Inhalable powder formulation of a stabilized vasoactive intestinal peptide (VIP) derivative: anti-inflammatory effect in experimental asthmatic rats.

Vasoactive intestinal peptide (VIP) exerts immunomodulating and anti-inflammatory activities through its specific receptors, such as VPAC1 and 2 receptors. Previously, a stabilized VIP derivative, [R(15,20,21), L(17)]-VIP-GRR (IK312532), was proposed as a candidate of anti-asthma drug, and a dry powder inhaler system of IK312532 was also developed for inhalation therapy with minimal systemic side-effects. In the present study, the anti-inflammatory properties of IK312532 respirable powder (RP) were characterized in an asthma/COPD-like animal model, with the use of newly developed ovalbumin (OVA)-RP for lung inflammation. Marked inflammatory events in the lung were observed after OVA-RP challenge in rats as evidenced by significant increase of inflammatory biomarkers such as eosinophil peroxidase (EPO), myeloperoxidase (MPO) and lactate dehydrogenase (LDH). However, intratracheal administration of IK312532-RP led to significant attenuation of plasma EPO, MPO and LDH activities, as well as significant reduction of recruited inflammatory cells in BALF, especially macrophages and eosinophils. In the rats pretreated with IK312532-RP, histochemical examinations revealed that the inflammatory cells infiltrating to the lung and the epithelial wall thickness decreased significantly by 85% and 58%, respectively. Thus, inhalable powder formulation of IK312532 exerts its anti-inflammatory activity by suppressing granulocyte recruitment to the lung and epithelial hyperplasia, followed by the reduction of cytotoxic peroxidases.