Reduction in intestinal leukocyte adherence in rat experimental endotoxemia by treatment with the 21-aminosteroid U-74389G

Gu-4 suppresses affinity and avidity modulation of CD11b and improves the outcome of mice with endotoxemia and sepsis

Background

Systemic leukocyte activation and disseminated leukocyte adhesion will impair the microcirculation and cause severe decrements in tissue perfusion and organ function in the process of severe sepsis. Gu-4, a lactosyl derivative, could selectively target CD11b to exert therapeutic effect in a rat model of severe burn shock. Here, we addressed whether Gu-4 could render protective effects on septic animals.

Methodology/Principal Findings

On a murine model of endotoxemia induced by lipopolysaccharide (LPS), we found that the median effective dose (ED50) of Gu-4 was 0.929 mg/kg. In vivo treatment of Gu-4 after LPS challenge prominently attenuated LPS-induced lung injury and decreased lactic acid level in lung tissue. Using the ED50 of Gu-4, we also demonstrated that Gu-4 treatment significantly improved the survival rate of animals underwent sepsis induced by cecal ligation and puncture. By adhesion and transwell migration assays, we found that Gu-4 treatment inhibited the adhesion and transendothelial migration of LPS-stimulated THP-1 cells. By flow cytometry and microscopy, we demonstrated that Gu-4 treatment inhibited the exposure of active I-domain and the cluster formation of CD11b on the LPS-stimulated polymorphonuclear leukocytes. Western blot analyses further revealed that Gu-4 treatment markedly inhibited the activation of spleen tyrosine kinase in LPS-stimulated THP-1 cells.

Conclusions/Significance

Gu-4 improves the survival of mice underwent endotoxemia and sepsis, our in vitro investigations indicate that the possible underlying mechanism might involve the modulations of the affinity and avidity of CD11b on the leukocyte. Our findings shed light on the potential use of Gu-4, an interacting compound to CD11b, in the treatment of sepsis and septic shock.

Hypertonic saline downregulate the production level of lipopolysaccharide-induced migration inhibitory factor in THP-1 cells

Purpose

Macrophage migration inhibitory factor (MIF) may serve as a general marker for systemic inflammation in septic and nonseptic acute critical illness. Additionally, our previous experiment has demonstrated that immunosuppressant Prostaglandin E₂ (PGE₂) lowered MIF levels and inhibited T-cells proliferation when compared to control levels. The addition of hypertonic saline (HTS) increased MIF production as compared with PGE₂-stimulated T-cells in concordance with restore PGE₂-suppressed T-cells proliferation. Generally, HTS has been well known for its anti-inflammatory effect so far. Therefore, the experiments were conducted to evaluate MIF after stimulating lipopolysaccharide (LPS) either in the presence or absence of HTS in monocyte, in response to early phase injury.

Methods

Human acute monocytic leukemic cell line (THP-1) cells were cultured in RPMI media, to a final concentration of 1 × 10⁶ cells/mL. The effect of HTS on LPS-induced MIF was evaluated in monocyte with 1 µg/mL LPS. HTS at 10, 20 or 40 mmol/L above isotonicity was added. MIF concentrations of the supernatant were determined by enzyme-linked immunosorbent assay, and cell lysates were used for Western blots analysis to determine the MIF expression.

Results

MIF concentrations in the cell supernatant increased in LPS-induced cells compared to control cells. Also, levels of MIF protein expression were higher in LPS stimulating cells. However, the addition of HTS to LPS stimulated cell restored MIF concentrations and MIF expression.

Conclusion

The role of HTS in maintaining physiological balance in human beings, at least in part, should be mediated through the MIF pathway.

