Exploration of the anticandidal mechanism of Cassia spectabilis in debilitating candidiasis

Candida albicans has become resistant to the commercially available, toxic, and expensive anti-Candida agents that are on the market. These factors force the search for new antifungal agents from natural resources. Cassia spectabilis had been traditionally employed by healers for many generations. The possible mechanisms of the C. spectabilis leaf extract were determined by potassium leakage study and the effect of the extract on the constituents of the cell wall and enzymes as well as the morphological changes on C. albicans cells were studied along with cytotoxicity assays. The cytotoxicity result indicated that the extract is nontoxic as was clearly substantiated by a half maximal inhibitory concentration (IC50) value of 59.10 μg/mL. The treated cells (C. spectabilis extract) demonstrated potassium leakage of 1039 parts per million (ppm) compared to Amphotericin B (AmpB)-treated cells with a released potassium value of 1115 ppm. The effects of the extract on the cell wall proteins illustrated that there were three major types of variations in the expression of treated cell wall proteins: the presence of new proteins, the absence of proteins, and the amount of expressed protein. The activities of two enzymes, α-glucosidase and proteinase, were determined to be significantly high, thereby not fully coinciding with the properties of the antifungal reaction triggered by C. spectabilis. The morphology of C. albicans cells treated with the C. spectabilis extract showed that the cells had abnormalities and were damaged or detached within the microcolonies. Our study verifies C. spectabilis leaf extract as an effective anti-C. albicans agent.

Effects of advanced glycation end-products (AGEs) on retinal pigment epithelial (RPE) cells lysosomal function:implications for age-related macular degeneration (AMD)

Purpose: RPE lysosomal dysfunction is a major contributor to AMD pathogenesis. Controlled activity of a major class of RPE proteinases, the cathepsins, is crucial in maintaining correct lysosomal function. Advanced glycation end-products (AGEs) accumulate in the Bruch’s membrane (BM) with age, impacting critical RPE functions and in turn, contributing to the development of AMD. The aim of this study was to assess the effect of AGEs on lysosomal function by analysing the expression, processing and activity of the cysteine proteinases cathepsins B, L and S, and the aspartic proteinase cathepsin D. Methods: ARPE-19 cells were cultured on AGE-containing BM mimics (matrigel) for 14 days and compared to untreated substrate. Expression levels and intracellular processing of cathepsins B, D, L and S, were assessed by qPCR and immunoblotting of cell lysates. Lysosomal activity was investigated using multiple activity assays specific to each of the analysed cathepsins. Statistical analysis was performed using the Student’s independent T-test. Results: AGE exposure produced a 36% decrease in cathepsin L activity when compared to non-treated controls (p=0.02, n= 3) although no significant changes were observed in protein expression/processing under these conditions. Both the pro and active forms of cathepsin S decreased by 40% (p=0.04) and 74% (p=0.004), respectively (n=3). In contrast, the active form of the cathepsin D increased by 125% (p=0.005, n= 4). However, no changes were observed in the activity levels of both cathepsins S and D. In addition, cathepsin B expression, processing and activity also remained unaltered following AGE exposure. Conclusions: AGEs accumulation in the extracellular matrix, a phenomenon associated with the natural aging process of the BM, attenuates the expression, intracellular processing and activity of specific lysosomal effectors. Altered enzymatic function may impair important lysosomal processes such as endocytosis, autophagy and phagocytosis of photoreceptor outer segments, each of which may influence the age-related dysfunction of the RPE and subsequently, AMD pathogenesis.