Insights on the in-vitro binding characteristics of human α-1-acid glycoprotein (HAG) with JAK inhibitor ocalcitinib: Multi-spectroscopic analysis combined with theoretical calculations

Abstract

A powerful Janus kinase (JAK) inhibitor, ocalcitinib has been authorized for controlling pruritus and atopic dermatitis from canine allergic dermatitis and many kinds of cytokines. To further understand the drug action, the interaction between ocalcitinib and HAG was explored using multi-spectroscopic approaches combined with theoretical calculations. The results demonstrated that ocalcitinib effectively quenched the intrinsic fluorescence of HAG protein through a mixed quenching and formed a stable ocalcitinib–HAG complex that had the association constant of 104–105M−1, outlining that ocalcitinib binding to HAG protein had a moderate affinity. In the ocalcitinib–HAG complex, ocalcitinib implanted into the bucket-shaped hydrophobic chamber of HAG, leading to the slight variety in the hydrophobicity of the microenvironment encircled Trp-and Tyr-resides as well as the secondary structure of HAG. And, the driving forces that forms the ocalcitinib-HAG complex were mainly the hydrogen bonding interaction, Van der Waals forces, and hydrophobic interaction. It is also confirmed that the common metal ions like Ca2+, Mg2+, Fe3+, Zn2+, Cu2+, Co2+, Ni2+ ions) except K+ ion had a greater negative influence on the complexation between ocalcitinib and HAG. This study should conducive to estimating the pharmacological natures of ocalcitinib, comprehending the distribution and operation of the drug in the body, and developing novel medication devise.