Experimental Endotoxemia Induces Leukocyte Adherence and Plasma Extravasation Within the Rat Pial Microcirculation

Disturbance of capillary perfusions due to leukocyte adhesion, disseminated intravascular coagulation, tissue edema is critical components in the pathophysiology of sepsis. Alterations in brain microcirculation during sepsis are not clearly understood. The aim of this study is to gain an improved understanding of alterations through direct visualization of brain microcirculations in an experimental endotoxemia using intravital microscopy (IVM). Endotoxemia was induced in Lewis rats with Lipopolysaccharide (LPS, 15 mg/kg i.v.). The dura mater was removed via a cranial window to expose the pial vessels on the brain surface. Using fluorescence dyes, plasma extravasation of pial venous vessels and leukocyte-endothelial interaction were visualized by intravital microscopy 4 h after LPS administration. Plasma cytokine levels of IL1-β, IL-6, IFN-γ, TNF-α and KC/GRO were evaluated after IVM. A significant plasma extravasation of the pial venous vessels was found in endotoxemia rats compared to control animals. In addition, a significantly increased number of leukocytes adherent to the pial venous endothelium was observed in septic animals. Endotoxemia also induced a significant elevation of plasma cytokine levels of IL1-β, IL-6, IFN-γ, TNF-α and KC/GRO. Endotoxemia increased permeability in the brain pial vessels accompanied by an increase of leukocyte-endothelium interactions and an increase of inflammatory cytokines in the plasma.

Effect of hypertonic saline and macrophage migration inhibitory factor in restoration of T cell dysfunction

Purpose

Trauma-induced suppression of cellular immune function likely contributes to sepsis, multiple organ dysfunction syndrome and death. T cell proliferation decreases after traumatic stress. The addition of prostaglandin E₂ (PGE₂), which depresses immune function after hemorrhage and trauma, to T-cells decreases T-cell proliferation; and hypertonic saline restores PGE₂-induced T-cell suppression. Recently, it has become apparent that macrophage migration inhibitory factor (MIF) plays a central role in several immune responses, including T-cell proliferation. However, the role of MIF in mediating hypertonic saline (HTS) restoration of T cell dysfunction is unknown. Therefore, we hypothesize that T cell immune restoration by HTS occurs, at least in part, by a MIF-mediated mechanism.

Methods

Jurkat cells were cultured in Roswell Park Memorial Institute media, at a final concentration of 2.5 × 10⁶ cell/mL. The effects of HTS on T-cell proliferation following PGE₂-induced suppression were evaluated in Jurkat cells: HTS at 20 or 40 mmol/L above isotonicity was added. MIF levels were determined by enzyme-linked immunosorbent assay and western blot analysis.

Results

PGE₂ caused a 15.0% inhibition of Jurkat cell proliferation, as compared to the control. MIF levels decreased in PGE₂-suppressed cells, as compared to the control. MIF levels were higher in cells treated with HTS than PGE₂-stimulated cells.

Conclusion

The role of HTS in restoring Jurkat cells proliferation suppressed by PGE₂, at least in part, should be mediated through a MIF pathway.

Protective effects of a superoxide dismutase/catalase mimetic compound against paraquat pneumotoxicity in rat lung

BACKGROUND AND OBJECTIVE

EUK-134 is one of the most promising of the superoxide dismutase (SOD)/catalase mimetic compounds. The antioxidant effects of EUK-134 were tested in a rat model of paraquat pneumotoxicity.

METHODS

Male Wistar rats (n = 72) were divided into three groups: group 1, controls; group 2, paraquat alone; group 3, paraquat + EUK-134. Paraquat dichloride was administered per os at a dose of 80 mg/kg. EUK-134 was injected intraperitoneally at 10 mg/kg 2 h before the paraquat and again 4 h later at 5 mg/kg.

RESULTS

On days 1, 3 and 5 after treatment with paraquat alone the LDH activity increased (P = 0.0001, P = 0.00001 and P = 0.03, respectively), and the total protein content increased (P = 0.00002, P = 0.001 and P = 0.01, respectively). The levels of acid phosphatase (AcP) in BAL fluid increased on days 1 and 3 (P = 0.006 and P = 0.04). In lung homogenates paraquat alone increased SOD activity on day 1 and decreased it on days 3 and 5. Combined treatment with paraquat and EUK-134 elevated LDH activity on day 3 (significantly less than paraquat alone) and day 5, elevated the total protein content on day 5 only, and did not change AcP activity. The combination of both agents did not alter SOD activity and decreased catalase activity on day 5 significantly less than treatment with paraquat alone (P = 0.05).

