Hypertonic saline dextran after burn injury decreases inflammatory cytokine responses to subsequent pneumonia-related sepsis

Intravitreal Injection of Normal Saline Induces Retinal Degeneration in the C57BL/6J Mouse

PURPOSE

To investigate the adverse effect of intravitreal injection of normal saline (NS) and phosphate buffered saline (PBS) in mouse eyes.

METHODS

NS or PBS was injected intravitreally into C57BL/6J mouse eyes. Retinal lesions were monitored by fundus imaging, spectral-domain optical coherence tomography (SD-OCT), and histological investigations. Retinal immune gene expression was determined by real-time polymerase chain reaction (PCR). The toxic effect of NS and PBS or retinal protein from NS- or PBS-injected eyes on retinal pigment epithelium (RPE) was tested in B6-RPE-07 mouse RPE cell cultures.

RESULTS

Intravitreal injection of NS dose-dependently induced localized retinal lesion in mice. Histological investigations revealed multiple vacuoles in photoreceptor outer segments and RPE cells. The lesions recovered over time and by 3 weeks post injection the majority of lesions vanished in eyes receiving 1 μl NS. Inflammatory genes, including TNF-α, IL-1β, IL-6, iNOS, and VEGF were upregulated in NS injected eyes. Intravitreal injection of PBS did not cause any pathology. The treatment of B6-RPE07 cells with 30% PBS or 30% NS did not affect RPE viability. However, incubation of 1-μg/ml retinal protein from NS-injected eyes, but not PBS-injected eyes induced RPE cell death.

CONCLUSION

NS is toxic to the C57BL/6J mouse retina and should not be used as a vehicle for intraocular injection. PBS is not toxic to the retina and is a preferred vehicle.

TRANSLATIONAL RELEVANCE

NS is not a physiological solution for intraocular injection in the C57BL/6J mice and questions its suitability for intraocular injection in other species, including human.

The cardioprotective effect of hypertonic saline is associated with inhibitory effect on macrophage migration inhibitory factor in sepsis

Sepsis can cause myocardial dysfunction, which contributes to the high mortality of sepsis. Hypertonic saline (HS) has been reported to increase myocardial contractility in sepsis. In the present study, mechanisms of action of HS resuscitation (4 mL of 7.5% NaCl per kilogram) on cardiac function have been evaluated in septic rats. HS was administered 1 h after LPS (10 mg/kg, i.v.) challenge. The mean arterial blood pressure significantly decreased 4 h after LPS challenge, and septic shock was observed at the end of experiment (6 h). Posttreatment with HS prevented hypotension caused by LPS and significantly improved cardiac function, evidenced by increases in left ventricular developed pressure, mean +dP/dt and -dP/dt. The amplitude of electrical-stimulated intracellular Ca(2+) transient in isolated single cardiomyocytes was significantly reduced after 6 h LPS insult, which was recovered by HS. In addition, LPS resulted in significant increases in neutrophil myeloperoxidase activity, macrophage migration inhibitory factor (MIF), and NF-κB phospho-p65 protein levels in myocardium at 6 h, which were significantly attenuated by HS. In conclusion, HS improved myocardial contractility and prevented circulatory failure induced by endotoxemia, which may attribute to improvement of intracellular calcium handling process and inhibitory effects on neutrophil infiltration and MIF production in hearts.

Oxidative stress decreases phosphatidylinositol 4,5-bisphosphate levels by deactivating phosphatidylinositol- 4-phosphate 5-kinase beta in a Syk-dependent manner

