Prevention of interleukin 2-induced acute lung injury in guinea pigs by pentoxifylline

T cell-directed IL-17 production by lung granular γδ T cells is coordinated by a novel IL-2 and IL-1β circuit

Immune-mediated lung is considered the result of an exacerbated innate injury immune response, although a role for adaptive lymphocytes is emerging. αβ T cells specific for S. aureus enterotoxin A orchestrate a Tγδ17 response during lung injury. However, the mechanism driving IL-17 production is unclear. Here, we show a role for IL-2 triggering IL-17 production by lung granular γδ T cells as IL-17 synthesis and neutrophil recruitment was reduced by IL-2 blocking mAbs in vitro and in vivo. Mass cytometry analysis revealed that lung γδ T cells responded directly to IL-2 as evident from STAT5 phosphorylation and RoRγt expression. IL-2 receptor blocking mAbs and JAK inhibition impaired STAT5 phosphorylation and IL-17 release. Moreover, inhalation of S. aureus enterotoxin A induced IL-2 secretion and caspase-1-dependent IL-1β activation to drive IL-17 production. This T-cell-mediated inflammasome-dependent IL-17 response is maximum when lung Tγδ17 cells were sequentially stimulated first with IL-2 then IL-1β. Interestingly, when IL-2 is given therapeutically to cancer patients it carries a known risk of lung injury that is largely indistinguishable from that seen in sepsis. Hence, this novel mechanism reveals therapeutic targets treating both acute lung injury and high-dose IL-2 toxicity in cancer.

Pretreatment with FK506 improves survival rate and gas exchange in canine model of acute lung injury

The novel effects of FK506 on shock induced by lipopolysaccharide and phorbol myristate acetate (LPS/PMA) were studied using beagles. Five groups were studied: endotoxin shock control group (both 0.5 mg/kg of LPS and 30 microg/kg of PMA, n = 6); methylprednisolone-treated endotoxin shock group (n = 5); FK506-treated endotoxin shock groups in which intravenous infusions of FK506 at 2.5 microg/kg/h (low dose, n = 5), 8 microg/kg/h (medium dose, n = 5), and 25 microg/kg/h (high dose, n = 5) were administered. In the control group, the survival rate was 33%. Also, arterial hypoxemia, systemic hypotension, and marked increases in pulmonary vascular resistance (PVR) and wet-to-dry weight ratio (W/D) were observed. FK506 treatment at both medium and high doses significantly attenuated these LPS/PMA-induced physiological changes, and the survival rates were 80 and 100%, respectively. On the other hand, in the methylprednisolone group, no obvious effects were observed. The present study suggests that FK506 could have prophylactic potential against acute lung injury in endotoxin shock.

Augmentation of endotoxin-induced pulmonary responses by mononuclear cell phagocytosis in the reticuloendothelial system

OBJECTIVE

To test the hypothesis that the effects of intravenous injection of latex particles would demonstrate the contribution of phagocytosis by mononuclear phagocytes to the development of Escherichia coli-induced acute lung injury in neutropenic guinea pigs.

DESIGN

Prospective, controlled, experimental study. Intravenously injected the latex particles into 41 guinea pigs to investigate the contribution of the phagocytosis in acute lung injury.

SUBJECTS

Forty-one guinea pigs.

INTERVENTIONS

Forty-one guinea pigs were divided into five experimental groups: a saline group (n=9); an endotoxin group (n=10) receiving 2 mg/kg of intravenous E. coli endotoxin; a latex group (n=7) receiving 2 x 10(9)/kg of intravenous polystyrene latex (mean diameter 3.19 micrometers); an endotoxin + latex group (n=8); and an E. coli group (n=7) receiving 2 x 10(9) live E. coli/kg.

