The α -Tomatine Exhibits Antiproliferative Activity, Rupture of Cell Membranes and Induces the Expression of APC Gene in the Human Colorectal Adenocarcinoma Cell Line (Ht-29)

Abstract The α-tomatine is a steroidal glycoalkaloid found in immature tomatoes (Lycopersicon esculentum) that has important biological functions including the inhibition of cancer cell growth and preventing metastasis. This study aimed to evaluate the effects of α-tomatine on cytotoxicity, cellular proliferation, apoptosis, and mRNA expression of APC, CCNA2, β-catenin, CASP9, BAK, BAX and BCL-XL in colorectal adenocarcinoma cell line HT-29. HT29 cells were treated with three concentrations of α-tomatine (0.1, 1 and 10 µg/mL), although only the 1 µg/mL concentration of α-tomatine was used to evaluate genetic expression patterns by real time-PCR. Results showed that α-tomatine was cytotoxic only at the 10 µg/mL concentration. Cell proliferation was significantly inhibited after the first 24 hours of treatment only with concentrations of 10 µg/mL. In contrast, there were no significant differences in apoptosis for any treatment. In the gene expression studies, only APC expression was significantly altered by α-tomatine treatment. In conclusion, α-tomatine has antiproliferative activity in the first 24h of treatment, does not induce apoptosis in this cell line and causes disruption of cell membranes, thereby increasing the expression of APC gene related to cell cycle.

Behavior of alfa-tomatine and tomatidine against several genera of trypanosomatids from insects and plants and Trypanosoma cruzi / Comportamento de alfa-tomatina e tomatidina contra vários gêneros de tripanossomatídeos de insetos e plantas e Trypanosoma cruzi

Glycoalkaloids are important secondary metabolites accumulated by plants as protection against pathogens. One of them, α-tomatine, is found in high concentrations in green tomato fruits, while in the ripe fruits, its aglycone form, tomatidine, does not present a protective effect, and it is usual to find parasites of tomatoes like Phytomonas serpens in these ripe fruits. To investigate the sensitivity of trypanosomatids to the action of α-tomatine, we used logarithmic growth phase culture of 20 trypanosomatids from insects and plants and Trypanosoma cruzi. The lethal dose 50% (LD50) was determined by mixing 107 cells of the different isolates with α-tomatine at concentrations ranging from 10-3 to 10-8 M for 30 min at room temperature. The same tests performed with the tomatidine as a control showed no detectable toxicity against the same trypanosomatid cultures. The tests involved determination of the percentage (%) survival of the protozoan cultures in a Neubauer chamber using optical microscopy. The LD50 values varied from 10-4 to 10-6 M α-tomatine. Slight differences were detected among the LD50 values of the analyzed samples, and none of them showed evidence of resistance to the action of tomatinase, as shown by some pathogenic fungi.

Os glicoalcaloides são metabólitos secundários importantes produzidos pelas plantas e estão envolvidos em sua proteção contra agentes patogênicos. Um deles, α-tomatina, é encontrado em altas concentrações em frutos de tomate verde, enquanto que, nos frutos maduros, sua forma aglicona, tomatidina, não apresenta um efeito protetor, sendo comum encontrar parasitas de tomates como Phytomonas serpens nesses frutos maduros. Para investigar a sensibilidade dos tripanossomatídeos à ação da α-tomatina, utilizamos formas de cultura em fase logarítmica de 20 tripanossomatídeos de plantas e insetos e Trypanosoma cruzi. A dose letal 50% (DL50) foi determinada, misturando 107 células das formas de cultura com concentrações de 10-3 a 10-8 M de α-tomatina durante trinta minutos a temperatura ambiente. Testes realizados com a tomatidina como controle não mostraram toxicidade detectável contra os mesmos tripanossomatídeos. Os testes foram avaliados pela porcentagem (%) de sobrevivência das formas de cultura dos protozoários observados por microscopia óptica em câmara de Neubauer. Os resultados da determinação de DL50 mostraram que esta variou entre 10-4 a 10-6 M de α-tomatina. Pequenas diferenças foram observadas entre os valores de DL50 das amostras analisadas, e nenhuma delas mostrou evidência de resistência pela ação da tomatinidase, como demonstrado em alguns fungos patogênicos.

Homeostatic unbalance via HSPA5 gene expression in HepG2C3A cells exposed to alpha-tomatine / Desequilíbrio homeostático através da expressão do gene HSPA5 em células HepG2C3A exposto a alpha-tomatine

The α-tomatine is a glycoalkaloid found in immature tomatoes (Lycopersicon esculetum). Currently, α-tomatine has shown anticancer effects due to its anti-proliferative property. Stressors are one of the factors contributing to the antiproliferative activity of α-tomatine that can modify cellular homeostasis.Among the cell stressors are the endoplasmic reticulum stress response elements, which can be alteredleading to cell death. In the course of this study, we verified the expression of genes involved in the stress response of the endoplasmic reticulum in HepG2/C3A cells. The α-tomatine reduced the viability of HepG2/C3A cells in a dose-dependent manner. Thus, we selected 2µg/mL of α-tomatine (62% incell viability) to evaluate the gene expressions. After 24 hours of exposure to α-tomatine, the level of HSPA5 transcripts was reduced. The HSPA5 chaperone reduced marker is an indicative of homeostasisunbalance with the consequent lack of cellular resistance and, probably, cell death. Our results indicate the involvement of oxidative stress mechanisms in the death of HepG2/C3A cells exposed to α-tomatine.

A α-tomatina é um glicoalcaloide encontrado no tomate imaturo (Lycopersicon esculetum). Atualmente,a α-tomatina tem mostrado efeito anticancerígeno devido sua propriedade antiproliferativa. O estresse celular é um dos fatores que contribui para a atividade antiproliferative da α-tomatina que pode modificara homeostase celular. Entre os estressores celulares esta os elementos de resposta ao estresse do retículo endoplasmático, que podem ser alterados, levando à morte celular. No decorrer deste estudo, verificamos que a expressão de genes envolvidos na resposta ao estresse do retículo endoplasmático em célulasHepG2/C3A. A α-tomatina reduziu a viabilidade das células HepG2/C3A de forma dose-dependente.Assim, selecionamos a concentração de 2μg/mL de α-tomatina (viabilidade celular de 62%) para avaliara expressão gênica. Após 24 horas de exposição a α-tomatina, o nível de transcrição de HSPA5 foireduzido. A redução de HSPA5 é um indicativo de desequilíbrio da homeostase, com a consequente falta de resistência celular e, provavelmente, a morte celular. Nossos resultados indicam o envolvimento de mecanismos de estresse oxidativo na morte de células HepG2/C3A exposto a α-tomatina e mostram a eficácia do sistema como um futuro candidato para os estudos de terapia de câncer.