trauma*

Ultrashort wave diathermy inhibits pulmonary inflammation in mice with acute lung injury in a HSP70 independent way: a pilot study

BACKGROUND

Acute lung injury (ALI) is a clinical syndrome characterized by pulmonary inflammation. Ultrashort wave diathermy (USWD) has been shown to be effective at in inhibiting ALI inflammation, although the underlying mechanism remains unclear. Previous studies have demonstrated that USWD generates a therapeutic thermal environment that aligns with the temperature required for heat shock protein 70 (HSP70), an endogenous protective substance. In this study, we examined the correlation between HSP70 and USWD in alleviating lung inflammation in ALI.

METHODS

Forty-eight male C57BL/6 mice were randomly divided into control, model, USWD intervention (LU) 1, 2, and 3, and USWD preintervention (UL) 1, 2, and 3 groups (n = 6 in each group). The mice were pretreated with LPS to induce ALI. The UL1, 2, and 3 groups received USWD treatment before LPS infusion, while the LU1, 2, and 3 groups received USWD treatment after LPS infusion. Lung function and structure, inflammatory factor levels and HSP70 protein expression levels were detected.

RESULTS

USWD effectively improved lung structure and function, and significantly reduced IL-1β, IL-10, TGF-β1, and TNF-α levels in both the USWD preintervention and intervention groups. However, HSP70 expression did not significantly differ across the experimental groups although the expression of TLR4 was significantly decreased, suggesting that USWD may have anti-inflammatory effects through multiple signaling pathways or that the experimental conditions should be restricted.

CONCLUSIONS

Both USWD intervention and preintervention effectively reduced the inflammatory response, alleviated lung injury symptoms, and played a protective role in LPS-pretreated ALI mice. HSP70 was potentially regulated by USWD in this process, but further studies are urgently needed to elucidate the correlation and mechanism.

Thymosin β4 has a major role in dermal burn wound healing that involves actin cytoskeletal remodelling via heat-shock protein 70

Rapid vascular remodelling of damaged dermal tissue is required to heal burn wounds. Thymosin β4 (Tβ4) is a growth factor that has been shown to promote angiogenesis and dermal wound repair. However, the underlying mechanisms based on Tβ4 function have not yet been fully investigated. In the present study, we investigated how Tβ4 improves dermal burn wound healing via actin cytoskeletal remodelling and the action of heat-shock proteins (HSPs), which are a vital set of chaperone proteins that respond to heat shock. Our in vitro results achieved with the use of human umbilical vein endothelial cells (HUVECs) revealed a possible signal between Tβ4 and HSP70. Moreover, we confirmed that remodelling of filamentous actin (F-actin) was regulated by Tβ4-induced HSP70 in HUVECs. Based on these in vitro results, we confirmed the healing effects of Tβ4 in an adapted dermal burn wound in vivo model. Tβ4 improved wound-healing markers, such as wound closure and vascularization. Moreover, Tβ4 maintained the long-term expression of HSP70, which is associated with F-actin regulation during the wound-healing period. These results suggest that an association between Tβ4 and HSP70 is responsible for the healing of burn wounds, and that this association may regulate F-actin remodelling. Copyright © 2015 John Wiley & Sons, Ltd.

Deficiency in Heat Shock Factor 1 (HSF-1) Expression Exacerbates Sepsis-induced Inflammation and Cardiac Dysfunction

In the present study, we investigated whether absence of heat shock factor 1 (HSF-1) and inability to increase myocardial expression of heat shock proteins alter septic responses of inflammatory cytokines and myocardial contractility. HSF-1 knockout (hsf ^-/-) mice and wild type litter mates underwent a sterile (lipopolysaccharide; LPS) or infectious (Streptococcus pneumoniae or Klebsiella pneumoniae) septic challenge. Production of cytokines, TNF, IL-1β, IL-6 and IL-10, in the blood and from cardiomyocytes was exaggerated in the hsf ^-/- mice compared to responses measured in wild type mice given an identical septic challenge. This enhanced compartmentalized myocardial inflammation was associated with significantly decreased cardiac contraction and diminished relaxation in the hsf ^-/- mice. However, lacking HSF-1 expression did not affect intracellular calcium and sodium responses in cardiomyocytes isolated from septic challenged mice, suggesting that ion loading was not a major or sustaining cause of the greater myocardial contractile defects in hsf ^-/- mice. In conclusion, our data indicated that HSF-1 and downstream heat shock proteins are essential components to support cardiac function in sepsis. Further studies are warranted to further define the precise mechanisms of HSF-1 mediated cardiac protection.

