Biomedical subjects

Mingchen Song

Publications and source records attributed to Mingchen Song.

11 recordsLinked to original sources

PubMed2006

Hyperchloremic acidosis increases circulating inflammatory molecules in experimental sepsis.

RATIONALE: Hyperchloremic acidosis is common in the critically ill and is often iatrogenic. We have previously shown that hyperchloremic acidosis increases nuclear factor-kappaB DNA binding in lipopolysaccharide-stimulated RAW 264.7 cells. However, evidence that hyperchloremic acidosis leads to increased inflammation in vivo has been limited to nitric oxide. OBJECTIVES: To determine if acidosis, induced by dilute hydrochloric acid (HCl) infusion, will increase circulating inflammatory mediator levels in an experimental model of severe sepsis in rats. METHODS: Eighteen hours after inducing lethal sepsis by cecal ligation and puncture in 20 adult, male, Sprague-Dawley rats, we randomized animals into three groups. In groups 2 and 3, we began an IV infusion of 0.1 N HCl to reduce the standard base excess (SBE) by 5 to 10 mEq/L and 10 to 15 mEq/L, respectively. In group 1, we infused a similar volume of lactated Ringer solution. In all groups infusion continued 8 h or until the animal died. MEASUREMENTS AND MAIN RESULTS: We measured arterial blood gases, whole-blood lactate, and chloride, tumor necrosis factor (TNF), interleukin (IL)-6, and IL-10 levels at 0 h, 4 h, and 8 h. All measured cytokines increased over time. Compared to group 1, animals in groups 2 and 3 exhibited greater increase in all three cytokines, with the greatest increases seen with severe acidosis. CONCLUSION: Moderate (SBE, - 5 to - 10) and severe (SBE, - 10 to - 15) acidosis, induced by HCl infusion, increases circulating levels of IL-6, IL-10, and TNF in normotensive septic rats.

Acid-Base Equilibrium↗

PubMed2005

The phase 2 enzyme inducers ethacrynic acid, DL-sulforaphane, and oltipraz inhibit lipopolysaccharide-induced high-mobility group box 1 secretion by RAW 264.7 cells.

The diuretic ethacrynic acid (EA) has been shown to inhibit signaling by the proinflammatory transcription factor nuclear factor-kappaB (NF-kappaB). Accordingly, we sought to determine whether this compound is capable of inhibiting the release of cytokines [interleukin (IL)-6 and IL-10] and NO from RAW 264.7 murine macrophage-like cells stimulated with lipopolysaccharide (LPS). Additionally, we sought to determine whether EA can inhibit secretion of high-mobility group box 1 (HMGB1), a nuclear protein that is secreted by immunostimulated macrophages and functions in the extracellular milieu as a proinflammatory mediator. In a concentration-dependent manner, EA inhibited secretion of IL-6, IL-10, nitric oxide, and HMGB1. As expected, EA inhibited NF-kappaB DNA binding in LPS-stimulated RAW 264.7 cells. Treating these cells with pyrrolidine dithiocarbamate, SN50 (amino acid sequence AAVALLPAVLLALLAPVQRKRQKLMP) or 5-(thien-3-yl)-3-aminothiophene-2-carboxamide (SC-514) also inhibited LPS-induced NF-kappaB DNA binding, but these compounds failed to inhibit LPS-induced HMGB1 secretion. These findings suggested that inhibition of HMGB1 secretion by EA might occur via a mechanism unrelated to the NF-kappaB signaling pathway. Because EA is an electrophilic compound that is known to be capable of inducing expression of so-called phase 2 proteins, we sought to determine whether two other phase 2 enzyme inducers, oltipraz and DL-sulforaphane, also are capable of inhibiting HMGB1 release from immunostimulated macrophages. Incubating RAW 264.7 cells with either oltipraz or DL-sulforaphane inhibited LPS-induced HMGB1 secretion. Moreover, both EA and DL-sulforaphane inhibited relocalization of nuclear HMGB1 into the cytoplasm of LPS-stimulated RAW 264.7 cells. These data suggest that phase 2 inducers may exert anti-inflammatory effects by inhibiting secretion of the cytokine-like nuclear protein HMGB1.

Active Transport, Cell Nucleus↗

PubMed2005

Interleukin-6.

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Animals↗

PubMed2004

Cytokine removal with a novel adsorbent polymer.

