Abstract
Exposure to particulate matter is a risk factor for various ocular surface diseases, including keratoconjunctivitis sicca (KCS). In this study, we investigated the protective effects of apricot kernel extract (AKE) and its bioactive compound, amygdalin, on KCS induced by exposure to urban particulate matter (UPM). In the in vivo experiments, eye drops containing 0.5 mg/mL AKE (AKE-0.5) or 1 mg/mL AKE (AKE-1) were administered directly into the eyes of female rats after UPM exposure. Additionally, the effect of AKE and amygdalin on matrix metalloproteinases (MMPs) activity and the expressions of inflammatory factors, including tumor necrosis factor (TNF)-α and interleukin (IL)-6, was investigated in conjunctival epithelial cells in vitro. Topical administration of AKE-1 attenuated UPM exposure-induced reduction of tear secretion. Both AKE-0.5 and AKE-1 inhibited UPM exposure-induced corneal epithelial damage and irregularity. AKE also protected against UPM exposure-induced disruption of the mucin-4 layer on the ocular surface. In addition, AKE and amygdalin prevented UPM-induced activation of MMPs and upregulation of TNF-α and IL-6 in conjunctival epithelial cells. Therefore, AKE may have protective effects against UPM exposure-induced KCS via the inhibition of MMPs and inflammation. The pharmacological activities of AKE may be in part due to its bioactive compound, amygdalin.
Highlights
Keratoconjunctivitis sicca (KCS) is a common ophthalmological disease that results in symptoms of discomfort and the disturbance of vision [1,2]
The method, and apricot kernel extract (AKE) was characterized by analysis of its major constituent,constituent, amygdalin
In our previous study [11], we reported that 1 g of AKE contains 127.34 ± 0.99 mg of amygdalin
Summary
Keratoconjunctivitis sicca (KCS) is a common ophthalmological disease that results in symptoms of discomfort and the disturbance of vision [1,2]. KCS arises as a result of a disturbance of the ocular surface system, a complex entity that conceptually results from functional integration of its anatomical components (conjunctival epithelium, limbal epithelium, corneal epithelium, glandular epithelia, and tear film) with the adjacent structures (vasculature, nerves, eyelids, eyelashes, lacrimal glands, Meibomian glands, and nasolacrimal duct) [3]. Particulate matter is composed of solid and liquid particles, those present in ambient air [5], and is a cause of air pollution that increases the public health risk [6]. Many studies have associated exposure to urban particulate matter (UPM) with respiratory diseases [7,8,9].
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