Intravenous glycine after cecal ligation and puncture has no effect on impaired hepatic microperfusion, leukocyte adhesion, and mortality in septic rats

The role of glycine in regulated cell death

The cytoprotective effects of glycine against cell death have been recognized for over 28 years. They are expressed in multiple cell types and injury settings that lead to necrosis, but are still not widely appreciated or considered in the conceptualization of cell death pathways. In this paper, we review the available data on the expression of this phenomenon, its relationship to major pathophysiologic pathways that lead to cell death and immunomodulatory effects, the hypothesis that it involves suppression by glycine of the development of a hydrophilic death channel of molecular dimensions in the plasma membrane, and evidence for its impact on disease processes in vivo.

Glycine selectively reduces intestinal injury during endotoxemia

BACKGROUND

Glycine is well known to protect the intestine against ischemia-reperfusion injury and during mechanical manipulation. Here, we studied whether glycine protects the small intestine during endotoxemia, even without being the site of the infection.

MATERIALS AND METHODS

Lipopolysaccharide (LPS) was infused at a rate of 1 mg/kg × h over a period of 7 h (subacute endotoxemia) in male Wistar rats. Glycine (single dose: 50 mg/kg × 15 min) was applied intravenously at 180 and 270 min after the beginning of the LPS infusion. Systemic parameters were periodically determined. The small intestine was analyzed for macroscopic (hemorrhages) and histopathologic changes (hematoxylin and eosin staining), and markers of inflammation (myeloperoxidase activity).

RESULTS

Glycine neither decreased mortality nor beneficially affected vital parameters (e.g., mean arterial blood pressure and breathing rate), electrolytes, blood gases including pH and base excess, and plasma parameters of tissue injury such as lactate concentration, hemolysis, and aminotransferases activities during experimental endotoxemia. It, however, specifically diminished the LPS-induced small intestinal injury, as indicated by less intestinal accumulation of blood, less intestinal hemorrhages, and reduced intestinal hemoglobin content.

CONCLUSIONS

The present results demonstrate that glycine selectively protects the small intestine during subacute endotoxemia, even after manifestation of a severe systemic impairment. Because glycine is non-toxic at low doses, an administration of a moderate glycine dose (50-100 mg/kg) may be suitable to protect from intestinal damage during sepsis. Its true clinical potential, however, needs to be verified in further experimental studies and clinical trials.

Effects of gadolinium chloride and glycine on hepatic and pancreatic tissue damage in alcoholic pancreatitis

OBJECTIVE

Systemic complications in alcoholic pancreatitis are supposed to be aggravated by inflammatory liver damage. Resident macrophages including hepatic Kupffer cells play a pivotal role in mediating systemic complications in severe necrotizing pancreatitis (SNP). The aim of this study was to evaluate the effects of Kupffer cell inhibition on the inflammatory liver damage in experimental alcoholic pancreatitis.

METHODS

Rats were fed with either alcohol or control diet for 6 weeks before induction of SNP. Animals were allocated into 4 groups: healthy controls, controls with SNP, SNP with gadolinium chloride or glycine (permanent vs temporary inhibition of hepatic Kupffer cells) prophylaxis. Hepatic microcirculation and morphologic damage of the liver and pancreas were assessed.

RESULTS

Alcohol feeding and SNP increased hepatic and pancreatic injury compared with SNP alone. Gadolinium chloride and glycine improved hepatic microcirculation. In contrast, pancreatic and hepatic morphological damage was reduced by gadolinium chloride but not by glycine.

CONCLUSIONS

Alcohol exposure aggravates hepatic and pancreatic injury in SNP. Gadolinium chloride reduces both microcirculatory and morphological damage, whereas glycine did not improve histological damage.

Therapeutic strategies targeting the LPS signaling and cytokines

Lipopolysaccharide (LPS) has been recognized as a major player in the pathogenesis of sepsis and neutralization of LPS or inhibition of its signal transduction mechanism is promising new treatment strategy in preclinical experiments. However, these therapeutic approaches have been shown unsuccessful in clinical trials. LPS activates Toll-like receptor 4 (TLR4) and induces pro-inflammatory and anti-inflammatory responses, the altered innate and adaptive immune responses eventually lead to the immunosuppressive state. The future therapeutic efforts in sepsis should focus on the immunosuppressive state. In this article, we will outline the current data on therapeutic strategies targeting LPS, TLR4 and single cytokine in sepsis and discuss the experimental and clinical evaluation of the immunomodulatory action of glycine and berberine. While we have demonstrated berberine in combination with yohimbine can modulate host immune responses in endotoxemia, it seems worthwhile to conduct clinical trials on the safe and efficacy of this new immunomodulatory therapy.

