Montelukast treatment does not affect peripheral blood neutrophil functions in asthma patients.

BACKGROUND: Leukotriene receptor antagonists have become an integral part of asthma treatment as an add-on therapy for patients with moderate disease activity. OBJECTIVE: To determine whether in vivo treatment with montelukast, a leukotriene receptor antagonist, at the recommended therapeutic dose affects neutrophil functions which are essential for host defense. METHODS: Twenty nonsmoking patients between the ages of 18 and 70 with moderate asthma were recruited to the study. All of them were receiving inhaled corticosteroids for at least 6 months and beta2-agonist as needed. After the 2-week run-in period, in addition to the regular medication, each patient was treated with 10 mg of montelukast for a 6-week period. Pulmonary function test was performed and blood was tested for neutrophil activity twice during the run-in period and twice during the treatment period. Each assay was performed in parallel to a matched control. RESULTS: The 6-week treatment period with montelukast did not significantly affect neutrophil chemotaxis or phagocytosis nor the elevated superoxide production. However, at 2 weeks of treatment some of the patients showed a reduction in neutrophil function. CONCLUSIONS: The study demonstrated that the recommended dose of montelukast has no significant effect on peripheral blood neutrophil activities, indicating that montelukast treatment does not induce an inflammatory process and does not interfere with the first line of host defense.

Intracellular acidification mediates the inhibitory effect of peritoneal dialysate on peritoneal macrophages.

Commercial peritoneal dialysis solution (CDS) is known to have a detrimental effect on the capacity of peritoneal macrophages (PM phi) to kill bacteria and produce acute phase cytokines. This cytotoxic effect is largely caused by the low pH of CDS. Because the cytoplasmic pH (pHi) is an important determinant of cellular function, the effect of CDS on the pHi of PM phi from continuous ambulatory peritoneal dialysis patients was studied. The pHi of PM phi was measured fluorometrically in N-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES)-buffered salt solution (HBSS) or CDS at pH values of 5.3, 6.5, and 7.0, values that represent the pH existing in dialysate during the first 30 min of dwell time. For any given pH of the experimental medium, the pHi was always more acidic in CDS than in HBSS. When PM phi were incubated with a lactate-containing HBSS, a cellular acidification was observed that was similar to that attained by exposure to CDS at the same pH. This supports the hypothesis that the decrease in pHi was due to the influx of lactic acid from the CDS into the PM phi. In order to demonstrate a causal association between the CDS-induced cellular acidification and a defect in phagocytosis and cytokine production, these functions were studied after pHi clamping by means of K+/nigericin. It was found that clamping pHi to values below 6.5 led to a markedly reduced tumor necrosis factor-alpha production and phagocytosis. However, at values of pHi > 6.5, these functions were normal. (ABSTRACT TRUNCATED AT 250 WORDS)

Commercial dialysate inhibits TNF alpha mRNA expression and NF-kappa B DNA-binding activity in LPS-stimulated macrophages.

Continuous ambulatory peritoneal dialysis is known to interfere with the normal inflammatory responses of macrophages in the peritoneal cavity. Commercial peritoneal dialysis solution (CDS) has been shown to inhibit tumor necrosis factor alpha (TNF alpha) release from LPS stimulated peritoneal macrophages. To further dissect the mechanism of this inhibition, we used human blood-derived macrophages or the murine macrophage cell line, P388D1, that were stimulated with LPS after pretreatment with CDS, and tested TNF alpha mRNA levels by Northern hybridization or reverse transcriptase polymerase chain reaction. Time course studies demonstrated that CDS lowered TNF alpha mRNA levels within 15 minutes of pretreatment of cells. In addition, the CDS inhibited DNA binding activity of NF-kappa B that is probably involved in regulation of LPS-mediated transcriptional activation of the TNF alpha gene. Inhibition was dependent on both the low pH and the lactate in the CDS, but was independent of the osmolarity or glucose concentration. The rate of catabolism of TNF alpha mRNA was not affected by CDS as demonstrated by actinomycin D chase experiments. Thus, impairment of LPS-stimulated macrophage function by CDS is associated with low TNF alpha mRNA which may be the result of the low activity of NF-kappa B. Since NF-kappa B is involved in transcription regulation of a large number of "early activation" genes, CDS may interfere with the production of additional immunomodulatory proteins that are encoded by genes possessing NF-kappa B site(s) in their promoter region.

Human peritoneal mesothelial cells synthesize IL-1 alpha and beta.

We studied the ability of human peritoneal mesothelial cells (HPMC) to produce the major pro-inflammatory cytokines interleukin-1 alpha (IL-1 alpha) and -beta when stimulated by lipopolysaccharide (LPS), tumor necrosis factor alpha (TNF alpha) or IL-1 alpha, or combinations of these three factors. Biological activity of IL-1 was measured by bioassay, and levels of IL-1 alpha and beta were determined using specific radioimmunoassays. We found that HPMC are capable of secreting IL-1 alpha and -beta in response to stimulation by these substances, but stimulation with a combination of LPS + TNF alpha, LPS + IL-1 alpha, or TNF alpha + IL-1 alpha, had a marked synergistic effect on cytokine production. A combination of all three substances together had a significantly enhanced synergistic effect. Using reverse transcription PCR, we found a peak in IL-1 alpha and beta mRNA levels three hours after stimulation. We found that LPS, TNF alpha and IL-1 alpha alone, or in combination, caused an increase in IL-1 alpha and -beta mRNA levels. Cycloheximide and actinomycin D blocked the production of IL-1 alpha and -beta protein, showing that de novo production of IL-1 or synthesis of mRNA stabilizing proteins are needed after stimulation. We thus conclude that HPMC play an important role in the amplification of the initial peritoneal inflammatory response which originates in the peritoneal macrophages, and these findings are of importance in understanding the peritoneal response to infection in continuous ambulatory peritoneal dialysis (CAPD) patients.