BACKGROUND/AIMS: We sought to characterize a novel adsorbent polymer in terms of cytokine removal. METHODS: We challenged 50 rats with lipopolysaccharide to obtain cytokine-rich blood and circulated this through cartridges containing polymer. In separate experiments, cell-free supernatants were passed through cartridges containing polymer. We measured tumor necrosis factor alpha, interleukin 10 and interleukin 6 concentrations under a variety of conditions to evaluate adsorption kinetics. RESULTS: All three cytokines were rapidly removed from the blood with less than 50% of the initial concentrations present after 1 h of circulation through the cartridge. There was no significant difference in the effect across a range of blood flows and Ca2+ concentrations. Adsorption was decreased somewhat by extremely low temperature (4 degrees C). CONCLUSION: The adsorbent polymer removes cytokines with high efficiency, and binding is relatively unaffected by a variety of physical conditions.

Animals↗

PubMed2004

Science review: extracellular acidosis and the immune response: clinical and physiologic implications.

Metabolic acidosis is among the most common abnormalities seen in patients suffering from critical illness. Its etiologies are multiple and treatment of the underlying condition is the mainstay of therapy. However, growing evidence suggests that acidosis itself has profound effects on the host, particularly in the area of immune function. Given the central importance of immune function to the outcome of critical illness, there is renewed interest in elucidating the effects of this all too common condition on the immune response. In this review we concentrate on the effects of extracellular acids on production and release of inflammatory mediators, and we demonstrate that different acids produce different effects despite similar extracellular pH. Finally, we discuss potential clinical implications.

Acid-Base Equilibrium↗

PubMed2004

Hemoadsorption removes tumor necrosis factor, interleukin-6, and interleukin-10, reduces nuclear factor-kappaB DNA binding, and improves short-term survival in lethal endotoxemia.

OBJECTIVES: Previous studies have shown that inflammatory mediators can be removed from the circulation with hemofiltration and that adsorption plays an important role. Because adsorptive capacity of hollow-fiber dialyzers is limited, we sought to determine whether hemoadsorption using high surface area beads would result in greater mediator removal and improved survival in experimental sepsis. DESIGN: Randomized controlled laboratory experiment. SETTING: University laboratory. SUBJECTS: Sixty-six adult Sprague-Dawley rats. INTERVENTIONS: We conducted two ex vivo and two in vivo experiments. For in vivo experiments, we administered Escherichia coli endotoxin (20 mg/kg) by intravenous infusion and then randomized each animal to receive either hemoadsorption or a sham circuit for 4 hrs. Hemoadsorption was performed for 4 hrs using an arterial-venous circuit and a CytoSorb cartridge containing 10 g of polystyrene divinyl benzene copolymer beads with a biocompatible polyvinylpyrrolidone coating. Survival time was measured to a maximum of 12 hrs. In a separate set of experiments, we studied 12 animals using the same protocol except that we killed all animals at 4 hrs and removed standardized sections of liver for analysis of nuclear factor-kappaB DNA binding. MEASUREMENTS AND MAIN RESULTS: Mean survival time among hemoadsorption-treated animals was 629+/-114 vs. 518+/-120 mins for sham-treated animals (p <.01). Overall survival (defined at 12 hrs) was also significantly better in the hemoadsorption group, seven of 20 vs. one of 20 (p <.05). Plasma interleukin-6 and interleukin-10 concentrations and liver nuclear factor-kappaB DNA binding were significantly reduced by hemoadsorption. Ex vivo experiments showed no endotoxin adsorption but strengthened our in vivo observations by showing rapid adsorption of tumor necrosis factor, interleukin-6, and interleukin-10. CONCLUSIONS: Hemoadsorption was associated with reduced inflammation and improved survival in this murine model of septic shock.

Analysis of Variance↗

PubMed2004

Hemoadsorption to improve organ recovery from brain-dead organ donors: a novel therapy for a novel indication?

