Benzo[a]pyrene affects Jurkat T cells in the activated state via the antioxidant response element dependent Nrf2 pathway leading to decreased IL-2 secretion and redirecting glutamine metabolism.

There is a clear evidence that environmental pollutants, such as benzo[a]pyrene (B[a]P), can have detrimental effects on the immune system, whereas the underlying mechanisms still remain elusive. Jurkat T cells share many properties with native T lymphocytes and therefore are an appropriate model to analyze the effects of environmental pollutants on T cells and their activation. Since environmental compounds frequently occur at low, not acute toxic concentrations, we analyzed the effects of two subtoxic concentrations, 50nM and 5µM, on non- and activated cells. B[a]P interferes directly with the stimulation process as proven by an altered IL-2 secretion. Furthermore, B[a]P exposure results in significant proteomic changes as shown by DIGE analysis. Pathway analysis revealed an involvement of the AhR independent Nrf2 pathway in the altered processes observed in unstimulated and stimulated cells. A participation of the Nrf2 pathway in the change of IL-2 secretion was confirmed by exposing cells to the Nrf2 activator tBHQ. tBHQ and 5µM B[a]P caused similar alterations of IL-2 secretion and glutamine/glutamate metabolism. Moreover, the proteome changes in unstimulated cells point towards a modified regulation of the cytoskeleton and cellular stress response, which was proven by western blotting. Additionally, there is a strong evidence for alterations in metabolic pathways caused by B[a]P exposure in stimulated cells. Especially the glutamine/glutamate metabolism was indicated by proteome pathway analysis and validated by metabolite measurements. The detrimental effects were slightly enhanced in stimulated cells, suggesting that stimulated cells are more vulnerable to the environmental pollutant model compound B[a]P.

Thermo-responsive poly(N-isopropylacrylamide) grafted onto microtextured poly(dimethylsiloxane) for aligned cell sheet engineering.

Poly(N-isopropylacrylamide) (PNIPAAm)-grafted poly(dimethylsiloxane) (PDMS) offers an inexpensive, biocompatible, oxygen permeable, and easily microtextured thermo-responsive substrate for producing cell sheets. This study introduces a method of grafting PNIPAAm onto microtextured PDMS that is suitable for generating aligned vascular smooth muscle cell (VSMC) sheets. We examined a wide range of processing parameters in order to identify the conditions that led to acceptable sheet growth and detachment behavior. Substrates grafted under these conditions produced confluent cell sheets that fully detached in less than 10 min after lowering the culture temperature from 37 °C to 20 °C. The grafted layer thickness was determined to be 496±8 nm by atomic force microscopy. Surface characterization by Fourier transform infrared spectroscopy showed a relative grafting yield of 0.488±0.10, defined as the ratio of the PNIPAAm 1647 cm(-1) to the PDMS 2962 cm(-1) absorbance peaks. The water contact angle of the substrates was shown to change from 89.6° to 101.0° at 20 °C and 37 °C, respectively. We also found that cell behavior on PNIPAAm-grafted PDMS was not directly related to surface wettability or relative grafting densities.