Lysosomal enzymes activity in patients with pseudoexfoliation syndrome

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Pseudoexfoliation syndrome (PEX) is a complex systemic disorder of the extracellular matrix affecting the eye and visceral organs. Pseudoexfoliation material deposits on various structures of the anterior segment of the eye and around blood vessels of connective tissue. Animal studies have suggested that the lysosomal trafficking regulator (LYST) gene is potentially important in PEX (Liton et al. 2009). Lysosomes are the cellular recycling centres responsible for the physiologic turnover of cell constituents. Inadequate enzyme activity results in disruption of the degradation process and accumulation of substrates for that specific enzyme, leading to variety of pathological changes. Increasing evidence suggests that the oxidative–antioxidative balance is disturbed in patients with PEX (Uçakhan et al. 2006; Lesiewska-Junk et al. 2013). The lysosomal proteolytic activity is compromised under oxidative stress conditions (Wenger et al. 2013). We studied 52 consecutive patients with PEX (16 males and 36 females), who presented for senile cataract surgery, median 75 years, range 59–89. The reference group consisted of 30 individuals (10 males and 20 females), matched for age and gender, with senile cataract without PEX, median 72 years, range 61–90. Both groups did not differ in stage of cataract nor body mass index and smoking habits. PEX was recognized based on typical material in the anterior segment seen after pupil dilation. The exclusion criteria were systemic and local diseases except cataract and PEX (including diabetes, rheumatoid arthritis, lipid profile disorders, intraocular surgery in history). The activity of four lysosomal enzymes in plasma was assessed as follows: acid phosphatase (AcP) with the use of Bessey method, alpha-1-antitrypsin (AAT) using Eriksson method, cathepsin D (CAT D) using Anson method and arylsulphatase (AS) using Robinson method. Kolmogorov–Smirnov test was used to assess normality of the data. Mann-Whitney test was used for comparison of data from small size independent samples. P-value of <0.05 was considered statistically significant. The values of activities of assessed enzymes are shown in Table 1. Reduced activity of proteolytic enzymes and subtle inflammatory processes may trigger the PEX-specific fibrotic matrix process (Schlötzer-Schrehardt 2012). Although Mizuno et al. (1980) found acid phosphatase activity significantly higher in the aqueous humour of eyes with PEX than in that of cataractous eyes without PEX, in our group, these values in blood plasma appeared to be lower in PEX patients. According to Cumurcu et al. (2008) serum A-1-AT activity was increased in patients with PEX, which is in accordance with our results. It may indicate the role of inflammation in this group of patients. To our best knowledge, this is the first study on AS and CAT D activities in PEX patients. Our observations may shed light on the complex metabolic contribution and molecular pathway of the disease.