Soluble P-selectin glycoprotein ligand 1 inhibits ocular inflammation in a murine model of allergy.

PURPOSE: To assess the anti-inflammatory modality of a soluble extracellular form of P-selectin glycoprotein ligand 1 (sPSGL-1) in a mouse model of ocular allergic response. METHODS: Potential anti-inflammatory effects of sPSGL-1 were investigated in SWR/J mice sensitized by topical application of short ragweed pollen to the nasal mucosa followed by a challenge of the ocular mucosa with the same allergen. Five experimental groups were included in these studies: A, mice neither sensitized nor challenged with pollen (control group 1); B, animals sensitized but not challenged (control group 2); C, animals not sensitized but challenged (control group 3); D, animals sensitized and challenged; and E, sensitized animals treated with sPSGL-1 before pollen challenge. All experimental groups were evaluated for gross morphologic ocular changes, and histologic assessments were made to determine the onset/progression of inflammatory reactions and to look for evidence of eosinophil infiltration. RESULTS: Mice sensitized and challenged with pollen developed clinical signs consistent with human allergic conjunctivitis. These signs correlate with histologic changes in the conjunctival epithelium and stroma (e.g., edema and extensive eosinophil infiltration). Moreover, the ocular changes also correlated with evidence of eosinophil degranulation. However, sensitized and challenged mice concurrently treated with sPSGL-1 displayed no inflammatory ocular changes associated with a ragweed-induced type-1 hypersensitivity reaction. The lack of ocular changes included the absence of histologic late-phase inflammatory changes of the conjunctiva and a 97% reduction in the induced eosinophil infiltrate. CONCLUSIONS: The antagonistic intervention of cell- cell interactions through the blockade of selectin-dependent leukocyte adhesion may offer novel therapeutic strategies to modulate inflammatory responses. The potent inhibitory effects on eosinophil recruitment and late-phase inflammation suggest a role for sPSGL-1 in the treatment of ocular allergic diseases.

Preclinical studies of recombinant factor IX.

Recombinant factor IX (rFIX) has been extensively evaluated in preclinical studies. Dog model study of hemophilia B indicated that rFIX was as effective as a highly purified plasma-derived replacement factor in normalizing indices of hemostasis. Pharmacokinetic studies indicated a dose-proportional profile for rFIX. Pharmacokinetic/pharmacodynamic analysis showed that increases in the plasma concentration of rFIX following administration were closely correlated with measured factor IX activity in the plasma. Appropriate in vitro and in vivo toxicology studies have been performed to support the clinical use of rFIX for the treatment of hemophilia B. Finally, experiments in a model of thrombogenicity indicated that in animals rFIX has a low thrombogenic potential. The preclinical results provided a basis for proceeding with human clinical trials.

Cholinergic mechanisms involved with histamine hyperreactivity in immune rabbit airways challenged with ragweed antigen.

The present study examines the effects of aerosolized ragweed antigen (RAg) on tracheal (TSM) and bronchial (BSM) smooth muscle contraction in rabbits actively immunized with RAg. Airway segments were isolated 48 h after aerosol challenge with either saline or RAg, and airway contractile responses to histamine were measured. Histamine remained a weak agonist in TSM segments after RAg challenge. In contrast, BSM responsivity to histamine was significantly increased after RAg challenge as evidenced by a parallel shift to the left (i.e., Fslope = 3.2; degrees of freedom (df) = 1,224; p = NS and Felev = 19.4; df = 1,225; p less than 0.001) of the mean dose-response relationship. In sham-immunized rabbits, the BSM contractile responses to histamine were similar after aerosol challenge with either RAg or normal saline. After the BSM segments were treated with 10(-6) M atropine, there was no significant difference in histamine reactivity between the RAg- and saline-challenged groups. The augmented BSM contractile response to histamine was only partially inhibited in the presence of either tetrodotoxin or hexamethonium. We conclude that 48 h after a single in vivo exposure to antigen in immune rabbits, the airway contractile responses to histamine in vitro are increased in BSM but not in TSM and that the mechanism of the augmented contractile responses in BSM likely involves the facilitated neural release of acetylcholine from both preganglionic and postganglionic sites.

The requirement for polymorphonuclear leukocytes in the late asthmatic response and heightened airways reactivity in an animal model.

The antigen-induced late asthmatic response (LAR) and subsequent heightened airways reactivity after this response have been associated with increased airways inflammation. Employing an animal model of the LAR in rabbits previously developed in our laboratory, 3 phases of experiments were performed to investigate the role of polymorphonuclear leukocytes (PML) in the LAR and heightened reactivity. In all 3 phases, airways reactivity to histamine and bronchoalveolar lavage analysis were performed 3 days before and 3 days after bronchial challenge with ragweed extract. In Phase 1, 2 groups of rabbits receiving nitrogen mustard were studied: an immune group received immune serum containing antiragweed IgE, and a control group received nonimmune serum. In Phase II, nitrogen mustard was administered to immune rabbits during aortic occlusion to allow the lungs to be exposed to nitrogen mustard while limiting exposure of the bone marrow to this drug, preventing depletion of PML. In Phase III, both an immune and a nonimmune group of rabbits received nitrogen mustard as in Phase I; however, prior to antigen challenge, they were repleted with a neutrophil-rich population of PML. In all experiments, no group of control (nonimmune) rabbits, whether depleted or repleted of PML, developed an immediate asthmatic response (IAR) or a LAR. In addition, no significant increases in lavage cells or airways reactivity occurred after ragweed challenge. In contrast, those animals receiving immune serum and nitrogen mustard developed an IAR; however, no LAR occurred, and no significant change in airways reactivity was observed. Rabbits receiving immune serum and nitrogen mustard with aortic occlusion developed an IAR and LAR, and airways reactivity increased.(ABSTRACT TRUNCATED AT 250 WORDS)