The inhibition of p38 MAPK blocked inflammation to restore the functions of rat meibomian gland epithelial cells.

ABSTRACT

Meibomian glands (MGs) are vital for ocular surface health. However, the roles of inflammation in the progression of meibomian gland dysfunction (MGD) are largely unknown. In this study, the roles of the inflammation factor interleukin-1ß (IL-1ß) via the p38 mitogen-activated protein kinases (MAPK) signaling pathway on rat meibomian gland epithelial cells (RMGECs) were explored. Eyelids from adult rat mice at 2 months and 2 years of age were stained with specific antibodies against IL-1ß to identify inflammation levels. RMGECs were exposed to IL-1ß and/or SB203580, a specific inhibitor of p38 MAPK signaling pathway, for 3 days. Cell proliferation, keratinization, lipid accumulation, and matrix metalloproteinases 9 (MMP9) expression were evaluated by MTT assay, polymerase chain reaction (PCR), immunofluorescence staining, apoptosis assay, lipid staining, and Western blot analyses. We found that IL-1ß was significantly higher in the terminal ducts of MGs in rats with age-related MGD than in young rats. IL-1ß inhibited cell proliferation, suppressed lipid accumulation and peroxisome proliferator activator receptor γ (PPARγ) expression, and promoted apoptosis while activating the p38 MAPK signaling pathway. Cytokeratin 1 (CK1), a marker for complete keratinization, and MMP9 in RMGECs were also up-regulated by IL-1ß. SB203580 effectively diminished the effects of IL-1ß on differentiation, keratinization, and MMP9 expression by blocking IL-1ß-induced p38 MAPK activation, although it also inhibited cell proliferation. The inhibition of the p38 MAPK signaling pathway blocked IL-1ß-induced differentiation reduction, hyperkeratinization, and MMP9 overexpression of RMGECs, which provides a potential therapy for MGD.