While brain-dead organ donors represent the majority of the organ donor pool, it appears that graft survival is adversely affected by brain death itself. Brain death has been shown to cause severe disturbances in the hormonal, hemodynamic and immunological homeostasis, which could in part be responsible for the inferior outcome of organs originating from brain-dead donors compared to living donors. Hemodynamic effects of brain death lead to a wide fluctuation in mean perfusion pressures, blood flow to the organs and systemic oxygen consumption, altering regional perfusion. In addition, a wide array of immunological changes has been shown to occur after brain death contributing to organ injury and hemodynamic instability. Recent studies have shown that brain death upregulates multiple lymphocyte- and macrophage-derived cytokines and the injured brain itself may be the source of proinflammatory factors such as S100B. This increased inflammatory response seen during and immediately after brain death has also been associated with poor allograft function. Furthermore, there is evidence to suggest that the massive inflammatory response seen in brain-dead donors could also lead to increased immunogenicity and accelerated allograft rejection after transplantation. Hence, we hypothesize that nonspecific downregulation of this inflammatory response by hemoadsorption could potentially lead to improved donor organ and allograft function. As a 'proof of concept' we tested the ability of a novel hemoadsorbent to remove S100B in vitro using two human glioblastoma cell lines. Our results indicate a >80% reduction in S100B after 2 h of circulation with the sorbent.

Brain↗

PubMed2004

Effects of hyperchloremic acidosis on arterial pressure and circulating inflammatory molecules in experimental sepsis.

STUDY OBJECTIVE: To determine the effects of hyperchloremic acidosis, induced by dilute HCl infusion, on BP and circulating inflammatory mediators in an experimental model of severe sepsis in the rat. DESIGN: Randomized, open-label, controlled experiment. SETTING: University research laboratory. PARTICIPANTS: Twenty-four adult, male, Sprague-Dawley rats. INTERVENTION: Eighteen hours after inducing lethal sepsis by cecal ligation and puncture, animals were randomized and classified into three groups. In groups 2 and 3, we began an IV infusion of 0.1 N HCl to reduce the standard base excess (SBE) by 5 to 10 mEq/L and 10 to 15 mEq/L, respectively. In group 1, we infused a similar volume of lactated Ringer solution. In all groups, infusions were continued for 8 h or until the animals died. MEASUREMENTS: We measured mean arterial pressure (MAP), arterial blood gases, electrolytes, plasma nitrate/nitrite, tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, and IL-10 levels at 0 h, 3 h, 6 h, and 8 h. RESULTS: MAP remained stable in group 1 but decreased in groups 2 and 3 (p < 0.001), such that at 8 h MAP was much higher in group 1 (94 +/- 9.2 mm Hg) [+/- SD] compared to either group 2 (71.6 +/- 20.1 mm Hg) or group 3 (49.4 +/- 33.2 mm Hg) [p = 0.01]. This change in MAP correlated with the increase in plasma Cl(-) (R(2) = 0.50, p < 0.0001) and less well with the decrease in pH (R(2) = 0.24, p < 0.001). After 6 h of acidosis, plasma nitrite levels were significantly higher in group 2 animals compared to either group 1 or group 3 animals (p < 0.05). Plasma TNF-alpha, IL-6, or IL-10 levels were not significantly different from control animals. CONCLUSION: Moderate acidosis (SBE of 5 to 10 mEq/L), induced by HCl infusion, worsened BP and increased plasma nitrate/nitrite levels but had no effect on circulating cytokines in septic rats. However, severe acidosis (SBE of 10 to 15 mEq/L), while still causing hypotension, did not affect plasma nitrate/nitrite levels.

Acid-Base Equilibrium↗

PubMed2003

Lactic and hydrochloric acids induce different patterns of inflammatory response in LPS-stimulated RAW 264.7 cells.

Metabolic acidosis frequently complicates sepsis and septic shock and may be deleterious to cellular function. Different types of metabolic acidosis (e.g., hyperchloremic and lactic acidosis) have been associated with different effects on the immune response, but direct comparative studies are lacking. Murine macrophage-like RAW 264.7 cells were cultured in complete medium with lactic acid or HCl to adjust the pH between 6.5 and 7.4 and then stimulated with LPS (Escherichia coli 0111:B4; 10 ng/ml). Nitric oxide (NO), IL-6, and IL-10 levels were measured in the supernatants. RNA was extracted from the cell pellets, and RT-PCR was performed to amplify corresponding mediators. Gel shift assay was also performed to assess NF-kappa B DNA binding. Inc easing concentrations of acid caused increasing acidification of the media. Trypan blue exclusion and lactate dehydrogenase release demonstrated that acidification did not reduce cell viability. HCl significantly increased LPS-induced NO release and NF-kappa B DNA binding at pH 7.0 but not at pH 6.5. IL-6 and IL-10 expression (RNA and protein) were reduced with HCl-induced acidification, but IL-10 was reduced much more than IL-6 at low pH. By contrast, lactic acid significantly decreased LPS-induced NO, IL-6, and IL-10 expression in a dose-dependent manner. Lactic acid also inhibited LPS-induced NF-kappa B DNA binding. Two common forms of metabolic acidosis (hyperchloremic and lactic acidosis) are associated with dramatically different patterns of immune response in LPS-stimulated RAW 264.7 cells. HCl is essentially proinflammatory as assessed by NO release, IL-6-to-IL-10 ratios, and NF-kappa B DNA binding. By contrast, lactic acidosis is anti-inflammatory.