Phosphatidylinositol 4,5-bisphosphate (PIP(2)) has many essential functions and its homeostasis is highly regulated. We previously found that hypertonic stress increases PIP(2) by selectively activating the beta isoform of the type I phosphatidylinositol phosphate 5-kinase (PIP5Kbeta) through Ser/Thr dephosphorylation and promoting its translocation to the plasma membrane. Here we report that hydrogen peroxide (H(2)O(2)) also induces PIP5Kbeta Ser/Thr dephosphorylation, but it has the opposite effect on PIP(2) homeostasis, PIP5Kbeta function, and the actin cytoskeleton. Brief H(2)O(2) treatments decrease cellular PIP(2) in a PIP5Kbeta-dependent manner. PIP5Kbeta is tyrosine phosphorylated, dissociates from the plasma membrane, and has decreased lipid kinase activity. In contrast, the other two PIP5K isoforms are not inhibited by H(2)O(2). We identified spleen tyrosine kinase (Syk), which is activated by oxidants, as a candidate PIP5Kbeta kinase in this pathway, and mapped the oxidant-sensitive tyrosine phosphorylation site to residue 105. The PIP5KbetaY105E phosphomimetic is catalytically inactive and cytosolic, whereas the Y105F non-phosphorylatable mutant has higher intrinsic lipid kinase activity and is much more membrane associated than wild type PIP5Kbeta. These results suggest that during oxidative stress, as modeled by H(2)O(2) treatment, Syk-dependent tyrosine phosphorylation of PIP5Kbeta is the dominant post-translational modification that is responsible for the decrease in cellular PIP(2).

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.

Influence of dextran-70 on systemic inflammatory response and myocardial ischaemia-reperfusion following cardiac operations

Introduction

Experimental studies have demonstrated that dextran-70 reduces the leukocyte–endothelium interaction, but clinical evidence is still lacking. Our objective was to justify the anti-inflammatory effect of dextran-70 following cardiac operations.

Methods

Forty patients undergoing coronary bypass surgery (n = 32) or aortic valve replacement (n = 8) were enrolled in this prospective, randomized, double-blind study. Two groups were formed. In group A (n = 20), dextran-70 infusion was administered at a dose of 7.5 ml/kg before the initiation of cardiopulmonary bypass and at a dose of 12.5 ml/kg after the cessation of cardiopulmonary bypass. Group B served as a control with identical amounts of gelatin infusion (n = 20). The plasma concentration of procalcitonin, C-reactive protein, IL 6, IL 6r, IL 8, IL 10, soluble endothelial leukocyte adhesion molecule-1, soluble intercellular adhesion molecule-1, cardiac troponin-I and various haemodynamic parameters were measured in the perioperative period. Multivariate methods were used for statistical analysis.

Results

In group A, lower peak (median) plasma levels of procalcitonin (0.2 versus 1.4, p < 0.001), IL 8 (5.6 versus 94.8, p < 0.001), IL 10 (47.2 versus 209.7, p = 0.001), endothelial leukocyte adhesion molecule-1 (88.5 versus 130.6, p = 0.033), intercellular adhesion molecule-1 (806.7 versus 1,375.7, P = 0.001) and troponin-I (0.22 versus 0.66, p = 0.018) were found. There was no significant difference in IL 6, IL-6r and C-reactive protein values between groups. Higher figures of the cardiac index (p = 0.010) along with reduced systemic vascular resistance (p = 0.005) were noted in group A.

Conclusion

Our investigation demonstrated that the use of dextran-70 reduces the systemic inflammatory response and cardiac troponin-I release following cardiac operation.

Trial registration number

ISRCTN38289094.

Translational systems biology: introduction of an engineering approach to the pathophysiology of the burn patient

The pathophysiology of the burn patient manifests the full spectrum of the complexity of the inflammatory response. In the acute phase, inflammation may have negative effects via capillary leak, the propagation of inhalation injury, and development of multiple organ failure. Attempts to mediate these processes remain a central subject of burn care research. Conversely, inflammation is a necessary prologue and component in the later stage processes of wound healing. Despite the volume of information concerning the cellular and molecular processes involved in inflammation, there exists a significant gap between the knowledge of mechanistic pathophysiology and the development of effective clinical therapeutic regimens. Translational systems biology (TSB) is the application of dynamic mathematical modeling and certain engineering principles to biological systems to integrate mechanism with phenomenon and, importantly, to revise clinical practice. This study will review the existing applications of TSB in the areas of inflammation and wound healing, relate them to specific areas of interest to the burn community, and present an integrated framework that links TSB with traditional burn research.

Attenuating burn wound inflammation improves pulmonary function and survival in a burn-pneumonia model

OBJECTIVE

We previously showed that topical inhibition of inflammatory signaling in burn wounds reduced systemic inflammatory response and burn-induced pulmonary inflammation. We hypothesized that this topical intervention would attenuate burn-induced lung injury, improve pulmonary function, protect lungs from bacterial invasion, and reduce mortality.

