MiR-221-3p Attenuates IL-33-Induced Mast Cell Cytokine Expression by Targeting KIT.

Background: Mast cells (MCs) are involved in type 2 inflammation in chronic rhinosinusitis with nasal polyps (CRSwNP), which depends on interleukin (IL)-33 stimulation. MiR-221 is reported to be an important regulator of MCs, and miR-221-3p can be expressed in CRSwNP. However, the role of miR-221-3p in CRSwNP is unclear.

Methods: Ethmoid tissues from control subjects (n = 12) and polyps from patients with CRSwNP (n = 40) were collected. The expression of miR-221-3p and cytokines was detected by real-time quantitative polymerase chain reaction (qPCR). The activation of P65 and ERK was determined by western blotting. The localization of miR-221-3p was detected via in situ hybridization combined with immunofluorescence (IF), and its target was identified via a luciferase reporter system. Human MCs were incubated with IL-33 or stem cell factor. MicroRNA mimics/inhibitor and lentiviral plasmids were used to determine the role of miR-221-3p in MCs.

Results: We observed increased expression of miR-221-3p in CRSwNP, and localized its expression in MCs. The expression of miR-221-3p was negatively correlated with that of IL-4, IL-5, and IL-13 in CRSwNP. MiR-221-3p can be induced by IL-33 in MCs and plays a negative regulatory role in cytokine expression and signaling pathways in IL-33-induced MC activation. As the direct target of miR-221-3p, the receptor KIT was negatively correlated with miR-221-3p and decreased in CRSwNP. In MCs, KIT is essential for an effective response to IL-33 stimulation. We here demonstrated that miR-221-3p regulates cytokine expression by targeting KIT in IL-33-activated MCs.

Conclusions: MiR-221-3p inhibits MC-dependent type 2 inflammatory conditions, rendering it a negative regulator of CRSwNP.