Therapeutic role of toll-like receptor modification in cardiovascular dysfunction

Toll-like receptors (TLR) are key pattern recognition receptors in the innate immune system. The TLR-mediated immune response against pathogens is usually protective however inappropriate TLR activation may lead to excessive tissue damage. It is well recognised that TLRs respond to a variety of endogenous as well as exogenous ligands. By responding to endogenous ligands that are exposed during cellular damage, TLRs have been implicated in a range of pathological conditions associated with cardiovascular dysfunction. Increasing knowledge on the mechanisms involved in TLR signalling has encouraged the exploration of therapeutic pharmacological modulation of TLR activation in conditions such as atherosclerosis, ischaemic heart disease, heart failure and ischaemic reperfusion injury. The aim of this review is to explore the translational potentials of TLR modification in cardiovascular dysfunction, where these agents have been studied.

Effects of propofol with hyperthermia in a rat model of endotoxemic shock

BACKGROUND

We aimed to investigate the effects of active mild hyperthermia and the effects of active mild hyperthermia with propofol on mortality and inflammatory responses during endotoxin-induced shock in rats.

METHODS

Intravenous Escherichia coli endotoxin (15 mg/kg over 2 min) was injected in 48 rats. The animals were randomly allocated to one of the following four groups (n = 12 per group): normothermia group (group N), rectal temperature maintained between 36 °C and 38 °C; hyperthermia group (group H), rectal temperature was moderate and maintained between 39 °C and 40 °C; propofol with normothermia group (group PN), propofol (10 mg/kg/h) was administered, and temperature was between 36 °C and 38 °C; Propofol with hyperthermia group (group PH), propofol (10 mg/kg/h) administrated, and temperatures were maintained between 39 °C and 40 °C. The primary outcome was mortality 8 h after endotoxin injection. Secondary outcomes included changes in haemodynamics, arterial blood gases and plasma cytokine concentrations for the 8-h observation period.

RESULTS

Mortality rates 8 h after endotoxin injection were 92%, 100%, 68% and 50% for N, H, PN and PH groups, respectively. There was no difference in hypotension, acidosis, and increase in plasma cytokine concentrations between N and H groups, but these parameters were attenuated in group PH.

CONCLUSION

The mortality rates in the present study were extremely high; further hypotension and elevations in plasma pro-inflammatory and anti-inflammatory cytokine concentrations after endotoxin injection were not attenuated by mild hyperthermia between 39 °C and 40 °C, but they were attenuated by propofol with mild hyperthermia.

Transpulmonary thermodilution for hemodynamic measurements in severely burned children

Introduction

Monitoring of hemodynamic and volumetric parameters after severe burns is of critical importance. Pulmonary artery catheters, however, have been associated with many risks. Our aim was to show the feasibility of continuous monitoring with minimally invasive transpulmonary thermodilution (TPTD) in severely burned pediatric patients.

Methods

This prospective cohort study was conducted in patients with severe burns over 40% of the total body surface area (TBSA) who were admitted to the hospital within 96 hours after sustaining the injury. TPTD measurements were performed using the PiCCO system (Pulsion Medical Systems, Munich, Germany). Cardiac Index (CI), Intrathoracic Blood Volume Index (ITBVI) (Stewart-Hamilton equation), Extravascular Lung Water Index (EVLWI) and Systemic Vascular Resistance Index (SVRI) measurements were recorded twice daily. Statistical analysis was performed using one-way repeated measures analysis of variance with the post hoc Bonferroni test for intra- and intergroup comparisons.

Results

Seventy-nine patients with a mean age (±SD) of 9 ± 5 years and a mean TBSA burn (±SD) of 64% ± 20% were studied. CI significantly increased compared to level at admission and was highest 3 weeks postburn. ITBVI increased significantly starting at 8 days postburn. SVRI continuously decreased early in the perioperative burn period. EVLWI increased significantly starting at 9 days postburn. Young children (0 to 5 years old) had a significantly increased EVLWI and decreased ITBVI compared to older children (12 to 18 years old). EVLWI was significantly higher in patients who did not survive burn injury.

Conclusions

Continuous PiCCO measurements were performed for the first time in a large cohort of severely burned pediatric patients. The results suggest that hyperdynamic circulation begins within the first week after burn injury and continues throughout the entire intensive care unit stay.