CONCLUSIONS

EUK-134, a superoxide dismutase/catalase mimetic compound decreased the pneumotoxic effect of paraquat in rats.

Circulating levels of macrophage migration inhibitory factor are associated with mild pulmonary dysfunction after cardiopulmonary bypass

Macrophage migration inhibitory factor (MIF) is a central mediator of inflammatory response and acute lung injury that is secreted in response to corticosteroids. A rise in systemic MIF levels was described after cardiac surgery in steroid-treated patients. This study aimed to investigate the circulating levels of MIF and the possible relationship of this cytokine to pulmonary dysfunction after cardiopulmonary bypass (CPB). We included 74 patients without previous organ dysfunction undergoing elective coronary artery bypass surgery (CABS). The same team performed all CABS via a standard technique adding methylprednisolone (15 mg/kg) to the CPB priming solution (Group MP, n = 37). In the remaining patients (Group NS, n = 37), methylprednisolone was withdrawn from the CPB priming. MIF, C-reactive protein (CRP), and total C3 were assayed in peripheral blood sampled immediately before anesthesia induction and 3, 6, and 24 h post-CPB. Preoperative risk scores and peri- and postoperative variables were documented. Postoperative kinetics of MIF and C3 were similar for both groups. Levels of CRP 24 h post-CPB were higher in Group MP (P = 0.003). Higher MIF levels were detected 6 h post-CPB, and returned to preoperative levels 24 h after CPB. MIF levels 6 h post-CPB were inversely related to the postoperative PaO2/FiO2 ratio (P = 0.0021) and were directly related to the duration of mechanical ventilation (P = 0.014). Perioperative use of methylprednisolone did not modify the MIF response to CPB, but it was related to an enhanced acute phase response. Higher circulating MIF levels 6 h post-CPB were associated with worse postoperative pulmonary short-course outcome.

Evaluation of the Potential Protective Effect of 21-Aminosteroid U-74389G on Liver Injury Induced by Reduced and Prolonged Partial Hepatic Ischaemia Reperfusion in Rats

The protective effect of the 21-aminosteroid U-74389G was studied in an experimental model of partial ischaemia reperfusion liver injury. Previous studies have proven the remarkable potency of 21-aminosteroids to prevent oxidant-induced cell injury in vitro and in vivo. However, the capability of these compounds to limit oxidative injury in clinical trials has been considered to be less certain. The potential protective effect exerted by U-74389G on reduced and prolonged models of ischaemia reperfusion liver injury was studied in male rats subjected to 75 min. of segmentary hepatic ischaemia followed by 1 or 24 hr of reperfusion. Liver injury was evaluated by measuring serum levels of liver enzymes and by histopathological studies. The oxidative status of liver cells was measured by evaluating the levels of liver lipid peroxidation products such as malondialdehyde and the levels of reduced glutathione. Our results lead us to think that treatment with U-74389G (6 mg/kg) does not bring about any protective effect neither in the levels of transaminases nor in the percentage of hepatocellular necrosis and cellular infiltration observed in any reperfusion-period groups. In fact and in contrast with our expectations, U-74389G seemed to increase enzyme release. Furthermore, at the dose used, this 21-aminosteroid is not capable of inhibiting the lipoperoxidation processes, although it induced an important increase of GSH levels at any time-period of reperfusion. This last finding seem to suggest that U-74389G could increase the resistance to oxidant-induced liver tissue damage. However, our results show that, at the dose used, this compound did not exert any protective effect on liver tissue, thus explaining, at least partially, the absence of beneficial effects on the part of these compounds in clinical trials carried out to limit organ injury in transplants.