SUMMARY1. An antisense oligonucleotide (ASO) is a short strand of deoxyribonucleotide analogue that hybridizes with the complementary mRNA in a sequence-specific manner via WatsonCrick base pairing. Formation of the ASO-mRNA heteroduplex either triggers RNase H activity, leading to mRNA degradation, induces translational arrest by steric hindrance of ribosomal activity, interferes with mRNA maturation by inhibiting splicing or destabilizes pre-mRNA in the nucleus, resulting in downregulation of target protein expression.2. The ASO is not only a useful experimental tool in protein target identification and validation, but also a highly selective therapeutic strategy for diseases with dysregulated protein expression.3. In the present review, we discuss various theoretical approaches to rational design of ASO, chemical modifications of ASO, ASO delivery systems and ASO-related toxicology. Finally, we survey ASO drugs in various current clinical studies.

Our findings suggest that inhibition of glycogen synthase kinase-3beta may provide a novel means for the treatment of allergic airway inflammation.

Asthma is a chronic inflammatory disease characterized by airway inflammation, mucus hypersecretion and airway hyperresponsiveness. Mechanisms underlying the pathogenesis of asthma are not fully understood. In recent years, there are mounting evidences demonstrating that mammalian chitinases may play a key role in mediating the T-helper 2 cell-driven inflammatory response that is commonly associated with asthma. Chitinases (e.g., chitotriosidase and acidic mammalian chitinase) are enzymes that degrade chitin, the second most abundant biopolymer that can be found in the cell walls of fungi, microfilarial sheaths of helminths, and exoskeletons of insects and crustaceans. There are also chitinase-like proteins (e.g., YKL-40, Ym1 and Ym2) that lack chitinolytic activity but retain chitin-binding ability. Therefore, chitinases were originally believed to function in host defense against parasitic infections, but the first discovery of their role in inflammatory airway diseases came as a surprise. There is ample evidence to support an association of acidic mammalian chitinase and YKL-40 with allergic bronchial asthma in patients. Our recent studies in a mouse asthma model revealed that anti-inflammatory drugs like corticosteroid and cysteinyl leukotriene receptor antagonist were able to suppress elevated pulmonary levels of mammalian chitinases. Taken together, mammalian chitinases may be useful as biomarkers for asthma. Notwithstanding, large-scale multi-center association studies are required to confirm this hypothesis. Besides, substantially more works using knockout mice, recombinant chitinases and siRNA technology are required to investigate a potential role of chitinases in the pathogenesis of asthma.