Molecular or pharmacologic inhibition of the CD14 signaling pathway protects against burn-related myocardial inflammation and dysfunction

Signaling through toll-like receptor 4 (TLR4) plays an obligate role in burn-related myocardial dysfunction. We hypothesized that signaling through CD14, a cellular receptor for endotoxin that lacks a transmembrane domain but is coupled to TLR4, also plays a role in postburn myocardial inflammation and dysfunction. Burn covering 40% total body surface area (or sham burn for controls) was produced in wild-type (WT) and CD14 knockout (KO) as well as vehicle-treated and geldanamycin-treated WT mice (1 microg/g body weight) to inhibit CD14 signaling. Groups included (1) WT shams, (2) CD14 KO sham, (3) WT burns, (4) CD14 KO burns, (5) vehicle-treated WT shams, (6) geldanamycin-treated WT shams, (7) vehicle-treated WT burns, and (8) geldanamycin-treated WT burns. Twenty-four hours after burn, cardiac function (Langendorff) and cardiomyocyte secretion of inflammatory cytokines TNF-alpha, IL-1 beta, and IL-6 (in pg/mL; 5 x 10(4) myocytes) were studied in all groups. Relative to sham WT controls, burn trauma in increased cardiac myocyte secretion of inflammatory cytokines (TNF-alpha, IL-1 beta, and IL-6 rose from 59 +/- 10 to 171 +/- 8; 6 +/- 0.2 to 78 +/- 1; and 88 +/- 3 to 170 +/- 12 pg/mL, respectively; P < 0.05) and produced robust cardiac contractile dysfunction (left ventricular pressure and +dP/dt fell from 105 +/- 4 to 73 +/- 5 mmHg and 2,400 +/- 73 to 1,803 +/- 90 mmHg/s; P < 0.05). Inability to signal through the CD14/TLR4 pathway (induced by CD14/KO or inhibition of CD14 expression by administration of geldanamycin) attenuated TNF-alpha, IL-1 beta, and IL-6 production in response to burn injury and improved postburn myocardial contractile function. Our data suggest that signaling through the CD14 pathway plays an obligate role in cardiac inflammation/dysfunction which occurs after major burn injury.

Induction of heat shock protein 70 by sodium arsenite attenuates burn-induced intestinal injury in severe burned rats

The present study was designed to assess the effects of induced heat shock protein 70 (HSP70) on intestinal injury after severe burn. Wistar rats were randomly divided into four groups: control group, burn group (B group), sodium arsenite pretreatment group (SA group), and sodium arsenite+quercetin pretreatment group (SA+Qu group). Plasma endotoxin and d-lactic acid content were determined at 3, 6, 12, 24, and 48h after severe burn. Samples of small intestine were obtained for histologic assessment of intestinal mucosal injury and the expression of HSP70 was assayed by Western blot. Apoptosis of the intestinal epithelial cells was examined by the TUNEL method. Results showed that SA pretreatment significantly increased expression of HSP70 in the small intestine. SA pretreatment attenuated the burn-induced increase in plasma endotoxin and d-lactic acid content, intestinal injury scores and the percentage of apoptotic intestinal epithelial cells. Co-administration of quercetin with SA abolished the SA-induced HSP70 over-expression and the beneficial effects of SA. Our findings suggest increasing expression of HSP70 induced by SA pretreatment attenuates burn-induced intestinal injury apparently by preventing apoptosis.

Cardiac molecular signaling after burn trauma

Research using mammalian burn models has defined significant cardiac deficits after burn injury. The physiologic response to burn and burn complicated by sepsis, including the cardiac dysfunction associated with these insults, remains a very complex physiologic process which, despite active study, remains unclear. The well-characterized inflammatory mediators such as tumor necrosis factor-alpha, interleukin-1beta, and interleukin-6 continue to play an active role in mediating cardiac dysfunction. However, perhaps of greater interest are the late mediators, high mobility group box 1 and macrophage migration inhibitory factor, because they offer a very realistic window for therapeutic intervention for controlling the inflammatory response. In addition, several other mediators of cardiac dysfunction have been identified and include the heat shock proteins, apoptosis, and the inflammatory caspases. These new mediators provide opportunities for therapeutic intervention, but further research is needed to clarify the importance of their mechanisms of action and the complex interactions between these various signaling pathways.

Expression of heat-shock protein 70 (Hsp70) in the respiratory tract and lungs of fire victims

Immunohistochemical investigation of the respiratory tract and lungs of 63 fire victims revealed a statistically significant enhanced expression of heat-shock protein 70 (Hsp70) in the epiglottis, the trachea, and the main and the peripheral bronchi compared with a control group. In the fire victims, a strong expression of Hsp70 was discernible not only particularly in the vessels but also in seromucous secretory cells, ciliated epithelial cells, smooth muscle cells, and alveolar cells. The results suggest a vital or supravital reaction due to the inhalation of hot fire fumes.

Expression of Hsp72 in lymphocytes in patients with febrile convulsion

The pathophysiology of febrile convulsion, the most common childhood neurologic disease, remains unclear. In this study, we investigated what role a heat shock protein plays in this disease. We enrolled eight boys and two girls with febrile convulsion and 10 age-matched healthy controls. We did a biosynthetic evaluation of both groups by separating lymphocytes and measuring the expression of heat shock protein 72 before and after heat shock treatment. Before the treatment, both groups were found to have small amounts of constitutive heat shock protein 72. Afterwards, its expression increased in both groups, and no statistical difference was found between the increases in the two groups. In addition, there was no obvious difference in the susceptibility to produce heat shock proteins. However, the febrile convulsion group was found to have a significant decrease in phosphorylation of heat shock protein 72. These results suggest the possible involvement of post-translational modification of heat shock proteins, most likely phosphorylation, in the pathogenesis of febrile convulsion.

