Inhibition of LOXL2 Suppresses Nasal Mucosal Inflammation and Remodeling in Allergic Rhinitis.

Background: Tissue remodeling is a key feature of allergic rhinitis (AR), but its underlying molecular mechanisms remain unclear. Lysyl oxidase-like 2 (LOXL2), a regulator of tissue remodeling, has not been studied in AR.

Methods: Proteomic analysis was performed on nasal mucosal tissues from 8 AR patients and 8 healthy controls (HCs) to identify differentially expressed proteins (DEPs). The top three upregulated DEPs and their association with tissue remodeling markers were validated by immunofluorescence, Western blot, and RT-qPCR in an independent cohort of 30 AR patients and 30 HCs. In vitro, human nasal epithelial cells (HNECs) were treated with IL-4, and the effects of candidate protein inhibitors on remodeling were assessed. An AR mouse model was used to evaluate the impact of these inhibitors on nasal inflammation and remodeling.

Results: Proteomic analysis revealed a disease-specific protein expression profile in the nasal mucosa of AR patients, with the top three upregulated proteins being LOXL2, TGF-β1, and TIRAP. Tissue validation showed that LOXL2 was significantly upregulated in the nasal mucosa of AR patients compared to HCs and was significantly correlated with EMT markers (TGF-β1, α-SMA, and E-cadherin). In vitro, IL-4 stimulation significantly upregulated LOXL2, TGF-β1, and α-SMA, while downregulating E-cadherin in a dose-dependent manner in human nasal epithelial cells. These effects were reversed by inhibition of LOXL2. Further investigations demonstrated that LOXL2 promotes tissue remodeling through activation of the TGF-β1/Smad signaling pathway. In the AR mouse model, LOXL2 inhibitors significantly reduced nasal mucosal inflammation and tissue remodeling.

Conclusion: Our proteomic analysis suggests that LOXL2 may be involved in the pathological remodeling processes of AR, potentially through modulation of the TGF-β1/Smad signaling pathway. These findings provide preliminary evidence that LOXL2 could serve as a candidate biomarker and a possible therapeutic target in AR, warranting further investigation.