Microbiology, safety, and pharmacokinetics of aztreonam lysinate for inhalation in patients with cystic fibrosis.

BACKGROUND: Aztreonam lysinate for inhalation (AI) is a novel monobactam formulation being investigated for pulmonary Pseudomonas aeruginosa infections in patients with cystic fibrosis (CF). METHODS: Pre-clinical studies investigated the pre- and post-nebulization activity of AI and its activity in the presence of CF sputum. A double-blind, placebo-controlled, dose-escalation trial determined pharmacokinetics and tolerability of AI in subjects with CF. Single daily escalating doses of AI 75, 150, or 225 mg, or placebo were self-administered using an eFlow Electronic Nebulizer. Sputum samples were collected up to 4 hr and blood samples up to 8 hr post-dose. RESULTS: AI activity against multiple CF isolates was retained after nebulization via eFlow, and activity was not inhibited by CF sputum. All 12 adult subjects and 11/12 adolescents tolerated all AI doses. One patient had an asymptomatic FEV1 decrease > 20% with the 150 mg dose. Median aztreonam sputum concentrations in adults 10 min after AI 75, 150, and 225 mg were 383, 879, and 985 microg/g, respectively. Median sputum concentrations in adolescents 10 min after AI 75, 150, and 225 mg were 324, 387, and 260 microg/g, respectively. Systemic exposure to AI was low. Plasma pharmacokinetics in adults receiving AI 75 mg were Cmax = 419 ng/g, Tmax = 0.99 hr, t1/2 = 2.1 hr. Aztreonam concentrations in sputum were at or above the MIC50 for at least 4 hr post-dose. CONCLUSION: These data support the continued development of AI for treatment of pulmonary infections in patients with CF.

Contrasting pattern of cytokines in antigen- versus mitogen-stimulated splenocyte cultures from chemically denervated mice.

Sympathetic nervous system (SNS) regulation of immune function has been studied by ablating the SNS with a peripheral injection of the neurotoxin 6-hydroxydopamine (6-OHDA). Our previous data indicate that sympathectomy of mice results in enhanced antibody production and in vitro levels of antigen-specific IL-2 and IFN-gamma. Other investigators have observed either increased or decreased immune function following sympathectomy. Here we present data showing that culture supernatants from spleen cells from the same denervated animals contain increased IL-2 and IFN-gamma levels in response to antigen-specific (keyhole limpet hemocyanin (KLH)) stimulation, but decreased cytokines levels in response to the T cell mitogen Con A compared to vehicle control mice. KLH-induced type 2 cytokines were also increased; no decrease in Con A-stimulated type 2 cytokines was observed. We evaluated whether the antigen presenting cell (APC) or the T cell might be the main target of the observed sympathectomy effects. Cell separation and mixing experiments suggest that the sympathectomy-induced alterations of antigen-specific and mitogen-induced type 1 cytokines are mediated primarily via the T cell. These data directly address some apparent discrepancies in the literature, and highlight potential regulatory sites to be further investigated in pathways of neural-immune communication.

The effects of chemical sympathectomy on T-cell cytokine responses are not mediated by altered peritoneal exudate cell function or an inflammatory response.

Ablation of the sympathetic nervous system by chemical sympathectomy is a standard model for the study of sympathetic nervous system regulation of immune function. We have previously documented that chemical denervation results in enhanced antigen-specific, but suppressed mitogen-induced, cytokine production by spleen cells. In our investigation into the mechanisms of sympathectomy-induced immune alterations, we first evaluated the peritoneal environment into which the protein antigen keyhole limpet hemocyanin is administered. Denervation resulted in increased production of tumor necrosis factor-alpha by peritoneal exudate cells and these cells appeared to have enhanced antigen presenting capability. We hypothesized that nerve terminal destruction may be inducing an inflammatory response by monocyte/macrophages and other cell types throughout the periphery that could differentially alter subsequent mitogen versus antigen-specific responses. However, no evidence of sympathectomy-induced systemic or local splenic inflammatory responses was observed, as indicated by measuring the proinflammatory cytokines tumor necrosis factor-alpha and interleukin-1beta. These experiments indicate that an inflammatory response is not likely to be responsible for sympathectomy-induced immune alterations, eliminating a potential confounding factor in interpreting sympathectomy studies.