Antioxidant up-regulation and increased nuclear DNA protection play key roles in adaptation to oxidative stress in epithelial cells

Cells are armed with a vast repertoire of antioxidant defense mechanisms to help prevent the accumulation of oxidative damage. It is becoming increasingly apparent that the cellular adaptive response has an important antioxidant function to counteract oxidative stress. To investigate this adaptive response we assessed the effect of sublethal H2O2 on cell viability, enzymatic activity, and nuclear (nDNA) and mitochondrial DNA (mtDNA) susceptibility to damage and repair in cultured human retinal pigment epithelium (RPE) cells. This nondividing cell type exists in a highly oxidizing microenvironment in vivo. Prior exposure to sublethal H2O2 confirmed an adaptive response, resulting in a greater cellular resistance to subsequent toxic exposures compared to nonadapted RPE (p < 0.05). A greater CAT, GPX, and CuZnSOD enzymatic activity (p < 0.05) and increased nDNA protection (p < 0.05) were also observed. However, there was no adaptive benefit for mtDNA protection or repair in response to oxidative stress. This study confirms a role for the adaptive response as an important antioxidant defense for cells located in inherently oxidizing microenvironments. Furthermore, it identifies that the mitochondria are a weak link in otherwise efficient oxidative stress defenses and that this may contribute to aging and age-related disease.

Protective effect of HSP70 on gastric mucosal cells against apoptosis

AIM: To investigate whether HSP70 can protect gastric mucosal cells from apoptosis induced by chronic emotional stress.

METHODS: Seventy mice were randomly devided into control group (n = 16), heat shock stress group (HS, n = 18), psychological stress group (PS, n = 18), heat shock stress plus psychological stress group (HPS, n = 18). Mice in HS, PS and HPS groups were subjected to heat shock stress, psychological stress, and heat shock stress plus psychological stress respectively. Apoptosis of gastric mucosal cells and the expression level of HSP70 were detected by TUNEL technique and immunohistochemical staining respectively after 1, 2, and 3 mo.

RESULTS: After 1 mo, apoptotic cells among the 4 groups were not significant. After 2 mo, apoptotic rate in PS group was significantly higher than control group (3.7 ± 1.9% vs 1.3 ± 1.4%, P = 0.017 < 0.05), SH group (3.7 ± 1.9% vs 1.2 ± 1.6%, P = 0.010 < 0.05), and HPS group (3.7 ± 1.9% vs 1.3 ± 1.1%, P = 0.012 < 0.05). After 3 mo, apoptotic rate in PS group was significantly higher than that in control group (4.1 ± 3.9% vs 1.0 ± 1.1%, P = 0.025 < 0.05), HS group (4.1 ± 3.9% vs 0.4 ± 0.7%, P = 0.009 < 0.05), and HPS group (4.1 ± 3.9% vs 1.4 ± 1.5%, P = 0.046 < 0.05). After 1 mo, HSP70 level was significantly higher in HS group and HPS group than that in control group (64 ± 11% vs 20 ± 11%, P = 0.00 < 0.05; 72 ± 6% vs 20 ± 11%, P = 0.00 < 0.05) and psychological stress group (64 ± 11% vs 34 ± 15%, P = 0.00 < 0.05; 72 ± 6% vs 34 ± 15%, P = 0.00 < 0.05). After 2 mo, HSP70 level was significantly higher in HS and HPS group than that in control group (84 ± 13% vs 25 ± 15%, P = 0.00 < 0.05; 87 ± 7% vs 25 ± 15%, P = 0.00 < 0.05) and PS group (84 ± 13% vs 46 ± 30%, P = 0.02 < 0.05; 87 ± 7% vs 46 ± 30%, P = 0.01 < 0.05). After 3 mo, HSP70 level was also significantly higher in HS and HPS group than those in control group (61 ± 16% vs 16 ± 9%, P = 0.02 < 0.05; 65 ± 29% vs 16 ± 9%, P = 0.01 < 0.05) and PS group (61 ± 16% vs 33 ± 29%, P = 0.09 < 0.05; 65 ± 29% vs 33 ± 29 %, P = 0.046 < 0.05). HSP70 level was negatively correlated with apoptotic rate of gastric mucosal cells (r = -0.320, P = 0.008 < 0.05).

CONCLUSION: Chronic emotional stress can induce apoptosis of gastric mucosal cells while HSP70 can protect them from apoptosis.

N/A

N/A