Animals↗

PubMed2003

Evidence that glutathione depletion is a mechanism responsible for the anti-inflammatory effects of ethyl pyruvate in cultured lipopolysaccharide-stimulated RAW 264.7 cells.

Ethyl pyruvate (EP), an effective scavenger of reactive oxygen species, is also an anti-inflammatory agent in a variety of in vivo and in vitro model systems. To gain a better understanding of the molecular basis for the anti-inflammatory effects of EP, we compared the pharmacological properties of EP andN-acetyl-l-cysteine (NAC), a well studied scavenger of reactive oxygen species and a precursor for the endogenous antioxidant glutathione (GSH). The studies were performed using RAW 264.7 murine macrophage-like cells that were stimulated with lipopolysaccharide (LPS). Although EP and NAC both inhibited LPS-induced nitric oxide and interleukin (IL)-6 secretion, the former compound was considerably more potent than the latter. EP markedly inhibited inducible nitric-oxide synthase, IL-6, and IL-10 mRNA induction, whereas the effects of NAC were minimal. EP inhibited LPS-induced nuclear factor-kappaB DNA binding to a much greater extent than did NAC. Both compounds inhibited LPS-induced lipid peroxidation, but the two compounds had qualitatively different effects on cellular levels of GSH. Although NAC increased GSH levels, EP had the opposite effect. The anti-inflammatory effects of EP were partially reversed when RAW 264.7 cells were treated with a cell-permeable GSH analog, glutathione ethyl ester. These data support the view that the anti-inflammatory effects of EP are mediated, at least in part, by the ability of EP to deplete cellular GSH stores. Moreover, the findings presented here suggest that an unusual combination of biochemical effects (inhibition of lipid peroxidation and GSH depletion) might account for the anti-inflammatory effects of EP.

Animals↗

PubMed2002

Resuscitation with Ringer's ethyl pyruvate solution prolongs survival and modulates plasma cytokine and nitrite/nitrate concentrations in a rat model of lipopolysaccharide-induced shock.

The glycolytic intermediate, pyruvate, is capable of scavenging reactive oxygen species (ROS). However, this compound is relatively unstable and hence is not useful as a therapeutic agent. Ethyl pyruvate, a simple derivative of pyruvate, appears to be more stable, and when formulated in a calcium-containing Ringer's-type balanced salt solution (REPS), has been shown to be salutary in rat models of two pathophysiological conditions--mesenteric ischemia/reperfusion and hemorrhagic shock/resuscitation--that are thought to be mediated, at least in part, by ROS. Because ROS also have been implicated in the pathogenesis of lipopolysaccharide (LPS)-induced shock, we carried out a series of experiments to determine if REPS is beneficial in this condition. Anesthetized rats were challenged with intravenous LPS (20 mg/kg). When mean arterial pressure (MAP) decreased to 60 mmHg, 3- to 5-mL boluses of either REPS (n = 10) or Ringer's lactate solution (RLS; n = 10) were infused as needed to prevent MAP from decreasing further. By design, the maximal volume of fluid infused was 7 mL/kg. Resuscitation with REPS as compared with RLS prolonged survival time (498 +/- 48 min vs. 362 +/- 30 min; P = 0.0014). Resuscitation with REPS as compared with RLS also was associated with significantly lower circulating concentrations of nitrite/nitrate and interleukin (IL)-6 and higher plasma levels of IL-10. These data support the view that delayed treatment with REPS modulates the inflammatory response to LPS, and prolongs survival time in a lethal model of endotoxic shock.

Animals↗