Targeting the phosphorylation site of myristoylated alanine‐rich C kinase substrate alleviates symptoms in a murine model of steroid‐resistant asthma

BACKGROUND:Myristoylated alanine-rich C kinase substrate (MARCKS), a protein kinase C (PKC) substrate, facilitates mucus production and neutrophil migration. However, the effects of therapeutic procedures targeting the phosphorylation site of MARCKS on steroid-resistant asthma and the mechanisms underlying such effects have not yet been investigated. We designed a peptide that targets the MARCKS phosphorylation site (MPS peptide) and assessed its therapeutic potential against steroid-resistant asthma. METHODS:Mice were sensitized with ovalbumin (OVA), alum, and challenged with aerosolized OVA 5 times a week for one month. The mice were intratracheally administered MPS peptides 3 times a week, 1 h before OVA challenge. Asthma symptoms and cell profiles in the bronchoalveolar lavage (BAL) were assessed, and key proteins were analyzed using western blotting. RESULTS:Phosphorylated (p)-MARCKS was highly expressed in inflammatory and bronchial epithelial cells in OVA-immunized mice. MPS peptide reduced eosinophils, neutrophils, mucus production, collagen deposition, and airway hyper-responsiveness (AHR). Dexamethasone (Dexa) did not alleviate steroid-resistant asthma symptoms. MPS peptide caused a decrease in p-MARCKS, nitrotyrosine and the expression of oxidative stress enzymes, NADPH oxidase dual oxidase 1 (Duox-1) and iNOS, in lung tissues. Compared to Dexa, MPS peptides inhibited C5a production and attenuated interleukin-17A (IL-17A) and KC production in the airway more effectively, thus suppressing asthma symptoms. CONCLUSIONS:Our findings indicate that targeting MARCKS phosphorylation through MPS treatment may inhibit neutrophilic inflammation and relieves asthma symptoms, thereby highlighting its potential as a therapeutic agent for steroid-resistant asthma.