Activation of Mapk Signaling Pathway and Nf-B Activation in Pterigium and Ipsilateral Pterygium-Free Conjunctival Specimens

Abstract

Purpose: : Pterygium is a proliferative ocular surface disease in which inflammation has been recently shown to play a relevant role. The aim of this study is to evaluate whether the pterygium-free conjunctiva of the same eyes suffering from this disease also shows signs of inflammation by measuring the activated signaling pathway of mitogen-activated protein kinases (MAPK) and nuclear factor-ΚB (NF-ΚB) activation.

Methods: : Three types of specimens were analyzed: 1) excised primary pterygium (pt) (n=21); 2) ipsilateral superior-temporal bulbar conjunctiva (conj-pt) (n=8 out of the 21 pterygium patients); and 3) healthy conjunctival biopsies from subjects undergoing cataract surgery with no other previous ocular disease and under no ophthalmic medications (norm-conj) (n=5). Tissues were homogenized and total, phosphorylated (p), and the ratio of p/total levels of the following markers were analyzed by an inmunobead based assay in a Luminex-IS 100: extracellular-regulated 1/2 (ERK1/2), p38 and c-jun N-terminal (JNK) MAP kinases (MAPK), and IΚB-α levels. Protein levels were compared using the Kruskal-Wallis test with Dunn's multiple comparison post-test. Average-linkage hierarchical cluster technique was used to identify patients with similar protein activation levels. To design a system able to accurately predict the origin of a potential new specimen based on its protein levels, the k-Nearest Neighbor classifier was used.

Results: : Pt and conj-pt showed significant differences (decreased total JNK and total IkBα levels) compared to norm-conj. Conj-pt also showed significantly increased levels of p-IΚB-α and p/total levels of JNK and IkBα compared to norm-conj. Clustering analysis of pt activation/conj-pt activation ratio revealed one patient characterized by a high JNK ratio and another patient characterized by a high ERK1/2, and moderate p38 and JNK ratios. The prediction accuracy value of the designed system was between 70-80% in the three proposed classifiers (total, p, and the ratio of p/total levels).

Conclusions: : Not only pterygium specimens but also pterigium-free ipsilateral conjunctival specimens showed alterations in MAPK and NF-ΚB pathways not present in normal conjunctiva that could have a role in pterygium pathogenesis.

Keywords: pterygium • conjunctiva • inflammation