Avaliação do efeito do ácido ascórbico, ascorbato e luz uv sobre células HEPG2 e o fungo filamentoso Aspergillus nidulans

Abstract

Ascorbic acid (AA), communly known as vitamin C has seen a remarkable increase in use and is currently one of the most frequently supplemented vitamins. This vitamin is necessary for amino acid metabolism and is also an essential cofactor for the catecholamines biosynthesis. In addition to its antioxidant activity, AA can act as a pro-oxidant under specific conditions. AA is an excellent reducing agent and easily undergoes two consecutive one-electron oxidations, forming ascorbate (ASC) and dehydroascorbate (DHA) radicals. At pH values normally found in the intracellular environment, AA is predominantly identified in its ionized form, ASC, which is its main form in the human body Objective: Evaluate the effect of AA, ASC, and Ultraviolet Light (UV) on the development and growth of A. nidulans, as well as their toxicity in human HepG2 cells in vitro. Consists of a basic research study with an experimental and quantitative approaches. Colony growth and conidia germination of A. nidulans were analyzed. Viability tests of human HepG2 cells in vitro were also performed. During the germination of conidia, an initial screening was performed using concentrations of 10, 25, 50, 100 and 200 μg per mL-1. At various time points, all concentrations showed significant difference compared to the control. Growth assays of A. nidulans colonies exposed to both AA and ASC demonstrated changes at different concentrations and days of analysis compared to the control. AA assays with HepG2 cells presented a significant increase in mean absorbance after 24 hours of treatment at a concentration of 40 ug/mL, indicating a stimulation of cell division. On the other hand, a significant decrease occurred after 72 hours of treatment at concentrations of 5, 10, 40 and 100 ug/mL. In the ASC assays with HepG2 cells, no significant difference were observved for any of the concentrations and timepoints tested in comparison to the negative control. Regarding cytotoxicity to UV light, it showed toxicity at all irradiation times (one, five, 10 and 20 s), after 24, 48 and 72 hours compared to the negative control. The current findings have shown that AA in lower concentrations increased the growth of A. nidulans, possibly by stimulating cell proliferation, while higher concentrations seem to decrease growth, delaying proliferation, or inducing apoptosis. For HepG2 cell culture, AA increased growth at a lower concentration and decreased growth at higher concentration, while ASC did not cause toxicity in this cell line. This response profile is similar to that found in the fungus.