Effect of post-treatment with granulocyte colony-stimulating factor on endotoxin-induced lung injury in sheep

THE EFFECTS OF GRANULOCYTE COLONY-STIMULATING FACTOR IN PRECLINICAL MODELS OF INFECTION AND ACUTE INFLAMMATION

The cytokine granulocyte colony-stimulating factor (G-CSF) is a potent endogenous trigger for the release of neutrophils from bone marrow stores and for their activation for enhanced antimicrobial activity. G-CSF has been widely evaluated in preclinical models of acute illness, with generally promising though divergent results. A recombinant G-CSF molecule has recently undergone clinical trials to assess its efficacy as an adjuvant therapy in community-acquired and nosocomial pneumonia, however, these studies failed to provide convincing evidence of benefit. We undertook a systematic review of the published literature reporting the effects of modulation of G-CSF in preclinical in vivo models to determine whether evidence of differential efficacy might explain the disappointing results of human studies and point to disease states that might be more likely to benefit from G-CSF therapy. G-CSF has been evaluated in 86 such studies involving a variety of different models. The strongest evidence of benefit was seen in studies involving intraperitoneal challenge with live organisms; benefit was evident whether the agent was given before or after challenge. G-CSF demonstrates anti-inflammatory activity in models of systemic challenge with viable organisms or endotoxin, but only when the agent is given before challenge; evidence of benefit after challenge was minimal. Preclinical models of intrapulmonary challenge only show efficacy when the cytokine is administered before the infectious challenge, and suggested harm in gram-negative pneumonia resulting from challenge with Escherichia coli or Klebsiella. There is little evidence for therapeutic efficacy in noninfectious models of acute illness. We conclude that the most promising populations for evaluation of G-CSF are neutropenic patients with invasive infection and patients with intra-abdominal infection, particularly those with the syndrome of tertiary, or recurrent, peritonitis. Significant variability in the design and reporting of studies of preclinical models of acute illness precludes more sophisticated data synthesis.

Effects of Granulocyte Colony-Stimulating Factor (G-CSF) and Neutrophil Elastase Inhibitor (ONO-5046) on Acid-Induced Lung Injury in Rats

It has been suggested that neutrophils play an important role in acid-aspirated lung injury. We examined the effects of the high dose of granulocyte-colony stimulating factor (G-CSF), which is capable of increasing peripheral neutrophils, and a specific neutrophil elastase inhibitor (ONO-5046) on acid lung injury in rats. Animals were anesthetized and normal saline (NS, 2 mL kg(-1)) or hydrochloric acid (HCl, 0.1 N 2 mL kg(-1)) was then instilled into trachea. Thirty minutes before HCl instillation, G-CSF (150 microg kg(-1)) was injected subcutaneously or ONO-5046 (10 mg kg(-1) h(-1)) was infused continuously into the right jugular vein. Animals were ventilated during the experiments. Five hours after HCl or NS instillation, bronchoalveolar lavage fluid (BALF) and lung tissue samples were obtained. Total nuclear cell count, absorbance, albumin, tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, cytokine-induced neutrophil chemoattractant (CINC), neutrophil elastase in BALF, wet-to-dry (W/D) ratio were measured. HCl aspiration markedly increased these values in BALF and W/D ratio. Both ONO-5046 and G-CSF attenuated the parameters increased by acid-induced lung injury in rats. The data suggests that neutrophils play an important role in acid-induced lung injury. However, high-dose G-CSF does not exacerbate acid-aspirated lung injury in rats, although this agent causes an increase in peripheral neutrophils.

Effect of tacrolimus on endotoxin-induced lung injury in sheep

Since tacrolimus (FK-506) is known to suppress the proliferation and generation of T cells and to inhibit the production of T cell derived cytokines, we examined the effect of FK-506 on endotoxin-induced lung injury. We administered FK-506 (0.1 mg/kg) intravenously before the infusion of endotoxin (1 microgram/kg) into conscious sheep. We measured pulmonary hemodynamics, lung fluid balance, circulating leukocyte count and arterial blood gas tensions. The increase in pulmonary arterial pressure was significantly attenuated by FK-506 during the late period (3-5 h after endotoxin). Arterial oxygen gas tension was significantly higher in the FK-506 treated sheep during this phase. However, no significant differences were observed in lung lymph balance and circulating leukocyte count between the endotoxin alone group and the FK-506 treated group. These findings suggest that FK-506 may improve gas exchange in acute lung injury although there is an increased pulmonary vascular leakage. It is probable that FK-506 may have a beneficial potential on endotoxin-induced lung injury in sheep.

Role of hematopoietic growth factors in non-neutropenic infections and sepsis

Therapy with colony-stimulating factors has been extended beyond their use in accelerating myeloid cell recovery to take advantage of their immune function-enhancing properties. Studies in animal models and with human subjects suggest a potential role as adjunctive therapy in infections of non-neutropenic hosts, including those with sepsis. Granulocyte colony-stimulating factor may play a pivotal role in the induction of lipopolysaccharide desensitization by nontoxic lipid A analogues proposed for the prevention of sepsis; granulocyte macrophage colony-stimulating factor may be useful in reversing the immune paralysis described in later stages of sepsis. Significant issues of exogenous colony-stimulating factor therapy must be addressed, however: the optimal timing, dose, and clinical context (e.g., type of immunosuppression, duration of infection-inciting stimulus) as well as tissue-specificity of the activities and net effect of potentially conflicting responses (e.g., immune restorative and procoagulant effects of granulocyte macrophage colony-stimulating factor). Resolution of these issues will require carefully designed clinical studies with meticulous monitoring of immunologic parameters.

Interferon-alpha elevates pulmonary blood pressure in sheep--the role of thromboxane cascade

We tested the effect of interferon-alpha on lung function to examine whether interferon-alpha causes some pathophysiological change in the lung. We prepared awake sheep with chronic lung lymph fistula, and measured the pulmonary hemodynamics, lung fluid balance and concentrations of prostanoid products. At 1 h after intravenous interferon-alpha administration (18 x 10(6) I.U.), pulmonary arterial pressure and pulmonary vascular resistance were significantly increased compared to the baseline values. The levels of thromboxane B2 in both plasma and lung lymph were increased concomitant with early elevation on pulmonary arterial pressure. In addition, OKY-046 [sodium-3[4-(1-imidazolylmethyl)phenyl]-2-propenoic acid] (10 mg kg(-1)), a selective thromboxane synthase inhibitor, significantly prevented the interferon-alpha-induced pulmonary hypertension and thromboxane B2 production. While no evidence of increased pulmonary vascular leakage was observed. These findings suggest that a single infusion of interferon-alpha stimulates a thromboxane cascade and causes transient pulmonary hypertension. However, interferon-alpha itself or increased thromboxane A2 might not affect the pulmonary vascular permeability in sheep.