MEASUREMENTS AND MAIN RESULTS

The lung wet/dry ratio was increased in the live E. coli-treated guinea pigs (6.71 +/- 0.16 [SEM], p < .01) as compared with the saline control (5.40 +/- 0.16, whereas the ratio was not increased in the endotoxin (5.52 +/- 0.14) or latex (5.58 +/- 0.20) groups. However, the lung wet/dry ratio was greater in the endotoxin + latex group (6.11 +/- 0.16, p < .05) than in the saline control. The 125I albumin lung tissue/plasma ratio was greater in the E. coli (2.00 +/- 0.29, p < .01) and endotoxin + latex (0.84 +/- 0.12, p < .05) groups than in the saline group (0.18 +/- 0.07), whereas no increases were observed in the endotoxin group (0.22 +/- 0.10) and the latex (0.34 +/- 0.13) group. More than 40% of the injected radiolabeled latex was observed to have accumulated in the reticuloendothelial system (liver and spleen), in both the saline control (40.1 +/- 2.3%, n=4) and endotoxin (57.3 +/- 6.8%, n=5) groups, with 2.6 +/- 1.5% and 3.1 +/- 1.7% in the lungs for the saline control and the endotoxin groups, respectively. The percent deposition of radiolabeled latex in the liver was greater in the endotoxin group (51.7 +/- 3.8%, p < .05) than in the saline group (37.6 +/- 5.9%).

CONCLUSIONS

These findings suggest that, in neutropenic guinea pigs: a) the combination of endotoxin and latex particles induces acute lung injury; and b) the phagocytic properties of mononuclear phagocytes in the reticuloendothelial system augment endotoxin-induced pulmonary responses and may play a role in the development of live E. coli-induced acute lung injury.

Pentoxifylline attenuates ischemia/reperfusion injury to the small intestine in the rat

There is a large body of evidence that neutrophils may play an important role in the mucosal injury that follows ischemia of the intestine. Pentoxifylline (PTF), a methylxanthine derivative, prevents leukocyte adherence to vascular endothelium and restores intestinal blood flow following hemorrhagic shock and sepsis. The purpose of this study was to evaluate the protective properties of PTF in an ischemia-reperfusion model of the intestine and whether its action is mediated through tissue neutrophils as assessed by myeloperoxidase (MPO) determination. Intestinal ischemia of either 1 or 2 h was induced in rats by clamping the superior mesenteric artery, followed by a 17-min reperfusion period. PTF (25 mg/kg) or saline solution was injected IP 10 min prior to ischemia. Multiple bowel samples were harvested at the end of the reperfusion period and evaluated for histology and tissue MPO. PTF significantly changed the resultant histologic damage to the intestinal mucosa exerted by prolonged ischemia of 1 and 2 h duration, although the beneficial effect of PTF in this animal model was independent of the number of tissue neutrophils as assessed by tissue MPO levels. Pretreatment with PTF can thus reduce the histologic damage caused by prolonged ischemia to the intestine.

The effects of oral pentoxifylline on interleukin-2 toxicity in patients with metastatic renal cell carcinoma

Interleukin-2 (IL-2) mediates the regression of metastatic renal cell carcinoma, but clinical application has been limited by associated toxicities. Preclinical studies show that pentoxifylline (PTXF), a methylxanthine derivative, inhibits IL-2 toxicity while preserving anti-tumour efficacy. This study was designed to determine whether oral PTXF would alter IL-2-induced toxicities. Patients with disseminated renal cell carcinoma were treated with continuous infusion of 18 x 10(6) IU/m2/24 h for 4 days followed by 3 days without treatment, for 4 consecutive weeks. After a 2-week interval, the 4-week treatment cycle was repeated. All patients concomitantly received oral PTXF (2000 mg/24 h) in five divided doses. Despite the co-administration of PTXF, all patients demonstrated a spectrum and severity of toxicities consistent with previous reports of continuous infusion of IL-2 alone. There was considerably more nausea and vomiting associated with the administration of PTXF which improved on withdrawal of PTXF. Oral PTXF in IL-2 therapy did not show any substantiated benefit. Indeed, patients suffered more severe nausea and vomiting than if they had received IL-2 alone, resulting in the early termination of the trial.

Caffeine consumption is associated with decreased severe late toxicity after radiation to the pelvis

PURPOSE

Recent studies have suggested that pentoxifylline, a methylxanthine, can prevent or ameliorate late radiation injury in animals and humans. Caffeine is a commonly consumed methylxanthine that provides a model for evaluating the impact of this category of drugs on radiation injury. A retrospective study was undertaken to determine if there is an association between caffeine consumption and a lower incidence of late radiation toxicity.

METHODS AND MATERIALS

From 1984 through 1990, 82 patients with cervical cancer and 53 patients with endometrial cancer were treated with primary or adjuvant radiation therapy at the University of Washington. Patients were interviewed regarding ingestion of caffeine-containing beverages, and average daily caffeine consumption during the time of radiotherapy was estimated. The evaluable patients (42 cervical, 31 endometrial) were stratified by quantity of caffeine consumption for correlation with the incidence of radiation toxicity.