DESIGN

Controlled, in vivo, laboratory study.

SETTING

University laboratory.

SUBJECTS

Female mice, 8-10 wks old.

INTERVENTIONS

Animals received 30% total body surface area burn followed by topical application of a specific inhibitor of p38 mitogen-activated protein kinase, a key inflammatory signaling pathway, or vehicle to the wound. Twenty-four hours after injury, pulmonary collagen deposition and pulmonary function were assessed. One day postburn, some of the animals received intratracheal instillation of Klebsiella pneumoniae and were subsequently monitored for 7 days.

MEASUREMENTS AND MAIN RESULTS

Topical inhibition of p38 mitogen-activated protein kinase significantly decreased pulmonary collagen deposition and prevented a decline in pulmonary function at 1 day after burn injury. Compared with sham controls, animals with burn injury had a significantly higher mortality in response to intratracheal bacterial challenge. Application of p38 mitogen-activated protein kinase inhibitor to the burn wound attenuated pulmonary neutrophil infiltration and reduced the mortality rate to a level experienced by sham controls.

CONCLUSIONS

Inflammatory source control in burn wounds with topical p38 mitogen-activated protein kinase inhibition attenuates acute lung injury, avoids pulmonary dysfunction, protects lungs from bacterial challenge, and improves survival.

Role of interleukin-6 in cardiac inflammation and dysfunction after burn complicated by sepsis

To examine the role of myocardial interleukin-6 (IL-6) in myocardial inflammation and dysfunction after burn complicated by sepsis, we performed 40% total body surface area contact burn followed by late (7 days) Streptococcus pneumoniae pneumonia sepsis in wild-type (WT) mice, IL-6 knockout (IL-6 KO) mice, and transgenic mice overexpressing IL-6 in the myocardium (TG). Twenty-four hours after sepsis was induced, isolated cardiomyocytes were harvested and cultured in vitro, and supernatant concentrations of IL-6 and tumor necrosis factor (TNF)-alpha were measured. Cardiomyocyte intracellular calcium ([Ca(2+)](i)) and sodium ([Na(+)](i)) concentrations were also determined. Separate mice in each group underwent in vivo global hemodynamic and cardiac function assessment by cannulation of the carotid artery and insertion of a left ventricular pressure volume conductance catheter. Hearts from these mice were collected for histopathological assessment of inflammatory response, fibrosis, and apoptosis. In the WT group, there was an increase in cardiomyocyte TNF-alpha, [Ca(2+)](i), and [Na(+)](i) after burn plus sepsis, along with cardiac contractile dysfunction, inflammation, and apoptosis. These changes were attenuated in the IL-6 KO group but accentuated in the TG group. We conclude myocardial IL-6 mediates cardiac inflammation and contractile dysfunction after burn plus sepsis.

The cellular, metabolic, and systemic consequences of aggressive fluid resuscitation strategies

Increasing evidence has demonstrated that aggressive crystalloid-based resuscitation strategies are associated with cardiac and pulmonary complications, gastrointestinal dysmotility, coagulation disturbances, and immunological and inflammatory mediator dysfunction. As large volumes of fluids are administered, imbalances in intracellular and extracellular osmolarity occur. Disturbances in cell volume disrupt numerous regulatory mechanisms responsible for keeping the inflammatory cascade under control. Several authors have demonstrated the detrimental effects of large, crystalloid-based resuscitation strategies on pulmonary complications in specific surgical populations. Additionally, fluid-restrictive strategies have been associated with a decreased frequency of and shorter time to recovery from acute respiratory distress syndrome and trends toward shorter lengths of stay and lower mortality. Early resuscitation of hemorrhagic shock with predominately saline-based regimens has been associated with cardiac dysfunction and lower cardiac output, as well as higher mortality. Numerous investigators have evaluated potential risk factors for developing abdominal compartment syndrome and have universally noted the excessive use of crystalloids as the primary determinant. Resuscitation regimens that cause early increases in blood flow and pressure may result in greater hemorrhage and mortality than those regimens that yield comparable flow and pressure increases late in resuscitation. Future resuscitation research is likely to focus on improvements in fluid composition and adjuncts to administration of large volume of fluid.