Enhancement of ovalbumin-induced pulmonary eosinophilia by intranasal administration of α1-proteinase inhibitor type 2 antisense oligonucleotides

To identify asthma-susceptibility genes, we did proteome analyses of the lung from control and ovalbumin-sensitized BALB/c mice. Among the 6 up-regulated proteins is α1-protease inhibitor (α1-PI) type 2, which is a member of the serine protease inhibitor superfamily of protease inhibitors that participate in a variety of physiological functions, including extracellular matrix remodeling and inflammation. The up-regulated expression of α1-PI type 2 was confirmed by real-time PCR. Then we examined mRNA expression of five members of the α1-PI family genes (α1-PI types 1-5) in several organs of BALB/c mice and found that in addition to the liver, all the organs tested also expressed different isoforms of α1-PI in a tissue-specific manner, albeit to a lesser extent compared with the liver. When a similar study was performed with C57BL/6 mice, which have been shown to be more susceptible to ovalbumin-induced asthma than BALB/c mice, a pair of remarkable differences between the mouse strains were revealed: (1) the magnitude of α1-PI type 2 mRNA in all the organs was much higher in BALB/c than in C57BL/6 mice and (2) α1-PI type 2 is the only isoform expressed in the lung of BALB/c, but not of C57BL/c mice. Using the antisense oligonucleotide technology to specifically down-regulate expression of α1-PI type 2, we demonstrated that pulmonary infiltration of eosinophils was significantly increased by intranasal administration of α1-PI type 2 antisense oligonucleotides in OVA-sensitized mice, suggesting that α1-PI type 2 may suppress the progress of asthma, probably by acting on neutrophil elastase, which can produce many of the pathological features of asthma.