COLON ASCENDENS STENT PERITONITIS-A MODEL OF SEPSIS ADOPTED TO THE RAT

The colon ascendens stent peritonitis (CASP) procedure creates an intestinal leakage of feces, resulting in diffuse peritonitis and polymicrobial sepsis. Mouse models of CASP have been used to study sepsis experimentally. The aim of the present study was to establish CASP sepsis in rats and to provide basic functional characteristics of this model. In analogy to the mouse model, 3 degrees of severity of CASP sepsis, 2 sublethal and 1 lethal, were established depending on the stent diameter. Radio-telemetric recordings in a sublethal model showed that the nonsurvivors remained hemodynamically stable until approximately 1 h before death, when heart rate and blood pressure fell rapidly. Intestinal microcirculatory changes were analyzed 3, 6, 12, and 18 h after CASP surgery using intravital microscopy in a sublethal model. After 18 h, the numbers of the leukocytes firmly adhering to the endothelium and of the ones temporarily interacting were significantly increased. The levels of IL-6 and IL-1beta increased continuously during the CASP experiments while remaining unchanged in the sham group. TNF-alpha and IL-10 levels of CASP animals reached a maximum after 12 h. In conclusion, a rat model of CASP sepsis has been established and characterized with regard to alterations in cardiovascular and microcirculatory function as well as plasma cytokine levels. In experimental settings where genetically engineered animals are not required, it will facilitate detailed examination of dynamic changes in integrated organ function during the course of sepsis and the investigation of treatment strategies.

Beneficial effects of statins on the microcirculation during sepsis: the role of nitric oxide

This review describes the laboratory evidence and microvascular mechanisms responsible for the beneficial effects of statins in sepsis. During sepsis, changes occur within the microcirculation including alterations in arteriolar tone influencing blood pressure, adaptations to endothelial cell integrity causing leakage of proteins and macromolecules, and adhesion and migration of leucocytes through the vascular endothelium. Statins are widely used as cholesterol-lowering agents, but appear to have anti-inflammatory actions during sepsis. We have discussed the effects of statins on specific pathological processed within the microcirculation and focused on the role of nitric oxide (NO). The main mechanism by which statins appear to be an effective treatment for sepsis is increased expression of endothelial nitric oxide synthase (eNOS), in conjunction with down-regulation of inducible nitric oxide synthase. Combined, this results in an increase in physiological concentrations of NO, thus restoring endothelial function. Laboratory studies have therefore suggested that enhancement of eNOS activity during sepsis may lead to restoration of microvascular tone, maintenance of microvascular integrity, and inhibition of cell adhesion molecules. However, other mechanisms independent of lipid-lowering effects, including antioxidant activity and alterations in the development of vascular atherosclerosis, may also contribute to the beneficial effects of statins. We have also addressed the influence on the effects of statins of lipid solubility and pre- and pro-phylactic administration.

Sepsis-induced cholestasis, steatosis, hepatocellular injury, and impaired hepatocellular regeneration are enhanced in interleukin-6 -/- mice

OBJECTIVE

Hepatic dysfunction is an important but poorly understood component of sepsis. In severe sepsis, liver dysfunction is characterized by cholestasis, steatosis, hepatocellular injury, impaired regeneration, a decreased response to the cytokine interleukin-6, and high mortality. To determine whether loss of interleukin-6 activity caused hepatic dysfunction and mortality, we induced sepsis in wild-type (interleukin-6 +/+) and interleukin-6 knockout (interleukin-6 -/-) mice. We hypothesized that sepsis in interleukin-6 -/- mice would increase cholestasis, steatosis, hepatocellular injury, and mortality and impair hepatocyte regeneration.

DESIGN

Randomized prospective experimental study.

SETTING

University medical laboratory.

SUBJECTS

Male adolescent C57Bl6 interleukin-6 +/+ and interleukin-6 -/- mice.

INTERVENTIONS

Mild sepsis was induced using cecal ligation and single puncture (CLP). Severe, lethal sepsis was induced using cecal ligation and double puncture (2CLP). Some mice received recombinant human interleukin-6 at the time of CLP/2CLP. All animals were fluid resuscitated at the time of surgery and every 24 hrs thereafter. In survival cohorts, mortality at 16, 24, 48, and 72 hrs was recorded. In separate cohorts, surviving animals were killed at 24 and 48 hrs, and liver tissue was harvested. A separate cohort of mice received bromodeoxyuridine for detection of regeneration.

MEASUREMENTS AND MAIN RESULTS

2CLP was 100% fatal within the first 12 hrs in interleukin-6 -/- mice. Mortality from 2CLP in interleukin-6 +/+ mice before 24 hrs was nil but was 90% by 72 hrs. At 72 hrs, CLP was 40% fatal in interleukin-6 +/+ mice but 90% in interleukin-6 -/- mice. CLP induced cholestasis, steatosis, and hepatocellular injury in interleukin-6 -/-, but not interleukin-6 +/+, mice. Regeneration was absent following CLP in interleukin-6 -/- animals but occurred in interleukin-6 +/+ mice. Early administration of recombinant human interleukin-6 did not reverse abnormalities in interleukin-6 -/- mice.

CONCLUSIONS

The absence of interleukin-6 is an important determinant of hepatic dysfunction and mortality in sepsis.