RESULTS

Acute radiation toxicity was not associated with caffeine consumption for cervical or endometrial cancer. There was a nonstatistically significant trend toward a decrease in overall late radiation toxicity with increased caffeine intake for cervical cancer patients. Subgroup analysis revealed this trend to be attributable to a decreased incidence of severe late radiation injury in cervical cancer patients who consumed higher levels of caffeine at the time of their radiotherapy (p = 0.02). This relationship was not observable for late toxicity in the endometrial cancer patients due to the low incidence of severe late injury following radiation for that disease.

CONCLUSIONS

This investigation is supportive of previous studies showing a radioprotective effect for pentoxifylline, and suggests that the mechanisms of radioprotection may be common to methylxanthines as a drug class.

Pentoxifylline suppresses irritant and contact hypersensitivity reactions

Pharmacologic suppression of the effector phase of contact hypersensitivity appears to have major relevance with regard to treatment of type IV reactions like contact dermatitis. Recently, tumor necrosis factor alpha has been shown to be a critical mediator in hapten-induced irritant and contact hypersensitivity reactions, thus offering new possibilities, for therapeutic intervention. Pentoxifylline, a methylxanthine derivative used in the treatment of vascular disorders, currently has been found to suppress the production of tumor necrosis factor alpha by human and murine leukocytes. Therefore, the effect of pentoxifylline on the elicitation phase of contact hypersensitivity was studied. Intraperitoneal injection of pentoxifylline into sensitized Balb/c and C3H/HeN mice before application of the challenging hapten dose resulted in a significant reduction of the outcome of the contact hypersensitivity reaction. The suppressive effect of pentoxifylline was dose dependent and maximally pronounced upon injection 3 h before hapten application. In contrast to the effector phase of contact hypersensitivity, induction of contact hypersensitivity was not affected by pentoxifylline when injected into naive mice before performance of sensitization. In addition, irritant dermatitis induced by 1% croton oil or 5% benzalkonium chloride was suppressed by pentoxifylline as well. These data suggest a potential pharmacologic intervention, with pentoxifylline as a means to treat contact dermatitis.

Pentoxifylline modulates activation of human neutrophils by amphotericin B in vitro

The antifungal agent amphotericin B (AmB) alters neutrophil (polymorphonuclear leukocyte [PMN]) function, and this may be the mechanism for some of the adverse effects caused by AmB. AmB is a potent inhibitor of PMN migration, increases PMN adherence and aggregation, and primes PMN for increased oxidative activity in response to a second stimulus. AmB also stimulates mononuclear leukocytes (MNLs) to release inflammatory mediators which augment the effects of AmB on PMN function. In the present study, we observed that the methylxanthine derivative pentoxifylline decreased the effects of AmB on PMN function. AmB (2 micrograms/ml) priming doubled PMN chemiluminescence stimulated by fMet-Leu-Phe. In the presence of MNLs, AmB priming increased fMet-Leu-Phe-stimulated PMN chemiluminescence to 622% of unprimed PMN activity. Pentoxifylline (100 microM) blunted the rise in AmB-augmented PMN chemiluminescence in the presence of MNLs to 282% of unprimed PMN activity, and pentoxifylline metabolites were active at 10 microM. Pentoxifylline (100 microM) also blocked AmB-augmented PMN oxidative activity in whole blood, as measured by nitroblue tetrazolium reduction. In the presence of MNL, AmB (2 micrograms/ml) doubled the expression of the important PMN adherence factor Mac-1. Pentoxifylline (1 mM) decreased AmB-stimulated PMN Mac-1 expression back to unstimulated amounts. In the presence of MNLs, AmB (2 micrograms/ml) decreased PMN nondirected and directed migration to fMet-Leu-Phe to 40 and 38% of control PMN migration, respectively. Pentoxifylline (300 microM) counteracted AmB inhibition of nondirected and directed migration to fMet-Leu-Phe, resulting in migration that was 71 and 87% of control PMN migration, respectively. In contrast, the methylxanthine caffeine (100 muM) increased AmB-enhanced chemiluminescence but did not affect AmB-inhibited PMN migration. Pentoxifylline should be evaluated as adjunctive therapy to lessen the inflammatory damage caused by AmB.