“Responses of zebrafish (Danio rerio) hepatocytes co-exposed to benzo[a]pyrene and to the carbon nanomaterial fullerene (C60)”

LONNÉ, M.N.; RIBAS FERREIRA, J.L.; SOARES CHAVES, I.; DE LA TORRE, F.R; MONSERRAT, J.M

Quito, Ecuador.

Congreso; First International Nanotechnology Congress; 2010

&amp;amp;amp;lt;!-- /* Font Definitions */ @font-face {font-family:"Cambria Math"; panose-1:2 4 5 3 5 4 6 3 2 4; mso-font-charset:0; mso-generic-font-family:roman; mso-font-pitch:variable; mso-font-signature:-1610611985 1107304683 0 0 159 0;} @font-face {font-family:Tahoma; panose-1:2 11 6 4 3 5 4 4 2 4; mso-font-charset:0; mso-generic-font-family:swiss; mso-font-pitch:variable; mso-font-signature:-520082689 -1073717157 41 0 66047 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-unhide:no; mso-style-qformat:yes; mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman","serif"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:ES; mso-fareast-language:ES;} .MsoChpDefault {mso-style-type:export-only; mso-default-props:yes; font-size:10.0pt; mso-ansi-font-size:10.0pt; mso-bidi-font-size:10.0pt;} @page WordSection1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.WordSection1 {page:WordSection1;} --&amp;amp;amp;gt; <!-- /* Font Definitions */ @font-face {font-family:"Cambria Math"; panose-1:2 4 5 3 5 4 6 3 2 4; mso-font-charset:0; mso-generic-font-family:roman; mso-font-pitch:variable; mso-font-signature:-1610611985 1107304683 0 0 159 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-unhide:no; mso-style-qformat:yes; mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman","serif"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:PT-BR; mso-fareast-language:PT-BR;} .MsoChpDefault {mso-style-type:export-only; mso-default-props:yes; font-size:10.0pt; mso-ansi-font-size:10.0pt; mso-bidi-font-size:10.0pt;} @page WordSection1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.WordSection1 {page:WordSection1;} --> Due to their high surface/volume relation, nanocompounds have a great adsortion capacity wich could facilitate the entrance of other toxic molecules into the cell. In this way, the nanocompounds would be acting as “Trojan Horses”. In this work the toxic responses to the coexposition of zebrafish hepatocytes to the polycyclic aromatic hydrocarbon benzo[a]pyrene (BaP) and the nanocompound fullerene (C60)  were studied. Hepatocytes were kept at 28 °C, in RPMI culture medium with 10% bovine serum albumin.  Mitochondrial functionality (MF), obtained by MTT reduction, was used as a cell viability estimate. Concentrations of 0.01, 0.1 and 1.0 mg BaP/L did not alter the viability when compared to the control group; whereas 10.0 and 100.0 mg BaP/L decreased it (p<0.05). The effect of coexposure to BaP (0.01-1.0 mg BaP/L) with 1 mg C60/L –a concentration that did not change the cell viability-  was evaluated. After 4 h of incubation, several parameters were evaluated: the MF and the intracelular concentration of reactive oxygen species (ROS); the glutathione-S-transferase (GST) activity and intracellular accumulation of BaP and its metabolites. Regarding ROS, the results showed that coexposition of hepatocytes to 1.0 mg BaP/L and 1 mg C60/L caused a significant decrease in their concentration in relation to the cells only exposed to 1.0 mg/L BaP. GST activity increased in a dose-dependent manner (p<0.05) without C60 for the concentrations of 0.1 and 1 mg/mL BaP; in presence of the nanocompound a significant reduction was observed for all concentrations tested. In addition, the intracellular accumulation of BaP and its metabolites was significantly higher both in the presence and absence of C60 for the 1 mg/L of BaP concentration. In relation to ROS, the result can not be interpreted as an antioxidant effect because at the same time a lower MTT reduction capacity was observed for all three concentrations of BaP when coexposed  with fullerene. Taking into account that the mitocondrias are the main source of ROS production, the decrease in their concentration and the lower MF in hepatocytes exposed to BaP and C60 suggest that mitochondrial functionality could be altered. The GST activity was higher for increasing values of BaP concentration, as expected, but the presence of the nanocompound caused a significant loss in the detoxifying capacity of the cells. Finally, BaP accumulation did not significantly increase in presence of fullerene, discarding the possible role of C60 as a “Trojan Horse” and suggesting other feasible mecanisms by wich this substance may increase the toxicity of BaP.